www.rxdentistry.net. information systems treatment systems technological trends in dentistry

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Information systems Treatment

systems

TECHNOLOGICAL TRENDS IN DENTISTRY

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INTRAORAL IMAGING SYSTEM

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COMPUTER IMAGING SYSTEM

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CAD-CAM SYSTEM

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DIGITAL RADIOGRAPHIC SYSTEM

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COMPUTERIZED PERIODONTAL PROBE

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RADIOGRAPHIC IMAGE PROCESSING SYSTEM

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TREATMENT SYSTEMS

Abrasive system Laser system

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CAD-CAM SYSTEM

Acronym for computer

aided designing and

computer aided milling or

machining.

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BRIEF HISTORY

Increasing demand

Restoration at a single

appointment

Development- began in 1970’s

with Duret in France.

French system - in 1983 by

Dr.Francois Duret

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On September 19, 1985, the first ceramic

inlay was produced- at the dental Institute of

the University of Zurich.

Mormann 1985 in Zurich, Switzerland

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FUNDAMENTAL PRINCIPLES OF

CAD/CAM SYSTEM

CSD

CAD CAM

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ADVANTAGES

One visit restoration

Time saving

Improved esthetics

Good morphology

Improved crown fit

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Excellent polish

Less fracture due to single homogenous block

Wear hardness similar to enamel (Craig 1980)

Minimize cross infection

Good patient acceptance

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DISADVANTAGES

Need for costly equipment

Need for extended training

Technique sensitive

Inability to image in a wet

environment

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MACHINABLE CERAMIC MATERIALS

Dicor MGC Vita Mark II Inceram Alumina Inceram Spinell Inceram Zirconia Pro-Cad Procera Allceram

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MACHINABLE CERAMIC FRACTURAL STRENGTH

Dicor MGC 229MPa

Vita Mark II 122MPa

Inceram Alumina 500MPa

Inceram Zirconia 700MPa

Inceram Spinell 350MPa

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CERAMIC BLOCKS

Available in wide range of shades and sizes

More homogenous Less porous Mounted on a metal stub

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Purpose

To determine the fracture strength of

various all ceramic crowns with and without

cyclic loading.

Effects of surface finish and fatigue testing on the fracture strength of CAD-CAM and pressed –

ceramic crown (Hickel - JPD 1999)

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Material & Method

Machinable ceramic material, Vita Mark II

and ProCAD and conventional heat-pressed IPS

– Empress crowns were fabricated, with either

a polished or an oven – glazed surface finish.

Cyclic loading that simulated oral

conditions were performed on half of each

group.

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Conclusion

The Cerec Pro-CAD crowns had significantly

greater strength than the Vita Mark II crowns,

better resistance to cyclic loading and lower

failure probability than laboratory fabricated IPS

empress crowns.

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Cyclic loading significantly reduced the

strength of all-ceramic crowns, but had less

effect on cerec crowns than on the IPS Empress

crowns.

Oven-glazing of ProCAD crowns resulted in

significantly higher strength and higher

resistance to cyclic loading than surface

polishing.

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An upto 5 year Clinical Evaluation of posterior

In-ceram CAD/CAM core crowns (Mormann – Int.

J Prosthodont 2002)

Evaluated the clinical performance of

posterior CAD-CAM generated In-ceram alumina

and In-ceram spinelll core crowns using the

corec 2 CAD-CAM system and after 5 years of

service concluded that the clinical quality of

CAD-CAM generated In-ceram Alumina and In-

ceram Spinell posterior crowns was excellent

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CLINICAL PROCEDURE

Preparation Design

Optical Impression

Computer generated restoration design

Milling

Polishing and cementation

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PREPARATION DESIGN

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OPTICAL IMPRESSION

Lacks reflectivity

Special Powder

Rubber dam

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COMPUTER GENERATED RESTORATION DESIGN

Restoration is designed

Operator moves the

cursor

3-D image

Design phase – 2 – 8 min.

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MILLING

Computer selects

Block is inserted

Milling device is

activated

Three axis of rotation

cutting machine

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PROCESSING TIME

Process Step Coping Bridge

framework

Scanning Approx. 10min Approx. 20min

Designing Approx. 2 min Approx. 6 min

Milling Approx. 15min Approx. 50min

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POLISHING

Rough ceramic surfaces are smoothed

with clean white stones

Polished with

- Rubber wheel of fine grit

- Diamond impregnated wheels

& points

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CEMENTATION

Composite resin cement

Zinc phosphate

Glass ionomer

Ceramic restoration that have been

etched internally and bonded with a composite

resin cement are 50% stronger than similar

restoration cemented with zinc phosphate

cement (Ludwig 1994)

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Effects of Preparation and Luting system on All-

ceramic computer generated crowns (Mormann

– Int. J Prosthodont 1998)

Examined the effect of inside crown form

on fracture strength of cemented and bonded

crowns.

Four preparation types were used

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Machined crown were placed on

abutments

a. Without any media as control group

b. Cemented with zinc phosphate

c. Bonded

And were loaded until fracture

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RESULTS

Zinc phosphate cemented crowns showed

significant increase of fracture load values

compared to uncemented control crowns.

Fracture load values of bonded crowns

were significantly higher than those for

cemented crowns.

Bonded crowns with thick occlusal

dimension showed the highest fracture load

values.

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He concluded that bonded all ceramic

CAD-CAM crowns with defect oriented inside

morphology and increased occlusal dimension

showed high fracture load values.

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CEREC CAD/CAM SYSTEM

PROCERA CAD/CAM SYSTEM

TITAN CAD/CAM SYSTEM

CELAY CAD/CAM SYSTEM

CICERO CAD/CAM SYSTEM

LAVA CAD/CAM SYSTEM

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CEREC SYSTEM

Chair side economical reconstruction of

esthetic ceramic.

- Cerec – 1985

- Cerec 2 – 1996

- Cerec 3 – Feb’ 2000

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CEREC CAD-CAM SYSTEM

Limitation

Cannot mill the occlusal

surface

Only inlays and onlays

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CEREC – 2 CAD-CAM SYSTEM

Milling of occlusal surface

possible

Inlays, Onlays, veneers and

crowns

Milling time approx. 10min

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The grinding precision of

the cerec-2 is 2.4 times

higher than cerec system

(Mormann 1997)

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CEREC – 3 CAD-CAM SYSTEM

Advanced version

Technical improvements

Designing and grinding- less

time (27%)

Grinding unit – 2 cutters

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Marginal and Internal Fit of Cerec 3 Cad/CAM All Ceramic Crowns (Kojima –

Int. J Prosthodont 2003)

Examined the effect of the occlusal

convergence angle of the abutment and the

computer luting space setting on the marginal

and internal fit of cerec 3 CAD-CAM all ceramic

crowns.

Mandibular second premolar all ceramic

crowns were fabricated for nine different

conditions using cerec-3 CAD-CAM system

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Occlusal convergence

angle of 4,8 and 12°

Luting space settings of

10, 30 and 50µm.

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Total Oclusal

Convergence

Luting Space

10µm

Luting Space

30µm

Luting Space

50µm

Marginal Gap

4°

8°

12°

108

108

95

66

66

53

61

67

55

Internal Gap

4°

8°

12°

119

135

136

116

132

141

135

162

146

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He concluded that when the luting space

was set to 30µm, crowns with a good fit could

be fabricated with the cerec 3 system,

regardless of the occlusal convergence angle of

the abutment.

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PROCERA CAD-CAM SYSTEM Nobel Biocare

Initially introduced in 1985

Titanium copings

Utilizing the latest scanning, CAD-CAM and manufacturing technologies

Procera Allceram crown in 1991

Procera Allceram bridge in 1999

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TITANIUM CROWN AND FPDS

SUBSTRUCTURE

Reading

Milling

Spark erosion

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READING

The prepared die is

attached

Contact probe registers

the surface

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MILLING

The probe tip of the

reader and the tip of the

milling tool are of same size.

The graphite electrode is

milled

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SPARK EROSION

Used in dentistry since

1982

Graphite electrode is

fitted

Removes the metal by

electricity in the form

of controlled sparks to

fabricate copings.

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PROCERA ALL CERAM CROWN

Composed of densely

sintered, high purity

aluminium oxide coping that

is combined with low-fusing

Allceram veneering

porcelain.

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Preparation of the tooth

Computer assisted design

Manufacture of the coping

Addition of the veneering porcelain

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PREPARATION OF THE TEETH

Recommendations for the

preparation

Depth orientation grooves

1.5mm

Incisal reduction – 2.0mm

Axial reduction – 1.5mm

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Rounded, smooth contours and lack of line

angles

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Impression is made

Die is fabricated

Articulated

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COMPUTER ASSISTED DESIGN

Die is oriented vertically

Tip of the scanner probe is

brought in contact

As the platform rotates,

one data point is collected at

every degree around the

360° circumference of the die.

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Scanning takes 3min

More than 50,000 data

points are registered

Verified on the computer

screen for completeness

Vertical gap

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The finish line of the preparation is

marked by the operator at every 10° around

the circumference of the die.

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Coping design is

selected

Merged with the die

and its finish line.

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MANUFACTURE OF THE COPING

When the design of the

coping is finalized, it is

saved and transferred

through a modem

communication link to

Procera Stanvik AB in

Stockholm Sweden, where

the coping is fabricated.

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ADDITION OF THE VENEER

PORCELAIN The coping is sent by mail to the dental

laboratory where the ceramist finalizes the

restoration by addition of Allceram veneering

porcelain to create the appropriate anatomic

form and esthetic qualities.

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Titanium copings veneered with Procera Ceramics : A longitudinal clinical study

(Nilson - Int.J Prosthodont 1994)

In 1989, 47 titanium copings veneered

with a low fusing ceramic were fabricated for

24 patients. 44 crowns could be examined

after a period varying between 26 and 30

months.

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CDA ratings for surface and color

changed markedly from the Excellent to the

acceptable level.

For marginal integrity it was recorded as

satisfactory for all crowns and a large

majority were rated excellent.

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A comparison of the Fit of Spark – Eroded Titanium Copings and cast gold alloy copings (Wickens - Int. J. Prosthodont

1994) Compared the fit of spark eroded

titanium and cast gold alloy copings and

showed that the overall fit of titanium

copings was comparable to that of gold

copings. In marginal areas, the space

between die and coping was found to be

larger for spark eroded than cast copings.

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TITAN CAD-CAM SYSTEM

Production of metal

copings for porcelain fused

to metal restorations

Digitizing

Processing

Milling

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Preparation Impression

Die

Preparation Impression

Die

WaxingInvestingCasting

DigitizingProcessing

Milling

Conventional Technique

CAD/CAM system

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DIGITIZING

Die is fabricated

Mounted on the

digitizer

Data are recorded

Short circuited

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Divided into 200µm x

200µm squares

Digitized at least

twice

The finish line and the

adjacent 1mm area are

recorded first

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PROCESSING

The main parameters

for the copings are then

determined – The

gap between the

coping and the die

- The width and

shape of the

coping

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MILLING

Uses titanium alloy dummies of various widths in the form of disks or blocks

Milling device consist of two major units

- A rotatory drilling element with

interchangeable bores

- A mobile platform to which the

dummy is fixed

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Three steps

Rough milling inside the

coping

Fine milling inside the

coping

Rough external milling

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MULTIPLE UNIT RESTORATION

Steps same as for the

single unit restoration

It uses master cast

made from a

multiple unit impression

Master cast allows the

computation of each

individual tooth and of the

corresponding residual

ridge

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Relative parallelism

between the CAD-CAM coping

margin and the tooth margin in

comparison with uneven

appearance of same area of a

coping manufactured with

traditional casting technique

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CELAY CAD-CAM SYSTEM

Introduced in 1992 by

Mikrona Technologies,

Switzerland

Inlays, onlays, crowns and

bridge framework

Not a true CAD-CAM system

Many features in common

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A light cured composite

replica

Either directly or indirectly

Replica is mounted

Scanning tools used to trace

Milling tools removes

ceramic

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Bulk reduction by rough

diamond milling disc

Fine milling disc

Contouring by diamond

point

Milling time 40mins –

three unit bridge

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CICERO CAD-CAM SYSTEM

Computer integrated crown reconstruction

First technical concept- by Denisson et al

in 1999

Crowns with different ceramic layers such

as high alumina core, dentinal and incisal

porcelain for maximal strength and

enhanced esthetic.

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Preparation of Scan Model

Optical Scanning

Design

Occlusion

Design of crown layer build-up

Production process

STEPS

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PREPARATION OF THE SCAN MODEL

Model is marked with

black/white contrast

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OPTICAL SCANNING

Obtained by laser

scanning of the cast

Upto 1,00,000 surface

points are recorded

per minute

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DESIGN

Appropriate tooth

selected

Mesial and distal

contact are outlined

The margin line of new

crown is adjusted

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OCCLUSION

The new crown is

superimposed on the

opposing teeth to check

for occlusion

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DESIGN OF CROWN LAYER BUILD-UP

The interior and exterior tooth surfaces

are designed and interface surfaces between

cement and ceramic core and between dentin

and incisal porcelain are defined.

Thickness of the ceramic core of 0.7mm

Ceramic core – die cement thickness of

0.02mm is adjusted.

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PRODUCTION PROCESS

Refractory block is

fitted

Negative of the

inside surface of the

crown is milled

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Cutting tools used

- Diamond cylinder of 5.3mm dia

- Diamond rounded disk of 09.3mm

dia

- Diamond pointed tool of 0.9mm

dia

Automatically exchanged

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High strength

aluminium oxide based

ceramic is applied and

sintered

Ceramic is grounded

to calculated oversize to

compensate the shrinkage

that will occur during the

final sintering

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Dental porcelain

applied and fired

After firing block is

placed on milling machine

and interface between

dentinal and incisal

porcelain is milled

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Translucent incisal porcelain is applied,

fired and milled

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LAVA CAD-CAM SYSTEM

Produce high strength all ceramic crowns and FPD’s

Uses yttrium tetragonal zirconia polycrystals (Y-TZP) based material

Introduced as a hip replacement material in early 1990’s

High fractured strength 900 – 1200MPa and biocompatibility

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Special scanner (Lava Scan)

Computerized milling machine

(Lava Form)

A sintering Oven (Lava Therm)

CAD-CAM software technology

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STEPS IN FABRICATION

Saw cut working cast is mounted on the

scanner

The configuration of the tooth

preparation are scanned

Scanning process takes

- Crown – Approx.5min

- 3 unit FPD – Approx.12min

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Produces an enlarged framework to

compensate shrinkage during sintering

process.

Average milling time

- Crown coping – Approx.35min

- 3 Unit FPD – Approx.75min

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The framework is sintered in the Lava

Therm

Pre programmed to run for 8hrs,

including the heating and cooling phases.

The sintered framework is then veneered

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To conclude,

Computer graphics and CAD-

CAM have revolutionized dentistry.

It is now possible to provide

equivalent of a cast restoration in

a single appointment

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BIBLIOGRAPHY

Philips Science of Dental Material, - ANUSAVICE

Art & Sciences of Operative Dentistry- STURDEVANT’S

Dental Clinics of North America – Fixed prosthodontics

Fundamentals of Fixed prosthodontics – SHILLINGBURG

Contemporary fixed prosthodontics – ROSENSTEIL

Restorative dental material – CRAIG

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