1. LASER HAZARDS AND SAFETY IN DENTISTRY

2. LASERS IN PERIODONTICS
Use of lasers in periodontal therapy is complex
Excellent hemostatic and soft tissue ablation characteristics
Carbonization and Thermal damage when used on root surfaces and alveolar bone
INDICATIONS
Gingivectomy
Frenectomy
Removal of melanin pigmentation
Subgingival curettage and debridement
Removal of granulation tissue during flap surgery
anagement of periimplantitis

3. Laser radiation hazards
A HAZARD is something with the potential to cause injury.
There are a number of hazards associated with laser use in a clinical environment, the most obvious being the laser light itself
Accidental exposure could be caused by a misaligned or misdirected laser beam, laser light escaping from the protective housing of the unit, or a broken or detached optical fibre

4. Laser radiation predominantly causes injury via thermal effects.
Even moderately powered lasers can cause injury to the eye.
Some lasers are so powerful that even the diffuse reflection from a surface can be hazardous.
Incidents have been reported involving injuries due to laser beam reflected off a droplet.
Other incidents include lasers that fail to stop after the foot pedal has been released, burns to lips tongue and cheeks, injuries to eye due to usage wrong eye wear not specific to the laser wavelength being used.

5. Laser hazards can be classified into:
BEAM HAZARDS
These include injuries associated with the radiation itself
The laser produces an intense, highly directional beam of light.
If directed, reflected, or focused upon an object, laser light will be partially absorbed, raising the temperature of the surface and/or the interior of the object, potentially causing an alteration or deformation of the material.
Therefore these include damages caused to the eye and skin by direct exposure.

6. 2. NON BEAM HAZARDS:
These non-beam hazards, in some causes, can be life threatening.
The only fatalities from lasers have been caused by non-beam hazards.
A few examples of non beam hazards include
Fire/Explosion
Electric Shock
Laser generated air contaminants

7. CAUSES OF LASER ACCIDENTS

8. Laser hazards may be listed as follows:
Ocular
Skin
Injury to non target tissues
Fire
Respiratory

9. 1. OCULAR EFFECTS
The primary ocular injury that may result from a laser accident is a retinal or corneal burn.
The coherence and low divergence angle of laser light, aided by focusing from the lens of an eye, can cause laser radiation to be concentrated into an extremely small spot on the retina.
A transient increase of only 10 °C can destroy retinal photoreceptor cells.
If the laser is sufficiently powerful, permanent damage can occur within a fraction of a second, literally faster than the blink of an eye.

10. Even low intensity beams can cause damage because of the focusing effect of the lens and cornea.
A laser beam can be focused to an intensity on the retina which may be up to 200,000 times higher than at the point where the laser beam enters the eye.
Most of the light is absorbed by melanin pigments in the pigment epithelium just behind the photoreceptors, and causes burns in the retina
Irreversible retinal burns resulting in permanent blindness can occur by conversion of incident radiation to heat energy within a fraction of a second.

11. Damage from laser beam maybe due to direct exposure to the beam or diffuse reflection or when wavelength specific eye wear are not used
A pulsed laser will cause more damage than a continuous beam of equal power because the peak power is greater than the average output power
The body's protective "blink reflex" response is triggered only by visible light. So people exposed to high power Nd:YAG laser emitting invisible radiation, may not feel pain or notice immediate damage to their eyesight. A pop or click noise emanating from the eyeball may be the only indication that retinal damage has occurred

12. Some visible wavelengths affect red and green cones resulting in color blindness.
Emissions below 400 nm are absorbed by the cornea and lens leading to cataracts
The eye focuses visible and near-infrared light onto the retina. Sufficiently powerful emissions in this spectral region ( nm) will penetrate the eyeball and heat up the retina causing retinal injury.
nm wavelength lasers cause lens damage
nm wavelengths cause corneal, aqueous and lens damage
nm wavelengths cause corneal damage

13. PRECAUTIONS
Use of glasses for protection (patient, operator, assistants) :
Protective eyewear in the form of spectacles or goggles with appropriately filtering optics can protect the eyes from the reflected or scattered laser light with a hazardous beam power, as well as from direct exposure to a laser beam. Eyewear must be selected for the specific type of laser, to block or attenuate in the appropriate wavelength range.
For e.g., if the eye wear is marked as nm, it means that the eye exposed to all wavelengths between these two outer limits are protected.

14. The wavelengths that the eye wear is specific for should be printed on it.
Lightweight goggles with plastic filters are used and these are made of a polycarbonate with a dye mixed into the material, or with an absorbing or reflecting coating.
For higher power, glasses  containing a lamination of filter glass and polymer layers are used
Glasses must cover the entire peri-orbital region and should be free of any surface scratches
Protocol for use is “patient first on and last off“ i.e as soon as the patient is seated protective eye wear is put on which is not to be taken off until the end of the procedure
The eye wear should be examined now and then for cracks of the protective material

16. Requirements of Safety Glasses:
a high level of attenuation of incident laser light by the glass, achieved by absorption and/or reflection
adequate protection against beams coming from the side
durability of the glass, even under conditions of strong heating by an incident laser beam
absence of photo-bleaching
low tendency for scratches
a label with clear indications concerning the kind of protection (to avoid that glasses are used in cases where they do not provide adequate protection)
ease of wearing, sufficiently large viewing angle , and a light weight for avoiding pain due to the excessive pressure on the skin

17. MAXIMUM PERMISSABLE EXPOSURE
The maximum permissible exposure (MPE) is the highest power or energy density of a light source that is considered safe i.e. that has a negligible probability for creating damage.
A calculation of the MPE for ocular exposure takes into account the various ways light can act upon the eye.
For e.g.  Infrared light with a wavelength longer than about 1400 nm is absorbed by the transparent parts of the eye before it reaches the retina, which means that the MPE for these wavelengths is higher than for visible light.
In addition to the wavelength and exposure time, the MPE takes into account the spatial distribution of the light

18. An MPE is usually expressed in terms of the allowable exposure time (in seconds) for a given irradiance (in watts/cm2) at a particular wavelength
Collimated laser beams are especially dangerous  because the lens focuses the light onto a tiny spot on the retina
 In the MPE calculation, the worst-case scenario is assumed, in which the eye lens focuses the light into the smallest possible spot size on the retina for the particular wavelength and the pupil is fully open.

19. OPTICAL DENSITY Eyewear is rated for optical density (OD)
Optical Density (OD) is a measure of the radiation permitted to pass through a filter and it's determined by the filter.
For e.g. OD of 2.0 allows 1/100 of the laser light energy to pass through the filter.
The OD specified on the glasses is the minimum OD sufficient to protect the user against a momentary intrabeam or specular reflection exposure.

20. 2. Use of wet gauze packs to avoid reflection from shiny metal surfaces
3. The patient and the dentist should wear the eye wear before the laser s switched on and should not take them off until the laser is switched off
4. Use of carbonized or non-reflective instruments

21. NON-TARGET TISSUE DAMAGE
Laser induced damage to the nontarget tissue (oral tissue) can result from thermal interaction of radiant energy with tissue proteins.
Can produce cell destruction by denaturation of cellular enzymes and structural proteins, which interrupts basic metabolic processes
Histologically, the thermal effect of absorbed radiant energy is manifested as thermal coagulation necrosis for wavelengths above 400 nm.
Other nonthermal tissue interactions are thought to induce injury through photochemical and photo acoustic mechanisms

22. Photochemical damage caused due to short wavelength light is due to chemical reactions triggered in the tissues. And it can be accumulated over the course of hours
With prolonged exposures of low power density from Nd:YAG laser, excess thermal necrosis that may not be apparent at the tissue surface can occur
The extent of damage depends on
Laser beam size
Absorption co efficient
Scattering co efficient
Exposure time
Size of the area exposed

23. PRECAUTIONS
Attention to focus the beam on target tissues

24. Avoid using glass mirrors as they absorb heat and shatter
Avoid using glass mirrors as they absorb heat and shatter. Rhodium coated mirrors can be used safely
Parallel monitoring of the adjacent tissues at the time of the procedure is to be ensured

25. RESPIRATIONAL HAZARDS
Laser plume poses a significant hazard and occurs as a result of the development of aerosol by-products due to laser-tissue interaction
These products can contain particulate organic and inorganic matter including viruses, toxic gases and chemicals
These hazards do not pertain to injuries resulting from direct exposure to laser beam.
Inhaled air borne contaminants can be emitted in the form of smoke or plume generated due to thermal interaction of lasers with tissues or escape of gases from the laser itself.

26. Some of the toxic gases and chemicals are:
Ethanol
Isopropanol
Anthracene
Formaldehyde
Cyanide
Airborne mutagenic particles
Fluoride
Hydrochloride gases
Toxic dyes

27. The hazard presented by the Laser Generated Airborne Contaminates (LGACs) may include:
Eye irritation
Nausea
Breathing difficulties
Vomiting
Chest tightness
Possibility of transfer of infective bacteria and viruses

28. PRECAUTIONS
Use of specific fine-mesh masks capable of filtering 0.1 micron particles.

29. Adequate high speed evacuation
Evacuation tube must be held as close as 1cm frm the target site as the evacuation efficiency reduces by 50% at 2cm

30. SKIN DAMAGE
Potential risks to the skin are considered secondary to risks to the eyes.
This is because skin injuries don’t often have the dire consequences (such as partial loss of vision) that eye injuries do.
Skin injuries may affect only the external dead layer of the skin cells; and even more penetrating damage usually will heal eventually
Large-area exposures that can lead to serious skin infections and other complications are not commonly associated with laser use because the beam is relatively small.

31. Laser radiation can affect the skin thermally or photochemically
The pain from thermal injury to the skin by most lasers is enough to alert the user to move out of the beam path.
But high-power visible and IR lasers are used now. They are capable of producing significant burns to the skin in much less than one second.
And users are unable to move out of the beam path before serious injury occurs

33. COMBUSTION HAZARDS
Flammable solids, liquids and gases used within the dental surgical setting can be easily ignited if exposed to the laser beam.
Solids: clothing, paper products, plastic, waxes and resins.
Liquids: ethanol, acetone, methylmethacrylate, solvents.
Gases: oxygen, nitrous oxide, general anesthetics, aromatic vapors.

34. PRECAUTIONS Use of flame resistant clothing is therefore recommended.
Use of flammable materials should be avoided

35. LASER CLASSIFICATION CLASS Use in Dentisrty Risks Safety Measures I
Caries Detection
No implicit risk
Blink Response
I M
Scanner
Possible risk with magnified beam
Laser safety labels II
Aiming beams
Possible risk with direct viewing
Sight aversion response
II M
Significant risk with magnified beam
III R
Photodynamic anti microbial chemotherapy devices
Eye damage
Safety eye wear
III B
Mucosal scanning devices
Skin risk
Protective clothing IV
All surgical lasers
Eye and Skin Damage
Non target tissue damage
Plume Hazard
Protective eye wear
Safety Personnel

36. LASER SAFETY SIGNS
Laser Area Signs are used to mark the area designated a laser hazard zone. The signs vary according to the classification of the laser or laser system
The signal word “CAUTION” is used on all signs associated with Class 2 lasers
The signal word “DANGER” is used with all signs associated with all Class 3a, Class 3b and Class 4 lasers
All signs and labels shall be conspicuously displayed in locations where they will best serve to warn onlookers

37. SAFETY MEASURES ENGINEERING CONTROLS
Stable mounting (beam not at eye level)
„ Protective housings, enclosures
„ Interlocks on housings, lasers, doors, etc.
„ Control of the beam path (beam tubes, beam stops, etc.)
„ Remote firing
„ Emergency buttons
„ Fume extraction system
„ Warning lights
„ Filters
„ Switch guards, covers
„ Alignment aid

38. 2. ADMINISTARTIVE CONTROLS:
„ Laser Safety Office or person--in--charge
„ Registration of laser equipment and users
„ Designated laser controlled areas
„ „ Warning signs
„ „ Standard operating procedures
„ Emergency and accident reporting procedures

39. 3. PERSONAL PROTECTIVE EQUIPMENT:
„ PPE as a last resort
„ appropriate laser protective eyewear to protect the eyes
„ suitable clothing to protect the skin

40. CONCLUSION
Laser use in dentistry is proven to be beneficial in treating a wide range of dental conditions and also as a therapeutic tool in tissue management.
Safety regarding the use of lasers is not optional. It should be the highest priority of all staff members involved in the surgical.
Prevention of accidents requires thorough knowledge of their causes and the application of measures to avoid them.

41. THANK YOU