Evaluation of some mechanical and physical properties of different types of injectable polymer materials used as a base for removable orthodontic appliances

Introduction
For many years, cold cure acrylic has been used to construct the removable orthodontic appliances that treated simple cases. The main problem with this type of acrylic is related to monomer release unlike the heat cure acrylic type. With the advances in materials, new injectable polymer materials were developed for construction of removable and complete dentures, but no study has been performed to compare their properties with Orthocryl used for removable orthodontic appliance construction.

Objectives
Aim of the study was to evaluate some mechanical and physical properties of two new materials for use in denture base construction in comparison with Orthocryl.

Material and methods
A total of 150 specimens, 50 each of self-cure acrylic (Orthocryl), polycarbonate (M10) and injectable acrylic (Acrilato), were fabricated according to the manufacturers’ instructions. The following properties were tested using 10 samples of each type: impact strength, hardness, surface roughness, flexural strength, and water sorption and solubility. One-way ANOVA followed by post-hoc Tukey tests compared results among the groups.

Results
Statistically significant group differences were found in all tests except those for water sorption and solubility, which showed non-significant differences.

Conclusions
The good properties of M10 and Acrilato make them suitable alternatives to Orthocryl. The major issue is the cost and the availability of the required softening device in dental laboratories.