Application of the Ricketts Analysis to Children in the Primary Dentition: Second Report: A Study of Annual Growth

This research was initiated to answer the question of whether Ricketts Analysis could be applied to the primary dentition of Japanese children.221 subjects with normal occlusion were followed longitudinally with lateral cephalograms from the ages of 3 to 10. Each one of the coefficients of regression was used to obtain the annual growth, then, mean values, standard deviations and annual growth rates were calculated to compare children in their primary dentition period (3 to 5 years old) to those in their mixed denture period (6 to 10 years old). The findings were as follows: 1) For the tooth measurements, no major changes were observed in molar relation and canine relation from the primary dentition to those of the mixed dentition. Major differences were observed, however, between the deciduous teeth and permanent teeth for the measurements of the incisors. 2) Convexity and lower facial height, which show the relationship between the upper and lower jaws, were almost the same in both the primary dentition and in the mixed dentition. 3) Concerning the relation between the cranial base and the face. Point A showed a lower degree of forward movement than that of Nasion duringe the period starting in the primary dentition and continuing up to the mixed dentition period. Pogonion was found to exhibit a smaller degree of forward growth during and after the period of mixed dentition than that reported in the past. 4) With regard to internal structure, it was found that cranial deflection decreased while the mandibular are chowed no changes during the period of change from primary dentition to mixed dentition. These findings differ from what has been reported until now. In other items examined, however, a discrete degree of growth was observed during this period. 5) In applying the Ricketts Analysis to children in their primary dentition, there is a need to take into consideration mean values and standard deviation values in the clinical norms and clinical deviations for each age.