The main points of using dental zirconia block in dental bridge system

The main points of the use of dental zirconia blocks in dental bridge work are as follows:

First, design points

Avoid stress concentration

In order to disperse chewing force and reduce stress concentration, the jaw curve is designed according to jaw dentition and occlusal condition.

The number of missing Bridges should be designed reasonably

According to the properties of zirconia porcelain block material, the number of tooth bridge missing is reasonably designed. For example, the front teeth of the ST porcelain block are connected at most three missing bits, the back teeth are connected at most two missing bits, and the free end is not more than one missing bit.

Abutment condition assessment

When the abutment conditions are not suitable for the production of zirconia, such as there is no common insertion path of the bridge, the maxillary gingival distance of the bridge is too small, the abutment is too large, and the shoulder preparation is unreasonable, the doctor should be communicated in time to adjust the design scheme.

Crown thickness design

The minimum thickness of the lingual side of the crown should be greater than 0.8mm, and the thickness of the missing body adjacent to the incisal end of the crown or the occludal surface should be greater than 1.0mm to ensure the strength and stability of the crown.

Connector cross-sectional area

The cross-sectional area of the anterior tooth connector should be greater than or equal to 9 square millimeters and the cross-sectional area of the posterior tooth connector should be greater than or equal to 12 square millimeters to provide adequate support.

Two, typesetting processing points

Strut placement

When typeset, the support rod should be placed symmetrically, as far as possible between 1/3 and 1/3 of the crown neck to provide stable support.

Support rod addition

Support rods are placed on the bridge body as far as possible to disperse the chewing force and reduce stress concentration. Try not to put the support rod on the connector part, so as not to affect the aesthetics of the bridge.

Tongue side reinforcement rod design

Add a tongue reinforcement bar (thickness of about 2mm is recommended) to increase the strength of the bridge. The design method of the tongue reinforcement bar can be manually trimmed by tooth row, etc., and the thickness of the trimmed bar should be as uniform as possible.

Selection of sintered rod for occlusal surface

You can choose whether to add a joint sintering rod or not. Generally, adding a tongue reinforcement rod does not require adding a joint sintering rod.

Support rod removal

When the bridge is removed from the porcelain block, only the lip cheek side of the bridge and the lateral support rod of the cross bar are removed. The support rod should be removed with care, and the amount of each removal should not exceed 0.5mm, in order to prevent the fracture of the tooth bridge or the internal crack during the removal process. It is suggested that the removal sequence of the support rod is the crown lip buccal support rod, the bridge body lip buccal support rod, and the lateral support rod of the cross bar.

Bridge lingual support rod treatment

The lingual support rod of the bridge can be selectively removed to a depth of 1/2-1/3 of the diameter of the support rod, starting from the neck of the bridge.

Three, internal dyeing and sintering points

Internal staining

According to the clinical requirements of staining, it is recommended to use brush method staining. Take out the dye liquid and cool it to room temperature 30 to 60 minutes before dyeing. After dyeing, the bridge should be dried for more than 60 minutes, and the drying temperature of the bridge is 90℃. After drying, the crown surface temperature should be cooled to room temperature before being placed in the crucible for sintering.

sintering

The heating rate of porcelain glaze should not be too fast, it is recommended that 45~65℃/min. The furnace temperature should be cooled to below 200℃ before it can be taken out.

Four, repair the form of occlusal key points

Morphological modification and occlusal adjustment

Use high speed mobile phone or slow mobile phone zirconia grinding tools for shape dressing and bite, adjacent adjustment. When grinding, pay attention to unidirectional and light pressing grinding to prevent hidden cracks in the grinding process.

Slit the teeth

When opening the teeth, pay attention to the point cutting mode rather than the direct cutting mode, and use the special opening tool to gently handle it to minimize the amount of grinding.

Sand blasting

After the crown is polished, it is recommended to use 50 micron (270 mesh) high-purity alumina sand for sandblasting at 2-2.5Bar (0.2-0.25mpa) to clean, restore the strength of the material, and facilitate subsequent dyeing and glazing.

Heat treatment

It is recommended to use a porcelain oven to heat treat the crown after grinding, so as to reduce the monoclinic phase content on the crown surface and improve the strength, while increasing the bonding force of zirconium porcelain.

V. Other precautions

Needle use

Check the use of the needle, long bridge processing is best to replace the new needle to ensure processing accuracy and surface quality.

Equipment calibration

Calibrate equipment before machining to ensure machining accuracy and stability.

Quality control

The parameters and steps are strictly controlled in the processing process to ensure the quality and performance of the tooth bridge.

To sum up, the main points of using dental zirconia block in dental bridge system involve design, typesetting, internal dyeing and sintering, shape modification and occlusion. By following these points, a high quality dental bridge can be made to meet the clinical needs of the patient.