Relationship Between Posterior Cranial Base Inclination and Skeletal Jaw Patterns

Introduction: Variations in nasion (N) could influence the measurement of ANB, thus affecting the interpretation of skeletal jaw relationship. Points sella (S) and N represent the anterior cranial base, a crucial role in determining the skeletal jaw patterns. Improper S-N line can affect results of lateral cephalometric analysis, as a highly tilted S-N line relative to the Frankfort Horizontal Plane (FHP) can lead to discrepancies between the analysis results and true morphology. Therefore, alternative methods, such as analysing the posterior cranial base (sella to basion, S-Ba), are needed to establish a diagnosis. Objective: To determine relationship between posterior cranial base inclination and skeletal jaw patterns. Materials and Methods: The study included male and female subjects aged 20-45 who had not undergone orthodontic treatment. The lateral cephalograms with clear visibility and a 5°-7° tilted of the S-N plane relative to the FHP were selected. The cephalograms were grouped based on skeletal jaw patterns: Class I, Class II, and Class III. Results: Spearman correlation tests showed a relationship between the posterior cranial base inclination in Class II and Class III skeletal jaw patterns (p<0.05). Conclusions: The average inclination of the posterior cranial base was greater in the Class II skeletal jaw patterns group (retrognathic mandible) compared to the Class III skeletal jaw patterns group (prognathic mandible). Significant differences were observed in the inclination of the posterior cranial base between Class I and Class III then between Class II and Class III skeletal jaw patterns. There was a moderate significant relationship between posterior cranial base inclination in Class II and Class III skeletal jaw patterns within the Indonesian subpopulation.