|Year : 2013 | Volume
| Issue : 3 | Page : 97-100
Prevalence, expression, and dichotomous nature of Carabelli's trait in permanent dentition of contemporary Jat Sikhs
Gaurav Agnihotri1, Sanju Singla2, Rajan Singla1
1 Department of Anatomy, Government Medical College, Amritsar, Panjab, India
2 Department of Oral and Maxillofacial Surgery, DIRDS, Faridkot, Panjab, India
|Date of Web Publication||20-Nov-2013|
44 AB, Lane no 2,Gopal Nagar, Majitha Road, Amritsar, Panjab
Source of Support: Self Financed, Conflict of Interest: None
Objective: The study determines distribution and forms of expression of Carabelli's trait in contemporary Jat Sikhs. It also ascertains the dichotomous nature of this trait. Study design: The study was conducted on 200 maxillary first molars (male: female ratio 50:50). The trait was scored either as present or absent. When present it was again assessed and categorized. All data was subjected to either chi-square analysis or Student t-test evaluation when indicated. The significance was noted at the 5% level. Results: Prevalence of trait came out to be 78.5%. The trait absent/present exhibits bilateral development. Groove form was the most common (35%) while pit form was least prevalent (2.5%). Each first molar and its antimere exhibit no statistical difference in the exhibition of trait. A definite statistically significant sexual dimorphism (P<0.05) exists in phenotypic expression of trait among sexes. Percentage frequency of pronounced tubercle was almost double in males while absence of tubercle was observed three times more in females. The ratio of nontubercular: Tubercular varieties is 1:1.5. Conclusion: The difference in this study was statistically significant at the 5% level, which was consistent with the greater crown reduction usually found in females. The present quantitative study in an endogamous group is of clinical, anthropologic, and forensic value and provides phylogenetic and ontogenic insights regarding the trait.
Keywords: Carabelli, Jat Sikhs, sexual dimorphism, variation
|How to cite this article:|
Agnihotri G, Singla S, Singla R. Prevalence, expression, and dichotomous nature of Carabelli's trait in permanent dentition of contemporary Jat Sikhs. SRM J Res Dent Sci 2013;4:97-100
|How to cite this URL:|
Agnihotri G, Singla S, Singla R. Prevalence, expression, and dichotomous nature of Carabelli's trait in permanent dentition of contemporary Jat Sikhs. SRM J Res Dent Sci [serial online] 2013 [cited 2023 Feb 1];4:97-100. Available from: https://www.srmjrds.in/text.asp?2013/4/3/97/121631
| Introduction|| |
Teeth are an excellent object for the study of human variation. They are very resistant to post mortem degradation and mechanical trauma; so they are generally better preserved than bones in archaeologically derived human remains. An additional advantage is that their morphological features are observable on extracted specimens, on specimens from skeletal-dental remains, on dental impressions or cast reproductions, and directly in the mouth of a living person. 
The Carabelli trait is an elevation, a groove or a pit, usually seen, when present on the palatal surfaces of the mesiopalatal cusp of the maxillary second primary, the maxillary first and second permanent molars.  It is a quasi-continuous variable, that is, it can be either present or absent but when present, it exhibits continuous variation in expression.  A pit and a groove are negative expressions of the trait, whereas a protuberance or a cusp are positive expressions.  Recent studies support a polygenic mode of inheritance.  The genetic factors underlying the expression of Carabelli's trait are best represented by the upper first molar, which is therefore used as the key teeth for population comparisons. 
Besides having an anthropologic and forensic value, Carabelli's trait plays an important role in phylogenetic and ontogenetic studies of dental development.  Some authors believe that the trait is increasing in frequency through evolution  while others hold that it is in the process of reduction. ,, A similar structure the cingulum is found among apes and gibbons. , A Carabelli cusp has been found in Australopithecus and Neanderthal man, where it is only a groove. Therefore it has been suggested that there has been an evolution in Carabelli's cusp from a simple groove to a well developed cusp. 
The pit and groove forms have clinical implications since they represent a predilection site for dental caries. The tubercle of Carabelli also interferes with banding techniques during fixed orthodontic therapy. 
The Carabelli's trait can be useful in establishing phylogenic relationships between closely related populations.  The cusp may rival the main cusps in size, whereas other related forms include a small ridge, pit or furrow. A literature review on this trait suggests an ethnic variation and in some cases sexual dimorphism in its expression.
The Jat Sikhs of Panjab are endogamous and primarily agriculturalists. Although various investigation of this trait among occidental populations have been reported, none have been carried out in Indian Jat Sikhs. The present study was undertaken to obtain information about the occurrence of various forms of Carabelli's trait in Indian Jat Sikhs. The findings are envisaged to have a clinical forensic, ontogenic, anthropological, and ethnic significance.
| Materials and Methods|| |
Our study on 200 maxillary first molars determines distribution and forms of expression of Carabelli's trait in contemporary Jat Sikhs. It also ascertains the dichotomous nature of this trait (male: female ratio 50:50). The study was conducted over a period of 11 years (2002-13) in Government medical and dental colleges situated at Patiala and Amritsar, Panjab. Due permission was taken from the ethical committee of the institutes and the students were informed regarding the purpose of the study. The Jat Sikh students in the age group of 17-21 years were selected as attrition is minimal for this age group and maxillary casts were prepared. The sample was restricted to students who resided in Panjab and whose mother tongue was Panjabi. Subjects with extensive caries or restoration on the maxillary first permanent molar were not included in the study. The study was conducted on 200 maxillary first molars (male: female ratio 50:50).
The trait was scored either as present or absent. When present, it was again assessed and categorized as follows:
- Pronounced tubercular form (TBP)
- Slight tubercle (TBS)
- Groove (GR)
- Pit (P)
according to the methodology available in literature. ,,
All data was subjected to either chi-square analysis or Student t-test evaluation when indicated. The significance was noted at the 5% level.
| Results and Discussion|| |
The prevalence percentage for Jat Sikhs came out to be 78.5% [Table 1]. The degree of prevalence, however, varies from one ethnic population group to another.  The prevalence of the trait has been reported to be 52.2% in Malaysians,  17.43% in Nigerians,  52.77% in Chennai population,  and 64.4% in Karnataka population.  The wide variation in the prevalence figures in different ethnic groups could be a result of differences in the assessment criteria used. It could also be due to differences in the genetic control of the trait. Pedersen  concluded that Carabelli's cusp and pit is practically nonexistent in Eastern Greenland Eskimos, which is the least occurrence recorded for any racial or local group. Dahlberg  found a high frequency of this trait in the form of prominent cusps of the first permanent molar of Caucasians.
The trait absent/present exhibits bilateral development [Table 1]. However, few unilateral cases were also observed (3.5%). This is in consonance with the findings of Dietz  on casts of American soldiers. The groove form was the most common (35%) while pit form was least prevalent (2.5%) [Table 2] and [Table 3]. Slight tubercle was observed more frequently (25%) than pronounced tubercle (16). These different phenotypes are depicted in [Figure 1]. These findings are in accordance to the findings in Gujaratis.  The ratio of nontubercular:tubercular varieties is 1:1.5 [Table 5], which is different to the ratio of 1:4 obtained for Saudi Arabian population.  In the present study the percentage frequency of pronounced tubercle was almost double in males while absence of tubercle was observed three times more in females.
|Figure 1: Clockwise from left to right Normal first molar (left side), Prominent carabelli cusp (left side), Moderate carabelli cusp (left side), Pit (left side), Groove (left side), Prominent groove (right side).|
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|Table 3: Statistical difference in each first molar and its antimere in the exhibition of the trait |
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Studies on ethnic Yorubas in Nigeria  indicate that although the tubercular variety is more frequently seen in either of the two dentition types, this is more so in the permanent dentition than in the primary dentition. The explanation for this could be related to differences in the development time period and the relatively shorter time span required for odontogenesis in the primary dentition compared with the permanent dentition. This may result in a less marked development of any morphological trait in the primary dentition.
Each first molar and its antimere exhibit no statistical difference in the exhibition of trait [Table 4]. A definite statistically significant sexual dimorphism exists in phenotypic expression of trait among sexes [Table 5]. Similar findings have been observed for Taiwan Chinese  and Australian aboriginal  populations, and in Jordanians.  However, contrasting results were obtained when studies were conducted on Malaysians,  Nigerian,  and Finnish subjects.  This therefore seems to confirm the suggestion made by Synder et al. in their study on Mexicans that this phenomenon of sexual dimorphism varies between populations.The findings on Carabelli's trait in different populations are depicted in [Table 6].The variation in expression between sexes has also been observed for other morphological tooth characteristics such as root sizes and incisor shoveling.  The males in this study had a higher percentage of occurrence of the tubercle on teeth than did the females. This is in agreement with the results obtained by other researchers. , The difference in this study was statistically significant at the 5% level, which was consistent with the greater crown reduction usually found in females.
|Table 4: Statistically significance of sexual dimorphism in the phenotypic expression of the trait |
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|Table 5: Statistically significance of sexual dimorphism in the tubercular and nontubercular forms |
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Genetic and environmental factors have been reported to influence the manifestations of Carabelli's trait. While a field theory suggests that the trait is induced, and therefore is subjected to environmental stress, clonal model theory suggests that the trait is intrinsic and therefore it would be less responsive to environmental factors.  It has also been suggested that Carabelli's cusp is an adaptation that enlarged the occlusal surface of the first molar in the buccolingual dimension as compensation for evolutionary reduction in the length (mesiodistal) diameter of the maxillary molar row. , Our findings suggest the presence of a strong genetic influence as evidenced by the finding of a bilateral symmetry, however, the differences in the phenotypic expression of the trait in the different dentition types and sexes, as reported by some workers (including the present study), may suggest that the trait is under polygenic influence.
| Conclusion|| |
The difference in this study was statistically significant at the 5% level, which was consistent with the greater crown reduction usually found in females. The present quantitative study in an endogamous group is of clinical, anthropologic, and forensic value and provides phylogenetic and ontogenic insights regarding the trait. The pioneer study on distribution and forms of expression of Carabelli's trait in contemporary Jat Sikhs is of definite significance as tooth morphology is known to be influenced by racial, cultural, and environmental factors.
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[Table 1], [Table 2], [Table 3], [Table 4], [Table 5], [Table 6]