Andreas Braun, Michael Berthold, Roland Frankenberger
REPRINT
The 445-nm semiconductor laser
in dentistry – introduction of a new
wavelength
Keywords
diode laser, excision, microbe reduction, mucosa, pathology, semiconductor laser,
traumatic fibroma
Abstract
Dental laser treatments are used successfully in surgery, endodontics, and periodontology to improve both the comfort of the patient and the outcome of the treatment. The
effectiveness of the laser crucially depends on how the tissue absorbs the electromagnetic radiation. The degree of absorption differs significantly in the three areas of use
mentioned. The wavelength and power of the laser play an important role in this. Up
until now, therapeutic diode lasers used in dentistry have usually had a wavelength
ranging from 810 to 980 nm. The development of a diode laser in the blue wavelength
range (445 nm) promises good energy coupling to pigmented cells and tissue, combined with low absorption in water, thus an improved cutting performance for surgical
procedures and deep decontamination for periodontic and endodontic treatment is
anticipated. This overview presents the theoretical background as well as the practical
applications of diode laser technology, with particular reference to the recently introduced blue wavelength. The clinical use for tissue excision is described in a case report.
Absorption of laser energy
When laser energy meets human tissue, part of the
energy is reflected, depending on the angle of incidence. The energy that penetrates the tissue is either
transmitted unchanged, scattered, deflected, or absorbed, and transfers the respective amount of energy
to the absorbing molecule. In connection with this,
various kinds of interaction with the tissue such as
photochemical, thermal, or ablative effects can be observed11. In human tissue, laser energy can be absorbed by water, porphyrin, hemoglobin, melanin, or
hydroxyapatite, for example. Which biological structures react to laser light, and how they react, depends
on the wavelength of the laser light, the power, and
the duration of radiation (Tab. 1).
Quintessenz 2015;66(2):205–211
205
Andreas Braun
Prof. Dr. med. dent.
Michael Berthold
Development engineer
Roland Frankenberger
Prof. Dr. med. dent.
Department of Restorative Dentistry
Medical Center for Dental and Oral Medicine
Philipps University of Marburg and
University Hospital of Gießen and
Marburg, Marburg site
Georg-Voigt-Straße 3
35039 Marburg
Email: [email protected]
GENERAL DENTISTRY
The 445-nm semiconductor laser in dentistry – introduction of a new wavelength
Indication
Wavelength range [nm]
Laser fluorescence detection of caries and calculus
405 to 655
Antimicrobial photodynamic therapy (aPDT)
635 to 810
Low level laser therapy (LLLT)
635 to 830
Laser-supported tooth brightening
445, 810 to 980
Tissue disinfection in endodontics and periodontology
445, 810 to 980
Soft tissue surgery
445, 810 to 980
Non-thermal semiconductor lasers
With regard to the effects of semiconductor lasers
used in medicine, a basic distinction can be made between non-thermal and thermal effects. In the case of
non-thermal effects, the capability of using the transmitted energy to trigger a photochemical reaction is
exploited. A typical example of this is antimicrobial
photodynamic therapy (aPDT). This is a method of affecting cells, microorganisms, or molecules by low
power density laser energy. For this purpose, three
components are needed in order to have an effect at
the target site: energy (here in the form of laser light),
a light-activated agent (photosensitizer), and oxygen3.
The photosensitizer is activated by laser energy in
such a way that energy can be transferred to the oxygen present, resulting in cytotoxic effects on microorganisms. Even microbes such as Enterococcus faecalis that are problematic for endodontic treatment can
be eliminated from root canal systems7.
Conventional semiconductor lasers
When utilizing thermal effects, there is a gradual, selective reaction in tissue structures depending on the
degree of heating. The reactions when a conventional
diode laser with wavelengths of 810 to 980 nm is used
are often coagulation and removal of tissue through
photoablation. Depending on the laser parameters,
diode lasers such as this can be used for coagulation
cutting or ablation of oral soft tissue12. Such tech206
Tab. 1 Indications for
diode lasers and typical
wavelengths
niques are useful for providing an essentially bloodfree surgical field and reducing the bacterial colonization of periodontal lesions1. For chronic periodontitis,
slightly better clinical parameters have been observed
with adjunctive treatment with a 980-nm diode laser
than after conventional treatment5. Since no clinically
significant improvement has been ascribed to the adjunctive diode laser treatment of periodontal lesions
in other studies6,13, additional investigations are needed in this area in the future. However, the results are
clearer in other fields of dentistry. For root canal preparation, for example, a significant improvement in microbe reduction was found for adjunctive laser treatment compared with rinsing with sodium hypochlorite
alone9. Furthermore, an antibacterial effect extending
to the depth of the dental hard substance was proven
when a 980-nm diode laser was used8.
Blue laser technology
Semiconductor lasers are being used in an increasing
number of fields in research, industry, medicine, and
to no small extent the consumer sector due to their
compact structure, high optoelectric efficiency, and
reliability. They have become indispensable even for
daily use such as in laser pointers, CD ROMs, Blu-Ray
storage formats, laser printers, distance measuring
devices, and barcode scanners, and for data transfer
and storage. In recent decades, great efforts have
therefore been made to develop semiconductor lasers
with certain wavelengths. Shuji Nakamura was the
Quintessenz 2015;66(2):205–211
GENERAL DENTISTRY
The 445-nm semiconductor laser in dentistry – introduction of a new wavelength
Case report
At the beginning of October 2014, a 44-year-old female
patient presented at the Medical Center for Dental and
Oral Medicine in Marburg. She reported a lentil-sized
mucosal lesion in the vestibular area of her right lower
lip that she had first noticed a few months previously
Quintessenz 2015;66(2):205–211
10,000
— HbO2
— HHb
— Water
— Melanin
— Lipid
1,000
Absorption coefficient (cm-1)
first person to present the gallium nitride laser diode
in the blue light range with a wavelength of 405 nm.
For this, he and his colleagues, Isamu Aksaki and
­Hiroshi Amano, were awarded the Nobel Prize for
Physics in 2014.
The wavelength used is of major significance for
the therapeutic effect. This is due to the absorption
properties of the irradiated tissue, as the interaction
with the tissue is determined by the energy input into
the tissue. High absorption of laser energy in the tissue results in a low penetration depth, and vice versa.
For coagulating cutting in surgical procedures, there
should therefore be high absorption rates in tissue
and blood. In such procedures, one of the most important advantages of blue laser light is that, due to its
shorter wavelength, it penetrates less deeply into tissue and is scattered less14. In turn, due to this low
penetration depth, the risk of accidental injuries in
deeper layers is drastically reduced and the beam can
be guided more precisely. At the same time, the thermal input to surrounding tissue from the scattering of
the laser light is reduced.
If we look at the individual components of human
and animal tissue, they contain high percentages of
water, hemoglobin, melanin, lipids, and proteins. The
absorption maximum for blood cells is in the range of
approximately 430 nm2,10 (Fig. 1), which leads to a
high energy input and can thus cause rapid coagulation. However, the absorption rate for water is not
high in this wavelength range, so limited heat buildup
from energy input into water can be expected. For surgical procedures, blue laser thus allows clean cutting
with little bleeding and a limited area of heat generation due to the special absorption properties in the
tissue components.
100
10
1
0.1
0.01
0.001
0.0001
400
500
600
700
800
900
1.000
Wavelength (nm)
Fig. 1 Range of absorption coefficients of endogenous
chromophores in tissue, adapted from Beard2. HbO2 =
oxyhemoglobin, HHb = deoxyhemoglobin
(Fig. 2). With the suspected diagnosis of traumatic fibroma, photo documentation was made in order to
record any changes in the size and surface structure
and also the reaction of the adjacent tissue. Although
according to the patient no significant change had taken place since the lesion was first noticed, she expressed the desire to have it removed. The patient was
offered the option of laser removal as an alternative to
conventional removal with a scalpel and subsequent
suture. With this treatment method it could be assumed that, given the coagulating effect of the laser,
sutures would not be necessary, thus avoiding also
the necessity of a second procedure to remove the
sutures. Treatment was scheduled for 30 October 2014,
to give the patient sufficient time to give her consent
to the surgical procedure.
To remove the lesion, the SIROLaser Blue (Sirona,
Bensheim), a Class IV 445-nm diode laser, was used
(Fig. 3). For the tissue excision, the manufacturer recommended a setting of 2 W in continuous wave (cw)
mode and a resulting duty cycle of 100%. The hand207
GENERAL DENTISTRY
The 445-nm semiconductor laser in dentistry – introduction of a new wavelength
Fig. 2 Initial situation prior to the surgical intervention.
Lentil-sized mucosal lesion in the vestibular area of the right
lower lip
Fig. 3 445-nm laser
system with pre-selectable indication-based
laser parameters that
can also be individually
adjusted
piece was used with a 320-µm (core diameter) fiber
and was activated via the finger switch.
Since the patient had no conspicuities in her general medical history, Ultracaine D-S 1:200,000 (Sanofi-­
Aventis, Frankfurt a. M.) was used for local anesthesia,
with a total of 0.9 ml used for circular infiltration
around the tissue to be removed. Following a check of
anesthesia using a sharp probe in the surgical area,
the patient and surgical team all put on laser safety
goggles suitable for a wavelength of 445 nm. The treatment room was designated as a laser workplace from
the outside. In addition, a warning light located at the
entrance door to the treatment area was activated.
After the mucosal lesion had been grasped with a
surgical forceps, the tissue was excised by guiding the
fiber from mesial to distal horizontal to the surface of
the healthy tissue (Fig. 4). Unlike conventional diode
lasers, it was not necessary to condition the fiber with
the 445-nm diode laser. The mucosal lesion was separated in toto from the tissue substrate by applying
slight tension with the surgical forceps (Figs. 5 and 6).
Due to the coagulating effect of the laser, there was no
acute bleeding which would have required a suture.
The area of the wound was flushed with normal saline
solution to clean and moisten the tissue. The excised
tissue was placed in a prepared container of formalin
and sent directly to the Marburg Institute of Pathology
for histological examination (Fig. 7).
After Solcoseryl dental adhesive paste (Valeant
Pharmaceuticals, Bad Homburg) was applied to the
wound surface, the patient was advised to protect this
area as much as possible. She was also given the option of taking a pain tablet should she experience pain
once the anesthetic had worn off. She was told to
avoid eating if possible while the anesthetic was still
effective in order to prevent unchecked biting into the
oral mucosa. The patient was requested to return for
routine wound checks 2 and 7 days after the procedure.
A non-irritated wound with the expected fibrin coating
was found at follow-up (Fig. 8). No postoperative hemorrhaging was seen or reported by the patient.
Fig. 4 Positioning of the tip of the 445-nm laser attachment
at the mesial base of the tissue lesion
208
Quintessenz 2015;66(2):205–211
GENERAL DENTISTRY
The 445-nm semiconductor laser in dentistry – introduction of a new wavelength
Fig. 5 Fixation of the tissue to be removed with a surgical
forceps during excision of the lesion
Fig. 6 Excision of the lesion from mesial to distal with the
activated laser
Fig. 7 Transfer of the excised lesion to a transport container
for the histological examination
Fig. 8 Follow-up of the wound 1 week after the procedure.
Non-inflamed wound with the expected fibrin coating and no
evidence of secondary bleeding
The Marburg Institute of Pathology described the
excised tissue after HE (hematoxylin eosin) and PAS
(periodic acid Schiff) staining as follows: 0.3 x 0.3 cm
tissue covered on one side with mucosa (Fig. 9), traumatic fibroma of the oral mucosa with slightly hyperplastic parakeratotic squamous epithelium with no
dysplasia and no significant inflammatory changes,
no evidence of fungus in the PAS staining, and no evidence of malignancy.
The latest wound follow-up was made 1 month after the procedure. At this time, the wound was completely healed and no new tissue formation was detected (Fig. 10). No scarring was detected on inspection
or perceived when eating. The patient reported that
she had felt a burning sensation at the tissue removal
site during the healing process, but that there was
now no pain or dysesthesia in the area. Another follow-up should be made 6 months from now as part of
a routine dental check-up.
Quintessenz 2015;66(2):205–211
209
GENERAL DENTISTRY
The 445-nm semiconductor laser in dentistry – introduction of a new wavelength
Originalvergrößerung x 100
Originalvergrößerung x 20
Originalvergrößerung x 100
Fig. 9 Histological sample of the tissue lesion. Tumor-free oral mucosa with the
finding of a traumatic fibroma (original enlargements 1:20 and 1:100)
Evaluation
In many cases, treatment methods based on laser
technology lead to results similar to those that can be
achieved with conventional methods. In the case described here, the indication for the use of laser was
supported by the patient’s desire for a minimally invasive procedure. In addition, a second procedure for
the removal of sutures was avoided, as has already
been described for other laser-based surgical interventions4. Furthermore, the possibility had to exist of acquiring a tissue sample suitable for histological evaluation to allow a diagnosis of the lesion to be confirmed.
This requirement was also complied with through the
use of the 445-nm laser. However, it should be taken
210
Fig. 10 Wound follow-up 1 month
after the procedure. Completely healed
wound area with no visible scar
formation and no evidence of new
tissue formation
into consideration that excessively high power settings can possibly lead to pronounced carbonization
of the tissue margins, which would make a histological evaluation more difficult.
From the practitioner’s viewpoint, it can be stated
that the fiber tips of conventional diode laser systems
(810 to 980 nm) must be conditioned in order to cut
effectively. For this, the fiber tip needs to be blackened
before treatment to generate more heat at the tip. In
addition, direct contact with the tissue is needed for
cutting. When the 445-nm system was used, neither of
these prerequisites was necessary. Even without direct contact with the surface of the tissue, cutting performance was considerable at a distance of approximately 1 mm.
Quintessenz 2015;66(2):205–211
GENERAL DENTISTRY
The 445-nm semiconductor laser in dentistry – introduction of a new wavelength
References
1. Assaf M, Yilmaz S, Kuru B, Ipci SD, Noyun U, Kadir T. Effect of the diode
laser on bacteremia associated with dental ultrasonic scaling: a clinical
and microbiological study. Photomed Laser Surg 2007;25:250-256.
2. Beard P. Biomedical photoacoustic imaging. Interface Focus 2011;1:
602-631.
3. Braun A. Antimikrobielle photodynamische Therapie im Rahmen der
Endodontie und Parodontitistherapie. Zahnmedizin up2date
2010;6:597-609.
4. Capodiferro S, Maiorano E, Scarpelli F, Favia G. Fibrolipoma of the lip
treated by diode laser surgery: a case report. J Med Case Rep 2008;
2:301.
5. Caruso U, Nastri L, Piccolomini R, d’Ercole S, Mazza C, Guida L.
Use of diode laser 980 nm as adjunctive therapy in the treatment of
chronic periodontitis. A randomized controlled clinical trial. New
Microbiol 2008;31:513-518.
6. Euzebio Alves VT, de Andrade AK, Toaliar JM et al. Clinical and
microbiological evaluation of high intensity diode laser adjutant to
non-surgical periodontal treatment: a 6-month clinical trial. Clin Oral
Investig 2013;17:87-95.
7. Fonseca MB, Júnior PO, Pallota RC et al. Photodynamic therapy for
root canals infected with Enterococcus faecalis. Photomed Laser Surg
2008;26:209-213.
Quintessenz 2015;66(2):205–211
8. Gutknecht N, Franzen R, Schippers M, Lampert F. Bactericidal effect
of a 980-nm diode laser in the root canal wall dentin of bovine teeth.
J Clin Laser Med Surg 2004;22:9-13.
9. Kreisler M, Kohnen W, Beck M et al. Efficacy of NaOCl/H2O2 irrigation
and GaAlAs laser in decontamination of root canals in vitro. Lasers
Surg Med 2003;32:189-196.
10. Naqvi KR. Screening hypochromism (sieve effect) in red blood cells:
a quantitative analysis. Biomed Opt Express 2014;5:1290-1295.
11. Niemz MH. Laser-tissue interactions – Fundamentals and applications.
3. ed. Berlin: Springer, 1996.
12. Romanos GE, Gutknecht N, Dieter S, Schwarz F, Crespi R, Sculean A.
Laser wavelengths and oral implantology. Lasers Med Sci 2009;24:
961-970.
13. Sgolastra F, Severino M, Gatto R, Monaco A. Effectiveness of diode
laser as adjunctive therapy to scaling root planning in the treatment of
chronic periodontitis: a meta-analysis. Lasers Med Sci 2013;28:
1393-1402.
14. Wilson SW. Medical and aesthetic lasers: semiconductor diode laser
advances enable medical applications. BioOptics World 2014;7:21-25.
211