Cephalometric features of skeletal Class I, II and III (A comparative study)


Aims: To identify the cephalometric features of three skeletal jaw relations (Class I, II and III).Materials and methods: one hundred thirty four students were selected aged 12–15 years fromsecondary schools in Mosul City, 45 with Class I normal occlusion as control, 44 with Class IImalocclusion and 45 with Class III malocclusion, after taking the lateral cephalometric radiographsaccording to ANB angle. A 20 variables (12 angular and 8 linear) were used in this study to correlatethese variables in the three skeletal Classes. Results: No significant sex differences were observed forthe majority of angular and linear measurements for the three skeletal types. Anterior cranial baselength (S–N) and saddle angle (NSAr) didn’t show significant difference among the three skeletalClasses, the posterior cranial base (S–Ar) was shorter in Class III which indicate the anteriorarticulation of the mandible. The length of maxillary base (ANS–PNS) was longer in Class II thanClass I and III which lead to maxillary prognathism. The body length of the mandible (Go–Pog),effective mandibular length (Ar–Gn) and lower anterior face height was significantly longer inClass III which lead to mandibular prognathism. The SNA angle was significantly smaller in Class IIIthan in the others. SNB and SNPog angles were larger in Class III followed by Class I and then ClassII. The gonial angle (Ar–Go– Me) was larger in Class III which acts to increase mandibular effectivelength. The (N–A–Pog) showed as convex in Class II and concave in Class III. (The U1–PP) angle waslarger in Class II followed by Class I and then by Class III. The (L1–MP) angle in Class II and III wassignificantly smaller than in Class I. Conclusion: Most of the angular and linear measurementsindicated that the skeletal differences between the Class I, Class II and Class III are concentrated within the maxillary and mandibular bases in both the anteroposterior and vertical dimensions and theirtype of articulation. The dental measurements appear to be compensated with that of skeletal one. Alsothese variables showed no significant sex differences in the majority of their measurements