Cephalometric evaluation in different phases of Jasper jumper therapy

All subjects of the sample initially had bilateral Class II Division 1 malocclusions, and they were treated with the Jasper jumper associated with fixed appliances and intermaxillary Class II elastics as active retention after removal of the Jasper jumper. Treatment phase III, with the use of Class II elastics,
was longer than the other 2 phases (Table II). This could be explained since Class II elastics needs patient compliance, and the other 2 phases did not depend on compliance. Furthermore, the time considered for comparison among the 3 phases was the time between the cephalograms, and some extra time could have been necessary for the patients to take the final records. There was restriction of maxillary growth from T1 to T4, and the effective maxillary length remained stable during all stages of treatment (Table III). These results agreed with previous studies that also found significant restrictions of maxillary growth during Jasper jumper therapy.2,4,6,9,13 Similar investigations found some restrictive effects, particularly when the SNA angle was evaluated.4,6,13 This phenomenon is described as the „headgear effect.4,6,13 The studies pointed out that this restrictive
effect could be related to changes that are similarly observed when extraoral appliances are used for Class II malocclusion treatment.4,6,13
There was a significant increase in mandibular length during treatment (Table III). Mandibular growth occurred during all phases and was not significantly
greater during the Jasper jumper period of use. Mandibular changes were probably inherent to normal growth, corroborating some previous reports.3,5,13 However, some studies described some mandibular protrusion during treatment with the Jasper jumper appliance.2,6,9,14,15 There was significant improvement in the maxillomandibular relationship during treatment, during both leveling and alignment, and use of the Jasper jumper (Table III). Several studies reported improvement in the maxillomandibular relationship with the use of the Jasper jumper appliance.5,6,16 Improvement of the maxillomandibular relationship seems to have resulted primarily from maxillary retrusion, as previously discussed, normal mandibular growth, and significant dentoalveolar effects. However, changes in the Wits appraisal must be carefully evaluated because it is not reliable as an indicator of 
sagittal change, since it is heavily influenced by changes in the cant of the occlusal plane angle, which the Jasper jumper greatly affects.
Another appliance that produces similar effects is the Herbst bite-jumping appliance. Some studies have shown that both skeletal and dentoalveolar effects are produced in patients with Class II malocclusions who have worn this appliance.17-22 But this mechanism has not been widely used because of difficulties in appliance management, including breakage, high cost, and comfort problems.
There was a reduction in facial skeletal convexity in the leveling and alignment phase that remained in the Jasper jumper and Class II elastics phases. This was also previously found3-6,23 (Table III). There was a significant increase in lower anterior face height during the first 2 phases of treatment (T1-T2 and T2-T3). No lower anterior face height increase was observed during the use of Class II elastics as active retention (Table III). These results agree with those of a previous study.6 Additionally, some studies of the Herbst appliance showed similar effects.20,21 The posterior face height increased during the initial stage and then remained stable. The growth pattern remained unchanged during the entire therapy with the maintenance of SN.GoGn angle (Table III). Previous findings indicated that the Jasper jumper might induce vertical changes and clockwise mandibular rotation. 4,6,13,14 However, other studies did not find significant changes in growth patterns, corroborating our results.5
The maxillary incisors were buccally tipped during the alignment and leveling phase (1.PP increased by 3.61
, 1.NA increased by 4.26
). With the Jasper jumper, lingual movement of the maxillary incisors was observed (1.PP decreased by 9.38
, 1.NA decreased by 9.22
), and a slight relapse was observed during the Class II elastics phase (1.PP increased by 3.95
, 1.NA increased by 3.77
) (Table III). Lingual movement of the maxillary incisors with the use of the Jasper jumper has already been described in several studies.3-6  During Jasper jumper use, extrusion of the maxillary incisors was observed (1-PP increased by 1.69 mm) (Table III). This effect was observed in several studies in which Class II Division 1 malocclusions were corrected with the Jasper Jumper or similar appliances.4-6,9,10 The Jasper jumper caused significant labial tipping of the mandibular incisors (IMPA increased by 5.07
, 1.NB
increased by 5.50
), corroborating previous studies.2,13 There was also a slight lingual tipping of these teeth during the use of Class II elastics, without returning to the original values (IMPA decreased by 3.15
, 1.NB decreased by 3.27
) (Table III). This can be explained because the Jasper jumper produces a continuous force, whereas Class II elastics are used in an intermittent manner. Although lingual torque had been incorporated in the rectangular archwire in the mandibular anterior teeth during use of the Jasper jumper to minimize buccal tipping of these teeth, buccal inclination of the mandibular
anterior teeth was observed.5 Labial inclination of the mandibular incisors has been reported as a result of Jasper jumper therapy.4-6,24 Intrusion of the mandibular incisors was observed during Jasper jumper use (1-GoMe decreased by 1.30 mm) in agreement with previous studies.3-6,9 However, 
extrusion of the mandibular anterior teeth occurred after Jasper jumper removal, maintaining the vertical position of the mandibular incisors as observed at T1 (1-GoMe increased by 0.86 mm) (Table III). There was mesial movement of the mandibular molars during Jasper jumper use (6-Pogperp decreased by 1.58 mm) (Table III). This mesial movement during mandibular advancement can be explained by the resultant  forces of the Jasper jumper appliance.4-6,24 The facial musculature applies forces through these modules to the anchor points to produce a variety of treatment effects. The treatment effects produced by the module mimic those previously described for the Herbst appliance and include posterior movement of the maxillary buccal segments and anterior movement of the mandible or mandibular dentition or both.2 Because of the maxillary molar intrusion, there was significant extrusion of the mandibular molars during leveling and alignment and during Jasper Jumper use (6-GoMe increased by 1.32mmduring leveling and alignment, and also increased by 1.72 mm during use of the Jasper jumper) (Table III). Mandibular molar extrusion was expected because previous reports also described
similar effects after Jasper jumper therapy.3,4,6,13,15 There was a decrease in overjet after Jasper jumper use (reduction of 5.07 mm). A slight but significant relapse of this overjet correction was observed during the use of Class II elastics, without returning to initial values (overjet increased by 1.45 mm) (Table III). The increase in overjet during the active retention phase with the use of the Class II elastics is explained by the overcorrection of skeletal and dental effects during Jasper jumper therapy. Reductions of overjet were reported in several studies with appliances with similar modes of action to the Jasper jumper.3-6,13 Overjet correction was obtained from maxillary forward displacement restriction, mandibular incisor protrusion, and normal
mandibular growth.3-6,23 Overbite decreased during the alignment phase (reduction of 2.46 mm) and continued to decrease in the orthopedic phase (reduction of 1.82 mm), showing a significant increase with Class II elastics use (increase of 1.17 mm) (Table III). Functional appliances can correct a deep overbite.3-6,13 Mandibular incisor intrusion and mandibular molar extrusion might have contributed to overbite correction.5,14,15 There was significant molar relationship correction with the Jasper jumper (correction of 4.52 mm) (Table III). Many studies showed the same effect with orthopedic appliances4-6,24; however, the phase in which the correction occurred and the real contribution of the Jasper jumper for the correction of Class II malocclusions have not been previously described. Molar relationship, overjet, and overbite corrections were probably due to the dentoalveolar and skeletal changes, which together contributed to the observed results. Correction of Class II malocclusions was mainly observed in the Jasper jumper phase. The changes responsible for this correction were primarily dentoalveolar, with minimum skeletal changes that were not clinically relevant.
In previous studies with the Jasper jumper appliance,  soft-tissue variables have not been widely studied; for this reason, their assessments were included in this study.3,4,9,13
There was an increase in the nasolabial angle from T1 to T3 that might be secondary to maxillary retrusion, and to maxillary incisor retrusion and uprighting (Table III). Soft-tissue convexity decreased during the use of the Jasper jumper; this agrees with some previous studies that evaluated fixed functional appliances5,25-27 (Table III).  There was profile improvement during the orthopedic phase. The upper lip was retruded with the use of the Jasper jumper, and the lower lip showed protrusion during the alignment phase and retrusion in the Class II elastics phase (Table III).