Speakers - 2026

Title: Comparison of micro-CT derived bone mineral density values using longitudinal versus split-mouth controls

Abstract

Introduction Micro-computed tomography (µCT) imaging is a critical tool in evaluating bone changes in accelerated tooth movement; however, the accuracy of measured bone mineral density (BMD) values is highly dependent on the imaging protocols used to track remodeling. Longitudinal study designs capture temporal changes within a specific region but are often limited by the reduced resolution and image quality inherent to repeated in vivo scanning. Split-mouth models offer a high-resolution ex vivo alternative by utilizing measurements from both an experimental tooth and a contralateral control tooth, yet the validity of using µCT-derived BMD measurements in a split-mouth model compared to a longitudinal baseline remains under-evaluated.

Methods In this work, orthodontic force was applied via a 20 cN coil spring attached between the left incisor and left maxillary first molar of four Wistar rats for 28 days. µCT scans were acquired at 35 µm/voxel resolution using a Bruker SkyScan 1176 immediately prior to insertion and after removal. BMD values were measured in the alveolar bone immediately anterior, posterior, lingual, and buccal to the anterior root from both pre-treatment (baseline) and post-treatment (experimental) scans, as well as from the anterior root of the contralateral molar in post-treatment scans (control). Methodological equivalence was assessed by comparing the BMD difference calculated via a longitudinal baseline (baseline minus experimental) against a split-mouth baseline (control minus experimental). Statistically significant differences between groups were evaluated using pairwise t-tests comparing the baseline and control, the baseline and experimental, and the control and experimental measurements.

Results The experimental group exhibited significant (p < 0.05) bone loss in all directions compared to pre-treatment baselines (p < 0.0001) and post-treatment controls (p < 0.0001). No statistically significant differences were observed between the baseline and the control (presented as Baseline vs. Control mean ± SD; p-value) in the anterior (1161.72 ± 134.26 vs. 1166.97 ± 117.40 HU; p = 0.87), posterior (1264.52 ± 186.88 vs. 1329.95 ± 114.61 HU; p = 0.09), or buccal (1185.98 ± 112.94 vs. 1128.45 ± 243.54 HU; p = 0.24) regions. In contrast, the lingual region exhibited a statistically significant difference between the baseline and control (1169.75 ± 161.46 vs. 1078.16 ± 80.56 HU; p = 0.003). Despite this, the calculated bone loss remained comparable; the split-mouth differences tracked the longitudinal differences (presented as Split-Mouth vs. Longitudinal mean ± SD) in the anterior (286.39 ± 248.10 vs. 281.14 ± 218.77 HU), posterior (586.21 ± 165.71 vs. 520.77 ± 218.10 HU), buccal (253.25 ± 283.48 vs. 344.85 ± 352.26 HU), and lingual (274.66 ± 307.94 vs. 332.19 ± 164.67 HU) regions.

Conclusion Our results demonstrate that µCT-derived baseline bone densities are comparable to contralateral control densities, suggesting that split-mouth models of orthodontic tooth movement yield results equivalent to longitudinal comparisons. Given this equivalence, investigators may utilize either split-mouth or longitudinal models depending on experimental constraints, with confidence that results remain comparable across study designs.

The audience take away from presentation:

• The audience will learn about methods to quantify bone density changes in orthodontic tooth movement.
• The audience will learn that bone mineral density changes can be reliably quantified using split-mouth or longitudinal studies. This will help researchers develop studies of bone mineral density changes in orthodontic tooth movement as well as provide information which will help clinicians and researchers interpret and compare research using both split-mouth and longitudinal comparisons of bone density.