Effect of different bonding protocols on degree of monomer conversion and bond strength between orthodontic brackets and enamel

Abstract

The objective of the present study was to evaluate the effect of different surface treatments and polymerization protocols on the bond strength of brackets to enamel, and the degree of conversion of the bonding agents. 120 bovine crowns were embedded in acrylic resin blocks and sanded. Next, the blocks were randomly assigned into 12 groups. Metal brackets were bonded to enamel according to the "surface treatment" factor (A: Phosphoric Acid; ATxt: Phosphoric Acid + Transbond XT Primer®; Tse: Transbond Plus Self Etching Primer®; and SBU: Scotchbond Universal®) and "polymerization" factor (R20: Radii-Cal®/20 seconds; V20: Valo Cordless®/20 seconds; and V3: Valo Cordless®/3 seconds). All samples were stored for 6 months (water, 37ºC) and then subjected to a shear bond strength test (SBS). Bond failures were classified according to the Adhesive Remnant Index (ARI) and analyzed with the Kruskal-Wallis and Mann-Whitney tests (5%). Using the same factors, 120 resin discs were made to assess the degree of conversion (DC) of the monomer. Data from the SBS (MPa) and DC (%) were analyzed by analysis of variance (2 factors) and Tukey's test (5%). For the SBS, the factors "polymerization" (R20 = 8.1B; V20 = 13.2A; V3 = 5.2C, p = 0.0001) and "surface treatment" (A = 3.1C; ATxt = 13.6A; Tse = 12.3A; SBU = 6.3B, p = 0.0001) were statistically significant among groups. The highest adhesion value were found for the ATxt/V20 group (22.2A) and the lowest value for the A/R20 group (1.2E). Regarding ARI, score 2 was the most prevalent in groups A, ATxt, V20 and V3, while score 4 was the most prevalent in the Tse, SBU and R20 groups, with no significant difference between them (p = 1.0). Regarding DC, the factors "polymerization" (R20 = 66.6A; V20 = 58.4B; V3 = 45.1C, p = 0.0001) and "surface treatment" (A = 52B, ATxt = 59.7A, Tse = 51.4B, SBU = 63.8A, p = 0.0001) were statistically significant. Tse was more sensitive to the variations in polymerization protocols than the other surface treatments. Treatment A did not present suitable bond strength or degree of conversion.

Effect of universal adhesive on shear bond strength of metal bracket to enamel and dental amalgam

“…All values either fell in the mentioned range or were substantially higher. This result is consistent to the study conducted by Sena et al (17). In both studies, the enamel group's SBS which followed by pre etching treatment was the highest, and the self-etches group significantly showed lower SBS, but clinically acceptable (17).…”

The Influence of Resin Infiltration Pretreatment on Orthodontic Bonding to Demineralized Human Enamel

“…The degree of conversion of adhesive could have also affected SBS of the tubes, as it has a direct effect on the chemical, physical and mechanical features of the resin material [42]. A recent study comparing different adhesives used in orthodontics showed no significant difference in the degree of conversion between Scotchbond and Transbond XT [43]. Unfortunately, we found no research investigating the degree of conversion of Assure PLUS, encouraging further investigations in this direction.…”

Effect of surface treatments on the adhesive properties of metallic brackets on fluorotic enamel

“…34 However, the varied number of cycles, the choice of temperature, time conditions, and intervals between baths hinder comparison of the results. 6,13,34 Therefore, further studies should be conducted to investigate if the NaOCl and sandblasting can preserve the resin cement-fluorotic enamel interface from degradation in longer periods of time.…”

“…Moreover, the conversion of monomer into polymer plays an important role in successful enamel-brackets bonding. 12 , 13 The conversion degree of orthodontics resin cement was previously reported; however, the authors 12 did not evaluate the conversion degree into the adhesive interface especially after sandblasting or deproteinization treatment in fluorotic enamel.…”