Nariyuki Maezawa

Publications (2)1.78 Total impact

• Article: [Influence of intensity of occlusal contact in implant-retained single restoration on stress distributions of crown surface and supporting bone].

  Nariyuki Maezawa, Noriyuki Wakabayashi, Sawako Yokoyama, Makoto Shiota, Tetsuya Suzuki
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  ABSTRACT: 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. 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. 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. 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.
  Nihon Hotetsu Shika Gakkai Zasshi 08/2007; 51(3):582-91.
• Article: Three-dimensional stress analysis of tooth/lmplant-retained long-span fixed dentures.

  Nariyuki Maezawa, Makoto Shiota, Shohei Kasugai, Noriyuki Wakabayashi
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  ABSTRACT: The aim was to assess the influence of connection of the canine teeth to implant-retained long-span fixed dentures on stress in mandibular bone using finite element analysis. Each 3-dimensional model included bone, 6 implants, both natural canines, and superstructures. Each model simulated 1 of 4 prosthetic designs: a tooth/implant-retained 1-piece superstructure (One-piece), 3-piece superstructures with an anterior and 2 posterior segments with unconnected teeth (UnConnect), 3-piece superstructures with the teeth connected to the posterior segments (PostConnect), and 3-piece superstructures with the teeth connected to the anterior segment (AntConnect). A nonlinear elastic modulus was applied to the periodontal ligament (PDL). Maximum intercuspal (IP), canine-protected (CP), and group-function (GF) occlusions were simulated. The maximum stresses in the peri-implant regions of the bone were lower for the One-piece than for the other superstructures. In PostConnect and AntConnect, the maximum stress in the PDL was lower than that in UnConnect, but the stress in the peri-implant bone was comparable in those 3 models. The stresses were lower in the GF model than in the CP model. The stress created in the peri-implant bone was insensitive to the modes of the teeth/implant connection in long-span fixed dentures. Within the limitation of the mechanical analysis, it is suggested that the connection of the canine tooth to the implant-retained long-span superstructures is an acceptable option in partially edentulous patients.
  The International journal of oral & maxillofacial implants 22(5):710-8. · 1.78 Impact Factor