Open Journal of Stomatology, 2013, 3, 329-333 OJST
http://dx.doi.org/10.4236/ojst.2013.36055 Published Online September 2013 (http://www.scirp.org/journal/ojst/)
Prevalence of Dental Anomalies in Norwegian School
Children
Linn Haugland1, Trond Storesund1, Vaska Vandevska-Radunovic2
1The Norwegian Dental Expertise Center West, Stavanger, Norway; 2Department of orthodontics, University of Oslo, Oslo, Norway
Received 4 July 2013; revised 4 August 2013; accepted 1 September 2013
Copyright © 2013 Linn Haugland et al. This is an open access article distributed under the Creative Commons Attribution License,
which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
ABSTRACT
Introduction: Dental anomalies have been widely ex-
amined, but no such studies have been conducted in
Norway. The purpose of this study was to examine
the prevalence of dental anomalies and investigate
their possible association with gender and dental oc-
clusion. Methods: Panoramic radiographs and study
models of 500, 12-year-old school children (273 girls,
227 boys) were analyzed for the presence of dental
anomalies including agenesis, taurodontism, pulp
stones, microdontia, macrodontia, impaction, short
roots, supernumerary teeth, ectopic eruption and
transposition. The subjects were divided into three
groups according to the Angle classification (Class Ι,
n = 252. Class ΙΙ, n = 227. Class ΙΙΙ, n = 21). Percen-
tages and chi-square test were used for evaluation of
the data. Results: In this population 28.2% of the sub-
jects showed at least one dental anomaly. Statistically
significant associations were observed between agen-
esis and Angle Class II dental occlusion (P = 0.03),
and between agenesis and gender (P = 0.004). Conclu-
sions: Agenesis was a predominant dental anomaly in
girls and was found twice as often in subjects with
Class ΙΙ, than with Class Ι dental occlusion.
Keywords: Dental Anomalies; Dental Occlusion;
Prevalence
1. INTRODUCTION
Malformations of the teeth are designated as dental ano-
malies, including aberrant dimensions, numbers, mor-
phology, and eruption patterns [1-5]. The causes of den-
tal anomalies are largely unknown, but published data
point out a possible genetic link between malocclusions
and dental anomalies [6,7]. However, environmental fac-
tors cannot be ruled out [8,9].
Studies on the prevalence of dental anomalies show di-
vergent results [5,8-10]. While some investigations show
the prevalence of tooth anomalies as low as 21% [11],
other studies show the prevalence at almost 75% [10].
Several investigations report a prevalence of tooth
anomalies to be between 34% and 40% [5,8,9]. The rea-
sons for such discrepancies can be multifold. Ethnical
differences can be one explanation, but the type of dental
anomalies investigated and the use of different diagnostic
criteria can also contribute to the divergent results.
Dental anomalies are more common among orthodon-
tic patients than the comparable population, and seem to
be associated with certain malocclusions [6,7]. Basdra et
al. [2] evaluated dental anomalies in relation to the Class
ΙΙ division 2 malocclusion in a sample of German indi-
viduals. The conclusion was that this malocclusion is
closely related to tooth anomalies. Peck et al. [6] identi-
fied systematically reduced tooth-size as a trait associ-
ated with Class ΙΙ division 2 malocclusion. These find-
ings indicate the presence of a common genetic influence
between skeletal and tooth-size features in this maloc-
clusion [6].
Dental anomalies can increase the risk of caries and
periodontitis, and can lead to endodontic, aesthetic or or-
thodontic problems [12]. If undiscovered, they can com-
plicate orthodontic treatment and affect the treatment
outcome.
The aim of the present study was to examine the pre-
valence of dental anomalies in a population of Norwe-
gian school children, and investigate their possible as-
sociation with gender and dental occlusion.
2. MATERIAL AND METHODS
Diagnostic records: panoramic and periapical radio-
graphs, dental casts and dental histories of 500 subjects
(273 girls, 227 boys) were drawn from the growth files
of the Department of Orthodontics, University of Oslo,
Norway [4]. All subjects were recorded during the year
of their 12th birthday. The subjects were classified into 3

L. Haugland et al. / Open Journal of Stomatology 3 (2013) 329-333 330
groups according to the Angle classification: Angle Class
Ι (143 girls, 109 boys), Angle Class ΙΙ (118 girls, 109
boys), and Angle Class ΙΙΙ (12 girls, 9 boys) [13].
Data were evaluated and classified by one of the au-
thors (LH) after calibration with an experienced ortho-
dontist (VVR). In order to reduce radiographic misinter-
pretations, blurred image teeth were left out. Permanent
third molars were also excluded from the examination.
The following ten types of dental anomalies were di-
agnosed from dental cast and radiographic material:
1) Agenesis: Congenital absence of one or more teeth,
excluding the third molars [14].
2) Taurodontism: A morpho-anatomical variation in
the shape of teeth in that the body of the tooth is enlarged
and the roots decreased in size [15].
3) Pulp stone: Discrete calcified bodies in the dental
pulp [16].
4) Microdontia: An inherited condition that produces
at least one disproportionately small tooth [17].
5) Macrodontia: An inherited condition that produces
at least one disproportionately large tooth [18].
6) Impaction: A tooth that is obstructed in its path of
eruption by an adjacent tooth, bone or soft tissue [8].
7) Short roots: Roots as long as or shorter than the
crowns in the incisors and visually evaluated as short in
the posterior teeth were recorded as short roots [19].
8) Supernumerary teeth: Teeth that appear in addition
to the regular number of teeth [5].
9) Ectopic eruption: Eruption of a tooth in an abnor-
mal position [5].
10) Tooth transposition: The positional interchange of
two adjacent teeth, especially their roots, or the deve-
lopment or eruption of a tooth in a position normally oc-
cupied by a non-adjacent tooth [20].
Statistical analysis was performed using the statistical
software SPSS, version 20 (IBM).
Numbers of subjects and rates of dental anomalies
were calculated for the overall study sample, and by sex
and malocclusion type. Chi-square test was conducted to
determine the statistical significance of dental anomalies
by sex and malocclusion type. P values ≤ 0.05 were con-
sidered significant.
3. RESULTS
A total of 141 subjects (28.2%) had at least one dental
anomaly (Table 1). The distribution was rather equal be-
tween girls and boys, but predominant in the Angle Class
I and Class II dental occlusions (Figure 1). The most
prevalent dental anomaly was impaction (8.4%), fol-
lowed by agenesis (6.6%) and taurodontism (6.2%) (Ta-
ble 1). Agenesis had significantly higher prevalence in
girls than boys (P = 0.004) (Table 1).
The distribution of dental anomalies by occlusion
group showed that agenesis was significantly lower in
Table 1. Distribution of children with one or more dental ano-
malies.
Dental anomaliesNo dental anomalies Total
n (%) n (%) n (%)
Boys 82 (36.1) 145 (63.9) 227 (45.4)
Girls 96 (35.2) 177 (64.8) 273 (54.6)
Total 178 (35.6) 322 (64.4) 500 (100)
Figure 1. Distribution of subjects with dental anomalies in
Angle Class Ι, Class ΙΙ and Class ΙΙΙ groups in girls and boys.
the Class Ι group than Class ΙΙ group (P = 0.03), and not
observed in Class ΙΙΙ group (Table 2). None of the other
dental anomalies showed significant differences between
the different malocclusion groups or with gender (Tables
1 and 2).
Subjects with 2 or more dental anomalies were scarce
and therefore merged in one group (Tables 3 and 4). The
distribution of dental anomalies by gender and malocclu-
sion groups and the subsequent results of Pearsons chi-
square test showed no significant differences between sub-
jects with and without a dental anomaly (Tables 3 and 4).
The distribution of dental anomalies by region was as
follows: the rate of agenesis (excluded third molars) was
highest in the mandibular premolar region (5.4%), fol-
lowed by the maxillary premolar region (3.0%) and the
maxillary anterior region (1.6%). Supernumerary teeth
and macrodontia were found only in the maxillary ante-
rior region. Pulp stones and taurodontism were found
only in maxillary and mandibular molars, and observed
at higher rates in the maxilla then in the mandible. Im-
paction was observed most often in the premolar (9.4%),
and in the maxillary canine region (2.2%).
4. DISCUSSION
There are numerous studies reporting the prevalence of
dental anomalies, however, a similar study has not been
conducted in Norway. The results obtained from the se-
lected group provide an estimation of the prevalence of
dental anomalies and their association with dental occlu-
sionand gender in the general population.

L. Haugland et al. / Open Journal of Stomatology 3 (2013) 329-333 331
Table 2. Distribution of children with one or more dental ano-
malies in Angle groups.
Dental anomalies No dental anomalies Total
n (%) n (%) n (%)
Angle Cl. Ι 84 (33.4) 168 (66.6) 252 (50.4)
Angle Cl. ΙΙ 85 (37.4) 142 (62.6) 227 (45.4)
Angle Cl. ΙΙΙ 9 (42.9) 12 (57.1) 21 (4.2)
Total 178 (35.6) 322 (64.4) 500 (100)
Table 3. Distribution of dental anomalies in girls and boys and
results of Pearson chi-square test.
No dental
anomaly
1 dental
anomaly
2 or more dental
anomalies Total
n (%) n (%) n (%) n (%)
P
Boys 163 (71.8) 50 (22.0) 14 (6.2) 227 (45.5)NS
Girls 193 (70.7) 61 (22.3) 16 (5.9) 273 (54.6)NS
Total 359 (71.8) 111 (22.2) 30 (6.0) 500 (100)-
Table 4. Distribution of dental anomalies in Angle Class Ι,
Class ΙΙ and Class ΙΙΙ groups, and results of Pearson chi-square
test.
No dental
anomaly
1 dental
anomaly
2 or more dental
anomalies Total
n (%) n (%) n (%) n (%)
P
Cl. Ι 188 (74.6) 48 (19.0) 16 (6.4) 252 (50.4)NS
Cl. ΙΙ 158 (69.6) 56 (24.7) 13 (5.7) 227 (45.4)NS
Cl. ΙΙΙ 13 (61.9) 7 (33.3) 1 (4.8) 21 (4.2)NS
Total 259 (51.8) 111 (22.2) 30 (6.0) 500 (100)-
The prevalence rate of the investigated dental anoma-
lies was 28.2% and was lower than most similar random
sample studies [5,8-10]. This may be due to the fact that
subjects selected in this study were gathered from a
school sample of 12-year-old children and not from a
pool of patients referred for orthodontic treatment. Pre-
vious studies have shown that orthodontic patients are
more likely to have dental anomalies than the general
population [10]. Nevertheless, divergent definitions of
dental anomalies, various diagnostic criteria, ethnic vari-
ations, and local environmental influences may also af-
fect this prevalence.
Statistically significant differences were observed be-
tween girls and boys in relation to agenesis; agenesis was
more prevalent in girls than in boys. However, no other
dental anomalies were gender related. There are con-
flicting reports on gender differences and dental anoma-
lies as some studies show no significant differences [8,
16,21], while other studies present opposite results [22].
Thongudomporn and Freer [10] showed that dental in-
vagination and short roots were significantly more pre-
valent in girls than boys, and Ezoddini et al. [9] showed
that dilacerations, taurodontism and supernumerary teeth
were more prevalent in boys than girls.
The prevalence of agenesis, excluding third molars,
was 6.6% which is comparableto the findings of Aasheim
and Ögaard [4]. They also reported a higher prevalence
of agenesis in girls (7.2%) than in boys (5.8%), but found
no statistically significant difference between genders. In
general, the prevalence of agenesis excluding third mo-
lars is shown to be between 4.19% and 10.60% [8,10,22].
Uslu et al. [5] reported a prevalence of 21.6%, however,
in this case, third molars were included in the investiga-
tion. Studies conducted among orthodontic patients show
a higher prevalence of agenesis [22] than studies with
subjects without the need of orthodontic treatment [4,8].
Hence, the relative low prevalence of agenesis found in
our sample can be due to the non-orthodontic sample and
the exclusion of third molar agenesis.
The subjects were divided in groups according to the
Angle classification. This classification enabled grouping
according to the sagittal molar relationship, but did not
necessarily mean that they required orthodontic treat-
ment. Agenesis was the only dental anomaly that showed
statistically significant difference between the occlusion
groups. Subjects with Angle Class ΙΙ occlusion had sig-
nificantly more agenesis than subjects with Angle Class Ι,
while none of the subjects with Angle Class ΙΙΙ occlusion
displayed agenesis. Uslu et al. [5] reported a slightly
higher rate (36.3%) of congenital tooth anomalies in sub-
jects with Class ΙΙ malocclusion, compared to 30.4% in
this study. This is not unexpected, as the subjects in their
investigation were all patients referred for orthodontic
treatment. Close association between Angle Class ΙΙ mal-
occlusion and congenital tooth anomalies has previously
been reported [6,7]. Peck et al. [6] indicated genetic in-
fluences for Class ΙΙ Division 2 malocclusion, which has
a low prevalence rate. It was also shown that Class ΙΙ
Division 2 malocclusions are related to gene-controlled
dental anomalies [6,7,23]. In the present study we did not
classify Class ΙΙ malocclusion in subgroups.
The prevalence of impaction was 8.4% when exclud-
ing third molars. Ezoddini et al. [9] and Thongudomporn
and Freer [10] found a somewhat similar prevalence of
respectively 8.3% and 9.9% in non orthodontic patients.
Afify and Zawawi [21] found a prevalence of impaction
of 21.1% when including third molars in non-orthodontic
patients. The prevalence of impacted third molars was
the highest (15.9%) compared to the upper canines (3.3%)
[21]. Gupta et al. [8] found a prevalence of 3.74% of
impacted teeth in non-orthodontic patients (excluding
third molars), while Uslu et al. [5] found that 2.9% of the
teeth including third molars where impacted in orthodon-
tic patients. The low prevalence could be explained by

L. Haugland et al. / Open Journal of Stomatology 3 (2013) 329-333 332
ethnical variation, different diagnostic criteria and/or mis-
diagnosis.
The rate of agenesis (excluding third molars) was
highest in the mandibular premolar region (5.4%), fol-
lowed by the maxillary premolar region (3.0%) and the
maxillary anterior region (1.6%). This agrees with the
findings by Aasheim and Ögaard [4] and Magnússon
[24], studies also undertaken in Scandinavian popula-
tions. Noticeably, supernumerary teeth and macrodontia
were found only in the maxillary anterior region. Pulp
stones and taurodontism were found only in maxillary
and mandibular molars, and observed at higher rates in
maxillary molars then in mandibular molars. Ranjitkar et
al. [16] found pulp stones in only six (0.4%) of 1632
premolars and in 327 (19.7%) of 1667 molars. Several
studies found taurodontism only in maxillary and man-
dibular molars [5,10,22].
Impaction was observed most often in the premolar
region (9.4%), and in the maxillary canines (2.2%). Si-
milar studies found the rate of impaction to be highest in
the maxillary canines when excluding third molars [5,8,
10,21]. Impacted premolars could have been overlooked
in these studies because of the late eruption of the pre-
molars.
5. CONCLUSIONS
1) The prevalence of subjects with at least one con‐
genital dental anomaly in a Norwegian population was
28.2%. Impaction occurred most often, followed by age-
nesis and taurodontism.
2) Agenesis was more predominant in girls than boys,
and was found twice as often in subjects with Angle Class
ΙΙ than with Angle Class Ι dental occlusion.
6. ACKNOWLEDGEMENTS
We would like to gratefully acknowledge the enthusiastic supervision
of Dr. Erling Thom during this work. We also thank the clinic of or-
thodontics at UiO and the Norwegian Dental Expertise Center West,
Stavanger for their support.
REFERENCES
[1] Brook, A.H. (1984) A unifying aetiological explanation
for anomalies of human tooth number and size. Archives
of Oral Biology, 29, 373-378.
doi:10.1016/0003-9969(84)90163-8
[2] Basdra, E.K., Kiokpasoglou, M.N. and Komposch, G.
(2001) Congenital tooth anaomalies and malocclusions:
A genetic link? European Journal of Orthodontics, 23,
145-152. doi:10.1093/ejo/23.2.145
[3] Kotsomitis, N., Dunne, M.P. and Freer, T.J. (1996) A
genetic aetiology for some common dental anomalies: A
pilot twin study. Australian Orthodontic Journal, 14, 172-
178.
[4] Aasheim, B. and Ögaard, B. (1993) Hypodontia in 9-
year-old Norwegians related to need of orthodontic treat-
ment. Sca ndinavian Journal of Dental Research, 101, 257-
260.
[5] Uslu, O., Akcam, M.O., Evirgen, S. and Cebeci, I. (2009)
Prevalence of dental anomalies in various malocclusions.
American Journal of Orthodontics and Dentofacial Or-
thopedics, 135, 328-335. doi:10.1016/j.ajodo.2007.03.030
[6] Peck, S., Peck, L. and Kataja, M. (1998) Class II division
2 malocclusion: A heritable pattern of small teeth in well-
developed jaws. The Angle Orthodontist, 68, 9-20.
[7] Basdra, E.K., Kiokpasoglou, M. and Stellzig, A. (2000)
The class II division 2 cranio facial type is associated with
numerous congenital tooth anomalies. European Journal
of Orthodontics, 22, 529-535. doi:10.1093/ejo/22.5.529
[8] Gupta, S.K., Saxena, P., Jain, S. and Jain, D. (2011) Pre-
valence and distribution of selected developmental dental
anomalies in an Indian population. Journal of Oral Sci-
ence, 53, 231-238. doi:10.2334/josnusd.53.231
[9] Ezoddini, A.F., Sheikhha, M.H. and Ahmadi, H. (2007)
Prevalence of dental developmental anomalies: A radio-
graphic study. Community Dent Health, 24, 140-144.
[10] Thongudomporn, U. and Freer, T.J. (1998) Prevalence of
dental anomalies in orthodontic patients. Australian Den-
tal Journal, 43, 395-398.
[11] Ooshima, T., Ishida, R., Mishima, K. and Sobue, S. (1996)
The prevalence of developmental anomalies of teeth and
their association with tooth size in the primary and per-
manent dentitions of 1650 Japanese children. Interna-
tional Journal of Paediatric Dentistry, 6, 87-94.
doi:10.1111/j.1365-263X.1996.tb00218.x
[12] White, S.C. and Pharoah, M.J. (2002) Oral radiology prin-
ciples and interpretation. 6th Edition, Mosby, St. Louis.
[13] Angle, E.H. (1907) Treatment of malocclusion of the
teeth: Angle’s system. S.S. White Manufacturing Co.,
Philadelphia.
[14] Ramazanzadeh B.A., Ahrari F. and Hajian S. (2013) Eva-
luation of tooth size in patients with congenitally-missing
teeth. Journal of Dental Research, Dental Clinics, Dental
Prospects, 7, 36-41
[15] Bronoosh, P., Haghnegahdar, A. and Dehbozorgi, M.
(2012) Prevalence of taurodontism in premolars and mo-
lars in the South of Iran. Journal of Dental Research,
Dental Clinics, Dental Prospects, 6, 21-24.
[16] Ranjitkar, S., Taylor, J.A. and Townsend, G.C. (2002) A
radiographic assessment of the prevalence of pulp stones
in Australians. Australian Dental Journal, 47, 36-40.
doi:10.1111/j.1834-7819.2002.tb00301.x
[17] Kocabalkan, E. and Ozyemişci, N. (2005) Restoration of
severe hypodontia associated with microdontia by using
an overdenture: A clinical report. Chinese Medical Jour-
nal, 20, 350-352.
[18] Daskalogiannakis, J. (2000) Glossary of orthodontic terms.
Quintessence Books, Michigan.
[19] Apajalahti, S., Hölttä, P., Turtola, L. and Pirinen, S. (2002)
Prevalence of short-root anomaly in healthy young adults.
Acta Odontologica Scandinavica, 60, 56-59.
doi:10.1080/000163502753472014

L. Haugland et al. / Open Journal of Stomatology 3 (2013) 329-333 333
[20] Cho, S.Y., Chu, V. and Ki, Y. (2012) A retrospective
study on 69 cases of maxillary tooth transposition. Jour-
nal of Oral Science, 54, 197-203.
doi:10.2334/josnusd.54.197
[21] Afify, A.R. and Zawawi, K.H. (2012) The prevalence of
dental anomalies in the Western region of Saudi Arabia.
ISRN Dentistry, 2012, Article ID: 837270.
doi:10.5402/2012/837270
[22] Guttal, K.S., Naikmasur, V.G., Bhargava, P. and Bathi,
R.J. (2010) Frequency of developmental dental anomalies
in the Indian population. European Journal of Dentistry,
4, 263-269.
[23] Walkow, T.M. and Peck, S. (2002) Dental arch width in
Class ΙΙ Division 2 deepbite malocclusion. American
Journal of Orthodontics and Dentofacial Orthopedics,
122, 608-613.
[24] Magnússon, T.E. (1977) Prevalence of hypodontia and
malformations of permanent teeth in Iceland. Community
Dentistry and Oral Epidemiology, 5, 173-178.