Pit and fissure caries exhibit a cone-shaped pattern of penetration because enamel rods in these areas are oriented obliquely and converge towards the occlusal surface. This structural arrangement creates a narrower entrance at the enamel surface but facilitates deeper bacterial progression towards the dentin beneath, resulting in a spreading lesion that widens as it approaches the dentinoenamel junction. Understanding this pattern is crucial for early detection and effective restorative intervention.

Reference: Sturdevant's Art and Science of Operative Dentistry, 7th Edition.