Incidence of Torsiversion in Mandibular Third Molars E. J. NEIBURGER

1 000 North Avenue, Waukegan, Illinois 60085, USA Two percent of 826 adults examined dur-

ing routzne dental check-up visits show torsiversion in their mandibular third molars. The degree of rotation ranges from 200 to 60° with the predominant position at 30° buccal. This condition is quite rare and appears to be genetically directed at the infracrypt level of development. J Dent Res 57(2): 209-212, February 1978.

Torsiversion (torsoversion) is the rotation of a tooth on its long access. This positioning causes the tooth to contact its neighbor with its buccal or lingual surface instead of the usual mesial (distal) contacts (Fig 1).' Few studies have been made of this condition in mandibular third molars. Most literature reviewed describes torsiversion of anterior teeth leaving little description of molar rotations.2 Fisher reports one case in 203 American Indian mandibles from central Wisconsin.4 Webb mentions one case of bilateral torsiversion in 19 ancient mandibles.5 I reported a 42% incidence (in 393 adult mandibles) of torsiversion in archaic Wisconsin and Illinois Indians,6 the largest in cidence on record. Review of recent literature has shown no other data as to incidence of modern-day third molar torsiversion and the degree of rotation.7 9 This study involves the examination of 826 adults, from 17 to 72 years of age, possessing all their mandibular dentition. The reason for this selection is to eliminate all persons with torsiversions encouraged by premature loss of adjacent teeth. These are a serially selected group of patients who entered my practice January through March of 1976 for routine dental examinations. Received for publication January 19, 1977. Accepted for publicationJuly 12, 1977.

Measurements were taken on the occurand degree of rotation of mandibular third molars. Readings were grouped into 12 categories: lingual (mesial) and buccal rotation for teeth positioned 10 0-20 °, 30 °, 45 0, 600 and 90 ° (no buccallingual rotation), and normal position (less than 100 rotation) based on the smallest mesial angle made by a line running through the third molar's central groove and intersecting a plane parallel to the buccal surfaces of the first and second molars and bicuspids. Measurements were made intra-orally under well-lit conditions. Readings were taken two to three times to check for accuracy. All patients examined possessed both lower third molars. No attempt was made to include those with one or several missing teeth since the resultant changes in arch length could artificially influence position and rotations.' The intent of this study is to establish the incidence and degree of torsiversion in modern-day adults. rence

Fic 1. -Torsiversion of the third molars (200 buccal, 600 buccal) in an American Indian mandible (Upper Misissippian period). 209

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21 0

J Dent Res February 1978



Patient Number


1 2 3 4 5 6





8 9 10





12 13 14 15 16 17 *




Incidence, Degree & Direction of Rotation Left Molar Right Molar

450L Normal 300L 300 B 300 B 600B 300 B 300B 200L 300B 200B 450 B 200L 600B 600B 300B 450B

450 L 450B 30"L 300B 200B 300B 300B Normal Normal 300B 200B 300B 200L 600B 600B 300B 300B

Race* C

La C C

C C La N N



C- Caucasian, N- Negro, La -Latin. L -Lingually rotated. B -Buccally rotated.


and the degree of rotation (Table 2). Of the third molars torsiversed, 77% showed a 30 buccal rotation. There was a 3 + to 1 ratio of buccal to lingual positions. There were no 900 rotated teeth in this sampling though 5% of prehistoric Wisconsin Indians exhibit this condition.6 Of patients with torsiversion, 65% showed bilateral symmetry in all classes of rotation. Thirty-five percent (35%) had unequal torsions comparing right to left molars. sex,

The sample consisted of 826 adults, 405 women and 421 men separated into three groups: 513 Caucasians (62%), 280 Negroes (34%), and 33 Latins (4%) (Table

1). Of these patients, 17 (2%) exhibited torsiversion in 31 third molars (1.8% of all mandibular third molars). Three individuals possessed a combination of 1 normal and 1 rotated third molar. The remainder (14) showed this condition bilaterally. The sampling (rotated third molars) was racially mixed, 13 Caucasians, 2 Negroes, and 2 Latins. There was no correlation of race,



Seven of the 17 individuals with torsiver-



Number of Teeth

Percentage of Total



200 300 450 600 Normal

6 15 5 5 3

18 43 15 15

3 13 3 5

3 2 2


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Vol. S 7 No. 2



sion were traced for family members (parents, children) with similar conditions. A mother (Table 1, patient 14) and daughter (Table 1, patient 15) were the only patients found with exactly the same rotations (Fig 2). There appears to be some genetic component in this condition, supporting observations described by Korkhaus,7 Frdlich,9 and Enoki2 for torsiversion of anterior teeth. Time of Torsion FIG 2. - Casts of mother-daughter unilateral 600 torsiversions.

FIcG 3. -Rotated third molar lodged in crypt of a 16-year-old Indian (Upper Mississippian period).

Does the third molar rotate in the crypt or after eruption? In the fully dentulous cases studied, all molars, especially in individuals 17 to 20 years of age, showed no radiographic or visual evidence of posteruptive rotations. The rotation occurred prior to eruption. Gorlin' reported that positions and shape of the second molar can influence the path of eruption and thus the final position of the wisdom tooth. This was not the case in the patients examined for this study. Figure 3 shows the intracrypt rotation of a 15- to 16-year-old Amerind's mandibular third molar. It can be seen rotated buccally 300 through the roof of the crypt. Figure 4 presents a similar condition in a ten-year-old Indian boy. Observations based on radiographic examination of patients in their early teens tend to support these findings in the populations seen in my practice as well as the above ancient Amerinds. Summary

Of the 826 adults examined, 2% showed torsiversion of the third mandibular molars. This is a much lower incidence than that found in archaic Indian populations. The predominant torsion is 30 0 toward the buccal. This appears to be an inherited condition in some cases manifested by intracrypt tooth bud rotation. Observations of these third molar rotations appear similar to torsiversion phenomena in anterior teeth. References FiG 4.

Rotated third molar in crypt of

old Indian. Right second molar (Mid Woodland period).




I 0-year-


1. GORLIN, R. J., and GOLDMAN, H. M.: Thomas' Oral Pathology, 6th Ed.; St. Louis: C. V. MOSBY, 1970, p 168.

2. ENORs, K., and NAKAMURA, E.: Bilateral

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Rotation of Maxillary Central Incisors, J Dent Res 38:204, 1959. 3. DAHLBERG, A. A.: A Wing-Like Appearance of Upper Incisors Among American Indians,JDent Res 38:203-204, 1959. 4. FISCHER, A. K.: The Dental Pathology of

the Prehistoric Indians of Wisconsin, Bulletin of the Public Museum of the City of Milwaukee, 10:3, 344, 1931. 5. WEBB, C.H.: Dental Abnormalities as Found in the American Indian,J Dent Res, 30:474-485, 1944. 6. NEIBURGER, E. J.: Dental Disease in the

J Dent Res February 1978 Midwest American Indians, Quintessence

International, 9:99-104, 1976. 7. KORKHAUS, G.: Anthropologic and Odontologic Studies of Twins, InternatJ Orthodont, 16:640-647, 1930. 8. SIEMENS, H. W., and HUNOLD, X.: Zwillings-Pathologigische Untersuchungen der Mundh6hle, Arch Derm Syph, 147: 409-423, 1924. 9. FROLICH, U., Odontologische Untersuchungen an jugendlichen Zwillingen, Deutch Zahnartz Wschr41:463-468, 1938.

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Incidence of torsiversion in mandibular third molars.

Incidence of Torsiversion in Mandibular Third Molars E. J. NEIBURGER 1 000 North Avenue, Waukegan, Illinois 60085, USA Two percent of 826 adults exam...
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