Background: According to the close proximity of hyoid bone with dentofacial structures and its muscular attachments, a probable

relationship between it and different types of skeletal patterns is suspected.

Objectives: The aim of this study is compare the position of hyoid bone in skeletal class I and class II patients.

Methods: In this study 50 cephalograms were divided into two groups, skeletal class I (1 ≤ ANB ≤ 4) and skeletal class II (ANB > 4),

with 24 and 26 patients in each group, respectively. Horizontal and vertical position of hyoid bone were evaluated. SPSS software

and student t-test were used to analyze the data.

Results: According to the results of our study, there is no statistically significant difference between the hyoid bone position in

skeletal class I and skeletal class II patients.

Conclusions: Since the hyoid bone position is similar in skeletal class I and class II patients, the skeletal pattern is not the only

determinant of the position of hyoid bon

Momeni, Mohammad Ali.

Soheilifar, Sanaz.

shahrekord university of medical scinces

Iran J Ortho. 2017 March; 12(1):e6500.Published online 2016 August 3.doi: 10.17795/ijo-6500.Original ArticleCephalometric Comparison of Position of the Hyoid Bone in Class Iand Class II PatientsSanaz Soheilifar,1 and Mohammad Ali Momeni1,*1Orthodontic Department, Hamadan University of Medical Sciences, Hamadan, IR Iran*Corresponding author: Mohammad Ali Momeni, Orthodontic Department, School of Dentistry, Shahid Fahmide Blvd., Hamadan, IR Iran. Tel: +98-9194886113, E-mail:alimomeni1362@gmail.comReceived 2016 May 08; Accepted 2016 June 28.AbstractBackground: According to the close proximity of hyoid bone with dentofacial structures and its muscular attachments, a probablerelationship between it and different types of skeletal patterns is suspected.Objectives: The aim of this study is compare the position of hyoid bone in skeletal class I and class II patients.Methods: In this study 50 cephalograms were divided into two groups, skeletal class I (1≤ ANB≤ 4) and skeletal class II (ANB > 4),with 24 and 26 patients in each group, respectively. Horizontal and vertical position of hyoid bone were evaluated. SPSS softwareand student t-test were used to analyze the data.Results: According to the results of our study, there is no statistically significant difference between the hyoid bone position inskeletal class I and skeletal class II patients.Conclusions: Since the hyoid bone position is similar in skeletal class I and class II patients, the skeletal pattern is not the onlydeterminant of the position of hyoid bone.Keywords: Cephalometry, Hyoid Bone, Angle Class II Malocclusion, Angle Class I Malocclusion1. BackgroundThe hyoid bone is a u-shaped (horse shoe shaped) bone,situated on the anterior midline of the neck between sym-physis and larynx, suspended from the tip of stylohyoidprocess of temporal bone by stylohyoid ligaments (1). Un-like the other bones of head and neck, it has no osseousjoint and is only distantly articulated to mandible, cra-nium and pharynx by muscles and ligaments (2). Functionof this bone is to maintain equilibrium of respiratory wayby serving as anchoring structure for the tongue and alsois to keep normal head posture (3-5).The hyoid bone position could be a good diagnos-tic guide to malocclusions elicited by destructive oralhabits such as atypic deglutition or mouth breathing (6,7). Changes in the anteroposterior head posture andmandibular inclination can affect the hyoid bone position(3, 8, 9). Treatment with functional appliances that posi-tion mandible downward and forward, may also displacethe hyoid bone (10-13). Recent orthodontic studies indicatethat evaluation of the hyoid bone position may play an im-portant role in assessment of dentofacial structures espe-cially in evaluation of relapse prevention after orthodontictreatment and orthognathic surgeries (14). Furthermore,in several studies, the hyoid bone position and pharyn-geal airway space are mentioned in relation. Jose et al,who evaluated this relation in different types of malocclu-sions, found a positive relationship between lower airwayand horizontal distance from the hyoid bone to the retrog-nathion only in class I skeletal patient with normal growthpattern (15). Guven et al. reported changes in the hyoidbone position and pharyngeal airway space after mandibu-lar body osteoctomy (16). In addition, Parkkinen observedlower hyoid bone position in children with breathing dif-ficulties during sleep. Although several studies reported apositive correlation between the hyoid bone position andmandible (17-19), the other studies concluded that there isno significant correlation between them (7, 20).2. ObjectivesThe aim of this study was to evaluate the cephalomet-ric hyoid bone position in patients with skeletal class I andskeletal class II pattern.3. MethodsBased on sample size in similar studies (21), 24 cephalo-grams were selected in class I group and 26 cephalogramsCopyright © 2016, Iranian Journal of Orthodontics. This is an open-access article distributed under the terms of the Creative Commons Attribution-NonCommercial 4.0International License (http://creativecommons.org/licenses/by-nc/4.0/) which permits copy and redistribute the material just in noncommercial usages, provided theoriginal work is properly cited.Soheilifar S and Momeni MAfor class II group from the archive of dentistry faculty ofHamedan University of medical sciences between “1389-92”.Inclusion criteria was as follows: being Ira-nian,“neither” adenoidectomy “nor” tonsillectomyhistory, lack of presence of pharyngeal lesions such astonsil hypertrophy or tonsilitis, having normal growthpattern (FMA = 22-28) (22), patients in the age group of 9-11years who didn’t attain the age of maturity (in the stageof CS1, CS2 and CS3) (23) and having comfortable nasalbreathing. The patients’ files were checked for inclusioncriteria. Any patient who didn’t meet these criteria wasexcluded. All the cephalograms were taken using the Sore-dex Digora machine; used in Hamedan dentistry schoolwith standard method in normal head posture and centricocclusion.Our comparing groups were skeletal class I (1 ≤ ANB≤ 4) and skeletal class II (ANB > 4) malocclusions includ-ing 24 and 26 patients, respectively. These two groups werematched regarding the stage of cervical vertebra and sex.Table 1 shows the frequency of patients in each group.Horizontal (24) and vertical (25) measurements of thehyoid bone position were conducted according to the pre-vious studies (Figure 1).All cephalograms were traced manually and 10cephalograms were randomly selected and traced againafter a week to evaluate systematic error.SPSS 19 software was used for data analysis. Paired t-testwas used for estimation of systematic error and indepen-dent t-test was used for analysis of difference between twogroups’ variables. Significance level was considered as P <0.05.4. ResultsIndependent t-test, shows no statistically significantdifference between two groups of skeletal class I and II mal-occlusions, considering horizontal dimension measure-ments. Table 2 illustrates the information related to thisevaluation.Independent t-test, shows no statistically significantdifference between two groups of skeletal class I and IImalocclusions, considering vertical dimension measure-ments. Table 3 illustrates the information related to thisevaluation. Pearson correlation showed that there was nostatistical correlation between ANB and variables.5. DiscussionThe position of the hyoid bone in class I, II and III mal-occlusions has been evaluated in several studies and vari-ous results are achieved (17-22). The position of the hyoidbone is different, not only from an individual to the otherone, but also in different time intervals in the same patient(15). Evaluation of the position, shape and function of thehyoid bone seems to be important due to its effect on equi-librium maintenance of surrounding tissues.In present study, we found no statistically significantdifference between class I and II malocclusions, regardingthe horizontal and vertical position of hyoid bone. Sim-ilar to our study, Carvalho et al. reported no statisticallysignificant difference in the hyoid bone position in class Iand II malocclusions and statistically significant differenceonly was shown with ANS-PNS measurement for the eval-uation of vertical position (7). Furthermore, in Jose et al.,who evaluated vertical and horizontal position of the hy-oid bone in class I, II and III malocclusions using Bibby andPreston analysis (3), no statistically significant differencewas found between these three groups (15).Unlike our study, in the study of Kuroda et al., therewas statistically significant difference in hyoid bone posi-tion in skeletal class I, II and III patients. The hyoid bone inthe class II patients was situated closer to the skull base incomparison with class III patients (17). The controversial re-sults are due to the fact that Kuroda et al. found differencein hyoid position in class II and class III subjects, but in thepresent study class I and class II subjects are compared.Adamidis and Spyropoulos evaluated the effect of hy-pertrophic adenoid tissue on the hyoid bone positionin children with mean age of 9 years. The results sug-gested that more downward inclination of mandible in themouth breathers as compared to nasal breathers (withouthypertrophy of tonsils), can be seen. This study also indi-cates that the hyoid bone position follows the mandibularposture in the mouth breathing patients and hence, the hy-oid bone shows downward inclination, too. The authorssaid that the reason is indirect effect of craniofacial com-plex and function of suprahyoid and infrahyoid muscleson the position of hyoid bone (18).Galvao et al. reported that the hyoid bone is locatedcloser to the rim of mandible in class II patients and is sit-uated farther in class III patients and difference was statis-tically significant (19). The reason of this finding may bedue to investigation of skeletal class II and III patients “not”skeletal class I and II ones.Haralabakis et al. reported that the distance from thehyoid bone to the palatal plane was found to be statisti-cally greater in the open bite class II group than class Inormal patients .They stated that the palatal plane plays arole in the development of skeletal malocclusions, and alsothe findings strongly suggest that the hyoid bone movesonly in close relation with pharynx, cervical spine andmandibular plane in patients with entirely different skele-tal pattern. Most of horizontal measurements revealed no2 Iran J Ortho. 2017; 12(1):e6500.Soheilifar S and Momeni MATable 1. Frequency of Males and Females in Each GroupGroup Sex TotalMale FemaleI 8 16 24II 9 17 26Total 17 33 50Figure 1. The Landmarks and Distances Are Shown in the Figure 1Landmarks: AH, The most anterosuperior point on the body of the hyoid bone; PH, Point of intersection of ANS-PNS and the line perpendicular from anterosuperior point of thebody of the hyoid bone to ANS-PNS line; PT, the rearmost point of the tongue contour, formed by a depression which, in radiographic terms, is situated below the mandibularrim, between the 2nd and 3rd cervical vertebra; BV, Posterior point of the base of epiglottis; PPW, Posterior wall of pharynx. Horizontal distances: AH-PPW, Perpendicular linefrom AH to the posterior wall of pharynx (PPW); BV-PPW, Perpendicular line from BV to PPW; PT-PPW, Perpendicular line from PT to PPW; ANS-PH, Distance between ANS and PHpoint. Vertical distances: H-SN, Distance from the hyoid bone (the most anterosuperior point of the hyoid bone) perpendicular to SN line along sella turcica; H-FH, Distancefrom the hyoid bone to the Frankfort plane; H-PP, Distance from the hyoid bone to the palatal plane; H-MP, Distance from the hyoid bone to the mandibular plane.Table 2. Mean, Standard Deviation and P Value Obtained from Independent t-test for Evaluating Horizontal Position of the Hyoid BoneVariable Mean± SD P ValueClass I Class IIANS-PH 59.733± 6.0168 58.905± 7.8352 0.671PT-PPW 8.650± 3.1763 8.952± 3.1061 0.737BV-PPW 14.817± 3.2042 13.905± 2.9649 0.308AH-PPW 26.967± 2.4738 25.714± 2.2168 0.070difference in the position of hyoid bone in male and femaleopen bite compared to normal patients (25).Kollias et al. investigated alterations in craniocervicalmorphology and the hyoid bone position in different agegroups using three series of cephalograms with 10 years in-terval between each series for each patient (males and fe-males). The mean age of patients was 22 years at the ini-tial evaluation. The results showed that in the males, thedescending of the hyoid bone was found to follow a grad-ual pattern when this bone was related to the sella, Frank-fort horizontal plane and the 3rd cervical vertebrae after 20years and in the female group, statistically significant dif-Iran J Ortho. 2017; 12(1):e6500. 3Soheilifar S and Momeni MATable 3. Mean, Standard Deviation and P-Value Obtained from Independent Test for Evaluating the Variables of Vertical Position of the Hyoid BoneVariable Mean± SD P ValueClass I Class IIH-SN 87.500± 14.6140 85.381± 18.1645 0.647H-FH 72.033± 5.3722 71.190± 6.0632 0.603H-PP 51.000± 5.2850 51.333± 9.1013 0.870H-MP 11.967± 4.9234 10.214± 4.5403 0.203ference was observed only in the horizontal position of thehyoid bone after three series of cephalometric evaluationrelative to T0 (26). In the present study all of the patientswere in the same age group (9-11 years), therefore it doesnot seem that the age of patients in two groups would af-fect the hyoid bone position.Valenzuela et al. didn’t find any statistically significantdifference between anteroposterior head posture and thehyoid bone (27). Smith et al. suggested that the hyoid boneposition varies with change in the posture from uprightto supine due to change in larynx posture and reductionin oropharyngeal airway (28). Since in the present studythe cephalograms were taken in natural head position, nodifference is expected in the position of hyoid bone due tochange in postures.The results of our study suggest that horizontal andvertical dimensions of the hyoid bone position have no sig-nificant difference in skeletal class I and class II patients.Some studies suggest that compensating function of sur-rounding muscles and soft tissues might result in similar-ity of the hyoid bone position in different skeletal groups(29).5.1. ConclusionHyoid bone position is not significantly different inskeletal class I and class II patients.Some compensationalmechanisms in surrounding structures of dentofacialcomplex may be responsible for maintaining the positionof hyoid bone, despite the difference in the position ofmaxilla and mandible in skeletal class I and class II sub-jects.References1. Williams PL, Warwick R, Dyson M, Bannister LH. Gray’s anatomy. 378.Churchill livingstone Edinburgh; 1989.2. Romanes GJ. 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Cephalometric Comparison of Position of the Hyoid Bone in Class I and Class II Patients

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Cephalometric Comparison of Position of the Hyoid Bone in Class I and Class II Patients

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