Functional Incisal Loading Regulates Nasal Septum Cartilage Ossification

Background: The mechanisms guiding ossification of the nasal septal cartilage (NSC) remain unclear. This investigation examined whether functional incisal forces influence the extent of nasal septal ossification. Methods: De-identified Cone Beam Computed Tomography (CBCT) scans from 205 adult orthodontic patients were analyzed. Subjects were classified by overbite and mandibular plane angle into deep bite (n = 68), open bite (n = 67), and control (n = 70) groups. Midsagittal CBCT views were used to measure the areas of the nasal septal cartilage, perpendicular plate of the ethmoid (PPE), vomer, and maxillary process. The percentage area of the PPE relative to the total septal area was calculated. The linear contact length between the PPE and vomer, and the cartilage extension (CE) between them, were also measured. To assess biomechanics, impact force during cutting of hard food (carrot) was measured in vitro using an Instron machine. In vivo, acceleration and velocity during carrot biting at impact were recorded in 5 volunteers using high-speed video. Results: Open bite patients demonstrated significantly greater ossification of the septal cartilage compared with deep bite patients. The contact length between the PPE and vomer was significantly shorter in deep bite cases, while CE length was significantly greater in deep bite cases compared with open bite cases. Gender, sagittal dental relationship, and overbite magnitude showed no significant influence on septal ossification. PPE-vomer contact was shortest when only the second molar was in occlusion, whereas CE length was greatest in patients with a reduced mandibular plane angle. Biomechanical analysis showed that incisal cutting of hard food generates high impact forces due to both bite force and rapid mandibular acceleration over a short distance, producing high-velocity impact loads. These forces were significantly reduced in hyperdivergent patients with an open bite greater than 5 mm. Conclusion: Functional incisal loading influences nasal septal development, with elevated incisal forces inhibiting endochondral ossification of the NSC. PPE-vomer contact length and CE length are useful indicators of the effect of incisor occlusion on septal ossification. These findings support a functional role of occlusion in shaping both the cartilaginous and bony nasal septum.