Which scenario does NOT require a patient pre-examination?

A routine cleaning appointment typically does not require a formal patient pre-examination, as this type of service is often based on regular maintenance of oral health rather than a thorough diagnostic evaluation. During routine cleanings, dental hygienists usually assess the patient's oral health informally while performing the procedure. This can include looking for any obvious signs of decay or periodontal disease but doesn’t necessitate a comprehensive pre-examination to proceed with the cleaning itself.

On the other hand, complex surgical procedures require a detailed pre-examination to assess the patient's health status, potential risks, and to plan the procedure appropriately. Similarly, beginning nitrous oxide administration necessitates a pre-examination to evaluate the patient's medical history, understand any potential contraindications, and ensure that the patient is a suitable candidate for sedation. Crown preparation also typically involves a pre-examination to determine the condition of the tooth, the need for additional treatments, and to assess the overall oral health of the patient.