The investigation of thermal behaviour and physical properties of several types of contemporary gutta-percha points

Abstract

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 β-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.

Keywords: chemical composition; gutta-percha; thermal conductivity.

FIGURE 1

Box plot of inorganic, gutta‐percha and wax/resin components of commercial dental gutta‐percha points. Different lowercase superscript letters indicate significant differences according to the Kruskal–Wallis and Dunn tests (p < .05).

FIGURE 2

The simple linear regression analyses. (a) The correlation between thermal conductivity and inorganic components. (b) The correlation between thermal conductivity and zinc element. (c) The correlation between thermal conductivity and gutta‐percha component.