Florez et al 2006.5


83

Dental morphology trait expressions have 
been used in anthropology and forensic sciences 
for determination of biological and geographical 
affiliations. Variations in morphology of crowns may be 
manifest in the primary and/or permanent dentitions. 
Dental variation is heritable, is caused by multiple 
genes, and is little influenced by environmental factors. 
Traditionally, three, four, five, six or seven cusps, 
specifically the protoconid, metaconid, hypoconid, 
rntoconid, hypoconulid, entoconulid and metaconulid, 
have been reported in morphological descriptions of 
lower molars for various human groups (Axelsson and 
Kirverskari, 1979; DeVoto and Perroto, 1972; Hanihara, 
1967; Harris and Bailit, 1980; Morris, 1965; Sciulli, 1977; 
Schroeder et al., 1983; Scott and Turner 1997; Suzuki and 
Sakai, 1973). This brief communication reports on the 
presence and asymmetry of a possible eighth cusp on 
mandibular primary second molars of a contemporary 
Argentinean boy.

MATERIALS AND METHODS

The teeth of a racially mixed boy five years of age 
from Cordoba City, Argentina, were examined in situ 
and on a plaster cast. An unusually shaped accessory 
occlusal cusp was observed on both the left and right 
mandibular primary second molars. Size of this eighth 
cusp was measured with sliding calipers. This case 
report is part of an anthropological study carried 
out on material provided by the Departamento de 
Ortodoncia, Facultad de Odontología, Universidad 
Nacional de Cordoba, Argentina.

Brief Communication:  Occurrence of an Eighth 
Cusp on Primary Second Mandibular Molars of a 
Contemporary Argentinean Child

Carlos David Rodríguez Florez1*, Gabriel Mario Fonseca2, and Maria Teresa de Villalba3

1Cátedra de Antropología Biológica y Cultural, Facultad de Ciencias Exactas, Físicas y Naturales, 
2Cátedra de Anatomía Patológica B, Facultad de Odontología, and 3Cátedra de Ortodoncia, Facultad de 
Odontología - Universidad Nacional de Córdoba, Argentina.

Grant Sponsor: Facultad de Odontología, Universidad 
Nacional de Córdoba, Argentina.

*Correspondence to: Carlos David Rodríguez Florez, 
Cátedra de Antropología Biológica y Cultural, Facultad 
de Ciencias Exactas, Físicas y Naturales - Universidad 
Nacional de Córdoba, Argentina.
E-mail:  david@syllabapress.com

ABSTRACT:   The presence and asymmetry of an eighth 
cusp observed on the primary second mandibular 

RESULTS

Figures 1 and 2 illustrate the presence and bilateral 
asymmetry observed on mandibular primary second 
molars. A small additional cusp occurs between 
hypoconulid and entoconulid cusps. The anomalous 
cusp is larger on the right molar (diameter: 0.245 mm) 
than the left (diameter: 0.165 mm).

DISCUSSION

This accessory, eighth cusp has been not reported 
previously. This rare variant on anomalous lower 
primary molars provides an interesting record of eighth 
cusp in human dental morphology. Bilateral presence 
and asymmetrical appearance of the eighth cusp suggest 
a possible factor of heritability in the expression of this 
infrequently human molar form. Brabant suggests 
that primary second mandibular molars with five 
cusps are most common. Six cusps are less frequent 
(2% to 30%), and the seven-cusp molar—with a cusp 
of Jørgensen (metaconulid)—is found in less than 10% 
of cases (Brabant, 1967). Kallay’s (1966) classification 

molars of an Argentinean boy is described.  Dental 
Anthropology 2006;19(3):83-85.



84

could be used to label this eighth cusp, perhaps the 
Protuberantio apulparis sited in the distal occlusal 
area of primary second lower molars. As mentioned by 
Brothwell (1967), the phenomenon of increasing world 
contact, immigration, and interbreeding between 
previously more isolated communities can produce 
new forms that enrich the variation observed in the 
human dentition.

LITERATURE CITED

Axelsson G, Kirveskari P. 1979. Sixth and seventh 
cusp on lower molar teeth of Icelanders. Am J Phys 
Anthropol 51:79-82.

Brabant H. 1967. Comparison of the characteristics 
and anomalies of the deciduous and the permanent 
dentition. J Dent Res 46:897-902.

Brothwell DR. 1967. Some problems and objectives 

related to the study of dental variation in human 
populations. J Dent Res 46:938-941.

DeVoto FCH, Perroto BM. 1972. Groove pattern and 
cusp number of mandibular molars from Tastilian 
Indians. J Dent Res 51:205.

Hanihara K. 1967. Racial characteristics in the dentition. 
J Dent Res 46:923-926.

Harris EF, Bailit HL. 1980. The metaconule: a 
morphologic and familial analysis of a molar cusp 
in humans. Am J Phys Anthropol 53:349-358.

Kallay J. 1966. Extra cusp formation in the human 
dentition. J Dent Res 45:1381-1394.

Morris DH. 1965. The anthropological utility of dental 
morphology. Ph.D. dissertation, Department of 
Anthropology, University of Arizona. Tucson, AZ.

Sciulli PW.  1977. A descriptive and comparative study 
of the deciduous dentition of prehistoric Ohio Valley 
Amerindians. Am J Phys Anthropol 46:71-80.

Fig. 1.  Occlusal view of case (in situ).

C. D. RODRIGUEZ-FLOREZ ET AL.



85EIGHT CUSPS ON PRIMARY MANDIBULAR MOLARS

Schroeder K, Zacherl W, Paulson R, Gaston P, Sciulli 
PW. 1983. Cusp tip abnormalities in the deciduous 
and permanent dentitions. J Dent Res 62:224.

Scott GR, Turner II CG. 1997. The anthropology of 
modern human teeth. Cambridge:  Cambridge 
University Press.

Suzuki M, Sakai T. 1973. Occlusal surface pattern of 
the lower molars and the second deciduous molar 
among the living Polynesians. Am J Phys Anthropol 
39:305-315.

Fig. 2. Occlusal view of the mandibular second molars as seen on the plaster cast.