[Analysis of movement in partial prostheses and abutment teeth with differences in retainer].

When designing a prosthesis in a clinical setting that takes into consideration the protection of the abutment teeth and alveolar ridge, it remains difficult to carry out a method of connecting the abutment tooth and prosthesis based on objective grounds. This is because there are still many matters that remain unclear about dynamics of the stomatognathic system, including the prosthesis, when attached in the oral cavity. The author created the following three prostheses on a stimulation model of a tooth bone saddle that included an artificial mucous membrane and periodontal membrane: (1) A fixed bridge, (2) A telescopic denture (Konuskronen Telescope), (3) An Akers clasp denture. Following this, flat-controlled random noise was applied to each denture to create a dynamic load that exhibits a state closer to a clinical situation. Modal analysis was carried out with a laser doppler vibrometer and observations were made of the prosthesis and the abutment tooth apex to obtain visual clarification of dynamics, The following results were obtained. 1. As far modal resonant frequency, in mode #1, the bridge measured at 483 Hz and 561 Hz, the Telescope at 452 Hz and 600 Hz and the clasp at 581 Hz and 596 Hz. In mode #2 the bridge measured at 1,355 Hz and 1,370 Hz, the Telescope at 1,343 and 1,040 Hz and the clasp at 1,114 Hz and 1,079 Hz. In mode #3, only the bridge was detected and the recorded values 1,906 Hz and 2,026 Hz. 2. The influence on the modal resonant frequency due to the difference in abutment devices was limited. 3. Observation of animation indicated that the tendency for lateral movement of the abutment teeth increased going from the bridge to the Telescope to the clasp. 4. Displacement of the abutment tooth root apex decreased in reverse proportion to the strength of the connection between the abutment tooth and the abutment device.