Evaluation and comparison of the effect of incorporating zinc oxide and titanium dioxide nanoparticles on the bond strength and microleakage of two orthodontic fixed retainer adhesives

J World Fed Orthod. 2023 Feb;12(1):22-28. doi: 10.1016/j.ejwf.2022.09.002. Epub 2022 Nov 28.


Background: An adhesive with both proper mechanical and antimicrobial properties seems to be beneficial. We aimed to investigate the effect of zinc oxide (ZnO) and titanium dioxide (TiO2) nanoparticles (NPs) on bond strength and microleakage of two different fixed retainer adhesives.

Methods: In this in vitro experimental study, 168 extracted human incisors were randomly divided into six groups of 28 (eight double-tooth specimens for the bond strength test and 12 specimens for the microleakage test). In three groups: Transbond XT (3M Unitek, Monrovia, CA) without NPs, with 1% ZnO NPs and with 1% TiO2 NPs were applied. The other three groups included Ortho Connect Flow (GC orthodontics, Tokyo, Japan) composite with the same order to bond a 0.175-inch multistrand wire to the lingual surfaces of the teeth. The bond strength was measured using the Universal Testing Machine, and the adhesive remnant index was reported using a stereomicroscope (Nikon, SMZ800, Tokyo, Japan). The dye-penetration method was used to determine the microleakage.

Results: For bond strength, there was no significant difference among groups. For microleakage, there was no significant difference between GC and Transbond XT groups. However, in subgroups of Transbond XT, the addition of TiO2 NPs increased the microleakage significantly in comparison with ZnO and control groups (P = 0.011). There was no significant statistical difference between the groups in terms of residual adhesives (P = 0.166).

Conclusions: Through the incorporation of 1% TiO2 and ZnO NPs into the fixed retainer adhesive, the bond strength was maintained within the clinically acceptable range. The addition of TiO2 NPs to Transbond XT significantly increased the percentage of microleakage.

Keywords: Bond strength; Fixed retainer; Microleakage; Nanoparticles; Titanium dioxide; Zinc oxide.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Dental Bonding* / methods
  • Dental Cements / adverse effects
  • Dental Cements / chemistry
  • Humans
  • Nanoparticles*
  • Orthodontic Appliances, Fixed
  • Zinc Oxide*


  • Dental Cements
  • titanium dioxide
  • Zinc Oxide