Establishment of Cephalometric Norms Using Tetragon Analysis in a Group of Yemeni Adults

Abstract

This cross-sectional study aimed to establish cephalometric norms for Yemeni adults using Tetragon analysis. They were then compared with Caucasian norms and the extent of gender differences was also determined. A total of 100 Class I skeletal relationship standard lateral cephalogram images (50 males, 50 females; ≥ 18 years) were taken and analyzed using the Dolphin Imaging software (v11.9). Linear and angular measurements were obtained from 20 cephalometric images, and the reliability of these measurements was assessed using the intraclass correlation coefficient (ICC), with values ranging from 0.946 to 0.997. Statistical analyses were undertaken using SPSS (v26) through which independent t-tests, Mann-Whitney U tests, and one-sample t-tests were utilized. The tetragon analysis showed lower Sella-Nasion-A point angle (SNA) (80.93° ± 3.613°) and Sella-Nasion-B point angle (SNB) (77.91° ± 3.441°) values of Yemeni adults in comparison to Caucasian norms which reflect relative bimaxillary retrusion. Inclination of the incisors to the palatal plane was also lesser while the Mandibular Plane to Palatal Plane angle (MP-PP) (24.92° ± 4.968°) indicated a horizontal growth tendency. The tetragon analysis resulted in increased Pterygomaxillare-Posterior Nasal Spine/Palatal Plane angle (Pt-PNS/PP) and decreased Pterygomaxillare-Orbitale-Posterior Nasal Spine angle (Pt-Or/PNS) which are characteristic of the tetragon. Markedly, skeletal protrusion was more pronounced in males (p=0.001) while females displayed vertical maxillary incisor height (p=0.004). As a whole, the Yemeni population exhibits distinct craniofacial features thereby signaling that the use of population-specific cephalometric standards is a must for accurate orthodontic diagnosis and treatment planning.