Dentists have a variety of different types of dental x-rays at their disposal to assist them in diagnosing oral diseases. The intraoral ones are the most frequently used by dentists and are probably what you’re most used to seeing. However, there are extraoral radiographs as well which can help diagnose more obscure or rare dental conditions.
Types of dental x-rays:
- Intraoral x-rays. The most common type of xrays that are used by dentists to radiographically visualize structures in the mouth (tooth, gums, & jaw bone).
- Extraoral x-rays. These xrays can show the teeth as well but they’re typically zoomed further out to visualize the surrounding head and neck structures. They can show problems with the TMJ, salivary glands, sinuses, and other soft tissues.
We will explain what each of them are in greater detail and what their purposes are for. Lastly, we’ll go over some radiation guidelines when it comes to taking radiographs because your safety is of utmost importance.
Intraoral X-rays
The intraoral dental x-rays consist of bitewings, periapicals, and occlusal films. Their primary use is in diagnosing oral diseases and conditions for the structures in your mouth which includes your teeth, gums, and jaw bone.
The images above show the equipment that is used to take intraoral dental x-rays. It is mounted to the wall with a long arm that can bend and flex at various positions. It is coupled with an intraoral sensor that captures the image digitally.
| Intraoral x-ray | What it shows | What it diagnoses |
|---|---|---|
| Bitewing | Molars and premolars | Cavities, tartar, fillings, bone health |
| Periapical | All of the teeth from crown tip to root tip | Periapical abscesses, fractures |
| Occlusal | Upper and lower arches | Jaw lesions, salivary stones |
Bitewing x-rays
The bitewing x-ray (BW) will show your upper and lower back teeth biting together, hence the name. They are the best tool to use for detecting cavities that are in between the teeth (interproximals). They can detect chewing surface (occlusal) decay as well but only the very large ones.
The two images above are sample bitewing xrays. As you can see, it shows the molars and premolars biting together. You can also see a lot of old fillings.
Periapical x-rays
The periapical x-rays (PA) will show you the entire length of the tooth, from the tip of the crown to the tip of the root. They can be used for front teeth and back teeth.
While they can be used to detect cavities, where they shine is in detecting periapical abscesses and changes in bone levels from periodontal disease. They will also show obscure dental conditions as well.
Occlusal x-rays
The occlusal x-rays can be taken for the upper or lower arch. They’re often used to evaluate jaw lesions in the bone or if your dentist suspects a salivary stone. They’re also sometimes taken on kids to see if the permanent teeth are growing in.
Extraoral X-rays
The extraoral dental x-rays are usually taken via equipment from outside of the mouth. A commonality among these is that they show much more than just the teeth such as your sinus, TMJ, and other soft tissues.
| Extraoral x-ray | What it shows | What it diagnoses |
|---|---|---|
| Panoramic | Both arches, sinus, TMJ | Impacted wisdom teeth, jaw fractures |
| Cephalometric | Lateral shot of the skull | Skeletal jaw deformities for orthodontics |
| CBCT | Upper and lower arches | 3D visualization of oral diseases |
| Sialogram | Salivary ducts | Salivary stones |
| Tomogram | Skull and jaw | Facial trauma, implants, jaw diseases |
Panoramic x-rays
The panoramic x-ray is widely used by oral surgeons because it visualizes the entire jaw with all of the teeth. However, where it shines is in showing impacted wisdom teeth and their proximity to the nerves.
Cephalometric
The cephalometric dental x-ray is typically used by orthodontists. They will take one prior to beginning treatment in order to check for skeletal jaw deformities
What it shows is the side view of the entire skull. It helps in visualizing the relation between the upper and lower jaw.
Cone Beam CT (CBCT)
A cone beam CT has gained immense popularity in dentistry over the past decade or so. Oral surgeons use it for implant planning and design while endodontists use it to find tooth fractures and extra canals.
What it does is take a three dimensional radiograph of the head, neck, and jaw but you can limit it to what structure you need. This is vastly different from the intraoral x-rays which can only take the image in two dimensions.
Infrequently used radiographs
- Sialogram. This is an x-ray taken of the salivary ducts and glands. You may need it if you think you have a blocked or clogged duct.
- Tomogram. Can take images or slices of the entire head and neck region. It is very useful for dental implant planning.
X-ray guidelines
Indications
Dental x-rays should be taken whenever you suspect that you have a pathological oral condition. Without them, your dentist will only be able to give you a partial evaluation and diagnosis because they cannot see beyond the surface of your teeth.
Information x-rays provide:
- Number, size, and position of the teeth
- Dental caries (tooth decay)
- Bone loss caused by periodontal disease
- Oral infections
- Jaw fractures
- Occlusion issues
- Jaw lesionsdentists just pushing x-rays onto them
- Other mouth abnormalities
Frequency
The frequency that you should have dental x-rays done will depend on your individual risk factors.
- Those at high risk for cavities and other dental issues should have it more frequently.
- Those at low risk can go for a longer period of time without x-rays.
Most dental insurance will cover a set of x-rays at least once a year regardless of risk. The average person usually does have them taken at least once a year since they don’t need to pay for it.
What is the best frequency interval for you should be discussed with your dentist and custom tailored to your personal risk. For that you will need an in person clinical examination as well as review your dental history to figure out.
We do understand that sometimes people feel like dentists just pushing x-rays onto them but there are reasons for that.
Safety & Risks
While there are many benefits to having x-rays taken on your mouth, it does come with risks since it induces radiation.
- Cancer later in life
- Cataracts
- Skin reddening
- Hair loss
Due to the potential risks involved, the guiding principle of radiation called ALARA (as low as reasonably achievable) was developed. It’s purpose is to minimize the amount of harm that can be done with x-rays.
ALARA principles:
- Minimize time. Minimize the amount of time spent near a radioactive source. Complete your task quickly and leave the area immediately.
- Maximize distance. Keep as much distance between you and the radioactive source.
- Use shielding. Shield yourself from radiation such as by using lead aprons.
Dental radiation chart
If you were wondering how much radiation is in dental x-rays, look no further than the research from the University of Michigan School of Dentistry.
We like how they put it into perspective for you by quantifying the radiation dose as what the equivalent amount of background radiation would be. Yes, you get natural radiation from the sun just from being alive on this planet earth.
| X-ray Type | Equivalent amount of background radiation |
|---|---|
| Natural background radiation | 1 day |
| 4 hour airline flight | 1 day |
| 4 bitewings | 1 day |
| Full mouth of x-rays | 4 days |
| Panoramic | 3 days |
| Cephalometric | < 1 day |
| Low dose CBCT (3 teeth) | 4-5 days |
| Medium FOV ( 1 jaw) | 14-17 days |
| Large FOV (both jaws) | 34 days |
| Chest x-ray | 1 day |
| Head CT | 8 months |
| Chest CT | 12 months |
| Abdominal CT | 20 months |
Hopefully that gives you some perspective on the safety for taking dental radiographs. As you can see, it is one of the lowest forms of radiation when compared to others.