seminar 8 CAD CAM.pptx presented by third year pg

Cad cam

1. 1 CAD/CAM IN RESTORATIVE DENTISTRY

2. CONTENTS 2 Introduction Evolution Conventional vs CAD/CAM Potentials of CAD/CAM Production concept of CAD/CAM Components of CAD/CAM Materials for CAD/CAM CAD/CAM systems Advantages and disadvantages of CAD/CAM Conclusion

3. INTRODUCTION From its inception to now dentistry has covered great milestones in terms of invention, innovation and precision which aim to provide us with better working conditions and increased comfort for both dentists and patients To add to the list of remarkable advancements is CAD/CAM Computer-aided design / computer-aided manufacturing technology for dentistry is allowing us to provide even better care for patients 3

4. CAD/CAM CAD – Computer Aided Designing is the use of computer systems in the design and development of a product CAM – Computer Aided Manufacturing is the use of a computer system to operate machine tools which allows the shaping of materials to form structures and devices 4

5. EVOLUTION OF CAD/CAM SYSTEM 5 Davidowitz G., et al. “The use of CAD/CAM in dentistry”. Dental Clinics of North America ,2011; 55(3): 559-570.

6. CONVENTIONAL VS CAD/CAM 6

7. OVERVIEW 7

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9. Potentials of CAD/CAM SYSTEMS 9 Data acquisition that transforms geometry into digital data that can be processed by the computer Restoration fabrication depending on the application, produces a data set for the product to be fabricated Restoration design that transforms the data set into the desired product.

10. CAD/CAM - PRODUCTION CONCEPTS 10 Based on the production methods , C hair side production L aboratory production C entralised fabrication in a production centre . Digital dentistry: an overview of recent developments for CAD/CAM generated restorations F. Beuer , 1 J. Schweiger and D. Edelhoff British Dental Journal volume 204 No. 9 May 10 2008.

11. CHAIRSIDE PRODUCTION 11

12. LABORATORY PRODUCTION The dentist sends the impression to the laboratory where a master cast is fabricated first. The remaining CAD/CAM production steps are carried out completely in the laboratory. With the assistance of a scanner, 3-dimensional data are produced on the basis of the master die. These data are processed by means of dental design software 12

13. After the CAD-process the data will be sent to a special milling device that produces the real geometry in the dental laboratory. Finally the exact fit of the framework can be evaluated and, if necessary, corrected on the basis of the master cast. The ceramist carries out the veneering of the frameworks in a powder layering or over-pressing technique 13

14. Advantages Automates steps or all of fixed restorative fabrication Accuracy Less opportunity for error compared to traditional technique Opportunity to subcontract CAD/CAM to avoid capital costs Opportunity to focus on artistic ceramics Scanned image transferred directly to the laboratory from the office Reduced chairside time Team approach to fixed restorations Disadvantages Requires two visits 14

15. Many production centres also offer laboratories without a scanner the possibility of sending the master cast to the centre for scanning, designing and fabrication. The additional veneering of the frameworks for prosthetic restorations is carried out in the dental laboratory. Recently, dentists have been offered the possibility of sending the impression directly to the production centre ( biodentist ). This application is presently limited to ceramic inlays only. 15

16. An additional simplification in CAD/ CAM production consists of intraoral data collection (optical impression) Possible to directly judge the quality of the preparation intraorally, before data are finally sent to the dental laboratory or production centre . 16

17. CAD/CAM COMPONENTS 17 CAD Digital impression Designing of the restoration CAM Machining unit

18. Computer assisted designing Digital impression (Data acquisition / Computerized surface digitization) Nowadays the shift from physical impressions to digital impressions have taken place. Basically, there are two different scanning possibilities : Optical scanners – direct / indirect Mechanical scanners 18

19. Scanner 19 It includes the data collection tools that measure three dimensional jaw and tooth structures and transform them into digital data sets.

20. Optical scanners The optical scanners works on the principle of collecting three dimensional data by a process called ‘ triangulation procedure’. The source of light and the receptor unit are in a definite angle in their relationship to one another . White light projections or a laser beam can serve as a source of illumination 20

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22. They can be direct or indirect. In direct scanner image is obtained by directly scanning inside the patient’s mouth In Indirect scanner data acquisition is done by scanning the impression or cast. 22

23. Examples of optical scanners : Lava Scan ST (3M ESPE, white light projections) Everest Scan ( KaVo , White light) e s1 (etkon, laser beam). 23

24. Mechanical scanner The master cast is read mechanically line-by-line by means of a ruby ball and the three-dimensional structure measured. The Procera Scanner from Nobel Biocare This type of scanner is distinguished by a high scanning accuracy, whereby the diameter of the ruby ball is set to the smallest grinder in the milling system 24

25. Drawbacks of the system: The apparatus is very expensive Long processing times compared to optical systems. Digital dentistry: an overview of recent developments for CAD/CAM generated restorations F. Beuer , 1 J. Schweiger and D. Edelhoff British Dental Journal volume 204 No. 9 May 10 2008. 25

26. Factors to be considered while scanning During scanning, all required details for the restoration fabrication should be captured by the scan and visualized Depending on the system, a light and rapid dusting of an opacifier may be required prior to capturing the digital scans The preparation can be viewed from every angle on the monitor. Slight movement of the patient while scanning would compromise data quality and may lead to restoration misfit. Al‑ Jubouri O, Azari A. An introduction to dental digitizers in dentistry; systematic review. J Chem Pharm Res 2015;7:10‑20. 26

27. RESTORATION DESIGN The restorations are designed using Special designated software called CAD software that is provided by the manufacturers for the design of various 3D dental restorations on computers With such softwares, crown and fixed partial dentures (FPD) frameworks can be constructed. Some systems also offer the opportunity to design full anatomical crowns, partial crowns, inlays, inlay retained FPDs, and telescopic primary crowns. 27

28. After recording the impression with scanner a 3 - dimensional image is generated, then the operator enters data and confirms the features of the preparation. INSERTION PATHWAY BLOCK-OUT MARGIN IDENTIFICATION MARGIN REINFORCEMENT VIRTUAL ARTICUATOR LIBRARIES 28

29. The operator enters the data acquired from the scanning process and confirms the features of the preparation. These data are stored in a special format called standard transformation language (STL) data When the designing of the restoration is completed by the software, it is then transformed into virtual model using specific set of commands. 29

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31. RESTORATION FABRICATION Fabrication of restoration in CAD/CAM system is via computer and can be broadly be done by a subtractive or additive method. Additive manufacturing uses images from a digital file to create an object by laying down successive layers of a chosen material. Subtractive manufacturing uses images from a digital file to create an object by machining (cutting/milling) to physically remove material and achieve the desired geometry Joerg R Strub , E Dianne Rekow , Siegbert Witkowski . Computer aided design and fabrication of dental restorations. J Am Dent Assoc 2006; 137 (9): 1289-1296 31

32. Subtractive technique After the design of the restorations is completed, data for processing is calculated automatically. CLASSIFICATION ACCORDING TO NO OF MILLING AXIS ACCORDING TO MILLING ENVIRONMENT ACCORDING TO NUMBER OF MILLING ENGINE 32

33. COPY MILLING The construction data produced with the CAD software are converted into milling strips for the CAM-processing and finally loaded into the milling device. Processing devices are distinguished by means of the number of milling axes: 3-axis devices 4-axis devices 5-axis devices. 33

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35. 3-axis milling devices This type of milling device has degrees of movement in the three spatial directions, and so the mill path points are defined by the X -, Y -, and Z – values A milling of subsections, axis divergences and convergences, however, is not possible This demands a virtual blocking in such areas of the milling block 35

36. The advantages of these milling devices are short milling times and simplified control by means of the three axis. Also these devices are less costly than those with a higher number of axes. Examples of 3-axis devises: I nLab (Sirona), Lava (3M ESPE), Cercon brain (DeguDent). 36

37. 4-axis milling devices In addition to the three spatial axes, the tension bridge for the component can also be turned infinitely variably . Hence it is possible to adjust long span bridges with a large vertical height displacements and it also facilitates in saving material and milling time compared to three axes milling devices. Example: Zeno (Wieland- Imes ). 37

38. 5-axis milling devices In addition to the three spatial dimensions and the rotatable tension bridge (4th axis), the 5-axis milling device has the possibility of rotating the milling spindle (5th axis) This e n a b les the m il l i n g o f co m plex geo m etr i es with complex shapes such as denture base resins. M. Andersson , L. Carlsson , M. Persson , B. Bergman - Accuracy of machine milling and spark erosion with a CAD/ CAM system – JPD 1996; 76(2):187-93. 38

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40. Exa m ple i n the Laboratory Area :Everest engine ( KaVo ). Exa m ple i n the Production C e ntre: H S C Milling Device ( etkon ). 40

41. ACCORDING TO MILLING VARIANTS Dry processing Applied mainly with respect to zirconium oxide blocks with a low degree of presintering . Advantages: Minimal investment costs for the milling device No moisture absorption by the die ZrO2 mould , as a result of which there are no initial drying times for the ZrO2 frame prior to sintering. Disadvantages: Higher shrinkage values for the frameworks. 48 41

42. EXAMPLES Zeno 4030 (Wieland- Imes), Lava Form and Cercon brain 42

43. Wet milling In this milling process diamond or carbide cutter is protected by a spray of cool liquid against overheating of the milled material. Use f ul f or all m et a ls a nd g l ass c era m ic m ater i al in order to avoid damage through heat development. ‘Wet’ processing is recommended, if zirconium oxide ceramic with a higher degree of pre-sintering is employed for the milling process. A higher degree of pre-sintering results in a reduction of shrinkage factor and enables less sinter distortion. 43

44. Examples Everest (KaVo), Zeno 8060 (Wieland-Imes), inLab (Sirona). 44

45. ACCORDING TO NUMBER OF MILLING ENGINE One motor i.e.. Cerec mc x5 Two motors Cerec inlab MC XL -The restoration milled from both sides simultaneously 45

46. Additive technique / rapid prototyping techniques Stereolithography Selective Laser Sintering (SLS) 3-D Printing Fused Deposition Modeling (FDM) Solid Ground Curing Laminated Object Manufacturing (LOM) 46

47. Stereolithography (SLA) Stereolithography is the most widely used rapid prototyping technology. It is the technique for creating 3 dimensional objects in which a computer controlled moving laser beam is used to build up the required structure layer by layer 47

48. Selective laser sintering (SLS) Selective laser sintering (SLS) is used for the low volume production of prototype models and functional components. Starts by converting the CAD data in series of layer. These layers are transferred to the additive SLS machine which begins to lay the first layer of powder. As the laser scans the surface, the material is heated and fuse together. 48

49. Once the single layer formation is completed, the powder bed is lowered and the next layer of powder is rolled out smooth & subjected to laser. Hence layer by layer formation of the object takes place 49

50. 3 D PRINTING It is another manufacturing approach to build objects, one layer at a time and adding multiple layers to form an object. It is also known as additive manufacturing or rapid prototyping (RP). 50

51. It may be used for the fabrication of metal structures either indirectly by printing in burn - out resins or waxes for a lost-wax process, or directly in metals or metal alloys like FPD and removable partial denture (RPD), polymerized prostheses, and silicon prosthesis. 51

52. Fused Deposition Modeling Fused deposition modeling (FDM) is an additive manufacturing process in which a thin filament of plastic feeds a machine where a print head melts it and extrude it in a thickness typically of 0.25 mm Materials used in this process are Polycarbonate(PC), Acrylonitrile butadiene styrene(ABS), Polyphenylsulfone (PPSF), PC-ABS blends 52

53. Advantages No chemical post-processing required, No resins to cure, Less expensive machine, and Materials resulting in a more cost effective process. Disadvantages The resolution on the axis is low compared to other additive manufacturing process (0.25 mm), so a finishing process is required for a smooth surface which is a slow process requiring days to build large complex parts. 53

54. The quality of the restoration need not necessarily increase with the number of milling axes. The increased number of milling axes provides benefit only in terms of fabricating complex restorations and not relating to the quality of the restoration. The quality of restorations is more from the result of the digitalisation process, data processing and production process than the milling devices. CAD/CAM: Principles, practice and manufacturing management. 2nd edition: Part-I. 54

55. MATERIALS USED IN CAD/CAM TECHNOLOGY 1 ) Metals 2) Resin materials 3) Silica based ceramics 4) Infiltrated ceramics 5) Oxide ceramics 55

56. METALS Titanium, titanium alloys and chrome cobalt alloys are processed using dental milling devices. The milling of precious metal alloys has been shown to be of no economic interest, due to the high metal attrition and the high material costs. Examples: Coron ( etkon : non-precious metal alloy), Everest Bio T-Blank ( KaVo , pure titanium). 56

57. Resin materials Resin materials can be used for the milling of lost wax frames for casting technology; on the other hand, it is possible to use resin materials directly as crown and FPD frameworks for long-term provisional or for full anatomical long term temporary prostheses Prefabricated semi-individual polymer blanks (semi-finished) with a dentine enamel layer are provided by one manufacturer ( artegral imCrown , Merz Dental). The exterior contour conforms to an anatomically complete anterior tooth crown, while the internal aspect of the crown is milled out of the internal volume of the blank. 57

58. Silica Based Ceramics Grindable silica based ceramic blocks are offered by several CAD/CAM systems for the production of inlays, onlays , veneers, partial crowns and full crowns It is usually available as monochromatic blocks Various manufacturers now offer blanks with multicoloured layers [Vitablocs TriLuxe (Vita), IPS Empress CAD Multi (IvoclarVivadent)], for the purpose of full anatomical crowns. 58

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60. Lithium disilicate ceramic blocks -full anatomical anterior and posterior crowns,copings in the anterior and posterior region and for three-unit FPD frameworks in the anterior region due to their high mechanical stability of 360 MPa 60

61. Glass Ceramics Glass ceramics are particularly well suited to chairside application due to their translucent characteristics, similar to that of the natural tooth structure. Provides esthetically pleasing results without veneering. Etchable with hydrofluoric acid due to their higher glass content – can be inserted very well using adhesive systems. 61

62. Infiltration Ceramics Grindable blocks of infiltration ceramics are processed in porous, chalky condition and then infiltrated with lanthanum glass. All blanks for infiltration ceramics originate from the Vita In-Ceram system (Vita) and are offered in three variations :  Vita In-Ceram Alumina (Al2O3)  Vita In-Ceram Zirconia (70% Al2O3, 30% ZrO2)  VITA In-Ceram Spinell (MgAl2O4) 62

63. Vita In-Ceram Alumina (Al2O3): suitable for crown copings in the anterior and posterior region, three-unit FPD frameworks in the anterior region Vita In-Ceram Zirconia (70% Al2O3, 30% ZrO2): suitable for crown copings in the anterior and posterior region, three-unit FPD frameworks in the anterior and posterior region. Suitable for discolo u red teeth due to its superior masking ability 63

64. VITA In-Ceram Spinell (MgAl2O4):  Highest translucency of all oxide ceramics and is thus recommended for the production of highly aesthetic anterior crown copings, in particular on vital abutment teeth and in the case of young patients. 64

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66. Oxide high performance ceramics At present, aluminum oxide and zirconium oxide are offered as blocks for CAD/CAM technology. Aluminum Oxide (Al2 O3 ) This oxide high performance ceramic is ground in a pre-sintered phase and is then sintered at a temperature of 1520°C in the sintering furnace. Aluminium oxide is indicated in the case of crown copings in the anterior and posterior area, primary crowns and three-unit anterior FPD frameworks. The ground frames can be individually stained in several colours with Vita In-Ceram AL Coloring Liquid 66

67. Examples of grindable aluminum oxide blocks In-Ceram AL Block (Vita), inCoris Al (Sirona) available in an ivory-like colour (Color F 0.7). 67

68. Yttrium stabilised zirconium oxide (ZrO2 , Y-TZP) Zirconium dioxide is a high-performance oxide ceramic with excellent mechanical characteristics. Its high flexural strength and fracture toughness compared with other dental ceramics offer the possibility of using this material as framework material for crowns and FPDs, and, in appropriate indications, for individual implant abutments. The addition of three molecules of Y2 O3 results in a stabilising tetragonal phase at room temperature, which, as a result of a transition to a monoclinic phase can prevent the progression of cracks in the ceramic (Transformation strengthening) 68

69. Examples of Zirconium oxide blocks Lava Frame (3M ESPE), Cercon Smart Ceramics ( DeguDent ), Everest ZS und ZH ( KaVo ), inCoris Zr (Sirona), In-Ceram YZ (Vita), zerion ( etkon ) and Zeno Zr (Wieland- Imes ) 69

70. Processing can take place in different density stages Green stage processing Green stage: blank without heat treatment, ie an object pressed from ceramic powder and binding agents. Since there was no pre-sintering, the object is as soft as chalk. This permits very easy processing, but results, due to the low degree of stability, in great problems in transport and application. Processing is by means of carbide metal grinders without liquid cooling. 70

71. The green stage has an open porosity, and in firing a 25% linear shrinkage is to be expected. At present, zirconium oxide is not processed as a green stage in any of the CAD/CAM systems on the market. 71

72. White stage processing White stage: pre-sintered blanks. As a result of the thermal pre-treatment the organic compressing additives have vanished and the blank has an adequate stability. As a result of pre-sintering, the white body has already had shrinkage of approximately 5%. In the case of CAD/ CAM production of objects from white bodies, the subsequent shrinkage of some 20% (linear) must be taken into consideration. Processing of white stage can be either with carbide metal grinders without water cooling or with diamond grinders with liquid cooling 72

73. Processing in hot isostatic pressing condition Some systems also process zirconium oxide in HIP (hot isostatic pressed) condition with diamond tools and water cooling Advantages: • No sinter shrinkage, as a result no sinter distortions • No sinter furnace necessary • No additional time needed for sintering procedure. 73

74. Disadvantages: Devices with high rigidity and stability necessary Longer milling times, resulting in lower utilisation of devices High wear of the cutters No coloured blanks available on the market yet. 74

75. Common CAD/CAM Systems Cercon : It does not have a CAD component. In this system, a wax pattern (coping and pontic ) with a minimum thickness of 0.4 mm is made. The system scans the wax pattern and mills a zirconia bridge coping from presintered zirconia blanks. The coping is then sintered in the Cercon heat furnace (1,350 C) for 6 to 8 hours Mantri , S, Bhasin , A, 2010, ‘Cad/Cam In Dental Restorations: An Overview’ Annals and Essences of Dentistry, vol II, issue 3, pp. 123-28 . 75

76. Everest The Everest system consists of scan, engine, and therm components . In the scanning unit, a reflection free gypsum cast is fixed to the turntable and scanned by a CCD camera in a 1:1 ratio with an accuracy of measurement of 20 μm . Its machining unit has 5-axis movement that is capable of producing detailed morphology and precise margins from a variety of materials. Examples: leucite reinforced glass ceramics, partially and fully sintered zirconia, and titanium 76

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78. Lava This system uses yttria stabilized tetragonal zirconia poly crystals (Y-TZP) which have greater fracture resistance than conventional ceramics. Lava system uses a laser optical system to digitize The Lava CAD software automatically finds the margin and suggests a pontic . The framework is designed to be 20% larger to compensate for sintering shrinkage 78

79. Procera This system has combined pantographic reproduction with electrical discharge (spark erosion) machining. It uses an innovative concept for generating its alumina and zirconia copings First, a scanning stylus acquires 3D images of the master dies that are sent to the processing center via modem. The processing center then generates enlarged dies designed to compensate for the shrinkage of the ceramic material. 79

80. Copings are manufactured by dry pressing high-purity alumina powder (> 99.9%) against the enlarged dies. These densely packed copings are then milled to the desired thickness. The Procera restorations have excellent clinical longevity and strength 80

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82. DCS Precident It is comprised of a Preciscan laser scanner and Precimill CAM multitool milling center. It can scan 14 dies simultaneously and mill up to 30 framework units in 1 fully automated operation Materials used: Porcelain, Glass Ceramic, In- Ceram, Dense Zirconia, metals, and Fiber- Reinforced Co mmposites . This system is one of the few CAD/CAM systems that can mill titanium and fully dense sintered zirconia 82

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84. CICERO System The computer integrated crown reconstruction was developed by CICERO Dental System B.V. (Hoorn, The Netherlands). The CICERO method for production of ceramic restorations uses official scanning, ceramic sintering, and computer assisted milling techniques to fabricate restorations with maximal static and dynamic occlusal contact relations. The system makes use of optical scanning, near net-shaped metal, ceramic sintering and computer-aided fabrication techniques 84

85. CEREC SYSTEM The computer- aided design/computer-aided manufacture (CAD/CAM) CEREC (computer-assisted CERamic REConstruction ) system is used for electronically designing and milling restorations 85

86. CEREC 1 In this, the ceramic block could be turned on the block carrier with a spindle and feed against the grinding wheel, which grinds the ceramic block to a new contour with a different distance from the axis at each feed step 86

87. CEREC 2 The introduction of an additional cylinder diamond enables the grinding of partial and full crowns. It introduced the design of the occlusion in three modes: extrapolation, correlation and function. However, the design still was displayed two dimensionally . With CEREC 1 and CEREC 2, an optical scan of the prepared tooth is made with a couple charged device (CCD) camera, and a 3-dimensional digital image is generated on the monitor. The restoration is then designed and milled 87

88. CEREC 3 This system skipped the wheel an introduced the two bur-system. The “step bur”, reduced the diameter of the top one third of the cylindrical bur to a small diameter tip enabling high precision form grinding with reasonable bur life . The most significant factor for three-dimensional scanning with the Cerec 3 intraoral camera is that tooth preparations for crowns and inlays have a unique characteristic: all points of interest can be seen from a single viewing line, representing the preparation and insertion axes, respectively 88

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90. CEREC in Lab Is a laboratory system in which working besides a laser-scanned and a digital image of the virtual model is displayed on a screen. After designing the coping or framework, the laboratory technician inserts the appropriate VITA In-Ceram block into the CEREC in Lab machine for milling. The technician then verifies the fit of the milled coping or framework 90

91. E4D Dentist System Presently it is the only system besides CEREC that permits same day in-office restorations. This system includes a laser scanner (Intraoral digitizer), a design center and a milling unit. The scanner is placed near the target tooth, and has 2 rubber feet that hold it to specific distance from the area being scanned. As each picture is taken, the software gradually creates a 3D image. The design system automatically detects the finish lines and marks them on the screen. 91

92. As soon as the restoration is approved, the data are transmitted to either the in-house milling machine or a dental laboratory. The office milling machine will then manufacture the restoration from the chosen blocks of ceramic or composite 92

93. CAD/CAM PREPARATION GUIDELINES POSTERIOR RESTORATIONS • Rounded internal angles • Reduction 1.5-2 mm and 1 mm at the margin • Heavy chamfer, shoulder, or butt joint margins • 6-10˚ taper 93

94. ANTERIOR RESTORATIONS • Facial and lingual reduction 1-1.5 mm • Incisal reduction 1-2 mm • Reduction at the margin 1 mm • 6-10˚ taper • Chamfer, or shoulder margin • Prep should follow three plane reduction based on natural anatomical shape . 94

95. ONLAY RESTORATIONS • Margins should have sharp edges for easy identification • Occlusal reduction >1.5 mm • Internal axial walls 6-10º • Rounded internal line angles • Interproximal flare 100-120º • Butt joint margin 95

96. INLAY RESTORATIONS • Margins should have sharp edges for easy identification • Occlusal reduction (1.5-2.0 mm) • Internal axial walls 6-10º • Rounded internal line angles • Interproximal flare 100-120º • Isthmus width 1.5-2.0 mm • Isthmus depth >1.5 mm 96

97. VENEER RESTORATIONS • A medium grit, round-ended, diamond bur is used to prepare uniform thickness on the facial enamel. • Depth cuts of 0.5 mm to 0.8 mm • Incisal reduction 1.0 mm to 1.5 mm if needed • Chamfer margins • Correct preparation of the chamfer margins interproximally allows the appropriate bulk of ceramic. 97

98. ASPECTS TO AVOID POSTERIOR RESTORATION FEATHER EDGE MARGINS 98

99. AVOID UNDERCUTS 99

100. AVOID ANGLED PREPS 100

101. AVOID SHARP ANGLES 101

102. AVOID THIN WALL ENDO PREPS 102

103. INLAY/ONLAY RESTORATIONS 103

104. ANTERIOR RESTORATIONS = rounded edge = undercuts = insertion axis 104

105. SOFT TISSUE MANAGEMENT When taking a digital impression, it is very important to ensure the margins of the restoration are visible. Supra-gingival margins are ideal, but in cases with equigingival or sub-gingival margins gingival deflection is required. 105

106. RETRACTION PASTE Paste retraction products (such as Traxodent ™ or Expasyl ™) are another option for revealing the margin. The paste is injected into the sulcus, exerting a stable, non-damaging pressure. 106

107. CORD Tissue retraction with cord will also create good results. By using this technique, ensure before taking the optical image that the cord is not covering the margin of the preparation. 107

108. If tissue retraction is not performed on equigingival and sub-gingival margins, the margins are usually difficult to identify. Inadequate retraction will lead to a poor model CAD/CAM PREPARATION GUIDELINES & TISSUE MANAGEMENT TECHNIQUES RECOMMENDATIONS FOR OPTIMAL SCANNING, DESIGNING, AND MILLING 108

109. Clinical application Veneers, crowns and bridges Full mouth rehabilitation Implant abutment Maxillofacial prosthesis Cast partial dentures Complete dentures Orthodontic appliances 109

110. ADVANTAGES One-visit restorative procedure with chairside No impression making Reduced potential for tooth sensitization No model or die pouring No laboratory costs Less opportunity for error Aids preparation, visualization 110

111. DISADVANTAGES Higher production required to cover the capital investment High learning curve Depending on the material and patient, customization may be required 111

112. CONCLUSION CAD/CAM systems have enhanced dentistry by providing high-quality restorations. The evolution of current systems and the introduction of new systems demonstrate increasing user friendliness, expanded capabilities, and improved quality, and range in complexity and application. Existing CAD/CAM systems vary dramatically in their capabilities, each bringing distinct advantages, as well as limitations. Emerging technologies may expand the capabilities of future systems, but they also may require a different type of training to use them to their full capacity. 112

113. REFERANCES Anusavice , Shen, Rawls; Phillip’s Science of Dental Materials 2013, 12 th edition, Elsevier. Ronald L Sakguchi , John M Powers; Craig’s Restorative Dental Materials 2013, 13 th edition, Elsevier. M. Andersson , L. Carlsson , M. Persson , B. Bergman - Accuracy of machine milling and spark erosion with a CAD/ CAM system – JPD 1996; 76(2):187-93. CAD/CAM: Principles, practice and manufacturing management. 2nd edition: Part-I. Mantri , S, Bhasin , A, 2010, ‘Cad/Cam In Dental Restorations: An Overview’ Annals and Essences of Dentistry, vol II, issue 3, pp. 123-28. PR Liu, ME Essig;A panorama of dental CAD/CAM restorative systems; Compendium 2008, 29(8): 482-493. 113

114. CAD/CAM PREPARATION GUIDELINES & TISSUE MANAGEMENT TECHNIQUES RECOMMENDATIONS FOR OPTIMAL SCANNING, DESIGNING, AND MILLING C Chen, FZ Trindade , N de Jager , CJ Kleverlaan , AJ Feilzer ; The fracture resistance of a CAD/CAM resin nano -ceramic (RNC) and a CAD ceramic at different thickness; Dent Mater 2014, 30: 954-62. Jeramies Hey, F Beur , T Bensel , AF Boeckler ; Single crowns with CAD/CAM fabricated copings from titanium: 6 year clinical results; J Prosthet dent 2014, 112: 150-154. SS Manthri , AS Bhasin ; CAD/CAM in dental restorations: An overview; Annals and Essens of Dentistry 2010, II (3): 123-28. 114

115. THANK YOU 115