Difficult impression appointment

 Today I had a difficult impression appointment. The case is for a full upper immediate denture and the patient has almost all of his upper teeth that are badly broken down and carious. The issue with the impressions is that the material kept flowing into the carious areas, locking in and when I tried to remove the tray, the alginate would peel off the tray and tear. I retook the impression 4 times and in the end accepted a compromised result. I don't know how it will come back to bite me down the line but I know it will in some form or another. An important failure of mine here is that I didn't analyse how the first few impressions failed and try to learn from them for the next impression.

Some thoughts:

-The combination of locking in on the anterior and posterior teeth was enough to overcome the adhesion to the tray. When considering impression debonding it is merely a tug of war between the impression sticking to the tray and the impression sticking to the teeth. I think the cavities in the molars were more severe as the undercuts on the teeth in the first place are larger than more slender anterior teeth. This is a good reason to remove posterior teeth as a phased treatment because it simplifies the final impression process -->different angles around the arch

-The holes in the tray were too small, just wider than the tip of a probe so firstly more pressure would be required to force the impression through. When loading the impression tray, the assistant needs to force the alginate on with some force to extrude it through the holes. Secondly, the diameter of the alginate plugs through the perforations will be thinner and therefore weaker. 

-The adhesive was done well but after the 3rd impression I added adhesive to the outside periphery as the border moulding will push the material out there and it woud be useful to have adhesion at all aspects of the material. 

-After the second impression I asked my assistant to put alginate on the outer surface of the tray to connect the alginate dots to add strength to the alginate tags. She put this in the middle of the palate but I realised after it would have been better to smear it over the ridge areas because this is where it was pulling away.

-Support the impression at the flange with a finger under sulcus to lever off the impression.

-Block out the impression. At first I didn't want to block out the impression because I wanted the detail that would allow the lab to identify the gingival margin and demarcation between the teeth so that they could cut the teeth off accurately. However, the priority should be  getting a good impression of the soft tissues and denture bearing area. Any imperfections at the ridge can easily be adjusted.

-Look at impression when it fails. Where it tore between teeth is where it is locking in and you need to be better at blocking this space out. It is undercuts you are worried about blocking out. Large open cavities aren't so much of a problem as smaller interproximal cavities adjacent to each other.

-Dont accept a compromised result, eventually I blocked out all of the spaces with wax, Took the impression and it didn't debond at the posterior but i hadn't positioned the tray correctly and it there was tray showthrough at the anterior aspect and the alginate tore there as it was too thin. I was tired after a long appointment so accepted the result and dismissed the patient. However this is not acceptable for a final impression to construct an immediate denture on so I will have to redo this in the future anyway.