3M ESPE manual Pouring the Cast, Troubleshooting Boxing Impressions and Pouring Casts

Figure 13

10

Pouring the Cast

Place the upper half of the container over the lower half — making sure the serrated top is punched out. The upper and lower halves will seat, but will not snap or lock. Make sure the upper and lower ledges are seated correctly.

Empty a complete package of Celara™ stone in a clean mixing bowl and add a full measuring cup (provided) of water. The proper amount of water for stone powder is 43 mL. Too much water which produces a thin, runny mix, can cause the stone to over expand — possibly resulting in an ill-fitting denture. If a vibrator is used to pour the stone cast the containers must be secured tightly with a rubber band to prevent the stone from running out between the containers (Figure 13).

Cover the entire surface of the impression with stone, placing the stone in the posterior of the impression and forcing the stone forward thus preventing trapping air. It will be noted that the stone will not completely fill the top half of the container.

The Celara stone will completely set in 5–7 minutes and is formulated to have the ideal expansion and hardness for dentures. It is not desirable to have a cast which is too hard. The acrylic of the denture can fracture upon deflasking if the cast is too hard. It is desirable to have a very slight expansion of the cast — enabling a thin layer of moisture between the denture and the ridge.

Troubleshooting — Boxing Impressions and Pouring Casts

•Avoid adding the alginate powder to water.

–This is too difficult to mix. Add the water to the alginate powder.

•Avoid leaving alginate powder in the bag when dispensing into mixing bowl.

–This can lead to too thin a mix.

•Avoid not measuring the water.

–To use alginate to box an impression, you want a thinner mix than is typically done for using alginate to make an impression. With the Celara Refill Kit, everything is pre-measured. USE THE LOWER CONTAINER FULL OF WATER AS THE WATER MEASURE FOR A FULL PACKAGE OF ALGINATE. This will produce the correct consistency for boxing the impression.

•Avoid filling the lower container full before immersing the denture.

–This will lead to excess alginate running over the ledge of the lower container.

•Avoid trapping air.

–Smear alginate over the palate and teeth prior to immersing in the alginate. Immerse the maxillary denture by rotating it from the anterior to the posterior.

•Avoid leaving any alginate over the impressed surfaces of the impression.

–This will affect the cast and ADVERSELY AFFECT THE FIT OF THE DENTURE, especially alginate in the posterior of the impression.

•Avoid mixing the stone too thin.

–This can result in the stone over-expanding and the cast being too soft.