Predicting bone remodelling around root-form dental implants

Abstract

Dental implants are a common treatment for the partially or fully edentulous patient. Increasing patient demands have driven implant development, most recently to patient-specific root-analogue implants that resemble the patient’s natural root-form. Laser sintering technology has increased the range of candidate implant materials, including metals, ceramics and polymers [1].
Screw-form dental implants result in an average of 0.5mm crestal bone loss over 5 years. Bone loss and subsequent gingival recession impairs the functional and aesthetic outcomes of implant therapy. Crestal bone loss may be caused by stress shielding, and finite element (FE) analysis can be used to predict the remodelling stimulus in orthopaedic applications by comparing the strain energy density (SED) in intact and implanted models. The aim of this study was to compare the remodelling stimulus generated by root-form implants using three differing stiffness materials.

A model of a mandibular canine and local osseous structures was produced from patient CT data. Intact and implanted model variants were generated and solved using Ti-6Al-4V (E=110GPa), zirconia (E=200GPa) and PEEK (E=4GPa) implant materials. Linear-elastic material properties were applied to the implant, enamel, dentin and cortical/cancellous bone. A hyperelastic material model was applied for the periodontal ligament in the intact case. The model was loaded with a typical bite-force of 200N at 12°. The SED change was interrogated in the elements surrounding the implant.

The mean change in cortical SED from the intact to the implanted models was -84.1%, -86.7% and -40.5% for the titanium, zirconia and PEEK respectively. In the intact model, the peak cortical stimulus was focused around the crestio-labial region. The titanium and zirconia models showed low stimulus at the labial crest, whilst the PEEK model exhibited relatively uniform stimulus over the labial cortical surface (Figure).

This study highlights the influence of implant material upon initial bone remodelling stimulus. The model indicated that high stiffness root-form implants create crestal load bypass by encouraging apical load transfer, like screw-form implants. This suggests that high stiffness implants may have a propensity for adverse cortical bone remodelling in a region of aesthetic and functional importance, which more flexible or compliant implants would avoid.

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Identifiers

ORCID for Martin Browne: orcid.org/0000-0001-5184-050X

ORCID for Alexander Dickinson: orcid.org/0000-0002-9647-1944

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