Paper
COMPARISON OF SHEAR BOND STRENGTH OF METAL AND CERAMIC ORTHODONTIC BRACKETS AFTER ADDING NANOPARTICLES OF SILVER
Published 2017 · Y. Althomali
Egyptian dental journal
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Abstract
Objective: To evaluate effect of nanoparticles of silver (NAg) added on Nano-Bond adhesive system and its effect on shear bond strength of brackets attached to enamel. Materials and methods: Thirty extracted premolar teeth for orthodontic reasons were divided into two groups; First group metal brackets and second group the ceramic brackets were bonded by Nano-Bond adhesive system containing (NAg) with concentration 0.05%. Every group was further subdivided into 2subgroups with 5 teeth each; Groups A1, B1 (Teeth not subjected to thermocycling and cyclic loading), Groups A2, B2 [(Teeth subjected to thermocycling (500cycles) and cyclic loading (90N, 0.8-1 cycles/sec. 100,000 cycles)] Enamel etched then the adhesives were applied to the entire enamel surface according to bonding agent containing (NAg) or not, then light cured for 10 seconds with LED. The base of brackets were filled by nano-filled composite resin and placed on the tooth and cured by LED for 40 seconds. The recorded values of bond strengths in (MPa) were collected, tabulated and statistically analyzed. One way analysis of variance (ANOVA) and Tukey’s tests were used for testing the significance between the means of tested groups which are statistically significant when the P value ≤ 0.05. Results: shear bond strength of metal brackets bonded by Nano-Bond adhesive containing nanoparticles of silver (NAg) (Group A) was significantly higher than shear bond strength of ceramic brackets (group B). Conclusions: The adhesive shear strengths are high for metal bracket bonded by Nano-Bond adhesive system containing nanoparticles of silver (NAg) with concentration 0.05% than ceramic bracket. (32) Yousef M. Althomali E.D.J. Vol. 63, No. 1 Although these brackets offer better esthetics, enamel fractures and cracks have been reported during debonding procedures. Increased bond strength usually results in bond failure at the enamel surface, rather than at the bracket-adhesive interface. Consequently, the continuing challenge is to develop a bond between orthodontic attachments and the enamel that is strong enough to accomplish treatment but can be broken for debonding without damage to the enamel surface6. The majority of complaints are regarding the discomfort encountered during the debonding phase of treatment. One of the crises the clinicians may face during treatment is bracket failure. This usually the outcome of either applying improper force to the bracket or due to deprived bonding technique– studies have shown that clinical bond failure occurs with 5% to 7% of brackets bonded with light cure or chemical cure composite resins for different reasons7. Measurement of shear bond strength is the most commonly used laboratory method to evaluate the performance of orthodontic bonding systems and a variety of techniques have been applied for shear bond strength measurements2. However, the lack of standardization of bond strength testing and the large distribution of results often prevent confident conclusions from being drawn8-10. Shear tests typically involve a combination of shear and peel forces because force is applied at a distance from the bonding interface11,12. The bonding procedure is based on enamel alteration created by acid etching of the enamel as developed by Buounocore (1955)13. Phosphoric acid is used in the form of a solution or gel etches at a concentration of 37%. The acid is applied on enamel surface thus cleanses the surface and improves the wettability of enamel by the resin. It also causes selective dissolution of enamel rods. The acid removes calcium salts from enamel, thus increases the size and number of micro spaces present in the enamel surface which is normally porous. When the resin is applied on such etched enamel surface, it can penetrate into micro spaces or irregularities, thus producing “resin tag” (finger like projections) with subsequent increase in bond strength and reduction of marginal staining and discoloration14. The use of bonding agents is known from restorative dentistry that it improves the adhesion of composite resins. The bonding agents create a micro-mechanical interlock between the dentin collagen and resin by forming the hybrid layers15. Bonding agents were adhere composite restoration to tooth structure to form a functional and durable interface16-18. Bonding agent compositions and bond strengths have been improved in previous studies19,20. Antibacterial adhesives are promising to combat bacteria and reduce recurrent caries at the tooth-restoration margins21,22. Nano-sized filler such as nano-sized aerosol silica filler were introduced to bonding agents by mean of nano technology. The nanofillers technology is claimed to increase adhesion to both enamel and dentin and improves marginal integrity23. Recently, a quaternary ammonium dimethacrylate (QADM) was synthesized and incorporated into resins to inhibit biofilm growth24,25. In addition, recent studies developed antibacterial nanocomposites containing nanoparticles of silver (NAg) with a potent antibacterial activity26. Hence, the cured QADM-containing adhesive could inhibit bacteria adherent on its surface, but would have no effect on bacteria in the culture medium away from its surface27. The resin containing NAg inhibit not only bacteria on its surface, but also bacteria in the culture medium away from its surface due to Ag ion28. For dental composites, it is desirable to incorporate silver nanoparticles with a high surface area into the resin to reduce the Ag particle concentration COMPARISON OF SHEAR BOND STRENGTH OF METAL AND CERAMIC (33) necessary for efficacy29. Low Ag filler levels in the resin would not affect the resin color25. Thermocycling is defined as the in vitro process of subjecting a restoration and tooth to temperature extremes that conform to those found in the oral cavity29. Thermocycling considered cycling regimes employing short dwell time to be more realistic clinically31. Cyclic loading application was made to simulate clinical occlusal stress condition in oral cavity32. The purpose of this study was to evaluate the effect of adding nanoparticles of silver (NAg) with concentration 0.05% into Nano-Bond adhesives on shear bond strength of brackets attached to enamel. MATERIALS AND METHODS An in vitro study was conducted to test the shear bond strength of orthodontic brackets after adding nanoparticles of silver (NAg) with concentration 0.05% on nano-bond adhesive. One type of adhesive available system was used as the control [Nano-Bond adhesive (Pentron Clinical technologies, USA, lot # 183421)], nanoparticles of silver (NAg) with concentration 0.05% was added into Nano-Bond adhesives, one type of nano-filled composite resin (Artiste Nanocomposite, Pentron Clinical technologies LLc, USA, lot # 182066-185215) and two type of orthodontics brackets: metal bracket (0.022x0.028) (Global orthodontics, LLc, Chanlitity USA) and ceramic bracket (Crystaline;Tomy, Tokyo, Japan) were used in this study. Twenty cariesfree freshly extracted human maxillary premolar teeth were collected to be used in this study. The teeth were cleaned by ultrasonic scaler and stored in distilled water at 370C before testing. Teeth were embedded in chemically cured dental acrylic (Palavit G, Heraeus Kulzer, Wehrheim,Germany) in plastic cylinders to allow for standardized and secure placement during testing. Teeth were randomly divided into two main groups (10 each) according to the bonding agent containing nanoparticles of silver (NAg). Group A: The metal brackets were bonded by Nano-Bond adhesive system containing nanoparticles of silver (NAg) with concentration 0.05% and Group B: The ceramic brackets were bonded by Nano-Bond adhesive system containing nanoparticles of silver (NAg) with concentration 0.05% Grouping of the teeth TABLE (1) Every group was further subdivided into 2 subgroups with 5 teeth Groups Subgroups Description No. of Specimens G ro up A Group A1 Teeth not subjected to cyclic loading. 5 specimens Group A2 Teeth subjected to thermocycling (500cycles) and cyclic loading (90N, 0.8-1 cycles/sec. 100,000 cycles). 5 specimens G ro up B Group B1 Teeth not subjected to cyclic loading. 5 specimens Group B2 Teeth subjected to thermocycling (500cycles) and cyclic loading (90N, 0.8-1 cycles/sec. 100,000 cycles). 5 specimens
Nano-Bond adhesive system containing nanoparticles of silver (NAg) significantly increases the shear bond strength of metal orthodontic brackets bonded to enamel compared to ceramic brackets.
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