Evaluation of Irrigant Penetration Depth of Varying Tapers Using Single Rotary System in Curved Mandibular Molars--An In Vitro Study.
Successful endodontic therapy requires shaping and cleaning of the root canal system and is performed using root canal instruments and irrigating solutions [1, 2]. However, it was shown that the canal preparation is influenced by the great variability of root canal anatomy. Indeed, the instruments (both manual and rotary) do not reach certain areas such as cracks, crevices, isthmus, accessory canals and apical deltas [3, 4]. So, instrumentation alone is inadequate for disinfection of root canals in the majority of cases, necessitating the addition of chemical irrigation [5, 6].
Several irrigation agents have been developed in response to chemical disinfection. However, sodium hypochlorite (NaOCl) remains the irrigant of choice [7-9] due to its antibacterial nature, dissolving both necrotic and organic matter within the smear layer . Currently, a final irrigation sequence is combination of EDTA and NaOCL to remove inorganic and organic components of root canal .
Salzgeber and Brilliant reported that SL and debris removal is less predictable in the apical region as compared with the coronal and middle third of the root . This can be due to comparatively smaller apical canal dimensions making it difficult to contact between canal walls and the irrigants . Bronnec et al  reported that improved shaping of the root canals enhanced the flow of irrigants. On the other hand, minimal apical enlargement has been suggested to conserve tooth structure and limit extrusion of filling materials .
The extent of apical enlargement, however, has been a matter of debate. A common recommendation is to enlarge the root canal to at least three sizes beyond the initial file . Effects of various sizes and tapers including 20.10 , 30.04 , 30.06 , or 40.04  on debridement of apical debris have been evaluated and reported.
Aim of the study is to evaluate the irrigant penetration depth of varying tapers using m-two files in curved mesiobuccal canals.
Materials and Methods
A total of 30 Mandibular molars with curved mesial roots extracted for periodontal reasons were stored in distilled water at 4[degrees]C until use. The root curvature was standardized according to Schneider's technique to 20-40[degrees].
All the teeth were decoronated to a length of 12mm with a tapered diamond bur using straight handpiece. A flat surface for easier access to the pulp chamber and to facilitate length measurement of the canal.
Standard Endodontic access cavities were prepared and the selected curved canals were explored with a pre-curved #8 Kfile. The working length was estimated by advancing this file passively into the root canal until the tip of the file was seen at the apical foramen. This was done by using the Heine HR 2.5x High Resolution Binocular Loupes with LED, working length was determined by subtracting 0.5 mm from this measurement (Fig 1).
Thirty root canals were selected, and working length was determined. The molars were randomly assigned to 3 experimental groups of 10 canals each. The canals were instrumented using M-two rotary files (VDW Gmbh) and motor controller device (X-SMART, Dentsply, Maillefer, Ballaigues, Switzerland) according to the manufacturer's instructions in the ordered sequence. Group 1: 35.04% (Fig 2). Group 2: 25.06% (Fig 3). Group 3: 20.06% (Fig 4). In each group the last instrument was considered the MAF.
After each rotary file, the canal was rinsed with 2ml of 3% NaOCl, delivered by 28-guage needles (Max I-probe, Franklin Park, IL, USA) inserted deeply and passively from coronal to middle third at the end of coronal pre-flaring. During the apical preparation sequence, the needle penetrated within the apical 3mm. Finally, the specimens were rinsed with 2 ml of 17% EDTA followed by 2 ml of 5.25% NaOCl each for 60s. Final flushing with 5 ml of distilled water was done to eliminate the irrigation solutions from the canals.
Measurement of irrigant penetration depth
28-guage needles (Max I-probe, Franklin Park, IL, USA) inserted 3mm short of apex in all the groups. Iohexol, radiopaque dye was delivered passively and irrigant penetration depth was measured using occlusal photo stimulable phosphor radiographs. The measurement was done using digital analogue scale from coronal to apical direction.
Statistical analysis was performed using the ANOVA test among all the groups. Post-hoc tukey HSD test was used for multiple comparisons at 95% confidence interval and P=0.05.
The results showed statistically significant differences in the irrigant penetration depth among the groups. Group 1 and 3 & 2 and 3 showed statistically significant difference in irrigant penetration depth. Group 1 and 2 doesn't have significant difference [Table 1].
No deformity or separation of rotary files, and no occurrence of apical perforations were seen during this study.
Results of this study showed significant differences between groups 35.04 and 20.06 & 25.06 and 20.06. There were no significant differences between 35.04% and 25.06%. These groups showed acceptable debridement. Our findings showed that increased size and taper of MAF at WL improved irrigant penetration depth.
In the present study, mesio buccal canals of mandibular molars with a similar root curvature (20[degrees]-40[degrees]) were prepared using mtwo rotary files. Mohammadzadeh Akhlaghi et al, used the same curvature with m-two rotary files .
Khademi et al also showed that MAF # 30.06 was effective for the removal of debris and SL from the apical portion of root canals . On the other hand, instrumentation to 30.06 caused less dentin removal and decreased the risk of errors like transportation, ledge formation, instrument separation and perforation .
Akhlaghi et al showed that V Taper # 30.10 maintained the canal centering and minimum root thickness in the apical part of curved canals . Brunson et al reported that root canal preparation by using K3 rotary instruments to size 40.04 will allow for tooth structure preservation and maximum volume of irrigation at the apical third of single-rooted teeth when using the apical negative pressure irrigation system .
Wu and Wesselink have recommended enlarging the canals to sizes over # 40 file to remove more debris from the canals and achieve better cleaning in the apical thirds of the root canals .
Albrecht et al instrumented the canals with various tapers of ProFile GT files and observed a significantly greater percentage of remaining debris in the apical areas of the canals enlarged to the size 20 compared to 40 in the .04, .06 and .08 taper categories; however when the taper was increased to .10 no significant difference was found between the sizes 20 and 40. Although the results showed that increasing the taper from .04 to .06 in file #30 led to more SL removal, it caused no statistical significance in debris removal .
This finding is supported by Arvaniti and Khabbaz who reported that root canal taper can affect debridement only when the final instrument size was smaller than 30 .
According to some previous studies, file 30.06 may be considered as the minimum size for acceptable debridement, in this present study, 25.06 & 35.04 showed good irrigant penetration depth in curved mandibular molars.
We conclude that apical enlargement plays a major role in the penetration of irrigant to the apical third, rendering complete canal debridement. From the results 35.04% and 25.06% taper file showed complete irrigant penetration depth & 20.06% taper file does not render complete debridement of curved mesiobuccal canal.
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S. Deepak, M.S. Nivedhitha
Department of Conservative Dentistry & Endodontics, Saveetha Dental College, Saveetha University, 162, Poonamallee High Road, Chennai 600077, India
Received 22 April 2017; Accepted 11 November 2017; Published online 31 December 2017
* Coresponding author: Dr. S. Deepak;
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Table 1: Comparison of irrigant penetration depth among 35.05%, 25.06% and 20.06% tapers (Post-hoc turkey HSD test) Comparison Mean STD Significance within Difference Error groups 1 25.06 0.290 0.41634 0.768 20.06 2.000 * 0.41634 0.000 2 35.04 -0.200 0.41634 0.768 20.06 1.710 * 0.41634 0.001 3 35.04 -2.000 * 0.41634 0.000 25.06 -1.710 * 0.41634 0.001 Comparison 95% Confidence within Interval groups Lower upper Bound Bound 1 25.06 -0.7423 1.3223 20.06 0.9677 3.0323 2 35.04 -1.3223 0.7423 20.06 0.6777 2.7423 3 35.04 -3.0323 -0.9677 25.06 -2.7423 -0.6777 Figure 6: Group 1 10.48 Group 2 10.19 Group 3 18.481 Note: Table made from bar graph.
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|Title Annotation:||Original Article|
|Author:||Deepak, S.; Nivedhitha, M.S.|
|Publication:||Trends in Biomaterials and Artificial Organs|
|Date:||Apr 1, 2017|
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