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List the componenets of a denture.
Saddles and artificial teeth
Connectors (major and minor)
What is a Kennedy class 1 denture?
Two distal extension saddles
What is a Kennedy class 2 denture?
One distal extension saddle
What is a Kennedy class 3 denture?
One bounded saddle
What is a Kennedy class 4 denture?
One bounded saddle that crosses the midline. Cant have any modifications.
What are two types of denture support?
Tooth support via rests
Tissue support (alveolar bone) via denture base
What are three types of rests?
Occlusal (molars and premolars)
Incisal (incisors, rarely used)
For distal extension saddles support may be from tissue support and tooth support via the abutment tooth. Where should an occlusal rest be placed on this abutment tooth?
On the mesial (ie away from the extension saddle to prevent pivoting)
For bounded saddles support may come from tissue support and tooth support via the abutment tooth/teeth. Where should an occlusal rest be placed on this abutment tooth/teeth?
For a distal abutment tooth the rest should be placed mesially, or for a mesial abutment tooth the rest should be placed distally. (ie close the the bounded saddle)
What are the different types of connectors? What is the definition of these?
Major and minor.
Major connectors link parts of the prosthesis on one side of the arch with the other side. eg lingual plate
Minor connectors unites the major connector with other parts of the denture. eg minor connector between an occlusal rest and lingual plate
List some different types of major connectors.
What is the desired type of major connector for the maxilla?
What is the desired major connector for the mandible if there is >6mm of space between gingival margin and the floor of the mouth? What if there <6mm?
Lingual bar if >6mm
Lingual plate if <6mm
What does a retainer do?
Resists outward displacement of the denture, away from the tissues along a defined path of insertion
What are two types of retainers?
Occlusally approaching (circumferential)
Gingivally approaching (I,T,L bars)
What limits how many retainers we can use?
Dont want to have too many as they act as plaque traps and make it difficult to take out.
Where is the ideal position for the retainer tip?
Where the undercut is most prominent.
What is reciprocation?
Proves stabilisation against the action of the retentive arm during insertion and removal
Where should a reciprocator lie with respect to the survey line?
It should be coronal to the survey line. If it is gingival it is a retainer.
Where should a retainer lie with respect to the survey line?
It should be 1/3 above, 1/3 on and 1/3 below the survey line.
What provides reciprocation for a circumferential retainer?
A circumferential retainer is self reciprocating
How is drawing a cobalt chrome denture different to drawing an acrylic denture?
You only draw the metal framework of a cobalt chrome denture. For an acrylic you draw the outline of the acrylic.
What is direct retention?
Direct retention is provided by strucutres that resist the displacement of the denture away from the tissue along the path of insertion.
What is an undesirable undercut and how are they dealt with?
One that will be crossed by a rigid part of the denture. They are blocked out.
What is a desirable undercut?
One that wcan be used for retention.
What determines if an undercut is desirable or not?
The location of it with respect to denture design.
What determies the path of insertion of a denture?
The abutment teeth, tissue contours and the angle set on the surveyor. Usually there will be a range of paths of insertion rather than being perfectly parallel.
How can you manipulate the position of undercuts?
By changing the path of insertion. This is done by altering the angle of the surveyor base.
What determines the amount of retention provided by a retainer?
The depth of the undercut and the flexibility of the clasp.
What property of a metierial determines the the depth of undercut it can withstand?
The flexibility of the material
What material used in dentures has the highest flexibility? What does this mean for the size of the undercut it can withstand?
Gold. It is the most flexible and can therefore tolerate the deepest undercuts.
What is indirect retention? What type of saddles depend on this type of retention?
Retention created by structures that are on the opposite side of the fulcrum line. Because they are on the opposite side of the fulcrum line, to provide indirect retention they must resist forces that push them toward the tissues. Distal extension saddles and curved bounded saddles.
What determines the fulcrum line for denture rotation?
It is the line between the two most distal retainers of a dentrue.
Which denture components can provide indirect retention?
Rigid parts of the denture base. eg lingual/palatal plates
What Kennedy classes always rely on indirect retention?
Classes I, II and IV. ie any class that has a distal extension saddle or a curved anterior bounded saddle.
What is the ideal location of an indirect retainer?
Half way between the two distal direct retainers and at right angles to the fulcrum line.
Why is it significant that teeth cannot be diplaced as much as mucosa when load is applied?
This means saddles that rely on tissue support will be displaced to a greater degree than abutment teeth. This places torquing forces on the abutment tooth that may lead to perio problems for that tooth.
What are some solutions to the problem of transferring damaging torquing forces to the adjacent abutment tooth from a saddle?
RPI system, the altered cast technique, stress breakers
Explain the components of an RPI system.
A mesial rest on the abutment tooth
An I bar
A distal proximal plate
How does an RPI system reducing torquing forces on the abutment tooth?
As occlusal force is applied to the distal proximal plate the abutment tooth is disengaged. The I bar directs force down the long axis of the tooth.
What is the altered cast technique?
It aims to record the mucosa at an already displaced level.
What is a stress breaker and what are the disadvantages of these?
A moveable hinge between distal extension saddle and denture base. Inherently less stable and increased ridge resorption.
What is the minimum reccommended number of occluding pairs in the oral cavity for industrialised countries?
10 occluding pairs
List the steps in construction of a removable partial denture.
Take primary impression and make study casts/occlusal rims
Take MMR (using occlusal rims if required)
Make special trays from study cast, articulate study casts and design denture
Perform mouth preparation (restorations etc)
Take secondary impressions using special trays and pour up master casts/occlusal rims
Take MMR (using occlusal rims if required)
Articulate working casts and set up teeth in wax
Wax try in
Primary and secondary issue of denture
what age does the permanent maxillary central incisor erupt?
What are the four stages of the eruptive phase?
What is leukopenia? What are the causes of leukopenia?
What happens when there is a decrease in extracellular K+?
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