Deformation of Nasal Septal Cartilage During Mastication

Objective: To measure the strains generated in the nasal septal cartilage during mastication and masseter stimulation in order to determine if the cartilage plays an active mechanical role in mid-facial mechanics and to build a biomechanical model of the snout.

Methods: Ten miniature pigs were used. Access to the nasal cartilage was gained through a window in the anterior part of the frontal bone. Differential variable reluctance transducers (DVRT) were implanted dorsally in an antero-posterior orientation across the septo-ethmoid junction and across the naso-frontal suture. The animals ate naturally while masticatory strains were recorded along with electromyography of the masseter and temporalis muscles. Animals were re-anesthetized and access to the anterior part of the cartilage was gained. A third DVRT was implanted dorsally in the antero-posterior orientation at that location. The masseter was then stimulated and the resultant strains at all three locations were simultaneously recorded.

Results: Masticatory strains were compressive with similar values at both the septo-ethmoid junction (-1108±495µe, n=7) and the suture (-1335±582µe, n=6). The suture showed similar strains during masseter stimulation (-682±410, n=9), whereas the septo-ethmoid junction showed no strain (-19±24µe, n=10), suggesting that the suture and the septo-ethmoid junction are loaded by different sources during mastication. The strains recorded in the anterior part of the cartilage during masseter stimulation were 10-fold higher than the naso-frontal suture (-7556±2891µe, n=9).

Conclusion: These results suggest that the nasal cartilage plays an active role in facial mechanics by damping and re-distributing the stresses generated during mastication. The finding of compression in the dorsal part of cartilage is consistent with a “bend-up” model of the snout.

Supported by PHS award DE08513 from NIDCR