RESUMO
Objetivo: Comparar diferentes técnicas de moldagem com silicone de adição, quanto à precisão e fidelidade da cópia através de medidas manuais e sobreposição em CAD/CAM. Material e método: Foram realizadas 4 moldagens com silicone de adição de um mesmo modelo nas seguintes técnicas: T1 dois passos com recorte; T2 dois passos com alívio de filme PVC; T3 dois passos sem alívio e T4 - simultânea. A fidelidade das 4 técnicas de moldagem foi avaliada por meio de mensurações de 5 dimensões nos modelos de gesso vazados em cada um dos moldes obtidos. Outra forma de análise foi a sobreposição de imagens no CAD/CAM, com a finalidade de verificar se há semelhanças ou diferenças dimensionais entre o modelo piloto e as amostras. As medidas obtidas foram submetidas ao teste ANOVA com comparações múltiplas pelo teste de Tukey (α=0,05). Resultados: De acordo com as mensurações, a técnica que apresentou maior discordância do modelo piloto foi a T4, não havendo diferença entre as outras técnicas. Na avaliação em CAD/CAM, as técnicas T4 e T3 apresentaram maiores diferenças em relação ao modelo original de acordo com as imagens sobrepostas. Conclusões: Todas as técnicas estudadas apresentaram alterações dimensionais, em especial a técnica simultânea e a sem alívio, tanto nas medidas obtidas quanto na análise em CAD/CAM.
Objetives: To compare different impression techniques with addition silicone, by means of copy accuracy through manual measurements and overlaping in CAD/CAM. Material and methods: Four impressions of a same pilot model were carried out with silicone addition in different techniques: T1 two steps with cut-back; T2 two steps with PVC film relief; T3 two steps without relief; and T4 one step. The accuracy of the 4 different impression techniques was assessed by measuring 5 dimensions on stone casts poured from the impressions of the pilot model. Another analysis was carried out in CAD/CAM using the overlaping of the casts and the pilot model, in order to verify dimensional similarities and differences between them. The values obtained were submitted to ANOVA and Tukey test, for multiple comparisons (α=0.05). Results: According to the measures done, the technique that generated the greatest difference from the pilot model was T4, with no difference among the other techniques. In CAD/CAM analysis, techniques T4 and T3 presented more differences from the original model. Conclusions: All studied techniques presented dimensional changes, mainly the 1 step and the 2 step without relief, in both methods, measures and CAD/CAM analysis.
RESUMO
This paper aims to present a clinical case of laminate veneers in lithium disilicate (LD) reinforced ceramic, complemented with scanning electron microscopy and energy dispersive x-ray spectroscopy analysis of this ceramic's surfaces submitted to some of the different post-etching cleaning protocols proposed by literature. Many dentists are applying all-ceramic restorations, especially veneers, with the most applied material being LD, due to its good mechanical properties, esthetics, and ability to adhere to tooth substrate. The cementation process is critical to clinical success of indirect restorations. Combination of hydrofluoric acid and silane application on the inner surface of ceramic has been the most recommended method to increase bond strength between ceramic and tooth substrate. As a result of surface corrosion, residual subproducts are formed and precipitate on the ceramic surface, affecting the bonding process to the resin cement. Elimination of residue is recommended in the literature and can be done via 3 common techniques: thorough washing with air/water spray for 30 seconds, 37% phosphoric acid for 60 seconds, or ultrasonic bath for 4 to 10 minutes. Little information on LD ceramics post-etching cleaning methods is available in the literature. For this ceramic, the thorough washing with air/water spray for 30 seconds appeared to remove most of the residue without damaging the material. Being also the most practical and easiest of the reviewed procedures, it was, therefore, the protocol of choice for the clinical cases presented in this paper with success after 18 months.
