2002 年 1 巻 1 号 p. 82-87
Purpose : The goal of this study was to clarify the frequency and reasons for crown failure, based on the longevity and quality of full coverage crowns evaluated in 226 patients.
Materials and Methods : Of a total of 529 patients who received full coverage crowns between 1980 and 1987 at the student clinic, 226 (42.7%) responded to a request to attend a recall examination. The crowns were fabricated and delivered in a uniform way according to the students' clinical manual used in the Department of Fixed Prosthodontics, School of Dentistry, Iwate Medical University.
Results : The 226 participants (61 men and 165 women with a mean age of 41.6 years) attended a recall examination between 1996 and 1997. Periodontal pocket depth was 2.2±0.1 mm (mean±S.D.) at the initial examination and 2.2±0.8 mm (mean±S.D.) at the recall examination. The gingival index at the initial visit indicated that 90.3% of recall subjects had either slight gingival inflammation or none at all. A 10-16 year follow-up examination on the 388 crowns revealed that 38 crowns (9.8%) were lost or replaced due to periodontal disease, caries, and/or fracture. Of the failed crowns, 19 abutments were extracted, 11 crowns were removed and remade as an abutment of a fixed bridge, and 8 crowns were replaced by new crowns. The survival rates of the crowns at 5, 10 and 16 years after placement were 96.9, 93.3, and 84.9%, respectively.
Conclusion : Although the recall rate of this follow-up study was low, it is suggested that the periodontal status at the initial stage of treatment played an important role in achieving a high survival rate of the crown. Following an approved procedural manual together with a fabrication manual and careful checking by a senior instructor were also thought to contribute to the excellent survival rate of the crowns.
