[Study on the finishing line of the metal framework in terms of modal analysis]

The finishing line on a metal framework strengthens the mechanized coupling between the metal and the resin. However, due to extreme variations in metal thickness on the finishing line section, stress tends to concentrate in certain areas during function, making the finishing line an area with frequent denture breakage in a clinical setting. The author used modal analysis to clarify the manner in which stress concentrates on the finishing line. The activity observed was them used to determine the influence on the activity of the finishing line from factors such as differences in the finishing line angle, differences in the major connector and differences in the skeleton configuration. The following results were obtained. 1. Regarding the resonance frequency of the test materials, modes 6-7 were detected. 2. Displacement in the periphery of the finishing line and for the major connector in each mode was extremely small compared to the amount of downward pressure on the mucose and the labio-lingual displacement of natural teeth. 3. The activity of the test materials between 200Hz and 300Hz was the rigid body mode for the entire test material using as a fulcrum the rest on the side where vibration was applied. There was resonance detected in the test materials between 1 kHz and 6 kHz. 4. It is believed that there is less concentration of stress on a palatal bar when the angle of the finishing line is an obtuse angle. 5. It was difficult to determine any effect on activity due to the difference in the angle of the finishing line on a palatal bar, lingual bar and lingual plate. 6. The skeleton configuration was more bended the lattice type than the ladder type.