Heat treatment following surface silanization in rebonded tribochemical silica-coated ceramic brackets: shear bond strength analysis

Abstract

6XEPLWWHG -DQXDU\ 0RGL¿FDWLRQ 0DUFK $FFHSWHG -XQHO bjective: This study aimed to evaluate the effects of heat treatment on the tribochemical silica coating and silane surface conditioning and the bond strength of rebonded alumina monocrystalline brackets. Material and Methods: Sixty alumina monocrystalline brackets were randomly divided according to adhesive base surface treatments (n=20): Gc, no treatment (control); Gt, tribochemical silica coating + silane application; Gh, as per Gt SRVWKHDW WUHDWPHQW DLU ÀX[ DW o C for 60 s). Brackets were bonded to the enamel premolars surface with a light-polymerized resin and stored in distilled water at 37 o C for 100 days. Additionally, half the specimens of each group were thermocycled (6,000 cycles between 5-55°C) (TC). The specimens were submitted to the shear bond strength (SBS) test using a universal testing machine (1 mm/min). Failure mode was assessed using optical and scanning electron microscopy (SEM), together with the surface roughness (Ra) of the resin cement in the bracket using interference microscopy (IM). 2-way ANOVA and the Tukey test were used to compare the data (p>0.05). Results: The strategies used to treat the bracket surface had an effect on the SBS results (p=0.0), but thermocycling did not (p=0.6974). Considering the SBS results (MPa), Gh-TC and Gc showed the highest values (27.59±6.4 and 27.18±2.9) and Gt-TC showed the lowest (8.45±6.7). For the Ra parameter, ANOVA revealed that the aging method had an effect (p=0.0157) but the surface treatments did not (p=0.458). For the thermocycled and non-thermocycled groups, Ra (μm) was 0.69±0.16 and 1.12±0.52, respectively. The most frequent failure mode exhibited was mixed failure involving the enamel-resin-bracket interfaces. Conclusion: Regardless of the aging method, Gh promoted similar SBS results to Gc, suggesting that rebonded ceramic brackets are a more effective strategy.

Shear Bond Strength and Bracket Base Morphology of New and Rebonded Orthodontic Ceramic Brackets

“…With the RP brackets, the median SBS of two groups fell into the clinically acceptable range: N (8.35 ± 3.87 MPa) and R-S (6.24 ± 3.57 MPa). Consistent with previous studies [ 12 , 17 , 19 , 20 ], the N brackets had the highest overall median SBS, with no significant difference between the two types. The R-NST group with the SC bracket had the second-highest median SBS (6.84 ± 4.36 MPa), where the value was within the clinically acceptable bond strength range, whereas, with the RP bracket, the R-NST group had the fourth highest median SBS (4.12 ± 3.83 MPa), where the value was below the acceptable range.…”

“…Potentially, a much higher temperature than the non-luminous zone of the butane lab torch may be needed to break down the resin remnants. While there is no previous research on the bond strength of ceramic brackets using flame followed by steam treatment prior to rebonding, two studies [ 19 , 20 ] have tested the effect of heat treatment on bond strength. Silva et al [ 19 ] tested the SBS of rebonded ceramic brackets after they were heat treated with a hot air dryer for 60 s. The results were consistent with this study for the SC bracket in that the SBS was significantly lower than that of new brackets.…”

“…While there is no previous research on the bond strength of ceramic brackets using flame followed by steam treatment prior to rebonding, two studies [ 19 , 20 ] have tested the effect of heat treatment on bond strength. Silva et al [ 19 ] tested the SBS of rebonded ceramic brackets after they were heat treated with a hot air dryer for 60 s. The results were consistent with this study for the SC bracket in that the SBS was significantly lower than that of new brackets. Consistent with our results for the RP bracket, Mirhashemi et al [ 20 ] obtained SBS for a flame-treated group where the values trended lower, although not significantly, when compared to that of new brackets.…”

Can the silane heat treatment influence the bond durability between resin cements and a dental ceramic?

“…The statistical difference in results between the thermocycled and non-thermocycled groups suggests that cement adhesion is significantly influenced by aging. This has also been observed in several previous studies in which ceramics are thermocycled, even when a loss of some specimens has occurred during this process [9,[17][18].…”

Shear bond strength of debonded ceramic restorations re-cemented by means of a cleaning and retreatment protocol

“…A study published by Silva uses an additional thermal treatment, using hot air at 100ºC for 60 seconds applied to previously silanized debonded brackets. The results obtained showed that the shear bond strength achieved was even higher than the original bond (18).…”