Operative Dentistry

Question 1

posselts envelope
1-7 name the positions

Answer 1

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

Question 2

clinically, what is the distance referred to between point 1 and 7 [ICP and rest]

Answer 2

freeway space

Question 3

in a relaxed, upright pt - what is the average distance in mm of freeway space

Answer 3

2-4mm

Question 4

the mandible is said to be on its retruded axis between which points

Answer 4

5 and 6
R and RCP
retruded axis position and retruded cuspal position

Question 5

what is a border position of the mandible

Answer 5

a jaw position which defined the boundaries or limitations of movement

Question 6

why is the retruded axis important in clinical dentistry

Answer 6

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

Question 7

what two records are required when mounting casts on a semi adjustable or average value articulator

Answer 7

facebow transfer record
ICP

Question 8

what is the average value of sagittal condylar guidance angle which may be used on an articulator

Answer 8

30 degrees

Question 9

what is the relevance of freeway space in complete denture construction

Answer 9

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

Question 10

what is the name of mandible position 6

Answer 10

RCP - retruded cuspal position

Question 11

what is the name of mandible position 1

Answer 11

ICP - intercuspal position

Question 12

what is the function of provisional restorations

Answer 12

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

Question 13

types of preformed provisional crowns

Answer 13

tooth coloured
- polycarbonate
- clear-plastic crown forms filled w composite

metal
- aluminium
- stainless steel

Question 14

advantages of prefabricated crowns

Answer 14

when no impression taken prior [trauma]
cheaper
no need for lab involvement so can tooth prep and cement crown in one appt

Question 15

disadvantages of prefabricated crowns

Answer 15

unlikely to fit accurately
large bank of crowns needed to accommodate pt
[costly]

Question 16

how to decide between conventional vs post + core crowns

Answer 16

is there enough tooth structure [ferrule] to maintain conventional crown support

Question 17

what is the function of the post in a post + core crown

Answer 17

retention of the crown/core
support for the core material
compensate for missing tooth structure
distribution of forces
reinforce weakened tooth

Question 18

materials for core and post

Answer 18

Post -
Metal = cast gold, stainless steel, brass, titanium
Ceramics = alumina, zirconia
Fibre = glass, quartz, carbon

Core -
Composite [fibre posts]
Amalgam
GI

Question 19

ways to determine post length

Answer 19

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

Question 20

problems if the post is too wide

Answer 20

root fracture
root perforation
compromised apical seal

Question 21

problems if the post is too narrow

Answer 21

reduced retention
more likely to fracture
increased stress concentration
insufficient strength
poor load distribution

Question 22

crown prep of an incisor
what is the margin design and reduction labially?

Answer 22

1.5mm, shoulder

Question 23

benefits of 1.5mm shoulder design

Answer 23

can incorporate porcelain and metal crowns
[0.9mm, 0.4mm]

Question 24

crown prep for incisor
palatal margin design and reduction

Answer 24

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

Question 25

properties of impression material suitable for crown prep

Answer 25

low viscosity
low viscoelasticity
high tear resisitance
low thermal expansion

Question 26

how to determine if impression is usable for inlays

Answer 26

all anatomical areas recorded
sufficient surface detail
material well mexied and adhered to try
detail reproduction
margin integrity
no bubbles/voids

Question 27

potential faults in impression

Answer 27

voids
airblows
dragging
tears upon removal
distortion
incomplete setting

Question 28

how to decontaminate an impression

Answer 28

rinse under cold water to remove gross debris and saliva
place in perform for a minimum of 10mins to disinfect [sodium benzoate]
take out and rinse in cold water
wrap in damp gauze and put in plastic bag

Question 29

Hanau’s Quint Five Factors Affecting Occlusal Balance

Answer 29

1. orientation of occlusal plane
2. condylar guidance angle
3. incisal guidance angle
4. cuspal angle
5. compensating curve

Question 30

name materials used for crowns

Answer 30

metal
- gold, nickel, chromium, titanium

metal ceramic
- porcelain fused to metal

all ceramic [milled]

Question 31

name 3 types of post which can be used

Answer 31

Metal, ceramic, fibre

Tapered, parallel, tapered, non-threading
Prefabricated

smooth/threaded/serrated
parallel or tapered
metal/fibre
prefabricated/casted

Question 32

what is the name given to the residual collar of dentine required before placing a post

Answer 32

ferrule

Question 33

how much gutta percha should be left in the canal space when placing a post

Answer 33

4-5mm apically

Question 34

describe the width of taper required for a metal ceramic crown

Answer 34

5-9 degrees

Question 35

what is the thickness of shimstock

Answer 35

8 microns

Question 36

how common is sensitivty post-bleaching

Answer 36

60%+

Question 37

3 predisposing factors likely to cause sensitivity

Answer 37

pre-existing sensitivity
high conc bleaching agent
frequency of change
bleaching method
gingival recession

Question 38

external cervical resorption what is it and how does it occur
how to stop

Answer 38

due to non-vital bleaching

due to diffusion of H2O2 through dentine into PD tissues

due to
- high conc H2O2
- heat
- trauma

stop;
place 1mm RMGIC over GP to seal canal, seals dentine and prevents root resorption