| Summary: | 碩士 === 國立陽明大學 === 臨床牙醫學研究所 === 98 === Purpose: To investigate the micromotion and bone biomechanics of an immediately loaded single dental implant located in the anterior maxilla, with different angulated abutments in different bone types. Materials and Methods: A finite element model with an implant, abutment and a simplified half pre-maxilla bone composed of cortical bone and cancellous bone was created. A bite force of 178N was applied to the tops of the angled abutments at a 120-degree angle to the abutment long axis. An immediate loading situation was simulated under six conditions including two different types of cancellous bone (type2 and type4) with three different abutment angles (0-degree, 15-degree and 25-degree) by using ANSYS 11.0 software featuring a non-linear contact algorithm.
Results: Under the condition of both bone types, the micromotion values for 15-degree and 25-degree angled abutments increased by 3.1%~10.1% compared to the corresponding values for straight abutments. In the type 4 bone, the micromotion values for 15-degree and 25-degree angled abutments increased by 79.4% and 134% , respectively, compared to the corresponding values in the type 2 bone. The influence of bone quality on micromotion was superior to that of abutment angles for implant osseointegration. All the calculated micromotion values were under the threshold of fibrous encapsulation. Besides, regardless of the abutment angles, strain values over buccal cortical bone near the implant neck were above 3000 microstrain, which were prone to aggravate buccal bone resorption jeopardizing esthetic concerns over the maxillary anterior area.
Conclusion: Under immediate loading conditions, the osseointegration could happen even if using abutment angulation up to 25-degree, but micromotion values were lower in the higher bone density. When patients had lower bone density, unfavorable prognosis of esthetics concerning higher bone strains in buccal cortical bone could happen even if using straight abutments. To achieve a favorable prognosis under immediate loading protocols of a maxillary anterior implant, the selection for abutment angles and bone quality should be under careful treatment plans and diagnoses.
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