Quintessence Journals - EAPGOIAS

CLINICAL APPLICATION

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Spectrophotometric Evaluation of the Influence of Different Backgrounds on the Color of Glass-Infiltrated Ceramic Veneers Dimitrios Charisis, CDT, DDS, MS Clinical Associate, Department of Prosthodontics, School of Dentistry National and Kapodistrian University of Athens, Greece

Spiridon-Oumvertos Koutayas, CDT, DDS, Dr Med Dent Assistant Professor, Department of Prosthodontics, School of Dentistry Albert-Ludwig University, Freiburg, Germany

Photini Kamposiora, DDS, MS, Dr Dent Lecturer, Department of Prosthodontics, School of Dentistry National and Kapodistrian University of Athens, Greece

Asterios Doukoudakis, DDS, MS, Dr Dent FICD Professor and Chairman, Department of Prosthodontics, School of Dentistry National and Kapodistrian University of Athens, Greece

Correspondence to: Dr Dimitrios Charisis 44 Eftihidou Str, Athens 116 34, Greece; fax: 30 210 7567117; e-mail: [email protected].

142 THE EUROPEAN JOURNAL OF ESTHETIC DENTISTRY VOLUME 1 • NUMBER 2 • AUGUST 2006

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Abstract The purpose of this spectrophotometric

trophotometer. Mean color differences (ΔE)

study was to evaluate the influence of dif-

between each study group and the control

ferent color backgrounds on Vita In-Ceram

group were: 3.79 for S2M2; 7.24 for S5M1;

(Vident) glass-infiltrated ceramic veneers.

5.86 for A2M2, and 7.32 for A5M1. Two-way

A total of 50 color background disks were

ANOVA showed statistically significant dif-

fabricated from Vitadur Alpha 2M2 (n = 30)

ferences in ΔE between all groups. Howev-

and 5M1 (n = 20) dentin porcelain (Vi-

er, a t test revealed that the statistically sig-

dent). Ceramic veneer disks were fabricat-

nificant differences only existed between

ed from In-Ceram Spinell (n = 20) or In-

groups S2M2/S5M1, A2M2/A5M1, and

Ceram Alumina (n = 20) glass-infiltrated

S2M2/A2M2. The results suggest that vac-

core veneered using Vitadur Alpha 2M2

uum infiltration with a translucent glass pro-

dentin porcelain. In addition, 10 ceramic

vides the Spinell and Alumina ceramic ve-

veneer disks were fabricated from felds-

neers with increased semi-translucency,

pathic dentin porcelain Vitadur Alpha 2M2.

which makes them highly influenced by

The

were

discolored backgrounds. In-Ceram Spinell

bonded onto the color background speci-

ceramic

veneer

specimens

glass-infiltrated ceramic veneers could be

mens using dual-curing luting composite

considered as an alternative to conven-

cement, creating the following groups

tional feldspathic veneers for the restora-

(each n = 10): S2M2 (Spinell/2M2), S5M1

tion

(Spinell/5M1), A2M2 (Alumina/2M2), A5M1

Spinell and Alumina ceramic veneers

(Alumina/5M1), and control (Vitadur Al-

could enhance the final color establish-

pha/2M2). L*a*b* color coordinates were

ment of discolored teeth, the results would

measured five times for each specimen

not be clinically acceptable.

using a Vita Easyshade (Vident) spec-

(Eur J Esthet Dent 2006;1:142–156.)

of

nondiscolored

teeth.

Although



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Esthetic treatment planning for discolored

fabricating ceramic veneers using these

anterior teeth using ceramic veneers has

materials in a 0.2- to 0.4-mm modified ce-

presented a significant restorative chal-

ramic core (instead of the 0.5 mm suggest-

1–4

Appropriate

ed for all-ceramic crowns) veneered with

bleaching usually offers good short-term

feldspathic porcelain (0.3 to 0.9 mm in

esthetic results for intact natural teeth with

width).24–26 It is assumed that these bilayer

slight or moderate discoloration; however,

veneers will provide adequate masking of

bleaching procedures are not always pre-

discoloration because of the controlled

dictable for severe discolorations.5–7 Ce-

opacity of the core and approximate natural-

ramic veneers are widely used in contem-

looking teeth with an essential depth

porary esthetic dentistry because they are

of translucency resulting from the semi-

lenge for several decades.

3,4,8

have good long-term

transparent behavior of the veneering

prognosis,9–11 and ultimately lead to an im-

material. Nevertheless, little scientific data is

minimally invasive,

12,13

proved esthetic outcome.

available concerning the ability of conven-

The clinical application of ceramic veneers is a very promising approach for the

tional feldspathic or bilayer veneers to successfully restore discolored teeth.

restoration of nondiscolored anterior teeth;

Zhang et al27 illustrated that a 0.2-mm

however, the viability of color matching ve-

densely sintered aluminium oxide core

neers in the discolored dentition mainly

(Procera, Nobel Biocare) has in itself a de-

depends on the severity of the discol-

gree of masking capability, while veneering

oration and the remaining tooth sub-

with feldspathic porcelain (Procera AllCer-

14,15

In these cases, the problem lies

am) in a total thickness of 0.6 mm can neu-

in achieving natural tooth shades using ce-

tralize the color of dark substrates and suc-

ramic veneers. Enamel preservation for

cessfully modify the final shade. In a

successful bonding leaves only 0.5 to 1.0

subsequent study of identical bilayer ve-

mm available (cervical to incisal third) for

neers, Zhang et al28 demonstrated that the

ceramic

the

increase of porcelain chroma produces a

stance.

layering,

thereby

16

limiting

Efforts to achieve pre-

yellow shade and decreases the value of

dictable color management have included

the final color of the restoration. Moreover,

methods such as adding opaque porce-

Okamura et al29 examined feldspathic ve-

lain masses to feldspathic ceramic ve-

neers (Procera AllCeram) with a total thick-

shade possiblities.

17–19

neers,

using porcelain veneering tech-

niques,20,21

or

selecting 22,23

opaque

ness of 0.7 mm and bilayer veneers with

luting

0.25- or 0.4-mm thick densely sintered alu-

However, it has re-

minium oxide core (Procera) and pro-

mained very difficult to fabricate a felds-

posed that the bilayer veneers with the

pathic ceramic veneer that can offer both

0.25-mm core could offer sufficient mask-

optimal masking and a natural appear-

ing for discolored teeth.

composite cements.

ance in the restoration of moderate or

Accurate and reliable color assessment

severe discolorations. Current technology

of both teeth and restorations is crucial for

in dental ceramics includes new high-

effective communication of instructions

toughness ceramics such as glass-infiltrated

to a dental laboratory and ultimately a

aluminium oxide and yttrium-stabilized zirco-

successful

nium dioxide. Many clinicians have begun

measurements performed using visual


clinical

outcome.

However,

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(ie, shade guides) or photographic tech-

Method and materials

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niques are highly subjective. Recently, electronic intraoral devices such as col-

A total of 50 disk-shaped color specimens

orimeters

and

10.0 mm in diameter and 2.0 mm in thick-

ShadeVision, X-Rite) and spectrophotome-

ness were made out of Vitadur Alpha felds-

ters (eg, Color-Eye 7000A, GretagMacbeth

pathic dentin porcelain. For the fabrication,

and Vita Easy-Shade, Vident) were intro-

two different color shades, 2M2 (n = 30)

duced to eliminate the subjectivity of the

and 5M1 (n = 20) were selected in order

human eye. These devices are easy-to-

to imitate the shade of a natural and a dis-

use, high-precision measurement tools

colored tooth, respectively (Fig 1).

(eg,

ShadeEye,

Shofu

that can objectively detect color differences

In addition, 50 disk-shaped ceramic ve-

and metrically deliver consistent results us-

neer specimens with a 10.0-mm diameter

ing the CIE (Commission International de

and a total thickness of 0.7 mm were fab-

l’Eclairage [illumination]) L*a*b* system in

ricated as follows: (1) 10 specimens of

order to improve the communication be-

Vitadur

Alpha

2M2

feldspathic

dentin

tween the dentist and the laboratory re-

porcelain, (2) 20 specimens of a 0.4-mm-

garding color determination.30,31

thick In-Ceram Spinell glass-infiltrated core

Vita Easyshade, the newly developed

veneered using the Vitadur Alpha 2M2

visible-range spectrophotometer used in

dentin porcelain, and (3) 20 specimens of

the present study, captures the full visible

a 0.4-mm-thick In-Ceram Alumina glass-

light spectrum of 400 to 700 nm. Using the

infiltrated core veneered using the Vitadur

color-matching functions of the standard

Alpha 2M2 dentin porcelain.

observer

and

the

spectrum

of

the

For the fabrication of the Spinell and Alu-

illuminant, it converts the measurement of

mina cores, a disk-shaped wax pattern 10.0

the spectral reflectance of the color into a

mm in diameter and 0.5 mm in thickness

tri-stimulus value (XYZ) or an international-

was initially carved with the use of a mod-

ly accepted numerical form (ie, L*a*b*),

eling wax (Bellewax, Belle de St. Claire),

which provides a highly detailed definition

and a silicone (Zetalabor, Zhermack) im-

of the color measured.32

pression was taken. The silicone index was

The purpose of this spectrophotometric

cut to the level of the wax disk, then fixed

study was to determine whether Vita

onto a plate made from class IV dental

In-Ceram (Vident) glass-infiltrated ceram-

stone (Velmix Stone, Kerr). This resulted in

ic veneers could mask discolorations sat-

a 10.0-mm-diameter, 0.5-mm-thick mold

isfactorily. Specifically, the study evaluated

with silicone walls and dental stone base to

the influence of two different color back-

facilitate duplicating procedures. After the

grounds (Vitadur Alpha 2M2 and 5M1, Vi-

application of an insulated gel (Insulation

dent) on the color of bilayer ceramic ve-

Gel, Vita) to the mold, In-Ceram slicker

neers made from a glass-infiltrated core

(Spinell or Alumina) was mixed according

(In-Ceram Spinell or In-Ceram Alumina)

to the manufacturer’s instructions and

veneered with a feldspathic porcelain (Vi-

placed in the mold using the slip-cast tech-

tadur Alpha).

nique. When the In-Ceram slicker had dried, the silicone material was displaced and the disk-shaped core was sintered on



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Fig 1

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Disk-shaped color background specimens made of feldspathic dentin porcelain. (left) 2M2 represents

normal tooth shade; (right) 5M1 represents discolored tooth shade.

the dental stone plate in a special furnace

held at this temperature for 10 minutes and

(Inceramat 3, Vita) at 1,180°C for Spinell and

under vacuum for 21 minutes. The glass-

1,120°C for Alumina (both for 2 hours at the

layered Alumina cores were initially pre-

final

sintering

dried at 600°C for 6 minutes, heated to

process, the final thickness of the cores was

1,120°C for 12 minutes, then held at this

controlled with 3-point measurements using

temperature for 30 minutes and under

a calliper (SDI original, Upplands Väsby),

vacuum for 41 minutes. After the glass-

and where necessary cores were leveled

infiltration firing, specimens were allowed

down using 400-grit glasspaper in order to

to cool to room temperature in the open

achieve a uniform thickness of 0.4 mm.

furnace.

temperature).

After

the

Excess

remaining

glass

was

lanthanum-glass

removed using a heatless rotating stone

powder Vita S11 (Vident) was mixed with

instrument at 10,000 rpm and afterwards by

distilled water, providing a homogeneous

sandblasting with aluminum oxide (50 μm)

mixture of which a thin layer was applied

at 2.5 bar compressed air. Finally, an addi-

to both sintered cores using a small brush.

tional glass control firing was accomplished

Glass infiltration for Spinell sintered cores

(starting at 600°C without pre-drying, heat-

was performed using a glass fiber pad

ing for 5 minutes, holding at 1,000°C for 5

(Fibrous Pad, Vita) and for Alumina cores

minutes) without vacuum, and excess glass

using a platinum firing foil (Pt/Au 95/5, Her-

again was removed by sandblasting (Fig 2).

A

semi-transparent

aeus) in a special furnace (Vacumat 40, Vi-

Veneering of both Spinell and Alumina

ta). The glass-layered Spinell cores were

cores was performed using the Vitadur Al-

initially pre-dried at 600°C for 6 minutes,

pha 2M2 feldspathic dentin porcelain ac-

heated up to 1,100°C for 12 minutes, then

cording to manufacturer’s instructions and


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Fig 2

In-Ceram Spinell (left) and Alumina (right) cores after glass infiltration with S11 glass (Vita) under vacuum.

Fig 3

In-Ceram Spinell (left) and Alumina (right) ceramic veneer specimens after veneering using the Vitadur

Alpha 2M2 feldspathic dentin porcelain.

fired at 950°C to 960°C. No internal or ex-

rpm and the specimens self-glazed at

ternal staining was used. All specimens

920°C without vacuum (Fig 3).

were polished following the same proce-

After bonding the ceramic veneer speci-

dure—rotating diamond burs of differing

mens onto the color background speci-

grits (654, Brasseler) were used at 15,000

mens, the 50 specimens provided were



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Fig 4

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Study specimens from control (far left), S2M2 (top left), S5M1 (top right), A2M2 (bottom left), and A5M1

(bottom right).

divided into five groups of 10 specimens

signed alignment apparatus33 (Fig 5) and

each (Fig 4): S2M2 and S5M1 groups con-

the dual-curing luting composite Panavia F

sisted of In-Ceram Spinell veneer speci-

Light (Kuraray) according to a protocol

mens, bonded onto Vitadur Alpha 2M2 and

published previously,34 resulting in a stan-

5M1 color backgrounds, respectively; A2M2

dardized mean thickness of composite.

and A5M1 groups comprised In-Ceram

The veneered surface of each disk was

Alumina veneer specimens bonded onto

fixed to a plexiglass acrylic tube with the

Vitadur Alpha 2M2 and 5M1 color back-

use of a bonding agent (Optibond, Kerr),

grounds, respectively; and the control group

then attached to the upper part of the

(CG) was Vitadur Alpha 2M2 veneer speci-

bonding apparatus. The dual-curing luting

mens, bonded onto 2M2 color back-

composite was then placed on the nonve-

grounds.

neered surface of each disk-like ceramic

trasonically cleaned in 96% alcohol for 2

veneer specimen and placed under 750g/cm2 pressure onto the appropriate color

minutes, then dried. The bonding proce-

background specimen. Excess composite

dure was performed using a specially de-

cement was removed with sponge pellets,

Prior to bonding, all specimens were ul-


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Fig 5

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The specially designed alignment apparatus used for bonding the ceramic veneer specimens onto the

color background specimens.

and after 20 seconds of light curing an

tion and measurement process, and the

oxygen-blocking gel (Oxyguard II, Kuraray)

other two analyze the light that is internally

was applied for 3 minutes.

scattered by the material. The spectrome-

The spectrophotometric evaluation was

ters

have

separate

receiver

elements

carried out using the Vita Easyshade spec-

spaced at different distances from the light

trophotometer, which uses a continuous

source and effectively measure the color of

light source over the full visible and near in-

a material at different depths.35

frared spectrums and a color temperature

A ceramic block of known color, provid-

of 3,350°K provided by a 20-W halogen

ed by the manufacturer, was used for the

stabilized tungsten lamp. The handpiece of

calibration of the spectrophotometer. When

the spectrophotometer contains an outer

the device was in the calibration mode, the

ring of 19 fiber optics 1 mm in diameter

probe of the device was placed into the cal-

used to illuminate the material (tooth or ce-

ibration holder and then, after a small

ramic) and three separate spectrometers;

amount of pressure was applied to activate

one spectrometer continuously monitors

the calibration switch, a series of spectrom-

the output of the lamp during the calibra-

eter measurements were made with the



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lamp shutter off (“dark” records) or on

found after the spectrophotometric proce-

(“white” records), and all three spectrome-

dure are shown in Fig 6. The evaluation of

ters were normalized. According to the

L* mean values (Table 1) showed that Alu-

manufacturer, the lamp spectrometer is nor-

mina veneers were whiter than convention-

malized to a white (artificial) light standard,

al feldspathic dentin porcelain or Spinell ve-

and the two sample spectrometers are nor-

neers when used in combination with 2M2

malized to the known color of the calibration

backgrounds. Moreover, Spinell veneers

block. This process permits all color vari-

were more grayish than Alumina veneers

ables in the system to be calibrated.35

when used in combination with 5M1 back-

Furthermore, in order to minimize the

grounds. The evaluation of a* mean values

“edge-loss” phenomenon of the diffused

revealed that both Spinell and Alumina ve-

reflectance, every specimen was firmly

neers presented a lack of red in combina-

adapted into a custom-made base, which

tion with 2M2 backgrounds, while they were

was fabricated from a self-curing acrylic

more reddish over 5M1 backgrounds. The

resin (Jet Tooth Shade, Lang Dental). For

evaluation of b* mean values exhibited a

the same reason, according to the manu-

significant lack of yellow in all study groups.

facturer, it is important to have the light re-

All study groups exhibited changes in

ceiver (probe) as close as possible to the

the color relative to the control group. Mean

specimen to collect the maximum amount

color differences were: 3.79 for S2M2; 7.24

of light from the specimen, independent of

for S5M1; 5.86 for A2M2, and 7.32 for A5M1

surface characteristics or angle. Therefore,

(see Table 1). The two-way ANOVA showed

during the spectrophotometric procedure,

statistically significant differences in ΔE val-

the fiber-optic probe of the spectropho-

ues between all groups (P = .011, α = .05)

tometer was tightly placed onto the center

(Table 2). However, the t test for equality of

of the external (polished) surface of each

variances (α = .05) revealed statistically

specimen, and L*a*b* color coordinates

significant differences between the groups

were registered and recorded five times for

S2M2 and S5M1 (P = .000); A2M2 and

36

each specimen.

Mean values of the color differences (ΔE) between the control group and each

A5M1 (P =.034) and S2M2 and A2M2 (P = .005), but not between the groups S5M1 and A5M1 (P = .834).

of the study groups were calculated using the equation ΔE = (ΔL*2 + Δa*2 + Δb*2)1/2 and compared to the reported clinical vis-

Discussion

ible threshold (ΔE ≥ 3.7) found by Johnston and Kao.30 The statistical analysis of the da-

Currently, many patients recognize the val-

ta was carried out by a two-way analysis of

ue of ceramic veneers as a conservative

variance (ANOVA) followed by a t test.

treatment alternative to traditional crowns primarily

because

they

promote

the

preservation of natural tooth structure and

Results

offer a natural-looking appearance.37 The clinical application of ceramic veneers can

Mean values of L*a*b* color coordinates of

embrace an extensive range of esthetic

each study group and the control group

restorative


situations;

however,

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100

Mean values

80 60 40 20 0

L*

a*

b*

S2M2

79.57 (± 0.40)

0.85 (± 0.07)

22.88 (± 0.64)

A2M2

79.26 (± 1.52)

0.64 (± 0.08)

20.17 (± 1.07)

CG

76.77 (± 1.06)

1.45 (± 0.23)

25.21 (± 0.59)

A5M1

75.39 (± 1.64)

1.73 (± 0.18)

18.31 (± 1.01)

S5M1

73.49 (± 0.85)

2.30 (± 0.20)

19.00 (± 0.69)

Fig 6

Individual mean L*a*b* values (± SD) registered by the spectrophotometer for control and

study groups.

Table 1 Groups S2M2 S5M1 A2M2 A5M1

Table 2

Color differences between the control group and each study group Mean ⌬L* 2.80 –3.28 2.49 –1.38

Mean ⌬a* –0.60 0.85 –0.81 0.28

Mean ⌬b* –2.33 –6.21 –5.04 –6.90

Minimum ⌬E 1.43 6.40 3.23 5.92

Maximum ⌬E 4.93 8.32 9.40 9.33

Mean ⌬E (± SD) 3.79 (± 1.06) 7.24 (± 0.62) 5.86 (± 1.74) 7.32 (± 0.99)

Two-way ANOVA of color differences

Source Corrected model Intercept Ceramic veneer Color background Ceramic veneer/ color background*

Type III sum of squares 81.596 1464.974 11.567 60.099 9.930

Error Total Corrected total

49.875 1596.417 131.470

df 3 1 1 1 1 36 40 39

Mean square 27.199 1464.947 11.567 60.099 9.930

F score 19.632 1057.415 8.349 43.380 7.168

P .000 .000 .006 .000 .011

Partial Eta squared 0.621 0.967 0.188 0.546 0.166

1.385

*R2 = 0.621 (adjusted R2 = 0.589).



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encountered

man teeth and represents an average

problems with shade matching, particular-

shade of discoloration. The 2M2 color

ly when attempting to match natural teeth

background was selected because it exists

to ceramic veneer restorations, especially

in 26% of human teeth and represents a

over discolored teeth.38

desirable color for prostheses.42,43

restorative

dentists

have

Conventional veneers made from felds-

Ceramic veneer specimens were fabri-

pathic porcelain provide an essential depth

cated using standardized methods to con-

of translucency that approximates that of

trol the thickness of both the core and ve-

natural teeth, but the final color of the

neering materials. The total thickness of

restoration is highly influenced by the color

each specimen corresponded to that of a

of the underlying prepared tooth.14,15,17 Con-

middle third of an all-ceramic veneer

24–26

and in vitro stud-

restoration. For the glass infiltration of both

ies27,28 have considered the use of bilayer

Alumina and Spinell cores, the study de-

veneer restorations, whose optical proper-

sign included as a standardized parame-

ties are mostly dependent on the thickness

ter the use of a clear glass (S11) under vac-

and consistency of the selected ceramic

uum procedure, which provides a more

core material to mask discolored teeth.39,40

translucent core.21 This particular core does

temporary clinical trials

The fabrication of glass-infiltrated ce-

not affect the color performance of the ve-

ramic veneers was not included in the ap-

neering material (Vitadur Alpha 2M2) and

plications for the In-Ceram system stated

therefore contributes to the masking abili-

by Claus in 1990.41 However, the fabrication

ty of the selected core materials in relation

of an In-Ceram ceramic veneer is viable

to their refraction index. In addition, no in-

with the slight modification of the ceramic

ternal or external staining was used, since

core from the proposed 0.6 to 0.4 mm. The

this procedure alters the color parame-

core potentially could offer enhanced op-

ters.44 Finally, all specimens were subject-

tical properties to a veneer restoration

ed to an identical polishing and glazing

based on the opacity of the material used

procedure to create a microstructure that

(Alumina or Spinell). The optical behavior

contributed to a uniform diffused re-

of such restorations could be further con-

flectance of incident light during the spec-

trolled during glass infiltration (with or with-

trophotometric evaluation.45,46

out vacuum), veneering, and cementation

A semi-translucent light-colored dual-

procedures. The present study examined

curing luting composite (Panavia F Light)

the feasibility of In-Ceram Alumina and

was selected for all study groups in order

Spinell glass-infiltrated ceramic veneers to

to minimize the influence of the color of the

provide an esthetic outcome and clinically

cementation mean and to allow a better

acceptable masking when combined with

evaluation of the optical properties of the

discolored teeth.

ceramic veneer specimens. In addition, it

To simulate teeth with and without

has been demonstrated that the bonding

discoloration, color backgrounds were fab-

procedure followed in this study provides

ricated from two different color shades—

a mean composite cement thickness of 80

feldspathic dentin porcelain 5M1 and 2M2,

μm,34 which is considered to be clinically

respectively. The 5M1 color background

acceptable for the middle third of a fixed

was selected because it exists in 2% of hu-

all-ceramic restoration.47 Therefore, the ce-


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ment thickness did not negatively impact

ferent backgrounds (2M2 or 5M1) signifi-

the standardization of the study.

cantly altered the final color shade of both

Current digital shade-scanning technol-

Spinell and Alumina veneer specimens.

ogy establishes a new standard for quality

The above conclusion was particularly re-

control, enhancing the communication be-

vealed by the t test, which showed statisti-

tween the restorative dentist, the laborato-

cally significant differences between the

ry, and the patient and offers a precise col-

groups S2M2 and S5M1 (P = .000) and

or

research

A2M2 and A5M1 (P = .034). In addition, the

purposes. The spectrophotometer used in

t test showed statistically significant differ-

the current study fulfills these expectations,

ences between the groups S2M2 and

providing a measurement accuracy of

A2M2 (P = .005), which suggests that the

measurement

32

device

for

and color reproduction that is more

use of In-Ceram ceramic veneers with a

reliable than human perception and hence

different glass-infiltrated core (Spinell or

more accurate than visual shade assess-

Alumina) can statistically influence the final

ment.48 When the fiber-optic probe of the

esthetic outcome for nondiscolored teeth.

spectrophotometer is placed on the exter-

The failure of the Alumina veneer speci-

nal surface of the specimen, the main

mens (group A2M2) to reproduce a clini-

problem encountered is a partial loss of

cally acceptable color when bonded over

the reflected light.43 As previously de-

2M2 backgrounds could be a result of the

scribed, the “edge-loss” effect of the dif-

increased opacity of the Alumina core rel-

fused reflectance was reduced by the use

ative to the Spinell core. On the other hand,

of a custom-made acrylic base and the

Spinell veneer specimens in combination

firm adaptation of the fiber-optic probe on

with the color background 2M2 (group

the surface of every specimen.

S2M2) showed a ΔE mean value of 3.79,

92%

The quantitative assessments of color

which is only marginally higher than the

differences (⌬E values) found between the

clinically visible threshold of 3.7; thus the

study groups and the control group can

color performance of these veneers could

only be compared to clinically visible

be considered reasonably accurate. For

thresholds reported by other research-

that reason, Spinell veneers could be con-

30,49–52

ers.

Because of a lack of clear param-

sidered an alternative to the conventional

eters (thresholds) for judging color differ-

feldspathic veneers for the restoration of

ences of materials as clinically acceptable

nondiscolored teeth.

or unacceptable, the ΔE value of 3.7 stat30

The color differences found between the

was adopted to

groups S5M1 and A5M1 were not statisti-

rate the color of the ceramic veneers ex-

cally significant (P = .834), indicating that

amined in the present study as a match in

the clinical application of In-Ceram ve-

the oral environment. All mean ΔE values

neers with a Spinell versus an Alumina

between the groups and the control group

core would not significantly affect the final

were greater than 3.7 units and therefore

shade of discolored teeth. Although the fi-

visually perceivable according the criteria

nal tooth shade was enhanced by both

of the study.

restorations, the esthetic outcome was not

ed by Johnston and Kao

This is of high clinical relevance be-

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clinically acceptable.

cause it indicates that the presence of dif-



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According to the results, both color

porcelain that presents increased chroma

backgrounds induced changes to the col-

(eg, 2M3) in combination with external

or of the glass-infiltrated ceramic veneers

staining and/or internal staining and/or dif-

relative to the control group. The Alumina

ferent color modifiers. Finally, the lack of

and Spinell veneers inherently exhibit a

yellow exhibited in both Spinell and Alumi-

dissimilar semi-translucency due to their

na veneer specimens potentially could be

ceramic cores; however, because of the

managed with the use of a yellowish glass

under-vacuum infiltration procedure, both

(eg, Vita Al1, Vident) instead of the semi-

glass-infiltrated veneers generally present-

transparent glass (Vita S11) used in the

ed an increased semi-translucency. In ad-

current study.

dition, the evaluation of the individual a*b*

In addition, the study revealed that when

and Δa*Δb* mean values (see Fig 6 and

restoring discolored teeth, Alumina ve-

Table 1) clearly indicated that chroma den-

neers might provide a whiter shade than

sity played an equally important role in the

Spinell veneers because of differences in

achievement of sufficient masking.

the opacity of the core materials. In regard

Since semi-translucency and chroma

to the control of the semi-translucency, it

density are the foremost decisive factors in

has been demonstrated that the perform-

the final tooth shade, it is important to re-

ance of the glass infiltration under vacuum

member that the present study examined

leads to the fabrication of ceramic cores

only the influence of the background color

with higher opacity because of a significant

on the shade of In-Ceram Alumina and

increase in density.21Moreover, it has been

Spinell ceramic veneers. Influencing factors

shown that the glass infiltration of In-Ceram

such as the layering technique and the use

Alumina under vacuum using a glass

of stains or color modifiers, a different glass,

originally

glass infiltration without vacuum, and a dif-

Spinell led to a 9.1% decrease in strength

ferent shade of luting resin cement were

of the Alumina ceramic material21; however,

beyond the purposes of the study.

this reduction in strength could be consid-

marketed

for

the

In-Ceram

According to the theory of complemen-

ered noncritical because the restoration

tary colors and the navigation of the Vita-

can still withstand the reported maximal

pan 3D-Master color guide (Vident), minor

incisive forces.54

color corrections can be accomplished us-

Finally, minor adjustments concerning the

ing the appropriate porcelain layering

control of the semi-translucency can be

technique.20,53 For example, the increased

made through the clinical application of lut-

value (brightness) (⌬L* = 2.80) because of

ing composite cement of the appropriate

the lack of red (⌬a* = –0.60) and yellow

shade.55 Especially when bonding veneers

(⌬b* = –2.33) found in group S2M2 (see

with increased translucency, the use of the

Table 1) can be altered by adding a

appropriate shade of luting composite

red/yellow modifier at a ratio of 1:4 to

cement can potentially contribute to an

achieve an intermediate shade with in-

enhanced color outcome. However, opaque

creased chroma (saturation). Increased

composite cements could be excessively

chroma also could be achieved when

reflective and lead to an unpredictable depth

needed with the use of a feldspathic dentin

of translucency in a veneer restoration.38


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Conclusions

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vo rbe ha lte n

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tional feldspathic veneers for the restora-

Within the limits of this in vitro study, the

tion of nondiscolored teeth. Furthermore,

following conclusions can be drawn:

In-Ceram Spinell and Alumina ceramic veneers could enhance the final shade

1. Vacuum infiltration with a translucent

of discolored teeth, although not to the

glass provides In-Ceram Spinell and Alu-

extent that the results would be clinically

mina ceramic veneers with increased

acceptable.

semi-translucency, which makes them highly influenced by discolored backgrounds. 2. Regarding the reported clinical visible thresholds,

In-Ceram

Spinell

glass-

infiltrated ceramic veneers could be considered as an alternative to conven-

Acknowledgments The authors are grateful to Vita Zahnfabrik, Bad Säckingen, Germany, for supplying the study materials. They also appreciate the statistical work performed by Sonia Striggon and the advice provided throughout the study by Prof Dr George Eliades.

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