Shear Bond Strength of Four Types of Orthodontic Retainers after Thermocycling and Cyclic Loading

Abstract

Objectives. This study assessed the shear bond strength (SBS) of four types of orthodontic retainers after thermocycling and cyclic loading. Materials and Methods. This in vitro, experimental study evaluated 120 extracted mandibular central and lateral incisors. The teeth were mounted in acrylic resin blocks in sets of three, such that the interdental contacts and positioning of the teeth resembled the dental arch. The acrylic blocks were divided into four groups (n = 10) for the use of 0.016 × 0.022-inch Bond-A-Braid® wire, 0.0195-inch twisted wire, 0.0175-inch coaxial wire, and 0.038 × 0.016-inch Ortho-Flex Tech® wire, as retainers. The retainers were bonded to the lingual surface of the teeth with Transbond XT adhesive in all groups, and the specimens underwent thermocycling and cyclic loading (125,000 load cycles applied to the incisal edge of the incisor tooth in the middle, simulating 6 months of clinical service). Any fracture in the process of aging was recorded. The teeth were then subjected to vertical loads applied along their occlusoapical axis in a universal testing machine to determine the SBS in Newtons. The adhesive remnant index (ARI) scores were also determined. Data were analyzed using ANOVA, the Monte Carlo chi-square test, and the Kruskal–Wallis test. Results. Thermocycling and cyclic loading did not cause degradation or fracture of the retainers. The SBS and ARI scores of the four groups were not significantly different ( P > 0.05 ). Conclusion. The SBS of retainers with flat rectangular-shaped cross-section was similar to that of retainers with a round cross-section; thus, they have no superiority over each other in this respect.

Bruxism’s Implications on Fixed Orthodontic Retainer Adhesion

“…As a result, the fixed retainer’s fracture or debonding could trigger a recurrence of the orthodontic issue [ 3 , 5 ]. In terms of bond strength, according to Golshah and Amiri Simkooei, there is no advantage between wire retainers with a round cross-section and those with a flat, rectangular-shaped cross-section [ 6 ].…”

Mechanical properties of combined packable and high-filled flowable composite used for the fixed retainer: an in vitro study

“…A score of 2 or 3 on the ARI index indicates bond failure at the adhesive and retainer wire interface, leaving more composite on the tooth surface, which can lead to a more time-consuming debonding process and a higher risk of enamel damage [ 27 , 42 ]. Conversely, scores of 0 or 1 on the ARI index signify bond failure at the enamel and adhesive interface, possibly due to incorrect bonding procedures or inadequate bond strength from the adhesive system [ 43 ]. In such cases, the debonding process is typically easier and less destructive to enamel integrity [ 42 ].…”