L3 Jaw relations Flashcards
What 2 types of position of the mandible are recorded in dentistry?
- Tooth determined positions
- Condyle determined positions
What are the two approaches to occlusion in restorative dentistry?
- Conformative occlusion: sufficient teeth for a stable bite, or no need to change the bite. Determined by tooth position. Prostheses conform to pre-existing occlusion.
- Reorganised occlusion: prostheses designed to fit a new or reorganised occlusion, based on condyle position. Challenging to record. For patients with a lack of contact points or edentulous.
What needs to be recorded for the conformative approach?
Static and dynamic occlusal contacts (tooth positions)
Need to ensure that these contacts remain the same after the denture has been fitted
When may hand articulation of casts be appropriate?
- Where there are sufficient tooth to tooth contacts, many teeth present and stable maximum intercuspation
- Conformative approach
- Usually used alongside other technique e.g. bite registration paste, partial wax occlusal rim
How is bite registration recorded?
- Using an addition cured cilicone (polyvinyl siloxane)
- Very stable material
- High accuracy
- Do not overload mouth with material
How is a partial wax occlusal rim performed?
- Wax rim placed into space
- Used for partial denture
- Used in addition to bite registration and hand articulation
What are the important points to remember with regards to the reorganising approach?
- There is no tooth determined occlusion
- There is no vertical reference point so the vertical dimension has to be estimated
- There is no horizontal reference point, so the condyle position is our only reference
What issues may arise for a patient with a denture resting on the mucosa?
- Reduced proprioception
- Dentures can be displaced easily
- Resistance to horizontal forces is reduced
- Ability of denture to withstand occlusal load is reduced
- Soft tissue trauma becomes common
What should be our main aims when reorganising the occlusion for a denture?
Ensure:
- Minimal displacement of the denture in function
- Minimal loading of soft tissues
- Maximum chewing efficiency
What are vertical jaw relations?
The position of the mandible in relation to the maxilla.
What are the 3 vertical jaw relation measurements?
- Resting vertical dimension: person seated at ease, upright, muscles relaxed and teeth not in contact
- Occluding vertical dimension: teeth in contact
- Freeway space: RVD-OVD, the amount by which teeth are separated, 2-4mm is ideal
What factors affect the resting vertical dimension?
- Stress/pain will make a patient tense
- Position of the patient and gravity
- Posterior oral seal (want a seal, place denture or occlusal rim in mouth for accurate RVD)
What factors affect the freeway space?
- If dentures are worn for many years and not maintained, OVD will reduce due to alveolar resorption and occlusal wear
- Average of 7mm of reduction in OVD over 7 years, RVD also reduces but to a less degree
- Ultimately, FWS reduces over time
- Loss of teeth, loss of proprioception encourages the mandible to take a more protrusive position
What is centric relation?
- Relationship of mandible to maxilla
- Condyles in the most anterior, superior position in the glenoid fossa
- A clinically useful, repeatable reference position
What is centric occlusion?
- The occlusion of the opposing teeth when the mandible is in centric relation
- With complete dentures or partial dentures with no tooth-tooth contacts, we aim for CR=CO
Otherwise, teeth would slide from CR to CO, and would mean the denture rubbing the underlying mucosa when the teeth come together.
