Restorative Dentistry

The Cerec 3—A quantum leap for computer-aided restorations: Initial clinical results

Werner H, Mormanfi, DDS, DMD, PhDVAndreas Bindl, DMD^

The Cerec 3 sysfem simplifies and accelerates fhe fabrication of cerarric inlays, onlays veneers and quarfer, half, and cor^plefe crowns for anferior and posferior teeth. Cerec 3 software simplifies occlusal and funcfional registration. Proper is esfablished accurately and quickly; manual adjustmenf is reduced fo a minimum. The separafe grinding device, working true fo morphologic detail and with fine sur- face qualify, is connecfed fo the opfical unit by radio control. Equipped wifh a laser scanner, il can also be used for indirect applicafion through a sfandard personal compufer. The Cerec 3 system is network and multimedia ready and, in combination wifh an intraoral color videocamera or a digital radiography unit can be used for patient education and for user training. The Cerec 3 system thus is a diagnostic, resforafive, training, and documentation center for the denfal pracfice, (Quintessence int 2000:31:699-712)

Key words: Cerec 3, computer-aided design-oomputer-aided machining, compufer-aided restoration, optical impression

he Cerec technique was developed in 1984 to For the Cerec 3, the construction and control soft- Tanswer the practical need for long-lasting dental ware was written for the Windows NT platform restorations with sound marginai seals,'-' On (Microsoft) and now runs on an efficient personal com- September 19, 1985. the first ceramic inlay produced puter (PC) integrated into the recording unit. Thus, the through a computer-aided design-computer-aided Cerec 3 is integrated at once into the rapid advances of machining (CAD-CAM) procedure was inserted adhe- computer technologi' in general; this provides a practi- sively at the Dentai Institute of the University of Zurich. cally unlimited computational performance. In turn, The Cerec technique and the Cerec 1 device were this permits acceleration of automatic processes and greeted with astonishment and skepticism and elicited provides a sufficiently user-friendly program to accom- numerous pubhcations that ultimately led to scientific modate the user with ordinary technical skills. In par- recognition in 1994,'"' In the same year, Siemens ticular, this means the elimination of all waiting periods introduced the Cerec 2 unit. The expanded shape- for picture adjustment, for data storage, and especially grinding technique permitted hard tissue-conserving, for picture superimposition in the construction of defect-oriented adaptation of the inlays at the floor occlusal surfaces with "correlation" and ''function." and walls, coverage of cusps (inlays, onlays), and the This provides certainty in the attainment of function- anatomic functionai arrangement of the occlusal sur- ally correct half-, 3-quarter, and complete crowns and face with efficient software," In this manner, design use of the Cerec technique at a single appoint- and fabrication procedures for all-ceramic posterior ment, consequently saving time. crowns were made possible,^-'^ However, the full All procedural steps profit from the numerous simpli- effects of the correlation and function modalifies were fications and increased automafion. The separate grind- severely limited by the efficiency of the computer,'* ing unit, which provides greater true detail and is fitted with 2 finger cutters, is connected via radio control wave to the control unit. The grinding unit receives data ^Director, Section tor Tooffi-colored and Corrpufer Reslorafions, Clinic lor from the control unit, independent of its locafion in the Prevenfii/e Dentisfry, Periodontics, and Cariology, Dental Sctiool, Universify ol Zuricti, Zurich, Switzerland. practice. The next restoration can be designed while the first is being milled. The grinding unit is fitted with a ^Leader, Clinic ot the Section forTootfi-colored and Compufer Restorafions, Clinic for Preventive Denfistry, Pericdontics, and Cariology, Denial Uriver- laser scanner (Cerec Scan) and also can he used by Eify ot Zurich, Zurich, Switzerland. itself with a standard PC for indirect applications. Reprinf Requests: Prof Werner H. Mormann, Director, Section for Tocth- With its direct opfical impression, the Cerec 3 once colcred and Computer Restorations, Clinic foi Preventive Dentisfry, Peri- again puts the dentist in the center while it permits odonfics, and Cariology, Denfal School, University of Zurich, Plattensfrasse 11, CH-2003Zuricfi, Swifzerland. E-mail: moormann @zzml(,unizh.cli joint efforts with the dental assistant and cooperation

Ouinfessence Internafional 699 • Mürmann/Bindl with the dental laboratory technician. The authors had In tbe Cerec 2 camera, the survey region depth scale the opportunity to use a Cerec 3 and a Cerec Scan for was limited to a single value of 6.4 mm. In tbe "adjust" 6 months. This article describes the clinical experience mode and with time-consuming effort required for soft- with these units. ware-supported adjustments, the depth scale could be stretched beyond the limits of the camera's optical depth of field of 14 mm. In the Cerec 3, the problem THE CEREC 3TECHNI0UE has been solved through "double triangulation." In this procedure, the triangulation projection of the single The Cerec 3 system (Sirona) has several technical optical impression is registered with 2 separate trianp- improvements over Cerec 2, including the 3-dimen- lation angles. This leads to a clear, expanded depth sional Cerec 3 intraoral camera, manipulation of the scale of 20 mm. The double set of data is processed picture, and the grinding unit. immediately through a specialized "twin grab board" {Tabie 1). intraoral camera Efficient registration of occlusion The most significant factor for surveying with the Cerec 3 intraoral camera is that preparations for The time-consuming adjustment to increase the depth crowns and inlays have a unique characteristic: All scale in the adjust mode is eliminated in the Cerec 3. points of interest can be seen from a single visual angle, The 2-impression "correlation" and "function" proce- ie, the angle preparation or insertion. The technical dures now can proceed as desired using occlusion and requirements, dcidsed by Mormann and Brandestini'-'' preparation optical impressions without loss of time, for the Cerec method and met by Cerec 1 and Cerec 2, thanks to computer efficiency. The rapid recording of are also met by Cerec 3. Surveying proceeds: occlusal impressions from an existing intact occlusal surface undermined by extensive caries or from a fully 1. With a single exposure from a single camera view- functional occlusal surface of an existing restoration ing angle. that is to be replaced is possible now in the correlation 2. Without touching the preparation {the camera is mode with significant decrease in time spent. For a guided in tbe manner of a contra-angle). large carious lesion with loss of cusps, and when the 3. Free-handed (the camera is supported bimanually occlusal surface is insufficient, the situation can be on the dental arch). recorded in the function design mode. The remaining 4. Without reference markings on the teeth. intact cusps and the fractional components of the 5. In fractions of a second. occlusal surface are recorded by an occlusion impres- 6. Reproducibly, as often as desired. sion and after preparation, are matched with the prepa- ration impression. The matched image orientation and The inventors of this procedure called it an optical design suggestions arising from the morphogic data impression, in analogy to the physical impression tech- bank are used to optimize occlusion. Alternatively, a nique.^ After the surveying procedure is completed, functionally generated path {FGP} or centric wax regis- the data are stored as a positive digital xyz data model tration can be recorded by an occlusion impression and and displayed as a video freeze frame image, or optical matched with the preparation impression for designing impression. The design lines are entered on this pic- the occlusai surface (eg, of a full crovvn). ture, the optical impression. Preliminary measurements showed significant The Cerec 3-dimensional surveying method uses the advantages for Cerec 3 compared with Cerec 2. For principle of active triangulation. Here, the camera pro- example, for design and grinding of an onlay with jects a linear pattern under a triangulation angle on the replacement of 3 cusps {3-quarter crown), Cerec 3 preparation, and the projected image is recorded. When required only 24 minutes, while Cerec 2 required 33 the projected lines on the preparation are viewed, the minutes under the same conditions. That is 27% saving course of the lines no longer appears to be straight, but time (Table 2). Another time saver, which has not yet rather appears shifted locally, the amount of shift been quantified but Is clinically obvious, is related to depending on the depth of the preparation. The surface the occlusal fit of the correlation and function restora- sensor in the camera registers this line shift, and the tions. In the correlation mode, the Cerec 2 system computer calculates the corresponding depth. The required significant expenditure of time,'" which was depth scale in this procedure depends, among other reduced to tbe unavoidable minimum (correlation and things, on the angle of triangulation. function) with the Cerec 3 system.

700 Voiurne31, Number 10, 2000 Mor m an n/B indi

TABLE 1 Technical characteristics of the Cerec 3 recording and design unit

New technoiogy Property Ad yan tag es Cerec camera Principie: Active doubie triangulation. Eliminates adjusting Sayes time, especiaily in Recording of the oavity from 2 procedure the 2-impression tech- different triangulation angles provides niques, function and immediate deplh scale of > 20 mm correlation.

image processing Rapid "twin grab board" for the Provides vertically orienled Eliminates relearning Sirocam Cerec intraorai measuring optical impression on the for previous users. camera. oblong formatt monitor eiiminates waiting time.

Computer Medically approved personai computer incorporates great Eiiminates waiting time with shock protected hard disk. Celeron versatiiity and efficiency in design, performs processor. 466 MHZ. 128 MB RAM, of the Windows system: grinding and construction 8-GB hard disk: CD-ROM, 1.44-MB network ready. simultaneously: makes 3.5-inch disk drive: accessory ports, patient data avaiiabie 1 paraliel. 1 sériai, 2x USB Ethernet, through Sidexis and net- RJ45TP, 100 MB, radio controi optional. work conneotion: aliows use of other programs.

TABLE 2 Fabrication time (min) of an onlay with replacement of 3 cusps (n = 3)

Cerec 2 Cerec 3 Program Mean (SD] Mean {SD) Extrapoiation Crown 1.x software for 3296{1.08) 23.68 (1.04] Cereo 2 and Cerec 3 crown software, both with morpboiogic proposal means, one optical impression, design, and grinding of form

Correlation Cerec 2 1 .x correlation software. 33.82 (0.82) 23.24 (0.34) Cerec 3 crown program, both with morphoioglc proposai means; 2 optical impressions, design, and grinding of form

Function Cerec 3 crown software with — 24.82 (0.49) morphologic proposai means; preparation and functionai impressions, design, and grinding cf form

Fig 1 Cerec 3 recording and construction unit ar.d tiie Cerec 3 grinding unit. The iartet is connected by radio controi to the recording and ocnslruotion unit to receive miiiing data, indepen- dent of its location within the practice.

701 Quintessence Internationai • Môrmann/BindI

TABLE 3 Technical characteristics of the Cerec 3 gritidmg unit and the radio control communication to the recording and design unit

New technology Property Advantages Doubie grinding unit Grinding 1,6-mm cylindricai diamond Provides an Saves time in tinishing instruments or 1.2- and t .6-mm cylindncai ceci usa i design of occlusion. diamonds with 45-degree that is true to taper angle on top detail. Controi of Symmetric grinding by the Aiiows tensicn-free Pi aces less stress grinding instruments. Predictive grinding, reducing stress en ceramic. Protects control of advance and on ceramic and grinding the grinding instruments. real-time ioad detection instruments. Lenglh ct 25-mm maximum at Is prepared for fixed restoration present; prepared for 35 mm partial .

Radio control communication Security 1 -m distance to other Allows cabie-free Aiiows pi ace ment of electric devices bi-directional data Cerec 3 unit compo- transfer to grinding unit. nents as desired. Effective 50 m in cicsed room: Ailcws radio range 300 m outside controi ot the grinding unit whiie the next design is generated on data acquisition and ccntrol unit. Power 10mW Connector V24/RS 232

Three-dimensionai chairside construction pm-grit diamonds. These burs are floor- and wall-cut- ting cylindrical diatnonds of 1,2 or 1,6 mm in diameter, Separation into the chairside Cerec 3 recording and as previously used in the Cerec 2 instrument for grind- design unit and the Cerec 3 grinding unit (Fig 1) was ing anterior tooth crowns. In addition, a tapered cylin- the result of user considerations and the possibility of drical diamond is used to shape the occlusal compo- using a proven radio control system (Tables 1 and 3), nent of the restoration. The angle of taper is 45 degrees. Cerec 3 thus is a CAD-CAM system that may be used The 2 instruments act together sytntnetrically in the as desired in the practice. In 6 months' clinical experi- shaping process. The control of anticipated forward ence, in routine use, the radio control system allowed movement and the real-time load detection permit a the operation to be free from disturbance, regardless more flexible and more precise design of the occlusal of the location of the units in the clinic. surface than is possible with Cerec 2, In turn, that In the dental practice, location of the devices will leads to better fit of complex onlays and half and 3- be detertnined by the availability of space for the sepa- quarter crowns overall. Moreover, it provides tnorpho- rate functions. Its versatility and flexibility in use logically better adaptation, as well as better appear- should fulfill the desires of a broad user specttitm. For ance of the occlusal design. example, work can continue with the design unit while grinding is carried out by the grinding unit. The Indirect (semichairside) fabrication of restorations expansion and combination possibilities of the Cerec 3 system with the Sirocam 2 intraoral camera and the The Cerec Sean unit consists of the Cerec 3 grinding Sidexis digital radiography system were not yet avail- unit with a laser-point sensor mounted on the drive able when the system was tested. Nevertheless, opticai motor of the conical bur (Table 4). With this device, a impressions and designs were transmitted without dental cast of a clinical situation (eg, a mesiodisto- problems via e-mail. occlusai cavity of a third ) can be scanned 3- dimensionally, hne by line, in about 5 minutes, Double grinding unit Tbe procedures for rapid impression and cast fabri- cation are described in the case reports. The scanning The computer-controlled double grinding unit dis- process is controlled by Cerec 3 software and proceeds penses with the grinding wheel and uses 2 individual in 2 steps witb different angulations. This makes the cutting devices, each of which is coated with 64- scanning dependable and corresponds to the measuring

702 Volume 31, Number 10, 2000 Mötmann/Bindl

TABLE 4 Technical characteristics of the Cerec Scan computer-aided design-computer-aided machining unit

Technology Property Advantages Laser scanner Laser triangulation scanner with Creates line-by-line Cost-saving smail triangulation angle, focused 3-dimensional model 3-dimensional process. measunng region with digitai sensor in minutes. Provides same precision guidance in the Cerec 3 grinding unit, as Cerec 3 technique. controlied iaser intensity

Cerec Scan grinding unit Cerec 3 gnnding unit with buiit-in Uses Cerec 3 grinding Allows rapid, direct laser scanner controls. tabrication of single-tooth restorations. Provides same precision ot fit as Cerec 3 technique. Restoration length: 25 mm Allows scanner ana Can be controlled from maximum at present; prepared for grinding to shape in the recording and design 35 mm a single unit. unit.

Computer Standard personal computer and Provides design and Allows use ot existing monitor or laptop, witii performance control of shaping. equipment capabilities and connectors for 3- dimensional picture and design unil

Software Cerec 3 design software Preferably extrapolation Allows cost-effective use.

TABLE 5 Technical characteristics of the Cerec 3 software and Cerec Link

Tecfinology Property Advantages Cerec 3 iniay/ontay Standard software for Cerec 3 and Allows inlay and onlay Suffices for conservative Cerec Scan design with extrapolation treaiment. and correlation modes.

Cerec 3 Supplemental software for Cerec 3 Aliows fabrication Supplements standard of veneers. software.

Cerec 3 crown Design software for Cerec 3 and Contains extrapolation. Provides complete soft- Cerec Scan for fabrication of design, and correlation ware package for Ihe full posterior tooth inlays, oniays, modes. range of applications. veneers, half, three-quarter, and complete crowns, and anterior tooth crowns and veneers

Cerec Link Software for design of Cerec 2 Contains Cerec 3 Provides Cerec 3 design restorations on a personal software. comfort to Cerec 2, computer or laptop

703 Quintessenae International Mörmann/Bindl precision of the Cerec 3 camera. Construction proceeds of the occlusal pattern. To simplify this process for the with Cerec 3 software directly on the scan view, analo- user, the initially indicated partial equators of the 2 gous to the well-known procedure (Table 5), Running adjacent teeth are automatically called up (Fig 2e). the program requires a standard PC or laptop with high The 2 computer images are superimposed in a matter capacity and interfaces as they exist for the 3-dimen- of a few seconds. sional recording and construction unit. After the floor lines were drawn along the prepara- tion margins, the principal mesiodistal direcfion of the design was established. In the next step, the position CASE REPORTS and height of the distolingual and buccal cusps were established (Fig 2f), For orientation to the oeclusal pat- In a 6-month trial, approximately 250 patients were tern (Fig 2g), it is possible to go back and forth between treated with the various types of restorations by 8 den- the preparation and the occlusal impressions at the tists. The clinical application of the technique is click of a button (swap mode). In this manner, the posi- described through 2 case reports. tion and the height of the cusps to be constructed were shown (Figs 2f and 2g). In the next design step, the Case 1: Direct (chairside) fabrication of an onlay equator proposed by the system was adapted to the individual situation (Fig 2h), Finally, the computer- A 48-year-old woman desired replacement of all exist- aided design was checked in cross section to compare ing restorations with ceramic substitutes. the cuspai heights of the design to the occlusal pattern Treatment was to begin with the maxillary right first and adjusted by moving the red dots up or down as molar (Fig 2a), The oral health of the patient was required, as has been described previously,'" restored in a prehminary phase through oral hygiene Activation of the grinding program automatically instruction and treatment of gingivitis and periodonti- stored the design on the hard disk and proposed a tis before treatment with a Cerec 3 onlay. ceramic block size, ProCAD ceramic (Ivoclar) was The occlusal relationships of the amalgam restora- selected and inserted into the milling chamber (Fig 2i), tions were evaluated with Hanel foil. The existing The program calculated the onlay automatically from occlusion served as the pattern for the computer-aided the floor, equator, marginal ridge, and fissure fines. design; only the mesiobuccal was to be raised The wall and floor cutters prepared the restoration within the framework of the reconstructioti. The simultaneously from the distal to the mesial (Figs 2] "Function 11" setting was selected as the design mode. and 2k), After about 15 minutes of shaping time, the This requires an optical impression of the oeclusal pat- prepared ceramic was removed from the chamber, and tern (occlusal impression), followed by an optical the connector was removed abrasively. impression of the preparation [preparation impres- The onlay was inserted, and, after adjustment of the sion). Following placement of a rubber dam (Premium proximai contacts, the marginal fit was checked (Figs Rubber Dam. Heraeus), the first molar and the 2 adja- 21 and 2m). The occlusal surface was refined with cent teeth were powdered, and the occlusal impres- flame-shaped diamond instruments (Nos, 9205 and sion was made (Fig 2h), 2504, Intensiv), 40- and 8-pm grit, and the milling The first molar was vital and restored with amal- grooves on the external surfaces were smoothed. To gam. The existing restoration, liner, and caries were coat the ceramic, the restoration was subjected to removed completely so that all remaining sound glaze firing at 1,050°C for 1 minute in the Atmomat dentin was exposed. An extensive dental substance furnace (Vita), defect was exposed: the buccal cusps no longer had The internal surfaces of the onlay were etched with support from dentin. These cusps therefore were Ceramics-Etch (Vita), as previously described," and shortened by 2 mm and included in the preparation. silanized with Monobond (Vivadent), Tbe tooth was Only the mesiolingual cusp was retained at its full prepared for adhesive restoration with the Syntac- height (Fig 2c). Heiiobond system (Vivadent), according to the direc- When the preparation had been powdered, the tions of Krejci et al,'^ as previously described by Bindl optical preparation impression was made (Fig 2d), and Mormann," The onlay was bonded with When this impression is made, it is important to Variolink UltraBase (Vivadent) and polymerized for a ensure that the preparation lies at the center of the total of 6 minutes with the Heliolux DLX polymeriza- monitor screen and that it is sharp and free of blur. tion lamp (Vivadent),™ Moreover, the optical impression must he made in After the rubber dam was removed, excess luting such a way that all regions of the prepared cavity are composite was removed with Proxoshape files visible. This impression should be made from a direc- (Intensiv), 40- and 8-nm grit, and with fiexible disks tion similar to that used for the first optical impression (Sof-Lex, 3M Dental), The centric occlusion was

704 Volume 31, Number 10, 2000 Mörmann/Binöi

Fig 2a Presenting occtusai appearance ot Fig 2b PowOered first molar ana adjacent ttie maxiiiary ngnt tirsl molar ot the 4a-year- teeth atter placement of the rubber dam. old patient. The ocoiusai surface ot the existing restora- tion can tie used as the oooiusai pattern.

Fig 2c Preparation foi recording a ceramic Fig 2d Powdered preparalion for an opti- Cerec 3 onlay to lepiace the buccai cusp cai impression wilh the Cerec 3 camera and the distoiingual cusp.

705 Ouintessence International • Mörmann/Bindi

Fig 2e Optical impression ol the preparation on the Cerec 3 Fig 2f Cusp Design proposed by ttie Cerec 3 system The posi- monitor. Partial mesiai and distai equators (yeiiow iines) are drawn tion and height of the cusps can be evaluated on the opticai lo simplify the ciioice of direction of the camera for the second impression. The height of the marked distciinguai cusp (red viewing by the user square) is shewn (17.68 mm).

Fig 2g Ciicking on the switching icon cails up the ccclusai pat- lern. The cusp markings remain in piaoe. The cusps to be con- structed can be adapted and modified to correspond to the amal- gam restoration.

706 yolume31, Number 10, 2000 /lörmann/Bindl •

Fig 2h Complete view of ihe monitor. The left window sinows tiie equator line (yeliow] and liie marginal ridge (blue] The upper right window (projection] shows the line cf the marginal ridge as seen frcm the cen- ter ol the (ioor of the cavily. The section shows the disial marginal ridge region with the distolinguai cusp (lett margin of the window] and the distobuccal cusp (right margin ct the windcw] The lower nghl window shows a cross section through the computer-aided design (blue) and the ccclusal pattern (green) in the region of the distai cusp. The red dots indicate section points of the marginai ridge, cuspiine, tissure, equa- tor, and floor iines.

Fig 2Í Milling chamber of the Cerec 3 miliing unit with the drive Fig 2j View of the chamber frcm abov. •• ind conical motor ot the conical bui (ieft). drive motor ot the tioor grinder burs work simultaneousiy. Copious water u„_'..::y :;. id removai of (right), and spindle tor the ceramic block (in place). grinding debris are provided by water sprayed from 2 directions.

707 Quintessenoe International /lörmann/Bindi

Fig 2k Delaii view of the partiaily formed onlay The conical bur Fig 21 Buccai view of the well-fitting oniay. (top) prepares the occlusal surfaoe and the cusps, the floor bur (bottom) forms ihe wall and floor regions.

Fig 2m (left) Occlusal view of the well-fit- ting onlay.

Fig 2n (right) Adhesiveiy inserted oniay after compietion of the giaze firing. The sec- ond premoiar also was restored with a Cerec onlay.

checked with Hanel foil and adjusted where neces- (Fig 4a), After placement of a rubber dam, the existing sary. Protrusion, niesiotrusion, and laterotrusion were restoration, liner, and caries were removed completely to checked with foils of a different color, and adjustments expose all remaining sound dentin (Fig 4b), An were made as required. The goal was to achieve inter- expanded niesio-oeclusodistal cavity with supragingival ferenee-free static and dynamic occlusion. The rough position of the mesial and distal shoulders remained. surface areas resulting from the grinding adjustments A small (approximately 3-cm-long) metal partial tray were smoothed with flexible Sof-Lex disks {Fig 2n). was used for the impression. The partial tray was brushed with an alginate adhesive (Fix Tray Adhesive Case 2: indirect (semichairside) for alginate, DeTrey/Dentsply), and an alginate im- fabrication of an inlay pression was formed (Blueprint Cremix, DeTrey/ Dentsply). This impression was poured in a quick-set- The Cerec 3 unit, with a closeup of the laser scanner in ting model silicone (Kwikk-Model Fiuid, R-Dentai} with place, is shown in Fig 3, A 44-year-old man desired re- the aid of a mixing cannula on plaster shaker. The car- placement of a resin composite restoration in the man- rier plate of the Cerec Scan holder was pressed into the dibular right second with a ceramic restoration still plastic silicone model. After 2 minutes' setting time,

708 Volume31, Number 10, 2000 Môrmann/Bindl

Fig 3 Cerec-Sca'i ur.r, •.viri posed View of the laser scanner

Fig 4a Occlusal view of fhe fractured com- Fig 4b Occlusal view of Ihe second pre- po5Íte resforafion on tfie mandibular right molar after placement of the rubber dam second premolar in a 44-year-old patient. and preparafion of fhe cavity.

Fig 4c (ieft) Scan holder. An alginafe impression of the cavify is made with fhe aid of a parfial tray. The impression is poured wifh a quick-setting silicone. The carrier plate of the Cerec Scan holder IS pressed direcfly into tiie plastic model

Fig 4d (below) Scan model. After (he alginale impression is removed and the silicone is trimmed, the carrier plate can be turned into position tor scanning through the ball joint

the partial model, still adhering to the scanner holder, applied to the partial model, the scanner holder was could be removed from the partial impression (Fig 4c), placed in the milling chamber of the Cerec-Scan unit Gross excess silicone flash was removed with a scalpel and scanning was begun. Scanning required approxi- mately 5 minutes. The scanner holder, with its mounted model, was placed in the proper optical orientation (Fig 4d), After the optical impression appeared on the moni- Adjustment of the direction of insertion was performed tor (Fig 4e), the construcfion of the mesio-occlusodistal with a ball-joint articulator. When powder had been inlay began in the extrapolafion mode,^' Activafion of

709 Quintessence Infernational • Mörmann/Bindi

Fig 4e Overall view of the monitor fol- iowmg completion of the computer- aided design ot the iniay. The ieft win- clow shows the marginal ridge (yeilow] and fissure iines (biue). The upper right window (projection) shows the fissure iine as seen from the oenter of the cav- ity lloor. A cross section through ttie computer-aided design is seen m the iower right window.

Fig 4f Buccal view of the tried in inlay. Fig 4g Lingual view of fhe adhesively tned m inlay

Fig 4h Occiusai view ot the adhesively inserted inlay after pol- ishing.

710 Volume31, Number 10, 2000 Mörmann/Bindl • the grinding icon led automatically to storage of the construction design on the hard disk and to the sugges- It was the intention of the initial developers to pro- tion (by the program) for use of a certain ceramic block yide the dentist with this sort of versatile technol- ogy.''' The Cerec 3 system continues this philosophy size. In the present instance, Vita Mark II ceramic while supporting both méthodologie alternatives. For (Vtta) was used. The program calculated the onlay the user experienced in direct (chairside) applications, automatically from the floor, equator, marginal ridge the completely optimized and accelerated design with and fissure lines. The shaping process was complete simultaneous control of projection and section views, after approximately 8 minutes. the elimination of adjustments, and the rapid superim- The restoration was tried in and, after adjustment of position of occlusal registrations are beneficial. These proximal contacts, precision of fit in the marginal qualities make precise, relaxed work with perfect regions was examined (Fig 4f). The ceramic and the results a reality. This is true for complete-quadrant tooth were prepared for adhesive insertion as described restorations as well. for the first case. Tetric fVivadent) light-curing poste- Scientific recognition of the Cerec method is based rior composite was used as a high-viscosity luting mate- on studies evaluating the quality of inlays and onlays ria! with the aid of a Siroson (Sirona) ultrasonic unit. prepared directly hy dentists.--' The oft-repeated, so- After removal of the rubber dam, excess composite called inferiority of the direct intraorai optical impres- was removed with files (40- and S-pm grit). Centric sion to optical surveying of the model can be attri- occlusion was checked with Hanel strips and adjusted buted, in the author's opinion, to the extent of pracfice by grinding. Protrusion, mesioclusion, and laterocclu- or the preference of the user rather than to deficien- sion were checked with contact strips of a different cies in the measuring technology.-^'^^ Studies also con- color, and grinding adjustments were made as firm this in terms of precision of fit of Cerec 2 crowns required. The intent was to obtain interference-free and their clinical quality.'"'' static and dynamic occlusion. The ceramic surface was This clinical trial did not reveal any differences in polished to a high gloss finish with flexible disks (Sof- precision of fit between Cerec 3 and Cerec Scan for Lex), polishing brushes (Occluhrush, Hawe-Neos], inlays, onlays, or crowns. In view of the computing and diamond polishing paste (Porcelain Paste, Shofu capacity of Cerec 3 and the related potential for Dental) (Figs 4g and 4h), expansion in superimposition and split-screen viewing of optical impressions, a broad spectrum of develop- ment is available for both direct and indirect fabrica- DISCUSSION tion of fixed partiai dentures.-"' Cerec Scan increases the fiexibility of the product Evaluation of innovations, particularly in dentistry, is and the number of possibilities for its use. First, Cerec directed toward the practical usefulness of the newly Scan makes fabrication of single-tooth restorations available product. For the Cerec 3 system, the innova- possible; later, expansion to complete-quadrant pro- tion is found in the technical improvement in all com- duction and fixed partial dentures by scanning of ponents. The improvements are reflected in increased occlusal registrations is planned. The unit offers prac- processing quality and processing expansion. They titioners with technically and financially limited provide clear improvements in the quality of the resources the opportunity to use CAD-CAM technol- ceramic restorations with natural morphology and fine ogy. Later expansion with the Ccrcc 3 intraorai cam- surfaces and their adaptation to individual tooth era and control unit provides a sensible buildup of the preparations. The product design is the result of 14 system. The Cerec 3 software also can be used with an years' development.^^ existing PC or laptop and the Cerec 2 unit. This makes it possible for the Cerec 2 user to learn the Cerec 3 The improved optical measuring process elimi- software and to construct additional restorations while nates the required adjustment of the depth scale. The the Cerec 2 unit is milling. benefit lies not only in time saved but also in the enormous simplification of use. A number of previ- The change in the form grinding system from disks ously required operating stcps-the physical reasoning to a cylindrical floor bur and a conical occlusal milling for which was complicated-are eliminated. This way, bur was made deliberately in the interest of a more one major difficulty in operating the Cerec was defin- flexible shaping technique, one that is better adapted itively eliminated, irrespective whether the optical to the individual tooth preparation and that can repli- impression was applied directly in the oral cavity or cate the occlusal morphology better. The special indirectly in the dental laboratory. In every case, the instrument control provides longer life for the dia- dentist decides, in accordance with his or her clinical monds and is more economical. and practical experience, whether he or she wants to work directly or indirectly with Cerec."

711 Quintessence International • Mörmann/Bindl

High value is provided for the system not only 12, Bindl A, Windisch S, Mörmann WH. Vollkeramische Cerec through use of a standard computer and operating sys- CAD/CIM frontzahnkronen und Frontzahnkronen kapp en. tem, but also by the possibility of additig the Sirocam Int [ Comput Dent 1999;2:97-111, 13, Mörmann WH, Bindl A, Die CEREC-Computerkrone-erste 2 intraoral color videocamera and the Sidexis digital klinische und wissenschaftliche Erfahrungen, Dent Magazin radiography system. It is a multimedia system as well, 1998:16:82-91. suitable for user training and patient education. Thus, 14, Mürmann WH, Bindl A, Lüthy H, Rathke A, Effects of this comhination of the Cerec 3 system is a center for preparation and luting system on all-ceramic computer-gen- diagnosis, restoration, training, and documentation in erated erowns, Int I Prosthodont 1998;ll:333-339, the dental practice. 15, Mörmann WH, Bindl A, Lüthy H, Rathke A. Der Einfluss von Praparation und Befestigungsmethode auf ccniputerge- fertigte Vollkeramikkronen. Quintessenz Zahntech 1999; 25:649-657, REFERENCES 16, Mörmann WH, Bindl A, Richter B, Apholt W, Toth RT, Cerec computer aided design: Full ceramic crowns. In: t, Mormann WH. Kompositinlay: Forschungsmodell mit Mörmann WH (ed), CAD-CIM Lihrary, Zurich: SFCZ Praxis-potential? Quintessenz 1982:33:891-1900. Publishing, 1999:2:56-100. 2, Mörmann WH. Ííeramikinlay-Die Seitenzahnfijllung der 17, Mörmann WH, Brandestini M, The fundamental inventive Zukunft, Presented at the 4th International Quintessence principles of CEREC CAD/CIM and other CAD/CAM Symposium, Karlsruhe, Germany, 30 March 1985, methods. In: Mörmann WH (ed), CAD/CIM in Aesthetic 3, Mörmann WH, Brandestini M. The CEREC Computer Dentistry, CEREC 10 Year Anniversary Symposium, Reconstruction-Inlays, Onlays, arid Veneers Berlin: Quin- Chicago: Quintessence, 1996:81-110, tessence, 1989. 18, Toth RT, Mörmann WH. Cerec 2 vollkeramische CAD/CIM 4, Mörmann WH, Brandestini M, Ferru A, Lutz F, Krejci I. Computerkronen, Konstruktionen im Front- und Sciteti- Marginale Adaptation von adhäsiven Porzellaninlays in zahnhereich. In: Mörmann WH (ed), CAD-CIM Library, vol vitro. Schweiz Monatsschr Zahnmed 1985;95:1118-1129. 1. Zurich: SFCZ Publishing, 1999:56-99. 5, Mörmann WH (ed¡. International Symposium on Computer 19 Krcjci I, Lutz F, Mörmann WH, Zahnfarhene adhäsive Restorations State of the Art of the Ceree Method. Chicago: Restaurationen im seitenzahnbereich, Zurich: Eigenverlag, Quintessence, 1991. 1998, 6, Mörmann WH (ed). CAD/CIM in Aesthetic Dentistry. 20, Besek M, Mörmann WH, Persi C, Lutz F, Die Aushärtung CEREC 10 Year Anniversary Symposium. Chicago: Quin- von Komposit unter CEREC-inlays. Schweiz Monatsschr tessence, 1996. Zahnmed 1995;105:1123-1128. 7, Schmalz G, Federlin M, Geurtsen W, Sind Keramik-Inlays 21, Richter B, Mörmann WH, Cerec 2 voll keramische CAD/ und-Veneers wissenschaftlich anerkannt? Dtsch Zahnärtztl CIM Inlays und Overlays In: Mörmann WH (ed). CAD- Z 1994:49:197-208, CIM Library, vol 3, Zurich: SFCZ Publishing, 1999:31-58, 8, Pfeiffer J, The character of Cerec 2. In: Mormann WH (ed). 22, Pfeiffer J, Dentai CAD/CAM technologies: The optical CAD/CIM in Aesthetic Dentistry. CEREC 10 Year Anni- impression, II. Int J Comput Dent 1999;2:65-72, versary Symposium. Chicago. Quintessence, 1996:255-265, 23, Folansky R, Arnetzl G, Smetan M, Haas M, Lorenzoni M, 9, Bindi A, Mörmann WH. Klinische und technische Aspekte The production of Cerec restorations from a plaster cast. Int der Cercc-In-Ceram-Krone, Quintessenz 1996;47:775-792. J Comput Dent 1999;2:37-44, 10, Bindl A, Mörmann WH, Chairside-Computer-Kroncn- 24, Reiss B, Walther W. Ereignisanalyse und klinische Verfahrenszeit und klinische Qualität, Acta Med Dent Helv Langzeitergebnisse mit Cerec-Keramlkinlays, Dtsch 1997:2:293-300, Zahnärzti Z 1998;53:65-68 11. Bindl A, Mörmann WH. Clinical evaluation of adhesively 25, Mehl A, Hickel R, Current state of development and per- placed Cerec Endo-crowns after 2-years-Preliminary spectives of machine-hased production methods for dental results, ] Adhesive Dent 1999;l:255-265. restorations. Int J Comput Dent 1999;2:9-35.

712 Volume 31, Number 10, 2000