Biomedical Engineering Reference
In-Depth Information
Silver 2-ethylhexanoate (Strem, New Buryport, MA) of 0.08 g was dissolved into 1 g of
TBAEMA (Sigma). TBAEMA could facilitate Ag-salt dissolution in resin
[21,51]
. This Ag solution
was mixed into SBMP primer at 0.05 wt% of silver 2-ethylhexanoate because preliminary study
indicated that this concentration had no adverse effect on dentin bond strength and color of the
primer. Hence, four primers were fabricated: (1) SBMP primer (control), (2) control primer
10%
1
QADM (termed “10QADM”), (3) control primer
0.05% NAg (termed “0.05NAg”), and (4) con-
1
trol primer
0.05NAg”).
A dental plaque microcosm biofilm model was used
[53]
. Saliva was collected from a healthy
donor having natural dentition without active caries or using antibiotics within 3 months. The donor
did not brush teeth for 24 h and abstained from food/drink intake for 2 h prior to donating saliva
[53]
. Uncured primers were tested by agar disk diffusion test (ADT). Saliva was added to growth
medium containing mucin at a concentration of 2.5 g/L, bacteriological peptone at 2.0 g/L, tryptone
at 2.0 g/L, yeast extract at 1.0 g/L, NaCl at 0.35 g/L, KCl at 0.2 g/L, CaCl
2
at 0.2 g/L, and cysteine
hydrochloride at 0.1 g/L (at pH 7)
[54]
. The inoculum was incubated (37
C, 5% CO
2
) for 24 h.
Three types of culture media were used. First, tryptic soy blood agar plates were used to determine
total microorganisms. Second, mitis salivarius agar (MSA) plates, containing 15% sucrose, were
used to determine total streptococci. Third, MSA plus 0.2 units of bacitracin per milliliter was used
to determine mutans streptococci
[53]
.
For ADT, a 0.4 mL bacterial suspension was poured onto each agar plate. Then, 30
10% QADM
0.05% NAg (termed “10QADM
1
1
1
L of each
primer was impregnated into a sterile paper disk with a diameter of 9 mm and a thickness of
1.5 mm
[47]
. The primer-impregnated paper disk was placed on a plate with bacteria and incubated
for 48 h. The bacterial
µ
inhibition zone size was calculated as: (outer diameter of inhibition
zone
paper disk diameter)/2.
The uncured QADM
2
NAg primers had a strong antibacterial activity, as shown in
Figure 6.7
.
As shown in (A),
the control primer had minimal
inhibition zones. In (B
D),
the primers
10QADM, 0.05NAg, and 10QADM
0.05NAg had much larger inhibition zones. The inhibition
1
zone sizes are plotted in (E
G) for total microorganisms, total streptococci, and mutans strepto-
cocci, respectively. The inhibition zone sizes for 10QADM
0.05NAg were ninefold those of the
1
control (P
0.05)
[53]
.
,
6.5
Antibacterial adhesive
As shown in
Figure 6.8
, six groups were used for dentin shear bond strength testing. The purpose
of groups 1
3 was to investigate the effects of QADM or NAg individually. The purpose of 3 and
4 was to examine the effect of NAg mass fraction. The purpose of comparing 2, 3, and 5 was to
examine the effect of combining QADM and NAg together in the same adhesive. The purpose of
comparing 5 with 6 was to investigate the effects of adding QADM and NAg into both the adhesive
and the primer on dentin bond strength and biofilm response.
To measure dentin shear bond strength, extracted caries-free human third molars were cleaned
and stored in 0.01% thymol solution. Flat mid-coronal dentin surfaces were prepared by cutting off
the tips of molar crowns with a diamond saw (Isomet, Buehler, Lake Bluff, IL)
[55]
. Each tooth
was embedded in a polycarbonate holder (Bosworth, Skokie, IL) and ground perpendicular to the
