Journal of Indian Society of Pedodontics and Preventive Dentistry
Journal of Indian Society of Pedodontics and Preventive Dentistry
                                                   Official journal of the Indian Society of Pedodontics and Preventive Dentistry                           
Year : 2006  |  Volume : 24  |  Issue : 4  |  Page : 186--191

In vitro comparison of NiTi rotary instruments and stainless steel hand instruments in root canal preparations of primary and permanent molar


PJ Nagaratna, ND Shashikiran, VV Subbareddy 
 Department of Pedodontics and Preventive Dentistry, College of Dental Sciences, Davangere, India

Correspondence Address:
N D Shashikiran
Department of Pedodontics and Preventive Dentistry, College of Dental Sciences, Davangere
India

Abstract

This study is an attempt to compare the NiTi rotary and K-files hand instrumentation on root canal preparation of primary and permanent molars for their efficiency in preparation time, instrument failure and shaping the canals. About 20 primary mandibular second molar (I) and 20 permanent mandibular first molar (II) were selected. Each was further divided into 10 for K-files (a) and 10 for NiTi (b) groups, respectively. Results showed that preparation time Ib<Ia and IIab<IIa, which was highly significant. In instrument failure, Ia (40%), IIa (30%) showed more deformation but not fracture and Ib (10%), IIb (20%) showed fracture, but not deformation. Profiles showed good canal taper and smoothness compared to the K-files. To conclude profile 0.04 taper 29 series, prepared canal rapidly than conventional K-file with good taper, smoothness though the flow was not satisfactory. Instrument failure with K-files was less. In primary teeth preparation time, instrument failure with profile was less compared to the permanent. To conclude itSQs encouraging to use the profiles in primary teeth.



How to cite this article:
Nagaratna P J, Shashikiran N D, Subbareddy V V. In vitro comparison of NiTi rotary instruments and stainless steel hand instruments in root canal preparations of primary and permanent molar.J Indian Soc Pedod Prev Dent 2006;24:186-191


How to cite this URL:
Nagaratna P J, Shashikiran N D, Subbareddy V V. In vitro comparison of NiTi rotary instruments and stainless steel hand instruments in root canal preparations of primary and permanent molar. J Indian Soc Pedod Prev Dent [serial online] 2006 [cited 2020 Aug 5 ];24:186-191
Available from: http://www.jisppd.com/text.asp?2006/24/4/186/28075


Full Text

 Introduction



Until 1960, root canal instruments were produced of carbon steel, which is now replaced by stainless steel alloys. Manufactures have developed new stainless steel alloys characterized by higher flexibility in bending compared with conventional stainless steel instruments to avoid undesirable shaping effects and removing excessive amount of tooth materials from inner aspect of curved canals. Up to now, even flexible stainless steel instruments with noncutting tips have not produced entirely enlargements of severely curved canals. In order to overcome this problem, modifications of stainless steel instruments, characterized by lower (E) module have been developed and which were highly flexible instruments made of new alloy nickel-titanium (NiTi). NiTi was developed by W. F. Buehler in early 1960, which is non-magnetic, salt resisting and water-proof alloy. This new combination alloy had unique properties of shape memory and super elasticity, which makes engine-driven instruments feasible. With this new technique, there was significant reduction in preparation time and better-cleaned and shaped root canals.

The study aims to compare the engine-driven method with Profile 0.04 taper 29 series technique and conventional manual methods with stainless steel K-files in primary and permanent teeth for their efficiency in

Shaping the canalsTime consumedInstrument failure.

 Materials and Methods



The present study was conducted in the Department of Pedodontics and Preventive Dentistry. Materials used were K-files (15-40) (Mani), Profile 0.04 taper 29 series NiTi rotary files (size2-7) (Dentsply Tulsa Dental), Stopwatch, Reduction gear Handpiece, Rubber based putty impression material (3M Express STD), Light bodied hydrophilic vinyl polysilioxane impression material (Reprosil, Dentsply caulk), Stereomicroscope.

Sample selection

40 freshly extracted molar teeth were collected. Among which were 20 primary mandibular second molar teeth of minimum 8 mm root length (Group I) and 20 were permanent mandibular first molar with complete root formation (Group II). Group I and II were further divided into subgroups into 10 each, respectively. 10 teeth of each group were prepared by Conventional methods with Stainless steel K files (a) and rotary method with NiTi files (b), respectively.

Sample preparations

Access opening was done for all samples. Canal length was determined by placing no: 10 files into each until the file was just visible at apical foramen and then canal shaping and cleaning was done.In conventional canal stainless steel K-files using quarter turn-pull technique. Instrumentation started with no 15 file then enlarged to no 25. In NiTi rotary methods, teeth were instrumented with profile 0.04 taper 29 series rotary instruments starting from size 2 to 7 in reduction gear hand piece. Files were advanced slowly towards the apex, which was withdrawn as soon as working length was reached. If the instruments failed before that time, information was recorded and new file was substituted. Time taken for preparation of the canal was recorded. Copious irrigation with saline was done after each filing. Approximate 10 ml saline was used per tooth. Canal preparation was done by step down technique of instruments.

Intracanal impressions

Internal 3D shapes of the canals was determined by intracanal impressions made using light bodied and heavy bodied vinyl poly silioxane impression materials. Light bodied materials were filled over the floor of the pulp chamber over which the putty material kneaded with hand to facilitate the product of light bodied material into the root canal. The heavy bodied also acts as support for the coronal part of the impression and for easy removal. The impression was viewed within 24 h under stereomicroscope to assess the following.

Flow

Good flow, when continuous flow of the materials from the orifice to apical stop. Poor flow, when abrupt change in direction and flow of the material is half way.

Taper

Good taper, when the canal has conical shape throughout the length. Poor taper, when the canal has an hourglass/cylindrical shape.

Smoothness of the walls

Good, if roughness/ledge formation is absent, poor, roughness/ledge formation is present data was recorded directly on coding sheets and analyzed statistically using, unpaired t -test and Fischer's exact test.

 Results



Comparison between the methods in primary teeth in terms of preparation time showed mean of 13.392.09 for conventional method and 8.511.45 for NiTi rotary method with P instrument failure in primary teeth 4(40%) teeth showed deformation for conventional method and 1(10%) teeth showed fractured instrument for NiTi rotary method. For deformation P =0.04 Sig (significant) and fractured instruments P =0.05 NS (not significant) [Table 1]. In terms of canal shaping in primary teeth, the flow showed in mesiobuccal canal, mesiolingual canal and distal canal was 6 (60%), 6 (60%) and 3 (30%) for the conventional method and 9 (90%), 9 (90%), 8 (80%) for NiTi method with P =0.14 NS, 0.14 NS and 0.03 Sig, respectively. Taper showed in mesiobuccal, mesiolingual and distal canal was 4 (40%), 3 (30%) and 2 (20%) for conventional and 8 (80%), 7 (70%) and 8 (80%) for NiTi method with P =0.08 NS, 0.07 NS and 0.01 Sig, respectively. Smoothness in mesiobuccal, mesiolingual and distal canal was 5 (50%), for conventional was 10 (100%) for NiTi with P =0.02 Sig [Table 1].

Comparison between the methods in permanent teeth in terms of preparation time showed mean of 15.992.99 for conventional method and 9.911.47 for rotary method with P instrument failure in permanent teeth 3(30%) showed deformation for the conventional method and 2(20%) teeth showed fractured instruments for NiTi rotary method. For deformation P =0.11 NS and fractured instruments P =0.24 NS [Table 2]. In terms of canal shaping , the flow showed in mesiobuccal, mesiolingual and distal canal was 9 (90%), 10 (100%) and 10 (100%) for conventional and 9 (90%), 9 (90%) and 9 (90%) for NiTi method with P =0.53 NS, 0.50 NS and 0.50 NS, respectively. Taper showed mesiobuccal, mesiolingual and distal canal was 6 (60%), 7 (70%) and 6 (60%) for conventional and 9 (90%), 10 (100%) and 9 (90%) for NiTi method with P =0.14 NS, 0.10 NS and 0.11 NS, respectively. Smoothness showed in mesiobuccal, mesiolingual and distal canal was 5 (50%) each for conventional method and 9 (90%), 10 (100%) and 9(90%) for NiTi method with P =0.06 NS, 0.02 Sig and P =0.06 NS [Table 2].

The preparation time between the two methods compared between primary and permanent peeth showed P instrument failure compared between primary and permanent teeth, showed P =0.33 NS for deformation and P =1.00 NS for fractured instrument for conventional method. In NiTi rotary method P =1.00 NS for deformation, P =0.39 NS for fractured instrument [Graph 2, [Table 4]]. The flow in primary and permanent for conventional method was P P taper compared between primary and permanent showed P P P P et al.[6] showed that at 150 r.p.m. NiTi had very low failure with experienced hands. Thus the experience of the operator is one of the main factors.[7],[8],[9],[10],[11] Deformity of the K-files was due to the less modules of elasticity.

Interestingly, larger profiles were associated with more fracture than the smaller instruments whereas the stainless steel K-files showed more deformities in narrow curved canals. This failure of larger instruments were due to the lack of the initial orifice enlargement, a reflection of increased taper of the instruments with results that they bound more at the orifice.[1] But further work should be carried out to the determine the exact cause. The elastomeric impressions were used to check the flow, taper, smoothness of the canal and it was found that the profiles 0.04 taper 29 series produce good tapering when compared with stainless steel K files. This might be due to increased taper of the instruments combined with their planning action during rotation.[3] Overall the profiles showed good smoothness, taper and flow compared to the K files.

 Conclusion



The profile 0.04 taper series 29 rotary instruments prepared canal rapidly with good taper and smoothness but fracture was noted more, which may be due to the unwinding, reverse winding with tightening of the spirals. Hence these instruments should be checked with each use. Canal preparation with K-files is time consuming with poor taper, smoothness but instrument fracture is less and it is more economic. In the primary teeth, preparation time, instrument failure with the profile 0.04 taper 29 series was less when compared to permanent teeth.

In general, the results of NiTi rotary were encouraging but operator had to weigh advantageous of the both groups of instruments. Better results can be obtained with NiTi, which depends on the efficiency of the operator and experience. Irrespective of the cost factors, there were good results with NiTi in primary teeth.

According to this study, NiTi rotary showed to be more advantageous in the child patient as the chair side time is significantly reduced. To establish the use of NiTi rotary in primary teeth more studies are yet to be done.

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