Simulation of oral environmental conditions through artificial aging of teeth for the assessment of enamel discoloration in orthodontics.

Background: The clinical performance of dental materials can be predicted via artificial aging approaches. The bracket bonding procedure may cause irreversible alterations to the enamel surface. The aim of this study was to introduce a novel artificial aging protocol and evaluate its effect on the discoloration of both bracket-bonded and unbonded teeth while also comparing the effects of four orthodontic adhesives on enamel color and whiteness.

Methods: One hundred permanent lower incisors from humans were randomly divided into five groups, each including 20 specimens. The lower incisor metal brackets were bonded to the teeth via four different orthodontic adhesives (Transbond XT, Kurasper F, Bisco ORTHO, and Light Bond), and a control group was established. To simulate the cumulative effects of aging on the oral cavity, all the samples were subjected to mechanical cyclic loading (50,000 cycles), hydrothermal cycling (10,000 cycles), or exposure to stained beverages (25 days). A colorimeter device was used to measure the color of the teeth before and after testing. Statistical differences were calculated via one-way analysis of variance (ANOVA) and Tukey's test.

Results: The combined aging protocol resulted in statistically significant and clinically unacceptable differences in tooth color alterations and whiteness index values across all groups (p < 0.05). The control group presented the least significant discoloration, whereas the bracket-bonded groups presented greater discoloration. Furthermore, there were statistically significant differences among the bracket-bonded groups (p < 0.05).

Conclusions: The combined artificial aging protocol can be employed to simulate the macroenvironmental conditions of the oral cavity in laboratory investigations. The composition of the orthodontic adhesive also influences the severity of tooth discoloration.