Comparative Study of Adhesion of Brackets with Metal Injection Molding (MIM) Technology and Welded bases: In vitro Study

Comparative in-vivo bond failure rate of orthodontic brackets when bracket base is treated with micro-abrasive blasting vs. acid etching: eighteen month randomized control trial and scanning electron microscope study

Background

The aim of this study was threefold. Firstly, it aimed to introduce and detail a novel method for chemically etching the bases of stainless-steel orthodontic brackets. Secondly, the study sought to investigate the structural alterations within the brackets' microstructure following chemical etching compared to those with sandblasted bases, using electron microscopy analysis. Lastly, the study aimed to evaluate and compare the long-term durability and survivability of orthodontic brackets with chemically etched bases versus those with sandblasted bases, both bonded using the conventional acid etch technique with Transbond XT adhesive, over an 18-month follow-up period.

Methods

The study was a randomized clinical control trial with triple blinding and split-mouth study design and consisted of two groups. The brackets in the sandblasted group were prepared by sandblasting the intaglio surface of the base of the bracket with 50 µm SiO2 particles. Hydrofluoric acid was used to roughen the base in the acid-etched group. The bases of the brackets were viewed under an electron microscope to analyze the topographical changes.

Results

A total of 5,803 brackets (3,006 acid-etch, 2,797 sandblasted) in 310 patients were bonded, in a split-mouth design by the same operator. The patients were followed for 18 months. The failure rate of 2.59% and 2.7% was noted in an acid-etched and sandblasted group, respectively. There was a close approximation of curves in the Kaplan-Meier plot, and the survival distribution of the two groups in the log-rank (Mantel-Cox) test was insignificant; x2 = 0.062 (P value = 0.804).

Conclusion

Acid etching if the bases of the brackets can be used as an alternative to sandblasting furthermore acid etching can be performed on the chair side.

Is An Orthodontic Hydrophilic Composite Resistant to Contamination and pH Cycling? In vitro Results

Objective:

To evaluate the adhesive strength of a hydrophilic composite submitted to contamination and pH cycling, compared to a conventional composite.

Materials and Methods:

Seventy-two bovine incisors were prepared and randomly divided into 6 groups (n=12), bonded with Hydrophilic Composite (HC)(Transbond Plus Color Change) or with Conventional Composite (CC)(Transbond XT; control), with or without contamination and pH cycling as follows: G1-HC, with contamination, with pH cycling; G2-HC, with contamination, without pH cycling; G3-HC, without contamination, with pH cycling; G4-HC, without contamination, without pH cycling; G5-CC, without contamination, with pH cycling; G6-CC, without contamination, without pH cycling. Contamination in G1 and G2 consisted of fresh saliva applied after the self-etching primer for 5min before bonding with HC. After bonding, G1, G3, and G5 were submitted to pH cycling, immersed in the demineralizing solution for 22h and for 2h in remineralizing artificial saliva, repeated for 15 days. G2, G4, and G6 were kept in deionized water. The shear bond strength was tested using a load cell of 100N and the Adhesive Remnant Index (ARI) was assessed. Intergroup comparison was performed with one-way ANOVA, Tukey, and chi-square tests.

Results:

There was a statistically significant difference in G1, G2, and G3 in relation to G6. The highest rate of adhesive failure between the resin/bracket interface occurred with the HC, while CC failed more at the resin/tooth interface.

Conclusion:

Contamination and pH cycling did not decrease the shear bond strength of brackets bonded with the hydrophilic composite. However, the adhesive strength of the conventional composite was higher.