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Assessing quality of obturation using kedo-S file, hand K file and reciprocating file- A comparative study

 Lakshimi Lakshmanan,  Ganesh jeevanandan


Aim: This article was to compare and evaluate the instrumentation time and quality of obturation between paediatric rotary file (Kedo-S), hand-K file and reciprocating files techniques in primary molars.

Methods: A double blinded randomised control trial was performed that included mandibular primary molars in children of age 4–8 years. Forty five primary mandibular molars were randomly divided into two groups: 15 were instrumented with paediatric rotary files Kedo-S and 15 with hand K-files and 15 with reciprocating files. The quality of obturation was recorded as optimal, under filled or over filled using immediate post-operative radiographs. The quality of obturation were analysed using independent t-test and Chi-square test.

Results: There was a significant improvement in the quality of obturation (p < 0.05) with paediatric rotary files (Kedo-S).

Conclusion: Clinical use of paediatric rotary files Kedo-S was effective during root canal preparation of primary teeth with better quality of obturation.


Keyword:  Kedo-S files · K-files · reciprocating files. Primary molars · Pulpectomy


One of the most important concerns in pediatric dentistry is the loss of necrotic primary molars leading to space loss. Although the morphology of root canals in primary teeth renders endodontic treatment difficult (Schafer et al., 2006a, Schafer et al., 2006b), pulpectomies of primary teeth with severe pulpal involvement should be considered as the treatment of choice.

Root canal preparation is performed with reamers, files, burs, sonic instruments, mechanical apparatuses, and with nickel–titanium (Ni–Ti) rotary file systems. Since most hand preparation techniques are time consuming and can lead to iatrogenic errors (i.e., ledging, zipping canal transportation, and apical blockage), much attention has been directed toward root canal preparation technique with Ni–Ti rotary instruments (Walton and Torabinejad, 2002). Numerous studies have reported that they could efficiently create smooth, predetermined funnel-form shapes with minimal risk of ledging and transportation (Dantas, 1997, Esposito and Cunningham, 1995, Thompson and Dummer, 1997). The design and high flexibility of Ni–Ti files allow instruments to closely follow the original root canal path, especially in curved canals (Esposito and Cunningham, 1995, Gluskin et al., 2001, Hidsmann et al., 2003, Sonntag et al., 2003).

The standardised method of cleaning and shaping of the canals in primary teeth as described in the literature is using hand files. Hand instrumentation, despite being the most acceptable and widely used method for canal debridement and shaping, it is time consuming and can result in iatrogenic errors (Silva et al. 2004). Nickel–titanium (Ni–Ti) rotary instrumentation maintains the original canal space during root canal preparation and widely used in permanent teeth. Bio-mechanical preparation with rotary files in primary teeth gained popularity when the first case was reported by Barr et al. (2000) using Profile 0.04 taper rotary instruments. Since then the practice of using various rotary Ni–Ti systems for instrumentation of the primary root canal is emerging among paediatric dentists. Studies have been conducted to evaluate the efficiency of using rotary instrumentation for pulpectomy in primary teeth (Selvakumar et al. 2016; Subramaniam et al. 2016).

A survey conducted among Indian dentists showed that about 50% of them used rotary systems for pulpectomy in children and 27% of the practitioners felt both length and taper of the existing rotary files caused potential difficulties in using them in children. Also, 66% of them felt that an exclusive paediatric rotary file should be invented for the ease of using it in children (Govindaraju et al. 2017). Kuo et al. (2006) also reported that an exclusive paediatric rotary file with modified length, taper and tip size would be more effective for performing pulpectomy in primary teeth.

An evolution in the field of endodontics in paediatric dentistry is the introduction of an exclusive paediatric rotary system—Kedo-S file system (Reeganz Dental Care Pvt. Ltd. India). Kedo-S rotary files is a single file system consisting of D1, E1 and U1 files. The total length of these files is 16 mm and the working area (cutting flutes) 12 mm in length. The uniqueness of these files is the presence of variable taper (4–8%) with varying tip diameter D1-0.25, E1-0.30 and U1-0.40 corresponding to its use in primary teeth (Jeevanandan 2017). D1 Kedo-S file is designed to prepare the narrower canals of the primary teeth namely the mesiobuccal and mesiolingual canals and E1 Kedo-S file is to prepare the wider canals namely the distal and palatal canals of the primary molar teeth. The U1 Kedo-S file is used to prepare the upper and lower anterior primary teeth. Kedo-S rotary files are recommended to be used with an endodontic motor in clockwise rotation at 300 (Revolutions Per Minute) RPM and 2.2 N cm torque. Kedo-S rotary files are to be used only in well lubricated and irrigated canals of primary teeth. In order to avoid instrument deformation and separation, Kedo-S rotary files are recommended to be used till the entire working length 1–2 times and for not more than 3–4 s in primary teeth. There are no studies in the literature evaluating the efficiency of the use of Kedo-S rotary file in primary teeth. The aim of the present study, therefore, was to compare the quality of obturation and instrumentation time between manual instrumentation and Kedo-S paediatric rotary system in primary molars.

Materials and methods

The current study was conducted in the Department of Paedodontics and Preventive Dentistry. Ethical approval was obtained from the institutional review board (STP/SDMD- S2015PED42D) in accordance to the ethical standards laid down in the 1964 declaration of Helsinki and its later amendments. The consent was obtained from the parents or the care-takers of the children who participated in the study prior to the start of the clinical procedure. CONSORT guidelines (Altman et al. 2001) for planning and reporting clinical trials in paediatric endodontics was followed during the different stages of the study.

Sample size estimation and study participant's selection

A sample of 45 primary mandibular second molars of children between 4 and 8 years of age indicated for pulpectomy participated in this double-blinded randomised control trial. The sample size was calculated considering the previously published studies with 95% power in detecting the true stastical significance among the two groups. Inclusion criteria: 1)Treatment is limited to patients in good health; 2) vital and non-vital pulp without a sinus tract; 3) Presence of enough coronal tooth and root structure; 4) No prior pulpectomy treatment on the involved tooth, 5) absence of perforation in the internal and/or external furcation area. A computer-generated randomisation method was used to allocate the selected tooth into two groups. Group A (15 teeth) the root canals were instrumented with Kedo-S rotary files and in Group B (15 teeth) the canals were instrumented with conventional hand K-files and Group C (15 teeth) the root canals were instrumented with reciprocating files.

Clinical procedure

All the procedures were performed by a single paediatric dentist having adequate knowledge with rotary and hand instrumentation techniques. Local analgesia (LOX* 2% adrenaline, Neon Laboratories limited, India) was administered for the tooth indicated for pulpectomy and rubber dam (GDC Marketing, India) isolation was applied. No.330 pear-shaped bur (Mani, Inc, Tochigi, Japan) was used for endodontic access opening and removal of decayed tissue. A spoon excavator (Hu-Friedy Mfg. Co. LLC) was used for removal of the coronal pulp followed by the use of a DG 16 (Hu-Friedy Mfg. Co. LLC) instrument to locate the canals. No.10 size K-File (Mani, Inc, Tochigi, Japan) was then used to access the root canal patency. Working length (WL) was determined using radiographs. No 15 size K-file was used to record the working length of each canal with one mm shorter than the radiographic apex.

Group A (N = 15): The root canals were instrumented with Kedo-S paediatric rotary files (Reeganz Dental Care Pvt. Ltd. India) as per manufacturer's recommendation. D1 rotary files were used for canal preparation of the mesiobuccal and mesiolingual canals and E1 rotary files were used for distal canal preparation using a lateral brushing motion. The rotary files were used with an X-Smart endodontic motor (Dentsply Maillefer, OK, USA) at 300 rpm and 2.2 N torque. Each file was used for up to five teeth as per the manufacturer's recommendation and to maintain uniformity during canal preparation.

Group B (N = 15): the root canals were instrumented from no 15 size—till 35 size K-files (Mani, Inc, Tochigi, Japan). The mesial canals were instrumented till 30 size K-files and the distal canal(s) were instrumented till 35 size K-files using a quarter-turn-pull technique. Each K-file was used up to five teeth in order to maintain uniformity during canal preparation.

Group C (N=15): the root canals were instrumented using reciprocating K files.

Root canals were irrigated with 1% sodium hypochlorite after use of each file followed by normal saline. EDTA gel 17% (RC help, Prime dental products, Pvt. Ltd. India) was used as a lubricating paste during the canal preparation. The canals were dried using sterile paper points and the root canal space was obturated using Metapex (Meta Biomed Co. Ltd. Chungbuk, Korea) using pressure syringe technique. The access cavity space was restored using type II glass ionomer cement (GC, India). The coronal seal of the tooth was achieved using a preformed metallic crown (3M ESPE) luted with type I glass ionomer cement (GC India).

Assessment of quality of obturation

Two examiners were allotted to evaluate the quality of obturation. Kappa test was performed to access the consistency and reliability of the examiners which resulted in a score of 0.90 (excellent). The Immediate post-operative radiographs were taken and the quality of obturation was assessed using the criteria laid down by Coll and Sadrian (1996) underfilled, optimal, or overfilled by two paediatric dentists who were blinded to the groups.

Statistical analysis

The statistical analysis was performed using SPSS software version 17.0. Chi square test was used for assessment of the obturation quality in the primary molars. The significance level was set at 5% for the present study.


A total of 20 girls and 25 boys in each group with a mean age of 5.80 + 1.3 years participated in the study. The mean instrumentation time on using Kedo-S paediatric rotary files group (78.53 + 9.6 s) was significantly less than hand K-files group (95.46 + 12.7 s) with a statistically significant difference (P < 0.05, Independent T-test). For the Kedo-S paediatric rotary file group, 2 of 15 teeth were underfilled, 9 of 15 were optimally filled and 4 of 15 were overfilled. For hand K-file group,  4 of 15 teeth were underfilled,  6 were optimally filled and 5 were overfilled. For reciprocating file group, 3 of 15 teeth were underfilled, 7 were optimally filled and 5 were overfilled. There was a statistically significant difference (P < 0.05, Chi square test).


The present study compared the quality of obturation of manual and one pediatric  rotary file and one reciprocating file in preparation of primary mandibular molars. The objective of treating an infected primary tooth in children is to retain it in the oral cavity until its physiological exfoliation to guide the erupting permanent teeth. Retention of the primary teeth can be made possible by performing root canal procedure. Pulpectomy of the primary teeth involves removal of the infected tissue from the root canal and filling it with a resorbable material.

A survey conducted on the use of rotary files by Indian dentist revealed 34% of the practitioners used ProTaper system for pulpectomy in primary teeth (Govindaraju et al. 2017). The morphology of the primary teeth differs greatly from that of the permanent teeth as the roots of the primary teeth are short, thin, curved and have softer and less dense root dentine with undetectable root resorp- tions (Finn 1973). In addition, the morphology of the root canals is ribbon-shaped which necessitates the need for an exclusive rotary file for cleaning and shaping of the primary root canals (Kuo et al. 2006). Also, the use of existing rotary systems in primary teeth has resulted in a higher fracture rate of the instruments (Nagaratna et al. 2006). This was supported by Govindaraju et al. (2017), who stated that about 26% of the practitioners experienced instrument breakage in the primary root canals.

Alteration in the length and taper of the existing rotary files was needed to facilitate its use in primary teeth (Kuo et al. 2006; Govindaraju et al. 2017). With all these facts considered, an exclusive paediatric rotary file, Kedo-S file system (Reeganz Dental Care Pvt. Ltd. India) was introduced (Jeevanandan 2017). It consists of three Ni–Ti files (D1, E1, U1) with an altered working length of 12 mm to expedite its use only in primary teeth. Another added feature of these files is the presence of variably variable taper. D1 and E1 files have been designed for instrumentation of molars and they have a tip diameter of 0.25 and 0.30 mm respectively. D1 file has 4, 5, 6, 8% tapers in different lengths enabling the file to be used only in narrower canals in primary molars namely mesiobuccal and mesiolingual. E1 file has 4, 6, 8% tapers in different length corresponding to be used in wider canals in primary molars namely distal canal(s).

In the present study, D1 files were used for the canal preparation of mesiolingual and mesiobuccal canals and E1 files were used for the distal canals as recommended by Jeevanandan (2017) and were compared with the standard method of preparing the canals with K-files (15–35) with regard to  quality of obturation. During root canal instrumentation, there was no evidence of instrument deformation or breakage in all the 3 groups.  A report was stated by Crespo et al. (2008) that the use of rotary files in primary teeth was efficient in root canal preparation and the time taken compared to manual instrumentation.

In the present study, A superior obturation quality was observed by using Kedo-S rotary files in primary molars, which was statistically significant (P < 0.05). Ni–Ti rotary instruments have an ability to prepare the curved canal(s) due to its shape memory capacity with minimal canal transportation. Ni–Ti instruments compared to stainless steel files had better flexibility with superior resistance to torsional fracture. The flexibility of the Ni–Ti rotary files enables the dentist to use the files with greater confidence in a curved primary canal(s). In this study, Kedo-S paediatric rotary files were used to evaluate if the newly designed exclusive rotary files for primary teeth with a shorter length and modified taper can be an alternative to the existing different adult rotary files used in primary teeth.Use of two-dimensional radiographic assessment method for determination of the quality of obturation can be a potential limitation of this clinical investigation. Further studies evaluating the patient's acceptance of exclusive Kedo-S rotary files and long-term clinical and radiographic success rates should be performed to arrive at precise conclusions.


Kedo-S exclusive paediatric rotary file system has shown reduced instrumentation time and superior obturation quality in primary molars. This system can be an effective alternative in performing root canal treatment in primary molars with great ease, thereby reducing the fatigue of dentists as well as the children.


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