Methacrylate-based Resin Research Articles

Aging of silorane- and methacrylate-based composite resins: effects on color and translucency

To evaluate the color stability and translucency of silorane-based low shrinkage composite after in vitro aging procedures of thermal cycling and water storage respectively, and to compare with those of conventional methacrylate-based posterior composite. Three light-cured composite resins, dimethacrylate-based composite A (Filtek™ Z350), B (Filtek™ P60) and silorane-based composite C (Filtek™ P90), were tested in this study. Ten specimens (10 mm in diameter, 1 mm in height) of each composite were prepared. The ten specimens in each group were then divided into two subgroups (n = 5). One subgroup underwent thermal cycling [(5.0 ± 0.5)~(55.0 ± 1.0) °C, 10 000 cycles] and the other was stored in 37 C° distilled water for 180 days. With a spectrophotometer, the CIE L * a * b * parameters of the specimens were tested before and after artificial aging against white, medium grey and black backgrounds, respectively. △E, TP and △TP were calculated and data were analyzed using independent-samples t test and partial analysis (P < 0.05). With regard to color stability, silorane-based composite showed color alteration above the clinically acceptable levels (△E > 3.3), and also showed higher △E with a statistically significant difference in comparison with the other composites (B and C) (P < 0.05) after artificial aging. With regard to translucency, composite C showed more alteration compared with composite B (P < 0.05) after thermal cycling. It may be concluded that the silorane-based composite underwent greater alteration with regard to color stability and translucency.

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

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

In-situ nano-silica deposition and air-abrasion with Bioglass 45S5 or aluminium oxide: Effects on methacrylate bonding to yttria-tetragonal zirconia polycrystal

This study aimed at assessing the bonding performance after water storage (24h/6-month) of a methacrylate-based cement applied onto Yttria-Tetragonal Zirconia Polycrystal(Y-TZP) pre-treated using an innovative in-situ silica nanoparticle deposition method and/or air-abrasion with Bioglass 45S5 (BAG) or aluminium oxide (AlO).Pre-sintered blocks of Y-TZP were coated with nano-silica using an experimental in-situ deposition method or used as received (control/silica-free). Air-abrasion was performed with AlO or BAG particles both on silica-coated and control Y-TZP specimens. All the specimens were then analysed using SEM–EDX. Further specimens were treated as described above, bonded using a dual-cure resin cement system and submitted to shear bond strength test after water storage (24h and 6 months). Fracture analysis was subsequently performed using a stereo-microscope.Uniform nano-silica deposition was achieved in the Y-TZP specimens after in-situ silica deposition treatment. However, AlO air-abrasion removed the nano-silica and roughened the Y-TZP surfaces. Conversely, BAG air-abrasion caused partial removal of the nano-silica layer and created only little retention in the control/silica-free Y-TZP specimens. The highest bond strength both at 24h and 6-month water storage was attained with the silica-coated specimens air-abraded with BAG and with those which received no air-abrasion. AlO air-abrasion increased the bond strength (24h) in the Y-TZP specimens compared to the control/silica-free specimens which received no air-abrasion or BAG air-abrasion.The in-situ nano-silica coating method employed in this study may be a suitable, simplified and low-cost approach to provide reliable bond strength to Y-TZP ceramics. No air-abrasion is required after in-situ nano-silica deposition. However, AlO air-abrasion can create micro-retentions on the surface of silica-free Y-TZP ceramics and increases the immediate bond strength of methacrylate-based resin cements.

Influence of filling technique and bevel preparation on marginal sealing of conventional and low shrinkage composite restorations

AIM: The aim of this study was to evaluate two composite restorations (conventional methacrylate-based and low shrinkage-based silorane), associated or not to beveling and incremental technique, in relation to the microleakage and marginal gap formation tests. MATERIAL AND METHODS: 30 sound human molars had their mesial and distal surfaces prepared with and without bevel. The teeth were divided into six groups according to the type of resin (conventional nanofilled or silorane resin), and restorative filling technique (incremental technique or builk). Microleakage and marginal gap formation data were statistically analyzed by Kruskal-Wallis and Chi-Square tests, with a significance level set at 5%. RESULTS: Group 1 (Z350 XT, without bevel, incremental technique) presented highest rate of microleakage and marginal gap in most of the restorations, with statistically significant differences. Groups 4 and 6 (P90, beveled, builk and P90, beveled and incremental technique) had lower rates of microleakage and absence of marginal gaps in most of the restorations. CONCLUSION: It’s concluded that the silorane showed lower rates of marginal gaps and microleakage, when compared to the conventional methacrylate-based resin. Bevel preparation was effective in reducing microleakage and marginal gaps for both resins used. Incremental technique was not necessary when associated with low shrinkage composite resin.

Fracture strength of root filled premolar teeth restored with silorane and methacrylate-based resin composite

ObjectivesTo compare fracture characteristics of root-filled teeth with variable cavity design restored with a low shrinkage silorane and methacrylate-based resin composite. Methods77 extracted maxillary premolars were divided randomly into seven groups: (Group 1) intact teeth; (Groups 2–4) MOD plus endodontic access with the buccopalatal width of the occlusal isthmus equals one third of the intercuspal width; (Groups 5–7) MOD plus endodontic access with the buccopalatal width of the occlusal isthmus equals one half of the intercuspal width. Groups 2 and 5 were left unrestored, Groups 3 and 6 were restored with a silorane-based resin composite (Filtek P90) and Groups 4 and 7 with a methacrylate-based resin composite (Z250). Teeth were loaded in a universal testing machine; load and fracture patterns were recorded and compared statistically using 2-way ANOVA and t-test for pairwise comparisons and 1-way ANOVA with Dunnett test for multiple comparisons. ResultsUnrestored teeth became progressively weaker with more extensive preparations, Group 5 (unfilled ½) showed the lowest fracture load among the groups (71±22N, P<0.001). Restorations increased the fracture strength of unrestored teeth regardless of cavity size (P<0.001), but was still significantly weaker than sound teeth, with no significant difference between silorane and methacrylate groups. Failure of restored teeth was mostly adhesive at the tooth restoration interface. ConclusionsSilorane-based resin composite have no superior strengthening effect over the conventional methacrylate-based resin composite in restoration of root filled teeth. Both materials showed similar fracture patterns. Clinical significanceRoot filled teeth are considerably weakened via restorative and endodontic procedures. A direct adhesive restoration will aid in preserving tooth structure as far as it provides enough strength.

Assessments of antibacterial and physico-mechanical properties for dental materials with chemically anchored quaternary ammonium moieties: Thiol–ene–methacrylate vs. conventional methacrylate system

ObjectiveFabrication of low shrinkage stress and strain dental resins containing highly available immobilized bactericidal moieties has been reported. The goal of this study is producing dental restorative materials with long-last antibacterial activity and reduced secondary caries.It is anticipated that antibacterial properties of quaternary ammonium moieties chemically immobilized in the backbone of dental resins is directly depended on accessibility of these functions. In the present study the antibacterial effect of a series of antibacterial monomers polymerized in a ternary thiol–ene–methacrylate system were compared with corresponding classical methacrylate system against Streptococcus mutans (an oral bacteria Strain). Physical and mechanical properties of dental materials obtained from these two systems were also evaluated and compared. MethodsThe viscosities of the resin matrixes were measured on a MCR 300 rheometer. Degree of conversion (DC%) of monomers was measured using FTIR spectroscopy. The shrinkage-strain of photocured resins was measured using the bonded-disk technique. A universal testing machine combined with a stress measurement device was utilized to measure the polymerization-induced shrinkage stress. Viscoelastic properties of the samples were also determined by dynamic mechanical thermal analysis (DMTA). Assessment of antibacterial properties was performed through agar diffusion test (AD) to confirm non-release behavior of chemically anchored moieties. Quantitative assay of antibacterial activity was evaluated through direct contact test (DCT) against S. mutans. Direct contact cytotoxicity assay with fibroblast cell line L-929 was also performed to find more insight regarding cytotoxicity of the antibacterial matrixes. The data were analyzed and compared by ANOVA and Tukey HSD tests (significance level=0.05). ResultsNeat methacrylate systems had significantly higher viscosity than thiol–ene–methacrylate analogous. The degree of conversion of methacrylate moieties in thiol–ene–methacrylate system was improved in comparison to conventional methacrylate system. Shrinkage stress and strain of thiol–ene–methacrylate system was lower than the neat methacrylate system. The thiol–ene-methacrylate systems show increased homogeneity and decreased glass transition temperature (Tg) and crosslink density (νc) in comparison to the neat methacrylate-based resins. The incorporated monofuctional quaternized monomer reduces degree of conversion, shrinkage stress and crosslink density of matrix. The results showed significant improvement in antibacterial activity and cytocompatibility of dental materials obtained from thiol–ene polymerization system. SignificanceIt was shown that with proper control of monomers molar ratio, significant improvement in antibacterial activity and cytocompatibility as well as acceptable mechanical properties can be attained for dental resins prepared through the application of thiol–ene polymerization methodology.

Temperature rise during polymerization of different cavity liners and composite resins.

Objective:The purpose of this study was to evaluate the thermal insulating properties of different light curing cavity liners and composite resins during light emitting diode (LED) curing.Materials and Methods:Sixty-four dentin discs, 1 mm thick and 8 mm in diameter, were prepared. Specimens were divided into four groups. Calcium hydroxide (Ca[OH]2), resin-modified glass ionomer cement, flowable composite and adhesive systems were applied to dentin discs according to the manufacturers’ instructions. The rise in temperature during polymerization with a LED curing unit (LCU) was measured using a K-type thermocouple connected to a data logger. Subsequently, all specimens were randomly divided into one of two groups. A silorane-based composite resin and a methacrylate-based composite resin were applied to the specimens. Temperature rise during polymerization of composite resins with LCU were then measured again. Data were analyzed using one-way ANOVA and post hoc Tukey analyses.Results:There were significant differences in temperature rise among the liners, adhesives, and composite resins (P < 0.05). Silorane-based composite resin exhibited significantly greater temperature rises than methacrylate-based resin (P < 0.05). The smallest temperature rises were observed in Ca(OH)2 specimens.Conclusion:Thermal insulating properties of different restorative materials are important factors in pulp health. Bonding agents alone are not sufficient to protect pulp from thermal stimuli throughout curing.

Comparative evaluation of surface hardness and depth of cure of silorane and methacrylate-based posterior composite resins: An in vitro study.

Aim:This in vitro study was carried out to compare the effect of LED light curing system on polymerization and hardness of silorane-based and methacrylate-based posterior composite resin.Materials and Methods:A total of 40 samples, 20 of silorane-based composite Filtek P-90 and 20 of methacrylate-based composite Heliomolar HB measuring 2 mm thickness and 8 mm diameter were prepared using Teflon molds and cured using LED curing light. The samples were polished and tested in Knoop hardness tester using a 50-gram load and dwell time of 15 seconds on top and bottom surfaces. The percentage depth of cure was calculated, and statistical analysis was performed using two-way ANOVA test and Student t- test.Results:Higher statistically significant values were seen for both the top and bottom surface hardness in silorane-based resins than methacrylate-based resins on LED light curing.Conclusion:Greater depth of cure was achieved in silorane-based posterior composite than in methacrylate-based posterior composite resins with a statistically significant difference.

Evaluating the shear bond strength of enamel and dentin with or without etching: A comparative study between dimethacrylate-based and silorane-based adhesives.

Background Silorane-based composites and their specific self-etch adhesive were introduced to conquest the polymerization shrinkage of methacrylate-based composites. It has been shown that additional etching of enamel and dentin can improve the bond strength of self-etch methacrylate-based adhesives but this claim is not apparent about silorane-based adhesives. Our objective was to compare the shear bond strength (SBS) of enamel and dentin between silorane-based adhesive resin and a methacrylate-based resin with or without additional etching. Material and Methods 40 sound human premolars were prepared and divided into two groups: 1- Filtek P60 composite and Clearfil SE Bond adhesive; 2- Filtek P90 composite and Silorane adhesive. Each group divided into two subgroups: with or without additional etching. For additional etching, 37% acid phosphoric was applied before bonding procedure. A cylinder of the composite was bonded to the surface. After 24 hours storage and 500 thermo cycling between 5-55°C, shear bond strength was assessed with the cross head speed of 0.5 mm/min. Then, bonded surfaces were observed under stereomicroscope to determine the failure mode. Data were analyzed with two-way ANOVA and Fischer exact test. Results Shear bond strength of Filtek P60 composite was significantly higher than Filtek P90 composite both in enamel and dentin surfaces (P<0.05). However, additional etching had no significant effect on shear bond strength in enamel or dentin for each of the composites (P>0.05). There was no interaction between composite type and additional etching (P>0.05). Failure pattern was mainly adhesive and no significant correlation was found between failure and composite type or additional etching (P>0.05). Conclusions Shear bond strength of methacrylate-based composite was significantly higher than silorane-based composite both in enamel and dentin surfaces and additional etching had no significant effect on shear bond strength in enamel or dentin for each of the composites. The mode of failure had no meaningful relation to the type of composite and etching factor. Key words:Shear bond strength, adhesive, composite resin, silorane, methacrylate.

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.

The influence of calcium hydroxide on adaptation and root canal penetration in teeth filled with methacrylate-based resin sealer

The influence of calcium hydroxide on adaptation and root canal penetration in teeth filled with methacrylate-based resin sealer

Investigation of polymerization of methacrylate-based composite resins those belong to different categories

The present study investigated the polymerization of composite resins which belong to different categories. Each four different composite resins (low shrinkage, nanohybrid, microhybrid, and flowable resins) from three different manufacturers were chosen and light cured. Through the study, polymerization shrinkage and flexural properties were evaluated. Regardless of product and manufacturer, low shrinkage and flowable resins showed the lowest (7.7-12.3 μm) and highest (26.2-35.4 μm) polymerization shrinkage, respectively. The shrinkage difference between nanohybrid and microhybrid products was low. The flexural properties (strength and modulus) from products of different categories and from products of the same manufacturer had no consistency. All these values showed inconsistently changing pattern after immersion in distilled water. The tested composite resins belong to different categories but products of the same manufacturer and composite resins belong to the same category but products of different manufacturers had inconsistently different flexural properties.

Color Stability Behavior of Methacrylate-based Resin Composites Polymerized with Light-emitting Diodes and Quartz-Tungsten-Halogen.

Despite significant developments in improving the optical properties of resin composite materials, their color stability remains a challenge. This study aimed to evaluate the shade stability of light-polymerized, methacrylate-based resin composites with different filler particle composition (microfill, minifill, nanohybrids, and microhybrids) polymerized with quartz-tungsten-halogen (QTH) and light-emitting diodes (LED). Composite discs were fabricated from Tetric EvoCeram, Premise, Artiste, and Beautifil II (nanohybrids); Filtek Supreme Plus and Vit-l-escence (microhybrids); Heliomolar (microfill); and Estelite Sigma Quick (minifill) using a Teflon mold. The specimens were irradiated either with QTH (Elipar 2500; 600 mW/cm(2)) for 40 seconds or with LED (Bluephase G2; 1200 mW/cm(2)) for 20 seconds. Color parameters were measured with a colorimeter before and after polymerization and at 24 hours, one week, one month, and three months. Color change was calculated among the different storage periods. There was a significant effect of the composite, time, and their interaction (p<0.001) but no effect of the polymerization unit on the color stability. Color changes immediately after polymerization and at 24 hours (4.22 and 3.88 for LED; and 4.08 and 3.82 for QTH) were not significantly different from each other but were both significantly higher than changes after one week (0.96 and 0.78), one month (1.12 and 1.02), and three months (1.27 and 1.11) for LED and QTH, respectively (p<0.001). Color changes were observed for all the materials that were dependent on the type of composite but not on the polymerization unit. These color shifts took place primarily immediately after polymerization and after 24 hours and were additive in nature.

Evaluation of light curing distance and mylar strips color on surface hardness of two different dental composite resins.

Introduction: Hardness is one of the basic properties of dental materials, specially composite resins which is relevant to their polymerization. The aim of this study was to evaluate the effect of light curing distance and the color of clear Mylar strips on surface hardness of Silorane-based (SCR) and Methacrylate-based composite resins (MCR).Materials and methods: 40 samples of MCRs (Filtek Z250) and SCRs (Filtek P90) were prepared in size of 5 mm×2 mm (80 samples in total). The samples divided into 8 groups (10 samples in each one) based on the color of clear Mylar strips (white or blue) and distance from light curing source (0 mm or 2 mm). All the samples cured for 40 second and stored in incubator for 24 hours in 37°C temperature. Surface hardness test was done by Vickers test machine and the collected data were analyzed by one-way ANOVA and paired T-test by using SPSS software version 13 at significant level of 0.05.Results: MCRs cured with blue Mylar strips from 0 mm distance had the highest (114.5 kg/mm2) and SCRs cured with white Mylar strips from 2 mm distance had the lowest (42.2 kg/mm2) mean of surface hardness. Also, the results of comparison among SCRs and MCRs showed significant differences among all groups (all P values <0.01).Conclusion: The hardness decreased as the distance increased and the blue Mylar strips provided higher hardness than clear ones. Also, Filtek Z250 showed higher hardness compared to Filtek P90.

Durability of silorane repair with silorane and methacrylate resin.

Objective: The durability of bonded interface between silorane (SIL) and methacrylate-based (MET) composite resins wasn’t investigated yet. The purpose was to evaluate the repair strength (RS) and nanoleakage of the SIL repair using silorane- or methacrylate-based materials immediately [IM] or after 6 months of water storage [6M]. Materials and Methods: fifteen resin blocks (Filtek P90, 3MESPE) were polished, sandblasted with 50-µm aluminum oxide sandblasting and cleaned with 37% phosphoric acid. Then the specimens were divided into three groups: SIL-SIL (adhesive and composite resin); SIL-MET (silorane adhesive and methacrylate based composite) and MET-MET (methacrylate-based adhesive and composite resin) were used for the repair. Composite-composite bonded sticks (0.9 mm2) were sectioned and divided to be tested in tension (1.0 mm/min) IM or 6M. Two sticks from each tooth, at each time, were immersed in a 50% silver nitrate solution and evaluated by SEM. Data were analyzed by two-way repeated measures ANOVA and Tukey´s tests. Results: The RS of the SIL was not dependent upon the adhesive and composite used for the repair. A significant reduction of the RS was observed for all groups after 6M. Conclusions: Both materials can be used for the repair of the silorane composite, despite degradation occur after 6M.

Preparation of low shrinkage methacrylate-based resin system without Bisphenol A structure by using a synthesized dendritic macromer (G-IEMA)

With the growing attention on estrogenic effect of Bisphenol A (BPA), the application of BPA derivatives like Bis-GMA in dental materials has also been doubted. In this research, new BPA free dental resin systems were prepared with synthesized dendritic macromer G-IEMA, UDMA, and TEGDMA. Physicochemical properties, such as double bond conversion, polymerization shrinkage, flexural strength and modulus, fracture energy, water sorption and solubility of BPA free resin formulations were investigated. Bis-GMA/TEGDMA resin system was used as a control. Results showed that the prepared BPA free resins could have higher double bond conversion, comparable or lower polymerization shrinkage and water sorption, and lower water solubility, when compared with Bis-GMA/TEGDMA resin. Though flexural strength and modulus of prepared BPA free polymers were lower than those of Bis-GMA/TEGDMA polymer, BPA free polymers had higher fracture energies and showed plastic deformation prior to fracture, all of these two phenomena showed that BPA free polymers in this research might have higher fracture toughness which would be good for the service life of dental materials.

Flexural Strength of Temporary Restorative Materials Stored in Different Solutions

Aim: The aim of this study was to evaluate the effects of different solutions on the flexural strength of one methacrylate-based resin and three bis-acryl resin provisional materials using an in vitro model test system. Methods: The specimens (25 × 2 × 2 mm) were prepared from interim materials and stored for 14 days at 37°C in different solutions (coffee, burn, cola) and distilled water (control group). A standard three-point bending test was conducted on the specimens with an Instron universal testing machine at crosshead speed of 0.5 mm/min. Data were analyzed using the one-way analysis of variance and Tukey HSD multiple comprasion tests. Results: The methacry-late-based resin (Takilon) showed the least fracture strength (61.6 - 85.6 MPa). One of the bis-acryl resins (Protemp 4-3M ESPE) showed the highest fracture strength (112 - 128 MPa). Conclusions: All bis-acryl resin composite materials exhibited high fracture strength over the traditional methyl methacrylate resin throughout the 14 day time interval of investigation. The different solutions have not statistically significant effect on the flexure strength values on four temporary materials.

Polymerization shrinkage, flexural and compression properties of low-shrinkage dental resin composites

This study evaluated the polymerization shrinkage, flexural and compressive properties of low-shrinkage resin composites. For the study, four methacrylate-based and one silorane-based resin composites were light cured using three different light-curing units (LCUs) and their polymerization shrinkage, flexural (strength (FS) and modulus (FM)) and compressive (strength (CS) and modulus (CM)) properties were evaluated. Data were statistically analyzed using ANOVA and a post-hoc Tukey test. The polymerization shrinkage ranged approximately 7.6-14.2 μm for 2-mm thick specimens depending on the resin product and LCU. Filtek LS showed the least shrinkage while the rest shrank approximately 13.2-14.2 μm. However, Filtek LS showed the greatest shrinkage difference for the used LCUs. FS and CS of the tested specimens ranged 96.2-152.1 MPa and 239.2-288.4 MPa, respectively, depending on the resin product and LCU. The highest and lowest FS and FM were recorded for the methacrylate-based resin composites. Among the specimens, Filtek LS showed the lowest CS and CM.

Human gingival response to methacrylate and silorane-based composite restoratives

Objective: The clinical acceptance of restorative material normally depends on its biological safety. This in vivo study considered the clinical and histological gingival response to methacrylate and silorane-based composites. Materials and Methods: Sixty patients with sub-gingival tooth defects were treated in two groups (n = 30) with Tetric N-Ceram and Filtek P90 composite restoratives with minimal finishing procedures. An additional 10 patients with pre‑existing gingival inflammation and no cervical tooth defects served as control. The gingiva in contact was assessed clinically and histologically at 2, 4 and 8 week intervals. Results: A significant time‑dependent gingival response was noted in both test groups (t-test, P < 0.05). Inflammatory cell infiltrates, cellular degeneration, epithelial hyperplasia, keratinization, and erosion were found in selected gingival biopsies. Conclusion: The results confirmed that minimally finished subgingival composite restorations contribute to significant histopathological changes to the contacting gingival tissues. However, the silorane‑based composite elicited less severe gingival inflammatory symptoms in comparison to the methacrylate-based resin system.

Effect of pre-treatment with chlorhexidine on the retention of restorations: a randomized controlled trial.

This study aimed to evaluate the effect of chlorhexidine (CHX) application on etched dentin on the 6-month retention of restorations placed on non-carious cervical lesions (NCCLs). A randomized controlled split-mouth and triple blind trial was carried out. Patients (n=42) with at least two non-carious cervical lesions were included. NCCLs were randomly assigned to two groups: control (placebo solution) or test group (2% CHX solution for 60 s after acid etching and before the adhesive application). Class V restorations (n=169) were performed with an etch-and-rinse adhesive system and composite resin by 10 trained operators. A calibrated examiner evaluated the restorations at 1 week (baseline) and at 6 months using the FDI criteria. The primary outcome was retention of the restorations. The analysis of factors associated to failure of restorations was carried out by Fisher's exact test (α=0.05). After 6 months of follow-up, 3.4% (CI 95% 1.3-7.3) of the restorations failed. There was no statistically significant difference between control and CHX (p=0.920). Regarding the cavity variables, deeper (p=0.04), wider (p=0.004) and wedge-shaped (p=0.033) cavities failed more. Both treatments provided acceptable clinical performance of the restorations. The use of CHX as a adjuvant in dentin adhesion did not influence the retention of Class V restorations after 6 months of follow-up.