Dental updates from Dr. Mckeever.

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Antibiotic overuse - "toxic megacolon"

As most of you probably know, the overuse of antibiotics for all sorts of maladies has resulted in the gowth of "super bugs" many of which are no longer affected by these drugs. The most familiar one in these times is the MRSA strain of bacteria which is a Stephylococcus aureus that is on our skin but can turn lethal if it gets into our system through a cut or scrape; we are running out of options for antibiotics that can kill this germ. And, there are others not as familiar.

Because dentists frequently give patients antibiotics for oral infections, we must be aware of adverse consequences. We also use them in patients with certain heart problems to prevent the possibility of contracting bacterial endocarditis (SBE) an infection of the heart valves that have defects. (Recently, the American Heart Association finally announced that most patients that here-to-for had to take antibiotics before invasive medical or dental procedures no longer needed to do so. The rationale is that there hasn't ever been a documented case of a patient acquiring SBE from a medical or dental procedure and that takling antibiotics to prevent SBE was much more likely to cause problems that any remote possiblility of contracting an infection!

Unfortunately, I have had two patients (that I know of) who experienced a life threatening reaction to antiobiotic therapy prescribed by me. This was extremely disturbing even though no one can predict such occurrances. The germ involved in most of these cases is the Clostridium difficile strain of bacteria and the resulting infection of the intestine is called "toxic megacolon" (CDAD). Over the last 10 years, the number of patients hospitalized as a result of CDAD in the U.S. has risen sharply doubling in occurrance per 100,000 population. Also, the severity has increased with more cases requiring surgery or more patients dying. Patients older than 60 years are four to five times more likely to contract the disease and are at an increased risk of dying from the disease.

C. difficile is spread by the fecal-oral route but how that happens is pretty much anybody's guess. After ingestion, the spore form germinate into a vegetative form in the small intestines and eventually colonize the mucosal crypts of the large intestine. They then proliferate when the normal bacterial colonies in the intestines are disrupted; the most common event that causes this disruption is through the use of antibiotics! A 2004 study addressed the role of this germ in the food supply most specifically in the consumption of particular meats. Other risk factors associated with acquiring C. difficile is long hospital stays, especially in long-term care facilities, nasogastric intubations and, perhaps, even taking anti-ulcer medications called "proton pump inhibitors" (although there is no consensus in their role in this disease).
Like other strains of the Clostridium species ( C. tetani {tetanus} and C. perfrigins {gangrene}), it is the toxins from the spore-forming bacteria that cause the disease and diagnosis is made by detecting the toxin from stool specimens.

The antibiotics most associated with causing CDAD are the cephalosporins, penicillins and clindomycin. (Unfortunately, these are the best medications for pulpal infections of the teeth). These antibiotics upset the natural balance of "good bacteria" that normally reside in the intestines. Cessation of the offending antibiotic, if possible, allows the bowel to repopulate with normal bacteria and, thus, limit the impact of the infection in a natural fashion. The ingestion of a probiotic food while on antibiotics can greatly reduce the chances intestinal problems of any kind! The British Medical Journal in their July, 2007, issue reported that patients that used a probiotic drink (DanActive) starting two day before, during and up to one week after antibiotic therapy reduced the incidence of diarrhea associated with antibiotic therapy. Of those who used the probiotic drink, only 12% had any intestinal distress v.s. 34% of those who ingested a placebo drink. Any probiotic food (I recommend eating yogurt to all of my patients on antibiotics) that contain the beneficial bacterial species Lactobacillus casei, L. bulgaricus and Streptococcus thermophilus can be used. These are listed on the labels of all yogurt tubs (along with several other bacterial species).
posted by Steve at 2:52 PM

 
"NO PREP" VENEERS

Over the past few years, the placement of veneers on the front of teeth has become a popular way to improve a patient's looks. Veneers are kind of like fake fingernails in that they are overlays that can change the shape and/or the color of teeth hopefully for the better. In cases where veneers are indicated, the dentist does not have to cut a whole tooth down to have a pleasing result (as is necessary in full croen preparations) because veneer preps only alter the facial part of the teeth which, obviously, is the part that shows.

There are two types of veneers - direct and indirect. Direct veneers are made from a resin material (composite resin) and, as the name suggests, placed directly on the teeth at the dental chair in a single visit. Composite material has really become natural-looking and can be polished to a very high gloss similar to natural tooth structure. Indirect veneers are made in a dental laboratory and can be made of either porcelain (which is a ceramic material) or composite material. The direct veneers are less costly because there are no lab bills and they require less chair time. Esthetically, they can be very acceptable and are mainly used to cover surfaces of teeth that have already had a lot of composite fillings or as a more economical way to change the appearance of these teeth. However, even the best placed composite veneers eventually become dull but can usually be re-polished albeit with a loss of texture. Direct veneers are certainly a consideration and, in some cases, are the only option (in teeth weakened by large old fillings). Lab-fabricated porcelain veneers are the gold standard. They look and feel more like natural teeth but are much more technique sensitive than, say, full porcelain crowns or direct veneers. The lab tech can control the shape and color of the veneers which are then bonded to the fronts of the teeth by the dentist using a composite cement. Porcelain never loses its color or its texture nor does it become dull over time. Porcelain bonded to enamel creates the strongest bond of any other procedure that we have in dentistry! Porcelain bonded to the dentin (the layer under the enamel) of the tooth is not as predictable over time and this is where diagnosis and tooth preparation is critical.

If the teeth are fairly straight, the enamel is adequate (i.e. at least one millimeter or so thick) and the teeth are not too dark (especially dark grey), then porcelain veneers are probably the way to go for long-term satisfaction and maintenance. If veneers are to be used for "instant orthodontics" to staighten teeth then all bets are off because, in order to have room for the veneers, the enamel of the teeth to be "straightned" often has to be ground away to make room for the porcelain material. This ends up with a porcelain to dentin bond which is still quite strong but not so much as the enamel bond. It is often wise to go ahead with full crowns for teeth that are out of line but that introduces the problem of matching the color of the full crowns with the other teeth which might be candidates for veneers in the same dental arch. (Teeth that are really crowded or in patients with deep overbites should have orthodontic correction before or instead of any restorations to the front teeth).

That brings up the question of a procedure that many of you have probably been exposed to in advertisements called "no-prep" veneers or Lumineers as the company call them. Let me say that, in order to make most teeth looks natural with veneers, a very small amount of tooth structure - less than one millimeter if possible (to stay in the enamel) -needs to be removed from the facial surface. Again, dentists try to stay in enamel for a stronger bond but sometimes it is necessary to involve the dentin layer. No-prep veneers overlay the teeth without any preparation i.e. without any tooth removal. There are only a few cases where we can get away doing this without the teeth looking "fat"! In other words, and as Dr. Mike DiTolla of Glidewell Dental Lab say so graphically, "Unless the patient's favorite athlete is Seabiscuit, this is probably a look he or she does not want to pursue". There are cases in which no -prep veneers will work and that is in patients:
-whose teeth shade is close to the final disired shade: trying to lighten dark teeth with veneers that are .3 millimeter thick requires an opaquing porcelain material that makes the teeth look like chicklets. Teeth can be lightened up to two shades only with these veneers
-whose teeth are as close to ideal profile as possible or even tipped backwards toward the tongue: if teeth are flared toward the lip at all, adding porcelain will only exaggerate the situation (see the Seabiscuit analogy above).
whose arch form is close to ideal: if the front teeth are misaligned, the final result will yield teeth that have significant different thickness at the biting edge. Also, misalignment that includes overlapping teeth will make it impossible to provide contours that appear natural.

People who ask about no-prep veneers are usually patients who do not want to have any tooth structure ground down, even minimally. I guess they think that, in a worst-scene scenario in which they hate the final result, these little buggers can be removed with any big loss (other than financial). A wake up call on this one; removing veneers is very difficult and it is pretty much impossible to do so without damaging the tooth structure underneath. It is also going to cost some money to have a dentist do this procedure. (A patient who insists on no-prep veneers against the dentist's better judgement, should be required to sign a release which allows that dentist to charge a fee for their removal).

In the right situation, veneers are really nice and have a long lasting prognosis. However, just like everything else that goes into the oral cavity, one or more may have to be replaced over the years for various reasons and, as long as patients go into treatment with that in mind, they can really be an enhancement to one's self esteem and willingness to smile.
posted by Steve at 9:48 AM