5 - Benefit of Early Class II Treatment Progress Report of a Two-phase Randomized Clinical Trial - Proffit

8/10/2019 5 - Benefit of Early Class II Treatment Progress Report of a Two-phase Randomized Clinical Trial - Proffit

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CONTINUING EDUCATION

Benet of early Class II treatment: Progress report of atwo-phase randomized clinical trial

J.F. Camilla Tulloch, BDS, FDS, DOrth, a Ceib Phillips, PhD, MPH, b andWilliam R. Proft, DDS, PhD c

Chapel Hill, N.C.

Preadolescent children with overjet greater than 7 mm were randomly assigned to observation only,headgear (combination), or functional appliance (modied bionator) and were monitored for 15months. Of the 166 patients who completed this rst phase of the trial, 147 continued to a secondphase of treatment. The data from the rst 107 patients to complete phase 2 are available and formthe basis of this progress report. During phase 1, on average there was no change in the jawrelationship of untreated children, but 5% showed considerable improvement and 15%demonstrated worsening. Both early-treatment groups had a signicant average reduction in ANBangle, more by change in maxillary dimensions in the headgear group and mandibular growth in thefunctional appliance group. There were wide variations in response, however, with only 75% of the

treated children showing favorable skeletal response. Failure to respond favorably could not beexplained by lack of cooperation alone. The preliminary results from phase 2 show that, onaverage, time in xed appliances was shorter for children who underwent early treatment, but thetotal treatment time was considerably longer if the early phase of treatment was included. Onlysmall differences were noted in anteroposterior jaw position between the groups at the completionof treatment, and the changes in dental occlusion, judged on the basis of Peer Assessment Ratingscores, were similar between groups. Neither the severity of the initial problem nor the duration oftreatment was correlated with the occlusal result. The number of patients who required extractionof permanent teeth was greater in the early functional appliance group than in the headgear orcontrol group. The option of orthognathic surgery was presented more often in the cases ofchildren who did not undergo early treatment, but surgery was accepted or was still beingconsidered almost as frequently in the previous headgear group as in the controls, less often in thepatients previously treated with functional appliances. (Am J Orthod Dentofacial Orthop 1998;113:62-72.)

F or preadolescent children with Class IImalocclusion, the optimal timing for treatment re-mains controversial, despite long experience andmany published ndings. Because most patients withClass II malocclusion have some type of skeletalimbalance, early (preadolescent) treatment often isaimed mainly at modifying the growth of the jaws.This early phase of treatment is usually followed bya second, and presumably simpler, later stage of tooth movement during adolescence. Thus patients with Class II malocclusion would benet from two-

stage treatment if skeletal growth could be modied,

and if this made a difference in terms of thesubsequent treatment duration, treatment complex-ity, or treatment outcome compared with one-stagetreatment during adolescence.

In this article we present a progress report on arandomized clinical trial being undertaken at theUniversity of North Carolina (UNC) to addresssome of the issues related to the timing of treatmentfor Class II malocclusion. The UNC trial was de-signed in two parts (Fig. 1). The rst phase of thetrial addressed the issue of whether the growth

pattern of Class II patients can be modied; thesecond phase approached the more difcult ques-tion of whethereven if differential growth effectscan be induced during early treatmentthese ef-fects in the end make any difference.

MATERIAL AND METHODS

To review briey, in the rst phase of the trialpreadolescent children with increased overjet ( 7mm) were randomly assigned (in blocks of six, stratied by

From the Department of Orthodontics, School of Dentistry, University of North Carolina.a Professor.b Research Professor.c Professor.Reprint requests to: J. F. Camilla Tulloch, BDS, FDS, DOrth, Departmentof Orthodontics, School of Dentistry, University of North Carolina, ChapelHill, NC 27599-7450.Copyright 1998 by the American Association of Orthodontists.0889-5406/98/$5.00 0 8/5/85971

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gender) to undergo early growth modication (headgear

or a functional appliance) or no treatment during anobservation period. To reduce the inuence of differencesin clinical prociency on the outcomes of early growthmodication, all phase 1 treatment was provided by oneclinician in accordance with a strict treatment protocol. All patients (treated and controls) were evaluated at 15months, which was felt to be a reasonable time frame in which to demonstrate possible differential growth effects.The comparison being made during phase 1 of the trial was the skeletal change seen in the two early-treatmentgroups compared with that seen in the control group.Procedures in phase 1 of the UNC clinical trial arepresented in detail elsewhere. 1

The second phase of the trial was designed to addressthe question, Does early growth modication make adifference in the subsequent treatment? After phase 1,patients were maintained in their assigned groups untiltheir primary teeth were lost. The patients were thenrerandomized, this time in blocks of eight, stratied on thebasis of their phase 1 group assignment, to one of fourdoctors for completion of treatment. Thus in phase 2 eachdoctor was assigned approximately equal numbers of observation only or early growth modication (headgearor functional appliance) patients. This rerandomization was undertaken to maximize the chance that each doctor would receive approximately equal distributions of boysand girls, good and poor early-treatment responders,compliant and noncompliant children, and children withother variables that might inuence treatment outcome.

The treatment protocol during phase 2 was not spec-ied. Rather, each doctor was permitted to determine what treatment the patient should receive. In this way theimpact of early growth modication on subsequent treat-ment and treatment outcome could be reviewed in light of the widely recognized differences between patients anddifferences in clinicians prociency. In phase 2 of theUNC trial the comparisons being made involve benetsaccruing to the patients who underwent early treatment,

compared with those who did not. The benets consideredin this report are the treatment outcome measured as theamount of skeletal change during late treatment, thechange in Peer Assessment Rate (PAR) score (a summaryof the alignment and occlusion of the teeth, 2 the durationof comprehensive treatment, and the complexity of treat-ment as indicated by extraction rate and the orthognathic

surgery rate.Phase 2 of the trial is ongoing at this writing. Thisreport is based on the 107 patients (of 147) who hadcompleted comprehensive treatment as of January 1997. At this point, median values are generally reported forphase 2 results because these data are less likely thanmean values to be skewed by the addition of later data;only descriptive statistics are reported as interim results.The progress of patients through the trial is shown inTable I.

RESULTS

At the start of the trial the three groups formed

by the rst randomization were equivalent withregard to age, sex, maturity, and morphologic mea-sures from the cephalograms and study models. Thepatients, 58% male, were in mixed dentition, with amean age of 9.9 years (range 7.712.4 years). Thechildren had moderate to severe Class II problems, with a mean ANB angle of 6.2 (range 0.412.2)and a mean overjet of 8.33 mm (range 715 mm). A bilateral Class II molar relationship was found in90.8%.

Fig. 1. Design of the two-phase randomized clinicaltrial used to evaluate benet of early orthodontic treat-ment for Class II malocclusion.

Table I. Progress of patients through the two phases of theUNC trial as of January 1997

Control Functional Headgear

Started phase 1 61 53 52Completed phase 1 61 53 52

Dropped after phase 1 9 8 2Moved 4 2 0Parent decision 1 2 0No reason 2 2 1Investigator decision 2 2 1

Started phase 2* 52 41 50Completed phase 2 38 37 361 Year recall 20 17 212 Year recall 9 11 123 Year recall 1 0 0

*Excludes four patients in functional appliance group who desired noxed-appliance treatment in phase 2.

American Journal of Orthodontics and Dentofacial OrthopedicsVolume 113, No . 1

Tulloch, Phillips, and Proft 63


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The maxillary and mandibular skeletal changesduring phase 1 are detailed elsewhere 1 and summa-rized here in Table II. The changes are reported asannualized change in an effort to adjust for minordifferences in the time each patient was observedand to facilitate comparison with other studies. Theresults of an analysis of variance (ANOVA) indi-cated that, between boys and girls, that there was nodifference in their cephalometric measures and nodifference in the pattern of change of boys and girlsin any of the three groups. The comparison betweenthe three phase 1 groups showed that early treat-ment with headgear or functional appliance did, onaverage, reduce the severity of the skeletal discrep-ancy. ANB changes were quite similar in the head-gear and functional appliance groups, but the mech-anism by which these changes occurred wasdifferent. Headgear patients had a greater tendencyto restricted maxillary forward movement, and thefunctional appliance subjects were more likely tohave increased mandibular length and improvedchin position.

Despite the small but statistically signicant dif-ferences seen between the three groups, there was wide variation within all three groups. By no meansdid all patients respond as one might have expected

from the pattern of average changes. In the controlgroup, 4% showed highly favorable growth and 15%unfavorable growth. When the magnitude of skele-tal change was categorized from highly favorable tounfavorable, about 75% of the treated childrenshowed favorable response; 25% did not (Fig. 2).Even though we noted a statistically signicantdifference in the distribution of these changes be-tween groups, the magnitude of the skeletal changecould not be explained in terms of the patients

initial skeletal severity, age/maturity at the outset of treatment, pattern of growth, or general compliance with treatment. 3

Fig. 3 shows the amount of skeletal change(measured as the ANB angle) in the three groups at

the different stages of treatment. We detected nodifference in ANB angle among the three groups atthe outset of the trial. After phase 1, the twoearly-treatment groups had statistically signicantreductions in ANB angle. The preliminary data fromphase 2(107 of 147 patients) show a larger averagereduction in ANB in the patients who had noprevious early treatment, so there is only a smalldifference between the groups at the end of phase 2.

The outcome of treatment in terms of the align-ment and occlusion of the teeth is given in Fig. 4.The PAR scoring system ranges from 0 (describing aperfect occlusion with ideal alignment and toothrelationships) to 50-plus (which categorizes a verysevere malocclusion). PAR scores below 5 generallydescribe near-ideal occlusions, whereas scores be-tween 5 and 10 usually denote acceptable occlusionsand scores of greater than 10 reect less satisfactoryalignment or occlusion. 2 Although the average im-provement in occlusion in the early-treatmentgroups was rather modest during phase 1, somepatients beneted greatly and others actually got worse. In general, the PAR score for control pa-tients increased over this period, most likely reect-ing the increase in crowding that occurs as perma-nent canines erupt. During phase 2 the treatmentchanges were such that the average PAR score atthe end of phase 2 was approximately the same forpatients who did not have early treatment as forthose who did. The distribution of near-ideal, ac-ceptable and less satisfactory nal results was alsoquite similar in the three groups (Table III). Wefound no systematic relationship between the sever-ity of the occlusal problem at the start of treatment,as measured by the PAR score, and the occlusionand alignment of the teeth at the end of phase 2treatment (Fig. 5).

Both the previous controls and the early-treat-

ment patients were treated in phase 2 in accordance with their assigned doctors preferences. At the startof phase 2 all children had lost their primary teethand were therefore at a stage at which full xedappliances could be placed. However, in some casesthe doctor elected to start phase 2 with preliminaryappliances such as an expansion device, lip bumper,headgear, or partial banding with a 2 4 setup. Thetreatment time described here is the total treatmenttime for phase 2that is, the time in full xed

Table II. Annualized mean change in the skeletal measuresduring phase 1

Skeletal measuresControl

(n 61) Functional

(n 53) Headgear (n 52)

ANB 0.17 0.93 1.07

SNA 0.26 0.11 0.92

SNB 0.43 1.07 0.15

Mandibularlength

2.36 3.69 2.97

The connecting underlines indicate where statistically signicant differ-ences exist ( p 0.01) between groups (two-way analysis of variance).

American Journal of Orthodontics and Dentofacial Orthopedics January 1998

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routine practice for clinicians to make useful gener-alizations about their own treatment decisions andpractices, the choice of early or later treatment forClass II malocclusion must inevitably be based onindividual experience and imperfect data. We hopethat the evidence from this and similar trials willhelp clinicians reevaluate their beliefs about theircurrent practices.

The question of whether early treatment canproduce statistically signicant and clinically rele- vant changes in growth was approached in phase 1 with the use of a carefully controlled prospectivestudy. In the past, comparisons of early treatmenteffect have most frequently been made against ex-isting cephalometric standards, alternative treat-ment groups, or untreated normals. 4-6 We question

the validity of such comparisons, particularly in theevaluation of the effect of treatment on growth. Notsurprisingly, few investigators have monitored un-treated Class II children longitudinally. The fewreports of untreated patients that do exist suggestthat growth is highly variable,7-9 difcult to predict, 10and different from that in normal subjects. 11,12Much of the success or failure of treatment thatclinicians deal with on a day-to-day basis may in factbe more attributable to differences in growth and

clinician prociency than to the efcacy of a partic-ular treatment approach. It may be salutary forclinicians to keep in mind the variability in growthshown in this and other untreated Class II groups when treatment results are evaluated.

In this trial one clinician was responsible forphase 1 treatment, using as simple an approach totreatment possible. The appliances were designed toavoid, or at least minimize, any movement of theanterior teeth and the concomitant alveolar boneremodeling that might affect some of the landmarksused to measure skeletal change. Our ndings of small but statistically signicant skeletal changesduring a short period of treatment may reinforce widely held beliefs about the effectiveness of bothheadgear and functional appliances in reducing the

severity of Class II malocclusion. However, eventhough the two early-treatment groups showed anincrease in the proportion of patients experiencingfavorable growth, the magnitude of the differentialeffects was small, there was much variability, and sofar we have been unable to identify any patientcharacteristics that could serve as useful predictorsof treatment response. 3 Although it can be arguedthat different appliances or different clinicians would have produced superior or different results,

Fig. 3. Distribution of subjects by ANB angle at the three different stages of the UNCtrial.




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this carefully controlled trial was designed to ex-plore the differential effects of two common meth-ods of Class II correction, controlling for variationresulting from growth, clinician prociency, or both.Questions such as the effect of change in magnitudeor direction of the headgear force, the amount of bite opening from a functional appliance, or theimpact of continuous compared with intermittent wearalthough important clinical issueswere notconsidered in this trial. The ability to carry out suchsubgroup analyses would greatly increase the num-ber of children who would have to be enrolled andmonitored. If these or other variables are believedto be critical issues in determining treatment re-sponse or treatment benet, separate well-con-

trolled trials addressing such specic issues could beplanned.Phase 2 of the trial addresses the question of

whether it makes a difference if treatment for ClassII malocclusion is started sooner or later, providedeffective treatment occurs at some point. Will smallskeletal changes produced by early treatment besustained over time, making the subsequent man-agement of and treatment outcomes for these pa-tients different from those of children whose treat-

ment was delayed? Alternatively, will the effects of early treatment gradually diminish so the early- andlate-treatment groups become once more indistin-guishable?

The preliminary data from this trial suggestthat the skeletal effects of early treatment, on

average, are not maintained. Instead, the ANBdifferences between the early-treatment and ob-servation groups diminish, so that little if anydifference remains after comprehensive treatmentis completed. It has been suggested that theskeletal changes in early treatment, particularlythe increase in mandibular growth seen withfunctional appliances, may simply represent anacceleration in growth rather than a net gain. 13The data lend some support to this contention.

Fig. 4. Distribution of PAR scores for each group at different time points in the UNCtrial.

Table III. Number of patients at the end of phase 2 of theUNC trial with near-ideal, acceptable, and less satisfactoryPAR scores

PAR category Control Functional Headgear

5 (ideal) 18 16 20610 (good) 7 11 7

10 (less satisfactory) 11 8 8




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Fig. 5. Initial severity of each patients malocclusion, plotted against treatment outcome,both measured by PAR score.

Fig. 6. Total time for phase 2 treatment (time in full xed appliances plus preliminaryappliances such as expansion devices or partial banding) for each group, by each doctor.




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Fig. 7. A, Total phase 2 treatment time for each patient, plotted against initial severity ofpatients malocclusion. B, Total phase 2 treatment time for each patient, plotted againstoutcome of treatment.




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The growth effects of early treatment (or notreatment), however, were far from uniform, andthis variability must be kept in mind when long-term skeletal effects are evaluated. It is possiblethat children who sustained large changes inskeletal jaw relationship during phase 1 showeda different response during phase 2 than thosethat did notthat is, the children who respondedmost favorably to phase 1 treatment (about 25%of those who underwent phase 1 treatment)achieved a benet that those with less favorable orno response did not. It will not be possible to fullyevaluate these ndings until the total data set forthe trial is available.

Treatment response is judged in two ways: tosome extent as the improvement in skeletal relation-ship, but to a much larger extent as the improvementin dental alignment and occlusion. Many of the fewprevious studies whose authors attempted to quan-tify the success (or failure) of orthodontic treatmentinvolved different indexes and operational deni-tions, making it difcult to compare successrates. 14-18

The PAR index was specically developed toassess not only the severity of malocclusion but theoutcome of treatment. 2 This index, tested and vali-dated in both European 19 and American 20 settings,reects clinicians beliefs about the importance of the various components of occlusion. The use of anobjective measure of the changes in alignment andocclusion of teeth that result from treatment should

remove much of the subjectivity in comparison of responses to alternative treatment approaches.However, the PAR index can only be regarded as ameasure of the proximate outcomes of care 21 thatis, the extent to which the clinician has succeeded inthe immediate goal of improving the patients dentalalignment. Little evidence relates reduction in PARscores with the ultimate outcomes of treatment thatpatients are presumed to care about, such as im-proved appearance, sociopsychologic well-being, or

oral health. It is also possible for two patients tohave the same PAR score with different relation-ships of tooth to basal bone. Although this possibil-ity poses a special problem in the comparison of theoutcome of treatment across groups of children who

have sustained more-or-less successful growth mod-ication during early treatment, the distribution of PAR scores (both percentiles and categories) do notseem different for the children who had early treat-ment than for those who did not. This nding,together with the observed changes in ANB, sug-gests that, with regard to the issue of whether earlytreatment makes a difference in treatment outcome,there is little difference in the effectiveness of earlyand delayed treatment for correction of Class IImalocclusion. The lack of any systematic relation-ship between the initial severity of the malocclusionand treatment outcome shown in Fig. 5 suggests thatexcellent treatment outcomes occur almost as oftenfor patients who initially had severe malocclusion asfor those with more moderate problems. Similarly,less satisfactory results can occur across a widerange of initial occlusal severity.

Clearly many of the children with high nal PARscores ( 10) were those for whom treatment wasdiscontinued early, frequently at the request of theparent or patient. Several of these patients andparents discussed but declined surgical correction. Although the distribution of boys and girls with highnal PAR scores was approximately equal in the twoearly-treatment groups, 8 of the 11 control fail-ures were male. It may well be that delay in thestart of treatment for boys compromises their abilityto cope with complex extended treatments as theyapproach adolescence. Growth modication itself may not be so important as the childs ability tocooperate with the treatment regimens given all theother changes occurring in their lives.

The ndings of previous studies have suggestedthat two-phase treatments generally take longerthan treatment provided as a single phase; 13,22 ourdata support this. Comparing the duration of phase2 treatment for children who started treatment in

mixed dentition with that in patients for whomtreatment was delayed until the permanent teetherupted, we see that in these initially equivalentgroups, the average phase 2 treatment time wasalmost always shorter for the headgear and func-tional appliance groups than for the control pa-tients. However, when the time in early treatment(approximately 15 months) is also included, onaverage the two-phase treatments are longer thanthe single phase undertaken by the controls. This

Table IV. Complexity of phase 2 treatment presented for all147 patients starting phase 2 treatment

ParametersControl

(n 52) Functional

(n 45) Headgear (n 50)

Number of extraction cases 9 14 7

Surgical optionsDiscussed 20 5 9 Accepted* 3 0 3Undecided 4 1 2

*As of January 1997, only two patients (both in the control group) havehad surgery, with BSSO and rigid xation.




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result must be viewed with some caution; the pro-tocol of the trial mandated a separation of phase 1and phase 2. It is possible that phase 1 could havebeen shorter for several of these patients or thatcomprehensive treatment could have been phased in

earlier. The question is one of patient preferenceand practice efciency: Even if some treatment timeis spent wearing simpler appliances and perhapsmaking less frequent ofce visits, is an increase inoverall treatment time justied?

A second consideration is the variation in treat-ment time seen from patient to patient (somepatients being treated in as little as 11 months andothers taking as long as 60 months) and betweendoctors (one doctor consistently taking a shortertime to treat all groups of patients). It has beensuggested that the initial severity of the malocclu-sion is one of the most important factors in thedetermination of treatment duration. 22 Our prelim-inary ndings do not support this. The plots in Fig.6 show no simple systematic relationship betweenduration of treatment and initial severity. Less sur-prisingly, the nal treatment outcome also seems tobear no systematic relation to treatment time. Per-haps clinicians have an ideal occlusion as a goal fortreatment and ght to achieve this goal; for somepatients their persistence works, whereas for otherspotential nally expires. It may well be that thebetween-doctor differences prove in the end to havemore of an effect on treatment time than does theeffect of early growth modication. These conclu-sions are tentative at best; approximately 25% of thepatients are still in treatment.

One of the goals of mixed-dentition treatment isthat later treatment should be simpler, perhapsrequiring fewer extractions and less surgery. 23,24 If early treatment does signicantly alter growth andimprove jaw relationships, the rates of extraction tocamouage a Class II skeletal pattern or orthog-nathic surgery to correct jaw relationships should bereduced. The extraction rates for the general ortho-dontic population have always been hard to esti-mate, with temporal trends reecting different cur-

rent clinical beliefs and practices. In the 1990s theextraction rate for patients attending the UNCorthodontic clinic (all types of patients, any extrac-tion pattern) is about 30%. 25 In the UNC Class IItrial the extraction rate was somewhat lower thanthat in all three groups, with the highest rate foundin the functional appliance group. This group had,on average, approximately 3 more proclination of the lower incisors than the control or headgeargroups during phase 1 and showed the greatest

variability in change in lower-incisor angulation.The high extraction rate, then, may have been aresponse to dental changes that clinicians believedcould compromise esthetics, stability, or gingivalhealth.

Surgical options were discussed frequently at thestart of phase 2, most frequently with the controlpatients who had had no early treatment and who were considerably older than the two early-treat-ment groups at the start of appliance therapy. Thisnding most likely reects not only the cliniciansdesire to fully inform the patients of all treatmentoptions but the prevalent belief that age and maloc-clusion severity interact to reduce the chances of successful correction with orthodontic treatmentalone. Whether such a belief is entirely justied inthe early-adolescent group is not clear. 26 The func-tional appliance groupwho, on average, had thesmallest ANB angle at the end of phase 2also hadthe lowest rate of surgery. The preliminary datafrom this trial suggest that early treatment mayinuence both the rate of extraction and the needfor orthognathic surgery, but not in the pattern thatmight have been expected. It is not yet clear whetherthese differences will prove statistically signicant when all the data are available, or how they might beexplained if they do prove signicant. Further analysis of the data set will permit more detailed evalu-ation of these important clinical questions.

CONCLUSION

We conclude that, for children with moderate tosevere Class II problems, early treatment followed by latercomprehensive treatment on average does not producemajor differences in jaw relationship or dental occlusion,compared with later one-stage treatment. The severity of the initial problem and the treatment time, surprisingly,are not important inuences on the nal outcome. Vari-ability in skeletal growth pattern appears to be a majorcontributor to variability in treatment response. Differ-ences in patient compliance, clinician prociency, and,probably, other (yet-unidentied) clinical factors alsomust affect treatment outcomes. It is likely that theindications for early treatment can be rened in the futureto permit better selection of those patients most likely tobenet from this type of intervention.

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5 - Benefit of Early Class II Treatment Progress Report of a Two-phase Randomized Clinical Trial - Proffit