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 Table of Contents  
ORIGINAL ARTICLE
Year : 2018  |  Volume : 30  |  Issue : 1  |  Page : 32-37

Root canal cleanliness after preparation with ultrasonic handpiece and hand instruments: An in vitro comparative scanning electron microscope study


1 Department of Conservative Dentistry and Endodontics, Yogita Dental College and Hospital, Khed, Maharashtra, India
2 Department of Conservative Dentistry and Endodontics, SDM, Dharwad, Karnataka, India
3 Department of Conservative and Endodontics, Bhabha Dental College, Bhopal, Madhya Pradesh, India

Date of Web Publication4-Jun-2018

Correspondence Address:
Dr. Shah Naman
Department of Conservative and Endodontics, Yogita Dental College and Hospital, Khed, Maharashtra
India
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/endo.endo_60_17

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  Abstract 

Aim and objective: This study aims to compare the efficacy of root canal cleanliness using hand instrumentation and ultrasonic handpiece under the scanning electron microscope.
Materials and Methods: Forty five central incisor were collected and access opening was done. cleaning and shaping of all the samples were done with three different groups 1- Ultrasonic file. group-2 with Hand files and Group-3 were prepared with Ultrasonic + hand files and debris and smear layer were evaluated with SEM .
Results: Group 1 (ultrasonic) removed smear layer superiorly, followed by Group 3 (ultrasonic/hand instrumentation) and Group 2 (hand instrumentation), and Group 3 (ultrasonic/hand instrumentation) showed superior cleanliness of debris followed by Group 1 (ultrasonic) and Group 2 (hand instrumentation).
Conclusion: (1) At the apical, middle, and coronal third level for removal of debris, Group 3 showed superior cleanliness followed by Group 1 and Group 2. (2) At the apical, middle, and coronal third level for removal of smear layer, Group 1 showed superior cleanliness followed by Group 3 and Group 2.

Keywords: Debris, scanning electron microscope, smear layer, ultrasonic files


How to cite this article:
Rao SB, Rao R N, Sunil Kumar V C, Babannavar R, Muniyappa M, Naman S. Root canal cleanliness after preparation with ultrasonic handpiece and hand instruments: An in vitro comparative scanning electron microscope study. Endodontology 2018;30:32-7

How to cite this URL:
Rao SB, Rao R N, Sunil Kumar V C, Babannavar R, Muniyappa M, Naman S. Root canal cleanliness after preparation with ultrasonic handpiece and hand instruments: An in vitro comparative scanning electron microscope study. Endodontology [serial online] 2018 [cited 2018 Sep 26];30:32-7. Available from: http://www.endodontologyonweb.org/text.asp?2018/30/1/32/233744


  Introduction Top


The ultimate goal of root canal cleaning and shaping is the removal of vital, necrotic tissue, microorganisms, and their byproducts and provide space for placing obturating materials. The question is if this goal is truly achievable using the standard techniques that are currently taught.[1],[2],[3]

According to Goerig,[4],[5],[6] one can see on these overlays that even with our improved NiTi file systems, all of the walls of the canals are not touched during cleaning and shaping. Moreover, studies have demonstrated that conventional hand preparation and techniques produce a considerable amount of smear layer, pulp tissue debris, dentin chips, and inorganic debris. The smear layer thus created when the dentinal walls of the root canal system interact with endodontic instruments. Comprise of inorganic and organic materials such as dentin filings and pulp tissue remnants.[7],[8],[9] The smear layer interferes with the tight adaptation of currently used root canal sealers to dentinal walls and may therefore promote microleakage.[2] Ahmed et al. 1990[6],[10],[11],[12] suggested that the removal of the smear layer decreases bacteria and improves adaptation of obturation materials to the canal walls.[6]

An advanced technique for instrumenting root canal systems utilizing ultrasonics was introduced by Martin and Hapasalo M(2010).[2] They reported that dentin-removing ability of ultrasonically energized files was superior to hand instruments.[13],[14],[15]

This system is based on the ultrasonic energizing of file for mechanical canal preparation and debris removal as well as ultrasonic cavitation and microstreaming of an irrigant for enhancing penetration, solvent, and bactericidal action.[16],[17],[18],[19]

Cunningham and Balekjian(1980)[20],[21],[22] believed that the ultrasonic energy can force a solution in all dimensions. Moreover, it can also dislodge debris from surface untreated by mechanical instrumentation by its cavitation and acoustic streaming.

This in vitro study aims to compare the efficacy of root canal cleanliness using hand instrumentation and ultrasonic handpiece under the scanning electron microscope.[15]


  Materials and Methods Top


Forty-five freshly extracted human maxillary central incisor with straight roots and intact root tips were selected for study. Conventional access cavities were prepared in all teeth using a high-speed round diamond point under air-water spray coolant. The teeth were selected where only ISO 15 file could be introduced into the canal without obstruction.

An ISO 10 file was passed through the canal until it was seen at the apical foramen. The working length was calculated by subtracting 0.5 mm from the canal length. This enabled the operator to make a rapid and accurate determination of working length. The apices of the root canals were sealed with pink boxing wax to prevent debris and irrigants from being forced out of the apex during chemo-mechanical preparation.

The teeth were randomly divided into three groups of fifteen teeth each and prepared with ultrasonics and hand instruments as followed.

Group-1 Ultrasonic Unit (Piezon Master 400) (Electrical Medical Systems, Le Sentier Switzerland)

The piezon master 400 represents a piezoelectric-driven ultrasonic unit (25–35 KHz) with all files available from ISO 15 to ISO 40. 3% sodium hypochlorite (Novodent, India) was used as irrigant. The unit was adjusted to a power setting and irrigant flow rate recommended by the manufacturer. Correct working length was measured and marked on the ultrasonic files with a permanent marker pen. Each file was instrumented using push-pull circumferential motion for 1 min.

The canal was enlarged serially from ISO 15 to ISO 30. The time taken for the preparation of each canal was 4 min. A constant flow of 3% sodium hypochlorite was delivered through the piezon master 400 unit.

To estimate the amount of solution that may be circulated through root canal during the use of ultrasonic, a calibrated test tube was used to collect the fluid that passed through the unit when the ultrasonic file was in use. The amount of fluid collected was 20 ml/min. Twenty milliliter of sodium hypochlorite per minute was taken as a standardization. These volumes were taken as intracanal equivalent amount of irrigant which was used in between instruments in the manually irrigated groups.

Group 2: Hand instrumentation

Hand instrumentation was performed using stainless steel K-type files and Hedstroem files (MANI Inc., Japan). The root canals were instrumented manually using the standardized preparation technique. The canals were enlarged serially using the same sequence of endodontic files to size ISO 30; irrigation was performed with a syringe and 26-gauge needle using 20 ml of 3% sodium hypochlorite following each ISO size.

Group 3: Ultrasonic followed by hand instrumentation with Hedstroem files

The canal was ultrasonically prepared as explained previously and followed by manual preparation with size ISO 25-Hedstroem file and irrigation with 20 ml of NaOCl.

Each canal was dried with a sterile paper point, and the pulp chamber was sealed with cotton pellet. All teeth were measured. Moreover, entire root length was divided into the coronal third, middle third, and apical third. They were then grooved on the buccal and lingual aspects using high-speed diamond disk (Gemflex, Jelenko, Germany) and were cracked longitudinally with a chisel and mallet. No grooves penetrated the root canal.

One of the root half was prepared for SEM (JEOL JSM-840A Tokyo, Japan) investigation. The specimens were dehydrated before sputtering with gold (JEOL JFC-1110E Tokyo Japan) on the prepared surface. Photomicrographs were taken on the midline of each root canal at three levels for each specimen 1 mm from the apical foramen.

Separate evaluations were undertaken for debris and smear layer. The criteria proposed by Griffith and Stock (1986) for the debris score were adopted.

  • Score 1 – No debris or flecks of debris
  • Score 2 – Debris covering less than one-third of the canal wall
  • Score 3 – Debris covering one-third or more of the canal wall.


The extent of smear layer was assessed according to smear layer scores adopted by Ahmad et al.

  • Score 0 – Absence of smear layer with all dentinal tubules opened
  • Score 1 – Little smear layer with more than 50% tubules opened
  • Score 2 – Moderate smear with <50% tubules opened
  • Score 3 – Heavy smear with outlines of tubules obliterated.


The scoring procedure was performed by an experienced endodontist who was not identical with the person who had prepared the root canals and had no knowledge of the study. The mean and standard deviation were compared, and the results were statistically analyzed using t-test.


  Results Top


The values of mean and standard deviation from [Table 1] indicate that Group 3 (ultrasonic/hand instrumentation) showed superior cleanliness of debris followed by Group 1 (ultrasonic) and Group 2 (hand instrumentation).
Table 1: Mean and standard deviation of debris group

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The values of mean and standard deviation from [Table 2] indicate that Group 1 (ultrasonic) removed smear layer superiorly, followed by Group 3 (ultrasonic/hand instrumentation) and Group 2 (hand instrumentation) [Figure 1], [Figure 2], [Figure 3].
Table 2: Mean and standard deviation of smear layer groups

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Figure 1: Specimens for Group 1 at the coronal third level

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Figure 2: Specimens for Group 1 at the middle third level

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Figure 3: Specimens for Group 3 at the apical third level

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The comparison of overall canal cleanliness in the three groups [Table 3] indicates that Group 1 and Group 2 differ significantly for debris (3.20) and also for smear layer (3.92); Group 1 and Group 3 do not differ significantly for debris (1.47) but differ for smear layer (3.24); and Group 2 and Group 3 differ significantly for debris (5.17) but do not differ for smear layer (1.43) [Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5], [Figure 6], [Figure 7], [Figure 8], [Figure 9].
Table 3: Comparisons of overall canal cleanliness in three groups

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Figure 4: Specimens for Group 2 at the coronal third level

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Figure 5: Specimens for Group 2 at the middle third level

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Figure 6: Specimens for Group 3 at the middle third level

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Figure 7: Specimens for Group 1 at the apical third level

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Figure 8: Specimens for Group 2 at the apical third level

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Figure 9: Specimens for Group 3 at the coronal third level

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  Discussion Top


Thorough debridement is considered to be the most important step in endodontic therapy. An old saying in endodontic has been that “what is taken out of the root canal may be more important than what is put into the root canal” (John).[4] The main objectives of root canal preparation are to remove pulp tissue, residual necrotic material, debris, and infected dentin, and thus reduce the number of microorganisms inside the root canal.[13],[23]

Instrumentation and irrigation are the current methods used to debride the root canal system. Irrigation acts as a flush to remove organic and inorganic debris that would otherwise be left in the canal after mechanical instrumentation. Considering irrigation, Cunningham WT, 1982[21] stated that “perhaps the most important factor is delivery system and not the irrigating solution per se.” Furthermore, it was found that the volume of irrigant is more important than the concentration or type of irrigant.

The results of this in vitro study demonstrate that ultrasonic synergistic system had a significantly superior ability to remove the smear layer of the root canal compared to conventional hand instrumentation techniques and ultrasonic/hand instrumentation techniques.[10]

This could be attributed to the ultrasonic system which provides a unique coupling of mechanical and chemical debridement.

According to Cunningham WT (1982),[22] ultrasonic techniques can produce very clean canals. She suggested that an improved understanding of the mechanisms involved was essential to utilize to the maximum, the inherent advantages of the technique. William and Slade suggested an equation to measure the liquid streaming velocity. They said the higher streaming velocities associated with the tip of the file, higher power settings, and smaller files are consistent with the following equation:[16],[20],[21]



Where Um is the liquid streaming velocity, is ω 2 times the driving frequency, ε0 is the displacement amplitude, and a is the radius of the wire.

Nyborg given an expression for hydrodynamic shear stresses in terms of a number of physical parameters namely. and given formula which is



Where t is the hydrodynamic shear stress, η is the kinematic viscosity of the liquid, f is the frequency, ε0 is displacement amplitude, a is the radius of the wire, and δ is the boundary layer thickness.

Ehrlich AD [9] in their study demonstrated that the ultrasonic system of root canal preparation was superior to conventional hand instrumentation techniques for root canal cleaning. This technique physically reduced the amount of necrotic debris within the canal as it is aided significantly by the use of continuous, high volume flow of irrigation, an integral component of the endosonic system, thus showing similar results to our study.

Haapasalo et al.[2],[12],[14] inferred from their study that when sodium hypochlorite and ultrasound are combined, as in ultrasonic irrigation, the efficiency of both components is increased. They concluded that 2% sodium hypochlorite activated by ultrasound will remove the smear layer within 3 min, thus strengthening the findings of our study.

Martin and Cunningham [18] conducted a study to evaluate the ability of an ultrasonic instrument in removing debris. Their results indicated that the ultrasonically powered filling was superior to hand filing in total dentin removed. They were the first to suggest the possibility of using an ultrasonic energizing device for use in endodontics.

The findings of this study are in concurrence with the earlier mentioned studies. The debridement effects of endosonic are most probably achieved through the synergistic effects of the biophysical aspects of ultrasound as well as use of an irrigant (Martin and Cunningham 1995; Walmsley 1989).[8] The two main biophysical effects of ultrasound thought to be of importance in endosonic are termed “acoustic cavitation” and “acoustic microstreaming” (Basrani), creating a pressure on walls of the canal that cleans the root canal wallls. During cavitation, bubbles are generated in the liquid which implode with tremendous force creating a pressure – vacuum effect that cleans the root canal walls as well as having a cidal effect on microorganisms (Thacker 1973; Martin and Cunningham 1985).[17] Acoustic microstreaming describes the hydrodynamic stresses generated in the ultrasonic field which aid in removal of debris and smear layer from the valves of the root canal.[3],[4] The superior cleansing ability of the ultrasonic system in our study is probably attributed to the increased flow of sodium hypochlorite irrigant and the acoustic streaming and acoustic cavitation mechanisms involved in the action of ultrasonically energized files. Certain authors have suggested that the heat produced by the vibrating file could enhance the antibacterial properties of sodium hypochlorite.

While there have been numerous studies which have proved the superior cleansing property of ultrasonic synergistic system, there has also been disagreement over its actual efficiency.

Ultrasonic/hand instrumentation technique was superior in removing the debris when compared to the other techniques. This could be attributed to the fact that the Hedstroem file which is used in a pull motion might have removed the minimal debris that was remaining following ultrasonic instrumentation.[22] Much is desired to be done regarding this technique and hence there have been a very few studies reported; hence providing the scope for further investigation. The technique also has some inherent disadvantages such as formation of smear layer following reinstrumentation with Hedstroem file.[24],[15]


  Conclusion Top


Within the limitation of the study, following conclusions were drawn:

  1. At the apical, middle, and coronal third level for removal of debris, Group 3 (ultrasonic followed by hand instrumentation with Hedstroem files) showed superior cleanliness followed by Group 1 (ultrasonic unit) and Group 2 (hand instrumentation)
  2. At the apical, middle, and coronal third level for removal of smear layer, Group 1 (ultrasonic unit) showed superior cleanliness followed by Group 3 (ultrasonic followed by hand instrumentation with Hedstroem files) and Group 2 (hand instrumentation) [Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5], [Figure 6], [Figure 7], [Figure 8], [Figure 9].


Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.

 
  References Top

1.
Mozo S, Llena C, Forner L. Review of ultrasonic irrigation in endodontics: Increasing action of irrigating solutions. Med Oral Patol Oral Cir Bucal 2012;17:e512-6.  Back to cited text no. 1
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2.
Haapasalo M, Shen Y, Qian W, Gao Y. Irrigation in endodontics. Dent Clin North Am 2010;54:291-312.  Back to cited text no. 2
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3.
Berutti E, Marini R. A scanning electron microscopic evaluation of the debridement capability of sodium hypochlorite at different temperatures. J Endod 1996;22:467-70.  Back to cited text no. 3
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4.
John I. Endodontics. 4th ed. Lief Balkland: William and William; 1994.  Back to cited text no. 4
    
5.
Cheung GS, Stock CJ. In vitro cleaning ability of root canal irrigants with and without endosonics. Int Endod J 1993; 26:334-43.  Back to cited text no. 5
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Ahmad M. Measurements of temperature generated by ultrasonic file in vitro. Endod Dent Traumatol 1990;6:230-1.  Back to cited text no. 6
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Yahya AS, ElDeeb ME. Effect of sonic versus ultrasonic instrumentation on canal preparation. J Endod 1989;15:235-9.  Back to cited text no. 7
    
8.
Walmsley AD, Williams AR. Effects of constraint on the oscillatory pattern of endosonic files. J Endod 1989;15:189-94.  Back to cited text no. 8
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9.
Ehrlich AD, Boyer TJ, Hicks ML, Pelleu GB Jr. Effects of sonic instrumentation on the apical preparation of curved canals. J Endod 1989;15:200-3.  Back to cited text no. 9
    
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Goldman M, White RR, Moser CR, Tenca JI. A comparison of three methods of cleaning and shaping the root canal in vitro. J Endod 1988;14:7-12.  Back to cited text no. 10
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Ahmad M, Pitt Ford TR, Crum LA. Ultrasonic debridement of root canals: An insight into the mechanisms involved. J Endod 1987;13:93-101.  Back to cited text no. 11
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Cameron JA. The synergistic relationship between ultrasound and sodium hypochlorite: A scanning electron microscope evaluation. J Endod 1987;13:541-5.  Back to cited text no. 12
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Cameron JA. The use of sodium hypochlorite activated by ultrasound for the debridement of infected, immature root canals. J Endo 1986;12:550-4.  Back to cited text no. 13
    
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Cameron JA. The use of sodium hypochlorite activated by ultrasound for the debridement of infected, immature root canals. J Endod 1986;12:550-4.  Back to cited text no. 14
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Chenail BL, Teplitsky PE. Endosonics in curved root canals. J Endo 1985;11:369-74.  Back to cited text no. 15
    
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Cunningham WT, Martin H. A scanning electron microscope evaluation of root canal débridement with the endosonic ultrasonic synergistic system. Oral Surg Oral Med Oral Pathol 1982;53:527-31.  Back to cited text no. 16
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Martin H, Cunningham W. Endosonic endodontics: The ultrasonic synergistic system. Int Dent J 1984;34:198-203.  Back to cited text no. 17
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Shilder H. Cleaning and shaping the root canal. Dent Clin N Am 1974;18:269-96.  Back to cited text no. 18
    
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Goerig AC, Michelich RJ, Schultz HH. Instrumentation of root canals in molar using the step-down technique. J Endod 1982;8:550.  Back to cited text no. 19
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Cunningham WT, Martin H, Pelleu GB Jr., Stoops DE. A comparison of antimicrobial effectiveness of endosonic and hand root canal therapy. Oral Surg Oral Med Oral Pathol 1982;54:238-41.  Back to cited text no. 21
    
22.
Cunningham WT, Martin H, Forrest WR. Evaluation of root canal débridement by the endosonic ultrasonic synergistic system. Oral Surg Oral Med Oral Pathol 1982;53:401-4.  Back to cited text no. 22
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Grossman LT, Seymour OL, Delrio CE. Endodontic. Indian: Varghese Publishing House; 1981. p. 212.  Back to cited text no. 23
    
24.
Cunningham WT, Balekjian AY. Effect of temperature on collagen-dissolving ability of sodium hypochlorite endodontic irrigant. Oral Surg Oral Med Oral Pathol 1980;49:175-7.  Back to cited text no. 24
    


    Figures

  [Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5], [Figure 6], [Figure 7], [Figure 8], [Figure 9]
 
 
    Tables

  [Table 1], [Table 2], [Table 3]



 

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