- Email: [email protected]
Comparison of muscle activity between conventional and neuromuscular splints
TAEJOURNALOFPROSTHETICDENTISTRY
AU ANDKLINEBERG
54. Toller PA. Opaque arthrography of the temporomandibular joint. Int J Oral Surg 1974;3:17-28. 55. Hargraves AS, Wardle JJM. The use of physiotherapy in the treatment of temporomandibular disorders. Br Dent J 1983;155:121-4. 56. Rocabado M. Arthrokinematics of the temporomandibular joint. Dent Clin North Am 1983;27:573-94. 57. Rocabado M. Arthrokinematics of the temporomandibular joint. In: Gelb H, ed. Clinical management of head, neck and TMJ pain and dysfunction. 2nd ad. Philadelphia: WB Saunders, 1985:525-46. 58. Bezuur JN, Habets LLMH, Jimenez Lopes V, Naeije M, Hansson TL. The recognition of craniomandibular disorders-a comparison between clinical and radiographic findings in eighty-nine subjects. J Oral Rehabil 1988;15:215-22. 59. Seligman DA, Pullinger AG, Solbar WK. Temporomandibular disorders. Part III: occlusal and articular factors associated with muscle tenderness. J PROSTHET DENT 1988;59:483-9.
Comparison of muscle activity neuromuscular splints
60. Merlini, Palla S. The relationship between condylar rotation and translation in healthy and clicking temporomandibular joints. Schweiz Mona&&r Zabnmed 1988;98:1191-9. Reprint requests to: DR. ANTHONY R. Au DEPARTMENT OF PROSTHETIC DENTISTRY UNIVEKSITY OF SYDNEY UNITED DENTAL HOSPITAL 2 CHALMERSST.
SURRYHILLS NSW 2010 AUSTRALIA
between
conventional
and
N. Carlson, DDS,a D. Moline, DDS,b L. Huber, DDS,c and J. Jacobsond Wash.,and The University of Iowa, Hospital and Clinic, College of Dentistry, Iowa
Wenatchee, City, Iowa
The muscle relaxation appliance (MRA) has been used in the treatment of myofascial pain dysfunction (MPD) patients. The neuromuscular orthotic is a version of the MRA and is constructed from a three-dimensional mandibular position when muscles are in a state of minimal electromyographic (EMG) activity. The purpose of this study was to investigate the affect of two muscle relaxation appliances and a placebo (cotton rolls) on EMG activity of the functional masseter and anterior temporalis muscles. A centric relation mandibular MRA and a neuromuscular orthotic were constructed under controlled protocols for 12 women MPD patients with a mean age of 33 years. EMG measurements were taken during a lo-second clench of both appliance and placebo. No statistical difference was found between the centric relation mandibular MRA and neuromuscular orthotic. A statistically significant difference was found between the mean EMG values of the placebo and two treatment appliances. (J PROSTHET DENT 1993;70:39-43)
T
he muscle relaxation appliance (MRA) has been used in the treatment of myofascial pain dysfunction (MPD) patients. The neuromuscular orthotic is a version of the MRA and is constructed from a three-dimensional mandibular position when muscles are in a state of minimal electromyographic (EMG) activity.
aPrivate Practice, Wenatchee, Wash. bProfessor (retired), former Director, General Practice Residency Program and Division of Family Dentistry, University of Iowa Hospital and Clinics. CClinical Associate Professor, Department of Prosthetic Dentistry, University of Iowa College of Dentistry. dResearch Assistant, Department of Preventive and Community Dentistry, University of Iowa, College of Dentistry. Copyright @ 1993 by The Editorial Council of THE JOURNAL OF PROSTHETIC DENTISTRY. 0022-3913/93/$1.00 + .lO.
1993
10/l/46046
The purpose of this study was to investigate the affect of two muscle relaxation appliances and a placebo on the EMG activity of the functional masseter and anterior temporalis muscles. A centric relation mandibular MRA and a neuromuscular orthotic were constructed under controlled protocols for 12 women MPD patients with a mean age of 38 years. EMG measurements were taken during a lo-second clench of both appliance and a placebo (cotton rolls). No statistical difference was found between the centric relation mandibular MRA and neuromuscular orthotic. The highest mean value for both muscle groups was seen consistantly with the placebo. The results suggest that functional EMG activity is the same for a conventionally constructed MRA and the neuromuscular orthotic. Temporomandibular disorders (TMD) often overlap and are accompanied, singly or in combination, by limitation of jaw movement, joint sounds, and palpable muscle tender-
39
THE
JOURNAL
OF PROSTHETIC
CARLSON
DENTISTRY
EM2
PUtSE
-Test 1 -Test2
1,2,3
photo's
remove
pre-amp
ET
At,.
Et22 -Test
l* I
4,s photo ’ s
&o-print Re*stration for Ortbotic Construction
Fig. 1. Suggested protocol for construction of neuromuscular orthotic using EM2 electromyograph. Function 2 test is not taken after pulsing because this would reprogram proprioceptive avoidance conditions. Test 1, resting EMG; test 2, functional EZHG. Photographs 1,2,3,4,5 are positions of the mandible recorded on the kinesiograph (MIiG). Pulsing, use of the Myomonitor instrument.
ness or joint soreness.’ Included within the description of TMD are masticatory muscle disorders, which can originate from muscle hyperactivity, with behavioral and occlusal management the predominant methods of treating the problem to date.2 Occlusal devices have been developed for use in the diagnosis and treatment of these disorders’ with technical specifications varying in interocclusal registration, design, and therapeutic goals3 MRA4 and the neuromuscular orthotic (NM0)5 in theory provide occlusal disengagement by altering the vertical dimension, thereby eliminating the malocclusion, which could contribute to neuromuscular stability.6 The NM0 is constructed from an interocclusal registration taken from a “myocentric position,” which has been defined as an isotonic closure of the mandible from physiologic rest position along a trajectory through interocclusal rest space.7The concept that the myocentric position of the mandible is the optimum neuromuscular relationship of the mandible to the skull8 is accepted by some dentists.g Neuromuscular stability theoretically can be achieved from measuring an interocclusal registration by using a kinesiograph, a Myomonitor instrument (Myotronits Inc., Seattle, Wash.) and electromyograph. To determine which device best benefits the TMD patient, a method of measurement that allows comparison of the devices’ effects is necessary. Electromyography (EMG) has been used qualitatively to estimate the level of muscle activity in patients with and without signs and symptoms of disorders of the masticatory system.lO Because there have been no systematic comparisons of electromyographic effects of similar occlusal devices,ll the purpose was to investigate the effects of a muscle relaxation appliance, neuromuscular orthotic, and placebo on functional masseter and anterior temporalis muscle activity. 40
MATERIAL
AND METHODS
Twelve women TMD subjects were chosen to participate in the experiment. A thorough review of the subjects’ medical and dental history was completed to ascertain past drug regimens or any related therapy for TMD. The primary investigator was responsible for all clinical measurements, all electronic instrum~tation utilized in the interocclusal registration for the experimental orthotic, and all electromyographic (EMG) recording of muscles in maximum clench for both devices and placebo. The primary investigator followed the testing procedures for the construction of the neuromuscular orf,hotic (Myotronics, Inc.) summarized in Fig. 1. The instrumentation used in this experiment included the J-4 Myomonitor, the K5AR kinesiograph, and the EM2 electromyograph (Myotronics, Inc.). The secondary investigator was responsible for the construction of the muscle relaxation appliance, which followed a protocol described by Okes& and provided assistance during the electromyographic testing of-both appliances. The secondary investigator placed appliances during electromyographic testing, thereby providing a blind test to the primary investigator and patient. Subjects were asked to fill out a questionnaire after the experiment so that socioeconomic status, stress level, and success of therapy could be assessed. Active and ground electrodes used in the experiment were 5 mm silver/silver chloride mceaaed elecgodes. The electrodes were placed over the bell& of the left and right masseter and anterior temporalis muscles. A common (ground) electrode was centered on the side of the neck.‘” A template was devisedI for work inveldng repeated removal and reapplication of electro&safter short or long intervals of time. Posture was important when the patient was introduced to all the measurement techniquee.14 Each subject was monitored by bubble levels mounted on the VOLUME
70
NUMBER
1
CARLSON
THE
ET AL.
FUNCTION TEST-blind Test Function 5 minute Test Function Test
C
5 minute
rest
5 minute
Test Function 5 minute
PLACEBO
B
Function
Teat Function
DENTISTRY
rest rest
5 minute
EXPERIHENTAL
design
OF PROSTHETIC
A
5 minute
Test Function
JOURNAL
D rest
E rest F rest
Fig. 2. Functional testing (test 2) of control, experimental, and placebo treatments under double-blind conditions.
headgear. According to Myotronics, Inc., the myocentric bite registration can be taken after EMG values demonstrate a relaxed muscle. A relaxed muscle is determined by the comparison of baseline resting EMG values with EMG values after 30 to 60 minutes of pulsing with the Myomonitor instrument. EMG values should be lower or approaching zero after pulsing. Study casts and interocclusal registrations were sent to laboratories familiar with the construction of either device. At the second appointment both appliances were adjusted to a point that satisfied the investigator responsible for its construction. Baseline functional testing (test 2) of the MRA, NMO, natural dentition, and cotton rolls were recorded with the EM2 electromyograph. Test 2 represents approximately 10 seconds of maximum clenching recorded on the EM2. Functional testing (test 2) of the MRA, NMO, and cotton roll treatments under double-blind conditions is graphed in Fig. 2. Briefly; Control represents the MRA, experimental represents NM0 and placebo represents cotton rolls. The design was constructed to compare electromyographic values represented in Table I. Cotton rolls were placed between the two dental arches to prevent tooth contact and were tested in the same manner as the NM0 and MRA. Each patient was therefore tested by the primary investigator six times with either the MRA and NM0 appliance or cotton rolls placed by the secondary investigator. The patients received the MRA as part of their treatment and were instructed to wear the device full time for 6 weeks, with appropriate adjustments made during this time frame. The statistical design used for this experiment was the repeated measures analysis. Randomization was accomplished by blinding the primary investigator and patient to the NM0 and MRA during functional EMG testing. JULY
1993
I. Tonic electromyographic values of maximal clenching on cotton rolls (placebo), NMO, and MRA splint treatments and natural dentition in intercuspal position Table
Variables
Standard deviation
Minimum value
Maximum value
153
61 64 50 59
59 85 12 71
255 255 255 255
RTA RMM LMM LTA
130 136 141 119
52 63 62 61
49 64 35 40
225 221 225 252
RTA RMM LMM LTA
124 135 130 116
56 68 59 61
28 54 21 35
254 255 255 255
122 120 102 116
70 84 81 76
30 32 18 34
255 245 250 252
PLC PLC PLC PLC
RTA RMM LMM LTA
EXP EXP EXP EXP CON CON CON CON ND ND ND ND
Mean
RTA RMM LMM LTA
161 185
186
PLC, placebotreatment(bilaterallyplaced cotton rolls); EXP, experimental treatment (neuromuscular orthotic); CON, control treatment (muscle relaxation split); ND, natural dentition; RTA, right anterior temporalis muscle; RMM, right masaeter muscle; LMM, left masseter muscle; and LTA, left anterior temporalis muscle.
Analyses of EMG mean values for both masseter (MM) and anterior temporalis (AT) muscle groups of the NM0 and MRA were compared with each other and with cotton rolls. Each muscle group was divided into right and left AT 41
‘FME
JCKRWAL
OF PROSTHETIC
CARLRON
DENTlSTRY
ET
AL.
Table II. F and p vaiues for comparison of tonic electromyographic values on function (test 2) of orthotic, muscle relaxation appliance, and cotton roll placebo Neuromuscular orthotic versus placebo Muscle group
Right anterior temporalis Right masseter Left masseter Left anterior temporalis
F Value
9.3 14.8 12.9 3.2
and right and left MM muscles. Results of this analysis are summarized in Table II. The level of significance for all testing was p < 0.05.
RESULTS A statistically significant difference was found between the cotton roll treatment and both occlusal devices. The cotton rolls consistently showed a higher mean value than either the MRA or NM0 or the natural dentition (Tables I and II). The patients’ medical histories revealed that all except one subject admitted to a present or past history of temporal headaches. Three of the patients had sought psychiatric care in the past. One patient returned with acute episodes of myofascial pain. All except one of the subjects reported beneficial effect after 6 weeks, which would indicate a therapeutic result. The majority of these patients were high achievers and were career-motivated, with stress predominant and a real concern for health a primary problem in their life. The results of this questionnaire agree with Lupton.15
DISCUSSION The results of this experiment did not show a statistical difference in electromyographic activity between a centric relation mandibular muscle relaxation appliance and a neuromuscular orthotic. A statistical difference was found in electromyographic activity between a placebo (cotton rolls) and the two splints. Although some clinicians believe that accurate measurement of electromyographic activity will help them to construct a better interocclusai appliance, this study indicates that this may not be the case. Many patients with TMD suffer from MPD manifesting itself as orafacial pain and tenderness of the muscles of mastication. Recent literature has correlated MPD with lack of stability of the jaws6 Full-arch appliances are said to provide good tools for the elimination of occlusal interferences to reduce neuromuscular activity and to obtain stable occlusal relationships, with uniform tooth contact throughout the dental arch. l6 It appears that the mean EMG values for the cotton rolls in both right and left MM
42
p Value
0.0111 0.0027 0.0042 0.1005
Muscle relaxatien appliance versus placebri F Value
p Value li.0016 0.9046 O.ON’N (J.0127
17.2 12.5 14.7 8.8
and AT muscles are similar. This similarity or balance of occlusion is what Myotronics, Inc. prefers in the adjusted NMO. The NM0 performed as well as the MRA but not as well as the cotton rols. The natural dentition consistently performed the most poorly. The NM0 did not. achieve consistent maximum values on clenching, whereas the MRA often did. The greatest variation among the treatment groups was between minimum (21) and maximum (255) values and was found within the MRA (Table II). Surface EMG is a useful tool for investigating muscle function in the laboratory, but it may have limitations in clinical dentistry. The EM2 electromyograph is an instrument that is supposed to measure accurate EMG muscle function. A true maximum value is not depicted if maximum EMG values of the EM2 electromyograph are truncated at 255. A question of validity as a result of saturation becomes apparent. The neuromuscular balance of the NM0 as depicted by mean EMG values could then be challenged. The NM0 interocclusal registration requiring 2ti to 3 hours chairside time, sophisticated instrumentation, and a working understanding of the principles of neuromuscular occlusion. Clinicians unfamiliar with the instrumentation would find it di5cult to achieve accurate results. The MRA interocclusal registration required 10 minutes chairside time with no instrumentation and achieved similar mean EMG values. The clinician does not have to worry whether his conventional bite registration is inferior to one that is generated from sophisticated instrumentation. This study would support the short-term use of a soft appliance for the myofascial patient. It may even be advantageous for the patient to place cotton rolls between the teeth in the interim time it takes to construct an appliance. Although the control and experimental appliances did not cause a signiiicant difference in functional muscle activity, it can be seen from the results that the therapy consistently showed a better functional result compared with the patient’s natural dentition. This study woutd therefore support the use of a neuromuscular orthotic or conventional muscle relaxation appliance to negate the detrimental &e&s of occlusal disharmony from the natural dentition.
VOLUME
70
NUMBEH
1
CARLSON
THE
ET AL,
SUMMARY This study investigated whether a neuromuscular orthotic would affect functional masseter EMG differently than a conventional muscle relaxation appliance. The results suggest that both appliances affect EMG equally with better stabilization compared with natural dentition. The placebo treatment provided better stabilization than either splint therapy. This experiment demonstrated no significant differences in stabilizing effects between a conventional muscle relaxation appliance and a neuromuscular orthotic. REFERENCES 1. M&l ND, McCall WD, Lund JP. Devices for the diagnosis and treatment of temporomandibuhu disorders. Part I: Introduction, scientific evidence, and jaw tracking. J PROSTHETDENT 1990;63:198-201. 2. Okeson JP. Conservative management of masticatory disorders. In proceedings American Equilibration Society 32nd annuaI meeting, Chicago: Feb. 11-12, 1987. 3. Clark G. Occlusal therapy. In: The President’s Conference on the Examination, Diagnosis and Management of Temporomandibular Disorders. Chicago: 1983:13’7-44. 4. Okeson JP. Fundamentals of occlusion and temporomandibular disorders. 2nd ed. St Louis CV Mosby, 1989:399-411. 5. Jankelson R, Pulley M. Electromyography in clinical dentistry. Seattle: Myotronics Research, 1984;19.
Availability
JOURNAL
OF PROSTHETIC
DENTISTRY
6. Jiminex ID. Dental stability and maximal masticatory muscle activity. J oral Rehabil 1987;14:591-8. 7. Jankelson B. The Myo-monitor: its use and abuse. Quintessence Int 1978;2:47-52. 8. DinhamGA. Myocentric:aclinicalappraisal.AngleOrthod1984;3:211-7. 9. Dao TT, Feine JS, Lund JP. Can electrical stimulation be used to establish a physiologic occlusal position? J PROSTHETDENT 1988;10:509. 10. Mann8 A, Miralles R, PaIazxi C. Emg, bite force, and elongation of the masseter muscle under isometric voluntary contractions and variations of vertical dimension. J PROSTHET DENT 1979;42:674-82. 11. Dahlstrom L, Haraldson T, Jansson T. A comparative electromyographic study of bite plates and stabilization splints. Stand J Dent Res 1985;93:262-8. 12. Drago C. Anatomy of the facial musculature and electrode placement. In proceedings of the 10th annual meeting of Biofeedback Society of America, San Diego: 1979. 13. Majewski R, Gale E. Electromyographic activity of anterior temporal area pain patients and non-pain patients. J Dent Res 1984;63:1228-31. 14. Mohl ND. Head posture and its role in occlusion. NY Dent J 1976;42:17. 15. Lupton DE. A preliminery investigation of the personality of female temporomandibular joint dysfunction patients. Psychother Psychosom 1966;14:199-216. 16. Humsi AK, Naeije M, Hippe JA, Hansson TL. The immediate effects of a stabilization splint on the muscular symmetry in the masseter and anterior temporal muscles of patients with craniomandibular disorder. J PROSTHET DENT 1989;62:339-42. Reprint requests tot DR. NORMAN CARLsON 2008 DAWN AVENUE NORTH WENATCHEE, WA 98801
of JOURNAL back issues, 1987-1992
Back issues of THE JOURNALOF PROSTHETIC DENTISTRY are available for purchase from the publisher, Mosby, at a cost of $7.50 per issue. (Foreign postage is not included.) The following quantity discounts are available: 25 % off on quantities of 12 to 23, and one third off on quantities of 24 or more. Please write to Mosby, Subscription Services, 11830 Westline Industrial Drive, St. Louis, MO 63146-3318, or call (800)325-4177, ext. 4351, or (314)453-4351 for information on availability of particular issues for that period from 1987 to 1992. If unavailable from the publisher, photocopies of complete issues are available from University Microforms International, 300 N. Zeeb Rd., Ann Arbor, MI 48106, (313)7614700.
JULY
1993
43
AU ANDKLINEBERG
54. Toller PA. Opaque arthrography of the temporomandibular joint. Int J Oral Surg 1974;3:17-28. 55. Hargraves AS, Wardle JJM. The use of physiotherapy in the treatment of temporomandibular disorders. Br Dent J 1983;155:121-4. 56. Rocabado M. Arthrokinematics of the temporomandibular joint. Dent Clin North Am 1983;27:573-94. 57. Rocabado M. Arthrokinematics of the temporomandibular joint. In: Gelb H, ed. Clinical management of head, neck and TMJ pain and dysfunction. 2nd ad. Philadelphia: WB Saunders, 1985:525-46. 58. Bezuur JN, Habets LLMH, Jimenez Lopes V, Naeije M, Hansson TL. The recognition of craniomandibular disorders-a comparison between clinical and radiographic findings in eighty-nine subjects. J Oral Rehabil 1988;15:215-22. 59. Seligman DA, Pullinger AG, Solbar WK. Temporomandibular disorders. Part III: occlusal and articular factors associated with muscle tenderness. J PROSTHET DENT 1988;59:483-9.
Comparison of muscle activity neuromuscular splints
60. Merlini, Palla S. The relationship between condylar rotation and translation in healthy and clicking temporomandibular joints. Schweiz Mona&&r Zabnmed 1988;98:1191-9. Reprint requests to: DR. ANTHONY R. Au DEPARTMENT OF PROSTHETIC DENTISTRY UNIVEKSITY OF SYDNEY UNITED DENTAL HOSPITAL 2 CHALMERSST.
SURRYHILLS NSW 2010 AUSTRALIA
between
conventional
and
N. Carlson, DDS,a D. Moline, DDS,b L. Huber, DDS,c and J. Jacobsond Wash.,and The University of Iowa, Hospital and Clinic, College of Dentistry, Iowa
Wenatchee, City, Iowa
The muscle relaxation appliance (MRA) has been used in the treatment of myofascial pain dysfunction (MPD) patients. The neuromuscular orthotic is a version of the MRA and is constructed from a three-dimensional mandibular position when muscles are in a state of minimal electromyographic (EMG) activity. The purpose of this study was to investigate the affect of two muscle relaxation appliances and a placebo (cotton rolls) on EMG activity of the functional masseter and anterior temporalis muscles. A centric relation mandibular MRA and a neuromuscular orthotic were constructed under controlled protocols for 12 women MPD patients with a mean age of 33 years. EMG measurements were taken during a lo-second clench of both appliance and placebo. No statistical difference was found between the centric relation mandibular MRA and neuromuscular orthotic. A statistically significant difference was found between the mean EMG values of the placebo and two treatment appliances. (J PROSTHET DENT 1993;70:39-43)
T
he muscle relaxation appliance (MRA) has been used in the treatment of myofascial pain dysfunction (MPD) patients. The neuromuscular orthotic is a version of the MRA and is constructed from a three-dimensional mandibular position when muscles are in a state of minimal electromyographic (EMG) activity.
aPrivate Practice, Wenatchee, Wash. bProfessor (retired), former Director, General Practice Residency Program and Division of Family Dentistry, University of Iowa Hospital and Clinics. CClinical Associate Professor, Department of Prosthetic Dentistry, University of Iowa College of Dentistry. dResearch Assistant, Department of Preventive and Community Dentistry, University of Iowa, College of Dentistry. Copyright @ 1993 by The Editorial Council of THE JOURNAL OF PROSTHETIC DENTISTRY. 0022-3913/93/$1.00 + .lO.
1993
10/l/46046
The purpose of this study was to investigate the affect of two muscle relaxation appliances and a placebo on the EMG activity of the functional masseter and anterior temporalis muscles. A centric relation mandibular MRA and a neuromuscular orthotic were constructed under controlled protocols for 12 women MPD patients with a mean age of 38 years. EMG measurements were taken during a lo-second clench of both appliance and a placebo (cotton rolls). No statistical difference was found between the centric relation mandibular MRA and neuromuscular orthotic. The highest mean value for both muscle groups was seen consistantly with the placebo. The results suggest that functional EMG activity is the same for a conventionally constructed MRA and the neuromuscular orthotic. Temporomandibular disorders (TMD) often overlap and are accompanied, singly or in combination, by limitation of jaw movement, joint sounds, and palpable muscle tender-
39
THE
JOURNAL
OF PROSTHETIC
CARLSON
DENTISTRY
EM2
PUtSE
-Test 1 -Test2
1,2,3
photo's
remove
pre-amp
ET
At,.
Et22 -Test
l* I
4,s photo ’ s
&o-print Re*stration for Ortbotic Construction
Fig. 1. Suggested protocol for construction of neuromuscular orthotic using EM2 electromyograph. Function 2 test is not taken after pulsing because this would reprogram proprioceptive avoidance conditions. Test 1, resting EMG; test 2, functional EZHG. Photographs 1,2,3,4,5 are positions of the mandible recorded on the kinesiograph (MIiG). Pulsing, use of the Myomonitor instrument.
ness or joint soreness.’ Included within the description of TMD are masticatory muscle disorders, which can originate from muscle hyperactivity, with behavioral and occlusal management the predominant methods of treating the problem to date.2 Occlusal devices have been developed for use in the diagnosis and treatment of these disorders’ with technical specifications varying in interocclusal registration, design, and therapeutic goals3 MRA4 and the neuromuscular orthotic (NM0)5 in theory provide occlusal disengagement by altering the vertical dimension, thereby eliminating the malocclusion, which could contribute to neuromuscular stability.6 The NM0 is constructed from an interocclusal registration taken from a “myocentric position,” which has been defined as an isotonic closure of the mandible from physiologic rest position along a trajectory through interocclusal rest space.7The concept that the myocentric position of the mandible is the optimum neuromuscular relationship of the mandible to the skull8 is accepted by some dentists.g Neuromuscular stability theoretically can be achieved from measuring an interocclusal registration by using a kinesiograph, a Myomonitor instrument (Myotronits Inc., Seattle, Wash.) and electromyograph. To determine which device best benefits the TMD patient, a method of measurement that allows comparison of the devices’ effects is necessary. Electromyography (EMG) has been used qualitatively to estimate the level of muscle activity in patients with and without signs and symptoms of disorders of the masticatory system.lO Because there have been no systematic comparisons of electromyographic effects of similar occlusal devices,ll the purpose was to investigate the effects of a muscle relaxation appliance, neuromuscular orthotic, and placebo on functional masseter and anterior temporalis muscle activity. 40
MATERIAL
AND METHODS
Twelve women TMD subjects were chosen to participate in the experiment. A thorough review of the subjects’ medical and dental history was completed to ascertain past drug regimens or any related therapy for TMD. The primary investigator was responsible for all clinical measurements, all electronic instrum~tation utilized in the interocclusal registration for the experimental orthotic, and all electromyographic (EMG) recording of muscles in maximum clench for both devices and placebo. The primary investigator followed the testing procedures for the construction of the neuromuscular orf,hotic (Myotronics, Inc.) summarized in Fig. 1. The instrumentation used in this experiment included the J-4 Myomonitor, the K5AR kinesiograph, and the EM2 electromyograph (Myotronics, Inc.). The secondary investigator was responsible for the construction of the muscle relaxation appliance, which followed a protocol described by Okes& and provided assistance during the electromyographic testing of-both appliances. The secondary investigator placed appliances during electromyographic testing, thereby providing a blind test to the primary investigator and patient. Subjects were asked to fill out a questionnaire after the experiment so that socioeconomic status, stress level, and success of therapy could be assessed. Active and ground electrodes used in the experiment were 5 mm silver/silver chloride mceaaed elecgodes. The electrodes were placed over the bell& of the left and right masseter and anterior temporalis muscles. A common (ground) electrode was centered on the side of the neck.‘” A template was devisedI for work inveldng repeated removal and reapplication of electro&safter short or long intervals of time. Posture was important when the patient was introduced to all the measurement techniquee.14 Each subject was monitored by bubble levels mounted on the VOLUME
70
NUMBER
1
CARLSON
THE
ET AL.
FUNCTION TEST-blind Test Function 5 minute Test Function Test
C
5 minute
rest
5 minute
Test Function 5 minute
PLACEBO
B
Function
Teat Function
DENTISTRY
rest rest
5 minute
EXPERIHENTAL
design
OF PROSTHETIC
A
5 minute
Test Function
JOURNAL
D rest
E rest F rest
Fig. 2. Functional testing (test 2) of control, experimental, and placebo treatments under double-blind conditions.
headgear. According to Myotronics, Inc., the myocentric bite registration can be taken after EMG values demonstrate a relaxed muscle. A relaxed muscle is determined by the comparison of baseline resting EMG values with EMG values after 30 to 60 minutes of pulsing with the Myomonitor instrument. EMG values should be lower or approaching zero after pulsing. Study casts and interocclusal registrations were sent to laboratories familiar with the construction of either device. At the second appointment both appliances were adjusted to a point that satisfied the investigator responsible for its construction. Baseline functional testing (test 2) of the MRA, NMO, natural dentition, and cotton rolls were recorded with the EM2 electromyograph. Test 2 represents approximately 10 seconds of maximum clenching recorded on the EM2. Functional testing (test 2) of the MRA, NMO, and cotton roll treatments under double-blind conditions is graphed in Fig. 2. Briefly; Control represents the MRA, experimental represents NM0 and placebo represents cotton rolls. The design was constructed to compare electromyographic values represented in Table I. Cotton rolls were placed between the two dental arches to prevent tooth contact and were tested in the same manner as the NM0 and MRA. Each patient was therefore tested by the primary investigator six times with either the MRA and NM0 appliance or cotton rolls placed by the secondary investigator. The patients received the MRA as part of their treatment and were instructed to wear the device full time for 6 weeks, with appropriate adjustments made during this time frame. The statistical design used for this experiment was the repeated measures analysis. Randomization was accomplished by blinding the primary investigator and patient to the NM0 and MRA during functional EMG testing. JULY
1993
I. Tonic electromyographic values of maximal clenching on cotton rolls (placebo), NMO, and MRA splint treatments and natural dentition in intercuspal position Table
Variables
Standard deviation
Minimum value
Maximum value
153
61 64 50 59
59 85 12 71
255 255 255 255
RTA RMM LMM LTA
130 136 141 119
52 63 62 61
49 64 35 40
225 221 225 252
RTA RMM LMM LTA
124 135 130 116
56 68 59 61
28 54 21 35
254 255 255 255
122 120 102 116
70 84 81 76
30 32 18 34
255 245 250 252
PLC PLC PLC PLC
RTA RMM LMM LTA
EXP EXP EXP EXP CON CON CON CON ND ND ND ND
Mean
RTA RMM LMM LTA
161 185
186
PLC, placebotreatment(bilaterallyplaced cotton rolls); EXP, experimental treatment (neuromuscular orthotic); CON, control treatment (muscle relaxation split); ND, natural dentition; RTA, right anterior temporalis muscle; RMM, right masaeter muscle; LMM, left masseter muscle; and LTA, left anterior temporalis muscle.
Analyses of EMG mean values for both masseter (MM) and anterior temporalis (AT) muscle groups of the NM0 and MRA were compared with each other and with cotton rolls. Each muscle group was divided into right and left AT 41
‘FME
JCKRWAL
OF PROSTHETIC
CARLRON
DENTlSTRY
ET
AL.
Table II. F and p vaiues for comparison of tonic electromyographic values on function (test 2) of orthotic, muscle relaxation appliance, and cotton roll placebo Neuromuscular orthotic versus placebo Muscle group
Right anterior temporalis Right masseter Left masseter Left anterior temporalis
F Value
9.3 14.8 12.9 3.2
and right and left MM muscles. Results of this analysis are summarized in Table II. The level of significance for all testing was p < 0.05.
RESULTS A statistically significant difference was found between the cotton roll treatment and both occlusal devices. The cotton rolls consistently showed a higher mean value than either the MRA or NM0 or the natural dentition (Tables I and II). The patients’ medical histories revealed that all except one subject admitted to a present or past history of temporal headaches. Three of the patients had sought psychiatric care in the past. One patient returned with acute episodes of myofascial pain. All except one of the subjects reported beneficial effect after 6 weeks, which would indicate a therapeutic result. The majority of these patients were high achievers and were career-motivated, with stress predominant and a real concern for health a primary problem in their life. The results of this questionnaire agree with Lupton.15
DISCUSSION The results of this experiment did not show a statistical difference in electromyographic activity between a centric relation mandibular muscle relaxation appliance and a neuromuscular orthotic. A statistical difference was found in electromyographic activity between a placebo (cotton rolls) and the two splints. Although some clinicians believe that accurate measurement of electromyographic activity will help them to construct a better interocclusai appliance, this study indicates that this may not be the case. Many patients with TMD suffer from MPD manifesting itself as orafacial pain and tenderness of the muscles of mastication. Recent literature has correlated MPD with lack of stability of the jaws6 Full-arch appliances are said to provide good tools for the elimination of occlusal interferences to reduce neuromuscular activity and to obtain stable occlusal relationships, with uniform tooth contact throughout the dental arch. l6 It appears that the mean EMG values for the cotton rolls in both right and left MM
42
p Value
0.0111 0.0027 0.0042 0.1005
Muscle relaxatien appliance versus placebri F Value
p Value li.0016 0.9046 O.ON’N (J.0127
17.2 12.5 14.7 8.8
and AT muscles are similar. This similarity or balance of occlusion is what Myotronics, Inc. prefers in the adjusted NMO. The NM0 performed as well as the MRA but not as well as the cotton rols. The natural dentition consistently performed the most poorly. The NM0 did not. achieve consistent maximum values on clenching, whereas the MRA often did. The greatest variation among the treatment groups was between minimum (21) and maximum (255) values and was found within the MRA (Table II). Surface EMG is a useful tool for investigating muscle function in the laboratory, but it may have limitations in clinical dentistry. The EM2 electromyograph is an instrument that is supposed to measure accurate EMG muscle function. A true maximum value is not depicted if maximum EMG values of the EM2 electromyograph are truncated at 255. A question of validity as a result of saturation becomes apparent. The neuromuscular balance of the NM0 as depicted by mean EMG values could then be challenged. The NM0 interocclusal registration requiring 2ti to 3 hours chairside time, sophisticated instrumentation, and a working understanding of the principles of neuromuscular occlusion. Clinicians unfamiliar with the instrumentation would find it di5cult to achieve accurate results. The MRA interocclusal registration required 10 minutes chairside time with no instrumentation and achieved similar mean EMG values. The clinician does not have to worry whether his conventional bite registration is inferior to one that is generated from sophisticated instrumentation. This study would support the short-term use of a soft appliance for the myofascial patient. It may even be advantageous for the patient to place cotton rolls between the teeth in the interim time it takes to construct an appliance. Although the control and experimental appliances did not cause a signiiicant difference in functional muscle activity, it can be seen from the results that the therapy consistently showed a better functional result compared with the patient’s natural dentition. This study woutd therefore support the use of a neuromuscular orthotic or conventional muscle relaxation appliance to negate the detrimental &e&s of occlusal disharmony from the natural dentition.
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SUMMARY This study investigated whether a neuromuscular orthotic would affect functional masseter EMG differently than a conventional muscle relaxation appliance. The results suggest that both appliances affect EMG equally with better stabilization compared with natural dentition. The placebo treatment provided better stabilization than either splint therapy. This experiment demonstrated no significant differences in stabilizing effects between a conventional muscle relaxation appliance and a neuromuscular orthotic. REFERENCES 1. M&l ND, McCall WD, Lund JP. Devices for the diagnosis and treatment of temporomandibuhu disorders. Part I: Introduction, scientific evidence, and jaw tracking. J PROSTHETDENT 1990;63:198-201. 2. Okeson JP. Conservative management of masticatory disorders. In proceedings American Equilibration Society 32nd annuaI meeting, Chicago: Feb. 11-12, 1987. 3. Clark G. Occlusal therapy. In: The President’s Conference on the Examination, Diagnosis and Management of Temporomandibular Disorders. Chicago: 1983:13’7-44. 4. Okeson JP. Fundamentals of occlusion and temporomandibular disorders. 2nd ed. St Louis CV Mosby, 1989:399-411. 5. Jankelson R, Pulley M. Electromyography in clinical dentistry. Seattle: Myotronics Research, 1984;19.
Availability
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DENTISTRY
6. Jiminex ID. Dental stability and maximal masticatory muscle activity. J oral Rehabil 1987;14:591-8. 7. Jankelson B. The Myo-monitor: its use and abuse. Quintessence Int 1978;2:47-52. 8. DinhamGA. Myocentric:aclinicalappraisal.AngleOrthod1984;3:211-7. 9. Dao TT, Feine JS, Lund JP. Can electrical stimulation be used to establish a physiologic occlusal position? J PROSTHETDENT 1988;10:509. 10. Mann8 A, Miralles R, PaIazxi C. Emg, bite force, and elongation of the masseter muscle under isometric voluntary contractions and variations of vertical dimension. J PROSTHET DENT 1979;42:674-82. 11. Dahlstrom L, Haraldson T, Jansson T. A comparative electromyographic study of bite plates and stabilization splints. Stand J Dent Res 1985;93:262-8. 12. Drago C. Anatomy of the facial musculature and electrode placement. In proceedings of the 10th annual meeting of Biofeedback Society of America, San Diego: 1979. 13. Majewski R, Gale E. Electromyographic activity of anterior temporal area pain patients and non-pain patients. J Dent Res 1984;63:1228-31. 14. Mohl ND. Head posture and its role in occlusion. NY Dent J 1976;42:17. 15. Lupton DE. A preliminery investigation of the personality of female temporomandibular joint dysfunction patients. Psychother Psychosom 1966;14:199-216. 16. Humsi AK, Naeije M, Hippe JA, Hansson TL. The immediate effects of a stabilization splint on the muscular symmetry in the masseter and anterior temporal muscles of patients with craniomandibular disorder. J PROSTHET DENT 1989;62:339-42. Reprint requests tot DR. NORMAN CARLsON 2008 DAWN AVENUE NORTH WENATCHEE, WA 98801
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