To etch or not to etch, Part III: On the hydrophobic-rich content and fatigue strength of universal adhesives after long-term ageing.

OBJECTIVES: To examine whether dentin-etching extension and/or the hydrophobic-rich content of hybrid layers would affect fatigue strengths of a mild universal adhesive after long-term aging. METHODS: Twin-bonded resin-dentin interfaces were produced by etching sound midcoronal dentin beams with 32 % ortho-phosphoric acid for 15 s (OPA15s), 3 s (OPA3s) or 10 % meta-phosphoric acid for 15 s (MPA15s). Samples were bonded with a mild universal adhesive with or without additional coating using a solvent-free bisGMA-based bonding resin. Self-etch application served as control. Composite buildups were made with a nanofilled composite. Bar-shaped twin-bonded interfaces (0.9 × 0.9 × 12 mm) were aged for two years in artificial saliva at 37 â„ƒ and tested under 4-point flexure at quasi-static (n = 16) and cyclic loads (n = 35) until failure. The stress-life fatigue behavior was evaluated using the staircase method at 4 Hz. Crack initiation and fracture patterns were evaluated by SEM. Cyclic-loaded data was analyzed by Kruskal-Wallis on Ranks (α = 0.05). RESULTS: Significantly higher fatigue life distributions and higher endurance limits were observed for less aggressive etch-and-rinse protocols (OPA3s and MPA15s) after long-term ageing. Hydrophobic-rich coating produced 20-32 % higher endurance limits, prevented micrometer-sized porosities at bonded interfaces, reduced etching-associated variability and lowered crack formation. Significance Long-term hydrolysis produces detrimental effects on the fatigue strength of resin-dentin interfaces. The bond-promotion effect of less aggressive etch-and-rinse protocols and the creation of hybrid layers with higher hydrophobic-rich content are critical to extend the durability of mild universal adhesives. Therefore, current oversimplification trends in adhesive dentistry may limit resin-dentin bonding performance.

Does the application of dimethyl sulfoxide improve resin bonding to eroded dentine? Four-year in vitro evaluation.

OBJECTIVE: To evaluate the effect of dimethyl sulfoxide (DMSO) on the microtensile bond strength (µTBS) and nanoleakage (NL) of universal adhesives on eroded dentine, immediately and after four years of water storage. METHODS: Sixty-four sound human molars were distributed into 16 groups according to (1) Dentine surface (sound and eroded dentine); (2) dimethyl sulfoxide application (with or without); (3) Application mode (etch-and-rinse or self-etch) and (4) Storage time (immediate and four years). One mild universal adhesive was used (Scotchbond Universal). The restoration was then performed with a composite resin and the specimens were sectioned into resin-dentine bonded sticks. Resin-dentine bonded sticks were tested (immediately and after four years of water storage) for µTBS (0.5 mm/min) or used to assess NL. Data on µTBS and NL were analyzed using four-way ANOVA and Tukey's test (α = 0.05). RESULTS: Only the 3-way cross-product interaction 'substrate vs DMSO vs time' was statistically significant (p = 0.007). Eroded dentine showed a lower mean of µTBS and a higher mean of NL values than sound dentine. However, when DMSO was applied, no significant decrease of µTBS or NL values was observed after four years of water storage, regardless of adhesive strategies, or dentine evaluated, when compared to immediate results. SIGNIFICANCE: Water-based DMSO pre-treatments not only prevent degradation of MDP-containing simplified adhesives but also serve as a potential alternative to improve long-term bonding properties to eroded dentine. The versatility of using a single pre-treatment for both self-etch or etch-and-rinse bonding to eroded dentin may facilitate future clinical applications.

Concentration effect of DMSO-dry bonding on the stability of etch-and-rinse bonds.

OBJECTIVES: To examine whether lower dimethyl sulfoxide (DMSO) concentrations would affect long-term bond stability of simplified or multistep water-based adhesives to dry-etched dentin. METHODS: H3PO4-etched mid-coronal dentin surfaces from human molars were randomly blot- or air-dried for 30 s and pretreated or not with 5 or 50 % (v/v) ethanolic DMSO solutions. Untreated samples served as control. Samples were bonded with a two-step or a three-step etch-and-rinse adhesive. Restored crown segments (n = 5/group) were stored in distilled water for 24 h and sectioned for microtensile bond strength testing. Resin-dentin beams (0.8 mm2) were tested under tension until fracture (0.5 mm/min) after 24 h and one year of storage in artificial saliva at 37 °C. Nanoleakage evaluation and hybrid layer characterization were performed by SEM. Bond strength data was examined by three-way ANOVA followed by the Tukey test (α = 0.05). RESULTS: Dry bonding produced significantly lower bond strengths than conventional wet bonding for both water-based adhesive systems (p < 0.05). DMSO-dry bonding restored bond strengths and reduced nanoleakage levels, regardless of adhesive type or DMSO concentration (p < 0.05). Bond strengths of DMSO-dry bonded samples were not significantly affected by long-term ageing regardless of adhesive type or DMSO concentration (p < 0.05). SIGNIFICANCE: Although bonding methacrylate-based resins to etched dentin is normally performed under wet conditions, hybridization of air-dried collagen can outperform conventional wet bonding by employing water-free DMSO solutions with concentrations as low as 5 %. Reduced moisture-related technique sensitivity, higher bonding performance and improved hybrid layer stability may contribute to extend the service life of resin-dentin bonding.

Evaluation of Er:YAG and Er,Cr:YSGG lasers on intraradicular bonding using modified glass fiber tips.

The aim of this study was to determine whether erbium laser irradiation emitted by modified glass-fiber tips would improve the intraradicular bonding of fiber posts. Forty human canines were endodontically treated and prepared for fiber-post placement. Roots were divided into five groups (n=8); according to the laser-tip combinations (2,940 nm Er:YAG and 2,780 nm Er,Cr:YSGG). Non-irradiated root canals served as control. Posts were cemented with self-adhesive resin cement and subjected to push-out test. Failure modes were characterized, and intraradicular bonded interfaces were analyzed by SEM and submitted to nanoleakage evaluation. Data were analyzed by two-way ANOVA and Tukey test (α=0.05). No significant differences were observed in cervical and middle sections (p>0.05), while significantly higher bond strengths were observed in apical sections (p<0.05). Laser irradiation reduced adhesive failures, cement-dentin gap formation, and nanoleakage apically. Laser-irradiation protocols employing end- or radial-firing tips improved bonding to apical intraradicular dentin contributing to more uniform bonded interfaces.

To etch or not to etch, Part II: On the hydrophobic-rich content and fatigue strength of universal adhesives.

OBJECTIVE: To determine whether smear layer management, via conservative etching protocols, and the hydrophobic-rich content of hybrid layers would affect the fatigue strength of resin-dentin interfaces. METHODS: Bar-shaped dentin beams obtained from sound third molars were wet-polished for 30 s. Dentin was etched with 32 % ortho-phosphoric acid for 3 or 15 s, 10 % meta-phosphoric acid for 15 s or by a prime-and-rinse application using a mild universal adhesive (Scotchbond Universal, 3M ESPE). Self-etch application served as control. Coating was performed with a solvent-free bisGMA-based resin. Composite buildups were made with a nanofilled composite. Resin-dentin beams with twin-bonded interfaces were sectioned and stored in deionized water for 24 h at 37 â„ƒ before 4-point flexural quasi-static monotonic testing (n = 16). Stress-life fatigue behavior was evaluated under cyclic loading (n = 35) by the staircase method at 4 Hz. The tension side of cyclic-loaded unfractured beams were evaluated under SEM, along with the micro-morphology of etched dentin surfaces. Monotonic data was analyzed by two-way ANOVA followed by the Tukey Test and cyclic-loaded data by Kruskal-Wallis on Ranks (α = 0.05). RESULTS: Etching protocols and higher hydrophobic-rich content produced significantly higher fatigue life distributions (p < 0.05). Dentin demineralization was ranked as OPA 15 s > MPA 15 s > OPA 3 s > P + R > SE. Less aggressive etching and coating reduced crack formation at hybrid layers. SIGNIFICANCE: Current oversimplification trends in resin-dentin bonding constitute a trade-off between hybridization quality and easier adhesive handling. Controlled dentin etching and increasing the hydrophobic-rich content of hybrid layers may be necessary to extend the longevity of mild universal adhesives.

Composite repair: On the fatigue strength of universal adhesives.

OBJECTIVES: To determine whether the composition of universal adhesives and the use of silane coupling agents could affect the fatigue strength of composite repair. METHODS: Composite samples were aged in water at 37 °C for 90 days and bonded to fresh composite to produce twin-bonded bar-shaped composite specimens (2 × 2 × 12 mm). Five universal adhesives, a multistep composite repair system and a hydrophobic solvent-free resin associated to a separate silane coupling agent application were used for bonding. Composite samples were tested under 4-pointflexure initially at quasi-static loading (n = 12) followed by cyclic loading (n = 25). The stress-life fatigue behavior was evaluated following the staircase method at 4 Hz. The unfractured side of cyclic loaded beams were evaluated under SEM to determine crack initiation sites. Fatigue data was analyzed by ANOVA and Tukey test and Wilcoxon Rank Sum Test (α = 0.05). RESULTS: Bonding protocols were unable to restore the cohesive strength of the nanofilled composite (p < 0.05). Fatigue testing was more discriminative to reveal discrepancies in composite repair than conventional quasi-static loading. While the composition of universal adhesives affected composite repair potential, the highest endurance limits occurred for the separate silane coupling agent application. Crack propagation sites were mostly located on the aged composite surface. SIGNIFICANCE: Although a trend for simplification invariably overruns current adhesive dentistry, composite repair using solely universal adhesives may result in inferior repair potential. The additonal use of silane coupling agents remains as an important procedure in composite repairs.

Dry bonding to dentin: Broadening the moisture spectrum and increasing wettability of etch-and-rinse adhesives.

OBJECTIVE: To determine whether the effect of dentin moisture on the etch-and-rinse bonding may be minimized by dry-bonding protocols utilizing aqueous or ethanolic dimethyl sulfoxide (DMSO) pretreatments. METHODS: H3PO4-etched mid-coronal dentin surfaces from human molars were randomly blot- or air-dried for 30 s and pretreated with DMSO/H2O or DMSO/EtOH solutions. Untreated samples served as control. Moisture control was performed by either blot- or air-drying. Samples were bonded with a multistep etch-and-rinse adhesive. Restored crown segments (n = 8/group) were stored in distilled water for 24 h and sectioned for microtensile bond strength testing. Resin-dentin beams (0.8 mm2) were tested under tension until fracture (0.5 mm/min) after 24 h and two years of storage in artificial saliva at 37 °C. SEM nanoleakage evaluation was performed on aged samples. Collagen wettability was also measured by sessile drops of the hydrophilic and hydrophobic bonding resins (n = 8/group). Data were examined by factorial ANOVA followed by the Tukey test (α = 0.05). RESULTS: Dry bonding to untreated collagen produced inferior immediate and long-term bond strengths than wet bonding (p < 0.05). Regardless of initial hydration and moisture control, DMSO-dry bonding produced initially higher and stable bond strengths after aging (p < 0.05). DMSO-pretreated groups presented improved collagen wettability with lower silver uptake (p < 0.05). SIGNIFICANCE: Despite the common belief that etch-and-rinse adhesives must be applied onto moist collagen, DMSO-dry bonding protocols not only improved bonding performance and hybrid layer integrity, but also brought more versatility to collagen hybridization by reducing overdrying-related issues.

The pursuit of resin-dentin bond durability: Simultaneous enhancement of collagen structure and polymer network formation in hybrid layers.

OBJECTIVE: Imperfect polymer formation as well as collagen's susceptibility to enzymatic degradation increase the vulnerability of hybrid layers over time. This study investigated the effect of new dimethyl sulfoxide (DMSO)-containing pretreatments on long-term bond strength, hybrid layer quality, monomer conversion and collagen structure. METHODS: H3PO4-etched mid-coronal dentin surfaces from extracted human molars (n = 8) were randomly treated with aqueous and ethanolic DMSO solutions or following the ethanol-wet bonding technique. Dentin bonding was performed with a three-step etch-and-rinse adhesive. Resin-dentin beams (0.8 mm2) were stored in artificial saliva at 37 °C for 24 h and 2.5 years, submitted to microtensile bond strength testing at 0.5 mm/min and semi-quantitative SEM nanoleakage analysis (n = 8). Micro-Raman spectroscopy was used to determine the degree of conversion at different depths in the hybrid layer (n = 6). Changes in the apparent modulus of elasticity of demineralized collagen beams measuring 0.5 × 1.7 × 7 mm (n = 10) and loss of dry mass (n = 10) after 30 days were calculated via three-point bending and precision weighing, respectively. RESULTS: DMSO-containing pretreatments produced higher bond strengths, which did not change significantly over time presenting lower incidence of water-filled zones. Higher uniformity in monomer conversion across the hybrid layer occurred for all pretreatments. DMSO-induced collagen stiffening was reversible in water, but with lower peptide solubilization. SIGNIFICANCE: Improved polymer formation and higher stability of the collagen-structure can be attributed to DMSO's unique ability to simultaneously modify both biological and resin components within the hybrid layer. Pretreatments composed of DMSO/ethanol may be a viable-effective alternative to extend the longevity of resin-dentin bonds.

To etch or not to etch, Part I: On the fatigue strength and dentin bonding performance of universal adhesives.

OBJECTIVE: To characterize whether the bonding performance and fatigue strength of resin-dentin interfaces created by a universal adhesive would be affected by different H3PO4-application times to more accurately assess long-term durability. METHODS: Mid-coronal flat dentin surfaces with standardized smear-layers were produced on sound third molars, etched with 32% H3PO4 for 0, 3 and 15 s, bonded with a mild universal adhesive (3M-ESPE) and restored with a nanofilled composite. Bonded specimens (0.9 × 0.9 mm) were stored in deionized water for 24 h and sectioned into beams for microtensile testing (n = 10). Resin-dentin beams were tested under tension until failure (0.5 mm/min) after 24 h or 6 month storage in artificial saliva at 37 ̊C. Bar-shaped resin-dentin beams (0.9 × 0.9 × 12 mm) were tested under 4-point-flexure initially at quasi-static loads (n = 22) and then under cyclic loads (n > 50). The stress-life fatigue behavior was evaluated using the twin-bonded interface approach by the staircase method at 4 Hz. Fractured interfaces and the tension side of unfractured beams were evaluated under SEM, along with the micro-morphology of the etched dentin surfaces and hybrid layers. Data were analyzed by ANOVA and Tukey test and Wilcoxon Rank Sum Test (α = 0.05). RESULTS: Quasi-static loads were limited to discriminate the bonding performance of resin-dentin interfaces. Application modes significantly affected etching patterns, fatigue strength, endurance limits and hybrid layer morphology (p < 0.001). SIGNIFICANCE: Reductions in fatigue strength of self-etched bonded interfaces raise concerns about the true ability of universal adhesives to properly bond to dentin.

Biomechanical behaviour of bulk-fill resin composites in class II restorations.

The aim of this study was to evaluate the biomechanical properties expressed by shrinkage stress, cuspal strain, fracture strength and failure mode in molars with large class II mesio-occlusal-distal restorations. Sixty-four human caries-free third molars were selected and distributed randomly into four groups: Z100 restorative material (Z100), Tetric N-Ceram Bulk-Fill (TNC), Filtek Bulk-Fill (FBF) and Aura Ultra Universal (ABF). The bulk-fill materials were inserted in one singular bulk increment and the conventional composite resin in three ones. Polymerisation shrinkage stress was evaluated by optical Fibre Bragg Gratings (FBG) sensors (n = 6). The cuspal deformation was measured using an extensometer during three moments: restorative procedure, axial compressive loading and at fracture (n = 10). The fracture strength was evaluated on a universal machine. The failure mode was analysed by Scanning Electron Microscopy (SEM). Data were analysed using one-way ANOVA tests with Tukey's posthoc test (α = 5%). Data of the failure mode were submitted to a likelihood ratio chi-square test. Z100 presented the highest mean value for the shrinkage stress (p < 0.05) by FBG evaluation, whereas bulk-fill resin groups presented low polymerisation stress mean value, especially the TNC (p < 0.05). The cuspal deformation test showed that Z100 presented a significant difference mean value compared to the other groups (p < 0.01) during the restoration and compressive axial force; however, load until the fracture presented a difference only between TNC and FBF (p < 0.05). The fracture strength of TNC was statistically different from Z100 (p < 0.01). The failure mode was not statistically different in all the groups (p > 0.05). Bulk-fill composites promoted less polymerisation shrinkage stress than conventional microhybrid composite during and after the light curing process in class II posterior resin composite restorations.

A novel dry-bonding approach to reduce collagen degradation and optimize resin-dentin interfaces.

In dentistry, the wet-bonding approach relies on water to maintain demineralized collagen expanded for proper resin infiltration; nevertheless, hydrolytic instability of the resin-dentin interface is inevitable with current bonding techniques. Considering dimethyl sulfoxide's (DMSO) ability to "biomodify" collagen and precipitate enzymes, the aim was to test whether the use of DMSO would permit adequate resin bonding to H3PO4-etched dehydrated dentin and assess its impact on collagen degradation by host-derived enzymes. Etched dentin surfaces from extracted sound human molars were randomly bonded in wet or dry conditions using aqueous or ethanolic DMSO solutions as pretreatments and bonding resins with or without DMSO. Bonded teeth were sectioned into resin-dentin slabs for confocal in situ zymography and beams for microtensile bond strength test. Demineralized powdered dentin was incubated in the tested DMSO -media and a hydroxyproline assay evaluated dissolution of collagen peptides. Zymography was performed on protein extracts obtained from dry and wet H3PO4-ecthed dentin powder treated with the DMSO- media. The correlative biochemical analysis demonstrated that reduction of water content during dentin hybridization by the innovative dry-bonding approaches with DMSO is effective to inactivate host-derived MMP-2 and MMP-9 and thus reduce collagen degradation while simultaneously optimizing resin-dentin bonding.

Selective dentin etching: A potential method to improve bonding effectiveness of universal adhesives.

OBJECTIVES: To evaluate whether selective dentin etching protocols using reduced phosphoric acid (H3PO4) etching-times would affect the resin-dentin interaction of a universal adhesive to improve long-term bonding effectiveness. METHODS: Mid-coronal flat dentin surfaces were produced on sound third molars, selectively etched with 32% H3PO4 for 3, 5, 10 or 15 s and bonded with a universal adhesive (Scotchbond Universal, 3 M ESPE: SU). SU in self-etch mode and a three-step etch-and-rinse adhesive were used as control groups. Bonded specimens were stored in deionized water for 24 h and sectioned into beams (cross sectional area of 0.7 mm2). Micro-tensile bond strength test (n = 6) and nanoleakage evaluation were performed immediately, after thermocycling or 6-month storage in artificial saliva. Energy dispersive X-ray analysis (n = 6) was performed to determine the residual Ca-content ratio at the hybrid layers and scanning electron microscopy (SEM) was used to observe the micromorphology of the etched dentin surfaces before and after SU application. Data were analyzed by ANOVA and Tukey test (α = 0.05). RESULTS: Selective dentin etching for 3 s improved the interaction depth of the tested universal adhesive without overexposing demineralized collagen or reducing Ca-content availability at the bonded interface. The improved immediate bond strengths of the selective etching protocol remained significantly higher (p < 0.05) after long-term aging producing hybrid layers without significant differences (p > 0.05) in silver uptake levels compared to those produced on non-etched dentin. CONCLUSIONS: Despite the adjunctive conclusion that universal adhesives used in self-etch mode produce superior long-term dentin bonding compared to the etch-and-rinse mode, selective etching for 3 s with conventionally used H3PO4 improves dentin bonding effectiveness; nonetheless, longer etching times should be strictly avoided.

Optimization of the etch-and-rinse technique: New perspectives to improve resin-dentin bonding and hybrid layer integrity by reducing residual water using dimethyl sulfoxide pretreatments.

OBJECTIVE: To determine whether bonding effectiveness and hybrid layer integrity on acid-etched dehydrated dentin would be comparable to the conventional wet-bonding technique through new dentin biomodification approaches using dimethyl sulfoxide (DMSO). METHODS: Etched dentin surfaces from extracted sound molars were randomly bonded in wet or dry conditions (30s air drying) with DMSO/ethanol or DMSO/H2O as pretreatments using a simplified (Scotchbond Universal Adhesive, 3M ESPE: SU) and a multi-step (Adper Scotchbond Multi-Purpose, 3M ESPE: SBMP) etch-and-rinse adhesives. Untreated dentin surfaces served as control. Bonded teeth (n=8) were stored in distilled water for 24h and sectioned into resin-dentin beams (0.8mm2) for microtensile bond strength test and quantitative interfacial nanoleakage analysis (n=8) under SEM. Additional teeth (n=2) were prepared for micropermeability assessment by CFLSM under simulated pulpar pressure (20cm H2O) using 5mM fluorescein as a tracer. Microtensile data was analyzed by 3-way ANOVA followed by Tukey Test and nanoleakage by Kruskal-Wallis and Dunn-Bonferroni multiple comparison test (α=0.05). RESULTS: While dry-bonding of SBMP produced significantly lower bond strengths than wet-bonding (p<0.05), DMSO/H2O and DMSO/ethanol produced significantly higher bond strengths for SBMP irrespective of dentin condition (p<0.05). SU presented significantly higher nanoleakage levels (p<0.05) and micropermeability than SBMP. Improvement in hybrid layer integrity occurred for SBMP and SU for both pretreatments, albeit most pronouncedly for DMSO/ethanol regardless of dentin moisture. CONCLUSION: DMSO pretreatments may be used as a new suitable strategy to improve bonding of water-based adhesives to demineralized air-dried dentin beyond conventional wet-bonding. Less porous resin-dentin interfaces with higher bond strengths on air-dried etched dentin were achieved; nonetheless, overall efficiency varied according to DMSO's co-solvent and adhesive type. CLINICAL SIGNIFICANCE: DMSO pretreatments permit etched dentin to be air-dried before hybridization facilitating residual water removal and thus improving bonding effectiveness. This challenges the current paradigm of wet-bonding requirement for the etch-and-rinse approach creating new possibilities to enhance the clinical longevity of resin-dentin interfaces.

Effect of various dimethyl sulfoxide concentrations on the durability of dentin bonding and hybrid layer quality.

The objective was to evaluate effect of dimethyl sulfoxide (DMSO) on microtensile bond strength (µTBS) and nanoleakage (NL). Superficial dentin was acid-etched and pretreated with DMSO. Etch-and-rinse adhesive was applied and restored with resin composite incrementally. After 24 h, teeth were sectioned, stored in artificial saliva for 24-h or 6-months before µTBS evaluation. Failure modes were examined. Six beams per group were submitted to nanoleakage evaluation using SEM. Data were analyzed using ANOVA and Tukey's test (α=0.05). Pretreatment had no significant effect on µTBS after 24 h (p>0.05). After 6 months storage, µTBS of control decreased significantly, more than with the groups treated with 0.01% or higher (p<0.05). DMSO-pretreated groups preserved µTBS in all groups. After 6-months, all groups except 0.001% showed significantly lower nanoleakege compared to control (p<0.05). DMSO (0.01-20%) may improve the hybrid layer integrity and bonding durability. The best results were seen with low (1-5%) of DMSO concentrations.

In situ analysis of gelatinolytic activity in human dentin.

Matrix metalloproteinases (MMPs) such as gelatinases are differentially expressed in human tissues. These enzymes cleave specific substrates involved in cell signaling, tissue development and remodeling and tissue breakdown. Recent evidences show that gelatinases are crucial for normal dentin development and their activity is maintained throughout the entire tooth function in the oral cavity. Due to the lack of information about the exact location and activity of gelatinases in mature human dentin, the present study was designed to examine gelatinolytic levels in sound dentin. In situ zymography using confocal microscopy was performed on both mineralized and demineralized dentin samples. Sites presenting gelatinase activity were identified throughout the entire biological tissue pursuing different gelatinolytic levels for distinct areas: predentin and dentinal tubule regions presented higher gelatinolytic activity compared to intertubular dentin. Dentin regions with higher gelatinolytic activity immunohistochemically were partially correlated with MMP-2 expression. The maintenance of gelatinolytic activity in mature dentin may have biological implications related to biomineralization of predentin and tubular/peritubular dentinal regions, as well as regulation of defensive mechanisms of the dentin-pulp complex.

A plataforma Moodle no treinamento de estudantes de Odontologia na avaliação de restaurações classe II em resina composta / Dental students training on the evaluation of class II composite restorations using the Moodle platform

O objetivo do estudo foi analisar o padrão de conduta de acadêmicos de Odontologia frente a restaurações classe II em resina composta cuja situação clínica seja de caráter duvidoso. Deste modo, pode-se detectar dificuldades comuns dos estudantes na tomada de decisão da conduta clínica, por meio de critérios de avaliação padronizados, bem como aperfeiçoar uma metodologia auxiliar de ensino digital baseada na plataforma Moodle. Participaram da pesquisa 65 estudantes da disciplina de Dentística que já haviam recebido treinamento teórico sobre critérios clínicos para avaliação de restaurações conforme FDI (World Dental Federation). A coleta de dados foi feita por meio de questionários disponíveis no site Aprender Unoeste (plataforma Moodle). Os estudantes analisaram 22 imagens de restaurações classe II em resina composta disponíveis no site observando os seguintes itens: parâmetros estéticos (brilho superficial, manchamento superficial e marginal, correspondência de cor e translucidez), parâmetros funcionais (fratura do material e retenção, adaptação marginal, forma anatômica proximal/contorno) e parâmetros biológicos (recorrência de cáries e integridade dental). A média de acertos dos alunos foi 6,3±0,7 (sobre pontuação máxima = 10), sendo que os parâmetros estéticos apresentaram menor percentual de acertos. Após o preenchimento do questionário os estudantes obtinham o feedback imediato de suas avaliações, tendo então a possibilidade de verificar seus erros e qual seria a resposta adequada. O estudo detectou dificuldades dos estudantes de Odontologia na análise de restaurações em resina composta e possibilitou que estes adquirissem experiência visual clínica, desenvolvendo seu senso crítico, como auxílio de novas metodologias de ensino-aprendizagem (AU).

The study aimed to evaluate the clinical conduct of dental undergraduate students regarding unsatisfactory Class II composite restorations with doubtful prognosis, in order to detect their difficulties and to improve learning methods using a Moodle online platform. A total of 65 sixth semester students were enrolled, they were attending Operative-Restorative Dentistry discipline and received previous theoretical training on restorations evaluation according FDI (World Dental Federation) criteria and randomly selected as volunteers. Data was collected using a questionnaire available on a specific online Moodle platform. Students analyzed 22 digital images of class II composite restorations observing aesthetic parameters (i.e., surface gloss, surface and marginal staining, color matching and translucency), anatomical aesthetic form, functional parameters (i.e., restoration fracture and retention, marginal adaptation, proximal anatomical shape/contour) and biological parameters (i.e., recurrence of caries and tooth integrity). The maximum individual score for correct answers was established as 10 points. Immediate feedback was provided allowing students to check the appropriate responses once the questionnaire was finished. The average of correct answers was 6.3 (0,7 standard deviation). Graduation students present a considerable high difficulty to determine the clinical success of composite restorations. The proposed new teaching/learning methodology enhances the visual experience and the critical contributes to accelerate the learning curve on this topic (AU).

Influence of dimethyl sulfoxide used as a solvent on the physical properties and long-term dentin bonding of hydrophilic resins.

OBJECTIVE: To examine the feasibility of dimethyl sulfoxide (DMSO) incorporation into relatively hydrophilic resins as a new potential method to improve the durability of resin-dentin bonds. METHODS: Six experimental light-curing BisGMA/HEMA resins solvated in ethanol and DMSO with increasing concentrations of DMSO (0, 0.5, 1, 2, 4 and 10wt%) were prepared. The degree of conversion (DC) was evaluated by Fourier Transform Infrared Spectroscopy (n=8); water sorption (Wsp) and water solubility (Wso) were gravimetrically assessed (n=10); and flexural strength (FS) and elastic modulus (E) were determined by a three-point bending flexural test (n=10). Flat dentin surfaces on sound third molars (n=10/group) were bonded with resins containing 0, 2, 4 and 10wt% DMSO used as a two-step etch-and-rinse system. Dentin microtensile bond strength was determined at 24h and after two-year aging in artificial saliva at 37°C. RESULTS: DMSO significantly affected Wsp (p=0.0006), DC, Wso, FS, and E (p<0.0001). In general, the resins' mechanical/physical properties were not affected by 2% or lower DMSO incorporation. Incorporation of 4% or higher DMSO content significantly increased DC, Wsp and Wso, but 2% or higher DMSO concentrations significantly reduced FS and E. No influence on immediate dentin bond strength occurred up to 4% DMSO incorporation. While 4% or higher DMSO concentrations impaired bond strength over time, the resin containing 2% DMSO presented significant higher dentin bond strength compared to the control resin after two year-aging. SIGNIFICANCE: The use of DMSO as a new solvent in adhesive dentistry improves dentin bonding of relatively hydrophilic resins over time. 2% DMSO incorporation in BisGMA/HEMA resins should be sufficient to reduce bond strength loss without compromising polymer mechanical strength and physical properties.

Dentin bond optimization using the dimethyl sulfoxide-wet bonding strategy: A 2-year in vitro study.

OBJECTIVE: This study evaluated a new approach, named dimethyl sulfoxide (DMSO)-wet bonding, to produce more desirable long-term prospects for the ultrafine interactions between synthetic polymeric biomaterials and the inherently hydrated dentin substrate. METHODS: Sound third molars were randomly restored with/without DMSO pretreatment using a total-etch (Scocthbond Multipurpose: SBMP) and a self-etch (Clearfil SE Bond: CF) adhesive systems. Restored teeth (n=10)/group were sectioned into sticks and submitted to different analyses: micro-Raman determined the degree of conversion inside the hybrid layer (DC); resin-dentin microtensile bond strength and fracture pattern analysis at 24h, 1year and 2 years of aging; and nanoleakage evaluation at 24h and 2 years. RESULTS: DMSO-wet bonding produced significantly higher 24h bond strengths for SBMP that were sustained over the two-year period, with significantly less adhesive failures. Similarly, DMSO-treated CF samples presented significantly higher bond strength than untreated samples at two years. Both adhesives had significant less adhesive failures at 2 years with DMSO. DMSO had no effect on DC of SBMP, but significantly increased the DC of CF. DMSO-treated SBMP samples presented reduced silver uptake compared to untreated samples after aging. SIGNIFICANCE: Biomodification of the dentin substrate by the proposed strategy using DMSO is a suitable approach to produce more durable hybrid layers with superior ability to withstand hydrolytic degradation over time. Although the active role of DMSO on dentin bond improvement may vary according to monomer composition, its use seems to be effective on both self-etch and etch-and-rinse bonding mechanisms.

Effect of dimethyl sulfoxide wet-bonding technique on hybrid layer quality and dentin bond strength.

OBJECTIVES: This study examined the effect of a dimethyl sulfoxide (DMSO) wet bonding technique on the resin infiltration depths at the bonded interface and dentin bond strength of different adhesive systems. METHODS: Flat dentin surfaces of 48 human third molars were treated with 50% DMSO (experimental groups) or with distilled water (controls) before bonding using an etch-and-rinse (SBMP: Scotchbond Multi-Purpose, 3M ESPE) or a self-etch (Clearfil: Clearfil SE Bond, Kuraray) adhesive system. The restored crown segments (n=12/group) were stored in distilled water (24h) and sectioned for interfacial analysis of exposed collagen using Masson's Trichrome staining and for microtensile bond strength testing. The extent of exposed collagen was measured using light microscopy and a histometric analysis software. Failure modes were examined by SEM. Data was analyzed by two-way ANOVA followed by Tukey Test (α=0.05). RESULTS: The interaction of bonding protocol and adhesive system had significant effects on the extension of exposed collagen matrix (p<0.0001) and bond strength (p=0.0091). DMSO-wet bonding significantly reduced the extent of exposed collagen matrix for SBMP and Clearfil (p<0.05). Significant increase in dentin bond strength was observed on DMSO-treated specimens bonded with SBMP (p<0.05), while no differences were observed for Clearfil (p>0.05). SIGNIFICANCE: DMSO-wet bonding was effective to improve the quality of resin-dentin bonds of the tested etch-and-rinse adhesives by reducing the extent of exposed collagen matrix at the base of the resin-dentin biopolymer. The improved penetration of adhesive monomers is reflected as an increase in the immediate bond strength when the DMSO-wet bonding technique is used with a water-based etch-and-rinse adhesive.

Influence of chlorhexidine on dentin adhesive interface micromorphology and nanoleakage expression of resin cements.

This study focused on adhesive interface morphologic characterization and nanoleakage expression of resin cements bonded to human dentin pretreated with 1% chlorhexidine (CHX). Thirty-two non-carious human third molars were ground flat to expose superficial dentin. Resin composite blocks were luted to the exposed dentin using one conventional (RelyX ARC) and one self-adhesive resin cement (RelyX U100), with/without CHX pretreatment. Four groups (n = 8) were obtained: control groups (ARC and U100); experimental groups (ARC/CHX and U100/CHX) were pretreated with 1% CHX prior to the luting process. After storage in water for 24 h, the bonded teeth were sectioned into 0.9 × 0.9 mm(2) sticks producing a minimum of 12 sticks per tooth. Four sticks from each tooth were prepared for hybrid layer evaluation by scanning electron microscope analysis. The remaining sticks were immersed in silver nitrate for 24 h for either nanoleakage evaluation along the bonded interfaces or after rupture. Nanoleakage samples were carbon coated and examined using backscattered electron mode. Well-established hybrid layers were observed in the groups luted with RelyX ARC. Nanoleakage evaluation revealed increase nanoleakage in groups treated with CHX for both resin cements. Group U100/CHX exhibited the most pronouncing nanoleakage expression along with porous zones adjacent to the CHX pretreated dentin. The results suggest a possible incompatibility between CHX and RelyX U100 that raises the concern that the use of CHX with self-adhesive cements may adversely affect resin-dentin bond.