<p>Mechanical properties of experimental resin cements containing different photoinitiators and co-initiators</p>

Abstract

AimThe aim of this study was to evaluate the influence of different concentrations of two photoinitiators and one co-initiator on the flexural strength (FS) and elastic modulus (E) of experimental resin cements.Materials and methodsA mixture containing BisGMA, TEGDMA, and barium-aluminum-silicate (BaAlSi) and silanized colloidal silica (SiO2) filler particles was prepared with two photoinitiators, viz. camphorquinone (CQ) and bisacylphosphine oxide (BAPO). Dimethylaminoethyl methacrylate (DMAEMA) was used as co-initiator. Thirty groups (n=10) were formulated with different photoinitiator systems (CQ/DMAEMA and BAPO/DMAEMA) and concentrations (wt%) of photoinitiator and co-initiator. The photoactivation was carried out for 20 s with a light-emitting diode (LED, Bluephase, Ivoclar Vivadent) with irradiance of 1200 mW/cm2. The FS and E were obtained in a three-point bending test on a universal testing machine (0.5 mm/min). Data were subjected to the Kolmogorov-Smirnov normality test, followed by two-way ANOVA and Tukey’s test (α=0.05).ResultsNo polymerization occurred in the CQ groups without DMAEMA (0 wt%). DMAEMA 0.5 %wt and 1 %wt groups showed statistically similar FS and E results for CQ and BAPO, except for CQ 0.3 wt% (FS), CQ 0.9wt% (E) and BAPO 1.76 wt% (FS and E) for DMAEMA 0.5 %wt. No significant difference was found for FS and E values for different concentrations of photoinitiators, except for CQ 0.25 wt% (FS and E) and BAPO 0.25 wt% (E) that showed the lowest values.ConclusionThe wt% of the photoinitiators and co-initiator influenced the mechanical properties and the performance of CQ was dependent on the DMAEMA concentration. BAPO can be used as substitute for the conventional CQ/DMAEMA photoinitiator system.

Effect of Photoinitiator Type and Photoactivation Condition on the Physical-Mechanical Properties of Orthodontic Resins

“…A better performance of the BAPO group was also observed through the mechanical properties analysis, showing results consistent to those found in similar studies 16,28 . The results can be justified by their polymerization reaction independent of the presence of a co-initiator (amine), allowing a fast photolysis of its molecule for free radical generation and greater molar extinction coefficient in relation to PPD and CQ.…”

Efectividad de fotopolimerización usando lámparas led: Una revisión de la literatura

“…De igual manera, entre las desventajas que presenta esta lámpara se encuentran el ruido que emite, su alto costo y su tamaño, que la hace poco práctica para transportar 19 . Las lámparas de tipo argón poseen una intensidad de 800 mw/cm 2 y un rango de onda de 476,5 a 480 nm, compatibles con los materiales que presentan como fotoiniciador a la canforoquinona 20 , pero son poco utilizadas porque emiten mucho calor y generan contracción de fotopolimerización elevada en los materiales 21 . A finales de los 90, aparecieron las primeras lámparas de diodo emisor de luz (lámparas led), que comenzaron a utilizarse en la odontología como lámparas de fotopolimerización.…”

From resin formulation and process parameters to the final mechanical properties of 3D printed acrylate materials

“…[60] They shed light on the different induction periods or conversion rates obtained depending on the nature of the photoinitiator. [58,60,61] Moreover, not only the nature but also the concentration of the photoinitiator influences the printing parameters. Indeed, with a lower amount of photoinitiator, longer exposure times are needed to reach the same layer thickness.…”

“…This shows a direct link between the photoinitiator content and mechanical properties. [61,63,64] Wang et al tried to optimize the concentration of the camphorquinone photoinitiator in their acrylate-based resin to achieve the best mechanical properties. [65] They observed that the degree of conversion (obtained by near-infrared spectroscopy), the mechanical properties (elastic modulus and hardness), as well as the curing depth D p (in Jacobs' law) were maximized for an optimum photoinitiator concentration.…”

“…Lima et al [61] Existence of an optimum amount of photoinitiator that maximizes hardness Musanje et al [63] Nature and concentration of photoinitiator influences yield strength. Maximum yield strength obtained for 1.18 wt % TPO-L Steyrer et al [64] Photoabsorber Decrease in compression strength (2.2 MPa to 0.1 MPa with a dye concentration from 0.025 to 0.075 wt%)…”