Annotation
Indications for use of solid and combined crowns:
1. Violation of the anatomical shape and color of the crowns of natural teeth.
2. Increased erasure of solid fabrics (solid cast, metal-ceramic).
3. The presence of structures from dissimilar metals.
4. Phenomenon of allergy to plastic facings of fixed structures (for a metal-ceramic crown).
Absolute contraindications to the use of solid-cast and combined crowns:
1. Prosthetics of teeth of children and adolescents with a live pulp.
2. Low, small or flat clinical crowns of the abutment teeth with thin walls.
Relative contraindications:
1. Anomalies of bite with deep incisal overlap.
2. Cutters of the lower jaw with live pulp and a small clinical crown.
3. Paralysis of the masticatory muscles.
The thickness of the removed tissue is on average equal to:
For solid crowns - 0.3-0.5 mm
For combined crowns, 1.2 mm.
Types of preparation:
1. Tangentially
2. With a ledge in the cervical part.
Ledge location:
Sublingual - 0.5-0.8 mm
Supragingo.
At the level of the gums.
In order to prevent trauma to the marginal gum during preparation, as well as to create a clearer contour of the gingival groove when removing the impression, retraction threads are used. The threads produce 2 types: simple cotton and threads impregnated with a solution of adrenaline (noradrenaline). Before preparation or before removing the cast, the thread is introduced into the periodontal groove for 5-7 minutes. Due to the mechanical action, absorption of gingival fluid, as well as due to the action of vasoconstrictor substances (threads with adrenaline), the gums retraction occurs, and the subgingival tissues of the tooth become available for preparation.
For preparation of hard tissues of a tooth under a solid-molded and combined crown, diamond burs are used: spear-shaped, cylindrical, cylindrical with a rounded end, flame-shaped. The toolkit also differs in the grain of the abrasive chips.