Tongue position for lingual frenulum assessment

Purpose: to compare the movements of elevation and protrusion of the tongue in order to determine which position provides better lingual frenulum assessment. Methods: a database of 92 audiovisual recordings of subjects over six-years of age diagnosed with ankyloglossia was used to verify the shape of the tip of the tongue during tongue elevation and protrusion. The Chi-Square Test for Proportion was applied to verify possible differences between the postures of elevation and protrusion. The significance level of 5% (p<0.05) was adopted. Results: the statistical analysis demonstrated that both shapes, i.e., the V-shaped one and the heart-shaped one are more visible during tongue elevation than during tongue protrusion. Conclusion: elevation is the position that allows the best observation of the shape of the tip of the tongue.

concerning the lingual frenulum tend to make the diagnosis difficult and doubtful, interfering with the reliability of the diagnosis 28 . Having standardized assessment criteria is essential to avoid such misunderstandings.
Based on those theoretical assumptions, the formulated hypothesis was that the tongue elevation is the posture that allows the best observation of the anatomical characteristic of the lingual frenulum during its assessment. Thus, this study aims to compare the movements of elevation and protrusion of the tongue, in order to determine which posture provides a better lingual frenulum assessment.

METHODS
Prior authorization of services for the realization of this study was requested, the signing of the Consent and Informed Form being exempted, for using secondary data, and the research was approved by the Research Ethics Committee of CEFAC Health and Education, CAAE 48132015.3.0000.5538, under opinion number 1,181,172. This is a cross-sectional exploratory descriptive retrospective study, in which a database of 92 audiovisual recordings of subjects over six-years of age diagnosed with ankyloglossia was used. The lingual frenulum assessment was performed by two speech language pathologies highly experienced in lingual frenulum evaluation. Both therapists assessed the lingual frenulum by means of the protocol proposed by Marchesan 26 .
All archives that did not allow accurate analysis of the tongue's elevation and protrusion position, as well as those belonging to subjects previously submitted to surgery for release of the lingual frenulum, or with a history of neurological and oncological diseases were excluded.
Only audiovisual recordings of tongue elevation and protrusion were considered for the study. The video recordings were analyzed frame by frame by using the Media Player Classic software, version 1.7.13. For the latter analysis, the sections of maximum elevation and maximum protrusion were selected. The cropped video imagens were inserted on a PowerPoint slide.
The following step consist of a blind evaluation performed by two other speech language therapists, who analyzed the shape of the tongue when elevated and protruded. They classified the shapes as round, V-shaped or heart-shaped ones (Figure 1).

INTRODUCTION
The lingual frenulum is a dynamic three-dimensional structure formed by a central fold in a layer of fascia that extends across the floor of the mouth. The range in the lingual frenulum morphology is created by variabilityon a spectrum -of several factors 1,2 . Ankyloglossia is characterized by a restriction of tongue movements 1,3 .
Ankyloglossia is a complex condition impacting both mothers and infants. This requires interdisciplinary approach for assessment and treatment. When ankyloglossia is characterized by a lingual frenulum attached to the apex of the tongue and visible from the inferior alveolar crest it can be easily diagnosed. Controversy around the diagnosis of ankyloglossia occur when the alteration is not so visible. That requires a structural and functional assessment of the oral cavity 4 .
Tongue movements are essential for the performance of orofacial functions. It must be highlighted that tongue elevation is needed for proper tongue rest posture, for adequate nasal breathing, swallowing and production of the 3,4 . An important aspect to remember is that protrusion of the tongue is not required for sucking, swallowing, breathing, chewing, and speaking.
In the clinical practice we come across professionals from several fields who assess lingual frenulum by asking the patient to protrude the tongue. If the subject can protrude the tongue beyond the vermillion border of the lower lip the professionals do not consider frenotomy to be indicated [23][24][25] . However, the literature cites a set of anatomical and functional characteristics that must be considered for ankyloglossia diagnosis [22][23][24][25][26] .
Brito et al. state that when both the assessment of lingual frenulum and therapy plan are performed through personal criteria, they may fail, and an interdisciplinary approach may be difficult 27 . Controversies among health professionals from different fields elevation. It was also observed whether the tongue could protrude the tongue beyond the vermillion border of the lower lip ( Figure 2).
During tongue elevation, it was observed whether there was concomitant elevation of both the back of the tongue and the floor of the mouth. Those aspects could not be observed during protrusion, only during

RESULTS
Ninety-two audiovisual recordings of subjects diagnosed with ankyloglossia were analyzed, 34 females (36.96%) and 58 males (63.04%), aged from 6 to 41, 8 years being the median. Table 1 shows the results from the descriptive statistical analysis of tongue protrusion and elevation. The statistical analysis demonstrated that both tongue tip shapes, the V-shaped or the heart-shaped (Figure 3), are more visible during tongue elevation than during tongue protrusion (p<0.001).
After the analysis, the data were tabulated by using MS-Excel spreadsheets and the software Statistical Package for Social Sciences (IBM SPSS), version 25.0, was used for statistical analysis. The Chi-Square Test for Proportion was applied to verify possible differences between the postures of elevation and protrusion. The significance level of 5% was adopted. This finding demonstrates that the protrusion position does not allow for an accurate identification of ankyloglossia. Table 2 shows that most subjects with ankyloglossia (97.83%) can extend the tongue beyond the vermillion border of the lower lip during protrusion (Figure 3).  state that elevation is the best posture to assess the lingual frenulum. Another relevant datum is that 97.83% of the subjects with ankyloglossia were able to extend the tongue beyond the vermillion border of the lower lip, during protrusion (Table 1).
A comparison of all variables between tongue elevation and the extending of the tongue beyond the vermillion border of the lower lip, during protrusion, in subjects with ankyloglossia, demonstrated a statistically significant difference (p<0.001), as shown in Table 2. Thus, protrusion is not a relevant posture for ankyloglossia diagnosis.
An important aspect to remember is that tongue protusion is not required for oral functions, such as sucking, swallowing, breathing, chewing, and speaking. On the other hand, tongue elevation is essential for swallowing, for producing many speech sounds, and for proper tongue rest posture 28,[34][35][36] .
It is important to emphasize that a proper lingual frenulum assessment must consider a set of characteristics for the diagnosis of tongue movement restriction 36 . Unlike tongue protrusion, tongue elevation allows for the assessment of the lingual frenulum, since this position favors the visualization of the anatomical characteristics regarding thickness, attachment of the tongue to the floor of the mouth, and shape of the tip of the tongue 36 .

DISCUSSION
This study aimed to compare the position of elevation and protrusion of the tongue to determine which position provides better lingual frenulum assessment.
Of the 92 subjects aged from 6 to 41 diagnosed with ankyloglossia, whose audiovisual recordings were analyzed, 58 were males (63.04%). This finding agrees with studies that report higher prevalence of ankyloglossia in males than in females 29,30 .
The statistical analysis demonstrated that both tongue tip shapes, the V-shaped and the heart-shaped, (Figure 3) are more visible during tongue elevation than during tongue protrusion (p<0.001). These findings demonstrated that tongue elevation is the position that allows for the best observation of the shape of the tip of the tongue, being possible to identify, more accurately, the presence of V-shaped or heart-shaped tip in subjects with ankyloglossia. Thus, those findings agree with proposals of most assessment tools 5,6,8,[12][13][14][17][18][19][20][21][22][31][32][33] .
A study on the anatomy of the lingual frenulum states that the elevation of the anterior and middle parts of the tongue and/or retraction creates tension in the fascial layer of the floor of the mouth, drawing the fascia and the overlying mucosa up into a midline sagittal fold that forms the lingual frenulum 1 . Thus, it is possible to