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NBDE II Board Busters > Operative Dentistry > Flashcards

Operative Dentistry Flashcards

1
Q

glass ionomer cements

A

hybrids of silicate and polycarboxylate cements

powder (calcium aluminofluorosilicate glass) + liquid (polyacrylic acid)

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2
Q

pros of GI cements

cons

A

releases fluoride, chemical adhesion to tooth, micromechanical to composite, high biocompatibility, good thermal insulators (equal to dentin), thermal expansion similar to tooth, after setting it has low solubility in mouth (least soluble cement!)

higher cement film thickness, limited strength and wear resistance

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3
Q

only __ cement is used as a luting agent and a permanent restorative material

A

GI

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4
Q

types of GICs

A
  1. conventional - luting agent ex. ketac-cem
  2. light-cured GIC - liner or base, ex. vitrebond and XR ionomer
  3. resin-modified (hybrid) light cured - ex. Fuji-II
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5
Q

GIs have higher or lower? compressive strength, tensile strength, hardness than composites

A

LOWER

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6
Q

zinc oxide eugenol (ZOE) cements

A

SEDATIVE or temporary filling, insulative base, interim caries tx

advantage - eugenol has palliative effect on pulp

powder is zinc oxide, liquid is eugenol

soluble in oral fluids, difficult to remove from cavity preps

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7
Q

properties of improved zinc oxide eugenol materials

A

good marginal seal, palliative on pulp, easily removed from cavity prep

do NOT have thermal insulation qualities that compare to dentin

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8
Q

ZOE contraindications

A

on dentin or enamel prior to bonding, as base or liner for composites -> eugenol interferes with composite polymerization!
pt allergy to egenol or oil of cloves, not for direct pulp cap (it’s irritating)

NOT NOT NOT for composites

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9
Q

4 types of ZOE materials

A

Type I - temporary cement
Type II - permanent cement
Type III (Reinforced) - temp filling material (IRM) and thermal insulating base
Type IV - cavity liner

basic composition = zinc oxide, eugenol, resin

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10
Q

zinc phosphate cement

A

oldest luting cement, longest track record

powder = zinc oxide, liquid = orthophosphoric acid

primary use as a cement for cast restorations, initial mix is ACIDIC, so use varnish first

has been replaced by polycarboxylate or GIC

superior strength compared to other cements, retention is mechanical

use cool glass slab to incr. working time

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11
Q

zinc phosphate cements can provide good pulpal pretection from ___ but can damage the pulp due to __

A

protection from thermal, electrical, pressure stimuli

damage pulp due to initial acidic/low pH

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12
Q

zinc polycarboxylate cement

A

first cement system developed with potential adhesion to tooth structure
liquid = polyacrylic acid + copolymers
powder = zinc oxide + magnesium oxide

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13
Q

how do zinc polycarboxylate cements compare to zinc phosphate cements? in compressive strength and tensile strength?

A

zinc polycarboxylate strength slightly LOWER than zinc phosphate cements, but HIGHER tensile strength

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14
Q

thermal conductivity of zinc polycarboxylate cement is high/low?

A

low - good protection against thermal stimuli

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15
Q

main advantage of zinc polycarboxylate cement is

con?

A

it can bond to tooth structure cause carboxylate groups can CHELATE TO CALCIUM in the tooth

con - short working time

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16
Q

bases are

A

1-2 mm thick, barriers against pulpally irritating agents, thermal insulation, resistance to compressive strength

a replacement or substitute for protective dentin destroyed by caries

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17
Q

materials used as bases (5)

A
  1. zinc phosphate cement - need varnish
  2. zinc polycarboxylate cement - provides ADHESION
  3. ZOE (type III or reinforced) - not under composites cause eugenol inhibits setting
  4. GIC - fluoride, adhesion
  5. calcium hydroxide Dycal - promote secondary dentin formation

all ok for amalgam and composite, except ZOE can’t work with composite

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18
Q

primary bases are placed on dentin close to the pulp. under amalgam and composite, __ is the primary base. under gold, it’s __, __, or __.

A

amalgam and composite - calcium hydroxide

under gold - zinc phosphate, zinc polycarboxylate, GIC

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19
Q

secondary bases, most common is __ cement

A

zinc phosphate cement over calcium hydroxide base

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20
Q

most important consideration for pulp protection is

A

thickness of remaining dentin

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21
Q

only difference btw a base, cement, and cavity liner is their final application thickness

A

cements 15-25 microns
cavity liners 5 microns
bases 1-2 mm

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22
Q

cavity liners are used to protect the pulp by

A

sealing the dentinal tubules

being replaced by new dentin bonding agents

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23
Q

2 types of cavity liners are

A
  1. cavity varnish (solution liner, Copalite) - reduces microleakage, NOT for composites, not a thermal barrier
  2. suspension liner (ZOE, CaOH) - thicker, CaOH prevents thermal shock
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24
Q

cavity varnish in amalgams is for

A

improving marginal seal, prevent dentin discoloration, prevent acid epenetration

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25
Q

2 types of bleaching

A
  1. office - light activated 35% H2O2

2. home - 10% carbamide peroxide

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26
Q

caries is initiated at the tooth surface by growth of __, which produce __

A

streptococci (mutans, mitis, sanguis (most in oral cavity), salivarius)

produce DEXTRAN SUCRASE (glucosyltransferase), forms extracellular glucans from dietary sucrose -> plaque -> holds lactic acid against tooth

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27
Q

predominant bacteria found in plaque

A
  1. strep sanguis (found earliest)
  2. actinomyces viscosus, naeslundii
  3. strep mutans, mitis, salivarius
  4. veillonella, lactobacilli casei, fusobateria
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28
Q

2 most common cariogenic bacteria found in man are

A

streptococcus mutans

streptococcus sobrinus

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29
Q

main cause of enamel decalcification is

A

lactic acid produced by acidogenic bacteria

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30
Q

main cause/etiology of caries is

A

bacteria, or plaque formation

-initiation of caries requires lots of strep mutans in plaque

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31
Q

pulp defense mechanisms to protect from irritation include

A

sclerotic dentin - peritubular - initial defense
reparative - irritation - 2nd line of defense
vascularity - inflammation

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32
Q

microorganism most assoc. with root caries is

A

actinomyces viscosus

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33
Q

zones of caries

A 
zone I - normal
zone II - carious, subtransparent, can remineralize
zone III - transparent, can remineralize
zone IV - turbid, must be removed
zone V - infected, decomposed, remove
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34
Q

4 zones of incipient caries in enamel

A
  1. translucent - deepest zone
  2. dark - no light, demin and remin
  3. body - demin
  4. surface - unaffected
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35
Q

enamel demin occurs at pH

A

5.5

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36
Q

ductility is

A

metal’s ability to easily be worked into desired shapes

depends on PLASTICITY and TENSILE STRENGTH

expressed in terms of % elongation

decreases as temp increases

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37
Q

malleability

A

metal’s ability to be hammered (compressed) into a thin sheet without rupture

depends on PLASTICITY

increases as temp increases

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38
Q

base metal alloys

A

less resistant to corrosion than noble metals, but they’re strong and are less dense

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39
Q

noble metals

A

resistant to corrosion, don’t oxidize

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40
Q

4 types of high gold alloys

A

Type I: highest content, small inlays, easily burnished cause high ductility

Type II: larger inlays and onlays

Type III: onlays, crowns, can be heat treated, quenched so malleability and dicutility are increased

Type IV: bridges, RPDs, can be heat treated

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41
Q

__ against __ materials is the combo that results in least occlusal wear?

A

gold alloy against gold alloy

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42
Q

disadvantages of cast gold

A

high thermal conductivity, need to use cement which is weakest point in the restoration

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43
Q

primary retentive feature for onlay prep is

A

parallelism of vertical surface (axial walls)

sharp point and line angles incr. retention

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44
Q

cap or shoe

A

cap - complete coverage of cusp, ALWAYS PREFERRED over

shoe - minimal or partial cusp coverage, NEVER indicated on functional cusps

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45
Q

while prepping an inlay or onlay, a gingival bevel is used to

A

remove unsupported enamel and compensate for casting inaccuracies

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46
Q

crystalline gold (mat gold) is used for

A

bulk filling of cavities

flow and adaptation not as good as gold foil or powdered gold

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47
Q

cause of porosities/pits in gold foil is related to

A

improper condensing technique and using oversized pellets

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48
Q

most important factor in securing adapation of gold foil to all parts of a prep is

A

direction the force is applied

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49
Q

during condensation, __ of gold foil is always increased

A

surface hardness

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50
Q

main indication for using a direct filling gold is a

A

small initial class III lesion

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51
Q

amt of force needed to compact direct gold is influenced mainly by

during condensation, what 3 properties of direct filling gold increase?

A

surface area of the condenser

surface hardness, tensile strength, yield strength

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52
Q

Class V prep retention vs resistance form

A

retention - sharp internal line and point angles, at axiogingival and axioocclusal line angles

resistance form provided by flat mesial and distal walls, and convex axial wall parallel to tooth

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53
Q

components of gypsum bonded investments

A
  1. refractory filler - regulates thermal expansions
  2. binder - decrease setting expansion, increase porosity of set material
  3. modifiers

strength of investments for gold alloys depends on amount of GYPSUM

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54
Q

gold alloys shrink upon solidification. dimensional compensation is accomplished by these 2 methods

A
  1. setting expansion - result of normal crystal growth, can be enhanced by allowing investment to set in water
  2. thermal expansion - upon heating, depends on refractory material, the MAIN CAUSE of MOLD EXPANSION
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55
Q

parts of a flame in gas-air blowtorch

A
  1. mixing zone - cool and colorless
  2. combustion - green blue, oxidizing
  3. reducing - dim blue tip, HOTTEST, only part that should be used to HEAT ALLOY
  4. oxidizing - outer zone, if it touches metal then “dross” scum develops
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56
Q

if a cast restoratio is in hyperocclusion, pt will complain of

A

cold sensitivity and pressure in the tooth

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57
Q

minimal reduction of working (functional) cusps is how many mm for amalgam, and cast gold?

minimal reduction of non-working (non-supporting) cusps is how many mm for amalgam, and cast gold?

A
  1. 5-3 mm amalgam
  2. 5 mm cast gold

2 mm amalgam
1 mm cast gold

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58
Q

for metal-ceramic (PFM), occlusal clearance is __ mm and __ facial and lingual reduction

A

occlusal clearance 1.5-2 mm

1.5 mm facial lingual reduction

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59
Q

enamel is etched with 37% phosphoric acid to

A

roughen enamel surface to form tags 10-25 micrometers for mechanical retention, increase surface area, better sealing of margins

will look dull white and chalky

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60
Q

most significant advantage to acid-etch technique is

A

reduction of microleakage

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61
Q

function of dentin conditioner

A

remove smear layer of dentin and etch intertubular dentin (after enamel etch)

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62
Q

unfilled resin adhesive (bonding agent)

A

after primer, cured, can bond to composite or amalgam

  • LOWEST thermal conductivity and diffusivity (good!)
  • offsets the HIGH coefficient of thermal expansion
  • lower modulus of elasticity than filled resins
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63
Q

unfilled resin compressive strength is __, yield and tensile strengths are

A

LOW, even LOWER

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64
Q

marginal leakage related to temp change occurs the most with

A

unfilled resin

-because it has high thermal expansion (bad!)

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65
Q

acrylic provisionals are usually cemented with

A

ZOE

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66
Q

main disadvantage of methyl methacrylate as a permanent restorative material is its

A

low resistance to abrasion

high coefficient of thermal expansion

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67
Q

filled resins (composite resin)

A

inorganic inert filler (silica or quartz)
harder, stronger, more resistant to abrasion, lower coefficient of thermal expansion than unfilled

most based on BIS-GMA or UDMA, diluted with TEGDMA

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68
Q

dental sealants are generally made of

A

Bis-GMA

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69
Q

__ is the property of filled resins that is primarily to blame for failure of CLass II composites

A

low wear resistance

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70
Q

composites are inferior to amalgam in what qualities?

A

compressive strength and wear resistance

no anti-caries effect like GIs

71
Q

composites classified on filler particle size and polymerization method. 2 kinds

A
  1. chemically activated (self cured) - 2 paste system (benzoyl peroxide initatior and tertiary amine activator)
  2. light activated - one paste system, photoiniator (camphor quinone) and amine activator
72
Q

resin filler particles include

A

colloidal silica, quartz, silicate glasses, ion

macrofills (traditional) 10-100 microns diam.
midfills 1-10
minifills 0.1-1
microfills 0.01-0.1 (smoothest finish)
nanofills 0.005-0.01 (new!)
73
Q

what size particles result in better finishing and greater resistance to occlusal wear?

A

small size

74
Q

hybrid and microfills use __ fibers to increase hardness and wear resistance while keeping polishability and esthetics

A

colloidal silica fillers

75
Q

composite filler particle fxns

A

decrease coefficient of thermal expansion and polymerization shrinkage

increase tensile and compressive strengths, hardness, improve wear resistance

76
Q

composite matrix is

A

bis-GMA or UDM

difficulty in finishing is due to softness of resin matrix and hardness of filler particles

77
Q

most desirable finished surface for composites is obtained with

A

aluminum oxide disks

78
Q

couple agent (silane) acts as a

A

adhesive btw inert filler and matrix

79
Q

visible light cure at wavelengths

advantages over UV

A

400-500 nm

greater depth can be cured, resin can be polymerized thru enamel

80
Q

DL of canines for class III should be filled with

A

amalgam NOT composite

-cause composite wont maintain MD dimension of tooth

81
Q

when 2 adjacent class II lesions, prepare which lesion first? fill which one?

A

prepare large lesion first and fill smaller one first

82
Q

retention form definition

A

form of prep to resist DISOLDGEMENT or DISPLACEMENT

ex. dovetail, retention grooves

83
Q

resistance form definition

A

form the walls take to RESIST FORCES OF MASTICATION to prevent fracture

ex. round the axiopulpal line angle, prep perpendicular to forces

84
Q

purpose of titration is to

A

coat alloy with mercury

85
Q

pins

A

largest one that can be safely placed should be used, place at line angles

if it enters pulp -> CaOH -> new site

should be 2 mm into dentin, 2 mm within amalgam, 1 mm from DEJ

86
Q

what tooth requires special attention when preparing the occlusal for a restoration?

A

mand 1st premolar, tilt lingually to avoid encroachment on pulp horn

87
Q

what margins are beveled in a class II amalgam

A

gingival cavosurface of box - only if in enamel

occlusal cavosurface

88
Q

difficult to adapt matrix band to what surface of what tooth

A

mesial of max 1st premolar

89
Q

thickness of a good class II matrix should be __ inches

A

0.002

90
Q

delayed expansion of amalgams is assoc. with

A

insufficient titration and condensation, amalgam contamination by moisture

91
Q

how does amalgam’s coefficient of thermal expansion compare to normal teeth

how does its tensile strength compare to compressive strength

A

2x

tensile is 1/5-1/8 its compressive

92
Q

most important in amalgam’s strength is its __ content

A

mercury

55% + shows loss in strength, fracture, corrsion, etc

93
Q

factors that influence final mercury content include

A

original mercury-alloy ratio
amt of trituration
condensation pressure

94
Q

strongest phase of set amalgam is the __ phase

weakest is

A

GAMMA

gamma-2

95
Q

amalgam facts

A
  • smaller particle size -> higher strength, low flow, better carvability
  • spherical amalgams high in copper have best tnesile and compressive strengths
96
Q

amalgam composition (5)

A
  1. silver 40-70: decrease set time, incr. setting expansion and strength
  2. tin 25-27: opposite effects of silver; causes contraction
  3. copper <3: more free mercury = more setting expansion
97
Q

amalgam’s strength

A

BRITTLE, but good compressive strength

98
Q

brittle describes

A

high compressive strength

low tensile strength

99
Q

mercury vaporization most likely to occur during

A

condensation

100
Q

high copper amalgam alloys

A

10-30% copper to decrease gamma-2 (tin-mercury) phase

  1. spherical - sets faster
  2. comminuted - zinc or zinc-free, cut or microcut
  3. combination (admix) - dispersed phase alloy, MOST COMMONLY USED ALLOY TODAY

better than amalgams cause less likely to corrode, less marginal breakdown

101
Q

creep

A

deformation with time in response to constant stress

high copper and low mercury content DECR. creep

under and overtrituration increase creep

102
Q

creep of a metal indicates it will deform under

A

static load

103
Q

corrosion produces tin __ and tin __accumulate in the gap btw restoration and tooth to make a good seal

A

tin oxide

tin sulfide

104
Q

amalgams should be finished and polished to

A

reduce marginal discrepancies, create more hygienic restoration, reduce marginal breakdown, prevent tarnishing, make it look better

avoid heat (damages pulp and draws mercury to surface)

105
Q

most common problem after placing amalgam is

A

cold sensitivity

cause POOR THERMAL INSULATOR
so place base of CaOH or ZOE

106
Q

restoring a cusp with amalgam requires at least __ mm removed to provide resistance form

A

2 mm

107
Q

adhesive potential is predicted by measuring

A

spreading or wetting of adhesive over a substrate surface

-the smaller the angle, the greater wetting and potential for adhesion

108
Q

3 types of stresses

A
  1. compression - squeezing of material from external forces
  2. tension - pulling, resulting in increase in length
  3. shear - sliding of one layer of a material relative to another layer
109
Q

toughness

A

total energy absorbed to point of fracture

-affected by yield strength, % elongation, modulus of elasticity

110
Q

brittleness

A

opposite of toughness, vulnerable to fracture at or near its proportional limit

has high compressive strength but low tensile strength

ex. amalgam (why it cant have beveled margins, need butt joints)

111
Q

modulus of elasticity

A

material’s stiffness or rigidity

the higher, the stiffer

112
Q

resilience

A

energy a material can absorb before onset of any plastic deformation

113
Q

galvanic shock

A

electrical charge created when 2 dissimilar metals contact

114
Q

consequence of thermal expansion and contraction is

A

percolation

115
Q

rank order of coefficient of thermal expansion

A

tooth (lowest ) -> direct gold (best) -> amalgam -> composite -> unfilled resin (highest, worst!)

116
Q

elastic limit

A

greatest stress a material can be subjected to and still return to its original dimensions when forces are released

117
Q

proportional limit

A

greatest stress produced in a material such that the stress is directly proportional to strain
-high limit has more resistance to permanent deformation

118
Q

yield strength

A

stress slightly higher than proportional limit

119
Q

% elongation of a metal is a measure of

A

ductility; related to permanent strain at fracture

120
Q

property that most closely describes ability of a cast gold inlay to be burnished is

A

% elongation

121
Q

4 types of excavators (remove caries and refine internal prep)

A
  1. hatchet
  2. hoe
  3. angle former
  4. spoon
122
Q

chisels are used to

A

cut enamel

123
Q

instruments used to trim restorative materials

A
  1. knives
  2. files
  3. discoid cleoid
124
Q

3 major parts of hand cutting instruments

A
  1. handle
  2. shank
  3. blade
125
Q

cutting instrument formulas

1-2-3-4 correspond with?

A

blade WIDTH-primary cutting edge angle-blade LENGTH-blade angle

126
Q

bur blades - 2 sides, 3 angles

A
  1. rake face - side toward direction of cutting, contacts tooth
  2. clearance face - away from direction of bur rotation
  3. rake angle - most important design characteristic of a bur blade, angle btw edge of blade to axis of bur
    - soft materials cut best with + angle burs
    - hard materials best with - angle burs
    - carbides usually have - rake angles
  4. edge angle - btw rake and clearance face
  5. clearance angle - eliminates friction, the greater the less friction
127
Q

on a carbide bur, greater number of cutting blades results in __ efficient cutting and a __ surface

A

LESS efficient cutting

smoother surface

128
Q

rotary instrument that produces the roughest tooth surface after use is a

A

cross-cut tapered fissure bur at slow speed

129
Q

less # of blades results in __ cutting

A

more efficient, but rougher surface

ex. cross cut fissure burs

130
Q

4 types of dentin

A
  1. primary - forms initial shape of tooth
  2. secondary - after completion of apical foramen
  3. reparative - formed rapidly in response to irritants, more irregular
  4. sclerotic - tubules that become calcified
131
Q

property most characteristic of current available cement bases is

A

low coefficient of thermal conductivity

132
Q

material with high proportional limit has more resistance to

A

permanent deformation

133
Q

when deep carie is excavated and cavity is close to the pulp,

A

place liner of calcium hydroxide, coat with cavity varnish, then zinc phosphoate cement

134
Q

__ registration of dynamic occlusion is the functionally generated occlusal registration in an indirect gold casting technique

A

static

135
Q

these cannot be used on dentin as a cavity medicament

A

alcohol, CaOH, ethyl chloride, silver nitrate, 10% H2O2

136
Q

__ is the agent most likely to cause necrosis of the sulcular epithelium and adj. CT when impregnated into retraction cord.

A

zinc chloride

you can use epi, aluminum sulfate, aluminum chloride

137
Q

locals reduce saliva during operative by

A

reducing sensitivity and anxiety during tooth prep

138
Q

a typical plymer reinforced ZOE cement retains 20% by weight of __ in the powder

A

polymethyl methacrylate

139
Q

relationship most used to design restorations is

A

acquired centric occlusion

140
Q

reason for cavosurface bevel on inlay is to

A

improve marginal adapation

141
Q

binder in casting investments does what?

A

strengthens investment, contributes to expansion through setting and hygroscopic expansions

142
Q

fluoride is easily exchanged with hydroxyl ion because

A

fluoride is smaller and it has a greater affinity for the hydroxylapatite crystal

143
Q

main disadvantage to using polymethyl methacrylate as a restorative material are its

A

low resistance to abrasion; high coefficient of thermal epansion

144
Q

symptoms of hyperemic pulp

A

pain of short duration, intensified by cold, respond to low levels of EPT

145
Q

porcelain of PFM separated at ineterface, this might have been caused by

A

degassing metal at too low of a tempo and fusing the porcelain at too low of a temp

146
Q

effects of cold working a metal are

A

decrease in ductility

increase in hardness

147
Q

drugs that act as anti-sialogogues (2)

A

atropine

methantheline (banthine)

148
Q

adding __ __ is the procedure indicated to produce cross-linking during polymerization of a linear polymer

A

difunctional monomers

149
Q

__ is the component that could replace eugenol in a zinc oxide paste

A

carboxylic acid

150
Q

chelation is a chemical phenomena common to these 2 cements

A

ZOE and polycarboxylate

151
Q

if fluoride level is 0.6 ppm, and it’s raised by 0.4 ppm, decay in kids should decrease by __% in 7 years

A

40

152
Q

if fluoride in water is upped from 1 - 4 ppm, how does this affect caries

A

no effect, but mottling of enamel increases

153
Q

2 properties that allow composites to be bulk placed with reasonable adaptation are

A

low polymerization shrinkage

low coefficient of thermal expansion

154
Q

2 materials contraindicated under/in contact with composites are

A

varnish

ZOE

155
Q

propantheline bromide (Pro-Banthine) to control salivary secretion is contraindicated in pts with

A

glaucoma or cardiovascular distress

156
Q

pit and fissure sealants are retained best on what teeth

A

max and mand premolars

157
Q

least likely microbial species found in dental plaque is

A

staph aureus

158
Q

Class II in a primary molar for amalgam doesn’t require a bevel because

A

enamel rods incline occlusally

159
Q

most effective way to reduce injury to pulp during restorative is to

A

minimize dehydration of the dentin

160
Q

to determine caries rate for older adults, epidemiologist uses what index

A

DMFT

161
Q

diff btw CLass V prep for amalgam and composite is the

A

angulation of the enamel cavosurface margins

162
Q

__ is the most rigid syringe material

A

polyether

163
Q

bonding of composites to detin depends on __ __ agents

A

difunctional coupling

164
Q

pulp chamber retained amalgam should be __ mm deep for retention

A

3 mm

165
Q

materials in ‘walking bleach’ are

A

sodium perborate

30% aqueous H2O2

166
Q

what determines outline form for Class III composite

A

convenience for access, size, shape, locaiton of caries

NOT extension for prevention

167
Q

reasons to bevel a prep for composite

A

increase surface area of enamel for etching, expose ends of rods, enhance marignal seal

168
Q

what color stain is used to change hue of porcelain

A

orange

169
Q

green and orange stains on mx incisors are from

A

poor oral hygiene

170
Q

stiffness or rigidity is best measured by

A

modulus of elasticity

171
Q

__ is an enzyme when incorporated into mouthwasy is most likely to interfere with microbial aggregation in plaque

A

dextranase

172
Q

most frequent cause of failure of amalgams is

A

improper cavity design

173
Q

pit and fissure caries has what configuration at the DEJ

A

conical on both sides, so bases of BOTH cones at DEJ

NBDE II Board Busters (11 decks)

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