In vitro study of structural and mechanical properties of latex and non-latex intermaxillary orthodontic elastics

We evaluated bacterial endotoxin adhesion, superficial micromorphology and mechanical properties of latex and non-latex intermaxillary orthodontic elastics.

To quantify the adhered bacterial endotoxin, elastics were divided into 5 groups: experimental (n = 12) latex and non-latex elastics, previously contaminated by an endotoxin solution, negative control (n = 6) latex and non-latex elastics without contamination, and positive control (n = 6) stainless steel specimens (metallic replicas), contaminated by an endotoxin solution. In parallel, the structural micromorphology (n = 6) and surface roughness of latex and non-latex intermaxillary orthodontic elastics were assessed using confocal laser microscopy. Force degradation (g) and deformation of the internal diameter change (mm) were also evaluated. Structural micromorphology, surface roughness (µm), force degradation (g) and internal diameter (mm) change were evaluated at time 0 and after 24 and 72 h in a deformation test. Data were analyzed by the Shapiro-Wilk, Kruskal-Wallis, Dunn, ANOVA and Bonferroni tests (α = 5%).

Endotoxin adhered similarly to both types of elastics with scores of 3 (> 1.0 EU/mL). The surface microstructure of both types of elastics showed irregularities and porosities at all times. Initially, the latex elastics had a higher surface roughness (p < 0.001) than the non-latex ones. After 24 h loading, surface roughness of the latex elastics was significantly reduced (p < 0.001), while after 72 h, the values were similar for both types (p > 0.05). The non-latex elastics had significantly higher force generation values (p < 0.05) at 0, 24 and 72 h compared with the latex elastics, although there was a significant reduction (p < 0.001) in force over time for both elastics. Despite similar initial values, non-latex elastics had a significantly larger internal diameter (p < 0.001) after the loading periods of 24 and 72 h compared with the latex elastics.

Both elastics showed high affinity with endotoxin and microstructural irregularities of their surface. The non-latex elastics generated higher force values but demonstrated greater deformation of the internal diameter after loading.