Light Curing Effectiveness of Two Liners/Bases

Objectives: The effectiveness of light-curing two liner/base materials to their recommended depth of cure was compared when the curing light was in direct contact and when it was at a clinically relevant distance.
Methods: A 1-mm thick PTFE mold with a 7-mm diameter hole was placed on top of a PET film. Liner/base material was placed into the hole and another piece of PET film was placed on top of the mold. The mold was hand-pressed to ensure there were no bubbles or voids, and the material was light cured on a white background.

Light curing was performed for 20 seconds using a 3M™ Elipar™ DeepCure-S LED Curing Light rigged to 1000 mW/cm². Five minutes after light curing had finished, hardness was measured on the top and bottom of the sample using a Barcol Hardness Test Impresser Device (GYZJ 935), and the ratio of the hardness of the bottom to the top was calculated to determine light-curing effectiveness. Testing was performed with the curing light directly on top of the sample and with the light approximately 7-mm above the sample.

The following liner/bases were tested: Experimental Liner/Base from 3M (EXP) and BISCO TheraCal LC® Resin-Modified Calcium Silicate Pulp Protectant/Liner (TLC).
Results: The mean values for Barcol Hardness at the top and bottom of the samples, the ratio of bottom hardness to top hardness (B/T Ratio), and standard deviations can be seen below. Data was analyzed using one-way ANOVA with a 95% confidence using Tukey method.
Conclusions: The EXP liner/base had a significantly higher B/T Ratio than TLC, at both 0-mm and 7-mm curing light distance, suggesting EXP was more effectively light-cured than TLC. A B/T ratio below 80% is commonly considered not effectively cured, suggesting that 1-mm of TLC may not be effectively cured when the curing light is at a clinically-relevant 7-mm distance.