Matters needing attention when preparing teeth

When producing porcelain teeth, whether the dental model is made accurately is also an important part. This is the basis for the molding of inner crowns and dentin porcelain, enamel, transparent porcelain, and other porcelain powders, and it is also the benchmark for whether the porcelain teeth are finally suitable for the patient's mouth. The following are the points that need to be paid attention to when making dental molds before producing porcelain teeth.

1. Tooth preparation

(1) The adduction angles of the buccal and tongue, mesial and distal adduction angles are all less than 5°;

(2) When the tooth is prepared, please check whether there is a gap between the head of the bur and the neck of the abutment tooth when the bur is in contact with the tooth surface. If there is a gap, it means that the neck has an undercut. The undercut should be removed according to the original angle. Note, The angle of the bur cannot be changed when removing undercuts;

(3) When preparing a pontic with multiple abutments, the buccal preparation angles of different teeth should be the same, and the lingual, mesial, and distal should all have the same angles, that is, the buccal angles of each tooth should be the same, the lingual angle is the same, the mesial angle is the same, and the distal angle is the same;

Note: The angle refers to the angle between the bur and the jaw plane, especially when there are multiple abutments, it should be noted that the common jaw plane is used as a reference, and the angle between the bur and the tooth cannot be referred to.

2. Take the dental models

(1) Alginate impression

A. The distal-free end is easy to demould, and a layer of adhesive tape can be pasted on the distal edge of the tray to prevent demoulding;

B. After the impression material in the oral cavity is cured, please keep it for 3 minutes. This item is easy to be ignored. The inside of the impression material is not fully cured, and demoulding is easy to cause deformation;

C. Fill the mold as soon as possible after taking the mold. When the weather is hot and the temperature is high, use wet paper towels to line around the impression to prevent the impression from drying out during the gypsum solidification process and causing the impression to shrink.

(2) Frequently asked questions about silicone rubber impressions

A. Honeycomb gypsum surface

Suggestion: After taking the mold, pour the plaster model at least half an hour later

reason:

a. After curing in the mouth, the inside of the silicone rubber is still reacting, and the by-product is continuously released: hydrogen

b. When the silicone rubber impression is taken out of the mouth, it takes at least 30 minutes for the silicone rubber to deform and recover due to the problem of tooth undercuts.

B. Layering of silicone rubber primary impression and secondary impression

Recommendation: Thorough cleaning after the initial impression and extensive revision of the impression

C. Elevation of occlusion (the secondary impression is partially too thick)

Suggest:

Extensive revision of the initial impression by a second impression

D. Silicone rubber impression curing delay

Suggest:

a. Do not wear latex gloves, mix hand-adjusted silicone rubber

b. It is not recommended to store silicone rubber in a low-temperature environment for a long time (stored at room temperature)

c. Substrate and catalyst are strictly 1:1

E. Angular defect

Suggest:

During the one-step impression, the tray is slowly positioned perpendicular to the long axis of the tooth

F. Silicone rubber is separated from the tray

Recommendation: 5 minutes before the impression, use tray adhesive