Lab 3- denture design part 1 Flashcards
Name the stages of designing a denture
- Saddle
- Support
- Retention
- Reciprocation
(5. Guide planes) - Connectors
What is the first thing you do when you are designing a denture
Outline the saddles
After outlining the saddles what do we need to identify
Is the denture:
tooth borne
tissue borne
or both
If the tooth is tooth borne what do we need to highlight on our design sheet
Occlusal rest
Cingulum rests
Where do we position on the rests on a bounded saddle
Use the nearest abutment tooth to the saddle
For a LOWER free end saddle where do we position the rest?
We use the furthest side of the abutment tooth
When placing our rests what do we need to consider
The occlusion - make sure occlusal rests don’t interfere with the occlusion
What can happen if a cingulum rest is sloping
It can have a tendency to push the tooth forwards
How do we want to place a cingulum rest
We want the rest seat to be perpendicular to the long axis of the tooth
How do we prep the tooth so that the cingulum rest is perpendicular to the long axis of the tooth
We can add composite onto the cingulum to ensure that the rest will be perpendicular to the long axis of the tooth
What does perpendicular mean
90 degree angle to
Why do we want the cingulum rest to be perpendicular to the long axis of the tooth
So that lateral force is directed downwards and doesn’t move the tooth from its original position
How can we add retention to a partial denture
- Clasps
- Adhesion/ cohesion of saliva
- Friction
- Accessory retention such as magnets
What do clasps require
Undercuts
how do we identify where undercuts are on a tooth
By surveying
What do we mark the survey line with
The SIDE of the surveyer lead
How do we orientate the lead when using the surveyor
We make sure the lead is perpendicular to the direction sticky food will pull the denture
What is a surveryer
A mechanical device that is used to identify where tissue and tooth undercuts are in the oral mucosa
What are surveyors used for
- Identifying undercuts for clasps
2. Identifying a path of insertion
What is the path of withdrawal?
The direction that sticky food pulls
How do we measure the horizontal depth of an undercut
Using pre measured gauges
List some materials we can use to make clasps
Cobalt chrome
Stainless steel
Gold
How much horizontal depth is needed for a cobalt chrome clasp
0.25mm
How much the horizontal depths needed for a Stainless steel clasp
0.5mm
How much the horizontal depth is needed for a Gold clasp
0.75mm
Why does cobalt chrome need less undercut
As it has a lower modulus of elasticity (it is stiffer) so needs less undercut
How can clasps approach the tooth
- Occlusally
2. Gingivally
Give examples of occlusally approaching clasps
- 3 arm clasps
2. Ring clasps
Give examples of gingivally approaching clasps
I bar
Name the 3 parts of a 3 arm clasp
- Retentive arm
- Reciprocal arm
- Occlusal rest
Where does the retentive arm go
Into the undercut so below the survey line
first 2/3 will be above the undercut and terminal 1/3 in undercut
Where does the reciprocal arm go
Above the survey line
Do we put 3 arm clasps on a molar
no as the clasp is too short
How long does the retentive arm need to be
15mm
What can happen If the retentive arm is too short
The material will stretch beyond its elastic limit and break
What are the advantages of gingivally approaching clasps
- More aesthetic
- Can be made longer than occlusal approaching clasps
- Can be used for pre molars and canines
What are the disadvantages of gingivally approaching clasps
- More damaging to periodontal health
2. Non undercut buccal surface may need to be built up first with composite
How can we manipulate undercuts
By adding composite (this can add or remove undercuts)
What happens to a patients smile/lip line as you get older
Lip line get lower so you can see more of the lower teeth
Ideally which teeth do we want to clasp
The closet teeth to the saddle
How many claps will give us maximum retention
One clasp on either end of the saddle (2 in total)
Other than saddles what else do we need to support
Extra components such as rests placed on teeth away from the saddle
What factors do we consider when choosing a clasp
Depends on:
- Undercuts
- Aesthetic demand
For molars what type of clasp do we sully choose?
Occlusally approaching clasps
Why do we choose occlusal approaching clasps for molars?
As they can be long enough and dont cover and gingival margins
For premolars what type of clasp do we choose?
Gingival approaching eg I bat
Why do we choose occlusal approaching clasps for molars?
They are long enough and more aesthetic
For premolars what type of clasp do we sully choose?
Gingival approaching eg I bat
Why do we choose Gingival approaching clasps for canines?
They are long enough and more aesthetic
What is the path of withdrawal
The direction sticky toffee wants to pull the denture
What is bracing
Resistance to lateral movement
List some potential functions of a connector
- To join one or more saddles together
- To provide rigidity to the design
- To provide support
- To provide bracing
List the major connectors we can use in the lower arch
- Lingual bar
- Sub lingual bar
- Lingual plate
- Dental bar
- Buccal bar
List the major connectors we can use in the UPPER arch
- Plate
- Post, middle and anterior bar
- Horeshoe
- Ring
Name the most common major connector we use in the lower arch
Lingual bar
What is a lingual bar made from
A prefabricated blank pattern
What are the disadvantages of a lingual bar
Offers no support or direct retention
What do we need to ensure we have before placing a lingual bar
Need minimum of 4mmx2mm to have sufficient rigidity
3mm gingival Clarence needed + 4mm height of bar
How much space do we need vertically to place a lingual bar
At least 7mm
What do we need to ensure we have before placing a sublingual bar
4mmx2mm
3mm gingival Clarence and 2mm height
How much space do we need vertically to place a sublingual bar
5mm
What are the disadvantages of a sub lingual bar
Offers no support or retention
Needs careful impression technique!!!
What is better sublingual or lingual bar
Sub lingual as they sit more comfortably in the patients mouth
What is an advantage of a lingual plate
Give support and indirect retention
What is an disadvantage of a lingual plate
Gingival coverage is detrimental to oral health
Needs to be supported by teeth at both ends
