Effects of fluorosed enamel on orthodontic bracket bonding : An in vitro study

To investigate the effect of enamel deproteinization and air abrasion on shear bond strength (SBS), adhesive remnant index (ARI) scores, and surface topography when bonding orthodontic brackets to fluorosed enamel.

The sample included 90 fluorosed and 30 normal premolars divided into four groups: group I (fluorosed premolars subjected to air abrasion before acid etching), group II (fluorosed premolars subjected to deproteinization before acid etching), group III (fluorosed premolars; control for groups I and II), and group IV (normal premolars; control for group III). Bonding procedures included etching with 37% phosphoric acid, priming with Transbond^TM XT primer (3M Unitek, Monrovia, CA, USA), and application of Transbond^TM XT adhesive paste (composite; 3M Unitek, Monrovia, CA, USA). Air abrasion was done using 50 µm aluminum oxide particles under 0.28 MPa pressure for 5 s with the micro-etcher held at a distance of 10 mm. Deproteinization was done for 60 s with 5% sodium hypochlorite (NaOCl).

Fluorosed premolars subjected to deproteinization showed the lowest (median = 6.57 MPa) SBS among the four groups, followed by 8.14, 8.90, 8.14 MPa for groups I, III, and IV respectively. ARI scores were significantly different between the four groups (p = 0.006). Fluorosed enamel etched after air abrasion or deproteinization with NaOCl showed a predominance of type 4 etching pattern with some areas appearing unetched.

Shear bond strength of all groups was within the 6-8 MPa acceptable range for orthodontic purposes. Fluorosed premolars subjected to deproteinization showed the lowest values. Further studies are recommended to scrutinize the deproteinization technique.