3-Dimensional Analysis and Systematic Review of Root Canal Morphology and Physiological Foramen Geometry of 109 Mandibular First Premolars by Micro-computed Tomography in a Mixed Swiss-German Population

Introduction: The aim of this study was to systematically revise the root canal configuration (RCC) literature and to investigate the root canal morphology of mandibular first premolars (Ma1Ps) of 2 populations by means of micro-computed tomographic imaging. Methods: This systematic review followed the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines including RCC randomized controlled trials and crosssectional, cohort, comparative, validation, and evaluation studies. Furthermore, the RCC, physiological foramina, the frequency of accessory and connecting canals, and the physiological foramina morphology of 109 Ma1Ps were investigated by means of micro-computed tomographic imaging. The RCC results are described using a 4-digit system code. Results: The most frequent RCCs observed were 1-1-1/1 (70.6%), 1-1-2/2 (7.3%), 1-2-2/2 (7.3%), and 1-2-1/1 (5.5%). Accessory canals were observed in 31.2%. Connecting canals were observed in 1-1-2/2 (4.6%), 1-2-2/2 (4.6%), 1-1-2/1 (1.8%), and 1-2-1/1 (1.8%) RCCs. Accessory foramina were observed in 52.3%; 30.3% of the Ma1Ps had 1 accessory foramen, 12.8% had 2, 2.8% had 3, 2.8% had 4, 2.8% had 5, and 0.92% had 6. The narrow and wide diameter mean of 136 physiological foramina was 0.28 mm (60.9) and 0.37 mm (60.11) when only 1 physiological foramen was present. Conclusions: This study provides detailed root canal morphology of Ma1Ps in a Swiss-German population. Within the limitations of the study, the authors recommend a final physiological foramen preparation size of instrument tip sizes 30-40; yet, such a decision should be carefully considered on an individual basis.