Which anomaly results in dental union of two embryologically developing teeth and two separate pulp chambers?

The dental anomaly that results in the union of two embryologically developing teeth while still maintaining two separate pulp chambers is fusion. During fusion, two individual tooth buds merge together during the development stage, leading to the formation of a single tooth structure that appears larger than a typical tooth. However, importantly, this fusion retains two distinct pulp chambers, which is a key characteristic that differentiates it from other anomalies.

In contrast, gemination involves the splitting of a single tooth bud to create two crowns on a single root, which typically results in one pulp chamber. Twinning refers to a similar process where a tooth resembles another due to the splitting of a single tooth bud, thus maintaining a single root and pulp chamber as opposed to having separate pulp spaces. Concrescence, on the other hand, is the joining of two adjacent teeth at their roots, generally due to an excess of cementum, without the involvement of the pulp chambers. Therefore, the defining feature of fusion is the presence of two pulp chambers in a single enlarged tooth resulting from the merging of two teeth, making it the correct answer to the question.