A systematic review of all-ceramic crowns: clinical fracture rates in relation to restored tooth type.

Purpose: The objective of this systematic review was to evaluate the clinical fracture incidence of tooth-supported all-ceramic crowns according to restored tooth type.

Materials And Methods: An electronic search of clinical trials published in English and Chinese was performed using four databases (Medline/PubMed, EMBASE, Cochrane Library, and the Chinese Biomedical Literature Database) from 1990 to 2011 and complemented by an additional manual search. The annual core and veneer fracture rates of various tooth types were estimated and compared using Poisson regression. Moreover, the 5-year cumulative incidence was calculated.

Results: Of 5,600 titles and abstracts retrieved, 37 publications were included, with a follow-up period that ranged from 36 to 97 months. Based on the calculated results, all-ceramic crowns demonstrated an acceptable overall 5-year fracture rate of 4.4% irrespective of the materials used. Molar crowns (8.1%) showed a significantly higher 5-year fracture rate than premolar crowns (3.0%), and the difference between anterior (3.0%) and posterior crowns (5.4%) also achieved significance. Fractures were classified as either core or veneer fractures. Core fracture rates were calculated as having a 5-year incidence of 2.5%, and a significantly higher core fracture rate was found in the posterior region (3.9%). The overall 5-year incidence of veneer fracture was 3.0%, and no clear difference was found between restored tooth types, with incidences of 2.0%, 2.5%, 1.0%, and 3.0% for incisor, canine, premolar, and molar crowns, respectively.

Conclusions: Within the limitations of this study, current dental ceramic materials demonstrated acceptable 5-year core and veneer fracture incidences when used for tooth-supported single crowns in both anterior and posterior segments. A higher fracture tendency for posterior crowns was the trend for all-ceramic crowns, while molar crowns showed a significantly higher fracture rate than premolar crowns. Moreover, it is recommended that randomized controlled trials with large sample sizes be undertaken to obtain more definitive results.