Current Issue
March/April, Volume 33, Number 3

Introduction:
During the past several years, the use of cohesive golds gradually has been increasing in the daily practice of dentistry. It is difficult to determine the motivating influence that has created the increase in interest in this type of restorative service. Perhaps some of the credit can be attributed to the research responsible for the development of new materials, the perfection of clinical techniques which have improved manipulative procedures and the ever-constant influence of the American Academy of Gold Foil Operators, which continually has been emphasizing the need for higher levels of operative services.

The purpose of this presentation is not to delve into all forms of cohesive golds, but primarily to discuss mat gold and its relationship to total restorative services. Mat gold is only one of the many types of cohesive golds available to the profession today. Each of these golds possesses certain qualities and properties which are suitable for specific restorative procedures.

SUMMARY:
The setting of dental composites is accompanied by significant polymerization contraction, resulting in the generation of stresses within the material and at the tooth-restoration interface. These stresses can have a deleterious effect on marginal integrity if they exceed the adhesive strength of the restorative, as well as on the properties of the composite. It has been determined that several factors affect these stresses, including the polymerization rate of the composite, its formulation, including filler and monomer composition and the constraints imposed by the geometry of the cavity preparation. Many strategies have been developed to reduce the effect of these stresses. Changes in the formulation of the composite have included experimentation with a variety of stress relieving additives, modified catalyst compositions and alternative monomer systems. Modifications to the placement techniques have included the use of incremental curing, altered light activation schemes and resilient liners. This manuscript will review many of the important scientific and clinical issues relating to the generation and quantitation of the stresses produced in dental composites during curing.

SUMMARY:
This investigation assessed the effectiveness of alternative treatments for the replacement of amalgam and resin-based composite restorations. Sixty-six patients (age 18 to 80 years, mean=26.6) with 271 (amalgam [n=193] and resin-based composite [n=78]) defective restorations were randomly assigned to one of five different treatment groups: A) Repair (n=27); B) Sealing of margins (n=48); C) Refurbishing (n=73); D) Replacement (n=42) and E) Untreated (n=81). USPHS/Ryge criteria were used to determine the quality of the restorations. Two calibrated examiners (Cohen's Kappa 0.74) assessed the restorations independently at the beginning of the study (baseline) and at two years after treatment using seven parameters from the USPHS/Ryge criteria (Marginal Adaptation, Anatomic Form, Roughness, Marginal Stain, Occlusal Contact, Secondary Caries and Luster). Results: Two-hundred and fifty-six restorations (178 amalgam and 78 resin-based composite) were examined at the two-year recall exam. The sealing of marginal defects showed significant improvements in marginal adaptation (p<0.05). Refurbishing of the defective restorations significantly improved anatomic form (p<0.0001), luster (p<0.016), marginal adaptation (p<0.003) and roughness (p<0.0001). The repair significantly improved anatomic form (p<0.002) and marginal stain (p<0.002). Replacement showed significant improvements for all parameters (p<0.05). The Untreated group showed significant deterioration on marginal adaptation (p<0.013). Conclusions: The two-year recall examination showed that sealant, repair and refurbishing treatments improved the clinical properties of defective amalgam and resin-based composite restorations by increasing the longevity of the restorations with minimal intervention.

SUMMARY:
The polymerization shrinkage of resin composites may affect restoration quality. A double blind, randomized clinical trial was carried out to compare two curing techniques-Soft-Start (SS) and the plasma arc curing light (PAC). The hypothesis that, delaying the gel point (with SS) improves marginal seal, was tested at alpha=0.05. Also, this report includes two-week, three-month, one-year and two-year results for post-op sensitivity. Twenty informed participants, each needing two Class II and/or complex Class I restorations, gave written consent. All the teeth were trans-illuminated to rule out pre-op crack lines before restoration placement. Fifty Z100-Single Bond restorations (25/SS and 25/PAC) were placed under rubber dam. Protocols: PAC (Control)-incremental curing <2.0 mm, 2000 mW/cm2 for 10 seconds for all layers, SS (Treatment)-incremental curing <2.0 mm, 600 mW/cm2 for 20 seconds, except the final layer or enamel replacement increment, which was cured as follows-(mW/cm2/time) 200/3 seconds, wait 3 minutes; 200/3 seconds, wait 5 minutes; 600/20 seconds from multiple angles.

Sensitivity to a standardized cold stimulus was performed preoperatively at 2 weeks and at 3, 12 and 24 months. Patients rated their sensitivity after stimulus by means of a Visual Analog Scale (VAS). In addition, two independent, calibrated investigators evaluated the restorations clinically at each appointment. There were no significant differences in VAS scores between the two groups at any appointment period (two-way ANOVA; p>0.05).

Several conditions were defined as indicating marginal stress before the start of the trial. At 24 months, there was no significant difference between the SS and PAC groups.

Conclusion: Within the limitations of this study, Class I and II restorations placed with a SS technique did not show significant changes in post-op sensitivity or decreased signs of marginal stress.

SUMMARY:

SUMMARY:
In this study, the microtensile bond strengths of an etch-and-rinse resin adhesive to dentin and enamel and a resin-modified glass ionomer adhesive to dentin were determined on teeth known to have originated from subjects over 60 years of age. The same tests were repeated on teeth originating from young subjects. The resin adhesive was Prime & Bond NT (Caulk/Dentsply), while the resin-modified glass ionomer adhesive was Fuji Bond LC (GC America). Both were paired with the same hybrid resin composite, TPH3 (Caulk/Dentsply). Testing was performed after 48 hours using a "non-trimming" microtensile test at a crosshead speed of 0.6 mm/minute. No significant differences were observed between the young and aged teeth for any comparison (p>0.05). SEM evaluation of the etched dentinal surfaces demonstrated less depth of decalcification in the intertubular areas of aged dentin, but there was no observable difference within the tubules of young and aged dentin.

SUMMARY:
This study analyzed the influence of the light polymerization mode on the degree of conversion (DC) and mechanical properties of two resin composites: a hybrid (Filtek P60) and a nanofilled composite (Filtek Supreme). The composites were light activated by three light polymerization modes (Standard-S: 650 mW/cm2 for 30 seconds; High intensity-H: 1000 mW/cm2 for 20 seconds and Gradual-G: 100 up to 1000 mW/cm2 for 10 seconds + 1000 mW/cm2 for 10 seconds). The DC(%) was measured by FT-Raman spectroscopy. Flexural strength and flexural modulus were obtained from bar-shaped specimens (1 x 2 x 10 mm) submitted to the three-point bending test. Microhardness was evaluated by Knoop indentation (KHN). Data were analyzed by ANOVA and Student-Newman-Keuls multiple range test and linear regression analysis. The results showed the following DC: H > S > G (p<0.0001) and hybrid > nanofilled (p<0.005). Correlation was found between DC and the radiant exposure (R2 = 0.92). With respect to mechanical properties, only KHN was significantly influenced by the light polymerization mode, as follow: H>S=G (p<0.0001). The hybrid composite presented higher flexural strength and flexural modulus than the nanofilled composite (p<0.0001). No significant difference was found in KHN between the two composites (p=0.1605). The results suggest that nanofilled composites may present a lower degree of conversion and reduced mechanical properties compared to hybrid composites.

SUMMARY:
This study compared the thickness of the hybrid layer formed using Scotchbond Multi-Purpose Plus, Single Bond 2, Prime & Bond 2.1 and Xeno III on a dentin surface prepared with a diamond bur in a high speed handpiece or prepared with an Er:YAG laser used with two parameters of pulse energy (200 and 400 mJ) and two parameters of frequency (4 and 6 Hz). Flat dentin surfaces obtained from 20 human third molars were treated with the two methods and were then prepared with the dentin adhesive systems according to the manufacturers' instructions. After a layer of composite was applied, the specimens were sectioned, flattened, polished and prepared for Scanning Electronic Microscopy observation. Five different measurements of the hybrid layer thickness were obtained along the bonded surface in each specimen. The results were statistically analyzed using Analysis of Variance and Student-Newman-Keuls tests (p?0.05). When analyzing the hybrid layer thickness and comparing the cavity preparation method, four groups were formed: Group I (diamond bur) > Group II (Laser 200 mJ/4 Hz) = Group III (Laser 200 mJ/6 Hz) > Group IV (Laser 400 mJ/4 Hz) > Group V (Laser 400 mJ/6 Hz). When comparing the dentin adhesive systems, there were no statistically significant differences. These results showed that the four tested dentin adhesive systems produced a 2.90 ? 1.71 ?m hybrid layer in dentin prepared with a diamond bur. This hybrid layer was regular and routinely found. In the laser groups, the dentin adhesive systems produced hybrid layers ranging from 0.41 ? 1.00 ?m to 2.06 ? 2.49 ?m, which were very irregular and not routinely found. It was also concluded that the Er:YAG laser, with the parameters used in this experiment, has a negative influence on the formation of a hybrid layer and cavity preparation methods influence formation of the hybrid layer.

SUMMARY:
Despite the successful use of dental amalgam for coronal-radicular dowel and core build-up in endodontically-treated posterior teeth, newer materials offer many potential advantages over amalgam and have better patient acceptance. This study compared the fracture resistance of coronal-radicular restorations made from three different direct restorative materials. Sixty human premolars were selected, 45 of which were root treated and decoronated. Fifteen of these premolars were restored using amalgam, 15 with composite and 15 using resin-modified glass ionomer. The 15 unrestored teeth were used as a control group. All the teeth were mounted in acrylic within steel containers and subjected to compressive loading to failure on a universal testing machine. The force required to fracture each core specimen was recorded as well as the proportion of core lost due to failure. The results showed dental amalgam as having the highest fracture resistance (mean 1.93kN, sd 0.22) followed by resin-modified glass ionomer (mean 1.05kN, sd 0.20), sound tooth (mean 0.79kN, sd 0.20) and composite (mean 0.75kN, sd 0.11). The differences among all groups were significant. These results demonstrate that, although resin-modified glass ionomer is significantly weaker than amalgam, these restorations were stronger than unrestored teeth and failed at forces in excess of those encountered in normal mastication. Amalgam cores, along with resin-modified glass ionomer, tended to fail less catastrophically than the other materials and, given their strength, would remain the material of choice in situations where abnormally high forces are expected.

SUMMARY:
Knoop Hardness (KH) ratios (HR) ? 80% are commonly used as criteria for the adequate cure of a composite. These per-specimen HRs can be misleading, as both numerator and denominator may increase concurrently, prior to reaching an asymptotic, top-surface maximum hardness value (HMAX). Extended cure times were used to establish HMAX and descriptive statistics, and non-linear regression analysis were used to describe the relationship between exposure duration and HR and predict the time required for HR-HMAX = 80%. Composite samples 2.00 x 5.00 mm diameter (n=5/grp) were cured for 10 seconds, 20 seconds, 40 seconds, 60 seconds, 90 seconds, 120 seconds, 180 seconds and 240 seconds in a 2-composite x 2-light curing unit design. A microhybrid (Point 4, P4) or microfill resin (Heliomolar, HM) composite was cured with a QTH or LED light curing unit and then stored in the dark for 24 hours prior to KH testing. Non-linear regression was calculated with: H=(HMAX -c)(1-e-kt) +c, HMAX = maximum hardness (a theoretical asymptotic value), c=constant (t=0), k=rate constant and t=exposure duration describes the relationship between radiant exposure (irradiance x time) and HRs. Exposure durations for HR-HMAX =80% were calculated. Two-sample t-tests for pairwise comparisons evaluated relative performance of the light curing units for similar surface x composite x exposure (10-90s). A good measure of goodness-of-fit of the non-linear regression, r2, ranged from 0.68-0.95. (mean = 0.82). Microhybrid (P4) exposure to achieve HR-HMAX = 80% was 21 seconds for QTH and 34 seconds for the LED light curing unit. Corresponding values for microfill (HM) were 71 and 74 seconds, respectively. P4 HR-HMAX of LED vs QTH was statistically similar for 10 to 40 seconds, while HM HR-HMAX of LED was significantly lower than QTH for 10 to 40 seconds. It was concluded that redefined hardness ratios based on maximum hardness used in conjunction with non-linear regression provides an improved method of evaluating curing performance relative to traditional per-specimen hardness ratios.

SUMMARY:
Objectives: The transmission of light through translucent posts was observed, and the microhardness of light-cured cement used to secure these posts was evaluated at different depths. Methods: Fifteen single-rooted standard bovine teeth, 16 mm in size, were used. The root canals were prepared using #3 drills Light-Post (five teeth) and Aestheti Post (five teeth) systems (BISCO), with a working-length of 12 mm. In five teeth, translucent posts were cemented (Light-Post #2), while another five teeth received opaque posts (Aestheti Post #2). The roots were painted with black nail varnish to prevent the passage of light through the lateral walls of the roots. The root canals of all the specimens were treated with the All-Bond 2 adhesive system (BISCO) and cemented with light-cured cement (Enforce, Dentsply). All the roots were transversally cut to obtain six specimens 1.5 mm thick. Every two sections corresponded to a specific region of the root (cervical, middle, apical), making it possible to observe the cement microhardness at different levels. The groups (n=10) were defined as: G1: translucent post (TP)/cervical region; G2: TP/middle region; G3: TP/apical region; G4: Opaque post (OP)/cervical region; G5: OP/middle region; G6: PO/apical region. Five root canals were only filled with cement for use as a control (G7). Then, Vickers microhardness analyses were performed. Results: In G3, G5 and G6, the cement was not sufficiently hard to allow for microhardness analysis. When submitted to the ANOVA test, G1 (35.07), G2 (24.28) and G4 (28.64) presented no statistical differences. When the previous groups were compared to G7 (51.00) using the Kruskal-Wallis test, a statistical difference was found. Conclusion: Translucent posts allow cement polymerization up to the middle portion of the root.

SUMMARY:
This study investigated the influence of the light guide shape on the polymerization efficacy of a light-activated resin-based composite cured with LED units as a function of the distance between the tip and the restoration.

Two different LED units, each with different light guides and shapes, were used. Their ability to cure a single restorative material was investigated. The efficacy of the light-curing system was evaluated by measuring the depth of cure using the Acetone Shake test.

Considering the ratio (R) between the entry diameter and the exit diameter of the light guide, the tips with a higher R-value proved to be more efficient if the tip and composite distance (D) was less than 5 mm, while for D>5 mm, the tips with a lower R-value showed better results.

The tip geometry of the tested light guide had a significant influence on the depth of cure of the tested resin composites. Therefore, depending on the distance, the more suitable light guide should be selected, based on the clinical situation. An R-value may be a better descriptor for the light guide shape than words such as "normal" or "turbo."

SUMMARY:
This in vitro study compared the effects of a gold alloy (Degulor M), four dental ceramics (IPS Empress, IPS Empress 2, Duceram Plus, Duceram LFC) and a laboratory-processed composite (Targis) on the wear of human enamel. The amount of wear of the enamel (dental cusps) and restorative materials (disks) were tested in water at 37?C under standard load (20 N), with a chewing rate of 1.3 Hz and was determined after 150,000 and 300,000 cycles. Before the test, the average surface roughness of the restorative materials was analyzed using the Ra parameter. The results of this study indicate that Targis caused enamel wear similar to Degulor M and resulted in significantly less wear than all the ceramics tested. IPS Empress provoked the greatest amount of enamel wear and Degulor M caused less vertical dimension loss. Targis could be an appropriate alternative material to ceramic, because it is esthetic and produces opposing enamel wear comparable to gold alloy.

SUMMARY:
This in vitro study observed and compared the resin and non-carious sclerotic dentin interfaces generated by three different adhesives and two different techniques, using a scanning electron microscope (SEM). Thirty-two human premolars, with buccal, non-carious cervical lesions, were used. The teeth were randomly divided into eight groups. Group 1: Sclerotic dentin was treated with Single Bond (3M). Group 2: After superficial sclerotic dentin was removed with a diamond bur (Diatech, Coltene), the dentin surfaces were treated with Single Bond. Group 3: Sclerotic dentin was treated with Clearfil SE Bond (Kuraray). Group 4: After superficial sclerotic dentin was removed with a diamond bur, Clearfil SE Bond was applied. Group 5: Sclerotic dentin was treated with Xeno III (Dentsply). Group 6: After superficial sclerotic dentin was removed with a bur, Xeno III was applied to the dentin surfaces. For Groups 7 and 8, after the superficial sclerotic dentin was removed with a diamond bur, Clearfil SE Bond, with an additional 37% phosphoric acid gel, was used on the sclerotic dentin surfaces in Group 7 and Xeno III was used in Group 8. In all groups, the cavities were restored with Filtek Supreme (3M). All the specimens were sectioned longitudinally and polished along the cut surface. The sections were treated with 37% orthophosphoric acid for five seconds, rinsed with water and treated with 5% NaOCL for 10 minutes. The specimens were then gold-sputter coated and evaluated under SEM. The thickness of the hybrid layer was measured on the gingival, occlusal and axial dentin interfaces. ANOVA was performed to determine whether there were any statistically significant differences in hybrid layer thickness. Post-hoc multiple comparisons were done with Tukey's test. Hybrid layer thickness was increased with all adhesives when superficial dentin was removed with a bur. Hybrid layer thickness showed significant differences between total-etch and self-etch systems.

SUMMARY:
This literature review summarizes the research on fiber post surface treatments and provides information related to their benefit in enhancing bond strength to composites, based on the results of original scientific full papers from peer-reviewed journals listed in Pub Med. The search was conducted using the terms "fiber post," "surface treatment," "surface conditioning," "etching" and "sandblasting." A consistent number of in vitro studies that investigated the surface treatment of fiber posts in an attempt to improve bond strength have been published to date. Their results have been summarized in the following categories: chemical treatments and micro-mechanical treatments of fiber post surfaces (or a combination of both principles). The majority of available literature data is based on studies that investigated different "chairside" post superficial treatments. According to the in vitro results, surface conditioning improves fiber post bonding properties, and the bond strength of pre-treated fiber posts to restorative materials is satisfactory. Long-term clinical studies are needed prior to making a general recommendation for their use.

SUMMARY:
Conventional box preparations, tunnel cavities and slot preparations have been recommended for the treatment of proximal carious lesions over the years. If the adjacent tooth is missing or the proximal surface becomes accessible at the time of cavity preparation of the adjacent tooth, a direct proximal access to the decay process can be performed. A similar procedure is supported by the use of adhesive composite restorations reinforcing the remaining sound tooth structure. The increasing patient and clinician's desire for ultraconservative treatment justifies this minimally invasive tooth preparation approach; however, appropriate materials and techniques need to be selected to achieve adequate bonding of the cavity walls and marginal adaptation of the composite.