77562247-CAD-CAm

CAD/CAM RESTORATIONS


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CONTENTS

INTRODUCTION

HISTORY OF MACHINING SYSTEMS

MACHINING SYSTEMS & THEIR CLINICAL PROCEDURE’S

STAGES OF FABRICATION : COMPUTERIZED SURFACE DIGITIZATION

COMPUTER-AIDED DESIGN

COMPUTER-ASSISTED MANUFACTURING

COMPUTER-AIDED ESTHETICS

COMPUTER-AIDED FINISHING

MACHINABLE CERAMICS

ADVANTAGE OF CAD/ CAM SYSTEMS

DISADVANTAGES OF CAD/ CAM SYSTEMS

ANALOGOUS SYSTEMS (COPYING / PANTOGRAPHY METHODS )

SUMMARY

CONCLUSIONS

BIBLIOGRAPHY

PHOTOGRAPHS

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TERMINOLOGY

CAD-CAM ceramic - a machinable ceramic material formulated for the

production of inlays and crowns through the use of a computer-aided design, computer-

aided machining process.

Castable dental ceramic - a dental ceramic specially formulated to be cast

using a lost-wax process.

Ceramic - a compound of metallic and non-metallic elements.

Ceramic, dental - a compound composed of metals (such as aluminium,

calcium, lithium, magnesium, potassium, sodium, tin, titanium, and zirconium) and

nonmetals (such as silicon, boron, fluoride, and oxygen) that may be used as a single

structural component, such as when used in a CAD-CAM inlay, or as one of several

layers that are used in the fabrication of a ceramic-based prosthesis. Dental ceramics are

formulated to provide one or more of the following properties: castability, mouldability,

injectability, color, opacity, translucency, machinability, abrasion resistance, strength,

and toughness. Note: all porcelains and glass ceramics are ceramics, but not all ceramics

are porcelains or glass-ceramics.

Copy - milling - a process of machining a structure using a device that traces

the surface of a master metal, ceramic, or polymer pattern and transfers the traced spatial

positions to a cutting station where a blank is cut or ground in a manner similar to a key-

cutting procedure.

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Core ceramic - a dental ceramic material that provides a mechanically strong

base onto which a body ceramic (also called dentine or gingival ceramic) can be

veneered.

Feldspathic porcelain - a ceramic composed of a glass matrix phase and one

or more crystal phases. An important crystal phase is leucite (K2O. Al2O3.4SiO2), which is

used to create a high-expansion porcelain that is thermally compatible with gold-based,

palladium-based and nickel-based alloys. A more technically correct name for this class

of dental ceramics is leucite porcelains, because feldspar is not present in the final

processed porcelain nor is it necessary as a raw material to produce leucite crystals.

Glass-ceramic - a solid consisting of a glassy matrix and one or more crystal

phases produced by the controlled nucleation and growth of crystals in the glass.

Glass-ceramic core - the substructure of a restoration, typically made by

casting glass containing a nucleating agent into a mould, divesting the cast structure,

removing the sprue extensions, and ceramming to produce a specific volume fraction of

crystals. If necessary for colour and opacity control, the core may then be veneered with a

specially formulated porcelain or other ceramic at an elevated temperature. An example

is Dicor glass ceramic.

Glass-infiltrated dental ceramic - a minimally sintered Al2O3 or MgAl2O4

core with a void network that has been sealed by the capillary flow of molten glass.

Examples include In-ceram (Al2O3) and In-ceram Spinell (MgAl2O4) core.

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Injection-moulded ceramic - a glass or other ceramic material that is used

to form the ceramic core of an inlay, veneer, or crown by heating and compressing a

heated ceramic into a mold under pressure. An example is IPS Empress.

Porcelain jacket crown (PJC) - one of the first types of all-ceramic crown,

made from a low-strength aluminous core porcelain and veneering porcelain (with

matching thermal contraction coefficient) without the use of a supporting metal substrate

except, in some instances, for a thin platinum foil (see ceramic jacket crown).

Shade guide, ceramic - a series of ceramic tooth-shaped tabs mounted on

metal or plastic strips that is designed for comparison of hue/ value, and chroma

characteristics with those of natural teeth or existing ceramic restorations. The letter and

number code on the metal strip allows the dentist to communicate the perceived

appearance properties to a dental technologist who may not be able to observe the teeth to

be restored.

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INTRODUCTION

Ceramics are thought to be the first material ever made by man. Dental Ceramic

- a compound composed of metals (such as aluminium, calcium, lithium, magnesium,

potassium, sodium, tin, titanium, and zirconium) and nonmetals (such as silicon, boron,

fluoride, and oxygen) that may be used as a single structural component, such as when

used in a CAD-CAM inlay, or as one of several layers that are used in the fabrication of a

ceramic-based prosthesis. Dental ceramics are formulated to provide one or more of the

following properties: castability, mouldability, injectability, color, opacity, translucency,

machinability, abrasion resistance, strength, and toughness. Note: all porcelains and

glass ceramics are ceramics, but not all ceramics are porcelains or glass-ceramics.

They are among the earliest group of inorganic materials to be structurally

modified by man. Although routine use of ceramics in restorative dentistry is a recent

phenomenon, the desire for a durable and esthetic material is ancient. Dental ceramics are

the most natural appearing replacement material for missing tooth substance available in

a range of shades and translucencies to achieve life like results. However, the mechanical

properties and physical properties and the manufacturing technique of so-called

conventional dental ceramics have revealed certain clinical shortcomings i.e. excessive

brittleness, crack propagation, low tensile strength, fracture of the restoration, wear of

antagonists and sintering shrinkage. These shortcomings among other factors have

limited the indications for dental ceramics. However regardless of the advanced state of

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the 300 year old technique of casting each it its steps could induces errors in the final

castings.

Until 1988, indirect ceramic restorations were fabricated by conventional method

(sintering, casting, and pressing) and neither was pore free. Pore free restorations can be

alternately produced by machining blocks of pore free industrial quality ceramics. The

tremendous advances in computers and robotic could also be applied to revolutionize

dentistry and provide both precision and reduce time consumption with the combination

of opto electronics computer technique and sinter technology, the morphologic shape of

the crown can be sculpted in an automated way. Registration of the mandibular jaw

movements or of the functionally generated path in the mouth provides the necessary data

for an interference free escape of cusps from their face. The introduction of CAD/CAM

systems in later 1980s to restorative dentistry represents a major technological

breakthrough. Its possible to design and fabricate ceramic restorations at single

appointment as opposed to the traditional method of making impressions, fabricating

prosthesis and using a laboratory for development of the restoration. The sophisticated

processing of advanced ceramics for dental restoration lead to the further development of

CAD/CAM technologies. The sophisticated processing of advanced ceramic for dental

restoration lead to the further development of CAD/CAM. The techniques necessitates

digitizing of the prepared teeth or the planned restoration itself and surfacing of the

acquired digital data surface before milling paths can be generated. CAD/CAM offers,

esthetic anterior crowns / bridges, veneers, as well as posterior restorations. In addition,

the use of dental CAD / CAM is supposed to eliminate potential sources of errors in the

craftsmanship of the conventional procedure for the manifesting of restoration. In order

to access the complex free form surfaces to be dealt within dentistry, 3D computers aided

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approaches appears to be most promising. Technical, recent material and clinical

innovation in restorative dentistry has increased the complexity of treatment planning and

decision making. Many of these advances have not replaced, but have augmented a wide

variety of existing materials or treatment protocols, as well as clinical technique and

skills. Dentists today can choose from a variety of ceramic materials in dentistry; hence,

should be familiar with the range of CAD/CAM systems and all-ceramic materials

available for fabrication of CAD/CAM ceramic restorations. This review outlines the

developments in the evolution of CAD/CAM ceramic restorations over the last three

decades and considers the state of the art in the several extended and innovative

applications of dental ceramics.

CAD/CAM is an acronym for Computer Aided Design/ Computer Aided

Manufacturing (or Milling).

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HISTORY OF MACHINING SYSTEMS

1971 - CAD/ CAM technologies were introduced to the dental profession.

1979 - Heitlinger and Rodder followed by,

1980 -Moermann & Brandestini began to share this approach.

1983 -First dental CAD/CAM prototype was presented at the Garanciere conference in

France.

1985 -The first CAD/ CAM crown was publicly milled and installed in a mouth without

any laboratory involvement.

1986 -The first generation Cerec 1 (Siemens Corp) was introduced.

1994 -The second generation Cerec 2 (Siemens Corp) was presented.

1999- The third generation Cerec 3 (Sirona,Benheim,Germany)

2003- Cerec 3D (Sirona,Benheim,Germany)

Since 1971 a considerable activity in research & development has emerged in the field of

machined restoration/reconstruction at different universities & industrial companies.

Parallel to CEREC, many other types of systems were introduced into the market. They

are CAP, COMET, DENStech, Inlac, Nissan, DCS-Precident & LAVA.

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Application of CAD/ CAM techniques was actively pursued by three

groups of researches

A. Group supported by Henson International of France.

B. Combined group effort between the University of Zurich and Brains,

Brandestini Instruments of Switzerland.

C. University of Minnesota, supported by the U.S. National Institute of Dental

Research.

Although each group had a slightly different philosophy and approach, they

worked towards a common goal of integrating engineering applications of automation in

the creation of dental restorations.

French system

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A. Optical impression – Laser scanner

B. Data processing – By Shape recognition software

C. It has a library (memory) describing theoretical teeth.

The system uses:

3-D probe system based on electro-optical method

Surface modelling and screen display

Automatic milling by a numerically controlled 4-axis machine

Swiss system

Optical impression - Optical topographic scanning using a 3-D oral camera Data

processing - By an interactive CAD unit

The system uses:

A desk top model computer

Display monitor permitting visual verification of quality of data being acquired

Electronically controlled 3-axis N/ C milling machine

Minnesota system

A. Optical impression - Photograph based system using a 35-mm camera with

magnifying lens.

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B. Data processing - Data obtained in the dental office is sent to another

location for processing and machining.

3-D Reconstruction uses:

Direct line transformation and an alternative technique proposed

by Grimson

Milling with a 5-axis N/ C machine.

Triad of fabrication: Fabrication of a restoration whether with traditional lost-wax

casting technique or a highly sophisticated technology such as a CAD/ CAM system has

three functional components:

A. Data acquisition

B. Restoration design

C. Restoration fabrication

Subtractive Methods

Grinding of porcelain restorations out of a preformed block either by means of CAD/

CAM or by using a copy milling unit can be done by the so-called subtractive methods.

Machinable Ceramic system (MCS) for dental restorations:

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Digital Systems (CAD/ CAM)

Direct

Indirect

Three steps :

1. 3-dimensional surface scanning

2. CAD - Modelling of the restoration

3. Fabrication of the restoration.

Analogous systems (Copying methods)

Copy Milling/ Copy Grinding or Pantography Systems

Two steps:

1. Fabrication of prototype for scanning;

2. Copying and reproducing by milling

Erosive techniques

Sono Erosion

Spark Erosion

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MACHINING SYSTEMS

CAD/CAM (Digital) COPYING SYSTEMS (Analogous)

Direct Indirect Copy Milling Erosion

Cerec 1

Cerec 2

Automill, DCS President,

Cicero, Denta,

Denti CAD,

Sopha - Bioconcept

Manual Automatic Sono-

erosion

Spark –

erosion

Celay Ceramatic II

DCP

DFE

Erosonic

DFE Procera

Cerec 3

TRIAD OF FABRICATION

Traditional technique High technology

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Data acquisition or information by

impressions and translated into

articulated stone casts

Data acquisition or information is captured

electronically, either by a specialized camera,

laser system, or a miniature contact digitizer.

Restoration design is the process of

creating the wax pattern

Restoration design is done by the computer

– either with interactive help from the user or

automatically.

Restoration fabrication includes all the

procedures from dewaxing upto the final

casting (lost wax technique)

Restoration fabrication includes machining

with computer controlled milling machines,

electrical discharge machining and sintering

CONTACT DIGITIZER

LASER

CAMERA

IMPRESSION

DATA

ACQUISITION

CASTS & DIE

COMPUTERIZED DESIGN

WAX PATTERN

RESTORATION

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DESIGN

INVEST

ELECTRICAL DISCHARGE MACHINE

MACHINE

SINTER

Fabrication

CAST

TRADITIONAL LOST – WAX TECHNIQUE CAD / CAM

Creation of a restoration with traditional & CAD/ CAM techniques

Digital Systems

Computer aided design and computer aided manufacturing (CAD/ CAM) technologies

have been integrated into systems to automate the fabrication of the equivalent of cast

restorations.

CAD/CAM milling uses digital information about the tooth preparation or a pattern of the

restoration to provide a computer-aided design (CAD) on the video monitor for

inspection and modification. The image is the reference for designing a restoration on the

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video monitor. Once the 3-D image for the restoration design is accepted, the computer

translates the image into a set of instructions to guide a milling tool (computer-assisted

manufacturing [CAM]) in cutting the restoration from a block of material.

Stages of fabrication : Although numerous approaches to CAD/ CAM for restorative

dentistry have evolved, all systems ideally involve 5 basic stages:

• Computerized surface digitization

• Computer-aided design

• Computer-assisted manufacturing

• Computer-aided esthetics

• Computer-aided finishing

(The last two stages are more complex and are still being developed for inclusion

in commercial systems).

Computerized surface digitization : 3D-surface digitizing or scanning methods are

separated into :

• Direct (at the tooth)

• Indirect methods(via impression making & model fabrication or via pro-inlay)

• Mechanical

• Optical sensors

Types of computerized surface digitization techniques:

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1. Photogrammetry

2. Moiré

3. Laser scanning .

4. Computerized tomography (CT) scanning

5. Magnetic resonance imaging (MRI)

6. Ultrasound

7. Contact profilometry

Mechanical scanning conducted by a profilometer or pinpoint sensor is very precise, but

have several shortcomings. Among the various methods of optical surface scanning, the

active (laser) triangulation has been proven the most suitable, however it requires non-

reflective surfaces for scanning (contact powder coating). Laser technique and contact

digitization are the most promising approaches from the point of view of cost and

accuracy.

FLOW CHART SHOWING SEQUENTIAL EVENTS OCCURING DURING

CAD-CAM TECHNIQUE OF FABRICATING A CERAMIC RESTORATION

The cavity preparation is scanned stereo-photogrammetrically, using a three-dimensional

miniature video camera

The small microprocessor unit stores the three dimensional pattern depicted on the

screen

The video display serves as a format for the necessary manual construction via an electric

signal

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The microprocessor develops the final three-dimensional restoration from the two

dimensional construction

The processing unit automatically deletes data beyond the margins of the preparation

The electronic information is transferred numerically to the miniature three-axis milling

device

Driven by a water turbine unit, the milling device generates a precision fitting restoration

from a standard ceramic block

The entire process of electronic designing and subsequent milling of a ceramic restoration

requires approximately 10 to 15 minutes.

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Chairside Economical Restoration of Esthetic Ceramics

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Cerec System

The CEREC (Ceramic Reconstruction) system ( Siemen/sirna corp.) was originally

developed by Brains A.G. in Switzerland and first demonstrated in 1986, but had been

repeatedly described since 1980. Identified as CEREC CAD/CAM system, it was

manufactured in West Germany and marketed by the Siemens group.

Cerec System consists of :

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• A 3-D video camera (scan head)

• An electronic image processor (video processor) with memory unit (contour

memory)

• A digital processor (computer) connected to,

• A miniature milling machine (3-axis machine)

The Optical impression

A small hand held video camera with a 1cm wide lens (scanner) when placed

over the occlusal surface of the prepared tooth, emits infrared light which passes through

an internal grid containing a series of parallel lines. The pattern of light and dark stripes

which falls on the prepared tooth surface is reflected back to the scanning head and onto a

photoreceptor, where its intensity is recorded as a measure of voltage and transmitted as

digital data to the CAD unit.

Procedure

• The prepared and surrounding tooth surfaces are coated with CEREC powder

(L.D. caulk – TiO2 and talc) to eliminate light reflections and to obtain an opaque

reflective surface (few μm thick only).

• The hand-held camera is positioned over the prepared tooth, and an image of the

preparation is then simultaneously projected onto the screen.

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• The camera is adjusted until the image is clear and properly angulated for all

aspects of the prepared tooth to be visible in complete focus.

• The video search mode enables assessment whether the camera viewing axis is

compatible with the inlay/ onlay path of insertion. If viewing is acceptable the

three dimensional scanning is triggered by the release of the foot pedal.

• The operator now checks the preparation and its three-dimensional representation

for corrections or modifications to be made, if necessary. Once the appropriate

optical orientation is generated, the operator can 'freeze-frame' the preparation

into a static image.

Designing the Restoration

The proposed restoration is designed by tracing frame lines on the optical

impression (fixed image) which is projected onto the screen. A cursor controlled by

reverse 'mouse' located on top of the unit is used to define the limits/ boundaries, starting

from the gingival margin and moved along the internal line angles at intermediate

positions commands the computer which draws a continuous line, through all placed

points and displays it on the screen. The operator can carefully examine, edit and if

necessary, even modify the pattern at any moment in the procedure. After the margins,

walls, proximal contour and contact as well as the location of marginal ridges are

established, the electronically designed proposed restoration can be viewed as a 3-

dimensional model on the monitor, and stored automatically on the program disk

(floppy).

Milling of the Ceramic restoration

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The restoration is milled (4-7minutes) with a diamond wheel from a pre-

manufactured and standardized ceramic block in the milling chamber of the CAM unit.

Factory standardized, preformed dental porcelain blocks are homogenous and almost

pore-free (Vita Cerec blocks; Dicor Cerec blocks).

The CAM unit

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A pump system with an attached water reservoir located at the base of the mobile

cart maintains the water pressure required for the hydraulic driven water turbine in the

milling chamber. During milling about 5 liters of water is cycled internally which

eliminates the need for external water supply and drainage. The water reservoir system

also contains a microporous filter that traps any of the loosened diamond particles

separated from the wheel for future retrieval.

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Procedure

• The appropriate ceramic block is selected from a series consisting of different

sizes and shades.

• The ceramic block is mounted on a metal stub (retainer), inserted into the milling

unit and the grinding operation is initiated.

• Grinding of the ceramic restoration is done by a diamond-coated disk/ wheel in

conjunction with a high velocity water-spray, which simultaneously cools and

cleans the milling disk. The restoration is milled from the mesial to the distal

proximal surfaces with the block rotating along its central axis and being steadily

advanced forward during the milling process. In addition, the diamond wheel not

only rotates but also translates up and down over the porcelain block being milled.

A series of steps or cuts (200-400) are required for milling a ceramic restoration.

• At the end of the milling operation, the completed restoration falls to the bottom

of the chamber from where it can be readily retrieved.

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The computer program associated with the milling process has additional interesting

features such as :

• Before the milling process, the screen displays the dimensions of the restoration

from one proximal surface to the other in 1/900th of an mm.

• During the milling operation, the screen continuously informs the operator of the

percentage of completion.

• A continuous readout is displayed concerning the cutting efficiency of the

diamond wheel, thereby indicating the probable need for replacement.

Clinical shortcomings of Cerec 1 system

• Although the CEREC system generated all internal and external aspects of the

restoration, the occlusal anatomy had to be developed by the clinician using a

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flame-shaped, fine-particle diamond instrument and conventional porcelain

polishing procedures were required to finalize the restoration.

• Inaccuracy of fit or large interfacial gaps.

• Clinical fracture related to insufficient depth of preparation.

• Relatively poor esthetics due to the uniform colour and lack of characterization in

the materials used.

Cerec 2 system

The Cerec 2 unit (Siemen/ Sirona), based on the process developed by Morman &

Brandestini was introduced in September 1994, and is the result of constant further

development via different generations of Cerec units to eliminate the previous limitations.

The major changes include :

• Enlargement of the grinding unit from 3 axes to 6 axes.

• Upgrading of the software with more sophisticated technology which allows

machining of the occlusal surfaces and the complex machining of the floor parts.

Other technical innovations of Cerec 2 compared to Cerec 1

• The improved Cerec 2 camera - new design, easy to handle, a detachable cover

(asepsis/sterilization), reduction in the pixel size/ picture element to improve

accuracy and reduce errors.

• Data representation in the image memory and processing increased by 8 times,

while the computing capacity is 6 times more efficient.

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• Magnification factor increased from x8 to x12 for improved accuracy during

measurements.

• Monitor can be swiveled and tilted, thus facilitating visual control of the video

image. Other changes include modification of the foot control and the keys and

their positions on the keyboard.

• Simultaneous grinding using cylindrical diamonds (2mm diameter, particle

#64um, 77,000rpm and cutting speed 8m/s) and radial grinding of the grinding

disk (#6um particle, 18000rpm and cutting speed 38m/s).

• Extended machining options facilitate grounding of complex floor shapes in

inlays/ onlays. Provides three different programs for Extrapolation, Correlation

and Veneer.

• Cerec 2 software (Cos 4.20) permits custom veneer preparation and class IV

preparations with incisal edge coverage.

• Improved in rigidity and grinding precision by 24 times.

• Improved accuracy of fit (reduction in inter-facial gap from 84+38µm for Cerec 1

to 56+27µm for Cerec 2).

Machinable ceramics (Ceramics used in machining systems) are pre-fired blocks of

feldspathic or glass-ceramics.

Composition : Modified feldspathic porcelain or special fluoro-alumino-silicate

composition are used for machining restorations.

Properties

• Excellent fracture and wear resistance

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• Pore-free

• Possess both crystalline and non-crystalline phase (a 2-phase composition permits

differential etching of the internal surface for bonding).

Ceramic CAD/ CAM restorations are bonded to tooth structure by :

• Etching the fitting surface for bonding to enamel

• Conditioning, priming and bonding (when appropriate)

• Etching (by HF acid) and priming (silanating)

• Cementing with luting resin.

CAD/ CAM restorations (inlay/ onlays) are fabricated primarily from ceramic

materials, while subtractive fabrications of metal alloys or titanium have only been

investigated for crowns, copings and bridges.

Machinable Ceramics

The industrially prefabricated ceramic ingots/ blanks used are practically pore-

free which do not require high temperature processing and glazing, hence have a

consistently high quality. The blanks measure approximately 9mm x 9mm x 13mm and

are industrially fabricated using conventional dental porcelain techniques. E.g.: Vitadur

353 N (Vita Zahnfabrik, Bad Sackingen, West Germany) frit powder is mixed with

distilled water, condensed into a 10mm x 10mm x l5mm steel die and fired under vacuum

(the temperature is increased at a rate of 60OC/min to 950oC and held for one minute).

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Two classes of machinable ceramics available are :

• Fine-scale feldspathic porcelain

• Glass-ceramics

Cerec Vitabloc Mark I : This feldspathic porcelain was the first composition used with

the Cerec system (Siemens) with a large particle size (10-50μm). It is similar in

composition, strength, and wear properties to feldspathic porcelain used for metal-

ceramic restorations.

Cerac Vitabloc Mark II : This is also feldspathic porcelain reinforced with aluminum

oxide(20-30%) for increased strength and has a finer grain size(4μm) than the Mark I

composition to reduce abrasive wear of opposing tooth.

Dicor MGC (Dentsply, L.D. Caulk Division) : This is a machinable glass-ceramic

composed of fluorosilica mica crystals in a glass matrix. The mica plates are smaller

(average diameter 2µm) than in conventional Dicor (available as Dicor MGC-light and

Dicor MGC-dark). Greater textural strength than castable Dicor and the Cerec

compositions. Softer than conventional feldspathic porcelain. Less abrasive to opposing

tooth than Cerec Mark I, and more than Cerec Mark II (in-vitro study results).

MGC - F (Corning Inc.) : Machinable glass ceramic developed to overcome the

deficiencies of the Vita Mark II and Dicor MGC. It is tetrasilic mica glass-ceramic with

minor compositional and microstructural changes from Dicor MGC to enhance its

fluorescence and machinability.

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Pro CAD (Ivoclar AG, Liechtenstein) : The Pro CAD line (Professional Computer

Assisted Design) is a product package suitable for all Cerec 2 applications. It is a high-

strength optimized, leucite-reinforced glass-ceramic material, available as blocks in

different sizes and shades.

Celay : This material can be used in both copy milling and CAD/ CAM techniques.

According to the manufacturer, it is fine-grained feldspathic porcelain used to reduce

abrasiveness with a composition identical to that of Cerec Vitabloc Mark II. In addition,

both In-Ceram and Spinell(Vita) are available for processing in the green state in

conjunction with Celay.

Y-TCP (Yttria Stabilized Tetragonal Circonia Polycrystal): is considered to be the

most successful oxide ceramic for dental-medical application. Outstanding mechanical

features of Y-TCP combined with light color and translucence provide fascinating

possibilities in modern ceramics restoration. The combination of this new material from

firm VITA with SIRONA INLAB SYSTEM opens the futuristic perspectives to its user.

Confirmed CAD/CAM technology breaks the technical limits of up to now applied dental

ceramic restoration in the maximal aesthetic way. Y-TCP confirmed its excellent

biological withstanding by over a 30-year long clinical using for hip joint prosthesis in

human body. After passing the sintering procedure suggested by firm VITA, with 3

points it possesses the density of bending to DIN EN ISO 6872 of more than 900 Mpa,

that is the one of maximal that can be achieved in dental application of ceramics

LAVA

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The Lava all-ceramic system (3M ESPE Dental Products, Seefeld, Germany) also uses a

CAD/CAM procedure, to produce a framework consisting of a Y-TZP-based ceramic

supplemented by a specially designed veneer ceramic.-The frameworks are fabricated

using contemporary CAD/ CAM procedures (scanning, computer-aided framework

design and milling) from presintered Y-TZP blanks .The shade of the core material may

also be stained to correspond with 1 to 7 shades of the Vita Classic shade system

resulting in the ability to develop shading of the restoration which, in turn, may provide

the technician with less of a challenge than when required to mask an opaque white

ceramic or a grey metal core.This may also eliminate the need to veneer the lingual and

gingival aspects of the bridgework connectors.'° In this respect, the Y-TZP core utilized

for the Lava system has been considered to exhibit increased translucency in comparison

with other zinconia-based ceramic core materials. The manufacturers have suggested that

an ideal translucency may be achieved as a result of inherent material properties and a

low wall thickness.

Lava relies on non-contact, photo-optical recording of the surfaces of dies prepared from

an impression of the teeth to be restored.The dies and bite registration are digitized by the

scanner and are viewed three-dimensionally on the computer screen. The bridge or crown

framework may be designed on the computer within the parameters of

the system, which set the thickness of the framework and the square area (9 mm') of

bridge connectors. Pontic designs are retrieved from a library of designs held by the

computer system. It could be considered that the solely computer-aided design is an

advantage over other systems which require the technician to make a wax build-up.

Long-term clinical data on restorations formed in Lava are not yet available, but

communication with a laboratory producing large numbers of Lava frameworks in the

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UK have not indicated any problems, such as fracture of the framework (Littlejohn L,

personal communication, August 2005). Laboratory experimentation by Sorensen with

the Lava system for CAD/CAM production of highstrength precision fixed

prosthodontics" has demonstrated excellent marginal fit of Lava bridges, while results of

a series of laboratory experiments carried out on Lava discs by Curtis and co-workerS14"

have indicated that Lava does not lose strength in moist condition,its not adversely

affected by grinding by a 20-40 pm bur with water coolant,Following surface loading at

simulated masticatory loads flexural strength is not affected and the possibility of

inducing a transformation toughening mechanism (counteracting crack propagation) may

have been identified.

These are promising results, indicating that Lava does not suffer from a common problem

with dental ceramics, namely, the adverse effect of oral fluids on their strength. For the

clinician, these data show that, if adjustment of the framework is required, this should be

carried out using a fine bur with water coolant.

At the time of writing, three Lava milling centres are in operation in the UK, while other

countries with a number

of milling centres include the USA, Italy and Germany. Technicians wishing to utilize the

Lava system for construction of bridge or crown frameworks cast dies in the conventional

manner, prior to sending these to the milling centre.

Other machinable ceramics being developed include :

• Bioglass (Alldent Corp., Rugell, Liechtenstein)

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• DFE (Keramik/Krupp Medizintechnir, Essen, Germany; Bioverit / Mikrodenta

Corp.)

• Empress / Vivadent (lvoclar Corp., Schaan, Liectenstein)

Clinical procedures for Cerec CAD/ CAM :

Tooth preparation & Optical registration

Simple, box shaped preparations suffice for the Cerec three-dimensional scanning

and fabrication process. The procedure is not dependent on any cavity preparation size.

Simple and complex proximal preparations for both inlays and onlays are readily and

correctly milled. Undercuts in cavity walls do not affect the optical scanning and are

filled in with composite resin during the cementation. Straight walls with right angles are

recommended The 4-6 degree divergence required for cast inlays is not necessary using

Cerec system; parallel walls suffice, thereby ensuring maximal preservation of hard

dental tissues. The occlusal and proximal cavity margins are not beveled. Instead, the

cavity walls and enamel edges are finished using diamond coated finishing stones. The

gingival floor is horizontal or declines between 5-15 degrees towards the gingival

margin. The optical scanning is facilitated by having clearly defined walls and cavity

margins and by the use of rubber dam during the optical scanning and cementation

stages. Gingival margins of the preparation must be made clearly visible by the

placement of retraction cord, or by use of electrosurgery/ incision surgery.

Cementation

39


The small quantities of composite resin cement required for cementation ensures

a thin layer between the ceramic and the enamel. This thin layer, together with the

microretentive bond within the ceramic and enamel apparently minimizes the negative

aspects of the polymerization shrinkage and the high thermal expansion of the cement.

Composite resin cements blend esthetically with the porcelain and enamel.

The clinical advantages of the Cerec system :

• The restorations made from prefabricated and optimized, quality-controlled

ceramic porcelain can be placed in one visit.

• Translucency and colour of porcelain very closely approximate the natural dental

hard tissues.

• Further, the quality of the ceramic porcelain is not changed by the variations that

may occur during processing in dental laboratories.

• The prefabricated ceramic is wear resistant. The optimized structure of the

ceramic enables optimal polishability of the material and low abrasion of the

opposing tooth. A tight marginal fit is provided by the adhesive system used

between the etched ceramic porcelain and enamel surfaces. The essential

measures are:

• Porcelain ceramic etching (HF 5% for 60 seconds): microretentive adhesive bond

between porcelain/ ceramic and the bonding agent/ composite resin cement.

• Enamel-etching technique (H3PO4 35% for 30 seconds): microretentive adhesive

bond between composite resin cement/ bonding agent and enamel.

CICERO System

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Computer Integrated Crown Reconstruction (Elephant industries). This Dutch

system was marketed with the Duret(French) system, Sopha Bioconcept and the

Minnesota system(Denti CAD) as the only three systems capable of producing complete

crowns and FPDs. The Cicero CAD/ CAM system developed for the production of

ceramic fused to metal restorations, makes use of:

• Optical scanning

• Nearly net-shaped metal and ceramic sintering

• Computer-aided crown fabrication techniques.

Alloy sintering eliminates casting and therewith many processing steps in the

fabrication of metal-ceramic restorations.

The unique feature of the Cicero system is that it produces Crowns, FPD's and

inlays with different layers such as metal and dentin and incisal porcelains, for maximum

strength and esthetics.

COMET System

(Coordinate Measuring Technique, Steinbichler Optotechnik, Neubeurn, Germany) This

system allows the generation of a 3-dimensional data record for each superstructure with

or without the use of a wax-pattern. For imaging, 2-dimensional line grids are projected

onto an object, which allows mathematical reproduction of the tooth surfaces. It uses a

pattern digitization and surface feedback technique, which accelerates and simplifies the

3-dimensional representation of tooth shapes while allowing, individual customization

and correction in the visualized monitor image.

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Other Digital Systems

The Duret System (Hanson International)

The Duret CAD-CAM system was developed by Francois Duret and produced by

Sopha (Lyon, France). It was made of 3 discrete units :

• A camera module

• A CAD module

• The milling module

Optical impression was made using Electro-optical method (a laser scanner)

combining Holography and Moire. The digitized data from the CAD unit is combined

with data relating to the dynamic movements of jaw which is provided by a proprietary

articulator called the Access Articulator linked to the CAD unit. This original Duret

system using highly sophisticated and complex imaging/ designing procedure was

designed primarily to fabricate full crowns. However, since its introduction, both the

original system and the derivative version the SOPHA system have had limited

commercial success.

The SOPHA System (Sopha Bioconcept, Inc. Los Angeles, CA )

It was commercially introduced in 1990/ 91 in France, but is apparently no longer

available.

The REKOW System (Digital Dental System)

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It was developed by Dr. Diane Rekow at the University of Minnesota. This

system initially used a photogrammetric method for intraoral surface digitization of the

preparation using a pen digitizer, but later used mechanical-manual scanning and was

marketed for dental laboratory use in Europe by Bego (Bremen, Germany).

The Denti CAD system

The Denti CAD system is capable of producing restorations from alloys,

composites and ceramics. It uses a unique robotic arm digitizer (a miniature mechanical

linkage), designed by Foster Miller Inc. (Waltham, Mass, U.S.A.) that can be used both

intraorally or on traditional models and dies for tracing the image.

The DUX’s system/ The Titan System (DCS groups Dental, Allschwill, Switzerland)

were introduced in 1991 by DCS/ GIM -Alldent.

It consists of:

• A miniature contact digitizer (pantograph)

• A central computer

• A milling unit

The digitizer consists of a table that shifts a die or model beneath the contact

stylus. This system is currently distributed under the brand name DCS -President (DCS/

Girrbach).

Advantage of CAD/ CAM(Cerec system) over other systems :

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• Eliminates the procedures like impression model making and fabrication of

temporary prosthesis.

• Dentist controls the manufacturing of the restoration entirely without laboratory

assistance.

• Single visit restoration and good patient acceptance.

• Alternative materials can be used, since milling is not limited to castable

materials.

• The use of CAD/ CAM system has helped provide void free porcelain

restorations, without firing shrinkage and with better adaptation.

• It can construct various types of ceramic restorations. Hence, can be used as an

alternative to metallic restorations allowing placement of esthetic inlays/ onlays in

stress bearing areas of posterior teeth (because of its high resistance to abrasion,

good marginal adaptation and also as an alternative to complete or full coverage

crowns that require extensive tooth reduction). Half and three-quarter crowns and

Cerec veneer laminates can also be directly placed as easily.

• CAD-CAM device can fabricate a ceramic restoration such as inlay/ onlay at the

chair-side.

• Eliminates the asepsis link between the patient, the dentist, operational field and

ceramist.

• The shapes created in the CAD unit are well defined, and thus a factor such as

correct dimensions can be evaluated and corrections/ modifications can be carried

out on the display screen itself.

44


• Using industrially prefabricated ceramic blanks compared to those fabricated by

the dental technician is the maintenance of consistently optimally high quality of

the material under industrial conditions controlled by the manufacturer.

• Glazing is not required and Cerec inlay/ onlays can be easily polished.

• Minimal abrasion of opposing tooth structure because of homogeneity of the

material (abrasion does not exceed that of conventional and hybrid posterior

composite resins).

• The mobile character of the entire system enables easy transport from one dental

laboratory to another.

Disadvantages

• Limitations in the fabrication of multiple units.

• Inability to characterize shades and translucency.

• Inability to image in a wet environment(incapable of obtaining an accurate image

in the presence of excessive saliva, water or blood).

• Incompatibility with other imaging systems.

• Extremely expensive and limited availability.

• Still in early introductory stage with few long-term studies on the durability of the

restorations.

• Lack of computer-controlled processing support for occlusal adjustment.

• Technique sensitive nature of surface imaging that is required for the prepared

teeth.

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• Time and cost must be invested for mastering the technique and the fabrication of

several restorations, to develop proficiency in the operator.

ANALOGOUS SYSTEMS (COPYING / PANTOGRAPHY METHODS )

Copy milling

It is the mechanical shaping of an industrially prefabricated ceramic material,

which is consistent in quality and its mechanical properties(an improvement over

conventional ceramics). Copy milling includes fabrication of a prototype (pro-inlay or

crown) usually via impression making and model preparation. Based on the model, a

replica of inlay/ crown is made and fixed in the copying device and transferred 1:1 into

the chosen material such as ceramic.

Materials used

The choice of material depends mostly on the type of margin required for the

restoration. Virtually any geometry and size can be copy milled as long as there is direct

access of the finger guide and cutting tool to the surfaces involved. Because titanium has

a very high melting temperature, it is difficult to conveniently cast; however it can be

copy milled easily and inexpensively. Composite and ceramic materials are most

commonly used for copy milling dental restorations.

Erosion methods

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It needs a copy-suitable pre-version (e.g.: pro-inlay) in the form of a negative

model of the interior and exterior contour of the restoration for its fabrication. The

(metal-based) negative form is prepared either by wax molding and casting or by

intensive copper plating of the impression.

• Sono erosion - for ceramic restorations

• Spark erosion - for metal restorations

Sono erosion

It is based on ultrasonic methods. First, metallic negative moulds (so-called

sonotrodes) of the desired restoration are produced, both from the occlusal as well as

from the basal direction. Both sonotrodes fitting exactly together in the equational plane

of the intended restoration are guided onto a ceramic blank after connecting to an

ultrasonic generator, under slight pressure. The ceramic blank is surrounded by an

abrasive suspension of hard particles, such as boron carbide, which are accelerated by

ultrasonics, and thus erode the restoration out of the ceramic blank.

Spark Erosion

It refers to 'Electrical Discharge Machining' (EDM) which was used by the tool

and die industry during the 1940's and was adapted into dentistry in 1982. It may be

defined as a metal removal process using a series of sparks to erode material from a

work piece in a liquid medium under carefully controlled conditions. The liquid medium

usually, is a light oil called the ‘dielectric fluid’. It functions as an insulator, a conductor

and a coolant and flushes away the particles of metal generated by the sparks.

47


Advantages of EDM desirable for dental applications :

• EDM is not affected by metal hardness because it is a thermal process.

• Adhesive characteristics of the workpiece do not affect EDM because it is a non-

contact method of removing metal.

• EDM provides a smooth bur-free surface.

• EDM can be used to machine thin objects without distortion because there are

virtually no mechanical forces created.

• EDM can be used to make long, small diameter cuts because there is little, if any,

torque on the electrode to cause breakage.

• EDM is accurate to within 0.0001 inch.

The major disadvantage is the cost of the equipment.

The Spark Erosion (SAE) unit (Dental Arts Laboratories Inc., Illinois)

A graphite or copper electrode acts as a tool that invades the piece of base metal

and erodes a negative form in the shape of the electrode. The process is accomplished by

lightening like sparks generated between the electrode and the restoration. The sparks

melt the alloy by heating it to between 3000°C and 5000°C. These sparks remove small

amounts of the metal substrate within microseconds. The entire process takes place in a

dielectric liquid bath that prevents the alloy from burning. Stress characteristics can be

eliminated through the application of spark erosion before or after the ceramic or acrylic

resin surface is added. The spark erosion method can be applied to any type of

conductible metal/ alloy such as gold, base metal and titanium. This method of erosion

has been named as SAE Secotec.

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CELAY System

The Celay System (Mikrona AG, Spreintenbach, Switzerland) became first

commercially available in 1992. It is a high precision, manually operated copy milling

machine and the fabrication principle is the same as for 'Key' duplication. This system

was originally designed and intended for use in the dental laboratory, however it may

also be used at the chairside.

Method

• An impression(silicone) of the prepared tooth is made and poured in die stone.

• A prototype resin coping of the restoration (prototype) called 'pro-inlay' (a

provisional inlay) is fabricated on the die using a blue light-cured resin(Celay-

Tech, Mikrona Technologies, AG, Switzerland).

• The cured resin prototype is removed from the die and fixed on the left side of the

relay unit using a special retaining device(rod shaped).

• A prefabricated ceramic blank(eg. - aluminous core ceramic 'In-Ceram') is fixed

in the carving chamber on the right side of the relay unit.

• The reference disk (tracing tool) mechanically traces or scans the surface of the

prototype (pro-inlay).

• Duplicating the movements of the reference disk, the rough milling disk(a coarse

diamond instrument with a grit size of 126 μm) and a high speed turbine driven

by air pressure, machines the rough contour of the ceramic restoration by

synchronized grinding over 8-axis for effective bulk reduction. For milling a

coping, the lumen of the coping is scanned and milled with coarse ball and round

49


tipped diamonds. Both sides of the relay unit are connected by a geometric

transfer mechanism to link the three-dimensional movement of the tracing device

with the milling device. During the milling process, the milling chamber is

protected with a clear cover and a cooling liquid(Celcool, Mikrona, AG,

Switzerland) is sprayed on the blank and on the instrument.

• Since the rough milling disk is slightly smaller than the scanning disk, it produces

a slightly oversized restoration. The final contour of the restoration is developed

with 64μm grit finishing diamond instruments.

• To ensure a complete and accurate tracing, the pattern is coated with contact or

indicating powder (Celtouch, Mikrona AG, Switzerland). This powder is removed

on contact with the tracing instruments so that areas already scanned can be

differentiated from the un-scanned areas.

• The external surfaces are finished with disks and the internal surfaces with round-

tipped and sharp/ fine-tipped diamond stones.

• Final fit of the machined inlay/ coping is examined, and internal discrepancies are

marked and reworked with repeated scanning.

• The internal surface is either acid-etched or air-abraded before silanization and

cementation.

By combining the Celay system, with elements of In-Ceram technology, copy

milled glass-infiltrated aluminous core restorations can be fabricated. In-Ceram or In-

Ceram Spinell materials are machined by Celay and then infiltrated with a sodium-

lanthanum glass in a manner similar to that of conventional In-Ceram restorations, and

finally veneered with Vitadur Alpha porcelain. The fabrication of copy-milled In-Ceram

50


crown substructures with the Celay system combines the positive mechanical properties

of glass-infiltrated aluminous core materials with the advantages of industrially

prefabricated ceramics.

Advantages over conventional In-Ceram technology :

• The processing time is considerably shorter because die duplication and 10 hour

sintering are not necessary.

• Glass infiltration can be performed in a conventional ceramic furnace in 40

minutes, because of the higher capillary effect of the industrially sintered alumina

blank (homogenous structure, even particle distribution).

• The industrially prefabricated material also has a higher flexural strength than the

conventional In-Ceram material.

PROCERA System

The Procera System (Nobel Biocare, Gioteborg, Sweden) embraces the concept

of CAD/ CAM to fabricate dental restorations. It was developed by Andersson M. &

Oden A. in 1993, through a co-operative effort between Nobel Biocare AB (Sweden) and

Sandvik Hard Materials AB (Stockholm, Sweden).

It consists of a computer controlled design station in the dental laboratory that is

joined through a modern communication link to Procera Sandvik AB in Stockholm,

Sweden, where the coping is manufactured with advanced powder technology and CAD/

CAM technique.

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Steps for fabrication

• Scanning : At the design station, a computer controlled optical scanning device

maps the surface of the master die and is sent via a modem to the Procera

production facility.

• Machining : At the production facility, an enlarged die is fabricated that

compensates for the 15-20% sintering shrinkage of the alumina core material.

High-purity alumina powder is pressed onto the die under very high pressure,

milled to required shape, and fired at a high temperature (1550°C) to form a

Procera coping.

• Veneering : The sintered alumina coping is returned to the dental laboratory for

veneering thermally compatible low fusing porcelains (All-Ceram veneering

porcelain) to create the appropriate anatomic form and esthetic qualities. All-

Ceram veneering porcelain (Ducera) has a coefficient of thermal expansion

adjusted to match that of aluminium oxide (7x10-6/ °C). It also has the fluorescent

properties similar to that of natural teeth and the veneering procedures require no

special considerations. The reported flexural strength of the Procera All-Ceram

crown (687 Mpa) is relatively the highest amongst all the all-ceramic restorations

used in dentistry (attributed to the 99.9% alumina content).

This system can be used to fabricate two types of dental restorations :

• A Porcelain-fused-to-metal restoration made of titanium substructure with a

compatible veneering porcelain using a combination of machine duplication and

spark-erosion (The Procera Method, Noble Biocare).

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• An all-ceramic restoration using a densely sintered high-purity (99.9%) alumina

coping combined with a compatible veneering porcelain.

Porcelain fused to metal restoration : The Procera System was initially used to fabricate

veneered crowns and fixed partial dentures by combining a titanium substructure with

compatible low-fusing veneering porcelain such as Ti-Ceram.

Components used

Pre-fabricated cold-worked bars or solid cylindrical blanks of Commercially pure

Titanium (CpTi) and a low fusing veneering porcelain Ti-Ceram fired at 750°C.

Procedure

The working time required to fabricate the titanium coping is about 35 minutes. It

requires two procedures :

• Mechanical milling process -external surface of titanium coping is milled from

the cylindrical titanium blank in 5-6 minutes.

• Spark erosion process - The internal configuration of the titanium coping is

developed in about 8-10 minutes. The internal surface of the titanium coping is air

abraded (120μm particles of Al2O3) to remove the surface oxide layer

accumulated during the spark erosion process. The external surface is also air

abraded and then veneered with a low-fusing veneering porcelain compatible with

titanium such as Ti-Ceram in the conventional manner and fired at 750°C.

• This method can also be used for milling implant system restorations.

53


Advantages (mainly related to use of titanium)

• Biocompatibility of titanium - suitable for use mainly in metal sensitive patients.

• Low cost of titanium relative to noble metal alternatives.

• Standardization of procedure for fabricating titanium coping with consistent results.

• Accuracy of fit

• Ti-Ceram is less abrasive than conventional porcelain.

All-ceramic restorations

The Procera system has also been used to produce an all-ceramic crown known as

Procera All-Ceram Crown which is composed of a densely sintered, high-purity(99.9%)

alumina coping combined with a compatible veneering low fusing porcelain such as All-

Ceram Porcelain(Ducera).

Other copying systems

• Ceramatic II Svstem (Askim Corp., Sweden)

In this system scanning is performed automatically, and this applies to the DCP

system as well.

• The DFE -system and Erosonic (ESPE Dental Medizin Corp., Seefeld

Germany)

They both make use of ultrasonic erosion for the machining of ceramic. For this

purpose sonotrodes must be made in advance as negative forms of the inner and outer

contours of the restoration.

54


Advantage of milling methods

• Reducing the labour time needed.

• Single appointment restorations (in a period of 3 to 13 minutes).

• Can be used for both direct and indirect fabrications.

Advantages of Celay system over the Cerec system

• Celay could recreate all surfaces of a restoration whereas Cerec I could not make

the occlusal surface.

• Celay has the potential to fabricate crowns and short-span bridges with In-Ceram

system (Vita, Germany).

SUMMARY

Ceramic materials have been used in dentistry for well over 200 years. They are

the most biocompatible dental restorative materials, because they are chemically very

55


stable. A desirable feature of ceramics is that their appearance can be customized to

simulate the colour, translucency and flourescence of natural teeth. A major problem with

the use of ceramics as tooth replacement materials is their very low fracture toughness,

and the fact that fracture occurs at a very low strain of about 0.1%. In other words, the

ceramic structure only exhibits a very low flexibility before fracture. Another problem is

that if the ceramic structure is formed by the condensation and sintering of fine frit

particles, fusion is accompanied by a relatively large firing shrinkage. Newer ceramic

materials and innovative ceramic processing techniques have been introduced in

restorative dentistry since the early 1980’s. Some of these ceramics still share roots with

research that originated in Europe in the 18th century. Today as in the era of Nicholas

Dubois De Chemant,most advances are derived from collaborations with the ceramics

engineering community. Notable recent progress includes; the advent of predictable

ceramic materials and techniques for esthetic complete crowns, partial coverage and

laminate veneer restorations; improved metal ceramic esthetics with the advent of

opalescent porcelains and framework modifications; introduction of CAD/CAM and

machining as a route to fabrication of restorations; improved understanding of the clinical

response of all ceramic prostheses and of the material factors that influence clinical

longevity. Strong scientific and collaborative foundations presently exist for continued

development and improvement of ceramic systems by increasingly well-informed teams

of researchers and dentists.

No currently available restorative system can be considered the ideal replacement

for natural tooth structure. However, in recent years there has been a great amount of

attention given to research on and development of ceramic systems for restorative use.

Ceramics are playing an increasingly important role in restorative dentistry, and further

56


improvements in fracture resistance and wear properties will no doubt enhance their

restorative use. The demand for esthetic dentistry is expected to continue and will be

influencial in determining the range of the products available.

In the future we expect to see dramatic improvements by the turn of the century,

not only in esthetic dental materials, but also the techniques of using these materials. The

creativity and artistic skill of the dental ceramists will be paramount in creating a realistic

illusion using these technologies. High technology will continue to improve the way we

diagnose and design treatment plans for patients with esthetic dental concerns. As high-

tech costs diminish, more dentists will introduce these technologies into their practices to

meet the ever increasing demand.

CONCLUSION

The aim of restorative and esthetic dentistry is to restore the decayed or missing

part of the teeth with a bio-compatible material that matches natural enamel in

appearance and physical characteristics and maintain occlusal anatomy to promote proper

57


oral function. Dental ceramic technology is one of the fastest growing areas of dental

material research and development. The past decades have seen the development of

several new groups of ceramics.

The diversity of dental ceramics continues to stimulate laboratory and clinical

research. Systems such as Dicor and Empress are now established, and data regarding the

in vitro and in vivo performance of such restorations have been reported widely.

Modifications to several systems have been suggested or introduced to overcome certain

disadvantages. The potential of the In-Ceram system, remains to be exploited to the full.

The diversity and sophistication of some of the CAD-CAM systems may prove to be

influential in the future.

Each system has its own merits, but may also have shortcomings. Combinations

of materials and techniques are beginning to emerge which aim to exploit the best

features of each. Glass-ceramic and glass-infiltrated alumina blocks for CAD-CAM

restoration production are examples of these and it is anticipated that this trend is likely

to continue….

BIBLIOGRAPHY

Text Book References

1. John. W. McLean - The Science & Art of Dental Ceramics, Vol. I; Quintessence

- 1979.

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2. John W. McLean - Science and Art of Dental Ceramics (Bridge Design & Lab

procedures), Vol II. Quintessence - 1980.

3. Jack. D. Preston - Perspectives in Dental Ceramics; Quintessence - 1985.

4. G.J. Chiche, Alain Pinault - Essentials of Dental Ceramics - 1988.

5. J. F. Roulet, S. Herder - Bonded Ceramic Inlays; Quintessence - 1991.

6. Barry G. Dale, Kenneth W. Ascheim - Esthetic Dentistry - 1993.

7. R. G. Craig - Restorative Dental Materials 9th ed. - 1993.

8. Ralph W. Phillips - Skinner's Science of Dental Materials 9th ed. - 1994.

9. Sturdevant C, M. Roberson, T. M. Heymann H.O., Sturdevant j.r. - The art

and Science of Operative Dentistry, 3rd ed. - 1995.

10. H. T. Shillingberg - Fundamentals of Fixed Prosthodontics ; 3rd edition - 1997.

11. William F. P. Malone, David L. Koth - Tylman's theory and Practice of Fixed

Prosthodontics, 8th ed., St Louis - 1997.

Journal References

1. Council on Dental Material, Instruments and Equipment (ADA Report) –

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1985;10(4):548-9.

2. Dianne Rekow - Computer-aided design and manufacturing in dentistry : A

review of the state of the art - JPD 1987; 58(4):512-6.

3. K. A. Malament - The Cast Glass - Ceramic restoration – JPD I987;57(6):674-

83.

4. F. Duret, Blouin, B. Duret - CAD-CAM in dentistry - JADA 1988;117:715-22.

5. John. W. McLean - Ceramics in clinical dentistry - BDJ 1988; Mar19:187-94.

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6. Karl. F. Leinfelder, Barry P. Isenberg, Milton E. Essig - A new method for

generating ceramic restorations : a CAD-CAM system - JADA 1989;118:703-7.

7. W.H.Mormann, M. Brandestini, F. Lutz, F. Barbakow - Chairside Computer-

aided direct ceramic inlays - Q Int 1989;20(5):329-39.

8. J. E. Qualtrough, N. H. F. Wilson, G.A. Smith, - The Porcelain Inlay: A

Historical View - Op Dent 1990;15:61-70.

9. Rill G. Banks - Conservative posterior ceramic restorations - A literature review

– JPD 1990;63(6):619-26.

10. E. Dianne Rekow - Dental CAD-CAM Systems : what is the state of the art? –

JADA 1991;122:43-8.

11. S. O. Hondrum - A review of the strength properties of dental ceramics – JPD

1992;67(6):859-65.

12. N. B. Van Roekel - Electrical Discharge Machining in Dentistry – IJP

1992;5(2):114-21.

13. E. Dianne Rekow - High-Technology Innovations and Limitations For

Restorative Dentistry. – DCNA 1993;37(3):521-24.

14. Heiner Weber, Gerd Frank - Spark erosion procedure : A method for extensive

combined fixed and removable prosthodontic care – JPD 1993;69(2):222-27.

15. Kenneth J. Anusavice - Recent Developments in Restorative Dental Ceramics –

JADA 1993;124:72-84.

16. M. Vander Zel – Ceramic-fused-to-metal restorations with a new CAD/ CAM

system - Q Int. 1993;24(11):769-78.

17. K. Kawai, M. Hayashi, M. Torii, Y. Tsuchitani -Marginal Adaptability and Fit

of Ceramic Milled Inlays - JADA 1995;126:1414-9.

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18. H. O. Heymann, S. C. Bayne, J. R. Sturdevant, A. D. Wilder Jr, T. M.

Roberson –The Clinical performance of CAD-CAM generated ceramic inlays (A

four-year study) - JADA 1996;127:1171-4.

19. J. Robert Kelly, I. Nishimura, S. D. Campbell - Ceramics in dentistry :

Historical roots and current perspectives - JPD 1996;75(1):18-32.

20. M. Andersson, L. Carlsson, M. Persson, B. Bergman - Accuracy of machine

milling and spark erosion with a CAD/ CAM system – JPD 1996;76(2):187-93.

21. Sven Rinke, A. Huls - Copy-milled aluminous core ceramic crowns : A Clinical

report. - JPD 1996;76(4):343-6.

22. W. H. Mormann, A. Bindl - The new creativity in ceramic restorations : Dental

CAD-CAM - Q. Int. 1996;27(12):821-8.

23. Marc.A.Rosenblum, Allan.Schulman - A Review of All-Ceramic Restorations.

– JADA 1997;128:297-307.

24. R. Hickel, W. Dasch, A. Mehl, L. Kremers - CAD-CAM: Fillings of the future?

- IDJ 1997;47(5):247-58.

25. Irfan Ahmad - Yttrium-Partially Stabilized Zirconium Dioxide Posts : An

approach to Restoring Coronally Compromised Non-vital Teeth - Int. J.

Periodont. Rest. Dent. 1998;18(5):455-65.

26. Derek. W.Jones - A brief Overview of Dental Ceramics - J. Can.Dent Assoc

1998;64(9):648-50 & Dental Abstracts 1999;44(2):61.

27. P.Ottl, A. Piwowarczyk, Hans Chritoph Laue, E. A. Hegenbarth - The

Procera All-Ceram System - Int. J. Periodont. Rest. Dent. 2000;20(2):151-5

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