Craniofacial Growth in Adolescence and its Influence on the Mandibular Incisor Crowding

To analyze craniofacial growth during adolescence from the ages of 12 to 21 years and its relation to late mandibular incisor crowding.

The study included 61 orthodontically untreated subjects (49% males). Lateral cephalograms were used to assess the jaw growth and inclination of the incisors. Little's Irregularity Index and the anterior mandibular dental arch depth of mandibular dentition were measured.

A reduction of the skeletal class angle (ANB) was observed in both genders, although it was significant only in males (η2=0.188; p=0.015). The growth of the mandible was more prominent compared to that of the maxilla, and it was more prominent in males than in females. The skeletal vertical dimension, however, demonstrated a significant reduction in both genders (η2=0.527-0.593, p<0.001). The mandibular incisors tended to retrocline in both genders, while the maxillary ones tended to procline in males, and slightly retrocline in females. A decrease in the mandibular dental arch depth occurred in both genders (η2=0.259; p<0.05). An increase in the irregularity of incisors for 1.8±1.7 mm on average (95% CI 1.3-2.2; η2=0.520; p<0.001) was observed in both genders. A logistic regression revealed that less sagittal growth of maxilla (increase of SNA angle ≤2°) and reduction of convexity in skeletal sagittal interjaw relationship (reduction of ANB ≥1°) were significant predictors of the occurrence of crowding (Δ Little Irregularity Index ≥1mm) yielding odds ratios of 4.9 and 4.8.

The differential growth of the maxilla and mandible is related to the occurrence of late crowding, mostly in smaller amounts in maxillary sagittal growth compared to the mandible.