Final answer:
Dental Class 3 is the classification that impacts unit combat effectiveness due to the high risk of dental emergencies and typically these individuals are not deemed worldwide deployable.
Step-by-step explanation:
The dental class that compromises unit combat effectiveness, increases the risk of a dental emergency, and is not considered worldwide deployable is Dental Class 3. This classification indicates that the individual has dental conditions that if not treated or addressed, could result in a dental emergency within 12 months. Dental Class 3 patients are a concern for military readiness because they can potentially require urgent dental care, impacting both their health and the effectiveness of their unit during deployment.
Due to their severity and urgency, Class 4 dental conditions are often not treatable in combat zones or during deployments, and may require evacuation to receive proper dental care in a fixed dental facility outside the operational theater.