Curing efficiency of modern LED units

Abstract

Recent reports claim that modern light-emitting diode (LED) curing units improve curing efficiency by increasing the units' irradiance. In this context also, short polymerisation times up to 5 s are proposed. The aim of this study was to examine whether there are differences in the curing efficiency of modern LED curing units by assessing their effect on two different composite materials and by varying the irradiation time. A nano- and a micro-hybrid resin-based composite (RBC) were polymerised for 5, 10 and 20 s with three commercial and a Prototype LED unit (Elipar™ S10). Cylindrical specimens (6 mm in depth, 4 mm in diameter) were prepared in three increments, each 2-mm thick, and were consecutively cured. Degree of cure was measured for 20 min in real time at the bottom of the samples, starting with the photoinitiation. The micro-mechanical properties (modulus of elasticity, E and Vickers hardness, HV) were measured as a function of depth, in 100-μm steps, on the above described samples stored in distilled water for 24 h at 37°C. Data were analysed with multivariate ANOVA followed by Tukey's test, t test and partial eta-squared statistics. In descending order of the strength of their effect, the type of RBC, depth, polymerisation time and curing unit were significant factors affecting the micro-mechanical parameters (p < 0.05). The degree of cure at 6-mm depth was less but significantly influenced by the curing unit and curing time and was independent from the type of RBC. A 5-s irradiation time is not recommended for these units. Whereas a 5-s irradiation is acceptable at the sample's surface, a minimum of 20 s of irradiation is necessary for an adequate polymerisation 2 mm beyond the surface.

Seramik restorasyonların mikrosızıntısı üzerine yüksek yoğunluklu LED işık kaynağı mesafesinin değerlendirilmesi

“…Resin cements should be adequately cured during ceramic restoration in order to ensure good biological and physical properties (Alpöz et al camphorquinone (CQ), the most frequently used photoinitiator in resin composites. In general, LED lights have the following advantages: extended lifetimes of more than 10,000 hours, little light output degradation over time, and resistance to shock and vibration (Rencz et al 2012). High-intensity LED curing units are claimed to reach irradiances of 2.000-3.200 mW/cm 2 , depending on the selected mode of use (Rueggeberg 2011).…”

“…Third generation LED curing units that have multiple diodes (violet/blue diodes, polywave), which therefore affect curing of CQ containing cements and those containing its other alternatives, have been introduced to the market recently (Rueggeberg 2011). Shorter irradiation periods are reportedly adequate in most of the recently introduced high-power LED units (Rueggeberg 2011, Rencz et al 2012). …”

Atenuação da intensidade de luz e profundidade de polimerização de resinas compostas

“…Porém, vários parâmetros devem ser observados e respeitados para que o material final alcance as propriedades esperadas. Dentre eles destacam-se: intensidade de luz, tempo de exposição, comprimento de onda adequado para sensibilizar a molécula da canforoquinona, distância entre a ponta do aparelho fotopolimerizador e a resina, bem como a formulação do material [2][3][4][5][6] . Entretanto, quando a luz atinge o material, vários fenômenos podem ocorrer, incluindo absorção, reflexão e dispersão.…”

“…Entretanto, quando a luz atinge o material, vários fenômenos podem ocorrer, incluindo absorção, reflexão e dispersão. Isto significa que apenas uma parte da radiação luminosa pode ser transmitida pelo material 3,5,7 . Como consequência, regiões mais profundas receberão menor quantidade de luz, o que pode reduzir ou impedir que a reação de polimerização ocorra 5,6 .…”

“…Isto significa que apenas uma parte da radiação luminosa pode ser transmitida pelo material 3,5,7 . Como consequência, regiões mais profundas receberão menor quantidade de luz, o que pode reduzir ou impedir que a reação de polimerização ocorra 5,6 . Estes fatores resultam na atenuação da luz à medida que atravessa o material, fazendo com que na superfície da restauração a polimerização seja maior do que nas regiões mais profundas, desta forma, determinando a profundidade de polimerização do material 6,8 .…”