Blue Laser for Polymerization of Bulk Fill Composites: Influence on dentin bond strength and temperature rise during curing and co-curing method.

Blue diode lasers are alternative curing devices for dental composites. The aim of this study was to investigate the influence of blue diode laser polymerization on shear bond strength of bulk fill composites to human dentin and temperature rise during two types of polymerization. Composite cylinders of SDR Plus(SDR) and Ever X Flow(EX) were bonded to dentin slabs using Adhese Universal and curing devices blue diode laser (449 nm, 1.6 W) and Power Cure LED. For each material and curing device there were two polymerization approaches: 1)conventional: separate curing of adhesive; 2)co-curing: simultaneous adhesive and composite curing. Polymerization modes for each material in conventional and co-curing(c) approach were: blue laser 2000 mW/cm2 for 5 s (L5 and L5c); blue laser 1000 mW/cm2 for 10 s (L10 and L10c); Power Cure 2000 mW/cm2 for 5 s (LED5 and LED5c); Power Cure 1000 mW/cm2 for 10 s (LED10 and LED10c). Temeperature was measured using thermal vision camera. For SDR, the highest bond strength was 24.3 MPa in L10c, and the lowest 9.2 MPa in LED5c. EX exhibited the highest bond strength(21.3 MPa) in LED5, and the lowest in L5(7.7 MPa). The highest temperature rise for SDR was in L10 and L5 (7.3 and 7.2 °C), and the lowest in LED5(0.8 °C). For EX, the highest temperature rise was in L5 (13.0 °C), and the lowest in LED5 (0.7 °C). Temperature rise was higher during blue laser polymerization, especially at high intensity and with conventional curing. Preferable blue laser curing mode is co-curing at 1000mW/cm2 for 10 s.

Assessment of Damage of Endodontic Instruments with Naked Eye and Optical Instruments.

OBJECTIVES: To determine the accuracy of visual damage evaluation of rotating and reciprocal endodontic instruments with the naked eye and optical devices. MATERIAL AND METHODS: Four examiners were involved, divided into two age groups: I. 20-30 years, n = 2, II. 40-50 years, n = 2. They visually assessed the existence of damage to rotating or reciprocal endodontic instruments by their naked eye and with two types of optical aids. A total of 239 instruments from different manufacturers were evaluated by each examiner. Before damage estimation, each examiner calibrated the eye on a new instrument. Sensitivity of the detection method was calculated as by the naked eye. When an instrument was detected as damaged by the naked eye, the damage assessment was stopped and the instrument was considered to be damaged by the other two methods, as well. RESULTS: Damage was found in 178 instruments. Sensitivity of the naked eye was calculated to be 49.7%, for the loupe 66.2% and for the operating microscope 76.5%. The three methods of damage assessment had significant differences (p < 0.05) in sensitivity. CONCLUSION: It was concluded that there is a significant difference between age groups in estimating instrument damage. Also, it was noted that the damage assessment with the naked eye and optical aids were different. Finally, in terms of ease of damage recognition, significant differences between the types of engine-driven endodontic instruments were found. However, no type of instrument was more prone to damage than any other type of instrument.