Biomedical Engineering Reference
In-Depth Information
soft and hard tissues including the enamel, dentin, and gingiva. Consequently, recurrent caries evolves
around these restorations, which as a matter of course is treated by restoration replacement, resulting
in additional tissue loss. A diverse management strategy comprises the abolition of the cause for den-
tal caries in terms of antimicrobial treatment.
Antimicrobial agents are chemical compounds capable of killing or inhibiting the growth of
pathogenic microorganisms
[5]
. Several studies have provided restorative composites that possess
antibacterial activity
[6-9]
; some of which were affixed with a soluble antimicrobial agent, and some
carry a stationary antibacterial agent. The approach for preparing antibacterial restorative composites
with a soluble agent is to impregnate them with an antibacterial agent, which is gradually released
over time. However, discharge of the antibacterial agent from the bulk of the material has several
disadvantages; adverse influence on mechanical properties of the base material; the release of the
agent may generate a porous structure; the efficacy is time limited, and possible toxicity to the adja-
cent tissues given that the rate of diffusion is difficult to monitor. A number of the soluble antibacte-
rial agents that have been introduced are low molecular weight agents, such as antibiotics, fluoride,
chlorhexidine, silver ions, iodine, and quaternary ammonium compounds.
Residual toxicity of low molecular antibacterial agents may be solved by generating antibacterial
macromolecules. The latter may be accomplished by polymerization of biologically active monomers
[10,11]
or by immobilization of disinfectants/antibiotics onto polymeric surfaces
[12]
.
3.2
ANTIBACTERIAL RESTORATIVE COMPOSITES
Restorative composite materials typically involve a dispersed phase of filler particles that are distrib-
uted within a continuous (matrix) phase. Usually the inorganic filler particles, which are zirconium/
silica-based, are dispersed in an organic matrix of resin components such as bisphenol A glycidyl
methacrylate (BIS-GMA), urethane dimethacrylate (UDMA), and triethylene glycol dimethacr-
ylate (TEGDMA) that are cured during application. Addition of an antibacterial component can be
achieved through modifications made to the filler phase
[7-9]
or the matrix phase
[13,14]
of the
restorative composite.
3.2.1
Filler Phase Modification
Restorative composites consist of filler (70-90% w/v). Various modifications of the filler components
to achieve antibacterial composites have been reported, e.g., using silver.
3.2.1.1 Released Antibacterial Agents
Silver has a long history in medicine and pharmacology as an antibacterial agent. Consequently, addi-
tion of a silver component into the filler or replacement of the filler with silver-supported materials
has been evaluated. Pure silver ions implanted in SiO
2
filler particles exhibited an antibacterial effect
against oral streptococci
[7]
. Moreover, leaching of silver ions from restorative composites loaded
with high concentrations of silver-containing fillers resulted in antibacterial activity attributed to the
anti-adherence property of the silver-supported substratum
[15,16]
. Furthermore, antibacterial activity
was demonstrated in Ag-silica glass prepared by the sol-gel method
[17]
.
An additional component used as an anticariogenic agent is fluoride. The anticariogenic effect of
fluoride is attributed to various mechanisms, such as reduction of the demineralization, enhancement
