Occlusion for Partial Dentures

Question 1

What is occlusion?

Answer 1

the static relationship between the incising or masticating surfaces of the maxillary and mandibular teeth or tooth analogues (dentures)

Question 2

What is intercuspal position (ICP)

Answer 2

the complete intercuspation of the opposing teeth independent of condylar position, sometimes referred to as the best fit of the teeth regardless of the condylar position

• tooth position
• can change throughout life
• dependent on extraction and restorations

Question 3

What is retruded contact position (RCP)

Answer 3

guided occlusal relationship occurring at the most retruded position of the condyles in the joint cavities

• condylar position
• fixed throughout life (unless condylar fracture)

Question 4

What are index teeth?

Answer 4

contact facets of teeth in the intercuspal position

Question 5

What are the key facts about intercuspal position (ICP)?

Answer 5

• need sufficient index teeth
• stable occlusion
• may vary through life
• depends on tooth relationships
• sometimes more anterior than RCP

Question 6

What are the key facts about retruded contact position (RCP)?

Answer 6

• insufficient index teeth
• unstable occlusion
• most reproducible position
• condylar position
• sometimes more posterior than ICP

Question 7

When should occlusion be conformed to for partial dentures?

Answer 7

• where possible should always try to conform to the existing occlusion
• works best for stable occlusion with sufficient index teeth
• prosthesis should not alter the occlusion
• usually uses ICP

Question 8

When should occlusion be changed for partial dentures?

Answer 8

• when occlusion is unstable and lacks sufficient index teeth
• usually uses RCP
• more challenging to record occlusion

Question 9

How are study casts articulated when there are sufficient index teeth present?

Answer 9

• casts can be articulated together without the need for any formal recording of occlusion
• more accurate articulate by obtaining an inter-occlusal record

Question 10

What can be used to take an interocclusal record?

Answer 10

• bite registration paste
  
  • usually silicon based
• wax wafer
  
  • modelling wax
  • can distort relatively easily
• modified wax wafer
  
  • alminax (aluminium reinforced wax)
  • harder to distort
  • easier to mount on casts

Question 11

What different types of record block are available?

Answer 11

• wax
• wax with wire strengthener
  
  • especially for lower dentures
• wax on Co/Cr base
• wax on shellac base
  
  • useful for complete dentures

Question 12

How is occlusal registration recorded with record blocks?

Answer 12

once the record blocks have been adjusted to the appropriate dimensions, they should be stuck together with soften wax or bite registration paste, ensuring not to prop open the bite