Physico-chemical investigation of endodontic sealers exposed to simulated intracanal heat application: epoxy resins and zinc oxide-eugenols.

AIM

To gain information in a laboratory setting about the effect of thermal treatment of epoxy resin-based and zinc oxide-eugenol-based sealers.

METHODOLOGY

AH Plus and Pulp Canal Sealer (PCS) were exposed to thermal treatment at 37, 47, 57, 67, 77, 87 and 97 °C for 30 s. According to clinically relevant considerations, intracanal sealer temperature is likely not to exceed 60 °C during warm vertical root canal filling. Heat application is recommended for less than 30 s during continuous wave technique, but might exceed this threshold in complex cases. Furthermore, heat treatment at 97 °C was performed for 60 and 180 s to simulate inappropriate implementation of warm vertical filling techniques. Specimens were heated inside 2-mL plastic tubes in a thermo-controlled water bath until the temperatures were reached and kept at this temperature for the determined period of time. Afterwards, specimens were cooled to body temperature and physical properties (setting time, flow, film thickness according to ISO 6876) were assessed. Chemical properties (Fourier transformed infrared spectroscopy) were assessed after complete setting of the specimens in an incubator at 37 °C and 100% humidity. Statistical analysis of physical properties was performed using Kruskal-Wallis test (P = 0.05).

RESULTS

The setting time of AH Plus and PCS decreased when temperature and duration of heat application increased. Whilst the setting time of AH Plus decreased from 622 min at 20 °C (for 30 s) to 381 min at 97 °C (for 180 s; P < 0.05), heat treatment of PCS at 97 °C for 180 s led to an immediate setting of the material. From 20 °C (for 30 s) to 97 °C (for 30 s), the setting time of PCS decreased from 80.1 to 41.0 h (P < 0.05). Film thickness and flow were not relevantly influenced by thermal treatment except for PCS at 97 °C for 180 s. FT-IR spectroscopy did not reveal any chemical changes of either sealer after thermal treatment.

CONCLUSIONS

Thermal treatment simulating clinically relevant temperature levels and heating times did not lead to any substantial physical or chemical changes at all temperature levels when heating did not exceed 60 s. AH Plus and Pulp Canal Sealer can be considered suitable for warm root filling techniques.