Factors affecting the stability of miniscrew implants: A stepwise three dimensional finite element study

Titanium orthodontic miniscrew implants are often utilized in orthodontics nowadays to provide skeletal anchorage. The mechanical stability of miniscrew implants in alveolar bone is essential since they are commonly loaded immediately and osseointegration is usually completely or partially absent. The objective of this study was to evaluate the effect of several factors on the stress in bone surrounding the miniscrew implants and on the stress within the implants to predict how these factors affect the stability of miniscrew implants in bone. Thirty five three-dimensional assemblies of miniscrew models placed in alveolar bone blocks were constructed using a commercial Finite Element Analysis software package. The model variables included implant design factors, implant placement angulation and bone-related factors. All miniscrew implants were loaded in the mesial direction with a linear force equal to 2 N. Peak von Mises and principal stress values in cortical bone, cancellous bone and the miniscrew implants were compared between the different models for each factor. The results demonstrated that most factors had a considerable effect on the stresses in bone (implant diameter, implant head length, thread size, placement angulation and cancellous bone quality) while other factors did not affect the stresses similarly (thread shape, thread pitch and cortical bone thickness). Based on the results, the study provides clinical recommendations to enhance the stability of miniscrew implants.