Frequency of supernumerary teeth in Mexican population

SALCIDO-GARCÍA JF, LEDESMA-MONTES C, HERNÁNDEZ-FLORES F, PÉREZ D, GARCÉS-ORTÍZ M. FREQUENCY OF SUPERNUMERARY TEETH IN MEXICAN POPULATION. MED ORAL PATOL ORAL CIR BUCAL 2004;9:403-9.

ABSTRACT

Supernumerary teeth (ST) are a not uncommon developmental anomaly which appears in 0.3 to 3.8 percent of the population. We studied the corresponding radiographs from 2241 patients, both sexes who seeked dental attention at the Outpatient Clinic of the División de Estudios de Posgrado e Investigación, Facultad de Odontología, UNAM in Mexico City. Of them, we found 72 patients (3.2%) with 102 ST. Of the 72 patients, 39 were males (54.2%) and 33 females (45.8%). Mesiodens was the most common ST (48.6%), followed by supernumerary premolars (26.4%), supernumerary laterals (11.1%) and fourth molars (9.7%). This series includes cases with one, two and three ST and one case comprising 10 ST. Our results suggest that frequency of ST in the population studied differs in some aspects with previously reported series and that frequency of ST shows different rates depending the population studied. As our results demonstrate, it is encouraged the need to have panoramic radiographs of all patients attended in dental offices, clinics and schools of Dentistry in order to detect and diagnoseundiscovered pathologies.

Key words: Supernumerary teeth, mesiodens, supernumerary incisors, supernumerary canines, supernumerary premolars, supernumerary molars.

INTRODUCTION

Supernumerary teeth (ST) are a not uncommon developmental dental anomaly which apears anywhere of the dental arch and can affect any tooth. Regularly, the cause of these developmental anomalies are the "duplication" of the dental lamina which gives place to one or several teeth in one or more anatomic locations. The most common SP are mesiodens, followed by premolars and 4^th molars. SP located in the anterior portion are conoid in shape and no similarity with their normal counterparts are found. Commonly, this condition is named "hyperdontia" and frequently some syndromes (sy) as cleidocranial dysplasia, Down's sy, Leopard sy, tricho-rhino-phalangeal sy, Gardner's sy, Ellis van Creveld sy and others (1-6) are involved. The aim of this study was to know the frequency of non-syndrome associated SP in the population attendeded in one of the largest Outpatient Dental Clinics in Mexico.

PATIENTS AND METHODS

This study included all the patients who sought stomatological attention in the Outpatient Clinic of the División de Estudios de Posgrado e Investigación, Facultad de Odontología, UNAM in Mexico City between September 2001 and February 2002. All the patients received an oral and maxillofacial review made by specially trained students who were in the last year of the DDS training. This review included carefull observation and palpation of the soft and hard oral tissues and palpation of the head and neck area, including periodontal and caries indexes.

A panoramic radiograph was taken to all the patients, all radiographs were reviewed and discussed by the panel in a negatoscope and a 7X lens was used. Inter-examiner discrepancies were solved by consensus and agreement. In selected cases, dento-alveolar (periapical) and occlusal radiographs were made. Photographs of the clinical and radiographic findings were made by means of a Canon Photo Shop G-1 digital camera. Data were stored in the Microsoft Excel Program analyzed by a Student's t test and p< 0.05 was considered statistically significant.

RESULTS

During the above mentioned time 2245 Mexican Mestizo patients were reviewed. Of them, 2241 accepted a panoramic radiograph as a complement of their oral and maxillofacial examination. In 394 radiographs (17.6%) we found one or more radiolucent or radiopaque abnormal areas in their maxillofacial bones or teeth and eightteen different developmental dental abnormalities were diagnosed in 119 cases. These cases represented 30.5% of the patients with abnormalities (PWA) and 0.5% of all the reviewed patients (RP). Of them, 103 supernumerary teeth were found in 72 patients (Table 1), they were18.2% of the PWA population and 3.21% of the whole sample. In this table, the sum of cases is 75 becauseone of them was included in four categories since she presented four types of ST: mesiodens, laterals, premolars and paramolars.

It is important to point out that from the 72 patients with ST, only two of them with erupted mesiodens (2.8%) were aware of the presence of the ST and 70 of them (97.2%) were diagnosed during the rutinary review of the panoramic radiographic material. Figures on ST presented in this article were calculated taking in count 75 cases and not based in 72 patients.

Of the patients with ST (PST), 39 were males (54.2%) and 33 females (45.8%). Age varied from 2 to 55 years with a mean age of 14.4 years. As it is indicated in table 1, the most common ST was mesiodens followed by premolars and lateral. ST was most frequently found during the 1^st to 3^rd decades of life (84.7%), only 15.3% of the sample was 30 years or older (Fig 1).

Since several cases contained multiple ST, number of ST is higher to the cases registered, 45 cases presented ST located in the anterior portion (53 teeth), 20 in the premolar zone (37 teeth) and 10 in the molar area (10 teeth). 51 patients were located in maxilla (61 teeth), 18 in mandible (24 teeth) and 3 cases were located in both mandible and maxilla (14 teeth). (Table 2)

As it is shown in table 1, mesiodens was the ST most commonly found in this study. Patients with mesiodens (n= 36) represented 48.6% of the PST, they were 9% of the PWA and 1.6% of the RP. Of the 35 cases, there were 21 men (60%) and 14 women (40%). Age range was between 2 and 55 years with a mean age of 15.3 yr. Mean age between sexes was not statistically significant (p<0.05) since it was 15.3 yr for females (range 2-55 yr) and for males it was 15.2 yr (range 5-41 yr). In this study, mesiodens were 40 teeth, the majority of cases contained an isolated teeth (62.9%), in some cases the mesiodens was inverted within the bone (22.8%) and five cases were doble mesiodens (14.3%). There were 24 teeth in males (60%) and 16 teeth in females (40%). Of them, the shape of the recovered teeth were: 20 conical (50%), 15 were tuberculated (37.5%) and 4 were of the supplemental type (10%). In our sample, only four mesiodens were found erupting to the oral cavity. Relationship between shape and eruption was as follows: conical erupted, two cases; erupted suplemental and tuberculated, one case each. Five mesiodens were located transverse to the sagital plane of the maxilla.

Supernumerary premolars were 19 cases comprising 31 teeth. These patients were 26.4% of the PST, 4.8% of the PWA and 0.8% of the RP. These cases comprised 10 males (52.6%) and nine females (47.4%). Age range was 3-30 years with a mean age of 15.4 years. Female mean age (16.75yr) was not significantly different form male mean age (14.6 yr). Only two cases (10.5%) comprising two teeth (6.4%) were located in maxilla and 17 cases (89.5%) including 29 teeth (93.6%) were found in the mandible. Female cases included 12 teeth (38.7%) and male cases were 19 teeth (61.3%).

Supernumerary laterals were eight cases. Of them, five were in males (62.5%) and three in females (37.5%). Age range was 4-20 with a mean age of 8.3 years. Mean age was higher for females (10.7 yr) and for males it was 6 yr.

Of the seven fourth molars four cases were found in females (57.1%) and 6 cases were located in maxila (87.5%), age range was 12-41 with a mean age of 27 years. Mean age for female patients was 31.5 yr and for males it was 22.5 yr.

Paramolars were three teeth in two females aged 10 and 14 years, both cases were located in the maxillary second molar area. Only one case of multiple SP was found in a girl.

DISCUSSION

Developmental dental anomalies reflect either a change in number of teeth, eruption rate, location (ectopia), size, shape or structural anomalies. Alterations in the normal number of teeth received several names: supernumerary teeth, hyperdontia, multiple teeth, extra teeth, oligodontia and others. ST are an uncommon developmental anomaly most frequently associated to syndromes (1-6) also seen in non-syndromic population (7,8). Etiology is controversial and several theories have been proposed, one of them proposes that ST is the result of dichotomy of the dental bud (7). Another theory suggests that ST are formed by local, independent and conditioned hyperactivity of the dental lamina (7,8). Other theory suggests that ST follows a simple non-Mendelianpattern (9), but numerous case reports support a familial tendency.

There are published numerous series of ST in different kinds of populations around the world (7-29), almost all of them were made in children populations and series including adolescents are rare (30,31). We were able to find only one series in the literature reporting ST frequency in adults (31) and large series on developmental anomalies in general population were not found.

ST can be defined as an abnormal tooth or set of teeth formed in excess or additional to the normal series, they adopt different size, shape and location and can be found in any region of the dental arch, some times they closely resemble the teeth of the group to which it belongs (supplemental), but more frequently they are conoid or tuberculated. Odontomas should not be considered in the ST group since they have been classified as odontogenic tumors by the WHO (32).

Occurrence varies depending the involved type of ST and the population studied. Prevalence of ST has been reported from 0.1% to 3.8% of the population (10,11,24) but this prevalence can be as high as 28% in patients with cleft and lip palate (12). Results of this study showed it was 3.2% of the RP. It has been reported that there are no significant difference in sex distribution in the primary dentition and others report that males are affected approximately twice as frequently as females in the permanent dentition (18,19). In this study, we found that SP were slightly more frequent in males than in females with a M:F ratio of 1.2:1. As it has been reported, the ST more commonly found is mesiodens (13,16,17), some authors consider that mesiodens are followed by 4^th molars and premolars (28), but others found that mesiodens were followed by maxillary lateral incisors and 3^rd premolars¹². Interestingly, in 1990, Yuzof made a brief review of the literature and found that premolars were the most frequent ST followed by molars and mesiodens (25). Results of this study suggest that in our population, mesiodens is the most frequent ST followed by premolars, lateral incisors and 4^th molars. Figures of this study are completely different compared with previous reports from another populations.

The most commonly found ST is the mesiodens (9,13,14), incidence of mesiodens among ST has been reported to occur between 17% to 44% (13,16,17), in our study, we found that mesiodens were the most common ST but it was 46.8% of our sample, this figure is higher to previously reportedstudies (9,13-17) made from other populations. In this study, we found that erupted mesiodens comprised less than 10%, this figure is lower to that reported in other studies (7,13,15), but very close to that found in Israeli population (21). Our figure on inverted, transverse and double mesiodens islower than previously reported (7).

Supernumerary premolars occupied the second place of frequency in our sample, other series mentioned they were the third most frequent ST (13,28) and others found they were the most common ST 25. It has been reported that their frequency is among 0.09% to 0.64%^17,26. In this study we found they were 0.8% of the RP, this figure is higher to previous reports (13,18,23,25,28).

Unexpectedly, we found that lateral incisors occupied the third place in frequency of ST, they comprised 3.9% of ST and patients were 0.36% of the RP. As it was previously reported, 4^th molars are the second place in frequency (18), in our series they were in 4^th place and comprised 6.8% of the ST and 0.31 of the RP. Paramolars are extremely rare supernumeraries and they are most commonly found erupted. In this study, they were 2.9% of the ST and comprised 0.09% of the RP. Characteristically, all of them were unerupted. Our figure is in agreement with the Grimanis et al report (22). As it is well known, supernumerary canines are uncommon teeth and they occupied the last place of occurrence (29), we found only one patient.

Some authors suggested that hyperdontia can be associated with an increased likelihood of anomalies in the permanent dentition (20,24), our results do not support this point of view since any of the patients with ST showed clinical or radiographic signs of alteration in their permanent dentition.

It is interesting to note that the frequency of impacted ST is larger in the first three decades than it is in later age groups. This an unexpected and strange finding, because ST do not disappear by themselves. The most plausible explanation is their removal as a result of dental treatment. But this could not be confirmed in the clinical history. Factors influencing this phenomenon can not be explained in this moment.

The main reason because our results are different with series of ST previously published is that we did not study an isolated age group and the reviewed radiographic material was from a general population which included patients from two to 55 years. Despite the results of Ignelsi et al (26), results of this research support the point of view that panoramic radiograph is of great value in detecting dental abnormalities and we suggest that a dentoalveolar or occlusal film always should be taken in order to confirm the initial findings from the orthopantomographic radiograph.

It is interesting to note that the frequency of ST in the three initial decades of the life is larger than in the older groups. This feature was an unexpected finding since ST do not disappear by themselves. The most plausible explanation is that they were extracted previously, but this could not be verified in the clinical files. The factors influencing this phenomenon can not be explained in this moment.

In view of the scarcity of data on radiographic studies from general population, it is necessary to publish new research data on dental and bone anomalies in the general population.

ACKNOWLEDGEMENTS

The authors are indebted with Drs. Gloria Valencia and Rosario Gonzalez for their help in the initial review of the radiographic material.

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