Success Rate, Healing Time, and Implant Stability of
Photofunctionalized Dental Implants
Akiyoshi Funato, DDS1/Masahiro Yamada, DDS, PhD2/Takahiro Ogawa, DDS, PhD3
Purpose: This is the first study to report the clinical outcomes of photofunctionalized dental implants. Materials
and Methods: This retrospective study analyzed 95 consecutive patients who received 222 untreatedimplants and 70 patients who received 168 photofunctionalized implants over a follow-up period of 2.5 years.
Photofunctionalization was performed by treating implants with UV light for 15 minutes using a photo device
immediately before placement. The generation of superhydrophilicity and hemophilicity along with a substantial
reduction in atomic percentage of surface carbon was confirmed after photofunctionalization. In both groups,
90% of the implants were placed in complex cases requiring staged or simultaneous site-development surgery.
The implant stability was measured at implant placement and loading using the implant stability quotient (ISQ)
values; then, the rate of implant stability development was evaluated by calculating the ISQ increase permonth. Results: The healing time before functional loading was 3.2 months in photofunctionalized implants
and 6.5 months in untreated implants. The success rate was 97.6% and 96.3% for photofunctionalized anduntreated implants, respectively. The ISQ increase per month for photofunctionalized implants ranged from
2.0 to 8.7 depending on the ISQ at placement, and it was considerably higher than that of untreated implants
reported in the literature ranging from –1.8 to 2.8. Photofunctionalization resulted in a more frequent use of
implants of 10 mm or shorter length and an overall decrease in implant diameter. Conclusions: Within thelimits of this retrospective study, despite the more frequent use of shorter and smaller-diameter implants, theuse of photofunctionalization allowed for a faster loading protocol without compromising the success rate.
The outcome was associated with an increased rate of implant stability development. The results suggest thatphotofunctionalization may provide a novel and practical avenue to further advance implant therapy. Int J Oral
Maxillofac Implants 2013;28:1261–1271. doi: 10.11607/jomi.3263
Key words: hydrocarbon, superhydrophilic, super osseointegration, titanium, ultravioletUltraviolet (UV) light treatment of titanium implants
has been reported to increase bone-to-implant contact (BIC) from 55% to a near maximum level of 98.2%
in an animal model.1–3 The increased BIC resulted ina threefold increase in the strength of bone-implant

1Private Practice, Kanazawa, Japan.
2 Assistant Professor, Department of Removable

Prosthodontics and Gerodontology, Tokyo Dental College,
Chiba, Japan.
3 Professor, 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 (LBIS), 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, USA.
Fax: +1 310-825-6345. Email: togawa@dentistry.ucla.edu©2013 by Quintessence Publishing Co Inc.

integration.1–3 Moreover, the increased BIC is demonstrated to contribute to even distribution and reduced
levels of mechanical stress in the peri-implant marginal
bone.4 The effectiveness of UV treatment in challenging
conditions such as bone healing with short implants anda significant peri-implant gap has also been demonstrated.5,6 The enhancement in osseointegration is attributed
to the generation of superhydrophilicity, a significant
decrease in surface hydrocarbons, and improvement in
the electrostatic status of titanium surfaces after UV treatment.1,7–9 These surface property changes were demonstrated to result in an increased recruitment, attachment,
retention, proliferation, and overall phenotype of osteogenic cells.1–3,7,8,10–12 The biological effects along with UVenhanced surface properties are collectively defined as
photofunctionalization of titanium implants.2,3,7,13–15
Despite establishment as a routine procedure, implant therapy still faces many challenges in applicationand treatment outcomes. The extended healing timerequired for osseointegration needs to be shortened todecrease patient morbidity and to accommodate thegrowing demands of modern implant therapy. Various
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Funato et al

Table 1   Patient Data
Implants Patients

Mean age (range)

Sex(female/male)

Untreated implants

222

95

52.7 ± 16.9 (20–76)

63/32

Photofunctionalized
implants

168

70

55.6 ± 11.0 (22–78)

50/20

Fig 1 (right)  The device used for photofunctionalization of dental implants (TheraBeam Affiny). Implant fixtures are placed on the sliding stage. The device performs
an automatic program of 15-minute UV exposure.

pre-implant surgeries, including bone augmentationand sinus lift procedures, have proven useful for expanding the indications of implant therapy; however, theclinical outcomes of implant placement in such cases
may not be as predictable as those in regular placementcases.16,17 More rapid and complete establishment ofbone–implant integration has been a persistent goal.
A crucial question exists: do the biologically andscientifically proven acceleration and enhancementof osseointegration by photofunctionalization actually contribute to current clinical implant dentistry? In
this study, we retrospectively evaluated consecutive
patient populations who received either untreated implants or photofunctionalized implants and analyzed
the success rate, dimensions of implants, implant stability development, and healing time before loading.

MATERIALS AND METHODSPatients

There were two patient groups (untreated implant andphotofunctionalized implant groups) formulated fromconsecutive patients who visited the Nagisa Dental
Clinic (Kanazawa, Japan) for implant therapy during
20 months from April 2009 through November 2010.
Photofunctionalization was implemented in the clinic
in February 2010, after which point all implants were
photofunctionalized. The photofunctionalized implantgroup included 168 implants placed in 70 patients who
visited the clinic after February 2010, whereas the untreated implant group included 222 implants placed in
95 patients who visited before February 2010. The demographic data for each group are presented in Table
1. Patients were included if they were at least 20 years
old, compliant with oral health care instructions andnecessary visits, and provided consent for documentation and public presentation of their clinical data. Patients with systemic conditions that could potentiallyaffect bone and soft tissue healing such as osteoporosis, diabetes, or radiation treatment were excluded.

Clinical Procedure andPhotofunctionalization of Implants

Implant therapy was proposed and performed in thesame manner for the untreated and photofunctionalized implant groups. Following routine procedures
for local anesthesia and full-thickness flap reflection,
implants were placed with a torque of 25 to 45 Ncm
per the manufacturer’s instructions. The implants
used in this study possessed a tapered root form andidentical surface morphology (Osseotite Certain,
Biomet 3i). Photofunctionalization was performed
at chairside immediately before implantation (Fig 1)
by treating the implants with UV light for 15 minutes
using a photo device (TheraBeam Affiny, Ushio). The
photofunctionalization-induced change in surface
property from hydrophobic to superhydrophilic wasconfirmed prior to patient visits by examining several
implants for their wettability with double-distilled water (Figs 2a and 2b). Photofunctionalization was also
confirmed by observing blood spiraling up the implant
immediately after it was in contact with the drilled site,
as typically seen in Fig 2c. This hemophilicity was notobserved for the untreated implants. Furthermore,
the chemical composition of implant surfaces wasevaluated by x-ray photoelectron spectroscopy (XPS)(ESCA3200, Shimadzu). The atomic ratio of carbon to titanium (C/Ti), which was 109% before photofunctionalization, decreased to 38% after photofunctionalization.

Implant Location and Proportion ofComplex Cases

Neither the number of implants placed in each location
nor the distribution between the maxilla and mandible was significantly different between the untreatedand photofunctionalized implant groups. The mostcommon implant location was the posterior mandible,
followed by the posterior maxilla, anterior maxilla, andanterior mandible in both groups. The implants usedin this study largely involved complex procedures with
pre-implant or concomitant surgery in both groups.
Implant placement in fresh extraction sockets, bone1262 Volume 28, Number 5, 2013
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Funato et al

a

b

c

Figs 2a to 2c   (a) Hydrophobic implant surface before photofunctionalization with three droplets of 3 μL double-distilled water (total
9 μL) showing very limited area of water contact on implant surface. (b) Superhydrophilic surfaces were generated on implants after
photofunctionalization, showing that 9 µL of water (three droplets of 3 µL) was sufficient to spread and cover the entire implantsurface. (c) A highly hemophilic implant after photofunctionalization. A typical intraoral image of photofunctionalized implants after
contact with an implant site. Note the dynamics of the blood spiraling up along the implant threads and reaching the coronal portion.

Table 2   Implant Data
Overall implant length
Mean (mm)≤ 10 mm(%)≥ 13 mm(%)

Untreated implants(n = 222)

12.04 ± 1.69

56 (25.2)

Photofunctionalized
implants (n = 168)11.76 ± 1.69NS

63 (37.5)

Implant diameter

Complex cases

Mean (mm)≥ 5 mm
(%)

Implant length(mm)

Implant
diameter (mm)109 (49.1)

4.71 ± 0.75

123 (55.4)

12.20 ± 1.65

4.64 ± 0.73

72 (42.9)

4.51 ± 0.71**

66 (39.3)

11.71 ± 1.30*

4.50 ± 0.76NS

Statistically significant differences between untreated and photofunctionalized gropus: *P < .05, **P < .01, NS: not significant.

with simultaneous or staged guided bone regeneration (GBR) and/or simultaneous or staged sinus elevation was defined as complex cases, accounting for84.2% and 91.7% implants in the untreated and photofunctionalized implant groups, respectively.

Implant Dimensions

The lengths and diameters of implants used are presented in Table 2. The use of implants 10 mm or shorter
was more frequent in the photofunctionalized implantgroup (37.5%) than in the untreated implant group(25.2%). The implant diameter was significantly smallerin the photofunctionalized implant group than in theuntreated implant group; implants 5 mm or wider indiameter were used less often in the photofunctionalized group. Implants used in complex cases were significantly shorter in the photofunctionalized implantgroup.

Implant Stability

Implant stability was evaluated by measuring the impant stability quotient (ISQ) at implant placement andcommencement of functional loading using Osstell ISQ(Osstell). Furthermore, the rate at which implant stability was established was evaluated by calculating the
ISQ increase per month, which was defined as [(ISQ atloading) − (ISQ at implant placement)]/(healing time

before loading). Implant stability measurement was
performed for all photofunctionalized implants. The average ISQ from four measurements (four different directions at the mesial, distal, buccal, and lingual surface ofan implant) was used for further statistical analysis. The
ISQ device was implemented in the clinic after photo­functionalization was introduced. Therefore, ISQ data
were only available for photofunctionalized implants.

Implant Success

Implant success was evaluated according to the success criteria of Smith and Zarb18 after follow-up periods of 2.5 to 3.5 years and 1.5 to 2.5 years after final
restoration for the untreated and photofunctionalized
implant groups, respectively. Implant failure was confirmed by the presence of significant mobility, radiographically confirmed failure of osseointegration or
progressive disintegration, significant marginal boneloss, pain, inflammatory signs, and/or rapid and continuous decrease in ISQ values.

Potential Surgical Complications

Potential surgical complications were monitored, including duration and level of pain, bleeding, inflammatory reaction of tissues, improper or delayed woundhealing, postoperative infection, damage to neighboring natural teeth, or postsurgical sensory disorders.
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4
2

8
7
6

5
4
3
8
2
7
1
6
0
5
4
3
2
1
0

8
7
6
5
4
3
8
2
7
1
6
0
5

0
Pf

Ut

Pf

Fig 3  mandible
Healing time before functional
Anteriorloading of untreated and photofunctionalized implants. Shaded and white boxes ac5.2
count for 50% and 80% percentile, while
the mean values are denoted above eachbox. Ut: Untreated implants, Pf: photofunctionalized* implants, *P < .05.
Anterior mandible
Anterior mandible
8
0.5
5.2
5.2
7

Ut

6
5
Pf
4

*

3
2
0

3.2

2

Ut

4

1

*

4

Healing time before loading (mo)

0

8
Pf
3.2
6

*

6

6.5

*

3
0.5
2

0.5

1

Posterior mandible
0

Ut
Pf
Ut
Pf Analysis
Statistical
5.9

6

6
2.8
5
Ut
Pf
RESULTS
4

*

4
12
2
10
0
8

Anterior maxilla
12
7.4
Ut

6
4
2
0

*

Ut

10

Anterior maxilla

8

7.4

7

*

6

8
Pf
4.1
6

4.1

3
2

2
0
Pf

5
4

4

Ut

Pf

0

Posterior maxilla

10

6
4
12
2
10
0
8

4.1

7.3

Ut

6
4
2
0

8

*
Posterior maxilla
12

Ut

3

2
The averagehealing time before functional loading1
was two-foldshorter for photofunctionalized implants
than for0untreated implants: untreated implants wereUt
Pf
Utloaded 6.5
Pf months after placement while photofunctionalized implants were loaded 3.2 months after
placement (Fig 3). A substantial reduction in healing
time was consistently seen in all regions. A drastic decrease in the healing time in the anterior mandible wasa result of a general reduction of healing and increased
instances of immediate loading.
The distribution of healing times is plotted in Fig 4.
The overall results showed that none of the untreated

*

10
8
Pf
4.1
6

7
6
5

5.2
Anterior mandible
5.2

*

4
3

0.5

*

2
1
0

Ut

0.5
Pf

Ut

Pf

Posterior mandible

7.3

8

8

1

12

2.8

Healing Time

Anterior mandible
4.1

Differences in healing time between untreated andphotofunctionalized
implants were examined us*
ing the2.8
Mann-Whitney U test. Differences in implant
length and diameter between the two groups and ISQ
Posteriorchangeswithtime mandible
were examined by analysis of variPosterior
mandible8
5.9A P value of < .05 was considered statisance(ANOVA).
5.9
7
tically significant.
**8

Healing time before loading (mo)Healing time before loading (mo)

Ut

10

7.4

Healing time before loading (mo)Healing time before loading (mo)

6.5

10

Healing time before loading (mo)Healing time before loading (mo)08Overall

Overall
12

4
12
2
10

3.2

12

Healing time before loading (mo)*6

Healing time before loading
Healing(mo)time before loading (mo)8

Healing time before loading (mo)Healing time before loading
Healing(mo)time before loading (mo)6.5
Funato et al

Healing time before loading
Healing(mo)time before loading (mo)10

Healing time before loading
Healing(mo)time before loading (mo)Healing time before loading
Healing(mo)time before loading (mo)Overall
127Posterior maxilla

6

5

7.3

4
3

*

4

4.1

2

8
7
6
5

5.9
Posterior mandible
*
2.8
5.9

4

*

3

2.8

2
1
0

Ut

Pf

1
0

Ut

Pf

2
0

implants wereimmediately
loaded, whereas 17% ofUt
PfPfphotofunctionalized implants were immediately loaded. Taken together, 50% of the photofunctionalized
implants were either loaded immediately or within aperiod of 3 months. None of the untreated implants
were loaded during this early stage. Photofunctionalization resulted in a considerable decrease in the proportion of healing times greater than 6 months. Less
than 10% of photofunctionalized implants and 50%of untreated implants were subjected to such long
healing. Region-specific distribution of healing time
revealed that 75% of photofunctionalized implants
placed in the anterior mandible were immediately
loaded. Early loading within 3 months was applied in
35%, 100%, 37%, and 54% of photofunctionalized implants in the anterior maxilla, anterior mandible, posterior maxilla, and posterior mandible, respectively.

Success Rate

The overall success rate for untreated implants was
96.3%. Eight out of 222 implants in seven patients
failed. Seven out of the 8 implants were not integrated
at second-stage surgery. One implant failed after provisionalization. The success rate for photofunctionalized
implants was 97.6%. Four out of 168 implants failed. All

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Frequency of different healing times (%)

Funato et al100

6 months +3–6 months
0–3 months
Immediate loading

80
60
40
20
0

Ut
Pf
OverallUt PfAnterior
maxillaUt PfAnterior
mandible

Ut Pf
PosteriormaxillaUt Pf
PosteriormandibleFig 4   The distribution of specific healing times before functional loading of untreated and photofunctionalized
implants. Ut: Untreated implants, Pf: photofunctionalized implants.

Table 3   ISQ Change and Increase for Photofunctionalized Implants
ISQ
Primary stability range

Implants

At placement (ISQi)

At loading

Increase/m
4.6 ± 0.4

ISQi < 403

37.7 ± 2.3

63.0 ± 7.5**

ISQi 40–49

8

47.6 ± 1.8

73.8 ± 8.6***

8.7 ± 4.1

ISQi 50–59

13

56.1 ± 2.7

66.8 ± 8.7***

2.6 ± 2.4

ISQi 60–69

18

66.5 ± 2.6

70.5 ± 12.4NS

NA

ISQi 60–64

462.8 ± 1.5

74.0 ± 7.2*

2.0 ± 1.5

ISQi 65–69

14

67.6 ± 1.5

69.5 ± 13.5NS

NA

33

76.1 ± 1.9

72.4 ± 11.5NS

NA

82.7 ± 1.980.4 ± 6.1NS

NA

ISQi 70–79
ISQi ≥ 80

24

ISQi 60–69 was subdivided into ISQi 60–64 and 65–59 groups to precisely determine threshold of significant change in
ISQ at loading.
Statistically significant differences between time points; *P < .05; **P < .01; ***P < .001; NS: not significant.
ISQi: initial ISQ at implant placement; NA: not applicable.

failures were associated with early provisionalization
within 3 months (1 implant placed in a fresh extraction
socket, 2 in sinus lift sites, and 1 at a vertical GBR site).
There was no disintegration observed before provisionalization. Therefore, the failure rate before functionalloading was 3.15% for untreated implants and 0.0% forphotofunctionalized implants. There was no late failure
after the final prostheses were placed for both groups.

Implant Stability

Implant stability was evaluated by categorizing implants according to the range of initial ISQ (ISQi) at
placement. First, implants were divided into six groups
by a 10-point ISQi interval (Table 3). When the ISQi was
lower than 60, the ISQ at loading increased significantly. The increase (a difference between implant place-ment and loading) ranged from 10.7 to 26.2 points andwas more remarkable when the ISQi was low (Fig 5
and Table 3). When the ISQi was 60 or higher, the subsequent ISQ did not change significantly (Fig 5 andTable 3). To precisely determine the ISQi threshold that
leads to a significant change at loading, “ISQi 60 to 69”
group was subdivided into “ISQi 60 to 64” and “ISQi 65
to 69,” as shown in Table 3. It was shown that when the
ISQi was 60 to 64, the ISQ at loading was significantly
increased from the level at placement, whereas the
ISQi of 65 to 69 did not show a subsequent significant
change. Furthermore, for the implants that showeda significant ISQ increase between placement andloading, the ISQ increase per month was calculated(Table 3). The ISQ increase per month was the highest
at 8.7 ± 4.1 when the ISQi was 40 to 49.
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Funato et al

DISCUSSION
NS
80
NS

75
70

NS

ISQ

65
***

60

***

55
50

**
45
40
35
Placement (ISQi)

LoadingFig 5   The ISQ values at implant placement and functional loading. Implants were divided into six groups depending on their initial ISQ at placement (ISQi). Mean and standard deviations areplotted for each group. Statistically significant differences wereobserved between the two time points. **P < .01, ***P < .001.
NS: not significant. See Table 3 regarding further determinationof significant ISQ change in the ISQi 60 to 69 group.

Complications

Surgical complications were documented in association with 11 untreated implant placements: periimplant infection observed with titanium (Ti) mesh
exposure (3 implants), peri-implant infection with soft
tissue dehiscence in a case of simultaneous GBR (1 implant), noninfectious Ti mesh exposure (5 implants),
exposure of the cover screw (1 implant), and tentativeand mild sensory disorder (1 implant).
Photofunctionalization, which takes 15 minutes,
was initiated several minutes before anesthetizing thepatients. By the time the drilling was complete, thephoto­
functionalized implants were ready for placement, which resulted in no delay or time loss during
surgery. No surgical complication that required an extra
procedure was documented in association with photofunctionalized implants. One implant was associatedwith a noninfectious minor Ti mesh exposure. The surgical complication rate was 4.95% (11 incidents/222
implants) for untreated implants and 0.59% (1 incident/
168 implants) for photofunctionalized implants.

Implant placement in complex cases is considered toincrease the risk of implant failure and requires a substantially longer healing time. In general, 6 months isrequired to secure osseointegration before loading inaugmented bone.19 Bone with multiple augmentation
procedures such as a combination of vertical ridge
augmentation and sinus lift may require an extended
healing time of up to 13 months.20 Implants placedin extraction sockets should be left unloaded for 4
months21 or 5 to 6 months.22 If horizontal and verticalperi-implant gap is anticipated in the socket, implant
placement should take place after 5 months or more,
followed by an additional healing time of 9 months ormore for osseointegration.23,24 In this study, successful
osseointegration was demonstrated after an averagehealing time of 3.2 months using photofunctionalized
implants, a majority of which were placed in bone withthe above-mentioned challenging conditions.
Findings from animal studies may be helpful inunderstanding the high clinical performance of photofunctionalized implants in the present study. A rat
study showed that implant placement without corticalbone support reduced the strength of osseointegration by 60%.5 However, photofunctionalized implants
placed in the same site achieved the strength of osseointegration equivalent to the implants with cortical support. The effect was explained by the robust
osteogenesis initiating at the implant interface, which
rapidly spread to the remote cortical bone. In contrast,
osteogenesis around untreated implants was initiatedat the surface of remote cortical bone and slowly approached the implant interface. More than 75% of
implants in this study involved simultaneous GBR and
fresh extraction sockets with a significant peri-implantgap. The successful result for these implants is wellsupported by the previous animal study.
Another animal study addressed a potential disadvantage caused by the use of short implants and further determined whether photofunctionalization could
mitigate this disadvantage.6 In that study, implants with
40% shorter length resulted in a 50% or more decreasein the strength of osseointegration. However, when the
short implants were photofunctionalized, the osseo­
integration strength doubled and this disadvantage ofshort implants was eliminated.6 This was explained byincreased bone coverage around photofunctionalized
implants that offset the reduced surface area. Photofunctionalization is known to increase the percentage
of bone-implant contact by nearly two times.1 Most implants in the present study were placed in complex cases and had a limited area supported by native bone. The
successful outcome for these implants may arise fromthe evidence of this animal study. More convincing is1266 Volume 28, Number 5, 2013
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Funato et al

the fact that photofunctionalization allowed for more
frequent use of 10-mm or shorter implants, thus opening a new avenue of minimally invasive implant therapy even in challenging cases. Moreover, the average
length and diameter were significantly smaller for thephotofunctionalized implants than untreated implants.
This study presents only results based on a retrospective study design, and the obtained differences wererelatively small. The authors believe future studies withmore controlled designs will address the clinical impactof these findings by identifying how short and narrowdental implants can be used with photofunctionalization to generate a load-bearing capacity high enoughto tolerate specific bone conditions.
Measuring implant stability at placement, as well as
the subsequent change during healing, provides useful information for monitoring the process of osseointegration, planning a loading protocol, and evaluating
various conditions of osseointegration on the implantand host sides.25–31 The use of ISQ values based onresonance frequency analysis has been extensively reported for its reasonable reliability and validity.27,32–37
In addition to observing the expected progress of osseointegration, the timing of the stability decrease
has been a focus in evaluating implant surfaces anddetermining loading protocols. ISQ values are sensitive enough to detect the stability decrease between
weeks 1 and 8 after implant placement.26,28,33,38–41
In this study, to ensure the reliability of ISQ data, themean value obtained from four time measurements
was used for statistical analyses.
The authors postulated that the evaluation of implant stability using ISQ values was more meaningfulwhen the initial value at implant placement and theperiod of time required to reach the final value areconsidered. In this way, ISQ values could be standardized and allow for a comparison among implants withdifferent healing times and different primary fixations.
Therefore, in the present study, the ISQ change between the time of placement and functional loading
was first calculated. Next, the ISQ change was divided
by the time required before loading to obtain the ISQ
increase per month and evaluate the rate of implantstability development. ISQ change between two time
points has been presented as a useful parameter inmany previous studies along with a description ofwhen they were measured.25,33,38,42,43 The ISQ increase
per month was further calculated by dividing the ISQchange by time as an indicator for the rate of implantstability development.
The obtained data of implant stability change and
ISQ increase per month strongly supported the highsuccess rates of photofunctionalized implants, evenwith the accelerated loading protocol. In this study,
ISQ data were only available for photofunctionalized

implants, and therefore, the data were compared withuntreated implants in the previous articles after a thorough literature search (Table 4). Because there is a general trend in the literature that implants with an initial
ISQ of 70 or higher show no significant change during
subsequent healing, the authors searched and listed
papers that dealt with implants with an initial ISQ ofless than 70.22,25,26,33,38–40,43–48 There were two major
findings from this search: (1) the ISQ increase between
the first and second measurements for photofunctionalized implants, ranging from 10.7 to 26.2, was substantially greater than those in the literature, ranging
from –5.0 to 4.6, and (2) the ISQ increase per month ofphotofunctionalized implants, ranging from 2.0 to 8.7,
was notably higher than that reported in the literature,
ranging from –1.8 to 2.8.
Several reports specifically examined ISQ changes
under compromised bone conditions. The ISQ values
for implants placed in fresh extraction sockets generally remains unchanged or slightly decreased, evenafter 6 to 12 months.22,49 Implants placed in anterior
maxilla sites augmented with graft material did notshow a significant increase, even after sufficient healing.43 Against the common understanding, the present
study, which largely included compromised bone conditions, showed a significant ISQ increase, supporting
the application and successful outcome of early loading within 3 months in a large number of cases.
Limited information is available regarding ISQ
changes when their initial values are below 55. It is assumed that implant placement in such high-risk cases
has been avoided because of low primary stability.
According to the limited number of reports, implants
placed in fresh extraction sockets with an initial ISQ
of below 55 do not result in successful osseointegration.22 Implants placed in the grafted anterior maxilla
with an initial ISQ of approximately 50 to 55 showed ahigh failure rate of 35%.43 In the present study, all photofunctionalized implants with an initial ISQ of below
50 exhibited successful osseointegration, implying thepossible expansion of indications for implant therapy.
The failure rate before functional loading was 0%
for the photofunctionalized implants, as opposed to
3.15% for the untreated implants, indicating that noneof the photofunctionalized implants showed destructive changes in peri-implant bone during the initialhealing stage. This may be of great importance in understanding another therapeutic advantage of photofunctionalization. The osteoconductive capability of Ti
is known to correlate negatively with the amount of
surface carbon on Ti surfaces.1,9 Currently available
commercial implants are unavoidably contaminatedwith hydrocarbons to a significant degree.50–56 The
average amount of surface carbon is 35% to 55%, andit varies significantly from less than 20% to more thanThe International Journal of Oral & Maxillofacial Implants 1267

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Funato et al

Table 4   Comparison of ISQ Changes in the Literature Between Implant Types
ISQ
Implant surface

Placement conditions

Initial(at placement)

Secondary§

Healing
period (mo)ISQ
increase
per moTiUnite44 (Anodic oxidized)

Maxilla63.3 ± 6.1

64.3 ± 5.3

3

0.33

TiUnite43

Anterior maxilla
Grafted anterior maxilla

58.5 ± 4.7
61.5 ± 9.0

60.9 ± 4.3
60.2 ± 6.9

6
6

0.4
–0.2

TiUnite45

Grafted anterior maxilla

61.4 ± 5.1

61.0 ± 7.9

6

–0.1

TiUnite46

Maxilla60.1 ± 3.6

62.8 ± 1.6

4

0.68

TiUnite26 *Primarily GBR and extraction
sockets

68.0

63.0

3

–1.67

TiOblast47 (sandblasted)

MaxillaGrafted maxilla
Grafted maxilla

62.3 ± 5.1
56.9 ± 4.7
60.7 ± 6.1

63.9 ± 5.5
58.2 ± 4.7
61.4 ± 5.2

6
6
6

0.27
0.22
0.12

Not specified22

Fresh extraction socket maxilla
Fresh extraction socket mandible

61.1 ± 1.1
65.1 ± 2.6

63.9 ± 5.6
64.0 ± 2.1

5.6
5.6

0.5
–0.2

SLA 25 (sandblasted and acidetched)

Overall
MaxillaMandibleType I boneType II boneType III bone

57.4 ± 6.8
55.0 ± 6.8
59.8 ± 6.7
62.8 ± 7.2
56.9 ± 5.9
56.0 ± 7.8

60.3 ± 6.1
57.9 ± 6.0
63.9 ± 6.0
60.7 ± 3.6
60.1 ± 5.8
60.6 ± 7.2

3
3
3
3
3
3

0.9
0.9
1.3
–0.7
1.1
1.5

SLA38 *

MaxillaMandible

54.0
60.0

57.2
62.7

2.5
2.5

1.3
1.1

SLA33 †

ISQi < 50
ISQi 50–59
ISQi 60–69  ISQi 60–64  ISQi 65–69

NA
NA
NA
NA
NA

NA
NA
NA
NA
NA

3
3
3
3
3

2.8
1.1
0.46
0.63
0.15

SLA40

MaxillaMandible

55.4 ± 3.8
65.5 ± 5.5

57.0 ± 2.8
62.8 ± 5.4

1.5
1.5

1.06
–1.8

SLActive40 (sandblasted andacid-etched; chemically modified)

MaxillaMandible

52.4 ± 7.4
64.2 ± 5.0

53.5 ± 5.3
64.1 ± 3.5

1.5
1.5

0.73
–0.06

SLA and TPS48 ‡Maxilla48.8 ± 3.6

53.1 ± 9.5

> 12

0.36

SPI39 (sandblasted and acid-etched) Type IV bone

68.9 ± 4.3

69.9 ± 4.3

2

0.51

Photofunctionalized surface(most were complex cases)

37.7 ± 2.3
47.6 ± 1.8
56.1 ± 2.7
62.8 ± 1.5

63.0 ± 7.5
73.8 ± 8.6
66.8 ± 8.7
74.0 ± 7.2

AH
AH
AH
AH

4.6
8.7
2.6
2.0

ISQi < 40
ISQi 40–49
ISQi 50–59
ISQi 60–64*Values read from the graph.
†Data provided only for differences in ISQ between placement and 3 m follow-up.
‡ISQ data obtained from different patient groups: initial from unloaded patients and secondary from patients loaded > 12 mo.
§Most data obtained at loading, while some obtained at pre-scheduled follow-up time points.
AH: actual healing time before loading; ISQi: initial ISQ at implant placement; NA: not applicable.

75% among different implants.54,56,57 These indicatethat the atomic percentage of carbon is greater thanthat of titanium in most titanium implants. The C/Ti ratio, which was 109% before photofunctionalization in
the present study, was consistent with the literature.
Because of carbon removal by photofunctionalization,
the implants in the present study may have regained
the highest level of innate osteoconductivity, which
led to minimal interimplant variation in osseointegration capability.

The known mechanisms underlying the biological effects of photofunctionalization include not only
an increased hydrophilicity but also reduced carbon
and optimized electrostatic status.2,3,58 The role of thesurface hydrophilicity of biomaterials in determining
their bioactivity is contentious.59 It is not a universal
principle that the more hydrophilic the surface, themore biocompatible the material. For instance, undera certain condition, a fewer number of cells attachedto hydrophilic titanium surfaces than on hydrophobic

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Funato et altitanium surfaces.60 A polymer surface with improvedhydrophilicity reduces fibroblast proliferation.61 Morehydrophobic polymer scaffold materials are effective in promoting bone regeneration.62 Although theconversion from hydrophobicity to hydrophilicity is aconcomitant phenomenon during UV photofunctionalization, there is not sufficient evidence to support
the cause-result relationship between the degree ofhydrophilicity and osseointegration capability. In fact,
the contact angle of water did not correlate with therate of osteoblast attachment, although there seems
to be a positive effect of higher hydrophilicity on its
cell attractiveness.1,12 Instead, as mentioned above, asubstantially reduced amount of surface carbon after
photofunctionalization may have contributed more to
the present clinical outcome.1
A recent study uncovered the importance of surface
electric charge to determine the degree of osteoconductivity of titanium.8,10 Because biological cells areelectronegatively charged, if titanium surfaces areelectronegative, they repel each other. These studies suggested that the electrostatic property of titanium is important enough to supersede the positiveeffect of hydrophilicity.8,10 Unfortunately, sufficiently
aged titanium surfaces are known to be negatively
charged.2,3,8,10,63–65 Photofunctionalized titanium surfaces are demonstrated to attract more cells becauseof their electropositive conversion.8,10 There are commercially available hydrophilic dental implants, which
are stored in a specific solution.66,67 Recently, the necessity of careful interpretation of the clinical advantage of these surfaces has been pointed out.59 Little
information is available regarding their physicochemical properties, including carbon percentage, electrostatic status, and their time-related changes, whichmake the interpretation of these surfaces difficult.
The definitive difference between photofunctionalized implants and those commercial products is thatphotofunctionalized implants are dry and converted
to chemically clean and genuine titanium surfaces, not
wet or accompanied with ions or molecules prior to
implantation.
The interpretation of the present results should
be limited to the retrospective study design and thefollow-up period of up to 2.5 years. Implant stability
was evaluated only in photofunctionalized implants.
However, the authors believe the reported successful
outcomes based on thorough comparison with the
fully-searched literature warrant further clinical studies, such as a randomized clinical trial, to establish photofunctionalization as an effective measure to advance
implant dentistry in multiple directions. Another advantage of photofunctionalization is that it was proveneffective on all surface topographies of Ti-based materials examined,7,68–70 implying versatile applicability

to a wide range of dental implants. In other words, thetechnology does not provoke a competition among
different implant products, but rather has potential toincrease the inherent biological capability of a given
product. Finally, no surgical complications were observed in relation to photofunctionalization, and surprisingly, the percentage of surgical complications was
lower with the use of photofunctionalization, suggesting the practicality and safety of this technology.

Conclusions
Within the limits of this study, which mainly included
implant placement in complex cases, the use of photofunctionalization resulted in a high success rate of
97.6%, even with a substantially decreased healing
time of 3.2 months before loading as compared with
6.5 months for untreated implants. The ISQ increase
per month for photofunctionalized implants ranged
from 2.0 to 8.7 depending on their initial ISQ values,
and it was considerably higher than that reported in
the literature, which ranged from –1.8 to 2.8. The use ofphotofunctionalization resulted in the more frequent
use of implants in 10 mm or shorter and a decrease inaverage implant diameter. In conclusion, despite more
frequent use of shorter and smaller diameter implants,
the use of photofunctionalization allowed for a fasterloading protocol without compromising the successrate. The outcome was associated with the increased
rate of implant stability development for photofunctionalized implants. The results suggest that photofunctionalization may provide a novel and practicalavenue to further advance implant therapy.

Acknowledgment
The authors reported no conflicts of interest related to this study.

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