LASER In Dentistry

ByDr. Manal Rafie Hassan

Associate prof., Cr. & Br. DepartmentMinia University

LASER is define as “Light Amplification by Stimulated Emission of Radiation”.

LASER Apparatus: Laser beam is produced within a closed system called the cavity or the optical cavity that consists of 3 components: 1- active medium: it is the source of laser light which can be atoms or molecules in the solid, liquid, or gas phase.

It determines the wavelength at which the laser operates.

2-Incident energy source: which may be a flash light , an electric discharge, or high injection current . It is used to stimulate the atoms or the molecules of the active medium to emitting light photons.

3-Amplification system: which composed of two highly polished concave mirrors placed at both sides of the optical cavity, used to amplify the photon chain resulted from stimulation of the active medium in the cavity.

Characters of the LASER Beam

1. Coherent: All photons exist in the same phase.

2. Collimated: does not scattered with any prism.

3. Monochromatic: all photons have one particular wavelength.

4. Concentrated.

Mode of Action of the LASER Beam

1. Continuous: the pulses are emitted in a continuous manner.

2. Pulsed: the energy is emitted according to a set of repetitive series of pulses.

3. Gated: A trained of pulses can be produced & gated via a mechanical shutter. gate can be further broken into single smaller gate of timed period. This type of laser gives more penetration depth for deep tissues as melanin cells that are found in the deep layer of dermis.

Types of LASER Tissues Interaction

The interaction depends on the following variables :

1. Wavelength of LASER emission.

2. The power density of the laser beam which is the concentration of photons in a unit area , and pulse duration , repetition rate& the mode of action: [pulsated, continuous ,focused ,gated]

3. The optical characters of the particular target tissue.

The inter action could be one or a combination of more than one of the following:

1. Photo-chemical inter action: specific wavelengths of LASER are absorbed by a specific molecules or tissues components and subsequently release the energy again as light. These types are known as tissue fluorescence & used for caries detection.

- Argon laser energy will offer considerable

promise for early caries detection when used

to illuminate teeth (Diagnodent). Decalcified

areas appear as a dull, opaque, orange color.

2- Photo thermal inter action; most of the LASER application get their advantages from this mode of inter action. Radiant light energy absorbed by tissue transformed into heat energy , which produces the tissue effect. it is manifested clinically as photo ablation or removal of tissues by vaporization. First ,heating with denaturationoccurs at 450c-60oc.then coagulation and necrosis occurs above these temp..At100oc water inside tissues vaporizes. Above 300oc carbonization and pyrolysis (destruction of tissues due to heat) with vaporization of the bulky tissues occurs.

This type of inter action used in surgical application.

3-Photo mechanical inter action: The LASER radiation leads to fast heating and boiling of water inside the mineralized tissue matrix followed by an explosive volume expansion the material will destroyed mechanically with little thermal damage. This type is used in caries removal e.g.-YAG LASER.

4-Photoelectrical inter action: These include photo-plasmolysis(the shrinking of protoplasm away from the cell wall due to water loss ,in which the tissues are removed through formation of electrically charged ions , leading to breaking and shattering ( into minute particles ) of the target tissues.

**Types of LASER used in dentistry: Co2

laser ,in soft tissue surgery & caries removal ,Nd:YAG used in cutting dentin ,treatment of hyper sensitivity ,remove external stains (bleaching of teeth) ,Argon laser used in composite curing ,Er:YAG ,cutting enamel & dentin , etching of enamel & dentin.

First type of laser system used.

It is made of synthetic ruby (AlO) with chromium oxide.

Its wave length is 0.694 nm.

It is destructive due to scattering of the beam.

1. Ruby LaserT y p e s o f L a s e r s

It is made of N2 & CO2 in the form of gas.

Its wave length is 10.6 nm.

It is effective in sealing pits and fissures

Welding of metals.

(improves the ab take of fluorides by the dental tissues.Prevention of dental carries.

but produce high surface temperature.

2. CO2 LaserT y p e s o f L a s e r s

Ionized Argon Gas is used as an active medium.

Its wave length ranges from 488 – 510 nm.

It is used to cure polymers. (e.g. curing of composite resin)

3. Argon LaserT y p e s o f L a s e r s

Its main active medium is a garnet crystal made of Yttrium & Aluminum

There are 3 types of YAG Lasers according to the rare earth elements used, which are doped in the main crystal neodymium Holmium & Erbium

So YAG could be:Nd – YAGHo – YAGEr – YAG

4. YAG LaserT y p e s o f L a s e r s

This is considered to be the most recent types of lasers nowadays.

It combines a halogen and Nobel gas as active medium such as Argon Fluoride Excimer laser, Krypton Fluoride or Xenon Chloride.

5. Excimer LaserT y p e s o f L a s e r s

Ex. Biolytic

6. Diode LaserT y p e s o f L a s e r s

The development of micro-structure diode cells that are capable of laser light production has dramatically reduced the bulk of laser machines (Desktop diode laser machine).wavelength(approx 400-1,000 nm) . Only solid material active media are used in these lasers.In a diode laser, the active medium is sandwiched between silicon wafers

Uses of LASER in Fixed Prostheses

Soft tissue treatment: these inter actions are performed by cutting , coagulation and vaporization of soft tissues .

1. Crown lengthening .

2. Gingival contouring or removal of hypertrophied tissues.(gingival retraction)

3. Implant exposing in the second stage after osseous integration.

4. Pre prosthetic surgery to remove any abnormal soft tissues.

Gingival recontouring& gingivectomy by the traditional way

LASER Incision used in pocket eradication [bloodless ,sterile ,clean field]

Good tissues healing

Removal of impacted canine ,no

bleeding

Cutting of fibero-

epithelial polyp of

dorsum of the tongue .

He-Ne pointing

beam

Correction of high

labial frenum

Implant exposure after osseous integration (two stage type) using LASER

Healing cap after implant

exposure. see the clean

incision]

Excellent gingival contour around

the crown

Crown lengthening .

Gingival contouring & bone contouring.

The Waterlase system from Biolase types is a hard tissue laser thatsafely and conservatively removes and re-contours osseous tissue.

This type of quick, complete healing is typical of laser surgery.

Extreme close-up of right lateral incisor. Note the optimum gingival health

A closer look at the smile shows a dramatic difference when compare to the pre-oprative smile

Composite Curing

LASER could be used in composite curing with the following advantages:

1. Deep penetration of curing leaving no monomer this leads to increased strength and decreased shrinkage .This gives us the chance to use resin bonded restoration in more questionable situations like long span bridge or in posterior bridges.

2-Etching of the tooth surface with LASER before bonding with composite resin leads to homogenous penetration thus decreasing the shrinkage of polymerization .

3- Etching of the metal surface with LASER gives rise to microscopic pores ready to be luted with composite ,specially noble alloys which cannot be etched with other chemicals (base metals are etched with electrolytic etching & conc.acides) .Reported increase in bond strength in lased metal than in conventional method.(noble alloys)

Posterior resin bonded bridge

debonding

Hard tissues treatment

Lased enamel is more resistant to caries & attack with acids .In addition ,there is an increase in enamel up take of acidulated phosphate fluoride(rinsing fluoridated solution) after LASER exposure .

Finishing cavity walls with a LASER beam decreased marginal leakage in restorations luted with glass ionomer cement.

Reduction of hypersensitivity. (reduces the opening of dentinal tubules )

Removal of caries: Er:YAG (erbium yttrium garnet ) LASER is used with no thermal side effect . Also Nd:YAG (neodymium YAG , Co2

LASER had been used but with carbonation and traces of enamel crazing lines side effects.

Etching of dental tissues with reported increase in bond strength of composite to the dentine (%bonding increase compared with etching with 10% phosphoric acid)

Laboratory Applications

Laser welding of dental alloys: this technique consists of focusing the powerful LASER beam on the two parts to be joined , with no inter mediate solder alloy. It is used to build up contact area ,welding of alloys difficult to be cast e.g. titanium alloys ,clasps or precession attachment connection to the restorations . Wide range of dissimilar metals could be joined by this technique.

Welding near plastic or ceramic veneers is possible without any distortion (very precise beam)

LASER welding computerized machine supplied with a

screen to observe the steps of welding.

Computer Aided Design (CAD)

CAD is the process of using software to assist

in precision drawing and designing models to aid

in their manufacturing.Computer Aided Manufacturing (CAM)

CAM is the process of using software to

manufacture models.

LASER is used as a scanner in some systems

of newly developed CAD-CAMs

+Scanner

3D scanner

softwareComputer

Designing

software

Milling

machine

Digitizing (scanners)

Designing (software)

Milling

–Tools

–Materials

CADCAM

Laser Scanning : the use of a laser to collect

dimensional data in the form of a "point cloud".

Point Cloud : the collection of points in 3D space

resulting from scanning an object; represent the

surface of the object.

Line-of-Sight : the extent to which a laser scanner

or other measurement device can capture 3D

data from its corresponding object point. Only

points which can be "seen" by the laser will be

captured.

Point cloud measurements

3 D laser scan

Accurate LASER

scanned image of

onlay.

Laser visible stone

Milled copings

Cast scan Die scan

LASER Scanning

Wax pattern

Under scanner

head

Wax pattern

Being scanned

Laser beam digitizing a die of laser visible stone

Moving the die to allow laser to capture all surface

details

1) The Cerec System (Sirona)

– It is the longest established CAD CAM

system.

– The InLab system is compact, milling unit and

laser scanner are incorporated in the same

unit.

– The scanning stage takes 8-10 minutesfor a single die and approximately 15 minutes for a 3-unit bridge.

– Milling a single unit can takes 10-15 minutes, depending on the coping

size and the sharpness of the two

milling burs and the blank material.

3D camera

Design software

Milling machine

Cerec 3

Cerec Scan

Cercon Smart Ceramics (DeguDent)

Cercon Brain

Digitizing

( laser)

Milling

Cercon Heat

Sintering

GN-I (GC)

5-axis laser

scanner

Milling

machine

Color ; rapid LASER scanning color machines can create parts from a full 24-bit palette of colours which can

be blended together.

Selective Laser Sintering (SLS)

It uses laser to draw cross-sections in a bed of fine, heat-fusible powder. The laser raises the temperature of the powder particles momentarily to where they sinter (“Sintering,”

means welding without melting.).

SLS works with a broad range of materials powder, including thermoplastics, metal powder, casting wax and ceramic powder.

Laser source

Powder feeder 1 Powder feeder 2Work platform

Powder is raised to be

cured with laser beam.

Laser beam curing

of ceramic from

nano powder.

Crown is build up

in layers.

Laser Forming

This process involves melting pure metal

powder to produce a homogeneous

metallurgical structure free of pores without

using a binding agent directly from the CAD

model.

BEGO process charting MEDIFACTURING

CO2 Laser with an output power range

from 2000 to 6000 W

Cicero CAD-CAM System

LASER stripe scanning method to

measure 3 D geometry of the

preparation, its surrounding ,& opposing

teeth.

LASER SAFTY

1. Reflective surfaces like mirrors & instruments or polished restorations have the ability to redirect the LASER beam , matt instruments are preferred .

2. Protective eyeglasses for patient & staff (green colored glasses are used with Nd:YAG &amber glasses with Argon laser while clear glasses are used with Co2

laser

3- The patient’s eyes must be covered with moist gauze pad .

4-Non target tissues must be covered by wet packs.

5- LASER plum created if vaporized tissues were infectious , so all the team must wear protective masks.

6- Adequate ventilation must be available in the operation room.

7- Caution in operating with LASER ,all parameters should be precisely calibrated to prevent any burn or even blindness or in some cases death if electric shock occurred.

Working with LASER