Cone-beam Computed Tomographic Evaluation of the Quality of Obturation Using Different Pediatric Rotary File Systems in Primary Teeth

INTRODUCTION

Pediatric endodontics is a fundamental aspect of dentistry that preserves the primary teeth in its functional form. Effective debridement and restoration of the pulpally involved primary teeth should be considered as the treatment of choice for space maintenance, function, and esthetics.¹ The complex, ribbon-shaped root canal morphology of the primary molars challenges the success of pulpectomy in achieving a three-dimensional seal. Mechanical preparation with conventional hand instruments is time-consuming and may lead to iatrogenic errors (canal transportation, apical blockade, ledging, zipping, etc.) when compared with rotary instrumentation, which can efficiently prepare the root canals.

Barr et al. in 1999 pioneered rotary biomechanical preparation with Profile 0.04 taper files in primary teeth.² Studies on rotary instrumentation outlined the uniform root canal preparation and predictable obturation with a significant reduction in the working time.^2,3 The modified protocol of the Pro Taper, Heroshaper, and K3 rotary files was used in primary molars.^4–6 But, these conventional rotary files designed for permanent teeth, are longer (21 or 25 mm) with a constant taper (6 or 8%) are inconvenient to be used in the oral cavities of children. Pediatric endodontics has evolved with the introduction of exclusive pedodontic rotary file systems with modified length and taper. Kedo-S is the first pedodontic rotary file system introduced by Reeganz Dental care Pvt. Ltd., India followed by Prime Pedo (Sky International Enterprises, India), Pro AF Baby Gold (Dentobizz, India), DXL-Pro Pedo (Kraft Dental, India), Pedo Flex (Orikam Health care, India), Denco Kids files (Shenzhen Denco medical Ltd., China), and Sani Kid rotary files (Chengdu Sani medical equipment Co. Ltd., China).⁷

To date, no study has reported the comparative evaluation of different pediatric rotary file systems using cone-beam computed tomography (CBCT). Hence, a study was planned to compare and evaluate the efficacy of three different pediatric rotary file systems viz., Kedo SG Blue, Pro AF Baby gold, and Pedo Flex rotary files using CBCT.

MATERIALS AND METHODS

• Thirty mandibular primary molars extracted either due to gross caries, loss of bone support, or over retention with at least two-thirds of root length (7–12 mm) were included in the study. The teeth were rinsed and stored in normal saline for 1 week. Ethical clearance for the study was obtained from Institutional Ethical Committee. The teeth were divided into three groups based on the pediatric rotary files used for the root canal preparation.
• Group I (n = 10): Kedo SG Blue rotary files (Reeganz Dental Care Pvt. Ltd., India).
• Group II (n = 10): Pro AF Baby gold rotary files (Dentobizz, India).
• Group III (n = 10): Pedo Flex rotary files (Orikam Health Care, India).

Access cavity preparation was done using No. 8 round bur (Mani Inc., Japan) followed by working length determination using Radiovisiograph (RVG, Carestream Health, Inc., USA) with the endodontic file placed 1 mm short of the apical foramen. Rotary instrumentation was done after the canals were enlarged up to #20 hand K-files.

RESULTS

When the quality of obturation was compared among the three groups, Kedo SG Blue showed the highest number of optimal fillings (Fig. 2A) in nine teeth (42.9%) followed by Pro AF Baby gold group in eight teeth (38.1%) and the least was found in Pedo Flex group in four teeth (19%). Only one tooth (11.1%) was underfilled in the Kedo SG Blue group, whereas two teeth (22.2%) and six teeth (66.7%) were underfilled in Pro AF Baby gold and Pedo Flex groups, respectively (Fig. 2B). There was a statistically significant difference with p = 0.036 (Table 1). In specific to the mesial and distal canals, the highest number of optimally filled canals were found in the Kedo SG Blue group (11 mesial and 9 distal canals) followed by Pro AF Baby gold (10 mesial and 9 distal canals) and Pedo Flex (6 mesial and 6 distal canals), although there was no statistical significance (Table 2).

When analyzed for the presence or absence of voids, 7 teeth (26.9%) of the Kedo SG Blue group had voids, while 9 teeth (34.6%) and 10 teeth (38.5%) of Pro AF Baby gold and Pedo Flex groups had voids, respectively (Table 3). In specific to the canals, the Kedo SG Blue group showed minimal voids (5 mesial and 8 distal canals), followed by Pro AF Baby gold (9 mesial and 8 distal canals) and Pedo Flex (11 mesial and 7 distal canals) (Table 4).

The intergroup comparison of quality of obturation showed a statistical significance between Kedo SG Blue and Pedo Flex groups (p = 0.019) (Table 5). For the presence or absence of voids, a statistically significant difference was observed between Kedo SG Blue and Pedo Flex group with respect to the mesial canals (p = 0.025) (Table 6).

DISCUSSION

The complex endodontic configuration of the primary teeth and the possible limitations of the conventional NiTi rotary files like file separation,⁹ discomfort for the children in mouth opening due to the length (21–25 mm) of the files, having no specific protocol for the rotary instrumentation in primary teeth, etc.,¹⁰ made it mandatory for the introduction of exclusive pediatric rotary file systems with specific protocols. Application of the protocols recommended for the permanent teeth may lead to lateral perforation of the primary root canal system.^4,9

The present study holds its uniqueness in comparing the exclusive pediatric rotary file systems viz., Kedo SG Blue, Pro AF Baby gold, and Pedo Flex rotary file systems in primary teeth. Each file system has their own file design, speed, and torque specifications and instrumentation protocol. These files are readily available and cost-effective.

The obturation quality is one of the major factors that determine the favorable outcome of pulpectomy.¹¹ This can be evaluated using radiographs, digital radiography like radiovisiography or CBCT, dye penetration, radioisotopes, fluid filtration, bacterial leakage, microscopic analysis, etc.¹² Among all, CBCT provides a faster and an accurate three-dimensional view of the root canal system. During imaging, a cone-shaped X-ray beam is directed through the area of interest at 180 to 360° around the patient’s head in a single sweep within 10 to 40 seconds.¹³

Once the image is digitalized, it can be manipulated and displayed in three orthogonal planes [axial, sagittal, and coronal (Fig. 2C)] simultaneously. So to procure in detail information regarding the volumetric filling, CBCT was used as the diagnostic tool in the study.

Using CBCT, evaluation of the canal morphology and adaptation of the obturating material was done in permanent teeth.^14–16 Studies were done to evaluate the cleaning efficacy of hand and conventional NiTi rotary files^10,17,18 in primary teeth. Volumetric evaluation of various obturation techniques was done in primary teeth.^12,13,19 However, in the literature, there are no studies that have evaluated the cleaning efficacy and volumetric filling of root canals using different pedodontic rotary files in primary teeth.

According to the results obtained in the present study, the Kedo SG Blue group showed a maximum number of optimally-filled teeth with minimal voids. When compared with the distal canals, more mesial canals were optimally filled.

Considerable research was done by Jeevanandan and Govindaraju,²⁰ Govindaraju et al.,²¹ and Panchal et al.²² proving Kedo S rotary files’ efficacy on comparison with hand K-files. The attributing factors for the better obturation quality with Kedo S rotary files can be anticipated to the NiTi nature, shorter length of the files (17 mm), varying tip diameter, and variably variable (VV) taper. With this taper, higher cervical enlargement and restricted apical preparation are seen which facilitates optimal obturation. The superior performance of the Kedo SG Blue files is due to the additional titanium coat and higher flexibility to negotiate the narrow canals, which lead to a better flow of the obturating material. Similar results were obtained by Priyadarshini et al.²³ where clinical comparison was done using hand K-files, Kedo S files, Kedo SH-files, and Kedo SG Blue files. They found Kedo SG Blue files to be better than others. Its unique features prevent inadvertent file separation thereby increasing its efficacy over its predecessor Kedo S files.²³

When the Kedo SG Blue group was compared with the Pro AF Baby gold group, no much difference was found. Pro AF Baby gold files are heat-treated NiTi controlled memory (CM) wire flexible files. They are 17 mm in length with a constant taper of 4% (B1, B2, B4, B5 files) and 6% (B3 file). The deformities while preparing the root canals and file separation are reduced due to their CM wire technology. The files have a sharp edge with super-high cutting efficiency, a well-polished surface by advanced potent polishing technology, and a non-cutting tip with an accurate tip grinding.²⁴ Because of these features, Pro AF baby gold files showed efficiency comparable to Kedo SG blue files.

A striking difference in the obturation quality was noticed between the Kedo SG Blue group and the Pedo Flex group. Neo Endo flex files are one of the recently introduced rotary endodontic files. These files were manufactured to overcome the limitations of conventional NiTi files. Modifying the length of Neo Endo flex files to 16 mm with a constant taper of 4%, Pedo Flex files were introduced to be conveniently used in pediatric patients. These files are heat-treated exclusively to give them superior flexibility characteristics. It has a triangular cross-section with sharp cutting edges. It has a non-cutting safety tip, which prevents accidental apical transportation. Generally, due to the heat treatment, an alloy may be prone to plastic deformation which reduces its cutting ability and disruption of the cutting edges during its use. Proprietary heat treatment reduces the restoring forces, thus centering the instrument within the canal. This might have led to the incomplete removal of the dentin, compromising the obturation quality.²⁵

The outcome of an endodontically treated primary tooth is affected not only with the chemomechanical preparation but also the obturating material used and the technique of obturation. The ideal root canal filling technique must provide optimal filling of the canal with minimal or no voids.²⁶ In the present study, the void was a constant finding in all the groups but the Kedo SG group showed minimal voids. Factors that influence the presence or absence of voids include not only the instrumentation technique but also the type, viscosity, and consistency of the paste, obturation technique, and operator skills. Materials that have been reported to be successful in obturating the primary root canals are ZOE, iodoform, calcium hydroxide, endoflas, and vitapex. Zinc oxide eugenol paste was the material of choice as it is one of the most conventional, cost-effective, and widely used materials for primary teeth pulpectomy. As the reamer technique of obturation was used, the irregularities in the root canal configuration could not be obliterated completely, which entrapped tiny air bubbles creating voids. Root canal obturation with voids may provide potential pathways for leakage which increases the risk of endodontic failure.²⁷

Clinically, Kedo SG blue files were very feasible as they negotiated the canals easily on gentle insertion through the canal orifice. Only a single file was used per canal according to the manufacturer’s instructions. Though Pro AF Baby gold files were convenient enough, two files per canal should be used depending upon the working width. As per the protocol of Pedo Flex, three files should be used sequentially. The sequential instrumentation indirectly determines the working time, ability, and quality of obturation. As it is an in vitro study with a small sample size, it might limit the acceptance of the results.

CONCLUSION

Within the study limitations, the Kedo SG Blue file system proved its efficacy along with Pro AF Baby gold files in achieving an ideal root canal filling. Cone-beam computed tomography serves perfectly in the three-dimensional evaluation of the quality of root canal filling. Clinically, pediatric rotary instrumentation will provide a comfortable and faster endodontic treatment in children. As new rotary endodontic systems are continually updated, further clinical studies should be planned to evaluate their efficacy.

CLINICAL SIGNIFICANCE

The present study will guide the pedodontists regarding the efficacy of pediatric rotary file systems and their usage protocols.

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