Biomedical Engineering Reference
In-Depth Information
evaluated in persisting root canal infections containing isolates of Enterococci. The killing efficacy
against the bacteria was significantly better with the nanosized treatment material
[38]
.
Bioactive glass 45S5, similarly to CaOH, has also been used for treatment of traumatized front
teeth with open apices. The conventional treatment with CaOH may affect mechanical dentin prop-
erties by decreasing its flexural strength over time. Recently, Marending et al.
[39]
used suspen-
sions of nanoparticulate bioactive glass 45S5 as dressing material and compared it to CaOH in
traumatized front teeth with open apices. The results showed a 35% drop in dentin mean flexural
strength values with CaOH and a 20% drop with bioactive glass 45S5 indicating superiority of
the latter. However, these results should be interpreted with caution since the affected dentin was
mainly in the superficial layers. Furthermore, Mohn et al.
[40]
prepared nanosized particles of bio-
active glass and modified it with bismuth oxide to obtain radiopaque properties. They evaluated the
performance of it as a filling material. Based on scanning electron microscopy (SEM), the authors
concluded that bioactive glass modified with bismuth oxide is a radiopaque bioactive root canal
filling material.
21.2.3.2
Sealers
Sealer materials used during obturation are grouped based on their prime constituent, such as zinc
oxide-eugenol, calcium hydroxide, resins, glass ionomers, or silicones. The use of a sealer during
root canal obturation is essential and enhances the possible attainment of an impervious seal and
serves as filler for canal irregularities and minor discrepancies between the root canal wall and gutta-
percha. Sealers are often expressed through lateral or accessory canals, and they can assist in micro-
bial control should there be microorganisms left on the root canal walls or in the tubules
[41
43]
.
Sealers can also serve as lubricants to assist in the thorough seating of the core-filling material during
compaction. In canals where the smear layer has been removed, many sealers demonstrate increased
adhesive properties to dentin (in addition to flowing into the patent tubules)
[44
46]
.
As stated by Gutmann and Witherspoon [47], the future directions for the ideal sealer should
focus on materials that (i) penetrate the patent dentinal tubules, (ii) bind intimately to both the
organic and inorganic phases of dentin, (iii) neutralize or destroy microorganisms and their products,
(iv) predictably induce a cemental regenerative response over the apical foramen, and (v) strengthen
the root system. Since the size of nanoparticles can penetrate the dentinal tubules to ensure that all
the spaces have been sealed effectively, the development of a sealer based on nanotechnology
may be an important step to achieve a better sealer material in endodontics. Chen et al.
[48]
in their
study used a new root canal filling sealer primarily composed of nanohydroxyapatite crystals in
279 nm after setting in an extracted tooth model. The sealer demonstrated superior antimicrobial
activity (Actinomyces naeslundii, Peptostreptococcus anaerobius, Porphyromonas gingivalis,
Porphyromonas endodontalis, and Fusobacterium nucleatum) as well as minimal microleakage com-
pared to two other materials.
Another preliminary report
[49]
demonstrated that nanocrystalline tetracalcium phosphate had
significantly higher antimicrobial potency in an agar-diffusion test. The formation of amorphous
Ca(OH)
2
during setting was thought to increase the pH value in the agar gel around the specimens
yielding a zone of inhibition. However, a similar study reported contradictory results. Masudi et al.
[50]
evaluated the apical sealing ability of an experimental NHA (40
60 nm) resin-based endodon-
tic sealer and compared it to a commonly used resin-based sealant material. Teeth in the first group
were obturated using gutta-percha with AH26. The second group was obturated with the
