The purpose of this retrospective longitudinal study was to compare 7 cepha
lometric measurements of the cranial base in subjects with Class I and Clas
s It skeletal patterns at ages 1 month, 2 years, and 14 years. A sample of
22 Class I and 21 Class II subjects was selected; the inclusion criteria we
re overjet, ANB, and Harvold unit difference. Analyses of head circumferenc
e, crown-rump length, and weight revealed no significant (P > .15) differen
ces between the Class I and Class II infant subjects at the initial age (1
month). One angular and 6 linear measurements were first compared with a mu
ltivariate analysis of variance, which revealed significant effects for age
(P = .0001) and the age by skeletal pattern interaction (P = .0266) but no
t for skeletal pattern (P = .3705). Analyses of variance showed significant
(P < .0001) age effects for each of the cephalometric variables but no sig
nificant skeletal pattern effects (P > .10). The anterior cranial base meas
urement of nasion to sphenoethmoidal suture was the only variable found to
have a significant age by skeletal pattern interaction (P < .006), which re
vealed a difference in the timing of its growth spurt that occurred between
1 month and 2 years in the Class I subjects and between 2 years and 14 yea
rs in the Class II subjects. There were no significant differences between
the skeletal classes at any of the 3 ages evaluated. Conclusions from this
study indicate that cranial base growth patterns are similar for Class I an
d Class ii subjects and that the premise of a more obtuse "saddle angle" or
cranial base angle in Class II skeletal patterns was not supported.