Occlusion Blocks in Dentistry

10 Questions

What is a common material used to make occlusion rims?

Pink modeling wax

What is the average height of the upper occlusion rim anteriorly?

22 mm

What is one of the uses of an occlusion rim?

Registration of jaw relationships

What is the name of the method used with modeling compound occlusion rims?

Graphic tracing method

What is the average distance from the lower sulcus to the incisal edge of the lower central incisor?

16 mm

What is the primary purpose of occlusion blocks in denture construction?

To record jaw relations and carry the occlusion rims

Which of the following is a requirement of a trial denture base?

It should be accurately adapted to the cast with proper extensions

What is the advantage of using resin temporary trial denture base over shellac base?

It provides a more accurate fit to the cast

What is the disadvantage of using permanent trial denture base?

It undergoes additional shrinkage on second processing when the teeth are added

What is the advantage of using metal bases in denture construction?

It is more accurate and hygienic with less porosity

Study Notes

Occlusion Blocks

Occlusion blocks consist of occlusion rims attached to well-fitting trial denture bases.
Uses of trial denture bases:
- Carries occlusion rims for recording jaw relations
- Carries teeth for the try-in stage
- Checks accuracy of the final impression

Requirements of a Trial Denture Base

Must be:
- Rigid
- Accurately adapted to the cast with proper extensions
- Dimensionally stable with minimal warpage
- Relieved from undercuts to avoid scraping the cast
- Clean and smooth for patient comfort
- Proper thickness (2mm in H.P.)
- Easy to construct

Types of Trial Denture Bases

Temporary trial denture base
Permanent trial denture base

Materials Used for Temporary Trial Denture Base

Hard base plate wax
Shellac base-plate
Cold curing acrylic resin
Swaged tin

Advantages of Resin T.D.B over Shellac Bases

Accurate fit to the cast
High strength
Dimensionally stable in the mouth

Materials Used for Permanent Trial Denture Base

Heat cured acrylic resin
Cast gold
Chromium-nickel alloy
Chromium-cobalt alloy

Advantage of Permanent Trial Denture Base

Gives good idea about extension, retention, and stability of the final denture

Disadvantage of Permanent Trial Denture Base

Additional shrinkage on second processing when teeth are added

Heat Cured Acrylic Resin (H.C.A.R.)

Advantages:
- Strong and rigid
- Control thickness during waxing up
- Minimizes dimensional changes
- T.D.B becomes part of the denture
Disadvantages:
- Time-consuming
- Need to construct mounting casts
- Warpage occurs during second processing to attach teeth

Metal Bases

Advantages:
- No acrylic warpage
- More strength
- More accurate
- Less tissue change under the base
- More hygienic (less porosity)
- Good thermal conductivity
- Less deformation in function
Disadvantages:
- Cost
- Difficulty in relining
- Time-consuming

Stabilization of Recording Bases

Additional stabilization required with temporary trial denture bases through relining with Zn & Eugenol impression material after adaptation of tin foil to the master cast

Occlusion Rims

Made of pink modeling wax
Uses of occlusion rim:
- Registration of jaw relationships
- Choice of artificial teeth
- Setting up of teeth
- Support for lip and cheeks

Dimensions of Occlusal Rims

Average height of upper occlusion rim anteriorly: 22mm
Average distance from lower sulcus to incisal edge of lower central incisor: 16mm
Posterior vertical height of maxillary occlusion rim: 6-8mm
Posterior vertical height of mandibular occlusion rim: equal to a point representing one-half the height of the retromolar pad
Labial surface of maxillary occlusion rim in central area: 8-10mm anterior to the incisive papilla
Mandibular occlusion rim from canine to canine area: inclined slightly forward but remains within the border of the recording bases