Facial prognathism and its relation to the cranial base in Brazilian children with Class I malocclusion

The objective of this work was to study the degree of the facial prognathism, considering the relationships between the SNA and SNB angles with the saddle angle (NSAr and NSBa). The sample consisted of eighty cephalometric roentgenograms, taken in lateral norm, of Brazilian white children, forty boys and forty girls, with both dental and skeletal, class I malocclusions, with ages between 9 years and 2 months old and 13 years and 7 months old. Data were statistically analysed and the sample was divided in three groups considering the mean value and the standard deviation of the NSAr angle. Sixteen subjects (seven boys and nine girls, 20 percent of the sample) presented an NSAr angle that was smaller than 119.5 degrees (x - 1s); twenty subjects (forteen boys and six girls, 25 percent of the sample), showed an NSAr angle more than 127.5 degrees (x + 1s) and forty-four subjects (nineteen boys and twenty-five girls, 55 percent of the sample) had an NSAr angle value between 119.5 and 127.5 degrees (x +/- 1s). The results led to the following

Conclusions: 1. There is a negative correlation, statistically significant between the saddle angle (NSAr and NSBa) with the SNA angle in subjects with class I malocclusions. An NSAr or NSBa angle higher than the mean value plus one standard deviation, it is associated with of the maxilla retrognathism and contrariwise. 2. There is a negative correlation, statistically significant between the sadle angle (NSAr and NSBa) with the SNB angle in subjects with malocclusions. An NSAr or NSBa angle higher than the mean value plus one standard deviation, it is associated with the mandible retrognathism and contrariwise. 3. The normal values of the SNA and SNB angles for an individual and the degree of the facial prognathism should be determined individually, since that the values of these angles might be affected for cranial base morphology.