Dendritic copolymers and particulate filler composites for dental applications: degree of conversion and thermal properties.
OBJECTIVE
The aim of this study was to determine the degree of double bond conversion and thermal properties of photopolymerized dendritic copolymers and particulate filler composites that may be used as dental restorative materials.


METHODS
The resins consisted of a multifunctional dendritic monomer, methyl methacrylate and varying proportions of acetoacetoxyethyl methacrylate. In addition, one of the composites contained 1,4-butanediol dimethacrylate. Camphorquinone and 2-(N,N-dimethylamino)ethyl methacrylate were used as the light-activated initiation system. The degree of conversion was determined with Fourier transform infrared spectroscopy and the thermal properties with differential scanning calorimetry.


RESULTS
The degree of conversion of copolymers varied from 52 to 60% and increased with increasing concentration of acetoacetoxyethyl methacrylate. The values for the composites were 32-44%. Reaction exotherms of 0.2-9.6J/g were measured for the photopolymerized experimental materials indicating residual reactivity that increased with increasing concentration of acetoacetoxyethyl methacrylate. The residual reactivity trend seemed counter intuitive to the degree of conversion. The glass transition temperatures for the completely polymerized copolymers containing acetoacetoxyethyl methacrylate were 112-116 degrees C and for the particulate filler composites 84-87 degrees C.


CONCLUSIONS
The addition of acetoacetoxyethyl methacrylate increased the degree of conversion. The polymerization characteristics of the experimental materials were comparable to those of control materials.
Viljanen
Eeva K
EK
Department of Prosthetic Dentistry and Biomaterials Science, Institute of Dentistry, University of Turku, Turku, Finland. eeva.viljanen@utu.fi
Skrifvars
Mikael
M
Vallittu
Pekka K
PK
D017438:Bisphenol A-Glycidyl Methacrylate / Q000737:chemistry; D002152:Calorimetry, Differential Scanning; D003188:Composite Resins / Q000737:chemistry* / Q000528:radiation effects; D050091:Dendrimers / Q000737:chemistry* / Q000528:radiation effects; D003793:Dental Restoration, Permanent; D008027:Light; D008689:Methacrylates / Q000737:chemistry; D020366:Methylmethacrylate / Q000737:chemistry; D008768:Methylmethacrylates / Q000737:chemistry; D015394:Molecular Structure; D044367:Phase Transition; D011092:Polyethylene Glycols / Q000737:chemistry; D011108:Polymers / Q000737:chemistry* / Q000528:radiation effects; D011109:Polymethacrylic Acids / Q000737:chemistry*; D017550:Spectroscopy, Fourier Transform Infrared; D044366:Transition Temperature
D003188:Composite Resins; D050091:Dendrimers; D008689:Methacrylates; D008768:Methylmethacrylates; D011108:Polymers; D011109:Polymethacrylic Acids; C020946:triethylene glycol dimethacrylate; D020366:Methylmethacrylate; C090000:poly(2-(acetoxy)ethylmethacrylate); D011092:Polyethylene Glycols; D017438:Bisphenol A-Glycidyl Methacrylate; C009931:poly(ethylmethacrylate); C102737:1,4-butanediol dimethacrylate