Table 1.
Commercial aligner substrates and bonding agents evaluated in this study, with their manufacturer and principal chemical composition.
Fig 1.
Each material was split into two surface-treatment conditions: no treatment and sandblasting. Within each surface condition, specimens were bonded using either a two-step universal primer-orthodontic adhesive combination or a one-step aligner adhesive. After thermocycling, all bonded specimens underwent shear bond strength testing.
Table 2.
Surface roughness (Ra) by aligner material and sandblasting.
Fig 2.
Scanning electron micrographs (×1000) of aligner surfaces before (left panel) and after sandblasting (right panel).
A,B, PETG; C,D, TPU; E,F, PCTG; G,H, TA-28; I,J, TC-85DAC; K,L, DCA. Thermoformed foils and TA-28 showed pronounced ploughing, pits, and sharp asperities after sandblasting. TC-85DAC and DCA showed comparatively shallower micro-cracking and less crater formation.
Table 3.
Three-way ANOVA for shear bond strength (MPa).
Table 4.
Shear bond strength by material and sandblasting-primer combination.
Fig 3.
Box plots of shear bond strength (MPa) by material, surface treatment (non-sandblasted versus sandblasted), and primer (universal primer–orthodontic adhesive combination versus one-step aligner adhesive).
Fig 4.
Distribution of failure modes with Adhesive Remnant Index (ARI) across combinations of material, primer, and surface treatment.
PETG bonded with Bond Aligner tended to show higher ARI 3, whereas PCTG showed mostly ARI 0.
Fig 5.
Representative failure modes as per Adhesive Remnant Index (ARI).
A, ARI 0, adhesive fully on the composite cylinder; B, ARI 1, mixed failure with <50% adhesive left on tray; C, ARI 2, mixed failure with >50% adhesive left on tray; D, ARI 3, cohesive failure within the adhesive or tray polymer.