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Michigan Splint

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    5. Toller PA. Opaque arthrograph of the temporomandibular joint. Int JOral Surg 1974;3:17-28.

    6. Farrar WB. Characteristics of the. condylar path in internal derange-ment of the TMJ. J PROSTHET DENT 1978;39:319-23.

    7. Isberg-Helm AM, Westess on PL. Movement of disc and condyle intemporomandibular joints with and without c licking. Acta Odontol&and 1982;40:165-77.

    8. Barghi N, Aguilar CD, Martinez C, Wooda ll WS, Maaskent BA. Prev-alence of types of temporomandibular joint clickings in subjec ts withmissing posterior teeth. J PROSTHE-T DENT 1987;57:617-20.

    9. Green C, Turner C, Laskin DM. Long-term outcome of TMJ clicking in100 MPD patients [Abstract]. J Dent Res 1982;61:218.

    10. Roth RH. Temporomandibular pain-dysfunction syndrome and oc-clusa l 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 bi-

    laminar zone in internal derangement of the temporomandibular joint.Oral Surg 1984;58:375-81.

    14. Johnstone DR, Templeton M. The feasibility of palpating the lateralpterygoid muscle. J PROSTHFT DENT 1980;40:318-23.

    15. Okeson JA. Fundamentals of occlus ion and temporomandibular disor-ders. St Louis: CV Mosby Co, 1985.

    16. Shumaker PE. The prevalence of TMJ dysfunction (PRI) in restoredpatients [Thes is]. Ann Arbor, Mich: University of Michigan Schoo l ofDentistry, 1986.

    17. Lederman KH, Clayton JA. Patients with restored o cclusio ns. 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 jointexamination data in an initial survey population. J PROTHET DENT1976;35:299-306.

    19. Shields JM, Clayton JA, Sindledecker LD. Using pantographic tracingsto detect T MJ and muscle dysfunction. J PROSTHE T DENT 1978;39:80-7.20. Perez-Mantes N. TMJ dysfunction, a pantographic evaluation inpatients wa iting for fixed restorations [Thes is]. Ann Arbor, Mich:Uni-versity of Michigan, Schoo l of Dentistry, 1981.

    21. Beard CC, Clayton JA. Effects of occlu sal splin t therapy on TMJ dys-function. J PROSTHET DENT 1980,44:324-35.

    22. Eriksson L, Westesaon PL, Sjoberg H. Observer performance indescribing temporomandibular joint sounds. J Craniomand Pratt 1987;5~32-5.

    23. Roberta CA, Tallenta RH, Katxberg RW, et el. Clinical and arthro-graphic evaluation of temporomandibular joint sounds. Oral Surg1986;62:373-6.

    24. Ramjford S. Discus sion from Solberg W, Clark W. Abnormal jaw me-chanic s: diagnosis and treatment. Proceedings of the Second Interna-tional Symposium. Chicago: Quintessence International, 1984;89.

    25. Farrar WB , McCarty WL Jr. Inferior join t spa ce arthrography andcharacteristics of condylar paths in internal derangements of the TMJ.J PRoST HET DENT 1979;41:548-55.

    26. Van der Weele LT, Dibbeta JM. Helkimos index: a scale or just a set ofsymptoms? Chicago: Quintessence International 1984;89.

    27. Greene CS, Marbach JJ. Epidem iologic studies of mandibular dysfunc-tion: a critical review. J PROSTHET DENT 1982;48:184-90.

    Reprint requests to:DR. J. A. CLAYTQNSCHOOL OF DENTIST RYUNWEWJTY OF MICHIGANANN ARBOR, MI 48109-1078

    A graphic evaluation of the intermaxillary relationshipbefore and after therapy with the Michigan splint

    S. Carossa, M.D., D.D.S.,* E. Di Bari, M.D.,** M. Lombardi, M.D.,** andG. Preti, M.D., D.D.S. ***Universityof Turin, School f Dentistry, Turin, ItalyThe eff ect of the Michigan split was evaluated graphically in a group of 19patients. Gothic arch tracings were registered before and after a period of therapyof 4 months, and the two tracings were compared photographically. The position ofthe apex of the Gothic arch was displaced in most patients, while the shape of thearch was more regular in almost all patients. The validity of the use of theMichigan splint was conf irmed. (J PROSTHET DENT 1990;63:586-92.)

    M ost patients with disorders of the stomatog-nathic system suffer from hypertonic masticatory muscu-lature. This problem can lead to (1) overloading of the ar-titular structures,l (2) a painful symptomatology eitherspontaneousor consequent on mandibular movements,and (3) an alteration of the amplitude and regularity offunctional movementsof the jaw that makes t difficult or*Lecturer,Department f Prosthodontics.**Postgraduatetudentof prosthodontics.***Professor and Chairman, Department of Prosthodontics.10/1/19214

    impossible o carry out a correct occlusalanalysis.4* Thefirst objective in treating these patients must therefore beto relax the musculature.6Many therapeutic approacheshave been proposed forrelaxing the muscles including pharmacologic inter-ventions, Psychologic techniques,8physiotherapy,g elec-tromyography biofeedback techniques,lOand the use of asplint.l* l2 At the Department of Prosthodontics, TurinUniversity, the occlusalsplint developed at Ann Arbor byRamfjord and Ash,13-15 known as the Michigan splint, isusually used.16Many author& 12* 7-20 ave studied the therapeutic

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    INTERMAXILLARY RELATIONSHIP WITH MICHIGAN SPLINT

    Fig. 1. Comparison grid with round hole in center.

    function of this splint on the basis of clinica l evaluation ofthe symptoms before and after splint therapy. Less atten-tion has been paid to the effects of therapy with an occlusalsplint on the mobility and position of the mandible.jv 21* 2Kowaleski and De Boever21 measured mandibular dis-placement in 11 patients with dysfunction after 1 month oftherapy with the splint through reference points markeddirectly on the splint itself. Roura and Clayton6 usedpan-tographic recordsbefore and after therapy with an occlusalsplint.This study verified the action of the Michigan splint af-ter a certain interval of time on the position and mobilityof the mandible in a group of patients with craniomandib-ular disorders,with prevalent muscular tension. The eval-uation was carried out graphically.MATERIAL AND METHODS

    A group of patients suffering from craniomandibulardisorders were chosen from among those attending theprosthodontics Department, Turin University. The pa-tients examined were 19 white Caucasians, 5 men and 14women, anging n age rom 17 o 37 years, and with symp-tomatology primarily of the muscular type. The patientswere treated using the Michigan splint16 or a period of 4months. The splint was worn during the night and for asmuch of the day as was compatible with the patients oc-cupation. The patient wasexamined weekly and the splintwas adjusted to provide optimal tooth contact.The effect of the splint was evaluated before and aftertherapy on the basisof mandibular mobility in the hori-zontal plane, using the intraoral registration of the Gothicarch with a central bearing point technique.s31s4he trac-TEE JOURNAL OF PROSTHET IC DENTIS TRY

    Fig. 2. Construction of plaster base or lower registrationplate.ings of the Gothic arch were analyzed by photographiccomparison.A specialplaster basewasconstructed for each egistra-tion plate using the following equipment: (1) a parallelom-

    587

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    CAROSSA ET AL

    Fig. 3. Tracing of Gothic arch.eter, and a metal pin that could be connected to the par-allelometer by means of a horizontal plaque; (2) a trans-parent comparison grid with sides of 1 cm, with a roundhole 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 sizeof the plaster base to the parallelometer.

    The lower registration plate was placed on liquid plasterin the mold, and the horizontal metal p laque connected tothe paral lelometer was lowered to a predetermined heightand was attached to the registration plate (Fig. 2). After theplaster had hardened, the plaster base was removed andwas trimmed square. Thus a series of plaster bases withparalle l registration plates all at the same height was con-structed.

    The patient was asked to make jaw movements to locatethe area of the registration plate that would be used by theGothic arch. The grid was then positioned on the registra-tion plate so that the tracing of the Gothic arch fell withinthe hole in the grid. Then the grid was glued to the regis-tration plate with a cyanoacrylic adhesive. The registrationplate had to be perfectly flat and smooth for this operationto succeed.

    The registration plate was smeared with a white felt penin the circle not covered by the comparison grid, and thetracing of the Gothic arch was made (Fig. 3). The registra-tion plate was then placed on the plaster base and wasphotographed using a Hasselblad 500 CM (Victor Hassel-blad, Goleborg, Sweden) camera and a Zeiss Planar 2.8/80(Carl Zeiss, Frankfurt, West Germany) lens (Fig. 4). Aftertherapy, a second registration was made on the same reg-istration plate, without removing the grid, and the platewas photographed as before. All photographs were madewith the aid of a high precision stand to keep the photo-graphic conditions constant. Slides, 6 X 6 cm with a 1:l re-production of the subject, were obta ined, Slides of the same

    Fig. 4. Photographic apparatus used in investigation.

    patient were of the same enlargement. In order to comparethe Gothic arches before and after treatment, pairs of slideswere examined with a diaphanoscope and a Peak (Jokay,Tokyo, Japan) grid lens with a 7X enlargement power. Thetwo slides were superimposed and the apices were made tocoincide, keeping the grids parallel. The displacement be-tween the two grids was measured (Fig. 5). Changes in po-sition of the Gothic arch were evaluated, together with theshape and size of the mandibu lar movements. The systemafforded a resolution of 0.1 mm.RESULTS AND DISCUSSIONDisplacement of the Gothic arch

    In 14 of 19 patients, a mean posterior displacement of themandible of 0.3 mm was found after therapy. Displacementranged from 0.1 to 0.5 mm (Fig. 6). As proposed by Helkimoand Ingervall,22 this displacement can be explained by ahyperactivity of the lateral pterygoid muscles. This activ-ity would cause a protective protrusion of the articularstructures, displacing the condyle away from the inflamed

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    1NTERMAXlLLARY RELATION SHIP WITH MICHIGAN SPLINT

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

    ~~-~ t&t&l mm]

    Fig. 6. Bar histogram of anteroposterior displacements after therapy with Michigansplint. Negative numbers indicate posterior displacement of mandible ; positioe numbersindicate anterior displacement.

    region in patients with pathologic dysfunction, above all inthe acute phase. Shafagh et af.25 proposed an explanationin terms of variations in the consistency and quantity of thefluids in the joint.

    In three patients an anterior displacement of the man-dib le was recorded. The mean value was 0.4 mm, varyingbetween 0.2 and 0.6 mm. Kowaleski and De Boever21explained this behavior as being due to a pain-relieving

    hyperactivity of the posterior part of the temporal musclethat is resolved by muscle relaxing therapy. In two patients,no anteroposterior displacement was found.

    A lateral displacement of the apex of the Gothic arch oc-curred in al l patients. In Xl patients, this displacement wastoward the left, with a mean value of 0.3 mm and a rangebetween 0.1 and 0.8 mm. In eight patients, the displace-ment was toward the right, with a mean value of 0.4 mm,

    THE JOURNAL OF PROSTHE TIC DENTIS TRY 589

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    CAROSSA ET AL

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

    4

    3

    2

    1

    0

    -1

    -2

    Fig. 8. Graph of variat ion in laterolateral symmetry of Gothic arch after therapy withMichigan splint. Initial difference in laterolateral movements (asymmetry) is comparedwith that after therapy (reduction of difference). As can be seen, the greater the initialasymmetry between two lateral displacements, the more this was reduced by therapy.ranging from 0.2 to 0.6 mm (Fig. 7). One explanation could the increase in symmetry of the left and right lateralbe that an asymmetrical spasm of the masticatory muscu- movements-i.e., the capacity to make laterotrusive move-lature, or iginating in relief of pain and parafunctional in ments of the same extension. This increase in symmetrynature, is resolved. The same explanation could apply to came about in 13 patients in whom the difference between

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    INTERMAXILLARY RELATIONSHIP WITH MZCHIGAN SPLINT

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

    Fig. 10. Clinical patient. Gothic arch before (left) and after (right) therapy with Mich-igan splint.the two la~rotrusions had an absolute value of 2.7 mm atthe first registration, and 1.3 mm at the second registration.Two patients already had lateral asymmetry that remainedunaltered, whereas in three patients slight worsening of lessthan 1 mm was found (Fig. 8).Amplitude of the Gothic arch

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

    a range between 0.3 and 1.8 mm. In five patients, there wasno variat ion. In six patients, there was a reduction of theamplitude of this movement, with a mean value of 1.85 mmand a range from 0.5 to 2 mm.The amplitude of the laterotrusive movements wasincreased in 14 patients, with a mean of 2.18 mm and arange of 0.3 to 8 mm. There was no variat ion in five patients(Fig. 9).

    There was a tendency toward regularity in the shape ofTHE JOURNAL OF PROSTHETIC DENTIS TRY 591

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    the tracings in the second registration in al l patients (Fig.10). This f inding can be correlated with the increased har-mony in mandibular dynamics due to the induced muscu-lar relaxation.6CONCLUSIONSFrom the analysis of the results obtained, the Mich igansplint was confirmed to be a valid treatment procedure inmuscular relaxation therapy. Therefore the Michigan splintcan be recommended both for use in symptomatologictreatment of muscular hypekonicity and before carryingout def initive occlusal analysis or therapy in these patients.Both the anteroposterior and the laterolateral cranioman-dibular relationships are effectively modified in mostpatients.REFERENCES

    1. Zarb GA, Thompso n GW. Asses sment of clinic al treatment of patientswith temporomandibular joint dysfunction. J PFUXTHE T DENT1970;24:552-4.

    2. Franks AS. Masticatory muscle hyperactivity and temporomandibularjoint dysfunction. J PROSTHE T DENT 1965;15:1122-31.

    3. McNeil1 C, Danzig WM, Farrar WB. Craniom andibu lar (TMJ) diso r-ders-the state of the art. 3 PROSTHFZ DE NT 1980;44:434-7.

    4. Perry HT Jr. Muscular changes asso ciated with temporomandibularjoint dysfunction. J Am Dent Asso c 1957;54:644-53.

    5. Perry HT Jr. The symptomology of temporomandibular joint distur-bance. J PROWHET DENT 1968;19:288-98.6. Roura N, Clayton J A. Pantographic records on TMJ dy sfunction sub-jects treated with oc cluaal splinta: a progress report. J PROSTRE T DENT197833442-53.

    7. Greene CS, Laskin DM. Meprobamate therapy for the myofa cial paindysfunction (MPD) syndrome: a double blind evaluation. J Am DentAssoc 1971;82:587-90.

    8. Mikami DB. A review of psychogenic aspects and treatments of brux-ism. 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 diagno sis for treatmentplanning. J Craniomand Pratt 1987;5:130-8.

    10. Bydyzenski T, Stayva J. An electromyographic feedback technique forteaching of voluntary relaxation of the masseter muscle. J Dent F&s197x52:116-9.

    11. Okeson JP, Kemper JT, Moody PM. A study of the use of occlus ionsplints in the treatment of acute and chronic patients with cranioman-dibular disorders. J PROSTHET DENT 1982;48:708-12.

    12. Okeson JP , Moody PM, Kemper JT, Haley JV . Evaluation of occlu salsplint therapy and relaxation procedures in patients with temporoman-dibular disorders. J Am Dent Ass oc 1983;107:420-4.

    13. Ramfjord SP, Ash MM. Occlusion. 1st ed. Padova, Italy: Picc in Editor,1969:226-30.

    14. Ramfjord SP, Ash MM. Occlusion. 3rd ed. Philadelphia : WB SaundersCo, 1983365-75.

    15. Ramfjord SP, Ash MM. Biteplanes in the treatment of TMJ dysfunc-tion. G Stomatologia Ortognat 19&l;(suppl 111):65-77.

    16. Geering AH, Lang NP. Die Michigan-Schiene, ein diagnos tisches undtherapeutisches Hilfsmittel bei Funktionsstorungen im Kausystem. I.Herstellung im Artikulator and Eigliederung am Patienten. Schwe isMschr Zahnheilk 1978;88:32-8.

    17. Carraro JJ, CaResse RG. Effects of occlu sal splints on the TMJ symp-tomology. J PROSTHET DENT 1978;40:563-6.

    18. Goharian RK, Neff PA. Effects of occlu sal retainers on TMJ and facialpain. J PROSTHET DENT 1980;44:206-8.

    19. Beard CC, Clayton JA. Effects of occlus al therapy on TMJ dysfunction.J PROSTHEX DEN T 1980;44:324-35.

    20. Okeson JP, Hayes DK. Long-term results of treatment for temporo-mandibular joint disorders: an evaluation by patients. J Am DentAssoc 1986;112:473-8.

    21. Kowaleski WC, De Boever J. Influence of occlu sal s plints on jaw posi-tion and musculature in patients with TMJ dysfunction. J PROSTHETDENT 1975;33:321-7.

    22. Helkimo M, Ingervall B. Recording of the retruded position of themandible in patients with mandibular dysfunction. A&a Odontol Stand1978;36:167-74.

    23. Gerber A. Ftegistrirte chnik fur prothetik okklus iondiag nostik, okklu-sionterapie. Z urich, Switzerland: Condylator service manual. 1974.

    24. Rat&&no G. Indagine sulla variabilita delle registrasioni intraorali diarchi gotici: nuova metodica d i confronti (Thesis). Dental S chool, Uni-versity of Turin, 1987.

    25. Shafagh I, Yoder JL, Thayer KE. Diurnal variance of centric relationposition. J PROSTHET DENT 1975;34:574-82.

    Reprint requests o:PROF. G. PRETISCHOOL OF DEN~~TRYUNIVERSITY OF TURINCORSO POLONIA 1410126 TORINOITALY

    Bound volumes available to subscribersBound volumes of the JOURNAL OF PROSTHETIC DENTISTR Y are available to subscribers(only) for the 1989 issues from the publisher at a cost of $44.00 ($56.00 internat ional) forVol. 61 (January-June) and Vol. 62 (July-December). Shipping charges are included. Eachbound volume contains a subject and author index, and all advertising is removed. Copiesare shipped within 30 days after publication of the last issue in the volume. The bind ingis durable buckram with the journal name, volume number, and year stamped in gold onthe spine. Volumes 59 and 60 are also avai lable. Payment must accompany al l orders.Contact The C. V. Mosby Co., Circulation Department, 11830 Westline Industrial Drive,St, Louis, MO 63146-3318, USA, phone (800) 325-4177, ext. 7351.Subscriptions must be in force to qualify. Bound volumes are not availablein place of a regular JOURNAL subscription.

    592 MAY 1090 VOLUME 63 NUMBER 5