CAD/CAM Technology

This dental CAD/CAM technology allows the creation of high quality all-ceramic crowns, veneers, inlays and onlays ON-SITE the SAME DAY by your dentist.

Normally, such restorations take at least 2 weeks to be made in a dental laboratory and at least 2 visits to the office before the permanent prosthesis is put in place permanently. With CAD/CAM, a special infrared camera is used to take a picture of the tooth in need of repair and then computer software is used to design the restoration from the picture. Diamonds in a milling chamber carve the restoration out of a solid ceramic block of a color and size that matches your tooth, and then Dr. Nick customizes the final result by applying stains and then a glazing material which is permanently fused to the restoration in a high temperature glazing oven. The final result is then fused to the tooth with bonding materials and matches beautifully!

Dr. Nick is an expert in CAD/CAM Technology. He has written a book which you can view here for more information.

Advantages of CAD/CAM to the patient:

- Single visit procedure: no need to take a 2nd or 3rd day off of work or school. 1 visit is all it takes, typically 90 minutes per tooth, only ~15 of which is spent in your mouth. The rest of the time you are relaxing or watching us create your tooth in the virtual world and then subsequently in the real world...

- Your dentist is in complete control of the final result: because the crown or veneer is designed beside you with the computer software, Dr. Nick has complete control over how it will look and fit, whereas laboratory made restorations are being made by a technician who has not ever even seen the patient. In addition, tiny improvements that mean a world of difference as to the fit of the final result can be made instantly since the patient is still sitting right there!

- No nasty molds of your teeth: instead, a picture is taken

- No temporary restorations: Ever have a crown or veneer done the normal way? Chances were it was lose, leaky, sensitive, looked off, tasted badly, etc. Not any more with CAD/CAM.

- Only one set of local anesthetic injections: Remember, it's all done in one visit...!

- VERY accurate seal means less sensitivity: CAD/CAM restorations are typically accurate to within 50 microns, which is 5/100 of a millimeter. A good laboratory crown can achieve a similar fit ONLY IF the mold was accurate and did not distort. Remember, there is no impression or mold or outside laboratory with CAD/CAM.

- Chairside customization: All CAD/CAM's in this practice are stained and glazed to beautify and increase their strength. See stain and glaze tab...

- No gray edges at the gum line: because there is no metal in this fix, there is no metal to show through along the edge of the crown at the gum line.

- Less breakage: As of November 2011, our office has created over 3,800 CAD/CAM restorations, with only 2 fractured restorations over our 7 years of providing this amazing service.

- Teeth that are oftentimes not restorable with a crown can sometimes be saved: As long as you have some enamel on your tooth, we can almost flat-top the tooth and expect success with a bonded all-ceramic CAD/CAM crown...

- Veneers can be created the same day: Wow. Not possible otherwise. Not to mention the subtle nuances associated with the looks and shapes of your front teeth that can be tweaked while you watch, interjecting your own input along the way!

- Onlays and Inlays can be created that same day for your tooth: A dentist without CAD/CAM is bound to prescribe a crown to fix a tooth because it is less likely that your temporary will fall off. A crown removes more tooth structure than say an onlay. Common sense dictates that the less of mother nature that is removed in a surgery, the better. An onlay or inlay is preferable to a crown as less tooth structure is removed.

- X-rays can visualize underneath the restoration: Most lab crowns have metal underneath. X-rays can not penetrate metal. CAD/CAM restorations have no metal, only porcelain, and X-rays do penetrate porcelain. This allows your dentist to more readily catch a problem underneath your prosthesis over time.

When do we not use CAD/CAM?

- When there is very little enamel left on the tooth as where an old lab crown is removed and the edges are VERY deep below the gum line onto the root surface or cementum. The bond of an all-ceramic restoration is dependent on the white enamel of the tooth. The more enamel, the better the bond, the less enamel, the poorer the bond. Lab crowns can be attached with cements which can bond better to the root or cementum of the tooth.

- When the person is a grinder/bruxer since these are all-ceramic, they do not have the luxury of a metal surface or substructure that might wear down rather than fracture. However, we do use a particular type of block which is stronger than the rest for these individuals when they want to use the CAD/CAM for it's convenience and looks.

- When what little is left of the tooth is black looking because of an old root canal: Since these are all porcelain and translucent, the darkness can show-through.

- When we are making bridges that span large gaps we use laboratory made bridge restorations, though manufacturers will one day soon provide we CAD/CAM users with a millable all-ceramic alternative.

 

 

Overview Implantology Endodontics Orthodontics Cosmetic Dentistry Dental Hygiene Practice Management General Dentistry Dental Lab

Fig. 7: Automatic reconstruction of inlay cavities. Top: undamaged original tooth; centre: cavity; bottom: occlusal surface automatically reconstructed given only the remaining tooth substance (centre). (Image: Mehl)

May 8, 2009 | COSMETIC DENTISTRY

CAD/CAM was just the beginningby Manfred Kern, Germany Share on facebook Share on twitter More Sharing Services

Today, practising dentistry without digital technology and CAD/CAM procedures is unimaginable. Intra- and extra-oral imaging, scanning of antagonists and impressions, on-screen 3-D designing, the use of innumerable tooth shapes from the tooth database, the design of anatomic occlusal surfaces, functional articulation on virtual models, subtractive processing of high-performance ceramics—none of this would be possible without the use of computers.

The groundwork for this quantum leap in dental technology was laid in 1985. Using a Fairchild video sensor (which at the time was only used for military purposes and for which special permission was required for use in dentistry), for the first time it was possible for a preparation—

made visible intraorallywith a triangulation camera—to be measured multidimensionally and transferred onto a screen. Then, with the help of a PC, imaging software, and a connected CNC grinding unit, the first inlay of silicate ceramic was produced at the University of Zurich.

In those days, only a few could imagine the new technologies and revolutionary treatment possibilities awaiting dentistry thanks to this development. Since then, more than 28 million all-ceramic restorations have been produced worldwide using CAD/CAM technology, both chairside and in the dental laboratory. Computerised milling machines have made subtractive processing of glass- and oxide ceramics possible from which to fabricate aesthetic, high-quality restorations with a reproducible, consistent material quality at a reduced cost.

Relatively recently, discussion was centred on accuracy of fit, cost-effectiveness, and userfriendliness.The quality of CAD/CAM restorations was viewed critically, and only a few leaders in the field investigated this technology with scientific rigour. Currently, the initially hesitant, and even sceptical, attitude towards computer-manufactured dental prostheses has been replaced by one of approval, and this technology has become a standard procedure.

From a technical point of view, the development of 3-D image capture was propelled not only by more powerful microprocessors, but also by CCD image sensors with high-resolution photodiodes, as well as optical and tactile scanners that help read and upload preparations and models to the software. Laser scanners provide an impulse capacity for reproducing tooth surfaces at a rate of thousands of measured points per second. Upgraded CAD software with 3-D graphics applications receives the digital signals and recreates the clinical surface needing restoration.

Using ‘occlusal settling’ with preformed occlusal surfaces from the tooth databank, the software then virtually rebuilds the tooth surface. The cusps of the occlusal surface are ‘settled’ into their occlusal position. An articulation programme takes the occlusal characteristics of antagonists and the adjacent teeth’s occlusal surfaces and creates a contact-point pattern that fulfils the criteria of the individual function. An acquired, regional functional generated path registry detects sites that interfere with the gliding space and reduces them automatically (Fig. 1).

The impetus for this development in dental technology stems from two sources. The first was protagonists of computerised chairside restoration desiring to process an industrially fabricated ceramic with defined physical properties directly at the treatment unit (chairside) and provide the patient with the definitive restoration (omitting temporaries) in one appointment. The second was the idea of employing oxide ceramics, like ZrO2, for crownand bridge frameworks, by using CAD/CAM technology or digitally controlled milling techniques.

Other ceramics, such as lithium disilicate, also exhibit better properties after mechanical processing, as the blanks used are industrially manufactured under optimal conditions. In addition, the technology of CAD/CAM systems has been substantially improved. In the 1990s, computers became more powerful and measurement methods more effective, making it possible

to adapt 3-D data acquisition systems to the needs of dentistry and simplify equipment handling. The evolution of CAD software enabled the development of a variety of construction possibilities and improved the quality of grinding/milling units (Fig. 2). Cost-effectiveness and high-quality restorations are the defining characteristics of CAD/CAM technology. Dentist and dental technician alike profit from this through standardised and controlled treatment and manufacturing processes—and so does the patient. Today, approximately 82 per cent of all-ceramic restorations in Germany are made using computer technology, which indicates that CAD/CAM technology is establishing itself in dental offices and laboratories. The next step in its evolution is now anticipated.

Figs. 1–4: Virtual automatic reconstruction: the scan data of the antagonist, the functional movement, the adjacent teeth, and the preparation can be taken into consideration in their entirety to design an occlusal surface that fits according to all requirements (Fig. 1; Image: Mehl). CAD construction of a widespanning ZrO2 bridge framework. The system examines the connectors for minimum thickness and loadbearing capacity (Fig. 2; Image: Mehl). Individual intra-oral images are anatomically correct, as they are compiled in a virtual quadrant model (Fig. 3; Photo: Sirona). The intra-oral camera scanner enables an optical impression of the entire maxilla or mandible, leading the way for the impression-free practice (Fig. 4; Image: Wiedhahn).

Where do we stand today?

New methods constantly change customary processes, and advancements simplify the workflow. This is reflected in the increased mention of construction models, articulation on a Windows interface, biogeneric occlusal surface design using intelligent software, rapid prototyping, and 3-D printing in the context of CAD/CAM in scientific publications. The impression-free practice is the latest step in this development. At IDS 2009, the use of intra-oral 3-D measurement to, in part, make the impression-free practice possible will be demonstrated (Figs. 3 & 4). With data from an intra-oral image sequence, e.g. of a quadrant, working models can be produced using a wax-processing 3-D printer in a rapid prototyping system, on which prostheses can be manufactured conventionally or with CAD/CAM.

Via internet portals, the dentist can send optical impressions from intra-oral scans to the dental technician, which are then fed into the stationary CAD system. The impression-free practice is much more comfortable for patients because impression-taking and its incident gag reflex are eliminated.  Additionally, production time can be cut and the dental technician’s productivity increased considerably.

What is the future of CAD/CAM?

Those long familiar with the field were able to predict early on that manufacturing centres would play a crucial role: high efficiency, specialised personnel, centralised material purchasing, and high quality standards for the ‘standard restoration’ enable an efficient output that in turn makes it possible to pay off investments in high-tech manufacturing machines, while increasing cost-effectiveness (Figs. 5 & 6). Mid-sized and smaller dental laboratories will make best use of their core competency in the computer-supported manufacture of high-quality aesthetic restorations and in the specialised production of partial and implant-supported prostheses.

Figs. 5 & 6: Milling centres have an ingenious quality-control system for processing ZrO2 ceramic for crown- and bridge frameworks (Fig. 5; Photo: Etkon–Straumann). Milling centres operate costeffective and according to standardised manufacturing procedures (Fig. 6; Photo: Heraeus Kulzer).

Another trend is the computerised fabrication of inlays, onlays, and partial and single crowns, either chairside or in the office’s own CAD/CAM-equipped laboratory. Biogeneric occlusal surface design enables the reconstruction of the missing occlusal surface with inlays, onlays, and partial crowns as naturally as possible (Fig. 7). The one-appointment treatment saves the patient

time and removes the need for provisional restoration, which minimises the risk of cusp fracture, enamel-margin chipping, and weakening of the dentine bond.

CAD/CAM and all-ceramics are frequently mentioned together, which falsely implies that CAD/CAM is limited to all-ceramics. The enormous potential inherent in the milling and, most recently, the laser sintering of metals is often completely overlooked. The fabrication of metal restorations (e.g. nonprecious metals and titanium) will eventually become a domain of CAD/CAM technology.

In the field of implantology, it is already possible to create long-term provisional restorations, abutments, and crowns using computer-assisted methods, which also shorten treatment steps. Digital volume tomography (DVT) yields a 3-D image of the bone structure, thus enabling much higher quality diagnosis, including the exact localisation of the alveolar nerve. Particularly in dental arches bearing partial prostheses, the DVT image quality is better than that of CT images, and the X-ray dosage required is much lower. The DVT thus provides the basis for the surgical planning of the implant.

In the future, the implant site and adjacent teeth will be scanned with an intra-oral digital camera, and a virtual model will be calculated. The 3-D volume tomogram will be superimposed on this model and the crown will then be exactly positioned in the X-ray image (Fig. 8). The position of the endosseous abutment will be suggested in the centre of the crown’s basal surface and in its insertion pathway, and based on this the situation will be examined for its surgical feasibility. When selecting the implant system for a given case, the case will be able to be completely simulated in a three-dimensional radiograph. Using special software, it will soon be possible to construct a stereolithographically manufactured drilling template, which will guarantee that the holes drilled in the bone and the implants are exactly positioned (Fig. 9).

Figs. 8 & 9: DVT image with superimposed suprastructure to determine implant postion (Fig. 8; Image: Bindl/Sicat). Special software will help construct a stereolithographically manufactured drilling template for exact positioning of drilling holes and implants (Fig. 9; Image: Nobel Biocare/Geiselhöringer).

The demands of CAD/CAM technology have inspired topics in basic research and hence propelled progress in other areas of dentistry too. Universities and industry can collaborate and thereby promote and shape these exciting developments. Thus far, CAD/CAM or computerised dentistry has not been a central area of interest at universities. But as CAD/CAM technology is relatively new and its performance potential is significant, this is likely to change in the next few years. In turn, this development will influence dental education curricula and thereby influence treatment options in private practices to the benefit of our patients.

Editorial note: This article was originally published in Cosmetic Dentistry Vol. 3, Issue 1, 2009.

Contact info

Manfred Kern, Secretary Society for Dental Ceramic (SDC) can be contacted at info@ag-keramik.de.

The Clinical Application of CAD/CAM Technology and MaterialsCategory: CAD/CAM Speaker(s): Michael Skramstad, DDS Cost: $29.00 CE Contact Hours: 2Login or Register to Complete Course

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Educational ObjectivesThe overall goal of this article is to provide the reader with information about the use of CAD/CAM technology and materials for the fabrication of definitive restorations. After reading this article, the reader will be able to:

1. Delineate the main differences between digital impressions and traditional techniques

2. List and describe the various CAD/CAM materials and their uses

3. Review the treatment of restorative surfaces and luting agent options

4. Describe the chairside steps required to deliver an indirect, resin nano-ceramic, same-day restoration

AbstractRestoring indirect restorations using digital impressions and CAD/CAM technology is a topic that has created a tremendous amount of interest in both the dental office and the dental laboratory. CAD/CAM technology has evolved into several systems that can be used for the fabrication of indirect restorations, together with the development of several restorative materials. The properties of these restorative materials and their indications and appropriate use must be understood in order to enable the achievement of predictable and esthetic results for patients.

About the AuthorDr. Michael Skramstad graduated from the University of Minnesota School of Dentistry in 2000. He currently is on the faculty in the CAD/CAM Department at the Scottsdale Center for Dentistry and a national website for continuing education in CEREC Dentistry.  He is a basic and advanced trainer for Patterson Dental and has lectured internationally on digital dentistry. Dr. Skramstad is an Alpha/Beta tester for Sirona Dental Systems and a product consultant for multiple dental companies.  Dr. Skramstad maintains a private practice in Orono, MN focusing on esthetic and CAD/CAM computerized dentistry. Dr. Skramstad can be reached at skramy@hotmail.com.

Introduction

CAD/CAM technology and materials are currently used in a number of clinical applications, including the fabrication of indirect restorations, occlusal splints, and implant-related components.1,2 More recently, CAD/CAM has become available for the treatment planning and execution of orthodontic treatment, and it is also possible for clinicians to measure and track the morphology of gingival tissues during treatment associated with different clinical disciplines.3,4 Indirect single-unit restorations are one of the most common procedures currently performed in the dental office. For many years, porcelain-fused-to-metal (PFM) and gold crowns were the materials of choice for the fabrication of indirect restorations for teeth with inadequate tooth structure remaining for direct restorations. In addition, porcelain-only single-unit restorations were fabricated in selected non-stress-bearing situations due to their esthetic qualities relative to PFM crowns. In the last several years, a number of different material options have been introduced as alternatives to these more traditional materials, including some that have the ability to be milled in the office for indirect same-day restorations. Digital scanning and CAD/CAM fabrication of indirect single- and multi-unit restorations is a procedure performed with increasing frequency. Furthermore, more advanced adhesive luting cement systems have become available that enable reliable placement and retention of these restorations. This paradigm shift, involving both CAD/CAM technology and new materials, has changed the way both dentists and dental laboratories think about restoring teeth, and the use of CAD/CAM technology has increased.5 Many of these restorations not only make the dentistry more predictable, but offer great convenience to patients. Patients also are increasingly demanding all-ceramic restorations.6

Fabrication of Indirect Single-Unit Restorations Using Traditional TechniquesTraditional materials used for restoring a tooth indirectly include the use of cast metal crowns, metal-ceramic crowns with or without porcelain margins, and ceramic crowns. All these materials are used for the fabrication of single-unit crowns using traditional techniques. First, the preparation must be made in accordance with the restorative material being used, and the adjacent soft tissue managed to prevent bleeding or fluid encroaching on the preparation and to expose any subgingival margins. For this purpose, one or more of the following may be used: retraction cord, lasers, hemostatic agents, electrosurgery, or one of the more recently introduced silicone polymer retraction materials. Gingival retraction cord was reported in one survey to be the most frequently-use method.7 Clinical preference, ease-of-use, the specific clinical case and familiarity play a role in the selected method. The next step is to take an impression of the preparation as well as the adjacent and opposing teeth so that the die and models can be poured for laboratory fabrication of the crown. During this period, the patient is provided with a provisional restoration for function and/or esthetics, as well as to protect the preparation and gingival margins, prevent sensitivity in a vital tooth, and maintain periodontal health and the position of the prepared tooth relative to the adjacent and opposing teeth.8-10 This traditional procedure is still the most prevalent method of restoring teeth with indirect restorations – it is what clinicians have been most familiar with and how they were taught in dental school. As such, there is no new learning curve for the clinician.

While generally reliable, this traditional approach involves some limitations, including the period of time it takes to fabricate the restorations (typically one to two weeks), the need for a

provisional restoration, and the need for the patient to return for a second visit. Physical models are necessary to create the restoration and must be poured from the impression. However, the impression itself is a potential source of error, despite the availability of highly accurate and dimensionally stable impression materials; some common errors include the inclusion of voids, marginal discrepancies, and minor tears. High-precision impression materials must be handled according to the manufacturers’ instructions, and the soft tissue at the clinical site appropriately managed, to help avoid such errors. Other factors that can result in inadequate impressions include how soon the model was poured, and the manner in which the impression was stored and transported before pouring. This is especially important for alginate, which is typically the material of choice for the opposing (preparation-free) arch due to its ease-of-use and low cost. If left out to dry or transported without being wrapped in damp gauze or a damp towel, these impressions will shrink which causes dimensional errors in the model.11

Similarly, models may also include voids and other dimensional errors. These errors are related to the mixing, pouring and handling of the stone (or plaster) models. Marginal discrepancies may not be evident until after the models have been poured or until the time of try-in of the restoration, resulting in additional time and costs. Digital photography and modern shade selection options and techniques have increased the ability of the clinician and the laboratory to communicate, and therefore to deliver a case with the desired esthetics. Nonetheless, this setup may still not be ideal for a given case. Well-executed indirect restorations fabricated using the traditional approach offer excellent fit, functionality, and esthetics.

CAD/CAM TechnologyCAD/CAM technology has been around long enough that is not “new”; earlier versions of the technology have been available in dentistry for almost 30 years.12 It is now accepted as a viable, predictable, and efficient alternative to traditional methods.13 As with the traditional approach, the preparation design must consider multiple factors, including the material that will be used to fabricate the indirect restoration and the required dimensions, as well as the amount of retention that will be achieved as a result of the preparation form. CAD/CAM technology has evolved into several versions using different devices and combinations of techniques: 1) taking the CAD/CAM scans chairside and transmitting these through a secure Internet portal to a standard laboratory or to a central location for fabrication of the indirect restoration in a milling machine; 2) taking the CAD/CAM scans chairside and sending these through a secure Internet portal to a central location for digital creation of the models, after which they are sent to a standard laboratory for traditional fabrication of the restoration; and 3) taking the scan chairside and milling the indirect restoration chairside using CAD/CAM technology at the same visit (Figure 1).

When the clinician uses any of these devices and techniques, it is not necessary to take a traditional impression or to pour dies and models. This removes the risk of associated errors and increases patient comfort. Both chairside milling and laboratory milling of restorations removes the possibility of abrading or damaging dies and models during their use for restoration fabrication – abraded models would result in restorations that were either too tight and left insufficient space for the luting agent, or simply would not seat on the preparation. Of course, to avoid incurring errors when using CAD/CAM technology, the clinician must accurately take

scans and follow procedures according to the instructions of the given manufacturer. All available CAD/CAM devices involve the use of a handheld scanner, although each uses different technology to capture the images. Options for capturing images include continuous video streaming of the teeth, the acquisition of multiple still images that are then melded together with software, and the use of a laser that captures images by reflecting off the surface of the tooth or preparation. “Bite registration” and the determination of centric relation also differ by system.

For CAD/CAM restorations milled in a laboratory or central location, a provisional restoration is required as with the traditional impression technique (Table 1).

Provisionalization for Laboratory-Milled or Fabricated Indirect RestorationsProvisionalization materials include acrylic resins, pre-fabricated composite resin temporary crowns, and metal-based prefabricated temporary crowns. The use of acrylic resins allows the provisional restoration to be customized chairside. Desirable features of a provisional material are a setting reaction that does not produce heat (or produces minimal heat) and that avoids shrinkage of the material during setting, as well as being sufficiently durable to last until the definitive indirect restoration is ready for placement. Bis-acryl results in less heat production during the setting reaction than other acrylics, has low polymerization shrinkage and offers adequate durability for provisional restorations, although it is a more costly acrylic compared to polyethyl or polymethyl methacrylate.14 Prefabricated temporary crowns may be quicker to place, and still offer a smooth surface provided only minimal adjustments are required. On the other hand, they are only available in a number of shapes and sizes, require marginal adjustments, and may not be suitable for a given case.  Recently, fillers have been added to bis-acryl to increase surface smoothness and gloss for provisional restorations. Scanning and chairside same-visit milling of the restoration is the only option that removes the need for a provisional restoration or for a second patient visit for try-in and placement of the restoration. 

Preparation and CAD/CAM ScanningFor all systems, as with the traditional technique, the preparation must be isolated and the soft tissue managed at the margins. The same techniques are used for soft tissue management as with the traditional approach. Depending on the system, a light and rapid dusting of an opaquing powder agent may be required prior to capturing the digital scans of the preparation arch, opposing arch, and buccal bite registration. Digital scanning and rapid transmission of the scans to the laboratory, and/or chairside viewing of the scans, allows for immediate or almost immediate feedback on margins and clearance. If corrections are needed, it takes just minutes with the patient still in the chair and anesthetized. This avoids having to bring the patient back for a second visit involving adjustments to the preparation or/and a second impression, or not discovering the error until the patient’s seat appointment when the restoration has already been fabricated and then causing additional laboratory costs to be incurred as well as causing patient disappointment.

Clinical ResultsSeveral studies have evaluated CAD/CAM restorations and found that they have a marginal fit as good as or superior to that of traditional impressions.15-16 A further benefit found with CAD/CAM restorations has been the reduced incidence of secondary caries (the leading cause of direct restoration failure with both amalgam and composite materials), attributed to the high accuracy of the approximal fit and the ability to ascertain that this is accurate prior to completion of the restoration and cementation. In fact, the longevity of CAD/CAM restorations was reported by Mjör et al to be close to that of gold restorations.17 A recent review assessed the survival rates of single-tooth indirect restorations fabricated with CAD/CAM and found the long-term survival rate to be similar to indirect restorations fabricated using the traditional approach.18

CAD/CAM scanning and fabrication of indirect restorations has been proven in numerous studies and is now accepted as a viable, predictable alternative to traditional methods.19-20

As with all treatments, proper procedures and techniques must be followed to achieve clinically acceptable results. CAD/CAM technology also requires the use of specific materials that can be milled to fabricate durable and esthetic restorations.

CAD/CAM Restorative MaterialsThe movement toward CAD/CAM fabrication of restorations has been directly responsible for a number of material innovations over the past few years. For quite some time, both leucite and feldspathic glass ceramics have been used for laboratory-based fabrication of ceramic restorations. These materials result in beautifully esthetic restorations regardless of which method is used for their fabrication, particularly in the anterior region. However, their relatively low flexural and compressive strengths have limited their use in posterior stress-bearing areas. High-strength leucite also has been used as a block for CAD/CAM milled restorations. These materials must be adhesively resin-bonded to the preparation and cannot be placed using traditional luting cements. In recent years, we have seen the evolution of high-strength ceramics – lithium disilicate, alumina, and zirconia – that have allowed CAD/CAM dentistry to move into new territory. The advantages of these materials are twofold: they possess very high compressive and flexural strength, and can be bonded or cemented. This has resulted in a very strong, predictable, and esthetic option for posterior ceramic dentistry. In a recent study, both alumina and zirconia crown copings fabricated using CAD/CAM were found to have clinically acceptable marginal adaptations.21 A separate study recently conducted on milled lithium disilicate crowns found these to be free of fractures, chipping, or other defects two years post-placement.22 For CAD/CAM restorations milled with these materials, in addition to the CAD/CAM device a porcelain furnace is required for crystallization of lithium disilicate, and a sintering oven for full-contour zirconia. In the case of lithium disilicate, this can add 15 to 30 minutes to the fabrication time, and with zirconia up to an additional 8 hours may be required. It should be noted that high-speed sintering ovens for zirconia are now sintering these restorations in about 90 minutes and other options include semi-sintered zirconia and fully-sintered zirconia. The advantage of using zirconia for milling and then sintering it is the increased strength following sintering and the relative ease of milling prior to sintering.

Composite resin blocks are also available for CAD/CAM restorations. Another option is the use of a new resin nano-ceramic block that consists of ceramic clusters within a highly cross-linked resin matrix. The resulting block is homogenous, and the restoration can be CAD/CAM-milled chairside or in the laboratory. The wear resistance of this material is reported to be comparable to that of felspathic glass ceramic and lithium disilicate, and it has a compressive strength similar to high-strength ceramics. Unlike lithium disilicate and zirconia, no porcelain furnace or sintering oven is required, saving fabrication time. In fact, a recent study found that composite blocks (and experimental composite blocks) were more resistant to fracture than reinforced ceramics when used for ultra-thin veneers.23 The use of nano-fillers and resin technology has improved the strength and esthetics of composite blocks.  A 2006 study comparing resin nano-ceramic and zirconia used for CAD/CAM four-unit bridges found that the margins were most accurate and marginal gaps least using the resin nano-ceramic material.24

Placement and Retention of CAD/CAM RestorationsAs noted above, some CAD/CAM restorative materials can be cemented with either traditional luting cements such as zinc phosphate, polycarboxylate cement, glass ionomers, or resin-modified glass ionomers. Materials that can be luted with these include zirconia, lithium disilicate, alumina, and resin nano-ceramics. The caveat for non-bonded materials is that the preparation form was sufficiently retentive in the first place. Resin-based bonding can be used for all CAD/CAM restorative materials, including those mentioned above (Table 2). Resin-based luting cements bond to the ceramic restorations, not only the tooth structure, and are now regarded by some clinicians as the preferred luting agent for ceramic and other non-metal restorations. They offer excellent esthetics and retention of the restoration to the preparation.25 These luting cements utilize etching and bonding technology, and they bond by micromechanical locking of the cement to both the tooth and the restorative material. The resin-based luting cement itself may be dual-cured, self-cured, or light-cured – the latter is only suitable if the restoration is thin enough to enable the transmission of light for curing. A further requirement is roughening of the intaglio surface to increase the area available for bonding,26 with either hydrofluoric acid or sandblasting/air abrasion depending on the restorative material used. The intaglio surface of lithium disilicate restorations is treated with 5% hydrofluoric acid for 20 seconds to etch and roughen that surface.27 The intaglio surfaces of feldspathic porcelain and leucite-containing restorations are also treated with hydrofluoric acid, with the time of etching depending on the material. Options for other materials are the use of sandblasting or treatment with a silica coating, with the method depending on the material – the restoration material manufacturer’s instructions must be followed and the correct treatment used. Irrespective of the luting agent and technique, the primary objectives are retention and sealing of the restoration-tooth interface.

Case StudiesWhen considering milling and delivering same-day restorations, there are many options available.

The two case studies below will concentrate on the use of resin nano-ceramic blocks for the chairside fabrication of an inlay and a veneer. Case Study #2 involves the complication of an aligner with attachments that were on the fractured tooth to be veneered.

Case Study #1A 17-year-old male presented for examination with no chief complaint. Upon routine full-mouth examination and after bitewing radiographs were taken, carious lesions were found on the distal of tooth #12, the mesial and distal of tooth #13, and the mesial and occlusal of tooth #14 (Figure 2). 

A traditional way to restore these lesions would be to prepare class II preparations on tooth #12 and tooth #14 and mesial and distal one-surface restorations on tooth #13. It is always the goal to restore teeth in a minimally invasive fashion. When carious lesions are limited in size, it is ideal to restore conservatively with direct composite restorations. However, when carious lesions are more extensive, this method can be complicated with large-cavity preparations28 by a number of factors that include operatory time, polymerization shrinkage, layering in proper thicknesses, and especially contours and contacts. There are many different band, matrix, and wedge combinations on the market that all promise to deliver ideal contours and contact; in this author’s experience, however, these methods rarely provide the predictability of indirect CAD/CAM restorations. After discussing the options with the patient, it was decided to restore these teeth indirectly with resin nano-ceramic CAD/CAM restorations. Prior to preparing the teeth, these teeth were isolated with a non-latex rubber dam and preoperative scans were taken (Figure 3). When these preoperative scans are taken, the software allows use of a design method called “biogeneric copy” (since the carious lesions did not compromise the natural shape and contour of the virgin teeth). It is quite advantageous for the final restorations to be exact duplicates of what nature created, provided the contacts and contours are functionally ideal and esthetically pleasing.

After taking the initial images, all caries was removed and the preparations were finalized. Care was taken to avoid encroaching on the interproximal papillae during preparation, by placing small wooden wedges between the teeth. The preparations should be smooth and flowing, with no undercuts and with clear separation from the adjacent teeth. After removal of the wedges, a light dusting of the CAD/CAM powder (Optispray) was applied, and the preparations were captured by scanning to create the digital impressions (Figure 4). Figure 5 shows the preparations that were scanned. Once the preparations were digitized and marginated, the software used the overlay of the preoperative condition (Figure 6) to create proposals that were an exact replicate of the patient’s virgin teeth (Figure 7). Furthermore, all interproximal contacts can be manipulated to the desired contact size and strength directly in the software with intuitive three-dimensional tools. This case demonstrates one of the advantages of chairside CAD/CAM fabrication of Class II restorations: by eliminating the need for bands and wedges, predictability for contacts and contours was realized.  

After the inlay designs were finalized, the restorations were milled from resin nano-ceramic blocks with the milling unit. Milling resin nano-ceramic material results in excellent marginal integrity; SEM images of restorations milled with these blocks show less marginal chipping than

with traditional glass ceramics. When the milling of the restorations was complete, the inlays were steam-cleaned (to remove all milling oil) and the sprue was removed with coarse So-Flex discs. Initial extra-oral polishing was performed using coarse, medium, and fine rubber wheels. Since the restorations were quite small and therefore difficult to handle, final polishing was completed intraorally post-bonding. It should be noted that because this material does not need to be fired in a porcelain furnace, milling and polishing can be completed quite efficiently intra-orally or extra-orally. The restorations were next tried-in to ensure that their marginal fit and contours were correct.

To prepare for bonding of the inlays, the intaglio surface of the restorations was sandblasted with aluminum oxide at two bars (30psi), to increase the surface area available for bonding,29 and was then cleaned with alcohol. A universal adhesive agent was then applied to the intaglio surface for 20 seconds and air-dried for five seconds. The restorations were placed aside without curing the adhesive. Note also that using a universal adhesive that contains silane primer eliminates the need for a separate silanation step. To prepare the teeth for the restorations, the enamel was selectively etched with phosphoric acid for 15 seconds, rinsed, and dried. The same adhesive agent was agitated on the enamel for 20 seconds with two applications, and then air-dried for five seconds to evaporate the solvents. The resin-based luting cement was then placed into the inlay preparations (with no prior curing of the adhesive), and the restorations were all seated. Initial cleanup was performed with a gingival stimulator, and the remaining excess was tack-cured for one second with an LED light prior to being removed with a curved explorer. Removing excess cement when it is only tack-cured, and before it has set, helps retain the bond while the material is still not at full strength.30 The resin-based luting cement in the restorations was then light-cured for 20 seconds per surface. Finally, the resin-bonded nano-ceramic inlays were polished with diamond-impregnated composite cups and polishing paste. No adjustments to the occlusion were necessary, and the final restorations mimicked the contours of the original teeth extremely closely and offered excellent esthetics (Figure 8).

Case Study #2An 18-year-old male presented with a significant fracture on tooth #8, sustained while playing basketball (Figure 9). An existing composite bonding was present on both the remaining tooth and the fractured fragment; the fracture did not involve the pulp. To significantly complicate matters, the patient was midway through orthodontic treatment with an aligner, and tooth #8 had two attachments present: one still present on the tooth (cervical) and one that had fractured off with the incisal portion of the tooth. Under normal circumstances, restoring an anterior tooth with these aligner attachments is quite a daunting task; it is often necessary to have the orthodontist replace the attachments and review the patient’s orthodontic treatment plan. Using the tools available with CAD/CAM technology, however, it was possible to restore this tooth to its original shape without compromising the orthodontic treatment. The success rate for CAD/CAM fabricated veneers is high, with one study finding a high clinically acceptable result up to nine years after placement and a 94% survival rate.31

Since the patient had found the fractured portion of the tooth, it was possible to etch and bond this back into position with a total-etch technique (Figure 10). Under some circumstances, rebonding the fragment is a good short-term solution for this situation. However, since this

patient was leaving for college and had an esthetic concern with the tooth, it was decided to fabricate a CAD/CAM veneer. In this situation, temporarily bonding the fragment to the tooth in its natural position allowed positioning of the aligner attachments at the appropriate places. The patient’s current aligner was then tried-in to verify proper fit. Prior to preparing the tooth and after rebonding the fragment to the tooth, a preoperative scan was taken (after applying a light dusting of powder). As with Case Study #1, this scan served as a guide for the final restoration using biogeneric copy. The veneer preparation was then made and the tooth isolated with retraction cord (Figure 11). A digital impression of the preparation was taken, which showed the marginated veneer preparation clearly and accurately (Figure 12). The preoperative scan can also be overlaid on top of the preparation using this CAD/CAM technology, and can be copied on a 1:1 basis to obtain a proposed final restoration that exactly duplicates the existing tooth. Note how precisely the camera (scanner) captured the two aligner attachments with the preoperative scan (Figure 12) and how the software reproduced them in the final initial proposal (Figure 13).

As discussed earlier, when choosing the appropriate material, one has to consider many factors. In this particular situation a low-translucency resin nano-ceramic CAD/CAM block was selected because of the patient’s age, the flexibility of the material, its excellent polishability, the precise marginal edge quality, and the low translucency (which would prevent shine-through, helping to ensure an esthetic result). But the most important factor, considering that the patient would be using an aligner for the next year, was the material’s reparability. After the restoration was milled, the initial polish was achieved using medium and fine diamond-impregnated rubber wheels. Care was taken to avoid over-polishing the surface of the restoration, which would affect the surface texture and aligner attachments. In order to facilitate natural shade transitions and provide an excellent match with the contralateral central incisor, the restoration was characterized with light-cured resin in several shades. To accomplish this, the external (non-bonding side) of the restoration was sandblasted with aluminum oxide at 30psi, cleaned with alcohol, and dried. As with Case Study #1, universal adhesive was applied to the surface, thinned appropriately, and light-cured. Several shades of resin were then applied to the surface of the restoration and light-cured to characterize the restoration and match it as closely as possible to tooth #9. Final polishing of the restoration was achieved using a fine polishing paste on a #9 soft brush at low rpms (< 10,000 rpm), and a final buff was performed with a muslin rag wheel. Finally, the restoration was bonded using universal adhesive and a resin-based luting cement. The final restoration exhibited contours almost identical to the original, pre-fracture contours, and the patient’s esthetic concerns were satisfied (Figure 14). Furthermore, the aligners snapped into place with no adjustments at all (Figure 15).

SummaryCAD/CAM technology has transformed the ways in which clinicians can provide patients with functional, esthetic, and durable indirect restorations. CAD/CAM technology removes the risk of some errors and offers the opportunity to review restoration designs (and adjust them, if necessary) before they are completed. As the demand for CAD/CAM indirect restorations grow, more advanced materials have become available that can be resin-bonded to preparations with excellent results. The material of choice depends on the clinical situation, with consideration given to strength, esthetics, and ease of use.

ReferencesReferences

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2. Beuer F, Schweiger J, Edelhoff D. Digital dentistry: an overview of recent developments for CAD/CAM generated restorations. Br Dent J. 2008 May 10;204(9):505-11.

3. Fukawa R. Lingual orthodontics in the new era treatment according to criteria for occlusion and aesthetics. Int Orthod. 2009 Dec;7(4):370-402. 

4. Ronay V, Sahrmann P, Bindl A, Attin T, Schmidlin PR. Current status and perspectives of mucogingival soft tissue measurement methods. J Esthet Restor Dent. 2011 Jun;23(3):146-56. 

5. Davidowitz G, Kotick PG. The use of CAD/CAM in dentistry. Dent Clin North Am. 2011 Jul;55(3):559-70.

6. Miyazaki T, Hotta Y. CAD/CAM systems available for the fabrication of crown and bridge restorations. Aust Dent J. 2011 Jun;56 Suppl 1:97-106. 

7. Hansen PA, Tira DE, Barlow J. Current methods of finish-line exposure by practicing prosthodontists. J Prosthodont. 1999 Sep;8(3):163-70.

8. Burke FJ, Murray MC, Shortall AC. Trends in indirect dentistry: provisional restorations, more than just a temporary. Dent Update. 2005;32(8):443-52.

9. Wassell RW, St. George G, Ingledew RP, Steele JG. Crowns and other extracoronal restorations: provisional restorations. Brit Dent J. 2002;192(11):619-30.

10. Bral M. Periodontal considerations for provisional restorations. Dent Clin North Am. 1989;457-65.

11. Nassar U, Hussein B, Oko A, Carey JP, Flores-Mir C. Dimensional accuracy of 2 irreversible hydrocolloid alternative impression materials with immediate and delayed pouring. J Can Dent Assoc. 2012 Jan;78:c2.

12. Calamia JR. Advances in computer-aided design and computer-aided manufacture technology. Curr Opin Cosmet Dent. 1994:67-73.

13. Fasbinder DJ. Digital dentistry: innovation for restorative treatment. Compend Contin Educ Dent. 2010;31 Spec No 4:2-11.

14. Seelbach P, Finger WJ, Ferger P, Balkenhol M. Temperature rise on dentin caused by temporary crown and fixed partial denture materials: influencing factors. J Dent. 2010;38(12):964-73.

15. Sorensen JA, Sorensen PN, Mizuro K. Marginal fidelity of crowns made with optical versus conventional impressions. IADR Abstract #1599. April 2009.

16. Hirayama H, Chang YC. Fit of zirconia copings generated from a digital impression technique and a conventional impression technique. Tufts University of Dental Medicine master’s thesis.

17. Mjör IA, Davis ME, Abu-Hanna A. CAD/CAM restorations and secondary caries: a literature review with illustrations. Dent Update. 2008 Mar;35(2):118-20.

18. Wittneben JG, Wright RF, Weber HP, Gallucci GO. A systematic review of the clinical performance of CAD/CAM single-tooth restorations. Int J Prosthodont. 2009;22:466-471.

19. Otto T, Schneider D. Long-term clinical results of chairside CEREC CAD/CAM inlays and onlays: a case series. Int J Prosthodont. 2008 Jan-Feb;21(1):53-9.

20. Estefan D, Dussetschleger F, Agosta C, Reich S. Scanning electron microscope evaluation of CEREC II and CEREC III inlays. Gen Dent. 2003:51(5):450-4.

21. Alghazzawi TF, Liu PR, Essig ME. The effect of different fabrication steps on the marginal adaptation of two types of glass-infiltrated ceramic crown copings fabricated by CAD/CAM technology. J Prosthodont. 2012 Apr;21(3):167-72. 

22. Fasbinder DJ, Dennison JB, Heys D, Neiva G. A clinical evaluation of chairside lithium disilicate CAD/CAM crowns:A two-year report J Am Dent Assoc 2010;141(6 suppl):10S-14S.

23. Schlichting LH, Maia HP, Baratieri LN, Magne P. Novel-design ultra-thin CAD/CAM composite resin and ceramic occlusal veneers for the treatment of severe dental erosion. J Prosthet Dent. 2011 Apr;105(4):217-26.

24. Piwowarczyk HC, Lauer C. Determining the marginal fit of CAD/CAM bridge frameworks. Pan Eur Fed Conf. 2006; Abstract #0254.

25. Haddad MF, Rocha EP, Assunção WG. Cementation of prosthetic restorations: from conventional cementation to dental bonding concept. J Craniofac Surg. 2011 May;22(3):952-8.

26. Tsuo Y, Yoshida K, Atsuda M. Effects of aluminablasting and adhesive primers on bonding between resin luting agent and zirconia ceramics. Dent Mater. 2006;25(4):669-674.

27. Pisani-Proenca J, Erhardt MC, Valandro LF, et al. Influence of ceramic surface conditioning and resin cements on microtensile bond strength to a glass ceramic. J Prosthet Dent. 2006;96;412–7.

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31. Wiedhahn K, Kerschbaum T, Fasbinder DF. Clinical long-term results with 617 CEREC veneers: a nine-year report. Int J Comput Dent. 2005;8:233-46.  

Webliography

Fasbinder DJ. Clinical performance of chairside CAD/CAM restorations. JADA 2006;137(9 supplement):22S–31S. Available at: http://jada.ada.org/content/137/suppl_1/22S.abstract?ijkey=24969cbaa0bb04f7453ddfdf45afb2725a09b127&keytype2=tf_ipsecsha

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Trost L, Stines S, Burt L. Informed decisions about incorporating CEREC into a practice. JADA 2006;137(9 supplement):32S–36S. Available at: http://jada.ada.org/content/137/suppl_1/32S.full.pdf+html

Wittneben JG, Wright RF, Weber HP, Gallucci GO. A systematic review of the clinical performance of CAD/CAM single-tooth restorations. Int J Prosthodont. 2009 Sep-Oct;22(5):466-71. Abstract available at: http://www.ncbi.nlm.nih.gov/pubmed/20095195

Unsere Zahnärzte aku gigi, mulut rumahku....

Minggu, 27 Februari 2011RESTORASI VENEER ALL CERAMIC ANTERIOR MENGGUNAKAN METODE PRESSABLE (IPS EMPRESS) DAN METODE CAD-CAM (CEREC 3) PENDAHULUAN

         Keramik adalah bahan yang telah dipergunakan lebih dari 10.000 tahun lalu, dengan komposisi keramik pertama kali adalah batu – batuan seperti obsidian, batu lava, quartz (kuarsa), dan silica. Pada saat itu digunakan sebagai bahan untuk membuat peralatan sederhana seperti barang pecah belah dan artefak (Anusavice, 2003). Keramik merupakan bahan yang paling cepat berkembang baik dalam penggunaan maupun metode pembuatannya. Sekarang ini komposisi porselen gigi yang konvensional adalah berupa keramik vitreus (seperti kaca) yang berbasis pada anyaman silicate (SiO2) dan Feldspar potas (K2O AL2O3 6SiO2) atau Feldspar soda (Na2O AL2O3 6SiO2), atau keduanya (Anusavice, 2003).

Sejalan dengan perkembangan bahan keramik, kemajuan pembuatan veneer keramik akhir – akhir ini juga terbilang pesat. Prosedur perawatannya diperkenalkan antara akhir tahun 1920an hingga tahun 1930an (Castelnuovo dkk, 2000). Metode pelapisan veneer menggunakan keramik sebagai bahan intinya diawali oleh Buonocore (1955), dengan teknik pengetsaan (etching) pada enamel, setelah itu di tahun 1960an, Bowen, memperkenalkan resin BIS-GMA dan diikuti oleh perkembangan komposit gigi. Selanjutnya di tahun 1973 ditemukan cara pengikatan (bonding) keramik oleh Rochette. Kemajuan perawatan permukaan keramik dan proses pengikatan (bonding) diikuti juga dengan kemajuan acid gels yang sangat efektif digunakan sebagai bahan perlekatan untuk restorasi keramik (Dunitz, 1999).

Selain itu ditahun 1980an komposit juga mengalami suatu perkembangan. Bahan ini kemudian digunakan sebagai bahan semen yang di-bonding dengan bahan keramik. Semen ini digunakan

bersama dengan silanebonding antara veneer porselen dan gigi (Dunitz, 1999).  untuk mendapatkan

      Veneer keramik ditemukan untuk memperbaiki estetik, karena memiliki warna serupa dengan gigi asli (Anusavice, 2003). Namun penggunaan veneer untuk memperbaiki estetik gigi ini belum sepenuhnya diketahui oleh masyarakat khususnya para teknisi laboratorium, salah satu penyebabnya adalah karena proses pembuatannya yang cukup rumit sehingga membuat harganya menjadi sangat mahal (Dunitz, 1999).

Pengertian dari veneer keramik itu sendiri adalah suatu bahan yang digunakan dalam kontruksi mahkota atau pontik, berupa suatu lapisan untuk gigi atau sebagai bahan pewarnaan gigi, biasanya dari bahan porselen dan resin komposit dengan cara dipadukan langsung, disemen atau dengan retensi mekanis pada permukaan gigi (Zwemer, 1993).

Veneer keramik diindikasikan untuk memperbaiki kosmetik gigi anterior yang mengalami

perubahan warna atau hipoplastik (Anusavice, 1996). Perubahan warna yang dimaksud adalah

perubahan warna yang sedang. Perubahan warna ini bisa diakibatkan karena tetracycline,

fluoride, dan umur. Selain itu dapat dipilih untuk restorasi yang disebabkan karena trauma,

fraktur (keretakan), serta pertumbuhan gigi yang kurang bagus. Anatomi dari gigi yang kurang

normal atau malposisi dapat juga diperbaiki dengan veneer. Prosedur ini tidak hanya memberi

estetik yang baik, tetapi juga dapat diandalkan fungsi kekuatannya (Castelnuovo, 2000). Selain

itu veneer juga digunakan untuk kasus khusus seperti diastema, hilangnya keratan gigi taring

(caninus) pada posisi lateral, pelapisan keramik pada bagian lingual, lapisan veneer keramik di

atas mahkota keramik dan mahkota gigi yang pendek (Dunitz, 1999). Pemakaian veneer tidak

dianjurkan pada penderita dengan relasi oklusi  edge to edge dan gigitan silang, oklusi berat,

kesehatan mulut (oral hygiene) yang buruk, kekurangan mineral dan fluoride pada gigi.

Komplikasi pada veneer keramik dapat terjadi karena ketidakhati – hatian saat preparasi,

kerusakan pulpa, iritasi jaringan periodontal yang parah dan penampilan gigi yang tidak natural

(Castelnuovo dkk, 2000).

Pelapisan atau penggunaan veneer keramik memiliki keuntungan (Dunitz, 1999), antara

lain bisa dilihat dari segi bentuk, posisi, tekstur permukaan serta pewarnaannya yang dapat

disesuaikan dengan keadaan natural gigi utama, memiliki ketahanan yang baik, pencahayaan

yang bagus di seluruh permukaannya, mendapatkan respons yang baik dari jaringan

penyangga gigi. Sedangkan kerugiannya adalah memiliki prosedur preparasi yang tidak mudah,

metode pembuatan di laboratorium yang cukup rumit serta dibutuhkan ketelitian, biaya yang

relatif mahal, apabila terjadi kerusakan sangat sulit diperbaiki bahkan mungkin tidak dapat

diperbaiki lagi, Penggantian warna sulit dilakukan setelah penyemenan.

Saat ini metode pembuatan veneer keramik juga berkembang dengan pesat, diantaranya

adalah pembuatan veneer all-ceramic anterior dengan metode pressable dan machinable /

CAD-CAM.

IPS Empress merupakan metode Pressable Ceramic. Teknologi yang digunakan adalah

Heat Pressed dengan Lost – wax Technique (Van Nort, 2002). Restorasi yang dihasilkan

memiliki estetik yang baik sehingga gigi terlihat natural. Komposisi utama bahan IPS Empress

adalah silicate glass matrix (SiO2) dengan susunan fase kristalnya berupa kristal leucite dengan

konsentrasi tinggi. Bahan lain yang digunakan meskipun dalam persentase kecil adalah K2O,

Al2O3, Na2O, B2O3, CaO, TiO2, CeO2 (IPS Empress Ivoclar Vivadent AG).

Metode machinable keramik yaitu CAD CAM system dirancang untuk menghasilkan

keindahan. Sistem ini menggunakan scan 3D untuk informasi digital mengenai bentuk preparasi

giginya. Metode ini diperkenalkan didunia kedokteran gigi tepatnya pada Februari tahun 2000

sebagai versi yang lebih canggih dan lebih baru. Perangkat lunak (software) yang digunakan

dalam CEREC adalah berformat windows NT dan dijalankan dari Personal Computer atau PC

(Bindl dkk, 2002). Komposisi utama bahan CAD-CAM untuk pembuatan veneer keramik adalah

Silica (SiO2), Alumina (Al2O3), selain itu ada beberapa komposisi kimia lain yang terdapat dalam

material blocks CAD-CAM meskipun dalam jumlah yang relatif kecil, yaitu: Na2O (6 - 9%), K2O

(6 - 8%), CaO (0,3 - 0,6%), TiO2 (0,0 - 0,1%) (www.cereconline.ecomaXL).

Timbul suatu permasalahan, bagaimana metode pembuatan veneer keramik dengan menggunakan metode Pressable (IPS Empress) dan CAD CAM (CEREC 3)?

 

Veneer keramik

1. Definisi Veneer keramik

Veneers adalah suatu bahan yang digunakan dalam kontruksi mahkota atau pontik, berupa suatu lapisan pada gigi atau sebagai bahan pewarnaan gigi, biasanya dari bahan porselen dan resin komposit. Perlekatan pada gigi dapat dilakukan dengan cara dipadukan langsung, disemen atau dengan retensi mekanis pada permukaan gigi (Zwemer, 1993).

Veneers keramik direkatkan pada bagian enamel gigi yang telah dipreparasi sebelumnya. Enamel dihilangkan dari bagian permukaan gigi yang akan diberi pelapisan ini, tujuannya adalah memberi ruang sebagai tempat melekatnya veneers. Dibandingkan dengan veneers berbahan komposit, veneers keramik lebih mempunyai sifat tahan lama dalam hal pemakaiannya dan lebih tahan terhadap stain. Estetik yang dihasilkan veneer keramik lebih terlihat natural menyerupai gigi asli dibandingkan veneers dari komposit. Namun, dalam hal proses pembuatan memang veneers berbahan keramik lebih rumit dibanding bahan komposit, sehingga membuat harganya jauh lebih mahal. (www.fourseasonsfamilydentistry.com). Metode ini merupakan restorasi keramik terbaik untuk mengembalikan kapasitas pencahayaan dari warna alami gigi. Ada beberapa faktor yang harus benar – benar diperhatikan dalam pembuatan veneer keramik, yaitu warna yang menjadi dasar strukturnya, pemilihan bahan semen, dan kedalaman preparasi. Pemilihan bentuk preparasi keramik dan bondingbiokompabilitas, dan masa pakainya (Dunitz, 1999). (perlekatannya) berpengaruh pada: peningkatan sifat mekanis, sifat

Konsep umum teknik pembuatan veneer keramik diperkenalkan oleh H.R.Horn pada tahun 1983. Metode ini mungkin untuk digunakan seiring dengan kemajuan resin komposit dan bahan penyambungan silane. Pada metode Horn, porselen dibakar di atas lembaran platinum, tetapi pada teknik mutakhir, porselen dibakar secara langsung diatas model cetakan tahan api (refraktori) sehingga menghasilkan adaptasi yang bagus. Penyempurnaan – penyempurnaan telah dilakukan terhadap kekuatan perlekatan bahan – bahan penyambung (silane), maupun terhadap kekuatan dan daya tahan, baik dari porselen maupun resin (Haga dan Nakazawa, 2002).

2. Indikasi dan Kontraindikasi Veneer keramik

Veneer keramik diindikasikan untuk memperbaiki kosmetik dari gigi anterior yang

mengalami perubahan warna atau hipoplastik (Anusavice, 1996). Perubahan warna yang

dimaksud adalah perubahan warna yang sedang tidak terlalu parah. Perubahan warna ini bisa

diakibatkan karena tetracycline, fluoride, dan umur. Selain itu dapat digunakan untuk restorasi

yang disebabkan trauma, fraktur (keretakan), serta pertumbuhan gigi yang kurang sempurna.

Anatomi dari gigi yang kurang sempurna atau malposisi dapat juga diperbaiki dengan veneer.

Prosedur ini tidak hanya memberi estetik yang baik, tetapi juga dapat diandalkan fungsi

kekuatannya (Castelnuovo dkk, 2000). Selain itu diindikasikan untuk kasus khusus seperti

diastema, hilangnya keratan gigi taring (caninus) pada posisi lateral (Dunitz, 1999). Menurut

Haga dan Nakazawa, 2002, veneers keramik juga diindikasikan untuk karies apabila tidak

terlalu luas tetapi dangkal, dan perubahan warna gigi akibat penambalan.

Kontraindikasi pemakaian veneer adalah penderita dengan relasi oklusi edge to

edgeexcessive stress selama pemakaian veneer keramik. Perawatan ini juga tidak dianjurkan

untuk pasien dengan oklusi berat, kesehatan mulut (oral hygiene) yang buruk, kekurangan

mineral dan fluoride pada gigi. Komplikasi pada veneer keramik dapat terjadi karena ketidakhati

– hatian saat preparasi, kerusakan pulpa, iritasi jaringan periodontal yang parah dan

penampilan gigi yang tidak natural (Castelnuovo dkk, 2000). Selain itu bruxism dan tidak cukup

tersedianya email gigi yang sehat juga termasuk dalam kontraindikasi, hal ini karena bahan –

bahan bonding dentin saat ini meskipun telah berkembang namun kekuatan perlekatan dengan

dentin terlalu lemah, sehingga veneer keramik bergantung pada perlekatan dengan email. Oleh

karena itu terbukanya dentin sebaiknya dijaga sesedikit mungkin (Haga dan Nakazawa, 2002).

dan gigitan silang yang menyebabkan terjadinya

3. Bentuk Preparasi Veneer keramik

Bentuk preparasi dari pelapisan veneer keramik harus memperhatikan empat prinsip

dasar berikut: kestabilan, kekuatan, retensi, dan adhesi. Prinsip ini memiliki tujuan agar

gabungan antara fungsi, pengaruh biologis, maupun nilai estetiknya dapat dicapai. Apabila

hanya mengandalkan adhesi saja tanpa memperhitungkan ketiga faktor lainnya, umumnya

cepat atau lambat akan menimbulkan kegagalan. Mempertahankan enamel alami gigi sebanyak

mungkin meskipun diperlukan, tidak boleh membahayakan rencana restorasi karena minimnya

preparasi (Dunitz, 1999).

Untuk gigi yang terkena karies, preparasi dilakukan setelah karies dibuang. Preparasi

gigi harus dilakukan dengan sangat hati – hati dan perlahan – lahan mengikuti kontur

permukaan gigi untuk menghindari terbukanya dentin. Selain itu pada saat pembuatan, veneer

harus dibuat membulat halus tanpa adanya tepi – tepi yang tajam, hal ini bermaksud untuk

memperbaiki ketepatan dari veneer dan menghindari pemusatan stress (Dunitz, 1999).

Rata – rata kedalaman preparasi enamel adalah 0,5 mm. Pada kasus perubahan warna

yang parah, cenderung terjadi peningkatan kedalaman preparasi menjadi 0,7 – 0,8 mm.

Kedalaman preparasi dibawah 0,3 mm tidak dianjurkan. Secara umum, kedalaman antara 0,7 –

0,8 mm atau 0,6 – 0,7 mm pada incisal dan pertengahan area, dalam beberapa kasus secara

berturut – turut dapat melindungi lapisan enamel yang tersisa. Pada daerah servikal dengan

kedalam kurang dari 0,3 mm sering dilakukan pembongkaran tambalan gigi (Dunitz, 1999).

Permukaan facial gigi dipreparasi sebagai tempat untuk melekatnya veneer dengan ketebalan

sesuai ketentuan. Pengurangan bagian facial adalah 0,3 – 0,6 mm pada daerah 1/3 cervical

dan 0,5 – 0,7 mm dari pertengahan gigi sampai 1/3 incisal. Preparasi gigi diperpanjang sampai

kontak interproximal (Castelnuovo, 2000).

Menurut Haga dan Nakazawa, 2002, email pada bagian labial gigi anterior rahang atas

yang paling tebal adalah dekat tepi Incisal, yakni 1,0 sampai 1,3 mm dan secara perlahan

menipis ke bagian cervical yakni 0,3 sampai 0,6 mm. Email ini menjadi lebih tipis lagi pada garis

sudut gigi. Sedangkan untuk gigi bawah ketebalannya kurang lebih 0,9 sampai 1,1 mm pada

daerah incisal, dan menipis pada daerah cervical, karena preparasi hanya dibatasi oleh oleh

email, maka pengurangan dilakukan hanya ± 0,5 sampai 0,7 mm, meskipun sering menjadi 0,3

mm di daerah dekat cervical.

Cervical margin ditempatkan pada epigingivally dan akhirnya membentuk

chamferCervical Margin ditentukan menurut bentuk dan ukuran mini chamfer-nya yakni rata –

rata 0,3 mm. Garis ini disejajarkan dengan gingival atau lebih rendah sampai pinggiran gingival,

hal ini merupakan persyaratan yang umum digunakan (0,5 mm biasanya untuk kebanyakan

kasus perubahan warna gigi yang parah) (Dunitz, 1999). Pengurangan ini sudah mencukupi

kebutuhan untuk konstruksi veneers (Bindl dkk, 2002). Tidak dianjurkan untuk memasukkan

margin terlalu dalam ke-sulcus gingival. Pelapisan veneers keramik umumnya dapat

memperlihatkan ketegasan batas gingival gigi karena memiliki optical properties yang baik.

Selain itu yang paling utama adalah dapat mengembalikan bentuk serta fungsi gigi (Dunitz,

1999). (Bindl dkk, 2002).

Untuk bonding, kesejajaran margins selalu diutamakan, alasannya adalah untuk:

menambah area enamel dalam preparasinya, mengontrol kelembaban, menegaskan bentuk

margin yang fit, untuk memudahkan proses finishing dan polishing, memudahkan pemeliharaan

rutin margin sebagai prosedur kesehatan gigi (Dunitz, 1999).

Perbaikan chamfer dengan ukuran 0,3 mm merupakan bentuk margin yang ideal untuk

pelapisan veneer keramik atau mahkota sebagian, karena memungkinkan dalam: pembentukan

kembali profil alami gigi, menghindari over contour pada daerah cervical, keakuratan dari garis

batas gigi dapat ditentukan sehingga mempermudah pencetakan serta identifikasi dan

pembentukan kembali di laboratorium, margin jadi lebih tahan retak selain itu dapat mengindari

retak pada edge dari pelapisan veneer dalam rangkaian konstruksinya, pelapisan veneer

menjadi lebih mudah dimasukkan saat penempatan terakhir pada gigi (Dunitz, 1999).

            Tepi Incisal umumnya tidak ditutup, dan dipreparasi hanya dengan bevel saja, supaya

tidak meninggalkan email yang tidak terdukung. Posisi bagian tepi yang baik adalah pada tepi

gingival, dan jika veneer diperluas sampai masuk kedalam sulcus gingiva, hendaknya lapisan

veneer dibuat sesedikit mungkin. Tepi gingival dibuat berbentuk chamfer (Haga dan Nakazawa,

2002). Semua margin dibuat sedalam enamel. Untuk melindungi jaringan keras, incisal margin

yang dipreparasi tidak boleh sampai mengenai incisal edge atau sebaiknya preparasi dilakukan

sejauh mungkin dari incisal edge gigi (Bindl dkk, 2002).

Batas proximal preparasi ditempatkan pada pertengahan proximal dengan pemotongan

kontak area proximal kurang dari 50% (Bindl dkk, 2002). Bentuk preparasi dari proximal surface

sudah dapat digambarkan / direncanakan pada waktu preparasi labial dan pembuatan cervical

margin. Dua prinsip utama dalam preparasi proximal surface adalah: melindungi kontak area

dan penempatan margins harus terlihat. (Dunitz, 1999).

Kedalaman yang minimum dari preparasi perlu diperhatikan terutama untuk perlekatan

dan juga dapat memberikan ketebalan yang cukup untuk kekuatan pelapisan veneers keramik.

Kedalaman kurang lebih antara 0,8 - 1 mm, dengan lapisan enamel pada sepertiga okklusal gigi

lebih tipis (Dunitz, 1999).

Bagian proximal tidak boleh sampai hilang, meskipun ketika dilakukan preparasi, hal ini

karena bagian tersebut dapat menjaga kontak area dengan gigi sebelah, selain itu lereng /

lekuk buccolingual harus dilindungi. Perpanjangan interproximal, dibuat secara menyambung

satu sama lain seperti keadaan sebenarnya, ini untuk memperbaiki stabilitas dan sifat mekanis

dari perlekatan veneer (Dunitz, 1999).

Pada daerah kontak Interproximal apabila memungkinkan dibiarkan saja, dan preparasinya

dibuat meluas sampai tepat di bagian depan daerah kontak. Untuk memberikan retensi dan

kekuatan serta supaya pemasangan menjadi mudah, maka bentuk preparasinya dibuat

menyerupai “U”. Gigi juga dipreparasi sedikit kearah lingual tepatnya pada daerah papilla

interdental sehingga batas porselen tidak terlihat, daerah ini menentukan arah masuknya

veneer, bentuk preparasi tidak boleh ada undercut (Dunitz, 1999).

Menjaga kontak area sangat penting hal ini dikarenakan keistimewaan bentuk

anatominya sangat sulit untuk dibentuk kembali seperti semula jika hilang, mencegah

perubahan tempat dari gigi – gigi lainnya sewaktu preparasi dan penempatan gigi, untuk

mempermudah prosedur perawatan, terutama saat prosedur bonding dan finishing., contact

area yang baik dan tidak hilang dapat memberikan kemudahan dalam hal perawatan sendiri di

rumah (Dunitz, 1999).

Metode Pembuatan Veneer Keramik

A. Metode Pressable (IPS Empress)

Merupakan salah satu restorasi keramik dengan sebuah metode yang disebut dengan

press. IPS Empress juga sebagai alternatif dalam pembuatan restorasi all keramik yang dapat

diandalkan fungsi dan kekuatannya. Metode ini digunakan pada pasien untuk memberikan

suatu kepuasan estetik dari restorasi yang terlihat natural karena berbahan utama keramik.

Pemakaian bahan restorasi yang dilekatkan dengan keramik diharapkan dapat mengembalikan

fungsi, bentuk, kontur, warna (hue, value, dan chroma), pencahayaan / penyebaran cahaya

yang natural dan memiliki kekuatan seperti gigi natural. Metode ini dapat memberi suatu estetik

yang memuaskan disebabkan karena memang bahan – bahan yang digunakan dibuat terlihat

sangat natural (www.chandigardentist.com).

1. Komposisi

Bahan inti keramik dari metode ini berbentuk ingots pre-sintered. Bahan dasarnya berupa

glass yang dibentuk pada saat pembentukan inti. Untuk IPS Empress bahan Ingot mempunyai

komposisi kimia berupa silicate glass matrix (SiO2) dengan susunan fase kristalnya berupa

kristal leucite yang berkonsentrasi tinggi, fungsinya adalah agar tahan terhadap penyebaran

crack. SiO2 yang terkandung dalam ingot-nya sebanyak lebih dari 55%. Koefisien expansi dari

bahan IPS Empress adalah 15,0 ppm/0 C lebih tinggi dari sistem lain yang juga menggunakan

metode pressable, yakni IPS Empress 2 (9,7 ppm/0 C). Perbedaan ini akan sangat berpengaruh

pada translucency-nya (Anusavice, 2003).

Keuntungan menggunakan bahan ini adalah sangat akurat, tepat, translucency yang

sangat baik sehingga menghasilkan estetik yang baik pula, bebas dari struktur metal, dan

flexural strength tinggi (Anusavice, 2003).

Bahan lain yang digunakan meskipun dalam persentase yang kecil adalah K2O, Al2O3,

Na2O, B2O3, CaO, TiO2, CeO2 (IPS Empress Ivoclar Vivadent AG).

Bahan tanam yang dipakai adalah bahan tanam khusus untuk IPS Empress. Untuk

Liquid-nya menggunakan IPS Empress Esthetic Speed Investment Material Liquid. Bahan

tersebut mempunyai komposisi colloidal silicic acid sebanyak 30 % wt. Liquid harus dicampur

dengan air yang telah disuling atau air yang di-ionisasi terlebih dahulu untuk mendapatkan

konsentrasi liquid yang diinginkan baru kemudian dapat di-mix dengan powder. Sedangkan

powder-nya menggunakan IPS Empress Esthetic Speed Investment Material Powder, dengan

komposisinya berupa SiO2 (quartz powder) 80 % wt, MgO dan NH4H2PO4 20 % wt (IPS

Empress Ivoclar Vivadent).

Untuk staining dan glazing juga memakai bahan yang khusus digunakan untuk IPS Empress,

yakni IPS Empress Universal Glaze and Stain Liquid 15 ml dengan komposisi 100 % wt

butandiol (IPS Empress Ivoclar Vivadent).

Bahan untuk separasi die-nya berupa Liquid dengan komposisinya berupa wax yang

dilarutkan didalam lebih dari 95 % wt hexane. Digunakan untuk melapisi die selama proses

pembuatan veneer berlangsung. Bahan separasi ini berfungsi menjaga die agar tidak melekat

pada bahan – bahan keramik selain itu juga untuk mencegah timbulnya tegangan permukaan

(IPS Empress Ivoclar Vivadent).

2. Metode Pembuatan

Semenjak teknik dicor sudah jarang digunakan lagi, teknik yang digunakan dalam

Pressable sistem ini berupa lost-wax technique (Anusavice, 2003). Model master terbuat dari

dental stone ekstra keras (IPS Empress Ivoclar Vivadent AG).

 Pada bagian / gigi yang akan dibuat aplikasi veneer dibentuk die yang dapat dilepas dan

dipasang kembali. Bersihkan die untuk menghilangkan kotoran – kotoran yang dapat

menyebabkan noda pada hasil akhir veneer (Haga dan Nakazawa, 2002).

Lalu ulasi permukaan die dengan die separator, kemudian tahap selanjutnya adalah

pelilinan dengan ketebalan sesuai bentuk bagian gigi yang dipreparasi menggunakan beige

wax. Pembuatan sprue juga dilakukan pada tahap ini (Castelnuovo, 2000). Malam yang

digunakan adalah malam yang tidak meninggalkan residu / sisa pada saat dilakukan buang

malam (Ivoclar Vivadent AG).

Setelah itu ditanam dengan menggunakan bahan tanam khusus untuk IPS Empress dan

dibiarkan dahulu sampai menjadi setting dalam muffle (Gurel, 2003) atau mold (Anusavice,

2003) tersebut sebelum dihilangkan malamnya (Anusavice, 2003).

Lalu di bakar untuk menghilangkan malam (Gurel, 2003). Malam dihilangkan untuk

menciptakan ruang yang akan diisi dengan bahan ingot untuk IPS Empress. Proses pengisian

ingot keramik untuk IPS Empress dilakukan dengan menggunakan proses viscous flow atau

dengan mengalirkan glass ceramic (ingot) dengan konsentrasi agak kental pada suhu 11800 C

ke dalam mold selama 1 jam. Teknik seperti ini disebut juga dengan hot-pressing,

keuntungannya adalah dapat diperoleh hasil yang tinggi dalam hal ketepatan marginal-nya

dibandingkan menggunakan teknik sintering (Van Noort, 2002).

Setelah semua tahapan selesai dilakukan, keluarkan keramik dari dalam mold atau muffle

(Anusavice, 2003). Kemudian keramik di potong dan dibentuk disesuaikan pada model kerja

(IPS Empress Ivoclar Vivadent  AG).

Ketebalan pemotongan pada bagian facial adalah 0,2 mm pada 2/3 incisal atau bisa juga

0,5 mm (Castelnuovo, 2000). Lapisi bagian incisal-nya dengan menggunakan bahan silicone,

sebelum dilakukan cut-back procedure. Hal ini untuk memudahkan dalam mengontrol dan

mengecek ketinggian incisal-nya setelah prosedur cut-back dilakukan (IPS Empress Ivoclar

Vivadent AG).

Setelah itu lepas keramik dari model dan silicone guna dilakukan sand blasting pada

permukaan restorasi. Lakukan secara hati – hati karena bahan untuk sand blasting-nya sangat

abrasive. Bahan yang digunakan Al2O3 dengan tekanan 0,5 bar, bersihkan dengan

menggunakan air yang telah disuling atau di-ionisasi (IPS Empress Ivoclar Vivadent AG).

Lalu tahap pelapisan veneer dilakukan, porselen dentin, email dan bahan

translucentPembentukan ini harus dilakukan dengan hati – hati dan memerlukan kecermatan

dari teknisi gigi. Bila diperlukan, penggunaan opaq porselen juga dianjurkan terutama untuk

menutupi bagian gigi yang berubah warna. Pelapisan opaq juga memerlukan keahlian dan

kecermatan agar menghasilkan efek penutupan tanpa menimbulkan bintik – bintik atau noda.

Tepi Incisal harus dibuat translucent (tembus cahaya) agar pelapisan veneer terlihat alami. Oleh

karena itu, opaq porselen jangan digunakan pada daerah ini (Haga dan Nakazawa, 2002).

dibentuk berlapis – lapis.

Porselen dibentuk dengan lapisan - lapisan tipis yang merata, sehingga dapat memberikan efek kelembaban pada porselen selama proses pelapisan dan pembakaran. Lapisan pertama adalah opaq, setelah itu dentin, email dan bahan translucent (Haga dan Nakazawa, 2002).

 

Setelah itu dilakukan pembakaran pertama dengan suhu 8500C selama 2 jam (IPS

Empress Ivoclar Vivadent AG).

 Pelapisan dan pembakaran porselen sebaiknya dilakukan dalam beberapa tahap, agar

jika ada kontur yang kurang sesuai atau tidak tebentuk, maka dapat diperbaiki lagi, sehingga

terbentuk menjadi suatu bentukan yang sesuai dengan anatomi gigi, selain itu dengan metode

tersebut retak dapat dicegah dan diminimalisir (Haga dan Nakazawa, 2002). Sesudah

pembakaran pertama (enamel) selesai, gunakan diamond burs untuk mengurangi kelebihan

dan pembentukan sesuai anatomi. Apabila terjadi pengurangan secara berlebihan sehingga

menyebabkan berubahnya bentuk kontur, maka dapat dibentuk kembali dengan pemberian

bubuk leucite-reinforced glass ceramic yang di-bonding menggunakan teknik sintering

konvensional (Castelnuovo, 2000). Kemudian dibakar lagi untuk yang kedua kalinya dengan

suhu ± 8300C selama 2 jam (IPS Empress Ivoclar Vivadent AG). Ketepatan perlekatan veneer

dapat diperiksa dengan green aerosol. Semprotkan pada seluruh permukaan die (Castelnuovo,

2000) atau dengan menandai silicone menggunakan pensil merah, setelah itu veneer keramik

di pasang pada model serta di-fit kan dengan silicone yang telah diberi tanda untuk disesuaikan

atau fitting (IPS Empress Ivoclar Vivadent AG). Apabila terdapat noda / spots pada veneer

keramik pada saat di-fit kan, hilangkan dengan diamond medium grit round bur. Pengurangan

veneer dilakukan sampai 0,3 mm pada 1/3 cervical dan 0,5 mm pada 2/3 incisal. Dimensi akhir

dari veneer keramik adalah 0,3 mm dan 0,5 mm ketebalan pada 1/3 cervical dan 2/3 incisal

(Castelnuovo, 2000).

Aplikasi diakhiri dengan proses staining dan glazing keramik. Staining digunakan untuk

membentuk karakteristik dari veneer keramik agar terlihat seperti gigi alami. Sebelum proses

staining dilakukan pastikan restorasi bersih atau bebas dari noda, agar hasil akhirnya tidak

ditemukan adanya bercak noda pada veneer keramik, lalu ulasi liquid untuk staining pada

permukaan restorasinya sampai didapat warna yang sesuai dengan karakteristik dari gigi alami,

setelah itu dengan suhu 7800C dibakar dalam furnace selama 1 jam.

Glazing digunakan untuk melengkapi proses pembuatan veneer, dengan glazing

pencahayaan yang baik dari restorasi akan didapatkan. Aplikasi ini hanya dapat  digunakan

pada akhir proses veneering, agar hasil yang didapat maksimal. Setelah itu dibakar di dalam

ceramic oven / furnace dengan temperatur ± 7800C selama 1-2 jam (Castelnuovo, 2000 dan

IPS Empress Ivoclar Vivadent AG).

Sesudah tahap pembakaran selesai veneer keramik siap diaplikasikan atau dipasangkan

pada model. Penyesuaian kecil terhadap veneer dapat dilakukan pada model (Haga dan

Nakazawa, 2002).

B. Metode CAD-CAM (CEREC 3)

          CAD-CAM adalah Computer Aided Design-Computer Aided Machining, yaitu suatu teknologi dari sistem pembentukan keramik generasi baru yang dijalankan menggunakan komputer (Denissen et al, 2002). CAD-CAM sistem terkadang disebut juga CAD-CIM sistem, dimana CIM adalah Computer Integrated Machining atau Milling (Van Noort, 2002). Untuk pembuatan veneers, sistem CAD-CAM yang digunakan adalah CEREC 3. Diperkenalkan di dunia kedokteran gigi pada Februari 2000. Merupakan versi yang lebih canggih dari CEREC 2. Software yang digunakan dalam sistem ini adalah Windows NT-formatted dan dijalankan melalui Personal Computer (PC). PC yang termodifikasi dan bertenaga lebih telah diintegrasikan pada CAD unit, PC jenis ini menyediakan waktu pengoperasian yang singkat, cetakan optic, serta desain restorasi. Cetakan optic digunakan untuk memasukkan informasi fungsional oklusal dan menyimpan data sebagai dokumentasi. Sedangkan CAM unit-nya terpisah dari CAD yang dilengkapi dengan sebuah silinder dan sebuah conical diamond-coated bur. Sistem pengasahan baru ini menyediakan pembentukan restorasi yang kompleks dengan adaptasi presisi yang tinggi terhadap berbagai macam bentuk preparasi gigi. Komunikasi antara CAD unit dan CAM unit adalah melalui wireless via radio. CEREC 3 memiliki kecanggihan yang

lebih tinggi dari generasi – generasi sebelumnya dalam hal produksi veneers, bahkan memiliki bentuk preparasi yang kompleks, memberi morfologi alami seperti gigi natural, serta ketepatan fitting yang tinggi (Bindl dkk, 2002).

1. Komposisi

Bahan atau material untuk CAD-CAM berbentuk feldspatic porcelain block (Anusavice,

2003). Komposisi kimia dari bahan CAD-CAM tersebut adalah:

Silica (SiO2), terdapat dalam empat bentuk yang berbeda yakni quartz kristalin,

kristobalit kristalin, tridymite kristalin, dan silika gabungan non-kristal. Silika gabungan non-

kristal adalah bahan dengan titik leleh tinggi (high fusing), hal ini disebabkan oleh anyaman tiga

dimensi dari ikatan kovalen antara tetrahedral silica, yang merupakan struktur dasar dari

anyaman kaca (glass). Fluks seringkali ditambahkan untuk menurunkan temperature, yang

diperlukan pada saat proses sintering dari partikel bubuk porselen. Meskipun demikian,

penambahan modifier seperti fluks, tidak boleh terlalu banyak karena akan mengakibatkan

kurangnya durabilitas kimia (ketahanan terhadap air, asam, dan basa) dari glass. Selain itu, jika

tetrahedral yang terganggu terlalu banyak, maka glass akan banyak ter-kristalisasi selama

proses pembakaran porselen. Bagaimanapun juga, keseimbangan antara kisaran leleh dan

durabilitas kimia yang baik harus dipertahankan (Anusavice, 2003). Konsentrasi SiO2 yang

terdapat dalam bahan blocks dari CAD-CAM adalah sebanyak 56 – 64%

(www.cereconline.ecomaXL).

Alumina (Al2O3), mengandung kristal – kristal alumina dalam jumlah yang memadai

(Anusavice, 2003). Bahannya terdiri atas feldspatik glass yang berisi ± 40-50% alumina. Partikel

alumina digunakan karena lebih kuat daripada glass, lebih efektif untuk mencegah penyebaran

crack daripada quartz dan bertindak cepat menghentikan crack jika terjadi. Mengingat flexural

strength dari porcelen feldspatik adalah yang terbaik yakni 60 Mpa, maka setelah penggunaan

aluminous core porselen dengan alumina kekuatan flexural-nya dinaikkan sampai mencapai

120-150 Mpa (van Noort, 2002). Bahan ini juga diperlukan dalam pembuatan dentin dan

pewarnaan enamel dari feldspatik porselen. Komposisi poselen ini mengandung alumina yang

tinggi yakni 40 – 85%, sedangkan konsentrasi dari silica oxide diturunkan dari 60% ke 15%.

Komposisi aluminum oxide-nya tidak lebih dari 50%. Bahan ini digunakan untuk preparasi full

crown dan untuk pelapisan veneer porselen (Font, 2006). Penggunaan bahan alumina sebagai

bahan blocks CAD-CAM dikonsentrasikan sebanyak 20 - 23% (www.cereconline.ecomaXL).

Selain itu ada beberapa komposisi kimia lain yang terdapat dalam material blocks dari

CAD-CAM meskipun dalam jumlah yang tidak relatif besar ,yaitu: Na2O (6 - 9%), K2O (6 - 8%),

CaO (0,3 - 0,6%), TiO2 (0,0 - 0,1%) (www.cereconline.ecomaXL).

Vitadur Alpha veneering ceramic digunakan unuk membangun estetiknya sedangkan

Vita Akzent stains dan glazing digunakan untuk membentuk karakterisasi dari lapisan veneer

keramik (Bindl dkk, 2002). Bahan – bahan yang digunakan untuk membangun estetik veneer,

staining serta glazingnya memiliki komposisi utama berupa keramik feldspar dan glass ceramic

(terutama bahan block-nya) (CEREC Sirona Dental System).

2. Metode Pembuatan                                       

Menurut (bindl dkk, 2002) pembuatan veneer keramik dimulai dengan pengaplikasian Cerec liquid pada hasil preparasi dan gigi tetangga pada cetakan. Kemudian dilakukan pelapisan opaq secara tipis pada permukaan yang akan dilakukan perawatan. Opaq yang digunakan adalah cerec powder. Tujuan dari pelapisan opaq adalah agar high-contrast 3D dapat membaca permukaan yang akan dirawat. Hasil dari scan 3D ini disebut dengan ”optical impression”. Setelah itu mengikuti mode start-up Cerec 3D, pilih mode desain veneer, lalu data base mengenai morfologi gigi akan diaktifkan, dan gigi yang akan diproses veneer dimasukkan.

Optical impression akan direkam oleh Cerec 3D dengan mengggunakan kamera, pusat preparasinya diletakkan pada pertengahan layar / monitor, gigi kemudian dibuat menjadi vertikal, agar seluruh bagian dari preparasi dapat terfokuskan dengan baik.

Bagian mesial dan distal gigi disarankan mengikuti garis “equator” atau garis tengah

yang terlihat pada monitor setelah itu diidentifikasikan dengan gigi sebelah untuk memberikan

informasi dan memperhitungkan letak / posisi proximal dari gigi tetangga. “Bottom line” atau

garis batas bawah dari 3D menandai bahwa preparasi margin telah lengkap. Lalu sistem secara

otomatis akan membuat “contact line” atau garis kontak yang menggambarkan keadaan

maksimal circumference dari veneer, dan menentukan kontak proximal dengan gigi yang

berdekatan.

Sistem kemudian membentuk 2 garis mesiodistal melewati permukaan labial sampai gigi

sebelahnya. Pada layar monitor akan tampak suatu garis melintang yang terletak paling atas,

merupakan bagian paling tinggi dari permukaan labial yang akan diberikan veneer dan garis

melintang paling bawah merupakan bagian yang paling rendah. Kedua garis ini akan dirubah

menjadi suatu bagian untuk membentuk morfologi gigi. Desain veneer yang halus dapat

dihasilkan menggunakan perlengkapan penghalus permukaan (surface tools) yang ada pada

layar monitor komputer. Perlengkapan ini dapat memeriksa bagian melintang dari veneer

dengan beberapa petunjuk yang ada. Sedangkan bagian melintang yang cocok untuk kontruksi

veneer. Bagian horizontal berpedoman pada bagian yang melintang antara mesial sampai distal

(ditandai dengan garis merah horizontal).

Pada saat muncul gambar icon mesin pada layar monitor diaktifkan, konstruksi secara

otomatis akan tersimpan dalam hard disk komputer dan user akan diminta memasukkan

keramik block.

Setelah keramik block dimasukkan, sistem akan memperhitungkan bentuk veneer

melalui data yang dihasilkan atau didapat dari optical impression dan pemilihan batas

konstruksi. Mesin bekerja dengan menggunakan 2 burs yang dilapisi diamond (diamond-coated

burs), satu silinder dan cone pembentuk (cone shaped) bekerja secara bersama. Setelah 10

menit bentuk mulai di-grinding, kemudian veneer keramik siap dipotong dengan mesin

pemotongan (Bindl dkk, 2002).

Sesudah dilakukan pemotongan, veneer dicobakan pada plaster cast. Untuk

memberikan estetik pada veneer, area yang akan dikurangi seperti mesioproximal dan 1/3

incisal dari permukaan buccal ditandai dengan pensil merah. Mesin akan menipiskan bagian

tersebut, labial area yang ditandai kemudian ditipiskan kira – kira sebanyak 50% menggunakan

diamond bur. Vitadur alpha veneering ceramic, digunakan untuk membangun estetiknya. Untuk

bagian incisal dibentuk dengan transparent blue, opalescent, dan clearenamel keramik. Bagian

leher keramik, berwarna lebih gelap daripada body, warna ini diaplikasikan pada 1/3 gingiva.

Setelah itu dikeringkan selama 5 menit, lalu veneer di bakar di dalam mesin vacuum furnace.

Dengan suhu 9500 C. keramik bersama dengan aplikasi

Veneer yang telah dibakar dapat dihaluskan dan dibentuk konturnya menggunakan

flame shaped diamond bur. Untuk mendapatkan estetik yang sempurna dapat ditambahkan

ceramic paint-on shade yang diaplikasikan pada permukaan gigi (stainning), kemudian dibakar

lagi dengan suhu 8500C agar warna dari keramik cocok dengan gigi aslinya, pelapisan tipis dari

glaze keramik dapat digunakan untuk mendapatkan kilauan alami gigi. Setelah di-glaze veneer

dibakar lagi dengan suhu 9400C, kemudian cobakan pada model. Terakhir bagian internal

surface dari restorasi di sandblasting dengan aluminum oxide yang berukuran 50 µm untuk

menghilangkan kelebihan glazing keramik pada bagian tersebut (Bindl dkk, 2002).

Setelah semua tahapan antara IPS Empress dan CEREC 3 CAD-CAM selesai dilakukan dan hasil akhir veneer telah di-Finishing, maka tahap selanjutnya adalah proses perlekatan, antara veneer all ceramic dengan gigi yang telah dipreparasi sebelumnya. 

PEMBAHASAN

Kemajuan teknologi di dunia kedokteran gigi diikuti  berkembangnya teknik – teknik baru

dalam pembuatan veneer keramik. Ada beberapa faktor yang harus diperhatikan pada

pembuatan veneer keramik, yaitu warna yang menjadi dasar strukturnya, pemilihan bahan

semen, dan kedalaman preparasi. Pemilihan bentuk preparasi keramik dan

bondingbiokompabilitas, dan masa pakainya (Dunitz, 1999). (perlekatannya) sangat

berpengaruh pada: peningkatan sifat mekanis, sifat

Perlekatan veneer porselen dengan gigi diawali dengan proses pengetsaan yang akan

menghasilkan suatu perlekatan secara kimiawi dan mekanik antara porselen dengan gigi.

Pengetsaan pada gigi menggunakan 35 % phosphoric acid gel selama 15 detik, kemudian

dibilas dengan air selama 30 detik. Sedangkan pada porselen pengetsaan dilakukan selama 1

menit dengan fluoridric acid etching gel (Castelnuovo et al, 2000) atau dengan 10 % ammonium

difluoride gel untuk bahan keramik dari glass (Dunitz, 1999) kemudian dibilas dengan air

selama 30 detik (Castelnuovo, 2000). Dalam kondisi tersebut semen masih belum dapat

melekat pada porselen, oleh karena itu untuk menyatukan semen dan porselen digunakan

suatu bahan penyambung silane. Bahan ini merupakan suatu monomer silicon organic yang

reaktif dan didalam satu molekulnya bahan organic dan anorganic masing – masing bereaksi

sendiri – sendiri. Bahan ini merupakan suatu senyawa yang mempunyai gugus fungsional untuk

perlekatan secara kimia. Dengan mengoleskan bahan penyambung silane pada permukaan

dalam (internal surface) veneer porselen, maka porselen dan semen dapat disatukan, juga

semen dan struktur gigi dapat dilekatkan. Dengan menggunakan bahan penyambung silane,

kekuatan perlekatan dari semen dengan porselen dapat melebihi 300 kgf/cm2, ini merupakan

kekuatan perlekatan yang sangat kuat (Haga dan Nakazawa, 2002).

Pelapisan atau penggunaan veneer keramik yang dilekatkan pada enamel gigi memiliki

beberapa keuntungan (Dunitz,1999), antara lain pelapisan veneer dapat diaplikasikan pada

bentuk serta beberapa posisi gigi sehingga estetik dapat diperbaiki. Selain itu veneer dapat juga

merubah atau menambah panjang gigi, seperti misalnya untuk memperpanjang bagian incisal

dari gigi incisivus yang patah, disebabkan karena kecelakaan. Tekstur permukaan dari gigi yang

rusak dapat dirubah secara permanen dan elegan, seperti misalnya penghilangan dysplaasia

atau dystrophy pada enamel. Penggunaan enamel pengganti seperti ini merupakan teknik

terbaik karena tanpa merusak jaringan gigi terlalu banyak. Pewarnaannya dapat disesuaikan

dengan keadaan alami gigi penderita. Pelapisan Veneer dapat dijadikan suatu pilihan

perawatan untuk meningkatkan atau merubah warna natural gigi. Namun perubahan ini memiliki

keterbatasan, bergantung pada: warna gigi utama, pemilihan keramik, bonding / perlekatan

semen yang digunakan, dan kedalaman preparasi. Selain itu veneer keramik juga memiliki

ketahanan yang sangat baik terhadap kondisi biologis, kimia dan mekanik mulut, akan tetapi

ada beberapa sistem keramik yang memiliki ketahanan buruk terutama saat digunakan untuk

menghilangkan noda pada permukaan gigi. Pasta gigi ber-fluoride tinggi dapat menyebabkan

abrasi mekanik pada permukaannya (Dunitz, 1999).

Penggunaan porselen gigi dengan variasi chroma, seperti transparan, translusion, atau

opalesen (selain opaq) porselen, dimungkinkan untuk mendapatkan suatu karakteristik dari

enamel alami, misalnya seperti adanya crack, fissure, dan opalescence. Pelapisan veneer

memang memberikan efek pencahayaan yang bagus di seluruh permukaannya. Warna akhir

merupakan hasil dari sejumlah bentuk penyinaran yang direfleksikan dan terserap secara

keseluruhan oleh permukaan keramik. Tekstur dan bahan opaq yang tidak sesuai dari keramik,

atau translusi bonding komposit yang tidak mencukupi, akan menyebabkan hilangnya

transmisirefleksi cahaya yang lebih besar dan tidak diperlukan sehingga membuat warna opaq

tidak nampak natural (Dunitz, 1999). cahaya secara tiba – tiba kemudian akan berakibat pada

Menurut Haga dan Nakazawa, 2002 keuntungan penggunaan veneers keramik

dibandingkan dengan tipe – tipe protesa yang lebih umum digunakan seperti mahkota porselen

– logam dan mahkota selubung (jacket crown) adalah dipertahankannya struktur gigi, karena

preparasi gigi dilakukan terbatas pada pengurangan selapis tipis email pada bagian labial

sedangkan bagian lingual-nya tidak dipreparasi, sehingga struktur gigi dapat dipertahankan dan

pulpa terlindungi, maka gejala – gejala seperti tidak nyaman karena karies sekunder dan

hipersensitivitas dapat dikurangi. Selain itu bagian tepi incisal-nya juga dibiarkan tidak

dipreparasi, bahkan juga untuk gigi anterior rahang bawah sehingga tinggi oklusal tetap dapat

dipertahankan dan pembuatan gigi tiruan dapat dilakukan tanpa mengubah hubungan oklusal.

Tepinya diletakkan pada batas gingival, sehingga kondisi jaringan periodontal setelah

perawatan juga akan tetap baik.

Sedangkan kerugiannya adalah memiliki prosedur preparasi yang tidak mudah, teknik

pembuatan di laboratorium yang cukup rumit serta dibutuhkan ketelitian, biaya yang relatif

mahal, apabila terjadi kerusakan sangat sulit diperbaiki bahkan mungkin, tidak dapat diperbaiki

lagi, penggantian warna sulit dilakukan setelah penyemenan, adanya retak (fractures) yang

setiap saat bisa muncul (Dunitz, 1999). Selain itu kerugian lainnya dalam penggunaan veneer

keramik diantaranya adalah sulitnya mencari kesesuaian warna yang sempurna dari lapisan

porselen / keramik, karena veneer merupakan lapisan yang sangat tipis. Prosedur preparasi

yang sulit disebabkan minimnya daerah yang harus dipreparasi untuk mempertahankan

sebagian jaringan yang masih sehat, maka pada saat preparasi akan mudah sekali terjadi

pengurangan yang berlebihan mengingat rumitnya preparasi yang harus dilakuakan.

Pemolesan kembali sulit dilakukan setelah pengasahan, dan jika veneer sudah dipasang pada

gigi, sulit untuk dilepas tanpa membuatnya pecah (Haga dan Nakazawa, 2002).

Pembuatan veneer keramik menggunakan metode pressable memiliki keuntungan

memiliki sifat translucent (tembus cahaya) sehingga menghasilkan estetik yang baik, ketepatan

fitting yang sangat baik (Anusavice, 2003). Selain itu menurut (Gurel, 2003) keuntungannya

adalah aman dalam pemakaiannya, tidak memerlukan waktu pembuatan yang lama, tingkat

keberhasilannya tinggi, indikasi penggunaanya banyak.

Sedangkan kerugiannya adalah potensinya dalam membentuk fracture dan memerlukan

penggunaan resin semen untuk proses bonding secara micro-mechanical pada mahkota dan

struktur gigi (Anusavice, 2003)

IPS Empress memiliki kekuatan relative (flexural strength) yang sedang / cukup yakni

sebesar 112 Mpa, ketahanan terhadap fracture (fracture toughness) 1,3 Mpa.m1/2, termal

expansi (Coeficient of thermal expansion) 15,0 ppm/0C, kualitas margin-nya sangat baik,

kekerasan relatifnya (relative toughness) cukup tinggi, sifat abrasive bahan intinya sedang,

proses pembuatannya cukup mudah tapi perlu ketelitian, untuk harganya relatif murah

dibanding dengan teknik lain seperti CAD-CAM. (Anusavice, 2003)

Metode lainnya yaitu Metode CAD CAM dirancang untuk menghasilkan keindahan,

CEREC 3 memiliki kecanggihan yang lebih tinggi dari generasi – generasi sebelumnya dalam

hal produksi veneers, bahkan memiliki bentuk preparasi yang kompleks, memberi morfologi

alami seperti gigi natural, ketepatan fitting yang tinggi (Bindl dkk, 2002).

Keuntungan dari Teknik ini adalah dapat memilih jenis inti keramik yang akan digunakan

sesuai dengan kekuatan dan ketahanannya terhadap fraktur, dapat mengurangi sifat

abrasivetranslucency atau sifat tembus cahayanya sangat cocok dipadukan pada pelapisan

keramik, kesempurnaan fitting dari restorasi ini sangat baik, estetik yang dihasilkan baik, proses

pembuatannya cepat, dapat digunakan untuk banyak indikasi, hasil restorasinya aman

digunakan, sifat porus dari inti dapat diabaikan (Gurel, 2003). Sedangkan kerugiannya adalah

peralatannya sangat mahal dan teknik menggambar atau pembentukan inti-nya memerlukan

ketelitinan yang lebih agar didapatkan suatu hasil restorasi yang terlihat natural seperti gigi

aslinya (Anusavice dan Gurel, 2003). (Anusavice, 2003), Tingginya sifat

CEREC 3 memiliki kekuatan relative (flexural strength) yang tinggi yakni sebesar 113-

154 Mpa, ketahan terhadap fracture (fracture thoughness) 1,7-2,2 Mpa.m1/2, termal expansi

(Coeficient of thermal expansion) 9,4 ppm/0C (www.cereconline.ecomaXL), kualitas margin-nya

cukup baik, hasil akhir dengan teknik ini sifat tembus cahanya (translucensi) sangat tinggi, 

kekerasan relatifnya (relative toughness) sangat tinggi, sifat abrasive bahan intinya kecil, proses

pembuatannya cukup rumit, untuk harganya sangat mahal (Anusavice, 2003).

KESIMPULAN

 Hasil akhir dari restorasi veneer all-ceramic anterior yang menggunakan metode CAD-

CAM (CEREC 3) lebih baik dibandingkan dengan metode Pressable (IPS Empress) terutama

pada flexural strength serta ketahanan terhadap fracture, kekurangannya terletak dalam proses

pembuatan, metode CAD-CAM lebih rumit serta lebih membutuhkan ketelitian yang tinggi dari

teknisi dibanding Pressable, sehingga membuat harga dari restorasi CAD-CAM (CEREC 3)

lebih mahal jika dibandingkan dengan Pressable (IPS Empress)

DAFTAR PUSTAKA

Anusavice, KJ. 2003, Phillips’ Science of Dental Material, 11th ed,      

Saunders an Imprint of Elsevier, St. Louis, Missouri, p. 655-697

Brau, BJ. 2002.  Preventive and Cosmetic Dentistry, Retrieved: Desember

15, 2007, from http://www.fourseasonsfamily dentistry com/cosmetic_dentistry.html

Bindl, A; Apholt, W; Mormann, WH. 2002. Computer Veneers with the

Cerec 3, Quintessence International, 44th ed,  p. 153-162

Castelnuovo, J et al. 2000, Fracture Load and Mode of Failure of Ceramic

Veneers with Different Preparation, TheJournal of Prosthetic Dentistry, 83th edition, Mosby Inc,

St. Louis MO, p. 171-180.

CEREC Blocks. Industrial Manufactured Structured Feldspatic Ceramic

Blocks Operating Instruction, Retrieved: Desember 30, 2007, From www.cereconline.ecomaXL.

Denissen, HW et al. 2002, Porcelain-veneered computer-generated partial

crowns, Quintessence International, 33th ed, By Quintessence Publishing Co, Inc. Chicago,

Berlin, London, Tokyo; p. 723-730

Dunitz, M. 1999,  Esthetic Dentistry and Ceramic Restoration, London NWI

OAE, p. 161-213

Font ,AF et al. 2006, Choice of Ceramic for Use in Treathments with

Porcelain Laminate Veneers, Medico Oral Pathologic Oral Buccal, 11th ed, p. 297-302.

Gupta. A. 2007, IPS Empress Crown, Retrieved: Desember 26, 2007.

chandigarhdentist.com/crowns-bridges.htm

Gurel G. 2003, The Science and Art of Porcelain Laminate Veneers,

Quintessence Publishing Co.Ltd, Germany; p. 30-479

Haga M; Nakazawa A. 2002, Veneer Porselen Laminasi, Agus Djaya dan

Lilian Yuwono, Hippkrates, Jakarta 10042, Hipokrates, h. 1-30

IPS Empress Esthetic, Ivoclar Vivadent AG, Schaan Leichtenstein,

Retrieved: Desember 12, 2007, from www.heimdal tannteknikk.no/filer/empress.pdf and

www.ivoclarvivadent.com

Van Noort R. 2002, Introduction to Dental Materials, 2nd ed, Elsevire

Science Limited, London, p. 235-246

 Zwemer TJ. 1993, Boucher’s Clinical Dental Terminology A Glossary Of

Accepted Terms in all Disceplines of Dentistry, Philadelphia.Mosby, p. 325

Lithium Disilicate: Masking Discolored Teeth Written by Jason C. Horwitz, DDS Thursday, 06 October 2011 14:36

INTRODUCTIONRecent developments in ceramic material sciences have led to improvements in modern ceramics and restorative procedures.1 These improvements have prompted a substantial increase in the clinical use of all-ceramic restorations.1 Simultaneously, advances in chairside computer-aided design (CAD) and computer-aided manufacturing (CAM) techniques have enabled clinicians to offer restorations that are created faster and easier than ever before.1 Whether in the office or in the dental laboratory, these new technologies and materials give clinicians in-office treatment options for even the most challenging cases.1

A Brief Overview of Lithium Disilicate Lithium disilicate is a ceramic material that contains approximately 70% by volume needle-like crystals in a glassy matrix.2,3 The controlled size, shape, and density of this structure results in all-ceramic restorations that demonstrate greater strength and durability, with a relatively low refractive index.2-4 Such characteristics allow the material to display outstanding optical properties and optimal aesthetics.2-4

Presently, lithium disilicate can be fabricated using 2 different processing techniques; it can be either pressed or milled.3,5 Pressable lithium disilicate restorations are fabricated with a wax hot-press technique, while the milled CAD/CAM version is fabricated with either laboratory or chairside CAD/CAM technology.3,5 Although both products are composed of the same material, the flexural strength of pressable lithium disilicate is slightly higher at 400 MPa, while the CAD/CAM milled monolithic material (once crystallized in the furnace) posseses a flexural strength of 360 MPa.3,6 These strengths result from the difference in crystal size found in the 2 different forms of lithium disilicate; however, all other properties are similar.3,6 Due to the presence of a glassy matrix and this all-ceramic's excellent strength characteristics, dentists can choose to either conventionally cement or adhesively bond restorations, based on the clinical parameters in each individual case.3,6

Figure 1. Preoperative view of a discolored tooth with an existing perforated gold onlay.

Figure 2. The appropriately shaded IPS Empress CAD block (Ivoclar Vivadent) was chosen, which closely corresponds to the final IPS e.max shade (Ivoclar Vivadent) after firing the blue block in the furnace.

Figure 3. The old restoration with any recurrent decay was removed.

Figure 4. Initial excavation showing depth cuts. Note the stained amalgam that presented in the canals of the tooth.

Figure 5. After the amalgam was excavated, the tooth was etched with phosphoric acid gel (Ultra-Etch [Ultradent Products]).

Figure 6. The bonding agent (ExciTE F VivaPen [Ivoclar Vivadent]) was used in preparation for a composite resin crown buildup.

Figure 7. The dual-cured resin buildup (LuxaCore [DMG America]) was placed under rubber dam isolation (Flexi Dam [Coltène/Whaledent]).

Figure 8. The buildup material was then light-cured.

Figure 9. View of the initial crown preparation.

Figure 10. View of the completed crown preparation.

CAD Lithium DisilicateCertain techniques have been developed to maximize the ease of use and aesthetics of lithium disilicate (such as IPS e.max CAD [Ivoclar Vivadent]). CAD/CAM processing techniques allow the clinician and dental laboratory team to efficiently produce restorations stronger than those composed of conventional materials. IPS e.max CAD is indicated for the fabrication of veneers, inlays, and partial or full-crown restorations for individual teeth.7 Exhibiting an unusual blue-coloring in the block form, e.max CAD is machined in a soft, intermediate state.7 To ensure a proper fit, the material may also be manually cut back or adjusted in just a few quick and easy steps.7

It comes in 3 different levels of translucency and 2 sizes.7 High translucency blocks are ideal for minimally invasive, full-contour restorations, such as inlays, onlays, and veneers, and can be characterized with staining materials.7 Low translucency blocks were created for the anterior region, when partial and full crowns are required, allowing for a cut-back and layering technique (using IPS e.max Ceram [Ivoclar Vivadent]) for enhanced aesthetic results.7 Because of the material's opalescence, high opacity blocks can be used to produce frameworks for vital and slightly discolored prepared teeth that are then veneered with e.max Ceram.7 The CAD blocks for fabricating full-contour restorations are available in 16 A to D shades and 4 BL (bleach) shades.7 When creating the tooth's opacity, the e.max CAD medium opacity blocks are available in group shades and work exceptionally well when utilizing a layering technique.7

Chairside CAD/CAM FabricationOne of the chairside CAD/CAM systems currently available (used to fabricate the clinical restoration demonstrated in this article) is the CEREC System (Sirona Dental Systems). It provides efficient and high-performance milling machines to save dentists and patients both time and expenses.8 The software is easy to use and intuitive and automatically adjusts the restorations into occlusion, and color coding ensures proximal contacts meet the dentist's specifications before milling.8 By using CEREC software (the new 4.0 version was just released in September 2011) and 3-dimensional models, dental professionals can realize predictable and aesthetic outcomes.8

The CEREC MC XL, the larger of the 2 milling machines available to dentists, delivers high speed and simplicity, with low noise levels.8 The machine has the ability to produce one-visit single-tooth and quadrant restorations at the chair.8 It has a precision in the range of +/- 25 µm, with a 6-minute milling time for full-contour crowns and 3 to 4 minutes for partial coverage crowns.

The second system, the CEREC MC L Compact Milling Unit, delivers economical, highly aesthetic restorations in one visit.8 This unit can efficiently mill restorations for

minimally invasive procedures and conservative preparations.8

Let's look at a restorative case that was done in our office using lithium disilicate and chairside CAD/CAM technology to efficiently provide a functional and aesthetic result for our patient.

CASE REPORTDiagnosis and Treatment Planning A 53-year-old female presented with a previously treated root canal on tooth No. 19 (Figure 1). The core buildup had been completed with an amalgam and had since leaked corrosive byproduct into the dentin and cementum. This created a severely stained underlying tooth structure that had subsequently been restored with a gold onlay. Since the gold restoration did not cover the buccal aspect of the dark tooth, the patient had been self-conscious when smiling, talking, and laughing.

To correct these issues, the treatment plan consisted of removing the previously placed and leaking amalgam core. Remaining tooth structure that had been affected by recurrent decay would also be excavated, and the core of the tooth would be rebuilt with a dual-cured resin material. To cover the dark tooth, the most opaque CAD block of lithium disilicate would be used.

Figure 11. The preparation was checked to ensure adequate occlusal clearance.

Figure 12. The surrounding gingival tissue was troughed with a diode laser (AMD Lasers) in preparation for final optical impression.

Figure 13. After taking an antagonist bite impression, the rubber dam was replaced, and images of the teeth were taken.

Figure 14. The preparation was powdered, and the final preparation images were taken (CEREC 3D (Sirona Dental Systems).

Figure 15. Final design using the CEREC 3D software before milling shows where to expect some high spots (these were kept for illustration in final milling).

Figure 16. View of the crown in the "blue block" stage after the occlusion was initially checked. (Compare to figure 15).

Figure 17. Glaze and characterizations were applied to the crown before final baking.

Figure 18. View of the final try-in after cooling from oven.Figure 18. View of the final try-in after cooling from oven.

Figure 19. The crown was resin cemented (Multilink Automix [Ivoclar Vivadent]) under rubber dam isolation with easy cleanup.

Figure 20. View of the completed in-office CAD/CAM lithium disilicate (IPS e.max CAD (Ivoclar Vivadent]) full-coverage restoration.

Clinical ProtocolThe patient's soft tissues were initially anesthetized with one carpule of 4% prilocaine HCL (Citanest 4% [DENTSPLY Pharmaceutical]). One and a half carpules of 2% lidocaine with 1:100,000 epinephrine (Lidocaine ANES 50 [Patterson Dental]) were then used to anesthetize the mandible. A latex-free rubber dam (Flexi Dam [Coltène/Whaledent]) was then placed to protect the patient from the mercury vapors produced during the removal of the old amalgam.

Then, by using an IPS Empress CAD block (Ivoclar Vivadent) as a comparison for shade taking against the natural tooth, the proper shade of IPS e.max CAD block was selected (Figure 2). It is important to note that in this author's opinion, the e.max block shades are extremely similar to Empress shades, which made it possible to use these blocks as a guide. As an alternative and more traditional method, a shade guide (such as the Chromoscope Shade Guide [Ivoclar Vivadent]) can also be used.

The old restoration was removed (Figure 3), and the tooth was then prepared with a 1.5 mm shoulder and 1.5 mm of occlusal clearance (Figure 4). A total etch of 35% phosphoric acid (Ultra-Etch [Ultradent Products]) was then used on the surface of the preparation (Figure 5), after which the preparation was cleansed and dried. A fifth-generation bonding agent (ExciTE F VivaPen [Ivoclar Vivadent]) was then placed on the tooth (Figure 6), air-dried, and then light-cured. A dual-cure resin (LuxaCore [DMG America]) then placed for the core buildup and cured (Figures 7 to 10).The preparation was checked to ensure adequate occlusal clearance (Figure 11). The surrounding gingival tissue was troughed with a diode laser (AMD Lasers) in preparation for final optical impression (Figure 12). An antagonist bite impression was then taken (Figure 13). To facilitate digital imaging, the tooth was powder coated (PowderPro [Advanced Dental Instruments]), and the digital impression (CEREC 3D [Sirona Dental Systems]) was taken (Figure 14).

The crown was digitally designed using the CEREC 3D software (Figure 15) and then milled (Figure 16). Upon completion of the milling process, the crown was tried into the mouth in the "blue block" stage to verify the fit and occlusion. Any necessary adjustments to the crown were completed during this time prior to crystalization in a chairside furnace (V.I.P. Universal X-Press [Jelrus]). The crown was then glazed (IPS e.max Universal Glaze [Ivoclar Vivadent]) and customized using subtle orange, cream, and blue stains to create natural characteristics that would make it indistinguishable from the surrounding natural dentition (Figure 17). The restoration was then ready for the final firing.

After the crown had cooled, it was tried in the patient's mouth once again to verify fit (Figure 18). A rubber dam was placed once again. The internal surface of the crown was treated with silane (Monobond [Ivoclar Vivadent]) in preparation for its cementation with a resin cement, per manufacturer instructions. The restoration was subsequently bonded using a self-adhesive composite (Multilink Automix [Ivoclar Vivadent]) (Figure 19). Once seated with the uncured cement in place, the crown was tacked for 7 seconds with a light-curing unit (FLASHlite [Discus Dental]). Then, any excess cement was carefully trimmed away from the margins and the tooth was gently flossed to clean interproximally. Immediately following, to complete the polymerization of the resin cement, the restoration was light-cured again for a full 60 seconds.

Next, the rubber dam was removed, and the occlusion was checked in centric occlusion and all excursive movements. The patient was dismissed from the office after satisfactory function and aesthetics were verified in the completed restoration. The patient was very pleased with the aesthetics and function of the chairside fabricated lithium disilicate restoration and the final results of treatment (Figure 20).

The total treatment time from seating the patient to dismissal was approximately 70 minutes. This included the 40-minute cycle in the oven, during which time other treatments or hygiene checks could have been performed.

CONCLUSIONThrough the use of the latest developments in material sciences and CAD/CAM fabrication

technologies, proper training and teamwork, and the wise use of chair time, dental professionals are able to complete many cases in a highly efficient manner. By utilizing appropriate modern dental materials, indications such as discolored teeth and amalgam leakage can be addressed quickly and easily, thus saving time and reducing expenses for both the doctor and the patient. Patients can also expect to receive highly aesthetic restorations since materials like lithium disilicate (even when milled chairside) can be customized artistically in the dental office to provide lifelike results.

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