Mechanobehavior and mandibular ramus length in different facial phenotypes

Area of Science:

• Orthodontics and Craniofacial Biology
• Biomechanical Engineering
• Human Anatomy

Background:

• Understanding the relationship between craniofacial structure and jaw mechanics is crucial for diagnosing and treating various conditions.
• Mechanobehavior scores (MBS) offer a quantitative measure of temporomandibular joint (TMJ) function.
• Facial phenotypes are known to influence craniofacial morphology and potentially biomechanical behavior.

Purpose of the Study:

• To investigate the correlation between mandibular ramus length (Co-Go) and MBS.
• To determine if MBS differ significantly between distinct facial phenotypes (dolichofacial and brachyfacial).

Main Methods:

• Cephalometric radiography and cone beam computed tomography were used to measure Co-Go and mandibular plane angles (SN-GoGn).
• Dynamic stereometry and electromyography measured TMJ energy densities (ED) and duty factors (DF) to calculate MBS.
• Polynomial regressions, K-means cluster analysis, and ANOVA were employed for statistical analysis.

Main Results:

• MBS demonstrated a significant correlation with Co-Go in both females (R² = 0.57) and males (R² = 0.81).
• Cluster analysis revealed three distinct groups, with dolichofacial subjects exhibiting shorter normalized Co-Go and differing MBS compared to brachyfacial subjects.
• The mandibular plane angle (SN-GoGn) was significantly larger in dolichofacial subgroups than in the brachyfacial group.

Conclusions:

• MBS are significantly correlated with mandibular ramus length (Co-Go) within each sex.
• Significant differences in MBS and Co-Go exist between brachyfacial and dolichofacial individuals, highlighting the influence of facial phenotype on jaw biomechanics.