In Vitro Study of the Soft Tissue Effects of Microsecond-Pulsed CO2 Laser Parameters During Soft Tissue Incision and Sulcular Debridement

Abstract

Carbon dioxide (CO(2)) lasers are an important part of dental treatment. Advances in laser technology have produced microsecond pulse durations and small beam sizes. The histological effects of porcine intraoral soft tissue with a range of microsecond-pulsed CO(2) laser parameters used for incision and sulcular debridement were evaluated in vitro and compared with historical histologic data.
Fresh pig mandibles were used to perform incision and sulcular debridement using a microsecond-pulsed CO(2) laser. lambda = 10,600 nm, articulated arm delivered non-contact with spot size 200 microm, 500 microm, and 1 mm, and focal distance of 1 mm. For sulcular debridement, epithelium within periodontal pocket (6 mm x 6 mm) was removed. Laser parameters for incision were from 30 Hz, 350 microseconds, 28 mJ and energy density of 143 J/cm(2) to 90 Hz, 1,000 microseconds, 60 mJ, and 1,911 J/cm(2). Width and depth of tissue removed, as well as coagulation effects of the tissue treated were measured. These were compared to historical histologic database. Laser-treated surfaces were observed qualitatively using scanning electron microscopy (SEM).
All laser parameters studied were able to reach the defined simulation objectives in reasonable amounts of time, less than a minute for incision and <20 seconds for sulcular debridement. The depth of the cut was significantly greater than the historical 95% confidence interval, but equivalent for width, lateral, and deep coagulation to the historical database. Sulcular debridement was achieved with minimal coagulation, <100 microm. SEM analysis did not identify any alteration to enamel, dentin, or bone during sulcular debridement.
The treatment objectives of incision and sulcular debridement were achieved with minimal lateral and deep coagulation in reasonable amount of time. Microsecond-pulsed CO(2) lasers can be safely and effectively used for incision and sulcular debridement.

Full text

Lasers in Surgery and Medicine 42:257–263 (2010)
In Vitro Study of the Soft Tissue Effects of
Microsecond-Pulsed CO
2
Laser Parameters During
Soft Tissue Incision and Sulcular Debridement
Ram M. Vaderhobli, DDS,MS,* Joel M. White, DDS,MS, Christine Le, BS, Sunita Ho, PhD,
and Richard Jordan, DDS,PhD
Department of Preventive and Restorative Dental Sciences, Department of Oral Facial Sciences,
University of California San Francisco (UCSF), San Francisco, California 94143
Background and Objectives: Carbon dioxide (CO
2
)
lasers are an important part of dental treatment. Advances
in laser technology have produced microsecond pulse
durations and small beam sizes. The histological effects of
porcine intraoral soft tissue with a range of microsecond-
pulsed CO
2
laser parameters used for incision and sulcular
debridement were evaluated in vitro and compared with
historical histologic data.
Study Design/Materials and Methods: Fresh pig
mandibles were used to perform incision and sulcular
debridement using a microsecond-pulsed CO
2
laser.
l¼10,600 nm, articulated arm delivered non-contact with
spot size 200 mm, 500 mm, and 1 mm, and focal distance of
1 mm. For sulcular debridement, epithelium within perio-
dontal pocket (6 mm6 mm) was removed. Laser parame-
ters for incision were from 30 Hz, 350 microseconds, 28 mJ
and energy density of 143 J/cm
2
to 90 Hz, 1,000 micro-
seconds, 60 mJ, and 1,911 J/cm
2
. Width and depth of tissue
removed, as well as coagulation effects of the tissue treated
were measured. These were compared to historical histo-
logic database. Laser-treated surfaces were observed
qualitatively using scanning electron microscopy (SEM).
Results: All laser parameters studied were able to reach
the defined simulation objectives in reasonable amounts
of time, less than a minute for incision and <20 seconds for
sulcular debridement. The depth of the cut was signifi-
cantly greater than the historical 95% confidence interval,
but equivalent for width, lateral, and deep coagulation to
the historical database. Sulcular debridement was
achieved with minimal coagulation, <100 mm. SEM anal-
ysis did not identify any alteration to enamel, dentin, or
bone during sulcular debridement.
Conclusion: The treatment objectives of incision and
sulcular debridement were achieved with minimal lateral
and deep coagulation in reasonable amount of time. Micro-
second-pulsed CO
2
lasers can be safely and effectively used
for incision and sulcular debridement. Lasers Surg. Med.
42:257– 263, 2010. ß2010 Wiley-Liss, Inc.
Key words: dentistry; laser; in vitro; incision; debride-
ment
INTRODUCTION
Since the development of the first laser in the 1960s,
dental researchers have investigated the effects of laser
radiation on teeth, bone, pulp, and oral mucosal tissues [1].
Many authors have reported the use of carbon dioxide (CO
2
)
lasers for soft tissue applications in dentistry [2,3]. The
Food and Drug Administration (FDA) granted clearance for
marketing CO
2
lasers for soft tissue procedures such as
frenectomy, gingivectomy, biopsies, and removal of benign
and malignant lesions. Specific indications for use in
dentistry include apthous ulcer treatment, coagulation of
extraction sites, sulcular debridement, and intraoral soft
tissue surgeries such as ablating, incising, and excising
(U.S. FDA 510(k) marketing clearance). The original CO
2
lasers were continuous wave or interrupted pulse durations
of about 0.5 seconds to 50 milliseconds with non-contact
delivery and large beam diameters up to 1 mm and larger.
Previous studies with these continuous wave CO
2
lasers
showed a variety of structural and ultrasonic changes of the
hard tooth structure. These included cracking, flaking,
crater formation, charring, melting, and recrystallizaton
due to the highly efficient absorption of CO
2
wavelengths by
the apatite mineral of hard tissues [4–8]. The thermal
effects of these CO
2
lasers at various parameters have also
been studied extensively [9,10]. These studies indicated
that application of CO
2
laser created unacceptable thermal
damage to adjacent tissue. Because of these reasons early
CO
2
laser system had been limited by their continuous
wave operations and delivery system constraints.
With new technologies, dental laser manufacturers
now claim to have shorter pulse durations (as short as
150-microsecond pulse duration) with beam diameters of
as small as 100 mm. These lasers are now marketed for soft
tissue intraoral procedures as described earlier. The
advantages compared to scalpel wounds include relatively
bloodless surgery with little if any bleeding post-surgery;
site-specific wound sterilization; minimal swelling and
scarring; reduced necessity for suturing; decreased inci-
dence of mechanical trauma; shorter operative time;
Contract grant sponsor: Great Planes Technology, Inc. (GPT,
Fairfield, Nebraska).
*Correspondence to: Ram M. Vaderhobli, DDS, MS, Health
Sciences Assistant Professor, Department of Preventive and
Restorative Dental Sciences, Box# 0758, 707 Parnassus Avenue,
San Francisco, CA 94143. E-mail: ram.vaderhobli@ucsf.edu
Accepted 18 November 2009
Published online 23 March 2010 in Wiley InterScience
(www.interscience.wiley.com).
DOI 10.1002/lsm.20888
ß2010 Wiley-Liss, Inc.

favorable patient acceptance; decreased use of local
anesthesia; and little or no post-operative pain [11,12].
However, little work has been done to study the cutting and
coagulation efficiency of these microsecond pulse CO
2
lasers.
Previous studies determined the boundaries of the 95%
confidence limits for the time of procedure, length, width,
lateral coagulation, and deep coagulation [12]. Due to the
potential for accidental contact with adjacent hard tissue it
also becomes necessary for us to understand the interaction
of lasers with dental hard tissues. The purpose of this study
was to investigate the newer microsecond pulse duration
and smaller diameter delivery system to determine the
histologic effects of CO
2
laser used for: cutting and
coagulation (incision and sulcular debridement) of oral
porcine soft tissue at various power and frequency settings,
in relation to histological histologic databases.
MATERIALS AND METHODS
A microsecond-pulsed CO
2
dental laser (Spectra-
Denta
TM
, Lutronics, Great Planes Technology, Inc., Fair-
field, Nebraska) with a wavelength of 10,600 nm and an
articulated arm non-contact delivery mode was used. Pulse
profile was measured at room temperature using an
HgCdZnTc detector (Boston Electronics, Boston, MA).
The laser tips utilized were micro-0.1, cone-0.2, 0.5, and
1 mm. The defined laser parameters (incision, and sulcular
debridement settings, historical data) functioned as inde-
pendent variables. Dependent variables included histolog-
ical assessment of incision width, depth, lateral and deep
coagulation, adverse events (qualitative assessments), and
accidental exposure to adjacent tissues. Experiments were
conducted on porcine tongue and gingiva that was acquired
within 24 hours of animal sacrifice, from a local slaughter
house through permit of the United States Department of
Agriculture. The tissue specimens were stored during
transit at 48C and 100% humidity to prevent tissue
degradation. Specimens were allowed to return to room
temperature before experiments were conducted. Fifteen
millimeters incisions were performed on the porcine tongue
by an experienced operator at the rate of 2.5 mm per second
and a force of 24 9 g of pressure. One excision 15 mm
excision for each laser parameter was conducted. The
treatment objective was to cut through the epithelium to
the basement membrane. The range of laser parameters is
shown in Table 1.
Following incision, the tissue specimens were bio-
prepared for histologic examination to determine
cutting and degree of histologic coagulation, fixed in
formalin, sectioned at 5 mm, and stained with hemotoxylin
and eosin. The sections were taken from the middle of the
cutting zone to ensure that each specimen represented the
characteristics of that incision. Light microscopy and a
measuring microscope (Olympus BX51), using the 10
objective was used to determine the depth and width of
tissue removed as well as the lateral and deep coagulation
effects at the borders of the incision. Multiple sections of
the most characteristic zone of each tissue specimen were
measured, with a minimum of three measurements made
for each set of specific laser parameters. Measurements
were then compared to the histologic historical database
[13].
Using a 3
4universal scaler, the periodontal pockets were
scaled to remove any calculus or foreign particles that
would interfere with sulcular debridement. Sulcular
debridement was then performed on porcine gingiva at five
different laser parameters. The objective was the removal
of the epithelium within the periodontal pocket
(6 mm6 mm) using the same microsecond-pulsed CO
2
laser. Three sulcular debridement procedures were con-
ducted for each laser parameter. The laser parameters for
sulcular debridement are shown in Table 1.
Direct Intentional exposure to the tooth was made during
the incision of porcine oral mucosa. Also, exposure to
adjacent hard tissue during sulcular debridement was
evaluated for the presence of laser tissue interaction.
Scanning electron microscopy (SEM) was utilized with
a charge free anticontamination system, CFAS. Samples
were imaged from 10 to 500magnifications. Qualitia-
tive assessments were made. If there was a visual or
microscopic interaction, then an assessment of ‘‘mild,’’
‘‘moderate,’’ or ‘‘severe’’ during accidental exposure, assess-
ment was made.
Statistical analysis was performed using a multifactorial
randomized analysis of variance (P0.05) for parametric
data of histologic measurements and time. Data were
TABLE 1. Incision Laser Parameters for Selected Tip Types (0.5, 1.0, Cone, and Micro) With Time Taken and
Average Power Output
Tip size
0.5 mm 1.0 mm Cone 0.2 mm Micro 0.1 mm
Time Avg. width Time Avg. width Time Avg. width Time Avg. width
30 Hz/350 microseconds (28 mJ)
a
0.55 0.202 0.55 0.44 1.04 0.61 0.54 0.42
50 Hz/500 microseconds (28 mJ)
a
0.56 0.637 0.53 0.97 0.50 1.34 0.56 0.85
70 Hz/700 microseconds (28 mJ)
a
0.53 0.908 0.50 1.53 0.47 2.13 0.56 1.71
90 Hz/1,000 microseconds (28 mJ) 0.32 1.39 1.11 2.66 0.53 3.54 0.55 2.39
3 W 0.59 1.16 1.03 1.96 1.04 3 0.58 1.78
a
Laser parameters for sulcular debridement.
258 VADERHOBLI ET AL.

compared with the existing extensive histologic database
for lasers, using the established confidence intervals set at
95% so that trends outside this range could be identified.
RESULTS
Pulse Profile
The measured pulse duration confirmed that the pulses
were in the microsecond regime as shown in Figure 1. Pulse
durations were found to be between 40 and 200 micro-
seconds. The range of calculated energy densities studied
for excision were from 36 to 1,911 J/cm
2
and for sulcular
debridement were 143 –270 J/cm
2
, although due to energy
loss at the tip, the actual energy density may be much lower
than the calculated energy density (of similar proportion as
the power loss from the smaller tips).
Histologic Evaluation
Examination of the laser incisions revealed the length
and width of the cut as well as both lateral and deep thermal
coagulation histologically. Figure 2 is a representative
histologic section of porcine tongue after incision with CO
2
laser at 50 Hz/500 microseconds and 1.34 W with a 0.2 mm
cone tip. Epithelium was removed to the basement
membrane; width and depth of cut are easily identified as
are the lateral coagulation and deep coagulation, shown in
Figure 2. The surrounding area adjacent to the cut and
coagulation was histologically normal.
Cutting Efficiency
The length of cuts with the CO
2
laser was significantly
deeper than the historical database and deeper than the
treatment objective (incision through the epithelium to the
basement membrane, about 1 mm) as represented by
Figure 3a. The data points were beyond the upper limit of
the 95% confidence interval. However, the width of the cuts,
lateral coagulation, and deep coagulation were similar to
the historical data and fell within the 95% confidence
intervals as depicted in Figures 3b and 4a,b. The duration of
cuts ranged from 30 seconds to around 2 minutes and was
within the 95% confidence intervals, Figure 5 and Table 1.
Lateral and deep coagulation ranged from 0.2 to 1.2 mm for
all tips. In all cases soft tissue excision began between 0.2
and 1 W. The time taken to make an incision was less than
a minute.
Sulcular Debridement
Sulcular epithelium was removed with minimal coagu-
lation <200 mm as shown in Figure 6 for 0.2 –0.6 W. Figure 7
is a representative section of the specimen prepared for
sulcular debridement histological measurements. No coag-
ulation of the epithelium was observed at 0.1 W. Coagu-
lation increased when power was increased to 1 W. Hand
scalers caused characteristic surface scratches, Figure 8a.
Hard tissue examination of the tooth revealed no visible
alteration to the tooth or to the root attachment at any of the
tested settings as shown in Figure 8b.
Hard Tissue Examination
Direct exposure to dentin and bone at powers >1W
caused visible change revealing bone and dentin ablation.
SEM analysis on these surfaces revealed characteristic
laser melting as shown in Figure 8c.
DISCUSSION
This study determined the safety and effectiveness of a
microsecond-pulsed CO
2
laser. The study confirmed the
microsecond pulse duration and small spot size of this new
laser device and delivery system and determined its
histological effects in an in vitro model. The histological
method used in this study is commonly used for measuring
immediate histologic cutting and coagulation of oral
tissues. The 10.6 mm microsecond-pulsed CO
2
laser tested
yielded comparable results. The histologic model utilized,
Fig. 1. Pulse profile depicting the pulse duration in the
microsecond regime. [Figure can be viewed in color online via
www.interscience.wiley.com.]
Fig. 2. Measurement sites for histologic evaluation: W, width
of incision; D, incision depth; LC, lateral coagulation; DC, deep
coagulation. [Figure can be viewed in color online via
www.interscience.wiley.com.]
MICROSECOND-PULSED CO
2
LASER PARAMETERS 259

tongue, and gingival tissues in vitro, are the standard for
testing the cutting efficiency of dental lasers. Histologic
measurements are widely used to measure the coagulation
effects [12]. Wilder Smith et al. [14] used the same model as
was utilized in the present study, and determined the
histological and incisional effects using a continuous wave
9.3 and 10.6 mmCO
2
laser in soft tissues. These tests
confirm in an in vitro model, that the laser parameters used
reach the treatment objective and result in acceptable
levels of coagulation. The treatment objective as defined
by years of laser research is the incision of the epithelium
through to the basement membrane. The applied science
approach undertaken in this study defines specific laser
parameters that result in specific tissue changes, which
include both lateral and deep coagulation.
In this study, the aims were to characterizing the specific
effects of various powers, frequencies on soft tissue
excision, sulcular debridement and hard tissue effects in
order to apply the newer microsecond pulse CO
2
laser
technology in the safest, most efficient manner. As the
pulse duration increases, so does the interaction times and
coagulation effects. This study found that the depths of
incision for these laser parameters and delivery system
were deeper than historical data. This could have impor-
tant clinical ramifications, as in the oral cavity, oral
mucosa, and gingival can be <1 mm in thickness. Based
on the depth of cut data reported here, clinicians are
encouraged to use the minimum parameters which reach
Fig. 4. a: The lateral coagulation were the same as our
historical data. b: Deep coagulation of cuts were the same as
historical data.
Fig. 3. a: Length of cuts were significantly deeper than
historical data. b: Width of cuts was same as our historical
data and mostly fell within the 95% confidence intervals.
260 VADERHOBLI ET AL.

the treatment objective and to carefully observe the tissue
being removed so as not to perforate thin, delicate oral
tissues.
In this controlled laboratory model, laser incisions were
done to manually simulate the clinical settings. Using an in
vitro model, either with porcine or bovine tissues, has its
own advantages in being able to evaluate many laser
parameters including high power, which would not be
utilized in vivo. Using a 15 mm incision provides sufficient
variability and samples for histologic analysis. Because
these lasers are very accurate in the production of laser
energy, there is little need to do multiple repetitions, as a
single incision is sufficient to obtain a large number of
histologic sections. Multiple incisions of the same param-
eters do not provide any additional information, and are
costly and time consuming to conduct the histologic
examination. Therefore, one 15 mm incision was used
and then sampled this incision multiple times for histologic
analysis. For the sulcular debridement technique a
6mm6 mm area was exposed within the periodontal
sulcus, with three repetitions per laser parameter. This
provided three individual tissue specimens for each laser
parameter, which was then sampled multiple times for
histologic analysis. Similarly, the entire root surface
adjacent to the sulcular debridement laser-treated site
was inspected. This experimental technique provides a
large amount of tissue specimens for multiple sectioning
and histologic analysis and a large area of root surface for
inspection.
The zone of coagulation adjacent to the laser incision was
kept to a minimum and compared well to historical
histological data. This signifies good wound healing
capabilities clinically with minimum damage to the vitality
of underlying tooth structures such as periodontium and
pulp. Depth of incision, although larger than historical
data, correlated well with average power. During incision,
the width of cut, lateral and deep coagulation, all correlated
with historical data.
This study also investigated the use of this device for
sulcular debridement. This technique is advocated in
conjunction with conventional scaling and root planning
for treatment of periodontal disease. This investigation
found that epithelium is removed within the periodontal
sulcus with minimal coagulation in a reasonable amount
of time. It is generally understood that complete epithelium
removal is a critical factor in obtaining a connective tissue
attachment during healing. Epithelium remaining within
the periodontal sulcus proliferates faster than connective
tissue and results in a weaker long junctional epithelial
attachment. There is a significant concern raised regarding
the use of lasers within the periodontal sulcus. The primary
concerns are either too extensive coagulation, with necrosis
of soft tissue, or accidental exposure and damage to the
Fig. 7. Representative histologic specimen for sulcular
debridement with measurements of coagulation. [Figure can
be viewed in color online via www.interscience.wiley.com.]
Fig. 6. For sulcular debridement the minimal coagulation was
<200 mm. [Figure can be viewed in color online via www.inter-
science.wiley.com.]
Fig. 5. Duration of cuts were within the 95% confidence
interval.
MICROSECOND-PULSED CO
2
LASER PARAMETERS 261

cementum, dentin or bone of the tooth, and periodontium.
The results found with these CO
2
laser parameters are
within the range of reported coagulation from fiberoptic
delivered Nd:YAG, diode, Er:YAG, and Er,Cr:YSGG lasers,
as demonstrated by the 95% confidence intervals reported
from historical data. For the sulcular debridement portion
of the study, it was confirmed that epithelium was removed
without detrimental effects to adjacent tissues, which has
been shown with Nd:YAG, diode, Er:YAG, and Er,Cr:YSGG
lasers. Nothing specific was done to limit or control the
thermal side effects of CO
2
laser parameters studied. The
device used has a low volume air flow at the tip, primarily to
keep ablation products from entering and clogging the tip.
There was no air or water spray used, and the tissue
specimens were irradiated in a moist condition, not wet and
not with a water stream or immersed in a water bath. This
study demonstrated in an in vitro model, epithelium
removal, with minimal coagulation and no evidence of
alteration of the cementum, dentin, or bone. This was due
primarily because the beam was aimed at the soft tissue to
be removed, away from the hard tissues, and the technique
utilized was to keep the delivery system moving. No
damage to adjacent tissues was seen on inspection of the
multiple repetitions of the sulcular debridement techni-
ques. On intentional exposure, directly to the tooth surface,
and no movement of the delivery system, damage to the
adjacent hard tissues was found. This moderate damage
was characteristic charring of the dentin surface, which can
be seen visually and by SEM. By comparison, scaling and
root planning with hand instrumentation caused moderate
changes to the tooth surface, not visible without magnifi-
cation. Direct intentional exposure of these lasers at high
power output results in damage to the hard tissue.
However, when the proper technique and laser parameters
are used for sulcular debridement, no evidence of hard
tissue alteration is seen. It is theorized that inadvertent
exposure would produce similar results clinically, resulting
in visible charring of the root surface. This is clinically
important because of the need to avoid surface charring
when performing sulcular debridement and soft tissue
surgery around teeth.
The histologic model allows for the determination of the
cutting and coagulation in vitro. It is easy to obtain fresh
tissues and allows for multiple laser parameters to be
tested at relatively low cost. In order to measure the
inflammation and healing events, then an in vivo model
must be utilized. In vivo experimentation is expensive and
very time consuming. It is preferable to utilize the in vitro
model first to survey a large number of laser parameters
and evaluate the tissue effects. If needed, an in vivo model
can then be utilized, with less parameters studied and
greater costs, but will allow for healing events to be
determined.
CONCLUSION
All laser parameters studied were able to reach the
defined simulation objectives in reasonable amounts of
time, less than a minute for excision and are equivalent to
other lasers tested previously. This study also provides
preclinical safety and effectiveness data for the use of
microsecond-pulsed CO
2
lasers for incision and sulcular
debridement. Sulcular debridement with microsecond
pulses and small beam diameters is possible with newer
CO
2
lasers. Direct exposure to tooth and root surface should
be avoided.
ACKNOWLEDGMENTS
This work was partially supported by a research grant
from Great Planes Technology, Inc. (GPT, Fairfield,
Nebraska). We are thankful to Dr. Dan Fried for the pulse
duration measurements, Larry Watanabe for the scanning
electron microscopy analysis.
REFERENCES
1. Taylor R, Shklar G, Roeber F. The effects of laser radiation on
teeth, dental pulp, and oral mucosa of experimental animals.
Oral Surg Oral Med Oral Pathol 1965;19:786– 795.
2. Pick RM, Pecaro BC. Use of the CO
2
laser in soft tissue dental
surgery. Lasers Surg Med 1987;7(2):207– 213.
3. White JM, Chaudhry SI, Kudler JJ, Sekandari N, Schoelch
ML, Silverman S, Jr. Nd:YAG and CO
2
laser therapy of oral
mucosal lesions. J Clin Laser Med Surg 1998;16(6):299.
4. Boehm R, Rich J, Webster J, Janke S. Thermal stress effects
and surface cracking associated with laser use on human
teeth. J Biomech Eng 1977;99:189– 194.
5. Featherstone JDB, Nelson DGA. Laser effects on dental hard
tissues. Adv Dent Res 1987;1(1):21– 26.
Fig. 8. Dentin surface showing characteristic scratched caused by hand scalers (a) whereas laser-treated surface on accidental
exposure (b) shows no change in morphology, and direct exposure (c) show characteristic laser melting.
262 VADERHOBLI ET AL.

6. McCormack SM. Scanning electron microscope observations
of CO
2
laser effects on dental enamel. J Dent Res
1995;74(10):1702– 1708.
7. Stern RH, Sognnaes RF. Laser beam effect on dental hard
tissues. J Dent Res 1964;43(5):873.
8. Stern RH, Vahl J, Sognnaes RF. Lased enamel: Ultra-
structural observations of pulsed carbon dioxide laser effects.
J Dent Res 1972;51(2):455– 460.
9. Leighty SM, Pogrel MA, Goodis HE, White JM. Thermal
effects of the carbon dioxide laser on teeth. Lasers Life Sci
1991;4(2):93– 102.
10. Malmstro
¨m HS, McCormack SM, Fried D, Featherstone
JDB. Effect of CO
2
laser on pulpal temperature and surface
morphology: An in vitro study. J Dent 2001;29(8):521– 529.
11. Pick RM, Powell GL. Laser in dentistry. Soft-tissue proce-
dures. Dent Clin North Am 1993;37(2):281– 296.
12. White JM, Gekelman D, Shin KB, Park JS, Swenson TO,
Rouse BP, Tran KT, Bullard SL, Scott-Beckles LB, Oto MG.
Laser interaction with dental soft tissues: What do we know
from our years of applied scientific research? In Lasers in
Dentists VIII Proceddings of SPIE Vol 4610, 2002:39–48.
13. Perry DA, Goodis HE, White JM. In vitro study of the effects
of Nd:YAG laser probe parameters on bovine oral soft tissue
excision. Lasers Surg Med 1997;20(1):39– 46.
14. Wilder-Smith P, Arrastia AMA, Liaw LH, Berns M. Incision
properties and thermal effects of three CO
2
lasers in soft
tissue. Oral Surg Oral Med Oral Pathol Oral Radiol Endod
1995;79(6):685– 691.
MICROSECOND-PULSED CO
2
LASER PARAMETERS 263