Effect of Cementation Protocol on the Marginal Adaptation of Indirect Overlay Restorations Fabricated from Two Different All-Ceramic CAD/CAM Materials
Author(s): Zaidoon Hasan Mohammed* and Manhal A Majeed
Abstract
The objective of this in vitro study was to measure and compare the marginal adaptation of indirect overlay restorations fabricated from two different all-ceramic CAD/CAM materials (lithium disilicate and reinforced composite blocks) cemented with three different cementation protocols (adhesive resin cement, preheated composite, and sonically-activated composite). Fortyeight human maxillary first-premolar teeth were prepared for indirect overlay restorations with butt joint preparation design. The prepared teeth were divided into two main groups of twenty-four teeth each according to the type of CAD/CAM material used for the fabrication of the restorations: Group A: overlays fabricated from lithium disilicate blocks (IPS e.max CAD, Ivoclar Vivadent, Liechtenstein), Group B: overlays fabricated from reinforced resin blocks (BRILLIANT Crios, Coltene/ Whaledent AG, Switzerland). Each group was then further subdivided into three subgroups of eight teeth each according to the cementation protocol used: Subgroups (A1, B1): cemented with adhesive resin cement (RelyX Ultimate, 3M ESPE, USA), Subgroups (A2, B2): cemented with preheated composite (Filtek Z350 XT, 3M ESPE, USA) and Subgroups (A3, B3): cemented with sonically-activated composite (SonicFill 2, Kerr Corp., USA). The prepared teeth were then scanned using CEREC Omnicam digital intra-oral scanner, then overlay restorations were designed using Sirona InLab 15.1 software and milled with InLab MC XL milling unit. Overlay restorations of group A were then subjected to crystallization /glaze firing at 840 C0 while those of group B were finished and polished only. Each restoration was then seated on its respective tooth using a custom-made specimen holding device. The marginal gap was then measured using a digital microscope at four points on each surface of the tooth at a magnification of 230x and the mean value of these measurements was recorded. Each restoration cemented on its respective tooth according to the aforementioned sample grouping following the manufacturers’ instructions of each material. The results of this study were then analyzed statistically using independent t-test, one-way ANOVA test, LSD test, and Dunnett T3 test. The results of this study showed that the overlay restorations fabricated from reinforced resin blocks (Briallant Crios) recorded less marginal gap than those restorations fabricated from lithium disilicate blocks (IPS e.max CAD) with statistically significant difference (p<0.05), pre- and post-cementation regardless of cementation protocol used. The results of this study also showed that, for both block types, cementation with adhesive resin cement provided significantly better marginal adaptation than cementation with preheated composite and sonically-activated composite, with the statistically non-significant difference between the latter two cementation protocols.