Cucina et al. 2008.2


46

The dental morphology of Maya populations 
belongs to the Sinodont family (Turner, 1990) and falls 
into the Sino-American group (Scott and Turner, 1997). 
It is characterized by, among other features, a high 
frequency of undivided roots in the lower second molar 
(Scott and Turner, 1997). Root morphology is one of 
the many traits commonly employed in dental studies 
of population affinities. Mandibular second molars are 
described according to a one- or two-roots dichotomy 
(with the very rare cases of three roots falling into the 
two-roots category) (Turner et al., 1991; Scott and Turner, 
1997). The frequency of single rooted second lower 
molars in North and South American native populations 
has been reported to range between 30% and 35% (Scott 
and Turner 1997). Frequency of such traits in the Maya 
region ranges between 15% and 30% (Jacobi, 2000; 
Wrobel, 2004; Cucina et al., 2005).

From an endodontic perspective, single rooted lower 
second molars are described as C-shape, due to the pulp 
chamber morphology that appears as a “C” in the roots´ 
cross section (see Jafarzaed and Wu, 2007 for a review). 
Generally, the fused root is associated with the C-shape 
canal, even though the endodontic treatment that exposes 
the chamber cannot detect the actual morphology of the 
root.

The C-shape chamber morphology has been 
reported to be strongly associated with certain ethnic 
affiliations. High frequencies of C-shape second molars 
have been registered in Sinodont populations such as 
Chinese, Japanese and Koreans, while being relatively 
uncommon in Caucasoid or African peoples (Yang et al., 
1988; Habbad et al., 1999; Gulabivala et al., 2001; Seo and 
Park, 2004; Jin et al., 2006; Jafarzaed and Wu, 2007). The 

Morphology of Root and C-Shape Canal in Prehispanic 
and Modern Maya Groups from Northern Yucatan

Andrea Cucina,1 Elma Vega Lizama,2 Marco Ramírez,2 G. Alvarado Cárdenas,2 and Vera Tiesler1

1Facultad de Ciencias Antropológicas, Universidad Autónoma de Yucatán, Mérida, Yucatán, México; 2Facultad de 
Odontología, Universidad Autónoma de Yucatán, Mérida, Yucatán, México

ABSTRACT     One-rooted mandibular second molars are 
labelled “C-molar” because of the root’s morphology. 
The frequency of C-molars is strongly associated 
with ethnic origin, being most common in North-East 
Asians. The present study analyzed the frequency of 
one-rooted molars and associated pulpal chamber in 48 
Prehispanic Mayans and in 142 modern subjects studied 
at the School of Endodontics, UADY. The frequency of 
one-rooted molars in the Prehispanic sample is 35%, 
with 32% of these having C-canals. Similarly, 42 of 142 

Correspondence to: Andrea Cucina, Facultad de Ciencias 
Antropológicas, Universidad Autónoma de Yucatán, 
Mérida, Km. 1 Carretera Mérida-Tizimín, 97305 Mérida, 
Yucatán, México
E-mail:  acucina@yahoo.com

Maya population’s ancestry is Sinodont, yet the conquest 
has led to admixture with European and African 
populations in the region, likely altering the genetic 
(and morphological) structure of the population.

The goal of the present study is twofold: firstly, it aims 
at inferring the frequency of C-shape second molars in the 
Maya populations according to their ancestry in order to 
assess the continuity or discontinuity in the prevalence 
of this trait in the region in an evolutionary perspective; 
secondly, the actual correlation between root and canal 
form is measured in order to infer to what extent the 
single root (as a morphological trait) corresponds to a 
C-shape canal in its inner structure.

MATERIALS AND METHODS

The archeological sample consists of 48 mandibular 
second molars dated to the Classic period (250-800 
AD), recovered from Xcambó and Noh Bec in northern 
Yucatán. They were selected randomly (Fig. 1); in most 
of the cases, the bony structure was missing or partly 
destroyed, so that the tooth had fallen out naturally. No 
tooth was extracted from its socket, since single rooted 
molars can be removed more easily than two-rooted 
ones, introducing a bias in its frequency. The one-rooted 
molars were then X-rayed to assess the shape of the 

(30%) modern teeth exhibit a C-canal. The similarity 
between ancient and modern samples suggests that 
genetic admixture since the European conquest has not 
affected trait expression, and it implies that the Maya 
express the Sinodontic pattern of dental morphology. 
Endodontically, the significant correlation between 
C-molar and C-canal is an advantage for recognizing 
the canal’s anatomy if treatment is indicated.  Dental 
Anthropology 2008;21(2):46-49.



47

canal (Fig. 2). No archeological tooth was sectioned 
or partially destroyed to inspect the morphology of 
the inner chamber on ethical and legal grounds, as 
destructive analysis of archeological materials requires 
the permission of the Archeology Council under 
Mexican law. Once scrutinized, the teeth were returned 
to their own individual’s storage boxes.

The modern sample consists of 142 second lower 
molars. It was registered by one of the authors (EVL) 
on patients attending the School of Endodontics of 
the Universidad Autónoma de Yucatán (UADY) for 
treatment during the fall semester of 2007. In this dental 
series, the form of the canal could be assessed visually 
from the occlusal surface (Fig. 3). X-rays were performed 
for every subject to provide additional information on 
the root morphology, even though this set of data could 
not be used directly in the present study.

Patients receiving treatment at the School of 
Endodontics of the UADY usually come from low 
income sectors of society. Relying on the subject’s patient 
records, they are all of native origin and even though 
most of them were born in the town, their parents 
commonly originated in villages in northern Yucatán. 
Despite admixture, which makes any direct comparison 
to Prehispanic series problematic, this sample is largely 
representative of the natives’ genetic background.

RESULTS

Among the 48 archeological roots under study, 17 
were fused, constituting 35% of the total. Radiographic 
analysis revealed that 15 out of 16 individuals possessed 
a C-shape morphology in at least some parts of their 
root canal. One tooth was excluded because the X-ray 
did not permit inspection of the form of its chamber. 
The resulting ratio corresponds to 32% of the overall 
sample (15/47). The modern cohort represents a 29% 
of second lower molars with a C-shape canal (42/142). 
The difference between the archeological and modern 
sample is not significant (chi-square = 0.014; P = 0.905) 
(Table 1). As mentioned, no reliable information is 
available on the frequency of the one-rooted molar in 
the modern sample. We can assume that at least 42 out 
of 142 teeth were single-rooted; however, we cannot rule 
out the possibility that not all the one-rooted molars 
presented the C-shape. At the same time, two partly 
fused roots (forming a C-shape canal) may diverge 
towards the apical end. In anthropological terms, when 
the root is separated for at least one third of its length, it 
is considered as two roots.

DISCUSSION

Genetic admixture (gene flow) is one of the reasons 
for changes in trait frequencies, and dental attributes 
are no exception. In opposition to other populations, 
like the Caribbean Tainos, who suffered a profound 
demographic collapse that led to its extinction within 

Fig. 1. Archeological example of a second mandibular 
molar from northern Yucatan, dated to the Classic 
period, which may possess a C-canal.

Fig. 2. X-ray image of the pulp chamber in an 
archeological second mandibular molar. The C-shape 
canal can be appreciated from the apical surface.

C-SHAPE MOLAR ROOT CANALS



48

few decades after the conquest (Rouse, 1963; Moya-Pons, 
1982), the Maya became an integrated part of the newly 
formed, multi-ethnic society. The genetic admixture 
that occurred in Yucatan as a natural consequence of the 
European conquest and introduction of African slaves 
surely had an impact in the gene pool in the region. 
Here, demic movement also could have led to noticeable 
changes in the patterns of dental morphology. Jacobi 
(2000) reported that the greater morphological distance 
between historic Tipu and Historic Lamanai in Belize 
was likely the consequence of a major admixture of 
Mayas from northern Yucatán fleeing to Lamanai.

The present study has centered on just two traits. 
Clearly, it will be necessary to inspect a broader set of 
dental morphological traits in order to assess the extent 
to which admixture and time have modified the genetic 
structure of the modern Maya population compared to 
their Prehispanic status. This will be the goal of future 
studies.

Single-rooted second mandibular molars are very 
common in Maya populations, slightly less common 
in Europeans, and they appear to be rare in Africans 
(Scott and Turner, 1997). Since the frequency of fused 

roots in European groups is slightly lower than in 
Mesoamerican ones, admixture might not have led to 
profound changes in the modern sample. The frequency 
is very much lower in Africans (Scott and Turner, 1997). 
Specifically for sub-Saharan regions, from which the 
initial forced migration into the New World started in 
the 16th century AD, Irish (1997) reported a value of 
7%. Even though African populations are considered 
to be the third root of the modern Mexican population 
(Tiesler et al., 2008), their genetic contribution may not 
have been large enough to produce noticeable changes, 
at least not in the Yucatan region that has experienced 
a lower presence of African descendents than in 
neighboring states.

Conversely, the distribution in canal shapes differs 
significantly between the Maya and Old World groups 
(Europe and Africa). C-shape root canals appear at 
comparable frequencies in the modern and Prehispanic 
Yucatecan population, while being uncommon in Old 
World groups (Jafarzaed and Wu, 2007). As a result 
of admixture, we were initially expecting a reduced 
frequency of “C” canals in the modern sample when 
comparing it to the Prehispanic series. It is puzzling, 
instead, that the frequencies are very much alike.

The form of the root canal is listed among dental 
anatomical anomalies (Jerome and Hanlon, 2007) and, 
at least until now, it does not seem to have specific 
evolutionary implications like other morphological 
traits that have been associated with dental reduction. 
Yet, the persistence of single-rooted second molars and, 
notably, the C-shape pulpal chamber in the modern series 
under study might indicate a genetic (or morphological) 
stability of this feature. Even though we stress the fact 
that a single trait is not sufficient to assess the extent 
of admixture, the persistence of this feature can be 
indicative of a persistent homogeneous composition of 
the modern Maya population in northern Yucatan.

Much remains to be done. From a joint anthropological 
and clinical perspective, the strong correlation between 
root form and canal morphology in the Prehispanic 
sample might be instrumental in understanding the 
occurrence of these traits in modern populations. The 
endodontic literature (see Jafarzaed and Wu’s review, 
2007) does not report the ethnic affiliation of those 
samples with low occurrence of C-shape canal. Given 
the extensive information on the C-shape canal in Asian 
peoples and the relative paucity in the other continents, 

TABLE 1. Counts and frequencies of C-shape canals and single-rooted second mandibular molars

    Frequency C-shape C-shape
 Sample Total One-root One-root Count Frequency

Prehispanic 48 17 35.4% 15 31.9%†
Modern 142 ?? ?? 42 29.4%

†One single-rooted molar could not be scored for canal form.

Fig. 3. Occlusal view of a C-shape root canal in a 
modern patient before being treated at the School of 
Endodontics, UADY.  Mesial is to the right of the picture, 
and buccal is to the top.

A. CUCINA ET AL.



49

further studies will shed light on this trait within the 
broader Mesoamerican sphere and in European and 
African groups.

ACKNOWLEDGEMENTS

We are grateful to Thelma Sierra Sosa, Xcambó 
Archaeological Project, and Agustín Peña Castillo, 
Noh Bec/El Escondidio Archaeological Project, for the 
archeological materials scrutinized in this study.

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