Reporting of light irradiation conditions in 300 laboratory studies of resin-composites

Abstract

Objective: To evaluate how the light delivered to resin-composites was described in recent articles.

Method: PubMed was searched for 300 articles published between January 2017 and May 2018 with keywords relating to photocuring of dental materials. The articles examined a wide range of resin-composite properties and performance. For each article, the information provided about the light curing unit (LCU), the light curing conditions and the characteristics and quantity of the light used in the study were recorded. Specifically, the type of LCU used; the irradiance; how the irradiance was measured; the exposure times; whether the light energy (radiant exposure) received by the specimen was determined, or if only the light output at the LCU tip was measured; whether the distance between the tip of the LCU and the specimen was reported; and whether the emission spectrum from the LCU was reported. Where possible, the resin manufacturer's minimum energy requirement (MER: the product of the recommended minimum exposure time and irradiance) was compared to the radiant exposure delivered to the specimen.

Results: Of the 300 articles examined, 217 were published in 2017 and 83 in 2018. Of these articles, 130 (43%) were found in open access journals, and 170 (57%) were in subscription-based journals. The name of the LCU used was not provided in 31 articles, 14 articles did not provide the exposure time, and 227 articles did not report the distance to the specimen. An irradiance value was reported in 231 articles, but this was the irradiance received by the specimen in only 48 instances. The emission spectrum from the LCU was reported in 15 articles. There was a large range in the radiant exposures from below 10J/cm² to greater than 100J/cm².

Significance: The majority of articles from 2017 and early 2018 did not include sufficient description of the characteristics and quantity of the light received by the resin-composite specimens to allow the study to be replicated. It is recommended that future articles should report: (1) the identity of the LCU used; (2) the radiant exposure received by the specimen (J/cm²); and (3) appropriate reference to the emission spectrum from the LCU.

Keywords: Bond strength; Bulk fill; Light curing; Light measurement; Research reproducibility and replicability; Resins.