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A Study On Morphometry Of The Human Mandible In Relation To Sex

Dr.Praveen Vaddadi

Assistant Professor,Department Of Anatomy,Maharajah's Institute Of Medical Sciences , Nellimarla,Vizianagaram, Andhra Pradesh, India

Abstract Background:

Mandible Is The Hardest And Most Durable Bone Of The Skull Exhibiting High Degree Of Sexual Dimorphism. This Characteristic Feature Of Mandible Helps A Sex And Age Determination In Medicolegal Cases. Dimensions And External Features Of The Mandible Are Necessary For The Dental Surgeons In Inferior Alveolar Nerve Anaesthesia And The Otorhinolaryngology Surgeons For Laryngoscopy And Endotracheal Tube Intubation.

In Anthropological Excavations, The Morphometric Features Of The Mandible Help To Identify The Race, Sex, Age And Food Habits Of The Population And Also Help To Understand The Human Evolution.

Objectives:

To Measure And Document The Metric And Non-Metric Parameters In Dry Human Mandible Of Males And Females. The Non-Metric Parameters, Observed Was Shape Of The Chin And Contour Of The Lower Border Of The Mandible. The Metric Parameters Measured Was Mandibular Length, Gonial (Mandibular) Angle, Condylar Height, Coronoid Height, Minimum Ramus Breadth, Maximum Ramus Breadth And Bigonial Breadth.

To Analyse The Morphometric Data Of Mandible In Relation To Sex.

To Know Any Statistical Difference In The Morphometric Features Of The Mandible In Relation To Sex.

Methods:

100 Adult Human Mandibles. The Non-Metric Parameters Were Observed And Interpreted Based On Their Definitions. The Metric Measurements Were Measured With The Help Of Instruments

Mandibulometer And Vernier Calipers In Millimeters Or To The Nearest Of 0.1mm.

Conclusion :

The Bilobate Chin Of Male Mandibles Possess Rocker Bottom Contour Of The Lower Border Of The Mandible With Wider Bigonial Breadth And Acute Gonial Angle. The Pointed Chin Of Female Mandibles Showed Either Rocker Or Straight Contour With Obtuse Gonial Angle And Lesser Bigonial Breadth. The Right Cornoid And Condylar Height Showed Significant Values, But Mandibular Length Was Almost Equal In Both Sexes. The Minimum And Maximum Ramus Breadth Show Significant Difference Among The Gender.

Key Words: Mandible; Sex; Non-Metric Parameters; Metric Parameters.

Introduction

The Mandible Is The Largest, Strongest And Lowest Bone In The Face.1 The Temporomandibular Joint Formed Between The Mandibular Head And Mandibular Fossa Of Temporal Bone Allows Free Movement Of The Mandible Which Facilitates The Chewing Of Food And Digestion. The Mandible Receives The Insertion Of Masticatory Muscles [Masseter, Temporalis, Medial And Lateral Pterygoid Muscles]. The Morphological Characteristics Vary According To The Different Life Style, Level Of Nutrition, Chewing Habits And Genetic Background. Therefore The Morphological And Morphometric Characteristics Of

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The Presence Of Dense Layer Of Compact Bone Makes Mandible Hardest And Most Durable Bone; Hence It Remains Well Preserved Than Other Bones In The Body.2

It Is Evident From The Past Studies That Skull Is The Most Dimorphic And Easily Sexed Portion Of The Skeleton After The Pelvis; It Gives Accuracy Upto 92%. If Entire Skull Is Not Available, Mandible Helps In Sex Determination As It Is The Most Dimorphic Bone Of The Skull.2 The Shape And Size Of Mandible Differ Between The Male And Female Because Both Sexes Differ In Development Of Deciduous Tooth And Size Of Masticatory Muscles.

The Size Of Ramus Differs Between Male And Female According To The Stage Of Mandibular Development And Muscle Growth. Growth Rate Of Mandible In Male And Female Differs Because Puberty Occurs Earlier In Female Than In Male. Hence Sexual Differences May Manifest Themselves In Skull And Mandible Of Female Earlier Than In The Later And Longer Maturing Male.

Morphological And Morphometric Parameters Help The Forensic Expert For Race, Sex And Age Determination. The Knowledge Of External Features And Dimensions Of The Mandible Are Necessary For Dental Surgeons In Inferior Alveolar Nerve Anaesthesia, Otorhinolaryngologists For Accessing Feasibility For Laryngoscopy And Endotracheal Tube Intubation, For Reconstruction Of Mandible In Case Of Fracture / Disease For Plastic Surgeons And For Orthopaedician In Temporomandibular Joint Replacements. To Anthropologist, In Anthropological Excavations. The Morphometric Features Of Mandible Help To Identify The Race, Sex, Age And Food Habits Of The Population And Also To Understand Human Evolution.

In The Present Study An Attempt Is Made To Study The Shape Of Chin, Contour Of The Lower Border Of The Mandible And Morphometric Parameters3 Like Mandibular Length, Mandibular Angle, Condylar Height Coronoid Height, Minimum Ramus Breadth, Maximum Ramus Breadth And Bigonial Breadth In Dry Human Mandibles Of Male And Female. And A Statistical Analysis Of Parameters Is Also Made To Know The Difference Between Male And Female.

Aim & Objectives

I. To Measure And Document The Following Parameters In Dry Human Mandibles Of Male And Female.

A. Non-Metric Parameters : i. Shape Of The Chin

ii. Contour Of The Lower Border Of The Mandible.

B. Metric Parameters

i. Mandibular Length

ii. Gonial (Mandibular) Angle iii. Condylar Height

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iv. Coronoid Height

v. Minimum Ramus Breadth vi. Maximum Ramus Breadth vii. Bigonial Breadth.

II. To Analyse The Morphometric Data Of Mandible In Relation To Sex.

III. To Know Any Statistical Difference In The Morphometric Features Of The Mandible In Relation To Sex.

Materials And Methods

The Present Study Was Conducted On 100 Dry Human Mandibles (57 Males, 43 Females) With Age Between 45 – 60 Years. All Mandible Were Collected From The Departments Of Anatomy And Forensic Medicine, Maharajah’s Inistitute Of Medical Sciences, Nellimarla, Vizianagaram, A.P

Inclusion Criteria:

1. Unbroken, 2. Intact

3. Well Formed

4. Complete Human Adult Mandibles Were Taken For The Study.

Exclusion Criteria:

1. Damaged 2. Mutilated

3. Deformed Mandibles Were Excluded From The Study.

Each Mandible Was Examined And Sex Determination Was Made Based On Anatomical Features Of Mandible As Described In Text Book.3

In Each Mandible Following Parameters Were Examined And Measured.

I. Non Metric Parameters II. Metric Parameters.

Instruments:

1) Vernier Calipers

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2) Mandibulometer Statistical Method:

Results Were Expressed As Mean ± Standard Deviation And Range. Paired

‘T’ Test Was Used To Compare Between Males And Females.

Results

The Present Study Was Done On 100 Mandibles (57 Males, 43 Females) All Were

Table – 1: Shape Of The Chin

Shape Of Chin Male (57) Female (43)

No. % No. %

Bilobate 36 63.16 12 27.91

Square 17 29.82 9 20.93

Pointed 4 7.02 22 51.16

Most Common Shape Of Chin In Male Is Bilobate (63.16%) And Next Other Common Shape Of Chin Is Square (29.82%).

Pointed Shape Of Chin Is More Common In Females (51.16%) (Table -1).

Table – 2: Contour Of Lower Border Of The Mandible

Contour Of Lower Border The Mandible

Male (57) Female (43)

No. % No. %

Rocker Bottom 44 77.19 30 69.76

Straight 8 14.03 11 25.58

Undulating 5 8.77 2 4.65

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In Both Males And Females Predominant One Is Rocker Bottom. (77.19% & 69.76).

Straight Contour Is Seen In 14% Of Males And (25.58%) Females. The Least Common Is Undulating In Both The Sexes. (Table -2).

Gonial Angle:

In The Present Study Gonial Angle Of Mandibles Varied From 96° - 134° In Both Sexes, Mean Gonial Angle Is 115° ± 7.76 In Males And 120° ± 7.28 In Females.

The Gonial Angle Of Female Is Significantly Greater Than Males (P<0.0029)(Table-3).

Table – 3: Gonial Angle

Measurements Male (57) Females (43)

Range 96° – 134° 98° – 134°

Mean 115° 120.39°

Sd 7.76 7.28

Se 1.02 1.11

Mandibular Length:

In The Present Study, The Mean Mandibular Length In Male Is 94.5mm And In Female Is 94.67 Mm (Table-4)

Table – 4: Mandibular Length

Measurements Male (57) Females (43)

Range 79 – 107mm 84– 110mm

Mean 94.50mm 94.67mm

Sd 6.21 5.15

Se 0.82 0.78

Condylar Height:

In The Present Study The Mean Condylar Height On The Right Side In Male Is 60.75mm And In Female 58.5mm. The Standard Deviation Of Condylar Height In Male Is 5.71 And In Female 5.77

On The Left Side The Mean Condylar Height In Male Is 59.77mm With Standard Deviation Of 5.81 Whereas In Female The Condylar Height And Standard Deviation Are 58.1mm And 5.86 (Table-5).

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Table – 5: Condylar Height

Details Of Measurement Male (57) Female (43)

Right Left Right Left

Range 50 – 76mm 48 – 72mm 47 – 70mm 49 – 70mm

Mean 60.75mm 59.77mm 58.5mm 58.1mm

Sd 5.71 5.81 5.77 5.86

Se 0.75 0.777 0.88 0.89

P-Value For Right Condylar Height In Male And Female Is 0.032 Whereas For Left Condylar Height P-Value Is 0.0921 Which Is Non-Significant.

Coronoid Height:

In The Present Study, The Mean Value Of Right Coronoid Height In Males Is 59.14mm And In Female Is 56.93mm. The Standard Deviation For Right Coronoid

Height In Both Sexes Males Is 5.9.The Mean Value Of Left Coronoid Height In Males Is 59.08mm And In Females 57.45. The Standard Deviation In Male Is 5.37 And In Female Is 5.61

Table – 6: Coronoid Height

Details Of Measurement Male (57) Female (43)

Right Left Right Left

Range 49 – 76mm 48 – 72mm 46 – 71mm 47 – 71mm

Mean 59.14mm 59.08mm 56.93mm 57.45mm

Sd 5.9 5.37 5.9 5.61

Se 0.78 0.711 0.899 0.86

Maximum Ramus Breadth:

In The Present Study The Mean Value Of The Right Maximum Ramus Breadth In Male Is 36.04 Mm And In Females Is 35.3mm And On The Left Side. The Mean Maximum Ramus Breadth Is 36.55 Mm In Male And 35.47 Mm In Female.

Table – 7 : Maximum Ramus Breadth

Details Of Measurement Male (57) Female (43)

Right Left Right Left

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Range 30 – 44mm 47 – 3 Mm 25 – 4 Mm 28 – 41mm

Mean 36.04mm 36.55 Mm 35.3 Mm 35.47 Mm

Sd 3.13 3.4 3.21 3.19

Se 0.41 0.45 0.48 0.48

Minimum Ramus Breadth:

In The Present Study, The Mean Val E Of The Right Minimum Ramus Breadth In Male Is 30.2 Mm And In Female 29.11 Mm. On The Left Side The Value In Male Is 30.64 Mm And In Female 29.63 Mm. (Table -8).

Table – 8: Minimum Ramus Breadth

Bigonial Breadth:

In The Present Study, The Mean Value Of Bigonial Breadth In Male Is 95.18 Mm And In Female 90.18 Mm (Table-9).

Table – 9: Bigonial Breadth

Details Of Measurement Male (57) Female (43)

Right Left Right Left

Range 22–39mm 23–39 Mm 22 – 34 23 – 39

Mean 30.20 Mm 30.64 Mm 29.11 29.63

Sd 3.57 3.41 2.65 3.29

Se 0.47 0.45 0.4 0.501

Details Of Measurement

Male (57) Female (43)

Range 83 – 110mm 73 – 102 Mm

Mean 95.18 Mm 90.18 Mm

Sd 7.15 5.87

Se 0.94 0.89

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Bigonial Breadth Is Highly Significant In Male Than Female (P- Value<0.00011)

Discussion

Sex Determination Is A Key Analaysis That Forensic Investigators Perform In Order To Construct Biological Profile Of Human Remains.4 Accuracy In Identification Of Sex Is Atmost If Complete Skeleton Is Available For Analysis However Finding A Completely Intact Skeleton Is Highly Unlikely; Hence It Is Important To Develop A Set Of Predictors (Using Morphological Variables) For Each Bone.5, 6 Assessing Bone For Dimorphism Involves Visual Method Which Is Definitely Subjective And Hence May Pose High Inter-Observer Variation. Even With Trained Observers This Method Cannot Be Universalized As Inter-Population Difference In The Morphological Traits Exists. However Methods Based On Measurements And Morphometry Are More Accurate And Therefore Can Be Used In Determination Of Sex From Skull.7

In The Present Study The Bilobate Shape Is More Common In Male (63.16%) Next One Being Square (29.82%) Not Correlating With Observation Of Hu. Ks, 7 On Korean Mandibles (Bilobate 33.3% And Square 58.3%) . But The Present Study Shows Correlation With Hu. Ks Observation In That Pointed Mandible Is Least Common Type In Males. 7

In The Present Study, The Pointed Mandible Was Common In Female (51.16%) Which Is Correlating With Study Of Hu. Ks, (54.5%) But Not For Other Shapes.

The Present Study Shows Correlation With The Observations Of Hu. Ks 7 In That Rocker Bottom Is More Common In Males (77.19%), Next Common One Being Straight (14.03%). The Present Study Observed The Undulated Lower Border Of Mandible In 8.77%, Which Was Not .Observed By Hu Ks 7

In Case Of Female, Observation Was Not Correlating With Hu. Ks 8 Study, The Common Being Rocker (69.76%) And The Next One Is Straight (25.58%). The Present Study States The Least Incidence Of Undulating Border In Female Also (4.65%).

In The Present Study, The Mean Gonial Angle Of The Female Mandible Was Significantly Greater Than The Male Mandibles, Which Was Similar To The Observations Of The Earlier Authors. The Mean Gonial Angle Of The Female Mandibles (120.39°) Was Similar To The Observations Made By Rosa On Canary Island Mandibles (121.82°), Rai 11 On Karnataka Mandibles (121°) And Kharoshah

8 On Egypt Mandibles (121.1°). However It Was Lower Than The Observations Made By Mbajiorgu On Zimbabwe Mandibles (128°). 10

The Mean Gonial Angle Of The Male Mandibles (115°) In The Present Study Was Similar To The Observations Made By Rosa 5 On Canary Island Mandibles (118.47°) And Rai On Karnataka Mandibles (118°). However It Was Lower Than The Observations Made By Mbajiorgu 10 On Zimbabwe Mandibles (123.06°) And Kharoshah On Egypt Mandibles (122.8°).

In The Present Study, The Mean Mandibular Length Of The Male Mandibles (94.50 Mm) Was Not Similar To Observations By Earlier Authors. It Was Higher Than The Observations Made By Mbajiorgu 10 On Zimbabwe Mandibles (77.8mm);

Kharoshah 8 On Egypt Mandibles (76.2 Mm) And Rosa On Canary Island

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Mandibles (83.19 Mm). However It Was Lower Than The Observation Made By Steyn On South African Mandibles (111.2mm).

In The Present Study The Mean Mandibular Length Of The Female Mandibles (94.67 Mm) Was Lower Than The Observation Made By Steyn On South African Mandibles (107.8 Mm). However It Was Higher Than The Values Observed By Mbajiorgu 10 On Zimbabwe Mandibles (72.3 Mm), Kharoshah On Egypt Mandibles (83.1 Mm) And By Rosa On Canary Island Mandibles (80.26 Mm). 8

In The Present Study, The Mean Condylar Height Of The Male Mandibles (Right 60.75 Mm; Left 59.77 Mm) Was Similar With The Observations Made By Saini On Tirupathi Mandibles (60.67 Mm). However It Was Lower Than The Observation Made By Kharoshah On Egypt Mandibles (65.1 Mm). 8

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The Mean Condylar Height Of The Female Mandibles (Right 58.5 Mm, Left 58.1 Mm) Was Lower Than The Value Reported By Kharosha 8 On Egypt Mandibles (64.7 Mm) And Higher Than The Value Reported By Saini On Tirupati Mandibles (54.46 Mm).

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In The Present Study, The Mean Coronoid Height Of Male Mandibles (Right59.14 Mm, Left 59.08 Mm) Was Similar With Values Reported By Saini 9on Tirupati Mandibles (61.68mm) And Lower Than The Value Reported By Indira On Bangalore Mandibles (119.7 Mm).

In Females The Mean Coronoid Height Of The Present Study (Right 56.93 Mm, Left 57.45 Mm) Was Similar With Values Reported By Saini On Tirupati Mandibles (54.89mm) But Lower Than The Value Reported By Indira On Bangalore Mandibles (111.15 Mm). 9

In The Present Study, The Mean Minimum Ramus Breadth Of The Male Mandibles (Right 30.20 Mm, Left 30.64 Mm) Was Similar To The Observations Made By Steyn On South African Mandibles (31.1 Mm), Saini 9 On Tirupati Mandibles (31.29 Mm) And Rosa On Canary Island Mandibles (32.64mm). 5 However It Was Lower Than The Values Reported By Indira On Bangalore Mandibles (51.35mm) And Pokhrel On Pune Mandibles (36.59mm). It Was Higher Than The Value Reported By Kharoshah On Egypt Mandibles (28.7mm). 8

In The Female Mandibles, The Mean Minimum Ramus Breadth (Right 29.11mm, Left 29.63mm) Was Similar With Observations Made By Steyn On South African Mandibles (28.5mm), Kharoshah On Egypt Mandibles (27.96.Mm), Saini On Triupati Mandibles (29.65mm) And Pokhrel On Pune Mandible (28.71mm).

However The Values Are Lower Than The Reported Values Of Rosa On Canary Island Mandibles (31.85mm) And Indira On Bangalore Mandibles (46.96 Mm).5 In The Present Study, The Mean Bigonial Breadth Of The Male Mandibles (95.18 Mm) Was Similar With Reported Values Of Steyn On South African Mandibles (99.6mm) And Rosa On Canary Island Mandibles (97.45mm), But Lower Than The Reported Value Of Kharoshah On Egypt Mandibles (104.8mm). 8

In The Female Mandibles, The Mean Bigonial Breadth (90.18mm) Was Similar With The Values Observed By Steyn On South Africa Mandibles (91.5mm) And Rosa On Canary Island Mandibles (93.01mm). But The Values Were Lower Than The Kharoshah On Egypt Mandibles (100.8mm).

Conclusion

The Present Study On 100 Dry Human Mandibles Indicates That The Morphometric Features Of The Mandible Are Dimorphic In Nature. They Are –

• The Shape Of The Chin In Male Is Bilobate (63.16%) And In Female Pointed (51.16%).

• Most Of The Bilobate Male Chin Showed Rocker Bottom Contour (77.19%) Of The Lower Border Of The Mandible And Also Highly Significant Bigonial Breadth (95.18mm) And Significant Right Condylar Height(60.75mm) And Right Coronoid Height (59.14mm) But Lesser Gonial Angle (115°).

• The Pointed Female Chin (51.16%)Showed Higher Incidence Of Rocker Bottom (69.76%) Than Straight (25.58%) Contour Of The Lower Border Of The

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Mandible, And Also Greater Gonial Angle (120.39°). But The Right Condylar Height (58.50mm) And Right Coronoid Height (56.93mm) Were Significant. The Bigonial Breadth Of The Female Mandible (90.18mm) Is Lesser Than Male Mandible. These Findings Were Similar To Those Of Previous Workers

• Left Mean Coronod Height In Males (59.08mm) And In Females (57.45mm) And The Left Mean Condyar Height In Males (59.77mm) And In Females (58.10mm) Are Less Significant .

• In Both Sexes, Mandibular Length Was Similar, The Mean Values In Males (94.5mm) And In Females (94.67mm), But It Is Dimorphic In Previous Studies.

• In The Present Study, The Mean Maximum Ramus Breadth In Males (Right -36.04mm; Left. 36.55mm) And In Females (Right 35.30mm, Left 35.47mm) And The Mean Minimum Ramus Breadth In Males (Right- 30.20mm, Left 30.64mm) And In Females (Right 29.11mm Left 29.63mm) Are Not Significant, Whereas The Values Of Previous Workers Were Significant.

Acknowledgment

The Author Is Thankful To Department Of Anatomy For Providing All The Facilities To Carry Out This Work.

Conflict Of Interest None

Financial Support Nil

References

1.Standring S, Ellis H, Hely Jc, Johnson D, Williams A. Gray’s Anatomy– The Anatomical Basis Of Clinical Practice. 40th Edn, London : Elsevier Churchill Livingstone;

.P.530-533.

2.Krogman Wn. The Human Skeleton In Forensic Medicine. 23rd Edn.Thomas Publishers; 1973 .P.115.

3.Singh Ip, Bhasin Mk. A Manual Of Biological Anthropology, Delhi: Kamal Raj Enterprises; 2004 .P.134-144.

4.Roger Tl. Determination Of Sex Of Human Remains Through Cranial Morphology. J Forensic 2005 May;50(3):493-500.

5.Rosa Ma, Reimers Eg, Fregel R, Vazquez Jv, Darias Td, Gonzalez Am, Laruga Jm. Canary Islands Aborigin Sex Determination Based On Mandible Parameters Contrasted By Amelogenin Analysis. Journal Of Archaeological Science 2006;20:1-8.

6..Patil Kr, Modi Rn. Determination Of Sex By Discriminant Function Analysis And Stature By Regression Analysis : A Lateral Cephalometric Study. Forensic Sci Int 2005;147(2-3):175-80.

7.Hu Ks, Koh Ks, Han Sh, Shin Kj, Kim Hj. Sex Determination Using Non-Metric Characteristic Of The Mandibles In Koreans. J Forensic Science 2006 Nov;51(6).

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8.Kharosha Maa, Almandari O, Ghaleb Ss, Zaki Mk, Fattah Yaa. Sexual Dimorphism Of The Mandible In A Modern Egyption Population. Journal Of Forensic And Legal Medicine 2010;17:213-215.

9.Saini V, Shamal Sn, Pandey Ak, Tripathi Sk. Sex Determination Using Mandibular Ramus Flexure : A Preliminary Study On Indian Population. Journal Of Forensic And Legal Medicine 2011 July;18(5):208-212.

10.Mbajiorgu Fe, Zivanovic S, Asala Sa, Mawera G. A Pilot Study Of The Mandibular Angle In Black Zimbabweans. Cent Afr J Med 1996 Oct;42(1):285-7.

11.Rai R, Ranade Av, Prabhu Lv, Pai Mm, Madyastha S, Kumaran M. A Pilot Study Of The Mandibular Angle And Ramus In Indian Population. Int J Morphol 2007;25(2):353-356.

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