Simulation of occlusion in Restorative Dentistry

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Simulation of occlusion in Restorative Dentistry

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1.Fuctional of the Masticatory Organ
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1.Fuctional of the Masticatory Organ

• 1. chewing function
• 2. non-masticatory action verbal and non-verbal
  communication(facial musculature and the
  masticatory apparatus)

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1.1 Physiologic Function

• occlusion any contact between maxillary and
  mandibular teeth
• static occlusion tooth contact without
  mandibular excursion
• maximum intercuspation maximum interlocking of
  upper and lower cusps in static occlusion
• habitual occlusion the static occlusion a
  personss teeth normally assume.

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• Under normal circumstance, habitual occlusion is
  identical with maximum intercuspation and the
  most cranial mandibular position as determined
  manually by dentists and dental technicians when
  positioning diagnostic cast
• However, some patient are unable to achieve
  maximum intercuspation of mandibular and
  maxillary teeth either the habitual occlusal
  position does not correspond to maximum potential
  registration of the teeth rows, or diagnostic
  indicate different matching at maximum
  intercuspation

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• Centric relation(CR)
• the foremost, upmost and midmost position of
  both condyles given a physiologic condyle-to-disc
  relationship and physiologic load application to
  the tissue involved
• Centric occlusion
• when combined with maximum intercuspation,
  this centric condyle position
• centric contact position
• Initial tooth contact in the centric condyle
  position

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• hinge axis
• Fixed rotational axis involved in the opening
  and closing the mandible
• centric hinge axis
• The hinge axis determined in the centric
  condyle position
• hinge axis path
• Three-dimensional path of motion of the hinge
  axis in a skull-based coordinate system at the
  point of registration

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• Condylar path
• Three-dimensional path of movement of the
  condyle in a skull-based coordinate system
• protrusion
• Every ventral movement of the mandible
• retrusion
• Every dorsal movement of the mandible
• mediotrusion- movement of one side of the
  mandible
• mediotrusive side- toward the median plane
• laterotrusion- movement aways from the median
  plane toward the laterotrusive side

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• Bennett movement
• lateral shift in the laterotrusive condyle
• immediate side shift plus the angle measured
  in the horizontal plane between the sagittal line
  and a line connecting the starting point to each
  point on the mediotrusive path of the condyle
  i.e. the bennett angle
• Excursion of these mandibular movements in
  occlusion dynamic occlusion

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• Incisal guidance
• Dynamic occlusion between anterior maxillary
  and mandibular teeth only
• Canine-guided occlusion
• Guidance by canine only
• Group guidance
• gliding contact(dynamic occlusion) of several
  teeth at the laterotrusive side

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1.2 Pathologic Function

• Non-occlusion
• Lack of opposing contact and may thus
  involved single teeth, groups of teeth or entire
  sides of the dental arch
• Premature contact
• the tooth or group of teeth with first
  contact during jaw closure
• Condyle luxation
• movement of the condyle up to the articular
  tubercle and its retention in that position
• Condyle hypermobility
• self-repositioning form of this disturbance

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• Disc dislocation
• - all non-physiologic disc to-condyle
  relation
• - Partial or total
• - Non-repositioning or self-repositioning
• - May occur either at maximum
  intercuspation or during
• excursive movement

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• Non-physiologic mandibular movement
• 1. limitation
• any restriction of physiologic mandibular
  movement due to non-repositioning disc
  dislocation
• 2. Deviation
• shift of the incisal point during
  mandibular movement with a return to the median
  plane
• 3. Deflection
• the same disturbance with
  non-repositioning of the incisal point to the
  median plane

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2. Diagnostics and Restorative Therapy

• To avoid unnecessary occlusal disturbance as well
  as any iatrogenic damage or exacerbation

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2.1 clinical examination

• History
• Oral inspection
• Periodontal status
• Condition of teeth and elementary occlusion
  status
• Functional status of masticatory musculature and
  temporomandibular joints

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2.1.1 General History

• One element common to most initial examination
  records
• Mainly practical aspects and items of a general
  medical nature

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2.1.2 Special History

• Pain, complaints, therapeutic wishes
• Other discomforts in the cranimandibular and
  cranial area(valuable in diagnosis of functional
  disturbance)

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2.1.3 Extraoral Findings/Functional Analysis

• Inspection for unusual swelling and odors, the
  functional analysis

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• Are the movement involved in opening and closing
  the mouth asymmetrical ?
• Shifts to one or both sides with to the midline
  deviation
• Differentiated from shifts not followed by a
  return to the midline - deflection

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• Is the size of the oral aperture limited when
  intentionally opened?
• Determined whether rotation and translation of
  the temporomandibular joint are hindered
• General rule more than 38mm

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• Do cracking or rubbing noises occur in the area
  of the temporomandibular joints
• Differentiated as to their specific sound(rubbing
  or cracking), localization(left/rigt/bilateral),
  exactly when they occur during the particular
  movement(initial/intermediate/terminal) and the
  degree to which they can be influenced by
  specific application of pressure

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• Do asynchronous noises occur at gnathic closure?
• In both habitual and centric occlusion, premature
  occlusal contacts cause asynchronous closure
  noises

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• Is palpation of the masticatory muscles painful?
• the main chewing muscles m. masseter and m.
  temporalis anterior, digastric muscle(ventral,
  posterior) and the lateral pteygoid muscles

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• Is eccentric occlusion traumatic?
• Pronounced facets of wear been formed due to
  parafunction habits and possibly leading to loss
  of canine-guided occlusion?

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2.1.4 intraoral finding /Oral Inspection

• Oral inspection is openly and emphatically
  defined by US dentists as a cancer prevention
  measure
• function, sublingual space, buccal and
  pharyngeal space, soft tissue

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2.1.5 general Periodontal Finding
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2.1.6 Dental finding

• 1. Identification of carious lesions
• 2. Oriented occlusive pattern check(traumatizing
  contact)
• - check with thinnest occlusion, 8-10um thick,
  by having the patient make excursive and
  incursive movement
• -then making with a colored foil(red)
• -then preliminary centric contact can be
  detected
• -then habitual occlusion check(darker)

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2.1.7 Radiographic finding

• Bite-wing X-ray interproximal caries
• Check for findings from other source and
  tentative dagnosis

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2.1.8 Tentative Diagnosis

• Describes the situation of a positive screening
  result before the results of more specific
  testing are available

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2.2 Concept for resotrative therapy

• Dental technique used in treatment of
  functionally physiologic masticatory organs are
  also used in specific preliminary treatment of
  dysfunctonal masticatory organs and in subsequent
  intergration of functionally adapted restoration

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2.2.1 Indication for restorative therapy

• Indicate a probable dysfunction, no attempt
  should be made at restoration until a more
  specific examination
• Latent dysfunction at first be left as the
  patient has tolerated it in the past.
• the new restorations should be intergrated with
  an eye to functional harmonization

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2.2.2 Restoration Design

• When it comes to material processing, both direct
  and indirect filling techniques are available
• Direct fillings
• include surface area and depth of the cavity
• - restricted to a maximum of 1/3 of the
  occlusal surface
• Indirect fillings
• extensive defect and weaken individual cusp
• - should be shortened and capped to avoid
  fracture

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• Critical weakening of the clinical crown due to
  deep plastic filling or enlargement of the
  preparation to cover more than 1/3 of the
  occlusal surface justifies the indication for a
  cast onlay

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• Avoid both static and dynamic occlusal contacts
  with the margins of the restoration
• Broadened

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• Elastic deformation of the clinical crown and
  abrasion in dynamic occlusion by counterparts in
  the highs-stress posterior tooth area may also
  occurs.

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• purely occlusal restorations may fail due to
  secondary marginal defects, in patients with a
  tendency to bruxism
• cover and surround the entire occlusal surface
  with cast restoration

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• liberalocclusion concept (interrelationships in
  static occlusion)
• Harmonization of the habitual and centric
  condylar positions.
• In full dentition, matching of the hinge axis
  position in habitual and centric occlusion at
  given points(point centirc)
• Strict avoidance of premature contacts
• Desirable cusp slope support pattern for occulsal
  contacts dictates bipodal or tripodal support at
  these points
• Maxillary and mandibular incisors contacts should
  be as light as a feather

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• Dynamic occlusion
• 1. canine-guided occlusion resulting in
  disclusion of all other teeth
• unilaterally balanced occlusion an
  occlusion concepts with guidance of all teeth on
  the laterotrusion side resulting in disclusion of
  all other teeth
• 2. anterior tooth protrusive movements are not
  necessary initial
• 3. absolute freedom from interference is
  necessary at least within this narrow
  functional range

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• Requirements apply to restoration of posterior
  teeth with partial crown
• 1. within the framwork of therapeutic planning,
  evaluation of the interocclusal situation
  static occlusion, sufficient free guidance space
  in dynamic occlusion

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• Should avoidance of such balance contacts in
  dynamic occlusion lead to the loss of this
  support in static occlusion on the mediotrusive
  side, the therapeutic plan must include
  restoration of canine-supported occlusion

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• Balance contacts must be avoided entirely on the
  mediotrusive side

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• In posterior tooth preparations, sufficient
  amount of substance must be removed, in
  particular around the functional roof

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• C-contacts can be left out of consideration in
  static occulsion

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• In view of this situation, various authors have
  developed special wax buildup technique for
  additive programmed design of functional
  occlusal surface
• harmony occlusion by point-by-point matching
  of hinge axis position in habitual and centric
  occlusion(point centirc)

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• Wax buildup technique
• - by Thomas, Payne and Lundeen
• - modeling of steep-angle triangular ridges
• - it must be added that, using this method,
  interference free dynamic occlusion of the
  posterior teeth is feasible within narrow limits
  only

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• Biomechanical Wax Buildup technique(by Polz)
• - conventional triangular ridges off near the
  cusp tips and an additional backpack in the
  central third of the triangular ridges
• - counterpart cusp is supported in static
  occlusion by the highly convex backpaks

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• If. Loss of anterior and canine-guided occlusion
• - lateral bruxism, premature contacts between
  posterior teeth occur on the laterotrusive side
• - additional balanced contacts can be expected
  on the mediotrusion side
• avoid or eliminate these eccentric contact
  between posterior teeth with suitable new
  restoration designs
• Restoration of canine-supported occlusion

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2.3 Restoration-Material and Techniques
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2.3.1 registration and Transfer of Maxillary
Position

• If a change is necessary in the vertical
  dimension, require arbitrary hinge axis
  localization and skull based transfer of the
  maxillary position to the articulator

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Indication

• 1. determination of jaw position in centric
  occlusion
• 2. occlusion guidance splints and splints with
  adjusted occlusion
• 3. extensive restorations with bite-raising
  and/or other restoration of the vertical
  dimension
• 4. individual simulation of dynamic occlusion

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• If the arbitrarily localized hinge axis does not
  corresponding well to the axis mormally used by
  the patients, kinematic hinge axis localization
  is indicated(Rotography, axiography,
  condylography, pantography)

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2.3.2 Registration and Transfer of static
Mandibular Position

• As long as the current occlusal situation is to
  be retained and clearly match the model both
  before and after preparation, the restorations
  will not change static occlusion
• Required if the vertical dimension is to be
  change in the further course of treatment
  determination of jaw position in centric condylar
  position

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• When the bite position has been lost and/or there
  is evidence of static malocclusion, the
  mandibular model should be matched by means of
  jaw position determination in both habitural and
  centric condylar positions

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2.3.3 Registration and transfer of Dynamic
Mandibular Position

• Simulation of the dynamic movement of the
  mandible in eccentric position on the basis of
  values with individual registration in the form
  of eccentric positioning registration, or with
  graphic records
• Indication for calibration based on mean value
• - dynamic occlusion is undisturbed, no
  aggravating contacts are expected following
  treatment

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• Determination of jaw position relation in
  eccentric occlusion by means of eccentric
  position registrations (check bites)
• 1. canine-guided occlusion applies
• 2. unilaterally balanced occlusion(at least
  should not traumatically corrected)

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• Such a comparatively defensive indication aims
  to avoid unnecessary traumatization of the TMJ
  region

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• The Influence of correct simulation of the
  condylar inclination on the form of the resulting
  occlusal surface is comparatively greater than
  that of correct Bennet angle adjustment
• Besides providing a current record of eccentric
  positions, graphic records of excursive movements
  facilitate complete registration of the paths of
  movement

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• Proschel
• 15 change in condylar path inclination of the
  posterior dentition may results in a malocclusion
  of 0.5mm

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2.3.4 Simulation of Static and Dynamic Parameters

• Semi-adjustable individual articulator
• Skull-based transfer and mounting of the
  maxillary model using a facebow is necessary to
  achieve skull-based simulation of the maxillary
  position
• Individual simulation of dynamic occlusion
• condylar inclination and Bennett angle
• ( Arcon articulator eccentric positional
  registrations)

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• Additional retrusion setting simulation of the
  movement from habitual occlusion into the
  retrusion space
• Additional distraction setting compensation of
  a temporomandibular joint compression

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• Condylar position mesurment instrument Denar
  VeriCheck, SAM MPI, Panadent CPI, Artex/Reference
  CPM)
• --- 3-dimensional graphics and capable of
  metric evaluation

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2.3.5 Analysis of Finding and Documentation

• intrumental Registration Artex system
• Condyle movement posterior guidance
• Incisal Guidance anterior guidance given by the
  setting of the adjustable incisal block
• Condyle position the condylar shift from
  centric relation in habitual occlusion

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• Condyle movement
• - all recording related to posterior guidance
• - individual dynamic tracings and settings on
  condyle housing based on checkbites

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• Condyle position
• attachment of self-adhesive self-marking
  labels for transfering the recordings of condyle
  positions to the appropriate sites on the patient
  record