CT and Topographic Evaluation of Human Mandible for Implant Placement

Objectives: Despite importance and extensive use in surgical and implant practice, several anatomical features of mandible anterior region (AR), between mental foramen and symphysis, still require careful study. The objective was to evaluate the anatomy of AR using applied techniques in anatomical specimens and patients who underwent CT scans.
Methods: 300 AR CT scans of dentate group (GDen) and 300 of edentulous group (GEde) were evaluated through Xoran 3.1.62 software. The presence and/or size of the following structures were observed: mental loop, incisive canal, cortical bone thickness, sublingual foveas, mental fossa, lingual foramen. In 15 of dry scanned mandibles each group was injected acrylic resin (vinylite) through mental foramen. Posteriorly decalcification was performed by immersion in 10% hydrochloric acid for 7 days. From molding obtained was evaluated the presence, measures and limits of incisive canal, mental loop and main foramens of AR. On 5 half heads per group, 2cm thickness fragments were removed from AR for vessels and nerves detection, through conventional histology and scanning electron microscopy. Moreover, lingual foramina of 100 dry mandibles framed in GDen and another 100 in GEde were valued at Lupa (Carl Zeiss).
Results: Partial results demonstrated that dry mandibles may show structures not detected by CT scan. Mental loop was present in 65% of cases, measuring 2.5 mm on average. 40% of the cases demonstrate lingual foramen.Incisive canal was visualized in 70% of cases and sublingual fovea showed 1.5 mm depth on average. Scanning electron microscopy (SEM) of dry mandible sections showed the presence of compact bone enclosing incisive canal and the presence of foramens on the mental loop.
Conclusions: The evaluated anatomical regions, as well as preliminary results, reveal the importance of surgical and implant planning using CT when AR is addressed, in order to avoid complications such as vessels and nerves rupture.