Ability of new obturation materials to improve the seal of the root canal system: a review

Abstract

New obturation biomaterials have been introduced over the past decade to improve the seal of the root canal system. However, it is not clear whether they have really produced a three-dimensional impervious seal that is important for reducing diseases associated with root canal treatment. A review of the literature was performed to identify models that have been employed for evaluating the seal of the root canal system. In vitro and in vivo models are not totally adept at quantifying the seal of root canals obturated with classic materials. Thus, one has to resort to clinical outcomes to examine whether there are real benefits associated with the use of recently introduced materials for obturating root canals. However, there is no simple answer because endodontic treatment outcomes are influenced by a host of other predictors that are more likely to take precedence over the influence of obturation materials. From the perspective of clinical performance, classic root filling materials have stood the test of time. Because many of the recently introduced materials are so new, there is not enough evidence yet to support their ability to improve clinical performance. This emphasizes the need to translate anecdotal information into clinically relevant research data on new biomaterials.

Keywords: Leakage models; Root canal; Root filling materials; Sealability; Treatment outcome.

Figure 1

A. Stereoscopic microscope image of incomplete coating (open arrowhead) of resin-coated gutta-percha points (G) that are used with a hydrophilic self-priming methacrylate resin-based root canal sealer (S). Some obturation points are devoid of resin coating (arrow). B. Environmental scanning electron microscopy (ESEM) image of a partially resin-coated gutta-percha point (G), taken at 95% relative humidity, showing a gap between the resin coating (open arrowhead) and sealer; D: root dentin. C. SEM of the surface of a bioactive glass particle-coated gutta-percha point (G) that is used with a glass ionomer-based root canal sealer. Distribution of the glass particles is limited to some areas only (open arrow). D. High magnification of Figure 1C. Area on the left is devoid of glass particles (open arrowhead). Areas previously occupied by glass particles (open arrowhead) are denoted by depressions on the gutta-percha surface (arrow).

Figure 2

A. SEM image of the heat-pressed surface of thermoplastic polycaprolactone-based root filling material (C) showing phase separation of the methacrylate resin component (arrow) from the polycaprolactone. F: fillers. Bar = 5 μm. B. SEM image of the polycaprolactone-based root filling material after surface etching of the polycaprolactone root filling material with 0.1 N NaOH revealing exposed, partially-coalesced methacrylate resin droplets (arrow). Open arrowhead: unexposed fillers. Bar = 20 μm.

Figure 3

A. Subsurface confocal laser scanning microscopy of a gap-free region of a root canal that is obturated by a root filling material and sealer. B. Subsurface confocal laser scanning microscopy of a gap-containing region (arrow) of a root canal that is obturated by a root filling material and sealer. In both specimens, penetration of the root canal sealer into the dentinal tubules is evident (pointer), irrespective of the presence or absence of gaps. F: root filling material; S: root canal sealer; D: root canal dentin.

Figure 4

A. Pre-operative periapical radiograph of the upper left first molar (second tooth from the right). Although the tooth was non-vital, there was no periapical radiolucency associated with the palatal root. B. Post-operative periapical radiograph of the upper left first molar after root canal treatment and obturation with a polycaprolactone-based root filling material and accompanied resin-based sealer. Four radiopaque filled canals can be identified: 2 canals in the mesiobuccal root (open arrow), one canal in the distobuccal root (arrow) and one canal in the palatal root (open arrowhead). C. Three-year post-treatment cone beam computer tomography image (sagittal projection across the palatal root) of the same root-treated upper left first molar showing partial disappearance of the polycaprolactone root filling material (arrow) and the development of a periapical lesion at the root tip of the palatal root. D. Three-year post-treatment cone beam computer tomography image of the same tooth taken along an oblique coronal projection, revealing the palatal root and the distobuccal root. Disappearance of the polycaprolactone root filling material from the apical third of the root canal (arrow) is also evident from this angulation.

Figure 5

A. SEM of a polyvinylsiloxane impression negative replica of a section of a single-rooted canal that was obturated using a gutta-percha-based core-carrier technique. The gap-free interface between the plastic core (C) and the gutta-percha (G) can be seen (open arrowheads). A gap is evident within the canal fin (arrow). D: root dentin. Bar = 200 μm. B. High magnification of Figure 5A showing the aforementioned gap as a protruded piece of impression material (arrow) between the gutta-percha (G) and root dentin (D). Open arrowhead: interface between the obturator core and gutta-percha. Bar = 50 μm. C. SEM image obtained by direct observation of a single-rooted canal obturated using a gutta-percha-based core-carrier technique. Extension of the root filling material and sealer into patent dentinal tubules can be seen. C: plastic core; G: gutta-percha; D: root dentin. Bar = 200 μm. D. High magnification of Figure 5C showing extension of highly granular gutta-percha (G) into the dentinal tubular orifices (arrow). The rest of the tags that occupied the dentinal tubules is contributed by the root canal sealer. D: root dentin. Bar = 5 μm.

Figure 6

A. SEM image of the surface of a bioactive calcium silicate-based root canal sealer showing the presence of apatite crystalline clusters (open arrow) after exposure to a phosphate ion-containing simulated body fluid for 24 hours. B. High magnification of Figure 6A showing the needle-shaped apatite crystallites, some of which were sprouting from the calcium silicate filler particles.