Morphology and Dimensions of the Mandibular Jaw Bone in the Interforaminal Region in Patients Requiring Implants in the Distal Areas

This study aimed to analyse variations in the mandibular interforaminal morphology in an attempt to identify potential risks or contraindications for surgery, especially implant installation, in this particular region. A total of 210 spiral computer tomography (CT) examinations of patients requiring endosseous implant installation in the lower jaw were re-evaluated to explore anatomical variations in bone morphology (shape and contour), and to measure parameters concerning height, width and inclination of the bone in the symphyseal atrea. All measurements were performed on the cross-sectional reformatted images mesial to the mental foramina. A lingual concavity (with a depth of 6 +/- 2.6 mm) was observed in 2.4% of the jaws, with a remaining bone height in that area ranging from 4.2 to 11.9 mm. A clearly lingual tilted/inclined morphology was seen in 28.1% of jaws with a mean angle of 67.6 +/- 6.5 degrees, but a relatively constant width (> 8.8 mm). The remaining jaws (69.5%) showed a slight broadening in the caudal direction. The morphologic parameters were influenced neither by age nor by gender. In conclusion, mandibles with a lingual concavity or a severe slope of the lingual cortex might confer increased risks of lingual perforations during trepanation surgery or graft harvesting as well as fenestrations during implant installation. The detection frequency of such variations within the lower jaw seems to advocate a profound dissection of the lingual site and, in the case of some special treatment strategies, additional cross-sectional radiography.