Journal of Forensic Science and Medicine

ORIGINAL ARTICLE
Year
: 2016  |  Volume : 2  |  Issue : 2  |  Page : 98--101

Determination of Cusp Number and Occlusal Groove Pattern in Mandibular Molars: A Preliminary Epidemiological Study in an Indian Population


Urvashi Ashwin Shetty1, Pushparaja Shetty1, Audrey Madonna D'Cruz2,  
1 Department of Oral Pathology and Microbiology, A. B. Shetty Memorial Institute of Dental Science, Nitte University, Mangalore, Karnataka, India
2 Department of Public Health Dentistry, A. B. Shetty Memorial Institute of Dental Science, Nitte University, Mangalore, Karnataka, India

Correspondence Address:
Audrey Madonna D'Cruz
Department of Public Health Dentistry, A. B. Shetty Memorial Institute of Dental Sciences, Nitte University, Mangalore - 575 018, Karnataka
India

Abstract

Teeth are excellent material in living and nonliving populations for anthropological, genetic, odontologic, and forensic investigations. The present study aims to study the number of a number of cusps in the first and second mandibular molar and to assess the frequency and expression of different types of occlusal groove pattern. The cross-sectional study is carried out. One hundred patients attending the Outpatient Department of the hospital were recruited for the study based on exclusion and inclusion criteria. Clinical examination was done, and the morphological details of the crown (the number of cusps) were recorded. Dental casts of the mandibular teeth were made. The occlusal grooves were highlighted by using Indian ink and observed under the 2× magnification for the groove pattern (+ or y type). Descriptive statistics were carried out for the study. In the case of mandibular first molar, the 5 cusp form was the most frequent occlusal configuration (82%) followed by 6 cusp variety (12%) and 4 cusp variety (4%) bilaterally. The predominant occlusal groove pattern seen in mandibular first molar was “y” shape (65%) followed by “+” pattern (28%). Hence, the most frequent occlusal surface configuration in case of first mandibular molar was “y5” form. In the case of mandibular second molar, the 4 cusp form was the most frequent occlusal configuration (86%), followed by 5 cusp type (12%) bilaterally. The predominant occlusal groove pattern seen in mandibular second molar was a “+” shape (85%) followed by “y” pattern (11%). Hence, the most frequent occlusal surface configuration in case of mandibular second molar was “+4” form. The study of dental morphological characteristics is important in forensic and anthropological research as it can provide information on the phylogenetic relationship between species, as well as variation and diversities within a population.



How to cite this article:
Shetty UA, Shetty P, D'Cruz AM. Determination of Cusp Number and Occlusal Groove Pattern in Mandibular Molars: A Preliminary Epidemiological Study in an Indian Population.J Forensic Sci Med 2016;2:98-101


How to cite this URL:
Shetty UA, Shetty P, D'Cruz AM. Determination of Cusp Number and Occlusal Groove Pattern in Mandibular Molars: A Preliminary Epidemiological Study in an Indian Population. J Forensic Sci Med [serial online] 2016 [cited 2020 Nov 24 ];2:98-101
Available from: https://www.jfsmonline.com/text.asp?2016/2/2/98/179323


Full Text



 Introduction



Teeth are excellent material in living and nonliving populations for anthropological, genetic, odontologic, and forensic investigations.[1] Their morphometry is known to be influenced by cultural, environmental and racial factors.[2] The key pieces of evidence needed for dental comparisons are twofold, the presence of dental remains and accurate antemortem dental records. With the proper evidence, forensic odontologists can make dental identifications very rapidly and with a high degree of certainty due to the inherent variability within the human dentition. Typical antemortem dental records may include radiographs, dental charts, both intra- and/or extra-oral photographs, dental casts, and notes.[3]

The variations in tooth form and groove pattern are a common occurrence, and these can be studied by measurements.[2] Tooth size standards can be used in age and sex determination.[4] Further morphological features of teeth provide the basis for the reconstruction of details of the everyday life such as the types of foods consumed and migratory patterns of communities in a given geographical area. Hence, tooth morphology is a part of the biological heritage that humans carry as they migrate, along with their blood types, fingerprint patterns, and other biological characteristics.[5]

Morphological categories used to describe the variations in occlusal surfaces of the mandibular molars are based on a topology developed by Gregory and Hellman [6] and Hellman.[7] The criterion for determining whether a pattern is a “y” or a “+” is a contact of the metaconid with the hypoconid. If contact occurs, the pattern resembles a “y” if no contact occurs, the pattern resembles a “+”.[8] According to Gregory and Hellman, the basic pattern is the “y-5” type, with 5 cusps and a y-shaped occlusal configuration.[6] However, it is observed that there are different degrees of expression and frequency of certain traits and variation of tooth morphology in different populations.[9]

Loh observed a relatively high incidence of 5-cusp second molars in Singaporean population.[10] Another observation on the teeth of the Chinese from Mainland China was made by Montelius, who reported a high incidence (56%) of 5-cusp forms in this tooth.[11] In 1997, Guo et al. by observations in new population of China stated that the rate of “+4” in the second mandibular molars is the Highest, while the rate of “y-5” is the lowest.[12] A study by Mosharraf et al. on occlusal morphology of mandibular second molars in Iranian adolescents found that the most frequent occlusal surface configuration was the “+4” form.[13]

There are no studies in literature regarding the frequency and expression of different types of occlusal groove pattern in Indian population. Hence, the objectives of the present study were to study the number of cusp in the first and second molar and to assess the frequency and expression of different types of occlusal groove pattern and to establish the importance of the confirmed morphological differences among Indian population as this would help in sex determination and identification.

 Subjects and Methods



A cross-sectional survey was conducted on the hundred patients attending the Outpatient Department of a Private Hospital in Mangalore. Ethical clearance to conduct the study was obtained from the Institutional Ethical Committee, A. B. Shetty Memorial Institute of Dental Sciences, Mangalore, Karnataka, India. Patients between the age group of 20 and 50 years having mandibular first and second molar bilaterally present and willing to participate were included in the survey. Equal distribution based on gender was done (50% males, 50% females). Subjects', whose teeth were restored, worn or heavily fractured, had missing teeth, or developmental disorders of teeth were excluded. A specially prepared and pretested proforma was prepared which had two sections. Section 1 collected information on the subjects' sociodemographic profile (age and gender) and section 2 contained proforma for recording the clinical findings.

Clinical examination was done and the morphological details of the crown, viz., the number of cusps (4, 5 or 6 cusps) were recorded. Subsequently, impressions of the mandibular teeth were made using alginate (Alginoplast) impression material, and the dental cast was immediately made using dental stone type 3. The study was repeated on the dental cast. The occlusal grooves were highlighted by using Indian ink, and the dental casts were observed under the 2× magnification for the groove pattern (+,× or y type) [Figure 1]. If the contact of mesiolingual cusp with distobuccal cusp occurs the pattern resembles a “Y” form and if no contact occurs then pattern resembles “+” form and if distolingual cusp contacts with mesiobuccal cusp pattern resemble “X” form.{Figure 1}

Data were entered in Microsoft Excel 2007 and was analyzed using SPSS version 16.0 (SPSS Inc., Chicago, IL, USA). Descriptive statistical analysis was carried out in this study. Significance was assessed at 5% level of significance.

 Results



In the case of mandibular first molar, the 5 cusp form was the most frequent occlusal configuration (82%) followed by 6 cusps variety (12%) and 4 cusps variety (4%) bilaterally. Only in 2% of the cases, there was mixed number of cusps (4 and 5 cusps unilaterally) [Table 1]. The predominant occlusal groove pattern seen in mandibular first molar was “y” shape (65%) followed by “+” pattern (28%) and mixed type of pattern (“+ and y”) were seen in 7% of cases [Table 2]. Hence, the most frequent occlusal surface configuration in case of first mandibular molar was “y5” form where “y” stands for the groove pattern and “5” for the number of cusps [Figure 2].{Table 1}{Table 2}{Figure 2}

In the case of mandibular second molar, the 4 cusp form was the most frequent occlusal configuration seen (86%), followed by 5 cusp type (12%) bilaterally. Only in 2% of the cases there was mixed number of cusp (4 and 5 cusps) [Table 3]. The predominant occlusal groove pattern seen in mandibular second molar was a “+” shape (85%) followed by “y” pattern (11%), and mixed type of pattern (“+ and y”) were seen in only 4% of cases [Table 4]. Hence, the most frequent occlusal surface configuration in case of mandibular second molar was “+4” form where “+” is the occlusal groove pattern and “4” stands for the number of cusps [Figure 3]. “X” groove pattern was not found in any molars in this study.{Table 3}{Table 4}{Figure 3}

 Discussion



The present study was done to assess the frequency/number of cusps and occlusal groove pattern for the mandibular first and second molars among patients attending the Outpatient Department of a Private Hospital in Mangalore. The results of the survey showed that the most predominant occlusal surface configuration in case of the first molar was “y5” form which was in accordance with the study findings of Gregory and Hellman.[6] A study on Alaskan Eskimo dentition by Hasund and Bang also showed similar findings.[14]

The most frequent occlusal surface configuration in case of mandibular second molar was the “+4” form. As stated by Loh,[10] the distal cusp is the most variable and in the evolutionary advanced type, it disappears and, therefore, leads to a 4-cusp form. However, Loh [10] and Montelius [11] observed a relatively high incidence of 5-cusp second molars in the Singaporean population and Chinese population respectively which was in contrast to the present study.[10] However, Guo et al. in 1997 have observed that the rate of “+4” in the second mandibular molars was the highest while the rate of “y 5” is the lowest in a new population of China,[12] a finding which was in accordance to the present study. Devoto and Perrotto have also observed a similar finding where the “+” groove pattern appeared on the second molar more often than other two molars. They stated that this fact may be due to gradual evolution in the morphology of mandibular molar occlusal grooves that have changed from pattern “y” to pattern “+.”[15]

 Conclusion



The study of dental morphological characteristics and odontometry is important in forensic and anthropological research as it can provide information on the phylogenetic relationship between species, as well as variation and diversities within a population. In this study, which was carried out in a Private Hospital in Mangalore, it was seen that the most common occlusal configuration of mandibular first molars was “y5” and in the case of second mandibular molars was “+4” form which is in accordance with the results of Guo et al. in Chinese population. This shows a gradual evolution in the morphology of mandibular molar occlusal grooves that have changed from pattern “y” to pattern “+.” Furthermore, knowing common variations in dental anatomy and morphology about each individual tooth can help in performing some dental treatments such as restorative, endodontic and orthodontic treatments. Therefore, the results of this anatomical study can be used in both anthropological researches and clinical aspects of dental sciences.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.

References

1Williams PL, Bannister LH, Berry MM, Collins P, Dursek JE, Fergusson MW. The teeth. In: Gray's Anatomy. 39th ed. New York: Churchill Livingstone; 2008.
2Nagle RJ, Seasrs VH. Anterior tooth arrangement. In: Complete Dentures. 1st ed. St. Louis: The CV Mosby Company; 1958. p. 353.
3Adams BJ. The diversity of adult dental patterns in the United States and the implications for personal identification. J Forensic Sci 2003;48:497-503.
4Black GV. Description of human teeth. 4th ed. Philadelphia: S.S White Mfg. Co.; 1992.
5Inda G, Vazdar M, Vodanovic M. Human molar crown traits in Croatian medieval and contemporary populations. Int J Oral Sci Dent Med 2010;44:3-16.
6Gregory WK, Hellman M. The crown patterns of fossils and recent human molar teeth and their meaning. Nat Hist 1926;26:300-9.
7Hellman M. Our third molar teeth. Their eruption, presence and absence. Dent Cosm 1936;78:750.
8Ash MM, Nelson SJ. Wheelers Dental Anatomy, Physiology and Occlusion. St. Louis: Saunders; 2003.
9Kieser JA, van der Merwe CA. Classificatory reliability of the Carabelli trait in man. Arch Oral Biol 1984;29:795-801.
10Loh HS. Mongoloid features of the permanent mandibular second molar in Singaporean Chinese. Aust Dent J 1991;36:442-4.
11Montelius GA. Observations of teeth of Chinese. J Dent Res 1933;13:501-9.
12Guo L, Ren L, Sun DL, Shen J. Morphological study on occlusal grove of mandibular molar of Chinese adults. Shanghai Kou Qiang Yi Xue 1997;6:129-31.
13Mosharraf R, Ebadian B, Ali Z, Najme A, Niloofar S, Leila K. Occlusal morphology of mandibular second molars in Iranian adolescents. Indian J Dent Res 2010;21:16-9.
14Hasund A, Bang G. Morphologic characteristics of the Alaskan Eskimo dentition: IV. Cusp number and groove patterns of mandibular molars. Am J Phys Anthropol 1985;67:65-9.
15Devoto FC, Perrotto BM. Groove pattern and cusp number of mandibular molars from Tastilian Indians. J Dent Res 1972;51:205.