The prevalence of posterior tongue tie in patients with transverse maxillary deficiency

Objectives To investigate the prevalence of posterior tongue tie in orthodontic patients using numerical and clinical assessment methods in order to identify an association between posterior tongue tie and transverse maxillary deficiency. Materials and methods Seventy-nine participants from an orthodontic clinic were divided into two groups. The first group of 44 patients exhibited a skeletally narrow maxilla and required maxillary skeletal expansion (MSE group) and 35 patients without a transverse discrepancy comprised a control group. Posterior tongue tie was examined by the Kotlow tongue tie classification, tongue range of motion ratio (TRMR) and via a clinical assessment. The prevalence of posterior tongue tie was compared between the two groups. Results There was no significant difference in the level of the Kotlow classification grade between the two groups (p > 0.05) and the overall majority was diagnosed as normal. However, a higher proportion of posterior tongue tie was found in the MSE group than in the control group by clinical assessment (MSE group, 72.7%; control group, 42.9%; p = 0.005). The proportion of TRMR grade 2 was also higher in the MSE group than in the control group (p = 0.001). Of the subjects diagnosed with posterior tongue tie by clinical findings, approximately 94% showed TRMR grades 2 or 3. Conclusions A clinical assessment of posterior tongue tie was found to be simple and accurate, whereas a numerical assessment alone provided diagnostic difficulty. Considering the high prevalence of observed posterior tongue tie in the MSE group, there was a significant association between posterior tongue tie and transverse maxillary deficiency.