Analysis of composition and structure of hard autopolymerizing reline resins

Abstract

The authors investigated the composition and structure of six hard auto-polymerizing reline resins. The chemical compositions, glass transition temperatures, molecular weights and particle size distributions of the powders, and the chemical compositions of the liquids were examined. The powder compositions were classified into three groups. The first group contained poly(methyl methacrylate). The second contained poly(ethyl methacrylate) and poly(methyl methacrylate/ethyl methacrylate) and the third contained poly(ethyl methacrylate). The average molecular weights of these powders was about 2 x 10(5). The indexes of molecular weight dispersion suggested that all powders contained polymers that had a narrow molecular weight distribution. The particle size distribution of these powders was classified into two groups. The first group was mainly in the range of 50-100 microns and the second mainly between 20 and 50 microns. The composition of the liquids was classified into three groups. The first group contained a monofunctional methacrylate monomer. The second contained a monofunctional methacrylate monomer and a plasticizer and the third contained monofunctional methacrylate monomers and cross-linking agents. The results of this experiment showed the differences in composition among the products. This will be useful for examining the relationship between the composition and mechanical properties of hard autopolymerizing reline resins.

Evaluation of glass transition temperature and dynamic mechanical properties of autopolymerized hard direct denture reline resins

“…The principal composition of Rebaron is similar to that of general heat-polymerized denture base resins; i.e., poly(methyl methacrylate) as the powder and methyl methacrylate as the liquid components. Aliphatic ester dibutyl sebacate is also contained at approximately 10 wt% in the liquid 4) . In the case of New Truliner, the powder consists of poly(ethyl methacrylate), and the liquid portion consists of 92 wt% iso-butyl methacrylate and 8 wt% aromatic esters dibutyl phthalate 4) .…”

“…Aliphatic ester dibutyl sebacate is also contained at approximately 10 wt% in the liquid 4) . In the case of New Truliner, the powder consists of poly(ethyl methacrylate), and the liquid portion consists of 92 wt% iso-butyl methacrylate and 8 wt% aromatic esters dibutyl phthalate 4) . As for Kurarebase, the powder is also poly(ethyl methacrylate), while the liquid components are fluorinated monomer and another methacrylate monomer.…”

“…In addition, other factors such as the type of monomers and residual monomer content also may influence Tg. Methyl methacrylate monomer causes irritation to oral mucosa and occasionally allergic responses in patients, whereas iso-butyl methacrylate monomer is far less irritating to oral mucosa and causes fewer exothermic reactions during polymerization 4,5,32) . A fluorinated monomer was also reported to have satisfactory biocompatibility in addition to chemical stability, water and oil repellency and contamination resistance 3,12,33) .…”

“…A direct method (chair-side reline system) using autopolymerized hard direct denture reline resins is more often applied for relining of ill-fitting dentures in clinical situations as compared with an indirect method (laboratory-processed reline system) using heat-polymerized denture base resins, because the former does not require sending the denture to a dental laboratory, and is also less time consuming and more convenient 3,4) . However, autopolymerized hard direct denture reline resins have a lower level of stiffness than heat-polymerized denture base resins, as well as unpleasant taste and odor, and cause irritation of the oral mucosa from the monomer components 1,[3][4][5]13,14,31) . Ideally, an autopolymerized hard direct denture reline resin should have the same dynamic mechanical properties and Tg value as a heat-polymerized denture base resin 15,16,31) .…”

“…Although an indirect (laboratoryprocessed reline system) method has also been used, the direct method (chair-side reline system) using autopolymerized hard direct denture reline resins is applied in nearly all clinical situations, because sending the denture to a dental laboratory is not required and the procedure is easier than that of an indirect method 3) . In general, the powder component used in autopolymerized reline resins is based on poly(methyl methacrylate), poly(ethyl methacrylate), or poly(methyl methacrylate/ethyl methacrylate), while the liquid component consists of a monofunctional methacrylate monomer, polyfunctional monomer (cross-linking agent), or those in combination 4) . A chemically activated accelerator such as tertiary amine is also added to the liquid to produce the autopolymerization reaction 5) .…”