Factors Affecting the Energy Delivered to Simulated Class I and Class V Preparations(4)

Approval for the study was obtained from the Dalhousie University Health Sciences Research Ethics Board. The Research Ethics Board required that all the participants remain anonymous.

The MARC device for measuring both irradiance and energy received at the pre

paration site was constructed by fixing a 3.9-mm diameter cosine corrected irradiance probe (CC3-UV, Ocean Optics, Dunedin, FL) at the bottom of 2 different types of cavity preparations (Fig. 1) within a dentoform (NIS-SIM simulation head, Kilgore, Coldwater, MI) attached to a dental chair. The teeth were fixed to the dentoform with epoxy resin. For the Class I preparation, the detector was fixed inside tooth 26, with epoxy resin 2 mm deep from the occlusal surface and 4 mm from the cusp tips. For the Class V preparation, the detector was fixed 2 mm from the buccal surface of tooth 37. A laboratory-grade spectroradiometer (USB 4000, Ocean Optics) was attached to the probes using a bifurcated fibre optic cable (Avantes, Broomfield, CO) to determine the light irradiance (mW/cm²) delivered from the commercial curing lights during simulated photo-curing of the resin at the floor of the preparation. Before use, the equipment was calibrated for both frequency and irradiance using a light source (LS-1-CAL, Ocean Optics) with a National Institute of Standards and Technology (NIST; Gaithersburg, MD) traceable light source. The equipment was zeroed to the ambient light before each recording, and the absolute error in calibrating the spectroradiometer was ± 5%. The mouth opening was fixed at 43 mm, as measured at the incisors.⁴³

Twenty operators (10 dentists and 10 fourth-year dental students) were instructed to position the head of the mannequin as they would position a patient's head and then to perform simulated light-curing for 10 seconds on each of the 2 preparations with a variety of commercially available blue LED-type curing lights: the VALO unit (Ultradent Products, South Jordan, UT) used in the standard mod