metal ceramic restorations

the metal-ceramic restoration consists of a ______ substructure supporting a ______ veneer that is _________ and _______ bonded to it

a metal substructure supporting a ceramic veneer that is mechanically and chemically bonded to it

how is does the chemical componentof the bond achieved 

through firing 

1

metal substructure

2

opaque porcelain

3

gingival porcelain

4

body porcelain

5 

incisal porcelain 

what are the types of metal ceramic restorations

• metal ceramic crowns 

• porcelain fused to metal (PFM) crowns 

• ceramic-veneered crowns 

indications for metal ceramic restorations (5)

similar for complete cast crowns:

• extensive coronal destruction

• maximum retention and resistance form 

• correction of axial wall 

• restore endodontically tx tooth 

• esthetic demands 

are all-ceramic restorations or metal ceramic restorations more esthetic 

all ceramic restorations 

contraindications for metal ceramic restoration 

• pt has active caries or untx periodontal disease 

• young pts w large pulp chamber 

• when more conservative restoration is feasible 

advantages of metal ceramic restorations (3)

• strength of complete cast restoration w esthetics of all ceramic crown 

• is the better choice to serve as a retainer for fixed partial denture (FPD) 

• can be used for survey crowns 

why are metal ceramic restorations better used to serve as a retainer for a FPD

its metal substrate can accommodate cast or soldered connectors

why can metal ceramic crowns be used for survey crowns

modified to incorporate occlusal and cingulum rests and milled proximal and reciprocal guide planes in their metal structure

disadvantages of metal ceramic restoration (6)

• requires significant tooth reduction 

• in highly esthetic areas, margin needs to be placed subgingivally → inc potential for periodontal disease 

• have slightly inferior esthetic compared to ceramic restoration 

• fx of ceramic layer when it is not designed or processed properly 

• difficult shade selection 

• more expensive laboratory costs 

what are the 4 classifications of metal alloys for metal ceramic restorations

• high noble alloys 

• titanium alloys 

• noble alloys 

• predominantly base alloys 

examples of noble metal content

gold, platinum group metal

requirement for high noble alloys 

noble metal content >/= 60% and gold >/= 40%

requirement for titanium and titanium alloys

titanium >/= 85%

requirement for noble alloys

noble metal content >/= 25%

requirement for predominatly base alloys

noble metal content < 25%

is silver a noble metal alloy

NO

high noble/noble-metal alloys have good ________ resistance

corrosion resistance

what high noble/noble-metal alloys have desirable yellow color 

Au-Pt-Pd 

what high noble/noble-metal alloys are added to for oxide layers to produce a desirable ceramic-metal bond 

indium (In), Tin (Sn), and Iron (Fe) 

what base-metal alloys provides tarnish and corrosion resistance 

chromium 

what base-metal alloys are added to dec the thermal coefficient of expansion 

molybdenum 

what base-metal alloy becomes important for metal ceramic restorations in the future/oxide layer 

Ti alloys 

what is the importance of the oxide layer

for when you want a bond between cermic and metal

do base-metal alloys or noble/high-noble alloys have a superior mechanical property (elastic moduli and hardness are high)

base metal alloys

base metal alloys can also be _____ for resin bonding

etched

negative characteristics of base metal alloys (6)

• markedly higher corrosion in acidic environments

• difficult finishing and polishing

• dark, thick oxides

• risk of pt allergy

• difficult soldering

• harder to cast and ensure appropriate marginal fit of restoration

why are base metal alloys harder to cast and ensure appropriate marginal fit of restoration

their liquidus temperatures are the highest among all prosthodontics alloys

what are the 3 types of dental ceramic (porcelain)

• quartz (Silica-SiO2)

• feldspar 

• kaolin/other oxides 

what is feldspar ceramic

potassium aluminum silicate orthoclase and sodium aluminum silicate 

rank silica, kaolin, and feldspar from msot to least common dental ceramics 

feldspar > silica > kaolin 

classifications of dental ceramic

• high fusing porcelain 

• medium fusing 

• low fusing 

• ultralow fusing 

what is the fusion temperature

temp at which the powder particles of dental ceramic fuse together 

applications for high fusing porcelain 

denture teeth and fully sintered alumina and zirconia core ceramics 

sintering temperature range for high fusing porcelain

> 1300 C

applications for medium fusing porcelain

denture teeth, presintered zirconia

sintering temperature range for medium fusing porcelain

1101-1300 C

applications for low fusing porcelain

crown and bridge veneer ceramic

sintering temperature range for low fusing porcelain

850-1100 C

applications for ultralow fusing porcelain

crown and birdge veneer ceramic

sintering temperature range for ultralow fusing porcelain

< 850 C

porcelain is _____ (strong/weak) under compression but ______ (strong/weak) when placed under tension 

porcelain is strong under compression but weak when placed under tension 

what is the coefficient thermal expansion 

the change in length per unit length of a material for a 1 degree C change in temperature 

the coefficient thermal expansion of the metal alloy needs to be slightly ______ (higher/lower) than the dental cermic

metal needs to be slighly higher than ceramic

what factors can affect the bond between the ceramic and metal

• the oxide layer between the metal and cermic 

• airborne-particle abrasion w aluminum oxide (alumina) on alloy castings to provide mechanical interlocking 

• the linear coefficients of thermal expansion for th emetal and ceramic must closely match to achieve a strong bond interfacial bond

what technique is commonly used in the fabrication of porcelain 

lost wax technique 

what are the layers of procelain during fabrication

• opaque layer

• body porcelain

• enamel porcelain

• surface glaze

what is waxing to anatomic contour

full anatomic contour and then cutting back for a consistant amount of porcelain

having even porcelain thickness will provide superior ______ properties in the completed restoration and standardizing ______ reproduction 

superior mechanical properties; standardizing shade reproduction 

shape of metal preparation

• avoid sharp angles on the veneering surface  

• convex surfaces and rounded contours 

• smooth surface

why should you avoid sharp angles on the veneering surface of the metal preparation 

bc they can contribute to internal stress in the fired porcelain

purpose of smooth surface in the shape of metal preparation

facilitates wetting of the framework by the porcelain slurry 

the intended metal-ceramic junx should be as ______ and as ______ as possible 

should be as definite (90 degree angle) and as smooth as possible 

metal framework thickness requirements for noble metal alloys vs base metal alloys

• noble metal alloys: 0.3 mm 

• base metal alloys: 0.2 mm 

the metal-ceramic interface must be far away from all centric occlusal contacts and must be distinct, it needs to be at least ___ mm away 

1.5 mm 

after investment removal, how should it be cleaned

• ultrasonic 

• airborne particle abrasion 

• steam 

during metal preparation, the oxide layer has been formed on the metal surface duing ____ must be partially removed w ____ or _____ abrasion 

during casting; removed w acid or air abrasion 

achieving a successful bond depends on a controlled thickness of the…

metal-oxide layer 

how should you do metal finishing

one direction without dragging the metal over itself- entrapping air and grinding debris

in metal preparation, what do you want to finish w

ceramic-bound stones or tungsten carbide burs

after the metal surface has been smoothed, what should you do

should be airborne-particle abraded w aluminum oxide according to the manufacturer instructions 

what is necessary to verify that the metal substructure conforms to all specified minimum dimensions 

dial or metric caliper 

in metal preparation, less than ____ mm may lead to distortion during firing 

0.3 

steps of finishing in metal preparation

1. (A) nonveneering surface: rubber wheel stage 

2. (B) (C) metal ceramic junction: tungsten carbide bur 

3. (D) veneering surface: ceramic bound stone 

4. (E) airborne-particle abrasion of the veneering area

how to protect the margins during finishing

soft wax

how to clean metal in metal preparation

• immersion in a general-purpose cleaning solution in an ultrasonic unit for 5 minutes 

• steam clean 

a controlled oxide layer must be created on the metal surface to establish…

chemical bond between metal and porcelain

how to create the oxide layer

insert substructure into a porcelain furnace above the porcelain firing temp w or w/o vacuum

to create an oxide layer, which requires a longer holding time

• high noble alloy 

• noble 

• base metal 

high noble alloy

to create an oxide layer, which requires a less holding time

• high noble alloy 

• noble 

• base metal 

noble 

to create an oxide layer, which has no required oxidizing cycle

• high noble alloy 

• noble 

• base metal 

base metal

purpose of opaque porcelain

• bonds to alloy 

• masks the color of the alloy 

________ (body/enamel) of dental porcelain powders provides the most shade to match natural teeth and bonds to the opaque porcelain

body

________ (body/enamel) of dental porcelain powders is the most translucent

enamel

condensation techniques is by ______ action in the dental porcelain technique

capillary

how to do the condensation technique

gentle patting w a brush and light tapping on the cast produces adequate vibration during the preliminary stage of condensation; a tissue is held close for removal of excess surface moisture 

what is sintering 

when the mass is heated, individual porcelain particles conglomerate and bridge together 

during sintering, a loss of interstitial space occurs, accompanied by as much as a ___% to  ____% volumetric shrinkage after firing 

27%-45%

outcome of bisque bake

not as shiny as tooth

to create a shiny surface similar to the natural teeth, a bisque baked ceramic needs to be _____

glazed

what happens to porcelain after being glazed

the surface porcelain is vitrified a glossy and smooth surface is created 

what is autoglazing

oven temp is raised to the fusion temp and the bisque baked is maintained in that temp before cooling, occlusal contacts are altered during glazing 

what is overglazing 

a seperate mix of powder and liquid is applied to the surface and the restoration is fired 

to create a natural looking tooth, ___________ may be incorporated

colored pigments

how to add internal characterization

pigments can be incorporated in the opaque, body, or incisal powder

when is external characterization done

is preformed during overglazing

what is external characterization

pigments are added to the surface of the bisque baked porcelain then they are fired in glazing temp

steps for metal-ceramic restoration as the same as

complete cast crown 

what can cause fx during bisque bake (4)

• improper condensation

• improper moisture control

• poor framework design 

• incompatible metal-porcelain combination 

what can cause bubbles in metal-ceramic restorations (5)

• too many firings 

• air entrapment during buildup of restoration 

• improper moisture control 

• poor metal preparation 

• poor casting technique 

what can cause unsatisfactory appearance in metal-ceramic restorations (4)

• poor communication w technician

• inadequate tooth reduction 

• excessive thickness of opaque porcelain 

• excessive firing 

what can cause clinical fx in metal-ceramic restorations (3)

• poor framework design 

• centric stops too close to metal-ceramic interface 

• improper metal preparation 

christensen’s survery estimated the longevity of crowns to be from…

21 to 22 years 

survey by Maryniuk and Kaplan survey for longevity of metal-ceramic crowns were

12.7 years

in review of records in 40 Dutch dental offices, leempoel et al told of 10-year survival rates in _____% for full crown and ___% for metal ceramic crowns

98% full crowns; 95.3% for metal ceramic crowns