Biomedical Engineering Reference
In-Depth Information
21.2.2.2
Medicaments
For endodontic procedures that require more than one visit to complete, the remaining bacteria
within the system can grow and reinfect the root canal space between appointments
[31]
.
Historically, placement of intracanal medicaments became a popular method of preventing bacterial
regrowth. Some form of calcium hydroxide (CaOH) is an intracanal medicament often used
between visits. Although E. faecalis is an insignificant organism in infected but untreated root
canals
[32]
, it is extremely resistant to most of the intracanal medicaments used, particularly to the
calcium hydroxide-containing dressings
[33]
. It can also survive in root canals as monoinfection,
without any synergistic support from other bacteria
[32,34]
.ThusE. faecalis is a recalcitrant candi-
date among the causative agents of failed endodontic treatments.
Nanoparticulates such as chitosan (CS-np) and zinc oxide (ZnO-np) have been shown to possess
significant antibacterial properties. Shrestha et al. in their study
[35]
tested the efficacy of fresh and
aged CS-np and ZnO-np in disinfecting and disrupting E. faecalis biofilms. Using confocal laser
scanning microscopy, total elimination of planktonic bacteria was observed in contrast to the bio-
film bacteria, which survived even after 72 h. There was a significant reduction in the thickness of
biofilm after nanoparticulate treatment and the authors concluded that the rate of bacterial killing
by the nanoparticulates depended on the concentration and time of interaction and that aging for
90 days did not affect their antibacterial properties. Although these findings need to be further
investigated and confirmed in animal and in vivo studies, the preliminary reports seem promising.
21.2.3
Material modifications
21.2.3.1
Obturating materials
The American Association of Endodontists published “Appropriateness of Care and Quality
Assurance Guidelines”
[36]
regarding contemporary endodontic treatment. In that publication, root
canal obturation is defined and characterized as:
The three-dimensional filling of the entire root canal system as close to the cementodentinal
junction as possible. Minimal amounts of root canal sealers, which have been demonstrated to
be biologically compatible, are used in conjunction with the core-filling material to establish
an adequate seal.
Although a number of materials have been advocated over the last 150 years for root canal
obturation, gutta-percha has remained as the material of choice. Gutta-percha has satisfied a num-
ber of the tenets for an ideal root filling material highlighted by Grossman
[37]
. However, its main
disadvantages cited include lack of rigidity and adhesiveness, ease of displacement under pressure,
minimal antimicrobial property, and shrinkage if thermo-plasticized. Proper adaptation of obturat-
ing materials to the cleaned and shaped root canal walls and in increased antimicrobial activity
would be important to reduce gaps and microleakage.
The incorporation of nanoparticles may increase the surface area between the dentin and the
obturating material leading to enhanced adaptation. Bioactive glass 45S5 is one of the recent nano-
particles used in endodontic therapy. It has amorphous nanoparticles of 20
60 nm in size. The
smaller particle size increases the contact surface area and thereby possesses a higher antimicrobial
effect than the macrosized material. The clinical antimicrobial efficacy of bioactive glass 45S5 was
