Dados do Trabalho

Título

Evaluation of the physical-mechanical properties of dental waxes employed as individualized custom bolus during radiotherapy

Introdução

Dental waxes (7 wax and utility wax) have been considered as the prime choice for bolus preparation during radiotherapy (RT) due to its affordable cost, non-toxic and easy to handle characteristics. It also presents similar electron scattering and absorption capability to soft tissues. Nevertheless, the radiation’s effect on the physical-mechanical properties of these waxes remain unknown.

Objetivo

The purpose of this study was to determine the radiation dose tolerated by dental waxes without alterations, identify the best type of wax to use as bolus, and evaluate the need of bolus replacement during RT sessions.

Métodos

This study was approved by the Research Commission of the A.C.Camargo Cancer Center (1194/17).The sample consisted of 96 specimens made of utility wax (n= 48) and 7 wax (n= 48). They were distributed and allocated into two groups: control (non-irradiated) and experimental (irradiated). Groups were composed by 24 specimens of each wax type. The 48 test specimens from the experimental group received radiation dose at the same time. Dosimetry measurements were performed with a linear accelerator (Varian 6EX), at a 6 MV electron beam energy value, and a total dose of 69.9Gy. The whole dose was divided into 2.12Gy per fraction, totalizing 33 RT sessions. Analyzes were performed in three phases: phase 1 (at the 10th RT session), phase 2 (at the 20th RT session), and phase 3 (at the 33th RT session). The control group was evaluated at the same phases as the experimental group under the following parameters: dosimetry, weight, height, width, length, density, hardness, and stiffness.

Resultados

Significant height (p=0.004) and weight (p=0.002) alterations were observed in the irradiated utility wax specimens, where as the 7 wax specimens demonstrated weight variation (p=0.011) only at Phase 3. Both, 7 and utility waxes, submitted to 10 sessions of RT did not show significant values when compared before and after irradiation (p=0.535).However, there was a significant difference in the density (HU) between irradiated blocks submitted to 20 and 33 sessions (p=≤0.001). The utility wax hardness changed significantly during RT sessions (p =0.007). When stiffness was analyzed, 7 wax demonstrated a higher statistically values (487.5) when compared to utility wax (200.1) throughout the different phases (p≤0.001). The ANOVA test showed that the irradiated specimens presented higher values in relation to height (p= 0.005), length (p=0.004), weight (p≤0.001), density (p≤0.001), and hardness (p≤0.001) when compared to the control group.

Conclusões

Radiation caused alterations in the physical mechanical properties of the studied waxes. The 7 and utility waxes have a good performance in the face of physical-mechenical analysis and can be used as the material of choice for bolus confection, and it is not necessary to make new bolus during RT sessions.

Palavras-chave

Alumina Silicata. Radiotherapy/methods. Inlay Casting Wax. Dose-Response Relationship. Radiation. Life of quality