Bond strength of porcelain laminate veneers to dental hard tissues

Objectives: The aim of this in vitro study was to evaluate shear bond strength of porcelain laminate veneers to three different surfaces by means of enamel, dentin and enamel-dentin complex using three different resin cements. Methods: Onehundredthirtyfive extracted, noncarious human maxillary central incisor teeth were used and the teeth were randomly divided into 9 groups(n=15). The teeth were embedded in acrylic molds and prepared with three different levels for bonding surfaces of enamel(E), dentin(D) and enamel-dentin complex(E-D). Porcelain discs(IPS e.max Press/Ivoclar Vivadent) of 2 mm in thickness and 4 mm in diameter were prepared according to the manufacturer's instructions. Porcelain discs were luted to the tooth surfaces by using two light-cured[RelyX Veneer(RV); Variolink Veneer(VV)] and a dual-cured[Variolink II(V II)] resin cements according to the manufacturers' instructions. All the samples were stored in distilled water for 24 h at 37oC and were thermal cycled for 5000 cycles in 5oC ve 55 oC deionized water. Shear bond strength test was performed in a universal testing machine(MCE 2000ST, Quicktest Prüfpartner GmbH) at 0.5 mm/min until bonding failure. The datas were statistically analyzed using 1-way ANOVA and Tukey-HSD post hoc-test(p =0.05). Results: Group RV-D exhibited the lowest bond strength value(5.42±6.6 MPa). There was statistically no difference between RV-D, V II-D(13.78±8.8 MPa) and VV-D(13.84±6.2 MPa) groups(p>0.05). However, significant differences were found between the group RV-D and the other groups(p<0.05). Group VV-M exhibited the highest bond strength value (24.76±8.8 MPa). Group VV-M was statistically different from the groups RV-D, VV-D and V II-D(p<0.05). Conclusions: Porcelain laminate veneers bonded to dentin surfaces only effected the shear bond strength values negatively. When dentin exposure is necessary during the preparation, enough sound enamel must be protected as possible to maintain a good bonding and to obtain a maximum bond strength, preparation margins should be on sound enamel.