|Year : 2015 | Volume
| Issue : 1 | Page : 11-15
Lasers in prosthodontics
Sakshi Kaura, Anuj Wangoo, Ramanpreeet Singh, Simratdeep Kaur
Department of Prosthodontics, Luxmi Bai Institute of Dental Sciences and Hospital, Patiala, Punjab, India
|Date of Web Publication||30-Jul-2015|
Dr. Sakshi Kaura
1, Ranbir Marg, Near Model Town Police Post, Patiala, Punjab
Source of Support: None, Conflict of Interest: None
The introduction of lasers in the field of prosthodontics has replaced many conventional surgical and technical procedures and is beginning to replace the dental handpiece. Since its first experiment for dental application in the 1960's the use of the laser has increased rapidly in a couple of decades. Today lasers have become an integral part of effective treatment planning. This article reviews the literature on lasers with the aim of providing a complete understanding of fundamentals of lasers and their applications in various fields of prosthodontics.
Keywords: crown, dental lasers, prosthodontics
|How to cite this article:|
Kaura S, Wangoo A, Singh R, Kaur S. Lasers in prosthodontics. Saint Int Dent J 2015;1:11-5
The laser is an acronym, which stands for light amplification by stimulated emission of radiation. Lasers were developed and actually used in light shows and for other purposes. Today the laser is used in the scanners at the grocery store, in compact disc players, and as a pointer for lecturer and above all in medical and dental field. The image of the laser has changed significantly over the past several years.
With dentistry in the high tech era, we are fortunate to have many technological innovations to enhance treatment, including intraoral video cameras, computer-aided design-computer-aided manufacturing units, RVGs and air-abrasive units. However, no instrument is more representative of the term high-tech than, the laser. Dental procedures performed today with the laser are so effective that they should set a new standard of care.
| Invention of Laser|| |
Einstein's atomic theories on controlled radiation can be credited as the foundation for lasers technology in 1917.
Nearly 40 yearly, American physicists Townes first amplified microwave frequencies by the stimulated emission process and the acronym microwave amplification by stimulated emission of radiation (MASER) came into use.
In 1958, Schawlow and Townes extended the MASER principle to the optical portion of the electromagnetic field; hence the name laser.
In 1960, the first working laser, a pulsed ruby instrument, was built by Maiman of Hughes research laboratories, of 0.694 mm and in 1961 s laser neodymium (Nd) laser by Snitzer.
Goldman in 1962 established the first laser in Medical Laboratory at University of Cincinnati, as he is recognized as the first physician to use laser technology initially working with the ruby laser.
L'esperence was the first to use argon laser in 1988 in ophthalmology. Keifhabes et al. in 1977 first to use Nd:yttrium-aluminum-garnet (YAG).
| Different Laser Systems Used in Prosthodontics|| |
The argon laser system uses argon as an active medium and is fiberoptically delivered in the wave and gated pulsed modes. Argon lasers have two wavelengths used in dentistry: 488 nm (blue) and 514 nm (blue-green) in the spectrum of visible light. The 488 nm wavelength is used for curing composite restorative materials, light activation of whitening gels and impressions and in caries detection. Advantages of using argon curing system include better physical properties of resins when compared with a resin cured with ordinary blue filtered light and shorter curing time.  The 514 nm wavelength is used for oral soft tissue surgeries like acute inflammatory periodontal disease and highly vascularized lesions, such as hemangiomas because of its peak absorbance in tissues containing hemoglobin, hemosiderin, and melani. 
The diode laser is a solid state semiconductor laser which uses a combination of gallium, arsenide, aluminum, and indium. The wavelengths used in dentistry are in a range of 800-980 nm and are poorly absorbed in water, but highly absorbed in hemoglobin and other pigments. This laser is excellent for soft tissue procedures as these do not interact with dental hard tissues. Diode laser systems as low laser therapy have also been used for biostimulation of osteoblasts around implants. 
Neodymium:yttrium aluminum garnet laser
Nd:YAG laser is a pulsed wave, free running laser with a wavelength of 1064 nm. Since these lasers are easily absorbed in water, they are useful for soft tissue surgeries and produce a thick coagulation layer on the lased surfaces, thereby creating a strong hemostasis. These lasers are well absorbed by dark substances; hence Indian ink or other kinds of black pigment are often applied to increase the efficiency of ablation.  These lasers are commonly used in surgeries of potentially hemorrhagic soft tissues, removal of enamel caries, periodontal procedures, bleaching, welding of titanium components of prostheses and in implant disinfection.
Holmium:yttrium aluminum garnet lasers
The manufacture of the only holmium (Ho) laser dental instrument ceased several years ago. It is a solid crystal of YAG sensitized with chromium and doped with Ho and thulium with a wavelength of 2100 nm. It is absorbed by water 100 times greater than Nd:YAG and used in oral surgery for arthroscopic surgery on the temporomandibular joint and has many medical applications. 
Two distinct wavelengths that use erbium are erbium, chromium:yttrium scandium gallium garnet (Er:Cr:YSGG) and Er:YAG. Er:Cr:YSGG has a wavelength of 2780 nm and the active medium is a solid crystal of yttrium, scandium, gallium garnet that is doped with Er:Cr. Er:YAG is a solid medium of yttrium, aluminum garnet that is doped with erbium and has a wavelength of 2940 nm. The absorption of Er:YAG laser in water is greatest because its high wavelength coincides with the large absorption band for water and thus is very well absorbed by all biological tissues that contain water molecules. Er:Cr:YSGG are more highly absorbed by hydroxyl ions and have a performance similar to that of the Er:YAG lasers. These properties make erbium family of lasers ideal for use in soft tissue procedures as well as hard tissue procedures such as caries removal, cavity preparation, tooth preparation, osteotomy and implant site preparation. 
CO 2 Lasers
The CO 2 laser has a gas-active medium which is pumped via the electrical discharge current. The wavelength of these lasers is 10,600 nm and is placed at the end of the mid-infrared invisible nonionizing portion of the electromagnetic spectrum. This wavelength is well absorbed by water, second only to the erbium family. Due to its property of easy cutting, coagulability and shallow depth of penetration into tissues, CO 2 lasers are important in treating mucosal lesions and vaporizing dense fibrous tissue. 
| Applications of Lasers in Prosthodontics|| |
- Crown lengthening
- Soft tissue management around abutments
- Osseous crown lengthening
- Formation of ovate pontic sites
- Altered passive eruption management
- Bleaching 
- Veneer removal 
- Tooth preparation for veneers and full coverage crowns and bridges 
- Removal of the carious lesion and faulty composite restorations before placement of final restorations. 
- Crown fractures at the gingival margins
- Enamel and dentin Etching. 
Lasers have an advantage in crown lengthening regard as they cut only at the tip and can be held parallel to long axis of the tooth to remove bone immediately adjacent to cementum without damaging it.  Furthermore, using lasers is less complicated and achieves maximum patient comfort.
Soft tissue management around abutments
Argon laser energy has peak absorption in hemoglobin, thus lending itself to providing excellent hemostasis and efficient coagulation and vaporization of oral tissues.  These characteristics are beneficial for retraction and hemostasis of the gingival tissue in preparation for an impression during a crown and bridge procedure.  Argon laser with 300 um fiber, and a power setting of 1.0 W, continuous wave delivery, and the fiber is inserted into the sulcus in contact with the tissue.
Modification of soft tissue around laminates
The removal and re-contouring of gingival tissues around laminates can be easily accomplished with the argon laser. 
Osseous crown lengthening
Like teeth mineralized matrix of bone consists mainly of hydroxyapatite (HA). The water content and HA are responsible for the high absorption of the Er:YAG laser light in the bone. Er:YAG laser has the very promising potential for bone ablation. 
Lasers can be used to create a trough around a tooth before impression taking. This can entirely replace the need for retraction cord, electrocautery, and the use of hemostatic agents.  The results are predictable, efficient, minimize impingement of epithelial attachment, cause less bleeding during the subsequent impression, reduce postoperative problems, and reduce chair time.  It alters the biological width of gingiva. Nd:YAG laser is used.
Aesthetics and smile have become important issues in modern society. Bleaching has become the common method for tooth whitening. Bleaching using diode lasers results in immediate shade change and less tooth sensitivity and is preferred among in-office bleaching systems. 
Lasers like Er:YAG and Er Cr:YSGG can be used remove unwanted or failed veneers. 
Crown fractures at the gingival margins
Er:YAG or Er, Cr:YSGG lasers can be carried out to allow correct exposure of the fracture margin. 
Formation of ovate pontic sites
The use of an ovate pontic receptor site is of great value when trying to create a natural maxillary anterior fixed bridge. This is easily accomplished with the use of a laser. 
- Second stage uncovering.
- Implant site preparation.
One advantage of the use of lasers in implantology is that impressions can be taken immediately after second stage surgery because there is little blood contamination in the field due to the hemostatic effects of the lasers.  There also is minimal tissue shrinkage after laser surgery, which assures that the tissue margins will remain at the same level after healing as they are immediately after surgery. ,
Implant site preparation
Lasers can be used for the placement of mini implants especially in patients with potential bleeding problems, to provide essentially bloodless surgery in the bone. 
Removal of diseased tissue around the implant
The diode lasers alone or with toluidine O dye, CO 2 lasers, and Er:YAG lasers have been used for implant maintenance, because of their bactericidal effect and technical simplicity.  Debridement of implant abutment surface with lasers can effectively decontaminate the surfaces, reduce the bacterial count and improve the success rate of ailing implants. Schwarz et al. demonstrated the effectiveness of Er:YAG laser treatment to remove subgingival calculus from surfaces of titanium implant fixtures without any thermal damage.  Among the disadvantages of using lasers for the purpose are that not all the lasers can be used, for example, Nd:YAG lasers and Ho:YAG lasers are unsuitable for peri-implantitis and caused melting, loss of porosity and other surface alterations even with the lowest settings. 
- Tuberosity reduction
- Torus reduction
- Soft tissue modification
- Epulis fissurata
- Denture stomatitis
- Residual ridge modification
- Treatment of flabby ridges
- Sulcus deepening
- Osseoectomy during tooth/root extraction or ridge recontouring
- Treatment of soft tissue and hard tissue undercuts.
Treatment of unsuitable alveolar ridges
Hard tissue surgery may be performed with the erbium family of wavelengths. 
Treatment of undercut alveolar ridges
Osseous surgery may be performed with the erbium family of lasers. 
Treatment of enlarged tuberosity
The soft tissue reduction may be performed with any of the soft tissue lasers. Erbium laser is the laser of choice for the osseus reduction. ,
Surgical treatment of tori and exostoses
Soft tissue lasers may be used to expose the exostoses and erbium lasers may be used for the osseous reduction. 
Laser applications in the dental laboratory
- Laser titanium sintering
- Laser ablation of titanium surfaces
- Laser-assisted HA coating
- Laser welding of titanium components of the prostheses.
Lasers have been used for deposition of HA thin films on titanium implants pulsed laser deposition has proven to be a promising method to produce pure, crystalline and adherent HA coatings which show no dissolution in a simulated body fluid. 
Use of lasers for surface treatment of titanium castings for ceramic bonding have shown improved bond strength when compared to acid etching techniques which are commonly used. Lasers can also be used for welding. 
Lasers in maxillofacial rehabilitation
- Planning the shape and position of the prostheses
- Three-dimensional acquisition of optical data of the extraoral defects.
The use of lasers in the maxillofacial prosthetics is mainly for the initial workup of three dimensional acquisitions of optical data of the extraoral defects. Laser technology has proved to be particularly useful for planning the shape and position of the prostheses. Lasers can totally eliminate the need for conventional impression techniques and associated disadvantages like deformation of the soft tissue and discomfort to patients. Lasers also overcome the drawbacks of three-dimensional computed tomography and magnetic resonance imaging reconstruction as the patient is not exposed to considerable radiation and any stress. 
| Laser Hazards|| |
The subject of dental laser safety is broad in scope, including not only an awareness of the potential risks and hazards related to how lasers are used, but also recognition of existing standards of care and a thorough understanding of safety control measures.
Laser hazard class for according to ANSI and OSHA standards:
Class I : Low powered lasers that are safe to view
Class IIa : Low powered visible lasers that are hazards only when viewed directly for longer than 1000 s.
Class II : Low powered visible lasers that are hazardous when viewed for longer than 0.25 s.
Class IIIa : Medium powered lasers or systems that are normally not hazardous if viewed for <0.25 s without magnifying optics.
Class IIIb : Medium powered lasers (0.5 W max) that can be hazardous if viewed directly.
Class IV : High powered lasers (>0.5 W) that produce ocular, skin and fire hazards.
The types of hazards can be grouped as follows
- Ocular injury
- Tissue damage
- Respiratory hazards
- Fire and explosion
- Electrical shock.
Potential injury to the eye can occur either by direct emission from the laser or by reflection from a specular (mirror like) surface or high polished, convex curvature instruments. Damage can be manifested as injury to the sclera, cornea, retina and aqueous humor and also as cataract formation. The use of carbonized and nonreflective instruments has been recommended.
Laser-induced damage to skin and others non-target tissues can result from the thermal interaction of radiant energy with tissue proteins. Temperature elevation of 21°C above normal body temp (37°C) can produce cell destruction by denaturation of cellular enzymes and structural proteins. Tissue damage can also occur due to cumulative effects of radiant exposure. Although there have been no reports of laser induced caroinogenesis to date, the potential for mutagenic changes, possibly by the direct alteration of cellular DNA through breathing of molecular bonds, has been questioned. The terms photodisruption and photoplasmolysis have been applied to describe these type of tissue damage.
Another class of hazards involves the potential inhalation of airborne biohazardous materials that may be released as a result of the surgical application of lasers. Toxic gases and chemical used in lasers are also responsible to some extent.
During ablation or incision of oral soft tissue, cellular products are vaporized due to the rapid heating of the liquid component in the tissue. In the process, extremely small fragments of carbonized, partially carbonized, and relatively intact tissue elements are violently projected into the area, creating airborne contaminants that are observed clinically as smoke or what is commonly called the 'laser plume'. Standard surgical masks are able to filter out particles down to 5 nm in size. A particle from laser plume, however, may be as small as 0.3 nm in diameters. Therefore, evacuation of laser plume is always indicated.
Fire and explosion
Flammable solids, liquids and gases used within the clinical setting can be easily ignited if exposed to the laser beam. The use of flame-resistant materials and other precautions, therefore, is recommended. Flammable materials found in dental treatment areas.
Solids : Clothing, paper products, plastics, waxes, and resins
Liquids : Ethanol, acetone, methyl methacrylate, solvents
Gasses : Oxygen, nitrous oxide, general anesthetics, aromatic vapors
These can be:
- Electrical shock hazards
- Electrical fire or explosion hazards.
| Precaution and Management of Laser|| |
The laser safety is an issue limited not only to the performances of treatment with dental operators, but one that also encompasses the interrelationship among the health care providers, educational institutes, and government.
Personnel protective equipment
While using lasers one must wear adequate eye protection, including the patient. This can be provided by either safety goggles or screening devises. However the means selected must be designed specifically for use with the particular wavelength of laser radiation.
While selecting appropriate protective eyewear following should be considered:
- Wavelength of laser emission
- Maximum permissible exposure limits.
- Degradation of absorbing media or filter.
- Optical density of eyewear
- Radiant exposure limits
- Need for corrective lenses
- Multiple wavelength requirements
- Restriction of peripheral vision
- Comfort and fit.
Control of airborne contaminants
The laser plume, which is the smoke or vapor emitted from the site of surgery during exposure to laser energy, is a special concern. The plume should be regarded as potentially hazardous both in terms of particulate matter and infectivity.
Airborne contaminants can be controlled by ventilation, evacuation or other methods of respiratory protection. Airborne contaminants should be removed as near as possible from the point or origin by evacuation and ventilation to the outside if possible. Adequate suction in the cut surgical field must be maintained at all times, especially when treating pathologic conditions that are suspected of being viral in origin to limit the possibility of spreading that virus via the laser plume. Accordingly, the evacuation system should be able to remove particle as small as 0.3 μm with at least 80% efficiency. Surgical staff should wear a mask to remove the particles. Eyewear, face shield, and caps or gowns should be worn to protect the personnel from splatter and laser light.
The beam alignment should be checked before any surgical procedure by using a moistened tongue depressor and firing the laser to prevent combustion.
Polished instruments should not be used because of the potential for reflected lasers energy to cause damage only anodized ones should be used.
The use of fire is always a concern when the laser is used when using laser noncombustible materials should be used. All combustible materials must be kept in closed cabinets, and any combustion fluids that are used in surgical preparation must be dried before surgery.
When the laser is used for nasotrachial surgery, the moist pack must be used to protect the tube from accidental laser damage because any exposure of the anesthetic agent to the laser beam can cause combustion in biomaterial system.
When the laser is used for tissue incisions, the power density and the time used by the laser should be respected. It can cause tissue damage, and it can be prevented by preventing carbon arcing, the tissue should be regularly wiped clean of CO 2 .
| Conclusion|| |
The laser has become a ray of hope in dentistry. When used efficaciously and ethically, lasers are an exceptional modality of treatment for many clinical conditions that dentists treat on a daily basis. However, laser has never been the "magic wand" that many people have hoped for. It has got its own limitations. However, the future of dental laser is bright with some of the newest ongoing researches.
Financial support and sponsorship
Conflicts of interest
There are no conflicts of interest.
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