Marginal and Internal Adaptation of All-Ceramic Crown Restorations Fabricated with CAD/CAM Technology and the Heat Press Technique.
Abstract: "Statement of problem:" The accuracy of the chair-side CAD/CAM restorations is still questionable and the effect of the die spacer settings is not well stated in the literature. "Purpose:" The purpose of this study was to evaluate the marginal and internal adaptation of CAD/CAM lithium disilicate crowns fabricated with different die spacer thicknesses and compare them to crowns fabricated ... read moreby the heat press technique. "Materials and Methods: " 40 identical acrylic master dies were manufactured and randomly assigned to 4 groups of 10 dies each. The E4D system was used to fabricate 30 lithium disilicate crowns by scanning the dies from the first 3 groups. Each CAD/CAM group had different spacer thickness settings: 30μm, 60μm and 100μm. In the fourth group, 10 lithium disilicate crowns were fabricated by the heat press technique using 2 layers of die spacer. Evaluation of the marginal and internal gaps was performed by the X-ray microtomography. Occlusal gap (OG), Axial gap (AG), vertical marginal gap (VMG) and absolute marginal discrepancy (AMD) were evaluated at 120 different points for each crown. The data were analyzed using an independent samples t-test. "Results: " The AG demonstrated a statistically significant difference between all groups except the CAD/CAM-30 and the heat-press groups. The OG showed a statistically significant difference between all groups except the CAD/CAM-60 and heat-press group, and between the CAD/CAM-30 and the CAD/CAM-60 groups. The MG showed a statistically significant difference between all groups except the CAD/CAM-30 and the CAD/CAM-60 group, and between the CAD/CAM-60 group and heat-press group. The AMD showed a statistically significant difference between the heat-press and all the remaining groups. No statistically significant difference was found between the CAD/CAM groups. "Conclusions: " Within the limitations of this study, both the fabrication technique and spacer thickness affected the marginal and internal adaptation of all-ceramic crown restorations. The heat press group gave the best results regarding both marginal and internal crown adaptation. Considering all factors of marginal and internal adaptation of all-ceramic crowns, 60μm spacer settings were recommended for the E4D system.
Thesis (M.S.)--Tufts University, 2013.
Submitted to the Dept. of Posthodontics.
Advisor: Hiroshi Hirayama.
Committee: Yong Jeong Kim, Roya Zandparsa, and Matthew Finkelman.
Keyword: Dentistry.read less