Elongation distortion occurs when the central ray is

• A. Central Ray Perpendicular to the Receptor and the Tooth
• B. Central Ray Perpendicular to the Tooth and Receptor
• C. Central Ray Perpendicular to the Object but Not Perpendicular to the Receptor
• D. Central Ray Parallel to the Tooth

Answer: (C)

Elongation distortion arises from misalignment among the tooth, the receptor, and the central ray. When the central ray is perpendicular to the tooth but not perpendicular to the receptor, the projection of the tooth onto the image receptor is stretched along the tooth’s length. The receptor plane isn’t orthogonal to the ray, so the path of X-rays creates a longer image than the actual tooth. To avoid this, the central ray should be perpendicular to both the tooth and the receptor (or the tooth should be positioned parallel to the receptor) so the image reflects true dimensions. Therefore, the scenario where the central ray is perpendicular to the object but not perpendicular to the receptor yields elongation.