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Review
. 2020 Oct 14;7(4):127.
doi: 10.3390/bioengineering7040127.

Sol-Gel Derived Hydroxyapatite Coatings for Titanium Implants: A Review

Alaa Jaafar  1 , Christine Hecker  1 , Pál Árki  1 , Yvonne Joseph  1
Affiliations
Review

Sol-Gel Derived Hydroxyapatite Coatings for Titanium Implants: A Review

Alaa Jaafar et al. Bioengineering (Basel). .

Abstract

With the growing demands for bone implant therapy, titanium (Ti) and its alloys are considered as appropriate choices for the load-bearing bone implant substitutes. However, the interaction of bare Ti-based implants with the tissues is critical to the success of the implants for long-term stability. Thus, surface modifications of Ti implants with biocompatible hydroxyapatite (HAp) coatings before implantation is important and gained interest. Sol-gel is a potential technique for deposition the biocompatible HAp and has many advantages over other methods. Therefore, this review strives to provide widespread overview on the recent development of sol-gel HAp deposition on Ti. This study shows that sol-gel technique was able to produce uniform and homogenous HAp coatings and identified the role of surface pretreatment of Ti substrate, optimizing the sol-gel parameters, substitution, and reinforcement of HAp on improving the coating properties. Critical factors that influence on the characteristics of the deposited sol-gel HAp films as corrosion resistance, adhesion to substrate, bioactivity, morphological, and structural properties are discussed. The review also highlights the critical issues, the most significant challenges, and the areas requiring further research.

Keywords: biocompatibility; hydroxyapatite; implant; sol-gel; titanium alloy.

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Conflict of interest statement

The authors declare no conflict of interest.

Figures

Figure 1
Figure 1
Fundamental stages of sol-gel HAp preparation and deposition by dip and spin coating.
Figure 2
Figure 2
(a): DTA and (b): XRD for HAp coating aged up to 24 h [66], reprinted with permission from Elsevier.
Figure 3
Figure 3
HAp coating on Ti alloy sintered at (a): 600 °C, (b): 700 °C and (c): 800 °C. Note: (i,ii) indicate different magnification of the micrographs [117].
Figure 4
Figure 4
SEM images of HAp coating dried at 500 °C and calcined at 800 °C with (a); (a): rapid heating rate and (b): slow heating rate [118], reprinted with permission from Taylor & Francis Ltd.
Figure 5
Figure 5
Cross-sectional SEM images of (a) HAp and (b) FGC HAp-TiO2 coatings [33], reprinted with permission from Elsevier.
Figure 6
Figure 6
Effect of TiO2 addition and sintering parameters on the coating hardness (Data from [134]).
Figure 7
Figure 7
XRD patterns of HAp-MWCNTs composites [89].
Figure 8
Figure 8
SEM images of the cross-section of (a) HA, (b) 10% PCL/HA, (c) 30% PCL/HA, and (d) 50% PCL/HA [91], reprinted with permission from Elsevier.
See this image and copyright information in PMC

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