dental ceramic & cad cam

GOOD MORNING

DENTAL CERAMICSDENTAL CERAMICS & CAD-CAM

FLOW CHART -INTRODUCTION

-HISTORICAL BACKGROUND

-CLASSIFICATION

-COMPOSITION OF CERAMICS

-GENERAL PROPERTIES OF CERAMICS

-FABRICATION OF CERAMIC RESTORATIONS

- METAL CERAMIC RESTORATIONS

ALL CERAMIC RESTORATIONS

_ PORCELAIN JACKET CROWNS - HI – CERAM

_LEUCITE INFILTRATED CERAMICS - DUCERAM LFC

- OPTEC HSP

_ CASTABLE CERAMICS - DICOR -CERA PEARL

_ PRESSABLE CERAMICS : - OPTEC OPC - IPS EMPRESS

-INFILTRATED CERAMIC RESTORATIONSIN –CERAM

- MACHINED CERAMIC RESTORATIONS • CAD- CAM SYSTEMS

-CERAC –I -CERAC – II-CERAC –III

- CAVITY PREPARATION FOR CAD CAM- FABRICATION OF CAD CAM RESTORATIONS

- PORCELAIN INLAYS : - ADVANTAGE / DISADVANTAGE

- INDICATION / CONTRAINDICATION

• CAVITY PREPARATION OF CERAMIC INLAY: -CLASS I -CLASS II -CLASS III-CLASS IV-CLASS V

- FABRICATION OF CERAMIC INLAYS

• PORCELAIN LAMINTAES AND VENEERS•INDICATION / CONTRAINDICATION•ADVANTAGE / DISADVANTAGE•PREPARATION TECHNNIQUE•FABRICATION OF VEEENR

CLASSIFICATIONCLASSIFICATION

Classification of ceramics :

1. By content : - Regular feldspathic

porcelain -Aluminous porcelain - Leucite reinforced porcelain - Glass infiltrated alumina -Glass infiltrated spinel

2.By use : -Artificial teeth -core ceramic -veneer ceramic3. By processing method :

-sintering -casting - machining

4. By their firing temperature :4. By their firing temperature :

-high fusing : 1300 c - medium fusing : 1100-13000 c -low fusing : 850 – 1100 c -ultra low fusing : less than 850C

5. By method of firing ;5. By method of firing ; - Air fired -vaccum fired

- diffusable gas

6. 6. By their area of application :By their area of application :

-core porcelain -body dentin porcelain - gingival dentin porcelain -incisal enamel

Composition of ceramics :

1. Feldspar : -when mixed with metal oxides and fired, it forms a glass phase that is able to soften and flow slightly -This softening of glass allows porcelain particles to coalesce together. This is called sintering sintering -. Seen in concentration of 75-85 %.

1. Kaolin / clay : -it acts as the binder. -When mixed with water , it forms a sticky mass which allows unfired porcelain to be easily worked and molded.

-On heating it reacts with feldspar and gives rigidity.

-Its white in color and reduces translucency .so its added only in concentration of 4-5 %.

3. Quartz : -It imparts more strength, firmness and

translucency. -It gives stability of mass during heating by

providing a frame work.13-14%

• GLAZES: It decreases pores on the surface of fired porcelain.

• This increases strength by decreasing the crack propagation. if glaze is removed by grinding, the transverse strength is half of glazed porcelain.

1. self glazing :-External glaze layer is not applied here. -the completed restorations is subjected to glazing here.

2.Add on glazes: -external glaze layer is applied here. -They are uncolored glasses whose fusing temperature is lowered by the addition of glass modifiers. -Disadvantages : low chemical durability, difficulty to apply evenly, difficult to get exact surface characteristics.

• 6.Colouring agents :-These coloring pigments are produced by fusing metallic oxides together with fine glass and feldspar -Ex : iron / nickel oxides- brown , copper oxides-green, titanium oxide –yellowish brown, cobalt oxide – blue.

7.Opacifying agents: -Opacifying agents consists of a metal oxide ground to a very fine particle size . ex :cerium oxide, titanium oxide, zirconium oxide –most popular.

8.Stains: -These powder is mixed with water and the wet mix is applied with brush to the surface of porcelain before glazing.

-Internal staining is preferred as it gives life like results and prevents direct damage to stains by surrounding environment.

9.Glass former : Glass formers are silica. 1.crystalline quartz2.crystalline cristobalite3.crystalline tridymite4.non crystalline fused silica

10.Glass modifiers :- Potassium oxide , Sodium oxide , Calcium oxide are used as glass modifiers - they act as fluxes by lowering the softening temperature of a glass

11. Intermediate oxides : -Glass modifiers reduces the viscousity of porcelain . -It needs a high viscosity as well as low firing temperature. This is done by the addition of AL 2

O3 and B2O3 .

GENERAL PROPERTIES OF CERAMICS

1.BIOLOGICAL PROPERTIES : -They have excellent biocompatibility .

2. CHEMICAL PROPERTIES :- It resist attack by chemicals.

-They have to be roughened by etching with hydrofluoric acid or sand blasting to improve the retention of a cement to the internal surface of the restoration

3.MECHANICAL PROPERTIES : - Low tensile strength-Exhibits little plastic deformation-Have good compressive strength

1.Compressive strength : 50000psi 2.tensile strength : 5000psi 3.shear strength:16000psi

4.elastic modulus : 10 × 106 psi 5.knoop hardness : 460

6. C T E :12 × 10 -6psi7. R.I : 1.52 – 1.54

4. THERMAL PROPERTIES : -They have insulating capacity.

5. OPTICAL PROPERTIES :-They have good optical properties

-They are translucent because of absence of free electrons.

FABRICATION OF CERAMIC FABRICATION OF CERAMIC RESTORATIONRESTORATION

Condensation of porcelainCondensation of porcelain :

• POWDER + LIQUID BINDERPOWDER + LIQUID BINDER→ CONDENSATION→ CONDENSATION

• The process of packing the powder particles together and removing the liquid binder is known as condensation.

• The main objective of building porcelain is to achieve maximum packing density of the powder so as to reduce porosity and shrinkage during firing.

Types of binder :Types of binder :1.distilled water : most popular binder

• 2.propylene glycol: used in alumina core build up• 3.alcohol or formaldehyde based liquids:for core build up

Building up of porcelain : Building up of porcelain : 1.The powder is mixed on a glass slab2.Mix should not be over stirred to avoid air bubbles3.High room temperature and dry atmosphere avoided as powder can dry out rapidly due to which air spaces are created in powder bed.

Methods of condensation :Methods of condensation : 1.vibration ; mild vibrations are used to pack wet powder .vibra brush is used2.spatulation : small spatula is used to apply and smoothen the wet porcelain.this brings excess water to surface.3.Dry brush technique : dry powder is placed with a brush.water is drawn towards the dry powder and wet particles are pulled together4.ultrasonic: mild vibrations given electrically

• FACTORS DETERMINING EFFICIENCY OF FACTORS DETERMINING EFFICIENCY OF CONDENSATION:CONDENSATION:

1. SIZE OF THE POWDER PARTICLES:

If only one sized particles are used – 45% voids two sized particles _ 25% voids

three sized particles_ 22% voids system that use 3 sized particles is called Gap grading

system

2.SHAPE OF THE POWDER PARTICLES Round particles give better packing than angular

particles.

Firing of dental porcelain:

-During firing, the glass particles soften at their contact areas and fuse together. this is referred to as sintering.

-Temperature is raised gradually to the desired one, to allow the air and gas bubbles to escape via the grain boundaries. The powder becomes dense and shrinks.

CHANGES DURING FIRINGCHANGES DURING FIRING 1-Loss of water which was added to the powder. free and

combined water is lost till a temperature of 480 degree

2-With further rise in temperature, particles starts fusing together by a process called sintering.

3-Firing shrinkage – decrease in volume 32% for low fusing porcelain28% for high fusing porcelain

4-Glazing occurs at temperatures of 965 – 10650c

Stages of firing :Stages of firing : 1.Low bisque : -The surface of porcelain is porous. - Porcelain has started to soften .-Shrinkage will be minimal and fired body is extremely weak and friable. -Lacks translucency and glaze.

2.Medium bisque : -The surface will be slightly porous - The flow of glass grains will have increased. -Definite shrinkage would have happened. -Lacks translucency and glaze.

3.High bisque : -Porcelain has smooth surface with a shine -Shrinkage is complete.

• FIRING TECHNIQUESFIRING TECHNIQUES- Temperature method

- Temperature time method

• MEDIAS FOR FIRINGMEDIAS FOR FIRING • AIR• VACCUM• DIFFUSABLE GAS

AIR FIRINGAIR FIRING - All porcelain mixes have some amount of porosity in

them. So once in air furnace, the furnace atmosphere occupies the voids.

- More chance of porosity

VACCUM FIRINGVACCUM FIRING- Reduces porosity- Vaccum removes air from the interstitial spaces

before surface sealing occurs.- Vaccum is then removed when porcelain is in hot

zone of furnace, and then when the air gets in, it exerts a compressive effect on the surface, which compresses the internal voids to 1/ 10 th of its original size.

DIFFUSIBLE GAS FIRINGDIFFUSIBLE GAS FIRING

• Air is driven out of porcelain powder and diffusible gasses like helium , hydrogen are used

• With these gases interstitial spaces donot enlarge under increasing temperature , but decrease in size or disappear.

• This is beacause the gases diffuse outwards through the porcelain or actually dissolve in the porcelain.

Glazing :Glazing : -glazing seals the open pores on the surface -gives polish and smoothness to the surface

overglaze overglaze ::external glaze layer has to be applied. These are ceramic powders containing more amount of glass

modifiers thus lowering fusion temperature.

self glazeself glaze : All the constituents on the surface are melted to form a molten mass of about 25 µm thickness.

Procedure :Procedure : Introduce into muffle entrance for 1 minute. Place on firing platform at 800c for 2 minutes. Hold for 940c for 2 minutes

and air fire.

• PORCELAIN POWDER FOR METAL CERAMIC PORCELAIN POWDER FOR METAL CERAMIC RESTORATIONS:RESTORATIONS:- Greater quantity of feldspar is required to increase the thermal expansion to a level compatible with the metal coping.- Increased amounts of metallic oxide opacifiers to conceal the underlying metal BONDING MECHANISMS BETWEEN CERAMICBONDING MECHANISMS BETWEEN CERAMIC

AND METAL :AND METAL :1. Mechanical entrapment2. Compressive forces3. Vander vals forces4. Chemical bonding – chromic oxide with base metals,

tin oxide and iridium oxide with noble metals

Advantages/ Disadvantages

Advantages:– Metal reinforcement– Better fracture resistance– Better marginal fit due metal frame

Disadvantages- Less esthetic- Margins may appear dark due to metal

Anterior teethAnterior teeth • Depth orientation grooves- flat end taper

• Incisal reduction – 2mm, flat end taper

• Facial reduction, incisal half- flat end taper

• Facial reduction, gingival half-flat end taper1.2-1.4mm to compensate for porcelain

• Wing to be given if only porcelain facing is there with metal backing. It is given lingual to contact area.

• Contra indications for wing:Contra indications for wing:– If tooth structure is less due to caries proximally, then

wing is not to be used– If there is over all full coverage of porcelain then wing

is not to be prepared.

– Functions of wing :Functions of wing :• Preserve tooth structure• Add torque resistance to preparation • Reinforce the restoration • Helps the lab person to know the exact point

where ceramic and metal meets

• Lingual reduction : small wheel diamond• Lingual axial reduction : torpedo diamond• Chamfer and shoulder finishing;

• Torpedo carbide finishing bur for metal• No.171 bur for shoulder area

• RADIAL SHOULDER GIVEN RADIAL SHOULDER GIVEN • since it decreases the stress concentration• roundened internal angles • so less chance of fracture.

POSTERIOR TEETH• Occlusal reduction-1.5-2mm for porcelain

• Functional cusp bevel-round end taper( lingual of upper , buccal of lower), 1.5 mm if only metal,2mm if porcelain

• Facial reduction ,occlusal half-flat end taper

• Facial reduction , gingival half- flat end taper,1.2 for base metal,1.4mm for noble metal.

METAL CERAMIC RESTORATION

BOND FAILURE IN METAL CERAMICSBOND FAILURE IN METAL CERAMICSBY O BRIEN BY O BRIEN

• Between metal and porcelain

• Between metal oxide and porcelain

• Between metal and metal oxide

• Between metal oxide and metal oxide

ALL CERAMICSALL CERAMICS

CLASSIFICATION:1.CONVENTIONAL POWDER & SLURRY CERAMICS

1. HI-CERAM ( ALUMINA REINFORCED) 2.OPTEC HSP(LEUCITE REINFORCED)

3.DUCERAM LFC 2. CASTABLE ALL CERAMIC RESTORATIONS

1. DICOR2.CERAPEARL

3.PRESSABLE ALL CERAMIC RESTORATIONS1.IPS EMPRESS

2.OPTEC PRESSABLE CERAMIC4.INFILTRATED ALL CERAMIC RESTORATIONS

1.IN- CERAM5. MACHINABLE ALL CERAMIC RESTORATIONS

1.CAD- CAM, COPY MILLING2.EROSION TECHNIQUE

CONVENTIONAL POWDER CONVENTIONAL POWDER AND SLURRY TECHNIQUEAND SLURRY TECHNIQUE

1. PORCELAIN JACKET CROWNS:1. PORCELAIN JACKET CROWNS:

- they were very brittle and fractured easily. -They were called as half moon fractures.-they also showed poor marginal adaptation.

Processing :- PJC are made using platinum foil technique-a platinum foil is first adapted to the dye. The foil acts as a matrix and supports the porcelain during firing.

ALUMINOUS PORCELAIN JACKET ALUMINOUS PORCELAIN JACKET CROWN ( HI – CERAM )CROWN ( HI – CERAM )

• -so McLean and Hughes in1965, introduced porcelain jacket crown with aluminous core to improve the strength of traditional PJC.

• -Increased content of alumina ( 40-50%) in the core strengthened the porcelain by interruption of crack propagation.

--Factors affecting strength & opacity ofFactors affecting strength & opacity of aluminous porcelain: aluminous porcelain:

1.1. Finer the grain size, greater the strength.

2.2.coarse grains are less opaque.

-so there is a compromise between strength and esthetics.-so average grain size to be 25mm which allows light transmission of atleast 15%

3.3.size of glass powder is less than 40 mm as this sized powder softens and flows more easily around alumina grains producing high sintered densities.

4.4.Rounded grains are preferred over angular ones, since angular ones interfere with the flow of glass phase producing flaws around the grains and reducing the strength.

5.5.Alumina concentration should be around 40-50% by weight . Concentration higher than this would prevent complete flow and wetting by glass matrix. PROPERTIES :PROPERTIES :

Compressive strength: 3,16000 psiTransverse strength : 20000 psiShear strength : 21 000 psiModulus of rupture : 15000 psi

Uses Uses ::

-- Due to reduced translucency , aluminous porcelain is limited to forming refractory framework capable of supporting weaker more translucentdentin and enamel porcelains

- Only these two types of all ceramic restorations are called porcelain jacket crowns.

-The rest of them were called ceramic jacket crowns or CJSCJS or glass ceramic crowns.

Uses Uses ::

-- Due to reduced translucency , aluminous porcelain is limited to forming refractory framework capable of supporting weaker more translucentdentin and enamel porcelains

- Only these two types of all ceramic restorations are called porcelain jacket crowns.

-The rest of them were called ceramic jacket crowns or CJSCJS or glass ceramic crowns.

CASTABLE CASTABLE CERAMICSCERAMICS

OR OR GLASS CERAMICSGLASS CERAMICS

1.A metal stable glass is first formed after casting.

2. during subsequent heat treatment controlled crystallization occurs with nucleation and

growth of internal crystals. 3. this conversion process of a glass to a partially

crystalline glass is called ceramming.ceramming.

Thus a glass ceramic is a multiphase solid containing residual glass phase with a finely

dispersed crystalline phase

- It decreasing the crack propagation .

DICORDICOR

• It is composed of Sio2, K2o,Mgo, Mgf2

• Alo2, Zro2.added for durability

• Flourescing agent for esthetics

• Flouride acts as a nucleating agent and improve fluidity of molten glass.

• After ceramming material is 55% crystalline

Fabrication :-wax pattern made

-invested in phosphate bonded refractory material. -molten glass (1358ºc)is then cast to the heated mold after

dewaxing.

-cast restoration is then freed from investment , covered by protective embedment materialembedment material and made to ceramming.

- It takes 114 minutes to reach casting temperature of 1075ºc and maintain this for 1 hour. embedment tray is

then removed.

- cerammed glass is then build up with enamel and dentin

Properties :compressive strength : 120000 psimodulus of elasticity : 10.2 ×106psesthetics :- Esthetic due to their translucency which matches that of natural tooth enamel- Its made entirely of 1 material , and so no opaque Its made entirely of 1 material , and so no opaque substructure substructure - - It gives a chameleon effect in which the It gives a chameleon effect in which the restoration acquires part of color from adjacent restoration acquires part of color from adjacent teethteeth-Precision fit is seen with dicor

-durability: it can withstand 20 years of tooth brush abrasion without any changes

-Tissue acceptance : it is high to periodontal tissues because ,

1. there is no need for opaque porcelain to cover metal substructure2.absence of opaque layer helps clinician to 2.absence of opaque layer helps clinician to obtain natural translucency in gingival areaobtain natural translucency in gingival arealittle discomfort occurs on contact with hot or little discomfort occurs on contact with hot or cold foods because of its extreme low thermal cold foods because of its extreme low thermal conductivityconductivity

Advantages :Advantages :-excellent marginal fit-high strength-surface hardness & occlusal wear similar to enamel-can reproduce wax pattern precisely with lost wax technique-excellent estheticsinherent resistance to plaque accumulationdisadvantages :disadvantages :-chance of losing the low fusing feldspathic shading porcelain, which have been applied for good colour matching

MACHINABLE MACHINABLE CERAMICSCERAMICS

From 1988, machined ceramics came into being. there are 2 major systems for the fabrication of this technique

1. Analogous systems:-Copy milling / grinding technique -Erosive techniques

2.digital systems:-cad-cam technology

COPY MILLING TECHNIQUE :CELAY,CEROMATIC II,

-copy milling uses a replica like wax, plastic, stone or metal of the desired form as a guide for a milling machine. the surface of the replica is traced by turning the pattern

and touching the patterns surface with a finger stylus. Thus the block of appropriate size is copy milled from the

ceramic block.-The cavity receiving the restoration should be free of The cavity receiving the restoration should be free of

any undercutsany undercuts..-The pro-inlay is scanned with a scanning device and a

coarse diamond coated disc (124mm grain size)

simultaneously roughens out the shape of the restoration. A fine white powder is applied to the inlay and the scanning is done again using a smooth disc and fissured and tapered burs.

- matching fine diamond discs and burs (60-70 mm thick) refine the shape of the gross ceramic restoration.

Once the white powder is completely taken off, the milling is considered to be complete. Stains and glazes may be added before the restoration is etched and silanised. Copy milling takes about Copy milling takes about 20-30 minutes20-30 minutes..

CAD – CAM CAD – CAM RESTORATIONSRESTORATIONS

STAGES IN CAD- CAM FABRICATIONSTAGES IN CAD- CAM FABRICATION ; ;

1.computerized surface digitization2.computer aided design3.computer assisted manufacturing4.computer aided esthetics5.computer aided finishing

Mormann and BrandestiniMormann and Brandestini was the first ones to use cad- cam device in 19881988.the first model which came was called cerec I.--CEREC ICEREC I (1988)(1988)-cannot prepare the occlusal anatomy of the preparation .-camera not good

--CEREC –II: ( 1994) CEREC –II: ( 1994) -They had better image processing systems .-it also has a cylindrical diamond stone which is able to finish off undercuts at buccal extensions -occlusal anatomy could be produced heredisadvanatage- - has many parts ,so the operator had to move around -impression not good-marginal fit not good.

• CEREC 3 :CEREC 3 :-different parts could be magnified in detail

• more finer details noted• disadvantage: not capable of producing

margins of restoration

• CEREC 3-DCEREC 3-D• marginal fit good• contacts can be chosen • 3 dimensionally movable camera

CERECCEREC II II CEREC IIICEREC III

CAVITY CONSIDERATION FOR CAD- CAM :- NNo convexitieso convexities should be present on the pulpal and gingival walls .

-The occlusal step should be 1.5mm – 2mmocclusal step should be 1.5mm – 2mm in depth

- Isthmus should be at least 1.5mmIsthmus should be at least 1.5mm wide to decrease the possibility of fracture of the restoration.

-Buccal and lingual walls of the preparation may Buccal and lingual walls of the preparation may converge towards the occlusal. converge towards the occlusal.

-This feature is unique to cerec systems as it can unique to cerec systems as it can automatically block out any undercutsautomatically block out any undercuts during optical impression.

-axial walls should be straightaxial walls should be straight and not follow the convex contour of the proximal surface of the tooth-no cavo surface or marginal bevels should be given.no cavo surface or marginal bevels should be given.

VARIOUS INGOTS USED FOR MACHINABLE CERAMICS ARE :

1.cerec vitablocks mark I1.cerec vitablocks mark I :its composition strength are similar to that of feldspathic porcelain. Used first with cerec system.2. 2. Cerec vita blocks mark II:Cerec vita blocks mark II:high strength feldspathic porcelain with grain size finer than that of mark I composition. -less abrasive wear of the opposing tooth

• 3.Dicor Mgc:3.Dicor Mgc:glass ceramic with fluorosilicate mica crystals in a glass matrix.flexural strength higher than castable dicor and cerec systems.

• softer and less abrasive than cerec vitablocks mark I ,but not as much as cerec vita blocks mark II.

ADVANCES IN ALL CERAMIC ADVANCES IN ALL CERAMIC RESTORATIONSRESTORATIONS

• Procera• Shrink free ceramic• Cad-cim restoration• Copy milling with bcelay on extracted teeth• Porcelain inlays• Porcelain veneers

conclusion conclusion