Abstract
Improvement of the antibacterial properties of acrylic resins, used in the construction of removable orthodontic appliances, is an important strategy to reduce the incidence of caries and oral diseases in orthodontic treatments. The addition of antimicrobial agents to acrylic resins is one of the effective methods to enhance the antimicrobial properties of these materials. However, one main concern is that modification of acrylic resin has negative effects on its mechanical properties. Recently, chitosan nanoparticles (NPs), as biocompatible and biodegradable polysaccharides with remarkable antimicrobial properties, have been used in different areas of dentistry and medicine. This study aimed to investigate the effects of adding chitosan NPs on the mechanical properties of a cold-cure orthodontic acrylic resin. The chitosan NPs were added to the acrylic resin in various weight percentages: 0% (control), 0.5%, 1%, 2%, and 4%. The flexural strength, compressive strength, Vickers microhardness, and impact strength measurements were performed for all five groups. The results showed that adding up to 1% (w/w) chitosan NPs to an acrylic resin had no significant negative effects on its flexural strength and compressive strength, while it decreased these parameters at weight percentages of 2% and 4% (w/w). The results also revealed that modification of acrylic resin with chitosan NPs up to 4% had no significant negative effects on the microhardness and impact strength of acrylic resin. In conclusion, the addition of chitosan NPs up to 1% (w/w) had no significant negative effects on the mechanical properties of cold-cure acrylic resin.
Highlights
The growing demand for orthodontic treatments has led to an increasing need for the use of orthodontic acrylic resins in the fabrication of removable orthodontic appliances and retainers
With increasing the concentration up to 1% chitosan NPs, the flexural strength did not change significantly, but in 2% and 4% chitosan NPs, flexural strength decreased compared to other three groups
The present results showed that adding up to 1% (w/w) chitosan to acrylic resin had no significant negative effects on its flexural strength, while 2% and 4% (w/w) chitosan NPs decreased this parameter
Summary
The growing demand for orthodontic treatments has led to an increasing need for the use of orthodontic acrylic resins in the fabrication of removable orthodontic appliances and retainers. Poor oral hygiene in orthodontic patients and surface porosities are two factors that lead to the accumulation of residual foods and microorganisms, such as Streptococcus mutans and Candida albicans on acrylic resins. The accumulation of these microorganisms increases the incidence of caries and oral diseases and jeopardizes the efficiency of orthodontic treatments [1]. This is especially important for cold-cure acrylic resins that have a higher porosity than heat-cure acrylic resins [2]. Mechanical and chemical methods, as well as their combinations, are suggested for cleaning acrylic resins in removable orthodontic appliances. Chemical and mechanical methods, such as manual brushing with a toothbrush, depend on patient cooperation
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