Botzenhart, U.,Braun, A., & Frentzen, M. (2012). Laser treatment of dentine hypersensitivity
I overview
Fig. 1_Clinical situation of a patient
with gingival recession. The
occurrence of gingival recession is a
precursor to the loss of cement,
owing to poor oral hygiene, the
exposure of tooth necks and dentine
hypersensitivity.
laser treatment of dental hypersensitivity
_Introduction
More than two decades ago, laser applications in
the treatment of dentine hypersensitivity were introduced to dentistry. Many clinical studies using
different laser types have been published since. This
overview summarises the basic and clinical aspects,
including treatment protocols.
_The hypersensitive dental neck
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Dentine hypersensitivity is a widespread painful
condition in dentistry (Orchardson et al. 2006;
Schwarz et al. 2002). Unfortunately, this clinical
condition is often poorly understood (Pesevska et
al. 2010). It is important to understand this condition in light of dental therapy because the need for
treatment is increasing (Gerschman et al. 1994;
Miglani et al. 2010). Hypersensitivity occurs when
tooth necks are exposed. Brannström’s hydrodynamic theory describes these mechanisms. Chemical, osmotic, physical or mechanical stimuli induce
movement of fluid in dental tubules, which activates pain fibres—mainly A- fibres—at the pulpdentine border (Brannström 1992). Afflicted patients describe an intense and sharp pain of short
duration that cannot be ascribed to any other form Botzenhart, U.,Braun, A., & Frentzen, M. (2012). Laser treatment of dentine hypersensitivity
of dental defect or disease (Canadian Advisory
Board on Dentin Hypersensitivity 2003). In a huge
number of cases, these symptoms are triggered by
cold and are not related to restorative or caries
therapy. The well-being of patients who suffer from
dentine hypersensitivity is often affected. Daily
stimulation, for example eating or teeth brushing,
could induce considerable pain (Rösing et al. 2009;
Tengrungsun et al. 2008).
Today, more than 30 % of the adult population
of industrialised nations is thought to be affected
(Ritter et al. 2006; Gillam et al. 1997), but the actual
prevalence is still unknown (Rösing et al. 2009). The
reported incidence mainly depends on the population under examination and the methodology of
the studies, which vary a lot. Middle-aged patients
are most often affected (Al Sabbagh et al. 2004), but
a growing number of young persons are affected by
dentine hypersensitivity (Sykes 2007). The higher
frequency of hypersensitivity, even in middle-aged
adults, could be explained by increasing exposure of
tooth necks, which occurs increasingly early on in
young people (Dowell et al. 1983). The main reasons
for exposure are erosion, abrasion and attrition.
However, erosion is most likely to be the main factor (Addy et al. 1994; Gillam et al. 1997). This comes
from an increasing awareness of dental hygiene,
which has resulted in well-intentioned but incorrect brushing (Fig. 1). For these reasons, sensitive
tooth necks frequently occur opposite the hand
that is brushing. The loss of the thin cementum
layer in the tooth-neck area is responsible for more
than 90 % of the hypersensitive surfaces (Orchardson et al. 1987). As a result, dentine hypersensitivity can be characterised as a tooth-wear phenomenon (Bamise et al. 2008). Restorations, functional
overload and bleaching of vital teeth are also
causes of dentine hypersensitivity (Brannström
1992; Jacobsen et al. 2001; Haywood 2002). Nowadays, one therefore speaks of a multifactorial genesis of dentine hypersensitivity associated with
tooth wear.
Despite intensive research, the precise physiological mechanisms of pain production and transmission in the dental pulp have not been sufficiently determined (He et al. 2011; Bal et al. 1999;
Zhang et al. 1998). The surface texture of dentine,
that is the number of open tubules at the root neck,
is of great relevance to the process of dentine hypersensitivity (Absi et al. 1987; Markowitz 1993;
Fig. 2). The extent of hypersensitivity depends on
Laser treatment of
dentine hypersensitivity
An overview Part I
Authors_Dr Ute Botzenhart, Dr Andreas Braun & Prof Matthias Frentzen, Germany
20 I laser
1_2012
Fig. 1 Botzenhart, U.,Braun, A., & Frentzen, M. (2012). Laser treatment of dentine hypersensitivity
overview I
the number of exposed tubules (Ngassapa 1996).
Clinical studies (Narhi et al. 1992) and SEM examinations (Absi et al. 1987) have demonstrated that
the dentine of hypersensitive teeth has a considerably higher number of exposed dental tubules
(eight times the number) with a considerably
greater aperture (twice the size) compared with
teeth with no hypersensitivity symptoms (Absi et al.
1987). Since dentine hypersensitivity can occur
even after the closure of most of the dental tubules,
other factors, like inflammatory mediators, are assumed to be involved in nerve stimulation and pain
(Narhi et al. 1992; Ngassapa 1996) in addition to the
hydrodynamic theory.
_Conventional therapy
Currently, a multitude of desensitising agents
are available on the market. Normally, the therapeutic mechanism is based upon the hydrodynamic
theory. By occluding dentinal tubules, movement of
fluid should be reduced. Furthermore, the reduction of pulpal pain-nerve fibre firing should contribute to reduced sensitivity.
The spectrum of applications ranges from
agents for topical application, dentine adhesives,
light-curing primer systems, mucogingival surgery
for soft-tissue management, conventional fillings,
to endodontics as ultima ratio. Topical applications
are the most important for desensitisation; among
them are fluorides, potassium and calcium compounds, hydroxyapatite, bioactive glass and glassceramics, oxalates, glutaraldehyde, formalin and
chlorhexidine. These ingredients are mostly found
in toothpastes, mouth rinses, gels, suspensions,
varnishes or pastes for topical application. They can
also be applied via chewing gum or iontophoresis.
Today, the application of nano-sized particles of
different mixtures is also very popular.
In 1935, Grossman formulated a set of criteria
that desensitising agents are to fulfil. These criteria
are still valid today (Renton-Harper et al. 1992):
– no irritation of pulp tissue;
– painless application;
– easy to apply;
– rapid in effect;
– sufficient efficiency;
– no side-effects; and
– long-term effectiveness.
The predominant number of compounds lead to
a rapid resolution of symptoms, but often they are
only short-lived. In most cases, a long-term occlusion of dentinal tubules cannot be attained. Thus
far, no desensitising substance or method of application has fulfilled all the criteria Grossmann postulated in 1935. There has been a constant improvement in terms of the available means of treatment and active substances, but the reports still
demonstrate difficulty in relieving the pain (Romano et al. 2011). Until recently, no universally applicable substance was available (Mitchell et al.
2011; Tirapelli et al. 2010; Dabahne et al. 1999).
_Laser application
Precipitates and surface coverings disintegrate
after some time, for example owing to the influence
of acid or toothbrush abrasion (Addy et al. 1983).
Conventional desensitising treatments had to be
applied repeatedly at regular intervals to ensure a
durable analgesia (Gillam et al. 1992; Cuenin et al.
1991). The application of laser beams of different
wavelengths and energy levels, alone or in combination with topical application, for example fluoride, is an alternative method for the treatment of
dentine hypersensitivity. Botzenhart, U.,Braun, A., & Frentzen, M. (2012). Laser treatment of dentine hypersensitivity
_Studies on the effects of
laser application
In vitro and in vivo studies document high effectiveness rates and comparatively long-lasting pain
relief. The most commonly used types of lasers for
the treatment of dentine hypersensitivity already
determined in vivo can be divided into two groups.
Those lasers with a lower output power, low-level
lasers (He-Ne and GaAlAs diode lasers), are applied
to biostimulation and are distinguishable from
laser types with a middle-output power, middleoutput power lasers, which have the ability to morphologically alter dental hard tissue.
The middle-output power lasers include the
Nd:YAG, Er:YAG laser and CO2 lasers (Dederich et al.
1984; Melcer et al. 1985; Featherstone et al. 1987).
The effect of these laser types can probably be attributed to the sealing of the dentinal tubules, nerve
analgesia and placebo effects. The sealing has been
observed to be of long-lasting effect, whereas in
Fig. 2_SEM examination of a human
cervical dentinal surface with open
tubules, after experimental removal
of the smear layer with 50 % citric
acid for one minute
(1,000x magnification).
I 21 laser
1_2012
Fig. 2
I overview
the case of nerve analgesia and placebo effects, the
effects are not durable (Kimura et al. 2000a). Despite the precise mechanisms of laser action, the
long-term value of laser therapy in treating dentine
hypersensitivity is uncertain; current evidence is
based upon a slight superiority compared with conventional topical applications (He et al. 2011).
Laser therapy with low-output power has been
applied to humans since the 1970s and was originally used for wound healing (Kimura et al. 1991,
1993, 1997). In the 1980s, the inhibition of inflammation (Karu 1988, 1989) and the stimulation of
nerve cells were demonstrated (Kimura et al. 1993;
Jarvis et al. 1990).
_Low-level lasers:
GaAlAs laser
Thus far, GaAlAs diode lasers of three wavelengths have been used clinically to treat dentine
hypersensitivity: 780, 830 and 900 nm. The 780 nm
wavelength has been used with good clinical success (30 mW in continuous wave mode [cw] and an
application time of about 0.5 to three minutes;
Matsumoto et al. 1985a). The 830 nm wavelength
for the treatment of dentine hypersensitivity was
first described by Matsumoto in 1990. With an energy setting of 20 to 60 mW in cw mode and an application time of 0.5 to three minutes, the effectiveness of therapy was 30 to 100 %, depending on
the energy level (Matsumoto et al. 1990). The effectiveness of therapy using the 900 nm wavelength
and an output power of 2.4 mW at 1.2 Hz for 2.5
minutes was approximately 73 to 100 % (Kimura et
al. 2000b). Yamaguchi et al. (1990) compared the
application of a GaAlAs diode laser of a wavelength
of 790 nm and an output power of 30 mW and a
placebo in vivo. Significant differences between
laser application and the placebo group were
found. At two hours, one day and five days after
laser application, a significant improvement was
detected (Yamaguchi et al. 1990). Overall, compared with the placebo, an improvement of 60 to
22 % was achieved. GaAlAs laser application with a
maximal energy output of 60 mW did not damage
enamel or dentine surfaces morphologically
(Watanabe et al. 1991).
According to another in vitro study, the application of GaAlAs laser diodes with energy levels of
30 mW (cw, 780 nm), 60 mW (cw, 830 nm) and
10 W (pulsed, 900 nm) did not lead to a significant
increase in the temperature in the dental pulp
(Arrastia et al. 1994). Gerschman et al. (1994) accomplished a clinical double-blind study with
GaAlAs lasers compared with a placebo. During the
therapy, the apical and cervical regions of the tooth
were irradiated for one minute; this procedure was
repeated in one-week, two-week and eight-week
intervals. Dentine hypersensitivity evoked by tactile
and thermal stimuli was measured at each control
and compared with the placebo group. A significant
difference concerning dentine hypersensitivity
was detected during the analysis. It was therefore
deduced that the GaAlAs laser is an effective
method for dentine desensitisation (Gerschman et
al. 1994).
_Combined application of GaAlAs laser
and fluoride Botzenhart, U.,Braun, A., & Frentzen, M. (2012). Laser treatment of dentine hypersensitivity
In another clinical study, a laser with an energy
density of 3 and 5 J/cm2was applied up to six times
in an interval of 72 hours after each application
(Marsilio et al. 2003). Dentine hypersensitivity was
measured initially after each application, and at 15
and 60 days after application. In more than 85 % of
the teeth treated, an improvement was detected.
Side-effects were not observed (Marsilio et al.
2003). In a comparative study of GaAlAs laser application (630–670 nm) at energy levels of 15 mW
in contact mode for 20 seconds and fluoride application (Fluor Protector, Ivoclar Vivadent), significant and complete relief from pain after three sessions was achieved in 86.6 % of the cases compared
with 26.6 % after fluoridation only (Pesevska et al.
2010). The clinical findings of Noya et al. (2004)
proved that just a single application of GaAlAs laser
(670 nm, 15 mW, 5 J/cm2) yields a statistically significant reduction in sensitivity to mechanical and
thermal stimuli and that two applications are
enough to reduce sensitivity to air. No other application led to any additional benefit (Noya et al.
2004).
A significant reduction in VAS scores was also
detected with laser application for 160 seconds at
an energy density of 4 J/cm2 per dental element at
24 hours and seven days after application compared with a placebo application (Orhan et al. 2010).
All teeth remained vital and no adverse effects were
found radiographically, but the results were not
significantly different from any conventional desensitiser (Gluma Desensitizer, Heraeus Kulzer;
Orhan et al. 2010).
A combined application of GaAlAs laser light
with sodium fluoride (NaF) at an energy output of
15 mW and density of 4 J/cm2 led to no statistically
significant differences between laser application
and combined laser and fluoridation treatment
(Corona et al. 2003).
Whether a combined application of GaAlAs laser
and fluoride is effective in treating dentine hyper22 I laser
1_2012
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GNYDM_2012_A4_engn.pdf 1 NYDM_2012_A4_engn.pdf 1 20.03.12 17:34 0.03.12 17:34
I overview
24 I laser
1_2012
sensitivity is questionable. Results are contradictory, often masked by placebo effects and highly
dependent on laser parameters and the given circumstances for each patient. Both methods of
treatment, GaAlAs laser application and fluoridation, are suitable for dentine hypersensitivity therapy.
_Biostimulative mechanisms of
GaAlAs lasers
The GaAlAs laser mechanism is thought to be
biostimulative rather than effecting morphological
changes in dentine. It is assumed that the laser energy is transmitted to the dentine–pulp complex,
interacts with the pulp tissue and causes a photobiomodulating effect, increasing the cellular metabolic activity of the odontoblasts and obliterating
the dentinal tubules by means of tertiary dentine
production (Ladalardo et al. 2004; Walsh 1997).
Tengrungsun et al. (2008) compared the efficiency of a GaAlAs laser (790 nm, 30 mW, 1 min)
with a dentine bonding agent (Scotchbond, 3M
ESPE) and found a statistically significant reduction immediately and 15 days after treatment in
both of the two groups. No additional reduction in
the level of hypersensitivity 30 days after treatment
was observed. The dentine bonding agent was significantly superior to the GaAlAs laser within all
measuring periods, thus confirming the assumption that laser light may act in a different way from
occluding dentinal tubules (Tengrungsun et al.
2008).
The immediate laser effect is assumed to be triggered by placebo effects as a result of endorphin release induced by the activation of the pain inhibition system of the organism. This leads to the release of endorphins by the central nervous system,
possibly controlling the painful stimulus at the periphery, and causing biostimulative effects that
happen gradually within a few days (Tuner et al.
2002; Kimura et al. 2000b; Trowgridge et al. 1990).
Another assumption is the blocking of the depolarisation of C-fibre afferences (Wakabayashi et al.
1993). The exact mechanism of action of low-intensity lasers in dentine hypersensitivity is not
thoroughly understood (Orhan et al. 2010).
_Infra-red wavelengths and highpower density
Laser diodes, some of which have already been
tested in vitro and in vivo, with wavelengths in the
infra-red area and a high-power density are easily
available on the market. Because of the laser–tissue
interaction of this laser type with high energy per
surface density, its results are comparable to that of
an Nd:YAG laser. The sealing ability of this laser type
was observed with the parameters 810 nm, 2 W and
30 ms, and was found to be less than that of CO2,
Er,Cr:YSGG lasers and Nd:YAG lasers (Gholami et al.
2011). Botzenhart, U.,Braun, A., & Frentzen, M. (2012). Laser treatment of dentine hypersensitivity
Clinical findings with the use of a GaAlAs laser
of a wavelength of 810 nm at 1.5 to 2.5 mW for one
minute resulted in a rapid reduction of discomfort,
15 minutes and 30 minutes after laser irradiation
(37 % after 15 minutes and 41 % after 30 minutes)
compared with placebo laser application with a reduction of 9 %. The improvement remained stable
until two weeks (72 %) and two months (66 %) after application compared with placebo laser application (a 28 % reduction at two weeks and 26 % at
two months) and the application of 10 % potassium nitrate gel (a 36 % reduction at two weeks
and 30 % at two months; Sicilia et al. 2009).
_Different effects in different
age groups
Ladalardo et al. (2004) evaluated the clinical desensitising effect of red and infra-red GaAlAs laser
light application (660 nm and 830 nm, 4 J/cm2
, cw,
114 seconds, contact mode) in adult patients of
different age groups (25–35 years and 36–45
years) as an immediate (15 minutes and 30 minutes after application; four sessions with intervals
of seven days between each session) and late therapeutic effect (15, 30 and 60 days after the conclusion of treatment). Significant desensitising
levels were only found in patients aged between 25
to 35 with the 660 nm red laser, which was found
to be more effective than the 830 nm infra-red
laser immediately after and in the follow-up periods at 15, 30 and 60 days after the conclusion of
treatment.
In the group of 36- to 45-year-old patients, the
effect of the red laser was only moderate, with recurrence of sensitivity, and the infra-red laser was
ineffective. The authors concluded that the desensitising effects immediately after laser irradiation
resulted from a suppression of evoked potential of
the pulp nociceptive nerve fibres, with a better tissue response in the younger group. Pathological
processes, regressive or atrophic alterations of the
odontoblasts and the dentine pulp complex may
lower the reaction potential in older patients, with
reduced effectiveness of the laser biostimulation
(Ladalardo et al. 2004).
A significant clinical improvement was also observed after the combined application of GaAlAs
laser (808 nm, cw, contact mode, 25 seconds) and
desensitiser toothpaste compared with the toothpaste alone (Dilsiz et al. 2010a).
_GaAlAs laser and acid resistance
Recently, the GaAlAs diode laser was tested to
establish enhancement of the acid resistance of
dentine surfaces as a preventive method for hypersensitivity. A degree of improvement in the acid resistance of dentine specimens after laser irradiation (808 mn, cw, 60 J/cm2
) and erosive challenge (1
M hypochlorous acid for five minutes) was found
without creating thermal or structural damage
(De-Melo et al. 2010). However, the exact mechanism of action remains unclear. Laser treatment can
be a useful tool for rapid reduction in pain, and possibly in the improvement of acid resistance of dentine. Nevertheless, more basic research and longterm clinical trials are needed to evaluate the longterm efficiency of this method and to explain the
exact mechanism of action. Botzenhart, U.,Braun, A., & Frentzen, M. (2012). Laser treatment of dentine hypersensitivity
_Low-level lasers: He-Ne laser
The He-Ne laser has a wavelength of 633 nm
(Moritz et al. 2006) and is a low-level laser. The first
application of the He-Ne laser in the therapy of
dentine hypersensitivity was described by Senda et
al. (1985), who used an output power of 6 mW and
chose two different modes (cw and pulsed, 5 Hz).
Effectiveness ranged from 5 to 100 %. In another
study, an effectiveness of 5 to 18 % was achieved
(Wilder-Smith 1988). To date, the mechanism of action of the He-Ne laser has not been explained completely (Moritz et al. 2006). An energy level of 6 mW
does not alter the enamel or dentinal surface structure morphologically; however, laser energy transmits through enamel and dentine and reaches the
pulp tissue (Watanabe 1993). Physiological experiments have shown that the He-Ne laser application
does not influence nociceptors of circumferential
A– or C-fibres (Jarvis et al. 1990), but it does influence electrical activity (action potential), which
in healthy nerves is enhanced by about 33 % after
application (Rochkind et al. 1986). The effect is
long-lasting and leads to an increase in the action
potential of nerve fibres for more than eight
months after laser application (Rochkind et al.
1986).
_He-Ne laser compared to Nd:YAG laser
In a clinical study (Gelsky et al. 1992), which was
aimed at testing the effectiveness and confidence
of the Nd:YAG laser in the therapy of dentine hypersensitivity in vivo (see below), the He-Ne laser
was applied to one group and the He-Ne laser and
the Nd:YAG laser were applied to the other group
(30–100 mJ, 10 pps increments of ten to 40 seconds,
total application time < two minutes, without local
anaesthesia). Dentine hypersensitivity was measured mechanically (dental probe) and thermally
(stream of cold air) with the aid of a VAS. Additionally, the pulpal sensibility was evoked electrically.
Initially and after three months, X-rays were taken
to identify possible side-effects of the laser application. Directly after laser application and three
months later, a reduction in the level of discomfort
was observed. After three months, dentine hypersensitivity evoked by thermal stimuli was scaled
back to 63 % and hypersensitivity evoked by mechanical stimulation was scaled back to 61 %. Compared with the combined application of He-Ne and
Nd:YAG lasers, there was not much difference (reduction of dentine hypersensitivity evoked by thermal stimulation to 58 %; evoked by mechanical
stimulation to 61 %). All of the teeth were vital after application and no side-effects or complications could be detected.
If dentine hypersensitivity is conditioned by the
hydrodynamic mechanism exclusively, (thermal)
effects of Nd:YAG laser application should reduce
dentine hypersensitivity primarily (Gelsky et al.
1992). In contrast, He-Ne laser application should
not lead to important effects. Thus, it is assumed
that a surficial modification is not the only desensitising factor, but that there is apparently also a
neurophysiological component (Gelsky et al. 1992),
which is affected by biostimulative effects.
In a study with a similar design, the reduction of
dentine hypersensitivity after He-Ne laser application alone, as well as after combined He-Ne laser
and Nd:YAG laser application, was detected. It remained stable for six weeks (Halket et al. 1996)._
Editorial note: To be continued in our next issue of Laser.
A list of references is available from the publisher. Botzenhart, U.,Braun, A., & Frentzen, M. (2012). Laser treatment of dentine hypersensitivity
overview I
I 25 laser
1_2012
Dr Ute Botzenhart
Department of Orthodontics
Centre of Dentistry and Oral Health
Ernst Moritz Arndt University of Greifswald
Germany
Dr Andreas Braun/Prof Matthias Frentzen
Department of Periodontology, Operative and Preventive Dentistry
University of Bonn
Germany
_contact laser Botzenhart, U.,Braun, A., & Frentzen, M. (2012). Laser treatment of dentine hypersensitivity