Comparative Evaluation of Cleaning Efficiency and Apical Extrusion of Debris Using Two Pediatric Rotary Endodontic Files: An In Vitro Study

INTRODUCTION

Primary teeth with signs and symptoms of irreversible pulpitis and also pulpal necrosis are indication for root canal therapy.¹ Hand instrumentation is a traditional approach to perform an endodontic procedure. Although a conventional procedure, hand instrumentation may lead to canal aberrations, perforations, inadequate cleaning, transportation, instrument failure, and long chair time for children.^2–4 Nickel-titanium instruments, which were introduced, have revolutionized the practice of endodontics in an efficiently beneficial way.⁵

Use of the NiTi rotary instruments in primary teeth was initiated by Barr et al.⁶ and others.^3,7 As per Barr et al.,⁶ a quicker preparation with cost efficiency and consistent results can be achieved with the help of NiTi instruments. But a rotary NiTi file specially designed for permanent dentition was used for performing cleaning and shaping during pulpectomy. According to Silva et al.,⁷ the important factor is the reduction of procedural time while using NiTi instruments during pediatric endodontic therapy without hampering the quality of treatment. Additionally, this will also reduce the fatigue of the patient as well as the dental team. Contemporary endodontics aims to complete the cleaning of the root canals with the help of chemomechanical preparation.⁸ However, the success is questionable even with this advancement in endodontics.⁹ Cleaning efficacy of the file defines its ability to efficiently and completely remove the pulpal remnants and microorganisms from the root canal space.

The apical extrusion of debris, as per several studies, resulted in postoperative/post instrumentation inflammation, pain, and failure. The rationale for this study was based on the argument that endodontic treatment in deciduous dentition differs from adult endodontics since primary teeth exhibit anatomical differences from permanent teeth in terms of size and morphology (internal and external).^10–12 Also, the morphological changes in terms of physiological or pathological radicular resorption should be taken into consideration.¹³ Thus, the results concluded from the adult endodontics cannot be applied to pediatric endodontics. Moreover, even if a correctly determined working length (WL) is used but the instrumentation is done using files designed for permanent dentition, it may extrude debris periapically and may cause damage to the permanent tooth bud. Limited data concerning the use of NiTi files specially designed for pediatric endodontics are available.^6,7

The apical extrusion of debris as well as cleaning efficacy in primary root canal treatment has not been well elucidated. Thus, the aim of this in vitro study to compare the amount of apically extruded debris and cleaning efficacy during the preparation of primary molar root canals using Pro AF Baby Gold and Kedo-S pediatric rotary files. The null hypotheses tested were that (a) no difference exists between the amounts of apically extruded debris associated with various pediatric NiTi rotary files systems and (b) no difference exists between the cleaning efficacy of various pediatric NiTi rotary files systems.

MATERIALS AND METHODS

This in vitro study was carried out in the Department of Pediatric and Preventive Dentistry in collaboration with the Department of Oral Pathology and Microbiology, Sharad Pawar Dental College, Sawangi (Meghe), Wardha, for evaluating cleaning efficacy and in collaboration with College of Pharmacy, Wardha, for evaluation of apical extrusion of debris. Institutional ethical committee clearance was obtained from Datta Meghe Institute of Medical Sciences (Deemed to be University), Sawangi (Meghe), Wardha, with reference number DMIMS (DU)/IEC/2017-18/6746. The sample for each group consisted of 10 teeth.

Human primary molars that had recently been extracted were collected from patients aged 5–8 years, for periapical pathology and orthodontic reasons, and stored in distilled water at 4°C. Teeth with root lengths affected by resorption were included in the study since primary root canal treatment is indicated where pathologic root resorption involves less than one-third (minimum 7 mm of root length) of the root. Primary molar teeth with any previous pulp therapy, cracks, any restorations, perforation in the furcation area, periapical cyst, root fracture, and internal resorption were excluded from the study. Twenty teeth that met all of the inclusion criteria were finally divided into two groups randomly; group I—Pro AF Baby Gold (DentAlyze) (n = 10) and (b) Kedo-S (n = 10). A #10 K-file was inserted into the root canal such that it was visible apically under a magnifying loupe, for determination of the WL, which is 1 mm less than the real length. A # 15 No. K-file (Mani, Japan) was then introduced into the root canal followed by the introduction of India ink with an insulin syringe. This was done until the Indian ink leaked from the apical foramen. The ink was again injected 3–4 times into the canals after diffusion and dried for at least 48 hours after each application.

ROOT CANAL PREPARATION

RESULTS

The mean values and standard deviations of the amount of apically extruded debris (g) for all groups are shown in Table 1. The results showed that all instrumentation techniques caused a significant amount of extruded debris. The amounts of apically extruded debris were significantly less for the Pro AF Baby Gold (group I) (0.000073 g) compared to the Kedo-S (group II) (0.000126 g) (p %3C; 0.05). Similarly, Table 2 shows the results related to cleaning efficacy. Scoring criteria are depicted in Figure 1 for the cleaning efficacy.

DISCUSSION

Endodontic procedures are ideally performed efficiently with the help of rotary files as per literature.⁵ Studies in the literature have evaluated instrumentation time, the cleaning efficacy of the files, canal aberrations, etc.^3,10,16 Among these factors, the cleaning efficiency of an instrument along with its ability to limit the extrusion of the debris periapically, is the most important consideration to be taken into account while deciding a file for cleaning and shaping. The instruments which are used in coronal-apical direction are bound to extrude a certain amount of debris periapical but this should be minimal, as it might cause have toxic effects on the underlying bud of the permanent tooth.^11,17

There are many techniques to evaluate cleaning efficacy in the root canal system, such as scanning electron microscopy (SEM), micro-CT, stereomicroscopy, splitting the tooth longitudinally for microscopic evaluation. According to Tomar et al.¹⁸ in 2018, stereomicroscopy with diaphanization process is a more sensitive and reliable technique to evaluate root canal three-dimensionally and is a cost-effective method when compared with other methods. Silva et al.⁷ in 2004, Honardar et al.¹⁹ in 2014, and de Souza et al.¹⁴ in 2015 have successfully used stereomicroscope for assessment of cleaning efficacy in their study. Therefore, stereomicroscopy was considered for evaluating the cleaning efficacy of the pediatric rotary files systems in root canals at three different levels namely apical, middle, and coronal one-thirds. The stereomicroscopy for evaluating cleaning efficacy requires the introduction of Indian Ink in the root canals followed by diaphanization process.¹⁴

Studies conducted by different authors took root apex as a reference point for evaluating canal centricity (at different levels from the apex).^19–21 However, considering the continuous physiological root resorption associated with primary roots, CEJ was considered as a reference point for this study. This also helped in standardizing the protocol for evaluating canal centricity. Levels at which canal centricity was evaluated were—1 mm from CEJ, 3 mm from CEJ, and 6 mm from CEJ.

In the current study, cleaning efficacy was also evaluated between the second- and third-generation rotary files in primary teeth. In comparison, there was a significant difference at apical levels of maxillary mesial root canals with a mean score of 0.28 ± 0.48 for Pro AF Baby Gold and 1.00 ± 0.00 for Kedo-S. Similarly, maxillary distal root canals had a mean score of 1–0.14 ± 0.37 for Pro AF Baby Gold and 83 ± 0.40 for Kedo-S files. Whereas no significant difference was found at middle and cervical levels of distal roots and at all levels of under-prepared palatal roots (Table 2).

In the mandibular teeth, statistically significant differences were found at the apical level of all roots except disto-lingual roots (p %3E; 0.05) in cleaning efficacy. No significant differences were found at the middle and cervical of all the roots of the mandibular primary molar teeth (Table 2). These results obtained are in contrast with the study done by Katge et al.,²² who showed that the second-generation files had superior cleaning ability in primary teeth at both middle and coronal third rather than apical third. The results are also contrasting with the study done by Javan et al.²³ in 2006 on primary molars, in which no significant was found between the second- and third-generation rotary files in terms of cleaning efficacy at various levels in all the canals and this was in accordance with Silva et al.⁷ in 2004. Foschi et al.²⁴ in 2004 found that when hand and rotary files were compared in primary teeth, no significant difference was found among the two for cleaning ability. The contrasting results may also be attributed to the “taper lock” lock effect. The taper lock effect states that NiTi instruments may cause aggressive preparation of root canal which results in to increase in torsional stress which may affect cleaning efficacy.²⁵

Cleaning efficacy measured in the present study as seen in Table 1 shows that the results were in favor of Pro AF Baby Gold rotary files over Kedo-S with a significant difference in the apical region. These findings are supported by Devi et al.²⁶ who mentioned that a wider portion of the variable taper file engages in the coronal and middle regions. This leaves the apical region un-instrumented. While efficient circumferential filling of canals with thin constant taper files will engage the canal intimately. According to Gu et al.,²⁷ heat-treated third-generation NiTi instruments maintained better canal centricity.²⁷ Thus by maintaining centricity, the endodontic file comes in contact with the root canal in 360°, thereby cleaning the canal efficiently. Whereas, when the files are comparatively stiffer, like in second-generation rotary files, they tend to straighten in the root canal, thereby partially contacting the anti-curve portion of the canal and hence results in reduced cleaning efficacy. It is also seen in the results that the values are most significant in relation to the mesial canals. In the present study, root canal preparation was done till #25/0.04 file only, which binds efficiently with the walls of the mesial canals. This is also suggestive that in wider canals we should use 25/0.06, 30/0.04 of Pro AF Baby Gold file and E1 of Kedo-S files. But may again affect the centricity of the canal significantly, especially with Kedo-S files.

Myers and Montgomery and also Tanalp and Gungor have suggested many different methodologies for the quantifiable evaluation of periapically extruded debris.^15,28 The above-mentioned methodology also describes the one used by Myers and Montgomery, which is also one of the most-used methods in the dental literature.²⁸ In our study, the simulation of periapical tissue was not done. This was due to the simulations done using materials to close the apical foramen may hamper the results by the absorption of the irrigant and debris as per Burklein and Schafer.¹⁰ Sodium hypochlorite (NaOCl) is the common irrigation material used in endodontics,¹⁷ still distilled water was used for the present study as an irrigant to avoid the possibility of crystallization by NaOCI, which may alter the results.

As per the literature, all the endodontic instruments cause some amount of apical extrusion of debris.^10,28 To the best of our knowledge, no previous study has compared the amount of apically extruded debris with Pro AF Baby Gold and Kedo-S. However, in a study on primary molars by Topcuoglu et al.,¹⁷ the amount of periapical extrusion of debris was studied using Revo-S, Mtwo, ProTaper Next, and hand files. Their work also revealed that all the instruments caused apical extrusion of debris with no significant difference. Although the results of the present study show that ProAF Baby Gold pediatric rotary files have significantly less periapical extrusion of debris (Table 1).

The results of the present study support the “taper lock effect”. In the taper lock effect, the file gets engaged in the coronal region of the root canal, thereby not allowing the collected debris to come out of the canal and thereby pushing the debris apically.

The findings of the present study may be due to the difference in a cross-sectional design, working mechanism, and the number of instruments used. In terms of the number of instruments used in each canal, Albrecht et al. have shown that reducing the number of files will help in reducing the canal aberrations along with reduced apical extrusion.²⁹

Fully formed non-resorbed roots should be taken into consideration for future studies as apical extrusion with closed apex will be comparatively less when compared to resorbed roots.

CONCLUSION

The null hypothesis was rejected, as significant differences were found among the instruments used. Cleaning efficacy is better with Pro AF Baby Gold in all the regions of the canals but was significantly better in the apical region when compared to Kedo-S. Within the limitations of the present in vitro study, both the instrumentation systems caused debris extrusion. However, Pro AF Baby Gold pediatric rotary files extruded significantly less debris than did Kedo-S pediatric rotary files.

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