Obturator prostheses have been extensively used in the functional rehabilitation of maxillectomy patients. The purpose of this study was to evaluate in vitro the vibration movements of three types of obturator prostheses. Three types of bulbs were used: the solid type, the buccal flange type, and the hollow type. Modal analysis was performed to identify the better form. The three types of obturator prostheses were excited by a shaker, and the frequency response functions were recorded on an FFT analyzer to identify their modal shapes. In addition, transient response simulations were carried out, and decay rates of the resultant transient response waves were compared to evaluate the energy absorption after the obturator prosthesis had experienced an impact. The results showed that the modal shapes were closely similar, while the amplitudes at the rests and clasps of the hollow type bulb were the smallest. In the transient response simulation, the decay rates of the hollow type were significantly the highest (p < 0.01). In this study, modal analysis demonstrated that the hollow type obturator prosthesis showed the steepest vibration decay slope, indicating that it might be the best among the three types of bulbs for use in clinical treatments.