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J Dent. 2015 Jul;43(7):814-22. doi: 10.1016/j.jdent.2015.04.009. Epub 2015 Apr 27.

In vitro comparison of polymerisation kinetics and the micro-mechanical properties of low and high viscosity giomers and RBC materials.

Author information

1
Department of Operative/Restorative Dentistry, Periodontology and Pedodontics, Ludwig-Maximilians-University of Munich, Goethestr. 70, 80336 Munich, Germany. Electronic address: nilie@dent.med.uni-muenchen.de.
2
Materials Science Unit, Dublin Dental University Hospital, Trinity College Dublin, Dublin, Ireland.

Abstract

OBJECTIVES:

The study aims to characterise a low and high viscosity giomer bulk fill resin restorative with established low and high viscosity resin-based composite (RBC) restoratives at simulated clinical relevant specimen depths.

METHODS:

The irradiance of a light curing unit (Bluephase 20i) was measured on a laboratory-grade spectrometer at distances up to 10mm from the light tip (in 1mm increments). Polymerization kinetics (real-time decrease of CC double bond and degree of cure, DC) and micro-mechanical properties (Vickers hardness/HV; Depth of cure/DOC; Indentation modulus/E) were assessed at varying specimen depths (0.1-6mm in 100μm steps for E, DOC and HV and 0.1, 2, 4 and 6mm for DC) for a 20s irradiation.

RESULTS:

One and two-way ANOVA (α=0.05) were performed. The parameter material has a significant (p<0.001) effect on DC (ηP(2)=0.839), HV (ηP(2)=0.683), and E (ηP(2)=0.536), whereas the specimen depth influenced only DC (ηP(2)=0.584) but not HV (p=0.093) or E (p=0.133). The polymerisation kinetic could be described by an exponential sum function, distinguishing between the gel and the glass phase. The hardness drop out was lower than 20%, indicated a depth of cure of 6mm for all materials.

CONCLUSIONS:

The low and high viscosity giomer bulk-fill restoratives fulfil the requirements of bulk-fill placement, since under the analysed irradiation conditions an adequate depth of cure of >4mm was identified. Variation of DC with specimen depth was low, with little variation at specimen depths of <4mm. The micro-mechanical properties of the giomer materials were higher compared with the conventional RBC materials.

KEYWORDS:

Bulk fill; Giomers; Hardness; Modulus of elasticity; Polymerisation kinetics; Resin based composite

PMID:
25930017
DOI:
10.1016/j.jdent.2015.04.009
[Indexed for MEDLINE]

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