The physical and chemical properties of some polymeric dental materials
Abstract
A study was made of three groups of materials used in
dentistryq i. e. denture base acrylics, "Gel-type" tissue conditioners
and epimine resins.
Conventional denture base acrylic made by curing a dough of
methyl methacrylate and poly(methyl methacrylate) beads is considerably
weaker than homogeneous poly(methyl methacrylate). The
reasons for this were revealed by a comparison of their fracture
mechanics and morphology. Phase inhomogenuity was found in denture
base acrylic, the interstitial phase having lower Mv and Young's
modulus than the bead phase. A viscoelastic and autoradiographic
study of the denture base acrylic revealed that the two phases were
interpenetrating polymer networks.
It was found possible to improve the strength of denture base
acrylic by the addition of methacrylic acid thus improving the 19
v of the interstitial polymer. The combination of methacrylic acid
and cross-linking agent also facilitated the control of phase stiffness.
Improving the molecular weight and matching the phase stiffness
produces a conventional denture base material of comparable
strength to homogeneous poly(methyl methacrylate)o
A study of the effects on "Gel-type" tissue conditioners of
an oral environment revealed the reasons for their loss of compliance
during clinical use. The alcohol desorption and water absorption
characteristics of the gels were studied. prom such studies and a
knowledge of their chemical composition conclusions were drawn regarding
the best ccr. positions for tissue conditioner gels intended for long
service in the mouth.
Two epimine ccnpounds, an impression rubber and a temporary
crown and bridge material were studied. Their physical properties
and chemical composition were determined.
A car. parison of known long term behaviour of analogous resins;
canbined with the determined physical properties of the epimine
resins studiedt revealed some of the clinical limitations of such
systems.
Authors
Causton, Brian EdwardCollections
- Theses [4223]