Use of Micro-CT Imaging to Assess Ventral Mandibular Cortical Thickness and Volume in an Experimental Rodent Model With Chronic High-Phosphorus Intake

Abstract

Adverse effects of high dietary phosphorus on bone health have been observed in both animal and human studies. The aim of the investigation was to examine chronic effects of high phosphorus diet on the apical mandibular cortical thickness and volume in a hystricomorph rodent (Octodon degus) using microcomputed tomography. Male degus were randomly divided into two groups fed by different mineral contents from the age of 12 weeks till the age of 17 months. The micro-CT scanning and wall thickness analysis were applied on the region of the mandible exactly under the apices of the 4th premolar tooth, first molar tooth, and second molar tooth in two animals from each group. General overview and mapping of the ventral mandibular bone thickness revealed pronounced bony mandibular protrusions in all the animals fed a high-phosphorus diet with obvious bone thinning apically to the 4th premolar and first and second molar tooth apices. Mandibular bone volume and thickness located apically to the premolar and molars were statistically significantly smaller/thinner in the group fed by a high phosphorus diet. The thinnest bone measured 0.004 mm, where the mandibular 4th premolar tooth almost perforated the mandibular cortex. Similar studies of metabolic bone disease and its influence on alveolar bone were also published in rats and mice. The influence of different environmental, infectious, or metabolic factors on the growing tooth, alveolar bone formation, and bone pathologies must be done experimentally on growing animals. In contrast, degus have continuously growing dentition, and the effect of any of the above listed factors can be studied in this animal model at any age and for longer time periods.

Keywords: cortical bone; degu (Octodon degus); dental disease; dentistry; micro-CT; rodent; volume thickness.

Figure 1

Degu mandible. Quantifying the mandibular bone thickness at the area of apical tooth elongation using the first method. (A) Three-dimensional render of scanned jaw with tooth labeling, (B) sagittal, and (C) coronal cross section showing the regions under the tooth apex analyzed by wall thickness analysis. P4—4th premolar tooth; M1—1st molar tooth; M2—2nd molar tooth.

Figure 2

Computed tomography imaging of the mandibular cortical bone thickness at the apical area of the mandibular 4th premolar tooth and mandibular molars teeth in degus fed by normal (A) and high-phosphorus diets (B). Note: severe thinning of the cortical bone ventral to the apex of P4 and M1 (B). Apical elongation of mandibular 4th premolar and molar teeth was also palpable as bony swellings on the ventral mandibular surface (B). Legend: P4—4th premolar tooth; M1—1st molar tooth; M2—2nd molar tooth.