Photofunctionalized Dental Implants:
A Case Series in Compromised Bone
Akiyoshi Funato, DDS1/Takahiro Ogawa, DDS, PhD2
Purpose: Ultraviolet (UV) light treatment of titanium, or photofunctionalization, has been shown to enhance
its osteoconductivity in animal and in vitro studies, but its clinical performance has yet to be reported. Thisclinical case series sought to examine the effect of photofunctionalization on implant success, healing
time, osseointegration speed, and peri-implant marginal bone level changes at 1 year after restoration.
Materials and Methods: Four partially edentulous patients were included in the study. Seven implants withidentical microroughened surfaces were photofunctionalized with UV light for 15 minutes. Osseointegration
speed was calculated by measuring the increase in implant stability quotient (ISQ) per month. Marginal
bone levels were evaluated radiographically at crown placement and at 1 year. Results: All implants placed
into fresh extraction sockets, vertically augmented bone, simultaneously augmented sinuses, or the siteof a failing implant remained functional and healthy at 1 year, even with an earlier loading protocol (2.1 to
4.5 months). ISQs of 48 to 75 at implant placement had increased to 68 to 81 at loading. In particular, implants
with low primary stability (initial ISQ < 70) showed large increases in ISQ. The speed of osseointegrationof photofunctionalized implants was considerably greater than that of as-received implants documented in
the literature. Mean marginal bone levels were –0.35 ± 0.71 mm at crown placement and had significantly
increased to 0.16 ± 0.53 mm at 1 year, with coronal gains in marginal bone level that surpassed theimplant platform. No implants showed marginal bone loss. Conclusions: Within the limits of this study,
photofunctionalization expedited and enhanced osseointegration of commercial dental implants in various
clinically challenging/compromised bone conditions. Photofunctionalization resulted in preservation—andoften a gain—of marginal bone level, and long-term large-scale clinical validation is warranted. Int J Oral
Maxillofac Implants 2013;28:1589–1601. doi: 10.11607/jomi.3232
Key words: hydrocarbon, photofunctionalization, superhydrophilicity, titanium implants, ultravioletIn spite of many successful developments and improvements in implant dentistry, clinical challenges remain. It would be an advantage to reduce thehealing time required for osseointegration to reduce
patient morbidity and accommodate the growing demands of modern implant therapy. Several risk factors,

1Private Practice, Nagisa Dental Clinic, Kanazawa, Japan.
2Professor, Laboratory for Bone and Implant Sciences,

The Weintraub Center for Reconstructive Biotechnology,
Division of Advanced Prosthodontics, UCLA School of
Dentistry, Los Angeles, California, USA.
Correspondence to: Dr Takahiro Ogawa, Laboratory for Boneand Implant Sciences, The Jane and Jerry Weintraub Center
for Reconstructive Biotechnology, Division of Advanced
Prosthodontics, Biomaterials and Hospital Dentistry,
UCLA School of Dentistry, 10833 Le Conte Avenue(B3-081 CHS), Box 951668, Los Angeles, CA 90095-1668.
Fax: +310-825-6345. Email: togawa@dentistry.ucla.edu©2013 by Quintessence Publishing Co Inc.

such as poor bone quality and quantity, diabetes, osteoporosis, and smoking, may limit its application anddecrease success rates.1–4 Preimplantation surgery,such as bone augmentation and sinus elevation, hasbeen introduced to expand the indications for implant
therapy. However, the additional surgical intervention
increases patient morbidity, and prognosis in thesecomplex cases is not as predictable.5,6 Protocols designed to expedite treatment, such as implant placement into fresh extraction sockets and immediateloading, may also compromise outcomes.7,8 Further
improvements in the ability and capacity of dental implants to osseointegrate are therefore required.
It is well known that implants fail because of unsuccessful, or destructive changes in, osseointegration.9–11
However, it remains uncertain why bone tissue does
not completely form around implant surfaces, evenunder normal biologic conditions. The average total
implant area eventually covered by bone (bone-implant contact [BIC]) is reported to be only 45% ± 16%,12or between 50% and 75%,13–15 which is far lower than
the ideal 100%.
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Ultraviolet (UV) light–mediated photofunctionalization of titanium has recently attracted considerable
attention as a means to improve the osteoconductivity of titanium implants.16–18 UV treatment of titanium
surfaces has been shown to increase their bioactivity
and osteoconductivity because it restores their superhydrophilicity, reducing surface carbon and optimizing surface electrostatic charges.19–21 These biologic
and physicochemical features are collectively known
as photofunctionalization.16,18,22,23 Photofunctionalized surfaces show increased protein adsorption andincreased migration, attachment, and proliferation of
osteogenic cells (two- to fivefold) in vitro.20,24,25 The
biomechanical strength of photofunctionalized implants is threefold higher than that of untreated implants at the early healing stage in animal modeling invivo.24 This enhanced osseointegration persists, evenin late healing stages, and is associated with 98.2% BIC
around photofunctionalized implants, compared toless than 55% around untreated controls.24
This enhanced level of peri-implant bone morphogenesis has been termed “superosseointegration,”where “super” represents the maximum degree of, andminimum resistance to, the phenomenon.22,23,26–28
In addition to near-maximal BIC, osteomorphogenesis around photofunctionalized implants is characterized by significantly reduced amounts of soft tissue
between the implant and bone. Soft tissue growth
between an implant and bone is a barrier to osseointegration but is reduced to less than 1% aroundphotofunctionalized implants, compared to morethan 20% around untreated implants.24 The potential
advantages of photofunctionalized implants in unfavorable bone milieu have also been demonstrated inanimal models. Enhanced osseointegration by photofunctionalization overcomes the reduced loading
capacity of short implants and a lack of cortical bone
support.17,29 Photofunctionalization is therefore proven not only to expedite osseointegration but also toincrease overall levels of osseointegration, which may
potentially overcome the drawbacks of compromised
healing environments.
The long-term stability of the peri-implant tissues
is of critical clinical importance, but no complete solution has yet been put forth.30–34 In particular, maintenance of marginal bone levels (MBLs) around implants
has been a challenge.30 It is accepted that unavoidable
marginal bone loss occurs, which may cause esthetic
problems and eventually lead to unfavorable mid- andlong-term prognoses of implants.8,35–40 Marginal boneloss of 1 mm or more can be expected during the initialstages after placement, depending on the geometricfeatures of the surrounding bone and healing conditions.35–37,39,41–43 Furthermore, progressive reductionof 0.2 mm per year, after the first year, is reluctantly

considered to be a clinical success.40 The authors hypothesize that the enhanced osteoconductive capability of photofunctionalized implants may not only
improve osseointegration around the main body andapical part of an implant but also osteomorphogenesis
around the implant neck, which would be expected
to result in an improved bone seal and bone maintenance toward the coronal zone.
Photofunctionalization is different from other surface modification techniques because of its simple
and unique delivery method and versatility. Photofunctionalization is neither an additive nor a subtractive method of surface modification. Titanium implantsurfaces, regardless of experimental or commercial
use, are chemically contaminated with unavoidable
and progressive deposition of hydrocarbons.24,25,44–54
Photofunctionalization cleanses these surfaces by removing these hydrocarbons through titanium dioxide(TiO2)–mediated photocatalysis and direct decomposition by UV light.20,55 As a result of this chemical cleaning,
the superhydrophilicity that is lost on sufficiently agedtitanium surfaces can be regained.21,56 Photofunctionalization is effective on various types of titanium surfaces, including so-called smooth (eg, machined) andmicroroughened (eg, acid-etched and sandblasted)surfaces, without altering their existing topography,roughness, or other morphologic features.24,29
It remains unknown whether photofunctionalization is effective in clinical use. Therefore, to obtainpreliminary data regarding the effects of photofunctionalization, the authors undertook a clinical caseseries of photofunctionalized dental implants placedin compromised bone. The present paper discusses
whether the clinical outcomes of photofunctionalized
implants at 1 year of follow-up are comparable to theefficacy observed in animal and in vitro studies.

MATERIALS AND METHODSPatient Selection

Four patients (two men and two women) aged 38
to 72 years (average, 52 years) visited Nagisa Dental
Clinic during August and November 2010 for implant
therapy and provided consent for documentation andpublic presentation of their cases. These patients met
the following criteria: They were at least 20 years old;they complied with oral health care instructions andattended necessary visits; and all had indications for
implant placement in clinically difficult conditions ofa fresh extraction socket, staged or simultaneous vertical or lateral bone augmentation, sinus-augmented
site, replacement of failing implants, or a combinationof these. Patients with systemic or behavioral conditions that could potentially affect bone and soft

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Beforephotofunctionalization

Afterphotofunctionalization

Fig 1a  The photo device used for photofunctionalization ofdental implants (TheraBeam Affiny). Implants are placed on asliding stage. The device performs an automatic program of 15
minutes of UV exposure and 5 minutes of ventilation.

Fig 1b   Superhydrophilic and superhemophilic surfaces of dental implants after photofunctionalization. Images show dropletsof 3 µL of double-distilled water and rat blood placed on implantsurfaces (left) before and (right) after photofunctionalization.
After photofunctionalization, 9 µL of double-distilled water orblood (three droplets of 3 µL each) was sufficient to spread andcover the entire surface of a dental implant.

tissue healing, such as osteoporosis, diabetes, radiation treatment, bruxism, or smoking, were excluded
from the study.

complex case. Implants were functionally loaded with
provisional restorations if the patient was free fromdiscomfort or pain and there was no (1) immature
healing or inflammation in the peri-implant tissues,(2) peri-implant radiolucency, or (3) implant mobility.
Loading was performed if implant stability quotients(ISQs) were 65 or higher. ISQs between 60 and 65 areconsidered sufficiently healed for successful loading or
definitive restoration,57–61 and implants with an ISQ of
65 and higher have been shown to successfully withstand immediate and early loading; this is therefore
often used as a criterion in these protocols.62–65

Clinical Procedures and Photofunctionalizationof Dental Implants

Standardized consultation and diagnostic procedures
were provided to all patients, and a treatment plan waspresented to and approved by each patient. Following
administration of routine local anesthesia and reflection of a full-thickness flap, implants were placed with atorque of 25 to 45 Ncm following the standard surgicalprocedure recommended by the manufacturer. The implants used in this study had a tapered root-form geometry and were of identical surface topography (Osseotite
Certain, Biomet/3i). All implants were photofunctionalized through treatment with UV light for 15 minuteswith a photo device (TheraBeam Affiny, Ushio); this wasdone chairside immediately before placement (Fig 1a).
The photofunctionalization-induced change in surface
property, from hydrophobic to superhydrophilic, wasconfirmed prior to the procedure by examining several
implants for their wettability to double-distilled waterand blood (Fig 1b). The tested implants were from a separate group of the same type of implants and were notused in patients after hydrophilicity testing. The flap wasclosed by a submerged or nonsubmerged technique.
Patients returned to the clinic at approximately
halfway through the healing time based on a routine
protocol established in the clinic for each specific

Assessment of Osseointegration

Successful osseointegration was determined clinicallyand radiographically according to the criteria established by Smith and Zarb.40 Osseointegration speed wasevaluated by measuring the increase in ISQ per monthusing the Osstell ISQ implant stability device (Osstell).
The ISQ increase per month was defined as ([ISQ at thecommencement of loading] – [ISQ at implant placement])/(healing time required before loading).

Implant Success

Implant success was determined according to the criteria of Smith and Zarb.40 If an implant showed significant
mobility, radiographically determined failure of osseointegration or progressive disintegration, significant marginal bone loss, pain, inflammatory signs, or rapid andcontinuous decreases in ISQ, it was considered a failure.
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Table 1   Case Description and Clinical Outcome Parameters
ISQ
Patient

Surgical procedure

MBL

Time before At implantAt
Increaseloading (mo) placement loading per month

Patient 1

Immediate replacement offailing implant

2.1

Patient 2

Simultaneous sinus elevation

3.8

At definitive
restoration

After 1 yChange–0.8 (M)–1.4 (D)

–0.2
–0.7

+0.6
+0.7

48

76

7.36

0.4 (M)
1.0 (D)

0.4
1.0

0.0
0.0

49

80

8.16

1.0 (M)–0.6 (D)

1.0
–0.4

0.0
+0.2

Patient 3

Fresh extraction socket

2.1

67

72

2.38

–0.3 (M)–1.1 (D)

0.5
–0.6

+0.8
+0.5

Patient 4

Staged approach: Vertical
GBR and sinus elevation

4.5

67

80

2.89

–0.8 (M)–0.7 (D)

–0.2
0.0

+0.6
+0.7

75

81

1.33

–0.2 (M)–0.6 (D)

0.5
0.2

+0.7
+0.8

73

68

–1.11

–0.7 (M)–0.2 (D)

0.5
0.2

+1.2
+0.4

Mean

3.6

63.2

76.2

3.5

–0.35

0.16

0.51

SD

1.0

11.8

5.2

3.5

0.71

0.53

0.35

GBR = guided bone regeneration; M = mesial; D = distal.

Marginal Bone Change

Marginal bone change was evaluated by measuring thepotential difference in peri-implant MBL occurring at 1
year after placement of the definitive prostheses. Periapical radiographs were taken at the time of definitive prosthesis placement and 1 year later. A hard plastic occlusal
jig was used to standardize the film angulation. Whenrequired, the measured dimensions were calibrated on
the basis of the known implant length. The most coronalpoint of BIC was identified, and the difference between
the implant platform and the contact end was considered as the MBL. The values were negative when the firstbone contact was located apical to the implant platform,
whereas they were positive when the first bone contact
was located coronal to the implant platform. Measurements were performed on both the mesial and distalsides of an implant. If the MBL decreased at the 1-year
visit, the value was considered a negative change.

Assessment of Surgical and Prosthetic
Complications

Potential surgical complications, including durationand level of pain, bleeding, inflammatory reactionsof tissues, inadequate primary stability of implants,
improper or delayed wound healing, and postoperative infection, were monitored with regard to the useof photofunctionalized implants. The authors determined whether these complications were significantly
different from those observed with conventional protocols without the use of photofunctionalization.

With respect to the use of photofunctionalized implants, potential prosthetic complications were monitored, including the necessity for extra procedures orsignificant procedural modifications or any difficulty
experienced during abutment connection, provisionalization, definitive restoration, and follow-up visits.

Statistical Analysis

MBLs were measured on both the mesial and distalsides of an implant (n = 14). A paired t test was used
to examine the difference between the time of crownplacement and 1 year after crown placement; P < .05
was considered statistically significant.

RESULTSClinical data on the treated patients are summarizedin Table 1.

Case Presentations

Patient 1: Immediate replacement of a failing implant with simultaneous guided bone regeneration.
A 38-year-old man was referred to the clinic because of
an implant that was failing as a result of placement into
suspected overheated bone at the site of the mandibular left second premolar (Figs 2a and 2b). Immediately
after removal of the failed implant (4 mm in diameter,
10 mm in length) and curettage, a photofunctionalized implant (5 mm in diameter, 10 mm in length) was

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Figs 2a to 2h   Patient 1. Immediate replacement of a failing implant performed with simultaneous guided bone generation.
Figs 2a and 2b   Intraoral and periapical radiographic images of a failing implant placed at thesite of the lower left second premolar.
Fig 2c  A photofunctionalized implant placed
after removal of the failing implant. The photofunctionalized implant surface was highly hemophilic.

ab

Figs 2d and 2e  A significant horizontal and vertical gap waspresent between the new implant and the alveolus and was filledwith bone graft material.

placed into the site (Fig 2c). The highly hemophilic
surface of the photofunctionalized implant was confirmed during placement. The failed and new implants
had identical surface topography and had been obtained from the same manufacturer. There was little
supporting bone; the gap between the implant andthe existing alveolar ridge was 3.5 mm (Fig 2d). Thisgap was filled with bone substitute materials (BioOss Cancellous 0.25- to 1.00-mm particles, Geistlich)(Fig 2e) and closed using a submerged technique witha titanium membrane (Frios Boneshield, Dentsply
Friadent) without fixation.
After 2.1 months of healing, radiographs showedthat mature bone surrounded the replaced implant.
The membrane was removed, and stage-two surgery
was carried out. The implant, along with an existing one at the first molar site, was provisionalized at
this time and functional loading was initiated. Fourmonths after implant placement (1.9 months after
functional provisionalization), the definitive prosthesis was placed (Figs 2f and 2g). There were no surgicalor prosthetic complications during the treatment andfollow-up visits up to 1 year. Periapical radiographs at
the time of crown placement and the 1-year follow-up
visit were compared to evaluate potential changes in
MBLs (Fig 2h). The radiolucency around the implantneck that was present at the time of crown placement disappeared or was less apparent at the 1-year
follow-up visit at both the mesial and distal aspects of
the implants. Accordingly, the BIC moved closer to theplatform level (arrows in Fig 2h).
Patient 2: Implant placement with simultaneous
sinus elevation. A 45-year-old man visited the clinic
for restoration of the maxillary right second premolar
and first molar with a particular consideration for dental implants. These teeth had been extracted becausecFigs 2f and 2g   Radiographic and intraoral images with thedefinitive prosthesis in place.

Fig 2h  A radiographic comparison of marginal bone levelat (left) the time of crown placement and (right) at the 1-year
follow-up visit. Blue arrows indicate the first BIC.

of severe caries and infected root canals (Fig 3a). Twomonths after extraction (Fig 3b), two photofunctionalized implants were placed into the sites, with theposterior one requiring simultaneous sinus elevation(Fig 3c). The implant in the second premolar site was
4 mm in diameter and 13 mm in length, whereas theimplant at the first molar site was 5 mm in diameter and
13 mm in length. Support from the native bone for the
first molar implant was limited, with only the coronal
6 mm of the implant being in contact with the native
bone; the remaining structure (the apical 7 mm) was in
the elevated sinus (Fig 3d). Clinically, the quality of thenative bone was poor (spongy and soft), as evidenced
by low ISQs (< 50; see Table 1). The sinus was elevatedusing the lateral window technique and bone substitute was used to fill the cavity (Bio-Oss Cancellous
0.25- to 1.0-mm particles). The implant in the second
premolar site was placed entirely within native bone
(Fig 3e). Both implants underwent submerged healing.
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Figs 3a to 3f

Patient 2: Implant placement with simultaneous sinus elevation.

ab

Figs 3a and 3b   Intraoral images (a) immediately and (b) 2 months after extraction of
the maxillary right second premolar and first molar.

dFig 3c   Two months after the extractions,
implants were placed with simultaneous
sinus elevation in the first molar region.

eFigs 3d and 3e  Computed tomographic images ofthe (d) first molar and (e) second premolar implants.
Note that the implant at the site of the first molar is
supported by native bone only for the coronal 6 mm(green line).

Fig 3f   Definitive restorations in place.

After 3.8 months of healing, a second surgery was
performed, and the implants were loaded on the sameday. The definitive restoration was placed 1.2 months
after provisionalization (Fig 3f ). In this patient, changes
in implant stability were evaluated by measuring the
ISQs at implant placement and at loading. At implant
placement, the ISQs were 48 and 49 for the second
premolar and first molar sites, respectively; 3.8 months
later, at loading, these had increased to 76 and 80. The
osseointegration speed, defined as the increase in ISQ
per month, was 7.36 and 8.16 for the second premolar
and first molar sites, respectively.
Patient 3: Implant placement into a fresh extraction socket. A 53-year-old woman presenting with adistal periodontal lesion and bone resorption aroundthe maxillary left first premolar visited the clinic forpotential implant treatment. Clinical and radiographic
examination indicated that the lesion was caused by adistal crack of the tooth (Fig 4a). The first premolar was
extracted, and a photofunctionalized implant (4 mmin diameter and 13 mm in length) was placed immediately (Fig 4b). Although little cortical support was available, as shown by a 2.5-mm gap between the implant
and the buccal alveolar ridge (Fig 4c), the apical halfof the implant was within the native bone, with goodprimary stability (ISQ > 65). Blood clot was maintainedin the gap by means of carbon dioxide laser–mediatedhemostasis and the wound was closed using a non-submerged technique without any grafting materials(Fig 4d). The patient received antibiotic treatment for
3 days postsurgery.
At 2.1 months after placement, the implant wasfunctionally provisionalized and also utilized as an
orthodontic anchor to extrude the second premolar(Fig 4e). The definitive restoration was placed 6 months
after initial implant placement, ie, 3.9 months after provisionalization (Fig 4f ). The extrusion was performedfor 3 months with 0.16-inch nickel-titanium wire, withgeneration of a constant force of approximately 50 g
anticipated. Extrusion of the neighboring tooth, in combination with the use of the photofunctionalized implant, effectively increased the MBL. A significant gainin the MBL at both the mesial and the distal aspects of
the implant was clearly demonstrated by radiographs
before and after tooth extrusion (blue arrows in Fig 4g).
Moreover, the maturation of bone stretching from the
middle third of the implant to the existing peri-implantmarginal gap was uniquely observed as developing
intensity and continuity of mineralization along theinterface (yellow arrows in Fig 4g). Accordingly, formation of the mesial and distal interproximal papillae was achieved, as seen in the definitive restoration(Fig 4f ). This implant was also evaluated for stability
during healing. At implant placement, the ISQ was 67,
whereas at the time of provisionalization it was 72, indicating an average ISQ increase of 2.38 per month.

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Fig 4a to 4g   Patient 3: Implant placement into a fresh extraction socket.

Fig 4a   Radiograph of a maxillary left first premolar presenting a distal bone resorption
associated with a crack.

Fig 4d  The implant site was sutured
without grafting materials using a nonsubmerged technique. Blood clot was formed
and retained in the peri-implant gap by using
carbon dioxide laser–mediated hemostasis.

Figs 4b and 4c   Intraoral images obtained during implant placement. The implant surface was highly hemophilic after photofunctionalization. The light-colored blood plasma
could be seen climbing up the implant surface along the thread as soon as the implantmakes contact with blood. Blood plasma reaches the coronal end first, with the denser,
red, erythrocyte-containing blood constituents following. There was no crestal bone
support and a significant horizontal gap of 2.5 mm between the buccal alveolus andthe implant surface.

Fig 4e  After 2.1 months of healing, theimplant was provisionalized and used as
an orthodontic anchor to extrude the second premolar.

Fig 4f   Definitive restoration.

Fig 4g   Radiographic comparison (left) before and (right) after
the orthodontic procedure. Bone maturation is seen along theimplant interface (yellow arrows). New bone formation is in progress within the peri-implant gap at both the mesial and the distal sides, significantly increasing the marginal bone level. Bluearrows indicate the most coronal BIC.

Patient 4: Staged placement after vertical ridge
augmentation and sinus elevation. A 72-year-old
woman visited the clinic for implant restoration in
the maxillary left quadrant. The alveolar ridge in thearea was highly resorbed, as seen in the radiographs(Fig 5a). A combination of vertical ridge augmentation and sinus elevation was performed in this area
to obtain a sufficient quantity of bone for implant
placement (Figs 5b to 5d). After 6.5 months of healing, three photofunctionalized implants were placed
for nonsubmerged healing (second premolar, 4 × 13mm; first molar, 5 × 13 mm; second molar, 6 × 10 mm)(Fig 5e). As seen radiographically before site develop-

ment (Fig 5a), there was limited native bone supportof only 25% to 30% for the two posterior implants. After 4.5 months, the implants were provisionalized forfunctional loading, followed by definitive restoration
at 6 months after implant placement (Figs 5f and 5g).
Radiographic comparison of images taken at the timeof crown placement and 1 year later showed relocation of marginal bone contact toward the coronal endsof the implants in many areas (arrows in Fig 5h).

Implant Success

The healing time before functional provisionalization
ranged from 2.1 to 4.5 months in these difficult cases.
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Figs 5a to 5h

Patient 4: Staged implant placement after vertical ridge augmentation and sinus augmentation.

Fig 5a  A panoramic radio- Figs 5b and 5c   Intraoral images before and during a combination ofgraph was obtained with a sinus elevation and vertical ridge augmentation.
surgical stent before site development surgery.

Fig 5d  Radiograph confirms
placement of the sinus graft.

Fig 5e  Three implants wereplaced 6.5 months after site
development.

Figs 5f and 5g   Intraoral view and periapical radiograph withdefinitive restorations in place.

Fig 5h   Radiographic comparison highlighting marginal bonelevels (left) at the time of crown placement and (right) at 1
year. Blue arrows indicate the first BIC.

During the 1-year follow-up period after placement of
the definitive prostheses, all seven photofunctionalized implants were stable and functional, without painor other signs of inflammation. There was no peri-implant radiolucency or marginal bone loss, as summarized in Table 1.

Implant Stability and Osseointegration Speed

The ISQ was between 48 and 75 (63.2 ± 11.8) at thetime of implant placement and between 68 and 81(76.2 ± 5.2) at the commencement of loading (Table 1,
Fig 6). The ISQ was greater than 65 at the time of loading for all implants tested. Five of the six implants tested
showed an increase in ISQ during healing. In particular,
the implants with initial ISQs below 70 showed impressive increases at the time of loading, ranging from 5 to 31.
The osseointegration speed ranged from –1.11 to 8.16.

Marginal Bone Change

The marginal bone change measured at the mesial
and distal aspects of each implant is listed in Table 1
and plotted in Fig 7. The MBL, which was an average of–0.35 ± 0.71 mm at the time of crown placement, hadsignificantly increased to 0.16 ± 0.53 mm after 1 year,
indicating an overall coronal gain in marginal bone contact, which in some cases even exceeded the level ofthe implant platform (P < .05). Marginal bone gain wasseen at 11 of the 14 aspects measured, and no implants
had marginal bone loss at 1 year of follow-up (Fig 7). In
particular, all MBLs that were apical to the platform atcrown placement increased, whereas those MBLs thatwere coronal to the platform maintained the same level(Fig 7). The average MBL change was 0.51 ± 0.35 mm
after 1 year, which resulted in platform-level or supra–platform-level marginal bone in the majority of areas(9 of 14).

Complications

The 15-minute photofunctionalization process was
initiated several minutes before anesthetizing thepatient. By the time drilling was complete, the photofunctionalized implants were ready for placement,
which resulted in no delays in surgery. Because of thesuperhydrophilic nature of the photofunctionalized

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80
Marginal bone level (mm)

75
70

ISQ

65
60
55

0.5

0

–0.5

–1.0

50
45

*

1.0

Implant
placement

Loading

–1.5

Crown
placement

After 1 y

Fig 6   Changes in implant stability for photofunctionalized implants. ISQ values were measured at the time of implant placement and at the start of functional loading.

Fig 7  MBL changes around photofunctionalized implants.
MBLs were measured at the time of definitive restoration andat 1 year. Negative numbers represent bone levels apical to theimplant platform, and positive numbers represent bone levels
coronal to the platform. Refer to Table 1 for mean values for
MBLs and changes in MBLs. *P < .05.

implant surfaces, particular attention was given to ensuring that the implant did not contact saliva or surrounding soft tissue when being placed. No prosthetic
or surgical complications or procedural difficulties
were observed with regard to the use of photofunctionalization.

of remote cortical bone and slowly approaches theimplant interface with untreated implants. In otherwords, photofunctionalized implants are capable of inducing contact osteogenesis,66 even under suboptimal
conditions, while untreated implants rely on distant osteogenesis.66 These findings suggest that photofunctionalized implants may overcome the compromisedbone healing associated with a significant peri-implant
gap; the case of implant placement into a fresh extraction socket (patient 3) may have represented this scenario. Implant placement into a fresh extraction socket
is known to be associated with a higher failure rate thanplacement into healed sites, and failures usually occur
during the early stage of healing.7 According to the literature, implants placed into extraction sockets should
be kept unloaded for 4 months39 or 5 to 6 months61;
it was therefore noteworthy that, in the present study,a degree of osseointegration sufficient for loading wasachieved after only 2.1 months of healing after placement of a photofunctionalized implant. With respect toestablishing and maintaining the strength of osseointegration, ISQs for implants in extraction sockets havebeen shown to remain unchanged or even decreaseslightly after 6 to 12 months of healing.42,61 The high
ISQ of 72 at provisionalization obtained with photofunctionalization in this patient, in addition to the average ISQ increase of 2.4 per month, was exceptional andjustified early loading (2.1 months after placement).
Furthermore, it was impressive that the process of

DISCUSSION
This is the first study to report on the clinical use ofphotofunctionalized dental implants. Despite the challenging bone conditions studied in this case series, all
implants demonstrated successful osseointegrationand functioned as expected, with excellent soft tissue
health and esthetics that were maintained at 1 year offollow-up.
An animal study that examined the effect of deficientcortical bone support on osseointegration showed that
implants placed without cortical bone support had
a 60% reduction in the strength of osseointegrationcompared to those with cortical support.29 Photofunctionalized implants improved this osseointegration tolevels observed for implants with cortical support. The
effect was explained by the enhanced capability of thephotofunctionalized implants to induce osteogenesis,
beginning at the implant interface and rapidly spreading to, and connecting with, the surrounding bone. In
contrast, delayed osteogenesis begins at the surface

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Funato/Ogawa

osseointegration continued to mature and extend evenafter functional provisionalization, as vividly detectedin radiographs (Fig 4g). This phenomenon appeared toembody the aforementioned contact osteogenesis in
the local environment without cortical support.
Placement of an implant into the site of a currently
failing, or previously failed, implant is considered oneof the most challenging clinical scenarios.67–69 Preexisting inflammation and a decreased potential for
osteogenesis may compromise bone-implant integration, resulting in substantial decreases in success rates
to levels as low as 70%.67 Moreover, horizontal andvertical gaps are often present between the implant
and the alveolar bone. In such cases, an extended healing time of 5 months or more may be required before
placement of implants, along with additional healingof 9 months or more after placement.69,70 In patient 1,
despite the peri-implant gap of 3.5 mm, a photofunctionalized implant placed immediately after removalof the failing implant osseointegrated and was successfully loaded after 2.1 months, followed by an asymptomatic and complication-free outcome up to 1
year. Therefore, the clinical outcomes obtained in patients 1 and 3 appear to be consistent with the resultsof published animal studies.
The degree of reduction in the strength of osseointegration caused by the use of short implants has
been assessed in an animal model.17 Implants with
40% shorter length resulted in a decrease in implantanchorage of 50% or more. Shorter implants that were
photofunctionalized had a strength of osseointegration that was double the usual strength, eliminating
the disadvantage of short implants.17 This was explained by the expansion of the load-bearing interface around photofunctionalized implants,17 which
benefitted from the significant increase in BIC.24 Whilesinus grafting has been proven an effective measure to
expand the indications for implants and improve implant stability, success rates after sinus augmentation
are not as high as those seen for regular implant placement without such surgical intervention.71 In patient 2,
an implant was placed into a first molar site with simultaneous sinus elevation. The implant was supported
only by native bone for the coronal 45% of its length,with the additional challenge of poor bone quality, as
confirmed by an ISQ of < 50. Even under this condition, the ISQ increased from 49 to 80 after 3.8 months,
yielding an ISQ increase of 8.16 per month. The rate of
ISQ increase obtained here was much higher than thatreported for maxillary implants in the literature (0.0 to1.0).58,59,61,72 With respect to the healing time required,implant placement combined with sinus elevation isoften performed using a staged approach, with a total
healing time of 8 to 14 months.73 The use of a photofunctionalized implant and a simultaneous approachto grafting and implant placement resulted in successful loading after only 3.8 months in this case.
Implant osseointegration in augmented bone isconsidered to be difficult because of the limited availability of regenerative cells and decreases in other
osteogenic metabolic activities.74,75 This requires a longer healing time and results in more frequent soft tissue encapsulation and progressive peri-implant bone
resorption.76–78 Furthermore, the extent to which thenative bone supports the implant is a crucial factor in
determining implant prognosis.5 When implants areplaced in augmented bone, it is generally thoughtthat a 6-month healing period is required to secure
osseointegration prior to loading.79 Implant placement
in a site after multiple site development procedures,such as a combination of vertical ridge augmentationand sinus elevation, may require a healing time that isfurther extended, up to 13 months.80 Here, photofunctionalized implants were placed into a site treated withcombined vertical ridge augmentation and sinus elevation and were successfully loaded after 4.5 months(patient 4). This was in spite of a very low percentage ofnative bone support (between 25% and 30%).
Contrary to the current understanding that marginal bone loss is unavoidable within the first year of
implant placement,72,81–84 there was an overall gain in
MBLs in this clinical series. The average gain after 1 year
was approximately 0.5 mm, which resulted in an MBL
above the implant platform. Notably, none of the sites
showed marginal bone loss. One interesting finite element analysis–based study simulated the distributionof peri-implant stress when BIC was 98.2% and 53.0%
in implants with and without photofunctionalization,
respectively.85 The concentration of stress around theimplant neck was significantly reduced by the 98.2%
BIC, as demonstrated by the fact that the stress around
7-mm-long implants with 98.2% BIC was even lower
than the stress around 13-mm-long implants with 53%
BIC. This study suggested that, although it is unclear
what concentration of stress triggers bone resorption
around the area, increased BIC effectively improved the
distribution pattern of peri-implant stress and may be
a potential strategy to preserve peri-implant marginal
bone. The observation in this report warrants further
longer-term studies to establish the effect of photofunctionalization on the anatomical stability and physiologic health of peri-implant bone and soft tissue.
Photofunctionalization-induced physicochemicalchanges include the removal of hydrocarbon, optimization of electrostatic charges on titanium surfaces, andregeneration of superhydrophilicity.16,53,86–88 In vitro
studies have demonstrated that hydrophilicity alone
does not increase the amount of protein and number ofosteogenic cells attached to titanium surfaces, and thatunfavorable electrostatic charges on titanium surfaces

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substantially reduce the recruitment of osteogenic
cells to titanium surfaces, even when they are hydrophilic.87,88 It is also known that the number of cells attached to titanium surfaces correlates with reductionsof surface carbon, but not with the degree of hydrophilicity.21,24,44 In the general field of biomaterials research, the role of surface hydrophilicity in determining
bioactivity remains contentious.89 It has not been universally demonstrated that a more hydrophilic surface
makes for a more biocompatible material. For instance,a polymer surface with improved hydrophilicity reduces fibroblast proliferation,90 while more hydrophobicpolymer scaffold materials are effective in promotingbone regeneration.91 There are commercially availablehydrophilic dental implants that are stored in solution
to preserve their hydrophilicity.92,93 However, thesesurfaces need careful interpretation with respect totheir clinical advantage,89 since there is little information regarding their other physicochemical properties,
including carbon percentage, electrostatic status, andtime-related physicochemical changes. In fact, fewer
cells attach to these hydrophilic surfaces than to hydrophobic surfaces with identical surface morphology.94
This biologic property is completely different from thatof photofunctionalized surfaces, which enhance the recruitment and attachment of cells considerably.21,24 In
addition, one definite difference between photofunctionalized implants and these commercial implants
is that photofunctionalized implants are dry prior touse but highly wettable when they make contact withblood, whereas the commercial products are wet withsolution before use. It should also be remembered thatphotofunctionalized surfaces are converted to chemically clean and genuine titanium surfaces.
Although various site development procedures enable or facilitate implant placement, they are also risk
factors for implant failure and necessitate protracted
healing. In this case series, all implants showed ISQs
higher than 65 at loading and were safely loaded earlier than reported in the literature or earlier than suggested in common protocols. In the present series, theosseointegration that was established early was maintained during 1 year of follow-up. Although interpretation is necessarily limited by the number of patients
reported here and the relatively short-term followup period, these successful outcomes suggest thatphoto­functionalized implants are useful and effective
for challenging clinical cases and warrant further clinical study. Since photofunctionalization is effective on
all examined surface topographies of titanium-basedmaterials,25–27,56 the technology seems versatile andapplicable to a wide range of dental and orthopedic
implants. Finally, no surgical or prosthetic complications were observed, suggesting that the technique
is both practical and safe. If surface modification tech-

nologies are needed to expand the indications for implant therapy, shorten the healing time, and increase
success rates, particularly in challenging clinical situations, photofunctionalization appears highly suited toachieving these goals.

Conclusions
Within the limits of interpretation of a small case series, the use of photofunctionalized dental implants inthese clinically challenging cases appeared to resultin osseointegration in a shorter period of time thancurrently suggested by standard protocols and the
published literature. In addition, the increases in implant stability and osseointegration speed were considerably greater for photofunctionalized implants
than similar results reported in the literature. During
a 1-year follow-up period, the marginal bone level increased toward the coronal for all photofunctionalized
implants whose platform had been subcrestal at crownplacement, while those implants that had supracrestal
peri-implant bone at crown placement maintained
their marginal bone level without loss. No surgical or
prosthetic complications were reported up to 1 year
after loading. The procedure for photofunctionalization is simple and applicable to titanium-based andtitanium alloy–based materials of various surface
types. Together with other in vitro and in vivo data, thepromising clinical outcomes presented in this preliminary study suggest that photofunctionalization is useful and effective for challenging clinical situations andrepresents a novel avenue to overcome some of theongoing challenges in implant dentistry. Further midand long-term clinical studies are warranted.

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