Assessment of the effects of digit sucking habit on the masticatory musculature using motion mode Ultrasonography

Abstract

Objective : This study assessed the effect of active digit sucking on muscle thickness and fractional shortening of the masseter, lateral pterygoid, and temporalis in a population of Nigerian children using motion mode ultrasonography.
Methods : The sample consisted of 100 selected children aged 7-12 years, divided into two equal groups of digit sucking and nonsucking. Participants were matched for age groups and gender. Ultrasonography evaluation (2 D and motion mode) of the masticatory muscles was performed using a linear probe of 7.5 MHz. The muscle thickness at contraction/relaxation and fractional shortening was determined. Independent t-test, Pearson correlation coefficient, and Two-way ANOVA were used for data analysis.
Results : Whilst temporalis and lateral pterygoid muscles demonstrated a significant increase in thickness during relaxation (p<0.0001), a significant reduction in fractional shortening was observed (p<0.0001) in the sucking when compared to the non-sucking group.
Similarly, only the temporalis muscle was significantly reduced during the contraction phase (p<0.01). For masseter mid-belly, both right and left sides in digit sucking subjects showed a significant increase in the thickness at contraction. At the same time, a reduction was observed in fractional shortening (p<0.05). Males and females with digit habit showed significantly greater muscle thickness in temporalis and lateral pterygoid during contraction and relaxation phases, whereas a reduction was observed in fractional shortening. Significant associations were observed between the frequency of sucking and muscle thickness in masseter and temporalis in fractional shortening (p<0.05).
Conclusion : Our findings corroborate the assumption that persistent digit sucking in children can affect the morphology and function of the masticatory muscles.