Analysis of stress and strain around orthodontically loaded implants: an animal study

The aim of this study was to describe the stress and strain fields around orthodontically loaded dental implants using the finite element method and to evaluate the relationship between the generated strain and the biologic reaction expressed through histomorphometric parameters. Finally, this study aimed to evaluate the interaction between the orthodontic loading and the deformation generated by normal occlusal function.

Sixteen titanium dental implants were inserted in extraction sockets after the removal of the second premolars and first molars of 4 adult Macaca fascicularis monkeys. After 17 weeks of healing, the implants were loaded by a pair of Sentalloy springs (50 cN) for 16 weeks. After sacrifice, tissue blocks including the implants and surrounding bone were excised. Five tissue blocks were scanned with a synchrotron radiation-based microtomography (microCT) scanner and sample-specific finite element models were generated. Subsequently all samples were prepared for histomorphometric analysis.

All implants were osseointegrated, although the surrounding alveolar bone differed from sample to sample. As a consequence the finite element analyses showed that the stresses and strains in the peri-implant alveolar bone greatly varied among the samples. A high level of remodeling activity was found close to the implants.

Individual differences between the receptors (in this case, the monkeys) have a large effect on both the biologic and morphologic parameters. These variations were indeed found to have a substantial impact on the (re)modeling dynamics and the load transfer mechanisms around the implants.

By integrating different analysis techniques to evaluate bone (re)modeling around orthodontically loaded implants, this study has demonstrated the complexity and case-specific character of alveolar adaptation to orthodontic loading. Furthermore, stresses generated by combined functional and orthodontic forces should not be neglected.