Original article

A cephalometric study of tongue position

Obstructive sleep apnea (OSA) is a multifactorial disorder. Pathophysiological factors associated with OSA include airway collapsibility, poor pharyngeal muscle responsiveness, a low arousal threshold, and a high loop gain. Children with sleep-disordered breathing (SDB) present with alterations in posture and mobility of the stomatognathic system components. Orofacial myofunctional therapy in children with OSA promotes changes in the orofacial musculature of the upper airways and helps to reestablish correct habits and functioning of orofacial muscles. Orofacial myofunctional exercises could serve as an adjunct therapy to other OSA treatments. Early identification and intervention during childhood development is essential to optimize normal airway growth and for durable results related to the treatment of SDB.

To determine the relationship between AOB and factors such as dental arch dimensions and tongue position during swallowing and phonation.

A case–control study was performed in two groups: 132 children with Anterior Open Bite (AOB) and 132 with normal vertical overbite (NVO), aged 8-16 years selected from the records taken by a previous study from five public schools. Dental arch dimensions were assessed through digitalized study models. Swallowing was evaluated using the Payne technique, and phoniatric assessment included an adaptation of the articulation test used to describe phonemes. Statistical analysis: Chi-Square or Fisher's exact test for comparisons between qualitative variables and the Mann Whitney or T-student were applied to compare the dental arch dimensions according to bite type. A logistic regression model was applied to control the effect of confusion between independent variables and to describe its simultaneous effect on the type of bite.

Intercanine, interpremolar and intermolar widths showed higher values in AOB patients with a mean deviation (MD) of 0.536 (P = 0.031), 0.60 (P = 0.043) and 1.15, (P < 0.001) respectively. Distortions caused by tongue interposition and thrust, tongue protrusion during swallowing, mandibular arch intermolar width, total maxillary arch length, maxillary arch perimeter, and posterior arch depth accounted for 64.6% of AOB and allowed for correct predictions in 83.8% of the cases observed in the study population.

A significant association between tongue position and function, as well as alterations such as tongue interposition and thrust during swallowing and phonation in individuals with AOB, were observed. There is a relationship between AOB and the presence of a wider mandibular arch and a narrower, longer, and deeper maxillary arch.

The aim of this study was to investigate the relationship between the hyoid bone position and skeletal or dental openbite and to investigate dentofacial characteristics as indicated by the hyoid bone position.

In our study, 182 patients were included on the basis of skeletal and dental openbite. The hyoid bone position of the subjects was compared and evaluated. In addition, by dividing the samples according to the hyoid bone position, dentofacial characteristics of the subjects were compared and analyzed.

There were significant differences in the hyoid bone position according to the skeletal pattern, not dental pattern. The skeletal openbite group showed low hyoid bone position. In addition, the low hyoid bone group showed short ramus height, short posterior facial height, retrusive chin, and clockwise-rotated mandible.

Patients with low hyoid bone had a tendency toward skeletal openbite, even though there was no dental openbite. Moreover, low hyoid bone position had relevance to retrognathic dentofacial characteristics.

The bony nasopharynx increases its capacity predominantly by means of vertical development. Analogous to the facial structures is an expression of some somatotopic features that give rise to a higher and more shallow pharyngeal dimension in the dolichocephalic growth pattern. The nasopharynx's ultimate patency, however, depends on the growth and relative size of the soft tissues that line the skeletal boundaries. A decreased patency of the oropharyngeal airway can induce some postural adaptations, which secure a constant sagittal dimension at that level. However, at a certain critical point, purely nasal respiration will be turned into an oronasal breathing pattern, which in turn will elicit more compensatory mechanisms. This muscle recruitment is a possible cause of a deviant vertical craniofacial growth pattern.

The relationship between dentoskeletal and tongue soft-tissue variables has been quantified in a sample of 60 adult females with normal and anterior open-bite malocclusions. Three lateral rest-position head films were obtained for each subject. A principal component analysis reduced the data base and six significant canonical correlations were identified. The first canonical correlation (r₁ = 0.962) represented a size-related correlation factor between the two groups of variables. Subjects with characteristics of a short face syndrome and some evidence of overbite had tongue tips positioned below the lower occlusal plane (r₂ = 0.929). In contrast, skeletal open-bite subjects (r₄ = 0.759) revealed tongue tips ahead of and above the lower incisor teeth with the mandible in the rest position. Undererupted mandibular teeth (r₅ = 0.666) were associated with a reduced tongue height and an inferior epiglottis; short tongue length (r₆ = 0.563) correlated with a linear combination of upright central incisors, a small overjet, a low ANB angle, unerupted maxillary and mandibular teeth, and a steep occlusal plane. The multivariate statistical analysis extracted clinically significant associations between tongue soft-tissue and dentoskeletal variables. Tongue posture at rest in skeletal open-bite subjects appeared to be related to incisor position.

Little is known concerning the adaptation of the tongue and hyoid bone after surgical mandibular advancement. This study was undertaken to evaluate the relationship between tongue and hyoid bone posture and their adaptation following mandibular advancement in fourteen adults. The data indicate that (1) there is no statistically significant correlation between changes in the posture of the tongue and hyoid bone; (2) the hyoid bone returns toward its presurgical posture; and (3) the tongue assumes a new position relative to both the cranial base and the mandible. The changes in tongue position occurred immediately after surgery and persisted 2 years postoperatively.