Laser Applications in

EndodonticProcedures in endodontics

A Research Submitted

To the council of college of dentistry- University of Misan in partial Fulfillment of

the requirement for the degree of Bachelor in dentisty.

Douaa Mohammed AbbasLujain Ali Ahmed

HussianBalasim Mohammed

Supervised by

Dr.Younis Mohammed AtiahDr.AliSalih Al-Taei

Abstract LASER is light amplification by stimulated emission of radiation. Laser light is a

man-made single-photon wavelength. The process occurs when an excited atom is

stimulated to emit a photon. This is followed by subsequent release of another

photon and so on. Stimulated emission generates, coherent (synchronous),

monochromatic (single wave length), and collimated form of light LASER light

when it reaches tissues gets reflected/absorbed/scattered/transmitted to

surrounding tissues. This is due to the presence of water, proteins, and pigments in

biological tissues. This absorption coefficient of biological tissue strongly depends on

the wavelength of LASER. The primary concern in Endodontics is to achieve

optimum disinfection of root canal system. Various methods have been described in

literature to have clean root canal such as chemical irrigation, use of ultrasonic

system. Nowadays, laser dentistry has made revolutionary impact in dentistry.

In the field of Endodontics, LASER primarily known to use for disinfecting root

canal with better results.LASER made possible to penetrate in those complex areas

of root canal such as lateral canal, which are very difficult to clean .With laser

technology, better results achieved by increasing cleaning ability of canal and

removing smear layer and debris from infected canal

Keywords: LASER, sterilization, root canal treatment

.Introduction1

LASER light when it reaches tissues gets reflected/absorbed/scattered/transmitted

to surrounding tissues. This is due to presence of water, proteins, and pigments in

biological tissues. This absorption coefficient of biological tissue strongly depends on

the wavelength of LASER.[1]

Wavelengths emitted at ultraviolet spectrum appear promising in endodontics.

ArF LASER at 193 nm is well suited for removal of necrotic debris from root canal,

leaving behind smooth, crack free and fissure free melted, dentine walls XeCl (308

nm) capable of melting dentin and closing of dentinal tubules.[2]

With laser technology, better results achieved by increasing cleaning ability of canal

and removing smear layer and debris from infected canal [3]. In 1971, lasers in

Endodontics were first documented by Weichman and Johnson, which they used to

seal the apical foramen using CO2 laser in vitro [4].

The use of lasers has increased greatly in clinics. Nowadays, lasers are suggested to

use in a variety of dental treatments. Different types of laser are used in dental

practices such as Argon, Carbon dioxide laser, Nd: YAG, Erbium: yttrium-

aluminum-garnet (Er: YAG), Kryptonfluoride, Xenon-fluoride [5, 6]

Applications of lasers in Endodontics for various procedures have been now well

known. For example, in analgesia, the pulsed Nd:YAG laser is vastly used for

analgesia or to relieve pain of tooth in Endodontics [7].

The wavelength of this laser interferes with the sodium pump mechanism

leading to change permeability of cell membrane. To check the Pulp Vitality, laser

Doppler is used for this purpose, which is a noninvasive method to assess and

measure the rate of blood flow in a tissue.

In Direct Pulp Capping by laser, CO2 laser irradiation is used. Pulsed Nd: YAG,

Argon, semiconductor diode, and Er:YAG can also be used. CO2 laser can also be

implicated to Ablate and accessory treatment for vital pulp amputation [8,9].

In Root Canal Treatment, laser has been used widely from initial to last steps

of root canal procedure [10]. Er, Cr:YSGG (2780 nm) and Er:YAG (2940 nm) can be

used for access cavity preparation, root canal shaping and cleaning. Nd:YAG (1064

nm) are used for root canal wall preparation [11]. When pulsed Nd:YAG laser is

used at 15 Hz/1.5 W, smear layer can be eradicated completely with sealing of

dentinal tubules [12]. Nd:YAG application can be used to remove of pulp remnants

and debris at the apical foramen as well as control of hemorrhage. Obturation of

root canals can also be done with lasers using vertical condensation. These lasers

also have significant role in endodontic surgery procedures. For example, treatment

of periapical lesions of sinus tract can be done by Pulsed Nd:YAG and CO2 lasers.

These lasers fasten the healing of wound. In Periapical Curettage, Apicoectomy and

Retrograde Cavity Preparation, these Lasers proved to be effective by providing

relatively bloodless and much less or no postsurgical pain. Treatments by lasers

have many advantages due to their selective and précised interaction with diseased

tissues. Laser also reduces the amount of bacteria and other oral pathogens in the

surgical field. There is less pain in most cases. Laser applications provide good

hemostasis with reduced need for sutures [13-15].

2.Applications of LASER in Dentistry

2.1 Diagnosis of Dental Pulp Vitality

LASER Doppler flowmetry is a non-invasive method of assessing and measuring the

blood flow of pulp tissue. Advantages include the technique is more objective and

reliable in assessing the health of pulp tissue. It has advantages of storing data, for

measurements to be compared at later stages. Drawbacks include its technique

sensitive, requires preparation of putty splint to hold probes and expensive.[16]

2.2 LASERS in Vital Pulp Therapy

Vital pulp therapy (pulpotomy) procedures using a LASER produce a bloodless field

by vaporization and coagulation sealing smaller blood vessels and sterile wound.

Melceret al. used CO2 LASER on beagle dogs and monkeys to achieve hemostasis

after pulp tissue exposure.[17] Moritz et al. used CO2 LASER for direct pulp

capping compared with calcium hydroxide. Results showed, after 12 months,

success rate of 89% with LASER and 68% with calcium hydroxide. Another study

was conducted by Nair et al. using CO2 LASER in 5 teeth. After 7 days, none of 5

teeth showed any pathologic changes at pulp-dentin complex 3 months post-

operative 2 teeth showed subtle, yet, distinct apposition of tertiary dentin.[18]

2.3 LASERS in Disinfection of Root Canal System

The main uses of lasers in root canal therapy are killing of bacteria, shaping of the

canal, and activation of chemical irrigation solutions. The action of the laser in such

treatments is explained by the thermal effects that are generated by the laser beam.

The Nd: YAG laser is classified as solid-state laser because it contains a solid lasing

medium (Neodymium-doped yttrium aluminum garnet). The wavelength of this

type is 1064 nm and it is also available as a second harmonic generation with 532

nm. The laser beam in this wavelength could be delivered optically by using optical

fibers. The Nd: YAG laser is considered as a soft tissue laser since the laser beam

has a peak absorption in pigmented tissues that contains dark pigments such as

melanin and hemoglobin. There are many types of bacteria that produce pigments

(e.g., black pigmented bacteria), and these types can absorb the Nd: YAG beam

easily [19]. The Nd: YAG laser has a good penetration depth through the dentinal

tubules. Berkiten, et al., has tested the antibacterial efficiency of Nd: YAG laser and

measure the penetration depth of the laser beam under SEM [20]. He used 2

powers: 1.8 watts and 2.4 watts. The 1.8 W laser beam shows a penetration depth

ranged from 400 µm to 800 µm. While for the 2.4 W laser the depth was 600 µm to

about 750 µm. In this study, The Nd: YAG laser shows a weak bactericidal effect

when it is used alone. This indicates weak absorption of bacterial cells to Nd: YAG

laser. This result agrees with the study conducted by Meire, et al., where they grew

E. faecalis on dentin disks and expose it to ND: YAG laser [ 21].

2.4 Effect of LASER on Root Canal Dentin Walls

In recent years, laser systems were widely involved in dental treatments. Many

applications of lasers in treatment protocolsfor dental hard and soft tissues are in

use now or being developed. Also, new wavelengths and different methods are being

applied in the dental field. In various laser systems used in dentistry, the emitted

energy can be delivered into the root canal system by a thin optical fiber (Nd: YAG,

Er, Cr: YSGG], argon, and diode) or by a hollow tube (CO2 and Er: YAG). Thus, the

potential bactericidal effect of laser irradiation can be efficiently used for the

additional cleaning of the root canal cavity after biomechanical instrumentation.

This effect was studied extensively using lasers such as CO2 ,Nd: YAG, excimer,

diode, and Er: YAG [22]. Previous endodontic studies using different wavelengths of

high-intensity laser light have shown the ability of their thermal impacts in the

sterilization procedure of dental hard tissues, either in the reduction of bacterial

counts in contaminated root canals or in the apicectomies at the surgical site. This

has been considered as a significant advantage over the traditional root canal

disinfection procedures [23]. Nd: YAG laser (1064 nm) is one of the laser systems

that have many applications in the dental field. Irradiation with Nd: YAG laser is

absorbed by protein (high affinity to melanin) and mineral structures, such as

phosphates and carbonate hydroxyapatite, as well as water (low affinity). Utilizing

thermal stresses created inside the tissue, Nd: YAG disorganizes the skeleton of

bacterial cells. In this process, protein denaturation takes place and the bacterial

cells die [24].

3 Bactericidal effect of a810‑nm diode laser in the root canal

wall dentin of bovine teeth 3.1 The interaction of light on a target

The interaction of light on a target follows the rules of optical physics. Light can be

reflected, absorbed, diffused or transmitted.

Reflection is the phenomenon of a beam of laser light hitting a target and being

reflected for lack of affinity. It is therefore obligatory to wear protective eyewear to

avoid accidental damage to the eyes.

Absorption is the phenomenon of the energy incident on tissue with affinity being

absorbed and thereby exerting its biological effects.

Diffusion is the phenomenon of the incident light penetrating to a depth in a non-

uniform manner with respect to the point of interaction, creating biological effects

at a distance from the surface.

Transmission is the phenomenon of the laser beam being able to pass through

tissue without affinity and having no effect.The interaction of laser light and tissue

occurs when there is optical affinity between them. This interaction is specific and

selective based on absorption and diffusion. The less affinity, the more light will be

reflected or transmitted (Figure. 1).

Fig (1)The interaction of light on a target

3.2 The thermal effect of the lasers

The thermal effect of the lasers, utilised for its bactericidal effect, must be

controlled to avoid damage to the dentinal walls. Laser irradiation at the correct

parameters vaporises the smear layer and the organic dentinal structure (collagen

fibres) with characteristics of superficial fusion as shown in Figure(2) Only the

Erbium lasers have a superficial ablative effect on the dentine, which appears more

prevalent in the intertubular areas richer in water than in the more calcified peri-

tubular areas. When incorrect parameters or modes of use are employed, thermal

damage is evident with extensive areas of melting, recrystallisation of the mineral

matrix (bubble), and superficial microfractures concomitant with internal and

external radicular carbonisation.

Conventional chemomechanical debridement (CMD) of deciduous root canals can

significantly reduce the intracanal bacterial load but cannot assure predictable

disinfection due to the inherent anatomical complexities.

Newer methods are thus being employed to enhance the efficacy of

pediatricendodontic disinfection, and the use of laser technology is at the forefront

of

this endeavor

Fig (2)The thermal effect of the lasers

3.4 Clinical procedure Local anesthesia was administered with lignocaine and rubber dam (Hygenic,

Coltene/Whaledent) was placed for isolation. Access opening was achieved, and the

roof of the pulp chamber was removed with a spherical rotary round bur no. 2

[Figure 2]. The root length was measured with the help of digital radiovisiography

(X‑ray vision, SATELAC). A sterile paper point compatible with the anatomic

diameter of the root canal was introduced into each canal and left in place for 30 s

[Figure 3]. This was the first sample (Group 1) which was immediately transferred

into an Eppendorf tube containing reduced transport fluid (RTF) medium. A

number 10 K‑file (MANI, Inc., Japan) was used to negotiate the root canals and

CMD was performed up to 25 number K‑file with intermittent 3% NaOCl irrigation.

Sterile number 25 paper points (MANI, Inc., Japan) were introduced into the

debrided canals and transferred into an Eppendorf tube containing RTF medium

(second sample – Group 2).

Thereafter, 810 nm diode laser (Elexxion, Germany) with a specific endodontic

E‑series tip of 200 μm diameter [Figure 3] operating at 1W/CW was introduced into

the root canals [Figure 4] 2 mm short ofthe radiographic apex.

Figure 3: Endodontic E-series tip 200μm Figure 4: Diode Laser into the rootcanal

While the laser was irradiated,the tip was gently withdrawn from the root canal in

a helical zigzag motion over 15 s, repeated for three cycles with intermittent 3%

NaOCl irrigation.

Microbiological sampling and culture All the samples were cultivated to detect the total number of viable bacteria.

Homogenization was performed for 3 min in a tube agitator . Sowing was performed

using three aliquots seeded with a micropipette onto the surface of blood agar plates

[Figure 5]. The plates were incubated in anaerobic jars (Oxoid Inc.) for 5 days at

37°C in 85% nitrogen, 10% carbon dioxide, and 5% hydrogen atmosphere [Figure 6].

Figure 5: Seeding on blood agar plate Figure 6: Incubation in anaerobic jar

After 5 days, the total numbers of viable bacteria unit‑forming colonies (ufc) were determined

for each sample [Figures 7] using colony counter by a blinded assessor.

Figure 7: Culture done on mannitol salt agar, blood agar, Rogosa agar plates

The present study thus focused on the evaluation of the efficacy of an 810 nm diode

laser when used as an adjunct to conventional CMD in deciduous root canal

disinfection. In this study, 98.46% of disinfection was achieved by 3%NaOCl , where

chemical disinfectants likeNaOCl penetrate no more than 130–300 μm of

dentin.The resultant 100% bacterial kill achieved in thepresentstudy ,the

combination therapy of chemical irrigation and laser irradiation could totally

eliminate all root canal pathogens including the dreaded E. faecalis, we concluded

that laser irradiation following chemomechanical irrigation was more effective than

NaOCl irrigation alone for eliminating E. faecalis as shown in Figures 8,9,10.[25]

Figure 8. Mean unit forming colonies before chemomechanical debridement

Figure 9: Mean unit forming colonies postchemomechanicaldebridementusing 3%

sodium hypochlorite

Figure 10. Mean unit forming colonies postlaser treatment

Conclusions

The results of this research show that the 810-nm diode laser can eliminate bacteria

that has immigrated deep into the dentin, thus being able to increase the success

rate in endodontic therapy.

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