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Changes in shoulder and leg strength in athletes wearing mandibular orthopedic repositioning appliances
ARTICLES
Varsity football players wore two types of mouthpieces for eight weeks to test upper and iower body strength.
Changes in shoulder and leg strength in athletes wearing mandibular orthopedic repositioning appliances M ark M. Schubert, DDS, M SD R onald L. Guttu, DDS, M SD Letha H. Hunter, MD
o
cclusal splints have been used for m any years by clinicians for the treatm ent of a variety of conditions that affect the m uscles of m astication and the tem poro m an d ib u lar jo in t (TMJ).1,2 Recently, a new use for occlusal splints has been pro posed, based on the claim that reposition in g th e m a n d ib le c a n in c re a se body strength in athletes .3 A particular type of s p l i n t , th e M O RA ( m a n d ib u la r o r thopedic repositioning appliance), has been recom m ended for use by athletes based on the results of several uncon trolled studies and personal testim onials, and has been publicized in new spapers and m agazines .4'7 Sm ith 8 has stated that the MORA increased the strength of some members of a professional football team. This study, how ever, lacked control sub jects, w as not perform ed in a double blind fashion, and was not statistically analyzed. Garabee 9reported the results of a three-year study of splint use by ru n ners, suggesting that these athletes had increased en d u ran ce w h en they wore m outh splints that “correct” jaw posture. 334 ■ JADA, Vol. 108, M arch 1984
R ichard Hall, RPT Ronald Thom as, M S
However, this study also lacked control subjects and presented data that were not statistically analyzed. Neither of these studies used placebo m outh splints. W illiam s a n d o th e rs 10 rec e n tly r e ported that m andibular position affects appendage m uscle strength and is im por tant to total well-being. This study com-
pared appendage m uscle strength at three jaw positions and found a statistically significant m uscle strength increase in the upper appendages. No placebo splint was evaluated in this single observation study. A nonrigid splint m aterial was used. Considerable variability in m uscle • strength increase was noted w ithin the
Fig 1 ■ Treatment appliance that covered occlusal surfaces of mandibular posterior teeth and occupied freeway space.
Fig 2 ■ Placebo appliance that did not cover occlu sal surfaces of teeth and did not change vertical di mension.
ARTICLES
same subject, and the optimum jaw posi tion for the arm abductors was not neces sarily optimum for the arm adductors. It has also been suggested that mouth splints may increase upper body strength more than lower body strength,7-11 and that the amount of biting pressure on the splint may be significant.6 In addition, it has been stated that chiropractic-applied kinesiologic evaluations can show that an athlete has TMJ dysfunction, even if that person is asymptomatic. Criticism and careful analysis of these claims are beginning to appear in several professional journals.11,12 Greenburg and others13 found, in a double-blind study of 14 college basketball players, that there was no statistical difference between the effect of placebo splints and treatment splints on upper body strength improve ment. In a similar study by Burkett and others,14 no statistical difference was found between placebo and treatment splints and their effect on upper and lower body strength. Both of these studies were single-observation experiments. The purpose of this study was to evalu ate the previously stated claims of the MORA advocates. A controlled, double blind study was performed on college football players. One group of athletes wore treatment splints and the other group wore placebo splints. In addition, in d e p e n d e n t c h ir o p r a c tic -a p p lie d kinesiologic evaluations were performed to predict which athletes would benefit from an equilibrated mouth splint.
Methods and m aterials Selection of subjects Twenty varsity football players, who reported for spring football at the University of Wash ington, were randomly assigned to either the treatment or placebo group without regard to position played or present physical condition. These subjects had not started organized con ditioning programs when the study began. All subjects had medical and dental evalua tions before the stud$ was started. During the medical evaluation the athletes were asked about pertinent orthopedic/sports medicine considerations such as a history of athletic in juries, back and neck problems, symptoms of overuse syndromes, and evaluation of joint range of motion and flexibility. The dental evaluation included any history of temporo mandibular joint trauma or symptoms such as joint popping or pain, parafunctional habits, clinical evidence of muscle tenderness, devia tions in opening or closing patterns, mandibu lar range of motion, amount of freeway space, and general status of the dentition. In addition, all subjects underwent a chiropractic-applied kinesiologic evaluation performed by a licensed chiropractor to test isometric muscle strength. During this evaluation, special atten tion was paid to generalized loss of muscle strength when in forced occlusion in an effort to predict which subjects would be most likely to benefit from a MORA. None of the evaluators
was aware of the findings of the other evaluators until the study was completed.
Table 1 ■ History findings from dental examination: 19 subjects._____________________
Splint design
Finding
Maxillary and mandibular alginate impres sions were taken and stone casts were made for the 20 subjects. The treatment splints were fab ricated using the design recommended by Gelb.15 This splint design uses two acrylic saddles that cover the occlusal surfaces of the mandibular teeth and that are connected by a rigid lingual bar. The occlusal portion of the splint occupied the subject’s freeway space and was adjusted to provide even contact in centric occlusion (Fig 1). The placebo splints were the same design as the treatment splints except that the occlusal surfaces of the poste rior teeth were not covered (Fig 2). The placebo splint did not alter the vertical dimension of occlusion or affect mandibular placement when in place. Ten subjects were given treatment splints and ten subjects were given placebo splints. The subjects were told that this was a study to evaluate different splint designs and no men tion of a placebo splint was made.
Clench or grind teeth Headaches Orthodontic treatment TMJ noise Jaw dysfunction
No. of subjects with finding 6 1 1 0 0
T ab le 2 ■ C linical d e n ta l ex am in atio n results: 19 subjects. Finding TMJ noise: Early opening click Midopening click Early closing click ' Reciprocal click Occlusion class: Class 1 Class II Class III TMJ pain to palpation Muscle tenderness Incisal opening (mean) + Chiropractic examination
Number of subjects 8 3 1 3 1 14 2 3 0 0 55 mm 9
Muscle strength testing Subjects were introduced to the testing equip ment and procedures immediately after the ini tial medical and dental histories and examina tions. At that time and at each subsequent test session, the subjects were allowed to warm up before the muscle testing. Upper and lower body muscle strength was evaluated with an isokinetic dynomometer. The strength of shoulder abduction and adduc tion was evaluated at both 10 and 30 rpm set tings, according to the manufacturer’s specifi cations. The quantitative isokinetic muscle work levels were then recorded. Similarly, the strength of knee flexion and extension was measured at settings of 10 and 40 rpm. Both right and left sides (dominant and nondomin ant) were measured. All muscle testing was done by one inves tigator. The subjects closed their teeth in cen tric occlusion without the splint in place, with the splint in place, and with light force (sub jects were instructed to close their teeth lightly against the splint), and with the splint in place and biting with heavy force (subjects were in structed to close their teeth firmly against the splint) for each of the 16 exercises. The order of these three jaw positions was varied for each of the test sessions. The investigator performing the evaluation was unaware of the type of splint being worn by the subject. The test period extended for eight weeks and subjects were evaluated during week 1, during week 4, and at the end of week 8.
Statistical methods Mean strength calculations from Cybex mea surements for treatment and placebo groups were made for both light and heavy bites; t-tests were used to compare the means with P-values which at less than or equal to .05 were considered significant. Strength tests for subjects who were selected by chiropractic-applied kinesiologic criteria were analyzed by a two-by-two contingency
test for significance (Fisher’s exact test). The treatment splint group was compared with the placebo splint group as to whether strength was improved from control sessions to exper imental sessions. A confidence level of .05 was used to determine significance.
Results Nineteen of the 20 subjects selected completed the study; one subject withdrew from inter collegiate athletics three weeks into the study and was not included in this study. Ten sub jects received treatment splints and nine re ceived placebo splints. A detailed dental and TM area history and examination of each sub ject showed few abnormal findings (Table 1,2). Forty-two percent of the subjects had clicking in the TMJ, but none of the subjects had palpa tion tenderness of the muscles of mastication or the TMJ. The chiropractic-applied kine siologic examination showed that nine sub jects would benefit from wearing a MORA. Five of these subjects received treatment splints and four wore placebo splints. A series of two-tailed t-tests were conducted to test the difference between the treatment and placebo groups (Table 3-6). Of the 16 tests for upper and lower body strength, while using a “light” occlusion, only two P-values were in the .08 to .09 range, and 14 of 16 P-values were strongly nonsignificant (P > .25). The two lowest P-values are associated with negative test statistics that imply that in these two in stances a greater gain in strength was realized by the placebo group when compared with the treatment group. Similarly, tests for strength when teeth were closed firmly on the splint produced no significant changes (P > .111). In no instance was there any statistically significant effect of splint use on either upper or lower body strength. Upper and lower ex tremity muscle strength was not improved whether the subject closed lightly or heavily on the MORA.
Schubert-Others : EFFECT OF MANDIBULAR APPLIANCES ON BODY STRENGTH ■ 335
A R T IC L E S
Table 3
Table 4
■ S tr e n g th te s tin g w ith “ l i g h t ” b ite .
■ S tre n g th te s tin g w ith “ l ig h t ” b ite .
Pooled variance estimate: Exercise
Variable
Shoulder abduction Right 10 rpm T reatm ent
Mean
1.8000
Standard deviation T-value
2-tail probability
7.534 .69
Placebo 30 rpm Treatm ent
-.0 9 2 6 -.4 1 6 7
2.750
Placebo
-.0 1 8 5
4.147
Variable
Mean
-.5 8 3 3
6.622
-2.4444
8.378
3.4500
13.356
.7037
6.424
-4.3667
8.266
Placebo 40 rpm Treatm ent
2.0926
6.708
.2167
4.347
Placebo Knee extension Right 10 rpm T reatm ent
3.2593
7.678
-1.9000
9.243
Placebo 40 rpm Treatm ent
-2.2037
10.823
.9167
5.095
Placebo
2.6111
5.570
10 rpm T reatm ent
-7.0000
13.481
.500
3.451
Placebo 40 rpm Treatm ent -.2 5
.806 Placebo
Left .0833
10 rpm T reatm ent
3.437 .38
Placebo 30 rpm T reatm ent
-.3 7 0 4
1.086
1.2000
4.105
Placebo Shoulder adduction Right 10 rpm Treatm ent
-.3 8 8 9
3.373
.4500
5.229
Placebo 30 rpm T reatm ent
1.2222
9.794
-.2 1 6 7
6.287
.92
-.2 2
-.3 0 Placebo
.6481
.710
.373
.830
.768
6.291
Left
.596
.56
.583
- 1 .8 6
.081
-1 .0 8
.296
.07
.948
- .6 9
.498
-1 .8 0
.089
-1 .0 1
.329
Left 10 rpm T reatm ent
-1 .1 5 0
7.964 .24
Placebo 30 rpm Treatm ent
-1 .8 7 0 4
4.596
2.9167
6.281 .17
Placebo
2.4815
.815 Placebo 40 rpm Treatm ent
2.7407
9.460
-.5833
4.205
Placebo
1.8148
6.113
.870
4.925
Table 6
■ S tr e n g th te s tin g w ith “ h e a v y ” b ite.
■ Strength testing w ith “heavy” bite.
Pooled variance estim ate Exercise
.54
Left 10 rpm Treatm ent
Table 5
Exercise
Knee flexion Right 10 rpm Treatm ent
Pooled variance estim ate Standard deviation T-value 2-tail probability
Variable
Shoulder abduction Right 10 rpm Treatm ent
Mean
.8000
Standard deviation T-value
2-tail probability
5.453 .71
Placebo 30 rpm T reatm ent
-.6 4 8 1 -.7 8 3 3
2.409
Placebo
-1.0185
2.577
Exercise
Variable
Knee flexion Right 10 rpm Treatm ent
-.2 0 0 0
8.135
-2.2037
8.000
.489
2.959
Placebo 40 rpm Treatm ent .21
Mean
Pooled variance estimate Standard deviation T-value 2-tail probability
1.3000
12.403
Placebo
-.9 2 5 9
5.559
10 rpm T reatm ent
-1.6000
9.534
-.0741
6.202
-1.3667
6.058
.4444
3.505
-.6333
11.893
-4.7037
10.043
-1.8167
4.321
.4259
4.222
.840
Left
.54
.596
.49
.627
-.4 1
.688
- .7 9
.443
.80
.434
Left 10 rpm T reatm ent
1.3667
3.476 1.68
Placebo 30 rpm Treatm ent
-.9 4 4 4
2.327
.6167
2.760
Placebo Shoulder adduction Right 10 rpm Treatm ent
-.1 2 9 6
3.037
-1 .0167
12.051
-1.6111
4.770
-1.0833
4.303
Placebo 40 rpm Treatm ent .56
-.4 2 5 9
.892 Placebo 40 rpm Treatm ent
- .2 9 Placebo
.582 Placebo Knee extension Right 10 rpm Treatm ent
-.1 4 Placebo 30 rpm Treatm ent
.111
.779
-1 .1 4
5.720
Placebo
Left
.269
Left 10 rpm Treatm ent
-.7 3 3 3
10 rpm Treatm ent
10.586 .68
Placebo 30 rpm Treatm ent
-3 .5185
6.702
1.4333
4.149
Placebo 40 rpm Treatm ent .00
Placebo
1.4444
336 ■ JADA, Vol. 108, M arch 1984
6.394
-.0 5
14.606
-1.0741
10.727
-2.3 0 0
5.896
.508
.996 Placebo
-.7593
5.860
.17
.865
- .5 7
.576
A R T IC L E S
The reports by other authors of positive responses to the MORA may be the result of a placebo effect or faulty research design rather than from any direct benefit of wearing the splint.
‘
Table 7 show s the dental and TM history and exam ination findings for the nine subjects w ho had a positive chiropractic-applied kinesiological exam ination. These nine subjects experi‘ enced a general decrease in isometric m uscle strength during forced occlusion. An exam ina tion of the dental and TMJ findings in this group failed to show specific factors that m ight * ac c o u n t for th e c h iro p ra c tic fin d in g . An analysis of the strength testing data for this group is presented in Table 8. Five subjects had treatm ent splints and four had placebo splints. * No P-value approached significance in this separate analysis of a group of subjects iden tified by ch iro practic-applied kinesiologic testing as likely to benefit from a MORA.
Discussion
None of the 19 subjects who participated in this study had any historical or exami nation findings that would suggest m an d ib u la r p a in d y sfu n c tio n sy n d ro m e. However, nine of our subjects were found to have a generalized loss of m uscle strength w hen they closed th eir teeth firmly during applied kinesiologic evalu ation. This finding has been suggested to be diagnostic for TMJ dysfunction by some auth o rs ,5'8 but does not correlate w ith any obvious finding of the TMJ e v a lu a tio n . T he ex p la n a tio n for th is * applied-kinesiologic exam ination fin d ing is unclear at this time. This study failed to find a statistically T ab le 7 ■ Dental exam ination findings for subjects w ith positive chiropractic exam ina significant difference between the treat m ent group and the placebo group in tion (n = 9). spite of repeated evaluations during an Num ber of subjects eight-w eek period. In stantaneous im w ith finding Findings provem ent was not observed, nor was History there any im provem ent over time. The 4 Clench or grind teeth 0 Headaches reports by other authors of positive re 0 O rthodontic treatm ent sponses to the MORA may be the result of 0 TMJ noise a placebo effect or faulty research design 0 Jaw dysfunction Clinical exam ination rath er than from any direct benefit of TMJ noise w earing the splint. reciprocal click 1 The group of subjects designated by Occlusion class (angle) 7 Class I chiropractic-applied kinesiologic evalua 1 Class II tion to be likely to respond to the MORA 1 Class III failed to show a statistically significant 0 TMJ pain to palpation 0 M uscle tenderness difference betw een the treatm ent splint 55 mm Incisal opening (mean) and the placebo splint. This finding dis putes the claim that chiropractic-applied k in e s io lo g ic e v a lu a tio n can p re d ic t Table 8 ■ S t r e n g t h i m p r o v e m e n t i n c h i- w h ic h a th le te s sh o u ld re sp o n d to a * r o p ra c tic T M J d y s f u n c tio n g ro u p p la c e b o v s MORA. tre a tm e n t. Exercise S houlder abduction Right Left '
Shoulder adduction Right Left Knee flexion Right Left Knee extension Right Left *Fisher’s Exact Test.
Variable
P-value*
10 30 10 30
rpm rpm rpm rpm
.476 .317 .476 .317
10 30 10 30
rpm rpm rpm rpm
.317 .476 .317 .317
10 40 10 40
rpm rpm rpm rpm
.317 .357 .317 .119
10 rpm 40 rpm 10 rpm 40 rpm
.317 .556 .317 .357
Conclusion A controlled double-blind study of the ef fects of the MORA on college athletes failed to show a statistically significant difference betw een a treatm ent splint and a placebo splint. N either upper nor lower body strength was improved, nor did the am ount of biting force significantly alter the results. The group of subjects desig n a te d by c h iro p ra c tic -a p p lie d k in e siologic evaluation to be likely to respond to MORA splints, failed to show statisti cally significant differences in strength w hen treatm ent splints were com pared w ith placebo splints. There was also no o b v io u s c o r r e l a t i o n b e tw e e n a ch iro p ractic-d efin ed TMJ dysfunction
group and the findings of a dental TMJ evaluation. These findings contradict re ports advocating the use of MORA splints in athletes and are consistent w ith more re c e n t carefu lly co n tro lled scie n tific
The inform ed consent of all hum an subjects w ho participated in the experim ental investigation re ported or described in this m anuscript was obtained after the nature of the procedure and possible discom forts and risks had been fully explained. Drs. Schubert and Guttu are faculty m em bers, de partm ent of oral medicine, School of Dentistry; Dr. H unter is assistant professor, and Mr. Hall is a physi cal therapist, departm ent of orthopedics and sports m edicine, School of M edicine; and Mr. Thomas is a statistician, departm ent of biostatistics, University of W ashington. A ddress requests for reprints to Dr. Schubert, departm ent of oral m edicine, SC-63, U ni versity of W ashington, Seattle, 98195. 1. Greene, C.S., and Laskin, D.M. S plint therapy for m yofascial pain-dysfunction (MPD) syndrom e: a com parative study. JADA 84(3):624-628, 1972. 2. Clark, G.T., an d others. N octurnal electro m yographic evaluation of myofascial pain dysfunc tion in patients undergoing occlusal splint therapy. JADA 99(4):607-611, 1979. 3. Smith, S.D. Sports dentistry: protection and per form ance from m outhguards and bite splints. A th letic Training 16(2):100-106, 1981. 4. Kaufman, R.S. Case reports of TMJ repositioning in scoliosis and the perform ance by athletes. NY State Dent J 46(4):206-209, 1980. 5. Verschoth, A. W eak? Sink your teeth into this. Sports Illustrated 52:37-42, June 2, 1980. 6. Burfoot, A. A m iracle device that can im prove your running. R unner’s W orld 16(9):50-54, 1981. 7. Carlton, D. T here’s hope for hunting athletes. Seattle Post-Intelligencer, Jan 17, 1982. 8. Smith, S.D. M uscular strength correlated to jaw posture and the tem porom andibular joint. NY State Dent J 44(7):278-285, 1978. 9. Garabee, W.F. C raniom andibular orthopedics and athletic perform ance in the long distance runner: a three year study. Basal Facts 4(3):77-81,1982. 10. W illiam s, M.O.; Chaconas, S.J.; and Bader, P. The effect of m andibular position on appendage m u s cle strength. J Prosthet Dent 49(4):560-567,1983. 11. Moore, M. Corrective m outh guards: perfor m ance aids or expensive placebos? Physician Sports M edicine 9(3):127-132,1981. 12. Jakush, J. Can dental therapy enhance athletic perform ance? JADA 104(3):292-298, 1982. 13. Greenburg, M.S., and others. M andibular po si tion and upper body strength: a controlled clinical trial. JADA 103(4):576-579, 1981. 14. Burkett, L.N., and Bernstein, A.K. S trength testing after jaw repositioning w ith a m andibular or th o p e d ic ap p lian ce. P h y sician S ports M ed icin e 10(2):101-107, 1982. 15. Gelb, H. Effective m anagem ent and treatm ent of the craniom andibular syndrom e. In Gelb, H., ed. Clinical m anagem ent of head, neck, and TMJ pain and dysfunction. P hiladelphia, W. B. Saunders Co, 1977, p 288.
S chubert-O thers : EFFECT OF MANDIBULAR APPLIANCES ON BODY STRENGTH ■ 337
Varsity football players wore two types of mouthpieces for eight weeks to test upper and iower body strength.
Changes in shoulder and leg strength in athletes wearing mandibular orthopedic repositioning appliances M ark M. Schubert, DDS, M SD R onald L. Guttu, DDS, M SD Letha H. Hunter, MD
o
cclusal splints have been used for m any years by clinicians for the treatm ent of a variety of conditions that affect the m uscles of m astication and the tem poro m an d ib u lar jo in t (TMJ).1,2 Recently, a new use for occlusal splints has been pro posed, based on the claim that reposition in g th e m a n d ib le c a n in c re a se body strength in athletes .3 A particular type of s p l i n t , th e M O RA ( m a n d ib u la r o r thopedic repositioning appliance), has been recom m ended for use by athletes based on the results of several uncon trolled studies and personal testim onials, and has been publicized in new spapers and m agazines .4'7 Sm ith 8 has stated that the MORA increased the strength of some members of a professional football team. This study, how ever, lacked control sub jects, w as not perform ed in a double blind fashion, and was not statistically analyzed. Garabee 9reported the results of a three-year study of splint use by ru n ners, suggesting that these athletes had increased en d u ran ce w h en they wore m outh splints that “correct” jaw posture. 334 ■ JADA, Vol. 108, M arch 1984
R ichard Hall, RPT Ronald Thom as, M S
However, this study also lacked control subjects and presented data that were not statistically analyzed. Neither of these studies used placebo m outh splints. W illiam s a n d o th e rs 10 rec e n tly r e ported that m andibular position affects appendage m uscle strength and is im por tant to total well-being. This study com-
pared appendage m uscle strength at three jaw positions and found a statistically significant m uscle strength increase in the upper appendages. No placebo splint was evaluated in this single observation study. A nonrigid splint m aterial was used. Considerable variability in m uscle • strength increase was noted w ithin the
Fig 1 ■ Treatment appliance that covered occlusal surfaces of mandibular posterior teeth and occupied freeway space.
Fig 2 ■ Placebo appliance that did not cover occlu sal surfaces of teeth and did not change vertical di mension.
ARTICLES
same subject, and the optimum jaw posi tion for the arm abductors was not neces sarily optimum for the arm adductors. It has also been suggested that mouth splints may increase upper body strength more than lower body strength,7-11 and that the amount of biting pressure on the splint may be significant.6 In addition, it has been stated that chiropractic-applied kinesiologic evaluations can show that an athlete has TMJ dysfunction, even if that person is asymptomatic. Criticism and careful analysis of these claims are beginning to appear in several professional journals.11,12 Greenburg and others13 found, in a double-blind study of 14 college basketball players, that there was no statistical difference between the effect of placebo splints and treatment splints on upper body strength improve ment. In a similar study by Burkett and others,14 no statistical difference was found between placebo and treatment splints and their effect on upper and lower body strength. Both of these studies were single-observation experiments. The purpose of this study was to evalu ate the previously stated claims of the MORA advocates. A controlled, double blind study was performed on college football players. One group of athletes wore treatment splints and the other group wore placebo splints. In addition, in d e p e n d e n t c h ir o p r a c tic -a p p lie d kinesiologic evaluations were performed to predict which athletes would benefit from an equilibrated mouth splint.
Methods and m aterials Selection of subjects Twenty varsity football players, who reported for spring football at the University of Wash ington, were randomly assigned to either the treatment or placebo group without regard to position played or present physical condition. These subjects had not started organized con ditioning programs when the study began. All subjects had medical and dental evalua tions before the stud$ was started. During the medical evaluation the athletes were asked about pertinent orthopedic/sports medicine considerations such as a history of athletic in juries, back and neck problems, symptoms of overuse syndromes, and evaluation of joint range of motion and flexibility. The dental evaluation included any history of temporo mandibular joint trauma or symptoms such as joint popping or pain, parafunctional habits, clinical evidence of muscle tenderness, devia tions in opening or closing patterns, mandibu lar range of motion, amount of freeway space, and general status of the dentition. In addition, all subjects underwent a chiropractic-applied kinesiologic evaluation performed by a licensed chiropractor to test isometric muscle strength. During this evaluation, special atten tion was paid to generalized loss of muscle strength when in forced occlusion in an effort to predict which subjects would be most likely to benefit from a MORA. None of the evaluators
was aware of the findings of the other evaluators until the study was completed.
Table 1 ■ History findings from dental examination: 19 subjects._____________________
Splint design
Finding
Maxillary and mandibular alginate impres sions were taken and stone casts were made for the 20 subjects. The treatment splints were fab ricated using the design recommended by Gelb.15 This splint design uses two acrylic saddles that cover the occlusal surfaces of the mandibular teeth and that are connected by a rigid lingual bar. The occlusal portion of the splint occupied the subject’s freeway space and was adjusted to provide even contact in centric occlusion (Fig 1). The placebo splints were the same design as the treatment splints except that the occlusal surfaces of the poste rior teeth were not covered (Fig 2). The placebo splint did not alter the vertical dimension of occlusion or affect mandibular placement when in place. Ten subjects were given treatment splints and ten subjects were given placebo splints. The subjects were told that this was a study to evaluate different splint designs and no men tion of a placebo splint was made.
Clench or grind teeth Headaches Orthodontic treatment TMJ noise Jaw dysfunction
No. of subjects with finding 6 1 1 0 0
T ab le 2 ■ C linical d e n ta l ex am in atio n results: 19 subjects. Finding TMJ noise: Early opening click Midopening click Early closing click ' Reciprocal click Occlusion class: Class 1 Class II Class III TMJ pain to palpation Muscle tenderness Incisal opening (mean) + Chiropractic examination
Number of subjects 8 3 1 3 1 14 2 3 0 0 55 mm 9
Muscle strength testing Subjects were introduced to the testing equip ment and procedures immediately after the ini tial medical and dental histories and examina tions. At that time and at each subsequent test session, the subjects were allowed to warm up before the muscle testing. Upper and lower body muscle strength was evaluated with an isokinetic dynomometer. The strength of shoulder abduction and adduc tion was evaluated at both 10 and 30 rpm set tings, according to the manufacturer’s specifi cations. The quantitative isokinetic muscle work levels were then recorded. Similarly, the strength of knee flexion and extension was measured at settings of 10 and 40 rpm. Both right and left sides (dominant and nondomin ant) were measured. All muscle testing was done by one inves tigator. The subjects closed their teeth in cen tric occlusion without the splint in place, with the splint in place, and with light force (sub jects were instructed to close their teeth lightly against the splint), and with the splint in place and biting with heavy force (subjects were in structed to close their teeth firmly against the splint) for each of the 16 exercises. The order of these three jaw positions was varied for each of the test sessions. The investigator performing the evaluation was unaware of the type of splint being worn by the subject. The test period extended for eight weeks and subjects were evaluated during week 1, during week 4, and at the end of week 8.
Statistical methods Mean strength calculations from Cybex mea surements for treatment and placebo groups were made for both light and heavy bites; t-tests were used to compare the means with P-values which at less than or equal to .05 were considered significant. Strength tests for subjects who were selected by chiropractic-applied kinesiologic criteria were analyzed by a two-by-two contingency
test for significance (Fisher’s exact test). The treatment splint group was compared with the placebo splint group as to whether strength was improved from control sessions to exper imental sessions. A confidence level of .05 was used to determine significance.
Results Nineteen of the 20 subjects selected completed the study; one subject withdrew from inter collegiate athletics three weeks into the study and was not included in this study. Ten sub jects received treatment splints and nine re ceived placebo splints. A detailed dental and TM area history and examination of each sub ject showed few abnormal findings (Table 1,2). Forty-two percent of the subjects had clicking in the TMJ, but none of the subjects had palpa tion tenderness of the muscles of mastication or the TMJ. The chiropractic-applied kine siologic examination showed that nine sub jects would benefit from wearing a MORA. Five of these subjects received treatment splints and four wore placebo splints. A series of two-tailed t-tests were conducted to test the difference between the treatment and placebo groups (Table 3-6). Of the 16 tests for upper and lower body strength, while using a “light” occlusion, only two P-values were in the .08 to .09 range, and 14 of 16 P-values were strongly nonsignificant (P > .25). The two lowest P-values are associated with negative test statistics that imply that in these two in stances a greater gain in strength was realized by the placebo group when compared with the treatment group. Similarly, tests for strength when teeth were closed firmly on the splint produced no significant changes (P > .111). In no instance was there any statistically significant effect of splint use on either upper or lower body strength. Upper and lower ex tremity muscle strength was not improved whether the subject closed lightly or heavily on the MORA.
Schubert-Others : EFFECT OF MANDIBULAR APPLIANCES ON BODY STRENGTH ■ 335
A R T IC L E S
Table 3
Table 4
■ S tr e n g th te s tin g w ith “ l i g h t ” b ite .
■ S tre n g th te s tin g w ith “ l ig h t ” b ite .
Pooled variance estimate: Exercise
Variable
Shoulder abduction Right 10 rpm T reatm ent
Mean
1.8000
Standard deviation T-value
2-tail probability
7.534 .69
Placebo 30 rpm Treatm ent
-.0 9 2 6 -.4 1 6 7
2.750
Placebo
-.0 1 8 5
4.147
Variable
Mean
-.5 8 3 3
6.622
-2.4444
8.378
3.4500
13.356
.7037
6.424
-4.3667
8.266
Placebo 40 rpm Treatm ent
2.0926
6.708
.2167
4.347
Placebo Knee extension Right 10 rpm T reatm ent
3.2593
7.678
-1.9000
9.243
Placebo 40 rpm Treatm ent
-2.2037
10.823
.9167
5.095
Placebo
2.6111
5.570
10 rpm T reatm ent
-7.0000
13.481
.500
3.451
Placebo 40 rpm Treatm ent -.2 5
.806 Placebo
Left .0833
10 rpm T reatm ent
3.437 .38
Placebo 30 rpm T reatm ent
-.3 7 0 4
1.086
1.2000
4.105
Placebo Shoulder adduction Right 10 rpm Treatm ent
-.3 8 8 9
3.373
.4500
5.229
Placebo 30 rpm T reatm ent
1.2222
9.794
-.2 1 6 7
6.287
.92
-.2 2
-.3 0 Placebo
.6481
.710
.373
.830
.768
6.291
Left
.596
.56
.583
- 1 .8 6
.081
-1 .0 8
.296
.07
.948
- .6 9
.498
-1 .8 0
.089
-1 .0 1
.329
Left 10 rpm T reatm ent
-1 .1 5 0
7.964 .24
Placebo 30 rpm Treatm ent
-1 .8 7 0 4
4.596
2.9167
6.281 .17
Placebo
2.4815
.815 Placebo 40 rpm Treatm ent
2.7407
9.460
-.5833
4.205
Placebo
1.8148
6.113
.870
4.925
Table 6
■ S tr e n g th te s tin g w ith “ h e a v y ” b ite.
■ Strength testing w ith “heavy” bite.
Pooled variance estim ate Exercise
.54
Left 10 rpm Treatm ent
Table 5
Exercise
Knee flexion Right 10 rpm Treatm ent
Pooled variance estim ate Standard deviation T-value 2-tail probability
Variable
Shoulder abduction Right 10 rpm Treatm ent
Mean
.8000
Standard deviation T-value
2-tail probability
5.453 .71
Placebo 30 rpm T reatm ent
-.6 4 8 1 -.7 8 3 3
2.409
Placebo
-1.0185
2.577
Exercise
Variable
Knee flexion Right 10 rpm Treatm ent
-.2 0 0 0
8.135
-2.2037
8.000
.489
2.959
Placebo 40 rpm Treatm ent .21
Mean
Pooled variance estimate Standard deviation T-value 2-tail probability
1.3000
12.403
Placebo
-.9 2 5 9
5.559
10 rpm T reatm ent
-1.6000
9.534
-.0741
6.202
-1.3667
6.058
.4444
3.505
-.6333
11.893
-4.7037
10.043
-1.8167
4.321
.4259
4.222
.840
Left
.54
.596
.49
.627
-.4 1
.688
- .7 9
.443
.80
.434
Left 10 rpm T reatm ent
1.3667
3.476 1.68
Placebo 30 rpm Treatm ent
-.9 4 4 4
2.327
.6167
2.760
Placebo Shoulder adduction Right 10 rpm Treatm ent
-.1 2 9 6
3.037
-1 .0167
12.051
-1.6111
4.770
-1.0833
4.303
Placebo 40 rpm Treatm ent .56
-.4 2 5 9
.892 Placebo 40 rpm Treatm ent
- .2 9 Placebo
.582 Placebo Knee extension Right 10 rpm Treatm ent
-.1 4 Placebo 30 rpm Treatm ent
.111
.779
-1 .1 4
5.720
Placebo
Left
.269
Left 10 rpm Treatm ent
-.7 3 3 3
10 rpm Treatm ent
10.586 .68
Placebo 30 rpm Treatm ent
-3 .5185
6.702
1.4333
4.149
Placebo 40 rpm Treatm ent .00
Placebo
1.4444
336 ■ JADA, Vol. 108, M arch 1984
6.394
-.0 5
14.606
-1.0741
10.727
-2.3 0 0
5.896
.508
.996 Placebo
-.7593
5.860
.17
.865
- .5 7
.576
A R T IC L E S
The reports by other authors of positive responses to the MORA may be the result of a placebo effect or faulty research design rather than from any direct benefit of wearing the splint.
‘
Table 7 show s the dental and TM history and exam ination findings for the nine subjects w ho had a positive chiropractic-applied kinesiological exam ination. These nine subjects experi‘ enced a general decrease in isometric m uscle strength during forced occlusion. An exam ina tion of the dental and TMJ findings in this group failed to show specific factors that m ight * ac c o u n t for th e c h iro p ra c tic fin d in g . An analysis of the strength testing data for this group is presented in Table 8. Five subjects had treatm ent splints and four had placebo splints. * No P-value approached significance in this separate analysis of a group of subjects iden tified by ch iro practic-applied kinesiologic testing as likely to benefit from a MORA.
Discussion
None of the 19 subjects who participated in this study had any historical or exami nation findings that would suggest m an d ib u la r p a in d y sfu n c tio n sy n d ro m e. However, nine of our subjects were found to have a generalized loss of m uscle strength w hen they closed th eir teeth firmly during applied kinesiologic evalu ation. This finding has been suggested to be diagnostic for TMJ dysfunction by some auth o rs ,5'8 but does not correlate w ith any obvious finding of the TMJ e v a lu a tio n . T he ex p la n a tio n for th is * applied-kinesiologic exam ination fin d ing is unclear at this time. This study failed to find a statistically T ab le 7 ■ Dental exam ination findings for subjects w ith positive chiropractic exam ina significant difference between the treat m ent group and the placebo group in tion (n = 9). spite of repeated evaluations during an Num ber of subjects eight-w eek period. In stantaneous im w ith finding Findings provem ent was not observed, nor was History there any im provem ent over time. The 4 Clench or grind teeth 0 Headaches reports by other authors of positive re 0 O rthodontic treatm ent sponses to the MORA may be the result of 0 TMJ noise a placebo effect or faulty research design 0 Jaw dysfunction Clinical exam ination rath er than from any direct benefit of TMJ noise w earing the splint. reciprocal click 1 The group of subjects designated by Occlusion class (angle) 7 Class I chiropractic-applied kinesiologic evalua 1 Class II tion to be likely to respond to the MORA 1 Class III failed to show a statistically significant 0 TMJ pain to palpation 0 M uscle tenderness difference betw een the treatm ent splint 55 mm Incisal opening (mean) and the placebo splint. This finding dis putes the claim that chiropractic-applied k in e s io lo g ic e v a lu a tio n can p re d ic t Table 8 ■ S t r e n g t h i m p r o v e m e n t i n c h i- w h ic h a th le te s sh o u ld re sp o n d to a * r o p ra c tic T M J d y s f u n c tio n g ro u p p la c e b o v s MORA. tre a tm e n t. Exercise S houlder abduction Right Left '
Shoulder adduction Right Left Knee flexion Right Left Knee extension Right Left *Fisher’s Exact Test.
Variable
P-value*
10 30 10 30
rpm rpm rpm rpm
.476 .317 .476 .317
10 30 10 30
rpm rpm rpm rpm
.317 .476 .317 .317
10 40 10 40
rpm rpm rpm rpm
.317 .357 .317 .119
10 rpm 40 rpm 10 rpm 40 rpm
.317 .556 .317 .357
Conclusion A controlled double-blind study of the ef fects of the MORA on college athletes failed to show a statistically significant difference betw een a treatm ent splint and a placebo splint. N either upper nor lower body strength was improved, nor did the am ount of biting force significantly alter the results. The group of subjects desig n a te d by c h iro p ra c tic -a p p lie d k in e siologic evaluation to be likely to respond to MORA splints, failed to show statisti cally significant differences in strength w hen treatm ent splints were com pared w ith placebo splints. There was also no o b v io u s c o r r e l a t i o n b e tw e e n a ch iro p ractic-d efin ed TMJ dysfunction
group and the findings of a dental TMJ evaluation. These findings contradict re ports advocating the use of MORA splints in athletes and are consistent w ith more re c e n t carefu lly co n tro lled scie n tific
The inform ed consent of all hum an subjects w ho participated in the experim ental investigation re ported or described in this m anuscript was obtained after the nature of the procedure and possible discom forts and risks had been fully explained. Drs. Schubert and Guttu are faculty m em bers, de partm ent of oral medicine, School of Dentistry; Dr. H unter is assistant professor, and Mr. Hall is a physi cal therapist, departm ent of orthopedics and sports m edicine, School of M edicine; and Mr. Thomas is a statistician, departm ent of biostatistics, University of W ashington. A ddress requests for reprints to Dr. Schubert, departm ent of oral m edicine, SC-63, U ni versity of W ashington, Seattle, 98195. 1. Greene, C.S., and Laskin, D.M. S plint therapy for m yofascial pain-dysfunction (MPD) syndrom e: a com parative study. JADA 84(3):624-628, 1972. 2. Clark, G.T., an d others. N octurnal electro m yographic evaluation of myofascial pain dysfunc tion in patients undergoing occlusal splint therapy. JADA 99(4):607-611, 1979. 3. Smith, S.D. Sports dentistry: protection and per form ance from m outhguards and bite splints. A th letic Training 16(2):100-106, 1981. 4. Kaufman, R.S. Case reports of TMJ repositioning in scoliosis and the perform ance by athletes. NY State Dent J 46(4):206-209, 1980. 5. Verschoth, A. W eak? Sink your teeth into this. Sports Illustrated 52:37-42, June 2, 1980. 6. Burfoot, A. A m iracle device that can im prove your running. R unner’s W orld 16(9):50-54, 1981. 7. Carlton, D. T here’s hope for hunting athletes. Seattle Post-Intelligencer, Jan 17, 1982. 8. Smith, S.D. M uscular strength correlated to jaw posture and the tem porom andibular joint. NY State Dent J 44(7):278-285, 1978. 9. Garabee, W.F. C raniom andibular orthopedics and athletic perform ance in the long distance runner: a three year study. Basal Facts 4(3):77-81,1982. 10. W illiam s, M.O.; Chaconas, S.J.; and Bader, P. The effect of m andibular position on appendage m u s cle strength. J Prosthet Dent 49(4):560-567,1983. 11. Moore, M. Corrective m outh guards: perfor m ance aids or expensive placebos? Physician Sports M edicine 9(3):127-132,1981. 12. Jakush, J. Can dental therapy enhance athletic perform ance? JADA 104(3):292-298, 1982. 13. Greenburg, M.S., and others. M andibular po si tion and upper body strength: a controlled clinical trial. JADA 103(4):576-579, 1981. 14. Burkett, L.N., and Bernstein, A.K. S trength testing after jaw repositioning w ith a m andibular or th o p e d ic ap p lian ce. P h y sician S ports M ed icin e 10(2):101-107, 1982. 15. Gelb, H. Effective m anagem ent and treatm ent of the craniom andibular syndrom e. In Gelb, H., ed. Clinical m anagem ent of head, neck, and TMJ pain and dysfunction. P hiladelphia, W. B. Saunders Co, 1977, p 288.
S chubert-O thers : EFFECT OF MANDIBULAR APPLIANCES ON BODY STRENGTH ■ 337