Bond strengths of bulk-fill resin composite repairs: effect of different surface treatment protocols in vitro

To evaluate the effect of different surface treatment protocols on the microtensile bond strength (μTBS) of bulk-fill resin composite repairs. Thirty-five bulk-fill resin composite samples (Filtek Bulk Fill) were prepared (5 × 5 × 5 mm) and aged by thermocycling (X5000). Samples were randomly divided into five groups (n = 7): a control (no treatment) and four surface treatment groups (Single Bond Universal [SBU]; phosphoric acid (37%) + SBU; Er,Cr:YSGG laser + SBU; aluminum oxide sandblasting + SBU). Filtek Ultimate Universal composite was used as a repair material. After storage for 24 h in distilled water (37 °C), sticks were obtained and subjected to a μTBS test. The data (MPa) were analyzed by one-way ANOVA with a post hoc test (α = 0.05). Failure mode was evaluated using a light microscope (10×). There were significant differences between the groups (p < 0.05). The lowest bond strength values were obtained in the control group (p < 0.05). No significant difference was observed between Group II (universal adhesive) and Group III (acid etch + universal adhesive) (p > 0.05). The bond strength of Group II was significantly lower than that of the other surface treatment groups (p < 0.05). While Group III showed significantly lower values than those of the laser treatment group (Group IV), similar values were obtained with Al₂O₃ sandblasting group (Group V). The highest repair bond strength was obtained in Group IV (p < 0.05) which was not significantly different from the Al₂O₃ sandblasting group (p > 0.05). The predominant failure mode was adhesive. Treatment of aged bulk-fill resin composite surfaces with laser and Al₂O₃ sandblasting provided higher repair bond strength values.     

Fracture strength of composite resins for endodontically treated molars

Objectives: The purpose of this study was to evaluate the effect of different fabrication techniques on the fracture strength of the composite resin-based inlay restorations of endodontically treated molars. Methods: Sixty mandibular molars were divided into six groups (n = 10) designated according to the treatment as: Group-1: Control group, intact teeth; Group-2: Filtek Ultimate Universal restorative with incremental technique; Group-3: Filtek Bulk Fill Posterior restorative; Group-4: Biodentine with Filtek Ultimate Universal restorative; Group 5: everX Posterior with Filtek Ultimate Universal restorative; and Group-6: Lava Ultimate CAD/CAM restorative. The standard mesio-occluso-distal cavities were prepared and the roots filled for all the teeth, except those of the control group. Following the placement of the restorations, the fracture resistance of the specimens was measured. The data were analyzed by the one-way analysis of variance and Tukey’s post hoc test. Results: While Group-1 (2815.80 N) exhibited significantly higher fracture strength than the other groups (p < 0.05), Groups-2 (2062.20 N), 3 (2166.00 N), 5 (2355.60 N), and 6 (2340.70 N) exhibited statistically similar results (p > 0.05). The Biodentine group (1480.50 N) exhibited significantly lower fracture strength than the rest of the groups (p < 0.05). Conclusions: The CAD/CAM and manual build-up techniques exhibited statistically similar results with the exception of Biodentine, which exhibited a significantly lower in vitro performance compared to the other composites used in the study. The fiber-supported composite everX Posterior increased the fracture strength of the endodontically treated teeth.     

Comparison of eluted monomer from different indirect and direct resin composites

Indirect resin composites used in indirect restorations have been used as alternative methods to avoid the negative effects of a direct application. The composition and structure of these are similar to a direct composite. Several authors have discussed the elution monomer from resin composites because it is a crucial factor in optimizing the physical properties and biocompatibility of resin composites. The aim of this study was to compare the elution of monomers from different resin composites using high-performance liquid chromatography (HPLC). Indirect composites including Signum, Gradia, and Solidex, and direct composite Filtek Ultimate were used. The samples (2 x 5 mm) were prepared and polymerized for 20 seconds with a light-emitting diode unit. A secondary curing was then applied to the indirect resin composites. After fabrication, each sample was immediately immersed in a 75 wt% ethanol/water solution and analyzed by HPLC. The obtained data were analyzed with one-way ANOVA and Tukey HSD (p < 0.05). Residual monomers were eluted from indirect and direct resin composites and the amount of eluted monomers increased over time. The highest mean concentrations of residual Bis-GMA, UDMA, TEGDMA, and HEMA were detected with the Filtek Ultimate (2,342 µM), Solidex (7,908 µM), Signum (2.8 µM), and Filtek Ultimate (9.7 µM), respectively. The highest amount of eluted monomer concentrations detected was viewed as critical for toxic reactions in human cells.     

Effect of surface conditioning methods,adhesive systems and resin composite on repair strength of dimethacrylate and silorane resin composites

This study evaluated the effect of surface conditioning methods and adhesive systems on the repair bond strength of resin composites. Specimens (FLS: Filtek LS) (N = 144) were prepared using a silicone matrix. The specimens were stored in distilled water and then were randomly divided into the twelve groups (n = 12) according to the surface conditioning method (unground or diamond bur) and adhesive system (no adhesive, LS: Filtek LS, AS: Adper Scotchbond SE Plus) and resin composite (FLS: Filtek LS; FS: Filtek Supreme). The specimens were fixed in an hourglass-shaped silicone matrix and the other half of the specimen was restored. Hourglass-shaped specimens (n = 12) were used as positive control to measure the cohesive strength of the resin composite (Filtek LS). Microtensile bond test was performed (0.5 mm/min) and failure types were analyzed. Data were analyzed using two-way analysis of variance, Tukey’s and Dunnett’s tests (α = 0.05). Adhesive protocol and resin composite significantly affected the results (p < 0.05). For the FS composite, the highest results were obtained using LS adhesive with (18.4 ± 7.7) and without (18.8 ± 4.8) bur roughening. For FLS composite, the highest results were obtained using AS adhesive with (33.2 ± 7.1) and without (25.7 ± 3.6) bur roughening. Without the use of adhesive resin, significantly lower bond strength results were observed with both LS (5 ± 2.1, 4.5 ± 1.5) and FLS (2.2 ± 1.2, 4.4 ± 1.1) for unground and diamond bur roughened groups, respectively (p < 0.0001). Cohesive strength of the FLS (52.3 ± 7.6) was significantly higher than any of the repaired groups (p < 0.0001). FS–LS combination and the groups repaired without adhesive presented more adhesive (Type I) failures.     

Effect of material and fabrication technique on marginal fit and fracture resistance of adhesively luted inlays made of CAD/CAM ceramics and hybrid materials

This study evaluated the fracture resistance and marginal fit of CAD/CAM ceramic and composite inlays. Molars (N = 80) were prepared to receive Mesio-occlusal-distal (MOD) inlays and randomly divided into four groups to be restored depending on the materials: (a) HLD: heat-pressed lithium disilicate ceramic (IPS e.max Press), (b) CLD: CAD/CAM-fabricated lithium disilicate ceramic (IPS e.max CAD), (c) NC: CAD/CAM nano-ceramic resin (Lava Ultimate), (d) RC: Indirect resin composite (Filtek P60). Each group was randomly divided into two subgroups regarding the resin cement: (a) High-viscosity resin cement (Syntac, Variolink II), (b) Self-adhesive low-viscosity cement (RelyX Ultimate). After marginal gap and cement thickness measurements, specimens were loaded to fracture in a Universal Testing Machine (1 mm/min). Intact molars acted as the control group (n = 10). Data were analyzed using one-way and two-way ANOVA, Tukey’s tests (α = 0.05). Before cementation, CLD group showed significantly lower mean marginal gap (65 ± 22.4 μm) and after cementation, cement thickness was again the lowest with CLD (82.6 ± 24.6 μm) and the highest with HLD (108.4 ± 21.3 μm) (p < 0.001). The mean marginal gaps of inlays at the gingival margin were significantly higher than at the occlusal and the axial margins (p < 0.05). While material type significantly affected the mean fracture resistance (p < 0.001), the cement type had no effect on the results (p = 0.083). NC group (2486 ± 40 N) showed significantly higher mean fracture load compared to those of other three groups (1997.5 ± 60–2007 ± 30) (p < 0.05). The mean fracture resistance of control group with the intact teeth was significantly higher than those of all groups (p < 0.05) except for NC (p > 0.05).     

Load-bearing capacity and failure types of premolars restored with sonic activated bulk-fill-, nano-hybrid and silorane-based resin restorative materials

This study evaluated the load-bearing capacity of premolars restored with three types of resin composite materials in mesio-occluso-distal (MOD) cavities. Extracted human premolars (N = 30, n = 10 per group) were randomly divided into three groups; MOD cavities were prepared and restored with one of the following resin materials: Group BFC: Bulk-fill composite (SonicFill, Kerr Corporation), Group NC: Nanohybrid resin composite (Filtek Z550, 3M ESPE), Group SC: Silorane-based composite (Filtek Silorane, 3M ESPE). For NC Clearfil SE Bond (Kuraray, Japan) and for SC, Silorane adhesive resin (Filtek Silorane System Adhesive, 3M ESPE) were used. The cavities in NC and SC groups were restored incrementally, while those in BFC groups were restored in bulk. After water storage (24 h, 37 °C), each tooth was subjected to compressive loading with a stainless steel ball (diameter: 4 mm) perpendicular to the occlusal surface (1 mm/min). Failure types were categorized according to being repairable or irrepairable. Data were statistically analysed using Kruskal-Wallis test (α = 0.05). Two-parameter Weibull distribution values including the Weibull modulus, scale (m) and shape (0) values were calculated. Fracture resistance of premolars restored with BFC (829.84), NC (701.35) and SC (807.73) did not show significant difference (p = 0.72). Weibull distribution presented lower shape (0) for SC (m = 2.77) and NC (m = 3.09) compared to BFC (m = 5.01). The incidence of repairable failures was more common in BFC (80%) compared to NC (60%) and SC (50%). Adhesive failures were more often observed in NC (80%) and SC (70%) groups.     

The effect of Er:YAG laser and bulk filled composite type on marginal adaptation of class II cavities: an SEM analysis study

Purpose: To evaluate the effect of cavity preparation method (Er:YAG laser or diamond bur) and bulk-filled composite material type on marginal adaptation mesial occlusal (MO) class II cavities. Materials and Methods: Two-surface box cavities (4-mm proximal depth and 5-mm occlusal width) were prepared on 60 human mandibular molar teeth. Cavities were prepared using Er:YAG laser or diamond burs in an air-turbine hand-piece. All cavities were applied Single Bond Universal dentin bonding agent. The cavities were further subdivided into three subgroups according to the restorative material used; two bulk-filled composites [Filtek Bulk Fill Posterior (3M ESPE) and SonicFill 2 (Kerr)] and one traditional composite material Filtek Ultimate Universal Restorative (3M ESPE). Restorations were evaluated using scanning electron microscopy at ×200 magnification for their adaptation to the approximal margins of the tooth. Results were analyzed using the two-way ANOVA and Tukey Post Hoc Test (p < 0.05). Results: A total of 900 SEM figures were obtained from all groups. Filtek Bulk Fill Posterior, SonicFill 2, and Filtek Ultimate Universal Restorative exhibited statistically similar gapped margins. However, the lowest scores of gapped margins were observed with SonicFill 2 (4.22%). Conclusions: Completely gap-free margins were not obtained with any of the tested materials. Bulk-fill composite materials showed similar marginal adapatation compared with standard composite. Marginal adaptation of Er:YAG laser prepared cavities was more irregular and had more gaps, but was statistically similar to diamond bur-prepared cavities.     

Shrinkage stress,long-term adaptation and bond strength of low-shrinkage composite resins

PurposeTo evaluate the internal adaptation, bond strength, and polymerization stress of silorane- and methacrylate-based composite resins.Material and methodsThree methacrylate-based composite resins (Heliomolar; Tetric N-Ceram and Aelite LS) and one silorane-based composite resin (Filtek Silorane) were tested. Polymerization stress (n=5) was determined by the insertion of the composite resin between rods of polymethyl methacrylate. The ratio of the maximum force of contraction was recorded and the cross-sectional area of the rod was used to calculate the nominal stress. Bond strength was evaluated by microtensile bond test. Dentin surfaces of human third molars were bonded, sectioned, and stored for 24 h or 1 year in distilled water before the bond strength test. The ratio of maximum force and the adhered area was used for the bond strength calculation. For internal adaptation analysis, third molars received Class II cavities and were restored according to either an incremental oblique or bulk-filling technique. After being sectioned perpendicularly, impressions were taken and epoxy resin replicas were obtained of the internal surfaces of the restorations (after 24 h and 1 year of storage) to analyze gap formation using scanning electron microscopy.ResultsFiltek Silorane showed the highest​ bond strength after one year of storage, the lowest formation of gaps, and polymerization stress similar to methacrylate-based materials.ConclusionSilorane restorative material presented polymerization stress comparable to that of methacrylate-based composite resins, stable dentin bond strength after one year and better internal adaptation to the cavity walls, showing good alternative to traditional composite resins and promising longevity.     

The effects of water flow rate on shear bond strength of self etch resin cement to dentin surface after Er,Cr:YSGG laser etching

The aim of the present study was to evaluate the effect of water flow rate on the morphological features of dentin and shear bond strength (SBS) of self-etching resin cement after Er,Cr:YSGG laser etching. Dentin specimens obtained from extracted human third molars were randomly assigned to four groups (n = 23), including one that received no laser irradiation (control-group D) and three others with different laser parameters: 2.25 W, 50 Hz, 60% air with water flow rates of 19 mL/min-100% water (group A), 2.25 W, 50 Hz, 6.75 mL/min-50% water (group B), and 2.25 W, and 50 Hz, 2.75 mL/min-25% water (group C). The morphological features of each group were examined with scanning electron microscopy and atomic force microscopy. The SBS of resin cement disks (Panavia F2.0, Kuraray; Tokyo, Japan) (3 mm in diameter and 2 mm in height) to the dentin specimens was measured using a universal testing machine at a cross head speed of 0.5 mm/min. Bond strength values were analyzed with one-way ANOVA/Tukey tests. There were no significant differences between the SBS values of groups A and B (p > 0.05). However, the SBS values of these groups were significantly higher when compared to groups C and D (p < 0.001). Er,Cr:YSGG laser application with water flow rates of 6.75 or 19 mL/min resulted in better dentin surface alterations and increased the SBS of self-etching resin cement to dentin.     

Effects of monomer compositions on physicochemical properties of composite resins

The aim of this study was to evaluate the cohesive strength (CS), surface roughness (Ra), and weight loss (WL) of different composite resins. Three composite resins (Filtek Z100; Filtek Z350; Filtek P90, 3M ESPE) were tested. To evaluate CS, an hourglass silicone mold (11 × 2 × 1 mm) was used (n = 10). The Ra and WL tests were performed using a circular mold (5 × 2 mm, n = 10). The composite resins were light-cured with an LED light curing device (FreeLight 2, 3M ESPE) for 40 s and 1000 mW/cm². The CS test was performed using a universal testing machine (Instron 4411, Instron) at a crosshead speed of 0.5 mm/min and cell load of 500 N. The initial mass weight was registered (analytical digital balance) and the initial Ra reading evaluated using a profilometer (Surftest 211, Mitutoyo). The specimens were submitted to 30,000 brushing cycles. The WL and the final Ra were evaluated. All data were subjected to one-way ANOVA, followed by Tukey’s test (p < 0.05). Filtek Z100 showed the highest values of Ra and Filtek Z350 the lowest values of Ra. When considering CS, Filtek Z350 and Z100 had the highest mean values. Filtek P90 had the highest mean value of WL. The organic matrix and the type, shape, and size of fillers may influence the physicochemical properties of composite resins.     

Efficacy of different surface treatments and universal adhesives on the microtensile bond strength of bulk-fill composite repair

Abstract

The purpose of this in vitro study was to evaluate the influence of different surface treatments and aging on the microtensile bond strength (μTBS) of bulk-fill composite resins. Bulk-fill composites (Filtek One; 3M ESPE) randomly received five different surface treatments: (1) no treatment, control, (2) 37% phosphoric acid etching (PA), (3) 9% hydrofluoric acid etching (HF), (4) air-borne particle abrasion with 50-μm alumina particles (Al₂O₃), (5) tribochemical silica coating (CoJet). Following, the specimens were divided into three subgroups according to universal adhesive applied: Clearfil Universal Bond (CU; Kuraray), Prime&Bond Universal (PBU; Dentsply Sirona), or Single Bond Universal (SBU; 3M ESPE). A nanofill composite (Filtek Ultimate; 3M ESPE) was employed as a repair. Bonded specimens were stored in water for 24?h at 37?°C or thermal aged, then subjected to the μTBS test. Additionally, specimens were analyzed with a contact profilometer and were evaluated with scanning electron microscopy. Control and PA treatments were showed the lowest µTBS (p?<?0.05), and there was no significant difference between these two groups (p?>?0.05). Al₂O₃ and CoJet treatments generally exhibited a similar influence on µTBS values. In addition, a correlation was found between surface roughness and bond strength (r?=?0.831). CoJet resulted in significantly higher repair µTBS values when compared to the other surface treatments. In addition, the use of silane-containing universal adhesive was increased the cohesive failure rate and maintained the repair µTBS values after thermocycling.     

The bonding effect of adhesive systems and bulk-fill composites to sound and caries-affected dentine

Purpose: To investigate the influence of adhesive type and increment thickness on shear bond strength of flowable bulk-fill resin composites compared with a flowable conventional resin composite, in both sound and caries-affected dentine.

Methods: Shear bond strength was tested in 100 extracted human molars with coronal dentine caries. Half of the teeth were restored with Adper? Easy Bond and the other half with Adper? Single Bond Plus. Bonded surfaces were restored with Filtek? Ultimate Flow and two bulk-fill composites (SDR and X-tra base) (n = 10 teeth for each subgroup). Restorations of 4 mm were performed with incremental or bulk-fill technique. The shear bond was determined and statistically analysed using three-way ANOVA and Bonferroni multiple comparison post hoc tests (p ≤ 0.05). Dentine–resin interfaces were evaluated by scanning electron microscopy.

Results: For both adhesives, the highest shear bond strength values were obtained for sound dentine. In sound dentine, the highest bond strength observed with Easy Bond when used in 2-mm increments of SDR. In caries-affected dentine, Single Bond in combination with SDR displayed significantly lower bond strength.

Conclusion: There was no significant difference in shear bond strength between the incremental and bulk-fill groups for molars with sound dentine when the etch-and-rinse adhesive system was used; however, for the self-etch adhesive system, incremental application caused higher bond strength than bulk application.     

Bond strength of repaired composite resins: surface treatments,adhesive systems,and composite type

The aim of the present study was to investigate the effects of three different surface treatments and two different adhesives on the microtensile bond strength (μTBS) of repaired composites using the same or different type of resin. Twenty-four nano-hybrid (Ceram X mono-C) and 24 nanofilled (Filtek Ultimate-F) composite discs were prepared. The specimens were aged with 5000 thermocycles and randomly divided into groups according to the surface treatment methods: (a) phosphoric acid (b) Er:YAG laser and (c) aluminum trioxide particle (air abrasion). Fresh composite resins (C and F) were added to the treated surfaces with two different adhesives (two-step and one-step self-etch adhesives). Then, the specimens were aged again. The stick-shaped specimens were prepared from the discs (n = 25) and the sticks were subjected to the μTBS test. Results indicated that significant differences were found in μTBS values among the surface treatment methods. In the C groups, the highest μTBS value (41.3 ± 8.3 MPa) was recorded in the air abrasion and one-step self-etch adhesive group, which were repaired with the same kind of composite. In the F groups, the highest μTBS value was observed in the air abrasion and one-step self-etch adhesive (37.6 ± 12.3 MPa) group. The treatment with air abrasion is more effective than the others, and it may be suggested for composite repair.     

Comparison of microleakage of a multi-mode adhesive system with contemporary adhesives in class II resin restorations

Aim: The aim was to compare the microleakage of resin composite bonded with different adhesive systems in class-II cavities at enamel or dentine margins. Material and methods: 60 extracted human molar teeth received slot cavity preparations on mesial and distal surfaces (mesial cervical margin was prepared in enamel and distal in dentine). They were randomly divided into five groups (n?=?12) according to the adhesive system: Group-A: Silorane Bond (S), Group-B: Adper Single Bond 2 (SB), Group-C: Clearfil SE Bond (CSE), Group-D: Single Bond Universal (USel) (selective etch-and-rinse), Group-E: Single Bond Universal (USE) (all-in-one). The preparations were restored using the same resin composite (Filtek Ultimate) except Group A which was restored by Silorane composite. The teeth were thermocycled, immersed in dye, sectioned, and dye penetration was evaluated quantitatively using image analysis. The data were analyzed using the two-way analysis of variance and Bonferroni test. Results: In all groups, there was no statistically significant difference between enamel margins at occlusal and gingival sites (p?>?0.05). The statistical difference between Group-A (S) and Group-B (SB) was significant at all margins. Group-B (SB) presented the greatest microleakage amounts at all margins and the highest scores were obtained in the dentine. Likewise, SB demonstrated statistically significant differences between dentine and enamel margins (occlusal and gingival)(p?<?0.05). Conclusion: All adhesive systems showed similar microleakage values between enamel margins in occlusal and gingival regions. However, when the gingival margin is located in the dentine, etch&rinse adhesive systems may not be a choice in terms of microleakage prevention.     

Adhesion of bulk-fill resin composites as core and intraradicular post materials only versus the use of glass-fiber posts in different regions of root dentin

This study assessed adhesion of bulk-fill resin-composites as core and post materials only versus the use of fiber resin composite (FRC) posts. Human teeth (N?=?84) were cut at the CEJ and endodontically treated and randomly divided into seven groups: TP: Titanium post (Flat Head T); SFRC: S2-glass FRC (Pinpost); EFRC1: E-glass FRC (GC Everstick) directly bonded; GFRC: E-glass FRC (Glassix Nordin); EFRC2: E-glass FRC (Everstick); BF1: Bulk-fill resin (Surefill SDR); BF2: Bulk-fill resin (SonicFill). Groups TP, SFRC, EFRC and GFRC were cemented (Panavia 21), while other groups were bonded directly to the intraradicular dentin. The core parts were constructed using a resin composite (G-aenial) except for Groups BF1 and BF2. The core-cervical dentin interface was loaded under shear forces. Push-out tests were performed in a Universal Testing Machine (1?mm/min). Data (MPa) were analyzed using two-way ANOVA and Tukey`s tests (α?=?0.05). Not the root level (p?>?0.05) but the type of core and post material significantly affected shear and push-out bond results (p?<?0.001). BF1 (9.2?±?2.1) and BF2 (9.3?±?3.1) showed significantly lower bond strength to the cervical dentin (p?<?0.05) compared to other groups (11.6?±?2.5–19?±?6.8). FRC post types did not show significant difference being higher than those of TP, BF1 and BF2 (0.57?±?0.37–2.34?±?1.98) (p?>?0.05). Partial cohesive core fracture was more common while BF1 and BF2 showed exclusively adhesive failures. Cohesive failure in the cement was frequent in Group TP (53%) compared to other groups (3–24%). BF1 and BF2 presented exclusively complete adhesive failure of the bulk-fill material.     

Effect of laser etching on the fracture strength of the monolithic zirconia and fiber-reinforced composite inlay-retained fixed partial dentures

Aim: The aim of this study was to evaluate the fracture strength of monolithic zirconia and fiber-reinforced composite (FRC) inlay-retained FPDs, both of which are cemented to the laser-etched cavity surfaces.

Materials and Methods: Eighty freshly extracted sound human teeth were used. A premolar and a molar tooth were embedded in an autopolymerizing acrylic resin. Forty acrylic resin models were randomly divided into two groups including monolithic zirconia and FRC inlay-retained FPDs (n = 20). Then, these groups were divided into two subgroups according to conditioning of the cavity surfaces with or without Er:YAG laser etching. Monolithic zirconia inlay-retained FPDs were produced by an inLab MC XL milling device using monolithic zirconia blocks. Tescera? Fiber Reinforcement Materials were used for the FRC inlay-retained FPDs. After 10.000 thermal cycles, fracture strength test was applied to the specimens.

Results: The monolithic zirconia inlay-retained FPDs exhibited the highest fracture strength than the FRC inlay-retained FPDs. Fracture strength was increased with laser etching for both restorative materials (p < 0.05).

Conclusion: Laser etching had positively effect on the fracture strength of the inlay-retained FDPs.     

Effect of 2% chlorhexidine gluconate cavity disinfectant on microtensile bond strength of tooth-coloured restorative materials to sound and caries-affected dentin

This study evaluated the effect of 2% chlorhexidine gluconate-based cavity disinfectant (CHX) on the microtensile bond strength (μTBS) of glass ionomer, resin-modified glass ionomer and packable resin composite to sound and caries-affected dentin. Sound and occlusal caries-affected human third molars (N?=?36, n?=?3 per group) were randomly divided into three experimental groups to receive one of the following restorative materials. (a) Glass ionomer (Ketac Molar, 3 M ESPE; GI), (b) resin-modified glass ionomer (Vitremer, 3 M ESPE; RMGI) and (c) packable resin composite (Surefil, Dentsply; PRC) with a bonding agent (Prime Bond NT, Dentsply De Trey). Caries was removed using a caries-detecting dye (Caries Detector, Kuraray Medical Ltd.) and flat dentin surfaces were achieved by finishing up to 1200-grit silicon carbide abrasive. Half of the teeth in each group received 2% CHX (Consepsis, Ultradent). Dentin surfaces were built-up with the respective materials incrementally and were sectioned with a slow-speed saw into multiple beams. The beams were subjected to μTBS test (0.5 mm/min) in a Universal Testing Machine. The data were analysed using two-way analysis of variance and Tukey’s tests. For each restorative material, μTBS results were not affected by the application of CHX (p?>?0.05) on both sound and caries-affected dentin (p?>?0.05). PRC in combination with the corresponding bonding agent showed significantly higher results (p?<?0.05) than those of GI and RMGI, on sound and caries-affected teeth, respectively. Cohesive failure in dentin was not observed in any of the groups. The use of 2% chlorhexidine-based cavity disinfectant did not impair the adhesion of the restorative materials tested to either sound or caries-affected dentin.     

Nanomechanical Characterization of Flowable Dental Restorative Nanocomposite Resins Using AFM

In this study, exploring the possible connections between the structure and the functionality of a dental restoration material on the sub-micrometric scale is aimed, especially by focusing on the elastic mechanical properties of materials. Five flowable dental resin composites were investigated by atomic force microscopy nanoindentation. G-ænial? Universal Flo, Filtek? Ultimate XT, Vertise? Flow, Revolution Formula 2?, and Filtek? Supreme Plus comprising nanofillers have been selected for this study. Young’s modulus was between 12.61?±?0.35?GPa (for G-ænial? Universal Flo) and 11.86?±?0.35?GPa (for Filtek? Supreme Plus), which were quite similar for all commercial flowable resins.     

Stress distribution in carbon-post applied with different composite core materials: a three-dimensional finite element analysis

The aim of this study was to investigate, using three-dimensional finite element analysis [3D-FEA], the stress and/or strain distribution of five different resin composites used in combination with carbon fibre posts. FEA models of five different light-cured composites were employed. The stress distribution of composite in combination with carbon fibre post was analysed under two different loading conditions: (i) polymerization shrinkage and (ii) load of 150 N with a 35° tilt to the long axis of the tooth. The Material Fatigue Rate [MFR%] of composite materials, dentin and fibre post was calculated. The highest stress values were recorded for Heliomolar and Clearfil-Photo P. The lowest stresses and MFR% values were attained when using Diamond Crown. High MFR% value [>45%] for carbon posts were found in all the tested cases under load. Composite materials with a Young’s modulus similar to that of dentin should be selected for the restoration of endodontically-treated teeth when using carbon fibre posts. The peak of the polymerization stress of the composite core is localized at the ferrule level. This might induce an open margin with higher risk of coronal leakage.     

Shear Bond Strength of Indirect Composites Luted with Three New Self-Adhesive Resin Cements to Dentin

The aim of this study was to evaluate the shear bond strengths of indirect composites (those cured outside the mouth) luted by three different, recently developed, self-adhesive resin cements to dentin. Seventy caries-free mandibular third molar teeth embedded in acrylic resin and with exposed dentin surfaces were used. Teeth were randomly divided into seven groups. The following application protocols were carried out: a) Group 1 (control group)—direct composite resin restoration (Alert) with total-etch adhesive system (Bond 1 primer/adhesive); b) Group 2—indirect composite restoration (Estenia) luted by a resin cement (Cement-It) combined with the same total-etch adhesive; c) Group 3—direct composite resin restoration with self-etch adhesive system (Nano-Bond); d) Group 4—indirect composite restoration luted by the resin cement combined with the same self-etch adhesive; e) Groups 5–7—indirect composite restoration luted with self-adhesive resin cements (RelyX Unicem®, Maxcem®, and Embrace WetBond®, respectively) onto untreated dentin surfaces. Shear bond strengths of the groups were performed with a universal testing device. Results were statistically analysed by student-t and one way ANOVA tests. The fractured surfaces were also examined by SEM. The indirect composite restorations luted with the self-adhesive resin cements (Groups 5–7) showed successful results compared with the other groups (p < 0.05). Group 4 showed the weakest bond strength (p > 0.05). Open dentin tubules were observed on the total-etch adhesive applied surfaces whereas a smear rich layer was found by SEM on the self-etch adhesive applied surfaces. The new universal self-adhesive resins may be considered an alternative for luting the indirect composite restorations onto the untreated dentin surfaces.