The Influence of Thermocycling Testing on Enamel Microcracks following the Metal Orthodontic Brackets Debonding

Enamel microcracks (EMCs) arising during the removal of metal orthodontic brackets represent a considerable challenge in dentistry. This in vitro study aims to explore the impacts of thermocycling, the types of orthodontic bonding agent, and curing techniques on the enamel surface of the tooth structure following the debonding of orthodontic metal brackets. It also examines the incidence, number, length, and direction of EMCs on the buccal surface of the tooth. Additionally, the study compares adhesive remnant index (ARI) scores and bracket failure post-debonding. Forty extracted human maxillary canines were divided into ten groups, including intact enamel negative controls (groups 1, 2) and groups (3–8) with metal brackets bonded using two different bonding agents and curing techniques. Following bonding, half of the groups underwent thermocycling testing. EMCs, ARI scores, and bracket failure modes were evaluated. The formation, length, and direction of cracks did not significantly differ among groups, regardless of experimental conditions. Thermocycling had no significant effect on ARI scores or bracket failure modes. However, significant variations were observed among curing technique groups, with seventh-generation bonding agents demonstrating potential effectiveness in achieving complete adhesive removal. The study underscores the importance of considering bonding agent systems and curing protocols to optimize bond outcomes and minimize the risk of metal bracket failure in orthodontic treatment.