CSL Book 1 Yellow Flashcards
number and use of rugby ball-shaped bur
285/773
- occlusal and lingual reduction
- shaping cingulum and cusp areas (all ceramic crown prep, cingulum reduction)
shape and use of 877 bur
torpedo shaped (tapered) axial surfaces to produce chamfer in crown prep)
shape, size and use of 520 bur
rosehead, fast handpiece, 1mm
access to caries
class II self-retentive box
class III access (anterior interproximal)
shape and use of 637 bur
Six 37 –> Ceramic
tapered, rounded end
all ceramic crown prep, chamfer finish lines
(similar to 877 but wider
a. length of cutting head of 544
b. distance enamel- dentine
a. 3mm
b. 2mm
define torque
tendency of a force to cause rotation about an axis
probe used to check adequate caries removal
no 18
speed of fast handpiece
450-500 000rpm
speed of slow handpiece
3-4000rpm
range of acceptable cavo-surface angles
70-120
90+- 20
what lining to use for amalgam fillings and why
setting calcium hydroxide 2:
- remineralise remaining slightly altered dentine
- stimulate odontoblasts to produce more dentine
a. why apply cavity varnish
a. reduce microleakage
2 effects of leakage
- post-op sensitivity
- secondary caries
a. mixing time and working time of setting calcium hydroxide
b. where to apply calcium hydroxide lining and why
5-10s mixing
6 minutes working (humidity dependent)
b. pulpal floor and axial wall (protects pulp but amalgam contacts walls for stronger bond
contents of cavity varnish
copal resin dissolved in ether solvent (makes eSther)
how to apply cavity varnish and why
use sectioned paper point.
3 coats, air drying between each.
because as the solvent evaporates, circular voids are created
how long to amalgamate amalgam capsule
8 seconds, slower setting
why is y shaped spillway important
direct food away from contact area during eating`
4 ways to store waste amalgam
- water
- old x ray fixer
- potassium permanganate soln
- container with vapour lock chemical
when should eugenol-containing material not be used and why
with composite
it would plasticise the resin base
what lining to use with composite 2
setting calcium hydroxide
light cured GIC
advantages of GIC lining 5
- command curing
- fluoride leach
- bond to dentine
- allows bond to overlying composite
- similar co-efficient of expansion to dentine
what ingredient of GIC makes it light-cured
hema (2 hydroxylethylmetharylate)
wavelength of blue light cure
470-480nm
how long to cure
a. GIC lining
b. bond
c. composite
a. GIC lining: 30s
b. bond: 10s
c. composite: 40s
what lining material is easier to see
setting calcium hydroxide
what material is used to etch
36% phosphoric acid
how to etch and why
30s enamel
15s dentine
-rinse for at least as long as etch time (water only first, then water and air. water removes hydroxyapatite crystals and create micro-porosities in enamel)
-dry gently, max 5 secs
results of over-etching dentine
pulpal inflammation and pain
compare power and torque in fast and slow handpieces
slow: high torque, low power
fast: low torque, high power
how to apply bond and why
apply, leave for 30s
allows resin to penetrate dentinal tubules, around collagen triple helix
-gently air blow (remove acetone solvent, leaves penta and organic resins)
-10s light cure
contents of prime and bond xp
7nm nanofillers (improve physical properties)
acetone solvent
penta and active organic resins
orders of oblique incremental curing and why it is done
palatal-buccal-occlusal
avoid polymerisation shrinkage away from the cavity wall (would cause microleakage)
function of teflon coating
stops composite adhering (tip- so does bond!)
what causes white colour of fissure sealant
0.5% TiO2
Blacks caries classification
I: occlusal surface, pit and fissure II: interproximal posterior III: interproximal anterior IV: incisal edge V: cervical VI: cuspal
3 functions of a matrix band
- forms missing wall of tooth
- helps restore contact area
- permits close adaptation of amalgam to cervical margin of tooth using wooden wedge
most common place for fracture in class II restorations
isthmus
what matrix system to use with class II composite
palodent sectional matrix
what is xeno and its contents and why
combined etch-bond
butanol solvent –> longer working time than more volatile acetone solvent
filler particle size in composite
5nm-7um
3 reasons for lots of filler in composite
- strength
- wear resistance
- minimal polymerisation shrinkage (1%)
4 indications of full gold crown
- restoration of heavily restored tooth
- part of dental bridge
- part of tx of tooth wear
- combination with partial denture construction
name functional cusps
upper: palatal
lower: buccal
fvg reduction of
a. functional cusp
b. non-functional cusp
a. functional cusp: 1.5mm
b. non-functional cusp:1mm
when to use 554 bur
- occlusal reduction in fvg crown preps
- incisal reduction (all ceramic crown prep)
width of 554 bur at tip
1mm
reduction of
a. functional cusp bevel
b. non-functional cusp bevel
a. functional cusp bevel: 1.5mm
b. non-functional cusp: 1mm
angle of bevels
45 degrees to long axis of tooth
should mirror angle of cusp slopes of opposing tooth
angle of taper
a. fvg crown prep
b. all ceramic crown prep
a. 5-8 degrees???
b. all ceramic crown prep: 3-6 degrees
angle, good and bad points of these marginal finishes:
a. knife edge
b. chamfer
c. shoulder
a. knife edge: near 180. difficult to see–> casting may be distorted during finishing BUT close adaptation to tooth surface
b. chamfer: 135. gd compromise
c. shoulder: 90. seen clearly–>no distortion BUT gold does not cast well, bad adaptation tooth surface
2 reasons to use vertical sawing action with 877 bur interproximally
- improve view as cut is made
- improve cutting efficiency of small diameter bur
2 ways to measure mesio-distal width of provisional crown required
- -Williams probe
- plastic measuring kit in ion crown kit
biggest and smallest cusps of molars
biggest: mesiopalatal
smallest: distopalatal
use of bebe crown and collar shears
reduce provisional ion crown
use of crown former pliers
curve cervical margins of ion crown inwards to reduce cervical opening
contents of Trim and why
poly iso-butyl methacrylate
lower exotherm and polymerisation shrinkage than methyl methacrylate
a. what bond to use with provisional ion crowns and why.
b. describe formulation of this
Temp Bond: luting zinc oxide and eugenol paste
it removes cleanly from the preparation when provisional crown is removed
b. base, catalyst and modifier pastes.
(modifier paste only used when cementing/luting metal casting as temp measure)
the provisional ion crown interferes with occlusion but is as thin as it can be. what do you do and why?
go through alloy structure- trim can withstand forces of mastication and occlusion until permanent crown is fitted
6 indications of porcelain crown
IMPROVE AESTHETICS and function:
- heavily restored (anterior) tooth
- trauma resulting in fracture
- hereditary and acquired hypoplasia
- tooth wear
- alter size and shape of tooth
- in combination with bridges/ partial dentures
alternatives to porcelain crowns 4 and why
porcelain crowns v destructive of remaining tooth structures
- ->
- internal/walking bleaching after root canal
- external bleaching (using carbamine peroxide in special constructed trays)
- composite restoration/veneer
- porcelain veneer
how to do incisal reduction for all ceramic crown prep
554 bur, 45 degrees to long angle of tooth (45 degrees inciso-palatal angle)
1-2mm/quarter of clinical height of tooth is removed, leave incisal corners to avoid damage to adjacent teeth
order of processes for all ceramic crown prep
- incisal reduction
- labial reduction
- axial reduction/interproximal
- palatal reduction
- cingulum reduction
- shoulder placement
- final definition and finishing
what 2 things does retention of crowns rely on
- clinical height
- minimal taper
how to do labial reduction on all ceramic crown prep
2 planes. (see csl book pics)
- plane 1: incisal cut
- plane 2: depth grooves at cervical end of crown using 5013 bur (1mm)
why must ensure sufficient labial reduction 2
other technician will:
- overbulk labial surface–> tooth overly bulbous, sticks out
- make crown with thin labial surface and poor appearance (not enough dentine/enamel porcelain covering core material)
how to do axial reduction on all ceramic crown prep
-5013 bur to reduce labial surface to depth grooves (of labial reduction), including 1mm ROUNDED SHOULDER just above gingival level
hold bur upright –> 3-6degree taper
-interproximal reduction: labial –> palatal, hold 5013 bur within bulk of tooth structure to avoid adjacent tooth damage
-remove chips of tooth at interproximal areas with instruments
how to do palatal reduction on all ceramic crown prep
- 5013 bur PARALLEL to gingival (2nd) part of labial reduction
- cut 1mm depth grooves
- bur held upright, join depth grooves and shoulder from axial/interproximal reduction
why to cut palatal reduction parallel to gingival part of labial reduction
maximise retention
how to do cingulum reduction on all ceramic crown prep
285 rugby-ball shaped bur on to cingulum surface til 1mm reduction
all ceramic crown prep shoulder placement:
a. labial and approximal surfaces
b. palatal surface
all ceramic crown prep shoulder placement:
a. labial and approximal surfaces: appearance important –> shoulder just in gingival crevice
b. palatal surface: appearance not important –> shoulder above gingival level –> ease of cleaning/professional inspection
effect of sharp line angles on shoulder
wedging –> fracture of crown
how to smooth incisal edge of all ceramic crown prep and why
5013 bur, held at angle towards palatal surface -> avoid stress point for overlying ceramic material, sharp line angles eliminated
why must there not be sharp line angles/rough surface in all ceramic crown prep
- prevent dragging of impression
- provide surface that crown can fit well
SEE DIAGRAM Q251 all ceramic crown prep: function of a. rounded shoulder b. axial reduction c. concave cingulum
a. rounded shoulder: marginal integrity, structural durability
b. axial reduction: resistance, retention form
c. concave cingulum: interocclusal clearance, structural durability
difference between temporary and provisional crowns, when each may be used
temp: short term, eg when permanent crown is made in lab
provisional: slightly longer term eg to allow evaluation of endo or perio tx
3 requirements of temp restoration
BAM
- Biological 4: protect prepared dentine, prevent gingival tissue overgrowing prep margins, prevent overerupting/tilting of prepared tooth –> maintain contact points/occlusion. materials must not irritate dentine/pulp (anti-caries prophylaxis, pulp protection function)
- Aesthetic: shade matched to pt dentition, same surface topography
- Mechanical: resists occlusal/functional forces without fracturing
2 main functions of temp crown
- stabilise position
- protect underlying tooth prep
what is monocular vision used to check for
- marginal finish (shoulder, chamfer etc)
- no undercuts`
how to adapt marginal fit of directa temp crown
- to reduce height: green stone, slow handpiece
- labio-palatal width: crimping pliers (not fully closed)
when to remove crown in terms of resin setting and why
when resin at snap stage
too short –> not set, distortion
too long –> fully polymerise, difficult to remove
burs to use in class III prep
520 (fast handpiece round bur) to access cavity
slow handpiece round burs to remove caries, angled in all directions
what parts of class III cavity are undercut and why
incisal point, gingival point.. these are created naturally when caries is removed at the EDJ. not recommended to be placed intentionally
4 ways to increase retention in class III cavity
- acid etching enamel surfaces
- total etch (–> bonding to enamel and dentine)
- bevelling of enamel margins –> larger surface area
- retention grooves
what happens during
a. 30s enamel etch
b. 15s dentine etch
a. 30s enamel etch: micromechanical bonding by formation of 40um? pores
b. 15s dentine etch: removes calcified tissue, leaves collagen fibres for hybrid layer
advantages of bevelling enamel margins 4
- provides large sa for bonding
- reduces microleakage
- cross-cuts prisms, better etch pattern
- blends composite in to surrounding tooth surface (no distinct finish line, better aesthetics)
disadvantages of bevelled enamel margins 4
- increased cavity size
- damage to :adjacent teeth, gingivae, rubber dam
when should bevelled enamel margins be considered
where labial margin of cavity is visible and damage to adjacent tooth/supporting structures is minimal
3 poss linings for class III cavity
- light-cured GIC
- setting calcium hydroxide
- total etch and resin alone (bc of small cavity size and dentine tubules sealed by bonding agent)
contents of
a. prime & bond
b. xeno
c. trim
d. bond for provisional ion crowns
a. prime & bond: (PP) penta, acetone, organic resins.
b. xeno: butanol solvent (newer, less volatile)
c. trim: polyisobutylmethacrylate (lower exoterm/ shrinkage than MMA)
d. bond for provisional ion crowns: zinc o-e (plus modifier paste, easy to remove)
hema and penta
HEMA: methacrylate, allows light-cured GIC and bonding resins.
-In bonding resins, HEMA has low molecular weight and low viscosity flows better om etched tooth surface
-allows covalent bonding with collagen adds to final bond strength [NB Trim is higher molecular weight]
PENTA: phosphated ester of bis-GMA
-prime and bond xp and prime and bond NT. Penta (resin) left behind. Penta is polar hydrophilic, forms ionic bonds with HA and penetrates tubules/ spaces around collagen
define thixotropic. relevance
only flows when pressure applied
ideal property of impression materials
when is dry dam used
anterior teeth
where to use each rubber dam clamp
front: C,EW,L
middle: C,EW,L,DW
back: AW,BW,K
common sites for fissure sealant
SAME AS FUNCTIONAL CUSPS
mandibular: buccal fissure
maxillary: palatal fissure
types of fissure sealant
Type I: Sealant only
Type II: Composite and sealant
Type III: Glass ionomer and sealant
type IV: Glass ionomer and composite and sealant
at what stage of caries should fissure sealant be used
enamel caries
resin present in fissure sealant and function
bisGMA/ UDMA
isolates bacteria, stopping them using carbohydrates to produce acids
relationship between intensity of light and distance from surface
intensity of light reduces by the square of the distance away from the surface
(eg 3mm–> 9x less intensity)
difference between siqveland and tofflemire matrix band holders
tofflemire is bent and good for SUBGINGIVAL?
tofflemire holder can be removed separately from the band, less likely to fractre amalgam in EARs
minimal light intensity of light cure
300mW/cm2
what is plain cusp contour
in crown prep occlusal reduction: full width of fissure cut during occlusal reduction and same depth of enamel is cut in mesio-buccal direction to maintain gross anatomical contour (occlusal surface not flat)
why is plain cusp contour important 2
- structural rigidity
- ensures even thickness of gold –> less porosity in thinner layers, more accurate casting
what has higher molecular weight: Trim or MMA?
trim
angle and why and bur used to drill class III cavity
MESIAL. if come from distal/ right angles, more enamel removed from marginal ridge
520 small round bur (fast handpiece)
what parts of class III cavity prep CAN have unsupported enamel and why
labial aspect- it is not subjected to occlusal forces (palatal surface is occluded with by mandibular teeth)
risk of not lining class III cavity
resin in composite may hydrolyse over time (but dentine tubules should have been sealed by bond)
