Comparison between the Antibacterial Effects of 810 and 980-Nanometer Diode Lasers in Combination with Sodium Hypochlorite on Enterococcus Faecalis in the Root Canal System-In Vitro Study

Murtadha Mustafa^* and Salah A Alkurtas

^*Correspondence: Murtadha Mustafa, Department of Biomedical Applications Institute of Laser for Postgraduate Studies, University of Baghdad, Iraq, Email:

Author info »

Introduction

Because of its complex anatomy, bacteria's ability to penetrate dentinal tubules and the presence of a smear layer formed during mechanical instrumentation, disinfecting the root canal system is difficult [1]. Endodontic treatment's primary goal is to effectively remove bacteria and necrotic pulp tissue remnants from the root canal system [2]. However, it has been demonstrated that after root canal preparation with a rotary Ni-Ti system, 35% of the root canal surface area remains unchanged [3]. Furthermore, a biomechanical preparation cannot completely eliminate the microorganisms in the root canal system; each technique has its own set of limitations [4]. The most commonly used root canal irrigants during routine endodontic treatment are sodium hypochlorite, chlorhexidine gluconate, and ethylenediaminetetraacetic acid (EDTA), but none of these chemicals can be considered an ideal irrigation solution [5]. These irrigants solutions cannot penetrate dentin for more than 100 micrometers due to surface tension, and it is well known that pathogenic bacteria can invade deep into dentin for up to 1000 micrometers, making these chemical irrigants ineffective against these deep-seated microorganisms [6]. The irrigation process in the apical third of the root canal has its own unique challenges, and the key issue here is achieving a balance between safety and effectiveness [6]. Diffusion of the irrigants solution through dentinal tissue is generally slow, and it is influenced by a number of factors such as irrigant concentration and temperature [7].

Enterococcus faecalis (E. faecalis) is the most common bacterial species in endodontic treatment failures due to resistant or recurrent infections [8]. Through various mechanisms, these cocci can withstand antibacterial agents such as NaOC [9]. By invading dentinal tubules and resisting nutritional deprivation, it has been successful in competition with other microorganisms [10]. It is also resistance to alkaline pH and consequently to calcium hydroxide pastes that normally inhibits other bacteria. The related mechanism could be linked to the presence of a functioning active proton pump in this bacteria's cellular membrane [11].

Because of the limitations of common irrigants in root canal treatment, new methods such as lasers have been introduced in recent years to clean the root canal system effectively. Due to properties such as high penetration depth into the dentinal tubules and proper antibacterial effect, the diode laser is the most desirable type of laser among the various types [12].

However, it has been demonstrated that by using a diode laser alone or in combination with irrigating solutions, E. faecalis can be largely or completely eradicated [13,14]. The available diode laser wavelengths for dental applications range from 800 nm to 1064 nm [15]. Previous studies have assessed the antimicrobial efficacy of 810 nm and 980 nm lasers separately, and the results show that they are both effective. Because of its small size, availability, thin flexible fibers, and output power of 0.5 to 7W, the 980 nm diode laser was recently introduced to dentistry and soon gained popularity [16]. Furthermore, the 980 nm diode laser is well absorbed by water but only slightly by hydroxyapatite crystals, resulting in light scattering in the dentin [17]. Gutknech et al. reported that the bacteria lodged to a depth of 500 m in dentinal tubules were successfully eliminated using a 980 nm laser [18]. Many studies have shown that the bactericidal effect of a diode laser (810 nm) is due to thermal properties, and that bacteria cannot develop resistance to laser exposure [19].

Aim of study

The antibacterial effects of diode lasers with wavelengths of 810 and 980 nm in combination with chemical irrigation solutions (NaOCL and EDTA) on E. faecalis biofilm in the root canal system were compared in this in vitro study.

Materials and Methods

Preparation step

This study used forty extracted single-rooted human teeth with a single canal. All of the teeth are approximately the same size, have fully formed apices, and have never had root canal therapy. All collecting teeth are then debrided and rinsed in 5.25 NaOCl (Chlorax d 5.25%, Cerkamed, Poland) for 30 minutes before being soaked in normal saline (0.9% sodium chloride) at room temperature till the next step.

The root lengths were standardized to a 15 mm length to obtain uniform working length for all teeth specimens, and the specimens were cut off at the cement enamel junction with a disc bur using a high-speed handpiece.

#15 K-file (Dentsply Maillefer, Switzerland) was used for working length determination. The file was introduced into the canal until its tip was visible at the apical foramen.

Protaper rotary file system SX-S1-S2-F1-F2-F3 (Dentsply Maillefer, Switzerland) was used to prepare the root canals. After each file, 3 ml of 5.25% sodium hypochlorite was injected using a 30-gauge irrigation needle (Sinalident, China). The irrigation needle was placed 1 mm from the canal apices, with a delivery rate of 3 ml/min, to ensure that each canal received the same total irrigation time. Then, for 4 minutes, 2ml of 17% EDTA (17% EDTA, IL CHUNG, Korea) was injected into each canal, followed by a final irrigation with 5.25 % NaOCl. With an ultrasonic tip, both solutions (EDTA and NaOCl) were activated for 30 seconds. Finally, all specimen canals were washed with sterile water and dried with sterile paper points.

The apical foramens were sealed with composite resin fillings (Z350, 3M, USA) after the cleaning and shaping step, and all of the specimens were autoclaved for 20 minutes at 121oC under 15 psi pressure. After sterilization, each specimen was placed in an eppendorf tube with 2 mL of sterile Luria-Bertani broth (LB broth) and incubated at 37 °C for 48 hours with daily checks to ensure that the broth is free of turbidity.

Experimental contamination and incubation step

Enterococcus faecalis bacteria were isolated from infected root canals using a #15 K-file (Dentsply Maillefer, Switzerland) with a circumferential filing motion for 20 seconds and inoculating each sample with 20 l of LB broth. After inoculating the suspension in Pfizer selective enterococcus media (PSE agar), the E.faecalis bacteria were identified using vitek (Vitek 2 comnpact, Bio). Spectrophotometric dilution of the bacterial suspension to match 0.5 McFarland standard turbidity (1.5 × 108 CFU/ml). After injecting this bacterial suspension into the canals of prepared teeth, the orifices were dried and sealed with light-cured temporary fillings (IL CHUNG, Korea). The specimens placed into Eppendorf tube contain 2ml of LB broth and incubated at 37°C under anaerobic conditions for 14 days. The broth and the tube was changed every three days for nutrition purpose.

Selection of Laser parameters and pilot study

Table 1 and 2 show the maximum temperature elevation of external root surface above the room temperature during laser irradiation

Table 1: 810 nm diode laser

Table 2: 980 nm diode laser

Experimental specimens disinfection

After two weeks of incubation under anaerobic condition the teeth specimens brought out from the incubator and soaked in CHX solution for 2 minutes then washed with sterile water and divided into 4 groups each one contains 10 teeth specimens group A (control group) specimen with no treatment, group B (its specimens treated with 5.25% sodium hypochlorite and 17% EDTA), group C ( specimen treated with 17% EDTA and 5.25% NaOCL then radiated with 810 nm diode laser ) and group D (specimen treated with 17% EDTA and 5.25% NaOCL then radiated with 980 nm diode laser ).

Group A, control group (n=10)

Assuming that the infection rate of teeth specimens with E. faecalis are 100% to compare it with bacterial reduction rate of other 3 experimental groups.

Group B (n=10): NaOCL and EDTA

In this group, 2 ml of 17% EDTA for 3 minutes and 3 ml of 5.25% sodium hypochlorite for other 3 minutes respectively were used for canals disinfection, using 30-gauge irrigation needle with lateral opening at the closed end of it then irrigates with 3 ml of 0.9% normal saline. all the canals were dried with sterile paper points than 0.1 ml of sterile water (09% normal saline) was introduced into each canal and sealed coronary with temporary filling and incubated for 24 hours under anaerobic conditions.

Group C (n=10): 810 nm diode laser, NaOCL and EDTA

After elimination of temporary fillings, The tooth specimens in laser group were disinfected by 810 nm diode laser with an endodontic fiber tip (200 μm) with output power of 1 watt at continuous emission mode (CW) after application of 2 ml of 17% EDTA for 3 minutes and 3 ml of 5.25% sodium hypochlorite for other 3 minutes respectively, using 30-gauge irrigation needle with lateral opening at the closed end of it then irrigates with 3 ml of 0.9% normal saline then the canals were dried using #F3 sterile paper points. Each canal was irradiated with 5 seconds laser exposure four times, followed by 20 seconds interval for each exposure. The laser tip was inserted directly into the root canal 1 millimeter beneath the working length and moved in a helicoid pattern downward and upward. After lasing procedure, each specimen received 0.1 ml of sterile water then sealed coronary with temporary filling restoration and incubated for 24 hours under anaerobic conditions.

Group D (n=10): 980 nm diode laser, NaOCL and EDTA

The specimens irradiated with 980 nm diode laser with an endodontic fiber tip (200 μm) with output power of 1 watt at continuous emission mode (CW) with 5 seconds exposure time four times followed by 20 seconds resting interval for each exposure after treated with 5.25% NaOCL and 17% EDTA. The procedure was same in group B.

Determination of bacterial count

After 24 hours of incubation period of disinfected specimens, all specimens groups brought out and their temporary fillings were removed then received 0.1 ml of sterile normal saline to serve as transport media inside the canals. A #25 K-File was inserted inside each canal with circumferential filing motion for 30 seconds in order to disrupt the bacterial biofilm and collecting the dentin chips. A #F3 sterile paper point was used for each canal to collect the dentin chips with its transporting media. Then each paper point and k-file of each canal was inserted inside Eppendorf tube containing 2 ml of sterile LB broth. The Eppendorf tube was shaken in vortex mixer for 1 minute and incubated for 24 hours under anaerobic conditions.

After incubation, 0.5 ml was taken from each Eppendorf tube (using micropipette) and undergoes tenfold serial dilution then inoculated in a plate containing blood agar followed by incubation for 24 hours. After the incubation period, the number of colony-forming units (CFU) was determined by using the formula:

{No. of CFU X Dilution factor = No. of CFU/ml},

We compared the means of groups (B, C, D) with the mean of group A (Control group) to determine the bacterial colonies reduction in each disinfected experimental group.

Statistical analysis

Data of the study were analyzed using one way analysis of variance (ANOVA) model to compare the mean CFUs/ml among the groups. Then multiple comparisons of mean CFU/ml between groups were made using Dunnett’s T3 post hoc test. P value <0.05 was considered statistically significant.

The statistical analysis was performed using SPSS for windows (SPSS INC, Chicago, Il, USA) version 21.0.0.

Results

Evaluation of Bacteriological growth after disinfection

After 24 hours of incubation, group C (17% EDTA, 5.25% NaOCL and 810 nm diode laser) exhibited less bacterial growth on the blood agar media in comparison with other disinfected groups. The number of CFUs showed below in Table 3 which was counted after collecting the bacterial colonies on blood agar plate after tenfold serial dilution.

Table 3: Evaluation of bacteriological growth after disinfection

Descriptive statistics for the CFUs/ml including mean, standard deviation (SD), standard error (SE), minimum values and maximum values are in Table 4 below.

Table 4: Descriptive statistics of bacterial count among groups.

Figure 1, compares between the mean of control group with those of the treated groups can be made to assess the bacterial reduction in each treated group. Group C has the greatest bacterial reduction as 97.9% of bacteria were killed followed by group D (94.2% bacterial reduction) and then group B (81.6% bacterial reduction) respectively. It’s clear that the powerful bactericidal effect against E. faecalis biofilm achieved by combining NaOCl and EDTA with diode laser radiation inside infected root canal. Statistical test of CFU among groups using One way Analysis Of Variance (ANOVA) revealed highly significant difference as p=0.00. Multiple comparisons of CFU/ml between groups were made using Dunnett’s T3 post hoc test (Table 5 below). All comparisons with control group revealed highly significant differences.

Figure 1. Mean bacterial count

Table 5: Multiple comparisons of CFU Between groups using Dunnett T3 post hoc test

Discussion

Although several chemical agents are available with different properties, as far as cleaning of root canals is concerned, Clearly, none of the presently available irrigating solutions can be regarded as optimal, or even close to that. In clinical practice, use of a combination of solutions in a specific sequence is necessary in order to maximally contribute to the success of root canal treatment.

Due to its ability to penetrate deep into dentinal tubules and forming a biofilm, E. faecalis remains viable after mechanical and chemical root canal preparation. However, 20-23% of patients with endodontic failure after one year of treatment were attributed to the presence of E. faecalis inside their treated root canals.

The smear layer produced by files and drills during root canal instrumentation is a film of debris attached to dentin surface, composed by excised dentin particles, remnants of vital or necrotic pulp tissue, microorganisms (involving E. feacalis) and their byproducts, and retained chemical irrigants. The smear layer interrupts the penetration of root canal irrigants and acts as a barrier between the root filling and the canal wall, which is a potential path of leakage for bacteria contamination between the 2 surfaces. The difficulty of smear layer removal in the apical region could be caused by the inability to deliver agents such as NaOCl and EDTA, due to the smaller dimensions of the apical canal, which obstructs irrigation delivery.

Laser therapy is known as an efficient modality in endodontic treatment due to multiple advantages such as smear layer removal, decreasing the bacterial count and reducing the apical micro leakage. Diode lasers are highly popular due to their small size and cost effectiveness. Also, they have a flexible and thin fiber, which enables easy access to narrow canals and enhances the efficacy of disinfection in the radicular dentinal tubules to a depth of 500μ. Diode laser is recommended for endodontic treatment because its wavelength is within the infrared range and its thin and flexible fibers help to remove the smear layer. In this vitro study, results showed that application of 810 and 980 nm diode lasers with 1 Watt power decreased the E. faecalis bacterial colonies in the root canal system compared to the control group. The effect of 810 nm diode laser in combination with NaOCL and EDTA on decreasing E. faecalis colony counts was significantly greater than that of 980 nm diode laser with NaOCL and EDTA. The reduction of bacterial count was 97.9% CFU with 810 nm diode laser while the bacterial reduction was 94.2% CFU with 980 nm diode laser under same conditions.

Different studies showed the effects of 810 nm and 980 nm diode lasers on intracanal E. faecalis, In 2018, Martins et al. reported the reduction of the bacterial count in deep layers of the infected root canal wall up to 74% by means of the diode laser (810 nm).while 980 nm laser, despite using higher distal output power, decreased the bacterial count by 57%.

The absorption coefficient of diode lasers in water is low (μa =0.04–0.05 cm−1) and as a consequence, they have low absorption in dentin. The greater depth of penetration of diode laser irradiation can be the reason for its superior bactericidal effect (more than 1000 μm into dentinal tubules).

These lasers can interact with pigments (e.g. melanin) of the root canal pathogens directly and exert a great bactericidal effect.They also because thermal photo disruptive action in the unreachable parts of root canal dentin, resulting in an enhanced bactericidal effect there. In 2014, Ashofteh et al performed a study on infected root canals to compare the antibacterial effect of intracanal irrigants and diode lasers. They used an 830 nm diode laser and output power of 1.5 W and a frequency of 20 Hz. They concluded that diode lasers were not as effective as irrigants in disinfecting the root canal but they showed increased disinfection in deep dentin due to deeper penetration.

Sodium hypochlorite (NaOCl) is the most commonly used root canal irrigant. Among the current available endodontic irrigating solutions, sodium hypochlorite is known for its ability to digest organic tissues during chemo mechanical debridement of the root canals. The optimal chemical concentration of NaOCl is between 1% and 6%. Studies have shown that a concentration of 5.25% NaOCl can kill E. faecalis and C. albicans within 15–30 seconds. Ethylenediaminetetraacetic acid (EDTA) is a synthetic amino acid, it is often used as a chelating agent. EDTA demineralizes the inorganic components of dentin by chelating calcium ions, which reduces the micro hardness. The EDTA solution can completely remove the inorganic components from the smear layer and open dentinal tubules within 1 minute. However, a prolonged treatment (>10 minute) may lead to erosion of the intertubular and peritubular dentin. Sodium hypochlorite is still the most effective ‘gold standard irrigant’. Unlike with sodium hypochlorite, the extrusion of iodine and chlorhexidine is thought to be more forgiving to the soft tissues as they do not dissolve organic tissue. Chelators in liquid form are not a replacement for antimicrobial irrigants like NaOCl. The antimicrobial properties of chelators are low yet they can be used to remove the smear layer, increasing the penetration of other irrigants such as NaOCl and hence increasing their antimicrobial effects The inorganic portion of smear layer can be removed by the use of 15–17% concentrations of EDTA and the organic portion can be removed by NaOCl in concentrations exceeding 1%.

In this study, 2 ml of 17% EDTA with 3 ml of 5.25% sodium hypochlorite were used respectively for root canal disinfection. The bacterial reduction was 81.6% CFU. In a similar study, de Souza et al. concluded that diode laser irradiation following chemomechanical irrigation was more effective than NaOCl irrigation alone in root canal disinfection and elimination of E. faecalis.

The antibacterial effect of the diode laser on the infected root canal wall. The laser used in this study was diode laser. The results showed that a combination of irrigation with NaOCl and laser irradiation is more effective than conventional endodontic therapy for a reduction in bacterial flora from the root canal system [20-47].

Conclusion

In comparison between the effects of diode laser radiation on the E. faecalis in the root canal system at 1 watt, the bactericidal effect of 810 nm was greater than 980 nm. The reduction of bacterial count was 70.8% CFU with 810 nm diode laser while the bacterial reduction was 29.1% CFU with 980 nm diode laser under same conditions. However, 5.25% sodium hypochlorite with 17% EDTA has better antibacterial effect on E. faecalis biofilm (The reduction of bacterial count was 81.6%) than diode lasers. Results showed greater effect of diode lasers on E. faecalis reduction when they applied in combination with other chemical irrigants like NaOCL and EDTA.

References

1. Torabinejad M, Handysides R, Khademi AA, et al. Clinical implications of the smear layer in endodontics: A review. Oral Surg Oral Med Oral Pathol Oral Radiol Endod 2002; 94:658-666.

Indexed at, Google Scholar, Cross Ref

2. Vahdaty A, Ford TP, Wilson RF. Efficacy of chlorhexidine in disinfecting dentinal tubules in vitro. Dent Traumatol 1993; 9:243-248.

Indexed at, Google Scholar, Cross Ref

3. Cumbo EM, Cusimano P, Russo R, et al. Effects of two Ni-Ti preparation techniques on root canal geometry assessed by electronically profiling the endodontic space. In50° International Congress GIRSO 2006; 47:40-41.
4. Peters Ove A, Schönenberger K, Laib A. Effects of four Ni-Ti preparation techniques on root canal geometry assessed by micro computed tomography. Int Endod J 2001; 34.3:221-230.

Indexed at, Google Scholar, Cross Ref

5. Ordinola-Zapata R, Bramante CM, Brandão Garcia R, et al. The antimicrobial effect of new and conventional endodontic irrigants on intra-orally infected dentin. Acta Odontol Scand 2013; 71:424-31.

Indexed at, Google Scholar, Cross Ref

6. Berutti E, Marini R, Angeretti A. Penetration ability of different irrigants into dentinal tubules. J Endod 1997; 23:725-7.

Indexed at, Google Scholar, Cross Ref

7. Haapasalo M, Shen Y, Wang Z, et al. Irrigation in endodontics. Br Dent J 2014; 216:299-303.

Indexed at, Google Scholar, Cross Ref

8. van der Sluis LW. Endodontics in motion: New concepts, materials and techniques 3. The role of irrigants during root canal treatment. Nederlands Tijdschrift Voor Tandheelkunde 2015; 122:533-538.

Indexed at, Google Scholar, Cross Ref

9. Evans M, Davies JK, Sundqvist G, et al. Mechanisms involved in the resistance of Enterococcus faecalis to calcium hydroxide. Int Endod J 2002; 35:221-8.

Google Scholar, Cross Ref

10. Flanagan D. Enterococcus faecalis and dental implants. J Oral Implantol 2017; 43:8-11.

Indexed at Google Scholar Cross Ref

11. Ran S, Gu S, Wang J, et al. Dentin tubule invasion by Enterococcus faecalis under stress conditions ex vivo. Eur J Oral Sci 2015;123:362-8.

Indexed at Google Scholar Cross Ref

12. Weckwerth PH, Zapata RO, Vivan RR, et al. In vitro alkaline pH resistance of Enterococcus faecalis. Braz Dent J 2013;24:474-6.

Indexed at Google Scholar Cross Ref

13. Gutknecht N, Van gogswaardt D, Conrads G, et al. Diode laser radiation and its bactericidal effect in root canal wall dentin. J Clin Laser Med Surg 2000; 18:57-60.

Indexed at Google Scholar Cross Ref

14. Beer F, Buchmair A, Wernisch J, et al. Comparison of two diode lasers on bactericidity in root canals-an in vitro study. Lasers Med Sci 2012; 27:361-4.

Indexed at Google Scholar Cross Ref

15. Preethee T, Kandaswamy D, Arathi G, et al.Bactericidal effect of the 908 nm diode laser on Enterococcus faecalis in infected root canals. J Conserv Dent 2012; 15:46.

Indexed at Google Scholar Cross Ref

16. Camargo SC. The antibacterial effects of lasers in endodontics. Infection 2012; 1:8-14.

Google Scholar

17. Marchesan MA, Brugnera-Junior A, Ozorio JE, et al. Effect of 980-nanometer diode laser on root canal permeability after dentin treatment with different chemical solutions. J Endod 2008; 34:721-4.

Indexed at Google Scholar Cross Ref

18. Schoop U, Kluger W, Dervisbegovic S, et al. Innovative wavelengths in endodontic treatment. Lasers Surg Med 2006; 38:624-630.

Indexed at Google Scholar Cross Ref

19. Asnaashari M, Safavi N. Disinfection of contaminated canals by different laser wavelengths, while performing root canal therapy. J Lasers Med Sci 2013; 4:8.

Indexed at Google Scholar

20. Krishnan SN, Nayarisseri A, Rajamanickam U. Biodegradation effects of o-cresol by Pseudomonas monteilii SHY on mustard seed germination. Bioinformation 2018; 14:271.

Indexed at Google Scholar Cross Ref

21. Karaman R, Khamis M, Abbadi J, et al. Paracetamol biodegradation by activated sludge and photocatalysis and its removal by a micelle-clay complex, activated charcoal, and reverse osmosis membranes. Environ Technol 2016; 37:2414-27.

Indexed at Google Scholar Cross Ref

22. Haapasalo M, Shen Y, Qian W, et al. Irrigation in endodontics. Dent Clin 2010; 54:291-312.

Indexed at Google Scholar Cross Ref

23. Figdor D, Davies JK, Sundqvist G. Starvation survival, growth and recovery of Enterococcus faecalis in human serum. Oral Microbial Immunol 2003; 18:234-9.

Indexed at Google Scholar Cross Ref

24. Ng YL, Mann V, Rahbaran S, et al. Outcome of primary root canal treatment: systematic review of the literature-Part 2. Influence of clinical factors. Int Endod J2008; 41:6-31.

Indexed at Google Scholar Cross Ref

25. Kokkas AB, Boutsioukis AC, Vassiliadis LP, et al. The influence of the smear layer on dentinal tubule penetration depth by three different root canal sealers: an in vitro study. J Endod 2004; 30:100-2.

Indexed at Google Scholar Cross Ref

26. Wang Z, Shen Y, Haapasalo M. Effect of smear layer against disinfection protocols on Enterococcus faecalis-infected dentin. J Endod 2013; 39:1395-400.

Indexed at Google Scholar Cross Ref

27. Lui JN, Kuah HG, Chen NN. Effect of EDTA with and without surfactants or ultrasonics on removal of smear layer. J Endod 2007; 33:472-5.

Indexed at Google Scholar Cross Ref

28. Kimura Y, Wilder-Smith P, Yonaga K, et al. Treatment of dentine hypersensitivity by lasers: a review. J Clin Periodontol 2000 ;27:715-21.

Indexed at Google Scholar Cross Ref

29. Muhammad OH, Rocca JP, Fornaini C, et al. Evolution of the role of phototherapy during endodontic decontamination. Laser Ther 2015; 24:291-302.

Indexed at Google Scholar Cross Ref

30. de Souza EB, Cai S, Simionato MR, et al. High-power diode laser in the disinfection in depth of the root canal dentin. Oral Surg Oral Med Oral Pathol Oral Radiol Endod 2008; 106:e68-72.

Indexed at Google Scholar Cross Ref

31. Wang X, Sun Y, Kimura Y, et al. Effects of diode laser irradiation on smear layer removal from root canal walls and apical leakage after obturation. Photomed Laser Surg 2005;23:575-81.

Indexed at Google Scholar Cross Ref

32. Martins MR, Franzen R, Depraet F, et al. Rationale for using a double-wavelength (940 nm+ 2780 nm) laser in endodontics: literature overview and proof-of-concept. Lasers Dent Sci 2018; 2:29-41.

Google Scholar Cross Ref

33. Gutknecht N, Franzen R, Schippers M, et al. Bactericidal effect of a 980-nm diode laser in the root canal wall dentin of bovine teeth. J Clin Laser Med Surg 2004; 22:9-13.

Indexed at Google Scholar Cross Ref

34. Gutknecht, Norbert, et al. Diode laser radiation and its bactericidal effect in root canal wall dentin. J Clin Laser Med Surg 2000; 18.2: 57-60.

Indexed at, Google Scholar, Cross Ref

35. Juric IB, Anic I. The use of lasers in disinfection and cleaning of root canals: A review. Acta Stomatol Croat 2014; 48.1: 6-15.

Indexed at Google Scholar Cross Ref

36. Mehrvarzfar P, Saghiri MA, Asatourian A, et al. Additive effect of a diode laser on the antibacterial activity of 2.5% NaOCl, 2% CHX and MTAD against Enterococcus faecalis contaminating root canals: An In vitro study. J Oral Sci 2011; 53:355-60.

Indexed at Google Scholar Cross Ref

37. López-Jiménez L, Arnabat-Domínguez J, Viñas M, et al. Atomic force microscopy visualization of injuries in Enterococcus faecalis surface caused by Er, Cr: YSGG and diode lasers. Med Oral Patol Oral Cir Bucal 2015; 20:e45.

Indexed at Google Scholar Cross Ref

38. Ashofteh K, Sohrabi K, Iranparvar K, et al. In vitro comparison of the antibacterial effect of three intracanal irrigants and diode laser on root canals infected with Enterococcus faecalis. Iran J Microbiol 2014; 6:26.

Indexed at Google Scholar

39. Rahimi S, Janani M, Lotfi M, et al. A review of antibacterial agents in endodontic treatment. Iran Endod J 2014; 9:161.

Indexed at Google Scholar

40. Podar R, Kulkarni GP, Dadu SS, et al. In vivo antimicrobial efficacy of 6% Morinda citrifolia, Azadirachta indica, and 3% sodium hypochlorite as root canal irrigants. Eur J Dent 2015; 9:529-34.

Indexed at Google Scholar Cross Ref

41. Hülsmann M, Heckendorff M, Lennon A. Chelating agents in root canal treatment: mode of action and indications for their use. Int Endod J 2003; 36:810-30.

Indexed at Google Scholar Cross Ref

42. Cruz-Filho AM, Sousa-Neto MD, Savioli RN, et al. Effect of chelating solutions on the microhardness of root canal lumen dentin. J Endod 2011; 37:358-62.

Indexed at Google Scholar Cross Ref

43. Adarsh V, Kiran MM, Jamsheed ET, et al. A Comparative evaluation of smear layer removal by using three different irrigating systems in endodontics: An in-vitro scanning electron microscopic study. J Int Oral Health 2016; 8:80.

Google Scholar

44. Bergmans L, Moisiadis P, Teughels W, et al. Bactericidal effect of Nd: YAG laser irradiation on some endodontic pathogens ex vivo. Int Endod J 2006; 39:547-57.

Indexed at, Google Scholar, Cross Ref

45. de Souza EB, Cai S, Simionato MR, et al. High-power diode laser in the disinfection in depth of the root canal dentin. Oral Surg Oral Med Oral Pathol Oral Radiol Endod 2008; 106:e68-72.

Google Scholar, Cross Ref

46. Tilakchand M, Singh NN, Yeli MM, et al. Evaluation of the antibacterial efficacy of EZLASE diode LASER on the infected root canal system: An in vivo study. J Conserv Dent 2018; 21:306.

Indexed at, Google Scholar, Cross Ref