Biomedical Engineering Reference
In-Depth Information
13.4
Nanostructured Dental Composite
Restorative Materials
In recent years, materials used for dental restorations have
comprised principally acrylate or methacrylate polymers. However,
acrylic materials exhibit high coeficients of thermal expansion
relative to the coeficient of thermal expansion for the tooth
structure, therefore these substances by themselves proved to be
less than satisfactory. The disparity in thermal expansion, coupled
with high shrinkage upon polymerization, resulted in poor marginal
adaptability and ultimately led to secondary decay. Furthermore,
the wear and abrasion characteristics and the overall physical,
mechanical, and optical properties of these unilled acrylic resinous
materials were quite poor. Composite dental restorative materials
containing methacrylate resins and illers were thus developed.
The nanotechnology and nanoscience approach is to design
and develop new dental composite materials with superior
properties [29]. The iller composition comprises at least a bound,
nanostructured, and silica. The silica is in the form of nano-sized
particles, preferably spherical particles. The individual particles
have the largest dimension or diameter in the range from about
10 to about 100 nm and preferably from about 10 to about 50 nm.
The silica particles are furthermore bound to each other so as to
result in chains having lengths in the range from about 50 nm to
about 400 nm. In order to improve bonding with the resin matrix, the
bound colloidal silica iller particles may optionally be treated with
a silane. These illed compositions are useful for a variety of dental
treatments and restorative functions including crown and bridge
materials, illings, adhesives, sealants, luting agents or cements,
denture base materials, orthodontic materials and sealants, and
other dental restorative materials.
In addition to the bound, nanostructured silica, the iller
composition may further comprise one or more of the inorganic
illers currently used in dental restorative materials. Preferred
additional illers include those which are capable of being
covalently bonded to the resin matrix itself or to a coupling agent
which is covalently bonded to both. Examples of suitable illing
materials include but are not limited to, silica, silicate glass, quartz,
barium silicate, strontium silicate, barium borosilicate, strontium
