Biomedical subjects
Publications and source records attributed to John W Osborne.
UNLABELLED: The use of dental amalgam is on the decline, yet its many advantages, including the contrast in colour with the tooth, increase the possibility that the patient's dentition will last a lifetime. CLINICAL RELEVANCE: Dental amalgam is still a viable restorative material. A recipe for the placing of better amalgam restorations along with clinical restorations of 30-year longevity using these techniques is presented.
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OBJECTIVES: Silver amalgam alloy has been used as a dental restorative material since the beginnings of restorative dentistry. It rose as an easily manipulated and low cost material in comparison to other restorative techniques of the time, but it had poor dimensional stability and clinical behavior. Successive research led to the standardization of both its composition and some aspects of its mechanical properties, which have contributed to its widespread acceptance. Nevertheless, the risk of environmental toxicity generated by mercury and its poor esthetics have given rise to the search for alternative and more promising materials. This article endeavors to give a brief historical description of the main events which have led to development of modern silver amalgam alloys. SIGNIFICANCE: It is concluded that extensive knowledge of the use of silver amalgam alloy has made it the most widely used restorative material for the posterior oral cavity. However, in recent years its preponderance has been brought into question even though some innovative ideas have been suggested which could help improve this material in the future.
Dental amalgam seals itself over time. The reduction of microleakage in amalgam restorations has been explained by corrosion products filling in the interface gap between amalgam and tooth structure in order to seal the restoration interface. This concept has been widely accepted; yet, curiously, there is little research supporting this theory. The creep mechanism may be a plausible alternative to explaining why microleakage is reduced over time in amalgam restorations. Amalgam restorations are confined to the fixed space of the cavity preparation; expansion of the amalgam through internal phase changes in this confined area must be relieved. The resultant creep-expansion of the amalgam restoration fills in the tooth/amalgam interface gap. Once the interfacial gap is filled and amalgam has made intimate contact with the cavity wall, the dental amalgam slides along the tooth preparation plane as predicted by classic metallurgical studies. The results of the creep of amalgam have been observed clinically as the extrusion of amalgam from the cavity preparation. This explanation for amalgam sealing the tooth/amalgam gap fits many clinical observations and certain research data.
Reports of longevity for multi-surface amalgam restoration have been limited. This paper reports a case where a five-surface complex amalgam restoration has been followed and documented for 40 years. The pictorial series will help to identify some of the factors a dentist should consider before replacing the restoration.
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This clinical study compared the performance of complex amalgam restorations retained with self-threading pins or bonded with a filled, 4-META-based resin. Sixty amalgam restorations (28 pin-retained and 32 bonded), each replacing at least one cusp, were placed. Self-threading stainless steel pins (Coltene-Whaledent) were used in the pin-retained group. A filled, 4-META-based bonding resin (Amalgambond Plus with HPA powder) was used in the bonded group. For both groups, any retention form remaining after removal of an old restoration was left in place but not enhanced. At six years, 11 restorations had failed; eight of which were pin-retained and three bonded. Using Fisher's exact test to compare the groups at six years, there was no significant difference in failure rate, marginal adaptation, marginal discoloration, secondary caries, tooth sensitivity or tooth vitality. At six years, there was no difference in the performance of pin-retained amalgam restorations and bonded amalgam restorations.
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Explore the source record for details and available documents.