Class II Treatment Efficiency in U4 Extraction & Non Extraction Protocols 2007

ORIGINAL ARTICLE

Class II treatment efficiency in maxillarypremolar extraction and nonextractionprotocolsGuilherme Janson,a Sérgio Estelita Cavalcante Barros,b Marcos Roberto de Freitas,a

José Fernando Castanha Henriques,a and Arnaldo Pinzanc

Bauru, Brazil

Introduction: In this study, we compared the efficiency of nonextraction and 2-maxillary-premolar-extractionprotocols in complete Class II malocclusion treatment. Methods: A sample of 112 records from patients withcomplete Class II malocclusion was divided into 2 groups with the following characteristics: group 1,comprising 43 patients treated nonextraction with an initial mean age of 12.63 years; and group 2, comprising69 patients treated with extraction of 2 maxillary premolars with an initial mean age of 13.91 years. Tocompare the efficiency of each treatment protocol, the initial and final occlusal statuses were evaluated ondental casts with the peer assessment rating (PAR) index, and the treatment time of each group wascalculated from the clinical charts. Treatment efficiency was calculated by the ratio between the percentageof PAR reduction and the treatment time. PAR scores, treatment times, and treatment protocols’ efficienciesof the groups were compared with the t test. Results: The 2-maxillary-premolar-extraction protocol had asmaller final PAR score, a greater percentage of PAR reduction, and greater treatment efficiency than thenonextraction protocol of complete Class II malocclusion. Conclusion: The 2-maxillary-premolar-extractionprotocol has greater treatment efficiency than the nonextraction protocol of complete Class II malocclusion.
(Am J Orthod Dentofacial Orthop 2007;132:490-8)
It is known that treatment protocol and malocclusionseverity can influence the results, the duration, and,consequently, the efficiency of orthodontic treat-

ment.1-9 Because malocclusion severity is an inherentcharacteristic that cannot be controlled, efforts have beenmade to evaluate the influence of treatment protocol onthe efficiency of orthodontic treatment.3,10,11 Efficiency isdefined as the capacity of producing the best results withthe least time expense.12 It was demonstrated that com-plete Class II malocclusion treatment with 2 maxillarypremolar extractions produces a better occlusal successrate than the 4-premolar-extraction protocol,6 becauseobtaining a Class I molar relationship in the 4-premolar-extraction protocol requires more anchorage reinforce-

From the Department of Orthodontics, Bauru Dental School, University of SãoPaulo, Bauru, Brazil.aProfessor.bGraduate student.cAssociate professor.Based on research by the second author in partial fulfillment of the require-ments for the degree of master of science in orthodontics at Bauru DentalSchool, University of São Paulo.Reprint requests to: Guilherme Janson, Department of Orthodontics, BauruDental School, University of São Paulo, Alameda Octávio Pinheiro Brisolla9-75, Bauru, SP, 17012-901, Brazil; e-mail, [email protected], January 2005; revised and accepted, October 2005.0889-5406/$32.00Copyright © 2007 by the American Association of Orthodontists.
doi:10.1016/j.ajodo.2005.10.031
490

ment with removable appliances and more patient com-pliance than maintaining Class II molar relationship in the2-maxillary-premolar-extraction protocol.2,5,6,13,14 Treat-ment time is also shorter in the 2-maxillary-premolarprotocol than in the 4-premolar-extraction protocol15 be-cause molar relationship correction, inherent to nonextrac-tion and 4-premolar-extraction protocols, is considered toincrease Class II treatment time.3,8,11,16 According to thisrationale, it could be speculated that probably a 2-premo-lar-extraction protocol also has a better occlusal successrate and a shorter treatment time than a nonextractionprotocol in complete Class II malocclusion patients. Al-though treatment results and treatment times have beencompared between treatment protocols, the amounts ofchange in a time period have not been related to each otherto evaluate treatment efficiency.

The purpose of this study was to test the followingnull hypothesis: complete Class II malocclusion treatmentefficiency is similar in nonextraction and 2-maxillary-premolar-extraction protocols. Therefore, occlusal results,treatment times, and efficiency index values were com-pared between the 2 groups treated with these protocols.

MATERIAL AND METHODS

The sample was retrospectively selected from the
files of the Department of Orthodontics at Bauru Dental

American Journal of Orthodontics and Dentofacial OrthopedicsVolume 132, Number 4

Janson et al 491

School, University of São Paulo, Brazil; the filesinclude 3592 documented and treated patients. Recordsand the initial and final dental study models of allpatients who initially had complete bilateral AngleClass II malocclusion (molar relationship) and weretreated without extractions or with 2 maxillary premo-lar extractions and standard fixed edgewise applianceswere selected and divided into 2 groups. Sampleselection was based exclusively on the initial antero-posterior (AP) dental relationship, regardless of anyother dentoalveolar or skeletal characteristic. Addition-ally, the patients selected had all permanent teeth up tothe first molars and no dental anomalies of number,size, and form. Group 1 consisted of 43 patients (21male, 22 female) treated nonextraction at an initialmean age of 12.63 � 1.45 years (range, 9.39-16.03years). Thirty-six of these patients had Class II Division1 malocclusions, and 7 had Class II Division 2 maloc-clusions. Group 2 consisted of 69 patients (38 male, 31female) treated with extraction of 2 maxillary firstpremolars at an initial mean age of 13.91 � 2.71 years(range, 9.42-27.08 years). Fifty-one of these patientshad Class II Division 1 malocclusions, and 18 hadClass II Division 2 malocclusions.

Orthodontic mechanics included fixed edgewiseappliance, with 0.022 � 0.028-in conventional bracketsand the usual wire sequence characterized by an initial0.015-in Twist-Flex or a 0.016-in Nitinol, followedby 0.016, 0.018, 0.020, and 0.021 � 0.025 or 0.018 �0.025-in stainless steel wires (all from 3M Unitek,Monrovia, Calif). Deepbite was corrected with accen-tuated and reverse curve of Spee. In the 2-maxillary-premolar-extraction patients, the anterior teeth wereretracted en masse with a rectangular wire and elasticchains for overjet and Class II canine correction.Extraoral headgear was used to correct the Class II APrelationship in the nonextraction group, whereas, in theextraction group, an extraoral appliance was used toreinforce anchorage and maintain the Class II molarrelationship. When necessary, Class II elastics wereused in the nonextraction group to help obtain a ClassI molar relationship; in the extraction group, thisprocedure was used to help maintain a Class II molarrelationship.

The patients’ records were used to determine initialage (IAge), sex, date of treatment onset, date oftreatment completion, and total treatment time (TT).During this procedure, it was observed that 21 of the 43patients (48.8%) treated without extractions received2-phase treatment and used the combined headgear-activator appliance for 11.2 � 6 months before treat-ment with a fixed appliance. On the other hand, 22 of
the 69 patients (31.8%) treated with extractions of
maxillary premolars had the extractions because of theunsuccessful attempt of Class II malocclusion treatmentwithout extractions. Because the nonextraction group’s2-phase treatment and the extraction group’s delayedextractions could influence the occlusal results andTT,17-23 the nonextraction patients were divided into 1-and 2-phase treatment subgroups (subgroups 1A and1B), whereas the extraction patients were divided intoimmediate-extractions and delayed-extractions sub-groups (subgroups 2A and 2B). These subgroups werealso compared to investigate whether 2-phase treatmentand delayed extractions affect the results.

The peer assessment rating (PAR) index24 wascalculated on the pretreatment and posttreatment studymodels of each patient, according to the Americanweightings suggested by DeGuzman et al.25 Initial andfinal occlusal characteristics were ranked by scores formolar and premolar AP relationship, overjet, overbite,midline, crossbite, and crowding to quantify the initialmalocclusion severity (I-PAR), the occlusal treatmentresults (F-PAR), and the percentage of PAR reduction(PcPAR),3,7,26 which is a better estimate of occlusalimprovement.10

Because the PAR index analyzes a set of occlusalcharacteristics at the same time and does not discrimi-nate the participation degree of each in the total score,the posttreatment scores obtained for each PAR com-ponent were individually compared to determine thesuccess rate achieved. Therefore, the PAR score at theend of treatment was again separated into its severalcomponents to allow an individual evaluation.

The treatment efficiency index (TEI) was evaluated bythe relationship between PcPAR and TT in months,expressed as TEI � PcPAR/TT. The TEI increased whena greater PcPAR was associated with a shorter TT.

Initial and final PAR scores were recalculated bythe same examiner (S.E.C.B.) in the pretreatment andposttreatment study models of 30 randomly selectedpatients. The casual error was estimated by Dahlberg’sformula (Se2 � �d2/2n), where S2 is the error varianceand d is the difference between the 2 determinations ofthe same variable; the systematic error was calculatedwith dependent t tests, at P �.05.27,28

Statistical analyses

Compatibility of the groups regarding the propor-tions of Class II Divisions 1 and 2 malocclusions andsexes was evaluated with chi-square tests. T tests wereused to compare the groups regarding IAge, I-PAR,F-PAR, PcPAR, TT, and TEI. Because there was astatistically significant difference in the IAges thatcould influence F-PAR and TT,3,18,20,22,29-32 some pa-
tients were eliminated from both groups to match the

American Journal of Orthodontics and Dentofacial OrthopedicsOctober 2007

492 Janson et al

IAges, and the groups were compared again with the ttest. Descriptive statistical analysis was used to showthe patient distribution according to the F-PAR. Theocclusal results obtained for each component of thePAR were individually compared between the groupswith the Mann-Whitney U-test. A nonparametric testwas used because the values of each PAR componentdid not have normal distribution, according to theKolmogorov-Smirnov test.33

To investigate whether 2-phase treatment or de-layed extractions had influenced F-PAR and TT, thefollowing comparisons were made: group 1 and sub-groups 2A and 2B were compared with each other withANOVA, followed by Tukey tests; subgroup 1B wascompared with group 2, and subgroups 1A and 2A werecompared with t tests.

RESULTS

The I-PAR and F-PAR did not have significantsystematic errors, and the casual errors were withinacceptable levels (Dahlberg: I-PAR � 0.8062, F-PAR �0.5916). The groups were similar regarding theproportion of Class II Divisions 1 and 2 malocclusiontypes and sexes (�2 � 1.4696 and P � .2254; �2 �

Table I. Results of independent t test between groups 1

Variable

Group 1 (n � 43)(nonextraction)

Mean SD

IAge 12.63 1.45I-PAR 24.32 7.67F-PAR 5.67 5.62PcPAR 72.69 31.38TT 30.14 9.74TEI 2.95 1.32

*Statistically significant at P �.05.

Table II. Results of independent t test between groups

Variable


Mean SD

IAge 12.92 1.09I-PAR 24.08 7.93F-PAR 5.27 5.80PcPAR 73.78 33.33TT 29.72 9.65TEI 2.78 1.52


0.4131 and P � .5204, respectively). IAge, Pc PAR,

and TEI were statistically greater and the F-PAR wasstatistically smaller for the extraction group (thesmaller the F-PAR score, the greater the occlusalsuccess rate) (Table I). Similar results were obtainedwhen IAge was matched in the groups (Table II). At theposttreatment stage, the extraction group had a greaterpercentage of patients with PAR scores equal to zeroand a smaller PAR range (Table III). When severalocclusal characteristics of the F-PAR index were indi-vidually compared between the groups, a better APrelationship of the buccal occlusion was observed in theextraction group (Table IV). The immediate-extractionssubgroup had a statistically shorter TT and a higher TEIthan the delayed-extractions subgroup and the nonex-traction group. The F-PAR score and the PcPAR weresimilar between the immediate and the delayed-extrac-tions subgroups, and statistically greater and smaller inthe nonextracion group, respectively (Table V). The2-phase nonextraction subgroup had a greater F-PARscore, a smaller PcPAR, and a smaller TEI than theextraction group (Table VI). A statistically longer TTand a smaller TEI were found for the 1-phase nonex-traction subgroup compared with the immediate-extrac-

2

Group 2 (n � 69)maxillary premolar

extractions)

df PSD

2.71 110 .0053*7.40 110 .80082.88 110 .0001*

13.91 110 .0002*10.16 110 .10781.27 110 .0013*

2 with comparable initial ages

Group 2 (n � 58)(maxillary premolar

extractions)

df Pn SD

1 1.29 92 .26391 7.18 92 .91517 2.88 92 .0017*4 14.28 92 .0030*2 10.53 92 .17004 1.39 92 .0022*

and

(

Mean

13.9123.952.42

88.8726.993.78

1 and

Mea

13.223.92.3

88.926.73.7

tions subgroup (Table VII).

4.2 95


Janson et al 493

DISCUSSION

Our subjects were selected primarily on the basis ofa complete bilateral Class II malocclusion, independentof the associated cephalometric skeletal characteristics.Since both groups were similarly chosen, it could beexpected that these characteristics would be evenlydistributed between them. Usually, it is not the skeletalcharacteristics of a Class II malocclusion that primarilydetermine whether it should be treated with or without2 maxillary premolar extractions but, rather, the pa-tient’s development stage, because maxillary-premolar-extraction treatment has been preferentially used innongrowing Class II patients.2,14,34-37 Nevertheless, thesimilarity of the malocclusion types and the initialmalocclusion severity points toward cephalometriccompatibility of the groups.38 Additionally, the primary

Table III. Descriptive analysis of the patients’ percenta

F-PAR (score) 0 2 3 4 5 6

Cumulative %, group1(nonextraction) 30.2 37.2 41.8 51.1 53.4 62.7 6

Cumulative %, group 2(maxillary premolarextractions) 44.9 62.3 65.2 81.1 86.9 89.8 9

Table IV. Results of the comparison of the F-PAR indiU test)

Variable

Group 1 (n � 43) (nonextraction) Group 2

Mean rank

AP 64.97OVJ 61.86OVB 62.04ML 57.60CB 60.30C 55.48

OVJ, overjet; OVB, overbite; ML, midline; CB, crossbite; C, crowdi*Statistically significant at P �.05.

Table V. Results of ANOVA and Tukey tests between

Variable


Subgroup 2A (n(maxillary pre

extractions, immextractions

Mean SD Mean

I-PAR 24.32a 7.67 24.34a

F-PAR 5.67a 5.62 2.80b

PcPAR 72.69a 31.38 87.41b

TT 30.14a 9.74 23.60b

TEI 2.69a 1.43 3.95b

Different letters represent statistically significant differences.*Statistically significant for P �.05.

objective was to investigate whether there was a dif-

ference in the final occlusal success rate between these2 treatment protocols. Further studies on the influenceof skeletal pattern on our results are being conducted.

At the beginning of treatment, the groups weresimilar, except for IAge (Table I). Even though ayounger age would favor Class II treatment of thenonextraction group,31,39 the extraction group had morefavorable occlusal results (Table I). Nevertheless, toeliminate any concern, the groups were divided intosubgroups with matching IAges, which were comparedwith the t test (Table II).

The F-PAR and the PcPAR results had statisticallysignificant differences between groups 1 and 2, withmore favorable results for group 2, as shown in Table I.This demonstrates that Class II malocclusion treatmentwith extraction of 2 premolars not only allows a better

groups 1 and 2 according to F-PAR

8 9 10 11 12 14 15 16 18 20

81.3 81.3 86 86 88.3 90.6 95.3 97.6 100

.6 95.6 98.5 98.5 100 100 100 100 100 100

components between groups 1 and 2 (Mann-Whitney

9) (maxillary premolar extractions)

Z PMean rank

51.21 �2.180 .0292*53.15 �1.379 .167953.04 �1.426 .153655.81 �0.284 .776254.13 �0.978 .328057.11 �0.257 .7969

1 and subgroups 2A and 2B

Subgroup 2B (n � 22)(maxillary premolarextractions, delayed

extractions) ANOVA

Mean SD F P

23.13a 7.35 0.223 .80021.59b 2.08 8.82 .0002*

91.99b 12.56 7.27 .0010*34.21a 12.93 11.37 .0000*3.08a 1.28 10.31 .0000*

ges in

7

7.4 72

vidual

(n � 6

ng.

group

� 47)molarediate)

SD

7.473.13

14.406.311.26

occlusal success rate, but also produces a greater


494 Janson et al

proportion of changes in the initial improper dentalrelationships. Results of the subgroups’ comparisonwith matching IAges showed a similar tendency of thegroups (Table II). The better occlusal success rate ofgroup 2 is also shown by the greater percentage ofpatients with a PAR score equal to zero in relation togroup 1 at the end of treatment. According to Rich-mond et al24 and Buchanan et al,40 when the PAR indexat the end of treatment is smaller than or equal to 5, theocclusion is considered almost perfect. The extractiongroup had 86.9% and the non-extraction group had 53.4%of the patients in this correction range (Table III).

To determine which PAR components had primar-ily contributed to the occlusal success rate differencebetween the groups, they were individually compared.The extraction group had a statistically smaller post-treatment score and, consequently, a greater occlusalsuccess rate of molar and premolar AP relationshipcorrection than group 1. This showed that AP relation-ship correction was the primary component that con-tributed to the poorer occlusal results in group 1 (TableIV). This seems logical because nonextraction Class IItreatment requires twice as much anchorage reinforce-ment and consequently more patient compliance toachieve a molar Class I relationship than the 2-maxillary-premolar-extraction protocol to maintain the Class II

Table VI. Results of independent t test between subgro

Variable

Subgroup 1B (n � 21)(nonextraction, 2-phase)

Mean SD

I-PAR 26.42 7.84F-PAR 4.95 5.75PcPAR 77.89 26.69TT 31.96 10.53TEI 2.74 1.42


Table VII. Results of independent t test between subgro

Variable

Subgroup 1A (n � 22)(nonextraction, 1-phase)

Mean SD

I-PAR 22.31 7.11F-PAR 6.36 5.53PcPAR 67.73 35.19TT 28.40 8.82TEI 2.65 1.48


molar relationship.13 Therefore, these results support the

findings of other studies that suggest that treatmentdifficulty increases when a full-cusp Class II molarrelationship must be completely corrected.2,4-6,8,9,13,14

The following paragraphs theoretically illustrate thegreater difficulty of the nonextraction approach.

Treatment of complete Class II malocclusions withextraction of only 2 maxillary premolars requires an-chorage reinforcement to avoid mesial movement of theposterior segment during retraction of the anteriorteeth. Because the average mesiodistal diameter ofpremolars is 7 mm, the anterior teeth should thereforebe distalized through this distance.13 Appliances thatprovide this anchorage reinforcement are primarilyextraoral, thus requiring patient compliance for a suc-cessful treatment result.

In complete Class II therapy without premolarextractions, the need for anchorage reinforcement iseven greater, because the posterior segment must bedistalized 7 mm to achieve a Class I molar relationshipat the end of treatment.41,42 Afterwards, all anteriorteeth must be distalized 7 mm (or “space units”13),corresponding to the distalization of the posterior seg-ment. Therefore, there will be 7 mm of distalization ofthe posterior segment added to 7 mm of the anteriorsegment, for a total of 14 mm of distalization for bothposterior and anterior segments; this is twice the

and group 2

Group 2 (n � 69)(maxillary premolar

extractions)

df Pn SD

5 7.40 88 .18992 2.88 88 .0078*7 13.91 88 .0144*9 10.16 88 .05487 1.33 88 .0067*

A and 2A

bgroup 2A (n � 47)(maxillary premolarxtractions, immediate

extractions)

df Pn SD

4 7.47 67 .29170 3.13 67 .0011*1 14.40 67 .0015*0 6.31 67 .0121*5 1.26 67 .0003*

up 1B

Mea

23.92.4

88.826.93.6

ups 1

Su

e

Mea

24.32.8

87.423.63.9

amount required for Class II correction with extraction


Janson et al 495

of only the maxillary premolars.13 Consequently, theneed for anchorage reinforcement in those patients istwice as great, and treatment success depends evenmore on patient compliance.

These explanations obviously illustrate only stati-cally the amount of required anchorage and patientcompliance for the various situations. Nevertheless,such mechanisms of correction should be associatedwith growth, which might help in achieving a satisfac-tory occlusal outcome.30,31,43-46 If the patient is stillgrowing, the probability of success of the mentionedprotocols is considerably increased because the ex-traoral appliances for anchorage reinforcement not onlydistalize the maxillary teeth, but also redirect maxillarygrowth, restricting its anterior displacement, which willbe valuable for Class II correction. Moreover, mandib-ular growth, as well as its normal anterior displacement,will increase the probability of correction of the APdiscrepancy.31,43,47 This growth potential is even moreimportant in Class II patients who receive nonextrac-tion treatment because, as previously shown, they willrequire more distalization of the maxillary teeth; thismight be reduced by an association with redirection ofgrowth of the apical bases.31,45,47 Therefore, the greatlimitation of nonextraction Class II treatment in adultsand nongrowing patients can be noticed.

TT was similar between the 2 groups (Tables I andII). However, because 31.8% of the patients in theextraction group had delayed extractions, which caninfluence treatment time, the group was subdivided.

The TEI was defined as the ratio between PcPARand TT (TEI � PcPAR/TT), creating a TEI thatallowed a true and objective comparison of treatmentefficiency. The 2-maxillary-premolar-extraction grouphad a statistically greater TEI than the nonextractiongroup because the occlusal changes were greater duringa similar treatment time period (Tables I and II).

When the extraction subgroups of immediate ex-tractions and delayed extractions (subgroups 2A and2B) were compared with group 1, both subgroups hadstatistically smaller F-PAR and greater PcPAR valuesthan group 1 (Table V). This suggests that even thepatients previously assigned to nonextraction treatment,who had delayed extractions because of deficient com-pliance, complied with the lesser anchorage require-ments of the 2-maxillary-premolar-extraction proto-col13 and had a better occlusal success rate than thecompliant patients of the nonextraction approach.

TT in the immediate-extractions subgroup wasstatistically smaller than in group 1 and similar betweenthe delayed-extractions subgroup and group 1 (TableV). This demonstrates that it was the delayed-extraction
patients that accounted for a similar treatment time in
groups 1 and 2 when directly compared. Therefore,when the 2-maxillary-premolar-extraction protocol isimmediately undertaken, it has a statistically shorter TTthan the nonextraction protocol. These results contra-dict others that associated the number of extractionswith increased TT.3,7,8,10,16,48,49 However, in thesestudies, the malocclusions were not homogeneous inmalocclusion type and severity.7,8,10,16,48,49 Conse-quently, the shorter TT of the nonextraction patientsmight reflect simpler treatments for localized problems;extractions, in contrast, tend to be strongly associatedwith the treatment of more marked discrepancies3,7,10,16

(which require more extensive tooth movements). It isreasonable to speculate that treatment of a Class Imalocclusion without extractions is faster than that withextractions, since retraction of the anterior teeth de-mands additional time. Also, it would be expected thatnonextraction treatment of Class I malocclusions wouldhave a shorter TT than nonextraction treatment of ClassII malocclusions because of the additional time tocorrect the AP relationship. Therefore, the influence ofthe number of extractions on TT requires investigationwith similar malocclusion type and severity and withdifferent treatment protocols to assess the actual con-tribution of the extractions on TT. In this study, withthese controlled parameters, it was shown that theimmediate-extraction protocol of 2 maxillary premolarshad even a statistically shorter TT than the nonextrac-tion approach.

As a consequence of a statistically shorter TT of theimmediate-extractions subgroup, its treatment effi-ciency was also significantly greater than the nonex-traction group with a higher value than the extractiongroup. Furthermore, the smaller occlusal success rate(greater F-PAR) of the nonextraction group also ac-counted for the smaller TEI observed in this group(Table V). Therefore, it can be concluded that thedifficulty in correcting the Class II molar relationshipwas the factor that most contributed to the smaller TEIof the nonextraction protocol because the failure toachieve this treatment goal significantly compromisedits TT and F-PAR. The TEI of the delayed-extractionssubgroup was similar to the nonextraction group eventhough it had a greater PcPAR. This was because theTT of this group was longer, although not significantlyin relation to the nonextraction group.

The claim that 2-phase Class II malocclusion treat-ment produces better orthodontic results than thoseaccomplished in only 1 phase finds support in somestudies,23,50,51 although several controversies existabout this subject.19,21,52-54 Because, in the nonextrac-tion group in 21 of 43 patients (subgroup 1B), treatment
was divided into orthopedic and orthodontic phases, it


496 Janson et al

was speculated that this subgroup could have achievedocclusal success similar to that of the extraction groupand that the less satisfactory result of the nonextractiongroup was due to the nonextraction subgroup treated inonly 1 phase (subgroup 1A). However, results obtainedwith the 2-phase nonextraction treatment showed asmaller occlusal result success rate (greater F-PAR) anda smaller PcPAR than the extraction treatment (TableVI). Therefore, these results do not support the hypoth-esis that 2-phase treatment significantly influencesClass II treatment results and evidences the difficulty ofmolar relationship correction as the factor that mostcompromised the nonextraction treatment re-sults.2,4,6,8,9,13,14,55

TT in the 2-phase nonextraction treatment wassimilar to the extraction group, because the delayed-extraction subgroup contributed to prolong TT, asalready discussed (Table VI). Reports stating that2-phase Class II malocclusion treatment increases TTsuggest that this treatment protocol would have influ-enced TT of the nonextraction group.7,16,17,19,21,53

However, the 1-phase nonextraction subgroup had asignificantly longer TT than the immediate-extractionssubgroup (Table VII). Thus, the longer TT of thenonextraction group cannot be attributed to the 2-phasesubgroup. Therefore, the greater difficulty imposed bythe attempt to correct the Class II molar relationship inthe nonextraction group was the factor that mostcontributed to increase TT.2,8,11,16,17

Despite similar TTs, the TEI of the extraction groupwas statistically greater than that of the 2-phase non-extraction subgroup (Table VI), alike results of thegroups comparison (Table II).

The compliance necessary for treatment successvaries according to patient age and malocclusion sever-ity.4,9,30,31 Compliance, age, and malocclusion severityare clinical variables that cannot be controlled by theoperator, because they are inherent to the patient.Because 2-maxillary-premolar-extraction Class II mal-occlusion treatment reduces by half the compliancerequired from the patient,13 our findings show that agreater occlusal success rate and a shorter TT can beexpected with this protocol, increasing treatment pre-dictability, even when used in patients with reducedgrowth potential or severe malocclusions. In spite ofthis evidence, a certain reluctance persists in the liter-ature for 2-maxillary-premolar-extraction Class II treat-ment in growing patients, restricting its application tonongrowing patients.2,34-37,56 This approach appears tobe a conditioned attitude rather than a decision based onscientific evidence, since orthodontic treatment resultsduring the growth period are predominantly dentoalve-
olar regardless of orthodontic technique, treatment
protocol, or appliance type.19,57-63 Therefore, there isevidence to justify the 2-maxillary-premolar-extractionprotocol during the pubertal growth period becauseit requires less patient compliance.2,5,6,13,14 Conse-quently, moderate patient compliance with extraoralheadgear or functional appliance can be insufficient tosuccessfully treat by nonextraction a complete Class IImalocclusion, but it can be suitable for a 2-maxillary-premolar-extraction protocol.4,9

Because treatment success is an expectation thatinvariably falls on the orthodontist’s clinical conduct,64

and noncompliance is not always accepted by theparents or the patient as an excuse for unsatisfactoryresults or increased TT, the treatment protocol choiceshould be based, preferably, on treatment efficiency.

CONCLUSIONS

According to these results, the null hypothesis wasrejected because Class II malocclusion treatment with 2premolar extractions showed a better occlusal successrate, in a shorter TT, with consequently greater treat-ment efficiency than the nonextraction protocol. Theless satisfactory results of the nonextraction Class IItreatment were related primarily to the smaller APrelationship correction success, because of the greaterpatient compliance required with anchorage reinforcingappliances.

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Class II Treatment Efficiency in U4 Extraction & Non Extraction Protocols 2007