Comparative in-vitro study of marginal gap of four cad/cam all ceramic systems with thermal aging

Abstract

Aim: Marginal fit evaluation of diverse all ceramic systems before and after thermal agingObjectives: To assess the impact of thermocycling on marginal adaptations of CAD/CAM ceramic crowns manufactured from distinctive prefabricated blocks. Background: Good marginal adaptation guarantees gingival health and comes about in less cement disintegration and few occasions of caries and discoloration improper marginal fit lead to plaque maintenance, microleakage and cement breakdown. Marginal accuracy can be measured via inspection, exploratory probing and radiographic examination. Glass ceramics are used to replace missing or damaged tooth structure because of their high translucency, superior biocompatibility and low thermal conductivity. However, they are brittle materials which display a high compressive and low tensile strength. Zirconia is a strong substitute veneering for glass ceramics, but it has more opacity. That opacity decreased recently by addition of more translucent feldspathic porcelain to achieve the desired esthetics.Methods: Four groups of 20 crowns each (Celtra DUO, e-max CAD, bilayered zirconia and monolithic zirconia) were cemented on identical all ceramic artificial teeth. Marginal gaps measured before and after thermal aging as half of specimens were thermocycled 500 times between the maximum and minimum temperatures that the mouth is subjected to (5±1°C and 55±1°C) respectively. Statistical analysis was performed using Graph-Pad In-Stat statistics software for Windows.Results: Marginal gaps of all tested materials within clinical range (<120 μm). The highest marginal gap mean value and standard deviation (SD) before and after thermal aging recorded with bilayered zirconia (39.73 ± 9.43) and (50.23 ± 14.6) respectively. E-max CAD showed the lowest values before thermal aging (19.65 ± 10.2) while Celtra DUO showed the lowest values after thermal aging (32.21 ± 7.88) with significance between all groups except Celtra DUO before and after thermal aging. Irrespective of material type, totally it was found that thermally aged groups recorded higher marginal gap mean value (41.56 μm) than non-aged ones mean value (28.94 μm) with statistical significance.Conclusion: Bilayered zirconia recorded the highest marginal gap in aged and non-aged subgroups among all tested all ceramic systems with statistical significance. E-max CAD and Celtra DUO recorded the lowest marginal gaps. Thermal aging increased marginal gap mean values as a total result of all ceramic systems.