Anatomic considerations for immediate implant placement in the mandibular molar region: a cross-sectional study using cone-beam computed tomography

Background: There is concern regarding immediate implantation in the molar region because of discrepancy between socket size and inserted implant diameter. The purpose of this study was to assess the local anatomy of the posterior mandibular region in relation to immediate implant placement using cone-beam computed tomography (CBCT).Materials and methods: Using CBCT imaging data, 204 mandibular first molars and 201 mandibular second molars were assessed for the interradicular and alveolar bone dimensions, tooth sizes and proximity to vital structures. The cross-sectional mandibular shape and root configuration of these molars were determined.Results: Distances to the inferior alveolar canal (IAC) from the root apices of the first molar were significantly greater than the second molar. Up to 14.5% of second molars had less than 10 mm of vertical bone height between the IAC and furcation bone crest. Interradicular bone width of < 3 mm was found in 57% of second molars. All first molars in this study had two to three roots while 16% of second molars presented with a single root. The prevalent mandible shape at the first and second molars was the parallel and undercut ridges, respectively.Conclusions: The mandibular second molars from samples of a Southeast Asian population presented with greater anatomical difficulties for immediate implant placement which include absent or inadequate interradicular bone thickness, higher incidence of unfavourable mandible shape and increased proximity to vital structures