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Azerbaycan Saytlari

 »  Home  »  Endodontic Articles 9  »  The effect of instrument type and preflaring on apical file size determination
The effect of instrument type and preflaring on apical file size determination
Materials and methods.

Tooth selection.
Intact extracted maxillary and mandibular permanent premolars and molars (total:60 teeth) displaying normal pulp chamber, patent root canals and fully formed apices were selected (Table 1).Teeth with complicated anatomy, external root resorption or extreme root curvature were excluded from the study.
Standard access cavities were cut; the pulp tissues were removed with an extra-fine (XF) barbed broach (Antaeos CC-cord, Munchen, West Germany). Care was taken to ensure that the barbed broach engaged only the pulp tissue without contacting the apical third of the root canal. Canals were then irrigated with copious 1% sodium hypochlorite solution (Milton solution1, Procter and Gamble Australia, Parramatta, Australia). Apical patency was determined by inserting a size 6 K- file into the root canal until the tip of the file was visible at the apical foramen; the WL was set 0.5 mm short of the apical foramen. Cusp tips were used as reference points. Both the WL and the reference point of each individual canal were recorded. All the canals in each tooth (except the second mesio-buccal canals of maxillary molars) were included in the study. A total of121canals were eventually utilized. Each tooth was stored in an individually labelled, capped plastic vial containing 10% buffered formalin.

Table 1. Distribution of teeth selected for sizing.

Distribution of teeth selected for sizing

Sizing of canals.
Each canal was sized four times using two instrument types before and after coronal flaring. Each canal was sized with both stainless steel K-files (Mani, Matsutani Seisakusho Co., Takanezawa-Machi Tochibi-Ken, Japan) and hand-held LS rotary instruments (Lightspeed Technology Inc., San Antonio, TX, USA) in random order. Files were inserted passively into the canal with a light ‘watch-winding’ action, and care was taken to avoid any force during sizing. For K-files, measurement was undertaken starting from ISO size 8, whereas for LS instruments, measurement began with size 20 (i.e. the smallest file).The biggest file size that reached the correct WL was recorded. The same procedure was used for each canal before and after coronal flaring.
The following precautions were taken to reduce systematic bias during measurement:
  1. K-files and LS instruments were alternated as the first instrument used to size canals.
  2. Sizing with the second file type was conducted in random order of teeth, without knowledge of the previous measurement result.
  3. Each measurement was recorded on a separate sheet to prevent the operator from knowing the previous reading.
The only information the operator had each time before sizing a canal was the WL and its corresponding reference point.

Coronal and middle third flaring.
Coronal flaring and middle third flaring were done with Profile instruments (Maillefer-Dentsply, Ballaigues, Switzerland) using a crown-down approach to eliminate all interferences, cervical to the apical third region. flaring was terminated 4 mm short of the WL so that the apical third region remained unprepared. Recommended guidelines by the manufacturer (Profile 0.06/0.04 series) were adopted. Their sequence was as follows: Profile orifice shaper 3 (#40,0.06);  Profile orifice shaper 2 (#30, 0.06);  Profile #25, 0.06;  Profile #20, 0.06; Profile #25, 0.04; and  Profile #20, 0.04. Instruments were used sequentially until a point 4 mm short of the WL was reached. The final size used depended on the size of each canal. The typical instruments used up to 4 mm from the WL were  Profile orifice shaper 2 (#30,0.06) for premolar canals,  Profile#25,0.06 for moderate size mesial or distal molar canals, and Profile#25,0.04 for narrow mesial canals.

Statistical analysis.
A univariate analysis of variance (anova) was conducted to examine the effect of instrument type and flaring on the apical file size determination (dependent variable: apical file size; independent variables: instrument type, flaring). The interaction between instrument type and flaring was also examined. Post hoc tests (pair wise comparisons) were conducted only if there was a significant interaction between the two independent variables. All statistical analyses were performed at the 0.05 level of significance.