Prostetics Flashcards
What is support
Resistance to a vertical force directed at the mucosa
How can a denture be supported
- Tooth borne
- Mucosa borne
- Tooth and mucosa borne
How is support achieved on a tooth and mucosa bourne denture
Occlusal rest acts a tooth borne and the free end saddle acts as mucosa borne
How is tooth support gained
- Occlusal rests
2. Cingulum rests
Give examples of some mucosa borne dentures
- The every denture
- The soon denture
- the transitional denture
Describe an every denture
A denture with no occlusal rests and the whole thing is borne on the palate
Describe a soon denture
Is used as a temporary measure to replace a small number of teeth
Describe a transitional denture
Covers a large palatal area and touches the teeth
What is another name for a transitional denture
A gum stripper as it can lead to perio disease
What is a saddle
An edentulous area of the alveolar ridge
Saddles can be…
Bounded or free end
What is a bounded saddle
An edentulous area with a tooth on either side
What is a free ended saddle
An edentulous area with only ONE tooth on the mesial side
Which type of support is used on a bounded saddle
Tooth borne
Which type of support is used for a free ended saddle
Tooth and mucosa borne
What is retention
The resistance to a vertical force directed away from the mucosa
What is the path of displacement
The vertical force directed away from the mucosa
How is retention gains don a denture
By using clasps
What can a loose denture be caused by
- Lack of retention
- Bracing
- Support
Where is the retentive clasp placed
In an adequate undercut on the tooth
How do retentive clasps work
As the denture moved up the clasp expands
This residence to expansion holds the denture in
What is an undercut
The area under the survey line
What is the survey line
The maximum bulbosity of the tooth
Name the 2 different types of clasps
- Gingivally approaching
2. Occlusally approaching
What is Bracing
Resistance to a horizontal force
What is reciprocation
Resistance to specific horizontal forces generated by retentive clasps
What are the 2 main functions for the reciprocating arm
- Resists dentures moving horizontally
2. Prevents tooth being pushed into the PDL as the denture is taken in and out
What would happen if we didn’t put a retentive arm on our dentures
The tooth would move over a period of months
What is indirect retention
The resistance to rotational displacement in a tooth and mucosa borne denture
How is indirect retention achieved
By placing a rest perpendicular to the terminal hinge axis
What is the sulcus
A space that is created by impression materials between the tongue, lips and cheeks
Where should flanges extend to
Flange should extend to the functional depth
When are flanges said to be over extended
When they extend beyond the functional depth of the denture
What can happen if flanges are over extended
They are unstable in function. as the sulcus pushes the denture out
What can happen if flanges are under extended
They are unstable in function due to loss of suction
What is occlusion
The precise way in which the upper arch meets the lower arch
What do occlusal rests to
They act as tooth support and keep the clasps in position
Where do occlusal rests sit
They sit on top of the tooth and extend up to 1/3 of the occlusal surface
What do occlusal rests act on
The long axis of the tooth
how much horizontal depth is required for cobalt chrome dentures
0.25mm
How long must clasp be
15mm
Why do clasps have to be 15mm
So that it is flexible enough to be taken in and out of the undercut
Which teeth can’t we clasp with occlsuallt approaching clasps and why
we can’t clasp canines/premolars As the clasps require at least 15mm
What are guide places
Flat surfaces cut into the enamel of teeth which are parallel to the path of insertion
Which system do we need to use on lower free ended saddles
RPI
What does the RPI system stand for
media Rest
distal guide Plane
retentive I bar
What are connectors
They are th rigid component of the denture that holds all the other parts together
Name the 2 subcategories fro connectors
Major and minor
What do major connector do
Connect the left and right side of the denture
What do minor connector do
Branch from majors to various components
How do we classify saddles
Using the Kennedy class system
Name the different Kennedy classes
Class I, II, III, IV
What is a Kennedy class I
Bi lateral free end saddle
What is a Kennedy class II
Uni lateral free end saddle
What is a Kennedy class III
Bounded saddle
What is a Kennedy class IV
Saddle anterior to abutment teeth
Name the 4 principles of designing cobalt chrome dentures
- Avoid gingival overage as this promotes plaque accumulation
- Provide a denture with good support
- Make sure the connector is rigid to distribute the loads evenly
- Keep it simple
Name the 8 steps to designing cobalt chrome dentures
- Saddles
- Support
- Retention
- Bracing/ Reciprocation
- Guide planes
- Connectors
- Review points of design
- Review principles of design
Why might we decide to replace teeth
- Aesthetics
- Masticatory efficiency
- Prevent drifting and over eruption
- phonetics
Why might we decide against replacing teeth
- Plaque trap
- Trauma
- Patient tolerence
- Cost
Where do saddles extend to in the lower arch
Functional depth of the sulcus
As far back as the pear shaped pad
Where do saddles extend to in the lower arch
Functional depth of the sulcus
As far back as the hamular notch
Why do we extend the saddles as far back as possible?
To distribute the load over greater area
This is to decrease the pressure on underlying mucosa
Where do we look for support on bounded saddles
On the nearest surface of each abutment tooth
On lower free ended saddles where do we look for support
On the mesial side of the abutment tooth
Why do we look for support on mesial side of the abutment tooth on a lower free ended saddle
As it reduces the amount of torque on the abutment
Important on the lower arch as there is no palatal coverage to spread load
When deciding where to put a rest seat what must we consider?
Must make sure there is room in the occlusion for rest seat
What determines the retentive force?
The horizontal depth of the undercut
Which portion of a ring claps engages in the undercut
The terminal third
What can we do if the tooth we want to clap has no undercut
We can add composite
How big must our undercut be
0.25MM
What can happen is there is too much undercut
The posterior 2/3 will engage with the undercut resulting the clasp distortion and damage to the tooth
How can we remove undercuts
By cutting a guide plane or adding composite
Why might we want to place a guide plane?B
- For single path insertion
- For reciprocation on vulnerable teeth
- For indirect restoration
- To create a path of insertion hat is radically differ from the path of displacement
What must major connectors be able to do
Must be rigid enough to spread lateral forces across the arch
Name some connectors we can place in the upper arch
- Anterior palatal bar
- Mid palatal bar
- Posterior palatal bar
- Horse shoe
- Palatal plate
- Ring
When might a ring connector not be suitable
For free ended saddles as there is not enough coverage to spread load and create suction
Name some connectors we can place in the upper arch
- Lingual bar
- Sub lingual bar
- Lingual plate
- Dental bar
- Buccal bar
How much lingual sulcus depth do we need for a lingual bar
5MM
How much lingual sulcus depth do we need for a SUB lingual bar
8MM
Where is the denture bearing area in the lower arch
- As far as the external oblique ridge
- As far back as depressor anguli oris & depressor labial inferior
- Buccal shelf
Where is the buccal shelf
Portion between the alveolar ridge that remains after extraction & EOR
What do find in the lingual sulcus
The mylohyoid muscle & further back the retromylohyoid area
Where is the denture bearing area in the upper arch
- The buccal sulcus
2. The palate
Name the 4 different impression philosophies
- Muco displasie
- Muco static
- Differential pressure
- Functional
Which impression philosophy have we adopted right now
aim to be relatively muco static at rest
List some of the properties the materials we use to take impressions need to be
- Lowish viscosity
- Elastic
- Dimensional stability
- Hydrophilic
- Handling properties (decent working time, mixing time and setting time)
Name the different types of impression trays
- Ridgid acrylic tray
- Spaced fro lower pressure
- Perforated tray
What do we want our impressions to capture
- The teeth
- Extent of the denture bearing area
- Functional depth of the sulcus (where denture flange will be imposing)
- Oral mucosa at rest
- Good surface detail achieved
When recording the occlusion what are we aiming to capture
- The Spatial relationship between upper and lower arch
2. The position the technician should place the missing teeth
When do we conform to the original occlusion
- Patients with a stable ICP
2. When occlusal contacts are good
When do we rearrange the original occlusion
- When there is no occlusal stop
- The occlusal stops are unstable
- Advanced dentistry reason
How can we record the occlusion
- Hand articulated models
- Tooth borne registration
- Mucosa borne restoration
When is it suitable to use hand articulated models
stable ICP and teeth require no guide
What do you need to note down when using a hang articulated model
Points of contacts
What is tooth borne registration down with
pink beauty wax perfected with a blue mouse record
When is it suitable to use tooth borne registration
Need a good occlusal stop and good ICP to use this method
When is it suitable to use mucosa borne registration
Suitable when there isn’t a stable ICP on the cast & position of replacement teeth needs a guide
What is mucosa borne registration down with
We use a wax block and place blue moose over the top and get pt. to bite down
Out of the 3 methods for recording occlusion which one do we use
mucosa borne registration
How must the operator and patient be positioned when taking a lower impression
- Patient should be sat up right
- Mouth should be at elbow height
- Head should be supported
- Should have direct vision into lower arch
How must the operator and patient be positioned when taking a upper impression
- Hand on the right side of the patient
- Should be slightly retroclined (about 45 degrees)
- Use left hand to retract the cheek
How do we place a loaded tray into the mouth to take an impression
1, Insertion
2. Position
3, Seating
What steps do we need to take before taking a priory impression
Select the tray
Adapt the tray
Take an alginate impression
Name the different types of trays
Box tray
curved tray
when are boxed trays used
in dentate patients
When are curved trays used
For edentulous patients
