Serial extraction is contraindicated in the presence of deep bite or open bite because extraction may worsen the vertical discrepancy. Removing teeth can lead to unfavorable occlusal changes, exacerbating the bite problem rather than correcting it. Serial extraction aims to relieve crowding primarily by allowing eruption space, not to correct vertical malocclusions. In cases of deep or open bite, other orthodontic or surgical interventions are preferred to address the vertical dimension effectively. Hence, serial extraction is avoided to prevent aggravation of these vertical skeletal or dental issues.

Reference: Graber’s Orthodontics, 7th Edition.