Growth Relationships Between the Mandible and Standing Height by Occlusion

Objective: To measure longitudinal growth of the mandible and standing height from 6-13 years in Class I normal occlusions (CINO) and Class II malocclusions (CIIM), and correlate the variables to describe the strength of the associations in the occlusion groups.    

Method:

Cephalograms of 30 male and 28 female participants in the Iowa Growth Study were used [IRB approval].  Dial calipers were used to measure mandibular length between articulare-pogonion (Ar-Pg).  Standing height measurements were obtained from the Iowa Growth Study. Spearman correlations were used to correlate growth of standing height and articulare-pogonion in subjects with CINO (15 males and 15 females) and CIIM (15 males and 13 females).  The Fisher Z method tested for significant differences in correlation coefficients of growth measures.

Result: CINO correlation coefficients ranged from -0.01 to 0.7.  No CINO males had significant correlations but CINO females aged 9 and 10 had significant correlations (r=0.7235 p=0.0052, r=0.5804, p=0.0479).  CIIM correlation coefficients ranged from -0.2 to 0.8.  CIIM males age 13 and females age 11 had significant correlations (r=0.8333, p=0.0102, r=0.6993, p=0.0114, respectively). The only significant difference in correlations between the two occlusion groups occurred at age 9 in females (r=0.7235 [CINO]; r= -0.0070 [CIIM], p=0.0448).  Growth curves for mandibular length and for standing height were similar but key differences occurred in growth acceleration in both genders in both occlusion groups.  Conclusion:

Correlations between growth in standing height and length of mandible in CINO and CIIM subjects were low to moderate positive.  The correlations have minimal clinical application.  

Study support: University of Iowa Dows Research Award