Epidemiology of Supernumerary Teeth in 5000 Radiography Films: Investigation of Patients Referring to the Clinics of Ardabil in 2015–2020

Background Supernumerary tooth is defined as any extra tooth or odontogenic structure that is formed on normal dentition. Supernumerary teeth cause such problems as deficiency in tooth growth, ectopic growth, displacement, crowding, diastema, odontogenic cyst formation, decay of the adjacent tooth, malocclusion, and esthetic problems. This study was conducted aiming at determining epidemiology of supernumerary teeth in Ardabil city in 2020. Materials & Methods. In this retrospective descriptive analytical study, 5000 panoramic radiographs of patients referring to Rad and Baser Oral and Maxillofacial Radiology Centers were selected through multistage sampling method during 2015–2020. The data were collected by checklist and analyzed with using SPSS-21 and chi-squared, Fisher, and one-way ANOVA tests with a significance level less than 5%. Results The prevalence of supernumerary teeth was estimated as 1.06% (n = 53), and no significant difference between the males and females was seen. Most supernumerary teeth were found in the distomolar (44.1%) and parapremolar (29.4%) locations. The majority of supernumerary teeth were present in the maxilla (73.5%) and were impacted (77.9%) and unilateral (71.7%). The number of supernumerary teeth was 68 cases and majority of patients (86.8%) had one supernumerary tooth. Conclusion Supernumerary tooth in this study had a high prevalence compared to similar studies, and unlike most previous studies, the most common type of supernumerary tooth was distomolar. Early diagnosis and proper medical planning are essential for managing supernumerary teeth.


Introduction
Supernumerary tooth is defined as any extra tooth or odontogenic structure that is formed on normal dentition.
is position is also called hyperdontia. Supernumerary teeth can be unilateral or bilateral, single or multiple, in any parts of the dental arch. ese teeth also form in both the deciduous and permanent teeth systems [1][2][3].
e etiology of supernumerary teeth is not clearly defined and various theories have been reported for it, the most common theory being the formation of teeth as a result of horizontal growth and hyperactive dental lamina [1,4,5]. In general, a combination of environmental and genetic, factors has been proposed to explain the occurrence of supernumerary teeth [6]. e prevalence of supernumerary teeth in different populations in permanent dentition is between 0.5% and 5.3% and in deciduous teeth is between 0.2% and 0.8% [4,7,8]. In general, the prevalence of supernumerary tooth is higher in the Asian population [9][10][11]. e prevalence of hyperdontia in countries between the Caspian Sea and the Black Sea is about 0.1% to 3.8% and has a higher prevalence (between 0.4% and 3.8%) in the Arab and East Asian countries [12][13][14].
Supernumerary teeth can cause problems such as defects in tooth growth, ectopic growth, displacement, crowding, diastema, odontogenic cyst formation, decay of the neighboring tooth, malocclusion, and esthetic problems [15]. Supernumerary teeth may be associated with a variety of syndromes, including Gardner syndrome, EhlersDanlos syndrome, Cleidocranial dysplasia, and AndersonFabry [1,6]. Supernumerary teeth often manifest in many forms. However, these teeth may also develop in patients without the syndrome. ese teeth may present as single teeth, two teeth, or multiple teeth, or as unilateral or bilateral [1,9]. Also, the presence of an undeveloped supernumerary tooth can make the site unsuitable for possible future implants and make implant placement difficult [16].
Since the majority of supernumerary teeth (93-80%) can cause clinical complications, early detection and orthodontic and surgical interventions are of significant value in reducing future clinical problems and establishing proper occlusion of adjacent permanent teeth [12,15].
Familiarity with these teeth is important for orthodontists, pediatricians, and general dentists, who usually see children at an early age and can be more effective for early diagnosis and planning for long-term multifaceted treatment [4].
Knowing the prevalence and pattern of supernumerary teeth can be helpful in the timely diagnosis and prevention of dental malformations side effects by dentists. erefore, this study was presented to investigate the frequency of supernumerary tooth in Ardabil.

Materials and Methods
is descriptive cross-sectional study was performed on the 5000 panoramic radiographs from the archives of two specialized centers of maxillofacial radiology, i.e., Rad and Baser from 2015 to 2020 in Ardabil. In total, 36,340 panoramic radiographs were recorded in two centers (26,440 radiographs in the center of Baser and 9900 radiographs in the center of Rad). e multistage sampling method was used for sampling. In the first stage, according to the total number of radiographs in these two centers, the number of samples in each center was calculated and allocated as a quota.
In the second stage, the regular random sampling method was used to select the samples, so that by presenting the number from the extracted list, a number to the radiographs were assigned and one radiograph out of every 10 numbers were regularly selected. To extract the data, a checklist prepared based on specific objectives was used. Checklists included variables of gender/type of jaw/unilateral, bilateral/type of growth/location/single, double, multiple/number of supernumerary teeth. us, by observing the selected radiographs in the sampling method, if there was a supernumerary tooth, the checklist was completed.
Descriptive and inferential statistics were used to analyze the data. To report the number and percentage of supernumerary teeth, relative frequency, mean, and standard deviation were used, and to compare the status of supernumerary teeth based on unilateral and bilateral, type of growth (erupted, impacted), location by sex, and type of jaw, chi-squared and Fisher tests were used. To compare the number of supernumerary teeth by type of jaw, sex, and type of growth, the independent t test was used. To compare the number of supernumerary teeth by single, double, multiple and unilateral and bilateral, midline, one-way analysis of variance was used. e tests were analyzed with a significance level of less than 5% using SPSS software version 21.
Out of the 68 supernumerary teeth, 30 (44.1%) in distomolar, 20 (29.4%) parapremolar, 8 (11.8%) mesiodens, 5 (7.4%) in the lateral incisor area, 2 (2.9%) in the canine area, and 3 cases (4.4%) of paramolar were found ( Figure 2). e number of supernumerary teeth was in average 1.28 (minimum 1 and maximum 6 supernumerary teeth) per person and the average number of supernumerary teeth in women is more than men, but this difference between the two sexes was not significant. Table 2 shows that 82.9% (34 teeth) of supernumerary teeth in women and 59.3% (16 teeth) of supernumerary teeth in men were in the maxilla. e chi-squared test showed a significant difference in the distribution of supernumerary teeth between men and women by jaw type (P ≤ 0.05). Also, in both genders, the majority of supernumerary teeth were impacted, but no significant difference in this variable between the two sexes was seen (Table 3). Also, in both genders, the majority of supernumerary teeth were unilateral, and there was no significant difference in this variable between the two sexes.
e results showed that the majority of supernumerary teeth in men (45.8%) were in parapremolar location and in women (55.2%) were distomolar type, and a significant difference in terms of supernumerary teeth location was found between the males and females (P ≤ 0.05). (Table 4).
Also, the majority of supernumerary teeth with parapremolar location, 70% (14 teeth) were in the mandible, and 30% (6 teeth) in the maxilla, and all teeth with distomolar, mesiodens, and paramolar locations were located in the maxilla. Fisher test showed a significant difference in the location distribution of supernumerary teeth by jaw type (P ≤ 0.05). (Table 5).

Discussion
In this study, 5000 panoramic radiographs were examined, of which 53 patients had a total of 68 supernumerary teeth. e prevalence of supernumerary tooth was 1.06%. According to the reports presented in the literature, the frequency of supernumerary teeth in different populations was reported between 0.5% and 5.3% in permanent tooth and between 0.2% and 0.8% in deciduous teeth [1,7,8]. Amini et al. (2013) [20], Palestine [21], and Madrid [22], respectively. Variation in prevalence among populations can be attributed to racial factors, sampling method, differences in sample size, age of subjects, diagnostic tools, and selection of individuals from medical centers [23]. e present study showed that the frequency of supernumerary tooth is higher in women than in men, but this difference between the two sexes was not significant. In most studies, the frequency of supernumerary teeth in men has been reported more than women, such as the study of  [19] reported the prevalence of supernumerary teeth in women more than men. One of the reasons that has been stated in most studies reporting higher prevalence of supernumerary teeth in men than women can be related to the fact that X-dependent transmission has been suggested for the occurrence of hyperdontia, which can also explain the higher prevalence in men. However, a clear reason for this subject was not been found yet [17].
e present study showed that the majority of supernumerary teeth were located in the maxilla in both males and females, which is consistent with the results of few similar studies, such as those of Singh VP et al.  [9,15,17,18,20,22,[24][25][26][27]. Although the reason for this was not fully understood, one reason given for it could indicate a higher prevalence of Hyperdontia in the maxillary forearm [17].
It seems that the prevalence estimation of supernumerary tooth can be affected by sampling methods, genetic and environmental factors as well as the age of the subjects. According to studies, the appearance of supernumerary teeth is more common in the first 3 decades of life than in the older age groups. In studies that included mostly the younger age groups (children), the prevalence of supernumerary teeth is higher (about 1.28% to 2.4%) and mostly in the premaxillary part, but in the studies that examined the older age groups (adults), a lower prevalence (about 0.4% to 1%) was reported, which was mostly in the maxilla and posterior parts of the dental arch [30,31].
In a study by leco_berrocal et al., the most common location of supernumerary teeth in children was in the premaxillary location and in adults was in the distomolar location [22]. On the other hand, this can be explained as   International Journal of Dentistry follows: having supernumerary tooth in the premaxillary location, especially mesiodens, which is very effective in a person's beauty and aesthetics, it is possible that a person had extracted that tooth in childhood and therefore does not have the desired tooth in older ages. Also, one of the reasons people go to the dental office in the puberty period is wisdom tooth extraction, and it is possible that, during this time, they have noticed supernumerary distomolar teeth in that area.
According to the results of the present study, distomolar supernumerary tooth is the most common among other types of supernumerary tooth. In this study, according to the explanations and results of various studies, we can guess that most of the people studied in this study were adults, and according to this case, this issue can be justified to some extent. However, the genetic and environmental factors should not be ignored.
In this study, most of the supernumerary teeth in men were in the parapermular position, and in women, most of the supernumerary teeth were in the distomular position.
is finding was consistent with the study by Rajab et al. (2002), Sasaki et al. (2007), Hyun et al. (2008) [5,32,33]. However, in several studies, distomolar has been reported more in men, such as in studies by Kurt et al. (2015), Kaya et al. (2015), and omas et al. (2013), which differed from the results of the present study [34][35][36]. It seems that this difference can be due to racial differences and other biological and environmental factors.
In this study, 70% of parapremolar supernumerary teeth were in the mandible and 30% in the maxilla. e results also showed that all distomolar, mesiodens, and paramolar teeth were located in the maxilla. Numerous studies have reported that the incidence of distomolars in the maxilla is between 69% and 91% [37,38]. In the study of Kaya et al. (2015), 90% of distomolars were present in the maxilla (37). Also, in the study of Kokten et al. (2003) and Menardia-Pejuan V (2000), distomolars were seen more in the maxilla than in the mandible [39,40]. In the study of Arandi et al. (2020), all distomolars were present in maxilla [21].
In the present study, out of 68 extra teeth, 77.9% were impacted and 22.1% were erupted. In the study of Demiriz et al. (2015), 84% of supernumerary teeth were impacted and 16% were erupted [19]. In the study of Leco_Berrocal et al. (2007), 95.8% of supernumerary teeth were impacted and only 4.2% of them were erupted [22]. While in the study of Singh et al. (2014), 56.36% of supernumerary teeth were erupted and 43.63% of them were impacted, and in the study of Arandi et al. (2020), 52.2% were erupted and 47.8% of supernumerary teeth were impacted [20,21].
In this study, the majority of supernumerary teeth were unilateral in both sexes. us, 71.7% of patients had unilateral supernumerary teeth and 13.2% had bilateral supernumerary teeth. Consistent with the results of our study, in the study of Amini et al. (2013), all supernumerary teeth were unilateral but no bilateral supernumerary teeth were seen in any of the patients [17]. In other similar studies, the majority of supernumerary teeth were unilateral [4,5].

Conclusion
In the present study, the prevalence of supernumerary teeth in Ardabil was 1.06%, which can be said to have a high prevalence compared to similar studies. e prevalence of supernumerary teeth was not significantly different between the two sexes (P ≥ 0.05). e most supernumerary teeth found in this study were distomolar (44.1%), and the majority of supernumerary teeth were in maxilla (73.5%), impacted (77.9%), and unilateral (71.7%). e location of supernumerary teeth by gender in this study is inconsistent with the majority of similar studies.

Recommendations.
Due to the high prevalence of supernumerary teeth in the study population and the consequences caused by this type of tooth, it is recommended that, in each dental care for patients requiring radiography, supernumerary tooth screening be considered to prevent subsequent problems.

Limitations.
One of the limitations of the present study is the lack of investigation of the relationship between age and other socioeconomic variables in the prevalence of supernumerary teeth, which is due to the lack of patient information in the records. It is suggested that future studies be performed prospectively and investigate the role of these variables in estimating and predicting supernumerary teeth.

Data Availability
e data the questionnaire used to support the findings of this study are available from the corresponding author upon request.

Conflicts of Interest
e authors declare that they have no conflicts of interest.