The effects on tooth position and maxillofacial vertical growth during treatment of scoliosis with the Milwaukee brace

American Journal of ORTHODONTICS Volume 52, Number 3, MAR C H, 1966

ORIGINAL ARTICLES

The effects on tooth position and maxillofacial vertical growth during treatment of scoliosis with the Milwaukee brace RICHARD G. ALEXANDER, B.A., D.D.S., M.S.D. Arlington, Texas

THIS study was initiated to determine the effects upon the dentition and surrounding maxillofacial complex during treatment of scoliosis with the Milwaukee brace. Scoliosis 1 is the term applied to lateral curvature of the spine. Although there are more than thirty etiologic factors for this disease, it is usually classified as idiopathic, paralytic (postpoliomyelitic), or congenital (anomalous). Scoliosis, a disease related to the upright position of man, is usually discovered in childhood and progresses during the period of growth. It is potentially a catastrophic disease because of the spatial abortion of cardiopulmonary function caused by extreme angulation of the spine. Digestive, respiratory, and cardiac function can be so impaired that life itself becomes impossible. The deformity in scoliosis tends to increase until the spine is mature. This maturity coincides with that of the maxillofacial complex. The orthopedist has been successful in treating scoliosis with the Milwaukee brace. 2 This brace (Fig. 1) which combines the most effective forces used in the correction of scoliosis, is constructed so that a pelvic girdle fits tightly around the waist and rides atop the iliac crests instead of pressing against the sides of the pelvis. Vertical bars are attached to the girdle-two posteriorly and one anThis paper, one of two awarded first prize in the 1965 Milo Hellman Prize Essay Contest, was presented at the annual meeting of the American Association of Orthodontics, in Dallas, Texas, May 11, 1965. This work was conducted at the University of Texas Dental Branch in partial fulfillment of the requirements for the degree of Master of Science in Dentistry.

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Fig. 1. The Milwaukee brace. Th.· brae,; is "onstructed of st,'d fl.lld l!Plll'Y leather. Til" verti('al steel bars al'e adjust.able, enabling the pati('ut to ,~ontinuc ,waring th,' saBle \>I':U'I; II'hi1<, spinal curvature is being reduced. '1'he lateral Rtraps ('xert }Jl'(,SSlll'(' at areas where t b,' spinal "un"~ extends. The pelvic girdle is ('ustom made so that it rests on top of the ilia,~ uests of til(' p('lvi(', bone in the individual patient. Tlw mandibular :tn.l oeeil'ital pn,]s an' uot formfitting. ;-.rote position of mandible as it r('sts on th" pad.

teriorly-and extend to the neck region, where supports for the mandible and occiput are engaged. These bars can be lengthened to exert a greater amount of pressure upon the mandible and occiput as the curvature of the spine decreases during treatment. However, if this brace is in use during the patient's period of growth, there may be certain detrimental effects on the dental occlusion and possibly on the normal development of the lower face. Blount and associates 3 stated that prolonged use of the Milwaukee brace will sometimes give rise to malocclusion and prominence of the upper incisor and canine teeth but that this was a small (and correctable) price to pay in exchange for the prevention of a severe scoliosis. The creation of a malocclusion as a result of using the orthopedic brace opens new channels through which the problem can be studied. In effect, the normal developmental cycle is reversed when normally positioned teeth are exposed to constant pressure which realigns them into mal positions.

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PROBLEM. Two interesting questions arise: (1) What effect, if any, does Milwaukee brace therapy have upon maxillofacial growth f (2) What means can be taken to stabilize the maxillofacial complex against the pressure exerted by the brace during orthopedic treatment of scoliosis f PURPOSE. The purpose of this investigation is threefold: 1. To observe a control group of patients under brace therapy with no auxiliary aids to stabilize dentures. Particular attention will be focused on maxillofacial growth and artificially produced malocclusion. 2. To follow and observe this initial group for several years after the brace is removed to see if the occlusion relapses back to a more normal and functional occlusion. 3. To observe an experimental group of patients who, throughout the entire period of Milwaukee brace therapy, wear an auxiliary aid (mouthpiece) to stabilize the denture and prevent collapse of the lower face. It is hoped that this appliance design can be easily tolerated by the patient and worn comfortably at all times that the brace is in place. While wearing the mouthpiece, the patient should be able to function properly in opening and closing the mouth, talking, drinking liquids, and breathing (even if he is a mouth breather). The mouthpiece should prevent further malocclusion and, on occasion, be designed to correct some minor orthodontic problem. It should be emphasized, though, that the major consideration in this portion of the study is stabilization of the denture rather than orthodontic treatment of it. REVIEW OF THE LITERATURE

Normal growth of the face takes place during the same time periods in which scoliosis is best treated. Sicher4 has noted that the growth center located in the mandibular condyle moves the mandible away from the maxilla to make space for eruption of the teeth. Thompson 5 observed that if these growth centers in the condyle are retarded, either unilaterally or bilaterally, a progressive deformation of the entire dental and craniofacial complex can occur. These deformations occur in children more often than adults. Key 6 recognized that bones do have the capacity to respond to stimuli, and their growth may be influenced by forces within the organism. Wolff's law7 governing transformation of bone states that changes in function of a bone are accompanied by definite alterations in the internal structure and form of the bone. It seems feasible, then, to add that a change in the direction of forces being placed upon the bone can lead to a change in the shape of the bone. Gray 8 found that bone resorption occurs during the period of pressure and that bone repair occurs when pressure is relieved. If an abnormal pressure diminishes or destroys the blood supply and drainage of bone tissue, the inevitable reaction is resorption of bone. 9 The avascular fibrous covering of the mandibular condyle and temporal articulating surfaces can withstand great amounts of pressure without detrimental effects. If, however, BONE REACTION TO EXTERNAL PRESSURE.

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the pressure is exerted against a surface of a bone that is eo\'el'ed by per'iosteulll (such as the lower border of the body of the mandible), the result could be bone resorption. The harmful results of the pres..'Iure, whether constant 01' iutermittent, depend upon its effect on the blood circulation. External pressure has been shown to influence the growth of bones. Every mother knows that her baby's head will flatten if the child is allowed to lie too long in one position. Stallard10 believes that extraoral pressure habits have profound effects upon the occlusion. After careful observation over a period of 5 years, he demonstrated dental anomalies and malocclusion caused by pressure habits, such as arm, hand, forearm, and shoulder pillowing, thumb-sucking, chinpropping, cheek-resting, etc. Kjellgren l l showed experimentally how extraoral habits could affect the dental occlusion. He placed a 7 cm. rubber ball around the head under a pressure of about 50 Gm. per square centimeter for 2 to 3% hours daily for a period of several days, The amount of movement produced by this force, which is no stronger than that produced by sleeping with the face resting on the fist, is worthy of notice and shows that various extraoral pressure habits can result in deformation of bone structure. GrayS found that the absence of necessary stimuli supplied by muscle tone and function during the growth period causes osseous atrophy and results in lighter bone which is smaller in diameter and weaker than corresponding normal bone. This was reflected in 1955, when Daniel 12 discovered that the mandible was retarded in poliomyelitis patients in whom the growth period had not been completed, whereas adult patients with the same type of disease displayed no such characteristic. He also noted that cephalometric roentgenograms and study models revealed that the young patients generally tended toward a protruded maxilla with procumbent anterior teeth and lingually collapsed mandibular teeth. Oppenheim13 presented experimental proof that pressure is the sole explanation of tooth movement. StillweIP4 noted the relationship between Class II, Division 1 malocclusion and curvature of the spine. DENTAL ASPECTS OF SCOLIOSIS TREATMENT, 'With these thoughts in mind concerning bone and its reaction to external pressure, it must be recognized that the continuous pressure exerted by the Milwaukee brace could very possibly alter the growth pattern and potential shape of the bone against which it is applied, The first documented case in the literature appeared in 1926, when Howard15 reported the case of a patient wearing a plaster body cast. Three weeks of cast pressure produced marked infraclusion of the posterior teeth, and within 6 months there was a shortening of the lower part of the face. Howard16 later discussed the changes which occurred in his patients during a one year period following removal of orthopedic casts. He found that these patients showed only a slight tendency to relapse to their former normal states at the end of a 12 month period following cessation of treatment. The gingiva, which was normal before treatment, became highly inflamed in the upper and lower molar, premolar, and lower incisor regions by the end of treatment, but 12 months later it displayed marked improvement without medication or any other therapy. Howard's diagnosis, based upon his definite history, found that the molars and

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premolars were depressed, causing the face to become shorter from the nose to the chin. The lower incisors and canines had pressed superiorly upon the lingual inclined surfaces of the maxillary anterior teeth, causing these teeth to tip labially. In attempting to prevent malocclusion during treatment of scoliosis, Howard used a removable splint adjusted to the maxillary and mandibular arches to maintain the proper relationships. He reasoned that stabilizing all the teeth in each arch would produce a unit of resistance that would counteract the force of the orthopedic cast. He found, however, that this appliance did not prevent depression of the teeth or reduction in vertical dimension of the lower third of the face. Recent work in this field was published in 1961 by Bunch,11 who treated forty scoliosis patients with the dental tooth positioner introduced by Kesling. 1s Using this approach, he also attempted to accomplish corrective orthodontic movements while stabilizing the dental components against the pressures of the orthopedic appliances. He recognized that growth interference, abnormal muscular tensions or pressures, and continuous external pressures produced by the brace could alter the normal relationship of the teeth to their environment. After 3 112 years of study, Bunch concluded that the rubber dental positioner maintained or improved the dental and craniofacial relationships and increased the stability of the orthopedic brace during treatment of scoliosis. Of the twelve cases in which he repositioned teeth, ten showed improvement, with the positioner being well tolerated by the patient, and two cases were classified as failures because of the patient's lack of cooperation. Bunch stated that each patient wore the positioner day and night and removed it only for eating, cleaning the teeth, and talking. The positioner used by Bunch was very effective. Expecting the patient to wear this at all times, however, seems impractical, especially since the patient cannot talk (or breathe, if he is a mouth breather) when the positioner is in place. This seems to be demanding too much of a young person who is undergoing the tremendous psychological as well as physical strain of the Milwaukee brace itself. Since there were no controls to compare with Bunch's treated cases, it is impossible to know exactly what might have happened if no appliance had been worn. It can only be assumed that all the patients would have developed malocclusions similar to those that developed in the two who were uncooperative. Since the dental positioner "maintained or improved the craniofacial relationships," there was no apparent loss of vertical height in any of Bunch's patients. The most recent publication on this subject was contributed in 1962 by Logan,19 who has been working with a newly established scoliosis clinic at the University of Edinburgh. He reported the case of a child who had worn the Milwaukee brace for more than 9 years. This patient's facial appearance was such that the chin and nose were much closer to each other than usual. The upper incisors were horizontal, the incisal edges being above the level of the anterior palatine mucosa. Although no initial records were available on this patient, a spontaneous rise in bite and repositioning of teeth took place 9 months after the brace was removed. It appeared that the dentomaxillary structures were assuming their genetic shape. Logan measured the force applied to the mandible by the Milwaukee brace

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and noted that an average intermittent pressure of 4 pounds is produced. After 18 months of study, the findings thus fat' have indicated that the orthopedic appliances used to treat scoliosis have had an effect on the developing dentition. This effect is greatest when the brace is worn at an (~arly age for a prolonged period and least when the brace is worn for a short period of time after the dentition development is complete. The primary effect-a deepening of the biteis probably due to the sinking of the molars and premolars, and it is reversible.' At the time the article was written, more than 50 cases were under observation. Logan hopes to establish fundamental facts concerning the definition of the malocclusion produced and its causative factors before the question of treatment is undertaken. He also ,yishes to determine whether the process is reversible and whether the malocclusion will clear up spontaneously upon removal of the brace. Even if this process is reversible, Logan makes no observations concerning the possible effect that Milwaukee brace therapy may have on vertical growth; nor does he comment on whether or not it could be reversible. His study seems to be concerned mainly with the dentition and malocclusion. The critical factor of maxillofacial growth, which is surely being affected in these developing adolescents, is not stressed. Furthermore, in ignoring the question of treatment, he seems to be reversing the historical medical approach to disease. An analysis of the abnormal dental and growth changes which might result from Milwaukee brace therapy should lead to several interesting observations relative to the usual orthodontic coneept of maxillofacial vertical growth and its control. It was with these thoughts and questions in mind that the present study was undertaken. METHODS AND MATERIALS SOURCE OF PATIENTS. The Texas Institute for Rehabilitation and Research maintains the central scoliosis treatment clinic for the entire Southwest and is conveniently located across the street from the University of Texas Dental Branch in Houston, Texas. The Milwaukee brace is not worn by all scoliosis patients; however, those persons for whom it is prescribed usually wear it from the time scoliosis is detected until their gro'\\1;h period is eompleted. Dr. Paul H. Harrington, orthopedic surgeon and director of this clinic, has cooperated fully in this study by making available his patients and facilities as well as his personal guidance. MOUTHPIECE FABRICATION. A mouthpiece was constructed and placed in each of seven new patients, and seven other new patients served as a control group. Complete records taken on each patient included study models, lateral cephalograms, and profile, front-view, and intraoral photographs. "When applicable, a mouthpiece was inserted at the time the Milwaukee brace was first placed and was to be worn at all times except during meals and when brushing the teeth. For construction of the mouthpiece, maxillary and mandibular study casts were mounted in centric occlusion on an articulator (Fig. 2). In cases in which not all permanent teeth were fully erupted, adjustments were made so that this appliance would not interfere with normal eruption. This was accomplished by

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A

B

Fig. 2. Study models mounted on articulator with mouthpiece. A, Lateral and anterior views showing the articulator adjustment producing a 2 mm. free-way space between the teeth. B, Lateral and anterior views of finished thermoplastic mouthpiece. C, Inferior view of mouthpiece showing occlusal impression of mandibular teeth. D, Superior view of mouthpiece showing occlusal impression of the maxillary teeth. Note full palatal coverage.

building up, with dental stone, the areas where eruption would take place. A sheet of opaque copolymer vinyl thermoplastic 20 material was gently heated with a brush flame and adapted to the upper arch of the cast in accordance with the manufacturer's instructions; this produced an accurate "impression" of the upper teeth. The material extended over the facial and lingual surfaces of the upper teeth, as well as into the palatal and buccal alveolar mucosa. (It was later found that full palatal coverage is necessary.) The articulator was then adjusted so that, when closed, the upper and lower arches were approximately 2 to 3 mm. apart. The occlusal surfaces of the lower teeth were then recorded on the material, and caution was exercised to make sure that there was sufficient bulk of material covering both buccal and lingual surfaces of the lower teeth. This was accomplished by heating the occlusal portions of the material when fitted on the upper arch; the articulator was then closed down to its adjusted height. Thus, a 2 to 3 mm. cushion of material was left between the two arches.

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The thermoplastic material useu for this appliatH:l! is presently marketed for use in making mouth protectors for athletes. \Ye thought that the properties which make this material acceptable for use in a mouth guard would also fulfill our demands. PROCEDURES AND INSTRUCTIONS FOR PATIENTS. The full cooperation oj' Dr. Harrington and his staff enabled us to have our first appointment with each patient before the Milwaukee brace was placed, usually 2 weeks before the patient began orthopedic therapy. It was at this time that the patient was measured for the form-fitting pelvic girdle used in the Milwaukee brace. Orthodontic records were made at this appointment, and the decision was made as to ·whether or not the patient should wear the mouthpiece. It was thought that optimum cooperation would be gained from each patient by allowing him to choose the investigational group in which he would like to participate. One important factor involved here was the permanent residence of the patient; seven were from other cities within the state, and three were from other states. If the patient lived too far away, it was impractical to have him wear the mouthpiece, since he would not return as often for checkups. The mouthpiece was ready for placement on the day that the Milwaukee brace \Vas affixed. There was one exception to this procedure in the case of a patient who had been undergoing Milwaukee brace therapy for 3 months before he began wearing the mouthpiece. The patients wearing the mouthpiece were given the following instructions: 1. Clean the mouthpiece properly and follow good oral hygiene procedures. (An electric toothbrush was recommended, since these patients find it difficult to hold the mouth open over long periods of time.) 2. \Vear the mouthpiece at all times except when eating and brushing the teeth. (Emphasis was placed on continual wearing of the appliance during the first 48 hours after placement. This was considered the critical period.) 3. Gargle with hot salt water ·when teeth become sore (which usually begins 4 to 5 hours after initial placement) and continue for the next 2 to 3 days until all soreness is gone. 4. Relieve sore spot areas by cutting away the irritating spot on the mouthpiece with cuticle scissors. When the patient was seen at the appointed 3 month intervals, the progress of the scoliosis treatment was recorded by Dr. Harrington and, when convenient, the previously mentioned customary orthodontic progress records were made and analyzed. Every 3 months each member of the experimental group filled out a questionnaire as to how many hours a day the mouthpiece was worn and the problems encountered while wearing it. Patients were specifically asked to note the following: (1) sore teeth, (2) sore gums, (3) sore tongue, (4) discolored mouthpiece, (5) odor in mouthpiece, (6) difficulty in cleaning mouthpiece, and (7) difficulty in speech. A chart was made on which the patient could check anyone of four answers (always, often, sometimes, or never) with respect to each problem. It was believed that in order to determine the amount of pressure placed upon

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MP to SN

Fig. 3. Cephalometric anatomic landmarks, and angular and linear measurements used in this study.

the mandible by the Milwaukee brace, it was necessary to know the amount of spinal-curvature correction being obtained. Dr. Harrington's staff supplied us with the degree of curvature reduction in each patient at the time our final records were taken. The amount of correction obtained was rated as follows: Excellent-Curvature decreased 30 degrees or more. Good-Curvature decreased between 20 and 30 degrees. Fair-Curvature decreased between 10 and 20 degrees. Poor-Curvature decreased less than 10 degrees. The palatal vault depth was measured on the before- and after-treatment study models of each patient. A straight edge was placed across the mesiolingual cusps of the right and left upper first permanent molars. A perpendicular rule was then dropped to the deepest portion of the midpalatine suture. The difference in these two measurements was recorded as the decrease in palatal vault depth. CEPHALOMETRIC PROCEDURE. There are several approaches whereby an analysis may be obtained. It seems, however, that there should be a limit to the amount of data that can be conscientiously analyzed in one paper. It is hoped that, in the future, others will apply different methods in the study of these records. After tracing several before- and after-treatment cephalograms in an attempt to find which angles and measurements best described the changes taking place, it was decided that five angles and six linear measurements should be used (Fig. 3). A tracing was made on each before- and after-treatment cephalogram, and the following anatomic landmarks were recorded: Nasion (N )-The junction of the frontal and nasal bones. Anterior nasal spine (ANS )-The spinous process of the maxilla

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forming the most anterior pl'ojcetion of the floor oj' the nasal cavity. Gnathion (Gn)-The most outward and everted point on the profile cUrYature of the symphysis of the mandible. Gonion (Go)-The most outwul'd and everted point on th(~ angle formed by the junction of the ramus and body of the mandible on its posterior-inferior aspect. Articulare (AR)-The point formed by the intersection of the posterior ramus of the mandible and the superstructure of the skull (temporal bone). Sella (S)-The center of sella turcica. Palatal plane (PP)-A line connecting the anterior nasal spine and the posterior nasal spine. The five angles recorded on each tracing include the following: Upper incisor to lower incisor (UI to Ll)-The angle formed by the intersection of the lines representing the long axes of the most labial maxillary and mandibular incisors. It is a measure of the procumbency of the teeth. Lower incisor to mandibular plane angle (I1l1.PA)-The axial inclination of the mandibular incisor to a line drawn from the most inferior portion of the symphysis bisecting the gonial angles. This indicates the incisor's relationship to basal bone and its labial inclination. Upper incisor to sella-nasion (UI to SN)-The axial inclination of the upper incisor to the line connecting sella and nasion. This is an indicator of the protrusion of the most labial incisor. Mandibular plane to sella-nasion (MP to SN)-The angle formed by the intersection of the mandibular plane and the SN line. This gives an indication of vertical or horizontal growth and indicates whether or not the bite is opened during treatment. Gonial angle-The angle formed by the intersection of a line representing the most inferior border of the body of the mandible with a line drawn from articulare to the most posterior portion of the ramus near the mandibular angle. The purpose of this measurement was to determine whether there was any change in the anatomic region where the body and ramus of the mandible joined. To eliminate any variables in the beforeand after-treatment tracings, these tracings were superimposed, using the lower border of the body of the mandible and the posterior ramus as reference lines. The before-treatment articulare point was used in both tracings, since this point changed during treatment. A common reference point was used at the inferior-anterior border of the mandible. This gave consistency to each end of the angle, so that any changes recorded were strictly due to the anatomic change in the gonial angle. Under normal growth conditions during this time period, all of these angles will remain relatively constant. The six linear measurements recorded on each tracing were as follows: Total anterior face height (1)-The distance, in millimeters, from nasion to gnathion.

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Upper anterior face height (2)-The distance, in millimeters, from nasion along a line from nasion to gnathion to a point perpendicUlar to the anterior nasal spine. Lower anterior face height (3)-The distance, in millimeters, from gnathion along a line from nasion to gnathion to a point perpendicUlar to the anterior nasal spine. Upper molar height (4)-The distance, in millimeters, from the occlusal tip of the mesial cusp of the upper first molar perpendiCUlar to the palatal plane. Lower molar height (5)-The distance, in millimeters, from the occlusal tip of the mesial cusp of the lower first molar perpendicular to the mandibular plane. Lower posterior face height (6)-The distance, in millimeters, from articulare to gonion. Under normal growth conditions, all of these linear measurements will increase. To maintain consistency throughout the cephalometric analysis, several landmarks were transferred from the before-treatment tracing to the aftertreatment tracing. These included gonion and gnathion on the mandible. Gnathion was marked after the most posterior portion of the mandibular symphysis of the after-treatment tracing was superimposed upon that of the before-treatment tracing in relation to the lower border and ramus of the mandibles. Gonion was marked after alignment of the posterior border of the rami with the lower borders of the mandibles. The original palatal plane was transferred to the after-treatment tracing after ANS and the inferior border of the maxilla were superimposed upon the before-treatment tracing. Throughout all tracings, when double images appeared on the cephalogram at the ramus, the lower body of the mandible, or the molars, an unbiased attempt was made to bisect these images as their borders were outlined. RESULTS

The results of this study are shown in Tables I to VI. When patients' initials are used in the tables, they are arranged according to age, with the younger patients listed first. In Table I the mean age of the control group as Milwaukee brace therapy began was 12.48 years, and the mean age of the experimental group was 12.84 years. The average time that the control group had worn the Milwaukee brace was 5.4 months. The experimental group averaged 6.7 months in the brace. The information concerning the amount of spinal curvature correction being obtained with the Milwaukee brace was furnished by Dr. Harrington's staff. In Table II the palatal vault depth decrease shows two instances where a negative number is present. This indicates an increase in palatal depth. Two patients had no palatal vault depth change. The remaining ten exhibited a mean palatal vault depth decrease of 1.6 millimeters. The mouthpiece was fabricated for seven patients; one patient would not wear it. The other six averaged eighteen hours per day wearing the mouthpiece.

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Table I. Scoliosis data

Name

Age

Sex

Diagnosis

Total estimated tTefttment time (months)

---

Time brace worn to ! COI"Tcction I being date I (months)i obtained

I

I

Control L.B.

8 yrs.

8 mos.

F

E.H. L.L. L.D. W.S. S. B. B. P.D.

11 11 12 13 14 14

yrs. 10 mos. yrs. 10 mos. yrs. 3 mos. yrs. 9 mos. yrs. 4 mos. yrs. 9 mos.

F F F M F It'

K.P. S.R. P.G. S.C. M.G. S.A.B. R.T.

10 11 12 12 12 12 16

yrs. 8 mos. yrs. 9 mos. yrs. 9 mos. yrs. 10 mos. yrs. 10 mos. yrs. 11 mos. yrs. 2 mos.

F F F F F F M

N eurofibromatosis Idiopathic Idiopathic Idiopathic Idiopathic Idiopathic Idiopathic

18 to 24 ]8 to ]8 to 12 to 18 to 18 to ]8 to

24 24 24 24 24 24

4

Good

3

Excellent Good Fair Good Poor Good

S 6

8 4

;,

Experimental Idiopathic Idiopathic Idiopathic Idiopathic Idiopathic Idiopathic Idiopathic

18 to 24 18 to 24 18 to 24 lR to 24 18 t(} 24 lR to 24 18 to 24

8 8 4 ;,

R 8 6

Good Excellent Excellent Poor Excellent Poor Eair

Table II. Dental data

Patient

Skeletal pattern (Downs)

l\f.G.

Class Class Class Class Class Class Class Class Class

B.A.B. W.S.

Class II Class I

S.B.B. P.D. R.I.

Class I Class I Class II

L.B. K. P. S. R. E.H. L.L. L.D. P.G. S.C.

I I II II I II I II

I

Dental pattern (Angle) Class I End-on End-on End-on Ewl-on Class I Class I Class I Class I, unilateral End-on End-on cross-bit" Class I Class II Class I

Dentition-' Mixed Mixed Mixed Permanent Permanent Permanent Mixed Permanent Permanent

Palatal vault depth dec'I"easc (mm.)

WOTe mouthpiece?

1.0 4.5 1.5

No Yes Yes

0.5

No No

2.D

Average hours worn per day 22 Hi

~.;)

Xo

-1.5 0.0 1.0

Yes ):res

16 20

Yes

2~

Mixed Permanent

0.;'

Y('sl

1.5

No

Permanent Permanent Permanent

].0 0.0 -1.0

XO No Yes

0

12

'-If any deciduous teeth were present, the patient had a "mixed" flentitioll. If all deciduous teeth had been lost, the patient had a permanent dentition.

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The cephalometric results of this study are found in Tables III and IV. The statistical analysis of these cephalometric results are found in Tables V and VI. DISCUSSION VARIABLES INVOLVED. The variables found in this study must have a bearing on the validity of the statistical analysis as reported in the results. These variables include the following: 1. Age of patient. If the patient is under pubertal age and normal growth

Table III. Cephalometric data -

experimental group Patient

Measurement

K. P.

P. G.

S. C.

119.5 117 2.5

133 131.5 1.5

119.5 117 2.5

R.I.

UI to LI ( degrees)

128 Before After 114.5 Difference 13.5

IMPA ( degrees)

Before 93 After 105 Difference -12

96 98.5 -2.5

95.5 96 -0.5

94 96 -2

UI to SN (degrees)

Before 109 After 118 Difference -9

106.5 109 -2.5

99.5 104 -4.5

107 108.5 -1.5

MP to SN ( degrees)

Before After Difference

37.5 35 2.5

32 30 2

40 39 1

30 28.5 1.5

Gonial angle ( degrees)

Before 127 After 122 Difference 5

128 121 7

132 127 5

132 127.5 4.5

123 116.5 6.5

134 131 3

123 121 2

Total anterior face height (mm.)

Before 112 After 100.5 Difference 11.5

114.5 106 8.5

103 99 4

116 113 3

106 104 2

114.5 110.5 4

125.5 123.5 2

Upper anterior face height (mm.)

Before After Difference

47.5 47.5 0

51 51 0

49 49 0

47.5 47.5 0

49 50 -1

49.5 51 -1.5

52.5 54 -1.5

Lower anterior face height (mm.)

Before After Difference

64.5 53 11.5

63.5 55 8.5

54 50 4

68.5 65.5 3

57 54 3

65 59.5 5.5

73 69.5 3.5

Upper molar height (mm.)

Before After Difference

20.5 17 3.5

21 18.5 2.5

17.5 16.5 1

20.5 20 0.5

20 19 1

20.5 19.5 1.0

24.5 24 0.5

Lower molar height (mm.)

Before After Difference

30 27.5 2.5

28 24 4

28 27 1

33 31.5 1.5

27 25 2

29 26.5 2.5

36 35 1

Lower posterior face height (mm.)

Before After Difference

49 43 6

43 33 10

42 39 3

32 29 3

45.5 44.5 1

36.5 33 3.5

48 46 2

31 22.5 8.5

110.5 104 6.5

134 136 -2

159 160 -1

102 104 -2

88 86 2

79 80 -1

118 123 -5

95 97.5 -2.5

85 85 0

43.5 40 3.5

37 34.5 2.5

1 7 -+

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Table IV. ('ephalO1netrir data -- ('onirol fItmrp i Jll casu·rcment

VI to LI (degrees)

IMPA (degrees) VI to SN ( degrees)

MP to SN ( degrees)

Gonial angle ( degrees)

Total anterior face height (mm.) Vpper anterior face height (mm.) Lower anterior face height (mm.) Upper molar height (mm.)

Lower molar height (mm.) Lower posterior face height (mm.)

I--~·-·--·---·-·

I

! R.lI.

L.B.

Before After Difference

9X

~

77

Before After Difference

106 ]23

]7

11 l.ii -1.3.ii

Before After Difference

:14 31 :l

40.ii .16 4.ii

Before Aftpr Diffen'nce

134 ] 27

Before After

108 101.ii 6.ii

Before After Difference Before

After Difference

Before After Difference Before After Difference Before After Difference

L. 11.

7

:'...)

jOfi

10:1 115.5

HI 100

J :1O

-12.G

-f)

-:)~

96

12:Lfi

118 G.ii 114 ]07

7

ii4 52 2

:'j2 fiLii 0.5

54 49.5 4.5

62 5:3.5 6.ii

20

23.5

18.5 1.ii

21 2.ii

W. S.

104 111 ·7

102 1:ll 29

H.I

1'.

ji.

1 ·,

101 II:; 12

94.G

!J7

100.ii -Ii

102 - .3

119.ii 1:.l(i --G.fi

104 ]] 0 - ()

:lii'5 :l+.5

~8

d

10:.1 IO(j

33

30

:n

28.5

2

1.5

llH

i ,~. Ii.

I ml.G !lX.;' 11

11:l.;i iii

121

Before After D iffprcnce

Difference

L. L.

I:ll 120 II

~R

o

llfi

1:·Hi J:lI

l:lO 127.ii 2.5

]21.5 ]20 l.ii

110 106 4

lOR

11:1

9H 9

10~

114.5 114 fI.ii

111 ]09

49 49

GO

:31

4!l 1

51

,'ill ;30 Il

G2 57 ii

6+ 6.1.5 0.5

(j0.5 58.5

21

:n

21.5

20

20

~

20 19

1:30 ]25 G

o 61

57 4 21.5 20 1.5

.,.,

.J

()

o

\,;3

]

()

:1O

22.5

30

19.5 il

26

30.5 29

4

l.G

45 36.5

41 40

43.5

48

8.5

1

34.5 9

39 9

7

50.5 50.;;

o

1 26 2:1 :l

iiO.;:; 50.5

3

~(j.5

26 0.5 40 40

o

29.5 28 1.5 44

40 4

is still taking place, the possibility of influencing this growth is greater. The developing face and dentition would be more adversely affected by Milwaukee brace pressure than a mature face. 2. Total length of tirne 1JIilwaukee brace is 'Worn. This can Yury from 1 to 5 years. The longer the Milwaukee brace IS worn, the greater will be the effect upon the maxillofacial complex. 3. Amount of scoliosis correction obtained. The greater the pressure

Effects of Milwaukee brace

Volume 52 Number 3

175

Table V. Statistical data comparing changes in measurements of experimental group and control group

Measurement UI to LI (degrees) IMPA (degrees) UI to SN (degrees) MP to SN (degrees) Gonial angle (degrees) Total anterior face height (mm.) Upper anterior face height (mm.) Lower anterior face height (mm.) Upper molar height (mm.) Lower molar height (mm.) Lower posterior face height (mm.)

Mean

Standard deviation

Standard error

Experi.! COn· mental trol

Experi-j Conmental trol

Experi-I Conmental t1'01

"t" test

Frobability

3.4 2.6 3.6 3.1 4.7

19.2 10.5 12 2.5 4.2

5.2 4.4 2.9 2.5 1.7

10.6 6.7 9.1 1.9 1.9

2.0 1.7 1.1 1.0 0.6

4.1 2.6 3.5 0.7 0.7

3 2.7 2.4 0.2 0.5

0.02 0.04 0.05 0.8 0.6

5.0

4.9

3.2

2.9

1.2

1.2

0.5

0.6

-0.6

0.5

0.2

0.2

0.9

0

0

5.6

4.4

3.2

2.5

1.2

0.8

0.4

1.4

1.2

1.0

0.2

0.4

0.9

0.4

0.7

2.1

2.4

1.0

1.2

0.4

0.5

0.5

0.6

4.1

5.5

3

3.8

1.2

1.5

0.8

0.4

.07

.09

Table VI. Statistical data comparing the changes in measurements in before- and after-treatment tracings of all fourteen patients Standard deviation

Mean Measurement

Before

I After

MP to SN (degrees) Gonial angle (degrees) Total anterior face height (mm.) Upper anterior face height (mm.) Lower anterior face height (mm.) Upper molar height (mm.) Lower molar height (mm.) Lower posterior face height (mm.)

35.1 128 128

Standard error

at" test

Frobability

1.2 1.6

1.6 2.4

0.1 0.03

1.4

1.6

2.5

0.03

Before

After

Before

32.3 123.6

5.2 3.7

4.5 5.9

1.4 1.0

107

5.3

5.9

I After

50.2

50.3

1.82

1.76

0.49

0.48

0.17

0.9

61.9

56.9

5.2

5.9

1.4

1.6

2.5

0.03

20.9

19.6

1.6

1.8

0.43

0.48

2.1

0.05

29.0

26.8

3.2

3.7

0.86

1.0

2.2

0.05

42.1

37.3

4.6

2.9

1.2

0.78

3.4

0.01

17 fi

Al e:cander

,I ill, J. I)rtitodontir,. Mareh 1906

t~xet't(;d h,\' the .Milwaukt·(· bt'HI'p, tllP g't'('ilip], tltI' 1'()I'l,(,(~ti()tI ill spinal (·ur\'at.u1'e will he, RegaJ'dJess of age Ot' length or l1nl(' ill the Milwauk(,(' brace, any correlation ,,'ould be insigni1i('allt it' lIdpquak I'ot'l'petion of spinal CUI'Yature were not b·eing obtained, 4, Initial relationship of teeth to each other, The force of the Milwanke(~ brace is transferred from the lower teeth to the upper teeth, The direetion of this applied force is critical in relation to the amount of tooth movement produced, The larger the upper ineisor to lower incisor angle, the more upright the opposing teeth will be toward each othel'. This relationship will haw less tendency to change than one in which the angle is smaller. In the smaller-angle case, the teeth are opposing each other at a more acute angle and thus have a greater tendency to be displaced, 'When considering the factors involved in these extreme conditions, an additional idea 21 should be presented. The idiopathic disease process that produced the scoliosis is still present during Mihvaukee brace therapy, The body is in a diseased state, and there arises the possibility that these severe dental and growth results are directly related to this disease process. The Milwaukee brace might not produce these extreme conditions in the normal state. CEPHALOMETRIC ANALYSIS. Tables III and IV contain the cephalometric data found in this study, This information is included here so that individual readings for patients may be compared and judged in accordance with the variables involved. Keeping these variables in mind, an analysis of the cephalometric findings will be made. Table V gives the statistical analysis comparing the changes in measurements of the experimental group to those of the control group, using Student's "t" test, A probability of 0.05 or less indicates that the differences in the two groups are significant, Any probability over 0.05 shows that the differences were probably due to chance. Thus, it can be seen that the first three measurement.s showed a significant difference between the two groups. The thermoplastic mouthpiece maintained the stability of the incisors while they were under the influence of the Milwaukee brace. No conclusion could he made as to whether the upper or the lower anterior teeth evidenced the greatest amount of change. In the control group, the mean difference in the upper incisor to SN angle was 12 degrees and the mean difference in the 100ve1' incisor to mandibular plane angle was 10.5 degrees. This differrnre of only 1.5 degrees between the two means has little clinical significance "',hen one considers thr many variables involved. The experimental group had a mean difference of 3.6 degrees in the upper incisor to SN angle and a mean difference of 2.6 degrees in the lower incisor to mandibular plane angle. Again, although in both groups the upper incisors moved more than the lower incisors, more variables must be eliminated before any definite conclusions can be drawn. In both groups, the least change in the upper incisor t.o lower incisor angle oc('urred in the oldest patients. The mouthpiece did not significantly prevent loss of face height, molar depression, or change in gonial angle. In Table VI the eight measurements whose differences were insignificant

Volume 52 Number 3

Effects of Milwaukee brace 177

are analyzed statistically in a different manner. Since the mouthpiece did not statistically affect these eight measurements, all patients were grouped together, and Student's" t" test was calculated comparing the before-treatment measurements to the after-treatment measurements. The MP-SN angle and upper face height exhibited no significant changes due to the pressure of the Milwaukee brace. The statistical insignificance of the changes that occurred in the MP to SN angle could be related to the method of transferring the point gonion. Rather than transfer gonion from the original to the later tracing, it might be well to mark this independently on each tracing. This might be desirable because of the change in the anatomic gonial angle which will be discussed later. Another explanation for the small decrease in this angle could be that the posterior face height and the anterior face height decreased proportionally, maintaining nearly parallel relationships between the before- and after-treatment mandibular planes. In the small group studied, there appeared to be some relationship to the amount of change in the MP to SN angle with the loss of anterior and posterior face heights. No trend was established, but this point may be considered in future studies. There was no significant change in the anterior upper face height, and the experimental group actually demonstrated an increase in upper face height. This can be related to the normal growth of the patient This growth should be added to the total face height loss, since this additional amount was lost. The greatest amount of loss in anterior face height was found in the lower face. The upper molars demonstrated slight depression, but a greater amount of depression was found in the lower molars. The permanency of these depressions can be determined only after Milwaukee brace therapy is concluded and posttreatment observations are made. The decrease in distance from articulare to gonion was noted as very significant. The cause of this decrease in lower posterior face height poses an interesting question. It seems feasible to assume that the mandibular condyle is being pushed superiorly-posteriorly into the glenoid fossa. What is actually occurring in this area can only be assumed. The possibilities include (1) compression of the soft tissues in the temporomandibular joint area; (2) slipping forward of the articular disc with the head of the condyle resting directly on the posterior portion of the glenoid fossa; (3) resorption of the articular disc; ( 4) posterior-superior resorption of the glenoid fossa; (5) resorption of the head of the condyle; (6) a combination of any of these. In future studies the cephalometric records will provide a means by which accurate assessments can be made and conclusions drawn. CONTROL GROUP. All control patients complained of sore teeth. The teeth were most hypersensitive for approximately one hour after the patient awoke in the morning. The teeth, especially the anterior teeth, were also most mobile during this same time interval. This was probably due to the constant pressure of the Milwaukee brace upon the mandible while the patient was completely relaxed in sleep. Thrrc was no consistency in the ging"ival tissue reaction. No one complained of pain associated with the gingiva, but frequent bleeding occurred during

17;';

Alexander

,[ ;", ,I, Orthodontics Mftrchl96~

brushing. In this initial group, all pati('nis had ae('('l)tahle oral hygiene. As stated earlier, an electric toothbrush \vas recommendl'd in ordcr that the tepth might be cleaned more thoroughly in a shorter tim(~. It :-;honld also he noted that daily vitamin C therapy was initiatNl as each patient began treatment with the Milwaukee brace; the orthopedist pn·scribed one 250 mg. tablet four times a day, or 1,000 mg. daily."2 Those control patients whose upper incisor to lower incisor angle deCl'eafw
Volume 52 Number 3

Effects of Milwaukee brace

179

ance, had a tendency to absorb odors and, consequently, sometimes made the mouthpiece unpleasant to wear. Once the film collected on the appliance, it was difficult to remove; on occasion, it was necessary to make a new mouthpiece. Having learned their lesson, the patients kept the second mouthpiece clean and free of odor. Although patients were asked to wear the mouthpiece at all times except when eating, the average time for wearing it was just over 16 hours. The range was from 0 to 22 hours (Table II). The patients exhibited little trouble in their speech while wearing the mouthpiece. They were instructed to talk or sing aloud as often as possible during the first few days after receiving the appliance. Although this mouthpiece was somewhat more bulky than an orthodontic retainer, the patients became accustomed to it in a similar manner and soon had little difficulty in speaking. MOUTHPIECE DESIGN. The mouthpiece performed well under constant pressure over the 3 to 8 month periods covered in this study. In two instances the material failed after 4 months of continuous use. In these two cases the patients had developed nocturnal bruxism. New mouthpieces were made on the original

c D Fig. 4. Appearance of Patient S. C. with (B awl D) and without (A and C) the mouthpiece inserted. Mouthpiece had been worn during 4 months of Milwaukee brace therapy with no visible changes in the dentition. Note position of mandibular and occipital pads of Milwaukee brace. A and B, Before treatment. C and D, After treatment.

180

Alexander

.tll' J. (),·thodontic8 .~[(trch

1 %1;

models, and no noticeable changes ill oc-elusion were ObSl'l'H·tL Esthetically, thp white color of the thermoplastic material was well [lecepted hy the patients, but discoloration of the mouthpiece, as discussed earlier, was 11 problem. The present design of the mouthpiece can be altered, t'ithcl' functionally 01' csthetically. A labial bulk of material sCE'med necessary to provide adequate stability for the anterior teeth. This bulky portion of the mouthpiece, howeve!', caused the upper lip to protrude abnormally (F'ig. 4). Neyertheless, since this was the initial study, it had to be determined whether or not the mouthpiece would function as intended. After its value had been rea lized, a more esthetic design was attempted for one patient. This latter mouthpiece tapered down in the canine region oyer the labial side, so that there was no material ('overing the labial surface of the six upper anterior teeth. The incisal edges of these teeth were ('overed with the fabricating material. The esthetic quality was much improved, but maintenance of the functional characteristies of the mouthpiece can be determined only after sufficient time has elapsed. The original design of the mouthpiece did not include palatal coyerage. The purpose of this was to enable the patient to speak more distinctly. However, aftl'l' observing the depressed palatal yault in ten eases (Tabh~ II), it was deemed necessary to covel' the anterior palate in the mouthpiece construction to produce a more stable appliance (Fig. 2). Full palatal coverage, then, is essential. DISCUSSIOX 01<' INDIVIDUAL PATIENTS. Patient S. B. B., of the control group, showed the least amount of vertical height loss. She was a 14-year-old Negro girl and had worn the Milwaukee brace for 4 months. Her scoliosis correction to date was poor. M. G. was the only patient in this study whose initial records were taken after Milwaukee brace therapy had begun. She had worn the brace for 3 months when she was first observed. The upper incisors were labially inclined, with spaces on either side. The lower incisors had created imprints on the upper palate, and this palatal area was highly inflamed. The patient and her parents were extremely concerned about the forward movement of the upper incisors. They stated that the spaces between the teeth and the labial inclination had occurred since the Milwaukee brace had been applied. Because of their concern and their excellent attitude, it was decided that a mouthpiece should be made for the patient. After studying her models, the decision was made to reset the upper incisors on the study models and attempt to close the spaces with the mouthpi('ce. Four months and two monthpieres later, the spaces were closed. The cephalom('tric analysis, however, showed that the incisors had slipped forward, as d('monstrated by a decrease of 6.fi degrees in the ~lpper incisor to lower ineisor angk Had the mouthpiece heen worn from the heginning of Milwaukee hraec therapy, the teeth might hav(' heen more stable. Bven so, this decreasp was onl.v half til\' (ken'asp ohsel'Ved ill 1Il1,\' of tllP e(Jutl'ol patients. The inflamed gingival tisslw S('('II al tlit' initial appointult'1I1 hwl disapp('al'(>(l IIll(l s('pmt'd in l'x('plh'llt ('ollditioll within -l months a nt']· t hl' Illoutitpil'(;e Iwd bet'll inserted. Patit'nt S. R., in the experimental group, presented a difficult situation. fIN skeletal and dental pattern exhibited a Class II maloerlusion, anil the uPlwr

Volume 52 Number 3

Effects of Milwaukee brace

181

permanent right canine was impacted. The left canine was beginning to crupt labially with no room within the arch to take its normal functional position. Thc lower arch had a discrepancy of 8 mm. Since this was a definite extraction case and the patient and her parents were exceedingly cooperative, it was decided to extract four first premolars and construct the mouthpiece so as to guide the teeth into their proper positions. Since the right canine was horizontally impacted, it was necessary to expose it surgically and ligate it so that it would be guided into its now available space. The study models upon which the mouthpiece ,ms to be constructed were adjusted by resetting the lower anterior teeth to a more normal alignment. Upper canine space was made available by building canines in dental stone at the canine sites. The mouthpiece was then constructed upon these altered models; the patient has continued her good cooperation, with favorable results beginning to appear. Patient K. P. showed the greatest change in the upper incisor to lower incisor angle in the experimental group, although she very conscientiously kept the mouthpiece in place 22 hours a day throughout the 8 month period. Why, then, did so much movement take place? Two of the variables mentioned earlier should be considered. This was the youngest patient in the experimental group, and she wore the Milwaukee brace for 8 months. I believe that one possible explanation for the failure to hold the teeth at their proper inclinations lies in the fact that the patient wore the same mouthpiece during this entire period. Because of uncontrollable circumstances, she was not observed at any time between the dates on which the before- and after-treatment records were taken. The material fatigued during this period, and loss in resilience was noted. The patient was given a new mouthpiece, made on the original study models, in the hope of repositioning the teeth to their original angulation. Another factor should be mentioned at this point. This patient's loss in lower face height was the greatest seen in all fourteen patients. Again, her age and the time that she was in the Milwaukee brace could be the reason for such a result. When this patient was first seen, her dental occlusion was in the mixeddentition stage. Eight months later she had lost four of her five upper deciduous teeth. Only a partially erupted permanent upper left first premolar was present between the permanent left lateral incisor and left first moJar. On the right side the only tooth separating the permanent lateral incisor and the permanent first moJar was an almost exfoliated deciduous first molar. This lack of support in the upper arch might have played an important role in the patient's loss of lower face height. Patient L. D. exhibited the greatest change in the upper incisor to lower incisor angulation of all fourteen patients. Figs. 5 and 6 show the before- and after-treatment records of this 12-year-old white girl who had been under Milwaukee brace therapy for 8 months. When the cephalometric tracings were superimposed upon line SN at sella (Fig. 5, A), an elevation of the entire maxilla was noted. Also shown was the reduction in face height, the movement of the incisor teeth, and the change in the soft-tissue profile. When the maxilla was superimposed (Fig. 5, B), the change in position of the teeth within the maxilla was most noticeable. The depression of the lower molar and the extrusion of the

18:2

Alexand/'1'

;I)n, J Orthoduntics March 196(;

,

I

\ ~

'- ~

- --..

Before - - After - - - - B

,, ... '

\~~I

~ I

J I

1/

c,

I

II

~!

PMS

Fig. 5. Cephalometric tracings of Patient L. D. exhibiting the greatest change in upper jnciRor to lower incisor angulation. Before amI after tracings are superimposed upon line RN at sella (A); maxillary palatal plane (B); and posterior mandibular symphysis (P1f1S) in relation to the lower horder of t.he body and posterior ramus of the mandible (C).

lower incisor (F'ig. 5, C) were noted when the mandibles were superimposed. The increase in anteroposterior length of the mandible, as noted by the space between the lines representing the posterior borders of the rami, was partially due to growth. Whether this increase in length of the body of the mandible was in part a result of the abnormal pressure exerted by the Milwaukee brace could not be determined. That possibility should be considered as this study progresses. MANDIBULAR CHANGES. Using serial cephalograms, Brodie 23 has shown that the contour of the gonial angle does not change appreciably during normal growth. This fairly constant gonial angle stabilizes the growth pattern of the mandible.

Volume 52 Number 3

Effects of Milwaukee brace

183

Fig. 6. Photographs of face of Patient L. D. showing the greatest change in upper incisor to lower incisor angulation.

Broadbent24 stated that the normally developing face continues to grow downward, forward, and outward, with the greatest amount of increase taking place along the lower border of the body of the mandible and at the chin point. The lower border of the body of the mandible (as well as the inferior surface of the occipital bone) is the area in which the pressure of the Milwaukee brace is transferred to the skull. The mandibular pad covers approximately the middle to anterior two thirds of this area of the mandible. An area of about 1h inch anterior to the angle is not supported by the pad. This pad is the same size and shape on each Milwaukee brace worn in this study; it is not contoured to the individual mandible. This gives freedom of movement of the head in a lateral direction. The pressure points on the mandible are not constant but can vary as the patient turns his head. The majority of the time, however, the mandible rests in the middle of the pad. To determine what effects, if any, this pressure had upon the mandible,

J S4

Alexander

,1111 .

.1. ()rthodonUC8 JIarrh [!)6I;

Before - - After -

J ~

\

\

, ~~~----------~~

,

A.

I

J

\

\

,

B.

~

c. I

\

D.

Pig. 7. Cephalometric tracings with mandibles superimposed. The posterior ramus and the lower border of the body of the mandible were used as refert'nce lines. These patients had the greatest decrease in the gonial angle. A, Patient E. H., under treatment 3 months; B, Patient L. B., under treatment 4 months; C, Patient M. G., under treatment 8 months; D, Patient S. R., under treatment 8 months.

the gonial angle was measured on all before- and after-treatment cephalograms. A mean decrease of 4.5 degrees was noted, with individual measurements varying from 1.5 degrees to 7 degTees. This decrease was statistically significant. As mentioned earlier, before- and after-treatment cephalometric tracings of the mandible were superimposed upon each other, with the posterior ramus and the lower border of the body of the mandible serving as reference lines. In each of the fourteen cases, what appeared to be specific and abnormal growth had taken place around the gonial angles (Fig. 7). These angles could not be superimposed as can normally developing gonial angles. This" gonial notch" was more accentuated in the younger patients who had worn the Milwaukee brace for a longer period of time. These tracings also revealed, in some cases, the abnormal lowering of the symphysis in relation to the lower border of the body of the mandible. These possible phenomena could be a direct result of the inhibition of growth

Volume 52 Numbe,.3

Effects of Milwaukee brace

185

along the middle to anterior two thirds of the lower border of the body of the mandible by the mandibular pad of the Milwaukee brace. Since the pad does not exert its constant pressure on the angles and (in some cases) at the chin, these two areas could continue to grow, thus causing formation of the "gonial notch" and the downward and forward movement of the symphysis. Only time and a continuation of this study will determine more definite trends. MAXILLARY CHANGES. In his studies on growth and development, Broadbent24 noted that the posterior ends of the hard palate remained constant, and throughout his study on healthy children the hard palate maintained a parallel relation during the entire growth range. \Veinmann and Sicher9 stated that the palatal plane, along with other facial planes, maintains a fairly constant angular relation to the base of the skull. In at least three cases the inferior border of the palate had been depressed superiorly (Fig. 5). This was noted by superimposing line SN on sella. This seems a valid observation since the greatest time span between cephalograms is only 8 months. Model analysis showed a change in vault depth from deep to shallow or fiat. These three patients were all 12 years of age or younger. The palatal vault depth decreased in ten of the fourteen patients (Table II). In two patients there was no change, and in two others there was an increase in palatal vault depth. If palatal coverage had been incorporated into the mouthpiece design, the depression of the palatal vault might not have been noticeable. Instead, it is assumed that there would be a greater tendency for the palatal plane to be displaced superiorly. I believe that when the Milwaukee brace is worn over longer periods of time a definite directional change in vertical growth in the maxilla will be demonstrated in the younger patients. This will cause a superior tipping of the palatal plane. RECOMMENDATIONS FOR FUTURE STUDY. In discussing this article one cannot help but consider some far-reaching possibilities that this study could produce. Before this is attempted, however, several recommendations will be made to aid and add continuity to future studies on this subject: I. A new mouthpiece with palatal coverage should be constructed every 4 to 5 months or oftener II. All records should be standardized A. Cephalometries 1. Beginning cephalograms should include an open-jaw view to reveal the condylar head and an anteroposterior view as well as the lateral view 2. The Milwaukee brace should be removed before all cephalograms are taken 3. The use of metal implants, placed at critical growth areas in the mandible to permit more accurate cephalometric measurements and analysis, should be considered B. Photographs should be made with patients properly oriented for the sake of consistency C. For study models, trimming height and angles should be standardized

1~ 6

Alexander

n.

A

/I, .

.f. Orthodontics March 196.;

Full-mouth iILtl'a-onti x-I'uys should Ill' tilhn ilt till' h('gillllilig o[ tn'atllH'nt and thcJ','al'tpl' Wi I)('!'fkd ITI. Thcl'e should hI' ('omplrt(' stnd:' on how (h,' t('IlII)()]'OIlUIl](lilllllal' .ioint and glenoid fossa m'l' aff,'('«'d h:' this 1>l'('S81\1'(' IV. The intraoral Ill'PSSHl'(' trarmfplTcd f)'om til(' lOin'!' (('('til to til!' upper teeth while in Mihnmk('(' b1'lwe tl'iletiol1 should be llIpa8Ul'ed V. A cephalometric study of patjents who ha\'e completed lVlilwaukc(' brace therapy should be made to determine any consist'~IH'Y ill skeletal patterns alld an~- history of temporomandibular joint disturbances EFFECTS ON GROWTH. One of the long-range purposes of this investigation is to study patients after they have completed Milwaukee bracr therapy and to observe any relapse of the malocclusion, as suggested by IJogan.19 After this abnormal pressure has been relieved, it seems feasible that the faeial muscles surrounding the anterior teeth will have a tendency to tip these teeth back into more acceptable positions. This information may shed new light on the continuing orthodontic question of where is "upright position on basal bone." These teeth have been expanded a far greater distance than would bl' observed in the practice of orthodontics. "Yhen they relocate til('mselves, a eomparison of their new location with their original location will he interesting. 1'he depressed molars should re-('rupt, thus increasing tIl!' lower anterior fae(' height. TIl!' amonnt of increase ,\'ill be the intel'esting' point, and it should be rOilipared with that seen in patirnts who have undergone normal growth. The effect of th,' Milwaukee brace on maxillofaeial growth will 1)(' more definitely deti'l'mined at this tim('. Growth and development are beginlling to gain theil' proper plaees in tIl(' mind of today's orthodontist, and much work has been done in t.his area. Many believe that horizontal growth in the mctxilla can be retarded by the use of extraoral appliances, such as headgears. The yprtical growth of the lmvpr faee, howeyer, presents another and as yet uneontrollable factor which must be considered. One of the orthodontist's greatest problems is the case in which a high mandibular angle results from excessive grmvth in wrtical height. In many Class II mix('d-dentition cases thc accepted treatment is posterior force vvith the headgear to the upper molars t.o l'('tard maxillary horizontal grmvth, letting' the mandible" ('atch np" with th(, maxilla. It St'ems feasible to have some t~'pe of appliance whieh could retal'd or redired the vPl,tical growth in the high-mandibular-plane-angle rases. It is possible that this retarded vertical growth would be rcyersible. This does not seem feasible, howevcr, since the horizontal growth change effected with the headgear is not considered reversibk. Also, to prevent a relapse of the spinal curvature, the ~lilwaukee brace is worn until growth is eompleted. By the same logic, it seems doubtful that the affected structures in the lower face will revert to their original growth patterns when the abnormal pressure is relien~d. The teeth will seek more stable positions, tnt the directional change in growth may be permanent. It will be 1 to 3 years brfore the final records can be taken on the cases presented in this article. Only after these final records arc assessed will any conclusive results be determined concerning the effect of this pressure upon growth.

Volume 52 Number 3

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The phenomena that are being witnessed in this study lend themselves to special comment. Maxillofacial growth is being observed under abnormal conditions. It is apparent that growth changes are taking place in the lower face of the growing child wearing the Milwaukee brace. To say that vertical growth is being inhibited or retarded would be a mistake; that vertical growth is being affected by this pressure, resulting in a directional change in the normal growth pattern, has been ascertained in this study. In this study, growth in another dimension has been observed. The reaction of the lower face to this abnormal pressure may demonstrate as yet unrecognized concepts of growth response within the maxillofacial complex. This response must be identified as resorption, inhibition, retardation, directional change, or other growth reactions. When it is determined, the principles involved may possibly be applied to clinical orthodontics. In relating this possibility to clinical orthodontics, the use of such a mandibular pad seems feasible in certain cases in which vertical growth is predominant. The design of the appliance could be such that the opposing pressure, instead of coming from the pelvic girdle as with the Milwaukee brace, could come from specially designed shoulder pads. A revival of the chin cap or elastic pad, with opposing pressure being placed in the superior portion of the skull, seems a real possibility. SUMMARY AND CONCLUSIONS

This study was initiated to determine the effects upon the dentition and surrounding maxillofacial complex during treatment of scoliosis with the Milwaukee brace. The Milwaukee brace, used in the treatment of scoliosis, has been shown to produce detrimental effects upon the occlusion. Beginning and progress study models, cephalograms, and photographs of fourteen patients who were being treated for scoliosis with the Milwaukee brace were obtained. Seven patients (considered as the control group) wore no auxiliary appliance to stabilize their dentures. The other seven wore a positioner type of appliance to stabilize their dentures and, in two instances, to correct orthodontic problems. Certain angular and linear measurements were recorded to determine what effect the Milwaukee brace had upon the dental components and upon vertical growth in the lower face. The technique used in fabricating the mouthpiece and the patients' instructions for its use were described. Progress reports indicated that the mouthpiece stabilized the denture but did not prevent loss of vertical height. Lower-molar depression was noted in all patients; in addition, the control group demonstrated an extrusion of the incisor teeth. A shortening of vertical height, especially lower anterior face height, was noted in all patients. Vertical growth seemed to be affected in the lower border of the body of the mandible, with possible growth occurring at the gonial angle and symphyseal area. Indications are that the palatal plane was elevated. The variables involved, the problems encountered, and comments on certain individual cases were discussed. A long-range plan of study, which included recommendations and possible findings, was presented. CONCLUSIONS. No final conclusions can be made at the present time, since SUMMARY.

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the results thus fa!' analyzed (lI'C progress l'('sults. {i!}(jPI' the ('ollditioIlS or this study, however, cPI·tain trl'nrts haY(' nIHil!' ih('m~wly('s apl)I]]'Pllt. TIH'SP incll1de 1h(' following: 1. The Milwaukee brace, used in 1h(' treatment of stoliosis, dpI1l011stnlt('s a directional change of growth in the lower face of the growing child. 2. The normal maxillofacial growth pattern is affected by }Iilwaukee brace therapy. Obsel'Yations made in this article include depression of the total anterior face height; questionable depression o[ uPlwr anterior face height; depression of 10\\'er anterior face height; d('pression of lower posterior face height; eleyation of the palata I plane with a tendency to flatten the palatal vault; increase in body structure at the mandibular angle, causing a more acute gonial angle; and ahnormal forward and downward movement of th0 symphyseal area. 3. The Milwaukee brace affects the dentition hy extruding the incisor teeth and depressing the molars. The effect is more pronounced in the lower molars. 4. The copolymer vinyl thermoplastic mouthpiece prevents extrusion of the anterior teeth and appears to enhance the efficiency of the Milwaukee brace. The mouthpiece can be worn at all times, pyen whilp talking, except at mealtimes and when brushing the teeth. 5. The copolymer vinyl thermoplastic mouthpiece does not prevent collapse of the lower face height or depression of the molars. 6. By taking advantage of the forces involved, it is possible to accomplish minor tooth movement with the mouthpiece. The author wishes to express his sincere gratitude to the man who made this all possible, Dr. A. P. Westfall. REFERENCES

1. Harringon, P. R.: Scoliosis in the Growing Spine, Pediat. Clin. North Ameriea 10: 225-245, 1963. 2. Blount, W. P., Schmidt, A. C., and others: Making the Milwaukee Braco, .r. Bone & .Toint Surg. 40A: 526·528, 1958. 3. Blount, W. P., Schmidt, A. C., and others: The Milwaukee Brace in the Operative Treatment of Scoliosis, J. Bone & Joint Surg. 40A: 511-525, 1958. 4. Sicher, Harry: Skeletal Disharmonies and Malocclusions, AM ..r. OR1'HOOONTlCS 43: 679684, 1957. 5. Thompson, J. R.: Oral and Environmental Factors as Eriologi"al Faetnl's in MaJoeclUl,ion of the Teeth, AM .•r. ORTHODONTICS 35: 33-53, 1949. 6. Key, J. A.: Bone Atrophy and Absorption, Int .•r. ORTHODON'rIA 15: 9'49, 1929. 7. Wolff, Julius: Das Gesetz dCI" Transfonnation del' Knochen, original manus{~ript, Berlin, 1892. 8. Gray, J. T.: The Influence of Pressure on Osseous Growth and Function, INT.•J. ORTHO' DONTIA 20: 318-324, 1934_ 9. Weinmann, J. P., and Sicher, Hurry: Bone and Bones, ed. 2, St. Louis, 1955, The C. V. Mosby Company, pp. 101, 137. ]0. Stallard, Harvey: External Pressures in the Etiology of MaIO<'e1usiolls, J Wf. ;r. ORTHODONTIA 16: 475·526, 1930. 11. Kjellgren, Birger: Experiments Concerning the Influence of External Pressure on the Occlusion, Dental Cosmos 68: 705-708, 1926.

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12. Daniel, R. G.: An Evaluation of the Effeets of Bulbar·Spinal Poliomyelitis on the Oeclusion of the Teeth, AM. J. ORTHODONTICS 41: 721, 1955. (Abst.) 13. Oppenheim, Albin: Bone Changes During Tooth Movement, INT. J. ORTHODONTIA 16: 535, 1930. 14. Stillwell, F. S.: The Correlation of Maloeclusion and Seoliosis to Posture and Its Effeet Upon the Teeth and Spine, Dental Cosmos 69: 154·163, 1927. 15. Howard, C. C.: A Preliminary Report of Infraocclusion of the Molars and Premolars Produced by Orthopedic Treatment of Scoliosis, INT. J. ORTHODONTIA 12: 434·437, 1926. 16. Howard, C. C.: A Second Report of Infraocclusion of the Molars and Premolars Produced by Orthopedic Treatment of Scoliosis, INT. J. ORTHODONTIA 15: 329·333, 1929. 17. Bunch, W. B.: Orthodontie Positioner Treatment During Orthopedic Treatment of Scoliosis, AM. J. ORTHODONTICS 47: 174·204, 1961. 18. Kesling, H. D.: The Philosophy of the 'I'ooth Positioning Appliances, AM. J. ORTHODONTICS & ORAL SL'RG. 31: 297·304, 1945. 19. Logan, W. R.: The Effect of the Milwaukee Bra(!e on the Developing Dentition, D. Practi· tioner, 12: 447·454, 1962. 20. Stern, Alfred: Personal communieation, Houston, Texas, 1964. 21. Harrington, P. R.: Personal communication, Houston, Texas, 1964. 22. Jerome, Gross: Studies on Formation of Collagen. IV. Effect of Vitamin C Deficiency on the Neutral Salt·Extractible Collagen of Skin, J. Exper. Med. 109: 557·569, 1959. 23. Brodie, A. G.: On the Growth Pattern of the Human Head From the Third Month to the Eighth Year of Life, Am. J. Anat. 68: 209, 1941. 24. Broadbent, B. H.: Practical Orthodontics, ed. 8, St. Louis, 1955, The C. V. Mosby Company p. 301.

821 Benge Dr.