The impact of interproximal band thickness on treatment and retention

The impact of interproximal band thickness on treatment and retention John Buffalo,

J. Cunat, N. Y.

D.D.S.,

M.S.*

I

t is common knowledge that mechanical orthodontic therapy has, over the years, taken a variety of forms. The two major appliance systems, fixed and removable, have each had strong defenses, sometimes real, sometimes imaginary, on both biologic and technical grounds. Moreover, within each school of thought, a good deal of controversy exists with regard to diagnostic philosophy and treatment objectives. The purpose of this article will be to examine one area of disagreement among those who advocate the use of fixed appliances, namely, the effect of the physical size of interproximal band material upon diagnosis, treatment planning, and retention. Some proponents of orthodontic systems which utilize only a few bands have suggested that leaving the teeth comparatively free of appliances allows natural forces to assist in guiding teeth into their proper positions. On the other hand, those who choose to band essentially all of the erupted teeth favor the notion that this more elaborate type of appliance system allows the practitioner to precisely control the relationships of the teeth in all three planes of space, both individually and collectively. If these were the only considerations, appliance selection could be relatively straightforward, in that one would only have to decide how much liberality he would allow the dentition in any given situation. Of a far more serious nature are the allegat,ions that diagnosis is very much affected by the dictates of the appliance. For example, Wilson,l in commenting on the interproximal thickness of bands and cement common to all multibanded appliances, has made the following charge : “In some instances, this is more space than is required to treat the case if such an appliance were not used. Additional arch increase under Presented before the Chicago Association of Orthodontists, March 22, 1971. “Chairman, Department of Orthodontics, School of Dentistry, State University New

York

of

at Buffalo.

481

Fig. 1. Measurement

of

strips

corresponding

to

interproximal

band

thickness

in

a single

arch.

these conditions is difficult. Herein lies the SOUIW of many needless extractions just to accommodate the appliance.” In a later article,2 he adds: “Objectives in orthodontic treatment must not be subordinate to the limitations of the appliance.” Tarpley,3 in considering treatment approaches to borderline extraction cases, makes this statement: “There are many borderline cases in which the labio-lingual appliance could adequately work the teeth into place and still not produce a bimaxillary result. If a full-banded technique were used and the four premolars retained, the patient would have a bimaxillary appearance because of the thickness of twenty-eight bands. I am sure that this has influenced many orthodontists who use a full-banded technique to remove more teeth than those who use either a labio-lingual or a Crozat appliance.” Exponents of multibanded techniques make no denial of the space requirements of the appliance itself. Thurow, 4 for example, in discussing multibanded appliances, says : “Maximum banding places heaviest demands on space due to the thickness of band material introduced between the teeth.” Renfroe” points to the fact that if one adds up the thickness of the bands for an individual arch, its length is increased by 0.1 inch. This is theoretically true if the first permanent molars are banded with material 0.005 inch thick and all the other teeth receive bands 0.004 inch thick. However, if flat band strips corresponding to the mesial and distal band widths of all twelve teeth are combined and measured, the total is greater than 0.1 inch because of manufacturing tolerances and the space between the strips (Fig. 1). In actual banding procedures, arch length is necessarily increased beyond this level because of the technical problems of absolutely perfect, band adaptation on curved surfaces and the thickness of the cement between the teeth and the bands. These interproximal additives to the mesiodistal widths of

V&me Number

62 5

Fig. 2. Comparison

Impact

of

arch

lengths

of

a case

of iderproximal

when

banded

bad

and

thickness

debanded

with

483

distal

coincident.

the teeth result in arch length increments which are widely recognized but frequently ignored. That is, in spite of universal awareness of the fact that bands occupy a significant portion of arch length, how often is the transitory nature of this increase taken into account before or after active treatment? Of far greater concern is the question of whether or not we are guilty, perhaps subconsciously, of modifying our diagnosis on occasion in order to allow for the accommodation of our appliances. During the course of treatment it is easy to lose sight of the width of interproximal band material and the possibilities this offers in arch length manipulation. We begin a case by considering and measuring all sorts of dental, physical, and radiographic records which help us formulate a treatment plan. After this, the mechanics involved in reaching these objectives fully occupy us until we have established an acceptable interdigitation of the teeth, frequently with a particular tooth bearing a specific relationship with some plane that happens to be in vogue that season. Then, having successfully negotiated all of the hurdles placed in our paths, we are ready for retention. Not infrequently, this means removing all of the bands at one sitting, taking some impressions, and quickly placing Hawley appliances, elastic devices, fixed retainers, or some other mechanical contrivance that we favor. At this point, all of the diagnostic acuity, technical excellence, and philosophic justification can be destroyed by relegating the act of retention to an inferior position in our treatment program. After all the care that has been exercised in placing the teeth in finite positions, how often do we stop to consider the tooth movement that must take place after band removal’2 In fact, if a patient’s retainer does not fit well during the “tapering off” period, we usually attribute it to laxity on the patient’s part or to morphogenetic dominance or, on occasion, we even blame ourselves for questionable diagnosis and/or treatment. Perhaps, however, it can just as easily be the result of shifting teeth which have finally been liberated enough to seek their ultimate positions. On the other hand, if we exercise some control over the direction in which

Fig. 3. menton

Lower incisor tipped 3 mm. lingually (A) and through original apex (B).

at

the

incisal

tip

with

its

long

axis

through

this band space is consumed, the retention phase of treatment may actually be a misnomer, for it can be an active adjunct to banded appliance therapy. To illustrate this thought more adequately, we can consider the arch length of an actual case when it was fully banded and compare it with the arch length after the bands had been removed and the spaces closed, In this case, in which intermolar width was kept constant and the distal ends of the arches on either side coincided, the anterior arc of the incisal edges after bands had been removed was 3 mm. interior to that of the banded case (Fig. 2). If this 3 mm. is considered in the sagittal plane, as measured along the occlusal table and a new long axis of the lower incisor projected to the point menton, we find that the tooth can be tipped 13.5 degrees lingually (Fig. 3, A), Even if one conservativel) constructs a new axial inclination for the lower incisor, using its apex as the pivotal point, this 3 mm. difference at the level of the occlusal plane allows the tooth to be tipped 7.0 degrees lingually (Fig. 3, B). The converse of these statements is also significant. That is, the act of banding, by itself, could advance the incisors a similar number of degrees. These figures are, of course, only possibilities and not inflexible rules, since the manner in which the tooth is tipped, its original axial inclination, and the morphology of the symphysis are critical. Let us now look more closely at some of the diagnostic implications and, more important, the retention possibilities of multibanded orthodontic procedures. All of the patients were treated with edgewise appliances by postdoctoral orthodontic students in the Department of Orthodontics at the State University of New York at Buffalo. The first patient, a IO-year-old white boy, was selected to illustrate a rather conventional treatment plan and retention procedure. His Class II, Division 1 malocclusion was treated with cervical traction. Initial cephalometric analysis showed an interincisal angle of 136 degrees, with the lower incisor at 6 degrees to the mandibular plane and the upper incisor at 97 degrees to S-N (Fig. 4, A). At the conclusion of treatment, but while the teeth were still fully banded, the angular relationships had changed so that the interincisal angle was 127 degrees,

Fig. 4. Class II, Division (B), and immediately after

1 case before treatment debanding with band

(A), spaces

after closed

treatment (C).

while

still

banded

the lower incisor-mandibular plane angle was 9 degrees, and the upper incisorS-N angle was 103 degrees (Fig. 4, B) . These changes, of course, reflected not only band size but such treatment necessities as leveling and rotational correction. The premolars were debanded first; then, approximately 3 weeks later, the

Fig. 5. removed.

Comparison

of

lip

posture

while

case

was

banded

and

after

bands

had

been

remaining bands were removed. The band spaces were allowed to close by themselves and, about 5 weeks later, impressions were taken for retainers. At that time, the interincisal angle had returned to 135 degrees, the lower incisormandibular plane angle to 7 degrees, and the upper incisor-S-N angle to 97 degrees (Fig. 4, C) . The change in axial inclination of the incisors between the banded and posttreatment phases also resulted in an improvement in lip posture (Fig. 5). The next type of case that we will examine is one in which an attempt was made to gain space for banding in the lower arch without advancing the incisors. This lo-year-old white girl was treated by means of cervical traction 14 hours a day in the lower arch and by the use of a lower lip bumper the rest of the day. Superimposed mandibular tracings show that when the finished case, while still banded, was compared with the pretreatment record, the lower molar had tipped distally and the axial inclination of the lower incisor was more upright than on the initial head film (Fig. 6, A). At this point bands were removed from the premolars and incisors and intramaxillary elastics were used to close the spaces, with no attempt being made to hold the lower molar back. This resulted in a substantial forward tipping of the molar and a further retraction of the lower incisor (Fig. 6, B). The net result of treatment in this case was to leave the crown of the lower molar in essentially the same mesiodistal position it had been in prior to treatment, with the root slightly further to the mesial and the axial inclination of

Impact

BAN&~

of interproximal

bnnd thi&less

487

----

Fig. 6. Case banded and

treated with posttreatment

lower cervical traction stages (B), and initial

comparing initial and posttreatment

and banded stages (C).

stages

(A),

the lower incisor more upright than it had been initially (Fig. 6, C) . Further comparison of the lateral head films between the banded state and the posttreatment period revealed that a similar course of treatment in the maxillary arch had enabled the maxillary incisor to upright during the debanding period. This resulted in a change of 8 degrees in its relationship to S-N, which, coupled with all of the other changes that occurred in the debanding procedure, permitted the interincisal angle to change from 115 degrees to 132 degrees (Fig. 7). A similar case, that of a 13-year-old white boy with a Class II, Division 1 malocclusion, illustrates the transient nature of some of the interim problems that can occur during treatment with upper and lower headgear and multibanded appliances. Superimposition of the maxilla shows a rather typical reaction to cervical traction, with the molars tipping distally and the incisors slightly to the lingual (Fig. 8). Mandibular comparison showed similar changes, but to a lesser degree. This combined action resulted in the opening of the mandibular plane from 22.5 degrees to 25.5 degrees, with pogonion dropping downward and backward to decrease the facial angle from 87.0 degrees to 35.5 degrees (Fig. 9). Later, after active treatment had been completed, the bands were removed

BfiNdrd ‘Posf

Fig. 7. Comparison

of interincisal

angle

-----

between

banded

and

posttreatment

stages.

gradually and intramaxillary elastics were used to close the spaces. This resulted in bite closure, so that when the immediate posttreatment head film was compared with the pretreatment record, the mandibular plane was within 0.5 degree of the original and the facial angle had increased by 1.0 degree (Fig. 10). It must be stressed that this was immediately after the bands had been removed and the spaces closed without the influence of long-range growth or function. In the next case, that of a 13-year-old white girl, the incisors were intentionally advanced in order to reduce their verticality. During the debanding process, lip bumpers were employed in both arches to hold the molars distally while intramaxillary elastics were used to close the spaces. This course of action resulted in the lingual tipping of both the upper and lower incisors and the maintenance of the mesiodistal positions of the molars. In comparing the original and posttreatment positions of the incisors, we see that they were both advanced as intended but not to the degree they were at the banded stage. This treatment procedure saw a change in the relationship of the upper incisor to S-N from 84 degrees initially to 112 degrees when banded and a return to 108 degrees (Fig. 11, A, B, and C) . In a like manner, the relationship of the lower incisor to the mandibular plane changed from a pretreatment -18 degrees, to a right angle when banded, and back to -7.5 degrees after band-space closure. These factors allowed the interincisal angle to change from 161 degrees to 125 degrees when banded and to 138 degrees upon completion. The next case, that of a 12-year-old white girl, was selected to illustrate some of the changes that can occur in the soft tissues as bands are removed. The case

J M.

Fig.

8. Tooth

movement

in

maxilla

and

mandible

in

response

to

upper

and

lower

head-

gear.

Fig.

9.

mandibular

Fig.

10.

Changes

in

mandibular

plane

and

mandibular

plane

and

facial

angles

in

response

to

maxillary

headgear. Recovery

of

facial

angles

after

bands

were

removed.

and

490

Fig.

CM ut

11.

immediately

Case

in which after

incisors

debanding

were with

advanced. band

spaces

A,

Before

closed.

treatment;

6,

while

banded;

C,

P*sT

Fig.

12.

Appearance

and

after

a lower

Kg. ing

13. Tongue with band

of headgear

case was

after used

and lip posture while spaces closed (B).

lower during case

-

incisors band was

were space

banded

advanced closure (A) and

during

treatment

(A)

(B). immediately

after

deband-

was banded, and in the course of treatment the lower incisors were tipped labially to a marked degree (from 81.5 degrees to 99 degrees) (Fig. 12, A). This caused a very protrusive appearance, so that as debanding proceeded a lower headgear was employed to make absolutely certain that the molar would not drift forward. This proved to be successful, since the molar was held distally while the incisor was brought back from 99 degrees to 90.5 degrees (Fig. 12, B) .

492

t ‘wat

Fig.

14.

Frontal

roentgenograms

before

(A) and

after

(B) sutural

expansion.

It is of interest to note that;, during this tlobantling procetl~m, lip bala~~~c~ was greatly improved in response to changes in the clentition. Also the tongue underwent a great postural change during this time, rising from a relatively low position when the case was banded to a much higher attitude when the spaces had been closed (Fig. 13, A and B). One possible explanation of this is that the reduction in the procumbency of the incisors and the increase in overbite may have decreased the intra-oral volume, t,hcreby allowing the tongue to arc higher in the oral cavity. This could be a purely mechanical situation where a given tongue mass is physically pushed higher because of reduced space, or perhaps it is a functional response to a lcsscr riced for the tongue to create an anteriol oral seal in deglutition because of the more vertical incisors anil deepcnccl overbite. The next type of case to be examined is one in which sutural expansion was used during treatment. The patient, a 12-year-old white boy had an edge-toedge molar occlusion and a posterior cross-bite. Maxillary cervical traction was employed in addition to sutural opening. Frontal roentgenograms taken before and after expansion confirm the success of the procedure (Fig. 14, A and B). Superimposed maxillary tracings made initially and after treatment, while teeth were still fully banded, show that the maxillary molar moved slightly distally and that the gain in arch length because of the expansion actually permitted the maxillary arch to be banded while tipping the incisor linguall) (Fig. 15). Therefore, a comparison of lateral tracings at these two stages of

Vcalume Number

Impact

62 5

of interproximal \ \ \ \

Bmdcd

Fig. fully

15. Maxillary banded.

and

Fig.

mandibular

16.

Lateral

493

and

was

\ \

-----

comparisons

tracings

band thickness

before

before

and

treatment

after

banding.

after

the

case

Fig. 17. Comparison elastic retainer was

of used.

incisor

and

molar

positions

in

maxilla

and

mandible

after

an

treatment show the upper incisor to S-N angle to have decreased from 103 degrees to 101 degrees (Fig. 16). Moreover, even though the lower incisor was advanced slightly, the interincisal angle changed from 128.5 degrees to 131 degrees. Further uprighting of these teeth is expected with band-space closure. The next case will be shown to illustrate the effect of using an elastic material to close band spaces and establish a final interdigitation of teeth. The patient, an ll-year-old white girl, had a Class II posterior occlusion. During treatment, the maxillary molars were moved distally with cervical traction and the upper incisors advanced because of band width. In the lower arch, the molar erupted during treatment and the incisors were tipped slightly to the labial. The bands were removed at one sitting, and impressions were taken so that the elastic retaining device could be constructed. After it had been placed and the spaces were closed, superimposed maxillary and mandibular tracings showed virtually the same results. That is, in both arches the molars came forward slightly and the incisors tipped slightly to the lingual (Fig. 17). This latter action allowed the lower incisor to recover essentially the same axial inclination it had at the beginning of treatment. Comparison of the lateral head films showed the m&llary incisor to S-N relationship to have gone from 96 degrees initially to 101 degrees when fully banded and back to 97 degrees when the spaces had been closed (Fig. 18, A, B, and C). Similarly, the relationship of the lower incisor to the mandibular plane went from 11 degrees to 15 degrees and back to 10 degrees during the same period, and the interincisal angle went from 136 degrees to 127 degrees and back to 135 degrees. The last case to be discussed is one that involved the extraction of four pre-

lnlpact

Fig. 18. 8, while

Tracings banded;

of a case in which C, after debanding

an with

elastic band

of

interproximal

retainer was spaces closed.

band

used.

A,

thichess

Before

treatment;

495

Fig. 19. Case

in which

four

first

premolars

were

extracted.

molars. Here the same possibilities of band-space recovery exist, except that the total width of the band material is shortened by the thickness of two bands. Thus, instead of having a theoretical total band width of 0.1 inch, it is reduced to 0.084 inch. Again, of course, banding techniques and cement width add to the total amount of recoverable space. Extraction can provide adequate room for banding, but when treatment is finished additional modification of tooth positioning occurs to adjust to the debanding process. This is illustrated by the case of a 15-year-old white girl who had four first premola,rs extracted as part of her treatment program. Comparison of the maxillary tracings initially and before debanding show that the molar came forward slightly and the incisor tipped to the lingual (Fig. 1.9). In the mandible, space was not as critical, so the incisor tipped markedly to the lingual and the molar was allowed to come forward to help c,orrect the edgeto-edge posterior occlusion. Sfter bands were removed, both maxillary and mandibular comparisons showed that the molars came forward slightly and the incisors tipped further to the lingual (Fig. 19). The lateral tracings showed that both incisors uprighted during treatment and that, upon debanding, the upper incisor tipped 5 degrees further lingually and the lower incisor 4.5 degrees further (Fig. 20, A, B, and C). This resulted in a change in the interincisal angle from 122 degrees initially to 136.5 degrees while teeth were still banded and to 145;5 degrees after treatment. Perhaps it should be noted that during this time the tongue also gradually elevated in position, so that in the final x-ray film, it had a very acceptable posture. This report has not completely cxploretl the subject of band-space recovery, for many other areas deserve examination. For example, in those Class II or Class III cases that just do not seem to settle in, premolars can be debanded

Volume Number

62 5

Fig.

20.

Tracings

(A),

while

Impnct

banded

of

an (B),

extraction and

after

case debanding

noting

of iderproxirnal

tooth with

band

and

tongue

spaces

lmnd

position closed

(C).

thickness

before

treatment

497

and the appropriate elastics can be utilized to establish a better intcrtligitation. Blso, in one-arch-treatment cases, selective debanding can assist, in gradually reducing the arch length discrepancy that is produced when bands are used on only the maxillary or the mandihu1a.r teeth. Further, it seems as if the lingmrl tipping of the incisor crowns that occurs when bands are removeti ant1 the spats arc closed should be anticipated, particularly in cases where (‘arc has bcc~ll exercised in torquing the roots lingually during act,ivc treatment. Jn summary, it seems that substantial modificat,ions occur in tooth position as bands arc removed. If one protects the anchorage posteriorly with a headgear or a lip bumper, a good deal of this space can be taken up distally so that the position of the incisors can be altered dramatically. In fact,, changes of 8 degrees were seen in the relationship of the upper incisor to S-N, 17 degrees in the interincisal angle, and more than 8 degrees in the angle between the lower incisor and the mandibular plane. In response to these tooth movements, changes were also observed in other skeletal relationships, such as t,he mandibular plane angle and the facial angle. In addit,ion, modifica.tion in the posture of the tongue and lips was noted in several cases. The major point is to regard this band space much as we would a bank deposit t,hat is payable to us on demand. Jt is hoped t,hat through this mechanism those of us who choose to use multibanded orthodontic devices can more adequately plan treatment and nercw be accused of promiscuous extraction simply to accommodate our appliances. REFERENCES

1. Wilson, William L.: A critical analysis of orthodontic concepts and objectives, A&l. J. ORTHOD. 43: 891-918, 1957. 2. Wilson, William L.: The development of a treatment plan in the light of one’s concept of treatment objectives, AM. J. ORTHOD. 45: 561-573, 1958. 3. Tsrpley, Boyd W.: Technique and treatment with the labio-lingual appliance, St. Louis, 1961, The C. V. Xosby Company. 4. Thurow, R.aymond C.: Technique and treatment with the edgewise appliance, St. Louis, 1962, The C. V. Mosby Company. 5. Renfroe, Earl W.: Technique training in orthodontics, I4nn Arbor, 1960, Edwards Brothers, rnc. d3t? Capen

Hall