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21

Treatment of Peri-implantitis Around
TiUnite-Surface Implants Using
Er:YAG Laser Microexplosions

Atsuhiko Yamamoto, DDS, PhD1
Toshiichiro Tanabe, DDS, PhD2
Implant therapy can lead to peri-implantitis, and none of the methods used
to treat this inflammatory response have been predictably effective. It isnearly impossible to treat infected surfaces such as TiUnite (a titanium oxide
layer) that promote osteoinduction, but finding an effective way to do so isessential. Experiments were conducted to determine the optimum irradiation
power for stripping away the contaminated titanium oxide layer with Er:YAG
laser irradiation, the degree of implant heating as a result of Er:YAG laser
irradiation, and whether osseointegration was possible after Er:YAG laser
microexplosions were used to strip a layer from the surface of implants placedin beagle dogs. The Er:YAG laser was effective at removing an even layer oftitanium oxide, and the use of water spray limited heating of the irradiatedimplant, thus protecting the surrounding bone tissue from heat damage.
Peri-implantitis can be effectively treated using Er:YAG laser irradiation. (IntJ Periodontics Restorative Dent 2013;33:21–29. doi: 10.11607/prd.1593)

Lecturer, The Japan Institute for Advanced Dental Studies (JIADS), Osaka and Tokyo,
Japan; President, Perio-Implant Hospital AUTIS, Osaka, Japan.
2Associate Professor, Department of Implantology, Division of Oral Pathogenesis andDisease, Asahi University School of Dentistry, Gifu, Japan.
1Correspondence to: Dr Atsuhiko Yamamoto, 5-4-16 Fujisawadai, Tondabayashi, Osaka,
Japan; fax: +81 721-29-4182; email: autis@silver.ocn.ne.jp.
©2013 by Quintessence Publishing Co Inc.

Although osseointegrated dental
implants have been documented
to have high survival rates, the surrounding tissues may be subject
to inflammatory conditions similar
to periodontal disease. There are
two types of inflammatory conditions: peri-implant mucositis andperi-implantitis. Peri-implant mucositis is defined as the presence of
inflammation in the soft tissue surrounding a dental implant without
any loss of supporting bone. Periimplantitis involves both soft tissue
inflammation and loss of implantbony support. Associated with risk
factors such as inadequate oral hygiene, a history of periodontitis,and cigarette smoking,1 peri-implantitis has been reported to occurin 28% to 56% of subjects.2 While
many methods of treating periimplantitis have been proposed,
none have been established as
overwhelmingly superior.3–8 Various lasers have been used to treat
peri-implantitis but only to sterilize
the surface of the implant, not toremove the contaminated matter.9
One promising treatment protocol is decontamination of thesurface of a failing implant with an
Er:YAG laser.10–16 Until recently, theVolume 33, Number 1, 2013
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22
Er:YAG laser has been used to treat
peri-implantitis without opening aflap. Inflammation has been treatedby irradiating the pocket around theimplant. However, this only aims totreat the inflammation, not address
the underlying cause of the inflammation.17 Therefore, no consensus
exists regarding the optimal methodology for using Er:YAG lasers totreat peri-implantitis.
This study aimed to (1) determine the optimal irradiation power
for stripping away a layer of the
TiUnite (titanium oxide) implantsurface using Er:YAG laser irradiation, (2) determine the degreeof implant heating resulting from
Er:YAG laser irradiation, and (3) determine whether osseointegration
was possible in an animal model
after stripping the surface of thecontaminated titanium oxide layer
with Er:YAG laser microexplosions.

Method and materials
Optimal irradiation power

To determine the optimal irradiation conditions to steam-strip a titanium oxide surface layer using an
Er:YAG laser (Erwin AdvErl, J. Morita), 15 3.75 × 13-mm Brånemark
MkIII RP TiUnite implants (Nobel
Biocare) were irradiated using thePS600T tip (J. Morita) on the Er:YAG
laser; the flat quartz tip tapers from600 μm in the upper portion to400 μm in the lower portion. An
electric X-Y stage was used (ALD904-H1, Chuo Precision Industrial)and set at a speed of 0.2 mm/s.
The distance from the end of the

tip to the implant surface was set
at 0.05 mm. Surface ablation was
set to 50 mJ/mm2, 100 mJ/mm2,
and 200 mJ/mm2 by monitoring theenergy at the top of the tip with apower meter rather than relying
on the display value indicated by
the laser since the light-guiding fiber and the tip attenuate the laser
power. A new tip was used for each
implant, and the laser power wasmeasured every time. The pulse
was set to 20 PPS, water was injected at a rate of 5 mL/min, and theirradiation time was 15 seconds.
Changes at the irradiated surfaces
were examined using an optical
microscope and a phase contrast
electron microscope.

Implant heating

The neck of a 3.75 × 13-mm Brånemark MkIII RP TiUnite implant was
fixed in an acrylic resin plate tosimulate clinical conditions. Usingan Er:YAG laser (Erwin AdvErl) witha PS600T tip, the implant head wasirradiated at tip-end output powers of 100 mJ (10 PPS) and 50 mJ(20 PPS) for 15 seconds (total,
1,500 mJ of energy). Irradiation was
performed both with and withoutwater spray at a rate of 5 mL/min.
The implant was irradiatedunder four conditions: (1) with water spray at 100 mJ and 10 PPS,
(2) without water spray at 100 mJ
and 10 PPS, (3) with water spray at
50 mJ and 20 PPS, and (4) withoutwater spray at 50 mJ and 20 PPS. The
increase in temperature was monitored using a thermograph (NeoThermo TVS-700, Nippon Avionics).

Five implants were heated for eachcondition, and the next set of conditions was tested using the same
implants after they had cooled toroom temperature, as monitoredby the thermograph. Temperature increase was monitored witha thermograph instead of a thermocouple since measuring the surface temperature should reflect thetemperature of the portion in contact with bone cells and because
preliminary experiments show thatthe temperature cannot be accurately measured with a thermocouple since Er:YAG irradiation causes
temperature increases in the thermocouple as well. In order to compare the level of implant heatingwhen using different types of lasers,
a separate experiment was carriedout using a carbon dioxide (CO2)
laser (Laserwin, J. Morita). The CO2
laser unit was not equipped witha spray, so the authors performed
a separate test using it with andwithout a separate spray device.
The difference in heating was approximately 10°C. Therefore, it was
decided to use the CO2 laser unit
without spray and as it was originally intended with a flow of cooling
air at a rate of 260 mL/min.

Osseointegration of newly
laser-irradiated implants

All molars were extracted fromboth sides of the mandible in six
18-month-old female beagle dogs,
eachweighing
approximately
12.0 kg. After 3 months, radiographs were taken to confirm thatthe extraction cavities had healed

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23

Tiunite

Er:YAG laser irradiatedbaFigs 1a to 1c   (a and b) Phase contrast electron micrographs. The TiUnite layer
has been completely stripped away by microexplosions. The newly exposed surface has not melted or been deformed by the heating effect of laser irradiation.
The left and top portions show the surface before Er:YAG laser irradiation, while
the right and bottom portions show the surface after laser irradiation. (c) Implantwith laser treatment on the apical portion.

Er:YAG laser irradiatedcproperly. An Er:YAG laser was used
to irradiate and strip one-half of thesurface of 24 3.75 × 13-mm TiUnite
implants. Two implants were placedin each extraction site, with an initial torque of 35 to 45 Ncm. The
implants were placed so that the irradiated half was on the buccal aspect and the nonirradiated half wason the lingual aspect. Two animals
were sacrificed after 2 weeks, twomore were sacrificed after 4 weeks,
and the final two were sacrificed
after 6 weeks. Tissue samples were
dyed with hematoxylin-eosin without decalcification to prepare theobservation samples. Images withmagnifications of 10× and 200×were captured at 2, 4, and 6 weeks.
For consistency, images at 200×
magnification were taken between
the fourth and fifth threads.

TiUniteAt 200 mJ/mm2, the TiUnite layer
as well as the titanium layer underneath had melted.

Implant heating

Results
Optimal irradiation power

At 50 mJ/mm2, the TiUnite layer
could not be entirely removed.
At 100 mJ/mm2, an even layer of
the TiUnite surface was effectively
removed, and the newly exposed
surface did not appear to be deformed by melting, carbonization,or other effects of heating (Fig 1).

The results are shown in Fig 2. Whenthe implant was irradiated with the
Er:YAG laser using the water sprayfor cooling, the temperature of theimplant increased by a maximumof 3°C for both output conditions(100 mJ at 10 PPS and 50 mJ at
20 PPS). However, when usedwithout water spray, the temperature of the implant head increasedby 30°C and 33°C at 100 mJ andVolume 33, Number 1, 2013
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24

Er:YAG, 100 mJ/10 PPPS, no water
Er:YAG, 100 mJ/10 PPS, water
Er:YAG, 50 mJ/20 PPS, no water
Er:YAG, 50 mJ/20 PPS, water
Co2, 1W, no water

Temperature increase (°C)

60

Fig 2  Temperature increases with laser
irradiation. The results dictate that the
Er:YAG laser be used with water spray totreat peri-implantitis.

50
40
30
20
10
0

0

5

10

15

20

25

Time (s)10 PPS and at 50 mJ and 20 PPS,
respectively. The CO2 laser raised
the temperature of the implant
head by 50°C, even with the cooling air set for maximum flow.

filled in approximately one-thirdof the gap (Fig 4c). Figures 5a to
5c show an implant after 6 weeks
at 10× and 200× magnifications.
Bone formation can be observed
on both the nonirradiated (Fig 5b)
and irradiated surfaces (Fig 5c).

Osseointegration of newly
laser-irradiated implants

Discussion
Figures 3a to 3c show an implant
after 2 weeks at 10× and 200×
magnifications. Slight incursion ofbonelike tissue was noted on boththe nonirradiated (Fig 3b) and irradiated surfaces (Fig 3c). Figures 4a
to 4c show an implant after 4 weeks
at 10× and 200× magnifications.
Bonelike tissue was still being
formed on the nonirradiated surface (Fig 4b), and bonelike tissue
was also forming along the surface of the irradiated surface andOptimal irradiation power

If the structure in question has acavelike structure similar to TiUnite, a laser could hypotheticallybe used to remove the bacteria
and impurities embedded in it.
However, it is difficult for lasers, thebeams of which travel in a straight
line, to penetrate deep into suchirregular structures. Therefore, theauthors believe that it is desirable

for the TiUnite surface layer (thecontaminated titanium oxide layer)
to be stripped away. The Er:YAG
laser has by far the greatest degreeof absorption with water—almost
10× more than CO2 lasers, almost
70,000× more than Nd:YAG lasers,
and almost 600,000× more than
diode lasers. When the Er:YAG laser energy is absorbed by water,
the water immediately turns into
steam. The volume of the water expands by 1,000×, resulting in microexplosions. The authors believe
this effect might be useful for periimplantitis treatment.
These findings suggest thatwhile using a power setting of lessthan 100 mJ/mm2 might effectively
disinfect the surface, the TiUnite
layer will be completely strippedaway by the Er:YAG laser micro­
explosions.

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25

A

B

Fig 3a  Histologic sample 2 weeks after
implantation.

A

Fig 3c   Er:YAG laser–stripped surface(magnified view of highlighted area B in
Fig 3a; original magnification ×200).

Fig 4b  Nonirradiated TiUnite surface(magnified view of highlighted area A in
Fig 4a; original magnification ×200).

Fig 4c The Er:YAG laser–stripped surface
clearly shows the growth of new bone cells(magnified view of highlighted area B in
Fig 4a; original magnification ×200).

B

Fig 4a Histologic sample 4 weeks after
implantation.

A

Fig 3b  Nonirradiated TiUnite surface withthe original, nonablated TiUnite surface
layer (magnified view of highlighted area A
in Fig 3a; original magnification ×200).

B

Fig 5a  Histologic sample 6 weeks after
implantation.

Figs 5b and 5c  Bone growth can be observed on both (b) nonirradiated (magnified viewof highlighted area A in Fig 5a) and (c) Er:YAG laser–irradiated surfaces (magnified viewof highlighted area B in Fig 5a). Thus, osseointegration is possible for the Er:YAG laser–
stripped surface (original magnification ×200).

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26

Fig 6   Radiograph showing considerable bone loss around the implants in the mandibularleft posterior quadrant.

Implant heating

Boulnois18 found that individual
cells begin to deform and die between 43°C and 45°C and that proteins degenerate and coagulate at
60°C. Although the CO2 laser has
been reported to be only slightly
absorbed by titanium and to cause
no changes in surface morphology,
the present results indicate that
irradiation of a titanium implant by
a CO2 laser may heat it sufficiently
to cause bone tissue necrosis.
Use of an Er:YAG laser without water spray could cause similar
damage. However, when an Er:YAG

laser is used with water spray, heating is minimized and no irreversible
damage is caused.

Osseointegration of newly
laser-irradiated implants

The animal experiments showedthat osseointegration occurred on
the fresh, uncontaminated surface
produced by laser irradiation. Further, Kreisler et al10 reported thatthe implant surface is sterilized by
Er:YAG laser irradiation. These results strongly suggest that the difficulties of treating peri-implantitis

can be overcome with Er:YAG laser
irradiation because it is possible tostrip away the contaminated titanium oxide layer and create a fresh,disinfected implant surface without damaging the implant threads.
This new surface appears to haveosteoinductive properties that are
as effective as the original (non–laser irradiated) TiUnite surface.

Clinical case
The following clinical case illustrates the use of an Er:YAG laser totreat a patient with peri-implantitis.

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27
Fig 7  After raising a buccal flap, a large
amount of inflamed granulation tissue wasremoved using the Er:YAG laser.

Figs 8a and 8b  The key to removing contaminated granulation tissue with an Er:YAG
laser is to irradiate not the granulation tissue itself but the layer where the granulation
tissue and healthy bone tissue meet. In this way, the contaminated granulation tissue canbe removed in a single mass. After removing the granulation tissue, the contaminated
TiUnite surface layer was stripped away and sterilized.

In September 2006, an 81-year-old
woman received a total of nine implants, five of which are shown in
Fig 6: the mandibular left canine
site, first and second premolar,
and first and second molar. After
4 months, provisional restorations
were placed, and 6 months later,
the definitive restorations weredelivered. After 1 year, the patientcomplained of swelling around her
implants. Radiographic examination showed considerable resorption around the implants in theregion of the mandibular left posterior quadrant (Fig 6). The superstructure was removed, and it was

discovered that the implants were
not loose. However, the inflammation extended to the bone—a clear
case of advanced peri-implantitis.
Further examination determinedthat this was a CIST (cumulative interceptive supportive therapy) ClassD case (probing depth > 5 mm,
positive for bleeding on probing, and bone loss > 2 mm). The
peri-implantitis was treated using
Er:YAG laser irradiation.
After the patient had received
a local anesthetic (2% xylocaine),
a buccal flap was reflected at themandibular left quadrant. Although
the implants were not loose, consid-

Fig 9  Using the Er:YAG laser with water
spray keeps the implant from overheating.
The microexplosions created when thelaser strikes the water remove blood andother visual obstructions.

erable bone resorption and granulation tissue were found (Fig 7).
The infected granulation tissue wasablated and removed by laser irradiation using a PS600T tip at 50 mJ
power and 20 PPS with a 5-mL/minsterilized water spray (Figs 8a and8b). Granulation tissue is normally
removed using a curette, but theresultant bleeding prevents a clear
view of the treatment area. The
Er:YAG laser with water spray eliminates this problem. The applicationof water spray and the microexplosions caused by the laser light hitting the water maintain visibility inthe treatment area (Fig 9).

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28

a

b

c

Figs 10a to 10c  Radiographs taken (a) 3 months and (b) 2 and (c) 3 years after treatment showing
stabilized bone growth.

After removing the infectedgranulation tissue, the contaminated implant surface was sterilized
by ablating a layer of the TiUnite
surface. A PS600T tip was lightly
guided over the surface at 50 mJ
power and 20 PPS with a 5-mL/minwater spray. The contaminated layer was stripped away by the microexplosions caused by the Er:YAG
laser reaction with the water spray.
Slightly dark gray areas could beseen on the ablated surface, whichwere not a result of carbonization
but rather the new titanium surface

showing through. Implants are usually placed vertically, and when thelaser is applied perpendicular to
the implant, it can easily reach detailed features of the threads andthoroughly sterilize the contaminated titanium oxide layer by stripping away an even layer.
An autogenous bone graft wasplaced and covered with a resorbable membrane, and the site wasclosed in the conventional manner.
Radiographs were taken 3 months
and 2 and 3 years after surgery(Figs 10a to 10c), all of which

Fig 11  Computed tomography scan 4 years after treatment. The peri-implantitis
had been resolved, and thearea around the implant hadstabilized.

showed apparent bone regeneration. A computed tomographyscan (buccolingual cross section)
was obtained 4 years after treatment (Fig 11). The area around theimplant had stabilized.

Conclusions
The microexplosions produced by
an Er:YAG laser can effectively remove the contaminated titaniumoxide layer from an implant that is
failing because of peri-implantitis.

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29
When accompanied by water spray,
irradiation with the Er:YAG laser
limits heating of the implant to afew degrees, which is not enoughto damage the surrounding bone
tissue and inhibit osseointegration.
The animal experiments reported
also showed that osseointegrationis possible on the fresh surface produced by laser irradiation.

Acknowledgments
The authors would like to thank Drs Yoshihiro Ono, Yasukazu Miyamoto, Toshiaki Yoshino, and Akira Aoki for their continuing
support. The authors reported no conflictsof interest related to this study.

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