Prevalence of C-shaped canal morphology using cone beam computed tomography - a systematic review with meta-analysis

Background and aim: To perform a systematic review of anatomical studies using cone beam computed tomography (CBCT) to assess the influence of demographic factors (age, gender and geographic region) on the prevalence of C-shaped canal anatomy in maxillary molars, mandibular premolars and molars.

Data sources: A search was conducted between May and August 2018 in four electronic databases and five peer-reviewed journals. The authors of included articles were also contacted for additional studies and the bibliographic references hand-searched.

Study eligibility criteria, participants and interventions: The research protocol was previously registered in the International Prospective Register of Ongoing Systematic Reviews (CRD42018095201) and included defined inclusion/exclusion criteria. Prevalence studies on C-shaped canal anatomy in maxillary molars, mandibular premolars and molars were searched.

Study appraisal and synthesis methods: The selected studies were submitted to full-text analysis and critical appraisal by two evaluators using the Joanna Briggs Institute Critical Appraisal tool. The final group of papers (n = 25) were pooled and forest plots with proportions and odds ratio with a 95% confidence interval performed. Meta-regression was undertaken to evaluate possible sources of heterogeneity and funnel plot visual analysis to assess publication bias.

Results: The included studies reported data on 25 445 teeth of 13 142 patients. A significant difference in the average prevalence proportion of C-shaped configuration was observed between mandibular first (0.3%; 0.1-0.6%) and second (12%; 10.3-13.7%) molars (P < 0.05). No significant difference in the prevalence of C-shaped configurations was observed comparing males (13.5%; 8.8-18.3%) and females (20.5%; 13.7-27.4%) in mandibular second molars (P > 0.05), although males were associated with significantly lower odds (0.573; 0.511-0.641) (P < 0.05). The pooled proportion of C-shaped anatomy in mandibular second molars in East Asian countries (39.6%; 36.0-43.1%) was significantly higher compared with other regions.

Limitations: Because of the limited number of studies, no statistical analysis was performed for maxillary molars and mandibular premolars.

Conclusion: Meta-analysis revealed that gender and geographic region may act as a confounding factor for the prevalence of C-shaped anatomy in mandibular second molars, whilst age did not influence the prevalence of C-shaped configurations in this tooth group. Knowing these preoperative factors would help to anticipate complex morphologies in clinics.