CAD – CAM

CAD / CAM 3,4,9,13

The need for the restorative dentist to achieve excellence in aesthetics and function has driven modern

advances in materials and restoration fabrication.

Metal-free prosthetic materials offer unprecedented strength without compromising the aesthetics and

biocompatibility of traditional all-ceramic

CAD /CAM - Computer Assisted Designing/ Computer Assisted Machining This is another recent technique of fabricating ceramic restorations.

This method uses computer technology to produce the restoration in one visit. After the tooth is prepared

the preparation is optically scanned and the image is computerised.

The restoration is designed with the aid of a computer and machined from the machinable ceramic blocks

by a computer assisted milling machine.

Until 1988, ceramic restorations were fabricated mainly by sintering and /or casting techniques. Machined

restorations have thereafter gained in popularity. There are two principle machining approaches for dental

restorations.

Analogous Systems

Copy milling/ grinding technique: automatic [ Ceromatic II] and Manual [ Celay].

Copy milling uses a replica (eg wax,plastic) 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 pattern’s surface with a

finger stylus.

The position of the stylus and the pattern are used to adjust the positions of a block of machinable

material and a milling tool cutting the block.

A variety of materials eg:- titanium, composite ceramics are being copy milled. Any geometry

size can be copy milled as long as there is direct access of the finger guide and cutting tool to the

surface involved.

Schematic representation of copy milling.

Digital Systems

CAD/CAM Technology.

CAD/CAM uses digital information about the tooth preparation( computer surface digitization

[ CSD] ) or a pattern of the restoration to provide a computer aided design on a video monitor for

inspection and modification.

The image is a reference for designing a restoration.

When the three dimensional image is accepted, the computer translates the image to a set of

instructions to guide a milling tool (i.e CAM-computer aided milling) in cutting the restoration

from a block of material.

Objectives and Potentials of CAD/CAM System

As a starting point, possible improvements and changes in dental restoration manufacturing should be

reviewed. The expected shifts are:

To Eliminate traditional impression methods.

To design, for example, with the aid of a computer, the future restoration in accordance with the

preparation, the function, and the natural anatomy.

To produce the restoration chairside.

To machine the restoration.

To improve restoration qualities: mechanical resistance, marginal fit, surface quality and

esthetics.

Techniques for CAD/CAM fabricated restorations

Five steps are basically involved in any type of CAD/CAM systems. These include :

1. Computerized surface Digitization.

2. Computer aided Designing.

3. Computer aided Manufacturing.

4. Computer aided Esthetics.

5. Computer aided Finishing.

The last two steps are very difficult and hence as yet are not a feature in commercial systems.

Various surface digitization techniques have been explored:

Laser scanning

Computed tomography,

Magnetic resonance imaging,

Ultrasound,

Contact profilometry.

Laser ( optical) technique and contact digitization are the most promising from the point of view of cost

and accuracy.

Schematic summary of CAD/CAM and copy milling operations.

CERAMIC MACHINING SYSTEMS

CAD-CAM (Computer Assisted Design-Computer Aided Manufacturing) system has been introduced to

the dental profession recently. Development of CAD-CAM system for the dental profession began in

1970"s with DURET in France. ALTSCHULER in US & BRANDESTINI in Switzerland.

Optical scanning and computer generation of restoration were attempted as early as 1971

(ALTSCHULER 1971/1973). With the continued improvement in the technology, a number of systems

are currently being investigated.

The introduction of CAD/CAM system to restorative dentistry represents a major technological

breakthrough. It is now possible to design and fabricate ceramic restoration at a single appointment, as

opposed to the traditional method of making impression, fabricating a provisional prosthesis and using a

laboratory for development of a restoration. Certain errors, which are inherent to the indirect method,

have been eliminated in these systems. Additionally CAD CAM generated save the dentist and patient

time, provides an esthetic restoration and have the potential for extended wear resistance.

All CAD / CAM system are technically complex & involves three distinct and complex steps:

1. Collection of information

2. Designing of restoration

3. Fabrication of the restoration

The popular CAD / CAM systems used in dentistry are :

• CELAY system

• CEREC system

• DCS Precident system

• PROCERA system

CEREC [ Ceramic Reconstruction System] 3,4,19

CEREC is a dental CAD CAM machine. CAD/CAM stands for computer assisted design,

computer aided manufacturing.

Mormann's work led to the development of Siemens' CEREC CAD-CAM system . It was

developed in Zurich Switzerland.

The basic philosophy of the CEREC unit was to associate an optical impression method with a

computer driven fabrication module in a single mobile workstation.

It is used to fabricate inlays. Onlays, 3/4 crowns, 7/ 8 crowns and Veneers.

This system enables the direct chair side placement of ceramic restoration without auxillary

laboratory support.

CEREC CAD/CAM machine is used to produce full ceramic restorations in one patient visit. It has been

used clinically since 1986.

CEREC 2 was introduced in 1996:

CEREC 3 and Scan were introduced by Sirona Dental Systems (Germany ) in 2000

The CEREC technique consists of:

1. Three -dimensional scanning of the cavity or taking an optical impression.

2. Immediate data transformation

3. Axial milling, which is integrated into a mobile unit.

Occlusal surfaces can now be machined on the Cerec 2 unit smaller pixel size/ higher accuracy in depth

measuring = increased resolution of the optical impression.

Fabrication of CEREC restoration includes several distinct and original steps:

1. Optical Impression.

2. Powdering of the preparation.

3. Computer aided design of the restoration.

4. Computer driven milling of the restoration.

5. In mouth development and refinement of occlusal anatomy.

There are 3 different programs for Design

(l) Anatomically adapted (extrapolation)

(2) Correlated to functionally generated path (correlation)

(3) Function

The Cerec system is the only method in dentistry to permit the exact machining of ceramic veneers.

The precision of Cerec 2 grinding unit has been found to be 2.4 times higher than Cerec 1

There have been improvements from the Cerec 1 system, in an SEM examination marginal widths of

Cerec 2 were considerably smaller than Cerec1

CEREC design modes

DESIGN TECHNIQUE RESTORATIVE METHOD APPLICATION

Correlation Copy the tooth to be restored Most often used,

very simple

Replication Copy any tooth surface Ensures bilateral

Symmetry

Dental Database Start from scratch Maximum freedom

(with Antagonist) to Alter morphology

(taking antagonist into

account when designing

occlusion)

Correlation mode design steps

DESCRIPTION ACTIVITY AVG. TIME REQUIRED

Margin Finder Draw the prep margin 30 seconds

Labial Contour Establish the proper 1 minute

emergence profile

Copying Line Define the area copied 30 seconds

Finish Refine the contours 1 minute

CEREC milling unit in action: water acts as the driving

medium for the wheel and coolant for

the diamond-coated cutting disk.

The restoration part is contoured from

the mesial to the distal aspect by

a three-axis milling process

THE CEREC FAMILY

CEREC CAD / CAM was developed in Zurich, Switzerland.

It has been in clinical use since 1985/86.

Since the introduction of CEREC CAD /CAM in 1985 there has been major advancement CAD CAM

systems, which has resulted in the development of CEREC 2 AND CEREC 3 systems.

CEREC 3 is the latest version.

CEREC 3 has many advantages over CEREC 2 system.

Those having CEREC 2 systems by incorporating new software called CEREC Link can exploit these

advantages. The following section gives a brief introduction to the CEREC family.

CEREC:

The CEREC was first introduced in 1986.

It consisted of a

1. Mobile unite containing a small camera

2. A computer with scan and 3-axis-of rotation milling machine.

This is old milling machine was water-pressure driven "hydro" version.

CEREC 2:

It is a tried-and-tested compact CAD CAM (Computer Aided Design-Computer Integrated

Machining) system for chairside applications.

It is the CAD/CIM system with the largest number of users worldwide, several million successful

restorations and clinical experience since 1986.

It consists of

1. Mobile unit containing a small camera,

2. A computer with scan and 3-axis-of-rotation milling machine.

The milling machine has an electric motor called “E" version to provide a better and smoother cutting of

ceramic resulting in better fitting restorations.

The occlusal surfaces can now be machined on the Cerec 2 unit. It has smaller pixel size/higher accuracy

in depth measuring which increases the resolution of the optical impression.

There are 3 different programs for designing: Extrapolation. Correlation, and linear.

(I) Anatomically adapted (extrapolation)

(2) Correlated to functionally generated path (correlation)

(3) Bucco-linearly flat (linear).

The precision of Cerec 2 grinding unit has been found to be 2.4 times higher than Cerec.

Advantages of CEREC 2 over CEREC 1

1. CEREC 1 can not prepare the occlusal anatomy of the restoration, whereas CEREC 2 can.

2. In addition to the grinding wheel, the CEREC 2 unit is also equipped with a cylindrical diamond

stone which is able to finish off undercuts at buccak extensions, curved shoulders at cusp

preparations and the proximal areas.

3. Also when comparing the camera systems and image processing of CEREC-1 and CEREC-2

units, CEREC-2 is a definite improvement over the former.

CEREC 3:

It is the modular CAD/CAM system that adapts flexibly to practice requirements. It provides virtually

unlimited scope for incorporating the CEREC 3 modules into the practice layout. It gives flexible

integration into the practice workflow (direct or indirect working; labside or chairside: one or more

treatment sessions.

It provides rapid imaging, design, handling hygiene through the integration of the SIDEXIS intraoral X-

ray system and the SIROCAM 2 intraoral camera.

CEREC 3 is flexible and offers the most advanced solution for every practice concept.

The new highlight in the CEREC product range is the modular CEREC 3, which offers virtually unlimited

scope to optimize practice workflow. Consisting of a separate imaging unit and milling unit.

The systems are designed for multiple as well as single restorations and enable to use the imaging unit

for other tasks during the milling process.

The imaging and milling units can be located in one room or in separate locations. They communicate

with each other either via cable or via radio signals.

The CEREC 3 milling unit can be installed in a wide variety of different locations like in the treatment

room itself (easy access), in a cupboard (reduced noise), in an unused corner or niche (saves space), in the

practice lab or as a fascinating eye-catcher in the waiting room.

The multiple functions of the CEREC3 imaging unit are

Creating optical impressions,

Designing the ceramic restoration

Chairside patient communication.

Advantages of CEREC 3:

1. The CEREC 3 imaging unit incorporates a mobile PC. which has been specially approved for medical

applications. Milling chamber is separate form the imaging / designing unit.

2. The system is now Windows - based.

3. Cerec 3 can be used in conjunction with a Cerec 2 by using the "Link"" software.

4. Two burs (one is tapered) do the cutting instead of one bur and one diamond wheel.

5. No "adjust" process (time savings)

6. Faster milling times (5 minute savings)

7. Greater occlusal anatomy. It simplifies occlusal and functional registration.

8. The second restoration can be designed while the first is being milled.

9. The grinding unit is also equipped with a laser scanner and can be used for indirect applications

through a personal computer.

Cavity considerations for CAD/CAM Inlays 3,4

Tooth preparation for ceramic inlay/onlay requires conventional cavity design with slight modifications to

accommodate computerized milling device. These modifications are:

1. No convexities should be present on the pulpal and gingival walls.

2. The occlusal step should be prepared 1.5-2mm in depth, and any isthmus or groove extension

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

3. The buccal and lingual walls of the occlusal portion of the preparation may converge towards the

occlusal.

4. This Feature is unique to CEREC system as it can automatically block out any undercuts during

the optical impression.

5. Axial walls should be straight and not follow the convex contour of the proximal surface of the

tooth.

6. No cavosurface or marginal bevels should be given.

FABR1CAT1NG PROCEDURE:

1. Following the preparation phase the assistant takes a conventional in situ impression and then produces

a partial model made of quick-setting silicone

2. This model is then clamped into the holder of the milling unit, where it is scanned by the built-in laser

(duration: approx.5 minutes).

3. The design process is performed on a separate a PC in the dental practice. The actual production of the

ceramic restoration takes place in the milling unit.

Although the CEREC Sean restorations are produced indirectly they can still be completed in a single

treatment session, due not least to the speed of the laser scanning operation.

The patient can watch the fascinating scanning and milling process "live".

The CERECE Scan is geared to the same broad range of clinical indications as the CEREC 3. The

production process can be delegated to an assistant or dental technician in the practice laboratory. This

cuts costs and helps to integrate the CEREC concept into the existing treatment procedure.

In LAB from SIRONA:

Introduced at the 2002 Chicago Mid-Winter meeting, the inlab system is designed specifically for

Laboratory applications.

The idea is to use CEREC's fast manufacturing processes for producing crown "copings" and bridge

"frameworks".

These substructures are to be milled from VITA INCERAM SPINELL, ALUMINA and ZIRCONIA

blocks. The flexural strength of these materials is as follows:

• INCERAM SPINELL: 350Mpa.

• INCERAM ALUMINA: 550Mpa.

• INCERAM ZIROCONIA: 750Mpa.

Ideally, the clinician and the technician can apply the appropriate strength material for varying clinical

applications. Once the substructure has been milled, the technician glass infiltrates the pre-sintered

framework and then builds up the final restoration with a traditional porcelain stacking procedure with

VITADUR ALPA porcelain.

The process of building the substructure (coping or bridge framework) is as follows:

1) Scanning of the model 8-12 minutes

|2) Designing the substructure (on a PC) 5 minutes

3) Milling the substructure 12-30 minutes

4) Glass infiltration 5-10 minutes

Another bonus to this system over, is the choice of color matching.

When the substructure is infiltrated with glass there is a choice of four colors. No opaqueing is required.

This alone makes the inLab system more desirable but the laser scanning system is more accurate than

mechanical systems. In fact the marginal accuracy of the in Lab's is excellent.

OPTICAL IMPRESSION:

After tooth preparation the impression of the prepared tooth should be taken. In the CEREC CAD-CAM

system instead of a conventional impression with elastomeric impression material.

An optical impression with a CEREC camera is taken. Before taking an optical impression the prepared

tooth surfaces arc powdered with a special powder, which has the ability to reflect the infrared light

emitted from the camera.

BACKGROUND IN FORMA TION ON POWDERING:

To take an optical impression it is necessary to powder (or opaque) the tooth surface to be imaged

because of two reasons:

1. The surface of the tooth must be covered with a non-reflective coating to make it easier for the

infrared camera to see detail. Without the non-reflecting coating the effect on the camera is

similar to our looking into a very bright light.

2. Because of the high translucency of enamel, without an opaque surface applied to the tooth, the

infrared beam would be projected back to the camera from totally different depths within the

tooth.

METHODS OF POWDERING:

Powdering of the prepared tooth surface can be done using cither:

1. BUTANE-PROPELLED POWDERIGN SYSTEM

2. PAINT ON SYSTEM or SCAN WHITE

3. POWDER ME1STER SYSTEM

Applying Powder to the Preparation :

1. Before applying powder to the preparation, it is helpful to spray the first bit of powder on a non-

critical area, such as an adjacent tooth. This frees the powder tube of any large Hakes of powder and

allows a preview of the powder flow.

2. Any time the airflow through any powdering device (including the powder Meister) is stopped, powder

settles in the powdering tube and a few large flakes form.

3. Each time the flow is started again some of these large flakes can be seen as the powder is applied to

the tooth.

Camera

C-STAT is a camera accessory used to support SIROCAM 2 camera.

Anterior Region :

To take pictures form crown preparation in the anterior region, cut both rests to about 1.5-2 mm. The

camera can be stabilized over the two rests on the incisal edges or the premolar cusps and rotated to the

desired position.

Premolar and Molar Region :

For use in the premolar and molar regions, grind away the anterior rest. Taper the posterior rest by

grinding it to a point. In this way realize a stable support in an interproximal space. To take the picture,

slide the camera through the support, to find the appropriate position. The distance between the camera

lens and the occlusal surface should be 4-5 mm. Angulate the camera slightly to the occlusal surface on

the posterior rest of the support.

Function and Correlation :

For the Function and Correlation programs, which demand congruent digital pictures, it is recommended,

to make an impression. Shorten the anterior rest and remove the posterior rest. Perforate the posterior rest

base with a round burr (no-8) 6-7 times. With occlusal wax. such as Moyco Beauty Pink, make a small

impression. It is easy to take another congruent picture with this positioning support.

Controlling the tongue during the Optical Image:

Some patients have tongues that can be almost unmanageable during the taking of the optical image.

This can be quite difficult because these unruly tongues will invariably wipe away the powder form

critical parts of the tooth preparation or fight the camera position as it is being aligned.

This problem can be overcome by using Dry Tips by Microcopy.

Dry Tips are water absorbant. and when placed between the tongue and the preparation, are extremely

effective at protecting the preparation form intrusion by the tongue.

When the camera is placed in the mouth, the camera pushes on the Dry Tip. which in turn pushes the

tongue out of the way.

The proper software should be selected for designing and milling the restoration.

Designing of the Restoration: :

1. The restoration is designed from the images shown on the computer screen by using series of

icons or symbols.

2. The operator can electronically design the restoration by moving a cursor along the limits of the

preparation thereby defining the boundaries.

3. The internal limits are created, as are the walls and cavosurfaces margins.

4. Thus the gingival floor, axial walls, cavosurfaces margins. proximal contours (contacts) and

marginal ridges are established.

The procedure can be stopped at anytime and edited to override the computer and allow the operator to

correct the electronically generated features.

Once the restoration has been designed, the computer develops and onscreen, three-dimensional model or

image of the inlay or onlay or veneer.

The entire information generated can be stored automatically on a programmed floppy disk. The design

phase usually takes 2 to 8 minutes even when designing multiple cusp replacement or veneers.

An example of designing of a restoration is given below:

• The following examples illustrate how simple it is to create high-quality ceramic Restorations.

• Begin by selecting the type of restoration (inlay, onlay, partial crown, crown or veneer), the design

method (extrapolation, tooth database, correlation or function), as well as the tooth in question.

• The optical impression can be taken directly in the patient's mouth or from a model. The outcome is a

three-dimensional data model, which is automatically stored.

• Begin by encircling the equators of the neighbouring teeth. Following this you trace the precise

baseline. The integrated tooth database adapts the selected restoration to the anatomical situation

of the neighboring teeth.

• The orientation of the crown and the height of the proximal marginal ridges are determined on the

basis of the neighboring fissures.

• The positions and height of the cuspal apices are calculated with reference to the neighboring teeth

and then displayed. All the other design lines are calculated automatically. The restoration is then ready

for immediate milling.

Alternatively, you can view-each design step in turn and modify each line individually.

• If you decide not to mill the restoration immediately, you have the option of viewing the equator and

the relevant contact points with the neighbouring teeth.

Various viewing modes and cross sections allow you to cheek the thickness and height of the contact

points. In this window you can view any cross-section of your choice through the restoration. All the

verticals can be individually edited.

In addition, this window allows you to determine the thickness of the ceramic material in the occlusal

region.

Milling Procedure: :

After all the data have been supplied, the computer selects the size of the ceramic block required. There

are many types of preformed blocks present commercially to be used with CEREC CAD CAM system.

The blocks used in this system are as follows:

• 3M MZ100

• VITA Mark II and Master

• Ivoclar ProCAD

• VITA Mark II Esthetic Line

• VITA Alumina and Spinell

• Other blocks.

DENTA TEC SOLUTION AND EXTENDED MILLING:

While milling too much heat is generated.

This heat generated is harmful to the milling machine and the diamants used.

So it should be dissipated using a coolant like Dentatec solution.

Ceree suggests a change of water at the start of every 6th milling.

The Dentatec solution also act as a lubricant in the milling process.

In addition to providing a lubricating function, which increases the life of the milling instruments, the

solution also contains an antimicrobial.

Even with the antimicrobial, if the CEREC 2 is not used for a period of time, an odor come form the

milling chamber.

To eliminate this, change the water after prolonged period of unuse.

When the milling pictogram is clicked the CEREC 3 software tells what size of ceramic blocks is

required.

Then insert the corresponding block into the milling unit and initiate the milling process.

The imaging and milling units communicate via a wireless link (option).

Before the milling process begins the computer control system automatically detects and compensates for

tool wear.

A cylindrical and a conical diamond bur shape the restoration.

The conical bur enables very fine details to be created on the occlusal surface.

Speed of CEREC CAD/CAM System:

The main advantage of using CEREC CAD /CAM system is its speed in manufacturing a restoration in a

very short period of time, the following table shows the time taken to produce various restorations by

using CFRFC CAD/CAM system.

Process step Coping bridge framework

Scanning (automatic) approx. l0min approx.. 20 min.

Design approx. 2min approx. 6min.

Milling (automatic) approx. I5min. approx. 50 min.

Staining and Glazing :

1. In certain circumstances it may be necessary and/or appropriate to "naturalize" the CEREC

restorations.

2. This can be accomplished by adding stain to the restoration and then firing (glazing) it in an oven.

The Ney Miniglaze oven is a simple, manual and inexpensive chairside oven available for this process.

To add porcelain a more expensive (and automatic) vacuum furnace like the Labs use, such as the Vita

Vacumat 30 is needed.

Cementation of Restoration :

1. The weakest part of the CEREC restorations are the luting agent layer is exposed at the margin.

2. The long-term success of the restorations depends mainly on the success of luting agent, which

requires a low shrinkage rate, high wear resistance, bonding to both tooth structure and the

ceramic, polishability. and color stability.

3. Previous result have generally indicated that dual cure resin composites are preferred for the

luting of ceramic inlays, because of their ability to set completely and have greater resistance to

occlusal loading compared with GIC.

4. The GIC chemically bond to tooth structure and has fluoride release capability.

5. The final smoothening is achieved using a polishing paste applied with a rubber cup.

Finishing & Polishing :

1. The frequent frustration with a CEREC2 restoration is the time it takes to finish the restoration after it

has been bonded.

2. This obstacle can easily be overcome. The place to start, especially when using extrapolation, is

before the tooth has been prepared for the CEREC 2 restoration.

3. Observe carefully the shape of the existing occlusion, marginal ridge heights, and cusp.

4. An intra-oral picture, frozen on the monitor, would be helpful. Later, when the restoration has been

bonded, any areas of gross excess can be quickly reduced.

5. When reducing excess porcelain, the appropriate diamond is essential.

6. It is possible to crack porcelain, even after the restoration has been bonded, with a diamond that is too

coarse.

7. The wonderful characteristic of the Vita Mark II porcelain that allows it to be nonabrasive to the

opposite tooth also allows it to be easily carved with a fine-grit diamond.

8. The bur used for occlusal reduction is a 1923 F (F is for fine) football - shaped Neodiamond form

Microcopy. The Neodiamond is an inexpensive, "one use'- diamond.

9. This football-shaped diamond can he used more than once, but should be discarded at the first sign of

dullness.

10. One of the most common mistakes leading to frustration in finishing the restoration is using a

diamond past its useful life.

11. Make the initial gross occlusal reduction and the finishing of the interproximal areas with the rubber

dam in place.

12. Be sure to use water spray during gross reduction. A diamond used at high speed against porcelain

can cause heat buildup and porcelain cracking.

13. It is also possible to crack the porcelain restoration by having the patient close too hard on the

articulating paper in the adjustment process.

14. This porcelain has excellent strength characteristic. However, a sharp opposing cusp under premature

excess pressure can crack a bonded porcelain restoration.

15. The interproximal finishing is done with a round end taper 850012 F from Axis.

16. Because of the vertical nature of the proximal box walls. the infrared camera is not able to process

data as accurately as it can on the occlusal. As a result of this situation there may be more

discrepancy in the fit in this area, causing the need for extra finishing at the vertical part of the

proximal box wall.

17. This is easily done with the taper diamond or a Profin from Dentatus.

18. Once the appropriate occlusion has been established, smooth any rough areas with the same fine-grit

football-shaped diamond as above but now at low speed and without water spray.

19. Caulk Enhance polishing cups used in a slow speed followed by brown rubber points used in a high-

speed handpiece at low RPM, gives a very acceptable polish.

DCS PRECIDENT

The DCS Precident system (Digitizing Computer System) called the Dux or titan system in USA was

developed in 1988 and introduced to the market in 1990.

Since then about 150 units have been used in Germany and other countries.

Originally this system was designed for fabricating metal copings for porcelain fused to metal crowns and

FPD's.

The following features are available in this system:

1. Acquisition of data form the prepared tooth is performed manually on the digitizer.A touch probe is

traced along the conventional stone cast. The 3 dimensional morphology of the prepared tooth can be

easily obtained and reconstructed from a limited amount of data.

2. Up to 7 units FPD on one side of the are can be made with this system.

a. All ceramic coping can also be produced with the specially designed end-mill and porcelain

block.

b. It takes about 30 to 45 minutes form digitizing to milling process in the

fabrication of a single crown.

c. The marginal accuracy of milled coping has been proved clinically acceptable.

This system consist of 3 main parts:

1. A desktop computer.

2. A digitizer

3. A milling machine with 3 degree of freedom.

FABRICATION TECHNIQUE: DIGITIZING:

1. Tooth preparation and impression making are performed in the conventional manner.

2. The trimmed working die of the prepared tooth is placed on the digitizer table.

3. The sensor tips l.0 mm in diameter and 10.0mm in length is used to trace the prepared tooth.

4. On the display a 2-dimensioanl outline of the prepared tooth with a marginal line and a

0.2*0.2mm grids will be indicated.

5. When each grid is touched with the sensor tip, 3-dimensioanl outline of the prepared surface area

will he measured and transferred to the data bank.

6. The areas for which data are already stored will be changed to blue. Once the entire area has

been digitized, the 3-dimensional reconstruction of the stored data about the prepared tooth is

displaced.

7. The white line on the 3-dimensional reconstruction represents the marginal line. If the line is not

smooth, digitization should be done again.

COMPUTER-AIDED DESIGNING:

1. Data for fabricating a metal coping can be obtained by adding offset for the desired thickness of

metal on the top of the prepared tooth surface data.

2. Thickness can be varied according to the coping design. This coping data for complete or partial

porcelain coverage can be developed in this system.

3. Occlusal morphology cannot be designed by this system. The time required for digitizing,

designing and the data conversion to milling path data is about 15 to 20 minutes for a single

crown and 20 to 30 minutes for a 3 unit FPD.

COMPUTER AIDED MILLING:

1. Metal copings are milled from titanium blocks.

2. In accordance with CAD data, the milling program selects the titanium block that will results in

the minimum remaining material.

End mill of 3 and 2 nm in diameter are used in the milling process. The steps in the milling process are:

1. A titanium block is fixed in the milling machine with the jig.

2. The inside of the coping is milled with the CAD data.

3. The titanium block is removed, turned over and replaced when the milling of the inside of the coping

is finished, the milling machine will automatically stop to allow the side of the titanium block to be

changed.

4. The outer surface of the coping to which the porcelain or the resin material will be attached later is

milled.

5. To allow the removal of the coping from the block, the connecting part between the coping and the

remaining block is cut.

6. The time required for milling a single crown coping is about 30 to 45 minutes. About 90 to 120

minutes are required for the 3 unit FPD coping.

7. The infrastructure for ceramic crown can also be milled using this system form a block of high

performance METROXIT ZIRCONIUM OXIDE TZP BIOCERAMICR type TAP (tetragonal

polycrystalline Zirconium oxide).

FINISHING AND POLISHING:

Finishing and polishing are performed in the conventional manner on the die. Porcelain or composite

resin can be used as a facing material and is applied with the conventional method.

ACCURACY AT THE MARGINS:

The average gap between the coping and die at the margin is 30 to 50 micrometer. Although there is

stillroom for improvement, it is fair to conclude that this system is able to achieve clinically acceptable

marginal accuracy comparable to that of conventional complete cast crown (30 to 50 microns) and other

CAD/CAM system (50 to 100 microns).

PROCERA SYSTEM

This process for manufacturing crowns, process and implant superstructures uses a combination of copy

milling, spark erosion and laser welding.

PROCERA technology was first developed for processing titanium.

The application of PROCERA system for manufacturing individual crown made of extremely dense

sintered aluminium oxide ceramics resulted with the increasing demand for improved aesthetics.

Aluminium Oxide Ceramics

Crowns manufactured with PROCERA system shows strength values never reached by an all-ceramic

system.

The PROCERA All-Ceramic System

Procera system scans the surface of the prepared tooth and transmit the data to the milling unit to produce

an enlarged die through a CAD-CAM process

The three main parts of the PROCERA system are:

1. A scanner

2. A personal Computer

3. A disk for transmission of data to the workstation.

FABRICATING PROCEDURE:

1. The die of the prepared tooth is first mechanically scanned.

2. The scanner has a sapphire ball tip that reads the die shape by circular scanning, describing the

tooth using approximately 20000 measured values.

3. When scanning is completed the technician can design the coping on the computer monitor.

Various programs are offered to the operator such as design of the crown, its desired shape and

preparation margins.

4. 15 to 25% shrinkage of the aluminum oxide ceramic material is expected during sintering

process. This is compensated by enlarging the design in the computer files.

5. The data are collected and then transferred to a PROCERA workstation via modem. This

means that the master cast need no longer be sent out of the dentist office.

6. The process of manufacturing the coping could theoretically be initiated at any point on the earth

and at the workstation an enlarged die model is precision milled by a computer-controlled milling

machine.

7. High - purity aluminium oxide powder with a defined grain size is then pressed onto the die using

very high pressure. This enormous pressure give the material a high packing density, a main

factor in the material strength.

8. The outside of the coping is milled before the sintering process. By sintering at a very high

temperature (1550°C) the coping will shrink to the original dimension and will have excellent

marginal fit.

VENEERING THE PROCERA CROWN:

A special ceramic material with co-efficient of thermal expansion adjusted to aluminium oxide has been

developed for the PROCERA technique.

THE BASE KIT:

It consist of

• 16 dentin shades

• 5 translucent shades

• 4 incisal shades.

THE MASTER KIT:

It has 12 modifiers accurately adjusted to each other and it also offers 8 basic dentin shades.

This leads to a wide range of possibilities for customized design of the restoration.

CELAY

The CELAY SYSTEM employs a copy milling machine and uses manufactured porcelain blank's to mill

out ceramic inlays, onlays, crowns and bridges in the CELAY system.

This system is a precision copy- milling machine.

The Celay system is unique in its milling capabilities. Its milling arms are able to move in 8 axes

of freedom, which allows the milling of complex, three-dimensional shapes.

Thus, it can mill the occlusal aspects of restorations in very fine detail.

The marginal fidelity of these milled restorations is excellent. According to the manufacturer,

marginal gap of only 50mm can be achieved.

Marginal gaps of 60 mm were attained in an independent study.

The Celay system provides the ability to fabricate both direct and indirect ceramic restorations.

Copy milling technology requires the generation of a pattern of the desired restoration. This

pattern can be fabricated directly from the mouth or on a pattern of the desired restoration. This

pattern is then copy milled using the Celay machine to generate the final restoration. The system

uses an approach similar to the pantographic method of duplicating keys.

FABRICATION TECHNIQUE:

1. Preparation of porcelain inlays should allow for a porcelain thickness of 1.5 mm, and the ideal

occlusal depth and the isthmus width of the porcelain inlays is 2mm.

2. Preparation should be slightly conical with rounded internal line angles. Cavo surface margins should

be sharp and not beveled.

3. Any undercut or deep areas are filled in with light polymerized glass Ionomer cement.

4. The dies are then sealed with 2 coats of thin cyanoacrylate and any undercuts are blocked out with wax.

5. An ultra thin die lubricant is placed as a separator. An appropriate amount of a special blue composite

resin is placed in the die and carved to shape, creating what is termed a "Pro-inlay".

6. The occlusal aspect of the pro-inlay can be created with carving instruments or burs after it had been

light polymerized for a minimum of 2 minutes.

7. After this, the pro-inlay is then removed form the die and polymerized form the bottom for another

minute.

8. The pro-inlay is fixed in the Celay using the "point" method an then ready to be copy milled. One or

two inlays are mounted with the "rod" method. This procedure requires that a small hole be drilled in one

of the central surfaces, after which a special pin is cemented with cyanoacrylate for positioning in the

Celay.

9. The reference -scanning disk is placed in the machine, and the appropriate size porcelain blank is

chosen. The reference disk acts as a scanning stylus that is moved across the surface of pro-inlay.

MILLING INSTRUMENTS:

The following milling instruments and polishing instruments are used:

1. A coarse diamond disk with a grit size of 126 um (Diametal, Biel. Switzerland) for efficient bulk

reduction.

2.. A finishing diamond disk with a grit size of 64um (Diametal) for precision milling of the final contour.

3. Round tipped diamonds with a grit size of 64um (Diametal) for narrow concavities that is secondary

occlusal anatomy.

4. Sharp tipped diamond with a grit size of 64um (Diametal) for secondary occlusal anatomv.

5. Polishing instruments loaded with diamond powder.