The only two issues you may find uncomfortable while getting a dental impression are the taste of the alginate material and if you have a gag reflex – the latter depends on your personal level of sensitivity. The impression material does not have flavor added, but its natural flavor only lasts while the impression is being taken. Feel free to ask your dentist for a sip of water or a swish of an antibacterial mouthwash like Colgate Total® Advanced Pro-Shield™ Mouthwash, to help get rid of the taste once the impression has been taken.
If you find that having the impression material in your mouth or having the dentist work on your back teeth is triggering your gag reflex, try breathing through your nose or asking the dentist if you can sit up during the procedure (reclining can put your throat in an awkward position). This can help you feel more comfortable for the time it takes to have the impression completed.
Once your impression is done, your dentist may deem it necessary to install a temporary crown or bridge until the permanent one has been manufactured and sent to the office. When finished, though, you'll find dental impressions were and are nothing to worry about. Their purpose is to create an exact mold of the tooth or teeth that need to be restored, creating healthier teeth, less pain and a repaired smile.