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.

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.

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.

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.

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.

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 organic acids present in oral biofilm on the durability of the repair bond strength, sorption and solubility of resin composites

PURPOSE

To evaluate the repair bond strength after storage in water, lactic and propionic acid after 7 days and 6 months and the sorption and solubility of resin composites used.

METHODS

Five cylinders of each resin composite (microhybrid, nanofilled and silorane-based composite) were prepared. Specimens were aged with thermocycling (5 and 55°C) 5,000 times. A repair procedure was performed using intraoral sandblasting with 50-µm aluminum oxide, application of an adhesive system and cylinder of composite was fabricated. Specimens were sectioned into beams and stored in three immersion media: water, propionic acid and lactic acid. The microtensile bond strength was measured after periods of 7 days and 6 months. Sorption and solubility were evaluated using 15 specimens (0 = 6 mm; h = 1 mm) of each resin composite, which were prepared and assigned into three groups (n = 5) according to the immersion media (water, propionic acid and lactic acid). Data were analyzed using one-way/two-way/three-way ANOVA and Tukey's test (α = 0.05).

RESULTS

The resin composites, immersion media and time of immersion did not affect the repair bond strength (microhybrid 38.3 to 40.9 MPa; nanofilled 38.7 to 42.2 MPa; silorane 41.2 to 51.1 MPa). Additionally, the immersion media did not affect the sorption and solubility. The silorane-based composite presented the lowest sorption (10.5 to 12.1 µg/mm3) and solubility (-2.4 to -2.7 µg/mm3), while the nanofilled methacrylate-based composite showed the highest sorption (32.1 to 33.6 µg/mm3). Regarding solubility, the nanofilled and microhybrid methacrylate-based composites did not present statistically significant differences.

[Effect of thermal cycling on the composite- composite repair bond strength]

OBJECTIVE

To evaluate the effect of aging of the composite and the adhesive interface on composite-composite repair bond strength.

METHODS

Methacrylate-based composite resin (Clearfil AP-X, composite A) and silorane-based composite resin (Filtek P90, composite B) and their corresponding adhesive, Clearfil SE Bond (adhesive a) and Filtek P90 System Adhesive (adhesive b), were selected in this study. Twenty-four substrates were prepared from composite A or B separately and divided into three groups, each group had 8 substrates: group one, new composites were adhered to the substrates with the use of adhesive a or b, followed by cutting the blocks into sticks; group two, new composites were adhered to the substrates using adhesive a or b, followed by cutting into sticks and thermal cycling; group three, substrates were thermocycled, then polished and adhered new composites using adhesive a or b, followed by cutting into sticks. Each group had 8 combinations of substrate(A, B)-adhesive(a, b)-repair composite (A, B). Fifteen sticks without flaws in each combination of 3 groups were selected utilizing stereomicroscope. The data were analyzed by independent samples t test.

RESULTS

In group two, the microtensile strength(MS) of combinations using adhesive a and composite A or B to repair [A-a-A: (45.0 ± 3.2) MPa, B-a-A: (41.7 ± 3.3) MPa, A-a-B: (28.6 ± 3.9) MPa, B-a-B: (47.7 ± 6.6) MPa], and using adhesive b and composite A to repair [A-b-A: (44.2 ± 4.7) MPa, B-b-A: (38.0 ± 3.2) MPa] decreased significantly compared with corresponding combinations in group 1[A-a-A: (70.7 ± 5.5) MPa, B-a-A: (60.3 ± 5.1) MPa, A-a-B: (44.2 ± 1.6) MPa, B-a-B: (54.1 ± 3.2) MPa, A-b-A: (65.6 ± 7.2) MPa, B-b-A: (59.1 ± 4.1) MPa] (P<0.05). However, there was no significant difference between the MS of combinations using adhesive b and composite B to repair in group one and the MS of combinations in group two (P>0.05). The MS of all combinations in group three decreased significantly (P<0.05).

CONCLUSIONS

Aging of the composite and the adhesive interface might affect the composite-composite repair bond strength.

In situ characterization of resin-dentin interfaces using conventional vs. cryofocused ion-beam milling

OBJECTIVE

The introduction of focused ion beam (FIB) milling has facilitated preparation of hard tissue samples for transmission electron microscope (TEM). However, this technique generates high temperature that may alter or damage morphological features in biological tissue. Therefore, the aim of this study was to determine the effects of cryogenic cooling on the morphological features of dentin interfaces with dental restorative materials in samples prepared by FIB for TEM examination.

METHODS

After preparation of a cylindrical-shaped cavities in extracted, non-carious premolar teeth, the specimens were restored with dental adhesive/composite and categorized into two restorative materials groups; (PB) a combination of Clearfil Protect Bond (Kuraray Noritake Dental, Japan)/Estelite Sigma Quick composite (Tokuyama Dental, Japan), and (SB) Filtek Silorane restorative system (3M ESPE, USA). The specimens were subjected to interfacial cross-sectioning, followed by observation and area selection using confocal laser microscopy. Later, ultrathin sections were prepared using FIB with cryogenic cooling (PB-C) and (SB-C), or without cooling (PB-NC) and (SB-NC) that all were examined under TEM.

RESULTS

Resulting TEM images of the ultra-morphological features at the resin-dentin nano-interaction zone were improved when FIB preparation was conducted in the cryogenic condition and no sign of artifacts were detected.

SIGNIFICANCE

Conducting ion beam milling with cryogenic cooling was advantageous in minimizing the elevation in specimen temperature. This led to preservation of dentin microstructures that revealed additional information about substrates that are necessary for advanced characterization of tooth-biomaterial interactions.

Repair Bond Strength of Aged Silorane-based Composite Using Intermediate Adhesive Systems Based on Different Monomers

PURPOSE

To investigate the effect of pre-repair aging periods and intermediate adhesive systems based on different monomers on the repair bond strength of silorane-based resin composite.

MATERIALS AND METHODS

A total of 32 Filtek P90 (3M ESPE) substrate specimens (4 mm diameter and 4 mm height) were made. Substrate specimens were grouped according to the pre-repair time periods into four groups (n = 8/group): 15 to 30 min, 24 h, 1 month, and 3 months. All substrate specimens were ground flat using a diamond stone and were etched using Scotchbond phosphoric acid etchant (3M ESPE). The specimens of each pre-repair time period were equally distributed among the two repair groups, using either silorane-based (P90 System Adhesive) or acrylamide-based (AdheSE One F, Ivoclar Vivadent) intermediate adhesive systems. Specimens of P90 System adhesive received Filtek P90 as the repair resin composite, and Tetric N-Ceram (Ivoclar Vivadent) was used with AdheSE One F specimens. Additional specimens were made from the repair resin composite materials to study the cohesive strength. Specimens were sliced into sticks (0.6 ± 0.01 mm2) for microtensile bond strength testing (μTBS). Modes of failure were determined.

RESULTS

Two-way ANOVA with repeated measures revealed no significant effect for the pre-repair aging periods, intermediate adhesive systems based on different monomers, or their interaction on repair bond strength of silorane-based resin composite.

CONCLUSION

Up to 3 months of pre-aging the repaired silorane-based resin composite had no negative effect on its repair bond strength, even when an intermediate adhesive system based on a different monomer (acrylamide) was used.

Using Multiple Bonding Strategies

There are many ways to bond to tooth structure, some micro-mechanical some chemical, some a combination. Different dentin bonding materials have different bonding strengths to differently prepared surfaces, and because of differences in their nature, different areas of tooth structure present peculiar bonding challenges. This paper will review a variety of material types, elucidating their particular bonding strengths and commenting on improved bonding strategies to increase durability, strength, and favorable pulpal response. In this discussion, resin dentin bonding systems, glass ionomers, Gluma, resin cements, and newer combined products will br reviewed.

Two-year clinical performance of dimethacrylatebased composite restorations repaired with a silorane-based composite

PURPOSE

To investigate the clinical performance of a silorane-based composite resin used for repairing dimethacrylate- based composite restorations.

MATERIALS AND METHODS

One operator repaired defective dimethacrylate-based resin restorations that were randomly assigned to one of two treatment groups: control (n=50), repaired with Adper SE Plus and Filtek P60 Posterior Restorative (3M ESPE); or test (n=50), repaired with P90 System Adhesive Self-Etch Primer and Bond and Filtek P90 Low Shrink Posterior Restorative (3M ESPE). After 1 week, restorations were finished and polished. Two calibrated examiners (weighted Kappa≥0.78) evaluated the repaired restorations, blindly and independently, at baseline, after 6 months, 1 and 2 years. The parameters examined were marginal adaptation, anatomic form, surface roughness, marginal discoloration, postoperative sensitivity, and secondary caries. The restorations were classified as Alfa, Bravo, or Charlie, according to modified US Public Health Service criteria. Variation in the levels of clinical parameters over time was evaluated by Friedman's ANOVA (α=0.05). The Mann-Whitney test assessed the differences between the materials for all clinical criteria at baseline, 6-month, 1- and 2-year recalls (α=0.05). The Wilcoxon test compared each composite resin for all clinical criteria at the same recalls (α=0.05).

RESULTS

After two years, 79 repaired restorations were re-examined. No statistically significant differences were found between the materials at baseline or at the 2-year recall (p>0.05). Comparing baseline and 2-year recall, there was a statistically significant difference for marginal discoloration (p=0.029) in silorane-based composite restorations.

CONCLUSION

After two years, the clinical performance of the silorane-based composite was similar to that of the dimethacrylate-based composite when used to make repairs.

Effect of different monomer-based composites and acid etching pre-treatment of enamel on the microleakage using self-etch adhesives systems

OBJECTIVE

To evaluate quantitatively the marginal microleakage of restorations carried out with self-etching adhesives with or without prior phosphoric enamel acid etching of silorane or methacrylate resin-based composite restorations subjected to thermal cycling.

MATERIALS AND METHODS

Forty cavities were prepared at the proximal surface of bovine incisors and randomly divided according to the etching of the enamel and restorative system used. The groups were restored with methacrylate [Adper SE Plus adhesive (3M ESPE) + Filtek Z250 (3M ESPE)] or silorane [Filtek LS adhesive (3M ESPE) + Filtek LS composite (3M ESPE)] restorative systems, light-cured using a LED unit (Bluephase 16i, Vivadent). After restorative procedure and thermocycling (1000 cycles), the specimens were immersed in methylene blue for 2 h. The specimens were triturated and the powder was used for analysis in an absorbance spectrophotometer. Data were statistically analyzed by 2-way ANOVA (alpha = 0.05).

RESULTS

No statistical difference between the restorative materials tested with or without previous acid etching of enamel in Class II marginal microleakage was observed (p > 0.05).

CONCLUSIONS

The use of acid etching prior to self-etching adhesives did not interfere on the microleakage of methacrylate- or silorane-based restorations.

An in vitro evaluation of wear and surface roughness of particulate filler composite resin after tooth brushing

OBJECTIVE

To evaluate the influence of tooth brushing on wear and surface roughness of four different particulate filler composite resins.

MATERIALS AND METHODS

Six specimens (2 mm thick and 8 mm in diameter) of each tested material (Filtek Z250-Microhybrid, SpectrumTPH3-Submicron hybrid, Filtek Z350XT Nanofiller and Filtek P90- Microhybrid) were prepared according to the manufacturer's directions. A brushing sequence of 5000, 10,000 and 20,000 cycles was performed for all the samples. A non-contact profilometer was used to determine average surface roughness (Ra) and wear of the material assessed using an analytic electronic balance at baseline and each cycle interval. The data obtained were analyzed using one-way ANOVAs and post-hoc multiple comparison tests. Paired t-test was used for comparisons between cycle intervals for each material. Analyses with scanning electron microscopy (SEM) were also performed.

RESULTS

The resin composite Filtek P 90 presented an increase in percentage weight loss after final toothbrushing cycles over the rest of the materials. Brushing significantly increased roughness (Ra) for all composites. Filtek Z250, after brushing, was significantly rougher than the other resins followed by Filtek P 90, Spectrum TPH 3 and Filtek Z350 XT. However, SEM images indicated severe change in surface topography of 'sub-micron hybrid' specimen compared to each other after tooth brushing.

CONCLUSIONS

Wear and surface roughness increased with each cycle interval for all the materials and one composite resin demonstrated a higher increase in surface roughness than the other three tested brands of composite resins. Not much difference was observed in the weight loss between tested samples.

Clinical evaluation of silorane-based and dimethacrylate-based resin composites: 1-year follow-up

This study sought to evaluate the 1-year clinical performance of silorane-based and dimethacrylate-based Class II resin composite restorations using 2 bonding strategies. Eighty-two restorations were placed in 32 patients (median age 37 years) by a single operator. Only Class II restorations were included. Each patient received 1-2 pairs of resin composite restorations with both restoration materials. Between-group comparisons were made using an adjusted chi-square test and an adjusted McNemar's chi-square test to analyze the intrasystem data (α = 0.05). Both systems demonstrated acceptable clinical performance after 1 year.

Sealing of silorane-based composite in laser-prepared primary teeth: effect of acid etching

PURPOSE

The purpose of this study was to evaluate the influence of prior etching on the sealing of silorane composite restorations in Class V cavity preparations prepared with an Er,Cr:YSGG laser compared to bur preparation in primary teeth.

METHODS

Standard Class V cavity preparations were prepared on the buccal surfaces of 56 extracted primary canines and randomly divided into four groups of 14 teeth each, according to laser or bur preparation and the use of prior acid etching in the preparation. All cavity preparations were restored with silorane adhesive and silorane composite. After water storage and thermocycling, the specimens were placed in 0.5 percent basic fuchsin dye solution. Dye penetration was evaluated with a stereomicroscope. The data were analyzed with nonparametric tests (P=.05).

RESULTS

Laser preparation and prior etching in bur-prepared cavity preparation had no significant effect on enamel sealing (P>.05), but significantly increased microleakage at the dentin margin (P<.001 and P=.001, respectively). Prior etching in laser-prepared cavity preparations significantly improved sealing at the enamel and dentin margins (P=.009 and P=.003, respectively).

CONCLUSIONS

Prior acid etching may be necessary to ensure good marginal sealing when laser preparation is used. However, this step is not required when bur cutting is used in primary teeth.

A three-year prospective randomized study of silorane- and methacrylate-based composite restorative systems in class II restorations

PURPOSE

To evaluate and compare the 3-year clinical performance of a silorane-based composite with that of a methacrylate-based composite in Class II restorations.

MATERIALS AND METHODS

Seventy-eight patients, each with two class II restorations under occlusion, were enrolled in this study. One hundred fifty-six restorations were placed, 50% for each material: a silorane-based composite, Filtek P90/ P90 System Adhesive and a methacrylate-based resin composite, Quixfil/ Prime &Bond NT. 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 slightly modified USPHS criteria. The changes in the USPHS parameters during the three-year period were analyzed with the Friedman test. The baseline scores were compared with those at the recall visits using the Wilcoxon signed rank test. The level of significance was set at p < 0.05.

RESULTS

All restorations were evaluated at 3 years. Post-operative sensitivity was observed in 6 patients (2 Filtek P90, 4 Quixfil) between 1 and 3 weeks. Seven failed restorations (4.5%) were observed during the follow up: 4 in the Filtek P90 (5.1%) and 3 in the Quixfil group (3.8%). This resulted in non-significantly different annual failure rates of 1.7% and 1.2%, respectively. Fracture of restoration was the main reason for failure.

CONCLUSION

After 3 years, no significant difference was seen in overall clinical effectiveness between the silorane- based and methacrylate-based composite restorative systems.

Effects of preheating on the properties of silorane- and methacrylate-based composites

This study evaluated how preheating affected the properties of a silorane-based composite restorative material and 4 methacrylate-based composites. Viscosity, compressive strength, depth of cure, and polymerization shrinkage were examined. Data were analyzed with a 2-way ANOVA per physical property and composite type. With the exception of the flowable composite, significant reductions in viscosity were found between all preheated and room temperature composites, with no significant difference in other properties. In general, preheating the restorative composites decreased viscosity, but did not affect compressive strength, depth of cure, or shrinkage per composite type.

Influence of different staining beverages on color stability, surface roughness and microhardness of silorane and methacrylate-based composite resins

AIM

To investigate the influence of different staining beverages on color stability, surface roughness and microhardness of silorane and methacrylate-based composite resins.

MATERIALS AND METHODS

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.

RESULTS

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).

CONCLUSION

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.

Sorption and solubility of self-etching adhesives immersed in organic acids present in oral biofilm

PURPOSE

This study evaluated the sorption and solubility of self-etching adhesive systems after immersion in distilled water, lactic acid, and propionic acid.

MATERIALS AND METHODS

Specimens of 2 two-step (P90 System Adhesive [P90], Clearfil SE Bond [CSE]) and 1 single-step (Adper Easy One [AEO]) adhesive systems were prepared and divided into 4 groups: P90 primer ( P90-P), P90 bond (P90-B), AEO, and CSE bond (CSE-B). Specimens were placed in a desiccator and weighed daily until achieving a constant mass (m1). The specimens (n = 5) were then immersed in the respective media and weighed until a achieving a constant mass (m2). The specimens were again desiccated (m3). Sorption and solubility data were analyzed with two-way ANOVA and Turkey's test. Specimens were also observed using SEM without immersion, after 24 h, and at the end of the respective total time of immersion.

RESULTS

For all immersion media, the highest sorption values were obtained for AEO and P90-P, followed by CSE-B and P90-B, which presented the lowest sorption. The time required for adhesives to absorb the solutions was: 11 to 19 days for P90-P, 12 to 13 days for P90-B, 15 to 19 days for AEO, and 14 to 18 days for CSE-B. The highest values of solubility were shown for AEO and P90-P in all immersion media. In water and propionic acid, the adhesives with the lowest solubility values were CSE-B and P90-B. CSE-B had the lowest solubility in lactic acid.

CONCLUSION

The greatest surface degradation was observed after each respective total time of immersion. AEO specimens presented more evident surface degradation and the highest sorption and solubility.

Repair bond strength in aged methacrylate- and silorane-based composites

PURPOSE

To evaluate the tensile bond strength at repaired interfaces of aged dental composites, either dimethacrylate- or silorane-based, when subjected to different surface treatments.

MATERIALS AND METHODS

The composites used were Filtek P60 (methacrylate-based, 3M ESPE) and Filtek P90 (silorane-based, 3M ESPE), of which 50 slabs were stored for 6 months at 37°C. The surface of adhesion was abraded with a 600-grit silicone paper and the slabs repaired with the respective composite, according to the following surface treatment protocols: G1: no treatment; G2: adhesive application; G3: silane + adhesive; G4: sandblasting (Al2O3) + adhesive; G5: sandblasting (Al2O3) + silane + adhesive. After 24-h storage in distilled water at 37°C, tensile bond strength (TBS) was determined in a universal testing machine (Instron 4411) at a crosshead speed of 0.5 mm/min. The original data were submitted to two-way ANOVA and Tukey's test (α = 5%).

RESULTS

The methacrylate-based composite presented a statistically significantly higher repair potential than did the silorane-based resin (p = 0.0002). Of the surface treatments for the silorane-based composite, aluminum-oxide air abrasion and adhesive (18.5 ± 3.3MPa) provided higher bond strength than only adhesive application or the control group without surface treatment. For Filtek P60, the control without treatment presented lower repair strength than all other groups with surface treatments, which were statistically similar to each other. The interaction between the factors resin composite and surface treatment was significant (p = 0.002).

CONCLUSION

For aged silorane-based materials, repairs were considered successful after sandblasting (Al2O3) and adhesive application. For methacrylate resin, repair was successful with all surface treatments tested.

Microleakage and microtensile bond strength of silorane-based and dimethacrylate-based restorative systems

OBJECTIVE

To evaluate the microleakage and bond strengths (microTBS) of silorane-based (SBC) and dimethacrylate-based (DBC) restorative systems. The null hypotheses are: 1) there is no difference in microleakage between the resin composites and the adhesive systems tested at the enamel and dentin margins; 2) there is no significant difference in microTBS between the composite restorative systems using self-etch and etch-and-rinse adhesive versions.

METHODS AND MATERIALS

Microleakage: Class V cavity preparations with cervical margin in dentin were performed on pristine extracted human molars and were randomly distributed among the following three groups: Group 1-DBC/etch-and-rinse adhesive system (Filtek™ Supreme Ultra/Adper™ Single Bond Plus, 3M ESPE, www.3MESPE.com); Group 2-SBC/self-etch adhesive (Filtek LS Low Shrink Posterior Restorative System/LS self-etch adhesive, 3M ESPE); Group 3-DBC/self-etch adhesive (Filtek Supreme Ultra/ Adper Easy Bond Self-Etch, 3M ESPE). Restorations were thermocycled and immersed in 0.2 percent methylene blue dye for 24 hours. Samples were assessed visually under 10x magnification; microTBS: Bond sticks (0.9 mm2) were prepared from each group and tested on a universal testing machine.

RESULTS

The Kruskal-Wallis test revealed no significant difference in microleakage among the experimental groups at the enamel margin (P=0.191). At the dentin margins, silorane/self-etch restorative system showed significantly less leakage than the dimethacrylate/etch-and-rinse restorative system (P=0.008). Tukey's B rank order test showed that the dimethacrylate/etch-and-rinse restorative system presented the highest microTBS.

CONCLUSIONS

SBC/self-etch system showed less microleakage at the dentin margins, while DBC/etch-and-rinse system presented higher bond strength.

Bond strength of silorane- and methacrylate-based composites to resin-modified glass ionomers

This study evaluated the shear-bond strength of a resin-modified glass ionomer (RMGI) restorative material to a new silorane-based composite and a methacrylate-based composite in a sandwich technique with various combinations of surface treatments and bonding agents. Two composites, 2 bonding agents and 4 surface preparations were used to create 16 groups with 10 specimens each. After 24 hours storage at 37°C in 100% humidity, the specimens were tested for shear bond strength; means and standard deviations were determined per group. Surface modifications did not affect the shear-bond strength of the silorane or methacrylate composites to the RMGI. The new silorane composite had significantly lower bond strength to the RMGI compared to the methacrylate composite. The new silorane system adhesive agent had significantly higher bond strength to the RMGI compared to the methacrylate adhesive agent. The greatest bond strengths to the RMGI were produced when using the silorane system adhesive agent with the methacrylate composite.

Microleakage of Class II restorations and microtensile bond strength to dentin of low-shrinkage composites

PURPOSE

To evaluate the microleakage of Class II cavities restored with experimental low-shrinking resin composites proposed for bulk filling and to measure their microtensile bond strength (microTBS) to dentin and compare to those of previously marketed low-shrinkage composites.

METHODS

Class II cavities (7 mm occluso-gingival height, 2 mm mesio-distal depth of the box, 4 mm occlusal depth, 4 mm bucco-lingual width) were prepared in 50 molars and randomly divided into five groups (n = 10), according to the material: SureFil SDR flow (SDR), Filtek Silorane (FS) and experimental materials (G-aenial Flo bulk fill, GF; G-aenial Universal Flo bulk fill, GUF; GC Kalore bulk fill, GK). Microleakage was separately assessed at enamel and dentin margins by scoring the depth of silver-nitrate penetration. Twenty teeth divided into five groups (n = 4) were selected for microTBS testing. The same materials as for microleakage assessment were placed in bulk to mid-coronal dentin. Microtensile beams were loaded in tension, and microTBS at failure was calculated in MPa. Microleakage and microTBS data were analyzed by ANOVA on ranks, followed Dunn's post hoc test (P< 0.05).

RESULTS

Microleakage was not observed at the enamel interface in any of the groups. At the dentin interface, SDR recorded significantly higher microleakage than the other materials. microTBS of GF, GUF and GK did not differ among each other (33 +/- 12 MPa, 31 +/- 11 MPa, 30 +/- 9 MPa, respectively), while SDR (63 +/- 17 MPa) and FS (55 +/- 17MPa) achieved significantly higher microTBS values. No direct association between the sealing properties and the bond strength values was observed.

Practice-based, clinical trial of a silorane-based composite resin system in posterior teeth

INTRODUCTION

Newer monomer systems have been introduced in an attempt to improve the success rate of direct composite restorations by minimising shrinkage.

AIMS AND OBJECTIVES

To evaluate the in vivo performance of a silorane-based resin composite system (Filtek Silorane, also known as P90), used together with a two-step self-etch bonding system (P90 System Adhesive, Self-Etch Primer and Bond), for the restoration of Class I and Class II cavities in human permanent posterior teeth.

MATERIALS AND METHODS

A total of 53 restorations were completed and patients were recalled one year later. The restorations were assessed by two ndependent clinicians, using the Modified U.S. Public Health Service evaluation criteria for the following parameters: retention, colour match, marginal discolouration, secondary caries, anatomic form, marginal adaptation, surface texture, occlusal and interproximal contacts.

RESULTS

Of the 41 restorations assessed at the one year follow-up, 92.7% showed clinically acceptable scores for all the parameters evaluated. Cronbach's alpha values ranged from 0.72-1.00 showing a good inter-examiner agreement and reliability.

CONCLUSION

Silorane-based composite, Filtek Silorane, when used in conjunction with the recommended adhesive system showed a clinically acceptable performance in posterior teeth restorations over a one year clinical service.

Hydrolytic degradation of silorane- and methacrylate-based composite restorations: Evaluation of push-out strength and marginal adaptation

OBJECTIVES

This study compared the hydrolytic degradation of composite restorations based on methacrylate and silorane systems regarding bond strength and marginal adaptation. Materials and methods. Sixty bovine incisors were ground flat to obtain a 2-mm thick slice in which conical preparations were made. The specimens were randomly distributed into four groups (n = 15) according to the restorative system (silorane-Filtek LS/P90 adhesive; methacrylate-Filtek P60/Adper Easy Bond) and the degradation protocol (control: immediate evaluation; hydrolytic degradation: 6 months storage in water at 37°C). Marginal adaptation was evaluated using a dye staining technique. Digital images of the stained gaps were obtained to calculate the marginal gap (%), the ratio between the stained margins and the total length of the margin. Push-out bond strength test was conducted (0.5 mm/min). Marginal adaptation data was submitted to Kruskal-Wallis test and the bond strength data to two-way ANOVA/Tukey's test (α = 0.05). Results. The marginal adaptation was neither affected by the restorative system nor by the degradation protocol, although the number of perfect sealed reduced after 6 months. No significance was observed among the groups. No significance was noted between the silorane- and the methacrylate-based restorations for immediate bond strength. After the hydrolytic degradation, the silorane system showed higher bond strength then the methacrylate restorations. Conclusion. The silorane and methacrylate restorative systems produce restorations with similar immediate interfacial quality and 6 months of water storage does not cause significant bonding degradation for both systems. The silorane restorations show an increase in the bond strength after 6 months.

Effect of cigarette smoke on color stability and surface roughness of dental composites

OBJECTIVE

To evaluate the color stability and surface roughness of 3 dental composites subjected to cigarette smoke and brushing.

METHODS

Twenty specimens were prepared for each type of restorative material used: nanohybrid (Tetric N-Ceram); hybrid (Z250-3M ESPE) and silorane-based microhybrid (Filtek P90-3M ESPE), which were divided into 2 groups (n=10), according to the type of finishing/polishing received: Group 1 - papers with decreasing abrasive grit and Group 2 - polyester matrix (without polishing). After initial readouts of color (Easy Shade-VITA) and surface roughness (SJ-201P Mitutoyo), specimens were subjected to action of smoke from 20 cigarettes, (Marlboro Red-Philip Morris). After each cigarette, the samples were submitted to brushing in a standardised device. After this, final readouts were taken to calculate change in color (ΔE and ΔL) and roughness (ΔRa), which were statistically analysed (2-way ANOVA, Bonferroni, and Student's-t tests respectively, p<0.05).

RESULTS

Tetric N-Ceram presented color change at clinically unacceptable levels (ΔE>3.3) when the polyester strip was used for finishing, a result differing (p<0.05) from those of the other composites, which presented no difference between them (p>0.05). Unpolished composites presented higher Ra values than those that were polished (p<0.05), with exception of the silorane based composite.

CONCLUSION

Absence of polishing increases cigarette capacity to stain composites and surface roughness of composites, with exception of the silorane based type.

Surface modification of several dental substrates by non-thermal, atmospheric plasma brush

OBJECTIVE

The purpose of this study was to reveal the effectiveness of non-thermal atmospheric plasma brush in surface wettability and modification of four dental substrates.

METHODS

Specimens of dental substrates including dentin, enamel, and two composites Filtek Z250, Filtek LS Silorane were prepared (∼2mm thick, ∼10mm diameter). The prepared surfaces were treated for 5-45s with a non-thermal atmospheric plasma brush working at temperatures from 36 to 38°C. The plasma-treatment effects on these surfaces were studied with contact-angle measurement, X-ray photoemission spectroscopy (XPS) and scanning electron microscopy (SEM).

RESULTS

The non-thermal atmospheric argon plasma brush was very efficient in improving the surface hydrophilicity of four substrates studied. The results indicated that water contact angle values decreased considerably after only 5s plasma treatment of all these substrates. After 30s treatment, the values were further reduced to <5°, which was close to a value for super hydrophilic surfaces. XPS analysis indicated that the percent of elements associated with mineral in dentin/enamel or fillers in the composites increased. In addition, the percent of carbon (%C) decreased while %O increased for all four substrates. As a result, the O/C ratio increased dramatically, suggesting that new oxygen-containing polar moieties were formed on the surfaces after plasma treatment. SEM surface images indicated that no significant morphology change was induced on these dental substrates after exposure to plasmas.

SIGNIFICANCE

Without affecting the bulk properties, a super-hydrophilic surface could be easily achieved by the plasma brush treatment regardless of original hydrophilicity/hydrophobicity of dental substrates tested.

Randomized controlled trial of the 2-year clinical performance of a silorane-based resin composite in class 1 posterior restorations

PURPOSE

To compare the 2-year clinical performance of a silorane-based resin composite with that of an established nanoceramic resin composite for class 1 posterior restorations.

METHODS

In this randomized controlled study, 100 class 1 molar cavities were prepared in 50 subjects. Each subject received a restoration with Filtek Silorane and Ceram.X Duo in different quadrants. The restorations were evaluated using the modified USPHS criteria at baseline and 6, 12, and 24 months. Parametric changes over the 2-year period were assessed with the Friedman test. The baseline and recall scores were compared by using the Wilcoxon signed-rank test (P < 0.05).

RESULTS

No subject developed secondary caries or postoperative sensitivity. Further, the resin composites showed no significant differences in all the evaluated parameters over 2 years (P > 0.05). At 2 years, four Filtek Silorane and seven Ceram.X Duo restorations had Bravo scores for anatomic form, marginal adaptation, and surface texture (P < 0.05); however, these changes were mainly the effect of scoring shifts from Alfa to Bravo. Overall, both materials showed good clinical results with predominantly Alfa scores.

Marginal leakage and microhardness evaluation of low-shrinkage resin-based restorative materials

This study sought to compare the marginal leakage and microhardness of low-shrinkage resin-based dental restorative materials containing ormocer- and silorane-based composites to that of conventional methacrylate-based systems. A total of 50 noncarious extracted human teeth were collected after debridement and standard Class V cavities were prepared. Teeth were randomly assigned to five groups (n = 10) and restored with 5 types of resin-based restorative material composites: hybrid, microhybrid, nanohybrid, ormocer-based, and silorane-based. After thermocycling, all teeth were placed in a silver nitrate solution, sectioned longitudinally in a buccolingual direction, and observed under a stereomicroscope to determine the degree of dye penetration. Data were analyzed using a non-parametric Kruskal-Wallis test (P < 0.05). For the microhardness test, five specimens were made for each restorative material, using Teflon molds with disk-shaped specimen wells. Specimens were photocured and placed in distilled water (at 37°C) for 24 hours. Vickers Hardness Number (VHN) measurements were performed using a microhardness tester. Data were analyzed by one-way ANOVA and Bonferroni post hoc tests. In terms of microhardness, there was no statistically significant difference among the resin-based restorative materials (P > 0.05). The degree of microleakage at the gingival margins was lowest for the silorane composite, followed by microhybrid and nanohybrid. The silorane composite was significantly lower than that of the ormocer and hybrid composites (P < 0.05). Based on the results of this study, it was concluded that the silorane-based composite material could provide a marginal seal comparable to that provided by microhybrid or nanohybrid resin composites.

Microtensile bond strength of a new silorane-based composite resin adhesive

Filtek LS is a new composite resin restorative system with a unique, low-shrinking, silorane-based monomer matrix. The current study was conducted to compare the durability of the bond to dentin of the new silorane-based bonding agent, Filtek Silorane System Adhesive, to the gold standard methacrylate-based bonding agent, Clearfil SE Bond. Extracted human molar teeth were sectioned to expose dentin. Either Filtek Silorane System Adhesive with Filtek LS composite or Clearfil SE Bond with Clearfil Majesty Posterior composite was applied to the dentin according to the manufacturer's instructions. The composites were placed incrementally and sectioned perpendicular to the composite-tooth interface to obtain rectangular beams. The beams were stored for 24 hours, 6 months, or 12 months in distilled water and stressed in tension in a universal testing machine. Data were analyzed with a two-way ANOVA/Tukey test. The 24-hour microtensile bond strengths were significantly greater than the 6- and 12-month bond strengths. Overall, there was no significant difference in the microtensile bond strength to dentin between the Filtek Silorane System Adhesive and the Clearfil SE Bond adhesive bonding agents. After one year of water storage, the new silorane-based composite resin bonding agent performed as well as the methacrylate-based composite resin bonding agent.

Microleakage of silorane- and methacrylate-based class V composite restorations

The marginal integrity of class V restorations in a silorane- and a group of methacrylate-based composite resins with varying viscosities was tested in the present study. Different adhesives (OptiBond FL, KerrHawe; AdheSE One, Vivadent; or Silorane System Adhesive, 3M ESPE) were applied to 168 standardized class V cavities. The cavities (n = 12) were filled with a wide range of different viscous composite resins: Filtek Silorane, 3M ESPE; els and els flow, Saremco; Tetric EvoCeram and Tetric EvoFlow, Vivadent; Grandio, Voco; and Ultraseal XT Plus, Ultradent. Microleakage of the restoration was assessed by dye penetration (silver staining) on multiple sections with and without thermocycling and mechanical loading (TCML: 5,000 × 5-55°C; 30 s/cycle; 500,000 × 72.5 N, 1.6 Hz). Data were statistically analyzed with the Mann-Whitney U test and the Error Rates Method (ERM). The silorane-based composite resin yielded the lowest dye penetration after TCML. Microleakage of methacrylate-based composite restorations, in general (ERM), was statistically significantly influenced by the adhesive system, Moreover, dye penetration at enamel margins was significantly lower than dye penetration at dentin margins. The chemical basis of composite resins and adjacent tooth substance seems to strongly influence marginal sealing of class V restorations for methacrylate-based materials. Moreover, the steps of dental adhesives used affected marginal integrity. The silorane-based composite resin evaluated in the present study exhibits the best marginal seal. The three-step adhesive yielded better marginal sealing than the one-step adhesive for methacrylate-based class V composite restorations.