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Flashcards in Operative Dentistry Deck (173):
1

glass ionomer cements

hybrids of silicate and polycarboxylate cements

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

2

pros of GI cements

cons

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

3

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

GI

4

types of GICs

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

5

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

LOWER

6

zinc oxide eugenol (ZOE) cements

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

7

properties of improved zinc oxide eugenol materials

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

do NOT have thermal insulation qualities that compare to dentin

8

ZOE contraindications

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

9

4 types of ZOE materials

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

10

zinc phosphate cement

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has been replaced by polycarboxylate or GIC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

11

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

protection from thermal, electrical, pressure stimuli

damage pulp due to initial acidic/low pH

12

zinc polycarboxylate cement

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

13

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

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

14

thermal conductivity of zinc polycarboxylate cement is high/low?

low - good protection against thermal stimuli

15

main advantage of zinc polycarboxylate cement is

con?

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

con - short working time

16

bases are

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

17

materials used as bases (5)

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

18

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

amalgam and composite - calcium hydroxide
under gold - zinc phosphate, zinc polycarboxylate, GIC

19

secondary bases, most common is __ cement

zinc phosphate cement over calcium hydroxide base

20

most important consideration for pulp protection is

thickness of remaining dentin

21

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

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

22

cavity liners are used to protect the pulp by

sealing the dentinal tubules

being replaced by new dentin bonding agents

23

2 types of cavity liners are

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

24

cavity varnish in amalgams is for

improving marginal seal, prevent dentin discoloration, prevent acid epenetration

25

2 types of bleaching

1. office - light activated 35% H2O2
2. home - 10% carbamide peroxide

26

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

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

27

predominant bacteria found in plaque

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

28

2 most common cariogenic bacteria found in man are

streptococcus mutans
streptococcus sobrinus

29

main cause of enamel decalcification is

lactic acid produced by acidogenic bacteria

30

main cause/etiology of caries is

bacteria, or plaque formation
-initiation of caries requires lots of strep mutans in plaque

31

pulp defense mechanisms to protect from irritation include

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

32

microorganism most assoc. with root caries is

actinomyces viscosus

33

zones of caries

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

34

4 zones of incipient caries in enamel

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

35

enamel demin occurs at pH

5.5

36

ductility is

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

37

malleability

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

depends on PLASTICITY

increases as temp increases

38

base metal alloys

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

39

noble metals

resistant to corrosion, don't oxidize

40

4 types of high gold alloys

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

41

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

gold alloy against gold alloy

42

disadvantages of cast gold

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

43

primary retentive feature for onlay prep is

parallelism of vertical surface (axial walls)
sharp point and line angles incr. retention

44

cap or shoe

cap - complete coverage of cusp, ALWAYS PREFERRED over

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

45

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

remove unsupported enamel and compensate for casting inaccuracies

46

crystalline gold (mat gold) is used for

bulk filling of cavities

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

47

cause of porosities/pits in gold foil is related to

improper condensing technique and using oversized pellets

48

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

direction the force is applied

49

during condensation, __ of gold foil is always increased

surface hardness

50

main indication for using a direct filling gold is a

small initial class III lesion

51

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

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

surface area of the condenser

surface hardness, tensile strength, yield strength

52

Class V prep retention vs resistance form

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

53

components of gypsum bonded investments

2. 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

54

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

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

55

parts of a flame in gas-air blowtorch

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

56

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

cold sensitivity and pressure in the tooth

57

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?

2.5-3 mm amalgam
1.5 mm cast gold

2 mm amalgam
1 mm cast gold

58

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

occlusal clearance 1.5-2 mm
1.5 mm facial lingual reduction

59

enamel is etched with 37% phosphoric acid to

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

60

most significant advantage to acid-etch technique is

reduction of microleakage

61

function of dentin conditioner

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

62

unfilled resin adhesive (bonding agent)

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

63

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

LOW, even LOWER

64

marginal leakage related to temp change occurs the most with

unfilled resin
-because it has high thermal expansion (bad!)

65

acrylic provisionals are usually cemented with

ZOE

66

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

low resistance to abrasion
high coefficient of thermal expansion

67

filled resins (composite resin)

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

68

dental sealants are generally made of

Bis-GMA

69

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

low wear resistance

70

composites are inferior to amalgam in what qualities?

compressive strength and wear resistance

no anti-caries effect like GIs

71

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

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

resin filler particles include

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

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

small size

74

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

colloidal silica fillers

75

composite filler particle fxns

decrease coefficient of thermal expansion and polymerization shrinkage

increase tensile and compressive strengths, hardness, improve wear resistance

76

composite matrix is

bis-GMA or UDM

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

77

most desirable finished surface for composites is obtained with

aluminum oxide disks

78

couple agent (silane) acts as a

adhesive btw inert filler and matrix

79

visible light cure at wavelengths

advantages over UV

400-500 nm

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

80

DL of canines for class III should be filled with

amalgam NOT composite

-cause composite wont maintain MD dimension of tooth

81

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

prepare large lesion first and fill smaller one first

82

retention form definition

form of prep to resist DISOLDGEMENT or DISPLACEMENT

ex. dovetail, retention grooves

83

resistance form definition

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

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

84

purpose of titration is to

coat alloy with mercury

85

pins

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

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

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

87

what margins are beveled in a class II amalgam

gingival cavosurface of box - only if in enamel
occlusal cavosurface

88

difficult to adapt matrix band to what surface of what tooth

mesial of max 1st premolar

89

thickness of a good class II matrix should be __ inches

0.002

90

delayed expansion of amalgams is assoc. with

insufficient titration and condensation, amalgam contamination by moisture

91

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

how does its tensile strength compare to compressive strength

2x

tensile is 1/5-1/8 its compressive

92

most important in amalgam's strength is its __ content

mercury

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

93

factors that influence final mercury content include

original mercury-alloy ratio
amt of trituration
condensation pressure

94

strongest phase of set amalgam is the __ phase

weakest is

GAMMA

gamma-2

95

amalgam facts

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

96

amalgam composition (5)

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

amalgam's strength

BRITTLE, but good compressive strength

98

brittle describes

high compressive strength
low tensile strength

99

mercury vaporization most likely to occur during

condensation

100

high copper amalgam alloys

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

creep

deformation with time in response to constant stress

high copper and low mercury content DECR. creep

under and overtrituration increase creep

102

creep of a metal indicates it will deform under

static load

103

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

tin oxide
tin sulfide

104

amalgams should be finished and polished to

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

most common problem after placing amalgam is

cold sensitivity

cause POOR THERMAL INSULATOR
so place base of CaOH or ZOE

106

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

2 mm

107

adhesive potential is predicted by measuring

spreading or wetting of adhesive over a substrate surface
-the smaller the angle, the greater wetting and potential for adhesion

108

3 types of stresses

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

toughness

total energy absorbed to point of fracture
-affected by yield strength, % elongation, modulus of elasticity

110

brittleness

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

modulus of elasticity

material's stiffness or rigidity

the higher, the stiffer

112

resilience

energy a material can absorb before onset of any plastic deformation

113

galvanic shock

electrical charge created when 2 dissimilar metals contact

114

consequence of thermal expansion and contraction is

percolation

115

rank order of coefficient of thermal expansion

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

116

elastic limit

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

117

proportional limit

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

118

yield strength

stress slightly higher than proportional limit

119

% elongation of a metal is a measure of

ductility; related to permanent strain at fracture

120

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

% elongation

121

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

1. hatchet
2. hoe
3. angle former
4. spoon

122

chisels are used to

cut enamel

123

instruments used to trim restorative materials

1. knives
2. files
3. discoid cleoid

124

3 major parts of hand cutting instruments

1. handle
2. shank
3. blade

125

cutting instrument formulas
1-2-3-4 correspond with?

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

126

bur blades - 2 sides, 3 angles

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

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

LESS efficient cutting
smoother surface

128

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

cross-cut tapered fissure bur at slow speed

129

less # of blades results in __ cutting

more efficient, but rougher surface

ex. cross cut fissure burs

130

4 types of dentin

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

property most characteristic of current available cement bases is

low coefficient of thermal conductivity

132

material with high proportional limit has more resistance to

permanent deformation

133

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

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

134

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

static

135

these cannot be used on dentin as a cavity medicament

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

136

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

zinc chloride

you can use epi, aluminum sulfate, aluminum chloride

137

locals reduce saliva during operative by

reducing sensitivity and anxiety during tooth prep

138

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

polymethyl methacrylate

139

relationship most used to design restorations is

acquired centric occlusion

140

reason for cavosurface bevel on inlay is to

improve marginal adapation

141

binder in casting investments does what?

strengthens investment, contributes to expansion through setting and hygroscopic expansions

142

fluoride is easily exchanged with hydroxyl ion because

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

143

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

low resistance to abrasion; high coefficient of thermal epansion

144

symptoms of hyperemic pulp

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

145

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

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

146

effects of cold working a metal are

decrease in ductility
increase in hardness

147

drugs that act as anti-sialogogues (2)

atropine
methantheline (banthine)

148

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

difunctional monomers

149

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

carboxylic acid

150

chelation is a chemical phenomena common to these 2 cements

ZOE and polycarboxylate

151

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

40

152

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

no effect, but mottling of enamel increases

153

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

low polymerization shrinkage
low coefficient of thermal expansion

154

2 materials contraindicated under/in contact with composites are

varnish
ZOE

155

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

glaucoma or cardiovascular distress

156

pit and fissure sealants are retained best on what teeth

max and mand premolars

157

least likely microbial species found in dental plaque is

staph aureus

158

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

enamel rods incline occlusally

159

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

minimize dehydration of the dentin

160

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

DMFT

161

diff btw CLass V prep for amalgam and composite is the

angulation of the enamel cavosurface margins

162

__ is the most rigid syringe material

polyether

163

bonding of composites to detin depends on __ __ agents

difunctional coupling

164

pulp chamber retained amalgam should be __ mm deep for retention

3 mm

165

materials in 'walking bleach' are

sodium perborate
30% aqueous H2O2

166

what determines outline form for Class III composite

convenience for access, size, shape, locaiton of caries

NOT extension for prevention

167

reasons to bevel a prep for composite

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

168

what color stain is used to change hue of porcelain

orange

169

green and orange stains on mx incisors are from

poor oral hygiene

170

stiffness or rigidity is best measured by

modulus of elasticity

171

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

dextranase

172

most frequent cause of failure of amalgams is

improper cavity design

173

pit and fissure caries has what configuration at the DEJ

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