An in vitro evaluation of aligner force decay in artificial saliva

The present study aimed to compare the force decay of invisible aligners for maxillary anterior teeth with 0.1 mm (D₁), 0.2 mm (D₂), and 0.3 mm (D₃) labial movement within a simulated oral environment over 7 days.

The prepared invisible aligners were immersed in saliva (S) and subjected to applied force (F) for 7 days. The aligners were set and placed on the maxillary right central incisor with 0.1 mm (D₁), 0.2 mm (D₂), and 0.3 mm (D₃) labial movement. Thin-film pressure sensors were used to measure the aligner force changes. The data were collected and analyzed by statistical methods.

Significant differences were observed in the initial and first-day force between the D₂ and D₃ groups under simulated oral environment force (SF) (P < 0.05). There was a significant difference in force decay between Day 1 and Day 7 for all groups (P < 0.05). The SFD₁ group showed a significant decrease in force on Day 5 (P < 0.05), while the SFD₂ and SFD₃ groups showed significant force decay on Day 4 (P < 0.05). The force decay ratio on Day 7 was higher in the SFD₃ group than in the SFD₁ and SFD₂ groups, but no significant difference was observed.

Larger labial movement of the aligners resulted in higher force decay under artificial saliva environments, and the force decay of invisible aligners was increased by immersion time in artificial saliva.