Chronological List of Articles

SUMMARY:
This comparative in vivo/in vitro study investigated the interfacial adaptation between dentin and composite resins in totally bonded adhesive restorations placed under clinical and laboratory conditions in the same tooth. Cavities were prepared in buccal or lingual surfaces of 47 third-molar teeth scheduled for extraction and randomly assigned for treatment with the following bonding systems/restorative materials: Clearfil Liner Bond 2/Clearfil AP-X (Group I, n=10), Resulcin AquaPrime+Monobond/MFR Merz (Group II, n=9), Prime&Bond 2.1/Dyract AP (Group III, n=9), Scotchbond Multi-Purpose/Z-100 (Group IV, n=10), and Ecusit Primer AB-Mono/Ecusit (Group V, n=9). In Group V, a thin layer of a low-viscous compomer (Primaflow) was interposed between the dentin and the composite resin during restoration placement (according to the manufacturer’s directions). After extraction a second filling was placed in each tooth with identical materials in the same manner as in vivo. The restoration-dentin interface was evaluated in longitudinally cut sections of the specimens by SEM-analysis, and the frequency of gap formation between restoration and dentin was calculated. Median percentages for the in vivo/in vitro frequency of interfacial gap formation were 29.2%/13.9% in Group I, 33.3%/20.0% in Group II, 40%/5.3% in Group III, 53.9%/30.4% in Group IV and 13.8%/0% in Group V. Comparison of gap formation frequency between fillings placed in vivo and in vitro revealed significant differences (p<0.05) in Groups II, III and IV. However, in Groups I and V the internal adaptation was not significantly different between in vivo and in vitro applied restorations. A significant (p<0.01) correlation (Spearman-Rho rank correlation coefficient) was found for the corresponding in vivo and in vitro fillings placed in the individual teeth with regard to interfacial gap formation. It was concluded that achievement of a completely gap-free internal adaptation between restorative material and dentin in totally bonded composite-resin restorations is difficult to predict under in vivo as well as in vitro conditions.

SUMMARY:
This study compared the clinical performance of a polyacid-modified resin composite and a resin-modified glass-ionomer restorative material over two years. Thirty-four pairs of restorations of Compoglass and Fuji II LC were placed in caries-free cervical erosion/abfraction lesions without tooth preparation. Restorations were clinically evaluated at baseline, 6, 12, 18 and 24 months using modified Ryge/USPHS criteria. A significantly higher incidence of failed restorations was found with the polyacid-modified resin composite (p<0.05).

SUMMARY:
One hundred non-carious cervical lesions were restored with either Silux Plus or Estio LC resin composite using Fuji Bond LC as the bonding agent. Thirteen patients of mean age 60.5 years participated in the study. The retention rate at three years was: Silux Plus, 94%; Estio LC, 100%; total, 97%. Marginal discoloration of aesthetic significance was present around three restorations, two of which were in one patient.

SUMMARY:
One hundred non-carious cervical lesions were restored with either Silux Plus or Estio LC resin composite using Fuji Bond LC as the bonding agent. Thirteen patients of mean age 60.5 years participated in the study. The retention rate at three years was: Silux Plus, 94%; Estio LC, 100%; total, 97%. Marginal discoloration of aesthetic significance was present around three restorations, two of which were in one patient.

SUMMARY:
This study investigated the influence of the direction of dentinal tubules on resin-dentin tensile bond strength (µTBS) using four commercially available bonding systems and observed the resin-dentin interfaces with an SEM. The dentin bonding systems used in this study were Clearfil Liner Bond II (LB, Kuraray), Imperva Fluoro Bond (FB, Shofu), Single Bond (SB, 3M) and One-Step (OS, BISCO). Thirty-six extracted caries-free human molars were used for micro tensile bond testing and eight additional teeth were used for scanning electron microscopy (SEM). The teeth were divided into two groups according to the direction of the dentinal tubules at the resin-dentin interface: a perpendicular group, in which the occlusal enamel was removed perpendicular to the long axis of the tooth, and a parallel group, in which the mesial half of the tooth was removed parallel to the long axis of the tooth, and the coronal dentin surface was used for bonding. After the flat dentin surfaces were polished with #600 silicon carbide paper, each surface was treated with one of the four adhesive systems according to the manufacturer’s recommendation, then covered with resin composite (Clearfil AP-X, Kuraray) to provide sufficient bulk for micro-tensile bond testing. After 24 hours in 37°C water, the resin-bonded teeth were serially sliced perpendicular to the adhesive surface, the adhesive interface trimmed to a cross sectional area of 1 mm2 an subjected to tensile forces at a crosshead speed of 1 mm/min. Statistical analysis of the tensile bond strengths were performed using two-way ANOVA and Fisher’s PLSD test at 95% level of confidence. The tensile bond strength of the group with tubules parallel to the bonded interface was higher than that of tubules cut perpendicularly. This tendency reached statistical significance using SB and OS.

SUMMARY:
This investigation evaluated the fluoride-releasing properties of various fluoride-releasing restorative materials, including resin-modified glass-ionomer cements (Fuji ionomer TypeII LC, Photac-Fil Aplicap, Vitremer), compomers (Ionosit FIL, Compoglass, Dyract) and fluoride-releasing resin composites (Heliomolar radiopaque, Degufill mineral). The study also estimated the effects of those materials on the inhibition of artificial secondary caries around restorations using a bacterial caries-inducing system. The amount of fluoride released from the materials in deionized water was measured every one week for 10 weeks. Class V cavities with the gingival margin located in the root were prepared in extracted human premolars and restored with each of the materials. The restored teeth were incubated in the bacterial artificial caries chamber, and the artificial lesion created around the restoration was observed microradiographically. The resin-modified glass-ionomer cements released the largest amount of fluoride and created a thick radio-opaque zone in the artificial lesion along the restoration-dentin interface. These results indicated that the fluoride-releasing restorative materials have the potential to inhibit secondary caries formation around restorations. Resin-modified glass-ionomer cements presented a particularly strong effect, compared with compomers and fluoride-releasing resin composites.

SUMMARY:
This study compared the shear bond strength of four filled dentin bonding agents (Prime & Bond NT, One Coat Bond, OptiBond Solo, PermaQuik1) to a conventional unfilled Dentin Bonding agent (3M Scotchbond Multipurpose Plus). A column of composite resin (Herculite XRV Restorative Resin) was bonded to human dentin using the five dentin-bonding systems following the manufacturers’ directions. The specimens were thermocycled 1000 cycles from 6 to 60°C. Each specimen was tested on an MTS machine in shear-to-failure. The data were subjected to One-Factor ANOVA and Newman-Kuels post-hoc tests. Statistical analysis revealed that One Coat Bond had significantly greater shear bond strength than all other materials tested.

SUMMARY:
This study compared the shear bond strength of four filled dentin bonding agents (Prime & Bond NT, One Coat Bond, OptiBond Solo, PermaQuik1) to a conventional unfilled Dentin Bonding agent (3M Scotchbond Multipurpose Plus). A column of composite resin (Herculite XRV Restorative Resin) was bonded to human dentin using the five dentin-bonding systems following the manufacturers’ directions. The specimens were thermocycled 1000 cycles from 6 to 60°C. Each specimen was tested on an MTS machine in shear-to-failure. The data were subjected to One-Factor ANOVA and Newman-Kuels post-hoc tests. Statistical analysis revealed that One Coat Bond had significantly greater shear bond strength than all other materials tested.

SUMMARY:
Materials that release fluoride have been recommended for patients with high caries risk, but there is no conclusive evidence of their effect on fixed prostheses abutments. This study evaluated the influence of a resin-modified glass-ionomer cement on in vitro caries development in enamel and root dentin around metallic restoration. The cervical portion of 12 human third molars were sectioned in four blocks that were randomly divided into four Groups (n=12; 1 block from each tooth/group): ZP (restoration + zinc phosphate cement), GI (restoration + resin-modified glass-ionomer cement), C1 (no restoration and no pH cycling), and C2 (no restoration and pH cycling). In ZP and GI, metallic restorations were luted at the crown-root junction. ZP, GI and C2 were submitted to a pH-cycling model. All blocks were sectioned, embedded and polished. Enamel and root dentin demineralization were evaluated through cross-sectional microhardness Knoop measures at 20 to 80 µm of depth (from the outer surface) and at 20 to 220 µm of distance from the cavity margins. Mineral loss values were calculated from Knoop hardness numbers. Data were analyzed by ANOVA, Tukey’s test and regression analysis. Groups ZP, GI and C2 showed demineralization in relation to C1, which was more superficial in enamel than in root dentin. In root dentin, mineral loss in ZP and GI was smaller than in C2. Distance from the cavity margins was not significant. There was no difference between resin-modified glass-ionomer cement and zinc phosphate cement regarding artificial secondary caries development in both dental substrates.

SUMMARY:
This study evaluated the microleakage at the cervical margins of Class II composite resin restorations restored with different techniques. Slot cavities were prepared on both proximals of 40 unerupted third molars with one cervical margin located above and the other below the cementoenamel junction. The prepared teeth were randomly assigned to four groups and restored using the following techniques: (I) 3-Sited, (II) Directed-Shrinkage, (III) Resin-Modified Glass-Ionomer Cement or a (IV) Flowable Composite as the gingival increment. All restorations were placed with the same bonding agent and composite resin. The difference among the groups was on the first increment and on its insertion and polymerization techniques. After restoration, the teeth were thermocycled and exposed to a dye. Results showed that all the techniques worked well for enamel, with almost no leakage. However, on cementum, all techniques demonstrated moderate to severe leakage.

SUMMARY:
This study evaluated the microleakage at the cervical margins of Class II composite resin restorations restored with different techniques. Slot cavities were prepared on both proximals of 40 unerupted third molars with one cervical margin located above and the other below the cementoenamel junction. The prepared teeth were randomly assigned to four groups and restored using the following techniques: (I) 3-Sited, (II) Directed-Shrinkage, (III) Resin-Modified Glass-Ionomer Cement or a (IV) Flowable Composite as the gingival increment. All restorations were placed with the same bonding agent and composite resin. The difference among the groups was on the first increment and on its insertion and polymerization techniques. After restoration, the teeth were thermocycled and exposed to a dye. Results showed that all the techniques worked well for enamel, with almost no leakage. However, on cementum, all techniques demonstrated moderate to severe leakage.

SUMMARY:
The rapid decrease in the size of dental restorations has increased the demand for the smallest rotary cutting instrument possible. The width of cavities prepared with two experimental diamond points and the smallest commercial diamond point were compared and significant differences found. SEM observation of the head surfaces of the three diamond points revealed that the experimental points had comparable cutting characteristics with the commercial diamond point.

SUMMARY:
Resin adhesive was visualized in this in vitro study of amalgam bonding using methylene blue dye incorporated into the resin or by scanning electron microscopy. Class II amalgam cavities were prepared in extracted teeth previously stored in buffered formalin. The preparations were then restored following manufacturers’ instructions, but included methylene blue dissolved in ethanol into the adhesive resin mixture. This procedure had little effect on the setting time of the resin. Following condensation and carving, excess resin was incorporated into the body of the restorations as well as onto all adjacent coronal surfaces with significant occlusal and proximal accumulations. Resin also accumulated in significant amounts on the gingival floor of the proximal box and at line angles and retentive grooves within the preparation. In conclusion, radiological studies demonstrated that arifacts produced by resin accumulation at the gingival floor of the box could be mistaken for an open margin or recurrent caries. Other potential clinical consequences of resin residue on tooth surfaces are discussed, including the problem of interproximal ledges and occlusal discrepancies. The incorporation of a radiopaque material in the resin systems should be a universal requirement.

SUMMARY:
This investigation measured the fracture resistance of a wide range of currently available light-activated-composite restoratives. Products intended solely for anterior use were tested together with universal materials and products intended for posterior application. All materials were handled according to manufacturers’ instructions. For products evaluated in this investigation, universal and posterior materials yielded higher mean torque to fracture (T) values overall in comparison to the anterior products. One Microfilled and two Polyglas filled products designated for posterior application yielded relatively modest mean fracture resistance values.

SUMMARY:
This study evaluated the effect of the thickness of the adhesive resin layer of two commercially available resin bonding systems on bond strengths (Single Bond and Liner Bond 2V). The adhesive of Single Bond contains ethanol and water as solvents and is applied using the moist-bonding technique. The adhesive of Liner Bond 2V contains no solvents and is applied after a self-etching primer treatment. Forty-six caries-free molars were ground flat to expose the dentin surface and polished with #800-grit silicon carbide paper under running water. A vinyl tape punched with a 6 mm diameter hole was then placed on the dentin surface to demarcate the area for bonding. The thickness of the adhesive resin layer was varied by stacking an increasing numbers of vinyl tapes together. The teeth were randomly divided into two groups and treated with either Clearfil Liner Bond 2V or Single Bond. They were further divided into subgroups according to the number of tapes placed on the dentin surface. After the bonding procedures the teeth were incrementally restored with Clearfil AP-X resin composite, building a 5 mm high crown to produce sufficient bulk for the microtensile bond test and stored in tap water at 37°C for 24 hours. The teeth were then sectioned along their long axis into 0.7 mm thick slabs and trimmed for the microtensile bond test using a super-fine diamond bur. The thickness of the adhesive resin layer was then measured with a light microscope and the slabs tested in tension at a crosshead speed of 1 mm/minute. The results were subjected to statistical analysis by a one-way analysis of variance and linear regressions with 95% confidence intervals.

The thickness of the Clearfil Liner Bond 2V adhesive layer ranged from 5 mm–1500 mm, and for Single Bond, it varied from <7.5 mm–430 mm. For Clearfil Liner Bond 2V, bond strengths increased significantly as the thickness of bonding layer increased (p<0.05). However, the bond strengths of the Single Bond decreased significantly with increased thickness of the bonding layer (p<0.05).

SUMMARY:
This study evaluates the one-year clinical performance of a polyacid-modified resin composite material, Dyract (DeTrey Dentsply, Konstanz, Germany), in Class III cavities.

Sixty-two Class III cavities in 30 patients were restored with Dyract. Restorations were evaluated at baseline and one-year recall according to modified Ryge criteria by two experienced, calibrated examiners.

At one-year recall the rate of retention was 98.4%. None of the restorations were clinically unacceptable in regard to color match, wear or loss of anatomical form, marginal discoloration, caries, marginal adaptation and surface texture. After one year, color change and marginal discoloration in restorations were statistically significant (p=0.031) but did not require the replacement of any of the restorations. At baseline, only one patient reported postoperative sensitivity and two months later, endodontic treatment was performed.

Dyract’s clinical performance in Class III cavities at one year recall is promising but further long-term clinical research on color change and marginal discoloration is needed.

SUMMARY:
This study evaluated the microleakage performance of a new generation of composites known as “packable” composites within a high C-factor preparation. Class V cavity preparations with occlusal margins in enamel and gingival margins in dentin were prepared on extracted human molar teeth. Prepared teeth were randomly distributed into four treatment groups (n=18) consisting of three “packable” composites—Alert, Solitaire, and SureFil—and a traditional anterior/ posterior small particle hybrid composite Z-100. Prime & Bond NT bonding agent was used with each composite. Samples were stored in tap water for 24 hours, thermocycled, stained with dye, sectioned into halves and scored for microleakage. All test groups showed a significant increase in both linear and penetrating dentinal microleakage when compared to enamel microleakage. Z-100 had significantly less dentinal marginal microleakage than SureFil. There was no significant difference in the enamel microleakage values between groups. However, the “packable” composites exhibited significantly higher percentages of enamel crazing adjacent to the cavity walls when compared to Z-100. The enamel crazing within the “packable” composite groups warrants further investigation to determine if this is a characteristic related to the composition of this class of composites, the mode of light curing used in this study or the result of the cavity/marginal design.

SUMMARY:
During the last few years a number of one-bottle adhesive systems have been developed. However, no “universal” adhesive system recommended for use with different polyacid-modified resins (PMR) is currently available. This study compared the shear bond strengths of four PMR Dyract AP (D), Compoglass F (C), F 2000 (F) and Hytac (H)) to enamel and dentin using (1) the adhesive system provided by the manufacturer and (2) a new one-step “universal” adhesive system (Prompt L-Pop).

Seventy enamel and 70 dentin-surfaces were prepared for 10 replications of each bonding combination (C1, C2, D1, D2, F1, F2, H1/2). After the bonding procedure and subsequent storage of the specimens in distilled water at 37°C for 24 hours, shear bond strengths were determined using a Universal Testing Machine at a cross-head speed of 0.75 mm min-1 until failure occurred. Fracture modes were examined at 25x magnification under a light microscope.

The median shear bond strength values (MPa) to enamel were 13.2 (C1), 16.5 (C2), 17.7 (D1), 41.2 (D2), 12.7 (F1), 41.2 (F2), 33.9 (H1/2); to dentin, values of 3.3 (C1), 3.7 (C2), 7.4 (D1), 12.2 (D2), 11.4 (F1), 8.6 (F2) and 4.6 (H1/2) were measured. In both enamel and dentin, bond strengths of the tested PMR were either not significantly different or significantly higher using the universal adhesive system compared to the adhesive systems provided by the manufacturers. Bond strengths to enamel and dentin were not significantly different from each other in D and F with their corresponding adhesive system. In all other groups, bond strengths to enamel were significantly higher compared to dentin. Failure modes were mostly adhesive in dentin and mixed adhesive/ cohesive in enamel. SEM observations revealed similar hybrid layer and tag formation in dentin for the four adhesive systems. On enamel, a clearly visible etch pattern was detected only for the universal adhesive system.

In conclusion, the universal adhesive system achieved equal or higher bond strengths of the tested PMR to enamel and dentin compared to the adhesive systems provided by the manufacturers.

SUMMARY:
Occlusal contact area (OCA) wear has been shown to exceed contact-free area wear by three-to-five times in clinical studies. A reciprocal compression sliding wear device was used to investigate the influence of contact stress on OCA wear of four resin composite restoratives (Silux, Z100, Ariston and Surefil). A dental amalgam (Dispersalloy) was used for comparison. The pattern and mechanisms of wear, and the relationship between wear and composite surface hardness were also studied. Thirty wear specimens and six hardness specimens were made for each material. Wear specimens were tested at 20 to 60 MPa contact stresses against SS304 counter-bodies with artificial saliva as lubricant up to 20,000 cycles. Wear depth (µm; n=6) was measured using profilometry. Hardness testing (KHN) was done with a digital microhardness tester (load=500 gf, dwell time=15 seconds). Results were analyzed using ANOVA/Scheffe’s test (p<0.05). At all contact stresses Dispersalloy had significantly better OCA wear resistance than the composites. The wear of Z100 was significantly greater than Silux, Ariston and Surefil. The influence of stress on wear and counter-body loss was material dependent. Correlation between contact stress and wear was significant for all materials with correlation coefficient (r) ranging from 0.96 for Z100 to 0.88 for Ariston. The wear mechanisms for the different composites varied depending on their microstructure and the contact stress. There was no significant correlation between material hardness and wear/counter-body loss.

SUMMARY:
This investigation studied the three-body abrasive wear resistance and wear patterns of five composite restoratives. The possible relation between three-body wear and surface hardness was also investigated. A three-body wear instrumentation was used to investigate the wear resistance of five composite restoratives [Silux Plus (SX), Z100 (ZO), Ariston pHc (AR), Surefil (SF) and Tetric Ceram (TC)]. An amalgam alloy [Dispersalloy (DA)] was used as control. The amalgam alloy (DA) had the lowest three-body wear (0.3±0.27 µm) and the highest surface hardness (KHN 131.5±27.87). TC had the most wear (2.14±0.58 µm) and SX was the softest restorative (KHN 34.04±2.73). Ranking was as follows: Wear resistance—DA>ZO>SF>AR>SX>TC; Hardness—DA>SF>ZO>TC>AR>SX. With the exception of ZO, DA was significantly more wear resistant than all the composites evaluated. ZO was significantly more wear resistant than SX and TC. DA was significantly harder than all the composites evaluated. SF was significantly harder than AR and SX. For the composite restoratives, correlation between hardness and wear was significant, with a correlation coefficient of r=-0.45. A significant negative but weak correlation exists between hardness and three-body wear of composite restoratives.

SUMMARY:
Newer composite restoratives used in the posterior dentition are marketed as high viscosity, condensable or packable materials. The in-vitro wear characteristics of three newer generation materials were compared to three conventional hybrid composites. Specimens were subjected to wear in a Leinfelder wear simulator equipped with a conical stylus tip to simulate localized wear. Using surface profilometry, computer generated surface maps were analyzed to determine both volumetric loss and maximum depth of wear facets for the materials tested. Volume loss (mm3) was as follows: Z100 – 0.010 ± 0.003; SureFil – 0.014 ± 0.004; Alert 0.016 ± 0.005; Spectrum TPH – 0.042 ± 0.003; Prodigy – 0.055 ± 0.005; Solitaire – 0.062 ± 0.008. Maximum depth of the wear facets (mm) was as follows: Z100 – 69.2 ± 8.8; Alert 80.9 ± 15.4; SureFil – 82.6 ± 11.4; Spectrum TPH – 125.2 ± 15.4; Solitaire – 159.2 ± 14.9; Prodigy – 162.9 ± 22.2. The results of this study indicate that there are significant differences in the wear rates of composite materials. However, there was no clear trend that the newer high viscosity composites exhibited superior wear characteristics when compared to conventional composites.

SUMMARY:
This in vitro study 1) investigated the composite-to-dentin bond strength, 2) analyzed the micromorphology of the resin-dentin interface and 3) evaluated the marginal adaptation of resin composite restorations in Class II cavities using three self-etching priming agents. In the first part of the study 30 extracted human third molars were embedded in acrylic resin and ground flat with 800-grit paper. The following three self-etching priming agents/composite resins were applied to the dentinal surfaces of 10 teeth each: Clearfil Liner Bond 2/Clearfil AP-X (Group I), Etch & Prime 3.0/Degufill mineral (Group II), Resulcin AquaPrime + Mono Bond/Arabesk (Group III). Shear bond strength values measured on a T 22 K testing machine (Lloyds Instr) at a crosshead speed of 1 mm/min were: 21.7 ± 2.6 MPa (Group I), 22.4 ± 1.4 MPa (II) and 29.5 ± 2.5 MPa (III). ANOVA revealed significant (p<0.001) differences in shear bond strength between groups, except comparison of Group I and II. In the second part of the study specimens were prepared by application of the above mentioned bonding materials to wet-ground dentinal surfaces of 24 freshly extracted caries-free human premolars. Morphology of the resin- dentin interface was studied by scanning and transmission electron microscopic analyses. Tag formation could be detected with all bonding agents. Thickness of the demineralized zone/resin infiltrated layer at the dentinal surface varied from 0.8 to 2.3 µm (Group I), 2.5 to 4.0 µm (Group II), 3.5 to 6.5 µm (Group III). In the third part of the study 18 standardized Class II cavities with the proximal box extending 0.5 mm beyond the CEJ were prepared in extracted human molars. Enamel margins were beveled, dentinal cavosurface margins were prepared as butt joint and the teeth were divided into three groups (n=6, each). Cavities were restored with composite resin using the self-etching priming agents Clearfil Liner Bond 2 (Group I), Etch & Prime 3.0 (Group II) and Resulcin AquaPrime + MonoBond (Group III). Marginal adaptation of the restorations was analyzed by SEM after thermocycling (5-55°C, 2,500 cycles) and mechanical loading (100 N, 500,000 cycles). Mean/median percentages of excellent, gap-free marginal adaptation observed at the restorations proximal dentinal margins after loading were 97.5%/99% in Group I, 90.7%/98.5% in Group II and 76.3%/98% in Group III. There were no statistically significant differences between the three groups (p<0.01). It was concluded that the three self-etching priming agents evaluated in this in vitro study have the potential to provide an effective bonding between composite and dentin.

SUMMARY:
This study compared the color stability of a conventional glass ionomer (Ketac-Fil), a light polymerized resin-modified glass ionomer (Photac-Fil), a polyacid-modified resin composite or compomer (Dyract) and a microfilled resin composite (Silux Plus). Thirty-two specimens (n=8/material) were fabricated and stored in artificial saliva at 37°C for seven weeks. A colorimetric evaluation, according to the CIE L*a*b* system, was performed at 24 hours (baseline) and at the end of each week. Color difference values (DE*ab) were calculated. The conventional glass ionomer, resin-modified ionomer and compomer materials underwent significant color changes over time (p<0.01). Those materials darkened and showed color shifts in both the red-green and yellow-blue axes.

SUMMARY:
This study evaluated the marginal sealing ability of five “One Bottle” fifth generation dentin adhesive resins. Bond 1, Single Bond, Tenure Quick with fluoride, One-Step and Prime & Bond 2.1 were evaluated. Tenure All-Surface Bonding System, a fourth generation dentin adhesive resin, was used as the control group.

A Class V preparation (3 mm diameter, 1.5 mm deep) was placed at the cemento-enamel junction of 60 extracted human premolar teeth. A 1 mm 45° bevel was placed at the enamel margin. Each group of cavities were restored using one of the dentin adhesives and the same restorative resin. Following five days storage in 37°C water, the restored teeth were thermocycled for 500 cycles between 5°C and 55°C for one minute in each cycle. Microleakage was assessed by dye penetration using 0.2% Basic Fuchsin dye. After 24 hours the teeth were sectioned longitudinally and evaluated for microleakage. The results were analyzed using the non-parametric Kruskal-Wallis Test.

Microleakage at the enamel margins was not evident in any group. However, leakage was present at the gingival margin (cementum) in all of the treated groups. There were no significant differences between gingival margins (0.75>p>0.5). When comparing the gingival margin microleakage scores between two groups or within the same group, statistical analysis showed no significant difference. The new “One Bottle” dentin adhesives have similar marginal sealing ability to that of the control group.

SUMMARY:
This in vitro study determines the minimum irradiance values required for adequate polymerization of a microfill and a hybrid resin composite when cured for 40 and 60 seconds.

A curing light (Optilux 401) with an 8-mm-diameter tip (SaniCure) was used as the light source. The irradiance output of the light unit, measured with a laser power meter, was varied by altering the input voltage using a variable power supply. Two-mm-thick hardness test specimens were made with a microfill composite (Silux Plus) and a hybrid composite (Z-100) for each combination of exposure time (40, 60 seconds) and irradiance value (100 mW/cm2 to 700 mW/cm2 in 25-mW/cm2 increments). After 24 hours, Knoop hardness (KH) measurements were made for each side of each specimen, means were calculated and a top/bottom KH percentage was determined. A value of at least 80% was used to indicate satisfactory polymerization. A linear regression of irradiance versus KH percentage was performed and the resulting equation used to predict the irradiance value required to produce a KH value of 80% for the test conditions.

Results showed that the hybrid composite, Z-100, required 260.1 mW/cm2 @ 40 seconds or 185.0 mW/cm2@ 60 seconds for satisfactory polymerization. The microfill, Silux Plus, required 542.9 mW/cm2 @ 40 seconds or 449.0 mW/cm2 @ 60 seconds. These findings indicate that previously stated minimum irradiance values may be insufficient for adequate polymerization of microfill resin composites.

SUMMARY:
In vitro measurements were made to reveal the heat transference to the pulp chamber during light curing. Ten extracted human teeth were kept in physiologic saline at body temperature. In the first part of the study, five light curing exposures of 40 seconds were given to the occlusal surface of each tooth with a light curing unit.The temperature of the pulp was measured by a thermocouple probe that was inserted into the pulp through the apex. The maximal temperature rise was 2.2°C. Thereafter, standard occlusal cavities were prepared in all 10 teeth and filled with composite resin filling material in three parts. The dental adhesive was light cured for 20 seconds and each composite increment for 40 seconds. An extra cycle of 40 seconds was given when the cavity was filled as a post cure. The maximal temperature difference during the total procedure was 7.2°C. The heating effect of light curing should thus be taken into account when restorations are cured.

SUMMARY:
After polishing or glazing, slight color changes of machined porcelain restorations may be perceived, compared to the originally selected shade. This study compared the precision of the tristimulus colorimeter with the spectrophotometer to quantitatively measure the color changes of milled porcelain restorations after polishing or glazing and to evaluate the relationship between the color changes and the surface roughness. Ten two-millimeter thickness specimens of each shade were prepared from five shades of Vita Cerec Mark II porcelain blocks. Each specimen was ground with #220 grit SiC paper on an automatic polishing machine to simulate the surface roughness of milled restoration ground with 54 or 64 µm diamond grinding tools. To compare the precision of the spectrophotometer with the tristimulus colorimeter, CIE Lab* values of each specimen were measured and the coefficients of variation (CV) for each instrument computed. Ra values were also obtained using a Surface Analyzer. After verifying the precision of the tristimulus colorimeter, a second set of measurements were taken after the polishing or glazing procedure to quantitatively evaluate the effect of these procedures on the shade of the milled restorations. To evaluate the relationship between the color change and the surface roughness, a second set of Ra measurements were taken and the correlation between them analyzed. The tristimulus colorimeter measured the L* value more precisely than the spectrophotometer (p<0.05), but on the a* and b* color coordinates, it was not significantly superior to the spectrophotometer (p>0.05). The color difference values produced by polishing or glazing were greater than 2 DE units. After polishing and glazing, among the three coordinates examined, DL* was the most prominent determinant on DE*(DR2/polishing=0.9744 and DR2/glazing=0.9413), but Da* and Db* had little effect. There was no statistically significant correlation between the changes in surface roughness and color in either polishing (r=0.3555, p=0.0812) or glazing (r=-0.1570, p=0.4520).

SUMMARY:
This study determined the influence of a flowable composite lining on marginal microleakage and internal voids in a Class II composite restoration. Forty-eight extracted molars were prepared with Class II cavities and randomly divided into four groups: Group I–Prodigy filling/ Revolution lining; Group II–Prodigy filling only; Group III–Tetric Ceram/Tetric Flow lining; Group IV–Tetric Ceram filling only. After thermocycling tests and dye soaking, these teeth were sectioned longitudinally. Gingival-marginal microleakage and internal voids in three separate portions of the restoration (Interface, Cervical and Occlusal voids) were observed with a stereomicroscope. Results revealed no significant difference in the marginal sealing between pairs with or without the flowable composite lining. Restorations conducted with a flowable composite lining (Groups I and III) exhibited fewer total voids and fewer voids in the interface (p<0.05). However, there was no significant correlation between the number of restoration voids and the associated microleakage. A flowable composite lining in a Class II resin filling could effectively reduce the voids in the interface and the total number of voids in the restoration, but may not necessarily improve marginal sealing.

SUMMARY:
Pulp tissue reactions to four commonly used dental cements were histo-pathologically evaluated by placing the cements on exposed monkey dental pulp followed by a surface-sealed adhesive restoration. Evaluations were done at 3 or 5, and 30 and 90 days after operation. No serious inflammatory reaction of the pulp, such as necrosis or abscess formation, was observed. However, the conventional dental cements showed irritating effects on the exposed monkey dental pulp without bacterial contamination. Reactions of exposed dental pulp beneath the dental cements differed depending on the materials used.

SUMMARY:
Pre-impregnated fiber reinforced composites (FRC) can be used chairside for splinting and immediate tooth replacement. These materials may provide a more predictable long-term result than previous adhesive techniques employing composite reinforcement because of their improved mechanical properties. This article describes a technique using pre-impregnated FRC for the immediate replacement of an extracted tooth using the crown of the extracted tooth as the pontic.

SUMMARY:
This study evaluated, in vivo, the pH stabilizing properties of a posterior resin composite (Ariston pHc, Vivadent Ets, Schaan/ Liechtenstein). Fifteen human subjects with four or more active carious lesions were selected. Their salivary pH, in relation to the occlusal surface of these lesions, was recorded. The teeth were restored with resin composite, and the pH in relation to the restorations was recorded one day, one week, one month and two months post-operative. Results showed that the resin composite countered the acidic pH of saliva and maintained it at levels where demineralization would not occur.

SUMMARY:
This study compared the diagnostic accuracy of bitewing images for detection of simulated recurrent caries using the following imaging modalities: Ektaspeed Plus film and different digital imaging system technologies comprised of a charge-coupled device (CCD) based digital imaging unit, a photo-stimulable phosphor (PSP) based unit and contrast-and brightness-enhanced PSP images.

Study Design: Twenty-four extracted posterior teeth with MOD inlay preparations were secured in models simulating a natural arrangement of teeth. Lesions were created in proximal boxes using dental burs of varying sizes. Defects were filled with wax and plaster and preparations were restored with composite or amalgam.

Results: Averages of receiver operating curve areas (Az) revealed diagnostic performances of Az=0.74 for film, Az=0.80 for CCD, Az=0.73 for unenhanced PSP and Az=0.64 for enhanced PSP. The differences between these means were significant (MANOVA p<0.0001). Unenhanced PSP produced significantly poorer performance than other modalities. CCD performance was not significantly better than enhanced PSP. Lesions under radiopaque composite restorations were easier to detect, followed by those under amalgam and radiolucent composites across imaging modalities and lesion locations. Based on lesion location, those located at the buccal point angle were easiest to detect, followed by those at mid-gingival floor and lingual-point angle sites.

Conclusions: Contrast and brightness-enhanced digital images enabled better signal detection and a comparable performance with film for detection of artificially induced recurrent caries.

SUMMARY:
This study assessed the effect of an acidulated phosphate fluoride (APF) gel on the surfaces of eight modern esthetic restorative materials. Five specimens each of three high powder: liquid ratio conventional glass ionomer cements (ChemFlex, Fuji IX GP, Ionofil Molar), four polyacid-modified resin composites (compomers) (Compoglass F, Dyract AP, Freedom, F2000) and an alkaline glass filled resin composite (Ariston pHc) were prepared and immersed at 37°C in 2 mL of artificial saliva for six weeks. The aged specimens were then coated with 1.23% APF gel for four minutes, rinsed and again immersed in artificial saliva for another six weeks. The immersed, fresh specimens for each material were then examined with SEM and surface profilometry. After APF gel application, mean surface roughness (Ra) measurements and SEMs showed that roughness increased significantly, generally from the resin composite and compomers to the conventional glass ionomer cements (p<0.05).

SUMMARY:
Applying a bonding agent and a resinous adhesive layer before amalgam condensation has become a common clinical procedure. However, interactions between the different interfaces formed, and the extent of sealing obtained, have not been extensively studied. This study characterized the interfaces formed in the bonded amalgam restoration. Specifically, the individual contributions of the bonding agent (One-Step) and the adhesive resin (Resinomer) were examined, along with their mode of application on the prevention of microleakage and the formation of a tight, continuous adhesion to amalgam. To this end, a dye penetration assay and scanning electron microscopy (SEM) were used, including high resolution elemental analysis, for the characterization of the sealing properties and the interface structure obtained following various procedures of applying amalgam adhesives. Results indicated that placing bonding material under the amalgam restoration is essential to preventing microleakage. When condensed against uncured or cured adhesive material, the adhesive resinous glass layer creates a thick interface with protrusions and inclusions in the amalgam, though microleakage studies indicate that condensation over the uncured adhesive results in a better seal than that of the cured adhesive. SEM combined with elemental analysis indicates that the adhesion between amalgam and adhesive material is mainly of mechanical character and is formed by interdigitations of the adhesive material protruding into the amalgam. Gaps formed at the various interfaces in the different modalities could be localized. In addition, resinous glass composite alone, without bonding, was found to provide an unacceptable degree of sealing between the tooth and amalgam. The clinical significance of these findings is further discussed.

SUMMARY:
Conditioning agents used on dentin with composite materials are biologically active and may have deleterious effects on the pulpal microcirculation. No data are available on the immediate vascular effect of etching materials applied on a constant thin pulpal dentin. In this study the authors examined whether the application of 36% phosphoric acid (Conditioner 36, 15 seconds) or itakonic acid with 10% maleic acid (NRC Non-Rinse Conditioner, 20 seconds), as recommended by the manufacturers, alters the blood circulation in the pulp of the rat’s lower incisors. The effect of prolonged etching time (60 seconds) was also assessed (Conditioner 36). The application of saline served as the untreated control. The technique of vitalmicroscopy was used on the first lower incisor of 40 (10-10 in each group) male Sprague-Dawley rats (weighing 350 ± 8g SE) to record the changes in vessel diameter prior to and at 5, 15, 30 and 60 minutes after the test materials were administered on the dentin. In the control rats, the vessel diameter was stable during the entire experiment. Acid conditioning as recommended by the manufacturers tended to cause vasodilatation, though these alterations were statistically not significant when compared to the control group (ANOVA, p>0.05). After prolonged etching time (Conditioner 36, 60 seconds) significant vasoconstriction (-14.4 ± 6.13; -10.59 ± 4.2; -11.96 ± 6.75; -5.49 ± 5.78%) was observed (ANOVA, p<0.05). In this group, stasis developed in pulpal blood circulation in 40% of rats (Cochran’s-Q test, p<0.05), gas-bubble formation was observed in 30% and the disappearance of the pulpal wall occurred in 20%. These results suggest that exposition time with acid is crucial to the pulpal microcirculation. That is, acid conditioning applied as indicated (for 15-20 seconds) onto a very thin layer of dentin only slightly affects the blood supply to the dental pulp; however, prolonged etching time (for 60 seconds) results in immediate failure of microcirculation in the dental pulp of rats.

SUMMARY:
This study compared marginal leakage of Class II cavities with gingival margin in cementum using different techniques. Twenty-four recently extracted third molars were used. Proximal standard box cavities were prepared in both mesial and distal surfaces. The gingival margin was located apical to the cemento-enamel junction. All the preparations and restorations were performed by the same operator. Standard cavities were randomly divided into three groups (n=16) and restored as follows: Group 1–light-cured composite resin; Group 2–self-cured composite resin + light-cured composite resin and Group 3–amalgam + light-cured composite resin. After polishing, the teeth were thermocycled and their gingival margins exposed to dye. Specimens were sectioned and leakage scores observed in accordance with a standard ranking. Data were subjected to statistical analysis (Kruskal-Wallis). Results showed that the amalgam/resin composite combination demonstrated the least leakage.

SUMMARY:
This study investigated the influence of soft-start polymerization on the effectiveness of cure and post-gel shrinkage of a visible light cured resin composite (Z100). Three cure modes (LH–high intensity; LA–soft-start polymerization involving step-wise modulation of light intensity and LL–low intensity) of a commercial light-cure unit (Kavo PolyLUX II) were examined and compared to another light-cure unit (Spectrum). The effectiveness of cure with the different cure modes was assessed by computing the hardness gradient between top and bottom surfaces of 2 mm composites specimens after different light exposure times. A strain-monitoring device was used to measure the linear polymerization shrinkage associated with the different cure modes and exposure times over 180 minutes. A sample size of five was used for both experiments. Data was analyzed using one-way ANOVA and Scheffe’s post-hoc test at significance level 0.05. Results showed that effectiveness of cure generally increased with increase cure time. Although modulation of light energy intensity (LA 40/80 seconds) resulted in lower polymerization shrinkage compared to LH 40 seconds, no significant difference was observed between these three cure regimes. Curing with the Spectrum curing light resulted in the lowest polymerization shrinkage.

SUMMARY:
Controversy exists over the most favorable material and type of restoration to be used to transitionally restore teeth destined to be crowned. This in vitro study uses fracture resistance testing to compare eight different transitional restorations in maxillary premolars. Ninety sound maxillary premolars were randomly selected and allocated to nine groups, each comprising 10 teeth. One group remained unrestored and was used as the control. Teeth in the remaining groups were prepared to a standard cavity form using: a copy milling process removing the palatal cusp. Restorations were placed using amalgam with dentin pins and cavity varnish; amalgam with an amalgam bonding agent; resin composite with dentin pins and a dentin bonding agent; resin composite with a dentin bonding agent only; resin-modified glass ionomer with dentin pins; resin-modified glass ionomer cement alone and cermet with dentin pins and cermet alone. Each restored tooth was then subjected to axial loading via a bar contacting the buccal and restored palatal cusps until failure of the restored tooth occurred. The mean load-to-fracture values were statistically compared and the modes of failure recorded. It was found that the choice of restorative material and type of restoration had little effect on the fracture resistance of the restored tooth with the exception of those teeth restored with reinforced glass ionomer cement alone, which exhibited a significantly lower resistance to fracture than the other restored teeth. However, the choice of restorative material/technique did influence the mode of failure. Failure in teeth restored with resin-modified glass ionomer cement alone produced the least damage to the remaining tooth tissue when failure occurred. Consequently, this material may offer the most favorable range of properties for the transitional restoration of extensively broken-down maxillary premolar teeth destined to be crowned. Furthermore, the findings of this study fail to support the use of dentin pins in the placement of bonded build-up restorations.

SUMMARY:
This study investigated the microleakage associated with the repair of non-carious amalgam defects using flowable resin composite. Occlusal amalgam preparations were accomplished on 36 non-carious mandibular molars. A standardized 40-micron marginal defect was made by condensing amalgam against a mylar matrix strip. Specimens then underwent a corrosion protocol designed to simulate intraoral corrosion seen with amalgam restorations. The resultant specimens were divided into three treatment groups: 1) No treatment (control); 2) Air abrasion of the amalgam defect surface, acid etching of both amalgam and enamel surfaces, then placement of a flowable composite and 3) Air abrasion of the amalgam defect, application of a fifth-generation dentin bonding agent and placement of the flowable composite. Specimens were thermocycled, sealed with glass ionomer and fingernail polish to within 1 mm of repaired margins, then immersed in basic fuchsin for 24 hours. Specimens were sectioned and microleakage assessed. Results indicated that a flowable resin composite significantly reduced marginal microleakage compared to the control (p<0.05). There was no difference in microleakage between flowable resin composite repairs done with or without the use of a dentin-bonding agent.

SUMMARY:
This study’s objectives were: 1) to determine the combination of bonding procedures (with or without acid etching, moist or dry substrate, one or two applications of primer/adhesive) that would produce the highest shear bond strength of Prime & Bond and Dyract AP and 2) to characterize the resin-dentin/enamel interface produced by these bonding procedures. Ninety-six bovine incisors were randomly assigned to eight groups for shear bond testing to enamel (n=6) and dentin (n=6). Prime & Bond and Dyract AP were applied and cured following manufacturers’ instructions. Shear bond testing was conducted in a Universal Testing Machine. Thirty-two bovine incisors were sectioned to produce blocks with enamel and dentin, then bonded in pairs for evaluation of interfacial morphology. They were polished and argon ion-etched using a high-speed argon ion-etching machine and examined by SEM. The groups where enamel was etched, kept moist or dry and received a single application of Prime & Bond produced the highest shear bond strength. Dentin bond strengths were high in the groups where dentin was etched and kept moist. The number of Prime & Bond applications had no effect on dentin bond strength. Acid etching results in better adaptation of Prime & Bond to enamel and dentin regardless of whether moisture is present.

SUMMARY:
Fracture of anterior teeth by trauma is a common problem in children and teenagers. Complex metal-ceramic crowns with considerable loss of remaining sound structure are no longer necessary due to adhesive techniques, such as composite restorations and re-attachment techniques. This study compared the fracture strength of sound and restored anterior teeth using a resin composite and four re-attachment techniques. A “one bottle” adhesive system (One-Step, BISCO) and a dual cure resin cement (Duo-Link, BISCO) were applied. Thirty-five sound permanent lower central incisors were fractured by an axial load applied to the buccal area and randomly divided into five groups. The teeth were restored as follows: 1) bonded only = just bonding the fragment; 2) chamfer-group = after bonding, a chamfer was prepared on the enamel at the bonding line and filled with composite; 3) overcontour group = after bonding, a thin composite overcontour was applied on the buccal surface around the fracture line; 4) internal dentinal groove = before bonding, an internal groove was made and filled with a resin composite; 5) resin composite group = after a bevel preparation on the enamel edge, the adhesive system was applied and the fractured part of the teeth rebuilt by resin composite. Restored teeth were subjected to the same loading in the same buccal area. Fracture strength after restorative procedure was expressed as a percentage of the original fracture strength and the results analyzed by Kruskal-Wallis statistical analysis. The mean percentages of fracture strength were: Group 1: 37.09%, Group 2: 60.62%, Group 3: 97.2%, Group 4: 90.54% and Group 5: 95.8%. It was concluded that the re-attachment techniques used in Groups 3 and 4, as well as the composite restored group (Group 5), were statistically similar and reached the highest fracture resistance, similar to the fracture resistance of sound teeth.

SUMMARY:
This study investigates the mechanical properties (hardness, flexural strength and compressive strength) of a new light-cured resin-modified glass ionomer cement (Fuji II LC Improved). Effects of the increased powder:liquid ratio on mechanical properties and the correlation between different mechanical properties were also studied. Mechanical properties of the cement at manufacturer’s recommended powder: liquid ratio (F), 2% (F2) and 4% (F4) increased powder weight were measured after one day, one week and one month storage in distilled water at 37°C. Hardness testing (KHN; n=5) was done with a digital microhardness tester (load=500g, dwell time=15 seconds). Flexural and compressive strength testing (MPa; n=5) were conducted based on ISO 4049 and BS6039, respectively. Results were analyzed using ANOVA/Scheffe’s test (p<0.05) and Pearson’s correlation (p<0.01). The maximum mechanical properties of Fuji II LC Improved were achieved at one week. The hardness, flexural and compressive strength at one week was significantly higher than at one day. A decrease in all mechanical properties was observed at one month. Mechanical properties were significantly affected by increased powder: liquid ratio. After one month storage, significance was as follows: Hardness–F, F2>F4; Flexural strength–F4>F, F2 and F>F2; Compressive strength–F, F2>F4 and F2>F. A significant very strong and negative correlation was observed between flexural and compressive strengths (r=-0.97).

SUMMARY:
The use of flowable composites as liners in Class II packable composites has been suggested by some manufacturers. However, the contributions of this technique are unproven. This study evaluated marginal microleakage in Class II packable composite restorations with and without the use of a flowable composite liner. A conventional microhybrid composite was used as a control. Microleakage at occlusal and gingival margins of Class II cavities was evaluated using 45Ca and autoradiographs.

Fifty non-carious, restoration-free human molar teeth were used. Separate mesio-occlusal and disto-occlusal Class II cavity preparations were made in each tooth. Gingival margins of all cavities were placed 1 mm apical to the cementoenamel junction (CEJ). Four Packable composites (Alert, Surefil, Pyramid and Solitaire) and one conventional microhybrid composite (Renew) with their respective manufacturer’s bonding agents were used to restore the cavities. One side of each tooth was restored with composite alone, while the other side was restored with the composite lined with that manufacturer’s flowable liner. The restored teeth were thermally stressed and 45Ca was used to evaluate microleakage. Two independent evaluators scored leakage based on the autoradiographs.

The results showed flowable composites helped reduce microleakage at gingival margins of Class II restorations (p<0.05). Gingival margins had higher microleakage than occlusal margins (p<0.05). Without flowable liners, three packable composites (Alert, Pyramid and Surefil) showed higher leakage (p<0.05) than the microhybrid control. Only Solitaire packable composite without liner showed no significant difference in microleakage to the control (p>0.05). Although the flowable liners help reduce microleakage, Alert and Pyramid packable composites with liners still showed higher leakage than the control (p<0.05). Surefil and Solitaire packable composites with flowable liners showed no significant difference in microleakage (p>0.05) to the control.

SUMMARY:
This study assessed cavity preparations produced with different air abrasion tip parameters. Twelve test groups of extracted teeth were prepared to evaluate the parameters of 80° or 45° nozzle angles and 0.38 or 0.48 mm inner tip diameters. All other factors were held constant. A device was made to hold the specimen and air abrasion handpiece that standardized the distance and position relative to the tooth and time of application. The cavities were evaluated by assessing the rounding of the cavosurface margins and cavity floor. Measurements of cavosurface angles and the angle of concavity were made at the deepest portion of the abraded surface using scanning electron micrographs. The cavosurface angles were compared using paired t-test, and the effects of the tip design parameters were analyzed by ANOVA and Duncan’s Multiple Range test. From the cavity patterns found in this study, the authors suggest that 80° angle tips are more appropriate than 45° angle tips for making narrow, deep cuts for preventive resin restorations. Conversely, when shallow preparations are needed, as in the case of Class V cavity preparations, cutting patterns of 45° angle tips are more suitable.

SUMMARY:
The development of one-bottle dentin adhesive systems resulted in much optimism about providing simplified predictable esthetic dentistry. However, laboratory testing of these systems continues to provide significant variations between facilities. A potential effect of the number of applications was noted in this author’s laboratory. This study evaluated the effect of doubling the manufacturer’s recommended number of applications on shear bond strength to dentin.

Ninety human molars were divided into groups of 15. The occlusal surfaces were finished to 600 grit SiC to provide a flat dentin bonding surface. Prime & Bond NT—Dyract, Optibond Solo—Elan and One Step—Dyract were evaluated. Each material was tested using: (1) the recommended number of adhesive applications and (2) twice the number of applications recommended. All adhesive applications were accomplished before light curing the adhesive. The specimens were thermocycled after one week of storage and tested in shear after two weeks.

Specimens were also fabricated after adding Rhodamine D to the adhesive to allow for visualization using confocal microscopy. These teeth were sectioned and viewed 24 hours after fabrication.

A t-test was used to compare differences within product groups. The results showed a significant effect (p<0.001) when a double application of Prime & Bond NT was used. No difference was seen with Optibond Solo or One Step. All specimens appeared to have a uniform, glossy appearance of adhesive during fabrication. Therefore, the appearance of the adhesive after application may not be a reliable predictor of acceptable bonding. Confocal microscopy showed that single application Prime & Bond NT specimens did not exhibit a uniform thickness of adhesive across the entire interface. Tubule penetration and hybridization was apparent for all specimens.

SUMMARY:
Dental adhesive techniques have led to a significant simplification of the immediate and definitive treatment of traumatic dental injuries. Composite restoration of fractured teeth, bonding of tooth fragments, the use of laminate veneers or porcelain onlays and resin retained bridges are some of the ways adhesive techniques are used to treat fractured teeth. Furthermore, splinting of luxated teeth almost entirely relies on the combination of adhesion and a flexible resin which simulates the mobility of a normal periodontal ligament during the healing period. The internal strengthening of immature root-filled teeth with composite using an adhesive technique may possibly prevent late root fractures caused by weakening of the tooth structure resulting from endodontic procedures. Finally, the adhesive principle using a retro-seal with composite after apicoectomy significantly increases the healing rate and healing mode.

SUMMARY:
The effects of inflammatory activity following surgical intervention can injure pulp tissues; in severe cases it can lead to pulpal complications. With this article, the authors report on the effects of cavity preparation and restoration events and how they can interact together to reduce or increase the severity of pulpal inflammatory activity in 202 restored Class V cavities. Although some inflammatory activity was observed in the absence of bacteria, the severity of pulpal inflammatory activity was increased when cavity restorations became infected. Zinc oxide eugenol and resin-modified glass ionomer cement prevented bacterial microleakage in cavity restorations, with no severe inflammatory activity observed with these materials. Bacteria were observed in cavities restored with enamel bonding resin and adhesive bonded composites and were associated with severe grades of inflammatory activity. The cavity remaining dentin thickness influenced the grade of inflammatory activity. In the absence of infection, the grade of inflammatory activity decreased after 20 weeks post-operatively. In the presence of infection, the grade of pulpal inflammation remained stable until a minimum of 30 weeks had elapsed.

SUMMARY:
This study investigated the wear resistance of three restorative reinforced glass ionomer cements (Fuji IX GP FAST [FJ], Miracle Mix [MM] and Ketac Silver [KS]). Microfilled (Silux [SX]) and mini-filled (Z100 [ZO]) composites were used for comparison. Six specimens were made for each material. The specimens were conditioned for one week in distilled water at 37ºC and subjected to wear testing at 20 MPa contact stress against SS304 counterbodies using a reciprocal compression-sliding wear instrumentation. Distilled water was used as lubricant. Wear depth (µm) was measured using profilometry every 2,000 cycles up to 10,000 cycles. Results were analyzed using ANOVA/Scheffe’s test (p<0.05). After 10,000 cycles of wear testing, ranking was as follows: KS>ZO>MM>FJ>SX. Wear ranged from 26.1 µm for SX to 71.5 µm for KS. The wear resistance of KS was significantly lower than FJ, MM and SX at all wear intervals. Although KS had significantly more wear than ZO at 2,000 to 6,000 cycles, no significant difference in wear was observed between these two materials at 8,000 and 10,000 cycles. Sintering of silver particles to glass ionomer cement (KS) did not appear to improve wear resistance. The simple addition of amalgam alloy to glass ionomer may improve wear resistance but results in poor aesthetics (silver-black color). FJ, which relies on improved chemistry instead of metal fillers, showed comparable wear resistance to the composites evaluated and is tooth-colored. It may serve as a potential substitute for composites in low-stress situations where fluoride release is desirable and aesthetic requirements are not high.

SUMMARY:
This study investigated the effects of thermal cycling on wear of four commercial composite resins (Silux, Z100, Ariston and Surefil). Specimens of each material were divided into three treatment groups comprising a control and two different thermal cycling regimes. Control specimens were stored in distilled water at 35ºC for 178 hours. Thermal cycled specimens were stored in distilled water at 35ºC for 173 hours and subjected to five hours (300 cycles) of a thermal cycling regime consisting of the cycle ABAC, where A and B represent the fixed temperatures of 35ºC (28 seconds) and 15ºC (two seconds) and C, depending on the treatment group, was either 45ºC or 60ºC (two seconds). All specimens were subsequently subjected to wear testing at 20 MPa contact stress against SS304 counterbodies with distilled water as the lubricant. Wear depth (µm; n=6) was measured using profilometry every 2,000 cycles up to 10,000 cycles. Results were analyzed using ANOVA/Scheffe’s test (p<0.05). The effect of thermal cycling on wear was material-dependent. The wear of Silux and Z100 were not significantly affected by thermal cycling. Thermal cycling of Ariston at an upper temperature of 60ºC significantly decreased wear resistance. Thermal cycling affected only the early wear resistance of Surefil.

SUMMARY:
This in vitro study compared the proximal marginal adaptation of direct composite restorations with composite and ceramic inlays inserted with different resin cements. Standardized MOD Class II inlay cavities with one proximal box extending below and the other above the CEJ were cut in 48 extracted human molars and randomly assigned to six groups (n=8). Incrementally layered direct composite restorations (P60), composite inlays (P60) and ceramic inlays (Empress; Cerec Vitablocs Mark II) were placed in the cavities. Three different resin cements (RelyX ARC; Variolink II high viscosity; Panavia 21) were used for luting the composite inlays. All ceramic inlays were cemented with RelyX ARC. After finishing and polishing, the teeth were stored for 24 hours in Ringer solution at 37°C before they were subjected to thermal and mechanical loading (5/55°C, 2000x; 50 N vertical load, 50000x). Margins were evaluated on epoxy replicas using a scanning electron microscope at X200 magnification. Statistical analysis was performed with non-parametric test methods (a=0.05). The adhesive interfaces to enamel exhibited high percentages of perfect margins for all groups (91.8% to 96%) and a maximum of 5.2% marginal gap formation. Dentin-limited cavity segments demonstrated more marginal openings and less perfect margins than enamel- bound areas; however, this was only statistically significant for direct composite restorations and composite inlays inserted with Variolink II and Panavia 21. RelyX ARC showed a significantly better adaptation to P60 inlays compared with the leucite-reinforced Empress ceramic but not the Vitablocs Mark II ceramic.

SUMMARY:
Clinical long-term success of all-ceramic dental restorations can be significantly influenced by marginal discrepancies. As a result, this in vitro study evaluated the marginal fit of alumina- and zirconia-based fixed partial dentures (FPDs) machined by the Precident DCS system. Different master steel models of three-, four- and five-unit posterior FPDs with an 0.8 mm chamfer preparation were produced. FPDs made of DC-Zirkon and In-Ceram Zirconia core ceramics were machined by the Precident DCS system. The marginal fit of the milled frameworks placed on the master steel models was determined by a replica technique using a light-body silicone to fill the discrepancies between crown and tooth and a heavy-body material to stabilize the light-body impression material. The impressions were poured into an epoxy resin material and each model was cross-sectioned with a low speed diamond saw to better visualize marginal discrepancies. The marginal fit of the FPDs was evaluated by scanning electron microscopy. The measurements of the marginal fit exhibited mean marginal discrepancies in a range between 60.5 and 74.0 µm, mean marginal gaps in a range from 42.9 to 46.3 µm, mean vertical discrepancies in a range from 20.9 to 48.0 µm and mean horizontal discrepancies in the range of 42.0 to 58.8 µm. Statistical data analysis was performed using the non-parametric test of Kruskal-Wallis and Mann-Whitney. The analysis revealed no significant differences (p>0.05) between the mean marginal gaps and vertical and horizontal discrepancies. How-ever, for some FPDs the mean values of the marginal discrepancies were significantly different (p=0.05). The wide range of the measured values may be attributed to the complex geometrical design of long span FPDs and difficulties regarding the milling process of brittle ceramic materials. Based on the selection of 100 µm as the limit of clinical acceptability, the results of this study can conclude that the level of marginal fit for alumina- and zirconia-based FPDs achieved with the Precident DCS system meet the clinical requirements.

SUMMARY:
This study evaluated the effects of cutting dentin with different types of burs on tensile bond strength using three self-etching primer bonding systems (Clearfil Liner Bond 2 [LB2], Clearfil Liner Bond 2V [2V] and Clearfil SE BOND [SE], Kuraray, Co, Ltd, Osaka, Japan). Thirty-six intact extracted human third molars were ground flat to expose occlusal dentin, followed by polishing the dentin surfaces with #600 SiC paper. The teeth were divided into four groups according to bur type and grit: fine cut fissure steel bur (SB600), cross cut fissure steel bur (SB703), regular grit diamond bur (DB). Controls were abraded with #600 grit SiC paper (AP#600). The dentin surfaces of the SB600, SB703 and DB groups were cut under copious air-water spray with the respective burs mounted in a dental handpiece. The teeth were treated with one of three adhesive systems, then composite buildups were created with Clearfil AP-X (Kuraray Co, Ltd, Osaka, Japan). After soaking in water at 37°C for 24 hours, serial vertical sections (0.7 mm thick, 7-8 slices per one tooth) were made, trimmed to form an hour-glass shape with a 1.0 mm2 cross-section and tensile bond strengths were determined at a cross-head speed of 1 mm/min. Statistical analysis was made using one and two-way ANOVA and Fisher’s PLSD test (p<0.05). Eight additional molars were prepared. Burs or abrasive paper were used for SEM observations of the dentin surfaces of each group before and after treatment with the self-etching primers. All adhesive systems yielded the same ranking of bond strengths to the surfaces prepared with different abrasives: from highest to lowest, AP#600 > SB600 > SB703 > DB. This ranking reached statistical significance using Clearfil Liner Bond 2V (p<0.05). Therefore, when cutting dentin, selecting the adequate bur type is important for improved bonding of adhesive systems using self-etching primer to dentin.

SUMMARY:
This study evaluated in vitro the influence of five solutions used to treat cavity preparations on microleakage of amalgam restorations. Seventy-two standard Class V cavities were prepared in buccal and lingual surfaces of 36 recently extracted human third molars. The cervical wall was located in cementum and the occlusal wall was located in enamel. Specimens were randomly divided into six groups (n=12) according to the solution employed to treat the cavities: Group I–2.5% sodium hypochlorite; Group II–Calcium hydroxide solution; Group III–1.23% Acidulated phosphate fluoride; Group IV–2% digluconate of chlorhexidine; Group V–anionic detergent solution (1.25% sodium lauryl sulfate) and Group VI–control group. The solutions were applied for one minute, followed by washing and drying. Two coats of copal varnish were applied in each cavity. The cavities were filled with capsuled amalgam GS-80 (SDI). After finishing and polishing, the specimens were submitted for thermal cycling followed by immersion in methylene blue. Then, the specimens were sectioned and microleakage was evaluated based on a standard ranking under magnification (40x). Data were subjected to statistical analysis using non-parametric tests. Results of the study concluded that leakage was higher in cementum than enamel (p<0.01). The substances employed have no influence on microleakage except for sodium hypochlorite, which increased leakage values in enamel (p<0.05).

SUMMARY:
Marginal adaptation of four resin composites, Clearfil APX, Estelite, Silux Plus and Z-100 cured with two irradiation methods (soft-start or high-power start) of a commercial soft-start halogen lamp unit (Elipar Highlight) were evaluated by measurement of the wall-to-wall contraction gap width. One-hundred and sixty cylindrical cavities, 3 mm in diameter and 1.5 mm in depth, were prepared in extracted human molars. The 80 cavity walls were treated with the Megabond system and each 20 cavities were filled with one of four resin composites. Then, each 10 fillings were irradiated by the soft-start method (soft-power light for 10 seconds followed by high-power light for 30 seconds) or high-power light for 40 seconds. The other 80 cavity walls were treated with an experimental bonding system consisting of 0.5M EDTA as a conditioner, 35% glyceryl mono-methacrylate as a primer and Clearfil Photo Bond as a bonding agent. The cavities were restored wtih the four resin composites and two irradiation methods, the same as the Megabond group. The contraction gap was measured with a light microscope and expressed in % of the cavity diameter. In addition, the curing capability of these two light sources was evaluated by measurement of the curing depth of the four resin composites using a split Teflon mold 4 mm in inner-diameter and 8 mm in height. Marginal gap formation of Clearfil APX, Estelite and Silux Plus with the experimental bonding system was completely prevented regardless of the kind of irradiation methods used. The deterioration of marginal adaptation caused by the Megabond system could not be improved by use of the soft-start method programmed in Elipar Highlight.

SUMMARY:
This study compared the amount of artificial plaque synthesized in vitro by Streptococcus sobrinus on various dental materials using radioisotopes. In particular, plaque-retaining capacities of new types of ceramics were the focus of this study.

Specimens were fabricated from the following materials (one amalgam alloy [Spherical-D], one casting gold alloy [Casting Gold TYPE I], one resin composite [Herculite XR] and three ceramics [Vita Celay Blanks, IPS Empress and Dicor MGC]). The amount of bacteria and glucans adhered on the specimens was measured after incubation for 24 hours at 37°C with radio-labeled cariogenic bacteria and sucrose. This adhesion test was performed using two different surfaces with 600-grit roughness and clinical smoothness. Irrespective of the surface roughness, the least amount of plaque adhered to the ceramics. However, in the case of the resin composite and amalgam, the amount of bacteria and glucan adhesion decreased dramatically by polishing, though there were no statistically different changes in the amount of bacteria and glucans that adhered to the ceramics even after polishing. In general, the amount of adhered bacteria showed almost the same tendency as that of glucans. Although no statistical differences in the amount of bacteria and glucan adhesion were detected among the three ceramics investigated in this study, a lesser amount of bacteria and glucans adhered to them compared to the other materials.

SUMMARY:
The effectiveness of four surface protectors for resin-modified glass ionomer cements was evaluated by spectrophotometrically determining dye uptake. Ninety specimens, 3.0 mm in diameter and 1.0 mm in height, were made with Photac-Fil, Fuji II LC and Vitremer and divided into six groups for each material. Positive and negative controls were not protected while experimental specimens were protected with proprietary glaze, nail varnish, flowable resin and glaze. The discs were immersed in 0.1% methylene blue solution for 10 minutes after mixing, except for those negative control specimens that were immersed in deionized-water. After 24 hours, the specimens were washed and the protectors trimmed with Sof-Lex discs. The specimens were then removed from the matrixes and individually placed in 1.5 mL of 65% nitric acid for five hours. The absorbance was determined spectrophotometrically at 590 nm. Dye uptake was expressed in µg dye/specimen. The data were analyzed by two-way ANOVA and Tukey-Kramer tests. All surface protectors tested were effective. For Fuji II LC and Vitremer no differences were observed among tested protections. For Photac-Fil, nail varnish showed better performance than the proprietary glaze.

SUMMARY:
This study measured deformation of cusps and gap formation associated with MOD resin composite restorations in maxillary premolars with and without the use of low elastic modulus liners. Low elastic modulus liners may reduce the deformation by absorbing polymerization shrinkage stress. Forty maxillary premolars were mounted in stone and slot MOD cavities were prepared. Teeth were randomized into four groups. In Group A, cavities were etched, Single Bond was applied and the cavities were restored with Z-100 composite. In Group B, the same was done except that a layer of flowable composite (Revolution) was place and cured after the bonding agent. In Group C, the same steps were followed as Group A but a layer of glass ionomer (Vitrebond) was placed and cured before the bonding agent. In Group D, a thin layer of composite was placed (after the bonding agent) as a base and cured and the cavities were filled. The distance between indexed cusp tips was measured before the restorations were finished and five minutes and 24 hours after the restorations were completed. The samples were then sectioned mesiodistally and epoxy resin replicas were made and prepared for SEM evaluation of gap formation. The mean contraction of the cusps in µm at 5 minutes and 24 hours, respectively, for each group was A) 47 and 30, B) 35 and 21, C) 23 and 8 and D) 40 and 28. Groups A and D resulted in the highest deformation, B was intermediate and C was the lowest. There was no statistically significant difference in gap formation between the groups.

SUMMARY:
All 65 dental schools in the United States and Canada were contacted to obtain information relevant to their cariology teaching effort, the caries management philosophy, the diagnostic threshold for surgical intervention and the non-surgical treatment alternatives implemented.

Forty-three schools (66%) responded to the request for information. Marked variations in the teaching of cariology and the implementation of modern diagnostic and treatment modalities were noted. The results indicate that with exceptions, efforts to increase curricular time and make organizational changes that would promote cariology as an important academic and clinical endeavor have fallen far short of predictions made more than 20 years ago for North America.

Many cariology programs in North American dental schools lack the detail and depth expected for this important area of clinical dentistry.

SUMMARY:
Interproximal dental wedges are commonly used in Class II and Class III restorations. They force teeth apart enough to compensate for the thickness of the matrix, support the matrix against packing pressures of filling materials, prevent matrix displacement or filling excess/overhang and preserve anatomical tooth and tissue contours of the interdental space (Qualtrough & Wilson, 1991). Occasionally, concavity at the gingival cavosurface margin of a prepared cavity makes this area difficult to restore properly with amalgam or resin composite (Figure 1). Such concavities are frequently seen in the cervical area of maxillary premolars, in the mesial roots of mandibular molars and occasionally in the distal aspects of maxillary molars.

Existing preformed triangular-shaped wooden wedges are not adaptable to concavities and other conditions such as root caries or irregular tooth contours. Other wedge material, such as clear acrylic dental wedges used with light-cured composite fillings, are difficult to adapt and adjust. New innovative methods are frequently proposed to tackle such challenges (Ireland, 1985; Khera & Swift, 1989; Woodmansey, 1998).

A new product, Flexi Wedge (Common Sense Dental Products, Inc, Spring Lake, MI), has been specifically designed to solve some of the problem. However, the technique for the placement of Flexi Wedge is quite different from wooden wedges and requires special college pliers, hemostat, Howe pliers or a similar-type instrument. Strong driving force, plus a gentle up-and-down rocking motion, is required to drive the wedge into the correct position.

This paper offers a simple solution for a few of those clinical situations where difficulties are encountered. The solution lies in use of an elastic cord material capable of deforming sufficiently to take on and conform to any concave aspects of adjacent tooth surfaces. Such an elastic cord is readily available in rubber dam procedures. The clinician can employ the conventional wooden wedges for this technique without extra equipment or expense for new products.

SUMMARY:
This study evaluated the clinical performance of four packable resin composite restorative materials in posterior teeth (Class I and II) compared with one hybrid composite after one year. Eighty-four restorations were placed in 16 patients. Each patient received at least five restorations. The tested materials were: (1) Solitaire + Solid Bond; (2) ALERT + Bond-1; (3) Surefil + Prime & Bond NT; (4) Filtek P60 + Single Bond and; (5) TPH Spectrum + Prime & Bond 2.1. All restorations were made using rubber dam isolation, and the cavity design was restricted to the elimination of carious tissue. Deeper cavities were covered with calcium hydroxide and/or glass ionomer cement. In shallow and medium cavities, no protection was performed except for the respective adhesive system used in each group. Each adhesive system and resin composite was placed according to the manufacturer’s instructions. One week later, the restorations were finished/polished and evaluated according to the USPHS modified criteria. All patients attended the one-year recall, and the 84 restorations were evaluated at that time based on the same evaluation criteria. The scores were submitted to statistical analysis (Chi-square test, p<0.05). Solitaire and TPH showed some fractures at marginal ridges. Solitaire, ALERT and TPH showed some concerns related to color match and surface texture. Surefil and Filtek P60 showed an excellent clinical performance after one year.

SUMMARY:
This study investigated the differences in color perception among distinct groups of dental personnel. Four groups of dental personnel (10 dental technicians, 15 final-year dental students, 15 general practitioners and 10 prosthodontists) were asked to match seven test tabs of shades A1, A4, B2, B3, C2, C4 and D3 (Z100 shade guide, 3M Dental Products, St Paul, MN 55144, USA) against a standard Vita shade guide under similar lighting conditions. The results obtained were computed into L*a*b* values using a small-area colorimeter (Dental Colorimeter, Minolta Camera Pte Ltd). The data were analyzed using one-way ANOVA/post-hoc Scheffe’s test at significant level p<0.05. The results showed significant differences in ?E (color difference) between the dental technicians and the clinicians for shade C4. The significant difference that was observed in ?E for dark shades between dental personnel was mainly contributed to a disparity in L* values. A significant difference in ?L* was observed between dental technicians and prosthodontists for shade C4.

SUMMARY:
Interaction between resin tags and microtags of adhesive systems and dentinal collagen fibrils is a poorly understood aspect of adhesion. This study evaluated this interaction in 25 recently extracted human third molars. Each tooth was embedded in an epoxy resin and cross-sectioned to obtain two 1-mm-thick dentin disks. The outer dentin surfaces were polished with wet 600-grit sandpaper to create a uniform smear layer. After etching with 35% phosphoric acid for 15 seconds, the primer and adhesive of Scotchbond Multi-Purpose and the resin composite Z100 (3M Dental Products, St Paul, MN 55144, USA) were placed on the dentinal surfaces according to the manufacturer’s instructions. The disks were left in distilled water at 37°C for two weeks, then fractured perpendicular to the bonded surfaces in order to obtain two hemi-disks. The fractured surfaces were treated with 2N-chloridric acid and processed for scanning electron microscopy. Gold-coated specimens were examined with a JEOL 6100 scanning electron microscope. Results showed a hybrid layer with resin tags of approximately 100 µm in length and numerous and fine branching resin microtags. The tags and microtags created by this three-step adhesive system were observed in intimate contact with the collagen fibrils of dentin, even in deeper zones which were not affected by acid etching. It suggests that adhesion to dentin may include both micromechanical and chemical aspects.

SUMMARY:
This study evaluated the effect of adhesives on the inhibition of secondary caries around compomer restorations in vitro. Two adhesive systems with a Bis-GMA resin, Scotch bond Multi-purpose (MP) and Single Bond (SB), and one adhesive system with no Bis-GMA resin, F2000 compomer primer/adhesive (PA), were used prior to placement of the compomer (F2000), and non-fluoride releasing resin composite (Z100) was used as a control. Class V cavities prepared on extracted human premolars were restored with various combinations of materials: F2000/MP, F2000/SB, F2000/PA, Z100/MP, Z100/SB and Z100/PA. The restored teeth were incubated in bacterial medium containing sucrose with Streptococcus mutans for two weeks after storage for 14 days. On microradiographs, the radio-opaque layers adjacent to the F2000 restorations were thick and clear, while the layers in the Z100 restorations were unclear. In the F2000 restorations, the mean thickness of the radio-opaque layers in the PA group was significantly greater than that of the MP and SB groups. In fluoride-releasing measurement, F2000 coated with PA showed a significantly higher amount of fluoride release than MP and SB, and no significant difference in the amount of fluoride release from uncoated F2000.

These results indicated that applying an adhesive without Bis-GMA resin to compomer restoration has no suppressive effect on the fluoride release from compomer and might be beneficial for inhibiting secondary caries in vitro.

SUMMARY:
Although several in vitro studies have attempted to investigate the microleakage of Class V resin composites under loading, the effect of load cycling on marginal seal is still unclear. This may be due to the fact that axial loads were applied to the specimens. This study investigated the effect of flexural loads on marginal sealing of cervical resin composites. One hundred and fifty cervical wedge-shaped cavities were restored with Clearfil Photo Bond, Clearfil Liner Bond 2, Scotchbond Multi-Purpose with 10% maleic acid, Scotchbond Multi-Purpose with 35% phosphoric acid or Mac-Bond 2 according to the manufacturers’ instructions. After the restorations were finished, 10 specimens from each group were immersed in 0.5% basic fuchsin solution to examine microleakage. Prior to dye solution immersion, 20 specimens were subjected to flexural load cycling (1 mm labio-lingual or linguo-labial displacement at the incisal edge, 10,000 cycles, 1 cycle/second). The data were analyzed using the Kruskal-Wallis test and the Mann-Whitney U-test (p<0.05). When the flexural loads were not applied, both the incisal and apical margins showed good marginal sealing, regardless of the adhesive system used. Labio-lingual loading significantly deteriorated the marginal integrity at the incisal enamel margins, except for those restored with Clearfil Photo Bond. However, only Clearfil Photo Bond demonstrated a significant increase in microleakage along the apical dentin margins. Linguo-labial loading had no significant effect on the marginal seal.

SUMMARY:
This study investigated the influence of light energy density (intensity x time) on the effectiveness of composite cure in view of the curing profiles of new light-polymerization units. This investigation used a digital microhardness tester to evaluate the hardness of the top/bottom surfaces and hardness ratio of 2 mm thick composite specimens after exposure to different light energy densities. Parameters included five light intensities (200, 300, 400, 500 and 600 mW/cm2) and nine irradiation times (10, 20, 30, 40, 60, 80, 100, 120 and 180 seconds). Six samples were evaluated for each light energy density. KHN values and the hardness ratio obtained with 40 seconds cure at 400 mW/cm2 was used as control. Results were analyzed with one-way ANOVA and Scheffe’s post-hoc test at significance level (0.05). Correlation between curing time and hardness values and ratio was done using Pearson’s correlation at significance level 0.01. Results showed that the adequate hardness for surface finishing could be obtained with 20 seconds irradiation at lower intensities of 200 or 300 mW/cm2. Optimal cure of the bottom surfaces could not be achieved with 200 mW/cm2, but was attained with 300 mW/cm2 only after 120 seconds of irradiation. Optimal cure of the bottom surfaces was possible with 30 and 20 seconds irradiation at 500 and 600 mW/cm2, respectively. Effective cure was not achieved with low light intensities (200 to 300 mW/cm2) but could be achieved with high intensities (500 and 600 mW/cm2) after 30 seconds of irradiation.

SUMMARY:
This study investigated the influence of fiber reinforcement on the flexural properties of four commercial (Artglass, Belleglass HP, Herculite XRV and Solidex) veneering composites (Series A) and two experimental composites (Series B&C). This study investigated how the composition of the veneering composites influenced the enhancement of strength and modulus produced by fiber reinforcement. The formulation of the experimental composites were varied by changing the filler load (Series B) or the resin matrix chemistry (Series C) to assess the effect these changes would have on the degree of reinforcement.

In Series A, the commercial veneering composites were reinforced by an Ultra-High-Molecular-Weight Polyethylene fiber (UHMW-PE/Connect) to evaluate flexural properties after 24 hours and six months. In Series B, experimental composites with the same organic matrix but with different filler loads (40% to 80% by weight) were also reinforced by Connect fiber to evaluate flexural properties. In Series C, experimental composites (Systems 1-4) with the same filler load (76.5% by weight) but with different organic matrix compositions were reinforced by Connect fiber to evaluate flexural properties. For Series B and C, flexural properties were evaluated after 24 hours water storage.

All the samples were prepared in a mold 2 mm x 2 mm x 25 mm and stored in distilled water at 37°C until they were ready for flexural testing in an Instron Universal Testing Machine using a crosshead speed of 1 mm/minute. The results showed no significant differences in the flexural strength (FS) between any of the commercial reinforced composites in Series A. The flexural modulus (FM) of the fi