[Microshear bond strength of transbond XT and assure universal bonding resin to stainless steel brackets, amalgam and porcelain]

Assure universal bonding resin is marketed with fluoride releasing potential. The manufacturer claims that it provides adequate bond strength between the bracket and amalgam and porcelain. This study compared the shear bond strength of Transbond XT and Assure universal bonding resin to stainless steel brackets, amalgam and porcelain in vitro. In this vitro study, 20 standard brackets of the maxillary central incisors, 20 feldspathic porcelain specimens and 20 self-cure acrylic cavities filled with amalgam were divided into 2 groups bonded with Transbond XT, and Assure. After surface preparation in each group, Transbond XT composite was applied to the surfaces using silicon tubes and light-cured for 20 seconds. Then, the microshear bond strength was determined using Zwick Roell machine. The data were subjected to two-way ANOVA, Tukey's post hoc test, Student's t-test and the Kruskal Wallis test. Different microshear bond strengths were obtained for the bond to stainless steel brackets, amalgam and porcelain by Transbond XT and Assure resin [p<0.000]. Using Assure for bonding to amalgam [7.2 +/- 1.46 vs. 10.12 +/- 4.97] and brackets [16.14 +/- 3.2 vs. 20.16 +/- 5.12; p<0.05] decreased microshear bond strength. However, Assure significantly increased the bond strength to porcelain compared to Transbond XT [28.84 +/- 6.42 vs. 22.48 +/- 3.6; p<0.01]. Non-parametric Kruskal-Wallis test showed significant differences in adhesive remnant index [ARI] between the two bonding agents only in the amalgam group [p=0.029]. Although the bond strength values of Assure were less than those of Transbond XT, Assure was able to create sufficient bond strength especially to porcelain

[Effect of nano-hydroxyapatite incorporation into resin modified glass ionomer cement on ceramic bracket debonding]

Preventing enamel demineralization around brackets is a concern for orthodontists. Fluoride releasing materials have been recommended to overcome this problem. The aim of this study was to evaluate the effect of incorporating nanohydroxyapatite [NHA] into resin modified glass ionomer cements [RMGIC] on ceramic bracket debonding. In this experimental study, 80 human premolars were divided into 4 bonding groups as follows: group 1: Transbond XT [TBXT] [control group], group 2: Fuji II LC [RMGIC], group 3: 5% NHA added to RMGIC and group 4 10% NHA added to RMGIC. After enamel etching, ceramic brackets were bonded. The shear bond strength [SBS] and the adhesive remnant index [ARI] were calculated for each group. The data were analyzed using one-way ANOVA, Tukey's post hoc HSD test and the Kruskal Wallis test. According to ANOVA, 10% NHA added to RMGIC had a significantly lower SBS compared to other groups [11.93 +/- 2.11] but no significant difference was found among the remaining groups. The mean SBS was 17.33 +/- 4.07 MPa in group 1, 17.22 +/- 3.55 MPa in group 2 and 16.56 +/- 2.59 MPa in group 3. According to ARI, the predominant failure mode in RMGIC groups was cohesive. Resin modified glass ionomer cements containing 5% NHA can be as effective as composite resins for bonding ceramic brackets

[Comparative evaluation of the shear bond strength of metal brackets bonded to porcelain using different porcelain surface treatments]

The aim of this in vitro study was to compare shear bond strength of metal brackets bonded to dental porcelain on the basis of presence or absence of silane, type of acid [hydrofluoric acid [HF] or phosphoric acid [H3PO4]] and roughness of porcelain surface [glazed or deglazed] within mouth-like environment. Eighty glazed ceramic disks were randomly divided into 8 groups of 10 disks: group 1 [HF+silane], group 2 [deglazed+HF+silane], group 3 [HF], group 4 [deglazed+HF], group 5 [H3PO4+silane], group 6 [deglazed+H3PO4+silane], group 7 [H3PO4], group 8 [deglazed+H3PO4]. Then the brackets were bonded and thermocycled. After that, shear bond strength test was done using the Zwick device and the type of bond failure was determined under stereomicroscope at 4X magnification. 3-way ANOVA and Kruskal-Wallis were used for statistical analyses. The shear bond strength for the test groups were as follows: group [1]:13.05 +/- 7.7 MPa, group [2]:25.16 +/- 10.66 MPa, group [3]:6.7 +/- 5.86 MPa, group [4]:15.39 +/- 8.97 MPa, group [5]:12.76 +/- 7.91 MPa, group [6]:13.57 +/- 7.85 MPa, group [7]:0.54 +/- 0.67 MPa, group [8]: 9.34 +/- 6.52 MPa. The type of bond failure in all groups was adhesive failure except for group 2. No significant difference in the interaction between [glazed or deglazed], [presence or absence of silane], and type of acid was found [P>0.05]. Under the conditions of this study, the best clinical method was the use of 37% phosphoric acid and silane that resulted in the optimal clinical strength and adhesive bond failure