Restoring mandibular arch Eength in the mixed and early permanent den&ion

Jacob Harris Bethesda, Mel.

T he goals of virtually all orthodontic treatment fall into one or both of two broad categories. First, treatment may be undertaken to improve the facial appearance of the patient. The desired change in appearance may involve only the alignment of teeth, or it may require altering the relationship of one jaw to the other or to the cranium itself. Second, treatment may be undertaken to alter occlusal relationships which the orthodontist considers potentially damag- ing, either at present or at some time in the future. This also may entail altering only dental relationships or the relationships of one or both jaws to each other and to the cranium.

It has been apparent to many orthodontists that the best chance of achieving these goals lies in early intervention when the dynamic changes associated with growth can be utilized to the maximum in aiding treatment. It is also probable that a large number of cases in which the extraction of permanent teeth for esthetic or functional reasons is required were at one time “borderline” extrac- tion cases in which early intervention would have obviated the need for removing permanent teeth.

The objectives of this article will be, first, to set up treatment goals and, second, to describe the treatment planning and appliances used to achieve these goals. Special emphasis will be placed on means to develop arch length in the lower jaw, since this is usually the prime factor in determining the need for premolar extraction. Three cases, typical of the majority of those that respond well to early intervention with lip bumpers, will be illustrated.

Treatment goals

Maintainance of a full permanent dent&on. In our preoccupation with the attainment of certain tooth relationships, as determined by cephalometric and subjective appraisal, we have often lost sight of the fact that we are, first and foremost, dentists and that our prime goal in treatment should always be to save teeth. A careful examination of tooth anatomy will reveal that approximat- ing surfaces of teeth are very close to being mirror images of each other; thus,

606

Volume 62 Num her 6

Restoring mandibular arch length 607

the mesial half of a lower first premolar closely resembles the distal half of the adjacent canine and its distal half resembles the mesial half of the second premolar. Removal of the first premolar destroys this gradual change from tooth to tooth and forces the approximation of two surfaces that do not match. The same situation obtains anywhere in the mouth where intra-arch continuity is destroyed. For this reason, extraction should always be regarded as a compromise in treatment. Certainly, there are patients for whom the extraction of teeth is indicated, but our treatment should be aimed at minimizing the number of patients in this group. Orthodontists should not accept the extraction of teeth as the usual method of treatment.

A practice survey reveals that of those cases begun in the full dentition, almost two thirds required the extraction of one or more permanent teeth. Of those cases started in the early mixed dentition, extraction was necessary in less than 20 per cent. The reason for this difference is probably that most of the cases which eventually require the extraction of teeth are “borderline” cases which respond favorably if treatment is started at an early age. If retention of

a full dentition is a treatment objective, then early treatment may be of great benefit to the patient.

Development of a functional occlusion. For too long, orthodontics has been hobbled by a preconceived “ideal” occlusion. Attainment of this ideal has re- quired extensive treatment for many patients who might have benefited as much or more from simpler techniques. Orthodontists should have firmly in mind a set of sound dynamic interarch relationships in centric occlusion and in the various excursions of the mandible, rather than a static ideal which tells little or nothing about how the teeth will actually “work.” Listed below are the intra- and interarch tooth relationships that are basic in any treatment planning.

Intra-arch functional goals. The alignment of teeth should be such that nor- mal gingival architecture and health can be maintained. Slightly rotated or overlapped incisors may be considered acceptable if the gingival response to the condition is not adverse and if the esthetics satisfy the patient. Severe rotations or crowding are virtually always accompanied by gingival change and are not acceptable.

Marginal ridges of adjacent posterior teeth should be even. Discrepancies in ridge relationships are often accompanied by the impaction of food and resultant opening of contact points. Lower second molars may also present a mesial marginal ridge that is higher than the distal ridge of the first molar; the result is a nonworking prematurity with the lingual cusps of the upper first molars. The same type of prematurity is often associated with upper second molars which present a marginal ridge that is more occlusal than the distal ridge of the first molar. This situation most often occurs when second molars are not banded. For this reason, no treatment should be considered complete until it has been determined that the second molars are in good relationship to their adjacent and opposing teeth, If they are not, additional treatment, consisting of equilibration or mechanical intervention, should be instituted.

Contacts should be either tight enough to prevent food impaction or wide open to allow self-cleansing. Probably no condition is more prone to later

608 Harris Am. J. Orthod. Pecember 1972

periodontal breakdown than the contact which is “almost” closed. This situation may result from incomplete closure of extraction sites, from improper alignment of the long axes of adjacent teeth, from poor interarch oeclusal relations which drive plunging cusps between contacts, or from incorrect band removal and retention procedures which leave band spaces after treatment. In the posterior region, correction may require retreatment, equilibration, or dental restorations to close these spaces. Further anteriorly, it may be better to open contacts far enough to allow self-cleansing. In either case, the result must be such that the gingiva and bone are protected from the destructive effects of food impaction.

Teeth should not be moved into a position where they would adversely affect the int.egrity of the labial or lingual cortical plates. It may be possible to satisfy all of the above intra-arch criteria and still have problems affecting the thin labial and lingual cortical bone. Flaring teeth labially or torquing roots lingualI)- can also cause fenestrations or dehiscences to develop, and this often proves to be a limiting factor in the range of labial or lingual tooth movement that can be accomplished in a particular case.

Interarch fmctional goals. Centric relation and maximum occlusal contact should coincide, and there should be no “slide” from initial contact to centric occlusion. It is helpful to have all models trimmed in centric relation, and not centric occlusion, for purposes of evaluating the true amount of discrepancy in interarch relationship.

There should be sufficient incisal guidance to provide disarticulation of posterior teeth in protrusive movements. Conversely, any overbite that is too shallow to disarticulate posterior teeth in protrusive excursions is unacceptable. Any overbite that does not allow easy movement of the lower jaw into eccentric movements (such as a Class II, Division 2 type of overbite) is unacceptable. Any overjet that is severe enough so that immediate incisal guidance cannot take place in protrusive movement is unacceptable,

Contact of working-side teeth should disarticulate nonworking-side teeth in lateral excursions. Group function is desirable, but canine disarticulation is acceptable and may be the only contact attainable in many cases. Conversely, nonworking-side contact is considered a prematurity in function a.nd is not acceptable.

All of these intra-arch and interarch functional goals are basic in every orthodontic case, and treatment should be planned to achieve each of them.

Esthetic goals of orthodontic treatment. Determination of what is a desirable esthetic result following orthodontic treatment is of paramount importance since the extent of treatment is often based on the need for changes in facial appear- ance. The orthodontic literature is filled with descriptions of analyses based on the attainment of an ideal facial appearance, and the concept that a “good” facial appearance and a stable and physiologically sound dentition are mutually synonymous has been widely accepted in the specialty of orthodontics. It is interesting to note, however, that experience with parents and patients seems to show that the general public’s idea of facial esthetics embodies a greater degree of dental protrusion than many orthodontists consider “correct.” It has never been shown that persons with procumbent incisors are more subject to dental

Volume 62 Num bet- 6 Restoring mandibular arch length 609

problems than those with upright incisors, and the general public also seems to prefer a somewhat ‘Lfuller” dental appearance. It becomes highly questionable, therefore, whether orthodontic treatment, including the extraction of permanent teeth, designed primarily to reduce dental protrusion is valid.

Assuming that sound function and stability are not sacrificed, then the decision as to what degree of protrusion is desirable should rest with the patient and parent and not with the orthodontist. Certainly no attempt should be made to tie esthetic goals to physiologic benefits unless the orthodontist is prepared to show valid justification for the connection. If the parents request a degree of “flattening” in dental protrusion that can be accomplished only by an extraction procedure, then the orthodontist is justified in carrying out such treatment, assuming that an acceptable functional result can be achieved. However, he should also indicate that the procedure is being carried out to satisfy esthetic and not physiologic requirements. Unfortunately, there are too many eases in which functional improvement can be achieved only by the extraction of permanent teeth. Every attempt should be made to reduce the number of addi- tional cases that fall into this category.

The most common esthetic factors that parents and patients find dissatisfying seem to be the following:

1. A degree of dental protrusion which results in a perversion of lip posture, such as lack of lip seal in repose or muscular strain in swallowing.

2. Excessive lower facial height, which also results in the muscular perversions noted above.

3. Rotation or overlapping of incisors. 4. “Rabbiting-in” of upper incisors associated with gingival tissue

showing above these incisors in speech and smiling. 5. Retrusive lower jaw. Again this often results in lip strain in an

attempt to maintain lip closure. In summary, it would seem that the esthetic goals we must achieve to satisfy

the public are few : (1) alignment of upper and lower anterior teeth and (2) an unstrained perioral muscular envelope. If these can be satisfied, then most pa- tients and parents will accept the esthetic results of treatment as successful.

Experience has indicated that a proportional analysis, such as that developed by Sassouni,l produces a facial balance that the public generally finds satisfying. The treatment planning for all of the cases to be described later is based on this analysis.

Treatment planning

Selection of borderline cases for early treatment. Much time has been spent in defining the esthetic and functional goals considered to be important, since they will obviously affect both the selection and the treatment of cases. If the treat- ment goals outlined above are not considered acceptable to the orthodontist, then the treatment described below will be a waste of time, since it will produce results that differ markedly from what he considers satisfactory.

With this point in mind, let us consider just which patients can be treated

610 Harris

with this regimen. It may be easier to list the types of patient for whom this type of early treatment, aimed at maintaining a full dentition, is of little or no value and then to consider the great majority of those patients remaining as satis- factory candidates for early intervention.

Severe Class I bimaxillary protrusion cases in which normal, relaxed lip closure is not possible will, in most cases, require the extraction of four pre- molars in order to achieve a satisfactory esthetic result, even though the func- tional aspects of the occlusion are good. For these patients, it is usually best to defer treatment until the full dentition erupts. Similarly, early treatment that leads to the creation of a bimaxillary protrusion, in which the muscular envelope is strained in lip closure, will be of no benefit to the patient, since full treat- ment, with the extraction of teeth, will eventually be necessary. A small percen- tage of borderline cases treated in the early mixed dentition will end up in this category, but it is a small price to pay when measured against the much greater number of patients who will benefit from the early treatment. Proper selection of patients through accurate diagnosis and treatment planning can virtually eliminate this situation. Mild Class II bimaxillary protrusion cases should be treated to a normal mesiodistal molar relation before a decision is made on the need for extractions and full banding later. Often, a patient with what appears to be a Class II four-premolar-extraction case will take on a sa.tisfactor>- facial appearance when the Class I molar relation has been achieved.

Severe arch-length deficiency in both arches, with normal molar relation and good facial esthetics, illustrates the textbook serial extraction case that will usually benefit greatly if a carefully timed extraction procedure is undertaken early enough. Experience has shown that these criteria are present in only a very small percentage of cases, and it would be prudent to err on the side of conservatism rather than extraction if doubt persists in the orthodontist’s mind about the benefits of serial extraction in a particular case.” This conservative course of action will allow for alternative treatment, including extraction, at a later time if necessary. The reverse of this situation, in which serial extraction is tried first, leaves little room for changing treatment procedures at a later date.

Arch-length deficiencies (moderate or severe) may be associated with anterior open-bites. Since the treatment to be described often shows a tendency to decrease anterior overbite, it stands to reason that it will not generally prove beneficial in this type of case. Dental open-bites associated with skeletal open-bite patterns do not usually benefit at all from early intervention, and most often correction of any associated tongue or finger habits will have no discernible effects on the malocclusion, Most other types of borderline extraction case seem to benefit from early intervention as described later.

Sequence of correction in the early mixed dentition. When one states a definite sequence to be followed in the correction of developing malocclusions, numerous examples may be cited of cases that would not, for various reasons, fit these patterns. Yet it has been noted that a general sequence seems to prevail in the majority of cases and it may be helpful to use this order of priorities as a guide in developing one’s own treatment rationale.

ELJMINATI~NoR ~ONTROLOFPERVERSE MUSCULARANDL~~ALH.~HT~. Normaliza-

'Volume 62 Nwnber6 Restoring mandibular arch length 611

tion of the muscular envelope surrounding the developing dentition is one of the key benefits to be derived from early orthodontic intervention, and a careful examination will reveal that virtually all malocclusions are associated with some degree of perversion of the facial muscles. 3 In the most obvious cases, this will take the form of a tongue or lip habit. In other more insidious instances, breathing problems may force an alteration in the integrity of the labial musculature, as in mouth-breathing associated with obstructive adenoidal or tonsillar tissue.4 Quite obviously, an attempt to create a normal anatomic con- figuration of the dentition is doomed to fail if all aspects of the system affecting the teeth are not considered. Since the orofacial complex is, in effect, a closed system, the alteration of one factor in the system will require compensatory changes in other parts of the system in order for an equilibrium to be achieved. Failure of this compensation to take place leads to relapse of the new anatomic configuration achieved through orthodontic treatment.

The means to achieve control of the factors involved in the alteration of the muscular and soft-tissue envelope may consist of surgical intervention, habit- breaking appliances, and counseling. The main point is that the degree of control that can be achieved over these causative factors will directly affect the degree to which the remaining treatment will be successful. While there are cases in which orthodontic correction to the norm will eliminate perverse habits, it is far more logical to control these factors first, or at least simultaneously with tooth movement.

ACHIEVEMENT OF CLASS I MOLAR RELATIONS. The physical anthropologist is often able to make quite remarkable estimations of the size, form, and physiology of complete animals from small fragments of skull or skeleton. Similarly, the localization of one relationship in the dentition, such as the upper to lower permanent first molars (both to each other and to their respective skeletal bases) aids markedly in helping us to determine the location of the remaining teeth as they erupt.5 Indeed, the correct positioning of these teeth seems to be a sig- nificant factor in causing other teeth to erupt into a normal position. Even though a few cases may benefit from other than a normal molar relationship, the attainment of normal occlusion should be a prime goal of treatment. Based on this one factor, all other static and functional tooth relationships become easier to achieve.

ACHIEVEMENT OF NORMAL INCISOR POSITIONING. Once molars have been posi- tioned correctly, incisors should be moved to their correct positions, both with respect to each other and with respect to the investing tissues. This means developing sufficient overbite, either by opening or closing anterior teeth, to disocclude posterior teeth without “locking in” the occlusion. Care must also be taken to ensure that an unstrained labial and buccal musculature is developed by not forcing anterior teeth forward against the lips. For this reason, lower incisors are rarely banded during this early stage of treatment and are allowed to position themselves labiolingually.

Certain simple appliances, which will be described later, are used in the lower arch during this period to eliminate perverse lip pressure on the lower incisors which might force them into a more lingual position than they would otherwise

612 Harris

assume. Overzealousness in attempting to treat all patients on a nonextraction basis often leads the orthodontist to go for an extra 1, 2, or 3 mm. of arch length at this point by banding teeth and flaring them labially. This is not recommended unless esthetic considerations are such that the patient an(l parents are willing to accept instability of the finished case as a part of trent- merit. I do not believe that any one part.icular angulation of lower incisors to a reference plane represents the stable position of these teeth and thus do not attempt to correlate their movement with any cephalomet,ric ideal. Each CHSC is determined individually according to the muscular factors involved.

DETERMINATIOS OF THE NEED FOR EXTRACTIONS AND FURTHER TREKIJIEST

BASED ON THE AMOUNT OF ARCH LEXGTH AVAILABLE, THE SIZE OF ERlJF1'ING TEETH,

AND THE POSITION OF THESE TEETH. At this point, the first phase of treatment, is over. lt may represent the only treaimcnt nccdcd, but in the majorit)- of cases additional second-phase therapy lvill now be needed. If insufficient arcah length is available to accommodate all teeth, this is the time to determine it. If fllll banding of one or both arches is necessary to complete alignment, this is the time to place these appliances.

With these factors in mind, the mechanical procedures that can be utilized to achieve these treatment goals can be considered.

The experience of many orthodontists seems to be that t,he lower arch presents the more difficult problem in determining whether or not a case will require extraction.Thc maxillary arch is often amenable to treatment with various types of headgear and/or palatal splitting devices in order to increase arch length. First-phase treatment has too often been confined to the upper arch only, with the result that the second phase of treatment has often been as complex as if no prior treatment had been carried out at all. Obviously, some form of effective therapy has to be instituted in the lower arch in order to justif! early treatment. In certain selected cases, a lingual arch is sufficient to main- tain arch length. In many cases, however, associabed muscular patterns are un- affected and complex treatment still remains to be provided at a later date.

The lip bumper, with its modifications, offers a simple and effective method of

treating borderline cases. An additional benefit is that it provides a dcfinitc means of deciding whether extraction is needed in order to complete treatment. The appliance consists of double buccal tubes welded onto molar bands on the mandibular permanent first molars (or, rarely, the deciduous second molars) An 0.045 inch wire is adapted to fit into the tubes and stand 1 to 2 mm. away from the buccal and labial surfaces of all teeth. Headgear stops are welded to the wire and, as the lower arch form changes, additional stops are added to advance the arch labially. To facilitate cleaning, the wire is not tied in and is removed by the patient during toothbrushing. This appliance can be used with any maxillary treatment devices deemed necessary, such as bite plate, palatal splitting appliances, headgear, or full banding. The main effect, based on cephalo- metric appraisal, seems to be buccal and labial expansion of the lower arch. Distal movement of the molars seems to be minimal in most cases, and im- paction of the second molars has occurred only once in more than 300 patients.

The explanation of how the appliance works seems to be that removal of

Volume 62 ~Vumber 6 Restoring mandibular arch length 613

Fig. 1.

lip pressure against the labial surfaces of the lower incisors and the labial alveo- lar tissue disturbs the muscular equilibrium, and the teeth and investing tissues migrate labially and buccally until a new equilibrium has been established. Fig. 1 shows the appliance. Note that no springs or plastic shields are used on the wire. It has been found that in the overwhelming majority of cases the wire is well tolerated as is. When continued irritation occurs, a soft plastic tube can be slipped over the wire in the anterior region to increase the bulk of the appliance.

Several cases are presented to illustrate how mechanical therapy is carried out in the first phase of treatment. Some of these cases will require further treatment for completion ; others will be completed with only one phase of treat- ment. The main objective of presenting these cases will be to show the magni- tude of the effect of early intervention on each malocclusion, changing it from an apparent extraction case to one in which extractions were not necessary.

Patient 1. 5.

A description of the first phase of treatment used for this patient will serve as an intro- duction to the application of the lip bumper. Figs. 2, B and 3, 8, B, E, and G illustrate the facial photographs and plaster casts of this patient. Both lower deciduous canines had been extracted to permit alignment of the lower incisors. Cephalometrically, according to the Sassouni analysis, the patient had a skeletal Class I malocclusion with normal vertical development. The labial muscular envelope was unstrained. There was no indication of any adverse problems associated with growth that would require orthodontic intervention. Intraoral radiograms showed a full complement of permanent teeth in an apparently normal eruptive position. No perverse muscular habits were noted.

Treatment goals of the first phase of treatment. The patient’s orthodontic problem was

614 Harris

Fig. 2.

diagnosed as being completely dental in nature, with no associated skeletal complications. It involved a lower arch length deficiency of 5.5 mm. associated with a deep anterior overbite that prevented normal movement of the lower jaw from centric relation to lateral anal protrusive relations. The goals of the first phase of treatment would be to regain sufficient lower arch length to allow eruption of all teeth and to develop a degree of overbite which would not interfere with normal functional jaw movements. At that point, the first phase of treatment would be considered completed and an evaluation would be made of the type and extent of additional treatment needed to complete the case. Since the patient showed a favorable skeletal pattern with no adverse growth problems, a bite plate could be utilized during the first phase of treatment to lessen the anterior overbite without hinging the mandible downward and backward. Posttreatment stability could be anticipated. In the lower arch, both permanent first molars were banded, a lip bumper similar to that shown in Fig. 1 was placed, and the patient was instructed in its care and application. Roth the bite plate and the bumper could be removed during toothbrushing.

With the change in the muscular equilibrium caused by the removal of labial lip pressure on the lower incisors and alveolar process, and with the increase in over-jet created by the presence of the bite plate, the lower incisors began to move labially. As the space between these teeth and the wire decreased, additional stops were added to the wire to maintain the clearance. This regimen was maintained until all deciduous teeth had been lost 13 months later.

Evaluation of the results of the first phase of treatment. At this point, the first phase

Restoring mandibular arch length 615

Fig. 3.

of treatment mas completed and an evaluation was made to determine the need for further treatment. The plaster cast in Fig. 3, H illustrates the lower arch at this point. All permanent teeth mesial to the first molar had now erupted. Arch length was somewhat excessive, and a few rotations and some anterior crowding were present. Full banding of the lower arch was necessary to complete the alignment of these teeth. In addition, the upper canines had begun to erupt lingually. Since the parents and the patient showed no interest in cor- recting the slight overlapping of the incisors, upper treatment at this point consisted of banding the permanent first molars and canines to expand the latter to their correct position. Fig. 3, C, D, F, and I also shows the models after 5 months of the second phase of treat- ment, and Fig. 2, B illustrates the unstrained labial musculature and pleasing facial ap- pearance in the final facial photographs. Retention consisted of a lower removable retainer, worn full time for 6 months, nightly for 1 year, and every second or third night there-

616 Ilawis

Fig. 4.

after. The cage was equilibrated in centric occlusion when full-time retainer use was dis- continued. N$@uilibration was needed in the excursive movements of the mandible.

Patient N. S.

Figs, 4 and 5 show this patient’s pretreatment and posttreatment casts and facial photo- graphs. Moderate strain is evident in lip closure at the age of 7 years. The dental evalu- ation was that of a Class II, Division 1 malocclusion with a mild anterior open-bite and a lingual cross-bite of the upper left posterior teeth. Only 1 mm. of space remained for erup- tion of the lower right lateral incisor, and 3 mm. of space was missing for eruption of upper lateral incisors. Cephalometrically, the analysis showed a Class II skeletal open-bite pattern with a short mandible and a normal maxilla. Intraoral radiograms showed a full complement of teeth, normally positioned for eruption. No perverted tongue or finger habits were noted.

Treatment goals of the first phnse of treatment. The goals of first phase treatment were to correct the cross-bite, to attempt to regain arch length for the eruption of all upper and lower teeth, and to correct the Class II molar relations. The parents mere told that an ex- tensive second phase of treatment, quite possibly involving the extraction of permanent teeth, might be necessary. Skeletal and dental components were involved; satisfying the dental component might aggravate the skeletal component by rotatiug the mandible downward and backward, resulting in an increased lip strain and a less pleasing facial appearance. Early treatment will often allow growth to overcome the results of treatment procedures that would be disastrous in a more mature patient, as will be shown here.

R&o&g ma~dihzslnr arch length 617

Fig. 5.

With this in mind, palatal splitting was used to correct the cross-bite and to gain the missing upper arch length for eruption of the lateral incisors. Even though the initial result of this procedure might be an undesirable clockwise rotation of the mandible, subsequent growth would result in full recovery to the original facial pattern. The appliance consisted of cast-gold shims covering each upper buccal segment which were soldered to a hygienic type of transpalatal screw assembly. A bumper was also placed in the lower arch. After the palatal area had recovered from the palatal splitting, the upper appliance was removed. The permanent first molars were then banded, and an oblique headgear was placed to gain a normal molar relationship. Fig. 5, H shows the appearance of the lower arch 18 months after the start of treatment. All of the criteria of the first phase of treatment had now been satisfied. Although 2 mm. was still missing for eruption of the lower right canine, almost 4 mm. would

618 Harris Am. J. Orthod. Tkcemher 1972

Before 81.0

SNB 72.0 FMI 56.0 IMP 101.0 FMP 23.0 OCCI-MP 18.5 Y-AXIS 69.0

After 80.5 73.5 55.0

103.0 22.0 14.5 71.5

Fig. 6.

be available when the second deciduous molars were lost. The lower bumper was continued during exfoliation of the remaining deciduous teeth. An upper removable retainer was used at night.

The final casts shown in Fig. 5 illustrate the case when the patient was 11 years 1 month of age. The upper retainer and the lower bumper were removed at this time. The permanent first molars were not yet in a normal mesiodistol relationship, but this will occur on the loss of the lower second deciduous molars. Self-alignment of all teeth resulted to such a satisfactory degree that no further treatment was necessary. Teeth which are allowed to erupt into good alignment are much more stable than those which have been moved into good alignment.~ This is very probably due to the fact that those periodontal fibers connecting cementum to gingival tissue are allowed to develop on well-aligned teeth, rather than on malposed teeth, with the result that they arc not under stress after treatment, as would be the case if treatment began after eruption of the teeth. Space is created before eruption and in many cases the teeth will not require mechanical intervention for alignment.

Fig. 6 shows a superimposition of cephalometric tracings on the De Coster line before

Volume 62 .??umber 6 Restoring mandibular arch length 619

Fig. 7.

and after treatment. Even with the palatal splitting, there has been no hinging of the mandible. Four years of growth has allowed a complete recovery from whatever initial hinging may have occurred. At this point, a satisfactory argument could be made for a second phase of treatment aimed at the perfection of interarch relationships. Yet it is likely that the case will be stable as it now stands and that all of the criteria of esthetics and functional occlusion have been achieved. Any additional improvement would be of question- able value and would not justify the treatment involved. Fig. 4, B shows the facial appearance when retention was discontinued.

Patient D. S.

This case has been included in the presentation because it illustrates both the tremendous benefits to be derived from early intervention and the difficulties tvhich can develop from failure to intervene as soon as problems are apparent.

Fig. 7, a shows the patient at the age of 9 years 1 month, prior to any treatment. The original casts in Fig. 8 show a Class I malocclusion with lingual cross-bite of the maxillary left posterior teeth and an associated mandibular shift to the left. The lower left deciduous canine had been lost and the space completely closed by the shifting of the permanent lower incisors to that side. The upper left lateral incisor was in lingual cross-bite, but there was no upper arch length discrepancy. Evaluation of the lateral head film showed a skeletal Class III anterior open-bite pattern with a long mandibular body and a normal maxilla. Intraoral radiograms showed a full complement of normally positioned permanent tooth buds.

Treatment goals of the @st phase of treatment. This case had both skeletal and dental

620 Harris Am. J. Orthod. December 1972

Fig. 8.

components. The dental component required correction of the cross-bite, reopening of the space for the lower left permanent canine, and reduction of the overjet. Skeletal Class III open-bites do not respond promptly to orthodontic treatment. If the patient shows a tendency for this pattern to become more severe, surgical correction may be indicated. The orthodontist’s responsibility is to introduce no factors in treatment which might tend to worsen the facial deviation by hinging the mandible downward and backward. This would have the effect of lengthening the lower facial height and worsening facial nppearance. It would also create an anterior open-bite.

Upper and lower permanent first molars were banded and a transpalatal arch was used in the upper arch for correction of the cross-bite. A lip bumper was used in the lower arch to recover the lost space in the canine area. With the loss of the upper deciduous canines,

Volume 62 Ntcmber 6 Restorkg ma~?1dibular arch length 621

SNA

SNB FMI IMP FMP Occl-MP Y-AXIS

Before After 81.5 81.5 77.0 77.0 72.0 63.5 80.0 86.5 28.0 30.0 18.0 17.5 69.0 70.5

Fig. 9.

the incisors were banded to improve arch form and tooth alignment. Since some distal move- ment of the lower permanent first molars had occurred with the use of the lip bumper, cervical traction was used for a short time to improve molar relations. Twenty months after the start of treatment, the first phase of therapy was stopped. Figs. 7, C and D and 8 show the casts and facial appearance of the patient at this point.

Reszllts of the first phase of treatment. Mention was made earlier of the need for careful evaluation of the progress of treatment in order to avoid introducing additional problems into the correction of these cases. In this instance, two problems arose which might have been avoided. First, cervical traction was used to correct molar relations. The immediate effect was to displace the mandible and create a noticeable increase in lower facial height. A more logical solution would have been to use an oblique headgear. Subsequent growth has overcome this initial mandibular hinging, but in a child with lesser growth potential the results might not have been so good. It is interesting to note that on the cephalometric super- imposition (Fig. 9), it has been vertical, not horizontal, mandibular growth that has corrected this problem. Perhaps too much emphasis has been placed on the importance of the horizontal

622 Harris Am. J. Orthod. December 1972

component of mandibular growth as a factor in treatment and not enough on the vertical component.

A second problem arose in the correction of the posterior cross-bite. Measurement across the upper permanent first molars showed 180 mm. of expansion, seemingly sufficient to correct the cross-bite. The models show, however, that the cross-bite still exists. The reason is that mandibular molar expansion has also occurred. This can be traced to the lower bumper which became bent by the patient in removing it for toothbrushing. This remained undetected for some time and resulted in gross buccal tipping of the lower molars, thus perpetuating the cross-bite. While this problem can be corrected in a second phase of treatment, it might have boen avoided with closer control during the first phase. While both of these problems were reversible, it becomes apparent that there is the possibility of introducing irreversible factors into the treatment of a case, and care must be taken to avoid this.

This patient required a second phase of treatment consisting of cross-bite correction by lingual tipping of the lower molars. The upper incisors were also banded to complete their rcalignmcnt. Successful first-phase treatment (with the exception of the cross-bite correction) permitted correction of the dental irregularity and eliminated the need for the extraction of permanent teeth.

Summary

The main purpose of this article has been to illustrate that certain problems, common to a large number of orthodontic cases, will respond well to rather simple procedures if these procedures are carried out in the early mixed dentition. Moderate arch length deficiencies, pernicious habit patterns, and gross discrepancies in arch form and interarch relationships are problems that prove difficult to treat if postponed for correction in the permanent dentition.

Early intervention should also be considered as a prime method of “therapeutic diagnosis,” a term used by Ackerman, in which the correctness of the diagnosis and treatment plan are validated or disproved by the results ob- tained. Re-evaluation of the patient’s progress at the end of the first phase of treatment allows for the possibility of changing treatment procedures if the response to the original plan is not satisfactory.

REFERENCES

1. Sassouni, Viken: A classification of skeletal facial types. AM. J. ORTHOD. 55: 109-123, 1969. 2. Dewel, B. F.: Prerequisites in serial extraction, AM. J. ORTHOD. 55: 633-639, 1969. 3. Harvold, Egil P.: The role of function in the etiology and treatment of malocclusion.

AM. J. ORTHOD. 54: 883-898, 1968. 4. Ricketts, R. M.: Respiratory obstruction syndrome, AM. J. ORTHOD. 54: 495-507, 1963. 5. Atkinson, Spencer R.: A key to occlusion, AM. J. ORTHOD. 54: 217-233, 1968. 6. Reitan, Kaare: Clinical and histologic observations on tooth movement during and after

orthodontic movement, AM.J. ORTHOD.~~: 721-744,1967.

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