Prosthodontics Flashcards Preview

NBDE II Board Busters > Prosthodontics > Flashcards

Flashcards in Prosthodontics Deck (243)
Loading flashcards...
1
Q

mechanical properties of resins are influenced by

A
  1. MW of the polymer
  2. degree of cross-linking
  3. composition of monomers
  4. EXPAND in water and distort when dried out
2
Q

acrylic resin powder (polymer) is made of

A
polymethyl methacrylate (PMMA) polymer, benzoyl peroxide initiator
-cross linking contributes to strength
3
Q

acrylic resin liquid (monomer) is made of

A

PURE methyl methacrylate (MMA) monomer, hydroquinone inhibitor, cross-linking agents, checmical activator (dimethyl-p-toluidine)

-other monomers like ethyl methacrylate are less irritating to the pulp

4
Q

heat is used as an accelerator to decompose ___ (initiator) into free radicals to initiate polymerization of MMA PMMA

A

benzoyl peroxide

5
Q

the liquid monomer most frequenly used in polymer systems in dentistry

A

MMA

6
Q

heat cured resins have more/less residual monomer and higher MW than self-cured resins

A

LESS, so they are stronger and have better color

7
Q

in self-cured materials, a chemical activator like __ (tertiary armine) is added to the monomer MMA to decompose the benzoyl peroxide into free radicals -> polymerization

A

dimethyl-p-toluidine

8
Q

what kind of resins are used for repairs

A

self-cured (instead of heat) because risk of distorting the denture is less

9
Q

denture STABILITY involves

A
  • relationship of denture base to bone that resists DISLODGEMENT in horizontal direction
  • resistance to horizontal, lateral, torsional forces
10
Q

denture SUPPORT involves

A

resistance to VERTICAL seating provided by rests and the denture base

MOST important design characteristic for oral health

11
Q

denture RETENTION involves

A

resisting force to gravity, sticky foods, forces assoc. with mandibular movement
-direct and indirect retainers, clasps in undercuts provide retention

12
Q

denture RECIPROCATION involves

A

part of restoration counters effects in another

ex. lingual clasp arm counteracts buccal arm
- achieved by opposing flexible retainers with guide planes, minor connectors, rigid clasp arms, plating

13
Q

bracing is

A

horizontal force ransmission by placing rigid parts of clasps or other parts in non-undercut areas of abutment teeth

14
Q

guidance is

A

during insertion and removal, obtained by contact of rigid parts of framework with areas on axial tooth surfaces parallel to path of insertion

15
Q

impression taking for complete dentures recommend

A
  • border molding

- best for pt with loose hyperplastic tissue is to register it in a PASSIVE position

16
Q

primary indicator of accuracy of border molding is

A

stability and lack of displacement of custom tray in mouth

17
Q

most critical area in border molding for max denture is the

A

mucogingival fold above the maxillary tuberosity

  • important for retention
  • other areas: labial frena in midline and bicuspid area
18
Q

in border molding, the distofacial extension is determined by position and action of the __ muscle

distolingual is limited by action of the __ muscle

A

MASSETER (anterior fibers pass outside buccinator)
-the buccinator lies under the flange in this area but the fibers run anteroposterior in a horizontal plane and their action is weak

SUPERIOR CONSTRICTOR

19
Q

most likely tissue rxn to gross overextension is

A

epulis fissuratum

  • due to clefts found in hyperplastic tissue
  • occurs in vestibular mucosa
  • appears as PAINLESS FOLDS of fibrous tissue
20
Q

localized or generalized chronic inflammation. trauma and secondary fungal infection are the most likely causes

A

denture stomatitis

tx: better OH, rest, anti-fungal (Nystatin)

21
Q

condition frequently observed under ill-fitting denture, esp. with a relief chamber, masses are painless, firm, pink or red nodular proliferations, candida albicans may contribute

A

inflammatory papillary hyperplasia

22
Q

masseter’s superficial layer originates from the maxilla’s __ and inserts in the mandible where?

A

maxilla’s zygomatic process and inserts at the angle and lower lateral side of the ramus of the mandible

23
Q

a tendon that lies btw the buccinator and superior constrictor is the

A

pterygomandibular raphe

24
Q

a thin, curved bony process extension of the medial pterygoid plate of sphenoid bone that serves as the superior attachment of the pterygomandibular raphe

A

hamulus

25
Q

thin cleft btw maixllary tuberosity and hamulus, where a max denture must extend into is the __ __

A

hamular notch

26
Q

group of mucous gland ducts, posterior to jxn of hard and soft palates near midline is

A

fovea palatini

27
Q

palatoglossus, superior pharyngeal constrictor, mylohyoid and genioglossus are influential in border molding what area?

A

LINGUAL of mandibular impression

28
Q

difference btw border molding with ZOE instead of modeling plastic is that

A

ZOE has to be border molded in one insertion and within setting time

29
Q

what regulates the paths of the condyles in mandibular movements?

A

size and shape of bony fossae and menisci and muscles

30
Q

primary support for max denture are

A
  1. residual ridges

2. palatal rugae

31
Q

if pt complains that when they smile, upper denture doesn’t hold, you need to adjust

A

buccal notch and buccal flange due to excessive thickness

32
Q

if pt complains that max denture is loose when mouth is wide open, might be because

A

maxillary DB flange being too thick can interfere with movement of the coronoid process

33
Q

if pt has sore gums and aching muscles at bottom of face after wearing dentures for hours it means

A

opposing teeth of denture have enough space -> reduce VDO

34
Q

tingling or numbing at corner of mouth or lower lip after few days is caused by

A

excessive pressure from lower buccal flange in region of mental foramen

35
Q

posterior palatal seal in max complete denture

A
  • excessive depth usually causes unseating of the denture
  • always done by the DENTIST
  • width of seal AP is concave, 3 mm in midline and 6 mm in lateral areas

Functions

  1. completes border seal
  2. prevents food impaction
  3. improves retention
  4. ** compensates for polymerization and cooling shrinkage of denture resin during processing
36
Q

posterior palatal seal landmarks

A

posterior outline - vibrating line, the hamular notch is ON the posterior border

anterior outline - formed by “blow” valsalva line at distal extent of hard palate, approximation of the jxn of hard and soft palate

37
Q

changes on max arch in pt who wears complete max denture and LACKS posterior occlusion includes

A
  • hyperplastic tissue on anterior max ridge
  • poor bone structure
  • fibrous tuberosities
  • pt’s CC: loose denture, can’t see upper teeth
38
Q

pt with upper complete and mand bilateral distal extension may show

A

decreased VDO, prognathic appearance

39
Q

when a complete max denture opposes natural mand. anterior teeth, what happens to the max anterior ridge?

A

becomes FLABBY

40
Q

when the posterior max buccal space is entirely filled with the denture flange, interference may occcur with movement of the

A

coronoid process -> dislodgement

41
Q

max. sinus enlarges throughout life if it’s not restricted by teeth or dentures. as it enlarges, what happens to the tuberosity?

A

moves downward

-if there is no contact with the retromolar pad at VDO, the tuberosity must be reduced

42
Q

submucosal vestibuloplasty

A

usually on upper arch to improve denture base area

43
Q

palatal tori occur in __ % of population and are more common in males/females?

A

20-25%, women

  • tissues covering it are thin with poor blood supply, post-op healing is slow
  • NOT usually removed for denture fab but MANDIBULAR ones are!
44
Q

indications for palatal tori removal include

A

impinging on soft tissue, fills vault and prevents formation of adequate denture base, undercut, extends so far posterior that it interferes with posterior palatal seal, psychologically disturbing to the pt

45
Q

primary support area for mandibular complete denture is

A
BUCCAL SHELF (bone structure, right angle to occlusal plane)
-if residual ridges are large and broad then it's also support
46
Q

second peripheral seal for mand. coimplete denture is the __ border

A

anterior lingual

47
Q

what will happen to the alveolar ridge is a mand. complete denture base terminates short of the retromolar pad?

A

RESORPTION of the alveolar ridge

48
Q

underlying __ __ under the retromolar pad resists resorption

A

basal bone

49
Q

mand. dentures don’t rely on suction, but rely on STABILITY from

A

covering as much basal bone as possible without impinging on muscle attachments

50
Q

mandibular molars should NOT be placed over ascending area of the mandible because

A

the occlusal forces over the inclined ramus dislodge the denture

51
Q

most common cause of POROSITIES in a denture is from

A

insufficient pressure on the flask during processing

  • acrylic resin for repairs should be under 20-30 psi air pressure
  • usually happens in THICKEST part of the denture
  • also occur if packing and processing of powder and liquid is too plastic (stringy/sandy)
52
Q

purpose of occlusal rims is to

A

determine and establish VDO
make jaw relation records
establish and locate future position of teeth

53
Q

in a complete denture pt, when the teeth, rims and central bearing point are in contact and mandible in CR, then the length of the __ is the occlusal vertical dimension

A

length of the face

54
Q

correct VDO is evaluated using 4 methods

A
  1. appearance of facial support
  2. observation of space btw rims at rest
  3. measurement btw dots on face
  4. observation when S sound is enunciated, check speaking space
55
Q

excessive VDO can result in

A

trauma to underlying supporting tissues

56
Q

__ is the most likely cause of cheilosis

A

closed vertical dimension

57
Q

what has the greatest effect on setting of mandibular 2nd molars?

A

posterior determinants of occlusion (2/3 height of retromolar pads)

58
Q

frankfort horizontal plane extends from

A

outer canthus of eye to ear tragus

59
Q

what 3 factors affect correct positioning of the lips in complete dentures

A
  1. VDO
  2. thickness of anterior border
  3. teeth position
60
Q

changes assoc. with the edentulous state

A
  • deepening of nasolabial groove and narrowing of lips
  • prognathic appearance, increase in columella-philtral angle
  • loss of labiodental angle and decrease in horizontal labial angle
61
Q

after first few days of new dentures, pt should expect some difficult in masticating most foods and excess saliva cause of

A

reflex parasympathetic stimulation of salivary glands

62
Q

2-step schedule for tooth removal prior to delivery of immediate completes

A

step 1 - ext all posterior teeth except max 1st PM and opposing tooth (a stop to keep VDO)

step 2 - after ridges heal, anterior teeth are ext at time of insertion

63
Q

1st day of wearing immediates instructions

A

not to remove denture
eat soft foods
return in 24 hrs for eval

64
Q

primary role of anterior teeth is

A

esthetics

most common error is placing teeth directly over the edentulous ridge

labial surface of central incisor should be 8 mm anterior to the incisive papilla

65
Q

BL width on denture teeth are more narrow to

A

reduce stress transferred to denture support area while eating, and increases tongue space

66
Q

common errors when arranging denture teeth

A

-set mand teeth too far forward to meet max teeth
-fail to make canines turning point of arch
-set mand 1st PM buccal to canines
-establish occlusal plane arbitrarily
0not rotating anterior teeth enough to give narrower effect

67
Q

why do you use plastic instead of porcelain teeth

A

plastic bonds well to acrylic resin

68
Q

immediate dentures should be relined when?

A

in 5 and 10 months post-ext

69
Q

a flabby max anterior ridge under a complete denture is often assoc. with

A

retained natural mandibular anteriors

70
Q

benefit of an overdenture (root-retained) is

A

PRESERVATION of the ALVEOLAR RIDGE

71
Q

potential probs with new dentures

A
  1. cheek biting caused by
    - posterior teeth set edge-edge, need proper horizontal overlap
    - inadequate VDO
    - bite corners of mouth -> reset canines and PMs
  2. lip biting - caused by reduced muscle tone or overbite
  3. tongue biting - posterior teeth too far lingual
  4. speech - bad tooth position, palatal contours
72
Q

pt edentulous for many yrs has more distorted speech than pt edentulous for a short time due to

A

loss of tonus of tongue muscles

73
Q

what might you see in an uncontrolled diabetic

A

impaired healing
poor tissue tolerance
rapid bone resorption

74
Q

Sounds

A
  1. S - bring mandible close to maxilla
  2. hissing - incisal edges almost touching
  3. Th - tongue protrudes 2-4 mm btw max and mand teeth
  4. F and V - incisals of max and lower lip
  5. P and B - lips
  6. T - if teeth are too lingual it will sound like a D and vice versa
  7. whistling - from high palatal vault or constricted palate, insufficient overjet, overbite, bad palatal contour
75
Q

if pt complains of irritation of basal seat, can be cause of

A

premature occlusal contacts (most common cause!)
bad OH
nutrition imbalance
excessive VDO

76
Q

pt with max denture complains of burning sensation means

A

pressure on INCISIVE FORAMEN

in mandibular anterior -> MENTAL FORAMEN

77
Q

facebow records

A

pt’s maxilla/hinge axis relationship

  • orients maxillary cast to hinge axis on articulator
  • hinge axis facebow enables dentist to alter VDO on articulator
78
Q

pantograph is used for

A

tracing paths of the condyle, uses 2 facebows

79
Q

preferred method to preserve facebow transfer is a __ index

A

plastic index

2 methods

  1. plaster index of max denture before removing denture from articulator and cast
  2. place a piece of 10x wax on occlusal of mandibular and close the articulator in CR, chill, drop incisal guide pin to touch the table
80
Q

ARCON articulator

A

condyle on LOWER member
condylar paths on UPPER

angle btw condylar inclination and occlusal plane is FIXED
-used for dx mounting of study casts

81
Q

NON-ARCON articulator

A

condyle on UPPER member
condylar paths on LOWER

angle btw condylar inclination and occlusal plane is NOT fixed
-more proper to fabricate DENTURES

82
Q

diabetes is assoc. with

A

delayed healing
rapidly progressing perio disease with bone loss
increased calculus
predilection for periapical abscesses

83
Q

can surveying determine areas of support?

A

no

84
Q

kennedy classifications are based on

A

the most posterior edentulous area to be restored

85
Q

4 Kennedy Classes

A

I - bilateral distal extension
II - unilateral distal extension
III - unilateral edentulous spaces bound by teeth, tooth-borne
IV - anterior teeth missing and across midline

86
Q

Craddock Classification is based on the denture type

A

Type I - mucosa borne
Type II - tooth borne
Type III - mucosa and tooth borne

87
Q

major connector

A

connects parts of the prosthesis located on one side of the arch to the other

  • must be RIGID
  • should be free of movable tissues and shouldn’t impinge on gingiva
  • relief should be provided
  • bony and soft tissue prominences should be avoided
88
Q

major connectors most frequently encounter interferences with what teeth

A

lingually inclined mandibular premolars

89
Q

mandibular major connectors

  1. lingual bar
  2. lingual plate
  3. labial bar
A
  1. lingual bar - upper border at least 4 mm below gingiva
  2. lingual plate - upper border should be at middle 1/3 of lingual surface
  3. lingual bar - 3 mm below gingiva
90
Q

maxillary (palatal) major connectors

  1. transpalatal bar
  2. horseshoe
  3. AP bar
  4. palatal plate connector
A
  1. palatal bar - lack rigidity, for toothborne, short span
  2. horseshoe - for torus
  3. AP bar - MOST RIGID
  4. palatal plate connector - for simple edentulous areas and full palatal coverage
91
Q

distal extension RPD receives support from

A

residual ridge, tissue-bearing areas, selected abutment teeth, fibrous CT over alveolar process

92
Q

most important factor in determining success of distal extension RPDs is

A

proper coverage over residual ridge

-should go over retromolar pad for stability and minimizing torque

93
Q

if pt complains of sensitivity to percussion on abutment tooth of distal extension RPD, prob is most likely

A

OCCLUSION

-defective occlusal contacts can also cause a feeling of “looseness”

94
Q

altered cast technique purpose

A

record form of edentulous segment without tissue displacement and to accurately relate edentulous segment of teeth via metal framework

impression materials can’t record anatomic form of teeth and physiologic form of soft tissue in a functional relationship simultaneously

95
Q

stress breaker

A

device that relieves abutment teeth to which FPD or RPD is attached, of all or part of forces generated by occlusal function

96
Q

when a stress breaker is incorporated next to a free-end distal extension RPD, the functional stress is directed onto the

A

residual ridge, and only minimal transfer of functional stress to abutment teeth occurs

97
Q

3 types of stress breakers

  1. wrought-wire clasp
  2. split-bar major connector
  3. stress-breakers with movable joint
A
  1. wrought wire - simplest form, higher yield strength, flexible, ductile, resilient, greater tensile strength
  2. split bar (Ticonium ‘hidden-lock’) - flexible btw direct retainer and denture base
  3. with movable joint - btw direct retainer and denture base (DE hinge, dalbo attachment, Crismani attachment, ASC-52 attachment)
98
Q

cast metal is

A

any metal melted and cast into a mold

-when the casting is cold-worked ex. wire, it’s a “wrought metal” (tensile strength, hardness, strength > cast)

99
Q

elongation is

A

the most important mechanical property involved when a base metal RPD clasp is adjusted

100
Q

cast wire compared to wrought wire

A

less yield strength, less flexibility, less ductility and resilience
-cast wire has unavoidable POROSITIES

101
Q

indirect retainers include

A

rests, minor connectors, proximal plates

  • fxn to prevent/counteract vertical dislodgement of distal extension base of RPD
  • ANTI-ROTATIONAL
  • counteracts upward rotation of base and serves as a 3rd reference for seating the framework and making altered cast impressions
  • protects soft tissues
102
Q

minor connector

A

connects major connector or base of RPD with other units (clasps, indirect retainers, occlusal rests)

2 functions

  1. transfer functional stress to abutment teeth
  2. transfer effect of retainers, rests, stabilizing components
103
Q

indirect retainer design

A
  • should be at right angles to fulcrum line
  • IR should be in rest seats
  • IR located farthest from clasp tips closets to edentulous areas provides best leverage against lifting/dislodging
104
Q

rests are to provide

  1. occlusal
  2. cingulum
  3. incisal
A

VERTICAL support for RPD

  1. occlusal - forms acute angles with minor connectors, thickness 1.5 mm
  2. cingulum - usually confined to maxillary canines, sometimes max centrals
  3. incisal - not esthetic
105
Q

direct retainers

  1. intracoronal attachment
  2. clasps (extracoronal retainers)
A
  1. intracoronal - most esthetic!

2. clasps - most common, 2 types

106
Q

2 types of clasps

  1. Suprabulge
  2. Infrabulge
A
  1. suprabulge - originate from ABOVE survey line
    - circumferential
    - ring clasp: encircles nearly all of tooth to engage an undercut on same side of tooth as the rest
    - embrasure clasp: when no edentulous space
    - reverse action clasp (hairpin): engage undercut on same side of abutment as the rest or any posterior tooth
    - extended arm: circumferential that extends to increase splinting and get better undercut
    - 1/2 and 1/2 clasp: one circumferential from rest and another from minor connector on opposite side
  2. Infrabulge (Roach, I, J, U, L, T bar) - approaches crown from below height of contour, must not be placed in tissue undercuts
107
Q

pros/cons of infrabulge retainers

A

pros - efficient retention, less distortion of coronal contours, cleaner, esthetic, adjustable

cons - irritating to vestibule, not good for bracing

108
Q

infrabulge retainers provide retention by

A

resistance of metal to DEFORMATION (rather than frictional resistance by contact of clasp to tooth)

109
Q

intracoronal retainers

A

produce mechanical and frictional retention, esthetic, not used for distal extension

110
Q

short arm clasp < 7 mm should be made in a __ gauge wire

A

20 gauge, need finer gauge for flexibility

111
Q

flexibility of a retentive clasp depends on

A
  1. clasp length
  2. thickness
  3. width
  4. cross-sectional form
  5. clasp taper
  6. clasp material
112
Q

failure of RPDs due to clasp design is best avoided by

A

altering tooth contours

113
Q

reciprocating element must be placed __ the direct retainer, and contact the abutment where?

A

OPPOSITE

-must contact abutment as the retentive tip passes over the tooth’s height of contour

114
Q

clasp assembly consists of

A

retentive clasp arm, reciprocal (stabilizing clasp arm), minor connectors/rests

115
Q

reciprocal clasp arm functions on RPD include

A

reciprocation, staiblization, indirect retention (bracing)

116
Q

facial and proximal contours of __ and __ most often need to be altered

A

premolars and molars

117
Q

guiding planes serve to assure

A

predictable clasp retention

118
Q

precision attachment restoration

A

metal male and female parts that fit together

semi-precision attachment - cast into the crown and RPD

con - NEVER in distal extension RPD without stress breaker

119
Q

base metal alloys

A

compared to gold: lower density, higher resistance to deflection, higher modulus of elasticity, higher melting point temp, lower yield strength

120
Q

advantages of rpd cast chromium cobalt alloys

A

corrosion resistant, high strength, low specific gravity, low density, high modulus of elasticity (stiffness), cheap

BUT very inflexible (no ductility or malleability)

121
Q

chromium responsible for

cobalt is for

nickel?

A

corrosion resistance
-RPD is resistant to tarnish and corrosion cause of its surface oxide layer

cobalt - incr. rigidity, strength

nickel - ductility

122
Q

ADA Classes of Alloys (I-IV)

A

I: small inlays
II: larger inlays and onlays
III: onlays, crowns, short-span FPDs
IV: thin veneer crowns, long-span FPDs and RPDs

123
Q

elongated grains in wrought wire indicates it has been

A

cold worked

124
Q

Paget’s Disease (osteitis deformans) often discovered in dental office cause

A

pt’s dentures don’t fit due to widening of alveolar ridges

  • a chronic bone disorder, bones enlarge and are deformed
  • enlarged head, hearing loss, blindness
125
Q

__ is the most common change assoc. with systemic disease

A

osteoporosis

126
Q

veneers should be treated with

A
  • silane, protected with light cured unfilled resin
  • etch tooh and apply unfilled bond resin
  • composite applied on veneer
  • stick on veneer
127
Q

a reverse 3/4 crown is most often made for what tooth

A

mandibular molar

128
Q

7/8 crown is

A

3/4 crown with vertical distobuccal margin positioned slightly mesial to the middl of the buccal surface
-good esthetics, good abutment

129
Q

bevel (feather-edge) margin

A

best for CAST FULL GOLD but in practice it’s hard to read on impression and die

least marginal strength

-> an ACUTE edge/angle is the optimum margin for casting

130
Q

chamfer margin

A

PREFERRED FINISHING LINE for cast full gold

-adv of easily definable margin and minimal tooth prep

131
Q

shoulder margin (BUTT)

A

for porcelain jacket and ALL CERAMIC

  • edge strength of porcelain is low
  • provides resistance to occlusal forces and minimizes stress
  • disadvantage is inaccuracies in crown fit are reproduced at margin -> incr. thickness of cement
  • POOREST for cast metal
132
Q

shoulder with bevel

A

allows sliding fit

-for proximal box of inlays and occlusal shoulder of mand 3/4 crowns, labial margins of PFMs

133
Q

most common cause of crown failure is

A

lack of attention to tooth shape, position, contacts

134
Q

greatest potential for wear exists btw what 2 materials

A

porcelain and tooth

  • gold is better for occlusal cause its wear is more like enamel
  • porcelain wears opposing dentition faster
  • gold preferred for bruxism
135
Q

FULL GOLD CROWNS

A

circumferential and occlusal reduction 0.5-1.0 mm

136
Q

ALL-CERAMIC CROWNS

A

tendency to fracture at minimum deformation

-LOW FLEXURAL STRENGTH

137
Q

rank porcelain flexural strengths

A
  1. in-ceram zirconia = 800 Mpa
  2. procera
  3. in-ceram
  4. IPS empress
  5. aluminous = 100
  6. feldspathic = 60-90
138
Q

preps for what restorations must be well rounded with no sharp angles

A

all-ceramic

139
Q

porcelain is much stronger under __ forces than tensile forces from opposing teeth

A

compressive

140
Q

CAD-CAM

A

ceramics processed via a computer controlled milling machine

141
Q

porcelain layers - restoration is bulked out to compensate for 20% shrinkage

  1. opaque
  2. body
  3. incisal
A
  1. opaque - mask color of the metal
  2. body - makes up bulk and color shade
  3. incisal - translucent to incisal or cuspal 1/3
142
Q

metamerism

A

phenomenon that causes teeth/porcelain to appear color matched under one light, but different under another

  • staining porcelain decreases value and increases metamerism
  • light source must contain wavelength of the color matched to see that color
143
Q

fluorescence

A

optical property by which a material (teeth) reflects UV radiation
-contributes to brightness and vital appearance

human teeth fluoresce BLUE-WHITE (400-450 nm)

blue fatigue accelerates yellow sensitivity

144
Q

color of a pigment is determined by

A

selective absorption and selective radiation

145
Q

SHADE is matched on the color’s

  1. value
  2. chroma
  3. hue
A
  1. value - color’s brightness, almost impossible to increase value
  2. chroma - saturation, most important in shade matching
  3. hue - color families, orange is most often used
146
Q

dental porcelain is a mixture of

A

feldspar*, quartz, metallic oxides

COMPRESSIVE strength > tensile or shear strengths

BRITTLE

147
Q

3 classes of dental porcelains

  1. high fusing
  2. medium fusing
  3. low fusing
A
  1. high - DENTURE teeth
  2. medium - all ceramic and porcelain jacket
  3. low - PFM
    - aluminum oxide to increase resistance to “slumping”
    - calcium oxide
    - other oxides to reduce cross linking to lower fusing temp
148
Q

degassing (heat tx)

A

casting is heated in a porcelain furance to 980C to burn off impurities before adding porcelain
-too low of temp will form bubbles

149
Q

causes of porcelain fracture at porcelain metal interface

A

main cause - bad metal framework design

also: degass at low temp ,contamination, fuse opaque coat too low temp

150
Q

metal and ceramic must have closely matched

A

coefficients of thermal expansion (alloy usually harder) to avoid TENSILE stresses at PFM interface

151
Q

alloys should have a high __ and high __ to reduce stress on porcelain

A

proportional limit

high modulus of elasticity

152
Q

types of composition all ceramic crowns

A

feldspathic porcelain - conventional porcelain jacket
aluminous porcelain - to reinforce glass [Inceram]
mica glass - [Dicor, Cerapearl]
crystalline-reinforced glass - leucite added [Empress]

153
Q

types of fabrication method all-ceramic crowns

A

refractory die technique - Inceram
casting - Dicor
press - Empress

154
Q

3 stages in firing dental porcelain

A
  1. low bisque
  2. medium
  3. high
155
Q

glazed porcelain is

A

non-porous, resists abrasion, esthetic, well tolerated by gingiva

156
Q

PFMs requirements

A

porcelain 0.7 mm
metal coping 0.3-0.5 mm for high noble gold
(base metal alloys 0.2 mm)

need space for 1.5 mm, supporting cusps require 2.0 mm reduction -> ideal is 1.5-2.0 mm (labial is 1.5)

opposing walls converge < 10 deg

157
Q

how do PFM and all ceramic compare in tooth reduction

A

SAME

1.5-2.0 mm

158
Q

metal coping (substructure) must have all of its surfaces __ to prevent porcelain shrinkage

metal coping ensures __ and maximizes strength of the porcelain veneer

A

smooth and round

proper crown fit and maximizes strength of porcelain veneer

159
Q

outer jxn of porcelain to metal should be at what angle

A

90 deg

to avoid burnishing the metal and prevent subsequent porcelain fracture

160
Q

3 kinds of PFM alloys

A
  1. high gold noble alloys - 98% gold, platinum, palladium, don’t oxidize on casting, BEST
  2. palladium-silver: oxidizes on casting
  3. nickel-chromium: readily oxidizes
161
Q

sprue diameter should be

A

equal or greater than the thickest portion of wax or plastic

162
Q

gypsum bonded investments

A

for GOLD alloys
strength depends on amt of gypsum

CAN’T be used for titanium crowns/copings, Type IV gold alloys, susbstructure for PFMs

163
Q

phosphate bonded investments

A

base metal alloys for PFMs

casting temp > 2100 F (1150 C)

164
Q

silica bonded investments

A

base metal alloys for RPDs

mag phosphate + ammonium phosphate for room temp.

higher temps, SILICOPHOSPHATES give it strength

165
Q

quartz or cristobalite

A

refractory materials to provide thermal expansion

166
Q

4 mechanisms to compensate for solidification shrinkage of alloy during casting

A
  1. setting expansion - crystal growth, restricted by metal investment ring
  2. hygroscopic expansion - let investment set in water
  3. thermal expansion - when it’s heated in burnout oven
  4. wax pattern expansion - wax pattern warmed while investment is still fluid
167
Q

porcelain adheres to metal primarily by

A

CHEMICAL BOND

silicon dioxide and metal alloy

168
Q

cements do NOT increase crown retention, apply cement to both restoration and the tooth, 3 types

A
  1. composite resin - for CERAMIC crown, STRONGEST bond, after etching tooth
  2. zinc phosphate - can be used for ceramics, good compressive strength, high pH so must use varnish!
  3. zinc polycarboxylate or ZOE - bio compatible, better resistance to solubility than zinc phosphate, adhere to calcified dental tissue
169
Q

occlusion of gold restorations is best checked with

A

silver plastic shim stock

170
Q

radiographic signs of occlusal trauma

A

hypercementosis, root resorption, alteration of lamina dura, wide PDL space (NOT pockets)

171
Q

non-rigid connector

A

key and keyway, SHORT-SPAN bridge replacing one tooth

indicated when retainers can’t be prepared to draw together without excessive tooth rdxn

T-shaped most common

path of insertion of key into keyway should be parallel to path of the RETAINER

solder joints

172
Q

replacing how many teeth is the max?

A

3 teeth, under ideal conditions

173
Q

most likely indication for tooth splinting is

A

tooth mobility with pt discomfort

174
Q

can you splint natural teeth and implants in a FPD?

A

controversial, DON’T

175
Q

types of pontics (3)

A
  1. modified ridge lap - esthetic zones, all convex surfaces for easy cleaning
  2. sanitary - space btw pontic and ridge, not esthetic, conical pontic for thin ridge
  3. saddle - looks most like tooth, covers ridge, hard to clean and NOT used! ovate pontic is a sanitary substitute
176
Q

pontic should be convex/concave M-D? touch the ridge? be convex/concave F-L?

A

CONVEX M-D
touch residual ridge (passive pinpoint)
CONCAVE F-L

177
Q

quenching

A

metal is rapidly cooled, to maintain mechanical properties assoc. with crystalline structure

to achieve a softened condition for Type III dental gold alloy, quench in 30-40 sec

advantages - noble metal alloy is left in an annealed condition, casting is more easily cleaned

178
Q

burnishing

A

related to polishing, surface is drawn or moved

179
Q

annealing (degassing)

A

soften metal by controlled heat and cooling

to make the metal TOUGHER and LESS BRITTLE

gold foil is annealed to remove volatiles prior to placement in cavity

180
Q

fritting

A

manufacturing low and medium fusing porcelains

181
Q

soldering

A

join 2 metals using a filler material or solder

gold - fixed bridges
silver - ortho

CLEANLINESS is most important prereq of soldering, cause it depends on WETTING surfaces to achieve bonding, flux displaces gases and removes corrosion products

182
Q

fluxing

A

oxidative cleaning of area to be soldered
-potassium fluoride - agent most commonly added (steel or cobalt chromium alloys)

anti-flux: outline the area, soft graphite pencil

183
Q

pickling

A

heat casting then place in acidic solution -> can warp! or you can place it in solution then heat it

50% HCl

removes surface oxide film on gold castings

184
Q

cold work (strain hardening or work hardening)

A

HARDENING (deformation) of metal at room temp ex. bend a wire

  • polycrystalline metal, defects build up at grain boundaries
  • result of strain hardening with increase in cold work is FRACTURE

surface hardness, strength, proportional limit are INCREASED while ductility and resistance are DECREASED

185
Q

SLIP

A

deformation process, simultaneous displacement of entire plane of atoms relative to plane and below plane

186
Q

electrosurgery objectives

indications

contraindications

A

obj - coagulation, hemostasis, access to cavosurface margins, reduce inner wall of gingival sulcus

indications - remove hyperplastic tissue, in place of gingival retraction cord, for crown lengthening

contraindications - thin attached gingiva, dehiscence suspected, NOT pts with cardiac pacemakers

187
Q

temperomandibular joint is?

lower and upper compartment contain

A

combined HINGE and GLIDING joint (ginglymoarthrodial joint)

lower (condyle-disc) compartment: HINGE (rotary), only in CR

upper (mandibular fossa-disc) compartment: SLIDING (translation), when lateral pterygoids contract simultaneously, discs and condyles slide forward down over articular eminence

188
Q

muscle groups acting on TMJ include (3)

A
  1. elevator muscles (CLOSE) - masseter, medial pterygoid, temporalis (anterior fibers)
  2. depressor muscles (OPEN) - lateral pterygoid, anterior belly of digastric, omohyoid
  3. protrusion - lateral pterygoids
189
Q

centric relation (retruded contact position)

A

-ligament guided, supero-anterior position of condyle along articular eminence of condyle with articular disc interposed btw condyle and eminence

most unstrained, retruded anatomic and functional position of mandibular condyle heads in the glenoid fossae

a BONE-to-BONE relationship independent of tooth contact

closing end point of the retruded border movement

190
Q

centric occlusion (intercuspal position)

A

TOOTH-guided position, MI, during typical swallowing

  • masseters contract and tongue tip touches roof of mouth
  • tooth contacts are longer in swallowing than chewing
191
Q

freeway space

A

2-6 mm, mandible at rest

  • tonic stretch reflex of mandibular elevator muscles
  • muscle guided position
192
Q

vertical dimension of occlusion (VDO)

A

vertical length of face as measured btw 2 arbitrary points when teeth are in CR

  • verify by phonetics
  • excessive VDO causes CLICKING of denture teeth (also lack of retention can cause clicking)
  • decreased VDO often results in cheek biting
193
Q

vertical dimension of rest (VDR)

A

length of face measured btw 2 points when mandible is in rest

VDR = VDO + interocclusal difference

194
Q

condylar guidance

A
  • totally dictated by patient

- inclination depends on: shape and size of bony contour, action of muscles, limiting effects of ligaments

195
Q

what record is the least reproducible maxillomandibular record?

A

protrusive record

196
Q

retrusive movement requires condyles to move

A

backward, upward

197
Q

in lateral movements, working condyle moves ___, non-working condyles move __

A

working - down, forward, laterally

non-working - down, forward, medially

198
Q

what factor is the most important aspect of condylar guidance that affects the selection of posterior teeth with appropriate cusp height?

A

inclination of condylar path during protrusive movement

199
Q

in complete dentures, the condyle path during free mandibular movements is governed mainly by the

A

shape of the fossa and meniscus (articular disc) and muscular influence

200
Q

4 dentition features that directly effect PDL health & hard tissue anchorage to resist occlusal force

A
  1. anterior teeth have slight or no contact in MI
  2. occlusal table < 60% of F-L width
  3. occlusal table at right angles to long axis
  4. tooth position in arch
201
Q

jaw relation most used in actual design of restorations is

A

ACQUIRED centric occlusion

202
Q

compensating curve

A

anteroposterior and lateral curve

  • under the DENTIST’S control
  • helps balanced occlusion
203
Q

5 factors that govern balanced articulation

A
  1. inclination of condylar guidance
  2. ” of incisal guidance (horizontal and vertical overlap)
  3. ” of occlusal plane (plane of orientation)
  4. convexities of compensating curve
  5. angle and height of cusps
204
Q

bilateral eccentric occlusion

A

NOT for RPDs unless the it opposes a complete denture

205
Q

group function occlusion (unilateral balanced)

A

NO non-working side contacts in natural dentition, only working side

206
Q

purpose of protrusive record

A

register condylar path, adjust condylr guides of articulator

207
Q

protrusive movement, mandible can protrude __ mm

how do the condyles move

A

10

condyles move DOWN and FORWARD

208
Q

how do you correct centric interference (forward slide)

A

grind MESIAL inclines of maxillary teeth and DISTAL inclines of mandibular

209
Q

mutually protected “canine guided” occlusion

A

anterior teeth protect posteriors in all mandibular excursions
-vertical overlap of max and mand canines cause disculsion of ALL posterior teeth when mandible moves to either side

210
Q

anterior guidance (coupling)

A

result of horizontal and vertical overlap of anterior teeth, produce disclusion of posteriors

the greater the overlap, the longer the cusp height

211
Q

incisal guidance

A

second end-controlling factor in articular movement, influenced by esthetics, phonetics, ridge relations, arch space, inter-ridge space

212
Q

these are end-controlling factors

A

incisal guidance

right and left condylar mechanisms

213
Q

supporting cusps (stam or centric cusps)

characteristics

A

more robust, suited to crush food

characteristics

  1. contact opposing tooth in intercuspal position
  2. support vertical dimension of face
  3. closer to F-L center of tooth
  4. outer incline has potential for contact
  5. broader, more round cusp ridges
214
Q

non-supporting cusps (guiding or shearing)

A

maxillary buccal cusps
mandibular lingual cusps

have narrower and sharper cusp ridges

inner occlusal inclines leading to guiding cusps are guiding inclines

215
Q

selective grinding in complete dentures in centric relation (CR)

what cusps can you grind and not grind?

A

primary centric holding cusps are - Max lingual cusps (NEVER GRIND)

secondary centric holding cusps are - Mand. buccal cusps ONLY grind if there is a balancing (non-working) side interference

only grind BULL cusps!

216
Q

functionally generated pathway technique

A

allows cuspal movements of the dentition to be recorded in wax intra-orally then transferred to articulator in the form of a static plastic cast (functional index)

all mandibular motion must be directed from an ECCENTRIC centric position

217
Q

in ideal intercuspation,

ML cusps of permanent mandibular molars occlude with __

buccal cusp tips of permanent maxillary premolars oppose __

A
  1. LINGUAL embrasure between their counterpart and the tooth MESIAL to it
  2. FACIAL embrasure between their counterpart and the tooth DISTAL to it
218
Q

which maxillary cusps and mandibular cusps are GUIDING cusps?

A

maxillary buccal cusps

mandibular lingual cusps

guiding = guide away from midline

219
Q

BENNETT movement

A

lateral transition (sideshift) of WORKING condyle during lateral excursions

  • also called lateral shift or immediate side shift
  • influences the MESIODISTAL position of the posterior teeth cusps
220
Q

translation in mandibular opening occurs in lower/upper compartment of TMJ?

A

UPPER

221
Q

what are the muscles involved in closing (elevating) the mouth to centric

A

medial pterygoid
masseter
temporalis

222
Q

what kind of load is the most destructive on the periodontium?

A

horizontal

223
Q

bite registration material should

A

offer minimum resistance to pt’s jaw closure and have LOW FLOW at mixing

addition-reaction silicone materials

224
Q

2 types of polymerization in impression materials

A
  1. addition - formation of polymer without forming any other chemical
  2. condensation - when chemicals or byproducts are produced that are not part of the polymer
225
Q

hydrocolloids have the advantage of __

A

wetting intraoral surfaces BUT have limited dimensional stability

226
Q

reversible hydrocolloid (agar-agar)

A

physical state can be changed from a GEL SOL by applying heat and is reversed back by removing heat

pros - easy to pour, no mixing req, no costum tray, good shelf life (1-2 yrs), cheap

cons - must be poured immediately, finish line difficult to read

227
Q

irreversible hydrocolloid (alginate)

A

very limited dimensional stability

cons - unstable, fragile, must be poured immediately

sodium phosphate controls setting time (retarder)

FAST removal of impression from mouth increases the compressive and tear strength

228
Q

alginate sets via a chemical rxn

A

double decomposition rxn

calcium sulfate + potassium alginate

229
Q

gelation

A

setting process of alginate

  • higher temp = shorter gelation time (sets faster)
  • calcium sulfate “reactor”
  • inaccuracies can be caused by fracture of fibrils
  • SYNERESIS (shrinkage in alginate)
230
Q

elastomers are?

4 types

A

NON-AQEOUS polymer based rubber impression materials with good elasticity

  1. polysulfides
  2. silicones
  3. polyvinyl siloxanes
  4. polyethers
231
Q

Polysulfides (rubber base, mercaptan, thiokol)

A

base of liquid polysulfide polymer and accelerator of lead dioxide (brown, stinky).

  • requires custom tray
  • sets in 12-14 min (LONGEST set time)
  • 18 mo. shelf life
  • need occlusal stops
  • good flow, high flexibility, good tear strength
232
Q

Silicones (condensation or convention)

A

base is liquid silicone polymer (dimethyl siloxane) and reactor a cross-linking agent (ethyl ortho-silicate) and activator (tin octoate)

-evaporation of alcohol causes shrinkage of material and resultant poor dimensional stability

cons - custom tray req, low tear strength, pour shortly after removal, hydroPHOBIC, medium stiffness

  • long setting time 6-10 min.
  • “putty/reline” form allowing delayed pouring up to 6 hrs.
233
Q

Polyvinyl Siloxanes (additional silicones or vinyl polysiloxanes)

A

upon mixing there’s an addition of silane hydrogen groups, PVS can be poured up to 1 week

  • don’t wear latex! sulfur retards the setting
  • moderate set time 6-8 min.
  • very good dimensional stability and low permanent deformation
  • poor tear strength, high stiffness, temp sensitive

most widely used, most accurate! less polymerization shrinkage, low distortion, can be poured up to 1 week

234
Q

Polyethers (Impregnum/Premier & Polygel (Caulk))

A

rubber base has polyether, accelerator has cross linking agent (aromatic sulfonic acid ester)

pros - good dimensional stability, clean, fAST set, tolerates moisture the best

cons - most rigid (STIFFER!), difficult to remove from mouth, poor tear strength, adheres to teeth

shortest working and set time (6-7 min)

use custom tray, more accurate in uniform thin layers 2-4 mm thick

235
Q

zinc oxide eugenol is an impression paste

pros

cons

A

accelerated by adding water. to retard the set add inert oils

pros - record soft tissue at rest, sets in 5 min, stable

cons - messy, sticky, tiissue irritant, not elastic, hard to manipulate

SET HARD in mouth

a chemical rxn to form a CHELATE

236
Q

gypsum

A

weaker in tensile strength than compressive strength

-all products are reacted with water to form calcium sulfate dehydrate

237
Q

Type I gypsum - Plaster

A

rarely used

238
Q

Type II gypsum - Plaster, Model

A

model or lab plaster

  • make casts when strength isn’t important (ortho)
  • WEAKEST gypsum product
239
Q

Type III gypsum - Dental stone

A

Class I Dental Stone

-high strength improved die stone

240
Q

Type IV gypsum - Dental Stone, high strength

A

Class II Stone or improved stone

-for making stone “dies”

241
Q

main constituent of dental plasters and stone is

A

calcium sulfate hemihydrate

dental stone (alpha)
dental plaster (beta) (plaster of paris)
242
Q

dental stone v. plaster

A

main diff is particle size and shape

-plaster requires 2x more water, has higher setting expansion

243
Q

when packing cord for a pt with HTN< use a cord impregnanted with

A

ALUM - aluminum potassium sulfate

zinc chloride is caustic and causes delayed healing