Evaluation of marginal adaptation of partial laminate veneers manufactured with different materials and techniques: in vitro study

Fabricating minimal invasive restorations with natural looking became a need due to the improvements in technology and increasing esthetic expectations of the patients. Dental crowns were used for restoration of the anterior teeth for many years but the dental crowns are accepted as an invasive method for esthetic treatments anymore. In the case of tooth fracture, diastema or any defect of tooth, restoration of only the related area of the tooth is a more conservative option instead of restoration with crowns. Marginal adaption of these minimal invasive restorations is so important criteria to accept their clinical importance. However up till now, the researches comparing the marginal adaptations of partial laminate veneers prepared with minimal invasive methods are so limited. The purpose of this study is in vitro comparison of marginal adaptation of partial laminate veneers fabricated with different methods and materials that are the ones of the minimal invasive treatment options. In this in vitro study, lithium disilicate glass ceramic (IPS e.max CAD,LT A2/ C16, Ivoclar Vivadent, Liechtenstein, IPS e.max Press HT, Ivoclar Vivadent, Liechtenstein), feldspathic porcelain (VITABLOCS Mark II, Vita Zahnfabrik, Bad Säckingen, Germany) and resin nano ceramic (Vita Enamic, Vita Zahnfabrik, Bad Säckingen, Germany) were used as partial laminate veneer materials. In this study with 5 groups, 4 of them obtain partial laminate veneers with minimal tooth preparation and one of the groups obtains partial laminate veneers without tooth preparation (prepless). Computer-aided design/Computer-aided manufacturing (CAD/CAM) and heat-pressing were selected as production methods of the partial laminate veneers. All partial laminate veneers were bonded to epoxy resin in terms of the standardization of the specimens. All specimens were fabricated with the thickness of 0,2-0,4 mm and all finishing and glazing procedures were carried out on the all specimens to avoid marginal discrepancies. Marginal gaps of the specimens were imaged and recorded using scaning electron microscopy (SEM) without the need for gold coating. Image J 1.37v (Wayne Raspand National Ins. Of Health, USA) computer software was used to measure marginal gaps on all four different zones with 7 measurements on each zone (28 measurements per crown). All the means of the marginal measurements were collected for each zone and the 5 groups were compared among them. SPSS 21.0 (SPSS Inc., Chicago, USA) computer software was used for the statistically analysis of data. The normality of data was tested with Shapiro-Wilk test and Levene test was used to assess the equality of variances for data. The groups were compared with each other by using one-way ANOVA test. To the results of this study; the highest marginal gap was seen in the group of lithium disilicate porcelain partial veneers with minimal tooth preparation fabricated with CAD/CAM method. The lowest marginal gap was seen in the group of prepless lithium disilicate porcelain partial veneers fabricated with heat-pressing method. Within the groups fabricated with CAD/CAM method, the group of feldspathic porcelain partial veneers with minimal tooth preparation showed the lowest marginal gap values, the group of lithium disilicate porcelain partial veneers showed the highest marginal gap values. Within the groups fabricated with heat-pressing method, the difference of marginal gap between the groups of partial laminate veneers with tooth preparation and without tooth preparation are statistically important. (p0.01) At the end of this study, although marginal gap values of partial laminate veneers fabricated with different materials and methods were different from each other, all data are in a clinical acceptable scale.