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Azerbaycan Saytlari

 »  Home  »  Endodontic Articles 7  »  A preliminary study of the percentage of gutta-percha-filled area in the apical canal filled with vertically compacted warm gutta-percha
A preliminary study of the percentage of gutta-percha-filled area in the apical canal filled with vertically compacted warm gutta-percha
Discussion - References.

When the dimensions of the root canal are not sufficiently large, the placement and replacement of the irrigant solution is restricted. Various investigators have found the apical root canal to be less clean than the middle and coronal portions of the root canal (Senia et al. 1971, Cofiae & Brilliant1975,McComb & Smith1975, Svec & Harrison 1977, Littman 1977,Wu & Wesselink 1995). This suggests that bacteria remain in the apical canal. If the root ¢fillings fail to ensure a long-term seal, seepage of tissue £fluids may provide the residual bacteria with a nutritive substrate, and the growth of the remaining bacteria in the apical root canal may cause the persistence of periapical lesion (Nair et al.1990, Molander et al.1998). The apical root ¢filling should provide a seal, especially because after post space preparation only the apical root ¢filling of 3 or 4 mm in length is left, and the cemented post may leak (Fogel1995,Wu et al.1998). Unfortunately, the quality of the root ¢filling obtained by warm vertical compaction has been found to be compromised 2 mm from the apex (Silver et al.1999, Wu et al.2001a). In order to ascertain why this is so, the PGFA was measured 1.5 mm from the AF, which in this study was considered the apical end of the root ¢filling.
No sealer was used although generally recommended. In this study, percentage of gutta-percha ¢filled canal area was measured. If sealer had been used, not only the width of the root canal or the depth of heat application, but also the size of the sealer ¢filled canal area would have been avariable. The larger the sealer ¢filled area, the smaller the gutta-percha ¢filled area. Because it would be difficult to standardize the amount of sealer in the apical canal, no sealer was used in this study and other similar studies (Smith et al. 2000). Although including sealer may facilitate gutta-percha movement, the reasons to leave sealer out were more important; and besides, both groups were treated in the same way. Without a sealer, high PGFAs (average 96.1%) were achieved in the 2-mm group, demonstrating that the low PGFA in the 4-mm group was not the result of the decision not to use sealer.

Figure 3. The cross-section of an extremely large root canal from the 2-mm group. The canal area was 0.55 mm2, larger than a #80 file. The PGFA was 78.9%. Two large areas were left unfilled (original magnification 50x).

The cross-section of an extremely large root canal from the 2-mm group

Figure 4. A cross-section from the 4-mm group. The canal area was 0.31mm2, comparable in size to the one shown in Fig.1. Gutta-percha was not heated sufficiently, leaving unfilled space. The PGFA was 80.6%(original magnification 50x).

A cross-section from the 4-mm group

Figure 5. Another cross-section from the 4-mm group. The canal area was 0.38 mm2, comparable in size to the one shown in Fig. 2. The PGFA was 66.7%. A large unfilled area can be seen (original magnification 50x).

A large unfilled area can be seen

Figure 6. Percentage of PGFA at 1.5 mm from the AF (2-mm group).

Percentage of PGFA at 1.5 mm from the AF

Figure 7. Percentage of PGFA at 1.5 mm from the AF (4-mmg roup). The PGFAs were lower in wide canals.

The PGFAs were lower in wide canals

In many cases spaces were found that were not ¢filled with gutta-percha (Figs 3-5). Whether these spaces can be completely ¢filled with sealer depends on the amount of sealer available in the root canal close to the AF. If sufficient sealer is available, the canal can be sealed before the dissolution of the sealer (Kontakiotis et al. 1997).
It was assumed that heat can be transferred about 4 mm apically along the gutta-percha cone (Ruddle 1994), and that therefore, the gutta-percha in the entire apical root canal may be expected to have been heated after the application of heat 4 mm from the AF. However, in this study relatively low PGFAs were achieved in the 4-mmgroup (Figs 4-6), indicating that the gutta-percha 1.5 mm from the AF was not always heated sufficiently. Therefore, the PGFA reached 100% in only 13% of the canals. When heat was applied 2 mm from the AF, however, a PGFAof100%was achieved in 70%of root canals.
In order to standardize the size of the AF, a size 30 ¢le was used to prepare the canal up to the AF. The vertical compaction extruded gutta-percha in seven teeth (12%). It has been found that, in general, warm guttapercha techniques extrude more gutta-percha than cold lateral compaction (ElDeeb 1984, Gutmann et al. 1993). In comparison with the other warm gutta-percha techniques, gutta-percha extrusion occurred less frequently during vertical compaction, probably because the gutta-percha in the most apical root canal could not be heated. It may be assumed that extrusion will occur more frequently when heat is applied 2 mm from the AF than when it is applied 4 mm from the AF. However, the multiple linear regression did not bear out this assumption, probably owing to the small sample size. On the other hand, although in the 2 mm group gutta-percha extrusion occurred in more cases, the amount per extrusion was small (Table 2). Material extrusion is dependent on apical size. Although all canals were prepared to the AF using a size 30¢le, the size of the original AF could be larger than size 30 in many canals.
Another factor that influenced the PGFA was the width of the apical root canal (P ј 0.038). Although in this study, all canals were instrumented to the same size, the cross-sectional canal area varied from 0.15 to 0.69 mm2, indicating that many original canals were wider than the largest instrument used. There was a 4.5-fold difference between the largest and smallest canals. A single gutta-percha cone of the same size was placed in each canal. The amount of gutta-percha was sufficient to ¢ll the small canals but insufficient to ¢ll the very large ones (Fig. 3). Tug-back was achieved in all canals, clearly, this procedure did not assure that the amount of gutta-percha was sufficient. The association between the PGFA and the canal area was less significant in the 4-mm group (Fig.7) than in the 2-mm group (Fig. 6), because the heat applied in the 4-mm group was often insufficient, which also influenced the PGFA.
Although great differences in canal dimension exist between the largest and smallest canals, clinically it is impossible to know which canal is large. It has been found that the ¢first ¢le that binds does not measure the apical diameter (Wu et al. 2002). Therefore, it is not always avoidable that in some cases insufficient amount of gutta-percha is present in the apical canal, and that the apical ¢filling contains more sealer. Heating to 2 mm from the AF promoted the PGFA in those not so wide canals only, but did not solve the problem in wide canals (Figs 3 and 6). On the other hand, heating to 2 mm leads to a higher risk of extruding material. When sealer is used, more extrusion is expected. The apical extrusion of material beyond the apex has been found in clinical studies to influence healing (Kerekes & Tronstad 1979, Sjogren et al.1990, Saunders et al.1997).
Suitable statistical methods must be found to investigate the simultaneous influence of several potential factors on either the PGFA or gutta-percha extrusion. It is incorrect to analyze each potential factor separately, using a chi-square test (Weiger et al.1998). It was for this reason that multiple linear regression was selected for this study. On the basis of our results, it can be concluded that after warm vertical compaction, the quality of the adaptation of gutta-percha to the wall of the apical root canal varies, and that a sufficient amount of guttapercha present in the apical canal and sufficient heating are essential in achieving a good adaptation in canals of widely varying diameters.


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