It is the mutual goal of both dentist and laboratory to create lifelike restorations that seat efficiently and satisfy patients. When seating posterior restorations, the primary determinants of success are interproximal and occlusal contact, contour, shade, and marginal integrity. Of these, interproximal contact is a subject we often discuss with our clients. We thought it would be helpful to share our “standard” for contact design in the following drawings and descriptions, which we have found satisfi es the majority of our clients. If you prefer a different design please use this reference as a guide to communicate your preferences. This information, added to your “customer profile,” will enable us to always meet your expectations.
1. Contacts should be football-shaped and located below the marginal ridge. The ROE standard is to establish broad, rather than point contact. Note how the surface area of the contact is approximately 1/3 the width of the occlusal table. The ROE standard for tightness is for the restoration to “hold” shim stock (12 microns) when fully seated on the solid model.
2. Some dentists request extra broad contacts and want contours as shown from this occlusal view. X and Z show ideal contour while W and Y show “extra-broad” contact. The image to the lower left shows the proximal view, and the outline in red indicates the broadened contact.
3. From an occlusal perspective, contact between the cuspids, bicuspids and 1st molars should be placed 1/3 lingual and 2/3 buccal so the embrasures are deeper on the lingual than the buccal. The contact between the 2nd and 3rd molars is placed approximately 1/2 buccal and 1/2 lingual.
4. Proximal surfaces gingival to the contacts should be contoured so the embrasure is symmetrical and triangular in shape, as indicated in red.
5. This diagram shows an under-contoured buccal embrasure as indicated by Y. Proper contour is shown with the dotted line indicated by X.
6. From a gingival–occlusal perspective, contacts are positioned as shown. Maxillary posterior contacts move progressively towards the gingiva as they move away from the midline, while mandibular posterior contact points are at the same general level or plane.
Special thanks to Dr. William Sweeney Jr. for his contribution to this article.
Thursday, September 1, 2011
Precious metal costs continue to skyrocket. In an effort to simplify our pricing we now offer fl at-fee pricing on two more of our C&B restorations. Semi-precious PFM’s (Pd 25% Co 42%, Cr 20%, Mo 6%, Mo 12% ) are now $185 per unit ,and our yellow, full-cast crown (Pd 79%, Au 2%, Sn 8.4%, Co 5%) is just $150. We offer a fi xed-fee for all our non-precious, semi-precious, and all-ceramic restorations.
It is accepted practice that during an implant impression an x-ray should be taken to ensure the transfer post is fully seated in the implant. Lately, we have had discussions with dentists regarding the benefi t of an additional x-ray at the seating appointment to ensure the abutment is fully engaged. An abutment not properly seated will produce high occlusion or post-placement screw loosening. It is recommended that x-rays be taken at both the impression and seating appointments.
HemCon Dental Dressing is a hemostatic product that was invented for U.S. forces on the battlefield.The company, HemCon Medical Technologies Inc., introduced their product to the dental fi eld because of its multiple benefits such as sutureless surgery, reduced chairtime, and quicker healing. The dressing is available in 10mm x 12mm blocks or 1” x 2” strips that are easily trimmed and set in place. The effects are almost immediate and the dressing dissolves within 48 hours. The Portland-based company can be reached by visiting www.hemcon.com.
Thommen, a Cleveland, Ohio based implant company, has two announcements. Now, due to Thommen’s compatibility with our scanning and milling equipment, we can create custom titanium and zirconia abutments. Until recently we have been limited to restoring Thommen implants with stock abutments. Also, Thommen now offers a multi-unit abutment (straight or angled) compatible with Nobel Biocare’s design, which allows us to fabricate titanium bars for Thommen overdenture cases.
When non-vital roots are present, consider the Zaag attachment from Zest Anchors. Zaag is a partial denture or overdenture root-borne abutment that is cemented into a prepared site. Once seated, a conventional pick-up and curing technique is used to attach the Zaag into the prosthesis. When a stable root is present, Zaag is a wonderful alternative for stabilizing removable prosthetics. Visit the website
Easy Abutments, such as Zimmer’s Short, Nobel’s Snappy and Straumann Solid Abutments, are popular options due to their ease-of-use and decreased component cost. The simple impression technique works by snapping an implant replica onto the fi nal abutment (placed at surgery), instead of using the traditional impression post. In most systems, the abutment and screw are separate, allowing the abutment to be torqued post transfer. The one-piece Straumann Solid Abutment is different because the abutment does not have an independent screw. The abutment must not be re-tightened at any time after the impression. If it is turned, the impression will not be accurate, and consequently the crown will not fi t. The process for Easy Abutments is straight forward, and the possibility of laboratory error has been virtually eliminated by this implant design.