Full Coverage Aesthetic Restoration of Posterior Primary Teeth
Stainless Steel Crowns

Stainless steel crowns were introduced to pediatric dentistry by the Rocky Mountain Co. in 1947, and made popular by W. P. Humphrey in 1950. Until then the treatment for grossly decayed primary teeth was extractions. Stainless steel is composed of iron, carbon, chromium, nickel, manganese and other metals. The term stainless steel is used when the chromium contents exceeds 11% (usually a range of 12 to 30%). The chromium oxidizes and forms a protective film of chromium oxide which protects against corrosion. Although, more durable and retentive than amalgam or composite, they are unaesthetic, especially on the anterior teeth. With aesthetics of their child’s smile of extreme importance to parents, many opted for extraction and prosthetic replacement of severely decayed teeth, rather than placement of stainless steel crowns. The advent of composite bonding allowed for a composite facing to be placed on the facial surface of the tooth, thus improving aesthetics. Open-faced stainless steel crowns combine strength, durable and improved aesthetics; however, they are time consuming to place as the composite facing cannot be placed until the stainless steel crown cement sets. Bleeding of the metal margin color surrounding the composite adds a grayish tinge to the tooth that is accentuated next to the white enamel of an adjoining or opposing primary tooth.

The advantages and disadvantages of stainless steel crowns are:

Advantages

• They are very durable, wear well and retentive.
• The time for placement is fast compared to other techniques.
• They may be used when gingival hemorrhage or moisture is present or when the patient exhibits less than ideal cooperation.
• They are less expensive than other full coverage restorations (approximately $6/crown).

Disadvantages

• Aesthetics are extremely poor. Some parents may opt for extractions in lieu of restoration of the teeth.

Technique

The technique for the fabrication of stainless steel crowns and open-faced crowns is as follows:

• Anesthetize the teeth to be restored and place the rubber dam.

• Following isolation with a rubber dam, the first step is mesial and distal reduction using a 169L taper fissure bur, making a ledge on the distal marginal ridge.

• As the bur cuts gingivally 1mm past the contact point, a slice preparation is made. There is no ledge at the gingival level of the preparation.

• Depth cuts are established by placing the bur on its side.

• Occlusal reduction is approximately 1-1.5 mm (diameter of the bur).

• The occlusal buccal and occlusal lingual thirds of the tooth are reduced.
• The buccogingival and linguogingival thirds of the tooth are not usually reduced except when a tooth has a large buccal bulge the gingival third.

Occlusal and buccal views after reduction.

• Select the appropriate shape and size crown after the preparation is complete. As seen by the pictures below, crowns come in multiple sizes and conform to the shapes of the first and second molars.

• Seat the crown. The crown should extend 1 mm under the gingival margin. The fit of the crown should be snug without rocking.
• Trimming, if necessary, is best done with a scissor followed and heatless stone on a straight slow speed handpiece and polished with a rubber point.

• If contouring and crimping are necessary to ensure a good marginal fit, use a #114 or #109 plier to adapt the margin. Check the marginal fit with an explorer.

• Seat the crown to insure the bite is not open more than 1 mm. The crown may be cemented with either glass ionomer or polycarboxylate cement.

• Remove excess cement from the crown with a wet gauze. The cement must be completely set before preparation and placement of the open-faced veneer.⁶