RPD design and surveying Flashcards
Kennedy Class I
bilateral free end saddle
Kennedy Class II
unilateral free end saddle
Kennedy Class III
bounded saddle (that does not cross the midline)
Kennedy Class IV
bounded saddle that crosses midline
Craddock Class 1
tooth borne
Craddock Class 2
mucosa borne
Craddock Class 3
tooth AND mucosa borne
support
resistance to occlusally directed load
retention
resistance to vertical displacement
benefits of occlusal rests
- prevent movement of RPD towards mucosa
- distribute occlusal load
- prevent over eruption of unopposed teeth
why is the default position for free end saddle rests the opposite side of the tooth
to reduce axial torque on the abutment
indirect retention
resistance to rotational displacement
reciprocation
prevents clasp arm moving clasp tooth
bracing
resistance to lateral movement
where should plates be in relation to gingival margins
either completely away or completely covering
those that end at gingival margins known as ‘ gum strippers’
RPI
stress relieving clasp system common in mandibular arch R - mesial rest P - proximal plate I - I bar clasp
what is the purpose of the guide plate on an RPI
ensures forces directed down vertical plane
how much sulcus height is needed for gingivally approaching clasp s
7mm
CoCr minimum clasp length
15mm
CoCr undercut depth
0.25mm
stainless steel undercut depth
0.75mm
gold undercut depth
0.5mm
how much clearance is needed between gingival margins and floor of mouth to place a lingual bar
8mm
what teeth are best for providing support
canines and molars
how long a saddle can teeth support before it becomes partially mucosa borne
healthy teeth can carry 1.5 similar teeth
so bounded saddle could be 3 teeth wide and still be fully tooth borne
what is the primary objective of surveying
to find a suitable path of insertion
what is a dental surveyor
a paralleling instrument used to identify and mark the maximum contours of tooth hard and soft tissues in order to fabricate a removable denture
common path of displacement
90 degrees to the occlusal plane - horizontal
why do we alter the path of insertion
to eliminate spaces which in turn provides better aesthetics and better retention
what does the chiselled edge of the graphite marker allow for
allows it to go interproximal
what must be done with undercuts when creating a rpd
they must be either used or blocked out
