CSL Book 2 Blue Flashcards
2 things that can lead to class IV restoration
- trauma
- progression of class III caries
who is most at risk for trauma injuries to teeth
children
normal angle of fracture across crown
45 degrees towards palatal surface
3 special investigations with trauma cases
- clinical exam/history: discolouration of crown, mobility of tooth, position of tooth in occlusion
- vitality: at least 2 methods inc pulp tests to eliminate concussion
- radiographs: 2 views periapicals with different angulations to identify fracture lines
2 complications of trauma leading to class IV
- root fracture
- damage to adjacent teeth
is enamel bevelling usual for class IV restorations? why?
no because it removes more tooth structure.
what bevel is normal for class IV and how is it done
labial margin only is bevelled so composite can be blended with tooth structure
use D&Z850 at 45 degrees or greater to long axis of tooth –> 1mm bevel
not to edges to avoid damage to adjacent teeth
what lining to use for class IV cavities
- total etch and bond (shallow -moderate depth cavities, this is enough to seal dentine tubules)
- light-cured GIC (bonds to dentine AND composite)
- setting calcium hydroxide (when deep cavity nr pulp)
usually use GIC or setting calc hydroxide
type of wax used to box the impression in lost wax technique and why this is done 2
ribbon wax
- contain die stone, prevent distortion
- ensure the model has sufficient thickness for drilling in to its base
what type of gypsum is used for cast metal restoration
modified alpha hemi-hydrate (artificial/die stone)
thickness of model and why 2
15mm gingival margin to base
- avoids fracture during drilling
- ensures base is flat for next stage
are labial/lingual pins longer and colour of sleeve
LONG, WHITE, LIPS
labial: longer, white sleeve
lingual: shorter, grey sleeve
LONG LIPS, WHITE IS LONGER WORD
what is used to base the model
50:50 plaster stone mix
3 advantages of pindex system
- PRECISE location in to plastic sleeves
- DURABLE- plastic sleeves prevent wear
- STABLE (twin pin system- 2 pins per area –> no danger of rotation)
what can be applied to die and adjacent teeth to prevent damage/distortion, how do they work
stone die and plaster hardeners (resins in soln)
absorb in to die stone material –> seal/waterproof surface while protecting definition of margins (don’t create another layer, just blend in to surface)
what material is the plastic coping made of
polythene
thickness and positions of pieces of plastic foils
thicker 0.6mm below thinner 0.1mm (thinner one contacts the die)
0.6-0.1-die
how far above margin to trim plastic coping
1mm
size and angle of sprue
2mm
45 degrees to thickest section of wax pattern
why must sprue be fairly large
allow free flow of molten alloy
where should sprue be positioned in crucible former and why
no less than 7mm from upper edge
prevents molten alloy from breaking through when entering the mould
when is wetting agent applied and why
prior to investing
reduce surface tension–> smooth cast surface
why must investment be mixed under vacuum
eliminate air inclusions that may result in air pockets forming against pattern surface
% shrinkage of casting gold and what compensates for it
1.5%
compensated for by 3 EXPANSIONS: setting, hygroscopic and thermal of investment material
4 requirements of an investment
SERS
- produce smooth Surface to casting
- permit Escape of gases to casting
- facilitate easy Removal of casting
- sufficient Strength to withstand temps in furnace
order, time and temp of casting
-1 hour: allowed to set crucible removed -30 mins (min), 250C hotplate -10 mins 740C furcace -few minures: allowed to cool -cold water *the hotter the process, the shorter the time*
details of gold alloys
types I-IV. contain Au,Ag,Cu,Pt/Pd,Zn
I:85% gold
IV: 65% gold
melting point 950-980C
other name for class V 2 materials used to fill class V cavity
abrasion cavity
GIC, compomer
3 causes of class V cavities
- caries due to poor plaque control
- abrasion due to horizontal scrubbing when brushing
- abfracture (occlusal stresses concentrate at thin enamel near enamo-cemental junction –> fracture of enamel)
what to clean class V cavity with and why
clean to remove pellicle and surface plaque
oil, glycerine, fluoride-free prophylaxis paste (would decrease bonding,use a pumice slurry)
rubber polishing cup (not brush-may break rubber dam and damage gingivae)
what to do after washing/drying class V cavity and why 2
CONDITION: 25% polyacrylic acid with cotton wool, leave for 30s, wash for 30s,dry gently
- remove smear layer
- improve bond strength for GIC
what matrix to use for class Vcavity and why 3
cervical matrix
- forms missing surface –> contains filling material
- compresses filling material while it sets
- smooth finish surface
how long to amalgamate gic
10s
how long to press gic for and why
2 secs
rupture membrane –> polyalkenoic acid contacts aluminosilicate glass
2 advantages of encapsulated gic
- viscosity and quality are reproducible
- can be injected directly in to cavity
ratio of gic powder to liq
2:2
mixing time of gic
max 25 secs
how long to leave class 5 gic (cervical)
5 mins to ensure fully set
when to finish gic restorations and why
24hours after unless gross excess present. allows second ion exchange (with aluminium) to take place
what is used to protect gic for first 24hrs and why. how to apply
light-cured bis GMA resin (best) or varnish
stop it gaining/ losing water –> weaker
resin: leave for 30s to penetrate voids in material, light cure 20s
what to use to polish gic/compomer class v
prisma glosses
felt polishing cup (NOT rubber)
contents of compomer and why
- aluminosilicate glass (gic filler)
- acid polymerisable resin (TCB tetracarboxylic acid butate, allows methacrylate groups to polymerise in to long chains while pendant acid groups react with glass surface)
does gic or compomer have better aesthetics
compomer
why must dentine not be desicated
will prevent hydrophilic bonding resin from wetting the tooth surface
prime and bond contents
elastomeric resins and penta
contents of penta and why
phosphate ester of methacrylate. it is polar – wets surface (hydrophilic) and forms ionic bonds with apatite crystals
what matrix is used with compomer class v and what is it made of
hawe neos cervical matrix (must use transparent matric with light cured material)
cellulose actate
2 ways to increase bond strength of compomer
- non rinse conditioner: maleic and polyacrylic acids , leave for 20s then air dry
- phosphoric acid etchant: same as always, leave for 30s, water 30s, gently air dry,
what to use to remove excess compomer from class v
excavator
3 parts of porcelain-metal bond
- chemical (tin/indium oxides come to the surface for passivation)
- mechanical
- shrinkage/compression bonding (this is the reason there must be no pits/hollows on buccal surface
5 indications for porcelain fused to metal pfm crown
- improve strength/appearance of heavily filled teeth
- where porcelain crown repeatedly fractures
- where occlusion unfavourable (deep overbite, minimal overjet)
- conjunction with bridge of partial denture construction
- occlusal reconstruction (crowning all standing teeth to re-establish correct clinical height)
how much occlusal reduction to do where and why
buccal: 1.5mm (room for porcelain and metal)
lingual: 1mm (bonding alloy better than gold, less reduction needed, even for functional cus)
2 functions of functional cusp bevel pfm
- provides clearance between upper and lower teeth
- brings cusp tip back in to line with unprepared cusp position
order of pfm crown prep
- occlusal reduction
- functional cusp bevel
- axial wall reduction
- interproximal reduction
- palatal/lingual surface
axial wall prep buccal and lingual/palatal pfm crown
buccal: shoulder, 1.3mm reduction
lingual/palatal: 135 degree chamfer, max 5 degree taper 1mm reduction
width of straight enamel chisel and why
1.5mm; used to check buccal reduction of PFM is 1.3mm
(also used to
2 stages of interproximal reduction pfm
- break contact with adjacent teeth
- chamfer prep of margin
on which side of the tooth is wing position critical and why
mesial- metal must not be visible
mesial and distal position of wings
mesial: interface position, midway between buccal embrasure and midpoint of contact area
distal: buccal embrasure point
[mesial wing is more palatal than distal]
chamfer position of pfm crown prep
same but when restoration present
just above gingival level
restoration present: just cervical to margin of filling
3 things used to smooth surfaces and line angles
- superfine diamond burs
- multi-fluted tungsten carbide burs
- green stones
2 instruments used to smooth and define shoulder and why
- enamel chisel (moves unsupported enamel but v sharp –> tissue damage)
- shoulder file (safer, only cuts in 1 direction)
pfm crown prep function of:
a. shoulder
b. chamfer
c. buccal reduction
d. wings
e. bevel
a. shoulder: structural durability
b. chamfer: marginal integrity
c. buccal reduction: retention, resistance
d. wings: retention, resistance
e. bevel: structural dirability
advantages of wingless design
- easier to prepare
- less chance of undercut
disadvantages of wingless design
- less resistance form
- less conservative of tooth structure
which tooth has a canine fossa
maxillary first premolar
which cusp is thin for extensive amalgam restoration
buccal
symptoms of cracked tooth syndrome
pain on release from biting
how to cut buccal wall for EAR
45 degrees towards occlusal plane
with of buccal shoulder in EAR. bur used
1mm, 554
when to line EAR and why
before drilling hole/ groove (or lining may block holes)
+before pin placement (or pins get in the way)
where to place pins and why
1mm in from EDJ –> no perforation of periodontal ligament and pulp
1mm of amalgam should be placed around pins
where to line EAR
horizontal pulpal floor and vertical axial walls
what is used to make dimples for pins EAR
number 1 round bur (slow handpiece)
thicknesses of dentine/amalgam required for EAR and why
(grooves/ holes max 1mm depth) 1mm in from ADJ 1-2mm of amalgam covering 1mm dentine around pins 2.5mm overall thickness of dentine max 2mm protruding in cavity --> room for 2mm overlying amalgam (may need to reduce height of pins with diamond coated bur) protect against pulpal or periodontal perforation
how far apart should pins be EAR
5mm
how to make holes for pins EAR
twist drill in speed reducing handpiece –> less speed, more torque
bur aligned with outer surface of tooth
pushed down in one firm movement, taken out while still rotating
DO NOT put twist drill back in- will make hole too big
where is widened seat on EAR pin and where should it sit
midway along length. should sit on dentine surface
how far out of tooth should pin be and why
no more than 2mm -doesnt help retetion of amalgam
allow for 2mm of amalgam covering pin (may have to shorten pin with diamond coated bur)
speed of handpiece when inserting pin and why
slow-moderate
too fast –> threads will strip from dentine wall, retention compromised
what to use to alter position of pin
pickle fork shaped pin bender
how to make groove / size in EAR
701 fissure bur
1.5mm deep
disadvantage of siqveland matrix band for EAR. better alternative
cannot be removed from holder while still attached to tooth –> hinders removal, risks fracturing amalgam while trying to remove band
tofflemire is better
advantages/disadvantages of copper band matrix
- advantages: can be left in situ until pt returns
- disadvantages: not flared–> poor shape of tooth, thicker–> poor contact point
3 ways heavily restored tooth can interfere with occlusion
- centric occlusion
- lateral excursions
- protrusion of mandible
use/ contents of kalsogen
temp dressing
zinc oxide-eugenol
3 ways to stop kalsogen adhering to flat plastic
water
alcohol
kalsogen powder
what accelerates setting reaction of zinc oxide-eugenol cements
contact with water
what is added to kalsogen to strengthen it
–> modified use
cotton wool
–> onlay cavity dressing, hold occlusal contacts/stops
compare strengths of GIC and zinc polycarboxylate cements
similar
suggest use of zinc polycarboxylate
where strength and no bond to overlying restorative necessary and need to see difference between cement and tooth eg v deep cavities pulp capping
most common method used for casting gold from dies
centrifugal force
2 ways to melt gold during casting
- melted over casting ring (over reducing zone of flame, middle triangle)
- in a crucuble (torch/induction melting)
2 reasons investment is washed in cold water
- enable easier deflasking
- produce fine grain structure
newly made cast gold crown: what is used to smooth
a. axial surfaces
b. angular primary casting
c. fissure pattern
a. axial surfaces: white flexi rubber wheel
b. angular primary casting, c. fissure pattern: rubber points
position of contact point in relation to marginal ridge
1mm below marginal ridge
how porcelain is built up for
a. crowns
b. veneers
a. crowns: build up on platinum foil (foil removed after glazing)
b. veneers: build up on refractory model
what is tinners joint
fold in TIN foil to make incisal edge in porcelain crown build up
POLISHING:
faster or slower better and why
faster better: shallower scratches
reduces wear of abrasive practicals
quicker result
compare coarse and fine abrasives
coarse: fast removal of material, deep scratches
fine: slower abrasion, smoother surface
compare abrasion and polishing
abrasion= producing gradually finer scratches --> smooth reflective surface polishing= producing smooth reflective surface with surface flow and BEILBY LAYER (molecular disorganised, shiny layer)
examples of dental abrasives 7
-pumice
-sand
-diamond
-carbides
-Kieselguhr
-garnet
emery
examples of polishing agents 5
whiting rouge tripoli tin oxide chromium oxide
rubber dam thickness
0.15-0.35mm
is liquid or gel etch preferable for class IV restorations and why
gel- easier to control where it goes
function of applying copal ether varnish to adjacent teeth during class IV restoration
- prevent composite sticking
- prevent inadvertent etching
type of composite to use for initial part of class IV restoration and why
opaque, dentine shade
stops restoration looking too translucent
for what materials does oxygen prevent polymerisation of surface during setting reaction
composite
bond
when may it be desirable to leave the surface layer of composite uncovered so that it is not cured due to oxygen inhibition
all except the last layer, so the overlying composite bonds to the non-fully-set composite
2 techniques used to make wax pattern
- wax addition (PK thomas instruments)
- carve down technique (Ney)
during investment furnacing, which way should the sprue face and why
downwards -> allow wax to escape
what force makes casting work
centrifugal
why must investment be cooled before deflasking 2
- easier deflasking
- fine grain structure
3 substances that may decrease bonding of restorative material to tooth
-oil (eg from compressor)
-glycerine
-fluoride
in prophylactic pastes
what is ketac and when is it used
unfilled bis GMA resin
used to cover GIC for first 24 hours to reduce water gain/ loss
what restorative material do you NOT etch with
compomer (uses prime and bond), amalgam
composite uses etch, gic uses conditioner (polyacrylic acid
depth of cure of compomer, cure time
3mm, 40s
function in EAR of
a. pin
b. groove
a. pin: resistance form
b. groove: resistance and direct retention
order of procedures in restoration stages of EAR
- cavity varnish (3 layers)
- matrix application
- amalgam insertion
- carving
- occlusion check
EAR lecture: adhesives to use for EAR
- 4META (amalgam bond)
- MDP (methacryloxydecyl dihydrogen phosphate)
advantages of EAR over cast restoration
quicker
cheaper
less invasive
