Effect of instruction, light curing unit, and location in the mouth on the energy delivered to simulated restorations.

Purpose: To determine the amount of energy (Joules/cm²) delivered by students to simulated restorations in a patient simulator based on the restoration location, the curing light unit used, and before vs. after instruction on how to improve their light curing technique.

Methods: 30 dental students "light cured" two simulated restorations (that were 1-mm deep anterior and 4-mm deep posterior) using three light-curing units (LCUs) : VALO, Bluephase G2, and Optilux 401. A MARC Patient Simulator was used to measure the irradiance (mW/cm²) received by the restorations in real-time to calculate the radiant exposure (J/cm²) delivered during a 20-second exposure. At first, students were asked to use the light curing technique that they had been previously taught. They were then given 5 minutes of additional verbal instructions and a practical demonstration on proper curing technique using the patient simulator. They then light cured the restorations again. Based on a literature review, 16 J/cm² was considered the minimum acceptable radiant exposure.

Results: Before receiving instruction using the simulator, some students delivered as little as 4 J/cm² to the restoration. A mixed model test determined that the radiant exposure delivered to the anterior restoration was significantly greater than that delivered to the posterior restoration (Plt; 0.001). Additionally, when the locations were compared for each LCU individually, a paired t-test determined that before the students received the additional instruction, the anterior restoration received a significantly greater radiant exposure than the posterior restoration, for all three LCUs. Further paired t-tests and Wilcoxon signed-rank tests determined that after instruction, the radiant exposure improved significantly at both the anterior and posterior locations, for all three LCUs. The Bluephase G2 and the VALO each individually delivered 45% more radiant exposure than the Optilux 401 (P< 0.001 for both). The Bluephase G2 and VALO lights delivered similar mean radiant exposures (25.4 J/cm² and 25.7 J/cm², respectively). This difference was not significant. Depending on the light unit used, at the posterior location, there was a 24 to a 52% increase in the mean radiant exposure that was delivered after instruction compared to before instruction.

Clinical Significance: Prior to using the patient simulator, students and their instructors thought that the students were delivering an adequate amount of energy when light curing. This was not always the case. The location of the restoration, the curing light output, its size and shape and how it is used all affected the amount of energy delivered to a restoration. Dental professionals and educators should be aware that appropriate training can improve the amount of energy delivered, and that restorations in posterior teeth will require longer exposure times than those in anterior teeth.