Influence of surface treatment on shear bond strength of orthodontic brackets

Comparative Evaluation of the Repair Bond Strength of Dental Resin Composite after Sodium Bicarbonate or Aluminum Oxide Air-Abrasion

The dental prophylactic cleaning of a damaged resin-based composite (RBC) restoration with sodium bicarbonate can change the surface characteristics and influence the repair bond strength. The purpose of this study was to compare the effect of sodium bicarbonate (SB) and aluminum oxide (AO) surface treatments on the microtensile bond strength (µTBS) of repaired, aged RBC. Bar specimens were prepared from microhybrid RBC and aged in deionized water for 8 weeks. Different surface treatments (AO air-abrasion; SB air-polishing), as well as cleaning (phosphoric acid, PA; ethylene-diamine-tetraacetic-acid, EDTA) and adhesive applications (single bottle etch-and-rinse, ER; universal adhesive, UA), were used prior to the application of the repair RBC. Not aged and aged but not surface treated RBCs were used as positive and negative controls, respectively. The repaired blocks were cut into sticks using a precision grinding machine. The specimens were tested for tensile fracture and the µTBS values were calculated. Surface characteristics were assessed using scanning electron microscopy. AO-PA-UA (62.6 MPa) showed a 20% increase in µTBS compared to the NC (50.2 MPa), which proved to be the most significant. This was followed by SB-EDTA-UA (58.9 MPa) with an increase of 15%. In addition to AO-PA-UA, SB-EDTA-UA could also be a viable alternative in the RBC repair protocol.

Genetic polymorphisms influence shear bond resistance of orthodontic brackets

OBJECTIVES

The purpose of this study was to determine if shear bond resistance of orthodontic brackets bonded to enamel is associated with genes implicated in the enamel mineralization process.

METHODS

Ninety-two permanent, caries-free premolars extracted for orthodontic purposes and their associated saliva samples were obtained. Eighteen single nucleotide polymorphisms (SNPs) were studied for association with shear bond resistance. The genes of interest in this study were those previously associated with dental caries by our group. All tooth samples were bonded on the buccal surface with metallic lower lateral brackets, and then subjected to physical debonding. The force required to debond the bracket was recorded in Newtons (N) and converted to a shear bond resistance value in Megapascals (N/mm²). The data were analyzed for statistical significance as compared with the mean shear bond resistance value via PLINK whole genome analysis software.

RESULTS

Associations were found between the SNPs for tuftelin (rs7526319, P = 0.004) and amelogenin (rs17878486, P = 0.04) and a higher shear bond resistance.

CONCLUSION

The collected data support the proposed hypothesis that genes involved in the mineralization process affect the bonding of orthodontic brackets, and such an association is of value for the field of orthodontics, particularly in evaluating the efficacy of enamel-resin bond strength for patients receiving treatment.

Comparison of the Shear Bond Strength of Metal Orthodontic Brackets Bonded to Long-term Water-aged and Fresh Porcelain and Composite Surfaces

Objective

The aim of the present study was to compare the shear bond strength (SBS) of metal orthodontic brackets bonded to long-term water-aged and fresh porcelain and composite surfaces.

Methods

One porcelain (Vitadur Alpha (VA)) and three composite (Filtek Ultimate (FU), Tetric EvoCeram (TEC), and Gradia Direct Anterior (GDA)) materials were evaluated in the present study. First, 10 discs from each material were prepared and subjected to the aging procedure for 5 years. Then, for comparison, another 10 discs from each material were prepared as fresh surfaces and stored in distilled water for 24 h. Metal brackets were bonded to the prepared disc surfaces, and after being stored in water for 24 h, they were subjected to shear bond test using a universal testing machine. Adhesive remnant index (ARI) scores were obtained by examining the disc surfaces under a stereomicroscope at 10× magnification. Kruskal-Wallis test was used to compare the aged and fresh groups.

Results

Although the difference between the SBS between the aged and fresh groups with VA, FU, and TEC was not significant, the SBS was significantly higher in the fresh group with GDA. With regard to ARI scores, there was no significant difference between the aged and fresh groups with FU and GDA, whereas the ARI scores of the aged groups with VA and TEC were higher.

Conclusion

It was concluded that the aged restoration materials have a distinctive influence on the SBS of metal orthodontic brackets.