A Novel GCE-Containing Antibacterial Adhesive Cement Used in Orthodontics

Objectives: Galla chinensis, a natural agent, has a significant inhibitory effect on cariogenic bacteria. In orthodontic treatment, adding antibacterial agents into adhesives can effectively prevent enamel demineralization caused by increased cariogenic bacteria level in dental plaque around brackets. Thus this study aims to evaluate antibacterial effect and mechanical property of an orthodontic adhesive cement containing Galla chinensis extract (GCE).
Methods: GCE was dissolved in distilled deionized water and adjusted to pH 5.5. We incorporated GCE into a resin-modified glass ionomer cement (GC Fuji Ortho LC, Japan) at five mass fractions (0% (control group), 0.25%, 0.5%, 0.75%, 1.0%) respectively, to prepare GCE-containing cement for analysis. 1) Antibacterial activity (agar diffusion test): cement specimens were placed on the surface of agar inoculated with Streptococcus mutans (strain ATCC 25175). After incubation (48h), the diameter of inhibition halo was measured. 2) Bacteria colonization susceptibility: scanning electron microscopy (SEM) was used to semi-quantitatively evaluate bacteria adhesion to cement specimens incubated in S. mutans suspensions (48h). 3) Mechanical property: 50 metal brackets were bonded on human premolar surface by using cement (10 teeth per group). After immersion in artificial saliva (3d), universal testing machine was used to measure shear bond strength (SBS).
Results: GCE-containing samples exhibited larger bacterial inhibition halo than control, and inhibition zone increased as GCE mass fractions increased. SEM analysis showed that S. mutans presented a weaker adherent capacity to all GCE-containing cements compared with control, but the difference between each GCE-containing group was not significant. Compared with control, no significant SBS difference was found in 0.25%, 0.5% GCE-containing group, but 0.75% and 1.0% group presented lower SBS value.
Conclusions: GCE-containing adhesive cement exhibits a promising inhibitory effect on S. mutans growth and adhesion. Without compromising mechanical property, adding low concentration (<0.5% approximately) GCE in adhesive cement may be an attractive option for orthodontic bonding.