Degree of polymeric conversion, bond strength of the tooth/cement interface, and optical changes after adhesive/cement photoactivation by transillumination of ceramic veneers with different translucency and thickness.

• Grant number: 23/12258-4
• Support Opportunities: Scholarships in Brazil - Master
• Start date: January 01, 2024
• End date: February 28, 2025
• Field of knowledge: Health Sciences - Dentistry - Dental Materials
• Principal Investigator: José Maurício dos Santos Nunes Reis
• Grantee: Rafael de Pauli Santos
• Host Institution: Faculdade de Odontologia (FOAr). Universidade Estadual Paulista (UNESP). Campus de Araraquara. Araraquara , SP, Brazil

Abstract

The aim of this study is to evaluate the degree of polymeric conversion, the bond strength of the tooth/cement interface and optical changes after photoactivation of the adhesive-resin cement set by transillumination of ceramic veneers of lithium disilicate with different translucency and thickness. Discs (7.5 x 1.0 mm; N=540) of IPS e.Max (Ivoclar Vivadent) with two levels of translucency (HT and LT) and three thicknesses (0.5; 1.0 and 1.5 mm); and enamel (N=240) and dentin of bovine teeth (N=240) will be obtained. Two resin cements will be used, one dual (Variolink Esthetic DC, Ivoclar) and one light-cured (Variolink Esthetic LC, Ivoclar). In order to analyze the degree of conversion, the IPS e.Max discs, of different thicknesses and translucency, will be positioned on the different cements (dual and light-cured) with the use of matrix (standardization of cement thickness) and photoactivated. After 24 h of storage at 37°C, the degree of conversion of each experimental condition (n=5) will be measured with Fourier transform infrared spectroscopy (FTIR). For bond strength and optical changes analyses, IPS e.Max discs of different thicknesses and translucency (n=10) will be cemented onto enamel or dentin substrates. For cementing the discs, Variolink Esthetic DC or Variolink Esthetic LC cements will be used, which will receive photoactivation by transillumination (Valo Cordless Grand 3200, Ultradent), with or without prior photopolymerization of the adhesive system. Before the bond strength tests, the specimens will undergo thermocycling simulating 10 years of hydrothermal aging (12,000 cycles, 5ºC -> 37ºC -> 55ºC, baths of 30 s/temperature). Then, they will be submitted to microshear tests by tensile force until failure, with values expressed in MPa. For the analysis of optical and colorimetric changes, the specimens will be analyzed in a spectrophotometer (CM-2600d/2500d, Konica Minolta), on a white background and on a black background, evaluating the influence of three illuminants (D65, A and F2) on the luminosity data, color coordinates, total color difference, reflection, transmission, absorption and light dispersion. These readings will be obtained immediately after cementation and after hydrothermal aging (12,000 cycles). Quantitative data will be subjected to normality and homoscedasticity tests, and then submitted to the most relevant analyses with a significance level of 95%. Qualitative data will be discussed in a descriptive/interpretative way.