Introduction
The nature of a Class II malocclusion is related to many factors, such as facial structure, maxillary and mandibular growth patterns, and dentoalveolar development ( McNamara, 1981 ) . Individual variations of these factors have to be considered in relation to treatment procedures to correct malocclusions.
The effects of treatment combining extraoral force and functional appliances have been reported in several studies, illustrating the variability of responses in the importance of controlling the posterior vertical dimension ( Meach, 1966 ; Bass, 1982 ; Williams and Melsen, 1982 ; Altu ğ et al. , 1989 ; Jacobsson and Paulin, 1990 ; Dermaut et al. , 1992 ; Öztürk and Tankuter, 1994 ; Cura et al. , 1996 ; Ba ş çiftçi et al. , 2003 ; Janson et al. , 2004 ) .
In general, Class II division 1 malocclusion correction using high-pull headgear -activator combination therapy produces restriction of forward maxillary growth, inhibition of the mesial and vertical displacement of the maxillary teeth, improvement of the mandibular posterior teeth, condylar and glenoid fossa remodelling, and an improvement in muscle pattern ( Wieslander and Lagerström 1979 ; Vargervik and Harvold, 1985 ; Janson et al. , 2004 ) .
Angle Class II malocclusions have been studied extensively regarding their skeletal and dental characteristics, timing, and method of treatment. In subjects with maxillary excess, orthopaedic forces are directed on the maxilla to inhibit further maxillary growth. Functional appliances may be combined with extraoral force applied to either the maxilla or the mandible ( Pfeiffer and Grobéty, 1982 ; Ülgen et al. , 1984 ; Van Beek, 1984; Graber and Swain, 1985 ; Teuscher, 1986 ; Kigele, 1987 ; Altu ğ et al. , 1989 ; Bishara and Ziaja, 1989 ; Gögen and Parlar, 1989 ; Lehman and Hulsnik, 1989 ; Lagerström et al. , 1990 ; Deguchi, 1991 ; Dermaut et al. , 1992 ; Öztürk and Tankuter, 1994 ; Cura et al. , 1996 ; Weiland et al. , 1997 ; Yüksel et al. , 1997 ) . The majority of studies on the effects of functional appliances have tended to focus on hard tissue changes as opposed to the soft tissue profi le despite the fact that the soft tissue profi le is the ultimate determinant of treatment success ( Vargervik and Harvold, 1985 ; Malmgren et al. , 1987 ; Ba ş çiftçi et al. , 2003 ) . The main reason for this is the diffi culty in reliably investigating the soft tissues. Forsberg and Odenrick (1981) reported that lip retrusion and forward movement of soft tissue pogonion were signifi cantly increased in subjects treated with the activator and McDonagh et al. (2001) a signifi cant forward positioning of soft tissue pogonion after treatment with the Bass appliance. Ülgen et al. (1984) found that an insignifi cant retrusion of the upper lip occurred with an activator -headgear combination, whereas Gögen and Parlar (1989) reported a signifi cant retrusion of the upper lip with these appliances. Hansson et al. (1997 Hansson et al. ( , 2000 , Singh and Thind (2003) , and Mergen et al. (2004) reported that a fl attened soft tissue profi le was produced with functional and headgear combination appliances.
The purpose of this investigation was to evaluate quantitatively, on lateral cephalograms, the skeletal, dentoalveolar, and soft tissue facial parameters before (T0) and after 1.1 ± 0.3 years (T1) of activator and high-pull headgear appliance treatment. In order to compare the effects of growth versus activator and high-pull headgear treatment, cephalogram data taken at the start (T0) and after a period of 1.2 ± 0.4 years (T1) from a matched group of untreated Class II subjects were analyzed.
Subjects and methods
The subjects for both the study and control groups were Caucasian and selected from a single centre (Department of Orthodontics, Faculty of Dentistry, Istanbul University). The following selection criteria were used: 11 -12.5 years of age; overjet greater than 5 mm; Class II molar relationship, with at least half a cusp width distal molar relationship; and no history of previous orthodontic therapy.
Patients satisfying these criteria were divided into two groups: a control group, 28 subjects (14 girls, 14 boys), and a treatment group, 28 subjects (13 girls, 15 boys), who underwent activator and high-pull headgear therapy. The control and treated groups were matched with respect to initial age, malocclusion, and observation period. The control group was selected from subjects who declined activator -headgear therapy.
The appliance used was an acrylic monobloc attached to the upper arch by a high-pull occipital headgear placed into the tubes attached to the acrylic in the premolar area on each side. A central screw was placed and activated only to follow maxillary transversal growth. The incisal edges of the maxillary and mandibular incisors were capped to prevent tipping. A labial wire, placed in front of the upper incisors, was used for the retention of the appliance.
The activator was produced from a construction bite that positioned the mandible anteriorly in an edge-to-edge incisor relationship ( Moore et al. , 1989 ) . The lower jaw was postured forward in to a Class I molar relationship to stimulate mandibular growth. As a general rule, the bite registration was obtained 3 mm short of maximum protrusion, with care being taken to ensure that lateral displacement did not occur. The height of the bite exceeded the freeway space by 2 -3 mm. During treatment, contact was maintained between the appliance and the maxillary posterior teeth; the mandibular posterior teeth were encouraged to erupt by trimming the acrylic on the occlusal and lingual aspect. The high-pull headgear placed the force through the presumed centre of resistance of the maxilla. Treatment commenced with 400 -500 g of force per side. The patients were instructed to wear the appliance for a minimum of 14 hours a day.
The skeletal, dentoalveolar, and soft tissue profi le changes that occurred were assessed from two lateral cephalograms. In the treatment group, the fi rst lateral cephalogram was taken before treatment (T0) and after 1.1 ± 0.3 years, when the appliance was removed (T1). In the control group, the cephalograms were obtained at the start (T0) and after 1.2 ± 0.4 years (T1). All cephalograms were taken with the teeth in occlusion and the lips in a relaxed position.
The initial cephalometric patterns of the control and treated subjects, as well as the alterations due to growth or treatment, were assessed using the following angles and distances ( Figure 1 ) -sagittal analysis: SNA (degrees), SNB (degrees), ANB (degrees), Ao -Bo (mm), N perp -A (mm), N perp -Pg (mm), NSCo (degrees), Co -A (mm), CoGn (mm), Go -Me (mm), FH -NA (degrees), FH -NPg (degrees); vertical analysis: FMA (degrees), FH -OL (degrees), SN -PP (degrees), PP -Go -Me (degrees), N -ANS (mm), ANS -Me (mm); and dental analysis: U1 -FH (degrees), IMPA (degrees), interincisal angle (degrees), overjet (mm), overbite (mm), L1 -OL (mm).
Other points and reference lines used were those defi ned by Pancherz (1984) . These linear measurements for the assessment of sagittal relationships were performed using the occlusal line (OL) and the occlusal line perpendicular (OLp) drawn through sella. The reference grid, taken from the fi rst head fi lm (T0), was transferred to the T1 tracing using the sella -nasion (SN) line, with sella as the registration point ( Figure 2 ).
All sagittal registrations were performed to the same reference line (OLp) and parallel to OL: OLp -Co, OLp -A, OLp -B, OLp -Pg, OLp -U1, OLp -L1, OLp -U6, OLp -L6 ( Figure 2 ).
For soft tissue variables, an x -y cranial base co-ordinate system was constructed on the cephalograms through sella, with the x -axis drawn 7 degrees to the SN line and the vertical axis passing through sella perpendicular to the xaxis. The aesthetic line (E line, Ricketts, 1972 ) , constructed between Pronasale and Pg ′ , was used as the soft tissue aesthetic line. The initial soft tissue analysis of the control and treated subjects, as well as the alterations, due to growth or treatment, were assessed using the following distance to the y -or x -axis.
Horizontal -y -axis: Pn, Cm, Sn, Sls, Ls, Stms, Stmi, Li, Mlf, Pg ′ , Me ′ , mentolabial fold depth (Mlf -E line). Vertical -x -axis: Pn, Cm, Sn, Sls, Ls, Stms, Stmi, Li, Mlf, Pg ′ Me ′ . Angular: upper lip inclination (Ls -Sn -x -axis angle), lower lip inclination (Mlf -Li -x -axis angle), nasolabial angle (Cm -Sn -Ls angle), facial convexity angle (G ′ -Sn -Pg ′ ).
Each cephalogram was traced and measured manually. All measurements were repeated after a period of 7 days and the mean value of the two measurements was used. All measurement error coeffi cients were found to be close to 1.00 and within acceptable limits using Dahlberg's (1940) formula.
Statistical analysis
Descriptive statistics included the mean and standard deviation (SD). The collected data were subjected to statistical analysis using the Statistical Package for Social Sciences (SPSS for Windows, Release 7.5.1, Chicago, Illinois, USA). Wilcoxon's ranked-sum test was used for intra-group comparisons. Differences between groups were evaluated by t -test and Bonferroni's test. The level of signifi cance was P < 0.05.
Results

Sagittal analysis
In the treatment group, SNA angle decreased on average -2.0 degrees (SD 1.5, P < 0.05) and OLp -A distance -2.3 mm during therapy (SD 3.0, P < 0.05; Tables 1 and 2 and supplementary data). Co -A distance signifi cantly increased 3.1 mm (SD 4.4, P < 0.01) while FH -NA decreased − 2.0 degrees (SD 4.0, P < 0.05). ANB angle diminished during therapy on average 3.4 degrees (SD 2.7, P < 0.001). The relative sagittal position of the jaws, when measured along the OL (Ao -Bo), showed an average reduction of 1.2 mm (SD 1.8, P < 0.01). In the treated group, the increase in SNB was on average 2.6 degrees (SD 1.6, P < 0.001).
There was a signifi cant increase in the horizontal measurements at pogonion after treatment. The variables N perp -Pg and FH -NPg increased on average 3.1 mm (SD 2.5, P < 0.001) and 2.3 degrees (SD 2.7, P < 0.05). Co -Gn distance increased signifi cantly in both groups after therapy (treatment group 6.1 mm, SD 5.3, P < 0.001; control group 2.3 mm, SD 2.4, P < 0.001). Table 1 Comparison of the differences between pre-and post-treatment, pre-and post-observation periods using Wilcoxon's ranked-sum test, and treatment changes with a t -test.
Skeletal and dentoalveolar measurements Pre-treatment Table 2 The differences between the pre-and post-observation, pre-and post-treatment variables evaluated with Wilcoxon's ranked-sum test, and treatment effects with a t -test.
Pre-observation The angle NSCo, an expression of the position of the articular complex and the condyle, decreased in the control group ( − 0.4 degree; SD 5.6; ns), while in the treatment group it decreased signifi cantly ( − 1.3 degree, SD 6.4, P < 0.05).
The linear measurements performed to OLp and parallel to OL showed horizontal changes in the position of the mandible. Condylion (OLp -Co) moved forward signifi cantly in the treated group ( − 2.0 mm, SD 2.7, P < 0.001).
There was a signifi cant advancement of the mandibular structures in the treated group (Go -Me: 4.6 mm, SD 3.5, P < 0.001; OLp -B: 2.7 mm, SD 2.5, P < 0.001; OLpGo:2.2 mm, SD 2.4, P < 0.05, OLp -Pg: 2.2 mm, SD 4.4, P < 0.05).
Vertical analysis
Lower anterior face height (ANS -Me) signifi cantly increased 3.9 mm (SD 3.3, P < 0.001) and 1.3 mm (SD 1.9, P < 0.01) in the treated and control groups, respectively. The difference between the groups was signifi cant ( P < 0.01, Table 1 ).
Dental analysis
Activator and high-pull headgear combination therapy moved the maxillary incisors palatally (U1 -FH: − 5.3 degrees, SD 6.0, P < 0.01) and the signifi cant correction in overjet, which averaged − 5.4 mm (SD 2.4, P < 0.001) was due to this palatal movement. The mandibular incisors moved labially, with IMPA angle signifi cantly increased 2.0 degrees (SD 4.8, P < 0.05).
Dental measurements performed to the reference line (OLp) showed a forward movement of the lower incisors in the treated group (OLp -L1: 2.7 mm, SD 3.4, P < 0.001) while the upper incisors showed a backward movement (OLp -U1: − 2.5 mm, SD 3.6, P < 0.01). The variables interincisal angle and overbite also improved (interincisal angle: 3.5 degrees, SD 4.6, P < 0.05; overbite: − 2.2 mm, SD 1.0, P < 0.001).
The mandibular molars (OLp -L6) signifi cantly moved forward in the treated group (3.5 mm, SD 3.5, P < 0.001). While maxillary molars (OLp -U6) showed distal movement ( − 0.6, SD 3.9, ns).
Soft tissue analysis
The positive effects of treatment on the facial profi le were accompanied by an increase in the facial convexity angle (G ′ -Sn -Pg ′ ; 2.3, SD 3.8 degrees, P < 0.01).
The Mlf -y -axis and Pg ′ -y -axis vertical distances increased signifi cantly when compared with the control group (5.6, SD 4.0 mm, P < 0.01, and 5.3, SD 4.1 mm, P < 0.01, respectively). This means that the depth of the labiomental fold decreased and pogonion moved anteriorly in the treatment group. The superior labial sulcus (Sls) to x -axis distance signifi cantly increased in the treated group (3.8, SD 4.9 mm, P < 0.05).
Horizontal growth of soft tissue menton (Me ′ ) according to the Me ′ -x -axis parameter increased signifi cantly in the treatment group (5.1, SD 4.7 mm, P < 0.01). The horizontal growth of the labiomental fold, according to the Mlf -E line (Mlf depth), signifi cantly decreased in the treatment group.
Discussion
The aim of the present investigation was to evaluate the skeletal, dentoalveolar, and soft tissue changes occurring in subjects treated with an activator -high-pull headgear combination appliance. In an attempt to determine if there are signifi cant growth changes over those expected, a nonrandomized control group was examined. This appears to be the best method to differentiate growth changes from treatment changes.
Maxillary effects
The results show that an orthopaedic retraction of the maxillary complex seemed to be consistent. Point A moved backward by − 1.4 mm when measured vertical to N perpendicular and by − 2.3 mm when measured vertical to OLp in the treatment group. This fi nding is in agreement with Pfeiffer and Grobéty (1982) , Pancherz (1984) , Van Beek (1984) , Lagerström et al. (1990) , Öztürk and Tankuter (1994) , and Cura et al. (1996) .
The difference between the two groups was signifi cant ( P < 0.05). During treatment with activator and high-pull headgear appliances, it has been claimed that forward growth of the maxilla may be inhibited ( Pfeiffer and Grobéty, 1982 ; Van Beek, 1984; Kigele, 1987 ; Lehman and Hulsnik, 1989 ; Lagerström et al. , 1990 ; Dermaut et al. , 1992 ; Öztürk and Tankuter, 1994 ; Cura et al. , 1996 ; You and Chen, 2002 ; Janson et al. , 2004 ) . In the present analysis, SNA decreased in the treatement group, while in the controls it increased.
Mandibular effects
It has been reported that an increase in mandibular growth is the distinguishing aspect of functional therapy with respect to the other treatment modalities ( Demisch, 1972 ; Owen, 1981 ; Luder, 1982 ; Toth and McNamara, 1999 ) while others believe that mandibular length is unaltered by functional appliance therapy ( Harvold and Vargervik, 1971 ; Weislander and Lagerström, 1979; Vargervik and Harvold, 1985 ; Jacobsson and Paulin, 1990 ) and that the treatment changes appear to be similar to those resulting from growth ( Forsberg and Odenrick, 1981 ) .
In the present study there was an advancement of the mandibular structures in the treated group, when the cephalometric values related to the lower jaw were compared with the controls. Activator and high-pull headgear treatment resulted in approximately 3 mm of anterior mandibular displacement.
The increase in SNB of 2.6 degrees in the treated group, compared with the slight increase of 0.4 degrees in the controls, was statistically signifi cant. Mandibular length, expressed as Go -Me increased in both groups, but signifi cantly more in the treated group.
The results of the present study may be related to changes in the condyler glenoid fossa complex: remodelling and anterior relocation of the glenoid fossa may have contributed to the correction of the skeletal Class II malocclusion, as evidenced by NSCo angle, which decreased signifi cantly, and by linear measurement OLp -Co which moved forward ( Woodside et al. , 1987 ; Ruf et al. , 2001 ). This assumes the condyle was fully seated in the fossa.
Effects on dentition
Ba ş çiftçi et al. (2003) , Sar ı et al. (2003) , and Janson et al. (2004) observed signifi cant dentoalveolar changes during activator and headgear combination treatment. In the present study, correction of upper incisor prominence appeared signifi cant in the treated group. The overjet correction was due to a combined maxillary and mandibular orthopaedic effect, in addition to lingual movement of the upper dentition, in spite of the teeth being capped in the acrylic.
Activator and headgear combination therapy retroclined the maxillary incisors by 5.3 degrees and reduced the overjet by 5.4 mm, while the control group showed no signifi cant differences during the observation period.
The upper dental component of overjet correction was similar to the data in the literature ( Öztürk and Tankuter, 1994 ; Cura et al. , 1996 ; Ba ş çiftçi et al. , 2003 ; Türkkahraman and Say ı n, 2006) . Pancherz (1984) found that more than 50 per cent of overjet correction was produced by upper incisor tipping. The initial angulation of the upper incisors is of importance in infl uencing treatment outcome ( Barton and Cook, 1997 ) . OLp -U1, used for assessing the position of the upper incisors, demonstrated a forward movement in the control group, but this was not signifi cant.
The mandibular incisors proclined slightly in the treated group and IMPA signifi cantly increased by 2.0 degrees. Other studies have reported that the mandibular incisors procline or advance signifi cantly during functional appliance treatment in spite of capping ( Ahlgren and Laurin, 1976 ; Pancherz, 1984 ; Nelson et al. , 1993 ) .
The dentoalveolar changes included a signifi cant decrease of the overbite by 2.2 mm in the treated group. These fi ndings are in agreement with Ahlgren and Laurin (1976) , Pancherz (1984) , Lagerström et al. (1990) , and Nelson et al. (1993) . This could be a refl ection of the increase in face height. Activator and headgear combination therapy caused dentoalveolar changes in the molar area.
In the present analysis, these appliances resulted in a signifi cant 3.5 mm of forward movement of the mandibular molars (when measured parallel to OL). This is in agreement with Vargervik and Harvold (1985) , Malmgren et al. (1987) , and Weiland et al. (1997) who concluded that the mandibular molars come forward with the mandible and not just by tooth migration. Forward movement of the maxillary molars was reduced by 0.6 mm in the treated group in comparison with the controls, but the difference was not signifi cant.
Effects on vertical growth of the jaws and dentition
Activator and headgear combination therapy appears to increase vertical development of the mandible. A number of authors ( Williams and Melsen, 1982 ; Ruf et al. , 2001 ; Cozza et al. , 2004a , b ) have found that the majority of mandibular growth is expressed vertically with activator therapy because of backward rotation of the mandible. An increase in face height in the fi rst molar region disturbs the balance of vertical development and thereby infl uences displacement of pogonion in a backward direction; variations in the vertical dimensions of the maxilla are thus related to the sagittal discrepancy.
For this reason, it appears that control of the vertical dimension is imperative for an optimal forward displacement of the correction of a skeletal Class II malocclusion. The results of the present study did not show signifi cant modifi cations in vertical development of the maxillomandibular complex: the angular measurements indicated a slight increase in FH -OL and SN -PP angles in the treated subjects, while FMA angle did not change signifi cantly; similarly, the vertical relationship appeared to be stable in the control group.
The vertical dental relationship expressed by overbite is an important feature in functional therapy associated with a good prognosis for treatment outcome ( Charron, 1989 ) . During therapy, the incisors were passively prevented from erupting by double capping as the molars erupted, which resulted in a statistically signifi cant correction of the overbite in the treated group, while in the controls overbite remained stable.
Effects on soft tissue facial profi le
The positive effects of treatment on the facial profi le were accompanied by an increase in the facial convexity angle, while in the control group there was a reduction in this parameter. Singh and Thind (2003) reported a signifi cant improvement in the soft tissue profi le after treatment with the Teuscher appliance combined with headgear. McDonagh et al. (2001) found that greater forward positioning of soft tissue pogonion occurs after treatment with a functional appliance and headgear combination.
The upper lip -x -axis distance was increased in this study. Sar ı et al. (2003) found an insignifi cant increase after treatment with activator -headgear combination appliances, whereas Ülgen et al. (1984) reported insignifi cant retrusion and Gögen and Parlar (1989) and Quintão et al. (2006) signifi cant retrusion of the upper lip.
The Mlf -y -axis and Pg ′ -y -axis vertical distances increased signifi cantly compared with the control group, where there were slight increases in these two parameters. This means that the depth of the labiomental fold decreased and pogonion moved anteriorly in the treatment group. Slsx -axis distance signifi cantly increased in the treated group while a slight increase in this parameter was observed in the control group. The antero-posterior effect of the high-pull headgear may be responsible for this decrease in the depth of Sls. Hansson et al. (1997 Hansson et al. ( , 2000 reported inhibited sagittal growth of the maxilla, increased anterior face height, and a fl attened soft tissue facial profi le with a less pronounced labiomental sulcus after treatment with functional -headgear combination appliances.
Horizontal growth of soft tissue menton (Me ′ ) according to the Me ′ -x -axis parameter increased signifi cantly in the treatment group when compared with the control group. A slight decrease was observed in the control group. This means that activator and high-pull headgear therapy may be effective on horizontal growth of soft tissue menton. Horizontal growth of the labiomental fold, according to the Mlf -E line distance significantly decreased in the treatment group when compared with the control group where a slight increase was observed. Thus, activator -high-pull headgear therapy may decrease the depth of the labiomental fold. Singh and Thind (2003) and Mergen et al. (2004) reported that significant antero-posterior growth of the mental regions occurs after treatment with functional appliances combined with headgear. According to Forsberg and Odenrick (1981) , Remmer et al. (1985) , and Bishara and Ziaja (1989) , growing Class II patients can undergo significant profile improvement with functional appliance -headgear combination treatment.
Conclusions
The results of the present investigation indicate that activator and high-pull headgear combination therapy is effective in treating Class II malocclusions and improving the soft tissue facial profi le. Functional therapy is of clinical benefi t in actively growing patients and should be initiated during the middle to late mixed dentition period. Dentoalveolar effects seem to play an important role in this correction, but a relative maxillo-mandibular displacement, mainly a mandibular advancement, was also apparent. 

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