BACKGROUND Mechanoreceptors situated in the periodontal ligament provide detailed information about intensive and spatial aspects of tooth loads, which support the neural control of masticatory forces. We asked whether a reduced periodontal ligament due to periodontitis, and, thus, an altered mechanoreceptive innervation of the teeth, would affect masticatory behavior when subjects used incisors to hold and split food. METHODS We tested 11 subjects with reduced periodontal tissue support that rendered 30% to 70% alveolar bone loss for at least one pair of opposing anterior incisors. Forces were recorded when subjects used their affected incisors to hold half of a peanut for approximately 4 seconds and then split it. Age- and gender-matched healthy subjects served as the control group. None of the participants showed acute oral symptoms or massive periodontal inflammation. RESULTS The test group used greater force when holding food between the teeth (1.1+/-0.4 N [ mean+/-1 SD]) compared to the control group (0.4+/-0.2 N). Hold forces used by subjects in the test group were also more variable, both within and between trials. The increase in bite force applied to split the peanut was slower and more hesitant for subjects in the test group compared to the control group. CONCLUSIONS Reduced periodontal tissue support accompanies impaired regulation of masticatory forces. Faulty mechanoreceptive innervation of the periodontal ligament explains the elevated hold force, whereas a change in biting strategy due to the weakened support of the teeth may account for the more defensive food-splitting behavior.