Tuesday, July 26, 2011

A Lecture Note On Lasers Used In Operative Dentistry...with ppt download

INTRODUCTION
  • Dentistry has advanced a lot.
  • Among various advances, one which has good scope of improvement is the use of lasers in dentistry.
  • Recent advances in laser technology will bring revolution in dentistry.
  • Laser is an acronym for light amplification by stimulated emission of radiation.
DISCOVERY OF LASERS:
  •  It was discovered by Shallow & Towns in 1958.
  •  First working laser was built by Mailman of Hughes research laboratories in 1960.
HISTORY OF LASERS IN DENTISTRY:

  • Vain used a ruby laser & reported extensive deep destruction of carious tissue along with melting of dentin.
  •  Paghdiwala[U.S.A] in 1988,first time tested the ability of Er:yag laser on dental hard tissue.
  • In 1997,Er:yag laser was cleared for marketing by Food & drug administration of U.S.A.




COMPONENTS OF LASER
There are 3 main parts of laser delivery system.
   
   (1).LASING OR ACTIVE MEDIUM
  • It is the material which is capable of absorbing the energy produced by the external source through subatomic configuration of its component molecules & subsequently giving the excess energy as photons of light.
  • It can be solid, liquid or gas.
   (2).ENERGY OR PUMPING SOURCE
  • It is used to excite or pump the atoms in lasing medium to their higher energy levels that are essential for laser production.
  • It can be electrical,thermal,chemical or optical.
  (3).OPTICAL OR RESONATING CHAMBER

  • The lasing medium is located within the optical chamber.
  • It is a cylindrical structure with fully reflecting mirror on one side & partially reflecting mirror on other side--parallel  to each other.
  • This arrangement allows reflection of photons of light, back & across the chamber.
  • It will result in production of intense photo resonance within the medium
TYPES OF LASERS
2 categories of lasers are used in medicine & dentistry
    (1).HARD LESARS

  •        Longer wavelength
  •        Cuts the tissue by ablation.
  •        Used for tooth & bone applications.
   (2).SOFT LASERS OR LOW LEVEL LASERS

  •        Low energy wavelengths
  •       Cuts tissues by coagulation,vapourisation & carbonisation.
  •       They are believed to stimulate circulation & cellular activity & causes various effects such as anti inflammatory,vascular,muscle  relaxant,analgesia & tissue healing
 There are many types of lasers used in dentistry, depending upon their active medium

(1).CARBONDIOXIDE LASER
     - WAVELENGTH: 10.6um
     - USES: SOFT TISSUES , DENTIN DESENSITIZATION
(2).ARGON LASERS
     - WAVELENGTH: 488,514.5um
     - USES: CURING , SOFT TISSUE DESENSITIZATION
(3).Nd:YAG [NEODYMIUM:YTTRIUM-ALLUMINIUM GARNET] LASER
     - WAVELENGTH: 1.064um
     - USES: SOFT TISSUE DESENSITIZATION , ANALGESIA
                  TOOTH WHITENING , PERIODONTICS,
                  ENDODONTICS
(4).KTP[POTASIUM-TITANYL PHOSPHATE] LASER
(5).HELIUM-NEON[He-Ne]
(6).RUBY LASER
(7).EXCIMER LASER
(8).HOLMIUM[Ho]:YAG LASER
(9).ERBIUM[Er]:YAG LASER
   - WAVELENGTH: 2.94um
   - USES: HARD TISSUE
 (10).ERBIUM-CHROMIUM[Er-Cr]:YSGG LASER
   - WAVELENGTH: 2.79um
   - USES: HARD TISSUE
(11).DIODE
     - WAVELENGTH: 800-830um
     - USES:SOFT TISSUE , PERIODONTICS


Effects of lasers
          PHOTO-THERMAL: Ablation of tissues by vaporisation.
           PHOTO-CHEMICAL : Bio-stimulation by stimulated ATP production.
          PHOTO-ACOUSTIC : Dehydration, burning & carbonization.

Effects on tissues on certain temperatures
             60`: Proteins begin to degenerate
          100` : Vapourisation
          200` : Dehydration, burning & carbonisation


APPLICATION OF LASERS IN  OPERATIVEDENTISTRY

DIAGNOSIS OF DENTAL CARIES

(A).INFRARED LASER FLUORESCENCE [DIAGNODENT]

  •   Diagnodent is an instrument, recently designed to facilitate the detection of dental caries.
  •   Used for detection of caries on occlusal and; smooth surface.

(B).LASER INDUCED FLUORESCENCE

  •    Kutsch in 1992,illuminated carious & non carious tissue with argon laser along with dark field photography.
  •    He reported that while illuminating, carious lesion has clinical appearance of dark,fiery,orange-red colour.
CAVITY PREPARATION WITH LASER
 NUMBER OF STUDIES HAVE BEEN PERFORMED FOR THE USE OF Er:yag LASER FOR CAVITY PREPARATION.
  • Results of studies says that little or no noticeable pulp reaction is produced while preparing the cavity with Er:yag laser.
  • It is safe & can be used for cavity preparation.
             ADDITIONAL BENEFITS
A.)minimises patient fear of the drill.
B.)no irritating sound like traditional drills.
C.)the cavity with laser preparation appears open,patent,fresh & devoid of all debris.
D.)mono-infection with Enterococcus faecalis is avoided - hence sterile cavity.
E.)melts the dentin & blocks the tubules,thus hydrodynamic theory of dentin sensitivity is ruled out.








PREVENTION OF DENTAL CARIES WITH LASERS


  • Laser can be used for prevention of dental caries.
  • Different types of lasers increases the resistance to dental caries by reducing the rate of demineralization of substance of enamel & dentin.
  • Argon laser alters the surface characteristics of enamel to make it caries resistant.




MECHANISM OF ACTION

  1.  Carbonate is lost from carbonated appetite mineral of tooth during laser irradiation
  2.  Pulsed co2 laser irradiation interacts with the phosphate group in dental materials
  3.  It gets preferentially absorbed & transformed efficiently to heat
  4.  Carbonated hydroxyapetite in the surface & in the immediate subsurface of enamel is heated at temp. greater than 400`c
  5. Carbonate is decomposed, leaving behind the a hydroxyapetite like mineral that is less soluble
BLEACHING WITH LASERS
 Power bleaching is the term used for accelerated in-office tooth whitening procedures, using laser orXenon plasma arc-curing light.
  (A). ARGON LASER

  •      A true laser light is delivered to chemical agent.
  •      The action is to stimulate crystals in the chemical.
  •      No thermal effect, so less dehydration of enamel.
  •      The treatment time is 10sec. per application per tooth.
  •      It is the advantageous for clinician & patient.
  (B). DIODE LASER


  •     A true laser light produced from a solid state source.
  •     It is ultra fast, taking 3 to 5 sec. to activate bleaching agent.
  •     This type of lasers produce no heat.






PHOTOPOLYMERIZATION OF COMPOSITE RESIN WITH LASER


  •     Argon lasers are used for this purpose.
  •     For polymerization of camphorquinone
  •     Activated composite resin,the argon laser,
INCREASES;
              the depth of cure
              the diametric tensile strength
              adhesive bond strength
              degree of polymerization of  materiels.
 REDUCES;
              Acid solubility of surrounding enamel
               Decreases the time of activation Significantly


 ADVANTAGES OF LASERS
(1).Minimal damage to surrounding tissues.
(2).Haemostatic effect by sealing blood vessels.
(3).Reduction of postoperative inflammation & edema.
(4).Little postoperative scarring.

(5).Reduction in postoperative pain sensation since nerve endings are blocked.
(6).Dressing & suturing is not required for wound closer.
(7).Operating time is reduced.
(8).Sterilization of wound due to reduction in amount of microorganisms exposed to laser irradiation.
(10).Excellent wound healing.
(11).Laser exposure to tooth enamel causes reduction in caries activity.

DISADVANTAGES OF LASERS
(1).Laser beam could injure the patient or operator By direct beam or reflected light, causing retinal burns.
 (2).It available only at big hospital & treatment is very expensive.
(3).Specially trained person is needed.

            ... Download ppt lecture note...

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