22CERAMIC BLOCKS Available in wide range of shades and sizes More homogenousLess porousMounted on a metal stub
23Effects of surface finish and fatigue testing on the fracture strength of CAD-CAM and pressed – ceramic crown (Hickel - JPD 1999)PurposeTo determine the fracture strength of various all ceramic crowns with and without cyclic loading.
24Material & MethodMachinable ceramic material, Vita Mark II and ProCAD and conventional heat-pressed IPS – Empress crowns were fabricated, with either a polished or an oven – glazed surface finish.Cyclic loading that simulated oral conditions were performed on half of each group.
25ConclusionThe Cerec Pro-CAD crowns had significantly greater strength than the Vita Mark II crowns, better resistance to cyclic loading and lower failure probability than laboratory fabricated IPS empress crowns.
26Cyclic loading significantly reduced the strength of all-ceramic crowns, but had less effect on cerec crowns than on the IPS Empress crowns.Oven-glazing of ProCAD crowns resulted in significantly higher strength and higher resistance to cyclic loading than surface polishing.
27An upto 5 year Clinical Evaluation of posterior In-ceram CAD/CAM core crowns (Mormann – Int. J Prosthodont 2002)Evaluated the clinical performance of posterior CAD-CAM generated In-ceram alumina and In-ceram spinelll core crowns using the corec 2 CAD-CAM system and after 5 years of service concluded that the clinical quality of CAD-CAM generated In-ceram Alumina and In-ceram Spinell posterior crowns was excellent
28Computer generated restoration design Polishing and cementation CLINICAL PROCEDUREPreparation DesignOptical ImpressionComputer generated restoration designMillingPolishing and cementation
35PROCESSING TIME Process Step Coping Bridge framework Scanning Approx. 10minApprox. 20minDesigningApprox. 2 minApprox. 6 minMillingApprox. 15minApprox. 50min
36POLISHING Rough ceramic surfaces are smoothed with clean white stones Polished with- Rubber wheel of fine grit- Diamond impregnated wheels & points
37CEMENTATION Composite resin cement Zinc phosphate Glass ionomer Ceramic restoration that have been etched internally and bonded with a composite resin cement are 50% stronger than similar restoration cemented with zinc phosphate cement (Ludwig 1994)
38Four preparation types were used Effects of Preparation and Luting system on All-ceramic computer generated crowns (Mormann – Int. J Prosthodont 1998)Examined the effect of inside crown form on fracture strength of cemented and bonded crowns.Four preparation types were used
39Machined crown were placed on abutments a. Without any media as control groupb. Cemented with zinc phosphatec. BondedAnd were loaded until fracture
40RESULTSZinc phosphate cemented crowns showed significant increase of fracture load values compared to uncemented control crowns.Fracture load values of bonded crowns were significantly higher than those for cemented crowns.Bonded crowns with thick occlusal dimension showed the highest fracture load values.
41He concluded that bonded all ceramic CAD-CAM crowns with defect oriented inside morphology and increased occlusal dimension showed high fracture load values.
42PROCERA CAD/CAM SYSTEM TITAN CAD/CAM SYSTEM CELAY CAD/CAM SYSTEM CEREC CAD/CAM SYSTEMPROCERA CAD/CAM SYSTEMTITAN CAD/CAM SYSTEMCELAY CAD/CAM SYSTEMCICERO CAD/CAM SYSTEMLAVA CAD/CAM SYSTEM
43CEREC SYSTEM Chair side economical reconstruction of esthetic ceramic. - Cerec 3 – Feb’ 2000
44CEREC CAD-CAM SYSTEM Limitation Cannot mill the occlusal surface Only inlays and onlays
45CEREC – 2 CAD-CAM SYSTEM Milling of occlusal surface possible Inlays, Onlays, veneers and crownsMilling time approx. 10min
46The grinding precision of the cerec-2 is 2 The grinding precision of the cerec-2 is 2.4 times higher than cerec system (Mormann 1997)
47CEREC – 3 CAD-CAM SYSTEM Advanced version Technical improvements Designing and grinding- lesstime (27%)Grinding unit – 2 cutters
49Marginal and Internal Fit of Cerec 3 Cad/CAM All Ceramic Crowns (Kojima – Int. J Prosthodont 2003) Examined the effect of the occlusal convergence angle of the abutment and the computer luting space setting on the marginal and internal fit of cerec 3 CAD-CAM all ceramic crowns.Mandibular second premolar all ceramic crowns were fabricated for nine different conditions using cerec-3 CAD-CAM system
50Occlusal convergence angle of 4,8 and 12° Luting space settings of 10, 30 and 50µm.
52He concluded that when the luting space was set to 30µm, crowns with a good fit could be fabricated with the cerec 3 system, regardless of the occlusal convergence angle of the abutment.
53PROCERA CAD-CAM SYSTEM Nobel BiocareInitially introduced in 1985Titanium copingsUtilizing the latest scanning, CAD-CAM and manufacturing technologiesProcera Allceram crown in 1991Procera Allceram bridge in 1999
54TITANIUM CROWN AND FPDS SUBSTRUCTURE ReadingMillingSpark erosion
55READING The prepared die is attached Contact probe registers the surface
56MILLINGThe probe tip of the reader and the tip of the milling tool are of same size.The graphite electrode is milled
57SPARK EROSION Used in dentistry since 1982 Graphite electrode is fittedRemoves the metal by electricity in the form of controlled sparks to fabricate copings.
64COMPUTER ASSISTED DESIGN Die is oriented verticallyTip of the scanner probe is brought in contactAs the platform rotates, one data point is collected at every degree around the 360° circumference of the die.
65More than 50,000 data points are registered Scanning takes 3minMore than 50,000 data points are registeredVerified on the computer screen for completenessVertical gap
66The finish line of the preparation is marked by the operator at every 10° around the circumference of the die.
67Coping design is selected Merged with the die and its finish line.
68MANUFACTURE OF THE COPING When the design of the coping is finalized, it is saved and transferred through a modem communication link to Procera Stanvik AB in Stockholm Sweden, where the coping is fabricated.
69ADDITION OF THE VENEER PORCELAIN The coping is sent by mail to the dental laboratory where the ceramist finalizes the restoration by addition of Allceram veneering porcelain to create the appropriate anatomic form and esthetic qualities.
71Titanium copings veneered with Procera Ceramics : A longitudinal clinical study (Nilson - Int.J Prosthodont 1994)In 1989, 47 titanium copings veneered with a low fusing ceramic were fabricated for 24 patients. 44 crowns could be examined after a period varying between 26 and 30 months.
72CDA ratings for surface and color changed markedly from the Excellent to the acceptable level. For marginal integrity it was recorded as satisfactory for all crowns and a large majority were rated excellent.
73A comparison of the Fit of Spark – Eroded Titanium Copings and cast gold alloy copings (Wickens - Int. J. Prosthodont 1994)Compared the fit of spark eroded titanium and cast gold alloy copings and showed that the overall fit of titanium copings was comparable to that of gold copings. In marginal areas, the space between die and coping was found to be larger for spark eroded than cast copings.
74TITAN CAD-CAM SYSTEMProduction of metal copings for porcelain fused to metal restorationsDigitizingProcessingMilling
75Conventional Technique PreparationImpressionDieWaxingInvestingCastingDigitizingProcessingMillingConventional TechniqueCAD/CAM system
76DIGITIZING Die is fabricated Mounted on the digitizer Data are recordedShort circuited
77Divided into 200µm x 200µm squares Digitized at least twiceThe finish line and the adjacent 1mm area are recorded first
78PROCESSINGThe main parameters for the copings are then determined – The gap between the coping and the die- The width and shape of the coping
79MILLINGUses titanium alloy dummies of various widths in the form of disks or blocksMilling device consist of two major units- A rotatory drilling element with interchangeable bores- A mobile platform to which the dummy is fixed
80Rough milling inside the coping Three stepsRough milling inside the copingFine milling inside the copingRough external milling
81MULTIPLE UNIT RESTORATION Steps same as for the single unit restorationIt uses master cast made from a multiple unit impressionMaster cast allows the computation of each individual tooth and of the corresponding residual ridge
82Relative parallelism between the CAD-CAM coping margin and the tooth margin in comparison with uneven appearance of same area of a coping manufactured with traditional casting technique
83CELAY CAD-CAM SYSTEMIntroduced in 1992 by Mikrona Technologies, SwitzerlandInlays, onlays, crowns and bridge frameworkNot a true CAD-CAM systemMany features in common
84A light cured composite replica Either directly or indirectly Replica is mountedScanning tools used to traceMilling tools removes ceramic
85Bulk reduction by rough diamond milling disc Fine milling discContouring by diamond pointMilling time 40mins – three unit bridge
87CICERO CAD-CAM SYSTEM Computer integrated crown reconstruction First technical concept- by Denisson et al in 1999Crowns with different ceramic layers such as high alumina core, dentinal and incisal porcelain for maximal strength and enhanced esthetic.
88Preparation of Scan Model Design of crown layer build-up STEPSPreparation of Scan ModelOptical ScanningDesignOcclusionDesign of crown layer build-upProduction process
89PREPARATION OF THE SCAN MODEL Model is marked with black/white contrast
90OPTICAL SCANNING Obtained by laser scanning of the cast Upto 1,00,000 surface points are recorded per minute
91DESIGN Appropriate tooth selected Mesial and distal contact are outlinedThe margin line of new crown is adjusted
92OCCLUSIONThe new crown is superimposed on the opposing teeth to check for occlusion
93DESIGN OF CROWN LAYER BUILD-UP The interior and exterior tooth surfaces are designed and interface surfaces between cement and ceramic core and between dentin and incisal porcelain are defined.Thickness of the ceramic core of 0.7mmCeramic core – die cement thickness of 0.02mm is adjusted.
94PRODUCTION PROCESS Refractory block is fitted Negative of the inside surface of the crown is milled
95- Diamond cylinder of 5.3mm dia - Diamond rounded disk of 09.3mm dia Cutting tools used- Diamond cylinder of 5.3mm dia- Diamond rounded disk of 09.3mm dia- Diamond pointed tool of 0.9mm diaAutomatically exchanged
96High strength aluminium oxide based ceramic is applied and sintered Ceramic is grounded to calculated oversize to compensate the shrinkage that will occur during the final sintering
97Dental porcelain applied and fired After firing block is placed on milling machine and interface between dentinal and incisal porcelain is milled
98Translucent incisal porcelain is applied, fired and milled
99LAVA CAD-CAM SYSTEM Produce high strength all ceramic crowns and FPD’s Uses yttrium tetragonal zirconia polycrystals (Y-TZP) based materialIntroduced as a hip replacement material in early 1990’sHigh fractured strength 900 – 1200MPa and biocompatibility
101Saw cut working cast is mounted on the scanner STEPS IN FABRICATIONSaw cut working cast is mounted on the scannerThe configuration of the tooth preparation are scannedScanning process takes- Crown – Approx.5min- 3 unit FPD – Approx.12min
102- Crown coping – Approx.35min - 3 Unit FPD – Approx.75min Produces an enlarged framework to compensate shrinkage during sintering process.Average milling time- Crown coping – Approx.35min- 3 Unit FPD – Approx.75min
103The framework is sintered in the Lava Therm Pre programmed to run for 8hrs, including the heating and cooling phases.The sintered framework is then veneered
106To conclude,Computer graphics and CAD-CAM have revolutionized dentistry. It is now possible to provide equivalent of a cast restoration in a single appointment
107BIBLIOGRAPHY Philips Science of Dental Material, - ANUSAVICE Art & Sciences of Operative Dentistry- STURDEVANT’SDental Clinics of North America – Fixed prosthodonticsFundamentals of Fixed prosthodontics – SHILLINGBURGContemporary fixed prosthodontics – ROSENSTEILRestorative dental material – CRAIG