Mandibular jaw movement capacity in10–17-yr-old children and adolescents:normative values and the influenceof gender, age, and temporomandibulardisorders

Christian Hirsch1, Mike T. John2,3,Christine Lautenschl�ger4, ThomasList5

1Department of Preventive Dentistry andPediatric Dentistry, Martin-Luther-UniversityHalle-Wittenberg, Halle (Saale), Germany;2Department of Prosthodontics and MaterialsScience, University of Leipzig, Germany;3Department of Oral Medicine, University ofWashington, Seattle, WA, USA; 4Department ofMedical Epidemiology, Biostatistics, andInformatics, Martin-Luther-University Halle-Wittenberg, Halle (Saale), Germany; 5OrofacialPain Unit, Department of StomatognathicPhysiology, Malmç University, Malmç, Sweden

Measurement of jaw movement capacity is an import-ant clinical variable used in the diagnosis of temporo-mandibular disorders (TMD). Limitations concerningjaw opening may be an indication of temporomandib-ular joint (TMJ)-related diseases, such as disc dis-placement (with or without reduction), arthritis of theTMJ, or juvenile chronic arthritis (1, 2). In the diag-nostic process, jaw movement measurements, combinedwith a clinical examination of the masticatory systemand the subjective report of pain, can indicate thepresence or absence of the above-mentioned conditions(3,4). This procedure requires cut-off values that arebased on clinical (expert) knowledge or, more often,values that are based on the distribution of a particularcharacteristic in a reference population. Frequently, thegeneral population is the target, and population-basednormative values (�norms�) are derived from this popu-lation to provide a frame of reference for each indi-vidual patient.

As for other health states, factors such as age andgender can potentially influence the distribution of jawmovement capacity in the general population. Duringchildhood and adolescence, craniofacial measures aredependent on age and gender owing to differences ingrowth (5). Moreover, TMD have a notable prevalencein this age range (6). This may be another potentialinfluence on the �norms� concerning jaw movements.Substantial differences in the distribution of a measurewould make a stratification of the �norms� necessary, inorder to make it more useful in clinical practice – asituation that occurs with psychosocial measures such asdepression (7) or oral health-related quality of life (8).However, population-based �norms� for jaw movementcapacity in children and teenagers that are based on theeffect of influential variables and have been determinedwith any sort of methodological rigor – such as highresponse rates, standardized assessment methods, andsufficient reliability – are lacking.

Hirsch C, John MT, Lautenschlager C, List T. Mandibular jaw movement capacity in10–17-yr-old children and adolescents: normative values and the influence of gender, age,and temporomandibular disorders. Eur J Oral Sci 2006; 114: 465–470. � 2006 TheAuthors. Journal compilation � 2006 Eur J Oral Sci

The aims of this study were, first, to report normative values for jaw movements inCaucasian children and adolescents (maximum opening, laterotrusion, and protru-sion) and, second, to investigate the influence of age, gender, and temporomandibulardisorders (TMD) on jaw movement capacity. The population-based study included1,011 randomly selected German children and adolescents, aged 10–17 yr. Case his-tories, as well as mandibular movements and the presence of TMD, were assessedaccording to the Research Diagnostic Criteria for Temporomandibular Disorders(RDC/TMD). The mean ± standard deviation for maximum opening was50.6 ± 6.4 mm, for laterotrusion to the right was 10.2 ± 2.2 mm, for laterotrusion tothe left was 10.6 ± 2.3 mm, and for protrusion was 8.2 ± 2.5 mm. Bivariable (t-test)and multivariable (linear regression) analyses showed that normative values for jawopening capacity were influenced by age and gender. No influence on jaw movementcapacity was seen when TMD were present. Based on the distribution of the meas-urements in the population (lowest decentile), the mandibular mobility of subjects witha maximum opening of <43 mm and laterotrusive movements < 8 mm or protrusivemovements < 5 mm might be considered as being limited. However, these limitationsdo not necessarily require treatment.

Dr Christian Hirsch, Department of PreventiveDentistry and Pediatric Dentistry, Martin-Luther-University Halle-Wittenberg, Harz 42a,06108 Halle (Saale), Germany

Telefax: +49–345–5571142E-mail: christian.hirsch@medizin.uni-halle.de

Key words: adolescents; children; gender; jawmovements; temporomandibular disorders

Accepted for publication July 2006

Eur J Oral Sci 2006; 114: 465–470Printed in Singapore. All rights reserved

� 2006 The Authors.Journal compilation � 2006 Eur J Oral Sci

European Journal ofOral Sciences

It was the aim of this study to derive �norms� formaximum opening (unassisted), laterotrusion, and pro-trusion in 10–17-yr-old Caucasian children and adoles-cents. In addition, hypotheses on whether age, gender,and the presence of TMD influence jaw movementcapacity were tested.

Material and methods

Study subjects and setting

The children and adolescents (n ¼ 1,011) came from aregional survey of 1,190 10–17-yr-old subjects in Halle(Saale) (85% response proportion). A two-stage clustertechnique was used to select the participants from aregister comprising all of the children and adolescents inHalle (Saale) who were required to attend school betweenthe ages of 10 and 17 yr. The sample is representative for24,129 children and adolescents who attended generalschools in Halle (Saale) in 1999. Of the 189 non-respondingsubjects, 62 (33%) did not have parental permission toundergo a school examination, 48 (25%) were absentowing to illness, and 79 (42%) gave no reason. Regardingage, gender, and school type, responders and non-responders were comparable. Data were collected in anadditional part of the regular dental school examination(yearly dental check-up) carried out between February2000 and March 2001. The study protocol was reviewedand approved by the ethics committee of Martin-Luther-University Halle-Wittenberg, the local education authority,and the parent’s council.

Jaw movement and TMD measurement and reliabilityassessment

A questionnaire was filled out by the participants before theclinical examination, and investigators were on hand toexplain, if necessary, the questions and to check the ques-tionnaires for completeness and legibility. The participantswere examined once by one of the three involved examinerswho were blind to the results of the questionnaire. All jawcapacity measurements (maximum unassisted opening, lat-erotrusion, and protrusion), as well as the TMD assessment,were conducted according to the German version (9) of theResearch Diagnostic Criteria for TMD (RDC/TMD) (3)(available at http://www.rdc-tmdinternational.org).The RDC/TMD classifies the most common forms of

TMD into the following three categories (myofascial pain;disc displacements; and arthralgia, arthritis, and arthrosis)and allows multiple diagnoses to be made for a given patient(3). In this study, the presence of TMD was assumed if thesubjects were assigned a diagnosis according to the RDC/TMD.In a previous multicenter study, the reliability of clinical

examinations and diagnoses according to the RDC/TMDwas assessed (10). Inter-rater reliability was assessed usingthe intraclass correlation coefficient (ICC), which wasderived from an analysis of variance (anova) where sub-jects and raters were treated as random effects. According tothe guidelines (11), the ICC was excellent for mouth opening(ICC ¼ 0.92), and fair to good for laterotrusion (ICC ¼0.44) and protrusion (ICC ¼ 0.75). The reliability of theassessments of the RDC/TMD diagnoses was fair (arthral-gia ICC ¼ 0.49; myofascial pain ICC ¼ 0.58) to good (discdisplacement with reduction ICC ¼ 0.70) (10).

Statistical analysis

To describe the association between the influential variablesand the outcomes, t-tests were used to find statistically sig-nificant differences between the two age groups (10–13 yrand 14–17 yr), regarding gender or the presence of TMD,which would be considered as an indication to stratify jawmovement �norms�. Holm’s multiple comparison procedurewas used to adjust the level of statistical significance formultiple testing (12). A difference of 1 mm or more in thejaw movements was considered relevant for a report ofstratified �norms�.In another part of the investigation, the associations

between the influential variables and the outcomes wereanalyzed when the influence of all variables on the outcomeswere considered simultaneously, that is, included in onestatistical model (regression analyses). We used ordinaryleast squares regression to analyze linear relationshipsbetween the variables because they were deemed mostimportant. These analyses included age (as a continuousvariable), gender, and the presence of any RDC/TMDdiagnosis. Results were interpreted as follows: a coefficientof the variable X of 0.5 represents a 0.5-mm increase in themeasurements per unit of the variable X (after controllingfor the influence of all other variables in the model). Inter-cepts in the multivariable models were centred at the age of10 yr, which represents the lower border of the model’srange of applicability. Finally, reference values for theoutcomes – �norms� – were reported as means for eachvariable (or stratified variable) and as decentiles.All analyses were carried out using the statistical software

package stata (Stata Statistical Software: Release 8;StataCorp, College Station, TX, USA).

Results

Patient characteristics

Of the 1,011 subjects, 486 (48%) were male and 525(52%) female. Mean age was 13.1 ± 2.0 yr. Jaw move-ments were measurable in all of the subjects. Every 10thsubject (n ¼ 103, 10.2%) had a TMD diagnosis accord-ing to the RDC/TMD (axis I). Subjects with TMD wereslightly older (13.8 ± 2.0 yr) than those without TMD(13.1 ± 2.0 yr). TMD subjects were more often femalethan male, but this was not statistically significant[11.2% vs. 9.0%, chi-square (1) ¼ 1.32, P ¼ 0.25]. Themost prevalent RDC/TMD diagnosis was disc displace-ment with reduction (group IIa: n ¼ 80, 7.9%); 23 sub-jects (2.3%) had an RDC/TMD pain diagnosis (groupIa, IIIa/b). Group Ib, IIb/c, and IIIc diagnoses were notpresent in the sample.

Jaw movements and influential variables

The mean ± standard deviation for maximum openingwas 50.6 ± 6.4 mm, for laterotrusion to the right was10.2 ± 2.2 mm, for laterotrusion to the left was10.6 ± 2.3 mm, and for protrusion was 8.2 ± 2.5 mm.The difference between laterotrusion to the right and leftwas significant (t-test: P ¼ 0.001). Mouth opening rangedfrom 31 to 76 mm, laterotrusion to the right from 3 to17 mm, laterotrusion to the left from 3 to 21 mm, andprotrusion from 1 to 22 mm.

466 Hirsch et al.

Maximum unassisted opening for male and femalesubjects between 10 and 17 yr is presented in Fig. 1. Inmultiple testing according to Holm’s procedure, onlygender (male subjects 1.9-mm larger opening) andage (14–17 yr age group, 1.3-mm larger opening)were significant indicators for differences in maxi-mum opening and relevant for the report of �norms�(Table 1).Subjects with TMD had a smaller maximum opening

(50.1 ± 6.2 mm) than those without (50.7 ± 6.4 mm).This difference was non-significant (Table 1). The 23subjects with a TMD pain diagnosis had a 51.0 ± 5.9-mm maximum opening that was not different when

compared with the overall sample mean (t-test: P ¼0.75).

Regression analyses

In addition, multivariable regression analyses were per-formed to consider simultaneous effects of the influentialvariables on the jaw movements (Table 2). All regres-sion coefficients were small in magnitude. Age and gen-der effects were found to be nearly identical when abivariable or multivariable approach was used (Tables 1and 2). In the multivariable model, maximum unassistedopening increased by 0.4 mm per year of age, and girlshad a 1.8-mm smaller opening than boys. Laterotrusionto the right was only influenced by age (+0.1 mm per yrof age), and protrusion was influenced by age ()0.1 mmper yr of age), gender ()0.3 mm for girls), and thepresence of TMD (+0.5 mm for subjects with RDC/TMD diagnoses).

Reference values

In light of these results, only one outcome – maximummouth opening – had variables that were deemed suffi-ciently influential for which stratified �norms� could bedesignated – age and gender (Table 3). All other out-comes are presented non-stratified. Laterotrusion isreported separately for each direction because the dif-ference between laterotrusion to the right and to the left

Table 1

Comparison of jaw movements between groups according to age, gender, and temporomandibular disorder (TMD) diagnosis

Influential variable Maximum opening Laterotrusion right Laterotrusion left Protrusion

GenderFemale 49.7* 10.1 10.5 8.0Male 51.6* 10.2 10.7 8.3

Age10–13 yr 50.0* 10.1 10.4* 8.4*14–17 yr 51.3* 10.3 10.8* 7.9*

RDC/TMD-diagnosisYes 50.1 10.3 11.0 8.6No 50.7 10.1 10.6 8.1

*t-test, statistically significant according to Holm’s procedure.RDC/TMD, Research Diagnostic Criteria for TMD.

Table 2

Coefficients (with 95% confidence interval) of the multivariable linear regression analyses (intercepts centred at the age of 10 yr)

Age Female gender RDC/TMD Intercept

Maximum opening 0.4* )1.8* )0.8 50.0*(0.2, 0.6) ()2.6, )1.0) ()2.1, 0.5) (49.5, 51.2)

Laterotrusion right 0.1 )0.2 0.1 10.0*(0.0, 0.1) ()0.4, 0.1) ()0.3, 0.6) (9.7, 10.3)

Laterotrusion left 0.1* )0.2 0.4 10.4*(0.0, 0.2) ()0.5, 0.1) ()0.1, 0.9) (10.0, 10.7)

Protrusion )0.1* )0.3* 0.5* 8.7*()0.2, 0.0) ()0.6, 0.0) (0.0, 1.0) (8.3, 9.0)

*P < 0.05.

30

40

50

60

70

80

10 11 12 13 14 15 16 17 10 11 12 13 14 15 16 17

Male Female

mm

Age in yr

Fig. 1. Maximum unassisted opening for boys and girlsbetween 10 and 17 yr.

Norms for jaw movement 467

was present in all subgroups (Table 1). In Table 3, the50th percentile (median) represents the �norm� of jawmovement capacity for Caucasian children and adoles-cents between 10 and 17 yr.

Discussion

This study presents �norm� values for jaw movementcapacity in 10–17-yr-old Caucasian children and teen-agers. In contrast to other studies, our study has severaladvantages: (i) it is population-based; (ii) the responseproportion was high; (iii) all measurements were assessedusing a standardized protocol according to the RDC/TMD; (iv) data concerning reliability are given for clin-ical measurements and diagnoses; and (v) the influencesof age, gender, and TMD were simultaneously analyzedin a population-based sample using a multivariableapproach.Based on our results, a stratification of the reported

reference values seems to be largely dispensable becausethe effect of the influential variables on the outcomemeasurements was small. Only for maximum unassistedopening did gender and age have a significant and clin-ically relevant influence. The results of the multivariablemodel showed that the age and gender effects were notconfounded by each other and, as far as we know, thishas not been reported in the literature. Age and genderdifferences in jaw opening were also reported in otherstudies (13–18). In most of the previous studies, changesover time and across genders were only suggestive andnot significant (6). Nontheless, Ogura et al. (18) andGazit et al. (14) reported a 5-mm difference in verticalmandibular opening between boys and girls – a magni-tude that is clinically relevant. It seems that gender andage differences in mouth opening are present in thepopulations and should be considered in the presentationof �norms�. Although our definition of a relevant differ-ence in mouth opening is open to debate, other investi-gators share our view of stratifying �norms� of mouthopening according to age and gender (19, 20).The comparison of jaw motion investigations in the

literature presents a different picture. Nielsen et al. (21)reported a 52.2-mm mouth opening, a 10.8-mm latero-

trusion to the right, a 10.7-mm laterotrusion to the left,and a 9.4-mm protrusion in 14–16-yr-old Danish ado-lescents, which are almost identical to our findings.Ogura et al. (18) reported an average range of openingof 49.5 mm in 10–18-yr-old Japanese children and ado-lescents, which is � 2 mm less than found in the presentsample. However, this difference was probably caused bythe measurement method because the authors of theJapanese study used the interincisal distance withoutconsidering overbite. Using the RDC/TMD specifica-tions, List et al. (6) found more than 55 mm (mean) formaximum unassisted opening in Swedish adolescents,which is 4 mm larger than in our sample. We have noexplanation for this difference; it seems that there may bedifferent �norms� in different populations.Interestingly, our data confirm the former findings of a

greater laterotrusion to the left, which was observed inboth adult TMD patients and healthy adults (19, 22).Others did not find differences between laterotrusion tothe right and left (21, 23). However, in the generalpopulation, differences in joint mobility between the leftand right side are not limited to the jaw joints, they werealso observed in other joint pairs (knee, elbow) (24).Therefore, it seems justified to consider differencesbetween right and left laterotrusion in the report of�norms� for populations. As an explanation for the dif-ferences between left and right laterotrusion, Turp et al.(21) hypothesized functional differences in the left andright inferior head of the lateral pterygoid muscle.However, the clinical importance of the individual dif-ferences between laterotrusion to the right and leftshould be the subject of further studies.Furthermore, our results showed that TMD have only

a negligible influence on the measurements, which wassupported by Szentpetery et al. (19). In contrast tothese results, other studies found differences in the rangeof jaw motion between TMD populations and healthycontrols (6,25). A probable reason for this difference isthat the majority of the TMD subjects in our study had anon-painful TMD condition, whereas the other twostudies included painful TMD conditions. It should beborne in mind that jaw movement capacity can also belimited for other reasons, for example, surgical proce-dures by Ear, Nose and Throat specialists (26); in other

Table 3

Percentiles of jaw movement capacity (in mm)

Percentiles

Maximum mouth opening Laterotrusion

ProtrusionAll Female Male 10–13 yr 14–17 yr Right Left

10 43 42 43 42 43 7 8 520 45 45 46 45 46 8 9 630 47 47 48 47 48 9 10 740 49 48 50 48 49 10 10 850 51 50 52 50 51 10 11 860 52 51 53 52 53 11 11 970 54 52 55 53 55 11 12 1080 56 55 57 55 57 12 12 1090 59 57 60 57 60 13 14 11

468 Hirsch et al.

words, not all subjects who have limitations in their jawmovement have TMD. This may have limited the study’sability to detect a TMD influence on jaw mobility.Only 2.3% of the participants in this study had an

RDC/TMD pain diagnosis, which is slightly lower thanthe prevalence of 4–7% that has been reported in otherstudies (27, 28). Unfortunately, we have no informationindicating whether TMD status differed in respondersand non-responders, which is a limitation of our study.However, it seems unlikely that possible existing differ-ences would influence the results of this investigationbecause the response rate was so high. The low preval-ence of pain diagnoses, however, limits the ability of thisstudy to determine cut-off points for specific TMD painconditions.The different TMD pain prevalences in various studies

are often the result of different assessment methods. Forexample, Nilsson et al. (28) asked for �… pain in thetemples, face, jaw joints, or jaws once a week or more�and found a prevelance of 4.2%. The period prevalencein the present sample, using a question from the RDC/TMD (�Have you had pain in the face, jaw, temple, infront of the ear, or in the ear in the past month?�), wassubstantial, namely 15%, which was reported earlier(29). In contrast, an RDC/TMD pain diagnosis requiresa positive pain report at the moment of the examination(�point prevalence�), which is lower than a period pre-valence. RDC/TMD diagnoses with limitations of jawmotion per definitionem (i.e. muscle pain with limitedopening, disc displacement without reduction with lim-ited opening) were not present in our adolescent sample.This is not surprising, because they are also extremelyrare in adult populations (30), and even in populations ofTMD patients they occur only infrequently (31, 32).Owing to their rare occurrence, these conditions do notinfluence population �norms� of jaw motion.The results of this study are applicable in routine

dental practice and for dental public health: First, thereported �norms� and the presentation of the percentileswill allow clinicians to categorize a patient’s mandibularmovements as �normal� (i.e. frequently occurring incomparison to other individuals), or as �not normal�. The�normal� Caucasian child or teenager aged 10–17 yr has a51-mm maximum unassisted opening (50 mm for girls,52 mm for boys, 50 mm for 10–13-yr-old subjects,51 mm for 14–17-yr-old subjects), a 10-mm laterotrusionto the right, an 11-mm laterotrusion to the left, and an 8-mm protrusion. We are aware of the limitations of adistribution-based approach to distinguish between�limited� and �normal� mandibular motion, but at present,in the absence of convincing data on the relevance of anyrange of mandibular motion influence on importantphysical and psychosocial outcomes, this method, com-bined with clinical expertise, serves as the only availableapproach for clinical decision-making.Second, the normative values are helpful in further

studies to determine cut-off points for specific TMDconditions, such as myofascial pain with limitations, anddisc displacements without reductions and with limitedopening. We suggest that the lowest decentile should beused (i.e. the lowest 10% of each measure’s distribution

in the general population) for defining �limited mandib-ular movement�. Thus, Caucasian children and teenagerswith <8 mm for laterotrusive movements or <5 mmfor protrusive movements, in addition to <43 mm formaximum mouth opening, should be regarded as havinglimited mandibular mobility.In conclusion, normative values for jaw movement

capacity (maximum jaw opening, laterotrusion, protru-sion) in Caucasian children and adolescents are influ-enced by age and gender, but not by the presence ofTMD. However, the age and gender influence is only fora mouth opening of relevant magnitude which, conse-quently, requires age and gender stratification of thisvariable. The percentiles presented in this study on jawmovement measurements can be used in combinationwith clinical expertise to diagnose severe divergences inan individual subject based on the frequency of thevariables in the population.

Acknowledgements – This study was supported by Kultusmin-isterium Sachsen-Anhalt (grant 3292A/0080G).

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