Petra Mosskull Hjertton

Institutionen för Odontologi
Odontologi, Examensarbete/D
(Medicine Magisterexamen i Odontologi)
(Master of Medical Science in Odontology)
Objective and Subjective Evaluation of
Er:YAG Laser versus High-speed Bur for
Cavity Preparation in Swedish Adolescents
Petra Mosskull Hjertton
Stockholm 2008
Nr 146
Objektiv och Subjektiv Utvärdering av Er:YAG Laser och
Highspeed Borr för Preparation av Kaviteter på Svenska
Ungdomar
Sammanfattning
Borren är och har varit det dominerande redskapet för preparation i tänder. Borren är
också en vanlig orsak till uppkomst av tandvårdsrädsla. Laser är ett allt vanligare
alternativ till borren. Syftet med denna studie var att jämföra tidsåtgång, upplevelser och
förändringar i puls hos svenska ungdomar vid preparation med borr och laser.
Metod: Arton (9M, 9F) 14-17 år deltog i studien. Efter bedövning preparerades
kontralaterala intakta premolarer med Er: YAG laser och highspeed diamant borr till ett
djup av 2 mm vid den buckala prominensen. Tidsåtgång och puls noterades. Subjektiva
upplevelser utvärderades med VAS-skalor och ett frågeformulär.
Resultat: Medeltiden för preparation med laser (89±45s) var signifikant (P<0.001)
längre jämfört med highspeed borr (12±4sec). Signifikanta skillnader i pulsförändring
noterades. Lukten från lasern var sämre enligt VAS-skalan (P<0.01). 72 % uttryckte
mindre obehag och 78 % mindre ljud vid preparation med laser. 83 % föredrog laser
framför borr vid eventuell framtida behandling.
Slutsats: Preparation med laser tog längre tid och luktade sämre jämfört med highspeed
borr, men laser föredrogs av 83% av de svenska ungdomarna.
Handledare: Dr. Mats Bågesund, Centrum för Ortodonti/Pedodonti, Specialisttandvården,
Linköping
Examinator: Docent Xie Qi Shi, Avdelningen för Oral Radiologi, Institutionen för Odontologi,
Karolinska Institutet, Stockholm
2
Objective and Subjective Evaluation of Er:YAG Laser
versus High-speed Bur for Cavity Preparation in Swedish
Adolescents
Abstract
The bur has been, and still is, the dominating tool for removing caries in teeth. The bur
is also a common cause of dental fear. Laser has become an alternative to the bur. The
aim of this study was to evaluate the time consumed, pulse changes and subjective
experience during removal of healthy tooth substance using high-speed bur and Er:
YAG laser.
Method: Eighteen (9M, 9F) 14-17 year-olds participated. After local anaesthesia, Er:
YAG laser and high-speed diamond bur were used on contra-lateral healthy maxillary
premolars. Cavity preparation was performed to a depth of 2mm on the middle of the
buccal surface. Time for preparation was measured and the pulse was recorded.
Subjective experience was evaluated using VAS-scale and questionnaire.
Results: Mean time used for preparation with laser (89±45sec) was significantly
(P<0.001) longer than for high-speed bur (12±4sec). Significant differences according
the pulse changes were found. The smell was worse - according to the VAS-scale when laser was used (P<0.01). 72% expressed less discomfort and 78% less sound when
laser was used. 83% preferred laser for possible future treatment.
Conclusion: Laser preparation was more time consuming and caused unpleasant smell,
but was preferred by 83% of the adolescents.
Keywords: Laser; paediatric dentistry; adolescents; cavity preparation; treatment
time; smell
3
Introduction
The bur has been, and still is, the dominating tool for removing caries in teeth. The bur
is also a common cause of dental fear. Dental fear, together with dental behaviour
management problems, are the most common reasons for referral to specialist paediatric
dental clinics in Sweden [Klingberg et al. 2005]. The backgrounds of these causes
depend on several factors on different levels. They could be connected to the child’s
previous dental treatments. In this case, experience of pain, the feeling of not being in
control, the noise and vibrations of rotary instruments are usual reasons for
establishment and maintenance of fear [Peretz and Efrat 2000]. Dental fear could also
result from personal factors of the patient (temperament) or from external factors in the
child’s environment (influence of parents or other close persons). Direct conditioning personal experiences - according to Rachman´s pathways, is though found to be the
main reason for the development of dental fear [Milgrom et al. 1995; Townend et al.
2000]. Dentistry in general, and paediatric dentistry in particular, is struggling to make
dental care as comfortable as possible and to find new treatment ways. Alternatives to
the bur have shown up during the years of which laser is one of them, and has been used
in dentistry for over 40 years [Pelagalli et al. 1997]. Since Goldman et al. made the first
attempts in 1964 to use Ruby lasers in dentistry, many studies and advancements have
been made.
History and Theory
Albert Einstein presented the basic theory of laser in 1916. The word LASER is an
acronym for Light Amplification by Stimulated Emission of Radiation. Einstein’s
4
theory was further developed and in 1960 Mainman introduced the first working laser
[Tunér 2003; Coluzzi et al. 2005].
Laser radiation is, just like the light from the sun, electromagnetic in nature. That is, it
consists of energy in form of photons, which travels in waves at the speed of light.
There are many different kinds of electromagnetic radiation divided and named after the
length of the waves and contained energy. The spectrum is wide, from the long radio
waves (1000-1m) with low energy, to the very short gamma rays (1000-1fm) with high
energy. In between we find microwaves (1000-1mm), infrared radiation (1000-0,8μm),
visible light (800-400nm), ultraviolet radiation (400-1nm) and x-rays (1000-1pm). The
energy from the electromagnetic source is transmitted to the target and influences it in
different ways. The shorter the wavelength, the more dangerous it is. Wavelength
shorter than 320nm is called ionised radiation and is able to injure living organisms and
cause cancer. Radiation with low energy is only able to cause excitation and heating.
Photons from the visible, ultraviolet or infrared light can be reflected, transmitted or
absorbed in contact with different matter [Tunér and Hode 2004]. We know that lightcoloured material reflects sunlight, while dark-coloured objects absorb it. If absorbed,
most of the energy is often transformed to heat. In this spectrum we find the laser
radiation. The emitted wavelengths from dental lasers vary between 488nm to 10
600nm and are all non- ionising [Coluzzi et al. 2005]. What differs laser from ordinary
light is that the laser beam is concentrated to a small area, is coherent and
monochromatic and gives light with high intensity. In this way the absorbed radiation
affects the target tissue more than by heating. It can melt or vaporise the hit material.
Different lasers emit different wavelength. Various substances do not react in the same
way to a specific wavelength. Hard tissues absorb other wavelengths than soft tissues.
5
The efficiency of the laser depends on the ability of the material to reflect or absorb the
laser beam of a specific wavelength [Convissar and Goldstein 2003; Tunér and Hobe
2004; Coluzzi et al. 2005]
There are many different kinds of lasers- for soft- and hard-tissue applications- used in
medicine and dentistry. As mentioned before, the word LASER stands for Light
Amplification by Stimulated Emission of Radiation. The laser is a light amplifier.
Depending on which amplifying medium is used, lasers are named differently and have
various indication areas. The amplifying medium can be solid, liquid or gas, and is kept
in a tube. In each end of this tube, there are mirrors, one of them being semi permeable.
The semi permeable mirror concentrates the light, causing the characteristic coherent
laser light to leave the device. Besides the medium and the mirrors, a laser also consists
of an energy source in the form of electrical current or by the use of a rapid strobe lamp
[Niu et al. 1998; Tunér and Hobe 2004; Coluzzi et al. 2005].
The first laser lanced 1960 by Mainman was a Ruby laser (694 nm). Many different
types of lasers have been developed since then like the Carbon dioxide (10 600 nm),
Helium-neon (633 nm), Nd: YAG (1064 nm), Argon (514,5nm) and the Er: YAG (2940
nm) laser. The Carbon dioxide laser- with a wavelength of 10 600 nm, has high affinity
for water and soft tissue and is great for surgery treatments. The Nd: YAG laser has a
good coagulating capacity and is used in general surgery and in dentistry. The first
treatment with laser in the oral cavity was surgery of tumours [Matsumoto 2004]. An
early idea was to use laser in dentistry and it was expected to replace the conventional
mechanical bur. However, the powerful energy needed to ablate dental hard tissues
showed to cause pulp necrosis, injuries to surrounding tissues and melting of enamel
6
and dentin [Matsumoto et al.1996; Pelagalli et al.1997; Keller et al.1998]. It took some
time before the solutions of the problems were found. In the end of 1980s, the Erbium:
YAG laser was introduced. With this laser it was possible to remove dentin and enamel
without the earlier problems. Through a pulsed laser beam in combination with water
spray, it did not give significant pulp temperature changes [Burkes et al. 1992].
Erbium:YAG Laser
Erbium is a rare metallic element. The Erbium: yttrium-aluminium-garnet laser emits a
wavelength of 2940nm. This wavelength is found in the middle infrared spectrum and is
less harmful to the eyes as compared to the Nd: YAG laser. It has high affinity for
hydroxyapatite and water. This potential of Er: YAG laser was shown already in 1989
[Hirbst and Keller1989]. The Er: YAG laser can also be used in some dental surgery
procedures as tongue-tie operations and frenectomies. Even in areas of endodontics and
periodontics it has fields of application [Tunér and Hobe 2004].
Mechanism of Action on Hard Tissue
As mentioned before, the energy from the Er: YAG laser beam is highly absorbed in
water and in the OH-ion in the hydroxylapatite. When the laser light together with the
water spray is directed to the tooth surface, the light-energy is transformed and absorbed
in the water within hydroxylapatite and from the water spray. This results in a fast
heating and volumetric expansion of the water in a small area, causing micro explosions
of the dental hard tissues. It all happens in microseconds and in a thin surface layer
(diameter of 1mm). The effect is accelerated by water spray, which makes one of the
important factors of adding water to the laser beam. If the laser energy continues to be
absorbed in the absence of water, carbonisation occurs and may lead to tissue damage.
7
Burkes et al. [1992] found that the pulpal temperature rose more than 27 degrees
Celsius when dry teeth were irradiated and that the ablation rate was very low without
water added. With water spray, the intra pulpal temperature raised an average of four
degrees and the ablation rate increased.
Enamel, dentin and caries all contain different amounts of water. Because of that, they
need various levels of energy to be ablated. More energy is required to remove enamel
than decayed tooth substance. Aoki et al. showed in 1998 that carious dentin was
effectively removed with Er: YAG laser but the preparation required more care and
treatment time as compared to the conventional bur [Aoki et al.1998; Coluzzi et al.
2005].
Morphological Changes
Cavities prepared with Er: YAG laser appeared visually to have a white surface and
observations by light microscope and SEM showed a rough cavity margin and surface
[Keller and Hibst 1995; Matsumoto 2004] and absence of smear layers [Tokonabe
1999; Parkins 2000; Clarkson 2001; Cavalcanti et al.2003]. Pelagalli et al. [1997] were
not able to find any significant differences in pulpal histology in teeth after conventional
cavity preparation with mechanical drill compared to ablation with Er: YAG laser. The
histological variations though, were found to be greater for pulpal tissue, odontoblasts
and predentin after preparation with dental drill as compared to the laser. These findings
could indicate that the laser may be less harmful to the tooth than the bur [Margolis
2005].
8
Pulpal Reaction
Less pulpal damage has been noticed using laser compared to the bur. The heat of
friction generated by burs causes a major risk of pulpal damage and discomfort for the
patient [Parkins et al. 2000]. Laser treatment also causes temperature raises but only
slight, since most energy probably is consumed in the ablative process [Hoke et
al.1990]. Approximately 3-4 degrees of increase has been described [Burkes et al. 1992;
Cavalcanti et al.2003] like even initial temperature reduction of 5 degrees in the pulp as
a consequence of water-spray cooling [Glockner et al.1998; Margolis 2005]. An
increase of 5 degrees in the pulp has been assumed to be safe [Burkes et al. 1992].
Inflammatory reactions in the pulp have been found when the temperature exceeds 43
degrees [Glockner et al. 1998]. After laser treatment of deep cavities, no pathological
[Margolis 2005] or structural changes have been observed [Keller et al.1991; Pelagalli
et al.1997; Liu et al. 2006]. The heat effect is less in larger cavities [Keller and Hibst
1995] and Class 1 preparations in enamel, generates the greatest rise of temperature
[Bader and Krejci 2006].
Bacteria
One goal is to make treatment of teeth as comfortable as possible. Another is to keep
teeth comfortable after treatment. To achieve the second goal, reduction of bacteria
levels in the cavities is important. Many authors mention the bactericidal effect of laser
treatment [Ando et al.1996; Parkins 2000; Convissar and Goldstein 2003; Sharon-Buller
et al.2003; Birardi et al.2004; Coluzzi 2005]. Sharon-Buller and colleagues [2003]
compared the bacteria levels in cavities prepared by Er: YAG laser with conventional
preparations. They found absence of bacterial growth in 90% of the lased cavities. In
two cavities, dilute bacteria growth could be seen, compared to over 150 colonies in the
9
control mechanical group. Ando [1996] found that irradiated bacteria produced smaller
colonies than the non-irradiated control group. Further, they discuss the explanation for
the bactericidal effect of Er: YAG laser. Like the micro explosions occur in dental hard
tissue, when the laser energy is absorbed in water and hydroxylapatite, micro explosions
happen when the water in bacteria absorbs it. Also the extremely high immediate
temperature rise may destroy bacteria. This bactericidal effect of laser ablation would be
expected to improve tooth prognosis in superficial as well as in very profound caries
lesions [Sharon-Buller et al. 2003].
Removal of Dental Filling Materials
Secondary caries could be created underneath dental filling materials. Hibst and Keller
found [1991] that Er: YAG laser was able to remove most common used cements,
composites and amalgam. Amalgam, however, should not be removed by laser ablation
due to the evaporation of mercury. Gold and ceramic materials could not be removed
because these materials reflect the laser light [Keller and Hibst 1995].
Micro Leakage and Bond Strength
To be an appropriate tool for hard tissue removal in dentistry, the technique must allow
a close adhesion between dental filling material and tooth with a minimum of micro
leakage. Varying results are described in different available studies comparing cavities
prepared with Er:YAG lasers versus bur. Some indicated no significant difference in
resin filled cavities [Weidong et al. 1998; Yamada et al. 2002; Hossain et al. 2003].
Other showed better results without acid etching of lased cavities [Kohara et al. 2002],
while the opposite also have been found [Borsatto et al. 2001; Lupi-Pegurier et al.
2003]. An explanation to these last findings could be the irregular ablation pattern
10
following laser ablation and the existence of non-conditioned areas. However, it is
important to notice the energy level used during laser ablation. Just like the surface
structure differs when using varying diamond grain sizes to the drill, different energy
levels influences the surface appearance after laser ablation. Ablation- energies over
300-mJ show higher degrees of micro leakage between tooth and filling material
compared to bur treated cavities. With lower energies, no significant differences were
found. The use of low laser energy requires long treatment times. Finishing high-energy
preparations using lower laser energy level even combined to acid etching is shown to
be a compromising way [Bader and Krejci 2006].
Results from Visuri et al on the bond strength of composite to tooth cavities prepared by
laser or bur, indicated improved ability of bonding to lased dentin. Contradictory results
also have been reported and it is partly dependent on the energy level and the material
used. Copious water flow has shown to have a positive effect on the bond strength, like
using conditioner prior to filling material in lased cavities [Bader and Krejci 2006].
Further studies hopefully will find the perfect way and the optimal filling material to
obtain great bond strength of composite to laser treated teeth.
Endodontics and Periodontology
Due to the bactericidal effect of laser it has been proved to be an appropriate tool in
endodontics and periodontal treatment of teeth. The smear layer of the root canals wall
is removed leaving a surface with open dentin tubuli and free of debris. Er: YAG laser
has been shown to be able to remove calculus. The effectiveness is less compared to
classical scaling and root planning, but the cement is not removed. Faster healing and
improved prognosis after laser treatment also is noticed [Tunèr and Hode 2004; Bader
and Krejci 2006].
11
Safe and Effective Method
Out of 5 different laser classes, the Er: YAG laser is classified as class 4. What the
safety concerns it is the most dangerous one because even diffuse reflections of the laser
beam might cause injuries to the eyes and skin. Specific protecting eyewear for the
dental team and patients must be used during laser treatment [Coluzzi 2005]. Er: YAG
laser treatment is described to be a safe and effective method for many surgical
operations and cavity preparations [Pelagalli et al.1997; Margolis]. Good knowledge of
the specific laser apparatus is of importance as one company’s laser may act differently
from another’s [Coulter 1995].
Lasers in Paediatric Dentistry
Laser treatment totally differs in technique as compared to the conventional bur. Light
energy is used instead of rotational instruments and sharp blades. Laser gives the
paediatric dentist new possibilities to completely change some treatments, modify
others, or to complement some. Many authors establish that local anaesthesia is most
often not necessary [Matsumoto et al 1996; Pelagalli et al.1997; Parkins 2000]. This is
probably partly explained by disrupted nerve ends in dentin tubules due to the ablation
and less vibration. The vibration speed is almost 400 times less when tooth substance is
removed with laser as compared to high speed drilling [Takamori et al. 2003]. Laser
irradiated primary and permanent teeth have been found to have an increased uptake of
fluoride and a changed solubility of enamel. After laser exposure, the critical pH for
enamel is reduced from 5.5 to 4.8 and consequently more resistant to acid. Still caries is
the most common chronic childhood disease and laser could be another tool for non-
12
invasive caries prevention [Zhang et al. 1996; Hicks et al. 2003; Birardi et al. 2004;
Westerman et al. 2004; Westerman et al. 2006].
The permeability of dentin and enamel reduces after laser radiation leading to a
decrease in hypersensitivity and an analgesic effect on the tooth surface [Schwarz et al.
2002; Birardi et al. 2004]. Better compliance among paediatric patients is noticed,
mainly owing to the possibility to work without anaesthesia and less produced
vibrations [Birardi et al. 2004]. Liu et al. [2006] recognised less body and head
movements during laser preparation in children as compared to conventional
mechanical preparation. These described advantages for laser could be factors making
laser suitable in paediatric dentistry.
Previous studies have shown that booth children and adults prefer laser when compared
to the conventional bur, although laser most often has a longer preparation time. Keller
et al. [1998] showed that 80% of the patients above 18 years of age rated the
conventional preparation with bur as more uncomfortable compared to the Er: YAG
laser. 82% of their patients preferred laser for further caries therapy. According to a
study by Matsumoto et al. [1996] 80% of the adult patients felt no pain and Class V
preparations were concluded without anaesthesia.
Jeng-Fen Liu et al. [2004] suggested that laser therapy could be an option for fearful
children. They made a comparison between caries removal in children with Er: YAG
laser and the conventional bur. The 40 children, between 4 and 12 years of age, were
evaluated during preparation without anaesthesia. The time spent was 2.35 times longer
when laser was used. 82.5% of the children felt no pain and 92% of the children
preferred laser for future caries therapy.
13
In a study by J Pelagalli et al. [1997] 60 patients who were treated with Er: YAG laser
for cavity preparation, expressed that they preferred laser to the bur. Because there was
no need for anaesthesia during preparation with the laser, the procedural time was
approximately equal between the laser and the dental drill.
In previous in vivo studies, preparations with laser versus bur have been performed on
carious teeth. It is impossible to standardize caries lesions regarded extension in depth
and width, and since carious tooth substances differ in hardness, it is impossible to
objectively compare the two methods without preparing sound tooth substance.
The aim of the present study was to evaluate possible differences between Er: YAG
laser and conventional high speed bur regarding the time spent, the pulse changes and
the subjective experiences among Swedish adolescents during removal of anaesthetized
healthy permanent tooth substance.
Our Hypothesises Were:
1) Er: YAG laser treatment is more time consuming than conventional bur.
2) There is no difference regarding pulse change during preparation with laser and
bur.
3) Adolescents prefer cavity preparation with Er: YAG laser to conventional bur.
4) Laser produces less sound than high-speed bur during preparation.
5) Adolescents experience less discomfort during removal of tooth substance with
Er: YAG laser than with high speed bur - as expressed in a VAS-scale and
according to pulse changes during treatment.
14
15
Materials and Methods
This is a split-mouth study based on measurements of time, pulse and loudness, and the
subjective experiences, expressed by the participants during preparation of 2mm deep
cavities using Er: YAG laser and high speed bur, on the buccal surfaces of contra lateral
intact premolars in Swedish adolescents.
Subjects
Patients from 14 years of age planned for orthodontic treatment including extractions of
two intact contra lateral maxillary premolars were invited to the study. All participants
should consider themselves as capable to undergo the described dental treatment.
Patients and parents were informed about the procedure and aim of the study and that
they were allowed to interrupt participation in the study without influence on further
other treatment. Written informed consent was achieved from each patient and parent or
guardian of the patients participating in the study.
Protective eye wears- to protect the eyes against the laser light- were used by each
patient, parent and dental assistant and dentist, who was present in the room during laser
treatment.
The ethical committee at Linköping University approved the study. Ethical approval
was not available for children below 14 years of age.
Laser System
The Er: YAG laser system used in this study was Elexxion Delos. The preset values in
the Elexxion Delos Er: YAG laser for “Hard Tissue Ablation High” was used during the
16
laser preparation. The levels used were: wavelength: =2940nm, pulse energy: =400mJ,
pulse duration: =300μs, frequency: 20Hz, mean output power: 8W. The diameter of the
sapphire point used was 800µm. As recommended by the manufacturer, the sapphire
point was not in contact with the tooth surface during the preparation.
High-Speed Drill
The high-speed drill apparatus used in this study was the high-speed drill hand piece of
KaVo (Toplight 896). The diamond round bur had a diameter of 1,2mm (No 801.314
produced by Drendel+Zweiling (D+Z)).
The decibel measurement equipment used was produced by Premier Farnell Ltd,
model: ST-805.
Methods
The same dentist performed all treatments and the evaluations. Before the start of the
treatment, the patients were offered a 500 mg paracetamol (Panodil®) tablet to reduce
the inflammatory response and to minimize the risk for eventual postoperative pain.
Application of topical anaesthetic Lidocain 5% gel during 5 minutes was followed by
local injection of totally 4,5ml Xylocain-adrenalin 2% using the Wand (computercontrolled anaesthetic delivery system). Five minutes after finished injection,
preparation was started on the middle of the buccal prominence of the upper first
premolar. With nine (5M, 4F) patients laser was used during the first preparation and
with the other nine (4M, 5F) patients bur was used for the first preparation. The
schedule used for the order of treatment is shown in table1. Tooth substance was
17
removed to a depth of 2mm using laser on one maxillary premolar and high-speed bur
on the contra lateral tooth. A new bur was used for each preparation. The depth was
measured with a pocket probe from the mesial part of the cavities inferior limitation.
Table 1. Four different orders for treatments and teeth were used in a repeated schedule
______________________________________________________________________
1st preparated tooth
2nd preparated tooth
_____________________
_____________________
Patient No Schedule
Tooth No.
Laser/Bur
Tooth No.
Laser/Bur
1
A
14
laser
24
bur
2
B
14
bur
24
laser
3
C
24
laser
14
bur
4
D
24
bur
14
laser
Objective Evaluations
The time used to remove 2mm tooth substance for the different preparation methods
was measured with a stopwatch. The laser device shows the time used on the display
and for the drilling procedure the time was measured from the first contact between bur
and tooth until preparation was finished.
The pulse was measured with a pulse oxiometer immediately before and after
preparation.
A decibel-measurement device was used to register the loudness of the laser and the
bur. The distance from the device to the measure pint was approximated to be 10 cm –
18
comparable to the distance between the patient’s mouth and ear. The measurements
were accomplished with and without the dental vacuum ejector.
Subjective Evaluations
After each preparation the patient’s evaluation of pain, loudness, smell and discomfort
was registered on four separate, 100mm VAS-scales (visual analogue scale) as shown in
figure 1.
______________________________________________________________________
How painful was the method?
How loud was the method?
Did you experience any smell during treatment?
How uncomfortable was the method?
not at all
worst imaginable
______________________________________________________________________
Figure 1. VAS-scales used for evaluation (1-100) of subjective experience during
preparation.
Evaluation of subjective experience of pain was used to exclude patients, who did not
experience complete anaesthetic effect, from the evaluation of discomfort.
19
When the treatment session was finished, the patients noted preferred method regarding
the variables pain, discomfort, sound and preferred method for possible future treatment
in a questionnaire.
Statistical Analyses
Wilcoxon Signed Rank Test has been used for comparisons between the two treatment
methods, laser and bur, for the variables treatment time, pulse changes and VAS-smell.
To see if significant differences were found between laser and bur according to the
answers from the questionnaire (discomfort, loud and future choice) Chi-2 test was
used.
The level of significance was set at 5%, i.e. P<0.05. However, because this report is
based on so far collected data, the interpretation of the results should be made with
caution. The program used for statistical analyses was Minitab.
20
Results
Of twenty invited adolescents, eighteen (9M, 9F) patients with a mean age of 15.7±0.9
(14-17) years accepted to participate in the study.
Objective evaluation
Time
The time used for laser ablation (89±45[40-190] sec) was significantly (P<0.001) longer
than for excavation with the high-speed bur (12±4[7-23] sec).
Pulse
The mean pulse increased with 2% during high-speed preparation (from 78 to 80), while
the pulse decreased with 5% during the laser treatment (from 79 to75), as shown in
figure 2. The differences in pulse changes before and after preparation were significant.
82
Pulse
80
78
Bur
Laser
76
74
72
Before start
During
injection
Before
preparation
After
preparation
Figure 2. Pulse changes during the study when laser and bur was used. (P=0,05)
21
Decibel Measure
Table 2. Decibel measure of sound produced during laser and bur treatment.
______________________________________________________________________
Method
without dental vacuum 10cm
_______________
with dental vacuum 10cm
_______________
Great
High-speed
79.7
85.1
Laser
77.1
83.3
Small
80.7
______________________________________________________________________
The laser device’s stand by noise was measured to be 62,5dB.
22
Subjective Evaluation
VAS-Scales
The patients’ ratings regarding loudness/sound, smell and discomfort are shown in
figure 3.
The patients expressed significantly more smell (P=0.002) according to the VAS-scale
when laser was used (33.2±33.2) as compared to when the bur was used (7.7±21.3).
One person rated pain greater than 10 on the (0-100) VAS-scale and was therefore
excluded from the evaluation of discomfort.
70
VAS-scale (0-100)
60
50
40
Bur
Laser
30
20
10
0
Sound
Smell
Discomfort
Figure 3. The patients’ ratings regarding loudness/sound, odour/smell and discomfort
presented as mean values and standard deviations.
23
Questionnaire
Answers in the questionnaire are presented in figure 4. 72% of the patients found laser
to be less uncomfortable compared to the bur. 78% noted laser as less loud. 83% of the
adolescents in this study would prefer laser for eventual future dental treatment. These
three results were all significant (P=0,005).
100%
Percent of patients
80%
60%
No preferance
Laser
Bur
40%
20%
0%
Least
uncomfortable
Least sound
Future
preferance
Figure 4. Patients’ preferences regarding least uncomfortable (n=17), least noisy (n=18),
and eventual future dental treatment (n=17). One patient rated more than 10 on the (0100) VAS-scale regarding pain, and was therefore excluded from the evaluation of
discomfort and future dental treatment.
24
Discussion
Since Nelson et al. developed the dental turbine in 1945, the bur still is the mainly used
tool for preparations in teeth. The bur has well known disadvantages and is often
described to produce uncomfortable noise and vibrations and is also a common cause of
establishment of dental fear when experienced in early ages. Laser is an alternative to
the bur and the main purpose of this study was to find out if Swedish adolescents
preferred Er:YAG laser or high-speed bur for preparation of tooth substance. Further,
the aim was to compare advantages and disadvantages and to consider if Er:YAG laser
is the future and the solution in paediatric dentistry in Sweden.
To make a fair comparison between preparations with high-speed bur versus laser, our
choice of study population was healthy, non-fearful Swedish adolescents with the need
of orthodontic extractions of intact bilateral maxillary premolars. One girl considered
herself as fearful to dental treatment. The procedure could be preformed without any
difficulties, and therefore she was included in the study.
In the present clinical study, the time used for laser ablation was significantly longer
than for excavation with the high-speed bur. In the literature, various reports of the time
spent preparing teeth with laser are described, but the majority of previous studies found
laser preparation of tooth substance more time consuming as compared to drilling. Liu
et al. [2006] found that laser preparation was 2.35 times longer, Kohara et al. [2002] 3-5
times longer, Yamada et al. [2002] 5.7 times longer and Hossain et al. [2003] found,
just like in the present study, that laser treatment was 6.8 times longer than preparation
with bur.
25
It is difficult to compare different studies because the effectiveness of lasers depend on
a complex interaction of wavelength, pulse duration, frequency and energy. Another
important influencing factor is the hardness of the tooth substance. Less energy is
necessary to ablate carious dentin as compared to sound enamel. The laser energy has to
be even higher for effective removal if fluoride apatite partly has replaced hydroxyl
apatite in the sound enamel [Donald and Coluzzi 2005]. The fact that we only prepared
intact enamel where inclusion of fluoride apatite may have occurred, could be one
reason why the laser therapy in our study was quite time consuming. Thus, the energy
used (400mJ) was the highest standardized level for ablation in the laser device and if
caries is present a lower energy must be applied.
A higher energy level allows faster laser ablation. Higher energy also increases the risk
for unwanted side effects. Matsumoto et al. [2007] studied a recently developed and
more powerful Er:YAG laser (Smart 2940 D) with the pulse energy of 700mJ. Without
any negative effects it cut through intact enamel in 3 seconds.
Our first hypothesis that; Er:YAG laser treatment is more time consuming than
conventional bur, was found to be true in this study but in a near future it may be
different.
When human beings are exposed to danger, the body prepares for fight or flight,
resulting in an increased heart rate among other responses [Lundgren et al. 2001;
Kreibig et al.2007]. Liau et al. [2008] showed that preoperative dental anxiety caused
increased heart rate. As an objective value of fear response, we measured the heart rate
during the treatment with a pulse-oximeter. The heart rate increased 2% during drilling
while it decreased 5% when the laser was used. These pulse changes were significant
(P=0,05). It may be related to the longer time used during laser ablation or that laser
26
treatment appeared less dangerous. The second hypothesis: There is no difference
regarding pulse change during preparation with laser and bur, seemed to be true.
The study group expressed their experiences of pain, noise, smell and discomfort
immediately after the preparations in a visual analogue scale (VAS-scale). This
assessment scale was chosen as it is recommended for children older than 12 years of
age. For younger children the Bieri face scale [Hicks et al.2001] or Wong-Baker Face
scale are more suitable [Wong and Baker 1988].
According to the patient’s experiences of pain, the aim was painless preparations. Local
anaesthesia was administered before the preparations. If pain was experienced,
insufficient anaesthetic effect could be the reason. One person rated pain greater than 10
on the (0-100) VAS-scale and was excluded from the estimation of the preparations
discomfort and preference for future treatment. Pain should not be the reason for finding
the method less comfortable or less preferable.
What the loud concerns, the VAS-results were quite equal between laser and bur. The
mean value on a 0-100 VAS-scale was approximately 27 for both. We all knew that
high-speed drilling not is quiet, but these results indicate that the laser also emits sounds
to almost the same degree. Interesting is that 78% of our study group, at the end of the
treatment, in the questionnaire, considered laser treatment as less loud. Here the
difference between the two methods was much greater which indicate the importance of
how, and when, questions are asked, for a reliable answer. Many authors declare the
noise as a great advantage when comparing laser versus dental drill. The annoying
sound of the bur could be terrifying to children and make patients uncomfortable
[Coulter 1995; Niu et al 1998; Takamori 2003; Liu et al 2006]. Stress and fear have
27
been shown to reduce during dental drilling when masking noises have been used
[Canbek and Willershausen 2004]. Aoki et al. [1998] described the sound from the
Er:YAG laser as a “relatively loud popping noise”. Our patients did not find laser
treatment quiet, but it is another sound and not as connected to dentistry and pain as the
sound from the high-speed bur.
To compare the loudness between the methods further, we used a decibel-meter and
measured the sounds during preparation. Without the dental vacuum, the sound from the
high-speed bur was not significantly higher than the laser. During preparation with
Er:YAG laser we used a smaller dental vacuum, than the water amount not is that big
and because the water is important for the ablative process. In that case the difference
between the bur and the laser was greater. The duration of the noise is another thing to
consider. Laser treatment lasts longer and after treatment the laser device has to
refrigerate for a couple of minutes before turning off. The stand-by sound was measured
to be 62.5 dB. The total exposed noise is in that way greater for the laser preparation.
Daily exposure to sounds between 80-85 dB in Sweden implies requests of achievement
[AFS 2005]. Ear protection should therefore probably be recommended for excavation
with both laser and bur. Our fourth hypothesis, that laser is less loud than high-speed
bur during preparation, may to be true, but that is not proven in these few
measurements.
Smell is a variable not found to be previously valuated in previous studies. Aoki et al.
[1998] describes the smell during laser treatment as a “charring smell”. In the present
study, it was the only VAS-scale-parameter with significant difference between the bur
and the laser. Swedish adolescents found laser ablation smelling significantly worse
than drilling. One factor influencing this evaluation of smell could be the smaller dental
28
vacuum ejector used during laser preparation. The reason for the use of the smaller
vacuum ejector is that the water is necessary for the ablating process.
The bur got higher discomfort score than the laser in our last VAS-scale. 72% of our
study population found laser treatment as less discomfort in the questionnaire. These
results correspond with previous studies where laser preparation is described as more
comfortable [Keller et al.1998] and they also confirm the fifth hypothesis: Adolescents
experience less discomfort during removal of tooth substance with Er:YAG laser than
with high speed bur - as expressed in a VAS-scale and according to pulse changes
during treatment.
Previous studies have shown that 80-90% of the patients prefer laser to bur [Keller et
al.1998; Liu et al. 2006]. In spite of the long time used, the noise and the smell, the
majority of our patients (83%) also would prefer laser ablation for eventual future caries
treatment. This confirms our third hypothesis that adolescents prefer treatment with
Er:YAG laser to conventional bur.
4 of 5 hypotheses were confirmed in this study. Important to mention is the limitation of
the values in the study because of the small sample size. We will though continue this
study until 40 patients have been treated. Since the study is not a blind-study we cannot
exclude the influence of placebo effect in the patients` subjective evaluations.
We know that the adolescents in the present study prefer laser treatment, but we did not
ask why. Many advantages are seen and have been described for laser in dentistry like
enhanced comfort [Keller and Hirbst 1998], less vibrations and pressure [Takamori et
29
al. 2003; Liu et al. 2006] and a noise not connected to pain and dentistry. Disadvantages
are also found like the extra time consumed for preparation [Kohara et al. 2002; Hossain
et al. 2003] and inspection [Matsumoto 2004] and that the bur still have to be used for
removal of metals and ceramics [Hibst and Keller 1991] and for polishing of
restorations [Liu et al. 2006].
Perhaps patients, parents and dentists also have another attitude towards laser. It is a
new modern method, which is successfully used in other medical areas. 31% of adult
Americans find laser in dentistry as very important [Dederich and Bushick 2004] and
69% think laser can make their dental visit faster and less painful [Wigdor 1997].
According to the available literature, authors/dentists also tend to emphasize the
advantages of laser. Aoki [1998] demonstrates that “Er:YAG laser removed infected
and softened carious dentin to the same degree as the bur treatment”. Referring to this
study, Bader [2006] wrote “carious dentin is removed at the same speed with Er:YAG
lasers as with the classical bur method”. The time used in this latter study was actually
three times longer with laser.
We all want and long for finding the optimal tool for comfort dental treatments. Laser
really is a good alternative and in a near future it may even be perfect. In paediatric
dentistry, laser is recommended due to the less traumatic preparation method and the
possibility to perform hard tissue removal without anaesthesia. 10-20% of the patients
still need anaesthesia for laser treatment [Clarkson 2001]. Fearful patients tend to react
earlier and stronger to pain and the percentage could though be a little greater for those
children [Boj J et al.2005]. Dental fear is one of the most common reasons for referral to
specialist paediatric dental clinics in Sweden [Klingberg et al. 2005]. Swedish paediatric
dentistry is struggling towards painless treatments. This goal can never entirely be
reached, but as far as possible, risks of pain should be eliminated. From my point of
30
view, great experience of laser preparations and paediatric treatment must be achieved
before decisions can be made, when not to use anaesthesia in the typical paediatric
dental patient.
Besides preparations, lasers have other fields of applications and benefits as described
earlier. The bactericidal effect, the enhanced resistance towards caries and acid like the
increased uptake of fluoride are very welcome, and not least, suitable in paediatric
dentistry. Above all treatment goals, of course, are healthy non-carious teeth and noninvasive dental care.
Acknowledgements
31
This work could not have been done without help from my mentor and supervisor odont
Dr. Mats Bågesund. Thank you for your never ending enthusiasm and support.
I also want to express my gratitude to Louise for your positive attitude and practical
help with the patients and the administration.
I would like to thank the Public Dental Service in Östergötland for admitting me to do
this work and the Orthodontic clinic in Linköping for the help with the collection of the
patients.
Not at least I will thank my loving family, parents and parents-in-law for making this
work possible.
32
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