الفهرس 
Introduction and Literature ReviewOnly 14 pages are availabe for public view
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Abstract
Background. Fragment tooth reattachment is a global challenge nowadays. A variety of techniques and materials have been developed for tooth fragment reattachment following fracture. However, there is no consensus in the literature on which one has the best results in terms of the bond strength between the fragment and the dentin over time. The important aspects for tooth fragment reattachment techniques are the choice of the adhesive bonding of the fractured fragment and intermediate materials to be used, which may be composite resin, flow resin, resin cement, or glass ionomer. The available commercial resin cements fail to provide the desired strength and therefore innovation will be important in this field.
Objectives. The aim of this study is to assess what is the best tooth fragment reattachment technique. In the current study, zirconium oxide nanoparticles (ZrO2NPs) were used for the first time to modify the commercially available adhesive resin cement (ARC) exemplified by (Rely X Unicem Clicker) aiming to increase its mechanical properties.
Methods. ZrO2 NPs were synthesized using the co-precipitation approach and were then mixed in different mixing ratios (1-5 wt%) with ARC forming ZrO2/ARC. Both the produced
ZrO2 NPs and ZrO2NPS@ARC were characterized using high resolution transmission electron microscope (HR-TEM), scanning electron microscope (SEM) and Fourier-transform infrared (FTIR) technique. Human fibroblast-like fetal lung cell line (WI 38) and human normal melanocytes (HBF-4) were used to assess the biocompatibility of ZrO2NPS@ARC after 72 hours of incubation. Only non-toxic mixture ratios were further tested. Sixty intact human maxillary central incisors freshly extracted with close similarity were selected and randomly grouped into four groups (n=15/group) according to ZrO2NPs concentration within the tested complex. A control group was included in which pure ARC was used. Fracture resistance of reattached tooth fragment, compressive strength, diametral tensile strength and microhardness nanoindentation were evaluated.
Results revealed that the synthesized ZrO2NPs were spherical in shape with an average diameter of 12 nm. Their incorporation with ARC up to 3 wt% did not cause significant cell death compared to ARC alone. ZrO2/ARC exerted significantly higher mechanical properties and the peak value of incorporation was at 3 wt %.
Conclusions. Our study revealed that, it is therefore recommended to incorporate 3 wt % of ZrO2,NPs with the resin cement, which was the optimum amount for the best tooth fragment reattachment.