**Core Concept**
Incomplete overbite is a dental malocclusion characterized by the upper incisors not overlapping the lower incisors by more than 2-3 mm. This anomaly can lead to difficulties with mastication, speech, and aesthetics.

**Why the Correct Answer is Right**
In an incomplete overbite, the upper incisors fail to cover the lower incisors, resulting in inadequate protection of the lower incisors from wear and tear. This can be due to a combination of factors, including genetic predisposition, habits such as thumb sucking or tongue thrusting, or developmental anomalies. The maxillary (upper jaw) and mandibular (lower jaw) bones may not align properly, leading to an abnormal occlusal relationship.

**Why Each Wrong Option is Incorrect**
**Option A:** A deep overbite is characterized by an excessive overlap of the upper incisors over the lower incisors, typically more than 4-5 mm. This is the opposite of an incomplete overbite.
**Option B:** A class III malocclusion is characterized by a protrusive lower jaw and/or a retruded upper jaw, often resulting in an underbite rather than an incomplete overbite.
**Option C:** A class II malocclusion is characterized by a retruded lower jaw and/or a protrusive upper jaw, often resulting in an overbite rather than an incomplete overbite.

**Clinical Pearl / High-Yield Fact**
Incomplete overbite is often associated with a narrow maxillary arch and/or a deep bite, which can lead to increased risk of dental wear and tear, especially on the lower incisors.

**Correct Answer: D. Incomplete overbite is a dental malocclusion characterized by the upper incisors not overlapping the lower incisors by more than 2-3 mm.