Aims To assess the success rates of secondary root canal treatment (2oRCT) and identify factors influencing outcome.
Methodology Longitudinal clinical studies investigating outcome of 2oRCT were identified by electronic (medline) and hand searches. Inclusion criteria were data on: number of samples, those successful and definition of success. Two reviewers independently assessed the studies and extracted the data onto a proforma. The pooled weighted success rates by each potential prognostic factor were estimated using the binomial random effect model (MLwiN version 2.02) whilst their pooled effects (expressed as odds ratio) on success rates were estimated using fixed and random effects meta-analysis with DerSimonean and Laird's methods (Stata version 9.2). Meta-regression models were used to explore potential sources of statistical heterogeneity. Study characteristics considered in the meta-regression analyses were: decade of publication, study-specific criteria for success (radiographic, combined radiographic & clinical), unit of outcome measure (tooth and root), duration after treatment when assessing success (at least 4 years or shorter), geographic location of the study (North American, Scandinavian and other countries), and qualification of the operator (undergraduate students, postgraduate students, general dental practitioners, specialist or mixed group).
Results Of the 41 studies identified, 18 studies published between 1921 and 2005 were included. The majority of studies were retrospective (n = 13) and only five prospective. The pooled weighted success rate of 2oRCT judged by complete healing was 77.6% (95% CI 73.2%, 81.4%) and by incomplete healing, 77.4% (95% CI 64.1%, 86.7%). The success rates were similar by ‘year of publication’ and ‘country of study’. Eighteen clinical factors were investigated in various combinations in previous studies. The most frequently investigated were ‘periapical status’ (n = 13), ‘size of lesion’ (n = 7), ‘culture results prior to RF’ (n = 5), and ‘apical extent of root filling (RF)’ (n = 4). The effect of different aspects of previous treatment and re-treatment technique has been poorly tested.
Conclusions The pooled weighted estimated success rate of 2oRCT was 77%, which was significantly (P ≤ 0.001) influenced by the presence and size of pre-operative periapical lesion. The effects of existing canal content, procedural error and re-treatment technique were poorly investigated.