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Techniques to prevent deformation in the process of taking the model

This article is published in the [Skills] column

In dental restoration, a perfect restoration requires an accurate model and the perfect cooperation between the doctor and the technician. There are many cases of rework because of the deformation of the model, which has a great impact on the processing plants, clinics, and patients. In order to reduce the deformation of the dental model, here are some ways to avoid the deformation of the model to the doctor.

1. Pouring plaster model

After the doctor removes the model from the patient's mouth, wash the impression with warm water at 5~8°C, and then blow it dry. The super anhydrite should not be too thin or too thick.

The plaster is too thin and will be very weak after the model is cured and the model shoulders will be blurred. If the plaster is too thick, it is likely to cause problems such as incomplete shoulder removal. It is not allowed to mix ordinary white gypsum and super anhydrite. The thinner the gypsum, the weaker the model, and the thicker and stronger the model.

2. Storage of plaster models

After pouring the super anhydrite, do not expose the model to the sun, let alone place it in a damp or watery place to wait for curing. It should be placed in a place that can ensure a constant temperature and dryness, so as to reduce the probability of deformation of the model. Because the super anhydrite produces heat when it undergoes a chemical reaction, there will be slight changes, and exposure to the sun will cause the model to expand violently.

When the restoration is completed and brought into the patient's mouth, crown loosening or gingival encapsulation will occur. For example, when super anhydrite produces a chemical reaction, the opposite is true if it is too cold.

3. Trimming of plaster model

After taking off the model 3 hours after filling the super anhydrite, the doctor must check the model carefully and trim the shoulder and neck so that the technician can see the exact position of the shoulder and neck more clearly during production.

When making dental molds, not only should pay attention to preventing deformation, but also:

1. The free end of the far center is easy to demould, and a layer of tape can be pasted on the far side of the tray to prevent demoulding;

2. After the impression material in the oral cavity is cured, please continue to hold for 3 minutes. This item is easy to be ignored. If the impression material is not cured completely inside, it is easy to cause deformation when demolding;

3. Fill the mold as soon as possible after taking the mold. When the weather is very hot and the temperature is high, use a wet paper towel to line the periphery of the impression to prevent the impression from being dry and shrinking during the process of plaster curing.


Preparation of materials:

Conventional materials: treatment tray, mouth cup, saliva tube, lip oil, cotton swabs, masks, hats, gloves

Professional products: trays, impression materials, mixing bowls, mixing knives, trapezoidal tongs, measuring cups, measuring spoons, red paste

Patient preparation:

1. Lead the patient into the consultation room, assist in sitting on the dental chair, tie the drape, and apply lip oil

2. Inform patients of the purpose, operation process and precautions of the model

Oral examination

1. Open the treatment tray, adjust the chair position and light

2. In the order of up and down, left and right

3. First observe the shape of teeth and dental arches, whether there are caries, missing, ectopic, fillings, restorations, whether wisdom teeth erupt, such as whether there is ectopic eruption

4. Observe the condition of the vestibular sulcus on the lip and buccal side: whether there is any abnormality in the dental bone, whether there are ulcers and inflammations in the soft tissues, maxillary tuberosity, buccal labial frenulum, etc., and whether there are teeth with buccal displacement

5. Palatal lingual side: the condition of the palatal vault, whether there are ectopic teeth on the palatal and lingual side, whether there is a lingual protuberance, and whether there is abnormality in the tongue system.

Test tray

1. Adjust the chair position so that the upper jaw plane is at a 45-degree angle to the ground, the lower jaw plane is parallel to the ground, and the operator's elbow joint and the patient's shoulder joint are in the same plane.

2. Select the appropriate tray according to the shape of the dental arch, and make appropriate adjustments according to the specific situation.

3. When trying the upper jaw tray, the operator is at the right rear of the patient, his left hand gently pulls the patient’s left corner of the mouth, the right hand holds the tray from the right corner of the mouth, puts one side of the mouth into the mouth, rotates it into place, and observes whether the tray will grind the last teeth with the mouth mirror Take it, whether the edge of the tray is 2mm away from the teeth, whether the ectopic teeth are in the tray, whether there is pressure on the vestibular sulcus mucosa, ask the patient whether they feel uncomfortable, and then adjust the tray according to the specific situation, and at the same time tell you to open your mouth and breathe with your nose when taking the mold If you have nausea, the chin is lowered to the chest, and the symptoms will be reduced.

4. When trying the mandibular tray, the operator is at the front right of the patient, and the left hand gently pulls the patient's right mouth corner, and the right hand holds the tray from the left mouth corner and puts one side into the mouth and rotates it into position. The observation content is the same as that of the upper jaw. When the tongue moves, when the impression material is not in place, the tongue is pushed up against the upper palate, and after it is in place, it swings from side to side for a few times, and then the tongue sticks out.

Imprinting material

1. According to the prescribed ratio of water and powder, mix for 30-45S, in the mouth for 1.5-2 minutes.
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