Investigation of the cytotoxic and genotoxic effects of removable retention appliances.

Introduction: This study aimed to examine and compare the cytotoxic and genotoxic effects of Hawley and Essix removable retainers on tissues.

Methods: A total of 50 patients who had completed fixed orthodontic treatment were randomly assigned to 1 of 2 groups based on the type of retainer they would use for retention: Essix group (n = 25) or Hawley group (n = 25). For biochemical evaluation, saliva samples were collected at 3-time points: before appliance use, 1 month after appliance use (TB1), and 3 months after appliance use. The levels of 8-hydroxy-2'-deoxyguanosine (8-OHdG), nuclear factor erythroid 2-related factor 2, and Kelch-like ECH-related protein 1 (Keap1) were then analyzed. For cytologic evaluation, swab samples were collected before and 14-21 days after the use of the appliance, and the occurrence of micronucleus, pyknosis, karyorrhexis, and karyolysis were analyzed.

Results: Biochemical evaluation revealed that the 8-OHdG level was higher in the Hawley group at TB1 and TB2. Conversely, no significant differences were observed in nuclear factor erythroid 2-related factor 2 levels between the groups. Although no significant difference in Keap1 value was observed between the 2 groups at TB1, a notable elevation in Keap1 levels was evident in the Hawley group at TB2. A cytologic evaluation revealed that the levels of micronuclei, pyknosis, karyorrhexis, and karyolysis were higher in the Essix group at 14-21 days after appliance use.

Conclusions: The application of both appliances was observed to increase the number of findings indicating nuclear degeneration. However, the Hawley retainer increased the 8-OHdG level, whereas the Essix retainer showed a decrease in this 8-OHdG level.