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The impacted maxillary canine: a proposed classification for surgical exposure
Vol. 113 No. 2 February 2012
The impacted maxillary canine: a proposed classification for surgical exposure Andrew R. Chapokas, DMD, MDS,a Khalid Almas, BDS, MSc, FDSRCS,b and Gian-Pietro Schincaglia, DDS, PhD,c Farmington, CT UNIVERSITY OF CONNECTICUT
Objective. One of the treatment options for the impacted maxillary canine is surgical exposure followed by orthodontic forced eruption. Several surgical techniques have been introduced in the literature for the exposure of the impacted canine. The aim of this study was to review the current literature and to introduce a classification for maxillary canine impactions that includes guidelines for selecting the proper surgical approach. Methods. Epidemiology of canine impaction, diagnosis, and surgical options for the exposure of an impacted maxillary canine are discussed based on the current literature. Results. Careful clinical examination and proper diagnostic imaging should be used to define the anatomical position of the impacted canine. The surgical approach for exposure of impacted maxillary canines should consider the anatomical position of the tooth in relation to the alveolar ridge and the amount of keratinized mucosa/gingiva. Conclusions. The proposed clinical classification provides a structured approach to treatment based on impacted tooth location and anatomical factors. (Oral Surg Oral Med Oral Pathol Oral Radiol 2012;113:222-228)
Impaction is defined as the failure of tooth eruption at its appropriate site in the dental arch, within its normal period of growth.1 The maxillary permanent canine is the most commonly impacted tooth after the third molar. Following these, in decreasing frequency, are mandibular canines, premolars, and incisors.2,3 Aside from their importance in an ideal mutually protected occlusal scheme, the maxillary canine also plays a key role in esthetics and continuity of the dental arch.4 Several complications may result from impaction of teeth, including esthetic and phonetic compromises, loss in arch length, and referred pain.5,6 Options for management of impacted canines include surgical exposure followed by orthodontic forced eruption, replacement using fixed prosthodontics with and without dental implants, and removable prosthodontics. The purpose of this article was to review the literature on the impacted maxillary permanent canine and a
Former Resident of Graduate Programs in Prosthodontics and Periodontology, Department of Reconstructive Sciences, University of Connecticut, School of Dental Medicine. Currently in private practice, San Diego, CA. b Director International Fellowship in Advanced Periodontics & Associate Professor, Division of Periodontology, University of Connecticut, School of Dental Medicine. c Graduate Program Director and Associate Professor, Division of Periodontology, University of Connecticut, School of Dental Medicine. Received for publication Dec 7, 2010; returned for revision Feb 9, 2011; accepted for publication Feb 14, 2011. © 2012 Elsevier Inc. All rights reserved. 2212-4403/$ - see front matter doi:10.1016/j.tripleo.2011.02.025
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introduce a classification that will guide the clinician selecting the treatment sequence and the surgical technique for exposure.
ETIOLOGY AND PREVALENCE OF MAXILLARY CANINE IMPACTION An extensive list of etiologies causing maxillary permanent canine impaction has been reported.6-9 Some common local causes include one or a combination of the following: (1) overlying cysts or tumors, (2) supernumerary teeth, (3) loss of arch space, (4) over-retained primary teeth, (5) ankylosis, (6) root dilacerations, (7) trauma, (8) reconstructive surgery for cleft lip/palate repair, (9) thickened overlying bone or soft tissue, (10) missing adjacent lateral incisor,10 or (11) idiopathic.6 Generalized tooth impaction has been associated with certain host systemic disorders, including (1) endocrine disorders, (2) febrile illness, (3) irradiation, (4) Gardner syndrome,8 (5) cleidocranial dysostosis,9 and (6) Yunis-Varon syndrome.11 Prevalence of maxillary canine impaction ranges from 1.0% to 2.5%,2,3,12-16 where 8.0% to 10.0%6,17 of these cases are bilateral (Table I). Impaction of remaining teeth in the permanent dentition is quite rare and its documented prevalence ranges only from 0.04% to 0.35%.13 Considering gender and location, impaction of the maxillary permanent canine is twice as common in females.6 Palatal impaction of the maxillary permanent canine has been reported to occur approximately 3 times more frequently than facial impaction.18 In a more recent investigation using cone-beam computed tomography (CBCT), 45.2% of maxillary canines were
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ORIGINAL ARTICLE Chapokas et al. 223
Table I. Prevalence and male/female ratio for unilateral maxillary canine impaction Investigators
Location
n
Age, y
Prevalence
Dachi, 1961 Bass, 196715 Rayne, 196916 Thilander, 19683
Dental school, Portland, OR Royal Victoria Hospital, Bournemouth, England Department of Oral Surgery, Oxford, England School system, Umeå, Sweden
1685 9102 12,000 384
13-20⫹ 10-20
0.92% 1.65% 1.5% 1.8%
Grover, 19852 Ericson, 198612
Walter Reed Medical Center, Washington, DC Departments of Oral and Maxillofacial Radiology and Orthodontics, Jönköping, Sweden
13
5000 505
Unclear Followed from mean ⫽ 11.5 – mean ⫽ 17.8 17-26 8-12
1.42%*** 1.7%
Male: Female 0.5:1 0.5:1 — 4:3 — —
—, Information was not reported by the authors.
impacted labially, 40.5% were impacted palatally, and 14.3% were impacted in the midalveolus.19
nates the need for a second surgical procedure if spontaneous eruption fails to occur.
DIAGNOSIS In subjects with a canine retained in the maxillary arch, after the normal period of growth, the diagnosis of impacted maxillary canine is immediate. Conversely, in a patient with developing dentition, maxillary canine impaction is more difficult to diagnose. The presence of certain clinical conditions, such as lack of available arch space, have been considered as risk factors significantly correlated to lack of spontaneous eruption.1,12,20,21 However, this may be dependent on the location of the impacted tooth. According to Jacoby,22 approximately 85% of palatally impacted maxillary canines have sufficient arch space for eruption, whereas only 17% of impacted maxillary canines are located in a facial position. Increased angulation of the canine long axis with respect to the interincisor vertical midline has also been associated with risk of impaction.12 Information on the prevalence of spontaneous eruption of the impacted maxillary canine in growing subjects is lacking. Data are available only on the prevalence of spontaneous eruption of impacted maxillary incisors.21 Sixty-three patients with retained permanent maxillary incisors were followed after removal of the associated supernumerary tooth/teeth. Only 50% of these teeth erupted without surgical and orthodontic assistance. No relationship could be determined between spontaneous eruption and several potential risk factors, which included patient age, number of supernumeraries, extent of root formation, and marked apical displacement of the impacted tooth. In a similar study, 53 children had surgical removal of supernumerary teeth associated with impaction of maxillary incisors.20 Approximately half of the patients required a second operation to facilitate orthodontic forced eruption of the impacted tooth. Because only 50% of impacted teeth seemed to erupt without orthodontic assistance, these studies support immediate application of orthodontic forces after surgical exposure. This elimi-
PATIENT ASSESSMENT Clinical evaluation of the patient with an impacted maxillary canine is initiated by careful inspection of the labial and palatal tissues, and measurement of the width of keratinized gingiva present in the canine area. During the visual examination, the clinician will evaluate arch space available and maxillary lateral incisor inclination. Afterward, palpation is performed labially and palatally in search for the canine bud. This provides information regarding potential location of the impacted canine and periodontal anatomy.23,24 If the primary canine is present, mobility is assessed. The presence of significant mobility may relate to eruptive movement of the permanent canine. Also, periodontal parameters of adjacent teeth should be recorded, including the amount of keratinized gingiva, presence of tooth mobility, and attachment loss. RADIOGRAPHIC ASSESSMENT Radiographic methods used for localization of impacted maxillary canines include orthopantomogram, lateral cephalometry, parallax method, occlusal radiography, CT, and CBCT with or without use of stereolithographic models.23,25 Lateral cephalometry has overlap as its major disadvantage for evaluation of impacted maxillary canines. CBCT scans are useful for determining presence of lateral incisor root resorption and precise location of the impacted tooth.19,25 However, CT and CBCT scans are more costly and have higher radiation exposure compared with conventional radiography26-28; therefore, they are often reserved for complex cases that have other imaging requirements or when localization of impacted canines cannot be determined with traditional methods. As CBCT technology advances, more affordable 3-dimensional imaging with decreased radiation exposure will become available. In the near future, increased CBCT usage compared with conventional techniques is expected. At this time, or-
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Fig. 1. A, The maxillary left impacted canine is approaching a position medial to the long axis of the adjacent lateral incisor, which suggests palatal impaction in the orthopantomogram. B, However, the corresponding lateral incisor inclination shown in the clinical photograph suggests labial or midcrestal impaction. Palatal impaction is expected for the maxillary right canine. Its cusp tip is medial to the adjacent lateral incisor long axis, which presents with normal inclination seen clinically.
thopantomogram and parallax methods are the most commonly selected and their use is described in more detail herein. The orthopantomogram yields a 2-dimensional view of maxillary canine location. If the cusp tip of the maxillary canine is medial to the long axis of the adjacent lateral incisor, palatal location is most probable.29 If the cusp tip of the canine radiographically overlaps the root of the adjacent lateral incisor and is palpated labially, labial impaction is suspected. Severe tipping of the adjacent maxillary lateral incisor often accompanies labial canine impaction with this type of medial radiographic orientation (Fig. 1, A and B). Ericson and Kurol30 examined prognostic factors for orthodontic treatment of maxillary impacted canines based on the radiographic presentation on orthopantomograms. According to the authors, as the canine cusp tip approaches the midline and the inclination of its long axis increases, an increased length of orthodontic treatment time is expected. In addition, the risk of root resorption of the adjacent lateral incisor is increased. In a separate investigation, Crescini et al.31 evaluated the prognostic role of pretreatment radiographic features on the posttreatment periodontal status of intraosseous impacted maxillary canines. Pretreatment variables included tooth location and inclination on panoramic radiographs. Posttreatment variables included pocket depth and width of keratinized gingiva. Based on their results, no pretreatment radiographic findings could be used as prognostic indicators of the final periodontal status of orthodontically repositioned maxillary canines.31 The parallax method, also known as Clark’s rule (Same Lingual Opposite Buccal [SLOB]), is a radiographic technique used to detect an object’s spatial orientation. Briefly, 2 periapical radiographs are taken at different x-ray tube projection angles. During comparison of these radiographs, a radiographic reference point is selected on the image and the impacted tooth is related to this reference.32,33 If the impacted tooth appears to shift in the same direction as the second x-ray
tube projection, it is located on the lingual aspect and vice versa (Same-Lingual Opposite-Buccal). For example, if the x-ray tube is shifted in a distal direction and the canine moves distally with respect to a selected radiographic reference, the location is determined as palatal (Fig. 2, A and B). Shifting periapical radiographs can help to provide more information about the 3-dimensional location of the impacted tooth.
CLINICAL CLASSIFICATION AND TREATMENT PLANNING Surgical approach will be based on the location of the impacted tooth. A classification with 3 categories is presented (Table II). Class I A Class I impacted maxillary canine is located palatally. For this category of impacted canines, a surgical approach with gingivectomy is recommended. Immediately after exposure of the impacted tooth, a fixed attachment appliance should be connected (Fig. 3). Advantages of this approach include relative simplicity of the procedure, potential for spontaneous eruption following surgical exposure, and presence of a fixed attachment should spontaneous eruption fail to occur.34 According to Schmidt and Kokich,35 most palatally impacted canines will spontaneously erupt with simple surgical excision of the overlying palatal tissue. Conversely, Ferguson and Parvizi34 showed that 5.1% of impacted canines exposed with gingivectomy required a second surgical procedure because of lack of spontaneous eruption. Immediate application of orthodontic force after surgical exposure of a palatally impacted canine should be considered with caution.1 A lateral direction of erupting force may result in impaction of the crown against the alveolar process. This can induce nonphysiologic bone resorption that may increase the duration of orthodontic treatment.1
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Fig. 2. In this series of periapical radiographs, the x-ray tube was shifted distally for radiograph B in relation to radiograph A. Because the canine appears to have moved in a mesial direction, its position is toward the labial according to the buccal object rule.
Table II. A proposed classification for the surgical approach of maxillary impacted canines Classification
Location
I II
Palatal Center of alveolar ridge or labial Labial to long axis of adjacent lateral incisor root
III
Surgical technique Gingivectomy Repositioned flap Apically positioned flap
Potential for a longer postoperative recovery period is the primary disadvantage reported for gingivectomy.36 Postoperative discomfort questionnaires and evaluation of analgesic usage have been studied to assess differences in pain threshold between open and closed eruption approach in the management of impacted maxillary canines. Chaushu et al.36 found a longer recovery period for the open compared with the closed approach. However, no difference in general daily activity was noted. Class II A Class II impacted maxillary canine is located in the center of the alveolar crest or labial to the alveolar crest, but not superimposed labially to the root of the adjacent lateral incisor. In this case, a closed eruption technique using a repositioned flap is recommended (Fig. 4, A and B).18,37-41 For the closed eruption technique, a full-thickness mucoperiosteal flap is reflected, allowing the clinician adequate access to the impacted tooth. Following follicular debridement, a fixed attachment is bonded to the impacted tooth, including a wire or chain. The crestal incision should be made with 3
Fig. 3. Gingivectomy is the recommended surgical procedure for a palatally impacted canine. A gold button and chain were attached at the time of surgical exposure.
mm of keratinized gingiva labial to its location. Afterward, the flap is returned to its original position and sutured. The wire or chain will exit the flap and the labial keratinized gingiva is totally preserved (Fig. 4, B). Ideally, depending on the direction of force, this surgical technique can facilitate forced eruption through an adequate zone of keratinized gingiva. In cases where keratinized gingiva is lacking, the patient must be informed that a revision with additional mucogingival surgery may be needed to optimize esthetics. The primary advantages of this technique include less postoperative discomfort compared with gingivectomy,36 as well as management of forced eruption through a zone of keratinized gingiva. Disadvantages include increased technique sensitivity, related to
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Fig. 4. The maxillary left canine is positioned apically to the mucogingival junction and labially in the alveolar process. A, A repositioned flap procedure was used. B, A chain was connected to the impacted tooth, exiting the flap through the crestal incision after suturing.
proper soft tissue flap management, and increased length of surgical treatment time, compared with the open eruption approach. Class III A Class III impacted maxillary canine is located labial to the root of the adjacent lateral incisor. The radiographic evaluation of an orthopantomogram will reveal a canine with its cusp tip over the root of the lateral incisor, whereas the tooth bud will be palpable labially. The lateral incisor is usually inclined palatally to accommodate this orientation. For impacted canines in a Class III position, an apically positioned flap (window flap)17 is indicated.39 A partial thickness dissection, including 2 to 3 mm of the coronally attached gingiva is carried out. The flap is then apically positioned using 2 parallel, vertical releasing incisions (Fig. 5). Using this approach, the clinical crown of the impacted tooth will be completely exposed. This allows the orthodontist to visualize the impacted tooth. Eruption force vectors may then be selected minimizing potential damage to the lateral incisor.39 Also, following this technique, the width of the keratinized gingiva will increase during orthodontic forced eruption.42 Hence, increase in the visibility of tooth orientation and preservation of keratinized gingiva are the primary advantages of this approach. Disadvantages of the window flap include its higher level of technique sensitivity compared with gingivectomy and repositioned flap previously described. Also, several authors have reported complications, including risk of soft tissue recession and inadequate access to labial bone.1,18,37,38 For class II and class III canine impaction, the application of orthodon-
Fig. 5. The maxillary right canine is positioned labial to the long axis of the adjacent lateral incisor root. An apically positioned flap (Window flap) was performed. (Courtesy of Dr. Murad Shaqman.)
tic force should start within a few days after surgical exposure.1
DISCUSSION A surgical classification of impacted maxillary canines has been presented relating the width of keratinized gingiva and tooth location to the recommended surgical approach. Several potential complications may arise following surgical exposure and orthodontic forced eruption of the impacted maxillary canine, including root resorption, periodontal defects, poor esthetic outcome, and immobility. Root resorption of incisors occurs quite commonly when adjacent to impacted maxillary canines. The
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prevalence is higher in females compared with males ranging from 2:1 up to 10:1.43-47 Using CBCT, 27% to 38% of adjacent laterals and 9% to 23% of adjacent centrals have been shown to exhibit root resorption associated with an impacted canine.19,48 Although there has been anecdotal concern of periodontal complications following forced eruption of impacted maxillary canines, no significant increase in periodontal pocket depth, recession, or width of keratinized gingiva has been reported.10,17,31 In a retrospective study, the esthetic outcome on 16 patients treated with forced eruption of unilaterally impacted canines was evaluated. A panel of orthodontists and orthodontic residents were able to identify the previously impacted tooth 78.9% of the time in posttreatment photographs.35 Several reasons for identification include torque/tooth inclination (28%), attached gingiva height compared with contralateral tooth (27%), alignment (17%), crown length/wear (13%), and recession (6%). To optimize esthetic outcome, orthodontic finishing tooth movements and surgical soft tissue management require careful attention to detail. There are 3 possible causes of immobility: (1) bone remaining around the crown of the impaction, (2) inappropriate orthodontic mechanics, and (3) ankylosis.1 Literature reporting the prognosis of treatment in relation to immobility is lacking. If forced eruption of the impacted tooth is unsuccessful, other prosthodontic options for tooth replacement may be considered, including extraction followed by implant placement, conventional fixed dental prosthesis, and removable prosthesis. Dental implant placement may have complications associated with extraction of the impacted tooth. Hence, reconstruction of the alveolar process may be necessary to optimize the esthetic outcome. Fixed prosthodontic options, such as mesial cantilever and 3-unit fixed dental prosthesis have acceptable long-term survival49-52; however, these often require preparation of an otherwise healthy, noncarious or restored tooth. Questionable long-term and short-term survival has been reported for resin-bonded fixed dental prostheses.53-55 More evidence is needed regarding orthodontic prognosis of forced eruption postsurgical exposure.
CONCLUSIONS The impacted maxillary canine poses challenging interdisciplinary diagnoses and treatment. The proposed classification provides guidelines for selecting the surgical approach based on impacted tooth location and anatomical factors. Special thanks to the University of Connecticut Health Center, Department of Orthodontics, for their refe-
ORIGINAL ARTICLE Chapokas et al. 227 rrals and support. Thanks to Dr. Murad Shaqman for providing the clinical image in Fig. 5. REFERENCES 1. Kokich VG, Mathews DP. Surgical and orthodontic management of impacted teeth. Dent Clin North Am 1993;37:181-204. 2. Grover PS, Lorton L. The incidence of unerupted permanent teeth and related clinical cases. Oral Surg Oral Med Oral Pathol 1985;59:420-5. 3. Thilander B, Jakobsson SO. Local factors in impaction of maxillary canines. Acta Odontol Scand 1968;26:145-68. 4. Pokorny PH, Wiens JP, Litvak H. Occlusion for fixed prosthodontics: a historical perspective of the gnathological influence. J Prosthet Dent 2008;99:299-313. 5. Nordenram A. Impacted maxillary canines—A study of surgically treated patients over 20 years of age. Swed Dent J 1987;11:153-8. 6. Bishara SE. Impacted maxillary canines: a review. Am J Orthod Dentofac Orthop 1992;101:159-71. 7. Frank CA. Treatment options for impacted teeth. J Am Dent Assoc 2000;131:623-32. 8. de Oliveira-Ribas M, Martins WD, de Sousa MH, de Aguiar Koubik AC, Avila LF, Zanferrari FL, et al. Oral and maxillofacial manifestations of familial adenomatous polyposis (Gardner’s syndrome): a report of two cases. J Contemp Dent Pract 2009;10:82-90. 9. Bayar GR, Ortakoglu K, Sencimen M. Multiple impacted teeth: report of 3 cases. Eur J Dent 2008;2:73-8. 10. Becker A, Smith P, Behar R. The incidence of anomalous maxillary lateral incisors in relation to palatally displaced cuspids. Angle Orthod 1981;51:24-9. 11. Lapeer GL, Fransman SL. Hypodontia, impacted permanent teeth, spinal defects, and cardiomegaly in a previously diagnosed case of the Yunis-Varon syndrome. Oral Surg Oral Med Oral Pathol 1992;73:456-60. 12. Ericson S, Kurol J. Radiographic assessment of maxillary canine eruption in children with clinical signs of eruption disturbance. Eur J Orthod 1986;8:133-40. 13. Dachi SF, Howell FV. A survey of 3,874 routine full-month radiographs. II. A study of impacted teeth. Oral Surg Oral Med Oral Pathol 1961;14:1165-9. 14. Kuftinec MM, Shapira Y. The impacted maxillary canine: I. Review of concepts. ASDC J Dent Child 1995;62:317-24. 15. Bass TB. Observations on the misplaced upper canine tooth. Dent Pract Dent Rec 1967;18:25-33. 16. Rayne J. The unerupted maxillary canine. Dent Pract Dent Rec 1969;19:194-204. 17. Quirynen M, Op Heij DG, Adriansens A, Opdebeeck HM, van Steenberghe D. Periodontal health of orthodontically extruded impacted teeth. A split-mouth, long-term clinical evaluation. J Periodontol 2000;71:1708-14. 18. Fournier A, Turcotte JY, Bernard C. Orthodontic considerations in the treatment of maxillary impacted canines. Am J Orthod 1982;81:236-9. 19. Liu DG, Zhang WL, Zhang ZY, Wu YT, Ma XC. Localization of impacted maxillary canines and observation of adjacent incisor resorption with cone-beam computed tomography. Oral Surg Oral Med Oral Pathol Oral Radiol Endod 2008;105:91-8. 20. Ashkenazi M, Greenberg BP, Chodik G, Rakocz M. Postoperative prognosis of unerupted teeth after removal of supernumerary teeth or odontomas. Am J Orthod Dentofac Orthop 2007;131:614-9. 21. Witsenburg B, Boering G. Eruption of impacted permanent upper incisors after removal of supernumerary teeth. Int J Oral Surg 1981;10:423-31. 22. Jacoby H. The etiology of maxillary canine impactions. Am J Orthod 1983;84:125-32.
ORAL AND MAXILLOFACIAL SURGERY 228 Chapokas et al. 23. Maverna R, Gracco A. Different diagnostic tools for the localization of impacted maxillary canines: clinical considerations. Prog Orthod 2007;8:28-44. 24. Jacobs SG. Localization of the unerupted maxillary canine: How to and when to. Am J Orthod Dentofac Orthop 1999;115:314-22. 25. Alqerban A, Jacobs R, Lambrechts P, Loozen G, Willems G. Root resorption of the maxillary lateral incisor caused by impacted canine: a literature review. Clin Oral Investig 2009; 13:247-55. 26. Silva MA, Wolf U, Heinicke F, Bumann A, Visser H, Hirsch E. Cone-beam computed tomography for routine orthodontic treatment planning: a radiation dose evaluation. Am J Orthod Dentofac Orthop 2008;133:e641-5. 27. De Vos W, Casselman J, Swennen GR. Cone-beam computerized tomography (CBCT) imaging of the oral and maxillofacial region: A systematic review of the literature. Int J Oral Maxillofac Surg 2009;38:609-25. 28. Ludlow JB, Davies-Ludlow LE, Brooks SL, Howerton WB. Dosimetry of 3 CBCT devices for oral and maxillofacial radiology: CB Mercuray, NewTom 3G and i-CAT. Dentomaxillofac Radiol 2006;35:219-26. 29. Kuftinec MM, Shapira Y. The impacted maxillary canine: II. Clinical approaches and solutions. ASDC J Dent Child 1995; 62:325-34. 30. Ericson S, Kurol J. Early treatment of palatally erupting maxillary canines by extraction of the primary canines. Eur J Orthod 1988;10:283-95. 31. Crescini A, Nieri M, Buti J, Baccetti T, Pini-Prato GP. Pretreatment radiographic features for the periodontal prognosis of treated impacted canines. J Clin Periodontol 2007;34:581-7. 32. Ericson S, Kurol J. Radiographic examination of ectopically erupting maxillary canines. Am J Orthod Dentofac Orthop 1987;91:483-92. 33. Jacobs SG. Localisation of the unerupted maxillary canine: additional observations. Aust Orthod J 1994;13:71-5. 34. Ferguson JW, Parvizi F. Eruption of palatal canines following surgical exposure: a review of outcomes in a series of consecutively treated cases. Br J Orthod 1997;24:203-7. 35. Schmidt AD, Kokich VG. Periodontal response to early uncovering, autonomous eruption, and orthodontic alignment of palatally impacted maxillary canines. Am J Orthod Dentofac Orthop 2007;131:449-55. 36. Chaushu S, Becker A, Zeltser R, Branski S, Vasker N, Chaushu G. Patients perception of recovery after exposure of impacted teeth: a comparison of closed-versus open-eruption techniques. J Oral Maxillofac Surg 2005;63:323-9. 37. Hunter SB. Treatment of the unerupted maxillary canine. Part 1 Preliminary considerations and surgical methods. Br Dent J 1983;154:294-6. 38. Wong-Lee TK, Wong FC. Maintaining an ideal tooth-gingiva relationship when exposing and aligning an impacted tooth. Br J Orthod 1985;12:189-92. 39. Kokich VG. Surgical and orthodontic management of impacted maxillary canines. Am J Orthod Dentofac Orthop 2004;126: 278-83. 40. Magnusson H. Saving impacted teeth. J Clin Orthod 1990; 24:246-9.
OOOO February 2012 41. Crescini A, Nieri M, Buti J, Baccetti T, Mauro S, Prato GP. Short- and long-term periodontal evaluation of impacted canines treated with a closed surgical-orthodontic approach. J Clin Periodontol 2007;34:232-42. 42. Vanarsdall RL, Corn H. Soft-tissue management of labially positioned unerupted teeth. July 1977. Am J Orthod Dentofac Orthop 2004;125:284-93. 43. Arens DE. An alternative treatment for the severely resorped maxillary lateral incisor: a sequela of ectopic eruption. J Endod 1995;21:95-100. 44. Bjerklin K, Ericson S. How a computerized tomography examination changed the treatment plans of 80 children with retained and ectopically positioned maxillary canines. Angle Orthod 2006;76:43-51. 45. Brin I, Becker A, Zilberman Y. Resorbed lateral incisors adjacent to impacted canines have normal crown size. Am J Orthod Dentofac Orthop 1993;104:60-6. 46. Ericson S, Kurol J. Resorption of maxillary lateral incisors caused by ectopic eruption of the canines. A clinical and radiographic analysis of predisposing factors. Am J Orthod Dentofac Orthop 1988;94:503-13. 47. Ericson S, Kurol J. Incisor resorption caused by maxillary cuspids. A radiographic study. Angle Orthod 1987;57:332-46. 48. Ericson S, Kurol PJ. Resorption of incisors after ectopic eruption of maxillary canines: A CT study. Angle Orthod 2000;70:415-23. 49. De Backer H, Van Maele G, De Moor N, Van den Berghe L. Single-tooth replacement: Is a 3-unit fixed partial denture still an option? A 20-year retrospective study. Int J Prosthodont 2006;19:567-73. 50. De Backer H, Van Maele G, De Moor N, Van den Berghe L, De Boever J. A 20-year retrospective survival study of fixed partial dentures. Int J Prosthodont 2006;19:143-53. 51. De Backer H, Van Maele G, Decock V, Van den Berghe L. Long-term survival of complete crowns, fixed dental prostheses, and cantilever fixed dental prostheses with posts and cores on root canal-treated teeth. Int J Prosthodont 2007;20:229-34. 52. Walton TR. An up to 15-year longitudinal study of 515 metalceramic FPDs: part 1. Outcome. Int J Prosthodont 2002;15: 439-45. 53. Chai J, Chu FC, Newsome PR, Chow TW. Retrospective survival analysis of 3-unit fixed-fixed and 2-unit cantilevered fixed partial dentures. J Oral Rehabil 2005;32:759-65. 54. Djemal S, Setchell D, King P, Wickens J. Long-term survival characteristics of 832 resin-retained bridges and splints provided in a post-graduate teaching hospital between 1978 and 1993. J Oral Rehabil 1999;26:302-20. 55. Pjetursson BE, Lang NP. Prosthetic treatment planning on the basis of scientific evidence. J Oral Rehabil 2008;35(Suppl 1):72-9. Reprint requests: Gian-Pietro Schincaglia, DDS, PhD Division of Periodontology University of Connecticut School of Dental Medicine 263 Farmington Ave Farmington, CT 06030-1710 [email protected]
The impacted maxillary canine: a proposed classification for surgical exposure Andrew R. Chapokas, DMD, MDS,a Khalid Almas, BDS, MSc, FDSRCS,b and Gian-Pietro Schincaglia, DDS, PhD,c Farmington, CT UNIVERSITY OF CONNECTICUT
Objective. One of the treatment options for the impacted maxillary canine is surgical exposure followed by orthodontic forced eruption. Several surgical techniques have been introduced in the literature for the exposure of the impacted canine. The aim of this study was to review the current literature and to introduce a classification for maxillary canine impactions that includes guidelines for selecting the proper surgical approach. Methods. Epidemiology of canine impaction, diagnosis, and surgical options for the exposure of an impacted maxillary canine are discussed based on the current literature. Results. Careful clinical examination and proper diagnostic imaging should be used to define the anatomical position of the impacted canine. The surgical approach for exposure of impacted maxillary canines should consider the anatomical position of the tooth in relation to the alveolar ridge and the amount of keratinized mucosa/gingiva. Conclusions. The proposed clinical classification provides a structured approach to treatment based on impacted tooth location and anatomical factors. (Oral Surg Oral Med Oral Pathol Oral Radiol 2012;113:222-228)
Impaction is defined as the failure of tooth eruption at its appropriate site in the dental arch, within its normal period of growth.1 The maxillary permanent canine is the most commonly impacted tooth after the third molar. Following these, in decreasing frequency, are mandibular canines, premolars, and incisors.2,3 Aside from their importance in an ideal mutually protected occlusal scheme, the maxillary canine also plays a key role in esthetics and continuity of the dental arch.4 Several complications may result from impaction of teeth, including esthetic and phonetic compromises, loss in arch length, and referred pain.5,6 Options for management of impacted canines include surgical exposure followed by orthodontic forced eruption, replacement using fixed prosthodontics with and without dental implants, and removable prosthodontics. The purpose of this article was to review the literature on the impacted maxillary permanent canine and a
Former Resident of Graduate Programs in Prosthodontics and Periodontology, Department of Reconstructive Sciences, University of Connecticut, School of Dental Medicine. Currently in private practice, San Diego, CA. b Director International Fellowship in Advanced Periodontics & Associate Professor, Division of Periodontology, University of Connecticut, School of Dental Medicine. c Graduate Program Director and Associate Professor, Division of Periodontology, University of Connecticut, School of Dental Medicine. Received for publication Dec 7, 2010; returned for revision Feb 9, 2011; accepted for publication Feb 14, 2011. © 2012 Elsevier Inc. All rights reserved. 2212-4403/$ - see front matter doi:10.1016/j.tripleo.2011.02.025
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introduce a classification that will guide the clinician selecting the treatment sequence and the surgical technique for exposure.
ETIOLOGY AND PREVALENCE OF MAXILLARY CANINE IMPACTION An extensive list of etiologies causing maxillary permanent canine impaction has been reported.6-9 Some common local causes include one or a combination of the following: (1) overlying cysts or tumors, (2) supernumerary teeth, (3) loss of arch space, (4) over-retained primary teeth, (5) ankylosis, (6) root dilacerations, (7) trauma, (8) reconstructive surgery for cleft lip/palate repair, (9) thickened overlying bone or soft tissue, (10) missing adjacent lateral incisor,10 or (11) idiopathic.6 Generalized tooth impaction has been associated with certain host systemic disorders, including (1) endocrine disorders, (2) febrile illness, (3) irradiation, (4) Gardner syndrome,8 (5) cleidocranial dysostosis,9 and (6) Yunis-Varon syndrome.11 Prevalence of maxillary canine impaction ranges from 1.0% to 2.5%,2,3,12-16 where 8.0% to 10.0%6,17 of these cases are bilateral (Table I). Impaction of remaining teeth in the permanent dentition is quite rare and its documented prevalence ranges only from 0.04% to 0.35%.13 Considering gender and location, impaction of the maxillary permanent canine is twice as common in females.6 Palatal impaction of the maxillary permanent canine has been reported to occur approximately 3 times more frequently than facial impaction.18 In a more recent investigation using cone-beam computed tomography (CBCT), 45.2% of maxillary canines were
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Table I. Prevalence and male/female ratio for unilateral maxillary canine impaction Investigators
Location
n
Age, y
Prevalence
Dachi, 1961 Bass, 196715 Rayne, 196916 Thilander, 19683
Dental school, Portland, OR Royal Victoria Hospital, Bournemouth, England Department of Oral Surgery, Oxford, England School system, Umeå, Sweden
1685 9102 12,000 384
13-20⫹ 10-20
0.92% 1.65% 1.5% 1.8%
Grover, 19852 Ericson, 198612
Walter Reed Medical Center, Washington, DC Departments of Oral and Maxillofacial Radiology and Orthodontics, Jönköping, Sweden
13
5000 505
Unclear Followed from mean ⫽ 11.5 – mean ⫽ 17.8 17-26 8-12
1.42%*** 1.7%
Male: Female 0.5:1 0.5:1 — 4:3 — —
—, Information was not reported by the authors.
impacted labially, 40.5% were impacted palatally, and 14.3% were impacted in the midalveolus.19
nates the need for a second surgical procedure if spontaneous eruption fails to occur.
DIAGNOSIS In subjects with a canine retained in the maxillary arch, after the normal period of growth, the diagnosis of impacted maxillary canine is immediate. Conversely, in a patient with developing dentition, maxillary canine impaction is more difficult to diagnose. The presence of certain clinical conditions, such as lack of available arch space, have been considered as risk factors significantly correlated to lack of spontaneous eruption.1,12,20,21 However, this may be dependent on the location of the impacted tooth. According to Jacoby,22 approximately 85% of palatally impacted maxillary canines have sufficient arch space for eruption, whereas only 17% of impacted maxillary canines are located in a facial position. Increased angulation of the canine long axis with respect to the interincisor vertical midline has also been associated with risk of impaction.12 Information on the prevalence of spontaneous eruption of the impacted maxillary canine in growing subjects is lacking. Data are available only on the prevalence of spontaneous eruption of impacted maxillary incisors.21 Sixty-three patients with retained permanent maxillary incisors were followed after removal of the associated supernumerary tooth/teeth. Only 50% of these teeth erupted without surgical and orthodontic assistance. No relationship could be determined between spontaneous eruption and several potential risk factors, which included patient age, number of supernumeraries, extent of root formation, and marked apical displacement of the impacted tooth. In a similar study, 53 children had surgical removal of supernumerary teeth associated with impaction of maxillary incisors.20 Approximately half of the patients required a second operation to facilitate orthodontic forced eruption of the impacted tooth. Because only 50% of impacted teeth seemed to erupt without orthodontic assistance, these studies support immediate application of orthodontic forces after surgical exposure. This elimi-
PATIENT ASSESSMENT Clinical evaluation of the patient with an impacted maxillary canine is initiated by careful inspection of the labial and palatal tissues, and measurement of the width of keratinized gingiva present in the canine area. During the visual examination, the clinician will evaluate arch space available and maxillary lateral incisor inclination. Afterward, palpation is performed labially and palatally in search for the canine bud. This provides information regarding potential location of the impacted canine and periodontal anatomy.23,24 If the primary canine is present, mobility is assessed. The presence of significant mobility may relate to eruptive movement of the permanent canine. Also, periodontal parameters of adjacent teeth should be recorded, including the amount of keratinized gingiva, presence of tooth mobility, and attachment loss. RADIOGRAPHIC ASSESSMENT Radiographic methods used for localization of impacted maxillary canines include orthopantomogram, lateral cephalometry, parallax method, occlusal radiography, CT, and CBCT with or without use of stereolithographic models.23,25 Lateral cephalometry has overlap as its major disadvantage for evaluation of impacted maxillary canines. CBCT scans are useful for determining presence of lateral incisor root resorption and precise location of the impacted tooth.19,25 However, CT and CBCT scans are more costly and have higher radiation exposure compared with conventional radiography26-28; therefore, they are often reserved for complex cases that have other imaging requirements or when localization of impacted canines cannot be determined with traditional methods. As CBCT technology advances, more affordable 3-dimensional imaging with decreased radiation exposure will become available. In the near future, increased CBCT usage compared with conventional techniques is expected. At this time, or-
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Fig. 1. A, The maxillary left impacted canine is approaching a position medial to the long axis of the adjacent lateral incisor, which suggests palatal impaction in the orthopantomogram. B, However, the corresponding lateral incisor inclination shown in the clinical photograph suggests labial or midcrestal impaction. Palatal impaction is expected for the maxillary right canine. Its cusp tip is medial to the adjacent lateral incisor long axis, which presents with normal inclination seen clinically.
thopantomogram and parallax methods are the most commonly selected and their use is described in more detail herein. The orthopantomogram yields a 2-dimensional view of maxillary canine location. If the cusp tip of the maxillary canine is medial to the long axis of the adjacent lateral incisor, palatal location is most probable.29 If the cusp tip of the canine radiographically overlaps the root of the adjacent lateral incisor and is palpated labially, labial impaction is suspected. Severe tipping of the adjacent maxillary lateral incisor often accompanies labial canine impaction with this type of medial radiographic orientation (Fig. 1, A and B). Ericson and Kurol30 examined prognostic factors for orthodontic treatment of maxillary impacted canines based on the radiographic presentation on orthopantomograms. According to the authors, as the canine cusp tip approaches the midline and the inclination of its long axis increases, an increased length of orthodontic treatment time is expected. In addition, the risk of root resorption of the adjacent lateral incisor is increased. In a separate investigation, Crescini et al.31 evaluated the prognostic role of pretreatment radiographic features on the posttreatment periodontal status of intraosseous impacted maxillary canines. Pretreatment variables included tooth location and inclination on panoramic radiographs. Posttreatment variables included pocket depth and width of keratinized gingiva. Based on their results, no pretreatment radiographic findings could be used as prognostic indicators of the final periodontal status of orthodontically repositioned maxillary canines.31 The parallax method, also known as Clark’s rule (Same Lingual Opposite Buccal [SLOB]), is a radiographic technique used to detect an object’s spatial orientation. Briefly, 2 periapical radiographs are taken at different x-ray tube projection angles. During comparison of these radiographs, a radiographic reference point is selected on the image and the impacted tooth is related to this reference.32,33 If the impacted tooth appears to shift in the same direction as the second x-ray
tube projection, it is located on the lingual aspect and vice versa (Same-Lingual Opposite-Buccal). For example, if the x-ray tube is shifted in a distal direction and the canine moves distally with respect to a selected radiographic reference, the location is determined as palatal (Fig. 2, A and B). Shifting periapical radiographs can help to provide more information about the 3-dimensional location of the impacted tooth.
CLINICAL CLASSIFICATION AND TREATMENT PLANNING Surgical approach will be based on the location of the impacted tooth. A classification with 3 categories is presented (Table II). Class I A Class I impacted maxillary canine is located palatally. For this category of impacted canines, a surgical approach with gingivectomy is recommended. Immediately after exposure of the impacted tooth, a fixed attachment appliance should be connected (Fig. 3). Advantages of this approach include relative simplicity of the procedure, potential for spontaneous eruption following surgical exposure, and presence of a fixed attachment should spontaneous eruption fail to occur.34 According to Schmidt and Kokich,35 most palatally impacted canines will spontaneously erupt with simple surgical excision of the overlying palatal tissue. Conversely, Ferguson and Parvizi34 showed that 5.1% of impacted canines exposed with gingivectomy required a second surgical procedure because of lack of spontaneous eruption. Immediate application of orthodontic force after surgical exposure of a palatally impacted canine should be considered with caution.1 A lateral direction of erupting force may result in impaction of the crown against the alveolar process. This can induce nonphysiologic bone resorption that may increase the duration of orthodontic treatment.1
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Fig. 2. In this series of periapical radiographs, the x-ray tube was shifted distally for radiograph B in relation to radiograph A. Because the canine appears to have moved in a mesial direction, its position is toward the labial according to the buccal object rule.
Table II. A proposed classification for the surgical approach of maxillary impacted canines Classification
Location
I II
Palatal Center of alveolar ridge or labial Labial to long axis of adjacent lateral incisor root
III
Surgical technique Gingivectomy Repositioned flap Apically positioned flap
Potential for a longer postoperative recovery period is the primary disadvantage reported for gingivectomy.36 Postoperative discomfort questionnaires and evaluation of analgesic usage have been studied to assess differences in pain threshold between open and closed eruption approach in the management of impacted maxillary canines. Chaushu et al.36 found a longer recovery period for the open compared with the closed approach. However, no difference in general daily activity was noted. Class II A Class II impacted maxillary canine is located in the center of the alveolar crest or labial to the alveolar crest, but not superimposed labially to the root of the adjacent lateral incisor. In this case, a closed eruption technique using a repositioned flap is recommended (Fig. 4, A and B).18,37-41 For the closed eruption technique, a full-thickness mucoperiosteal flap is reflected, allowing the clinician adequate access to the impacted tooth. Following follicular debridement, a fixed attachment is bonded to the impacted tooth, including a wire or chain. The crestal incision should be made with 3
Fig. 3. Gingivectomy is the recommended surgical procedure for a palatally impacted canine. A gold button and chain were attached at the time of surgical exposure.
mm of keratinized gingiva labial to its location. Afterward, the flap is returned to its original position and sutured. The wire or chain will exit the flap and the labial keratinized gingiva is totally preserved (Fig. 4, B). Ideally, depending on the direction of force, this surgical technique can facilitate forced eruption through an adequate zone of keratinized gingiva. In cases where keratinized gingiva is lacking, the patient must be informed that a revision with additional mucogingival surgery may be needed to optimize esthetics. The primary advantages of this technique include less postoperative discomfort compared with gingivectomy,36 as well as management of forced eruption through a zone of keratinized gingiva. Disadvantages include increased technique sensitivity, related to
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Fig. 4. The maxillary left canine is positioned apically to the mucogingival junction and labially in the alveolar process. A, A repositioned flap procedure was used. B, A chain was connected to the impacted tooth, exiting the flap through the crestal incision after suturing.
proper soft tissue flap management, and increased length of surgical treatment time, compared with the open eruption approach. Class III A Class III impacted maxillary canine is located labial to the root of the adjacent lateral incisor. The radiographic evaluation of an orthopantomogram will reveal a canine with its cusp tip over the root of the lateral incisor, whereas the tooth bud will be palpable labially. The lateral incisor is usually inclined palatally to accommodate this orientation. For impacted canines in a Class III position, an apically positioned flap (window flap)17 is indicated.39 A partial thickness dissection, including 2 to 3 mm of the coronally attached gingiva is carried out. The flap is then apically positioned using 2 parallel, vertical releasing incisions (Fig. 5). Using this approach, the clinical crown of the impacted tooth will be completely exposed. This allows the orthodontist to visualize the impacted tooth. Eruption force vectors may then be selected minimizing potential damage to the lateral incisor.39 Also, following this technique, the width of the keratinized gingiva will increase during orthodontic forced eruption.42 Hence, increase in the visibility of tooth orientation and preservation of keratinized gingiva are the primary advantages of this approach. Disadvantages of the window flap include its higher level of technique sensitivity compared with gingivectomy and repositioned flap previously described. Also, several authors have reported complications, including risk of soft tissue recession and inadequate access to labial bone.1,18,37,38 For class II and class III canine impaction, the application of orthodon-
Fig. 5. The maxillary right canine is positioned labial to the long axis of the adjacent lateral incisor root. An apically positioned flap (Window flap) was performed. (Courtesy of Dr. Murad Shaqman.)
tic force should start within a few days after surgical exposure.1
DISCUSSION A surgical classification of impacted maxillary canines has been presented relating the width of keratinized gingiva and tooth location to the recommended surgical approach. Several potential complications may arise following surgical exposure and orthodontic forced eruption of the impacted maxillary canine, including root resorption, periodontal defects, poor esthetic outcome, and immobility. Root resorption of incisors occurs quite commonly when adjacent to impacted maxillary canines. The
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prevalence is higher in females compared with males ranging from 2:1 up to 10:1.43-47 Using CBCT, 27% to 38% of adjacent laterals and 9% to 23% of adjacent centrals have been shown to exhibit root resorption associated with an impacted canine.19,48 Although there has been anecdotal concern of periodontal complications following forced eruption of impacted maxillary canines, no significant increase in periodontal pocket depth, recession, or width of keratinized gingiva has been reported.10,17,31 In a retrospective study, the esthetic outcome on 16 patients treated with forced eruption of unilaterally impacted canines was evaluated. A panel of orthodontists and orthodontic residents were able to identify the previously impacted tooth 78.9% of the time in posttreatment photographs.35 Several reasons for identification include torque/tooth inclination (28%), attached gingiva height compared with contralateral tooth (27%), alignment (17%), crown length/wear (13%), and recession (6%). To optimize esthetic outcome, orthodontic finishing tooth movements and surgical soft tissue management require careful attention to detail. There are 3 possible causes of immobility: (1) bone remaining around the crown of the impaction, (2) inappropriate orthodontic mechanics, and (3) ankylosis.1 Literature reporting the prognosis of treatment in relation to immobility is lacking. If forced eruption of the impacted tooth is unsuccessful, other prosthodontic options for tooth replacement may be considered, including extraction followed by implant placement, conventional fixed dental prosthesis, and removable prosthesis. Dental implant placement may have complications associated with extraction of the impacted tooth. Hence, reconstruction of the alveolar process may be necessary to optimize the esthetic outcome. Fixed prosthodontic options, such as mesial cantilever and 3-unit fixed dental prosthesis have acceptable long-term survival49-52; however, these often require preparation of an otherwise healthy, noncarious or restored tooth. Questionable long-term and short-term survival has been reported for resin-bonded fixed dental prostheses.53-55 More evidence is needed regarding orthodontic prognosis of forced eruption postsurgical exposure.
CONCLUSIONS The impacted maxillary canine poses challenging interdisciplinary diagnoses and treatment. The proposed classification provides guidelines for selecting the surgical approach based on impacted tooth location and anatomical factors. Special thanks to the University of Connecticut Health Center, Department of Orthodontics, for their refe-
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