The aim of this study was to evaluate the thermal effects of different light sources used for in-office bleaching by simulating intraoral conditions and measuring temperature changes within the pulp chamber. Thirty recently extracted human teeth were used in this experimental study. The roots were sectioned approximately 2 mm below the cementoenamel junction (CEJ), and a K-type thermocouple was inserted into the pulp chamber through the root canal access to record temperature variations. Each tooth was exposed to four different light sources: Nd:YAG laser (1064 nm; 200 mJ, 5 Hz, 30 s), KTP laser (532 nm; 200 mJ, 5 Hz, 30 s), diode laser (810 nm; 10 Hz, 100 ms, 30 s), and diode laser (980 nm; 10 Hz, 100 ms, 30 s). The temperature changes were recorded during irradiation and statistically analyzed. The highest temperature increase was observed with the 980 nm diode laser (1.8 °C), followed by the Nd:YAG laser at 1064 nm (1.7 °C), diode laser at 810 nm (1.07 °C), and KTP laser at 532 nm (0.37 °C). Although significant differences were observed among the tested groups, all temperature increases remained below the critical threshold of 5.6 °C associated with irreversible pulpal damage. These findings indicate that the investigated laser systems can be considered thermally safe for in-office bleaching procedures under the applied experimental conditions. However, appropriate selection of laser parameters is essential to minimize thermal stress on dental tissues.
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