Assoc. Prof. d-r T. Uzunov, PhD

Digital technology has profoundly impacted the dental profession. Significant progress has already been made in computerized digital

technologies, such as digital cast scanners, intraoral digital impression-capture devices, cone beam computed tomography, laser sintering

units, milling machines and three-dimensional (3D) printers.

VIRTUAL MODEL IS A SET OF THREE

DIMENSIONAL MODELS, WHICH ARE

LOCATED IN THREE-DIMENSIONAL

SPACE AND ARE FULLY ACCURATE

IMAGE OF PHISICAL PRODUCT

The three-dimensional (3D) model represents a physical

body using a collection of points in 3D space, connected by

various geometric entities such as triangles, lines, curved

surfaces, etc.

EVOLUTION OF COMPUTERIZED DENTISTRY

• In the early 1970s, Dr. Francois Duret, conceptualized

how digital technology being used in industry might be

adapted to dentistry for digital impression making.

EVOLUTION OF COMPUTERIZED DENTISTRY • He conceived of the idea of an application of laser imaging to make optical

impressions of teeth and milling out a restoration, representing the original

process for capturing data used in what ultimately became the computer-

assisted design/computer-assisted manufacturing (CAD/CAM) of

dental restorations.

• Dr. Duret first introduced the CAD/CAM concept to dentistry in 1973 in

Lyon, France in his thesis entitled Empreinte Optique, which translates to

Optical Impression. The concept of CAD/CAM systems was further

developed by Dr. Mormann, a Swiss Dentist, and Mr. Brandestini, who was

an electrical engineer.

For the purpose of digital

information acquisition the dentist

can use three technological

devices:

1. Extraoral laboratory scanner

2. Intraoral optical scanner

3. CBCT

3 D DIGITALIZATION

Persson A, Andersson M, Oden A, Sandborgh-Englund G (2006) A three-dimensional

evaluation of a laser scanner and a touch-probe scanner. J Prosthet Dent 95: 194-200.

Within extra oral group of 3D digitization

systems we can use two types of systems:

1) first contact systems,

2) second noncontact optical systems

Lab scanners demonstrate very high

precision and accuracy of impression

acquisition - to 6 micrometers (μm).

At this moment these are the most precise

capture devices in dental profession.

3 D DIGITALIZATION

Persson A, Andersson M, Oden A, Sandborgh-Englund G (2006) A three-dimensional

evaluation of a laser scanner and a touch-probe scanner. J Prosthet Dent 95: 194-200.

Traditional impression

3 D DIGITALIZATION

Persson A, Andersson M, Oden A, Sandborgh-Englund G (2006) A three-dimensional

evaluation of a laser scanner and a touch-probe scanner. J Prosthet Dent 95: 194-200.

Traditional impression

3 D DIGITALIZATION Plaster models

3 D DIGITALIZATION

These devices are

intensively developed in

recent years and are

already recognized as

highly significant in the

field of prosthetics

dentistry.

INTRA ORAL SYSTEMS

3 D DIGITALIZATION

The benefits of using a digital impression

system are many, including the improved

collaboration and treatment planning. You

can see tooth preps in 3D and can catch

any impression glitches while the patient is

still on the chair, and in this way the time is

decreased from the patient’s first visit to final

seating of prosthesis because you won’t

need to send the impression to the

laboratory. You have only to sent the digital

data via Internet.

Condor is innovative intra-oral impression scanner. Developed in

partnership with Professor Duret and subsidized by the European Union,

the technology is radically different from any of the early systems in the

market. It distinguishes itself by simplicity and freedom of use.

3 D DIGITALIZATION

We can use for digital acquisition three scan strategies.

In strategy A, first the buccal surfaces

of the teeth are scanned starting from

the distobuccal aspect of the maxillary

right second molar and returning from

the occlusal-palatal side.

3 D DIGITALIZATION

We can use for digital acquisition three scan strategies.

The second strategy B starts at the occlusal-

palatal surfaces of the maxillary right second

molar, moving towards the other side of the

arch and always including two surfaces, and

returning from the buccal side.

3 D DIGITALIZATION

We can use for digital acquisition three scan strategies.

The third strategy C is sequentially scanning the

three surfaces of a tooth (buccal to occlusal to

palatal), performing an S-type movement from the

maxillary right second molar to the maxillary left

second molar, all in one direction and without

returning to the starting point.

3 D DIGITALIZATION

The second scan strategy has the highest trueness and precision in full-arch scans and

therefore minimizes inaccuracies in the final reconstruction.

3 D DIGITALIZATION

Mangano FG, Veronesi G, Hauschild U, Mijiritsky E, Mangano C (2016)

Trueness and Precision of Four Intraoral Scanners in Oral Implantology: A Comparative in Vitro Study.

PLoS ONE 11(9): e0163107. doi:10.1371/journal. pone.0163107

American Dental

Association (ADA)

specification No. 8 shows

that the luting agent’s type I

thickness should be not

more than 25 μm.

Contemporary optical 3D digitalization devices

offer a measuring accuracy under 20μm. This

means that the resolution of 20 micrometers of

digital intraoral acquisition is quite good for

precise fitting of the fixed dentures.

3 D DIGITALIZATION

Mangano FG, Veronesi G, Hauschild U, Mijiritsky E, Mangano C (2016)

Trueness and Precision of Four Intraoral Scanners in Oral Implantology: A Comparative in Vitro Study.

PLoS ONE 11(9): e0163107. doi:10.1371/journal. pone.0163107

The shorter the distance, the more accurate

results will be achieved with intraoral

scanning. The precision of image acquisition

in case one will be better than in case two.

American Dental

Association (ADA)

specification No. 8 shows

that the luting agent’s type I

thickness should be not

more than 25 μm.

3 D digitalization Virtual design

The third option is to take the

information directly from the

CBCT examination and to use for

digital reconstruction of

anatomical structure. This will

permit planning of implant

treatment as well as surgical

guide and provisional implant

prostheses.

3 D digitalization Virtual design

3 D digitalization Virtual design

After data acquisition and transfer to the CAD software the dentist can virtually make the prototype of prosthetic reconstruction. For example fixed denture. You can choose anatomical patterns from the software library or you can copy and paste the shape and size of the natural teeth from the other side of the dental arch.

All CAD/CAM systems have three functional

components:

1) A digitalization tool/scanner that transforms geometry into

digital data that can be processed by a computer.

2) Software which processes scanner data and produces a data

set readable by a fabrication machine.

3) A manufacturing technology that takes the data set and

transforms it into the desired product by fabricating the restoration.

All CAD/CAM systems have three functional

components:

To fabricate a physical object in

medicine, two different approaches

have been utilized: subtractive and

additive.

SUBTRАCTIVE METHOD

ADDITIVE METHOD

HYBRID

METHOD

SUBTRАCTIVE METHOD

Early CAD/CAM systems relied almost

entirely on cutting a restoration from a

prefabricated block with the use of burs,

diamonds or diamond disks. This is usually

accomplished by conventional numeric

control (NC) machining such as milling.

Subtractive process uses carefully-

controlled tool movements to cut material.

Ø 1.0 mm

Ø 4.0 mm SUBTRACTIVE METHODS

HAVE SOME LIMITATIONS

o The precision fit of the inside contour of the

restoration depends on the size of the

smallest usable tool for each material.

SUBTRАCTIVE METHOD

o In a typical subtractive method in dentistry,

approximately 90 percent of the initial block is removed

and wasted to create a typical dental restoration.

SUBTRАCTIVE METHOD

o In a typical subtractive method in dentistry,

approximately 90 percent of the initial block is removed

and wasted to create a typical dental restoration.

o Milling tools are exposed to heavy abrasion and wear,

therefore, withstanding only short running cycles.

SUBTRАCTIVE METHOD

o In a typical subtractive method in dentistry,

approximately 90 percent of the initial block is removed

and wasted to create a typical dental restoration.

o Milling tools are exposed to heavy abrasion and wear,

therefore, withstanding only short running cycles.

o Microscopic cracks can be introduced into ceramic

surfaces due to machining of this brittle material.

Chipping and cracks caused by milling. (Micrograph

courtesy Dr. Isabelle Denry.)

SUBTRАCTIVE METHOD

o In a typical subtractive method in dentistry,

approximately 90 percent of the initial block is removed

and wasted to create a typical dental restoration.

o Milling tools are exposed to heavy abrasion and wear,

therefore, withstanding only short running cycles.

o Microscopic cracks can be introduced into ceramic

surfaces due to machining of this brittle material.

o It is neither easy nor economic for big, full undercuts and

complex milling parts.

ADDITIVE METHOD

Rapid prototyping (RP) techniques, exhibit the potential to overcome the

described disadvantages. RP simply consists of two phases: virtual

phase (modeling and simulating) and physical phase (fabrication).

ADDITIVE METHOD

This is a process in which the final desired part is manufactured by adding

layers of material on top of one another (layer-by-layer manner). It is a

special class of machine technology that quickly produces models and

prototype parts from 3D data using an additive approach to form the

physical models.

The key idea of this innovative method is that the three

dimensional CAD (3D-CAD) model is sliced into many

thin layers and the manufacturing equipment uses this

geometric data to build each layer step by step until the

part is completed.

• The obtained surface model is usually exported to an STL file format based

on triangular polygons, which is a suitable format for virtual dental

surveying and virtual sculpting environments.

Virtual design

ADDITIVE METHOD

The term “3D Printing” should be clarified to prevent

confusion. Currently in literature and mainstream media, the term

“3D Printing” is being used to refer to all additive technologies

(e.g. fused deposition modeling, selective laser sintering, etc.).

But you have to know that 3D Printing is only one of this 30

technologies - the liquid binder-based inkjet technology.

Orthodontic labs are using it to make models and aligners,

and restorative labs are using it to make patterns for fixed

prosthodontics, surgical guides, and complete removable

dentures.

ADDITIVE METHOD

RAPID PROTOTYPING

SLA - StereoLithography

3D printing

LOM - Laminated Object Manufacturing

SGC - Solid Ground Curing

MJM - Multi jet Modeling

FDM - Fused Deposition Modeling

SLS – Selective Laser Sintering

SLM - Selective Laser Melting

Nowadays 30 different 3 D technologies could be found on the market,

provided by 40 companies.

ADDITIVE METHOD

Stereolithography (SLA) machine

The term “Stereolithography” (SLA)

was introduced in 1986 by Charles

Hull, who patented it as a method

and device for making solid objects

by “printing” thin layers of an

ultraviolet curable material one on top

of the other with a concentrated

beam of ultraviolet light focused onto

the surface of a vat filled with liquid

photopolymer.

The birth of the Additive Manufacturing can be traced back to 1988 when

the first Stereolithography (SLA) machine was introduced.

3D models in medicine (Stratasys J750)

The additive techniques have

been employed to build complex

3D models in medicine since the

1990s. These models can be

produced with undercuts, voids,

intricate internal geometrical

details and anatomical

landmarks such as facial sinuses

and neurovascular canals.

A 3D model, created in collaboration with the

anaplastologist Jan De Cubber (Materialise)

А complex design can be

produced in one

fabrication cycle unlike in

Subtractive Manufacturing

Technology where

different parts would need

to be fabricated and

assembled.

ПРИЛОЖЕНИЕ

The additive technology is currently employed to

improve medical diagnosis and to provide a precise

surgical treatment plan. The innovations in molding

materials and forming procedure have improved the

additive techniques so that this technology is no longer

adopted only for prototyping; it is used for reproduction

of real functional elements.

ПРИЛОЖЕНИЕ

1. Surgical drilling templates during dental implant insertion

2. Orthognathic surgery

3. Prosthesis

4. Orthodontic appliances

1. Surgical drilling templates during dental implant insertion

Start with CBCT examination

After that we have to scan intraorally the dental

arch and the patient’s teeth directly.

With CAD software we can merge the

information from the CBCT and the intraoral

scan. On this fused digital model we design the

surgical guide for implant placement.

The STL file is sent to the 3D printer and the physical objects are produced.

The guided surgical template has metallic sleeves that direct and allow precise implant placement in the three space axes. With the master sleeve integrated into the acrylic guide template we can control initial trajectory and osteotomy depth.

We can control through the master sleeve the angulation of the surgical drill and the depth of penetration.

2. Orthognathic surgery

Conventional orthognathic wafers are made by a process involving manual movement of stone dental models and acrylic laboratory fabrication. In addition, a facebow record and semi-adjustable articulator system are required for maxillary osteotomy cases. In orthognatic surgery we can use the digital design to place in the right central position the lower and upper jaws and digitally to construct wafer. 3D printer will reproduce the real prototype of the wafer, which will be used during the time of surgery. This is a novel process of producing both intermediate and final orthognathic surgical wafers using a combination of computerized digital model simulation and three-dimensional print fabrication, without the need for either a facebow record or the additional ionizing radiation exposure associated with cone beam computerized tomography.

2. Orthognathic surgery

Virtual wafer The plastic wafer fitted on

the models in order to

check the final occlusion

Intra-operative

photographs during

mandibular and maxillary

osteotomies

3. Prosthsis

One of the most popular application of

3D printing is the fabrication of working

models, which have the same features

like the conventional models. Fabricated

using the PolyJet additive manufacturing

process, these models are made with

resolutions down to 30 microns.

Many studies have proved that 3D digital

models of dental casts have the same

accuracy and precision like the traditional

plaster casts.

3. Prosthsis

We can use additive

technology and specially the

wax deposition modeling

(WDM) technology to produce

wax-ups of removable or fixed

dentures with wax-like

materials. These materials

burn-out with no residue,

material shrinkage, cracking or

expansion.

This image shows the progression from 3D Printed framework, to polished part

in the frontal area, and then finally on the right site veneered finished product.

3. Prosthsis

A case of removable partial denture made by selective laser sintering

3. Prosthsis

3. Prosthsis

CONCLUSIONS