The main objective of traditional endodontic treatment is to remove the infected pulp and clear the root canal system of microbes, which further prevents inflammation of the surrounding tissues and promotes rapid healing [1]. Successful endodontic therapy ultimately restores the tooth’s form and function, enabling it to serve its intended purpose in the oral cavity [2]. Microorganisms, including the resilient Enterococcus faecalis, known for biofilm formation, are primary contributors to inflammation and delayed healing in endodontic infections [3]. The presence of these bacteria often leads to persistent pain following endodontic procedures [4].
Various mechanical and chemical aids play integral roles in facilitating successful root canal treatments. Mechanical and chemical aids, including rotary instruments, ultrasonic devices and intracanal medications like calcium hydroxide, are essential for effective root canal treatment [5]. Although endodontic procedures generally have high success rates, treatment failures can occur due to persistent bacteria, inadequate cleaning and filling, untreated accessory canals, or coronal leakage [6].
Conventional biomechanical instrumentation has a limited ability to completely eradicate microorganisms from root canals, leaving a substantial portion of the canal surface contaminated. To address these shortcomings, laser technology has emerged as a potential solution for managing post-endodontic complications [7]. Lasers have gained significant traction across various dental fields since their inception in 1960 by Maiman. The subsequent Food and Drug Administration (FDA) approval in 1990 for oral healthcare applications marked a pivotal moment in the integration of laser technology into dentistry [8,9].
Laser therapy operates by interacting with dental tissues and cells through photons, a process known as photobiomodulation [10,11]. Lasers can be delivered in pulsed or continuous wave modes, often using optical fibres for precision [12]. This technology holds promise for improving the effectiveness and accuracy of endodontic treatments, leading to enhanced patient outcomes.
Lasers exhibit diverse properties and advantages, making them applicable to various dental procedures. Their capabilities in debridement, tissue removal, inflammation reduction and wound healing have led to their use across different wavelengths, such as Erbium-doped Yttrium-aluminum-garnet (Er:YAG) and diode, and power settings [13]. The focused and amplified light energy effectively interacts with dental hard and soft tissues, allowing precise access to root canal spaces [13-15].
Studies have shown that lasers can influence pain perception by modulating the release of endorphins, prostaglandins and histamine [16,17]. Laser-activated irrigation, a technique involving the use of lasers to enhance the cleaning of root canals, is another area of active research [18,19]. Commonly used laser types in endodontics include Neodymium:YAG (Nd:YAG), diode, Erbium:YAG (Er:YAG), Erbium Chromium:Yttrium, Scandium, Gallium and Garnet (Er,Cr:YSGG) and Helium:Neon (He:Ne) lasers [20].
Laser technology remains a central focus in endodontic research, with numerous studies exploring its diverse applications in modern clinical practice. The present narrative review was aimed to comprehensively map the existing literature on the various uses of lasers in contemporary endodontics.
Materials and Methods
The present narrative review synthesises the existing literature on the various applications of lasers in contemporary endodontic practices. A comprehensive exploration of relevant studies was undertaken to gain a detailed understanding of the potential uses of Light Amplification by Stimulated Emission of Radiation (LASER) in endodontics. A thorough literature search was conducted across five major databases (PubMed, Scopus, Google Scholar, Elton Bryson Stephens Company (EBSCO), and the Cochrane Controlled Register of Trials) to identify relevant studies on the role of lasers in endodontics. After removing duplicates and conducting a meticulous review of titles and abstracts, twenty-one articles were included in this narrative review.
The review covers a broad range of sources, including randomised controlled trials and in-vitro studies published in English over the last decade. The literature search focused on two primary concepts: laser and endodontics. Articles were selected based on their relevance to specific MeSH terms, keywords, and associated topics such as minimally invasive dentistry, laser therapy, endodontic treatment, postoperative pain management, root canal treatment, irrigation, sterilisation, tissue healing, dentinal hypersensitivity, pulp capping and pulpotomy. Studies that provided significant insights into these areas were included in the review.
Data from the selected studies were meticulously extracted by the author, who recorded key information such as the author’s name, year of publication, country of origin, study objective, design, comparison parameters, assessment tools and outcomes. This structured approach allowed for a comprehensive analysis of the diverse applications of lasers in endodontics.
Results
Postoperative Pain
The available evidence suggests that laser therapy is effective in reducing postoperative pain following endodontic procedures [21-31]. While the majority of studies employed diode lasers [21,22,24-29], other laser types, such as Nd:YAG [31] and Er:YAG [23], have also shown promising results. Although the specific mechanisms underlying pain reduction remain to be fully elucidated, the consistent findings across multiple studies support the potential benefits of laser therapy in this area [Table/Fig-1] [21-31].
Studies evaluating effects on post-endodontic pain by lasers [21-31].
| Author/country | Study design/sample size | Experimental agent (laser) | Comparator agent | Outcome | Conclusion |
|---|
| Ismail HH et al., Egypt [26] | RCT/180 | Low-level Laser Therapy (LLLT): diode laser, 10 Hz, 980 nm, 15 WCWLaser-activated Irrigation (LAI)-diode laser, Frequency=100 Hz, wavelength=980 nm and power=2.5 W | Mock laser | Visual analogue scale | After 24 hours, LLLT (median pain score=2) was found superior to LAI (median pain score=3) and the control group (median pain score=4) in controlling post-endodontic pain, equal effectiveness was observed after 48 hours. |
| Fazlyab M et al., Iran [24] | RCT/36 | Diode laser, 980 nm, 6.89 W/cm2, 0.5 W power, and a tip diameter of 10 mm | Placebo (Laser not activated) | Visual analogue scale | The laser group showed a mean pain score of 0.22 after 24 hours whereas it was 0.72 in the control group. |
| Tunc F et al., Turkey [31] | RCT/102 | 200-μm fiber attached.1064 nm Nd:YAG laser, 1 W, 100 mJ/s, 15 Hz940 nm diode laser, 100 mJ/s, 15 Hz | Traditional chemo-mechanical preparation | Visual analogue scale | Nd:YAG laser group showed the lowest mean pain score at the end of the study in vital teeth; the difference in pain score was insignificant among non vital teeth. After 24 hours, Nd: YAG group showed a mean score of 0.3. |
| Kaplan T et al., Turkey [27] | RCT/60 | Diode laser, 980 nm, 50 Hz, 2.4 W, 12 J pulsed mode with each pulse of a duration of 20 μs | Chemo mechanical root canal preparation | Visual analogue scale | The laser group showed lower pain levels than the control group after 24 hours and 48 hours. |
| Aggarwal A and Dewan R, India [21] | RCT/36 | Diode laser, 940 nm, 70 J/cm2, 0.8 W, continuous mode | Mock laser therapy (placebo) | Visual analogue scale | Canal disinfection and periapical stimulation were found to have equal effects (mean pain score 0.08±0.28), and both produced better results than the placebo group. |
| Naseri M et al., Iran [29] | RCT/75 | 808 nm, 100 mW, 600 μm diameter fiber | Placebo (Mock laser therapy) | Visual analogue scale | Buccal and lingual radiation of laser showed the lowest mean pain score of 1.6, 48 hours after treatment. |
| Dagher J et al., Lebanon [23] | RCT/56 | Er:YAG laser, 2940 nm, 20 mJ, 15 Hz, 0.3 W, 50 μs pulse duration | Sodium hypochlorite irrigation | Visual analogue scale | Both the methods of irrigation did not significantly differ from each other. |
| Nunes EC et al., Brazil [30] | RCT/70 | Indium-gallium-aluminum laser, 808 nm, 100 mW, continuous mode | Ibuprofen 600 mg | Numerical rate scale and verbal rate scale | The outcome was superior in the laser group. |
| Morsy DA et al., Egypt [28] | RCT/56 | Diode laser, 980 nm, 1.2 W, pulsed mode | Conventional endodontic treatment | Numerical rating scale | Lower pain scores were observed in the laser group in comparison with the endodontic group at 6,12,24,48 hours and 7 days (p-value <0.05). |
| Genc Sen O and Kaya M, Turkey [25] | RCT/84 | Diode laser, 940 nm, 200-lm fiber tip, 1 W, continuous mode | Placebo (mock application of laser) | Numeric rating scale for pain assessment | The laser group exhibited a mean pain score of 0.22 while the placebo group showed a higher score of 0.72. |
| Arslan H et al., Malaysia [22] | RCT/36 | Diode laser, 970±15 nm, 14 W | Placebo (mock LLLT) | Visual analogue scale | The mean postoperative pain in the laser group after 24 hours was 17.94 and after 7 days was 0.56. |
Antibacterial Effects
Laser therapy has demonstrated antimicrobial properties, making it a potential adjunct to traditional endodontic treatment. While diode lasers were predominantly used in the reviewed studies, the limited number of investigations restricts definitive conclusions. Morsy DA et al., and Wenzler JS et al., compared lasers with traditional endodontic treatment protocols [28,32]. While the study by Camacho-Alonso F et al., compared traditional endodontic treatment protocols with chitosan [33]. All studies reported a reduction in bacterial load associated with laser treatment [Table/Fig-2] [12,28,32,33]. However, the precise mechanisms and long-term efficacy require further exploration.
Description of studies assessing the anti-bacterial effects of lasers [12,28,32,33].
| Author/country | Study design/sample size | Experimental agent (laser) | Comparator agent | Outcome | Conclusion |
|---|
| Wenzler JS et al., Switzerland [32] | RCT/57 | Diode laser, 445 nm, 0.59 W, continuous mode | Sodium hypochlorite rinsing | Microbiological analysis of bacterial load | Sodium hypochlorite rinsing alone showed a bacterial load reduction of 80.5%. Laser group exhibited a reduction of 58.2%, and the combination produced the highest reduction of 92.7%. |
| Morsy DA et al., Egypt [28] | RCT/56 | Diode laser, 980 nm, 1.2 W, pulsed mode | Conventional endodontic treatment | Bacterial count | The average bacterial count (aerobic and anaerobic) in the laser group was found to be 13.678 and 8.75 respectively which was less than the control group. |
| Camacho-Alonso F et al., Spain [33] | In-vitro study/102 | 660 nm, 100 mW | Chitosan | Colony forming units (CFU/mL) of Enterococcusfaecalis | The mean bacterial count was 3.81 in the group subjected to laser therapy compared to 4.47 in the Chitosan group. |
| Asnaashari M et al., Iran [12] | In-vitro study/50 tooth specimens | Diode lasers, 810 and 980 nm, 0.5 W to 7 W | - | E. faecalis Colony Forming Units (CFU) | Irradiation of both 810 and 980 nm lasers significantly decreased the E. faecalis count in the root canal system; the 810 nm laser was more effective. |
Tissue Healing Effects
Martins MR et al., (2013) and Verma A et al., (2020) compared laser irradiation with traditional irrigation techniques, such as sodium hypochlorite and ultrasonic irrigation [8,34]. The results of these randomised controlled trials are comparable to those of existing irrigation techniques. Overall, the current body of research does not support a definitive conclusion regarding the efficacy of laser therapy in promoting tissue regeneration within root canals [Table/Fig-3] [9,34].
Description of studies assessing the healing effect of lasers [9,34].
| Author/country | Study design/sample size | Experimental agent (laser) | Comparator agent | Outcome | Conclusion |
|---|
| Verma A et al., India [9] | RCT/69 | Nd:YAG laser, 1.5 W, 15 Hz pulsed mode | Ultrasonic irrigation | Clinical assessment and CBCT-PAI score | Healing was shown by about 42.1% in the laser group compared to 36.8% in the group subjected to ultrasonic irrigation. |
| Martins MR et al., Portugal [34] | RCT/36 | Radial Firing Tip (RFT)-2, 140 μs, 37.5 mJ, 20 HzRFT-3 duration=140 μs, 62.5 mJ, 20 Hz | 3% sodium hypochlorite | Change in bone density using periapical index | Both the groups gave similar outcomes. |
CBCT-PAI: Cone beam computed tomography periapical index
Smear Layer Removal
Few in-vitro studies have been conducted, utilising scanning electron microscopy and tooth section images for assessment [35-37]. The results varied; one study advocated for a combination of laser, NaOCl, and Ethylenediamine Tetraacetic Acid (EDTA) to improve smear layer removal efficacy [37]. While another study favoured the NaOCl and EDTA combination over laser techniques for smear removal [Table/Fig-4] [35-37].
Description of studies assessing smear layer removal from root canal [35-37].
| Author/country | Study design/sample size | Experimental agent (laser) | Comparator agent | Outcome | Conclusion |
|---|
| Passalidou S et al., Belgium [35] | In-vitro study/50 mandibular molars | Er:YAG laser, 2.940 nm, conical 400 and 600 mm diameter fibre to activate the irrigant. 20 mJ, 20 Hz, 50 microseconds | Manual dynamic and passive ultrasonic irrigation | Tooth section images | Smear removal was better than control but similar to passive ultrasonic irrigation. |
| Wang X et al., China [37] | In-vitro study/100 mandibular premolar specimens | Er,Cr:YSGG laser, 2780 nm, 25 mJ, 50 Hz, 1.25 W, 24% air, 60 ls pulse duration, closed water spray. Two conical fiber tips, RFT2 and RFT3. | Conventional irrigation using sodium hypochlorite and EDTA | Scanning electron microscopy analysis | LAI+NaOCl+EDTA combination was found to be the most effective in removing the smear layer from the root canal wall. |
| Shahriari S et al., Iran [36] | In-vitro study/60 mandibular teeth specimens | Nd:YAG laser, 1064 nm, 1 W, 50 mJ/pulse, 20 Hz, 100 μs | Conventional irrigation using sodium hypochlorite and EDTA | Scanning electron microscopy analysis | 5% NaOCl LAI significantly showed more efficiency in smear layer removal than 1% NaOCl LAI and 2.5% NaOCl LAI. |
LAI: Laser-activated irrigation
Sealer Cement Penetration
A couple of in-vitro studies have assessed sealer cement penetration [38,39]. The efficacy of lasers in enhancing sealant penetration into dentinal tubules, and thus reducing the likelihood of microleakage, has yielded inconsistent results across different sealer cements, indicating the need for further investigation in this area [Table/Fig-5] [38,39].
Description of studies assessing cement penetration following laser irradiation [38,39].
| Author/country | Study design/sample size | Experimental agent (laser) | Comparator agent | Outcome | Conclusion |
|---|
| Jardim Del Monaco R et al., Brazil [38] | In-vitro study/40 mandibular premolars | Nd:YAG laser; 1064 nm, 1.5 W, 15 Hz, 100 mJ, 150 μs pulse duration. | Conventional obturation with sealer | Confocal laser scanning microscopy analysis | Laser-induced penetration of bio-ceramic sealer showed a higher perimeter of penetration than the control group. This was however observed at a depth of 5 mm only. |
| Moura-Netto C et al., Brazil [39] | In-vitro study/168 tooth specimens | Nd:YAG laser, 1.5 W, 100 mJ, 15 Hz)Diode laser: 2.5 WCW and Er:YAG laser: 1 W, 100 mJ, 10 Hz. | Placebo (no laser) | Environmental scanning electron microscope images | Better penetration of hydrophobic epoxy resin cement was not favourable in the case of other resin sealers. |
Discussion
Managing post-endodontic pain presents a longstanding challenge for endodontists, prompting significant research into the potential of lasers to alleviate this discomfort. Studies in conventional laser endodontics, employing diode, Nd:YAG, Er:YAG and Indium-gallium-aluminum lasers, consistently report positive outcomes, demonstrating a significant reduction in post-endodontic pain compared to control groups [21-31].
Notably, diode lasers exhibit a marked decrease in pain levels at 24 hours and 48 hours post-treatment, attributed to their antibacterial properties [21,25,27,28]. The efficacy of Nd:YAG lasers can be linked to their impact on the C fibres of the periodontal ligament, effectively suppressing pain. However, in the case of non vital teeth, Nd:YAG lasers were found to be less effective than diode lasers, as demonstrated by Tunc F et al., [31]. Additionally, Er:YAG lasers utilising the Photon-induced Photoacoustic Streaming (PIPS) protocol significantly reduce postoperative pain but do not surpass the efficacy of sodium hypochlorite irrigation, as observed in the study by Dagher J et al., [23]. Nunes EC et al., utilised an Indium-gallium-aluminium laser employing photobiomodulation therapy, which increases local surface temperature, circulation, cellular respiratory processes, and metabolism, ultimately enhancing healing and pain management [30].
All studies incorporating Low-level Laser Therapy (LLLT) demonstrated a significant reduction in post-endodontic pain [22,24,26,29]. However, Ismail HH et al., reported no difference in pain reduction between LLLT and light-activated irrigation [26]. LLLT functions by inhibiting the release of inflammatory mediators from affected tissues, inducing vasodilation, and enhancing the metabolism of injured tissues, thereby resulting in diminished post-treatment pain. Moreover, LLLT was associated with lower mean pain scores compared to conventional laser applications.
Despite the overall effectiveness of LLLT, patients with symptomatic irreversible pulpitis exhibited a mean pain score of 1.6 even after 48 hours, though this reduction was superior to the placebo group, as observed by Naseri M et al., [29]. Similarly, in cases of root canal retreatment, the efficacy of LLLT in reducing post-endodontic pain was lower but still superior to the placebo group, according to Arslan H et al., [22]. These findings suggest that chronic lesions may require a longer duration to heal completely, even with the use of laser technology, highlighting the need for further research in the field of LLLT to enhance pain relief in chronic lesions.
Four studies investigating the antibacterial effects of diode laser irradiation were included in the present review, all of which demonstrated a reduction in bacterial load [12,30,32,33]. In the study by Wenzler JS et al., it was noted that over 90% bacterial count reduction occurred only when laser irradiation was combined with sodium hypochlorite irrigation [32]. Laser therapy alone resulted in approximately a 50% reduction. Notably, laser therapy proved effective in cases of necrotic teeth with chronic periapical lesions, showing a greater reduction in anaerobic bacteria compared to aerobic microbes.
Furthermore, when assessing the effect of different wavelengths on endodontic microflora, Asnaashari M et al., found that a laser with a wavelength of 810 nm was more effective [12]. These findings underscore the potential of diode laser therapy in reducing bacterial load in endodontic procedures, particularly when combined with adjunctive irrigation methods and utilising specific wavelengths tailored to optimise antibacterial efficacy.
Light-activated irrigation demonstrated superior efficacy in tissue healing compared to passive ultrasonic irrigation, which is attributed to its enhanced disinfection effects [8]. Given the escalating global antimicrobial resistance, the healing properties of laser-activated irrigation are particularly significant, as they could potentially reduce the reliance on chemical solutions and systemic antibiotics associated with conventional treatments.
However, Martins MR et al., reported no significant difference between sodium hypochlorite and Er,Cr:YSGG laser with endodontic Radial Firing Tips (RFT) in terms of tissue healing [34]. The study concluded that lasers were non inferior to traditional sodium hypochlorite irrigation in promoting bone healing. These findings highlight the potential of laser-activated irrigation as a viable alternative for promoting tissue healing, with implications for reducing antimicrobial resistance and minimising reliance on conventional chemical solutions and antibiotics.
Light-activated irrigation utilising Er:YAG and Er,Cr:YSGG lasers in conjunction with sodium hypochlorite and EDTA has proven to be highly effective in removing the smear layer from root canal walls. Interestingly, radiation without an irrigant also demonstrated efficacy in smear layer removal, albeit resulting in rougher root canal walls. However, when combined with irrigants, lasers enhanced the diffusion ability of sodium hypochlorite and EDTA, leading to superior smear removal and a synergistic effect of all three components. This improved diffusion capability ensured access to the apical third of the canals, thereby enhancing treatment outcomes. Notably, no significant difference was observed between Er:YAG and Er,Cr:YSGG lasers when combined with sodium hypochlorite, EDTA, or a combination of both [37].
In contrast, Shahriari S et al., reported better results with conventional irrigant treatment compared to laser-activated irrigation using sodium hypochlorite alone, underscoring the importance of combining lasers with chemotherapy (sodium hypochlorite+EDTA) for effective smear removal [36]. Another noteworthy alternative is canal irrigation using Er:YAG lasers employing the PIPS protocol. Erbium lasers emit radiation that is highly absorbed by water-based root canal irrigants. This laser irradiation leads to the formation of vapor bubbles at the fibre tip, inducing significant fluid movement within the canal, generating shock waves at the point of collapse, and creating secondary cavitation, ultimately facilitating acoustic streaming and smear removal [35].
Proper sealing of dentinal tubules to prevent microleakage is a crucial objective in endodontic practice. Achieving this goal requires optimal penetration of root canal cement into the tubules. Nd:YAG and diode lasers have demonstrated reduced leakage and increased penetration of hydrophobic epoxy resin cement and bioceramic sealers following irradiation [39]. This enhanced penetration may result from the melting and resolidification of dentin, which leads to the occlusion of dentinal tubules. This process reduces the permeability of canal walls and decreases dentin hydration, thereby improving sealing capacity. However, Nd:YAG lasers have been associated with negative sealant capability for EndoREZ and Epiphany SE sealers due to hydration loss.
Similarly, Er:YAG lasers have reduced the penetration index of resin sealers by degrading collagen fibres, thereby compromising sealant hybridisation [38,39]. Additionally, Nd:YAG lasers have demonstrated superior penetration of bioceramic cement only at a depth of 5 mm. This may be attributed to the increasing number, advancing diameter and uniform distribution of dentinal tubules at this depth [38].
The use of lasers in endodontics has shown considerable promise in various aspects of treatment, including postoperative pain management, antibacterial effects, smear layer removal, tissue healing and dentinal tubule sealing. With advancements in laser technology and a deeper understanding of their mechanisms of action, the integration of lasers into routine endodontic practice is expected to increase.
One area of future development lies in optimising laser parameters and protocols to further enhance treatment outcomes. Research should focus on refining laser settings, such as wavelength, energy density and pulse duration, to maximise efficacy while minimising adverse effects. Additionally, investigations into novel laser delivery systems and techniques, such as photodynamic therapy and laser-activated irrigation, hold the potential to improve treatment efficacy and efficiency.
Furthermore, the combination of lasers with conventional endodontic techniques, such as irrigation solutions and root canal obturation materials, could lead to synergistic effects, enhancing disinfection, smear layer removal and dentinal tubule sealing. Future studies should explore optimal combinations and sequences of laser and chemo-mechanical treatments to achieve superior clinical outcomes.
Limitation(s)
While the present review aimed to comprehensively explore the applications of lasers in contemporary endodontic practices, several limitations should be acknowledged. Despite efforts to conduct a thorough search across electronic databases, the scope may have been restricted due to limitations in search terms or databases utilised, potentially resulting in the omission of relevant studies. Moreover, the review may have been subject to publication bias, as it primarily included published articles, potentially overlooking insights from unpublished studies or grey literature. Variations in the methodology of included studies may also pose a challenge, impacting the interpretation of results. Additionally, the review was constrained by language bias, focusing primarily on articles published in English and excluding studies published in other languages. Furthermore, the review’s time constraints, limited to articles published between 2013 and 2023, may have overlooked recent advancements in the field. Given the heterogeneity of the included studies, drawing definitive conclusions or generalising findings may be challenging. Moreover, the absence of quantitative synthesis (meta-analysis) limits the ability to assess the effects of laser applications in endodontics comprehensively.
Conclusion(s)
Innovative approaches, such as LLLT for pain management and tissue healing, offer promising directions for future research and clinical use. Further investigation into laser mechanisms, including interactions with dental tissues and microbial biofilms, will enhance our understanding and aid in the development of targeted therapies. Additionally, integrating laser technologies into endodontic education and training programs will ensure practitioners’ proficiency. As evidence of laser efficacy and safety in endodontics accumulates, widespread adoption in clinical practice is anticipated, leading to improved treatment outcomes and increased patient comfort.