Dental X-rays, When and Why

X-rays done during dental visits have seemingly become a routine part of the examination. But did you know that the American Dental Association (ADA) in conjunction with the U.S. Food and Drug Administration (FDA) has developed guidelines for when and why they should be performed?
   
Why perform x-rays of teeth?   Dental x-rays can provide valuable information to help guide the dentist in providing the best care possible. Some of the advantages to the dentist as well as to patients include:

• Being able to detect areas of decay that are not visible on oral examination
   
• Identifying decay occurring beneath a filling
   
• Finding bone loss due to gum disease
   
• Revealing an abscess at the root of the tooth
   
• Allowing certain dental problems to be addressed at an early stage

Types of dental x-rays.  The three most common types of dental x-rays are the bitewing, periapical and panoramic.  Of these, the bitewing is the one most often performed.  The bitewing is performed by having the patient bite down on a piece of plastic with x-ray film.  These x-rays are designed to primarily view the molars and specifically look for decay between the teeth. A periapical x-ray provides an image of the entire tooth from crown to root.  These are particularly useful when evaluating for a cyst or abscess. Panoramic x-rays provide a view of the upper and lower teeth in a single view.  This type is particularly useful in evaluating children's tooth development or for the emergence of wisdom teeth.

Key recommendations from the ADA/FDA regarding dental x-rays in adults:

1. For new patients, an "individualized radiographic exam consisting of posterior bitewings with panoramic exam or posterior bitewings and selected periapical images", is considered to be appropriate.
    
2. In a new patient with evidence of dental disease or a history of extensive dental treatment, a “full mouth intraoral radiographic exam is preferred.”
    
3. For patients returning for dental evaluation, who have evidence of dental decay or who are at increased risk of developing cavities, a posterior bitewing exam at 6-18 month intervals" is recommended.
    
4. In return patients with no evidence of dental decay and no increased risk of developing cavities, "posterior bitewing x-rays at 24-36 month intervals" are advised.

Factors related to an increased risk of developing dental disease. Everyone is at risk of developing tooth decay, but a number of factors increase the likelihood of developing dental caries (cavities) including:

• Poor dental hygiene
   
• Foods that stick to teeth for a long time such as milk or sweets.
   
• Inadequate fluoride intake which is typically not present in bottled water.
   
• Worn fillings or dental devices.
   
• Dry mouth due to certain medical conditions, radiation to the head or neck, and taking medications that inhibit saliva production.
  
  
• Younger or older individuals who are more prone to developing cavities

It should be noted that these are recommendations only, with the final decision on when and why to perform x-rays left up to the dentist's clinical judgement. These guidelines vary somewhat in children, adolescents or in adults who do not have teeth. The ADA/FDA guidelines also state that the dentist should have dental x-rays performed only after reviewing the patient's health history and completing a clinical examination.

Additionally, measures should be taken to minimize radiation exposure by limiting the number of images produced, using "fast" speed film, and providing patients with radiation-blocking aprons and collars when appropriate.

Sources for article:
The Selection of Patients for Dental Radiographic Examinations from the FDA and ADA
American Dental Association Oral Health Topics---X-rays

Reviewed on April 13, 2016 by our Medical Director

Sunglasses---merging fashion with function

Rather than considering the amount of protection that they afford, new sunglasses are often selected for their frames, the size of the lenses, or for a particular coating on the lenses. It is important to remember, however, that the most important job for sunglasses is to prevent damage to the eyes from the sun's harmful rays. Fortunately, with a little knowledge about Ultraviolet (UV) radiation and sunglasses technology, fashion does not have to take a backseat to safety.

What does UV protection indicate? The amount of UV protection is the single most important factor to consider when shopping for sunglasses. The three types of invisible high-energy UV rays are UVA, UVB, and UVC.  At present, UVC waves are being blocked by the earth's ozone layer and are not a factor in causing eye damage. UVA and UVB rays are the ones that are most damaging to the eyes. Fortunately, even inexpensive sunglasses can provide complete protection against these rays. Always select sunglasses with labeling that indicates that they block "99 to 100% of UVA and UVB rays". If this is not indicated on the label, pass them up.

What other features provide help protect the eyes? In general, larger lenses provide more protection than smaller lenses. In addition, "wraparound" styles of sunglasses help prevent sunlight from reaching the eye from the sides of the glasses.

Why are some sunglasses more expensive than others? This has to do with a number of factors, such as the optical clarity of the lenses, the exclusivity of the frames, or the special coatings that are applied to the lenses. So long as they are both providing complete UV protection, however, a twenty-dollar pair of sunglasses can be just as protective as a two-hundred dollar pair.  Typically, however, the more expensive brands of sunglasses, include a higher quality lens capable of producing a clearer, sharper, image with less distortion.

Does being darker mean that the lens is more protective? How deeply tinted the lenses of sunglasses has no bearing on the amount of protection that they provide. Lightly tinted sunglasses that block 99 to 100% of UV rays are more protective than a darker pair with a lower UV rating.

What about the protection provided by Transitions® sunglasses?  Transition lenses are also known as "photochromic lenses" since they darken on exposure to UV light. Their manufacturer indicates that they provide 100% UV protection whether they are clear or as dark as regular sunglasses. Not all manufacturers of photochromic lenses offer complete UV protection, so be sure to check the product label.

What is the advantage of polarized glasses? Polarized glasses are best for preventing glare, particularly when near the water. That makes them particularly useful when fishing or boating. They can also prevent eyestrain from glare when driving. In most cases, polarized sunglasses also provide complete UV radiation protection, but this is worth confirming before purchasing.

Are certain lens colors better than others? As long as the lenses are providing complete protection against UV radiation, the American Academy of Ophthalmology indicates that color is a matter of personal preference. Gray, green, or brown lenses are the most popular shades of lenses for sunglasses.

What about shaded lenses? These are popular with many designer sunglasses manufacturers. They are also known as "gradient lenses", since they are permanently shaded from top to bottom or top and bottom toward the middle. This variation in tinting of the lens does not affect the UV protection and can be as protective as sunglasses with a uniform tint.

From this discussion, it becomes clear that eye protection from the sun and stylishness can co-exist. The most important issue is to make sure that the sunglasses you choose provide complete protection against UV rays. Be aware that even though contact lenses can provide some UV protection, sunglasses should be worn outside since contacts do not cover the entire eye. Also, considering the amount of time that children spend in the sun, they should wear UV-protective sunglasses also.

Sources for article:
How to choose the best sunglasses from the American Academy of Ophthalmology
Guidance Document For Nonprescription Sunglasses from the U.S. Food and Drug Administration

Cologuard, a new screening method for colon cancer

Guidelines published by the U.S. Preventive Services Task Force recommend that adults ages 50-75 who are at average risk for the development of colon cancer can reasonably be screened by one of three methods: 1) fecal occult blood testing, 2) sigmoidoscopy, or 3) colonoscopy.  Fecal occult blood testing involves the use of "cards" onto which a stool sample is placed and tested for the presence of blood which may not be readily apparent. Sigmoidoscopy is a more limited version of colonoscopy in which the lower portion of the colon is viewed using a flexible fiber optic “scope”.  Colonoscopy, in which the entire colon is directly visualized, is currently considered to be the “gold standard” for colorectal cancer screening.
 
In 2014, an alternative to these screening methods was approved by the U.S. Food and Drug Administration (FDA) as well as by the Centers for Medicare & Medicaid Services. This screening method is called Cologuard, and like the fecal occult blood test, is stool-based.

How does Cologuard work?  The test detects microscopic amounts of blood in the stool as well as detecting altered DNA that could have been caused by colon cancer or pre-cancer.  Cologuard is available only by prescription.  It is performed at home by collecting two samples of stool that are sent to a laboratory for analysis.

Who should consider having this test?  Screening rates for colon cancer fall below the targets set by the U.S. Centers for Disease Control. Reasons for this include the expense and typically unpleasant nature of preparation for colonoscopy and the requirement that fecal occult blood testing must be repeated on an annual basis.  Cologuard represents an alternative for someone who would otherwise not undergo colon cancer screening due to these and other reasons. It should be noted that the test is intended for people who are at average risk for developing colon cancer. It is not currently recommended for those at increased risk, such as someone with a family history of colon cancer or with an inflammatory condition affecting the colon such as ulcerative colitis. People at higher than average risk may require more frequent or a different method of screening.

How accurate is Cologuard?   Prior to FDA approval, Cologuard was evaluated in a large clinical trial involving more than 10,000 people.  Cologuard was found to detect 92 percent of colorectal cancers as compared to 74 percent of cancers detected using a home-based stool test (Fecal Immunochemical Test--FIT).  Cologuard also detected 42 percent of precancerous lesions compared to a 24 percent detection rate with the FIT test. One downside of Cologuard testing is that is has a higher likelihood of a false positive result.  This means that the test can come back positive even in the absence of disease.  In these cases, follow-up testing with colonoscopy is recommended.

Will this test replace other methods of screening?   Colonoscopy remains the best single test for colorectal cancer screening. Not only is the entire length of the colon directly visualized, but the doctor also has the ability to perform biopsies and remove polyps during the procedure.  As mentioned previously, Cologuard’s main application may be to provide people who are unable or unwilling to undergo other forms of testing with a reliable screening method. As of now, Cologuard is listed as an acceptable method of screening for colorectal cancer by the American Cancer Society and as an “alternative” method of screening by the USPSTF.

How much will Cologuard cost?  Cologuard is a very sophisticated test that will not come cheaply. This is primarily due to the component of the test that looks for abnormal DNA. An estimated cost is somewhere in the $500-650 range.  This is much more expensive than the basic stool test costing in the $5-10 range but considerably less than a colonoscopy at around $6000 per procedure.
Article sources:

1. USPSTF recommendations regarding colorectal screening
2. FDA Press Announcement regarding Cologuard
3. Cologuard by Exact Sciences