Effects of the application techniques of self-adhesive resin cements on the interfacial integrity and bond strength of fiber posts to dentin

ABSTRACT Objective: To evaluate the influence of an application technique of a glass-fiber post using self-adhesive resin cements on the push-out bond strength and the presence of bubbles in the root thirds. The cements were either applied according to the manufacturer's instruction or using a commercial delivering system (Centrix), at which the cement pastes were collected and applied after manipulation. Material and Methods: Self-adhesive resin cements (RelyX U200/3M ESPE-U200; Maxcem Elite/Kerr-MAX; Clearfil SA Cement/Kuraray-CSA) and a conventional cement (RelyX ARC/3M ESPE-ARC) were used to cement a post and applied either based on the manufacturer's instructions or using a Centrix syringe to deliver the cements directly onto the post of choice, or directly into canal. The roots were scanned with a micro-computed tomography (μCT) and then sectioned into nine 1-mm thick slices for a push-out bond strength test. The μCT images showed the percentage of bubbles in the root thirds (cervical, medium, and apical). Data were analyzed with three-way ANOVA/Tukey (α=0.05). Results: Triple interaction was not significant (p>0.05). The interaction “material” vs “root third” was not significant. A significant interaction was observed between “material” vs “application technique” (p<0.05). For ARC, U200, and MAX, significantly lower percentages of bubbles were observed when the Centrix syringe delivered the cements. Equivalent percentages of voids were observed for CSA, irrespective of the application technique (p>0.05). Significantly higher bond strength was observed when the self-adhesive resin cements were applied using the Centrix delivery system, in comparison with the manufacturer's instructions (p<0.05). Bond strength varied with the root third: cervical>medium>apical (p<0.05). No correlations were found between the bond strength and voids. Conclusions: Bond strength and voids are negatively influenced by the conventional application technique for luting fiber posts. The delivery system (Centrix) seems to produce better results when cementing fiber posts.

Effects of solvent evaporation on water sorption/solubility and nanoleakage of adhesive systems

Objective: To evaluate the influence of solvent evaporation in the kinetics of water diffusion (water sorption-WS, solubility-SL, and net water uptake) and nanoleakage of adhesive systems. Material and Methods: Disk-shaped specimens (5.0 mm in diameter x 0.8 mm in thickness) were produced (N=48) using the adhesives: Clearfil S3 Bond (CS3)/Kuraray, Clearfil SE Bond - control group (CSE)/Kuraray, Optibond Solo Plus (OS)/Kerr and Scotchbond Universal Adhesive (SBU)/3M ESPE. The solvents were either evaporated for 30 s or not evaporated (N=24/per group), and then photoactivated for 80 s (550 mW/cm2). After desiccation, the specimens were weighed and stored in distilled water (N=12) or mineral oil (N=12) to evaluate the water diffusion over a 7-day period. Net water uptake (%) was also calculated as the sum of WS and SL. Data were submitted to 3-way ANOVA/Tukey's test (α=5%). The nanoleakage expression in three additional specimens per group was also evaluated after ammoniacal silver impregnation after 7 days of water storage under SEM. Results: Statistical analysis revealed that only the factor "adhesive" was significant (p<0.05). Solvent evaporation had no influence in the WS and SL of the adhesives. CSE (control) presented significantly lower net uptake (5.4%). The nanoleakage was enhanced by the presence of solvent in the adhesives. Conclusions: Although the evaporation has no effect in the kinetics of water diffusion, the nanoleakage expression of the adhesives tested increases when the solvents are not evaporated. .

Degradação das interfaces resina-dentina: uma revisão da literatura / Degradation of resin-dentin interfaces: a literature review

Restaurações adesivas vêm sendo amplamente utilizadas em diversos procedimentos odontológicos na atualidade. Diversas pesquisas demonstram uma união satisfatória dos materiais resinosos à dentina, principalmente logo após sua aplicação. No entanto, a efetividade dos procedimentos restauradores adesivos promovida por diferentes protocolos de aplicação tem sido questionada com relação à durabilidade da união ao substrato dentinário. A degradação da união, atribuída principalmente à hidrólise dos componentes resinosos e à digestão enzimática dos constituintes da interface, tem se mostrado mais severa para alguns sistemas adesivos do que para outros. O objetivo desta revisão de literatura foi abordar os possíveis mecanismos de degradação das interfaces resina-dentina obtidas com os diferentes protocolos de aplicação disponíveis atualmente. Foram analisadas as diferentes metodologias para estudar o comportamento das interfaces ao longo do tempo. Os estudos das propriedades físico-mecânicas das interfaces e da nanoinfiltração têm se mostrado ferramentas importantes para estimar a longevidade dos adesivos no meio oral. Os trabalhos mostram que a nanoinfiltração ocorre com diferentes severidades, mas praticamente em todos os adesivos. A maioria dos materiais mostra-se eficiente logo após a sua aplicação; no entanto, o comportamento da união ao longo do tempo ante a presença de água varia consideravelmente. Os adesivos autocondicionantes de passo único são os mais susceptíveis à degradação após armazenagem em água. De acordo com os trabalhos revistos, concluiu-se que a degradação da união está relacionada à hidrofilia dos materiais

Adhesive restorations have been increasingly used in many dental procedures in the latest years. Several studies have demonstrated an effective bonding to dentin, especially immediately after application. However, the effectiveness of adhesive restorative procedures has been questioned with regard to the durability of the bond to dentin substrate. Degradation of bonds has been attributed to hydrolysis of resinous components or to enzymatic digestion of the resin-dentin interface, and has been shown to occur in different rates for different adhesive systems. The aim of this literature review was to examine the possible degradation mechanisms of resin-dentin interfaces obtained with currently available adhesive systems of different application protocols. Different methods for studying resin-dentin interfaces behavior over time were examined. The studies of interfaces physicomechanical properties and nanoleakage patterns have been proven to be important tools for predicting the long-term behavior of adhesive systems in the oral environment. The studies have demonstrated that no adhesive system is able of totally preventing nanoleakage. Most adhesives proved to be effective right after application; however, the behavior of bonded interfaces after long-term water-storage varies considerably. Single-step self-etching adhesives are the most susceptible to degradation after storage in water. Based on the studies analyzed it can be concluded that degradation of bonds is related to the hydrophilicity of the materials .