13,14-Ceramics-93-end

Question 1

soft machining followed by sintering what is the microstructure of these like? flexural strength? -clinical probs with these systems?

Answer 1

-microstructure of these polycrystalline 3Y-TZP has dense packed zirconia grains -have highest flexural strength and highest fracture toughness of all available dental ceramics -most probs are crazing or cracking at the interface bw veneering porcelain and core ceramic

Question 2

soft machining followed by sintering what makes it possible to fabricate resto at chair side in one visit? what type of strength for these cermaics made with this technique?

Answer 2

-hard machining make this possible -ceramics made with these techniques =low-moderate strength, this restricts applications to single unit restorations

Question 3

soft machining followed by sintering -benefit of fabricating resto in one office visit? -how is this counterbalanced?

Answer 3

-benefit is lost with soft machining techniqes since restos require sintering at high temps after they are machined -this disadvantage is counterbalanced by unique properties of 3y-TZP, making it possible to make both single and multiunit anterior and posterior restorations

Question 4

soft machining followed by sintering -how is marginal accuracy? how is the negative impact of high opacityof zirconia attenuated?

Answer 4

-margins were once a concern but their accuracy is improving, becoming more accurate -negative impact of high opacity zirconia is attenuated by the ability to decreace coping thickness to 0.4-0.5mm

Question 5

what do metal ceramic restorations consist of?

Answer 5

consist of a cast metallic framework (or core) on which at least 2 layers of ceramic are baked

Question 6

metal ceramic restorations what does it look like in cross section?

Answer 6

from inside to outside -metal coping -opaque porcelain -body (dentin) -enamel porcelain layers

Question 7

metal ceramic restoration how is the first layer applied? what is its role?

Answer 7

first layer=opaque layer, consisters of porcelain modified with opacifying oxides -role is to mask darkness of oxidized metal framework to have good esthetics -this thin layer contributes to the metal ceramic bond

Question 8

metal ceramic resto -2nd step?

Answer 8

buildup on dentin and enamel (most translucent) porcelains to obtain appearance similar to natural tooth -dental or enamel porcelain powder is mixed with modelling liquid (distilled water mostly), apply this on the opaque layer -then pocerlain condensed by vibration and dried large shrinkage (25-30%) with this sintering process

Question 9

metal ceramic resto what occurs after buildup of porcelain powders? why is this done and what is the result? what are these bad boys like in the strength and aesthetics department? -what are used for casting the substructure?

Answer 9

after buildup of porcelain powders, ceramic restos are sintered under vacuum in porcelain furnace -this helps to elimate pores, result is mostly pore free porcelain -excellent aesthetics, great strength (bc of metal framework support) -alloys used for casting substructure, usually gold based w/ tin and indium

Question 10

metal ceramic restorations -coeff of thermal expansion- what does it have to be compared to alloy?

Answer 10

CTE of veneering porcelain needs to be slightly lower than alloy to ensure the ceramic is in slight compression after cooling -this establishes a better resistance to crack propagation of the ceramic part of the restoration

Question 11

in metal ceramic system what melting temp does the alloy need to have? why? -what about a fusing temp? why?

Answer 11

-high melting temp (greater than 100C) than firing temp of veneering porcelain and solders used to join segments of a fixed partial prosthesis -veneering porcelain need low fusing temp, so no creep, sag, or distortion of framework takes place during sintering

Question 12

does the porcelain need to wet the alloy when applied? -is a crap bond bw ceramic and metal ok?

Answer 12

needs to readily wet alloy when applied as a slurry, this prevents voids from forming at the metal ceramic interface -good bond is essental bw ceramic and metal - this is achieved by chemical rxn of porcelain with metal oxides on surface of metal and by mechaincal interlocking make possible by roughening of metal coping

Question 13

what do coeff of thermal expansion of ceramic and metal need to be like? -what does stiffness and strength of alloy core need to be like?

Answer 13

CTE need to be compatible so cermic doesnt crack during fabrication -adequate stiffness and strength of alloy core importante (esp for fixed bridges and post crowns) -high stiffness in the allow reduces stress in ceramic by reducing deflection and strain -high strength=essental in interprox regions in fixed bridges

Question 14

metal ceramic system sag resistance?

Answer 14

high sag resistance=essential -alloy copings are thin, no distortion should occur during firing of the ceramic or the fit of restoration will be compromised

Question 15

requirement for metal ceramic system -is an inaccurate casting of metal comping very nice? -is an inadequate design of the resto very nice?

Answer 15

-an accurate casting of metal coping is required even with higher melting range of the allot -adequate design of the restoration is critical - the prep should provide for adequate thickness of alloy as well as enough space for an adequate thickness of ceramic to yield esthetic resto

Question 16

5 requirements for metal ceramic restorations

Answer 16

1. must simulate appearance of natural teeth 2. must fuse at low temps 3. CTE compatiable for alloy used for metal frameworks 4. must age well in oral environment 5. must have low abrasiveness

Question 17

failure and repair of metal ceramic resto -10 year success rate? -what are reasons for most re treatments?

Answer 17

-10 yr success rate of 95% -most retreatment due to biological failures such as tooth fracture, PD disease, and 2ndary caries

Question 18

most common reason for re treatment in metal ceramic fixed partial?

Answer 18

-prosthesis fracture is among most common reason for retreatment, -long spans of five or more units having 2x incidence of failure compared to short span prosthesis

Question 19

when metal ceramic prosthesis fails… what is it usually due to? what do you do?

Answer 19

-often due to adhesive failure bw porcelain and metal or cohesive failure within ceramic near metal ceramic interface -prosthesis should be retrieved, metal surfaces cleaned and new oxide layer should be formed on exposed area of metal prior to porcelain application and fitting -this cant be achieved intra-orally, removing bridge usually out of the question

Question 20

when metal ceramic prosthesis fails, usualyl cant remove the bridge, so what do you do?

Answer 20

-other techniques that dont need to remove prostheesis, but these all have the challenge of bonding chemically dissimilar materials -silane coupling agents can be used to achieve good adhesion between composite and porcelain when there is no functional loading on porcelain surfaces

Question 21

metal ceramic resto repair -are the techniques that dont require removal or prosthesis permanent? (sorry this card isnt very good. the notes are hard to make into a slide for these points)

Answer 21

-they are temporary -systems are available for coating metal surface with silica particles through an abrasion process -particles of silica are embedded in metal surface upon impact, then silane coupling agent applied -then add composite to provide temporary restoration

Question 22

general indications and contraindications for use in dental ceramics:

type:feldspathic pocelain

primary and secondary applications? contraindications?

Answer 22

Question 23

general indications and contraindications for use in dental ceramics:

type:aluminous porcelain primary and secondary applications? contraindications?

Answer 23

Question 24

general indications and contraindications for use in dental ceramics:

type: leucite glass ceramic primary and secondary applications? contraindications?

Answer 24

Question 25

general indications and contraindications for use in dental ceramics:

type:lithium disilicate glass ceramic

primary and secondary applications? contraindications?

Answer 25

Question 26

general indications and contraindications for use in dental ceramics:

type:alumina

primary and secondary applications? contraindications?

Answer 26

Question 27

general indications and contraindications for use in dental ceramics:

type:glass infiltrated spinel

primary and secondary applications? contraindications?

Answer 27

Question 28

general indications and contraindications for use in dental ceramics:

type: glass infiltrated alumina

primary and secondary applications? contraindications?

Answer 28

Question 29

general indications and contraindications for use in dental ceramics:

type:glass infiltrated alumina/zirconia

primary and secondary applications? contraindications?

Answer 29

Question 30

general indications and contraindications for use in dental ceramics:

type: zirconia (with veneering ceramic)

primary and secondary applications? contraindications?

Answer 30

Question 31

general indications and contraindications for use in dental ceramics:

type:zirconia (without veneering ceramic)

primary and secondary applications? contraindications?

Answer 31