Title: 0734 - Murine Hypoplastic Amelogenesis Imperfecta Analyzed by Micro-Computed Tomography


Aaron Agirre (Presenter)
University of Texas Health Science Center at San Antonio

roberto fajardo, University of Texas Health Science Center at San Antonio
Yuanyuan Hu, University of Michigan
Jan C.-C. Hu, University of Michigan
James Simmer, University of Michigan
Yong-Hee Chun, University of Texas Health Science Center at San Antonio


Objectives: Amelogenesis imperfecta (AI) is a single gene disorder affecting dental enamel that results in malocclusion, inefficient mastication, tooth sensitivity, and poor esthetics. It is classified according to the thickness and mineral content of the malformed enamel. Differences in clinical presentation reflect the time point in which the disruption occurs. Phenotype diversity complicates the diagnosis of AI and has implications for treatment planning and outcome. The aim of this study was to analyze enamel mineral volume and density in mice with non-functional enamel proteins, exhibiting hypoplastic AI.

Methods: Eight murine genotypes (age: 7 weeks, n=10) were examined: wild-type (WT), heterozygous and homozygous null mice for ameloblastin (Ambn), enamelin (Enam), amelogenin (AmelX), and ameloblastin mutant (Ambn mutant). Mandibular incisors were analyzed with micro-computed tomography (mCT) using a protocol previously described based on manually drawn regions of interest. Enamel mineral volume and density were estimated for six segments from the apical loop to the point of eruption. Density analyses were calibrated to hydroxyapatite phantoms of known density.

Results: WT enamel mineral density and volume exceeded all gene knockout groups. Animals with homozygous deletions in Ambn, Enam and Ambn mutant exhibited negligible density and volume compared to WT group. Both groups had extensive ectopic mineralization in the enamel organ. In contrast, amelogenin homozygotes deposited a thin layer of mineral at the dentinoenamel junction. Interestingly, the mineral density was initially higher than WT in early maturation stage but did not increase further during mid and late maturation stages. Animals heterozygous for Ambn, Enam and AmelX were found to have values for enamel mineral density and volume lower than WT animals, but higher than homozygous null mice.

Conclusions: Precise timing of the expression of enamel proteins during amelogenesis is critical. Deletions and mutations in enamel genes result in AI with reduced mineral density and volume.

Student Presenter

This abstract is based on research that was funded entirely or partially by an outside source:
NIH, NIDCR R21DE025758, R01DE026769

Disclosure Statement:
The submitter must disclose the names of the organizations with which any author have a relationship, the nature of the relationship, and the clinical or research area involved. The following is submitted: NONE

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