Influence of LCU on Mechanical Characteristics of a Nano-Hybrid Composite

Aim of this investigation was to compare the influence of different curing lights (QTH vs. a high power LED) on the mechanical features of a nano-hybrid composite.

Method:

The evaluated LCUs were the QTH Translux Energy (Heraeus Kulzer, Germany) and the LED Valo (Ultradent, USA). QTH was operated for 20s (840 mW/cm²), LED was used for 2x4s (1200mW/cm²) followed by 3s (3200mW/cm²). The tested nano-hybrid composite was Venus Pearl HKA2.5 (VP, Heraeus Kulzer, Germany). Depth of cure (DC, n=5/LCU), flexural strength (FS, n=10/LCU), flexural modulus (FM, n=10/LCU) were determined according to ISO 4049. Compressive strength was evaluated according to DIN EN ISO 9917-1:2003 (n=6, 4mm diameter, 6mm height) after 23h water storage using a universal testing device. For Vickers hardness (HV, n=4/LCU) tests composite was filled into molds (diameter: 10mm, height 2mm). After light curing and 24h water storage hardness was measured on top and bottom surface and ratio between top and bottom surface was determined. Shrinkage stress (SS) was evaluated using the photoelastic method (n= 3) after 15min, 60 min, 1d and 7d water storage. Degree of conversion (DE) was measured using FTIR spectrophotometer immediately after curing, at 5min and 10 min at the bottom of a 2mm composite layer.

Statistics for each parameter were calculated with Mann-Whitney-U-tests (p≤0.05).

Result:

Table shows mean values and standard deviations (SD) of evaluated parameters:

No statistical significant differences between both lamps were found.

Conclusion:

Within the limitations of this study the tested type/mode/time of LCU had no influence on the mechanical characteristics of the investigated nano-hybrid composite. Both LCUs allow proper curing of VP.