Resto Flashcards
Indication for inlays
Caries not extending 1/3 of intercuspal width
Types of material used in inlays
Gold - 40 degree bevel at CSM, 30 degree gingival CSM (0.5mm to 1mm wide)
Porcelain - no bevel
Composite - no bevel
*Taper 2-5 degrees diverging occlusal
Discovered phosphoric acid as etchant
Buonocore (1955)
Sugar that prevents glucose from binding to cariogenic microorganisms
Xylitol - increases pH of saliva
Adhesive used by microorganisms to stick to the tooth?
Dextrans, levans
Shape of caries
Pit and fissure -most common
Enamel - base of triangle towards DEJ, apex towards occlusal
Dentin - base of triangle towards DEJ, apex towards pulp
Smooth surface
Enamel - base of triangle towards outer surface, apex towards DEJ
Dentin - base of triangle towards DEJ, apex towards pulp
Best preventive measure for pit and fissure caries? Smooth surface caries?
PFS
Smooth surface: flossing and fluoride
Most sensitive part of the tooth during cavity preparation
DEJ (hydrodynamic theory)
Most common site of proximal caries
Slightly below or gingival to the contact area
Retention, resistance, convenience form
Retention - resist displacement (converging walls)
Resistance - withstand masticatory forces (diverging/parallel mesial/distal walls, 90 degree CSM, flat pulpal floor, depth)
Convenience - ease of operation (1/3 of buccal cusp tip to lingual cusp tip)
Which permanent teeth is mostly subjected to accidental pulp exposure?
Mandibular 1st premolar (facial pulp horn)
Bevels in class II amalgam prep??
Axiopulpal line angle
Gingival cavosurface margin
Retentive feature of class II amalgam prep
Depth 1/2 the size of a 1/4 round bur: 0.25mm
At axiofacial line angle
Axiolingual line angle
Line angle vs point angle
Line angle - where two walls meet
Point angle - where three line angles meet
Difference of class ii gold inlay and class ii amalgam?
Buccal and lingual walls of gold: 2-5° diverging occlusally
Reverse bevel at the axiogingival line angle for gold (proximal lock) vs slightly rounded gingivo-axial line angle
Occlusal CSM: 40° gold, 90° amalgam
Proximal CSM: 40° g, 90° a
Gingival CSM: 30° g, 90° a (beveled 15-20°) for permanent
No bevel in deciduous!!! enamel rods at the cervical are oriented towards occlusal!
Best resto material for the restoration of the distolingual surface of canine?
Gold!
Best approach in preparing class III caries
Lingual
Retentive feature of class III
0.25mm or 1/2 of 1/4 round
Gingivoaxial and incidoaxial line angle
Orientation of walls of class V
Diverging!!! You see all the walls
What is class VI (SIMON)
incidal edge of anterior teeth or cusp of posterior teeth
What is a cervical burnout
Radiolucency Found below the cej on the root due anatomic variation or a gap between enamel and bone covering the root (roots are concave)
Caries that progressed just into the DEJ
Frank caries
Other term for root caries
Senile caries - associated with aging due to gingival resorption
Decrease coronal caries (sclerotic dentin formation)
Zone of carious enamel
Translucent zone -deepest
Dark zone -zone of remineralization
Body zone -largest zone -demineralized zone
Surface zone -outer most, unaffected by carious lesion
Zone of carious dentin
Normal dentin - no bacteria
Subtransparent
Transparent - demineralized softened dentin but no bacteria in tubules
Turbid dentin - zone of bacterial invasion, remove
Infected - outermost carious zone with numerous microorg, remove
Where is the fastest progression of caries?
DEJ
Enamel vs dentin: dentin - less mineralized
Common bleaching agent in dentistry
Hydrogen peroxide ~30% (tx: vitamin E)
Sodium perborate
Light activated/inactive: carbamide peroxide
Movement of fluid through small channel or porous material
Percolation
Setting of amalgam via?
Crystallization
24hrs for complete setting
Mercury to alloy ratio
Traditional is 8:5 but high mercury was associated with extensive expansion (we only want minimal expansion for sealing)
Eame’s technique 1:1
Modern dentistry <1: 1 or <50:50
Amalgam composition
Silver, copper, tin, mercury, zinc
Silver and copper
⬇️ working time and creep, ⬆️expansion and strength
(copper decreases corrosion)
Tin
⬆️ working time and creep
⬇️ expansion and strength
Mercury (must be <50%)
⬆️ working time and creep, expansion
⬇️ strength
Produces different phases
Zinc
⬆️⬆️ expansion when contaminated
Prevents oxidation; acts as scavenger for oxides
⬆️ shelf life
Types of amalgam alloy particles, pros and cons
Spherical - less condensation force needed, faster working time
Admixed - more condensation force needed, easier to carve
Irregular - irregular shape particles (lathe-cut particles)
Which amalgam alloy needs the most amount of mercury?
Irregular - more spaces need to be filled by mercury
Spherical - least amount of mercury
Phases of amalgam reaction
Gamma phase (30% of amalgam)
silver + tin alloy
Strongest and corrodes least
Gamma-one phase (60% of amalgam)
Silver + mercury
Second strongest phase
Gamma-two phase (10%)
Tin + mercury
Weakest and softest
Corrodes the most
Prone to microporosities
Copper-tin phase
Decreased corrosion
Replaces gamma-two phase
Type of amalgam that almost completely eliminates gamma-two phase
High copper amalgam (>9% to 30% copper)
Remember: Low copper amalgam (<6% copper)
Increased expansion of amalgam is related to:
Increase mercury
Short trituration time
Decrease condensation pressure (less mercury moves up, more mercury content)
Increase particle size
Moisture contamination (zinc)
Gradual time-dependent dimensional change due to constant stress
Creep
Chemical reactions between amalgam and local environment
Tarnish - thin layer of corrosion at the top of restoration, loss of luster of amalgam
Corrosion - formation of oxides resulting in weakening of the metal
Advantage of corrosion byproducts of amalgam
Increased sealing properties
Ex. Tin sulfide
Process of mixing an alloy with mercury
Trituration
Undertriturated - dull, rough, grainy, low strength
Properly triturated - shiny, wet, homogenous, optimal strength
Overtriturated - wet, sticky appearance, moderate strength
What is the procedure in which amalgam is rubbed using the index finger and the thumb
Mulling
Most common cause of amalgam chipping during carving
Carving after working time
When there is ditching of amalgam resto, when is it indicated for replacement?
> 0.5mm depth of ditch
How do you prevent ditching when amalgam carving
Resting the sharp instrument on the cusp while carving
Distance from the margin of the mesial and distal wall to proximal surface must not be less than
Premolar: 1.6mm
Molars: 2mm
Most difficult tooth to adapt a matrix band
Mesial of maxillary 1st premolar due to the mesial developmental depression
Why is the matrix band extended occlusally when restoring class II cavities
To allow for overfilling
Working end of cutting instrument is called? Non-cutting instrument?
Blade - cutting instrument
Nib - non-cutting instrument
Face - working surface of the nib or end part of nib
Four unit formula for cutting instruments
W A L A
1st number - Width of blade (#÷10 = mm)
2nd number - angle of cutting edge: always > 50% (#% x 360)
3rd number - Length of blade (mm)
4th number - angle of blade: always less than 50% (#% x360)
Three unit formula
W L A
W A L A
1st number - Width of blade (#÷10 = mm)
2nd number - Length of blade (mm)
3rd number - angle of blade: always less than 50% (#% x360)
Remember: for 3 unit formula, the
Cutting edge angle is 90°
Used mainly to remove caries and refine internal walls of preparation
Excavators
Creates retentive features, sharpening internal line angles
Ordinary hatchets
For planing walls
Sharpening line angles especially in class iii and class v direct gold
Hoe
Sharpening line angles
Creating retentive features
Enamel margin beveling
Combination of gingival margin trimmer and chisel
Mono angled only
Angle former
Amalgam carving
Caries removal
Can be bin-angled or tripled angled
Cleioid and discoid (spoons)
Types of chisel: carpenter’s chisel
Straight chisel
Type of chisel: Wedelstaedt design
Slightly curved chisel
Double angled chisel
Bin-angled
For cutting and planing enamel surfaces
Enamel hatchets
For beveling gingival enamel margins
Gingival marginal trimmer
Most common filler used in composites
Colloidal silica
Most common coupling agent
Silane
Most common Resin matrix? Discovered by? Others?
BIS-GMA: bisphenol A-glycidyl methacrylate (Bowen, 1962)
UEDMA: urethane dimethacrylate
TEGDMA: triethylene glycol dimethacrylate
Effect of filler material to polymerization shrinkage
High filler (packable) = less PS
Less filler (flowable) = more PS
Increment for composite
2-3mm
Curing time for composite
2 cycles of 20 secs
*Faster the polymerization, the greater the shrinkage
*Darker shade needs more curing time
Used to polish composites
Aluminum oxide
Used to polish amalgam
Tin oxide
Zinc oxide
Used to produce radiopacity (to provide contrast against secondary caries)
Barium
Zinc
Boron
Zirconium
Yttrium
Substances that inhibit polymerization
Eugenol (oil of cloves)
Cavity varnish
Greatest disadvantage of polymerization
Shrinkage
Ratio of bonded surfaces to the unbonded surfaces
Configuration factor (c-factor)
Lower c factor, lower p.shrinkage, lower risk for debonding and microleakage
C factor of cavity preps
I - 5:1 (5)
II - 4:2 (2)
III - 3:3 (1)
IV - 2:4 (0.5)
V - 5:1 (5)
Purpose of etching
Reduce microleakage
Create microporosities for micromechanical retention
Removes smear layer
Conserves tooth structure
Increases surface energy which promotes wetting and adhesion
Cleanses surface
Used for etching or conditioning
37% phosphoric acid (most common)
EDTA
maleic acid
Citric acid
Beveling prior to etching is recommended due to:
Reduces microleakage
Improves esthetics
Improves bond strength (by exposing enamel rods)
Increases surface area
Critical pH of dentin
6.2
Discolored, corroded, superficial layer frequently seen on the surface of a dental amalgam resto is most likely a ____
Sulfide
Latin name for enamel
Substantia adamantina
Latin name for dentin
Substantia ebornea
Latin name for cementum
Substantia ossea
inhibitor of polymerization to prolong shelf life of monomer
hydroquinone (iba function neto sa developer -brings out contrast)
initiator of heat cure polymer
benzoyl peroxide
initiator of self cure polymer
bezoyl peroxide
initiator of composite resin
benzoin methyl ether (use UV light)
Camphorquinone (visible light?)
composition of dental amalgam alloys
silver - 70%
tin - 26%
copper - 3-5%
zinc 1%
