Dental radiography is one of the most frequently performed tasks in dental assisting and one of the most technically demanding to do consistently well. A good X-ray is diagnostic — it shows the dentist exactly what they need to see. A poor X-ray is worse than no X-ray: it either fails to answer the clinical question or gets retaken, doubling the patient's radiation exposure. This guide covers everything you need to take consistently diagnostic radiographs.

ALARA — the guiding principle: As Low As Reasonably Achievable. Every radiographic decision — how many images, what technique, what equipment settings — should minimize radiation exposure while achieving the diagnostic information needed. Retakes due to poor technique are the most preventable source of unnecessary exposure.

Understanding the equipment

Digital vs traditional film

Most practices now use digital radiography — either direct digital (sensor in patient's mouth) or phosphor plate systems. Digital requires 50 to 80% less radiation than traditional film and produces images that are immediately visible on-screen. The technique principles are the same regardless of the imaging medium.

Kilovoltage and milliamperage

kVp (kilovoltage peak) controls the penetrating power of the X-ray beam — higher kVp produces more penetrating rays and greater contrast. mA (milliamperage) controls the quantity of X-rays produced. These settings are preset on most office machines — your job is to ensure proper positioning, not to adjust exposure settings without direction.

Periapical X-ray technique

Periapical films show the entire tooth from crown to root and the surrounding bone. The two main techniques are the paralleling technique (preferred) and the bisecting angle technique.

Paralleling technique

The sensor/film is placed parallel to the long axis of the tooth and positioned away from the tooth using a film holder. The X-ray beam is directed perpendicular to both the film and the tooth. This produces the most dimensionally accurate image with minimal distortion.

  1. Place the film holder with sensor/film in the holder ring and position it in the patient's mouth so the sensor is parallel to the tooth of interest.
  2. The sensor should extend approximately 3mm beyond the incisal/occlusal edge of the tooth and be centered mesiodistally on the target tooth/teeth.
  3. Ask the patient to close gently on the bite block — not hard enough to move the sensor.
  4. Align the aiming ring on the position-indicating device (PID) with the ring on the film holder. The cone should be centered on the ring with no overlap.
  5. Confirm the patient is still, make the exposure.

Bitewing X-ray technique

Bitewing X-rays show the crowns of upper and lower posterior teeth on one image. They are the primary tool for detecting interproximal decay and assessing bone height.

  1. Place the sensor/film in the bitewing holder or loop with the white or active side facing the teeth.
  2. Position in the patient's mouth — the sensor should be centered on the teeth of interest and parallel to the long axis of the teeth.
  3. Ask the patient to close on the bite tab. The occlusal plane should be parallel to the floor.
  4. Direct the beam with a slight vertical angulation (typically 5 to 8 degrees positive) and center horizontally between the contact points of the teeth.
  5. For horizontal angulation: the beam must pass directly through the contacts — if it's angled mesially or distally, contacts will overlap on the image and interproximal surfaces can't be evaluated.

Panoramic radiograph technique

The panoramic machine rotates around the patient's head to capture a single image of all teeth and both jaws. Patient positioning is critical — even small errors cause significant distortion.

  1. Remove all metal from the patient — earrings, piercings, glasses, removable dental appliances, hearing aids.
  2. Position the patient in the machine — chin on the rest, biting on the bite block, Frankfort plane (ear-to-eye line) parallel to the floor.
  3. Ensure the spine is straight — ask the patient to stand or sit tall with shoulders down.
  4. Position the midsagittal plane (the centerline of the face) in the center of the machine.
  5. Ask the patient to place the tongue on the roof of the mouth and hold still for the duration of the exposure (typically 12 to 20 seconds).

Common errors and how to prevent them

📐

Cone Cut

Part of the image is unexposed — a clear semicircle on one edge. Caused by the beam not being centered on the sensor. Center the aiming ring carefully.

🔲

Overlapping Contacts

Interproximal spaces not visible — teeth appear to touch. Caused by incorrect horizontal angulation. The beam must pass directly through the contact points.

↕️

Elongation / Foreshortening

Teeth appear too long (elongated) or too short (foreshortened). Caused by incorrect vertical angulation. Paralleling technique with a holder minimizes this.

⚡

Blurring

Image is not sharp. Caused by patient movement during exposure. Confirm patient is stable and still before exposing.

⬛

Dark / Light Images

Overexposed (too dark) or underexposed (too light). Check exposure settings and sensor/film positioning.

💥

Herringbone Pattern

A distinctive error pattern indicating the film was placed backward (film side away from beam). Active side of sensor/film must face the tube.

Patient management during radiography

The bottom line

Consistent, diagnostic-quality radiographs come from disciplined technique, proper patient positioning, and attention to the details that prevent errors before they happen. Every retake is a failure of preparation — and a dose of radiation the patient shouldn't have received. Take your time with positioning, verify alignment before exposing, and commit the common errors to memory so you can prevent them before they happen.