Preformed metal crowns for primary and permanent molar teeth: review of the literature

Author(s): Ros C. Randall PhD Mphil BChD
Journal: Pediatric Dentistry
Volume (number): 25; 5
Month, Year: 2002
Major topic: Literature review concerning the indications for, method and characteristics of preformed metal crowns for primary and permanent teeth
Type of Article: Literature Review
Overview of method of research: Literature Review
Findings: Indications for use in primary molars: after pulp therapy, for restorations in high caries risk children, multisurface caries, where an amalgam is likely to fail, fractured teeth (now with dentin bonding we may reconsider this depending on severity), teeth with extensive wear and as an abutment for a space maintainter although most would say that crowning an otherwise healthy tooth just to abut a space maintainer is overkill. It is not recommended to crown teeth within 12 months of exfoliation. In permanent teeth, a PMC may be used as an interim restoration for a broken down /traumatized tooth or even as a pre-ortho treatment, financial considerations, teeth with developmental defects and covering a decayed partially erupted molar. The article outlines a step by step preparation method which should be read but not transcribed here. Some salient points: placing wooden wedges before prepping can help prevent damage to adjacent teeth, refer to marginal ridges of adjacent teeth for reduction if occlusal table is marred by decay, buccal and lingual undercuts are where you get most of your retention so if you prep these surfaces do so minimally, primary teeth can spontaneously adjust to hyper-occlusion as high as 1-1.5mm, measuring the contralateral tooth can be helpful in determining crown size, post-cementation radiographs may be taken to assure no over-extension, abrasive wheels followed by rubber wheels are most highly recommended to trim crowns, if placing a crown on a 1o 2nd molar be sure to prep the distal because not doing so will cause overextension of the crown which could hinder the eruption of the permanent first molars, solder can be added to the interior occlusal surface to increase wear resistance, gingivitis is common around PMC’s particularly poorly fitting ones. For permanent molars: some recommend no buccal or lingual preparation to retain the possibility of using an onlay instead of a full coverage crown, marginal contour and crimping is essential to maintain periodontal health, cannot be left in hyper-occlusion and a post cementation radiograph is recommended since an explorer is often inadequate to ensure interproximal fit. Nickel sensitization is no longer an issue since the more modern SSC’s contain only 9-12% nickel as compared the older versions which were as high as 70%. Esthetics have become more of an issue in recent years and while anterior veneered crowns have enjoyed some success, posterior crowns remain a point of contention for many parents. PMC’s have exhibited considerably more success than amalgams in terms of retention and failure. The Hall Technique is cementing a crown with no caries removal, preparation or anesthesia; it has shown moderate success and further studies are in the works.
Key points/Summary: Preformed metal crowns are an effective and vital tool in the treatment of primary molars and as a quality interim restoration in permanent teeth.

Assessment of article: GREAT article. A great review of the indications and use of preformed metal crowns. It validates a lot of what we do here as well as presenting some new ideas.