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Institutionen för Odontologi Odontologi, magisteruppsats D, 30 poäng Vårterminen 2007 Long-term treatment outcomes for ectopic maxillary canine teeth, to evaluate incisor root resorption. Chanelle Houmet Guitirokh Supervisor: Associate professor Krister Bjerklin, Department of Orthodontics, Institute for Postgraduate Dental Education in Jönköping, Sweden Examiner: Professor Sigvard Kopp, Department of Oral rehabilitation, Karolinska Institute, Stockholm, Sweden Nr (ej klart ännu) Institutionen för Odontologi Odontologi, magisteruppsats D, 30 poäng Vårterminen 2007 Long-term treatment outcomes for ectopic maxillary canine teeth, to evaluate incisor root resorption. Abstract Background: Before the advent of CT as a diagnostic aid, many resorptive lesions were previously undetected. Little is known of the long-term viability of these resorbed incisors. Aim: To monitor the fate of the maxillary incisors with root resorptions in patients treated in Jönköping,Sweden, up to 28 years ago, for severely ectopic maxillary canines. Subjects and Method: The records of 39 patients were found: 35 could be contacted and 25 agreed to participate in the study. Thus the material comprised a total of 37 incisors in the 25 subjects. The post-treatment follow-up times ranged from 13 to 28 years. Clinical examination was followed by intraoral radiographs and CT. The degree of resorption was 2 collated with the clinical characteristics of the incisor. Resorptive lesions were described and the intraoral radiographs were compared with those taken immediately post-treatment. Results: In all, 22 incisors with root resorption were identified. In 17, the lesions were unchanged. Resorption had decreased in 2 cases and increased slightly in two. In one case, the resorption had progressed to the pulp, necessitating endodontic treatment. Two subjects had lost 3 incisors post treatment. Most of the resorptive sites showed enhanced definition of the periodontal ligament and improved trabeculation of the lamina dura, indicating inactive sites. Incisors with resorption exhibited no clinically distinguishable characteristics. Conclusions: The results suggest that incisor root resorption induced by an ectopic maxillary canine does not tend to progress post-treatment and should not threaten the long-term viability of the affected incisors. Teeth with root resorption show no clinically relevant symptoms at follow-up. 3 Långtidsuppföljning på incisiver med rotresorptionsskador orsakade av ektopiskt erupterande överkäkshörntänder Sammanfattning: Bakgrund: Många resorptionsskador kunde tidigare inte detekteras på periapikala röntgen innan CT användes som en diagnostisk metod. Det finns lite information om prognosen för tänder med resorptionsskador. Syfte: Att göra en långtidsuppföljning på incisiver med rotresorptionsskador orsakade av ektopiskt erupterande överkäkshörntänder på patienter som har behandlats i Jönköping, under 70 och 80 talet. Metod: Journaler för 39 patienter kunde hittas: 35 kunde kontaktas och 25 accepterade att deltaga i undersökningen. Sammanlagt undersöktes 37 incisiver på 25 patienter. Uppföljningstiden varierade mellan 13 till 28 år. Patienterna fick genomgå en klinisk undersökning, en intraoral röntgenundersökning och en CTundersökning. En bedömning gjordes om skadans omfattning utifrån intraorala röntgen och CT. Resorptionsskadan sattes i relation till kliniska karakteristika och skadorna jämfördes med skadorna vid avslutad behandling. Resultat: 22 av 37 undersökta incisiver visade olika grad av resorption. 17 incisiver visade oförändrade resorptionsskador. På 2 incisiver hade rotresoptionen läkt ut till viss del och i 2 tänder hade rotreorptionsskadan ökat något. En incisiv visade fortsatt rotresorption som hade nått pulpan vilket hade nödvändiggjort en rotbehandling. Två patienter hade förlorat 3 incisiver efter avslutad behandling. 4 De flesta tänder visade god parodontal läkning. Vi fann ingen skillnad mellan kliniska karakteristika hos incisiver som hade resorberats och incisiver utan resorptioner. Konklusion: Resorptionsskador orsakade av ektopiska hörntänder verkar inte försämras efter avslutad behandling. Tänder med rotresorptionsskador visar inga relevanta kliniska symptom. Keywords Canine Impacted, Root Resorption, Incisors, Long-term follow-up 5 Introduction Ectopic eruption of maxillary permanent canines is relatively common and often requires lengthy and expensive treatment, including surgical exposure and repositioning of the canine, followed by orthodontic realignment of the maxillary anterior teeth (Becker 1998b). A serious complication associated with this condition is resorption of the roots of neighboring permanent teeth, usually the lateral incisors. Early detection of canine impaction is therefore of fundamental importance to treatment outcome. Careful assessment of the site and severity of any associated resorption of the roots of adjacent teeth is essential. Concern has been expressed that general dental practitioners may underestimate the importance of early intervention in avoiding complications. Treatment planning today is based on detailed examination to determine the precise location of the impacted canine and to diagnose the location and extent of any resorption induced on the roots of adjacent teeth. Pre-treatment conventional intraoral and panoramic radiographs provide limited information because of superimposition of structures on the films. Resorptive lesions may be undetected on pre-treatment radiographs because the canine is often superimposed on the lateral incisors. In recent years the advent of computerized tomography (CT) as a diagnostic aid has allowed more detailed documentation of resorptive lesions. Before the introduction of CT many such teeth were extracted on the assumption of severe resorption, but many resorptive lesions also remained undetected and the teeth were retained. With respect to the response of incisors with resorbed roots following treatment of impacted canines, short-term follow-up studies suggest that once the impacted canine has been treated there is minimal risk for further resorption (Becker 2005). However, lateral incisors with suspected resorption are often extracted because it is believed that the resorption threatens the long-term viability of these teeth. There is little information available about whether in the long-term the resorptive lesions on retained lateral incisors undergo progression, arrest or repair. Data from longterm follow-up studies of patients treated for ectopic canines would provide evidencebased guidelines to support the orthodontist in therapy planning. Incidence of impacted maxillary canines The maxillary permanent canines are, after the third molars, the teeth most frequently impacted. Dachi and Howell (1961) reported an incidence of 0.9%, whereas Thilander and Myrberg (1973) estimated the cumulative prevalence in 7-13 year olds to be 2.2%. An incidence of 1.7% was reported by Ericson and Kurol (1986b). The condition is twice as common in females (1.17%) as in males (0.51%) and bilateral in an estimated 8% of cases. The left side is slightly more often affected than the right (Dachi and Howell 1961). 7 Diagnosis Diagnosis, usually made by the general practitioner, is based on clinical and radiographic examination. In most children, clinical examination, including digital palpation at the age of 9-11, suffices. In 7-10 % of children, supplementary radiographic examination is required (Ericson and Kurol 1986a, Ericson and Kurol 1987a). A study of 107 children with 156 ectopic maxillary canines disclosed that in relation to the roots of the adjacent incisors, 50% of the canines were in lingual or distolingual position, 18% were distobuccal and 21% buccal (Ericson and Kurol 2000b). Jacoby (1983) claimed that it is difficult to establish an accurate rate for palatal versus labial impaction. He attributed this to the difficulty in determining whether a labially impacted tooth might eventually erupt on its own, often further superiorly and labially than its normal position. Etiology The most common reason proposed for palatal displacement of the permanent maxillary canine is the fact that it has a long and tortuous eruption path, beginning close to the floor of the orbit. At the age of three, the canine is high in the maxilla, with the crown directed mesially and somewhat palatally. On its way toward the occlusal plane it seems to strike the distal aspect of the lateral incisor and then assumes a more vertical position. The permanent canine takes almost twice as long as the first permanent molar to erupt (Moyers 1988). 8 The etiology is still obscure, but several theories apart from the eruption path have been proposed. Lack of space was suggested as a causative factor by Hitchin (1951), although he offered no evidence to support this contention. Others have reported dental crowding to be more often associated with labial impactions than with palatal impactions. One study showed that 85% of the palatally impacted canines had sufficient space for eruption, compared with only 17% of labial impactions (Jacoby 1983). Enlarged canine follicles have been proposed as factors contributing to deviations in adjacent permanent roots or inducing root resorption of adjacent incisors. However Ericson et al. (2002) found no confirming evidence and concluded that root resorption is probably a result of physical contact between the erupting canine and the adjacent root. The dental follicles of ectopically positioned canines are, on average, wider than those of normally erupting canines and asymmetry of the dental follicle is also more common. However the main reason for an enlarging dental follicle seems to be availability of space (Ericson and Bjerklin 2001). In general, retarded eruption of teeth may be multifactorial and either systemic or local or a combination of both (Moyers 1988). Systemic causes may include endocrine deficiencies, febrile diseases and irritation. The most common causes of canine impactions are believed to be local and are the result of any one factor, or combinations of different factors. Congenital absence of the maxillary lateral incisor and variation in the root size of the canine, as well as variation in the timing of its root formation, have been implicated as important etiologic factors associated with canine impaction (Jacoby 1983, Bishara 1992). 9 A genetic origin for the palatally displaced canine has also been proposed. This is supported by the fact that other anomalies are associated with the palatally displaced canine such as anomalies of tooth form, size or position, congenital absence of various teeth (particularly maxillary lateral incisors), delayed patterns of development and eruption and transposition with the first premolar (Becker et al. 1981, Bjerklin et al. 1992, Peck et al. 1994, Camilleri 2005). An association has also been shown between ectopic eruption of the maxillary first permanent molar and that of the maxillary canine (Bjerklin et al. 1992) . Further evidence supporting a genetic origin is: The risk of palatal canine displacement is significantly higher in patients with hypoplasia, peg-shaped or congenital dysplasia of upper lateral incisors, further impacted and congenitally missing teeth (Pirinen et al. 1996, Leifert and Jonas 2003). There is a four to fivefold greater risk for palatally impacted canines in patients who have family members with the same anomaly (Svinhufvud et al. 1988, Peck et al. 1994). The prevalence of the condition seems to vary in different ethnic groups: compared to African-Americans and Chinese, Caucasians have more palatally displaced canines (Kramer and Williams 1970, Oliver et al. 1989, Peck et al. 1994). Impaction is twice as common in females as in males (Dachi and Howell 1961). 10 Effects on neighboring permanent teeth Various types of pressures on teeth can lead to root resorption. Examples include orthodontic forces, excessive occlusal forces, pressure from impacted or supernumerary teeth, and pressure from tumors and cysts. Without early intervention, an ectopic canine in close proximity to the lateral incisor root will induce complex physiological and chemical processes, and the root of the lateral incisor may undergo resorption (Arens 1995, Ericson and Kurol 2000b). This biological resorption process is still not well understood, although there is anecdotal evidence that it can lead to the loss of permanent teeth (Saldarriaga and Patino 2003). In a recent study on 19 patients with 27 impacted teeth, con-beam computed tomography disclosed resorption in 67% of the adjacent lateral incisors, 11% of the central incisors and 4% of the premolars (Walker et al. 2005), confirming that the most common site of resorption associated with an ectopically erupting canine is the root of the maxillary lateral incisor. Two major contributing factors are proposed: the location of the root apex of the lateral incisor deep in the palate, where palatally impacted canines often present and secondly the susceptibility of the incisor root to resorption (Ericson and Kurol 1987a, Ericson and Kurol 1988b, Ericson and Kurol 2000a). In a study of 107 children with 156 ectopic maxillary canines, resorption was reported on 38% of adjacent lateral incisor roots and on 9% of adjacent central incisors. Of the 58 lateral incisors affected, resorption was severe in 60% (pulpal involvement), moderate in 9% and slight in 31% (Ericson and Kurol 2000b). 11 A review of the associated factors indicates that it is not possible to predict when resorption will occur (Ryan 1997). Ericson and Kurol (1988b) showed that resorption was three times more likely to be associated with impacted canines in females than in males and that a more medial position and horizontal inclination of the canine increased the risk. Despite the association between an impacted canine and a reduction in size of the adjacent lateral incisor, resorption is more likely to occur in cases of canine impaction where the lateral incisor is of normal size (Brin et al. 1993). Clinical considerations A review by Bishara (1992) concluded that canine impaction may be indicated by the following clinical signs: Delayed eruption of the permanent canine or prolonged retention of the deciduous canine Absence of a normal labial canine bulge: the canine position cannot be ascertained by intraoral palpation of the alveolar process, or palpation discloses asymmetry of the canine bulge Presence of a palatal bulge Delayed eruption, distal tipping, or migration of the lateral incisor In this context, Ericson and Kurol (1986a) suggested that the absence of the “canine bulge” should be considered in relation to the age of the child. In a material of 505 12 children aged 10 to 12 years, they found nonpalpable canines in 29% at age 10 years, but in only 5% at 11 years and 3% after age 11. Thus in cases where eruption of the maxillary permanent canines is late in relation to the age of the patient, clinical examination should be supplemented by radiographs. Except in rare cases of pathology, root development proceeds in a constant manner, regardless of tooth eruption or the fate of the deciduous predecessor. Thus dental age may be accurately assessed in terms of tooth development, determined by examination of periapical or panoramic radiographs (Becker 1998a). Periapical radiographs A study by Ericsson and Kurol (1987b) disclosed that in 92% of cases, periapical radiographs enable the clinician to evaluate the position of the canine with sufficient accuracy. In cases of tipped or proclined lateral incisors, it is difficult to determine the position of the canine. Only in 37% of the cases was it possible to project the lateral incisor image away from that of the canine. Axial films and panoramic radiographs show the relationship to the lateral incisor less clearly. Fox et al. (1995) studied 100 pairs of radiographs showing 139 ectopic canines. Panoramic radiographs allowed accurate depiction of the position of a palatally displaced canine crown in only about 80% of cases. Panoramic radiographs result in relative magnification of objects located palatal to the image layer and relative diminution of objects to the buccal. In radiographic examination to confirm clinical suspicion of ectopic eruption of a maxillary canine, a panoramic radiograph is not enough and should be complemented by intraoral radiographs. 13 Intraoral radiographs are unreliable for detection of lingual or buccal root resorption. This was demonstrated in an experimental study by Folin and Linvall (2005), undertaken to evaluate the potential of intraoral radiographs to disclose root resorption on the palatal aspect of the roots of maxillary incisors. Although radiologists were better than orthodontists and pedodontists at detecting areas of resorption, lesions located on the middle third of the roots were not readily detected until a considerable area was affected, of the order of 3.5mm Computed Tomography Computed Tomography (CT) is an imaging method that has proved to be superior to other radiographic methods in visualizing hard tissue (Traxler et al. 1989, Preda et al. 1997). Originally known as computed axial tomography (CAT or CT scan) and body section roentgenography, computed tomography is a medical imaging method employing tomography where digital geometric processing is used to generate a three-dimensional image of the interior of an object from a large series of two-dimensional X-ray images taken around a single axis of rotation. The word "tomography" is derived from the Greek tomos (slice) and graphia (describing). The spiral CT used today produces a volume of data which can be manipulated, through a process known as windowing, in order to demonstrate various structures, based on their ability to block the x-ray beam. Although historically the images generated were in the axial or transverse plane, modern scanners allow this volume of data to be reformatted in various planes or even as volumetric (3D) representations of structures. 14 Ericsson and Kurol (1987b) demonstrated that compared to intraoral radiographs, polytomography disclosed 50% more resorptive lesions. In this material, half the teeth with resorption had lesions involving the pulp. In 50 per cent of cases there were resorptive lesions on the labial or palatal aspects of the roots: such lesions would not be detectable on conventional periapical radiographs. A CT-study by Ericsson and Kurol (2000b) disclosed that 48% of subjects with ectopically positioned maxillary canines had root resorption on the adjacent incisors. The major advantages of CT are that blurring and overlapping of the teeth are eliminated and tissue contrast is excellent. Thus the potential to detect root resorption is substantially enhanced. Investigation by Ericson and Kurol (2000a) confirmed that CT scanning performed with good technique is a reliable method of accurately disclosing tooth root resorption. In cases of ectopic eruption of maxillary canines, the prognosis for the lateral incisor is a major determinant in clinical decision-making and treatment planning. Bjerklin and Ericson (2006) analysed treatment outcome and treatment planning before and after a CT investigation of 80 children with 113 impacted maxillary canines. Supplementary information from CT led to modification of treatment plans for 35 (43.7%) of the children. Without the CT investigation, severe resorption (pulpal involvement) of the incisor root would have been undetected in 11 children and 13 who had no root resorption would have had one or both lateral incisors extracted. In recent years digital volume tomography such as Accu- I- Tomo has been proposed as an alternative to routine CT for diagnosis and treatment planning of impacted teeth 15 (Chaushu et al. 2004): this method provides the same information as conventional CT, but at less cost and a lower radiation dose. Treatment of impacted maxillary canines In principle, treatment comprises surgical exposure of the canine and fixed orthodontic appliance therapy, applying elastic traction to reposition the canine in the dental arch. This orthodontic–surgical treatment is sometimes followed by extraction therapy because of space deficiency. Other approaches are presented in the literature (Jacoby 1979; Caprioglio et al. 2007). Removable appliances can also be used (Fournier et al. 1982, McDonald and Yap 1986). A study by Ericsson and Kurol (1988a) confirmed that when palatally displaced maxillary canines are detected early, by 10-11 years of age, the prognosis for normalization of the eruption path is good: after extraction of the deciduous canine, the permanent successor can erupt into the correct position in the dental arch. Of the 46 palatally displaced canines in this study, 36 (78%) changed from palatal to normal eruption paths after intervention: the positions of 23 had improved after 6 months and 13 after 12 months. The remaining canines showed no improvement 12 months after intervention. Cases in which there was more severe overlap of the canine over the lateral incisor were less likely to respond well to this intervention. Leonardi et al. (2004) showed only a 50% success rate for extraction of the deciduous canine as an isolated measure to intercept palatal displacement of maxillary canines: not 16 significantly greater than for unerupted controls. Use of headgear in conjunction with extraction of the deciduous canine induced successful eruption in 80% of the cases. A study by Bruks and Lennartsson (1999) comparing interceptive and corrective treatment groups showed the major determinant for the final outcome to be age at the time of recognition and referral, while the position of the canine can be a compromising factor. Ericsson and Kurol (2000b) emphasized the importance of early supervision of the maxillary canine germ and the eruption path of the canine to allow early, less invasive intervention in cases of disturbed eruption. Associated root resorption of adjacent teeth In routine orthodontic treatment of uncomplicated malocclusions, shortening of the roots of the teeth by resorption is not uncommon. It is generally acknowledged that resorption seldom progresses after orthodontic forces are discontinued (Copeland and Green 1986, Levander and Malmgren 2000). Whether the same applies to resorptive lesions induced on the roots of adjacent teeth by ectopic canines has yet to be confirmed. A search of the literature discloses few investigations into the response of resorptive lesions on the roots of maxillary incisors and the long-term survival of these teeth following treatment of ectopic canines. Severely resorbed incisors have been extracted on the assumption that the teeth have a poor long-term prognosis (Rabie et al.1996, Rimes et al.1997, Savage and Kokich 2002). 17 Of the few available reports, Parker (1997) indicated that extraction or orthodontic distancing of the impacted canine seems to arrest the resorptive process without the need for root canal therapy if the vitality of the tooth has been maintained. Other reports have disclosed progressive root resorption although minimal, in follow-up radiographs (Shellhart et al. 1998, Saldarriaga and Patino 2003). Before the advent of CT investigation, ectopic maxillary canines were treated without ascertaining the presence of root resorption on the adjacent incisor roots. As it is now known that there is associated resorption in almost half such cases, it follows that many patients who underwent treatment for ectopic maxillary canines some years ago would have retained incisors with undiagnosed root resorption. The literature suggests that after intervention to correct the ectopically positioned maxillary canine, the resorption process is arrested and the affected tooth is not susceptible to further damage. Hence these teeth should not exhibit increased mobility or discoloration. The condition of the incisor root is an important determinant of the outcome of treatment for ectopically positioned canines. More needs to be known about the effect of root resorption on the long term prognosis for these incisors. Such information would provide valuable guidance for the clinician in deciding whether to recommend treatment based on extraction or retention of these incisors, or which tooth to extract. The present retrospective study is based on long-term clinical and radiographic follow up-of patients with ectopic maxillary canines, treated in Jönköping, Sweden up to 28 years ago i.e. before the adoption of CT as a diagnostic aid in evaluating impacted teeth. 18 The aim of the study was to document the condition of the maxillary incisor teeth adjacent to the treated canines, with special reference to resorptive lesions on the roots. Hypothesis: We believe that after intervention to correct the ectopically positioned maxillary canine, the resorption process is arrested and the affected tooth is not susceptible to further damage and these teeth should not exhibit increased mobility or discoloration. 19 Subjects and Methods Subjects The Orthodontic Department of the Institute for Postgraduate Dental Education in Jönköping, Sweden, is the regional referral centre for cases of severe ectopically erupting canines. The study sample comprised children referred for consultation and treatment of ectopically positioned maxillary canines, during the late 1970’s and 1980’s. Inclusion criteria were resorption discernible on radiographs or a high probability of an existing resorption due to the ectopic position of the maxillary canine. Treatment with fixed appliances had started between 1974 and 1990. All treatment had been completed over 10 years ago. Post-treatment radiographs were available. A search of the records disclosed 39 former patients who met the criteria. Four had moved abroad and could not be contacted. The remaining 35 were contacted and offered follow-up examination. Ten of them did not participate in the study: eight had relocated, one was pregnant and one patient expressed concerns about the CT-examination. Thus the final material comprised twenty-five participants. Treatment start was defined as start of the fixed appliance therapy. Most of the patients had previously undergone extraction of the deciduous canine. The mean age at the start of treatment was 13.9 years (SD 3.65). All subjects had severely ectopically positioned canines with suspected root resorption on the adjacent incisors. In two cases in which the lateral incisors had been extracted due to resorptive damage, the central incisors were examined. The mean duration of treatment was 2.6 years (SD 1.20). Treatment comprised surgical exposure of the canine and elastic 20 traction in combination with fixed appliances. One patient went abroad for 1 year and 4 months and continued treatment after her return. The mean age at the end of treatment was 17.1 years (SD 4.45). Treatment was completed between 1978 and 1994 (mean 1983). The mean age of the subjects at follow-up was 37.1 years (SD 9.48). The study was approved by the Research Ethics Committee, Faculty of Health Science, Linköping University, Linköping, Sweden. Method The author (C.H. Guitirokh) conducted a clinical examination of the maxillary anterior teeth of 24 of the subjects, recording the following variables: vitality, pocket depth, palpation, percussion, apical tenderness, mobility, discoloration and position of the incisors. One subject was not examined by the author and was excluded from the clinical part of the study. To compare vitality responses, vitality tests were conducted on the maxillary anterior teeth, from the maxillary right canine to the maxillary left canine. An Analytic Technology model 2006 vitality scanner (Redmond, Washington, USA) was used throughout. Periodontal condition was recorded by probing at eight sites on each anterior tooth: mesial, mesiopalatal, palatal, distopalatal, distal, distobuccal, buccal and mesiobuccal. All four maxillary incisors were palpated buccally for apical tenderness. A percussion test was conducted on each tooth from the maxillary right canine to the maxillary left canine to record normal or ankylotic sounds. 21 Mobility of the incisors was registered as present or not. The incisors were evaluated with respect to aesthetics, in terms of tooth colour, position in the dental arch and inclination. Tooth shape and tooth colour were recorded as normal or otherwise. Tooth position, inclination and rotation were documented. The examiner’s assessment of treatment outcome was recorded, as was patient satisfaction. Two patients who had lost their lateral incisors post-treatment were excluded from this evaluation. Another two patients with resorption attributable to the orthodontic treatment itself were also excluded from the clinical evaluation. The patients were interviewed, study models were made, digital intraoral photographs and intraoral radiographs were taken. The radiographs were taken with a digital Focus 2004 apparatus (Imaging Instrumentarium), using the parallel technique, in which the x-ray beam is different projections. All radiographs were compared with the post-treatment radiographs. Twenty-one patients with in all thirty-three incisors “of concern” were referred for more detailed examination by contiguous transverse CT. Four patients were not referred for further CT examination. One patient became pregnant during the study and could not undergo CT and one patient had such obvious and extensive resorption that CT was considered unnecessary. Two patients had lost the incisor in question post-treatment. The CT examinations were conducted in the city where the patient was resident. In Jönköping a Siemens Somatome Plus CT scanner (Siemens AG, Germany) was used for contiguous transverse CT scans with a slice thickness of 1- 2mm. Two patients were scanned in another hospital with a General Electric Light Speed X-steam with slice thicknesses of 0.625mm and 1mm. One patient attended a third hospital where CT scans 22 with slice thicknesses of 1mm were taken by 3D Accu- I- Tomo (J Morita MFG.Corp., Kyoto, Japan). The radiographs were analysed by two oral radiologists and the author. Resorption was described in terms of position: buccal/distobucccal, palatal, distopalatal, distal or apical. The site of the resorptive lesion on the root was also recorded as: cervical, middle or apical third or on the apex. Taking into account both radiographs and CT results, the author graded the resorptive lesions as slight, moderate or severe, based on whether the location was apical or lateral. The location of resorbed areas was determined in three planes. Signs of apical root resorption were registered with index scores from 0 to 4 (Figure 1a) as described by Levander and Malmgren (1988, 2000). Figure 1b shows three different patients with incisors that show apical root resorption in various degrees. Figure 1a. Root resorption index for quantitative assessment of root resorption. 1. Irregular root contour; No resorption 2. Root resorption apically, amounting to less than 2 mm; Slight resorption. 3. Root resorption apically, from 2mm to one third of the original root length; Moderate resorption. 4. Root resorption exceeding one third of the original root length; Severe resorption (Levander and Malmgren 1998; Levander and Malmgren 2000). 23 Figure1b. Slight apical root resorption (left). Moderate apical root resorption (centre). Severe apical root resorption (right). The severity of mesial, distal, buccal or lingual resorption was scored on a 4 point scale according to Ericson and Kurol (2000): 1. No resorption- intact root surfaces, except for loss of cementum. 2. Slight resorption- up to half of the dentine thickness. 3. Moderate resorption- half way to the pulp or more; the pulp is covered with dentine. 4. Severe resorption- the pulp is exposed. 24 Statistical analyses The results were analysed by a statistician. Different findings within the sample were too small to give an accurate statistical significance. There are also dependent variables such as one patient having 2 teeth with resorption within the sample which makes the statistic very uncertain. Ethical considerations The study was approved by the Research Ethics committee, Faculty of health science, Linköping University, Linköping, Sweden. Special Significance The evaluation of the incisor root adjacent to ectopically positioned maxillary canine teeth is of great importance to both the patient and orthodontist in treatment planning. We need to know more about how root resorption affects the long term prognosis of these incisors. This ought to be taken into account when deciding on extraction/nonextraction or which tooth to extract. 25 Results In all, a total of 37 incisors was examined in 25 subjects. However, different subgroups within the sample were too small to allow statistical analysis. The results of the intraoral radiographs at follow-up are shown in Table 1. Seven subjects exhibited resorption on two or more incisors, while no resorption was discernible in eight subjects, despite the severely ectopic canine and grave suspicion of damage to the adjacent roots. Table 1. Number of subjects and incisors with root resorption visible on intra oral radiographs at followup. Without Resorption Uncertain Resorption Resorption Post-treatment Extracted Subjects(n=25) 8 2 13 2 Incisors(n=37) 9 3 22 3 Resorption was detected on intraoral radiographs in 22 incisor roots and could not be ruled out in 3 incisors. Only one of the incisors with resorption was adjacent to a buccally impacted canine. Three incisors showed signs of resorption that were difficult to differentiate from orthodontically induced resorption. In two subjects, three incisors had been extracted post treatment. One subject had lost two lateral incisors due to trauma. His pre-extraction radiographs were retrieved from 26 the clinic where he had undergone treatment. These did not show any extensive root resorption at the time of extraction. One subject with a unilateral ectopic canine and missing lateral incisor had lost a central incisor due to advanced periodontitis approximately 10 years after treatment. Unfortunately her records at the time of extraction had been destroyed. The results of the intraoral radiographs and CT examination were then compared and compiled. Although the CT examination was superior in detecting buccal and lingual resorptions, intraoral radiographs were found to be more useful in disclosing and comparing apical resorption. The two subjects who had undergone extractions were excluded from the comparison as it was uncertain why the incisors were lost. Figure 2 shows an intraoral radiograph and CT of the maxillary left central incisors. The root resorption on the palatal aspect of the cervical third of the root, disclosed by CT examination, is impossible to see in intraoral radiographs. Figure 2.Distopalatal root resorption on the cervical third of the root of the maxillary left central incisor. Comparison of intraoral radiograph (left) and CT-examination (right). Examination of the 22 incisors with root resorption disclosed 27 affected root surfaces in 13 patients. One patient had 4 resorbed incisor roots, 6 patients had 2 resorbed incisor 27 roots and the remaining 6 patients had each only one tooth resorbed. In 11 of these teeth the resorptive lesion was located on the palatal or distopalatal aspects of the root and 14 incisors showed signs of apical resorption (Table 2). Table 2. Number of resorbed surfaces disclosed by intraoral radiographs and CT examination. Some incisors were resorbed on more than one surface. Thus of 22 affected incisors, resorption was recorded on 27 surfaces. Buccal, Distobuccal Palatal, Distal Apical Total 10 Distopalatal Lateral incisors - 5 - 5 incisors 1 6 1 9 17 Total 1 11 1 14 27 Central Comparison of the location of the resorptive lesions along the roots in a vertically divided scheme revealed 9 of the total 22 incisors with resorption of the apex, 2 with resorption in the apical third of the root, 9 with resorption in the middle third of the roots and 2 in the cervical third (Table 3). Table 3.Number of diagnosed resorbed root surfaces in a combined intraoral and CT investigation. Only one surface from each tooth is registered. Teeth Cervical Middle Apical Apex Total third third third 1 6 - 2 9 incisors 1 3 2 7 13 Total 2 9 2 9 22 Lateral incisors Central 28 Severity was graded as slight, moderate or severe, as described earlier. Of eight incisors with severe resorption, six were central incisors. Five lateral incisors and two central incisors showed moderate resorption. Slight resorption was noted in the remaining 7 teeth (Table 4). Table 4. Severity of incisor root resorption induced by ectopic canines in 22 patients Teeth Slight Moderate Severe Total Lateral incisors 5 5 2 12 Central incisors 2 2 6 10 Total 7 7 8 22 All radiographs taken at the follow-up were compared to radiographs taken at completion of treatment (Table 5). Table 5. Resorption on the incisor roots: comparison of radiographs at follow-up and those taken on completion of treatment Incisors Improved Laterals 1 Centrals 1 Total 2 Unchanged 8 Increased Total 3 12 9 0 10 17 3 22 In two cases the follow-up radiographs showed slight improvement. The condition was unchanged in seventeen teeth (Figure 3): in fifteen of these the periodontal ligament and lamina dura were more distinct, with much improved trabeculation of the periapical area with further maturation and smooth edges (Figures 3, 4 and 5). One patient with two central incisors and a resin-bonded bridge showed obliterated pulps and 29 indistinguishable lamina dura (Figure 6). In one case the lamina dura was well-defined but the edges were still rough (Figures 7). Resorption was more pronounced in three teeth (Figure 8). In one of these cases the resorption had progressed and the lamina dura was still poorly defined at the resorption site. This tooth had undergone endodontic treatment(Figure 9). Figure 3. Patient with severe resorption on the lateral incisors due to ectopically erupting canines (left). The lateral incisors were extracted and replaced with a resin bonded bridge. The centre radiograph was taken on completion of treatment and the radiograph to the right is 22 years post treatment. The followup radiograph shows slightly better definition of the PDL and the lamina dura. Figure 4.Patient with slight apical resorption of maxillary left incisor at completion of treatment (left and centre) and 16 years post treatment (right). Note that the root shape is even and lamina dura is welldefined. 30 Figure 5. Radiographs on completion of treatment (left) and 19 years post treatment (right). Patient with moderate apical root resorption on maxillary right lateral incisor. At follow-up the resorbed area shows a better-defined PDL and lamina dura. Figure 6.A patient with severe root resorption on both maxillary central incisors. The maxillary lateral incisors were extracted due to severe resorption. 11 and 21 were orthodontically aligned at the midline. The crowns of the maxillary lateral incisors were replaced by a resin bonded bridge. Radiograph on completion of treatment (left) and at 17 years post retention (right). The pulps of the central incisors are obliterated. The surface of the roots appears smoother and rounder. Lamina dura is indistinguishable. 31 Figure 7. Patient with slight resorption on the maxillary left lateral incisor at completion of treatment (left), and 16 years post treatment (right). There are no signs of the progression of the resorption on the root. Lamina dura is well-defined. At follow-up the resorbed area shows a better-defined PDL and lamina dura but the edges are still rough. Figure 8. Radiographs at treatment end (left) and 16 years post treatment (center and right ). Right lateral incisor was extracted during treatment and both central incisors show resorption due to ectopic eruption of the maxillary canines. Right maxillary incisor with severe distopalatal resorption and left maxillary central incisor show apical and distal resorption. The area of resorption shows slight progression . Figure 9. Patient with severe distopalatal root resorption at completion of treatment (left). Endodontic treatment was undertaken many years later. Radiograph to the right is 19 years post treatment. The resorption has progressed slightly towards the pulp and the lamina dura at the resorption site still lacks definition. 32 Clinical results The results of the clinical findings are summarized in Table 6. All subjects were satisfied with the overall aesthetic outcome, although some commented on the rotation or inclination of the laterals and two were dissatisfied with the colour of the maxillary incisors. The author and subjects were in agreement with respect to the aesthetic results in all cases. During the study, it was observed that some of the incisors examined responded more slowly to the electric vitality test than contralateral teeth within the same subject. For this reason it was decided to document whether a tooth reacted at minimum 10 levels higher than adjacent maxillary incisors. Delayed response to the vitality test was recorded in 42% of teeth with resorption: the corresponding result in incisors without detectable resorption was 25%. One subject without signs of resorption was very sensitive to the electrical vitality test and found it very painful. No other symptoms were registered for this subject. One incisor with root resorption and one incisor without root resorption showed crown discoloration. 33 Table 6. Summary of clinical findings at follow-up registration in 20 patients with 29 lateral and/or central incisors with suspected resorptive damage attributable to an ectopic canine. Two incisors were excluded because of orthodontically induced resorption Resorption Without Total resorption (n=19) (n=10) (n=29) Discoloration 1(5%) 1(10%) 2(7%) Sensitive tooth - 1(10%) 1(3%) 1(10%) 3(10%) Pockets Ankylotic sound 2(11%) 2(11%) - 2(7%) 1(10%) 2(7%) Palpation tenderness 1(5%) Vitality test reacting more than ten levels later than other maxillary incisors 5 (26%) 2 (20%) 7 (24%) Root treatment post-treatment 1 (5%) - 1(3%) Deviant inclination, rotation, position Increased mobility 8 (42%) - 6 (60%) - 12 (41%) - In the resorption group two subjects had pockets > 4mm: 6mm and 4.5mm, respectively. In the group of subjects without resorption only one had a 4mm pocket. Two subjects exhibited tenderness to buccal palpation of the apical area. Only one showed resorption on the incisor root. These subjects were double checked, as the apical tenderness was an unexpected finding. The incisor with resorption also had a delayed reaction to the vitality test whereas the other incisor had no other symptoms. 34 In two subjects, ankylotic percussion sounds were recorded on central incisors with resorption. One of these subjects had a history of trauma in the maxillary anterior region and the other had a resin-bonded bridge on the maxillary central incisors, following extraction of 12 and 22 due to severe root resorption. An apical periodontitis had developed on one severely resorbed lateral incisor, necessitating endodontic treatment a few years post-treatment. The precise date for the endodontic treatment could not be determined. At follow-up many of the patients had proclined, retroclined, or mesially or distally rotated incisors, irrespective of the presence or absence of resorption. None of the incisors showed signs of increased mobility. 35 Discussion The present study was undertaken to investigate the long-term fate of teeth with resorptive lesions induced by ectopic canines. Current clinical and radiographic status was compared with the data recorded on completion of treatment some 20 years earlier. Analysis of such long-term treatment outcomes provides evidence-based information to support orthodontic treatment decisions. A study with such a long follow-up period offers a challenge with respect to gathering the sample and also ensuring that the data retrieved from treatment records can be compared. It offers valuable information, but it is difficult to draw conclusions from some of the findings. Although the departmental records were searched for all patients treated for ectopic maxillary canines over a 20 year period, only 39 cases were found with complete radiographic records from start of treatment and post-treatment. Many records had been destroyed. Three patients had moved abroad and could not be contacted. Thirty-six patients were contacted: eleven could not participate, mostly because of relocation, which is a limitation in long-term clinical follow-up studies. A further limitation is pregnancy as many pregnant women would be reluctant to undergo radiographic examination. While the sample was limited to subjects with severely ectopic canines, the incidence of resorption was still quite low (65%), confirming previous reports that it is difficult to predict which cases will develop resorption (Ericson and Kurol 1988b). Treatment of the ectopic canines had been undertaken during the 1970’s and 80’s. At this time computed tomography had not been established as a diagnostic aid for dental 36 impactions. In many cases of suspected root resorption of adjacent teeth, these teeth were extracted. The follow-up study disclosed eight incisors with severe resorption, seven with moderate resorption and seven with slight resorption. As many teeth with severe resorption are extracted during treatment, it is difficult to gather a sample of subjects with severe resorption at follow-up. In this sample, the treatment plans of two patients had included extraction of two severely resorbed lateral incisors due to their poor prognosis. In all patients, the resorption had occurred before the fixed appliance treatment and the patients then underwent significant orthodontic movement, after distancing the impacted canine. The mean treatment time for the impacted canine with elastic traction in combination with fixed appliances was 2.6 years (SD 1.20). This was in line with the appropriate radiographic monitoring for further root shortening. In no patient had it been necessary to discontinue treatment for this reason. There are very few follow-up studies of root resorption induced by impacted canines. There are some similarities with root resorption induced by orthodontic forces: both lesions comprise an area of sterile inflammation causing loss of hard tissue (Brezniak and Wasserstein 2002). It is generally acknowledged that orthodontically induced resorption is arrested when the force is removed. In analogy, resorption induced by an impacted canine should not progress once the canine is distanced from the root (Copeland and Green 1986, Becker 2005). 37 A literature review by Brezniak and Wasserstein (1993) led to the conclusion that even extensive orthodontically induced resorption does not affect the functional capacity or the effective life of the tooth. However, Levander and Malmgren (2000) showed increased mobility in maxillary incisors that undergo severe root resorption during orthodontic treatment. It can be difficult to distinguish apical resorption induced by an ectopically positioned canine from orthodontically induced resorption. However, orthodontically induced resorption is usually more generalized, affecting all four anterior incisors. When the impacted canine is very close to the incisor root, the clinician must distance the canine from the incisor root as early in the treatment as possible, in order to minimize the risk of resorptive damage. Many incisors with severe root resorption are extracted on the assumption the long-term prognosis is poor (Ryan 1997, Rimes 1997, Ericson and Kurol, 2000a). Some case reports have indicated that retaining severely resorbed incisors can be an alternative (Shellhart et al.1998, Saldarriaga and Patino 2003). Resorptive damage is assessed primarily on radiographic evidence. On intraoral radiographs it is difficult to detect resorptive damage on the buccal or palatal aspects of the roots. It may also be difficult to differentiate between damage attributable to orthodontic treatment and that induced by the ectopically positioned canines, particularly because orthodontic treatment frequently involves movement of the lateral and central incisors. 38 Computed Tomography (CT) can provide more reliable information than conventional radiography and is useful for discerning the contour of the root and the resorbed area. CT examination discloses sites of resorption not detectable in intraoral radiographs. In this study intraoral radiographs proved more useful for determining apical resorption and root shortening, particularly because it was possible to compare the follow-up radiographs with those taken on completion of treatment. Because of the low radiation dose, limited 3- dimensional cone-beam computed tomography is recommended in management of impacted canines. Examples are Tom QR-DVT 9000 or Accu-I-Tomo ( Walker et al. 2005, Chaushu et al. 2004, Nakajima et al. 2005). This method provides information about the size of the follicle, relative buccal and palatal positions, the amount of bone covering the tooth and 3D proximity and resorption of roots of adjacent teeth. The radiation dose is only one-sixth of conventional computer tomography and its cost is considerably less (Lofthag-Hansen et al. 2007). The present study is unique because of the very long follow-up time (13-28 years post retention). Most of the resorptive lesions (15 of 22) were unchanged in area, but with a better defined lamina dura and improved trabeculation of the periapical area, with further maturation and smooth edges. Areas of active resorption are characterised by a poorly defined lamina dura and PDL (Ericson and Kurol 1987b): in a few cases the lamina dura was not distinct, or the edges of the teeth were sharp and spiky at follow-up. In two cases the lesions showed minor improvement. In three cases the resorptions were more pronounced. In two of these 39 cases it was in the author’s opinion a result of the contouring the root and had to do with the shape of the initial damage. One patient had developed apical periodontitis on the lateral incisor several years post-treatment and had undergone endodontic treatment. In this case the resorption had progressed to pulpal involvement post-treatment. The results of the present study were in agreement with those of Becker et al. (2005) which also showed a minimal risk of further resorption when these teeth were subjected to orthodontic forces. Becker et al. (2005) studied 11 subjects with 20 severely resorbed incisors and reported that none of the incisors was lost during follow-up. However, the follow-up period was much shorter than in the present study. In the present study, two subjects had lost their incisors post-treatment. One had lost two lateral incisors due to trauma and one with a unilateral ectopic canine and missing lateral incisor had lost a central incisor due to advanced periodontitis approximately 10 years after treatment. Today she has severe contralateral periodontal involvement, but the incisors are still in function. No records of her periodontal treatment were available. Clinically no increased mobility or discoloration was observed. This is also in agreement with Becker (2005). In the group with resorption, a metallic percussion sound indicating ankylosis was recorded in two subjects and 5 had a delayed reaction to the electrical vitality test, compared to the 2 subjects in the group without resorption. Although such a limited material allows no extrapolation of the findings, the results show that in this sample of subjects who presented with severely ectopic canines, longterm follow-up of the fate of the retained lateral incisors confirmed that the resorption 40 did not tend to progress following intervention to correct the canine impaction. Despite the resorptive damage, these incisors had tolerated the orthodontic forces applied during realignment of the anterior teeth. In the majority of cases there had been no progression of resorptive lesions and few post-treatment complications. Most of the teeth with resorption induced by the ectopic canines were in function some 20 years after completion of the orthodontic treatment. In general the subjects were satisfied with the treatment outcomes. It is very difficult to find a large sample of incisors with severe resorption, partly because improved screening of children at appropriate stages facilitates early detection of the ectopic canine and intervention before resorptive damage occurs on the adjacent teeth, but also because many such teeth are extracted as part of the orthodontic treatment, to avoid future complications. A multi-center long-term follow-up of severely resorbed incisors is warranted, in order to study clinical and radiographic changes in a sample large enough to allow statistical analysis. 41 Conclusions Root resorption induced by an ectopically positioned canine does not progress post-treatment in the majority of cases. Apical and periodontal health around a resorbed root often normalizes and the lamina dura is more well-defined at follow-up. 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