Rigidity of three different types of mandibular major connector through vibratory observations

The purpose of this study was to investigate the vibration characteristics of three different designs of mandibular major connectors in vitro by observing modal animation, decay rate, and maximum amplitude.

Three removable partial denture frameworks--lingual bar, Kennedy bar, and lingual plate--were studied. They were excited by a shaker, and the frequency response functions were recorded on a Fast Fourier Transformational analyzer to identify their modal shapes. Natural frequency and animation of motion at each natural mode of vibration of the three frameworks were observed. In addition, transient response simulations were recorded, and decay rates and maximum amplitude of the resultant transient response waves were computed.

The mean decay rate calculated from all the measurement points of the lingual bar, Kennedy bar, and lingual plate was 3.10 s-1 (standard deviation [SD] 0.07), 2.42 s-1 (SD 0.04), and 2.01 s-1 (SD 0.03), respectively. Significant differences in decay rate were found among all pairs (P < .001). Maximum amplitude of the direct and indirect retainers at the nonimpacted side also differed (P = .008).

All three designs demonstrated no elastic deformation at each natural mode of vibration. In terms of vibration analysis, the lingual bar demonstrated the maximum decay rate and the minimum maximum amplitude of the direct and indirect retainers, both on impacted and nonimpacted sides, indicating that the lingual bar will dissipate the energy through vibration faster than the other designs. Hence, the possibility of creating harmful effects to the oral tissue is lesser.