Stainless steel crowns are extra-coronal restorations that are used particularly in the restoration of grossly broken down teeth and large multi-surface cavities. The placement of traditional stainless steel crowns can be challenging for the patient as well as the clinician since it is associated with tooth preparation.
Stainless steel crowns, also referred to as preformed metal crowns were introduced by Humphrey to pediatric dentistry in 1950. They are used as an alternative to silver and tooth-colored fillings. Most of them last four years or more and they also have a polished surface that makes it easy to cleanse. They are also known as silver crowns and are employed in the case of badly broken primary teeth or milk teeth. They are durable, corrosion-resistant, inexpensive, and help in safeguarding the decayed teeth of children.
Stainless steel crowns are used to repair a decayed molar by professional dentists. It also prevents the teeth from further decaying. They are made in the exact size of a child’s molar. They are subjected to negligible sensitivity during replacement and offer the advantage of full coronal coverage. It is possible to place a well-fitting crown without compromising the quality or longevity of a crying child. Therefore, stainless steel crowns are used in restoration due to an inability to control the secretion of saliva.
Stainless steel crowns:
- Contains only safe metals
- Does not impair the growth of permanent teeth
- Are easy and simple to apply
- Will fall out naturally when the child’s teeth fall out
- Offers an alternative in removing a decayed tooth
Classifications of stainless steel crowns
These crowns are pre-contoured and also festooned. Some contouring and trimming might be necessary but is usually minimum. The pre-contour is lost and the crown will fit more loosely if the trimming of the crown becomes necessary.
These crowns have non-contoured, straight sides to follow a parallel line to the gingival crest. The crowns still need contouring and trimming.
These are the crowns that have resin-based composite to create a more aesthetic posterior crown. They are bonded to the occlusal and buccal surfaces. They are more expensive than the other stainless steel crowns, require tooth reduction, and allow for only less crimping for crown adaptation.
Indications for Use
- Restoration of young or primary teeth with extensive carious lesions. The primary molars with interproximal lesions are also included.
- It is used on primary molar when an amalgam possibly fails. For example, when the proximal box goes beyond the line angles in a cavity.
- It is considered to be the restoration of choice after pulp theory.
- An extreme risk of recurrent caries and extensive decalcification around an already restored tooth.
- Immoderate tooth wear from bruxism.
- There should be strong consideration given to the children who need general anesthesia for general treatment
- Developmental defects like dentinogenesis im-perfecta, amelogenesis im-perfecta, and hypocalcified teeth.
- As a prop to space maintainers or prosthetic appliances.
- Fittings for orthodontic appliances and habit- breaking.
- Disabled children with poor oral hygiene.
- Patient ineffective to cooperative with the treatment
- Patient having nickel hypersensitivity
- Primary tooth approaching exfoliation. Half of the primary tooth will be shown resorbed in X-ray.
- Esthetics in teeth is the main reason.
Technique for Placement
Effective anesthesia is given as the preparation will extend with the inevitable trauma of gingiva. There are different conditions under which general anesthesia in pediatric dentistry is indicated:
- Patients in need of significant dental treatment with medical conditions
- physical and mental disabilities
- Very young patients with nursing bottle caries
- Patients from remote areas with extensive dental needs where access to regular dental care is not available.
- Extreme anxiety, non-cooperation, and fearfulness
- Allergy to local anesthetics
To obtain the clearance of 1mm, occlusal reduction is carried out. The contact points like mesial and distal are cleared, a taper from occlusal to gingival is acquired free of ledges. The line angles are surrounded off and all carriers are removed.
The preparation of stainless steel crowns does not have to be accurate because they are not close-fitting. The gingival finishing line should not have ledges, it should be a feather edge. A reasonable taper will help achieve this if a ledge is present. The operator will feel difficulty in placing the crown and there are possibilities to trim it unnecessarily but it is the ledge that should be removed. There is no preparation needed on the lingual or buccal surfaces except when there is a mesiobuccal convexity. These crowns can spring over as they are flexible enough.
The adjacent surfaces of the teeth are trimmed slightly more than usual. In this way, the multiple crown placements will be easier. The finishing line should be 1mm beneath the gingival margin. The crown with the correct size is selected after measuring the width of mesiodistal connecting the contact points of the adjoining teeth with calipers or the mesiodistal width of identical teeth in an opposite arch will be measured if teeth are missing. It is preferable to go for a small crown to fill in the place.
While fitting a crown for a second primary molar in a place where the permanent molar has not yet erupted, care must be taken when measuring the mesiodistal dimension for the crown. If the stainless steel intrudes on the space needed for eruption, its eruption pathway may be distorted. The crown is placed lingually and rolled over the preparation to the buccal margin to place it on a prepared tooth. As the crown springs into place over the gingival undercut area, it will make an audible “click”. To place the crown, firm pressure is usually necessary.
The marginal gingiva is seen to flinch with a well-fitting crown as it seats. The crown margin is placed approximately 1mm subgingivally both to give confinement and a good cement seal. The crown will need to be trimmed if excess gingival blanching.
A sharp scalar or bur is used to trim the crown to 1mm below the scribe line along the gingival contour. The occlusion is examined and the crown removed with a sharp excavator. Crown scissors are used for trimming. The crown will have a larger cervical gap after trimming and must be crimped to recover its retentive contour. To crimp stainless steel crowns, crimping pliers are recommended. The crown should be thinned and smoothed slightly with a large “heatless” stone once the adjustments are completed. A rubber wheel is used for final polishing.
The crown is now ready to be cemented with glass ionomer, zinc phosphate cement, or polycarboxylate. The crowns are not a tight fit except at the margin therefore larger volume of cement should be mixed. Excess cement flowing from the margins is an indication of an inadequate volume of cement. To remove excess cement from this region, a dental flow is passed below the contact point and interproximal area.
The crown is finally checked for occlusion. The patient should be informed that there may be some temporary discomfort in the gingival area when the anesthetic wears off.
All after-care instructions given by your dentist must be followed to the T. Measures to prevent such tooth infections should also be taken.