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RESEARCH Evaluation of the short-term effectiveness of education versus an occlusal splint for the treatment of myofascial pain of the jaw muscles Ambra Michelotti, DD...

RESEARCH Evaluation of the short-term effectiveness of education versus an occlusal splint for the treatment of myofascial pain of the jaw muscles Ambra Michelotti, DDS; Giorgio Iodice, DDS, PhD; Stefano Vollaro, DMS; Michel H. Steenks, DDS, PhD; Mauro Farella, DDS, PhD yofascial pain is the most M common temporoman- dibular disorder (TMD).1-3 The main symptoms of AB STRACT Background. The authors conducted a clin- ® ✷ J A D A ✷ N CON this condition are pain, limited jaw ical trial to compare the effectiveness of an edu- IO T movements or a combination of the cation program with that of an occlusal splint in T A N I U C U two, and they usually are aggra- treating myofascial pain of the jaw muscles across A 3 IN G ED RT vated by function. No specific thera- a short period. I C LE pies have been proven to be more Method. The authors assigned 44 patients randomly to two treat- effective than others, and conserva- ment groups; 41 patients completed the study. The first group (four tive and reversible therapies (such male, 19 female; mean [standard deviation {SD}] age, 31.4 [14.0] as self-care, education and splints) years) received information regarding the nature of temporoman- have been advocated to reduce pain dibular disorder (TMD) and self-care measures, whereas the second and improve jaw function at least as group (five male, 13 female; mean [SD] age, 31.1 [8.8] years) much as have invasive and irre- received an occlusal splint. One of the authors evaluated each versible treatments.1-3 patient every three weeks during a three-month treatment period. Treatment outcomes included pain-free maximal mouth opening, Occlusal splints are the most pop- spontaneous muscle pain, pain during chewing and headache. ular treatment modality for TMD.4 Results. After three months, changes in spontaneous muscle Investigators have described various pain differed significantly between the education and occlusal types of occlusal splints with dif- splint groups (P =.034; effect size = 0.33). Changes in pain-free ferent designs, indications and func- maximal mouth opening did not differ significantly between groups tions.4-6 Nevertheless, the most (P =.528; effect size = 0.20). Changes of headache and pain on common design is the full-arch, flat- chewing did not differ significantly between groups (P ≥.550, effect plane maxillary stabilization splint. size ≤ 0.10). Researchers in several trials have Conclusions. During a short period, education was slightly more reported that occlusal splints are effective than an occlusal splint delivered without education in clinically successful.7-10 Occlusal reducing spontaneous muscle pain in patients with TMD. Pain-free splint therapy can provide centric mouth opening, headache and pain during chewing were not signif- relation occlusion, eliminate pos- icantly different between the two treatments. terior interferences, provide anterior Key Words. Education; occlusal splint; myofascial pain; random- guidance on anterior teeth, reduce ized controlled clinical trial. neuromuscular activity and establish JADA 2012;143(1):47-53. stable occlusal relationships with Dr. Michelotti is an associate professor and the head, Clinic for Temporomandibular Disorders and Orofacial Pain, University of Naples Federico II, Italy. Dr. Iodice is a research assistant and lecturer, Department of Orthodontics, School of Dentistry, Department of Dental and Maxillo-Facial Sciences, Univer- sity of Naples Federico II, Via Pansini, 5. I-80131, Naples, Italy, e-mail “[email protected]”. Address reprint requests to Dr. Iodice. Dr. Vollaro is a clinical lecturer, Clinic for Temporomandibular Disorders and Orofacial Pain, University of Naples Federico II, Italy. Dr. Steenks is an associate professor and the head, Division of Prosthodontics and Special Dental Care, University Medical Center, Utrecht, the Netherlands, and an associate professor, Department of Oral Function and Prosthetic Dentistry, College of Dental Sciences, Radboud University Nijmegen Medical Centre, the Netherlands. Dr. Farella is a professor and the head, Orthodontics, Department of Oral Sciences, Faculty of Dentistry, University of Otago, Dunedin, New Zealand. JADA 143(1) http://jada.ada.org January 2012 47 Copyright © 2012 American Dental Association. All rights reserved. RESEARCH uniform tooth contacts throughout the dental range, 18-53 years; mean [standard deviation arch.4,11 Nevertheless, the mechanism of action of {SD}] age, 31.2 [11.8] years) met the inclusion occlusal splints is still unknown. Results from and exclusion criteria. We assigned the patients several studies in which investigators compared to two treatment groups by means of a balanced stabilization splints with nonocclusal splints block randomization. The first group consisted failed to show any statistically significant differ- of 23 patients (four men and 19 women; age ence for any of the outcomes measured.4,6,12-15 A range, 20-53 years; mean [SD] age, 31.4 [14.0] possible working mechanism of occlusal splints years) who received education only. The second could be based on nonspecific effects linked to the group consisted of 21 patients (six men and 15 patient-doctor relationship, the patient’s educa- women; age range, 18-49 years; mean [SD], 30.3 tion and the patient’s expectations.4,16 [11.4] years) who received occlusal splints but Investigators have hypothesized that an edu- no further information. A second examiner (G.I.) cation program emphasizing reduction of jaw who was masked as to the patient’s treatment muscle activity would be as successful as an performed the baseline assessment and, three occlusal splint given to the patient without months after the start of treatment, collected much further information.17-23 Consequently, the data again (still masked as to each participant’s aim of our study was to compare, by means of a treatment). randomized clinical trial, the effectiveness of an During the entire study period, no participants education program with that of occlusal splint received any other form of treatment—including therapy for the treatment of myofascial pain of drugs, physical therapies or occlusal adjust- the jaw muscles across a short period. ments—other than that assigned to their group. We obtained written informed consent from all METHODS participants before they entered the study. Participants. One hundred ninety-eight consec- Treatments. Education. Participants in the utively seen patients seeking treatment for orofa- education group received general information cial pain were referred to the Clinic for Temporo- about self-care of jaw musculature. The home mandibular Disorders and Orofacial Pain of the exercise program in the education group was University of Naples Federico II across nine focused on habit-reversal techniques.25-27 The cli- months. The patients underwent a routine stom- nician (S.V.) reassured the patient by explaining atognathic examination to detect signs and the problem, the suspected etiology and the good symptoms of TMD. A dentist (A.M.) who was prognosis for this benign disorder. He explained trained in TMD diagnosis according to the the normal jaw muscle function, emphasizing Research Diagnostic Criteria for Temporoman- that overuse of these muscles could be one of the dibular Disorders (RDC/TMD)24 performed a clin- causes of their pain. He told the participants to ical and functional examination of each patient. pay close attention to their jaw muscle activity, Inclusion criteria were myogenous pain and to avoid their usual oral habits and excessive report of ongoing pain, either recurrent or con- mandibular movements, and to follow a soft diet. stant, for a duration of more than three months The clinician instructed them to keep the mus- (diagnostic categories Ia and Ib in the RDC/ cles relaxed by holding the mandible in its pos- TMD), as well as absence of objective evidence tural position (teeth apart) and not in occlusion, of joint pathology or dysfunction. To be included because occlusion requires unintentional muscle in this clinical trial, participants had to report contraction.28 The clinician determined man- at baseline having spontaneous muscle pain dibular rest position by asking the participants greater than 30 millimeters on a visual analog to pronounce the letter “N” several times and to scale (VAS). Exclusion criteria were disk dis- hold the tongue behind the maxillary incisors, placement with or without reduction (diagnostic with the lips in slight contact. Furthermore, he category II of the RDC/TMD); arthrogenous requested that the participants practice what TMD with pain or radiographic alterations in they learned at home and during their common the temporomandibular joints (diagnostic cat- activities by using visual aids to alert them to egory III of the RDC/TMD); other orofacial pain tooth contact, as well as by holding the mandible conditions; other TMD treatments performed in in a relaxed position. He also informed the par- the preceding three months; neurological or psy- ticipants about the relationship between chronic chiatric disorders or both; history of or current abuse of pain medication; and use of an occlusal ABBREVIATION KEY. RDC/TMD: Research Diag- splint in the preceding year. nostic Criteria for Temporomandibular Disorders. Forty-four consecutively seen patients with TMD: Temporomandibular disorder. VAS: Visual myogenous TMD (10 men and 34 women; age analog scale. 48 JADA 143(1) http://jada.ada.org January 2012 Copyright © 2012 American Dental Association. All rights reserved.  RESEARCH pain and psychosocial stress. during chewing and headache by using three Occlusal splint. The participants in the separate 100-mm horizontal VASs.30,31 The left other group received an occlusal splint as the endpoint of each scale indicated no pain or only treatment. The occlusal splint used in this headache at all, and the right endpoint indi- study was the stabilization (Michigan) splint.29 cated the worst pain or headache imaginable. This is a rigid splint constructed for the maxil- During the assessment of pain during lary arch, including all of the maxillary teeth, chewing, the examiner asked participants to with a flat occlusal plane. A technician con- chew bilaterally for 60 seconds a stick of structed it under the direction of the clinician chewing gum. Participants reported any pain on (S.V.) with minimal increase in vertical dimen- the scale immediately after completing the task sion, and the clinician adjusted it so that the (according to the method reported by Farella opposing dentition occluded uniformly, evenly and colleagues32). and simultaneously with the occluding surface Pain-free maximal mouth opening. The of the splint in centric occlusion. Coverage of the clinician conducting the assessments (G.I.) labial surfaces and buccal surfaces of the maxil- measured maximal “pain free” opening as the lary teeth provided frictional retention for the distance between the maxillary and mandibular splint. The splint extended approximately 10 incisal edges and added the overbite measure- mm into the palate beyond the palatogingival ment. We defined “pain free” as the maximum margin. The clinician instructed participants to distance the participant could open his or her use the splint only during sleep. mouth without experiencing any additional pain Procedure. For all participants, the clini- and discomfort. cian (S.V.) took accurate alginate impressions of Statistics. Preliminary analyses consisted of both arches and an interocclusal record with a descriptive statistics, normality tests and tests wax wafer. After one week, the participants in for homogeneity of variances. The outcome meas- the occlusal splint group received the occlusal urements were maximum pain-free mouth splint accurately adjusted in the centric occlu- opening, spontaneous muscle pain, pain during sion, and the participants in the education chewing and headache. We analyzed the outcome group received an explanation of the etiology measures by means of repeated-measurements and of the good prognosis for TMD, as well as analysis of variance, using time (before and information about self-care for the jaw muscula- after) as the within-participant factor and treat- ture. The same clinician (S.V.) administered ment group (education and splint) as the both therapies. between-participant factor. We performed base- All participants received written instructions line and post hoc multiple comparisons by about their own treatment program (that is, means of paired and unpaired t test for interval counseling or occlusal splint instructions), and data and by means of Fisher exact tests for pro- the clinician (S.V.) told them to continue with the portions. All tests were two-tailed. We set the α prescribed therapy throughout a three-month level at.05. We performed post hoc power period even if they were pain free. The clinician analyses, considering the smallest detectable who provided the therapy evaluated each partici- differences of 5 mm for jaw opening and of 28 pant every three weeks during the whole treat- mm for VASs.33 We performed all calculations by ment period. The length of each visit was about using a commercial statistical software package 15 minutes. After the clinician obtained the his- (SPSS Version 5.0 for Windows, SPSS, Chicago). tory and conducted the clinical examination, he asked the participants in the education group RESULTS about their compliance and reinforced their moti- Three participants (one male, two female) (6.8 vation; he evaluated participants in the occlusal percent), all from the occlusal splint group, splint group to determine any need for adjust- dropped out of the study. Hence, 23 participants ment of the device to eliminate local irritation of in the education group and 18 participants in the soft and hard oral tissues and to adjust the the occlusal splint group completed the study. occlusal surface so that mandibular teeth would The table summarizes participants’ baseline touch the splint evenly and simultaneously. characteristics, according to both treatment Three months after the start of treatment, group and whether they completed the study. the baseline examiner (G.I.) collected data again Baseline characteristics did not differ signifi- while being masked as to each participant’s cantly between the two groups (P ≥.05). treatment. Overall, pain-free maximal mouth opening Assessments. Pain. One of the examiners did not differ between treatment groups (F = (G.I.) assessed spontaneous muscle pain, pain 0.99; P =.325), but changed significantly over JADA 143(1) http://jada.ada.org January 2012 49 Copyright © 2012 American Dental Association. All rights reserved. RESEARCH TABLE Pretreatment data*† for all participants. CHARACTERISTIC PARTICIPANT DATA, ACCORDING TO PARTICIPANT DATA, ACCORDING TO STUDY TREATMENT GROUP AT BEGINNING OF STUDY COMPLETION STATUS Education Occlusal Splint Completed Dropped Out (n = 23) (n = 21) (n = 41) (n = 3) Age, in Years* 30.2 (13.0) 30.3 (11.4) 30.4 (12.0) 31.8 (11.0) Sex Male 4 6 9 1 Female 19 15 32 2 Mouth Opening, 43.2 (6.3) 41.5 (7.9) 42.5 (7.1) 41.6 (5.5) in Millimeters* Spontaneous 41.6 (19.4) 39.1 (20.2) 39.9 (20.4) 40.8 (19.3) Muscle Pain*‡ Pain During 44.8 (23.3) 49.6 (28.9) 47.1 (26.7) 46.7 (24.6) Chewing*‡ Headache*‡ 33.3 (19.6) 33.9 (21.1) 33.7 (19.2) 32.3 (20.7) * Data are shown as means (standard deviations). Mean values were compared by using an unpaired Student t test. Ratios were compared by means of the Fisher exact test. † None of the P values was significant. ‡ According to score on a 100-mm visual analog scale. time (F = 12.1; P =.001). The effect of treatment reduced pain levels found only in the education on pain-free maximal jaw opening did not differ group across a short period. To the best of our significantly between the two groups (interac- knowledge, this is the first randomized con- tion time × treatment group; F = 0.41; P =.528; trolled trial in which investigators evaluated effect size = 0.20) (Figure 1). Post hoc analysis the efficacy of an occlusal splint prescribed with revealed that the test for this interaction term a minimum amount of information about treat- had 58 percent power. ment, including any other form of education and VAS scores for spontaneous muscle pain did self-care. For instance, it is possible that unlike not differ between treatment groups (F = 0.25; the participants in the education group, the par- P =.623) and did not change significantly across ticipants in the occlusal splint group clenched time (F = 1.7; P =.197). The effect of treatment their jaws during the treatment period. There- on spontaneous muscle pain score, however, was fore, teaching patients that the overuse of the significantly different between the two groups jaw muscles could be the major cause of their (interaction time × treatment group; P =.034; pain may be more effective than the simple use effect size = 0.33). Post hoc tests revealed that of an occlusal splint. spontaneous muscle pain changed significantly In support of this hypothesis, investigators in a across time in the education group (P =.017) previous study found that habit reversal was as but not in the occlusal splint group (P =.540). effective as a splint therapy for TMD-related Pain during chewing and headache scores were pain.26 This finding could confirm that the key to not significantly influenced by time, treatment achieving a good outcome in TMD management group and effect of treatment (F ≥ 1.1; P ≥.106; seems to be success in educating the patient effect size ≤ 0.10) (Figure 2). The power of these about the disorder to enhance self-care. Some statistical tests was 70 percent or greater. research findings indicate that self-management programs in TMD have long-term positive DISCUSSION effects.25 On the other hand, investigators in sev- In this study, three participants (6.8 percent) eral studies found a statistically significant asso- did not complete the trial and the scheduled ciation between daytime clenching or grinding therapeutic protocol. This percentage of drop- and myofascial pain,35-39 confirming that clenching outs is lower than that in other clinical or grinding is an important risk factor for myofas- studies.18,34 The three participants who dropped cial pain.37,39 Explanations for the association out were assigned to the occlusal splint group, between clenching and myofascial pain can be and their reason for dropping out was the found in the literature. In participants experi- splint’s cost. encing myalgia, investigators have found that Changes in spontaneous muscle pain differed either muscular fibers are damaged40 or blood significantly between treatment groups, with supply is reduced.41 In particular, the perfusion of 50 JADA 143(1) http://jada.ada.org January 2012 Copyright © 2012 American Dental Association. All rights reserved.  RESEARCH the masseter muscle is reduced statistically significantly in CHANGES IN MOUTH OPENING (mm) people performing voluntary iso- 6.00 metric contractions.42 Further- more, investigators in previous 5.00 electromyographic studies iden- 4.00 tified a range of minimal mus- cular activity in the first 3 to 3.00 4 mm of mouth opening, con- firming that a jaw posture with 2.00 a few millimeters of interoc- clusal resting space involves a 1.00 great reduction of masticatory muscle activity and supporting 0.00 Education Occlusal Splint the validity of clinical advice to patients to keep the teeth TREATMENT GROUP apart.28 Another possible explanation Figure 1. Changes in pain-free maximal jaw opening (measured in millimeters on a visual analog scale) experienced by participants in the two treatment groups (education could be that, contrary to par- and occlusal splint). The whiskers represent standard deviations. There were no statisti- ticipants in the occlusal splint cally significant differences (P >.05). mm: Millimeters. group, participants in the edu- cation group received extensive information and considerable Spontaneous Muscle Pain During Headache Pain Chewing patient-doctor interaction. 6.00 Therefore, participants’ im- provement could be linked to 4.00 CHANGES IN VAS SCORES (mm) the positive effects of psycho- 2.00 physiological mechanisms asso- ciated with education and reas- 0.00 surance and mediated by each –2.00 participant’s coping skills, mood and emotional state. With this –4.00 type of chronic disorder, educa- –6.00 tion and reassurance are pow- 4 erful tools for remission. –8.00 Results from studies regard- –10.00 ing patient education compared TREATMENT GROUP with those of studies regarding –12.00 Education other rehabilitation treatment Occlusal Splint –14.00 modalities show that enforcing * patients’ responsibilities, and –16.00 thereby addressing psychosocial factors, can yield better Figure 2. Relative changes in visual analog scale (VAS) scores for spontaneous muscle results.26,27,43 This has been pain, pain during chewing and headache. The whiskers represent standard deviations; found in TMD research as well. the asterisk indicates a statistically significant difference (P <.05). mm: Millimeters. Indeed, Dworkin and colleagues44,45 concluded that carefully structured influence of the medical context on specific minimal interventions emphasizing self- neural systems.46 This factor could explain the management of TMD may offer real benefit to a great benefit of education and reassurance in the substantial number of patients with myogenous treatment of chronic conditions such as TMD.4 TMD. Addressing both dental and psychological To be included in this clinical trial, partici- factors by means of stress management results pants had to report spontaneous muscle pain in a better long-term outcome than does using greater than 30 mm on a VAS at the baseline. an intraoral splint alone. On the other hand, dif- Using this threshold, we selected a sample of ferent kinds of occlusal splints combined with patients with TMD who had moderate to severe education are able to reduce the myofascial pain; therefore, one cannot extrapolate the find- pain.15 Experimental evidence indicates the ings to a general TMD population, which also JADA 143(1) http://jada.ada.org January 2012 51 Copyright © 2012 American Dental Association. All rights reserved. RESEARCH includes participants with slight or mild pain. 13. Forssell H, Kalso E. Application of principles of evidence-based medicine to occlusal treatment for temporomandibular disorders: are The effect of the occlusal splint or the education there lessons to be learned? J Orofac Pain 2004;18(1):9-22. might be different in patients with TMD who 14. Al-Ani Z, Gray RJ, Davies SJ, Sloan P, Glenny AM. Stabiliza- are experiencing less intense pain. tion splint therapy for the treatment of temporomandibular myofas- cial pain: a systematic review. J Dent Educ 2005;69(11):1242-1250. Our trial lacked a nontreatment or placebo 15. Alencar F Jr, Becker A. Evaluation of different occlusal splints control group, so we cannot discard the possi- and counselling in the management of myofascial pain dysfunction. J Oral Rehabil 2009;36(2):79-85. bility that a natural reduction of pain occurred 16. Roberts AH, Kewman DG, Mercier L, Hovell M. The power of in some participants.47 Furthermore, we did not nonspecific effects in healing: implications for psychosocial and bio- ask the participants to complete a daily diary of logical treatments. Clin Psychol Rev 1993;13(5):375-391. 17. Magnusson T, Carlsson GE, Egermark I. Changes in clinical their pain, so we did not investigate the influ- signs of craniomandibular disorders from the age of 15 to 25 years. ence of the treatment modalities on the fre- J Orofac Pain 1994;8(2):207-215. quency of pain. 18. Michelotti A, Steenks MH, Farella M, Parisini F, Cimino R, Martina R. The additional value of a home physical therapy regimen versus patient education only for the treatment of myofascial pain of CONCLUSIONS the jaw muscles: short-term results of a randomized clinical trial. J Orofac Pain 2004;18(2):114-125. Our findings show that during a short period, 19. Truelove E, Huggins KH, Mancl L, Dworkin SF. The efficacy of education was slightly more effective than an traditional, low-cost and nonsplint therapies for temporomandibular occlusal splint in treating spontaneous muscle disorder: a randomized controlled trial. JADA 2006;137(8):1099-1107. 20. Turner JA, Mancl L, Aaron LA. Short- and long-term efficacy of pain. 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