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Operative Dentistry - Best Practices

Light Curing (last modified 18AUG2014)

Dalhousie Light Curing Symposium May 2014 comments to be published in  Journal of Adhesive Dentistry, Dental Materials, Operative Dentistry, and the Journal of the Canadian Dental Association.  Blanket copyright license is given for the table and figure below to be freely used, in whole or in part, for all derivative works without permission from the copyright holder. 

Light Curing – Guidelines for Practitioners

A Consensus Statement from the 2014 Symposium on
Light Curing in Dentistry held at Dalhousie University, Halifax, Canada*

 

When selecting a light curing unit (LCU):

  • Recognize that all lights are not created equal. Use a LCU from a manufacturer who provides contact information, a user manual, and service. Preferably the LCU should have received a favorable report or certification from a reputable independent 3rd party.
  • Know the key performance parameters of your LCU, when new:
    (i) the light output (averaged irradiance over the beam incident area in mW/cm2 and spectral output from the LCU), (ii) whether the beam has a uniform and effective output (profile) across the light tip, and (iii) the diameter of the light beam.
  • Be cautious when using high (above 1,500 to 2,000 mW/cm²) output LCUs that advocate very short (e.g. 1 to 5 seconds) exposure times. When used for such short times, it is critical that the light tip is stabilized over the resin during exposure. Although some resin composites are matched to specific high output curing lights, high output LCUs may not adequately cure all of today's resin-composites to the anticipated depth when used for short exposure times. Seek peer-reviewed literature validating the efficacy and safety of such lights and materials.

 

Before you light cure, remember to:

  • Regularly monitor and record the light output over time, with the same measurement device and light guide. Repair or replace the LCU when it no longer meets the manufacturer’s specifications.
  • Inspect and clean the LCU before use to ensure it is on the correct setting, in good working order, and free of defects and debris.
  • Consider that every resin-based material has a minimum amount of energy that must be provided at the correct wavelengths to achieve satisfactory results.  . However, minimum irradiation times are also required.
  • Follow the light exposure times and increment thickness recommended by the resin manufacturer, making allowances if you use another manufacturer’s light. Increase your curing times for increased distances and darker or opaque shades.
  • Select a LCU tip that delivers a uniform light output across the light tip and that covers as much of the restoration as possible. Cure each surface independently, using overlapping exposures if the light tip is smaller than the restoration.
  • Position the light tip as close as possible (without touching) and parallel to the surface of the resin composite being cured. 
  • Stabilize and maintain the tip of the LCU over the resin composite throughout the exposure.
  • Always use the appropriate “blue blocking” glasses or shield to protect your eyes as you watch what you are doing with the curing light.

 

Precautions:

  • Avoid conditions that will reduce light delivery to the resin-composite, e.g.:
    • Holding the light tip several millimeters away.
    • Holding the light tip at an angle to the resin surface.
    • Dirty or damaged light-guide optics.
  • Supplementary light exposures should be considered under circumstances that may limit ideal light access, such as shadows from matrix bands, intervening tooth structure, or from restorative material.
  • Beware of thermal damage potential to the pulp and soft tissues when delivering high energy exposures or long exposure times.
  • Air-cool the tooth when exposing for longer times, or when using high output LCUs.
  • Never shine the LCU into the eyes, and avoid looking at the reflected light, except through an appropriate ‘blue-blocking’ filter.
  • Testing surface hardness of the resin-composite in the tooth using a dental explorer provides NO information about adequacy of curing depth. 

 

Table 1  Glossary of Terms for Light Curing

 

Term

Unit Commonly Used in Dentistry

Symbol

Notes

Radiant energy

Joule

J

This describes the energy from the curing light.

Radiant exposure

Joule per square centimeter

J/cm2

Also referred to as fluence and sometimes incorrectly as “energy density”.

Radiant energy density

Joule per cubic centimetre

J/cm3

This is the correct definition of “energy density”.

Radiant flux or radiant power

Watt

W or J/s

Radiant energy per time unit.

Radiant exitance (excitance) or Radiant emittance

milliWatt per square centimeter

mW/cm2

Radiant power/flux emitted from a surface (eg, a curing light). To be used instead of power density or irradiance when describing the output from a curing light.

Irradiance (incident irradiance)

 

milliWatt per square centimeter

mW/cm2

Radiant power/flux incident on a surface. This is what the resin receives.

Spectral radiant power

milliWatt per nanometer

mW/nm

Radiant power per wavelength.

Spectral irradiance

milliWatt per square centimeter per nanometer

mW/ cm2/nm

Irradiance received by the resin at each nanometer.