In vivo evaluation of root canal disinfection using a combination of ultrasonic activation and diode laser therapy

Abstract

Aim:

In vivo evaluation of root canal disinfection using a combination of ultrasonic activation and diode laser therapy.

Objective:

The primary aim of this study was to evaluate the effectiveness of ultrasonic activation of sodium hypochlorite and diode laser irradiation in enhancing root canal disinfection by reducing bacterial load.

Materials and Methods:

Thirty patients aged 20–60 years with necrotic lower premolars and periapical infections were selected. After access opening, initial microbial samples (S1) were collected. The canals were then instrumented using ProTaper Next rotary files and irrigated with 2.5% sodium hypochlorite, which was activated ultrasonically using EndoX for 1 min. The second microbial sample (S2) was collected. Subsequently, 980 nm diode laser irradiation was applied in a pulsed mode, and the final microbial sample (S3) was obtained. All the samples were cultured in Brain Heart Infusion Agar (BHI) agar, and colony-forming units (CFU/ml) were determined. Statistical analysis was performed using the SPSS software with a significance threshold of P ≤ 0.05.

Results:

The mean CFU/ml count significantly reduced from S1 (22.93) to S2 (6.03) after ultrasonic activation and further decreased to S3 (1.04) following diode laser application. The reduction was statistically significant (P < 0.001).

Conclusion:

The combination of ultrasonic activation of sodium hypochlorite and diode laser irradiation significantly enhances root canal disinfection. Ultrasonic activation improves irrigant penetration, while diode laser provides deeper antimicrobial action.

INTRODUCTION

The primary objective of endodontic therapy is to thoroughly cleaning and shaping of the root canal system to remove debris, infected pulp tissue, and microbial load. For necrotic teeth with periapical infections, the aim is to create an aseptic environment devoid of bacteria within the root canal system. This is enhanced by irrigation which is a key part of successful root canal treatment. Achieving this goal is impeded by two main obstacles: The complex anatomical structure of the root which can make it difficult to reach even with the recent available armamentarium and the distinctive characteristics of the bacteria residing within it.

Irrigation and mechanical instrumentation are the two distinct treatment methods that are employed to reduce bacterial load. This study focuses on the enhancement of disinfection of the root canal system. Sodium hypochlorite is the most widely used endodontic irrigant.[1]

Several agitation techniques have been developed to achieve sufficient disinfection and debridement of the root canal system.[2] One of the most widely embraced techniques is the use of ultrasonic devices to promote the ultrasonic activation of irrigation.[3] The use of laser technology has recently raised considerable interest in endodontic procedures due to its antimicrobial properties. Diode lasers are increasingly being used for root canal disinfection.[4]

The purpose of this study was to evaluate the effect of ultrasonic activation of irrigant and diode laser irradiation for the reduction of bacterial count in the root canal system.

MATERIALS AND METHODS

This exploration study was conducted in the department of conservative dentistry and endodontics. Patients written consents were acquired, and received ethical approval by MUHS/Acad/E2/PG/247.1/2024 date October 9, 2024. Thirty patients reported in the range of age of 20–60 years were selected. All patients provided their informed permission before being enrolled in this study.

Inclusion criteria

Individuals who were between the ages of 2 years had a mature lower premolar, with pulpal or periapical diseases were included in this study. The diagnosis was confirmed by a combination of preoperative radiograph and electric pulp test.

Exclusion criteria

Pregnancy or lactation, calcified canals, root resorption, open apex were excluded from the study.

Procedure

Local anesthesia (Lox 2%, Neon Lab Ltd, India) was administered, and single tooth isolation was performed using a suitable clamp and rubber dam. All caries and/or coronal restoration was completely removed with a sterile bur. The access cavities were prepared using sterile round burs. The patency of the canal was achieved using a stainless-steel hand K-file size K. The root canals were irrigated with ml of sterile saline solution and the first microbial sample (S1) was collected. The sample was collected by sterile paper points by inserting it into the root canal for 1 min [Figure 1a]. Care was taken to avoid contact between the paper point and access cavity walls to prevent contamination.

Figure 1.

(a) First paper point sample after access opening, (b) Ultrasonic activation of NaOCL, (c) Diode laser irradiation

An apex Locator was utilized to establish working length (Root ZX mini, J. Morita, Japan) and then confirmed with an intraoral periapical radiograph to be 0.5–1 mm shorter than the radiographic apex. Root canals were mechanically prepared using ProTaper Next nickel–titanium rotary instruments (Dentsply Maillefer, Ballaigues, Switzerland) up to X3. 2.5% sodium hypochlorite was activated by the flexible silver tip of ultrasonic (EndoX) for min, which was 21 mm in length and the size of the tip is 20/2%. The canal was irrigated with sterile saline and a second sample (S2) was obtained [Figure 1b].

Subsequently, root canals were irradiated with a 980 nm diode laser (Confident Clean Cut) size of the optical fiber was 200 μm. One millimeter short of the apex, the tip was positioned. The setting of the laser was 1.5 Watt power in the pulsed mode. The irradiation protocol was 10 s irradiation followed by a 5 s pause, which constituted one lasing cycle. The lasing cycle was performed three times. This was followed by activation during which it was slowly dragged at a speed of approximately 2 mm/s in a way that the root canals would be irradiated from the apical to the coronal portion, in a helicoidal movement without touching the canal walls. This was done to ensure equal diffusion of light inside the root canal lumen and the third sample (S3) was taken [Figure 1c].

All the samples were immediately inserted into sterile tubes containing a transport medium of 2 ml thioglycolate and transferred to the microbiology laboratory on the same day.

Microbiological analysis

All the samples were transferred to the microbiology department, the tubes containing the 2 ml of thioglycolate (transport medium) with the paper points. The culture medium used was BHI Agar.

Procedure

The given samples were mixed in a thioglycolate medium and vortexed for 30 s. 100 μl aliquots of the vortexed samples were serially diluted using sterile saline (up to two dilutions. The above dilutions were mixed thoroughly and 0.1 ml of the above dilution was spread plated onto BHI agar plates under aseptic conditions. The agar plates were placed in the anaerobic jar and incubated at 37°C for 48 h. Colonies were enumerated and the colony-forming unit (CFU/ml) was calculated following incubation.

Statistical analysis

By examining the data’s distribution and applying normality tests, numerical data were examined for normalcy. Data were presented as mean and standard deviation values. To evaluate the variations in bacterial counts within each group, Friedman’s test was employed. Data were analyzed using IBM SPSS Statistics for Windows, Version 23.0 (IBM Corp., Armonk, NY, USA). Friedman’s two-way ANOVA test; adjustments for multiple comparisons using the Bonferroni test; indicated a significant difference at P ≤ 0.05.

RESULTS

The CFU was the highest at the first sample (S1) time interval and lowest at the third sample (S3) interval. A CFU count showed a significantly lower CFU count after the S3 time interval as compared to S2 intervals. It was found that the log CFU value at the baseline level (S1) was 22.93 which reduced to 6.03 in ultrasonic irrigation (S2). In the diode laser group, bacterial count decreased from (S2) 6.03 to 1.04 (S3). The difference was statistically significant with P ≤ 0.05 [Table 1 and Graph 1]. Post hoc Bonferroni test was used for the comparison among the groups. The significant differences between baseline and both later time points indicate a strong antimicrobial effect of the laser treatment. The nonsignificant difference between S2 and S3 suggests that most of the microbial reduction occurred early and the effect plateaued afterward [Table 2].

Table 1.

Comparison of microbial colony-forming units count at three different time points

Interval	Mean	SD	F	P
S1	22.93	14.08	54.33	<0.001*
S2	6.03	4.06
S3	1.04	1.84

*P<0.05 significant. SD: Standard deviation

Graph 1.

Microbial colony-forming unit count at three different time points

Table 2.

Post hoc Bonferroni test multiple comparison

Group	Group	Mean difference	SE	P
S1	S2	16.90	2.20	<0.0001
	S3	21.89	2.20	<0.0001
S2	S3	4.98	2.20	0.078

SE: Standard error

DISCUSSION

The nature of endodontic infections is known to be polymicrobial, with a preponderance of anaerobic species and complex bacterial interactions. While doing the root canal procedure the large areas of the root canal such as fins, isthmus, and cul-de-sac remain untouched even after mechanical instrumentation, regardless of the use of rotary or hand instrumentation. For this reason, various combinations of disinfecting solutions and various irrigation devices are used.[5]

In this research, we employed NaOCl, which is the most widely used irrigating solution. One of the major drawbacks of NaOCl is the high surface tension, which affects the tubular penetration and thus antibacterial ability of NaOCl.

Radcliffe et al.[6] compared the effectiveness time of 0.5%, 1%, 2.5%, and 5.25% NaOCl on Actinomyces naeslundii, Candida albicans, and Enterococcus faecalis. All concentrations proved effective against C. albicans and A. naeslundii in <10 s. E. faecalis which is a species more resistant to NaOCl, there was a variation in cells inactivation time: The 0.5% concentration took 30 min; at 1%, took 10 min; at 2.5%, 5 min; and at 5.25%, 2 min to reduce the number of viable cells to zero.

The 2.5% NaOCl proved to be a better solution than the others, 2.5% NaOCl is capable of inhibiting 100% of the E. faecalis in 5 min.[7]

Instrumentation and irrigation alone eliminate 50%–70% of root canal bacteria.[8] The remaining bacterial population is attributed to the presence of many areas in the root canal system that remained untouched after mechanical preparation regardless of the technique used.[9]

Due to the limitations of basic needle irrigation, various activation techniques have been developed. Disinfection methods have changed over time, moving from traditional needle irrigation to more sophisticated methods such as rotary brushes, EndoVac, RinsEndo, EndoActivator, sonic and ultrasonic agitation, and, more recently, laser-activated disinfection.

Sonic activation operates at a frequency of 1–6 kHz and ultrasonic generates 25–20 kHz frequency.[10] Ex vivo studies in root canal systems with restricted flow through the apical foramen, which better simulate fluid flow in clinical conditions, revealed that penetration of solutions is enhanced by ultrasonics and, to a lesser degree, sonic activation.[11] Sonic activation was reported as significantly less effective than ultrasonic activation, regardless of the irrigant used (NaOCl or CHX).[12]

Martin and Cunningham[13] explain the success of ultrasonic instrumentation with the interaction between ultrasonic energy and the irrigating solution. They call this interaction a “synergistic system.” Cavitation and acoustic flow as the primary effect of ultrasonic activation. When the ultrasound is directed into a liquid medium, the ultrasonic wave creates bubbles that grow larger and larger until they collapse into a powerful explosion.[14] This causes deagglomeration of bacterial biofilm through acoustic streaming action.[15] Ultrasonic agitation of NaOCl is successful in disrupting bacteria, it cannot ensure complete disruption of all microorganisms.[16]

We applied EndoX (Waldent 40 kHz) which is an ultrasonic device that uses an ultrasonic tip to agitate in the root canal system. Various innovative methods are being introduced for root canal disinfection, including the use of different laser systems in the field of endodontics. Diode LASER provides better access to the apex. The penetration of diode LASER energy into the dentinal tubules is better than erbium, chromium: Yttrium-scandium-gallium-garnet laser.[17]

The superior bactericidal effect of diode laser irradiation in the present study could be attributed to its greater depth of penetration (up to 1000 μm into the dentinal tubules). It has been found that with progressive decrease in diameter of the deep dentinal tubules, the penetration of irrigants is restricted.[18,19]

The laser irradiation with its inherent properties of light scattering, local intensity enhancement, and attenuation allows light penetration deeper in the dentinal tubules contributing to a superior antimicrobial efficacy. The diode laser causes a thermal photodisruptive action in the unreachable parts of dentin, photothermal effect on bacteria that are reachable, photoacoustic effect that is occlude the dentinal tubule which prevent bacteria from becoming trapped, resulting in enhanced bactericidal effect in root canal dentin.[20,21]

Under calibration techniques and manufacturer recommendations for optimum outcomes, a power setting of 1.5 W was utilized. For root canal disinfection, there are two modes available. The continuous mode produces more heat but is appropriate for quicker disinfection. Another was the pulsed mode, which is still effective but lessens heat accumulation and is safer for tissues around it. The root dentin, periodontal tissues, and surrounding structures might suffer thermal damage as the consequence of excessive power or continuous mode use.[22]

The diode lasers can penetrate deeply into dentinal tubules; they have a stronger antimicrobial effect than ultrasonics. The most accomplished root canal system is cleaning and disinfection, which can often be achieved by combining ultrasonic irrigant activation and lasers.

The current study’s limitation was that, while diode laser disinfection and ultrasonic irrigation cannot completely replace shaping and cleaning, they can complement a flawless, standard endodontic treatment to enhance the results. Every stage of the standard endodontic treatment should be meticulously followed to maximize the benefits of adjunctive ultrasonically activated irrigation and diode laser irradiation treatment.

CONCLUSION

Combining ultrasonic activation of sodium hypochlorite and diode laser irradiation significantly enhances root canal disinfection. Ultrasonic improves irrigant penetration while the diode laser provides deep antimicrobial action. Although not a replacement for conventional methods, their adjunctive use considerably improves root canal disinfection. Further research should refine these techniques for greater efficacy.

Conflicts of interest

There are no conflicts of interest.

Funding Statement

Nil.