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Impacted central incisors: Factors affecting prognosis and treatment duration
ORIGINAL ARTICLE
Impacted central incisors: Factors affecting prognosis and treatment duration Stella Chaushu,a Tal Becker,b and Adrian Beckerc Jerusalem and Tel Aviv, Israel
Introduction: In this study, we aimed to assess the patient and treatment factors that influence the success rate and the duration of the orthodontic-surgical modality for impacted central incisors. Methods: The records of 60 consecutively treated patients (64 impacted incisors) were retrospectively evaluated. The success rate and the duration of each stage of treatment were examined in relation to age, sex, etiology of impaction, location of the impacted tooth, and type of surgical exposure performed. Logistic regression analyses were applied. Results: The group consisted of 26 male and 34 female subjects, 7.0 to 21.9 years old; 27 patients had impactions because of root dilaceration, 29 had impactions because of obstruction, and 4 had impactions with unknown causes. The overall success rate was 90.0%. Five of the 6 failures were dilacerated incisors. The average duration of treatment was 21.6 6 8.7 months. The only factor that significantly increased the duration was the height of the impacted tooth. Dilaceration was related to a longer stage of traction and, in older patients (late mixed and full permanent dentition), to a longer finishing stage. Conclusions: The orthodontic-surgical treatment of impacted incisors is generally successful, but relatively long. Patients and parents should be warned of the risk of failure and the increased treatment duration, especially for dilacerated incisors impacted high in the alveolus. (Am J Orthod Dentofacial Orthop 2015;147:355-62)
A
lthough the prevalence of noneruption or impaction of the maxillary central incisor is low, its occurrence is disfiguring for a young child and of considerable concern to the parents. The causes of this phenomenon can be divided into 2 main groups: obstructive and traumatic causes. The most common obstruction in the anterior maxilla is the presence of at least 1 midline supernumerary tooth.1-3 The frequency with which this occurs has been found to be between 1.5% and 3.5%4 in random population samples, although only between 28% and 60% of these patients will have resultant eruption disturbances of the incisors.5 Odontomes are much rarer findings that cause obstruction in this area, and they may vary in size and type (complex or composite).
a Associate professor and chair, Department of Orthodontics, Hadassah School of Dental Medicine, Hebrew University, Jerusalem, Israel. b Resident, Department of Endodontology, Maurice and Gabriela Goldschleger School of Dental Medicine, Tel Aviv University, Tel Aviv, Israel. c Clinical associate professor emeritus, Department of Orthodontics, Hadassah School of Dental Medicine, Hebrew University, Jerusalem, Israel. All authors have completed and submitted the ICMJE Form for Disclosure of Potential Conflicts of Interest, and none were reported. Address correspondence to: Stella Chaushu, Department of Orthodontics, Hadassah School of Dental Medicine, Hebrew University, PO Box 12272, Jerusalem 91120, Israel; e-mail, [email protected]. Submitted, August 2014; revised and accepted, November 2014. 0889-5406/$36.00 Copyright Ó 2015 by the American Association of Orthodontists. http://dx.doi.org/10.1016/j.ajodo.2014.11.019
Trauma at an early age, before the permanent teeth have erupted, can cause damage to the root-forming cells of the unerupted permanent tooth germ and an attenuated productivity rate of the root portion, and also change the orientation of the tooth in the alveolar process. This results in the development of a dilacerated tooth, which will then not usually erupt unaided.3,6 The parents of a child with an unerupted central incisor, unilaterally or bilaterally, will usually be motivated to seek treatment much earlier than the parents of a child with almost any other orthodontic problem. From the clinical point of view, early treatment is important for the following reasons: (1) an unerupted maxillary central incisor can cause unesthetic and compromised appearance, oral function, and speech; (2) it can cause tipping of adjacent teeth, thus reducing the space for the unerupted incisor; and (3) it is a significant environmental influence in delaying and altering the eruption path of the ipsilateral maxillary canine.7 The available treatment options for this condition include (1) extraction of the tooth followed by prosthodontic rehabilitation; (2) extraction of the tooth and realignment of the lateral incisor into the central incisor position, with the canine and premolar sequentially moved mesially and anatomically modified by grinding, crowning, and so on; or (3) the orthodontic-surgical modality.6 355
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Most patients seeking treatment for impacted central incisors are young children. Therefore, any prosthodontic solution can only be temporary and will need to be modified and updated several times before a more permanent solution becomes possible at age 18 years or so, at the cessation of growth. Extraction of the impacted tooth will also lead to severe alveolar bone loss that will undermine the future implant site. In contrast, the orthodontic-surgical solution aims for complete alignment of the natural teeth and requires no prosthodontic enhancement. The eruption of the impacted tooth draws the surrounding alveolar bone to produce a bony crest height and periodontium similar to those of the adjacent teeth. In the past, it had been assumed that space opening and elimination of the cause would be adequate to produce spontaneous resolution of the impaction. However, evidence-based studies have shown that autonomous eruption occurs in only 54% to 78% of patients,8-10 with a delay of up to 3 years8,10,11 and with spontaneous acceptable alignment occurring in only a few patients.10,12 More recent research has examined the effect of several variables on the eruption of impacted teeth in children after the removal of supernumeraries or odontomes.13 This study found disappointing outcomes regarding spontaneous eruption after extraction of the impediment, which varied in relation to its type and form. The authors did not investigate whether acceptable alignment occurred in the successful subjects, leaving the reader to assume that orthodontic treatment would still be necessary in many patients and justifying the need for a phase 1 procedure. The treatment of impacted central incisors with dilacerations requires a different approach and is usually lengthy and more complicated. This explains why many patients, dentists, and orthodontists prefer surgical repositioning or extraction with prosthodontic rehabilitation as viable alternatives.14 However, attitudes seem to have changed recently, with more case reports of orthodontic treatments appearing in the literature.15-20 In contrast to the parallel situation in regard to impacted canines,21-25 data concerning the success rate and duration of the orthodontic-surgical modality treatment of impacted central incisors are sparse.3,26,27 Most of the articles offer isolated and subjective clinical experiences. In a recent article addressing this subject, the authors did not specify whether the sample comprised only successfully treated patients or consecutively affected patients from their database, and they reported 100% success.26
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The aims of our study were to assess success rates and durations of the orthodontic-surgical modality of treatment of impacted maxillary central incisors in a group of consecutively treated patients and to examine factors that may influence these parameters to give accurate information to patients and parents. MATERIAL AND METHODS
The treatment records of 60 consecutive patients with 64 impacted incisors were gathered between 2002 to 2007 from the orthodontic department of Hebrew University in Jerusalem and from the private practices of the 2 senior authors (S.C. and A.B.). The project was approved by the institutional review board. The inclusion criteria were (1) impacted maxillary central incisors in healthy subjects; (2) a combined orthodontic-surgical approach by one of the 2 senior authors using the same treatment; (3) regular attendance for orthodontic appointments, as determined from the clinical notes; and (4) complete patient records, including diagnostic and treatment entries, pretreatment diagnostically essential radiographic views (good quality panoramic, periapical, and conebeam computed tomography images that were not available for the older patients), banding and bonding date, debanding and debonding date, date of surgical exposure, and date of full engagement of the impacted incisor bracket in the first plain stainless steel archwire. Subjects with craniofacial syndromes, cysts, or cleft lip or palate were excluded from the study. The diagnosis of impaction was made on the basis of a clinical examination and diagnostic plane radiographs. In each patient, the diagnosis was confirmed at the time of the surgical exposure by the orthodontist, who was routinely present for this. Treatment usually followed the order we have described elsewhere.6,28 It commenced with anchorage preparation. In most patients, an updated version of Johnson's twin appliance was used to avoid bonding deciduous teeth that were likely to be shed during treatment.29,30 Anchorage was provided by a palatal arch with or without a Nance button, and brackets were placed only on the erupted incisors. After orthodontic leveling, aligning, and reopening of the incisor space, a small attachment was bonded by the orthodontist to the exposed tooth at the end of the surgical procedure if a closed eruption procedure was performed, or within a few days thereafter in case of open surgery. Traction was applied immediately to the freshly bonded attachment. The tooth was brought to its place in the arch by light orthodontic extrusive traction maintained by the ligature wire.
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In patients with a classic dilaceration, 2 surgical exposures were usually required. The first was a closed procedure, and the second was an apically repositioned flap, open surgical procedure. This second surgery was needed to prevent the incisal edge of the incisor from breaking through the oral mucosa as it was rotated in the buccolingual plane; this was intended to encourage the emergence of the impacted tooth crown through the attached gingiva.28 The main outcome variables were the success rate and the duration of the orthodontic treatment. Treatment was considered successful if the incisor was brought into its place in the arch. The success rate was determined on the basis of the posttreatment records. The success rate was calculated as the percentage of successfully aligned incisors relative to the total number of incisors treated. This stage of treatment was specifically aimed for resolution of the impacted central incisor and was completed when the incisor was properly aligned in the arch. When more comprehensive treatment was considered, only that part of the treatment surrounding the resolution of the incisor was considered, but in general, the treatment of other features of the malocclusion was postponed until the patient was ready for a phase 2 protocol. The length of treatment in months was determined from each patient's records. Total treatment time refers to the period between bonding or banding and debonding or debanding of the orthodontic appliances, and this was arbitrarily divided into 3 constituent treatment periods. 1.
2.
3.
T1, from the date of bonding or banding to the date of the surgical exposure. In this preliminary or preparatory stage, bonding or banding was performed, anchorage was prepared, and space was opened for the impacted tooth. T2, from the date of the surgical exposure to the date that the tooth was fully ligated in the main arch with a nickel-titanium wire. This was the traction stage. T3, from the full ligation into the stainless steel wire to the date of debonding or debanding. During this finishing stage, more complex movements such as rotations, uprighting, and torquing were performed.
Success rate and duration of treatment were classified as follows: (1) age, younger group (\11 years) or older group ($11 years); (2) sex; (3) etiology of impaction, trauma, classic dilaceration (crown angulated labially relative to the root, with the palatal aspect facing labially, Fig 1), obstruction of the path of eruption
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Fig 1. Classic dilaceration: A, panoramic view; B, conebeam computed tomography view.
(supernumerary, odontoma), or unknown; (4) angulation of the impacted tooth to the midline (Fig 2, A), measured on panoramic views as the angle between the long axis of the impacted tooth and the midline drawn perpendicular to the occlusal plane through the anterior nasal spine; this parameter was omitted in the subjects with dilaceration; the cutoff angle of 20 was based on the median angulation value of the whole group, except for the subjects with dilaceration: \20 or $20 ; (5) vertical crown height (Fig 2, A), assessed in the panoramic views only for unilateral cases, at the level of the apical third of the root of the adjacent erupted central incisor, the middle third of the root of the adjacent erupted central incisor, and the coronal third of the root of the adjacent erupted central incisor; (6) distance of the impacted tooth to the midline (Fig 2, B), measured on panoramic views as the distance between the most mesial part of the crown of the impacted tooth and the midline, #0 mm (the crown crosses the midline) or .0 mm; and (7) type of surgical exposure: open, closed, or combined (closed at the first exposure, open at the second exposure). According to previous articles, different head positions have little influence on angular and linear measurements if changes in the position of the occlusal plane are equal to or less than 10 .31
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Table I. Patient characteristics
Fig 2. A, Angle of the incisor to midline and height relative to the contralateral normally erupted incisor; B, distance of the incisor to midline. Statistical analysis
The statistical methods for the associations between each variable, the success rate, and the treatment duration included chi-square tests and logistic regression analyses using SAS software (version 9.4; SAS Institute, Cary, NC) to calculate odds ratios and 95% confidence intervals. A multivariate regression model including 7 categorical variables was performed to identify the factors with a significant impact. All unilateral sides but only 1 side of the bilateral subjects were included in the multivariate analysis. The inclusion of each side as a separate case in the bilateral subjects was discounted because they are not independent variables. The side was chosen at random by the statistician, so that both affected sides had an even probability to be included in the analysis. All statistical tests were 2-sided at a 5 0.05. RESULTS
The patients' characteristics are presented in Table I. The mean age of the whole group was 19.3 6 2.5 years, with an age range of 7.0 to 21.9 years. The age groups comprised 33 patients in the young group (mean, 9.0 6 1 years) and 27 in the older group (mean,
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Characteristic Age (y) Younger Older Unilateral Bilateral Sex Male Female Etiology Trauma Classic dilaceration Obstruction Unknown Angulation ( )* #20 .20 Height Apical Middle Coronal Distance to midline (mm) #0 .0 Surgical exposure Closed Open Combined
No. of patients (no. of incisors) 33 (35) 27 (29) 56 (56) 4 (8) 26 (29) 34 (35) 14 (15) 13 (13) 29 (32) 4 (4) 13 (15) 16 (17) 32 (32) 18 (18) 6 (6) 31 (31) 29 (33) 44 (48) 11 (11) 5 (5)
*This variable was examined only in patients with impacted incisors due to obstructive causes.
12.2 6 1.6 years). Twenty-six patients were male, and 34 were female. Most patients had unilateral impactions (56), and only 4 were affected bilaterally. Fourteen patients had a history of trauma; however, most of the patients with classic dilacerations also reported trauma. Therefore, these 2 groups were combined for statistical purposes. In the statistical analysis, this group of 27 trauma-affected patients with or without dilaceration was compared with the group of 29 patients with obstructed incisors. In 4 patients, the specific etiology could not be determined. The 2 subgroups based on angulation to the midline were much smaller because this parameter was examined only in the obstruction group because of the difficulty of drawing the long axis of the tooth in the subjects with dilaceration. The angulation range was 0 to 140 . In the unilateral group, most of the incisors were at the level of the apical (32) or the middle (18) third of the adjacent erupted incisor. Only 6 were recorded as coronal, and these were therefore combined with the middle-third group for statistical purposes. The mean distance of the impacted tooth to the midline was 1.4 6 3.9 mm, with a range of 4 to 20 mm.
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Table II. Prognosis and treatment duration in relation to the variables Variable Age Younger Older Sex (n) Male Female Etiology Trauma and dilaceration Classic dilaceration* Obstruction Unknown Angulation ( )y #20 .20 Distance to midline (mm) #0 .0 Height Apical Middle and coronal Surgical exposure Closed and combined Open
SR (%) 90.0 93.9 85.2
Tt (mo) 21.6 6 8.7 19.2 6 13.0 25.8 6 10.1
T1 (mo) 4.9 6 3.6 4.1 6 2.4 6.0 6 4.1
T2 (mo) 8.7 6 4.4 8.0 6 4.6 9.6 6 5.4
T3 (mo) 8.2 6 4.8 7.5 6 10.1 9.5 6 5.2
80.1 97.1
20.1 6 8.8 21.0 6 12.6
5.5 6 4.2 4.4 6 2.5
7.4 6 3.3 9.6 6 5.9
7.7 6 5.3 7.1 6 6.7
81.5 69.2 96.6 100
21.4 6 8.8 22.1 6 6.1 18.0 6 7.4 31.8 6 15.5
5.6 6 4.4 5.5 6 2.8 4.9 6 3.2 5.5 6 7.2
10.1 6 5.5 10.8 6 5.6 7.0 6 3.3 13.7 6 7.6
5.7 6 3.2 5.8 6 3.4 6.1 6 4.6 12.5 6 4.9
-
19.6 6 8.7 19.6 6 5.2
7.8 6 6.5 6.1 6 3.4
7.4 6 3.1 7.0 6 3.2
4.4 6 4.1 6.5 6 3.7
90.3 89.6
21.6 6 10.1 23.3 6 15.1
5.5 6 4.1 4.8 6 3.6
8.2 6 3.6 9.1 6 6.1
7.6 6 5.8 9.3 6 10.1
84.4 95.8
23.2 6 15 19.3 6 10.1
4.8 6 3.4 4.9 6 3.4
9.6 6 5.0 7.5 6 5.0
8.7 6 10.1 6.9 6 6.5
89.8 90.9
18.1 6 8.8 23.6 6 12.4
5.0 6 3.9 6.3 6 3.5
8.1 6 4.1 11.6 6 8.2
7.8 6 6.1 5.2 6 4.8
SR, Success rate; Tt, total treatment time; T1, preparatory stage; T2, traction stage; T3, finishing stage. *The classic dilaceration group is part of the trauma and dilaceration group; ysuccess rate was not relevant, since most of the failed cases were dilacerated.
Table III. Characteristics of the failed patients Patient 1 2 3 4 5 6
Age (y) 13.2 21.9 11.1 10.0 9.9 13.5
Sex Female Male Male Male Male Male
Reason for failure Ankylosis Intractable position Ankylosis Ankylosis Invasive cervical root resorption Ankylosis
Etiology Classic dilaceration Classic dilaceration Classic dilaceration Classic dilaceration Ttrauma and nonclassic dilaceration Obstruction
Most patients (44) were treated with a closed surgical exposure, and only 11 had an open procedure. A few patients (5), all with dilaceration, had 2 preplanned surgical procedures, initially closed, and then, as the tooth approached its location in the arch, an apically repositioned flap to invest the tooth with attached gingiva on its labial side. This group was added to the closed surgery group in the statistical analysis because most of the treatment was performed according to the closed surgery approach. The prognosis (success rate) and the duration of the different stages of treatment are summarized in Table II. The success rate in the whole group was 90%: 54 patients were successfully treated, and 6 had failures. Table III describes the 6 failed patients. Four of them were older than 11 years (patient 2 was 21.9 years
Angle ( ) -
Distance (mm) 3 20 4 0 9
Height Apical Middle Apical Apical Apical
Surgical exposure Closed Closed Closed Closed Closed
111
4
Apical
Open
old); most (5) were male, with 1 female (patient 1). All had unilateral impactions. Four were impacted with classic dilacerations probably related to previous trauma, and the failures were due to ankylosis. One was severely dilacerated, but not classic, because of previous trauma (patient 5) and was subsequently diagnosed with invasive cervical root resorption (Fig 3). One incisor was extremely angulated and obstructed by the roots of neighboring teeth, in an intractable position (patient 6). Most (5) were impacted high in the alveolus and were treated with closed surgical exposures. The multivariate regression analysis of all variables and their effects on the prognosis of treatment are shown in Table IV. The angulation could not be introduced in the regression model because of the small
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Fig 3. Failure caused by invasive cervical root resorption (arrows): A, initial panoramic and periapical views; B, cone-beam computed tomography views showing the area of invasive cervical root resorption.
Table IV. Multivariate regression analysis for the prognosis of treatment Effect Age Sex Etiology Height Distance at midline Surgical exposure
Wald chi-square 0.7015 0.3241 5.3320 0.3979 0.0009 1.2286
Pr . chi-square 0.4023 0.5692 0.0209 0.5282 0.9767 0.2677
Pr, probability.
number of subjects (only obstructed) and because of the total absence of failures in mildly angulated teeth. The only variable that was statistically significant for prognosis was the etiology. Incisors impacted
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due to dilaceration had a significantly higher risk for failure than those impacted due to obstruction (P 5 0.02). The average duration for treatment for the whole group was 21.6 6 8.7 months, as follows: (1) the leveling, alignment, and space-opening stage (T1) took approximately 5 months; (2) a further 9 months of orthodontic traction (T2) were required to bring the tooth into the arch after the surgical exposure; and (3) on average, 8 months were needed to finish this phase 1 treatment (T3). The duration of the total treatment and each stage of treatment was longer in the older group. On average, 6 more months were needed to treat older patients; however, the differences reached statistical
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significance only for the finishing stage, T3. Treatment for the bilateral patients lasted longer than that for the unilateral patients, but because there were only 4 bilateral subjects, this figure should be treated with caution. Sex, tooth angulation, and distance to the midline did not influence treatment duration significantly. Treatment of impacted incisors due to dilaceration was more than 3 months longer than for impactions caused by obstruction. The differences were statistically significant only for T2 (P 5 0.04). The patients with classic dilaceration required the longest treatment (almost 2 years) because of the long period of traction (almost 11 months), and the difference between this group and the obstruction group was even more significant (P 5 0.02). Four separate multivariate analysis models were constructed to examine the impact of the variables on the duration of each treatment stage and on the total treatment duration. Thus, T1 was not significantly affected by the different variables. The variables that significantly influenced T2 in this model were the initial height of the impacted incisor and the etiology. The phases of traction were much longer for the apically located incisors (P 5 0.01) and for the incisors impacted because of dilaceration (P 5 0.05). The only variable that significantly influenced the T3 duration was age (P 5 0.02). T3 increased with the patient's age. The multivariate analysis for the total treatment time showed that the only variable with a significant impact was the initial height; this was probably due to the increase in the T2 component: ie, a longer period of traction for the apical incisors, as shown above (P 5 0.03). DISCUSSION
There can be no question that the conservative approach to the treatment of impacted maxillary incisors is a significant clinical challenge insofar as it requires close collaboration between an orthodontist and an oral surgeon and, not least, skilled management because it mainly involves a young patient. By all accounts, it is a highly successful approach, judging by the only 2 published studies on this subject.26,27 These investigations reported no failures in their samples of patients of impacted incisors, although it seems likely that they included nonconsecutive and only successful subjects. Our sample was taken from consecutively treated patients with incisor impaction in the database. In
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contrast to the study of Ho and Liao,26 our study included many more teeth impacted because of dilaceration (28). Farronato et al27 included only 10 successful subjects, all adults with impactions resulting from dilacerations (25-35 years old). Our study included failed cases, with 5 of the 6 failures occurring in the dilacerated group: an almost 18% failure rate. Although clinically significant, we considered this to be a risk worth taking, in light of the superior outcome that this approach offers compared with other treatment options. These alternative modalities engender bone loss and the need for prosthodontic rehabilitation in those methods. The poorer prognosis for dilacerated incisors finds a cogent explanation in the fact that most orthodontists believe that this phenomenon is due to trauma. Other clinical sequelae related to trauma include ankylosis and invasive cervical root resorption, both of which are potent factors in the nonresponse of an affected tooth to orthodontic forces; hence the increased failure rate with dilaceration.6,32,33 Following this line of thought still further and as would be expected in relation to the frequency of trauma, there was a higher incidence among the male subjects, with 5 of the 6 failures found in them. Relative to most phase 1 procedures, the treatment of impacted maxillary incisors was long and not expected to have any alleviating effect on the comprehensive orthodontic requirements that may be necessary in phase 2 treatment. Thus, taken together, the 2 phases of treatment are likely to be expensive for the patient; this should be considered in setting the fee. Ho and Liao26 reported only on the duration of the traction phase. The traction time in our study was 8.00 6 4.5 months, which was similar to the findings in their article. In terms of patient management, an important observation was that the duration of phase 1 treatment was greater in children whose impacted incisor was located higher in the maxilla. The traction stage (T2) was significantly longer in the dilaceration group because of the degree of rotation in the buccolingual plane that is needed to bring the crown tip down to the occlusal level. The finishing stage (T3), involving rotations, uprighting, and torquing, was significantly longer in the older patients, and this raised the possibility that phase 1 treatment would become continuous with phase 2 treatment. Ho and Liao26 found no difference in treatment duration between those who had an open vs a closed surgical procedure, whereas in our study, a nonsignificantly shorter treatment time was associated with a closed procedure.
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CONCLUSIONS
1.
2.
The prognosis of orthodontic-surgical treatment for impacted incisors is good; however, failures do occur, particularly when the etiology for the impaction is dilaceration. Treatment is relatively long—up to 2 years—and is significantly affected by the initial height of the impacted tooth.
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17. Lin YT. Treatment of an impacted dilacerated maxillary central incisor. Am J Orthod Dentofacial Orthop 1999;115:406-9. 18. Cozza P, Marino A, Condo R. Orthodontic treatment of an impacted dilacerated maxillary incisor: a case report. J Clin Pediatr Dent 2005;30:93-7. 19. Tanaka E, Hasegawa T, Hanaoka K, Yoneno K, Matsumoto E, Dalla-Bona D, et al. Severe crowding and a dilacerated maxillary central incisor in an adolescent. Angle Orthod 2006;76: 510-8. 20. Chew MT, Ong MM. Orthodontic-surgical management of an impacted dilacerated maxillary central incisor: a clinical case report. Pediatr Dent 2004;26:341-4. 21. Fleming PS, Scott P, Heidari N, DiBiase AT. Influence of radiographic position of ectopic canines on the duration of orthodontic treatment. Angle Orthod 2009;79:442-6. 22. Stewart JA, Heo G, Glover KE, Williamson PC, Lam EW, Major PW. Factors that relate to treatment duration for patients with palatally impacted maxillary canines. Am J Orthod Dentofacial Orthop 2001;119:216-25. 23. Zuccati G, Ghobadlu J, Nieri M, Clauser C. Factors associated with the duration of forced eruption of impacted maxillary canines: a retrospective study. Am J Orthod Dentofacial Orthop 2006;130: 349-56. 24. Becker A, Chaushu S. Success rate and duration of orthodontic treatment for adult patients with palatally impacted maxillary canines. Am J Orthod Dentofacial Orthop 2003;124: 509-14. 25. Bazargani F, Magnuson A, Dolati A, Lennartsson B. Palatally displaced maxillary canines: factors influencing duration and cost of treatment. Eur J Orthod 2013;35:310-6. 26. Ho KH, Liao YF. Predictors of surgical-orthodontic treatment duration of unilateral impacted maxillary central incisors. Orthod Craniofac Res 2011;14:175-80. 27. Farronato G, Giannini L, Galbiati G, Maspero CA. 5-year longitudinal study of survival rate and periodontal parameter changes at sites of dilacerated maxillary central incisors. Prog Orthod 2014; 15:3-8. 28. Becker A. Early treatment for impacted maxillary incisors. Am J Orthod Dentofacial Orthop 2002;121:586-7. 29. Johnson JE. Adaptability of the twin-wire appliance to modern day orthodontics (part 2). J Clin Orthod 1976;10:610-8. 30. Johnson JE. Adaptability of the twin-wire appliance to modern day orthodontics. J Clin Orthod 1976;10:546-55. 31. Nikneshan S, Sharafi M, Emadi N. Evaluation of the accuracy of linear and angular measurements on panoramic radiographs taken at different positions. Imaging Sci Dent 2013;43:191-6. 32. Becker A, Chaushu G, Chaushu S. Analysis of failure in the treatment of impacted maxillary canines. Am J Orthod Dentofacial Orthop 2010;137:743-54. 33. Becker A, Abramovitz I, Chaushu S. Failure of treatment of impacted canines associated with invasive cervical root resorption. Angle Orthod 2013;83:870-6.
American Journal of Orthodontics and Dentofacial Orthopedics
Impacted central incisors: Factors affecting prognosis and treatment duration Stella Chaushu,a Tal Becker,b and Adrian Beckerc Jerusalem and Tel Aviv, Israel
Introduction: In this study, we aimed to assess the patient and treatment factors that influence the success rate and the duration of the orthodontic-surgical modality for impacted central incisors. Methods: The records of 60 consecutively treated patients (64 impacted incisors) were retrospectively evaluated. The success rate and the duration of each stage of treatment were examined in relation to age, sex, etiology of impaction, location of the impacted tooth, and type of surgical exposure performed. Logistic regression analyses were applied. Results: The group consisted of 26 male and 34 female subjects, 7.0 to 21.9 years old; 27 patients had impactions because of root dilaceration, 29 had impactions because of obstruction, and 4 had impactions with unknown causes. The overall success rate was 90.0%. Five of the 6 failures were dilacerated incisors. The average duration of treatment was 21.6 6 8.7 months. The only factor that significantly increased the duration was the height of the impacted tooth. Dilaceration was related to a longer stage of traction and, in older patients (late mixed and full permanent dentition), to a longer finishing stage. Conclusions: The orthodontic-surgical treatment of impacted incisors is generally successful, but relatively long. Patients and parents should be warned of the risk of failure and the increased treatment duration, especially for dilacerated incisors impacted high in the alveolus. (Am J Orthod Dentofacial Orthop 2015;147:355-62)
A
lthough the prevalence of noneruption or impaction of the maxillary central incisor is low, its occurrence is disfiguring for a young child and of considerable concern to the parents. The causes of this phenomenon can be divided into 2 main groups: obstructive and traumatic causes. The most common obstruction in the anterior maxilla is the presence of at least 1 midline supernumerary tooth.1-3 The frequency with which this occurs has been found to be between 1.5% and 3.5%4 in random population samples, although only between 28% and 60% of these patients will have resultant eruption disturbances of the incisors.5 Odontomes are much rarer findings that cause obstruction in this area, and they may vary in size and type (complex or composite).
a Associate professor and chair, Department of Orthodontics, Hadassah School of Dental Medicine, Hebrew University, Jerusalem, Israel. b Resident, Department of Endodontology, Maurice and Gabriela Goldschleger School of Dental Medicine, Tel Aviv University, Tel Aviv, Israel. c Clinical associate professor emeritus, Department of Orthodontics, Hadassah School of Dental Medicine, Hebrew University, Jerusalem, Israel. All authors have completed and submitted the ICMJE Form for Disclosure of Potential Conflicts of Interest, and none were reported. Address correspondence to: Stella Chaushu, Department of Orthodontics, Hadassah School of Dental Medicine, Hebrew University, PO Box 12272, Jerusalem 91120, Israel; e-mail, [email protected]. Submitted, August 2014; revised and accepted, November 2014. 0889-5406/$36.00 Copyright Ó 2015 by the American Association of Orthodontists. http://dx.doi.org/10.1016/j.ajodo.2014.11.019
Trauma at an early age, before the permanent teeth have erupted, can cause damage to the root-forming cells of the unerupted permanent tooth germ and an attenuated productivity rate of the root portion, and also change the orientation of the tooth in the alveolar process. This results in the development of a dilacerated tooth, which will then not usually erupt unaided.3,6 The parents of a child with an unerupted central incisor, unilaterally or bilaterally, will usually be motivated to seek treatment much earlier than the parents of a child with almost any other orthodontic problem. From the clinical point of view, early treatment is important for the following reasons: (1) an unerupted maxillary central incisor can cause unesthetic and compromised appearance, oral function, and speech; (2) it can cause tipping of adjacent teeth, thus reducing the space for the unerupted incisor; and (3) it is a significant environmental influence in delaying and altering the eruption path of the ipsilateral maxillary canine.7 The available treatment options for this condition include (1) extraction of the tooth followed by prosthodontic rehabilitation; (2) extraction of the tooth and realignment of the lateral incisor into the central incisor position, with the canine and premolar sequentially moved mesially and anatomically modified by grinding, crowning, and so on; or (3) the orthodontic-surgical modality.6 355
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Most patients seeking treatment for impacted central incisors are young children. Therefore, any prosthodontic solution can only be temporary and will need to be modified and updated several times before a more permanent solution becomes possible at age 18 years or so, at the cessation of growth. Extraction of the impacted tooth will also lead to severe alveolar bone loss that will undermine the future implant site. In contrast, the orthodontic-surgical solution aims for complete alignment of the natural teeth and requires no prosthodontic enhancement. The eruption of the impacted tooth draws the surrounding alveolar bone to produce a bony crest height and periodontium similar to those of the adjacent teeth. In the past, it had been assumed that space opening and elimination of the cause would be adequate to produce spontaneous resolution of the impaction. However, evidence-based studies have shown that autonomous eruption occurs in only 54% to 78% of patients,8-10 with a delay of up to 3 years8,10,11 and with spontaneous acceptable alignment occurring in only a few patients.10,12 More recent research has examined the effect of several variables on the eruption of impacted teeth in children after the removal of supernumeraries or odontomes.13 This study found disappointing outcomes regarding spontaneous eruption after extraction of the impediment, which varied in relation to its type and form. The authors did not investigate whether acceptable alignment occurred in the successful subjects, leaving the reader to assume that orthodontic treatment would still be necessary in many patients and justifying the need for a phase 1 procedure. The treatment of impacted central incisors with dilacerations requires a different approach and is usually lengthy and more complicated. This explains why many patients, dentists, and orthodontists prefer surgical repositioning or extraction with prosthodontic rehabilitation as viable alternatives.14 However, attitudes seem to have changed recently, with more case reports of orthodontic treatments appearing in the literature.15-20 In contrast to the parallel situation in regard to impacted canines,21-25 data concerning the success rate and duration of the orthodontic-surgical modality treatment of impacted central incisors are sparse.3,26,27 Most of the articles offer isolated and subjective clinical experiences. In a recent article addressing this subject, the authors did not specify whether the sample comprised only successfully treated patients or consecutively affected patients from their database, and they reported 100% success.26
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The aims of our study were to assess success rates and durations of the orthodontic-surgical modality of treatment of impacted maxillary central incisors in a group of consecutively treated patients and to examine factors that may influence these parameters to give accurate information to patients and parents. MATERIAL AND METHODS
The treatment records of 60 consecutive patients with 64 impacted incisors were gathered between 2002 to 2007 from the orthodontic department of Hebrew University in Jerusalem and from the private practices of the 2 senior authors (S.C. and A.B.). The project was approved by the institutional review board. The inclusion criteria were (1) impacted maxillary central incisors in healthy subjects; (2) a combined orthodontic-surgical approach by one of the 2 senior authors using the same treatment; (3) regular attendance for orthodontic appointments, as determined from the clinical notes; and (4) complete patient records, including diagnostic and treatment entries, pretreatment diagnostically essential radiographic views (good quality panoramic, periapical, and conebeam computed tomography images that were not available for the older patients), banding and bonding date, debanding and debonding date, date of surgical exposure, and date of full engagement of the impacted incisor bracket in the first plain stainless steel archwire. Subjects with craniofacial syndromes, cysts, or cleft lip or palate were excluded from the study. The diagnosis of impaction was made on the basis of a clinical examination and diagnostic plane radiographs. In each patient, the diagnosis was confirmed at the time of the surgical exposure by the orthodontist, who was routinely present for this. Treatment usually followed the order we have described elsewhere.6,28 It commenced with anchorage preparation. In most patients, an updated version of Johnson's twin appliance was used to avoid bonding deciduous teeth that were likely to be shed during treatment.29,30 Anchorage was provided by a palatal arch with or without a Nance button, and brackets were placed only on the erupted incisors. After orthodontic leveling, aligning, and reopening of the incisor space, a small attachment was bonded by the orthodontist to the exposed tooth at the end of the surgical procedure if a closed eruption procedure was performed, or within a few days thereafter in case of open surgery. Traction was applied immediately to the freshly bonded attachment. The tooth was brought to its place in the arch by light orthodontic extrusive traction maintained by the ligature wire.
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In patients with a classic dilaceration, 2 surgical exposures were usually required. The first was a closed procedure, and the second was an apically repositioned flap, open surgical procedure. This second surgery was needed to prevent the incisal edge of the incisor from breaking through the oral mucosa as it was rotated in the buccolingual plane; this was intended to encourage the emergence of the impacted tooth crown through the attached gingiva.28 The main outcome variables were the success rate and the duration of the orthodontic treatment. Treatment was considered successful if the incisor was brought into its place in the arch. The success rate was determined on the basis of the posttreatment records. The success rate was calculated as the percentage of successfully aligned incisors relative to the total number of incisors treated. This stage of treatment was specifically aimed for resolution of the impacted central incisor and was completed when the incisor was properly aligned in the arch. When more comprehensive treatment was considered, only that part of the treatment surrounding the resolution of the incisor was considered, but in general, the treatment of other features of the malocclusion was postponed until the patient was ready for a phase 2 protocol. The length of treatment in months was determined from each patient's records. Total treatment time refers to the period between bonding or banding and debonding or debanding of the orthodontic appliances, and this was arbitrarily divided into 3 constituent treatment periods. 1.
2.
3.
T1, from the date of bonding or banding to the date of the surgical exposure. In this preliminary or preparatory stage, bonding or banding was performed, anchorage was prepared, and space was opened for the impacted tooth. T2, from the date of the surgical exposure to the date that the tooth was fully ligated in the main arch with a nickel-titanium wire. This was the traction stage. T3, from the full ligation into the stainless steel wire to the date of debonding or debanding. During this finishing stage, more complex movements such as rotations, uprighting, and torquing were performed.
Success rate and duration of treatment were classified as follows: (1) age, younger group (\11 years) or older group ($11 years); (2) sex; (3) etiology of impaction, trauma, classic dilaceration (crown angulated labially relative to the root, with the palatal aspect facing labially, Fig 1), obstruction of the path of eruption
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Fig 1. Classic dilaceration: A, panoramic view; B, conebeam computed tomography view.
(supernumerary, odontoma), or unknown; (4) angulation of the impacted tooth to the midline (Fig 2, A), measured on panoramic views as the angle between the long axis of the impacted tooth and the midline drawn perpendicular to the occlusal plane through the anterior nasal spine; this parameter was omitted in the subjects with dilaceration; the cutoff angle of 20 was based on the median angulation value of the whole group, except for the subjects with dilaceration: \20 or $20 ; (5) vertical crown height (Fig 2, A), assessed in the panoramic views only for unilateral cases, at the level of the apical third of the root of the adjacent erupted central incisor, the middle third of the root of the adjacent erupted central incisor, and the coronal third of the root of the adjacent erupted central incisor; (6) distance of the impacted tooth to the midline (Fig 2, B), measured on panoramic views as the distance between the most mesial part of the crown of the impacted tooth and the midline, #0 mm (the crown crosses the midline) or .0 mm; and (7) type of surgical exposure: open, closed, or combined (closed at the first exposure, open at the second exposure). According to previous articles, different head positions have little influence on angular and linear measurements if changes in the position of the occlusal plane are equal to or less than 10 .31
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Table I. Patient characteristics
Fig 2. A, Angle of the incisor to midline and height relative to the contralateral normally erupted incisor; B, distance of the incisor to midline. Statistical analysis
The statistical methods for the associations between each variable, the success rate, and the treatment duration included chi-square tests and logistic regression analyses using SAS software (version 9.4; SAS Institute, Cary, NC) to calculate odds ratios and 95% confidence intervals. A multivariate regression model including 7 categorical variables was performed to identify the factors with a significant impact. All unilateral sides but only 1 side of the bilateral subjects were included in the multivariate analysis. The inclusion of each side as a separate case in the bilateral subjects was discounted because they are not independent variables. The side was chosen at random by the statistician, so that both affected sides had an even probability to be included in the analysis. All statistical tests were 2-sided at a 5 0.05. RESULTS
The patients' characteristics are presented in Table I. The mean age of the whole group was 19.3 6 2.5 years, with an age range of 7.0 to 21.9 years. The age groups comprised 33 patients in the young group (mean, 9.0 6 1 years) and 27 in the older group (mean,
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Characteristic Age (y) Younger Older Unilateral Bilateral Sex Male Female Etiology Trauma Classic dilaceration Obstruction Unknown Angulation ( )* #20 .20 Height Apical Middle Coronal Distance to midline (mm) #0 .0 Surgical exposure Closed Open Combined
No. of patients (no. of incisors) 33 (35) 27 (29) 56 (56) 4 (8) 26 (29) 34 (35) 14 (15) 13 (13) 29 (32) 4 (4) 13 (15) 16 (17) 32 (32) 18 (18) 6 (6) 31 (31) 29 (33) 44 (48) 11 (11) 5 (5)
*This variable was examined only in patients with impacted incisors due to obstructive causes.
12.2 6 1.6 years). Twenty-six patients were male, and 34 were female. Most patients had unilateral impactions (56), and only 4 were affected bilaterally. Fourteen patients had a history of trauma; however, most of the patients with classic dilacerations also reported trauma. Therefore, these 2 groups were combined for statistical purposes. In the statistical analysis, this group of 27 trauma-affected patients with or without dilaceration was compared with the group of 29 patients with obstructed incisors. In 4 patients, the specific etiology could not be determined. The 2 subgroups based on angulation to the midline were much smaller because this parameter was examined only in the obstruction group because of the difficulty of drawing the long axis of the tooth in the subjects with dilaceration. The angulation range was 0 to 140 . In the unilateral group, most of the incisors were at the level of the apical (32) or the middle (18) third of the adjacent erupted incisor. Only 6 were recorded as coronal, and these were therefore combined with the middle-third group for statistical purposes. The mean distance of the impacted tooth to the midline was 1.4 6 3.9 mm, with a range of 4 to 20 mm.
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Table II. Prognosis and treatment duration in relation to the variables Variable Age Younger Older Sex (n) Male Female Etiology Trauma and dilaceration Classic dilaceration* Obstruction Unknown Angulation ( )y #20 .20 Distance to midline (mm) #0 .0 Height Apical Middle and coronal Surgical exposure Closed and combined Open
SR (%) 90.0 93.9 85.2
Tt (mo) 21.6 6 8.7 19.2 6 13.0 25.8 6 10.1
T1 (mo) 4.9 6 3.6 4.1 6 2.4 6.0 6 4.1
T2 (mo) 8.7 6 4.4 8.0 6 4.6 9.6 6 5.4
T3 (mo) 8.2 6 4.8 7.5 6 10.1 9.5 6 5.2
80.1 97.1
20.1 6 8.8 21.0 6 12.6
5.5 6 4.2 4.4 6 2.5
7.4 6 3.3 9.6 6 5.9
7.7 6 5.3 7.1 6 6.7
81.5 69.2 96.6 100
21.4 6 8.8 22.1 6 6.1 18.0 6 7.4 31.8 6 15.5
5.6 6 4.4 5.5 6 2.8 4.9 6 3.2 5.5 6 7.2
10.1 6 5.5 10.8 6 5.6 7.0 6 3.3 13.7 6 7.6
5.7 6 3.2 5.8 6 3.4 6.1 6 4.6 12.5 6 4.9
-
19.6 6 8.7 19.6 6 5.2
7.8 6 6.5 6.1 6 3.4
7.4 6 3.1 7.0 6 3.2
4.4 6 4.1 6.5 6 3.7
90.3 89.6
21.6 6 10.1 23.3 6 15.1
5.5 6 4.1 4.8 6 3.6
8.2 6 3.6 9.1 6 6.1
7.6 6 5.8 9.3 6 10.1
84.4 95.8
23.2 6 15 19.3 6 10.1
4.8 6 3.4 4.9 6 3.4
9.6 6 5.0 7.5 6 5.0
8.7 6 10.1 6.9 6 6.5
89.8 90.9
18.1 6 8.8 23.6 6 12.4
5.0 6 3.9 6.3 6 3.5
8.1 6 4.1 11.6 6 8.2
7.8 6 6.1 5.2 6 4.8
SR, Success rate; Tt, total treatment time; T1, preparatory stage; T2, traction stage; T3, finishing stage. *The classic dilaceration group is part of the trauma and dilaceration group; ysuccess rate was not relevant, since most of the failed cases were dilacerated.
Table III. Characteristics of the failed patients Patient 1 2 3 4 5 6
Age (y) 13.2 21.9 11.1 10.0 9.9 13.5
Sex Female Male Male Male Male Male
Reason for failure Ankylosis Intractable position Ankylosis Ankylosis Invasive cervical root resorption Ankylosis
Etiology Classic dilaceration Classic dilaceration Classic dilaceration Classic dilaceration Ttrauma and nonclassic dilaceration Obstruction
Most patients (44) were treated with a closed surgical exposure, and only 11 had an open procedure. A few patients (5), all with dilaceration, had 2 preplanned surgical procedures, initially closed, and then, as the tooth approached its location in the arch, an apically repositioned flap to invest the tooth with attached gingiva on its labial side. This group was added to the closed surgery group in the statistical analysis because most of the treatment was performed according to the closed surgery approach. The prognosis (success rate) and the duration of the different stages of treatment are summarized in Table II. The success rate in the whole group was 90%: 54 patients were successfully treated, and 6 had failures. Table III describes the 6 failed patients. Four of them were older than 11 years (patient 2 was 21.9 years
Angle ( ) -
Distance (mm) 3 20 4 0 9
Height Apical Middle Apical Apical Apical
Surgical exposure Closed Closed Closed Closed Closed
111
4
Apical
Open
old); most (5) were male, with 1 female (patient 1). All had unilateral impactions. Four were impacted with classic dilacerations probably related to previous trauma, and the failures were due to ankylosis. One was severely dilacerated, but not classic, because of previous trauma (patient 5) and was subsequently diagnosed with invasive cervical root resorption (Fig 3). One incisor was extremely angulated and obstructed by the roots of neighboring teeth, in an intractable position (patient 6). Most (5) were impacted high in the alveolus and were treated with closed surgical exposures. The multivariate regression analysis of all variables and their effects on the prognosis of treatment are shown in Table IV. The angulation could not be introduced in the regression model because of the small
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Fig 3. Failure caused by invasive cervical root resorption (arrows): A, initial panoramic and periapical views; B, cone-beam computed tomography views showing the area of invasive cervical root resorption.
Table IV. Multivariate regression analysis for the prognosis of treatment Effect Age Sex Etiology Height Distance at midline Surgical exposure
Wald chi-square 0.7015 0.3241 5.3320 0.3979 0.0009 1.2286
Pr . chi-square 0.4023 0.5692 0.0209 0.5282 0.9767 0.2677
Pr, probability.
number of subjects (only obstructed) and because of the total absence of failures in mildly angulated teeth. The only variable that was statistically significant for prognosis was the etiology. Incisors impacted
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due to dilaceration had a significantly higher risk for failure than those impacted due to obstruction (P 5 0.02). The average duration for treatment for the whole group was 21.6 6 8.7 months, as follows: (1) the leveling, alignment, and space-opening stage (T1) took approximately 5 months; (2) a further 9 months of orthodontic traction (T2) were required to bring the tooth into the arch after the surgical exposure; and (3) on average, 8 months were needed to finish this phase 1 treatment (T3). The duration of the total treatment and each stage of treatment was longer in the older group. On average, 6 more months were needed to treat older patients; however, the differences reached statistical
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significance only for the finishing stage, T3. Treatment for the bilateral patients lasted longer than that for the unilateral patients, but because there were only 4 bilateral subjects, this figure should be treated with caution. Sex, tooth angulation, and distance to the midline did not influence treatment duration significantly. Treatment of impacted incisors due to dilaceration was more than 3 months longer than for impactions caused by obstruction. The differences were statistically significant only for T2 (P 5 0.04). The patients with classic dilaceration required the longest treatment (almost 2 years) because of the long period of traction (almost 11 months), and the difference between this group and the obstruction group was even more significant (P 5 0.02). Four separate multivariate analysis models were constructed to examine the impact of the variables on the duration of each treatment stage and on the total treatment duration. Thus, T1 was not significantly affected by the different variables. The variables that significantly influenced T2 in this model were the initial height of the impacted incisor and the etiology. The phases of traction were much longer for the apically located incisors (P 5 0.01) and for the incisors impacted because of dilaceration (P 5 0.05). The only variable that significantly influenced the T3 duration was age (P 5 0.02). T3 increased with the patient's age. The multivariate analysis for the total treatment time showed that the only variable with a significant impact was the initial height; this was probably due to the increase in the T2 component: ie, a longer period of traction for the apical incisors, as shown above (P 5 0.03). DISCUSSION
There can be no question that the conservative approach to the treatment of impacted maxillary incisors is a significant clinical challenge insofar as it requires close collaboration between an orthodontist and an oral surgeon and, not least, skilled management because it mainly involves a young patient. By all accounts, it is a highly successful approach, judging by the only 2 published studies on this subject.26,27 These investigations reported no failures in their samples of patients of impacted incisors, although it seems likely that they included nonconsecutive and only successful subjects. Our sample was taken from consecutively treated patients with incisor impaction in the database. In
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contrast to the study of Ho and Liao,26 our study included many more teeth impacted because of dilaceration (28). Farronato et al27 included only 10 successful subjects, all adults with impactions resulting from dilacerations (25-35 years old). Our study included failed cases, with 5 of the 6 failures occurring in the dilacerated group: an almost 18% failure rate. Although clinically significant, we considered this to be a risk worth taking, in light of the superior outcome that this approach offers compared with other treatment options. These alternative modalities engender bone loss and the need for prosthodontic rehabilitation in those methods. The poorer prognosis for dilacerated incisors finds a cogent explanation in the fact that most orthodontists believe that this phenomenon is due to trauma. Other clinical sequelae related to trauma include ankylosis and invasive cervical root resorption, both of which are potent factors in the nonresponse of an affected tooth to orthodontic forces; hence the increased failure rate with dilaceration.6,32,33 Following this line of thought still further and as would be expected in relation to the frequency of trauma, there was a higher incidence among the male subjects, with 5 of the 6 failures found in them. Relative to most phase 1 procedures, the treatment of impacted maxillary incisors was long and not expected to have any alleviating effect on the comprehensive orthodontic requirements that may be necessary in phase 2 treatment. Thus, taken together, the 2 phases of treatment are likely to be expensive for the patient; this should be considered in setting the fee. Ho and Liao26 reported only on the duration of the traction phase. The traction time in our study was 8.00 6 4.5 months, which was similar to the findings in their article. In terms of patient management, an important observation was that the duration of phase 1 treatment was greater in children whose impacted incisor was located higher in the maxilla. The traction stage (T2) was significantly longer in the dilaceration group because of the degree of rotation in the buccolingual plane that is needed to bring the crown tip down to the occlusal level. The finishing stage (T3), involving rotations, uprighting, and torquing, was significantly longer in the older patients, and this raised the possibility that phase 1 treatment would become continuous with phase 2 treatment. Ho and Liao26 found no difference in treatment duration between those who had an open vs a closed surgical procedure, whereas in our study, a nonsignificantly shorter treatment time was associated with a closed procedure.
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CONCLUSIONS
1.
2.
The prognosis of orthodontic-surgical treatment for impacted incisors is good; however, failures do occur, particularly when the etiology for the impaction is dilaceration. Treatment is relatively long—up to 2 years—and is significantly affected by the initial height of the impacted tooth.
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17. Lin YT. Treatment of an impacted dilacerated maxillary central incisor. Am J Orthod Dentofacial Orthop 1999;115:406-9. 18. Cozza P, Marino A, Condo R. Orthodontic treatment of an impacted dilacerated maxillary incisor: a case report. J Clin Pediatr Dent 2005;30:93-7. 19. Tanaka E, Hasegawa T, Hanaoka K, Yoneno K, Matsumoto E, Dalla-Bona D, et al. Severe crowding and a dilacerated maxillary central incisor in an adolescent. Angle Orthod 2006;76: 510-8. 20. Chew MT, Ong MM. Orthodontic-surgical management of an impacted dilacerated maxillary central incisor: a clinical case report. Pediatr Dent 2004;26:341-4. 21. Fleming PS, Scott P, Heidari N, DiBiase AT. Influence of radiographic position of ectopic canines on the duration of orthodontic treatment. Angle Orthod 2009;79:442-6. 22. Stewart JA, Heo G, Glover KE, Williamson PC, Lam EW, Major PW. Factors that relate to treatment duration for patients with palatally impacted maxillary canines. Am J Orthod Dentofacial Orthop 2001;119:216-25. 23. Zuccati G, Ghobadlu J, Nieri M, Clauser C. Factors associated with the duration of forced eruption of impacted maxillary canines: a retrospective study. Am J Orthod Dentofacial Orthop 2006;130: 349-56. 24. Becker A, Chaushu S. Success rate and duration of orthodontic treatment for adult patients with palatally impacted maxillary canines. Am J Orthod Dentofacial Orthop 2003;124: 509-14. 25. Bazargani F, Magnuson A, Dolati A, Lennartsson B. Palatally displaced maxillary canines: factors influencing duration and cost of treatment. Eur J Orthod 2013;35:310-6. 26. Ho KH, Liao YF. Predictors of surgical-orthodontic treatment duration of unilateral impacted maxillary central incisors. Orthod Craniofac Res 2011;14:175-80. 27. Farronato G, Giannini L, Galbiati G, Maspero CA. 5-year longitudinal study of survival rate and periodontal parameter changes at sites of dilacerated maxillary central incisors. Prog Orthod 2014; 15:3-8. 28. Becker A. Early treatment for impacted maxillary incisors. Am J Orthod Dentofacial Orthop 2002;121:586-7. 29. Johnson JE. Adaptability of the twin-wire appliance to modern day orthodontics (part 2). J Clin Orthod 1976;10:610-8. 30. Johnson JE. Adaptability of the twin-wire appliance to modern day orthodontics. J Clin Orthod 1976;10:546-55. 31. Nikneshan S, Sharafi M, Emadi N. Evaluation of the accuracy of linear and angular measurements on panoramic radiographs taken at different positions. Imaging Sci Dent 2013;43:191-6. 32. Becker A, Chaushu G, Chaushu S. Analysis of failure in the treatment of impacted maxillary canines. Am J Orthod Dentofacial Orthop 2010;137:743-54. 33. Becker A, Abramovitz I, Chaushu S. Failure of treatment of impacted canines associated with invasive cervical root resorption. Angle Orthod 2013;83:870-6.
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