Factors influencing the patterns of invasion of the mandible by oral squamous cell carcinoma.

The pattern of tumour invasion of the mandible depends on the extent of invasion. Both the width (P = 0.02) and depth (P = 0.01) in patients with an invasive or infiltrative pattern of disease were greater than in tumours showing the less aggressive erosive pattern in which the tumour mass is separated from the resorbing bone by a connective-tissue layer. Evidence in this study suggests that the erosive pattern develops through a mixed pattern to the invasive pattern of disease as the tumour progresses through the bone. The invasive pattern of disease was evident at a much shallower depth in the molar region of the mandible (mean 9 mm), with a decreased ratio of alveolar to basal bone, than in the premolar and parasymphyseal region (mean 25 mm) (P = 0.02). The hypothesis to explain this phenomenon is that the more superficial alveolar bone responds by resorbing in advance of the tumour, but the basal bone is unable to respond in the same way and becomes widely infiltrated. The attached mucosa with its firm collagen attachment to bone is proposed as the main route of tumour entry into the mandible in both dentate and edentulous mandibles.