Microhybrid Resin Research Articles

Shear bond strength of different surface treatments in bulk fill, microhybrid, and nanoparticle repair resins.

ObjectivesThe purpose of this study was to evaluate the influence of surface treatment and different types of composite resin on the microshear bond strength of repairs.Materials and methodsSeventy-two specimens (n=72) were prepared using a nanoparticle resin and stored in artificial saliva at 37 ± 1°C for 24 h. After this period, the specimens (n=24) were restored with microhybrid resin P60 (3M ESPE), nanoparticle resin Filtek Z350 (3M ESPE), and Bulk Fill Surefil SDR Flow (Dentsply) composite resins. Previously, the surfaces of the samples were treated, forming the following subgroups (n=12): (A) conditioned with 37% phosphoric acid for 30 s, and (B) abrasioned with a diamond tip for 3 s and conditioned with 37% phosphoric acid. In all groups, before insertion of the composite resin, the adhesive system Adper Single Bond 2 was actively applied and photopolymerized for 20 s.ResultsThe microshear test was executed to assess bond strength. Kruskal–Wallis (p<0.05) and Mann–Whitney statistical tests showed significant statistical difference considering that the bulk-fill resin turned out to have a lower bond strength than the conventional nanoparticle and microhybrid composites. With regard to the technique, the roughening with diamond bur followed by the application of phosphoric acid exhibited values higher than the exclusive use of acid.ConclusionThe microshear bond strength of the composite resin repairs varies in accordance with the type of composite resin utilized, and roughening the surface increased the bond strength of these materials.

Relative biocompatibility of micro-hybrid and nano-hybrid light-activated composite resins.

Background. In vitro studies have revealed a direct association between resin content and cytotoxicity of composite resins; however, implantation studies in this regard are sparse. This study investigates the relationship between filler content of composite resins and biocompatibility.Methods. This research employed twelve 180‒200-gr male Wistar rats, 1 nano-hybrid (Prime-Dent Inc.) and 1 micro-hybrid (Medental Inc.) composite resins containing 74% and 80‒90% filler content, respectively. The samples were assessed on the 2nd, 14th and 90th day of implantation. Four rats were allocated to each day in this experimental study. A section of 1.5mm long cured nano-hybrid and micro-hybrid materials were implanted into the right and left upper and lower limbs of the rats, respectively. Eight samples were generated on each day of observation. Inflammation was graded according to the criteria suggested by Orstavik and Major. Pearson’s chi-squared test was employed to determine the relationship between the tissue responses of the two materials. Statistical significance was set at P < 0.05.Results. The average grade of inflammation for the nano-hybrid on the 2nd day of implantation was 3.3. The micro-hybrid resin had a score of 3.0 for cellular inflammation. On the 14th day, the micro-hybrid resin also exhibited a lower average grade for cellular inflammation. On the 90th day, the micro-hybrid resin had a higher grade of inflammation (0.9) compared to 0.3 recorded for nano-hybrid. The composite resins with higher filler content elicited a significantly lower grade of inflammation irrespective of the duration (χ=20.000, df=8, P=0.010) while the composite resins with lower filler content elicited a significantly lower inflammatory response on the 90th day (χ=4.000, df=1, P=0.046).Conclusion. The composite resins with higher filler content generally elicited significantly lower grades of inflammation, and the composite resins with lower filler content exhibited significantly lower inflammatory response on the 90th day of implantation.

Clinical Effectiveness of Different Polishing Systems and Self-Etch Adhesives in Class V Composite Resin Restorations: Two-Year Randomized Controlled Clinical Trial.

The aim of this randomized controlled clinical trial was to compare the clinical effectiveness of different polishing systems and self-etch adhesives in class V composite resin restorations. A total of 164 noncarious cervical lesions (NCCLs) from 35 patients were randomly allocated to one of four experimental groups, each of which used a combination of polishing systems and adhesives. The two polishing systems used were Sof-Lex XT (Sof), a multistep abrasive disc, and Enhance/Pogo (EP), a simplified abrasive-impregnated rubber instrument. The adhesive systems were Clearfil SE bond (CS), a two-step self-etch adhesive, and Xeno V (XE), a one-step self-etch adhesive. All NCCLs were restored with light-cured microhybrid resin composites (Z250). Restorations were evaluated at baseline and at 6, 12, 18, and 24 months by two blinded independent examiners using modified FDI criteria. The Fisher exact test and generalized estimating equation analysis considering repeated measurements were performed to compare the outcomes between the polishing systems and adhesives. Three restorations were dislodged: two in CS/Sof and one in CS/EP. None of the restorations required any repair or retreatment except those showing retention loss. Sof was superior to EP with regard to surface luster, staining, and marginal adaptation (p<0.05). CS and XE did not show differences in any criteria (p>0.05). Sof is clinically superior to EP for polishing performance in class V composite resin restoration. XE demonstrates clinically equivalent bonding performance to CS.

Evaluation of Surface Roughness of Different Direct Resin-based Composites.

Aims and Objective:To evaluate surface roughness of different resin-based composites.Materials and Methods:Three resin composites, one nanohybrid, one nanoceramic, and one bulk-fill resin-based composite, were used in this study. Cylindrical Teflon mold and 8 mm in diameter and 2 mm in thickness disc specimens were prepared. For each composite material, 15 discs were fabricated, with a total of sixty discs were obtained (n = 60). A glass slide 1–2 mm thick was placed over the strip before curing with the light-curing unit to flatten the surfaces. The specimens were then cured for 40 s through the Mylar strip and the glass slide. Five specimens per each material received no finishing treatment after being cured under Mylar strips; these specimens served as a control. Ten specimens from each composite material were finished/polished with Eve discs at coarse, medium, fine, and superfine grits for 30 s (using stopwatch) each on the specimens. After polishing, the composite surfaces were assessed quantitatively by profilometry and qualitatively by scanning electron microscopy. Data were analyzed using SPSS software.Results:Tetric Evo Ceram and Tetric Evo Ceram Bulk-Fill specimens polished with Eve revealed slightly the same surface appearance as the Mylar strip. Eve discs scratched and exposed fillers of Ceram-x. Eve discs for Z250 surfaces exposed and scratched the filler particles but less than occurred with Ceram-x.Conclusion:Bulk-Fill and nanohybrid resin composites exhibit smoothest surfaces compared with nanoceramic and microhybrid resin composites after polishing.

Clinical evaluation of microhybrid composites in noncarious cervical lesions: 24-month results.

To evaluate the clinical performance of two different microhybrid resin composites in noncarious cervical lesions (NCCLs) after 24 months. Ninety-seven NCCLs were restored with either TPH Spectrum (n = 48) or Filtek Z250 (n = 49) using an etch-and-rinse adhesive in 20 patients. The restorations were clinically evaluated using modified United States Public Health Service criteria for retention, color match, marginal discoloration, marginal adaptation, surface texture, anatomic form, postoperative sensitivity, and secondary caries. The restorations were assessed 1 week after placement (baseline) and after 6, 12, and 24 months. Restoration survival rates were calculated using the Kaplan-Meier procedure estimator, and a log-rank test was used to compare the survival distributions (P < 0.05). Statistical analysis was undertaken using Pearson's Chi-square test and Fisher's exact test to assess differences among the restorative materials (P < 0.05). Cochran's Q-test was employed for evaluating differences in the same restorative material between recall periods. The retention rates were 100% at 6 months, 89.6% and 91.8% at 12 months, and 85.4% and 89.8% at 24 months for TPH and Z250, respectively. TPH showed a statistically significant difference in marginal discoloration between the baseline and 24 months results (P < 0.05). Both TPH and Z250 showed statistically significant differences in marginal adaptation between the baseline and 24 months results (P < 0.05). Over the 24-month period, both microhybrid resin composites demonstrated acceptable clinical results in NCCLs.

Relationship between mechanical properties and bond durability of short fiber-reinforced resin composite with universal adhesive.

The purpose of this study was to determine the relationship between mechanical properties and bond durability of short fiber-reinforced resin composite with universal adhesive. As controls, micro-hybrid and nano-hybrid resin composites were tested. The universal adhesives used were Scotchbond Universal, Adhese Universal, and G-Premio Bond. The fracture toughness and flexural properties of resin composites, and shear bond strength and shear fatigue strength of universal adhesive with resin composite using both total-etch and self-etch modes were determined. In the results, short fiber-reinforced resin composite showed significantly higher fracture toughness than did micro-hybrid and nano-hybrid resin composites. The flexural strength and modulus of short fiber-reinforced and nano-hybrid resin composites were significantly lower than were those of micro-hybrid resin composites. Regardless of etching mode, the shear bond strength of universal adhesives with short fiber-reinforced resin composite did not show any significant differences from micro-hybrid and nano-hybrid resin composites. The shear fatigue strength of universal adhesives with short fiber-reinforced resin composite and micro-hybrid resin composites were significantly higher than that of nano-hybrid resin composites. The results of this study suggest that the mechanical properties of short fiber-reinforced resin composite improve their bond durability with universal adhesive.

Evaluation of the Effect of Different Herbal Tea on Discoloration of Different Kinds of Composite

Objectives: The aim of this study was to evaluate the effect of six herbal teas on the color stability of two types of nanohybrid and one microhybrid resin composite. Materials and Methods: 70 disc-shaped specimens, 210 in total (7*2mm), were fabricated from each of the following materials in metal mould : Tetric N ceram, Grandio, Gradia Direct Anterior. Specimens were stored in distilled water at 37°C for 24 hours in an incubator for completion of polymerization. After baseline evaluation (L*, a*, b*CIELAB scale), the specimens were divided into seven subgroups, according to the test and control storage solutions (n=10). Randomly selected specimens from each material were immersed in 20 ml of the test solutions (Borago, Green, Hibiscus, Thyme, Black and Lemon Verbena teas) at 37˚c for 24 hours and 48 hours. Solutions were refreshed every 24 hours. All samples were polished using Soflex discs with Medium, Fine, Superfine grit after storage in herbal teas. Specimens color was measured in 24, 48 hours and after polishing. The collected data was statistically analyzed using two-way analysis of variance with repeated measure and Tukey’s HSD at a significance level of 0.05. Results: All samples displayed color changes after immersion in the herbal teas. Hibiscus tea induced the highest level of discoloration after 24 hours immersion in all three composites. Black tea induced highest level of discoloration in (Grandio ΔE=7.44). Hibiscus tea and Thyme tea induced highest level of discoloration in (Tetric N ceram ΔE=11.) and (Gradia Direct ΔE=14.11), respectively, after 48 hours immersion. The least discoloration was found with Borage tea in 24 and 48 hours. After re-polishing the color change was reduced. Grandio showed the greatest color reduction in Black tea. Color improvement of Tetric N ceram was better than Gradia Direct. Conclusion: All tested restorative materials showed a color shift after immersion in herbal teas, which Tetric N ceram displayed the highest color change in Hibiscus tea and Borago tea induced lowest discoloration on Grandio after 24 h immersion. Thyme tea induced the highest level of discoloration on Gradia Direct and least discoloration was found in Borago tea on Grandio after 48 hours immersion.

Microleakage comparison of three types of adhesive systems versus GIC-based adhesive in class V composite restorations

Background and aims: New dentin bonding agents and techniques have been developed to reduce microleakage and create higher bond strength. This in-vitro study compared the microleakage of three resin-based adhesives versus a GIC-based adhesive on class V composite restorations. Materials and Methods: Class V cavities were prepared on the buccal surfaces of 72 sound premolars, randomly assigned to six groups (n=12) and treated as follows: without any treatment (negative control group); total-etch (OptiBond Solo Plus); two-step self-etch (OptiBond XTR); one-step self-etch (OptiBond All-in-One) and GIC-based adhesive (Fuji bond LC) with pre-cure and co-cure techniques. The treated cavities were filled with a micro-hybrid resin composite (Point 4, Kerr). Following finishing and polishing procedures, the specimens were placed in 100% humidity, stored in distilled water, thermocycled and then immersed in a methylene blue, sectioned, evaluated for microleakage and scored on a 0 to 3 ordinal scale. Results: None of the adhesives tested were capable of completely eliminating marginal microleakage. There were statistically significant differences among the test groups at occlusal margins; but at cervical margins were not. The Fuji Bond LC with co-cure and control groups had significantly greater microleakage scores at the occlusal margins. At the cervical margins, the bonded restorations with OptiBond XTR and OptiBond All-in-One adhesives presented significantly lower microleakage scores. Also, there were no significant differences between the resin adhesive groups both at occlusal and cervical margins. The microleakage scores at the cervical margins were markedly higher than the occlusal margins in the groups bonded with OptiBond Solo Plus and Fuji Bond LC with pre-cure. The differences between Fuji Bond LC adhesive with pre-cure and co-cure techniques were significant. Conclusion: This study encourages application of the Fuji bond LC adhesive with pre-cure technique instead of the resin adhesives for marginal seal in class V composite restorations.

Effect of Food Simulating Liquids and Thermo-cycling on flexural strength and surface hardness of a Resin Nano-Ceramic CAD/CAM Material

Purpose: Evaluate the effect of food simulating liquids and thermocycling on miniflexural strength and surface micro-hardness of a resin nano-ceramic material (Lava Ultimate) compared to indirect laboratory composite resin material (Nexco Paste) and direct composite resin material (Filtek Z350 XT).Material and Methods: A total number of 180 samples were fabricated. The samples were divided equally into 3 groups (n=60). Group 1 (M1) samples were fabricated from the resin nano ceramic CAD/CAM blocks (Lava Ultimate), group 2 (M2) samples were farbricated form indirect micro-hybrid resin composite (Nexco Paste), while group 3 (M3) samples were fabricated from direct resin composite (Filtek Z350 XT). Thirty bars (12X2X2mm) from each material were fabricated to evaluate the mini flexural strength. Thirty disks (8X2mm) were fabricated from each material to evaluate thesurface micro-hardness. The samples of M1 groups were fabricated by cutting from the CAD/CAM block using low speed diamond disk while samples of M2 and M3 samples were fabricated using teflon mold. Each material samples were further subdivided into 6 subgroups; the first subgroup was not immersed into food simulating liquids nor thermocycled,4 subgroups samples were immersed into food simulating liquids (water, ethanol, heptane and citric acid) and the last subgroup samples were thermocycled. Mini flexural strength test was done using universal testing machine and surface hardness was done using Vickers hardness tester.Results: Lava Ultimate showed the significantly highest mini flexural strength and surface micro-hardness values before and after immersion into food simulating liquids and thermocycling compared to the two other tested materials. Conclusion: According to the results of the present study, Lava Ultimate showed better mini flexural strength and surface micro-hardness compared to the two othertested materials.

Influence of various bleaching regimes on surface roughness of resin composite and ceramic dental biomaterials

Bleaching agents are commonly used in dentistry for treating the discolored teeth. A number of biomaterials and methods are in clinical applications. The major aim of this study was to evaluate the effects of two different bleaching agents on the surface roughness properties of dental resin nanocomposites and dental porcelains using various regimes. This study was conducted using direct restorative hybrid and nanocomposite materials and dental porcelains. The specimens were treated using the bleaching gels [(Opalescence Boost 40% OP) and (Whiteness HP 35% WHP)] for 30, 45, 60 and 120 minutes respectively. Treated samples were analyzed for surface roughness properties using contact mode surface profilometry and surface topography using scanning electron microscopy (SEM). Data was analyzed statistically using analysis of variance (ANOVA). There were no significant changes observed in the roughness of nanofill, nanohybrid composites and ceramic materials compared to microhybrid resin composites (p> 0.05). The SEM photomicrographs confirmed the results of the profilometer showing slight changes in the microhybrid resin composite. No remarkable difference was observed between the bleaching agents (Opalescence Boost and Whiteness HP Blue) for the surface roughness of tested dental materials. The bleaching agents can be used without harming the ceramic, nanofilled or nanohybrid resin restorations. However, if microhybrid or microfilled composite restorations are present in the oral cavity, bleaching may damage the surface finish and requiring replacement of restorations.

Two-body wear simulation influence on some direct and indirect dental resin biocomposites - A qualitative analysis.

The aim of this study was to qualitatively assess the outcomes of two in vitro aging methods, thermal-cycling and twobody wear simulation accomplished with a dual-axis chewing device, on the surface characteristics of eight direct and indirect dental resin biocomposites. Eighty mesial-occlusal-distal dental cavities were restored with four direct nanohybrid composite materials and with four nano- and micro-hybrid lab-fabricated resin composite inlays. After the restored teeth were subjected to thermal-cycling and wear simulation based on mechanical loading, the surface texture features of the restorations were separately analysed for each of the methods, on epoxy resin models using a digital camera, computer-aided-design system, optical stereo-microscopy and scanning electron microscopy. All the dental restorative resin based composites used in this investigation displayed different cyclic wear patterns after undergoing mechanical loading. After thermal-cycling, the group of resin composite inlays showed a better adaptation, a smoother and more polished occlusal surface compared with direct restorative materials. Only two of direct nanohybrid resin composites performed better after two aging methods. One nanohybrid and the other two microhybrid resin inlays did not perform as expected when they were subjected to simulated wear compared to the rest of test materials. The use of the two-body wear simulation method revealed important information about the behavior of the dental resin-based composites when multiple oral factors are involved in a lab-simulated condition. Furthermore, the macro- and micro-morphological analysis showed different abrasion patterns among the materials being tested according to the filler percentage and distribution of the particles within the resin matrix.

Cuspal Displacement Induced by Bulk Fill Resin Composite Polymerization: Biomechanical Evaluation Using Fiber Bragg Grating Sensors.

Polymerization shrinkage is a major concern to the clinical success of direct composite resin restorations. The aim of this study was to compare the effect of polymerization shrinkage strain of two resin composites on cuspal movement based on the use of fiber Bragg grating (FBG) sensors. Twenty standardized Class II cavities prepared in upper third molars were allocated into two groups (n = 10). Restorations involved the bulk fill placement of conventional microhybrid resin composite (Esthet•X® HD, Dentsply DeTrey) (Group 1) or flowable “low-shrinkage” resin composite (SDR™, Dentsply DeTrey) (Group 2). Two FBG sensors were used per restoration for real-time measurement of cuspal linear deformation and temperature variation. Group comparisons were determined using ANCOVA (α = 0.05) considering temperature as the covariate. A statistically significant correlation between cuspal deflection, time, and material was observed (p < 0.01). Cuspal deflection reached 8.8 μm (0.23%) and 7.8 μm (0.20%) in Groups 1 and 2, respectively. When used with bulk fill technique, flowable resin composite SDR™ induced significantly less cuspal deflection than the conventional resin composite Esthet•X® HD (p = 0.015) and presented a smoother curve slope during the polymerization. FBG sensors appear to be a valid tool for accurate real-time monitoring of cuspal deformation.

Effects of Preheated Composite on Micro leakage-An in-vitro Study.

Resin composites have been the pinnacle of direct esthetic restorations ever since its discovery. However, it comes with its own disadvantages. Post-operative sensitivity and marginal discoloration frequently occur due to polymerization shrinkage and micro leakage, which is the major cause of failure in resin composite restorations. To evaluate the effects of preheated composite at different temperatures on microleakage. A total of 60 extracted non-carious human premolars were collected and class 1 cavity (1.5x4x 3mm) was prepared in each and were randomly divided into three groups. Group 1 (n=20) was filled with microhybrid resin composite (Heraeus Charisma Smile) at room temperature. Group 2 (n=20) was filled with the same resin composite which was preheated to 50°C and Group 3 (n=20) was filled with resin composite preheated to 60°C. Teeth were subjected to a thermocycling regime (500X, 5 - 55°C), followed by a dye infiltration by immersing in basic fuschin for 24 hours. The tooth was sectioned longitudinally and the extent or absence of micro-leakage was determined by the amount of dye penetration along the resin composite-tooth interface using a confocal microscope. There was minor micro-leakage detected at the occlusal margin of the control tooth specimen. The sample with preheated composite restoration at 50°C showed an intact tooth-restoration interface with no micro leakage. However, the preheated composite at 60°C showed large amount of microleakage. Under the current limitation of the study, preheated composite at 50°C showed the least micro-leakage.

Microbiological characterization and effect of resin composites in cervical lesions.

BackgroundNon carious cervical lesions associated to muscle hyperfunctions are increasing. Microhybrid resin composites are used to restore cervical abfractions. The purpose of this study was to investigate if resin composites modify tooth plaque, inducing an increment of cariogenic microflora and evaluate their effect, in vivo and in vitro, against S. mutans.Material and MethodsEight abfractions were restored with two microhybrid resin composites (Venus, Heraeus-Kulzer® and Esthet-X, Dentsply®), after gnatological therapy, in three patients with muscle hyperfunctions. For each abfraction three samples of plaque were taken from the cervical perimeter: before the restoration, one week and three months after restoration. The samples were evaluated both by traditional microbiological methods and by Polymerase Chain Reaction (PCR). In vitro, disk-shaped specimens of the two composites were prepared to estimate the effects against pre-cultured S. mutans, after incubation at 37°C for 24h and assessed by a turbidimetric technique.ResultsIn vivo no differences were found in plaque growth, for all samples, before and after restoration with both composites; in vitro, instead, a significant reduction of S. mutans growth was found between specimens of two composites (Mann-Whitney U-test p>0,06).ConclusionsIn this study a relevant consideration was elicited: composite materials, in vivo, do not modify plaque composition of non carious cervical lesions to a potential cariogenic plaque. Key words:Abfraction, restoration, S. mutans, composite, class V.

Color evaluation of low viscosity bulk-fill resin with composite resin capping layer

Purpose: The purpose of this study was to measure the color of low viscosity bulk-fill resin with a capping layer and to compare it with the color of microhybrid composite resin. Materials and Methods: A low viscosity bulk-fill resin (SDR) and microhybrid composite resin of shade A2 (A2) or A3 (A3) were fabricated to 4 mm thickness and light cured for 20 seconds. CIE L*a*b* values of the resin specimens were measured with a colorimeter. Then shade A2 and A3 microhybrid composite resin was capped over low viscosity bulk-fill resins in 2 mm thickness (SA2, SA3). The resin specimens were light cured for 20 seconds and the color was measured and analyzed (n = 10). Color differences (ΔE) between SA2 and A2, SA3 and A3 were also calculated. Results: L* value was highest in SDR followed by SA2 and SA3. L* value of A2 and A3 was the lowest. a* value was lowest in SDR followed by SA2 and SA3, and A2 and A3 was the highest. b* value was lowest in SDR followed by A2 and SA2, and A3 and SA3 was the highest. ΔE between A2 and SA2 (ΔE = 3.4), and that between A3 and SA3 (ΔE = 3.1) was lower than the perceptible color difference threshold of ΔE = 3.7. Conclusion: ΔE between low viscosity bulk-fill resin with a capping layer and microhybrid resin was lower than the perceptible color difference threshold. (J Dent Rehabil Appl Sci 2015;31(4):294-300)

Fracture toughness comparison of five indirect resin composites under the effect of thermal cycling

ABSTRACTThis study investigated the microhardness and fracture toughness values of five dental indirect resin composites under the effect of thermal cycling by single-edge notched beam method. Highest microhardness and fracture toughness were reached in AP-X and Filtek P60 groups (microhybrid resin composite) (P < 0.05). After thermal cycling, significant changes of fracture toughness were found for the tested composites except AP-X. Microdifferences between scanning electron microscope images with and without thermal cycling were observed. It is concluded that irregular-shaped fillers and higher filler content contribute to higher mechanical properties, microhardness, and fracture toughness and result in superior fracture toughness under the effect of thermal cycling.

NaOCl degradation of one-step one-bottle self-etch adhesives bonded to bovine dentine

Objective: The aim of the present study was to assess the influence of an in vitro aging regime (NaOCl storage) on dentine microtensile bond strength (μTBS) of five one-step one-bottle self-etch adhesives in comparison with bond strength of two-step self-etch adhesive.Material and methods: Flattened dentine surfaces from 30 bovine incisors were bonded with five one-step one-bottle self-etch adhesives (iBond, Clearfil S3 Bond, AdheSE One F, G-Bond, Optibond all-in-one) and one two-step self-etching adhesive (Clearfil SE Bond). Composite buildups were done with microhybrid resin composite. Bonded samples were sectioned into resin–dentine sticks of 0.8 mm2 cross section. Randomly selected 20 sticks were tested directly by microtensile bond strength testing machine, whereas another randomly selected 20 sticks were tested after being stored in solution of 10% NaOCl for 5 h. Data were analyzed by two-way analysis of variance (ANOVA) and Tukey’s honest significant difference (HSD) tests (p < 0.05).Results: All adhesives exhibited similar dentine bond strength with exception of G-Bond. After NaOCl storage, μTBS reduced in all groups significantly. The lowest μTBS were found for G-Bond. Rest of one-step self-etch adhesives presented similar μTBS with two-step self-etch adhesive.Conclusion: Interfaces of resin–dentine bonding are susceptible to NaOCl degradation. The amount of the destruction depends on adhesive system. NaOCl degradation of the nonresin encapsulated collagen fibers might decrease long-term stability of resin bonding with dentine.

Vickers microhardness comparison of 4 composite resins with different types of filler.

Composite resins are the material election to restored minimal invasive cavities; conversely, it is important to explore their mechanical properties of commercial available dental materials. Objective: To compare the Vickers microhardness (VHN) of four available commercial composite resins of standardized samples and methods. Methodology: Composite cylinders were performed in a Teflon mould. We use the follow composite resins (n=4/gp): Microhybrid resins [Feeling Lux (Viarden) and Amelogen Plus (Ultradent)], Hybrid resin [Te-Econom Plus (Ivoclar)] and Nanohybrid resin [Filtek Z350 (3M ESPE)]. All samples were incubated in distilled water at 37 oC for five days. The test was carried out with microhardness indenter at 10 N, and a dwelling time of 10 s for 9 indentations across the specimens resulting in a total of 36 indentations for each group. Data were subject to Kolmogorov-Smirnov normality test and ANOVA (post-hoc) Tukey test. Results: The VHN mean values corresponded from harder to softer as follow: Filtek Z350 (71.96±6.44) (p˂0.01)˃Amelogen Plus (59.90±4.40) (p˂0.05)˃Feeling lux (53.52±5.72)˃Te-Econom Plus (53.26±5.19). Conclusion: According to our results, the microhardness of the evaluated conventional composite resin can withstand the masticatory forces but nanohybrid composite resins showed better Vickers microhardness that clinically can results in suitable option for restored minimal invasion treatments.

A 15-year randomized controlled study of a reduced shrinkage stress resin composite

ObjectivesThe aim of this randomized controlled study was to evaluate the long term effectiveness of a reduced shrinkage stress resin composite in Class II restorations. The material was compared intra-individually with a microhybrid resin composite. Materials and methodsEach of 50 patients with at least one pair of two similar sized Class II cavities participated (22 female, 28 male, mean age 43 years, range 18–64). Each participant received in each pair, in a randomized way, one Class II restoration performed with a reduced shrinkage stress resin composite (InTen-S) and the other restoration with a microhybrid resin composite restoration (Point 4). Both restorations were placed with an etch-and-rinse bonding system and an oblique layering technique. A total of 106 restorations, 33 premolar and 73 molars, were placed. The restorations were evaluated blindly each year using modified USPHS criteria. The overall performance of the experimental restorations was tested after intra-individual comparison using the Friedmańs two-way analysis of variance test. The hypothesis was rejected at the 5% level. ResultsAt 15 years, 91 restorations were evaluated. The drop out frequency was 15 restorations (5 male, 3 female participants; 2 premolar and 13 molar restorations). Except for 2 participants, who reported slight symptoms during a few weeks after placement, no post-operative sensitivity was observed at the recalls. The overall success rate at 15 years was 77%. Twenty-one non acceptable restorations were observed during the 15 years follow up, 10 InTen-S (21.7%) and 11 Point 4 (24.4%) restorations (p>0.05). Annual failure rates for the resin composites were 1.5% and 1.6%, respectively. The main reasons for failure were secondary caries (8) and resin composite fracture (7). The differences between premolar vs. molar restorations and between restorations in male vs. female participants were not significant. Significant differences were observed between 2-surface vs. 3-surface restorations. SignificanceDuring the 15-year follow up, the reduced shrinkage stress resin composite showed a good clinical durability in Class II cavities, but not significantly better than the control microhybrid resin composite. Secondary caries and material fracture were the main reasons of failure.

Wavelength of Experimental LEDS: Hardness, Elastic Modulus, Degree of Conversion and Temperature Rise of a Microhybrid Composite

The aim of this study was to evaluate the effect of different peak wavelengths (450nm, 468nm and 490nm) of experimental LEDs on hardness, elastic modulus, degree of conversion and temperature rise of a microhybrid resin composite – Venus® (Heraeus Kulzer). Hardness and elastic modulus were determined by nanoindentation technique (n=5), degree of conversion was measured by FTIR (n=5) and temperature rise was measured with a thermistor (n=30). Data were submitted to ANOVA and multiple comparisons tests (α=0.05). Mechanical properties and degree of conversion (p<0.001) were superior on the top surfaces of the specimens. 468nm showed the highest mechanical properties values. There was no statistical difference in the degree of conversion (p=0.51) and in temperature rise (p=0.06) among all LEDs. Hardness and elastic modulus were influenced by LED´s wavelength, whereas degree of conversion and temperature rise were not influenced.