Resistance of PETG Materials on Thermocycling and Brushing

Abstract

The aim was to assess the impact of thermocycling and brushing on the surface roughness and mass of PETG material-the most commonly used for orthodontic retainers. A total of 96 specimens were exposed to thermocycling and brushing with three different kinds of toothbrushes depending on the number and thickness of the bristles. Surface roughness and mass were evaluated three times: initially, after thermocycling, and after brushing. In all four brands, both thermocycling and brushing increased surface roughness significantly (p < 0.001), with Biolon having the lowest and Track A having the highest. In terms of brushing, only Biolon samples showed statistically significant increased roughness after brushing with all three types of brushes, in comparison to Erkodur A1, where differences were not statistically significant. Thermocycling increased the mass of all samples, but a statistically significant difference was found only in Biolon (p = 0.0203), while after brushing, decreased mass was found in all specimens, statistically significant only in Essix C+ (CS 1560: p = 0.016). PETG material showed instability when exposed to external influences- thermocycling produced an increase in roughness and mass, and brushing mostly caused an increase in roughness and decrease in mass. Erkodur A1 demonstrated the greatest stability, whereas Biolon demonstrated the lowest.

Keywords: PETG; brushing; retainers; thermocycling.

Figure 1

Surface roughness of top sides of specimens after thermocycling. Variables noted with the same letter show statistically significant differences. Ra presents initial Ra values, Ra_t presents surface roughness values after thermocycling.

Figure 2

Surface roughness of top sides of specimens after brushing simulation with three different toothbrush types. Variables noted with the same letter show statistically significant differences. Ra_t presents Ra values after thermocycling, Ra_tt presents Ra values after thermocycling and brushing.

Figure 3

Change in surface roughness of bottom sides of specimens after thermocycling. * statistically significant difference in surface roughness change in comparison to other brand groups.

Figure 4

Change in surface roughness of bottom sides of specimens after brushing simulation with three different toothbrush types. * the marked groups show statistically significant differences in surface roughness change.