J fô O A CLINICAL
REPORTS
CAD-CAM ceramic inlays and onlays: a case report after 3 years in place Werner H. Mormann, DMD, PhD; Marco Brandestini, PhD; Felix Lutz, MD, DMD, PhD; Fred Barbakow, BDS, HDD, MSc; Thom as Gotsch, DMD
A t least three d ifferent techniques are available fo r preparing computer-aided designed (C A D ) a n d c o m p u te r-a id e d manufactured (CAM) inlays and veneers. T h is p a p e r d eta ils a c lin ic a l case in which 13 Cerec CAD-CAM inlays have been functioning for 3 years. Advantages an d lim ita tio n s o f th is system are discussed.
ig h -te c h in d e n ta l offices is mainly lim ited to practice m an ag em en t an d d ata storage. However, com puters also record p e ri odontal findings, occlusal interferences, and during the last 15 years have been used in restorative dentistry to m ap cavity p re p a ra tio n s as well. In itia l w ork in this field began in the 1970s,13 but since the 1980s the Duret (H ennson Interna tional), Minnesota, and Cerec (Siemans) systems have evolved, and reviews of these three systems have recently been published.4’7 Currently, the Cerec system is the only commercially available CAD-CAM system w hich fabricates in lay s, onlays, an d veneers. T h e Cerec system (ceram ic rec o n stru ctio n ) con sists of a self-
H
contained mobile unit with a m iniature three-dimensional intraoral video camera, a m onitor, keyboard, and a computer th at co n tro ls the three-axis diam ondcoated m illing device (Fig 1). Three-dim ensional data of the cavity preparation are recorded when the camera snaps the “optical im pression,” using the p rin c ip le of active tria n g u la tio n . Additional data related to the restoration o u tlin e s are fed m an u a lly in to the co m p u ter, p ro d u cin g the view on the m onitor shown in Figure 2. All the stored data are subsequently used to direct the m illin g process, w hich is carried o u t by a rotating diamond-coated disk (Fig 3). T he inlay is milled from a hom og en o u s, q u a lity -c o n tro lle d , factoryp re p a re d stan dardized ceram ic block w ithin 4-7 minutes; the margins are then checked and the occlusal surface manually ground in. T he inlay and enamel margins are acid-etched, and the restoration is cemented w ith either a light-curing or a dual-curing posterior composite resin. Preferably, Cerec Inlays are cem ented w ith d u a l-c u rin g p o sterio r com posite resin because of its im proved c u rin g ability.7' 10 T his paper describes the first case in which all the amalgam restorations were rep laced by Cerec inlays an d onlays. These restorations have been in place for 3 years.
decided to offer tooth-colored posterior restorations in stress-bearing areas on an experimental basis. Indications and contraindications of the various methods available at the time were e x p lain e d to the p a tie n t. T hese methods included chairside-m ade com posite inlays; laboratory-made composite inlays; laboratory-m ade glass ceram ic inlays (D icor, C o rn in g G lass W orks); laboratory-m ade porcelain inlays; and Cerec system, chairside-m ade ceram ic in la y s .1114 (In fo rm ed co n sen t was o b ta in e d to replace the 13 a m alg am restorations with Cerec inlays and one onlay.) Figure 4 (top) shows the left and right bitewing radiographs taken at the onset of treatm ent. T h irteen Cerec system
CfREC
3 1 /0 1 /1 9 8 8
Report of case
Fig 1 ■ T h ree-d im en sio n al in tra o ra l cam era over a mesio-occlusodistal cavity displayed on the mobile u n it’s video screen.
A 32-year-old fem ale p a tie n t came to the departm ent of cariology, periodontology, and preventive dentistry, Zurich University, December 1985. She requested the rep lacem en t of all her am algam restorations w ith natural tooth-colored material for esthetic reasons. Her general m edical history was n o n co n trib u to ry , and as the p a tie n t’s oral hygiene and gingival condition were excellent, it was
Fig 2 ■ T hree-dim ensional appearance of the m esio-occlusodistal cavity show ing the m esial and distal restoration margins on the video screen.
JADA, Vol. 120, May 1990 ■ 517
CLINICAL
REPORTS
ceramic inlays were placed during five visits w ithin 3 months. Cavity walls were essentially prepared parallel to each other, but the enamel m argins were not bevelled. The gingival and lateral proxim al enamel m argins were short-bevelled by 45° to form adhesive margins for the bonding procedure. Occlusal enamel margins were not short-bevelled, thus n o t extending the cem entation interfaces reducing the potential loss of cem enting com posite resin. T h e in la y s were m illed from homogenous and almost porefree ceramic blocks (V ita-C erec, V ita Z ahnfabrik). T he ceramic and enamel m argins were etched w ith 5% H F (C erec-E tch, Vita Z ah n fab rik ) an d 35% H 3P 0 4 (E sticidGel, Kulzer), respectively. In this case, the inlays were finally cemented using lig h t-c u rin g co m p o site (H e lio m o la r, V ivadent), lig h t tra n s m ittin g wedges, and transparent m atrix bands.15’16 Figures 5 and 6, respectively, show details of the Cerec restorations in the m a x illa a n d m a n d ib le 3 years after p lacem ent. F ig u re 4 (bottom ) depicts the left and right bitewing radiographs 3 years after the Cerec ceram ic inlays were placed. T he 13 Cerec ceramic inlays were subjectively evaluated by an inde p en d en t clin ical assistan t (TG ) using US Public H ealth Service criteria mod ified to assess stre ss-b e a rin g ceram ic inlays.17 T he modified criteria are pres ented in Table 1 and the results of this clinical assessment are listed in T able 2. D is c u s sio n
T his is the first reported case in which all the a m alg am re sto ra tio n s were
F ig 3 ■ M illin g of th e ceram ic block in the cham ber seen in Figure 1 on the u n it’s lower left.
518 ■ JADA, Vol. 120, May 1990
Fig 4 ■ B itew ing rad io g rap h s d e ta ilin g the clin ical s itu a tio n w ith am algam resto ratio n s in the p a tien t’s left and rig h t sides respectively (top) in January 1986. T he patien t’s left side and rig h t side (bottom ) b itew in g rad io g ra p h s show the 13 Cerec ceram ic inlays after 3 years in place in June 1989.
replaced with Cerec CAD-CAM ceramic inlays. T h e p a tie n t is on a 12-m onth recall, has m a in ta in e d ex cellent oral hygiene during the 3 years, and considers the “experiment” totally successful. The subjective clinical assessment after 3 years is excellent (Table 2). T he Bravo type of defects along the cavity margins were minim al, appearing equally as overhangs an d u n d erfilled m argins, p artic u larly on the occlusal surfaces. T h e co lo r matches recorded after 3 years of function were the same as those noted at cemen tation as only a m inim al range of colors were available at that time. Currently, closer color m atching is possible. Also, a proto ty pe u n it was used to prepare the inlays, and a lth o u g h extensive in vitro testing had been done at that point, o u r clinical experience with the Cerec system was limited. Five visits were required to prepare, cement, and polish the 13 inlays. T he currently available Cerec units are more efficient than the prototypes. T he time required to scan the cavity, design, mill, finish, cement, and polish Cerec inlays and onlays has been recorded by clinicians d o in g field studies. T h e average time recorded in practice to place one-surface inlays (N = 27) was 3 2 + 1 1 min, twosurface inlays (N = 106) was 39 ± 9 min, three-surface inlays (N = 104) was 46 ± 12 m in, and four-surface inlays (N = 35) was 5 7 + 1 1 min. The demand for esthetic tooth-colored stress-bearing posterior restorations is increasing. Several m aterials and tech niques are available to meet this demand,
but problems related to polymerization shrinkage, secondary caries, insufficient resistance to w ear, an d chem ical d is integration still persist. Ceramic inlays, in c o n tra st to com posite types, have physical and chemical properties similar to those of enamel. As the only CADCAM system available to practitioners, the Cerec System fabricates restorations from high-grade, quality controlled VitaCerec ceram ic blocks and m achinable glass ceramic blocks (Cerec Dicor MGCblocks, C aulk). A lth o u g h the various materials used to fabricate indirect inlays are factory-standardized, their subsequent use by chairside assistants, clinicians, and te c h n icia n s has n o t alw ays been uniform. Etched ceramic bonds well to etchedenam el u sin g resin-based com posite cements.810’1418 20 The net polymerization shrin k ag e and net therm al expansion of composite resin cement are low; only a thin layer of composite cement is needed between ceramic and enamel, producing m in im a l w all-to -w all te n sio n .21 Tw o types of H eliom olar were used in this case: one w ith and one w ith o u t ra d i opaque material as shown in postop erative ra d io g ra p h s (Fig 4, bottom ). N either ceramic nor composite cement overhangs were detected clin ically or rad io lo g ically . T h e earlier com posite cem ents were less successful than the types presently used which combine lightand chemical-curing modes, for example, Cerec Cement (Kulzer), Di-Cement (Coltene AG), or Dual Cement (Ivoclar AG). The chemically cured component facil-
CLINICAL
REPORTS
itates the cu rin g in those parts of the cavity inaccessible to the light. Regardless of cavity size, simple box shaped preparations suffice for the Cerec system. Undercuts, which retained am al gams, need not be converted to divergent walls for Cerec inlays, thus conserving maximum amounts of enamel and dentin. In fact, the Cerec camera ignores under cuts when taking the “optical im pres sion.” Generally, am algam cavity m ar gins need only refinishing, and undercut areas are filled in w ith c e m en tin g composite resin during cementation. Cerec system advantages
The advantages of Cerec inlays include long-lasting esthetic appearance and at least a 3-year material stability, as shown in this case. A yet u n p u b lish e d study has recently been com pleted, d etailing the clinical findings of 81 other Cerec inlays in another 29 patients, which have also been in service for 3 years. Further, no abrasion of the o p p o sin g teeth by the ceramic material has been clinically detected. Im pressions of cavity p rep a rations are unnecessary and laboratory procedures are not needed. In addition, as the restorations are cemented in one visit, the p la c in g of tem porary resto rations is unnecessary. T he unit is fully mobile from one dental office to another, and the num ber and duration of visits are less for the placement of Cerec inlays compared with other conventional direct and indirect inlay systems. Cerec system disadvantages
System-related restrictions include the initial investment of the Cerec unit and the 2-day intensive training course needed to m aster the Cerec system . D entists enrolled for these courses have found the handlin g of the three-dim ensional camera and the management of the cavity design steps rath er ch allen g in g in the m ultifaceted clinical situations. Initial le a rn in g phases are stressful an d are considered a system-related restriction. According to a m an u factu rer’s report, Swiss and West G erm an d e n ta l p ra c titioners indicate that they feel totally comfortable with the system after placing 50 to 100 ceramic restorations.
Summary Cumulated laboratory data710-22 indicate that the Cerec CAD-CAM system is ready for use in d en tal offices. In a d d itio n ,
Fig 5 ■ Overview of the six Cerec inlays in the m axilla (top) detailing the p atien t’s m axillary left (middle) and right (bottom) quadrants.
Fig 6 ■ Overview of the seven Cerec inlays in the m a n d ib le (to p ) d e ta ilin g th e p a tie n t’s m a n d ib u la r left (m iddle) and rig h t (bottom ) quadrants.
M ormann : CAD-CAM CERAMIC INLAYS AND ONLAYS ■ 519
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Table 1 ■ Criteria and methods used to assess the quality of the Cerec CADCAM ceramic inlays (modified from the USPHS system). C ontour (using m irror and probe) Alfa Bravo Charlie
Surface m orphology correct, perhaps overcontoured Surface m orphology incorrect, perhaps undercontoured Defective restoration, exposed dentin, or base material
Margin quality: mesial, occlusal, distal (using m irror and probe) Alfa Bravo Charlie Delta
No catches at cavity margin; if present, overhangs and underfilled margins are invisible Probe catches at cavity margin, visible overhangs and underfilled margins; no exposed dentin or base material Probe catches at cavity margin, visible overhangs and underfilled margins; exposed dentin or base material, immobile and uncracked filling Fractured or missing filling
Surface texture (using m irror and probe) Alfa Bravo Charlie
Visual smooth surface, no tactile roughness Visual and tactile surface roughness, no pitting or craters, unpolished fissures Pitted or cratered surface, overall insufficient polish
Color m atching (using mirror) Alfa Bravo Charlie
No apparent color change retaining a shiny surface M inim al loss of translucency, but within the range of normal tooth color Severe surface dulling, not within the range of norm al tooth color
Table 2
■ Clinical assessm ent of the Cerec CAD-CAM ceram ic inlays using criteria characterized in Table 1. Margin quality
T ooth no. and restoration
Contour
4 OD* 5 M O DÏ 13 MOD 14 MOD 15 MOD 18 MO 19 MOD 20 OD 28 OD 29 MOD 30 MOD 31 MO
At A A A A A A A A A A A
Mesial
Occlusal
Distal
A A A A A B A A A A A B
B A A A A
A A A A A A
A A A
-
A A A A A -
Surface texture
Color matching
A A A A B A A A A A A B
A A B B A A A B A A A B
* = Distocclusal. t A = Alfa, B = Bravo. X - M e s i o - o c c lu s o d i s t a l .
the Cerec system is already integrated into the undergraduate operative dentistry course at the Zurich University Dental Institute. According to the manufacturer, 350 units have been placed since becom in g available in E urope in June 1988. T he Cerec system was accepted by the US Food an d D rug A dm inistration in Ju n e 1989. Of the 207 units placed by Ju ly 1989, 161 are in W est G erm any, 14 in Italy, 11 in Sw itzerland, five in D enm ark , 4 each in A u stria an d the United States, three in Sweden and one each in Belgium, Canada, France, H ol land, an d J a p a n (perso n al c o m m u n i cation, Siemens Co, 1989). In 1985, a 32-year-old female patient had 13 amalgam restorations. They were removed and the cavities refilled with 520 ■ JADA, Vol. 120, May 1990
12 Cerec inlays and one Cerec onlay. T his paper describes the clinical appear ance of these CAD/CAM resto ratio n s that have been in function for 3 years. ----------------------------J 'A O A
----------------------------
T h e au th o rs th an k the p a tie n t for perm ission to publish this case and Msses. L. Brandenberger and B. Muller for photographic assistance. In fo rm a tio n a b o u t products mentioned in from the authors. T he has no com m ercial mentioned.
the m an u factu re rs of the this article may be available American Dental Association interests in the p ro d u cts
Dr. M ormann is associate professor, departm ent of preventive dentistry, periodontology and cariology, Dental Institute, University of Zurich. Dr. Brandestini is president of Brains Inc in Zollikon, Switzerland.
Dr. Lutz is professor and chairman, department of preventive dentistry, periodontology, and cari ology; Dr. Barbakow is senior research associate; and Dr. Gotsch is clinical associate, Dental Institute, University of Zurich. Address requests for reprints to Dr. M o rm an n , U niversity of Z urich, D ental Institute, PO Box 138, CH-8028, Zurich, Switzerland. 1. A ltschuler BR. H olodontograph y : an in tro duction to dental laser holography: SAM-TR-734 Report, No. AD 758191 Texas, Brooks AFB, USAF, School of Aerospace Medical Div (AFSC). 1973;78:235. 2. Swinson WE. Dental fitting process. US Patent No. 3,861,044:1973. 3. M ushabac DR. Dental probe, US P aten t no. 4,182,312; 1980. 4. Rekow ED. Computer-aided design and m anu facturing in dentistry: a review of the state of the art. J Prosthet Dent 1987;58:512-6. 5. D uret F, B louin JL , D uret B. CAD-CAM in dentistry. JADA 1988;117:715-20. 6. M orm ann WH, Brandestini M, Lutz F, Bar bakow F. Chairside com puter-aided direct ceramic inlays. Quintessence Int 1989;20:329-39. 7. M o rm an n W, B ran d estin i M. Die CEREC com puter reconstruction. Inlays, onlays und veneers. Berlin: Quintessence, 1989. 8. B randestini M, M orm ann W, Ferru A, Lutz F, Krejci I. C om puter m achined ceram ic inlays: In vitro marginal adaptation. J Dent Res (Abstract no. 305) 1985;64:208. 9. M orm ann W, B randestini M, Ferru A, Lutz F, Krejci I. M arginale A daptation von adhesiven P o rz ellan -in lay s in vitro. Schweiz M onatsschr Zahnmed 1985;95:1118-29. 10. M orm ann W, Jans H , Brandestini M, Ferru A, Lutz F. Com puter m achined adhesive porcelain inlays: m arg in al a d a p ta tio n after fatig u e stress. J Dent Res (Abstract no. 339) 1986;65:763. 11. Fullem ann J, Lutz F. Direktes Kompositinlay. Das neve Verfah fen und Seine In-vitro Testresultat. Schweiz Monatsschr Zahnmed 1988;98:758-64. 12. Jam es DF. An esthetic inlay technique for posterior teeth. Quintessence Int 1983;14:725-31. 13. Adair PJ, Grossman DG. T he castable ceramic crown. Int J Periodont Res Dent 1984;4:32-46. 14. Je n sen ME. A tw o-year clin ical study of posterior etched-porcelain resin-bonded restorations. Am J Dent 1988;1:27-33. 15. Lutz F, Krejci I, Luscher B, Oldenburg TR. Im proved p ro x im a l m arg in a d a p ta tio n of Class II co m p o site resin re sto ra tio n s by use of lig h treflectin g wedges. Q uintessence Int 1986; 17:65964. 16. Lutz F, Krejci I, Oldenburg TR. Elim ination of polymerization stresses at the margins of posterior co m p o site resin resto ratio n s. A new resto rativ e technique. Quintessence Int 1986;17:777-84. 17. Leinfelder KF, Lemons JE. Clinical restorative m a te ria ls an d tech n iq u es. P h ila d e lp h ia : Lea 8c Febiger; 1988:201-21. 18. N a th an so n D, H assan F. Effect of etched porcelain thickness on resin-porcelain bond strength. J Dent Res (Abstract no. 1107) 1987;66:245. 19. S heth J, Je n sen M. L u tin g interfaces and m a te ria ls for etched p o rcelain resto ratio n s. Am J Dent 1988;1:225-35. 20. T aleghani M, Leinfelder KF, Land J. Posterior porcelain bonded inlays. Com pend C o n tin Educ Dent 1987;8:420-5. 21. Gotsch T , Krejci I, Lutz F, Reich T. Defor mation of cavity walls induced by different composite restorative techniques. J Dent Res (A bstract no. 1282) 1989;68:342. 22. Fett HP, Mormann W, Lutz F, Krejci I. Margin adaptation of com puter machined Cerec inlays in vitro. J Dent Res (Abstract no. 1141) 1989;68:324.
REPORTS
CAD-CAM ceramic inlays and onlays: a case report after 3 years in place Werner H. Mormann, DMD, PhD; Marco Brandestini, PhD; Felix Lutz, MD, DMD, PhD; Fred Barbakow, BDS, HDD, MSc; Thom as Gotsch, DMD
A t least three d ifferent techniques are available fo r preparing computer-aided designed (C A D ) a n d c o m p u te r-a id e d manufactured (CAM) inlays and veneers. T h is p a p e r d eta ils a c lin ic a l case in which 13 Cerec CAD-CAM inlays have been functioning for 3 years. Advantages an d lim ita tio n s o f th is system are discussed.
ig h -te c h in d e n ta l offices is mainly lim ited to practice m an ag em en t an d d ata storage. However, com puters also record p e ri odontal findings, occlusal interferences, and during the last 15 years have been used in restorative dentistry to m ap cavity p re p a ra tio n s as well. In itia l w ork in this field began in the 1970s,13 but since the 1980s the Duret (H ennson Interna tional), Minnesota, and Cerec (Siemans) systems have evolved, and reviews of these three systems have recently been published.4’7 Currently, the Cerec system is the only commercially available CAD-CAM system w hich fabricates in lay s, onlays, an d veneers. T h e Cerec system (ceram ic rec o n stru ctio n ) con sists of a self-
H
contained mobile unit with a m iniature three-dimensional intraoral video camera, a m onitor, keyboard, and a computer th at co n tro ls the three-axis diam ondcoated m illing device (Fig 1). Three-dim ensional data of the cavity preparation are recorded when the camera snaps the “optical im pression,” using the p rin c ip le of active tria n g u la tio n . Additional data related to the restoration o u tlin e s are fed m an u a lly in to the co m p u ter, p ro d u cin g the view on the m onitor shown in Figure 2. All the stored data are subsequently used to direct the m illin g process, w hich is carried o u t by a rotating diamond-coated disk (Fig 3). T he inlay is milled from a hom og en o u s, q u a lity -c o n tro lle d , factoryp re p a re d stan dardized ceram ic block w ithin 4-7 minutes; the margins are then checked and the occlusal surface manually ground in. T he inlay and enamel margins are acid-etched, and the restoration is cemented w ith either a light-curing or a dual-curing posterior composite resin. Preferably, Cerec Inlays are cem ented w ith d u a l-c u rin g p o sterio r com posite resin because of its im proved c u rin g ability.7' 10 T his paper describes the first case in which all the amalgam restorations were rep laced by Cerec inlays an d onlays. These restorations have been in place for 3 years.
decided to offer tooth-colored posterior restorations in stress-bearing areas on an experimental basis. Indications and contraindications of the various methods available at the time were e x p lain e d to the p a tie n t. T hese methods included chairside-m ade com posite inlays; laboratory-made composite inlays; laboratory-m ade glass ceram ic inlays (D icor, C o rn in g G lass W orks); laboratory-m ade porcelain inlays; and Cerec system, chairside-m ade ceram ic in la y s .1114 (In fo rm ed co n sen t was o b ta in e d to replace the 13 a m alg am restorations with Cerec inlays and one onlay.) Figure 4 (top) shows the left and right bitewing radiographs taken at the onset of treatm ent. T h irteen Cerec system
CfREC
3 1 /0 1 /1 9 8 8
Report of case
Fig 1 ■ T h ree-d im en sio n al in tra o ra l cam era over a mesio-occlusodistal cavity displayed on the mobile u n it’s video screen.
A 32-year-old fem ale p a tie n t came to the departm ent of cariology, periodontology, and preventive dentistry, Zurich University, December 1985. She requested the rep lacem en t of all her am algam restorations w ith natural tooth-colored material for esthetic reasons. Her general m edical history was n o n co n trib u to ry , and as the p a tie n t’s oral hygiene and gingival condition were excellent, it was
Fig 2 ■ T hree-dim ensional appearance of the m esio-occlusodistal cavity show ing the m esial and distal restoration margins on the video screen.
JADA, Vol. 120, May 1990 ■ 517
CLINICAL
REPORTS
ceramic inlays were placed during five visits w ithin 3 months. Cavity walls were essentially prepared parallel to each other, but the enamel m argins were not bevelled. The gingival and lateral proxim al enamel m argins were short-bevelled by 45° to form adhesive margins for the bonding procedure. Occlusal enamel margins were not short-bevelled, thus n o t extending the cem entation interfaces reducing the potential loss of cem enting com posite resin. T h e in la y s were m illed from homogenous and almost porefree ceramic blocks (V ita-C erec, V ita Z ahnfabrik). T he ceramic and enamel m argins were etched w ith 5% H F (C erec-E tch, Vita Z ah n fab rik ) an d 35% H 3P 0 4 (E sticidGel, Kulzer), respectively. In this case, the inlays were finally cemented using lig h t-c u rin g co m p o site (H e lio m o la r, V ivadent), lig h t tra n s m ittin g wedges, and transparent m atrix bands.15’16 Figures 5 and 6, respectively, show details of the Cerec restorations in the m a x illa a n d m a n d ib le 3 years after p lacem ent. F ig u re 4 (bottom ) depicts the left and right bitewing radiographs 3 years after the Cerec ceram ic inlays were placed. T he 13 Cerec ceramic inlays were subjectively evaluated by an inde p en d en t clin ical assistan t (TG ) using US Public H ealth Service criteria mod ified to assess stre ss-b e a rin g ceram ic inlays.17 T he modified criteria are pres ented in Table 1 and the results of this clinical assessment are listed in T able 2. D is c u s sio n
T his is the first reported case in which all the a m alg am re sto ra tio n s were
F ig 3 ■ M illin g of th e ceram ic block in the cham ber seen in Figure 1 on the u n it’s lower left.
518 ■ JADA, Vol. 120, May 1990
Fig 4 ■ B itew ing rad io g rap h s d e ta ilin g the clin ical s itu a tio n w ith am algam resto ratio n s in the p a tien t’s left and rig h t sides respectively (top) in January 1986. T he patien t’s left side and rig h t side (bottom ) b itew in g rad io g ra p h s show the 13 Cerec ceram ic inlays after 3 years in place in June 1989.
replaced with Cerec CAD-CAM ceramic inlays. T h e p a tie n t is on a 12-m onth recall, has m a in ta in e d ex cellent oral hygiene during the 3 years, and considers the “experiment” totally successful. The subjective clinical assessment after 3 years is excellent (Table 2). T he Bravo type of defects along the cavity margins were minim al, appearing equally as overhangs an d u n d erfilled m argins, p artic u larly on the occlusal surfaces. T h e co lo r matches recorded after 3 years of function were the same as those noted at cemen tation as only a m inim al range of colors were available at that time. Currently, closer color m atching is possible. Also, a proto ty pe u n it was used to prepare the inlays, and a lth o u g h extensive in vitro testing had been done at that point, o u r clinical experience with the Cerec system was limited. Five visits were required to prepare, cement, and polish the 13 inlays. T he currently available Cerec units are more efficient than the prototypes. T he time required to scan the cavity, design, mill, finish, cement, and polish Cerec inlays and onlays has been recorded by clinicians d o in g field studies. T h e average time recorded in practice to place one-surface inlays (N = 27) was 3 2 + 1 1 min, twosurface inlays (N = 106) was 39 ± 9 min, three-surface inlays (N = 104) was 46 ± 12 m in, and four-surface inlays (N = 35) was 5 7 + 1 1 min. The demand for esthetic tooth-colored stress-bearing posterior restorations is increasing. Several m aterials and tech niques are available to meet this demand,
but problems related to polymerization shrinkage, secondary caries, insufficient resistance to w ear, an d chem ical d is integration still persist. Ceramic inlays, in c o n tra st to com posite types, have physical and chemical properties similar to those of enamel. As the only CADCAM system available to practitioners, the Cerec System fabricates restorations from high-grade, quality controlled VitaCerec ceram ic blocks and m achinable glass ceramic blocks (Cerec Dicor MGCblocks, C aulk). A lth o u g h the various materials used to fabricate indirect inlays are factory-standardized, their subsequent use by chairside assistants, clinicians, and te c h n icia n s has n o t alw ays been uniform. Etched ceramic bonds well to etchedenam el u sin g resin-based com posite cements.810’1418 20 The net polymerization shrin k ag e and net therm al expansion of composite resin cement are low; only a thin layer of composite cement is needed between ceramic and enamel, producing m in im a l w all-to -w all te n sio n .21 Tw o types of H eliom olar were used in this case: one w ith and one w ith o u t ra d i opaque material as shown in postop erative ra d io g ra p h s (Fig 4, bottom ). N either ceramic nor composite cement overhangs were detected clin ically or rad io lo g ically . T h e earlier com posite cem ents were less successful than the types presently used which combine lightand chemical-curing modes, for example, Cerec Cement (Kulzer), Di-Cement (Coltene AG), or Dual Cement (Ivoclar AG). The chemically cured component facil-
CLINICAL
REPORTS
itates the cu rin g in those parts of the cavity inaccessible to the light. Regardless of cavity size, simple box shaped preparations suffice for the Cerec system. Undercuts, which retained am al gams, need not be converted to divergent walls for Cerec inlays, thus conserving maximum amounts of enamel and dentin. In fact, the Cerec camera ignores under cuts when taking the “optical im pres sion.” Generally, am algam cavity m ar gins need only refinishing, and undercut areas are filled in w ith c e m en tin g composite resin during cementation. Cerec system advantages
The advantages of Cerec inlays include long-lasting esthetic appearance and at least a 3-year material stability, as shown in this case. A yet u n p u b lish e d study has recently been com pleted, d etailing the clinical findings of 81 other Cerec inlays in another 29 patients, which have also been in service for 3 years. Further, no abrasion of the o p p o sin g teeth by the ceramic material has been clinically detected. Im pressions of cavity p rep a rations are unnecessary and laboratory procedures are not needed. In addition, as the restorations are cemented in one visit, the p la c in g of tem porary resto rations is unnecessary. T he unit is fully mobile from one dental office to another, and the num ber and duration of visits are less for the placement of Cerec inlays compared with other conventional direct and indirect inlay systems. Cerec system disadvantages
System-related restrictions include the initial investment of the Cerec unit and the 2-day intensive training course needed to m aster the Cerec system . D entists enrolled for these courses have found the handlin g of the three-dim ensional camera and the management of the cavity design steps rath er ch allen g in g in the m ultifaceted clinical situations. Initial le a rn in g phases are stressful an d are considered a system-related restriction. According to a m an u factu rer’s report, Swiss and West G erm an d e n ta l p ra c titioners indicate that they feel totally comfortable with the system after placing 50 to 100 ceramic restorations.
Summary Cumulated laboratory data710-22 indicate that the Cerec CAD-CAM system is ready for use in d en tal offices. In a d d itio n ,
Fig 5 ■ Overview of the six Cerec inlays in the m axilla (top) detailing the p atien t’s m axillary left (middle) and right (bottom) quadrants.
Fig 6 ■ Overview of the seven Cerec inlays in the m a n d ib le (to p ) d e ta ilin g th e p a tie n t’s m a n d ib u la r left (m iddle) and rig h t (bottom ) quadrants.
M ormann : CAD-CAM CERAMIC INLAYS AND ONLAYS ■ 519
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REPORTS
Table 1 ■ Criteria and methods used to assess the quality of the Cerec CADCAM ceramic inlays (modified from the USPHS system). C ontour (using m irror and probe) Alfa Bravo Charlie
Surface m orphology correct, perhaps overcontoured Surface m orphology incorrect, perhaps undercontoured Defective restoration, exposed dentin, or base material
Margin quality: mesial, occlusal, distal (using m irror and probe) Alfa Bravo Charlie Delta
No catches at cavity margin; if present, overhangs and underfilled margins are invisible Probe catches at cavity margin, visible overhangs and underfilled margins; no exposed dentin or base material Probe catches at cavity margin, visible overhangs and underfilled margins; exposed dentin or base material, immobile and uncracked filling Fractured or missing filling
Surface texture (using m irror and probe) Alfa Bravo Charlie
Visual smooth surface, no tactile roughness Visual and tactile surface roughness, no pitting or craters, unpolished fissures Pitted or cratered surface, overall insufficient polish
Color m atching (using mirror) Alfa Bravo Charlie
No apparent color change retaining a shiny surface M inim al loss of translucency, but within the range of normal tooth color Severe surface dulling, not within the range of norm al tooth color
Table 2
■ Clinical assessm ent of the Cerec CAD-CAM ceram ic inlays using criteria characterized in Table 1. Margin quality
T ooth no. and restoration
Contour
4 OD* 5 M O DÏ 13 MOD 14 MOD 15 MOD 18 MO 19 MOD 20 OD 28 OD 29 MOD 30 MOD 31 MO
At A A A A A A A A A A A
Mesial
Occlusal
Distal
A A A A A B A A A A A B
B A A A A
A A A A A A
A A A
-
A A A A A -
Surface texture
Color matching
A A A A B A A A A A A B
A A B B A A A B A A A B
* = Distocclusal. t A = Alfa, B = Bravo. X - M e s i o - o c c lu s o d i s t a l .
the Cerec system is already integrated into the undergraduate operative dentistry course at the Zurich University Dental Institute. According to the manufacturer, 350 units have been placed since becom in g available in E urope in June 1988. T he Cerec system was accepted by the US Food an d D rug A dm inistration in Ju n e 1989. Of the 207 units placed by Ju ly 1989, 161 are in W est G erm any, 14 in Italy, 11 in Sw itzerland, five in D enm ark , 4 each in A u stria an d the United States, three in Sweden and one each in Belgium, Canada, France, H ol land, an d J a p a n (perso n al c o m m u n i cation, Siemens Co, 1989). In 1985, a 32-year-old female patient had 13 amalgam restorations. They were removed and the cavities refilled with 520 ■ JADA, Vol. 120, May 1990
12 Cerec inlays and one Cerec onlay. T his paper describes the clinical appear ance of these CAD/CAM resto ratio n s that have been in function for 3 years. ----------------------------J 'A O A
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T h e au th o rs th an k the p a tie n t for perm ission to publish this case and Msses. L. Brandenberger and B. Muller for photographic assistance. In fo rm a tio n a b o u t products mentioned in from the authors. T he has no com m ercial mentioned.
the m an u factu re rs of the this article may be available American Dental Association interests in the p ro d u cts
Dr. M ormann is associate professor, departm ent of preventive dentistry, periodontology and cariology, Dental Institute, University of Zurich. Dr. Brandestini is president of Brains Inc in Zollikon, Switzerland.
Dr. Lutz is professor and chairman, department of preventive dentistry, periodontology, and cari ology; Dr. Barbakow is senior research associate; and Dr. Gotsch is clinical associate, Dental Institute, University of Zurich. Address requests for reprints to Dr. M o rm an n , U niversity of Z urich, D ental Institute, PO Box 138, CH-8028, Zurich, Switzerland. 1. A ltschuler BR. H olodontograph y : an in tro duction to dental laser holography: SAM-TR-734 Report, No. AD 758191 Texas, Brooks AFB, USAF, School of Aerospace Medical Div (AFSC). 1973;78:235. 2. Swinson WE. Dental fitting process. US Patent No. 3,861,044:1973. 3. M ushabac DR. Dental probe, US P aten t no. 4,182,312; 1980. 4. Rekow ED. Computer-aided design and m anu facturing in dentistry: a review of the state of the art. J Prosthet Dent 1987;58:512-6. 5. D uret F, B louin JL , D uret B. CAD-CAM in dentistry. JADA 1988;117:715-20. 6. M orm ann WH, Brandestini M, Lutz F, Bar bakow F. Chairside com puter-aided direct ceramic inlays. Quintessence Int 1989;20:329-39. 7. M o rm an n W, B ran d estin i M. Die CEREC com puter reconstruction. Inlays, onlays und veneers. Berlin: Quintessence, 1989. 8. B randestini M, M orm ann W, Ferru A, Lutz F, Krejci I. C om puter m achined ceram ic inlays: In vitro marginal adaptation. J Dent Res (Abstract no. 305) 1985;64:208. 9. M orm ann W, B randestini M, Ferru A, Lutz F, Krejci I. M arginale A daptation von adhesiven P o rz ellan -in lay s in vitro. Schweiz M onatsschr Zahnmed 1985;95:1118-29. 10. M orm ann W, Jans H , Brandestini M, Ferru A, Lutz F. Com puter m achined adhesive porcelain inlays: m arg in al a d a p ta tio n after fatig u e stress. J Dent Res (Abstract no. 339) 1986;65:763. 11. Fullem ann J, Lutz F. Direktes Kompositinlay. Das neve Verfah fen und Seine In-vitro Testresultat. Schweiz Monatsschr Zahnmed 1988;98:758-64. 12. Jam es DF. An esthetic inlay technique for posterior teeth. Quintessence Int 1983;14:725-31. 13. Adair PJ, Grossman DG. T he castable ceramic crown. Int J Periodont Res Dent 1984;4:32-46. 14. Je n sen ME. A tw o-year clin ical study of posterior etched-porcelain resin-bonded restorations. Am J Dent 1988;1:27-33. 15. Lutz F, Krejci I, Luscher B, Oldenburg TR. Im proved p ro x im a l m arg in a d a p ta tio n of Class II co m p o site resin re sto ra tio n s by use of lig h treflectin g wedges. Q uintessence Int 1986; 17:65964. 16. Lutz F, Krejci I, Oldenburg TR. Elim ination of polymerization stresses at the margins of posterior co m p o site resin resto ratio n s. A new resto rativ e technique. Quintessence Int 1986;17:777-84. 17. Leinfelder KF, Lemons JE. Clinical restorative m a te ria ls an d tech n iq u es. P h ila d e lp h ia : Lea 8c Febiger; 1988:201-21. 18. N a th an so n D, H assan F. Effect of etched porcelain thickness on resin-porcelain bond strength. J Dent Res (Abstract no. 1107) 1987;66:245. 19. S heth J, Je n sen M. L u tin g interfaces and m a te ria ls for etched p o rcelain resto ratio n s. Am J Dent 1988;1:225-35. 20. T aleghani M, Leinfelder KF, Land J. Posterior porcelain bonded inlays. Com pend C o n tin Educ Dent 1987;8:420-5. 21. Gotsch T , Krejci I, Lutz F, Reich T. Defor mation of cavity walls induced by different composite restorative techniques. J Dent Res (A bstract no. 1282) 1989;68:342. 22. Fett HP, Mormann W, Lutz F, Krejci I. Margin adaptation of com puter machined Cerec inlays in vitro. J Dent Res (Abstract no. 1141) 1989;68:324.
