Abstract
This study aims to assess the efficacy of a universal adhesive (Scotchbond Universal, 3M ESPE) (SB) in total-etch mode, compared to a traditional orthodontic primer (Transbond XT Primer, 3M ESPE) (XT Primer), to perform bonding of orthodontic fixed retainers along with the Transbond XT Light Cure Adhesive Paste (3M ESPE). For the in vitro study, a round section wire (Ortosmail Krugg) was bonded using XT Primer for 20 bovine incisors (Group 1) and SB for other 20 (Group 2). Samples were debonded in a universal testing machine applying a tangential force to specimens (crosshead speed of 1 millimeter per minute). Shear bond strength (SBS) and adhesive remnant index (ARI) scores were calculated. For the in vivo study, 100 patients needing upper and lower canine-to-canine fixed retainers after orthodontic treatment were randomly assigned to two groups of 50 participants each, i.e., group 1 (retainer bonding with XT Primer) and group 2 (retainer bonding with SB). Over two years, examinations were carried out monthly, and detachments were registered by considering the teeth and arches affected. In vitro, no statistically significant differences in SBS and ARI scores were demonstrated between the two groups, both showing a mean bond strength of about 12 MPa and major frequency of ARI “2” (>50% remnant adhesive on the enamel). Conversely, a significantly lower failure rate over 2 years was assessed clinically for group 2 in both arches. Independently of the adhesive and arch, incisors reported a significantly higher failure rate than canines. Scotchbond Universal used in total-etch mode could be a valid alternative to the traditional orthodontic Transbond XT Primer.
Highlights
After obtaining the desired position of the teeth, the final step of an orthodontic therapy consists of a retention procedure that attempts to keep the result achieved, avoiding a certain relapse due to the tendency of teeth to regain their pretreatment position [1]
The results obtained in vitro showed the absence of statistically significant differences between the conventional orthodontic primer and the universal adhesive, for both Shear Bond Strength (SBS) and adhesive remnant index (ARI). As regards this latter parameter, a major frequency of an ARI score of 2 has been shown for both materials tested, which indicates that a cohesive failure at the wire–composite interface occurs, and more than 50% of the adhesive remains on the teeth, with no failure of the bonding interface, in accordance with the results reported by other authors [38,39]
Score of 1 or 2 and that it should have a bonding strength in the interval of 5–50 MPa to sustain masticatory forces [40], the values of the two respective tested materials fall within these ideal ranges, but no significant difference was detected between them
Summary
After obtaining the desired position of the teeth, the final step of an orthodontic therapy consists of a retention procedure that attempts to keep the result achieved, avoiding a certain relapse due to the tendency of teeth to regain their pretreatment position [1]. These retention methods are usually preferred for the mandibular arch and used for the maxillary one [6] Despite this appliance not necessitating the active cooperation of the patient as required for removable retainers, its main disadvantage remains the risk of detachment [7,8]. Due to the need of removing the orthodontic device once the treatment outcome is obtained, the bonding system should not provide too high bond strength because removal of the device can cause damage to the enamel [11]
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