Investigation of the thermal and physicochemical behavior of two types of gutta-percha cones for back-filling the root canal

Abstract

Background: Gutta-percha (Gp) is an inert thermoplastic polymer used as a filling to replace the dental pulp space, which has been reformulated to improve its three-dimensional sealing properties. Therefore, this study aimed to analyze the physical, chemical and thermal properties of two types of gutta-percha filling. As well as measuring the temperature distribution along the cone at the time of cutting through an in-situ test.

Material and methods: Two commercially available brands of gutta-percha point were investigated: Conform Fit TM Gutta-Percha for ProTaper Gold® (PTG) (Dentsply Sirona), and Hygenic Gutta-Percha (Coltene whaledent). Differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) were selected for the thermal characterization of materials, and Fourier Transform Infrared Spectroscopy (FT-IR) for the chemical analysis of Gp cones. Regarding temperature distribution, it was evaluated using a thermographic camera (FLIR ONE® PRO by MicroUSB P/N 435-0011-01) at 0 to 20 s after the cutting process (n=11/group).

Results: Both materials have three fusion endotherms associated with the three crystalline phases of Gp, with similar temperatures but enthalpies that differ by 60%, the fusion enthalpy being higher for Conform Fit. In the chemical characterization, elements such as Zn, C, O, Ba, S and Si were found in both materials but in different proportions. Regarding the content of fillers, the Conform Fit presented around 30% of Gp polymer and 25% for the Hygenic. The morphological characterization shows a microtexturized coating in the form of bars on a micrometric scale for the Conform Fit, which could favor a better three-dimensional seal. In addition to that, in heat transfer studies they showed greater temperature control.

Conclusions: The characterization of the materials allowed us to see the variation in terms of their composition and configuration to the Gp cones of two commercial brands. These variations directly modify the thermal behavior of the material. Key words:Gutta-percha, Conform Fit, Infrared thermography, Differential Scanning Calorimetry, Infrared Spectroscopy.

Figure 1

a-e) Experimental procedure for the Heat Transfer Test In Situ. a) Base of the gutta-percha cone designed in acrylic, b) System designed for the adaptation of the thermal camera (FLIR ONE® PRO by MicroUSB P/N 435-0011-01), c-d) Condenser (Hu-friedy RCP10A of 29mm) and Micro Torch used for the cutting process, e) Images obtained with the FLIR Tools program. f-g) Average temperatures in GP cones, as a function of time after cutting for each reference point (Temperature profiles).

Figure 2

Infrared spectra of Gp Conform Fit and Hygenic.

Figure 3

Thermal analysis. a) DSC Heating Traces, b) DSC Cooling Traces, c) Gp Conform Fit TGA, and d) Gp Hygenic TGA.

Figure 4

Micrographs of the Cone of Gutta-percha overview. a) Conform Fit 50x, b) Conform Fit 500x, c) Conform Fit 1000x Zone A, d) Conform Fit 10000x Zone B, e) Hygenic 50x and f) Hygenic 1000x.