AN INSIGHT TO THE ANTHROPOMETRIC STUDY OF MENTAL FORA- MEN OF JAW BONE WITH RESPECT TO ITS SURGICAL IMPORTANCE

Original Research Article AN INSIGHT TO THE ANTHROPOMETRIC STUDY OF MENTAL FORA- MEN OF JAW BONE WITH RESPECT TO ITS SURGICAL IMPORTANCE Lekshmy Vijay. V.G 1, Ramakrishna Avadhani 2, Qudusia Sultana *3. ABSTRACT Background: Mental foramen is one of the two foraminas situated on the anterolateral aspect of the body of mandible below the interval between the premolar teeth. They are slightly lower in edentulous individuals, which gives path for mental nerves and vessels. Morphological and morphometric parameters of mental foramen in relation to surrounding landmarks is clinically important, for providing a suitable data for dental surgeons and anaesthetics for an effective mental nerve block anaesthesia and for avoiding post-surgical complications due to nerve damage. This also helps for age estimation in fossil study. The following parameters were assessed to determine the distance of mental foramen from them; a) Alveolar crest, b) Lower border of mandible, c) Symphysis menti, d) Posterior border of ramus, e) Angle to foramen. Shape of foramen and level of teeth where the foramen is situated were also assessed. Materials and Methods: This study was carried out in the Department of Anatomy, Yenepoya Medical College. A total of 102 dry human mandibles for location of mental foramens from various landmarks were studied using digital vernier calliper. Results and Discussion: The mean and standard deviation values are as follows. The distance of mental foramen from its alveolar crest is 10.18±3.18, lower border is 12.62±1.67, symphysis menti is 26.12±5.35, posterior border of ramus is 61.11±6.34, angle of mandible is 40.79±4.56, from alveolar crest to lower border of mandible is 22.8±3.78. Foramen was observed to be round in shape in 70% of cases and majority were seen at 2 nd premolar level. Conclusion: These variations are of diagnostic importance for dental surgeons during nerve block, periodontal surgeries and to avoid injuries to neurovascular bundle. Awareness of possibility of the anatomical variations while planning surgery to avoid nerve damage. KEY WORDS: Mental foramen, Human mandible, Shape, Position, Location. International Journal of Anatomy and Research, Int J Anat Res 2017, Vol 5(3.3):4343-48. ISSN 2321-4287 DOI: https://dx.doi.org/10.16965/ijar.2017.330 1 Post Graduate, Department of Anatomy, Yenepoya Medical College, Mangaluru, Karnataka, India. 2 Professor and HOD, Department of Anatomy, Yenepoya Medical College, Mangaluru, Karnataka, India. *3 Assistant Professor, Department of Anatomy, Yenepoya Medical College, Mangaluru, Karnataka, India. Address for Correspondence: Dr. Qudusia Sultana, Assistant Professor, Department Of Anatomy, Yenepoya Medical College, Mangaluru, Karnataka, India. E-Mail: nakulalekshmy@gmail.com Access this Article online Quick Response code Web site: International Journal of Anatomy and Research ISSN 2321-4287 www.ijmhr.org/ijar.htm DOI: 10.16965/ijar.2017.330 Received: 05 Jul 2017 Peer Review: 06 Jul 2017 Revised: 02 Aug 2017 Accepted: 16 Aug 2017 Published (O): 30 Sep 2017 Published (P): 30 Sep 2017 INTRODUCTION Mental foramen is situated on the anterolateral aspect of the body of mandible in the midway between upper and lower borders of the bone [1]. Normally it is located externally below the interval between the premolars [2], which gives Int J Anat Res 2017, 5(3.3):4343-48. ISSN 2321-4287 4343

path to mental nerves and vessels [3,4]. Variations of mental foramens are often encountered ranging from difference in shape and positions [5,6,7] to the presence of accessory foramen[8], or complete absence as mentioned in some cases [9,10]. The mental nerve and vessels radiate through the mental foramen and supply sensory innervation and blood supply to the soft tissues of the chin, lower lip and gingival on the ipsilateral side of the mandible. Additionally, local anaesthesia of the terminal incisive branches of the inferior alveolar and mental nerves can be obtained effectively if the mental foramen is correctly identified. Therefore, computerized tomography (CT) is more accurate for detecting the mental foramen than conventional radiographs reported by SonickM. et al [11]. The position of mental foramen has been studied by means of direct measurement on dry mandibles or by using radiographs of dry mandibles or in patients [12-14]. Standard anatomical [15] and radiological text books [16] contain conflicting statements regarding the location of mental foramen. The mental foramen is an important anatomical landmark to facilitate dental surgical, local anaesthetic and other invasive procedures [17] in accordance to its variations in the position, shape, size and presence of accessory mental foramen. Knowledge of variations of mental foraminas required as many dental surgical procedures on the mandible such as; curettage of premolars, filling procedures, implantation, root canal treatments and orthodontic surgeries [18] are highly related with the position of mental foramen. Aim: The current study is done to analyze morphological and morphometric features of mental foramen in dry adult human mandibles in South Indian population in relation to surrounding landmarks which may furnish a reference for dentists in clinical practices. Objectives: To evaluate the shape and position of the mental foramen, To assess the location of mental foramen with relation to various landmarks on the mandible MATERIALS AND METHODS 102 dry adult human mandibles of unknown sex and age obtained from the Department of Anatomy, Yenepoya Medical College formed the material for study. We observed the position of mental foramen with respect to teeth, its shape, and its location with respect to borders were noted. Morphometric measurements of mental foramens in dry human mandibles, with or without intact teeth, with preserved alveolar margins, were used for our study. Bones with gross pathological deformities were excluded from our study. Before measuring, mandibles were placed on a standard horizontal plane to which the lower border of mandible get its most contact when vertical pressure is applied to the molars [6,19,20]. The mandibles were observed macroscopically for the presence of mental foramen. The data obtained was tabulated and analyzed by descriptive statistics using the SPSS software package for windows version 22.0. All the measurements were recorded by one of the authors to reduce bias. We measured the distance of MF (in mm) from various landmarks including alveolar crest, lower border of mandible, symphysis menti and posterior border of the ramus of mandible with digital vernier caliper were calculated[21] (Figure 1). A-F : distance of alveolar crest to the upper margin of mental foramen. B-F : distance from lower border of mandible to the lower margin of mental foramen. C-F : distance from symphysis menti to medial margin of mental foramen. D-F : distance from posterior border of ramus of mandible to lateral margin of mandible. RESULTS Shape: The shape of MF was visually recognised and analysed. Out of 102 mandibles (204 sides), round in contour was more prevalent [68 (67%) on right side and 75(74%) on left side] followed by oval contour [34 (33.3%) on right side and 27 (26.5%) on left side] (Figure 2,3). The position of MF was classified in relation to teeth of the lower jaw in accordance with Tebo and Telford [22] (Figure 4). Int J Anat Res 2017, 5(3.3):4343-48. ISSN 2321-4287 4344

Foramen lying on a longitudinal axis through the first premolar; Foramen lying on a longitudinal axis passing between first and second premolar; Foramen lying on a longitudinal axis through second premolar; Foramen lying on a longitudinal axis passing between first molar and second premolar; Foramen lying on a longitudinal axis through the first molar; Foramen lying on a longitudinal axis passing between first and second molar Fig. 1: Relation of mental foramen to the body of mandible. Fig. 4: Variable relations of mental foramen to lower teeth (M-molars, PM-premolars, C-canine). Table 1: Position of right and left mental foramina. Right Frequency Percent Frequency Percent II Premolar 46 45.1 48 47.1 I Molar 20 19.6 18 17.6 Between I Molar & II Premolar 15 14.7 16 15.7 Between I & II Premolar 12 11.8 12 11.8 I Premolar 7 6.9 7 6.9 Between I & II Molar 2 2 1 1 Total 102 100 102 100 Left Fig. 2: Mental foramen in round shape. Fig. 3: Mental foramen in oval shape. Table 2: Parameters to locate the right and left mental foramina from the prominent landmarks. LOCATION A-F (Alveolar Crest to foramen) B-F (Lower border to foramen) C-F (Symphysis Menti to foramen) D-F (Posterior border of ramus to foramen) Int J Anat Res 2017, 5(3.3):4343-48. ISSN 2321-4287 4345 Mean 10.0853 Right Standard deviation Mean Left Standard deviation 3.19817 10.2726 3.16241 12.4751 1.72646 12.7805 1.62377 25.3068 1.93339 26.9457 7.24332 59.4663 7.11347 62.7679 4.99048 Table 3: Comparison of results of earlier studies with the present study with respect to shape of mental foramen. Author Population Right side Left side Oval Round Oval Round Present study South Indians 33.30% 66.70% 26.50% 73.50% Akhilandeswari and Priya (2016) [26] South Indians 55.10% 44.90% 50.60% 49.40% Singh and Srivastav (2010) [23] North Indians 6% 94% 13% 87% Junior et al. (2009) [24] Brazilian 73.80% 21.20% 71.30% 28.70% Souaga et al. (2004) [25] Africans 73.80% 26.20% 100% 0% Position: The most frequent position of mental foramen was in line with the apex of second premolar teeth (position-iii) in the present study (46 (45%) on right side and 48 (47%) on left side) [(Figure 4),(Table 1)] followed by first molar position-v, position-iv, position-ii, position-i, position-vi.

Table 4: Comparison of present study with similar studies by different groups with respect to the position of mental foramen in relation to teeth. Authors Population Side I II III IV V VI (btw 1 & 2 (btw 1 Molar & (1 Pre molar) (2 Pre molar) (1 Molar) (1 &2 Molar) Pre molar) 2 Pre molar) Right 6.9 11.8 45.1 14.7 19.6 2 Present study South Indian Left 6.9 11.8 47.1 15.7 17.6 1 Agarwal and Gupta (2011) [5] Yesilyurt et al. (2008) [20] Amorim et al. (2008) [19] AUTHOR Central Indian Turkish Brazilian Position of foramen (in percent) Right 0 7.8 81.5 2.7 7.9 0 Left 0 7.6 81.5 3.1 7.8 0 Right 5.7 34.3 55.7 4.3 0 0 Left 7.1 25.7 61.4 5.7 0 0 Right 0 19.8 71.4 8.8 0 0 Left 0 23.1 68.1 8.8 0 0 Table 5 : Comparison of the location of mental foramen from the prominent landmarks. A - F B - F C - F D - F Right Left Right Left Right Left Right Left Present study 10.08±3.19 10.27±3.16 12.47±1.72 12.78±1.62 25.30±1.93 26.94±7.24 59.46±7.11 62.76±4.99 Shukla RK. et al 2015 [31] 10.84±2.94 10.69±4.83 15.02±9.94 13.88±1.59 25.72±3.24 26.19±4.79 64.61±4.4 65.05±4.14 Udhaya K. et al 2013 [18] 12.02±2.48 12.21±2.61 12.65±1.59 12.77±1.73 25.79±1.78 25.29±2.29 63.92±4.26 64.51±4.06 Virendra B. et al 2013 [17] 29.30±0.36 29.20±0.31 15.25±0.24 15.40±0.22 25.39±0.66 25.29±0.30 65.76±0.70 66.13±0.77 Location: The statistical analysis of position of MF and its size in relation with borders in left side is presented in the Table-2. The distanceof A-F was 10.27±3.16 mm in left side. However, B-F was 12.78±1.62 mm in left side. The distance of C-F was observed to be 26.94±7.24 mm in left side and D-F was 62.76±4.99 (Table 2). The statistical analysis of position of MF and its size in relation with borders in right side is presented in the Table-3. The distance of A-F was 10.08±3.19 mm in right side. However, B-F was 12.47±1.72 mm in right side. The distance of C-F was observed to be 25.30±1.93 mm in right side and in D-F was 59.46±7.11 mm (Tab.2). DISCUSSION MF is usually a single opening seen on each side of the body of mandible. In some cases, there may be complete absence of MF or it may be in multiples [15]. Variations of mental foramen were reported in different races in different geographic populations. They were having same or different age, sex and ethnicity; which were assessed using dry human mandible or by radiographic studies. Different anatomy and radiology textbooks give contradicting statements regarding the morphometric characteristics of the mental foramen; thereby depicting variable racial trends [6]. Location, shape and position of mental foramen would facilitate the dental surgeons to apply nerve block in different surgical procedures involving the lower jaw. Shape: Mental foramen was seen oval in contour among various geographical populations. Comparison of the percentages of oval and round shapes were recorded in the present study with that of the previous studies have been highlighted in Table 3. Singh and Srivastav; 2010[23] reported round contour of mental foramen among a study conducted in North Indian dry mandible specimens (94% on right side and 87% on left side among 200 specimens), which is similar to that of our studies. The present study on South Indian mandibles also projects the presence of round shape of mental foramina more than that of oval shape. Studies of Akhilandeswari; et al 2016 [26], among South Indian population showed more prevalence of oval contour of mental foramen. This is contradictory to the present study. But, position of mental foramen was not a study objective by the above mentioned authors. Position: There are significant differences reported in the position of MF among different ethnic groups. Igbigbi and Lebona [21] in Malawians and Mbajiorgu et al. [27] in Zimbabweans mandibles reported position III as the commonest one, followed by position IV; however, Santini and Land [6] in British and Int J Anat Res 2017, 5(3.3):4343-48. ISSN 2321-4287 4346

Lekshmy Vijay. V.G, Ramakrishna Avadhani, Qudusia Sultana. AN INSIGHT TO THE ANTHROPOMETRIC STUDY OF MENTAL FORAMEN OF Green [28] in Chinese mandibles observed position II being the commonest followed by position III. In other studies on Kenyans mandibles [29], the position II was found most common followed by position I and in Malay populations [30] the most common position was III followed by II, but in the above-mentioned studies right and left sides were not considered separately from each other. Our study observed the III rd position of mental foramen (2nd premolar) were prevalent which was same as the studies of Agarwal and Gupta; 2011[5] among 100 dry mandibles of Central India (Table 4). But the studies on other different geographical regions were not similar with the present study. Variability in MF position may be related to different feeding habits subsequently affecting mandibular development [20]. Prior knowledge of common positions in local populations may be helpful in effective nerve blocks and surgeries in those regions. Location: Comparison of the location of mental foramen from the prominent landmarks is identified in the present study with other studies as shown in Table 5 respectively. The location of mental foramen was found to be more closer to A F in the present study. The comparative study was also showing almost the same results for the location parameter assessment. CONCLUSION Prior knowledge of mental foramen variations helps surgeons in planning surgery in that region to avoid nerve damage and also enable effective mental nerve block anaesthesia while planning for closed surgeries. Mental nerve paralysis is one of the principal complications of surgeries of the mental foramen regions. Mental foramen variations remain unnoticed and undiagnosed. In order to obtain effective nerve block and to avoid post procedural neurovascular complications in the mental region, particular attention should be paid to the morphology of the mental foramen. The present study suggests, majority of the mandibles have found round shaped foramina lying in the apex of II nd premolar teeth. However, the variations do exist in the location, orientation, shape, appearance and relation with teeth on lower jaw in different population groups. Therefore; it is essential to be aware of the possibility of these anatomical variations while planning surgery in that specific region to avoid nerve damage. This is also to enable effective mental nerve block anaesthesia. A prior CT scan can elucidate jaw structures and prevent patient morbidity. Therefore, a detailed knowledge of the mental foramen and it s variation in different population is essential for dentists, orthopedicians and anatomists. Also the knowledge about the direction of opening is important for dentists while doing mental nerve block. ACKNOWLEDGEMENTS Authors would like to thank Mrs. Megha H. Nair (Statistician) and Department of Anatomy for their support in the above study. Conflicts of Interests: None REFERENCES [1]. Black S. Head and neck- External skulls. In Gray s anatomy-the anatomical basis of clinical practice. 41 st edition. Edited by Standring S. Edinburgh: Elsevier Health Sciences; 2008:409-15. [2]. Gupta S, Soni JS. Study of anatomical variations and incidence of mental foramen and accessory mental foramen in dry human mandibles. Natl J Med Res 2012;2(1):28-30. [3]. Agthong S, Huanmanop T, Chentanez V. Anatomical variations of the supraorbital, infraorbital, and mental foramina related to gender and side. J Oral Maxillofac Surg 2005;63(6):800-4. [4]. Phillips JL, Weller RN, Kulild JC. The mental foramen: Part III. Size and position on panoramic radiographs. J Endod 1992;18(8):383-6. [5]. Agarwal DR, Gupta SB. Morphometeric Analysis of Mental Foramen in Human Mandibles of South Gujarat. People s J Sci Res 2011;4(1):15-8. [6]. Santini A, Land M. A comparison of the position of the mental foramen in Chinese and British mandibles. Cells Tissues Organs 1990;137(3):208-12. [7]. Živanoviæ S. Some morphological characters of the East African mandible. Cells Tissues Organs 1970;77(1):109-19. [8]. Sawyer DR, Kiely ML, Pyle MA. The frequency of accessory mental foramina in four ethnic groups. Arch Oral Bio 1998;43(5):417-20. [9]. De Freitas V, Madeira MC, Toledo Filho JL, Chagas CF. Absence of the mental foramen in dry human mandibles. Cells Tissues Organs 1979; 104(3):353-5. Int J Anat Res 2017, 5(3.3):4343-48. ISSN 2321-4287 4347

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