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Lecture-5-Alignment-and-Occlusion by xuyuzhu

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									Alignment and Occlusion




         Charles J. Arcoria, DDS, MBA
Alignment and Occlusion
        • Dental Anatomy
        • Introduction to Occlusion
        • Characteristics of an “Ideal”
               Occlusion
        • TMJ Anatomy
        • Mandibular Movement
        • Alignment, Static & Moving
               Occlusion
        • Determinants of Occlusal
               Morphology
        •Articulators & Face Bows
      Importance of Proper
     Alignment & Occlusion
•   Efficient mastication of food
•   Speech & enunciation
•   Swallowing
•   Appearance
  Interdisciplinary Approach
 ORTHODONTICS        PERIODONTICS
      Implantology            Oral Pathology

Pediatric
               OCCLUSION OF        Cosmetic
Dentistry       THE TEETH          Dentistry


Prosthodontics         ENDODONTICS
      Public            Oral & Maxillofacial
      Health                  Surgery
   Anatomy & Treatment
“You cannot successfully treat
    dysfunction unless you
    understand function”
             Jeffrey P. Okeson


  “Nothing is more fundamental
    to treating patients than
     knowing the anatomy”
                    JPO
  Factors Influencing the
  Alignment of the Teeth
• Arch size
• Occlusal contacts (bite)
• Musculature
  – A facial-lingual
    equilibrium
• Oral habits
• Missing teeth
Intra-arch Alignment of Teeth
                            • “An imaginary
                             line that
                             extends from
                             the cusp tip of
                             the mandibular
                             canine along
                             the facial cusp
                             tips of the
                             posterior teeth
 Maxillary arch = convex     resulting in an
                             anteroposterior
Mandibular arch = concave    curve”
     Curve of Spee
Angulation of the Mandibular Teeth
            (Sagittal View)



                              SINGLE-ROOTED
                              TEETH
                               Incisors
                                Canines
                                Premolars

                       MANDIBULAR MOLARS
                        Mesial roots
                        Distal roots
   Angulation of the
    Maxillary Teeth
   (Sagittal View)
SINGLE-ROOTED TEETH
 Incisors
  Canines
  Premolars
FIRST PREMOLAR
 Buccal roots
   Palatal roots
MAXILLARY MOLARS
  Mesiobuccal roots
 Distobuccal roots
 Palatal roots
Intra-arch Alignment of Teeth

                    • “From the frontal
                     view, an imaginary
                     curved line
                     connecting the facial
                     and lingual cusps of
                     the posterior teeth”

                    • Maxillary arch =
                      Convex
                    • Mandibular arch =
  Curve of Wilson
                      Concave
 Angulation of the Mandibular Teeth
              (Frontal View)




SINGLE-ROOTED TEETH
 Incisors
  Canines
  Premolars

MANDIBULAR MOLARS
 Mesial roots
 Distal roots
   Angulation of the
    Maxillary Teeth
       (Frontal View)
SINGLE-ROOTED TEETH
 Incisors
  Canines
  Premolars
FIRST PREMOLAR
 Buccal roots
   Palatal roots

MAXILLARY MOLARS
  Mesiobuccal roots
 Distobuccal roots
 Palatal roots
 Plane of Occlusion aka
“Plane of Occlusal Curvature”




   Combination of the Curves of
         Wilson & Spee
     Plane of Occlusion
• A line is drawn connecting the buccal cusp
  tips and incisal edges of the mandibular
  teeth
• This is broadened into a plane to include
  the lingual cusp tips
• Plane extends across
  the arch to include the
  opposite side
      Plane of Occlusion
• The plane is not flat
• A flat plane will not permit a simultaneous
  function contact in more than one area of
  the dental arch
• A curved plane permits
  maximum use of tooth
  contacts during function
• Teeth are positioned in
  the arches at varying
  degrees of inclination
Occlusal Forces Applied
  to Posterior Teeth




               Fulcrum
Engineering & Biomechanics
“Nature has blessed us with a
    marvelously dynamic masticatory
    system, allowing us to function
    and therefore exist.”
             Jeffrey P. Okeson
 “The clinician managing the
     masticatory structures needs to
     understand basic orthopedic
     principles”
                   JPO
               THE LEVER
• Simplest to machines
  to gain a mechanical
  advantage
• Rigid bar that is free
  to rotate about a fixed
  point
• Fulcrum (fixed point
  of rotation)
• Effort (applied force)
• Resistance (load)
Class 1 Lever




Class 2 Lever:
Class 3 Lever:




         Fulcrum
Occlusal Forces Applied
  to Posterior Teeth




               Fulcrum
    Occlusal forces placed on posterior teeth are
intended to go up & down the long axes of the roots
    Cusp-Fossa Relationship of
         Posterior Teeth
             Max. L Cusps  Max. B Cusps
             Mand. B Cusps Mand. L Cusps
             CENTRIC       Non-Centric

B       L    Functional    Non-Functional

             Supporting    Guiding

             “Stamp”       Shearing
             Occlusal Relationship of
                   Posterior Teeth




1. Occlusal contacts should ideally occur between a cusp tip
   and the depth of a fossa, or between a cusp tip and a flat
   surface (more stable).
2. Contacts should not occur on cuspal inclines (less stable).
              Occlusal Relationship of
                    Posterior Teeth




3. Park your car on a flat surface or at the bottom of the hill (not
    on an incline) otherwise…
4. Muscles have to “brake” and become tired & overworked
5. Can lead to mobility, abnormal wear or fracture of teeth
        Static Occlusion
• MI contacts on
  inclines can lead to
  mobility, excessive
  wear, fractures &
  other signs and
  symptoms of
  occlusal disease.
             Abfraction

“A mechanism that explains the loss of dentin
   tissue and tooth enamel caused by flexure
  and ultimate material fatigue of susceptible
     teeth at locations away from the point of
  loading. The breakdown is independent of
     the magnitude, duration, frequency, and
               location of the forces”
Abfraction
           Static Occlusion
• Angle’s Class I
  Occlusion:
  – ML cusp of Maxillary
    1st molar occludes in
    the central fossa of
    Mandibular 1st molar

  – MF cusp of Maxillary
    1st molar occludes in
    the MF groove of
    Mandibular 1st molar
          Static Occlusion
• Angle’s Class I
  Occlusion:
  – Each tooth occludes
    w/ its namesake in
    opposite arch
  – No occlusion occurs
    in distal fossae of
    maxillary teeth
  – No occlusion occurs
    in the mesial fossae
    of mandibular teeth
         Static Occlusion
• Occlusal contacts
  should occur
  between a cusp tip
  and:
  – the depth of an
    opposing fossa
  – a flat surface such
    as a marginal ridge

• An occlusal contact
  should not occur on
  a slope such as a
  triangular ridge
Angle’s Classifications
 MAXIMUM INTERCUSPATION
Terminology Describing Tooth Position:

• aka Centric
  Occlusion (CO)
• Habit Bite, Habitual
  Occlusion, Habitual
  Centric
• Maximum
  Intercuspation
  (MI or ICP*)
  describes an
  occlusal relationship
                          * ICP = Intercuspal Position
MAXIMUM INTERCUSPATION
     What is Considered Ideal?




 Angle Class I
 Long axis force distribution
 Simultaneous contact of cusps
    Posterior tooth dominance
 Adequate Anterior Overlapping
       Static Occlusion
• Angle’s Class I
 Definitions:
Maximum Intercuspation (MI, CO or ICP):
     An occlusal relationship that is established when
     the maxillary and mandibular teeth are in
     maximum contact with one another (full occlusion).
Centric Relation (CR): A condylar relation-
     ship in which each of the the condyles:
      1. articulates with the thinnest avascular
              portion of the articular disc while….
      2. it is in its most stable anterior-superior position
               (as dictated by muscle tonus) against the
               slope of the articular eminence
   Centric Relation (CR)
    Thinnest avascular   Most stable anterior-superior position
         portion            against the articular eminence




Muscles, ligaments and joint unstretched
             and unstrained
          Initial CR Contacts




Initial CR tooth contacts occur between mesial inclines of Max.
           and distal inclines of Mand. Posterior teeth
        Ideal Tooth Position
• When the mandible closes and
  the teeth come into contact
  with one another:

 1. There is an ideal way for the teeth to
    contact in order to dissipate the forces
    applied to the teeth
 2. There is an ideal place for the condyle
    and disc to be situated in order for the
    muscles, ligaments and joints to be
    relaxed, unstretched and unstrained
          Slide from CR to MI
• Only 10-15% of the
  population have no
  CR to MI discrepancy
• After the first contact
  in CR, the patient
  continues to close,
  and the teeth come
  together more stably
  (MI).
• The condyles must
  move out of their
  most ideal position.
Functional Occlusion
        Occlusal Relationship of
            Anterior Teeth




“Overbite”

                           Horizontal and Vertical
                          Overlap from the Proximal
                           and Frontal Viewpoints
                         Posterior Teeth Dominate in
             “Overjet”
                          Maximum Intercuspation
        Occlusal Relationship of
            Anterior Teeth




“Overbite”

                             Maxillary arch wider than
                                 Mandibular arch
                            In MI, incisal edges of mandibular
                         anterior teeth occlude with the marginal
             “Overjet”    ridges of the maxillary anterior teeth
The End

								
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