Case Report

By Dr. Tomoki Sumida , Dr. Akiko Ishikawa , Prof. Hiroyuki Hamakawa
Corresponding Author Dr. Tomoki Sumida
Department of Oral & Maxillofacial Surgery, Ehime University Graduate School of Medicine, 454 Shitsukawa - Japan 790-0295
Submitting Author Dr. Tomoki Sumida
Other Authors Dr. Akiko Ishikawa
Department of Oral and Maxillofacial Surgery, Ehime University Graduate School of Medicine, - Japan

Prof. Hiroyuki Hamakawa
Department of Oral and Maxillofacial Surgery, Ehime University Graduate School of Medicine, - Japan


Monozygotic twins, Impacted teeth, lower second premolar.

Sumida T, Ishikawa A, Hamakawa H. Impacted Teeth In The Same Location Of Monozygotic Twins: A Report Of Two Cases. WebmedCentral DENTISTRY 2010;1(10):WMC001048
doi: 10.9754/journal.wmc.2010.001048
Submitted on: 21 Oct 2010 11:23:01 AM GMT
Published on: 21 Oct 2010 05:31:08 PM GMT


We have presented here the cases of a pair of monozygotic twin sisters with impaction of the lower second premolars. Tooth extraction was necessary because of the orthodontic reasons, and the teeth were sequentially extracted under local anesthesia. The patients are currently undergoing orthodontic treatment, and their clinical course after tooth extraction was uneventful. Although the impaction of second premolar is not a rare situation, it is extremely rare that these impactions in the same location are observed. In our case, the twins were monozygotic. Therefore, we suspected that the cause of the tooth impaction in the same location was influenced by the genetic background.


Familial occurrence of impacted permanent teeth is a poorly studied condition. Like supernumerary teeth, impactions can be unilateral or bilateral, and can occur singly or a few at a time [1, 2, 3]. A review of the literature revealed that genetic factors are important in the etiology of familial cases [4]. The presence of impacted teeth in the same locations in monozygotic twins supports the genetic origin of this condition. Here, we describe the similarities in the teeth involved and in the positions of impacted teeth in monozygotic twins. The aim of this article is to report dental anomalies in monozygotic twin sisters.

Case Report(s)

A 9-year-old girl was referred to our hospital for the extraction of impacted teeth prior to orthodontic treatment. Her medical history was noncontributory, and she had an elder monozygotic twins. On intraoral clinical examination and a panoramic radiograph, both lower primary second premolars were found to be impacted (Illustration 1 A). These teeth were sequentially extracted under local anesthesia. Approximately 2 years later, the patient’s 11-year-old sister was referred to our hospital for the same reason. Her general condition was normal. On a panoramic radiograph, bilateral impaction of the lower primary second premolars was seen (Illustration 1 B). We performed tooth extraction (Illustration 2 A, B). Her second premolar was almost normal in shape because she was already 11 years old.


Familial occurrence of impacted teeth in the same location is a poorly appreciated issue. The impacted teeth are fail to erupt into dental arch when expected time. The most frequent tooth is the mandibular third molar. The maxillary third molar and the maxillary cuspids follow. However, these conditions can frequently occur singly.
In this study, we presented the presence of impacted teeth in the same location in monozygotic twins. Delayed eruption or impaction of teeth is frequently encountered in dental practice. Compared with single cases, our case suggests a genetic etiology, because these sisters have a same genetic background.
In terms of the environmental factors, that can also influence the differences in the dentitions of these sisters. However their mother mentioned that these two had been taking almost same food and any endocrine abnormalities were not indicated, which led to cause tooth eruption. Actually dentitions of this sisters was the almost identical, which demonstrated that the environmental factors that the twins were exposed did not influence in oral condition.
The presence of impacted teeth in the same locations in monozygotic twins is extremely rare, and we found few reports of this condition [5, 6, 7]. Although the etiology of this condition remains unknown, genetic factors have been speculated to play a part since monozygotic twins are genetically identical. In our case, the patient’s mother did not have same impacted teeth. This suggests that their father’s X-chromosome may contain a direct cause.


The presence of impacted teeth in the same locations in monozygotic twins is extremely rare. Therefore, we suspected that the cause of the tooth impaction in the same location was influenced by the genetic background.


1. Kramer RM, William AC. The incidence of impacted teeth. A survey at Harlem hospital. Oral Surg Oral Med Oral Pathol 1970; 29(2): 237-41.
2. Mitchell L. Supernumerary teeth. Dent Update 1989; 16: 65-9.
3. Babacan H, Ay S, Kö?ger HH. Impacted permanent first premolar: two case reports. Int Dent J 2006; 56(1): 49-54.
4. Lauweryns I, Carels C, Vlietinck R. The use of twins in dentofacial genetic research. Am J Ortho. Dentofacial Orthop 1993; 103(1): 33-8.
5. Zengin AZ, Sumer AP, Karaarslan E. Impacted primary tooth and tooth agenesis: a case report of monozygotic twins. Eur J Dent 2008; 2(4): 299-302.
6. Langowska-Adamczyk H, Karma?ska B. Similar locations of impacted and supernumerary teeth in monozygotic twins: a report of 2 cases. Am J Orthod Dentofacial Orthop 2001; 119(1): 67-70.
7. Oikarinen V, Guven O, Silaste H. Similarly impacted second and third maxillary and mandibular molars in a pair of monozygotic twins. Dentomaxillofac Radiol 1990; 19(3): 133-4.

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Competing Interests



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Impacted Teeth and Monozygotic Twins
Posted by Dr. William J Maloney on 13 Feb 2014 06:53:19 PM GMT Reviewed by Interested Peers

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