Abstract
Objective: This study attempted to investigate the effect of enamel deproteinization using citric acid, PEG 400 and NaOCL on the shear bond strength of orthodontic brackets to enamel using nano-silver modified resin for the prevention of white spot lesions. Material and Methods: 68 premolars were used in the study; nano-silver modified adhesive resin was used to bond orthodontic brackets to the enamel. Specimens were divided into 4 groups according to the applied surface treatment before bonding. Group I (control): acid etching with 37% phosphoric acid. Group II: deproteinization using 5.25% sodium hypochlorite (NaOCl) before acid etching. Group III:deproteinization using 10% citric acid before acid etching. Group IV:deproteinization using 5% polyethylene glycol (PEG 400) before acid etching. The specimens were then thermo- cycled for 6000 cycles. They were examined for surface roughness, shear bond strength and using electron microscope. electron microscope Results: In both surface roughness and shear bond strength tests, Group III (citric acid) showed the highest values, followed by Group II (sodium hypochlorite); (p < 0.001). The least values were shown for Groups I (control) and IV (PEG 400), with no statistically significant difference between them (p = 0.948). SEM revealed etching pattern type 1 and 2 in the citric acid group while PEG 400 showed shallower micro- porosities. Conclusions: Deproteinization of enamel using either NaOCl or citric acid increased the bond strength of nano-sliver modified resin to enamel, with citric acid showing greater increase in bond strength. Deproteinization using PEG 400 did not increase the bond strength. Keywords Deproteinization; Sodium hypochlorite; Citric acid; PEG 400; Nano- silver modified adhesives.
Highlights
White spot lesions encountered during orthodontic treatment are considered a major clinical problem, for compromising esthetics; and because they present the initial stage of caries [1]
[1] Enamel deproteinization, using NaOCl, to improve adhesive bond strength was discussed in the literature, [2,15,21,25] and its application offered an opportunity for taking both benefits
The wire loop method was chosen for shear bond strength (SBS) testing because it simulated clinical loads and offered better stress distribution at the bracket/ enamel interface compared to the knife edge chisel method[22,26,27,28] thermocycling was considered to be pivotal in simulating the clinical duration of orthodontic treatment and in inducing a thermal aging effect unlike other research which investigated short term bond strength [29]
Summary
White spot lesions encountered during orthodontic treatment are considered a major clinical problem, for compromising esthetics; and because they present the initial stage of caries [1]. Fixed orthodontic appliances complicate oral hygiene maintenance and increase the risk of developing white spot lesions [2,3,4,5]. Several mechanisms have been previously suggested to control the formation of white spot lesions which include the administration of topical agents containing fluoride or casein phosphopeptide-amorphous calcium phosphate (CPPACP). They had considerable limitations in noncompliant patients [6]. When nano-silver modified resin adhesives were used in bonding orthodontic brackets, the shear bond strength was decreased,[1,13] causing debonding and increased treatment time and cost [2,14]
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