Role of lasers in endodontics - A review

Transcription

1 Review Article Role of lasers in endodontics - A review M. Christopher Joel Simon 1, S. Pradeep 2, Revathi Duraisamy 3, M. P. Santhosh Kumar 4 * ABSTRACT A laser is a device which transforms light of various frequencies into a chromatic radiation in the visible, infrared, and ultraviolet regions with all the waves in phase capable of mobilizing immense heat and power when focused at close range. The purpose of this paper is to summarize laser applications in endodontics, including their use in pulp diagnosis, dentinal hypersensitivity, pulp capping and pulpotomy, sterilization of root canals, root canal shaping and obturation, and apicectomy. The effects of laser on root canal walls and periodontal tissues are also reviewed. This article also discusses whether a laser can provide equal or improved treatment over conventional care. KEY WORDS: Dentin hypersensitivity, Endodontic lasers, Lasers, Pain reduction, Pulp diagnosis INTRODUCTION Laser is a kind of electromagnetic irradiation source, having particular and exclusive properties. The word LASER is an abbreviation for light amplification by stimulated emission of radiation. [1] Classification of Lasers Based on Power High power, warm, or hard laser Lasers with moderate powers Low level or cold lasers. Classification of Lasers Based on Wavelength Ultraviolet (UV) range nm Visible light range nm Near-infrared (NIR) range nm Far-infrared range more than 1200 nm. Classification of Lasers Based on Source Material Gas lasers such as CO2, Ne, and He Liquid lasers such as dye lasers Solid lasers such as ruby lasers Semiconductor lasers such as GaAllnP, GaALAs, and GaAs. Access this article online Website: jprsolutions.info ISSN: During the past decade, there has been immense activity in the field of semiconductor lasers. Long wavelength lasers have now reached the developmental stage and are being used in high-speed optical fiber communications throughout the world. The use of lasers in dentistry has increased over the past few years. The first laser was introduced into the fields of medicine and dentistry during the 1960s. Since then, this science has progressed rapidly. Due to their many advantages, lasers are indicated for a wide variety of procedures. Conventional methods of cavity preparation with low- and high-speed handpieces involve noise, uncomfortable vibrations and stress for patients. Although pain may be reduced by local anesthesia, fear of the needle, noise, and vibration of mechanical preparation remain the causes of discomfort. These disadvantages have led to a search for new techniques as potential alternatives for dental hard tissue removal. Lasers are used to treat various conditions in dentistry. The use of laser needs minimum anesthesia and is time saving for patients. Sometimes, it is used as an adjunctive besides other treatments (with drugs, surgery, and physiotherapy) and sometimes as the principal treatment. It is the anti-inflammatory, analgesic, and biostimulative regeneration effects of laser which causes the reestablishment of tissue normal physiologic state. [1] 1 Department of Conservative Dentistry and Endodontics, Saveetha Dental College, Saveetha University, Chennai, Tamil Nadu, India, 2 Department of Conservative Dentistry and Endodontics, Saveetha Dental College, Saveetha University, Chennai, Tamil Nadu, India, 3 Department of Prosthodontics, Saveetha Dental College, Saveetha University, Chennai, Tamil Nadu, India, 4 Department of Oral and Maxillofacial Surgery, Saveetha Dental College, Saveetha University, Chennai, Tamil Nadu, India *Corresponding author: Dr. M. P. Santhosh Kumar, Saveetha Dental College and Hospital, Saveetha University, 162, Poonamallee High Road, Velappanchavadi, Chennai , Tamil Nadu, India. Phone: santhoshsurgeon@gmail.com Received on: ; Revised on: ; Accepted on:

2 History of Lasers The first experiment with lasers in dentistry was reported in a study about the effects of a pulsed ruby laser on human caries. Further work in the 1970 s focused on the effects of neodymium (Nd) and carbon dioxide (CO2) lasers on dental hard tissues. The first laser, synthetic ruby laser was invented by Theodore Maiman in Golman, Stern, and Sognnaes described the effect of ruby laser on dentin and enamel in [2] Early researchers found that CO2 lasers produced cracking and disruption of enamel rods, incineration of dentinal tubule contents, and excessive loss of tooth structure, carbonization, fissuring, and increased mineralization caused by the removal of organic contents. It was also reported that the use of the CO2 laser was unfavorable because of the loss of the odontoblastic layer. Therefore, it was concluded that, unless heat-related structural changes and damage to dentinal tissues could be reduced, laser technology could not replace the conventional dental drill. Further advances in laser technology, however, have identified acceptable biologic interactions. Furthermore, more education about dental lasers should be added to the curriculum of the undergraduate program since it is highly essential for students to know about newer technologies and apply it in their practice. [2] APPLICATIONS OF LASERS IN ENDODONTICS Prevention of Dental Caries Several studies examined the possibility of using laser to prevent caries. It is believed that laser irradiation of dental hard tissues modifies the calcium-to-phosphate ratio, reduces the carbonate-to-phosphorous ratio, and leads to the formation of more stable and less acid soluble compounds, reducing susceptibility to acid attack and caries. Laboratory studies have indicated that enamel surfaces exposed to laser irradiation are more acid resistant than non-laser treated surfaces. [3] The degree of protection against caries progression provided by the one-time initial laser treatment was reported to be comparable to daily fluoride treatment by a fluoride dentifrice. The threshold ph for enamel dissolution was reportedly lowered from 5.5 to 4.8, and the hard tooth structure was 4 times more resistant to acid dissolution. However, the actual mechanism of acid resistance by laser irradiation is still unclear, and studies, particularly in vivo, to test those claims are required. Dentin Hypersensitivity (DH) DH happens as a short and sharp pain from naked dentin in response to various stimuli. To treat DH, different antisensitivity substances are used. The prevalence of DH varies widely, depending on the mode of investigation. Potassium-containing toothpastes are the most widely used at-home treatments. Most in-office treatments employ some form of barrier, either a topical solution or gel or an adhesive restorative material. The reported efficacy of these treatments varies, with some having no better efficacy than the control treatments. [4] Since the development of the ruby laser by Maiman in 1960, to date, four types of lasers have been used for the treatment of dentine hypersensitivity, and the effectiveness ranged from 5.2 to 100%, which was dependent on the laser type and parameters used. [5] The mechanism involved in laser treatment of dentine hypersensitivity is relatively unknown. In more complicated cases such as reversible pulpitis, it is possible to use laser energy for improved results. Low-level laser (LLL) irradiation of cervical and apical region of sensitive teeth can be an appropriate treatment to eliminate sensitivity. Effect of this laser is based on changes created on pulp nerve transmission. It is possible to relate laser effect at the cell level to the prevention of the signal transmission of pain from peripheral to central parts as well as blocking of the depolarization of sensory C fibers. [6] Pulpal Diagnosis Vascular supply is the most accurate marker of pulp vitality. Tests for assessing vascular supply that relies on the passage of light through a tooth have been considered as possible methods for detecting pulp vitality. Laser Doppler flowmetry (LDF) is a noninvasive, objective, painless, semiquantitative method that has shown to be reliable for measuring pulpal blood flow. [7] LDF which was developed to assess blood flow in microvascular systems can also be used for the diagnosis of blood flow in the dental pulp. This technique uses helium-neon and diode lasers at a low power of 1 or 2 mw. The laser beam is directed through the crown of the tooth to the blood vessels within the pulp. Moving red blood cells causes the frequency of the laser beam to be Doppler shifted and some of the light to be backscattered out of the tooth. The reflected light is detected by a photocell on the tooth surface, and its output is proportional to the number and velocity of the blood cells. [8] The main advantage of this technique, in comparison with electric pulp testing or other vitality tests, is that it does not rely on the occurrence of a painful sensation to determine the vitality of a tooth. Moreover, teeth that have experienced recent trauma or are located in part of the jaw that may be affected following orthognathic surgery can lose sensibility while intact blood supply and pulp vitality are maintained. It was reported that 21% of teeth in patients who did not respond to electrical stimulation following Le Fort I 1882

3 operations showed an intact blood supply when tested with LDF. Diagnosis of the vitality of these pulps based mainly on electric pulp testing would have resulted in needless endodontic therapy. [9] LDF has some limitations. It may be difficult to obtain laser reflection from certain teeth. In general, the anterior teeth, in which the enamel and dentin are thin, do not present a problem. Molars, with their thicker enamel and dentin, and the variability in the position of the pulp within the tooth may cause variations in pulpal blood flow. [10] Furthermore, differences in sensor output and inadequate calibration by the manufacturer may dictate the use of multiple probes for accurate assessment. LDF assures objective measurement of pulpal vitality. When equipment costs decrease and clinical application improves, this technology could be used for patients who have difficulties in communicating or for young children whose responses may not be reliable. [11] Management of Post-Endodontic Treatment Pain Patient may sometimes experience pain the day after endodontic treatment. This is particularly common after the treatment of chronic complaints. This can be managed by LLL therapy (LLLT). LLLT includes light-emitting diodes and other light sources. The range of wavelength used now includes many in the red and NIR. Each wavelength has a unique interaction with the target tissues of the oral cavity. It is effective for reducing pain and inflammation after endodontic treatment and can be used as a diagnostic tool for pulp hyperemia. Laser irradiation increases circulation, and thus, a patient will feel a sharp pain when the laser is applied to a tooth with a hyperemic pulp. In trials that were studied, LLLT within the suggested dose range was administered to the acutely injured knee, temporomandibular, or zygapophyseal joints, and satisfactory healing was observed. Furthermore, the results showed a mean weighted difference in change of pain on VAS of 29.8 mm (95% CI, 18.9 to 40.7) in favor of the active LLLT groups. [12] Global health status improved for more patients in the active LLLT groups (relative risk of 0.52; 95% confidence interval ). LLLT with the suggested dose range significantly reduces pain and improves health status in chronic joint disorders, but the heterogeneity in patient samples, treatment procedures, and trial design call for cautious interpretation of the results. In a study, LLL was used to decrease the pain after one session treatment. LLLT seems to be an effective and non-pharmacological approach for the reduction of post-endodontic treatment pain. [13] LLLs refer to the use of red-beam or near-infrared lasers with a wavelength between 600 and 1000 nm power from 5 to 500 mw. In contrast, lasers used in surgery typically are of 300 W. These lasers are nonthermal. Although the exact mechanism of its effect is unknown, it is theorized that, due to the low absorption by human skin, the laser light can penetrate deeply into the tissues where it has a photobiostimulation effect. The therapy performed with such lasers is often called LLLT, and the lasers are called therapeutic lasers. Light in infrared spectrum at specific wavelength penetrates the tissue and is absorbed where the light energy is converted into biochemical energy, restoring normal cell function. [13] Currently, LLLT is practiced as part of physical therapy in many parts of the world. In fact, light therapy is one of the oldest therapeutic methods used by humans. LLLT may reduce pain related to inflammation by lowering, in a dose-dependent manner, levels of prostaglandin E2, prostaglandinendoperoxide synthase 2, interleukin 1-beta, tumor necrosis factor-alpha, the cellular influx of neutrophil granulocytes, oxidative stress, edema, and bleeding. The appropriate dose appears to be between 0.3 and 19 J/cm 2. Other theory proposed is the Neural inhibition as a mechanism of pain relief, which is widely accepted. [14] Root Canal Sterilization The long-term success of an endodontic therapy often fails due to remaining bacteria in the root canal or dentin tubules, which cannot be sufficiently eliminated through the classical root canal preparation technique or through rinsing solutions. Laser light which penetrates up to > 1000 μm into the dentin has scope for complete canal sterilization. The laser is an effective tool for killing microorganisms because of the energy and wavelength characteristics. Infected root canals are an indication for this laser treatment, but its application in extremely curved and narrow infected root canals appears difficult. Numerous studies have documented that CO2, neodymium: yttrium aluminum garnet (Nd: YAG), argon, Xe-Cl (308 nm), erbium, chromium: yttrium scandium gallium garnet (Er, Cr: YSGG), and erbium: yttrium aluminum garnet (Er: YAG) laser irradiation has the ability to kill the bacteria, remove debris, and smear layer from the root canal walls following biomechanical instrumentation. However, lasers which can be delivered through extremely fine flexible fiber optic systems and which can penetrate dentin to a depth that can eliminate bacteria are applicable. This particularly includes lasers in the NIR region. [15] The application of excimer lasers in dentistry for the treatment of dental root canals is reported in studies. High-energy UV radiation emitted by a XeCl excimer laser (308 nm) and delivered through suitable optical fibers can be used to remove residual organic tissue from the canals. To this aim, UV ablation thresholds of dental tissues have been measured, showing a Drug Invention Today Vol 10 Issue

4 preferential etching of infiltrated dentin in respect to healthy dentin, at laser fluencies of J/cm 2. This technique has been tested on extracted tooth samples, simulating a clinical procedure. Fibers of decreasing core diameters have been used to treat different sections of the root canal down to its apical portion, resulting in an effective, easy, and fast cleaning action. [16] Furthermore, the application of cold plasma in sterilization of a root canal of a tooth has recently attracted great attention. A reliable and user-friendly plasma-jet device, which can generate plasma inside the root canal, is reported. The plasma can be touched by bare hands and can be directed manually by a user to place it into root canal for disinfection without causing any painful sensation. When He/O2 (20%) is used as working gas, the rotational and vibrational temperatures of the plasma are about 300 K and ma. Preliminary inactivation experiment results show that it can efficiently kill Enterococcus faecalis, one of the main types of bacterium causing failure of root canal treatment in several minutes. [17] Laser-activated Irrigation (LAI) LAI with an erbium laser has been introduced as a method for activating the irritant. The effect is based on cavitation; in water, activation of the laser at subablative settings may result in the formation of large elliptical vapor bubbles, which expand and implode. These vapor bubbles may cause a volumetric expansion of 1600 times the original volume, which increases pressure and drives fluid out of the canal. When the bubble implodes after µs, an underpressure develops and sucks fluid back into the canal, inducing secondary cavitation effects. Therefore, the laser works as a fluid pump. Another technique, passive ultrasonic irrigation (PUI), is also based on the principle of cavitation and acoustic streaming. The ultrasonic activation of irritants, therefore, plays a pivotal role in contemporary endodontics. [18] The removal of dentin debris from the root canal using LAI has been investigated in only two studies. Both studies, Er, Cr: YSGG laser (2780 nm) and with an Er: YAG laser (2940 nm), have shown that LAI is significantly more effective in removing dentin debris from the apical part of the root canal than PUI or hand irrigation when the irrigant was activated for 20 s. It remains unknown whether the use of PUI for more than 20 s is as effective as 20 s of LAI. It is also unclear if there is a difference between the efficacy of LAI performed with an Er: YAG laser and Er, Cr: YSGG laser. [19] Pediatric Endodontics The goal of pediatric dentistry is to educate both children and parents about prevention to reduce dental pathologies in early and late childhood as well as in adolescence. The common objective is tissue preservation (preferably by preventing disease and intercepting its progress), which means performing treatment with as little tissue loss as possible. With the new techniques available (digital radiology with low radiation emission, diagnostic laser, and the dental operative microscope), we can aim for both an early diagnosis and a minimally invasive therapy using ozone therapy, air abrasion, rotary instruments for micropreparation, and the lasers. Children are the first in line to receive dental laser treatment, and based on the micro dentistry motto filling without drilling, it is agreed that laser-supported dental diagnosis and treatment are crucial for treating children successfully. [20] The idea of substituting a drill with a laser light has led to its introduction in dentistry. Besides being more accepted to patients, in pediatric dentistry, the laser has demonstrated safety compared with rotating instruments. Laser caries detection demonstrated a good reproducibility, reliability, and predictability to monitor the caries process over time. Erbium lasers have been found to be efficient for caries removal, tooth cleaning, and decontamination. The laser erbium technology represents a safe device to effectively and selectively remove carious tissues from decayed teeth. For children, all the recognized advantages of this technique play a decisive role in the successful dayto-day treatment of dental caries. [21] Detection of Dental Caries This is the application of laser most frequently and extensively investigated in pediatric dentistry. Of the 79 papers indexed under laser paediatric dentistry in the PubMed as of July 31, 2008, 31 studied the use of laser fluorescence (LF) for carious detection. This non-ablative laser emits fluorescence light, visible in the red spectrum at 655 nm (LF), which proved useful as an additional method for occlusal caries detection. Several studies compared different caries detection methods: Visual inspection alone, visual inspection with magnification, bite-wing X-ray, and LF and described the usefulness of LF in carious detection process. A study stated that LF could be used as an additional tool in the detection of occlusal caries in deciduous teeth, and its good reproducibility should enable monitoring of the carious process over time. [21] Nausea Management Nausea is one of the most common problems during dental treatments. Laser therapy can be used to reduce nausea during stages of root canal therapy and radiography. Some clinicians use acupuncture to reduce nausea. It is possible to use laser instead of special needles. For this purpose, at least 2J of energy is used in the hand wrist area and P6 Meridian point. Application of this method was accompanied with success in many patients. [22] 1884

5 Photo-activated Disinfection (PAD) of Root Canal As microorganisms play a crucial role in the development of pulpal and periapical disease, the prognosis of endodontic therapy is intimately related to the presence of bacteria within the root canal system. Microorganisms may persist in the apical region of the root canal system despite chemomechanical preparation. The usefulness of Class IV lasers (such as Nd: YAG, diode, potassium titanyl phosphate [KTP], and Er: YAG) for photothermal disinfection of the root canal has been demonstrated in numerous studies. [23] The antibacterial action of Er: YAG laser in infected root canals is very well demonstrated in a research study in which 48 maxillary central incisors were used. [24] After canal preparation, the teeth were autoclaved and divided into four groups: (1) Non-treated teeth (control group); (2) teeth treated with NaOCl; (3) teeth irradiated with Er: YAG laser (7 Hz, 100 mj, 80 pulses/canal, 11 s) to the working length; and (4) teeth irradiated similarly to, but 3 mm short, of the apex. The root canals from Groups 2, 3, and 4 were inoculated with four bacteria: Bacillus subtillus, E. faecalis, Pseudomonas aeruginosa, and Staphylococcus aureus, together with Candida albicans, and maintained for 24 h at 37 C. All suspensions were adjusted to tube 2 of the MacFarland scale. The intracanal material was then collected with sterile paper points, which were placed in the canals for 5 min and then immersed in 5 ml of BHI medium. This was then seeded onto agar and stained by Gram s method. The NaOCl solutions and the Er: YAG laser irradiation to working length were effective against all five microorganisms; however, 70% of the specimens irradiated 3 mm short of the apex remained infected. [24] An alternative approach to microbial killing in the root canal system by laser light involves the use of low-power lasers to drive a photochemical reaction that produces reactive oxygen species, a technique termed PAD. Using exogenous photosensitisers such as tolonium chloride, killing of all types of bacteria can be achieved. In vitro studies of PAD have demonstrated its ability to kill photosensitized oral bacteria (such as E. faecalis), and more recently, microbial killing in vivo in the root canal system has been demonstrated. While PAD can be undertaken as part of the routine disinfection of the root canal system, it also has potential use for eradicating persistent endodontic infections for which conventional methods have been unsuccessful. [25] Endodontic Retreatment The lasers are widely used in endodontic retreatments. Various lasers used are Er: YAG, 2940 nm; Er, Cr: YSGG, 2780 nm; Nd: YAG, 1064 nm; diode, 635 to 980 nm; KTP, 532 nm; and carbon dioxide (CO 2 ), 9600 and nm. [26] The lasers act on the root canal by absorption of their wavelengths in biological components and chromophores such as water, apatite minerals, and various pigmented substances (microorganisms). Wavelengths of the visible and near-infrared electromagnetic radiation (Nd: YAG, diode, and KTP lasers) are poorly absorbed in water and hydroxyapatite and have deeper bactericidal effects in dentine. On the contrary, mid-infrared erbium lasers, whose wavelengths are highly absorbed in water and hydroxyapatite, have a superficial effect on dentine walls and can be used for the removal of the layer and disruption of intracanal biofilms. [26,27] CONCLUSION Laser is very effective in dentistry and represents a good treatment option. 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