impacted canines-ericson & kurol copia

European Journal of Orthodontics 10 (1988) 283-295 1988 European Orthodontic Society

Early treatment of palatally erupting maxillary caninesby extraction of the primary caninesSune Ericson and Juri KurolJonkoping, Sweden

SUMMARY The effect of extraction of the primary canine on palatally erupting ectopic maxillarycanines was analysed. There were 46 consecutive ectopic canines, in 35 individuals, aged 10.0-13.0 years (mean age 11.4 years) at the time of discovery of the ectopic eruption. All casesshowed no or minor space loss. After extraction of the primary canine, the children wereinvestigated clinically and radiographed at 6-month intervals for up to 18 months.

In 36 of the 46 canines (78%) the palatal eruption changed to normal; 23 already showedimproved positions after 6 months and 13 after 12 months. No new cases normalized after 12months.

We suggest that extraction of the primary canine is the treatment of choice in young individualsto correct palatally ectopically erupting maxillary canines provided that normal space conditionsare present and no incisor root resorptions are found.

Introduction

The maxillary permanent canine is second onlyto the third molar in frequency of impaction,with a prevalence of approximately 2 per centof the population (Thilander and Jakobsson,1968; Ericson and Kurol, 1986a). The canine isfound palatal to the dental arch in about 85percent of the cases and buccal only in about 15percent (Hitchin, 1956; Rayne, 1969; Ericsonand Kurol, 1987a).

If orthodontic treatment is not started, thereis always a risk of retention and also of resorp-tion of the roots of the permanent incisors. Suchresorptions have recently been reported to occurin 12 percent of cases of ectopic eruption of themaxillary canines in the age range 10-13 years(Ericson and Kurol, 1987a). Resorptions maybe found as early as 10 years of age but occurmost often in the age groups 11 to 12 years(Ericson and Kurol, 1987b).

The most common treatment procedure inchildren and adolescents is surgical exposurefollowed by orthodontic appliance treatment,where, as a rule, the primary canines are left inplace until the orthodontist has moved theimpacted tooth to this region (Moyers, 1973;Clark, 1971; Bishara et al., 1976; Hunter,1983a, b; Fleury et al., 1985). Other proposed

strategies are 1. acceptance, i.e. no treat-ment, 2. extraction of the malerupting canine,and 3. surgical repositioning (Richardson andMcKay, 1983).

Several aetiological factors for ectopic canineeruption have been proposed, and include her-editary factors, lack of space, persistence ofprimary canines, a true ectopic path of eruption,reduced root length or aplasia of lateral incisors(Richardson and McKay,. .1982; Jacoby, 1983;Becker et al., 1984).

Delayed exfoliation of the primary canine wasbelieved by Lappin (1951) to be the principalaetiological factor and he presumed that itwould be possible to prevent the condition fromoccurring in a great many cases, by extractingthe primary canine. This was also suggested byMiller (1963) and Williams (1981). Berger, in1943, stated that widening of the arch in thepremolar region and early extraction of theprimary canines were advisable as precautionarymeasures to prevent incisor root resorptions.

A thorough search of the literature has shownthat sporadic case reports where extraction ofthe primary canine has favourably influencedthe future path of eruption have been pre-sented over the last 50 years (Buchner, 1936;Kettle, 1957; Lind, 1977; Williams, 1981; Leives-ley, 1984). In some of the presented case reports,

284 SUNE ERICSON AND JURt KUROL

however, only a slight displacement of the canineis present in the periapical intra-oral radio-graphs, for example with the crown in a goodposition but with an increased mesial angulation(Kettle, 1957). Other authors have made moreor less casual remarks that extraction of theprimary canine may offer a possibility of correct-ing impacted canines (Hotz, 1974; Howard,1978; Silling et al., 1979). On the other hand,there is also a case report in which extraction ofthe primary canine did not affect the eruptionof the permanent canine (Hotz, 1974).

No systematic longitudinal study to evaluatethe corrective effect of primary canine extraction

on the palatally deflected path of eruption ofmaxillary canines has been carried out, however.

The purpose of this prospective study was toanalyse the effect of extraction of the primarycanine on palatally erupting maxillary caninesin young individuals. It was also considered ofinterest to determine when such a correctiveeffect of the extraction could be ascertained.

Subjects and methodsForty-six consecutive ectopic palatally placedmaxillary canines were studied. The children, 14boys and 21 girls, were between 10 and 13 years

Figure 1 Orthopantomogram (A), intra-oral axial-vertex radiograph (B) and intra-oral periapical films (C) showing the leftmaxillary permanent canine in a true palatal ectopic path of eruption and the right canine with a lingual tendency. At thestart of treatment, the primary canines are present. Normal space conditions. Normalization of the left canine 6 monthsafter extraction of the primary canine (D).

ECTOPIC MAXILLARY CANINES 285

Table 1 Distribution according to age at thetime of extraction of the primary canine.

Age-group

10-10.911-11.912-12.9

Total

Number of teeth

171316

46

Percent

372835

100

old at the time of the discovery of the ectopicposition (Tablel) and were referred for treatmentfrom the Public Dental Service after the intro-duction of a digital palpation screening method(Ericson and Kurd, 1986b). Inability to locatethe canine in the normal position by digitalpalpation prompted a supplementary radio-graphic examination of the canine, where itsposition was carefully determined in three planes(Ericson and Kurol, 1986a, Fig. 1).

The eruption angles and positions of the

Means.d.Range

(degrees)

22.011.i2-55

di(mm)

14.73.2

9.S-2O.3

Figure 2 Mesial inclination (alpha, a) to the midline anddistance (dl) to the occlusal line, OL, of the permanentmaxillary canine in the frontal plane (orthopantomogram)at the start of treatment.

Sector

Number 13 11 20 2 0

Sector

Number 8 18 17Figure 3 Distribution of the 46 maxillary canines accordingto the medial position of the canine crown in sectors 1-5 inthe (A) frontal plane and (B) transverse plane (derived fromorthopantomogram and axial-vertex views) at the start oftreatment.

permanent maxillary canines were determinedas follows:—In the frontal view (orthopantomogram) (A)

the angle of the canine (B) the distance of thecusp tip to the occlusal line (Fig. 2) and themedial crown position in sectors 1 -5 (Fig. 3).

286 SUNE ERICSON AND JURI KUROL

Table 2 Effect of the extraction of the primary canine on the 46 maxillary canines with a palatally ectopicpath of eruption in 35 individuals, 14 boys and 21 girls, aged 10-13 years.

Canineposition(orthopantomogram)

Sector 1, 2Sector 3, 4

Total

Totalnumberof canines

2422

46

Improved

after6 months

194

23

position

after12 months

310

13

No changeafter18 months

26

S

Worseningafter18 months

2

2

—In the transverse plane (vertex projection) theposition of the crown of the canine relative tothe adjacent lateral incisor and dental archwas determined from the vertex projectionand the conventional intra-oral projections.The position of the canine crown relative tothe dental arch was classified as completelylingual, lingual tendency and correctly pos-itioned.

—In the sagittal plane (lateral head film), thedistances to the occlusal line.Immediately after diagnosis of the ectopic

palatal path of eruption, the primary canine wasextracted. The permanent canines were thenfollowed clinically and radiographically at six-month intervals up to 18 months for the radio-graphic procedure, if necessary, and clinicallyto full eruption or to the end of necessaryorthodontic appliance treatment. Thus, if aclearly noticeable improvement of the positionof the maxillary permanent canine was regis-tered, the radiographic follow-up was termi-nated at the 6 or 12-month control.

In four of the 46 cases (one boy and threegirls), the lateral incisors already showed rootresorption on the palatal side at start. Two ofthe resorptions were superficial and two wereextensive and reached the pulp. In the latter twocases, the treatment planning for orthodontictreatment of their malocclusion included extrac-tion of maxillary teeth and these two cases weretherefore included in this study.

The maximum width of the dental follicleof the canine was measured on the intra-oralperiapical radiographs.

All cases had good dental arches and no spacedeficiency was registered after measuring withsliding calipers. There had been no early extrac-tion of primary molars in the maxilla.

Conventional statistical methods were usedfor calculation of means and standard devi-ations. Student's /-test was used for parametricvariables and the chi-square test for non-para-metric variables for the analysis of differencesbetween the registrations (Nie et al., 1975).

ResultsThe main results are presented in' Table 2.Altogether 36 (78%) of the 46 ectopic caninesshowed normalization of the path of eruptionand later clinically correct position at the finalcontrol. For ten teeth no improvement wasregistered: seven showed no change at all, oneonly slight improvement and two an impairedposition with the crown moving more mediallyduring the observation period.

Time factorOf the 36 cases with normalization and clinicallycorrect position at the final control, 23 canines(64%) already showed improved positions radio-graphically at the 6-month control, Table 2.Nine of these had already normalized at thistime (for example, Fig. 1). After 12 months,another 13 teeth had normalized and another14 canines had improved positions and showedclinically good positions at the 18-month con-trol. No new cases of improvement occurredbetween the 12-month and 18-month obser-vations.

Medial position {sectors 1-5, Fig. 3)Of the 46 canines, 22 overlapped the adjacentlateral incisor (in the orthopantomogram) bymore than half of the lateral root, and 14 (64%)of these normalized (Table 3). Of the 24 canineswhich overlapped the lateral incisor root by less


Table 3 Distribution of the medial position of the maxillary permanet canine insectors 1-4 in the vertical plane as shown in the orthopantomogram. No teethwere in sector 5. At the start of treatment, after 12 and after 18 months. Numberand percent.

Registration

At start(n = 46)

12 monthsafterextraction(n = 37)

18 monthsafterextraction(n = 24)

Medial maxillary canine crownposition in sector

1

n(%)13(28)

28*(61)

36*(78)

2

n(%)11(24)

9(20)

2(4)

3.4

n(%)22(46)

9(20)

8(17)

Total number

46

46*

46*

* 9 canines had normal positions at the 6-month radiographic control and another 13 atthe 12-month control.

Table 4 The distribution of the canine crown position relative to themidline of the dental arch in the horizontal plane as shown in the axial-vertex radiogram. At the start of treatment, 12 months and 18 monthsafter extraction of the primary canine. Number and percent.

Registration

At start(n = 46)

12 monthsafter extraction(n = 37)

18 monthsafter extraction(n = 24)

Position

Palatal

n(%)27(59)

9(20)

8(17)

relative to the dental arch

Palataltendency

n(%)19(41)

15(33)

2(4)

Centralor buccaltendency

n(%)

22(48)*

36(78)*

Total number

46

46*

46*

* 9 canines had normal positions at the 6-month radiographic control andanother 13 at the 12-month control.

than half of the root at the start of treatment, 3) showed concordant results and will not be22 (91%) normalized (Table 2, Fig. 4). The reported in detail,change in medial canine crown position in re-lation to time after extraction can be seen from Position relative to the dental archTable 3, where eight of the ten teeth with no The distribution of the canine crown positionfinal normalization belonged to sectors 3 and 4 relative to the midline of the dental arch isand one to sector 2 at the start. The positions shown in Table 4. Of the 27 canines (59%) in aof the canines in the vertex projection (Fig. lingual position at the start of treatment (22 in


IFigure 4 Schematic illustration of the normalization of themaxillary permanent canine at the control 18 months afterextraction of the primary canines. The figures indicate therate of success for the permanent canine positions at thestart of treatment, mesial and distal to the midline ofthe lateral incisor in the orthopantomogram.

sectors 3 and 4, and 5 in sectors 1 and 2) only9 (20%) remained in this position and no change

could be seen for eight of the canines at the lastcontrol at 18 months. All the rest normalizedexcept one, which remained in a slight lingualposition (lingual tendency). This means completenormalization in 78% of all cases.

Mesial inclinationThe distribution of the mesial inclination of themaxillary canines at the start of treatment isshown in Figure 5. The inclination is approxi-mately normally distributed. The change afterextraction of the primary canines at the 6-monthand 12-month controls is shown in Table 5.The dynamic change in position and the meandifference at the different registrations arepresented. Note the large standard deviations(Table 5).Canine vertical distance to the occlusal planeThe distance from the canine cusp to the occlusalplane (Fig. 2) at the different registrations isshown in Table 6. The distance at the start oftreatment ranged from 9.5 to 20.3 mm. At thattime, the canines were on average positionedabout 15 mm from the occlusal line in theorthopantomogram and Table 6 shows thechange during the observation period up to12 months. The distance as measured on thelateral head film showed concordant resultscompared to Table 6.

10-

I l lO*-4* 5*-9* 15'-19* 20T-24" 25'-29* 3O'-34* 35*-39# 40*"44* 45'-49' 5O'-S5"

Mesial inclination to the midline(orthopantomogram)

Figure 5 Distribution of the mesial inclination (degrees) of the 46 maxillary canines to the midline in the orthopantomogramat the start of treatment


Table 5 Mesial inclination (degrees) of the canine to the midline in theorthopantomogram. Mean value and standard deviation at the differentregistrations and mean difference and level of significance.

Registration s.d. d±s.d.Level ofsignificance

At start(n = 46)6-monthcontrol(n = 46)12-monthcontrol(n = 37)

22.0

17.9

14.0

11.1

12.5

13.3

4.1+8.3 p < 0.01

13.3 9.8 + 9.1 p < 0.001

Table 6 The distance (mm) from the canine cusp to the occlusal planein the orthopantomogram. Mean value and standard deviation at thedifferent registrations and mean difference and level of significance.

Registration mean s.d. d±s.d.Level ofsignificance

At start(n = 46)6-monthcontrol(n = 46)12-monthcontrol(n = 37)

14.7

11.7

9.2

3.2

4.3

5.0

3.0 ±1.8

5.5 ±2.7

p < 0.01

p < 0.001

Table 7 Treatment procedures for 10 out of the 46 ectopic maxillary canines where noimprovement of position was registered 12 months after extraction of the primary canine.

Position in theorthopantomogram

Change of eruption path Treatment

Orthodonticimpaired surgical fixed appliance ' Extraction

No change position exposure treatment of lateral

Overlappingless than halfof thelateral (sectors 1, 2)Overlappingmore thanhalf of thelateral (sectors 3, 4)Total

6

8

2

2

8

9

8

8

2

2


No normalisationTen of the 46 canines showed no change oran impaired position. The clinical treatment isshown in Table 7. Nine of these teeth had a truelingual position at the start of treatment (Table4) and in eight cases the cusp was positionedmore medially to the midline of the lateral incisorin the orthopantomogram. Surgical exposureand orthodontic fixed appliance treatment wascarried out in eight cases (Table 7). After ortho-dontic treatment, all canines were in clinicallyfavourable positions.

ResorptionsIn the four cases with resorptions on the rootof the lateral incisor, diagnosed at the start oftreatment, the positions were normal in twocases, unchanged in one and one canine showedan impaired position. Three canines were pos-itioned in sector 3 and one in sector 2 in theorthopantomogram at the start of treatment.Two of the resorptions were severe and reachedthe pulp at the start of treatment. One remainedunchanged and one deteriorated during theobservation period and these two cases are theextraction cases, where the orthodontic treat-ment plan included extraction of lateral incisorsas one possibility from the start. No new casesof resorption were registered during the obser-vation period.

Dental follicleThe maximal width of the dental follicle of themaxillary canine, measured on the intra-oralperiapical radiographs, exceeded 3 mm in 13cases and varied between 1 and 5 mm for the46 canines. There was no association in thosecases which did not improve related to the sizeof the follicle.

DiscussionThe effect of extraction of the primary canineon the palatally deflected path of eruption ofthe maxillary canine, is analysed in this report.To our knowledge, this is the first prospectivelongitudinal study where such an effect on pala-tally erupting maxillary canines has been shown.Orthodontic textbooks and papers on treatmentof ectopic maxillary canines do not mention thistreatment approach, but there are sparse casereports in the literature (Buchner, 1936; Kettle,1957; Lind, 1977; Williams, 1981; Leivesley,

1984). Perhaps extraction of the primary caninehas been considered an 'oddity' and the successlimited to cases with only a minor deflection, asshown by Kettle (1957).

This study clearly shows that extraction ofthe primary canine has a favourable effect onpalatally malerupting maxillary canines. Almost80 per cent of the cases were corrected due tothe early extraction of the primary canines.Spontaneous corrections may occur but from

Figure 6 Ectopic palatal eruption of the right maxillarycanine in a girl aged 12 years 9 months at the start oftreatment. The mesial inclination and palatal position wherethe canine crown almost reaches the central incisor canbe seen in the orthopantomogram (A) and axial vertexprojection (B). The radiographs show the improvement ofposition and inclination from the start of treatment (C) to6 months after extraction of the primary canine (D, E).


clinical experience, it is not likely that ectopicallyerupting canines will be spontaneously correctedto such an extent, especially not those with thecrown in advanced medial positions, as shownin Figures 2 and 4, Table 2. However, a few ofthe canines in the youngest age groups with amoderate dislocation of the canine might havecorrected spontaneously, as shown by us earlier(Ericson and Kurol, 1986a). For ethical reasons,we have not been able to design a study with atraditional, untreated control group but it ishardly likely that 22 of 24 canines (92%) insectors 1 and 2 and 14 of 22 (64%) in sectors 3and 4 (in the orthopantomogram) would do so.The results will be discussed with this assumptionand reservation.

A positive change in the path of eruptioncould be observed radiographically in 50 percent of the cases, and in some cases (20%)also clinically, at the 6-month registration afterextraction of the primary canine (Figs. 1 and 6).At the 12-month control, all but nine had normal

or improved positions. If such a change ineruption is not detectable at that time, a newdecision must be made and some canines posinga risk of further root resorption of the incisors,may have to be surgically exposed and treatedwith orthodontic appliances, while in most othercases a further 6 months of observation may beallowed. If no improvement is detectable atthe 12-month control, we suggest alternativetreatment. If the diagnosis is made early accord-ing to denned criteria i.e. clinical palpation andif necessary radiographic examination (Ericsonand Kurol, 1986a), there should be enoughtime to carry out alternative surgical and/ororthodontic treatment.

This study has clearly demonstrated thefavourable effect on the maxillary canine evenin very medial positions of the canine crown(Table 3, Figs. 1 and 6) and up to a mesialinclination of the canine of 55 degrees to themidline in the orthopantomogram (Table 6).Note that canine teeth with similar positions

Figure 7 Palatal ectopic eruption of both maxillary canines in a boy aged 12 years 11 months at the start of treatmentMixed dentition period. The width of the dental follicle exceeded 3 mm fpr both canines. ID the orthopantomogram (A) themesial inclination to the midline is 31 degrees for the left canine and 27 degrees for the right canine. In the axial-vertexprojection (B) the cusp tips are positioned approximately in the same position lingually to the lateral incisor root Twelvemonths after extraction of the maxillary primary canines the orthopantomogram ( Q and axial-vertex projection (D) showan improved position of the left canine and a slightly impaired position of the right maxillary canine.

292 SUNE ER1CS0N AND JURI KUROL

Figure 8 Girl aged 12 years 8 months at the start of treatment. The right maxillary canine is erupting palatally and theorthopantomograms, axial-vertex radiographs and intra-oral radiographs show the development from the start (A, C, E) to12 months after extraction of the primary canine (B, D, F).

and angulations may react differently even inthe same individual, as shown in Figure 7. Inspite of a difference of only four degrees inmesial angulation and concordant medial andlingual positions, the left maxillary canine nor-malized but not the right. Due to the difficultyin predicting a favourable change of the path oferuption in the individual case, we recommendradiological and/or clinical supervision at six-month intervals after extraction of the primarycanine until the permanent canine erupts.

The degree of palatal position at the start oftreatment relative to the dental arch has beenshown to influence the result (Table 4). Maxillarycanines with a moderate lingual path of eruptionnormalized more often (90%) than canines intrue lingual positions (65%). Again, no reliableforecast of success or failure can be made in theindividual case, although the prognosis for thetreatment on the whole is very good. With earlierdiagnosis according to our earlier recommen-dations (Ericson and Kurol, 1986b), it may bepossible to achieve even better results as the

canine is then higher up and probably has a lessdeflected path of eruption. Note that one-thirdof the patients in this study were between 12and 13-years-old at the time of referral.

It has often been mentioned that a palatalpath of eruption may be seen in cases where theprimary canine is unresorbed (Dewel, 1949;Hotz, 1974; Salzmann, 1974). However, it is notestablished whether this is a consequence or theprimary cause of the ectopic palatal eruption.In this study, in individuals aged 10-13 years,i.e. during a normal eruption period, 21 (46%)of the 46 primary canines were unresorbed and25 (54%) showed various degrees of resorption.

In order to be successful with this procedureof extracting the primary canine, we must followthe eruption process radiologically by means ofcorrect and standardized radiographs. If this isdone, it will be possible to record even slight ormoderate ehanges, as studies of distortion inrotational panoramic radiography and cephalo-graphy have demonstrated great tolerance withrespect to angular and vertical distortions

ECTOPtC MAXILLARY CANINES 293

Figure 9 Girl aged 11 years at the start or treatment (A, C, E) and 12 months later (B, D, F); an impaired position of theleft maxillary canine is evident in the orthopantomogram, axial-vertex projection and intra-oral radiograph.

(Tronje, 1982; McDavid et al., 1985; Ahlqvist etal., 1986). Based on these reports, and applyinga relative scale for the mesio-distal and bucco-lingual determinations, it can be claimed thatthe registrations in this study have been per-formed with moderate errors, acceptable forpractical clinical purposes in the everyday clini-cal situation. Used together, we consider themethods describe the displaced canine and thechanges in position with sufficient accuracy inthree dimensions and are suitable for this clinicalpurpose. Guilford's coefficient of reliability(Guilford, 1965) was high for all our measure-ments (Ericson and Kurol, 1988).

In view of the positive results of this study wesuggest that primary canine extraction is thetreatment of choice in the age-group 10-13 yearswhen the permanent maxillary canine has apalatal ectopic path of eruption. Before the ageof 10, spontaneous correction of potentiallymalplaced canines may occur (Ericson andKurol, 1986b) and extraction is normally notindicated unless a very early somatic and dentaldevelopment is found. With late diagnosis or

crowding and in cases of resorption or veryhorizontal paths of eruption, alternative modesof treatment should be considered, as our experi-ence of the method in such cases is too small.Surgical exposure with subsequent orthodonticappliance treatment will be the main choice inthose cases.

Early extraction of the primary canine in orderto correct the malerupting maxillary permanentcanine has considerable advantages for the child,both economically and in terms of the discomfortthat result from more traditional treatment ap-proaches. In fact, periodontal damage to theectopic canine after surgical exposure and ortho-dontic alignment has been reported comparedto control canines (Wisth et al., 1976 a,b; Hans-son and Under-Aronson, 1972; Boyd, 1982;Kohavi et al., 1984; Oliver and Hardy, 1986).Incisor devitalization and some loss of alveolarbone support may also occur (Proffit and Acker-man, 4985).

The characteristics of those cases with nochange or an impaired position have to befurther analysed.


Conclusions and recommendationsIt has been clearly shown that extraction ofprimary canines in the upper jaw has a favour-able effect on palataUy erupting maxillary can-ines in most cases, if this extraction treatmentis performed in time. Early diagnosis of malerup-tion is important for success. The ectopic pos-ition and the path of eruption of the maxillarycanine should preferably be identified before theage of 11.

When a favourable effect of treatment occurs,the change in position and in the path of eruptionwill be observed at the latest 12 months afterthe extraction of the primary canine. If noimprovement can be found at that time, normal-ization is not to be expected and alternativetreatment should be considered. Due to thegreat individual variation in the position of themaxillary canines at the start of treatment andto some extent also in the response to treatment,it is not possible to predict success or failure inthe individual case, although the prognosis forthe treatment on the whole is very good. Clinicaland/or radiological controls at six-month inter-vals are recommended.

In view of the positive results, we suggest thatprimary canine extraction is the treatment ofchoice in the age-group 10-13 years when theerupting permanent maxillary canine has a pala-tal ectopic path of eruption. With later diagnosisor crowding, and in cases of resorption ofthe incisor roots or a very horizontal path oferuption, alternative modes of treatment shouldbe considered.

Address for correspondence:Dr Juri KurolDepartment of OrthodonticsThe Institute for Postgraduate Dental EducationJarnvagsgatan 9S-552 55 JonkopingSweden

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impacted canines-ericson & kurol copia

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