progress in orthodontics 1 3 ( 2 0 1 2 ) 226–236

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Original article

Orthodontic-surgical treatment: neuromuscular evaluationin skeletal Class II and Class III patients

Giampietro Farronato ∗, Lucia Giannini, Guido Galbiati, Giulia Sesso, Cinzia MasperoIRCCS Ca’ Granda, Ospedale Maggiore Policlinico, Department of Orthodontics, University of Milan, Italy

a r t i c l e i n f o

Article history:

Received 5 October 2011

Accepted 6 April 2012

Keywords:

Electromyography

Muscular activity

Skeletal class II

Skeletal class III

Surgical orthodontic treatment

a b s t r a c t

Objectives: The aim of this study was the evaluation of the neuromuscular response to treat-

ment according to diagnostic phases, as a follow-up of patients under surgical orthodontic

treatment. The patient sample was subdivided into sub-samples, according to clinical char-

acteristics.

Materials and methods: All of the patients who underwent orthognathic surgery in the Depart-

ment of Orthodontics (University of Milan) were subjected to periodic electromyographic

evaluation of the masticatory muscles (masseter and anterior temporal muscles), and to

electrokinesiographic evaluation of the mandibular movements. The patient sample com-

prised 80 patients (37 males; and 43 females) at the end of growth. The electromyographic

instruments used in the study included a Freely and a K6-I electromyography. Statistical

evaluation was carried out with the Student’s t-tests for independent samples.

Results: There are many differences between the skeletal Class II and skeletal Class III

patients that are shown through the analysis of these data obtained. In the beginning phases

of the treatment the muscular activities were higher in the Class II patients than in the Class

III patients. Nevertheless this difference was reversed at the end of the treatment. A similar

difference could be found in the mandibular kinesiology, in fact the maximum mandibular

opening movement was greater in the skeletal Class II patients than in the skeletal Class

III patients at the beginning of the treatment. At the end of the treatment this difference

was lost. At the beginning of the treatment the Class II patients showed a greater protrusive

movement of the mandibular than the Class III patients. At the end the treatment however

this gap was reduced without being reversed.

Conclusions: Functional evaluation in patients in surgical orthodontic therapy is an important

element in the diagnostic–therapeutic recordings, so as to reduce as much as possible any

incorrect neuromuscular activity that can result in relapse.

lishe

© 2012 Pub

∗ Corresponding author. Orthodontic Department, University of Milan,

E-mail address: giampietro.farronato@unimi.it (G. Farronato).1723-7785/$ – see front matter © 2012 Published by Elsevier Srl. on behhttp://dx.doi.org/10.1016/j.pio.2012.04.003

d by Elsevier Srl. on behalf of Società Italiana di Ortodonzia SIDO.

Milan, Italy.

alf of Società Italiana di Ortodonzia SIDO.

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progress in orthodonti

. Introduction

t is well known that facial growth is influenced by both geneticnd extrinsic factors, and that muscle function exercises canave important influences on both growth and craniofacialorphology.1,2 In skeletal Class II patients, the function of

he masticatory system is generally reduced.3 Patients whoresent a vertical excess of the maxillary jawbone asso-iated with a retroposition of the mandible have reduceduscular force and diminished amplitude of mandibularovement.4–6 Skeletal Class III patients show huge variabil-

ty both in morphology and function, as compared to skeletallass I patients.7

Tallgren et al.8 demonstrated that patients with largeandibular prognathism can express great muscular force,hile Fogle and Glaros9 obtained the opposite results. In

988, Miralles et al. showed that during rest, the posturalctivity of the masseter and temporal muscles is greatern skeletal Class III patients than in skeletal Class I and IIatients.10 Surgical orthodontic treatment was used to repo-ition the skeletal bone situation to a more normal positionn subjects where the position is not correct. However, mod-fications to the facial skeleton have consequences on all ofhe masticatory muscles, even if the majority of studies inhe literature have focused on the masseter and temporal

uscles, as these are the most accessible for methodologicalnalysis.7,11,12 Many studies in the literature have investigatedhe effects of orthognathic surgery on the neuromuscularystem. Here, the first modification of the neuromuscularystem is seen during the pre-surgical orthodontic phase,nd Precious et al.,13 showed that the maximum bite forces reduced after the beginning of fixed orthodontic ther-py. Dean et al.,14 showed that patients undergoing surgicalrthodontic treatment were able to express a lower bite force

n the pre-surgical phase, as compared to the bite force thathey could express before starting the therapy.14 Thomast al.15 confirmed that there was a reduction in the maximumandibular opening movement and in its movement in the

ertical direction, from before to after the orthodontic phase,hich is connected to the same protective mechanism that

xplains the reduction in the maximum bite force. Moreover,uring mandibular movement, there was a painful action fromhe brackets on the teeth and from the archwire in the soft tis-ues of the cheek and lips that limited the normal movementsf the patients. Furthermore, the pre-surgical orthodonticreatment can contribute to a reduction in the possible

andibular movements and a consequent reduction in thecclusal contacts, which increase the interference betweenhe dental elements, with a reduction in the mandibularxcursion.15–21

Many studies have analyzed the modifications consequento surgical repositioning of the bone structure. Finn et al.22

howed that there was no increase in the maximum muscularorce post-surgery with muscular advancement and maxil-ary retro-positioning. Also, Van den Braber et al.23 confirmed

hat oral function is not influenced by mandibular advance-

ent surgery. On the contrary, Athanasiou et al.,24 showedhat surgical correction of maxillary prognathism increaseshe intensity of occlusal contacts, and they hypothesized

( 2 0 1 2 ) 226–236 227

that such harmonization of the dentofacial skeleton wouldinfluence the neuromuscular system. Kobayashi et al.25

confirmed that the steadiness of the masticatory rhythm isimproved by orthognathic surgery in subjects with mandibu-lar prognathism. Tatsumi et al.26 showed that after surgicalorthodontic treatment, an aesthetic improvement, a reductionin the duration of the masticatory cycle, and an improvementin the activity of the masticatory muscles can be obtained.These advantages suggest that patients who undergo thisoperation gain functional readjustment in the post-surgicalphase. Proffit et al.,16 reported a maximum bite force increasein some patients in the post-surgical phase. Unfortunately,this increase was not an improvement compared to thebeginning of the therapy, but a return to the initial conditionsbefore starting the orthodontic therapy.15 These changesshowed large variability due to the different sensitivities ofthe patients at the dental, muscular and articulation levels.Indeed, in explaining the results obtained, the strength ofwill and emotional stress of the patients were probablymore important than the muscular advantages and thebiomechanics.27

The majority of studies have analyzed only a single phaseof the treatment. The present study thus considered the neu-romuscular response to treatment from the diagnostic phaseto the follow-up in a group of 80 patients undergoing surgicalorthodontic treatment. The analysis also included the possi-ble division of the patients into subgroups, depending on theclinical characteristics they presented.

2. Materials and methods

2.1. Sample selection

All of the patients presenting for treatment by orthognathicsurgery in the Department of Orthodontics (University ofMilan) underwent instrumental, clinical and radiographicexaminations, with periodic electromyographic evaluations oftheir masticatory muscles and electrokinesiographic evalua-tions of their mandibular movements.

The patient sample analyzed comprised 80 patients (37males and 43 females) at the end of growth (mean age, 32 ± 4.1years).

The three main criteria that had to all be satisfied for inclu-sion of the patients were: adult age (≥18 years); presence of adento-skeletal discrepancy; and need for combined surgicalorthodontic treatment. The exclusion criteria were: patientswith higher or lower vertical dimensions than the normalones; patients still in their growing phase; and non-compliantpatients.

The skeletal Class II patients had an ANB angle >4◦ andwere classified as dental Class II when the mesio-buccal cuspof the first upper molar was mesial to the embrasure ofthe lower first molar. The skeletal Class III patients had anANB angle <0 degrees, and were dental Class III when the

mesio-buccal cusp of the first upper molar was distal to theembrasure of the lower first molar. The patients included,either Class II and Class III, showed normal skeletal dimen-sions.

tics

228 progress in orthodon

2.2. Electromyographic and kinesiographic analyses

Two electromyographic examinations were carried out withtwo different electromyographic instruments: a Freely elec-tromyograph (De Gotzen, Legnano, Italy) and a K6-I elec-tromyograph (Myotronics, Tukwila, WA, USA). Every patientunderwent a kinesiographic examination of their mandibu-lar movements. Before these examinations, the patients wereasked if they wanted to be exempt from dental or skele-tal pain, to avoid any impediment for the correct carryingout of the subsequent treatment. The muscles consideredin the electromyographic evaluation were: the anterior tem-poral muscle and the masseter muscle, as its superficialcomponent.

The timing of the electromyographic and kinesiographicexaminations that were performed on the surgical orthodon-tic patients included: during the first medical examination;before the start of the orthodontic therapy; during the pre-surgical phase of the orthodontics; every month from threemonths before the surgical operation to three months after;the day before the surgical operation; during the intermaxil-lary fitting, to verify that there was no spasm of the muscles; atthe removal of the fitting; during the post-surgical orthodon-tic phase, with the same times as the pre-surgical orthodonticphase; at the removal of the surgical bite; and during thefollow-up.

The patients were examined in a specific, totally undis-turbed and noiseless room. They sat on a rigid stool with anadjustable height, to provide an angle of 90◦ between the thighand lower leg. The thighs were parallel to the floor, the backwas upright, and the gaze was to beyond the horizon. The headwas in a natural head position.

After thorough cleansing of the skin of the face with awad soaked in Neoxinal (0.5% clorhexidine in ≥70% alco-hol), to reduce the forehead impedance and to facilitateadhesiveness, the electrodes for the electromyographic acqui-sition were positioned on the patient. The electrode positionswere the same for both of the electromyographic instru-ments, and were not modified between the use of theinstruments. The electrodes used were disposable. Thesebipolar electrodes were positioned according to the followingprocedure:

Masseter muscle: from behind the seated subject, the oper-ator palpated the muscle mass while the patient clenched theteeth. To position the bipolar electrode parallel to the musclefibers, a line was drawn that connected the commissura labio-rum oris with the tragum, as well as one drawn following theesocanto-goniac line. The position of the electrode was suchthat the superior pole lay at the intersection point betweenthese two lines, with its major axis along the esocanto-goniacline.

Temporal muscle: the muscle mass was palpated while thepatient clenched the teeth, thus localizing the major axis ofthe zygomatic process of the frontal bone. The bipolar elec-trode was positioned along the line parallel to this process. Inthis way, the electrode was positioned parallel to the muscle

fibers, and positioned more or less superficially in comparisonwith the frontoparietal suture.

A grounding earth electrode was positioned on a silentmuscular area of the forehead.7

1 3 ( 2 0 1 2 ) 226–236

According to the protocol, the electromyographic evalua-tion was carried out with the Freely instrument, as the needfor more time for the K6-I acquisition would run the risk ofbeing too time consuming and of making the patient feel moretired.

During this electromyographic evaluation, the patientsmade an arch clench in a maximum voluntary clench on cot-ton rolls positioned around the first molar, for 5 sec (the ‘cottonclench’), and an arch clench in a maximum voluntary clenchwithout the interposed rolls for 5 sec (the ‘clench’). This pro-cedure followed that of the Sforza et al.7 protocol.

With the K6-1 electromyographic instrument, an analysisof the neuromuscular system at rest was carried out to pro-vided an objective measurement of the electrical activity ofthe examined muscle at rest, and to evaluate any eventualmuscle hyperactivity, which is typical of temporomandibu-lar dysfunction. Low levels of electric activity were analyzedduring the maximum voluntary clench and the clench on cot-ton rolls (cotton clench), to evaluate the linear correlationsbetween the electromyographic signal, recruit of the motorunit, and the force expressed in the isometric contraction.

The following indices were recorded and monitored: thetemporal, masseter, and mean percentage overlapping coeffi-cients (POC), as the index of symmetrical distribution of themuscular activities; the asymmetry, activation, and torquecoefficients; and the cotton clench, clench, and percentageimpact. These electromyographic evaluations were carried outwith the K6-1 instrument equipped with a ‘sensor-cage’ fittedto the head of the patient, and with the magnet positionedintraorally. The examination was for two electromyographicevaluations on the patients in the same position. The magnetused (Myotronics, Tukwila, WA, USA) was specifically made forthe kinesiographic instrument used. To allow correct adhe-siveness of the magnet, Bioadesive Stomatohesive was used(Myotronics, Tukwila, WA, USA).

For the mandibular kinesiography, the examinationincluded: maximum opening; opening and closing speeds;maximum protrusion of the mandible on the antero-posteriorplane; maximum right laterality; maximum left laterality;mandible rest position; centric occlusion; freeway space atrest; freeway space after transcutaneous electrical nerve stim-ulation (TENS); and distance between centric occlusion andmaximum aperture.

After the kinesiographic analysis of the mandible, the TENSwas carried out, which relaxes the muscles innervated by theV and VII pair of cranial nerves. The TENS lasted 45 min to50 min, and used three monopolar electrodes. (Myotrode SG,and Myomonitor J5; Myotronics, Tukwila, WA, USA). A secondtrial was performed on the muscle at rest, to determine theexpected muscular electric activity reduction and the efficacyof the therapy.

As it has already been shown that the first functionalexamination of a subject is not necessarily reliable for acontrol group, the whole examination was repeated twice,taking into consideration only the values obtained in thesecond trial.28 Furthermore, it should be noted that when-

ever an electromyographic evaluation or a kinesiographicexamination was carried out, each scan or electromyographictrial was repeated at least twice, to determine its reliabil-ity and its repeatability. In cases of discrepancy, the same

progress in orthodontics 1 3 ( 2 0 1 2 ) 226–236 229

Fig. 1 – The effects of the impact with the inclusion of the cotton rolls. Sk cl, skeletal Class. (The blue line indicates skeletalC pati

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lass II patients and the pink one indicates skeletal Class III

valuation was performed again, until repeatable results werebtained.

.3. Statistical tests

ata analysis was carried out with Student’s t test where theull hypothesis assumes that the differences between groupsere due to chance, while according to the alternative hypoth-

sis, the differences among the groups are real. The level oftatistical significance was set at P < 0.05.

. Results

nalysis of the data obtained revealed differences between thekeletal Class II and skeletal Class III patients according to theollowing measures.

Impact: The impact measures indicate the expression of

he muscular force over time. Here, these muscular activi-ies were higher in the skeletal Class II patients than in thekeletal Class III patients in the beginning phases of the treat-ent. This difference was statistically significant remained

ig. 2 – The effects of the impact on the clench situation (i.e. no ckeletal Class II patients and the pink one indicates skeletal Clas

ents).

pronounced into the later phases of the treatment. However, atthe end of the treatment, this difference was reversed. Thesechanges were similar for the patients regardless of the cottonclench (Figs. 1 and 2 – Tables 1 and 2).

Muscular activity: The muscular activity for the four mus-cular fasciae was higher in the skeletal Class II patients atthe beginning of the treatment, as compared with the skele-tal Class III patients, This difference was also statisticallysignificant, although it was lost in the successive treatmentphases. It was also not affected by the clench on cotton rollsor not, and at the end of the treatment, this difference waslost (Figs. 3 and 4 – Tables 3 and 4).

Maximum mandibular opening: For the mandibular kine-siology, the maximum mandibular opening movement wasgreater in the skeletal Class II patients than in the skeletalClass III patients at the beginning of the treatment. This dif-ference was lost following the surgical treatment, and theyremained similar at the end of the treatment (Fig. 5 – Table 5).

Maximum mandibular protrusion: The protrusive move-ment of the mandible was slightly greater in the skeletal ClassII patients than in the skeletal Class III patients at the begin-ning of the treatment. This gap appeared greater during the

otton rolls). Sk cl, skeletal Class. (The blue line indicatess III patients).

230 progress in orthodontics 1 3 ( 2 0 1 2 ) 226–236

Table 1 – Impact on cotton rolls.

skeletal Class II skeletal Class III Statistics

Mean SD Mean SD S/NS

Beginning of treatment 4000 10.2 4000 14.2 SBefore surgical intervention 1 5890 15.3 3573 12.3 SBefore surgical intervention 2 5320 11.2 4100 11 SAfter surgical intervention 1 2980 11.5 1650 18.3 SAfter surgical intervention 2 3810 12.4 2500 14.7 NSEnd of treatment 4900 15.6 6200 19.2 NS

values are expressed in �V.

Table 2 – Impact on clench.

skeletal Class II skeletal Class III Statistics

Mean SD Mean SD S/NS

Beginning of treatment 4320 25.2 4320 14.8 SBefore surgical intervention 1 5000 15.3 3789 17.6 SBefore surgical intervention 2 3232 17.8 3805 15.2 SAfter surgical intervention 1 3112 16.2 1742 13.2 SAfter surgical intervention 2 4118 13.9 2989 18.1 NS

End of treatment 4090 18

Values are expressed in �V.

treatment, although it was reduced in both size and signifi-cance at the end of the treatment, but without being reversed(Fig. 6 – Table 6).

Mandibular lateral movement: No statistically significantdifferences between the Class II and Class III patient groupswere seen for the mandibular right or left lateral movements.

4. Discussion

As indicated in the Results, there are a number of differencesbetween the skeletal Class II and skeletal Class III patientsrevealed in the analysis of the data from the present study.

Similarly, there are a number of previous studies that haveconsidered muscular activity after orthognathic surgery. Someof these have demonstrated improvements in muscular activ-ity of the masseter and anterior temporalis after orthognathic

Fig. 3 – The muscular activity in the Class II patients. TA, anterioright; cot, with cotton rolls; cle, without cotton rolls (clench).

6000 16.5 NS

surgery in skeletal Class II patients,5,28,29 although others havepresented different results, in which there was unchangedor worsened function after orthognathic surgery.4,5,16,28 Vanden Braber et al.,4 showed that orthognathic surgery does notincrease electromyographic values in the clench of retrog-nathic patients, while Maeda et al.,30 underlined that someskeletal Class II patients improve their function after orthog-nathic surgery. Furthermore, Throckmorton et al.,5 showedgreat functional improvement after orthognathic surgery.

There have also been reports that the stomatog-nathic function changed after mandibular advancementsurgery,4,5,16,28,29,31 although some of these same studiesfound that only few cases showed an improvement of

5,28,29

stomatognathic function.The impact measures in the present study were used

to indicate the expression of the muscular force over time.Here, the course of the impact in the test of the greatest

r temporal muscle; MM, masseter muscle; SX, left; DX,

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226–236

231

Table 3 – Muscular activity in Class II (considering clenching on cotton rolls and on teeth).

TA DX cotton TA SX cotton MM DX cotton MM SX cotton TA DX clench TA SX clench MM DX clench MM SX clench

mean SD mean SD mean SD mean SD mean SD mean SD mean SD mean SD

Beginning of treatment 159 6.1 150 7.2 150 4.8 158 5.2 158 5.7 152 7.2 160 6.7 158 4.2Before surgical intervention 1 118 5.8 109 6.5 120 6.4 113 5.7 125 7.1 114 6.5 118 8.3 125 5.6Before surgical intervention 2 119 7.1 110 6.8 119 5.3 113 6.3 113 3.4 119 6.8 119 5.6 124 4.9After surgical intervention 1 81 6.8 90 7.1 90 5.5 89 7.5 88 4.8 90 7.1 78 4.8 83 6.3After surgical intervention 2 106 8.1 106 7.5 130 7.1 130 6.3 114 6.1 113 7.5 106 6.9 130 7.1End of treatment 132 4.3 132 4.4 150 6.9 170 5.8 132 5.3 127 4.4 177 5.3 154 5

Values are expressed in �V.Statistical comparison is reported in table 4.

Table 4 – Muscular activity in Class III (considering clenching on cotton rolls and on teeth).

TA DX cotton TA SX cotton MM DX cotton MM SX cotton TA DX clech TA SX clench MM DX clench MM SX clench

mean SD mean SD mean SD mean SD mean SD mean SD mean SD mean SD

Beginning of treatment 142 7.2 142 6.2 136 4.8 134 6.6 130 5.7 142 7.2 142 6.7 142 6.2Before surgical intervention 1 120 6.5 109 6.1 114 6.4 107 6 112 7.1 118 6.5 120 8.3 114 6.1Before surgical intervention 2 124 6.8 110 5.8 119 5.3 120 5.5 115 3.4 126 6.8 124 5.6 119 5.8After surgical intervention 1 80 7.1 80 8.1 80 5.5 80 8.1 80 4.8 80 7.1 84 4.8 80 8.1After surgical intervention 2 101 7.5 107 7.5 130 7.1 130 7.3 122 6.1 110 7.5 121 6.9 130 7.5End of treatment 138 4.4 140 4.2 158 6.9 163 3.8 138 5.3 131 4.4 169 5.3 167 4.2Values are expressed in �V

STATISTICAL COMPARISON BETWEEN SKELETAL CLASS II AND III

TA DX cotton TA SX cotton MM DX cotton MM SX cotton TA DX clench TA SX clench MM DX clench MM SX clench

Beginning of treatment S S S S S S S SBefore surgical intervention 1 S S S S S S S SBefore surgical intervention 2 S S S S S S S SAfter surgical intervention 1 S S NS NS S S S SAfter surgical intervention 2 NS NS NS NS NS S NS NSEnd of treatment NS NS NS NS NS NS NS NS

232 progress in orthodontics 1 3 ( 2 0 1 2 ) 226–236

Table 5 – Maximum mandibular opening.

skeletal Class II skeletal Class III Statistics

Mean SD Mean SD S/NS

Beginning of treatment 38 2.5 38 2.3 SBefore surgical intervention 1 34 2.7 32 2.9 SBefore surgical intervention 2 34 3.2 32 3.8 SAfter surgical intervention 1 21 3.8 21 2.1 NSAfter surgical intervention 2 26 3.2 26 1.8 NS

.1 35 2.7 NS

End of treatment 34 2

Values are expressed in mm.

clench confirmed decreases in the impact prior to the surgicaloperation, although this was not completely superimposablebetween the two skeletal Classes. Thus, the impact values (as%*sec) highlighted by the two Classes were partially super-imposable through the treatment, with the exclusion of thelevel attained after the beginning of the orthodontic therapyin the Class II patients; here, the values tended to decrease,while they increased in the Class III patients. Finally, all ofthese impact values were relatively normal (100 ± 15%*sec),except for the level reached after the period of intermaxillaryblock. At the end of the treatment, these values were slightlylower than 100%*sec.

Observing in more detail the data of the Class II and IIIpatients, it can be noted that the Class II patients devel-oped minor muscular activity in comparison to the ClassIII patients. Nevertheless, in the other analyses, the ClassII patients developed greater electrical energy during all ofthe orthodontic fixed treatment, and the same observationscan be noted for the impact indices (as �V*sec). This mightbe connected to the reduced number of patients who hadimprovements in the initial phase, and it could be the samefor improvements at the end of the treatment. Considering theaforesaid points and according to the index of the mean POC,it can be seen that even if on the one hand the skeletal ClassIII patients developed a greater clench force, it is always truethat this was more balanced than the Class II patients (meanPOC: Class II patients, 80%; Class III patients, 78%).

By the comparison of the temporal muscle POC indices inthe present study, we have shown that in the initial phases, themuscular activity has reduced neuromuscular equilibrium.Skeletal Class II patients are particularly uncompensated at

the beginning of the treatment, whereby after the start of theorthodontic therapy, the POC index improves. However, thisremains at a level that is not within the physiological range,

Table 6 – Maximum mandibular anterior movement.

skeletal Class II

Mean SD

Beginning of treatment 5.3 0.25

Before surgical intervention 1 7 0.3

Before surgical intervention 2 6 0.3

After surgical intervention 1 5 0.1

After surgical intervention 2 5.1 0.34

End of treatment 5.6 0.43

Values are expressed in mm.

and that the surgical orthodontic treatment, the POC indeximproves, such that by the end of the treatment it is withinthe physiological range.

There have been fewer studies that have investigated mus-cular function more specifically in skeletal Class III patientsafter orthognathic-surgery.26,29 Di Palma et al.,32 consideringskeletal Class III patients with a mandibular protrusion statewhere electromyographic evaluation allowed the quantifica-tion of neuromuscular equilibrium, and they showed thatimprovements gained by surgical intervention are primar-ily due to better occlusal stability and not to biomechanicaladvantages. In the present study, our skeletal Class III patientshad a POC index that was closer to the physiological limit inthe pre-surgical phases, and they improved only in the follow-up, with physiological values seen at the end of the treatment.

Overall, our skeletal Class II patients had greater harmonyin the temporal muscle activity when compared with skeletalClass III patients. The masseter muscle POC index showed asmall reduction in the overriding range of the muscular activ-ity after the cementing of the appliance. This value improvedup to the end of the treatment, when the POC index was sim-ilar in all skeletal Classes.

It can be noted that for the POC mean, there was progres-sive improvement from the first acquisition at the beginningof the treatment until the end of the fixed orthodontic ther-apy. Class II patients were more overriding than the Class IIIpatients at the beginning of treatment. At the end of treat-ment, the POC values indicate sufficient neuromuscular equi-librium, although there is a difference of about two percentagepoints between the Classes (where the index is slightly bet-ter for the Class II patients). The progressive improvement of

skeletal Class III Statistics

Mean SD S/NS

5 0.3 NS4.7 0.1 S4.8 0.25 NS3 0.3 NS3.4 0.12 NS4 0.2 NS

the POC indices in all Classes shows that orthodontic treat-ment tends to develop a major equilibrium among differentmuscular activities. For the POC index, similar progression for

progress in orthodontics 1 3 ( 2 0 1 2 ) 226–236 233

ivity

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Fig. 4 – The muscular act

keletal Class II and III patients was noted even in this smallample.

The torque index shows similar values in the patients ofkeletal Classes II and III, except for the level at the beginningf the treatment; these data remain higher than the normalalue (considered as 10%) during the period of the orthodonticreatment, although at the end of the treatment, the torquealues were nearly normal.

The asymmetry index, shows that the side of prevalenceas an opposite course between the two Classes; i.e. while forlass III patients it diminishes up to the level performed in thenal part of the post-surgical orthodontic treatment, where

t starts to increase again, Class II patients have an oppositeesponse; nevertheless, these values are still relatively normal.

For the torque index, the Class II patients tend to have ancclusal prior to the centre of mass (negative value), in ordero become positive in post-surgical levels and to be close to

ig. 5 – The maximum mandibular opening, in Class II and Classatients and the pink one indicates skeletal Class III patients).

in the Class III patients.

zero at the end of the treatment. In the Class III patients, thetorque index always remains positive (posterior contact), andit always remains within the range of normality; at the end ofthe treatment, their torque index was close to zero. Therefore,the torque index has opposite courses in each of these Classes,although its values are near normal.

The ability to develop force in time in the test on cottonrolls shows a course that is in part superimposable betweenthe two skeletal Classes: the decrease in the force up to thelevels reached after the beginning of the orthodontic therapyand after the surgical operation remains constant, in order toget back to the previous values at the end of the treatment.

Overall, of note, every patient has their initial situation andtheir particular response to treatment. There is thus a wide

inter-individual variability in the neuromuscular responses tothe surgical orthodontic therapy. In the post-surgical phase,in most cases, the arrival at a state of functional well-being

III patients. (The blue line indicates skeletal Class II

234 progress in orthodontics 1 3 ( 2 0 1 2 ) 226–236

Fig. 6 – The maximum mandibular anterior movement, in Class II and Class III patients. (The blue line indicates skeletalClass II patients and the pink one indicates skeletal Class III patients).

initially takes place clinically, whereby the electromyographicinvestigations of the masticatory muscles and the analysis ofthe mandibular kinesiology demonstrate these further effectsin a successive phase.

Also, patients often indicate that they are satisfied withthe functional results obtained even before objective exam-inations demonstrate this improvement. The post-surgicalrehabilitation of these patients is highly subjective, andpresents large inter-individual variability, as suggested in theliterature.

Some parameters, such as the muscular activity, need ashort time to re-establish their physiological functions, whileothers, such as the maximal mandibular opening, need moretime to obtain the same results.

5. Conclusions

Through only the neuromuscular system and the mandibularkinesiology, it is possible to obtain a successful steady result.At the end of this study, it is possible to state that a seriousalteration of facial morphology is not always accompaniedby functional consequences, and if this happens, it does notalways involve all of the parameters that determine the correctneuromuscular function and mandibular kinesiology.

As shown in the results, there’re some differences in theneuromuscular system in Class II and in Class III before andafter the surgical intervention. In the beginning phases of thetreatment the muscular activities (both on dental and cottonclench) were higher in the Class II patients than in the Class

III patients. Nevertheless this difference was reversed at theend of the treatment.

A similar difference can be found in the mandibular kine-siology, in fact the maximum mandibular opening movement

was greater in the skeletal Class II patients than in the skeletalClass III patients at the beginning of the treatment. At the endof the treatment this different was lost.

At the beginning of the treatment the Class II patientsshowed a greater protrusive movement of the mandibularthan the Class III patients. At the end the treatment howeverthis gap was reduced without being reversed.

It is possible to conclude that functional evaluation inpatients in surgical orthodontic therapy is an important ele-ment in the diagnostic–therapeutic records for the reductionby as much as possible of incorrect neuromuscular activitythat can result in a relapse. It also helps if the clinicians canfollow the treatment phases and check on the results obtained.

Finally, morphologic differences between skeletal Class IIand skeletal Class III patients can be demonstrated also byinstrumental examinations, and their correction after surgicaltreatment is observable on electromyographic and electrog-natographic tracing.

Conflict of interest

The authors have reported no conflict of interest.

Riassunto

Obiettivo: Lo scopo di questo studio consiste nella valutazionedella risposta neuromuscolare in un followup di pazienti sottopostia intervento ortodontico-chirurgico. Il campione dei pazienti è statosuddiviso in due sotto-gruppi a seconda delle caratteristiche cliniche.Materiali e metodi: Tutti i pazienti sottoposti a intervento

ortognatodontico presso il Dipartimento di Ortognatodonziadell’Università di Milano) sono stati indagati con valutazioniperiodiche elettromiografiche dei muscoli masticatori (masseteree temporale anteriore) e elettrognatografiche dei movimenti

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andibolari. Il campione comprende 80 pazienti (37 maschi e3 femmine) a fine crescita. Le strumentazioni elettromiografichetilizzate comprendono gli elettromiografi Freely e K6-I. È stataondotta un’analisi statistica con test-t di Student per campionindipendenti.isultati: Tra i pazienti di II Classe scheletrica e quelli di IIIlasse scheletrica ci sono molte differenze, evidenziate dall’analisiei dati ottenuti. Nelle fasi iniziali del trattamento le attivitàlettriche muscolari dei pazienti di II Classe scheletrica eranoaggiori rispetto a quelle dei pazienti di III Classe scheletrica. Tali

ifferenze si sono significativamente attenuate a fine trattamento.na simile differenza è stata trovata anche nella kinesiologia mandi-olare, infatti il movimento di massima apertura mandibolare, a

nizio trattamento, era maggiore nelle II Classi scheletriche rispettolle III Classi scheletriche. A fine trattamento questa differenza ètata annullata. A inizio trattamento le II Classi scheletriche presen-avano un più ampio movimento di protrusiva mandibolare rispettolle III Classi scheletriche. A fine trattamento questa differenzaisultava ridotta ma non annullata completamente.onclusioni: La valutazione funzionale dei pazienti in terapiartodontico-chirurgica è un importante elemento nella raccolta diati diagnostico-terapeutici, così come nella diagnosi di un eventualecorretta attività neuromuscolare derivante da una recidiva.

ésumé

bjectifs: Le but de cette étude était d’évaluer la réponse neuromus-ulaire au traitement conformément aux étapes diagnostiques, sousorme de suivi de patients sous traitement orthodontique chirurgical.’échantillon de patients a été divisé en sous-groupes, sur la base desaractéristiques cliniques.atériels et méthodes: Tous les patients soumis à une chirurgie

rthognatique (Service d’Orthodontie, Université de Milan) ont étéussi soumis à un examen eléctromyographique périodique des mus-les masticateurs (muscles masséter et temporal antérieur) et à unevaluation eléctrokinésiographique des mouvements mandibulaires.otre échantillon était composé de 80 patients (37 hommes et 43

emmes) en fin de croissance. Les instruments électromyographiquestilisés dans l’étude comprenaient Freely et électromyographie k6-

. L’évaluation statistique a été effectuée par le biais des tests t detudent pour échantillons indépendants.ésultats: De nombreuses différences font surface entre les patientslasse II squelettique et les patients Classe III squelettique. Ces dif-

érences sont identifiées à l’aide de l’analyse des données obtenues.urant des étapes initiales du traitement, les activités musculaires’avèrent supérieures chez les patients de Classe II vis-à-vis desatients de Classe III. Toutefois, à la fin du traitement la situationvait complétement changé. Une différence similaire a été identi-ée dans la kinésiologie mandibulaire; à dire vrai, le mouvement’ouverture mandibulaire maximum s’est avéré supérieur chez lesatients Classe II squelettique par rapport aux patients Classe IIIu début du traitement. À la fin du traitement, cette différence avaitresque disparu. Au début du traitement, les patients Classe II ontait état d’un mouvement de protrusion supérieur de la mandibulear rapport aux patients Classe III. À la fin du traitement, cette brèche

’était réduite, mais la tendance ne s’était pas renversée.onclusions: L’évaluation fonctionnelle chez des patients sous

raitement orthodontique chirurgical est un élément important’information thérapeutique et de diagnostic, afin de réduire le plus

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possible toute activité neuromusculaire incorrecte pouvant engendrerune récidive.

Resumen

Objetivos: El objetivo de este estudio era valorar la respuesta neu-romuscular al tratamiento de acuerdo con las etapas diagnósticas,como seguimiento de pacientes bajo tratamiento ortodóncico quirúr-gico. La muestra de pacientes fue subdividida en sub-muestras, deacuerdo con las características clínicas.Materiales y métodos: Todos los pacientes que se sometieron acirugía ortognática en el Departamento de Ortodoncia (Universidadde Milán) también fueron sometidos a exploración electromiográ-fica periódica de los músculos masticatorios (músculos maseteroy temporal anterior) y a valoración electrokinesiográfica de losmovimientos mandibulares. La muestra estaba integrada por 80pacientes (37 varones y 43 mujeres) al final del crecimiento. Losinstrumentos electromiográficos utilizados en el estudio incluyeronFreely y electromiografía k6-I La evaluación estadística fue llevada acabo por medio de las pruebas t de Student para muestras indepen-dientes.Resultados: Existen muchas diferencias entre paciente Clase IIesqueletal y pacientes Clase III esqueletal que afloran graciasal análisis de los datos conseguidos. En las fases iníciales deltratamiento, las actividades musculares resultan superiores en lospacientes Clase II con respecto a los pacientes Clase III. Sin embargo,la situación resultaba trastocada al final del tratamiento. Una difer-encia similar fue identificada en la kinesiologia mandibular; dehecho, el movimiento máximo de abertura mandibular resultó supe-rior en los pacientes Clase II esqueletal que en los pacientes ClaseIII esqueletal al principio del tratamiento. Al final del tratamiento,esta diferencia casi desapareció. Al principio del tratamiento, lospacientes Clase II mostraron un movimiento de protrusión superiorde la mandíbula con respecto a los pacientes Clase III. Al final deltratamiento, esta brecha se redujo, sin que cambiara la tendencia.Conclusiones: La valoración funcional en pacientes bajotratamiento ortodóncico quirúrgico es un element de importan-cia en cuanto a la información terapéutica y de diagnostico, con talde reducir cuanto más cualquier actividad neuromuscular incorrectasusceptible de ocasionar una recidiva.

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