Effect of different activation modes on the degree of conversion, tensile bond strength and interfacial morphology of dual-cured cementing systems used in indirect composite restorations

Author(s)

Cesar Augusto Galvão Arrais

• Document type: Doctoral Thesis
• Press: Piracicaba, SP.
• Institution: Universidade Estadual de Campinas (UNICAMP). Faculdade de Odontologia de Piracicaba
• Defense date: 2006-12-14

Examining board members

Marcelo Giannini; Sillas Luiz Lordelo Duarte Junior; Roberto Ruggiero Braga; Carlos de Paula Eduardo; Guilherme Elias Pessanha Henriques

• Advisor: Marcelo Giannini

Abstract

The lack of light-activation of dual-cured bonding agents before the resin cement application has been an alternative technique of cementing indirect restorations when dual-cured cementing systems are used (DCS ¿ dual-cured bonding agents / dual-cured resin cements). However, few reports exist regarding the effectiveness of DCS when dual-cured bonding agents are left in the uncured state before the seating of the indirect restoration. Therefore, the aims of this study were: 1- to evaluate the microtensile bond strength (MTBS) and micromorphology of the adhesive interface of indirect restorations by confocal laser microscopy (CLSM) when the dual-cured bonding agents were left in the uncured state; 2- to analyze the degree of conversion (DC) by Fourier Transformed Infrared Spectroscopy and the bond strength of indirect restorations when DCSs were applied to the tooth and light activated or allowed to self-cure; 3- to evaluate the DC and ultimate tensile strength (UTS) of bonding agents light-activated with light curing units (LEDs and halogen light). The MTBS and UTS were analyzed using microtensile bond strength test. Different dyes were incorporated to the DCSs before they were applied to teeth for the CSLM analysis. For the DC analysis, the DSCs were applied to the diamond surface of attenuated total reflectance unit of the infrared device. The DC of the bonding agents related to the study evaluating the effectiveness of light-curing units was obtained from thin resin adhesive films. The results demonstrated that the MTBS was not affected, and the values were even higher for one 4th generation DCS, when the dual-bonding agents were left in the uncured state before the resin cement application. The CLSM analysis exhibited some variation in the micromorphological features, which depended on the DCSs and on the curing modes of bonding agents and resin cements. Some DCSs showed lower DC when pre-cured resin composite discs were used. The self-cured groups exhibited lower MTBS than the light-activated ones, except for one 4th generation DCS. The LED promoted lower DC in all bonding agents than did the halogen light. No difference in UTS was observed when LED was used. It was concluded that leaving the dual-cured bonding agent in the uncured state before seating the indirect restoration may be a reliable technique to ensure adequate MTBS, but most DCSs should be light-activated after seating the indirect restoration to provide optimal bond strength. Some LEDs can compromise the DC of adhesive systems (AU)