Is the Jaw Bone Micro-Structure Altered in Response to Osteoporosis and Bisphosphonate Treatment? A Micro-CT Analysis

Abstract

The aim of the study was to quantify the micro-architectural changes of the jaw bone in response to ovariectomy, exposed or not to bisphosphonate treatment. A total of 47 Wistar rats were ovariectomized (OVX) or sham-operated (shOVX) and exposed to osteoporosis preventive treatment for eight weeks either with bisphosphonates (alendronate, ALN; group OVX-ALN) three days/week at a dose of 2 mg/kg or with saline solution (untreated control condition; group OVX). The bone morphometric parameters of the trabecular jaw bone were assessed using ex vivo micro-computed tomography. The regions of interest investigated in the maxilla were the inter-radicular septum of the second molar and the tuber. The regions quantified in the mandible included the three molar regions and the condyle. A one-way analysis of variance followed by pairwise comparison using Tukey's HSD and the Games-Howell test was conducted to explore significant differences between the groups. In the maxilla, OVX decreased the bone volume in the inter-radicular septum of the second molar. Bisphosphonate treatment was able to prevent this deterioration of the jaw bone. The other investigated maxillary regions were not affected by (un)treated ovariectomy. In the mandible, OVX had a significant negative impact on the jaw bone in the buccal region of the first molar and the inter-radicular region of the third molar. Treatment with ALN was able to prevent this jaw bone loss. At the condyle site, OVX significantly deteriorated the trabecular connectivity and shape, whereas preventive bisphosphonate treatment showed a positive effect on this trabecular bone region. No significant results between the groups were observed for the remaining regions of interest. In summary, our results showed that the effects of ovariectomy-induced osteoporosis are manifested at selected jaw bone regions and that bisphosphonate treatment is capable to prevent these oral bone changes.

Keywords: bisphosphonates; jaw bone; ovariectomy; rat; trabecular bone micro-architecture.

Figure 1

Bar diagrams illustrating the micro-architectural parametric values of the trabecular bone of the second maxillary molar at the inter-radicular septum. *, $: Values with the same sign are statistically significantly different, with p < 0.05. BV/TV, bone volume/tissue volume; Tb.Th, trabecular thickness; Tb.Sp, trabecular spacing; Tb.N, trabecular number; Tb.Pf, trabecular pattern factor; SMI, structure model index; shOVX, sham-ovariectomy surgery; OVX, ovariectomy surgery; OVX-ALN, OVX group treated with the anti-resorptive bisphosphonate drug alendronate sodium trihydrate.

Figure 2

Bar diagrams illustrating the micro-architectural parametric values of the trabecular bone of the mandibular condyle. BV/TV, bone volume/tissue volume; Tb.Th, trabecular thickness; Tb.Sp, trabecular spacing; Tb.N, trabecular number; Tb.Pf, trabecular pattern factor; SMI, structure model index; Tot.Po, total porosity. #, *, $: Values with the same sign are statistically significantly different, with p < 0.05.

Figure 3

Micro-CT cross-sectional image of the rat maxilla showing the regions of interest (ROI). (A) Inter-radicular septum of M2 (manually drawn ROI delineating the trabecular bone); (B) Maxillary tuber (ellipsoid-shaped ROI). M: molar tooth.

Figure 4

Micro-CT image of the rat mandible showing the regions of interest (ROI). (A) Condyle (rectangular-shaped ROI); (B.1) Manually drawn ROI encompassing the trabecular bone surrounding the molar; (B.2) Ellipsoid-shaped ROI positioned in the lingual region from the roots of the molar; (B.3) Ellipsoid-shaped ROI positioned in the buccal region from the molar; and (B.4) Trabecular bone in ellipsoid-shaped ROI at the inter-radicular septum.