Insufficient Alloy Content Information Regarding Ordered and Delivered Casted Metal-Ceramic Dental Crowns

Abstract

The aim of this study was two-folded: 1) Determine whether the metal alloy information provided by the dental laboratories corresponds to the ordered alloy. 2) Examine the discrepancy between Norwegian and imported casted metal-ceramic dental crowns. Background: A few studies have previously conducted similar analyses on this topic. However, this study has increased the number of analysed specimens. 46 randomly selected casted metal-ceramic crowns, delivered from seven different dental laboratories, were analysed by using EDX-SEM. The laboratories were not aware of the testing. Patient impressions were taken of the pillars with elastomeric impression material, and then forwarded to the respective laboratories. The examination was non-destructive, and analysed prior to cementation. The quantification of element B5 to Am95 was performed in accordance to ISO-standard 22674: 2006. Requirement that the metal alloy information used in dental crowns must be enclosed with the crown rests on the Medical Devices Directive (MDD). Results: The material descriptions are arranged in to three groups: specified content, no content information and incorrect information. Deviations between a given alloy and analysed content were found in all crowns delivered with specified content. 11 crowns lacked information about the alloy composition. Norwegian produced crowns constitute 64% of metal-ceramic crowns with no content information or with incorrect information, in contrast to imported crowns which constitute 36%. One laboratory delivered all their crowns with fully absence of content information. Two laboratories delivered one crown each labelled as CoCr alloys, and one laboratory delivered a crown labelled as both CoCr and Precious. The analyses revealed precious composition in all three. Four alloys were found to contain elements not included in the enclosed alloy description. Two crowns were found to contain 8 wt.% higher content of Ag and a lower content of Pd according to the alloy description. Insufficient content of In, and a slight excess of Sn was found in both crowns. Throughout the study (began 2013, ended 2015), a trend was exhibited: Crowns analysed in the early phase of the project lacked metal alloy information. Conclusion: A common finding was small but negligible deviations that are improbable to affect the lifespan or the mechanical properties of the crowns. Major deviations may cause adverse effects in terms of uncertain mechanical and aesthetic properties. The use of crowns labelled with incorrect alloy composition may involve severe health issues in individuals with allergies. The analyses did not exceed the content limits on Cd and Ni according to ISO 22674. The study cannot conclude that there is a greater issue regarding information accompanying Norwegian crowns compared to imported crowns. The discrepancy may be explained by a greater number of Norwegian specimens.