Master’s Degree Awarded to Researcher Mohammed Mohammed Al-Najhi in Orthodontics

Researcher Mohammed Mohammed Ali Al-Najhi was awarded a Master’s Degree in Orthodontics for his thesis titled: Three-Dimensional Evaluation of Upper Airway Volume in Skeletal Class III Individuals with Maxillary Retrognathia‎, which was submitted to the Department of Orthodontics, Faculty of Dentistry – Sana’a University. The MA defense was held on Thursday, August 27, 2026‎.

The MA Viva-voce Committee, which was formed based on a resolution issued by the Graduate Studies and Scientific Research Council, consisted of the following:
• Prof. Khaled Ahmed Al-Dhara’i – Thamar University – External Examiner and Committee Chair.
• Prof. Ahmed Ali Obayya – Sana’a University – Principal Supervisor and Committee Member.
• Assoc. Prof. Fouad Lotf Al-Mutarrib – Sana’a University – Internal Examiner and Committee Member.
The study aimed to evaluate the three-dimensional dimensions of the upper airway in adults with skeletal Class III malocclusion resulting from maxillary retrognathia and compare them with individuals exhibiting a skeletal Class I relationship, thereby contributing to a better understanding of the relationship between maxillary skeletal changes and upper airway dimensions.
The comparative study analyzed cone-beam computed tomography (CBCT) images of 60 adults, divided equally into two groups: the first comprised 30 cases of skeletal Class III malocclusion associated with maxillary retrognathia, while the second was a control group of 30 individuals with a skeletal Class I relationship.
Volumetric measurements were obtained for several regions of the upper airway, including the nasopharynx (NP), oropharynx (OP) or velopharynx (VP), glossopharynx (GP), and laryngopharynx (LP), in addition to the total upper airway volume (TUV), using Dolphin Imaging Software, Version 12 Premium.
The minimum cross-sectional area (MCA) and its anatomical location were also recorded. Inter-examiner measurement reliability was assessed using the intraclass correlation coefficient (ICC), while statistical comparisons were performed using the independent-samples t-test and Mann–Whitney U test, with statistical significance set at P < 0.05.
The results showed that the skeletal Class III group with maxillary retrognathia had a statistically significant reduction in total upper airway volume (TUV), with a mean volume of 25,142.90 ± 5,500.45 mm³, compared with 29,253.63 ± 6,094.08 mm³ in the Class I group (P = 0.008).
The Class III group also showed a statistically significant reduction in oropharyngeal volume (OP), which measured 16,142.53 ± 4,890.06 mm³, compared with 19,248.47 ± 4,162.33 mm³ in the Class I group (P = 0.010).
Regarding the velopharynx (VP), the results demonstrated a statistically significant difference, with a volume of 9,919.33 mm³ in the Class III group versus 12,703.70 mm³ in the Class I group (P = 0.004).
By contrast, no statistically significant difference was observed in laryngopharyngeal volume between the two groups, with P = 0.564.
An upward shift in the location of the minimum cross-sectional area (MCA) was also observed in the Class III group, indicating a change in the location of the narrowest region of the upper airway consistent with the structural abnormality associated with maxillary retrognathia.
The study also identified sex-related differences within the Class I group, with females exhibiting a significantly larger minimum cross-sectional area than males (P = 0.031). No statistically significant sex-related differences were observed within the Class III group.
The measurement reliability assessment further demonstrated excellent inter-examiner reliability, with the intraclass correlation coefficient (ICC) exceeding 0.99, reflecting a high degree of accuracy and consistency in the measurements obtained in the study.
The study concluded that maxillary retrognathia in cases of skeletal Class III malocclusion is associated with a significant reduction in upper airway volume, particularly in the velopharyngeal and oropharyngeal regions. The findings also demonstrated an upward shift in the location of the most constricted part of the airway, reflecting the anatomical site of the skeletal abnormality.
The study emphasized the importance of incorporating upper airway assessment into orthodontic and orthognathic surgical treatment planning for Class III patients with maxillary retrognathia, as this can enhance diagnostic accuracy and facilitate the development of appropriate treatment plans
The defense session was attended by a number of academics, researchers, students, colleagues, and the researcher’s family.