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American Journal of Orthodontics and Dentofacial Orthopedics Kinzinger et al 579 Volume 136, Number 4 and, by dispensing with an acrylic button, also achieves better hygiene of the palatal mucosa. In an in-vitro study, Kinzinger and Diedrich 4 demonstrated that the distal jet coil-spring systems allowed almost translatory tooth movement in the sagittal plane with uprighting effects on the dental root over a simulated distalization section of 3 mm based on a constant distalization force of 200 cN, combined with a mesial tipping moment. In the transverse plane, a force constantly directed toward the buccal aspect and a mesially rotating moment resulted in combined buccal movement and therapeutically undesired mesial and inward rotation of the permanent first molar. The aims of this in-vivo study were to investigate clinically the efficiency of the skeletonized distal jet supported by additional miniscrew anchorage and to compare the outcomes with the in-vitro series of measurements. A review of the literature resulted in a discussion of the share of anchorage loss in the total movement in the sagittal plane, hence of the quality of the miniscrew-supported periodontal anchorage setup, when comparing it with other conventional intraorally anchored, noncompliance distalization appliances. MATERIAL AND METHODS A skeletonized distal jet appliance was placed for bilateral molar distalization in the maxilla in 10 patients (8 girls, 2 boys; average age, 12 years 1 month) with dentoalveolar Class II malocclusion and dental archlength discrepancies. The mean treatment duration was 6.7 months. Of the total of 20 second molars, 11 were germinating, and 5 were erupting. Only 4 had already reached the occlusal plane. For the distal jet used in this study, the palatal acrylic button was removed as a means of anchorage. Instead, the modified appliance was anchored skeletally to 2 miniscrews placed into the palate at a paramedian location and, additionally, dentally to 2 occlusal rests. In terms of laboratory technique, this meant that prefabricated telescope spring assemblies, whose wings were bent distally to form occlusal rests, were connected to each other by using a soldered or laser-welded transverse wire (Fig 1). Every patient’s bone supply in the anterior area of the palate was analyzed on lateral cephalographs to determine the length of the screw shaft. After a preoperative mouth rinse with 0.1% chlorhexidine gluconate solution and local terminal anesthesia with an adrenalin-free anesthetic, 2 miniscrews with neck and collar (length, 8-9 mm, diameter, 1.6 mm; Forestadent, Pforzheim, Germany; or System Dual Top, Jeil Medical Corporation, Seoul, South Korea) were placed at a paramedian location in the anterior area of the palate (at the line of the first Fig 1. Skeletonized distal jet appliance supported by additional miniscrew anchorage: treatment of a girl aged 11 years 1 month; duration of distal jet treatment, 5 months. A, Occlusal view immediately after skeletonized distal jet placement: in terms of laboratory technique, prefabricated coil-telescope systems, the wings of which are bent distally to form occlusal rests, are connected to each other with a wire soldered to them. This transverse connecting wire is fitted dorsally to the miniscrew necks. B, Occlusal view after molar distalization: clinical assessment shows bodily molar distalization and spontaneous second premolar dental drifting. premolars) with a manual screwdriver and adequate sodium chloride cooling. No predrilling was performed. All miniscrews were tested for primary stability by using a probe; they were loaded a week after placement. Skeletonized distal jet appliances were attached to the premolars by using occlusal wire rests and to the necks of the miniscrews with transverse wires fitted dorsally and secured with composite. The occlusal rests also resulted in transverse reinforcement of the appliances. Accordingly, the anchorage setup consisted of a periodontal
580 Kinzinger et al American Journal of Orthodontics and Dentofacial Orthopedics October 2009 UR2 UL2 A N S ANS-PNS´ UR6 mb cf db UL6 Ar PNS A ANS Go-Me´ MPR Fig 2. Cast analysis (changes in the horizontal plane): angular and linear measurements to determine changes in the transverse width of the dental arch and rotation of the first molars. Go B footing with the added support of miniscrews. The wings of the arc sections, which represent a bayonet bend, were fitted into the palatal sheaths of the molar bands. Then the loaded coil systems, with superelastic compression springs, were activated by fitting attachment screws dorsally with a distalization force of 200 cN for each system and reactivated every 4 weeks. To verify molar movement in the horizontal plane, plaster dental casts were taken at the start of treatment (T1) and after distal jet appliance removal (T2). The changes near the molars were assessed by measuring corresponding casts with a digital sliding caliper. Objects of analysis were changes in length of the supporting zone, increase or decrease of the transverse width of the dental arch at the line of the first molars, and extent and kind of tooth rotation. For every cast, the distance from the distal point of contact of the lateral incisor to the mesial point of contact of the first molar and, bilaterally, the distance from the lowest point of the central fossa to the mesiobuccal and the distobuccal cusps of the first molar were registered. In addition, the angles between a line running through the mesiobuccal and distobuccal cusps and the midpalatal raphe were measured (Fig 2). The cephalographs taken at T1 and T2 were analyzed to determine changes in the following parameters (Fig 3). 1. SNA: the angle between the anterior cranial base and the deepest point of the ventral concavity of the maxilla. 2. SNB: the angle between the anterior cranial base and the deepest point of the ventral concavity of the mandible. 3. S-N/ANS-PNS: the angle between the anterior cranial base and the palatal plane. B P S Pt PNS 4. ANS-PNS/Go-Me: the angle between the palatal plane and the mandibular plane. 5. Björk’s summation angle: the sum of the saddle angle (NSAr), the articular angle (SArGo), and the gonial angle (ArGoMe). Me Or N ANS Fig 3. Cephalometric analysis (changes in the sagittal plane): angles and distances registered on the lateral cephalograph before and after molar distalization: A, skeletal angular and linear values; B, dental angular and linear values.
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