Tooth survival after root canal treatment

Medline, the Cochrane Library, hand searches of the International Endodontic Journal, Journal of Endodontics, Oral Surgery Oral Medicine Oral Pathology Oral Radiology and Endodontics, Dental Traumatology (& Endodontics) and bibliographies of all relevant articles and review articles. Unpublished studies were identified by searching abstracts and conference proceedings. Personal contacts were used to identify ongoing or unpublished studies. Two reviewers independently assessed and selected the studies with disagreements being resolved by discussion.

Clinical studies of RCTx on more than 30 teeth and of at least six-month duration, where the success was based on survival of tooth and the proportion of teeth surviving was given, or could be calculated from the raw data, were included.

Data were extracted by two reviewers independently using custom-designed forms. The weighted pooled proportion of teeth surviving after treatment and the combined effects (expressed as odds ratio) of clinical factors on tooth survival were estimated using fixed and random effects meta-analyses using DerSimonean and Laird's methods. The survival data were pooled into three groups based on the duration after treatment: 2 or 3 years; 4 or 5 years; and 8, 9 or 10 years. Statistical heterogeneity amongst the studies was assessed by Cochran's (Q) test.

Of the 31 articles identified, 14 studies were included. The majority (10) were retrospective. The reported survival is shown in Table 1. Substantial differences in study characteristics were found to hinder effective direct comparison of findings. Evidence for the effect of prognostic factors on tooth survival was weak. Based on the data available for meta-analysis, four conditions were found to significantly improve tooth survival. In descending order of influence, the conditions increasing observed proportion of survival were as follows: (i) a crown restoration after RCTx; (ii) tooth having both mesial and distal proximal contacts; (iii) tooth not functioning as an abutment for removable or fixed prosthesis; and (iv) tooth type or specifically non-molar teeth. Statistical heterogeneity was substantial in some cases, but its source could not be investigated because of insufficient available information.

The pooled proportion of teeth surviving over 2-10 years following RCTx ranged between 86% and 93%. Four factors (listed above) were identified as significant prognostic factors with concurrence between all three strands of evidence.