The effects of extended curing time and radiant energy on microhardness and temperature rise of conventional and bulk-fill resin composites
- 103 Downloads
To investigate radiant energy, microhardness, and temperature rise in eight resin composites cured with a blue or violet-blue curing unit, using a curing protocol which exceeded manufacturer recommendations.
Materials and methods
Cylindrical composite specimens (d = 8 mm, h = 2 or 4 mm, n = 5 per experimental group) were light-cured for 30 s. Light transmittance through specimens was recorded in real time to calculate radiant energy delivered to the specimen bottom. Vickers microhardness was used to evaluate the polymerization effectiveness at depth. Temperature rise at the bottom of the specimens was measured in real time using a T-type thermocouple.
Radiant energy delivered from the blue and violet-blue curing unit amounted to 19.4 and 28.6 J/cm2, which was 19 and 13% lower than specified by the manufacturer. Radiant energies at bottom surfaces (0.2–7.5 J/cm2) were significantly affected by material, thickness, and curing unit. All of the composites reached 80% of maximum microhardness at clinically relevant layer thicknesses. The benefit of using the higher-irradiance violet-blue curing unit was identified only in composites containing alternative photoinitiators. Temperature rise during curing ranged from 4.4 to 9.3 °C and was significantly reduced by curing with the lower-intensity blue curing unit and by increasing layer thickness.
Curing for 30 s, which can be regarded as extended considering manufacturer specifications, produced radiant energies which are in line with the recommendations from the current scientific literature, leading to adequate curing efficiency and acceptable temperature rise.
Extended curing time should be used to minimize concerns regarding undercuring of composite restorations.
KeywordsResin composites Radiant energy Microhardness Temperature Polywave Monowave
Composite materials Tetric EvoCeram and Tetric EvoCeram Bulk Fill and curing units were generously provided by Ivoclar Vivadent.
This work received no external funding.
Compliance with ethical standards
Conflict of interest
The authors declare no conflict of interest.
This article does not contain any studies with human participants or animals performed by any of the authors.
For this type of study, formal consent is not required.
- 3.Nomoto R, McCabe JF, Hirano S (2004) Comparison of halogen, plasma and LED curing units. Oper Dent 29(3):287–294Google Scholar
- 18.Ozturk B, Ozturk AN, Usumez A, Usumez S, Ozer F (2004) Temperature rise during adhesive and resin composite polymerization with various light curing sources. Oper Dent 29(3):325–332Google Scholar
- 19.Vandewalle KS, Roberts HW, Tiba A, Charlton DG (2005) Thermal emission and curing efficiency of LED and halogen curing lights. Oper Dent 30(2):257–264Google Scholar
- 20.Yap AU, Soh MS (2003) Thermal emission by different light-curing units. Oper Dent 28(3):260–266Google Scholar
- 24.Baldissara P, Catapano S, Scotti R (1997) Clinical and histological evaluation of thermal injury thresholds in human teeth: a preliminary study. J Oral Rehabil 24(11):791–801. https://doi.org/10.1111/j.1365-2842.1997.tb00278.x CrossRefGoogle Scholar
- 31.Price RB, Fahey J, Felix CM (2010) Knoop hardness of five composites cured with single-peak and polywave LED curing lights. Quintessence Int 41(10):e181–e191Google Scholar
- 33.Gomes M, DeVito-Moraes A, Francci C, Moraes R, Pereira T, Froes-Salgado N, Yamazaki L, Silva L, Zezell D (2013) Temperature increase at the light guide tip of 15 contemporary LED units and thermal variation at the pulpal floor of cavities: an infrared thermographic analysis. Oper Dent 38(3):324–333. https://doi.org/10.2341/12-060-L CrossRefGoogle Scholar
- 43.Rodrigues JA, Tenorio IP, Mello GBR, Reis AF, Shen C, Roulet JF (2017) Comparing depth-dependent curing radiant exposure and time of curing of regular and flow bulk-fill composites. Braz Oral Res 31:e65. https://doi.org/10.1590/1807-3107BOR-2017.vol31.0065 Google Scholar
- 47.Rueggeberg FA, Giannini M, Arrais CAG, Price RBT (2017) Light curing in dentistry and clinical implications: a literature review. Braz Oral Res 31(suppl 1):e61. https://doi.org/10.1590/1807-3107BOR-2017.vol31.0061 CrossRefGoogle Scholar
- 49.Lloyd CH, Brown EA (1984) The heats of reaction and temperature rises associated with the setting of bonding resins. J Oral Rehabil 11(4):319–324. https://doi.org/10.1111/j.1365-2842.1984.tb00582.x CrossRefGoogle Scholar
- 52.Runnacles P, Arrais CA, Pochapski MT, Dos Santos FA, Coelho U, Gomes JC, De Goes MF, Gomes OM, Rueggeberg FA (2015) In vivo temperature rise in anesthetized human pulp during exposure to a polywave LED light curing unit. Dent Mater 31(5):505–513. https://doi.org/10.1016/j.dental.2015.02.001 CrossRefGoogle Scholar