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OPT-In Clinical Updates for November, 2013

• Announcing Dr. David Hornbrook, Contributing Author

• A Complete Understanding of Zirconia C & B

• Announcing Low Cost Lab Alternatives

• Implant Restorative Updates: Abutments, Ti, Zr, Custom, Stock

• OPT-In Laboratory Members Near You

by

Dean Mersky, DDS

Dr. David Hornbrook will be joining Clinical Updates, Beginning December, 2013.

Dr. Hornbrook will contribute with

Clinical Tips and Concepts.

Creating Excellence, Partnering in Growth

Who are We and Why are You Receiving This?

In October, 2012, Dr. Dean Mersky formed

A national cooperative of small dental laboratory owners

Dedicated to the growth and viability of Private Practice Dental Offices.

A part of our support is providing doctors with evidence-based

information about materials and techniques key to patient care.

Look for the Logo in Choosing your Laboratory Partner

How We Decide Which Materials and Manufacturer to Feature

Products and services we feature must have benefits supported by independent research and be offered by companies dedicated to education in best practices, or, provide services that support care at the highest levels.

Understanding Zirconia

Clearing the Mysteries and Myths

Zirconia in dentistry has a long history, even though it is only recently becoming a normal consideration for restorative dentistry. Its earliest uses include root canal posts since 1989, abutments since 1995, and all-ceramic posterior FPD's since 1998. (Coli P, Karlsson S. Fit of a new pressure-sintered zirconium dioxide coping. Int J Prosthodont 2004;17:59-64). Its use became even more prevalent around 2005, but then was blunted by veneering failures from a lack of understanding. Previous problems were rectified by appropriately matching CTE  and better management of the cooling cycle. Now, Zr is reasserting itself as the true viable restorative option it deserves to be.

Structure

Zirconia (Zr) is the 19th most plentiful mineral on earth. When in oxide form (photo, left), it is technologically a ceramic that is more resistant to bacterial adhesion than titanium (Ramesh, 2012). Zr exists in 3 phases, depending on temperature: cubic at 2370°C, tetragonal  at 1170°C, and monoclinic, at  termperatures below 1170°C. When Zr transforms from tetragonal to monoclinic, there is a simultaneous  volume increase of 4-5 %, as reported by Heuer, et al, (J Am Ceram Soc 1986;69:1-4). Yttria is added to Zr to prevent the tetragonal to monoclinic phase change, and is then referred to as Y-TZP.

When a flaw or crack develops in Y-TZP, the area of the flaw becomes monoclinic, and undergoes an associated volume expansion. As reported by Evans, et al, (Acta Metallurgica. Volume 34, Issue 5, May 1986, Pages 761-800) this phase transformation, also called toughening, compresses the flaw, retards its growth, enhances fracture toughness, and significantly extends the reliability and lifetime of the Zr restoration. This has been the reason air abrading the intaglio of Zr restorations has been accepted, even though research indicates a slight decrease in flexural strength.
 

Veneered Zirconia Restorations

As reported by Ramesh, historical differences in coefficients of thermal expansion, firing shrinkage of ceramic, flaws on veneering, and poor wetting during veneering of the core are factors that can lead to later veneer problems. To minimize these influences, special ceramics and techniques have been developed. Today, there is greater confidence in the longevity of veneered Zr restorations. A two-part review by Pjetursson compared the survival rates of Zr and other all-ceramic restorations to that of porcelain fused to metal. The investigators found 5 year survival rates of all ceramic restorations to be 93.3%, whereas metal ceramic restorations were 95.6%. When comparing Zr-ceramic restorations with other all-ceramic systems, zirconia frameworks were found to be the most reliable. (Pjetursson BE, Sailer I, Zwahlen M, Hammerle CHF. A systematic review of the survival and complication rates of all-ceramic and metal ceramic reconstructions after an observation period of at least 3 years. Part I: single crowns. Clinical Oral Implant Research 2007;18:73-85);  (Sailer I, Pjetursson BE, Zwahlen M, Hammerle CHF. A systematic review of the survival and complication rates of all-ceramic and metal ceramic reconstructions after an observation period of at least 3 years. Part II: fixed dental prostheses. Clinical Oral Implant Research 2007;18:86-96)                                                                                                                                                                                                                                                      Zr Photo Courtesy of BEGO USA

Biocompatibility

Zr does not induce cytotoxicity in soft tissues, as evidenced by Catelas, et al (J Biomed Mater Res. 1998;41:600-607).

Clinical Use

Zirconia fixed partial dentures (FPD's) have a wider application than other all-ceramics because of their predictably high strength for implants and molars, including posterior FPDs. However, FPD pontic spans are manufacturer specific and should not be tested beyond recommended lengths. Larsson suggested a maximum limit of five units, total, for Zr FPD's: (All-ceramic two to five-unit implant-supported reconstructions. A randomized, prospective clinical trial. Swed Dent J 2006;30:45-53).  

With respect to margin design, feather margins are possible but always lead to over contouring and provide the technician with a dilemma: Should they be thinned for tissue health, or, should they be left thicker to avoid margin failure, which can happen with any ceramic that is thinner than recommended. For example, even with the strength of Zr, an occlusal that is too thin, as in the photo at left, is at risk of failure. Consequently, Witowski suggested chamfer or rounded shoulder margins with at least 1.5 mm incisal and occlusal thickness, and 1 mm axial reduction, with 4 to 6°  taper: (CAD/CAM in dental technology. Quintessence Dent Tech 2005;28:169-184). Marginal overhang is an aspect of preparation design that is often overlooked. Rustum reported in 2010 that the shoulder preparation design was far better than the chamfer design with respect to horizontal overhang: http://www.thejpd.org/article/S0022-3913%2810%2960128-X/abstract.

Zr is now a popular material for full contour applications (FCZ), also due to its strength, biocompatibility, and reasonable esthetics. Testing for appropriate occlusal thickness, Jang reported in 2013, that 1 mm occlusal thickness provided twice the strength of .5 mm.

Also of importance is the amount of wear FCZ causes against opposing enamel. Januvula reported (January issue of JPD, 2013) that “Surface roughness ranked in order of least rough to roughest was: polished zirconia, glazed zirconia, polished then reglazed zirconia, veneering porcelain, and enamel… For enamel antagonists, polished zirconia caused the least wear, and enamel caused moderate wear. Glazed and polished then reglazed zirconia showed significant opposing enamel wear, and veneering porcelain demonstrated the most.”

There has been conjecture that moisture degrades the surfaces of FCZ. Chevalier reported slight degradation of femur heads, with the wearing surfaces exhibiting phase change to monoclinic at a 3-5 micron depth. However, this has been characterized as clinically insignificant due to the extended length of time required and the shallow depth. Burgess, et al, tested heat and moisture tolerance for Zr in an autoclave (July, 2013, Operative Dentistry) and reported that “Zirconia may be considered a wear-friendly material for restorations opposing enamel, even after simulated aging.”

Summary

Both veneered Zr and FCZ has come a long way, technically and clinically. Misunderstandings of its use are now only a historical consideration. Veneered Zr has proven itself to be a reliably esthetic alternative with veneer strengths similar to cast PFMs, while FCZ, generally less esthetic but stronger, can be a worthy consideration for parafunctioning and minimal clearance patients. Regardless of which Zr is ultimately decided upon, we can count on biocompatibility and the need for retentive preps with appropriate reduction.

Clinical Tips

Removing and Polishing Zirconia

Removing Zirconia

Premier Dental was contracted by Henry Schein to develop an exclusive diamond bur for their D4D milling of zirconia. Having successfully created a unique diamond bur for milling purposes, Premier's research and development team set about testing modification of the bur for clinical removal or adjusting of zirconia restorations. The result of their efforts is the Two-Striper ZTech®. The ZTech, using a fine diamond grit, can be used for the following:

• Adjust all ceramic restorations intra-orally
• Endo access through all-ceramics (CR Foundation rated Ztech excellent at reducing the degree of mircrofractures)
• Cut off all-ceramic restorations, especially zirconia

Premier is known for having the best diamond burs in dentistry. That's why we are presenting this for your review. That's also probably why Two Striper ZTech® received "rave" reviews in Reality, 2012. CRA also reviewed ZTech®, July 2012, and listed it amongst their Best Products for 2012.

To view the Two Striper ZTech® in action

http://: http://www.youtube.com/watch?v=HOwOXChH5m4

Polishing Zirconia

Premier Dental has developed a highly unusual system for polishing zirconia, other all-ceramics, and composites, with distinct chairside and intra oral applications. The system begins chairside with the new, open weave Fibra Point pre- polishers, available in barrel, wheel, or tapered shapes, that generate less heat. This is followed by Premier's  Diamond Twist SCL paste,™ using felt tip applicators. For intra oral polishing, Premier suggests their intra oral SCO™ Single-paste System for Ceramics and Composites. Combined, the two systems claimed highest honors from Reality and from CRA reviewers. Both pastes use extremely dense concentrations of diamond particles.  The intra oral SCO™ Single-paste System, is available with tapered or flat autoclavable polishing brushes and Micro Cloth felt discs, barrels, or tapers, for final high glaze buffing to a mirror-like finish. The polishing paste comes in a twist syringe to avoid cross-contamination and minimize waste.

To view the

Diamond Twist SCL™ / SCO™ Single-paste System for

Ceramics and Composites

http://www.youtube.com/watch?v=Yxjbj7behZw

Visit Premier Dental for More Information

http://www.premusa.com/dental/newproducts.asp

To Contact Us

info@optindentallab.com

http://www.optindentallab.com

855-321-OPTN (6786)

Announcing New Laboratory Category:

OPT-In Insurance: The Answer to Fee Restrictions

OPT-In laboratories with fees & products

Matched to the needs of insurance budgets

"It Should be Easier to

Find the Right Dental Laboratory!"

OPT-In Dental Laboratory Specialties

OPT-In Laboratories are grouped by their specific expertise

To simplify finding...

The Right Laboratory for your Needs

With Owners Eager to Help

Learn More about OPT-In Laboratory Specialty & Expertise

Visit

http://www.optindentallab.com/dentists/services/choose-a-laboratory-specialities/

BEGO Sponsored CE

Dr.David Hornbrook, FAACD, FACE

A Technician's Guide to Cements and Adhesion, Part 1

Tuesday, November 5th, 8 PM, Eastern

Presentation for OPT-In Member Laboratories

The live webinar for members of OPT-In Dental Laboratory Cooperative will help technicians better understand the complex nature of adhesively placing restorations to tooth structure.

Technicians will be exposed to the different classes of cements, traditional, glass ionomer, resin ionomer, and resins, plus their sub classes, auto-cure, dual-cure, and light cure. Each category will be explained in simple chemical terms, with more details about their proper uses, features & benefits, and their limitations. Additionally, there will be explanations of the three main classes of adhesives, three bottle total etch, two bottle total etch, and self-etching systems, and how their uses are applied to the cementation process. Included in the presentation will be how dual cure systems affect esthetics and the interactions of dual-cure and light-cure systems that are sometimes compatible, and sometimes not.

Dr. Hornbrook will use actual cases accompanied by materials research, their suggested uses, and helpful clinical tips that can be used by OPT-In members during case planning and knowledge sharing with clinicians.

"There is a general lack of understanding by technicians about exactly what is going on in the operatory. Likewise, we dentists are not completely aware of what our technical partners need in order to provide us with the best possible results. In an effort to narrow this schism, we hope to bring improvements through these types of activities, the first being, how restorations are placed and challenges managed."

Dr. David Hornbrook

Graduated from UCLA School of Dentistry in 1986. Serves on the faculty at Baylor University, Tufts University, SUNY at the University at Buffalo, and the University of California, Los Angeles. He also serves on the editorial boards of many leading scientific journals devoted to cosmetic dentistry, including Esthetic Dentistry Update, Practical Periodontics & Aesthetic Dentistry, Signature, and the American Academy of Cosmetic Dentistry's Journal of Cosmetic Dentistry. Founder of the Hornbrook Group, taking his knowledge and passion to dental programs across the country, founder and director of PAC-live (Pacific Aesthetic Continuum), and co-founder of the Las Vegas Institute as a pioneer of live patient programs – enhancing the quality of dentistry across the country and internationally. For details about Dr. Hornbrook's credentials view his CV

info@optindentallab.com

http://www.optindentallab.com/

Implant Retorative

Updates

This Clinical Update is Presented by Your

OPT-In Dental Laboratory Cooperative Partner

http://www.optindentallab.com/dentists/

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Tailored to the individual needs of each patient.

About the Author

Dr. Dean Mersky practiced general dentistry 26 years in Manhattan Beach, CA before spending 7     years    as  director of clinical communication for the Captek Company. Dr Mersky has been a dental lab implant coordinator, a national speaker, authored over a dozen published articles, is a regular on DentalTown.com. He launched OPT-In Management, LLC, in 2012, to help owners of small dental laboratories better understand dentists and the many clinical and business pressures facing today's private practice clinicians.