Today, most patients seeking correction of malalignment

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1 ORIGINAL ARTICLE Analysis of failure in the treatment of impacted maxillary canines Adrian Becker, a Gavriel Chaushu, b and Stella Chaushu c Jerusalem and Tel-Aviv, Israel Introduction: In this study, we aimed to evaluate the reasons for failure of orthodontic treatment for impacted maxillary canines and to recommend measures to overcome them. Methods: Twenty-eight patients (ages, years) with 37 maxillary impacted canines were referred after a failed attempt to resolve the impaction. Reasons for failure were analyzed, and corrective measures undertaken. The success rate of the revised treatments and the durations of both treatments were recorded. Results: The mean duration of the failed treatments was months. The failed treatments were mostly based on plane radiographs, intra-arch dental anchorage, and elastic traction directly to the labial archwire. The major reasons for failure were inadequate anchorage (48.6%), mistaken location and directional traction (40.5%), and ankylosis (32.4%). In several patients, there was more than 1 possible reason for failure. The success rate of the revised treatments was 71.4%, and the mean duration was months. Repeat surgery was needed for 62.9% of the canines in which corrective treatment was started, mostly to redirect the ligature wires. The corrective measures included the use of 3-dimensional imaging and a change in the direction of traction. Anchorage was reinforced by dental and skeletal means. Conclusions: Inaccurate 3-dimensional diagnosis of location and orientation of impacted teeth and failure to appreciate anchorage demands were the major reasons for failure in the treatment of impacted canines. (Am J Orthod Dentofacial Orthop 2010;137:743-54) Today, most patients seeking correction of malalignment and malocclusion of the erupted dentition are assured of a predictable, superb treatment outcome. This is reflected in the exacting demands established by the various examining bodies that have been set up worldwide to regulate the admission of professionals aspiring to the rank of specialist orthodontist or an equivalent title, and in the case presentations published in the clinical orthodontic literature. However, when the patient s malocclusion includes an impacted tooth, particularly a maxillary canine, some apprehension, doubt, or uncertainty creeps into the equation. The proposed treatment plan is usually accompanied by a warning to the patient that treatment of this particular element in the overall treatment plan might fail. a Clinical associate professor emeritus, Department of Orthodontics, Hebrew University, Hadassah School of Dental Medicine, Jerusalem, Israel. b Associate professor, Department of Oral and Maxillofacial Surgery, Maurice and Gabriela Goldschleger School of Dental Medicine, Tel-Aviv University, Tel-Aviv, Israel. c Associate professor and Chair, Department of Orthodontics, Hebrew University, Hadassah School of Dental Medicine, Jerusalem, Israel. The authors report no commercial, proprietary, or financial interest in the products or companies described in this article. Reprint requests to: Stella Chaushu, Department of Orthodontics, Hebrew University, Hadassah School of Dental Medicine, PO Box 12272, Jerusalem 91120, Israel; , drchaushu@gmail.com. Submitted, May 2008; revised and accepted, July /$36.00 Copyright Ó 2010 by the American Association of Orthodontists. doi: /j.ajodo The chief reason for this striking contrast includes the many complicating factors related to the impacted tooth that are not normally present in a fully erupted dentition. Thus, it is difficult to determine accurately the 3-dimensional (3D) position of the tooth in relation to both its crown and root, and the proximity to the roots of other teeth. 1-3 It is nearly impossible to clinically examine for crown anomaly, color, shape, mobility, and pathology of an impacted tooth. Surgery is needed, and it is difficult to determine directionally suitable orthodontic forces that will resolve the impaction, and whether they should include extrusion, rotation, crown tipping, or root uprighting components. 4,5 Treatment is likely to be extended and painful, 6 and the periodontal prognosis of the outcome is difficult to predict. 7-9 Analysis of the reasons for failure must consider many factors, which can be roughly divided into 3 groups as follows. 1. Patient-dependent factors: abnormal morphology of the impacted tooth, age, pathology of the impacted tooth, grossly ectopic tooth, resorption of the root of an adjacent tooth, and lack of compliance (eg, missed appointments, inadequate oral hygiene). 2. Orthodontist-dependent factors: mistaken positional diagnosis and inappropriate directional force, missed diagnosis of resorption of the root of an 743

2 744 Becker, Chaushu, and Chaushu American Journal of Orthodontics and Dentofacial Orthopedics June 2010 adjacent tooth, poor anchorage, inefficient appliance, and inadequate torque. 3. Surgeon-dependent factors: mistaken positional diagnosis, exposure on the wrong side, or rummaging exposure; injury to the impacted tooth; injury to an adjacent tooth; soft-tissue damage; and surgery without orthodontic planning. The purpose of this article was to examine the records of patients with an impacted tooth whose original orthodontic treatment did not resolve the impaction. The patients were referred to one of the authors. We analyzed the reasons for failure of the initial treatment approach, devised an alternative treatment approach, and evaluated its success. MATERIAL AND METHODS A sample of 28 patients (18 female, 10 male; ages, years) with 37 impacted canines was assembled from the private practices of the 3 authors. The patients initial records showed that 26 impactions were palatal, 9 were buccal, and 2 were in the midalveolus. All patients had been treated elsewhere for a malocclusion that included at least 1 impacted maxillary canine that did not respond to treatment. They were referred by general practitioners or orthodontists and were taken consecutively in the referral system for inclusion in our investigative sample. In this study, an orthodontist was defined as a dentist who has received specialty training in a state-recognized university graduate orthodontic course. Of the sample, 9 patients had bilateral impaction of the canines, and each failed canine was considered separately in the study. From the patient records, the following treatment information was gathered. 1. Details related to the initial treatment: had the treating practitioner received specialist orthodontic training (as detailed above) with more or less than 10 years of postgraduation experience, or was he or she a general practitioner with more or less than 10 years since graduating from dental school; was the patient transferred in relation to the surgical exposure (before, after); was the patient transferred in relation to the stage of orthodontic treatment (before orthodontic treatment or after the failed treatment); was radiographic documentation used for the original diagnosis; how many times was surgical exposure performed on the tooth; was the surgery successful; how was traction applied (patients were differentiated into those whose traction was performed directly to the labial archwire and those whose traction had 2 stages, first vertically downward to clear the root of the incisor and then laterally into its place in the arch); was the anchorage base intra-arch dental, interarch dental, extraoral, or implant; how much time elapsed between the start of treatment and the realization of failure; and what were the assumed reasons for failure. 2. Details related to the second orthodontic treatment: were additional radiographic records needed; what was the outcome of revised treatment (success or failure); how long was the revised treatment; what were the revised reasons for initial treatment failure; and what corrective measures were adopted (new surgery, altered direction of traction, reinforced anchorage). RESULTS The patients were referred by 26 clinicians. Twenty were specialists, including 15 who had over 10 years of experience, and 6 were general practitioners, including 3 with more than 10 years of experience. Most patients (26 of 28; 92.9%) were referred after surgery had been performed. In 2 (patients 11 and 22), space had been prepared for the impacted teeth without surgery. It had been optimistically expected that the teeth would erupt spontaneously, but that had not occurred. Twenty-five patients (89.3%) had been referred during active orthodontic treatment and 3 after the treatment was stopped because of failure. Table I describes the initial treatment plans. Panoramic and cephalometric films were available for all patients, together with variable numbers of periapical views. Two patients had undergone 3D imaging, one (patient 8) with conventional spiral computed tomography (CT), and the other (patient 12) with cone-beam CT (CBCT). Among the 35 canines that had previously been exposed, 10 (28.6%) had had 3 such episodes. In 1 bilateral case (patient 3), who had been treated by open exposure, the bonded attachments had failed on both canines, and the tissues had subsequently rehealed over the teeth. In 2 (patients 6 and 24), the surgeon had failed to find the impacted tooth because of misdiagnosis of labiolingual location. Elastic traction, directly to the arch, was used for 26 canines. For the 7 canines treated in 2 stages, an auxiliary spring was used, with the express aim of erupting the canine into the palate as the initial maneuver. The orthodontic anchorage used in all patients in this sample consisted exclusively of intraoral dental anchorage from other dental units with fixed bonded appliances; this was therefore omitted from Table I. The mean duration of treatment, from start to realization of failure, was months. The reasons for failure, as assumed

3 American Journal of Orthodontics and Dentofacial Orthopedics Becker, Chaushu, and Chaushu 745 Volume 137, Number 6 Table I. Descriptions of initial treatments Patient Records Surgeries (n) Traction Duration (mo) Assumed reason for failure 1 P, C, Pa 1 D 72 Unknown 2 P, C, Pa 1 D 40 Unknown 3 P, C, Pa, O 2 D 10 Attachment failure P, C, Pa, O 2 D 10 Attachment failure 4 P, C, Pa 1 D 12 Unknown 5 P, C, Pa 1 D 54 Unknown 6 P, C, O 1 X 10 Surgical 7 P, C, Pa 3 D 8 Attachment failure 8 CT 1 D 20 Ankylosis, incisor root resorption 9 P, C, Pa 1 D 36 Not enough time 10 P, C, Pa 1 D 32 Erupted intractable P, C, Pa 1 D 32 Erupted intractable 11 P, C, Pa - X 54 Inadequate follow-up 12 CT 1 D 35 Ankylosis CT 1 D 35 Ankylosis 13 P, C, Pa 1 TS 48 Ankylosis, incisor root resorption 14 P, C, Pa 1 D 36 Incisor root resorption 15 P, C, Pa 1 D 23 Incisor root resorption 16 P, C, Pa 3 D 39 Ankylosis 17 P, C, O 3 D 48 Ankylosis P, C, O 3 D 48 Ankylosis 18 P, C D 12 Unknown 19 P, C, Pa 3 D 28 Ankylosis 20 P, C, Pa 1 D 48 Unknown 21 P, C, Pa 1 D 30 Ankylosis 22 P, C, PA - X 30 Intractable position 23 P, C 1 D 18 Incisor root resorption P, C 1 D 18 Incisor root resorption 24 P, C, Pa 3 X 9 Surgical 25 P, C, O 1 D 9 Ankylosis P, C, O 1 D 9 Ankylosis 26 P, C, O 3 TS 7 Ankylosis P, C, O 3 TS 7 Ankylosis 27 P, C, Pa 1 TS 7 Ankylosis P, C, Pa 1 TS 7 Ankylosis 28 P, C, Pa 3 TS 14 Ankylosis P, C, Pa 3 TS 14 Ankylosis P, Panoramic; C, cephalogram; Pa, periapical; O, occlusal; CT, computerized tomography; D, direct traction to archwire; TS, 2-stage traction; X, surgery failed to find the tooth (patients 6 and 24) or spontaneous eruption failed to occur (patients 11 and 22). Two rows for a patient indicate bilateral impactions. by the practitioners, were ankylosis (17 teeth, 45.9%), incisor root resorption (6 teeth, 16.2%), intractable position (3 teeth, 8.1%), attachment failure (3 teeth, 8.1%), surgical failure (2 teeth, 5.4%), and inadequate follow-up period (2 teeth, 5.4%). In 6 teeth (16.2%), the orthodontist could find no explanation for the failure, and, for 2 patients, 2 reasons were given. Table II shows the supplementary records that were considered necessary for each patient. As the result of the new information and consequent practical steps taken, the success rate of the revised treatment plans was 67.6% for the whole group. However, 2 patients (2 canines) refused more treatment, yielding an actual success rate of 71.4%. The mean duration of the new treatment in the successful patients was months. After this, it became possible to diagnose the reasons for failure in each patient more accurately. The major causes were poor anchorage (18 teeth, 48.6%), mistaken positional diagnosis and directional traction (15 teeth, 40.5%), and ankylosis (12 teeth, 32.4%). Seven ankylosed teeth were treated by surgical luxation and subsequent traction, but only 3 were successfully brought in their place in the arch. In 5 patients (6 teeth, 16.2%), resorption of the incisor roots had escaped the practitioner s notice until treatment was advanced. Three teeth (8.1%) failed to erupt because of interference of soft tissues. In 3 patients (8.1%), inadequate space was considered to be a cause for noneruption. In one (patient 6), surgery was initially performed at the wrong site, and, in another patient (24), the tooth was in an extremely difficult position; therefore, these teeth remained unexposed after surgical intervention. In 2 patients (11 and 22), traction was never applied, and the first practitioner waited in vain for 54 and 30 months, respectively, for the teeth to erupt unaided. Repeated bond failure of the attachments after surgery in 2 patients (3 and 7) accounted for treatment failure. In 1 patient (24), both the first practitioner and the surgeon did not realize that the canine crown was situated on the palatal side between the central and lateral incisors, but its root was labial to the root of the lateral incisor. This created an intractable situation, from which there was no possibility of saving the tooth. In 1 patient (5), the treatment failed because of poor compliance (missed appointments) and inefficient appliances. In several patients, there were 2 or more possible reasons for failure. Table III summarizes the corrective measures taken for this group of potentially failed patients. Surgery was needed for 22 of the 35 canines (62.9%). Of these, 7 (in 5 patients) were to redirect the ligature wires to permit a change in direction of traction, 3 (in 3 patients) to clear soft tissues, 7 (in 4 patients) to luxate ankylosed canines; 3 teeth needed bond attachments, and 2 were reoperated to expose them in their newly diagnosed positions. In 2 patients, exposure was performed for the first time. Orthodontic corrective measures included the application of traction in 4 canines to which forces

4 746 Becker, Chaushu, and Chaushu American Journal of Orthodontics and Dentofacial Orthopedics June 2010 Table II. Descriptions of the revised treatments Patient Additional records Outcome Treatment duration (mo) Revised reasons for failure 1 No S 10 Direction, space, anchorage 2 No S 6 Direction, anchorage 3 No S 8 Attachment failure after surgery No S 8 Attachment failure after surgery 4 No S 6 Inadequate space 5 No S 12 Missed appointments, inefficient appliance 6 CT S 14 Exposure in wrong site 7 No S 12 Attachment failure, direction 8 No S 10 Soft tissue, anchorage, incisor root resorption 9 No S 11 Direction, space, anchorage 10 No S 17 Direction, anchorage No S 17 Direction, anchorage 11 CT S 6 No traction applied 12 No F - Ankylosis No F - Ankylosis 13 CT S 15 Direction, soft tissue, anchorage, incisor root resorption 14 Pa S 16 Direction, incisor root resorption 15 CT S 18 Incisor root resorption, direction, anchorage 16 No S 9 Ankylosis*, anchorage 17 No F - Ankylosis, anchorage No F - Ankylosis, anchorage 18 No S 8 Direction 19 CT No treatment - Unknown 20 CT No treatment - Direction 21 CT F - Ankylosis, anchorage 22 CT S 30 No traction applied 23 CT S 27 Incisor root resorption, direction CT S 27 Incisor root resorption, direction 24 CT F - Intractable (pseudotransposition) 25 No F - Ankylosis, direction No F - Ankylosis, direction 26 No F - Ankylosis, anchorage No F - Ankylosis, anchorage 27 No S 12 Soft tissue, anchorage No S 12 Soft tissue, anchorage 28 Pa S 25 Ankylosis*, anchorage Pa S 25 Ankylosis*, anchorage S, Success; F, failure; CT, computerized tomography; Pa, periapical. Two rows for a patient indicate bilateral impactions. *Canines whose ankylosis was resolved with surgical luxation, and the teeth were successfully brought into their place in the arch. had never been applied. A change in the direction of traction was mandatory for 15 canines. Anchorage was reinforced by various methods in 18 canines and included heavier base archwires, intermaxillary elastics, and temporary implant devices in the more recent cases. Additional space was needed in 2 patients (2 canines). Case presentations Patient 6 had a mistaken positional diagnosis of the labially impacted canine. The original clinician had referred the patient for full photographic facial and dental records, and cephalometric, panoramic, and anterior occlusal views (Fig 1).Basedonthese,she assumed that the canine was displaced on the palatal side, close to the midline. Using fixed multibracketed appliances, she had aligned and leveled the teeth to create space in the appropriate location. The patient wasthenreferredtoanoralandmaxillofacialsurgeon for surgical exposure. The surgeon reflected a palatal flap, removed bone on that side of the incisors, but failed to find the canine. He then sutured the flap back to its former place and sent the patient back to the orthodontic practitioner, who consulted with one of the authors (A.B.). Figure 2 shows the aligned and leveled dentition at the consultation visit. It also shows the iatrogenic periodontal defect on the palatal side of the left central incisor, caused by the futile surgical exposure.

5 American Journal of Orthodontics and Dentofacial Orthopedics Becker, Chaushu, and Chaushu 747 Volume 137, Number 6 Table III. Correctives measures taken in the revised treatment Corrective measure Number of teeth Surgical Expose in revised (correct) location 2 Reexpose to bond attachments 3 Reexpose to change the direction of ligatures 7 Reexpose to remove soft tissue 4 Luxation 7 Total number of teeth reoperated 22 Expose teeth not previously exposed 2 Orthodontic Apply traction when it had not been 4 applied before Reevaluate position and change direction 15 of traction Reinforce anchorage 18 Create space 2 Comparing these pictures with the initial clinical photographs shows how this stage of treatment had eliminated the clinical signs that were present initially, which should have indicated to the practitioner and the surgeon that the impacted canine was on the labial side. Moreover, this could have been positively confirmed by using the vertical parallax method of diagnosis, from the plane radiographic panoramic and anterior occlusal views that had been commissioned at the outset (Fig 1). Before the recommencement of treatment, a CBCT image (Fig 3) was taken to diagnose or negate any pathologic changes from the earlier orthodontic and surgical procedures and to accurately locate the tooth in 3 dimensions, along its entire length. The canine was exposed on the labial side (Fig 4, A) and aligned in the normal way with 2-stage traction first to the labial (Fig 4, B) and then to the distal to circumnavigate the root of the lateral incisor. The clinical and panoramic views at 5 years posttreatment show the alignment achieved and the similarity between the treated and untreated sides (Fig 5, A, B, and D). However, the palatal gingival defect from the first surgical procedure remained (Fig 5, C). For patient 23, the diagnosis of severe incisor root resorption was missed. Based on the clinical examination and a panoramic view, the first practitioner had diagnosed bilaterally impacted canines, with the right canine palatally and the left canine labially displaced (Fig 6). Surgical exposure was attempted after 15 months of active orthodontic treatment with fixed multibracketed appliances, during which the teeth had been aligned and leveled. No new radiographs were taken at this stage. It was only at the time of surgery that the surgeon noted severe root resorption of the adjacent incisors and recorded the condition both photographically and radiographically (Fig 7). He nevertheless bonded attachments to the canines, closing the surgical flap and referring the patient to an author (S.C.). A CBCT image was used to evaluate and confirm the severity and form of incisor root loss (Fig 8). Reoperation was indicated, especially for the palatal right canine, to redirect the ligature wires that had initially been drawn in the direction of the canine s final and desired location (Fig 9). This was done to permit the canine to be moved away from the incisors in the first stage. Figure 10 shows the final alignment of both canines and the radiographic view of the incisor area at 24 months posttreatment. The extent of root resorption, the regeneration of bone, and a distinct lamina dura around each tooth can be clearly seen. DISCUSSION The prevalence of canine impaction in the general population of most Western countries has been variously described as between 0.92% and 2.4% Since this problem is a local etiologic factor leading to malalignment and malocclusion of the teeth, it must be assumed that in any orthodontic practice there will be a disproportionately larger number of patients who suffer from this anomaly. Many will be treated successfully, but, as can be seen in this study, some clinicians will fail to resolve the impaction in at least 1 patient and will find it necessary to either refer the patient elsewhere to improve the chances of success or advise extraction. This appears to have no relationship to whether the clinician has had orthodontic specialist training or has many years of clinical experience. However, by its very nature, our sample was unquestionably biased, since affected patients will be usually treated by specialists, and most generalists will not undertake cases of this nature. Nevertheless, this study demonstrates that many specialists are inadequately equipped to diagnose the anomaly and frequently become aware of the problem only when treatment for the overall malocclusion is well advanced. Furthermore, although the treatments we analyzed had included all the elements needed for a successful treatment, including orthodontics and surgical exposure in every patient, with the exception of 2 patients, they had all failed. The orthodontic treatment for these 2 patients had been expected to cause the autonomous eruption of the teeth, without the need for surgery, when adequate space was provided. Even the waiting periods of 36 and 54 months had been insufficient to generate

6 748 Becker, Chaushu, and Chaushu American Journal of Orthodontics and Dentofacial Orthopedics June 2010 Fig 1. Patient 6: pretreatment views. Fig 2. Patient 6: clinical views at the referral consultation. Fig 3. Patient 6: CBCT images. A, Paraxial view (vertical slice) through the central incisor; B, axial view (horizontal slice). autonomous eruption. This indicates questionable judgment in the assessment of the patients in general and a lack of appreciation of the potential complexity of the problem in the treatment plan. Advancing age has been shown to reduce the chances of orthodontic resolution of impacted teeth, specifically in the fourth decade of life and beyond In our sample, only 1 patient (25) was over 30 years of age, and both maxillary canines were ankylotic and could not be moved. The initial location for 34 of the 37 impacted teeth in this sample had been determined with plane film

7 American Journal of Orthodontics and Dentofacial Orthopedics Becker, Chaushu, and Chaushu 749 Volume 137, Number 6 Fig 4. Patient 6: A, surgical exposure of the canine; B, auxiliary labial archwire in its active position, ligated into the pigtail ligature from the impacted canine; this exerts both labial and mildly distal forces. Fig 5. Patient 6: clinical views 5 years posttreatment. A, Normally erupted right canine; B, formerly impacted left canine; C, occlusal view showing the residual periodontal defect; D, panoramic view. (2-dimensional) radiography. Since it is not possible to depict depth on plane film radiographs, the buccolingual location of the crown, the orientation of the long axis, and the location of the root apex all need to be indirectly constructed from these and other radiographic views of the same tooth, taken at different angles This can be a complex assessment and is notoriously difficult to achieve with accuracy, considering the number of misdiagnoses that are made. As a result, patients with a tooth that buccolingually straddles the alveolar ridge (eg, patient 24) can be wrongly assessed as treatable with a good prognosis. Accurate diagnosis of the location of the tooth will permit a skilled surgeon to cause the least surgical trauma during the exposure episode, will dictate where the attachment is to be bonded, and is responsible for the decision to direct the forces of traction in a line that will lead to successful resolution. 5 Because of the absence of a definitive positional determination, the surgery for patients 6 and 24 was performed in the wrong site, failed to

8 750 Becker, Chaushu, and Chaushu American Journal of Orthodontics and Dentofacial Orthopedics June 2010 Fig 6. Patient 23: pretreatment views. locate the tooth, and, because of the rummaging search, inflicted considerable and superfluous surgical trauma. The other important entity that is difficult to diagnose from plane film radiographs is resorption of the roots of teeth adjacent to the impacted tooth A facially or palatally aberrant tooth is depicted superimposed on the root of a lateral or central incisor in the buccolingual plane. Thus, the most likely site to be affected on the incisor is the labial or lingual aspect of the root, facing and close to the canine. 25 Any consequent flaw in the integrity of the root of the tooth will become visible only on a panoramic or periapical film when resorption has affected the continuity of the mesiodistal profile of the root and only when this is not obscured by the superimposed images. The ultimate answer to all of these potential problems lies in the intelligent use of CBCT. It delineates impacted teeth clearly, in 3 planes of space and in relation to their surrounding structures, both dental and nondental. Furthermore and in contrast with plane film radiography, CBCT is free of projection distortion and eliminates the superimposition of neighboring teeth For the amount of information that it provides, the dosage of ionizing radiation is low, and the method is highly cost-effective, recommending it as a routine diagnostic aid in the proposed treatment of all but the most superficial of impacted teeth. 27 Since the positional diagnoses of the impacted teeth in the sample were almost exclusively made on the basis of plane film radiography, that was at least partially because several patients were treated some years ago, before the introduction of CBCT. Even now, many practitioners are unaware of this modality and its advantages, or consider it superfluous. In the reevaluation of the patients, CT was used in only 10, since the rest had been reviewed some years earlier. In any such reevaluation of a failed case today, CBCT would be considered a mandatory prerequisite. For both labially and palatally displaced canines, the direct path to their rightful place in the arch is frequently impeded by the root of the lateral incisor or, occasionally, even the central incisor. Therefore, to draw the canine in a direct line to this prepared space inevitably brings it into direct contact with the incisor root. In the simpler cases, a minor amount of angular interference can be overcome by an increase in the traction force, but movement of the impacted tooth will be resisted to a greater or lesser extent. Increasing the force will increase the load on the anchor units and lead to loss of anchorage. Furthermore, it might cause incisor root resorption or exacerbate a process that had been present before treatment a condition found in 66.7% of the lateral incisors and 11.1% of the central incisors in patients with maxillary canine impaction. 28 To eliminate this potential source of failure, traction in 2 separate stages and in 2 directions should be started. 30,31 The first stage is to move the impacted tooth away from the root of the incisor and into a location where the tooth has a direct path to its place in the arch. For a palatal canine, this is usually in a slightly palatal but mainly vertically downward direction. Once clear, the tooth can then be drawn buccally, with a simple labial tipping movement toward the labial archwire. Neither of

9 American Journal of Orthodontics and Dentofacial Orthopedics Becker, Chaushu, and Chaushu 751 Volume 137, Number 6 Fig 7. Patient 23: records taken during the first surgical procedure. A, Right canine (palatal); B, left canine (buccal); C and D, right and left periapical radiographs. Fig 8. Patient 23: paraxial views from CBCT. A, Right; B, left. these movements causes much danger of loss of anchorage, and there is no reason to expect resorption of the roots of the adjacent incisors. In terms of mechanotherapy, the second component of this 2-stage movement is simple to design and might take the form of an elastic tie or an auxiliary superelastic labial archwire. 5 However, the first stage of the 2-stage movement requires inventiveness and initiative from the operator in designing a custom-built auxiliary spring that will cause movement in the desired direction, neither along nor toward an archwire In most of these cases, the actual amount of movement, tipping or bodily, is taxing on dental anchorage. Accordingly, before the clinician s attention turns to the resolution of the impacted tooth, he or she should create a composite anchor unit involving all available erupted teeth in the same jaw and, often, in the opposite jaw as well. This is most conveniently done by using as large a base arch as will fill the slots of the brackets on all other teeth, with or without intermaxillary elastics. With the advent of temporary anchorage devices in routine orthodontic treatment, consideration should be given to their use in many of these cases. 34,35 An independent implant system for traction of the canine can be designed and used before or parallel to the regular orthodontic appliances that will be used for the overall malocclusion. 35 In our sample, for failure associated with loss of anchorage in 18 canines, each of the above remedies was variously used in the revised treatments, as indicated.

10 752 Becker, Chaushu, and Chaushu American Journal of Orthodontics and Dentofacial Orthopedics June 2010 Fig 9. Patient 23: clinical view of the right canine. A, At the referral consultation; B, during the repeat surgery to redirect the ligature through palatal tissue; C, traction is applied from a custom built auxiliary archwire with a loop spring to erupt the palatal impacted right canine through the palatal mucosa and away from the resorbed right lateral incisor root; D, the same auxiliary archwire has a second loop to erupt the labially impacted left canine away from the resorbed left lateral incisor root. Fig 10. Patient 23: clinical views 2 years posttreatment. A, Right canine; B, left canine; C and D, right and left periapical radiographs. Ankylosis of the impacted tooth is often an orthodontist s blanket diagnosis to cover all failed cases. However, as we have seen in this study, several of those teeth responded to orthodontic force that was appropriately applied, in terms of force level and direction. Nevertheless, there was a relatively high incidence of ankylosis, which might appear to be difficult to explain, since the incidence of ankylosis of impacted canines in

11 American Journal of Orthodontics and Dentofacial Orthopedics Becker, Chaushu, and Chaushu 753 Volume 137, Number 6 young patients is extremely low. 36,37 Ankylosis and external resorption have been reported as sequelae of orthodontic movement of impacted teeth when damage is caused to the periodontal ligament by ligating the teeth around the neck with a lasso wire. 38 Similarly, an overly ambitious exposure might denude the root surface, or the surgeon might push an elevator into the periodontal attachment of the tooth to loosen up the tooth, thereby injuring the cementum layer. The orthophosphoric acid etchant, in liquid form, can also seep into this area and produce chemical trauma to the cementum. These incidental and seemingly innocent addenda could cause an ankylosis or a cervical root resorption lesion of the impacted tooth; either will effectively stop all further orthodontic movement of that tooth. 5,39 Surgical luxation with appropriate traction was successful in 3 of the 7 teeth that had the procedure. Therefore, this procedure can be offered to the patient, even though its outcome is questionable and has never been addressed in the literature. Before these patients were referred for review of their failed treatments, 15 had already undergone 2.5 years or more of active orthodontic treatment with appliances; 6 others had passed the 1-year mark. The new treatment added a further considerable period of time to the task of attempting to achieve success in what was, in essence, the treatment of a single tooth and not all these attempts were successful. CONCLUSIONS There are many aspects and minutiae involved in the treatment of impacted maxillary canines that, singly or together, can lead to failure of the overall aim of the exercise. This study has shown that failure in this type of treatment is all too frequent for the following reasons. 1. Diagnosis of the location of the tooth and its immediate relationship with the roots of the adjacent teeth is generally treated with cavalier and often negligent simplicity, even though modern technology has provided the tools to achieve this with great accuracy in all 3 dimensions. 2. With inappropriate positional diagnosis, it follows that traction will be applied in the wrong direction. 3. A lack of appreciation of the considerable anchorage requirements of the case and the need to exploit all available means of enhancing them will inevitably lead to inefficient mechanotherapy and unnecessarily longer treatment. 4. Ankylosis might have afflicted the impacted tooth either a priori or as the result of the earlier surgical or orthodontic maneuvers. From this platform, we issue a cri de coeur to encourage the teaching of this subject as a separate entity in graduate orthodontic programs in which it is conspicuously absent at this time. REFERENCES 1. Wolf JE, Mattila K. Localization of impacted maxillary canines by panoramic tomography. Dentomaxillofac Radiol 1979;8: Jacobs S. Exercises in the localisation of unerupted teeth. Aust Orthod J 1987;10:33-5, Chaushu S, Chaushu G, Becker A. The use of panoramic radiographs to localize displaced maxillary canines. Oral Surg Oral Med Oral Pathol Oral Radiol Endod 1999;88: Kokich VG, Mathews DP. Surgical and orthodontic management of impacted teeth. Dent Clin North Am 1993;37: Becker A. The orthodontic treatment of impacted teeth. London: Informa UK Ltd; Chaushu S, Becker A, Zeltser R, Branski S, Vasker N, Chaushu G. 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