Bds2 Revision Flashcards
(29 cards)
What is support?
Resistance of the denture to the occlusally directed load
What are the 4 Kennedy classifications?
Class 1 - bilateral free end saddle
Class 2 - unilateral free end saddle
Class 3 - unilateral bounded saddle
Class 4 - anterior bounded saddle across midline
What is retention?
Resistance of the denture to vertical displacement (away from tissues)
What components of RPD provide support?
Rest seats (tooth support)
Mucosal support
What are the 3 types of retention and how are they achieved?
Mechanical - clasps
Muscular - shape of denture to allow control eg enough room for tongue
Physical - mucosal coverage
How are clasps successfully retained?
Clasp flexes over the maximum bulbosity of the tooth into the undercut (this force is greater than the force dislodging the denture)
What is the minimum undercut and length for cobalt chrome clasp?
Undercut - 0.25mm
Length - 15mm
What is the minimum undercut for a gold clasp?
0.5mm
What is the minimum undercut for a stainless steel clasp?
0.75mm
What are the components of an RPI?
Occlusal Rest (R)
Distal guide Plane (P)
Gingivally approaching I bar clasp (I)
What is indirect retention? And how is it achieved?
Resistance to rotational displacement of the denture .
Clasps engage with rotational displacement, resulting in rests acting as a point of pivot.
Therefore move the point of pivot further away from clasp axis by using components which usually provide support.
eg. Cingulum rest on canine/ lingual plate
Why is an occlusal rest recommended where placement of clasp?
To prevent the clasp sinking towards gingival margin
Which part of the clasp engages in the undercut?
Terminal third
What is reciprocation and why is it important?
Addition of a component to the opposite side of clasped tooth to resist horizontal load (or clasp can act as ortho appliance to move the tooth)
What is the most favourable pattern of retention?
Triangular
How much of a load can a healthy tooth carry?
It’s own load + one and a half similar teeth.
Depends on perio attachment
How is mucosal support achieved?
By covering as large an area as possible (reduction from the occlusal table). B
What are the areas of primary and secondary support in upper arch?
Primary- hard palate
Secondary - alveolar ridge, rugae
What are the areas of primary and secondary support in the lower arch?
Primary - buccal shelf, posterior ridge, pear shaped pad
Secondary - anterior ridge, buccal sulcus
Why is it better to have a larger rest seat?
Directs force down long axis of tooth rather than applying large forces per unit
Where is a rest seat placed for a free end saddle and why?
Rest seat is placed mesial of tooth
Movement of the saddle can rotate towards tissue and cause stress of abutment tooth.
What are the two types of connectors and their functions?
Minor- joins denture components eg rests to major connector
Major - joins componentes on each side of arch, provides bracing and indirect retention
What are the 4 properties of minor connector design?
Should be rigid
Finish above the survey line
Cross the gingival margins at right angles
Cover as little gingival tissue as possible
What are some major connector designs for upper arch?
Anterior plate
Mid palatal plate
Ring design (anterior and posterior design)
Horseshoe
Posterior bar
