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CASE REPORT Long-term stability of maxillary group distalization with interradicular miniscrews in a patient with a Class II Division 2 malocclusion Shingo Kuroda,a Natsuko Hichijo,b Minami Sato,b Akiko Mino,b Nagato Tamamura,c Mitsuhiro Iwata,d and Eiji Tanakae Tokushima, Amagasaki, and Okayama, Japan, and Jeddah, Saudi Arabia We successfully treated a Class II Division 2 patient with maxillary group distalization using interradicular miniscrews. A woman, aged 28 years 11 months, had a convex profile and an excessive overjet caused by a skeletal Class II jaw-base relationship. After leveling and alignment, titanium miniscrews were obliquely implanted between the maxillary second premolar and first molar. To distalize the maxillary dentition, nickel-titanium closing coil springs with a 2-N load were placed between the screws and the hooks on the archwire. After 28 months of active orthodontic treatment, a proper facial profile and an acceptable occlusion were achieved with a 4-mm distalization of the maxillary dentition. The resultant occlusion was stable throughout a 5-year retention period. Interradicular miniscrews were useful to distalize the maxillary dentition for correcting a Class II malocclusion. This new strategy, group distalization with miniscrews, can make the treatment simpler with greater predictability. (Am J Orthod Dentofacial Orthop 2016;149:912-22) I n the treatment of a Class II malocclusion, tooth extraction or nonextraction is a subject of much debate.1-3 In growing patients, growth modification is often tried to improve their anteroposterior jaw discrepancies without extractions.2 If a nongrowing patient has excessive overjet or a severe arch length discrepancy, orthodontists are likely to choose extraction treatment.3 However, most patients desire nonextraction treatment, if possible, and some do not accept extractions. In such patients, orthodontists must seek other treatment options. Molar distalization can be an alternative a Associate professor, Department of Orthodontics and Dentofacial Orthopedics, Institute of Biomedical Sciences, Graduate School, Tokushima University, Tokushima, Japan. b Postgraduate student, Department of Orthodontics and Dentofacial Orthopedics, Graduate School of Oral Sciences, Tokushima University, Tokushima, Japan. c Private practice, Amagasaki, Japan. d Private practice, Okayama, Japan. e Professor and chair, Department of Orthodontics and Dentofacial Orthopedics, Institute of Biomedical Sciences, Graduate School, Tokushima University, Tokushima, Japan; distinguished adjunct professor, King Abdulaziz University, Jeddah, Saudi Arabia. All authors have completed and submitted the ICMJE Form for Disclosure of Potential Conflicts of Interest, and none were reported. Address correspondence to: Eiji Tanaka, Department of Orthodontics and Dentofacial Orthopedics, Institute of Biomedical Sciences, Tokushima University Graduate School, 3-18-15 Kuramoto-Cho, Tokushima 770-8504, Japan; e-mail, [email protected]. Submitted, January 2015; revised and accepted, July 2015. 0889-5406/$36.00 Copyright Ó 2016 by the American Association of Orthodontists. http://dx.doi.org/10.1016/j.ajodo.2015.07.045 912 to correct a Class II malocclusion. However, it is not easy to distalize the maxillary dentition completely with traditional orthodontic mechanics.2 Various types of molar distalizers have been developed and clinically used, but they cannot prevent counteractions: eg, flaring of the maxillary incisors.4-7 In addition, a group distalization of the maxillary dentition was almost impossible in most patients. Recently, implant-anchored orthodontics has been shown to be effective in treating a wide variety of malocclusions.8-13 In particular, miniscrews have gained acceptance because they can provide stable anchorage for various types of tooth movement despite their small diameter and short length.12 Miniscrew anchorage can provide maxillary molar distalization without patient compliance and undesirable counteractions; therefore, now they are well regarded as a new treatment strategy for Class II correction.14-17 However, their long-term stability is still unknown. In this case report, we demonstrate the 5-year retention of a group distalization of the maxillary dentition with interradicular miniscrews in an adult patient with a Class II Division 2 malocclusion. DIAGNOSIS AND ETIOLOGY A woman, aged 28 years 11 months, had a chief complaint of esthetic problems of her maxillary incisors. Her facial profile was convex, and the frontal Kuroda et al 913 Fig 1. Pretreatment facial and intraoral photographs. TREATMENT OBJECTIVES view was almost symmetric Fig( 1). The molar relationships were Angle Class II on both sides Fig 2). ( Overjet The patient was diagnosed as having an Angle Class II and overbite were 5.0 and 0.0 mm, respectively. TheDivision 2 malocclusion with a skeletal Class II jaw-base maxillary and mandibular dental midline almost coin-relationship. An excessive overjet and a reduced overbite cided with the facial midline. In the panoramic radio-were also shown. The treatment objectives were to graph, the maxillary left central and right lateral achieve (1) an acceptable occlusion with a good funcincisors and the mandibular first molars were nonvital tional Class I occlusion and (2) an attractive smile and (Fig 3). Periapical lesions were observed in the mandib-balanced facial pro file. ular first molars. The maxillary third molars had already To achieve a functional Class I occlusion, distalization been extracted, but the mandibular third molars were of the maxillary dentition was necessary. Then, placeimpacted. ment ofi nterradicular miniscrews was planned in the The cephalometric analysis, when compared with the posterior maxilla. The mandibular first molars would be Japanese norm, showed a skeletal Class II jaw-base rela-extracted, and mesialization of the second and third motionship (ANB, 9.0) (Table).18 The mandibular plane lars was proposed to reduce the spaces for restorations. ). The maxillary was steep (mandibular plane-SN, 44.0 ), but the incisors were lingually inclined (U1-SN, 90.0 mandibular incisors showed an average inclinationTREATMENT ALTERNATIVES Several procedures were explored to achieve an ). As the result, the interin(L1-mandibular plane, 93.5 cisal angle was increased (134.0 ). acceptable occlusion. Extraction of the maxillary first American Journal of Orthodontics and Dentofacial Orthopedics June 2016 Vol 149 Issue 6 Kuroda et al 914 Fig 2. Pretreatment dental casts. Fig 3. Pretreatment lateral cephalogram, cephalometric tracing, and panoramic radiograph. June 2016 Vol 149 Issue 6 American Journal of Orthodontics and Dentofacial Orthopedics Kuroda et al 915 Table. Cephalometric summary Variable ANB ( ) SNA ( ) SNB ( ) Mandibular plane-SN ( ) U1-SN ( ) L1-mandibular plane ( ) Interincisal angle ( ) Overjet (mm) Overbite (mm) Japanese norm* 2.8 80.8 77.9 37.1 105.9 93.4 123.6 3.1 3.3 SD 2.4 3.6 4.5 4.6 8.8 6.8 10.6 1.1 1.9 Pretreatment 9.0 85.0 76.0 44.0 90.0 93.5 134.0 5.0 0.0 Posttreatment 8.0 84.0 76.0 44.0 88.5 90.0 137.0 3.0 3.0 Postretention 8.0 84.0 76.0 44.0 88.5 90.0 137.0 3.0 3.0 *Wada et al,18 1981. Fig 4. Treatment progress: A, 3 months after the start of treatment; after leveling and alignment, miniscrews were implanted at the mesial alveolus of the maxillary first premolar, and molar distalization was started with 200-g nickel-titanium closed-coil springs; in the mandible, the second molar mesialization was started. B, 12 months later, the mandibular second molars were completely mesialized, and uprighting of the right third molar was started. C, 18 months later, the mandibular third molars were completely uprighted. premolars was considered to reduce the excessive overjet. However, the maxillary third molars had already been extracted, and 2 maxillary incisors were nonvital. Therefore, premolar extractions should be avoided to retain as many intact teeth as possible. As for the mandibular first molars, prosthetic restorations without orthodontic treatment might shorten the total treatment period. However, this requires pulpectomy of the proximal teeth when bridge restorations are chosen. Moreover, dental implants are expensive American Journal of Orthodontics and Dentofacial Orthopedics June 2016 Vol 149 Issue 6 Kuroda et al 916 Fig 5. A and C, Distal movement of the maxillary molars: miniscrews are shown at the mesial alveolus of the first molars before distalization, but in B and D, the miniscrews are observed beside the second premolar after distalization, which meant a 4-mm distalization of the maxillary dentition. A and C, 2 months after the start of treatment; B and D, 24 months later; A and B, right side; C and D, left side. and cause considerable surgical invasion, and their longevity is still unclear. Therefore, molar mesialization was planned to reduce the spaces for prosthetic restorations and to reconstruct the whole mandibular dentition with vital teeth. TREATMENT PROGRESS The mandibular first molars were extracted, and 0.022-in slot preadjusted edgewise appliances were placed on both arches. After leveling and alignment June 2016 Vol 149 Issue 6 with nickel-titanium archwires, the mesialization of the mandibular second molars was started with closingloop mechanics and a stainless steel archwire (Fig 4, A). Two months after the start of treatment, miniscrews (diameter, 1.3 mm; length, 7 mm; Absoanchor; Dentos, Daegu, South Korea) were implanted at the distal alveolus of the maxillary second premolars (Fig 5, A and C). They were inserted obliquely in the surface of the cortical bone with the self-tapping method. After the 1-month latency period, distal movement of the American Journal of Orthodontics and Dentofacial Orthopedics Kuroda et al 917 Fig 6. Posttreatment facial and intraoral photographs. maxillary dentition was started with a 2-N load of theTREATMENT RESULTS nickel-titanium closed-coil springs (Sentalloy; Tomy, On the posttreatment facial photographs, a balanced Tokyo, Japan)Fig ( 4, A). facial profile was achievedFig ( 6). The occlusion was At 12 months of treatment, a molar tube was much more stable, and an acceptable intercuspation of bonded on the erupting mandibular right third molarthe teeth was achieved with Class I canine and molar re(Fig 4, B). After leveling with the nickel-titanium wires, lationshipsFig ( 7). The mandibular second molars were uprighting of the mandibular right third molar wascompletely mesialized to the position offirst themolars. initiated Fig ( 4, C). In the panoramic radiograph, proper root parallelism After removal of the edgewise appliances, a wrap-is shown, and the impacted mandibular third molars around type of retainer was placed on the maxillarywere uprighted and mesialized Fig (8). The posttreatarch, and a lingual bonded retainer was set on thement cephalometric evaluation still showed a Class II mandibular anterior teeth. The total active orthodonticjaw-base relationship (SNA, 84.0 ; ANB, 8.0 ). The treatment time was 28 months. During the retentionmaxillary molars were bilaterally distalized for 5.0 mm, period, tooth whitening was performed on both denti-but the mandibular plane angle was stable (mandibular tions, and the maxillary incisors were restored with zirco-plane-SN, 44.0) (Table). Both the maxillary and nia crowns. American Journal of Orthodontics and Dentofacial Orthopedics June 2016 Vol 149 Issue 6 Kuroda et al 918 Fig 7. Posttreatment dental casts. Fig 8. Posttreatment lateral cephalogram, cephalometric tracing, and panoramic radiograph. June 2016 Vol 149 Issue 6 American Journal of Orthodontics and Dentofacial Orthopedics Kuroda et al 919 Fig 9. Five-year postretention facial and intraoral photographs. mandibular incisors were lingually inclined (U1-SN, For group distalization of the maxillary dentition, it ), but the acceptable might be believed that temporary anchorage devices 88.5; L1-mandibular plane, 90.0 interincisal relationship was maintained. No symptomsshould be placed out of the dentition ̶ie, the screws of temporomandibular disorder were observedat midpalate or miniplates at the zygomatic prothroughout active orthodontic treatment. cess.14,15,19,20 However, miniplates requireflap At the 5-year postretention checkup, the occlusionsurgery at both placement and removal, and these was stable, and the good facial file prowas also retained procedures cause considerable pain and discomfort 21 Palatal screws need some kind of bulky (Fig 9). The panoramic radiograph and cephalometricfor patients. appliance to connect the screw and the archwire, and analysis showed little change Figs( 10 and 11 ; Table). these palatal devices are also unpleasant for patients. In contrast, interradicular screws are relatively DISCUSSION comfortable. Nevertheless, most orthodontists still In this patient, distal movement of the maxillary in- believe that they are not suitable for group distalization of the dentition because the screws would come cisors was required to treat the excessive overjet. Premoin contact with the surrounding root during tooth lar extractions were avoided because 2 maxillary incisors movement. Actually, interradicular miniscrews may were nonvital, and there was enough bone at the postenot interfere with tooth movement when they are rior maxilla for molar distalization. American Journal of Orthodontics and Dentofacial Orthopedics June 2016 Vol 149 Issue 6 Kuroda et al 920 Fig 10. Lateral cephalogram, cephalometric tracing, and panoramic radiograph at the 5-year postretention checkup. obliquely inserted in the alveolar bone with adequate buccolingual thickness.16 In this patient, the interradicular screws were placed at the mesial alveolus of the maxillary first premolars but are shown at the middle part of the second premolar after treatment (Fig 5, B and D). This means that the root of the maxillary second premolars could pass through the lingual side of the obliquely inserted miniscrews. Of course, such a tooth movement is not feasible in all patients. Analyses of the alveolar bone thickness with radiographs, and 3-dimensional computed tomography if possible, are essential before planning the treatment. Additionally, dental cast analysis measuring the buccolingual thickness of the alveolar basal bone is also useful for prediction. In distal movements of the maxillary molars, the maxillary sinus is a major concern because tooth movement through bone-deficient areas is considered challenging and might reduce the alveolar bone height or June 2016 Vol 149 Issue 6 the root length.22-24 Lindskog-Stokland et al23 in a dog experiment and Wehrbein et al24 in a human biopsy study described that root resorption and loss of osseous supporting tissue occurred in the basal cortical bone of the nasal sinus after translatory tooth movements. They suggested that differentiation of osteoblasts is required for compensatory subperiosteal bone apposition. However, the molar roots seemed to move into the maxillary sinus without any serious root resorption, even though the sinus seemed to be between the molar roots in the our patient. Several clinical reports also demonstrated the possibility of tooth movement into the sinus.25,26 A recent study provided histologic evidence that the sinus wall is a dynamic structure that responds favorably to mechanical stress, such as tooth movement.27 Therefore, the possibility of tooth movement into the sinus under suitable and safe conditions should ultimately contribute to expanding the limits of orthodontic treatment. American Journal of Orthodontics and Dentofacial Orthopedics Kuroda et al 921 Fig 11. Cephalometric tracings at pretreatment (black lines), posttreatment (red lines), and 5-year postretention (green lines) superimposed on A, the sella-nasion plane at sella; B, the anterior palatal contour; and C, the mandibular plane at menton. Maxillary group distalization improved the horizontal open bite and provided adequate anterior guidance. Extraction of the pathologic mandibular first molars and succeeding molar mesialization could make the mandibular dentition intact, avoiding any prosthetic restorations. Moreover, the maxillary left central and right lateral incisors were restored with zirconia jacket crowns after tooth whitening. This interdisciplinary approach, a combination of orthodontic and restorative treatment, significantly improved the patient's dental esthetics and function, contributing to the increase of her quality of life. In this patient, the occlusion was stable, and little relapse occurred during the 5-year retention period, even though a large amount of molar distalization was achieved with miniscrew anchorage. A recent longitudinal study with pendulum appliances for distalization showed that first molars were distalized for 4 mm with 10 of tipping, but almost half of the patients experienced relapse during the succeeding multibracket treatment.28 In our patient, the distalized molars were initially tipped back but controlled well during the finishing and detailing phase. Control of distal tipping after molar distalization might be 1 important key for the stability of the distalized dentition. In addition, the mandibular plane angle did not increase during active orthodontic treatment and was also stable during the retention period. With these simple molar distalizing mechanics with inerradicular screws, the distalized maxillary molars can be slightly intruded.16,17 As a result, the mandibular plane angle can be stabilized even though the molars are extremely distalized. The strict vertical control might also be important to prevent relapses. However, no authors have evaluated the long-term stability of molar distalization with interradicular miniscrews. Further studies are required to confirm their retention and stability. CONCLUSIONS Interradicular miniscrews are useful to distalize the maxillary dentition for correcting a Class II malocclusion. With this new strategy, group distalization with miniscrews can make the treatment simpler with greater predictability. REFERENCES 1. Vaden JL, Kiser HE. Straight talk about extraction and nonextraction: a differential diagnostic decision. Am J Orthod Dentofacial Orthop 1996;109:445-52. 2. de Almeida-Pedrin RR, Henriques JF, de Almeida RR, de Almeida MR, McNamara JA Jr. Effects of the pendulum appliance, cervical headgear, and 2 premolar extractions followed by fixed American Journal of Orthodontics and Dentofacial Orthopedics June 2016 Vol 149 Issue 6 Kuroda et al 922 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. 14. 15. 16. appliances in patients with Class II malocclusion. 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