Polymerization depths of conventional and bulk fill composites photoactivated by different methods

Willian Fernando Felipe,Milton Edson Miranda,William Cunha Brandt,Karina Andréa Novaes Olivieri,Weverteon Soares De Oliveira,Rafael Pino Vitti

doi:10.1590/s1517-707620200003.1124

Willian Fernando Felipe, Milton Edson Miranda + Show 4 more

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https://doi.org/10.1590/s1517-707620200003.1124

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Abstract

The aim of this study was to evaluate the depth of cure of conventional (Filtek Z350 and Esthet-X HD) and bulk fill resins composites (Filtek bulk fill flow and SDR) using different photoactivation methods. Samples were made using five discshaped matrices (1 mm high and 8 mm central diameter) with interposed polyester strips. The samples were photoactivated using different methods [continuous high-irradiance light (LCA), continuous low-irradiance light (LCB), and soft-start (SS)], maintaining 24 J/cm² radiant exposure. After 24h, Knoop microhardness test was performed at 5 depths (surface, 1 mm, 2 mm, 3 mm and 4 mm). The Knoop microhardness were analyzed by ANOVA two-way and Tukey’s test (5%). Conventional resins presented the highest results up to 2 mm depth, except for Esthet-X photoactived by LCB, which showed significant lower Knoop hardness from 2 mm depth. Bulk fill resins photoactivated with LCA and SS had the highest results in 4 mm depth. The LCA and SS photoactivation methods produce suitable photoactivation in conventional composites up to 2 mm and bulk fill up to 4 mm depth and the bulk fill composites present higher polymerization depth than conventional composites. Keywords: Dental curing lights; hardness test; photoactivation; polymerization; resin

Highlights

The optical properties and the adhesion capacity to the dental structures, provide wide utilization of composite resins in restorative dentistry [1]
Bulk fill resins photoactivated with LCA and SS had the highest results in 4 mm depth
The restoring technique involves the application of composite resin increments of up to 2 mm of thickness, in order to allow correct photoactivation of the increment and minimize the shrinkage and shrinkage stress resulting from the material polymerization process [2]

Summary

Introduction

The optical properties and the adhesion capacity to the dental structures, provide wide utilization of composite resins in restorative dentistry [1]. The restoring technique involves the application of composite resin increments of up to 2 mm of thickness, in order to allow correct photoactivation of the increment and minimize the shrinkage and shrinkage stress resulting from the material polymerization process [2]. The incremental technique is relatively sensitive and demands a considerable chair time These factors associated to clinical problems of the restorations, such as post-operative sensitivity, fissure formation on the tooth/restauration interface, marginal pigmentation, secondary caries, cusp deflection, fractures of the enamel edges, displacement of the restoration, and dental element fracture; encourage the development of new composite resins in an attempt to overcome these problems [3, 4]. Bulk fill composite resins have modified resinous monomers and reduction in the size for the filler particle [5-8]

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