Comparative Analysis of Abrasive Materials and Polishing System on the Surface Roughness of Heat-Polymerized Acrylic Resins

Effect of Chitosan and Acrylic Acid Addition to Acrylic Resin on Porosity and Streptococcus mutans Growth in Denture Base

OBJECTIVE

 This work aimed to determine the effect of adding chitosan and acrylic acid to acrylic resin denture base on the porosity of the material and the growth of Streptococcus mutans.

MATERIALS AND METHODS

 This study is an experimental laboratory research. Samples were divided into the following three groups (n = 10): group 1 was the control group, group 2 was the acrylic resin mixture with 1% chitosan and acrylate acid, and group 3 was the acrylic resin mixture with 2% chitosan and acrylate acid. S. mutans growth was tested using the dilution method, and porosity was examined using an optical microscope. Data were calculated by one-way analysis of variance (p < 0.05) and correlation analysis.

RESULTS

 The acrylic resin added with 2% chitosan and acrylic acid showed pores with an almost spherical shape and the smallest size. Significant difference (p < 0.05) was observed among all the groups. A positive and extremely strong correlation was found between porosity and S. mutans growth.

CONCLUSION

 Chitosan and acrylic acid at 1 and 2% concentrations can be added to acrylic resin to minimize the porosity of the denture base and reduce the growth of S. mutans. A less porous denture is associated with a low S. mutans growth rate.

The Effect of Salivary pH on the Flexural Strength and Surface Properties of CAD/CAM Denture Base Materials

OBJECTIVES

 This study aimed to evaluate the influence of different salivary pH on flexural strength, hardness, and surface roughness of computer-aided design and computer-aided manufacturing (CAD/CAM) milled and three-dimensional (3D)-printed denture base resins.

METHODS

 One heat-polymerized, two CAD/CAM milled (IvoCad, AvaDent), and two 3D-printed (FormLabs, NextDent) denture base resins were fabricated and divided into five groups (n = 10) according to the solutions: three groups were immersed in different salivary pH (5.7, 7.0, or 8.3), one group was immersed in distilled water (DW) as a positive control, and one group had no immersion (negative control). All immersions were performed at 37°C for 90 days. Flexural strength, hardness, and surface roughness were measured before and after immersion. Data was analyzed with analysis of variance and post hoc Tukey's test (α = 0.05).

RESULTS

 After immersion, all specimens had lower flexural strength values when compared with those with no immersion. Comparing the immersion groups, the highest flexural strength value (93.96 ± 3.18 MPa) was recorded with IvoCad after immersion in DW while the lowest value (60.43 ± 2.66 MPa) was recorded with NextDent after being immersed in 7.0 pH saliva. All specimens had significant decrease in hardness except IvoCad and AvaDent specimens where both presented the highest surface hardness (53.76 ± 1.60 Vickers hardness number [VHN]) after immersion in DW while NextDent showed the lowest hardness value (24.91 ± 2.13 VHN) after being immersed in 8.3 pH saliva. There was statistically significant difference between the baseline and different artificial salivary pH solutions in terms of surfaces roughness, with the highest surface roughness were found in 3D-printed resin materials.

CONCLUSION

 After exposure to artificial saliva with different salivary pH, the milled CAD/CAM denture base resins showed higher flexural strength, hardness, and lesser surface roughness than conventional and 3D-printed denture base resins.