Hygiene appointment times

I need some feedback quickly. I’m working with a client who operates the “HMA” system (healthy mouth assessments) – hygienist sees patient and dentist pops in to assess – you know the gig. Question – what’s the optimum time for the hygiene appointment?

1. 20 minutes nurse assisted?

2. 30 minutes?

3. 40 minutes?

4. 45 minutes?

There seem to be different systems at work out there. Can you please let me know what you do?