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The time is ripe: No one can ignore the topic of CAD/CAM any more. However, especially small and medium-sized laboratories wanting to start with zirconium dioxide technology face the question: “Should I look for a suitable milling center or rather buy my own equipment?”. Schütz Dental provides an efficient CAD/CAM system specifically designed to suit the needs of just such laboratories: “Tizian CAD/CAM”.
As I contemplate on my initial personal experience with CAD/CAM technologies with Dentsply Cercon Smart Ceramics, I vividly recall the number of questions that I had to contend with. How would I come to my final decision on one system over another? What could I realistically expect from any one system or manufacturer? Would the dentists that entrust me with the fabrication of prosthetics and embrace the technology? Would I be able to afford this technology and the associated upgrades that go along with venturing into this process? So many questions and a personal fear: am I making the right decision?
As a beginning apprentice at Shaw Laboratories in Toronto, I had the fortune to train under the guidance of a brilliant technician, Mr. Richard Hack, RDT. I recall often being perplexed and unsure on what specific tool to use for a particular task. Hack taught me a very basic rule to follow, “…you have to know what it is you will be doing, not hoping to do, not wishing to do, but doing, and then the choice will be simple”. These wise and practical words of advice would prove to be extremely influential in my future decision making and ultimately it would contribute in shaping my dental technologist career.
This philosophy I adopted when it was time to make a decision about which system would best suit the needs of my laboratory. The information that I needed to make this decision was already in my hands, starting with the last 5 years of prescriptions on file, I had to find out what I was really doing and how much of it. The results were quite surprising, the majority of the fixed prosthetics that were being fabricated were singles, multiple of singles in the same case, bridges from 1 x 3 to 1 x 8’s, combination cases consisting of crowns, veneers and in some situations matching of full ceramic products to porcelain fused to metal products. In actual fact the amount of full mouth bridges was surprisingly low, and these I still would rather fabricate from precious alloys, as this allows maximum freedom in fitting and laser welding if necessary. Simply put, you cannot cut and reposition a zirconium bridge, they fit or they do not fit, nothing in between.
Up to now the life-span of chair side fabricated prostheses was limited. Dental labs are equipped to produce durable interim prostheses but it is a costly and time consuming process. The rapid development of the CAD/CAM – Technology opened up new possibilities. With the right combination of materials and devices superior results can be achieved and the user can work more efficiently. The new Vita CAD-Temp composite blocks are used for the fabrication of long term prostheses and let the technician benefit from the CAD/CAM – Technology. The following article describes how these blocks are used in the fabrication of six temporary crowns.
Index: CAD/CAM, hard and soft tissue augmentation, implants, interim care
The patient came to me with an upper and lower denture which was preserved from a prosthetic point of view but not functioning properly. I noticed instantly that the upper jaw was protruding with tooth 11 and 21 being very loose and beyond restoration (Figs. 1 to 3). Due to the overall unsatisfactory situation, the patient requested not only a prosthetic but an aesthetic restoration. After the preliminary periodontal therapy was finalized we could take care of the posterior teeth in the form of fully ceramic restorations.
As previously stated, in dentistry most of the CAM machines are of the milling type, cutting a definitive design from a solid block of material, usually zirconia, contemporarily used as a substructure for all-ceramic crowns and bridges. There are several diverse machines now on the market with the number of new entries growing at an ever-increasing rate. Although most are employed to cut zirconia, there are a growing number which can mill assorted materials including other types of ceramics such as leucite glass, feldspathic porcelain (now being studied for laminates and inlay/onlays), metals including titanium for dentistry, and others such as those used by industry.
In the case of zirconia, the “CNC’ milling (computer numerical controlled) machines normally cut the softer “white state”, with sintering (or hardening) in an oven occurring secondarily. Some companies employ partially sintered (also known as pre-sintered) zirconia that lies somewhere between the green state and fully sintered zirconia, to be able to cut ‘wet’ and reduce subsequent processing time.
The much harder fully-sintered zirconia (sometimes referred to as HIP zirconia) can also be milled. The main advantage to cutting fullysintered zirconia is that the final product is the most dimensionally stable, with zero possibility of unwanted structural change by subjecting it to subsequent heating in an oven (there is an approximately 20% shrinkage associated with sintering). The obvious second advantage is the time-savings from not having to sinter overnight.
For an aesthetic and functional restoration, the abutment design plays a major role. For a just a while now, individualized abutments have been manufactured out of titanium or zirconium dioxide for the synOcta prosthetic system RN in cooperation with the company Sirona. The dental team of MDT Thomas Lassen and Dr. Horst Lohrmann, as well as prof. Dr. Dr. Heinz kniha and Dr. Michael Gahlert, describe the use of this system with reference to a case study.
In a first visit, a 48-year-old female patient complained of the poor aesthetics of her maxillary anterior teeth. Teeth 8 and 9 were provided with splinted crowns. The gingiva showed recessions with exposed crown margins and dark, discolored roots. At the unfortunately visible apical area of the splint connection, the interdental papilla had pulled back and thereby formed an unpleasant black triangle. The shape, shade and position of the teeth in the dental arch were not harmonious with the remaining teeth. The crowns were very thick in an orovestibular direction, and the vestibular surface projected too far in a labial direction.
The palatal functional surfaces were insufficient and did not correspond to the natural tooth morphology. The problems with the restoration were particularly noticeable since the patient had a high laugh line which exposed to the entire dento-gingival interface when she smiled (Fig. 1). Clinically, the patient manifested high periodontal probe values with bleeding upon probing. The x-ray revealed advanced horizontal bone degeneration and insufficient root filling at tooth (Fig. 2). After discussing the treatment alternatives with the patient with the option of the total restoration of her dental situation, we decided as a team to remove teeth 8 and 9. To bridge the long healing phase, a stable provisional was created in the form of a model cast.
The purpose of this analysis is to examine cemented versus screw retained implant supported zirconium oxide restorations (ZrO2). With the unprecedented growth of new CAD/CAM technologies emerging at an ever increasing rate, it seems relevant to discuss different methods of securing zirconium restorations to implants. There are distinct advantages and limitations to cement versus screw retained implant secured zirconium restorations. The most important distinction between the two strategies is that screw retained prosthesis can be removed and replaced by the clinician whereas a cemented restoration is not intended to be removed. To eliminate the prevalence of the screw hole in aesthetically challenging locations, other approaches have been utilised for attaching implant restorations. These methods consist of angled abutments which permit screw retention or cementation to angled or custom abutments and lateral set screws premanufactured or by the tap and screw method. After reviewing the reference literature the general opinion given, is that if a zirconium restoration on an implant should be in potential jeopardy of failure, then a retrievable custom set screw would be a more prudent approach compared to that of cementation. The fabrication technique on retaining and retrieving single and multiple zirconium restorations will be described and illustrated in detail.
The advent of CAD/CAM (computer-assisted design/computer-assisted milling) in the dental laboratory has freed the dental technician from the timeconsuming manual tasks associated with conventional vesting/devesting techniques. Using CAD/CAM, the manual wax-up phase can be replaced with threedimensional computerized restoration design. Copings and frameworks are machine-milled from single solid blocks of strong and esthetic materials, such as yttriumreinforced zirconia (known as “YZ”). A majority of the time that was once relegated to casting substructures can now be focused on the artistry of the restorative process, such as ceramic build-up. Treatment planning is also easier, with a comprehensive selection of materials available to satisfy specific clinical concerns more readily and with greater specificity to the unique parameters of any case.
This case involved a full-mouth rehabilitation in which the upper arch was completely restored with several types of lab-fabricated restorations, including 3- and 4-unit posterior bridges and five single-unit anterior crowns. The patient, a middle-aged computer science teacher, presented with several existing complications (Figure 1). She was partially edentulous with several missing teeth on both sides of the posterior maxillary arch, which warranted a bridge situation (Figs. 2 & 3). Additionally, the majority of her teeth suffered from discoloration, decay and wear (Fig 4). Unhappiness with the appearance of her teeth and the negative effect of her smile on her overall appearance prompted her to finally consult a dentist. The twelve teeth in her upper arch were ultimately restored with Sirona inLab CAD/CAM restorations.
Automated CAD/CAM scan-to-mill systems have captured the hearts and minds of dentists and dental technologists everywhere. You will never forget the first time you see a Computer Numeric Controlled (CNC) milling machine carve a block of material into a crown or bridge frame. In a word we have been “dazzled.” Costing manufacturer-developers tens of millions of dollars to bring to market, costing lab-users tens to hundreds of thousands of dollars to purchase, and threatened from its inception with a potentially brief product life cycle, dental CAD/CAM scan-to-mill technology has engendered industry commitment that is historically, unprecedented. How did they, the system sellers, manage to build this level of commitment?
To get beyond initial emotional appeal and create buying decisions on the part of dental labs, system sellers had to find a material that was uniquely different from those currently utilized in our industry. When they discovered
(1) that yttria-tetragonal-zircon-polycrystal (yttria-zircon) could be shown to have significantly higher strength than other cosmetic crown and bridge products, that is, higher strength as measured by the “catastrophic stress test” or “critical stress test” (critical break-strength test), and
(2) that yttria-zircon, by virtue of the fact it shrinks during sintering, could not be fabricated without the use of digital data and CAD/CAM processes – dental scan-to-mill msystems took off. Since then, dentists and labs have been inundated by marketing hype about the strength of yttria-zircon and how loose fit and open margins can be mitigated by using special cements.1
This article brings these realities into perspective with another automated fabricating process – a new technology that may be the best kept secret in dentistry.
Dental implant therapy is expanding in scope, yet the original therapy designated for edentulism remains a significant challenge. Often the attainment of osseointegration of implants is considered the primary or principle challenge for the clinician. mHowever, new implant surfaces, improved imaging mtechniques and guided surgical procedures enhance the clinical process of implant placement and may enhance the osseointegration outcome. Prosthetic outcomes and patient satisfaction with the prostheses are important additional measures of success(Feine).
Following osseointegration of the implants, the subsequent challenge is the production of a prosthesis that provides an opportunity to a) maintain peri-implant tissue health, b) restore function and c) enhance esthetics. A conventional method of treating edentulism using dental implants is the placement of sufficient endosseous implants to support a screw-retained prosthesis containing a metal framework veneered with processed acrylic resin and denture teeth. Introduced by Branemark and colleagues (Adell et al 1981) and further popularized by Zarb and Schmitt (1990), this approach to restoration has several advantages that include a) the ability to replace missing alveolar tissue with acrylic resin, b) the capacity to overcome compromised implant locations, c) the potential to be easily rejuvenated by replacement of the veneer should wear or aging dictate, and d) relative cost when compared to porcelain fused to metal restorations.
Success with these prostheses demands careful planning of implant placement in relationship to the location of prosthetic teeth. More specifically, common problems include bridge screw fracture and veneer failure (White and Lewis, 1992). Passivity of the framework fit to the abutments (or implant) is a key prosthesis feature that can reduce the incidence of bridge screw fracture. This fitting of large gold alloy castings is a significant challenge in for an implant supported fixed denture.
For many years I had heard about the IDS meeting in Cologne as being the largest dental convention in the world, and that one could see things there which were not available in the USA. It felt as though a visit to Cologne’s meeting would make a nice trip someday, but that someday, like many others, never seemed to come around.
This year was different. A last minute invitation placed me on a plane to Germany with only 3 days prior notice. It made sense in a way, since most travel I have done just happens without warning or time to think about it. And I kind of like it that way.
Those who described Cologne were right on the money. The convention facility was enormous! It was very organized with everything laid out in style, exemplified by the lavish concessions of the larger companies replete with small kitchens, sitting areas, cappuccino machines and selected edible goodies for the dental inquisitors. Okay, there possibly were some drinks offered, but only after hours. Plasma screens and live demonstrations (even surgical treatments) (fig. 2) dominated the convention-scape. The smaller companies were located in booths arranged by country (there was a whole USA section for example) and product type. Staff to assist you were present everywhere. The only disconcering factor I found was the enormity and number of display halls. For comparison sake, New York’s meeting has one main hall, compared to eight of the same size across several buildings at the Cologne event.
This year’s meeting entertained almost 100,000 visitors from over 140 countries. Needless to say, trying to see everything involved a lot of walking through crowded corridors and any“excuseme’s” (entschuldigung in German). It may have been an unkind irony that the move “Happy Feet” played in the plane, as mine were anything but…
The king of technology this year in Cologne was CAD/CAM. This subject inundates current dental journals, and is the hot topic in dentistry for both restorative materials and more recently, implant surgery. Through overhearing dentists and dental technicians ask questions, it was obvious that the CAD/CAM acronym in itself was much better understood than the processes it embodies. My charge here therefore, is to explain what is necessarily included in a basic understanding of CAD/CAM technology, and how it is influenced by the pre-requisites of the dental profession. Factors including model scanning, 3-D CAD design software (which extrapolates and processes information related to CAT and model scan), the materials employed and various machine types and milling strategies will be featured separately in subsequent installations.
In this contribution, we experience the reconstruction of the maxilla, anterior teeth, 13 to 23, and the creation of single crowns with Zircondioxide copings. Many articles about Zircondioxide miss the emotions, which are associated with this material. Often, the tremendous strength and color stability of the white substructure are discussed, yet the handling of the material is rarely examined. This article will further discuss the importance of handling various types of materials. When we use Zircondioxide, investing, casting and finishing of the frame are eliminated. The combination of the frame material with the right ceramic makes veneering an emotional experience.
Indications: Single crowns with Zircondioxide, the copy milling system, the wax up and the Zircondioxide veneering material.The Zircondioxide copings come warm out of the sinter furnace; this is one of the nicest acquisitions of this material. Zircondioxide is a functional material and is adequately used in prosthesis and aesthetic veneering.
The patient has very large fillings and wanted to change his anterior teeth with Zircondioxide crowns. The patient’s expectations are: an aesthetic, long lasting restoration.
In January 2000 David Lesh set out to create the world’s first dental lab exclusively for other dental labs for the manufacture of coping and bridge frameworks. Today, seven years later he’s succeeded and big. Dale Dental currently serves thousands of dental laboratories with copings and bridge frameworks for the most in demand restorative systems and he’s not stopping there. I talked with Dave to learn more.
Dave, tell us, where did the idea to start Dale Dental come from?
Great question. I was working for my family’s dental lab around 1990 when a new pressable system came out. We did not want to buy the system, but I knew our doctors wanted to try it. That’s when I got on the phone and tried to outsource a unit. I was able to find a lab we could outsource our units to, but it became clear to me their dentists work would always come first. Many of the cases would come back to us late and there were some quality and technical support issues as well. I also did not like the idea of sending work to labs that were my competitors in any way. I realized then that there had to be a better way to get the restorations I needed to provide to my customers.
So why did you wait 10 years after you had the idea before starting Dale?
I thought there were still some challenges with the idea. Back in 1990 when I had the idea, most labs were able to manufacture everything they needed themselves since there were not too many branded systems. And of the systems that did exist, few really meet my criteria as restorations I wanted to offer through outsourcing.