Jaw-specific stem cell dynamics are associated with distinct enamel architecture in mouse incisors

The continuously growing mouse incisor serves as a model for stem cell-driven tooth renewal. Although mice possess maxillary and mandibular incisors, most studies have focused on the mandible. Potential differences in structure and renewal between these serially homologous organs remain insufficiently characterized.

Mandibular incisors are longer and contain greater enamel volume, mineral density, and mineral content than maxillary incisors, whereas maxillary incisors are more curved and display a larger cross-sectional area. Mineral density increases along the apical-to-incisal axis in both teeth, although mandibular incisors exhibit greater mineral deposition and retention. The maxillary incisor contains a larger pool of cycling progenitors with proliferation dynamics comparable to those of the mandibular incisor. Although ameloblast differentiation initiates at a similar position in both incisors, the mandibular incisor contains a ~20% longer secretory-stage ameloblast region. Consistent with this observation, gene expression analysis reveals earlier Igfbpl1 expression onset in the mandible.

Homologous mouse incisors differ in progenitor pool size, ameloblast maturation, and enamel formation. Increased enamel output in the mandible is associated with a prolonged secretory phase, whereas the maxilla contains an expanded progenitor pool. These findings support the maxillary incisor as a complementary model for studying mechanisms that regulate tooth renewal.