Five-year evaluation of a low-shrinkage Silorane resin composite material: A randomized clinical trial

The evolution of adhesive dentistry: From etch-and-rinse to universal bonding systems

OBJECTIVES

This review aimed at presenting the mechanisms and pitfalls of adhesion to enamel and dentin, advances in the materials science and in the development of strategies to improve hybrid layer (HL) longevity.

METHODS

Search of the literature was performed on PubMed, Scopus and Web of Science with keywords related to the structure of the dental substrate, HL degradation mechanisms and strategies to contrast them.

RESULTS

Albeit the advances in the dental materials' properties, HL degradation is still a relevant and current issue in adhesive dentistry. However, adhesive materials have become more resistant and less operator sensitive, and good adhesion is currently in the hands of every practitioner. Numerous novel strategies are being developed, able to improve the resistance of adhesive resins to degradation, their ability to infiltrate and chemically bond to dentin, to remove the unbound/residual water within the HL, reinforce the dentin collagen matrix, and inhibit endogenous metalloproteinases. Many of the strategies have turned to nature in search for powerful biomodifying compounds, and for the inspiration as to mimic naturally occurring regenerative processes.

SIGNIFICANCE

Extensive knowledge on the structure of the dental substrate and the complexity of adhesion to dentin has led to the development of improved formulations of dental adhesives and numerous valid strategies to improve the strength and longevity of the HL. Nevertheless, for many of them the road from bench to chairside still seems long. We encourage practitioners to know their materials well and use the strategies readily available to them.

Low-Shrinkage Resin Matrices in Restorative Dentistry-Narrative Review

Dimethacrylate-based resin composites restorations have become widely-used intraoral materials in daily dental practice. The increasing use of composites has greatly enhanced modern preventive and conservative dentistry. They have many superior features, especially esthetic properties, bondability, and elimination of mercury and galvanic currents. However, polymeric materials are highly susceptible to polymerization shrinkage and stresses that lead to microleakage, biofilm formation, secondary caries, and restoration loss. Several techniques have been investigated to minimize the side effects of these shrinkage stresses. The primary approach is through fabrications and modification of the resin matrices. Therefore, this review article focuses on the methods for testing the shrinkage, as well as formulations of resinous matrices available to reduce polymerization shrinkage and its associated stress. Furthermore, this article reviews recent cutting-edge developments on bioactive low-shrinkage-stress nanocomposites to effectively inhibit the growth and activities of cariogenic pathogens and enhance the remineralization process.

Effect of post-irradiation polymerization on selected mechanical properties of six direct resins

This study evaluated the post-irradiation mechanical property development of six resin composite-based restorative materials from the same manufacturer starting at 1 h post irradiation, followed by 24 h, 1 week, and 1 month after fabrication. Samples were stored in 0.2M phosphate buffered saline until testing. Flexural strength, flexural modulus, flexural toughness, modulus of resiliency, fracture toughness, and surface microhardness were performed at each time interval. Mean data was analyzed by Kruskal Wallis and Dunn's post hoc testing at a 95% level of confidence (α=0.05). Results were material specific but overall, all resin composite material mechanical properties were found to be immature at 1 h after polymerization as compared to that observed at 24 h. It may be prudent that clinicians advise patients, especially those receiving complex posterior composite restorations, to guard against overly stressing these restorations during the first 24 h.

Six-year clinical evaluation of bulk-fill and nanofill resin composite restorations

OBJECTIVES

This study aims to compare the performance of a bulk-fill and a nanofill resin composite in class II restorations after 6 years.

MATERIALS AND METHODS

Fifty patients having at least two class II carious lesions were recruited for the study. One lesion in each patient was randomly assigned to be restored using either the Tetric EvoCeram Bulk Fill (TB) or Filtek Ultimate (FU) resin composites with their respective adhesives. One hundred four restorations were placed by two calibrated operators. Restorations were evaluated at baseline and annually over the course of 6 years by two examiners using modified USPHS criteria. Data were statistically analyzed using the Chi-square and Cochran Q tests (p < 0.05).

RESULTS

Sixty-six restorations in 33 patients were evaluated after 6 years. Only one restoration was lost from FU group at 5 years. At the end of 6 years, marginal discoloration was observed in three (9.1%) TB and eight (36.4%) FU restorations creating a significant difference between the groups (p < 0.05). The FU group showed a significant increase in marginal discoloration at 6 years from the baseline (p < 0.05). Marginal adaptation was rated as Bravo for 9.1% and 24.2% of TB and FU restorations, respectively (p > 0.05). Significant degradation was observed within each group in terms of marginal adaptation (p < 0.05). There were no statistically significant differences between the groups for the other criteria tested (p > 0.05).

CONCLUSIONS

Bulk-fill restorations performed better for marginal discoloration. The remaining clinical performance criteria of bulk-fill and nanofill resin composite restorations were similar after 6 years.

CLINICAL RELEVANCE

Bulk-fill resin might be a better alternative to incrementally placed restorative in terms of marginal discoloration under clinical conditions.

Adhesive dentistry: Current concepts and clinical considerations

OBJECTIVES

To address contemporary concepts in adhesive dental materials with emphasis on the evidence behind their clinical use.

OVERVIEW

Adhesive dentistry has undergone major transformations within the last 20 years. New dental adhesives and composite resins have been launched with special focus on their user-friendliness by reducing the number of components and/or clinical steps. The latest examples are universal adhesives and universal composite resins. While clinicians prefer multipurpose materials with shorter application times, the simplification of clinical procedures does not always result in the best clinical outcomes. This review summarizes the current evidence on adhesive restorative materials with focus on universal adhesives and universal composite resins.

CONCLUSIONS

(a) Although the clinical behavior of universal adhesives has exceeded expectations, dentists still need to etch enamel to achieve durable restorations; (b) there is no clinical evidence to back some of the popular adjunct techniques used with dental adhesives, including glutaraldehyde-based desensitizers and matrix metalloproteinase inhibitors; and (c) the color adaptation potential of new universal composite resins has simplified their clinical application by combining multiple shades without using different translucencies of the same shade.

CLINICAL SIGNIFICANCE

New adhesive restorative materials are easier to use than their predecessors, while providing excellent clinical outcomes without compromising the esthetic quality of the restorations.

Treatment options for large posterior restorations: a systematic review and network meta-analysis

BACKGROUND

The best treatment option for large caries in permanent posterior teeth is still a matter of uncertainty in dental literature. The authors conducted a network meta-analysis to address the challenges related to rehabilitation of these teeth.

TYPES OF STUDIES REVIEWED

The authors selected prospective and retrospective studies that compared at least 2 different treatment alternatives for permanent teeth with a minimum of 5 years of follow-up. The authors searched databases from MEDLINE, Scopus, Cochrane Library, and Web of Science in October 2019 without language or year of publication restrictions.

RESULTS

From 11,263 studies identified, 43 studies fulfilled the eligibility criteria and were included in the final review. Only 13 studies were randomized controlled trials and were classified as low risk of bias. Gold (annual failure rate of 0.29%) and metal ceramic (annual failure rate of 0.52%) crowns performed better for indirect restorations and direct resin composite performed better for direct restorations (annual failure rate of 2.19%). The most substantial comparisons were between feldspathic and glass ceramics, followed by direct resin composite and amalgam; there were no statistically significant differences between these interventions. Results of the pairwise meta-analysis showed mainly glass ionomer as significantly more prone to failure than amalgam and direct composite resin.

CONCLUSIONS AND PRACTICAL IMPLICATIONS

Reference standard direct and indirect materials except for glass ionomer can be used for restorations of large posterior caries.

Synthesis and characterization of Ciprofloxacin-containing divinyl oligomers and assessment of their biodegradation in simulated salivary esterase

OBJECTIVE

Two leading causes contributing to dental restoration replacement are the marginal breakdown at the composite/dentin interface and secondary caries mediated by bacteria. The objective of the present study was to synthesize oligomers which incorporated enhanced bio-stability but would also be able to generate antimicrobial function if they underwent degradation.

METHODS

Stability was incorporated into the oligomers by generating structural features that would physically hinder the availability of hydrolytically sensitive groups in the oligomers. As a proof-of concept for the antibacterial feature, antimicrobial function was achieved by covalently incorporating Ciprofloxacin (CF) into the backbone of cross-linking divinyl oligomers (referred to as EDV and HLH-CFPEG). The hydrolytic stability of the oligomers was studied in simulated human salivary esterase and compared to the commercial monomer 2,2-bis[4(2-hydroxy-3-methacryloxypropoxy)-phenyl]propane (BisGMA).

RESULTS

Both drug oligomers were found to be significantly more stable than BisGMA. Upon degradation, both drug oligomers released CF differentially in free form. Polymer synthesis from resin formulations containing 15wt% HLH-CFPEG showed a high degree of vinyl group conversion and gel content, and under hydrolytic conditions showed the release of CF during a 28-day monitoring study period.

SIGNIFICANCE

HLH-CFPEG can be used in dental resin adhesive systems for local delivery of CF to the marginal interface. Minimizing the growth of Streptococcus mutans at the marginal site can improve longevity by reducing esterase activity derived specifically from S. mutans.

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 performance of bulk-fill and conventional resin composite restorations in posterior teeth: a systematic review and meta-analysis

OBJECTIVES

The purpose of this systematic review was to compare the clinical performance of bulk-fill resin composites with conventional resin composites used for direct restorations of posterior teeth.

METHODS

This review followed the PRISMA statement. This review was registered at PROSPERO (registration number CRD42016053436). A search of the scientific literature was performed by two independent reviewers using the PubMed/MEDLINE, Embase, The Cochrane Library, and Web of Science databases from commencement until January 2018. The research question was "Do bulk-fill resin composites have a clinical performance comparable to conventional resin composites in posterior restorations?" Only studies evaluating class I and II direct restorations in permanent teeth with a follow-up period of at least 1 year were included. The RevMan 5 program was used for meta-analysis, calculating the relative risk (RR) and 95% confidence interval (CI) of the dichotomous outcome (restoration failure or success).

RESULTS

Ten articles were selected, comprising 941 analyzed restorations. The mean follow-up period was 33.6 months (12-72 months). No statistically significant differences in the failure rate were observed between conventional and base/flowable bulk-fill resin composites (p = 0.31; RR 1.49; 95% CI 0.69-3.25) or full-body/sculptable bulk-fill resin composites (p = 0.12; RR 1.89; 95% CI 0.84-4.24).

CONCLUSIONS

The present systematic review and meta-analysis indicate similar clinical performances of bulk-fill and conventional resin composites over a follow-up period of 12 to 72 months.

CLINICAL SIGNIFICANCE

Based on the results of this study, the bulk-fill resin composites could be an alternative for direct restorations in posterior teeth. However, clinical trials of longer duration are required.

Meta-analysis of the clinical behavior of posterior direct resin restorations: Low polymerization shrinkage resin in comparison to methacrylate composite resin

Polymerization shrinkage of resin composite can compromise the longevity of restorations. To minimize this problem, the monomeric composition of composites have been modified. The objective of this study was to conduct a meta-analysis to assess the clinical behavior of restorations performed with low polymerization shrinkage resin composite in comparison with traditional methacrylates-based resin composite. This systematic review was registered at Prospero data system (CRD42015023940). Studies were searched in the electronic databases PubMed, Web of Science, Scopus, Lilacs and EMBASE according to a predefined search strategy. The inclusion criteria were as follow: (1) randomized controlled clinical trials with at least six months of follow-up; (2) studies investigating composites with monomers designed to reduce polymerization shrinkage; (3) studies conducted with class I or II restorations in the permanent dentition; and (4) studies that assessed at least one of the following criteria: marginal integrity/adaptation, marginal discoloration, recurent caries, retention of composite restorations, and postoperative sensitivity. Two independent reviewers analyzed the articles to determine inclusion and risk of bias. The search conducted in the databases resulted in a total of 14,217 studies. After reviewing the references and citations, 21 articles remained. The longest clinical follow-up time was 60 months. The meta-analysis of the data in the included studies demonstrated that only one variable (marginal adaptation after 12 months) showed statistically significant outcomes, in which methacrylates-based composites presented significantly better results than resin composites containing modified monomers. The good level of the scientific evidence as well as the overall low risk of bias of the included studies indicate that composites with silorane, ormocer or bulk-fill type modified monomers have a clinical performance similar to conventional resin composites.

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.

Clinical Evaluation of Silorane and Nano-hybrid Resin Composite Restorations in Class II Cavities up to 3 Years

In this study, the clinical performance of a silorane-based resin composite (SC) vs a nano-hybrid resin composite (NHC) was evaluated in Class II cavities. From January 2012 to February 2013, a total of 29 patients (eight men, 21 women; mean age, 24 ± 5 years) received 29 pairs of restorations using both SC (Filtek Silorane, 3M ESPE) and NHC (Filtek Z550, 3M ESPE) materials. Patients were followed until February 2015. One operator performed all restorations using the corresponding adhesive resins according to the manufacturers' instructions. Two calibrated independent examiners evaluated the restorations at one week, six months, and then annually using the modified United States Public Health Service (USPHS) criteria for anatomic form, marginal adaptation, color match, surface roughness, marginal discoloration, secondary caries, and postoperative sensitivity. Changes in the USPHS parameters were analyzed with the McNemar test (α=0.05). The mean observation period was 31.2 months. Marginal adaptation was the only parameter that showed a significant difference and was worse for SC than NHC (p=0.012). At the final recall, 17 restorations from the SC group and five from the NHC group received a score of 1 (explorer catches). These scores were significantly different between baseline and final recall for SC (p&lt;0.001) but not for NHC (p&gt;0.05). Both NHC and SC performed similarly in Class II restorations up to three years except for marginal adaptation, for which the latter demonstrated significant deterioration at the final recall compared with baseline.

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.

Effect of Bleaching and Thermocycling on Resin-Enamel Bond Strength

The aim of this study was to evaluate the effect of bleaching and thermocycling on microshear bond strength of bonded resin composites to enamel. Enamel slices were prepared from ninety-six intact human premolars and resin composite cylinders were bonded by using Adper Single Bond 2 + Filtek Z350 or Filtek silorane adhesive and resin composite. Each essential group was randomly subdivided to two subgroups: control and bleaching. In bleaching group, 35% hydrogen peroxide was applied on samples. Thermocycling procedure was conducted between 5°C and 55°C, for 3.000 cycles on the half of each subgroup specimen. Then microshear bond strength was tested. Methacrylate-based resin composite had higher bond strength than silorane-based one. The meyhacrylate-based group without bleaching along with thermocycling showed the most bond strength, while bleaching with 35% carbamide peroxide on silorane-based group without thermocycling showed the least microshear bond strength. Bleaching caused a significant degradation on shear bond strength of silorane-based resin composites that bonded using self-etch adhesive resin systems.

Survival of direct resin restorations in posterior teeth within a 19-year period (1996-2015): A meta-analysis of prospective studies

OBJECTIVES

The aim of this study is to analyze the survival of posterior composite restorations published within the last 19 years (1996-2015).

METHODS

In this study only prospective, clinical trials with specification of the failure rate according to Class I/II composite fillings were included. Studies were analyzed according to the observation period (all studies vs. short-term vs. long-term studies). Retrospective studies and/or open laminate studies, tunnel restorations and Class V restorations were excluded. The following variables possibly influencing the failure rate were extracted from the studies: observation period, recall rate, average age of patients, number of patients, ratio of Class I/II fillings, number of restorations, ratio of premolars/molars, operator, method of isolation, bonding generation and filler size.

RESULTS

A total of 88 studies were included for statistical analysis. The observation period of the studies varied between 1 and 17 years, while most of the studies did not last longer than 5 years. Fracture of the restorations, secondary caries and marginal gap are the main causes for failure in the first 5 years (in descending order), while fracture and secondary caries are similarly distributed in long-term studies. Variables of investigation differed greatly in significance according to the respective observation period. The observation period, the recall rate, the ratio of Class I/II fillings and the number of restorations and patients had a significant influence on the overall failure rate when including all studies (short- and long-term). A linear correlation between the observation period and the failure rate was observed. In long-term studies these variables were not significant any longer. No significant difference in the failure rates between the materials per study was observed. The most common commercial composites investigated were: Tetric Ceram, Surefil, Filtek Supreme (incl. XT), Filtek Z250. The mean annual failure rate was 1.46% (±1.74%) for short-term studies and 1.97% (±1.53) for long-term studies. There is still a big need for clinical studies lasting longer than 5 years, as failure rates of composite restorations in posterior teeth increases with longer observation periods.

SIGNIFICANCE

A decreasing failure rate with an increasing recall rate as observed in our study suggests a patient selection in regard to availability and dental awareness. Internationally standardized evaluation criteria are mandatory in order to allow comparisons of the outcomes of clinical studies.

Development of methacrylate/silorane hybrid monomer system: Relationship between photopolymerization behavior and dynamic mechanical properties

Resin chemistries for dental composite are evolving as noted by the introduction of silorane-based composites in 2007. This shift in the landscape from methacrylate-based composites has fueled the quest for versatile methacrylate-silorane adhesives. The objective of this study was to evaluate the polymerization behavior and structure/property relationships of methacrylate-silorane hybrid systems. Amine compound ethyl-4-(dimethylamino) benzoate (EDMAB) or silane compound tris(trimethylsilyl) silane (TTMSS) was selected as coinitiators. The mechanical properties of the copolymer were improved significantly at low concentrations (15, 25, or 35 wt %) of silorane when EDMAB was used as coinitiator. The rubbery moduli of these experimental copolymers were increased by up to 260%, compared with that of the control (30.8 ± 1.9 MPa). Visible phase separation appeared in these formulations if the silorane concentrations in the formulations were 50-75 wt %. The use of TTMSS as coinitiator decreased the phase separation, but there was a concomitant decrease in mechanical properties. In the neat methacrylate formulations, the maximum rates of free-radical polymerization with EDMAB or TTMSS were 0.28 or 0.06 s(-1) , respectively. In the neat silorane resin, the maximum rates of cationic ring-opening polymerization with EDMAB or TTMSS were 0.056 or 0.087 s(-1) , respectively. The phase separation phenomenon may be attributed to differences in the rates of free-radical polymerization of methacrylates and cationic ring-opening polymerization of silorane. In the hybrid systems, free-radical polymerization initiated with EDMAB led to higher crosslink density and better mechanical properties under dry/wet conditions. These beneficial effects were, however, associated with an increase in heterogeneity in the network structure. © 2015 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 104B: 841-852, 2016.