This site is best viewed using Mozilla Firefox browser.

Dental

2003-11-01 14:34:00

Dental crowns in one visit?

: I read recently that some dentists in the area provide caps in a one-appointment process using a milling machine as opposed to the usual multiple visit variety.  Why wouldn't all dentists provide the convenience of the one appointment for their patients?

ANSWER: If I follow you correctly, you are referring to the Wichita Eagle article regarding the CAD/CAM  (Computer Assisted Design/Computer Assisted Manufacturing) technology, which mills a crown from a block of ceramic/porcelain material to be placed in the mouth for a restoration.  This technology has been around for several years and like all technology, it has advantages and disadvantages.  Dentistry is both an art and a science.  All dentists as small business owners must weigh the pros and cons of everything done in regards to their practices.  Most stereotyping of dentists is not from the best side as is true of most stereotyping, but if there is one thing that is nearly universal; it is a dentist's attraction to gadgets.  There could be multiple reasons for such an attraction.  Often it is a fatal attraction, in that the latest gizmo doesn't live up to its hype.  As a result of the accumulation of multiple devices in their storerooms, there is a tendency for many dentists to be conservative in the purchase of items to enhance their practice, especially high dollar items.   The article was informative even if in the opinion of some it was biased.  There seemed to be no disadvantages of having products from this machine.  The company has a product to sell and as is happening all throughout the health industry, the manufacturers are increasingly going to the consuming public to pitch their produce, in hopes that public pressure will enhance their sales, rather than rely on the providers to select a product or material to utilize.  The item of which you speak seems to me to be such a ploy.  The aspects that would instill caution for many, indeed perhaps most dentists (out of the 400+ dentists in the area, only some 15 or so have the device), are at least three in number.  I am obliged to speak only for myself and not for any others.     First and to me the most significant is the accuracy of the marginal fit for the final crown to the tooth.  The less accurate the fit, the more cementing or bonding material is exposed to the fluids in the mouth.  Cementing and bonding materials are not as durable as the restorative material and any roughness attracts more bacterial buildup than highly glazed porcelain or highly polished metal.  Today, although most cementing materials are actually bonding in nature regardless of the type of restoration, this is still the weak link in the restoration that will allow leakage and recurrent decay.   Second and perhaps the most important to the patient, is the esthetics or looks of the restoration.  I will agree that nearly anything close to the color of a natural tooth is better than the black fillings that show when laughing, talking or smiling will be more appealing to the eye.  The blocks, from which the restorations are milled, are of a uniform shade (that is the color from the top of the tooth to the bottom is the same).  It was not until quite recently that multiple shade options were available (still the same color top to bottom, but now one is able to have one tooth one color and another color for a different tooth).  Another consideration in the art of shading is characterization: the ability to make one part of the tooth different from another portion.  If one looks at a natural tooth, the biting surface or incising edge of a tooth is of a different color or hue than the body, which is still different from the gingival (close to the gums) area.  Although these differences can be added to the milled restoration, it is added to the surface and glazed, which adds more waiting time and the stain is over time lost to the acidic fluids of the mouth especially any phosphoric acid which is found in soft drinks.  In the laboratory processed restorations, the shades and characteristics are built into the restoration at all depths and as such are not changed by the fluids of the mouth.  An additional factor is if the milled restoration is not acceptable to the dentist the complete process must be repeated causing even longer single visits.  As with any procedure, there is a learning curve.   The third important precaution for me is the realization that I am responsible for the material if there is something that is defective in its application or function.  I really do not wish to have several thousand restorations in my patient's mouths only to have to replace them at no additional expense to the patient should they fail due to material shortcomings.  Even though it is at no additional expense to the patient, chances are they would not choose to have the procedures redone if there were more proven techniques.