Anthropological concepts in clinical /certified fixed orthodontic courses by Indian dental academy


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Anthropological concepts in clinical /certified fixed orthodontic courses by Indian dental academy

  1. 1. Anthropological Concepts In Clinical Orthodontics INDIAN DENTAL ACADEMY Leader in continuing dental education
  2. 2.                 Introduction What Is Anthropology? Classification of Anthropology Evolution The Various Eras of Evolution. Theories of Evolution Hominid Evolution Process Evolution of Human Face Evolution of the jaw and joints Evolution of teeth and its attachment apparatus Orthodontic aspects of dental anthropology Indices in anthropology Crown shape, winged and shovel shaped incisors Theory of overbite and buccal segment reproximation. Carabelli Trait Conclusion
  3. 3. Introduction    Orthodontists are functioning anthropologists. We measure the bones of the skull, face, and teeth and study the relationships of these structures. We should also be interested, then, in learning as much as possible about the origins of human beings and evolutionary development of our anatomy.
  4. 4. What is Anthropology ?   Anthropology is the study of humans in all places and at all times. The term itself comes from the Greek (anthropos=man, logos=the study of). Anthropologists study modern humans and their direct ancestors whom we will refer to as hominids.
  5. 5. CLASSIFICATION OF ANTHROPOLOGY     Physical Anthropology Cultural Anthropology Archaeology Linguistic Anthropology
  6. 6. Physical Anthropology It involves mechanisms of biological evolution, genetic inheritance, human adaptability and variation, primatology, and the fossil record of human evolution 
  7. 7. Cultural Anthropology  Branch of Anthropology that deals with Culture, subsistence and other economic patterns, kinship, sex and marriage, socialization, social control, political organization, class, ethnicity, gender, religion, and cultural changes .
  8. 8. Linguistic Anthropology It is the human communication process focusing on the importance of sociocultural influences; nonverbal communication; and the structure, function, and history of languages 
  9. 9. Archaeology Prehistory and early history of cultures around the world; major trends in cultural evolution; and techniques for finding, excavating, dating, and analyzing material remains of past societies. 
  10. 10. WHAT IS DENTAL ANTHROPOLOGY?  Dental Anthropology is the study of teeth in a perspective beyond clinical science. That perspective includes the study of dental growth, theories on dental origin, primate dentition, and population variation
  11. 11. Evolution  Evolution is a continuous process of change from one form to another.  Acc. to theory of evolution or origin of species ,all present forms of life have been derived from earlier simple forms.
  12. 12. Various eras of evolution
  13. 13. Paleozoic era    Fossil fish first appear in the rocks of silurian period. Fossil amphibians in the Devonian period. And the reptiles in the pennsylvanion period
  14. 14. Various eras of evolution
  15. 15. Mesozoic era  This era was dominated by reptiles.  In early triassic period fossils of first of primitive mammals were found, and later those of first birds were found.  In cretaceous period, fossils of first modern mammals appeared, but by the end of this period primitive mammals got extinct.
  16. 16.
  17. 17. Caenozoic era The tertiary  1. 2. 3. 4. 5. The paleocene The eocene The oligocene The miocene The piliocene The quaternary  1. 2. The pleistocene The halocene
  18. 18.     Fossil primates first appeared in the rocks of paleocene epoch . Fossil anthropoid apes appeared in the rocks of oligocene epoch. Australopithecus fossils from upper pliocene and lower pleistocene epoch. Earliest human fossils from pleistocene epoch.
  19. 19. Theories of evolution Four main theories to explain the method by which species of life that exist today have evolved from earlier simpler forms.  1. 2. 3. 4. The lamarckian theory. The theory of orthogenesis. The theory of natural selection. The mendelian theory.
  20. 20. The lamarckian theory    Characters acquired and changes taking place during life of an organism are inherited after the acquired character and changes have persisted for a long time. They are due to change in environment and to the concerned effects of use and disuse. Eg: girrafes with long necks.
  21. 21. Theory of orthogenesis [development in straight line]  Put forth by Haldane and Julian Huxley.  They considered that evolution proceeds in any particular direction ,not because of any advantage gained by the race or because of direct moulding effect by the surrounding, but because of some inner urge ,some necessity for the hereditary constitution to change in just that particular way.
  22. 22. Natural Selection or Survival Of The Fittest  Charles Darwin propounded this theory of organic evolution.  This theory assumes that every life on earth was developed from previous form.
  23. 23.  He attributed changes in living organisms to the action of natural selection and in many instances to the effect of use and disuse.
  24. 24. This theory can be summarized briefly as:  1. 2. 3. 4. Struggle for existence Natural selection Heredity Survival of the fittest.
  25. 25.  As the world has a limited surface, and more animals are born into it than it is capable of holding, this produces struggle for existence, the outcome of which is natural selection or survival of the fittest and new species originates.  Natural selection exterminates the unfit.
  26. 26. Mendel's law of inheritance  Mendel discovered the fact of segregation or dissociation of characters from each other in the course of formation of germ cell.  His research work was on edible pea.
  27. 27.
  28. 28. Hominid evolution      Hominids and apes have common ancestors. They parted their way about 6 million years ago. The study of the evolution of hominid provides important clues about locomotion, behavior, adaptation and lifestyle. Homosapiens, maturing more slowly than other primates, retained many primitive features, which may be why the genus has been successful. Hands and teeth, for eg, are quite primitive. Genera that become specialized tend to become extinct when their environment changes.
  29. 29. Hominid evolution process
  30. 30. The following order can be followed: 1) The Great apes : Chimpanzee, gorilla and orangutan. 2) The 'gracile' Australopithecines. 3) The 'robust' paranthropus group. 4) Homohabilis 'handy man' - early Homo. 5) Homo erectus 'upright man' 6) Neanderthals 'Archaic homosapiens' 7) Homo Sapiens 'wiseman'.
  31. 31. The Great Apes        Orangutan limited to borneo and Indonesia arboreal and frugiverous (fruit eaters). Legs are shortened with arms lengthened. skull and face are elongated and surrounded by fur. Dental formula I-2,C-1,PM-2,M-3. narrower jaws than Gorilla and molars are of equal size. enamel on molar shows marked wrinkling
  32. 32. The Great Apes         Gorilla Largest of living primates Restricted to Africa. Have clavicles which help in brachiating. Dental formula I-2,C-1,PM-2,M-3. Strong incisors with chisel like edges. Diastema between the laterals and canines in both arches. Well defined maxillary premolars Canines exhibit sexual dimorphism.
  33. 33. The Great Apes      Chimpanzees Closest match to Homo Sapiens genetically. Have a complex social behaviour. Dental formula I-2,C-1,PM-2,M-3. Have little wider arches than organgutan's Canines exhibit sexual dimorphism - male have heavier, longer and more curved canines.
  34. 34. The 'gracile' Australopithecines         Walked upright Small brains, cranial capacity of about 450 cc. Large protruding faces. Were highly dimorphic; male about twice the size of females. Dental features are intermediate between those of apes and modern humans. Arcade is omega shaped, intermediate between the box row and the parabolic curve in humans Lower first premolar has two cusps. Design of dentition being more effective for grinding.
  35. 35. The 'Robust' Paranthropus group      First identified by Robert Broom More sturdier Molars are enormous Lower jaws is very large The entire skull has been reorganized to accommodate the massives chewing apparatus.
  36. 36. Homohabilis 'handy man' - 'Early Home' The evolutionary trend towards:  relatively greater cranial capacity, i.e. about 600-650 cc.  orthognathy,  dental reduction,  greater body size, which had begun in H.Habilis, continued in its descendants.  Associated with stone tools.
  37. 37. Homo Erectus 'upright man'       thick cranial vault Cranial capacity of about 850 cc. prominent browridges and the sagittal keel sizes of the posterior teeth are decreased while anteriors are larger than modern humans upper central incisors are distinctively shovel shaped.
  38. 38. Neandertals, often called 'Archaic Ruggedly built, and short Homosapiens' stocky bodies        Developed skilled stone tool technology Had larger brains Skull had characteristic presence of an occipital 'bun' at the rear end. Have large canines and incisors relative to their molars and premolars Dentition as a whole is placed forward relative to the skull vault, because of this anatomical change - the retromolar space is seen. Frequent feature was taurodontism.
  39. 39. Homosapiens 'Wiseman'       Anatomically modern Homosapiens first appeared 100,000 years ago Skull is high and well rounded Orthognathic face Modern humans have small faces tucked under enlarged brain cases Cranial capacity increased to about 1300 cc. Teeth progressively reduced in size, concurrent with the reduction of masticatory apparatus.
  40. 40. Evolution of human face  In a typical non primates :dog ,sheep or hedgehog ,the facial skeleton projects in front of cranial region of skull.
  41. 41.  During primate evolution facial skeleton bent gradually more downwards until in man it lies below the overhanging frontal region of cranium.
  42. 42.  Erect posture in humans.  The arms and hands have become freed. The manipulation of food and other objects and defense, offense, and so forth, utilize primarily the hands, rather than the shortened jaws.
  43. 43. The large size of the human brain also relates to a rotation of the orbits toward the midline. This results in a binocular arrangement of the orbits, a feature that complements finger-controlled manipulation of food, tools, weapons, and so forth. The absence of a long, protrusive muzzle does not block the close-up vision of hand-held objects
  44. 44.  Complete orbital rotation into a forward-pointing direction, however, has also caused a marked reduction in the interorbital part of the face.  This is significant, because the area involved is the root of the nasal region, and the result of man's close-set eyes is a narrow nose
  45. 45.  Reduction in nasal protrusion is accompanied by a more or less equivalent reduction of the jaw .
  46. 46.  The downward rotation of the olfactory bulbs and the whole anterior cranial floor by the enlarged frontal lobes of the cerebrum has caused a corresponding downward rotation of the nasomaxillary complex.
  47. 47.    Facial rotation has led to the development of the human maxillary sinus beneath the orbital floor and above the shortened maxillary arch . Because of its adaptation to facial rotation, the human maxilla is uniquely rectangular, rather than triangular like that of most other mammals. It is a distinctively shaped upper jaw. An orbital floor has also been added to the human maxilla because the middle and lower parts of the face have been rotated to a position beneath the eyes.
  48. 48. Evolution of jaws and joints   The first vertebrates did not have jaws. These are collectively referred to as the "Agnatha" (a=without, gnath=jaws), or jawless fish.
  49. 49.  Placoderms, an extinct group of early fishes, had 7 arches. The first arch was lost. Their new ‘first’ arch became the mandibular arch that formed jaws.  The upper half of the mandibular arch became the palatoquadrate cartilage, the lower half became the mandibular or Meckel’s cartilage.
  50. 50.  At about the same time in the fossil record there appears several major groups of fishes, Elasmobrancs, in these groups, the jaws were formed by components of arch #1 and #2. Arch #2 is called the hyoid arch (upper half = hyomandibular cartilage, lower half = hyoid cartilage).
  51. 51.    Amphibians In amphibians, the hyomandibular cartilage became the stapes in the middle ear. The hyoid apparatus supports the tongue and larynx. With the loss of remaining gill arches, associated dermal bones that connected the head to pectoral girdle were also lost creating an independent neck region.
  52. 52. Reptiles and the evolution of the secondary palate and middle ear ossicles    Reptiles invented the secondary palate that allows us to eat and breathe at the same time. The reptile line that led to mammals substantially increased bite force by ultimately redesigning the articulation of the jaw joint. This in turn led to the development of the malleus (hammer) and incus (anvil) ossicles in the middle ear.
  53. 53. The secondary palate     Fish have good noses. They smell by passing water through a loop located on their snout and extract dissolved oxygen. The loop does not connect to the mouth cavity. The lobe finned fishes (Sarcopterygii) breathed atmospheric oxygen. One of the consequences of air breathing is that the olfactory loop became redirected. Instead of exiting back to the outside environment, the loop turned and entered the anterior margin of the mouth cavity, forming the internal nares. Thus, these fish could breathe by bringing the tip of their snout to the surface.
  54. 54.   Amphibians inherited this anatomy. Because the internal nares are at the anterior margin of the mouth, amphibians have to hold their breath while they eat. Amphibians can use cutaneous gas exchange until the prey is swallowed.
  55. 55.       Reptiles, with their hardened, dry skin do not have that luxury. Any reptile that did a better job of eating while breathing would be favored by natural selection. Over evolutionary time, the fossil record shows a second shelf of bone forming across the roof of the mouth. First the premaxilla bone, then later, the maxilla bone, then finally the palatine bone all extended a shelf from each side of the jaw and met in the middle. This shelf formed a separate passage for air from the external nares. Over time, the internal nares entered the mouth further and further toward the throat. This shelf is the secondary palate. We know it in humans as the hard palate.
  56. 56. Evolution of TMJ    In reptiles generally, including the now extinct early synapsid reptiles that gave rise to mammals, the jaw joint is formed by the articular (lower) and quadrate (upper) bones. The joint was a simple hinge at the posterior of the jaw. The jaw closed putting even pressure along its margin therefore, the force exerted on the joint was in proportion to the bite pressure.
  57. 57.      In mid to late synapsid reptiles, the dentary bone (lower jaw) increased in size as muscle and bite force increased, but force on the joint decreased. This was because muscle insertion points shifted to allow greater jaw mobility. The looser the joint became, the more control synapsids had over specialized processing of food along regions of the jaw margin. The articular and quadrate bones at the jaw joint became smaller and more loosely associated with the dentary. The coronoid process of the dentary bone formed to accommodate these changing forces.
  58. 58.  Ultimately, the jaw joint shifted from a articularquadrate joint to a dentary-squamosal joint.  The condyloid process formed to create a new articulating surface.
  59. 59.   Freed from jaw mechanics, selection pressure favoring perception of sound took the evolutionary opportunity of the articular and quadrate bones adrift at the margin of the jaw joint and incorporated them into the middle ear. The articular became the malleus (hammer) and the quadrate became the incus (anvil). Humans, and all mammals, have these bones to this day.
  60. 60. Functional adaptation of TMJ in various species.     In carnivora : They mainly shear the food. The condyle is almost on a level with the lower teeth. The condyle is much more rounded and shorter in A-P direction. But the condyle is elongated and large in the transverse plane and is locked in a closefitting glenoid cavity which allows only a hinged movement of the lower jaw.
  61. 61. In Omnivora:   There is a slight lateral movement in the omnivorous species where the condyle is less firmly held in glenoid cavity. The temporal muscle is huge and the masseter is highly developed
  62. 62. In herbivora:    The condyle is broad, flattened and slightly convex and the glenoid cavity is shallow to permit much free movement in all directions. They mainly grind the food. So it has a strong pterygoid muscles, i.e. the lateral pterygoid muscles and medial pterygoid muscles.
  63. 63. EVOLUTION OF HUMAN MOLAR OR TEETH  Six main theories : 1) Concrescence theory 2) Cingulum theory 3) Kinetogenetic theory 4) Tritubercular theory 5) Multitubercular theory 6) Dimer's theory
  64. 64. Concrescence theory : Ameghino, Rose and Kekentha  Given by  Mammalian teeth were developed from simpler cones (Haplodont teeth) and the modern multiple -cusped teeth are formed by the fusion of 2 or more of these simple haplodont teeth into a compound tooth.  This might be due to - shortening of jaws, uniting the teeth of the same series or by a fusion bucco-lingually, uniting the teeth of one series with those of their successors.
  65. 65. Cingulum theory  Mammalian tooth is derived from haplodont tooth.  "Marrett Tims" considers that basal ridge or cingulum, with surrounds a tooth at its neck, develops into a fresh cusp or cups- which explains to a great extent the evolution of complex tooth form.
  66. 66. Kinetogenetic theory  Ryder, who upholds this theory, again regards the earliest mammalian teeth as haplodont in origin.  He mentioned that the movements of TMJ, govern the form of the tooth.  The simple cones become flattened by mutual pressure, and the ridge and hollows are produced by the movements of the lower jaw in mastication.
  67. 67. Tritubercular theory or Cope - Osborn theory  He considered that multicuspid mammalian are developed from a simple haplodont or reptilian form of tooth by the addition of extra cusps.  In this theory - original haplodont cone is known as the protocone  When this original cone has two small accessory cones on its mesial and distal surface and it is known as protodont tooth.
  68. 68.  These small accessory cones develop in size until the tooth consists of 3 cones in a straight line and this is known as triconodont teeth. Tooth anterior middle posterior Maxillary Paracone Protocone Metacone Mandibular Paraconid Protoconid Metaconid
  69. 69. mesial lingual distal Paracone Protocone Metacone Paracone Protocone Metacone Paracone Metacone Protocone Hypocone M-B cusp D-B cusp Trigon M-L cusp D-L cusp
  70. 70. Lower molar Mesial Buccal distal paraconid protoconid metaconid paraconid protoconid metaconid protoconid metaconid protoconid hypoconid metaconid entaconid hypoconulid
  71. 71. Finally lower molar M-B cusp Trigon D-B cusp M-L cusp D-L cusp Talon Distal cusp
  72. 72. Multitubercular (or polybuny) theory  Forsyth Major, refutes the statement that the 1st mammalian tooth can be traced back to a simple haplodont or a tritubercular tooth.  Forsyth Major considers that human molars and modern mammalian molar (whether tritubercular or not) are derived from multitubercular teeth by reduction in the number of tubercles.
  73. 73. Dimer theory  It is the result of investigation by Prof. Bolk of Amsterdam and advances the view that there is one origin for all mammalian teeth, whether, incisors, canine, premolars or molars.  Bolk's views are expressed under 4 headings : i) Hypothesis of triconodonty Hypothesis of dimery Hypothesis of concentration Hypothesis of equivalence ii) iii) iv)
  74. 74. i) Hypothesis of triconodonty -  mammalian teeth are evolved from a triconodont teeth, not a haplodont with one large and 2 small cusps in a straight line anteroposteriorly.
  75. 75. ii) The hypothesis of dimery :        Every mammalian tooth = two reptilian teeth. Labial and incisal portion of the incisors, canines and buccal cusps of premolars and molars = one series of reptilian teeth. Cingulum of incisors, canine and lingual cusps of premolars and molars = second or later series of reptilian teeth. Each longitudinal half of human tooth = monomere buccal half = protomere lingual half = deuteromere together form a dimerous tooth.
  76. 76. iii) Hypothesis of concentration :  The polyphyodont in reptiles is reduced to diphyodontism in modern mammals.  There is a concentration of the tooth germs of two reptilian teeth to form one mammalian tooth.
  77. 77. iv) Hypothesis of equivalence :    Elements of mammalian set of teeth are all morphologically alike. The terms monocuspidate and multicuspidate possess only a descriptive anatomical value and do not indicate any morphogenetic differences. The tooth germ of every tooth possesses the potentiality of developing all the cusps found in the most complicated tooth of set.
  78. 78. Butler's Field Theory  In 1939, Butler, an English paleontologist, proposed that the mammalian dentition can be divided into several developmental fields - incisors, canines and check teeth.  Within each field there is one tooth that is presumed to be the stable 'best copy' - i.e., "Key" tooth, the remaining teeth within the field become progressively less stable.
  79. 79.  Considering each quadrant separately, the molar/premolar field would consist of the first molar as the key tooth, the second and third molars on the distal end of the field, and the first and second premolars on the mesial end.  The theory predicts that the third molar and first premolar would be most variable in size and shape
  80. 80. Evolution of socket or attachment of teeth  Four methods of attachment of teeth in animal world: 1. Fibrous Hinged Ankylosis Gomphosis 2. 3. 4.
  81. 81. Fibrous attachment  Seen in sharks and rays.  The teeth are fixed by the means of fibrous bands to the submucosa of the fibrous membrane which covers the jaws.
  82. 82. Hinged attachment  Three main fishes have to be discussed as they have different types of hinge attachments. 1. Angler Hake Pike 2. 3.
  83. 83. Angler  This fish has 2 rows of teeth an outer anchylosed and inner hinged row.  A hinged tooth is supplied posteriorly by fibrous elastic ligament, while its anterior free edge rests upon a buttress of bone.  The teeth bent towards the throat, the hinge compresses and teeth return to their original positions upon the force being removed.
  84. 84. The hake i) ii)    Calcified elastic part of hinge which prolong downwards to the bone of attachment ii) Uncalcified fibrous part of hinge which lies in front of the calcified, elastic portion. - Between two part of hinge is a triangular area containing interlacing fibres - elastic in nature. - The labial edge of base of teeth thickened and rounded - adapted for resisting shock. - This edge is at higher level - than the lingual edge and fits upon a buttress of bone. So that tooth cannot be bent outward without injury to lingual hinge.
  85. 85. Pike  The hinged teeth of pike sit anteriorly on a small pedestal of bone - but posterior hinge does not possess elasticity.  In pike teeth (osteodentine) , the central trabeculae do not calcify but remain soft and elasticresponsible for returning the teeth to their erect posture when backward pressure is released.
  86. 86. Anchylosis attachment     When a tooth is fixed to the jaw by calcified tissue it is said to be anchylosed. There is no intervention of fibrous or uncalcified tissue. Eel fish : The teeth of the Eel rest upon little cylinder or cups of bone of attachment and is described as " Acrodont anchylosis". Here dentinal tubules do not fuse with bone of attachment, but little fibrous "annular ligament" surrounds the base of tooth and allows a slight movement.
  87. 87. In Mackerel  Teeth are slung up between the plates of the jaws by means of osseous trabeculae which pass between the inner sides of the alveolus and outer sides of teeth, the bases of latter resting upon nothing hard, the attachment is pleurodont.
  88. 88. Gomphosis (attachment in sockets)  Seen in man, mammalia, reptiles and in some fish eg :saw fish, pristis.  In man, mammals and crocodile, a membrane (alveolar dental membrane) exists between the tooth and the socket of bone in which the tooth is situated.
  89. 89. Our field exists today due to excellent remodeling capacity of the PDL and alveolar bone in gomphosis type of attachment
  90. 90. Orthodontic aspects of dental anthropology
  91. 91. What is anthropometry ?  Anthropometry is a division of anthropology,it has been described by Hrlicka as the systemized art of measuring and taking observations on man ,his skeleton , his brain or other organs, by the most reliable means and methods and for scientific purposes.
  92. 92. Method of holding sliding caliper method of holding spreading caliper
  93. 93. Head height measurement
  94. 94. Face height measurement
  95. 95. Head length measurements
  96. 96. Head breath measurement
  97. 97. Face width measurement
  98. 98. What is craniometry ?  Craniometry, a subdivision of anthropometry, has been an important study in orthodontic research ,because orthodontics is concerned primarily with the correction of morphologic deviations from the accepted norms in dentofacial area.  Measurements of the extent of these deviations entails some knowledge of physical anthropology and the ability to recognize and use the anthropologic landmarks.
  99. 99. Indices in anthropology Cephalic index
  100. 100. Index of skull height [profile] basion – bregma height max. cranial length    Chamecephalic Orthocephalic Hypsicephalic < 69.9 70 – 74.9 > 75 X 100
  101. 101. Skull height [frontal] basion – bregma max. cranial breadth Tapeinocephalic  Matricephalic  Acrocephalic  X 100 < 91.9 92 - 97.9 > 98
  102. 102. Facial index
  103. 103. Palatal height index Given by Korkhaus.  Palatal height X 100 posterior arch width  Normal value is 42 in mixed dentition   39.3 51.3
  104. 104. Rivet’s angle  Nasion – prosthion – basion angle.  Prognathous < 69.9 Mesognathous 70 – 72.9 Orthognathous > 73.  
  105. 105. What is Orthodontic odontometry?  The anthropologic science of measuring the size and proportion of teeth is called odontometry.  Orthodontists practice some form of odontometry as a part of routine case diagnosis.  Traditionally, orthodontic odontometry has been limited to the determination of the amount of dental arch space deficiency.
  106. 106. Crown Shape   In some odontometric studies, crown shape has been found to be a determining factor in the presence and absence of mandibular incisor crowding. MD Crown shape = ------- ratio FL
  107. 107.  The maximum limit of desirable index values for lower incisors are 88-92 for the mandibular central incisors 90-95 for the mandibular lateral incisors.  Lower incisors within or below the ranges is considered favorably shaped.  Any lower incisor with MD/FL index above these ranges, possesses a crown shape deviation, which contribute to crowding phenomenon.
  108. 108. Clinical implication:  The relationship between tooth shape and lower incisor alignment is important in mesiodistal enamel's stripping or reproximation.
  109. 109. Overall and anterior intermaxillary ratio [Bolton]
  110. 110. Winged incisors      A peculiar arrangement often seen between central incisors, both maxillary and mandibular, was first reported by Leigh in 1926. Called incisor winging by Dahlberg. Characterised by mesiolinguo version of the central incisors creating a v-shaped notch in the arch at the midline. Noted in Mongoloid dentitions. Show unfavourable prognosis for permanent orthodontic correction.
  111. 111. Shovel shaped incisors  Present another variation of incisor morphology.  Prominence of the mesial and distal marginal ridges enclosing the central fossa in the lingual surface of incisor teeth.  Often present a problem in overjet correction.  In such cases, reducing the prominence of the marginal ridges is helpful.
  112. 112. Theory of Overbite     Overbite is present in greatly varying degrees among modern populations. Primitive people, past and present, tend to display edge - to edge anterior bite (labidonty) or at most, slight scissor bites (psalidonty) of less than two millimeters. Overbites in excess of two millimeters are largely limited to those living in relatively civilized environments. It is generally reasoned that overbite has accrued among the civilized because substantial tooth wear is no longer present to compensate for natural incisor eruption.
  113. 113.     Another insight into the origins of overbite in man has been suggested by Brace and Mahler in 1971. They observed that overbite was widely expressed among Europeans only after the Middle Age. At that time, also the table fork was introduced in Italy and aimed popularity in Europe. The personal fork and knife took the functions of holding and shearing food away from the incisors. Protrusive function, essential to the holding and shearing process, swiftly became obsolete, and deep overbite and its related occlusal deviations have since proliferated unchecked.
  114. 114. Buccal segment reproximation     The orthodontic community has known about natural tooth wear, largely through the work of Raymond Begg on the Australian aboriginal population. All teeth become smaller mesiodistally as they wear down with age. The contact areas between become flatter and broader. The mesiodistal enamel reduction of all permanent teeth in the developing adolescent dentition would be a method to produce artificial tooth wear mimicking the natural wear pattern of primitive population.
  115. 115. The Carabelli Trait  In 1842, Carabelli gave his name to a frequently occurring tubercle on the lingual aspect of mesio lingual cusp (protocone) of the maxillary first permanent molar.
  116. 116.      Many theories have been advanced explaining the occurrence of the Carabelli trait. One holds that the Carabelli cusp has its origin in the cingulum, and numbers among its proponents Gregory (1922), Cope (1888), Osborn (1907), Adioff (1908), and Korenhoff (1960). A second school, led by Rose (1892) and Baufjeiff (1896),.claims that the Carabelli cusp arose as a separate tooth germ. The third group bases its rea-soning upon the "Dimer" theory of Bolk (1914) in calling upon a "tritomere" for the origin of the cusp. Other explanations are brought forth by individual authors such as Weidenreich (1937), who considered the Carabelli cusp an accidental variation" of the procone.
  117. 117.  It is indeed a most remarkable phenomenon in the history of biological research that so little is known about a structure of which so much has been written.  As Jorgensen rightfully points out that “our actual knowledge of the evolutionary and racial significance of Carabelli's cusp is quite disproportionate to the number of pages published about this structure
  118. 118. Conclusion    Variation in size, shape, number, arrangement, and wear pattern of the teeth of man has long been an area of great interest to physical anthropologists. It is important that orthodontist cultivates an anthropologists eye for tooth variation. Since the orthodontist ponders many of these same variables in his daily battle with malocclusion, many aspects of dental anthropology can prove helpful in understanding orthodontic problems and in formulating their successful treatment.
  119. 119. References         Dimensions of anthropology – vol.2; V.Rami Reddy. Dental anthropology – vol.1; V.Rami Reddy. Anthropology and modern human teeth – Scott and Turner. Human adult odontometrics – Julius A. Kieser. Anthropology and orthodontics – AO vol.67(1);1997,73 – 77. Harmonious anthropometric relationships – AO vol.31(1);1961,18 – 34. Dental variation among population – an anthropologic view – DCNA vol.19(1);1975,125 – 139. Orthodontic aspects of dental anthropology – AO vol.45(2);1975,95 – 102.
  120. 120.         Crown dimensions and mandibular incisor alignment – AO vol.42;1972,148 – 53. Stone age man’s dentition – AJO vol.40;1954,298 – 312. Begg orthodontic theory and technique – Begg and Kesling – third edition. An index to assessing tooth shape deviations applied to mandibular incisors – AJO vol.61;1972,384 – 402. Textbook of orthodontics – Salzmann. Color atlas of orthodontic diagnosis – Rakosi. Evolution Atlas, Chapter 6: The Skeletal System: Axial Division.(internet) Functional adaptation of jaw joint,Evolution atlas,the skeletal system;axial division(internet)
  121. 121. Leader in continuing dental education