ORIGINAL ARTICLE Year : 2021  |  Volume : 24  |  Issue : 3  |  Page : 321-328

Cephalometric evaluation of hyoid bone position in subjects with different vertical dental patterns

OA Soyoye1, OD Otuyemi2, M Newman-Nartey3
1 Department of Child Dental Health, University of Medical Sciences, Ondo, Nigeria
2 Department of Child Dental Health, Obafemi Awolowo University, Ile-Ife, Nigeria
3 Department of Orthodontics and Paedodontics, University of Ghana Dental School, College of Health Sciences, University of Ghana, Korle-Bu Accra, Ghana

Date of Submission08-Jul-2019Date of Acceptance12-Sep-2020Date of Web Publication15-Mar-2021

Correspondence Address:
Dr. O A Soyoye
Department of Child Dental Health, University of Medical Sciences, Ondo
Nigeria

Source of Support: None, Conflict of Interest: None

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DOI: 10.4103/njcp.njcp_430_20

   Abstract 

Objective: This study investigated the relationship between hyoid position and vertical dental dimensions (overbite), and the influence of gender on the location of this bone. Methods: One hundred and seventy-four standardized lateral cephalometric radiographs were randomly selected from a pool of radiographs of patients seeking orthodontic treatment with ages ranging from 10 to 58 years. The subjects were divided into three groups according to their vertical dental dimensions (overbite) into reduced, normal, and increased overbite groups. The hyoid bone position was determined by four horizontal linear and three vertical linear line measurements. Associations between the position of the bone and different vertical dental patterns were analyzed using ANOVA and Tukey's multiple comparison analysis. Results: There was a progressive increase in the horizontal linear position of the hyoid bone parameters across the groups from the reduced through normal to increase overbite. Similarly, a statistical reduction in the vertical linear positions of the hyoid bone parameters was found across the groups from reduced overbite through normal overbite to increased overbite (P < 0.05). The vertical linear hyoid bone positions were located higher in the male than in female subjects. Tukey's multiple comparison analysis showed a highly statistically significant difference in the vertical linear hyoid bone positions between reduced and normal overbite groups and between reduced and increased overbite groups. Conclusion: The hyoid bone was positioned more antero-inferiorly and more postero-superiorly in subjects with reduced overbite and increased overbite, respectively.

Keywords: Cephalometric, hyoid bone, vertical dental patterns

How to cite this article:
Soyoye O A, Otuyemi O D, Newman-Nartey M. Cephalometric evaluation of hyoid bone position in subjects with different vertical dental patterns. Niger J Clin Pract 2021;24:321-8
How to cite this URL:
Soyoye O A, Otuyemi O D, Newman-Nartey M. Cephalometric evaluation of hyoid bone position in subjects with different vertical dental patterns. Niger J Clin Pract [serial online] 2021 [cited 2021 Dec 5];24:321-8. Available from: https://www.njcponline.com/text.asp?2021/24/3/321/311293    Introduction 

The hyoid bone is often described as a “U” shaped structure located at the root of the tongue in the anterior region of the neck. It anatomically lies between the base of the mandible approximately at the level of the C3 vertebra and the largest cartilage of the larynx, where it acts as a site of attachment for the anterior neck muscles.[1],[2]

The fact that it does not articulate with any other bones makes it a unique structure. It is suspended by the attachment of the muscles and ligaments of the head and neck region, and it is well protected by the mandible and cervical spine, thereby ensuring that fractures of the bone are relatively rare.[3] Apart from being the site of attachment for many muscles in the neck region, including muscles of the tongue, pharynx, hyoglossus, genioglossus, supra and infrahyoids, the hyoid bone serves as an anchoring structure for the tongue.[4]

Similarly, the hyoid bone plays an important role in masticatory, swallowing, and speech activities. At the onset of swallowing activity, the hyoid bone and the floor of the mouth are simultaneously elevated by the geniohyoid and mylohyoid muscles. Also, with the assistance of the stylohyoid and digastric muscles, the tongue is pressed upward against the palate, thus allowing food to be forced backward.[1] Concerning respiratory activities, the hyoid bone plays an integral role in the movement of the upper airway and its depression has been implicated in obstructive sleep apnea.[1],[4]

Many of the characteristic features of the long and short face syndromes could be adequately explained by the clockwise and counter-clock wise rotation of the mandible, in harmony with the hyoid bone, tongue, pharynx, and neck. The need to keep the airway open at the base of the tongue may be responsible for the clockwise rotation pattern in the long face syndrome.[5] Thus, the airway pattern and its stability are the major factors responsible for the hyoid bone position.[6]

Opdebeeck and associates[5] compared the position of the hyoid bone in subjects with short and long face syndromes and noted that the movement of the hyoid bone is in concert with the movement of the mandible, tongue, pharynx, and cervical spine. Thus, the positions of the hyoid bone and the tongue can be considered as indicators of the pharyngeal airway passage.

The need to further explore gaps in knowledge between the craniofacial skeleton and the hyoid bone necessitated the interest in the subject, though many investigators have tried to focus on the relationship between the craniofacial skeleton, pharynx, and the hyoid bone.[5],[7],[8] Other authors[7],[9],[10] have also attempted to establish a relationship between the hyoid bone and various malocclusion traits, but their findings have been inconclusive. As the development of malocclusion may be caused by prolonged oral habits, such as atypical swallowing and oral breathing, the hyoid bone position could serve as an important indicator or diagnostic guide in assessing developing malocclusion.[9]

Several studies have also reported changes in the hyoid bone position following orthognathic surgery involving the mandible.[11],[12],[13],[14] These studies reported that the position of the hyoid bone was shifted forward following mandibular advancement and backward after mandibular setback surgery. Subjects with severe vertical jaw dysplasia may require orthognathic surgery to improve occlusion, aesthetics, and function. Due to its location and role in mastication, this surgery usually results in alteration of the position of the hyoid bone and tongue, with consequent narrowing of the pharyngeal airway space. This is because the position of the hyoid bone is influenced by the position of the tongue, thus affecting the pharyngeal airway space.[15]

The relationship between hyoid bone position and the vertical growth patterns of the face is controversial as researchers have shown different and conflicting reports.[5],[15],[16],[17],[18] Some authors[5],[17] reported a more posteriorly positioned hyoid bone in subjects with short face syndrome, while another author[15] reported a more anterior and posterior positioning of the bone in short and long face syndromes, respectively. Haralabakis and coauthors,[18] however, found no difference in antero-posterior position of the hyoid bone in adult individuals with anterior open bite, compared with individuals with normal bite.

Several studies that related the craniofacial morphology to the hyoid bone position were mainly reported among Caucasians.[19],[20],[21] To our knowledge, none of such studies has been reported among Africans, thus necessitating this study.

This study, therefore, aimed to investigate the relationship between hyoid positions and vertical dental dimensions (overbite), including the influence of gender, using cephalometric radiographs.

   Materials and Method 

One hundred and seventy-four (174) standardized lateral cephalometric radiographs were randomly selected. The selection was from a pool of radiographs of patients seeking orthodontic treatment. The age range was from 10 to 58 years. The selected sample comprised radiographs of healthy individuals with no congenital anomalies involving the craniofacial skeleton. Radiographs of patients with facial asymmetry, history of sleeping disorders, or previous orthodontic treatment were excluded.

All the lateral cephalometric radiographs obtained from the subjects were taken by an experienced clinician, using a Vatech Machine Pax-i, (Scan type) an advanced digital diagnostic system. Each radiograph was taken with the subject correctly positioned in the machine and the head oriented to the natural head position. Also, the teeth were in centric occlusion while the lips were relaxed. The radiographs were traced manually by one of the investigators (S.O.A). The subjects were divided into three (3) groups according to their vertical dental dimensions (overbite); group 1 were subjects with normal overbite (2 to 3 mm), group 2 were subjects with reduced overbite (<2 mm, including anterior open bite), and group 3 were subjects with increased overbite (>3 mm).

Cephalometric landmarks and reference planes used for evaluation of the hyoid bone position are shown in [Figure 1]. A horizontal reference line angulated at 7 degrees clockwise to the S-N plane, and passing through the Sella was registered as the True Horizontal Line (THL). While the line perpendicular to the THL, constructed through the Sella was registered as the True Vertical Line (TVL).

Figure 1: Horizontal and vertical linear measurements of the hyoid bone position 1: Hy-Rgn: Linear distance from hyoidale to retrognation; 2: C3-Rgn: Linear distance from third cervical vertebra to retrognation; 3: Hy-C3: Linear distance from Hyoidale to the third cervical vertebra (C3); 4: Hy-TVL: Linear distance from Hyoidale to True Vertical Line; 5: Hy-PNS: Linear distance from Hyoidale to posterior nasal spine; 6: Hy-S: Linear distance from Hyoidale to Sella; 7:Hy-THL: Linear distance from Hyoidale to True Horizontal Line

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The hyoid bone position was determined by four horizontal linear lines: C3-Hy, which is the horizontal distance from C3 cervical vertebra to the hyoid bone; Hy-Rgn, which is the horizontal distance from the hyoid bone to retrognation; C3-Rgn- which is the horizontal distance from C3 cervical vertebra to the retrognation; and Hy-TVL- the horizontal distance from the hyoid bone to the true vertical line.

In addition, three vertical linear lines (Hy-PNS, Hy-S, Hy-THL), representing vertical distances from the hyoid bone to the Posterior Nasal Spine, Sella, and true horizontal line, respectively [Figure 1] and three angular measurements, C3-HyS, Hy-C3S, and NaBa-Cc-Hy [Figure 2] were also used to determine the position of the bone. These were all analyzed. All parameters were measured twice and the average was determined and analyzed.

Figure 2: Angular measurements of the hyoid bone position 1: C3/Hy/S: Angle measured between the third cervical vertebra, Hyoidale, and Sella; 2: Hy/C3/S: Angle measured between Hyoidale, third cervical vertebra, and Sella; 3: NaBa/CC/Hy: Angle measured between Nasion- Basion plane and Center of Cranium to Hyoidale

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Definitions of Cephalometric landmarks and reference planes used for evaluation of the hyoid bone position

Hy (Hyoidale): The most anterior and superior point of the hyoid body.

Rgn (Retrognation): The most posterior point of the mandibular symphysis.

C3: The most antero-inferior point on the third cervical vertebra.

S (Sella): The geometric center of the pituitary fossa.

PNS (Posterior Nasal Spine): The posterior spine of the palatine bone constituting the hard palate.

N (Nasion): The most anterior point on the frontonasal suture in the mid sagittal plane.

Ba (Basion): The lowest point on the anterior rim of the foramen magnum.

THL (True Horizontal line): Horizontal reference line angulated 7° clockwise to the Sella-Nasion plane.

TVL (True Vertical line): A line perpendicular to the THL, constructed through the Sella.

N-Ba: The plane joining Nasion and Basion.

S-N plane: A plane joining Sella and Nasion.

Statistical analysis

Data generated from this study were computer processed using SPSS Version 20 for data entry, editing, and analysis. The data were subjected to descriptive analysis for mean, range, and standard deviation of all variables. One way Analysis of variance (ANOVA) test was carried out and Tukey's multiple comparison analysis was used for multiple comparisons. Statistical significance was set at P < 0.05.

   Results 

The study sample consisted of a total of 174 subjects aged 10 to 58 years with slightly higher female preponderance (59.2%). The mean ages of male and female participants were 19.41 ± 8.79 years, and 18.85 ± 6.10 years, respectively. The overall mean age was 19.08 ± 7.30 years [Table 1].

Table 1: Socio-demographic characteristics of participants according to sex

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[Table 2] shows the sex distribution of the participants according to vertical dental dimensions (overbite). The proportions of different overbites were almost evenly distributed with 27.0%, 33.9%, and 39.1% for normal, reduced, and increased overbites, respectively. However, there were no statistically significant sex differences across the groups.

Table 2: Sex distribution of subjects according to their vertical dental dimensions (overbite)

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[Table 3] presents one-way analysis of variance (ANOVA) test comparing hyoid bone parameters with vertical dental dimensions (overbite). In the entire study population, there was a progressive increase in the horizontal linear measurements of the hyoid bone parameters across the groups (from the reduced through normal to increase overbite) except in C3-Hy. The highest mean value was recorded in the reduced overbite group. The differences were statistically significant (P < 0.05), except for C3-Rgn.

Table 3: One-way ANOVA of Cephalometric parameters (hyoid bone linear and angular measurements) and the vertical dental dimensions according to sex

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There was a progressive reduction in the vertical linear measurements of the hyoid bone parameters across the groups, and this was also statistically significant (P < 0.05). Additionally, the vertical linear measurements were higher in the male subjects than in the females.

There was also a significant difference in the mean value of angle C3HyS between the reduced and normal overbite and between the increased and normal overbite. The same pattern was also observed in the mean value of angle HyC3S amongst the groups. There was, however, no significant difference in the mean value of angle NaBaCcHy amongst the three groups.

The relationship of hyoid bone variables with different overbites was carried out using Tukey's multiple comparison analysis, as shown in [Table 4]. There was a high statistically significant difference in the vertical linear hyoid bone positions between reduced and normal overbite groups and between the reduced and increased overbite groups. However, in the horizontal linear hyoid bone parameters, a statistically significant difference was recorded between the reduced and normal overbite groups, and between the reduced and increased overbite groups for Hy-TVL. Similarly, a statistically significant difference was reported between normal and reduced overbite groups for C3-Hy, and between reduced and increased overbite groups for Hy-Rgn.

Table 4: Comparisons of hyoid bone variables with different vertical dental dimensions using Tukey's multiple comparison analysis

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   Discussion 

The positions of the hyoid bone in subjects with different vertical skeletal patterns have been evaluated in several studies and their findings were documented.[5],[6],[17],[18],[22],[23] Some studies have also reported variations in the position of the bone, not only for different individuals but also in the same individual at different time intervals.[16],[19] The divergence in findings from these studies could be due to differences in the craniofacial structures and landmarks used to define the planes from which the hyoid bone was measured.

This study showed gender variations in cephalometric horizontal linear variables relative to the hyoid bone position amongst the three groups. This was confirmed by the measures of C3-Hy and Hy-Rgn, in contrast to the findings of previous studies[17],[18],[23],[24] where male subjects were reported to have a more anteriorly positioned hyoid bone. However, the male subjects in this study had more inferiorly positioned hyoid bone as confirmed by the values of Hy-S, Hy-PNS, and Hy-THL. This is in agreement with findings from previous studies, which reported that the hyoid bone was positioned more inferiorly in males than in females.[17],[18],[21],[23],[25],[26] Similarly, a study conducted among Nigerian subjects with bimaxillary incisor proclination showed a more inferior position of the bone in males.[24]

Of the three overbite groups considered, the hyoid bone was more posterior to the mandible in the increased overbite group, and more anterior to the mandible in the reduced overbite group when compared with the control group. This is also demonstrated by a highly significant association in the horizontal distance between the hyoid bone and the mandible among the groups. These findings are consistent with the reports of previous investigations by Urzal et al.[17] and Paes et al.[27] These studies reported a more posteriorly positioned hyoid bone relative to the mandible in brachyfacial subjects with a deep overbite. The authors further found a more anteriorly positioned hyoid bone relative to the mandible in dolichofacial subjects with an anterior open bite when compared to the control group as seen in this study.

The plausible reason for this finding may be because the hyoid bone moves in concert with the mandibular movement as demonstrated in a previous study by Opdebeeck et al.[5] Jena and Duggai[15], however, provided a contrary finding that showed that the position of the hyoid bone was mostly anterior in subjects with short face syndrome and posterior in subjects with long face syndrome. This was attributed to the antero-posterior position of the hyoid bone, which is in tandem with the sagittal position of the chin. The variability in the findings may be associated with the differences in the reference planes used in determining the antero-posterior and horizontal position of the hyoid bone. While these authors[15] evaluated the hyoid bone position from the H-PTR perpendicular distance, which is the distance between a perpendicular plane drawn on the FH-plane at PTR (ptergomaxillary fissure) and the hyoid bone, this study used the distance between the hyoid bone and retrognation (Hy-Rgn) to evaluate the horizontal and antero-posterior position of the bone. Racial differences may also account for these differences. Nevertheless, other factors that may contribute to the antero-posterior positioning of the hyoid include the relative lengths of the muscles running from the base of the skull, mandible, and tongue to the hyoid bone, and maintenance of the patency of the pharyngeal airway space.[7],[16]

This study, however, did not show any significant difference in the horizontal distance between the hyoid bone to the cervical spine (C3-Hy) in the reduced and increased overbite groups. This report appears to be consistent with independent investigations of Haralabakis[18] and Opdebeeck et al.[5] in which it was concluded that the horizontal distance of the hyoid bone to the cervical spine was independent of vertical discrepancies, but may be related to antero-posterior skeletal discrepancies as demonstrated by Mortazavi et al.[21] Jose et al.[16] also agreed that the hyoid maintains a very constant relationship with the cervical vertebrae as shown by the C3-Hy values in the three groups of malocclusion considered. The reasons for these findings may be related to the fact that the hyo-laryngeal complex descends and moves relative to the face and cranial base, but not relative to the vertebral column. This descent is, however, necessary for speech and swallowing activities.[28]

Age may also play a significant role in the position of the hyoid bone within the head and neck region. It was documented that the position of the hyoid bone relative to the cervical vertebra is achieved at the age of 2 years, with the superior margin of the hyoid body lying between the third (C3) and fourth (C4) cervical vertebra.[29],[30] The youngest age of participants in our study was 10 years. This implies that the position of the hyoid bone would have been established at this age. This may also account for the lack of significant findings in the horizontal linear distance of the hyoid bone to the cervical spine (C3-Hy) in this study.

This study further shows that the hyoid bone was positioned more inferiorly to the sella turcica (S) and the posterior nasal spine (PNS) in subjects with reduced overbite, compared with the normal and deep overbite groups. This concurs with previous studies[17],[18],[27] in which it was reported that the hyoid bone was more inferiorly positioned relative to these reference lines. Furthermore, previous studies by Opdbeeck et al.[5] and Jena and Duggai[16] also confirmed that the vertical position of the hyoid bone in subjects with short face syndrome was slightly upward, compared to subjects with long face syndrome and normal anterior face height. Another author investigated the relationship between the hyoid bone position and skeletal or dental open bite and reported that patients with low hyoid bone position tended toward skeletal and dental open bite.[31]

In a recent study carried out to investigate any difference in the hyoid bone and posterior pharyngeal wall positions in normal and open bite subjects, it was discovered that there was no difference in the position of the tongue, hyoid bone, and posterior wall in the normal and open bite groups.[32] Similarly, another recent study that investigated the possibility of any difference in hyoid bone position among individuals with different growth patterns before and after treatment came up with a similar result. There was no significant correlation in the position of the hyoid bone in the normodivergent (which tend to have normal overbite) and hyperdivergent (which tend to have reduced overbite) groups considered. It was also reported that no change occurred in the position of the hyoid bone in these groups even after treatment. However, the study reported an inferior position of the bone in the tested subjects, a report consistent with the findings of this present study.[33]

A possible explanation for the more inferior and superior position of the hyoid bone in subjects with reduced and increased overbite, respectively could be the result of pull from the suprahyoid group of muscles, which occurs as the mandible rotates in an upward and forward direction.[34] This may be because the hyoid bone position depends on the relative balance of muscle attachment from the base of the cranium bilaterally and the region of the mandibular symphysis.[33]

In long face syndrome subjects who tend to have an anterior open bite, the mandible rotates in a downward and backward direction, resulting in a slightly downward positioning of the hyoid bone. Similarly, in short face syndrome subjects with deep overbite, the mandible tends to rotate in an upward and forward position, thus resulting in a slightly upward positioning of the hyoid bone relative to the sella turcica, and the posterior nasal spine.[34] In addition, the inferior position of the hyoid bone in subjects with reduced overbite had been claimed to be an adaptation that prevents encroachment of the tongue into the pharyngeal airway in these subjects.[33]

A more caudal position of the hyoid bone was also reported among subjects with enlarged tonsils, which have been reported to have an anterior open bite.[35] It was suggested by Ricketts[36] that the lower position of the hyoid bone in subjects with enlarged tonsils was necessary to create an oral airway. Also, patients suffering from obstructive sleep apnea were reported to suffer from narrowing of the airway and a low hyoid bone position.[37] Behlfest and associates[35] opined that factors such as low tongue posture, narrow pharyngeal airway passage, and large craniocervical inclination could be considered as important determinants for low hyoid bone posture. Additionally, the hyoid bone likely plays a role in growth aberrations resulting from nasal obstruction.

Furthermore, previous investigations[4],[11],[12],[13],[14] have reported changes in the hyoid bone position following orthognathic surgery of the mandible. These authors found that mandibular setback procedure in subjects with long face syndrome who tend to have an anterior open bite could result in further narrowing of the pharyngeal airway passage. This tends to result in postsurgical obstructive sleep apnea. In these subjects, therefore, the adoption of an orthognathic surgical approach needs to be thoroughly evaluated. Future studies on the subject would be required to assess other factors that may contribute to the relationship between hyoid bone positions and subjects with different vertical dental patterns.

   Conclusion The hyoid bone was positioned more antero-inferiorly in subjects with reduced overbite but more postero-superiorly in subjects with increased overbite.The hyoid bone maintained a near-constant position relative to the cervical vertebra in subjects with reduced and increased overbite.The hyoid bone in the male subjects appeared to be more inferiorly located

Acknowledgements

Sincere appreciation goes to Dr. D.O Soyoye for the analysis and arrangement of the manuscript.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.

 

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  [Figure 1], [Figure 2]
 
 
  [Table 1], [Table 2], [Table 3], [Table 4]