Thermal analysis of teeth irradiated with Er,Cr:YSGG at low fluences

Abstract

This study aimed to evaluate the surface and pulp temperature rises when teeth are irradiated with ErCr:YSGG laser at low fluences, with or without a photosensitizer. It was chosen 81 third molar human teeth which were randomly divided into six groups, according to the Er,Cr:YSGG laser fluences (2.8 J/cm2, 5.6 J/cm2, and 8.5 J/cm2) and the recovering or not of a photosensitizer (a thin layer of coal paste) over enamel surfaces. All samples were irradiated without coolant. The surface temperatures and heat propagation were recorded by thermographic camera, and the pulpal temperatures were registered by type-K thermocouples. After laser irradiation, enamel surfaces were analyzed by scanning electron microscopy (SEM). The intrapulpal temperature increases were below the threshold for pulp damages (5.6°C), and they were dependent on the fluence applied. The surface recovering with coal paste significantly reduced the intrapulpal temperature increments in 8.5 J/cm2 samples. The coal paste also influenced the surface temperatures, which reached 222.6°C when samples were irradiated at fluence of 8.5 J/cm2. The SEM analysis revealed a micro-ablation pattern for all fluences tested. The photosensitizer was efficient for reducing heat transfer to the pulp chamber, increasing laser absorption into the enamel. The fluences of 8.5 J/cm2 was able to achieve surface temperature rises that suggest crystallographic changes on enamel, which could propitiate an increase of acid-resistance of enamel. A table is presented. Maximum pulpal temperature rises during laser irradiation detected by thermocouples (mean and standard error). Means followed by distinct letters are statistically different by the Turkey test (p < 0.05).