is not necessarily related to the shape of the ridge. For example, in one individual a wide, bulky ridge may have very sparse, thin bone trabeculae; in another person the same shape ridge may have numerous dense ones. When the ridge is very bulky and heavily trabeculated, a dense shadow may appear on a radiograph. If the inferior margin of such a thickly trabeculated ridge abruptly ends, normal bone below the dense shadow can appear pathological in contrast — a diagnostic dilemma.

Fragility of the mylohyoid ridge should inspire extra caution in drilling an implant site. Too much pressure accidentally can drive the bur below the lower border of the ridge and into the submandibular fossa. It is also easier to fracture a more fragile ridge, either while inserting the implant or later through occlusal trauma. A bladevent also should not be seated close to the lingual border (crest) of a fragile ridge. Tension from muscle pull can fracture the thin wall of bone between the implant and the crest.

The position of the mylohyoid ridge on the body of the mandible also affects implant potential, in some cases because of its relationship to the residual alveolar ridge. For example, the mylohyoid ridge (13) may be almost level with the alveolar crest (14). In such a situation, after tooth loss tension from the mylohyoid muscle helps retard alveolar ridge resorption. The further the mylohyoid ridge from the alveolar crest, the less effective such stimulation for bone osteogenesis.

   In a few cases, the mylohyoid ridge is located so low that it closely approaches the inferior margin of the mandibular body. This situation is more characteristic of the anterior portion of the mylohyoid ridge than the posterior. Furthermore, the mylohyoid ridge tends to become reduced and lower, less promising for implantation, where the mandibular canal moves labially and discharges the bulk of its contents through the mental foramen, leaving the alveolar ridge proper more favorable for implantation.
   Typically in the molar region, the mylohyoid ridge and its crest (15) are level with the lower portion of the molar roots. As the alveolar ridge resorbs, the relationship between the alveolar crest and the mylohyoid ridge alters. Eventually the cancellous alveolar bone may resorb so extensively that the alveolar crest (16) lies below the mylohyoid ridge (17) and the external oblique ridge (18). At this stage, a conventional denture is difficult to fit because of the ridge's shape and the shallow buccal (19) and sublingual (20) vestibules. A poorly fitting denture irritates the soft vestibular tissues and mucoperiosteum, and often causes

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