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Diode lasers are becoming increasingly popular in everyday clinical practice. There is also a great variety of different applications for diode lasers in dentistry. Because of the fact that diode laser systems usually cause heat, which in turn leads to the question to what extent they contribute to thermal damage of the adjacent tissue.
The aim of the this study was to find out which temperature changes occur while using diode lasers in order to estimate their damage potential. This study focuses on scenarios with a fluid circulation in the pulp and also considers the dentin near the pulp chamber as well as the enamel-dentin border. Therefore, ten extracted human teeth with multiple roots were divided along their longitudinal axis in order to expose the two channels of tooth roots. Furthermore, plastic cannulas were attached in the apical canal area. These cannulas allowed for a connection through a tube system and thus a fluid circulation through the pulp cavity. The prepared half of the tooth was closed with a cover glass. Afterwards, the SIROLaser Blue (Sirona, Bensheim) was applied to radiate the tooth with the following settings: 600mW (SLB 600) and 800mW (SLB 800) each in an continuous wave mode and a 320µm fiber as well as the SIROLaser Advance (Sirona, Bensheim) - in a pulse mode, duty cycle 50%, 10 Hz, 320µm fiber with an average power of 750mW (SLA 750), for 40 seconds. The temperature measurements were made at flow rates of 0 ml/min, 2,6 ml/min and 6 ml/min with the aid of a thermal imaging camera (VarioCAM HD, InfraTec, Dresden). The corresponding temperatures were measured at the pulp chamber (C1) as well as in the dentin area (C2) and on the enamel-dentin border (C3).
The results of this study have shown that both the fluid circulation as well the power of the applied laser had a significant impact on the heat development. The previously set baseline temperature of 22 degrees Celsius marked the highest recorded temperature maxima for the laser SLB 800 in the C1 range without fluid circulation (Median: 7,0 K, Minimum: 3,9 K, Maximum: 9,0 K). The lowest temperature readings could be observed after application of the laser SLA 750 in the C1 range at a flow rate of 6 ml/min (Median: 0,2 K, Minimum: 0,1 K, Maximum: 0,5 K).
In conclusion, one can assume that if diode lasers are applied with the appropriate settings and a physiological blood circulation in the dental pulp chamber is present, the damage potential due to the laser energy can be estimated as low.