PMMA Surface Modification with PEGMA and PEGDA against Bacteria Adhesion

Polymethyl methacrylate (PMMA) is generally used in dentistry for denture base materials, maxillofacial prostheses, temporary restoration, and orthodontic appliances. Biofilm formation on the PMMA surfaces may cause chronic infection of surrounding tissues. The purpose of this study was to investigate the adhesion of Gram-positive Streptococcus mutans and Gram-negative Escherichia coli on PMMA surface modified with polyethylene glycol methacrylate (PEGMA) or polyethylene glycol diacrylate (PEGDA).  

Method:

PMMA disks (6 mm diameter and 1 mm thick) were fabricated from auto-polymerizing, MMA/PMMA orthodontic acrylic resin system (Ortho-Jet). PEGMA or PEGDA was grafted on PMMA surfaces by low-pressure plasma with a helium flow rate of 30 sccm and input power of 100 W controlled by a 13.56 MHz RF generator for 1 min. Contact angle and surface roughness measurements were used to characterize the surface hydrophylicity and roughness. Direct contact test of S. mutans and E. coli was used to examine bacteria adhesion.

Result:

The contact angle of PMMA was 69.19±2.53^o. The values decreased to 56.84±6.59^o after PEGMA modification but increased to 74.41±4.07^o after PEGDA modification. Ra roughness of PMMA, PMMA-PEGMA, and PMMA-PEGDA was 2.10±0.45 μm, 2.07±0.58 μm, and 7.64±1.48 μm, respectively. The OD values of S. mutans revealed that PMMA-PEGMA had the lowest value (0.81±0.07) followed by PMMA (0.96±0.12) and PMMA-PEGDA (1.59±0.24). In addition, the OD values of E. coli also showed that PMMA-PEGMA had the lowest value (1.02±0.06) followed by PMMA (1.06±0.07) and PMMA-PEGDA (1.74±0.19) although there was no significant difference between the groups of PMMA and PMMA-PEGMA. 

Conclusion:

PMMA surface modification with PEGMA increases the surface hydrophylicity and is effective against S. mutans adhesion.