ORIGINAL ARTICLE Dentoskeletal and soft-tissue changes with cervical headgear and mandibular protraction appliance therapy in the treatment of Class II malocclusions Danilo Furquim Siqueira,a Renato Rodrigues de Almeira,b Guilherme Janson,c Analu Giampietro Brandão,a and Carlos Martins Coelho Filhod Bauru, São Paulo, and São Luís, Maranhão, Brazil Introduction: In this study, we cephalometrically compared changes in the dentoskeletal and soft tissues after orthodontic treatment of Class II Division 1 malocclusions between the cervical headgear (CHG) and the mandibular protraction appliance (MPA) followed by fixed appliances. Methods: The sample consisted of 50 patients divided into 2 groups of 25 patients each (13 male, 12 female). Group 1 patients were treated with CHG and fixed appliance, and group 2 patients were treated with the MPA and fixed appliances. The patients were matched according to sex, age, treatment time, and initial cephalometric variables. The groups were compared regarding pretreatment stage and treatment changes, with t tests, at P ⬍.05. Results: The CHG group showed statistically greater restriction of the anterior displacement of the maxilla, improvement of the skeletal Class II relationship, decreased facial convexity, extrusion and distalization of the maxillary first molar, and extrusion of the mandibular incisors. The MPA group had statistically greater increases in maxillary length, mandibular protrusion, maxillary incisor retrusion, mesial displacement of the mandibular first molars, and protrusion of the lower lip. Conclusions: The changes in Class II malocclusion correction between the CHG and the MPA were that the CHG corrected the Class II malocclusion primarily through greater action on the maxillary skeletal and dentoalveolar structures as compared with the MPA, which corrected the malocclusion through greater action on the mandibular dentoalveolar structures. (Am J Orthod Dentofacial Orthop 2007;131:447.e21-447.e30) M any appliances are designed to correct Class II malocclusions with a nonextraction approach. One of the most used and studied mechanisms is the extraoral appliance that restricts the anterior displacement of the maxillary first molar and the maxilla and produces improvement in the maxillomandibular relationship.1-5 The choice of the best appliance depends on many factors, including patient compliance. The mandibular protraction appliance (MPA) is a fixed functional appliance that maintains continuous mandibular advancea Graduate student, Department of Orthodontics, Bauru Dental School, University of São Paulo, Bauru, São Paulo, Brazil. b Associate professor, Department of Orthodontics, Bauru Dental School, University of São Paulo, Bauru, São Paulo, Brazil. c Professor, Department of Orthodontics, Bauru Dental School, University of São Paulo, Bauru, São Paulo, Brazil. d Private practice, São Luís, Maranhão, Brazil. Reprint requests to: Analu Giampietro Brandão, Department of Orthodontics, Bauru Dental School, University of São Paulo, Alameda Octávio Pinheiro Brisolla 9-75, Bauru, São Paulo, 17012-901, Brazil; e-mail, analugb@uol. com.br. Submitted, August 2005; revised and accepted, April 2006. 0889-5406/$32.00 Copyright © 2007 by the American Association of Orthodontists. doi:10.1016/j.ajodo.2006.04.029 ment to correct Class II anteroposterior discrepancy and therefore does not depend on patient compliance.6-9 It has important features: easy chairside construction with ordinary and inexpensive wires; no special bands, crowns, or wire attachments; easily inserted, adjusted, and removed; and versatility. It is also an excellent mechanism for preserving maxillary molar and mandibular incisor anchorage.6-9 Investigations with the MPA demonstrated that the changes it produces are primarily dentoalveolar, with distalization of the maxillary dentoalveolar process and mesial displacement of the mandibular molars.6-9 Studies comparing removable functional appliances with headgear demonstrated that both appliances are effective in correcting Class II malocclusions, and reducing overjets and apical base discrepancies.10-12 Headgear showed distal effects on the maxilla and moved the maxillary first molars farther distally and occlusally,5,10,12 whereas removable functional appliances caused greater mandibular protrusion, and greater increases in mandibular length and mandibular molar extrusion.5,10,12 However, comparisons of headgear 447.e21 447.e22 Siqueira et al American Journal of Orthodontics and Dentofacial Orthopedics April 2007 Fig 1. MPA III. with fixed functional appliances have not been conducted. Similarly, the effects of the MPA have not been compared with other appliances, especially extraoral headgear, to demonstrate the different effects in the correction of Class II malocclusions. Therefore, the objective of this study was to cephalometrically compare the dentoskeletal and soft-tissue changes after treatment of Class II Division 1 malocclusions with cervical headgear (CHG) and the MPA followed by fixed appliances. MATERIAL AND METHODS The sample consisted of 50 patients divided into 2 groups of 25 patients each (13 male, 12 female). The primary selection criteria for both groups were a Class II Division 1 malocclusion with at least an end-to-end bilateral Class II molar relationship, all maxillary and mandibular teeth up to the second molars, a convex facial profile, and an accentuated overjet. Group 1 comprised patients with an initial mean age of 12.40 years (range, 10.00-13.83 years), treated with CHG and fixed appliances, from the files of the Orthodontic Department, Bauru Dental School, University of São Paulo. The mean treatment time was 2.39 years (range, 1.58-4.42 years). Patients used the CHG 16 hours per day, for a mean time of 16 months, with a mean force of 450 g on each side. After molar relationship correction, 0.022 ⫻ 0.028-in standard edgewise fixed appliances were placed. The usual wire sequence began with a 0.016-in nickel-titanium wire followed by 0.016, 0.018, 0.020, and finally 0.021 ⫻ 0.025-in stainless steel archwires (Unitek, Monrovia, Calif). Then the fixed appliances were removed, and Hawley retainers were used in the maxillary arches, and canineto-canine retainers were bonded in the mandibular arches. Group 2 consisted of patients with an initial mean age of 12.30 years (range, 9.25-16.08 years) treated simultaneously with the MPA and fixed appliances at the private practice of the fifth author in São Luís, Maranhão, Brazil, with a mean treatment time of 2.80 years (range, 1.33-4.00 years). The MPA (Fig 1) is an intraoral fixed appliance that induces continuous mandibular protrusion.6 It requires stainless steel edgewise archwires in both arches. The length of the appliance is determined by the distance from the mesial aspect of the maxillary tube to the stop on the mandibular archwire. Three versions were used in this study: MPA I, II, and III. The only difference between them was the protrusive mechanism. MPA III was a variation of the earlier versions, with a tube-and-plunger mechanism with 0.032-in stainless steel wire.8 MPA I and II were constructed with 0.032-in stainless steel wires as shown in Figure 2. However, their modes of action were similar.6-9 Previous use of fixed orthodontic appliances is indispensable to all types of MPA. Before placement of the MPA, 0.022 ⫻ 0.028-in edgewise fixed appliances were placed, and leveling progressed up to rectangular 0.021 ⫻ 0.025-in stainless steel archwires (Unitek). Then the MPA was placed to correct the Class II anteroposterior discrepancy. The rectangular arches must have enough extension distal to the molar tubes for the bend-down tieback and to support elastic chains.6 The mandible was advanced to an edge-to-edge incisor position. The mean MPA treatment time was 7 months; then the appliances were removed. At this stage, the molar relationship was corrected and the overjet reduced. Finishing of the occlusion was obtained with fixed appliances. Retainers consisted of Hawley plates in the maxillary arches and bonded canine-to-canine lingual arches in the mandibular arches. Lateral radiographs of the groups were obtained from each patient at pretreatment (T1) and posttreatment (T2), in different machines, which produced magnification factors between 6% and 9.8%. The lateral cephalograms were traced on acetate paper, and the cephalometric tracings and landmark identifications were performed by 1 investigator (D.F.S.) and then digitized with a digitizer (DT-11, Houston Instruments, Siqueira et al 447.e23 American Journal of Orthodontics and Dentofacial Orthopedics Volume 131, Number 4 Fig 2. A, MPA I; B, MPA II; C, MPA III. Austin, Tex) (Table I, Fig 3). These data were stored on a computer and analyzed with Dentofacial Planner 7.02 (Dentofacial Planner Software, Toronto, Ontario, Canada), which corrected the image magnification factors of the groups. Sixteen patients were randomly selected, and the radiographs were retraced, redigitized, and remeasured by the same examiner after a 2-month interval. Systematic errors were estimated by paired t tests (P ⬍.05), and casual errors were calculated according to Dahlberg’s formula, Se2 ⫽ ⌺d2/2n, where d is the difference between duplicate measurements, and n is the number of double measurements.13,14 Statistical analysis Means and standard deviations for each variable were calculated to enable characterization of the groups. Normal distributions were verified by the KolmogorovSmirnov test (for the initial and final stages and for treatment changes). Results of this test showed that all variables were normally distributed. Therefore, the t test was used for comparison between the groups at T1 and T2 and for treatment changes, at P ⬍.05. All statistical analyses were performed with software (Statistica for Windows 6.0, Statsoft, Tulsa, Okla). RESULTS Of the 29 variables, only 1 had a systematic error: L6-MP. The range of casual errors varied from 0.34 (SNB angle) to 2.64 (NLA angle) (Table II). The groups were compatible regarding initial ages, treatment times, and almost all cephalometric variables. Only U6-PP was statistically greater in group 1 than in group 2 (Table III). The cervical headgear group had statistically greater restriction of the anterior displacement of the maxilla (SNA angle), improvement of the skeletal Class II relationship (ANB angle), decreased facial convexity (NAP angle), extrusion (U-6PP), distalization of the maxillary first molar (U6-Fperp), and extrusion of the mandibular incisors (L1-MP). The MPA group had a statistically greater increase in maxillary length (Co-A), mandibular protrusion (SNB angle), maxillary incisor retrusion (U1-NA), mesial displacement of the mandibular first molars (L6-Fperp), and protrusion of the lower lip (LL-Fperp; Table IV). At T2, the CHG group showed a significantly retruded maxilla (SNA angle), smaller anteroposterior basal discrepancy (ANB angle), and mandibular protrusion (NAP angle), protruded maxillary incisors (U1NA), greater maxillary first molar dentoalveolar height (U6-PP), retruded maxillary molars (U6-Fperp), uprighted and greater dentoalveolar height of the mandibular incisors (IMPA, L1.NB, L1-MP), and retruded mandibular first molar crown (L6-Fperp) in relation to the MPA group (Table V). DISCUSSION When analyzing the results, one must bear in mind that they were obtained from the use of the CHG or the MPA with fixed appliances. Distinctions between the separate effects of the MPA were not possible because the treatment rationale of this appliance requires initial leveling and alignment up to a rectangular stainless steel archwire before placement of the Class II correction appliance.6-9 447.e24 Siqueira et al American Journal of Orthodontics and Dentofacial Orthopedics April 2007 Table I. Definitions of less usual lines, planes, and variables used Planes and lines Frankfort horizontal plane (FH): constructed by subtracting 7° from SN line, registered on S41,45 Mandibular plane Go-Me: constructed from Go to Me Palatal plane: constructed from ANS to PNS SN: line constructed from S to N NA: line constructed from N to A NB: line constructed from N to B AP: line constructed from A to P Fperp (Frankfort perpendicular): line constructed perpendicular to Frankfort horizontal plane, through S Skeletal cephalometric variables SNA: SN to NA angle SNB: SN to NB angle ANB: NA to NB angle NAP: NA to AP angle FMA (Sn.GoMe): Frankfort mandibular plane angle SN.PP: SN to palatal plane angle Go-Gn: distance between Go and Gn Co-A: distance between Co and A-point Co-Gn: distance between Co and Gn UAFH (upper anterior face height): distance from N to ANS LAFH (lower anterior face height): distance from ANS to Me PFH (posterior face height): distance from S to Go LPFH (lower posterior face height): distance from Ar to Go Dental cephalometric variables U1.NA: maxillary incisor long axis to NA angle U1-NA: distance between most anterior point of crown of maxillary incisor and NA line U1-PP: perpendicular distance between incisal edge of maxillary central incisor and palatal plane U6-PP: perpendicular distance between mesiobuccal cusp of maxillary first molar and palatal plane U6-Fperp: perpendicular distance between mesiobuccal cusp of maxillary first molar and Fperp L1.NB: mandibular incisor long axis to NB angle L1-NB: distance between most anterior point of crown of mandibular incisor and NB line IMPA: incisor mandibular plane angle L1-MP: perpendicular distance between incisal edge of mandibular incisor and mandibular plane GoMe L6-MP: perpendicular distance between mesiobuccal cusp of mandibular first molar and mandibular plane GoMe L6-Fperp: perpendicular distance between mesiobuccal cusp of mandibular first molar and Fperp Soft-tissue cephalometric variables NLA: nasolabial angle UL-Fperp: distance between upper lip and Fperp LL-Fperp: distance between lower lip and Fperp Dentoskeletal and soft-tissue changes and T2 status The CHG showed statistically greater restriction of the anterior displacement of the maxilla than did the MPA (Tables IV and V; Fig 4). This result could be expected because the MPA is similar to the Herbst appliance, which was shown to have no significant Fig 3. Cephalometric landmarks: S, sella turcica; N, nasion; A, subspinale; B, supramentale; P, pogonion; Me, menton; Go, gonion; Gn, gnathion; Co, condylion; Ar, articulare; ANS, anterior nasal spine; PNS, posterior nasal spine; UL, upper lip; LL, lower lip; Prn, pronasale; Sn, subnasale; Prn=, nasal columella; U1, most anterior point of maxillary incisor crown; L1, most anterior point of mandibular incisor crown; U6, point located on maxillary first molar mesial cusp; L6, point located on mandibular first molar mesial cusp. effect in forward maxillary displacement,15 whereas the CHG does.2,4,5,16-18 Probably, this greater restriction effect on forward maxillary displacement is consequent to the longer time that the CHG was used (16 months) compared with the MPA (7 months). Consequently, the effect on the increase in maxillary effective length was statistically smaller for the CHG, and the maxilla at T2 was significantly more retruded in group 1. The MPA produced greater mandibular protrusion than did the CHG, as is usually observed when comparing the treatment effects of functional appliances and headgears.10,12,19 This greater mandibular protrusion is consequent to the greater increase in mandibular length usually produced by functional appliances.15,20-24 Although this effect is still controversial, some have shown that it is possible.15,20-24 However, the mandibular length increase was greater but not statistically significant in group 2. Therefore, what could have accounted for this smaller mandibular protrusion in group 1 was the cumulative effects of a nonsignificant smaller increase in mandibular length Siqueira et al 447.e25 American Journal of Orthodontics and Dentofacial Orthopedics Volume 131, Number 4 Table II. Systematic and casual errors Groups Variable Maxillary component SNA (°) Co-A (mm) Mandibular component SNB (°) Go-Gn (mm) Co-Gn (mm) Maxillomandibular relationship ANB (°) NAP (°) Vertical component SN.GoMe (°) SN.PP (°) UAFH (mm) LAFH (mm) PFH (mm) LPFH (mm) Maxillary dentoalveolar component U1.NA (°) U1-NA (mm) U1-PP (mm) U6-PP (mm) U6-Fperp (mm) Mandibular dentoalveolar component IMPA (°) L1.NB (°) L1-NB (mm) L1-MP (mm) L6-MP (mm) L6-Fperp (mm) Dentoalveolar relationship Overjet (mm) Overbite (mm) Soft-tissue profile NLA (°) UL-Fperp (mm) LL-Fperp (mm) First measurement (n ⫽ 16) Second measurement (n ⫽ 16) Mean SD Mean SD Casual errors (Dahlberg) Systematic errors (P) 84.6 85.0 3.82 3.86 84.30 85.10 3.58 3.68 0.614 0.529 .178 .357 79.50 70.40 105.90 3.01 3.90 5.10 79.30 70.10 106.10 2.95 3.83 5.00 0.340 0.615 0.554 .064 .314 .083 5.10 7.50 2.25 6.17 5.00 7.30 2.27 6.25 0.375 0.705 .491 .617 31.40 4.80 46.70 60.10 68.80 39.60 4.52 3.21 3.99 5.08 4.04 3.16 31.60 5.00 46.60 60.20 68.80 39.60 4.58 3.27 4.03 5.46 4.55 2.90 0.542 0.550 0.398 0.386 0.753 0.788 .389 .393 .706 .800 .968 .791 27.10 5.70 26.50 20.70 39.50 7.24 1.49 2.44 1.91 3.51 26.40 5.50 26.70 20.70 39.10 6.97 1.66 2.43 1.84 3.41 1.351 0.406 0.449 0.424 0.729 .120 .204 .139 .842 .459 95.90 27.10 5.10 37.00 25.90 38.80 7.56 7.79 2.59 3.40 2.58 4.11 96.10 26.90 4.90 37.20 26.40 38.50 7.22 8.00 2.55 3.70 2.93 3.91 1.632 1.463 0.381 0.458 0.544 0.853 .756 .763 .205 .228 .006* .447 7.65 4.44 3.26 2.41 7.34 4.87 3.36 2.47 0.467 0.637 .060 .052 108.60 4.60 2.40 8.93 2.25 2.75 108.40 4.20 2.60 9.06 2.24 2.92 2.645 0.704 0.244 .843 .105 .231 *Statistically significant at P ⬍.05. associated with a statistically significant greater increase in maxillary first molar extrusion in this group; this caused clockwise rotation of the mandible with a consequent retrusive effect.1,5,16,25,26 Despite the greater mandibular protrusion produced by the MPA, there were no significant differences in the mandibular components between the groups at T2; this means that these appliances do not have discernible effect differences in these areas. The CHG produced a statistically greater improvement in the maxillomandibular relationship and consequently a greater reduction in facial convexity than did the MPA, in spite of the greater mandibular protrusion it produced, as discussed above. These differences in effect amounts between headgears and functional appliances were also observed previously.10,12,19 They are consequent to the greater restriction of maxillary forward displacement with headgear.1-5,16,25 Consequently, the CHG group finished with a smaller apical base anteroposterior discrepancy and a smaller facial convexity than did the MPA group; this is positive in Class II malocclusion treatment. Treatment changes in both groups were similar in the vertical components, which had similar char- 447.e26 Siqueira et al Table III. American Journal of Orthodontics and Dentofacial Orthopedics April 2007 Intergroup comparison at T1 (t test) Groups CHG (n ⫽ 25) MPA (n ⫽ 25) Variables Mean SD Mean SD P Initial age (y) Treatment time (y) Maxillary component SNA (°) Co-A (mm) Mandibular component SNB (°) Go-Gn (mm) Co-Gn (mm) Maxillomandibular relationship ANB (°) NAP (°) Vertical component SN.GoMe (°) SN.PP (°) UAFH (mm) LAFH (mm) PFH (mm) LPFH (mm) Maxillary dentoalveolar component U1.NA (°) U1-NA (mm) U1-PP (mm) U6-PP (mm) U6-Fperp (mm) Mandibular dentoalveolar component IMPA (°) L1.NB (°) L1-NB (mm) L1-MP (mm) L6-MP (mm) L6-Fperp (mm) Dentoalveolar relationship Overjet (mm) Overbite (mm) Soft-tissue profile NLA (°) UL-Fperp (mm) LL-Fperp (mm) 12.40 2.39 0.90 0.90 12.30 2.80 1.76 0.73 .788 .052 83.15 84.88 3.05 4.07 83.50 84.21 4.66 4.07 .753 .562 77.55 70.46 105.55 3.12 4.25 5.38 77.42 69.06 102.83 3.33 3.77 4.52 .886 .225 .059 5.60 8.64 1.38 4.42 6.08 10.25 2.76 6.16 .441 .296 33.84 6.82 48.00 60.36 67.27 39.29 3.73 3.97 3.36 4.69 3.69 2.71 32.71 7.22 46.93 58.10 65.51 38.02 5.48 3.91 3.11 5.90 3.88 3.25 .399 .721 .251 .140 .108 .141 29.11 6.11 25.94 20.80 37.90 8.83 2.08 2.47 1.79 3.80 30.74 6.16 24.74 19.40 38.86 6.71 2.20 3.22 1.79 4.61 .464 .942 .147 .008* .426 94.87 26.23 5.14 37.60 26.04 36.93 5.44 5.56 1.37 2.11 1.72 3.86 95.48 25.60 5.08 36.82 26.27 37.43 7.75 8.22 2.34 3.08 2.55 4.71 .746 .752 .901 .302 .708 .681 8.05 4.78 2.45 1.82 8.72 5.13 2.68 2.06 .359 .525 105.66 82.90 77.50 9.96 4.26 4.99 106.07 83.06 76.31 12.85 5.14 5.42 .900 .905 .424 *Statistically significant at P ⬍.05. acteristics at T2. Increases in lower anterior face height (LAFH) with these appliances are usually greater than those of normal growth, as previously shown.1,9,15,16,21,23,27-29 Therefore, similar concerns apply when using these appliances in patients who do not need increases in the LAFH.1,27,28 Appliances with the opposite effect would be preferable for those patients.1,28,30 The maxillary incisors had a statistically greater linear retrusion with the MPA appliance in relation to A-point, as compared to the CHG. This retrusion was greater in relation to A-point. The maxillary first molars were distalized in group 1, whereas they had mesial displacement in group 2, with a statistically significant difference. If the maxillary molars were distalized in group 1, it would follow that the incisors should have had statistically greater retrusion in group 1 as well. However, because of the skeletal effect of the CHG’s greater restriction of maxillary forward displacement, the incisor retrusion relative to A-point was smaller in group 1. Maxillary first molar extrusion was statistically greater with the CHG than with the MPA; this was expected because of the known predominant extrusive Siqueira et al 447.e27 American Journal of Orthodontics and Dentofacial Orthopedics Volume 131, Number 4 Table IV. Intergroup comparison of treatment changes (T2-T1, t test) Groups CHG (n ⫽ 25) Variables Maxillary component SNA (°) Co-A (mm) Mandibular component SNB (°) Go-Gn (mm) Co-Gn (mm) Maxillomandibular relationship ANB (°) NAP (°) Vertical component SN.GoMe (°) SN.PP (°) UAFH (mm) LAFH (mm) PFH (mm) LPFH (mm) Maxillary dentoalveolar component U1.NA (°) U1-NA (mm) U1-PP (mm) U6-PP (mm) U6-Fperp (mm) Mandibular dentoalveolar component IMPA (°) L1.NB (°) L1-NB (mm) L1-MP (mm) L6-MP (mm) L6-Fperp (mm) Dentoalveolar relationship Overjet (mm) Overbite (mm) Soft-tissue profile NLA (°) UL-Fperp (mm) LL-Fperp (mm) MPA (n ⫽ 25) Mean SD Mean SD P ⫺2.46 0.64 1.77 2.04 ⫺0.17 2.54 2.10 2.01 .000* .002* 0.26 3.06 6.39 1.17 3.06 2.90 1.36 3.25 6.38 1.96 2.87 3.03 .020* .824 .996 ⫺2.71 ⫺5.97 1.25 2.93 ⫺1.53 ⫺3.57 1.43 2.65 .003* .004* 0.31 1.26 2.81 4.04 5.30 4.04 1.48 1.71 1.51 2.33 2.18 2.24 ⫺0.63 0.37 2.34 2.92 4.95 3.97 2.86 2.35 2.31 2.29 2.64 2.30 .151 .131 .393 .092 .614 .911 ⫺6.41 ⫺0.98 1.33 2.20 ⫺0.78 9.40 2.46 1.82 1.67 2.55 ⫺11.16 ⫺2.86 1.13 1.00 1.26 7.79 2.03 1.88 1.45 2.60 .058 .005* .705 .009* .007* 2.03 2.62 0.85 1.10 2.65 2.50 6.26 6.11 1.37 1.99 1.08 2.69 5.23 5.98 0.92 ⫺0.12 3.02 4.99 8.38 7.73 1.32 2.23 1.01 2.87 .133 .095 .859 .046* .216 .003* ⫺5.24 ⫺2.23 2.73 2.10 ⫺5.93 ⫺2.63 2.70 1.88 .372 .477 3.54 0.78 2.62 7.43 2.42 2.42 4.54 0.96 4.54 9.94 2.49 2.66 .688 .805 .010* *Statistically significant at P ⬍.05. effect of the CHG.1,2,4,16-18,25,31 Usually, the forces generated by the MPA tend to cause maxillary first molar intrusion or, at least, restriction of its downward development.6-9,15,23 The maxillary first molar crown in group 1 experienced statistically significant distalization in relation to group 2 as was previously observed in comparisons between headgears and removable functional appliances.10,12 This result shows that distalization with the CHG is also greater than that with a fixed functional appliance. Therefore, it can be concluded that the CHG has a greater molar distalizing effect. These different changes in the maxillary component during treatment were reflected at T2: group 1 showed statistically protruded maxillary incisors, greater maxillary first molar dentoalveolar height, and retruded maxillary molars in relation to group 2. The mandibular incisors had similar anteroposterior behavior. However, the MPA tended to displace the mandibular incisors farther labially than did the CHG. This is in accordance with the effects of similar functional appliances.15,20-23,32-34 The nonsignificantly greater labial displacement of the incisors was reflected in restriction of their vertical development, whereas in group 1 the incisors experienced statistically significant vertical development compared with group 2. As the 447.e28 Siqueira et al Table V. American Journal of Orthodontics and Dentofacial Orthopedics April 2007 Intergroup comparison at T2 (t test) Groups CHG (n ⫽ 25) Variables Maxillary component SNA (°) Co-A (mm) Mandibular component SNB (°) Go-Gn (mm) Co-Gn (mm) Maxillomandibular relationship ANB (°) NAP (°) Vertical component SN.GoMe (°) SN.PP (°) UAFH (mm) LAFH (mm) PFH (mm) LPFH (mm) Maxillary dentoalveolar component U1.NA (°) U1-NA (mm) U1-PP (mm) U6-PP (mm) U6-Fperp (mm) Mandibular dentoalveolar component IMPA (°) L1.NB (°) L1-NB (mm) L1-MP (mm) L6-MP (mm) L6-Fperp (mm) Dentoalveolar relationship Overjet (mm) Overbite (mm) Soft-tissue profile NLA (°) UL-Fperp (mm) LL-Fperp (mm) MPA (n ⫽ 25) Mean SD Mean SD P 80.69 85.52 3.25 4.86 83.34 86.75 4.56 4.52 .022* .361 77.81 73.52 111.94 3.21 4.80 6.58 78.78 72.32 109.21 3.44 3.34 4.89 .307 .306 .103 2.89 2.68 1.32 3.99 4.55 6.68 2.54 6.47 .006* .011* 34.15 8.08 50.81 64.40 72.57 43.33 4.13 3.73 3.28 6.14 4.64 3.25 32.08 7.59 49.27 61.01 70.46 41.99 6.37 3.18 3.93 5.76 4.45 4.37 .179 .618 .139 .050 .108 .225 22.70 5.13 27.27 23.00 37.12 5.08 1.78 3.27 2.45 5.02 19.58 3.30 25.88 20.40 40.12 8.44 2.22 2.57 1.44 4.03 .120 .002* .100 .000* .024* 96.90 28.85 6.00 38.70 28.68 39.42 5.32 4.52 1.44 2.92 2.42 4.93 100.71 31.58 6.00 36.69 29.29 42.42 6.82 4.09 1.98 3.88 2.57 4.17 .032* .030* 1.000 .044* .396 .025* 2.82 2.55 0.60 1.00 2.80 2.50 0.58 0.69 .905 .831 109.20 83.69 80.12 10.37 5.28 5.40 110.62 84.02 80.85 11.36 5.31 5.25 .647 .826 .629 *Statistically significant at P ⬍.05. incisors are labially displaced, the distance to the mandibular plane decreases.15 These nonsignificantly greater labial displacements of the mandibular incisors in group 2 caused them to show statistically significant protrusion in relation to group 1 at T2. The mandibular first molars in the MPA group had a statistically greater crown mesial displacement than those in the CHG group. This is consequent to the mesial forces acting on the mandibular teeth from the forward mandibular displacement dictated by the appliance; this also helps in correcting the anteroposterior discrepancy.6-9,15,20,21,33,34 Mesial molar displacement in group 1 was within the normal developmental range because no mesial forces were applied to these teeth.17,26,35,36 Similar to the incisors, the statistically greater mesial displacement of the mandibular molars in group 2 placed their crowns significantly mesial to those of group 1 at T2. The amounts of reduction of overjet and overbite were similar between the appliances, and therefore there was also similarity in these variables at the end of treatment in both groups, showing that both appliances have equivalent potential in correcting these Class II malocclusion characteristics. As would be expected in Class II nonextraction treatment, both appliances produced similar increases Siqueira et al 447.e29 American Journal of Orthodontics and Dentofacial Orthopedics Volume 131, Number 4 Fig 4. Superimposition of average cephalometric tracings of groups 1 and 2 at T2: A, total superimposition on SN line, registered on S; B, maxillary partial superimposition on palatal plane, registered on ANS; C, mandibular partial superimposition on mandibular plane (Go-Me), registered on symphysis. in the nasolabial angles, primarily consequent to palatal tipping and retrusion of the maxillary incisors.37-40 Group 2 had statistically greater lower lip protrusion, consequent to the statistically greater mesial mandibular molar displacement and to the nonsignificant greater mandibular incisor labial displacement, as previously observed with similar fixed functional appliances.41,42 Despite the statistically greater lower lip protrusion in group 2, no significant differences were found in the soft-tissue profile at T2 between the groups, probably because of the great variability in the soft-tissue structures.43 Even though the differences in this variable and in many other variables were statistically significant, but small, between the groups, they can be considered clinically relevant when one attempts to deliver the best results to patients with specific characteristics.41-43 Clinical considerations Correction of Class II malocclusions in the groups treated with the MPA and the CHG, followed by fixed appliances, was consequent to distinct and specific dentoskeletal changes of each protocol. Clinically, the 2 appliances produced satisfactory results by reducing facial convexity; this is important in Class II malocclusion treatment.15,22,30,34,41-43 Although the primary changes of the MPA, as compared with normal growth, consisted of distalization of the maxillary dentoalveolar process,6-9 we showed that patients treated with the CHG and fixed appliances had greater skeletal changes in the maxilla because of the orthopedic action of this mechanism in restricting its anterior displacement. Consequently, there was also greater improvement in the skeletal Class II relationship. Maxillary molar distalization was also greater with the CHG. The MPA produced smaller skeletal changes and greater mandibular molar mesialization and labial displacement of the incisors that resulted in greater protrusion of the lower lip, as compared with the CHG group. From these effects, their indications can be derived. 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