Technology Development and Industrial Relations
Center for Biotechnology and Innovation
Objective:
We are seeking Concept Clearance for a Request for Applications (RFA). The purpose of this initiative is to encourage the use of nanotechnology and nanoscience approaches to design and develop new dental composite material with superior properties. Approaches that include modeling to enable rational design-driven modifications and/or the use of novel high-throughput combinatorial strategies are encouraged. The expected outcomes are new formulations for dental composites with improved adhesive bonding to dentin and enamel surfaces, improved durability, esthetics, and biocompatibility.
Background:
Magnitude of the Problem
Caries continues as the most prevalent malady in Dentistry despite remarkable advances in prevention over the past few decades. According to the NIDCR Strategic Plan, “dental caries begins early in life: 18 percent of preschoolers in the U.S. have already experienced tooth decay and by age 6–8, more than half have experienced this disease — making it 5–8 times more common than asthma. By age 17, more than 80 percent of the adolescent population is affected by caries. Dental caries is also a problem among adults; recurrent caries and root caries are prevalent among adults and the elderly.” Currently, the only treatment for carious lesions is tooth restoration by placement of an inert material that acts as a block to further decay.
Modern composite restorations are composed of silane-coated inorganic filler particles and adhesive resins (reactive monomers and cross-linking agents). Composites are more aesthetic and lack undesirable metals, but may have shorter lifetimes than amalgams, especially in molar teeth. Much of this decreased performance is due to the physical realities of the polymerization process as the composite material sets into the prepared site in the tooth. For example, marginal leakage due to polymerization shrinkage has been cited as a major problem of resin composites. Thus, while progress has been made on understanding the mechanisms that lead to composite restoration failure, there has been little progress in solving the underlying problem(s). Therefore, there is a need for research to develop the next generation of dental restorative materials that possesses the combination of the mechanical properties of amalgam and the tooth-like esthetics.
The essence of nanotechnology is the ability to work at the molecular level, atom by atom, to create large structures with fundamentally new molecular organization. Compared to the behavior of isolated molecules of about 1 nm or of bulk materials, behavior of structural features in the range of about 1 to 100 nm exhibits important changes. Therefore, nanostructured dental composites can have superior mechanical properties (e.g. increased elastic modulus, strength, or resistance to fatigue fracture) that can easily be tuned by small modifications of their building blocks.
New approaches employing nanoscience for a new generation of dental restorative composite materials are promising. Thus, the goal of this initiative is to encourage research that will lead to the development of nanostructured composite materials that are biocompatible, maintain the appearance of native teeth, and provide improved performance and longevity over the existing dental restorative materials.
Knowledge Gaps
Previous efforts have centered on maximizing the chemistries within the composite, such as driving the polymerization reaction to completion, excluding water from the binding surface of the dentin, and layering large restorations to dissipate heat and shrinkage stresses gradually. Nanosized fillers have been used in some composites in order to improve the wear and the aesthetics of these materials. However, these nanofilled composites show only incremental improvements over macrofilled composites. An advantage of nanostructured materials is that their bulk properties can easily be tuned by small modifications of the building blocks or in this case the monomer. These structural biomaterials will have superior mechanical properties such as toughness and wear compared to the existing composites. To date there is no commercially available material that meets these ideal requirements, especially in the degree of shrinkage.
The overall goal of this initiative is to encourage innovative research to advance the new generation of biocompatible dental restorative composite materials, which exhibit superior mechanical and aesthetics properties. The following are examples of potential research areas. These areas are not meant to be all-inclusive or restrictive.
- Development of methods for the fabrication of nanoparticles, nanospheres used as building blocks for nanocomposites
- Development of new techniques for the fabrication of novel dental nanomaterials with improved strength, wear resistance, toughness and aesthetics
- Studies on the interface of oral tissues and nanocomposites
- Development of novel surface modified nanofillers with traditional methacrylate-based resins and characterization of the resulting experimental composites
- Development of tools for screening combinatorial dental materials in an array format
- Production of a diverse dental nanomaterials library using a combinatorial approach
- Modeling to enable rational design-driven modification in complex dental nanocomposites
- Development of bio-inspired adhesives that optimize binding to the reactive moieties on the collagen of the interfacial dentin to relieve tensile/shear stresses
- High throughput, real-time measurements or assessments of cyclic loading to measure crack propagation or anticipate fatigue failure
- Assays to examine the biocompatibility of the new nanostructured materials.
Alignment with Institute goals:
This proposed initiative addresses the design and development of new, more effective and longer-lasting materials for use in the most common dental condition: caries. The objectives are aligned with NIDCR’s Strategic Plan Goal 1, Objective 19 (Enhance research on the interface between materials and tissues).
Current Portfolio Overview:
A search of the Computer Retrieval of Information on Scientific Projects (CRISP) database covering 2001-2005 reveals over two dozen NIDCR supported projects aiming to improve dental composite restorations by manipulation of their basic chemistry, and one Centers of Biomedical Research Excellence (COBRE) grant supporting investigations of new fluoride-releasing resin monomers funded by the Center for Research Resources. Seven projects exploit nanotechnology in addressing the challenges of developing the next generation of dental composites. The approaches used include: 1) modifications of filler particles for controlled surface topography at the particle-resin interface, 2) nanoscale computational modeling of complex chemistries at the hydrophobic-hydrophilic interface of tooth and composite resin, 3) use of nanostructured components (e.g. liquid crystal monomers, novel ring structures, and block co-polymers) spiked into traditional dental materials to minimize shrinkage stress and/or maximize phase integrations, 4) layering nanostructured materials within a composite to mimic the shock-absorbing transition zones in natural teeth, and 5) incorporation of nanofibers dispersed through the resin for fibrous reinforcement.
COLLABORATIVE ACTIVITIES:
Due to the highly focused nature of the initiative (i.e. next generation dental composites for restorations), we do not anticipate participation of other ICs in this initiative.
FUNDING MECHANISMS:
We are proposing to use the R21 (Exploratory/Developmental Grants) and the individual research project grants (R01) funding mechanisms.