THE EVALUATION OF HYOID BONE IN DIFFERENT SKELETAL MALOCCLUSIONS AND GROWTH PATTERNS IN INDIAN POPULATION.

Objective: The aim of the study was to investigate the relationship of the different skeletal malocclusions as well as various growth patterns to the position and orientation of the hyoid bone. Materials and methods: A total of 60 pretreatment digital lateral cephalograms were selected according to the criteria and grouped into 3 groups, group 1: Class I (n=20), group 2: Class II (n=20) and group 3: Class III(n=20). The original 60 lateral cephalograms were also grouped under three different growth patterns into hyperdivergent (n=17), hypodivergent (n=24) and neutral (n=19) which were given according to Jarabak. Lateral cephalograms were traced and analysed on different linear and angular parameters such as H-NSL, H-FH, H-NL, H-Pog, H-Me, H-C3, NSH and MPH. The arithmetic mean and standard deviation values were calculated for each measurement. Independent sample t- test was performed to compare the difference between the skeletal classes as well as with the growth patterns. Result: The linear measurements of H-FH, H-NL, H-Pog, H-Me, H-C3 showed statistically significant differences in Class I, Class II, and Class III (p-vaule=0.03, 0.01, 0.0, 0.0 and 0.009 respectively). The angular measurements of SNA, SNB, ANB, SNH were also statistically significant (p-value=0.006, 0.0, 0.0 and 0.030 respectively) indicating the differences in respective class malocclusions. However, in the study that was grouped according to different growth patterns, viz. hyperdivergent(Hp), hypodivergent(Ho), and neutral (Nt) did show statically significant differences. (p-value<0.05). Conclusion: The hyoid bone position and orientation is different in different skeletal malocclusions. In class III malocclusion, the hyoid bone is more anteriorly and inferiorly placed. In class II malocclusion, the hyoid bone position is more posterior and more superior. The anteroposterior dimensions in different class malocclusions remained constant. No relationship could be found between different facial morphologies (growth patterns) and hyoid bone position as well as orientation.