March-April 2014
Volume 93 - Number 2

Find Your Way by the Star of the North

Development of a National TMJ Implant Registry and Repository - NICDR's TIRR

The Thought That Counts

Golden: Recognizing the MDA's 25-Year Members and Retirees

Clinical Feature

Prevalence of Dental Anomalies in a Southeast Asian Population in the Minneapolis/Saint Paul Metropolitan Area

Shelly S. Stecker, D.D.S. M.S.,*
Soraya Beiraghi, D.D.S., M.S.D., M.S.,**
James S. Hodges,Ph.D.,***
Vacharee S. Peterson, D.D.S., †
and Sandra L. Myers, D.M.D. ‡


Dental anomalies involving alterations in number, size, and structure of teeth often present a major challenge for dental practitioners. One dilemma is whether the anomaly might be a transmitted trait or is associated with other clinical findings involved with craniofacial syndromes. Another dilemma is recognition of the dental anomaly and what, if any, dental treatment might be indicated.

The majority of dental anomalies in the United States have been investigated in Caucasian populations of European ancestry. These populations are often heterogeneous, the specific dental anomalies not always clearly elucidated, and the data not standardized or clearly described. Worldwide, the prevalence of dental anomalies has been found to vary according to race.

This paper reports on a retrospective radiographic study evaluating dental anomalies in a relatively homogeneous Southeast Asian population in the Minneapolis-Saint Paul metropolitan area.

The dental anomalies included supernumerary teeth, missing teeth, peg laterals (microdontia), fusion (including gemination), dens invaginatus, dens evaginatus, and talon cusp. The results make a contribution to the dental literature and should be of interest to dental practitioners.



The study was conducted at a large community dental clinic in the Minneapolis/Saint Paul metropolitan area, where the first author is employed. Sixty-eight percent of the patient population in this clinic is Southeast Asian.

After approval from the Institutional Review Board at the University of Minnesota, a random sample of 700 subjects was selected from 14,328 active patients. The clinic computer was used to determine subject ethnicity based on surname. Subjects with a known systemic disease or craniofacial syndrome were excluded. Raw data including ethnicity, radiographic findings, age, and gender were obtained from the chart. Dental radiographs, including bitewings, periapical, occlusal, and/or panoramic films, were evaluated by one reader (SS) for the different dental anomalies. Not all patients had full radiographic coverage of their oral cavities, and some radiographs showed missing teeth. Therefore, the entire oral cavity could not be evaluated in every patient for all dental anomalies. All statistical tests used Fisher’s exact test.


The observed dental anomalies are recorded in Table 1. Due to variations in radiographic coverage, cases of fusion and gemination were combined in the category of fusion. Prevalence was compared between two main groups: Asian versus non-Asian. Sixty-two percent (435/700) of patients were Southeast Asian, with 401 Hmong, 17 Cambodian, 12 Vietnamese, four Chinese, and one Laotian.

Further statistical tests checked whether the racial difference in  incidence of these anomalies depended upon other patient characteristics (e.g., gender) using logistic regression and the likelihood ratio test. None of these tests approached statistical significance (P > 0.05).


Dental anomalies involving the number of teeth include hypodontia (one or more missing teeth), oligodontia (six or more missing teeth), anodontia (complete absence of teeth), and hyperdontia (one or more extra teeth, also known as supernumeraries). In the population as a whole, the prevalence of hypodontia in the permanent teeth ranges from 1.6% to 9.6.% (excluding third molars); the incidence for third molar hypodontia is around 20%.1

Permanent second premolars and maxillary lateral incisors are the next most commonly missing teeth. Among Asians, mandibular incisors are reported as the most commonly missing teeth.2,3 In our study, Asians were not more likely than non-Asians to have one or more missing teeth. However, they were more likely to have missing permanent mandibular incisors (p = 0.025), while non-Asians were more likely to have missing premolars (p = 0.008). Asians and non-Asians did not differ significantly in missing canines, maxillary lateral incisors, or primary mandibular lateral incisors. In the population as a whole, hypodontia of primary teeth has incidence under one percent and usually affects the mandibular incisors.4 Prevalence of supernumerary teeth has been reported between one percent and three percent in Caucasians versus 2.7–3.4% in Asians,5 though in our study, no significant difference for supernumeraries was observed.

Alterations in the size of teeth include microdontia (teeth smaller than normal) and macrodontia (teeth larger than normal). Both of these conditions may be either generalized to all the teeth or isolated to one or several teeth. Generalized and relative macrodontia have a combined prevalence of 3.6% in southern Chinese.6 Neither isolated nor relative macrodontia were observed in our study. The permanent maxillary lateral incisor and the primary canine are the most commonly affected teeth in isolated microdontia of the permanent and primary dentitions. In the population as a whole, the prevalence of peg-shaped microdont laterals reportedly varies from 0.8% to 8.4%.4 A Japanese study found the prevalence of microdontia of the permanent and primary dentitions to be 1.9% and 2.3%, respectively.7 In our study, Asians were more likely than non-Asians to have peg laterals (p = 0.004).

Variations in the shape of teeth include double teeth (fusion and gemination), talon cusp, dens evaginatus, and dens invaginatus (dens in dente). Gemination and fusion are differentiated from isolated macrodontia by their clinical or radiographic appearance, and by counting the number of teeth present (Figures 1 & 2). The prevalence of fusion in the primary and permanent dentitions is about 0.1% to 1%.8 Bilateral cases of fusion have a prevalence of 0.02%.4

Fusion of the primary dentition is usually seen in the mandibular canine and lateral incisor regions.9 In 30%-50% of Caucasian and 75% of Japanese cases, fusion in the primary dentition is followed by anomalies in the permanent dentition, usually hypodontia.10,11 Among Asians generally, the prevalence of fusion in the primary dentition ranges from 1.2% to 5.2%, but in populations of European ancestry the prevalence is less than one percent.9 In our study, fusion was rarely identified in either non-Asians or Asians.

Talon cusps, also known as dens evaginatus of the anterior incisors, occur predominantly in the permanent dentition, and most occur as an additional lingual cusp on the maxillary lateral or central incisors (Figure 3).12,13 The prevalence for talon cusps is estimated at less than one percent to eight percent, but extensive prevalence studies have not been conducted.4 Talon cusp was not found in our study population.

The term dens evaginatus is usually reserved for a cusp-like elevation which most often occurs in the center of the occlusal surface of premolars and molars (Figure 4)14,15 Among Caucasians, the  occurrence of dens evaginatus is rare, but the prevalence among Asians is up to 15%,4 and in Native Americans and Alaskans the prevalence soars to close to 100%.4

Dens evaginatus can be difficult to identify based on radiographs alone. However, several cases of dens evaginatus and fusion were observed in Asians.

The term dens invaginatus is reserved for a deep surface invagination, or infolding, of the crown on the lingual surface of predominantly maxillary teeth (Figure 5).4 This condition presents with varying degrees of severity with an invagination or infolding of enamel and dentin that may extend into the pulp chamber, the root, or sometimes reach the root apex.4 The permanent maxillary lateral incisor is the most commonly affected tooth, and dens invaginatus occurs bilaterally in 43% of cases.16,17 In our study, Asians were significantly more likely than non-Asians to have dens invaginatus (p = 0.0002).


Our study points out differences in the prevalence of various dental anomalies between non-Asian and Asian dental populations in a major metropolitan dental practice. Asians, in this study, were more likely to present with a dental anomaly than non-Asians. Dental practitioners who are aware of ethnic differences in the occurrence of dental anomalies will be more alert to finding them in patients during routine examinations. This information can be helpful in evaluating siblings or family members for similar dental anomalies and may be predictive of normal patterns of tooth development and/or eruption. This will allow for prompt clinical interventions to avoid complicating pathology, such as a non-carious pulpal exposure in dens invaginatus and traumatic exposure due to cusp fracture in both dens evaginatus and talon cusp. The presence of hypodontia, hyperdontia, and microdontia such as conical teeth, may be important in the diagnosis of craniofacial syndromes such as ectodermal dysplasia or cleidocranial dyplasia.18,19

Undiagnosed and untreated, many of these dental anomalies may ultimately present complex treatment challenges in the areas of endodontics, orthodontics, prosthodontics, and restorative dentistry.


The authors thank Bla Xiong for her patience and help in management of patient records, and Dr. Shanti Kaimal for critical review of this manuscript.


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18. Pemberton T, Gee J, Patel P. Gene discoverycfor dental anomalies. A primer for the dentalcprofessional. JADA 2006;137:743-52.

19. Nunn J, Carter N, Gillgrass T, Hobson R,cJepson N, Meechan J, et al. The Interdisciplinarycmanagement of hypodontia: background and role of paediatric dentistry. Br Dent Jc2003;194(5):245-51.


*Dr. Stecker is in private practice at Community Dental Care in Saint Paul, Minnesota.

**Dr. Beiraghi is Professor, Department of Developmental and Surgical Science, and Head, Division of Pediatric Dentistry, University of Minnesota School of Dentistry, Minneapolis, Minnesota.

***Dr. Hodges is in the Division of Biostatistics at the University of Minnesota

Dr. Peterson is in private practice and is the CEO of Community Dental Care in Saint Paul, Minnesota.

Dr. Myers is Associate Professor and Director of NIDCR’s TIRR Laboratory, Department of Diagnostic & Biological Sciences, University of Minnesota School of Dentistry Minneapolis, Minnesota.



Copyright 2007. Minnesota Dental Association.

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