Mention Cerec, manufactured by Sirona Co., and dentists immediately think about cost, return on investment, learning curve, esthetics, marginal fit, strength and time to fabricate a Cerec restoration. These are all valid objections, however one must evaluate each concern objectively and consider the advantages to their practice and patients.
Since my practice is amalgam free, my restorative choices are resin or ceramic. Patients want natural looking restorations and wish to avoid metal because of esthetics and concerns about health risks. I use Cerec primarily for crowns and do all single unit posterior and anterior crowns in ceramic.
Before a doctor considers Cerec technology, there has to be a philosophical shift to doing ceramic dentistry. It is a different concept from the traditional dental school theories. I was unhappy with the restorative alternatives I was offering my patients. I would prefer Cerec restorations for my own mouth, so why should I settle for anything less for my patients?
I reviewed articles on www.planetcerec.com about Cerec restorations and visited offices where Cerec technology was successfully implemented. I soon discovered Cerec restorations compared favorably to lab-fabricated restorations. However, some of the additional benefits include, single office visits for patients and total control by the doctor over the entire process that provided more predictable results.
When considering the cost of Cerec technology for your practice you need to determine how many restorations—crown, inlays and onlays––you do in one month. How much do you spend on lab fees for these restorations? Then with that information, you can offset the total amount against a monthly Cerec payment. Without a doubt you will net a significant amount of money after you reach the breakeven point––where monthly lab costs equal the cost of the machine. My lab costs in 2002 for single units have been reduced by 66% while increasing the individual number of single units. The ability to do multiple units in one visit increases office productivity tremendously without increasing operating expenses. The delegation of the design and finish to staff can allow the doctor to do other productive procedures while restorations are being milled and finished by staff. The material costs are similar for lab vs. Cerec restorations when you consider costs of impressions, bite registration and temporary crown materials. The average material cost of a Cerec restoration is approximately $27 per unit. When you include the costs of the second appointment––room setup, sterilization and lost production that is eliminated by Cerec––you begin to realize the advantages of it.
The learning curve, like all procedures does require the clinician to spend time and it can be extensive. But with the numerous trainers, study clubs, and .com websites, such as DentalTown, PlanetCerec and the Yahoo Cerec group available, new users can quickly start producing restorations on their machines with excellent results. The new 3D software will dramatically shorten the learning curve because it is conceptually easier to understand. However, I do think the documentation, provided by Sirona, could be more explanatory and include more timesaving tips to help the new and experienced clinician.
The esthetics of Cerec restorations are excellent. Ceramic blocks come in the VITA and VITA 3-D Master shades from Vident as well as in Ivoclar Vivadent’s ProCAD shades. Manufacturers are introducing blocks that have more esthetic characteristics. It’s not necessary to stain and glaze your restorations since the ceramic does have a chameleon effect. For more demanding cases, you have the ability to stain and glaze these cases within a 20-minute time frame. Resin tints can be used to control the color of the restorations without staining and glazing. This can be done by either using the tints internally before cementing or externally. The occlusal surface can be characterized by grooving the pits and fissures with the use of a half round bur--etching, silanating, bonding agent, and staining with resin tints and placing a translucent flowable resin over the surface and light curing. This is a technique that I learned from Dr. Doug Voiers. It is called the D.A.T (Direct Aesthetic Technique). I have never had to use tints since patients are extremely pleased to have whiter teeth without the gray metallic of silver mercury fillings. I will glaze my anterior restorations to obtain a higher luster and occasionally add stain to match an adjacent tooth.
Strength of these restorations has not been an issue. In the past 2.5 years of my Cerec experience, I have had only four crowns fracture. One was due to inadequate reduction; the other was due to a defective block and the rest a result of inadequate occlusal adjustment. These failures occurred within the first 6 months of service. Restorations on recare visits look as good as the insertion date. (See Fig 1, 2, and 3)
Cerec allows the clinician the ability to select the design technique best suited to the clinical situation. With the 3D software, there is a dental database, correlation and veneer. The dental database consists of anatomical shapes for each tooth in the mouth that the software will propose for a particular restoration. You will use the dental database whenever you want a more ideal occlusion or anatomy. Correlation is a duplication of the patient’s existing tooth morphology. In the 2D software, the majority of dentists use correlation since it is the easiest of the designs to learn and master. With 3D software, correlation is still preferred, however the dental database is a large improvement because it provides a larger library of anatomical shapes to choose from and is less confusing design wise than the Cerec 3 2D software.
The key to a successful Cerec restoration, whether it is Cerec 3 or 3D is following the 3 Ps: Preparation, Powdering and Picture. The case, pictured below was one of my first Cerec restorations and was an upper right first bicuspid (Figs 4, 5, 6, 7). The patient had a large amalgam with undermined cusps and was experiencing sensitivity with hot, cold and chewing, so I recommended a crown. I choose correlation as the design technique since the patient was happy with the shape of their tooth and the occlusion was intact. Preparation was a shoulder prep with a 1.2mm diameter NTI KR Cylinder diamond with rounded angles from Axis Dental. The guidelines for an acceptable preparation are 2mm occlusal reduction and shoulder or chamfer with1.5mm reduction. The axial walls should be smoothed with a minimum six-degree tape.
The opitical impression reqiures a contrast medium of which there are several on the market––all a matter of personal choice. In this case, I used ProCAD adhesive and powder. The adhesive is painted on the prep and adjacent teeth to allow for better adherence of the powder. You want nice even powder with no clumping of material. Once the optical impression of the preparation is completed you are ready to start the design. The following will detail the steps in the design of this crown with both Cerec 3 2D and Cerec 3D.
The milling time for a crown will be 12-14 minutes depending on the complexity of the restoration and significantly less for an inlay. Once milling is complete, the restoration is tried in, contacts adjusted and polishing is done with the use of white silicone polishing wheel and NTI CeraGlaze polishing points and wheels from Axis Dental. The restoration is treated with 5% hydroflouric acid, silanated, painted with Prime&Bond NT self-activated bonding agent (Dentsply) and light cured. The tooth is cleaned with chlorhexidine, rinsed, and excess moisture is removed. Prime&Bond self-activating bonding agent is placed on the tooth and light cured. Varioink resin dual cure cement (Ivoclar Vivadent) is used to bond the restoration. In cases of anterior 3 restorations, only the Variolink base is used to avoid problems associated with discloration of dual cure products after a few years. The total chair time to produce this restoration was 1.5 hours. This is slightly less than my total chair time for lab fabricated cases. Figures 1, 2, & 3 are two-year post insertion of the crown used in the demonstration. Patient is pleased with her results and is scheduled to have additional Cerec crowns.
Patient acceptance has been excellent since many of the objections people have to crowns has been eliminated. Mention crowns to patients and they begin to think multiple appointments, shots, impressions with goop and artificial looking teeth with that gray line at the ginigva in the cases of the porcelain-to-metal crown. The ability to do onlays and preserve tooth structure is very appealing to patients (Figs. 8 and 9).
It is clear that Cerec technology has evolved over the years to allow for more capability, higher quality and ease of use. And as a result, ceramic dentistry will be more universal and eventually be the standard of care in the future. As the number of lab technicians decline and the cost of quality lab fabricated restorations skyrocket, dentistry will turn to CAD/CAM technology to control costs and quality. Either the dental office will have the capability to fabricate restorations on-site or labs will use technology such as Cerec inLab to meet the demand for high quality and low cost restorations.
Dr. Paul Caselle has maintained a successful dental practice for over 25 years with no welfare or managed care. Since 1986, he has been incorporating computer systems and digital technology in his office. This experience has afforded him the knowledge to understand how a practice management system and digital technology can benefit a practice.
Dr. Caselle is a graduate of Boston University College of Arts & Sciences and New York University College of Dentistry. He completed a residency in Family Dentistry at Forsyth Dental Center in Boston. He is a member of the American Dental Association, Massachusetts Dental Association and the Middlesex District Dental Society. Dr. Caselle is a consultant and lecturer on Cerec and other digital technologies.