The effect of surface roughening of orthodontic elastomers on hydrophobicity and in vitro adherence of Streptococcus gordonii.

OBJECTIVES: Biofilm formation around orthodontic appliances causes gingivitis, enamel decalcification and caries. Bacteria adhere less readily to superhydrophobic surfaces. The aim of this study was to determine whether a superhydrophobic surface could be generated on orthodontic elastomers by surface modification in order to reduce bacterial adhesion. MATERIALS AND METHODS: Orthodontic elastomers were modified with sandpapers of various grit sizes (80-600 grit). Surface roughness of the modified and unmodified surfaces was assessed qualitatively with scanning electron microscopy and quantitatively with confocal microscopy. Water contact angles were measured with a goniometer to quantify hydrophobicity. Measurements were performed on unextended elastomers (100% original length) and elastomers extended to 150%, and 200% of the original length. Adhesion of Streptococcus gordonii to saliva coated elastomers was measured by counting colony forming units on agar plates. RESULTS: Abrasion with different sandpapers produced elastomers with surface roughness (Ra) ranging from 2 to 12 µm. Contact angles followed a quadratic trend with a maximum contact angle of 104° at an Ra of 7-9 µm. Average water contact angles, when viewed perpendicular to the direction of extension, decreased from 99° to 90° when the extension was increased from 100% to 200% and increased from 100° to 103° when viewed parallel to the direction of extension. Bacterial adhesion increased as roughness increased and this effect was more pronounced with elastomer extension. CONCLUSION: The surface roughness of orthodontic elastomers influences both their hydrophobicity and bacterial adhesion. Superhydrophobicity of elastomers could not be achieved with sandpaper abrasion.

The effect of ligation methods on biofilm formation in patients undergoing multi-bracketed fixed orthodontic therapy - A systematic review.

BACKGROUND: Many modifications to fixed orthodontic appliances have been introduced to manage biofilm formation. The aim of this review was to investigate elastomeric ligation in comparison with stainless steel ligation and self-ligation with regard to microbiological and clinical indicators of biofilm formation in patients wearing multi-bracketed fixed orthodontic appliances. METHODS: The MEDLINE and the EMBASE databases were searched up to February 2021 and supplemented by additional manual searches of bibliographies. Parallel-group and split-mouth randomized controlled trials (RCTs) comparing different ligation methods were identified. The Cochrane Risk of Bias-2 tool was applied to assess the quality of evidence. RESULTS: A total of 11 RCTs were included in this review. Nine RCTs compared self-ligation and elastomeric ligation; two compared elastomeric ligation and stainless steel ligation. The included studies had either some concerns or were at a high risk of bias. Qualitative assessment of the studies identified that there were no significant differences in biofilm formation between elastomeric ligation and self-ligation, but that stainless steel ligation was less susceptible to biofilm formation than elastomeric ligation. CONCLUSIONS: There were no significant differences between self-ligation and elastomeric ligation for biofilm formation in patients wearing multi-bracketed fixed orthodontic appliances. Stainless steel ligation may accumulate less biofilm than elastomeric ligation; however, the clinical significance of the difference could not be evaluated. Further high-quality studies are required in order to determine which ligation method is better for managing biofilm formation in patients wearing multi-bracketed fixed orthodontic appliances.