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Azerbaycan Saytlari

 »  Home  »  Endodontic Articles 6  »  Efficiency of rotary nickel-titanium FlexMaster instruments compared with stainless steel hand K-Flexofile - PART 1
Efficiency of rotary nickel-titanium FlexMaster instruments compared with stainless steel hand K-Flexofile - PART 1
Results.



During the preparation of the 96 canals, a total of two instruments separated. Therefore, the following results were based on the remaining 94 canals. Two canals with 358 curves were excluded.

Instrument failure.
Table 1details the number of deformations and fractures of instruments which occurred during the study. Independent of the curvature of the canals, none of the stainless steel K-Flexo¢les separated. In the 288-curved canals, no fracture of the FlexMaster instruments occurred but in the 358-curved canals two nickel-titanium instruments (both 0.04 taper size 20, and used for the second canal) separated. The number of separated instruments (w2 ј0.511, P ј 0.478) and the number of permanently deformed instruments (w2 ј0.475, P ј 0.492) was not significantly different between the instrument types.

Preparation time.
The mean time taken to prepare the canals with the different instruments is shown in Table 2. Independent of the curvature of the canals, the shortest mean preparation time was recorded when FlexMaster instruments were used. Both in 288- and 358-curved canals, FlexMaster was significantly faster than K-Flexo¢ les (P < 0.001).

Table 1. Number of fractured and permanently deformed instruments.

Number of fractured and permanently deformed instruments

Table 2. Mean preparation time (min) and SD with the two different instruments.

Mean preparation time (min) and SD with the two different instruments

Table 3. Mean loss of working length (mm) and SD with the two different instruments.

Mean loss of working length (mm) and SD with the two different instruments

Table 4. Incidence of canal aberrations by instrument types.

Incidence of canal aberrations by instrument types

Change of working length.
All canals remained patent following instrumentation, thus, none of the canals became blocked with resin shavings. None of the canals showed overextension of preparation, whereas a loss of working distance was found in several canals. The mean loss of working length which occurred with the different instruments is listed in Table 3. The differences between the two instrument types were not statistically significant, in either the 288-curved (P ј 0.828) or 358-curved canals (P ј 0.628).

Canal shapes.
The results concerning the assessment of canal aberrations are summarized in Table 4. With respect to the different types of aberrations evaluated, both in canals with 288 and with 358 curves, there were no significant differences between the two instrument types (w2-test, P > 0.05), but, more zips and ledges were created with K-Flexo¢les. Only one perforationwas created by K-Flexo¢ le in a 358-curved canal.
On average, in the canalswith 288 curves, FlexMaster instruments removed material more evenly on the outer, as well as on the inner side of curvature (Fig. 4a).With the exception of three measuring points, significant differences (P < 0.05) occurred between resin removal achieved with the two different instruments (Table 5). The canals prepared with FlexMaster instruments remained better centred compared with those enlarged with K-Flexo¢les (Fig. 4).
In the canals with 358 curves, the FlexMaster instruments removed more material on the outer side of the curvature (Fig. 5a). On average, only limited material removal occurred at the inner side of the curvature in the apical part of the canals (Table 6). This elect was not significantly different compared with the material removal achieved with K-Flexo¢les at these measuring points (P > 0.05). Canals shaped with K-Flexo¢les had material removed mainly in the last 1-4 mm along the outer side of the curvature, resulting in moderate outer widening of the canal (Fig. 5b). In general, the FlexMaster instruments showed a more centred enlargement compared with the K-Flexo¢les (Fig. 5).

Figure 4. Mean changes in the canal shape of 288-curved canals as the result of instrumentation with (a) rotary nickel-titanium FlexMaster instruments and (b) stainless steel hand K-Flexo?les (n ¼ 24 canals in each case).

Mean changes in the canal shape of 288-curved canals as the result of instrumentation

Table 5. Mean material removed (mm) and SD at the different measuring points after instrumentation of simulated 288-curved canals.

Mean material removed (mm) and SD at the different measuring points after instrumentation of simulated 288-curved canals

Figure 5. Mean changes in the canal shape of 358-curved canals as the result of instrumentation with (a) rotary nickel-titanium FlexMaster instruments and (b) stainless steel hand K-Flexo?les (n ¼ 24 canals in each case).

Mean changes in the canal shape of 358-curved canals as the result of instrumentation

Table 6. Mean material removed (mm) and SD at the different measuring points after instrumentation of simulated 358-curved canals.

Mean material removed (mm) and SD at the different measuring points after instrumentation of simulated 358-curved canals