Correction of a bilateral maxillary canine-first premolar transposition in the late mixed dentition

CASE REPORT Correction of a bilateral maxillary canine-first premolar transposition in the late mixed dentition Anna Bocchieri, MD, DDS,a and Giovanni Braga , MD, DDSb Tricesimo, Italy A bilateral maxillary canine–first premolar transposition was treated during the late mixed dentition. The correct tooth order was obtained by moving the teeth into their proper positions. The treatment mechanics and the sequencing of treatment are described. (Am J Orthod Dentofacial Orthop 2002;121:120-8) axillary canine-first premolar (MxCP1) transposition is the most frequent tooth transposition, although its incidence in the general population is estimated to be low.1 Treatment planning for this anomaly centers on whether to maintain the transposed tooth order or correct it. There is general agreement1,2 on keeping the transposed tooth order in most cases, especially in adults. But when detected early enough, transpositions can sometimes be corrected without damaging the canine and the first premolar roots.1,2 For the best response to treatment, it is important1 that the cusp tip of the maxillary canine is positioned superior to the root of the first premolar. In this situation, the first premolar root can be tipped distally, thus correcting the transposition, so that the permanent canine can be guided into its correct position. M DIAGNOSIS The patient was a normally developing 10-year 7month-old white male in the mixed dentition. Radiographs showed unusual tooth position in the region above the primary maxillary first molars: a bilateral MxCP1 transposition. The patient had a biretrusive profile and slightly deficient anterior facial height (Fig 1). He had a Class II molar relationship on the right side, a Class I molar relationship on the left side, a Class I canine relationship on both sides, posterior crossbites, 6 mm of overbite, and 2.5 mm of overjet. The dental arches were symmetrical, and the maxillary first molars were rotated mesially. A moderate mandibular arch length discrepancy was noted (Figs 2 and 3). The panoramic radiograph (Fig 4) showed that all a,bPrivate practice, Tricesimo, Italy. Reprint requests to: Anna Bocchieri, Studio di odontoiatria e ortodonzia, Piazza Verdi 7, 33019 Tricesimo (UD), Italy; e-mail, bragabocchieri@mclink.it. Submitted, February 2001; revised and accepted, August 2001. Copyright © 2002 by the American Association of Orthodontists. 0889-5406/2002/$35.00 + 0 8/4/120755 doi:10.1067/mod.2002.120755 120 permanent teeth were present, with bilateral transposition of the canines and the first premolars. According to Clark’s image/tube shift method,3 with 2 periapical radiographs on each side, it was possible to establish that both maxillary canines were located buccally. The cephalometric analysis (Figs 5 and 6 and Table I) revealed a biretrusive skeletal pattern with mild mandibular deficiency and decreased lower anterior facial height. Maxillary and mandibular incisors were inclined lingually. Treatment objectives Because facial appearance was satisfactory, correcting tooth transposition was the highest priority. The treatment objectives were to (1) establish a Class I molar and canine relationship, (2) create ideal overjet and overbite and correct incisor lingual inclination, (3) correct the transposed canines and first premolars, (4) correct the rotation of the maxillary first molars, (5) correct the crossbites, and (6) maintain facial balance. Treatment progress Unfortunately, when the patient came to the office for the first time, the favorable stage described by Peck1 for correcting tooth transposition had already passed. The treatment strategy was therefore to keep the maxillary canines high while they were moved mesially. This would reduce the probability of root interference and the risk of root damage. Therefore, the maxillary canines would be bracketed as soon as they erupted high in the vestibule, to prevent their full eruption to the occlusal plane. Active treatment began in the late mixed dentition. The permanent first molars were banded, and Burstone’s buccal tubes with .018 × .025-in auxiliary tubes were added. Lingual tubes for .036-in lingual arches were added to the first molar bands. The primary canines and the molars were avoided at the initial bond- American Journal of Orthodontics and Dentofacial Orthopedics Volume 121, Number 2 Fig 1. Pretreatment facial photographs. Fig 2. Pretreatment intraoral photographs. Fig 3. Pretreatment dental casts. Bocchieri and Braga 121 122 Bocchieri and Braga American Journal of Orthodontics and Dentofacial Orthopedics February 2002 Fig 4. Pretreatment panoramic radiograph. Fig 6. Pretreatment cephalometric tracing. Fig 5. Pretreatment cephalometric radiograph. Table I. Cephalometric summary: pretreatment measurements Area of study Maxillary skeletal Nasion perp to Point A (mm) Maxillary dental Upper incisor to Point A vert (mm) Mandibular dental Lower incisor to A-Po line (mm) Mandibular skeletal Pogonion to nasion perp (mm) Vertical measures Mandibular plane angle Facial axis angle Midfacial length (mm) (Co-Pt A) Mandibular length (mm) (Co-Gn) Maxillo-mandibular differential (mm) Measurement Norm -5 (0) 3 (4-6) -1 (1-3) -9 (–8- –6) 23° 0° (25°) (0°) 92 116 (117-120) 24 Lower anterior facial height (mm) (ANS-Me) 60 (64-65) ing. Maxillary and mandibular .018-in stainless steel archwires supported 150-g superelastic nickel-titanium alloy (Sentalloy; GAC International, Islandia, NY) open coil springs to correct the lingually inclined position of the incisors in both arches. At the same time, a .036-in stainless steel transpalatal arch placed on the maxillary first molars was activated in Burstone and Koenig’s VI geometry4 to correct the mesiopalatal rotation of the maxillary first molars (Fig 7, A). When the cusp of the maxillary right permanent canine erupted high in the vestibule (Figs 7, B, and 8, B), a bracket was placed, and a .018 × .022-in stainless steel sectional archwire was inserted in the molar auxiliary tube and in the canine bracket. A 150-g Sentalloy open coil spring provided the force for canine mesial movement, while the distal reaction force helped to correct the Class II right molar relationship. During the mesial movement of the maxillary right canine, the right first premolar had erupted and was American Journal of Orthodontics and Dentofacial Orthopedics Volume 121, Number 2 Bocchieri and Braga 123 A B C D E F Fig 7. Progress photos. A, Beginning of treatment. B, After 2 months of treatment. C, After 7 months of treatment. D, After 9 months of treatment. E, After 20 months of treatment. F, After 22 months of treatment. 124 Bocchieri and Braga American Journal of Orthodontics and Dentofacial Orthopedics February 2002 A B C D E Fig 8. Periapical radiographs. A, Pretreatment. B, After 2 months of treatment. C, After 9 months of treatment. D, After 14 months of treatment. E, After 22 months of treatment. American Journal of Orthodontics and Dentofacial Orthopedics Volume 121, Number 2 Fig 9. Posttreatment facial photographs. Fig 10. Posttreatment intraoral photogrphs. Fig 11. Posttreatment dental casts. Bocchieri and Braga 125 126 Bocchieri and Braga American Journal of Orthodontics and Dentofacial Orthopedics February 2002 Fig 12. Posttreatment panoramic radiograph. Fig 14. Posttreatment cephalometric tracing. Fig 13. Posttreatment cephalometric radiograph. Table II. Cephalometric summary: posttreatment measurements Area of study Maxillary skeletal Nasion perp to Point A (mm) Maxillary dental Upper incisor to Point A vert (mm) Mandibular dental Lower incisor to A-Po line (mm) Mandibular skeletal Pogonion to nasion perp (mm) Vertical measures Mandibular plane angle Facial axis angle Midfacial length (mm) (Co-Pt A) Mandibular length (mm) (Co-Gn) Maxillo-mandibular differential (mm) Measurement Norm -4 1 3 4-6 0 (1-3) -8 (–6- –4) 21° 0° (24°) (0°) 100 126 (130-133) 26 Lower anterior facial height (mm) (ANS-Me) 68 (70-74) rotated mesiopalatally. A lingual button was bonded on the first premolar, and an elastic thread was stretched from the button to the first molar palatal tube (Fig 7, C). The elastic thread was periodically replaced to initiate first premolar distal crown movement. Meanwhile, brackets were bonded on the mandibular permanent canines and premolars, and a lower .016 × .022-in braided stainless steel (D-rect; Ormco, Glendora, Calif) archwire was applied. After 9 months of active tooth movement, the left side was proceeding satisfactorily, but, on the right, a pronounced mesial root tipping of the first premolar had occurred. So, a .016 × .022-in beta titanium (TMA; Ormco) cantilever was applied palatally on the first premolar to control the root distal movement (Figs 7, D, and 8, C). The cantilever was inserted in the vertical slot of a bracket placed palatally on the maxillary right first premolar. The wire was lying above the palatal tube of the first molar before being activated. A .019 × .025-in stainless steel archwire bypassing the maxillary canines and the premolars was directed occlusally against the Bocchieri and Braga 127 American Journal of Orthodontics and Dentofacial Orthopedics Volume 121, Number 2 right first premolar button to counteract its extrusion. The cantilever provided lingual root torque because of the palatal application of the extrusive force. A steel ligature between the first molar and the first premolar impeded the mesial movement of the first premolar crown. After 14 months of active treatment, both maxillary canines were in their correct sagittal positions but were still high in the vestibule. A passive .018 × .022-in stainless steel sectional wire was applied on the maxillary incisors and the canines to maintain their position. The maxillary left first premolar also erupted palatally. A lingual button was bonded to its only bondable surface. A .016 × .022-in TMA cantilever was inserted in the auxiliary tube on the left first molar and activated to move the maxillary left premolar buccally. After initial buccal movement, a power arm extending buccally was applied to the maxillary left first premolar (Fig 7, E), and an elastic thread was tied between the power arm and the buccal tubes on the maxillary left first molar to complete first premolar alignment and derotation. At the same time, the sectional archwire on the maxillary incisors and the canines was shortened to allow the canines to erupt freely. A .019 × .025-in stainless steel archwire was placed in the mandibular arch, and triangular interarch elastics were used to accelerate maxillary canine eruption. During first premolar retraction, a selective intrusion and labial crown torque of the maxillary incisors was accomplished with a .017 × .025-in TMA base arch (Fig 7, F). The point of application of intrusive force was placed between the maxillary central incisors to achieve incisor intrusion and palatal root torque. Twenty-five months after the beginning of active treatment, the palatal cantilever for uprighting the maxillary right first premolar root was removed, and .021 × .025-in braided nickel-titanium archwires were inserted. The crossbite between maxillary and mandibular left first molars was corrected by activating the transpalatal arch on the maxillary first molars and the .036-in stainless steel lingual arch on the mandibular first molars. Orthodontic finishing was performed with .019 × .025 TMA archwires and elastic chains to close spaces. Thirty-four months after the beginning of the active treatment, the fixed appliances were removed, and a removable retainer was placed in the maxillary arch. A .0195-in coaxial stainless steel fixed retainer was bonded to the cingula of the mandibular anterior teeth. RESULTS The maxillary canines and the first premolars were successfully positioned, and proper alignment and cor- rect tooth position were obtained. Ideal overjet and overbite were also achieved. Class I tooth relationships were established with correction of the crossbites. A small space remained between the maxillary right lateral incisor and the canine (Figs 9, 10, and 11). Good root parallelism was achieved (Fig 12). The maxillary first premolars showed mild root resorption. Facial balance was maintained (Figs 9, 13, and 14, and Table II) DISCUSSION The main difficulties in correcting the altered tooth position with maxillary premolar-canine transposition are avoiding root interference and resorption, and controlling root inclination of the transposed teeth.1 Another difficulty encountered in this patient occurred on the right side. Because of the supracrestal gingival fibers, the maxillary right first premolar migrated mesially after the canine mesial movement. The risk of forcing the premolar root against the canine root prevented the use of biomechanics that could have led to a locking of the first premolar root. So the use of a power arm to apply force at the center of resistance of the first premolar was avoided, and an elastic thread was connected between the first premolar lingual button and the first molar lingual tube (Fig 7, C). Thus, the premolar root was free to tip if root interference occurred during canine movement. The undesirable result was severe mesial root tipping of the maxillary right premolar (Fig 8, C); its correction this required 13 months of treatment with a palatal uprighting cantilever (Fig 7, D, E, and F, and Fig 8, D and E). If the tipping had been avoided, the total treatment time would have been much shorter. The inappropriate procedure was beginning the distal movement of the first premolar before controlling the orthodontic movement. The best method would have been a metallic tie, instead of an elastic thread, to reduce mesial premolar movement. The premolar crown distal movement should have been delayed until the canine had reached its correct sagittal position. On the left side, when this procedure was adopted, the tipping of the maxillary first premolar was avoided, and correcting tooth transposition proceeded easily. Keeping the canine high in the vestibule during the correction of the transposition was important in reducing the risk of root interference and damage. This patient showed the development pattern typical of MxCP1 transposition described by Peck1: “the transposed maxillary canine is found blocked out facially between the first and second premolars. The canine frequently is rotated mesiofacially, and the first premolar is usually tipped distally and rotated mesiopalatally.” In 128 Bocchieri and Braga this patient, the anomaly was not treated early, and the favorable stage described by Peck was already past. Buccal eruption of the canine in this type of transposition probably allows early inclusion of the canine in the fixed appliance and allows easier correction of the transposition. This method of treatment must be started before the canine has reached the occlusal plane. Careful observation of bitewing radiographs by pediatric dentists is essential for early diagnosis and treatment of these transpositions. American Journal of Orthodontics and Dentofacial Orthopedics February 2002 REFERENCES 1. Peck S, Peck L. Classification of maxillary tooth transpositions. Am J Orthod Dentofacial Orthop 1995;107:505-17. 2. Shapira Y. Transposition of canines. J Am Dent Assoc 1980;100: 710-2. 3. Clark CF. A method of ascertaining the relative position of unerupted teeth by means of film radiographs. Proc R Soc Med Odontol Sectn 1910;3:87-90. 4. Burstone CJ, Koenig HA. Force systems from an ideal arch. Am J Orthod 1974;65:270. 5. Burstone CJ. Deep overbite correction by intrusion. Am J Orthod 1977;72:1-22.