Two Years Retrospective Study of Metalceramic Crowns with Nickelchromium Alloy

Abstract

Crown and bridge stability in the human mouth is not easy to evaluate. The structure and quality of crown materials are directly connected with the hardness and composition of the surface. The aim of the study was to evaluate the long-term stability of 52 crowns (19 patients) made from ceramic material (Vita Omega, Vita) and nickelchromium ceramic bonding metal alloy (Wiron, Bego) in clinical practice. In accordance with the US Public Health Service System changes in occlusal anatomy, occlusal relief, marginal adaptation, material break age, changes of shape and color, were checked. Another objective of the study was to observe the two year clinical progress of attrition of crowns. Replica casts (Epoxy-die (Ivoclar) were prepared. A scanning electron microscope (JEOL ; JMS-5500 LV (JEOL) and standard model (Ivoclar - Williams) were used to evaluate the quality of restoration. No changes in the shape and color were found, postop sensitivity was present in 1.9 %, and caries presence has been detected in 1.9 %. After two years the labial or buccal coronal margin was recorded as being at the level ofthe adjacent gingiva for 34.6 % of the 52 crowns placed and above the gingival margin for 65.4% of the crowns. Marginal adaptation was rated as contiguous with the existing anatomic form in 71.2 %. Gingival health varied from 0 to 2 CPITN index.Abrasion in fissures was visible in the scanning electron microscope. The cusps were well formed. Two fractures of the ceramic layer were observed. A significant increase in the position of the gingival margins was found, and varied from 45.0 μm to 108.3 μm vestibular 89.1 (SE12.1) to 63 μm oral (SE 7.0)