Figure 1. In situ detection of apoptosis. (A,B) Formaldehyde-fixed, paraffin-embedded healthy periodontal tissues of 4 molar teeth from 2 monkeys were analyzed by means of a TUNEL detection kit (Boehringer Mannheim). TUNEL-positive cells are arrowed. (C) The apoptotic cell percentage was obtained as the ratio of TUNEL-positive cells relative to the total number of counted fibroblasts. (D) The apoptotic cell density was expressed as TUNEL-positive cells per mm². Mean ± SD (n = 12). **p < 0.01, t test, difference between PDLF and GF. Ce, cementum; PDL, periodontal ligament; AvB, alveolar bone; DG, deep gingiva.