[Three-dimensional finite element analysis of influence of occlusal surface height on stress distribution around posterior implant-supported single crown].

OBJECTIVE: To evaluate the effect of the occlusal surface height of a mandibular posterior implant-supported single crown on stress in bone tissues. METHODS: Three-dimensional finite element models of the implant-supported single crown replacing the missing right lower second premolar, mesial and distal natural teeth, periodontal membrane, alveolar bone, loaded rigid body and analog food of almond were established. Using the Federation Dentaire International (FDI) system, the first premolar, the second premolar and the first molar were represented with 44, 45, 46. Three occlusal surface heights of the crown were studied: (1) normal height; (2) 15 μm reduction in height; (3) 30 μm reduction in height. The models were loaded by independent loading with maximal occlusal force(44 by 280 N, 45 by 360 N, and 46 by 480 N) and average occlusal force(44 by 140 N, 45 by 180 N, and 46 by 240 N)on the single crown; combined loading (maximal occlusal force transformed into uniform load of 3.7 MPa on top of rigid body, in contact with points on the occlusal surface), and analog almond-like food loading (average occlusal force transformed into uniform load of 1.67 MPa in simulated food chewing, in contact with points on the occlusal surface). RESULTS: For maximal biting force under independent loading, Von Mises stress peak values in bone tissues around 44, 45, and 46 were 82.57 MPa, 45.26 MPa and 27.79 MPa; For average biting force, peak values were 41.28 MPa, 22.63 MPa and 13.89 MPa. Under combined loading, compared with the normal occlusal surface height group, Von Mises stress peak values decreased 4.6 MPa, by 0.84%; increased 7.52 MPa, by 20.04%, and decreased 1.8 MPa, by 5.84%, for 45, 46, and 44 in the 30 μm infra-occlusion group, respectively. Under food loading, Von Mises stress peak values decreased 0.34 MPa, by 1.62%; increased 1.11 MPa, by 2.66%; and increased 0.06 MPa, by 0.54%, and for 45, 46, and 44 in the 30 μm infra-occlusion group, respectively. CONCLUSION: Within the limitation of this study, within 30 μm reduction of the occlusal surface height of implant-supported single crown, no significant difference of the peak values was observed.