Tongue muscle strength and resting posture across sagittal skeletal patterns in adolescents: a cross-sectional study using mediation analysis and decision tree.

BACKGROUND

Tongue function significantly influences craniofacial development, yet the morpho-functional characteristics of the tongue across different sagittal skeletal patterns remain unclear. This study aimed to quantitatively evaluate tongue muscle strength and resting posture in adolescents, delineate their biomechanical pathways, and construct data-driven diagnostic models for sagittal skeletal patterns.

METHODS

A cross-sectional study was conducted on 182 adolescents (11-17 years) stratified into Class I, II, and III sagittal patterns based on the ANB angle. Maximum active tongue pressure (MTP) was measured using a digital dynamometer. Resting posture, including the Tongue Tip Index (TTI), Tongue Tip Distance (TTD), and Tongue Dorsum Distance (TDD), was evaluated using lateral cephalograms. Data were analyzed using multivariable linear regression analysis, mediation analysis, and a Chi-squared Automatic Interaction Detection (CHAID) algorithm.

RESULTS

The Class III cohort exhibited significantly reduced MTP (median: 1.65 kg) compared to Class I and II subjects (~ 2.20 kg; P < 0.001). Mediation analysis identified a partial mediation relationship: while MTP demonstrated a significant direct statistical association with the ANB angle, 32.4% of the total association was indirectly mediated through TTI. The CHAID model identified reduced MTP (≤ 1.85 kg) as the primary root node associated with Class III risk. TTI (≤ 2.57%) served as a critical secondary stratifier of Class III risk.

CONCLUSIONS

In adolescents, skeletal Class III malocclusion is associated with reduced tongue pressure and a lowered resting posture. Tongue muscle force demonstrates both a direct statistical association with the sagittal skeletal base and an indirect association mediated by the maintenance of an appropriate tongue tip position. The diagnostic model highlights reduced MTP as the primary risk indicator for Class III patterns, which is further stratified by TTI.