Treatment of Class II Division 1 malocclusion with orthopedic devices combined with fixed orthodontic appliances has shown excellent results when used in growing patients. We aimed to evaluate the long-term stability of the cephalometric changes obtained during Class II malocclusion correction with the Jasper jumper associated with fixed appliances.
The treatment group comprised 24 patients who were evaluated at 3 stages: pretreatment, posttreatment, and long-term posttreatment. The control group comprised 15 subjects with normal occlusion. Intratreatment group comparisons among the 3 stages were performed with repeated measures analysis of variance, followed by Tukey tests. Intergroup comparisons of posttreatment changes and normal growth changes of the treatment group were performed with t tests.
Apical base relationship, maxillary incisor anteroposterior position, and overjet demonstrated significant relapses in relation to the control group.
Most dentoalveolar changes obtained with the Jasper jumper followed by fixed appliances during treatment remained stable in the long term. However, apical base relationship, maxillary incisor anteroposterior position, and overjet demonstrated significant relapses in relation to the control group. Therefore, active retention time should be increased in the posttreatment period.
Long-term stability of Class II malocclusion treated with the Jasper jumper was studied.
Most dentoalveolar changes remained stable in the long term.
Apical base relationship, maxillary incisor anteroposterior position, and overjet relapsed.
Active retention time should be increased in the posttreatment period.
Class II malocclusions are of great concern to orthodontists, considering the high prevalence of this malocclusion. Class II Division 1 malocclusion affects 12% to 49% of the population and comprises approximately one third of patients seeking orthodontic treatment because of its important esthetic effect; it may be caused by varying combinations of skeletal and dental factors.
Early intervention in patients with active growth using a combination of functional and fixed appliances can generate great outcomes in the treatment of Class II malocclusion. The Jasper jumper appliance, a fixed device composed of a flexible force module, capable of promoting light and continuous force 24 hours a day through mandibular advancement, with freedom in jaw movement including laterality, ensures comfort without relying on patient compliance.
The appliance promotes restrictive effects in forward displacement of the maxilla, dentoalveolar retraction of the maxillary dentition, and dentoalveolar protrusion of the mandibular dentition. Additionally, it features an intrusion force that benefits vertical control in patients with an unfavorable growth pattern and increased overbite during correction of the maxillomandibular discrepancy, demonstrating it to be a successful treatment choice for this malocclusion.
As important as achieving malocclusion correction is the long-term stability of the dentoskeletal changes. However, follow-up studies in the literature have evaluated only the period from jumper removal to removal of the fixed appliances, or only during a short observation period of a few months with the use of retention, which does not represent the long-term stability of this treatment approach. Several authors have demonstrated the need for long-term stability studies of treatment with this appliance.
Noticing the lack of investigations in this area, we aimed to cephalometrically assess, after a minimum of 5 years, the long-term stability of the changes obtained in the correction of Class II Division 1 malocclusion with the Jasper jumper associated with fixed orthodontic appliances.
Material and methods
This study was approved by the ethics in research committee of the University of São Paulo, São Paulo, Brazil, and all subjects signed informed consent.
The main question was defined with the PICO format: population, Class II Division 1 malocclusion patients; intervention, orthodontic treatment with the Jasper jumper associated with fixed appliances; comparison, skeletal, dental, and soft tissue treatment outcomes and posttreatment changes; outcome, long-term stability of treatment changes.
The sample size was calculated based on an alpha significance level of 0.05 and a beta of 0.2 to detect a mean difference of 0.5° with a standard deviation of 0.5° in ANB angle change between the posttreatment and long-term posttreatment stages. The sample size calculation showed that 9 patients were needed; to increase the test power even more, it was decided to select 24 patients for the treatment group.
Therefore, 72 lateral cephalometric headfilms of 24 Class II Division 1 malocclusion patients (11 male, 13 female) treated with the Jasper jumper combined with fixed appliances were retrospectively selected from the files of the Department of Orthodontics, Bauru Dental School, University of São Paulo, São Paulo, Brazil. These subjects were part of an original Jasper jumper sample of 30 patients. However, for various reasons, 6 did not finish orthodontic treatment or were not finished satisfactorily. Consequently, only 24 patients who finished with a good occlusion (bilateral molar and canine Class I relationship, without crowding or diastemas, and normal overjet and overbite) were evaluated.
The sample was selected according to the following inclusion criteria: at least symmetric, half-cusp bilateral Class II molar relationship; no agenesis, or supernumerary or lost teeth; convex profile; mandibular arch with slight or no crowding; and no previous orthodontic treatment. No cephalometric characteristics were considered as inclusion criteria. All patients were treated without extractions for a mean period of 2.33 years (SD, 0.92; range, 1.54-5.43 years). The mean initial age of the patients was 12.46 years (SD, 1.18; range, 10.32-14.55 years), and the mean final age was 14.79 years (SD, 1.26; range, 12.74-17.53 years). The mean age at the long-term posttreatment stage was 21.98 years (SD, 1.16; range, 19.8-23.96 years). The mean long-term posttreatment period was 7.19 years (SD. 1.02; range, 4.6-8.06 years).
The treatment protocol consisted of use of the Jasper jumper appliance for Class II malocclusion correction, combined with fixed appliances ( Fig 1 ). The Jasper jumper was installed after leveling and alignment, which lasted 0.74 years (SD, 0.30; range, 0.43-1.74 years), when passive rectangular stainless steel archwires (0.019 × 0.025 in) were placed in the maxillary and mandibular arches and remained until overcorrection of the Class II anteroposterior discrepancy, which took a mean time of 0.68 year (SD, 0.19; range, 0.41-1.00 year). Overcorrection consisted of obtaining at least a quarter-cusp bilateral Class III molar relationship. The mean age of the patients at the beginning of the use of the Jasper jumper appliance was 13.22 years (SD, 1.15; range, 11.42-15.17 years).
After Class II anteroposterior correction and removal of the Jasper jumper appliance, Class II intermaxillary elastics were used as active retention. The patients were instructed to use the elastics 18 hours a day until the end of orthodontic treatment. After comprehensive treatment, each patient was given a fixed mandibular canine-to-canine retainer, used for a minimum of 5 years or until the end of growth, and a Hawley plate for daily use. Additionally, a Bionator was to be used during sleeping for 1 year.
The control group comprised 15 subjects (7 girls, 8 boys) with normal occlusion and an initial mean age of 14.05 years (SD, 1.01; range, 12.1-16.0 years), and a final mean age of 22.43 years (SD, 3.23; range, 17.0-26.0 years) comparable with the treatment group at the posttreatment and long-term posttreatment stages. This group was selected from the longitudinal growth study sample of the Iowa Facial Growth Study (Department of Orthodontics, College of Dentistry, University of Iowa, Iowa City) obtained from the online American Association of Orthodontists Foundation Craniofacial Growth Legacy Collection.
Three lateral headfilms were obtained of each patient in the following stages of orthodontic treatment: pretreatment; posttreatment, when the multibracket appliances were removed; and long-term posttreatment. The headfilms were digitized (ScanMaker, model i800; Microtek, Hainchu, Taiwan), traced, and analyzed with Dolphin software (version 11.5; Dolphin Imaging and Management Systems, Chatsworth, Calif). The software corrected the image magnification factors because the lateral headfilms were obtained from different x-ray machines. A customized cephalometric analysis generated 25 variables, 8 angular and 17 linear, for each tracing ( Table I ; Fig 2 ).
|Skeletal cephalometric variables|
|SNA (°)||SN to NA angle|
|A-NPerp (mm)||A-point to nasion-perpendicular|
|Co-A (mm)||Condylion to A-point distance|
|SNB (°)||SN to NB angle|
|Pg-NPerp (mm)||Pogonion to nasion-perpendicular|
|Co-Gn (mm)||Condylion to gnathion distance|
|ANB (°)||NA to NB angle|
|Wits (mm)||Distance between perpendicular projections of Points A and B on functional occlusal plane|
|FMA (°)||Frankfort mandibular plane angle|
|SNGoGn (°)||SN to GoGn angle|
|LAFH (mm)||Distance from ANS to menton|
|Nasolabial angle (°)||Angle formed by the Prn’-Sn line and UL-Sn’ line (Prn’ pronasal point, Sn subnasal point, UL upper lip)|
|Dental cephalometric variables|
|Maxillary dentoalveolar component|
|Mx1.PP (°)||Maxillary incisor long axis to palatal plane angle|
|Mx1-APo (mm)||Distance between incisal edge of maxillary incisor and A-Pg line|
|Mx1-PP (mm)||Perpendicular distance between incisal edge of maxillary incisor and palatal plane|
|Mx6-APerp (mm)||Distance between maxillary first molar occlusal and line perpendicular to palatal plane, tangent to A point|
|Mx6-PP (mm)||Perpendicular distance between maxillary first molar occlusal and palatal plane|
|Mandibular dentoalveolar component|
|Md1.NB (°)||Mandibular incisor long axis to NB angle|
|Md1-NB (mm)||Distance between most anterior point of crown of mandibular incisor and NB line|
|Md1-MP (mm)||Perpendicular distance between incisal edge of mandibular incisor and mandibular plane|
|Md6-PgPerp (mm)||Distance between mandibular first molar occlusal and line perpendicular to mandibular plane, tangent to Pg point|
|Md6-MP (mm)||Perpendicular distance between mandibular first molar occlusal and mandibular plane|
|Overjet (mm)||Distance between incisal edges of maxillary and mandibular central incisors, parallel to functional occlusal plane|
|Overbite (mm)||Distance between incisal edges of maxillary and mandibular central incisors, perpendicular to Frankfort plane|
|M.Rel (mm)||Distance between mesial points of maxillary and mandibular first molars, parallel to Frankfort plane|
Twenty-four lateral headfilms were randomly selected, redigitized, retraced, and remeasured by the same examiner (C.F.F.) after a 30-day interval. Random errors were calculated according to Dahlberg’s formula (Se2=∑d2/2n)
( Se 2 = ∑ d 2 / 2 n )
, and the systematic errors were evaluated with dependent t tests, at P <0.05.
Normal distribution was evaluated with Kolmogorov-Smirnov tests, and all variables showed normal distribution.
Therefore, intergroup comparisons regarding the chronologic ages at posttreatment and long-term posttreatment, and the posttreatment and observational periods of the treatment and control groups, respectively, were performed with t tests. Intergroup sex distributions and skeletal ages (cervical vertebral maturation method ) were compared with chi-square tests.
Repeated measures analysis of variance, followed by Tukey tests, was used for intragroup comparisons of the treatment group at the 3 stages. To compare the changes from posttreatment to long-term posttreatment in the treatment group with the changes during a comparable period for the control group, t tests were used.
The statistical tests were performed with software (STATISTICA for Windows, version 6.0; Statsoft, Tulsa, Okla). Results were considered statistically significant at P <0.05.
No variable showed random errors greater than 1.0 mm or 1.5°, and only 3 (SN.GoGn, SNB, and FMA) of the 25 evaluated variables showed statistically significant systematic errors.
The groups were comparable regarding chronologic and skeletal ages at posttreatment and long-term posttreatment, and for sex distribution ( Tables II and III ).
n = 24
n = 15
|T1 age (y)||12.46||1.18||—||—|
|T2 age (y)||14.79||1.26||14.05||1.01||0.058 ∗|
|T3 age (y)||21.98||1.16||22.43||3.23||0.543 ∗|
|Treatment period (T2-T1) (y)||2.33||0.92||—||—|
|Posttreatment period (T3-T2) (y)||7.19||1.02||8.38||3.0||0.082 ∗|
n = 24
n = 15
|8 33.3%||16 66.6%||—||—||—||—||—||—||—||—||—|
|—||3 12.5%||10 41.66%||10 41.66%||1 4.16%||—||2 10%||7 35%||9 45%||2 10%||0.859|
|—||—||—||—||24 100%||—||—||—||—||15 100%||—|
Treatment produced a significant reduction of maxillary protrusion, which remained stable during the posttreatment period. However, there were significant increases in effective maxillary length in the treatment and long-term posttreatment periods; ( Table IV ; Fig 3 ). Effective mandibular length increased during treatment, and mandibular protrusion and effective mandibular length significantly increased during the long-term posttreatment period. During treatment, there was significant improvement in the maxillomandibular relationship, which remained stable after treatment with no significant changes in the posttreatment period. The facial pattern angles remained stable with treatment but significantly decreased in the long-term posttreatment period, whereas the anterior facial height showed a significant increase during both periods.
|SNA||83.0 A||3.0||82.1 B||3.5||82.2 AB||3.3||0.025 ∗|
|A-NPerp||4.3 A||3.1||3.8 A||3.6||4.3 A||3.6||0.153|
|Co-A||82.4 A||4.4||83.8 B||5.0||86.0 C||4.9||0.000 ∗|
|SNB||77.6 A||2.5||77.6 A||3.2||78.2 A||3.1||0.099|
|Pg-NPerp||0.2 A||5.6||0.7 A||5.6||2.9 B||5.9||0.000 ∗|
|Co-Gn||104.2 A||5.4||108.9 B||5.5||113.2 C||6.5||0.000 ∗|
|ANB||5.4 A||2.4||4.5 B||3.2||4.0 B||3.2||0.000 ∗|
|Wits||4.5 A||2.4||1.3 B||2.4||1.5 B||2.6||0.000 ∗|
|FMA||22.2 A||4.4||22.3 A||4.6||19.6 B||4.2||0.000 ∗|
|SN.GoGn||31.5 A||4.6||31.5 A||4.6||29.2 B||4.3||0.000 ∗|
|LAFH||61.4 A||4.5||64.9 B||4.9||67.1 C||5.5||0.000 ∗|
|Maxillary dentoalveolar component|
|Mx1.PP||115.7 A||7.4||110.5 B||5.3||112.0 AB||5.9||0.010 ∗|
|Mx1-APo||8.1 A||2.6||5.7 B||1.4||6.4 B||1.4||0.000 ∗|
|Mx1-PP||26.5 A||2.5||28.0 B||2.7||29.3 C||2.9||0.000 ∗|
|Mx6-PP||16.9 A||2.1||17.8 B||2.1||19.8 C||2.7||0.000 ∗|
|Mx6-Aperp||27.4 AB||2.3||27.8 A||2.6||26.95 B||2.8||0.013 ∗|
|Mandibular dentoalveolar component|
|Md1.NB||28.0 A||6.2||32.3 B||5.6||31.4 B||6.3||0.000 ∗|
|Md1-NB||5.3 A||1.8||6.8 B||2.2||6.8 B||2.1||0.000 ∗|
|Md1-MP||36.5 A||2.7||35.9 A||3.0||38.0 B||3.6||0.000 ∗|
|Md6-MP||27.0 A||3.0||29.8 B||2.8||31.5 C||3.4||0.000 ∗|
|Md6-PogPerp||33.4 A||2.7||33.2 A||3.1||32.7 A||3.6||0.101|
|Overjet||6.6 A||2.1||2.5 B||0.7||3.1 B||0.6||0.000 ∗|
|Overbite||3.8 A||1.7||1.4 B||0.6||2.1 B||1.1||0.000 ∗|
|Molar relationship||2.1 A||1.2||−0.8 B||1.0||−0.8 B||0.7||0.000 ∗|
|Nasolabial angle||108.6 A||9.0||110.6 A||11.5||112.3 A||12.1||0.062|