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Br itish Jour nal o f Or thodonti cs/Vol . 25/1998/209216

Introduction

Orthodontics is considered to be a complex problem-solving doma in (H ultgren et al ., 1994). A good example o fthis is the large number of patient factors and treatmentvariables which must be considered when dealing withmaxillary canine ectopia. The complexity of this clinicalproblem is further compounded by the scarcity of properlycontro lled clinical research. The purpose of this paper is toreview t he various treatment options aga inst the a vailablescientifi c evidence.

Incidence/Epidemiology

The maxillary canine is second on ly to the mandibula r thirdmolar in its freq uency of impaction. The freq uency variesfrom less tha n 08 to 28 per cent (Sha h et al., 1978; G roverand Lorton, 1985). The condition is more than twice ascommon in girls (12 per cent) than in boys (05 per cent;D achi a nd H owell, 1961). C anine impaction is foundpala ta l to a the arch in 85 per cent of cases and labia l/buccalin 15 per cent (H itchin, 1956; R ayne , 1969; E ricson a ndKurol, 1987b). There is some evidence that patients withCla ss II d ivision 2 malocclusions and tooth aplasia ma y beat higher risk to the development of an ectopic canine(Kettle, 1957; Harzer et al., 1994; Mossey et al., 1994;

B renchley and O liver, 1997).

Normal Development and Eruption Pattern

B road bent (1941) stated tha t calcification of the permanentmaxillary canine crown starts at 1 year old, between theroots of the first primary molar, and is complete at 56years. By the age of 12 months the crown of the tooth isfound betw een the roots of the first primary molar. At 34years of age t he canine passes over the line of the primaryincisors to lie on the labial side of the root of the lateralincisor (Miller, 1963). At age 4 years the primary firstmolar, the fi rst premolar germ and t he canine lie in verticalrow. Subsequent grow th on the fa cial surface of the maxillaprovides space for the forw ard movement of the canine so

that its cusp comes to lie medial to t he root o f the deciduouscanine. Moss (1972) states that the canine remains high inthe ma xilla just abo ve the root of t he lateral incisor until thecrown is calcified . It then erupts along the distal aspect ofthe lateral incisor resulting in closure of the physiologicaldiastema if present and the correction of the so ca lled U glyD uckling dentition (Kurol et al., 1997).

In a recent paper, Coulter and Richardson (1997)q uantified the movements of the maxillary canine in threedimensions using lateral and posteroanterior cephalo-metric radiographs from the B elfast G rowth Study ta kenannually between 5 and 15 years of age. It was shown thatthe canine travels almost 22 mm during that time. In thelateral plane the ca nines showed a significant movement ina buccal direction betw een 10 and 12 years of age. B eforethis age the movement was in a palatal direction. Aboutthree-quarters of the root is formed before eruption androot formation is complete 2 years after eruption. Hurme(1949) stated that gingival emergence of the maxillarycanine after 123 years in girls and 131 years for boys waslate. Thilander and Jacobsson (1968) regarded 139 yearsfor girls and 146 years as very late for boys as by this time95 per cent should have erupted. The maxillary canine isthe last tooth to erupt in the upper arch with a deciduouspredecessor and, therefore, is most susceptible to environ-mental influences such as crowding.

Aetiology of the Ectopic Canine

The a etiology of the ectopic canine is obscure, but proba blymultifactorial. The maxillary canine has the longest path oferuption in the permanent dentition and this may be afactor in the aetiology (Coulter and Richardson, 1997).Arch length discrepancy (crowding and spacing) isimplicated in the aet iology of the ectopic canine. A spacedeficiency may result in the tooth erupting buccally or itsimpaction (J acoby, 1983). Thilander and J acobsson (1968)stated that crowding may be a factor in labial impaction,but not in pala ta l impact ion. Ja coby (1983) found t hat in 85per cent of cases where the ca nine erupted pa lata lly in hisstudy that adequate space was present in the arch. He

The E ctopic Ma xillary C anine: A R eview

P A T R I C K F . M C S H E R R Y B . A . , B .D E N T .S C . , M . S C . ( L O N D . U N I V ) , F . D . S . O R T H ( R . C . S .E D . ) , M . O R T H .

( R . C . S . E D ) , M . D E N T. S C . ( U N I V . D U B . ) , F . F .D . ( R . C . S . I . )

D epartment of O rthodontics, School of D entistry, Royal G roup of Hospitals and D ental Hospital, G rosvenor Roa d, B elfast B T12 6B P, U K

I ndex words: Ectopic Canine, Review.

0301-228X/98/003000+ 00$02.00 1998 B ritish O rthodontic Society

Review Article

Abstract.This article reviews the aetiol ogy and management of the ectopic maxill ary canine. M uch controversy surroundsthe causes of canine palatal ectopia. T he recent evidence sur rounding the genetic and gui dance theor ies are exami ned. Themanagement op tions are detailed and the indi cations for each treatment modali ty based on the availabl e scientific evidenceare presented. Finall y, the untoward sequelae of canine ectop ia are discussed.


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210 P. F. McSherry Scientific Section BJO Vol 25 No. 3

suggested that a possible explanation f or canine impactionto be excessive space in the canine area. Other suggestedcauses of palatal impaction are trauma to the maxillaryanterior region at an ea rly stage of d evelopment (B rinet al.,1993).

Studies have shown that there is a higher incidence ofpalatally ectopic canines in cases with peg shaped smalllateral incisors or in cases with missing lateral incisors(B ecker

et al., 1984). The G uida nce Theory in its simplest

form regard s the distal a spect of the latera l incisor root asthe guide to allow t he canine to erupt safely into position. Ifthe lateral incisor is anomalous or missing this guidance ismissing resulting in palatal displacement of the canine.Becker et al. (1981) found a 55 per cent ra te o f congen italab sence of la teral incisors in a large group of pa tients withpalatal canines. This was 24 times the rate in the generalpopulation. It wa s hypothesized that the latera l incisor wasnot sufficiently developed a t the time when its root wo uldbe most important fo r guidance of the canine. Oliver et al.(1989) found that lateral incisors on the side of canineimpaction were generally smaller than o n the non impactedside in a sample of 31 Causacian subjects. Other studiescould demonstrate no or a weak association betweenanoma lous latera l incisors and canine impaction (Mossey etal., 1994; B renchley a nd O liver, 1997).

D elayed exfoliation of the primary canine may result incontinued palatal movement of the permanent successor.However, Thilander and Jacobsson (1968) considered thispersistence of a primary canine to be a conseq uence ratherthan a cause of impaction. Other possible causes includepathological lesions, ankylosis, odontomes, or super-numerary teeth. There may also be a higher incidence ofimpaction of the maxillary canine following alveolar bonegrafting in patients with cleft lip and palate (Semb andScha rtz, 1997).

A genetic or fa milial trend has been pointed out by someworkers. Zilbermann et al. (1990) found tha t the relat ives ofpatients with pala tal ca nines are likely to exhibit palat allydisplaced canines, anomalous lateral incisors and latedeveloping dentitions. B jerklin et al. (1992) found thatectopic eruption of maxillary canines occurs in a higherfrequency than normal in children with other eruptiondisturbances such as ectopic first permanent molars andconcluded tha t the a etiology was presumably hereditary. Agenetic basis has been suggested by P ecket al. (1994). Theyreviewed the evidence regarding the palatally displacedcanine as a d ental a nomaly of genetic origin concluding thatpalata lly displaced canines appear to be a product of poly -genic, multifactorial inheritance. Pirinen et al. (1996)concluded from their study on 106 consecutive patientswith displaced canines having examined the 1st degreerelatives and the 2nd degree relat ives that palata l displace-ment of the canine is both genetic and related to geneticincisor-premolar hypodontia and peg-shaped lateralincisors. H ypodontia was noted in 1920 per cent o f 1st /2nddegree relatives and this was 25 times the populationprevalence. The prevalence of palatally displaced canineswa s 49 per cent (a lso 25 times the population prevalence).McSherry and Richardson (in press) quantified the move-ments of the 20 ectopic palatal maxillary canines in threedimensions using lateral and posteroanterior cephalo-metric radiographs from the B elfast G rowth Study ta kenannua lly betw een 5 and 15 years of age. I n comparison to

the norma l eruption, the ectopic canine alwa ys travelled ina pala ta l direction and fa iled to demonstrate the late buccalmovement w hich normally occurs at a ge 1012 yea rs.

Treatment Planning Considerations

The ectopic maxillary canine can often require complexmultidisciplinary treatment involving oral surgical,

restorative, periodont ic, a s well as ortho dontic components(B ishara , 1994).

M anagement Options

The patient with an impacted maxillary canine initiallymust undergo a comprehensive assessment of the maloc-clusion to loca lize the canine a nd decide on its prognosis foralignment. Factors affecting the prognosis include patientco-operation, age, general oral health, skeletal variation,and presence of spacing or crowding in the a rch (McSherry,1996). Other conditions to be taken into account are the

position of the canine in the three planes of space andwhether a ny resorption of the incisor roo ts has ta ken place.It is important that the specialist b e vigilant w ith respect tothe malposition of the maxillary canine especially during itsdevelopment a nd be conversant w ith the normal eruptionpattern. I nterceptive measures, when a ppropriat e, are mostadvantageous in terms of cost benefit than other moreinvasive procedures. P atient a nd pa rent counselling on thetreatment options and informed consent is essential toavoid a ny medicolegal problems (Ma chen, 1989).

The treatment alternatives include:

Interceptive treatment.Surgical exposure and orthodo ntic alignment.

O ther options.

Interceptive Treatment by Extraction of the DeciduousCanine

Ericson and Kurol (1988a) carried out an extensiveprospective longitudinal study on a preselected group of1013 year o ld children (mean a ge 114 years) w ith pa lata llyectopic canines and uncrowded a rches. They found that 78per cent of the canines reverted to a normal path oferuption following extraction of the primary canine. Thepercentage improvement depended on the degree ofoverlap of the canine over the lateral incisor root andvaried between 64 and 91 per cent. An improvement wasseen in 50 per cent o f the successful cases aft er 6 months. Ifno improvement w as seen aft er 12 mont hs then none couldbe expected. No control group w as used in this study a s theauthors considered it to be unethical and the presence orabsence of the lateral incisor was not specificallymentioned. Power and Short (1993) assessed the effect ofremoval of primary canines on the subsequent eruption ofthe successor. They found tha t the success rate w as lower at62 per cent, but a further 19 per cent showed someimprovement. The results showed that the presence ofcrowding inhibits eruption of the permanent canine. Thehorizontal overlap of the canine over the nearest incisorwa s found to be t he most significant fa ctor. If t his exceeded


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BJO A ugust 1998 Scientific Section Ectopic Maxillary Canine 211

half the t ooth width t hen success wa s unlikely. B oth studieswould seem to suggest tha t if the pa tient wa s over 13 yearsof age that alternative treatment options should be con-sidered.

B ased on the results of t hese studies it w ould seemappropriate to recommend the extraction of the primarycanine as a n interceptive measure when:

The patient is aged 1013 years.

The maxillary canine is not palpable in its normalposition and radiographic examination confirms palatalcanine ectopia. Removal of the primary canine mayshow less favourable results where the permanentcanine is located in a more medial position or w hen thepatient older than the ideal age group (Kurol et al.,1997).If there is no improvement in canine position within 12months on the OP G , alternative treatment is indicat ed.Clinical re-evaluation and follow-up radiographs shouldnormally be taken at 6-month intervals (Ericson andKurol, 1988a).

The elimination of dental crow ding in the a rch particularlyin the canine/premolar a rea ca n possibly stimula te eruptioninto the arch (Kurol et al. , 1997). However Kuftinec et al.(1995) recommend that irreversible decisions such as theextraction of permanent teeth to allow canine eruptionshould b e delayed for a s long as possible.

Localization of the Maxillary Canine

Lo calization of the unerupted ca nine involves inspection,palpa tion, and ra diogra phic assessment. The position of thecrown of the latera l incisor can give a clue as to the positionof the crown of the unerupted canine, for example, if thecanine is lying on the labial aspect of the lateral root thecrown may b e proclined (Moss, 1972; B ishara et al ., 1976).Often the crown of the unerupted canine can be palpatedeither in a buccal position or in a palata l position. C liniciansshould become suspicious of the possibility of canineectopia if the canine is not palpable in the buccal sulcusby the age of 1011 years or if palpation indicates anasymmetrical eruption patt ern. Inspection and palpation inthe canine region is recommended annually from age 8yea rs (Ericson and Kurol, 1986 a,b ).

It has been suggested tha t ra diographic procedures priorto the age of 10 years are of little benefi t. R ad iographs areindicat ed befo re 11 years of age if there is an a symmetricpath of eruption as determined by palpation, if the lateralincisor is late in erupting or is tipped labially, if the lateralincisor is missing or there is a family history of ectopiccanines. After age 11, radiographs are indicated in all indi-viduals with unerupted a nd no n-palpable canines (Kurol etal., 1997). Conventional radiography usually involvesta king a combination of radiogra phs (peri-apicals, standa rdupper anterior occlusal, orthopantomogra m) and t he use ofthe principle of vertical or horizontal parallax. The use ofan orthopantomogram or lateral cephalogram can alsoassist in determining the vertical position of the canine. Theuse of these radiographs will help to localize the canine inrelation to the dental arch and determine the angulation,height, and mesiodistal position of the canine (Southall andG ravely, 1989; Fox et al. , 1995). The use of computerized

tomography (CT) to localize canines has been described(E ricson a nd K urol, 1988b; Schmuth et al., 1992). I t is usefulto predict the exact position of the canine, the degree ofcrowding, incisor resorption, and the width of the dentalfollicle. However, this method is rarely used because ofthe high cost of equipment. A new development is the useof magnetic resonance imaging (MRI) and scanora-tomography in the localization of the canine (Kurol et al.,1997).

Exposure With or Without Orthodontic Traction

The conventional trea tment o ption for impacted canines isexposure and orthodontic alignment. The prognosis foralignment is dependent on a number of factors whichinclude the age of t he pat ient, spacing/crowding and thevertical, anteroposterior, and transverse position of thecanine crown and root. If the inclination of the canine inrelation to the midline is greater than 45 degrees then theprognosis for a lignment worsens. The closer the too th is tothe midline the poorer the prognosis. For successful

alignment, the tooth should not b e ankylosed and t he rootnot be dilacerated (Kurol et al ., 1997). The further thecanine needs to be mo ved then the poo rer the prognosis fora successful outcome. To provide for a stable result it isessential to obtain a good buccal overlap and correct rootpositioning (Z achrisson a nd Thilander, 1985).

The outcome o f surgical exposure and o rthod ontic align-ment will depend on a number of factors. As with allorthodontic treatment co-operation and motivation of thepatient is para mount, and t he general dental health shouldbe excellent since the trea tment t ime in these cases is oftenprolonged. It is generally agreed that the optimal timefor alignment is during adolescence (Altonen and

Mylla rniemi, 1976; G allow ay and S tirrups, 1989).

Palatal Ectopic Canines

Essentially, there are three methods for exposure andalignment o f the canine (McSherry, 1996).

Open surgical exposure and spontaneous eruption.Open surgical exposure and packing with subsequentbonding of a n auxiliary.Closed surgical exposure and bonding of a tta chmentintra-operatively.

The fi rst method is probab ly most useful when t he caninehas the correct inclination and will then erupt spon-taneously. The second option is the exposure of the crownof the canine with packing. The pack is removed about aweek postoperatively and an attachment bonded withsubsequent traction using a fixed appliance. There is someevidence that the periodontal stat us may be compromized(Kohavi et al. , 1984; B ecker et al. , 1996). This evidence isnot convincing and a rando mized contro lled clinical trial isongoing (B urden, personal communication).

The third option is the closed technique. This involvesthe reflection of a palatal mucoperiosteal flap. An attach-ment is bonded t o the crown of the to oth and an eyelet wireor gold chain exits through the flap to gain attachment tothe fixed appliance for immediate traction. The ability togain attachment permits a more conservative approach to


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the exposure (B ecker et al., 1996). However, a disad-vanta ge of this technique is that if bond f ailure occurs thenre-exposure is necessary . B ecker et al. (1996) suggests theuse of an eyelet bonded in a mid-buccal position on thecrown of the impacted tooth at surgery as these have thehighest success ra te.

Biomechanical Considerations

Light f orces of the magn itude of 2060 g should be a ppliedto a lign the canine (B ishara , 1994; Kuf tinec et al., 1995).Various methods have been described for aligning thecanine and these are described in detail by Hunter (1983),and Kokich and Matthews (1993). These usually includethe use of fi xed appliances with a transpalat al ba r and /orheadgea r to control vertical a nchorage. The provision andmaintenance of adequate space in the canine area isessential. Application of force can be in the f orm of elasticor w ire tra ction. U siskin (1991) described the use of go ldchain bonded to t he crown of a n unerupted canine to applytraction to align the tooth. A palatal arch with soldered

hooks attached to apply traction to pull the canine awayfrom t he latera l incisor is described. The use of the B allistaspring (a wire loop constructed of 0012-inch sta inless steelwire) has b een described b y J acoby (1979). R oberts-H arryand Harradine (1995) described the use of a sectionalapproa ch to maxillary ca nines using a tra nspalatal a rch foranchorage. They use a 0017- by 0025-inch TMA sectiona larchwire from the first molar to canine providing a lowforce over a long range, which is controllable and remainsstab le in the 0022-inch slot. B ennett a nd McL aughlin(1997) describe the use of a wound on auxiliary to achievefirst vertical movement and then lateral movement. It isconst ructed o f 0014-inch steel wound o n to 0019- by 0025-

inch stainless steel. Ort on et al. (1995) describe the use of alower removable appliance with soldered hooks on thecribs. E lastic traction is applied to t he canine which has agold chain with a hook bo nded to t he tooth. The vector offorce used to a lign the canine can be changed to fi rst movethe canine aw ay from the incisor roots and then verticallyand buccally. Fixed appliances are used to finish thealignment and create adequate buccal root torque andoverlap. Magnetic forces have been advocated by someauthors to a pply force to the ectopic canine for a lignment(Sandler et al., 1989; D arend elilier and Fr iedli,1994).

Retention ConsiderationsBecker et al. (1983) evaluat ed post-trea tment a lignment incases whose treat ment w as completed. They found spacingand rotations in 178 per cent of impacted canines and onlyin 87 per cent on the control side. Woloshyn et al. (1994)found in a sample of previously exposed pa lata lly impactedcanines approximately 40 per cent displayed noticeablerelapse and w ere judged t o b e intruded, lingually displaced,mesially rotated an a verage of 3 years and 7 months post-treatment. The contralatera l untreated side were found tobe 91 per cent normal in appearance. They also foundpulpal obliteration in 21 per cent of impacted canines anddiscoloration in 75 per cent of cases post-treatment.B ennett a nd McL aughlin (1997) suggest the follow ing toprevent relapse:

Full correction o f to rque.Early correction of rotations.C ircumferential supracresta l fiberot omy.P rovision of a bonded reta iner.

It would seem appropriate to recommend surgicalexposure and orthodo ntic alignment when:

The pa tient is willing to wea r o rthodontic a ppliances.The patient is well motivated and has good generaldental health.Interceptive measures are inappropriate (Ericson andKurol, 1988a).The degree of malposition is not too great to precludeorthodontic alignment. The long axis of the ectopiccanine should not be too ho rizontal or too oblique. Thecloser the crown is to the midline and the root is to themid-palatal suture the poorer the prognosis for align-ment (Kurol et al., 1997)Any evidence of tooth resorption or other pathologyshould be such that it is more desirable to preserve thecanine. For example, where a resorbed lateral incisorhas a very poor prognosis, it may be advantageous toattempt alignment of a poorly placed canine to replacethe lateral incisor.

Buccally Ectopic Canines

B uccal/lab ial impaction is much less freq uent tha n pala ta limpaction occurring in only 15 per cent of cases (Jacoby,1983). When a buccally ectopic canine is exposed it isessential that a closed technique or an apically repositionedfla p be used to preserve the attached gingivae (Va narsdalland C orn, 1977; Wong L ee a nd Wong, 1985). Vermet te etal. (1995) examined the use of t he apically repositioned flap

versus the closed technique, and found that the apicallyrepositioned flap resulted in more unaesthetic sequelaethan the closed technique in maxillary a nterior teeth.

No Active Treatment/Leave and Observe

In some cases it may be preferable to carry out no activetreatment except that of regular radiographic monitoring.The most frequent complication appears to be follicularcystic degeneration, although the frequency of this isunknown. Other odontogenic tumours may arise veryrarely. There may be localized loss of attachment and

marginal breakdown of the adjacent teeth, which maynecessitate the removal of the canine and the affectedteeth. There is a need to regularly monitor the uneruptedcanine with respect t o cystic degeneration, root resorption,and the other possible complications. It is not known w hatthe optimal time interval betw een radiogra phs should be toreduce the radiation dosage for the patient and detect anylesions which may be arising.

No a ctive treatment could be recommended if:

The patient does not wa nt treat ment.There is no evidence of resorption of adjacent teeth orother pathology.Ideally, there is a good contact between the lateralincisor a nd 1st premola r or good aesthet ics/prognosisfor the deciduous canine.


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There is a severely displaced canine with no evidence ofpathology, pa rticularly if it is remote from the dentition,provided it is monitored ra diographically.

Surgical Removal of Permanent Canine

Surgical removal of the tooth is indicated if there is poor

patient co-operation o r poor position for alignment (caninein an oblique or horizontal position). Id eally, there shouldbe a good lateral incisor/first premolar contact. I n caseswhere the patient is willing to undergo comprehensivetreatment, it is possible to use the first premolar as aadequate replacement for the canine by mesiopalatalrotation and the introduction of buccal root torque.G rinding of t he premolar palata l cusp is also necessary.Other factors to consider include tooth size discrepancy,and the difficulties in handling unilateral mechanics(B ishara , 1994). In a case where the primary canine is leftfollowing extraction of the permanent successor it is notpossible to tell how long the primary canine will remain

intact. Little longitudinal research has been carried out onthis aspect of canine ectopia. In the event of the primarycanine becoming unsightly or being lost it could beextracted and replaced by a prosthodontic restorationwhether fixed, removable, or osseointegrated implant.Orthodontic treatment may be required to open spaceprior to restoration.

The surgical remova l of ectopic canines is recommendedwhen:

P at ient declines act ive treatm ent and/or is happy w ithappearance.There is evidence of early resorption of adjacent teeth.The patient is too old for interception.

There is a good contact between the lateral incisor and1st premolar or the patient is willing to undergoorthodontic treatment to substitute the first premolarfor the canine.The degree of malposition is too great for surgicalrepositioning/tra nsplanta tion.

Surgical Repositioning/Alignment or Transplantation

The prognosis for autotransplantation of ectopic canines inadults is poor (Moss, 1974). Periodontal ligament healingwithout any root resorption varied between authors from25 per cent to 85 per cent. At a later stage of developmentthe root is fully formed and the chances of pulpal andperiodontal healing is reduced (Andreasen 1987; Schatz etal., 1992). The optimal developmental stage for autotrans-plantation is when the root is 5075 per cent formed(Kristerson, 1985). In light of the good prognosis for auto-transplantation of premolars documented by Andreasen(1992) canine transplanta tion should be planned a s early aspossible. The technique is described in deta il by And reasen(1992). In a recent paper by B erglund et al. (1996) a methodof exposure and partial alignment was described forcanines in oblique horizontal positions. Atraumaticremoval of these teeth may be difficult. The canine ispretreated with distal and vertical traction followingexposure in order to facilitate atraumatic removal and

autotransplantation. Of the 21 autotransplantations, 20have been successful.

Auto transplantat ion could be recommended when:

Interceptive measures are inappropriate or ha ve failed.The degree of malposition is too great to make ortho-dontic alignment feasible.Ad equa te space is available for the canine.The prognosis is good for the tooth to be transplanted

and it can be removed atra umatically.There is no evidence of a nkylosis of the can ine.

Sequelae of Canine Ectopia

Interna l or external root resorption of teeth adjacent to theectopic canine is the most common sequela. It has beenestimated tha t 07 per cent of children in the 1013-yea r-oldage group ha ve permanent incisors resorbed, as a result ofcanine ectopia. Root resorption can be expected in about125 per cent of the incisors adjacent to ectopic maxillarycanines (Ericson and Kurol, 1987a, b). Resorption of the

lateral incisor is more common than the central incisor.R arely t he fi rst premolar is resorbed (P ostletwaite, 1989).A number of studies have found that females are morelikely to be affected (Sasakura et al ., 1984; R imes et al.,1997). If t he canine ha s migra ted t o a position medial to t hemid-root of t he latera l incisor, the resorption is more likely.In a ddition, if the angulation of the long axis of the canineto the midline on an orthopantomogram exceeds 25degrees the risk increases by 50 per cent (Ericson andKurol, 1988c). Lateral incisors are more commonlyresorbed palatally and at the mid root level than at thecervical or apica l regions (E ricson a nd K urol, 1987b; R imeset al. , 1997). There appears to be no associat ion between

enlarged follicles surrounding the canine a nd t he potentialfor resorption. Cystic degeneration is uncommon and theprevalence is not known. However, Ericson and Kurol(1986a) found no evidence of cystic degeneration amongst3000 school children. This is not surprising as it would beexpected that cystic degeneration would increase infreq uency in older age groups. How ever, even in older agegroups the freq uency is thought t o be low (Mourshed, 1964;Brown et al., 1982). La stly, late resorption of the uneruptedcanine itself can occur (Kurol et al., 1997). L oss of vita lity ofthe incisors can occur and the poor aesthetics associatedwith the primary ca nine may b e a concern for the patient. Insome cases the canine may erupt at a late stage under a

prosthesis. Surgical risks include damage to adjacent teeth,re-exposure may sometimes be req uired a nd the potentialrisks from general anaesthesia. Orthodontic treatment isnot without risks which include root resorption decal-cification, periodontal problems, canine ankylosis, andfailure to complete treatment.

Acknowledgements

We a cknowledge the helpful assista nce of the O rthodonticAudit Working Pa rty (R C S E ng) in the prepara tion of thispaper. Many thanks to D r D . Burden, D r J. Husain, and DrR.T. Lee. for their collaboration. Thanks to Professor A.R ichardson for his helpful advice with t he ma nuscript.


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