Stock impression tray tip

Stock impression trays are generally designed to fit all of the population however as for anything designed with the average in mind they tend to fit absolutely no one. A particular issue I find in choosing the right sized stock tray are the arch form and the space between the maxillary molars and the coronoid process.

Patients with teeth crowded out of the arch or wider or narrower arch forms would benefit from a stock tray that is wider between the flanges, the peril of using this regularly however is it can encroach into the buccal and lingual soft tissue boundaries and make seating the impression more difficult. Individual modifications en be made to plastic stock trays by heating them in a flame till soft and bending the tray to suit the patient. This will then solidify when cool.

A particular issue I had today was on two separate patients where the stock trays fit seemingly well on the maxillary arch however the flange area in the maxillary molar area was not caught in the impression when it was attempted. Sadly for the first patient it took me four tries (a record) till I found the solution. For the second patient I learned from this mistake and got the impression first go. The issue I was experiencing was the patient had buccally tilted upper molars which lay in very close proximity to the coronoid process. When trying in the tray, the patient's mouth was almost closed at the coronoid process was moved distally and buccally. However when we attempted the impression the patient had the reaction to open slightly wider and the coronoid process moved forwards to contact the tray and hinder full seating. The strategy I employed in this case was to train the patient before hand to have an open mouth posture while we are rotating the tray into place and when I instructed them to they would slowly closed to a predetermined height (just open) while I was placing the tray. This would effectively move the coronoid process out of the way while the tray was being seated. What I would check before any impression in the future is to have "wriggle room" in a maxillary tray. I.e The tray can be seated and fit the arch form but also have some allowance for movement left and right once seated. If there is not much lateral room possible, this indicates a tight space in the buccal vestibule and it will be important to have the patient adopt a closed mouth posture while the impression is setting.