Abstract
Purpose:We evaluated occlusal contacts in the intercuspal position (ICP) of prostheses without stress absorbing elements on osseointegrated implants (the prostheses) and natural teeth.
Materials and methods: We selected 13 subjects who had shown excellent clinical progression for three years or more after placement of the prostheses on either an IMZ implant (5 subjects) or Brånemark implant (8 subjects) in mandibular unilateral free-end cases from whom informed consent had been obtained for the purpose of this research. The registration of occlusal contacts using silicone impression materials was made during clenching in ICP at two levels (10 and 30%MVC) under maximum EMG amplitude (100%MVC). To read the silicone occlusal records quantitatively, we used the addpicture inspection method which visualized occlusal contacts by digital image processing. We observed variations in the number and area of occlusal contacts between the two occlusal strengths. Statistical analysis was performed using the Wilcoxon test to compare between the two levels.
Results:The number and area of occlusal contacts increased with occlusal strength both on natural teeth and on the prostheses. However, the location of the contacts remained the same in both the healthy dentulous subjects and those with the prostheses. For each tooth, with the increase in occlusal strength, the number of occlusal contacts on natural teeth and the prostheses did not increase significantly, and thus the area of occlusal contacts on natural teeth and the prostheses increased significantly (p＜0.05). There was no significant difference between natural teeth and the prostheses in the rate of increase of the area of occlusal contacts with the increase in occlusal strength.
Discussion: The prostheses and the remaining teeth in ICP cooperated with each other, though there were no stress absorbing elements. These results were probably due to displacement of opposing teeth and strain on their supporting tissue.
Conclusion: A harmonious intercuspal position with natural teeth can be established by imparting appropriate occlusal contacts to the prostheses, even if there are no stress absorbing elements.
