Palatal Displacement of Canine is Genetic

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					                Journal of Dental Research

Palatal Displacement of Canine is Genetic and Related to Congenital Absence of Teeth
                                      S. Pirinen, S. Arte and S. Apajalahti
                                          J DENT RES 1996 75: 1742
                                     DOI: 10.1177/00220345960750100601

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J Dent Res 75(10): 1742-1746, October, 1996

Palatal Displacement of Canine is Genetic
and Related to Congenital Absence of Teeth
S. Pirinen*, S. Arte, and S. Apajalahti
Department of Pedodontics and Orthodontics, Institute of Dentistry, P.O. Box 41, FIN-00014 University of Helsinki, Finland; *to whom
correspondence should be addressed

Abstract. The palatally displaced canine is a harmful                                       Introduction
complication of dental development. It appears in 1 to 2% of
the Western population. According to our clinical                                           The palatally displaced canine is a relatively common dental
experience, this anomaly is seen in families in which                                       anomaly in man, with a prevalence of 1 to 2% (Thilander
missing and peg-shaped teeth are common. It could be                                        and Jakobsson, 1968; Shah et al., 1978; Grover and Lorton,
caused by the same genetic component that causes incisor-                                   1985; Ericson and Kurol, 1986). The condition is more
premolar hypodontia. We examined 106 patients who had                                       common in girls than in boys. The etiology has been
been operated on and treated orthodontically for palatally                                  explained with local factors, such as lack or excess of space
impacted canine(s). The patients and their family members                                   in the dental arch, and trauma or lack of guidance in
were examined for dental anomalies. One hundred and ten                                     eruption due to anomalous lateral incisors (Becker et al.,
first- and 93 second-degree relatives were clinically and                                   1981; Jacoby, 1983; Brin et al., 1986, 1993; Oliver et al., 1989;
radiologically examined, and 35 pedigrees were                                              Becker, 1995). However, a familial trend has also been
constructed. Thirty-six percent of the patients had                                         pointed out (Bass, 1967; Zilberman et al., 1990) and a genetic
congenitally missing permanent teeth (hypodontia), which                                    basis suggested (Bjerklin et al., 1992; Peck et al., 1994). In a
is 4.5 times the population prevalence. Hypodontia was                                      family study, we have earlier demonstrated an association
noted in 19 to 20% of both the first- and second-degree                                     of labial canine malposition to hypodontia (Svinhufvud et
relatives. This is 2.5 times the population prevalence.                                     al., 1988). The small (peg-shaped) lateral incisor is a
Frequency of missing teeth, analyzed by tooth groups, was                                   modified manifestation of the genotype that causes
of the same order as that shown for incisor-premolar                                        hypodontia (Alvesalo and Portin, 1969). Incisor-premolar
hypodontia in the Western population. In six of the 35                                      hypodontia is inherited as an autosomal-dominant trait
pedigrees, a palatally impacted canine was noted in several                                 with varying penetrance and expression (Grahnen, 1956;
generations of the same family. Prevalence of this anomaly                                  Alvesalo and Portin, 1969; Burzynski and Escobar, 1983;
was 4.9% in the studied group, which is 2.5 times the                                       Nieminen et al., 1995).
population prevalence. From the findings, we conclude that                                      Here we analyzed the occurrence of hypodontia and
the palatally displaced canine belongs to the spectrum of                                   palatally displaced canines in patients and their relatives to
dental abnormalities related to hypodontia.                                                 test the hypothesis that the palatally displaced canine is an
                                                                                            inherited trait and associated with hypodontia.
Key words: tooth eruption (ectopic), cuspid (impacted),
tooth abnormalities, genetics (medical).
                                                                                             Materials and methods
                                                                                            One hundred six consecutive patients (77 girls, 29 boys) who had
                                                                                            had surgical and orthodontic treatment for 105 palatally and one
                                                                                            labially displaced canine were found in the files of the
                                                                                            Department of Orthodontics, Institute of Dentistry, University of
                                                                                            Helsinki, and of the private practice of one author (SP). Eighty-
                                                                                            three of the probands were under 20 years of age at the time of
                                                                                            treatment; mean age was 14.5 years in this group. Ten of the
                                                                                            probands were over 20 and 13 older than 30. The probands' casts
                                                                                            and radiographs were examined; some of them were re-
                                                                                            examined. Their first-degree relatives (parents, children, brothers,
                                                                                            and sisters) were contacted with a questionnaire and invited to a
                                                                                            dental and radiographic examination. As many as possible of the
                                                                                            second-degree relatives (grandparents and grandchildren, aunts,
Received August 31, 1995; Accepted March 27, 1996                                           uncles, and cousins) were similarly contacted and examined.

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J Dcnt Res 75(10) 1996                                                                    The Palatally Displaced Canine                                                                         1743

                     the symbols are

                      A    female                                        palatal canine(s) and
                     6     no abnormalities                      i       missing tooth/teeth

                           male                                  i       labial canine(s) and
                           no abnormalities                              missing tooth/teeth

                     1     propositus                            [b      peg shaped upper lateral(s)

                     j     examined                             11 supernumerary tooth/teeth
                     b~    palatal canine(s)                    [f retained toothAteeth

                     b~    labial canine(s)                      W       too young

                           missing tooth/teeth                  0       dead
                      -    minor dental abnormalities (carabelli s cusps. invaginations in upper laterals
                     u     and/or rotated second premolars)

                                                                                                                                                 3                                          4
                                                                                                                                      St    12
                                                                                                                -7) 3      ii2

                                   5                                                                  7                                     8                                               9

                             -'I) 2)
                                   10                             11                                   12                              13                                               14

                                             2                         13.21                     O.I 1 2 3
                                        15                                           16                                                                                                     18

                           C}T               b                                                                                                                                     -' 1 3

                                                  A23                          -"3

                                   -19                                               20                                     21              22                 23                           24

                                                          O§5~-2                                                        -' 3 2 3       '23
                                                                                                                                                             o2t   4c
                                                                                                                                                                                  OT }2

                                                                               '1 3,23

                                                             26                           27                        28                                             29

                                                                                     A                              113.23            &7
                               30                           31                            32                                     33                          34                      35
                              -'I3      {1                                                                                                                     3

                                                                                          A i3                ,'I

Figure 1. Pedigrees of 35 of the propositi. In 3/35 families (8%), the propositus was the only member with the dental anomaly (pedigrees 7, 18,
and 21). An autosomal-dominant inheritance of missing teeth is seen in 13/35 pedigrees. Missing and/or peg-shaped teeth are seen in 28
families (80%). Minor dental abnormalities (Carabelli's cusps, invaginations in upper laterals, and/or rotated second premolars) and
hypodontia are seen in 32 families (91o%). In one case, hypodontia was seen in both the mother's and father's families (14). Ten families (1, 2, 3,
10, 11, 20, 24, 25, 29, and 32) have a palatally displaced or missing canine in at least two instances, in a parent and child (1, 3, 25, and 32), in
sisters (2), in a grandparent and a grandchild (10), in cousins (1, 20), in an aunt and her niece (11), in an aunt and her nephew (29), or in an
uncle and his nephew (24). In three families (1, 24, 32), missing canine(s) are seen.
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1744      Pirinen et al.                                                                                                                                    j Dent Res 7500) 1996
Table 1. The congenitally missing teeth by tooth groups in                                   Table 2. The number and percentage of persons with missing,
probands, first-degree relatives, and second-degree relatives                                impacted, peg-shaped, supernumerary, and transposed teeth
Tooth          Probands            First-degree               Second-degree                                                                            First-degree Second-degree
                                     Relatives                   Relatives                                                  Probands (%)               Relatives (%)  Relatives (%)
                                                                                                                               (N = 106)                 (N = 110)     (N = 93)
17                 1
15                 7                       7                            3                    Missing               38 (35.8)                            22 (20.0)      18 (19.4)
14                 3                       3                                                 Peg-shaped            10 (9.4)                              6 (5.5)        3 (3.2)
13                                         1                            2                    Transposed             2 ( 1.9)
12                 13                      9                            5                    Supernumerary          2 ( 1.9)                             3 (2.7)
22                 10                      8                            7                    Retained               3 (2.8)                              1 (0.9)        2 (2.2)
23                  1                                                   2                     (other than canine)
24                  1                      2                                                 Labial canine(s)       1 (100)                              2 (1.8)        2 (2.2)
25                  6                      4                             5                   Palatal canine(s)    105 (100)                              3 (2.7)        7 ( 7.5)
37                  1                      1
36                  1                     -                                                  is 4.5 times that of the normal population. The tooth groups
35                 18                      3                             3                   of the missing teeth of the patients are shown in Table 1. In
34                  1                      1                                                 addition, 10 of the probands (9.4%) had at least one peg-
31                  1                      2                                                 shaped upper lateral incisor. Of the probands, 45.3% had
41                 -                       1                                                 either hypodontia and/or peg-shaped teeth (Table 2).
42                                         1                                                 Retained (third molars not included), supernumerary
44                 2                       1                                                 (hyperdontia), and transposed teeth in probands were also
45                 18                      5                             2                   noted (Table 2). If missing third molars were considered, the
46                  1
                                                                                             prevalence of hypodontia was even higher (50%). However,
47                  2                      1                             1                   in three instances, a very late appearance of the third molar
Primary                                                                                      germ could be verified in post-treatment radiographs.
 teeth                                     3                             2

Total              87                     53                            32                   Dentition in first- and second-degree relatives
                                                                                             Hypodontia was observed in 22 (20%) of the first-degree
                                                                                             relatives (N = 110) and 18 (19.4%) of the second-degree
Seventy-nine first-degree relatives and 27 second-degree relatives                           relatives (N = 93) (Table 2). This is 2.5 times the population
out of 35 families were examined. In addition, reliable anamnestic                           prevalence. The tooth groups of the missing teeth of the
information was obtained from 97 family members (31 first-                                   first- and second-degree relatives are shown in Table 1. In
degree relatives and 66 second-degree relatives).                                            addition, three supernumerary teeth were seen in first-
   A detailed dental anamnesis was obtained with the help of a                               degree relatives (Fig. 1, pedigrees 26, 30, and 34). Nine peg-
check-list and by contacting dentists who had treated the                                    shaped upper laterals were noted in first- and second-
patients earlier. Pedigrees were constructed, and persons in                                 degree relatives (Table 2).
whom palatally displaced canine(s), hypodontia, hyperdontia,                                     Fifty persons (25%) had either hypodontia or
peg-shaped or very small upper laterals, or other                                            hyperdontia and/or peg-shaped upper laterals.
morphologically abnormal teeth were noted were marked as                                         Palatally displaced canines in first- or second-degree
affected (symbols shown in Fig. 1). Observations on third molars                             relatives of the patients (N = 203) were noted in 10 persons
were also made. If there was no sign of tooth development at the                             (Fig. 1, pedigrees 1, 2, 3, 10, 11,20, 25,and 29; pedigree 1, Fig.
age of 13, a third molar was considered missing.                                             2). The prevalence of palatally displaced canines (4.9%) in the
   Prevalences of numeric anomalies of dentition were                                        family members is 2.5 times the population prevalence. In
compared with the population prevalences for incisor-premolar                                addition to palatal impaction, four labially displaced canines
hypodontia (7.9%), hyperdontia (1.6%), and hypodontia with                                   were noted (Fig. 1, pedigrees 12, 29, 30, and 32).
third molars (20.8%) (Haavikko, 1971).
   This study is part of a large project related to the genetics of
incisor-premolar hypodontia. It has been approved by the                                     Discussion
Ethics Committee of the Institute of Dentistry.                                              The 106 patients with displaced and impacted canines
                                                                                             demonstrated a very high prevalence of hypodontia. The 35
                                                                                             pedigrees constructed clearly indicated the genetic character
Results                                                                                      of hypodontia in these patients. Palatally displaced canines
                                                                                             within the same family were shown in eight cases. Our
Dentition in probands with displaced canine(s)                                               findings thus support the hypothesis that the palatally
One or several congenitally missing permanent teeth were                                     malposed canine belongs to the spectrum of dental
seen in 38 (35.8%) of the probands (N = 106). The prevalence                                 anomalies related to incisor-premolar hypodontia. Other
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J Dent Res 7500) 1996                                               The Palatally Displaced Caninte

                                                                                                 developmental anomaly.
                                                                                                     From our family study, we conclude that palatal
                                                                                                 displacement of canine(s) is genetic and related to genetic
                                                                                                 incisor-premolar hypodontia and peg-shaped incisors. We
                                                                                                 stress the importance of carrying out screening for impacted
                                                                                                 canines in patients and families with hypodontia or peg-
                                                                                                 shaped teeth.

                                                                                                 We thank the Department of Orthodontics and 1edodontics,
                                                                                                 Institute of Dentistry, University of Helsinki, for a grant
                                                                                                 given to Dr. Satu Apajalahti, and Dr. Salla Norta for help in
                                                                                                 collecting the family material.
                                                                                                    A preliminary report was presented as a poster in the
                                                                                                 Fifth European Craniofacial Congress, 15-17 June 1995,
                                                                                                 Copenhagen, Denmark.

                                                                                                 Altonen M, Myllarniemi S (1976). Results of surgical exposure
                                                                                                      of impacted cuspids and bicuspids in relation to patients'
Figure 2. Four panoramic radiographs demonstrating hypodontia                                         somatic and dental matLration. lit I Oral Sur'5 5:180-186.
and palatally displaced and congenitally missing maxillary canines                               Alvesalo L, Portin P (1969). The inheritance pattern of missing,
in a family. In pedigree 1, the cousin (a) of the propositus at the age                               peg-shaped, and strongly mesio-distally reduced upper
of 44 had a palatally displaced canine and a congenitally missing                                     lateral incisors. Acta Odontol Scanid 27:563-573.
lateral incisor. Her daughter (b) at the age of 17 had retained and                              Arte S, Nieminen P, Pirinen S, Thesleff 1, Peltonieni L (1996).
congenitally missing second premolars. The aunt (c) of the
propositus had a palatally displaced canine and a congenitally                                        Gene defect in hypodontia: Exclusion of EGF, EGFR and
missing lateral incisor. Her daughter (d) at the age of 39 had both                                   FGF-3 as candidate genes. I Denit Res 75:1346-1352.
upper canines congenitally missing.                                                              Bass TP (1967). Observations of the misplaced upper canine
                                                                                                      tooth. Denit Pract 18:25-33.
dental anomalies related to hypodontia have been described                                       Becker A (1995). In defense of the guidance of palatal canine
earlier, namely, small tooth size (Garn and Lewis, 1970),                                             displacement (letter; comment). Comment on: Angle Ortihod
peg-shaped upper laterals (Alvesalo and Portin, 1969), labial                                         64:249-256, 1994. Anglc OQtliod 65:95-102.
malposition of canine (Svinhufvud et al., 1988) and                                              Becker A, Smith P, Behar R (1981). The incidence of anomalous
infraposition of deciduous molars (Bjerklin et al., 1992), short                                      maxillary lateral incisors in relation to palatally-displaced
root anomaly, and invaginations in incisors (Svinhufvud et                                            cuspids. Angle Ortlhad 51:24-29.
al., 1988; Kjaer, 1995). Hyperdontia was observed in five                                        Bjerklin K, Kurol J, Valentin J (1992). Ectopic eruption of
persons in the entire study population (1.6%,), which is the                                          maxillary first permanent molars and association with
population prevalence for supernumerary teeth (Brook,                                                 other tooth and developmental disturbances (see
1984). Concomitant hypo/hyperdontia has been previously                                               comments). Enr J Ortliod 14:369-375. Comment in: Enr i
reported (Peck and Peck, 1995).                                                                       Orthod 15:425, 1993.
    Our finding thus also supports the earlier suggestions                                       Brin 1, Becker A, Shalhav M (1986). Position of the maxillary
that the impacted canine is related to hypodontia (Bass,                                              permanent canine in relation to anomalous or missinig
1967) and small and peg-shaped upper laterals, and is                                                 lateral incisors: a population study. Euir J Orthiod 8:12-16.
familial and perhaps genetic.                                                                    Brin I, Solomon 1, Zilberman Y (1993). TrauLma as a possible
    The gene defects causing incisor-premolar hypodontia or                                           etiologic factor in maxillary canine impaction. An]i I Ortlod
other forms of hypodontia in man are not known. In our                                                Denhtofac Ortlioa 104:132-137.
family study, we have thus far been able to exclude several                                      Brook AH (1984). A unifying aetiological explanationi for
obvious candidate genes (Nieminen et al., 1995; Arte et al.,                                          anomalies of human tooth number and size. Arclh Oral Biol
1996) causing incisor-premolar hypodontia.                                                            29:373-378.
    The palatally impacted canine presents an urgent and                                         Burzynski N, Escobar VH (1983). Classification and genetics of
difficult treatment problem. According to clinical                                                    numeric anomalies of dentition. Birth Defects: Orig Art Scr
experience, treatment should be instituted as soon as the                                             19:95-106.
condition is recognized or when the normal eruption time                                         Ericson S, Kurol J (1986). Radiographic assessmenit of maxillary
has been exceeded (Altonen and Myllarniemi, 1976).                                                    canine eruption in children with clinical signs of eruption
Recently, it has been stressed that impacted teeth and teeth                                          distLrbance. Eir I Ortiod 8:133-140.
with the morphological characteristics listed above show a                                       Garn SM, Lewis AB (1970). The gradient and the pattern of
tendency to root resorption during orthodontic treatment                                              crown-size reduction in simple hypodontia. Angle Ortliod
(Kjaer, 1995), thus perhaps reflecting the nature of the                                              40:51 -58.
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1746     Pirinen et al.                                                                                                                               I Dent Res 75(10) 1996

Grahnen H (1956). Hypodontia in the permanent dentition.                                        maxillary canine. Br I Orthod 19:9-16.
     Odontol Revy 7(Suppl 3):1-100.                                                         Peck S, Peck L (1995). Classification of maxillary tooth
Grover PS, Lorton L (1985). The incidence of unerupted                                          transpositions. Am J Orthod Dentofac Orthop 107:505-517.
     permanent teeth and related clinical cases. Oral Surg Oral                             Peck S, Peck L, Kataja M (1994). The palatally displaced canine
    Med Oral Pathol 59:420-425.                                                                 as a dental anomaly of genetic origin (see comments).
Haavikko K (1971). Hypodontia of permanent teeth. An                                            Angle Orthod 64:249-256. Comment in: Angle Orthod 64:243,
     orthopantomographic study. Suom Hammaslaak Toim                                            246, 1995. Comment in: Angle Orthod 65:95-102, 1995.
     67:219-225.                                                                            Shah RM, Boyd MA, Vakil TF (1978). Studies of permanent
Jacoby H (1983). The etiology of maxillary canine impactions.                                   tooth anomalies in 7886 Canadian individuals. I: impacted
    Am J Orthod 84:125-132.                                                                     teeth. J Can Dent Assoc 44:262-264.
Kjaer I (1995). Morphological characteristics of dentitions                                 Svinhufvud E, Mylldrniemi S, Norio R (1988). Dominant
     developing excessive root resorption during orthodontic                                    inheritance of tooth malposition and their association to
     treatment. Eur J Orthod 16:25-34.                                                          hypodontia. Clin Genet 34:373-381.
Nieminen P, Arte S, Pirinen S, Peltonen L, Thesleff I (1995).                               Thilander B, Jakobsson SO (1968). Local factors in impaction of
     Gene defect in hypodontia: exclusion of MSX1 and MSX2                                      maxillary canines. Acta Odontol Scand 26:145-168.
     as candidate genes. Hum Genet 96:305-308.                                              Zilberman Y, Cohen B, Becker A (1990). Familial trends in
Oliver RG, Mannion JE, Robinson JM (1989). Morphology of the                                    palatal canines, anomalous lateral incisors and related
     maxillary lateral incisor in cases of unilateral impaction of                              phenomena. Eur J Orthod 12:135-139.

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