臼歯部遊離端欠損インプラント補綴症例の歯列上咬合力

抄録

Purpose: Unlike natural teeth, which are surrounded by a periodontal membrane, osseointegrated implants bond directly with bone, resulting in a difference in their displaceability. Accordingly, in partially edentulous patients with implants, it is important to consider the biomechanical and functional aspects of the occlusion of any prostheses. This study investigated basic features of occlusions on prostheses supported by implants in partially edentulous patients.
Methods: Subjects consisted of 18 patients (57.6±12.8 years old) wearing 2～3 implants in unilateral maxillary or mandibular posterior free-end saddles for 3.4±2.6 years. Occlusal force was measured with pressure sensitive film (Dental Prescale^® 50H Type R) at several levels of voluntary clenching. The mandibular dental arch was divided into four regions 1) IR: region of prosthesis supported by implants; 2) FR: region of residual teeth anterior to implants on the implanted side; 3) OR: region of residual teeth corresponding with implants on the opposite side; and 4) OFR: region of residual teeth anterior to OR. The occlusal force on each region and its ratio to total occlusal force (%) were calculated. In addition, a regression line was drawn with total occlusal force on the horizontal axis and occlusal force ratio on the vertical axis. The significance of differences was tested between the gradient of the regression line and gradient 0, which indicated that the occlusal force ratio was constant irrespective of any increase in total occlusal force.
Results and Discussion: Total occlusal force at maximum clenching and the asymmetry index were equivalent with those of a healthy dentition. In one group of patients, the occlusal force ratio at IR was constant irrespective of the level of occlusal force, while in another group the ratio varied with the level of occlusal force.
In this second group, there was no initial occlusal contact at IR, and the occlusal force on IR during maximum clenching was significantly lower than that at OR. Furthermore, there were more subjects in this group whose occlusal force ratio at FR changed with the level of occlusal force than in the first group. Variation in the occlusal force ratio at FR showed a pattern to compensate for insufficient occlusal force at IR.