[Analysis of the denture dynamics in R.P.D.'s. 2. Influence of retainers on the dynamics of free-end-saddle]

The ordinary denture movement during function is defined as the "Denture dynamics" in R.P.D.'s. by K. H. Körber (1975). The Author has already reported the evaluating method of the denture dynamics objectively by two ways: The displacement sensors of magnetoresistors detected the vertical and horizontal movements of denture saddle in free end situation. Tiny accerelometer also detected the accerelation during the movements. In this present study, the correlations among the retainers used, the extent of the denture dynamics in displacement and accerelation, the occluding force and the abutment tooth mobility induced by the denture support were correlatively evaluated in two patients with class I free end R.P.D.'s. with interchangeable retainers by above methods. All the data were collected simultaneously by the electronic measuring and recording apparatus. Following results were obtained: 1. The denture dynamics depended on the selection of retainers examined. The extent of the dynamics reduced from the denture with the wrought wire clasps, the denture with the cast clasps, then to the denture with cone crown telescopes in sequence. 2. The occluding force increased just as the changes in sequence of the denture dynamics. 3. The abutment tooth moved to the distal in each case. The highest value of the mobility was found in the denture with the cast clasps, then in the denture with the wrought wire clasps. The least value of the tooth mobility was found in the denture with the cone crown telescopes. These results will strongly support the concept of the free end saddle R.P.D.'s anchored and supported rigidly by the abutments and the residual ridges in clinics.