Comparison of Mechanical Properties of PMMA Disks for Digitally Designed Dentures

Abstract

In this study, the physical properties of a custom block manufactured using a self-polymerizing resin (Custom-block), the commercially available CAD/CAM PMMA disk (PMMA-disk), and a heat-polymerizing resin (Conventional PMMA) were evaluated via three different tests. The Custom-block was polymerized by pouring the self-polymerizing resin into a special tray, and Conventional PMMA was polymerized with a heat-curing method, according to the manufacturer’s recommended procedure. The specimens of each group were subjected to three-point bending, water sorption and solubility, and staining tests. The results showed that the materials met the requirements of the ISO standards in all tests, except for the staining tests. The highest flexural strength was exhibited by the PMMA-disk, followed by the Custom-block and the Conventional PMMA, and a significant difference was observed in the flexural strengths of all the materials (p < 0.001). The Custom-block showed a significantly higher flexural modulus and water solubility. The water sorption and discoloration of the Custom-block were significantly higher than those of the PMMA-disk, but not significantly different from those of the Conventional PMMA. In conclusion, the mechanical properties of the three materials differed depending on the manufacturing method, which considerably affected their flexural strength, flexural modulus, water sorption and solubility, and discoloration.

Water Sorption, Solubility, and Translucency of 3D-Printed Denture Base Resins

“…The absorbed water enters between the layers, and then the water molecules are diffused into the resin's polymer, which allows interpolymeric spaces to be filled with water, forcing the polymer chain away from other chains [1,29,30]. This phenomenon might adversely affect the layering interface, which leads to swelling of the resin and separates the printed layers [13,26]. The presence of voids in 3D-printed resins was confirmed with scanning electron microscopy [1].…”

“…Once the specimens were weighed for sorption, they were dried to achieve a constant mass (m3); the drying process was similar to the method used for m1 determination. The solubility values of the specimens were obtained using the following formula: (Wsl = (m3 − m1)/specimen volume (V)) [12,13].…”

“…Water solubility is an undesirable property, since more unreacted resin will exist; hence, unreacted monomers can have a negative influence on the oral tissue and can increase the tissue reaction. Therefore, prostheses are to be compatible and insoluble in patients' mouths [12,13].…”

Flexural Strength of CAD/CAM Denture Base Materials

“…Titles irrelevant to the research question, duplicate titles, and publications in languages other than English were excluded This process yielded 25 studies that were further scrutinized to ensure meeting inclusion criteria. At the end, nine studies[ 13 23 , 27 28 29 30 31 32 33 ] were included for data extraction and analysis. Table 1 presents a summary of extracted data.…”

“…Figure 2 summarizes the risk of bias for the included studies. Out of the nine included studies, six[ 13 23 , 28 29 30 31 ] showed medium risk, two[ 27 32 ] showed high risk of bias, and one[ 33 ] showed low risk of bias. The risks of bias reported were mainly due to missing information regarding sample size calculation and blinding of examiners.…”