Research Article Open Access

Effect of Light Curing Units on Knoop Hardness of Resin-Modified Glass-Ionomer Cements

Abstract

Background: Different light curing units are used in the dental clinic, and they may produce different hardness values on the surface of resinmodified glass ionomer cements (RMGICs). The purpose of this study was to assess surface hardness of a nanofilled (KetacTM N100 - 3M/ESPE) and three commonly used RM GICs (VitremerTM- 3M/ESPE, Vitro Fil LC® - DFL, Resiglass® - Biodinamica) using two different light curing systems: quartz tungsten halogen (QTH) and light-emitting diode (LED).

Methods: Sixteen specimens of each material were made according to manufacturer’s instructions, inserted in disc-shaped molds (ø6mm; 2mm thick). The half (eight specimens) of each material were light cured using halogen light - Optilux 401, Demetron or LED- LEDemetron I, Kerr) for 20 seconds, with exception of Vitremer (40 seconds). The specimens were stored in artificial saliva for 24h, at 37ºC. The surfaces were wet polished. Five Knoop Hardness Number (KHN) measurements were taken from on the upper surface with 25 g load and 30s dwell time with a Knoop indentator each sample and 7 days after.

Results: The means of KHN after 7 days were (QTH; LED), respectively: Vitremer (44.12; 40.68); N100 (35.14; 29.02); Vitro Fill LC (29.10; 30.71); Resiglass (37.90; 26.80). Vitremer showed significantly higher KHN values. No significant difference was found between the KHN in relation to light unit.

Conclusions: The type of light source has no influence on surface hardness of RM GICs.

Fabiana Bucholdz Teixeira Alves, Thiago Saads Carvalho, Stella Kossatz Pereira, Gisele Fernandes Dias, Daniela Procida Raggio

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