optical phenomenon of peri-implant soft tissue. part i

Optical phenomenon of peri-implantsoft tissue. Part I. Spectrophotometricassessment of natural tooth gingiva andperi-implant mucosa

Sang E. ParkJohn D. Da SilvaHans-Peter WeberShigemi Ishikawa-Nagai

Authors’ affiliations:Sang E. Park, Shigemi Ishikawa-Nagai,Department of Restorative Dentistry andBiomaterials Sciences, Harvard School of DentalMedicine, Boston, MA, USAJohn D. Da Silva, Department of Oral Health Policyand Epidemiology, Harvard School of DentalMedicine, Boston, MA, USAHans-Peter Weber, Professor and Chairman,Department of Restorative Dentistry andBiomaterials Sciences, Harvard School of DentalMedicine, Boston, MA, USA

Correspondence to:Sang E. ParkDepartment of Restorative Dentistry andBiomaterials SciencesHarvard School of Dental Medicine188 Longwood Avenue BostonMA 02115USATel.: þ1 617 432 2374Fax: þ1 617 432 3881e-mail: [email protected]

Key words: dental implants, esthetics, gingival color, gingival translucency, ITI, marginal

gingiva, peri-implant mucosa, soft tissues

Abstract

Objectives: The purpose of this study was to investigate the difference in optical

appearance of the soft tissues labial to dental implants and to analyze the effects of

titanium implant neck colors transmitted through the marginal mucosa.

Materials and methods: Fourteen patients with 15 Straumanns

single implant

replacements in the maxillary anterior region were recruited. Color measurements of the

peri-implant mucosa of test sites and the gingivae of contralateral or adjacent natural teeth

as controls were made at the facial aspect of the teeth using a spectrophotometer. The color

data (CIELAB color coordinates; Ln, an, bn and Cn) in five incremental areas of 1 � 2 mm from

the gingival margin toward the apical direction were obtained.

Results: A significant difference existed (Po0.01) between the test site and the control site

on the mean Ln and bn values in all five incremental areas (area 1–5). In contrast, there was

no significant difference in the mean an values. Discrepancies between color distributions of

soft tissues were stronger in areas close to the gingival margin and decreased toward the

apical direction. The mean color difference DE between the test site and the control site was

7.7 in area 1 and decreased toward area 5 with a value of 6.5. However, there was no

statistical difference in each of the mean values of differences in optical data, DLn, Dan and

Dbn, when five incremental areas of the control and the test sites were compared.

Conclusion: It was observed that the color of soft tissue around the titanium implant was

significantly different compared with the gingiva of natural teeth. Significantly lower

values of CIELAB color coordinates, Ln and bn were found in the peri-implant soft tissue.

Basic and clinical research in implant den-

tistry in the early years focused mainly on

the integration of endosseous dental im-

plants in hard tissue and the re-establish-

ment of masticatory function for patients

with complete and partial edentulism (Bra-

nemark et al. 1977; Adell et al. 1990; Buser

et al. 1991; Chaytor et al. 1991; Lekholm

et al. 1994; Avivi-Arber & Zarb 1996;

Scheller et al. 1998; Haas et al. 2002).

With the success of osseointegration based

dental rehabilitation in these indications,

the focus consequently shifted to the repla-

cement of missing teeth in the esthetic

region. In the maxillary anterior area, the

esthetic outcome is a critical determinant

in the overall success of implant therapy

and yet remains a challenge.

An important role in achieving an esthe-

tically optimal outcome is the morphology

and appearance of peri-implant soft tissue

associated with the implant and the result-

ing esthetics of the implant-supported

restoration (Reikie 1993, 1995; Garber

Date:Accepted 6 September 2006

To cite this article:Park SE, Da Silva JD, Weber HP, Ishikawa-Nagai N.Optical phenomenon of peri-implant soft tissue. Part I.Spectrophotometric assessment of natural tooth gingivaand peri-implant mucosa.Clin. Oral Impl. Res. 18, 2007; 569– 574doi: 10.1111/j.1600-0501.2007.01391.x

c� 2007 The Authors. Journal compilation c� 2007 Blackwell Munksgaard 569

1996). In natural teeth, a constant vertical

dimension of healthy periodontal soft tis-

sue, the biological width, is an essential

factor in establishing gingival esthetics

(Gargiulo et al. 1961; Vacek et al. 1994).

Studies on the biology of peri-implant soft

tissue indicated that supracrestal soft tis-

sues of approximately 3–4 mm are always

established following placement of an im-

plant and suggested that the position of

the peri-implant soft tissue margin may

be related to the level of bone support

around the implant (Berglundh et al.

1991; Abrahamsson et al. 1996; Berglundh

& Lindhe 1996). The biological width is an

important factor in achieving esthetic re-

sults of peri-implant soft tissue, especially

for the non-submerged, one-piece titanium

implants (Cochran et al. 1997; Hermann

et al. 2000, 2001).

Understanding the existence of the bio-

logical width, the recession of the peri-

implant soft tissue margin may result

from an attempt to establish appropriate

biological dimensions (Bengazi et al. 1996).

It is clear that gingival recession can cause

unacceptable soft tissue esthetics. Various

prosthetic and surgical techniques have

been proposed in an effort to overcome

these occurrences following implant ther-

apy, but the long-term success of these

procedures has been inconclusive. Many

surgical approaches have been used to en-

hance the esthetic appearance and gingival

contour of peri-implant tissues (Israelson &

Plemons 1993; Neale & Chee 1994; Pa-

lacci et al. 1995; Becker & Becker 1996;

Conte et al. 2002). However, questions

still remains regarding the viability and

predictability of surgical approaches

because the thickness of gingiva will

often define how restorations will appear

esthetically at the end of treatment (Kao

& Pasquinelli 2002). Unlike thick gingiva,

thin tissue is highly sensitive to trauma

and inflammation and, thus, more

susceptible to recession. In addition, thin

gingival tissue tends to be delicate and

almost translucent in appearance, contri-

buting to an undesirable shine-through

effect of the underlying titanium implants

with a grayish appearance of the gingival

cuff.

The predictability of an esthetic implant

outcome can be achieved by overcoming

this optical problem at the marginal peri-

implant mucosa of titanium implants. Few

studies exist in terms of color properties of

soft tissue around titanium dental im-

plants. Previous research on colorimetric

solutions to improve the esthetic appear-

ance of peri-implant soft tissue has not

been thoroughly performed and has re-

mained of subjective nature. The specific

aims of this study were to: (1) investigate

the difference in optical properties of the

soft tissues labial to dental implants and

the marginal gingivae of natural teeth, and

(2) analyze the effects of titanium implant

neck colors transmitted through the mar-

ginal mucosa in terms of areas. In this

study, the hypothesis that the peri-implant

soft tissue would exhibit a difference in

color compared with that of natural tooth

was verified, as measured by a color spec-

trophotometer.

Materials and methods

Color measurements of the peri-implant

mucosa of test sites and the gingivae of

contralateral or adjacent natural teeth as

controls were made at the facial aspect

of the teeth on five incremental areas in

1-mm increments (Fig. 1).

Human subjects and implants

Subjects who had already received Strau-

manns

implants (Institut Straumann AG,

Waldenburg/BL, Switzerland) during the

past 5 years for single-implant replace-

ments in the maxillary anterior region

were recruited from the patient pool at

the Harvard School of Dental Medicine.

At the first visit, an initial examination

including the location of the soft tissue

margin, plaque index, bleeding on probing,

probing depth and implant mobility was

performed. The patients who met the study

eligibility criteria were invited to a second

visit for color measurement. Fifteen sites

from 14 patients were included in this

study. This study was approved by the

Institutional Review Board (IRB) at Har-

vard Medical School.

Test siteControl site

54321

54321

Fig. 1. Five incremental areas for the color measure-

ment.Control Unit

USB 2.0

CCD sensor

(RGB)

Camera HeadNote PC

Fig. 2. A spectrophotometer used in this study.

Park et al . Optical phenomenon of peri-implant soft tissue

570 | Clin. Oral Impl. Res. 18, 2007 / 569–574 c� 2007 The Authors. Journal compilation c� 2007 Blackwell Munksgaard

Color measurements

Spectrophotometric measurements were

made using a multi-spectral camera system

(Handy-MSC; Olympus Co., Tokyo, Ja-

pan) as shown in Fig. 2. This spectrophot-

ometer (Handy-MSC) uses a new

technique of multi-band image acquisition

with a built-in light-emitting diode (LED)

lamp in the measuring head as a light

source. The acquired multiband image

data perform estimation of a spectrum

and colorimetric values with original algo-

rithm by exclusive software. Eight LED

lamps (Olympus Co.) are used as a source

of illumination. The area of illuminations

is 20 mm in diameter with a central area of

15 mm in diameter for measurement. Spec-

tra data acquisition requires about 0.2 s.

The spectrophotometer used in this study

has a 451/01 geometry and is accurate to

o0.1 DE for repeated measurements. Be-

fore specimen color measurement, a cali-

bration was performed with a standardized

calibration tile (Olympus Co.). The mea-

suring head was placed on the surface of the

object, and the display confirmed the ob-

ject and the area to be measured.

This machine generates a multi-spectral

image, that is, a digital image of an entire

object that features spectral data for each

pixel, and saves it to a computer (CF-W2;

Panasonic, Tokyo, Japan) to be used for

analysis. The image is expanded on the

computer, where areas of interest for spec-

tral analysis can be selected. Actual mea-

surement is performed for each area chosen

from the display image. Reflectance values

ranged from 380 to 780 nm at 1 nm inter-

vals. CIELAB color coordinates Ln (light-

ness), an (redness), bn (yellowness) and Cn

(chroma) were provided. The total DE

between the colors being compared was

determined by the following equation:

DE¼ (DLn2þDan2þDbn2)1/2 (Ishikawa-

Nagai et al. 2005).

The multi-spectral images of soft tissues

for the implant crown (test site) and the

natural tooth (control) were taken and saved

to the computer. The color data (CIELAB

color coordinates; Ln, an, bn and Cn) in five

incremental areas of 1 � 2 mm from the

gingival margin toward the apical direction

were calculated based on the reflectance

values from the wavelength of 400–

700 nm. Triplet color measurement was

performed, and the average of these mea-

surements was considered to be as the mea-

sured data. Color difference DE values and

its components (DLn, Dan, Dbn and DCn)

were analyzed in each of five incremental

areas. According to the CIELAB units, close

color mismatch was in the range of 2–4 DE

units. A DE of o1 was considered to be

excellent and that of over 3.6 was considered

a clinically distinguishable color difference

(Ruyter et al. 1987; Johnston & Kao 1989;

Ishikawa-Nagai et al. 2005).

Statistical analysis

Statistical analyses were performed using

Statcel computer software (OMS Ltd., Sai-

tama, Japan) and data were expressed as the

mean� 1 SD. Outcome values (DE, DLn,

Dan, Dbn) were plotted and skewness and

kurtosis values were computed to evaluate

the normality of the distributions. Those

distributions with confirmed normality

were analyzed using parametric methods

(one-way ANOVA). Scheffe’s test was

chosen a priori as a test for multiple

comparisons.

Results

The color of the test site (peri-implant

mucosa) demonstrated lower mean values

of Ln, an, bn and Cn than the control site

(gingiva of adjacent or contralateral natural

tooth) in all five areas (Table 1 and Fig. 3).

There was a significant difference

(Po0.01) between the test site and control

site in the mean Ln and bn values in all five

incremental areas, and in the mean Cn

values in all areas except for area 5. In

contrast, there was no significant differ-

ence in the mean an values. Both the Ln–

Cn map and the an–bn map showed discre-

pancies between color distributions of soft

tissues measured in the test and control

sites (Fig. 4). Lower Ln–Cn and an–bn va-

lues for the test site were observed com-

pared with those of the control site. The

color coordinates showed lower values

of Ln, an, bn and Cn for the peri-implant

mucosa compared with those of the control

site, indicating darkness, less redness, less

yellowness and less chroma, respectively.

The discrepancies were stronger in areas

close to the gingival margin and decreased

toward the apical direction.

The mean color difference DE between

the test and control site was 7.7 in area 1

and decreased toward area 5, which was 6.5

(Fig. 5). In addition, the mean DE value in

area 5 was45, which is a much greater

value than the clinical perceptual threshold

of 3.6. A trend toward decrease in color

coordinates DLn, Dan and Dbn between the

test site and control site was observed

toward the apical aspect (Fig. 6). Area 1

(gingival) showed the greatest mean values

of DLn, Dan and Dbn and these values

decreased toward area 5 (apical). However,

Table 1. Optical data of five incremental areas for the control (C) and test (T) sites

Area 1 2 3 4 5

Site C T C T C T C T C T

Ln

Mean 56.2 49.9 55.7 50.8 54.4 49.8 53.9 49.1 53.8 48.9SD 6.7 4.9 6.7 4.2 6.3 3.2 6.7 3.6 6.8 3.8

an

Mean 17 15.7 18.6 16.3 20.1 17.8 20.5 18.8 20.5 19.4SD 3.2 4.3 3.8 3.3 3.9 3.2 3.8 3.4 3.5 3.4

bn

Mean 17.2 12.7 14.7 11.2 15 11.7 15.3 12.3 15.3 12.6SD 3 4.2 3.1 2.8 3.1 2.4 3 2.6 2.9 2.8

Cn

Mean 24.1 20.4 23.6 19.8 25 21.4 25.5 22.5 25.4 23.2SD 3.6 5.2 4.2 3.9 4.4 3.6 4.2 3.9 3.9 4

C, control site; T, test site.


c� 2007 The Authors. Journal compilation c� 2007 Blackwell Munksgaard 571 | Clin. Oral Impl. Res. 18, 2007 / 569–574

there was no statistical difference at

Po0.05 on each of the mean values of

differences in optical data, DLn, Dan and

Dbn, when five incremental areas of the

control and the test sites were compared.

Discussion

The results of the present study revealed a

significant difference between the color of

soft tissue in natural tooth (control site)

and around the implant (test site). It was

reported that color differences between the

soft tissues of contralateral natural teeth

were within 2.7 (Ishikawa 1988). There-

fore, the color difference obtained in this

study between a test site and the corre-

sponding control site was much larger than

the color difference that can be observed

in soft tissues surrounding the natural

dentition.

The color differences between the soft

tissue of natural teeth and the soft tissue

around the titanium implant revealed a

greater amount of discrepancy in color

closer to the gingival margin (area 1),

which subsequently decreased toward the

apical direction (area 5). This finding

further supports the effect of optical phe-

nomenon of peri-implant soft tissue com-

pared with that of natural teeth. The overall

restorative esthetic outcome is frequently

dependent upon the quality and color of soft

tissue at or near the gingival margin (Garber

1996; Chang et al. 1999). It is in this region

that significant esthetic impairment can

occur, especially in patients with a high

smile line (Chang et al. 1999).

Changes in the position of the soft tissue

margin, especially at the facial aspect, can be

detrimental from an esthetic perspective

possibly leading to exposure of the titanium

implant below the crown margin (Furhauser

et al. 2005). The relationship between soft

tissue thickness and changes in the level of

the soft tissue margin in terms of recession

has been investigated in previous research,

and it was suggested that the thickness of

the peri-implant mucosa appears to be an

important factor for the height of the soft

tissue (Warrer et al. 1995; Wennstrom 1996).

Soft tissue thickness can also influence

the shine-through effect of the underlying

titanium implant, consequently compro-

mising the overall esthetics of the peri-

implant soft tissue (Ochsenbein & Ross

1969; Moberg et al. 1999). In these

instances, if conventional titanium

abutments are selected and an implant is

not submerged, there exists a risk of a me-

tallic gray tint becoming visible through thin

soft tissue. This darker coloring effect could

produce an unfavorable overall esthetic result,

C: Control site, T: Test site

C CT

T

T

TC C

Fig. 3. A shine-through effect of the underlying titanium implant.

C*

80

70

60

50

40

30

0 10 20 30 40

L*

0 0

5

10

15

20

25

0 10 20 30 40a*

b*

: Test site: Control site

: Test site: Control site

a b

Fig. 4. An Ln–Cn color map and a an–bn color map of test and control sites.

Area

∆E

0

2

4

6

8

10

12

1 2 3 4 5

Mean±D(n=15)

Fig. 5. Color difference DE between the test site and

control site.



especially in the esthetically sensitive max-

illary anterior region. In the current study,

the larger difference in color at the gingival

margin area indicates the possibility of the

shine-through effect of the implant neck of

one-piece non-submerged titanium implants.

For two-piece non-submerged or two-piece

submerged implants, the dark coloring effect

of conventional transmucosal metal abut-

ment could have a detrimental impact on

the esthetic appearance of patients with a

fragile gingival tissue (Moberg et al. 1999).

Ceramic abutments or gold color abutments

have been developed to help resolve this soft

tissue problem. Andersson et al. (2001) de-

monstrated the advantages of using ceramic

implant abutments for single-tooth replace-

ment in esthetically sensitive areas.

It is critical to understand how the gin-

gival tissue would respond to restorative

margins and gingival inflammation to en-

sure predicable peri-implant esthetics.

Moreover, subsequent recession of the soft

tissue margin following crown placement

has been reported in previous studies (Adell

et al. 1986; Apse et al. 1991; Jemt et al.

1994; Bengazi et al. 1996). In addition to the

position and quality of the labial margin of

the peri-implant mucosa, the optical effect

of soft tissue may be a contributing factor to

the final esthetic outcome. There has been

some research examining the optical phe-

nomenon affecting the colors of soft tissues

surrounding natural teeth (Ishikawa 1988;

Ishikawa et al. 1988); however, no current

literature describes the effect of optical phe-

nomenon and color analysis of the peri-

implant mucosa.

The use of a spectrophotometer in the

present study provided an objective and

predicable method to obtain reliable color

measurements. The color measurement of

the soft tissue is extremely sensitive to the

effects of pressure, especially for a measure-

ment of a small area such as marginal

gingiva. Therefore, measurements must

be acquired without soft tissue contact.

The color measurement instrument used

in this study can capture the relatively large

area of 15 mm diameter without any con-

tact on the surface of the measured object.

As an actual measurement is performed for

each area chosen from the display image,

any small area can be measured. This

feature conferred accuracy and consistency

to this study in color measurement.

In the current study, it was observed that

the soft tissue color around titanium im-

plant was significantly different compared

with that of natural teeth as measured by a

spectrophotometer. This seems to indicate

that the surface characteristics of the im-

plant and abutment may influence the

color effect. Further investigation measur-

ing the thickness of peri-implant mucosa

and its relationship with color analysis is

underway. Approaches to change the opti-

cal appearance at the marginal peri-implant

mucosa are of great interest and may offer

an important option to achieve the desired

soft tissue esthetics.

Acknowledgement: This research

was supported by the ITI Foundation

research grant, Project #298/2003.

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