Prosthodontics Flashcards
Definition of support ?
Resistance to occlusal directed forces towards the tissues.
Definition of retention ?
Resistance to vertical displacing forces.
Definition of indirect retention ?
Resistance to rotational displacement.
Definition of path of insertion ?
Path the denture takes from first making contact with the teeth to then being fully seated.
Definition of path of displacement ?
Direction of displacement during normal function.
Definition of bracing ?
Resistance to horizontal functional forces.
How do rests work ?
Transfer forces down the long axis of the tooth.
Requirements for rests ?
To be large and placed centrally (on midline) on the tooth to ensure forces are transferred down the long axis of the tooth.
Shouldn’t interfere with occlusion so tooth preparation or be careful with positioning.
How do clasps work ?
Terminal 1/3 of the clasp engages undercut - area below the maximum bulbosity of the tooth (0.25mm for CoCr).
Clasps should …
- Sit passively when in situ in the undercut to prevent stress on the tooth.
- Should be 15mm long.
Where are undercuts typically found on canines and premolars ?
Buccal or labial surface.
Where are undercuts typically found in maxillary molars ?
Mesial/distal buccal surface - depending on the tooth in question.
Where are undercuts typically found on mandibular molars ?
Mesial lingual surface.
What is the purpose of a major connector ?
- Join all components of a denture.
- Extension of connector aids bracing.
- Can provide indirect retention.
What is an RPI system ?
Stress relieving clasp system used on abutment teeth for free end saddles.
What is the purpose of an RPI system ?
Prevent torquing and tilting of the abutment tooth on a free end saddle.
What are the components of an RPI system ?
Mesial rest, proximal plate, I-bar gingivally approaching clasp.
What is the purpose of the I-bar clasp and proximal plate in the RPI system ?
Move downwards and forwards in compressive forces allowing saddle area to sink into undercut, reducing stress on the abutment tooth.
What is the requirements of the mesial rest in an RPI system ?
Should be rounded and prepared to allow rotation.
What are the advantages of an RPI system ?
- Prevent torque of abutment tooth during compression of mucosa and free end saddle.
- Protects PDL and ultimate tooth loss.
What are the disadvantages of an RPI system ?
- Creates windows for mesial rest which can cause food trapping.
- No limitation on free end saddle so can accelerate bone resorption.
Kennedy classification I ?
Bilateral free-end saddle areas.
Kennedy classification II ?
Unilateral free-end saddle area.
Kennedy classification III ?
Bounded saddle.
Kennedy classification IV ?
Anterior bounded saddle that crosses the mid-line.
Craddock classification 1 ?
Tooth borne i.e. Kennedy Class III or IV unless bounded saddle is >3 teeth (Craddock class 3).
Craddock classification 2 ?
Mucosa borne i.e. only full dentures.
Craddock classification 3 ?
Mucosa and tooth borne i.e. Kennedy Class I and II and inc. Kennedy Class III if saddle area is greater than 3 teeth.
