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Estimation of Root Canal Obturation
Leakage
Division of Oral Ecology in Health and Infection, Department ofOral Health Science, Course for Oral Life Science, Niigata
University Graduate School of Medical and Dental Sciences

Nunez Phides and Hoshino Etsuro

Visualization of the internal ramifications of theroot canal system has been a constant challenge forresearchers for many years. Various techniques suchas clearing (Robertson et al ., 1980) and sectioning(Kasahara et al ., 1990) had been proposed. Suchtechniques, however, involved demineralization orsubsequent destruction of the tooth to reveal internal
anatomy. One such study was made by Bramante et al(1987) who sectioned the teeth horizontally and thenreassembled them in stone to compare pre- and postinstrumentation shape of the canals.
Non-invasive methods to study the root canal havealso been developed. One of the earliest is by Weine etal (1975), in the form of simulated root canals, which
involved the use of a silver point as a template. While
this method showed excellent visualization, it wasconsidered simplistic and assessment can only be madein one plane (Rhodes et al ., 1999). In addition, otherworkers have cautioned against the interpretation ofresults and extrapolations from this method to beapplied to real root canals. (Thompson and Dummer,1997; Smith and Edmunds, 1997). Another non-invasive
method is the use of radiographic techniques but while
it is reproducible and relatively easy to employ, it
could only produce a two-dimensional record (Southardet al ., 1987). Such two-dimensional images are not
suﬃcient to give the best representation of the internal
structures of the root canal system as shown by thewealth of studies that have revealed its complexity.

has remained a prime requisite for the success ofendodontic treatment (Petersson et al ., 1986). Barthel etal . (1999) stated that the coronal restoration and theroot ﬁlling are primary safeguards against re-infection.
Gaps between the root canal filling and the dentinal
wall as well as air spaces within the filling forming
continuous channels to the apex may allow entry ofbacteria or bacterial products that may initiate orreactivate an inflammatory process. Oral fluids likesaliva and other extraneous products that could
nourish the growth of persisting bacteria may also
enter the canal via such spaces. Persisting bacteria
which are found on the apical portions of root canals ofobturated teeth are the cause of most treatment
failures. (Nair PNR et al ., 1990). These microorganisms
include Enterococcus faecalis, Actinomyces israelii,
Bacteroides gracilis , and many others. (Sundqvist G etal ., 1998). The visualization methods that have thus far
been mentioned focused more on the study of canals
before and after instrumentation. In light of this, theneed for a non-invasive, reproducible, and adequate
visualization technique for filled canals, therefore,
becomes paramount.
In 2003, Venturi et al . proposed a clearing
technique that will allow the visualization of filledcanals. However, demineralization of samples isinherent in clearing techniques and so it is still
considered invasive. Another more widely usedmethod is linear measurement of dye penetration
along a root filling. In a review by Wu MK andWesselink PR (1993), they concluded that more
research should be devoted to developing bettermethodology for such leakage studies, rather thancomparing the sealing ability of different materials.
Because leakage studies normally require sectioning ofteeth, and are thus also destructive (Clinton and Himel,
2001; Imai and Komabayashi, 2003; Gencoglu et al .,2002), a dye penetration test that will not require
sectioning would be a welcome development. As early

Aside from anatomy of the root canal, moreover,as the1990's, researchers like Tachibana et al . (1990)

endodontic studies also require the visualization of theand Nielsen et al . (1995) have used micro-computed

canal after it has been filled because the complete

tomography (MCT) as a tool for endodontic research.

obliteration of the canal space after instrumentation

They have shown the possibility of using this− 33 −206

新潟歯学会誌 37（2）：2007

technique in various ﬁelds of endodontic research like,(Analyze 5.0).

among others, the examination of the internal andexternal morphologies of the tooth and assessment of

The results of the study showed that qualitatively,

volume changes after instrumentation or obturation.

there was a good correlation between the histological

MCT was shown to be accurate for experimental

and MCT images. Master or accessory gutta percha

endodontology (Rhodes et al . 1999), with the distinct

cones, sealer, as well as voids were similarly

advantage of being completely non-invasive andrepresented in both histologic and MCT images.

reproducible.

Quantitatively, there was also a high correlation of thesurface area of the root canal filling between theSubsequent endodontic studies with the use ofhistologic and MCT images (Pearson correlation

MCT, however, were largely limited to the root canalcoeﬃcient = 0.992), although the results for the surface

shape before and after instrumentation. Few

area of the single gutta percha cones had a slightly

researchers have attempted the three-dimensional

greater diﬀerence.

evaluation of root canal obturations with the use ofMCT. One such study has been done by Jung M et al .,The conﬁrmation that MCT can produce images
that are in very close approximation to the actualand shall be the focus of this review.

conditions in a ﬁlled canal as compared to radiographs
The aim of the article The imaging of root canal

is important for studies dealing with certain failed

obturation using micro-CT , by Jung M, Lommel D andKlimek J (International Endodontic Journal 38: 617-26,2005) was to determine if MCT would be an accurate
imaging technique for obturated canals. Such aninvestigation is necessary because recent studies
regarding the study of root canals, with the use of
MCT has been increasing. An assessment of thistechnique is needed to determine if the results
obtained are reliable enough to be used as reference
for future studies. Unlike most articles which dealtlargely on the internal anatomy of root canals,
however, Jung M et al . focused on the evaluation ofobturated root canals.

endodontic treatments. It becomes a valuable tool forroot canal ﬁlling leakage studies, as it will aid in theanalysis of obturation defects that may serve as
pathways not only for oral fluids and bacteria, asmentioned earlier, but for medicaments as well.
Medications in the form of a mixture of certain
antibiotics have increasingly been used as endodontic
treatment, especially for teeth with periradicularlesions. (Takushige T, 2004; Ozan U, 2005).
As noted previously, although many techniques
had been suggested for the evaluation of the root canalsystem and obturation, they were mostly destructive.
The study reviewed in this article demonstrated theIn the study, four single rooted maxillary teeth

potential of MCT as a non-destructive tool forwere conventionally enlarged and filled by lateralendodontic research, in particular, root canalcondensation technique of gutta percha and thenobturation. Radiographic image analysis in this context

assessed radiographically. The samples were thenis not sufficient for the adequate evaluation of

examined with a MCT system SkyScan 1072 80kv. In

obturations, being only two-dimensional. The major

order to assess the accuracy of the MCT images, they

limitation of the MCT technique is obviously its

were compared with histological sections of theapplication in vivo . With this limitation in mind,samples. Eight to twelve slices were made from eachhowever, it is possible to create study designs that will

sample and prepared for histologic examination. The

maximize its advantages in order to produce a moreslices were viewed with a microscope at two-foldaccurate representation of root canal obturations.

magniﬁcation. For qualitative assessment, photographs
were taken for each slice which were then super-References:

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