Microhardness of resin-based materials polymerized with LED and halogen curing units

Abstract

The purpose of this study was to evaluate the microhardness of resin-based materials polymerized with a LED (light-emitting diode) light-curing unit (LCU) and a halogen LCU. Twenty cylindrical specimens (3.0 mm in diameter and 2.0 mm high) were prepared for each tested material (Z100, Definite and Dyract). Specimens were light-cured with two LCUs (Ultraled and Curing Light 2500) for either 40 or 60 s on their top surfaces. Hardness was measured on top and bottom surfaces of each specimen. Statistical analysis was done by ANOVA and Tukey's test (p<0.05). There was no significant difference in hardness between LED LCU and halogen LCU for Z100 and Dyract on top surface. Conversely, lower hardness was recorded when Definite was light-cured with the LED LCU than with the halogen lamp. On bottom surface, hardness was significantly lower for all materials light-cured with LED LCU. Z100 was harder than Dyract and Definite regardless of the light curing unit. There was no significant difference in hardness between the exposure times on top surface. Higher hardness was obtained when the materials were light-cured for 60 s on bottom surface. The tested LED was not able to produce the same microhardness of resin-based materials as the halogen LCU.

Post-irradiation vickers microhardness development of novel resin composites

“…Therefore, this high-density network of organic matrix together with the presence of hard-glass fillers yielding a hard structure may result into superior surface hardness of the ormocer composite 8 . This is almost in agreement with Cefaly's study found that Definite-ormocer was significantly hard, but in contradiction with the finding of Manhart 37,38 . On the other hand, the nanohybrid Tetric Evoceram composite presented the less hard material compared to Filtek ® P90 and Definite.…”

Análise Comparativa da Microdureza Superficial e Profunda entre uma Resina Composta Microhíbrida e uma Resina Composta de Nanopartículas

“…Não havendo, assim, praticamente nenhuma interferência na transmissão de luz, a qual atinge a área superficial com a maior intensidade possível. Entretanto, para o fundo (base), a luz primeiramente atravessa todo o corpo da resina composta e sendo, então, parte absorvida ou refletida; atenuando a intensidade e reduzindo a efetividade de fotoativação e consequente polimerização nas porções mais profundas do material acarretando, assim, um menor valor de microdureza Vickers [18][19][20][21] . Os valores de microdureza obtidos por um material resinoso são influenciados pelo grau de conversão dos monômeros em polímeros, mas também pela composição da matriz orgânica, pelo tipo, pelo volume e percentual das partículas de carga 6.22 .…”

Influência do tipo de ponteira condutora de luz na microdureza de uma resina composta

“…Os testes de microdureza têm sido utilizados em vários estudos como um método viável para avaliar a relativa profundidade de polimerização das resinas compostas e conseqüentemente a eficiência da fonte de luz [5,11,2,23] . Portanto, neste estudo, a microdureza foi usada como um mensurador indireto da profundidade de polimerização da resina composta utilizada.…”