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

Purpose: The purpose of this study was to investigate the vibration charact eristics of three different designs of mandibular major connectors in vitro by observing modal animation, decay rate, and maximum amplitude. Materials and Methods: Three removable partial denture frameworks-lingual bar, Kenne dy bar, and lingual plate-were studied. They were excited by a shaker, and the frequency response functions were recorded on a Fast Fourier Transforma tional analyzer to identify their modal shapes. Natural frequency and anima tion of motion at each natural mode of vibration of the three frameworks we re observed. In addition, transient response simulations were recorded, and decay rates and maximum amplitude of the resultant transient response wave s were computed. Results: The mean decay rate calculated from all the measu rement 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 am ong all pairs (P < .001). Maximum amplitude of the direct and indirect reta iners at the nonimpacted side also differed (P = .008). Conclusion: All thr ee designs demonstrated no elastic deformation at each natural mode of vibr ation. In terms of vibration analysis, the lingual bar demonstrated the max imum decay rate and the minimum maximum amplitude of the direct and indirec t retainers, both on impacted and nonimpacted sides, indicating that the li ngual bar will dissipate the energy through vibration faster than the other designs. Hence, the possibility of creating harmful effects to the oral ti ssue is lesser.