University Dental School & Hospital, University College Cork, Wilton, Cork, Ireland.
North Wales Centre for Primary Care Research, Bangor University, Bangor, UK.
J Dent. 2018 Dec;79:11-18. doi: 10.1016/j.jdent.2018.08.014. Epub 2018 Aug 31.
Based on histological studies from the 1960s, it is recommended that dental pulp temperature increases should not exceed 5.5 °C. However, no contemporary reliable models exist to explore the effects of heat on living dental pulp. The aim of this project was to develop a clinically valid model for studying temperature increases caused by three commonly-used light curing units (LCUs).
Temperature increases caused by LCUs at varying exposure times and via various thicknesses of dentine were recorded using traditional approaches (i.e. thermocouple device on a laboratory bench) and an ex-vivo tooth slice model. Histomorphometric and immunohistochemical (IL-1β, HSP70, caspase-3) analysis was performed of the tooth slice model following varying exposure and culture times.
Reduced dentine thickness and increased exposure time led to increases in temperature. Whilst the majority of temperature increases recorded using the traditional approach (53 of 60) were greater than the recommended 5.5 °C, 52 of the 60 reference points recorded using the ex-vivo tooth slice model resulted in temperature increases of less than 5.5 °C. Temperature increases of 5.5 °C or more that are prolonged for 40 s caused an immediate decrease in cell number. IL-1β was not detected in any samples, while HSP70 was detectable immediately after exposure to a temperature increase of 6 °C or more. Higher levels of HSP70 were detected after 24 h culture in tooth slices that experienced a temperature increase of 7.5 °C or more. Low levels of caspase-3 were detected in tooth slices exposed to temperature increase of 7.5 °C or more.
Experimental arrangements for assessing LCU performance that measure temperature increases using a thermocouple device on a laboratory bench should no longer be used. Future studies in this area should include replication of the clinical environment using greater sophistication, such as the use of an ex-vivo tooth slice model as described here. Temperature increases of 5.5 °C or more for 40 s caused an immediate decrease in cell number, which supports previous findings. However, complex interactions at an immunohistochemical level suggest that while temperature increases of 5 °C or less are ideal, there may be some cell damage between 5-7 °C which might not result in pulpal death. Further investigations are indicated.
基于 20 世纪 60 年代的组织学研究，建议牙髓温度升高不应超过 5.5°C。然而，目前还没有可靠的现代模型来研究热对活牙髓的影响。本项目的目的是开发一种临床有效的模型，用于研究三种常用光固化器（LCU）引起的温度升高。
使用传统方法（即在实验室台式机上使用热电偶装置）和离体牙切片模型记录 LCU 在不同曝光时间和不同牙本质厚度下引起的温度升高。对离体牙切片模型进行组织形态计量学和免疫组织化学（IL-1β、HSP70、caspase-3）分析，观察不同曝光和培养时间后的结果。
减少牙本质厚度和增加曝光时间会导致温度升高。虽然使用传统方法记录的大多数温度升高（60 个中的 53 个）都超过了推荐的 5.5°C，但在离体牙切片模型中记录的 60 个参考点中的 52 个结果导致温度升高低于 5.5°C。持续 40 秒的 5.5°C 或更高的温度升高会立即导致细胞数量减少。在任何样本中均未检测到 IL-1β，而在暴露于 6°C 或更高的温度升高后立即可检测到 HSP70。在经历 7.5°C 或更高的温度升高后 24 小时培养的牙切片中检测到更高水平的 HSP70。在暴露于 7.5°C 或更高的温度升高的牙切片中检测到低水平的 caspase-3。
用于评估 LCU 性能的实验装置，在实验室台式机上使用热电偶装置测量温度升高，不应再使用。在该领域的未来研究中，应包括使用更复杂的方法复制临床环境，例如这里描述的离体牙切片模型。持续 40 秒的 5.5°C 或更高的温度升高会立即导致细胞数量减少，这与之前的发现一致。然而，在免疫组织化学水平上的复杂相互作用表明，虽然 5°C 或更低的温度升高是理想的，但在 5-7°C 之间可能会发生一些细胞损伤，这可能不会导致牙髓死亡。需要进一步研究。
