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KMID : 0362420080460050479
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Journal of Korean Academy of Prosthodontics
2008 Volume.46 No. 5 p.479 ~ p.489
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Stress distribution in bone surrounding maxillary molar implants under different crown-to-fixture ratio: A 3D FEM analysis
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Park Jong-Chan
Kwon Kung-Rock
Shin Sang-Wan
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Abstract
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Statement of the problem: Under anatomical limitations on maxillary posterior region, a poor crown-to root ratio acting on dental implants can re-sult in undesirable stress in surrounding bone, which in turn can cause bone defects and eventual failure of implants.
Purpose: The purpose is tocompare stress distribution due to different crown-root ratio and effect of splinting between natural teeth and implants in maxillary molar area underdifferent loads.
Material and methods: Analysis of stress arising supporting bone of the natural teeth and the implant was made with 3-dimensionalfinite element method. The model simulated naturel teeth was made with 2nd premolar and 1st molar in the maxillary molar region (Model T). Themodel simulated implants placed on same positions with two parallel implants of Straumann Dental Implant cemented abutment (Model I). Eachmodel was designed in different crown-root ratio (0.7:1, 1:1, 1.25:1) and set cement type gold crown to make it non-splinted or splinted. After that,300 N force was loaded to each model in five ways (Load 1: middle of occlusal table, Load 2: middle of buccal cusp, Load 3: middle of lingual cusp,Load 4: horizontal load to buccal cusp of anterior abutment only, Load 5: horizontal load to middle of buccal cusp of each abutment), and stress dis-tribution was analyzed.
Results and conclusion: On all occasions, stress was concentrated at the cervical region of the implant. Under load 1, 2 and3, stress was not increased even when crown-root ratio increases, but under load 4 and 5, when crown-root ratio increases, stress also increased. Therewas difference in stress values between natural teeth and implants when crown-root ratio gradually increases; In case of natural teeth, splinting de-creased stress under vertical and horizontal loads. In case of implants, splinting decreased stress under vertical loads 1,2 and 3, but increased maximalstress under loads 2 and 3. Under horizontal loads, splinting decreased stress, however the effect of splinting decreased under load 5 than load 4.Furthermore, the stress was increased, when crown-root ratio is 1.25:1. Clinical implications: This limited finite element study suggests that thestress on supporting bone may be increased under non-axial loads and poor crown-root ratio. Under poor crown-root ratio, excessive stress was gen-erated at the cervical region of the implant, and decreased splinting effect for stress distribution, which can be related to clinical failure.
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KEYWORD
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Stress distribution, Implant, Maxillary molar, Finite element analysis, Crown-fixture ratio
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