SUMMARYThe periodontal membrane is markedly involved in about 30% of patients with systemic sclerosis and some widening occurs in about 20% of the teeth at risk. Thickening of the periodontal membrane is not specific to systemic sclerosis and can occur with clinically obvious chronic periodontal disease and, to a mild extent, in normal individuals in whom it mainly involves the coronal third of the teeth. In systemic sclerosis the whole root is more likely to be involved. There is no direct relationship in systemic sclerosis between widening of the periodontal membrane and other systemic changes, and prognosis.