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Abstract
Purpose
The aim was to investigate the effect of implant thread designs on the stress dissipation of the implant.
Materials and methods
The threads evaluated in this study included the V-shaped, buttress, reverse buttress, and square-shaped threads, which were of the same size (depth). Building four different implant/bone complexes each consisting of an implant with one of the 4 different threads on its cylindrical body (4.1 mm × 10 mm), a force of 100 N was applied onto the top of implant abutment at 30® with the implant axis. In order to simulate different osseointegration stages at the implant/bone interfaces, a nonlinear contact condition was used to simulate immature osseointegration and a bonding condition for mature osseointegration states.
Results
Stress distribution pattern around the implant differed depending on the osseointegration states. Stress levels as well as the differences in the stress between the analysis models (with different threads) were higher in the case of the immature osseointegration state. Both the stress levels and the differences between analysis models became lower at the completely osseointegrated state. Stress dissipation characteristics of the V-shape thread was in the middle of the four threads in both the immature and mature states of osseointegration. These results indicated that implant thread design may have biomechanical impact on the implant bed bone until the osseointegration process has been finished.
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Fig. 1.
Dimensions of a cylinder shaped implant body and the four different threads incorporated into the implant: (A) buttress, (B) V-shaped, (C) reverse buttress, and (D) square shaped threads (unit: mm).
Fig. 2.
Geometry of the implant and bone: (A) isometric view with the coordinate system used in this study, (B) antero-posterior view, (C) buccal view, (unit: mm).
Fig. 3.
The von Mises stresses in the interfacial bone around the implants with four different threads, i. e. (A) buttress, (B) V-shape, (C) reverse buttress and (D) square threads. Frictional contact conditions were assigned at the entire implant/bone interface using a friction coefficient of 0.3 to simulate immature osseointegration. Cut-off stress: 20 MPa.
Fig. 4.
The von Mises stresses in bone around the implants with (A) buttress, (B) V-shape, (C) reverse buttress and (D) square threads. Bond conditions were assigned at the entire implant/bone interface to simulate complete osseointegration. Cut-off stress: 20 MPa.
Fig. 5.
The von Mises stress distribution on the buccal surface of marginal cortical bone around the 4 implant models in an incompletely osseointegrated state.
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