Impact of diameter of short plateau implants on their load-bearing capacity in bone loss

Background

Among other reasons, dental implants often fail due to bone loss. Because of reduced length, short implants should be more susceptible to bone loss, especially if placed crestally. As a result of osseointegration loss, bone overload may take place under physiological functional loading, which, in turn, leads to bone loss progression. So, implant long-term prognosis would be heavily compromised.

Aim/Hypothesis

The aim of this study was to evaluate the role of implant diameter on long-term prognosis of short plateau implants in posterior maxilla considering bone loss.

Material and Methods

In order to compare load-carrying capacities of fully and partially osseointegrated (0.2 mm annual bone loss) 4.5 (N), 5.0 (M) and 6.0 mm (W) diameter and 5.0 mm length Bicon Short® implants, the concept of ultimate functional load (UFL) was proposed (Demenko, 2011). The implants 3D models were placed crestally and bicortically in posterior maxilla models with type III bone and 1.0 mm cortical crestal and sinus bone, which were generated in Solidworks 2016 software with a total number of up to 2,840,000 4-node 3D finite elements (FEs). Materials were assumed as linearly elastic and isotropic. Young moduli of cortical cancellous bone were 13.7 1.37 GPa and cortical bone compression strength was 100 MPa. The models were analyzed in FE software Solidworks Simulation. 120.92 N oblique load was applied to the center of 7.0 mm abutment. Maximal von Mises stresses (MESs) were evaluated in bone-implant interface to determine UFL magnitudes for fully and partially osseointegrated implants.

Results

Maximal MESs for osseointegrated implants (14…28 MPa) were found on the surface of crestal cortical bone. For implants with 0.2, 0.4, 0.6, 0.8, 1.0 mm bone loss, they were observed in migrating critical points inside crestal cortical bone: 23…35, 32…41, 38…45, 41…48, 43…50 MPa. For osseointegrated implants, UFL magnitudes were 432…864 N. For the ones with 0.2, 0.4, 0.6, 0.8, 1.0 mm bone loss, UFL magnitudes were 345…526, 295…378, 269…318, 252…295, 242…278 N. So, after 5 years in function (1.0 mm bone loss), the following reduction of implant load-bearing capacity was determined: 44, 58 and 69% for N, M and W implants. Comparing to osseointegrated state, UFL drop with 0.2, 0.4, 0.6, 0.8 and 1.0 mm bone loss was found: 20, 32, 38, 42, 44% for N; 33, 46, 52, 56, 58% for M; 39, 56, 63, 66, 68% for W implants. It was determined that W implant had 53, 28, 18, 17, 15% UFL magnitude increase for 0.2, 0.4, 0.6, 0.8, 1.0 mm bone loss relative to N implant.

Conclusion and Clinical Implications

All UFL magnitudes were found much higher than mean maximal functional loading (120.92 N). Furthermore, for all scenarios, UFL magnitudes were above 275 N maximal functional loading for molar area. By evaluating implant load-bearing capacity reduction, dental professionals may consider the factor of implant longevity in selection of a proper implant diameter.