Two Years Retrospective Clinical Study on Metal-Ceramic Prosthodonticswith Chromium-Cobalt-Nickel Alloy

Overview

The aim of the study was to evaluate the quality of metal-ceramic reconstructionfabricated from common metal alloy and ceramic material. In our Republic, this type oftreatment is commonly used in everyday clinical practice.We have evaluated 52 crowns placed in 19 patients (14 women, 5 men). The crowns were fabricated from ceramic material Vita andchromium-cobalt-nickel alloy. During clinical examination we have concentrated on the followingitems: Crown margin placement – parallel with marginal gingiva (34.6%), or placed abovemarginal gingiva (65.4%). As for the crown margin placement, no difference between thevestibular (34.6% and 65.4% respectively) and oral (32.7% and 59.6% respectively) side ofa tooth has been observed. Such crown margin placement is almost totally without risk ofsecondary caries development (1.9%). After two years of use the crowns remained mainly intact(96.2%), only in two cases (3.8%) we have found a crack, but without the metal alloy exposition.Neither the anatomical shape nor colour of the crowns has changed.We have detected optimummarginal adaptation in 71.2%, probing revealed impaired marginal integrity in 26.9% of cases,in one case (1.9%) we have discovered a gap between a crown margin and a tooth neck. In thescanning electron microscope the crown cusps were formed properly. The ridges were slightlysmoothed out. Vestibular side of the ceramic crown was as smooth as the tooth’s own surface.It is obvious that after two years of use an abrasion combined with a physiological change ofgingival margin have led to the gap formation and an impaired marginal adaptation of thecrown. The gap width ranges from 45.0 µm to 108.3 µm. On the vestibular side of the crown wehave discovered more serious impairment when compared to the oral side – 89.1 µm (SE 12.1)and 63 µm (SE 7.0) respectively. The difference is statistically significant.

Key words:
dentistry – prosthetics – crown – metal-ceramics – chromium-cobalt-nickel alloy.