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Efeito de diferentes tratamentos de superfície na resistência de união, ângulo de contato, morfologia e análise da distribuição de tensão de laminados ultrafinos de cerâmica reforçada por dissilicato de lítio

  • Escobar, Lorena Cristina Bogado
Publication Date
Nov 30, 2017
Repositório Institucional UNESP
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Laminate veneers are becoming a technique used in the conservative treatments by the ability to restore aesthetics and function. This study aimed to evaluate, in vitro, the effect of two surface treatments on ultrathin lithium disilicate specimens in bond strength between treated ceramics and resin cement. Ceramic ultrathin laminates (12 X 14 X 0.3 mm) were obtained and randomly distributed into two groups (n=20) according to the surface treatment: 5% hydrofluoric acid for 20 s and silane (HF) and Monobond Etch & Prime (Ivoclar, Vivadent) for 60 s (MEP). Two resin cement cylinders were made using cylindrical matrices. After 24 h storage, microshear bond strength tests were performed in a universal testing machine (1 mm/min) and failure mode was analyzed. Bond strength data were submitted to Student's t-test (α=0.05). The contact angle was measured. Micromorphogical analyses of representatives specimens were also performed (atomic force and scanning electron microscopy). Finite element analysis studied the distribution of stress in maxillary central incisors restored with ultrathin laminate veneers of lithium disilicate (0.3 mm). 3D model was elaborated in CAD Rhinoceros® software and exported to analysis software Ansys®. Four groups were modeled and analyzed under two experimental conditions: wear or non-enamel and type of preparation. A load of 100 N was applied at the palatal face. The stress was analyzed by Maximum Principal Stress criteria. Microshear bond strength values showed that HF group was not statistically different from MEP group (p=0.117). Microshear bond strength values showed that HF group was not statistically different from MEP group (p=0.117). Contact angle was influenced by surface treatments (p=0.001); specimens without surface treatment had the highest contact angle (65.37˚) whereas HF group exhibited the lowest contact angle (33.80˚). Surface morphological evaluation showed that hydrofluoric acid etching promoted a more obvious surface pattern regarding pores and irregularities with higher surface roughness in comparison to self-etching glass ceramic primer. Finite element analysis showed that laminates without enamel prepared generated the lowest stress in the enamel and in the laminate. Laminates with enamel prepared showed the stress concentration in the finishing lines of preparation in the tooth/laminate interface. Monobond Etch & Prime obtained statistically equivalent results in terms of bond strength to hydrofluoric acid and silane. Ultrathin laminate veneer cemented over sound enamel generate less stress on the surface of the tooth and laminate. Laminates veneers on prepared enamel do not cause additional tension in the tooth structure.

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