Better success rate for root canal therapy when treatment includes obturation short of the apex

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Initial screening identified studies on humans with radiographic information on the terminal point of obturation. Subsequently studies with (a) a minimum follow-up of at least 2 years; (b) data on termination of obturation/instrumentation; (c) failures of treatment defined adequately (with a minimum radiographic evaluation for failure outlined and defined); (d) data available on success/failure of root canal therapy in relationship to the obturation/instrumentation length; and (e) presence or absence of rarefaction included.

This meta-analysis considered three categories of obturation length from the radiographic apex: (a) 0-1 mm (group A), (b) >1 mm but <3 mm (group B), (c) obturated past the radiographic apex, including sealer (group C). The studies were independently assessed for quality with readers blinded to the names of the authors and their institutions, names of the journals, sources of funding, and acknowledgements. Statistical analyses were done using the DerSimonian and Laird estimates.

Four studies met the inclusion criteria. In terms of percentage rates of success, the meta-analysis showed that obturation 0-1 mm short of the apex (group A) was better than obturation 1-3 mm short of the apex (group B); both were superior to obturation beyond the apex (group C). The success rate in group A was 28.9% better than group C and 5.9% better than group B (95% CI=-3.8%, 61.5%), P=0.08 and (95% CI=-1.3%, 13.1%), P=0.11, respectively. After adjustment for quality, the results remained unchanged.

The results demonstrate that obturating materials extruding beyond the radiographic apex correlated with a poorer prognosis. In addition, we realised that standardised protocols are necessary in endodontic procedures and in dental research. If studies are to be compared and the information used clinically, the design of the studies must be similar and repeatable. The results of prospective studies will then be comparable and the data can be combined statistically, thereby creating a more powerful, clinically useful meta-analysis.