[Periodontal study on the form of plunger ridge. (1) (author's transl)].

This stdy was observed on the correlation between the extensive angle, height of the plunger cusp and ridge in the maxillary molars of the periodontal patients. On experimental methods, one hundred and two periodontal patients from thirty five to forty five ages. and from which one hundred and forty-four plaster model blocks included upper first and second molar were selected for this stdy. The examination of differences on the extensive angle, cusp and ridge height were calculated between the distal buccal cusp of the fist molar and menial buccal cusp of the the second molar. The results were obtained as follow:(1) The mean angle of the extensive angle was 61.6±15.9°, and there was a tendency of almost in 40.1° to 80°(2) The mean difference of cusp height was in 1.195±0.786mm, and also the ridge height was in 1.0±0.670mm.(3) No significant correlations were found between the extensive angle and height of cusp or ridge.(4) If the extensive angle was confined in 40.1°-80°, the smaller the extensive angle, the alveolar bone a resorption in relation to it on the X-ray photograph.