National Dental Assisting Examining Board (NDAEB) Practice Exam

A tooth with a necrotic pulp will not respond to which of the following stimuli?

1. Electrical stimulation

2. Cold

3. Hot and cold

4. Tapping on the tooth

The correct answer is: Hot and cold

A tooth with a necrotic pulp, meaning that the pulp tissue is dead and no longer functional, will not respond to thermal stimuli such as hot and cold. This lack of response occurs because the sensory nerves responsible for detecting temperature in the pulp are no longer functioning when the pulp is necrotic. When a healthy tooth is subject to cold or hot stimuli, the patient typically experiences sensation if the pulp is vital and healthy. However, in the case of necrosis, these nerve responses are absent, leading to a lack of sensation or response. While electrical stimulation can sometimes evoke a response in teeth with vital pulp, it may not yield any sensation in a tooth with a necrotic pulp. Similarly, tapping on the tooth may produce discomfort if there are other conditions affecting the tooth, but it is the thermal sensitivity—the ability to respond to hot and cold—that is specifically lost with a necrotic pulp. Therefore, the tooth will not respond to combined hot and cold stimuli, highlighting the correct interpretation of this question.