Biomedical subjects
Publications and source records attributed to W A Marjenhoff.
Novel materials and cutting-edge technologies developed at the American Dental Association Dental Health Foundation Center of Excellence for Materials Science Research are discussed. Some of these materials have already entered mainstream clinical practice, others are undergoing clinical trials and some are still being developed. The search for better posterior restorative materials continues.
Discussions between two group leaders at the National Institute of Standards and Technology (NIST) led to the suggestion that a mercury-free, silver-based material could be used for dental direct-filling applications. This concept brought about a new approach that, nonetheless, is still based on powder technology such as amalgams. The resulting material also retains the tin and silver components of conventional amalgams. The condensation of a loose powder mixture into a cohesive solid relies, however, on cold-welding across atomically clean silver-silver interfaces after a mild acid treatment of the surfaces. The National Institute of Dental Research (NIDR) and American Dental Association Health Foundation (ADAHF) became involved in the research in 1992, and ADAHF scientists continue to collaborate with NIST metallurgists and electrochemists toward the further development of this promising new technology.
Explore the source record for details and available documents.
Extrapolations based on the history of the development of composites and an adhesion system for bonding dental resins and composites to hard tooth tissues can rightfully be the basis for strong optimism regarding future improvements in esthetic and conservative treatment modalities. Improved understanding of mechanisms of action and the clinical application steps common to current adhesion systems will certainly lead to improved oral healthcare.
Most commercial dental composites contain liquid dimethacrylate monomers (including BIS-GMA or variations of it) and silica-containing compositions as inorganic reinforcing filler particles coated with methacrylate-functional silane coupling agents to bond the resin to the filler. They also contain initiators, accelerators, photo-initiators, photosensitizers, polymerization inhibitors, and UV absorbers. Durability is a major problem with posterior composites. The typical life-span of posterior composites is from three to 10 years, with large fillings usually fewer than five years. Polymerization shrinkage and inadequate adhesion to cavity walls are remaining problems. Some pulp irritation can occur if deep restorations are not placed over a protective film. Some have advocated the use of glass-ionomer cement as a lining under resin composite restorations in dentin. The concept of glass-ionomer cements (GICs) was introduced to the dental profession in the early 1970's. Current GICs may contain poly(acrylic acid) or a copolymer. Higher-molecular-weight copolymers may also be used to improve the physical properties of some GICs. Stronger and less-brittle hybrid materials have been produced by the addition of water-soluble compatible polymers to form light-curing GIC formulations. The ion-leachable aluminosilicate glass powder, in an aqueous solution of a polymer or copolymer of acrylic acid, is attacked by the hydrated protons of the acid, causing the release of aluminum and calcium ions. Salt bridges are formed, and a gel matrix surrounds the unreacted glass particles. The matrix is adhesive to mineralized tissues. Provisions must be made for maintenance of the water balance of restorations for the first 24 hours.(ABSTRACT TRUNCATED AT 250 WORDS)
This article outlines the authors' perceptions of the future of esthetic dental restorative materials such as composites, glass ionomer cements, pit and fissure sealants and laboratory fabricated resin.
Building on findings concerning adhesion to enamel, R L Bowen and his colleagues at the Paffenbarger Research Center, National Institute of Standards and Technology began addressing and solving problems associated with (1) silicate cements and unfilled resins, (2) bonding in an aqueous environment, and (3) the development of an adhesion system for both dentin and enamel that could withstand various stresses. This article reviews the development of an adhesion system for bonding dental composites to dentin and enamel.
Explore the source record for details and available documents.
Explore the source record for details and available documents.
Explore the source record for details and available documents.
The development of an adhesion system for bonding dental composites to dentin and enamel is reviewed. Building on findings concerning adhesion to enamel, a field pioneered by Dr. Michael Buonocore and others, Dr. R.L. Bowen and his colleagues at the Paffenbarger Research Center, National Institute of Standards and Technology, began addressing and solving problems associated with (1) silicate cements and unfilled resins, (2) bonding in an aqueous environment, and (3) the development of an adhesion system for both dentin and enamel that could withstand various stresses. Although commercial products based on this adhesion system are currently available in the dental materials marketplace, experimentation continues, focusing on the synthesis of potentially better component analogs, the optimization of the individual components, and on improved storage stability and ease of synthesis.
In the 1940s, dentists observed that secondary caries was rarely associated with silicate cement restorations. While the relatively stable dimensional properties of those restorations were undoubtedly a factor in this fortunate circumstance, the fact that fluoride was inherent in the composition of the material received the greater credit. By the mid-1980s, a wide variety of fluoride-releasing dental restorative materials were available to dentists and dental consumers, and the cariostatic effect of fluoride ions on enamel caries had been demonstrated in many studies. This paper reviews much of the fluoride-related research conducted on fluoride-releasing amalgam, glass-ionomer cements, composites, primers, sealants, liners, acrylic resins, and orthodontic bracket bonding materials. The need for standardization of test methods is addressed, as is the need for more controlled clinical trials and additional research.