Alveolar Bone Growth Accommodates Dental Arch Expansion During Adolescence

Objectives: During childhood and early adolescence, the dental arches can expand substantially in width and length. However, it remains largely unknown how alveolar bones in the two jaws grow to accommodate these changes. The present study examined alveolar bone modeling in the molar and incisor regions of adolescent pigs.
Methods: Ten domestic pigs, of two ages (3-month and 5-month, correspondent to pre- and post-emergence of the first permanent molars, respectively), were used. All pigs underwent injections of fluorescent labels, calcein and alizarin complexon (12.5mg/kg), 10 and 3 days before sacrifice, respectively. Alveolar bone specimens containing the maxillary and mandibular first molar and central incisor regions were processed into buccal-lingual and labial-lingual sections, respectively, without decalcification. Fluorescent images from the buccal/labial and lingual surfaces were captured, from which surface bone modeling was qualitatively and quantitatively assessed. Surface bone mineralization rate (MAR) and mineralization band width (MBW) measurements were compared using mixed-model repeated measures ANOVA tests to evaluate the differences between ages and jaws.
Results: Qualitatively, the buccal/labial surfaces were characterized by consistently abundant mineral apposition, while the lingual surfaces were characterized by resorption (molar region) or mixed resorption/scattered apposition (incisor region). Quantitatively, buccal surface apposition in the molar region remained unchanged with age, but was significantly greater in the mandible than in the maxilla (mean MAR: 25.0µm/day vs. 9.3µm/day, p=0.001; mean MBW: 446.7µm vs. 196.5µm, p=0.001). Labial surface apposition in the incisor region was neither different between age groups nor different between the two jaws (mean MAR: 29.8µm/day vs. 21.3µm/day, p=0.395; mean MBW: 428.8µm vs. 310.3µm, p=0.299).
Conclusions: During adolescence, alveolar bone consistently grows in the buccal and labial directions to accommodate molar and incisor movement, respectively. Transversely, buccal surface growth in the mandibular molar region exceeds that in the opposing maxillary region, likely to compensate for midpalatal suture growth in the maxilla.