Protemp 4 garant

All methods were carried out in accordance with relevant guidelines and regulations. The study was initiated after securing Internal Review Board (IRB). The samples in this study were prepared with human mandibular premolars, stainless steel lower premolar brackets (Victory Series, 3 M Unitek) and a bis‐acryl composite resin provisional material, Protemp 4 Garant (3 M ESPE). An adhesive resin (Transbond XT Light Cure Adhesive Paste; 3 M Unitek) was used to bond orthodontic brackets to tested substrates. Given that this is the first time that metal primer is used for bracket bonding there are no previous studies for a proper sample size calculation. Therefore, the number of 10 specimens per group was adopted which is a common number for decades of published papers dealing with the shear bond strength of orthodontic brackets.

Twenty specimens of the bis‐acryl composite resin provisional material Protemp 4 Garant (3 M ESPE) were fabricated in the shape of premolars by means of a rubber mold of a natural premolar tooth. After the mold had set, the bis‐acryl provisional material was injected into the mold and allowed to set. After setting, the specimens were removed from the mold and embedded in chemically cured dental acrylic. Then the specimens were ground with water coolant SiC papers up to 2000grit in a grinding/polishing machine (Polo250/3, Jean Wirtz) and polished with a polishing paste of (Buehler, Micropolish II, Lake Bluff, Ill), 1 and 0.05 μm particle size. All surfaces were sanblasted with airborne alumina particles (50 μm) for 10 s from a distance of 10 mm employing 0.55 MPa propulsion pressure (Microetcher ER, Danville Engineering Inc). The specimens were then equally divided between two groups (PM‐C and PM‐MP) and brackets were bonded by the two different bonding procedures as described previously for tooth specimens.