Dental radiographic artifacts are unintended marks or defects that interfere with the accurate diagnosis of patient conditions. These defects are common in traditional film-based radiography, which involves chemical development and careful handling. A dark spot or debris indicates a localized area of increased film density, meaning more silver halide crystals were developed into black metallic silver. Identifying the cause allows the dental professional to correct the error, ensuring the next radiograph is usable and avoids unnecessary radiation exposure from a retake. Causes of dark spots and debris are grouped into errors involving chemical processing, film handling, or the equipment and environment.
Artifacts Caused by Chemical Processing Errors
Chemical errors frequently cause unwanted dark spots when the film interacts with processing solutions in an uncontrolled manner. A common culprit is a developer spot, which appears as a concentrated, dark, round, or irregularly shaped area. This happens when a droplet of developer solution splashes onto the film emulsion before the film is fully immersed in the developer tank. The concentrated chemicals immediately reduce the silver halide crystals, causing a localized area of high density on the final film image.
Conversely, if the film is not left in the fixer solution for a sufficient amount of time, it will appear dark and eventually turn a yellowish-brown color as the undeveloped silver halide crystals oxidize.
Artifacts Caused by Film Handling and Exposure
Errors related to film preparation, exposure, and unwrapping often create distinctive dark marks. Static electricity produces dark, branching lines resembling a small lightning strike. This occurs when the film packet is opened too quickly, especially in low humidity, causing an electrical discharge that exposes the silver halide crystals along the path. Since the exposed crystals are developed, the static discharge path appears black on the final image.
Physical damage to the film emulsion before processing also results in dark spots or lines. Bending or creasing the film packet, often due to improper placement, creates a semi-circular or linear dark line. The pressure mechanically damages the emulsion, making the silver halide crystals more susceptible to the developer and resulting in a darker line.
Touching the film with fingers contaminated with developer can leave a distinct black fingerprint. Residual developer initiates the development process in the exact shape of the print before the film enters the tank, resulting in a dark, high-density pattern.
Artifacts Caused by Equipment and Environment
Mechanical devices and the darkroom environment can introduce dark spots or streaks, particularly when using automated film processors. Roller marks are a common equipment artifact appearing as dark, repetitive streaks running along the length of the film. These marks are caused by dirt, residual chemical sludge, or hardened emulsion accumulating on the transport rollers within the automatic processor. As the wet film passes, the debris or uneven pressure transfers to the film surface.
Dust and debris within the darkroom can also adhere to the film emulsion, leading to localized artifacts. If debris sticks to the film before it is completely dry, it can prevent proper chemical action or cause physical damage.
Films that are not fully dried after processing remain tacky, making them susceptible to picking up airborne dust during storage or handling. This contamination can lead to smudging that appears as dark spots when the film is viewed.