Orthodontic treatment with canines substitution for lateral incisors cases report

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1 Orthodontic treatment with canines substitution for lateral incisors cases report CHIN-YIN LIN 1 YA-HUI YANG 1,2 I CHEN 2 CHI-YING HUANG 1 SANG-HENG KOK 1,3 YI-JANE CHEN 1,4 EDDIE LAI 1 CHUNG-CHEN JANE YAO 1,4 1 Department of Dentistry, National Taiwan University Hospital, National Taiwan University, Taipei, Taiwan, ROC. 2 Graduate Institute of Dental Sciences, College of Medicine, National Taiwan University, Taipei, Taiwan, ROC. 3 Department of Oral-maxillofacial Surgery, School of Dentistry, College of Medicine, National Taiwan University, Taipei, Taiwan, ROC. 4 Department of Orthodontics, School of Dentistry, College of Medicine, National Taiwan University, Taipei, Taiwan, ROC. Treatment options for patients with missing maxillary lateral incisors include space closure (using canine substitution) and space reopening (for a single tooth implant or a traditional bridge). Although canine substitution seems to be an ideal approach for replacing missing lateral incisors without a future prosthesis, case selection and the procedures to improve the esthetic appearance should be seriously considered. The purpose of this article is to describe the treatment plan and treatment results of 2 cases in which canines were protracted to mimic missing maxillary lateral incisors, and also to address the guidelines for this camouflage approach. (J Dent Sci, 1(2):79-87, 2006) Key words: peg lateral, canine substitution, orthodontic treatment. Patients with a missing maxillary lateral incisor are often encountered in orthodontic clinics. Regardless of whether the incisor is congenitally missing or lost because of a pathologic condition or accident, this complicates treatment. Treatment options for patients with a missing lateral incisor include space closure (a canine protracted to the position of the lateral incisor and shaped as the missing incisor) and space reopening (a pontic space provided for a single tooth implant or traditional bridge). In a historical review, Angle 1, Wheeler 2, Dewel 3, and Strange 1 all contended that the proper treatment method for a missing lateral incisor was space reopening because space closure would lead to improper occlusion and a poor facial expression. But in recent studies, emphasis has been placed on canine substitution for missing maxillary laterals and premolar protraction to Received: February 4, 2006 Accepted: April 4, 2006 Reprint requests to:dr. Chin-Yin Lin, Department of Dentistry, National Taiwan University Hospital, No. 1, Chang-Te Street, Taipei, Taiwan 10048, ROC. the area of canine eminence to obtain a better contour of the face without a prosthesis. Few losses of occlusion were mentioned. Carloson 4 and Turverson 5 both described the canine contouring method to improve the appearance of the substitution. The ideal treatment should be the least invasive possible and one which meets the individual s esthetic and functional expectations. Although space closure (canine substitution) seems to be an ideal approach, other factors such as malocclusion, a patient s profile, and the shape and color of the canine should also be considered for individual cases 6. There are also several options for orthodontic treatment for patients with maxillary peg lateral incisors ranging from extraction and space closure to maintaining space and restoring the microdontic teeth to a normal mesiodistal width. For patients with indications for premolar extraction, 1 alternative is to extract a peg lateral incisor instead of a premolar followed by canine substitution. The cases particularly suited for canine substitution would be Angle class II malocclusions with no crowding in the mandibular arch or class I spacedeficiency cases. Generally, patients with a straight 79

2 C.Y. Lin, Y.H. Yang, I. Chen, et al. profile are good candidates, but those with a mildly convex profile may also be acceptable. The ideal canine to use to substitute for a lateral incisor is one with a similar color and shading as the central incisor, with smaller dimensions both at the cementoenamel junction (CEJ) buccolingually and mesiodistally, and with a relatively flat labial surface and narrow midcrown width buccolingually 6,7. Case 1 CASE PRESENTATION This patient was a 14-year-old girl whose upper right central incisor was impacted and had been treated orthodontically (surgical exposure and traction to pull it toward the line of the arch) in a local clinic. She asked for further orthodontic treatment to correct the upper midline deviation and interdental spacing due to a missing upper right lateral incisor. The upper right canine had erupted into the missing lateral incisor s position, resulting in a class II malocclusion on the right side. The patient had a straight to convex profile, and no crowding in the mandibular arch was noted (Figures 1, 2). To correct the deviated upper dental midline and bilateral class II canine relationship, the treatment plan was to extract #22 and close the space of lateral incisors (#12 and #22). Enamel-plasty was performed to shape #13 and #14 for replacement of #12 and #13, and #23 and #24 for replacement of #22 and #23. Results achieved. An intentional class II molar relationship with space closure of the upper anterior teeth, and improvement of esthetics were achieved (Figures 3-5). Although the root axis of #23 did not reach the ideal axis of the lateral incisor, the amount of enamel-plasty was reduced by this compromise because its slant on the distal side was greater than usual. Resin additions to the canines to create corners would possibly have enhanced the illusion of incisor teeth. However, this patient refused to receive restorations because she was completely satisfied with their appearance. The total treatment time was 3 years and 6 months. Figure 1. Case 1 pretreatment photographs. The upper right lateral incisor was congenitally missing. 80

3 Canine substitution for lateral incisors SNA 88 SNB 77 ANB 5 A-Nv -2.5mm Pg-Nv -15mm NAP 5 SN-FH 6 SN-OP 14 SN-MP 33 U1-SN 111 U1-L1 108 L1-OP 55 L1-MP 105 U1-NP 13mm Figure 2. Case 1 pretreatment lateral cephalometric, panoramic radiograph, and cephalometric analyses. Case 2 This patient was a 23-year-old male with subtle manifestation of hemifacial microsomia and mandibular deviation to the right side. A dental class I malocclusion was noted with an anterior crossbite and generalized spacing of the upper and lower anteriors. The upper left lateral incisor was congenitally missing, while the right lateral incisor was a peg-lateral (Figures 6, 7). The treatment plan was to restore #12 to a normal size, contour #23 to resemble a lateral incisor, and close Figure 3. Case 1 photographs taken during treatment. 81

4 C.Y. Lin, Y.H. Yang, I. Chen, et al. Figure 4. Case 1 post-treatment photographs. SNA 81 SNB 76 ANB 5 A-Nv Pg-Nv -3.5mm -17.5mm NAP 13 SN-FH 6 SN-OP 17 SN-MP 35 U1-SN 109 U1-L1 115 L1-OP 59 L1-MP 104 U1-NP 12.55mm Figure 5. Case 1 post-treatment lateral cephalometric, panoramic radiograph, and cephalometric analyses. 82

5 Canine substitution for lateral incisors Figure 6. Case 2 pretreatment photographs. The upper left lateral incisor was congenitally missing, and the right lateral incisor was a peg-lateral. the excessive space on the upper and lower arches. Since the patient already had spacing, extraction of #12 would have created additional space which would have had to be closed at the pre-surgical phase and which would have led to a longer treatment time. Two-jaw orthognathic surgery (with a LeFort 1 osteotomy in the maxilla and intraoral vertical ramus osteotomy and genioplasty in the mandible) was then arranged to correct the facial asymmetry and the canted occlusal plane. Results achieved. An efficient and functioning occlusion with an asymmetrical molar relationship was established since the molar relationship on the right side was class I and on the left side was class II. Closure of the space of the anterior teeth, although surprisingly difficult and time-consuming, was completed, and the facial appearance was improved (Figures 8-10). The total treatment time was 4 years and 2 months. DISCUSSION Canine substitution can be a good treatment alternative for patients whose canines have a reasonable shape to allow for recontouring and a favorable color to match the maxillary central incisors. Space closure and subsequent canine substitution eliminate the need for buildup restorations on the lateral incisors. In most canine substitution cases, the canine is much larger than the lateral incisor. Because of the wider crown and the more-convex labial surface, a significant amount of reduction is often required to achieve acceptable esthetics and a stable occlusion. Naturally, the canine can be either one or two shades darker than the central incisor. Therefore, in order to correct the color difference, canine bleaching or veneer fabrication may be indicated. The gingival margin of the natural canine is slightly incisal to the gingival margin of the central incisor which helps to camouflage the canine. However, to properly position the gingival margin, sometimes minor surgery (e.g., a gingivectomy) may need to be performed. 83

6 C.Y. Lin, Y.H. Yang, I. Chen, et al. SNA 89 SNB 89 ANB 0 A-Nv 3mm Pg-Nv 3mm NAP 2 SN-FN 2 SN-OP 11 SN-MP 35 U1-SN 129 U1-L1 99 L1-OP 57 L1-MP 100 U1-NP 15 FCA 12 UL-N Pg 8mm LL-N Pg 11mm Figure 7. Case 2 pretreatment lateral and posterior-anterior cephalometric, panoramic radiograph, and cephalometric analyses. Figure 8. Case 2 photographs taken during treatment. #12 had already been restored to a normal size. 84

7 Canine substitution for lateral incisors Figure 9. Case 2 post-treatment photographs. Canine contouring procedures adopted from 5 Tuverson 1. The tip of the canine is flattened to produce an incisal edge (Figure 11A, a). 2. Mesial and distal reduction, as indicated by the diagnostic setup, is accomplished mostly at the expense of the more-bell-shaped distal surface (Figure 11A, b). 3. The distal incisal angle is slightly rounded to simulate that of a lateral incisor (Figure 11A, c). 4. The canine eminence of the labial surface is then reduced (Figure 11B, a) to create a flatter, moreincisor-like appearance. Extreme care should be exercised in this reduction. The canines have a slightly darker shade than the central incisors, and too much labial reduction may result in a darkerappearing tooth. 5. The lingual surface is reduced at the incisal area to permit an adequate overbite and overjet to be established (Figure 11B, b). The canine-contouring procedure is accomplished without local anesthesia, as sensitivity is a useful indicator of the amount of enamel reduction. For enamel protection, topical fluoride is applied to the tooth immediately following the contouring procedure Bracket placement and arch wire manipulation 1. The brackets on the canines should be placed at a distance from the gingival margin that will cause these teeth to erupt into the appropriate lateral incisor vertical position. 2. A mesial arch wire outset is necessary to obtain a proper contact point between the canine and the central incisor. 3. Most canines need marked lingual root torque to look like lateral incisors and to reduce the root eminence. Typical canine offset bends are placed in the first premolar area to enable these premolars to simulate canines. Buccal root torque is also incorporated to produce root eminence. Orthodontic space closure in unilateral incisor agenesis can produce problems of matching size, shape, or color, or with midline control. The canine replacing the missing lateral incisor might not be in esthetic 85

8 C.Y. Lin, Y.H. Yang, I. Chen, et al. SNA 91 SNB 88 ANB 3 A-Nv 7mm Pg-Nv 6mm NAP 7 SN-FH 2 SN-OP 16 SN-MP 30 U1-SN 111 U1-L1 118 L1-OP 66 L1-MP 91 U1-NP 12 FCA 14 UL-N Pg 2mm LL-N Pg 2mm Figure 10. Case 2 post-treatment lateral cephalometric, panoramic radiograph, and cephalometric analyses. Figure 11. Canine contouring procedures adopted from Tuverson, (A) a, Tip of the canine flattened to produce an incisal edge. b, Mesial and distal reduction. Note the greater reduction at the more-bell-shaped distal surface. c, The distal incisal angle is slightly rounded. (B) a, Canine eminence on the labial surface is reduced. b, The lingual surface is reduced in the incisal area. 86

9 Canine substitution for lateral incisors harmony with the existing lateral incisor. Extraction of the existing lateral incisor has been advised for symmetry 8. Both cases reported in this article were unilateral incisor agenesis, but different treatment plans were adapted. The existing lateral incisor in case 1 was extracted and that in case 2 was preserved. In case 1, no excessive spacing existed in the upper arch, and the gingival line of #23 was slightly incisal to the gingival margin of the central incisor (Figure 1). It might have been easier to have corrected the upper midline with the extraction space and to have camouflaged the canine without further gingival surgery, which led to extraction of #22. However, in case 2, since the patient already had spacing, extraction of #12 would have created more space which then would have had to be closed in the pre-surgical phase leading to a longer treatment time, which later was verified due to the difficulty of closing the existing space during treatment. Furthermore, the gingival line of #13 was slightly gingival to the gingival margin of the central incisor (Figure 6). Therefore, #12 was preserved in case 2, and more enamel contouring was required to level the gingival line for better esthetics. In the final results of these 2 cases, the gingival line of the upper anterior teeth was harmonious. Although #13 and #23 were darker than #11 and #21, case 1 showed a better symmetrical and esthetic appearance. In case 2, the size and shape of #23 were harmonious with #12, but the color difference was more obvious. CONCLUSION Case selection is important when considering canine substitution in cases with a missing lateral incisor. Also, proper treatment planning is necessary to obtain better esthetic and functional results. These guidelines are provided to help orthodontists with this camouflage approach. REFERENCES 1. Senty EL. The maxillary cuspid and missing lateral incisors: esthetics and occlusion. Angle Orthod, 46: , Wheeler RC. The permanent canines, maxillary and mandibular. In Wheeler s Dental Anatomy, Physiology, and Occlusion 6 th ed, WB Saunders Co, Philadelphia, pp , Dewel BF. The upper canine: its development and impaction. Read before the Chicago Association of Orthodontics, November, Carlson H. Suggested treatment for missing lateral incisors. Angle Orthod, 22: , Tuverson DL. Orthodontic treatment using canines in place of missing maxillary lateral incisors. Am J Orthod, 58(2): , Kokich VO, Jr., Kinzer GA. Managing congenitally missing lateral incisors. Part I: Canine substitution. J Esthet Restor Dent, 17(1): 5-10, Rosa M, Zachrisson BU. Integrating esthetic dentistry and space closure in patients with missing maxillary lateral incisors. J Clin Orthod, 35(4): , Sabri R. Management of missing maxillary lateral incisors. J Am Dent Assoc, 130(1): 80-84,