Lingual and buccal mandibular bone depressions: a review based on 583 cases from a world-wide literature survey, including 69 new cases from Japan.

Objective: To review present knowledge of so-called lingual and buccal mandibular bone depressions (n = 583) based on studies of 247 contemporary and 267 archaeological cases from a world-wide literature survey in addition to 69 new cases from Japan.

Methods: The 69 cases from Japan were retrieved through examination of 42,600 consecutive panoramic radiographs.

Results: Bone depressions can be divided into four topographical variants: (1) lingual anterior mandibular body (incisor-canine- premolar area) above the mylohyoid muscle; (2) posterior to the mandibular angle-first permanent molar area, below the mandibular canal, and a third located to the ascending, lingual mandibular ramus, posterior to the lingual foramen, just below the neck of the condyle. An excessively rare fourth variant is located to the buccal aspects of the ascending mandibular ramus.

Conclusions: The present concept favours that all variants have a common origin: a hyperplastic/hypertrophic lobe (or aberrant lobe) of the sublingual, submandibular or parotid salivary gland, exerting pressure upon the cortex of the mandible by the respective gland, leading to focal atrophy or resorption of the bone. The bone depressions take years to develop, appearing radiographically not until the 5th to 6th decades.