Prevalence of Dental Anomalies in Norwegian School Children

doi:10.4236/ojst.2013.36055

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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

Email: [email protected]

Received 4 July 2013; revised 4 August 2013; accepted 1 September 2013

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

OPEN ACCESS

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 (%)

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 (%)

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.

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