RESUMO
Background/purpose: In the warm gutta-percha technique, soft-type and regular-type gutta-percha are using for backfilling thermoplasticized injection system. However, there are limited reports about the properties of these backfilling gutta-percha. This study aimed to analyze and compare the composition, thermal behavior and compact force of two types of backfilling gutta-percha. Materials and methods: Soft-type and regular-type backfilling gutta-percha (B&L BioTech, Fairfax, VA, USA) were investigated. The inorganic and organic fractions of these gutta-perchas were separated by quantitative chemical analysis (n = 6). Their composition was analyzed using energy dispersive spectroscopy. Thermal behavior in response to temperature variations was analyzed using differential scanning calorimetry. Additionally, a compaction model was used to investigate the relation between compaction force and temperature (n = 10). Results: The soft-type contained more gutta-percha (3.69-5.85%), carbon ratio (38.96-48.52%) and less inorganic substance (86.51-90.45%), zinc ratio (29.36-35.67%). The composition ratio of two types gutta-percha were statistically significant different (P < 0.05). There were three phase transitions of the soft-type gutta-percha which started at 39.84 °C, 49.32 °C and 54.15 °C while the two phase transitions of the regular-type gutta-percha started at 40.48 °C and 53.45 °C. The glass transition temperature of the regular-type gutta-percha (44.24 °C) was higher than that of the soft-type gutta-percha (40.66 °C). Under various setting temperature, the higher compaction force in the regular-type gutta-percha was required (P < 0.05). Conclusion: The different components in gutta-percha contribute to its differences in thermal behavior. The soft-type had a higher proportion of gutta-percha and lower ZnO which makes the fluidity better than the regular-type.
RESUMO
AIM: To analyse the contents and thermal behaviour of several brands of contemporary gutta-percha points due to the variable nature of the components of gutta-percha, and the impact they can have on the physical properties of this unique material during canal filling. METHODOLOGY: Six brands of gutta-percha were investigated: Conform Fit TM Gutta-Percha Points for ProTaper Gold® (PTG) (Dentsply Sirona), ProTaper® Universal Gutta-Percha Points (PTU) (Dentsply Sirona), Autofit TM Feathered Tip Gutta Percha (Kerr), Mtwo® Gutta-Percha (VDW), Gutta Percha Root Canal Points (GC, GC Corporation) and Gutta-Percha Points ISO Color-Coded (ISO; Dentsply Sirona). The organic and inorganic fractions of gutta-percha points were separated by quantitative chemical analysis. Thermal conductivity was detected using a laser flash method. In addition, the thermal behaviour of gutta-percha in response to temperature variations was analysed using differential scanning calorimetry (DSC). Kruskal-Wallis and Dunn tests were applied for comparisons amongst groups for chemical compositions and temperature obtained from DSC. The associations between compositions and thermal conductivity were determined using simple linear regression. A p value <.05 was considered to be statistically significant. RESULTS: There were significant difference in the inorganic fractions of the gutta-percha points in percentage by weight amongst the groups (p < .05). PTG had the lowest thermal conductivity (0.42 W/m K). A positive correlation was observed between the percentage of inorganic fraction and thermal conductivity (r = 0.95). The initial phase changing temperature and peak temperature measured by DSC were significantly different when the ß-form transformed to α-form (p < .05), whereas no significant difference was found during the α-form to the amorphous-phase transition (p > .05). CONCLUSIONS: Chemical compositions and initial phase changing temperature by DSC varied according to the various brands of gutta-percha points. Conform Fit TM gutta-percha had the lowest percentage of inorganic fraction and thermal conductivity amongst these six brands of gutta-percha. Thermal conductivity had the strongest positive correlation with the percentage of inorganic components and zinc, whilst there was a negative correlation to the amount (ratio) of gutta-percha.
