[Influence of bone quality on the stress distribution for three-posterior immediately loaded implants: a three-dimensional finite element analysis].

OBJECTIVE: To assess and compare the peri-implant stress distribution of three posterior implants under immediate loading with 4 different bone qualities using three dimensional (3D) finite element (FE) analysis. METHODS: A 3D finite element model representing three implants in a portion of mandible at the 654 region was developed, and three implants received a crown each. Four types of bone qualities (B1, B2, B3 and B4) were designed for the model. Load of 100 N was applied on the occlusal surfaces of the crowns at a 45° angle to the vertical axis of the implants. RESULTS: Von Mises stresses in the peri-implant bone of 4 in bone quality from B1 to B4 were (13.17 ± 9.32), (12.95 ± 9.14), (15.00 ± 9.44), and (16.81 ± 10.74) MPa, and those of 5 were (15.51 ± 10.32), (14.73 ± 8.96), (16.79 ± 8.40), and (18.34 ± 8.45) MPa. Stress in bone quality B4 showed the highest value, followed by B3 bone, the lowest stress were found in B1 and B2 bone. It was significantly different (P < 0.05). However, von Mises stresses in different quality of bone around 6 [(42.45 ± 25.71), (41.66 ± 25.29), (42.70 ± 23.24), (42.06 ± 23.66) MPa] were close to each other, and were as twice or three times as those of 4 and 5, irrespective of different bone qualities. CONCLUSIONS: The stress distribution around implant under immediate loading was not only affected by different bone qualities, but also by the direction of loading, and the latter may have a greater impact when a severe load delivered.