Occlusal groove patterns and cusp number in permanent mandibular first and second molar among Indian population - A pilot study

Background: The study of the origin and variations of the human dentition is called dental anthropology. It can be used as an effective tool to identify geographic or racial affinities. Dental anthropology includes metric and non-metric analysis. Non-metric analysis includes studying the morphology of teeth. Morphological analyses on extra cusp, shoveling of incisor, and Carabelli’s trait have been studied extensively in Indian population, but cusp number variation and variation in groove morphology are lacking. Thus, the aim is to determine the frequency of occlusal groove pattern and cusp number in permanent mandibular first and second molar among Indian population. Materials and Methods: A total of 150 subjects of Indian origin were considered (75 males and 75 females) in the age group of 18–25 years. Exclusion criteria included caries, restorations, and attrition of teeth. After obtaining consent, impression was obtained using alginate impression material and cast made using dental stone. Mandibular first and second molar was analyzed for occlusal groove pattern and cusp number based on Arizona State University Dentoanthropological System of State University of Arizona criteria. Results: The most frequent pattern in 36 and 46 was 5Y followed by 4+ and 6X. In 37 and 47, 4+ pattern was more frequent followed by 4X. Significant difference was observed in distribution of patterns between 36 and 37 and 46 and 47, respectively (P < 0.01) and between males and females significant difference was observed with respect to 37 and 47. Conclusion: The mandibular first molar showed 5Y pattern more frequently indicating a more conservative trend while the second molar showed 4+ pattern depicting a high evolutionary trend. There was a significant difference in the distribution of patterns between males and females with respect to the second molar. Nair, et al. Groove patterns and cusp number in mandibular molars 116 Journal of Advanced Clinical & Research Insights ● Vol. 5:4 ● Jul-Aug 2018 which is supported by the fact that the 4+ tooth is much smaller than the 5Y tooth Jorgensen in 1955 added an additional groove confirmation called the X form.[3] At present, the X form is considered to be the most evolved form. Studies determining the cusp number and groove patterns have been conducted in different populations such as Iranian, Croatian, and Alaskan populations. However, on literature search, such studies have not been done with regard to the Indian population. Thus, the aim of this study was to determine the frequency of occlusal groove pattern and cusp number in permanent mandibular first and second molar among Indian population. Materials And Methods The study was conducted at the department of oral pathology. A total of 150 subjects were considered (75 males and 75 females) in the age group of 18–25 years. Before commencement of the study, written consent was obtained and a detailed history of the patient was recorded to determine their Indian origin. There are a total of 28 states in India, subjects for this study belonged to 20 states of India. The exclusion criteria included caries, restorations, and attrition of the teeth that were to be studied. Impressions were obtained using alginate impression material and cast was poured using dental stone. Occlusal groove pattern was determined on the cast by delineating the groove using a sharp tip lead pencil. Classifications of the characteristics of the occlusal surfaces of the molars were determined according to the standards for characterization of morphological variants of permanent teeth of Arizona State University (ASU) (ASU Dentoanthropological System of the State University of Arizona). Classification of the groove pattern on the mandibular first (M1), second (M2), and third (M3) molars: • Y Contact of the second and third cusps. • + Contact of cusps from one to four. • X Contact of the first and fourth cusps. The groove pattern was calculated by means of loupe at x magnification. Classification of the number of cusps on the mandibular first (M1), second (M2), and the third (M3) molars: • 4 The presence of cusps 1–4 (1 protoconid, 2 metaconid, 3 hypoconid, and 4 entoconid). • 5 The presence of 5 cusps (hypoconulid) • 6 The presence of 6 cusps (entoconulid). The following parameters were observed: Table 1: General distribution of patterns Tooth no. 4+ (%) 4X (%) 5Y (%) 6X (%) 6Y (%) 36 18 (12) 2 (1.33) 120 (80) 9 (6) 1 (0/66) 37 135 (90) 8 (5.33) 6 (4) 1 (0.66) ‐ 46 20 (13.33) 1 (0.66) 119 (79.33) 9 (6) 1 (0.66) 47 135 (90) 8 (5.33) 6 (4) 1 (0.66) ‐ Table 2: Distribution in males ‐ (total ‐ 75) Tooth no. 4+ (%) 4X (%) 5Y (%) 6X (%) 6Y (%) 36 8 (10.66) 1 (1.33) 59 (78.66) 7 (9.33) ‐ 37 67 (89.33) 2 (2.66) 6 (8) ‐ ‐ 46 8 (10.66) 1 (1.33) 58 (77.33) 8 (10.66) ‐ 47 61 (81.33) 7 (9.33) 6 (8) 1 (1.33) ‐ Table 3: Distribution in females (total ‐ 75) Tooth no. 4+ (%) 4X (%) 5Y (%) 6X (%) 6Y (%) 36 10 (13.33) 1 (1.33) 61 (81.33) 2 (2.66) 1 (1.33) 37 70 (93.33) 5 (6.66) ‐ ‐ ‐ 46 11 (14.66) ‐ 62 (82.66) 1 (1.33) 1 (1,33) 47 74 (98.66) 1 (1.33) ‐ ‐ ‐ Figure 1: Cast showing mandibular 1st molar showing 5Y pattern and mandibular second molar showing 4+ pattern Figure 2: Cast showing mandibular 1st molar showing 4+ pattern and mandibular second molar showing 4+ pattern Groove patterns and cusp number in mandibular molars Nair, et al. Journal of Advanced Clinical & Research Insights ● Vol. 5:4 ● Jul-Aug 2018 117 1. The number of cusps on the teeth 2. The groove pattern on the teeth 3. Variations in groove pattern and cusp number between mandibular first and second molar 4. Variations in groove pattern and cusp number between males and females 5. Variations in groove pattern and cusp number in subjects belonging to different parts of India. The results were tabulated and statistically analyzed using Chi-square test and tests of significance were done to observe any correlation between the above-mentioned parameters.