The brackets were fixed on the tooth surface with a bracket placing plier (3M unitek) and the excess material was removed with a scaler and light-cured for 40 seconds with alight-emitting diode(LED) light-curing unit
at 800mW/cm2 (Demi LED Light Curing System, Kerr Corp, Orange, CA, USA) from a 5mm distance.
Multicore buildups (3mmx3mm) were performed using a rubber mold on the ceramic surfaces and cured using LED light-curing unit
For the photopolymerization process to be effective, the spectral radiant power of the light-curing unit
must fall within the spectral range required to activate the photoinitiator present in the resin .
Light-cured resin cement allows enough working time for clinicians before polymerizing it with light-curing unit
, but it is difficult to cure the resin cement in the areas that are far from the light source.
In Group 2, after placement in the mold the specimens were irradiated for 60 sec at the top surface using a dental LED light-curing unit
(Valo, Ultradent, South Jordan, UT, USA) operating at 1400mW/[cm.sup.2] with standard curing mode and wavelength range 395-480 nm.
After the light-transmitting post is reinserted, the adhesive is cured for 10 seconds with a suitable light-curing unit
. The light-transmitting post is again removed.
(1,2) Even though the mechanical and optical properties of the ceramic materials are important, many variables may contribute to the predictability and clinical longevity of all-ceramic restorations, including the adhesive and luting system used, the curing mechanism, the light-curing unit
, and the microstructure and thickness of the ceramic.
For polymerization, a conventional quartz tungsten halogen light-curing unit
(XL 2500, 3M ESPE, USA) calibrated at 500 m W/ [cm.sup.2] was used from a distance of 0.5 mm from its outer surface.
Woodpecker LED.B light-curing unit
(Guilin Woodpecker, China) at a light intensity of 1100 mW/ cm2 with an irradiated diameter of 10 mm was used to photo-cure composite samples.
Another consideration in relation to the degree of polymerization of resin-luting agents is the intensity of the light-curing unit
. In several studies, the curing efficacy of halogen and LED curing units has been compared.