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The role of the ocular disorders (OD) in pathogenesis of MMp is still a controversal issue. Ocular arc reflexes (OAR) may involve changes in head and neck posture and generate modifications of contraction resulting in muscle contraction and finally weakness. sEMG tests were performed on 28 patients 13 with masticatory muscles pain and myopia/15 healthy) in rest position with eyes open and eyes closed. Patients group control (healthy patients) showed no significance difference in sEMG record in open/close test. In non healthy patients there were great differences between the sEMG recordings with eyes closed and open. Temporalis and masseters showed a statistical difference of means activation in two tests (temporalis p =0.0010; masseters = 0.0006). Great difference there was in means muscles activation between open eyes healthy test and non healthy. No difference in close eyes test was evaluated in temporalis and masseters close test in the two groups. The exact causes of MMp are still unknown. The role how ocular disorders (OD) may play an important role in pathogenesis of MMp is still a controversal issue. Ocular arc reflexes (OAR) may involve changes in head and neck posture and generate modifications of contraction resulting in muscle contraction and finally weakness.
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Influence of vision on masticatory muscles function: surface electromyographic evaluation
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Influence of vision on masticatory muscles function: surface electromyographic evaluation
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                                                                                                      Original article



    Influence of vision on masticatory muscles
    function: surface electromyographic evaluation




                                                                                                                       li
                                                                     na
    Domenico Ciavarella, DDS, PhD1                               masseters close test in the two groups. The exact
    Antonio Palazzo, MD1                                         causes of MMp are still unknown. The role how oc-




                                                                   io
    Alfredo De Lillo, DDS1                                       ular disorders (OD) may play an important role in
    Lucio Lo Russo, DDS, PhD1                                    pathogenesis of MMp is still a controversal issue.
    Sergio Paduano, DDS3                                         Ocular arc reflexes (OAR) may involve changes in
    Luigi Laino, DDS, PhD1                                       head and neck posture and generate modifications




                                                                az
    Claudio Chimenti, DDS2                                       of contraction resulting in muscle contraction and
    Federica Frezza, DDS1                                        finally weakness.
    Lorenzo Lo Muzio, DDS,PhD1
                                                                 Key words: surface electromyography, masticato-




                                                             rn
                                                                 ry muscles pain, ocular disorders.
    1 Department of Clinical and Experimental Medicine,
      Faculty of Medicine, School of Dentistry, University
      of Foggia, Italy                                           Introduction




                                                          te
    2 Department of Surgical Sciences, Faculty of Medi-

      cine, School of Dentistry, University of L’Aquila, Italy   Masticatory muscles (MM) function is influenced by
    3 Department of the Health, University “Magna Grae-          many factors such as postural problems, traumas,
      cia” Catanzaro, Italy
                                                       In        psycho-physiological issues and occlusal alterations.
                                                                 Masticatory muscles pain (MMp) is a condition en-
                                                                 countred in temporo-mandibular joint disorder (TMD)
    Corresponding author:                                        and in head/neck facial pain. Its pathogenesis is still
    Domenico Ciavarella                                          unclear (Fig. 1) (1,2). Several studies have de-
                                                ni
    Department of Clinical and Experimental Medicine,            scribed how the level of electromyographic activity
    Faculty of Medicine, School of Dentistry,                    (EMG) in the pericranial muscle is higher in patients
    University of Foggia                                         with MMp than in healthy controls in rest position (3-
    Via Rovelli                                                  6). The interaction between muscle pain and muscle
                              o

    71100 Foggia, Italy                                          activity at rest is still unclear because the EMG activ-
    Phone: +39 347 6131225                                       ity in muscle pain patients has been shown to be
                          izi


    Fax: +39 0881 588080                                         higher as compared to control subjects (7,8). The
    E-mail: drdomenicociavarella2@yahoo.it                       maximal voluntary contraction (MVC) in painful mus-
                                                                 cles is decreased in patients with temporomandibular
                                                                 disorder (7,8).
           Ed




    Summary                                                      Other symptoms related to MMp are often acoustic
                                                                 alterations, vertigo, nausea, salivary disturbance,
    The role of the ocular disorders (OD) in pathogene-
    sis of MMp is still a controversal issue. Ocular arc
    reflexes (OAR) may involve changes in head and
    neck posture and generate modifications of con-
    C




    traction resulting in muscle contraction and finally
    weakness. sEMG tests were performed on 28 pa-
CI




    tients (13 with masticatory muscles pain and my-
    opia/15 healthy) in rest position with eyes open and
    eyes closed. Patients group control (healthy pa-
    tients) showed no significance difference in sEMG
    record in open/close test. In non healthy patients
    there were great differences between the sEMG
©




    recordings with eyes closed and open. Temporalis
    and masseters showed a statistical difference of
    means activation in two tests (temporalis p =
    0.0010; masseters = 0.0006). Great difference there
    was in means muscles activation between open
    eyes healthy test and non healthy. No difference in
    close eyes test was evaluated in temporalis and              Figure 1. Possible pathogenesis of MMs.


    Annali di Stomatologia 2014; V (2): 61-65                                                                         61
    D. Ciavarella et al.


    disfagy and sometimes language alterations (9). The        tion on the functional status of the craniomandibular
    muscular stress is often treated with an oral appli-       neuromuscular system and was useful in determining
    ance such as resin splint which helps reduce clench-       the proper cranio-mandibular relationship.
    ing (10-12).                                               To position the electrodes, subjects were requested
    The role how ocular disorders (OD) may play an im-         to close their mouths and clench (Fig. 2) (15,16). To




                                                                                                                         li
    portant role in pathogenesis of MMp is still a contro-     reduce electrode impedance, the skin was carefully
    versal issue. Ocular arc reflexes (OAR) may involve        cleaned prior to electrode positioning, and recordings




                                                                    na
    changes in head and neck posture and generate              were performed 5-6 min later, allowing the conductive
    modifications of contraction resulting in muscle con-      paste to adequately moisten the skin surface (17).
    traction and finally weakness. The aim of this study is    The analogue sEMG signal was amplified, digitised,
    to evaluate the influence of OD in MM contractions, in     and digitally filtered. The instrument was directly in-




                                                                  io
    patients with masticatory muscles pain and in healthy      terfaced with a computer, which presented the data
    subjects, using surface Electromyography (sEMG).           graphically. The signals were averaged over 25 ms,
                                                               with muscle activity of the four tested muscles
                                                               espressed in microvolts (μV).




                                                               az
    Materials and methods                                      The sEMG test was performed on each patient in
                                                               resting (i.e. no voluntary muscle contraction and no
    In this study, sEMG tests were performed on 28 pa-         dental contact) conditions and in different ocular
    tients (10 males and 18 females, ages 16 to 48) at         states (i.e. eyes open and eyes closed). In particular,




                                                            rn
    School of Dentistry, University of Foggia. The partici-    the sEMG test was performed in patients sitting, with
    pants and their parents provided written informed          their ocular plane parallel to the floor, after measur-
    consent to be involved in the study. The EMG activity      ing their body temperature, and with a room temper-




                                                         te
    at rest and clench in the temporal and masseter mus-       ature of 26° C. No other interferences were present
    cles was recorded in two groups of patients with dif-      in the room.
    ferent conditions: myopic patients and masticatory         An eight channel surface Electromyograph was
    muscles pain; asymptomatic subjects was used as a          used on 4 groups of muscles: temporalis and mas-
    control. On each patient the RDC questionnaire was
    submitted (13).
                                                      In       seters (masticatory muscles) and the digastrics and
                                                               sternocleidmastoids (neck muscles). On sEMG test
    Patients’ criteria selection was as follows: Angle’s       muscle contractions were represented on 5 window
    Class I Molar (i.e. normal intermaxillary dental rela-     displays and were calculated in microvolts (μV). On
    tionships), good symmetry of dental arches, no re-         view displays it is possible to see the activity level of
                                         ni
    fractive errors, patients’ anamnesis of temporo-           each monitored muscle. Each column of numbers
    mandibular disease (TMD) or facial pain history ab-        represents the average muscle activity (μV)
    sence, absence of neuromuscular pathology, and no          throughout a marked region and the time for the
    history of neuromuscular pathology, absence of neu-        muscle to exceed the activity level. This is mea-
                               o

    ropathic or myofascial pain, absence of any anterior       sured in milliseconds.
    or posterior/lateral cross-bite; no signs or symptoms
                           izi


    of TMD (according to the RDC questionnaire) (13).
    Subjects taking drugs other than nonsteroid inflam-
    matory drugs, paracetamol or minor opioid anal-
    gesics were excluded, as well as subjects presenting
           Ed




    with systemic pathologies such as diabetes, and
    subjects suffering from generalised diffuse muscle
    and/or articular pain. The non-healthy group (13 pa-
    tients; mean age 26,5 ± 6.9) suffering from either
    masticatory muscles pain (MMp) and myopia was
    enrolled in the study. Examinations were performed
    C




    using a standardized form in which the following
    were listed: history of the diseases, palpation at rest,
CI




    in maximal voluntary contraction and during
    mandibular motions of the masticatory and neck
    muscles, palpation of temporo-mandibular joint
    (TMJ), assessment of spontaneous and triggered
    pain using a visual analogue scale (VAS), mandibu-
    lar motions recorded by an electrognathograph as
©




    suggested by Okeson (14).


    Surface electromyography evaluation

    The tests, performed by means of Biopack elec-             Figure 2. Patient with surface electromyography elec-
    tromyography. This diagnostic test provided informa-       trodes.

    62                                                                             Annali di Stomatologia 2014; V (2): 61-65
    Influence of vision on masticatory muscles function: surface electromyographic evaluation


    Electromyography gives the operator the effective               activation in two tests. In open eyes test mean of acti-
    RMS (Root Mean Squared) value. RMS is calculated                vation was 23.85 μV. This value was greater than
    as the square root of the medium power in a date                mean in close eyes 3.538 μV. The medians differ sig-
    time interval (X RMS = √1/T t0∫x2 (t) dt). The Averaged         nificantly (P-Value < 0.0001) (Tab. 1).
    EMG display shows a rectified average of the muscle             Masseters changed their activity in close eyes test in




                                                                                                                           li
    signals which are contained within the zoom cursor.             respect to open eyes test. Non-healthy subjects
    The height of the graph (“mountain peaks”) repre-               showed a mean of activation in open eyes (24.46 μV)




                                                                       na
    sents the activity of the muscle averaged every 25              greater than close eyes test (4.923 μV). The medians
    milliseconds. The numbers below represent the aver-             differ significantly (P-Value < 0.0001).
    age firing strength of each muscle (μV). All tests were         Authors evaluated open eyes means of each muscle
    performed for 10 seconds duration.                              between healthy and non-healthy subjects. There




                                                                     io
                                                                    was a great difference in masseters means between
                                                                    open eyes healthy test and non-healthy test. Healthy
    Statistical analysis                                            showed masseters mean of activation of 3.200 μV
                                                                    while non-healthy subjects 24.46 μV. The medians




                                                                  az
    A statistical analysis of data with open and close              differ significantly (P-Value < 0.0001).
    eyes in healthy and non healthy were done. Data                 In close eyes test of masseters non-healthy subjects
    were evaluated on statistical “GraphPad” software               presented no difference with healthy subjects (mean
    performing a Paired t-test. Statistical significance was        non-healthy 4,923 μV, healthy 2,600 μV). The medi-




                                                               rn
    set at 0.05.                                                    ans do not differ significantly (p=0.1987).
                                                                    In open eyes temporalis presented a substantial dif-
                                                                    ference of activation as well (healthy 4.067 μV, non-
    Results




                                                            te
                                                                    healthy 23.85 μV). The medians differ significantly
                                                                    (P-Value < 0.0001).
    Control group showed no significant difference in               In close eyes test there was no difference between
    sEMG records in open/close tests. Temporalis activa-            the two groups of patients. No statistical difference
    tion (right and left mean) in two tests had the same
                                                         In
    range of activation. The medians do not differ signifi-
                                                                    was evaluated (p=0,7605) (Tab. 2).
                                                                    Authors observed a significant variation in switching
    cantly (P-Value = 0.3976) .                                     from eyes closed to eyes open in all non-healthy pa-
    Masseters activation (right and left mean) in healthy           tients.
    subjects, in open/close tests had no significant                An Electromyographic test in open and close eyes
                                                ni
    change in activation (open 3.200 μV; close 2.600                and in rest jaw position was conducted. During the
    μV). Values of 2.0/3.0 μV when recorded with the                test an error occurred because some patients closed
    mandible at rest are generally accepted as indicating           their eyes. Authors observed how 4 subjects during
    muscle posturing. The medians do not differ signifi-            physiologic open/close eyes produced an electromyo-
                              o

    cantly (P-Value = 0.3274) (Tab. 1).                             graphic image that was unusually. Every open/close
    In patients with muscles suffering (non-healthy) there          movement induced a great increase of electromyo-
                          izi


    were differences between the sEMG recordings with               graphic trace. Authors did not include this data in sta-
    close eyes and open. MM increased their work by vi-             tistical analysis because only a small sample present-
    sion. Temporalis showed great difference of means               ed this phenomena.
           Ed




    Table 1. Results of sEMG test in healthy and non-healthy subjects.

                                     Mean       SEM      Median    Min       Max          95 % CI        p-Value
    C




                                                                                                         (pairing means Test)
    Temporalis           open        4.067      0.82     2.000     1.000     24.000       2.374-5.759    0.3976
CI




    activation (μV)      close       3.567      0.7485   2.000     1.000     21.000       2.036-5.097
    healthy
    Masseter             open        3.200      2.511    2.000     1.000     12.000       2.263-4.137    0.3274
    activation (μV)      close       2.600      2.298    2.000     0.000     11.000       1.742-3.458
    healthy
©




    Temporalis           open        23.85      6.807    10.00     1.000     128.0        9.823-37.869   <0.0001
    activation (μV)      close       3.538      0.7590   2.000     0.0       17.00        1.975-5.102
    non healthy
    Masseter             open        24.46      5.708    15.00     2.000     100.0        12.703-36.22   <0.0001
    activation (μV)      close       4.923      1.105    2.000     0.0       21.00        2.647-7.199
    non healthy
    SEM: Standard error of means; CI: Confidence Interval; Significance level: p < 0.05

    Annali di Stomatologia 2014; V (2): 61-65                                                                              63
    D. Ciavarella et al.


    Table 2. Results of sEMG open/close test between healthy and non-healthy subjects.

                                        Mean     SEM       Median   Min       Max         95 % CI         p-Value
                                                                                                          (pairing means Test)
    Temporalis             Healthy     4.067     0.82      2.000    1.000     24.000      2.374-5.759




                                                                                                                                li
                                                                                                          <0,0001
    activation (μV)        Non healthy 23.85     6.807     10.00    1.000     128.0       9.823-37.869
    open




                                                                        na
    Temporalis             Healthy     3.567     0.7485    2.000    1.000     21.000      2.036-5.097     0,7605
    activation (μV)        Non healthy 3.538     0.7590    2.000    0.0       17.00       1.975-5.102
    close
    Masseter               Healthy     3.200     2.511     2.000    1.000     12.000      2.263-4.137




                                                                      io
                                                                                                          <0,0001
    activation (μV)        Non healthy 24.46     5.708     15.00    2.000     100.0       12.71-36.22
    open
    Masseter               Healthy     2.600     2.298     2.000    0.000     11.000      1.742-3.458




                                                                   az
                                                                                                          0,1987
    activation (μV)        Non healthy 4.923     1.105     2.000    0.0       21.00       2.647-7.199
    close
    SEM: Standard error of means; CI: Confidence Interval; Significance level: p < 0.05




                                                                rn
    Discussion                                                      known that when the ocular globes stir, all ocular




                                                             te
                                                                    muscles are stimulated. At the same time there is a
    The purpose of the authors was to evaluate if ocular            neurologic reflex that induces all the neck muscles to
    disorders (OD) may influence MM activity and pro-               change position for a better view of the object in inter-
    duce masticatory muscles pain (MMp). The MMp                    est. Some fibres coming from the macula do not
    pathogenesis is still unclear. Its association with OD
                                                          In
    is an actually item of discussion in literature research.
                                                                    reach the visual cortex of the brain but directly influ-
                                                                    ence postural mechanisms of the body (23,24).
    The association of upper activation of the muscles in           Anatomical researches show how the Optic Nerve
    rest position and the OD was observed (18). It was              starts from the retinal photoreceptors and stretches to
    evaluated a modification of EMG activity at rest with           corpus genicolatum laterale and then continues to
                                            ni
    closed eyes in patients with cranio-cervical disfunc-           parts 17/18/19 of Brodmann’s area of lobus occipitalis
    tion (19) and in patients with OD (20). No significant          (25). Some optic nerve fibres don’t follow the same
    difference of EMG over the anterior temporalis area             route through corpus genicolatum laterale but instead
    at mandible rest position comparing eyes closed with
                               o

    eyes open condition in young healthy people with
    normocclusion and without visual defects (21).
                           izi


    Authors evaluated MM contraction in healthy and non
    healthy (i.e. patients suffering of facial pain) subjects by
    use of sEMG. In the present paper authors observed no
    difference in healthy patients without OD in both condi-
           Ed




    tions open/close eyes and in patients with ocular disor-
    ders as myopia the modifications in open eyes are statis-
    tically significative when paired in close condition both for
    temporalis and masseters rest evaluation. The activation
    of the masticatory muscles in open eyes was greater in
    patients with OD than healthy subjects; no difference
    C




    was observed in close eyes test in two evaluated groups.
    It is well known that ocular vision (OV) has an impor-
CI




    tant role in controlling body equilibrium and move-
    ments. Vestibulo-ocular reflex and ocular reflex
    through substantia reticularis influences masticatory
    and postural muscles. In recent years, some authors
    have tried to discover if OV plays a role in MMp
    pathogenesis. Neuro-physiologicical sources show
©




    how there is a strong connection between the various            Figure 3. Possible neurologic connection. Corpus genicola-
    parts of the nervous system for some types of invol-            tum lateralis CGL; nucleus centralis (NC); nucleus rubrum
    untary reflexes. Control of conscious and subcon-               (NR); substantia reticularis (SR); nucleus motorius nervi
    scious movements and some functions are modified                trigemini (N mo V); ganglius trigemini (GT); apparatus sen-
    by neurologic sensitive afferent reflexes (22).                 sitivus nervi trigemini (ASV). [modified from Francis Hart-
    OV may influence many types of muscular activity by             mann, Gerard Cucchi. Le disfunzioni cranio-mandibolari
    activating neurologic sensitive reflexes. It is well            (SADAM). Ed. Springer, 1997]

    64                                                                                    Annali di Stomatologia 2014; V (2): 61-65
    Influence of vision on masticatory muscles function: surface electromyographic evaluation


    go to the superior colliculi via the brachium of colli-                 9. Hartmann F, Cucchi G. Stress and the problem of pain in my-
    culi. From the superior colliculi, fibres project to sub-                  ofascial pain dysfunction syndrome (M.P.D.S.). Prog Odon-
    stantia reticularis and the reflex ends in nucleus mo-                     toiatr. 1991;4(10):8-10.
    torius nervi trigemini (Fig. 3) (26). It is probable that              10. Coy RE, Flocken JE, Adib F. Musculoskeletal etiology and
                                                                               therapy of craniomandibular pain and dysfunction. Cranio Clin
    this type of arc reflex in patients, with OD, unevaluat-




                                                                                                                                            li
                                                                               Int. 1991;1(2):163-73.
    ed is overexpressed to generate a strong MM con-                       11. Kidder GM, Solow RA. Precision occlusal splints and the di-
    traction that may result finally in pain.




                                                                              na
                                                                               agnosis of occlusal problems in myogenous orofacial pain
                                                                               patients. Gen Dent. 2014;62(2):24-31.
                                                                           12. Koralakunte PR. Prosthetic management of a masticatory
    Conclusion                                                                 muscle disorder with customized occlusal splint. J Clin Di-
                                                                               agn Res. 2014;8(3):259-61.




                                                                            io
    sEMG evaluation showed how no modifications in                         13. Dworkin SF, LeResche L. Research diagnostic criteria for tem-
    open/close tests was presented in healthy subjects.                        poromandibular disorders: review, criteria, examinations and
    Non-healthy subjects presented great modification in                       specifications, critique. Craniomandib Disord. 1992;6 (4):
                                                                               301-55.
    open/close tests. These findings were of great interest in




                                                                         az
                                                                           14. Okeson J. Oro-facial pain: guideless for assessment, diag-
    patients with unexplainable masticatory muscles pain.
                                                                               nosis, and management. Chicago, IL: Quintessence Pub-
    The exact causes of MMp are still unknown; peripheral                      lishing Co, Inc. 1996.
    myofascial mechanisms and central dysregulation of                     15. Castroflorio T, Farina D, Bottin A, Piancino MG, Bracco P,
    pain processing structures play a role in MMp patho-




                                                                      rn
                                                                               Merletti R. Surface EMG of jaw elevator muscles: effect of
    genesis but their relative weight both with the frequency                  electrode location and interelectrode distance. J Oral Rehabil.
    of pain and among patients is still a controversial issue.                 2005;32(6):411-7.
                                                                           16. De Oliveira RH, Hallak JE, Siessere S, De Sousa LG, Sem-
                                                                               prini M, De Sena MF, et al. Electromyographic analysis of




                                                                   te
    Conflicts of Interest/Role of the Funding                                  masseter and temporal muscles, bite force, masticatory ef-
                                                                               ficiency in medicated individuals with schizophrenia and mood
    Source
                                                                               disorders compared with healthy controls. J Oral Rehabil.
                                                                               2014;41(6):399-408.
    All authors disclose any financial and personal rela-
    tionships with other people or organizations that
                                                                In         17. Tartaglia GM, Testori T, Pallavera A, Marelli B, Sforza C. Elec-
                                                                               tromyographic analysis of masticatory and neck muscles in
    could inappropriately influence (bias) their work.                         subjects with natural dentition, teeth-supported and implant-
                                                                               supporte prothesis. Clin Oral Implants Res. 2008;19:1081-1088.
                                                                           18. Veiersted KB, Westgaard RH, Andersen P. Electromyographic
                                                 ni
    References                                                                 evaluation of muscular work pattern as a predictor of
                                                                               trapezius myalgia. Scand J Environ Health. 1993;19:284-290.
     1. Svenson J, Cowen D, Rogers A. Headache in the emergency            19. Miralles R, Velenzuela S, Ramirez P, Santander H, Palazzi
        department: importance of history in identifying secondary             C, Ormeno G, et al. Visual imput effect on EMG activity of
                                o

        etiologies. J Emerg Med. 1997;15(5):617-21.                            sternocleidomastoid and masseter muscles in healthy sub-
     2. Silveira A, Armijo-Olivo S, Gadotti IC, Magee D. Masticatory           jects and in patients with myogenic cranio-cervico-mandibu-
                            izi


        and cervical muscle tenderness and pain sensivity in a remote          lar disfunction. Cranio. 1998;16(3):168-84.
        area in subjects with a temporomandibular disorder and neck        20. Monaco A, Cattaneo R, Spadaro A, Giannoni M, Di Marti-
        disability. J Oral Facial Pain Headache. 2014;28(2):128-37.            no S, Gatto R. Visual input effect on EMG activity of masti-
     3. Schoenen J, Gerard P, De Pasqua V, Sianard-Gainko J. Mul-              catory and postural muscles in healthy and in myopic chil-
                                                                               dren. Eur J Paediatr Dent. 2006;7(1):18-22.
            Ed




        tiple clinical and paraclinical analyses of chronic tension-type
        headache associated or unassociated with disorder of per-          21. Spadaro A, Monaco A, Cattaneo R, Masci C, Gatto R. Ef-
        icranial muscles. Cephalalgia. 1991;11:135-39.                         fect on anterior temporalis surface EMG of eyes open-closed
     4. Ashina M, Bendtsen L, Jensen R, Sakai F, Olesen J. Muscle              condition. European Juournal Of Paediatric Dentistry.
        hardness in patients with chronic tension-type headache: re-           2010;11:210-212.
        lation to actual headache state. Pain. 1999; 79(2-3):201-5.        22. Pierrot-Deseilligny C. Central oculomotor circuits. Rev Neu-
     5. Jensen R, Rasmussen BK. Muscular disorders in tension-                 rol (Paris). 1985;141(5):349-70.
    C




        type headache. Cephalalgia. 1996; 16:97-103.                       23. Horton JC. Ocular integration in the human visual cortex. Can
     6. Jensen R, Bendtsen L, Olesen J. Muscular factors are of im-            J Ophthalmol. 2006; 41(5):584-93.
        portance in tension-type headache. Headache. 1998;38:10-17.        24. Tzelepi A, Lutz A, Kapoula Z. EEG activity related to
CI




     7. Burdette BH, Gale EN. The effects of treatment on masticatory          preparation and suppression of eye movements in three-di-
        muscle activity and mandibular posture in myofascial pain-             mensional space. Exp Brain Res. 2004;155(4):439-49.
        dysfunction patients. J Dent Res. 1988;67:1126-30.                 25. Kuhl S, Haug H, Schliesser W. Morphometry of cortical neu-
     8. Raphael KG, Janal MN, Sirois DA, Dubrovsky B, Wigren PE,               rons. The best estimation of perikaryon volume from the pro-
        Klausner JJ, et al. Masticatory muscle sleep background elec-          jection area. Microsc Acta. 1982;86(4):315-22.
        tromyographic activity is elevated in myofascial temporo-          26. Lewis RF, Zee DS. Abnormal spatial localization with trigem-
©




        mandibular disorder patients. J Oral Rehabil. 2013.                    inal-oculomotor synkinesis. Evidence for a proprioceptive ef-
        40(12):883-91.                                                         fect. Brain. 1993;116 ( Pt 5):1105-18.




    Annali di Stomatologia 2014; V (2): 61-65                                                                                               65
