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Published on: July 10, 2014
Compositional design and formulation study of hydroxyapatite-chitosan nanocomposite-modified conventional glass
Neven S Aref1,2, Abeer A El-Fallal3,4, Mohamed A El-Farrash5
1Department of Basic Oral Sciences and Dental Education, College of Dentistry, Qassim University, Buraydah, Saudi Arabia. n.aref@qu.edu.sa.
Objectives:
To prepare hydroxyapatite/chitosan (HA/CTS) nanocomposites at four weight ratios (85/15, 70/30, 50/50, 30/70) and two concentrations (3 and 5 wt.%), incorporate them into conventional glass ionomer cement (GIC), and evaluate their effect on compressive strength, shear bond strength to dentin, and antibacterial activity.
Materials And Methods:
HA/CTS nanocomposites were synthesized by co-precipitation and characterized by TEM and FTIR. Nine groups were prepared (n = 10): one unmodified control (Group I) and eight modified groups (Groups II-IX). Compressive strength was tested per ISO 9917-1:2007; shear bond strength to human dentin and antibacterial activity (agar diffusion against Streptococcus mutans, Staphylococcus aureus, and Escherichia coli) were also evaluated. One-way and two-way ANOVA with Tukey's HSD were applied (P ≤ 0.05).
Results:
TEM confirmed nanoscale particles (7-50 nm) with dispersion improving at higher chitosan content. FTIR verified dual-phase incorporation and Ca2+-NH2 coordination bonding. Compressive strength (F(8,81) = 177.509; P < 0.0001) and shear bond strength (F(8,81) = 202.262; P < 0.0001) differed significantly among groups. A significant ratio × concentration interaction was confirmed for both properties (P < 0.0001). Only the 70/30 nanocomposite at 3 wt.% exceeded the control compressive strength (133.44 vs. 115.02 MPa; P < 0.05). All eight modified groups showed significantly higher shear bond strength than the control (6.04 MPa), with the 85/15 at 5 wt.% achieving the highest value (13.30 MPa). No inhibition zones were detected in any group.
Conclusions:
The 70/30 HA/CTS nanocomposite at 3 wt.% optimizes compressive strength, while the 85/15 at 5 wt.% optimizes dentin adhesion. Overall, the 70/30 HA/CTS nanocomposite at 3 wt.% demonstrated the most favorable balanced performance profile across both mechanical outcomes. The absence of detectable antibacterial activity under the present agar diffusion testing conditions may be related to chitosan immobilization within the nanocomposite matrix and the diffusion limitations of the assay method. Findings suggest the potential for application-specific optimization of HA/CTS-modified GIC under controlled in vitro conditions, pending further long-term and in vivo validation.
Clinical Significance:
HA/CTS nanocomposite modification enhanced the mechanical and adhesive performance of conventional GIC under the present experimental conditions. The observed improvement in compressive and shear bond strength across the modified formulations may support improved marginal integrity in esthetic GIC restorations. Two application-specific optimal formulations were identified based on the functional demands of the restoration site, with the 70/30 HA/CTS nanocomposite at 3 wt.% representing the most favorable overall formulation combining enhanced compressive strength with clinically acceptable dentin adhesion; however, further long-term and in vivo validation remains necessary before definitive clinical translation.
