Three-dimensional assessment of enamel and dentine in mouse molar teeth during masseter muscle hypofunction

Julián BALANTA-MELO, Maximilian BEMMANN, Viviana TORO-IBACACHE, Kornelius KUPCZIK, Sonja BUVINIC - 1. Institute for Research in Dental Sciences, Faculty of Dentistry, Universidad de Chile (Santiago, Chile). 2. School of Dentistry, Universidad del Valle (Cali, Colombia). 3. Max Planck Weizmann Center for Integrative Archaeology and Anthropology, Max Planck Institute for Evolutionary Anthropology (Leipzig, Germany). 4. Center for Quantitative Analysis in Dental Anthropology, Faculty of Dentistry, Universidad de Chile (Santiago, Chile). 5. Department of Human Evolution, Max Planck Institute for Evolutionary Anthropology (Leipzig, Germany.) 6. Center for Exercise, Metabolism and Cancer Studies CEMC2016, Faculty of Medicine, Universidad de Chile (Santiago, Chile).

Mouse molar is a widely used model for teeth development. However, the effect of masticatory function on enamel and dentine in adult individuals remains poorly understood. As reported, the unilateral masseter hypofunction induced by botulinum toxin type A (BoNTA) resulted in mandibular bone damage and signs of unilateral chewing in adult mice.

Enamel volume from treated side resulted unchanged after 2 weeks of unilateral masseter hypofunction. No differences for enamel volume were found between both sides of control individuals, and between these and samples from hypofunctional side in BoNTA-group. Enamel volume from saline-injected side was reduced when compared with experimental side (p<0,01). No differences in dentine volume, thickness of enamel and dentine, and mesial root length were found for any group. Conclusion: The amount of enamel in hypofunctional molars remains unaffected after unilateral BoNTA intervention in the masseter, but contralateral side showed reduced enamel volume. Therefore, increased functional wearing during unilateral chewing after BoNTA intervention should be considered.

How Amira-Avizo Software is used

In Avizo 9,2 (Thermo Scientific™, USA), the obtained 2D images were used to  segment the whole 3D volume around the crown and roots of the first mandibular molar (M1) (Figure 1A). A threshold-based selection with a
manual correction was implemented to select specifically the enamel and dentine.