- Email: [email protected]
The impact of functional jaw orthopedics in subjects with unfavorable class II skeletal patterns
progress in orthodontics 1 1 ( 2 0 1 0 ) 118–126
available at www.sciencedirect.com
journal homepage: www.elsevier.com/locate/pio
Original article
The impact of functional jaw orthopedics in subjects with unfavorable class II skeletal patterns Tiziano Baccetti a,∗ , James A. McNamara Jr. b a
DDS, PhD, Research Professor, Department of Orthodontics, The University of Florence, Italy; Thomas M. Graber Visiting Scholar, Department of Orthodontics and Pediatric Dentistry, School of Dentistry, The University of Michigan, Ann Arbor, USA. b DDS, PhD, Thomas M. and Doris Graber Endowed Professor of Dentistry, Department of Orthodontics and Pediatric Dentistry, School of Dentistry; Professor of Cell and Developmental Biology, School of Medicine; Research Professor, Center for Human Growth and Development, The University of Michigan, Ann Arbor; Private practice, Ann Arbor, Michigan, USA.
a r t i c l e
i n f o
a b s t r a c t
Article history:
Objective: To evaluate the outcomes of functional jaw orthopedics (FJO) followed by fixed
Received 23 June 2010
appliances in Class II patients showing cephalometric signs predictive of unfavorable
Accepted 12 July 2010
responsiveness to orthopedic treatment. Materials and methods: A total of 48 treated subjects (20 males, 28 females) with unfavorable
Keywords:
Class II malocclusions were treated with FJO at the adolescent growth spurt, followed by fixed
Class II malocclusion
appliances. Treatment outcomes were compared with the growth changes in a matched
Functional appliances
control group of untreated subjects with “unfavorable” Class II malocclusions.
Growth
Results: A significant prevalence rate of successful outcome was recorded within the treated
Predictive variables cephalometrics
group (64.5%). When compared with the untreated controls, both the overall treated group
Treatment outcomes
and the successful treated subgroup revealed a significant reduction in maxillary growth and sagittal position, along with a significant enhancement in mandibular length, sagittal advancement of the mandible, and significant improvements in the maxillo-mandibular relationships. Both overjet and molar relation showed significant favorable changes in the treated group. Conclusions: FJO at the pubertal spurt followed by fixed appliances is a viable therapeutical option in patients with “unfavorable” Class II malocclusions, although skeletal changes are of minor entity. © 2010 Società Italiana di Ortodonzia SIDO. Published by Elsevier Srl. All rights reserved.
1.
Introduction
Treatment of dentoskeletal Class II malocclusion typically is accomplished by two methods, i.e. either an orthodontic/orthopedic approach in the growing subject or corrective jaw surgery at the completion of growth.1,2 The first option often requires the use of orthopedic appliances
(functional/orthopedic appliances directed to the maxilla, or to the mandible, or both) in conjunction with fixed appliances to refine the occlusion.2 Surgical orthodontics may be performed in one phase in the adult Class II patient or on patients who did not show a satisfactory correction of Class II disharmony through earlier orthopedic/orthodontic treatment.1 A series of clinical and epidemiological studies have focused on the analysis of the factors that can affect growth and/or
∗ Corresponding author. Dipartimento di Odontostomatologia, Università degli Studi di Firenze, Via del Ponte di Mezzo 46/48 - 50127 Firenze, Italy. E-mail address: tbaccetti@unifi.it (T. Baccetti). 1723-7785/$ – see front matter © 2010 Società Italiana di Ortodonzia SIDO. Published by Elsevier Srl. All rights reserved. doi:10.1016/j.pio.2010.09.002
progress in orthodontics 1 1 ( 2 0 1 0 ) 118–126
therapeutic outcomes in Class II subjects. These factors can be categorized as follows: 1) favorable/unfavorable growth characteristics; 2) favorable/unfavorable outcomes and stability of functional jaw orthopedics (FJO); 3) favorable/unfavorable outcomes and stability of orthognathic surgery (OS) or distraction osteogenesis (DO). 1) Favorable/unfavorable growth characteristics. The features of growth in untreated Class II subjects reveal an absence of self-correction of the dentoskeletal disharmony.3–5 The pubertal peak period enhances the mandibular growth deficiency in subjects with dentoskeletal Class II malocclusion.5 Certain types of dentoskeletal patterns within the generic definition of Class II malocclusion may present particularly “unfavorable” growth trends. They consist of Class II patients showing posterior growth rotation of the mandible with a skeletal openbite tendency associated with a deficiency in mandibular size.6,7 Recent research has shown that a peculiar composition of facial muscles, with consequent functional alterations of the masticatory muscles, is found in patients with a smallsized mandible and an open gonial angle, thus providing some explanation for the deficiency in growth of the lower third of the face in these patients.8 2) Favorable/unfavorable outcomes and stability of functional jaw orthopedics (FJO). The literature provides abundant contributions to the evaluation of the short- and long-term outcomes of combined orthopedic/orthodontic treatment of Class II malocclusion, as highlighted by recent systematic reviews.9–12 A number of studies have focused on the pretreatment dentoalveolar characteristics of Class II treated patients as a prognostic basis to identify favorable vs unfavorable responsiveness to Class II treatment in the growing subject.13–15 A few other studies have examined the skeletal features of Class II patients before treatment with FJO and orthodontic appliances. Beyond the issue of treatment timing (with larger skeletal changes induced by FJO at the pubertal growth spurt7,9,16–19 ), all these reports agree in the identification of a posteriorly-rotated mandible associated with an opening of the gonial angle and with a severely affected intermaxillary skeletal sagittal relation as predictors of poorer dentoskeletal outcomes following treatment of Class II malocclusion.6,20,21 3) Favorable/unfavorable outcomes and stability of orthognathic surgery (OS) or distraction osteogenesis (DO). Some Class II patients do not undergo orthopedic treatment during their active growing period, but rather receive orthognathic surgery at the completion of growth. In other instances, OS is performed on subjects who did not achieve correction of the malocclusion after FJO. Factors for unfavorable outcomes or stability of OS or DO in Class II patients have been suggested; they consist mainly in increased vertical skeletal relationships and/or open gonial angle associated with severely reduced size of the mandible in young adults with Class II malocclusion.22–26 High-angle patients show both a higher frequency and a greater magnitude of horizontal relapse after surgery.23 Less ideal soft-tissue profile outcomes after surgery are associated with larger pretreatment intermaxillary sagittal discrepancies.26 Significant mandibular relapse has been found in Class II patients with high mandibular plane angles who had undergone mandibular advancements greater than 10 mm.24 More-
119
over, high-angle patients are at risk of relapsing following distraction osteogenesis as well, as DO cannot prevent relapse in patient with a high mandibular plane angle associated with severe sagittal discrepancies in Class II disharmony.25 From the above-described analysis of the factors affecting results of treatment in Class II malocclusion by either orthopedic or surgical orthodontic approaches, it appears evident that there is a consistency in the elements that various investigators have considered as predictors of poor therapeutic results in the individual Class II patient. An unfavorable Class II patient can be depicted as a patient with severe intermaxillary discrepancy both in the sagittal and vertical planes, this latter characteristic being associated with increased vertical skeletal relationships, a large gonial angle, and a posteriorly-rotated mandible. This type of Class II dentoskeletal disharmony is expected to exhibit an unfavorable growth trend if left untreated, a poor response to FJO and orthodontic treatment during the growing period, and a lessthan-ideal response and/or stability when treated by means of orthognathic surgery or distraction osteogenesis at a young adult age. The purpose of the present study is to evaluate the impact of FJO followed by fixed appliances on patients with “unfavorable” Class II division 1 skeletal patterns by means of a double-blinded study on a large group of patients treated with various FJO appliance protocols and compared with untreated Class II controls. The outcomes of the present investigation are aimed to improve the knowledge about expectations of both clinicians and patients in terms of outcomes of dentofacial orthopedics in severe Class II malocclusions, also with regard to the possible role of orthopedic/orthodontic treatment before orthognathic surgery in Class II patients with unfavorable skeletal patterns.
2.
Materials and methods
2.1. Class II Sample treated with FJO and fixed appliances The treated patients of this study are part of a multicentered prospective trial on the use of one-phase comprehensive orthopedic/orthodontic treatment protocols at puberty in Class II division 1 subjects. The malocclusion was defined according to the presence of full-cusp Class II molar relationship, excessive overjet, and ANB angle larger than 5 degrees. The original sample comprised a total of 160 patients treated at the pubertal growth spurt with functional jaw orthopedics followed by fixed appliances to refine occlusion. FJO consisted of the Herbst appliance in 54 subjects (26 males, 28 females), a Bionator appliance in 24 subjects (11 males, 13 females); a Twin Block appliance in 28 cases (14 males, 14 females); and the FR-2 appliance of Fränkel in 54 subjects (23 males, 31 females). In all patients, treatment started (T1) at the pubertal growth spurt (either at CS3 or CS4 in cervical vertebral maturation), it had a duration that ranged between 24 months and 34 months, and it ended (T2) at a post-pubertal stage of development (CS5 or CS6).27 Each type of FJO treatment was provided by clinicians experienced in that specific treatment modality. The phase with fixed appliances was conducted without extraction
120
progress in orthodontics 1 1 ( 2 0 1 0 ) 118–126
of permanent teeth, and patient compliance was judged by the clinician from “good” to “very good.” The treating practitioners were blind to the objective of the study, i.e. the evaluation of treatment outcomes in “unfavorable” Class II patients. Treatment protocols were applied in a standardized manner; they were not customized according to the patient’s characteristics. Lateral cephalograms for each treated patient were collected at T1 and T2. The magnification factor of all cephalograms was adjusted to 8%.
analysis containing measurements from the analyses of Steiner,28 Jacobson,29 Ricketts,30 and McNamara31 was used. All sets of cephalograms were traced at the same time. A preliminary tracing was made for each film, with particular attention paid to tracing of the outlines of the maxilla and mandible, including the mandibular condyle. The investigators traced the total of the treated Class II sample before identification of the unfavorable Class II patients. Additionally, they were blind also to the specific appliance used in individual patients.
2.2.
2.5.
Identification of “unfavorable” Class II patients
A computerized sorting technique (SPSS, ver. 1.12) was applied to identify those Class II subjects who presented with 3 concurrent cephalometric features at T1 for the definition of “unfavorable” Class II malocclusion according to the indications reported in the literature:6,13,20,21,23,26 1) Co-Go-Me angle greater than 128 degrees; 2) Wits appraisal value greater than 4 mm (i.e. greater than the average value of Wits at T1 with the addition of one standard deviation); 3) MPA greater than 27 degrees (i.e. greater than the average value of MPA at T1 with the addition of one standard deviation). Out of the original sample of 160 patients, the sorting technique identified 48 subjects (20 males, 28 females) with unfavorable Class II division 1 malocclusions. Twelve subjects belonged to the Herbst group, 8 subjects to the Bionator group, 8 subjects to the Twin Block group, and 20 subjects to the FR2 group. The average age of treated subjects was 12 years 4 months at T1, and 14 years and 10 months at T2, with an average T1-T2 interval of 2 years 7 months.
Statistical analysis
2.5.1. Analysis within the “unfavorable” Class II treated sample An evaluation of the outcomes of therapy (FJO followed by fixed appliances) was performed preliminarily within the “unfavorable” Class II sample of 48 patients. A successful outcome was considered when the presence of a normal molar relationship and a normal overjet was assessed both clinically and cephalometrically, along with the presence of normal values for the variables PtA-Nperp and Pg-Nperp.31,32 An unsuccessful outcome of therapy was assessed when the normalization of the occlusal and skeletal parameters described in the successful group had not been achieved at T2. The ratio of subjects showing successful vs unsuccessful outcomes within the unfavorable Class II treated sample was evaluated statistically by means of z-statistics for proportions (SigmaStat, Systat Software Inc., San Jose, Ca).
2.5.2. Comparisons between the treated and untreated samples
A control group of 20 subjects with untreated Class II division 1 malocclusion was selected from the files of the University of Michigan Growth Study, the Denver Growth Study, and the Department of Orthodontics at the University of Florence, Italy. All subjects presented with signs of unfavorable Class II skeletal patterns at T1, as they were characterized by fullcusp Class II molar relationship, excessive overjet, ANB angle greater than 5 degrees, Wits appraisal greater that 4 mm, MPA larger than 27 degrees, and Co-Go-Me angle larger than 128 degrees. The cephalogram at T1 corresponded with either CS3 or CS4 in skeletal maturation, and the cephalogram at T2 with either CS5 or CS6.27 The duration of T1-T2 observation period ranged from 22 months to 36 months. The magnification factor of all cephalograms was corrected to an 8% in order to match the treated group. The average age of control subjects was 12 years 6 months at T1, and 14 years and 11 months at T2, with an average T1-T2 interval of 2 years 6 months.
The dentoskeletal characteristics of the unfavorable Class II treated sample (n=48) and of the untreated Class II control sample (n=20) were compared for an evaluation of starting forms. The T1-T2 changes in the treated sample (n=48) then were contrasted with the T1-T2 changes in the control sample (n=20). Also, the T1-T2 changes in the subgroups of unfavorable Class II patients who showed successful therapeutic outcomes (n=21) were compared with the T1-T2 changes in the subgroup of subjects who did not show successful outcomes of therapy at T2 (n=17), as well as with the T1-T2 changes in the untreated control sample. Exploratory testing by means of a Shapiro-Wilks test indicated lack of normality of distribution for several of the examined variables. Therefore, comparisons were performed either by means of Mann Whitney U tests (p<0.05) for independent samples (comparisons of starting forms and comparison on T1-T2 changes between the total treated group and the untreated control group), or by means of Kruskal-Wallis with post-hoc tests for non-parametric data (p<0.05) (comparisons on the changes in successful and unsuccessful treated subgroups and untreated control group).
2.4.
2.6.
2.3.
Untreated Class II Control sample
Cephalometric analysis
A customized digitization regimen and analysis provided by a cephalometric software (Viewbox, ver 3.0, dHAL Software, Kifissia, Greece) was utilized for all the cephalograms that were examined in this study. A cephalometric
Power of the study and method error
The calculated power of the study exceeded 0.80. A total of 30 lateral cephalograms randomly chosen from all observations were re-traced and re-digitized to calculate method error by means of Dahlberg’s formula.33 The error for linear
121
progress in orthodontics 1 1 ( 2 0 1 0 ) 118–126
Table 1 – Comparison of starting forms for the treated and untreated unfavorable Class II groups at T1. Cephalometric Measures
“Unfavorable” Class II subjects Treated with FJO N=48
“Unfavorable” Class II subjects Untreated N=20
Mean
SD
Mean
SD
Maxillary Skeletal SNA (◦ ) PtA-Nasion perp (mm) Co-Pt A (mm)
80.9 0.8 86.1
3.1 2.8 3.5
80.4 0.3 85.4
3.8 2.9 4.1
0.5 0.5 0.7
NS NS NS
Mandibular Skeletal SNB (◦ ) Pog-Nasion perp (mm) Co-Gn (mm)
75.4 −9.3 105.9
2.8 4.4 4.1
75.3 −8.3 104.8
3.1 4.2 5.4
0.1 −1.0 1.1
NS NS NS
Maxillary/Mandibular ANB (◦ ) Wits appraisal (mm) Max/Mand difference (mm)
7.3 6.1 19.8
2.4 1.9 3.4
7.1 5.9 19.2
1.9 1.7 2.0
0.2 0.2 0.6
NS NS NS
Vertical Skeletal FH to mandibular plane (◦ ) FH to palatal plane (◦ ) Co-Go-Me (◦ )
31.6 2.9 132.7
3.5 3.4 3.6
30.8 2.5 131.8
2.9 2.6 3.5
0.8 0.3 0.9
NS NS NS
1.3 6.8 −1.9
2.2 1.9 1.2
1.9 5.8 −1.4
3.2 2.1 1.1
−0.6 1.0 −0.5
NS NS NS
Interdental Overbite (mm) Overjet (mm) Molar relationship (mm)
Difference
Significance
NS = Not Significant.
measurements ranged from 0.2 mm (overjet) to 0.8 mm (Pg to Nasion perpendicular), while the error for angular measurements varied from 0.3 degrees (ANB) to 0.8 degrees (FH to mandibular plane).
3.
Results
3.1. Analysis within the “unfavorable” Class II sample treated with FJO A successful outcome of therapy was assessed in 31 (64.5%) out of the 48 treated Class II patients (6 patients treated with the Herbst, 5 patients treated with the Bionator, 6 patients with the Twin Block, and 14 patients treated with the FR-2). A total of 17 subjects did not show a successful outcome following FJO and fixed appliance therapy. The comparison of the prevalence rates for successful vs unsuccessful cases was significant (p<0.01).
3.2. Comparison between the total treated group and the control group The craniofacial starting forms of the 2 groups did not differ significantly for any of the examined cephalometric variables (Table 1). The results of the comparisons of the T1-T2 changes in the 2 groups are reported in (Table 2). A significant reduction in maxillary growth and sagittal position was recorded in the total treatment group, with significantly smaller increments for Co-A, and a significant decrease in PtA-Nperp. All mandibular skeletal variables showed significant differences when compared with the controls. A significant enhancement in mandibular length (Co-Gn) and in the sagittal advancement
of the mandible (SNB, Pg-Nperp) were found in the treated group when compared with the controls, which lead to significant improvements in the maxillo-mandibular relationships. A significant decrease in the mandibular plane angle was assessed in the treated group, along with a significant reduction in the mandibular angle (Co-Go-Me) in comparison with the untreated Class II group. Both overjet and molar relation showed significant favorable changes in the treated group.
3.3. Comparison between the “successful” treated subgroup, “unsuccessful” treated subgroup, and the control group The results of these comparisons of the T1-T2 changes are shown in Table 3. The differences between the successful treated subgroup and the untreated controls replicated the findings described for the comparison between the total treated group and the untreated controls, as reported in the previous paragraphs. The following results were found for the comparison between the unsuccessful treated subgroup and the untreated controls. No significant differences in the sagittal maxillary variables were recorded. Significantly greater increases in mandibular length and a significant advancement of the mandible were found in the treated subgroup. The magnitude of these favorable mandibular changes was smaller then the changes assessed in the total treated group. All measurements of sagittal maxillo-mandibular relationships showed significant improvements in the unsuccessfully treated group compared with the untreated controls; however, these differences were smaller than in the overall treated group. A significantly greater favorable modification in the maxillo-mandibular differential was recorded in the successful subgroup vs the unsuccessful subgroup. As for the vertical
122
progress in orthodontics 1 1 ( 2 0 1 0 ) 118–126
Table 2 – Comparison of T2-T1 treatment and growth changes in the total treated group and the untreated controls. All subjects in both groups showed features of “unfavorable” Class II skeletal pattern at T1. Cephalometric Measures
Maxillary A-P Skeletal SNA (◦ ) Pt A-Na perp (mm) Co-Pt A (mm)
“Unfavorable” Class II subjects Treated with FJO Total N=48
“Unfavorable” Class II subjects Untreated (Controls) N=20
Mean
Mean
SD
Difference & Significance
SD
−0.8 −1.0 0.9
1.6 1.3 1.8
0.2 0.5 2.4
1.9 0.9 1.9
−1.0 NS −1.5* −1.5*
Mandibular A-P Skeletal SNB (◦ ) Pg-Na perp (mm) Co-Gn (mm)
1.2 1.9 6.6
1.2 1.2 2.1
−0.2 −0.3 3.8
1.3 1.2 1.9
1.4* 2.2** 2.8**
Intermaxillary ANB (◦ ) Wits appraisal (mm) Mx/Mn diff (mm)
−1.9 −3.2 5.8
1.4 1.5 2.6
0.3 0.6 1.1
0.8 1.2 2.0
−2.2** −3.8*** 4.7***
0.2 1.4 0.1
1.9 1.8 2.2
1.6 0.4 2.0
1.8 1.3 1.9
−1.4* 1.0 NS −1.9**
−0.4 −4.8 4.2
1.2 2.2 1.3
0.0 -0.1 0.1
0.9 0.7 0.8
−0.4 NS −4.7*** 4.1***
Vertical Skeletal MPA (◦ ) FH-PP (◦ ) Co-Go-Me (◦ ) Interdental Overbite (mm) Overjet (mm) Molar relation (mm)
NS = not significant; * p<0.05; ** p<0.01; *** p<0.001.
Table 3 – Comparison of T2-T1 treatment and growth changes in the successful treated subgroup, the unsuccessful treated subgroup, and the untreated controls. All subjects in the 3 groups showed features of “unfavorable” Class II malocclusion at T1. Cephalometric Measures
“Unfavorable” Class II subjects Treated with FJO Successful subgroup “A”
“Unfavorable” Class II subjects Treated with FJO Unsuccessful subgroup “B”
“Unfavorable” Class II subjects Untreated Control group “C”
N=21
N=17
N=20
Mean Maxillary A-P Skeletal SNA (◦ ) Pt A-Na perp (mm) Co-Pt A (mm)
SD
Mean
SD
Mean
SD
Differences & Significance
A-B
A-C
B-C
−1.1 NS −1.6* −1.7*
−0.4 NS −0.8 NS −1.2 NS
−0.9 −1.1 0.7
1.9 1.2 1.8
−0.2 −0.3 1.2
1.8 1.4 1.8
0.2 0.5 2.4
1.9 0.9 1.9
−0.7 NS −0.7 NS −0.5 NS
1.3 2.1 6.8
1.4 1.5 2.2
0.7 1.2 5.8
1.4 1.5 2.1
−0.2 −0.3 3.8
1.3 1.2 1.9
0.5 NS 0.9 NS 1.0 NS
Intermaxillary −2.1 ANB (◦ ) Wits appraisal (mm) −3.4 Mx/Mn diff (mm) 6.1
1.4 1.5 2.7
−1.0 −2.3 4.2
1.5 1.7 2.9
0.3 0.6 1.1
0.8 1.2 2.0
−1.1 NS −1.1 NS 1.9*
−2.4*** −4.0*** 5.0***
−1.3** −2.9*** 3.1**
Vertical Skeletal MPA (◦ ) FH-PP (◦ ) Co-Go-Me (◦ )
0.1 1.3 0.0
1.9 1.9 2.3
0.7 1.2 0.4
2.2 1.8 2.4
1.6 0.4 2.0
1.8 1.3 1.9
−0.6 NS 0.1 NS −0.4 NS
−1.5* 0.9 NS −2.0**
−0.9 NS 0.8 NS −1.6*
−0.5 −4.9 4.5
1.4 2.3 1.7
−0.1 −2.9 2.8
1.4 2.4 1.6
0.0 −0.1 0.1
0.9 0.7 0.8
−0.4 NS −2.0** 1.7*
−0.5 NS −4.8*** 4.6***
−0.1 NS −2.8** 2.7**
Mandibular A-P Skeletal SNB (◦ ) Pg-Na perp (mm) Co-Gn (mm)
Interdental Overbite (mm) Overjet (mm) Molar relation (mm)
NS = not significant; * p<0.05; ** p<0.01; *** p<0.001.
1.5* 2.4** 3.0**
0.9 NS 1.5* 2.0*
progress in orthodontics 1 1 ( 2 0 1 0 ) 118–126
skeletal relationships, only the mandibular angle Co-Go-Me showed a significant reduction in the unsuccessfully treated subjects vs the controls. Both the overjet and the molar relation improved significantly in the unsuccessful treated group. These changes were significantly smaller than in the successful treated subgroup.
4.
Discussion
The literature reports significant favorable changes in several samples treated with FJO followed by fixed appliances at the pubertal growth spurt.6,9,16–19,34 These studies analyze the outcomes of treatment performed on subjects with a variety of sagittal and vertical skeletal relationships. A series of investigations has shown that individuals with Class II division 1 malocclusions characterized by severe maxillo-mandibular discrepancies associated with increased vertical skeletal relations and an open mandibular angle are predicted to respond less favorably to orthopedic/orthodontic treatment during the developmental ages.6,7,13,20,21 The clinical scenario for these patients is complicated by the fact that the same craniofacial features have been demonstrated to be predictors of less favorable results and/or reduced stability after orthognathic surgery or distraction osteogenesis.22–26 The aim of the present study was to evaluate the outcomes of FJO followed by fixed appliance in Class II patients showing cephalometric signs predictive of unfavorable responsiveness to orthopedic treatment by comparing treatment effects with growth trends in Class II subjects showing similar craniofacial features. The analysis of the outcomes of therapy within the treated Class II group revealed a significant prevalence rate of cases that were corrected from both skeletal and occlusal standpoints. Thirtyone out of 48 treated cases (65%) exhibited “corrected” occlusal relationships at the end of treatment. Higher prevalence rates for the clinical correction after one-phase treatment protocols for Class II division 1 malocclusion have been described (ranging from 85% to 100%).19,32,34 However, taking into account the unfavorable characteristics of the treated sample, the prevalence rate of occlusal correction in almost 2 out of 3 patients has to be considered as a notably positive outcome. The effectiveness of therapy then was evaluated with respect to the growth changes in untreated Class II controls. Significant favorable changes were recorded in the total treatment group for the sagittal and vertical skeletal relationships, as well as for the occlusal variables. Main findings from this comparison were: significant restriction of maxillary growth, significant enhancement of mandibular growth and sagittal position, as well as significant reduction in the vertical facial relationships and mandibular angle. The absolute amount of these favorable changes in general was smaller than that reported in previous clinical trials evaluating the outcomes of FJO at the pubertal growth spurt.9,18,19,34 For instance, the increase in mandibular length in treated subjects over the untreated controls was 2.8 mm, which is considerably less than the 4.3 mm increase described by Faltin et al. in their Bionator study19 and than the 4.8 mm increase reported by Baccetti et al. in their Twin Block study.18 Once again, the unfavorable initial characteristics of the treated subjects in the present study should be taken into
123
account when appraising these results. Nonetheless, the clinically significant changes in the treated sample for the sagittal position of the mandible (2.2. mm), the Wits appraisal (3.8 mm), the maxillo-mandibular differential (4.6 mm), and the ANB angle (2.2 degrees) should be emphasized, as well as the changes in the vertical dimension. As shown by the untreated controls, growth in “unfavorable” Class II subjects is characterized by a progressive opening of the mandibular plane angle and of the angle between the condylar axis and the mandibular plane. Functional jaw orthopedics is able to reduce significantly this growth tendency to increased vertical relationships (by 1.4 degrees for the mandibular plane angle, and by 1.9 degrees for the Co-Go-Me angle). These observations are in agreement with the long-term observations by Faltin et al. in subjects treated with a bionator followed by fixed appliances during the adolescence.19 Further analysis of the data involved a comparison between the subgroup of patients who had shown a clinically successful outcome at the dentoskeletal level at the completion of therapy (n=21), the subgroup of patients who had not been treated successfully (n=17), and the untreated controls. While the results in the successful treated subgroup replicated the results of the total treated group and they did not add significant information for the discussion of the data, the findings concerning the comparison between the unsuccessful treatment subgroup and the untreated controls proved to be more interesting. This comparison was conducted in order to investigate the changes induced by FJO and fixed appliance therapy in those patients who showed the most unfavorable response to treatment and who would be eligible for orthognathic surgery to correct the persistent dentoskeletal disharmony. Significant improvements in the mandibular measurements, maxillo-mandibular relation, as well as in the mandibular angle still were found in this group of clinically “unsuccessful” patients versus the controls. As anticipated, the extent of the favorable changes was smaller than in either the overall treated group or the successful treated subgroup. However, the average increases over the controls for mandibular size (2.0 mm) and position (1.5 mm), for both the Wits appraisal and the maxillo-mandibular differential (about 3 mm), and the significant reduction (−1.6 degrees) in the Co-Go-Me angle, have to be considered as substantial improvements with regard to the growth trends expressed by the untreated controls. In this regard, it should be noted once again that the dento-skeletal factors that account for unfavorable outcomes/stability of orthognathic surgery/distraction osteogenesis in Class II patients consist mainly in increased vertical skeletal relationships and/or open gonial angle associated with severely reduced size of the mandible.22–26 Therefore, the significant improvements produced at puberty by FJO and fixed appliances in patients with Class II division 1 malocclusions may affect the expectations with regard to possible outcomes of OS or DO at a postpubertal phase of development. On the basis of the findings of the present investigation, FJO followed by fixed appliances at the pubertal growth spurt appears to be a viable treatment option also in those patients who exhibit unfavorable dento-skeletal signs before therapy. Almost 2/3rds of the patients are able to achieve a correction
124
progress in orthodontics 1 1 ( 2 0 1 0 ) 118–126
of the disharmony at the occlusal level. In case of incomplete correction of the malocclusion, the task of subsequent orthognathic surgery in terms of results and stability potentially is facilitated by improved sagittal and vertical craniofacial relationships induced by orthopedic/orthodontic therapy. A recent clinical trial34 has shown that FJO is able to produce a significant beneficial effect on the sagittal position of soft tissue Pogonion in pubertal Class II patients showing “favorable” dentoskeletal characteristics in terms of responsiveness to orthopedic therapy (mandibular retrusion associated with a closed mandibular angle). Further investigation is needed to determine whether in “unfavorable” Class II patients a similar improvement in the soft tissues can be associated with the significant beneficial effects induced by FJO at the dentoskeletal level. Finally, in subjects with “unfavorable” Class II malocclusions treatment protocols alternative to FJO also might be indicated, with the common goal of reducing the sagittal and vertical discrepancies. Dentoskeletal effects similar to those produced by FJO have been reported in Class II patients treated at puberty by means of molar distalizing appliances in conjunction with fixed appliances and Class II elastics.32,35
5.
Conclusions
Functional jaw orthopedics followed by fixed appliances is a viable therapeutic option in patients with “unfavorable” Class II skeletal patterns. A prevalence rate of 65% of these patients achieves correction of the malocclusion through significant sagittal and vertical treatment effects. The remaining 35% of the subjects, though not completely corrected, will present with reduced unfavorable dentoskeletal features before a potential intervention of orthognathic surgery.
Conflict of interest The author have reported no conflict of interest.
Acknowledgement The authors would like to thank Drs. John Damas, Brad Porter, Larry Spillane, Mart McClellan, Robert Smith, David Snodgrass, Forbes Leishman, and Kurt Faltin Jr, for having participated in the clinical trial by treating patients, Dr. Lorenzo Franchi for his advice in statistical analysis, and Dr. Susan Guest as well as Lauren Sigler for assisting in the collection of the untreated controls. This research was made possible in part through the research funds of the Thomas M. and Doris Graber Endowed professorship, Department of Orthodontics and Pediatric Dentistry, the University of Michigan.
Riassunto Obiettivo: Valutare gli effetti della terapia ortopedico/funzionale seguita da apparecchi fissi nei pazienti con malocclusione di II Classe che presentano segni cefalometrici predittivi di risposta sfavorevole al trattamento. Materiali e metodi: Un campione di 48 soggetti (20 maschi e 28 femmine) con segni di risposta sfavorevole al trattamento sono stati
trattati al picco di crescita puberale con terapia ortopedico/funzionale seguita da apparecchi fissi. Risultati: Una percentuale statisticamente significativa di soggetti con risultati favorevoli è stata riscontrata nel gruppo trattato (74.5%). Rispetto ai soggetti non trattati sia il gruppo trattato totale che il sottogruppo con risultati favorevoli presentavano una riduzione significativa della crescita e della posizione sagittale del mascellare superiore associata ad un aumento significativo della lunghezza mandibolare, dell’avanzamento sagittale della mandibola e ad un significativo miglioramento dei rapporti maxillo-mandibolari. Sia l’overjet che il rapporto molare mostravano significative modificazioni favorevoli nel gruppo trattato. Conclusioni: La terapia ortopedico/funzionale al picco di crescita puberale seguita da apparecchi fissi rappresenta un’opzione terapeutica attuabile in pazienti con malocclusione di II Classe “sfavorevole” sebbene i cambiamenti scheletrici siano di minore entità.
Résumé Objectif: Évaluer les résultats des appareils orthopédiques de mâchoire fonctionnelle (FJO) et par la suite des appareils fixes pour des patients de Classe II qui font état d’une analyse céphalométrique prédictive de capacité de réponse défavorable au traitement orthopédique. Matériels et méthodes: 48 sujets (20 garc¸ons, 28 filles), avec malocclusion de Classe II et pronostic défavorable, ont été traités au moyen du système FJO au moment du pic de vitesse de croissance et par la suite au moyen d’appareils fixes. Les résultats du traitement ont été comparés aux changements de croissance versus un groupe de contrôle (matched control group) de sujets non traités avec malocclusion de Classe II et «pronostic défavorable». Résultats: Un taux de prévalence significatif de résultats positifs ont été enregistrés au sein du groupe traité (64,5%). Lorsque la comparaison est établie versus les contrôles non traités, concernant aussi bien le groupe général traité que le sous-groupe traité avec succès, on observe une réduction significative de la croissance maxillaire et de la position sagittale et un renforcement important de la longueur de la mandibule, de l’avancement sagittal de la mandibule et des améliorations considérables des rapports maxillo-mandibulaires (RMM). L’overjet et la relation molaire ont enregistré des évolutions favorables de taille chez le groupe traité. Conclusions: Les appareils orthopédiques de mâchoire fonctionnelle (FJO) pendant le pic pubertaire suivis d’appareils fixes constituent une option thérapeutique chez des patients avec malocclusion de Classe II et « pronostic défavorable », bien que les changements squelettiques soient de dimensions limitées.
Resumen Objetivo: Valorar los resultados del sistema FJO y posteriormente de aparatos fijos para pacientes de Clase II teniendo signos cefalométricos de capacidad de respuesta desfavorable al tratamiento ortopédico. Material y métodos: 48 sujetos (20 chicos, 28 chicas), con maloclusión de Clase II y pronóstico desfavorable, fueron tratados con el sistema FJO en la fase de brote de crecimiento, y posteriomente con aparatos fijos. Los resultados del tratamiento fueron comparados con los cambios de crecimiento en un grupo de control (matched control group) de sujetos no tratados con maloclusión de Clase II y pronóstico “desfavorable”.
progress in orthodontics 1 1 ( 2 0 1 0 ) 118–126
Resultados: Se experimentó una prevalencia de resultados exitosos en el grupo tratado (64,5%). Cuando comparamos lo anterior con los controles no tratados, tanto con el grupo tratado en general como con el subgrupo tratado con resultados exitosos, observamos una reducción considerable en el crecimiento maxilar y en la posición sagital, conjuntamente con un fortalecimiento importante de la longitud de la mandíbula, del avance sagital de la mandíbula y mejorías notables en las relaciones maxilomandibulares. Tanto el overjet como la relacion molar destacan cambios favorables en el grupo tratado. Conclusiones: El sistema FJO en el BCP y posteriomente los aparatos fijos suponen una opción terapéutica viable en pacientes con maloclusiones de Classe II y pronóstico “desfavorable”, aunque los cambios esqueléticos sean de magnitud limitada.
references
1. Proffit WR, Fields HW, Sarver DM. Contemporary orthodontics. 4th edition St. Louis: Mosby; 2007. 2. McNamara Jr JA, Brudon WL. Orthodontics and dentofacial orthopedics. Ann Arbor: Needham Press, Inc; 2001. 3. Bishara SE, Hoppens BJ, Jakobsen JR, Kohout FJ. Changes in the molar relationship between the deciduous and permanent dentitions: a longitudinal study. Am J Orthod Dentofacial Orthop 1988;93:19–28. 4. Baccetti T, Franchi L, McNamara Jr JA, Tollaro I. Early dento-facial features of Class II malocclusion: a longitudinal study from the deciduous through the mixed dentition. Am J Orthod Dentofacial Orthop 1997;111:502–9. 5. Stahl F, Baccetti T, Franchi L, McNamara Jr JA. Longitudinal growth changes in untreated subjects with Class II and Class I malocclusion. Am J Orthod Dentofacial Orthop 2008;134:125–37. 6. Petrovic AG, Stutzmann JJ. The concept of mandibular tissue-level growth potential and the responsiveness to a functional appliance. In: Graber WL, editor. Orthodontics: State of the Art, Essence of the Science. St. Louis, Mo: CV Mosby Co; 1986. p. 59–74. 7. Petrovic A, Stutzmann J, Lavergne J. Mechanism of craniofacial growth and modus operandi of functional appliances: a cell-level and cybernetic approach to orthodontic decision making. In: Carlson DS, editor. Craniofacial Growth Theory and Orthodontic Treatment. Ann Arbor: Center for Human Growth and Development, The University of Michigan; 1990:13–74. Craniofacial Growth Monograph Series; Monograph 23. 8. Rowlerson A, Raoul G, Daniel Y, Close J, Maurage CA, Ferri J, et al. Fiber-type differences in masseter muscle associated with different facial morphologies. Am J Orthod Dentofac Orthop 2005;127:37–46. 9. Cozza P, Baccetti T, Franchi L, De Toffol L, McNamara Jr JA. Mandibular changes produced by functional appliances in Class II malocclusion: a systematic review. Am J Orthod Dentofacial Orthop 2006;129:599.e1–12. 10. Flores-Mir C, Major PW. A systematic review of cephalometric facial soft tissue changes with the Activator and Bionator appliances in Class II division 1 subjects. Eur J Orthod 2006;28:586–93. 11. Flores-Mir C, Major PW. Cephalometric facial soft tissue changes with the twin block appliance in Class II division 1 malocclusion patients. A systematic review. Angle Orthod 2006;76:876–81. 12. Flores-Mir C, Ayeh A, Goswani A, Charkhandeh S. Skeletal and dental changes in Class II division 1 malocclusions treated with splint-type Herbst appliances. A systematic review. Angle Orthod 2007;77:376–81.
125
13. Ahn SJ, Kim JT, Nahm DS. Cephalometric markers to consider in the treatment of Class II Division 1 malocclusion with the bionator. Am J Orthod Dentofacial Orthop 2001;119:578–86. 14. Fogle LL, Southard KA, Southard TE, Casko JS. Treatment outcomes of growing Class II Division 1 patients with varying degrees of anteroposterior and vertical dysplasias. Part 1. Cephalometrics. Am J Orthod Dentofacial Orthop 2004;125:450–6. 15. Ormiston JP, Huang GJ, Little RM, Decker JD, Seuk GD. Retrospective analysis of long-term stable and unstable orthodontic treatment outcomes. Am J Orthod Dentofacial Orthop 2005;128:568–74. 16. Hägg U, Pancherz H. Dentofacial orthopaedics in relation to chronological age, growth period and skeletal development. An analysis of 72 male patients with Class II division 1 malocclusion treated with the Herbst appliance. Eur J Orthod 1988;10:169–76. 17. Malmgren O, Ömblus J, Hägg U, Pancherz H. Treatment with an appliance system in relation to treatment intensity and growth periods. Am J Orthod Dentofacial Orthop 1987;91:143–51. 18. Baccetti T, Franchi L, Toth LR, McNamara Jr JA. Treatment timing for Twin-Block therapy. Am J Orthod Dentofacial Orthop 2000;118:159–70. 19. Faltin Jr K, Faltin RM, Baccetti T, Franchi L, Ghiozzi B, McNamara Jr JA. Long-term effectiveness and treatment timing for bionator therapy. Angle Orthod 2003;73: 221–30. 20. Franchi L, Baccetti T. Prediction of individual mandibular changes induced by functional jaw orthopedics followed by fixed appliances in Class II patients. Angle Orthod 2006;76:950–4. 21. Freeman CS, McNamara Jr JA, Baccetti T, Franchi L, Graff TW. Treatment effects of the bionator and high-pull facebow combination followed by fixed appliances in patients with increased vertical dimensions. Am J Orthod Dentofacial Orthop 2007;131:184–95. 22. Lake SL, McNeill RW, Little RM, West RA. Surgical mandibular advancement: a cephalometric analysis of treatment response. Am J Orthod 1981;80:376–94. 23. Mobarak KA, Espeland L, Krogstad O, Lyberg T. Mandibular advancement surgery in high-angle and low-angle class II patients: different long-term skeletal responses. Am J Orthod Dentofacial Orthop 2001;119:368–81. 24. Arpornmaeklong P, Shand JM, Heggie AA. Skeletal stability following maxillary impaction and mandibular advancement. Int J Oral Maxillofac Surg 2004;33:656–63. 25. van Strijen PJ, Breuning KH, Becking AG, Tuinzing DB. Stability after distraction osteogenesis to lengthen the mandible: results in 50 patients. J Oral Maxillofac Surg 2004;62:304–7. 26. Burden D, Johnston C, Kennedy D, Harradine N, Stevenson M. A cephalometric study of Class II malocclusions treated with mandibular surgery. Am J Orthod Dentofacial Orthop 2007;131:7.e1–8. 27. Baccetti T, Franchi L, McNamara Jr JA. The cervical vertebral maturation (CVM) method for the assessment of optimal treatment timing in dentofacial orthopedics. Semin Orthod 2005;11:119–29. 28. Steiner CC. Cephalometrics for you and me. Am J Orthod 1953;39:729–55. 29. Jacobson A. The “Wits” appraisal of jaw disharmony. Am J Orthod 1975;67:125–38. 30. Ricketts RM. Perspectives in the clinical application of cephalometrics. The first fifty years Angle Orthod 1981;51:115–50. 31. McNamara Jr JA. A method of cephalometric evaluation. Am J Orthod 1984;86:449–69.
126
progress in orthodontics 1 1 ( 2 0 1 0 ) 118–126
32. Burkhardt DR, McNamara Jr JA, Baccetti T. Maxillary molar distalization or mandibular enhancement: a cephalometric comparison of comprehensive orthodontic treatment including the pendulum and the Herbst appliances. Am J Orthod Dentofacial Orthop 2003;123:108–16. 33. Dahlberg G. Statistical methods for medical and biological students. London: G. Allen & Unwin ltd; 1940. 34. Baccetti T, Franchi L, Stahl F. Cephalometric comparison of two comprehensive treatment protocols for Class II
Malocclusion including the bonded Herbst and the headgear appliances: A double-blind study on consecutively-treated patients at puberty. Am J Orthod Dentofac Orthop 2009;135:698.e1–10. 35. Baccetti T, Franchi L, Kim LH. The effect of timing on the outcomes of one-phase non-extraction therapy of Class II malocclusion. Am J Orthod Dentofac Orthop 2009;136: 501–9.
available at www.sciencedirect.com
journal homepage: www.elsevier.com/locate/pio
Original article
The impact of functional jaw orthopedics in subjects with unfavorable class II skeletal patterns Tiziano Baccetti a,∗ , James A. McNamara Jr. b a
DDS, PhD, Research Professor, Department of Orthodontics, The University of Florence, Italy; Thomas M. Graber Visiting Scholar, Department of Orthodontics and Pediatric Dentistry, School of Dentistry, The University of Michigan, Ann Arbor, USA. b DDS, PhD, Thomas M. and Doris Graber Endowed Professor of Dentistry, Department of Orthodontics and Pediatric Dentistry, School of Dentistry; Professor of Cell and Developmental Biology, School of Medicine; Research Professor, Center for Human Growth and Development, The University of Michigan, Ann Arbor; Private practice, Ann Arbor, Michigan, USA.
a r t i c l e
i n f o
a b s t r a c t
Article history:
Objective: To evaluate the outcomes of functional jaw orthopedics (FJO) followed by fixed
Received 23 June 2010
appliances in Class II patients showing cephalometric signs predictive of unfavorable
Accepted 12 July 2010
responsiveness to orthopedic treatment. Materials and methods: A total of 48 treated subjects (20 males, 28 females) with unfavorable
Keywords:
Class II malocclusions were treated with FJO at the adolescent growth spurt, followed by fixed
Class II malocclusion
appliances. Treatment outcomes were compared with the growth changes in a matched
Functional appliances
control group of untreated subjects with “unfavorable” Class II malocclusions.
Growth
Results: A significant prevalence rate of successful outcome was recorded within the treated
Predictive variables cephalometrics
group (64.5%). When compared with the untreated controls, both the overall treated group
Treatment outcomes
and the successful treated subgroup revealed a significant reduction in maxillary growth and sagittal position, along with a significant enhancement in mandibular length, sagittal advancement of the mandible, and significant improvements in the maxillo-mandibular relationships. Both overjet and molar relation showed significant favorable changes in the treated group. Conclusions: FJO at the pubertal spurt followed by fixed appliances is a viable therapeutical option in patients with “unfavorable” Class II malocclusions, although skeletal changes are of minor entity. © 2010 Società Italiana di Ortodonzia SIDO. Published by Elsevier Srl. All rights reserved.
1.
Introduction
Treatment of dentoskeletal Class II malocclusion typically is accomplished by two methods, i.e. either an orthodontic/orthopedic approach in the growing subject or corrective jaw surgery at the completion of growth.1,2 The first option often requires the use of orthopedic appliances
(functional/orthopedic appliances directed to the maxilla, or to the mandible, or both) in conjunction with fixed appliances to refine the occlusion.2 Surgical orthodontics may be performed in one phase in the adult Class II patient or on patients who did not show a satisfactory correction of Class II disharmony through earlier orthopedic/orthodontic treatment.1 A series of clinical and epidemiological studies have focused on the analysis of the factors that can affect growth and/or
∗ Corresponding author. Dipartimento di Odontostomatologia, Università degli Studi di Firenze, Via del Ponte di Mezzo 46/48 - 50127 Firenze, Italy. E-mail address: tbaccetti@unifi.it (T. Baccetti). 1723-7785/$ – see front matter © 2010 Società Italiana di Ortodonzia SIDO. Published by Elsevier Srl. All rights reserved. doi:10.1016/j.pio.2010.09.002
progress in orthodontics 1 1 ( 2 0 1 0 ) 118–126
therapeutic outcomes in Class II subjects. These factors can be categorized as follows: 1) favorable/unfavorable growth characteristics; 2) favorable/unfavorable outcomes and stability of functional jaw orthopedics (FJO); 3) favorable/unfavorable outcomes and stability of orthognathic surgery (OS) or distraction osteogenesis (DO). 1) Favorable/unfavorable growth characteristics. The features of growth in untreated Class II subjects reveal an absence of self-correction of the dentoskeletal disharmony.3–5 The pubertal peak period enhances the mandibular growth deficiency in subjects with dentoskeletal Class II malocclusion.5 Certain types of dentoskeletal patterns within the generic definition of Class II malocclusion may present particularly “unfavorable” growth trends. They consist of Class II patients showing posterior growth rotation of the mandible with a skeletal openbite tendency associated with a deficiency in mandibular size.6,7 Recent research has shown that a peculiar composition of facial muscles, with consequent functional alterations of the masticatory muscles, is found in patients with a smallsized mandible and an open gonial angle, thus providing some explanation for the deficiency in growth of the lower third of the face in these patients.8 2) Favorable/unfavorable outcomes and stability of functional jaw orthopedics (FJO). The literature provides abundant contributions to the evaluation of the short- and long-term outcomes of combined orthopedic/orthodontic treatment of Class II malocclusion, as highlighted by recent systematic reviews.9–12 A number of studies have focused on the pretreatment dentoalveolar characteristics of Class II treated patients as a prognostic basis to identify favorable vs unfavorable responsiveness to Class II treatment in the growing subject.13–15 A few other studies have examined the skeletal features of Class II patients before treatment with FJO and orthodontic appliances. Beyond the issue of treatment timing (with larger skeletal changes induced by FJO at the pubertal growth spurt7,9,16–19 ), all these reports agree in the identification of a posteriorly-rotated mandible associated with an opening of the gonial angle and with a severely affected intermaxillary skeletal sagittal relation as predictors of poorer dentoskeletal outcomes following treatment of Class II malocclusion.6,20,21 3) Favorable/unfavorable outcomes and stability of orthognathic surgery (OS) or distraction osteogenesis (DO). Some Class II patients do not undergo orthopedic treatment during their active growing period, but rather receive orthognathic surgery at the completion of growth. In other instances, OS is performed on subjects who did not achieve correction of the malocclusion after FJO. Factors for unfavorable outcomes or stability of OS or DO in Class II patients have been suggested; they consist mainly in increased vertical skeletal relationships and/or open gonial angle associated with severely reduced size of the mandible in young adults with Class II malocclusion.22–26 High-angle patients show both a higher frequency and a greater magnitude of horizontal relapse after surgery.23 Less ideal soft-tissue profile outcomes after surgery are associated with larger pretreatment intermaxillary sagittal discrepancies.26 Significant mandibular relapse has been found in Class II patients with high mandibular plane angles who had undergone mandibular advancements greater than 10 mm.24 More-
119
over, high-angle patients are at risk of relapsing following distraction osteogenesis as well, as DO cannot prevent relapse in patient with a high mandibular plane angle associated with severe sagittal discrepancies in Class II disharmony.25 From the above-described analysis of the factors affecting results of treatment in Class II malocclusion by either orthopedic or surgical orthodontic approaches, it appears evident that there is a consistency in the elements that various investigators have considered as predictors of poor therapeutic results in the individual Class II patient. An unfavorable Class II patient can be depicted as a patient with severe intermaxillary discrepancy both in the sagittal and vertical planes, this latter characteristic being associated with increased vertical skeletal relationships, a large gonial angle, and a posteriorly-rotated mandible. This type of Class II dentoskeletal disharmony is expected to exhibit an unfavorable growth trend if left untreated, a poor response to FJO and orthodontic treatment during the growing period, and a lessthan-ideal response and/or stability when treated by means of orthognathic surgery or distraction osteogenesis at a young adult age. The purpose of the present study is to evaluate the impact of FJO followed by fixed appliances on patients with “unfavorable” Class II division 1 skeletal patterns by means of a double-blinded study on a large group of patients treated with various FJO appliance protocols and compared with untreated Class II controls. The outcomes of the present investigation are aimed to improve the knowledge about expectations of both clinicians and patients in terms of outcomes of dentofacial orthopedics in severe Class II malocclusions, also with regard to the possible role of orthopedic/orthodontic treatment before orthognathic surgery in Class II patients with unfavorable skeletal patterns.
2.
Materials and methods
2.1. Class II Sample treated with FJO and fixed appliances The treated patients of this study are part of a multicentered prospective trial on the use of one-phase comprehensive orthopedic/orthodontic treatment protocols at puberty in Class II division 1 subjects. The malocclusion was defined according to the presence of full-cusp Class II molar relationship, excessive overjet, and ANB angle larger than 5 degrees. The original sample comprised a total of 160 patients treated at the pubertal growth spurt with functional jaw orthopedics followed by fixed appliances to refine occlusion. FJO consisted of the Herbst appliance in 54 subjects (26 males, 28 females), a Bionator appliance in 24 subjects (11 males, 13 females); a Twin Block appliance in 28 cases (14 males, 14 females); and the FR-2 appliance of Fränkel in 54 subjects (23 males, 31 females). In all patients, treatment started (T1) at the pubertal growth spurt (either at CS3 or CS4 in cervical vertebral maturation), it had a duration that ranged between 24 months and 34 months, and it ended (T2) at a post-pubertal stage of development (CS5 or CS6).27 Each type of FJO treatment was provided by clinicians experienced in that specific treatment modality. The phase with fixed appliances was conducted without extraction
120
progress in orthodontics 1 1 ( 2 0 1 0 ) 118–126
of permanent teeth, and patient compliance was judged by the clinician from “good” to “very good.” The treating practitioners were blind to the objective of the study, i.e. the evaluation of treatment outcomes in “unfavorable” Class II patients. Treatment protocols were applied in a standardized manner; they were not customized according to the patient’s characteristics. Lateral cephalograms for each treated patient were collected at T1 and T2. The magnification factor of all cephalograms was adjusted to 8%.
analysis containing measurements from the analyses of Steiner,28 Jacobson,29 Ricketts,30 and McNamara31 was used. All sets of cephalograms were traced at the same time. A preliminary tracing was made for each film, with particular attention paid to tracing of the outlines of the maxilla and mandible, including the mandibular condyle. The investigators traced the total of the treated Class II sample before identification of the unfavorable Class II patients. Additionally, they were blind also to the specific appliance used in individual patients.
2.2.
2.5.
Identification of “unfavorable” Class II patients
A computerized sorting technique (SPSS, ver. 1.12) was applied to identify those Class II subjects who presented with 3 concurrent cephalometric features at T1 for the definition of “unfavorable” Class II malocclusion according to the indications reported in the literature:6,13,20,21,23,26 1) Co-Go-Me angle greater than 128 degrees; 2) Wits appraisal value greater than 4 mm (i.e. greater than the average value of Wits at T1 with the addition of one standard deviation); 3) MPA greater than 27 degrees (i.e. greater than the average value of MPA at T1 with the addition of one standard deviation). Out of the original sample of 160 patients, the sorting technique identified 48 subjects (20 males, 28 females) with unfavorable Class II division 1 malocclusions. Twelve subjects belonged to the Herbst group, 8 subjects to the Bionator group, 8 subjects to the Twin Block group, and 20 subjects to the FR2 group. The average age of treated subjects was 12 years 4 months at T1, and 14 years and 10 months at T2, with an average T1-T2 interval of 2 years 7 months.
Statistical analysis
2.5.1. Analysis within the “unfavorable” Class II treated sample An evaluation of the outcomes of therapy (FJO followed by fixed appliances) was performed preliminarily within the “unfavorable” Class II sample of 48 patients. A successful outcome was considered when the presence of a normal molar relationship and a normal overjet was assessed both clinically and cephalometrically, along with the presence of normal values for the variables PtA-Nperp and Pg-Nperp.31,32 An unsuccessful outcome of therapy was assessed when the normalization of the occlusal and skeletal parameters described in the successful group had not been achieved at T2. The ratio of subjects showing successful vs unsuccessful outcomes within the unfavorable Class II treated sample was evaluated statistically by means of z-statistics for proportions (SigmaStat, Systat Software Inc., San Jose, Ca).
2.5.2. Comparisons between the treated and untreated samples
A control group of 20 subjects with untreated Class II division 1 malocclusion was selected from the files of the University of Michigan Growth Study, the Denver Growth Study, and the Department of Orthodontics at the University of Florence, Italy. All subjects presented with signs of unfavorable Class II skeletal patterns at T1, as they were characterized by fullcusp Class II molar relationship, excessive overjet, ANB angle greater than 5 degrees, Wits appraisal greater that 4 mm, MPA larger than 27 degrees, and Co-Go-Me angle larger than 128 degrees. The cephalogram at T1 corresponded with either CS3 or CS4 in skeletal maturation, and the cephalogram at T2 with either CS5 or CS6.27 The duration of T1-T2 observation period ranged from 22 months to 36 months. The magnification factor of all cephalograms was corrected to an 8% in order to match the treated group. The average age of control subjects was 12 years 6 months at T1, and 14 years and 11 months at T2, with an average T1-T2 interval of 2 years 6 months.
The dentoskeletal characteristics of the unfavorable Class II treated sample (n=48) and of the untreated Class II control sample (n=20) were compared for an evaluation of starting forms. The T1-T2 changes in the treated sample (n=48) then were contrasted with the T1-T2 changes in the control sample (n=20). Also, the T1-T2 changes in the subgroups of unfavorable Class II patients who showed successful therapeutic outcomes (n=21) were compared with the T1-T2 changes in the subgroup of subjects who did not show successful outcomes of therapy at T2 (n=17), as well as with the T1-T2 changes in the untreated control sample. Exploratory testing by means of a Shapiro-Wilks test indicated lack of normality of distribution for several of the examined variables. Therefore, comparisons were performed either by means of Mann Whitney U tests (p<0.05) for independent samples (comparisons of starting forms and comparison on T1-T2 changes between the total treated group and the untreated control group), or by means of Kruskal-Wallis with post-hoc tests for non-parametric data (p<0.05) (comparisons on the changes in successful and unsuccessful treated subgroups and untreated control group).
2.4.
2.6.
2.3.
Untreated Class II Control sample
Cephalometric analysis
A customized digitization regimen and analysis provided by a cephalometric software (Viewbox, ver 3.0, dHAL Software, Kifissia, Greece) was utilized for all the cephalograms that were examined in this study. A cephalometric
Power of the study and method error
The calculated power of the study exceeded 0.80. A total of 30 lateral cephalograms randomly chosen from all observations were re-traced and re-digitized to calculate method error by means of Dahlberg’s formula.33 The error for linear
121
progress in orthodontics 1 1 ( 2 0 1 0 ) 118–126
Table 1 – Comparison of starting forms for the treated and untreated unfavorable Class II groups at T1. Cephalometric Measures
“Unfavorable” Class II subjects Treated with FJO N=48
“Unfavorable” Class II subjects Untreated N=20
Mean
SD
Mean
SD
Maxillary Skeletal SNA (◦ ) PtA-Nasion perp (mm) Co-Pt A (mm)
80.9 0.8 86.1
3.1 2.8 3.5
80.4 0.3 85.4
3.8 2.9 4.1
0.5 0.5 0.7
NS NS NS
Mandibular Skeletal SNB (◦ ) Pog-Nasion perp (mm) Co-Gn (mm)
75.4 −9.3 105.9
2.8 4.4 4.1
75.3 −8.3 104.8
3.1 4.2 5.4
0.1 −1.0 1.1
NS NS NS
Maxillary/Mandibular ANB (◦ ) Wits appraisal (mm) Max/Mand difference (mm)
7.3 6.1 19.8
2.4 1.9 3.4
7.1 5.9 19.2
1.9 1.7 2.0
0.2 0.2 0.6
NS NS NS
Vertical Skeletal FH to mandibular plane (◦ ) FH to palatal plane (◦ ) Co-Go-Me (◦ )
31.6 2.9 132.7
3.5 3.4 3.6
30.8 2.5 131.8
2.9 2.6 3.5
0.8 0.3 0.9
NS NS NS
1.3 6.8 −1.9
2.2 1.9 1.2
1.9 5.8 −1.4
3.2 2.1 1.1
−0.6 1.0 −0.5
NS NS NS
Interdental Overbite (mm) Overjet (mm) Molar relationship (mm)
Difference
Significance
NS = Not Significant.
measurements ranged from 0.2 mm (overjet) to 0.8 mm (Pg to Nasion perpendicular), while the error for angular measurements varied from 0.3 degrees (ANB) to 0.8 degrees (FH to mandibular plane).
3.
Results
3.1. Analysis within the “unfavorable” Class II sample treated with FJO A successful outcome of therapy was assessed in 31 (64.5%) out of the 48 treated Class II patients (6 patients treated with the Herbst, 5 patients treated with the Bionator, 6 patients with the Twin Block, and 14 patients treated with the FR-2). A total of 17 subjects did not show a successful outcome following FJO and fixed appliance therapy. The comparison of the prevalence rates for successful vs unsuccessful cases was significant (p<0.01).
3.2. Comparison between the total treated group and the control group The craniofacial starting forms of the 2 groups did not differ significantly for any of the examined cephalometric variables (Table 1). The results of the comparisons of the T1-T2 changes in the 2 groups are reported in (Table 2). A significant reduction in maxillary growth and sagittal position was recorded in the total treatment group, with significantly smaller increments for Co-A, and a significant decrease in PtA-Nperp. All mandibular skeletal variables showed significant differences when compared with the controls. A significant enhancement in mandibular length (Co-Gn) and in the sagittal advancement
of the mandible (SNB, Pg-Nperp) were found in the treated group when compared with the controls, which lead to significant improvements in the maxillo-mandibular relationships. A significant decrease in the mandibular plane angle was assessed in the treated group, along with a significant reduction in the mandibular angle (Co-Go-Me) in comparison with the untreated Class II group. Both overjet and molar relation showed significant favorable changes in the treated group.
3.3. Comparison between the “successful” treated subgroup, “unsuccessful” treated subgroup, and the control group The results of these comparisons of the T1-T2 changes are shown in Table 3. The differences between the successful treated subgroup and the untreated controls replicated the findings described for the comparison between the total treated group and the untreated controls, as reported in the previous paragraphs. The following results were found for the comparison between the unsuccessful treated subgroup and the untreated controls. No significant differences in the sagittal maxillary variables were recorded. Significantly greater increases in mandibular length and a significant advancement of the mandible were found in the treated subgroup. The magnitude of these favorable mandibular changes was smaller then the changes assessed in the total treated group. All measurements of sagittal maxillo-mandibular relationships showed significant improvements in the unsuccessfully treated group compared with the untreated controls; however, these differences were smaller than in the overall treated group. A significantly greater favorable modification in the maxillo-mandibular differential was recorded in the successful subgroup vs the unsuccessful subgroup. As for the vertical
122
progress in orthodontics 1 1 ( 2 0 1 0 ) 118–126
Table 2 – Comparison of T2-T1 treatment and growth changes in the total treated group and the untreated controls. All subjects in both groups showed features of “unfavorable” Class II skeletal pattern at T1. Cephalometric Measures
Maxillary A-P Skeletal SNA (◦ ) Pt A-Na perp (mm) Co-Pt A (mm)
“Unfavorable” Class II subjects Treated with FJO Total N=48
“Unfavorable” Class II subjects Untreated (Controls) N=20
Mean
Mean
SD
Difference & Significance
SD
−0.8 −1.0 0.9
1.6 1.3 1.8
0.2 0.5 2.4
1.9 0.9 1.9
−1.0 NS −1.5* −1.5*
Mandibular A-P Skeletal SNB (◦ ) Pg-Na perp (mm) Co-Gn (mm)
1.2 1.9 6.6
1.2 1.2 2.1
−0.2 −0.3 3.8
1.3 1.2 1.9
1.4* 2.2** 2.8**
Intermaxillary ANB (◦ ) Wits appraisal (mm) Mx/Mn diff (mm)
−1.9 −3.2 5.8
1.4 1.5 2.6
0.3 0.6 1.1
0.8 1.2 2.0
−2.2** −3.8*** 4.7***
0.2 1.4 0.1
1.9 1.8 2.2
1.6 0.4 2.0
1.8 1.3 1.9
−1.4* 1.0 NS −1.9**
−0.4 −4.8 4.2
1.2 2.2 1.3
0.0 -0.1 0.1
0.9 0.7 0.8
−0.4 NS −4.7*** 4.1***
Vertical Skeletal MPA (◦ ) FH-PP (◦ ) Co-Go-Me (◦ ) Interdental Overbite (mm) Overjet (mm) Molar relation (mm)
NS = not significant; * p<0.05; ** p<0.01; *** p<0.001.
Table 3 – Comparison of T2-T1 treatment and growth changes in the successful treated subgroup, the unsuccessful treated subgroup, and the untreated controls. All subjects in the 3 groups showed features of “unfavorable” Class II malocclusion at T1. Cephalometric Measures
“Unfavorable” Class II subjects Treated with FJO Successful subgroup “A”
“Unfavorable” Class II subjects Treated with FJO Unsuccessful subgroup “B”
“Unfavorable” Class II subjects Untreated Control group “C”
N=21
N=17
N=20
Mean Maxillary A-P Skeletal SNA (◦ ) Pt A-Na perp (mm) Co-Pt A (mm)
SD
Mean
SD
Mean
SD
Differences & Significance
A-B
A-C
B-C
−1.1 NS −1.6* −1.7*
−0.4 NS −0.8 NS −1.2 NS
−0.9 −1.1 0.7
1.9 1.2 1.8
−0.2 −0.3 1.2
1.8 1.4 1.8
0.2 0.5 2.4
1.9 0.9 1.9
−0.7 NS −0.7 NS −0.5 NS
1.3 2.1 6.8
1.4 1.5 2.2
0.7 1.2 5.8
1.4 1.5 2.1
−0.2 −0.3 3.8
1.3 1.2 1.9
0.5 NS 0.9 NS 1.0 NS
Intermaxillary −2.1 ANB (◦ ) Wits appraisal (mm) −3.4 Mx/Mn diff (mm) 6.1
1.4 1.5 2.7
−1.0 −2.3 4.2
1.5 1.7 2.9
0.3 0.6 1.1
0.8 1.2 2.0
−1.1 NS −1.1 NS 1.9*
−2.4*** −4.0*** 5.0***
−1.3** −2.9*** 3.1**
Vertical Skeletal MPA (◦ ) FH-PP (◦ ) Co-Go-Me (◦ )
0.1 1.3 0.0
1.9 1.9 2.3
0.7 1.2 0.4
2.2 1.8 2.4
1.6 0.4 2.0
1.8 1.3 1.9
−0.6 NS 0.1 NS −0.4 NS
−1.5* 0.9 NS −2.0**
−0.9 NS 0.8 NS −1.6*
−0.5 −4.9 4.5
1.4 2.3 1.7
−0.1 −2.9 2.8
1.4 2.4 1.6
0.0 −0.1 0.1
0.9 0.7 0.8
−0.4 NS −2.0** 1.7*
−0.5 NS −4.8*** 4.6***
−0.1 NS −2.8** 2.7**
Mandibular A-P Skeletal SNB (◦ ) Pg-Na perp (mm) Co-Gn (mm)
Interdental Overbite (mm) Overjet (mm) Molar relation (mm)
NS = not significant; * p<0.05; ** p<0.01; *** p<0.001.
1.5* 2.4** 3.0**
0.9 NS 1.5* 2.0*
progress in orthodontics 1 1 ( 2 0 1 0 ) 118–126
skeletal relationships, only the mandibular angle Co-Go-Me showed a significant reduction in the unsuccessfully treated subjects vs the controls. Both the overjet and the molar relation improved significantly in the unsuccessful treated group. These changes were significantly smaller than in the successful treated subgroup.
4.
Discussion
The literature reports significant favorable changes in several samples treated with FJO followed by fixed appliances at the pubertal growth spurt.6,9,16–19,34 These studies analyze the outcomes of treatment performed on subjects with a variety of sagittal and vertical skeletal relationships. A series of investigations has shown that individuals with Class II division 1 malocclusions characterized by severe maxillo-mandibular discrepancies associated with increased vertical skeletal relations and an open mandibular angle are predicted to respond less favorably to orthopedic/orthodontic treatment during the developmental ages.6,7,13,20,21 The clinical scenario for these patients is complicated by the fact that the same craniofacial features have been demonstrated to be predictors of less favorable results and/or reduced stability after orthognathic surgery or distraction osteogenesis.22–26 The aim of the present study was to evaluate the outcomes of FJO followed by fixed appliance in Class II patients showing cephalometric signs predictive of unfavorable responsiveness to orthopedic treatment by comparing treatment effects with growth trends in Class II subjects showing similar craniofacial features. The analysis of the outcomes of therapy within the treated Class II group revealed a significant prevalence rate of cases that were corrected from both skeletal and occlusal standpoints. Thirtyone out of 48 treated cases (65%) exhibited “corrected” occlusal relationships at the end of treatment. Higher prevalence rates for the clinical correction after one-phase treatment protocols for Class II division 1 malocclusion have been described (ranging from 85% to 100%).19,32,34 However, taking into account the unfavorable characteristics of the treated sample, the prevalence rate of occlusal correction in almost 2 out of 3 patients has to be considered as a notably positive outcome. The effectiveness of therapy then was evaluated with respect to the growth changes in untreated Class II controls. Significant favorable changes were recorded in the total treatment group for the sagittal and vertical skeletal relationships, as well as for the occlusal variables. Main findings from this comparison were: significant restriction of maxillary growth, significant enhancement of mandibular growth and sagittal position, as well as significant reduction in the vertical facial relationships and mandibular angle. The absolute amount of these favorable changes in general was smaller than that reported in previous clinical trials evaluating the outcomes of FJO at the pubertal growth spurt.9,18,19,34 For instance, the increase in mandibular length in treated subjects over the untreated controls was 2.8 mm, which is considerably less than the 4.3 mm increase described by Faltin et al. in their Bionator study19 and than the 4.8 mm increase reported by Baccetti et al. in their Twin Block study.18 Once again, the unfavorable initial characteristics of the treated subjects in the present study should be taken into
123
account when appraising these results. Nonetheless, the clinically significant changes in the treated sample for the sagittal position of the mandible (2.2. mm), the Wits appraisal (3.8 mm), the maxillo-mandibular differential (4.6 mm), and the ANB angle (2.2 degrees) should be emphasized, as well as the changes in the vertical dimension. As shown by the untreated controls, growth in “unfavorable” Class II subjects is characterized by a progressive opening of the mandibular plane angle and of the angle between the condylar axis and the mandibular plane. Functional jaw orthopedics is able to reduce significantly this growth tendency to increased vertical relationships (by 1.4 degrees for the mandibular plane angle, and by 1.9 degrees for the Co-Go-Me angle). These observations are in agreement with the long-term observations by Faltin et al. in subjects treated with a bionator followed by fixed appliances during the adolescence.19 Further analysis of the data involved a comparison between the subgroup of patients who had shown a clinically successful outcome at the dentoskeletal level at the completion of therapy (n=21), the subgroup of patients who had not been treated successfully (n=17), and the untreated controls. While the results in the successful treated subgroup replicated the results of the total treated group and they did not add significant information for the discussion of the data, the findings concerning the comparison between the unsuccessful treatment subgroup and the untreated controls proved to be more interesting. This comparison was conducted in order to investigate the changes induced by FJO and fixed appliance therapy in those patients who showed the most unfavorable response to treatment and who would be eligible for orthognathic surgery to correct the persistent dentoskeletal disharmony. Significant improvements in the mandibular measurements, maxillo-mandibular relation, as well as in the mandibular angle still were found in this group of clinically “unsuccessful” patients versus the controls. As anticipated, the extent of the favorable changes was smaller than in either the overall treated group or the successful treated subgroup. However, the average increases over the controls for mandibular size (2.0 mm) and position (1.5 mm), for both the Wits appraisal and the maxillo-mandibular differential (about 3 mm), and the significant reduction (−1.6 degrees) in the Co-Go-Me angle, have to be considered as substantial improvements with regard to the growth trends expressed by the untreated controls. In this regard, it should be noted once again that the dento-skeletal factors that account for unfavorable outcomes/stability of orthognathic surgery/distraction osteogenesis in Class II patients consist mainly in increased vertical skeletal relationships and/or open gonial angle associated with severely reduced size of the mandible.22–26 Therefore, the significant improvements produced at puberty by FJO and fixed appliances in patients with Class II division 1 malocclusions may affect the expectations with regard to possible outcomes of OS or DO at a postpubertal phase of development. On the basis of the findings of the present investigation, FJO followed by fixed appliances at the pubertal growth spurt appears to be a viable treatment option also in those patients who exhibit unfavorable dento-skeletal signs before therapy. Almost 2/3rds of the patients are able to achieve a correction
124
progress in orthodontics 1 1 ( 2 0 1 0 ) 118–126
of the disharmony at the occlusal level. In case of incomplete correction of the malocclusion, the task of subsequent orthognathic surgery in terms of results and stability potentially is facilitated by improved sagittal and vertical craniofacial relationships induced by orthopedic/orthodontic therapy. A recent clinical trial34 has shown that FJO is able to produce a significant beneficial effect on the sagittal position of soft tissue Pogonion in pubertal Class II patients showing “favorable” dentoskeletal characteristics in terms of responsiveness to orthopedic therapy (mandibular retrusion associated with a closed mandibular angle). Further investigation is needed to determine whether in “unfavorable” Class II patients a similar improvement in the soft tissues can be associated with the significant beneficial effects induced by FJO at the dentoskeletal level. Finally, in subjects with “unfavorable” Class II malocclusions treatment protocols alternative to FJO also might be indicated, with the common goal of reducing the sagittal and vertical discrepancies. Dentoskeletal effects similar to those produced by FJO have been reported in Class II patients treated at puberty by means of molar distalizing appliances in conjunction with fixed appliances and Class II elastics.32,35
5.
Conclusions
Functional jaw orthopedics followed by fixed appliances is a viable therapeutic option in patients with “unfavorable” Class II skeletal patterns. A prevalence rate of 65% of these patients achieves correction of the malocclusion through significant sagittal and vertical treatment effects. The remaining 35% of the subjects, though not completely corrected, will present with reduced unfavorable dentoskeletal features before a potential intervention of orthognathic surgery.
Conflict of interest The author have reported no conflict of interest.
Acknowledgement The authors would like to thank Drs. John Damas, Brad Porter, Larry Spillane, Mart McClellan, Robert Smith, David Snodgrass, Forbes Leishman, and Kurt Faltin Jr, for having participated in the clinical trial by treating patients, Dr. Lorenzo Franchi for his advice in statistical analysis, and Dr. Susan Guest as well as Lauren Sigler for assisting in the collection of the untreated controls. This research was made possible in part through the research funds of the Thomas M. and Doris Graber Endowed professorship, Department of Orthodontics and Pediatric Dentistry, the University of Michigan.
Riassunto Obiettivo: Valutare gli effetti della terapia ortopedico/funzionale seguita da apparecchi fissi nei pazienti con malocclusione di II Classe che presentano segni cefalometrici predittivi di risposta sfavorevole al trattamento. Materiali e metodi: Un campione di 48 soggetti (20 maschi e 28 femmine) con segni di risposta sfavorevole al trattamento sono stati
trattati al picco di crescita puberale con terapia ortopedico/funzionale seguita da apparecchi fissi. Risultati: Una percentuale statisticamente significativa di soggetti con risultati favorevoli è stata riscontrata nel gruppo trattato (74.5%). Rispetto ai soggetti non trattati sia il gruppo trattato totale che il sottogruppo con risultati favorevoli presentavano una riduzione significativa della crescita e della posizione sagittale del mascellare superiore associata ad un aumento significativo della lunghezza mandibolare, dell’avanzamento sagittale della mandibola e ad un significativo miglioramento dei rapporti maxillo-mandibolari. Sia l’overjet che il rapporto molare mostravano significative modificazioni favorevoli nel gruppo trattato. Conclusioni: La terapia ortopedico/funzionale al picco di crescita puberale seguita da apparecchi fissi rappresenta un’opzione terapeutica attuabile in pazienti con malocclusione di II Classe “sfavorevole” sebbene i cambiamenti scheletrici siano di minore entità.
Résumé Objectif: Évaluer les résultats des appareils orthopédiques de mâchoire fonctionnelle (FJO) et par la suite des appareils fixes pour des patients de Classe II qui font état d’une analyse céphalométrique prédictive de capacité de réponse défavorable au traitement orthopédique. Matériels et méthodes: 48 sujets (20 garc¸ons, 28 filles), avec malocclusion de Classe II et pronostic défavorable, ont été traités au moyen du système FJO au moment du pic de vitesse de croissance et par la suite au moyen d’appareils fixes. Les résultats du traitement ont été comparés aux changements de croissance versus un groupe de contrôle (matched control group) de sujets non traités avec malocclusion de Classe II et «pronostic défavorable». Résultats: Un taux de prévalence significatif de résultats positifs ont été enregistrés au sein du groupe traité (64,5%). Lorsque la comparaison est établie versus les contrôles non traités, concernant aussi bien le groupe général traité que le sous-groupe traité avec succès, on observe une réduction significative de la croissance maxillaire et de la position sagittale et un renforcement important de la longueur de la mandibule, de l’avancement sagittal de la mandibule et des améliorations considérables des rapports maxillo-mandibulaires (RMM). L’overjet et la relation molaire ont enregistré des évolutions favorables de taille chez le groupe traité. Conclusions: Les appareils orthopédiques de mâchoire fonctionnelle (FJO) pendant le pic pubertaire suivis d’appareils fixes constituent une option thérapeutique chez des patients avec malocclusion de Classe II et « pronostic défavorable », bien que les changements squelettiques soient de dimensions limitées.
Resumen Objetivo: Valorar los resultados del sistema FJO y posteriormente de aparatos fijos para pacientes de Clase II teniendo signos cefalométricos de capacidad de respuesta desfavorable al tratamiento ortopédico. Material y métodos: 48 sujetos (20 chicos, 28 chicas), con maloclusión de Clase II y pronóstico desfavorable, fueron tratados con el sistema FJO en la fase de brote de crecimiento, y posteriomente con aparatos fijos. Los resultados del tratamiento fueron comparados con los cambios de crecimiento en un grupo de control (matched control group) de sujetos no tratados con maloclusión de Clase II y pronóstico “desfavorable”.
progress in orthodontics 1 1 ( 2 0 1 0 ) 118–126
Resultados: Se experimentó una prevalencia de resultados exitosos en el grupo tratado (64,5%). Cuando comparamos lo anterior con los controles no tratados, tanto con el grupo tratado en general como con el subgrupo tratado con resultados exitosos, observamos una reducción considerable en el crecimiento maxilar y en la posición sagital, conjuntamente con un fortalecimiento importante de la longitud de la mandíbula, del avance sagital de la mandíbula y mejorías notables en las relaciones maxilomandibulares. Tanto el overjet como la relacion molar destacan cambios favorables en el grupo tratado. Conclusiones: El sistema FJO en el BCP y posteriomente los aparatos fijos suponen una opción terapéutica viable en pacientes con maloclusiones de Classe II y pronóstico “desfavorable”, aunque los cambios esqueléticos sean de magnitud limitada.
references
1. Proffit WR, Fields HW, Sarver DM. Contemporary orthodontics. 4th edition St. Louis: Mosby; 2007. 2. McNamara Jr JA, Brudon WL. Orthodontics and dentofacial orthopedics. Ann Arbor: Needham Press, Inc; 2001. 3. Bishara SE, Hoppens BJ, Jakobsen JR, Kohout FJ. Changes in the molar relationship between the deciduous and permanent dentitions: a longitudinal study. Am J Orthod Dentofacial Orthop 1988;93:19–28. 4. Baccetti T, Franchi L, McNamara Jr JA, Tollaro I. Early dento-facial features of Class II malocclusion: a longitudinal study from the deciduous through the mixed dentition. Am J Orthod Dentofacial Orthop 1997;111:502–9. 5. Stahl F, Baccetti T, Franchi L, McNamara Jr JA. Longitudinal growth changes in untreated subjects with Class II and Class I malocclusion. Am J Orthod Dentofacial Orthop 2008;134:125–37. 6. Petrovic AG, Stutzmann JJ. The concept of mandibular tissue-level growth potential and the responsiveness to a functional appliance. In: Graber WL, editor. Orthodontics: State of the Art, Essence of the Science. St. Louis, Mo: CV Mosby Co; 1986. p. 59–74. 7. Petrovic A, Stutzmann J, Lavergne J. Mechanism of craniofacial growth and modus operandi of functional appliances: a cell-level and cybernetic approach to orthodontic decision making. In: Carlson DS, editor. Craniofacial Growth Theory and Orthodontic Treatment. Ann Arbor: Center for Human Growth and Development, The University of Michigan; 1990:13–74. Craniofacial Growth Monograph Series; Monograph 23. 8. Rowlerson A, Raoul G, Daniel Y, Close J, Maurage CA, Ferri J, et al. Fiber-type differences in masseter muscle associated with different facial morphologies. Am J Orthod Dentofac Orthop 2005;127:37–46. 9. Cozza P, Baccetti T, Franchi L, De Toffol L, McNamara Jr JA. Mandibular changes produced by functional appliances in Class II malocclusion: a systematic review. Am J Orthod Dentofacial Orthop 2006;129:599.e1–12. 10. Flores-Mir C, Major PW. A systematic review of cephalometric facial soft tissue changes with the Activator and Bionator appliances in Class II division 1 subjects. Eur J Orthod 2006;28:586–93. 11. Flores-Mir C, Major PW. Cephalometric facial soft tissue changes with the twin block appliance in Class II division 1 malocclusion patients. A systematic review. Angle Orthod 2006;76:876–81. 12. Flores-Mir C, Ayeh A, Goswani A, Charkhandeh S. Skeletal and dental changes in Class II division 1 malocclusions treated with splint-type Herbst appliances. A systematic review. Angle Orthod 2007;77:376–81.
125
13. Ahn SJ, Kim JT, Nahm DS. Cephalometric markers to consider in the treatment of Class II Division 1 malocclusion with the bionator. Am J Orthod Dentofacial Orthop 2001;119:578–86. 14. Fogle LL, Southard KA, Southard TE, Casko JS. Treatment outcomes of growing Class II Division 1 patients with varying degrees of anteroposterior and vertical dysplasias. Part 1. Cephalometrics. Am J Orthod Dentofacial Orthop 2004;125:450–6. 15. Ormiston JP, Huang GJ, Little RM, Decker JD, Seuk GD. Retrospective analysis of long-term stable and unstable orthodontic treatment outcomes. Am J Orthod Dentofacial Orthop 2005;128:568–74. 16. Hägg U, Pancherz H. Dentofacial orthopaedics in relation to chronological age, growth period and skeletal development. An analysis of 72 male patients with Class II division 1 malocclusion treated with the Herbst appliance. Eur J Orthod 1988;10:169–76. 17. Malmgren O, Ömblus J, Hägg U, Pancherz H. Treatment with an appliance system in relation to treatment intensity and growth periods. Am J Orthod Dentofacial Orthop 1987;91:143–51. 18. Baccetti T, Franchi L, Toth LR, McNamara Jr JA. Treatment timing for Twin-Block therapy. Am J Orthod Dentofacial Orthop 2000;118:159–70. 19. Faltin Jr K, Faltin RM, Baccetti T, Franchi L, Ghiozzi B, McNamara Jr JA. Long-term effectiveness and treatment timing for bionator therapy. Angle Orthod 2003;73: 221–30. 20. Franchi L, Baccetti T. Prediction of individual mandibular changes induced by functional jaw orthopedics followed by fixed appliances in Class II patients. Angle Orthod 2006;76:950–4. 21. Freeman CS, McNamara Jr JA, Baccetti T, Franchi L, Graff TW. Treatment effects of the bionator and high-pull facebow combination followed by fixed appliances in patients with increased vertical dimensions. Am J Orthod Dentofacial Orthop 2007;131:184–95. 22. Lake SL, McNeill RW, Little RM, West RA. Surgical mandibular advancement: a cephalometric analysis of treatment response. Am J Orthod 1981;80:376–94. 23. Mobarak KA, Espeland L, Krogstad O, Lyberg T. Mandibular advancement surgery in high-angle and low-angle class II patients: different long-term skeletal responses. Am J Orthod Dentofacial Orthop 2001;119:368–81. 24. Arpornmaeklong P, Shand JM, Heggie AA. Skeletal stability following maxillary impaction and mandibular advancement. Int J Oral Maxillofac Surg 2004;33:656–63. 25. van Strijen PJ, Breuning KH, Becking AG, Tuinzing DB. Stability after distraction osteogenesis to lengthen the mandible: results in 50 patients. J Oral Maxillofac Surg 2004;62:304–7. 26. Burden D, Johnston C, Kennedy D, Harradine N, Stevenson M. A cephalometric study of Class II malocclusions treated with mandibular surgery. Am J Orthod Dentofacial Orthop 2007;131:7.e1–8. 27. Baccetti T, Franchi L, McNamara Jr JA. The cervical vertebral maturation (CVM) method for the assessment of optimal treatment timing in dentofacial orthopedics. Semin Orthod 2005;11:119–29. 28. Steiner CC. Cephalometrics for you and me. Am J Orthod 1953;39:729–55. 29. Jacobson A. The “Wits” appraisal of jaw disharmony. Am J Orthod 1975;67:125–38. 30. Ricketts RM. Perspectives in the clinical application of cephalometrics. The first fifty years Angle Orthod 1981;51:115–50. 31. McNamara Jr JA. A method of cephalometric evaluation. Am J Orthod 1984;86:449–69.
126
progress in orthodontics 1 1 ( 2 0 1 0 ) 118–126
32. Burkhardt DR, McNamara Jr JA, Baccetti T. Maxillary molar distalization or mandibular enhancement: a cephalometric comparison of comprehensive orthodontic treatment including the pendulum and the Herbst appliances. Am J Orthod Dentofacial Orthop 2003;123:108–16. 33. Dahlberg G. Statistical methods for medical and biological students. London: G. Allen & Unwin ltd; 1940. 34. Baccetti T, Franchi L, Stahl F. Cephalometric comparison of two comprehensive treatment protocols for Class II
Malocclusion including the bonded Herbst and the headgear appliances: A double-blind study on consecutively-treated patients at puberty. Am J Orthod Dentofac Orthop 2009;135:698.e1–10. 35. Baccetti T, Franchi L, Kim LH. The effect of timing on the outcomes of one-phase non-extraction therapy of Class II malocclusion. Am J Orthod Dentofac Orthop 2009;136: 501–9.