Basic Studies On High-temperature Injectable Obturation Of Thermoplasticized Gutta-percha

Root canal therapy(RCT) is a preferred treating method for various endodontic and periapical diseases. It includes three-dimensional root canal clearning, shaping and filling. Incomplete sealing is the most important factor leading to endodontic treatment failure. It is highly recommended that thermoplasticized obturation techniques could improve the canal sealing quality , and high-temperature injectable thermoplasticized gutta-percha system(Obtura II) is one of them. The basic study aimed at exploring the most suitable working conditions for Obtura II system.Objectives: To find out a well-matched instrument method for injectable thermoplasticized gutta-percha obturation; to evaluate whether the temperature rise on the root surface would result in thermal damage to periodontal tissues caused by Obtura II system with temperature settings of 160℃, 180℃and 200℃; to investigate whether there were differences of their canal sealing capacities and the effects of sealer usage.Methods: Scanning Electron Microscope(SEM) was used to observe surface cleanliness of root canal walls after being instrumented with three different methods(protaper,K file,profile); after instrumented with the preferred method, root canals were filled with Obtura II system at different temperature settings using canal sealer as control groups. Temperatures on root surfaces were measured using infrared thermal imaging camera during root canal obturation; the extrusion of gutta-percha and the microleakage of root canals were examined and analysed after obturation.Results: There were differences in surface cleanliness of root canal walls among three different instrument methods: hand protaper Ni-Ti instrument was better than stainless steel K file and profile rotory instrument, the difference of debris scale was statistically significant ( P < 0. 05), and the difference of smear layer and open tubules was not statistically significant ( P > 0. 05). The mean temperature rise on the root surfaces was below the critical level of 10℃. The differences in seal abilities between Obtura II system and cold lateral compaction were statistically significant ( P < 0. 05) , while there was no significant difference among three temperature sets(P > 0. 05).Conclusions: Cleanliness of root canal of hand protaper Ni-Ti instrument was better than that of stainless steel K file and profile rotory instrument. Temperature rise generated by Obtura II system did not cause damage to periodontal tissues when temperature settings were at 160℃, 180℃and 200℃. The sealing effect of Obtura II was better than cold lateral compaction, but there was no statistically significant difference in seal ability among three temperature sets. The use of sealer seemed to have no effect on lowering the temperature rise and reducing microleakage.