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Information systems Treatment systems TECHNOLOGICAL TRENDS IN DENTISTRY
INTRAORAL IMAGING SYSTEM
COMPUTER IMAGING SYSTEM
DIGITAL RADIOGRAPHIC SYSTEM
COMPUTERIZED PERIODONTAL PROBE
RADIOGRAPHIC IMAGE PROCESSING SYSTEM
TREATMENT SYSTEMS Abrasive system Laser system
CAD-CAM SYSTEM Acronym for computer aided designing and computer aided milling or machining.
BRIEF HISTORY Increasing demand Restoration at a single appointment Development- began in 1970s with Duret in France. French system - in 1983 by Dr.Francois Duret
On September 19, 1985, the first ceramic inlay was produced- at the dental Institute of the University of Zurich. Mormann 1985 in Zurich, Switzerland
FUNDAMENTAL PRINCIPLES OF CAD/CAM SYSTEM CSD CAD CAM
ADVANTAGES One visit restoration Time saving Improved esthetics Good morphology Improved crown fit
Excellent polish Less fracture due to single homogenous block Wear hardness similar to enamel (Craig 1980) Minimize cross infection Good patient acceptance
DISADVANTAGES Need for costly equipment Need for extended training Technique sensitive Inability to image in a wet environment
MACHINABLE CERAMIC MATERIALS Dicor MGC Vita Mark II Inceram Alumina Inceram Spinell Inceram Zirconia Pro-Cad Procera Allceram
MACHINABLE CERAMIC FRACTURAL STRENGTH Dicor MGC 229MPa Vita Mark II 122MPa Inceram Alumina 500MPa Inceram Zirconia 700MPa Inceram Spinell 350MPa
CERAMIC BLOCKS Available in wide range of shades and sizes More homogenous Less porous Mounted on a metal stub
Purpose To determine the fracture strength of various all ceramic crowns with and without cyclic loading. Effects of surface finish and fatigue testing on the fracture strength of CAD-CAM and pressed – ceramic crown (Hickel - JPD 1999)
Material & Method Machinable 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.
Conclusion The 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.
Cyclic 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.
An 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
OPTICAL IMPRESSION Lacks reflectivity Special Powder Rubber dam
COMPUTER GENERATED RESTORATION DESIGN Restoration is designed Operator moves the cursor 3-D image Design phase – 2 – 8 min.
MILLING Computer selects Block is inserted Milling device is activated Three axis of rotation cutting machine
PROCESSING TIME Process StepCopingBridge framework ScanningApprox. 10minApprox. 20min DesigningApprox. 2 minApprox. 6 min MillingApprox. 15minApprox. 50min
POLISHING Rough ceramic surfaces are smoothed with clean white stones Polished with -Rubber wheel of fine grit -Diamond impregnated wheels & points
CEMENTATION 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)
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
Machined crown were placed on abutments a. Without any media as control group b.Cemented with zinc phosphate c.Bonded And were loaded until fracture
RESULTS Zinc 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.
He concluded that bonded all ceramic CAD-CAM crowns with defect oriented inside morphology and increased occlusal dimension showed high fracture load values.
CEREC CAD/CAM SYSTEM PROCERA CAD/CAM SYSTEM TITAN CAD/CAM SYSTEM CELAY CAD/CAM SYSTEM CICERO CAD/CAM SYSTEM LAVA CAD/CAM SYSTEM
CEREC SYSTEM Chair side economical reconstruction of esthetic ceramic. -Cerec – Cerec 2 – Cerec 3 – Feb 2000
CEREC CAD-CAM SYSTEM Limitation Cannot mill the occlusal surface Only inlays and onlays
CEREC – 2 CAD-CAM SYSTEM Milling of occlusal surface possible Inlays, Onlays, veneers and crowns Milling time approx. 10min
The grinding precision of the cerec-2 is 2.4 times higher than cerec system (Mormann 1997)
CEREC – 3 CAD-CAM SYSTEM Advanced version Technical improvements Designing and grinding- less time (27%) Grinding unit – 2 cutters
Marginal 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
Occlusal convergence angle of 4,8 and 12° Luting space settings of 10, 30 and 50µm.
Total Oclusal Convergence Luting Space 10µm 30µm 50µm Marginal Gap 4° 8° 12° Internal Gap 4° 8° 12°
He 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.
PROCERA CAD-CAM SYSTEM Nobel Biocare Initially introduced in 1985 Titanium copings Utilizing the latest scanning, CAD-CAM and manufacturing technologies Procera Allceram crown in 1991 Procera Allceram bridge in 1999
TITANIUM CROWN AND FPDS SUBSTRUCTURE Reading Milling Spark erosion
READING The prepared die is attached Contact probe registers the surface
MILLING The probe tip of the reader and the tip of the milling tool are of same size. The graphite electrode is milled
SPARK EROSION Used in dentistry since 1982 Graphite electrode is fitted Removes the metal by electricity in the form of controlled sparks to fabricate copings.
PROCERA ALL CERAM CROWN Composed of densely sintered, high purity aluminium oxide coping that is combined with low-fusing Allceram veneering porcelain.
Preparation of the tooth Computer assisted design Manufacture of the coping Addition of the veneering porcelain
PREPARATION OF THE TEETH Recommendations for the preparation Depth orientation grooves 1.5mm Incisal reduction – 2.0mm Axial reduction – 1.5mm
Rounded, smooth contours and lack of line angles
Impression is made Die is fabricated Articulated
COMPUTER ASSISTED DESIGN Die is oriented vertically Tip of the scanner probe is brought in contact As the platform rotates, one data point is collected at every degree around the 360° circumference of the die.
Scanning takes 3min More than 50,000 data points are registered Verified on the computer screen for completeness Vertical gap
The finish line of the preparation is marked by the operator at every 10° around the circumference of the die.
Coping design is selected Merged with the die and its finish line.
MANUFACTURE 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.
ADDITION 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.
Titanium 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.
CDA 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.
A 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.
TITAN CAD-CAM SYSTEM Production of metal copings for porcelain fused to metal restorations Digitizing Processing Milling
Preparation Impression Die Preparation Impression Die Waxing Investing Casting Digitizing Processing Milling Conventional Technique CAD/CAM system
DIGITIZING Die is fabricated Mounted on the digitizer Data are recorded Short circuited
Divided into 200µm x 200µm squares Digitized at least twice The finish line and the adjacent 1mm area are recorded first
PROCESSING The main parameters for the copings are then determined – The gap between the coping and the die - The width and shape of the coping
MILLING Uses titanium alloy dummies of various widths in the form of disks or blocks Milling device consist of two major units -A rotatory drilling element with interchangeable bores -A mobile platform to which the dummy is fixed
Three steps Rough milling inside the coping Fine milling inside the coping Rough external milling
MULTIPLE UNIT RESTORATION Steps same as for the single unit restoration It uses master cast made from a multiple unit impression Master cast allows the computation of each individual tooth and of the corresponding residual ridge
Relative 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
CELAY CAD-CAM SYSTEM Introduced in 1992 by Mikrona Technologies, Switzerland Inlays, onlays, crowns and bridge framework Not a true CAD-CAM system Many features in common
A light cured composite replica Either directly or indirectly Replica is mounted Scanning tools used to trace Milling tools removes ceramic
Bulk reduction by rough diamond milling disc Fine milling disc Contouring by diamond point Milling time 40mins – three unit bridge
CICERO CAD-CAM SYSTEM Computer integrated crown reconstruction First technical concept- by Denisson et al in 1999 Crowns with different ceramic layers such as high alumina core, dentinal and incisal porcelain for maximal strength and enhanced esthetic.
Preparation of Scan Model Optical Scanning Design Occlusion Design of crown layer build-up Production process STEPS
PREPARATION OF THE SCAN MODEL Model is marked with black/white contrast
OPTICAL SCANNING Obtained by laser scanning of the cast Upto 1,00,000 surface points are recorded per minute
DESIGN Appropriate tooth selected Mesial and distal contact are outlined The margin line of new crown is adjusted
OCCLUSION The new crown is superimposed on the opposing teeth to check for occlusion
DESIGN 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 0.7mm Ceramic core – die cement thickness of 0.02mm is adjusted.
PRODUCTION PROCESS Refractory block is fitted Negative of the inside surface of the crown is milled
Cutting tools used -Diamond cylinder of 5.3mm dia -Diamond rounded disk of 09.3mm dia -Diamond pointed tool of 0.9mm dia Automatically exchanged
High 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
Dental porcelain applied and fired After firing block is placed on milling machine and interface between dentinal and incisal porcelain is milled
Translucent incisal porcelain is applied, fired and milled
LAVA CAD-CAM SYSTEM Produce high strength all ceramic crowns and FPDs Uses yttrium tetragonal zirconia polycrystals (Y-TZP) based material Introduced as a hip replacement material in early 1990s High fractured strength 900 – 1200MPa and biocompatibility
Special scanner (Lava Scan) Computerized milling machine (Lava Form) A sintering Oven (Lava Therm) CAD-CAM software technology
STEPS IN FABRICATION Saw cut working cast is mounted on the scanner The configuration of the tooth preparation are scanned Scanning process takes -Crown – Approx.5min -3 unit FPD – Approx.12min
Produces an enlarged framework to compensate shrinkage during sintering process. Average milling time -Crown coping – Approx.35min -3 Unit FPD – Approx.75min
The 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
To conclude, Computer graphics and CAD-CAM have revolutionized dentistry. It is now possible to provide equivalent of a cast restoration in a single appointment
BIBLIOGRAPHY Philips Science of Dental Material, - ANUSAVICE Art & Sciences of Operative Dentistry- STURDEVANTS Dental Clinics of North America – Fixed prosthodontics Fundamentals of Fixed prosthodontics – SHILLINGBURG Contemporary fixed prosthodontics – ROSENSTEIL Restorative dental material – CRAIG