EDUCATION
General Dentistry
X-RAYS
In terms of diagnosis, x-rays are second only to the clinician's knowledge and experience. It is an indispensable adjunct during the examination or recall process, as it gives information that the naked eye alone cannot detect. How does it work, and what does it show?
How Does It Work?
X-rays are emitted from the tube and passes through your body, some being absorbed and others passing through to the sensor (the film or digital sensor) inside your mouth. The denser the object the x-ray hits in your body, the more likely it will be absorbed or deflected from it's path. If the x-ray passes through your body and hits the film, it registers as a dark spot. If it hits something dense, say like bone, or teeth, it gets absorbed/deflected, and doesn't hit the film: a light spot. It sounds like a simple concept, and it is. But interpreting the light and dark spots is where it gets complicated.
With x-rays, we are able to diagnose several things:
- cavities, especially between the teeth
- infections
- trauma (broken roots, bone)
- health of the gum and bone tissues
Without routine x-rays, small problems will be undiagnosed until if becomes serious. For example, small cavities that start between the teeth will not elicit any pain or sensitivity until close to the nerve, and cannot been seen on a regular exam. X-rays are the only way to spot these before they get too big.
Safety Issues
There are always concerns regarding radiation exposure, and dentistry is no exception. So, what really is the risk from dental x-rays? First of all, we are constantly bombarded by radiation everyday, from cosmic radiation to everyday objects (red brick, red meat), and other sources as well. This results in about 100 to 200 mrads/yr.
One dental x-ray will result in about 1mrad total body dose, so you can see how little the radiation actually is. In fact, if your x-rays were taken digitally, the exposure will be even less, by 50% to 80%!
In reality, you are exposed to more radiation taking a long-haul flight than from a full series (20) of x-rays! The risk really is to healthcare professionals, for whom taking x-rays is a daily routine.
Silver Fillings
Most are familiar with the controversy regarding silver fillings, especially with respect to mercury content. In fact, there have already been several lawsuits in the United States, filed against several state dental associations and the American Dental Association. So far, all lawsuits have been defeated, and for a simple reason: there has not been well-researched literature linking mercury in silver fillings to health problems in the patient.
What is a Silver Filling?
So what are silver fillings made of? They consist of approximately one to one ratio of mercury to amalgam alloy (a mixture of silver, tin, copper, and zinc). Mixed together, they actually react to form different phases that bind the mercury into the mixture.
Safety Issues
A study done in 1985 looked at the urinary concentration of mercury in dentists, and found that they had levels of 14.2micrograms/litre. In the general population that level was 0 to 1.0micrograms/litre. As a reference, the government safety limit of urinary mercury concentration is 200micrograms/litre, and deleterious effects to the nervous system begin at around 500micrograms/litre. As with x-rays, it is the dentists who are most at risk with mercury poisoning! However, the prevalence of white fillings today means the risk is even less than before.
Is There A Place For Silver Fillings Today?
Thus far, white fillings are still inferior with respect to compressive strength than silver fillings. This means that in your back teeth, which are used to chew and grind your food, silver fillings for the most part are probably longer lasting than white fillings. Having said that, very small fillings on back teeth most likely can be restored by either white or silver, as natural tooth structure will bear the brunt of the chewing forces.
Root Canals
It is a term most associated with the pain of dental appointments, but what is it, and why do some need it? Simply put, root canals remove the nerve and blood supply (collectively called the pulp tissue) from the inside of the tooth. There are several reasons why you may need such a drastic procedure:
- a large cavity that is close to or already into the nerve tissue
- severe trauma, like an auto accident for bar room fight, which knocks the tooth or even chips it
- severe gum disease
All of these events will result in nerve death, which, like all dead things, become infected, and can spread through the tooth and out into the jaw bone – ouch! In extreme cases, they can even be life-threatening.
What Is Done In A Root Canal?
So, how do we remove the nerve and blood vessels, and what do we do afterwards? Good question. We access the nerves by drilling to it, similar to drilling out cavities, only deeper. Once there, we use little instruments to take out the pulp tissue, and plane the sides of the hole left behind, to clean out any bacteria residing inside and create a well-defined channel. We then fill it with a rubber-like material called gutta percha, or more recently, resin. We then cover the hole like a regular filling.
It does sound painful, but in reality, most root canals tend to result in only mild pain afterwards. As a rule of thumb, if you came into the office in a lot of pain, then it does tend to be a little more painful afterwards. Usually, though, it hurts a lot less than before you came in!
Afterwards
Most dentists will tell you to get a crown after a root canal done on back teeth. This is NOT because we want to make more money, although it may seem that way. The reason we advise crowns for root canalled teeth is that once the pulp tissue is removed, the tooth essentially dries out, making it more brittle and therefore more likely to fracture or chip. Imagine a branch taken from a tree. When alive, the tree branch is flexible and tends to bend rather than break. Let it dry for a day or too, and it snaps in two rather than flex. That same applies to your tooth, and your back teeth undergo tremendous forces when you chew, increasing the risk that you'll be chewing some tooth bits with your bread after a root canal!