dental ceramics : innovation and application

Vinay Pavan Kumar K

2nd year PG student

Dept of Prosthodontics

AECS Maaruti College of Dental Sciences

Metal ceramic prosthesis

Ceramic prosthesis

Advances in substructure

Advances in Composition

Innovation in processing methods

Introduction

Innovation in processing techniques

In 1903, Land : making of porcelain crowns

In 1938, Pincus : Concept of ceramic veneers.

In the evolution of ceramics the researchers

have strived hard to find innovative methods to

strengthen the most esthetic, but yet brittle.

Modify in processing

Modify the Composition

Techniques of Substructure

Conventional method

Digital method

Additive techniques

Selective laser sintering

3D printing

Substrative techniques

CAD CAM

Condensing and Sintering

Methods of condensation

The Vibration technique

The Spatulation technique

The Brush technique

Process of heating closely packed particles to

achieve inter particle bonding and sufficient

diffusion - ↓decrease surface area /↑ density of

structure

Partial fusion or compaction of glass

Selective laser sintering or selective laser melting produces a 3D model by laser sintering or melting a powder, layer by layer using a laser beam

The laser beam locally raises the temperature close to the melting point of the metal particle, to avoid complete melting

The platform is slightly immersed in the powder, and powder thickness is controlled by a cylinder rolling on the powder pool

After each new powder layer application, the laser

melting process is repeated until the 3D object is

completed

Oxidation of the metal can be controlled by

confining the melting to a sealed gas chamber.

Greater liquid flow between the metal particles andlower initial porosity results in the production of a lowporosity microstructure.

The selective melting process should not completelymelt the metal particles; the melted particles willaggregate and form larger spheres. Resulting inmajor dimensional discrepancies in the finalworkpiece

To avoid this, the metal particles should be heated tojust below the melting temperature to ensure meltingis confined to the external surface of the particlesand fusion contact forms necks between theadjacent powder particles

3D printing extrudes material from a nozzle that

solidifies as soon as it is deposited on the

manufacturing platform

The layer pattern is achieved through horizontal

nozzle movement and interrupted material flow.

This is followed by vertical movement for the

sequential layer deposition.

There are a range of materials that can be used

for 3D printing. This includes thermoplastic

materials, such as waxes, resins, or fused

filament

Pass through a heated nozzle and solidifies

immediately after extrusion.

Some systems allows multicolour production

This approach is used in dentistry to fabricate

dental models, facial prosthesis patterns, acrylic

prostheses, investing flasks, and castable or

ceramic frameworks

3D printing is distinguished from other fabrication

methods in the ability to print multiple materials at one

time

3D printing overcome the problems created bymilling, such as surface cracking, shrinkage, andmaterial wastage

high-strength zirconia frameworks have beenproduced by 3D printing

The reported strength was of the zirconiaprosthesis was 764MPa and the fracturetoughness was 6.7MPa

submicron-sized pores were also detected andattributed to the clogging of nozzles during theinjection of zirconia paste.

Subtractive manufacturing is based on milling the

workpiece from a larger blank by a computer

numeric controlled (CNC) machine.

The CAM software automatically translates the

CAD model into tool path for the CNC machine.

This involves computation of the commands

series that dictate the CNC milling, including

sequencing, milling tools, and tool motion

direction and magnitude

Basic components of CAD CAM Involes:

Digitalized Scanner

Optical Scanner

Mechanical scanner

Design Software

Processing Device or Computer numeric

control machine

Optical Scanner

Based on the principle of triangulation

The light source and the receptor unit are in a

definite angulation in relation to each other

Everest scan, Lava Scan, es1

Mechanical Scanner

The master cast is read mechanically line by line by

means of a ruby ball

The 3D structure is measured

Procera scanner

Design Software

Special software is provided by themanufacturer for designing wide variety ofrestorations

Ranging from copings, full anatomical crowns,inlays, onlays, FPDs frameworks, AdhesiveFPDs, telescopic primary crowns, post andcore.

The information for such designing is stored invarious formats such as StandardTransformation Language (STL)

Processing Devices

The dental CNC machines are composed of multiaxis milling devices to facilitate the 3D milling ofdental work pieces

To facilitates production of very complex geometriesand smooth external surfaces dental restoration,themilling machines combine burs with different sizes

Milling is better accomplished in two steps:

a rough milling is done at a low feed rate and high cuttingforce while the final fine milling is performed at a higherfeed rate and reduced cutting forces

The fine milling will reduce the chip thickness andminimise surface roughness

3 axis milling

In Lab (Sirona), Lava (3M ESPE),

Cercon brain(Degudent)

4 axis milling

Zeno (Wieland-Imes)

5 axis milling

Everest engine (KaVo), HSC

milling device (etKon)

Dry Milling zirconium oxide blanks with low degree of presintering

Advantages

Economical

no moisture absorption by the die ZrO2 mould

no additional time is spent on drying ZrO framework prior to sintering

Disadvantages

high shrinkage of framework

Zeno 4030, Lava form and Cercon Brain

Wet milling

Milling diamond /carbide cutter protected by a

spray of cool liquid against overheating

against over heating of milled materials

All metals and glass ceramics

Zirconium oxide (if presintered)

Reduction of shrinkage, less sinter distortion

Everest (KaVo), Zeno 8060, in Lab(Sirona)

Chair side Production

Laboratory production

Centralised fabrication in a production centre

• Chairside Economical

Restoration of Esthetic Ceramics

or

• computer-assisted CERamic

REConstruction

• Mörmann and Brandestini of

zurich university developed in

1980

• Dr. Alain Ferru, a young French

software engineer developed the

basic layout of the design

software in 1983

The CEREC was first introduced in 1986.

It consisted of a mobile unit containing :

1.A small camera

2.A computer with scan and

3.3-axis-of rotation milling machine

The Old milling machine water-pressure driven.

Clinical shortcoming

• Occlusal anatomy had to be created by the clinician

• Inaccuracy of fit or large interfacial gaps

• Clinical fracture

• Relatively poor esthetics

Mobile unit containing small

camera, computer with scan

and 3-axis-of-rotation milling

machine with electric motor

better and smoother cutting of

ceramic - better fitting

restorations

Upgrading of software -

allows machining of occlusal

surface

In 2003,three-dimensional virtual display of the preparation, of the antagonist and of the functional registration became available

The 2005 and 2006 versions include the automatic adjustment of a selected digital full-crown anatomy to the individual preparation, to the proximal contacts and to the occlusion

In 2006, a “step bur” replaced the cylinder

In 2007, a new generation of milling machine, MC

XL, was launched with increased precision which

resulted in attaching the crowns using dental

cement

In 2009, a new imaging technology, the CEREC

Bluecam, which is based on short-wave blue light

In 2011, the 4.0 version of the software simplified

the user interface with intuitive menu navigation

In 2012 the CEREC Omnicam intraoral

camera,powder-free digital impressions in natural

colors.

Lava System (3m Espe, Seefeld, Germany)

Procera System

Katana System

Celay System

Everest System

Cercon System

Dcs Precident

ZENOTec (Wieland Dental & Technik GmbH & Co KG)

DentaCAD system (Hint-ELs, Griesheim, Germany)

Cerasys (Cerasystems, Buena Park, CA)

Wol-Ceram (XPdent corporation, Miami, FL)

BEGO Medifacturing (BEGO Medical GmbH,Germany)

Turbodent System (U-Best Technology Inc, Anaheim, CA)

Etkon system (etkon USA, Arlington, TX)

iTero (Cadent, Carlstadt NJ, US)

SYSTEM

MARKET

LAUNCH

SCANNING

MECHANISM CAD PROGRAM CAM PROCESS PROCESS CENTRE

Cerec 3 2000 Optical

Yes, custom design

and database Fully automatic Chairside

Cerec InLab 2001 Laser

Yes, custom design

and database Fully automatic Dental Lab

DCS Precident 1989 Optical

Yes, custom design


Procera 1993 Manual

Yes, custom design

and database Fully automatic New Jersey or Sweden

Lava 2002 Optical

Yes, custom design


Everest 2002 Optical

Yes, custom design


Cercon 2001 Laser No Fully automatic Dental Lab

CAPTEK System

Capillary casting technology

Principle - Capillary attraction to produce a gold

composite metal

Composite alloy composed of 2 distinct alloy

phases

Inner and outer surface contains 97% Au

Available as Captek P and G

Renaissance crown (Unikorn Ltd, Israel)

Developed by Shoher and Whiteman

Delivered in a fluted shape

Swaged with a swaging instrument and

burnished on a die

Flame sintered

Veneered with porcelain and fired

Predominantly glass based : Vita Mark I and II

Particle filled glass : Inceram ,eMax

Polycrystalline : lava, Procera, emax ZirCAD

Conventional Sintered ceramics

Castable ceramics

Pressable/ injectable ceramics

Infilterated/slip cast ceramics

Machinable ceramics

Printable ceramics

Ceramic powders are mixed in water and the slurry is built up in layers on die and the sintered

The density of porcelain increases, it is associated with the volmetric shrinkage of 30-40 %

The sintered porcelain can be:

Leucite reinforced glass ceramic

Alumina based porcelain

Magnesia based core porcelian

Zirconia based porcelian

Contains 45 vol% tertagonal leucite

High modulus of rupture, compressive strength,

thermal contraction coefficient

Heat treatment -1 hr at temp 705 to 980°C forms

sanidine( KAlSi the expense of the glassy matrix

Crystallization of sanidine-translucent to opaque

No special processing equipment

Relatively high in vitro wear of opposing teeth

Hi-Ceram (Vident, Baldwin Park, CA) Baked

directly onto refractory die (1994)

Strengthening by dispersion of a crystalline phase

Alumina -high modulus of elasticity (350 GPa),

fracture toughness (3.5-4 MPa)

40-50% Alumina by wt

Core baked on Pt foil and later veneered with

matched-expansion porcelain

The core material is obtained by reacting

magnesia with silica glass between 1100-1150 c

Flexural strength is 131 Mpa due to formation of

Forsterite (Mg2SiO4)

In-Ceram Spinell (alumina and magnesia matrix)

the most translucent with moderately high

strength and used for anterior crowns

Conventional feldspathic porcelain -tetragonal

Zr fibers included

Zr undergoes a crystallographic transformation

from monoclinic to tetragonal at 1173°C

Partial stabilization -CaO,MgO,Y2O3

Transformation to stable monoclinic form -occur

under stress, associated with ↑ in slight particle

volume

These are polycrystalline glass-ceramic

material supplied has solid ceramic ingots

Used in fabrication ofCores/ full-contour

restorations by lost wax and centrifugal-casting

technique

Crystals can be:

Mica based

Hydroxyaptite based

Lithia based

Dicor , was developed by Corning Glass Works and

marketed by Dentsply international.

A full-contour transparent glass crown is cast at

1350 C, then is heat-treated at 1075 C for 10 hours

- “Ceramming”

fracture resistance is 152MPa

Indicated for Inlays,Veneers,Full crowns-accurately

Crystals - less abrasive to opposing tooth structure

a Castable ceramic developed by Kyocera, San

Diego, CA.

Main crystalline phase -oxyapatite, transformable

into hydroxyapatite when exposed to moisture

(Hobo and Iwata, 1985)

Refractive index, density, hardness, thermal

expansion, thermal conductivity similar to natural

enamel

Developed by Uryu

Composition: It contains mica crystals of NaMg3

(Si3AlO10) F2 and Beta Spodumene crystals of

LiO.AI2O3.4SiO2 after heat treatment

The crystalline phase, lithium disilicate

(Li2Si2O5) makes up about 70% of the volume

It has microstructure : small plate-like crystals

that are interlocking and randomly oriented

the needle-like crystals deflect cracks and arrest

the propagation of cracks

Supplied as ceramic ingots

Melted at high temp and pressed into a mold

created using the lost-wax technique

full contour/substrate for conventional feldspathic

porcelain buildup

Leucite Based

Spinell Based

Developed by Ivoclar USA, Amherst, NY

Leucite crystals ↑ resistance of crack propagation

Ingot placed under plunger, assembly is heated

(1150°C) plunger presses molten ceramic into

specialized refractory mold (pressure- 0.3-0.4

MPa) -20 minutes -automatic press furnace

Ingots -different shades- produced by sintering at

1200°C

Flexural strength -improve under subsequent heat

treatments - 126 Mpa to160-182MPa

Developed by Innotek Dental Corp, Lakewood,

Magnesium spinel -major crystalline phase

Initially introduced has "shrink-free" relied on

conversion of alumina and magnesium oxide to a

magnesium aluminate spinel

Advantages -excellent marginal fit (Wohlwend et al)

Dr. Micheal Sadorun (1980)

Supplied as powder (aluminum oxide/ spinel) -

porous substrate

Glass -infiltrated at high temperature into the

porous substrate

Core ceramics:

In-ceram Spinell

In ceram Alumina

In-ceram Zirconia

Prefired blocks of feldspathic or glass ceramics

Supplied -ceramic ingots in various shades

Machined restoration -stained and glazed

Do not require further high-temperature

processing

Based on composition

Silica based

Infiltrated ceramics

Oxide based

Cerec Vitablocs Mark I

Feldspathic porcelain-large particle size – 10-

50 um

Cerec Vitablocs Mark II

Feldspathic porcelain reinforced with

Aluminium oxide- increased strength, finer

grain size (4 um) -less abrasive wear

Sanidine -major crystalline phase within

glassy matrix - lack of translucency

IPS e.max

Includes lithium disilicate , high-strength

zirconium oxide

Thin veneers to 10-unit bridges

Esthetics and strength suitable for Press

technique and CAD-CAM

Dicor MGC

Fluorosilicic mica crystals in a glass matrix (70

vol% of crystalline phase)

Mica particles size - 2 um

Available as Dicor MGC light and Dicor MGC

dark

Procesed in porous,chalky conditions and

infiltered with lanthanum glass

Vita Inceram offers three variants:

Vita Inceram Alumina : coping in anterior and

posterior region, 3 unit fpd frameworks in

anterior region

Vita Inceram Zirconia : coping in anterior and

posterior region, 3 unit fpd frameworks in

anterior and posterior region

Vita Inceram spinel : highly esthetic, anterior

copings

Aluminium oxide:

milled in pre sintered state

sintering temp : 1520 c

coping in anterior and posterior region, 3 unit

fpd frameworks in anterior region

Yittrium stabilized Zirconium oxide

high flexural strength and fracture toughness

Framework of posterior FPDs and implant

abutments

3D printed ceramics is relatively rudimentary when

compared with a traditional lab ceramic system

3D printing ceramics differ from regular 3D printing

Once you "print" out your crown you still have to

fire your ceramic 3D printed object in the oven

The 3D model is rescaled 40% larger than the

original scanned model to obtain the correct size

after shrinkage

Green copings & crowns printed with ProMetal binder and Sumitomo AA-18 alumina

Green and post sintered crown parts

Anusavice, Phillip’s Science of DentalMaterials, 12th edition ,India, ElsevierPublishers, 2012, pp 418-474

Craig RG, Powers JM, Restorative DentalMaterials, 12th edition, India, ElsevierPublishers, 2006, pp 443-477

Srividya S, Recent advances inceramics,TPDI 2010 vol 1 no 2 pp 38-44

Robert Kelly J, Dental ceramics-current thinking

and trends, DCNA, 2004, 48(2): 513-544

Abduo J, Lyons K, Bennamoun M, Trends in

Computer-Aided Manufacturing in Prosthodontics:

A Review of the available streams, International

Journal of Dentistry Volume 2014, Article ID

783948, 15 pages

Prajapati A etal, Dentistry Goes Digital: A Cad-

Cam Way- A Review Article IOSR-JDMS.Vol13,

Iss8 Ver. IV (Aug. 2014), PP 53-59

Mörmann WH, The evolution of the CEREC

systemJADA 2006;137(9 supplement):7S-13S.

Utela B, Anderson R, Kuhn Advanced Ceramic

Materials and Processes for Three-Dimensional

Printing (3DP) Journal of Manufacturing Processes

Volume 10, Issue 2, July 2008, Pages 96–104

Li Yang, Shanshan Zhang, Gustavo Oliveira, Brent

Stucker, Development of a 3D Printing Method for

Production of Dental Application. Proceedings of

the 24th International Solid Freeform Fabrication

Symposium. Austin, TX, USA. 2013.