Early orthopedic treatment for Class III skeletal patterns

Ear@- orthopedic treatment for Class III skeletal patterns Leroy

Vego,

B.A.,

D.D.S.,

KS.*

Los Angeles, Calif.

A

ccording to a Health, Education and Welfare6 survey taken in 1963, 10 per cent of all children between 6 and 11 years of age have a mesiocclusion of one or both of the buccal segments. Of those 0.06 per cent or approximately 76,000 children have a lower overjet. The lower overjet is the more obvious aspect of the Class III malocclusion but manifests itself in a small percentage of the early age Class III patients. It is for this reason that orthodontists do not see Class III cases as early as the Class II malocclusions. Class III cases treated in the adult and late mixed-dentition stages do not enjoy the same favorable prognosis as other malocclusions. Class III skeletal malocclusions require early diagnosis and treatment. Review

of the

litemture

Early orthopedic correction of Class III malocclusion has been controversial for the past 70 years; yet various cultural groups have remodeled human bone growth for centuries. One well-known practice is that of binding female Chinese feet. The ultimate successful goal was the shortening of the horizontal components of the foot to a more vertical position. Normal function was not the desired goal. Various early Mayan tribes altered the cranial bones by binding the infant skull between boards. This was done in infancy, Kingsley,3 as early as 1878, advocated the use of the chin cup. Angle, in 1909 stated: “These appliances with their auxiliaries are no longer relied upon by the author to the extent formerly.” Angle’” felt that with his modern technique of complete arch control he could manipulate the offending jaw. His teaching had great influence on the succeeding generation of orthodontists. Case,’ in 1920, advocated the use of the chin cup (Fig. 6). “The application of occipital force to the chin for the bodily retrusive movement of the lower jaw, which has been in the past quite a popular practice, is now rarely considered of practical advantage after the years of childhood. If the apparatus can be made *Lecturer, Section Los Angeles.

of

Orthodontics,

School

of

Dentistry,

University

of

California

at

59

60

Vego

Am.

J. Orthod. Jtdy 1976

comfortable for the little ones so they will voluntarily wear it with sufficient persistence, no doubt much can be accomplished in this way.” Thompson” suggests that “distal force to the mandible will create a functional retrusion and cause temporomandibular joint disturbances.” Tweed4 advocated the use of the chin cup only in obtuse gonial angles in Class III cases. He also used the chin cup for retentive purposes. In the deciduous dentition he preferred a multiple-band technique to the maxillary arch instead of the cup. Strang and Thompson,” on the other hand, favored the use of the chin cup in the deciduous dentition. In 1967, Graber and associates’* advocated the use of extraoral appliances to correct the Class III malocclusion. They state: “It is good interceptive dental facial orthopedics to place appliances early where there is Class III malocclusion. ” Charlier and colleagues1o have shown that in organ culture the spheno-occiptal synchondrosis and the cartilage of the nasal septum have independent growth potential. This growth takes place by division of differentiated chondroblasts. On the other hand, the calvaria and facial sutures grow by division of young connective cells. They state that mechanical forces can increase the mitotic activity of young cells in the prechondroblastic zone. They showed additional growth of condylar cartilage of young rat mandibles placed in hpperpropulsion. Petrovic,!’ in a latter experiment with chin cups on rats, concentrated on the prechondroblastic layer of the condyle. His studies show that mechanical forces can inhibit or stimulate cells of the prechondroblastic zone. Joho,l” experimenting with distal retraction of the mandible on Macu.crr muldta~, found that the maxillae moved up and back. There was extensive bone resorption in the distal aspects of the condple, the roof of the mandibular fossa, and the anterior aspect of the postglenoid surface. He further found that there was bone deposition on the posterior surface of the posterior glenoid tubercle. He also showed that a. Class II distal relationship could be achieved and that mandibular development may be redirected through applieation of forces to mandibular teeth. Stockli and Willert,l reporting on hyperpropulsion of primate mandibles, found that the condyle assumed a new shape. The posterior aspects assumed a bulging shape. There was new bone in a new stable position after 120 days. There were no histopathologic changes. McNamara7 experimented with altered occlusal configurations in Ma.caca mulatto monkeys, He found that there was a chronologic correlation between the occurrence and disappearance of altered neuromuscular function and the re-establishment of skeletal balance. As skelet,al balance was restored through specific structural adaptations, the need for compensatory muscle function was reduced. The nature and extent of the specific skeletal and dental adaptations depended upon the level of maturation of the animal. It was primarily in the infant and primitive animals that the extent and direction of growth were altered. After 13 weeks, there was little histologic evidence of physiologic or pathologic responses to the induced protrusive function in the sacrificed animal. De Alba and co-workers,‘3 using photoelastic analysis, studied the stress areas

Fig. 1. An arrow placed on the patient’s nate impression material and, in turn, orientation in chin-cup construction.

Fig. 2. The chin effect

cup

a directional

Fig. 3. The general

as used change. outline

in this of the

chin

chin with be seen

study. cup

The

indelible on the

arms

showing

can the

pen plaster be

transfer

will transfer model for

moved

together

of the

arrow

to the algiappropriate or apart mark

to

to the

model.

Fig. 4. One

of

three

different-sized

customized

trays

used

to

take

the

impression

of

the

chin.

in the skull caused by chin cup therapy. Their model revealed little or no effect on cranial sutures. The resultant forces were distributed primarily in the mandible itself, and there was concentration of stresses in the posterior aspect of the glenoid fossa. From this report it is possible to assume that the only cranial suture that could possibly be affected would be the petrotympanic suture. It would remain for implant research to varify remodeling of this suture. The fact that there is resorption in the distal aspect of the fossa has been pointed out by Joho.16 It would be safe at t,his juncture to speculate that with

62

Vego

Fig. 5. The chin formities,

New

Am.

cup, York,

Fig. 6. The chin cup

made 1879, as used

of

brass,

D. Appleton by Calvin

used

in the

1870’s.

(From

Kingsley,

N.

W.:

J. Orthod. July 1976

Oral

De-

& Company.) Case

in the

early

1900’s.

excessive stress at the posterior aspect of the condyle there would be diminution of cell proliferation and differentiation, whereas the superior aspect of the condyle would be in an environment conducive to cellular proliferation. These studies indicate that the direction of bone growth can be altered without histopathologic change and that growth changes are more pronounced at the earlier stages of development. The importance of understanding cranial growth and change in Class III malocclusions has been well stated by Hopkins.” He reported on twenty cases of Class III occlusion and. stated that anteroposterior jaw relationships and occlusion may be affected by three factors: (1) maxillary growth, (2) mandibular growth, (3) growth changes in the base of the skull which result in changes of the position of the articular fossa relative to the maxilla. The position of the artitular fossa is altered by the downward and lateral growth of the middle cranial fossa. Changes in the position of the articular fossa are reflected in the position of articulare. In serial studies, articulare moves downward and backward. Individual variations in the extent of this movement are to be seen. In general, mandibular growth is greater than maxillary growth, but this is offset by the relative backward movement of articulare. Attention should also be called to the growth changes that take place in the posterior cranial base which affect the anteroposterior position of the maxillary fossa and hence the position of the mandible to the maxilla.

vozume

Early

70 1

Number

Fig.

Methods

7. Before-

ond

and

after-treatment

treatment

orthopedic

photographs

of

the

five

cases

for Class I71

used

63

in a study.

materials

Five skeletal Class III cases were treated with a chin cup only. The five cases were all classified as skeletal Class III by a computerized analysis.17 The three major Class III factors are (1) the distance from location of porion to the distal aspect of the pterygopalatine fossa (a more anterior fossa placement would result in a more forward mandible), (2) corpus length, measured from the center of the ramus to pogonion, and (3) facial depth or Downs’ facial angle indicating anterior or posterior mandibular position. The age range was 4 years to 9 years. Treatment time varied from 2 months to 9 months. The chin cups were constructed on plaster models (Figs. 1 to 4). The models were made by taking an impression of the chin with alginate impression material placed in a customized tray. Prior to impression taking, an indelible-ink pen is

64

Vega

Fig. 7 (Cont’d).

For legend,

see

p. 63.

used to draw an arrow in the center of the chin, and the arrow mark is transferred to the plaster models, Having a mark on the model aids in drawing the outline of the chin cup and, therefore, facilitates construction. Holes are drilled into the cup, and four wires are inserted. This is similar to the method and use proposed by Kingsley” in 1878 (Fig. 5). The forces used were between 150 and 300 grams on each side. The patient was alerted to the possibility of irritation from the chin cup. We advised that either talcum powder, moleskin, or a soft flannel cloth be used between the appliance and the skin. The parents’ cooperation was solicited and vital to the success of treatment. The chin cup as outlined here is comfortable, and there have been no problems during sleep. It is important that the relationship with the patient be positive in all respects, as appliance wear will be necessary any number of times during the growth period. Graber’s objective was to restrain all possible horizontal growth, or at least redirect it to a more vertical vector. He demonstrates a case treated intermittently for 6 years. I2 The cephalometric tracings reveal a cessation of horizontal growth during chin-cup wear and continuation of horizontal growth with cessation of wear. Graber also suggests the use of 3 to 4 pounds on each side. In this study, it was found that forces of this magnitude are not necessary and can cause discomfort. In all five cases (Fig. 7) the anterior cross-bite was corrected within 2 months.

Early

orthopedic

treatment

for Class

III

65

model.

The

08

Fig. 8. A differences Fig. the

posttreatment in these two

tracing tracings

9. A composite tracing forecast tracings. The

Fig.

10.

the

increased

A composite posterior

of the ramal

of

superimposed on the forecast is what is utilized in the statistical the black

posttreatment areas indicate

before-treatment height

tracings

as opposed

computerized table.

cases superimposed the changes and to the

the smaller

on due

posttreatment increase

to

a composite treatment. changes.

in facial

of Note

depth

Treatment continued until the first molar, or the deciduous second molars, achieved a flush terminal plane. At that point the chin cup was worn every other night for approximately 2 months. Three cephalometric tracings were made (Figs. 8 to 10). The first tracing was at the beginning of treatment. The second tracing was made up to 2 years posttreatment. The third tracing was a forecast tracing representing a mathematical norm for that individual. This norm was

66 Table

Vega

Am. J. Orthod. Julu 1976

I. Calculated

differences

between

observed

and

forecast

Lape Factor

Molar relation Canine relation Incisor overjet Incisor overbite Lower incisor extrusion Convexity Upper molar position Mandibular incisor protrusion Maxillary incisor protrusion Mandibular incisor inclination Occlusal plane ramus XI Occlusal plane inclination Maxillary inclination Lower face Facial depth Facial axis Facial taper Maxillary depth Maxillary height Palatal plane Mandibular plane Cranial deflection Cranial length, anterior Posterior facial height Ramus position Porion location (TMJ) Gonial angle Mandibular arc Corpus length 0

=

Observed

E =

Expected

D =

Difference

Stock

0

E

D

0

-.3 -2.2 .7 -2.2 -1.1 -1.2 4.8 -.3 .7 -3.3 0 0 2.3 -.3 - .7 -1.9 1.7 2.2 3.9 2.3 .6 .2 5.5 9.2 .8 -2.0 7.0 2.7 5.9

0 0 0 0 0

- .3 -2.2 .I -2.2 -1.1 - .7 2.8 - .3 .7 -3.3 -1.0 1.0 6.1 - .3 -1.6 -1.9 1.7 2.2 2.8 2.3 - .6 .2 .I 7.8 .8 -1.0 5.6 1.3 -2.4

1.5 2.3 6.8 2.9 .2 - .6 - .5 -2.3 3.8 -1.9 -1.1 1.9 6.7 .8 - .8 -2.0 1.9 -1.4 4.1 -.9 -1.6 .9 .8 3.9 -2.1 -3.5 4.0 0 1.3

- .5 2.0 0 0 0 -1.0 1.0 0 0 .9 0 0 0 1.1 0 1.2 0 4.8 7.4 0 -1.0 1.4 1.4 8.3

tracings

E

-

-

-

-

0 0 0 0 0 .4 1.4 0 0 0 .8 .8 0 0 .5 0 0 0 .7 0 .5 0 .4 1.7 0 .7 .8 .8 1.6

Hugo D

1.5 2.3 6.8 2.9 .2 - .2 -1.9 -2.3 3.8 -1.9 - .3 1.1 6.7 .8 -1.3 -2.0 1.9 1.4 3.4 .9 -1.1 .9 .4 2.2 -2.1 -2.8 3.2 - .8 - .3

0

.3 -.l 3.4 2.4 1.4 1.2

E

D

0 0 0 0 0 0

.3 - .l 3.4 2.4 1.4 1.2 - .3 -3.0 .2 -9.9 1.4 -1.5

.4

.l

-3.0 .2 -9.9 1.2 -1.3 1.5 -2.8 .3 .7 1.3 1.7 3.3 -1.7 -1.6 -.l .8 .9 -.6 -.5 1.0 4.2 - .3

0 0 0 - .2 .2 0 0 .l

0 0 0 .l 0 - .l 0 .2 .3 0 0 .2 .2 .2

change. change. between

0

and

E.

calculated for patients of similar age, race, sex, and facial volume. The time increments of the forecast tracings were equivalent to the time lapse for the patients under study. Tracings were digitized by means of an analog digital converter and run through a computer to calculate thirty different distances and angular relationships (Table I). In this way, each observed change could be compared directly with the expected change of the model (Fig. 8). The expected change is the forecast tracing t,hat was compared to observed treatment change. The differences between the observed change and the expected change were considered the result of treatment. The mean differences were calculated as well as standard deviations. The Student t test was then applied to determine if there were statistically significant changes due to treatment. The one weakness of this method is the fact that the computerized sample was not very large in the age range from 5 to 7 years. The forecasts were based primarily on those changes from 5 to 9. The norms, therefore, are not perfect,

1.5

-2.8 - .2 .7 1.3 1.7 3.2 -1.7 -1.5 - .l .6 .6 - .6 - .5 .8 4.0 - .5

Early

.8 2.2 4.1 -.9 -1.1 -1.0 1.9 -1.9 2.2 -8.3 - .5 1.5 .3 -.5 1.0 .9 -.3 0 - .I -.8 - .4 -.2 .3 1.2 .I .3 1.5 1.5 1.8

trentme?bt

for

Clnss 777

67

Tenney

Voelker 0

orthopedic

E

D

0

E

D

0 0 0 0 0

.8 2.2 4.1 - .9 -1.1 - .9 1.4 -1.9 2.2 -8.3 - .3 1.3 .3 - .5 - .8 .9 - .3 0 - .9 - .8 - .3 - .2 - .3 .2 .7 .5 1.3 1.3 .6

0 -2.3 2.8 -3.9 -2.8 1.1 2.9 -3.4 0 -12.8 1.7 -2.1 1.4 -1.3 - .3 .6 1.3 1.0 -2.5 .5 -1.3 -3 1.3 2.1 -1.5 -1.0 2.0 .4 1.3

0 0 0 0 0

0 -2.3 2.8 -3.9 -2.8 1.3 2.1 -3.4 0 - 12.8 2.3 -3.3 1.4 -1.3 - .6 .6 1.3 1.0 -3.0 .5 -1.0 - .5 1.0 .9 -1.5 -1.5 1.4 - .2 0

- .l .5 0 0 0 - .2 .2 0 0 .2 0 0 0 .2 0 - .l 0 .6 1.0 0 - .2 .2 .2 1.2

- .2 1.2 0 0 0 - .6 .6 0 0 .3 0 0 0 .5 0 - .3 0 .3 1.2 0 .5 .6 .6 1.3

Mean

S.D.

.46 - .02 3.56 - .34 - .68 .14 .94 -2.18 1.38 -7.24 .42 - .28 2.44 - .82 - .9 - .34 1.18 .7 1.1 - .12 - .9

.71 2.25 2.21 2.93 1.58 1.05 2.02 1.2 1.6 4.56 1.37 2.04 2.49 1.34 .56 1.47 .87 1.44 2.89 1.57 .46 .53 .49 .84 1.29 1.22 1.98 1.86 1.13

.48 1.14 - .54 -1.06 2.46 1.12 - .52

T

1.45 0 3.6 .26 .96 13.0 1.04 4.07 1.93 3.56 .69 .2 2.12 1.37 3.6 .52 3.05 1.09 .4 .2 4.35 .25 2.19 3.06 .94 1.94 2.78 1.35 1.03

Comment

Not significant Not significant Highly significant Not significant Not significant Not significant Not significant Highly significant More correct, not significant Significant Not significant Not significant Slight significance Not significant Significant Not significant Significant Not significant Not significant Not significant Highly significant Not significant Not significant Significant Not significant Fossa distal, not significant Significant Not significant Definite effect on some

and it certainly would have been better if a larger sample of patients from 5 to 7 years of age had been used. It would be still better if all the patients were treated for similar amounts of time. This would reduce the variation in expectancy. The ideal, of course, would be to have a twin study in which one twirl would be kept as a control. This method, however, is the next best thing. It is more accurate than comparing the measurements and simply saying that the gonial angle decreased. Those analyses were not as sophisticated as this, which at least takes into account expected changes that would occur without treatmenl-. This type of procedure has not been used before. Results

and

discussion

As of this writing, all of the cases have maintained their corrected occlusal positions. It is anticipated that the chin cup will be necessary again during active growth.

68

Vego

In reviewing the statistically significant findings in Table I, the most obvious and expected change is that of the lower incisor. It became more upright and, as a result, less protrusive. The maxillary incisors became more protrusive. Very likely, similar changes could be achieved with an intraoral appliance and simple “bite jumping,” Facial depth, or the Downs’ facial angle, was reduced significantly. This is a primary goal in the correction of prognathism of the mandible. The mandibular plane angle was reduced significantly, as well as the gonial angle. The posterior facial height was increased significantly. If one studies the composite tracings of the forecast face with the treated case (Fi g. 9), additional bone at the posterior inferior border of the mandible and the posterior aspect of the ramus can be seen. In viewing the composites of the before- and after-treatment tracings (Fig. lo), one can also readily observe the posterior changes. This is especially true if one keeps in mind that posterior facial height increases half the quantity of the increase in pogonion. These findings definitely support the work of Graber” who, in a study of thirty-five Class III cases, found that the better the patient’s cooperation, the more vertical the direction and the more successful the therapy. Angle S-NA-B was constant or reduced. Lower anterior face height remained the same or was reduced slightly. Posterior face height did increase, along with a decrease in the gonial angle. There is no question but that these patients will require more chin-cup therapy as prepubescence is approached. Graber and Swain12 have stated that the therapeutic requirement depends on the dominance of the morphogenic pattern. The greatest changes in the shortest time period took place in the two youngest patients. This was revealed in the change of the mandibular arc. The mandibular arc is a measure of the corpus and the condylar axis. The mandibles tended to become more square. Remodeling of the bone occurred around point B. This change was probably due to the direct pressure of the chin cup. During treatment this area occasionally becomes inflamed. One notable change is that of the soft tissues. The upper lip at the level of point A increases in thickness. In this may a desirable esthetic change is noted in all the patients. The only explanation for this phenomenon is that the upper lip is restrained by the lower lip in the Class III anterior occlusion. After the dental correction is achieved, the upper lip assumes an enlarged flaccid position. The patients were examined for temporomandibular joint pathosis and any masticatory muscular aberration. None was detected. Summary

ajnd

conclusions

Early short-term use of the chin cup resulted in the following significant findings in Class III skeletal problems: 1. A decrease in the gonial, mandibular, and SNB angles. 2. An increase in posterior facial height as a result of increased ramal height. 3. A faster and more pronounced result in the younger patients. 4. Correction of the Class III malocclusion.

These findings negate the idea that Class III traction simply repositions the condyle within the fossa. When tracings are superimposed, it is obvious that these changes are not that of a rigid body. It is believed that the change is tluc to remodeling of the mandible itself. The shape changes as a result of the extrin sic mechanical forces plus the intrinsic functional requirements of the newly determined position. The question arises as to what degree the new functional homeostatic relationship can overcome the genetic aberration of a more forwardgrowing mandible. This conflict will probably vary with each individual and may be predictable in the near future. However, should the aberrant growth manifest itself, it would simply require renewed force application. Appreciation J. Chaconas for

goes to Mr. his suggestions

Robert Schulhof and assistance

for with

his aid in the the manuscript.

statistics

and

to

Dr.

Spiro

REFERENCES

1. Stockli, P. W., and Willert, H. G.: Tissue reactions in the temporomandibular joint rtsulting from anterior displacement of the mandible in the monkey, AM. J. ORTHOD. 60: 142-155, 1971. 2. Case, C. : Dental orthopedics, Chicago, 1921, C. S. Case Company. 3. Kingsley, N. TV.: Oral deformities, New York, 1879, D. Appleton & Company. 4. Tweed, C. H.: Clinical orthodontics; St. Louis, 1966, The C. V. Mosby Company. 5. Strang, R. H. XV., and Thompson, W. M.: A text-book of orthodontia, Philadelphia, 1953, Lea & Febiger. 6. U. S. Department of Health, Education and Welfare: An assessment of the occlusion of the teeth of children 6-11 years, Health Resources Administration, 74-1612, Rockville, Md., November, 1973. 7. McNamara, J. A., Jr.: Neuromuscular and skeletal adaptations of altered orofacial fumtion, Ann Arbor, 1972, Center for Human Growth and Development, The University of Michigan. 8. Hopkin, G. B. : The growth factor in the prognosis of treated cases of Angle Class 111 maloc~clusion, Report of the Forty-first Congress, Stockholm, Sweden, June 15-19, 1965. 9. Petrovic, A. G.: Mechanisms and regulation of mandibular condylar growth, Acta Morphol. Neerl. Stand. 10: 25-34, 1972. 10. Charlier, J. P., Petrovic, A., and Herman-Stutzmann, J.: Effects of mandibular hyprrpropulsion of the prechondroblastic zone of young rat condyle, Am. J. Orthod. 55: 71-74, 1969. 11. Graber, T. M., Chung, D. D. B., and Aoba, J. T.: Dentofacial orthopedics versus orthodontics, J. Am. Dent. Assoc. 75: 1145-1166, 1967. 12. Graber, T. M., and Swain, B. F.: Current orthodontic concepts and techniques, Philadelphia, 1975, W. B. Saunders Company, p. 383. 13. De Alba, J. A., Chaconas, 8. J., and Caputo, A. A.: Orthopedic effect of the extraoral chincup appliance on the mandible, A&X. J. ORTHOD. 69: 29-41, 1976. 14. Graber, L. W.: The effects of orthopedic force on Class III malocclusion during the mixed dentition period, Master’s thesis, Northwestern University, 1955,. 15. Angle, E. H.: Treatment of malocclusion of teeth, Philadelphia, 1907, S. 8. White Dental Manufacturing Company. 16. Joho, J. P.: The effects of extraoral low-pull traction to the mandibular dentition of Mncacu mulatta, Ahl. J. ORTHOD. 64: 555-577, 1973. 17. Ricketts, R. M.: The university instruction manual, R.ocky Mountain Data Systems, lnl-., 1974. UCLA

School

of Dentistry

(90064)