Abstract
Statement of problem. Long-term clinical data on the survival of pressed lithium disilicate glass-ceramic when used with partial coverage restorations and the effect that different technical and clinical variables have on survival are sparse.
Purpose. The purpose of this clinical study was to determine the 10.9-year survival of pressed lithium disilicate glass-ceramic partial coverage restorations and associated clinical parameters on outcomes.
Material and Methods. Individuals requiring single unit defect-specific partial coverage restorations in any area of the mouth were recruited in a clinical private practice. Participants were offered the options of partial coverage cast gold or glass-ceramic (lithium disilicate) restorations. Only participants that chose glass-ceramic partial coverage restorations were included in the study. The overall survival of the glass-ceramic restorations was assessed by the clinical factors (participant's age, sex, dental arch, tooth position in dental arch, type of partial coverage restoration, and ceramic thickness) determined at recall. The effect of this clinical parameters was evaluated by using Kaplan-Meier survival curves accounting for attrition bias and other reasons for failure. The statistical significance of differences between parameters was determined by using the log rank test (alpha=.05).
Results. A total of 304 participants requiring 556 lithium disilicate restorations were evaluated. The mean age for the participant at the time of restoration placement was 62 with a range of 20 to 99 years, 120 were men and 184 were women. A total of 6 failures (bulk fracture or large chip) requiring replacement were recorded with the average time to failure of 2.4 (0.8-9.2) years. The total time at risk computed for these units was 1978.9 years providing an estimated failure risk of 0.3% per year. The 10-year estimated cumulative survival was 95.6%.
The estimated cumulative survival of inlays (n=246) and onlays (n=305) were 93.9% and 983%, at 9.9 and 9.8 years, respectively (P<.05). Of the 6, there were 3 failures recorded for the partial coverage inlay restorations. The total time at risk for these inlays was 786.79 years providing an estimated risk of 038% per year. The other 3 failures recorded occurred for the partial coverage on lay restorations. The total time at risk for the on lays was 1032.17 years providing an estimated risk of 0.29% per year. The failures occurred in the molar region only. There were no failures recorded for the anterior partial coverage inlays (n=5). The total time at risk computed for the anterior units was 21.55 years providing an estimated risk of 0% per year.
There was no statistically significant difference in the survival of partial coverage restorations among men and women, different age groups, or position in the dental arch. The thickness of the restoration had no influence on the survival of glass-ceramic partial coverage restorations.
Conclusions. Pressed lithium disilicate defect-specific partial coverage restorations reported high survival rate over the 10.9-year period with an overall failure rate of 0.3% per year and limited to the molar teeth. Risk of failure at any age was minimal for both men and women.