Clinical Study The Electrical Activity of the Temporal and ...downloads.hindawi.com/journals/bmri/2015/259372.pdf · The Electrical Activity of the Temporal and Masseter Muscles in

Clinical StudyThe Electrical Activity of the Temporal and Masseter Muscles inPatients with TMD and Unilateral Posterior Crossbite

Krzysztof Wofniak1 Liliana Szyszka-Sommerfeld1 and Damian Lichota2

1 Department of Orthodontics Pomeranian Medical University of Szczecin Al Powst Wlkp 72 70111 Szczecin Poland2Department of Conservative Dentistry Pomeranian Medical University of Szczecin 70111 Szczecin Poland

Correspondence should be addressed to Krzysztof Wozniak krzysztofwozniakpumedupl

Received 8 August 2014 Revised 13 September 2014 Accepted 16 September 2014

Academic Editor Mieszko Wieckiewicz

Copyright copy 2015 Krzysztof Wozniak et al This is an open access article distributed under the Creative Commons AttributionLicense which permits unrestricted use distribution and reproduction in any medium provided the original work is properlycited

The aim of this study was to assess the influence of unilateral posterior crossbite on the electrical activity of the temporal andmasseter muscles in patients with subjective symptoms of temporomandibular dysfunctions (TMD) The sample consisted of 50patients (22 female and 28 male) aged 184 to 263 years (mean 2084 SD 114) with subjective symptoms of TMD and unilateralposterior crossbite malocclusion and 100 patients without subjective symptoms of TMD and malocclusion (54 female and 46male) aged between 184 and 287 years (mean 2142 SD 106) The anamnestic interviews were conducted according to a three-point anamnestic index of temporomandibular dysfunction (Ai) Electromyographical (EMG) recordings were performed usinga DAB-Bluetooth Instrument (Zebris Medical GmbH Germany) Recordings were carried out in the mandibular rest positionand during maximum voluntary contraction (MVC) Analysis of the results of the EMG recordings confirmed the influence ofunilateral posterior crossbite on variations in spontaneous muscle activity in the mandibular rest position andmaximum voluntarycontraction In addition there was a significant increase in the Asymmetry Index (As) and Torque Coefficient (Tc) responsible fora laterodeviating effect on the mandible caused by unbalanced right and left masseter and temporal muscles

1 Introduction

Bilateral symmetry characteristic of vertebrates is extremelyimportant for describing the morphology of the masticatoryorgan This feature is strongly marked in the craniofacialarea and is an important determinant of its correct structureAssessment of bilateral symmetry in the craniofacial area is afundamental component of the examination and descriptionof people with and without disorders It must be statedhowever that slight facial asymmetry is acceptable beinga common and frequently observed morphological feature[1 2] Such a disruption of symmetry is not a significantexception but a commonly accepted structural deviationUnfortunately the extent of acceptable craniofacial asym-metry has not been clearly defined The concept of thebilateral symmetry of the human body is also connectedwith functional symmetry An assessment of this feature inthe craniofacial area is primarily related to the function ofthe largest and strongest facial bone namely the mandibleThe symmetrical function of this bone which is the single

and only movable bone of the skull is determined by twomorphologically coupled temporomandibular joints

In this context a harmonised relationship between thedental arches is essential for maintaining functional sym-metry Malocclusion particularly of the transverse typewhere disrupted symmetry of dental arches can be clinicallyobserved is a potential cause of functional disorders [3ndash6] Apriori knowledge clearly indicates the impact of the relation-ship between dental arches on the function of themasticatoryorgan [7ndash10]

The aim of this study was to assess the influence ofunilateral posterior crossbite on the electrical activity of thetemporal and masseter muscles in patients with subjectivesymptoms of temporomandibular dysfunctions (TMD)

2 Materials and Methods

Fifty patients (22 women and 28 men) aged between 184 and263 years (mean 2084 SD 114) with subjective symptoms of

Hindawi Publishing CorporationBioMed Research InternationalVolume 2015 Article ID 259372 7 pageshttpdxdoiorg1011552015259372

2 BioMed Research International

TMD (Ai II-III) and unilateral posterior crossbite malocclu-sion were selected from patients referred to the PomeranianUniversity in Szczecin Poland The control group consistedof 100 subjects (54 women and 46 men) aged between 195and 287 years (mean 2142 SD 106) with no malocclusionand subjective symptoms of TMD (Ai I) Patients who hadalready finished their orthodontic treatment and those whowere undergoing treatment at the time of the study wereexcluded

The anamnestic interviews included the patientsrsquo generalmedical history as well as detailed information about theirmasticatory motor system They were conducted accordingto a three-point anamnestic index of temporomandibulardysfunctionmdashAi (Table 1) [11 12]

The assessment of the function of the masticatory motorsystem included clinical examination and electromyographicprocedures Clinical examination consisted of visual andauscultatory assessment as well as palpation This made itpossible to accurately and precisely evaluate the function ofthemasticatory system Data obtained from the clinical studywas analysed using the clinical temporomandibular dysfunc-tion index (Di)

All the patients gave their informed consent to all of theprocedures performed

EMG recordings were performed using a DAB-BluetoothInstrument (Zebris Medical GmbH Germany) Each patientwas sitting on a comfortable chair without head support andwas requested to assume a natural head position

Surface EMG signals were detected by four silversilverchloride (AgAgCl) disposable self-adhesive bipolar elec-trodes (Noraxon Dual Electrode Noraxon USA) with afixed interelectrode distance of 20mm The electrodes wereaccurately positioned on the anterior temporal muscle andthe superficial masseter on both the left and the right sidesparallel to the muscular fibres Anterior temporal muscle isvertically along the anterior margin of the muscle massetermuscle is parallel to the muscular fibres with the upper poleof the electrode at the intersection between the tragus-labialcommissura and exocanthion-gonion lines A reference elec-trode was applied inferior and posterior to the right ear [13]

To reduce skin impedance the skin was cleaned with70 ethyl alcohol and dried prior to the placement of theelectrode The recordings were performed 5 minutes later

EMG activity was then recorded during three differenttests

(1) Rest activity of the masticatory muscles was per-formed in the clinical rest position

(2) Maximumvoluntary clench (MVC)was performed inthe intercuspal position and the subject was asked toclench as hard as possible for 5 seconds

(3) Maximum voluntary clench (MVC) was performedwith two 10mm thick cotton rolls positioned on themandibular second premolars and molars and thesubject was asked to clench as hard as possible for 5seconds

To avoid any effects of fatigue a rest period of at least 5minutes was allowed between each of the recordings

For each muscle the EMG potentials were expressedas a percentage of the MVC value using cotton rolls (unit120583V120583V) This kind of standardization should obviate anyvariability due to skin and electrode impedance electrodepositioning and relativemuscular hypo- or hypertrophy [14ndash16]

In the current study muscular coordination and symme-try of themasticatorymuscleswere expressed through the useof indices

The asymmetry between the activity of the left and rightjaw muscles was quantified by the Asymmetry Index (Asunit )This ranges from 0 (total symmetry) to 100 (totalasymmetry)

As =sum119873

119894=1

1003816100381610038161003816119877119894 minus 119871 1198941003816100381610038161003816

sum119873

119894=1(119877119894+ 119871119894)sdot 100 (1)

To assess the presence of a possible laterodeviating effecton themandible during the test caused by unbalancedTR andML and TL and MR couples the Torque coefficient (Tc unit) was calculated as follows

Tc =sum119873

119894=1

1003816100381610038161003816(119879119877 +119872119871)119894 minus (119879119871 +119872119877)1198941003816100381610038161003816

sum119873

119894=1[(119879119877 +119872119871) + (119879119871 +119872119877)]119894

sdot 100 (2)

Tc ranges from 0 no torque during the test to 100 asignificant laterodeviating effect on the mandible [17ndash19]

The Kruskal-Wallis test and the Mann-Whitney 119880 testwere used to verify the hypotheses relating to the existenceor absence of differences between the mean values of theindependent variables The level of significance was set at119875 = 005

The research was approved by the Ethics Committee ofthe PomeranianMedical University in Szczecin (number BN-0014507)

3 Results

The analysis of the results of EMG recordings confirmed theinfluence of unilateral posterior crossbite on the variabilityof muscle activity in the mandibular rest position (Table 2Figure 1)The rest activity of the temporalmuscles was higherin subjects with crossbite and subjective symptoms of TMD(711 120583V120583V 119875 lt 00249) compared with healthy subjects(407 120583V120583V) There were no significant differences in therest activity of themassetermuscles in either examined group(119875 lt 05902)

The results showed a significant increase in the Asymme-try Index in relation to both the rest activity of the temporal(2930 119875 lt 00001) and masseter muscles (3807 119875 lt00006) in patients with unilateral posterior crossbite (Figure2)

Additionally a significant increase was observed in thetorque for the pair of muscles responsible for the lateralfunctional shift of themandible in the rest position in patientswith crossbite (1456 119875 lt 00002 Figure 3)

The differences presented regarding asymmetry in spon-taneous muscle activity between the two examined groupswere confirmed only for women

BioMed Research International 3

Table 1 Anamnestic index of temporomandibular dysfunction (Ai)

Ai SymptomsI No subjective symptoms of temporomandibular dysfunction no symptoms reported by patient

IIMild symptoms of temporomandibular dysfunction temporomandibular joint noise feeling of ldquojawfatiguerdquo (fatigue of masticatory muscles) and feeling of ldquojaw rigidityrdquo (increased tone of masticatorymuscles)

IIISevere symptoms of temporomandibular dysfunction restricted mouth opening painful lower jawmovements temporomandibular joint pain masticatory muscle pain temporomandibular joint luxationand lockjaw

Table 2 Electrical activity of muscles at clinical mandibular rest position depending on transversal malocclusion

Region Variable GenderGroup

No malocclusion Crossbite119899 Mean SD 119899 Mean SD

Temporal muscles

Electrical activity [120583V120583V]Females 54 407 202 22 708 645Males 46 408 206 28 714 510Total 100 407 203 50 711 567

Asymmetry index []Females 54 2120 948 22 3635 1271Males 46 1712 900 28 2377 1560Total 100 1933 944 50 2930 1559

Masseter muscles



Temporalmasseter muscles Torque coefficient []Females 54 720 766 22 1943 1353Males 46 437 395 28 1073 1283Total 100 590 636 50 1456 1372

An analysis of the EMG recordings during MVC con-firmed the influence of transversal malocclusion on the activ-ity of the masticatory muscles (Table 3 Figure 1) In patientswith unilateral posterior crossbite a significant decrease inthe activity of the temporal (9159 120583V120583V 119875 lt 00000)as well as masseter muscles (9708 120583V120583V 119875 lt 00000)in relation to subjects without malocclusion (temporal andmasseter muscles 11627120583V120583V and 13199 120583V120583V resp)was observed

The importance of transverse defects was also reflectedin significantly higher rates of muscle asymmetry for thetemporal (1796 119875 lt 00000) and masseter muscles (1710119875 lt 00000 Figure 2) during maximum isometric contrac-tion in patients with unilateral posterior crossbite Analysisrevealed a considerable imbalance in the torque for the pairof muscles responsible for the lateral functional shift of themandible in patients with crossbite (433 119875 lt 00380Figure 3)

4 Discussion

In our study an analysis of the influence of the relationshipsbetween dental arches on the electrical activity of muscleswas performed with respect to two functions in the

mandibular rest position and during maximum isometriccontraction The results confirmed the significant impactof transversal malocclusions on the electrical activity of thetemporal and masseter muscles in patients with subjectivesymptoms of TMD In the analysis of the results of thisscientific experiment in addition to measurements whichwere specific for each research method quotient indicatorssuch as the Asymmetry Index and the Torque coefficient wereused The use of these mathematical tools made it possibleto significantly increase the possibilities of describing thebiomedical reality As a result the unbalanced torque of thetwo pairs of muscles responsible for the functional lateralshift of the mandible in subjects with unilateral posteriorcrossbite was observed This was consistent with the clinicalobservations Increased asymmetry in spontaneous musclesactivity was revealed only inwomen andmay suggest a highersensitivity of this examined group for asymmetry of dentalarches

A review of the literature presented by McNamara et al[20] indicates that there are relatively weak links betweenfunction and the alignment of dental arches Only fiveocclusal features such as skeletal anterior open bite overjetgreater than 6 to 7mm retruded cuspal positionintercuspalposition slides greater than 4mm unilateral lingual crossbite


Table 3 Electrical activity of muscles at maximal voluntary contraction (MVC) in intercuspal position depending on transversal malo-cclusion



Temporal muscles



Masseter muscles




No malocclusionLingual crossbite

407 212

11627

13199

711196

91599708

0

20

40

60

80

100

120

140

160

Temporal muscles

minus20Masseter muscles

Masseter muscles

Temporal muscles

MVC Spontaneous activity

Weighted means

Effective hypothesis decomposition

Elec

tric

activ

ity (120583

V120583

V

)

Current effect F(3444) = 30171 P = 00000

Figure 1 Electrical activity of muscles at clinical mandibularrest position and at maximal voluntary contraction (MVC) inintercuspal position depending on transversal malocclusion

and five ormoremissing posterior teeth have been associatedwith functional disorders of the masticatory motor system

Mohlin et al [21] in a methodical review of 58 studieson the correlations between symptoms of TMD and mal-occlusions found that there were small differences in termsof functional disorders between subjects with and withoutmalocclusions and thus the authors critically assessed these

Weighted means


1933

2699

927 983

2930

3807

1796 1710

5

10

15

20

25

30

35

40

45

Asy

mm

etry

inde

x (

)


Temporal muscles

Masseter muscles

Masseter muscles

Temporal muscles



Figure 2 Asymmetry Index (As) of muscles at clinical mandibularrest position and at maximal voluntary contraction (MVC) inintercuspal position depending on transversal malocclusion

studies Moreover they confirmed a lack of unanimity inthe denotation of correlations between function and specifictypes of malocclusion

The studies conducted by Egermark-Eriksson et al [22]in a group of 238 subjects aged 7 to 15 years also showed weakassociation between functional disorders and malocclusionsThe confirmation of this thesis was provided by a lack of


Weighted means


590

295

1456

433

Spontaneous activity MVC0

2

4

6

8

10

12

14

16

Torq

ue co

effici

ent (

)



Figure 3 Torque coefficient (Tc) of muscles at clinical mandibularrest position and at maximal voluntary contraction (MVC) in inter-cuspal position depending on transversal malocclusion

variability in the frequency of occurrence for the symptomsof functional disorders in the group who had receivedorthodontic treatment compared with the group of subjectswithout such treatment Nevertheless with regard to somemalocclusions such as crossbite both uni- and bilateralanterior open bite and post- and prenormal occlusion ahigher risk of developing functional disorders was recorded

Later a 20-year follow-up by Egermark et al [23] andMagnusson et al [24] showed weak correlations betweenmalocclusions and both symptoms and signs of TMD in agroup of 402 subjects Only unilateral crossbitewas correlatedwith symptoms of TMD (119903 = 034 119875 lt 001) Subjects withmalocclusion over a long period of time tended to reportmore subjective symptoms of dysfunctions and to show ahigher dysfunction index compared with subjects with nomalocclusion

An analysis of masticatory muscle activity in patientswith altered occlusal relationships due to malocclusion wasthe subject of studies conducted by Ferrario et al [25]The examined group consisted of 10 subjects aged 16ndash18years with posterior unilateral crossbite bilateral angle ClassI and an overjet and overbite between 2 and 5mm Thecontrol group consisted of 20 subjects with healthy dentitionand with no malocclusion Electromyographic recordings ofmasticatory muscles during chewing were performed Thefindings of the study showed a decisive influence of crossbiteon the electrical activity of the temporal and massetermuscles manifesting itself in their disturbed coordinationMoreover the functional changes were more apparent whenthe side with the altered transversal relationships was directlyinvolved Similar results were obtained by Rilo et al [26 27]

The relationship between transversal malocclusions andthe electrical activity of themuscles was described byAlarconet al [28] Electromyographic recordings of anterior andposterior temporal and masseter muscles as well as anteriordigastric muscles in 30 subjects with unilateral posteriorcrossbite and in a control group of 30 normocclusive subjectswere made at rest position during swallowing and duringmastication The results of the study revealed that the pos-terior temporal muscle on the noncrossbite side was moreactive than that of the same side in subjects with crossbiteat rest position and during swallowing The activity of bothanterior digastrics was higher in subjects with crossbiteduring swallowing Moreover during chewing the massetermuscle was less active in patients with crossbite than inthe subjects in the control group The similar findings werereported by Kecik et al [29] The influence of transversalmalocclusions on function was confirmed in the prospec-tive electromyographic studies conducted by Sohn et al[30] The authors obtained an improvement in masticatoryefficiency after orthodontic treatment of anterior crossbiteThe duration of muscle activity and the incidence of silentperiods in the superficial part of the masseter muscle duringchewing in fact decreased after treatment There were nosignificant differences in the electrical activity of the anteriorand posterior temporal muscles before and after treatment

Saifuddin et al [31] assessed the electrical activity ofthe temporal and masseter muscles in patients with lateraldeviations of the mandible (from 5 to 14mm) crossbitecrowding and those with no subjective symptoms in themasticatory motor system The control group consisted ofsubjects without significant craniofacial asymmetry (accept-able range from 0 to 3mm) malocclusions or subjectivesymptoms of functional disorders The electromyographicrecordings included not just selected activities but also thefull daily activity including speech eating drinking andsleeping The analysis of muscle activity was divided intothree periods ordinary daily activities mealtimes and sleep-ing The results showed that muscle activity in patients withdisorders was significantly lower during all three periods forthe masseter muscle and during ordinary daytime activitiesfor the temporal muscle in comparison to the control groupThe Asymmetry Index (AI) in patients with a lateral shift ofthe mandible was significantly greater during usual daytimeactivities and sleep for the temporal muscle and significantlysmaller during sleep for the masseter muscle in comparisonto the control group The results clearly revealed that theasymmetry in the electrical activity during ordinary daytimeactivities and sleep in patients with lateral deviations of themandible to a greater extent affects temporal muscles (ante-rior part) than masseter muscles According to the authors areduction in temporal andmasseter muscle electrical activitywith the accompanying asymmetry in the electrical activity ofthe temporal muscles is closely related to occlusal instabilitydue to malocclusions and lateral mandibular deviation

A review of the literature presented does not indicate aclear association betweenmalocclusions and TMDHoweverthe results of the aforementioned studies suggest a higher riskof the prevalence of TMD in patients with unilateral posteriorcrossbite


5 Conclusions

The use of sEMG in the assessment of the function of themasticatory motor system provided tangible evidence of thedetermining influence of unilateral posterior crossbite on theelectrical activity of the temporal and masseter muscles inpatients with subjective symptoms of TMD

Conflict of Interests

The authors declare that there is no conflict of interestsregarding the publication of this paper

References

[1] D Grummons and R M Ricketts ldquoFrontal cephalometricspractical applications part 2rdquo World Journal of Orthodonticsvol 5 no 2 pp 99ndash119 2004

[2] M G Piancino F Talpone P Dalmasso C Debernardi ALewin and P Bracco ldquoReverse-sequencing chewing patternsbefore and after treatment of childrenwith a unilateral posteriorcrossbiterdquo European Journal of Orthodontics vol 28 no 5 pp480ndash484 2006

[3] A D S Andrade G H Gameiro M DeRossi and M B DGaviao ldquoPosterior crossbite and functional changes a system-atic reviewrdquo Angle Orthodontist vol 79 no 2 pp 380ndash3862009

[4] J C Turp and H Schindler ldquoThe dental occlusion as a sus-pected cause for TMDs epidemiological and etiological consid-erationsrdquo Journal of Oral Rehabilitation vol 39 no 7 pp 502ndash512 2012

[5] S Tecco and F Festa ldquoPrevalence of signs and symptoms oftemporomandibular disorders in children and adolescents withand without crossbitesrdquo World Journal of Orthodontics vol 11no 1 pp 37ndash42 2010

[6] L J Pereira R C Costa J P Franca S M Pereira and P MCastelo ldquoRisk indicators for signs and symptoms of temporo-mandibular dysfunction in childrenrdquo Journal of Clinical Pedi-atric Dentistry vol 34 no 1 pp 81ndash86 2009

[7] M Wieckiewicz M Zietek D Nowakowska and W Wieck-iewicz ldquoComparison of selected kinematic facebows applied tomandibular tracingrdquo BioMed Research International vol 2014Article ID 818694 5 pages 2014

[8] B J Langberg K Arai and R M Miner ldquoTransverse skeletaland dental asymmetry in adults with unilateral lingual posteriorcrossbiterdquo The American Journal of Orthodontics and Dentofa-cial Orthopedics vol 127 no 1 pp 6ndash15 2005

[9] N Kilic A Kiki and H Oktay ldquoCondylar asymmetry in uni-lateral posterior crossbite patientsrdquo American Journal of Ortho-dontics and Dentofacial Orthopedics vol 133 no 3 pp 382ndash3872008

[10] I Veli T Uysal T Ozer F I Ucar and M Eruz ldquoMandibu-lar asymmetry in unilateral and bilateral posterior crossbitepatients using cone-beam computed tomographyrdquoAngle Ortho-dontist vol 81 no 6 pp 966ndash974 2011

[11] R A Leite J F Rodrigues M T Sakima and T Sakima ldquoRela-tionship between temporomandibular disorders and orthodon-tic treatment a literature reviewrdquoDental Press Journal of Ortho-dontics vol 18 no 1 pp 150ndash157 2013

[12] R Napankangas A Raunio K Sipila and A Raustia ldquoEffectof mandibular advancement device therapy on the signs and

symptoms of temporomandibular disordersrdquo Journal of Oraland Maxillofacial Research vol 3 no 4 article e5 2012

[13] V F Ferrario C Sforza G Zanotti and G M Tartaglia ldquoMax-imal bite forces in healthy young adults as predicted by surfaceelectromyographyrdquo Journal of Dentistry vol 32 no 6 pp 451ndash457 2004

[14] V F Ferrario C Sforza G Serrao A Colombo and J HSchmitz ldquoThe effects of a single intercuspal interference on elec-tromyographic characteristics of human masticatory musclesduring maximal voluntary teeth clenchingrdquo Cranio vol 17 no3 pp 184ndash188 1999

[15] V F Ferrario C Sforza A Miani Jr A DAddona and EBarbini ldquoElectromyographic activity of human masticatorymuscles in normal young people statistical evaluation of refer-ence values for clinical applicationsrdquo Journal of Oral Rehabilita-tion vol 20 no 3 pp 271ndash280 1993

[16] V F Ferrario C SforzaGMTartaglia andCDellavia ldquoImme-diate effect of a stabilization splint on masticatory muscle acti-vity in temporomandibular disorder patientsrdquo Journal of OralRehabilitation vol 29 no 9 pp 810ndash815 2002

[17] V F Ferrario C Sforza A Colombo and V Ciusa ldquoAn elec-tromyographic investigation of masticatory muscles symmetryin normo-occlusion subjectsrdquo Journal of Oral Rehabilitationvol 27 no 1 pp 33ndash40 2000

[18] U Santana-Mora J Cudeiro M J Mora-Bermudez et alldquoChanges in EMG activity during clenching in chronic painpatients with unilateral temporomandibular disordersrdquo Journalof Electromyography and Kinesiology vol 19 no 6 pp e543ndashe549 2009

[19] D R Bigaton K C S Berni A F N Almeida and M TSilva ldquoActivity and asymmetry index of masticatory musclesin women with and without dysfunction temporomandibularrdquoElectromyography and Clinical Neurophysiology vol 50 no 7-8pp 333ndash338 2010

[20] J A McNamara Jr D A Seligman and J P Okeson ldquoOcclu-sion orthodontic treatment and temporomandibular disor-ders a reviewrdquo Journal of Orofacial Pain vol 9 no 1 pp 73ndash901995

[21] B Mohlin S Axelsson G Paulin et al ldquoTMD in relation tomalocclusion and orthodontic treatmentrdquo Angle Orthodontistvol 77 no 3 pp 542ndash548 2007

[22] I Egermark-Eriksson G E Carlsson T Magnusson and BThilander ldquoA longitudinal study on malocclusion in relation tosigns and symptoms of cranio-mandibular disorders in childrenand adolescentsrdquo European Journal of Orthodontics vol 12 no4 pp 399ndash407 1990

[23] I Egermark T Magnusson and G E Carlsson ldquoA 20-yearfollow-up of signs and symptoms of temporomandibular dis-orders and malocclusions in subjects with and without ortho-dontic treatment in childhoodrdquo Angle Orthodontist vol 73 no2 pp 109ndash115 2003

[24] T Magnusson I Egermark and G E Carlsson ldquoA prospectiveinvestigation over two decades on signs and symptoms oftemporomandibular disorders and associated variables A finalsummaryrdquo Acta Odontologica Scandinavica vol 63 no 2 pp99ndash109 2005

[25] V F Ferrario C Sforza and G Serrao ldquoThe influence of cross-bite on the coordinated electromyographic activity of humanmasticatory muscles during masticationrdquo Journal of Oral Reha-bilitation vol 26 no 7 pp 575ndash581 1999

[26] B Rilo J L da Silva F Gude and U Santana ldquoMyoelectricactivity during unilateral chewing in healthy subjects cycle


duration and order of muscle activationrdquo The Journal of Pros-thetic Dentistry vol 80 no 4 pp 462ndash466 1998

[27] B Rilo J L D Silva M J Mora C Cadarso-Suarez andU Santana ldquoUnilateral posterior crossbite and masticationrdquoArchives of Oral Biology vol 52 no 5 pp 474ndash478 2007

[28] J A Alarcon C Martın and J C Palma ldquoEffect of unilateralposterior crossbite on the electromyographic activity of humanmasticatorymusclesrdquoTheAmerican Journal of Orthodontics andDentofacial Orthopedics vol 118 no 3 pp 328ndash334 2000

[29] D Kecik I Kocadereli and I Saatci ldquoEvaluation of the treat-ment changes of functional posterior crossbite in the mixeddentitionrdquo American Journal of Orthodontics and DentofacialOrthopedics vol 131 no 2 pp 202ndash215 2007

[30] B W Sohn S Miyawaki H Noguchi and K TakadaldquoChanges in jaw movement and jaw closing muscle activityafter orthodontic correction of incisor crossbiterdquoThe AmericanJournal ofOrthodontics andDentofacialOrthopedics vol 112 no4 pp 403ndash409 1997

[31] M Saifuddin K Miyamoto H M Ueda N Shikata and KTanne ldquoAn electromyographic evaluation of the bilateral sym-metry and nature of masticatory muscle activity in jaw defor-mity patients during normal daily activitiesrdquo Journal of OralRehabilitation vol 30 no 6 pp 578ndash586 2003

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Evidence-Based Complementary and Alternative Medicine

Volume 2014Hindawi Publishing Corporationhttpwwwhindawicom


TMD (Ai II-III) and unilateral posterior crossbite malocclu-sion were selected from patients referred to the PomeranianUniversity in Szczecin Poland The control group consistedof 100 subjects (54 women and 46 men) aged between 195and 287 years (mean 2142 SD 106) with no malocclusionand subjective symptoms of TMD (Ai I) Patients who hadalready finished their orthodontic treatment and those whowere undergoing treatment at the time of the study wereexcluded

The anamnestic interviews included the patientsrsquo generalmedical history as well as detailed information about theirmasticatory motor system They were conducted accordingto a three-point anamnestic index of temporomandibulardysfunctionmdashAi (Table 1) [11 12]

The assessment of the function of the masticatory motorsystem included clinical examination and electromyographicprocedures Clinical examination consisted of visual andauscultatory assessment as well as palpation This made itpossible to accurately and precisely evaluate the function ofthemasticatory system Data obtained from the clinical studywas analysed using the clinical temporomandibular dysfunc-tion index (Di)

All the patients gave their informed consent to all of theprocedures performed

EMG recordings were performed using a DAB-BluetoothInstrument (Zebris Medical GmbH Germany) Each patientwas sitting on a comfortable chair without head support andwas requested to assume a natural head position

Surface EMG signals were detected by four silversilverchloride (AgAgCl) disposable self-adhesive bipolar elec-trodes (Noraxon Dual Electrode Noraxon USA) with afixed interelectrode distance of 20mm The electrodes wereaccurately positioned on the anterior temporal muscle andthe superficial masseter on both the left and the right sidesparallel to the muscular fibres Anterior temporal muscle isvertically along the anterior margin of the muscle massetermuscle is parallel to the muscular fibres with the upper poleof the electrode at the intersection between the tragus-labialcommissura and exocanthion-gonion lines A reference elec-trode was applied inferior and posterior to the right ear [13]

To reduce skin impedance the skin was cleaned with70 ethyl alcohol and dried prior to the placement of theelectrode The recordings were performed 5 minutes later

EMG activity was then recorded during three differenttests

(1) Rest activity of the masticatory muscles was per-formed in the clinical rest position

(2) Maximumvoluntary clench (MVC)was performed inthe intercuspal position and the subject was asked toclench as hard as possible for 5 seconds

(3) Maximum voluntary clench (MVC) was performedwith two 10mm thick cotton rolls positioned on themandibular second premolars and molars and thesubject was asked to clench as hard as possible for 5seconds

To avoid any effects of fatigue a rest period of at least 5minutes was allowed between each of the recordings

For each muscle the EMG potentials were expressedas a percentage of the MVC value using cotton rolls (unit120583V120583V) This kind of standardization should obviate anyvariability due to skin and electrode impedance electrodepositioning and relativemuscular hypo- or hypertrophy [14ndash16]

In the current study muscular coordination and symme-try of themasticatorymuscleswere expressed through the useof indices

The asymmetry between the activity of the left and rightjaw muscles was quantified by the Asymmetry Index (Asunit )This ranges from 0 (total symmetry) to 100 (totalasymmetry)

As =sum119873

119894=1

1003816100381610038161003816119877119894 minus 119871 1198941003816100381610038161003816

sum119873

119894=1(119877119894+ 119871119894)sdot 100 (1)

To assess the presence of a possible laterodeviating effecton themandible during the test caused by unbalancedTR andML and TL and MR couples the Torque coefficient (Tc unit) was calculated as follows

Tc =sum119873

119894=1

1003816100381610038161003816(119879119877 +119872119871)119894 minus (119879119871 +119872119877)1198941003816100381610038161003816

sum119873

119894=1[(119879119877 +119872119871) + (119879119871 +119872119877)]119894

sdot 100 (2)

Tc ranges from 0 no torque during the test to 100 asignificant laterodeviating effect on the mandible [17ndash19]

The Kruskal-Wallis test and the Mann-Whitney 119880 testwere used to verify the hypotheses relating to the existenceor absence of differences between the mean values of theindependent variables The level of significance was set at119875 = 005

The research was approved by the Ethics Committee ofthe PomeranianMedical University in Szczecin (number BN-0014507)

3 Results

The analysis of the results of EMG recordings confirmed theinfluence of unilateral posterior crossbite on the variabilityof muscle activity in the mandibular rest position (Table 2Figure 1)The rest activity of the temporalmuscles was higherin subjects with crossbite and subjective symptoms of TMD(711 120583V120583V 119875 lt 00249) compared with healthy subjects(407 120583V120583V) There were no significant differences in therest activity of themassetermuscles in either examined group(119875 lt 05902)

The results showed a significant increase in the Asymme-try Index in relation to both the rest activity of the temporal(2930 119875 lt 00001) and masseter muscles (3807 119875 lt00006) in patients with unilateral posterior crossbite (Figure2)

Additionally a significant increase was observed in thetorque for the pair of muscles responsible for the lateralfunctional shift of themandible in the rest position in patientswith crossbite (1456 119875 lt 00002 Figure 3)

The differences presented regarding asymmetry in spon-taneous muscle activity between the two examined groupswere confirmed only for women









Temporal muscles



Masseter muscles






4 Discussion








Temporal muscles



Masseter muscles





407 212

11627

13199

711196

91599708

0

20

40

60

80

100

120

140

160

Temporal muscles


Masseter muscles

Temporal muscles


Weighted means


Elec

tric

activ

ity (120583

V120583

V

)





Weighted means


1933

2699

927 983

2930

3807

1796 1710

5

10

15

20

25

30

35

40

45

Asy

mm

etry

inde

x (

)


Temporal muscles

Masseter muscles

Masseter muscles

Temporal muscles







Weighted means


590

295

1456

433


2

4

6

8

10

12

14

16

Torq

ue co

effici

ent (

)











5 Conclusions




References








































of






Disease Markers



OncologyJournal of





PPAR Research



Journal of

ObesityJournal of
























Temporal muscles



Masseter muscles






4 Discussion








Temporal muscles



Masseter muscles





407 212

11627

13199

711196

91599708

0

20

40

60

80

100

120

140

160

Temporal muscles


Masseter muscles

Temporal muscles


Weighted means


Elec

tric

activ

ity (120583

V120583

V

)





Weighted means


1933

2699

927 983

2930

3807

1796 1710

5

10

15

20

25

30

35

40

45

Asy

mm

etry

inde

x (

)


Temporal muscles

Masseter muscles

Masseter muscles

Temporal muscles







Weighted means


590

295

1456

433


2

4

6

8

10

12

14

16

Torq

ue co

effici

ent (

)











5 Conclusions




References








































of






Disease Markers



OncologyJournal of





PPAR Research



Journal of

ObesityJournal of




















Temporal muscles



Masseter muscles





407 212

11627

13199

711196

91599708

0

20

40

60

80

100

120

140

160

Temporal muscles


Masseter muscles

Temporal muscles


Weighted means


Elec

tric

activ

ity (120583

V120583

V

)





Weighted means


1933

2699

927 983

2930

3807

1796 1710

5

10

15

20

25

30

35

40

45

Asy

mm

etry

inde

x (

)


Temporal muscles

Masseter muscles

Masseter muscles

Temporal muscles







Weighted means


590

295

1456

433


2

4

6

8

10

12

14

16

Torq

ue co

effici

ent (

)











5 Conclusions




References








































of






Disease Markers



OncologyJournal of





PPAR Research



Journal of

ObesityJournal of

















Weighted means


590

295

1456

433


2

4

6

8

10

12

14

16

Torq

ue co

effici

ent (

)











5 Conclusions




References








































of






Disease Markers



OncologyJournal of





PPAR Research



Journal of

ObesityJournal of

















5 Conclusions




References








































of






Disease Markers



OncologyJournal of





PPAR Research



Journal of

ObesityJournal of




























of






Disease Markers



OncologyJournal of





PPAR Research



Journal of

ObesityJournal of





















of






Disease Markers



OncologyJournal of





PPAR Research



Journal of

ObesityJournal of
















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Clinical Study The Electrical Activity of the Temporal and ...downloads.hindawi.com/journals/bmri/2015/259372.pdf · The Electrical Activity of the Temporal and Masseter Muscles in