Comparative evaluation of 3 microbond strength tests using 4 adhesive systems: Mechanical, finite element, and failure analysis.

STATEMENT OF PROBLEM: Bond strength (BS) values from in vitro studies are useful when dentists are selecting an adhesive system, but there is no ideal measuring method. PURPOSE: The purpose of this in vitro study was to investigate the influence of the evaluation method in the BS between dentin and composite resin. MATERIAL AND METHODS: Molars with exposed superficial dentin (N=240) were divided into 3 groups according to the test: microtensile (µTBS), microshear (µSBS), and micropush-out (µPBS). Each one was subdivided into 4 groups according to the adhesive system: total etch, 3- and 2-step; and self-etch, 2- and 1-step). For the µPBS test, a conical cavity was prepared and restored with composite resin. An occlusal slice (1.5 mm in thickness) was obtained from each tooth. For the µSBS test, a composite resin cylinder (1 mm in diameter) was built on the dentin surface of each tooth. For the µTBS test, a 2-increment composite resin cylinder was built on the dentin surface, and beams with a sectional area of 0.5 mm2 were obtained. Each subgroup was divided into 2 (n=10) as the specimens were tested after 7 days and 1 year of water storage. The specimens were submitted to load, and the failure recorded in units of megapascals. Original BS values from the µTBS and µSBS tests were normalized for the area from µPBS specimens. Original and normalized results were submitted to a 3-way ANOVA (α=.05). The correlation among mechanical results, stress distribution, and failure pattern was investigated. RESULTS: Significant differences (P<.05) were found among the adhesive systems and methods within both the original and normalized data but not between the storage times (P>.05). Within the 7 days of storage, the original BS values from µTBS were significantly higher (P<.001) than those from µPBS and µSBS. After 1 year, µSBS presented significantly lower results (P<.001). However, after the normalization for area, the BS values of the µTBS and µPBS tests were similar, and both were higher (P<.001) than that of µSBS in both storage times. In the µSBS and µTBS specimens, cohesive and adhesive failures were observed, whereas µPBS presented 100% of adhesive failures. The failure modes were compatible with the stress distribution. CONCLUSIONS: The storage time did not affect the results, but differences were found among the adhesives and methods. For comparisons of bond strength from tests with different bonding areas, the normalization for area seemed essential. The microshear bond test should not be used for bond strength evaluation, and the microtensile test needs improvement to enable reliable results regarding stress concentration and failure mode. The micropush-out test may be considered more reliable than the microtensile in the bond strength investigation, as demonstrated by the uniform stress concentration and adhesive failure pattern.

Clareamento dentário associado à facetas Indiretas em cerâmica: abordagem minimamente invasiva. / Tooth bleaching associated with ceramic veneers: a conservative approach.

O objetivo deste trabalho é relatar um caso clínico, demostrando protocolo conservador para reabilitação estética com facetas indiretas de cerâmica associadas ao clareamento dental. Paciente do gênero masculino insatisfeito em relação à estética do seu sorriso apresentou ao exame clínico restaurações em resina composta nos dentes anteriores com pigmentação e fraturas marginais. Foi realizada remoção das restaurações para avaliação dos diastemas. Inicialmente, foi realizado clareamento externo em consultório com peróxido de hidrogênio a 38%. Após uma semana, foram feitos preparos minimamente invasivos na superfície vestibular e moldagem. Os laminados foram confeccionados com cerâmica feldspática e cimentados adesivamente ao substrato dentário. Feita a cimentação, foi feito ajuste oclusal mantendo os contatos oclusais fisiológicos. A associação entre o clareamento dentário e laminados cerâmicos, com preparos conservadores, mostrou-se eficaz para a reabilitação estética e funcional do sorriso contribuindo para a satisfação do paciente.

The aim of this study is to describe a clinical case, showing conservative approach for aesthetic rehabilitation with ceramic veneers associated with tooth bleaching. A male patient presented dissatisfaction with smile was submitted to clinical examination and showing composite resin restorations on anterior teeth with marginal fractures and pigmentation. Restoration removal was performed for diastemata evaluation. Initially, was performed in-office tooth bleaching with hydrogen peroxide 38%. After one week, preparations were made with minimally removal of tooth structure at buccal surface and the impression was made. The veneers were fabricated with feldspathic ceramic and cemented adhesively to the tooth substrate. Once the luting procedure was performed, occlusal adjustment was made keeping the physiological occlusal contacts. The association between tooth bleaching and ceramic veneers with conservative approach was effective for the esthetic and functional rehabilitation of the smile contributing to patient satisfaction.