Set of Dental Casts and Impression Trays

This collection of casts, models, and custom trays tell a story of a complex case at the prosthodontist’s clinic that required not only experienced planning, but also resilience and patience. 

One area of the cast is carefully outlined, suggesting a spot in the mouth that needed extra attention and care. The intricate planning indicates that the patient had suffered from a trauma of some kind (likely a tumour that had needed surgical removal), before subsequently needing dentures. 

When this patient came to the clinic, the aim was to make them a set of dentures. But after the removal of a tumour, the dentist’s true skill was put to the test. Sometimes the delicate tissues in the mouth don’t cooperate, they can be difficult to work with. In this case, it took a careful balancing act, not just to rebuild the patient’s smile, but to help them feel like themselves again.

The dentist’s initial plan was cautious - they decided to follow a two-step impression taking technique to respect the variability between the anatomy of healthy and affected tissues. The dentist took an innovative approach. They chose to use a tray that completely eliminated the need of applying active pressure to the sensitive area and, instead, used a specially designed tray that avoided disturbing it altogether. With great skill, he relied on gentle, passive pressure from the lower jaw ridges instead.

This wasn’t just prosthodontics, the dentist read the tissues like a language, and instead of rushing the process and expecting the tissues to obey them, they chose to adapt. Listening, reassessing, and reevaluating is a reminder that dentistry is more humane than it seems, and isn’t just about rebuilding what’s lost, but also respecting what’s remaining. 

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What does this look like in objects? 

1. Cast of the upper arch and palate

The first item is a cast of the upper arch and palate, with an outlined area that involves the posterior left ridge and palate. 

The outlined area is likely to be a compressible soft tissue, likely to be caused by the removal of bone as a surgical intervention for treating tumours. The tumour that most likely is treated in this case is Squamous Cell Carcinoma (SCC) or Adenocarcinoma (involvement of palatal salivary glands).

Once the surgical site had fully healed, the soft tissue was still too delicate and compressible for a conventional denture to be made. To make sure the final denture would fit the patient properly, the dentist had to take extra care. At each stage, the materials used to take impressions of the mouth were spread evenly, avoiding too much pressure on the sensitive area, which could have led to a poor fit.

2. Cast with white dental stone and pink baseplate wax

The second cast is made of white dental stone with a layer of pink baseplate wax. Pink baseplate wax is usually added to ensure that the custom tray fabricated based on this cast would fit a bit looser, to allow the flow of the impression material appropriately. Adding pink baseplate wax is part of the custom try design protocol, as it aids to control pressure zones and material thickness.

The outlined area on the cast of the upper arch and palate was blocked out using plaster or a modelling wax. This is done to fabricate a custom tray for the rest of the upper arch, in a technique named the “window technique”. This ensures that the custom tray used for taking the secondary impression only captures the healthy, rigid tissues under it, excluding the healed site post-surgery. The impression of the healthy area, and the healed post-surgery site are done in two different steps, as different material will be used in each step, to ensure that all details are captured accurately, without disturbing the tissues, ensuring a correct fit of the denture.

3. Model for the fabrication of a custom window tray

This model is for the fabrication of the custom tray of the healthy tissues. This model doesn’t need to represent the accurate anatomy of the soft tissue, but is instead made from memory. It serves the purpose of creating a block out area in the special tray of the healthy tissues. The soft tissues will be later dealt with, after taking the impression of the healthy tissues, each using their own special tray.

4. Window tray

This item is the resulting window tray, with the “window” created around the previously outlined area in the cast of the upper arch and palate. An impression of the rigid healthy tissues would be taken using this tray, most likely using a silicone-based elastomeric impression material (addition silicon), as it flows well enough to capture details, is viscous enough to apply pressure where needed, and is known to stay in place when taking the impression.

5. Open tray

The final item tells a slightly different story. This item is a hollow/open special tray, and is a completely different design from the window tray. This acrylic design is made of borders, and pillar-like structures. This hollow tray is used when a passive impression needs to be taken, without actively applying any pressure on the palate.

The most probable scenario that occurred is that the dentist planned to use the two-step technique, by using two trays (window tray, and mini tray), but found the soft tissue and the healed post-surgical site to be manipulated for an impression were too delicate or mobile.

The lower tray is seated on the mandibular ridges, giving support to the tray fabricated to take an impression of the maxillary ridges.

6. Silicone impression

Afterwards, the chosen impression material (often a light-body silicone) is injected into the hollows that allow the material to flow towards the area of the tray designed to capture the details of the delicate tissues, without the need of applying pressure on the maxilla and palate, but just by using the support the pillars provide from the mandibular ridges.