Longitudinal analysis of bite force and strength of orofacial tissues during orthodontic aligner treatment

Orthodontic aligners have introduced new approaches in orthodontics, but their effects on the stomatognathic system remain debated. This longitudinal study evaluated the maximum molar bite force and strength of orofacial tissues during orthodontic treatment with aligners.

Twenty individuals (16 women and 4 men) participated, with an average age of 30.8 ± 10.9 years, all having natural permanent dentition except for the third molars and no temporomandibular dysfunction. All participants were indicated for treatment with aligners and monitored over four timepoints: pretreatment, 1 month, 3 months, and 6 months after the start of treatment. The variables measured included molar bite force (right and left) using a digital dynamometer and strength of orofacial tissues (lips, tongue, and buccinator muscles) using the Iowa Oral Performance Instrument. Statistical analysis was performed using repeated measures (analysis of variance, ANOVA) and Tukey's post hoc test (P < 0.05).

The maximum molar bite force significantly decreased after the start of treatment, with a trend of continuous reduction over 6 months (p = 0.04), although there were no significant differences between the timepoints and no significant changes in the left maximum molar bite force. The pressure exerted by the tongue and lips increased after the first month of aligner use, stabilizing afterwards, while buccinator muscle pressure progressively increased, showing significantly higher values compared to the pretreatment timepoint (right: 1 month, P = 0.002; 3 months, P = 0.0003; 6 months, P < 0.0001; left: 1 month, P = 0.007; 3 months, P = 0.0001; 6 months, P < 0.0002).

Orthodontic aligners significantly alter the function of the stomatognathic system, reducing bite force and increasing buccinator muscle pressure.