Wavelength of Experimental LEDS: Hardness, Elastic Modulus, Degree of Conversion and Temperature Rise of a Microhybrid Composite

Ferreira, Ana Paula Bonilauri; Júnior, Paulo César Soares; Souza, E. M.; Rached, Rodrigo Nunes; Pezzin, Sérgio Henrique; Vieira, Sérgio

doi:10.1590/1516-1439.267514

Cited by 4 publications

(3 citation statements)

References 39 publications

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“…In this context, the DC results showed there are no statistically significant differences for the ratio between residual monomers for conventional and exponential photoactivation techniques. Although this result is, by itself, very important, we should consider that the DC might be associated with the hardness of the cured resin composite, since there is a high correlation between the two methods 7 , 18 . From this, it can be inferred that mechanical properties of the composite resins photoactivated by the proposed method are similar to those of the resins photoactivated by the conventional method.…”

Section: Discussionmentioning

confidence: 99%

Minimization of polymerization shrinkage effects on composite resins by the control of irradiance during the photoactivation process

et al. 2018

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High levels of shrinkage stress caused by volumetric variations during the activation process are one of the main problems in the practical application of composite resins. Objective The aim of this study is to reduce the shrinkage stress and minimize the effects caused by composite resin volumetric variation due to the photopolymerization. In this way, this work proposes a systematic study to determine the optimal dimming function to be applied to light curing processes.Material and Methods The study was performed by applying mathematical techniques to the optimization of nonlinear objective functions. The effectiveness of the dimming function was evaluated by monitoring the polymerization shrinkage stress during the curing process of five brands/models of composites. This monitoring was performed on a universal testing machine using two steel bases coupled in the arms of the machine where the resin was inserted and polymerized. The quality of the composites cured by the proposed method was analyzed and compared with the conventional photoactivation method by experiments to determine their degree of conversion (DC). Absorbance measurements were performed using Fourier-transform infrared spectroscopy (FT-IR). A T-test was performed on DC results to compare the photoactivation techniques. We also used scanning electron microscopy (SEM) to analyze in-vitro the adhesion interface of the resin in human teeth.Results Our results showed that the use of the optimal dimming function, named as exponential, resulted in the significant reduction of the shrinkage stress (~36.88% ±6.56 when compared with the conventional method) without affecting the DC (t=0.86, p-value=0.44). The SEM analyses show that the proposed process can minimize or even eliminate adhesion failures between the tooth and the resin in dental restorations.Conclusion The results from this study can promote the improvement of the composite resin light curing process by the minimization of polymerization shrinkage effects, given an operational standardization of the photoactivation process.

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Section: Discussionmentioning

confidence: 99%

Minimization of polymerization shrinkage effects on composite resins by the control of irradiance during the photoactivation process

et al. 2018

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“…This reaction will then have formed a hydrogen bond in between the HEMA polymer and polycarboxylic acid.1-5 If the photoinitiator does not absorb enough photons at an appropriate wavelength, polymerization may be impaired. 16 Previous study by Alpo AR et al 9 founded that there was no significant difference between the compressive strength of hybrid ionomer with the different curing times of 20 seconds and 40 seconds neither with light emitting diodes nor halogen. In the contrary, this study was found significant difference (p<0,05) in compressive strength of hybrid ionomer with the curing times 20,30,40 and 50 seconds by using light curing unit halogen.…”

Section: Discussionmentioning

confidence: 92%

“…9 Adequate polymerization is an important factor in obtaining the maximum mechanical properties of the resin based material. 16 Inadequate of polymerization will result in discoloration, pulp irritation and failure in restoration. 9 Polymerisation of hybrid ionomer consists of two reactions: the acid base reaction and the free radical reaction.…”

Section: Discussionmentioning

confidence: 99%

Effects of Curing Time on Compressive Strength of Hybrid Ionomer (In Vitro Study)

2017

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Objective: The aim of this study was to investigate the compressive strength of hybrid ionomer with different curing times which are 20 seconds, 30 seconds, 40 seconds and 50 seconds. Methods:This was an experimental laboratory study with posttest only group design. With the total of 24 samples of hybrid ionomer specimens with disk shape (5mm in diameter and 2mm in thickness) were prepared and polymerized using Quartz Tungsten Halogen (QTH) for each group (n=6) of different curing times 20 seconds, 30 seconds, 40 seconds and 50 seconds respectively. All samples were immersed in distilled water with a dark container and stored in incubator at 37°C for 24 hours before the test. Compressive strength test was done by Universal Testing Machine with crosshead speed of 0.5mm/min. All data were analyzed by one way -ANOVA. Results:The mean and standard deviation of the compressive strength of hybrid ionomer with the curing times 20seconds, 30 seconds, 40 seconds and 50 seconds were 45.6± 0.4648MPa, 46.8 ± 0.8165MPa, 48.5 ± 0.4037MPa, 50.2 ± 0.5193MPa respectively. Statistic analyze showed there was significant difference between the effect of curing time of the compressive strength of hybrid ionomer. Conclusion:The increase of curing times will result an increase of compressive strength of hybrid ionomer.

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A study on light transmittance through red protective shields modified with different window films

et al. 2017

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Objectives/Aims:This study aimed to improve effectiveness of red protective shields in filtering unwanted light using window films.Materials and Methods:Red protective shields were modified by placing V-Kool (VK), Scotchtint (ST) or Hüper Optik (HP) window films on both sides. Percentage transmittance (%T) of light with a wavelength of 190–990 nm was determined using a double-beam ultraviolet (UV) and visible spectrophotometer.Results:In UV light (190–390 nm) and visible light (430–590 nm) ranges, %T in all modified groups and the control was below 2.5%. An increase in %T was observed at the wavelength of 630 nm, when all the modified shields showed superior effectiveness in light filtration over the control. In the infrared spectrum (700–990 nm), %T in the control was constantly high, ranging from 86 to 91%, compared to %T of 2–38% in all the modified groups, with the application of VK on both sides being the most effective group, followed by a combination of VK and HP.Conclusion:This study has introduced an economical and simple, yet highly effective, means of enhancing the efficiency of a red plastic protection shield in filtering unwanted infrared light, thereby additionally providing protection for dental personnel from potential ocular damages.

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Wavelength of Experimental LEDS: Hardness, Elastic Modulus, Degree of Conversion and Temperature Rise of a Microhybrid Composite

Cited by 4 publications

References 39 publications

Minimization of polymerization shrinkage effects on composite resins by the control of irradiance during the photoactivation process

Minimization of polymerization shrinkage effects on composite resins by the control of irradiance during the photoactivation process

Effects of Curing Time on Compressive Strength of Hybrid Ionomer (In Vitro Study)

A study on light transmittance through red protective shields modified with different window films

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