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Is the Etiology Behind Palatal Unilateral and Palatal Bilateral Maxillary Canine Ectopia Different? Zahra Shirazi, Inger Kjær Institute of Odontology, Faculty of Health Sciences, University of Copenhagen, Denmark Abstract Introduction: The purpose of this study is to elucidate whether dentitions and craniofacial profiles are different in unilateral and bilateral maxillary canine ectopia. Materials and Methods: Radiographic materials from 75 patients with non-syndromic palatally displaced maxillary canines were studied. Bilateral ectopia occurred in 37 patients and unilateral ectopia in 38 patients. Orthopantomograms were analyzed for dental deviation including taurodontic morphology, abnormal crown morphology, invaginations of the incisors and short root lengths. Skeletal morphology was studied cephalometrically according to Björk. Statistic analysis were included. Results: Significant more females than males had palatally ectopic maxillary canines. Gender differences were not observed between the uni- and bilateral ectopia groups. Orthopantomograms: the occurrence of taurodontia was significantly higher in the bilateral group while invaginations were significantly higher in the unilateral group. Patients with palatally displaced maxillary canines had an increased occurrence of agenesis. Profile radiographs: in the unilateral group significantly retroclined maxillary incisors in females and males and a significantly posterior inclined maxilla in females occurred. In the bilateral group a significantly reduced slope of the maxillary incisors was demonstrated. Compared to the individuals without palatally displaced maxillary canines, the maxillary incisors were significantly retroclined in both groups. Conclusion: The present paper indicates a difference in the dentition and craniofacial profile in palatal unilateral and palatal bilateral maxillary canine ectopia. It is presumed that the unilaterally displaced canines have a dental origin while the bilateral cases have a skeletal origin. If this is so, the diagnosis of the dental morphology (invagination and taurodontia) might help to distinguish between cases with dental etiology and cases with skeletal etiology. This distinguish may improve orthodontic treatment. Keywords: Canine, cefalometry, ectopia, human, orthpantomogram, profile radiographs INTRODUCTION The etiology behind maxillary canine ectopia is still debated. Several studies have focused on differences between labially displaced maxillary canines and palatally displaced canines. [1-4] It has been concluded that the labially displaced canines occur in normally developed dentitions, and it has been proposed that the etiology behind this dental deviations is lack of space in the dental arch. The palatally displaced canines have received much interest in the literature specially focusing on treatment problems. [5-11] The dentition in cases with palatally displaced canines has been described with deviation such as invaginations, taurodontia, agenesis and root deviation. [12-16] The precise etiology behind palatally displaced canines has not been proposed. Seemingly sufficient space in the dental arch occurs in these dentitions. [17-22] Skeletal cephalometric analyses of dentitions with palatally and labially displaced maxillary canines have concluded that the maxillary complex is significantly reduced in the sagittal dimension and apparently also reduced in the vertical and transversal dimensions. [19] Others studies found that patients with palatally displaced canines had hypodivergent mandible. [14,17] In the reported literature, distinction was seldom made between unilateral and bilateral cases with palatally displaced canines. [14] This aspect is of interest because different parts of the maxillary complex have different origins from the neural crest. The teeth on the Address for correspondence: Prof. Inger Kjær, Institute of Odontology, Faculty of Health Sciences, University of Copenhagen, 20 Nørre Allé DK-2200 Copenhagen N, Denmark. E-mail: [email protected] This is an open access journal, and articles are distributed under the terms of the Creative Commons Attribution-NonCommercial-ShareAlike 4.0 License, which allows others to remix, tweak, and build upon the work non-commercially, as long as appropriate credit is given and the new creations are licensed under the identical terms. For reprints contact: [email protected] How to cite this article: Shirazi Z, Kjær I. Is the Etiology Behind Palatal Unilateral and Palatal Bilateral Maxillary Canine Ectopia Different? Dent Hypotheses 2018;9:3-10. Access this article online Quick Response Code: Website: www.dentalhypotheses.com DOI: 10.4103/denthyp.denthyp_66_17 Original Research © 2018 Dental Hypotheses | Published by Wolters Kluwer - Medknow 3 [Downloaded free from http://www.dentalhypotheses.com on Friday, January 25, 2019, IP: 130.225.98.216]
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Page 1: Is the Etiology Behind Palatal Unilateral and Palatal ... · bilateral displaced maxillary canines. Taurodontia is observed in the maxillary molars and in the mandibular second molars.

Original Research

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Is the Etiology Behind Palatal Unilateral and Palatal BilateralMaxillary Canine Ectopia Different?

Zahra Shirazi, Inger Kjær

Institute of Odontology, Faculty of Health Sciences, University of Copenhagen, Denmark

Abstract

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Quick Response Code:

© 2018 Dental Hypotheses |

Introduction: The purpose of this study is to elucidate whether dentitions and craniofacial profiles are different in unilateral and bilateralmaxillary canine ectopia. Materials and Methods: Radiographic materials from 75 patients with non-syndromic palatally displacedmaxillary canines were studied. Bilateral ectopia occurred in 37 patients and unilateral ectopia in 38 patients. Orthopantomograms wereanalyzed for dental deviation including taurodontic morphology, abnormal crown morphology, invaginations of the incisors and short rootlengths. Skeletal morphology was studied cephalometrically according to Björk. Statistic analysis were included. Results: Significant morefemales than males had palatally ectopic maxillary canines. Gender differences were not observed between the uni- and bilateral ectopiagroups. Orthopantomograms: the occurrence of taurodontia was significantly higher in the bilateral group while invaginations weresignificantly higher in the unilateral group. Patients with palatally displaced maxillary canines had an increased occurrence of agenesis.Profile radiographs: in the unilateral group significantly retroclined maxillary incisors in females and males and a significantly posteriorinclined maxilla in females occurred. In the bilateral group a significantly reduced slope of the maxillary incisors was demonstrated.Compared to the individuals without palatally displacedmaxillary canines, the maxillary incisors were significantly retroclined in both groups.Conclusion: The present paper indicates a difference in the dentition and craniofacial profile in palatal unilateral and palatal bilateralmaxillary canine ectopia. It is presumed that the unilaterally displaced canines have a dental origin while the bilateral cases have a skeletalorigin. If this is so, the diagnosis of the dental morphology (invagination and taurodontia) might help to distinguish between cases with dentaletiology and cases with skeletal etiology. This distinguish may improve orthodontic treatment.

Keywords: Canine, cefalometry, ectopia, human, orthpantomogram, profile radiographs

Address for correspondence: Prof. Inger Kjær, Institute of Odontology, Facultyof Health Sciences, University of Copenhagen, 20 Nørre Allé DK-2200

Copenhagen N, Denmark.

INTRODUCTIONThe etiology behind maxillary canine ectopia is still debated.Several studies have focused on differences between labiallydisplaced maxillary canines and palatally displaced canines.[1-4]

It has been concluded that the labially displaced canines occurin normally developed dentitions, and it has been proposed thatthe etiology behind this dental deviations is lack of space inthe dental arch.

The palatally displaced canines have received much interest inthe literature specially focusing on treatment problems.[5-11] Thedentition in cases with palatally displaced canines has beendescribed with deviation such as invaginations, taurodontia,agenesis and root deviation.[12-16] The precise etiology behindpalatally displaced canines has not been proposed. Seeminglysufficient space in thedental archoccurs in thesedentitions.[17-22]

article online

Website:www.dentalhypotheses.com

DOI:10.4103/denthyp.denthyp_66_17

Published by Wolters Kluwer - Medknow

Skeletal cephalometric analyses of dentitions with palatallyand labially displaced maxillary canines have concluded thatthe maxillary complex is significantly reduced in the sagittaldimension and apparently also reduced in the vertical andtransversal dimensions.[19] Others studies found that patientswith palatally displaced canines had hypodivergentmandible.[14,17] In the reported literature, distinction wasseldom made between unilateral and bilateral cases withpalatally displaced canines.[14] This aspect is of interestbecause different parts of the maxillary complex havedifferent origins from the neural crest. The teeth on the

E-mail: [email protected]

This is an open access journal, and articles are distributed under the terms of theCreative Commons Attribution-NonCommercial-ShareAlike 4.0 License, which allowsothers to remix, tweak, and build upon the work non-commercially, as long asappropriate credit is given and the new creations are licensed under the identicalterms.

For reprints contact: [email protected]

How to cite this article: Shirazi Z, Kjær I. Is the Etiology Behind PalatalUnilateral and Palatal Bilateral Maxillary Canine Ectopia Different? DentHypotheses 2018;9:3-10.

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Shirazi and Kjær: Palatally displaced maxillary canines

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right maxillary half originate from the right neural crest,while teeth on the left maxillary half originate from the leftneural crest. From a developmental point of view, studies onthe neural crest fields in the palate have demonstrated threebilateral fields − these are as well in the right maxillary half asin the left maxillary half the naso-palatine field (anterior) themaxillary field (medial) and the palatal field (posterior)[23-27]

[Figure 1].

In a former study on maxillary canine transpositions,distinctions were made between unilateral transpositionand bilateral transposition. This recent study demonstrateddental and skeletal differences, which could indicate differentetiology.[28]

Former studies have also demonstrated that dental deviationscan occur within neural crest developmental fields.[24-27]

Focus on these fields has been elaborated in cleft-lip-andpalate patients, where different dental deviations within thedifferent fields characterized the three cleft types, cleft-lip,cleft-palate, and combined cleft-lip and palate.[29] Of specificinterest is the observation of taurodontic molars in isolatedcleft palates. This association might indicate a developmentalinter-relationship between abnormal palatal shelves andmolar development. Also the premolars were malformedand with short roots within the palatal shelves.[29] Thegenetic aspect in ectopic maxillary canines has beendiscussed in several clinical cases[30-34] also the inter-relationship between first maxillary molar ectopia andcanine ectopia have been elucidated[26] The eruptionprocess has also been in focus in the discussion ofetiology.[35-43]

On the background of former mentioned studies on dentaldifferences in palatally and buccaly displaced canines andmaxillary canine transpositions and furthermore on thestudies on the dentitions in cleft-lip and palate thehypotheses in this study is that the etiology behindunilateral and bilateral maxillary canine ectopia might be

Figure 1: Schematic drawing of the human palate colored according toneural crest fields. Yellow mark the bilateral nasopalatine fields. Redmarks the bilateral maxillary fields. Orange marks the bilateral palatalfields[21]

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different. It is therefore the goal to analyze dental and skeletalconditions in unilateral and bilateral ectopia cases.

MATERIAL AND METHODS

MaterialRadiographic materials from 75 patients with palatallydisplaced maxillary canines (PDC) were included in thisstudy. The materials were from 74 patients below 18 yearsof age and referred to the Dental School, University ofCopenhagen, Denmark from different community dentalclinics in Denmark after approvals from patients andparents. Material from one adult patient was included. Thematerial was composed of profile radiographs andorthopantomograms, all taken in connection withdiagnostics and orthodontic treatment planning. Figure 2demonstrates a case with a unilateral palatally displacedmaxillary canine, and Figure 3 demonstrates a case withbilateral palatally displaced maxillary canines.

Bilateral ectopia occurred in 37 patients and unilateral ectopiaoccurred in 38 patients. The distribution of the patientsaccording to gender appears in Figure 4 and according toages in Table 1.

The criteria for submitting the material to this investigationwere that the patients had either unilateral or bilateralpalatally ectopic maxillary canines and that none of thepatients were diagnosed with a syndrome.

Figure 2: Orthopantomogram of a female 16 years and 8 months oldwith unilateral displaced right maxillary canine. Invaginations appear inthe maxillary incisors and there is agenesis of the right mandibularsecond premolar

Figure 3: Orthopantomogram from a female 15 years of age withbilateral displaced maxillary canines. Taurodontia is observed in themaxillary molars and in the mandibular second molars. The lateralmaxillary incisors appear narrow

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Table 1: Age distribution in the bilateral palatally displaced group and the unilateral palatally displaced canine group

Age/years

Groups Gender Numbers Median Minimum Lower quartile Upper quartile 90th pctl Maximum

Bilateral PDC M 10 13.4 12.5 13.0 14.7 15.9 16.7F 25 13.8 9.3 11.5 15.2 15.9 53.8

Unilateral PDC M 10 13.5 12.3 12.5 14.2 15.6 16.1F 28 12.7 9.3 11.9 13.7 15.1 16.6

M=males, F= females.

Table 2: Distribution of the radiographic material frombilateral palatally displaced canines and unilateralpalatally displaced canines according to gender

Gender Bilateral PDC (number) Unilateral PDC (number)

Females 26 OP + 25 Profile 28 OP + 28 Profil

Males 11 OP + 10 Profile 10 OP + 10 Profil

Total 37 OP + 35 Profile 38 OP + 38 Profil

OP= orthopantomogram, Profile= profile radiograph of the head.

Figure 4: The distribution of the material according to gender

Shirazi and Kjær: Palatally displaced maxillary canines

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METHOD

The study consisted of two parts:

(1) Orthopantomograms were analyzed for dental deviation. (2) Cephalometric analyses were performed with focus on

sagittal and vertical dimensions.

Radiographic materials available in the different groups areshown in Table 2.

Comparison was performed between the unilateral group andbilateral group.

Ad 1. Orthopantomograms. The following dental criteriawere registered:

� Agenesis, inclusive agenesis of third molar. � Morphologic deviations. These were as follows:

(a) Taurodontic morphology according to morphologyof the pulp cavity;

(b) Crown morphology of the maxillary lateral such asnarrow crowns;

(c) Invaginations of the incisors;(d) Root length and short root were defined as root

length equivalent to or less than the height of thecrown.

Den

Eruption deviations, others than the maxillary displacedcanines.

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Ad 2. Profile radiographs were digitized according tomodification of Björk’s method.[44] As the magnificationof the radiographs was unknown, angular measurementswere performed. The angular measurements are listedin Table 3. The measurements were expressed in standarddeviations (SD) calibrated after age and gender. Due toethical reasons radiographs of a control group withoutorthodontic indications for radiography was not available.

StatisticsFishers exact test was used for the evaluation of differences indental deviations. For the evaluation of the inter-raterreliability, the kappa statistic was used.

For the evaluation of the cephalometric angularmeasurements,the Spearman rank correlation and the chi-square test wereused. Also Levenes test was used for demonstrating thehomogeneity of the groups.

P-values <0.05 were considered as significant.

RESULTS

Distribution of material: unilateral maxillary ectopia occurredin 38 cases (50.7%), They had 19 cases ectopia in the rightside and 19 cases ectopia in the left side. Bilateral ectopiaoccurred in 37 cases (49.3%). The gender distribution of the75 cases was: 21 males and 54 females responding to aratio 1:2.7. The bilateral group had 70.3% females, and theunilateral group had 73.7% females.

Analysis of orthopantomograms: the prevalence of dentaldeviations was high in both groups. Only four cases in thebilateral group and six cases in the unilateral group werewithout dental deviations. An overview of dental deviations isgiven in Table 4, which are graphi graphically illustrated inFigure 5.

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Table 3: Overview of the angles measured on the profile radiographs

Angular measurements Definition

Sagittal jaw relationship (ss-n-pg) Angle between the bone markers sella (s), nasion (n) og subspinal (ss)

Maxillary prognathia (s-n-ss) Angle between the bone markers subspinal (ss), nasion (n) og pogonion (pg)

Mandibulary prognathia (s-n-pg) Angle between the bone markers sella (s), nasion (n) og pogonion (pg)

Vertical jaw relationship (NL-ML) Angle between the nasal line (NL) og, mandibular line (ML)

Maxillary inclination (NSL-NL) Angle between the line connecting the bone markers nasion and sella (NSL) and the nasal line (NL)

Mandibular inclination (NSL-ML) Angle between (NSL) and the mandibular line (ML)

Upper incisor inclination (ILs/NL) Angle between the midaxes of the maxillary incisor (Ils) and the nasal line (NL)

Cranial base angle (n-s-ba) Angle between the bone markers nasion (n), sella (s) og basion (ba)

Table 4: Overview of dental deviations in the bilateral displaced canine group and in the unilateral displaced canine group

Groups Taurodontia Agenesis Agenesisthird molar

Agenesislateral incisor

Agenesispremolar

Invagination Narrowlaterals

Ectopia ofother teeth

Shortroots

BilateralPDC

23 (62%) 14 (38%) 12 (32%) 3 (8%) 0 (0%) 9 (24%) 3 (8%) 5 (14%) 2 (5%)

95% CL 45–78 22–56 18–50 22–90 0 12–42 2–22 5–29 1–19

UnilateralPDC

13 (34%) 16 (42%) 13 (34%) 2 (5%) 5 (13%) 21 (55%) 6 (16%) 4 (11%) 2 (5%)

95% CL 20–51 26–59 20–51 1–18 5–29 35–75 7–32 3–25 1–18

P-value 0.02* 0.8 1.00 0.67 0.05 0.009* 0.48 0.74 1.00

Note significant findings marked with asterisks of taurodontia in the bilateral group and of invaginations in the unilateral group.

Figure 5: Overview of dental deviations in unilateral and bilateralpalatally displaced maxillary canines

Figure 6: The distribution of dental deviations according to the maxillaryright (3+) and maxillary left (+3) side

Figure 7: Overview of taurodontia according to gender in cases withbilateral and unilateral palatally displaced maxillary canines

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Significant findings were the observation of taurodontia in thebilateral group (P= 2.02) and invaginations in the unilateralgroup (P= 0.009; Table 4).

Significant differences were not observed between left andright sides [Figure 6].

Taurodontia: the percentage of taurodontia was higher inmales compared to females, which is graphically illustrated inFigure 7.

Agenesis: the prevalence of agenesis was high in both groups,that is, 38% in the bilateral and 42% in the unilateral group[Figure 8]. There was no significant difference betweenagenesis in females and males.

Invaginations: in the bilateral group 24% had invaginations inone or several maxillary incisors and 55% had invaginationsin the unilateral group [Figure 9]. The difference between the

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groups was significant. There was no significant differencebetween females and males.

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38%

32%

8%

0%

42%

34%

5%

13%

0%

5%

10%

15%

20%

25%

30%

35%

40%

45%

All agenesis 3rd molar agenesis Lateral incisors agenesis Pre-molar agenesis

Bi-lateral PDC Uni-lateral PDC

Figure 8: Overview of the registration of agenesis in bi-lateral and uni-lateral palatally displaced maxillary canines (PDC)

Figure 9: Overview of the registration of invaginations according togender in bilateral and unilateral palatally displaced canines

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Eruption deviations: there was no significant differencebetween the groups.

The inter-rater liability demonstrated compliance.

Analysis of profile radiographsA total of 73 cases were analyzed cephalometrically twice. Atotal of 35 cases in the bilateral group were compared to 38cases in the unilateral group. The mean value for each angularmeasurements were compared to normal values given byBjörk. The results are demonstrated in Table 5.

Unilateral group: in the unilateral group the analysisdemonstrated significantly retroclined maxillary incisors(ILs-NL) in females and males. In the unilateral groupalso, the females demonstrated a significantly (P= 0.0363)posterior inclined maxilla (NSI-NL).

Bilateral group: in the bilateral group themales demonstrated asignificantly reduced slope of the maxillary incisors (ILs-NL)but this could not be demonstrated in females.

Dental Hypotheses ¦ Volume 9 ¦ Issue 1 ¦ January-March 2018

Compared to individuals without palatally displacedmaxillary canines the maxillary incisors were significantlyretroclined in both groups (P= 0.005).

SUMMARY OF FINDINGS

Orthopantomograms:

� Significant more females than males had palatally ectopic

maxillary canines. There were no gender differencesbetween the groups.

The occurrence of taurodontia was significantly higher inthe bilateral group.

The occurrence of invaginations was significantly higherin the unilateral group.

Patients with palatally displaced maxillary canines had anincreased occurrence of agenesis.

Profile radiographs:

� Unilateral group: a significantly retroclined maxillary

incisors were observed in females and males. Furthermorefemales demonstrated a significantly posterior inclinedmaxilla.

Bilateral group: the males demonstrated a significantlyreduced slope of the maxillary incisors, but his was notdemonstrated in females.

DISCUSSION

The main new findings in the dental analysis in thisinvestigation is the significant occurrence of taurodontia inthe bilateral group, while the significant occurrence ofinvagination occurred in the unilateral group. The normalprevalence of taurodontia have been described in a Germanpopulation.[45]

Furthermore, former results concerning gender distributionwere confirmed, such as findings of females showing moreoften ectopic displaced maxillary canines than males[3] andthe information on high prevalence of third molar agenesis[14]

were high in both groups.

In the cephalometric analysis of the craniofacial profile, thesignificant findings were the observation of retroclinedmaxillary incisors in the unilateral group (males andfemales) and in the bilateral group (males only).Furthermore, females demonstrated a significantly inclinedmaxilla in the unilateral group.

It can be discussed if the dental findings in this investigationcan be compared to dental findings in the study on maxillarycanine transposition by Danielsen et al.[28] They found intheir study on canine transposition that taurodontia occurredmore often in cases with transposition of first premolar andthe maxillary canine compared to cases with transpositions ofmaxillary canines and lateral incisors.

In the dental analysis, published in the paper by Riis et al. onCleft-lip and palate dentitions[29] taurodontia occurred moreoften in isolated cleft-palate patients compared to other clefttypes. Isolated cleft palate is a malformation of the maxillary

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Table 5: Overview of the cephalometric findings in patients with bilateral displaced maxillary canines and unilateraldisplaced maxillary canines according to gender (M=males and F= females)

Groups Gender Number Angle (SD) Mean Min. Max. Lower quartile Upper quartile P-value

Bilateral M 10 ss-n-pg −0.07 −1.50 1.25 −0.80 0.60 0.8195

s-n-ss 0.07 −1.00 1.95 −0.50 0.40 0.8134

s-n-pg 0.12 −1.50 3.05 −1.00 0.60 0.7837

ml-nl 0.08 −0.80 1.30 −0.50 0.40 0.7363

nsl-nl −0.34 −2.90 1.70 −0.90 0.20 0.4327

nsl-ml −0.11 −1.40 1.00 −0.50 0.40 0.6482

ils-nl −1.11 −2.70 1.30 −1.80 −0.20 0.0142*

n-s-ba −0.40 −1.85 1.30 −0.90 0.00 0.1743

F 25 ss-n-pg −0.14 −3.30 2.20 −0.80 0.90 0.6106

s-n-ss −0.06 −1.90 2.25 −0.80 0.75 0.8003

s-n-pg 0.04 −1.70 2.45 −1.00 1.30 0.8668

ml-nl −0.41 −3.30 1.90 −1.00 0.60 0.1362

nsl-nl 0.21 −2.20 2.05 −0.40 0.90 0.3376

nsl-ml −0.26 −2.60 2.00 −1.10 0.70 0.2929

ils-nl −0.52 −2.50 1.90 −1.50 0.00 0.0533

n-s-ba 0.12 −2.30 1.60 −0.50 0.90 0.5561

Unilateral M 10 ss-n-pg 0.35 −1.10 1.50 −0.20 1.10 0.1890

s-n-ss 0.04 −1.80 1.30 −1.00 1.00 0.9234

s-n-pg −0.21 −1.80 1.40 −1.00 0.70 0.5754

ml-nl 0.20 −0.90 1.55 −0.45 0.80 0.4682

nsl-nl 0.00 −1.70 1.40 −0.65 0.70 1.0000

nsl-ml 0.19 −0.70 1.40 −0.30 0.50 0.4000

ils-nl −1.15 −3.60 0.60 −2.30 0.00 0.0256*

n-s-ba 0.03 −1.30 1.35 −0.75 0.50 0.9278

F 28 ss-n-pg −0.07 −4.00 1.60 −0.55 0.90 0.7720

s-n-ss −0.30 −1.80 1.80 −0.98 0.45 0.0892

s-n-pg −0.24 −2.15 2.10 −0.88 0.55 0.2268

ml-nl −0.26 −2.10 1.50 −1.00 0.50 0.1709

nsl-nl 0.38 −1.20 2.20 −0.45 0.95 0.0363*

nsl-ml −0.04 −1.95 1.70 −0.75 0.98 0.8386

ils-nl −0.61 −2.50 2.10 −1.43 0.30 0.0161*

n-s-ba 0.17 −1.20 1.70 −0.53 0.83 0.2459

Significant findings in the unilateral group are retroclined maxillary incisors in females and males (ILs-NL). Furthermore females demonstrated a significantlyposterior inclined maxilla (NSL-NL). Note three asterisks indicating significance. Significant finding in the bilateral group is a reduced slope of the maxillaryincisors (ILs-NL) in males marked with an asterisk. This was not found in females.

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and palatal fields which have arisen from the palatalshelves.[29]

Inheritance in cleft lip and palate is well known. Alsoinheritance in dental deviations has been described.

Concerning the normal eruption process and the etiologybehind this process several proposals have been discussed.The importance of the crown follicle (ectodermal origin)is highlighted in a series of papers.[27,40,41] Also theinfluence of the supporting bone (ectomesenchymalorigin) has been described.[27] Furthermore, the focushas been given to the innervation of the rootmembrane.[27] As a conclusion, the eruption processseems to be dependent on different biological processes.It could be suggested that one of these different processesmight cause ectopia.

Prediction of ectopia is important for treatment planning.Dental deviations have been mentioned in connection with

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prediction of canine ectopia.[3,4,13] And also skeletalobservations have been associated with canine ectopia.[46]

The observations in the present study could indicate that adevelopmental deviation in the palatal processes possibly arerelated to the findings of taurodontia in the bilateral group. Ifso then the bilateral group of displaced maxillary caninescould indicate a skeletal etiology (ectomesenchymal origin)while the etiology behind the unilateral group of displacedmaxillary canines could have a non-skeletal origin(ectodermal origin). This is schematically illustrated inFigure 10.

In a recent paper, normal dentitions have been described indentition with agenesis of maxillary canines, not associatedwith other agenesis in the dentition.[47]

Diagnosis and treatment of palatal displaced canines are aclinical problem which creates a multiple disciplinarycollaboration. Some palatally displaced cases can be

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neural crest field involved

The normal loca�on of a maxillary canine

The displaced canine

Invagina�ons in the maxillary incisors

Taurodont morphology of a molar

Short root

Figure 10: Schematic overview of the human palate with colored neuro-crest fields according to Figure 1. Left figure indicates a case with unilateraldisplaced maxillary canine. Right figure indicates a case with bilateral displaced maxillary canines. Note the different morphology of the incisorspremolars and molars in the two different displaced conditions. Characteristic for the unilateral displaced canine case is the observation ofinvaginations and for the bilateral case the observations of short premolars and taurodontic molars

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treated interceptively with extraction of the primary caninefollowed by natural eruption of the permanent canine.[7,10,11]

Other cases require orthodontic and surgery treatment.

In recent papers by Naoumova et al.[10,11] the cone beamcomputerized tomography (CBCT) scanning has been used topredict normal eruption. CBCT scanning has renewed thepossibility for the prediction of eruption of the permanentcanine after extraction of the primary canine.

Still many cases are treated in troublesome and complicatedtreatments. For these types of treatments, distinguishingbetween skeletal and dental etiology could be valuable.

As a conclusion, the present paper might indicate that theunilaterally displaced canines have a dental origin while thebilateral cases have a skeletal origin. If this is so then diagnoseof the dental morphology (invagination and taurodontia) mighthelp todistinguishbetweencaseswithdental etiology and caseswith skeletal etiology. This distinguish may improve not onlythe diagnostics, but concurrently also the treatment.

AcknowledgementsMany sincere thanks to all those orthodontists whocontributed with materials for this study. Furthermore,

Dental Hypotheses ¦ Volume 9 ¦ Issue 1 ¦ January-March 2018

thanks are also due to “Union for Specialized Dentists inOrthodontics” (FSO), for support and establishing contact.

Financial support and sponsorshipNil.

Conflicts of interestThe corresponding author has editorial involvement withDental Hypotheses.

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Dental Hypotheses ¦ Volume 9 ¦ Issue 1 ¦ January-March 2018