Facial Flatness Indices: A Comparison of Two Methods of Assessment

OBJECTIVES: The objective of the study was to evaluate and compare facial flatness indices calculated from the trigonometric formula as opposed to those generated from the direct measurements on three-dimensional radiographs. MATERIAL AND METHODS: A total of 322 cone-beam computed tomography radiographs were digitized and three facial indices (frontal, simotic, and zygomaxillary) were assessed in two different methods and compared between different groups. RESULTS: There was a discrepancy between facial flatness indices generated from the two different approaches. The highest difference was seen in the findings of the simotic index and the lowest for the zygomaxillary index. No statistically significant difference was displayed in the three formula-generated flatness indices between males and females and between growing and non-growing subjects (P > 0.05). The zygomaxillary index was the only measurement revealing no statistically significant difference in Class III sagittal malocclusions (t = −0.5 P = 0.621). The orthodontic application would yield to the same interpretations for both ways of indices calculation. CONCLUSION: The validity of the trigonometric formula used to appraise facial flatness indices might be questionable. The zygomaxillary index could be more clinically considered compared to the frontal and simotic indices.