Long-term stability of Class II treatment with the Jasper jumper appliance

Introduction

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.

Methods

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.

Results

Apical base relationship, maxillary incisor anteroposterior position, and overjet demonstrated significant relapses in relation to the control group.

Conclusions

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.

Highlights

  • 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).

Fig 1
Illustration describing the Jasper jumper’s effects: arrows indicate the vectors of force.

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 ).

Table I
Skeletal and dental cephalometric variables
Skeletal cephalometric variables
Maxillary component
SNA (°) SN to NA angle
A-NPerp (mm) A-point to nasion-perpendicular
Co-A (mm) Condylion to A-point distance
Mandibular component
SNB (°) SN to NB angle
Pg-NPerp (mm) Pogonion to nasion-perpendicular
Co-Gn (mm) Condylion to gnathion distance
Maxillomandibular relationship
ANB (°) NA to NB angle
Wits (mm) Distance between perpendicular projections of Points A and B on functional occlusal plane
Vertical component
FMA (°) Frankfort mandibular plane angle
SNGoGn (°) SN to GoGn angle
LAFH (mm) Distance from ANS to menton
Soft-tissue component
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
Dental relationship
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

Fig 2
Unusual cephalometric variables: 1 , Mx1.PP; 2 , Mx1-Apo; 3 , Mx1-PP; 4 , Mx6-APerp; 5 , Mx6-PP; 6 , Md1-MP; 7 , Md6-PgPerp; 8 , Md6-MP.

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.

Statistical analysis

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.

Results

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 ).

Table II
Intergroup comparability regarding ages at T1, T2, and T3, treatment and long-term posttreatment periods, and sex distribution ( t and chi-square tests)
Stage/period Treatment group
n = 24
Control group
n = 15
P
Mean SD Mean SD
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
Sex Male
11 (45.83%)
Female
13 (54.16%)
Male
8 (53.33%)
Female
7 (46.66%)
0.333
T1 , Pretreatment; T2 , posttreatment; T3 , long-term posttreatment.

t test.

chi-square test.

Table III
Intergroup comparability regarding skeletal ages at T2 and T3 (cervical vertebral maturation method chi-square tests)
Stage Treatment group
n = 24
Control group
n = 15
P
2 3 4 5 6 2 3 4 5 6
T1
skeletal age
8 33.3% 16 66.6%
T2
skeletal age
3 12.5% 10 41.66% 10 41.66% 1 4.16% 2 10% 7 35% 9 45% 2 10% 0.859
T3
skeletal age
24 100% 15 100%
T1 , Pretreatment; T2 , posttreatment; T3 , long-term posttreatment.

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.

Table IV
Intratreatment group comparison of the cephalometric variables at the 3 stages (repeated measures ANOVA followed by Tukey tests)
Variable T1 T2 T3 P
Mean SD Mean SD Mean SD
Maxillary component
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
Mandibular component
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
Maxillomandibular relationships
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
Vertical component
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
Dentoalveolar relationship
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
Soft-tissue component
Nasolabial angle 108.6 A 9.0 110.6 A 11.5 112.3 A 12.1 0.062
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Dec 12, 2018 | Posted by in Orthodontics | Comments Off on Long-term stability of Class II treatment with the Jasper jumper appliance
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