The Importance of Panoramic Films

What a Panoramic Film Shows

A panoramic film is a single x-ray image, taken from outside the mouth, that shows the whole dental arch, both jaws, the jaw joints and the maxillary sinuses in one frame. It works as a map of the mouth: every tooth, erupted or not, appears in its position alongside the bone that holds it and the structures around it.

This wide view is what separates it from the smaller films taken inside the mouth. A periapical film shows one or two teeth from crown to root tip, and a bitewing film shows the upper and lower back teeth touching, which is useful for spotting decay between them. Each of these shows only a few teeth.

The panoramic image answers questions that a single intraoral film cannot. It shows whether a wisdom tooth is impacted and how it lies, whether there is a cyst or other lesion in the jawbone, how far bone has been lost around the teeth, and how much bone height is available where an implant is planned. It also shows developing permanent teeth in children, missing teeth and irregularities in the jaws.

The trade-off is detail. Because the image covers so much, it shows each tooth with less sharpness than a periapical or bitewing film, and small cavities between teeth can be missed on a panoramic image alone. In practice the two kinds of image complement each other: the panoramic film gives the overview, and intraoral films are added where a specific tooth needs a closer look.

How the Image Is Taken

A panoramic x-ray is quick and painless. You stand or sit at the machine, and your head is positioned and held still with a chin rest, a bite block and side supports.

Once you are positioned, the x-ray tube and the receptor rotate around your head, one passing behind while the other passes in front. The machine performs a 360-degree scan around the fixed head, and the whole exposure takes about 10 to 15 seconds. You feel nothing while it moves; the only thing asked of you is to stay still, keep your lips closed around the bite block and rest your tongue against the roof of your mouth.

Nothing is placed deep inside the mouth, which makes the panoramic film easier to tolerate than intraoral films for people with a strong gag reflex, for small children and for patients who find it hard to open wide for long.

With digital receptors the image appears on screen immediately. There is no film to develop, so the dentist can read it and discuss the findings within the same appointment. The digital file also goes straight into your record, where it can be compared with later images to follow changes over time,.

Radiation Dose Compared with Other Dental X-Rays

The dose from a panoramic film is low, but it is not zero, and the comparison with other dental x-rays is more specific than the common claim that panoramic films always carry less radiation.

Measured with a tissue-equivalent head phantom, effective doses were 14.2 microsieverts on one panoramic unit and 24.3 microsieverts on another, against 34.9 microsieverts for a full-mouth intraoral series with rectangular collimation and 170.7 microsieverts for the same series with round collimation (PubMed 18762634). So a panoramic image delivers less than a full-mouth series of intraoral films, and far less than a full-mouth series taken with round collimation.

Lower than a full-mouth series is different from lower than every intraoral film. In the same study, a four-image posterior bitewing set measured 5.0 microsieverts, well below either panoramic unit (PubMed 18762634). When the question is only about decay between the back teeth, bitewings answer it with less dose.

The same authors noted that doses calculated under the 2007 recommendations of the International Commission on Radiological Protection were 32 to 422 percent higher than under the 1990 guidelines, and that clinicians can reduce dose substantively by using digital receptors, rectangular collimation and radiographic selection criteria (PubMed 18762634). Selection criteria means that an image is taken because a clinical question needs it answered, and the type of image is chosen to fit the question.

This is why a panoramic film is taken on indication. Your dentist asks for one when the whole-arch view is needed, and uses smaller intraoral films when the question concerns a few teeth.

Shielding and Imaging During Pregnancy

Many patients expect a lead apron or a thyroid collar before any dental x-ray. Recommendations on this have changed, and the reasons are worth knowing.

An ad hoc committee of the American Academy of Oral and Maxillofacial Radiology reviewed the dose that dental and maxillofacial imaging delivers to the gonads, the breasts and the thyroid gland. Considering the negligible dose to the gonads and fetus, the committee recommended discontinuing shielding of the gonads, pelvic structures and fetuses during all dentomaxillofacial imaging, and recommended that thyroid shielding not be used during intraoral, panoramic, cephalometric and cone-beam imaging (PubMed 37530694).

Pregnancy is handled with care all the same. The usual guidance is to avoid radiographs during pregnancy unless the examination is necessary. When it is necessary, for example in an acute infection or after trauma, the diagnostic benefit is weighed against the dose, and treatment that depends on the image is not delayed for the sake of an exposure that reaches the fetus only negligibly.

Tell the dentist if you are pregnant or might be, even when the visit is routine. That decision belongs to the dentist and the treating physician together, and it is made for your situation.

Planning Orthodontic and Implant Treatment

Before orthodontic treatment, the dentist needs to know the current condition of every tooth and how the teeth relate to the bone around them. The panoramic film shows missing teeth, extra teeth, teeth that have not erupted and irregularities in the jaw structure in one view. In children it shows the developing permanent teeth in both jaws at once, which makes it useful for following tooth development and for deciding when treatment should start.

During treatment, a later image can show how the roots are positioned as the teeth move. Braces move the crowns that you can see, but the roots need to follow in a healthy direction, and the overview helps confirm that they do.

For implant treatment, the panoramic film is an early planning step. It shows the bone height available in the area of the missing tooth and the position of nearby structures such as the maxillary sinus in the upper jaw and the nerve canal in the lower jaw. A panoramic image cannot show bone width, and it does not measure bone density. Where an implant is planned close to these structures, a three-dimensional scan usually follows to assess the bone in all directions.

After an implant has been placed, panoramic and intraoral films are used at follow-up visits to check the bone level around the fixture.

Impacted Teeth, Cysts, Gum Disease and Trauma

Impacted teeth, especially wisdom teeth, are one of the most frequent reasons for a panoramic film. The image shows the position and angle of the tooth, how far it has developed and how close its roots lie to the nerve canal in the lower jaw or to the sinus in the upper jaw.

Cysts, tumours and other lesions in the jawbone often grow without pain and remain unnoticed until they are large. On a panoramic image they can appear as areas where the bone looks different from its surroundings. Finding them at an early stage allows them to be examined and treated while they are small. An image alone does not diagnose the nature of a lesion, and further imaging or a biopsy may be needed.

In periodontal care, the panoramic film shows the level of the bone around the teeth across the whole mouth. Bone loss is the part of gum diseases that cannot be seen by looking at the gums, and the overview shows how far it has progressed and whether it is general or limited to certain teeth. Intraoral films are often added where a particular tooth needs a sharper view.

After an accident or a blow to the face, the panoramic film is used to look for fractures of the jaw and cracks in the teeth. It shows both jaws and the jaw joints in a single exposure, which helps when an injured patient cannot open the mouth comfortably for intraoral films, and it supports planning before any surgical treatment.

When a Dentist Asks for a Panoramic Film

A panoramic film is requested when the question concerns the whole mouth or the bone around the teeth. Typical occasions are before orthodontic treatment, before implant placement, when an impacted tooth such as a wisdom tooth is suspected, when bone loss from gum disease needs assessing and after trauma to the face.

It is not a routine image for every check-up. The dentist weighs what the image will show against the dose, and when the question is limited to a few teeth or to decay between the back teeth, smaller intraoral films answer it with less radiation.

At the appointment, you can reasonably ask what the image is for and what the dentist expects to learn from it. If you have had a panoramic film recently at another clinic, bring it or ask for the digital file to be sent, since a recent image may make a new one unnecessary.

Used on indication and read together with a clinical examination, the panoramic film gives a view of the mouth that no single intraoral image can provide, and it is often the first step in planning treatment.