Effect of delivering light in specific narrow bandwidths from 394 to 515nm on the micro-hardness of resin composites.
OBJECTIVE
This study investigated the wavelength-dependent photosensitivity of eleven resin composites (Admira A2, Heliomolar A2, Herculite XRV A2, Pyramid Dentin A2, Solitaire 2 A2, Z250 A2, AElite LS A2, Vit-l-escence A2, Tetric Ceram Bleach XL, Tetric Ceram A2, Pyramid Enamel Neutral).


METHODS
Resin composites 1.6mm thick were exposed to narrow bandwidths of light at the following peak wavelengths: 394, 400, 405, 410, 415, 420, 430, 436, 442, 450, 455, 458, 467, 470, 480, 486, 493, 500, 505, and 515+/-5nm. A spectroradiometer was used to ensure that the same irradiance (mW/cm(2)) and total energy density (J/cm(2)) was delivered through each filter. For each resin composite, three specimens were exposed through each filter. The Knoop micro-hardness at the top and bottom of the composites was then measured. The wavelength-dependent photosensitivity of each resin composite was analyzed by plotting the mean hardness achieved at each wavelength.


RESULTS
The composites responded variably when they received light through the narrow bandpass filters. Six resin composites had a single peak of wavelength-dependent photosensitivity at approximately 470nm. Four resin composites had two peaks of wavelength-dependent photosensitivity at approximately 470 and approximately 405nm. One resin composite had a single peak of wavelength-dependent photosensitivity at approximately 405nm and was only sensitive to light below 436nm.


CONCLUSIONS
Using light delivered through narrow bandpass filters is a convenient method to determine the wavelength-dependent photosensitivity of resins and can be used to predict the performance of dental curing lights.
Price
Richard B T
RB
Department of Dental Clinical Sciences, Dalhousie University, Halifax, Nova Scotia B3H 1W2, Canada. rbprice@dal.ca
Felix
Corey A
CA
D000180:Acrylic Resins / Q000737:chemistry / Q000528:radiation effects; D003188:Composite Resins / Q000737:chemistry / Q000528:radiation effects*; D055117:Curing Lights, Dental / Q000145:classification; D003764:Dental Materials / Q000737:chemistry / Q000528:radiation effects*; D006244:Hardness; D006801:Humans; D008027:Light; D008422:Materials Testing; D008689:Methacrylates / Q000737:chemistry / Q000528:radiation effects; D055668:Photochemical Processes; D011108:Polymers / Q000737:chemistry / Q000528:radiation effects; D011140:Polyurethanes / Q000737:chemistry / Q000528:radiation effects; D011829:Radiation Dosage; D011874:Radiometry; D019279:Resin Cements / Q000737:chemistry / Q000528:radiation effects; D012833:Siloxanes / Q000737:chemistry / Q000528:radiation effects
D000180:Acrylic Resins; C485363:Aelite LS; D003188:Composite Resins; D003764:Dental Materials; C444701:Filtek Z250; C513708:Heliomolar; D008689:Methacrylates; D011108:Polymers; D011140:Polyurethanes; C428803:Pyramid Packable Composite; D019279:Resin Cements; D012833:Siloxanes; C469658:Solitaire 2 composite resin; C121818:Tetric ceram; C515948:Vit-l-escence Trans Ice; C479084:admira; C532950:tetric ceram bleach; C065770:Herculite XR