Hardness of a bleaching-shade resin composite polymerized with different light-curing sources

Abstract

The microhardness of a bleaching-shade resin composite polymerized with different light-curing units was evaluated. Composite samples (3M ESPE Filtek Supreme) were applied to brass rings (2 mm in thickness, 5 mm in diameter). Three commercial LED lights were used to polymerize the specimens and the results were compared to those of a conventional halogen light. The light sources used in the present study were: Demetron Optilux 401 (QTH), 3M ESPE Elipar FreeLight (LED 1); Kerr L.E. Demetron I (LED 2), and ColtoluxLED lights (LED 3). The microhardness of the top and bottom surfaces was assessed with a digital Vickers hardness-measuring instrument, under load. At the bottom surface, no significant difference among the light sources was observed (two-way ANOVA). At the top surface, the QTH light source presented significantly higher hardness values compared to the values observed when LED 1 and LED 3 were used. There were no significant differences between the QTH and LED 2 light sources. Significantly higher hardness values were also found at the top surface when compared to the values observed at the bottom surface. The power density of the polymerization light sources seemed to be responsible for the observed resin composite hardness, not their irradiance.

Knoop microhardness and FT-Raman evaluation of composite resins: influence of opacity and photoactivation source

“…8 The translucent resin (shade YT) showed no statistical differences between QTH or LED activation, and these results are similar to those of the present study, which showed similar KHN values independently of the light source. 25 Higher KHN values at a 2-mm depth have been reported for Charisma samples activated by LED 26 rather than by QTH. Nevertheless, these values are not in agreement with the values achieved in the present study; one probable explanation for this difference is the lower irradiance values in the prior study.…”

Hardness Evaluation of Composite Resins Cured with QTH and LED

“…They replace it with other initiator materials such as Phenyl propan dion (PPD) with absorbable spectrum of 410 nm or Bisacylphosphine oxide and Tribisacylphosphine oxide with absorbable spectrum of 320-390 nm. Gomes et al 14 said that combination of PPD and CQ together acts synergistically. In the first and the second versions of LEDs which have a narrow spectrum output (450–490 nm), some bondings and composites which use non-CQ photoinitiator may face with polymerization problems.…”

“…In the first and the second versions of LEDs which have a narrow spectrum output (450–490 nm), some bondings and composites which use non-CQ photoinitiator may face with polymerization problems. 13,14,16,18,19 As far as manufacturers do not state all photoinitiators’ combinations of their products, the efficiency of light cure devices in some composites is not predictable. …”

“…In contrast, indirect tests such as scraping test and hardness test are inexpensive and easier to conduct. 5,9-11,13,14 Surface hardness is defined as resistance to surface indentation and it is an indirect method for measuring the degree of polymerization. …”

“…Many studies have investigated the effect of light curing units on the hardness of composite resins, but different results have been obtained. 8,10-12,14 The aim of this study was hardness evaluation of two composite resins cured by halogen and new LED devices. It was hypothesized that various light curing units have different effects on composite hardness.…”