Short implants and bone loss – Evaluation of bone turnover
16200 POSTER DISPLAY BASIC RESEARCH
Background
Short implants are indispensable in posterior maxilla with insufficient bone height. Implant design, bone quality and degree of bone loss predetermine safe functional load transfer to adjacent bone. Adequate bone strains are key stimuli of bone turnover, but their extreme magnitudes lead to implant failure. Computer simulation allows to correlate bone and implant parameters with bone strain spectrum and to evaluate implant perspective.
Aim/Hypothesis
The aim of the study was to evaluate the impact of plateau implants and bone quality on strain levels in adjacent bone at several levels of bone loss to assess implant prognosis.
Material and Methods
Cortical and cancellous bone first principal strains (FPSs) were selected to evaluate bone turnover around fully and partially osseointegrated 4.5 (N), 5.0 (M) and 6.0 mm (W) diameter and 5.0 mm length Bicon SHORT® implants at five levels of bone loss from 0.2 to 1.0 mm. Implant 3D models were placed crestally in corresponding posterior maxilla segment models with type III bone and 1.0 mm cortical crestal and sinus bone layers. The models were designed in Solidworks 2016 software. All materials were assumed as linearly elastic and isotropic. Elasticity modulus of cortical bone was 13.7 GPa, cancellous bone – 1.37 GPa. Bone-implant assemblies were analyzed in FE software Solidworks Simulation. A total number of 4-node 3D FEs was up to 3,450,000. 120.92 N mean maximal oblique load (molar area) was applied to the center of 7 Series Low 0° abutment. Maximal FPSs were correlated with 3000 microstrain minimum effective strain pathological (MESp) to evaluate bone turnover around the implants.
Results
Maximal FPSs for osseointegrated implants (1800…3270 microstrain) were found in the cancellous bone at the first fin edge. For implants with bone loss, they were observed at the same location and were significantly dependent on bone loss level (2140…3600, 2300…4100, 2800…4900, 3500…5900 and 4200…7000 microstrain for 0.2, 0.4, 0.6, 0.8 and 1.0 mm bone loss). Maximal FPSs were also substantially dependent on implant diameter: diameter increase from 4.5 to 6.0 mm have led to 41, 44, 43, 41, 40% FPS decrease for 0.2, 0.4, 0.6, 0.8 and 1.0 mm bone loss. Comparing to the osseointegrated implants, the following FPS increase on five bone loss levels was determined: for N implants it was 10, 25, 50, 80 and 114%, for M implants – 12, 32, 62, 92, 131%, for W implants – 19, 28, 56, 94 and 133%.
Conclusion and Clinical Implications
Bone turnover was found to be significantly influenced by implant diameter and bone loss level. 4.5 mm diameter implant is not recommended for type III bone because bone strains exceed 3000 microstrain threshold even for the osseointegrated implant. 6.0 mm diameter implant caused positive bone turnover balance for up to 0.6 mm bone loss, while 5.0 mm – only for up to 0.3 mm bone loss. Clinicians should consider these findings in treatment with short plateau implants.