|Year : 2012 | Volume
| Issue : 6 | Page : 784-788
|Influence of the instrumentation technique and apical preparation diameter on calcium hydroxide filling in simulated curved canals
Fabiana Vieira Vier-Pelisser1, Ariane Meng2, Letícia Caroline Benedete Netto2, Marcus Vinícius Reis Só3
1 Post-graduate Program in Dentistry, Pontifical Catholic University of Rio Grande do Sul (PUCRS), Porto Alegre, RS, Brazil
2 Specialization Course in Endodontics, Uningá, Caxias do Sul, RS, Brazil
3 Department of Endodontics, Federal University of Rio Grande do Sul (UFRGS), Porto Alegre, RS, Brazil
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|Date of Submission||04-Jan-2010|
|Date of Decision||16-Jun-2010|
|Date of Acceptance||13-Nov-2010|
|Date of Web Publication||3-May-2013|
| Abstract|| |
Objective: This study evaluated the influence of the instrumentation technique and apical preparation size on the filling capacity of a calcium hydroxide (CH)-based paste.
Materials and Methods: Fifty simulated curved canals were prepared in acrylic blocks (five groups; n = 10 each). In three groups, the canals were preflared with Gates-Glidden drills and the apical stop was prepared with #25, 30 or 35 Flexofile files. In the other two groups, the canals were prepared with ProTaper rotary instruments and the apical stop was prepared with F1 and F2. A CH paste was injected into the canals using a special syringe. The four sides of the blocks were scanned with the root curvature to the mesial, buccal, distal and palatal faces. The amount (%) of filling in the total canal area and in the apical 5 mm was obtained [analysis of variance (ANOVA); Tukey's test; α = 0.05]. Qualitative analysis of apical filling was done (absence vs. presence of filling deficiencies) (chi-square test; α = 0.05).
Results: There was no significant difference in canal filling among the groups at any block side. Presence of voids was associated with the simulated mesial and distal faces.
Conclusions: An effective canal filling with the CH paste was not achieved in all cases. Canal filling failure occurred mostly in the apical third. Filling deficiencies can be better visualized in canals with mesial and distal root curvatures.
Keywords: Calcium hydroxide paste, curved root canals, filling, intracanal medication, preparation size
|How to cite this article:|
Vier-Pelisser FV, Meng A, Benedete Netto LC, Reis Só MV. Influence of the instrumentation technique and apical preparation diameter on calcium hydroxide filling in simulated curved canals. Indian J Dent Res 2012;23:784-8
The use of a calcium hydroxide (CH)-based intracanal medication between sessions in the treatment of asymptomatic apical periodontitis promotes a remarkable reduction or elimination of the endodontic microbiota, ,,, affording better periapical repair than the single-session therapy. ,, The antimicrobial efficacy of CH paste is associated with its direct contact with the canal walls and the filling of all spaces. ,,
|How to cite this URL:|
Vier-Pelisser FV, Meng A, Benedete Netto LC, Reis Só MV. Influence of the instrumentation technique and apical preparation diameter on calcium hydroxide filling in simulated curved canals. Indian J Dent Res [serial online] 2012 [cited 2020 Dec 4];23:784-8. Available from: https://www.ijdr.in/text.asp?2012/23/6/784/111260
While some studies have assessed the quality of CH filling in curved root canals, ,,, most of them have focused on the techniques used to take the CH paste to the root canals. According to Sigurdsson et al.,  canal curvature is a limiting factor for proper filling of the canal space with the CH paste, especially in the apical region, when an injection system is used. Canal diameter and curvature may influence its complete filling with the medication. , Placement of an intracanal dressing is obviously easier in wide straight canals.
Research-based data and daily clinical experience have shown that placing CH pastes in curved canals is challenging and that proper placement of CH into the root canal system may influence its effectiveness. Difficulty in enlarging the apical portion of curved canals is often observed during chemomechanical preparation. Due to the accentuated curvature and apical anatomy of these canals, the apical stop is established with small-sized instruments. Therefore, it remains unclear how the conicity of curved canals and the amount of apical enlargement may influence the filling capacity of CH intracanal medication. The purpose of this study was to evaluate in vitro the influence of hand instrumentation (Flexofile files) associated with Gates-Glidden drills and rotary instrumentation (ProTaper) on the filling capacity of a CH paste (Calen) in curved root canals.
| Materials and Methods|| |
Fifty simulated curved canals with 35° apical curvature (Dentsply/Maillefer, Ballaigues, Switzerland) were prepared in clear acrylic blocks and randomly assigned to five groups (n = 10), according to the instrumentation technique and diameter of apical preparation. In three groups, the canals were prepared with Gates-Glidden drills #1 (tip size 0.05) and #2 (tip size 0.07) (Dentsply/Maillefer) and FlexoFile files (Dentsply/Maillefer) in a step-down instrumentation, and the apical stop was prepared with file #25 (group GG/F25), #30 (group GG/F30) and #35 (group GG/F35). In the other two groups, the canals were prepared with ProTaper nickel-titanium rotary instruments (Dentsply/Maillefer) with the apical stop corresponding to instruments F1 (group PTF1) and F2 (group PTF2) with taper/tip diameter of 5.5-7%/0.20 and 5.5-8%/0.25, respectively.
Root canal preparation and filling with the CH paste were performed by a single operator blinded to the groups, maintaining the acrylic resin blocks in a fixed position with the aid of a holding device (NBLBC; Neboluz Comercial de Ferramentas Ltda., São Paulo, SP, Brazil).
The canals were initially irrigated with 1% sodium hypochlorite (NaOCl) (Biodinβmica Química e Farmacêutica, Ibiporã, PR, Brazil) and explored with size 15 K-files (Dentsply/Maillefer) at a working length (WL) of 16 mm. Throughout the preparation, the root canals were irrigated with 1 ml 1% NaOCl at each change of file and a suction cannula was used to remove excess of solution.
The preparation was initiated with a large-sized instrument, which penetrated approximately 2 mm at the canal entrance and was moved from right to left with a brushstroke action against the canal walls and no pressure toward the apex. Two sequential instruments of smaller sizes were used intercalating with NaOCl irrigation and a size 10 K-file at the WL between instruments. The cervical third was then preflared with Gates-Glidden drills, and new hand files of decreasing size were successively used with the same movements described above until reaching the WL. The apical stop was prepared using anti-curvature brushing movements with master apical file sizes 25 (group GGF25), 30 (group GGF30) and 35 (group GGF35). The apical third was prepared with three subsequent instruments of larger size than that of the master apical file, stepping back 1 mm from the WL at each change of file. During the crown-down preparation, the canals were explored with a size 10 K-file at the WL and irrigated with NaOCl. In the same way, during stepping back, the master apical file was used at each change of file at the WL.
ProTaper Universal System (Dentsply/Maillefer) instruments were used in a headpiece activated at 300 rpm by an electric engine (Endo-Pró; VK Driller Equipamentos Elétricos Ltda., São Paulo, SP, Brazil) with 2 N/cm torque. Instrumentation started with S1 and SX instruments at the cervical third, followed by the S2 instruments at the middle third, with a brushing action in a crown-down manner. In the groups PTF1 and PTF2, the apical stop was prepared with F1 and F2 instruments, respectively, using uniform, continuous and pressureless movements at the WL.
The hand and rotary instruments were discarded every five preparations. After instrumentation, the canals were dried with absorbent paper points of the same size as that of the master apical file.
Canal filling with the CH paste
A commercial CH paste supplied in a cartridge was used in this study [Calen ® ; S. S.White Artigos Dentários Ltda., Rio de Janeiro, RJ, Brazil; composition: 2.5 g CH, 0.5 g zinc oxide, 0.05 g colophony and 1.75 ml polyethylene glycol 400 (vehicle)]. The paste was delivered from the cartridge on a glass plate, mixed with 2 drops of blue Indian ink (Acrilex, São Paulo, SP, Brazil), and the homogenous mixture was repacked into the cartridge. The blue-stained paste was injected into the canals using a using a special endodontic syringe (ML syringe ® ; S. S. White Artigos Dentários Ltda.) with a threaded piston and a long 27-G needle (Septoject XL, Septodont, Saint-Maur-des-Fossés, Cedex, France) with a silicone stopper to limit penetration to the WL. The coronal 2 mm of the canal was sealed with a temporary coronal filling material (Coltosol ® ; Coltene-Whaledent, Cuyahoga Falls, OH, USA).
The four sides of the acrylic resin blocks (left, front, right, and back) were scanned with a flat-bed scanner (Genius ColorPage-HR6X, Kye Systems Corp., Houjie, China) at 600 dpi resolution. Having the operator as a reference point, the root curvature was disposed to the operator's left, which was considered as the mesial face in this study. The acrylic block was turned in a clockwise direction on the scanner bed in such a way that the root curvature was then disposed to the front, right, and back sides, simulating canals with root curvature to the buccal, distal and palatal faces, respectively. In this way, four images were obtained from each simulated canal: left or mesial (M), front or buccal (B), right or distal (D) and back or palatal (P). The acquired images were exported to AutoCAD ® 2004 (Autodesk Inc., McInnis Parkway, San Rafael, CA, USA) for quantitative and qualitative analyses.
The images were analyzed to measure the areas corresponding to the total canal space, apical 5 mm and regions without CH paste filling. After standardization of the working length (16 mm) using a tool of AutoCAD ® software (Polyline), the canal perimeter and the total canal area were determined. In a second moment, the same method was used to measure the area corresponding to the apical 5 mm. Then, the total area of the regions that were not filled with the blue-stained Calen paste was measured.
The amount of CH paste filling and the amount of filling deficiencies in the total canal space and the apical 5 mm were considered for statistical purposes. Data were analyzed statistically by analysis of variance (ANOVA) and Tukey's post hoc test at 5% significance level.
In the qualitative analysis, the presence or absence of voids in the apical third of the canals in all faces (B, M, D and P) was verified, regardless of their size and the studied group. These data were analyzed statistically by the chi-square test complemented by the adjusted residues analysis. A significance level of 5% was adopted.
| Results|| |
The results of the quantitative analysis are presented in [Table 1] and [Table 2].
|Table 1: Percentage of root canal filling with the calcium hydroxide paste in the total canal area|
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|Table 2: Percentage of root canal filling formed with the calcium hydroxide paste in the apical 5 mm|
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Regarding the total canal space and the apical 5 mm, intergroup comparisons showed no statistically significant difference (P > 0.05) in the percentage of filling in all aspects. Comparing the four aspects (B, M, D and P) in each group, statistically significant difference (P < 0.05) was found only between groups GG/F35 and PTF1. In GG/F35, the buccal aspect presented a more complete filling than the others, while in PTF1, the buccal aspect presented a more complete filling than the mesial and distal aspects.
The results of the qualitative analysis show that the presence of filling is associated with the buccal aspect, while the absence of filling is associated with the mesial and distal aspects [Table 3].
|Table 3: Absence and presence of voids (apical filling deficiencies) formed with the calcium hydroxide paste at the different surfaces|
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| Discussion|| |
Complete filling of curved root canals with CH pastes is a challenge experienced in daily endodontic practice. The popularity of rotary instruments with greater taper than those of hand files for root canal preparation has increased considerably. Thus, it seems opportune to investigate the influence of the type of preparation and the diameter of apical preparation on the filling of curved canals with a CH dressing.
In the present study, a single technique was used for placement of the paste into the canals, that is, an injection system that is simple to use and is widely widespread in the Brazilian market (ML syringe ® ), varying the instrumentation technique and the amount of apical enlargement.
Different methods have been employed for analysis of CH filling, among which radiographic techniques ,,,,, and clearing,  . In the present study, the four sides of the acrylic blocks (left, front, right and back) were scanned to simulate canals with root curvature to the mesial, buccal, distal and palatal faces and provide a more accurate analysis of CH filling. To date, apart from clearing, which also permits a three-dimensional analysis of the intracanal dressing filling,  only two-dimensional (buccolingual and mesiodistal) radiographs ,, and orthoradial radiographs , have been used.
Another important methodological issue of this experiment was the quantification of the mean percentage of canal filling also and not only the qualitative analysis based on scores, as used by several authors. ,,, The quantitative analysis of canal filling in the total canal area [Table 1] and in the apical third [Table 2] showed no significant differences among the techniques of root canal instrumentation and diameter of the apical preparation regarding the percentage of CH filling. However, although canal filling was very close to 100% in several specimens, complete filling was not observed in any case.
As expected, the quantitative and qualitative analyses showed that the apical third was the most difficult region to be completely filled and presented the largest number of empty spaces, as reported elsewhere. ,, Regardless of the placement technique, the occurrence of more filling deficiencies in the apical portion is explained by the difficulty in taking the paste to this part of the canal, which is further from the cervical third, narrower and invariably associated with the canal curvature.
An interesting clinical finding of the present study came from the qualitative analysis and was reinforced in the quantitative analysis in groups GG/F35 and PTF1. [Table 3] shows the presence and absence of voids in the apical filling on all faces (M, B, D and P) in each group. Extrapolating these results to clinical endodontics, it may be considered that canals with mesial and distal root curvatures have a greater probability of revealing CH filling deficiencies when compared to canals with buccal and palatal root curvatures. In order words, empty spaces in the filling of canals with buccal and palatal root curvatures may be overlooked radiographically because radiographs provide a two-dimensional image of a three-dimensional structure. In addition, in these cases, the filled areas are superposed over the non-filled areas, giving a false impression of lack of voids.
A single-session treatment does not ensure complete elimination of bacteria from the root canal system of teeth with asymptomatic apical periodontitis. For this reason, instrumentation associated with antimicrobial irrigants should be reinforced by the use of a CH-based dressing.  For CH to produce its desired effects, it should be in direct contact with all canal walls.  However, the placement of intracanal dressing in curved, narrow canals is not an easy procedure, and filling deficiencies may occur. Further studies investigating factors and conditions that might influence the complete filling of root canals CH-based medications should be performed to investigate the influence of the degree of apical root curvature, seeking a more effective action of the medication, especially in cases of apical periodontitis.
| Conclusions|| |
According to the employed methodology and the obtained results, the following conclusions may be derived.
- The preparation techniques did not differ significantly regarding the quality of CH filling.
- Complete root canal filling was not achieved in all cases.
- Regardless of the preparation technique, filling deficiencies were more common in the apical third.
- Filling deficiencies can be better visualized in canals with mesial and distal root curvatures.
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Fabiana Vieira Vier-Pelisser
Post-graduate Program in Dentistry, Pontifical Catholic University of Rio Grande do Sul (PUCRS), Porto Alegre, RS
Source of Support: None, Conflict of Interest: None
[Table 1], [Table 2], [Table 3]
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