Novel Orthodontic Adhesives Containing Bioactive-glass for Inhibition of Enamel Demineralization

Objectives: The aim of this study was to examine the acid neutralizing property and bond strength of experimental orthodontic adhesives containing three different melt-derived bioactive-glasses (BAG).
Methods: 45S5, 45S5F, S53P4 BAGs were prepared using melting technique and ground to fine particles (<25 µm). These particles were mixed with the silanized glass (180 ± 30 nm) and added into a resin matrix [Bis-GMA/TEGDMA 50/50 (wt.%) containing 1% of DMAEMA/CQ 2:1 (wt.%)] with varying filler proportions; 52.5% 45S5BAG + 17.5% glass (45S5BAG_52.5); 70.0% 45S5BAG (45S5BAG_70.0); 52.5% 45S5FBAG + 17.5% glass (45S5FBAG_52.5); 70.0% 45S5FBAG (45S5FBAG_70.0); 52.5% S53P4BAG + 17.5% glass (S53P4BAG_52.5); 70.0% S53P4BAG (S53P4BAG_70.0) and 70.0% glass (BAG_0) as well as commercially available Transbond-XT (3M Unitek, USA) were used as control groups. To evaluate the acid neutralizing properties, specimens of 2 × 2 × 25 mm were immersed in lactic acid solution (pH 4.0), yielding a specimen/solution ratio of 0.14/1 in volume. Then, the pH change and the time to raise the pH from 4.0 to 5.5 were measured. In addition, shear bond strength (SBS) was evaluated according to ISO 29022 (2013). The results of each test were analyzed with one-way ANOVA (PASW 18.0, IBM Co., USA) followed by Tukey’s statistical test (p=0.05).
Results: For all of BAG containing orthodontic adhesives, one with 70.0% of BAG showed significantly higher pH value and shorter time to raise the pH from 4.0 to 5.5 than one with 52.5% of BAG (p<0.05). BAG_0 and Transbond-XT had no effect on the pH change. Also, samples with 70.0% of BAG showed lower SBS than samples with 52.5% of BAG. In fact, 45S5BAG_52.5 showed no significant difference of SBS compared to BAG_0 (p>0.05).
Conclusions: The novel orthodontic adhesives containing 52.5% of 45S5BAG exhibited ideal neutralizing properties and appropriate bond strength compared to the other groups.