Contributions of anterior and posterior components of cranial flexure on skeletal classification: a cone-beam computed tomography study

Objectives: To evaluate the relationship between skeletal classification and the anterior and posterior components of cranial base flexure and glenoid fossa position. Materials and Methods: Pretreatment cone-beam computed tomography records of 420 patients were stratified by sex, age, and skeletal classification based on standards for maxillomandibular differential for age-specific patients. Cephalometric measurements (Basion, Nasion, superior aspect of glenoid fossa) were recorded, and their angular deviation, horizontal, and vertical distance from Sella were measured using a 7° constructed plane (H-P) from S-N as a reference. Results were analyzed using regression analysis and analysis of variance, along with intraclass correlation coefficient for reliability. Results: Cranial base flexure was found to be significantly smaller in Class III individuals than Class I or II, due to a larger deflection in posterior cranial base angle from the horizontal plane. The position of Basion relative to Sella was also noted to have a significantly shorter horizontal and significantly longer vertical length in these same individuals. The position of the glenoid fossa showed that Class II patients tended to have a more posterior horizontal displacement from Sella when than those in Class I or III. All measurements, except for cranial base flexure, were significantly larger in males than females. Statistical significance was measured at P < .05. Conclusions: Cranial base angle is significantly smaller in Class III individuals, due to an anteriorly positioned posterior cranial base. The posterior position of the glenoid fossa appears to contribute to the anteroposterior position of the condyle in Class II patients.