[Influence of intensity of occlusal contact in implant-retained single restoration on stress distributions of crown surface and supporting bone].
OBJECTIVE
This study investigated the influence of intensity of occlusal contact, or occlusal height of an implant-retained single restoration on the stress in the crown surface and supporting bone.


METHODS
A two-dimensional finite element model of the maxillary and mandibular first molars with supporting periodontal structures was created (Model M-M). One of the molars was replaced by a restoration retained by a thread-type implant to produce Model I-M (implant in maxilla) and Model M-I (implant in mandible). The models were isotropic and linearly elastic, except for the periodontal ligament with a non-linear material property to simulate the tooth movements. The tooth-to-tooth contact under the bite force was simulated by the vertical displacement of the mandible up to 0.24 mm from the initial occlusal contact. Non-linear contact analysis was conducted to calculate the stress in both the restoration and the supporting tissues.


RESULTS
To obtain a restoration that shows the same stress in the occlusal surface as that in the natural molars under the maximum bite force, the occlusal heights in Models I-M and M-I were to be reduced by 0.10 mm and 0.11 mm, respectively. The restorations were not expected to occlude with their natural molar antagonists under bite force lower than 13.0% and 15.8% of the maximum force, respectively.


CONCLUSIONS
Reduction in the intensity of the occlusal contact, or decreased occlusal height of an implant-retained single restoration, allows the establishment of an equivalent occlusal stress with the natural molars under the maximum bite force. This adjustment, either during fabrication or try-in procedure, can suppress excessive stress that may be created in the tissues. With this procedure, however, the restoration does not contact the antagonistic tooth under a relatively low bite force.
Maezawa
Nariyuki
N
Oral Implantology and Regenerative Dental Medicine, Department of Masticatory, Function Rehabilitation, Division of Oral Health Sciences, Graduate School, Tokyo Medical and Dental University.
Wakabayashi
Noriyuki
N
Yokoyama
Sawako
S
Shiota
Makoto
M
Suzuki
Tetsuya
T
D001732:Bite Force; D003442:Crowns; D003758:Dental Implantation, Endosseous; D015921:Dental Implants; D019094:Dental Prosthesis, Implant-Supported; D003799:Dental Stress Analysis; D008334:Mandible; D008437:Maxilla; D003765:Models, Dental; D013314:Stress, Mechanical
D015921:Dental Implants