j o u r n a l o f d e n t i s t r y 4 0 ( 2 0 1 2 ) 6 7 0 6 7 7

Available online at www.sciencedirect.com

elsInternal adaptation, marginal accuracy and microleakage of apressable versus a machinable ceramic laminate veneers

Moustafa Nabil Aboushelib a, Waleed AbdelMeguid Elmahy b, Mohammed Hamed Ghazy c,*aDental Biomaterials Department, Faculty of Dentistry, Alexandria University, EgyptbRestorative Department, Faculty of Dentistry, Alexandria University, EgyptcConservative Dentistry Department, Faculty of Dentistry, Mansoura University, Egypt

1. Introduction

Ceramic laminate veneers are considered as conservative

solution for patients requiring improvement of the shape,

colour, or position of their anterior teeth.1,2 These thin and

brittle restorations are bonded using adhesive resin cements

which establishes a chemical bond between the ceramic and

the tooth structure using standard hydrofluoric acid etching

and silane application. Once properly cemented, ceramic

veneers become an integral part of the tooth structure and

share part of applied loading stresses during masticatory

a r t i c l e i n f o

Article history:

Received 6 December 2011

Received in revised form

19 April 2012

Accepted 20 April 2012

Keywords:

Laminate veneers

Margin

Gap

Leakage

Film thickness

a b s t r a c t

Objectives: The aim of this study was to evaluate the internal adaptation and marginal

properties of ceramic laminate veneers fabricated using pressable and machinable CAD/

CAM techniques.

Materials and methods: 40 ceramic laminate veneers were fabricated by either milling

ceramic blocks using a CAD/CAM system (group 1 n = 20) or press-on veneering using lost

wax technique (group 2 n = 20). The veneers were acid etched using hydrofluoric acid,

silanated, and cemented on their corresponding prepared teeth. All specimens were stored

under water (37 8C) for 60 days, then received thermocycling (15,000 cycles between 5 and

55 8C and dwell time of 90 s) followed by cyclic loading (100,000 cycles between 50 and 100 N)

before immersion in basic fuchsine dye for 24 h. Half of the specimens in each group were

sectioned in labio-lingual direction and the rest were horizontally sectioned using precision

cutting machine (n = 10). Dye penetration, internal cement film thickness, and vertical and

horizontal marginal gaps at the incisal and cervical regions were measured (a = 0.05).

Results: Pressable ceramic veneers demonstrated significantly lower (F = 8.916, P < 0.005)

vertical and horizontal marginal gaps at the cervical and incisal margins and lower cement

film thickness (F = 50.921, P < 0.001) compared to machinable ceramic veneers. The inferior

marginal properties of machinable ceramic veneers were associated with significantly

higher microleakage values.

Conclusions: Pressable ceramic laminate veneers produced higher marginal adaptation,

homogenous and thinner cement film thickness, and improved resistance to microleakage

compared to machinable ceramic veneers.

Clinical significance: The manufacturing process influences internal and marginal fit of

ceramic veneers. Therefore, dentist and laboratory technicians should choose a

manufacturing process with careful consideration.

# 2012 Elsevier Ltd. All rights reserved.

* Corresponding author. Tel.: +20 2 0105025275.E-mail address: mghazy@mans.edu.eg (M.H. Ghazy).

0300-5712/$ see front matter # 2012 Elsevier Ltd. All rights reserved.http://dx.doi.org/10.1016/j.jdent.2012.04.019journal homepage: www.intl. evierhealth.com/journals/jden

structural defects. Nowadays, computer assisted design and

computer assisted milling technology (CAD/CAM) requires

nothing more than few keyboard clicks in order to design and

fabricate accurate restorations. Nevertheless, the shade and

colour of machinable ceramic produced ceramic veneers are

limited by the colour of the selected block used to mill these

restorations.2325

Up to the authors knowledges, there are no investigations

in the literature evaluating the influence of the fabrication

technique on the internal adaptation marginal accuracy and

microleakage of ceramic laminate veneers, Therefore, it was

the objective of this laboratory study to investigate these

parameters using pressable and machinable ceramics. The

null hypothesis to be tested was that neither the pressable nor

the machinable ceramic veneer fabrication technique would

have an effect on the internal adaptation, marginal accuracy

and microleakage of ceramic veneers.

2. Materials and methods

j o u r n a l o f d e n t i s t r y 4 0 ( 2 0 1 2 ) 6 7 0 6 7 7 671cycle. The adhesive resin cement is subjected to dynamic

loading, thermal cycling, and is influenced by the hydrolytic

effect of water and different chemicals present in the

mouth.3,4

External marginal adaptation of ceramic veneers, which is

defined as the vertical distance between the finish line of the

prepared tooth and the margins of the fabricated veneers5

plays an important role for their success. Close proximity

between the margin of the restorations and the tooth structure

protects the adhesive resin cement from excessive exposure to

the oral cavity leading eventually to slow process of gradual

disintegration of its chemical, physical, and mechanical

properties resulting in microleakage, recurrent decay, dis-

colouration of the tooth structure, and fracture of the

cemented veneers. On the other hand, internal marginal

adaptation is a direct measure of the cement film thickness

underneath the restoration and is significantly influenced by

the accuracy of fabrication process used.6,7

While external marginal adaptation could be measured

using different imaging methods as stereo or scanning

electron microscopy, internal marginal adaptation requires

sectioning of these restorations in order to assess the cement

film thickness underneath the cemented restorations.8,9

Holmes measured various points between the casting and

the tooth and clarified the terminology for misfit and defined

the internal gap as the perpendicular measurement from the

axial wall to the internal surface of the restoration.10 Non

destructive techniques which rely on measuring the thickness

of low viscosity impression silicon material used in place of

the resin cement were also used in previous investigations.11

13 Ucar et al. concluded that weighing the light body addition

silicon is a convenient method for 3 dimensional evaluation

the 3 dimensional internal fit of dental crowns.14 These

parameters play a significant role which directly influences

the clinical performance of ceramic veneers. From one hand,

these thin shells have supra-gingivally placed margins directly

exposed to the oral cavity and on the other hand the thickness

of resin cement is a parameter that significantly influences the

shade and colour of these restorations.1518

Traditionally, ceramic veneers are fabricated using layer-

ing technique which incorporates refractory dies used to

support the condensed layers of the ceramic slurry.19 This

technique gives the ceramist full control over the layers

incorporated resulting in a naturally looking restoration. On

the contrary, it requires investing time and effort in order to

produce accurately fitting restorations. Duplicating the work-

ing model with brittle refractory material is a sensitive process

and removal of the refractory material after firing the veneers

are sensitive procedures.20 A new generation of ceramic

materials were introduced to the dental field using pressing

technology.21,22 Pressable ceramics are fabricated by burning

out wax patterns using the conventional lost wax technique

and melting and pressing ceramic ingots under controlled

pressure, temperature, and vacuum using computer pro-

grammed press ovens. These ovens are equipped with a

pneumatic press that activates an alumina plunger used to

compress molten ceramic ingots. Press-on ceramics allow

accurate reproduction of the anatomical features carved in thewax pattern and controlled processing of the ceramic material

resulting in an accurate restoration with minimal internalA silicon index was made for a defect free maxillary right

central incisor in a student typodent (Frasaco, Tettnang,

Germany) with interchangeable hard resin teeth. Incisal lap

preparation for ceramic laminate veneers was made with

1.5 mm incisal edge reduction; 0.7 mm labial reduction

extended to proximal contact regions, and a chamfer finish

line placed 1.5 mm lingual to the incisal edge on the palatal

wall. Depth orientation grooves were cut followed by tapered

diamond point and finishing stones.2628 The sectioned

silicon index (Virtual Putty fastset, Ivoclar Vivadent, Schaan,

Liechtenstein) was used to ensure even tooth reduction, Fig. 1.

The tooth was polished with a nylon bristle brush and

polishing paste at 5000 rpm in a slow speed handpiece. A

heavy and light body impression (Virtual Putty fastset, Ivoclar

Vivadent) was taken for the full arch including the prepara-

tion and then poured in extra hard stone to produce the

working cast and die.

Fig. 1 Digital image demonstrating cut section of the

silicon index used to verify preparation dimensions andused as a reference using preparation and waxing

procedure.

j o u r n a l o f d e n t i s t r y 4 0 ( 2 0 1 2 ) 6 7 0 6 7 76722.1. Pressing fabrication technique

20 ceramic laminate veneers were fabricated using the

pressing technique (IPS e.max press A3; Ivoclar Vivadent). A

single layer of die spacer material (20 mm) was applied on

gypsum dies of the prepared tooth and allowed to dry. A wax

pattern was manually built on each gypsum die to restore the

anatomical features of the unprepared tooth using the

sectioned silicon index as a reference, Fig. 1. Five wax patterns

were attached to the pressing ring using a 3 mm round wax

sprue and a freshly vacuum mixed investment material was

cast on a vibrating table. Following chemical setting of the

investment, 45 min, the ring was transferred to a preheated

burn out oven (800 8C) after removal of the plastic base. After

2 h, preheated ceramic ingots were placed inside the ring and

transferred to the pressing oven (P500; Ivoclar Vivadent) which

was automatically programmed to complete the pressing

cycle. Pressable ceramic laminate veneers were devested by

gentle airborne particle abrasion using 50 mm glass particles

and cutting and finishing the location of the sprue.

2.2. Machining fabrication technique

Multichromatic blocks (Multishade A3; Ivoclar Vivadent) were

used to mill 20 veneers (CEREC 3D1 3.0, CEREC Mc XL, Sirona

dental system, Charrlotte, USA). A powder imaging spray was

thoroughly applied on the surface of the gypsum die of the

prepared tooth in order to form a reflection medium that is

necessary for the optical impression. 3D camera (Charge-

Coupled Device) was positioned over the powdered die and the

3D image was captured for each specimen in labial, palatal and

incisal directions. The acquired optical image was transferred

into the CAD software and the preparation finish line was

marked on the digital model. After selection of the required

anatomy, the contours were adjusted by labelling the

curvature lines.

2.3. Cementation procedure

Each ceramic laminate veneer was etched using 9.6% hydro-

fluoric acid gel for 30 s (Porcelain Etch Gel, Pulpdent Corp.,

Watertown, MA, USA), washed, dried, and finally coated with a

silane primer (Variolink S bond primer; Ivoclar Vivadent)

which was left to completely dry for 3 min. A freshly mixed

resin cement (Variolink A3) was applied on the fitting surface

of each laminate veneer which was then seated on the

prepared tooth using fixed pressure of 250 g for one min.

Excess cement was wiped off and the resin cement was light

polymerized for 60 s first from the lingual surface then from

the Labial surface.29

2.4. Artificial ageing programme

The cemented laminate veneers were stored under water for

60 days then received thermo-cycling (15,000 cycles between 5

and 55 8C with 90 s immersion time at each temperature) using

water as transfer medium followed by cyclic loading (100,000

cycles between 50 and 100 N at 4 Hz). Up on completion ofartificial ageing, the entire external surface of the restorations

and the supporting tooth was coated with two layers of nailvarnish without covering the margins before immersion in

penetration dye (15% basic fuchsine dye) for 24 h.

2.5. Sectioning technique

The root portion of each restoration was sectioned 2 mm below

the cervical line and the coronal section was imbedded in

transparent chemically polymerized acrylic resin. For each

fabrication technique, half of the specimens were vertically

sectioned in a labio-lingual direction (n = 10) and the other half

was sectioned in a horizontal direction using a diamond coated

disc and a precision cutting machine (Mikracut 120, Metkon,

Germany). At least two intact mid sections (0.5 mm thick) were

obtained from each specimen. Each section was polished on a

rotating metallographic polishing device (M3000, Buehler, Ltd.,

Evanston, IL, USA) using ascending grit tungsten carbide coated

paper. The polished sections were ultrasonically cleaned in

distilled water for 60 s to remove surface contaminants.

2.6. Internal adaptation, marginal accuracy andmicroleakage

The cut sections were examined under stereo microscope (SZ

11, Olympus, Japan) under different magnifications and using

scanning electron microscope (XL 30; Philips, Eindhoven, the

Netherlands). On vertical sections, marginal accuracy was

measured as the maximum distance between the finish line of

the underlying prepared tooth and the margin of the ceramic

laminate veneer on both the cervical and the incisal margins.

Internal adaptation (also defined as cement film thickness) was

measured as the maximum distance (perpendicular line to the

prepared surface) between the inner surface of the labial wall of

veneer and the outer surface of the prepared tooth at five fixed

locations. Measurements were also made on the horizontal

sections. Microleakage was defined as the distance the dye was

able to penetrate at both the cervical and the incisal margins.

One way analysis of variance was used to analyse the data

and based on the sample size (n = 10), chosen level of

significance (a = 0.05), and medium effect size difference

(F = 0.25) the chosen statistical test had adequate power to

detect significant differences which could be used to interpret

clinical recommendations.

3. Results

Because of limitations related to sample size used in this study

(n = 10), Levenes test of homogeneity of variables was used (8.8)

which indicated homogenous distribution of data confirming

also acceptable standard error of Skewness of data (0.37). Also

Data was analysed with ShapiroWilk test to confirm the

assumption of normal distribution of the data (0.165), therefore,

parametric statistics were used to evaluate the data.

Statistical analysis revealed that machinable ceramic

veneers, Fig. 2, were associated with significantly higher

marginal gap values compared to pressable ceramic veneers,

Fig. 3. Significantly higher horizontal (F = 8.916, P < 0.005) and

vertical (F = 43.393, P < 0.001) gaps were observed with machin-able ceramic veneers compared to the pressable veneers.

Moreover, machinable ceramic veneers were associated with

j o u r n a l o f d e n t i s t r y 4 0 ( 2 0 1 2 ) 6 7 0 6 7 7 673significantly higher (F = 50.921, P < 0.001) cement film thickness

which was irregular compared to pressable veneers. Cement

film thickness values were almost identical when measured in

either vertical or horizontal sections made for the same

specimen.

Higher marginal gaps resulted in significantly higher

microleakage at incisal (F = 37.708, P < 0.001) and cervical

(F = 18.245, P < 0.001) margins observed for machinable ce-

ramic veneers, Fig. 2. Few specimens belonging to both groups

demonstrated micro-cracks after completion of cyclic loading

programme. Previous data are summarized in Table 1.

4. Discussion

The results of the present investigation justify rejection of the

null hypothesis as there was significant influence of the

Fig. 2 (A) Horizontal cut section of machinable veneer demons

associated microleakage. (B) Vertical cut section of machinable

microleakage. Distance between two red lines represent vertica

demonstrating uneven cement film thickness, marginal gap, an

surface of the veneer. Red line represent internal cement film tfabrication technique on the internal adaptation, marginal

accuracy, and microleakage of the tested ceramic veneers. For

many decades, fabrication of refractory die material was used

for the production of porcelain laminate veneers where the

porcelain slurry was directly built on the heat resistant

material. After firing, the refractory material was removed

using airborne particle abrasion incorporating glass beads

which may also compromise marginal accuracy of the

veneers.30 This technique required extensive laboratory work

in order to duplicate the working die with a refractory one and

during building the porcelain slurry. The marginal quality of

laminate veneers fabricated using refractory technique

depends on the accuracy and skill of the dental ceramist.

In the pressable ceramic technique, wax patterns are

directly built on the prepared working model giving the dentist

more control during shaping, carving, and sealing the

margins. During pressing, the molten porcelain ingot is

trating uneven cement film thickness, marginal gap, and

veneer demonstrating cervical marginal fit and associated

l misfit. (C) Vertical cut section of machinable veneer

d associated microleakage. Notice angle lines on the fitting

hickness at incisal edge.

j o u r n a l o f d e n t i s t r y 4 0 ( 2 0 1 2 ) 6 7 0 6 7 7674pressed under controlled pressure, temperature, and vacuum

insuring accurate reproduction of fine details especially at the

margins. On the other hand, software limitations in designing

restorations, and hardware limitations of the camera, scan-

ning equipment, and milling machines could produce errors in

the CAD/CAM technique especially during manual tracing and

fine milling of the finish line which justifies the findings of this

study.31 An additional problem with computer-milled ceramic

restorations is that the cutting tool may be larger in diameter

than some parts of the tooth preparation, such as the inner

surface of the incisal edge causing misfits, Fig. 2C, resulting in

a inferior marginal properties.32

Marginal fit, accuracy or adaptation is synonymous for a

key criterion used in the evaluation of fixed restorations and

could be defined as a parameter that measures the proximity

between the margin of the restoration and the finish line on

the prepared tooth in two directions.33,34 In this study, all

Fig. 3 (A) Horizontal section of pressable veneer ceramic demo

the finish line. Distance between blue and red lines represent v

pressable veneer demonstrating marginal fit at the cervical reg

demonstrating marginal fit at the incisal region. Observe roundspecimens were fabricated on working dies directly repro-

duced from a single master tooth which eliminated any

possible differences between the specimens. In cut sections, it

was possible to precisely measure marginal accuracy in both

horizontal and vertical dimensions. In vertical sections, higher

marginal adaptation at the incisal and cervical regions were

observed for press-on veneers. Similar finding were observed

at the mesial and distal margins in horizontal sections. These

results are directly related to the fabrication technique of

choice like previously reported by Tinschert in 200435 and

Reich et al.32 Nevertheless, marginal adaptation and cement

film thickness values reported in this study were higher

than those observed for conventional porcelain veneers

(50195 mm).36Potincy and Klim,37 presented an overview of

the CEREC Acquisition Center with Bluecam system (Sirona

Dental Systems, Charlotte, NC) and available materials. The

results showed that on the basis of the growth of CAD/CAM,

nstrating even cement film thickness and marginal gap at

ertical and horizontal marginal gap. (B) Vertical section of

ion. (C) Vertical cut section of pressable veneer

ation of the veneer in this region.

ole

e at

j o u r n a l o f d e n t i s t r y 4 0 ( 2 0 1 2 ) 6 7 0 6 7 7 675the manufacturer has made substantial improvements to all

aspects of the CEREC AC system-including hardware, software

and materials-during the past 25 years. They concluded that

the dentists can create laboratory-grade restorations in their

offices with little disturbance to work-flow patterns. This is

possible, because of innovations to the system that make CAD/

CAM feasible for most dental practices.

In a step towards improving production accuracy of

machinable ceramics, blue light was incorporated in the

scanning device of the CEREC system which has improved

scanning potentials especially in highly curved areas claiming

an accuracy to capture 19 mm details without the need to

powder the teeth. The newly released version of the designing

software (3D 4.0) has improved features related to automatic

detection of the margins of the restorations which is also a

step towards preparing an accurate digital model. Compared

to earlier versions, these new improvements are expected to

improve final fit of the milled restorations as manufacturer

claim a scanning and cutting accuracy of (19 mm). However,

limited access at incisal edge or internal channels of implant

abutment may restrict full access of the milling tool in these

regions.38 Additionally, the type and curvature of finish line

are parameters that directly influences vertical misfit at finish

line region.39

An interesting observation for both pressable and machin-

able ceramic veneers was that the value of vertical misfit was

much higher than horizontal misfit, almost double the value,

indicating that it was more difficult to seat the veneers in

Table 1 Internal adaptation, marginal accuracy, and micr

Variable Fabrication technique

Cement film thicknessa Pressable

Machinable

Horizontal misfit Pressable

Machinable

Vertical misfit Pressable

Machinable

Incisal microleakage Pressable

Machinable

Cervical microleakage Pressable

Machinable

SD: standard deviation; F: frequency; P: significant at P > 0.5.a Cement film thickness was presented as the average value measurvertical direction. This observation could be related to the

labially applied pressure which neglected adequate vertical

seating or due to premature contact at the incisal edge of the

restoration which was commonly observed for machinable

ceramic laminate veneers, Fig. 2C. Milling of the fine details

present on the inner surface of the incisal edge presents a

challenge for CAD/CAM technique due to the limited access of

the milling tool in this narrow region.

Cement film thickness is measure of the internal fit or

adaptation of the restoration. Not only lower cement film

thickness was observed for pressable ceramic veneers in this

study but an even thickness as well, Fig. 3, which indicated

better seating compared to irregular and thicker cement film

thickness observed for machinable ceramic veneers. These

findings were in agreement with May et al.40who stated that the

cement space should be uniform to facilitate seating without

compromising retention or resistance forms. Application oftwo coats of die spacer material could facilitate easier seating of

the veneers, maintain even cement film thickness, and reduce

polymerization stresses.41 In a previous study, it was observed

that polymerization stresses resulted in strengthening the

bonded veneers due to generation of compressive forces on the

external surface, however, thermo-cycling could eliminate

such strengthening effect.42

According to CAD/CAM milling technology, restorations

with adequate marginal adaptation may not necessarily

demonstrate adequate internal adaptation.43 Reich et al.32

also reported that systems which depend on optical impres-

sion experience problems with rounded edges due to the

scanning resolution and positive error, which simulates peaks

at the edges. A thick cement film beneath the bonded veneer

could interfere with the mechanical integrity of the restora-

tion, increase polymerization pre-stresses, or influence final

shade and translucency of the restoration. Several incidences

of bulk cracks could be related to lack of rigid support under

the bonded veneers or extension of surface flaws under the

influence of thermo-cycling and dynamic fatigue.44 Under

clinical conditions, it is recommended to maintain prepara-

tion finish line in enamel in order to reduce chances of fracture

under functional loads.45

The artificial ageing programme used in this study

accelerated mechanical fatigue plus thermal and chemical

degradation of the restoration and resin cement.46,47 Increased

dye penetration was associated with inferior marginal

accuracy and thicker cement film thickness of the machinable

akage of tested veneers.

Mean (mm) SD (mm) F P

106.7380 29.5838 50.921 0.001

340.3569 143.3908

105.5820 63.2381 8.916 0.005

230.9664 176.8251

242.4017 36.9710 43.393 0.001

545.8161 195.8031

308.4561 95.3308 37.708 0.001

831.7576 368.9927

233.5116 66.5306 18.245 0.001

509.9443 281.6729

five fixed locations.ceramic veneers. While several studies questioned the

correlation between marginal adaptation and microleak-

age,48,49 the high horizontal and vertical misfits exposed more

area of the resin cement to hydrolytic effect of water under the

influence of thermo-cycling and this is might be the plausible

cause of cement degradation and increased microleakage. For

an aesthetic restoration as laminate veneers, microleakage is

considered as a direct failure requiring remake of the

restoration.33 Location of the margin,50,51 polymerization

method and type of adhesive resin,52 and type of finish line

and preparation design53 are factors that must be considered

in order to reduce microleakage under porcelain veneers.

In the present investigation, the maxillary central incisor

was selected to represent the most commonly indicated tooth

requiring a laminate veneer.21 Two fabricating techniques;

pressable and machinable ceramic, were compared as

regards to their internal adaptation, marginal accuracy,

j o u r n a l o f d e n t i s t r y 4 0 ( 2 0 1 2 ) 6 7 0 6 7 7676and microleakage properties. All veneers were first seated

on their corresponding prepared die using finger pressure to

achieve proper seating followed by a constant load to insure

accurate measurements of cement film thickness, A point of

concern was whether similar microleakage pattern could be

achieved if natural teeth were used in place of the resin dies.

Nevertheless, it is the restoration resin cement interface

that was of interest for this study as exploring the resin

cementtooth interface was beyond the scope of this

investigation.

5. Conclusion

Under the conditions of this investigation the following

conclusion could be drown: pressable ceramic laminate

veneers produced higher marginal adaptation, homogenous

and thinner cement film thickness, and improved resistance

to microleakage compared to machinable ceramic veneers.

Clinical implications

Pressing technique produced porcelain veneers with precise

marginal and internal adaptation which resulted in reduced

microleakage compared to CAD/CAM produced porcelain

veneers.

r e f e r e n c e s

1. Calamia JR, Calamia CHS. Ceramic laminate veneers:reasons for 25 years of success. Dental Clinics of North America2007;51:399417.

2. Chen JH, Shi CX, Wang M, Zhao SJ, Wang H. Clinicalevaluation of 546 tetracycline-stained teeth treatedwith porcelain laminate veneers. Journal of Dentistry2005;33:38.

3. Cotert HS, Dundar M, Ozturk B. The effect of variouspreparation designs on the survival of ceramic laminateveneers. Journal of Adhesive Dentistry 2009;11:40511.

4. Nikzad S, Azari A, Dehga S. Ceramic (Feldspathic & IPSEmpress II) vs. laboratory composite (Gradia) veneers; acomparison between their shear bond strength to enamel;an in vitro study. Journal of Oral Rehabilitation 2010;37:56974.

5. Celik C, Gemalmaz D. Comparison of marginal integrity ofceramic and composite veneer restorations luted with twodifferent resin agents: an in vitro study. International Journalof Prosthodontics 2002;15:5964.

6. Peumans M, Van Meerbeek B, Lambrechts P, Vanherle G.Porcelain veneers: a review of the literature. Journal ofDentistry 2000;28:16377.

7. Toh G, Setcos J, Weinstein A. Indirect dental laminateveneersan overview original research article. Journal ofDentistry 1987;15:11724.

8. Beuer F, Aggstaller H, Edelhoff D, Gernet W, Sorensen J.Marginal and internal fits of fixed dental prostheses zirconiaretainers. Dental Materials 2009;25:94102.

9. Bindl A, Mormann WH. Fit of all-ceramic posterior fixedpartial denture frameworks in vitro. International Journal ofPeriodontics and Restorative Dentistry 2007;27:56775.

10. Holmes JR, Bayne SC, Holland GA, Sulik WD. Considerations

in measurement of marginal fit. Journal of Prosthetic Dentistry1989;62:4058.11. Kararaya S, Sengun A, Ozer F. Evaluation of internaladaptation in ceramic and composite resin inlay bysilicon replica technique. Journal of Oral Rehabilitation2005;32:448543.

12. Reich S, Ahlen S, Gozdowski S, Lahbauer U. Measurement ofcement thickness under lithium disilicate crowns using animpression material technique. Clinical Oral Investigation2011;15:51226.

13. Kohorst P, Junghanns J, Dittmer M, Borchers L, Stiesch M.Different CAD/CAM processing routes for zirconiarestorations: influence on fitting accuracy. Clinical OralInvestigation 2011;15:52736.

14. Ucar Y, Akva T, Akyil M, Brantley A. Internal fit evaluation ofcrowns prepared using s anew dental crown fabricationtechnique: laser sintered Co-CR crowns. Journal of ProstheticDentistry 2009;102:2539.

15. Omar H, Atta O, El-Mowafy O, Khan SA. Effect of CAD-CAMporcelain veneers thickness on their cemented colour.Journal of Dentistry 2010;38:95104.

16. Xing W, Jiang T, Ma X, Liang S, Wang Z, Sa Y, et al.Evaluation of the esthetic effect of resin cements and try-inpastes on ceromer veneers. Journal of Dentistry2010;38(Suppl. 2):e87e94.

17. ALGhazali N, Laukner J, Burnside G, Jarad F, Smith P, PrestonA. An investigation into the effect of try-in pastes, uncuredand cured resin cements on the overall color of ceramicveneer restorations: an in vitro study. Journal of Dentistry2010;38(Suppl. 2):e78e86.

18. Sedanur T, Bora B. Colour stability of laminate veneers: anin vitro study. Journal of Dentistry 2011;39(Suppl. 3):e57e64.

19. Horn HR. Porcelain laminate veneer bonded to etchedenamel. Review. Dental Clinic of North America 1983;27:67184.

20. Taskonak B, Anusavice K, Mecholsky J. Role of investmentinteraction layer on strength and toughness of ceramiclaminates. Dental Materials 2004;20:7018.

21. Calamia JR. Etched porcelain facial veneers: a newtreatment modality based on scientific and clinicalevidence. New York Journal of Dentistry 1983;53:2559.

22. Shuman IE. Aesthetic treatment with a pressed ceramicveneer material: case reports. Dentistry Today 2004;23:804.

23. Mormann WH. The evolution of CEREC system. Journal ofAmerican Dental Association 2006;137:7S13S.

24. Rekow D. Computer-aided design and manufacturing indentistry: a review of the state of the art. Journal of ProstheticDentistry 1987;58:5126.

25. Vafiadis D, Goldstein G. Single visit fabrication of a porcelainlaminate veneer with CAD/CAM technology: a clinicalreport. Journal of Prosthetic Dentistry 2011;106:714.

26. Shetty A, Kaiwar A, Shubhashini N, Ashwini P, Naveen DN,Adarsha MS, et al. Survival rates of porcelain laminaterestoration based on different incisal preparation designs:an analysis. Journal of Conservative Dentistry 2011;14:105.

27. Walls A, Steek J, Wassell R. Crowns and extra-coronalrestorations; porcelain laminate veneers. Journal of ProstheticDentistry 2002;193:7382.

28. Brunton PA, Aminian A, Wilson NH. Tooth preparationtechniques for porcelain laminate veneers. British DentalJournal 2000;189:2602.

29. Christensen G. Why use resin cements. Journal of AmericanDental Association 2010;141:2046.

30. Lim C, Ironside J. Grit blasting and the marginal accuracy oftwo ceramic veneer systems a pilot study. Journal ProstheticDentistry 1997;77:35964.

31. Martin N, Jedynakiewicz NM. Interface dimensions ofCEREC-2 MOD inlays. Dental Materials 2000;16:6874.

32. Reich S, Wichmann M, Nkenke E, Proeschel P. Clinical fit ofall-ceramic three unit fixed partial dentures, generated with

three different CAD/CAM systems. European Journal of OralScience 2005;113:17483.

33. Baig MR, Tan KB, Nicholls JI. Evaluation of the marginal fit ofa zirconia ceramic computer-aided machined (CAM) crownsystem. Journal of Prosthetic Dentistry 2010;104:21627.

34. Bindl A, Mormann WH. Marginal and internal fit of all-ceramic CAD/CAM crown copings on chamfer preparations.Journal of Oral Rehabilitation 2005;32:4417.

35. Tinschert J, Natt G, Hassenpflug S, Spiekermann H. Status ofcurrent CAD/CAM technology in dental medicine.International Journal of Computerized Dentistry 2004;7:2545.

36. Harasani MH, Isidor F, Kaaber S. Marginal fit of porcelainand indirect composite laminate veneers under in vitroconditions. Scandinavian Journal of Dental Research1991;99:2628.

37. Potincy D, Klim J. CAD/CAM in-office technology inovationsafter 25 years for predictable, esthetic outcomes. Journal ofAmerican Dental Association 2010;141:5S9S.

38. White SN, Suh PS, Yu Z, Johnson R. Effect of fit adjustmenton CEREC CAD-CAM veneers. American Journal of Dentistry1997;10:4651.

39. Cho L, Choi J, Yi YJ, Park CJ. Effect of finish line variants onmarginal accuracy and fracture strength of ceramicoptimized polymer/fiber-reinforced composite crowns.Journal of Prosthetic Dentistry 2004;91:55460.

40. May KB, Russell MM, Razzoog ME, Lang BR. Precision of fit:the Procera AllCeram crown. Journal of Prosthetic Dentistry1998;80:394404.

41. Cho SH, Chang WG, Lim BS, Lee YK. Effect of die spacerthickness on shear bond strength of porcelain laminate

44. Guess P, Stappert C. Midterm results of a 5-year prospectiveclinical investigation of extended ceramic veneers. DentalMaterials 2008;24:80413.

45. Chun YH, Raffelt C, Pfeiffer H, Bizhang M, Saul G, BlunckU, et al. Restoring strength of incisors with veneers andfull ceramic crowns. Journal of Adhesive Dentistry2010;12:4554.

46. Regina L, Archegas P, Freire A, Vieira S, Caldas B, Souza E.Colour stability and opacity of resin cements and flowablecomposites for ceramic veneer luting after acceleratedageing. Journal of Dentistry 2011;39:80410.

47. Bonfante F, Coelho P, Guess P, Thompson V, Silva N. Fatigueand damage accumulation of veneer porcelain pressed onY-TZP. Journal of Dentistry 2010;38:31824.

48. Christgau M, Friedl KH, Schmalz G, Resch U. Marginaladaptation of heat-pressed glassceramic veneers to dentinin vitro. Operative Dentistry 1999;24:13746.

49. Christgau M, Friedl KH, Schmalz G, Edelmann K. Marginaladaptation of heat-pressed glassceramic veneers to class 3composite restorations in vitro. Operative Dentistry1999;24:23344.

50. Sim C, Neo J, Chua EK, Tan BY. The effect of dentin bondingagents on the microleakage of porcelain veneers. DentalMaterials 1994;10:27881.

51. Zaimoglu A, Karaagaclioglu L, Uctasli. Influence of porcelainmaterial and composite luting resin on microleakage ofporcelain laminate veneers. Journal of Oral Rehabilitation1992;19:31927.

52. Maleknejad F, Moosavi H, Shahriari R, Sarabi N,

j o u r n a l o f d e n t i s t r y 4 0 ( 2 0 1 2 ) 6 7 0 6 7 7 677veneers. Journal of Prosthetic Dentistry 2006;95:2018.42. Magne P, Versluis A, Douglas W. Effect of luting composite

shrinkage and thermal loads on the stress distribution inporcelain laminate veneers. Journal of Prosthetic Dentistry1999;81:33544.

43. Komine F, Iwai T, Kobayashi K, Matsumura H. Marginal andinternal adaptation of zirconium dioxide ceramic copingsand crowns with different finish line designs. DentalMaterials Journal 2007;26:65964.Shayankhah T. The effect of different adhesive types andcuring methods on microleakage and the marginaladaptation of composite veneers. Journal of ContemporaryDental Practice 2009;10:1826.

53. Hekimoglu C, Anil N, Yalcin E. A microleakage study ofceramic laminate veneers by autoradiography: effect ofincisal edge preparation. Journal of Oral Rehabilitation2004;31:2659.

Internal adaptation, marginal accuracy and microleakage of a pressable versus a machinable ceramic laminate veneersIntroductionMaterials and methodsPressing fabrication techniqueMachining fabrication techniqueCementation procedureArtificial ageing programmeSectioning techniqueInternal adaptation, marginal accuracy and microleakage

ResultsDiscussionConclusionClinical implicationsReferences