THE TREATMENT OF INFECTIONS ON TOOTH SURFACES AND IN ROOT CANALS WITH THREE DIFFERENT LASER MODALITIES: Photodynamic Therapy, Photothermal Therapy, Photoablation

1. THE TREATMENT OF INFECTIONS ON
TOOTH SURFACES AND IN ROOT CANALS
WITH THREE DIFFERENT LASER
MODALITIES:
Photodynamic Therapy, Photothermal
Therapy, Photoablation

2. Contents
I. Introduction
1.Conventional Treatment Methods of Tooth Surface Related Infections and Their Limitations
2.Conventional Treatment Methods of Root Canal Infections and Their Limitations
3.Laser Modalities as an Alternative to Conventional Treatment Methods
3.1. Photodynamic Therapy
3.1.1. Applications of PDT for the Removal of Tooth Surface Related Infections and Root Canal Infections
3.2. Photothermal Therapy
3.2.1. Applications of PTT the Removal of Tooth Surface Related Infections and Root Canal Infections
3.3. Photoablation
3.3.1. Applications of Photoablation by Er: YAG lasers for the Removal of Tooth Surface Related Infections and Root
Canal Infections
II. Discussion
III. Future Perspective

3. I. Introduction
 In order to avoid restrictions of conventional treatment methods in dentistry, supportive
new treatment methods are beginning to be needed.
 With the discovery of the antimicrobial efficacy of lasers, lasers have begun to be used
as an alternative or adjunt to conventional treatment methods for treating dental
infections in modern era. Laser treatments are more comfortable in aspects of patients
because they reduce pain and spend less time according to conventional treatment of
dental infections.

4. 1. Conventional Treatment Methods of Tooth Surface
Related Infections and Their Limitations
https://www.mouthhealthy.org/en/az-topics/s/scaling-and-root-planing
Figure 2. Scaling and root planing.
 Mechanical and chemical plaque control
techniques are primary procedures to inhibit the
dental plaque growth.
 Scaling and root planing is complex procedure
for treating periodontal diseases. Usage of
mechanical tools are painful for patient and
antiseptic agents that are used with SRP can
lead to bacterial resistance.

5. 2.Conventional Treatment Methods of Root
Canal Infections and Their Limitations
Figure 1. Conventional root canal treatment.
http://staroftexasdentalassistingschool.com/root-canal-therapy/

6. 3.Laser Modalities as an Alternative to
Conventional Treatment Methods
3.1. Photodynamic Therapy
Oxygen
Light source
Photosensitizer
3 main components
Ground singlet state
PS
light
Excited singlet state
PS*
Intersystem
crossing
PS**
Excited triplet state
phosphorescence
O2
1O2
Type II
Biomolecule
ROS
O2
Type I
fluorescence
Figure 3. Action mechanism of aPDT, type I and type II reactions. PS:
photosensitizer; PS*: photosensitizer in excited singlet state; PS**:
photosensitizer in excited triplet state; ROS: reactive oxygen species;
1O2: singlet oxygen.

7. 3.1.1. Applications of PDT for the Removal of Tooth
Surface Related Infections and Root Canal
Infections
 The efficacy of PDT in planktonic S mutans cultures.
 erythrocin and rose bengal at a concentration of 2 µM
 LED light source with a wavelength of 440- 460 nm,
an output power of 200 mW (energy of 36 J and
irradiation time of 180 s)
 CFU/ml was reduced by 6.86 log10 in the rose bengal
group and 5.16 log10 in the erythrocin group
Pereira da Costa ACB, Junior JC,Pereira CA et al. Susceptibility of planktonic
cultures of streptococcus mutans to photodynamic therapy with a light-emitting
diode. Braz Oral Res 2010; 24: 413-418
Figure 4. Mean and standard deviation of the number of
CFU/mL (log10) obtained for the different groups

8.  When Neves et al. applied PDT for the removal of
carious tissue of the deep dentin of deciduous
molars, they found that PDT using 0.01%
methylene blue dye followed by irradiation with
an InGaAlP diode laser (λ – 660 nm; 40 mW; 120
J/cm2; 120 s) would not be appropriate clinical
alternative to reduce bacterial contamination in
deep dentin.
Figure 5. Experimental design
NEVES, Pierre Adriano Moreno, et al. "Clinical effect of
photodynamic therapy on primary carious dentin after partial caries
removal." Brazilian oral research 30.1 (2016).
 There was no significant difference in the number of colony-
forming units (CFU) for any of the microorganisms
assessed

9. Belinello-Souza, Estéfani L., et al. "Antimicrobial
photodynamic therapy combined to periodontal
treatment: Experimental model." Photodiagnosis and
photodynamic therapy 18 (2017): 275-278
 Belinello et al. showed the efficacy of PDT with PpNetNI
(proto-porphyrin) as a photosensitizer with LED at 630
nm as a light source which has 400 mW output power
and scaling and root planing in terms of bone gain after
elimination of periodontitis in rats. They found that
aPDT provide 30% bone gain compared to SRP group
following 7 days from treatment. This might be due to
effects of low level laser therapy on osteogenic
differentiation and proliferation. The results
demonstrated that aPDT may be useful as an adjunct to
SRP by reducing periodontal tissue destruction.Figure 6. Quantification data of bone loss
comparing aPDT and SRP group.

10. Table Enterococcus faecalis Colony-forming
Units before and after Treatment
Afkhami, Farzaneh, Saba Akbari, and Nasim Chiniforush. "Entrococcus
faecalis elimination in root canals using silver nanoparticles, photodynamic
therapy, diode laser, or laser-activated nanoparticles: an in vitro study."
Journal of endodontics43.2 (2017): 279-282.
 Efficacy of PDT (ICG, 810 nm, 200 mW, 30
seconds) and combination of silver nanoparticles
(100 ppm AgNP) and PDT for elimination of
Enterococcus Faecalis in root canals.
 Conventional PDT is less effective. (68.47%
reduction).
 Combination of PDT with ICG and 810 nm diode
laser and AgNPs which had 99.12% reduction in
colony count can be used for increasing efficacy
of conventional PDT.

11. Figure 7. Comparison of CFUs/mL before and after endodontic
treatment with aPDT. Data are mean and standard deviation of Log10
(CFU/mL).
 In a case series carried out by Okamoto et al. 5
dedicuous teeth with pulp necrosis from 3 children were
treated firstly by standard root canal treatment, then
treated by photodynamic therapy as an adjunctive.
0.005% methylene blue as a photosensitizer and 660 nm
laser with an energy of 4J for 40s exposure were used in
aPDT application. The results of this study showed
bacterial reduction from 37.57% to 100%. As a conlusion,
it was found that aPDT can be clinically applied as an
adjunct to standard root canal treatment.
Okamoto, Camila Basilio, et al. "Antimicrobial Photodynamic Therapy as a Co‐adjuvant in
Endodontic Treatment of Deciduous Teeth: Case Series." Photochemistry and
photobiology (2018).

12. 3.2. Photothermal Therapy
• Damaging of cells by thermal effects such as
coagulation, hyperthermia and vaporization.
• If the temperature exceeds the threshold
value of 45 oC, it can affect the nerves in both
soft tissue and root canal, and may cause
serious pain and may decrease the comfort
of the patient.
• PTT can be preferred in the absence of
oxygen because its effect is not dependent
on oxygen.Figure 8. Basic mechanism of PTT

13. 3.2.1.Applications of PTT for the Removal of
Tooth Surface Related Infections and Root
Canal Infections
Figure 9. Effect of sub-lethal doses of photo-
activated disinfection on Porphyromonas
gingivalis cell viability. *Significantly different
from the control (no treatment), p < 0.05.
 Photothermal effect on biofilm formation ability of
Porphyromonas gingivalis as an anaerobic bacterium
associated with root canal infection.
 ICG at concentration of 4 mg/ml was added bacterial
suspension and irradiated with diode laser light for 0.5, 1,
and 2 min with fluencies of 15.6, 31.2, and 62.5 J/cm2,
respectively, at wavelength 810 nm.
 High concentrations of ICG and light irradiation time
significantly reduced the number of bacteria and the
formation of biofilm, up to 30.4% and 25.1%, respectively.
Pourhajibagher, Maryam, et al. "Photo-activated disinfection based on indocyanine green against cell
viability and biofilm formation of Porphyromonas gingivalis." Photodiagnosis and photodynamic
therapy 17 (2017): 61-64

14. Figure 11. Effects of (a)toluidine blue O-
photodynamic therapy and (b) indocyanine
green- photothermal therapy on Streptococcus
mutans biofilm formation. *Significantly different
from the control, p < 0.05.
Figure 10. Effects of (a) toluidine blue O- photodynamic
therapy and (b) indocyanine green- photothermal therapy
on Streptococcus mutans cell viability. Control was
3.23 × 105 colony forming unit (CFU)/mL. *Significantly
different from the control, p < 0.05.
 Comparison of the efficacy of
PTT with indocyanine green
and PDT with toluidine blue on
biofilm formation of
Streptococcus mutans.
 0.1 mg/ml TBO and 1 mg/ml
ICG
 diode laser at a wavelength of
635 nm with energy density of
17.18 J/cm2 and 810 nm with
energy density of 15.62 J/cm2Beytollahi, Leili, et al. "The efficacy of photodynamic and photothermal therapy on
biofilm formation of Streptococcus mutans: An in vitro study." Photodiagnosis and
photodynamic therapy 17 (2017): 56-60.

15. 3.3. Photoablation
Photoablation is the removal of tissue by applying high intense UV-light irradiation
without thermal damage. When a UV photon is absorbed, the bond energy of
molecules is exceeded by high energy gain and dissociation of atoms occurs.
 Excitation : XY + hv  (XY)*
 Dissociation : (XY)*  X + Y + Ekin
Figure 12. Physical steps of Photoablation

16.  UV lasers are not preferred much in dental applications because they
may affect DNA of tissues and cause mutations. Er: YAG lasers are
mostly preferred for removing carious tissue by its photoablative effect.
Er: YAG laser irradiation
Absorption by
water molecule
in carious tissue
Evaporation of water molecules
cause the carious tissue to
explode away
Figure 13. Er: YAG laser application for removal of caries.
Dental caries

17. 3.3.1. Applications of Photoablation
by Er: YAG lasers for the Removal
of Tooth Surface Related Infections
and Root Canal Infections

18. Figure 14. Caries removal and restorations after bur
preparation (A) or Er:YAG laser preparation (B).
 Caries removal by Er: YAG laser (at the
noncontact mode with focal distance of 7 mm,
a pulse energy of 250 mJ, a pulse frequency
of 4 Hz and an output beam diameter of 0.9
mm, an energy density of 39 J/cm2, and
under 6 ml/min water.
 Due to this study Er: YAG lasers have no
additive influence according to bur preparation
for caries removal.
Valério, Rodrigo Alexandre, et al. "Caries removal in deciduous
teeth using an Er: YAG laser: a randomized split-mouth clinical
trial." Clinical oral investigations 20.1 (2016): 65-73.

19. Figure 15. Reduction of the total bacterial count
and specific periodontal pathogens 6 months after
treatment in three treatment groups. *p < 0.05 vs
SRP, # p < 0.05 vs Er, § p < 0.05 vs NdErNd
Grzech-Leśniak, K., A. Sculean, and Boris Gašpirc. "Laser reduction of specific
microorganisms in the periodontal pocket using Er: YAG and Nd: YAG lasers: a
randomized controlled clinical study." Lasers in medical science (2018): 1-10
 The combination of Nd: YAG and Er: YAG group,
the Nd: YAG laser was used for pocket
disinfection (MSP = 100 μs, 2.5 W, 20 Hz, power
peak of 1250 W, 300-μm fiber tip, 10 to 30 s per
tooth) followed by root debridement with the Er:
YAG laser (MSP = 100 μs, 40 mJ/p, 40 Hz,
power peak of 400 W, 400-μm fiber tip, water
spray (28 ml/min)) and subsequent application of
the Nd:YAG laser for blood clot stabilization (VLP
= 600 μs, 3.5 W, 20 Hz, power peak = 291 W,
300-μm fiber tip, 10 to 30 s per tooth).
 The combination of Nd: YAG laser and Er: YAG
laser as a nonsurgical treatment of periodontitis
resulted greatest bacterial reduction (93.0%) of
Treponema denticola, Peptostreptococcus
micros, and Capnocytophaga gingivalis
according to Er: YAG laser alone (84.9%) and
SRP (46.2%).

20. A novel laser activation irrigation system, photon-
initiated photoacoustic streaming (PIPS), is used with an
Er: YAG laser. Low energy (20 mJ), pulse repetition rate
(15 Hz) and very short pulse length (50 µs) are used
with a radial, stripped novel tip in this system. PIPS
differs from other techniques in that the tip is placed in
the pulp chamber and kept stable without advancing into
the canal orifice. Researchers indicated that PIPS
improves canal cleanliness with a greater number of
open tubules compared to nonactivation irrigation and
also reduces thermal side effects.
http://www.fotona.com/media/aurora/dokumenti/2010/11/pips_brochure_fotona_web.pdf
Figure 16. Photon initiated photoacoustic streaming

21. II. Dıscussion
 Wavelengths which are shorter than 600 nm are absorbed highly by the endogenous
molecules. For this reason, a wavelength which is greater than 600 nm should be selected
in aPDT to minimize the possible side effects in the host tissue.
 Main problem of elimination of microorganisms in root canal system is reaching of laser
beam into deep root canals. With the use of an intracanal fiber may increase the
uniformity of light distribution along the root canal and improve PDT efficiency.
 Indocyanine green with the use of longer wavelength may be useful for elimination of
bacteria in root canal system due to penetration capability of deeper root canals and
photothermal effects.
 Er: YAG lasers could be the best choice for elimination of bacteria in complex root canal
system due to photoacoustic effect by using photon-initiated photoacoustic streaming.

22. III. Future Perspective
 For elimination of root canal infections by PDT, use of intracanal fiber optics should be
widespread. Intracanal fiber optics provide proper light distribution to root canal system.
Further studies for determining of appropriate PDT protocol or PS formulation, to optimize
PDT outcomes, more in vivo studies about treatment of root canal infections are suggested.
 Efficacy of PDT can be increased by using additive antimicrobial agents such as EDTA, silver.
 Additional cooling systems with photothermal therapy such as air flow may be helpful for
providing less pain to patient caused by thermal effect. And also further in vivo studies should
be increased for understanding its antimicrobial efficacy.
 Water spray is used to increase Er: YAG laser irradiation effect but it can be problem for
dentist who is applied laser because at the same time dentist should apply water supply.
Maybe in further studies this additional water supply mechanism could be developed as
automatic.