Ortholux led

The specimens were etched with 37% phosphoric acid for 30 s, washed for 20 s, and dried with oil‐free compressed air for 20 s, after which a thin uniform coat of primer (Transbond XT Primer; 3 M Unitek) was applied. The adhesive resin (Transbond XT Light Cure Adhesive Paste; 3 M Unitek) was placed onto the bracket base, and the bracket was positioned on the specimen surface. Excess adhesive resin was removed with an explorer. Adhesive resin was polymerized using curing light (Ortholux LED; 3 M Unitek) at approximately 1000 Mw/cm² for a total of 10 s from two directions (mesial and distal).

Sound bovine incisors were extracted, cleaned, pumiced, and stored in 1% aqueous solution of chloramine-T (Junsei Chemical, Tokyo, Japan) at 4 °C. After careful preparation to a uniform size (7.5 mm diameter and 2.6 mm thickness), the bovine incisor specimens were randomly divided into three groups according to surface treatment: no surface treatment control (BI), acid-etched surface (ET), and primed surface (PR). The ET specimens were etched with 37% phosphoric acid gel (3 M, Monrovia, CA, USA) for 20 s, rinsed, and air-dried. In the PR group, Transbond XT primer (3 M) was applied to the etched surface and light-cured for 30 s using OrthoLuxLED (3 M) after acid etching. For the adhesive specimen group (AD), Transbond XT adhesive (3 M) specimens were prepared to the same size as the bovine incisor specimens using a Teflon template. The template was placed on top of a glass slide and filled with Transbond XT adhesive to flush with the top of the plate. The next slide was placed on top of the adhesive and pressed to produce a flat surface of adhesive. They were then light-cured for 20 s each from the top and bottom according to the manufacturer’s instructions. A total of 76 disk-shaped specimens (19 specimens per group) was used in this study: 72 (18 per group) for surface analyses and biofilm formation and 4 (one per group) for scanning electron microscopy (SEM) analysis.