|Year : 2016 | Volume
| Issue : 4 | Page : 123-127
Lasers in Dentistry: Is It Really Safe?
Hamed Mortazavi, Maryam Baharvand, Maede Mokhber-Dezfuli, Niloofar Rostami-Fishomi, Maryam Doost-Hoseini, Orkideh Alavi-Chafi, Shalaleh Nourshad
Department of Oral Medicine, School of Dentistry, Shahid Beheshti University of Medical Sciences, Tehran, Iran
|Date of Web Publication||21-Dec-2016|
Department of Oral Medicine, School of Dentistry, Shahid Beheshti University of Medical Sciences, Daneshjoo Blvd, Tabnak St, Chamran Highway, Tehran
Source of Support: None, Conflict of Interest: None
Introduction: Lasers are used in various disciplines in dentistry such as restorative dentistry, endodontics, periodontics, pedodontics, and oral and maxillofacial surgery. Despite many advantages of dental lasers, this method might have some adverse effects. The aim of this review article is to debate about the impacts of lasers on orodental tissues. Methods: An electronic search was accomplished using specialized databases such as Google Scholar, PubMed, PubMed Central, Science Direct, and Scopus to find relevant studies by using keywords such as “laser”, “dentistry”, “adverse effect”, and “side effect”. Results: Several adverse effects of laser were identified such as impacts on dental pulp, effects on tooth surface, subcutaneous and submucosal effects, histopathological changes, and infection transmission due to laser smoke. During dental procedures, necrosis of the pulp, periodontal ligament and odontoblasts, cemental lysis, bone resorption, hypo/hyperpigmentation, burns, itching, and scarring might occur. In addition, laser can weaken the dentin by inducing surface cracks. Restorative procedures by laser might increase microleakage and decrease shear bond strength, as well as microhardness of tooth walls. Meanwhile, laser surgery might cause emphysema after abscess incision and drainage, frenectomy, flap elevation, and gingivoplasty. Conclusion: Practitioners should be very cautious in treatment planning and case selection during laser-based therapeutic procedures.
|How to cite this article:|
Mortazavi H, Baharvand M, Mokhber-Dezfuli M, Rostami-Fishomi N, Doost-Hoseini M, Alavi-Chafi O, Nourshad S. Lasers in Dentistry: Is It Really Safe?. Dent Hypotheses 2016;7:123-7
|How to cite this URL:|
Mortazavi H, Baharvand M, Mokhber-Dezfuli M, Rostami-Fishomi N, Doost-Hoseini M, Alavi-Chafi O, Nourshad S. Lasers in Dentistry: Is It Really Safe?. Dent Hypotheses [serial online] 2016 [cited 2019 Jul 23];7:123-7. Available from: http://www.dentalhypotheses.com/text.asp?2016/7/4/123/195967
| Introduction|| |
Laser was introduced in dentistry in 1960s. Thereafter, a continuous range of studies were conducted on various usages of laser in dental practice. Two major types of lasers were introduced in terms of clinical applications; hard lasers such as carbon dioxide (CO2), neodymium–yttrium aluminum garnet), and erbium–yttrium aluminum garnet (Er:YAG) with both hard and soft tissue usages. Because of high cost and a potential for thermal tissue damage, hard lasers have some limitations., On the other hand, soft or cold lasers have been predominantly used for biostimulation or low level laser therapy (LLLT). Lasers are used in various disciplines in dentistry such as restorative dentistry where they are used for diagnosis of caries, improving the resistance of dental enamel, and photopolymerization of composite resin;, endodontics for bactericidal cleansing of root canal; periodontics for gingivectomy, gingivoplasty, frenectomy, and vestibuloplasty; pedodontics to prepare tooth surfaces for sealant application; and oral and maxillofacial surgery to treat vascular malformation.,
Dental lasers are classified with regard to the lasting medium used such as gas laser or solid laser, application in different tissues such as soft tissue or hard tissue lasers, the range of wavelength, and the risk of laser usage [Table 1].
The literature about the inadvertent effects of laser irradiation on orodental structures is limited and scanty to provoke readers’ concerns regarding the potential hazards of laser therapy. Insufficient knowledge about unwanted effects of laser might give rise to overwhelming therapeutic pitfalls; hence, an efficient treatment alternative would serve as a potentially destructive modality.
The aim of the present review was to debate laser impacts on orodental hard and soft tissues during dental procedures. General precautions regarding prevention of laser damage to the patient and the operator have been discussed several times.,, Side effects of dental laser are summarized in five categories: (1) laser effects on dental pulp, (2) laser effect on tooth surface, (3) subcutaneous and submucosal effects of laser, (4) histopathological changes of laser, and (5) infection transmission due to laser smoke.
| Methods|| |
An electronic search was accomplished using specialized databases such as Google Scholar, PubMed, PubMed Central, Science Direct, and Scopus to find relevant studies by using keywords such as “laser”, “dentistry”, “adverse effect”, and “side effect”.
Laser side effects
Laser effects on dental pulp
Laser energy is converted into heat when absorbed by tissue components, such as DNA/RNA, chromophores, proteins, enzymes, and water. Tissue damage due to the thermal effects of laser is largely attributable to the degree of heating in a way that increasing temperature leads to more severe changes; hyperthermia begins at 42–45°C, which results in structural alteration and shrinkage of collagen. Reduction of enzymatic activity takes place at 50°C. Temperature of 60°C causes protein denaturation, coagulation of collagens, and membrane permeabilization. Tissue drying and formation of vacuoles occur at 100°C. Beginning of vaporization and tissue carbonization is the result of heat over 100°C. Temperature of 300–1000°C leads to thermoablation of tissues, photoablation, and disruption.
A study regarding the thermal effects of Nd:YAG, argon, and CO2 laser beams on enamel, dentin, and dental pulp demonstrated the potency of Nd:YAG laser beam to penetrate deeply through the enamel and dentin to the pulp. Although the effects of argon laser were closely associated with the degree of enamel surface cleanliness, the superficial and deep temperatures were reported to be low even after surface cleaning. With respect to CO2 laser, very high temperatures were yielded on the enamel and dentin surfaces; however, pulp chamber reached low temperatures.
An increase in temperature of 6°C can cause irreversible pulpitis, whereas pulpal necrosis occurs when temperature rises higher (11°C). There is no consensus in the literature about pulpal damage caused by laser thermal effects. Some studies reported different grades of pulpal damage whereas others showed no sign of pulpal changes in terms of laser type and power setting.,, In an article by von Fraunhofer et al., the effect of Nd:YAG laser at ≤240 J on third molars within 3 minutes after extraction was demonstrated that if the remaining dentin thickness was greater than 1 mm, irradiation causes no significant pulpal response. In contrast, thermal insult of CO2 laser at 5 × 103 J/cm2 was reported to cause calcification in the pulp chamber and an increase in pulpal volume by approximately one third. In another study, Bader and Krejci demonstrated that laser cavity preparation caused overheating of teeth leading to pulpitis. Moreover, different temperatures were recorded according to the anatomic site of cavity preparation; Class I preparations yielded the highest values, followed by Class V cavities in enamel. On the other hand, caries removal or preparation in cementum caused the lowest temperature increase.
Buchella and Attin showed that activation of bleaching agents by heat, light, or laser might increase intrapulpal temperature beyond the critical value of 5.5°C.
Laser effects on tooth surface
Tooth surface maybe impacted by laser irradiation as well; for example, significant decrease in shear bond strength of brackets to the teeth following bleaching with carbamide peroxide and diode laser has been reported. Although Er-YAG laser irradiation with water and 35 μs pulse duration did not result in surface visible cracks, it caused a 20% reduction in the bending strength of the dentin.
Er-YAG laser when used without water with 0.5 μs pulse durations left severe surface cracks which served as initial sites of destructive fractures, resulting in a 35% weakening of dentin under bending pressures. Meanwhile, ND:YAG 1064 nm and 980 nm diode lasers decreased the microhardness of root dentin compared to the application of ethylene diamine tetra acetic acid (EDTA) with manual agitation. Ghanbarzadeh et al. proved that in-office bleaching by means of laser significantly reduced the microhardness of enamel.
There is controversy regarding demineralization and acid-resistance of enamel and dentin after Er:YAG laser treatment in the literature. Subablative Er:YAG irradiation resulting in 20% change in calcium solubility produces no caries but fine cracks in the enamel surface. On the other hand, ablative dry laser treatment of 400 mJ resulted in the lowest acid demineralization in enamel and dentin, which on the micromorphological level induced thermal damage. Moreover, it has been shown that after bleaching with light emitting diodes (LED)/laser microhardness of tooth decreased. One week after using Diod laser, shear bond values were recorded to be diminished. The mechanical impact of Er:YAG laser on very breakable enamel is different when high or low energies are applied similar to drilling with different diamond bur sizes because Er:YAG laser causes vaporization of the water content in tissues to induce microexplosions. Most of the studies regarding microleakage and marginal adaptation used high energies (over 300 mJ) of Er:YAG, which induced subsurface damages into enamel leading to low marginal adaptation and a high degree of microleakage., Ozel et al. concluded that cavity preparation with Er:YAG laser caused more microleakage than preparation with bur in cervical regions. In addition, acid etching of enamel following Er:YAG, a kind of enamel finishing method, showed much better results. Microleakage of occlusal walls in acid etched cavities was significantly lower than that achieved by means of laser treatment; hence, laser treatment of enamel is not a superior alternative compared to acid etching prior to adhesion of resin composite materials. Conventional rotary preparation and acid etching yielded stronger adhesion to dentin and enamel in comparison to laser preparation.
Bahrololoomi et al. found that Er:YAG caused lower shear bond strength in both enamel and dentin compared to bur. The same findings were also reported by von Fraunhofer and Yildrim., Moreover, Nd-YAG and holmium:yttrium aluminium garnet (HO:YAG) lasers were found to decrease the tensile bond strength of a silicone-based liner to an acrylic denture.
Subcutaneous and submucosal effects of laser
Inappropriate use of dental lasers with air cooling spray might result in cervicofacial subcutaneous and mediastinal emphysema (CSE) according to numerous reports. Despite the fact that air pressure of an air turbine is higher than that of a dental laser, the application time of the instrument tip might be the causative factor for occurrence of CSE.,, Use of CO2 laser to treat gingival abscess, periapical lesion, and surgery of pharynx and larynx carcinoma has been associated with increased risk of CSE. It has been demonstrated that 69.2% of laser therapies lead to CSE, which is quite higher than those treated with routine dental operations. Regarding CSE after dental laser treatment, out of 10 patients in a case series (8 patients under CO2 laser and 2 under Er:YAG laser therapy), 9 developed emphysema following soft tissue incision. Emphysema occurred in 5 cases after abscess incision and drainage, 2 pediatric patients after frenectomy, 2 cases following anti-inflammatory laser treatment for periapical infection, and one case after each of subgingival scaling, flap elevation, and gingivoplasty. Dentists and oral surgeons should be familiar with the potential risk of emphysema caused by air cooling spray of dental lasers to ensure proper usage of lasers.
Histopathological changes of laser
Dental laser therapy causes some histopathological changes as well. Cell necrosis in the periodontal ligament (mostly due to thermal effect) was noticed 1 day after laser treatment, whereas teeth under conventional preparation developed no evidence of cell necrosis. Fifteen days following treatment, increased size and number of osteocytes and osteoclasts were evident in the periradicular bone in both laser and conventionally-treated teeth. Moreover, initial bone resorption was detected in laser-treated teeth. Conventionally-treated teeth began to return to normal morphology within 30 days posttreatment. On the other hand, the laser-treated teeth exhibited ankylosis, cemental lysis, and significant bone remodeling. Laser can cause pulpal vasodilation, and high power lasers cause edema and occasional inflammation., In an animal study, rat teeth irradiated with an acousto-optically Q-switched Nd-YAG laser at 10 W for 0.2 seconds or 5 W for 0.3 seconds using a beam diameter of 2 mm showed mild dilation of pulpal vessels at the lowest levels with some calcified tissue 4 weeks after laser irradiation. Adrian et al. reported pulpal damage due to ruby laser at 1880–2330 J/cm2, however, coagulation necrosis of the odontoblasts, edema, and occasional inflammation occurred between 2400 and 3000 J/cm2. In addition, delayed gingival healing following laser surgery was revealed with the presence of epithelial ulcerations and dense inflammatory infiltrate. Thermal interaction of laser radiant energy with tissue proteins induces damage to the skin and other nontarget tissues (oral tissue). An increase in temperature 21°C above 37°C (normal body temperature) can cause cell destruction by denaturation of cellular enzymes and structural proteins, which interrupts basic metabolic processes. The thermal effect of absorbed radiant energy is manifested histologically as thermal coagulation necrosis for wavelengths above 400 nm. Photochemical and photoacoustic mechanisms are responsible for other nonthermal tissue injuries. They occur with single or repetitive pulses of low duration. The potential for mutagenic changes of laser irradiation has been questioned; however, there have been no reports of laser-induced carcinogenesis to date. Penetration of specific wavelengths is potentially harmful to deeper tissues, e.g., prolonged exposures of low power density of continuous wave Nd:YAG laser can cause inapparent excess thermal necrosis.
In addition, several side effects of laser have been mentioned following surgical procedures such as burn, itching, tissue hyperpigmentation (especially in dark-skinned people), tissue hypopigmentation, scarring, and infection.
Infection transmission due to laser smoke
Copious amounts of noxious smoke or plume are released as a by-product of laser vaporization mostly by CO2 laser. In general, surgical smoke consists of 95% water and vapor and 5% other materials. One million to one billion particles have been found in laser smoke and aerosol, some of which have been identified as intact cells, cell parts, blood cells, and viral DNA fragments. Culture from tubing of the smoke evacuator yielded viable bacteria. It has been determined that high heat does not completely kill some bacterial spores regardless of the power and length of exposure. Of note, Staphylococcus aureus is more refractory to high temperatures than Escherichia More Details coli.,
The viability or risk of exposure to viruses in laser smoke remains a matter of debate. Viral DNA has been captured in laser smoke. Transmission of Human papilloma virus (HPV) during a laser procedure from patient-to-caregiver has been reported. Moreover, particles of Human immunodeficiency virus (HIV) have been detected in the inner lumen of a smoke evacuator tubing after in vitro laser vaporization of HIV particles. Although human-to-human transmission of viruses and bacteria from laser smoke has not been established, there is enough preliminary evidence to warrant a cautious and self-protective approach to laser plume by all operating room personnel.
Biologic hazards of laser smoke are viruses (e.g., HIV, HPV, hepatitis B and C); bacteria (e.g., S. aureus, Mycobacterium tuberculosis, E. coli, spores); and cells (e.g., carbonized tissue, aerosolized blood).,
By-products of laser smoke are considered to be potentially toxic chemicals. More than 600 organic compounds have been identified in plume generated by vaporized tissue. Many of these compounds have been documented to have harmful health effects including irritation to the eyes, nose, and respiratory tract; liver and kidney damage; carcinogenic cell changes; headaches; dizziness; drowsiness; stomach pains; vomiting and nausea; and rapid breathing. Some chemical compounds that may be found in laser smoke are as follows: acetylene, benzene, creosols, methane, ethylene, formaldehyde, hydrogen cyanide, propylene, styrene, toluene, and free radicals.
| Discussion|| |
Although general precautions are widely implemented to reduce physical hazards of therapeutic lasers, there have been several reports regarding the occurrence of laser side effects. During dental procedures, pulpitis, necrosis of the pulp, periodontal ligament, and odontoblasts, cemental lysis, bone resorption, hypo/hyperpigmentation, burns, itching, and scarring might occur.,,, In addition, laser beam can weaken the dentin through inducing surface cracks as well as reducing bending strength. Restorative and prosthodontics procedures with laser might increase microleakage and decrease shear bond strength and microhardness of dental walls.,,,,,, One of the most important side effects of laser surgery is soft tissue emphysema, which is frequently seen after abscess incision and drainage, frenectomy, flap elevation, and gingivoplasty. Transmission of some infectious agents such as HIV, HPV, hepatitis B and C, S. aureus, M. tuberculosis, and E. coli has also been reported during laser treatments., Meanwhile, chemical ingredients of laser smoke are potentially toxic to some organ systems of the body.
| Conclusion|| |
Despite many advantages of dental lasers, this method can be potentially hazardous due to impacts on dental pulp, tooth surface, subcutaneous and submucosal tissues, and risk of infection transmission. Therefore, dental practitioners should be aware of laser adverse effects during therapeutic procedures to minimize the potential risks for patients.
Financial support and sponsorship
Conflicts of interest
There are no conflicts of interest.
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