Effect of over-the-counter whitening strips and toothpaste on shear bond strength of orthodontic brackets

To investigate: 1) the effects of over-the-counter white strip enamel bleaching and 2-Step whitening toothpaste application on the shear bond strength of orthodontic brackets at 24-hours and 7-days post-bleaching latent period; and 2) the correlation bet

Mechanical properties of the NiTi Memoria Leaf Spring Activated Expander (NiTi MLSAE) for maxillary transverse discrepancy correction : an in-vitro study

To determine the mechanical properties of the NiTi Memoria® Leaf Spring Activated Expander (NiTi MLSAE) in two forms, unaltered (unbent) and altered (bent) to mimic clinical use. This in-vitro pilot study was conducted using eight NiTi MLSAE expanders (American Tooth Industries, Oxnard, California) representing four force magnitudes: 10mm 500g, 10mm 900g, 6mm 450g and 6mm 900g models. Two experiments were performed: the first tested the expanders in their unbent form and the second tested them after they were bent by one experienced technician. All expanders were adapted to a standard three dimensional printed maxillary study model. A Dillion Quantrol 500N (110lbf) load cell and a custom-made fixturing apparatus was used to determine the amount of expansive forces delivered. Prior to testing, the ligation compressing the NiTi MLSAE leaves was cut to allow the appliances to expand to their original form. Emperor? (force) Software was used to measure the expansion forces. The average expansion forces generated by the expanders were: unaltered = 897.4g (8.8N) and bent = 877.0g (8.6N) for the 10mm 900g model, unaltered = 489.5g (4.8N) and bent = 479.3g (4.7N) for the 10mm 500g model, unaltered = 458.9g (4.5N) and bent = 438.5g (4.3N) for the 6mm 450g model, and unaltered = 805.6g (7.9N) and bent = 785.2g (7.7N) for the 6mm 900g model. Regardless of whether the expander was straight or bent, the forces generated by the 10mm 900g, 10mm 500g and 6mm 450g Ni-Ti MLSAEs correlated with the benchmark study conducted by the manufacturer. However, the forces generated by the 6mm 900g Ni-Ti MLSAE were less than the data published by the manufacturer. Binding was observed when the expanders were manipulated to mimic clinical use, and this may account for the reported lower expansion force

Shear Bond Strength and Bracket Base Morphology of New and Rebonded Orthodontic Ceramic Brackets

The objectives of this study were to (1) to evaluate the shear bond strength (SBS) of two ceramic brackets when new and when rebonded following various bracket base conditioning methods, and (2) to determine bond failure mode relative to bracket base morphology. 100 Symetri ClearTM (SC) and 100 Radiance Plus® (RP) ceramic brackets were bonded to bovine incisors and divided into five groups: one group served as controls and four had brackets rebonded following conditioning by: no surface treatment, sealant, sandblasting, and flame then steam. SBS, adhesive remnant index, and bracket base morphology were evaluated. SBS showed no statistical difference between new and rebonded with no surface treatment or sealant (SC brackets) and with sealant or flame and steam (RP brackets). When comparing SC to RP, SBS was higher with SC, no surface treatment, and sandblasted groups. All groups had varying amounts of adhesive left on the tooth, with the sandblasted group having the most. SEM analysis showed that sandblasting damaged the retention features of bracket bases. In conclusion, when rebonded, the SBS of SC brackets that had no surface treatment and both SC and RP brackets that had sealant showed no significant differences to new brackets. Sandblasting damaged the retention features of SC and RP bracket bases, resulting in low SBS