Non-Invasive Digital Technique for Examination of Marginal and Internal Adaptation of Different Ceramic Table-Tops

Abstract

Background: Lacking of proper marginal adaptation and improper cement seal of occlusal table-tops resulted in plaque accumulation, and marginal discoloration with subsequent caries progression, while increasing the internal gaps, lead to reduction of fracture strength of these restorations due to unequal load transmission and stress concentration. Aim of the study:This study aimed to evaluate the effect of the use of various restorative CAD/ CAM materials on the marginal and internal adaptation of table-tops using a non-invasive digital method for evaluation of cement thickness space differences compared to the design cement setting. Materials and methods:Sixty-eight human mandibular first molars were prepared to receive 1mm thickness table-top restorations. The restorations were divided into four groups according to the constructed CAD/CAM restorative materials (n=17): Group (ED) Lithium disilicate; group (CD) Zirconia reinforced lithium silicate; group (PZ) High translucent zirconia; and group (LU): Resin nano-ceramic. The prepared teeth were scanned with bench scanner and the STL files were saved to design the table-top restorations with cement gap setting of 30µm at margin and 50µm internally, the restorations were milled and prepared following the manufacturer's instruction for each material. A layer of light body silicone replica placed on the intaglio surface of each table-top and adapted over corresponding prepared tooth, after material setting; rescanning the prepared teeth with the replica. Geomagic software was used for superimposition of the two STL files (with and without replica; double scan technique), the thickness of the replica were calculated and compared to the previous cement gap setting.Results: Marginal and internal gaps were statistically significant different from the cement setting in group ED, CD and PZ (p ≤ 0.05) when compared with the LU that showed the least mean marginal and internal gap values (43.64, 72.95) and the closest to the cement gap setting.