CASE REPORT
Atypical extraction of maxillary central incisors
Guilherme Janson,a Danilo Pinelli Valarelli,b Fabrıcio Pinelli Valarelli,c Marcos Roberto de Freitas and Arnaldo Pinzane
Bauru, Brazil
This case report describes a Class I crowded malocclusion with an ankylosed maxillary central incisor that was in infraocclusion and labially displaced. The patient had wide maxillary teeth, and the option of extracting the maxillary central incisors followed by space closure, with lateral incisors substituting for the central incisors, was chosen. (Am J Orthod Dentofacial Orthop 2010;138:510-7)
aProfessor and head, Department of Orthodontics, Bauru Dental School, University of Sa˜o Paulo, Bauru, Sa˜o Paulo, Brazil.
bPostgraduate student, Department of Orthodontics, Bauru Dental School, University of Sa˜o Paulo, Bauru, Sa˜o Paulo, Brazil.
cPrivate practice, Bauru, Brazil.
dProfessor, Department of Orthodontics, Bauru Dental School, University of Sa˜o Paulo, Bauru, Sa˜o Paulo, Brazil.
eAssociate professor, Department of Orthodontics, Bauru Dental School, University of Sa˜o Paulo, Bauru, Sa˜o Paulo, Brazil.
The authors report no commercial, proprietary, or financial interest in the products or companies described in this article.
Reprint requests to: Guilherme Janson, Department of Orthodontics, Bauru
Dental School, University of Sa˜o Paulo, Alameda Octa´vio Pinheiro Brisolla 9-75, Bauru, SP, 17012-901, Brazil; e-mail, jansong@travelnet.com.br.
Submitted, July 2008; revised and accepted, August 2008.
0889-5406/$36.00
Copyright 2010 by the American Association of Orthodontists.
doi:10.1016/j.ajodo.2008.08.042
Ankylosed permanent maxillary central incisors in a growing patient are a clinical challenge for any orthodontist. Ankylosis results from the fusion of a portion of the cementum of the root to the adjacent alveolar bone.1 Permanent ankylosis frequently occurs after trauma, especially intrusive luxation.
2 This means that the tooth becomes an integral part of the bone remodeling system, and, whereas the neighboring teeth erupt normally with alveolar growth, the ankylosed incisor does not erupt and eventually is in infraocclusion with a higher gingival margin and is often displaced labially.3 In these cases, extraction of the ankylosed tooth and space closure might be a solution. Decisions about the direction of treatment usually are based on several
factors: type of malocclusion, space conditions, lateral incisor width and root length, and shape and shade of the canines.4,5 From an orthodontic perspective, absence of maxillary anterior teeth can provide the space and opportunity to alleviate a crowded dentition or an enlarged horizontal overlap without extracting other teeth. However, this approach requires the lateral incisors to assume the functional and esthetic role of central incisors; the canines become the lateral incisors, and the first premolars take the role of the canines, with all the prosthetic camouflage that these positional changes require. Therefore, the objective of this article was to demonstrate this situation with a clinical patient and discuss the advantages and disadvantages of this approach.
DIAGNOSIS AND ETIOLOGY
A boy, aged 13 years 11 months, was brought to the Department of Orthodontics at Bauru Dental School, University of Sa˜o Paulo in Brazil, for evaluation. His chief complaint was impaired esthetics because of crowding. He had moderate dental irregularity and a Class I biprotrusive malocclusion (Figs 1-3). The left maxillary central incisor was ankylosed, with a higher gingival level than the adjacent teeth. He had a traumatic episode at age 11 years, and the maxillary left central incisor was avulsed. The tooth received endodontic treatment and was reimplanted. The periapical radiograph shows the endodontic treatment and the root resorption of the ankylosed maxillary left central incisor (Fig 3, D). His face was symmetric, but there was no passive lip competence at rest.
TREATMENT OBJECTIVES
The primary objectives were to eliminate the patient’s crowding and excessive lip protrusion and to improve his facial appearance. The maxillary anterior
gingival margins would need to be leveled, and the maxillary left central incisor ankylosis and root resorption would need to be addressed, to establish acceptable anterior dental esthetics.
TREATMENT ALTERNATIVES
Based on the objectives, 3 treatment options were proposed. The first option consisted of extracting the 4 first premolars to relieve the crowding and dentoalveolar protrusion followed by extraction of the ankylosed central incisor. A single-tooth implant would be considered as a prosthetic option to replace the extracted incisor after facial growth. A disadvantage of this option was that it would commit this young patient to a permanent prosthesis in an area of the mouth in which tooth shade, gingival contour, and margins are critical and not always easy to control.6-8 The second option consisted of extracting the ankylosed central incisor, the maxillary right first premolar, and the mandibular first premolars. The left lateral incisor would be moved into the central incisor extraction site. A composite buildup would transform the lateral into a central incisor.9 But the anterior dental esthetic result would be a problem. When a maxillary lateral incisor replaces a missing central incisor, the problem is to duplicate the shape of the contralateral central incisor.
It is difficult to create an ideal crown shape because of the reduced clinical crown height of the lateral incisor. In addition, the mesial and distal surfaces of the crown must be overcontoured, because of the narrower cervical region of the lateral incisor.10 The third option consisted of extracting both maxillary central incisors and the mandibular first premolars. This option seemed to be the most plausible, because the lateral incisors were unusually large mesiodistally, and they could easily be contoured as central incisors. The lateral incisors would be moved into the central incisor position, and
composite buildup would transform the lateral incisors into central incisors. The patient and his parents preferred this option, because fewer teeth would be extracted, and the overall esthetics would be easier to manage.
Fig 1. Pretreatment facial and intraoral photographs.
Fig 2. Pretreatment dental casts.
Fig 3. A, Pretreatment lateral cephalogram; B, pretreatment tracing; C, pretreatment panoramic radiograph; and D, pretreatment periapical radiograph.
Fig 4. A, Bone; and B, gingival defect after extraction.
Fig 5. A-D, Progress intraoral photographs.
TREATMENT PROGRESS
After completing the initial preorthodontic procedures, extraction of the maxillary central incisors and mandibular first premolars was requested. When the ankylosed central incisor was extracted, the labial bone was lost as expected, and a significant vertical and buccolingual defect appeared (Fig 4). The first molars were banded, and preadjusted 0.022 3 0.028-in brackets were placed on all remaining teeth. Prosthetic maxillary central incisors were fixed to the archwire at the extractions sites (Fig 5).
The artificial teeth were gradually reduced proximally, and both arches were leveled and aligned orthodontically. At the end of the alignment phase, the
narrow prosthetic teeth were replaced by 1 artificial tooth fixed on a palatal plate, which was removed later to facilitate space closure (Fig 5). Space closure was accomplished with rectangular 0.019 3 0.025-in stainless steel archwires and intramaxillary elastic chains. The anterior extraction spaces were partially closed, leaving welldistributed interproximal spaces to be filled by composite restoration of the maxillary lateral incisors. The bone defect
was filled progressively, while the lateral incisors were moved into the central incisor extraction sites. At the end of orthodontic treatment, gingivectomy
and direct composite buildup of the maxillary lateral incisors and canines transformed them into central and lateral incisors, respectively.
Fig 6. Posttreatment facial and intraoral photographs.
RESULTS
The patient returned 6 months after the end of orthodontic treatment, with the gingivectomy and esthetic restorative treatment completed. Favorable
facial changes were observed with reduction of the biprotrusion and attainment of passive lip seal (Figs 6-8). Upon smiling, an ideal amount of tooth
structure was displayed, and the anterior gingival margins were leveled. Intraorally, there was dramatic improvement in dental esthetics. The arch length
deficiency was eliminated in both arches, satisfactory tooth alignment was obtained, and overbite and overjet were improved (Figs 6 and 7). Extraction of
the maxillary central incisors and mandibular premolars facilitated coordination of the dental midlines with the facial midline. The Class I molar relationship was maintained, and a Class II canine relationship was obtained, with the canines replacing the maxillary lateral incisors. Composite restorations and labial surface reductions were necessary to transform the maxillary canines into lateral incisors. Direct composite was built up on the lateral incisors to transform them into central incisors. The cephalometric superimposition showed significant changes in the soft-tissue profile and the maxillomandibular relationship (Fig 8, Table). The posttreatment panoramic radiograph shows healthy supporting tissue and slight root blunting, despite the extensive tooth movement and lengthy treatment time (Fig 8). The patient and his parents were pleased with the final results.
Fig 7. Posttreatment dental casts.
DISCUSSION
An Angle Class I malocclusion with crowding and dentoalveolar biprotrusion is traditionally treated orthodontically with extraction of 4 first premolars.11 However, this patient also had an ankylosed maxillary central incisor, which caused marked infraocclusion of the ankylosed tooth and migration and malpositioning of adjacent teeth. Additionally, the patient had wide maxillary anterior teeth, with the maxillary lateral incisors measuring 9 mm, compared with the average width of 6.5 mm.12 These characteristics and the concern about anterior esthetics suggested the option of extracting the maxillary central incisors and closing the spaces by substituting the lateral incisors for the central incisors. But extracting an ankylosed tooth results in vertical and horizontal loss of alveolar bone.3 A technique for extracting the ankylosed tooth and avoiding such bone loss is to remove the crown and leave the ankylosed root in the alveolus to be replaced by bone. In children, new marginal bone will then be formed coronal to the resorbing root. The height of
the alveolar bone is thus improved vertically and preserved in a faciolingual direction.13 Although this treatment alternative could have avoided the bone defect and improved the conditions for subsequent prosthetic therapy, the selected treatment plan did not include a permanent prosthesis but, rather, the patient’s natural teeth, which were moved into the extraction sites. Tooth movement to fill bone defects is possible. Alveolar bone will be deposited ahead of the tooth if light and continuous forces are used and the gingival tissue is healthy.14,15 By moving the tooth slowly, the periosteum on the
buccal and lingual surfaces of the alveolus will form bone as the tooth is moved into the extraction site.15 The tooth is not moved like a mobile entity through a rigid bone channel but with its periodontal support.16 With the selected treatment protocol, bone graft surgery and a permanent prosthesis were avoided. In addition, the final anterior esthetic appearance was satisfactory. Nevertheless, the maxillary lateral incisors and canines needed to be equilibrated, reshaped, and restored. 17 For a successful esthetic and functional outcome, several issues had to be addressed and resolved. When a maxillary lateral incisor is substituted for a missing central incisor, the problem is to simulate the shape of the central incisor. It is difficult to create
an ideal crown form because of the reduced clinical crown height. In addition, the mesial and distal surfaces of the crown must be overcontoured because of the narrower cervical region of the lateral incisor.10 In this patient, extraction of both maxillary central incisors and substitution with the lateral incisors facilitated correction of the maxillary anterior esthetics with gingivectomy and composite buildup.
Fig 8. A, Posttreatment lateral cephalogram; B, superimposition of pretreatment and posttreatment tracings, on SN line centered at sella; C, posttreatment panoramic radiograph; and D, posttreatment periapical radiograph.
When the canines occupy the lateral incisors’ positions, the canines’ greater labiolingual dimension can create an occlusal interference with the mandibular incisors. Therefore, palatal trimming throughout treatment is necessary when occlusal prematurities with the mandibular incisors are detected to prevent having the canine positioned labially.9,17 The canine’s labial surface should also be reduced to make it flatter. Studies have
shown that fairly extensive dental grinding can be performed without significant discomfort, and with minor or no pulp and dentin reactions.18 Long-term
observations indicate that any unfavorable reactions are temporary.19 The cusp tip and the labial surface were reduced to produce a flat incisal edge, and composite buildups at the mesial and distal angles of the canine were needed to complete the canine transformation. When premolars are substituted for maxillary canines, they should look and function like canines. The premolars were extruded relative to the adjacent teeth and rotated mesially for a better contact point.9,17,20 The premolars’ roots were also torqued buccally to simulate a canine prominence.9 Canine-protected occlusion is not feasible when the canine is replaced by the premolar. As a result, the forces generated through lateral excursivemovements are placed on the roots of the first premolar21 or distributed by group function.5,17,22 Some investigators fear loss of periodontal attachment, because of the stresses placed on the premolars.22 However, long-term periodontal and occlusal studies on congenitally missing lateral incisors have shown that space closure with premolars substituting for canines was equally sound occlusally and preferable periodontally to orthodontic space opening with prosthetic replacement of the missing lateral incisor.23 The treatment plan for this patient addressed the problem of the ankylosed central incisor, which was replaced by adjacent teeth filling the extaction defect. All treatment objectives were satisfied, and the patient was pleased with the end result.
Conclusion
Extraction of the maxillary central incisors is not a usual treatment protocol in orthodontics. However, in some patients with ankylosis of the maxillary central incisors and wide maxillary anterior teeth, this might be a good alternative to preserve tooth structure and avoid permanent prostheses as long as the patient’s diagnostic characteristics will permit this plan. Additional cosmetic finishing on the anterior teeth might be necessary to provide good esthetic results.
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