Operative Dentistry Flashcards
posselts envelope
1-7 name the positions
1 - ICP = intercuspal position
2 - E = edge-edge
3 - Pr = protrusion
4 - T = maximum opening
5 - R = retruded axis position
6 - RCP - retruded contact position
7 - Rest
clinically, what is the distance referred to between point 1 and 7 [ICP and rest]
freeway space
in a relaxed, upright pt - what is the average distance in mm of freeway space
2-4mm
the mandible is said to be on its retruded axis between which points
5 and 6
R and RCP
retruded axis position and retruded cuspal position
what is a border position of the mandible
a jaw position which defined the boundaries or limitations of movement
why is the retruded axis important in clinical dentistry
stable and reproducible reference point to assess and construct occlusion
ensure prostheses fit comfortably and function within the full range of mandibular movement
used to mount on articulator
evaluate intercuspal position
ensures correct vertical dimension and occlusal relationships when extensive restorations
what two records are required when mounting casts on a semi adjustable or average value articulator
facebow transfer record
ICP
what is the average value of sagittal condylar guidance angle which may be used on an articulator
30 degrees
what is the relevance of freeway space in complete denture construction
if none - denture bearing tissues subjected to heavy loading, muscles unable to return to normal resting length so continuous activity, pain, noisy denture, show too much teeth/teeth too big
if too much - reduced load of tissues but reduction in masticatory efficiency and adversely affects appearance of pt [overclosed], cheek biting, TMJ symptoms
what is the name of mandible position 6
RCP - retruded cuspal position
what is the name of mandible position 1
ICP - intercuspal position
what is the function of provisional restorations
restore aesthetics and function
prevent sensitivity and bacteria microleakage
coronal seal of endo tx
preserve or improve function [mastication, speech]
prevent caries
maintain gingival health
types of preformed provisional crowns
tooth coloured
- polycarbonate
- clear-plastic crown forms filled w composite
metal
- aluminium
- stainless steel
advantages of prefabricated crowns
when no impression taken prior [trauma]
cheaper
no need for lab involvement so can tooth prep and cement crown in one appt
disadvantages of prefabricated crowns
unlikely to fit accurately
large bank of crowns needed to accommodate pt
[costly]
how to decide between conventional vs post + core crowns
is there enough tooth structure [ferrule] to maintain conventional crown support
what is the function of the post in a post + core crown
retention of the crown/core
support for the core material
compensate for missing tooth structure
distribution of forces
reinforce weakened tooth
materials for core and post
Post -
Metal = cast gold, stainless steel, brass, titanium
Ceramics = alumina, zirconia
Fibre = glass, quartz, carbon
Core -
Composite [fibre posts]
Amalgam
GI
ways to determine post length
minimum 1:1 length of the crown
below alveolar crest
2/3 length of root
4-5mm GP left apically
at least half the post in the root
problems if the post is too wide
root fracture
root perforation
compromised apical seal
problems if the post is too narrow
reduced retention
more likely to fracture
increased stress concentration
insufficient strength
poor load distribution
crown prep of an incisor
what is the margin design and reduction labially?
1.5mm, shoulder
benefits of 1.5mm shoulder design
can incorporate porcelain and metal crowns
[0.9mm, 0.4mm]
crown prep for incisor
palatal margin design and reduction
0.5mm - only metal required for this region as not seen and not in aesthetic zone so minimal prep is sufficient
1-1.5mm chamfer
