Michigan Splint

5. Toller PA. Opaque arthrograph Oral

Surg

of the temporomandibular

joint. Int J

19. Shields JM, Clayton JA, Sindledecker LD. Using pantographic tracings to detect TMJ and muscle dysfunction. J PROSTHET DENT 1978;39: 80-7. 20. Perez-Mantes N. TMJ dysfunction, a pantographic evaluation in patients waiting for fixed restorations [Thesis]. Ann Arbor, Mich:University of Michigan, School of Dentistry, 1981. 21. Beard CC, Clayton JA. Effects of occlusal splint therapy on TMJ dysfunction. J PROSTHET DENT 1980,44:324-35. 22. Eriksson L, Westesaon PL, Sjoberg H. Observer performance in describing temporomandibular joint sounds. J Craniomand Pratt 1987; 5~32-5. 23. Roberta CA, Tallenta RH, Katxberg RW, et el. Clinical and arthrographic evaluation of temporomandibular joint sounds. Oral Surg 1986;62:373-6. 24. Ramjford S. Discussion from Solberg W, Clark W. Abnormal jaw mechanics: diagnosis and treatment. Proceedings of the Second International Symposium. Chicago: Quintessence International, 1984;89. 25. Farrar WB, McCarty WL Jr. Inferior joint space arthrography and characteristics of condylar paths in internal derangements of the TMJ. J PRoSTHET DENT 1979;41:548-55. 26. Van der Weele LT, Dibbeta JM. Helkimos index: a scale or just a set of symptoms? Chicago: Quintessence International 1984;89. 27. Greene CS, Marbach JJ. Epidemiologic studies of mandibular dysfunction: a critical review. J PROSTHET DENT 1982;48:184-90.

1974;3:17-28.

6. Farrar WB. Characteristics of the. condylar path in internal derangement of the TMJ. J PROSTHET DENT 1978;39:319-23. 7. Isberg-Helm AM, Westesson PL. Movement of disc and condyle in temporomandibular joints with and without clicking. Acta Odontol &and 1982;40:165-77. 8. Barghi N, Aguilar CD, Martinez C, Woodall WS, Maaskent BA. Prevalence of types of temporomandibular joint clickings in subjects with missing posterior teeth. J PROSTHE-T DENT 1987;57:617-20. 9. Green C, Turner C, Laskin DM. Long-term outcome of TMJ clicking in 100 MPD patients [Abstract]. J Dent Res 1982;61:218. 10. Roth RH. Temporomandibular pain-dysfunction syndrome and occlusal relationships. Angle Orthod 1973;43:136-53. 11. PBllmann L. Sounds produced by the mandibular joint in young men. A mass examination. J Maxillofac Surg 1980;8:155-7. 12. Watt DM. Temporomandibular joint sounds. J Dent 1980;8:119-27. 13. Hall MB, Brown RW, Baughman RA. Histologic appearance of the bilaminar zone in internal derangement of the temporomandibular joint. Oral Surg 1984;58:375-81. 14. Johnstone DR, Templeton M. The feasibility of palpating the lateral pterygoid muscle. J PROSTHFT DENT 1980;40:318-23. 15. Okeson JA. Fundamentals of occlusion and temporomandibular disorders. St Louis: CV Mosby Co, 1985. 16. Shumaker PE. The prevalence of TMJ dysfunction (PRI) in restored patients [Thesis]. Ann Arbor, Mich: University of Michigan School of Dentistry, 1986. 17. Lederman KH, Clayton JA. Patients with restored occlusions. Part I: TMJ dysfunction determined by a pantographic reproducibility index. J PROSTHET DENT 1982;47:198-205. 18. Rieder CE. The interrelationships of various temporomandibular joint examination data in an initial survey population. J PROTHET DENT

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DR. J. A. CLAYTQN SCHOOL OF DENTISTRY UNWEWJTY OF MICHIGAN ANN ARBOR, MI 48109-1078

1976;35:299-306.

A graphic evaluation of the intermaxillary relationship before and after therapy with the Michigan splint S. Carossa, M.D., D.D.S.,* G. Preti, M.D., D.D.S.***

E. Di Bari,

M.D.,**

M. Lombardi,

M.D.,**

and

Universityof Turin, Schoolof Dentistry, Turin, Italy The effect of the Michigan split was evaluated graphically in a group of 19 patients. Gothic arch tracings were registered before and after a period of therapy of 4 months, and the two tracings were compared photographically. The position of the apex of the Gothic arch was displaced in most patients, while the shape of the arch was more regular in almost all patients. The validity of the use of the Michigan splint was confirmed. (J PROSTHET DENT 1990;63:586-92.)

M

ost patients with disorders of the stomatognathic system suffer from hypertonic masticatory musculature. This problem can lead to (1) overloading of the artitular structures,l” (2) a painful symptomatology either spontaneousor consequent on mandibular movements, and (3) an alteration of the amplitude and regularity of functional movementsof the jaw that makesit difficult or *Lecturer,Departmentof Prosthodontics. **Postgraduate studentof prosthodontics. ***Professor

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and Chairman,

Department

of Prosthodontics.

impossibleto carry out a correct occlusalanalysis.4*5 The first objective in treating these patients must therefore be to relax the musculature.6 Many therapeutic approacheshave been proposed for relaxing the muscles including pharmacologic interventions, Psychologic techniques,8physiotherapy,g electromyography biofeedback techniques,lOand the use of a splint.l’* l2 At the Department of Prosthodontics, Turin University, the occlusalsplint developed at Ann Arbor by Ramfjord and Ash,13-15 known as the “Michigan splint,” is usually used.16 Many author& 12*17-20have studied the therapeutic

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Fig. 1. Comparison grid with round hole in center. function of this splint on the basis of clinical evaluation of the symptoms before and after splint therapy. Less attention has been paid to the effects of therapy with an occlusal splint on the mobility and position of the mandible.‘jv 21*22 Kowaleski and De Boever21 measured mandibular displacement in 11 patients with dysfunction after 1 month of therapy with the splint through reference points marked directly on the splint itself. Roura and Clayton6 usedpantographic recordsbefore and after therapy with an occlusal splint. This study verified the action of the Michigan splint after a certain interval of time on the position and mobility of the mandible in a group of patients with craniomandibular disorders,with prevalent muscular tension. The evaluation was carried out graphically.

MATERIAL

AND

METHODS

A group of patients suffering from craniomandibular disorders were chosen from among those attending the prosthodontics Department, Turin University. The patients examined were 19 white Caucasians,15 men and 14 women,ranging in agefrom 17to 37 years, and with symptomatology primarily of the muscular type. The patients were treated using the Michigan splint16for a period of 4 months. The splint was worn during the night and for as much of the day as was compatible with the patient’s occupation. The patient wasexamined weekly and the splint was adjusted to provide optimal tooth contact. The effect of the splint was evaluated before and after therapy on the basisof mandibular mobility in the horizontal plane, using the intraoral registration of the Gothic arch with a central bearing point technique.s31s4 The trac-

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Fig. 2. Construction of plaster basefor lower registration plate. ings of the Gothic arch were analyzed by photographic comparison. A specialplaster basewasconstructed for eachregistration plate using the following equipment: (1) a parallelom587

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ET AL

Fig. 3. Tracing of Gothic arch. eter, and a metal pin that could be connected to the parallelometer by means of a horizontal plaque; (2) a transparent comparison grid with sides of 1 cm, with a round hole cut in the center (Fig. 1); (3) a mold for preparing casts; and (4) a base to be placed under the mold to adapt the size of the plaster base to the parallelometer. The lower registration plate was placed on liquid plaster in the mold, and the horizontal metal plaque connected to the parallelometer was lowered to a predetermined height and was attached to the registration plate (Fig. 2). After the plaster had hardened, the plaster base was removed and was trimmed square. Thus a series of plaster bases with parallel registration plates all at the same height was constructed. The patient was asked to make jaw movements to locate the area of the registration plate that would be used by the Gothic arch. The grid was then positioned on the registration plate so that the tracing of the Gothic arch fell within the hole in the grid. Then the grid was glued to the registration plate with a cyanoacrylic adhesive. The registration plate had to be perfectly flat and smooth for this operation to succeed. The registration plate was smeared with a white felt pen in the circle not covered by the comparison grid, and the tracing of the Gothic arch was made (Fig. 3). The registration plate was then placed on the plaster base and was photographed using a Hasselblad 500 CM (Victor Hasselblad, Goleborg, Sweden) camera and a Zeiss Planar 2.8/80 (Carl Zeiss, Frankfurt, West Germany) lens (Fig. 4). After therapy, a second registration was made on the same registration plate, without removing the grid, and the plate was photographed as before. All photographs were made with the aid of a high precision stand to keep the photographic conditions constant. Slides, 6 X 6 cm with a 1:l reproduction of the subject, were obtained, Slides of the same

588

Fig. 4. Photographic apparatus used in investigation. patient were of the same enlargement. In order to compare the Gothic arches before and after treatment, pairs of slides were examined with a diaphanoscope and a Peak (Jokay, Tokyo, Japan) grid lens with a 7X enlargement power. The two slides were superimposed and the apices were made to coincide, keeping the grids parallel. The displacement between the two grids was measured (Fig. 5). Changes in position of the Gothic arch were evaluated, together with the shape and size of the mandibular movements. The system afforded a resolution of 0.1 mm.

RESULTS AND DISCUSSION Displacement of the Gothic

arch

In 14 of 19 patients, a mean posterior displacement of the mandible of 0.3 mm was found after therapy. Displacement ranged from 0.1 to 0.5 mm (Fig. 6). As proposed by Helkimo and Ingervall,22 this displacement can be explained by a hyperactivity of the lateral pterygoid muscles. This activity would cause a protective protrusion of the articular structures, displacing the condyle away from the inflamed

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Fig. 5. Slides of first and second tracing superimposed.

~~-~

t&t&l

mm]

Fig. 6. Bar histogram of anteroposterior displacements after therapy with Michigan splint. Negative numbers indicate posterior displacement of mandible; positioe numbers indicate anterior displacement. region in patients with pathologic dysfunction, above all in the acute phase. Shafagh et af.25 proposed an explanation in terms of variations in the consistency and quantity of the fluids in the joint. In three patients an anterior displacement of the mandible was recorded. The mean value was 0.4 mm, varying between 0.2 and 0.6 mm. Kowaleski and De Boever21 explained this behavior as being due to a pain-relieving

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hyperactivity of the posterior part of the temporal muscle that is resolved by muscle relaxing therapy. In two patients, no anteroposterior displacement was found. A lateral displacement of the apex of the Gothic arch occurred in all patients. In Xl patients, this displacement was toward the left, with a mean value of 0.3 mm and a range between 0.1 and 0.8 mm. In eight patients, the displacement was toward the right, with a mean value of 0.4 mm,

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Fig. 7. Bar histogram of laterolateral displacements after therapy with Michigan splint. Negative numbers indicate displacement to left; positive numbers indicate displacement to right. (“0” bar includes interval -1 - +l. In reality, three patients under “0” underwent a small displacement of 0.1 mm to left in each instance.) 5

4

3

2

1

0

-1

-2

Fig. 8. Graph of variation in laterolateral symmetry of Gothic arch after therapy with Michigan splint. Initial difference in laterolateral movements (asymmetry) is compared with that after therapy (reduction of difference). As can be seen, the greater the initial asymmetry between two lateral displacements, the more this was reduced by therapy. ranging be that lature, nature,

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from 0.2 to 0.6 mm (Fig. 7). One explanation could an asymmetrical spasm of the masticatory muscuoriginating in relief of pain and parafunctional in is resolved. The same explanation could apply to

the increase in symmetry of the left and right lateral movements-i.e., the capacity to make laterotrusive movements of the same extension. This increase in symmetry came about in 13 patients in whom the difference between

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Fig. 9. To evaluate increase in laterolateral mobility after therapy with Michigan splint, two lateral displacements, left and right, were summed before and after therapy. (Falsification can occur when patient fails to reproduce movement to limit.)

Fig. 10. Clinical patient. Gothic arch before (left) igan splint. the two la~rotrusions had an absolute value of 2.7 mm at the first registration, and 1.3 mm at the second registration. Two patients already had lateral asymmetry that remained unaltered, whereas in three patients slight worsening of less than 1 mm was found (Fig. 8).

Amplitude

of the Gothic arch

In 14 patients, the amplitude of protrusion and retrusion movements increased, with a mean increase of 0.85 mm and

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and after (right)

therapy with Mich-

a range between 0.3 and 1.8 mm. In five patients, there was no variation. In six patients, there was a reduction of the amplitude of this movement, with a mean value of 1.85 mm and a range from 0.5 to 2 mm. The amplitude of the laterotrusive movements was increased in 14 patients, with a mean of 2.18 mm and a range of 0.3 to 8 mm. There was no variation in five patients (Fig. 9). There was a tendency toward regularity in the shape of

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the tracings in the second registration in all patients (Fig. 10). This finding can be correlated with the increased harmony in mandibular dynamics due to the induced muscular relaxation.6

CONCLUSIONS From the analysis of the results obtained, the Michigan splint was confirmed to be a valid treatment procedure in muscular relaxation therapy. Therefore the Michigan splint can be recommended both for use in symptomatologic treatment of muscular hypekonicity and before carrying out definitive occlusal analysis or therapy in these patients. Both the anteroposterior and the laterolateral craniomandibular relationships are effectively modified in most patients. REFERENCES 1. Zarb GA, Thompson GW. Assessment of clinical treatment of patients with temporomandibular joint dysfunction. J PFUXTHET DENT 1970;24:552-4. 2. Franks AS. Masticatory muscle hyperactivity and temporomandibular joint dysfunction. J PROSTHET DENT 1965;15:1122-31. 3. McNeil1 C, Danzig WM, Farrar WB. Craniomandibular (TMJ) disorders-the state of the art. 3 PROSTHFZ DENT 1980;44:434-7. 4. Perry HT Jr. Muscular changes associated with temporomandibular joint dysfunction. J Am Dent Assoc 1957;54:644-53. 5. Perry HT Jr. The symptomology of temporomandibular joint disturbance. J PROWHET DENT 1968;19:288-98. 6. Roura N, Clayton JA. Pantographic records on TMJ dysfunction subjects treated with occluaal splinta: a progress report. J PROSTRET DENT 197833442-53. 7. Greene CS, Laskin DM. Meprobamate therapy for the myofacial pain dysfunction (MPD) syndrome: a double blind evaluation. J Am Dent Assoc 1971;82:587-90. 8. Mikami DB. A review of psychogenic aspects and treatments of bruxism. J PRO~THET DENT 1977;37:411-9. 9. Rocabado M. The importance of soft tissue mechanics in stability and instability of the cervical spine: a functional diagnosis for treatment planning. J Craniomand Pratt 1987;5:130-8. 10. Bydyzenski T, Stayva J. An electromyographic feedback technique for teaching of voluntary relaxation of the masseter muscle. J Dent F&s 197x52:116-9.

Bound volumes

available

ET AL

11. Okeson JP, Kemper JT, Moody PM. A study of the use of occlusion splints in the treatment of acute and chronic patients with craniomandibular disorders. J PROSTHET DENT 1982;48:708-12. 12. Okeson JP, Moody PM, Kemper JT, Haley JV. Evaluation of occlusal splint therapy and relaxation procedures in patients with temporomandibular disorders. J Am Dent Assoc 1983;107:420-4. 13. Ramfjord SP, Ash MM. Occlusion. 1st ed. Padova, Italy: Piccin Editor, 1969:226-30. 14. Ramfjord SP, Ash MM. Occlusion. 3rd ed. Philadelphia: WB Saunders Co, 1983365-75. 15. Ramfjord SP, Ash MM. Biteplanes in the treatment of TMJ dysfunction. G Stomatologia Ortognat 19&l;(suppl 111):65-77. 16. Geering AH, Lang NP. Die Michigan-Schiene, ein diagnostisches und therapeutisches Hilfsmittel bei Funktionsstorungen im Kausystem. I. Herstellung im Artikulator and Eigliederung am Patienten. Schweis Mschr Zahnheilk 1978;88:32-8. 17. Carraro JJ, CaResse RG. Effects of occlusal splints on the TMJ symptomology. J PROSTHET DENT 1978;40:563-6. 18. Goharian RK, Neff PA. Effects of occlusal retainers on TMJ and facial pain. J PROSTHET DENT 1980;44:206-8. 19. Beard CC, Clayton JA. Effects of occlusal therapy on TMJ dysfunction. J PROSTHEX DENT 1980;44:324-35. 20. Okeson JP, Hayes DK. Long-term results of treatment for temporomandibular joint disorders: an evaluation by patients. J Am Dent Assoc 1986;112:473-8. 21. Kowaleski WC, De Boever J. Influence of occlusal splints on jaw position and musculature in patients with TMJ dysfunction. J PROSTHET DENT 1975;33:321-7. 22. Helkimo M, Ingervall B. Recording of the retruded position of the mandible in patients with mandibular dysfunction. A&a Odontol Stand 1978;36:167-74. 23. Gerber A. Ftegistrirtechnik fur prothetik okklusiondiagnostik, okklusionterapie. Zurich, Switzerland: Condylator service manual. 1974. 24. Rat&&no G. Indagine sulla variabilita delle registrasioni intraorali di archi gotici: nuova metodica di confronti (Thesis). Dental School, University of Turin, 1987. 25. Shafagh I, Yoder JL, Thayer KE. Diurnal variance of centric relation position. J PROSTHET DENT 1975;34:574-82.

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