Exploring Developmental Interactions Between Speech and Orofacial Functions in Preschoolers: A Cross-Sectional Study

Speech and orofacial functions (breathing, swallowing, and chewing) both develop within the stomatognathic system and share common anatomical structures and motor control mechanisms. Theoretical models suggest that early orofacial motor experiences may shape speech development. However, empirical evidence examining these relationships during the preschool years remains scarce.

This study explored the relationship between speech and orofacial functions in preschool children. We hypothesised that this relationship is not direct but indirect, with oral motor competence, operationalised through non-speech orofacial movements (NSOMs), acting as a candidate mediator. We examined (a) whether typically developing (TD) children and children with speech sound disorders (SSD) differ in orofacial functions and NSOMs, (b) the relationships among speech sound accuracy, NSOMs, and orofacial functions, and (c) whether NSOMs predict speech sound accuracy and orofacial functions, and whether orofacial functions predict speech sound accuracy.

A cross-sectional study was conducted with 168 French-speaking preschool children aged 3-5; 9 years (118 TD, 50 SSD). Speech sound accuracy was measured using percentage of consonants correct (PCC). NSOMs and orofacial functions (breathing, swallowing, and chewing) were evaluated using standardised protocols (OMES, TEST B, ABPA). Group comparisons were performed using MANCOVA, relationships were examined through partial correlations controlling for age, and multiple linear regression analyses.

Children with SSD demonstrated significantly lower scores than TD peers on both NSOMs (F(1162) = 11.45, p = 0.001) and orofacial functions (F(1162) = 11.66, p < 0.001). Partial correlations revealed significant associations among all three variables (NSOMs-orofacial functions: r = 0.36, p < 0.001; NSOMs-PCC: r = 0.36, p < 0.001; orofacial functions-PCC: r = 0.19, p < 0.05). Regression analyses demonstrated that NSOMs significantly predicted both speech sound accuracy (β = 0.87, p < 0.001) and orofacial functions (β = 0.21, p < 0.001), whilst orofacial functions also predicted speech sound accuracy (β = 0.78, p = 0.015).

Speech and orofacial functions appear interconnected early in the preschool years through a dual pattern: an indirect link, for which oral motor competence (NSOMs) is a candidate mediator, alongside a direct association best interpreted as co-occurrence. These interpretations remain preliminary and require longitudinal confirmation. If replicated, the findings suggest that orofacial screening could inform speech assessment in children referred for speech difficulties, and that speech screening could be considered when orofacial myofunctional disorders are suspected.

What is already known on this subject Theoretical models propose that speech and orofacial functions draw on shared motor control mechanisms, and that early orofacial motor experience may scaffold speech development. Empirical work has examined this relationship mainly as a direct link, in school-age children and clinical populations. The possibility of an indirect link, with oral motor competence as a candidate mediator, has rarely been explored, and almost never in preschoolers. What this study adds to the existing knowledge This study is among the first to examine the relationship between speech sound accuracy, NSOMs, and orofacial functions in preschool children, extending to this age group a question previously studied mainly in older samples. It reframes the relationship around an indirect rather than a direct link: oral motor competence, indexed by NSOMs, emerges as a candidate mediator, alongside a direct speech-orofacial association best understood as co-occurrence. What are the clinical implications of this study? If replicated in longitudinal studies, these findings suggest that assessing orofacial functions could provide complementary information when evaluating children referred for speech difficulties. Conversely, speech could be screened when orofacial myofunctional disorders are suspected. Such screening would enrich rather than replace comprehensive speech assessment. NSOMs and myofunctional exercises should not be assumed to treat speech directly, since treatment effects were not examined.