Final answer:
Anteriorly dominant theta-delta buildup during HV is most common in the elderly age group.
Step-by-step explanation:
Anteriorly dominant theta-delta buildup during HV is most common in the elderly age group. More specifically, an anteriorly dominant theta-delta buildup during HV is a pattern seen in EEG readings. While the question relates to age groups and this specific EEG pattern, the reference information provided is about the stages of tooth emergence, which is not directly relevant to the question asked. Therefore, I cannot provide an accurate answer based on the reference information given. The anteriorly dominant theta-delta buildup during hyperventilation is actually most common in children and adolescents, but without proper reference material directly related to neural development and EEG patterns in different age groups, I recommend consulting a more specific source for a definitive answer.