an analysis of the correttive activator

Angle Orthodontist, Vol 74, No 6, 2004741

Original Article

An Analysis of the Corrective Contribution inActivator Treatment

Paola Cozza, MD, DDS, MSa; Laura De Toffol, DDSb; Lucilla Iacopini, DDSb

Abstract: This retrospective study (1) cephalometrically investigates the effectiveness of activator ther-apy, (2) evaluates the contribution of skeletal growth in the self-correction of the Class II malocclusion,and (3) analyzes separately the dental and skeletal responses to activator treatment and the differencesbetween the incisor and molar areas. The subjects, all in the mixed dentition, were selected from a singlecenter and were divided into a group of 40 Class II patients treated with an activator and an untreatedgroup of 30 Class II patients. Dentoskeletal changes that occurred were compared on lateral cephalogramstaken before the treatment/observation period and after 21 months (standard deviation, three months). Whenthe activator patients were compared with the untreated control subjects, therapy promoted a combinationof skeletal and dental changes that led to an improvement of the sagittal discrepancy. Other changesobserved in the untreated Class II subjects did not bring about a correction of the malocclusion. An analysisof the corrective contributions in activator therapy in the posterior area showed that the orthopedic effectswere greater than the dental effects in correcting the posterior occlusal relationship. In the anterior area ofthe arch, although both the skeletal and dental changes were favorable toward the sagittal correction, theskeletal contribution was greater than the dental contribution. In general, the skeletal contribution (140%)exceeded the dental correction (60%), and the mandibular changes (73%) exceeded the maxillary contri-bution (27%) both in the anterior and posterior regions. (Angle Orthod 2004;74:741748.)

Key Words: Functional therapy; Activator

INTRODUCTION

Many articles demonstrate the effectiveness of the acti-vator in the treatment of Class II malocclusion caused bymandibular retrognathism in growing patients.19 Most re-port that the improvement of the sagittal problem dependson a combination of dental and skeletal effects on the max-illa and the mandible, including a retroclination of the upperincisor, a proclination of the lower incisor, a reduced max-illary forward growth, and an effective mandibular growth.However, very few quantify the relative weight of skeletaland dental contributions to the correction of the sagittalproblem.

A working hypothesis was introduced by Pancherz10 andlater by Weiland et al,11 Vardimon and Saduman,12 andOBrien et al13 to more precisely identify the mode of actionof the activator. In this work a study group (growing pa-

a Professor, Department of Orthodontics, School of Dentistry, Uni-versity of Rome Tor Vergata, Rome, Italy.

b Private Practices, Rome, Italy.Corresponding author: Paola Cozza, MD, DDS, MS, Via Veio 53,

00183 Rome, Italy(e-mail: [email protected]).Accepted: December 2003. Submitted: November 2003.q 2004 by The EH Angle Education and Research Foundation, Inc.

tients with treated Class II malocclusion) was comparedwith a control group (growing patients with untreated ClassII malocclusion). The aims of this study were to demon-strate the effectiveness of the activator therapy, to evaluatethe contribution of skeletal growth in the self-correction ofthe Class II malocclusion in the untreated subjects, and toanalyze separately the dental and skeletal responses to ac-tivator therapy and the differences between the incisor andmolar areas.

MATERIALS AND METHODS

The subjects for both the study and control groups wereselected from a single center (Department of Orthodontics,University of Rome Tor Vergata). The following selectioncriteria were used: (1) 911 years of age; (2) overjet greaterthan five mm; (3) Class II molar relationship, with at leasthalf a cusp width distal molar relationship; (4) skeletalClass II malocclusion with the ANB angle greater than 58;(5) retrognathic mandible, with the SNB angle ,788; and(6) no history of previous orthodontic therapy.

Patients satisfying these criteria were divided into a con-trol group of 30 subjects (15 girls and 15 boys), who haddeclined activator therapy, and a treatment group of 40 sub-jects (20 girls and 20 boys), who underwent activator ther-

742 COZZA, DE TOFFOL, IACOPINI


FIGURE 1. Cephalometric analysis: SNA angle, SNB angle, ANBangle, Go-Me (mm), Co-Gn (mm), FMA angle, FH-OL angle, IMPAangle, 1-FH angle, interincisal angle, overjet (mm), overbite (mm).

FIGURE 2. Sagittal registrations performed to the OLp and parallelto OL: A-OLp, Pg-OLp, Iu-OLp, Il-OLP, Mu-OLp, Ml-OLp.

apy. Only cases with good cooperation and treatment re-sponses from the patients were selected.

The appliance used was an acrylic monobloc with a cen-tral screw attached to the upper jaw by Adams clasps. Theappliance was designed to avoid undesirable anterior dentalmovements and two mm of the labial surfaces of the max-illary and mandibular incisors were capped to prevent tip-ping.

The appliance was produced from a construction bite thatpositioned the mandible anteriorly in an edge-to-edge in-cisal relationship. The lower jaw was postured forward ina Class I or overcorrected Class I molar relationship tostimulate mandibular growth. During treatment, contact wasmaintained between the appliance and the maxillary pos-terior teeth. The mandibular posterior teeth were encour-aged to erupt by trimming acrylic on the occlusal and lin-gual aspect.

The patients were instructed to wear the appliance a min-imum of 14 h/d. The skeletal and dental changes that oc-curred were assessed on two lateral cephalometric radio-graphs. In the treatment group, the first cephalogram wastaken before treatment (T0) and the second one at achievinga Class I occlusal relationship (after 21 1 3 months) (T1).In the control group, radiographs were obtained at the sameinterval.

The initial cephalometric patterns of the control andtreated subjects, as well as the alterations due to growth ortreatment, were assessed using the following angles anddistances:

Sagittal analysis: SNA angle, SNB angle, ANB angle,Go-Me (mm), Co-Gn (mm)

Vertical analysis: FMA angle, FH-OL angle Dental analysis: IMPA angle, 1-FH angle, interincisal an-

gle, overjet (mm), overbite (mm) (Figure 1)Other measuring points and reference lines used were

those defined by Pancherz.10 These linear measurements forthe assessment of sagittal relationships were performed us-ing the occlusal line (OL) and the occlusal line perpendic-ular (OLp) drawn through the sella. The reference grid wastaken from the first head film (T0) and transferred to theT1 tracing using the sella-nasion line (SN), with sella asthe registration point. All sagittal registrations were per-formed to the same reference line (OLp) and parallel toOL: A-OLp, Pg-OLp, Iu-OLp, Il-OLP, Mu-OLp, and Ml-OLp (Figure 2).

Method errorEach cephalogram was traced and measured by Dr Coz-

za. All measurements were repeated after a period of sevendays, and the mean value of the two measurements wasused. All measurement error coefficients were found to beclose to 1.00 and within acceptable limits (Table 1).

Statistical methodDescriptive statistics included mean and standard devia-

tion. The mean intragroup differences in cephalometricmeasurements at T0 and T1 were examined with Wilcoxonrank sum test and differences at T0 and T1 between thecontrol and treated groups with the Mann-Whitney test. Thelevel of significance used was P , .05. Nonparametric testsused as the variables studied were not normally distributed.

Percent evaluation of the corrective contributionSkeletal and dental effects in activator therapy were an-

alyzed excluding the physiological correction due to

743EFFECTS OF ACTIVATOR THERAPY


TABLE 1. Method Error CoefficientVariables R

123456

SNA (8)SNB (8)ANB (8)Go-Me (mm)Co-Gn (mm)FMA (8)

.99

.98

.98

.99

.98

.98789

101112

FH^OL (8)IMPA (8)1^FH (8)Interincisal angle (8)Overjet (mm)Overbite (mm)

.98

.97

.98

.97

.98

.99131415161718

A-OLp (mm)Pg-OLp (mm)Iu-OLp (mm)Il-OLp (mm)Mu-OLp (mm)Ml-OLp (mm)

.99

.98

.98

.99

.99

.97

growth. Therefore, the values considered (defined ddelta)were derived from the difference between the average (T12 T0) of the treatment group and the control group. Twoskeletal and two dental parameters were chosen both forthe incisor and molar areas.

The dental parameter considered the movement of theteeth inside a skeletal base, which itself undergoes a dis-placement during treatment. For example, the upper incisorhas been expressed as (Iu-OLp)-(A-OLp) or considering thenet dental movement from which the maxillary skeletalbase displacement was subtracted.

Molar correction

For the intermolar relationship correction, the followingparameters were considered:

A-OLp expresses the influence of therapy on the maxil-lary skeletal base growth

Pg-OLp expresses the influence of therapy on the man-dibular skeletal base growth

(Mu-OLp)-(A-OLp) expresses the influence of therapy onthe first upper molar movement

(Ml-OLp)-(Pg-OLp) expresses the influence of therapy onthe first lower molar movement

Overjet correctionFor the interincisor relationship correction, the following

parameters were considered:

A-OLp expresses the influence of therapy on the maxil-lary skeletal base growth

Pg-OLp expresses the influence of therapy on the man-dibular skeletal base growth

(Iu-OLp)-(A-OLp) expresses the influence of therapy onthe upper incisor movement

(Il-OLp)-(Pg-OLp) expresses the influence of therapy onthe lower incisor movement

The sum of the absolute values (without plus or minussign) of these parameters corresponds to the molar or over-jet correction. Each of these values was put into a propor-tion with the sum, giving the corrective contribution (inpercentage) of every maxillary and mandibular dental andskeletal component. The following proportion has beenused:

x:partial contribution 5 100:total contribution;x 5 partial contribution 3 100/total contribution.

RESULTSBefore treatment all patients had a dental and skeletal

Class II malocclusion and an increased overjet. Table 2shows the differences between the study and control groupsat baseline (T0). The changes observed in the measuredvariables are shown in Tables 3 and 4, which present theaverages and standard deviations of each cephalometricmeasurement considered before (T0) and after the treat-ment/observation period (T1). The comparison between thestudy and control group changes is shown in Table 5. Toevaluate skeletal and dental corrections during activatortreatment, the anterior and posterior areas were consideredseparately (Table 6).

Molar area

The amount of molar correction results from the sum ofdental ((Mu-OLp)-(A-OLp) 5 0.37 mm, (Ml-OLp)-(Pg-OLp) 5 1.17 mm) and skeletal (A-OLp 5 21.26, Pg-OLp5 3.14 mm) values and is 5.94 mm (Figures 3 and 4).

Using the proportion, the results show that the maxillarycontribution (27%) comprised 21% skeletal movement and6% upper molar drift. Although A-OLp value has a minussign (21.26 mm), which expresses a skeletal growth con-straint, (Mu-OLp)-(A-OLp) has a plus sign (0.37 mm),which indicates a mesial movement of the upper molar.

The mandibular contribution (73%) comprised 53% skel-etal movement and 20% lower molar drift. As in the max-illa, the skeletal parameter (Pg-OLp 5 3.14) has a plussign, which indicates a mandibular advancement. On thecontrary, the dental value has a minus sign ((Ml-OLp)-(Pg-OLp) 5 21.17 mm), which indicates a distal movement ofthe lower molars.

Incisor area

The amount of interincisor relationship correction resultsfrom the sum of dental ((Iu-OLp)-(A-OLp) 5 0.55 mm, (Il-OLp)-(Pg-OLp) 5 1.72 mm) and skeletal (A-OLp 521.26, Pg-OLp 5 3.14 mm) values and is 6.67 mm (Fig-ures 5 and 6).

Using the proportion, the results show that the maxillary



TABLE 2. Comparison Between Study and Control Groups at T0: Mean Values, Standard Deviations, and Significance

Variables

T1 2 T0Study Group

(n 5 40) SD

T1 2 T0Control Group

(n 5 30) SD P123456


81.8374.757.08

65.61101.6923.28

3.032.811.814.886.324.01

8377.335.70

69.83108.7320.67

1.642.251.034.503.651.48

*

**

**

NS**

**

789

101112


10.0295.67

115.25125.44

8.724.53

2.145.574.606.11.832.00

8.8096.40

113.07128

63.33

1.777.757.49

12.471.842.25

NSNSNSNS***

NS131415161718


75.5373.8382.6773.0547.5044.47

3.714.294.604.023.393.32

76.8377.678477.6750.1748

3.995.554.534.44.214.76

NS*

NS**

NS*

* P , .05; ** P , .01; *** P , .001. NS, not significant.

contribution (27%) comprised 19% skeletal movement and8% upper incisors movement. Both parameters consideredhave minus sign values and respectively express a skeletalgrowth constraint and an upper incisors retraction.

The mandibular contribution (73%) comprised 47% skel-etal movement and 26% lower incisors movement. As inthe maxilla, both parameters considered have positive val-ues and respectively express a skeletal mandibular advance-ment and a lower incisors proclination.

DISCUSSIONThe first aim of this work was to evaluate the effective-

ness of the activator in the treatment of the Class II mal-occlusion in growing subjects. When the patients of theactivator group were compared with untreated control sub-jects, a relative maxillomandibular displacement was ob-served (ANB, 22.148), which was mainly due to advance-ment of the mandibular structures (SNB, 1.648; Co-Gn,5.67 mm; Pg-OLp, 5.14 mm) and a less important maxil-lary growth inhibition (SNA, 20.58).

Dentoalveolar effects (proclination of the lower incisors[IMPA, 1.558] and retroclination of the upper incisors [1-FH, 25.648]) played an important role in this correction.The molar drifts had a favorable direction toward the cor-rection of the Class II molar relationship, even if the com-parison with the control group changes was not statisticallysignificant.14

The second aim was to evaluate the contribution of skel-etal growth to the self-correction of the Class II malocclu-sion in the untreated subjects. The changes in the untreatedcontrol subjects can be summed up as an increase of themandibular length and an advancement of the mandibular

structures (SNB, 0.178; Co-Gn, three mm; Pg-OLp, twomm), an advancement of the maxillary base (SNA, 0.338;A-OLp, 2.23 mm), a mesial drift of the lower molars (Ml-OLp, 2.67 mm), a mesial drift of the upper molars (Mu-OLp, 2.83 mm), a retroclination of the lower incisors(IMPA, 21.678), and a slight retroclination of the upperincisors (1-FH, 20.73 mm).

However, these changes do not bring about a correctionof the malocclusion. The differential growth of the skeletalbases is not enough for the correction of the sagittal dis-crepancy, and the teeth are not able to follow the movementof the bony bases. The reason for this has been identifiedas the intercuspation of the upper and lower dentition,which maintains the same dental relationship, independent-ly from the skeletal growth.15 Unlocking the intercuspationof the upper and lower dentition could negate the adaptivemechanism and allow the mandible to carry the overlyinglower dentition forward with it during normal growth.

The third aim of this study was to analyze separately thedental and skeletal responses to activator therapy on thedental arches and the differences between incisor and molarareas.

Molar area

The molar relationship was corrected one-fourth dentally(26%) and three-fourths skeletally (74%). The molar driftswere unfavorable toward the improvement of the Class IIrelationship but are subsumed into the favorable skeletalchanges. Thus, the orthopedic effects are greater than thedental effect in correcting the posterior occlusal relation-ship.

Probably the dentoalveolar adaptation mechanism is the



TABLE 3. Study Group (n 5 40): Averages and Standard Deviations Before and After Treatment; Means and Standard Deviations; andSignificance

Variables T0 SD T1 SD Mean SD P123456


81.8374.757.08

65.61101.6923.28

3.032.811.814.886.324.01

81.3376.394.94

67.97107.3623.75

2.812.951.405.397.444.42

20.51.64

22.142.365.670.47

11.311.764.851.83

NS***

***

***

***

NS789

101112


10.0295.67

115.25125.44

8.724.53

2.145.574.606.11.832.00

11.2897.22

109.61128.86

3.693.36

2.694.764.515.521.461.61

1.251.55

25.643.42

25.0321.17

2.243.094.126.41.452

*

NS***

*

***

*

131415161718


75.5373.8382.6773.0547.5044.47

3.714.294.604.023.393.32

76.5078.9782.8678.6449.4449.11

3.925.174.296.354.144.33

0.975.140.195.591.944.64

1.553.253.104.832.342.57

*

***

NS***

**

***


reason why the forward growth of the mandible did notcarry the dentition with it. The intercuspation of the upperand lower dentition was unlocked only when the appliancewas worn (14/24 h), which prevents the dentoalveolar pro-cesses from following the movement of the bony bases.15

Jakobsson16 and Wieslander and Lagerstrom17 were thefirst to introduce a reference grid system to evaluate dentaland skeletal changes during activator treatment using a per-pendicular to SN line16 or to Frankfort plane.17 Moreover,these studies used a control group of untreated Class IIsubjects. Jakobsson16 found no statistical differences in thechanges observed in treated and control subjects at the up-per molars.

Wieslander and Lagerstrom17 obtained similar results andreported no significant differences in the position of upperand lower molars between the activator and control groups.

Later, two other studies were reported using a cephalo-metric reference grid system (OLp) to determine the dentaland skeletal effects of an activator. However, the findingsare not entirely comparable with those reported in our workbecause values reported by Pancherz10 and Weiland et al11referred to the changes obtained with the appliance, withoutexcluding the effect of physiological growth.

Pancherz10 found that the molar correction (5.1 mm) wasthe result of the mandibular growth (4.7 mm) and the me-sial drift of the lower molars (2.3 mm). The skeletal max-illary changes (22.3 mm) were unfavorable, and the upperincisor movement (0.4 mm) was not significant.

Weiland et al11 found that, with the Herren activator ther-apy, the molar correction (2.73 mm), the dental (1.49 mm)and the skeletal (1.24 mm) components contributed equally.These results were compared with those obtained in a Jas-per Jumper group and a headgear-activator group. In the

Herren activator group the correction of the molar relation-ship was smallest, but it was mainly due to skeletal adap-tation. This confirms the opinion that rapid dentoalveolarcompensation prevents a more marked correction of theskeletal discrepancy in Class II malocclusion.

Two other studies in the literature analyzed the skeletaland dental effects in the treatment of Class II malocclusion,using other kinds of functional appliances. Moreover, thesearticles expressed the results obtained as a percentage. In-terestingly, these works used a control group and, therefore,changes observed were due to the net effect of therapy,excluding the effect of physiological growth.

Vardimon and Saduman12 used a removable functionalmagnetic system (FMS) for the treatment of skeletal ClassII malocclusion and reported different findings. The molarcorrection was achieved by distal movement of the uppermolar (32.5%), retraction of the maxillary base (28%), me-sial drift of the lower molar (21.5%), and mandibular skel-etal advancement (18%). The molar relationship was cor-rected half skeletally and half dentally.

OBrien et al13 used a modified Twin-Block and foundthat in the molar correction, the dental component (59%)exceeded the skeletal one (41%) as well. The major causeof molar relationship improvement was the mesial drift ofthe lower molar (33%), followed by the distal movementof the upper molar (26%), mandibular skeletal advancement(22%), and maxillary retraction (19%).

Incisor area

An analysis of our findings shows that the incisor rela-tionship was corrected one-third dentally (34%) and two-thirds skeletally (66%). In the anterior area of the arch, both



TABLE 4. Control Group (n 5 30): Averages and Standard Deviations Before and After Treatment; Means and Standard Deviations; andSignificance

Variables T0 SD T1 SD Mean SD P123456


8377.335.70

69.83108.7320.67

1.642.251.034.503.651.48

83.3377.505.83

72111.7319.33

1.482.281.573.756.835.23

0.330.170.132.173

21.33

0.490.410.611.713.685.22

NSNSNS**

**

NS789

101112


8.8096.4

113.07128

63.33

1.777.757.49

12.471.842.25

8.6794.73

112.33133.33

5.876.67

1.486.495.218.912.52.12

20.1321.6720.73

5.3320.13

3.33

1.901.294.084.170.881.18

NS**

NS***

NS***

131415161718


76.8377.678477.6750.1748

3.995.554.534.44.214.76

79.0779.678678.45350.67

3.883.973.463.62.353.92

2.23220.732.832.67

1.373.051.692.0522.55

***

NS**

NS***

**


TABLE 5. Changes in Study and Control Groups from T0 to T1: Mean Values, Standard Deviations, and Significance

Variables

T1 2 T0Study Group

(n 5 40) SD

T1 2 T0Control Group

(n 5 30) SD P123456


20.51.64

22.142.365.670.47

11.311.764.851.83

0.330.170.132.173

21.33

0.490.410.611.713.685.22

*

***

***

NSNSNS

789

101112


1.251.55

25.643.42

25.0321.17

2.243.094.126.41.452

20.1321.6720.73

5.3320.13

3.33

1.901.294.084.170.881.18

NS***

**

NS***

***

131415161718


0.975.140.195.591.944.64

1.553.253.104.832.342.57

2.23220.732.832.67

1.373.051.692.0522.55

*

*

*

***

NSNS


the skeletal and dental changes were favorable toward thesagittal correction. The skeletal contribution was greaterthan the dental effect, as can be seen in the molar regionof the dental arch.

Jakobsson16 found an improvement in overjet (23.3mm), a retroclination of the maxillary incisors (22.0 mm),and a proclination of the lower incisors (1.2 mm).

Wieslander and Lagerstrom17 obtained similar results andreported a significant retroclination of the upper incisors(23.33 mm) but no significant differences in the positionof lower incisors between the activator and control groups.

Pancherz10 found that the dental and skeletal effects of

the activator appliance are equivalent in both the molar andincisor areas. The overjet correction (5 mm) was mainlydue to a retroclination of the upper incisor (2.5 mm) andto the mandibular skeletal advancement (4.7 mm), whereasthe forward growth of the maxillary base (22.3 mm) wasconsidered unfavorable toward the correction. The lowerincisor did not change its position significantly (0.1 mm).

Weiland et al11 found that with Herren activator therapy,the overjet correction (3.58 mm) was due mostly to thedental component (2.09 mm) that was greater than the skel-etal component (1.49 mm). The retraction of the upper in-cisor (1.10 mm), together with the skeletal mandibular ad-



TABLE 6. Mean Changes (T1 2 T0) in Study and Control Groups,and Differences Between the Means (Delta)

Variables (mm)

Mean,StudyGroup

Mean,ControlGroup Delta

A-OLpPg-OLpIu-OLpIl-OLpMu-OLpMl-OLp

0.975.140.195.591.944.64

2.23220.732.832.67

21.263.14

21.814.86

20.8921.97

(Iu-OLp)-(A-OLp)(Il-OLp)-(Pg-OLp)(Mu-OLp)-(A-OLp)(Ml-OLp)-(Pg-OLp)

20.780.450.97

20.5

20.2321.27

0.60.67

20.551.720.37

21.17

FIGURE 3. Skeletal and dental changes in the molar area.

FIGURE 4. Contribution of skeletal and dental changes to molarcorrection. (Positive values indicate a favorable change toward thecorrection; negative values indicate an unfavorable change towardthe correction.)

FIGURE 5. Skeletal and dental changes in the incisor area.

FIGURE 6. Contribution of skeletal and dental changes to overjetcorrection. (Positive values indicate a favorable change toward thecorrection; negative values indicate an unfavorable change towardthe correction.)

vancement (2.02 mm), was the main change responsible forthe anterior correction. According to Pancherz, the lowerincisor proclination is slight (0.92 mm) and the maxillarygrowth does not favor the sagittal correction (20.53 mm).

Vardimon et al12 found that, with a removable FMS, theoverjet correction was achieved by retroclination of the up-per incisor (43.5%), lower incisor proclination (22%), max-illary skeletal growth constraint (21%), and mandibularskeletal advancement (13.5%). The incisor relationship wascorrected one-third skeletally and two-thirds dentally.

OBrien et al13 used a modified Twin-Block and foundthat the overjet correction was due mostly to the dentalchanges (73%), which included retroclination of the upperincisors (44%) and proclination of the lower incisors (29%).Skeletal changes (27%) consisted of a slight maxillary re-traction (13%) and mandibular advancement (14%).

CONCLUSIONSWhen the activator patients were compared with untreat-

ed control subjects, therapy promoted a combination ofskeletal and dental changes that led to an improvement ofthe sagittal discrepancy. The changes that occurred in theuntreated control subjects did not bring about a correctionof the malocclusion.

During activator treatment, the molar drifts are unfavor-able toward the improvement of the Class II relationshipbut are subsumed into the favorable skeletal changes. Thus,the orthopedic effects are greater than the dental effects incorrecting the posterior occlusal relationship.

In the anterior area of the arch, both the skeletal anddental changes are favorable toward the sagittal correction,but the skeletal contribution is greater than the dental con-tribution.

In general, the skeletal contribution (140%) exceeded thedental correction (60%) and the mandibular changes (73%)



exceeded the maxillary contribution (27%) both in the an-terior and posterior regions.

In functional therapy a slight dental response allows theskeletal changes to achieve a more marked correction ofClass II sagittal discrepancy, with a net improvement of thefacial profile.

REFERENCES1. Harvold EP, Vargervik K. Morphogenetic response to activator

treatment. Am J Orthod. 1971;60:478490.2. Vargervik K, Harvold EP. Response to activator treatment in

Class II malocclusions. Am J Orthod. 1985;88:242251.3. Baumrind S, Korn EL, Molten R, West EE. Changes in mandib-

ular dimensions associated with the use of force to retract themaxilla. Am J Orthod. 1981;79:1759.

4. Righellis EG. Treatment effects of Frankel, activator and extraoraltraction appliances. Angle Orthod. 1983;53:107121.

5. Remmer KR, Mamandras AH, Hunter WS, Way DC. Cephalo-metric changes associated with treatment using the activator, theFrankel appliance, and the fixed appliance. Am J Orthod. 1985;88:363372.

6. Jakobsson S-O, Paulin G. The influence of activator treatment onskeletal growth in Angle Class II:1 cases. A roentgenocephalo-metric study. Eur J Orthod. 1990;12:174184.

7. Lux CJ, Rubel J, Starke J, Conradt C, Stellzig A, Komposch G.Effects of early treatment in patients with Class II malocclusionevaluated by thin-plate spline analysis. Angle Orthod. 2001;71:120126.

8. Ruf S, Baltromejus S, Pancherz H. Effective condylar growth and

chin position changes in activator treatment: a cephalometricroentgenographic study. Angle Orthod. 2001;71:411.

9. Basciftci F, Uysal T, Buyukerkmen A, Sari Z. The effects of ac-tivator treatment on the craniofacial structures of Class II division1 patients. Eur J Orthod. 2003;25:8793.

10. Pancherz H. A cephalometric analysis of skeletal and dentalchanges contributing to Class II correction in activator treatment.Am J Orthod. 1984;85:125134.

11. Weiland FJ, Ingervall B, Bantleon H-P, Droschl H. Initial effectsof treatment of Class II malocclusion with the Herren activator,activator-headgear combination and Jasper Jumper. Am J OrthodDentofacial Orthop. 1997;112:1927.

12. Vardimon AD, Saduman K. An assessment of skeletal and dentalresponses to the functional magnetic system (FMS). Am J OrthodDentofacial Orthop. 2001;120:416426.

13. OBrien K, Wright J, Conboy F, et al. Effectiveness of early or-thodontic treatment with Twin-Block appliance: a multicenter ran-domized, controlled trial. Part 1: dental and skeletal effects. AmJ Orthod Dentofacial Orthop. 2003;124:234243.

14. Cozza P, De Toffol L, Colagrossi S. Dentoskeletal effects andfacial profile changes during activator therapy. Eur J Orthod.2004;26. In press.

15. You Z-H, Fishman LS, Rosemblum RE, Subtelny JD. Dentoal-veolar changes related to mandibular forward growth in untreatedClass II persons. Am J Orthod Dentofacial Orthop. 2001;120:598607.

16. Jakobsson SO. Cephalometric evaluation of treatment effect onClass II, Division 1 malocclusions. Am J Orthod. 1967;53:446457.

17. Wieslander L, Lagerstrom L. The effect of activator treatment onClass II malocclusions. Am J Orthod. 1979;75:2026.

an analysis of the correttive activator

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