CHANGES IN RESIDUAL RIDGE OF THE MANDIBLE AFTER EXTRACTION AND WEARING EXTENSION SADDLE TYPE OF REMOVABLE PARTIAL DENTURES

A longitudinal, clinical and roentgenographic investigation

抄録

A longitudinal investigation was carried out in the qualitative and quantitative changes of the mandible, especially the edentulous ridge, wearing the extension saddle type of removable partial denture. The materials were the patients who had attended the Department of Prosthetics, School of Dentistry, Tokyo Medical and Dental University, in Tokyo. They were complete dentition in upper jaw, but the lower molars and premolars were missing. On 68 patients during a limited period of time, the initial examination was performed. Forty-one patients appeared for re-examination after one year follow-up. At the initial and follow-up examinations, the standardized roentgenograms of mandible, the bite ability checking and other clinical registration were precisely performed. On these roentgenograms, the changes in mandibular height in edentulous parts of the alveolar were measured. And on these same films, the density of residual ridge was measured by the multiplier photometer. All these data were computed in statistical methods. The results of these investigations were as follows: 1. The reduction of residual ridge of free end saddle denture wearer who was in short term after extraction, was about 0.90 mm (in mean) at the first and second molar region for one year follow-up. But in the case, long term after extraction without denture, (disuse atrophy) the reduction was most remarkable, about 1.30 mm (in mean) on the same region. In the case of re-making denture, the amount of reduction was more smaller, 0.60 mm in the first and second molar, than other cases. 2. On the amount of reduction in residual ridge, the cobalt-chromium cast denture wearer was smaller than resin denture wearer. 3. In the case, long term after extraction without denture wearing (disuse atrophy), the extent of reconstruction in alveolar ridge against the denture wearing loads was signicantly poor than the case of short term after extracion. 4. The degree of increasing about abutment teeth mobility was concerned with the intensity of tooth-bearing loads of the denture. 5. The factors influencing on the amount of reduction and structural reconstruction against denture wearing, were the loading condition on residual ridge and the length of term after extraction without denture wearing.