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Clinical Considerations for Dentists

Combining advantages of fit, esthetics, strength, biocompatibility and radioluscency, enhanced Wol-Ceram helps patients get what they really want – a more natural smile and long term results.  Here’s why:

o      Fit – Wol-Ceram Center of the Palm Beaches has pioneered a process we call high resolution Nanofit™.  Our proprietary electrophoretic deposition nanoprocess achieves a coveted 5-micron fit on original die at the margin.  Occlusal surfaces of posteriors, lingual surfaces of upper anteriors and labial surfaces of lower anteriors are also close fitting.  Space for cement is provided on axial surfaces.  Specified surface-fitting is key to optimal pressure distribution and a stress-free, long-lived restoration.  Comparing cement gap and stability on the die, cores made by Wol-Ceram Palm Beaches consistently outperform cast-gold, pressables and CAD/CAM milled restorative products.

o      Esthetics – All Wol-Ceram crowns and bridges are internally shaded, the core imparting a translucent base-shade.  Opaque is not required so internal luminescence is consistently achieved.

o      Strength – With clinical success rates similar to PFM restorations (Dr. E. McLaren, FACP, professor UCLA, Las Angeles 2008 Ceramic Symposium), studies show this glass-infiltrated nanoprocessed material may be stronger (Dr. J. Tinschert, AP, Dept. of Prosthodontics, Aachen University, 2004 Wol-Ceram Study), with veneer and cement bond strengths higher than zirconia and other noninfiltrated cores (Dr. Y. Zhang, AP NYU, Zirconia-Based Functionally Graded Structures, 86th IADR Toronto 2008).  Enhanced Wol-Ceram assures you of treatments engineered to last.

o      Biocompatibility – Metal-free restorations have become dentistry’s best opportunity to deliver biocompatible treatments.

o      Radioluscency – Wol-Ceram restorations provide for clinical monitoring of tooth vitality.

As with any significant advance in laboratory technology, the potential for improved restorative treatments is contingent upon implementing compatible preparatory and delivery procedures.  High MPa strength can not preclude breakage irrespective of chair-side technique.  Wol-Ceram urges clinicians to apply the following precautions and procedures:

o      Indications – Crowns, splinted crowns, veneers, onlays, inlays, bridges up to 38mm and crowns/bridges on implants are appropriate Wol-Ceram treatment modalities.

o      Contraindications – Inlay bridges, onlay bridges and Maryland bridges are contraindicated, as are cases that will require provisional cementation.  Also contraindicated are undercut, irregular or rough feather-edge margins which significantly compromise processing.  If a margin has tiny bur-marks, for example, the core can lock onto the die during processing.  Fit resolution is that good.

o      Shade Guide – Clinicians and labs we work with prefer Vita’s Vita-Lumin and Vita-Pan 3D-Master shade guides from Vita (www.vident.com).

o      Tooth Preparation – Most clinicians prefer a light to medium chamfer margin.  Conventional PFM preparations are good, provided that feather-edge margins are not undercut, irregular or rough.  Incisal reduction should be 1.5mm and occlusal reduction should be 2mm.  To avoid risk of premature fracture, sharp angles should always be avoided.

o      Adjustments – As with any all-ceramic alumina or zirconia core restoration, avoid internal adjustments; when necessary, adjust prepared tooth.  Adjust the restoration after it has been permanently cemented.  Use a diamond with irrigation to equilibrate.  Avoid carbide use.

o      Cement – A favorite is Bistite II DC and Panavia 21 from J. Morita (www.jmoritausa.com).  Respective of all-ceramic treatments, any cement must have low viscosity (thin liquidity) and must not begin setting before the crown or bridge is completely seated.  Identifying compromised dentin such as sclerotic and carious dentin and using a self-etching primer may be helpful.  While the patient’s tooth may be etched, all-ceramic alumina and zirconia core restorations can not be etched, but, rather a silane coupling agent should be used to improve bond strength by about 20%.  Cements like Bistite II DC have been developed for bond-like cementation.  As with any all-ceramic alumina or zirconia core restoration, temporary cement is contraindicated.  Now controversial, glass-ionomer-resin cements have been associated with expansion issues and may in some cases, place tension on all-ceramic crowns and bridges.  Fractures of alumina and zirconia crowns after one to three years may have been caused by this expansion.  While glass-ionomer-resin cements have grown in popularity in recent years, long term research is still lacking.  Some clinicians are going to zinc-phosphate recognizing that with over 100 years of clinical success in dentistry, these cements have been proven to be safe when used with all-ceramic crowns and bridges.

Summary – With 1,100 to 1,540 MPa independently tested strength (Dr. J. Tinschert, University of Aachen, Germany) and with more than 1.2 million delivered units, Wol-Ceram has been shown to be an effective restorative modality when treatments are provided in accord with established laboratory and clinical protocol:

o      Equilibration – Equilibrate any all-ceramic after cementation.  Biting on high occlusals of uncemented crowns/bridges and vibrations produced during equilibrating may cause shifting, pressure points, and fractures.

o      Internal Adjusting – The crown or bridge abutments can not be adjusted internally to fit.  If required, the prep should be adjusted.  Grinding Wol-Ceram internally can create micro- and nano-cracks and fractures.

o      Provisional Cement – All-ceramic crowns and bridges can not be temporarily cemented.  Provisional cements allow the restoration to move slightly during mastication.  This movement can create pressure points and fractures.  In addition to this risk, removal by prying all-ceramic margins will chip the margins and this can create micro- and nano-cracks and fractures.

o      GIR Cement – Glass-ionomer-resin cements are contraindicated.  These cements should not be used under all-ceramic because they can expand from water sorption (2-4% linear, more by volume) after placement.  Expansion places tension on the all-ceramic which can result in fractures.  Another risk is, these cements my not be stiff enough to support all-ceramic under load.

o      Premature Set – When cement has been allowed to prematurely set, resulting uneven distribution of forces and pressure points often cause fractures during equilibration.

Predicated on standard-of-care excellence, enhanced Wol-Ceram has become the hallmark for metal-free crown and bridge treatments.  Wol-Ceram Center of the Palm Beaches, a division of Bio-CAM, LC, proudly offers enhanced Wol-Ceram crown and bridge core services exclusively to dental laboratories and clinicians with their own in-house lab.  Specify “Palm Beach Wol-Ceram” on cosmetic cases sent to your favorite crown and bridge ceramist.