Year : 2011 | Volume
: 29 | Issue : 1 | Page : 2--6
K-file vs ProFiles in cleaning capacity and instrumentation time in primary molar root canals: An in vitro study
N Madan, A Rathnam, AL Shigli, KR Indushekar
Department of Pedodontics and Preventive Dentistry, KLES's Institute of Dental Sciences, Belgaum - 590 010, Karnataka, India
Shree Bankey Bihari institute of Dental Sciences, Masuri, Uttar Pradesh
Objectives: This study compares the efficiency of manual K-files and rotary ProFiles in cleaning capacity and instrumentation time in primary molar root canals. Materials and Methods: Seventy-five maxillary and mandibular primary molar root canals were instrumented with ProFiles and K-files in the step-back manner from size #10 to #40. The teeth were decalcified, dehydrated and cleared, and analyzed for the presence of dye remaining on the root canal walls, which served as an evidence of cleaning capacity of both the techniques. Results: The results showed a significant difference in the cleaning capacity of the root canals with ProFiles and K-files, in apical and coronal thirds of the root canal. ProFiles have been found to be more efficient in cleaning the coronal thirds and K-files in cleaning apical thirds of the root canals. Both the techniques were almost equally effective in cleaning the middle thirds of the canals. The time taken during the cleaning of the root canals appeared to be statistically shorter with K-files than profiles.
|How to cite this article:|
Madan N, Rathnam A, Shigli A L, Indushekar K R. K-file vs ProFiles in cleaning capacity and instrumentation time in primary molar root canals: An in vitro study.J Indian Soc Pedod Prev Dent 2011;29:2-6
|How to cite this URL:|
Madan N, Rathnam A, Shigli A L, Indushekar K R. K-file vs ProFiles in cleaning capacity and instrumentation time in primary molar root canals: An in vitro study. J Indian Soc Pedod Prev Dent [serial online] 2011 [cited 2020 Apr 5 ];29:2-6
Available from: http://www.jisppd.com/text.asp?2011/29/1/2/79907
The specialty of endodontics has evolved and got revolutionized over the years. The modern endodontic specialty practice has little resemblance to the traditional endodontic practice. In pediatric dentistry, pulpectomy is the preferred treatment for infected pulp tissue. Significant alterations and complexities in root canal morphology of primary teeth demands improvement in the instruments to prevent undesirable complications, like ledges, strip perforations, zips, and transportation.
Rotary instruments were introduced to pediatric endodontics by Barr et al, 2000.  Initially, stainless steel was used for the fabrication of rotary instruments.  NiTi was developed 40 years ago in the Naval Ordinance Laboratory (NOL) in Silver Springs, Maryland  . Therefore, the acronym NiTiNOL is used worldwide for this special type of alloy.Stainless steel was replaced with nickel titanium due to better flexibility and fracture resistance.
There are two types of NiTi systems: The LightSpeed (LightSpeed Technology Inc., San Antonio, Texas) and the non-LightSpeed, e.g., ProFile (Dentsply, Tulsa, Oklahoma).  The profiles have been found to have two important characteristics of having a non-cutting tip and radial land. The former makes it a less-aggressive instrument to be used in primary teeth root canals and the latter helps to remove the debris coronally from the root canal and also keeps the file centered to prevent transportation of apical foramen.  For cleaning and shaping of root canals in primary teeth, ProFile 0.04 instruments  have been recommended to be used at slow speed of 150 to 300 rpm. 
This study has been undertaken with the sole purpose of evaluating the cleaning efficiency and time taken by rotary NiTi files (ProFiles, Maillefer/Dentsply) and manually used K-files (Kendo, Europe).
Materials and Methods
The present study was conducted in the Department of Pedodontics and Preventive Dentistry, KLES's Institute of Dental Sciences, Belgaum-590010, with the objective to assess the difference in the cleaning efficiency and instrumentation time of rotary Profiles (Maillefer/Dentsply) and manual K-files (Kendo, Europe) in the cleaning of root canals in primary molars.
The study was conducted on seventy-five primary molar root canals with at least two-third roots remaining. Examples of such teeth are as follows:
Infected primary molars with considerable bone loss.
Over-retained primary molars with altered root resorption pattern.
Primary molars with one root resorbed considerably more than the other, due to the altered path of eruption of its successor.
Infected primary molars with chronic recurrent infection.
Collection of teeth and their storage
Freshly extracted teeth were washed under running water and all the soft tissue was removed from their crown and root surface. They were then stored in formalin in different containers.
Selection of the root canal
The distribution of root canals is done with the purpose of maintaining standardization of using both techniques of root canal cleaning in homologous root canals and to obtain simplicity while analyzing the root canals for the presence of dye after clearing of the teeth.
Maxillary teeth (15) - Mandibular teeth (15)
Mesiobuccal RC (15) - Mesiobuccal RC (15)
Distobuccal RC (15) - Mesiolingual RC (15)
Palatal RC (7) - Distal RC (8)
Method of root canal preparation
Coronal access cavity was prepared with a large round bur (Diaburs, Prime Dental Products, Mumbai, India).The pulp chamber and root canals were irrigated profusely with 1.0 % sodium hypochlorite to remove the debris.#10-sized K-file was introduced into each root canal to determine the patency of the root canal.Working length determination: As the #10 file was introduced into the root canal, the tip of the file was visualized using magnifying glass. The final working length was established 1-mm short of this recorded length.Then, the teeth were mounted in the dental plaster, to carry on with an unbiased procedure for cleaning the root canals.India ink dye was then injected in each root canal. The ink was reapplied at least three to four times into the root canals.
Division of root canals for instrumentation
Profiles (30 RC)
Maxillary teeth (15 RC)Mesiobuccal (8 RC)Distobuccal (7 RC)Mandibular teeth (15 RC)Mesiobuccal (8 RC)Mesiolingual (7 RC)K Files (30 RC)
Maxillary teeth (15 RC)Mesiobuccal (7 RC)Distobuccal (8 RC)Mandibular teeth (15 RC)Mesiobuccal (7 RC)Mesiolingual (8 RC)The instrumentation with manual K-files (Kendo, Europe) was done with #10 file up to #30 file and then stepped-back to #35 and #40 file.The instrumentation rotary Profile 0.04 (Dentsply/Maillefer, Switzerland) was done with #10 file up to #30 file and then stepped-back to #40 file. The files were activated by gear-reduction hand piece (WandH, Austria) that rotates the file in the range of 150 to 300 rpm. The ProFiles were used in light pecking motion to clean the root canals.After each instrument change, each root canal was irrigated with 1.0% sodium hypochlorite solution in 5 ml quantity. Patency of each root canal was checked with #10 K-file.The instrumentation time in each root canal was measured by a chronometer during both the techniques.The instrumented teeth were then taken out of the mounting and coronal pulp chamber and apical ends were sealed with a sticking wax.
Method of decalcification of teeth
The teeth were decalcified in 10% nitric acid solution. The teeth were observed timely and the acid was renewed every 24 hours to maintain its efficiency in decalcifying the teeth. Freshly prepared acid was always used for the renewal.
The teeth were kept in acid till they were completely decalcified.
Method of dehydration of teeth
After decalcification, teeth were washed under running water for eight hours, till the acid completely gets washed away from the tooth surface.Then, the teeth were kept in freshly prepared 70% alcohol for sixteen hours and the solution was changed every eight hourly.Then, the teeth were hanged in 90% alcohol for 3 hours and the solution was changed after every one hour.After that, the teeth were kept in absolute alcohol for 3 hours and the solution was changed after every one hour.
Method of clearing of teeth
After decalcification and dehydration, the teeth were kept in methyl salicylate, till they get transparent in appearance.It took nearly 2 to 3 hours for teeth to get completely cleared.
The teeth then onward remained in the methyl salicylate solution at all times.
Analysis of the root canals
After the teeth appear clear, they were observed with a simple magnifying glass and each root canal was inspected carefully for the removal of India ink from the cervical, middle, and apical thirds. The removal of the dye was analyzed from all the walls of the root canal.
Scores given to each root canal are as follows:
Score 0: Total cleaning (No ink remaining in any part of root canal)
Score 1: Almost complete ink removal (Traces of ink found in some areas)
Score 2: Partial ink removal (Ink found on some walls in some areas)
Score 3: No ink removal (Appreciable amount of ink present)
All statistical analysis was done using SPSS (Statistical Package for Social Science).The scores obtained were analyzed with Mann-Whitney U test.The significance of values in time taken for instrumentation with both techniques was done with Student's t test.
In the coronal one-third of the root canal, ProFiles performed better than K-files, but the difference in their cleaning efficiency was not found to be statistically significant (P = 0.56). In the middle one-third of the root canals, both the cleaning techniques performed equally good and no statistical significance could be found (P = 0.19). In the apical one-third areas, K-files cleaned better than the ProFiles and the difference found was highly significant (P<0.001).
The ProFiles show significantly (P<0.05) better cleaning efficiency than K-files in the coronal thirds of the maxillary root canals. In the middle thirds, both K-files and ProFiles cleaned effectively and the difference in scores obtained did not show any statistical significance. In the apical one-third, K-files showed lesser scores, revealing better cleaning than ProFiles and the difference in their cleaning efficiency was found to be highly significant (P<0.001).
In maxillary teeth, ProFiles took on an average 4.97 (SD = 0.27) minutes and K-files took 3.61 (SD = 0.41) minutes. K-files were found to take significantly (P<0.001) lesser time than ProFiles. In the mandibular root canals, ProFiles took 4.30 (SD = 0.29) minutes and K-files took 3.52 minutes. The difference found is highly significant (P<0.001).
This study aims to revolutionize the field of pediatric endodontics by evaluating the effectiveness of use of rotary instruments in the cleaning of the root canals of the primary molars.There is abundant literature available on the use of NiTi files for endodontics procedures. Glossen et al  have provided a comparison of root canal preparations using NiTi and K-flex files. Zmener et al  has described the effectiveness of NiTi files in the negotiation of curved root canals.
Short et al  have compared the canal centering ability of four techniques and found profiles to be superior in this regard. Torsional properties of stainless steel and NiTi files have been compared by Wolcott et al  who stated that NiTi files are an improvement over stainless steel.
In the mandibular teeth, only the mesial root canals were prepared alternatively with Profiles and K-files. This was done to maintain the homogeneity of preparation done with both the techniques, as the distal roots in primary mandibular molars show maximum variation in the occurrence of single and two canals. Also, mandibular primary molars show maximum angulation in the mesial root (34.4 - 36.2 degrees). 
In the maxillary teeth, only mesiobuccal and distobuccal roots were instrumented alternatively with both the techniques. These two roots have been found to show similar curvatures of their root canals, whereas the diameter and angulation both are variable for the palatal roots.  The mesiobuccal roots with two canals in maxillary primary molars were excluded from the study.
The control groups in the study were prepared in order to confirm the proper penetration of India ink into the root canals of primary teeth, because of their hour glass shape. All the uninstrumented root canals, i.e., mandibular distal root canals and maxillary palatal root canals were treated as "controls."
The ink injection method used in the study followed the methodology given by Silva et al.  The clearing technique used in the study to make the teeth transparent is in accordance with that described by Silva et al. 
For the preparation of root canals using rotary technique, Profiles .04 taper were used. The literature suggests that rotary files with .04 taper are least aggressive to be used in primary root canals and they best recommended to be used by novice clinicians.  It is been found in various studies that with the greater taper of the instrument, higher range of torque are generated that can result in the instrument failure. 
The literature suggests the use of Profiles with "crown down" approach,  but Barr et al suggested that it is not necessary to use a "crown down" instrumentation technique in primary teeth as the dentin cuts more easily than in permanent teeth.  This was also been proved by the study done by Silva et al.,  in which step-back technique was used for the use of Profiles in primary teeth root canals.
It is strongly recommended to do preflaring with Gates Glidden drills before instrumentation in permanent teeth root canals by step-back technique with K-files and rotary files. But in primary teeth, Cohen and Burns  suggested that Gates Glidden drills should not be used as it may increase the chances of perforation.
Recent recommended technique for use of rotary NiTi instruments employs the use of "Hybrid Instrumentation technique." It employs the combination of tapered instruments (e.g., ProFiles) for crown-down technique and apical enlargement with flexible instruments (e.g., Flexo files, Lightspeed).  This combination is most ideal to instrument root canals in permanent teeth. No literature is available for its use in primary teeth.
The results obtained in the study in evaluating the cleaning efficiency of ProFiles and K-files suggest that none of the techniques completely clean the root canals, but on an average, better cleaning is observed in the middle third of the canal with both techniques. Similar results were obtained in a study done by Schδfer and Zapke  and Silva et al.,  though the results were not statistically significant.
In this study, the results showed increased instrumentation time taken with the use of ProFiles (4.97 minutes in maxillary root canals and 4.30 minutes in mandibular root canals), whereas it took lesser time with K-files (3.61 minutes in maxillary root canals and 3.52 minutes in mandibular root canals). This was in contrast with the results obtained by different authors on use of ProFiles in cleaning of primary root canals. , The difference in instrumentation time with ProFiles and K-files can be considered as a matter of operator's experience.
The study was worth doing in the extracted primary molars, as they provide more reliability of results compared with artificial resin canals. Through this study, it could be evaluated that ProFiles 0.04 taper show minimal instrumentation failure in the primary teeth root canals, if proper precautions are taken.
The authors thank all their postgraduate colleagues, teaching staff, especially Dr. Dayanand Shirol and Dr. Shivyogi Hugar and non-teaching staff of department of Pediatric dentistry.
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