Effect of light curing units on the polymerization of bulk fill resin-based composites

• Published in: Dental materials Vol. 34; no. 8; pp. 1211 - 1221
• Main Authors: Shimokawa, Carlos Alberto Kenji, Turbino, Míriam Lacalle, Giannini, Marcelo, Braga, Roberto Ruggiero, Price, Richard Bengt
• Format: Journal Article
• Language: English
• Published: England Elsevier Inc 01-08-2018; Elsevier BV
• Subjects: Bulk polymerization; Composite resins; Composite Resins - chemistry; Curing; Curing Lights, Dental; Dental curing lights; Dental equipment; Dental restorative materials; Dentistry; Emittance; Hardness testing; Hardness Tests; Light beams; Light distribution; Light effects; Light transmission; Light-Curing of Dental Adhesives - methods; Materials Testing; Microhardness; Photoactivation; Polymer matrix composites; Polymerization; Surface Properties; Variance analysis; Polymerization; Hardness tests; Composite resins; Dental curing lights
• ISSN: 0109-5641; 1879-0097
• DOI: 10.1016/j.dental.2018.05.002

•The characteristics of LCUs influence the polymerization of bulk fill RBCs.•Very little violet light reaches through to the bottom of 4mm of bulk fill RBC.•Wide tips delivering a homogeneous light output are preferred to photoactivate bulk fill RBCs.•It may be necessary to photo-cure bulk fill RBCs from more than one location.
To determine the potential effect of four different light curing units (LCUs) on the curing profile of two bulk fill resin-based composites (RBCs).
Four LCUs (Bluephase 20i, Celalux 3, Elipar DeepCure-S and Valo Grand) were used to light cure two RBCs (Filtek Bulk Fill Posterior Restorative and Tetric EvoCeram Bulk Fill). The effective tip diameter, radiant power, radiant emittance, emission spectrum and light beam profile of the LCUs were measured. Knoop microhardness was measured at the top and bottom surfaces of RBC specimens that were 12-mm in diameter and 4-mm deep (n=5). The distribution of the spectral radiant power that was delivered to the surface of the specimen and the light transmission through the 4-mm thick specimens was measured using an integrating sphere. Two-way ANOVA and Tukey tests (α=0.05) were applied.
The Valo Grand produced the most homogeneous microhardness across the surfaces of the RBCs (p>0.05). When the Celalux 3, Bluephase 20i and Elipar DeepCure-S lights were used, the center of the specimens achieved greater hardness values compared to their outer regions (p<0.05). Approximately 10% of the radiant power delivered to the top reached the bottom of the specimen, although almost no violet light passed through 4mm of either RBC. A positive correlation was observed between the radiant exposure and microhardness.
The characteristics of the LCUs influenced the photoactivation of the RBCs. The use of a wide tip with a homogeneous light distribution is preferred when light curing RBCs using a bulk curing technique.