[Elucidation of cross arch stabilization for the lower unilateral free end denture in terms of vibratory science]

Cases of lower unilateral free end defect are the source of many problems in clinical dentistry. The denture design method most commonly used is cross arch stabilization which involves creating a retainer on the side opposite the defect via a bar in order to stabilize the denture and protect the retaining teeth. Almost all research on this method involves experiments using a static load. Moreover, there are few studies that attempt to clarify the relationship between the major connector and the retaining teeth. As a means of clarifying these problems, the authors used the modal analysis method and a vibrometer, both of which have proven effective in general observation of lowr denture dynamics when dynamic force is applied. This allowed them to see the relationship between the metal framework configuration and the retainer in animation and thereby study displacement quantity and damping quantity. The following interesting were obtained. 1. There were four modes detected for fixed vibration on the individual metal frameworks: 500Hz band, 1kHz band 2kHz band and 4kHz band. 2. The dynamics of the individual metal frameworks were as follows: Mode 1 was a rigid body mode in a vertical direction with a fulcrum of angle 54. Mode 2 was a horizontal rigid body mode with a fulcrum of angle 54. Mode 3 was a mixture of a horizontal rigid bode and horizontal bend mode. There was a rolling type mode observed only from the plate type. Mode 4 consisted mainly of a horizontal bend mode. This showed that there were differences among the various modes. 3. Judging from the displacement rate computed at the 500Hz band, the rate of displacement decreases as the thickness and ratio decrease. 4. Judging from linear damping quantity and damping quantity in terms of frequency, the finishing line showed a greater tendency toward resonance. 5. Analysis in terms of vibratory science using modal analysis and octave band analysis hinted at the significance of cross arch stabilization.