CSAR Flashcards
what can’t an indirect restoration have?
undercut
4 disadvantages of crown?
- destructuve to tooth tissue
- potential for pulp damage
- fail eventually
- expensive
what is an inlay?
intra-coronal indirect restoration
2 types of ceramic crown?
Emax + zirconia
4 materials crowns can be made from?
- all metal
- ceramic
- PFM
- composite
can emax or zirconia be etched?
emax
2 types of cementation method?
mechanical - conventional
adhesive - resin cement
when an anterior tooth is under load what sort of force acts palatally and buccally?
tension palatally
compression buccally
what does marginal breakdown of posterior teeth lead to?
cuspal flexure = crack
3 stages of preparation for crown
- occlusal reduction
- axial reduction
- marginal configuration
what is the critical area of a tooth to retain tissue?
peri-cervical area
advantage of adhesive retention?
conservative to tooth tissue
main contraindication to indirect restoration
periodontal disease
5 considerations for restoring a tooth with a crown
- ability to retain core
- isolation ability
- ferrule necessary to retain indirect restoration
- retention/resistance form
- cold sensitivity
how much more preparation on functional cusp?
0.5mm more
what is retention form
prevents removal of restoration along long axis
what is resistance form
prevent removal of restoration in apical/oblique direction
what is minimum height a prep can be
~ 3-4mm
what is the ideal taper
6-12degrees
3 reasons margin of crown must be good
aesthetics
periodontal health
marginal seal = prevent microleakage
3 types of margin design
shoulder
chamfer
knife-edge
what type of margin for metal?
chamfer
what type of margin for porcelain?
shoulder
why should anterior margins be just subgingival?
aesthetics
what do adhesive restorations require?
enamel all way round tooth
what does an onlay require?
enamel all way round the tooth
9 steps for crown provision
- make matrix
- prepare tooth
- retraction
- use matrix to make provisional
- remove cord after 6 mins
- working impression
- jaw reg (if needed)
- facebow (if needed)
- cement provisional
5 reasons SA articulator may be used
- multiple restorations
- increasing VD
- reorganising occlusion
- removing occlusal interferences
- when occlusal stabilisation splint required
6 ways to create space for restoration
- increase OVD
- dahl concept
- enameloplasty
- distalisation of mandible
- crown lengthening
- Orthodontics
in what position is OVD measures?
ICP
definine CR
position of musculoskeletal stability provided by healthy TMJS when the condyles are in their most superior position within the glenoid fossa with the discs correctly interposed
how much unprepared axial surface below the prep needs to be recorded in the impression?
0.5mm
how does moisture effect impression material?
physical barrier
if you were making a crown but couldn’t get moisture control because of inflammation from a preexisting overhanging restoration, how would you proceed?
- prepare + place new restoration
- wait 3-4weeks
- prescrive 0.12% chlorhexidine for 2/52
2 types of haemostat agents used on retraction cord?
- vasoconstrictors
2. astringents
how do astringents work and what is an example?
precipitate proteins on contact with blood, physically obstruct blood vessels
e.g. ferric sulfate, aluminium chloride
why does ferric sulphate cause blue/black stain for 1-2 days?
precipitating protein contains iron
for adequate thickness of impression material, how wide do you need to horizontally open sulcus?
0.2-0.3mm
2 ways of opening up sulcus for impression?
- surgery
2. retraction cord
what is the first retraction cord you put in?
compression cord - finest 00 or 000
placed to depth of sulcus
to prevent haemorrhage + GCF
what is the second retraction cord you put in?
deflection cord - wide as you can fit, 0 or 1
half into sulcus
how long do you leave retraction cords for?
5-6mins
what instruments used to put cords in?
carver or Williamson probe
when do you remove deflection cord?
before impression
when do you remove compression cord?
after impression
what material is used for impression for crown?
light bodied silicone around prep
heavy bodied around surrounding arch
how to critique impression
check finish line + material past it
no critical air blows/drags/voids
sufficient occlusal defila
sulcus captured
4 reasons to make provisional restoration?
- diagnostic
- pulpal protection - must have marginal seal
- gingival management - must have marginal fit + contour
- position stability - must have ICP contact, contact point
3 methods for making provisional crown?
- matrix
- shell
- freehand
2 material choices for provisional restoration?
- acrylic e.g. Bosworth trim/snap
2. bis-acryl composite e.g. quicktemp, protemp
properties of acrylic provisional
hand mix slow set moderate exotherm + high shrinkage easy to add to more flexible
times you were use acrylic provisional
relining shell provisionals
provisionals around partial dentures
lateraling gingival contour
properties of bis-aryl provisional
automix - easier quick set low exotherm + low shrinkage harder to add to brittle/not flexible
when would you use bis-acryl provisional
simple matrix provisionals
how do you stop provisional bonding to composite core?
glycerine/vaseline
2 types of temporary cements
- zinc oxide cement - temp bond
2. zinc polycarboxylate cement - polyF, durelon
when do you use zinc oxide and when to use zinc polycarboxylate to cement provisional restorations?
zinc oxide = if satisfactory resistance/retention
zinc polycarboxylate = when resistance/retention lacking
what type of temp bond is used if composite core?
temp bond non eugenol
types of shell technique provisional crowns?
standard crown forms - polycarbonate, aluminium, stainless steel
lab made crowns - acrylic, composite
method for placing shell technique provisional crown
- pick crown
- trim if necessary
- make hole interproximal to help achieve contact point
- reline with acrylic temp material
- fill shell with acrylic
- seat
- remove in dough stage
if prep is occlusal stable and doesn’t need provisional how would you dress it?
fluoride varnish (? - can integrate into hydroxyapatite + change surface) zinc phosphate covering
what is index shrink-wrap?
putty made from wax up, putty filled with bis-acryl + cured straight to teeth
how would you temporise an occlusaly unstable resin bonded bridge prep limited to enamel?
composite to opposing tooth
how would you temporise veneer prep that extends through contact points?
composite cured to prep
how would you temporise occlusally stable resin bonded bridge prep that extends into dentine + sensitive?
zinc phosphate or zinc carboxylate covering
2 techniques for labs making indirect restorations
- lost wax technique
2. hand layered
advantages and disadvantages of bi layered restorations
\+ better aesthetics \+ combine best 2 qualities of materials - postnatal weak points at interfaces -risk of chipping/fracture - need for greater prep
advantages and disadvantages of monolithic restorations
\+ stronger \+ more conservative \+ cheaper - limited aesthetics - only character with stains
occlusal + marginal reduction for metal crown?
1-1.5mm
0.1mm chamfer
occlusal + marginal reduction for porcelain + metal areas of PFM
2-2.5mm
1-1.2mm
what technique can be used to reduce margin prep in posterior teeth?
high strength metal collar
what is the umbrella effect?
metal ceramic margin creates blueish appearance at margin
overcome by extending porcelain palatally
what type of restoration is zirconia?
conventional
difference between traditional zirconia and new high translucency zirconia
old - bilayered as opaque, stronger, hard to adjust
high translucency = monolithic or bilayer, weaker, easier to adjust
what type of zirconia is used as collars?
bilayered high translucency
does bilayering lead to better or worse aesthetics for zirconia?
better
what is Emax?
lithium dislocate
etch able glass ceramic
can be cast or CADCAM
is Emax normally monolithic or bilayered?
posterior teeth = normally monolithic as stronger
anterior teeth = make monolithic + then cut back and layer with feldspathic porcelain
2 types of etchable ceramics
Emax
feldspathic porcelain
advantages and disadvantages of indirect composite
\+ better conversion of monomer than normal composite \+ easier to adjust + repair \+ cheaper \+ thinner section - more flexible so weaker than emax - problems with debond
how are precious metal restorations made?
cast
how are non-precious metal restorations made?
cast of CADCAM
how are lithium disilicate restorations made?
cast or CADCAM
how are zirconia restorations made?
CADCAM
how are feldspathic poreclain restorations made?
hand layered or CADCAM
how are resin based restorations made?
hand layered or CADCAM
how does translucency of material affect aesthetics?
the more translucent = more potential
when core not favourable - must leave room for technicians
4 types of passive cements
- zinc phosphate
- zinc carboxylate
- GIC
- RMGIC
how do strength and translucency relate to each other?
as strength increases, become less translucent
order of crown materials from most strong (most opaque) to least strong (most translucent)
- metal
- zirconia
- high translucency zirconia
- emax
- feldspathic porcelain
advantages and disadvantages of adhesive indirect restorations
+ more conservative
+ less reliant on resisitance/retention form
+ advantages when limited crown height
- harder to temporise
- need to isolate
- bond is unpredictable
- cementation much more technique sensitive
what must you check on patient before trying in crown?
occlusion - find holding contacts with shim stock
check dynamic for reference
if bonding precious metal, why must you always use primer?
precious metals don’t have oxide layer to easily bond to
sulphur group f VBATDT in alloy proimer bonds to metal
what is a cantilever bridge?
attached on one side
3 types of conventional bridge?
cantilever, fixed-moveable, fixed-fixed
use crowns as retainers
2 types of adhesive/resing bonded bridge?
cantilever, fixed-fixed
approx longevity of conventional + resin bonded bridges?
conventional ~10yrs - take abutment with
resin bonded ~5yrs - abutment spared
if using a fixed-fixed conventional, what must both abutment teeth have? how can this be overcome?
common path of insertion
use fixed-moveable
structure of a fixed movable conventional bridge?
major retainer - rigid connector - Pontic - moveable connector - minor retainer
advantages + disadvantages of adhesive bridge?
\+ conservative \+ impression easier \+ failure less destructive - don't last as long - cannot shape abutment teeth - can discolour if thin - need enamel - technique sensitive
what is antes law?
total periodontal membrane of abutment teeth must equal or excess that of tooth to be replaced
now evidence to suggest as long as good perio + maintenance more extensive bridges can be successful
what should occlusion of a Pontic be?
contact in ICP but not In excursion
where are fixed-fixed and cantilever preferred and why?
posterior = vertical forces = fixed-fixed anterior = lateral forces = cantilever
what is the optimum and minimum crown:root ration for abutment teeth?
optimum 2:3
minimum 1:1
how does a big span effect the Pontic?
bigger the span = more bending/flexion of Pontic
+ increased load of abutment teeth
may lead to fracture, debonding of one retainer
what is minimum thickness of RBB retainer to prevent flexion?
0.7mm
2 features of anterior RBB prep
cingulum rest
finish line
3 features of posterior RBB prep
rest seat
guide plane - remove bulbosity to help with seating
finish line
what should existing restorations be replaced with (if not already) before RBB?
composite
3 types of periodontitis
- marginal
- apical
- both - perio/endo
to have apical perio what must the pulp be?
non-vital
how to treat perio-eondo lesion with communication?
endo first
perio after 1 month to allow some bony infill
what type of cells are responsible for resorption of dentoalveolar hard tissues?
giant cells - derived from mononuclear phagocytes
how long does transient resorption happen for and why?
2-3weeks
no constant stimulation of giant cells
what stimulates giant cells?
pressure + infection
3 systemic disorders linked with root resorption?
- hypo/hyperparathyroidism
- pagets disease
- benign/malignant tumours - causes pressure
how is resorption prevented after RSI?
epithelium migration
what is cervical resorption?
type of progressive external inflammatory resorption
lesions begin in cervical region + communication with mouth
what is richwil crown remover?
toffee like substance, chewed to remove crown
what is a masserran kit?
removes threaded post in anticlockwise direction
how do you remove gutta percha?
size 10 file + sodium hypochlorite
my need solvent - chloroform, eucalyptus + orange oils
