ANATOMIC ASSESSMENT OF THE ANTERIOR MANDIBLE AND RELATIVE HEMORRHAGE RISK IN IMPLANT DENTISTRY. A CADAVERIC AND CT SCAN STUDY.

Abstract Objectives: To evaluate prevalence, size, location and content of foramina and bony canals located on the lingual aspect of the mandibular midline. Material and methods: The prevalence and the size of midline lingual foramina and canals visible above and/or below genial spines and their distances from the alveolar crest and the mandibular base were measured either in 60 dry mandibles from adult human cadavers or in 100 CT scans from patients scheduled for dental implant surgery in mandible. In addition, macro-anatomic dissections were performed on another 20 mandibles injected with red latex to investigate the vascular canal contents associated with these midline lingual foramina and canals. Results: All mandibles investigated exhibited at least one lingual foramen at the midline above the genial spines (100% incidence). On the whole, a total of 118 and 188 foramina have been detected at the mandibular midline respectively in 60 dry mandibles and in 100 CT scans. The mean distance of the superior foramina and canals was 10.8 ± 2.7 (SD) mm from the alveolar crest by cadaveric analysis and 11.1 ± 2.1 (SD) mm in the CT scan study. Such distances were found to be far reduced in Class V to VI mandibles displaying a severe osseous atrophy, confirming the deep correlation between the “Class” of resorption of the anterior mandible (according to Cawood & Howell’s classification of 1988) and the distance of the lingual foramina to the alveolar crest. The mean diameter of the superior foramina, measured at the entrance of the bony canal, averaged 0.9 ± 0.5 mm (SD). Macro-anatomic dissections showed clear sublingual vascular branches entering the midline mandible in 19 out of 20 mandibles studied (95%). Conclusions: Blood vessels in the floor of the mouth may be in close proximity to the lingual cortical plate of the mandibular midline in most cases. This implies that bleeding can occur when the mandibular cortical plate is perforated even minimally and especially in case of severe osseous atrophies. Consequently, the Author suggests a careful planning of dental implant positioning at mandibular midline, possibly opting for the use of an even number of implants, in order to reduce the risk of violation of sublingual vessels afferent to midline lingual foramina.