Abstract
The aim of this study was to evaluate the effects of deproteinization with 5.25% sodium hypochlorite (NaOCl) prior to enamel conditioning with 10% polyacrylic acid (PAA) and 35% phosphoric acid (PA) on the bond strength (BS) of brackets bonded with resin-modified glass ionomer cement (RMGIC). One hundred human premolars extracted for orthodontic reasons were divided into 5 groups (n = 20 in each group): G1 (control), enamel conditioning with PA, application of adhesive and bonding of brackets with TransbondTM XT composite resin (3M/Unitek, Monrovia, CA, USA); G2, enamel conditioning with PAA and bonding with RMGIC (Fuji OrthoTM LC, GC America, Alsip, IL, USA); G3, NaOCl-treated enamel, conditioning with PAA and bonding with RMGIC; G4, enamel conditioning with PA and bonding with RMGIC; and G5, NaOCl-treated enamel, conditioning with PA and bonding with RMGIC. Once the brackets were bonded, the teeth were stored in distilled water for 24 hours at room temperature and pressure until being subjected to shear stress in a Universal Mechanical Testing Machine (EMIC® DL 500, São José dos Pinhais, PR, Brazil). The BS value was higher in G1 (17.08 ± 6.39) than in any of the experimental groups (p < 0.05). No statistically significant differences were noted between groups using RMGIC (p > 0.05), except between G3 (9.86 ± 2.90) and G5 (5.00 ± 2.49). No statistically significant differences were noted between the mean Adhesive Remnant Index values among the evaluated groups (p > 0.05). Conclusion: The use of NaOCl combined with PAA increased the BS of brackets bonded with RMGIC. The deproteinization of the group treated with PA reduced the shear bond strength of the brackets.
Highlights
The search for the ideal orthodontic bonding material persists, one that provides physical, chemical, mechanical and biological characteristics to more effectively meet the clinical needs of orthodontists
The groups treated with phosphoric acid (G4 and G5) exhibited lower mean bond strength (BS) values than did G2, no significant differences were identified (p > 0.05)
The authors of the present study considered testing and comparing the BS of brackets conditioned with polyacrylic acid (PAA) and phosphoric acid (PA) as one of the study goals
Summary
The search for the ideal orthodontic bonding material persists, one that provides physical, chemical, mechanical and biological characteristics to more effectively meet the clinical needs of orthodontists. One of the main challenges lies in achieving a sufficient bond strength that supports both masticatory and orthodontic mechanical loads without being too strong to jeopardize the integrity of the enamel upon removal of the accessories. The ideal bonding system should provide adequate working time for the orthodontist to position the accessories correctly, and it should be biocompatible[1]. The use of 5.25% sodium hypochlorite (NaOCl) as a enamel deproteinizing agent prior to acid conditioning and bracket bonding with RMGIC has been suggested as a means of increasing bond strength. The number of studies supporting these assumptions is limited and the type of acid (PA) used after deproteinization was not the one recommended by the RMGIC manufacturer
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