An e le c tro n ic device used to polym erize a sealant and a co m p o site resin has been fo u n d to em it 365-nanom eter ra diation at levels s u ffic ie n t to kill the bacterium Escherichia c o li rapidly (>14,000 ergs per square m illim e te r per second). Because of the absence of s h ie ld in g on the probe, s ig n ific a n t am ounts of energy (up to 45% of th a t at the probe tip) were m easured at th e sides o f the probe. These fin d in g s — supported by th e w ell-d o cu m e n te d fin d in g s of b io lo g ic a l dam age caused by n e a r-u ltra vio le t radiation, in c lu d in g skin cancer, dam age to th e lens of th e eye, and m u ta g e n ic effects— suggest that clin ic ia n s take a p p ro p ria te p recaution s to avoid p o tentia l hazards to them selves and th e ir patients.
Harmful effects of near-ultraviolet radiation used for polymerization of a sealant and a composite resin Dale C. Birdsell,
PhD, G ainesville, Fla
Patrick J. Bannon, Robert B. Webb,
DDS, M ayw ood, III
PhD, A rg o n n e , III
E lectronic devices * t emitting radiation in the near-ultraviolet range (320-400 nm) recently have been introduced to the dental profession to polym erize a resin sealant and a com posite restorative m aterial. K nown biological effects of near-ultraviolet light include skin c a n c e r,1 alteration of eye lens and aqueous hum or pro tein ,2 induction of thym ine-thym ine dim ers,3 lethality for bacterial cells4 and mammalian cells,5 m utagenesis in bacteria,6 inactivation of transform ing D N A ,7 and destruction of photoreactivating enzym e.8 It w as, therefore, appro priate to exam ine the emission spectrum , total radiant em ission, and biological effects of light energy em itted by the N uva-L ite. This device is in w idespread use by the dental profession.
M e th o d s
T w o N uva-L ite activator lamps were examined: lamp A was newly purchased (in use less than ten hours) and lamp B had been used extensively (in excess of 100 hours). T he em ission spectrum was m easured with a
calibrated G am m a Scientific R adiom eter^ at constant entrance and exit slit widths of 1.34 mm and 0.75 mm respectively (band w idth, 2 nm). T otal radiant flux density was determ ined with a calibrated radiom eter. § Stationary-phase cells of Escherichia coli K12 AB2480 (uvrA-6, r e c A -13) w ere obtained from nutrient agar plates, w ashed tw ice and dil uted in M9 salts buffer to give a concentration of 107 cells per milliliter for irradiation. T he cell suspension was irradiated in a 1-cm square quartz vessel and stirred by bubbling moist air. Lam p A was used at a distance of 6 mm from tip to center of vessel (irradiance at 6 mm was 9,000 ergs p er square millim eter per second). A ppro priate dilutions of the irradiated sam ples w ere plated in triplicate on nutrient agar plates and scored for survivors after tw o d ay s’ incubation at 37 C.
R e s u lts
The em ission spectrum o f lamp A is shown in Figure 1. T w o peaks of em ission were observed, JADA, Vol. 94, February 1977 ■ 311
RELATIVE
EMISSION
TO TAL EMISSION
DISTANCE , cm Fig 2 ■ Total radiant flux density emitted by Nuva-Lite as function of distance from surface at end of probe. W AVELENGTH,
nm
Fig 1 ■ Emission spectrum of Nuva-Lite.
at 365 nm (approxim ately 71% of the total em is sion) and at 405 nm (approxim ately 26% of the total em ission). Em ission was less than 0.1% of the 365-nm value at w avelengths below 350 nm. A small peak was detected at 334 nm (0.07% of the 365 nm value). Em ission was below detec tion (
Harmful effects of near-ultraviolet radiation used for polymerization of a sealant and a composite resin Dale C. Birdsell,
PhD, G ainesville, Fla
Patrick J. Bannon, Robert B. Webb,
DDS, M ayw ood, III
PhD, A rg o n n e , III
E lectronic devices * t emitting radiation in the near-ultraviolet range (320-400 nm) recently have been introduced to the dental profession to polym erize a resin sealant and a com posite restorative m aterial. K nown biological effects of near-ultraviolet light include skin c a n c e r,1 alteration of eye lens and aqueous hum or pro tein ,2 induction of thym ine-thym ine dim ers,3 lethality for bacterial cells4 and mammalian cells,5 m utagenesis in bacteria,6 inactivation of transform ing D N A ,7 and destruction of photoreactivating enzym e.8 It w as, therefore, appro priate to exam ine the emission spectrum , total radiant em ission, and biological effects of light energy em itted by the N uva-L ite. This device is in w idespread use by the dental profession.
M e th o d s
T w o N uva-L ite activator lamps were examined: lamp A was newly purchased (in use less than ten hours) and lamp B had been used extensively (in excess of 100 hours). T he em ission spectrum was m easured with a
calibrated G am m a Scientific R adiom eter^ at constant entrance and exit slit widths of 1.34 mm and 0.75 mm respectively (band w idth, 2 nm). T otal radiant flux density was determ ined with a calibrated radiom eter. § Stationary-phase cells of Escherichia coli K12 AB2480 (uvrA-6, r e c A -13) w ere obtained from nutrient agar plates, w ashed tw ice and dil uted in M9 salts buffer to give a concentration of 107 cells per milliliter for irradiation. T he cell suspension was irradiated in a 1-cm square quartz vessel and stirred by bubbling moist air. Lam p A was used at a distance of 6 mm from tip to center of vessel (irradiance at 6 mm was 9,000 ergs p er square millim eter per second). A ppro priate dilutions of the irradiated sam ples w ere plated in triplicate on nutrient agar plates and scored for survivors after tw o d ay s’ incubation at 37 C.
R e s u lts
The em ission spectrum o f lamp A is shown in Figure 1. T w o peaks of em ission were observed, JADA, Vol. 94, February 1977 ■ 311
RELATIVE
EMISSION
TO TAL EMISSION
DISTANCE , cm Fig 2 ■ Total radiant flux density emitted by Nuva-Lite as function of distance from surface at end of probe. W AVELENGTH,
nm
Fig 1 ■ Emission spectrum of Nuva-Lite.
at 365 nm (approxim ately 71% of the total em is sion) and at 405 nm (approxim ately 26% of the total em ission). Em ission was less than 0.1% of the 365-nm value at w avelengths below 350 nm. A small peak was detected at 334 nm (0.07% of the 365 nm value). Em ission was below detec tion (
