The Effect of Chemical Surface Treatments on Some Mechanical Properties of a Modified Auto Polymerizing Acrylic Resin as a Repaired Material

Background Polymer acrylic denture bases fracture is often occurrence, due to a low flexural strength of the resin, choice of the material, properties of the acrylic resin, faulty design and method of manipulation. Repaired of fractured denture bases are mandatory because it is time- consuming and expensive to make new prostheses. The aim of the study To evaluate the effect of different chemical surface treatments and the repaired surface design on the transverse and impact strength of the heat cure acrylic resin repaired with auto polymerized acrylic resin and modified auto polymerized resin with lignin. Materials and Methods A standard heat polymerized acrylic resin specimens were prepared according to ADA Specification No.12 for transverse strength, ISO 179- 1982 for impact strength and repaired with auto polymerized resin and modified auto polymerized resin with lignin after chemical surface treatment with monomer as a control group and acetone and chloroform as an experimental groups for butt and bevelled joint using Ivomet (pressure pot). A total of 200 samples were fabricated for this study. Transverse, impact and elongation were tested using Instron Universal testing device and Charpy impact machine. Results Repair of the specimens with a modified cold cure acrylic resin with lignin and treated with chloroform showed the highest value of transverse and impact strength. The repaired specimens with beveled joint design have a highly significant difference than those repaired with butt joint design. The adhesive type of failure found more in a butt joint, while the beveled showed a high percentage of cohesive and mixed type. Conclusion chemical treatment of repaired surface with chloroform have enhanced the transverse and impact strength of cold cure acrylic reinforced with lignin more than that treated with monomer and acetone. The type of material used, reinforcement of the acrylic resin, method of repair and design of the joint have a significant effect on the strength of the repaired denture.