Supreme XT Research Articles

Comparison of Various Properties of a Silorane Based Dental Composite with Two Methacrylate Based Dental Composites

AbstractThe synthesis of a new monomer system named silorane (obtained from the reaction of oxirane and siloxane molecules) gave way to the production of a novel low shrinkage silorane based composite. Objectives: The purpose of this study was to compare some physical properties of a silorane based composite (Filtek Silorane, 3MESPE) to those of two well-known low shrinkage methacrylate-based composites (Filtek Supreme XT, 3MESPE; Esthet X HD, Dentsply). The study also includes the effect of external media (food simulating solutions; distilled water, artificial saliva, 25% ethanol, coconut oil and Coke) on the three composites. Methods: Cured samples underwent water absorption (with immersion in food simulating solutions) and desorption. The data were analysed; the water absorption and desorption profiles were mapped, the diffusion coefficients and solubility of each sample were calculated. Curing efficiency was measured on the top and bottom surfaces of cured composite samples using Fourier Transform Infrared (FTIR) spectroscopy. Finally, the temperature profile during polymerisation of each composite sample was mapped, allowing the calculation of the sample‘s maximum exotherm. Results: From the results obtained from these experiments, overall, the properties of Filtek Silorane are comparable with those of Filtek Supreme XT and Esthet X HD.

COLOR STABILITY OF A NANOFILLED RESIN: INFLUENCE OF POLISHING AND FINISHING AND FLUORIDE SOLUTIONS ACCORDING TO TIME

AIM: The aim of the study was evaluate the finishing and polishing effect of the color stability of the composite resin Filtek Supreme XT, according to different fluoride solutions and time. MATERIAL AND METHODS: Specimens were prepared (n=140) with half of the samples finished and polished. The experimental groups were divided according to the presence or absence of finishing and polishing and immersion solutions (artificial saliva, sodium fluoride solution at 0.05% - manipulated, Fluordent Reach, Oral B, Fluorgard). The specimens remained in artificial saliva for 24 hours and were subjected to an initial color analysis using a spectrophotometer CIELab system. Then, they were immersed in the experimental solutions for 1 minute a day. The readings of the color change were made after 24 and 48 hours, 7, 14, 21, 30 and 60 days after the first immersion. The three-way mixed Analysis of Variance (ANOVA) ("finishing/polishing", "immersion medium" and “time”) were performed. For multiple comparisons, the Sidak test for repeated measure was used, with a 5% level of significance. RESULTS: The finishing and polishing factor showed significant variability, independently of the immersion media (p<0.001). CONCLUSION: Finishing and polishing procedures yielded better color stability to composite resin over time, regardless of the immersion media.

Multiaxial Strength and Stress Forming Behavior of Four Light-Curable Dental Composites

The resulting internal stress situation in curing dental composites is still oversimplified due to analytical inaccessibility of local information of state and loading. Similar applies to the strength behavior of cured dental composites. Using recent progress of a finite-element-based curing model, we developed and attempted to benchmark dental composites based on their mechanical behavior and tendency to form internal stress. Additionally, in order to understand the influence of restoration techniques on the mechanical loading, curing simulations were necessary. Three-point flexural strength, compressive strength and diametral tensile strength and the necessary curing parameters were studied for four state-of-the-art dental composites (Tetric EvoCeram, Venus Diamond, EsthetX, Filtek Supreme XT). The investigated composites fracture can be analyzed by the Drucker Prager failure criteria for each composite. The lowest resulting curing stresses were found for Tetric EvoCeram because of its low volumetric shrinkage and a high ratio of initiation phase to dark phase conversion. Venus Diamond showed the best overall mechanical properties because it can withstand tensile as well as compressive stress. In order to draw conclusions on comparisons between several composites, flexural strength tests, volume shrinkage measurements, cavity classifications and general preparation recommendations may still be a suitable way for the simplification of the immense complexity in curing and restoration. Nevertheless, finite-element-based simulations are necessary to include fundamental effects such as stress relaxation by flow and multiaxial strength of the composite.

Effect of polishing systems on stain susceptibility and surface roughness of nanocomposite resin material

Different polishing systems vary in their effect on reducing surface roughness and stain susceptibility of dental composite resin materials. The purpose of this study was to compare the effect of 3 polishing systems on the stain susceptibility and surface roughness of 2 nanocomposite resins and a microhybrid composite resin. Forty-five disks (2×10 mm) each were fabricated of 2 nanocomposite resins (Filtek Supreme XT and Tetric EvoCeram) and 1 microhybrid composite resin (Z250). Both sides of the disks were wet finished, and 1 side was polished with PoGo, Astropol, or Hi-Shine (n=5). Unpolished surfaces served as controls. The average roughness (Ra, μm) was measured with a profilometer, and the baseline color was recorded with a spectrophotometer. All specimens were incubated while soaking in a staining solution of coffee, green tea, and berry juice for 3 weeks. The color was recorded again, and the data were analyzed with 2-way ANOVA at α=.05 and Tukey multiple comparison tests. All polishing systems improved the staining resistance of Filtek Supreme XT and Z250 but did not affect that of Tetric EvoCeram. The surface color of Filtek Supreme XT was changed significantly and was the smoothest after polishing with PoGo, whereas Hi-Shine produced significantly rougher surfaces but with the lowest color change. Hi-Shine produced the highest color change in Z250. The surface roughness did not differ significantly between the other polishing systems. Tetric EvoCeram showed no significant differences in color change or surface roughness. Staining susceptibility and surface roughness depend mainly on material composition and on the polishing procedures. Polishing improves the staining resistance of composite resins. Nanocomposite resins did not exhibit better staining resistance or surface roughness than microhybrid composite resin.

The elution and breakdown behavior of constituents from various light-cured composites

ObjectivesConstituents of dental composites can be released from dental fillings after polymerization. The aim of this study was to examine the time-related elution and breakdown of separable constituents of polymerized composites using deuterated solvents. MethodElution and breakdown of constituents were investigated with deuterated solvents methanol and water by gas chromatography/mass spectrometry of following composites for 180 days: Filtek™ Supreme XT, Filtek™ Supreme XT Flow, Tetric Ceram®, Tetric Flow®, Grandio®, Grandio® Flow. ResultsWithin 180 days no compounds were formed as the products of breakdown. 19 compounds were identified as elution products: Bis-EMA, TEGDMA, DDDMA, EGDMA, MAA, BPA, CQ, HQME, DMABEE, CSA, BL, TEG, BHT, TINP, TPP, TPSB, DEDHTP, DCHP, ß-PHEA.The highest concentration of Bis-EMA was measured for Tetric Flow® in deuterated methanol on day 90 at 36.993mmol/l and in deuterated water also on day 90 at 0.031mmol/l.The highest TEGDMA concentrations were measured for Grandio® Flow in deuterated methanol on day 60 at 1.322mmol/l and for Filtek™ Supreme XT Flow in deuterated water on day 3 at 0.689mmol/l. The highest BPA concentration was measured for Tetric Flow® in deuterated methanol on day 90 at 1.469mmol/l. The highest BPA concentration was measured for Grandio® in deuterated water on day 180 at 0.007mmol/l.Significance Examination of time-related elution indicates that various elution products (e.g. Bis-EMA, BPA) were only released in small quantities during the first 90 days, but in high quantities between day 90 and day 180.

Dental Light-Cured Polymer Nanocomposites: A Brief Review of Experimental Results Obtained from the Study of Some Physicochemical Properties

This article is a brief review of the experimental results obtained from the study of some physicochemical properties of five dental commercial light-cured nanocomposites: Filtek Supreme XT Body (FSB) and Filtek Supreme XT Translucent (FST), both characterized as nanofill composites, and Grandio (GR), Tetric EvoCeram (TEC) and Protofill-nano (PR) characterized as nanohybrid composites. The properties presented are: volumetric shrinkage due to polymerization, sorption, solubility and volume increase after sorption of composites in water or artificial saliva SAGF® medium for 30 days, flexural strength and modulus after immersion in water or artificial saliva for one or 30 days and finally the dynamic mechanical properties (storage modulus E', loss modulus E'', tand=E''/E' and Tg) determined 1h after light-curing or after immersion in an oral/food simulating liquid (water, artificial saliva or ethanol/water solution 75%vol) for 1 month. It was found via physicochemical properties that the most corrosive solvent is EtOH which heavily affects the polymeric matrix, while water and saliva are smoother media. Moreover, the more rigid and concrete polymeric chains may sustain higher load during mechanical tests, so that the composites with stronger networks shall demonstrate resistance.

The effect of temperature on bisphenol: an elution from dental resins.

Bisphenol A (BPA) elution from baby bottles into content has been of great public interest and debate in recent year. Uncontrolled BPA elution due to temperature increase may create a risk factor for human health. However, dental resins that are used in pediatric dentistry also have BPA derivatives. The aim of this study is to evaluate BPA elution from dental resins and to determine the effect of temperature increase on this elution. Four dental resins containing BPA derivatives (Filtek Z250, Filtek Supreme XT, Fissurit FX, and Admira) and a control group (BPA free G-aenial) were used in this study. Each specimen was stored in 2 ml of 75% ethanol-water solution at 37°C. Water at a temperature of 59°C ± 1°C (preferred temperature of hot drinks) was added to the study samples at certain time intervals (1, 6, 24 hours and 2, 3, 4, 5 and 6 days). The methanol samples were analyzed using high-performance liquid chromatography (HPLC). Data was analyzed using multivariate and repeated measures analysis of variance (p < 0.05). The study samples generally eluted more BPA than the control samples (p < 0.05). The greatest amount of BPA for an individual time period was measured after 6 hours for the groups A to D; the same was found after 24 hours for group E. While the BPA elution levels evaluated in the study samples were more than control samples, all measured values were under the reference levels and the amounts do not constitute a risk. Resin-based dental materials can act as a source of BPA (within safety margins), especially when they react with hot water.

Influence of Different Staining Beverages on Color Stability, Surface Roughness and Microhardness of Silorane and Methacrylate-based Composite Resins

To investigate the influence of different staining beverages on color stability, surface roughness and microhardness of silorane and methacrylate-based composite resins. Three different composite resins (Filtek Silorane, Filtek P60, Filtek Supreme XT) were tested. Thirty cylindrical specimens (10 × 2 mm) per material were prepared and polished with a series of aluminum-oxide polishing disks. Each group was then randomly subdivided into three groups according to the test beverages: distilled water (control), cola and coffee. The samples were immersed into different beverages for 15 days. Color, surface roughness and microhardness values were measured by a spectrophotometer, prophylometer and Vickers hardness device respectively, at baseline and after 15 days. The data were subjected to statistical analysis. Immersion in coffee resulted in a significant discoloration for all the composites tested, although the color change was lower in Filtek Silorane than that of MBCs (p < 0.05). All the composites tested showed similar surface roughness changes after immersion in different beverages (p > 0.05). Besides coffee caused more roughness change than others. Immersion in coffee caused highest microhardness change in Filtek Supreme XT (p < 0.05). Cola and coffee altered, to some degree, the color, surface roughness and/or microhardness of the tested resin composites, depending on the characteristics of the materials.

Polymerization Shrinkage of Different Types of Composite Resins and Microleakage With and Without Liner in Class II Cavities

To determine the volumetric polymerization shrinkage of four different types of composite resin and to evaluate microleakage of these materials in class II (MOD) cavities with and without a resin-modified glass ionomer cement (RMGIC) liner, in vitro. One hundred twenty-eight extracted human upper premolar teeth were used. After the teeth were divided into eight groups (n=16), standardized MOD cavities were prepared. Then the teeth were restored with different resin composites (Filtek Supreme XT, Filtek P 60, Filtek Silorane, Filtek Z 250) with and without a RMGIC liner (Vitrebond). The restorations were finished and polished after 24 hours. Following thermocycling, the teeth were immersed in 0.5% basic fuchsin for 24 hours, then midsagitally sectioned in a mesiodistal plane and examined for microleakage using a stereomicroscope. The volumetric polymerization shrinkage of materials was measured using a video imaging device (Acuvol, Bisco, Inc). Data were statistically analyzed with Kruskal-Wallis and Mann-Whitney U-tests. All teeth showed microleakage, but placement of RMGIC liner reduced microleakage. No statistically significant differences were found in microleakage between the teeth restored without RMGIC liner (p>0.05). Filtek Silorane showed significantly less volumetric polymerization shrinkage than the methacrylate-based composite resins (p<0.05). The use of RMGIC liner with both silorane- and methacrylate-based composite resin restorations resulted in reduced microleakage. The volumetric polymerization shrinkage was least with the silorane-based composite.

Quantitative wear and wear damage analysis of composite resins in vitro

The aim of this study was to investigate volume loss and worn surfaces' morphologies of eight composite resins: Durafill VS (DUR), Clearfil AP-X (APX), Filtek Z250 (Z250), Filtek Supreme XT (FIL), Kalore (KAL), MI Flow (MFL), Venus Diamond (VED) and Venus Pearl (VEP). Disc-shaped specimens were fabricated and mounted in a ball-on-disc wear testing machine and abraded in water or with the third-body media, poppy seed slurry and polymethyl methacrylate (PMMA) slurry. Volume loss (n=5) was determined after 50k sliding cycles, and analyzed using two-way ANOVA (α=0.05). The worn surfaces were examined with SEM. Two-way ANOVA suggested significant interaction between composite and wear condition. DUR, KAL and MFL showed low wear in water. DUR, Z250 and FIL showed moderate wear with PMMA slurry, whereas APX, KAL and MFL were deeper abraded. Under the action of poppy seed slurry DUR proved high volume loss. SEM showed that Z250, FIL and MFL were uniformly abraded in water. KAL and MFL with poppy seed were heavily destructed, whereas VED and VEP appeared very smooth. KAL and MFL abraded with PMMA slurry showed many cracks, but VEP remained crack-free and smooth. Volume loss and worn surfaces' morphologies varied with type of composite and third-body media used.

Influence of chlorhexidine digluconate on the clinical performance of adhesive restorations: A 3-year follow-up

ObjectivesThe aim of this clinical study was to evaluate the long-term clinical performance of non-carious Class V restorations with and without application of chlorhexidine digluconate to acid-etched dentine. MethodsAfter the approval of the Ethics and Informed Consent Committee, 70 non-carious cervical lesions were selected and randomly assigned into two groups, according to the split mouth design. The control group was restored with a two-step etch-and-rinse adhesive (Adper Single Bond 2) following manufacturer's instructions; whereas in the experimental group 2% chlorhexidine digluconate solution was applied to acid etched dentine for 30s after etching and prior to the adhesive application. All lesions were restored with a nanofilled composite resin (Filtek Supreme XT) and polymerized with a light-curing unit operating at 600mW/cm2. Clinical performance was recorded after 1 week, 6, 12, and 36 months using modified Ryge/USPHS criteria in terms of retention, marginal discoloration, marginal integrity, post-operative sensitivity, and secondary caries incidence. Data were analyzed using Chi-Square, Fisher's exact test and McNemar tests (α=.05). ResultsAfter 36 months the control group showed a success rate of 88% in comparison to 76% of experimental group; however, no statistically difference between them was found (p=.463). Moreover, no statistical differences were observed between groups in the criteria post-operative sensitivity, marginal discoloration, marginal integrity, and secondary caries incidence between the two groups. ConclusionThe addition of 2% chlorhexidine digluconate conditioning step does not improve the clinical durability of adhesive restorations.

Fracture Resistance of Premolar Teeth Restored with Silorane‐Based or Dimethacrylate‐Based Composite Resins

To restore posterior teeth using low-shrinkage composite to minimize microleakage. To compare the fracture resistance of mesio-occlusal-distal (MOD) cavity preparations restored with either low-shrinkage composite or with dimethacrylate-based composite in conjunction with cavity liners and without them. The null hypothesis of the study is that there are no differences in either fracture resistance or fracture mode between the silorane group and dimethacrylate groups with and without the use of cavity liners. Sixty maxillary premolars were divided into six groups of 10. MOD cavities were prepared in four groups: F: posterior composite (Filtek P60); GF: 0.5-mm Glass Ionomer (Fuji LC) + posterior composite; FF: 0.5-mm flowable composite (Filtek Supreme XT) + posterior composite; and S: low-shrinkage composite (Filtek P90). Negative (N) and positive (P) control groups consisted of unrestored and sound teeth, respectively. The specimens were thermocycled and loaded. Data were analyzed using analysis of variance, Tukey, and chi-square tests (α = 0.05). Groups FF (1643.09 ± 187/80 N) and GF (1596.80 ± 163/93 N) (p = 0.06 > 0.05) were statistically identical, although less than group P (1742/33 ± 110/08 N), but still demonstrated greater fracture resistance than the other groups. The fracture resistance of group S (1434/69 ± 107/62 N) was identical to GF and FF (p = 0.06 > 0.05). The fracture resistance of F (1353/19 ± 233/90 N) was less than GF and FF, and statistically identical to S (p = 0.87 > 0.05). Silorane-based composite showed a resistance to fracture similar to methacrylate-based composite restorations regardless of whether cavity liners were used. The findings of this study support the selection of silorane-based composite for the restoration of maxillary premolars with standardized Class II cavity preparations in order to strengthen the resistance to fracture to the same extent as do dimethacrylate composites using cavity liners or without them.

Evaluation of cytotoxicity of six different flowable composites with the methyl tetrazolium test method

Abstract Background: The aim of this study was to investigate the cytotoxicity of six different flowable composites with the methyl tetrazolium test (MTT). Materials and Methods: For MTT, six different flowable composites (Bisco Aelite, Bisco Inc., USA; Esthet X Flow, Dentsply, USA; Filtek™ Supreme XT Flowable Restorative, 3M Espe, USA; Gradia ® Direct Flo, GC, USA; Estelite ® Flow Quick, Tokuyama Dental Corporation, Japan; and Clearfil Majesty Flow, Kuraray Medical Inc., Japan) were prepared according to the manufacturer’s instructions in standard Teflon disks (2 mm × 5 mm) and the samples were extracted in 7 ml of Basal Medium Eagle with 10% new born calf serum and 5% penicillin streptomycin gentamisin for 24 h. In the experiments: The L929 cells were plated (25.000 cells/ml) in wells of 96 well-dishes and maintained in a humidified incubator for 24 h at 37°C, 5% CO2, and 95% of air. After 24 h incubation of the cells, the incubation medium was replaced by the immersed medium in which the samples were stored. Then L929 cells were incubated in contact with evaluates for 24 h. The cell mitochondrial activity was evaluated by the MTT. 12 well used for each specimen and MTT tests applied 2 times. The data were submitted to the statistically analyzed by one-way ANOVA and Tukey’s honestly significant difference (HSD) tests. Results: According to the results of MTT test with L-929 fibroblasts demonstrated that all freshly prepared flowable composites did not reduce vital cell numbers (P&gt;0.05) in comparison to control group. Conclusion: This study revealed important information for clinical applications of flowable composites in dentistry.

A laboratory investigation of colour changes in two contemporary resin composites on exposure to spices

The aim of this study was to evaluate colour stability upon exposure to spices of a nano-filled and a micro-hybrid resin composite finished either with Sof-Lex™ discs (SLD) or against plastic strips (PS). Forty cylindrical specimens of 3mm thickness were fabricated from Filtek Supreme XT™ (FS) and Gradia Direct X™ (GD). The top surface of each specimen was polished with SLD while the bottom surface was finished against PS. All samples were immersed in staining solutions (0.1% weight turmeric, paprika and tamarind) and distilled water at 37°C. Colour after 0, 24, 72 and 168hours of immersion was recorded with a reflection spectrophotometer using CIE L*a*b* parameters and the results were statistically analysed with repeated measures of ANOVA and Bonferroni post hoc tests. Among all the staining solutions tested, the highest colour deviation was obtained in the turmeric group. FS finished against PS showed significantly more colour changes compared to specimens polished with SLD, while GD finished against PS were found to be more resistant to colour changes. Within the limitations of this study all the spices tested have the potential to stain resin composites with turmeric causing the most significant discolouration. Micro-hybrid and nano-filled resin composites appeared to respond differently to staining by spices when either finished with PS or polished with SLD.

Influence of light source and immersion media in surface roughness and hardness of a nanofilled composite resin

The study evaluated the influence of light curing units and immersion media on superficial roughness and microhardness of the nanofilled composite resin Supreme XT (3M/ESPE). Light curing units used were: XL 3000 (3M/ESPE), Jet Lite 4000 Plus (JMorita) and Ultralume Led 5 (Ultradent) and immersion media were artificial saliva, Coke®, tea and coffee, totaling 12 experimental groups. Specimens (10mm x 2mm) were immersed in each respective solution for 5 seconds, three times a day, during 60 days and so, were submitted to measure of superficial roughness (Ra) and Vickers hardness. Data were subjected to two-way ANOVA test (p&lt;0.05). Results showed that only the light source factor showed statistically difference for hardness. It was observed that the hardness of the composite resin Filtek Supreme XT (3M/ESPE) was influenced by the light source (p&lt;0.01) independently of the immersion media (p= 0.35) and the Jet Lite 4000 Plus (JMorita) was the light curing unit that presented lower values. In relation to surface roughness, it was noted no-significant statistical difference for light source (p=0.84), when specimens were immersed in different beverages (p=0.35).

Effect of sodium ascorbate on the bond strength of silorane and methacrylate composites after vital bleaching

We investigated the effect of sodium ascorbate (SA) on the microtensile bond strengths (MTBSs) of different composites to bovine enamel after vital bleaching with hydrogen peroxide (HP) or carbamide peroxide (CP). Thirty bovine incisors were randomly divided into five groups and treated with no bleaching application (control), 35% HP alone, 35% HP+10% SA for 10 minutes (HP+SA), 16% CP alone, or 16% CP+10% SA for 10 minutes (CP+SA). Specimens were restored with Silorane adhesive and Filtek Silorane composite (designated as S/group) or with Clearfil SE bond and Filtek Supreme XT (designated as F/group). Composite build-up was created on the enamel. Sectioned specimens (n=10 per group; 1 mm2; cross-sectional area) were created and stressed in a universal testing machine at 1 mm/min crosshead speed. The application of 10% SA immediately after bleaching with 16% CP or 35% HP increased the enamel MTBS, regardless of the adhesive/composite resin used. The resulting MTBS values were similar to those of the control groups. Use of 16% CP and 35% HP alone decreased the enamel MTBS, regardless of the adhesive/composite resin used, with F/CP+SA=F/HP+SA=F/CP=S/CP+SA=S/HP+SA=S/C>S/CP=S/HP=F/CP=F/HP (p<0.05). We concluded that the application of SA for 10 minutes immediately after vital bleaching increases the enamel BS for dimethacrylate- and silorane-based composites.

Shrinkage kinetics of a methacrylate- and a silorane-based resin composite: effect on marginal integrity.

To evaluate the relation between the linear displacement (LD), shrinkage force (SF) and marginal adaptation of a methacrylate- and a silorane-based composite. The LD and SF of 8 samples made of Filtek Supreme XT (methacrylate-based composite) and Filtek Silorane (silorane-based composite) were measured for 180 s from the start of polymerization. Large bulk-filled Class I cavities were restored with both resin composites, and two C-factors were simulated by applying the same adhesive system in different ways: the Silorane System Adhesive (SSA) was applied on enamel and dentin (C-factor 3.5) or only on enamel margins (C-factor of 0.4). Percentages of continuous margins (%CM) were quantitatively assessed with SEM before and after simultaneously loading with 1.2 million mechanical occlusal cycles (49 N; 1.7 Hz) and 3000 thermal cycles (5°C to 50°C) under dentinal fluid simulation. Significantly lower scores of LD and SF were observed for Filtek Silorane (LD: 12.0 µm ± 1.3, SF: 13.7 N ± 1.0) than for Filtek Supreme XT (LD: 25.0 µm ± 0.6, SF: 36.3 N ± 2.9). Both variables, ie, composite type and C-factor, had a significant effect on marginal adaptation (p < 0.05). In the groups with high C-factor (SSA was applied on the entire cavity surface) percent of continuous margin (%CM) (mean ± SD) before and after loading, respectively, was 24.4 ± 16.6 and 2.1 ± 2.4 for Filtek Supreme XT, and 58.8 ± 9.9 and 35.4 ± 4.1 for Filtek Silorane. When adhesion was confined to enamel margins (lower C-factor), %CM before and after loading, respectively, increased to 76.1 ± 9.6 and 64.2 ± 11.5 for Filtek Supreme XT, and 96.6 ± 1.7 and 94.2 ± 2.1 for Filtek Silorane. The silorane-based composite exhibited significantly lower shrinkage forces and better marginal adaptation than did the methacrylate-based composite.

Influence of Adhesive Application Methods and Rebonding Agent Application on Sealing Effectiveness of All‐in‐One Self‐Etching Adhesives

The choice of adhesive application methods could affect the microleakage of self-etch adhesives. To evaluate the effect of acid-etching, doubling adhesive application time, doubling adhesive coating, and rebonding agent application on microleakage of self-etch adhesives in Class V cavities. Seventy human third molars with Class V cavities assigned to five groups according to different adhesive application protocols for the three dentin adhesives (Clearfil S3 Bond, Kuraray Medical, Okayama, Japan; Optibond All-in-One, Kerr Corporation Orange, CA, USA; G-Aenial Bond, GC Corporation, Tokyo, Japan): group 1, manufacturer's recommendations; group 2, prior acid-etching of cavities; group 3, double application time; group 4, two consecutive coats of the adhesives; group 5, rebonding application on restoration margins. After bonding, the cavities were filled with a resin composite (Filtek Supreme XT, 3M ESPE Dental Products, St. Paul, MN, USA). The teeth were thermocycled, and the specimens were examined for microleakage using methylene blue as a marker. For Clearfil S3 Bond and Optibond All-in-One, microleakage in groups 2 and 5 were significantly lower than other groups' enamel margins. In groups 1, 2, 4, and 5, Clearfil S3 Bond exhibited significantly more leakage than the other dentin bonding agents in dentin margins. Microleakage was significantly higher on dentinal margins compared with the enamel margins for Clearfil S3 Bond in all of the groups. Optibond All-in-One showed significantly lower microleakage in dentin margins in all groups except groups 2 and 5. Acid-etching usually promoted the reduction of microleakage in enamel margins. On the other hand, rebonding application usually contributed to the reduction of microleakage more than other methods in enamel and dentin margins. Acid-etching or rebonding application may contribute to reduction of microleakage of all-in-one self-etching adhesives.

Clinical Performance of Ormocer, Nanofilled, and Nanoceramic Resin Composites in Class I and Class II Restorations: A Three-year Evaluation

This prospective long-term clinical trial evaluated and compared the three-year clinical performance of an ormocer, a nanofilled, and a nanoceramic resin composite with that of a microhybrid composite placed in Class I and Class II cavities. Forty patients, each with four Class I and II restorations under occlusion, were enrolled in this study. A total of 160 restorations were placed, 25% for each material, as follows: an ormocer-based composite, Admira; a nanofilled resin composite, Filtek Supreme XT; a nanoceramic resin composite, Ceram X; and a microhybrid resin composite, Tetric Ceram. A single operator placed all restorations according to the manufacturers' instructions. Immediately after placement the restorations were finished/polished. Clinical evaluation was performed at baseline and at yearly intervals after placement by two other independent examiners using modified US Public Health Service (USPHS) criteria. The changes in the USPHS parameters during the three-year period were analyzed with the Friedman test. Comparison of the baseline scores with those at the recall visits was made using the Wilcoxon signed rank test. The level of significance was set at p < 0.05. All materials showed only minor changes, and no differences were detected between their performance at baseline and after three years. Only two ormocer, one nanofilled, and one microhybrid restorations in molars failed because of loss of retention. Regarding the clinical performance, there were no statistically significant differences among the materials used (p>0.05). The ormocer, nanofilled, and nanoceramic composites provided acceptable clinical performance over a three-year period.

Influence of screw access on the retention of cement-retained implant prostheses

Many studies have compared cement-retained and screw-retained implant prostheses. One disadvantage of cement-retained crowns is the lack of predictable retrievability, which can be overcome by creating a screw access channel on the occlusal surface. The purpose of this study was to evaluate the influence of a screw access channel on the retention of cement-retained implant prostheses. Sixteen cast metal crowns were fabricated and divided into 2 groups of 8 specimens each: a control group (CG) comprising 8 cement-retained prostheses and an experimental group (EG) comprising 8 cement-retained prostheses with a screw access channel. Castings were cemented to abutments with RelyX U100, and the opening screw access channels of EG were filled with photopolymerized composite resin (Filtek Supreme XT). The tensile force required to separate the cemented castings from the abutments was measured after 24 hours of cementation with a universal load-testing machine (EMIC DL 2000). A significance level of 5% (α=.05) was considered statistically significant (Statistical analysis was performed by Kolmogorov-Smirnov non-parametric test and the Student t test). The mean force required to achieve the separation was 191 N for the control group (CG) and 161 N for the experimental group (EG). As shown by the nonparametric Kolmogorov-Smirnov test, the dependent variable followed a normal distribution (P=.923). The Student t test found no statistically significant difference (P=.353) between the groups. Fabricating cement-retained implant prostheses with screw access does not compromise or reduce the retention of the crowns.