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Good occlusal practice in simple restorative dentistry - PowerPoint

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					      Principles of Occlusal
        Practice In Simple
      Restorative Dentistry

Dr Wael AL-Omari
 BDS;MDent.Sci.;Ph.D.
    Why Clinical occlusion should be
               studied?
-   Most dental treatments involve occlusal
    surfaces of teeth.
-   Avoid either over or under treatment.
-    Provide therapeutic and successful dental
    treatment for patients.
-    Reduce the risk of failure
The masticatory system is made up of:
 Teeth.

 Periodontal tissues

 Articluatory system
What is occlusion?
The Articulatory System:
-TMJ as the hinge
- Masticatory muscles as
 the motor
- Dental occlusion as the
 contacts
- Interdependent
 elements make a system
Articulatrory
system and
masticatory
system are
very
interrelated
and
interdependent
systems
                     Analysis of Occlusion
Occlusion is defined as : Contacts between the teeth when -
mandible is closed and when is moving.
Static Occlusion:-
I- Centric Occlusion:
-Maximum intercuspation
-It is how unarticualted models fit together
- It is the habitual bite
  - Significance : Occlusal forces directed axially.
II- Centric Relation:

- It is not an occlusion but a jaw relation that is
reproducible with or without teeth present.

- Described Anatomically, conceptionally and
  geometrically
-Defined as- The position of manidble to the maxilla
with the intra-articular disc in position, and during
closure on its hinge axis, that is with the condyles
maximally seated in their fossa (uppermost and
foremost) and the muscles are at their most relaxed and
least strained position.
Significance of CR record:
1- it is reproducible position with or without teeth present
2- If CR involves tooth to be prepared, better remove
  deflective contacts prior to preparation
3- When re-organizing occlusion at new vertical dimension
4- To distalize mandible to create space lingually for
  anterior crowns
5- If restoring anterior teeth and CR contact results in strong
  anterior thrust against teeth to be prepared
Freedom in Centric (Long Centric)   Sliding from CR to CO
Dynamic Occlusion
   Def.: Occlusal contacts during the mandibular
    movements relative to the maxilla.
   Mandible movements are guided by muscles, teeth, and
    TMJ.
   Posterior guidance = TMJ
    Determined by intra-articular disc and articulatory
     surfaces of glenoid fossa
   Anterior guidance = Teeth.
   Any teeth contacts during eccentric movements.
       Anterior Guidance
Classified into:
I- Canine guidance
II- Group function (contacts are shared by
several teeth on the working side)
 Group function vs working side interferences.

 More Ideal if anterior guidance on front teeth.
 Canine
 Guidance




Group
function
The Mandibular Movements are
influenced by:

1- Neuromuscular control:
   muscles and nervous system
2- Guidance system: TMJ and teeth
Function:
• Elevation (closing) of the mandible :
  Temporslis muscle (anterior fibers), masseter
muscle & medial pterygoid muscle.
• Retrusion of the mandible: Temporalis muscle
(posterior fibers).
• Protrusion: Right and left lateral pterygoid acts
together, medial pterygoid
• Opening the mandible: Digastric and Inferior
pterygoid.
 Neural Pathways
-Mandible is controlled by voluntary movements and reflexes.

- Jaw-closing reflex: protects mandible and associated structures during violent
  whole body movement.

- Jaw-opening reflex: protects the teeth during sudden mastication of a hard
  object and protects lips, cheeks and tongue during mastication.

- Central and autonomic nervous systems receive input from peripheral
  receptors, higher centres and propioceptors.

- Propioceptors are located in deep muscles and periodontal ligaments

- Any occlusal changes are sensed by the nervous system via the propioceptors
    Direction of mandibular movement

 The head of the condyle on the non-working
  side moves: forwards, downwards and medially.
 The angle of downwards movement is known
   as the ‘condylar angle’
 The angle of medial movement is known as the
   ‘Bennet angle’.
 Immediate side shift = Bennet movement
Balancing side.             Working side.
Condyle has downward path   Condyle pivots
                  Occulsal Interferences
  Any tooth to tooth contact which hamper or hinder smooth
  guidance in excursions or closure into CO.
  - Working side and non-working side and CR interfernces.

Significance:
-May result in
destructive
oblique forces
-May interfere
with TMJ
guidance
Occulsal Interferences in Centric Relation
Non Working Side Occulsal Interferences
Protrusive occlusal interference
Ideal Occlusion:
1- The coincidence of CO
and CR,with freedom in CO
2- When mandible moves
   there is immediate and
lasting posterior disocclusion
Significance:
1- Pretreatment record
2- Treatment of TMD
3- Conformative versus
  reorganized approach.
    Requirements of Stable Occlusion

1- Stable stops on all the teeth when the
condyles are in Centric Relation (CR).
                                 Centric Stops

Point contacts are on
lingual cusp tips of
maxillary posterior teeth,
buccal cusp tips of
mandibular posterior
teeth, central pits or
marginal ridges on
posterior teeth, incisals
of lower anteriors and
linguals of upper
anteriors.



                             Brian Palmer, 2004
Ideal bite
• Should have point contacts of the maxillary posterior
lingual cusp tips and the mandibular posterior buccal cusp
tips to the central fossa or marginal ridges of opposing
posterior teeth.
• Forces exerted on the posterior teeth should be directed
through the long axis of the teeth.
• ‘Normal’ buccal positioning of the maxillary buccal
cusps should be ‘outside’ or buccal to the mandibular
teeth.


           (Brian Palmer, 2004)
2- Disocclusion of posterior teeth in protrusive
   mandibular movements

3- Disocclusion of posterior teeth on the working side
   during lateral excursive movement.

4- Disocclusion of posterior teeth on the non-working
   side during excursive lateral movements

5- Coincidence between Centric occlusion and centric
   relation
Correct Excursive
Contacts Marked in
Green




 (Brian Palmer, 2004)
Possible signs of non ideal occlusion:
• Giggling and loosening of teeth.
• Migration and drifting with resultant open contacts.
• Excessive tooth wear.
• Non carious cervical notching (abfraction).
• Misalignment of affected teeth.
• Sensitive or tender teeth.
• Fracture and cracking.
• Recurrent fracture of restorations.
• Bone loss.
• Deviation of mandible on closure.
• TMJ dysfunction symptoms ????
• Tori could develop.
Recording of the occlusion
Two dimensional records of the patient’s
 occlusion:
 These rely on marking the static
  and dynamic occlusal contacts
  between the teeth and then
  describing those marks in writing,
  by diagram or by photograph.
 Using of articulating paper, foil,
  floss or shimstock
 The T-scan uses a computer
  program to analyse the relative
  hardness of the contacts between
  the teeth.
Maintain the pre-
existing occlusion
     General Recommendations
  EDEC (examine design, execute, check) Rule.          
 Examine and record occlusion at preoperative          
                                              stage.
Design where to place the point contacts on the        
                             restoration (tripodal)
  Remove heavy point contacts on the inclines          
                         and restoration margins
 Re-establish the preoperative occlusal contacts       
               at the same intensity and poitions.
   Avoid both static and dynamic occlusal         
contacts with the margins of the restoration

                           • Weakening of tooth by
                           deep or wide (>1/3
                           occl.surface) filling may
                           indicate a provision of
                           cast restoration

				
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