Microleakage of thin-walled monolithic zirconia and polymer-containing CAD-CAM crowns

Abstract

Statement of problemMonolithic restorations facilitate computer-aided design and computer-aided manufacturing (CAD-CAM) processability and provide thin-walled restorations, which require less tooth reduction. For the long-term success of these restorations, their durable sealing is important. However, data in this regard are sparse. PurposeThe purpose of this in vitro study was to investigate the microleakage of monolithic complete crowns made from current CAD-CAM materials after mastication simulation. Material and methodsSixty-four identical test specimens (crown and tooth) were milled based on corresponding standard tessellation language data sets: one for the crowns and another for the human molar teeth. Four CAD-CAM restoration materials were investigated: 2 polymer-containing materials, Brilliant Crios (BC) and Vita Enamic (VE), and 2 zirconia materials, ultra-high-translucent Nacera Pearl Q³ Multi-Shade (ultraHT) and high-translucent Nacera Pearl Multi-Shade (HT). The crowns were adhesively luted to the CAD-CAM milled human molars with 1 of 3 luting systems: OneCoat7Universal and DuoCem (BC); A.R.T.Bond and DuoCement (VE); or EDPrimer/Panavia F2.0 (ultraHT and HT). The specimens were divided in 2 subgroups, and 2 different mastication simulations were applied: normal function (NF) and bruxism (B). A dye penetration test was used to detect microleakage, and the specimens were sectioned. A digital microscope (Zeiss) was used for analysis and to calculate the percentage of leakage in relation to the height of the tooth. Data were subjected to the Mann-Whitney and Kruskal-Wallis tests (α=.05). ResultsMicroleakage was identified in all groups. VE reported the highest leakage with a mean of 13.0%, followed by ultraHT (4.8%), HT (3.6%), and BC (3.0%). No significant difference was detected between the 2 simulation programs (normal function and bruxism). However, VE and the zirconia group HT exhibited a significant difference (P<.014), whereas no significant difference was noted among the zirconia groups or the polymer-containing groups BC and VE. ConclusionsThin-walled restorations made of CAD-CAM composite resin and zirconia exhibited reduced microleakage compared with the polymer-containing ceramic. Thus, from the specific viewpoint of microleakage, CAD-CAM composite resins and zirconia seem to be suitable materials for thin-walled complete crowns.