Cephalometric Study of Iraqi Adult Subjects with Cl I and Cl III Skeletal Relationships and Their Effects on Masseter Muscle Thickness by Using Ultrasonography


Background: Masseter muscle is one of the most obvious muscles of mastication and considered as one indicator ofjaw muscle activity. It has a major influence on the transverse growth of the midface and the vertical growth of themandible. This study undertaken to determine the role of cephalometric analysis for discrimination between Cl I andCl III skeletal relationships, determine the role of ultrasonography in determination of masseter muscle thickness,compare masseter muscle thickness between Cl I and Cl III skeletal relationships, and determine the effect of genderon masseter muscle thickness.Material and Method: The sample of the current study consisted of 70 Iraqi subjects 40 males and 30 females withage ranging 18-25 years. They were divided into 2 groups depending on ANB angle: class I skeletal relationship 20males and 15 females and class III skeletal relationship 20 males and 15 females. The collected sample includedpatients attended for different diagnostic purposes to the Dental Radiology Department at College ofDentistry/Babylon University, standardized lateral cephalogram was taken to determine facial morphology, sixangular and eight linear measurements were assessed. Masseter muscle thickness measured ultrasonography inAl-Hilla General Teaching Hospital/Ultrasonorgaphic Department, in relaxation and contraction conditions for bothsides.Results: Various parameters measured for males and females in each class and the comparison shown statisticallysignificant differences between them (P<0.05). No difference in muscle thickness between right and left sides in thesame class (P>0.05). Gender variation showed significant difference in masseter muscle thickness during rest andocclusion conditions (P<0.001).Conclusion: Cephalometric analysis served to demonstrate the skeletal morphologies and provide a base fordiscrimination between class I and class III skeletal relationships. Ultrasonographic scanning is an important imagingprocedure. It is reproducible and simple method for accurately measuring masseter muscle thickness. Theultrasonorgaphic study has revealed variations in masseter muscle thickness among individuals with different skeletalmorphologies in each gender on one hand and between males and females in each skeletal class on the otherhand.