Biomedical Engineering Reference
In-Depth Information
other restoratives in vivo
[12,13]
. Plaques contribute to secondary caries, which is the main
reason for restoration failure
[14]
. Replacing the failed restorations consumes 50
70% of the
dentist's time. Replacement dentistry costs $5 billion annually in the United States
[15]
.To
combat caries, antibacterial
resins and composites containing quaternary ammonium salts
(QAS) were developed
[16
21]
. Resins containing 12-methacryloyloxydodecylpyridinium bro-
mide (MDPB) significantly reduced the bacterial growth
[22,23]
. Other novel antibacterial
resins were synthesized by employing antibacterial agents such as methacryloxylethyl cetyl
dimethylammonium chloride (DMAE-CB) and cetylpyridinium chloride, among other compo-
sitions
[18
27]
.
Besides antibacterial restoratives, calcium phosphate (CaP) composites represent another
promising approach in inhibiting caries. CaP composites can release supersaturating levels of
calcium (Ca) and phosphate (P) ions to remineralize tooth lesions
[28
21,24
30]
. Recently, novel CaP
and calcium fluoride nanoparticles were incorporated into composites
[31,32]
. Nanoparticles of
amorphous calcium phosphate (NACP) were synthesized via a spray-drying technique
[33]
.The
NACP nanocomposite released Ca and P ions similar to those of traditional CaP composites,
while possessing much higher mechanical properties
[32]
. The NACP nanocomposite was
“smart” and greatly increased the Ca and P ion release at acidic pH, when these ions were
most needed to combat caries
[33]
. When immersed in a lactic acid solution at pH 4, the
NACP nanocomposite quickly neutralized the acid and increased the pH to a safe level of 6,
while the pH remained at 4 for commercial control restoratives
[34]
. However, little has been
reported on combining the best of both worlds: CaP ion release and remineralization, and anti-
bacterial activity of QAS-containing resins.
Besides composites, it is also important to develop novel antibacterial and remineralizing
adhesives because composite restorations are bonded to tooth structure via adhesives
[35
39]
. Extensive studies have been performed to improve, characterize, and understand
enamel and dentin bonding
[40
44]
. It
is desirable for the adhesive to be antibacterial to
inhibit recurrent caries at
composite margins
[16,25,26]
. Residual bacteria could
exist in the prepared tooth cavity, and microleakage could allow bacteria to invade the
tooth-restoration interface. Adhesives that are antibacterial in the cured state could help
inhibit the growth of residual and invading bacteria
[23,45]
. Indeed, MDPB-containing adhe-
sives markedly inhibited the growth of Streptococcus mutans (S. mutans)
[16,45]
.Another
study developed an antibacterial adhesive containing DMAE-CB
[25]
. Besides the adhesive
resin, it is also beneficial for the primer to be antibacterial because it directly contacts the
tooth structure
[46
the tooth
48]
. A primer containing MDPB achieved significant antibacterial effects
[46,47]
. Another primer containing chlorhexidine showed an effective antimicrobial activity
[48]
. There have been only a few reports on antibacterial adhesives and primers. To date,
there has been no report on antibacterial and remineralizing adhesives containing CaP nano-
particles, except recent studies in our group which are described in this chapter.
This chapter describes recent studies on dental nanocomposites containing novel antibacterial
agents as well as CaP nanoparticles for ion release and remineralization. Dental bonding agents
with a combination of antibacterial and remineralizing capabilities are also presented, and the
results are promising for caries-inhibition restorations.
