The Effect of Thermocycling on Interfacial Bonding Stability of Self-Etch Adhesives: OCT Study.

OBJECTIVE: The aim of this study was to monitor the behavior of interfacial gaps formed under different bonded polymeric restorations before and after thermocycling (TC), using swept-source optical coherence tomography (SS-OCT) and confirming the obtained findings with confocal laser scanning microscopy (CLSM). MATERIALS AND METHODS: Cylindrical class I cavities were prepared in twenty noncarious human premolar teeth (1.5 mm depth × 3.5 mm diameter) and divided randomly into two groups: TS and SN, according to the adhesive system (n = 10). In the TS group, one-step self-etch adhesive Clearfil Tri-S Bond Plus (Kuraray Noritake Dental, Japan) was used, followed by composite restoration using Estelite Sigma Quick (Tokuyama Dental, Japan). In the SN group, the cavities were restored with the two-step self-etch/composite silorane-based resin restoration system (3M ESPE, USA). All specimens were restored in bulk filling technique and cured in accordance with the manufacturers' instructions. Both groups were imaged under SS-OCT after 24 h and recorded as controls. Then, each group was subjected to thermal challenge using the TC machine (5-55°C) and B-scans were recorded at different TC intervals (2600, 5200, and 10000). In order to confirm the SS-OCT findings, additional specimens were prepared, scanned, and sectioned for CLSM observation. RESULTS: B-scans demonstrated white clusters at the tooth-resin interface that corresponded to the gap location on CLSM images. The TS group showed significantly less gap formation than the SN group before and after TC (p < 0.001). CONCLUSIONS: An optimal composite adaptation can be achieved when the bonded restoration comprises a combination of an adhesive containing 10-MDP monomer and a considerable highly filled composite.

Mechanical Degradation of Different Classes of Composite Resins Aged in Water, Air, and Oil.

A significant deterioration of the properties can drastically compromise the survival rate of restorative materials. The aim of this study was to assess flexural strength and hardness of three composite classes: hybrid composite resin (HCR), nanoparticulate composite resin (NCR), and silorane-based composite resin (SBCR). One hundred specimens were prepared for hardness testing by using a split metallic mold measuring 10 mm in diameter and 2 mm deep. Twenty specimens were prepared for each restorative material, randomly assigned for storage in air, distilled water, or mineral oil. After intervals of 24 hours, 30, 60, 90, and 120 days, hardness and flexural strength tests were initially compared in two levels: "storage medium" and "time" within each material group. A two-way analysis of variance was performed (p<0.05) on the variables "material" and "storage time" (p<0.05). The HCR showed to be stable with regard to the evaluation of flexural strength and hardness (p<0.05). A significant reduction occurs for the NCR in comparison to the other groups (p<0.05). The NCR presented the lowest values of hardness and flexural strength kept on water over time. The characteristics of material showed a strong influence on the decrease of the mechanical properties analyzed.

Influence of surface treatment on the performance of silorane-based composite resin in class I restorations: a randomized clinical trial.

OBJECTIVES: The aim of this study was to evaluate the clinical performance of silorane-based composite restorations applied after different surface treatments. MATERIALS AND METHODS: This controlled and randomized clinical trial included 26 patients with class I restoration indications. The teeth were randomly assigned to the following treatments: control 1/G1, silorane specific self-etching adhesive (P90 self-etch primer and bond) + silorane-based composite resin (Filtek™ P90 low shrink posterior restorative); G2, 37% phosphoric acid + silorane specific self-etching adhesive + silorane-based composite resin; G3, blasting with aluminum oxide + silorane specific self-etching adhesive + silorane-based composite resin; and control 2/G4, self-etching adhesive (Adper™ SE Plus self-etch adhesive) + dimethacrylate-based composite resin (Filtek™ P60 posterior restorative). The clinical performance was evaluated at baseline and after 1 year. RESULTS: A total of 141 restorations were made and evaluated. For all clinical criteria evaluated, no significant difference was found between the surface treatments at baseline and after 1 year (p > 0.05). After 1 year, only the group with 37% phosphoric acid + silorane specific self-etching adhesive (G2) showed a significant reduction in marginal adaptation (p < 0.05). CONCLUSION: In general, all surface treatments showed an adequate clinical performance for silorane-based composite resin in class I restorations. However, a reduction in the marginal adaptation after 1 year was found when additional phosphoric acid etching was used prior to silorane specific self-etching adhesive. CLINICAL RELEVANCE: The use of phosphoric acid etching prior to specific self-etching adhesive can adversely affect the marginal adaptation of silorane-based restorations.

Effect of food simulating liquids on the flexural strength of a methacrylate and silorane-based composite.

OBJECTIVE: The purpose of this study was to assess the effect of food-simulating liquids on the flexural strength of a methacrylate-based and a silorane-based resin composite. MATERIALS AND METHODS: In this in vitro study, sixty specimens of Filtek P90 and Filtek Z350 composite were prepared in a customized mold (2 × 2 × 25 mm). The specimens of each composite were divided into five subgroups as follows: one as a control group and the other four groups included distilled water, heptane, 2% citric acid, and 50% aqueous ethanol. The specimens were stored in the solutions for one week at 37°C, and the control group was stored at room temperature for the same period of time. Then, flexural strength values were measured. The statistical analysis was performed by One-Way ANOVA, Paired T test and post hoc LSD at a significance level of 0.05. RESULTS: In the control group, the mean flexural strength of Filtek P90 and Filtek Z350 were 155.1 MPa and 147.3 MPa, respectively, and there was no significant difference (P-value>0.05). The mean flexural strength of Filtek P90 and Filtek Z350 significantly decreased in ethanol (P-value <0.05). Immersion in 0.02 N citric acid and heptane had no significant effect on the flexural strength of Filtek P90 and Filtek Z350. The maximum flexural strength of Filtek P90 was in the heptane group (192.6 MPa) and minimum flexural strength was in ethanol group (92.7 MPa) the maximum flexural strength of Filtek Z350 was in the heptane group (163.2 MPa) and minimum flexural strength was in the ethanol group (104.7 MPa). CONCLUSION: The flexural strength of tested resin composites significantly affected by ethanol solution. The flexural strength of resin composites was not affected by other food simulating liquids.

Surface Roughness of Methacrylate- and Silorane-Based Composites After Finishing and Polishing Procedures.

OBJECTIVE: To compare the effect of surface finishing and polishing protocols on the surface roughness (Ra) of methacrylate-based and silorane-based resin composites. METHODS AND MATERIALS: Fifty specimens (5 mm x 2 mm) of each composite material were prepared using a split mold: Filtek™ Supreme Ultra (3M ESPE), Tetric EvoCeram® (Ivoclar Vivadent), Tetric Ceram™ HB (Ivoclar Vivadent), and Filtek™ LS Low Shrink (3M ESPE). Specimens were divided into five groups (n = 10) according to the following procedures: G1 - 15-µm fine diamond bur (FDB); G2 - 15-µm FDB followed by a 20-fluted tungsten carbide bur; G3 - 15-µm FDB followed by diamond-impregnated micropolishing points (D-FINE Double Diamond Polishing System, Clinician's Choice); G4 - 15-µm FDB followed by diamond-impregnated micropolishing points (Flame Point Pre-polisher and Shine, Brassseler USA); and G5 - 15-µm FDB followed by the application of a surface sealer (PermaSeal®, Ultradent Products, Inc.). Ra was measured in three different regions using a surface profilometer (Mitutoyo Surfest SJ-210, Mitutoyo America). RESULTS: Multiple comparisons were obtained using a one-way ANOVA with Tukey's B rank order test ( = 0.05). No significant differences in Ra were observed among the resin composites tested in the same condition. The use of a FDB generated the highest roughness values, while the use of a surface sealer resulted in the lowest roughness values for all resin composites tested (P < .05). No significant difference in Ra was observed between the use of a multi-fluted carbide bur and the rubber point D-FINE Double Diamond Polishing System for all resin composites tested.

Clinical Evaluation of a Silorane- and a Methacrylate-Based Resin Composite in Class II Restorations: 24-Month Results.

OBJECTIVE: To compare the 24-month clinical performance of two different resin composites in class II slot restorations. METHODS AND MATERIALS: Thirty-seven patients having at least two approximal carious lesions were enrolled in the study. A total of 116 teeth (58 pairs) were restored with either a silorane-based composite (Filtek Silorane) and its self-etch adhesive (Silorane Adhesive System, 3M ESPE) or a methacrylate-based packable resin composite (X-tra Fil) and its self-etch adhesive (Futurabond NR, VOCO GmbH) according to the toss of a coin. The restorations were evaluated at baseline and at six-, 12-, and 24-month recalls by two calibrated examiners according to the modified US Public Health Service criteria. The comparison of the two restorative materials for each category was performed with the Pearson chi-square test. Within group differences of the materials at different recall times were compared using the Cochran Q and Friedman tests. Bonferroni-adjusted McNemar test was used when significant difference was found (p<0.05). RESULTS: After 24 months, no statistically significant differences were found between the two restorative materials for the criteria evaluated. CONCLUSIONS: Both silorane- and methacrylate-based resin composites showed clinically acceptable performance in class II slot restorations after 24 months.

Effect of timing of repair on repair bond strength of methacrylate- and silorane-based composite resins.

Successful repair of defective composite resin restorations is considered a conservative treatment. The aim of this study was to compare the repair bond strengths of a methacrylate composite (MC) and a silorane composite (SC) repaired after 5 different intervals. Seventy-two test specimens of each material (MC and SC) were prepared. The specimens of each material were divided into 6 groups (n = 12): 1, control (additional composite bonded immediately after polymerization of the substrate composite resin); 2, repaired after 20 minutes; 3, repaired after 24 hours; 4, repaired after 1 week; 5, repaired after 1 month; and 6, repaired after 6 months. Repair consisted of placement of a layer of adhesive bonding agent and then new composite using a plastic mold. Each repair was made with the same material as the original specimen but in a different shade to facilitate fracture assessment. The repaired specimens were stored in distilled water at 37°C for 24 hours before they were submitted to a shear test. There was no statistically significant difference between group MC1 and the other MC groups, except for group MC4, which had lower shear bond strength (SBS) values than groups MC1, MC2, and MC3. Among the SC specimens, all the groups had significantly lower SBS values than group SC1. The mean SBS values of groups SC4, SC5, and SC6 were significantly lower than the SBS of group SC2. All the SC repair time groups presented significantly lower SBS values compared to their corresponding MC groups (P ≤ 0.004). The results showed that the repair bond strength of SC was adversely affected at all time periods, while this effect was not detected for MC groups except for group MC4. The SC material exhibited less repairability than the MC material.

An approach to understanding tribological behaviour of dental composites through volumetric wear loss and wear mechanism determination; beyond material ranking.

OBJECTIVE: To investigate the fundamental wear mechanisms of six resin-based composite (RBC) formulations during short-term in vitro wear testing. MATERIALS: RBC materials were condensed into rectangular bar-shaped specimens and light irradiated using the ISO 4049 specimen manufacture and irradiation protocol. Wear testing (n=10 specimens for each RBC) was performed on a modified pin-on-plate wear test apparatus and wear facets were analysed for wear volume loss using a white light profilometer. The wear tested RBC specimens and their corresponding antagonists were analysed using scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS), respectively to determine the wear mechanism. RESULTS: Data generated using the profilometer showed variations in the mean total wear volume (mm3) between the RBCs tested (p<0.05). Abrasive wear was evident in all RBCs investigated with varying degrees of damage. Material transfer/deposition of the filler particles on the corresponding antagonists was evident in two RBC materials (Filtek Supreme and Kalore) indicative of a further adhesive wear mechanism. CONCLUSION: It is proposed that the approach employed to use a combination of measurement and analytical techniques to quantify the wear facet volume (profilometry), wear trough (SEM) and material transfer (EDS) provides more useful information on the wear mechanism and the tribology of the system rather than relying on a simple wear ranking for the RBC materials as is routinely the case in dental research studies.

Effect of decontamination on micro-shear bond strength of silorane-based composite increments.

AIM: The aim of the present study was to evaluate the micro-shear bond strength of silorane-based composites after saliva/blood decontamination. METHODS: A transparent mold (1 × 2 × 1 cm) was used to make 11 flat, silorane-based composite blocks. One block served as the control. After contamination, the blocks were treated as follows: group 1: 10-s air spray; group 2: 10-s water spray + 10-s air spray; group 3: 10-s water spray + 10-s air spray + 10-s etching with phosphoric acid; group 4: 10-s air spray + 10-s etching + bonding; group 5: 10-s water spray + 10-s air spray + 10-s etching + bonding; and groups 6-10: treated the same as groups 1-5, the only difference being that blood was used instead of saliva. Ten tubes (0.7 mm × 1 mm) containing silorane-based composites were attached to each decontaminated block and light cured for 40 s. After 24-h storage in distilled water, specimens were tested under micro-shear loading at a cross-head speed of 0.5 mm/min. Data were analyzed using one-way anova and Tukey's honest significant difference (HSD) test (P < 0.05). RESULTS: One-way anova showed significant differences in the micro-shear bond strength among the experimental groups (P < 0.001). Tukey's HSD test revealed that the bond strengths in groups 5, 9, and 10 were similar to the control group (P > 0.05). CONCLUSION: Decontamination by water and air spray, etching, and bonding was effective in restoring the bond strength of silorane-based composite increments.

Effect of preheating and shade on surface microhardness of silorane-based composites.

AIM: The aim of the present study was to evaluate the effect of preheating and shade on the surface microhardness of silorane-based composites. METHODS: Three shades of two different types of composites were evaluated: a silorane-based composite and a methacrylate-based composite. The composites were tested at 23°C, and after preheating at 55°C. Five specimens were prepared for each experimental group. The top surface of the specimens was irradiated for 20 s using an LED unit. Vickers microhardness test was used to evaluate both top and bottom surfaces of the specimens, followed by 24-h storage in the dark. Statistical analysis was performed using one-way anova and Tukey's post-hoc test at a level of significance of α = 0.05. RESULTS: There was a significant rise in microhardness as the temperature increased from 23 to 55°C for both the top and bottom surfaces of the tested composites (P < 0.05). The C2 shade of both composites exhibited the lowest microhardness (P < 0.05), while the A2 and A3 shades did not show significant differences compared to each other (P > 0.05) Filtek Silorane presented significantly lower microhardness than Filtek Z250 (P < 0.05), regardless of the temperature, shade, or depth of measurement. CONCLUSIONS: Preheating, shade, and composition of the tested composite resins affected their surface microhardness.

Low Shrinkage Silorane Composites.

Polymerization shrinkage of methacrylate composites utilizing bisphenol-A glycidal methacylate or urethane dimethacrylate has typically been about 3-3.5% by volume. Though adjustments have been made to filler loading, filler size, filler particle distribution, and improved silanization, the polymerization contraction still creates some significant clinical problems. A new composite utilizing a completely different chemistry has been released, with polymerization shrinkage of less than one percent. This article will review the clinical effects of polymerization contraction of composite resins, the nature and properties of this chemical form of composite, and potential clinical applications.

The Silorane-based Resin Composites: A Review.

This article aims to review the research done on the silorane-based resin composites (SBRC) regarding polymerization shrinkage and contraction stresses and their ability to improve the shortcomings of the methacrylate-based resin composites (MRBC). Special attention is given to their physical and mechanical properties, bond strength, marginal adaptation, and cusp deflection. The clinical significance of this material is critically appraised with a focus on the ability of SBRC to strengthen the tooth structure as a direct restorative material. A search of English peer-reviewed dental literature (2003-2015) from PubMed and MEDLINE databases was conducted with the terms "low shrinkage" and "silorane composites." The list was screened, and 70 articles that were relevant to the objectives of this work were included.

Marginal integrity of low-shrinking versus methacrylate-based composite: effect of different one-step self-etch adhesives.

The aim of the study was to evaluate the influence of composite type and adhesive system on the quality of marginal adaptation in standardized Class V cavities before and after thermo-mechanical loading (TML). The cavities were restored using different combinations of three adhesive systems [(Silorane System Adhesive (SSA), Clearfil S3 Bond (S3), G-Bond (G-B)] and two resin composite materials (Filtek Silorane, Clearfil AP-X). Six groups (n = 10): Group A (SSA-Primer + SSA-Bond, Filtek Silorane), Group B (SSA-Primer + SSA-Bond, Clearfil AP-X), Group C (S3 + SSA-Bond, Filtek Silorane), Group D (S3 + SSA-Bond, Clearfil AP-X), Group E (G-B + SSA-Bond, Filtek Silorane) and Group F (G-B + SSA-Bond, Clearfil AP-X) were defined. Marginal adaptation was assessed on replicas in the SEM at 200 × magnification before and after TML (3000 × 5-55 °C, 1.2 106 × 49 N; 1.7 Hz) under simulated dentinal fluid. The highest scores of continuous margins (%CM) were observed in the group F (G-B + SSA-Bond, Clearfil AP-X: before loading 96.4 (±3.2)/after loading 90.8 (±7.0)). A significant effect of adhesive system, composite type and loading interval was observed on the results (p < 0.05). Significantly lower scores of %CM were observed for silorane-based composite (Filtek Silorane) after TML in comparison with methacrylate-based composite (Clearfil AP-X) considering total marginal length (p < 0.05). For both Filtek Silorane and Clearfil AP-X, G-Bond performed significantly better than SSA-Primer and Clearfil S3 Bond (p < 0.05). For all combinations of one-step self-etch adhesives and SSA-Bond resin coating, silorane-based low-shrinking composite exhibited inferior marginal adaptation than did the methacrylate-based composite.

Repair Strength in Simulated Restorations of Methacrylate- or Silorane-Based Composite Resins.

The study verified the bond strength in simulated dental restorations of silorane- or methacrylate-based composites repaired with methacrylate-based composite. Methacrylate- (P60) or silorane-based (P90) composites were used associated with adhesive (Adper Single Bond 2). Twenty-four hemi-hourglass-shaped samples were repaired with each composite (n=12). Samples were divided according to groups: G1= P60 + Adper Single Bond 2+ P60; G2= P60 + Adper Single Bond 2 + P60 + thermocycling; G3= P90 + Adper Single Bond 2 + P60; and G4= P90 + Adper Single Bond 2 + P60 + thermocycling. G1 and G3 were submitted to tensile test 24 h after repair procedure, and G2 and G4 after submitted to 5,000 thermocycles at 5 and 55 ?#61616;C for 30 s in each bath. Tensile bond strength test was accomplished in an universal testing machine at crosshead speed of 0.5 mm/min. Data (MPa) were analyzed by two-way ANOVA and Tukey's test (5%). Sample failure pattern (adhesive, cohesive in resin or mixed) was evaluated by stereomicroscope at 30?#61655; and images were obtained in SEM. Bond strength values of methacrylate-based composite samples repaired with methacrylate-based composite (G1 and G2) were greater than for silorane-based samples (G3 and G4). Thermocycling decreased the bond strength values for both composites. All groups showed predominance of adhesive failures and no cohesive failure in composite resin was observed. In conclusion, higher bond strength values were observed in methacrylate-based resin samples and greater percentage of adhesive failures in silorane-based resin samples, both composites repaired with methacrylate-based resin.

Repair Strength in Simulated Restorations of Methacrylate- or Silorane-Based Composite Resins

Abstract The study verified the bond strength in simulated dental restorations of silorane- or methacrylate-based composites repaired with methacrylate-based composite. Methacrylate- (P60) or silorane-based (P90) composites were used associated with adhesive (Adper Single Bond 2). Twenty-four hemi-hourglass-shaped samples were repaired with each composite (n=12). Samples were divided according to groups: G1= P60 + Adper Single Bond 2+ P60; G2= P60 + Adper Single Bond 2 + P60 + thermocycling; G3= P90 + Adper Single Bond 2 + P60; and G4= P90 + Adper Single Bond 2 + P60 + thermocycling. G1 and G3 were submitted to tensile test 24 h after repair procedure, and G2 and G4 after submitted to 5,000 thermocycles at 5 and 55 ?#61616;C for 30 s in each bath. Tensile bond strength test was accomplished in an universal testing machine at crosshead speed of 0.5 mm/min. Data (MPa) were analyzed by two-way ANOVA and Tukey's test (5%). Sample failure pattern (adhesive, cohesive in resin or mixed) was evaluated by stereomicroscope at 30?#61655; and images were obtained in SEM. Bond strength values of methacrylate-based composite samples repaired with methacrylate-based composite (G1 and G2) were greater than for silorane-based samples (G3 and G4). Thermocycling decreased the bond strength values for both composites. All groups showed predominance of adhesive failures and no cohesive failure in composite resin was observed. In conclusion, higher bond strength values were observed in methacrylate-based resin samples and greater percentage of adhesive failures in silorane-based resin samples, both composites repaired with methacrylate-based resin.

Resumo O objetivo neste estudo foi verificar a resistência de união em restaurações simuladas de compósitos baseados em metacrilato ou silorano reparadas com compósito à base de metacrilato. Compósitos baseados em metacrilato (Filtek P60; 3M ESPE) ou silorano (Filtek P90; 3M ESPE) foram associados com adesivo (Adper Single Bond 2; 3M ESPE). Vinte e quatro amostras em forma de semi-ampulhetas foram reparadas com cada material (n=12), conforme os grupos experimentais: G1- P60 + Adper Single Bond 2 + P60; G2- P60 + Adper Single Bond 2 + P60 + termociclagem; G3- P90 + Adper Single Bond 2 + P60; e G4- P90 + Adper Single Bond 2 + P60 + termociclagem. Os grupos G1 e G3 foram submetidos ao ensaio de tração após 24 horas do procedimento de reparo e os grupos G2 e G4 depois de submetidos a 5.000 ciclos térmicos de 5 e 55 ?#61616;C por 30 s em cada banho. O teste de resistência à tração foi efetuado em máquina universal atuando numa velocidade de 0,5 mm/min. Os dados (MPa) foram submetidos a ANOVA a dois fatores e teste de Tukey (5%). O padrão de fratura das amostras (adesivo, coesivo em resina ou misto) foi avaliado em estereomicroscópio com aumento de 30x e imagens representativas foram obtidas em MEV. Os valores de resistência à tração das amostras feitas com compósito à base de metacrilato e reparadas com compósito à base de metacrilato (G1 e G2) foram maiores do que nas amostras feitas com compósito à base de silorano e reparadas nas mesmas condições (G3 e G4). A termociclagem diminuiu os valores de resistência à tração para ambos os compósitos. Todos os grupos mostraram predominância de fraturas adesivas e nenhuma falha coesiva foi observada em compósito. Em conclusão, valores maiores de resistência à tração foram observados em amostras de resina à base de metacrilato e maior porcentagem de fraturas adesivas nas amostras de resina à base de silorano, ambos os compósitos reparados com resina à base de metacrilato.

Effect of filling technique on the bond strength of methacrylate and silorane-based composite restorations.

The bond strength of methacrylate (Z350, 3M ESPE) and silorane (P90, 3M ESPE) restorations, using different cavity filling techniques, was investigated. Cavities (6 × 3 × 3) in bovine teeth were filled using bulk, oblique, or horizontal increments. A push-out test was carried out after 24 h. Data were statistically analyzed (α = 5%). Methacrylate-based composites and the horizontal filling technique showed the highest bond strength values (10.2 ± 3.9, p < 0.05). Silorane-based composites showed no statistically significant differences regarding the filling techniques (p > 0.05).

Mechanical properties of silorane-based and methacrylate-based composite resins after artificial aging.

The aim of this study was to compare the compressive strength of a silorane-based composite resin (Filtek P90) to that of conventional composite resins (Charisma, Filtek Z250, Fill Magic, and NT Premium) before and after accelerated artificial aging (AAA). For each composite resin, 16 cylindrical specimens were prepared and divided into 2 groups. One group underwent analysis of compressive strength in a universal testing machine 24 hours after preparation, and the other was subjected first to 192 hours of AAA and then the compressive strength test. Data were analyzed by analysis of variance, followed by the Tukey HSD post hoc test (α = 0.05). Some statistically significant differences in compressive strength were found among the commercial brands (P < 0.001). The conventional composite resin Fill Magic presented the best performance before (P < 0.05) and after AAA (P < 0.05). Values for compressive strength of the silorane-based composite were among the lowest obtained, both before and after aging. Comparison of each material before and after AAA revealed that the aging process did not influence the compressive strength of the tested resins (P = 0.785).

Influence of Cavity Margin Design and Restorative Material on Marginal Quality and Seal of Extended Class II Resin Composite Restorations In Vitro.

PURPOSE: To investigate the influence of three cavity designs on the marginal seal of large Class II cavities restored with low-shrinkage resin composite limited to the enamel. MATERIALS AND METHODS: One hundred twenty (120) intact human molars were randomly divided into 12 groups, with three different cavity designs: 1. undermined enamel, 2. box-shaped, and 3. proximal bevel. The teeth were restored with 1. an extra-low shrinkage (ELS) composite free of diluent monomers, 2. microhybrid composite (Herculite XRV), 3. nanohybrid composite (Filtek Supreme XTE), and 4. silorane-based composite (Filtek Silorane). After artificial aging by thermocycling and storage in physiological saline, epoxy resin replicas were prepared. To determine the integrity of the restorations' approximal margins, two methods were sequentially employed: 1. replicas were made of the 120 specimens and examined using SEM, and 2. the same 120 specimens were immersed in AgNO3 solution, and the dye penetration depth was observed with a light microscope. Statistical analysis was performed using the Kruskal-Wallis and the Dunn-Bonferroni tests. RESULTS: After bevel preparation, SEM observations showed that restorations did not exhibit a higher percentage of continuous margin (SEM-analysis; p>0.05), but more leakage was found than with the other cavity designs (p<0.05). The lowest percentage of continuous margin was observed in ELS restorations (p<0.05). More fractured margins were observed in the undermined enamel cavity design groups (p<0.05). CONCLUSION: Bevel preparation failed to improve margin quality in large Class II composite restorations and is no longer recommended. However, undermined enamel should be removed to prevent enamel fractures.

Correlation of elution and sensitivity of cell lines to dental composites.

OBJECTIVES: The aim of the present study was to understand the role played by composition on the elution of dental composites and the subsequent cytotoxicity, the sensitivity of different cell lines to eluates on a temporal basis and the correlation of the two parameters elution and cytotoxicity. METHODS: LC-MS was done to analyze the eluates. MTT assay was done to assess cytotoxicity on two cell lines. RESULTS: Eluates were found to have matrix monomers, photoinitiators and their degradation products. The short-term viability of other mammalian cell line was inferior to human cell line. However human cell line became more sensitive to long-term incubation with composites. There was a strong inverse correlation to elution of monomers and photoinitiators and cell viability for both cell lines. Bisphenol A elution did not correlate to cell viability. SIGNIFICANCE: Other mammalian cell lines may be more sensitive to acute toxin build-up than human cell line while the latter may be more sensitive to prolonged toxin exposure. Dimethacrylate based composites elute more and exert strong cytotoxicity than Ormocer and Silorane based composites. Most of the eluates correlated linearly to cytotoxicity.

Effects of age condition on the distribution and integrity of inorganic fillers in dental resin composites.

OBJECTIVES: The aim of this study is to evaluate the distribution of the filler size along with the zeta potential, and the integrity of silane-bonded filler surface in different types of restorative dental composites as a function of the material age condition. MATERIALS AND METHODS: Filtek P60 (hybrid composite), Filtek Z250 (small-particle filled composite), Filtek Z350XT (nanofilled composite), and Filtek Silorane (silorane composite) (3M ESPE) were tested at different stage condition (i.e., fresh/new, aged, and expired). Composites were submitted to an accelerated aging protocol (Arrhenius model). Specimens were obtained by first diluting each composite specimen in ethanol and then dispersed in potassium chloride solution (0.001 mol%). Composite fillers were characterized for their zeta potential, mean particle size, size distribution, via poly-dispersion dynamic light scattering. The integrity of the silane-bonded surface of the fillers was characterized by FTIR. RESULTS: The material age influenced significantly the outcomes; Zeta potential, filler characteristics, and silane integrity varied both after aging and expiration. Silorane presented the broadest filler distribution and lowest zeta potential. Nanofilled and silorane composites exhibited decreased peak intensities in the FTIR analysis, indicating a deficiency of the silane integrity after aging or expiry time. CONCLUSION: Regardless to the material condition, the hybrid and the small-particle-filled composites were more stable overtime as no significant alteration in filler size distribution, diameter, and zeta potential occurred. A deficiency in the silane integrity in the nanofilled and silorane composites seems to be affected by the material stage condition. CLINICAL SIGNIFICANCE: The materials conditions tested in this study influenced the filler size distribution, the zeta potential, and integrity of the silane adsorbed on fillers in the nanofilled and silorane composites. Thus, this may result in a decrease of the clinical performance of aforementioned composites, in particular, if these are used after inappropriate storage conditions.