OCCLUSION

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OCCLUSION

• Dental Anatomy Occlusion
• Dent 202

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Occlusion

• Definition
• The act of closure or being closed
• A static morphological tooth contact relationship
• Includes all factors concerned with the
  development and stability of the masticatory
  system and the use of teeth in oral motor
  behavior
• Includes the integrated system of functional
  units involving teeth, joints and muscles of the
  head and neck

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Concepts of occlusion

• Balanced occlusion
• Bilateral contacts in all functional excursions
• Prevent tipping of the denture bases
• Not necessarily existing in natural dentition
  because each tooth is a separate unit
• Intercuspal position
• Centric occlusion
• Concepts developed in relation to orthodontics,
  complete dentures and full mouth rehabilitation
• None are completely applicable to natural
  dentition

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Overview of primary occlusion

• Each tooth occludes with 2 teeth of the opposing
  jaw
• Exceptions
• Mandibular central incisor
• Maxillary second molar
• Occlusion is supported and made more efficient
  after eruption of first permanent molars
• Interdental spacing is important for future
  sufficiency of space in permanent teeth
• Probability of crowding in permanent teeth is
  related to the amount of interdental spacing in
  primary dentition

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Primary molar relationship

• Terminal plane relationship
• Flush
• 56 - Class I Angles molar relationship
• 44 - Class II Angles molar relationship
• Distal step
• Class II Angles molar relationship
• Mesial step
• A greater probability for Class I Angles molar
  relationship
• A lesser probability for Class III Angles molar
  relationship

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Primary molar relationship

• Factors influencing the effect of terminal plane
  relationship on Angles molar relationship
• Differential growth of the jaw
• Forward growth of the mandible
• Sufficient Leeway space to accommodate a mesial
  shift of the permanent molars
• Leeway space is the amount of space gained by the
  difference in the mesiodistal diameter between
  deciduous molars and premolars

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Permanent occlusion

• Anteroposterior relationship
• Incisors Class I, II, III
• Canine Class I, II, III
• Molars Angles Class I, II, III
• Faciolingual relationship
• Premolars
• Molars

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Incisal relationship

• Class I
• Class II
• Class III
• Overjet
• Reverse
• overjet
• Overbite

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Canine relationship

• Class I
• Class II
• Class III

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Molar Occlusal relationship

• Angles Class I
• Angles Class II
• Angles Class III

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Arch Occlusal relationship
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Curves of occlusion

• Curve of Spee
• Curve of Wilson
• Sphere of Monson

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Inclination angulation of the roots of the teeth

• Mandibular arch is wider than maxillary arch
• Each tooth must be placed at the angle that best
  withstands the line of forces brought against it
  during function
• If the tooth is placed at a disadvantage, its
  longevity may be at risk
• Anterior teeth are placed at a disadvantage

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Antagonists

• With the exception of mandibular incisors and
  maxillary third molars, each tooth contacts two
  antagonist teeth in the opposing arch
• Loss of one tooth keeps the adjacent tooth in
  contact with opposing antagonist
• Mesial or distal drifting into the space disturbs
  occlusal contact with antagonist teeth

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Centric stops

• Lingual cusp tips of maxillary posterior make
  contact with opposing fossae and marginal ridges
  of mandibular posterior teeth
• Buccal cusp tips of mandibular posterior make
  contact with opposing fossae and marginal ridges
  of maxillary posterior teeth
• Lingual cusps of maxillary posterior teeth and
  buccal cusps of mandibular posterior teeth are
  called supporting cusps
• Areas of occlusal contact that a supporting cusp
  make with opposing teeth in centric occlusion are
  centric stops
• The tip of that cusp is also a centric stop
• Knowledge of centric stops are important in
  restorative dentistry

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Movements away from centric occlusion

• Lateral
• Working side
• Non-working side
• In complete dentures
• Balancing side
• Non-balancing side
• Movement in TMJ
• Tooth guidance
• Group function
• Canine guidance
• Protrusive
• Incisal guidance
• Retrusive
• The most retrusive position is the centric
  occlusion in complete dentures