Mandibular rotation and remodeling changes during early childhood.

OBJECTIVE

To describe the mandibular rotation and remodeling of younger children.

MATERIALS AND METHODS

The sample included 43 males and 43 females who participated in the Bolton-Brush Growth Study at Case Western Reserve University in Ohio. They were chosen on the basis of having Class I (n = 45) or Class II (n = 41) molar relationships and longitudinal lateral cephalograms at three developmental stages of the dentition: late primary (T1: 5.7 +/- 0.5 y), early mixed (T2: 8.4 +/- 0.6 y), and full permanent dentition (T3: 15.4 +/- 0.5 y). Each subject's cephalograms were traced and four landmarks were digitized. Cranial base and mandibular superimpositions were performed with the use of natural reference structures.

RESULTS

Yearly rates of true rotation, apparent rotation, and angular remodeling showed significant (P < .05) changes throughout. True rotation was moderately correlated with angular remodeling and apparent rotation. Although no significant sex differences in annual rates of rotation were noted, subjects with Class I molar relationships showed significantly more angular remodeling from T2-T3 than did subjects with Class II molar relationships. Rates of true forward rotation were significantly greater with T1-T2 than with T2-T3 (1.3 and 0.7 degrees/y, respectively).

CONCLUSION

Although significant amounts of true mandibular rotation and angular remodeling occur during childhood and adolescence, true rotation is greatest during the transition from late primary to early mixed dentition.