Prevalence of Supernumerary Teeth in Maxillary and Mandibular Anterior Region in A Group of Egyptian Children: A Retrospective Study

Introduction: One of the most common causes of impacted permanent anterior teeth is the presence of Supernumerary teeth (ST) which has an impact on developing teeth, and dental arches as well. Aim/ Objective: To evaluate the prevalence, distribution, characteristics, and complications of ST in maxillary and mandibular anterior region in a sample of Egyptian children.


INTRODUCTION
Supernumerary teeth (ST) are teeth or toothlike structures that develop in both primary and permanent dentitions.ST either erupt or may be revealed in the routine radiographic examination.A series of clinical complications can be caused by ST, including malalignment, crowding of teeth, delayed eruption, midline diastema, and cyst formation (Syriac et al., 2017).
ST also known as hyperdontia; is the presence of a greater number of teeth than the normal set of teeth (32 in permanent dentition and 20 in deciduous dentition).The most common ST type occurs in the upper jaw's central region.When ST occur between the two maxillary central incisors, they are called mesiodens.ST are twice as prevalent in males than females.As well as it is quite rare in primary dentition, but it is the most common dental anomaly in permanent dentition (Ray et al., 2005).
The prevalence of ST ranges from 0.2 to 0.8% in deciduous dentition.In permanent dentition 0.5 to 5.3%, and 0.9% in mixed dentition (Wang & Fan, 2011), (Lu et al., 2017).ST have different distribution, it can be single, multiple, unilateral, or bilateral.Also, ST can be found in different locations; maxilla, mandible "very rare", buccal, palatal, or interfering with the existing dentition (He et al., 2017).
The etiology of ST remains unclear.Many theories were proposed as an explanation of ST formation; atavism (evolutionary throwback), dichotomy, hyperactivity of the dental lamina, and genetic and environmental factors.The hyperactivity of the dental lamina theory is the one most accepted, and it suggests that due to genetic factors a localized, independent and conditional hyperactivity of the remaining epithelial cells of the dental lamina occurs (Fleming et al., 2010).
Previous studies have shown that several genes are associated with ST; Pax6 mutant, Fam20B, and USAG-1ST.Heritability of ST is complex and polygenic, involving many regulatory signals from several key molecules' activators and inhibitors.(Kriangkrai et al., 2006;Munne et al., 2009;Tian et al., 2016).
Although ST are one of the most common dental anomalies, there are no published studies about the prevalence of ST in Egypt.So, this study was conducted to study the prevalence, distribution, characteristics, and complications caused by supernumerary teeth in non-syndromic Egyptian pediatric population.

II. MATERIALS AND METHODS
The data for the study was collected from patients who attended the outpatient clinic of Pediatric Dentistry and Dental Public Health Department, Faculty of Dentistry, Cairo University.From the first of March 2019 to the first of March 2022.All the patients were examined clinically using a dental mirror and probe under adequate lighting.Data about patient age, sex, teeth erupted was recorded.
Suspected cases were examined radiographically using periapical films.Cone beam CT and occlusal view were done to some cases for better characterization and localization of ST.Exclusion criteria were patients with one or more of the following pathological situations: patients with systemic disease, History of dental trauma, patients with cleft lip and palate, and patients with hereditary diseases, or syndromes.
ST were found in 189 cases.Data analysis for these cases was performed by two pediatric dentists with over 10 years of experience.Data collected was as follow; number of ST and eruption status (erupted, impacted).Sagittal position (buccal or palatal) and morphology (conical, tuberculate, supplemental).Amount of tooth formed (only crown, crown and part of the root, whole tooth).Direction of the crown (vertical, inverted, horizontal).As well as complications (displacement, impossibility of eruption, resorptions of adjacent tooth, and presence of follicular cysts).
ST were considered impacted in case of presence of a physical barrier, nonvertical orientation of the teeth, or remaining in the jaw for more than 2 years after its mean age of eruption (Syriac et al., 2017).
The data collected were statistically analyzed.Qualitative data were expressed as numbers and percentages.Microsoft Excel was used for generation of representative figures.
The prevalence of ST in the studied sample was 0.3%.Out of 51421 patients who visited the outpatient clinic, in Pediatric Dentistry Department, Cairo University, 189 patients were diagnosed with ST.
The number of ST per patient was single in 65% of the 189 patients, double in 31% and triple in 4% of the patients.The total number of ST was 248; of theses 247 were in the maxilla (99.6%) and one case was in the mandible (0.4%) Regarding the Sagittal position, 230 (93%) of the ST occurred palatal and 18 (7%) were buccal.While the shape of the ST was conical in (53%) of the cases, tuberculate in (32%) and supplemental in (15%).
The direction of the crown was vertical in (74%) of the cases, inverted in (14%) and horizontal in (12%).Only crown was formed in (55%) of the cases, while (35%) had partial root and (10%) had entire tooth.
Delayed eruption was the most common complication (80%), while diastema and crowding were observed in (11%) and (6%) of the cases respectively.Three percent of the cases were asymptomatic.
Most of the cases (95%) were treated by surgical extraction, while only 5% were treated by simple extraction  As regards the location and sagittal position of ST; only one ST was in the mandible (0.04%),While 247 (99.06%) were found in maxilla.Sagittal position results revealed, 230 (93%) of the ST occurred palatal, and 18 (7%) were buccal.This comes in accordance with von Arx, 1992, De Oliveira Gomes et al., 2008, and Limbu et al., 2017 who stated that most of the ST erupt palatal to maxillary incisors.On other hand Some researchers found that the position of ST was usually found between maxillary incisors which results in impaction of the maxillary incisors (Yusof, 1990), (De Oliveira Gomes et al., 2008).
The scientific evidence available about the amount formed of ST is scarce.In the present study 55% of the ST showed only crown formed, while 35% had partial root, 10% had entire tooth.These findings are different from those of Limbu et al., 2017, who reported that 7% of ST showed only crown formed, 7% had partial root, and nearly 55% had entire tooth.
In terms of the shape observed in this study; 53% of the cases were conical, 32% tuberculate, and 15% supplemental.These results are in line with Burhan et al., 2015, Herath et al., 2017, and Aren et al., 2019.While the direction of the crown of ST was found as follow; vertical in 74% of the cases, inverted in 14% and horizontal in 12%.Most of the published data have reported similar results to our study; the normal orientation was the most prevalent (Burhan et al., 2015), (Herath et al., 2017).While few previously published studies have reported that inverted ST were the most common (Tay et al., 1984), (Liu, 1995).
The main clinical consequence of ST is the effect on developing dentition.The results of the current study showed that delayed eruption was the most common complication 80%.These results come in line with Celikoglu et al., 2010 and Brinkmann et al., 2020, who found that delayed eruption is the most common complication 25.1% and 16.7% respectively.The great difference in the percentages is because this study Is mainly concerned about ST in anterior region while the other two study have investigated both anterior and posterior regions, with wider age range.
On the other hand, diastema and crowding were observed in 11% and 6% of the cases in our study respectively.While 3% of the cases were asymptomatic.There were no root anomalies, cyst formation or intraoral infection in any case.This comes in accordance with Park et al., 2020, who stated that the incidence of cysts formation increases significantly with age.
Finally, most of the cases (95%) were treated by surgical extraction, while only 5% were treated by simple extraction.The timing of the treatment was the same time of the diagnosis 6 -11 years.Treatment decisions were taken according to clinical and radiographic findings of each case.Worthy to mention that there is a great debate in the available scientific evidence about proper timing, and line of treatment of ST.
Some authors have suggested that extraction of ST should be in the early mixed dentition period to limit the deleterious effects on developing dentition (Tay et al., 1984), (Russell & Folwarczna, 2003), (Park et al., 2020).Others have suggested that surgical intervention should be delayed until age 8 to 10 years when root development of the maxillary central and lateral incisors is almost complete (Meighani & Pakdaman, 2010).

V. CONCLUSION
From this retrospective study we found prevalence of ST is 0.3% in a sample of Egyptian children.Most of the ST were diagnosed at age 6 -11 years.Most of them are single, vertically impacted in the palatal maxillary region, both conical and tuberculated in shape.Males: female ratio is 1.7:1.