Micro finite element analysis of continuously loaded mini-implants:​ a micro-CT study in the rat tail model

Kerberger, Robert<sup>1,2</sup>; Brunello, Giulia<sup>3,4</sup>; Drescher, Dieter<sup>1</sup>; van Rietbergen, Bert<sup>5,*</sup>; Becker, Kathrin<sup>1,2,*</sup>

Affiliations

¹Department of Orthodontics, University Hospital Düsseldorf, Moorenstraße 5, 40225 Düsseldorf, Germany

²Department of Orthodontics and Dentofacial Orthopedics, Charité, Charité Centrum CC03, Institute for Dental and Craniofacial Sciences, Aßmannshauser Straße 4-6, 14197 Berlin, Germany

³Department of Oral Surgery, University Hospital Düsseldorf, Moorenstraße 5, 40225 Düsseldorf, Germany

⁴Department of Neurosciences, School of Dentistry, University of Padova, Via Giustiniani 2, 35128 Padova, Italy

⁵Orthopaedic Biomechanics, Department of Biomedical Engineering, Eindhoven University of Technology, Groene Loper 3, 5612 AE Eindhoven, the Netherlands

Abstract and keywords

Implant migration has been described as a minor displacement of orthodontic mini-implants (OMIs) when subjected to constant forces. Aim of this study was to evaluate the impact of local stresses on implant migration and bone remodelling around constantly loaded OMIs. Two mini-implants were placed in one caudal vertebra of 61 rats, connected by a nickel‑titanium contraction spring, and loaded with different forces (0.0, 0.5, 1.0, 1.5 N). In vivo micro-CT scans were taken immediately and 1, 2 (n = 61), 4, 6 and 8 (n = 31) weeks post-op. Nine volumes of interest (VOIs) around each implant were defined. To analyse stress values, micro-finite element models were created. Bone remodelling was analysed by calculating the bone volume change between scans performed at consecutive time points. Statistical analysis was performed using a linear mixed model and likelihood-ratio-tests, followed by Tuckey post hoc tests when indicated. The highest stresses were observed in the proximal top VOI. In all VOIs, stress values tended to reach their maximum after two weeks and decreased thereafter. Bone remodelling analysis revealed initial bone loss within the first two weeks and bone gain up to week eight, which was noted especially in the highest loading group. The magnitude of local stresses influenced bone remodelling and it can be speculated that the stress related bone resorption favoured implant migration. After a first healing phase with a high degree of bone resorption, net bone gain representing consolidation was observed.

Keywords: Biomechanics; Implants; Bone QCT/μCT; Injury/fracture healing; Preclinical studies

Links

DOI: 10.1016/j.bone.2023.116912

PubMed: 37739299

WoS: 001085283700001

History

Received: 2023-07-8

Revised: 2023-09-13

Accepted: 2023-09-14

Online: 2023-09-20

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