# In situ micro-computed tomography to characterize periodontal ligament behavior

Laura Preiss, Rémy Gauthier, Hervé Richard, Loic Courtois, Anne-Lise Chopard-Lallier, Damien Fabrègue, Jérôme Chevalier, Nicolas Courtois

► To cite this version:

Laura Preiss, Rémy Gauthier, Hervé Richard, Loic Courtois, Anne-Lise Chopard-Lallier, et al. In situ micro-computed tomography to characterize periodontal ligament behavior. 50th congress of the Société de Biomécanique, Oct 2025, Marseille, France. 10.46298/mbj.16150. hal-05191702v2

HAL Id: hal-05191702

https://hal.science/hal-05191702v2

Submitted on 23 Oct 2025

HAL is a multi-disciplinary open access
archive for the deposit and dissemination of sci-
entific research documents, whether they are pub-
lished or not. The documents may come from
teaching and research institutions in France or
abroad, or from public or private research centers.

L'archive ouverte pluridisciplinaire HAL, est
destinée au dépôt et à la diffusion de documents
scientifiques de niveau recherche, publiés ou non,
émanant des établissements d'enseignement et de
recherche français ou étrangers, des laboratoires
publics ou privés.

<figure><img src="image_1.png" /></figure>

Distributed under a Creative Commons Attribution 4.0 International License
# *In situ* micro-computed tomography to characterize periodontal ligament behavior

Rémy Gauthier<sup>a*</sup>, Laura Preiss<sup>a</sup>, Hervé Richard<sup>b</sup>, Loic Courtois<sup>c</sup>, Anne-Lise Chopard-Lallier<sup>b</sup>, Damien Fabrègue<sup>a</sup>, Jérôme Chevalier<sup>a</sup>, Nicolas Courtois<sup>b</sup>

<sup>a</sup> Univ Lyon, INSA Lyon, UCBL, CNRS, MATEIS, UMR5510, 20 Avenue Albert Einstein, Villeurbanne, 69621, France

<sup>b</sup> Anthogyr SAS, 2237 Avenue A. Lasquin, 74700, Sallanches, France

<sup>c</sup> 3Dmagination, Harwell, United Kingdom

* Corresponding author: remy.gauthier@cnrs.fr

Received date: 04/04/2025

Accepted date: 27/06/2025

Publication date: 27/10/2025

**Keywords:** microcomputed tomography, periodontal ligament, bone, digital volume correlation

© 2025 The Authors

Licence CC-BY 4.0

Published by Société de Biomécanique

## 1. Introduction

The periodontal ligament (PDL) plays a major role in the mechanobiological homeostasis of the periodontium system (Gauthier et al., 2021). In particular, the PDL compressive and tensile loadings during physiological loadings are directly involved in the surrounding alveolar bone remodeling. Interestingly, dentists have extensively taken advantage of this mechanobiological behavior in the context of orthodontics. By applying a static load on specific teeth, the PDL is submitted to both compressive and tensile loading, thus promoting bone resorption and formation, respectively (Dutra et al., 2016). This results in an orthodontic movement of the teeth along the tension-compression direction. While this phenomenon is known, the associated mechanobiological mechanism remains poorly understood. This limit can be explained by the difficulty to accurately characterize PDL behavior under loading due to its complex geometry. Finite Element Models (FEM) have provided relevant insights in that context. However, simulations still lack from experimental validations, in terms of loading considering a physiological geometry. In that context, *in-situ* X-ray microcomputed tomography (µCT) has proven its capacity to analyze periodontal tissue behavior under complex loadings (Preiss et al., 2025). In this previous study, *in situ* µCT was performed to follow strain distribution across peri-implant bone during dental implant insertion. In the present study, *in-situ* µCT is used to investigate PDL mechanical

behavior during static loading to better understand the biomechanical features at the bone-PDL interface.

## 2. Methods

### 2.1 *In situ* set up

A block from a pig manidble was cut to perform the µCT analysis on the PDL around a molar root. The surrounding teeth were maintained to keep realistic biomechanical boundary conditions during loading. A static orthodontic force (10 N) was applied on the molar crown in the vestibular-lingual direction through a steel wire. The sample and set up were placed in a tomograph (GE Phoenix v | tome |, GE Sensing & Inspection Technologies Phoenix X | ray). Tomographic scans, with an isotropic voxel size of 15 µm³, were acquired before and after the static loading.

### 2.2 Images processing

The first step of the image processing consisted in the measurement of the PDL thickness around the root before and after the static loading. The relative thickness variation was calculated on each pixel belonging to the PDL before and after loading.

A FEM was built from the tomographic data. A fine tetrahedral mesh was generated for the PDL region. Digital volume correlation was used to obtain the displacement applied to the tooth surface. These displacements were interpolated to the tooth-PDL surface nodes and used as the boundary conditions. The bone-PDL nodes were blocked in all the directions.
In a second analysis, bone surrounding the PDL was added to the model to evaluate the behavior at the bone-PDL interface. This analysis was performed on a smaller region of interest (ROI) located close to the apical region of the root to reduce calculation time. The PDL and bone were considered as purely elastic materials with 0.4 MPa / 0.49 and 15.8 GPa / 0.33, for the elastic modulus / Poisson ratio, respectively (Karimi et al., 2020). The linear behavior assumption was defined as a first simple configuration to investigate the protocol feasibility. The images processing and FE analyses were performed using the Avizo software (Thermal Fischer Scientific).

**3. Results and discussion**

The PDL thickness varied from 100 to 600 µm both before and after the static loading. The thickness variation over the PDL voxels was normally distributed between -50% and 50% (Figure 1b). These variations appeared to be lower close to the root apex. Thickness variations were measured mostly on the mesial and distal regions of the PDL. Accordingly, compressive and tensile radial strains were measured on the region of negative and positive thickness variations, respectively (Figure 1a). The distribution of radial strain around the PDL was close to the distribution of PDL thickness variation. This result suggests that the numerical model built from the µCT data and the associated FE analysis are adapted and can be considered for further discussions.

At the bone-PDL interface level, radial strain can be observed both in the PDL and at the bone-PDL interface (Figure 1c and Figure 1d). Both compressive and tensile strain can be observed. This can be explained by the sub-region chosen that is located close to the apical region, where the strain becomes positive. This is due to the loading. The load is punctually applied on the tooth crown what may induce some rotation of the tooth root. Such data could be implemented in mechanobiological models of orthodontic tooth movement as the mechanical stimulus driving PDL fibroblast and bone osteoblasts, osteoclasts, and osteocytes activities (Van Schepdael et al., 2013). In particular, bone and PDL strain-mediated remodelling could be tuned locally using the present method.

It has to be noticed that considering an isotropic elastic behavior for the PDL is highly inaccurate. Introducing a viscoelastic behavior with properties depending on the location around the root would be of great interest

<figure><img src="image_2.png" /><figcaption>**Figure 1.** Top. schematic of the dental arch and load on the tooth. The red arrow represents the load direction. a. Radial strain distribution obtained through FEM and b. thickness variation through image processing around the PDL. c. Radial strain distribution on the bone-PDL ROI. d. Radial strain distribution on the bone at the bone-PDL interface.</figcaption></figure>

to provide realistic data. This viscoelastic behavior is known to depend on fluid circulation in and out of the PDL (Gauthier et al., 2021). As bone mechanobiology is known to be driven by fluid flow, such viscoelastic behavior would provide interesting insights on the bone-PDL mechanobiology. Additionally, the periodontal complex presents a hyperelastic behavior. The FE model was only used to measure the distribution of strain, with the boundary conditions being the initial
and final state of the PDL. While, a non-linear con-
stitutive law would not have an influence on the finale
strain state, this influence would be significant for the
stress calculation.

4. Conclusions

An in situ microcomputed tomography method to follow
the PDL mechanical behavior during a static loading
was introduced. This method has shown its potential
to estimate the local strains within the PDL and at its
interface with the surrounding alveolar bone.

Acknowledgements

The authors would like to thank J.Adrien for his help
and support.

Conflict of Interest Statement

None.

Contributor Roles

**LP:** Writing-original draft, Project administration, Methodology, Investigation, Formal analysis, Data curation, Conceptualization. **HR:** Methodology. **LC:** Methodology, Data curation. **RG:** Writing-original draft, Validation, Formal analysis. **ALCL:** Writing - review & editing, Supervision. **DF:** Supervision: **JC:** Writing-review & editing, Supervision. **NC:** Writing-review & editing, Supervision.

References

Dutra, E. H., Nanda, R., & Yadav, S. (2016). Bone response of loaded periodontal ligament. *Current Osteoporosis Reports, 14*(6), 280–283. https://doi.org/10.1007/s11914-016-0328-x

Gauthier, R., Jeannin, C., Attik, N., Trunfio-Sfarghiu, A.-M., Gritsch, K., & Grosgogeat, B. (2021). Tissue engineering for periodontal ligament regeneration: biomechanical specifications. *Journal of Biomechanical Engineering, 143*(3). https://doi.org/10.1115/1.4048810

Karimi, A., Razaghi, R., Biglari, H., Rahmati, S. M., Sandbothe, A., & Hasani, M. (2020). Finite element modeling of the periodontal ligament under a realistic kinetic loading of the jaw system. *Saudi Dental Journal, 32*(7), 349–356. https://doi.org/10.1016/j.sdentj.2019.10.005

Preiss, L., Gauthier, R., Richard, H., Courtois, L., Chopard-Lallier, A.-L., Fabrègue, D., Chevalier, J., & Courtois, N. (2025). Bone mechanical behavior around dental implants: Densification and deformation follow-up by in-situ computed tomography. *Journal of the Mechanical Behavior of Biomedical Materials, 167*(February), 106966. https://doi.org/10.1016/j.jmbbm.2025.106966

Van Schepdael, A., Vander Sloten, J., & Geris, L. (2013). A mechanobiological model of orthodontic tooth movement. *Biomechanics and Modeling in Mechanobiology, 12*(2), 249–265. https://doi.org/10.1007/s10237-012-0396-5