**Core Concept**
The interocclusal space refers to the distance between the occlusal surfaces of the upper and lower teeth. It is an essential concept in dentistry and orthodontics, as it affects the alignment and occlusion of teeth.

**Why the Correct Answer is Right**
The interocclusal space is determined by the vertical dimension of occlusion (VDO), which is the distance from the occlusal surface of the maxillary central incisors to the occlusal surface of the mandibular central incisors. The VDO is influenced by the length of the dental arches, the curvature of the dental arches, and the position of the condyles in the glenoid fossae. The interocclusal space is critical in maintaining proper occlusal relationships and preventing dental malocclusion.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect as it does not accurately describe the interocclusal space. The interocclusal space is not the distance between the upper and lower lip or the distance between the upper and lower border of the mandible.
**Option B:** This option is incorrect as it does not accurately describe the interocclusal space. The interocclusal space is not the distance between the upper and lower dental arches or the distance between the upper and lower molars.
**Option C:** This option is incorrect as it does not accurately describe the interocclusal space. The interocclusal space is not the distance between the upper and lower incisors or the distance between the upper and lower canines.

**Clinical Pearl / High-Yield Fact**
Remember that the interocclusal space is a critical factor in maintaining proper occlusal relationships and preventing dental malocclusion. A discrepancy in the interocclusal space can lead to various dental and orthodontic problems, including malocclusion, temporomandibular joint disorders, and dental wear.

**Correct Answer: D. The distance between the occlusal surfaces of the upper and lower teeth.**