Intraoral Techniques & Error Correction
Mastering the Physics of a Perfect Image
🎯 Learning Objectives
- Master the Paralleling Technique vs. the Bisecting Technique.
- Identify the causes of Horizontal and Vertical angulation errors.
- Recognize the visual “telltale signs” of common technique failures.
- Apply corrective actions to eliminate non-diagnostic images.
1. The Gold Standard: Paralleling Technique
The Paralleling Technique is preferred because it produces the most accurate image with the least amount of distortion. It follows two strict rules:
- The sensor/film is placed parallel to the tooth’s long axis.
- The central X-ray beam is directed perpendicular (90 degrees) to both the tooth and the sensor.
2. Troubleshooting: Horizontal Errors
Horizontal angulation refers to the side-to-side movement of the PID (tubehead).
If the central ray is not directed straight through the contact points of the teeth, the interproximal surfaces will “overlap” on the image, making it impossible to see decay.
The Fix: Direct the beam straight through the contacts.
3. Troubleshooting: Vertical Errors
Vertical angulation refers to the up-and-down movement of the PID. This is the most common area for exam questions.
| The Visual Error | The Technical Cause | The Fix |
|---|---|---|
| Elongation | Too little (flat) vertical angulation. | Increase the steepness of the angle. |
| Foreshortening | Too much (steep) vertical angulation. | Decrease the steepness (flatten) the angle. |
4. Miscellaneous Exposure Errors
- Cone-Cutting: A clear/white unexposed area on the image.
Cause: The PID was not centered over the sensor.
- Herringbone Pattern: A tire-track or diamond pattern on a film.
Cause: The film was placed backward in the mouth (lead foil side facing the teeth).
- Phalangioma: An image of the patient’s finger on the radiograph.
Cause: The patient held the sensor with their finger (The “Digital Method”).
🚨 DANB EXAM ALERT: Dropped Corner
If you see an image where the occlusal plane is tilted or “dropped” at one corner, the cause is Incorrect Placement. The sensor was not placed straight in the bite block, or the patient was not biting down firmly on the holder.