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Developmental Morphology


									Developmental Morphology

      Charles J. Arcoria, DDS, MBA
1. Compare & contrast the dentitions of
   other vertebrates
2. Understand the trends or commonalities
   regarding tooth development
3. Know the various tooth and cusp forms
4. Know the various jaw outlines, arch
   constructs and positions
5. Relate human dentition form and
   function to other animals
6. Understand the structural and
   developmental morphology of molars
Arch Form Alignment & Terminology
                   Isognathous: equal-jawed or
                   symmetrical arch alignment

                   Anisognathous: unequal-jawed
                   or asymmetrical arch alignment

                   Humans have an arch alignment
                   that is considered “partially
Cusp Design in Vertebrates
                Bunodont: tooth-bearing
                conical cusps, exhibited
                in primarily carnivores

                Selenodont: crescent-
                shaped cusps, exhibited
                in primarily herbivores

                Humans have a primarily
                bunodont form that may
                change with age to a
                partially selenodont shape
Diet & Mandibular Movement in Vertebrates
                       Carnivorous: meat
                       ingesting, bunodont cusp
                       form, and vertical
                       mandibular movement

                       Herbivorous: plant
                       ingesting, selenodont
                       cusp form, and horizontal
                       mandibular movement

                       Omnivorous: plant and
                       animal ingesting,
                       primarily bunodont cusp
                       form, both vertical and
                       horizontal mandibular
Mammalian Phylogenetic Development
   Classification of Cusp Forms

          Haplodont: Single cone structure

          Triconodont: Three cusps in a straight

          Tritubercular Molar: Three cusps in a
          primary triangle

          Quadritubercular Molar: Four cusps in a
          rectangular or rhomboid form
Alligator Teeth & Skull

          Typical “Haplodont” or single cusp
         design. Arch movement is vertically-
            oriented with little or no lateral
                 movement exhibited.
     Barracuda Dentition

Haplodont design with a predilection toward some canine
Palatal Teeth on a Bowfin

            Haplodont design exhibiting
            multiple locations within the
                   arch structure
Seal Skull & Dentition Features

                       Large canines,
                      with very pointed
                      bunodont shaped
                       posterior teeth.
Dog Skull & Features



               >Multiple posterior
               teeth with
               bunodont shaped
       Additional Carnivores

     Both have large,
overdeveloped canines and
  multiple molars, with a
 primate space or “gap”
  between anterior and
      posterior teeth
Baboon Skull & Traits

                Omnivorous, with
                an orientation
                toward being
                vegetarians. Note
                the overdeveloped
                canines and
                bunodont cusp
Monkey Skull & Dentition Traits
                    Omnivorous, with a
                    strong predilection
                    toward being
                    vegetarians. Canines
                    are less developed
                    than exhibited in other
                    apes, but a bunodont
                    cusp design is seen.
                    Also note the
                    existence of 3
                    premolars in each
Chimpanzee Dentition & Traits
                   Omnivorous, with a
                   preference toward
                   being vegetarians.
                   Note the
                   overdeveloped canines
                   and bunodont cusp
                   design. Also note the
                   same number of
                   canines, premolars
                   and molars that
                   humans display.
Tritubercular Molar Cusp Theory

Haplodont   Triconodont    Tritubercular   Tritubercular   Quadritubercular
                                               Molar           Molar
 For this postulate, the tritubercular stage represents premolars
     while the tritubercular molar stage represents molars.
Note that the protocone and protoconid are the initial or primary
               bunodont cusps present in all stages
Humanoid Mandibular Molars

                                   Mesiofacial cusp = protoconid

                                   Distofacial cusp = hypoconid

                                   Distal cusp = hypoconulid

                                   Mesiolingual cusp = metaconid

                                   Distolingual cusp = entoconid

Note that the distal cusp (hypoconulid) is considered an accessory
  cusp in that a four cusp design mandibular molar excludes it.
   Paleontological vs.
Odontological Nomenclature
Talon Cusp Morphology
                            Talon structure on a
                           Maxillary Lateral Incisor

                                 Talon cusps or talon
                                    structures are
                                 secondary, accessory
   Talon cusp = distolingual           entities
   cusp of a Maxillary Molar
Trigon Primary Cusp Triangle

                   Primary cusp triangle
                      consists of the
                     Mesiofacial cusp,
                   Distofacial cusp, and
                   Mesiolingual cusp of
                     maxillary molars
Maxillary Molar Comparative Anatomy Nomenclature

  Detailed Paleontological Entities on the Maxillary Molar
Mandibular Molar Comparative Anatomy Nomenclature

  Detailed Paleontological Entities on the Mandibular Molar
Anterior Transverse Ridge on
   the Maxillary 1st Molar

          Anterior Transverse Ridge is exhibited
          only on Permanent Maxillary Molars and
          is confluent with the mesial marginal
          ridge, obliterating much of the mesial
          triangular fossa.
Tuberculum Intermedium on
  the Mandibular 1st Molar
                The Tuberculum
                Intermedium is exhibited
                only on permanent
                mandibular molars and is
                considered an
                of either the distal cusp
                ridge of the mesiolingual
                cusp or the mesial cusp
                ridge of the distolingual
Sextum Tuberculum on the
   Mandibular 1st Molar
                The Sextum Tuberculum
                is exhibited primarily on
                permanent mandibular
                first molars and is
                produced by an
                of the distal cusp ridge of
                the distolingual cusp
Primate Dentitions
          All of these examples display
          the I = 2/2, C = 1/1, P = 2/2,
           M = 3/3 dentition formula
          The primary difference is
          exhibited in the size,
          shape, and occlusion of
          the canines

          Note the primate space
          between the Maxillary
          Lateral Incisor and
          Canines for the non-
          human species
 Maxillary First Molar
Primitive Cusp Names

MF cusp = paracone; DF cusp = metacone;
ML cusp = protocone; DL cusp = hypocone
          Mandibular 1st Molar
         Primitive Cusp Names

MF cusp = protoconid; DF cusp = hypoconid; D cusp = hypoconulid
           ML cusp = metaconid; DL cusp = entoconid
The End

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