Impact of Functional Appliances on Muscle Activity: A Surface Electromyography Study in Children

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1 CLIICAL RESEARCH e-iss Med Sc Mont, 2015; 21: DOI: /MSM Receved: Accepted: Publshed: Impact of Functonal Applances on Muscle Actvty: A Surface Electromyography Study n Chldren Authors Contrbuton: Study Desgn A Data Collecton B Statstcal Analyss C Data Interpretaton D Manuscrpt Preparaton E Lterature Search F Funds Collecton G ABCDEFG 1 Krzysztof Woźnak BCDEF 1 Dagmara Pątkowska BCEF 1 Llana Szyszka-Sommerfeld BC 2 Jadwga Buczkowska-Radlńska 1 Department of Orthodontcs, Pomeranan Medcal Unversty of Szczecn, Szczecn, Poland 2 Department of Conservatve Dentstry, Pomeranan Medcal Unversty of Szczecn, Szczecn, Poland Correspondng Author: Source of support: Dagmara Pątkowska, e-mal: dagmara_patkowska@onet.eu Self-fnancng Background: Materal/Methods: Results: Conclusons: MeSH Keywords: Full-text PDF: Electromyography (EMG) s the most objectve tool for assessng changes n the electrcal actvty of the mastcatory muscles. The purpose of the study was to evaluate the tone of the masseter and anteror temporals muscles n growng chldren before and after 6 months of treatment wth functonal removable orthodontc applances. The sample consted of 51 patents wth a mean age 10.7 years wth Class II maloccluson. EMG recordngs were performed by usng a DAB-Bluetooth nstrument (Zebrs Medcal GmbH, Germany). Recordngs were performed n mandbular rest poston, durng maxmum voluntary contracton (MVC), and durng maxmum effort. The results of the study ndcated that the electrcal actvty of the muscles n each of the clncal stuatons was the same n the group of grls and boys. The factor that determned the actvty of the muscles was ther type. In mandbular rest poston and n MVC, the actvty of the temporals muscles was sgnfcantly hgher that that of the masseter muscels. The maxmum effort test ndcated a hgher fatgue n masseter than n temporals muscles. Surface electromyography s a useful tool for montorng muscle actvty. A 6-month perod of functonal therapy resulted n changes n the actvty of the mastcatory muscles. Electromyography Mastcatory Muscles Myofunctonal Therapy Ths work s lcensed under a Creatve Commons Attrbuton-onCommercal-oDervs 3.0 Unported Lcense 246 Indexed n: [Current Contents/Clncal Medcne] [SCI Expanded] [ISI Alertng System] [ISI Journals Master Lst] [Index Medcus/MEDLIE] [EMBASE/Excerpta Medca] [Chemcal Abstracts/CAS] [Index Coperncus]

2 Woźnak K. et al.: The mpact of functonal applances on muscle actvty Med Sc Mont, 2015; 21: CLIICAL RESEARCH Background The cause-and-effect relatonshp between functon and morphology has been reported n many prevous studes, whch ndcates the paramount role of functon over shape [1 3]. The treatment of malocclusons durng the growth perod through the use of functonal orthodontc applances s therefore justfed, and thus acheves equlbrum n the mastcatory muscles and consequent further harmonous development of the jaws. There are many types of functonal removable applances that produce changes through varous mechansms, but n essence they all create a pattern of functons that encourages a new morphologcal pattern n dental and skeletal facal structures [4]. The man reason for usng functonal removable applances s to establsh muscular balance, elmnate oral dysfuncton, and allow for proper grown of both the maxlla and the mandble. Another purpose has been to correct or dmnsh maxllary ncsor protruson [5]. Montorng muscular actvty durng the course of functonal treatment can be helpful n gudng the therapy [6]. Changes n muscle actvty has been analysed through many supplementary studes [7 10]. EMG s an element n the quanttatve assessment of patents n dentstry [11], and the most objectve and relable dagnostc tool for assessng changes n the electrcal actvty of the mastcatory muscles, thus determnng the effectveness of the orthodontc procedures appled. In chldren, surface electromyography (semg) s commonly performed because t s a non-nvasve and easy way to montor muscle actvty through the use of surface electrodes nstead of a needle or fne wres used n the ntramuscular type of electromyography. The purpose of ths study was to evaluate the tone of the masseter and anteror temporals muscles n growng chldren before and after 6 months of treatment wth functonal removable orthodontc applances. Addtonally, muscle symmetry, Actvty Index, and Torque coeffcent before and after 6 months of therapy were also analysed. Materal and Methods Sample We selected 51 patents wth a mean age (31 grls mean age 10.78; and 20 boys mean age 10.65) wth Class II maloccluson from the patents referred to the Pomeranan Unversty n Szczecn. All the patents and ther parents gave nformed consent to all clncal and electromyographc procedures. After a conventonal clncal assessment, mpressons of the jaws were taken and the overbte and overjet were measured on the dagnostc casts. The mean overbte and overjet before treatment were 3.20 mm and 5.52 mm, respectvely. The patents were treated wth the followng functonal applances: a doppelplatte applance (32 subjects), an actvator (14 subjects), and a Lehmann applance (5 subjects). The constructon bte for the doppelplatte was taken, showng an average protruson for the mandble of 4.26 mm and 3.46 mm between the frst permanent molars. The actvator and Lehmann applances had constructon btes wth an average of 3.57 mm and 3.60 mm, respectvely, n the forward dsplacement of the mandble, and vertcal dstances of 3.57 mm and 3.60 mm, respectvely, between the frst permanent molars. The patents were nstructed to wear the applances for at least hours durng the day. A quanttatve EMG assessment before and after 6 months of functonal therapy was performed as follows. Instrumentaton EMG recordngs were performed usng a DAB-Bluetooth nstrument (Zebrs Medcal GmbH, Germany) at the start of the nvestgaton and after 6 months of treatment wth the functonal applances. Durng the EMG examnaton, each patent was sttng on a comfortable char wthout head support. The patents were nstructed to assume a natural head poston. Surface EMG sgnals were detected by 4 slver/slver chlorde (Ag/AgCl), dsposable, self-adhesve, bpolar electrodes (aroxon Dual Electrode, aroxon, USA) wth a fxed nterelectrode dstance of 20 mm. The electrodes were placed on the superfcal masseter and the anteror temporals muscles on both the left and the rght sdes parallel to the muscular fbers. The postons of the electrodes were exactly the same as prevously descrbed by Ferraro and Sforza [11]. Temporals anteror muscle: vertcally along the anteror margn of the muscle; masseter muscle: parallel to the muscular fbres wth the upper pole of the electrode at the ntersecton between the tragus-labal commssura and exocanthon-gonon lnes. The reference electrode was stuated nferor and posteror to the rght ear [11]. In order to reduce mpedance, the skn was carefully cleaned wth 70% ethyl alcohol and dred pror to the placement of the electrode. The recordngs were performed 5 mnutes later. The DAB-Bluetooth nstrument was nterfaced wth a computer whch presented the data graphcally and recorded t for further analyss. The EMG sgnals were amplfed, dgtzed, and dgtally fltered. Ths work s lcensed under a Creatve Commons Attrbuton-onCommercal-oDervs 3.0 Unported Lcense 247 Indexed n: [Current Contents/Clncal Medcne] [SCI Expanded] [ISI Alertng System] [ISI Journals Master Lst] [Index Medcus/MEDLIE] [EMBASE/Excerpta Medca] [Chemcal Abstracts/CAS] [Index Coperncus]

3 CLIICAL RESEARCH Woźnak K. et al.: The mpact of functonal applances on muscle actvty Med Sc Mont, 2015; 21: Measurement protocol and EMG data analyss The frst recordng for the standardzaton of EMG potentals was made as descrbed by Ferraro et al. [12]. Two 10-mm thck cotton rolls were postoned on the mandbular second premolars and molars, or on the mandbular second mlk molars and the frst permanent molars of each patent, and a 3-second maxmum voluntary clench (MVC) was recorded. For each muscle, the maxmum EMG potentals were expressed as a percentage of ths value (unt µv/µv%). Ths knd of standardzaton elmnates any varablty n results due to skn and electrode mpedance, electrode postonng, and relatve muscular hypo- or hypertrophy [12 14]. EMG actvty was then recorded durng 3 dfferent tests: 1. Rest actvty of the mastcatory muscles was performed n the clncal rest poston. 2. Maxmum voluntary clench (MVC) statc sometrc test was performed n the ntercuspal poston and the subject was nvted to clench as hard as possble and to mantan the same level of contracton for 5 seconds. 3. Maxmum effort test was performed durng a 10-second maxmum sometrc contracton (MVC) of the jaws. To avod any effects of fatgue, a rest perod of at least 5 mnutes was allowed between each of the recordngs. To assess muscular actvty as well as the coordnaton and symmetry of the homologous, synergstc, and antagonstc muscles, electromyographc ndces were calculated. To ndvdualze the most prevalent par of the mastcatory muscles, the Actvty Index (Ac) was assessed. It ranges from 0 (no actvty of the masseter) to (no actvty of the temporals muscles) [14]. Ac = 1 ( MR ML ) / 1 ( TR TL ) The asymmetry between the actvty of the left and rght jaw muscles was quantfed by the Asymmetry Index (As). It ranges from 0% (total symmetry) to 100% (total asymmetry) [15]. As = 1 R L / 1 ( R L ) 100 To evaluate a possble laterodevatng effect on the mandble caused by unbalanced rght and left masseter and temporals muscles, a Torque Coeffcent (Tc, unt%) was calculated as follows: Tc = TR ML TL MR / 1 1 [( TR ML) ( TL MR)] 100 Tc ranges between 0% (no torque durng the test) and 100% (a sgnfcant laterodevatng effect on the mandble) [16]. Statstcal analyss The Kruskal-Walls test and the Mann-Whtney U test were used to statstcally analyze the results. In addton, AOVA/ ACOVA (Analyss of Varance/Analyss of Covarance) tests were also performed. The level of sgnfcance was set at 5% for all statstcal analyses. Results Rest actvty The results of the EMG recordngs n the clncal rest poston before and after 6 months of functonal orthodontc therapy are presented n Tables 1 and 2. The rest actvty for both the masseter and temporals muscles was the same n the groups of grls (4.47 μv/μv%) and boys (3.59 μv/μv%). The factor whch determned ths actvty was the type of muscle (P<0.0005). The rest actvty of the temporals muscles was hgher (4.64 μv/μv%) than the masseter muscles (3.42 μv/μv%). The 6-month perod of treatment dd not affect the rest actvty of both the muscles. The mean total actvty of the muscles before treatment was 4.10 μv/μv%; and after 6 months of therapy t was 3.96 μv/μv% (P<0.7881). The process of treatment also dd not nfluence rest actvty wth regard to the groups of boys and grls (P<0.6452), or wth regard to partcular muscles (P<0.6881). The assessment of masseter actvty n relaton to the temporals muscles (Ac) at rest showed hgher actvty n grls (1.03) than n boys (0.74), P< The actvty ndex was not nfluenced by the 6-month functonal orthodontc treatment (P<0.3853). The analyss of varance n the asymmetry ndex (As) dd not show any sgnfcant dfference n ether grls (23.19%) or boys (22.63%) (P<0.8279). Ths ndex was not affected by the type of muscles (P<0.2987) or the treatment procedures (P<0.4672). The analyss of the Torque coeffcent (To) also dd not ndcate any sgnfcant nfluence of the treatment n ths respect (P< ). Dfferent patterns of changes wth regard to ths ndex were observed n the groups of grls and boys (P<0.0845). Maxmum voluntary contracton (MVC) The results of EMG recordngs n maxmum voluntary contracton before and after 6 months of treatment wth functonal applances are presented n Tables 3 and 4. Ths work s lcensed under a Creatve Commons Attrbuton-onCommercal-oDervs 3.0 Unported Lcense 248 Indexed n: [Current Contents/Clncal Medcne] [SCI Expanded] [ISI Alertng System] [ISI Journals Master Lst] [Index Medcus/MEDLIE] [EMBASE/Excerpta Medca] [Chemcal Abstracts/CAS] [Index Coperncus]

4 Woźnak K. et al.: The mpact of functonal applances on muscle actvty Med Sc Mont, 2015; 21: CLIICAL RESEARCH Table 1. Rest actvty of the temporals muscles on both the rght and left sdes before and after sx months of treatment wth functonal applances. Sde Gender Mean 95% CI +95% CI Medan Mn. Max. SD SEM Grls Boys Total Grls Boys After sx months of therapy Total Grls Boys Total Grls Boys Total Table 2. Rest actvty of the masseter muscles on both the rght and left sdes before and after sx months of treatment wth functonal applances. Sde Gender Mean 95% CI +95% CI Medan Mn. Max. SD SEM Grls Boys Total Grls Boys After sx months of therapy Total Grls Boys Total Grls Boys Total The total actvty of the evaluated muscles n ntercuspal poston was slghtly lower n grls (98.35 μv/μv%) than n boys ( μv/μv% P<0.5935). The factor whch determned ths actvty was the type of muscle fbers (P<0.0002). The temporals muscles had a hgher actvty ( μv/μv%) than the masseter muscles (93.54 μv/μv%). The sex of the patents dd not affect the MVC actvty (P<0.0911). Ths work s lcensed under a Creatve Commons Attrbuton-onCommercal-oDervs 3.0 Unported Lcense 249 Indexed n: [Current Contents/Clncal Medcne] [SCI Expanded] [ISI Alertng System] [ISI Journals Master Lst] [Index Medcus/MEDLIE] [EMBASE/Excerpta Medca] [Chemcal Abstracts/CAS] [Index Coperncus]

5 CLIICAL RESEARCH Woźnak K. et al.: The mpact of functonal applances on muscle actvty Med Sc Mont, 2015; 21: Table 3. The actvty of the temporals muscles of both the rght and left sdes durng maxmum voluntary contracton (MVC) n the ntercuspal poston before and after functonal orthodontc therapy. Sde Gender Mean 95% CI +95% CI Medan Mn. Max. SD SEM Grls Boys Total Grls Boys After sx months of therapy Total Grls Boys Total Grls Boys Total Table 4. The actvty of masseter muscles of both the rght and left sdes durng maxmum voluntary contracton (MVC) n the ntercuspal poston before and after functonal orthodontc therapy. Sde Gender Mean 95% CI +95% CI Medan Mn. Max. SD SEM Grls Boys Total Grls Boys After sx months of therapy Total Grls Boys Total Grls Boys Total The mpact of the 6-month orthodontc therapy for MVC actvty of the muscles was on the borderlne of statstcal sgnfcance; ths value was hgher before ( μv/μv%) than after treatment (95.16 μv/ μv%, P<0.0598). Ths effect was the same n each of the groups of grls and boys (P<0.6648). A sgnfcant decrease n MVC actvty was observed n relaton to the temporals muscles ( μv/μv% before, and μv/μv% after therapy; P<0.0006). Ths work s lcensed under a Creatve Commons Attrbuton-onCommercal-oDervs 3.0 Unported Lcense 250 Indexed n: [Current Contents/Clncal Medcne] [SCI Expanded] [ISI Alertng System] [ISI Journals Master Lst] [Index Medcus/MEDLIE] [EMBASE/Excerpta Medca] [Chemcal Abstracts/CAS] [Index Coperncus]

6 Woźnak K. et al.: The mpact of functonal applances on muscle actvty Med Sc Mont, 2015; 21: CLIICAL RESEARCH Table 5. Changes n the mean power frequency (MPF%) of muscles durng maxmum voluntary contracton before and after 6 months of functonal orthodontc therapy. Sde Gender Mean 95% CI +95% CI Medan Mn. Max. SD SEM Grls Boys Total Grls Boys After sx months of therapy Total Grls Boys Total Grls , Boys Total The assessment of the actvty ndex (Ac) for the masseter muscles n relaton to the temporals muscles n MVC ndcated hgher actvty of the masseter n grls (1.01) than n boys (0.86; P<0.0904). The nfluence of 6 months therapy for those actvty proportons of both muscles was at the lmt of statstcal sgnfcance (P<0.0724). The relatve ncrease of the masseter actvty after functonal orthodontc treatment was notceable (Ac=0.86 before therapy, and Ac=0.99 after therapy) n both groups grls and boys (P<0.9751). Multvarate analyss of varance n the asymmetry ndex (As) dd not show any sgnfcant dfferences n grls (9.44%) and boys (9.89%, P<0.7902). ether the type of muscles (P<0.3902) nor the functonal therapy (P<0.2962) determned the averages for ths ndex. The torque coeffcent ndex (To) was sgnfcantly hgher n boys (7.56) than n grls (5.02; P<0.0269) and t was not nfluenced by orthodontc therapy (P<0.7751). Maxmum effort Changes n the mean power frequency (MPF%) of muscles durng a 10-second maxmum voluntary contracton n the ntercuspal poston before and after 6 months of functonal treatment are presented n Table 5. Changes n the MPF were determned by the type of muscles both before and after therapy. A greater decrease n MPF was observed wth regard to the masseter (before and after therapy: 11.79%, P<0.0021; and 10.13%, P<0.0009, respectvely) than to the temporals muscles (before and after therapy: 7.34% and 5.31%, respectvely). These changes were the same for both grls and boys (P>0.05). Sx months of therapy dd not nfluence the MPF shft ether wth regard to the temporals muscles (P<0.2451) or to the masseter muscles (P<0.6292) n grls or boys. Dscusson The notceable rse n nterest of electromyography n orthodontcs s connected wth the need for a relable and effectve treatment for malocclusons. Awareness of the causes of malocclusons confrms the nfluence of functon on morphology and justfes the objectves of functonal orthodontc therapy, whch am to mprove the balance of the mastcatory muscles and promote the further correct development of the facal skeleton. Surface EMG permts an objectve and non-nvasve evaluaton of the mastcatory muscles. The masseter and the anteror temporals muscles are the most frequently studed muscles because they are easly accessble for surface electrode recordngs. The parameters whch are the most frequently assessed by means of EMG are rest poston and maxmum Ths work s lcensed under a Creatve Commons Attrbuton-onCommercal-oDervs 3.0 Unported Lcense 251 Indexed n: [Current Contents/Clncal Medcne] [SCI Expanded] [ISI Alertng System] [ISI Journals Master Lst] [Index Medcus/MEDLIE] [EMBASE/Excerpta Medca] [Chemcal Abstracts/CAS] [Index Coperncus]

7 CLIICAL RESEARCH Woźnak K. et al.: The mpact of functonal applances on muscle actvty Med Sc Mont, 2015; 21: voluntary clenchng (MVC). Addtonally, n our research, maxmum effort was also evaluated. Rest actvty s one of the most mportant statc actvtes analysed. From the bomechancal pont of vew, the absence of electrcal actvty of the muscles at rest s the optmal condton. However, more recent research has shown that the clncal rest poston s an actve muscle poston because of the tone of the muscles nvolved [17]. Thus, n proper occluson ths actvty should be as low as possble. The results of our study revealed no sex dfferences n the rest actvty of both the masseter and temporals muscles. Ths s n accordance wth Ferraro et al. [13], who also dd not observe any dfferences n the rest poston of the masseter and temporals muscles between females and males on the bass of the recordngs performed n 92 healthy subjects. The same results relatng to rest actvty were descrbed by Cha et al. [18]. The sample whch they nvestgated ncluded 105 patents wth an average age of 22 years. Conversely, Pnho et al. [19] ndcated a hgher actvty of the masseter and temporals muscles n women (2.64 μv) than n men (1.37 μv). The factor whch determned the rest actvty n our study was the type of muscle fbers. The temporals anteror belles had hgher rest actvtes than the masseter muscles. These fndngs were n accordance wth the fact that the temporals muscles are the most nvolved at rest. The analyss of the changes n the rest electrcal actvty before and after 6 months of treatment dd not show any dfferences. Another mportant statc condton whch has been prevously analyzed s maxmum voluntary contracton (MVC). The results of our study showed no dfferences between the groups of grls and boys n ths actvty. These fndngs correspond to the results descrbed by Ferraro et al. [16], who also dd not notce any dfferences n the MVC actvty of the mastcatory muscles between males and females. Moreno et al. [20] found hgher MVC actvty n males wth regard to the masseter. Ths value was estmated at μv on the rght sde and μv on the left sde, whereas n females t was μv and μv on the rght and left sdes, respectvely,. The actvty of the temporals muscles was the same n both groups. Varous studes descrbed by Ferraro et al. [13] found that males had hgher MVC actvty (temporals actvty μv; masseter actvty μv) than females (temporals actvty μv; masseter actvty μv). In our study of MVC, we observed hgher actvty n the temporals muscles than n the masseter muscles. The maxmum effort test ndcated greater fatgue n the masseter than n the temporals muscles. Pancherz and Anehus-Pancherz [21] also observed lower MVC actvty of the masseter muscles n comparson to the temporals muscles. Ther sample, smlarly to our sample, ncluded only patents wth Class II malocclusons. These studes are n accordance wth a study descrbed by Moss [22], who also confrmed hgher MVC actvty of the temporals muscles than of the masseter muscles n patents wth Class II malocclusons. In the control group wth correct occlusons, the MVC actvty of the masseter and temporals muscles was almost at the same level. Smlar fndngs n ths respect to our own studes seem to confrm the varablty of decreased masseter actvty regardng MVC n patents wth Class II malocclusons. An analyss of the record of changes n the electrcal actvty of muscles after 6 months of treatment through the use of functonal applances ndcated ts selectve nfluence on muscle actvty. The nfluence of functonal therapy manfested tself manly n the decrease of electrcal actvty n the evaluated muscles durng maxmum sometrc contracton n the ntercuspal poston. Ths effect was predomnant n the case of the temporals muscles, whose actvty sgnfcantly decreased n ths stuaton after 6 months of treatment. Ingervall and Thuer [23] also descrbed a decrease n the MVC actvty of the temporals anteror muscles durng functonal orthodontc therapy. The mean values descrbng the actvty of the anteror temporals belles before, after 4 months, and after 12 months of treatment were μv, μv, and μv, respectvely. Moreover, the authors also observed a decrease n the MVC actvty of the temporals posteror fbers. An nterestng study relatng to the nfluence of functonal orthodontc therapy was descrbed by Erdem et al. [24]. The sample conssted of 25 chldren wth Class II malocclusons wthout temporomandbular dysfunctons. Ffteen patents were treated by the use of an actvator, and the remanng ones were n the control group. The actvty of the temporals and masseter muscles durng clenchng, chewng, and swallowng ncreased after 12 months n both groups, but the ncrease was greater n the treatment group. Dfferent results were presented by Uner et al. [25], who dd not observe any sgnfcant changes wth respect to the restng and MVC actvty of the masseter and temporals muscles after functonal treatment. Tartagla et al. [26] verfed the effcency of the Pre-Orthodontc Traner T4K functonal postoner. The treatment was performed n a group of 10 boys aged 8 13 years. After 6 months of Ths work s lcensed under a Creatve Commons Attrbuton-onCommercal-oDervs 3.0 Unported Lcense 252 Indexed n: [Current Contents/Clncal Medcne] [SCI Expanded] [ISI Alertng System] [ISI Journals Master Lst] [Index Medcus/MEDLIE] [EMBASE/Excerpta Medca] [Chemcal Abstracts/CAS] [Index Coperncus]

8 Woźnak K. et al.: The mpact of functonal applances on muscle actvty Med Sc Mont, 2015; 21: CLIICAL RESEARCH therapy, overbte and overjet decreased. The therapy dd not nfluence the actvty of the mastcatory muscles. The overvew of research presented above ponts to the dffculty n provdng clear answers relatng to the mpact of functonal therapy on the actvty of the mastcatory muscles. Ths dffculty stems from dfferences n research methodology, ncludng the methods of selectng study groups, the perod over whch the treatment results were evaluated, and the methods for measurng or estmatng the electrcal actvty of the muscles. Undenably, however, the ncluson of electromyography n the repertore of dagnostc methods allows objectve assessment of the mpact of therapy on functon. Conclusons 1. The actvty of the muscles was determned by the knd of actvty performed. 2. Sex dd not nfluence the actvty of the mastcatory muscles n any of the actvtes performed. 3. 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