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Vertical control: A multifactorial problem and its clinical implications
Vertical control: A multifactorial problem and its clinical implications Meropi
N. Spyropoulos,
D.D.S.,
MS.,*
and
Monigeh
Askarieh,
D.D.S.,
MS.**
Ann
Arbor, Mich., and Teheran, Zmn
T
he concept of “vertical control” initially appeared in the orthodontic literature about a decade ago. As aware orthodontists began to evaluate and reevaluate cases, the significance of this concept became one of the most important concerns of current orthodontics. What is meant by “vertical control”? Let us think about it first as dentists and then as orthodontists. Control of vertical dimension in dentistry means assessing, and or re-establishing, the individual’s proper vertical facial proportions during operative or prosthetic procedures (for example, the tedious and meticulous steps of bite registration during denture construction). In orthodontics, the term refers to the orthodontist’s awareness of the possible changes in the vertical facial dimensions of the growing orthodontic patient and the implications in the control of these changes toward achieving the best possible end result. The purpose of this article is to describe the changes that occur during orthodontic treatment, to analyze the desirable and undesirable aspects of these changes, and to survey the factors involved in their production and the clinical implications of their control or lack of control. Changes
in the
vertical
fadcal
dimensions
The changes that can be observed in the vertical dimension of a growing orthodontic patient involve always the concept of relativity. To assess a change, we have to compare two basic situations, values, or ratios. We should, therefore, define in these terms what we are going to compare when we refer to changes and focus our attention on the clinically significant ones. If we compare the over-all vertical facial dimension on pretreatment and posttreatment cephalometric tracings of an orthodontic patient by superimposi*Assistant
Professor,
Department
of Orthodontics,
School
of Dentistry,
University
Michigan. ‘*Assistant 70
Professor,
Department
of Orthodontics,
National
School
of Iran.
of
Vertical
conlrol
71
tion on SN and registration at S (or on DeCoster’s line), we may observe one o1 the following : A. A harmonious increase in the anterior as well as the posterior facial heights, with the palatal, occlusal, and mandibular planes changing in a parallel direction. This would give constancy in the pretreatment, and posttreatment ratio of the upper (N-ANS) to the lower (ANS-31) anterior facial height; also, in the ratio between the posterior facial height (Ar to mandibular plane tangent to the posterior border of the ramusls) and the lower anterior facial height. This type of change: will be referred to as change type A. B. An increase in the anterior facial height without a proportional increase in the posterior facial height. An accompanying feature is a backward movement of the chin, expressing a downward and backward rotation of the mandible (clockwise). This lack of proportionality of anterior facial height increase as related to the posterior facial height increase may be due to (1) an increase in the X-ANS distance, (2) an increase in the ANS occlusal plane distance, (3) an increase in the occlusal plane-mandibular plane distance, and (4) a combination of all or some of the above. Consequently, there may be a change in the ratio between the upper and lower anterior facial heights as well as in the ratio between the posterior and anterior lower facial heights. This type of change will be referred to as cha.nge type B. C. An increase in the posterior facial height without a proportional increase in the anterior facial height which might have increased to a lesser degree or not at all. An accompanying feature is a forward and upward rotation of the mandible (counterclockwise). In this case, there will also be a change in the ratio between the posterior and lower anterior facial heights. This type of change will be referred to as change type C. D. The fourth possibility that exists is rather rare; it is the possibility of no relative or absolute change whatsoever. This is most likely to occur in nongrowing (adult) patients and will be referred to as chrrngr: type D. Andysis
of
the
changes
mentioned
Desirable and undesirable chatages. Usually in patients with Class I malocclusions with a lmlanced skeletal pattern with satisfactory anteroposterior jaw relationship and no facial hyperdivergence,lF type A change is most likely to be seen, with the chin moving in a downward and forward direction. This type of change is also the most desirable since the facial balance remains undisturbed. In patients with hyperdivergent facial skeleton and a steep mandibular plane, there are two subcategories : 1. Those with a convex profile, an increased ANB angle, and a Class II, Division 1 malocclusion accompanied by an open-bite tendency. In these patients, the most probable changes are those of type B, which arc
72
Xpyropoulos
and Askarieh
Am.
J. Orthod. July 1976
also very undesirable because they (1) result in an increase of facial hyperdivergence, (2) accentuate the chin recession and the facial convexity, (3) accentuate the anteroposterior jaw discrepancy (B point moves downward and backward), (4) accentuate the lower anterior facial height which is usually long already, and (5) increase the openbite tendency. The clinical problems related to these changes are: difficulty in reducing the ANB angle, difficulty in correcting molar relationship, and extrusion of upper incisors to overcome the open-bite tendency. The extrusion of the upper incisors makes torque control a problem and causes display of upper gingival tissue on smiling. On the other hand, for this type of patient, change type C is very desirable as it will affect favorably both the profile and the correction of the malocclusion. 2. Those with a concave profile, a negative ANB angle, and a Class III malocclusion described by Tweedz3 as Class III, Category B malocclusion. In these patients, the change type B, by moving B point posteriorly, tends to reduce the anteroposterior jaw discrepancy and to decrease the chin protrusion. Yet, this type of change has the following undesiraable aspects: (1) it increases the facial hyperdivergence, (2) it increases the open-bite tendency, and (3) it accentuates the length of the already long face. We cannot, however, claim that change type C would be desirable either. Depending, therefore, on the severity of the case, surgical orthodontics sometimes provides the solution of choice. In patients with hypodivergent facial skeleton with a very flat mandibular plane, decreased anterior lower facial height, and deep-bite tendency, there are also two subcategories : 1. Patients with an anteroposterior jaw discrepancy expressed by an increased ANB angle and a Class II, Division 2 malocclusion. In these cases, the most desirable change is type B because it would (1) increase the lower anterior facial height and thus improve the facial profile, (2) help in the correction of the deep-bite, and (3) correct the hypodivergency of the face. However, this type of change would also accentuate anteroposterior jaw discrepancy (through the downward and posterior movement of B point) and increase the ANB angle. In order to assess correctly the clinical significance as well as the desirability of type B change, we should, however, take into consideration the fact that, in many of these cases, the large ANB value is due to a posteriorly locked mandible and a very upright position of the upper incisors, causing the A point to come forward. 2. Patients with a concave profile, a negative ANB angle and a Class III, Category A malocclusion. 23 In these cases, type B change is desirable as it will have a beneficial effect on both the profile and the correction of the malocclusion. Type C change is undesirable as it will (1) accentuate the concavity
of the face by bringing the chin forward, (2) increase the tendency for deep-bite, (3) accentuate the hypodivergency of the face, and (4) decrease the already reduced anterior facial height. Factors
involved
in changing
the
vertical
facial
dimension
&o&h. Ever since the publication of SchudyW article on the effect of vertical versus anteroposterior growth upon facial type, a new aspeat in tlls evaluation of orthodontic cases came into focus; this aspect is oriented toward the factors causing downward and/or forward movement of the chin during growth. Some years earlier, Scott 22 had observed that ‘icertain types of faCeS are associated with a tendency toward certain kinds of malocclusion.” Through the study of “the facial frame,” the “pogonion formula,” and the “clockwise” and L’anti~lo~kwise” rotation of the mandible, 18,10 the mechanism of growth in hygerand hypodivergent faces was documented. It is well understood today that the differential growth at the condyles and at the molar alveolar bone is responsible for the rotation of the mandible and hence the position of the chin. If the total vertical growth of the face (that is, the growth between the cranial base, the palate, the occlusal plane, and the lower border of the mandible) equals the total increase in length of the mandible through condylar growth, then the chin grows downward and forward in a uniform pattern; if we superimpose progress head film tracings on the Ala-nasion plane registered on R, WC observe that the mandibular plane remains parallel to t,he original.‘” More vertical growth at the molar area than at the mandibular condyles results in a clockwise rotation of the mandible (type B change). On the other hand, counterclockwise rotation of the mandible (type C change) is a result of more condylar growth as compared to vertical growth at the molars. In other words, an increase in the vertical growth at the molar area has the same effect on the direction of the chin as a decrease in the condylar growth and vice versa,2o Clinical observations and studies of cephalometric films of both orthodontically treated and untreated patient+ 3, l3~16 provided us with some indications of the probable growth potential of the various skeletal patt,erns. These indications can be summarized as follows: 1. The degree of facial divergence has an effect upon the degree of rotation of the mandible; that is, the more divergent a face, the greater the tendency toward vertical growth. 2. The size of the gonial angle affects the amount of rotation of the mandible; that is, the more obtuse the angle, the greater the tendency toward vertical growth. 3. The greater the antegonial notch, the greater the tendency toward vertical growth. Treatment. Several studies on orthodontically treated patients as well as on untreated persons have documented the fact that forces applied to the teeth through orthodontic appliances have a substantial influence on the vertical facial dimension. This influence is as follows : 1. Extraoral forces. One of the most extensively studied forces used during orthodontic treatment is the one applied through extraoral anchorage.
74
~p~rOpOul0s
ad
flskarieh
Am.
J. Orthod. July1976
The first appliance used in this respect was Kloehn’s cervical face-bow. Ever since, many modifications of the original pattern have been made, with the hook-on headgear type extensively used. Klein6 was one of the first investigators to report a retardation in forward movement of point A and a downward tipping of the anterior aspect of the palatal plane in patients undergoing treatment with extraoral force. Schudy17 documented these findings, and since then a number of authors have studied the influence of the direction of pull of the extraoral forces on the teeth and the palatal and occlusal planes.1s 3t s-11>24 The conclusions from these studies seem to coincide in that the direction of pull of the extraoral forces can influence the direction of mandibular rotation. If the direction of the extraoral force is : A. Downward and backward, that is, cervical pull, there may be extrusion of teeth, resulting in a potential clockwise rotation of the mandible, causing the chin to move downward and backward. There may also be a potential for temporomandibular joint disturbances as the teeth move into the freeway space and the condyles are guided into new positions so that the teeth occ1ude.14 B. Backward in a straight direction, that is, straight pull, there will be no extrusion of teeth and hence no influence on the movement of the chin. C. Obliquely backward and upward, that is, high pull, there will be control or even suppression of the eruption of teeth which will minimize the clockwise rotation of the mandible or even enhance an anticlockwise rotation ; this happens by allowing the growth of the condyles to be expressed in a forward direction since the growth at the molars is minimized or eliminated. The orthodontist’s decision as to what kind of pull should be used in each case should be based on the results that he wishes to obtain on the facial esthetics. 2. Internzaxillary elastics. Intermaxillary elastics may cause extrusion of teeth and changes in the facial vertical dimension. RickettPv I3 reported a 2.5 to 3.3 mm. elevation of the lower first molar after use of Class II elastics. It is worth while mentioning how well aware Tweed was of this fact. Even though it has never been precisely mentioned by him, the whole concept of anchorage preparation in the lower arch as a prerequisite for the use of Class II elastics is an answer to the side effects of their use. The most common types of intermaxillary elastics used in orthodontic treatment are: A. Class ZI elastics. If used with care on a prepared and stabilized lower arch, the amount of tooth extrusion can be minimal. B. Class III elastics. If used in conjunction with the appropriate directional extraoral force, tooth extrusion can be very well controlled. C. Vertical elastics. Used usually when extrusion of teeth is indicated or to counteract intrusive forces applied through other procedures.
D. Cross-bite
elastics. They may cause a certain amount of tooth extrusion. 3. Arch wires. Any arch wire can cause extrusion of teeth, depending on the irregularity of the teeth, the severity of the curve of Spee, the shape of the arch wire, etc. A reverse curve of Spee in a mandibular arch wire applied on an already leveled dental arch is said to cause extrusion of the premolarsi which, in turn, will influence the rotation of the mandible in a clockwise manner. 4. Bite planes. Bite planes may cause an intrusion of the lower incisor teeth and/or eruption of the upper and lower posterior teeth. They, therefore, may influence the rotation of the mandible. 5. Actiuutor. It is reported in the literature that the use of an activator can influence the vertical facial dimension in growing persons; this depends on which teeth are stopped by the plate occlusally and which are left free to erupt.4 Clinical experience, however, supports the view that the use of an activator is contraindicated in cases with a very steep mandibular plane and increased lower anterior facial height. 6. Orthopedic forces. A. Palntal expnGo?l. The effect of palatal expansion on the facial vertical dimension is very well summarized in the following: “The change in maxillary posture (forward and downward movement of point A), invariably causes a downward and backward rotation of the mandible which dec.reases the effective length of the mandible and increases the vertical dimension of the lower face.“” B. Chin cop. The use of a chin cap may influence t,he vertical dimension of the lower face by holding or pulling the chin upward. It is indicated, therefore, in combination with the palatal expansion proccdure when clockwise rotation of the mandible is undesirable or in cases with increased lower facial height and a tendency toward mandibular prognathism as, for example, in early treatment of skeletal Class III cases. Combimtio?L of the above nzention.ed factors. One of the current concepts of orthodontic diagnosis and treatment is that “terminal growth and differential anchorage are relied upon for the final harmony of the masticatory apparat,us.‘“’ It is, therefore, obvious and of the utmost clinical significance that the orthodontist should be well aware of the effects that any of the possible combinations of the above factors may have on any specific case. IIis efforts and success in controlling them are the essence of vertical control. Unfortunately, Creekmore” says, “the high angle faces tend to become even higher, whereas the low angle faces tend to get lower.” However, “the control of posterior tooth eruption is the most manageable factor available to t,he orthodontist in the overall control of anterior vertical dimension of the lower facc.“8 In patients with steep mandibular planes and unfavorable growth patterns, it seems that the musculature (force and direction of muscle pull) is also nnfavorable; molars will extrude readily in response to even the lightest forces and will seldom reintrude after the end of treatment. On t,he contrary, in patients
76
8pyropoulos
Fig.
1. A case
case, growth by
treatment
and
Askarieh
illustrating the effect of did-not help in any respect procedures alone.
Am. J. Orthod. July1976
good and
treatment the very
on the satisfactory
“vertical control.” end result was
In this achieved
with flat mandibular planes, it is usually very difficult to cause extrusion of the molars and hence clockwise rotation of the mandible ; furthermore, if this ever happens during treatment, there is a strong tendency toward reintrusion and reestablishment of the flatness of the mandibular plane through the influence of the musculature. The main conclusions as regards the effect of the combinations of growth and treatment procedures on the vertical facial dimension can be summarized as follows : A combination of proper treatment procedures with a poor skeletal and muscular pattern and growth or a combination of poor treatment planning with a favorable skeletal and muscular pattern and growth can create tolerable results. On the other hand, a combination of improper treatment with a poor skeletal and muscular pattern and growth can turn out to be literally disastrous. Case
reports
The cases selected for discussion in this article were treated in the Department of Orthodontics of the University of Michigan by graduate students. Core
1
M.S., a 14year-old, ?ngle, and an open-bite. both the mad& and
girl, had a Class II, Division 1 malocclusion, The case was complicated by an excessive mandibular arches and an overjet of 8 mm.
a high mandibular plane amount of crowding in Taking into consideration
Vertical
Fig. 2. A case This occurred molars. The
control,
illustrating the undesirable effects of “clockwise” mandibular because growth at the condyle did not compensate for the extrusion forces used during treatment were not the proper directional forces.
77
rotation. of the
the age and sex of the patient as well as her skeletal pattern, one can realize the problems involved in the treatment of this case. The patient was treated for 2 years with a full-banded edgewise Tweed technique, and treatment involved the removal of all first premolars. Throughout the whole treatment period, anchorage and vertical control were taken care of with directional extraoral forces, namely, high-pull face-bow, straight-pull headgear, and high-pull headgear. Toward the end of treatment, vertical elastics were used in conjunction with the high-pull headgear to establish proper vertical relationship of the anterior teeth. When superimposing the tracings of the pretreatment and posttreatment cephalometric x-ray films on SN registered on S (Fig. l), we can observe the following: Growth did not help whatsoever in the treatment of t.his case and the corrections achiev-i4 were the results of accurate and proper treatment procedures. As regards vertical control in this ease, we can characterize it as very satisfactory. None of the undesirable changes (type B) took place, since there was no increase in the mandibular plane angle, the ANB angle, or the lower anterior facial height. When we superimpose the beforeand after-treatment, tracings of the upper and loner jaws separately, it becomes obvious that no extrusion of the molars took place, which is to the credit of the treatment procedures used. Care
2
LX., a 12-year-old girl had a Class II, Division 1 malocclusion, deficient mandible; there was a high mandibular plane angle, moderate mandibular crowding, an excessive overjet, and a minimal The period of active treatment, which involved the extraction the patient was 2 years with a full-banded edgewise technique;
a convex profile, and a an excessive maxillary and overbite. of all four first premolar’s was very cooperative. Yet,
78
Spyropoulos
md
Fig. 3. The favorable treatment just with
the
Am. J. Orthod. Jztlf/ 1976
Askarieh
growth use
of
that the
occurred activator.
in this
case
made
possible
the
completion
of
when we superimposed the tracings of the pre- and posttreatment cephalometric x-ray films on SN, registered on 5, we have to admit that this case lacked vertical control (Fig. 2). The negative factors involved in this case can be summarized as follows: Unfavorable growth. The tendency for vertical growth which this case exhibited before treatment was expressed in its maximum during the treatment time. Improper treatment procedzcres. The forces applied during treatment were not the appropriate ones to minimize the expression of the mandibular growth in a vertical direction ; on the contrary, by their use, both the upper and lower molars were extruded (Fig. 2). As a consequence, type B change occurred; that is; the lower anterior facial height increased, the whole lower face dropped backward and downward, the soft tissues appeared strained, the convexity of the face increased, the nose became more prominent in the convex profile, the upper incisors extruded, and a substantial amount of gingiva was displayed upon smiling. Going through the record of this patient, we can pinpoint the causal forces during the various stages of treatment: straight-pull extraoral forces, Class III elastics, and excessive reverse curve of Spee in the lower leveling arches. This case illustrates very clearly the detrimental effects that a combination of improper treatment procedures and unfavorable growth may have on orthodontic objectives. Case
3 (Appliance
used:
AcfivaWr)
When the activator is used in the Orthodontic Department of the University of Michigan, it is generally as a precomprehensive orthodontic appliance ; the cases treated initially with the activator usually undergo a later second stage
Vertical
codrol
79
of full-l)an&d comprehensive treatment. The ease 1)resented here was an c~ccl)tion to tlic rule and was selected because trcatmcnt was completed with the activatar alone as the growth was estremcly favorable. A 12-year-old boy, P.C., with a Class II, Division 1 malocclusion, an excessive overjet, and He was a very cooprratiw patient, :~ni a deep overbite was subjected to activator treatment. his active treatment was completed in 16 months without any need for further treatment, 1”‘” cedures. The superimposition of the tracings of his pretreatment and posttreatment cephalometri(, films on SN, registered on S, shows some very satisfactory changes (Fig. 3 ). The palatal, o(’ clusal, and mandibular planes remained parallel. The overjrt as well as the owrbitc KCW ~c’r! much reduced, and the lower face as a whole came forward and dowwnrtl. In this case, growth was the unique factor for the correction of the malocclusion; tlrl$ did not interfere \vith It e treatment procedures did not extrude the molars and, therefore, maximal
expression
of the favorahle
growth
potential.
Summary
In this article we have tried to analyze the importance of vertical control in orthodontic cases, as well as the factors affecting it. From the cases presentett, it can be assumed that : 1. In vertically growing or nongrowing persons (high-angle cases), thelapplication of proper directional forces becomes cstremely critical because a cloclrwise rotation of the mandible can occur very promptly and is very undesirable. 2. In cases with favorable growth potential, the results may be acceptable, even if the forces applied during t,reatment arc not absolutely controlled; in other words, Mother Xature may often compensate for inappropriate or miscalculated treatment procedures. REFERENCES
I. Armstrong, M. M.: Controlling the magnitude, direction, and duration of extraoral forw Aar. J. ORTHOD. 59: 217,1971. 2. Bjork, A.: Prediction of mandibular growth rotat,ion, AU. J. ORTHOD. 55: 585, 1969. 3. Creekmore, T. D.: Inhibition or stimulation of the vertical growth of the facinl complex, Angle Orthod. 37: 285, 1967. 4. Harvold, E. P., and Vargervik, K.: Morphogenetic response to activator treatment, AAI. J. ORTHOD. 60: 478, 1971. 5. Haas, A. J. : Palatal expansion: Just the beginning of dentofacial orthopedics, Ant. .I.
ORTIIOD. 57: 219, 1970. 6. Klein, P.: An evaluation of cervical traction on the maxilla and the upper first permanent molar, Angle Orthod. 27: 61, 1907. 7. Klontz, H., and Noffel, E.: Directional forces in edgewise Tweed technique, short course, University of Michigan, Ann Arbor, Jan. 17-18, 1975. 8. Kuhn, R. J.: Control of anterior vertical dimension and proper selection of extraoral mchorage, Angle Ort.hod. 38: 341, 1968. 9. Merrifield, L. L., and Cross, J. J.: Directional forces, AM. J. ORTHOD. 57: 435, 1970. 10. Pearson, L. E.: Vertical control through use of mandibular posterior intrusive forces, Angle Orthod. 43: 194, 1973. 11. Poulton, D. R.: The influence of extraoral traction, Aar. J. ORTHOD. 53: 8, 1967. 12. Ricketts, R. M.: Planning treatment on the basis of facial pattern and estimate of its growth, Angle Orthod. 27: 11, 1957. 13. Ricketts, R. M.: The influence of orthodontic treatment on facial growth and development, Angle Orthod. 30: 103, 1960.
80
Spyropoulos
and Askarieh
Am.
J. Orthod. July 1976
14. Roth, R. D.: Temporomandibular pain dysfunction and occlusal relationships, Angle Orthod. 43: 136, 1973. 15. Root, T. L.: Anchorage concepts based upon the vertical dimension, monogral)h, unpublished material, 16. Sassouni, V.: A classification of skeletal facial types, AM. J. ORTHOD. 55: 109, 1969. 17. Schudy, F. F.: Cant of the occlusal plane and axial inclinations of teeth, Angle Orthod. 33: 69, 1963. 18. Schudy, F. F.: Vertical growth versus anteroposterior growth as related to function and treatment, Angle Orthod. 34: 75, 1964. 19. Schudy, F. F.: The rotation of the mandible resulting from growth: Its implications in orthodontic treatment, Angle O&hod. 35: 36, 1965. 20. Schudy, F. F.: The control of vertical overbite in clinical orthodontics, Angle Orthod. 38: 19, 1968. 21. Schudy, F. F.: Sound biological concepts in orthodontics, AM. J. ORTHOD. 63: 376, 1973, 22. Scott, J. H.: The analysis of facial growth, AM. J. ORTHOD. 44: 507, 1958. 23. Tweed, C. H.: Clinical orthodontics, St. Louis, 1966, The C. V. Mosby Company, pp. 716, 720. 24. Worms, F. TV., Isaacson, R., and Speidel, T. M.: A concept and classification of centers of rotation and extraoral force systems, Angle Orthod. 43: 385, 1973.
THE JOURNAL 60 YEARS AGO July,
1916
The question of postgraduate instruction in the dental profession is at the present time somewhat of a problem, and courses are only in a developmental state. Among the first endeavors which we noticed of a post-graduate nature were the study clubs, which it is our impression were organized first in Iowa by men who took up certain lines of work under the tutelage of prominent men in the profession. The activities of these study clubs in Iowa had a very marked effect, for it seems that the dental profession in Iowa displayed greater interest in this subject than is manifested anywhere else by dentists in the United States. The plan adopted by these clubs could be followed advantageously by dentists in other parts of the country. (Martin Dewey: Editorial. Orthodontia and Postgraduate Instruction, International Journal of Orthodontia, predecessor of the American Journal of Orthodontics, 2:328, 1916.)
N. Spyropoulos,
D.D.S.,
MS.,*
and
Monigeh
Askarieh,
D.D.S.,
MS.**
Ann
Arbor, Mich., and Teheran, Zmn
T
he concept of “vertical control” initially appeared in the orthodontic literature about a decade ago. As aware orthodontists began to evaluate and reevaluate cases, the significance of this concept became one of the most important concerns of current orthodontics. What is meant by “vertical control”? Let us think about it first as dentists and then as orthodontists. Control of vertical dimension in dentistry means assessing, and or re-establishing, the individual’s proper vertical facial proportions during operative or prosthetic procedures (for example, the tedious and meticulous steps of bite registration during denture construction). In orthodontics, the term refers to the orthodontist’s awareness of the possible changes in the vertical facial dimensions of the growing orthodontic patient and the implications in the control of these changes toward achieving the best possible end result. The purpose of this article is to describe the changes that occur during orthodontic treatment, to analyze the desirable and undesirable aspects of these changes, and to survey the factors involved in their production and the clinical implications of their control or lack of control. Changes
in the
vertical
fadcal
dimensions
The changes that can be observed in the vertical dimension of a growing orthodontic patient involve always the concept of relativity. To assess a change, we have to compare two basic situations, values, or ratios. We should, therefore, define in these terms what we are going to compare when we refer to changes and focus our attention on the clinically significant ones. If we compare the over-all vertical facial dimension on pretreatment and posttreatment cephalometric tracings of an orthodontic patient by superimposi*Assistant
Professor,
Department
of Orthodontics,
School
of Dentistry,
University
Michigan. ‘*Assistant 70
Professor,
Department
of Orthodontics,
National
School
of Iran.
of
Vertical
conlrol
71
tion on SN and registration at S (or on DeCoster’s line), we may observe one o1 the following : A. A harmonious increase in the anterior as well as the posterior facial heights, with the palatal, occlusal, and mandibular planes changing in a parallel direction. This would give constancy in the pretreatment, and posttreatment ratio of the upper (N-ANS) to the lower (ANS-31) anterior facial height; also, in the ratio between the posterior facial height (Ar to mandibular plane tangent to the posterior border of the ramusls) and the lower anterior facial height. This type of change: will be referred to as change type A. B. An increase in the anterior facial height without a proportional increase in the posterior facial height. An accompanying feature is a backward movement of the chin, expressing a downward and backward rotation of the mandible (clockwise). This lack of proportionality of anterior facial height increase as related to the posterior facial height increase may be due to (1) an increase in the X-ANS distance, (2) an increase in the ANS occlusal plane distance, (3) an increase in the occlusal plane-mandibular plane distance, and (4) a combination of all or some of the above. Consequently, there may be a change in the ratio between the upper and lower anterior facial heights as well as in the ratio between the posterior and anterior lower facial heights. This type of change will be referred to as cha.nge type B. C. An increase in the posterior facial height without a proportional increase in the anterior facial height which might have increased to a lesser degree or not at all. An accompanying feature is a forward and upward rotation of the mandible (counterclockwise). In this case, there will also be a change in the ratio between the posterior and lower anterior facial heights. This type of change will be referred to as change type C. D. The fourth possibility that exists is rather rare; it is the possibility of no relative or absolute change whatsoever. This is most likely to occur in nongrowing (adult) patients and will be referred to as chrrngr: type D. Andysis
of
the
changes
mentioned
Desirable and undesirable chatages. Usually in patients with Class I malocclusions with a lmlanced skeletal pattern with satisfactory anteroposterior jaw relationship and no facial hyperdivergence,lF type A change is most likely to be seen, with the chin moving in a downward and forward direction. This type of change is also the most desirable since the facial balance remains undisturbed. In patients with hyperdivergent facial skeleton and a steep mandibular plane, there are two subcategories : 1. Those with a convex profile, an increased ANB angle, and a Class II, Division 1 malocclusion accompanied by an open-bite tendency. In these patients, the most probable changes are those of type B, which arc
72
Xpyropoulos
and Askarieh
Am.
J. Orthod. July 1976
also very undesirable because they (1) result in an increase of facial hyperdivergence, (2) accentuate the chin recession and the facial convexity, (3) accentuate the anteroposterior jaw discrepancy (B point moves downward and backward), (4) accentuate the lower anterior facial height which is usually long already, and (5) increase the openbite tendency. The clinical problems related to these changes are: difficulty in reducing the ANB angle, difficulty in correcting molar relationship, and extrusion of upper incisors to overcome the open-bite tendency. The extrusion of the upper incisors makes torque control a problem and causes display of upper gingival tissue on smiling. On the other hand, for this type of patient, change type C is very desirable as it will affect favorably both the profile and the correction of the malocclusion. 2. Those with a concave profile, a negative ANB angle, and a Class III malocclusion described by Tweedz3 as Class III, Category B malocclusion. In these patients, the change type B, by moving B point posteriorly, tends to reduce the anteroposterior jaw discrepancy and to decrease the chin protrusion. Yet, this type of change has the following undesiraable aspects: (1) it increases the facial hyperdivergence, (2) it increases the open-bite tendency, and (3) it accentuates the length of the already long face. We cannot, however, claim that change type C would be desirable either. Depending, therefore, on the severity of the case, surgical orthodontics sometimes provides the solution of choice. In patients with hypodivergent facial skeleton with a very flat mandibular plane, decreased anterior lower facial height, and deep-bite tendency, there are also two subcategories : 1. Patients with an anteroposterior jaw discrepancy expressed by an increased ANB angle and a Class II, Division 2 malocclusion. In these cases, the most desirable change is type B because it would (1) increase the lower anterior facial height and thus improve the facial profile, (2) help in the correction of the deep-bite, and (3) correct the hypodivergency of the face. However, this type of change would also accentuate anteroposterior jaw discrepancy (through the downward and posterior movement of B point) and increase the ANB angle. In order to assess correctly the clinical significance as well as the desirability of type B change, we should, however, take into consideration the fact that, in many of these cases, the large ANB value is due to a posteriorly locked mandible and a very upright position of the upper incisors, causing the A point to come forward. 2. Patients with a concave profile, a negative ANB angle and a Class III, Category A malocclusion. 23 In these cases, type B change is desirable as it will have a beneficial effect on both the profile and the correction of the malocclusion. Type C change is undesirable as it will (1) accentuate the concavity
of the face by bringing the chin forward, (2) increase the tendency for deep-bite, (3) accentuate the hypodivergency of the face, and (4) decrease the already reduced anterior facial height. Factors
involved
in changing
the
vertical
facial
dimension
&o&h. Ever since the publication of SchudyW article on the effect of vertical versus anteroposterior growth upon facial type, a new aspeat in tlls evaluation of orthodontic cases came into focus; this aspect is oriented toward the factors causing downward and/or forward movement of the chin during growth. Some years earlier, Scott 22 had observed that ‘icertain types of faCeS are associated with a tendency toward certain kinds of malocclusion.” Through the study of “the facial frame,” the “pogonion formula,” and the “clockwise” and L’anti~lo~kwise” rotation of the mandible, 18,10 the mechanism of growth in hygerand hypodivergent faces was documented. It is well understood today that the differential growth at the condyles and at the molar alveolar bone is responsible for the rotation of the mandible and hence the position of the chin. If the total vertical growth of the face (that is, the growth between the cranial base, the palate, the occlusal plane, and the lower border of the mandible) equals the total increase in length of the mandible through condylar growth, then the chin grows downward and forward in a uniform pattern; if we superimpose progress head film tracings on the Ala-nasion plane registered on R, WC observe that the mandibular plane remains parallel to t,he original.‘” More vertical growth at the molar area than at the mandibular condyles results in a clockwise rotation of the mandible (type B change). On the other hand, counterclockwise rotation of the mandible (type C change) is a result of more condylar growth as compared to vertical growth at the molars. In other words, an increase in the vertical growth at the molar area has the same effect on the direction of the chin as a decrease in the condylar growth and vice versa,2o Clinical observations and studies of cephalometric films of both orthodontically treated and untreated patient+ 3, l3~16 provided us with some indications of the probable growth potential of the various skeletal patt,erns. These indications can be summarized as follows: 1. The degree of facial divergence has an effect upon the degree of rotation of the mandible; that is, the more divergent a face, the greater the tendency toward vertical growth. 2. The size of the gonial angle affects the amount of rotation of the mandible; that is, the more obtuse the angle, the greater the tendency toward vertical growth. 3. The greater the antegonial notch, the greater the tendency toward vertical growth. Treatment. Several studies on orthodontically treated patients as well as on untreated persons have documented the fact that forces applied to the teeth through orthodontic appliances have a substantial influence on the vertical facial dimension. This influence is as follows : 1. Extraoral forces. One of the most extensively studied forces used during orthodontic treatment is the one applied through extraoral anchorage.
74
~p~rOpOul0s
ad
flskarieh
Am.
J. Orthod. July1976
The first appliance used in this respect was Kloehn’s cervical face-bow. Ever since, many modifications of the original pattern have been made, with the hook-on headgear type extensively used. Klein6 was one of the first investigators to report a retardation in forward movement of point A and a downward tipping of the anterior aspect of the palatal plane in patients undergoing treatment with extraoral force. Schudy17 documented these findings, and since then a number of authors have studied the influence of the direction of pull of the extraoral forces on the teeth and the palatal and occlusal planes.1s 3t s-11>24 The conclusions from these studies seem to coincide in that the direction of pull of the extraoral forces can influence the direction of mandibular rotation. If the direction of the extraoral force is : A. Downward and backward, that is, cervical pull, there may be extrusion of teeth, resulting in a potential clockwise rotation of the mandible, causing the chin to move downward and backward. There may also be a potential for temporomandibular joint disturbances as the teeth move into the freeway space and the condyles are guided into new positions so that the teeth occ1ude.14 B. Backward in a straight direction, that is, straight pull, there will be no extrusion of teeth and hence no influence on the movement of the chin. C. Obliquely backward and upward, that is, high pull, there will be control or even suppression of the eruption of teeth which will minimize the clockwise rotation of the mandible or even enhance an anticlockwise rotation ; this happens by allowing the growth of the condyles to be expressed in a forward direction since the growth at the molars is minimized or eliminated. The orthodontist’s decision as to what kind of pull should be used in each case should be based on the results that he wishes to obtain on the facial esthetics. 2. Internzaxillary elastics. Intermaxillary elastics may cause extrusion of teeth and changes in the facial vertical dimension. RickettPv I3 reported a 2.5 to 3.3 mm. elevation of the lower first molar after use of Class II elastics. It is worth while mentioning how well aware Tweed was of this fact. Even though it has never been precisely mentioned by him, the whole concept of anchorage preparation in the lower arch as a prerequisite for the use of Class II elastics is an answer to the side effects of their use. The most common types of intermaxillary elastics used in orthodontic treatment are: A. Class ZI elastics. If used with care on a prepared and stabilized lower arch, the amount of tooth extrusion can be minimal. B. Class III elastics. If used in conjunction with the appropriate directional extraoral force, tooth extrusion can be very well controlled. C. Vertical elastics. Used usually when extrusion of teeth is indicated or to counteract intrusive forces applied through other procedures.
D. Cross-bite
elastics. They may cause a certain amount of tooth extrusion. 3. Arch wires. Any arch wire can cause extrusion of teeth, depending on the irregularity of the teeth, the severity of the curve of Spee, the shape of the arch wire, etc. A reverse curve of Spee in a mandibular arch wire applied on an already leveled dental arch is said to cause extrusion of the premolarsi which, in turn, will influence the rotation of the mandible in a clockwise manner. 4. Bite planes. Bite planes may cause an intrusion of the lower incisor teeth and/or eruption of the upper and lower posterior teeth. They, therefore, may influence the rotation of the mandible. 5. Actiuutor. It is reported in the literature that the use of an activator can influence the vertical facial dimension in growing persons; this depends on which teeth are stopped by the plate occlusally and which are left free to erupt.4 Clinical experience, however, supports the view that the use of an activator is contraindicated in cases with a very steep mandibular plane and increased lower anterior facial height. 6. Orthopedic forces. A. Palntal expnGo?l. The effect of palatal expansion on the facial vertical dimension is very well summarized in the following: “The change in maxillary posture (forward and downward movement of point A), invariably causes a downward and backward rotation of the mandible which dec.reases the effective length of the mandible and increases the vertical dimension of the lower face.“” B. Chin cop. The use of a chin cap may influence t,he vertical dimension of the lower face by holding or pulling the chin upward. It is indicated, therefore, in combination with the palatal expansion proccdure when clockwise rotation of the mandible is undesirable or in cases with increased lower facial height and a tendency toward mandibular prognathism as, for example, in early treatment of skeletal Class III cases. Combimtio?L of the above nzention.ed factors. One of the current concepts of orthodontic diagnosis and treatment is that “terminal growth and differential anchorage are relied upon for the final harmony of the masticatory apparat,us.‘“’ It is, therefore, obvious and of the utmost clinical significance that the orthodontist should be well aware of the effects that any of the possible combinations of the above factors may have on any specific case. IIis efforts and success in controlling them are the essence of vertical control. Unfortunately, Creekmore” says, “the high angle faces tend to become even higher, whereas the low angle faces tend to get lower.” However, “the control of posterior tooth eruption is the most manageable factor available to t,he orthodontist in the overall control of anterior vertical dimension of the lower facc.“8 In patients with steep mandibular planes and unfavorable growth patterns, it seems that the musculature (force and direction of muscle pull) is also nnfavorable; molars will extrude readily in response to even the lightest forces and will seldom reintrude after the end of treatment. On t,he contrary, in patients
76
8pyropoulos
Fig.
1. A case
case, growth by
treatment
and
Askarieh
illustrating the effect of did-not help in any respect procedures alone.
Am. J. Orthod. July1976
good and
treatment the very
on the satisfactory
“vertical control.” end result was
In this achieved
with flat mandibular planes, it is usually very difficult to cause extrusion of the molars and hence clockwise rotation of the mandible ; furthermore, if this ever happens during treatment, there is a strong tendency toward reintrusion and reestablishment of the flatness of the mandibular plane through the influence of the musculature. The main conclusions as regards the effect of the combinations of growth and treatment procedures on the vertical facial dimension can be summarized as follows : A combination of proper treatment procedures with a poor skeletal and muscular pattern and growth or a combination of poor treatment planning with a favorable skeletal and muscular pattern and growth can create tolerable results. On the other hand, a combination of improper treatment with a poor skeletal and muscular pattern and growth can turn out to be literally disastrous. Case
reports
The cases selected for discussion in this article were treated in the Department of Orthodontics of the University of Michigan by graduate students. Core
1
M.S., a 14year-old, ?ngle, and an open-bite. both the mad& and
girl, had a Class II, Division 1 malocclusion, The case was complicated by an excessive mandibular arches and an overjet of 8 mm.
a high mandibular plane amount of crowding in Taking into consideration
Vertical
Fig. 2. A case This occurred molars. The
control,
illustrating the undesirable effects of “clockwise” mandibular because growth at the condyle did not compensate for the extrusion forces used during treatment were not the proper directional forces.
77
rotation. of the
the age and sex of the patient as well as her skeletal pattern, one can realize the problems involved in the treatment of this case. The patient was treated for 2 years with a full-banded edgewise Tweed technique, and treatment involved the removal of all first premolars. Throughout the whole treatment period, anchorage and vertical control were taken care of with directional extraoral forces, namely, high-pull face-bow, straight-pull headgear, and high-pull headgear. Toward the end of treatment, vertical elastics were used in conjunction with the high-pull headgear to establish proper vertical relationship of the anterior teeth. When superimposing the tracings of the pretreatment and posttreatment cephalometric x-ray films on SN registered on S (Fig. l), we can observe the following: Growth did not help whatsoever in the treatment of t.his case and the corrections achiev-i4 were the results of accurate and proper treatment procedures. As regards vertical control in this ease, we can characterize it as very satisfactory. None of the undesirable changes (type B) took place, since there was no increase in the mandibular plane angle, the ANB angle, or the lower anterior facial height. When we superimpose the beforeand after-treatment, tracings of the upper and loner jaws separately, it becomes obvious that no extrusion of the molars took place, which is to the credit of the treatment procedures used. Care
2
LX., a 12-year-old girl had a Class II, Division 1 malocclusion, deficient mandible; there was a high mandibular plane angle, moderate mandibular crowding, an excessive overjet, and a minimal The period of active treatment, which involved the extraction the patient was 2 years with a full-banded edgewise technique;
a convex profile, and a an excessive maxillary and overbite. of all four first premolar’s was very cooperative. Yet,
78
Spyropoulos
md
Fig. 3. The favorable treatment just with
the
Am. J. Orthod. Jztlf/ 1976
Askarieh
growth use
of
that the
occurred activator.
in this
case
made
possible
the
completion
of
when we superimposed the tracings of the pre- and posttreatment cephalometric x-ray films on SN, registered on 5, we have to admit that this case lacked vertical control (Fig. 2). The negative factors involved in this case can be summarized as follows: Unfavorable growth. The tendency for vertical growth which this case exhibited before treatment was expressed in its maximum during the treatment time. Improper treatment procedzcres. The forces applied during treatment were not the appropriate ones to minimize the expression of the mandibular growth in a vertical direction ; on the contrary, by their use, both the upper and lower molars were extruded (Fig. 2). As a consequence, type B change occurred; that is; the lower anterior facial height increased, the whole lower face dropped backward and downward, the soft tissues appeared strained, the convexity of the face increased, the nose became more prominent in the convex profile, the upper incisors extruded, and a substantial amount of gingiva was displayed upon smiling. Going through the record of this patient, we can pinpoint the causal forces during the various stages of treatment: straight-pull extraoral forces, Class III elastics, and excessive reverse curve of Spee in the lower leveling arches. This case illustrates very clearly the detrimental effects that a combination of improper treatment procedures and unfavorable growth may have on orthodontic objectives. Case
3 (Appliance
used:
AcfivaWr)
When the activator is used in the Orthodontic Department of the University of Michigan, it is generally as a precomprehensive orthodontic appliance ; the cases treated initially with the activator usually undergo a later second stage
Vertical
codrol
79
of full-l)an&d comprehensive treatment. The ease 1)resented here was an c~ccl)tion to tlic rule and was selected because trcatmcnt was completed with the activatar alone as the growth was estremcly favorable. A 12-year-old boy, P.C., with a Class II, Division 1 malocclusion, an excessive overjet, and He was a very cooprratiw patient, :~ni a deep overbite was subjected to activator treatment. his active treatment was completed in 16 months without any need for further treatment, 1”‘” cedures. The superimposition of the tracings of his pretreatment and posttreatment cephalometri(, films on SN, registered on S, shows some very satisfactory changes (Fig. 3 ). The palatal, o(’ clusal, and mandibular planes remained parallel. The overjrt as well as the owrbitc KCW ~c’r! much reduced, and the lower face as a whole came forward and dowwnrtl. In this case, growth was the unique factor for the correction of the malocclusion; tlrl$ did not interfere \vith It e treatment procedures did not extrude the molars and, therefore, maximal
expression
of the favorahle
growth
potential.
Summary
In this article we have tried to analyze the importance of vertical control in orthodontic cases, as well as the factors affecting it. From the cases presentett, it can be assumed that : 1. In vertically growing or nongrowing persons (high-angle cases), thelapplication of proper directional forces becomes cstremely critical because a cloclrwise rotation of the mandible can occur very promptly and is very undesirable. 2. In cases with favorable growth potential, the results may be acceptable, even if the forces applied during t,reatment arc not absolutely controlled; in other words, Mother Xature may often compensate for inappropriate or miscalculated treatment procedures. REFERENCES
I. Armstrong, M. M.: Controlling the magnitude, direction, and duration of extraoral forw Aar. J. ORTHOD. 59: 217,1971. 2. Bjork, A.: Prediction of mandibular growth rotat,ion, AU. J. ORTHOD. 55: 585, 1969. 3. Creekmore, T. D.: Inhibition or stimulation of the vertical growth of the facinl complex, Angle Orthod. 37: 285, 1967. 4. Harvold, E. P., and Vargervik, K.: Morphogenetic response to activator treatment, AAI. J. ORTHOD. 60: 478, 1971. 5. Haas, A. J. : Palatal expansion: Just the beginning of dentofacial orthopedics, Ant. .I.
ORTIIOD. 57: 219, 1970. 6. Klein, P.: An evaluation of cervical traction on the maxilla and the upper first permanent molar, Angle Orthod. 27: 61, 1907. 7. Klontz, H., and Noffel, E.: Directional forces in edgewise Tweed technique, short course, University of Michigan, Ann Arbor, Jan. 17-18, 1975. 8. Kuhn, R. J.: Control of anterior vertical dimension and proper selection of extraoral mchorage, Angle Ort.hod. 38: 341, 1968. 9. Merrifield, L. L., and Cross, J. J.: Directional forces, AM. J. ORTHOD. 57: 435, 1970. 10. Pearson, L. E.: Vertical control through use of mandibular posterior intrusive forces, Angle Orthod. 43: 194, 1973. 11. Poulton, D. R.: The influence of extraoral traction, Aar. J. ORTHOD. 53: 8, 1967. 12. Ricketts, R. M.: Planning treatment on the basis of facial pattern and estimate of its growth, Angle Orthod. 27: 11, 1957. 13. Ricketts, R. M.: The influence of orthodontic treatment on facial growth and development, Angle Orthod. 30: 103, 1960.
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Spyropoulos
and Askarieh
Am.
J. Orthod. July 1976
14. Roth, R. D.: Temporomandibular pain dysfunction and occlusal relationships, Angle Orthod. 43: 136, 1973. 15. Root, T. L.: Anchorage concepts based upon the vertical dimension, monogral)h, unpublished material, 16. Sassouni, V.: A classification of skeletal facial types, AM. J. ORTHOD. 55: 109, 1969. 17. Schudy, F. F.: Cant of the occlusal plane and axial inclinations of teeth, Angle Orthod. 33: 69, 1963. 18. Schudy, F. F.: Vertical growth versus anteroposterior growth as related to function and treatment, Angle Orthod. 34: 75, 1964. 19. Schudy, F. F.: The rotation of the mandible resulting from growth: Its implications in orthodontic treatment, Angle O&hod. 35: 36, 1965. 20. Schudy, F. F.: The control of vertical overbite in clinical orthodontics, Angle Orthod. 38: 19, 1968. 21. Schudy, F. F.: Sound biological concepts in orthodontics, AM. J. ORTHOD. 63: 376, 1973, 22. Scott, J. H.: The analysis of facial growth, AM. J. ORTHOD. 44: 507, 1958. 23. Tweed, C. H.: Clinical orthodontics, St. Louis, 1966, The C. V. Mosby Company, pp. 716, 720. 24. Worms, F. TV., Isaacson, R., and Speidel, T. M.: A concept and classification of centers of rotation and extraoral force systems, Angle Orthod. 43: 385, 1973.
THE JOURNAL 60 YEARS AGO July,
1916
The question of postgraduate instruction in the dental profession is at the present time somewhat of a problem, and courses are only in a developmental state. Among the first endeavors which we noticed of a post-graduate nature were the study clubs, which it is our impression were organized first in Iowa by men who took up certain lines of work under the tutelage of prominent men in the profession. The activities of these study clubs in Iowa had a very marked effect, for it seems that the dental profession in Iowa displayed greater interest in this subject than is manifested anywhere else by dentists in the United States. The plan adopted by these clubs could be followed advantageously by dentists in other parts of the country. (Martin Dewey: Editorial. Orthodontia and Postgraduate Instruction, International Journal of Orthodontia, predecessor of the American Journal of Orthodontics, 2:328, 1916.)