Chairside staining with e.max CAD/CAM crown

1. Esthetics
Implants
Inside Restorative
Treatment options
Continuing Education
Chairside CAD/CAM
Lithium disilicate restoration for anterior teeth made simple.
By Gregg A. Helvey, DDS
I
n 1904, Dr. Hart J. Goslee porcelain crown he could fabricate, the creating a marginal gap. dentistry to digital impressions (iTero™,
from Chicago, Illinois, presen­ whole process taking under 2 hours. Dr. After Buonocore’s discovery of enamel Cadent, www.cadentinc.com; and Lava™
ted his paper entitled, “The Goslee probably would have smiled at etching in 1955,4 all-ceramic restorations C.O.S., 3M ESPE, www.3mespe.com) and
Mechanical Requirements the idea because he directed at the end had a re-emergence into the marketplace. single-visit chairside restorations using
and Cosmetic Possibilities of his paper to, “attempt to stimulate The most popular all-ceramic restoration CEREC® AC (Sirona) and E4D Dentist™
of Modern Artificial Crown others to aid in the elevation of the was IPS Empress® by Ivoclar Vivadent (D4D Technologies, www.d4dtech.com).
Work” at the Fourth Inter­ profession in general, and of dental art (www.ivoclarvivadent.us). Enamel and Several manufacturers have contributed
national Dental Congress in St. Louis, and dental mechanics in particular, to dentin bonding helped to increase the to the development of the restorative
Missouri.1 Dr. Goslee said, “Since it is a sphere beyond that of mere artisan, popularity of this restoration. materials used by the single-visit CAD/
the very highest achievement of true and more in accord with the higher de­ Then computer-aided design/com­ CAM systems. 3M ESPE manufactures
art to copy nature, we have contribut­ gree of art which modern possibilities puter-aided manufacturing (CAD/CAM) the Paradigm™ MZ100 composite block,
ed liberally thereto by the development offer.” He went on to say such possibili­ entered dentistry with CEREC® (Sirona Vident (www.vident.com) provides the
of procedures which enable us in our ties, however, are not the product of the Dental Systems, www.sirona.com) in the Vitablocs® Mark II ceramic block, and
particular field to so closely simulate day, but are an outgrowth of a gradual early 1990s. As the computer software Ivoclar Vivadent offers the IPS Empress
nature in her perfections and imperfec­ development to achieve results beyond technology grew, so did the milling ceramic and their newest lithium disili­
tions as to be able to substitute the natu­ the ordinary.2 hardware capability. That has brought cate ceramic additions, the CAD LT and
ral with the artificial in such a manner Esthetic dentistry has come full circle
as to preclude detection.” He concluded since Dr. Goslee presented his paper in
his paper with, “the special advantages 1904. One of the other points he read in
to be obtained from the application of his paper was that metal was used indis­
porcelain crowns lie in the artistic man­ criminately in the fabrication of ante­
ner and facility with which the natural rior crowns. The all-porcelain “jacket”
conditions and varying characteristics crown was first introduced by Charles
may be closely simulated, together with H. Land and patented in 1889.2 The
the increased possibilities for securing a restoration was improved by Dr. E. B.
degree of strength exceeding any other Spaulding of Detroit, and later was ex­
style of construction.” tensively used and publicized by Dr. W.
Imagine what Dr Goslee’s reaction A. Capon of Philadelphia.2 In 1909, Dr. R.
would have been if someone at that H. Riethmueller described a method of
meeting had told him that in 105 years making an all-porcelain jacket crown us­
a small portable machine would take a ing platinum foil in Dental Cosmos.2 The fig. 1
picture of an anterior tooth and then porcelain “jacket” crown was not known
mill the exact shape and contour from a for its strength but was nevertheless used
ceramic block. Then the clinician would quite extensively up to the 1950s.
stain it and cement it. The all-ceramic The technique of bonding feldspathic
restoration would be stronger than any porcelain to a metal framework was in­
vented in the late1950s by Dr. Abraham
Weinstein.3 Using the “lost wax” cast­
Gregg A.
ing technique, gold was used to create
Helvey, DDS
Adjunct Associate Professor
a metal coping onto which porcelain
Virginia Commonwealth was fused. The fit was much better than
University School of Dentistry the porcelain jacket crown, which em­
Richmond, Virginia ployed a platinum foil as a matrix during
fabrication. The marginal integrity of fig. 2
Private Practice
Middleburg, Virginia
the porcelain jacket crown was always
questionable because after completion PREOPERATIVE CONDITION (1.) Facial view of the discolored canine.
of the crown the foil was removed, thus (2.)Lingual view shows the previous endodontic access filling.
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2. INSIDE Restorative
CAD HT blocks. The use of the CAD LT cycle, the restoration shrinks by a factor
ceramic block will be illustrated in the of 0.2%. The computer software takes
following single-visit case study. this shrinkage into account during the
milling process.
Lithium Disilicate During the crystallization cycle there
To increase the strength, thermal ex­ is a controlled growth of the grain size
pansion, and contraction behavior of (0.5 µm to 5 µm). This transformation
ceramics, manufacturers have added leads to a glass ceramic that is made up
crystalline filler particles.5 Other types of prismatic lithium disilicate dispersed
of filler additions include particles of in a glassy matrix.10 This alteration
high-melting glasses that are stable at increases the flexural strength of the
the firing temperature of the ceramic.6 restoration to 360 MPa,11 an increase fig. 3 fig. 4
Kelly5 refers to a ceramic as a “glass-ce­ of 170%. A random orientation of small
ramic” when the filler particles are add­ interlocking plate-like crystals makes
ed mechanically during manufacturing up the lithium-disilicate restoration.
precipitate within the starting glass by The orientation and size of the crys­
special nucleation and growth heating tals can account for crack deflection
treatments. Two examples of glass ce­ and blunting which, in turn, accounts
ramics that contain high concentrations for the increase in fracture toughness
of lithium disilicate are IPS e.max® Press over leucite-reinforced cermics.12
and IPS e.max® CAD (Ivoclar Vivadent). There are two basic fabrication meth­
The press form is used in the laboratory, ods. The first method is to mill the
whereas the CAD form is used in con­ restoration to full anatomical contour.
junction with CAD/CAM technology for Before crystallization, the incisal edge
chairside and laboratory settings. Both is preserved by creating a silicone in­
fig. 5
materials can be pressed or milled to full dex.13 The incisal edge is cut back, cre­
contour, then stained and glazed or cut ating mamelons and layered with the
CAD BLOCKS (3.) The remaining side portions of a large CAD block were
back and layered with the appropriate appropriate incisal porcelains back to removed with a diamond disk. (4.) A small diamond bur inscribed the
layering ceramics. the original contour using the silicone identification of the shade tab. (5.) The slight difference between the plas-
Lithium disilicate was first intro­ index as the guide. The restoration is tic shade tab and the actual shade of the crystallized lithium disilicate.
duced in 1998 as IPS Empress® 2 then crystallized in the furnace using the
(Ivoclar Vivadent).7 It was developed standard firing program. A variation of a large lingual composite that was placed disilicate block material, which helps
in response to a high demand for all- this technique is crystallizing before the where endodontic access had been made in eliminating inconsistencies in shade
ceramic fixed partial dentures (FPDs).8 layering steps. This method allows the (Figure 2) and wear on the incisal edge selection (Figure 5).
It was used mainly as a single-core or operator to see the color of the restora­ was present. Various treatment options The correlation mode was selected in
FPD framework to which a veneering tion before application of the layering were discussed, which led to using a full- the CEREC computer program, which
ceramic was applied. ceramics. This does require a wash coat coverage all-ceramic crown fabricated makes a copy of the existing tooth. To
Today, the lithium disilicate CAD firing of the layering ceramic before the using CEREC technology. capture the tooth, a reflective surface
blocks come partially crystallized. In this build-up ceramic is applied. The patient requested to duplicate must be created using titanium dioxide
state, the lithium metasilicate crystals The second method is to mill the the same shape but change the color to that is evenly powdered over the entire
provide sufficient strength for milling crown to full contour, then stain, glaze, match the adjacent teeth. The first step tooth and the adjacent teeth. Five pre­
and try-in purposes. The manufacturing and crystallize. This method also has was to select the correct shade. Shade operative images were taken to pre­
process uses a glass technology that pro­ a variation that includes applying the selection should always be made before serve a copy of the unprepared tooth.
vides a material void of any defects and stain and glaze after the crystallization any powdering or tooth preparation. The tooth was then prepared using a
an even distribution of color pigments. step. This allows the operator to see the The manufacturer supplies a shade 6847KR 018 modified shoulder diamond
The grain sizes of lithium metasilicate final color of the crown while applying guide but the shade tabs are plastic and bur (Brasseler USA, www.brasseler.com).
crystals range from 0.2 µm to 1 µm, ren­ the stains. It may be easier to apply the not made of lithium disilicate. Selecting The minimum amount of reduction is 1
dering a flexural strength of 130 MPa stains, but it involves a second 12-min­ the shade with a different material than mm at the cervical margin, 1.2 mm of
to this material. This is comparable to ute firing cycle. that of the final restoration can result axial reduction in the facial and lingual
the other mill-ready leucite-reinforced in the wrong selection. mid-body area, and 1.5 mm of incisal
CAD/CAM (ProCAD, Ivoclar Vivadent) Case Study A customized shade guide can easily reduction. In cases with a dark stump
blocks and the feldspathic CAD/CAM A 43-year-old woman presented with be fabricated. There are, at times, side shades, increasing the facial reduction
blocks (Vitabloc Mark II).9 a darkened right maxillary canine that portions of the CAD block remaining to 2 mm will increase the ceramic thick­
The standard 27-minute crystalliza­ had been endodontically treated 10 after the restoration is milled. These ness and provide a greater masking effect
tion process reaches a temperature of years earlier (Figure 1). The patient unmilled portions can be separated of the underlying shade of the prepared
840ºC to 850ºC (1,544°F to 1,562°F) in experienced blunt trauma as a result from the remainder of the block with a tooth. The modified shoulder will create
a two-stage ceramic furnace. A shorter of a fall and the tooth became non-vital diamond disk (Figure 3) and inscribed a flat 1-mm depth at the cervical margin
firing cycle (under 20 minutes) can be some time after the incident. The color using a small diamond bur with the with a slightly rounded internal line an­
used with this type of oven, providing of the tooth darkened progressively. The appropriate shade name (A2, A3 etc) gle. Sharp line angles are areas of higher
no more than two restorations at a time tooth had now become her chief com­ (Figure 4) and then crystallized dur­ stress concentrations and should always
and the spray-type glaze is used rather plaint. Radiographic examination was ing a firing cycle. This will create an be avoided with all-ceramic restorations.
than the paste version. During the firing negative. Clinical examination revealed exact shade tab of the actual lithium Rounded internal line angles minimize
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3. INSIDE Restorative
stress concentrations.14 impregnated wheel (Brasseler). The
The last step in the preparation pro­ crown was then re-inserted for staining
cess was to use a 10839 014 end-cutting (Figure 8).
diamond bur (Brasseler) to remove any
reverse or troughed edges on the mar­ Staining Technique
gin, which are contraindicated in all- Chairside staining is an art form. For
ceramic restorations.15 Creating a 90° the beginner, it can be very difficult to
exit angle will facilitate the scanning determine the correct stain, how much
process and prevent thinning of the ce­ to use, where to place it, and how to
ramic margins. Flat, defined margins keep the various stains from “bleed­
also will enhance the accuracy of the ing” into each other. The first step is to
margin tracing step during that phase observe the matching tooth, whether it
fig. 6 fig. 7
of the computer program. A diode la­ is contralateral or adjacent. The color
ser was used on the mesial portion to in teeth has to be looked for, and even
expose the margin (Figure 6). we, as clinicians, overlook what makes
The prepared tooth was once again up a natural tooth. As well-respected
powdered with titanium dioxide. Several dentist/ceramist Dr. Robert Stein once
images were taken, which included the said to the author at a lecture in 1979,
adjacent teeth. A common anatomical “Your eyes see the color but your brain
landmark in both the preoperative and does not perceive it.” It takes a con­
postoperative images is necessary for scientious effort to observe the color
the software to merge or “stitch” the im­ in teeth. Nakagawa’s study found that
ages together creating a virtual model anterior teeth have 4 different modes
(Figure 7). of color. The most frequent occurrence
Once the design process was com­ is when there are different colors in the
fig.8 fig. 9
pleted, an IPS e.max CAD LT block in cervical, mid-body, and incisal. Having
shade A-2 was selected. Recently, the no color change is second, followed by
manufacturer has introduced a new ver­ color change in the cervical area only.
sion of the CAD material with a higher Least frequent is a color change only
level of translucency referred to as the in the mid-body of the tooth.16 Because
CAD HT block. the tri-colored mode has the greatest
The appropriate shade block (LT frequency, the clinician should initially
version) was inserted into the milling look for this mode.
machine. Selecting the correct milling To find the correct stain, a thinned out
program is important in achieving the amount of stain can be applied to the
proper physical properties of the mate­ matching tooth to see if there is a blend­
rial. There are ways of “fooling” the soft­ ing. This process can be repeated until
fig. 10 fig. 11 ware into thinking that a different ce­ the stain and the color of the matching
ramic material is in the milling machine, tooth are the same. The chroma or sat­
which will allow the operator to use a uration of the stain can also be deter­
“fast-milling” mode. The difference in mined with this exercise. The next step
milling modes may save 10 minutes of is to determine exactly where to place
mill time but the adverse effect on the the stain and keep it there. One method
lithium disilicate may be beyond healing is to use a red wax margin liner pencil
during the crystallization cycle (written that is used for marking the margins on
personal communication with manufac­ the dies of working models. Using the
turer’s ceramic engineer). The manufac­ wax pencil, areas can be drawn on the
turer strongly advises not to use this ac­ surface of the crown where the differ­
celerated milling program. Not only are ent stains are to be applied (Figure 9).
there adverse effects on the material to These areas should have the polished
fig. 12 fig. 13 consider, there is a decrease in longevity surface removed with a fine slow-speed
of the diamond milling burs. diamond or green stone. The wax keeps
After the milling process was complet­ the stains in place and allows the opera­
CRYSTALLIZATION STAGE (6.) The prepared canine after using a diode ed, the small remaining milling sprue was tor to place numerous stains in a small
laser on the mesial aspect of the tooth. Note the severe discoloration. (7.)
Virtual model of the prepared tooth. (8.) The pre-crystallized crown was removed. The crown was steam-cleaned area. During the crystallization firing,
tried in to verify fit and occlusion. (9.) After the polished surface was re- to remove the milling slurry film. This the wax pencil lines burn off and leave
moved, a red wax pencil was used to draw areas where stains were to be film also can be removed using an ultra­ no traces. This method can be referred
applied. (10.) The crown was removed from the tooth and secured from
the lingual. (11.)The crown was secured to the silver nitride firing pin with sonic bath. The crown was then tried to as “staining within the lines” similar
IPS e.max Object Fix Putty. (12.) Once the crown was fixed to the firing in to confirm the fit and the bite. Next, to our early grammar school exercise of
pin, IPS e.max CAD Crystall./Glaze Spray was applied in short bursts. the crown was removed and the mar­ “coloring within the lines.”
(13.) During the crystallization stage, the red wax pencil marks burned off
and the crown shade changed. ginal areas were finished and polished In this case it was determined that
using a pink and grey Dialite diamond- the contralateral tooth had an increased
4 inside dentistry | November/December 2009 | insidedentistry.net

4. INSIDE Restorative
chroma in the cervical area where the firing cycle. Any excess putty is then of removing the putty material can be was dependent on the elastic modulus
Khaki stain matched. The mid-body smoothed with a porcelain or plastic accomplished with an ultrasonic bath. mismatch between the ceramic, the
contour ridge also had an increase in spatula and removed from the sides of cement, and the supporting material.
chroma where the Khaki stain matched. the crown with a wet brush (Figure 11). Cementing Materials The greater bond strength between the
It was also determined that the mesial While holding the crown, the IPS e.max What is unique about the IPS e.max ceramic and the supporting material
and distal depressions had more trans­ CAD Crystall./Glaze Spray is applied to CAD lithium disilicate ceramic is hav­ prevented delamination and allowed
lucency and this was duplicated using the entire crown. Holding the spray can ing the ability to insert a restoration for more stress transfer between the
Incisal 1 stain. After the stains were ap­ about 4 inches away and short bursts, using either adhesive, self-etching ceramic and the tooth. Increasing the
plied, the crown was carefully removed spray glaze is applied to the crown, al­ adhesive or conventional cementing bond strength (more stress transfer)
from the patient and secured from the lowing each coat to dry before applying methods. The question then should be: was more advantageous than increas­
lingual aspect of the crown with college the next (Figure 12). A paste type glaze Which cementing medium produces ing the flexure strength of the ceramic.
pliers (Figure 10). is also available. the best result, or are they equal in By increasing the cement elastic modu­
It is important that no other type of terms of retention, fracture resistance, lus, the ceramic-cement-dentin com­
Lithium-Disilicate firing tray, such as a honeycomb tray, be and sealing ability? There are a number plex became stiffer, therefore, decreas­
Crystallization used during this crystallization process. of studies that find that resin-based ce­ ing the stress in the ceramic. Lee et al24
The next step is the crystallization The rate of cooling after the crystalliza­ menting materials show similar results found greater resistance to fracture of
process, where the crown is placed on tion process is critical in preserving the compared to glass-ionomer cement. Al- bonded ceramics when comparing the
a silver nitride firing tray by means of physical properties of the lithium disili­ Wahadni et al,17 in their study, found no stiffness of the adhesive cement. Rekow
an IPS e.max CAD crystallization pin. cate. The silver nitride tray and pin ma­ significant difference in fracture resis­ et al25 reported that the thickness and
There are several different sizes of pins. terial hold the heat longer, so the rate of tance when premolar lithium-disilicate type of ceramic were the determinants
The largest pin that does not contact cooling is slower. It is critical that this crowns were cemented with glass-iono­ of ceramic strength, and those factors
the internal walls of the crown is se­ step not be hurried (Figure 13). mer and resin cement. A study was con­ having some influence included cement
lected. The crown is first filled with IPS After the crystallization step was com­ ducted on anterior and posterior 3-unit elastic modulus, the position and angle
Object Fix Putty or Flow material. This pleted and the crown cooled to the touch, lithium-disilicate fixed partial dentures of the applied load, and the supporting
material fixes the crown to the crystal­ the crystallization pin was removed. (FPDs) cemented with glass-ionomer tooth core.
lization pin and protects the margins The putty material was removed using and resin cement. Wolfart et al18 found A monolithic IPS e.max CAD lithium-
from rounding off during the 840°C a steam cleaner. An alternative method that the 8-year survival rate according disilicate crown, with a flexural strength
to Kaplan-Meier was 93%. They con­ of 360 MPa, which is seconded only
cluded that short-span, crown-retained, by the pressed form, is the strongest
three-unit FDPs made from lithium- ceramic available. If the tooth prepa­
disilicate glass-ceramic can be used ration provides the required ceramic
clinically irrespective of an adhesive thickness, then, according to Rekow et
or conventional cementation. al,25 using adhesive cement with a high
Zhang et al19 reported that the frac­ elastic modulus will contribute to the
ture mode of monolithic dental ceram­ over-all strength of the restoration. The
ics is thickness-dependent and fracture use of an adhesive cement with a higher
resistance was strongly dependent on elastic modulus would correlate with
the support material. The less stiff sup­ the findings of Zhang et al,19 Dong and
port material resulted in flexure of the Darvell,23 and Lee et al.24
cement side of the ceramic, increasing
tensile stresses that produced radial Ceramic Surface
fractures. Radial fractures can be ini­ Preparation and Insertion
tiated by sandblasting or grinding from Conditioning or treatment of the bond­
fig. 14 a dental bur. They concluded that high ing surface of all-ceramic crowns is
elastic-modulus cement reduced the necessary to create a strong ceramic-
risk of fractures. Fleming et al20 stud­ to-resin bond. Peumans et al26 reported
ied the effect of resin cement increas­ a significant difference in microtensile
ing the performance of all-ceramic bond strength between ceramic speci­
crowns. They found the combination mens treated with hydrofluoric acid,
of ceramic surface pre-treatment and silane, and resin versus specimens
cement moved the fracture origin from that either had no treatment or were
the ceramic/cement interface to the treated with phosphoric acid only. In
cement surface. Two previous studies their study, Öztürk et al27 tested the
that had been proposed by Marquis21 bond strength of two different luting
(crack healing) and Nathanson22 (res­ cement systems to lithium-disilicate
in-polymerization shrinkage-strength­ and leucite-reinforced ceramic inlays.
ened ceramic) were based on the pres­ One system used hydrofluoric-acid
ence of defects on the ceramic surface. conditioning for 60 seconds then neu­
fig. 15 Fleming found ceramic strengthening tralized (Ceramic Etchant Neutralizer,
was independent of the defect popu­ DENTSPLY Ceramco, www.ceramco.
FINAL RESULTS (14.) Lingual view of the finished lithium-disilicate crown. lation. Dong and Darvell23 found that com) followed with the application of
(15.) Facial view of the finished lithium-disilicate crown. generation of critical tensile stress silane (Monobond-S, Ivoclar Vivadent)
insidedentistry.net | November/December 2009 | inside dentistry 5

5. INSIDE Restorative
for 60 seconds. The specimens were Treatise for the Use of Dental Students and 2006;85(3):272-276.
then cemented with Variolink II with Practitioners. Lea and Febiger, New York; 1922. 21. Marquis PM. The influence of cementson
its respective bonding agent. The other 3. Asgar K. Casting metals in dentistry: Past, the mechanical performance of dental ceram­
cement system used phosphoric acid for present, future. Adv Dent Res. 1988;2:33-43. ics. Bioceramics. 1992;5:317-324.
5 seconds to condition the cementing 4. Touati B, Miara P, Nathanson D. Esthetic 22. Nathanson D. Principles of porcelain use
surface, then was rinsed and air-dried Dentistry and Ceramic Restorations. Martin as an inlay/onlay material. In: Garber DA,
followed by the application of Clearfil™ Dunitz Ltd, London; 1999:10. Goldstein RE, eds. Porcelain and Composite
Ceramic Primer (Kuraray Dental) for 5. Kelly JR. Dental ceramics: What is this stuff Inlays and Onlays: Esthetic Posterior Restorations.
60 seconds. The specimens were then anyway? J Am Dent Assoc. 2008:139:4S-7S. 1993; Chicago, Ill; Quintessence. 23-32.
cemented using Panavia F ED and its 6. Denry IL. Recent advances in ceram­ 23. Dong XD, Darvel BW. Stress distribution
respective bonding agent. Microtensile ics for dentistry. Crit Rev Oral Bio Med. and failure mode of dental ceramic structures
bond strength testing showed no dif­ 1996;7(2):134-143. under Hertzian indebtation. Dent Mater.
ferences between the two systems. In 7. Giordano R. Materials for chairside CAD/ 2003;19:542-551.
fact, Krishnan et al28 found lower bond CAM-produced restorations. J Am Dent Assoc. 24. Lee JJ-W, Wang Y, Lloyd IK, Lawn BR.
strengths of hydrofluoric-acid-etched 2006;137(1 Suppl):14S-21S. Joining veneers to ceramic cores and denti­
IPS Empress ceramic than untreated 8. Powers JM, Sakaguchi RL. Craig’s tion with adhesive interlayers. J Dent Res.
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In this case, the Clearfil Esthetic 9. Seghi RR, Sorensen JA. Relative flexural Factorial analysis of variables influencing
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conditioned with phosphoric acid for Ma t e r i a l s . E l s e v i e r He a l t h S c i e n c e s, Effects of ceramic surface treatments on bond
5 seconds (manufacturer’s recommen­ Philadelphia, Pa; 2002:244. strength of an adhesive luting agent to CAD/
dation), thoroughly rinsed with water, 11. Helvey GA. Retro-fitting an existing crown CAM ceramic. J Dent. 2007;35(4):282-288.
air-dried, and followed with an appli­ adjacent to a removable partial denture in a 27. Öztürk AN, Inan Ö, Inan E, Öztürk B.
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with the automix tip and placed in the evaluation of lithia-disilicate-based all-ce­
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seconds on each side. The excess was 14. McLaren EA, White SN. Glass-infilrated
then removed and the occlusion was airconia/alumina-based ceramic for crowns
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Conclusion 15. Gürel G. The Science and Art of Porcelain
In the 105 years since Dr. Goslee pre­ Laminate Veneers. Quintessence Publishing,
sented his paper, the art and mechanics Chicago; 2003:267-268.
of “artificial crown work” have made 16. Nakagawa Y. Analysis of natural tooth color.
tremendous strides. The use of an all- ShiKai Tenbo. 1975;46:527.
ceramic material milled from a com­ 17. Wahadni AM, Hussey DL, Grey N, Hatamieh
puter program and inserted at the same MM. Fracture resistance of aluminum oxide
appointment would have most likely and lithium disilicate-based crowns using
impressed him. It is hard to imagine the different luting cements: An in vitro study. J
technology that will be used to restore Contemp Dent Pract. 2009;10(2):51-58.
that same canine 105 years from now. 18. Wolfart S, Eschbach S, Scherrer S, Kern M.
Clinical outcome of three-unit lithium-disili­
Acknowledgment cate glass-ceramic fixed dental protheses: Up to
Special thanks to Ruth Egli, RDH, for her 8 years results. Dent Mater. 2009 (in press).
editorial contribution. 19. Zhang Y, Kim JW, Bhowmick S, et al.
Competition of fracture mechanisms in mono­
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6 inside dentistry | November/December 2009 | insidedentistry.net