Annotation
Artificial crowns are used to prevent further destruction of tooth tissues, to restore its anatomical shape, as well as to locate fixing and supporting elements, making bridges, dentures, orthodontic, maxillofacial and other devices.
Types of artificial crowns:
By function:
1. Recovery.
2. Fixing.
3. Support.
4. Splinting
By design:
1. Complete.
2. Jacket (half-crowns, three-quarter).
3. Telescopic.
4. Crowns with a pin.
5. Fenster.
Depending on the material:
1. Metallic
a. base metals alloys: IX18H9T, KHS
b. noble metal alloys: gold, silver-palladium
2. Plastic.
3. Porcelain.
4. Combined:
a. metal plastic
b. metal ceramics
c. glass ceramics.
According to the method of manufacture:
1. stamped.
2. cast.
3. polymerized.
4. firing method.
5. combined.
Clinical indications for the use of artificial crowns:
1. Prevention of further destruction of the tooth (TOSFI = 0.6-0.8) and restoration of the anatomical shape of the tooth.
2. With non-carious lesions of the teeth.
3. Violations of aesthetics.
4. Anomalies of the size and shape of crowns.
5. The phenomenon of Popov-Godon.
6. As fixing and supporting parts of various designs.
Contraindications to the use of artificial crowns:
1. In children until the end of the period of growth of the jaws and the formation of the roots of teeth.
2. mobility of teeth of the third degree.
3. On teeth with affected pulp or poorly treated endodontically.
4. In the presence of chronic pathological processes in the periodontal period.
Indications for use of all-metal stamped crowns:
1. Restoration of damaged teeth (TOSFI = 0.6-0.8).
2. Pathological abrasion of hard tooth tissues is not more than 1/3 of the vertical size of the crown.
3. As supporting and fixing elements of various orthopedic structures.
The sequence of preparation of teeth according to G. Staegemann for an all-metal stamped crown:
1 chewing surface (cutting edge)
2 buccal and lingual surface
3 separation and processing of contact surfaces
4 smoothing of edges
According to E.I. Gavrilov:
1 separation and processing of contact surfaces
2 buccal and lingual surface
3 chewing surface
4 smoothing of edges
When applying the Gavrilov technique, it is possible to control the direction of the long axis of the tooth.
Dissection of the contact surfaces is considered complete if all overhanging edges are removed from the contact surface of the tooth in the cervical area. Grinded contact surfaces should be parallel to the long axis of the tooth. The convergence of contact walls of 1-3 ° is allowed.
From the buccal and lingual surfaces of the tooth, the equator and the near-gum roll are ground to ensure that its neck is the widest part of the prepared tooth, and also to achieve a smooth transition of one surface to another.
When grinding the chewing surface, it is necessary to preserve the anatomical shape of the tooth.
The thickness of the removed tissue 0,25-0,3 mm.
Requirements for a properly prepared tooth for an all-metal stamped crown:
1 prepared tooth should resemble a cylinder, its perimeter should be equal to the neck of the tooth
2 preservation of the anatomical shape of the tooth
3 thickness of polished fabrics 0,25-0,3 mm
4 tooth withdrawn from contact with antagonists
5 smooth transition of one tooth surface to another
Methods for taking impressions:
1 choice impression tray
2 kneading impression material and filling it with an impression spoon
3 introduction of the impression spoon with the material into the oral cavity and the formation of the edges of the impression
4 curing impression material
5 removal of the impression from the mouth
6 quality assessment of print
Reprints:
1 anatomical 1 simple
Basic 2 double
Auxiliary
2 Functional
Properties characteristic of alginate masses:
1. elasticity at sharp and short-term loading
2. plasticity and fluidity in gel state
3. solidification time 3-4 minutes
Negative properties of alginate impression masses:
1. Syneresis phenomena - release of alginic acid after hardening, which slows down the setting of gypsum.
2. significant shrinkage after 15-20 minutes. After hardening.
3. constant and slow load causes residual deformation.
4. low sticking to the surface of the spoon.
Representatives: Stomalgin, Ipen, Geltreyd, Kromopan, Freyz, Ortopren (with antiemetic additive), Palgafleks, Dupalfleks ...
According to the degree of difficulty in determining the central ratio of the jaws, there are four groups of teeth:
1. tooth rows having a large number of antagonizing teeth.
2. tooth rows with preserved pairs of antagonists, but this does not allow making models into central occlusion.
3. There is not a single pair of antagonists.
4. toothless jaws
Stages of crown stamping:
1. removing the impression
2. model casting
3. modeling of the tooth crown
4. cutting a plaster post
5. casting plaster block
6. low tide stamp
7. low tide
8. Pre-stamping
9. free forging
10. final stamping
11. trimming the edges of the crown
12. whitening.
Requirements for a properly made crown:
1. smooth, smooth - without dents and folds - the surface of the crown
2. full coverage by the edge of the crown of the neck of the plaster column
3. minimal overlap of the clinical neck of the tooth by the edge of the crown.
4. must reproduce the anatomical shape of the tooth
5. easy to apply on prepared tooth
6. minimum immersion in the gingival sulcus
7. tightly covers the edge of the crown of the tooth neck
8. participates in the formation of contact points (if before that there were no three and diastem)
9. contacts with antagonists, not overstating the occlusion and not creating a supercontact during lateral and anterior occlusions.
Determination of the depth of immersion of the crown in the gingival sulcus:
Angular probe probe the edge of the crown under the gum around the perimeter of the tooth neck; Special attention is paid to interdental papillae.
At the closing of the dentition, slight whitening of the marginal part of the gum is allowed; severe anemia of the marginal or papillary part of the gums, as well as the patient's painful sensations indicate a deep immersion of the crown edge in the gingival sulcus.
The wide crown will be badly fixed on the teeth, and a little narrowed - does not completely overlap and prevents the closure of the dentition.
The gingival sulcus is an anatomical formation bounded by the marginal part of the gum on the one hand (in which free and attached parts are isolated) and by the tooth tissues on the other. There is also an anatomical gingival sulcus up to 0.5 mm in depth, which is determined without sensing and a clinical gingival sulcus, which is determined by sensing; it is normally from 1 to 2 mm.
Evaluation of the quality of polishing of the crown is carried out visually: the surface of the stamped crown should be smooth, mirror-like; on the surface there should be no grooves, strokes, scratches left by the abrasive tool.
Before fixation of the stamped crown, it must be treated with 3% hydrogen peroxide solution and alcohol. The surface of the tooth is also cleaned from food debris and dental plaque, placed on cotton rollers, disinfected with alcohol, and dried.
The consistency of the kneaded cement depends on the density of the crown against the walls of the tooth. Crowns are filled with cement 1/3 with a spatula or trowel, smearing the inner walls of the crown, and placed on the teeth.
Possible errors and their complications in the manufacture of stamped crowns:
1. wrong preparation of tooth tissues - thermal burn of the pulp - pulpitis.
2. excessive preparation - opening of the cavity of the tooth.
3. excessive convergence of the tooth walls - poor fixation of the crown, frequent disintegration of the crown.
4. excessive dissociation with antagonists - cracking of the cement under the crown, disintegration of the crown.
5. shortening of the crown, loose fit - disintegration of the crown.
6. excessive immersion of the edge of the crown under the gum - gingivitis.
7. lack of contact points and the equator - gingivitis.
8. the presence of supercontact or overestimation of occlusion - traumatic periodontitis.
Clinical - laboratory stages of manufacturing all-metal extruded crown:
Clinical stage.
1 tooth preparation
2 removal of working and auxiliary impressions
3 casting models
3 a - if necessary, fixation of the central occlusion
Laboratory stage.
4 modeling wax tooth crown
5 cutting a plaster post
6 manufacture of gypsum block
7 making a stamp from a low-melting metal
8 manufacture of countershtamp
9 pre stamping
10 free annealed forging
11 final annealed stamping
12 trimming the edges of the crown
13 whitening
Clinical stage.
14 construction check on a plaster post
15 fitting of the crown in the mouth
Laboratory stage.
16 grinding and polishing of the crown
Clinical stage.
17 fixing crown on cement