stainless steel crown

Stainless Steel Crown(SCC)

By; Mhmood Mohd.Hassan Radhi

BDSfinal year

Introduction• It is a semi-permanent restoration used

in primary & young permanent teeth .• It was introduced as chrome-steel

crowns by Humphrey in 1950.• Now it is commonly called as stainless

steel crown.• The stainless steel crown is used more

frequently in deciduous dentition because of two reasons:-

1st in a relatively small deciduous teeth neglected carious can destroy tooth’s integrity faster than in large teeth in permanent dentition.

2nd the deciduous teeth pulp is larger than permanent pulp whereas the enamel and dentin is less in thickness, thus it is difficult to make dentinal stump for a gold casting or to use a pin system of retention for more extensive amalgam restoration.

Advantages

1. It has respect to life span, replacement, retention and resistance.

2. They are acceptable by both patient &dentist.

3. They are also more cost effective because of comparatively simple procedures in restoring.

Objective Of Using

To achieve biological compatible ,competent for mastication .

To maintain the form and function and when possible the vitality of the teeth to be maintained .

Type

1. Untrimmed crowns: e.g. Rocky mountain2. Pretrimmed crown: straight, non

contoured sides but are festooned to follow a line parallel to the gingival crest, e.g. (Unitek stainless steel crowns, 3M Co., and Denvo crowns, Denvo Co. Arcadia, CA).

3. Precontoured crown : festooned and precontoured, (e.g. Ni-Chro Ion crowns and Unitek stainless steel crowns and 3M Co.).

Stainless Steel Crown

Composition

Stainless Steel Crowns 17-19% chromium 10-13% nickel67% iron4% minor element • These crowns are available in various sizes.• Mostly these crowns are used in posterior

teeth which undergone pulp therapy.

Nickel – base Crowns

72% nickel14%chromium 6-10% Iron0.04% carbon 0.35% manganese 0.2% silicon• The alloys have good formability and

ductility necessary for clinical adaptation of crowns and wear resistance to resist opposing occlusal forces.

Indication of SCC1. Extensive decay in primary & young permanent

teeth.2. For teeth deformed by developmental defects

or anomalies.3. For teeth with hypoplastic defects.4. Following pulp therapy.5. As preventive restoration. 6. As an abutment.7. Temporary restoration of a fractured tooth.8. In sever cases of bruxism.9. Single tooth crossbite.10. For replacing prematurely lost anterior teeth.

Factor to be considered in preoperative

1. Dental age of the patient. 2. Cooperation of the patient.3. Motivation of the parents. 4. Medically compromised/disabled child.

Clinical Procedure Evaluate the preoperative occlusion• Take the alginate impression of U/L jaws.• Pour the cast with dental stone• Note the dental midline and the cusp fossa relationship

bilaterally

Selection of crown • The correct size crown is selected by the M-D

dimensions of the tooth to be restored using Boley gauge.

• To produce steel crown margins of similar shape examine the contour of gingiva of the buccal & lingual marginal gingiva.

Tooth preparation

L.A. should be administrated

Isolation by rubber dam or cotton rolls

Remove the decay

Reduction

Occlusal reductionA 69L or 169L bur is used to reduce the occlusal surface by 1.5-2.0mm .

Proximal slicesplace the wooden wedges in the interproximal embrasures, the 69L bur is moved B-L acrossthe proximal surface.

Buccolingual reduction Round off all the line angles

It is done by using side of bur.

Initial adaptation of crown

Two principles related to SSC length and margin shape that are based on an understanding of the tooth morphology and gingival tissue contours were presented by Spedding 1984

The crown should be of a correct length and its margins should be adapted closely to the tooth.

For shaping the crown margins mark 3 light points on the metal at the (mesiolingual, lingual and distolingual)and at (mesiobuccal, buccal, distobuccal) surfaces at the crest of respective marginal gingiva without compressing the marginal gingiva.

Final finished margins are placed approximately 1mm below these marks.

Seating the crown Now the crown is tried on the preparation

by seating the lingual first and applying pressure in a buccal direction so that the crown slides over the buccal surface into the gingival sulcus.

Resistance should be felt as the crown slips over the buccal bulge.

Crown contouring

Initial crown contouring is performed with a 114 plier in the middle 1/3rd of the crown to produce a belling effect.

This will give the crown a more even curvature.

Crown crimping The tight marginal fit aids in:1. Mechanical retention of the crown.2. Maintenance of gingival health. 3. Protect of cement from exposure to oral fluids.

Crown contouring

Crown crimping

Checking the final adaptation of the crown

The crown should be replaced on the preparation after the contouring procedure to see that it snaps securely into place.

The occlusion should be checked at this stage to make sure that the crown is not opening the bite or causing a shifting of mandible into an undesirable relationship with opposing teeth.

Finishing and polishing

Accumulation of plaque and inflammation of gingiva is commonly seen in practice of restorative dentistry due to rough and unpolished restoration.

To avoid these complications crown should be polished prior t o cementation with rubber wheel to remove all scratches.

Radiographic confirmation of the gingival fit

Before cementation a bitewing is taken to verify proximal marginal integrity

Cementation

SSC should be cemented only on clean dry mouth, isolation of teeth with cotton roll is recommended.

Rinse and dry the crown inside & out side and prepare to cement it.

A zinc phosphate, polycarboxylate or GIC is preferred.

Before the cements set ask the patient to close into centric occlusion by applying pressure through a cotton roll and confirm that the occlusion has not been altered.

Remove the excess cement by an explorer or scaler & for interproximal area can be cleaned by passing dental floss through them.

Result

special consideration for ssc

Quadrant dentistry ( Nash, 1981)-Prepare the occlusal reduction of one tooth completely before beginning the other as there is tendency to under reduce both when reduction on them is done at the same time.-Reduce the adjacent proximal surface of the teeth being restored more than when only one tooth is restored.-Both crown should be trimmed, contoured and prepared before cementation simultaneously to allow for adjustment in inter proximal space and establish proper contact area.

Crown in area of space loss(Mc - Evoy 1977) Preparing a SSC adjacent to a class II amalgam

(Mc - Evoy 1985)

Stainless steel crown modifications

In 1971, Mink & Hill report several way of modifying the SSC when they are either too large or too small

1. Undersize tooth or the oversize crown.2. Oversize tooth or undersize crown.3. Deep subgingival caries.4. Open contact.5. Open-faced stainless steel crown.

Complications

Interproximal ledge. Crown tilt. Poor margins. Inhalation or ingestion of crown.

References

Shoba Tandon, 2nd edition McDonald . Avery . Dean, 8th edition

Thank You