INFLUENCE OF THE CHEMICAL COMPOSITION UPON INFLUENCE OF THE CHEMICAL COMPOSITION UPON THE PROPERTIES OF SOME EXPERIMENTAL DENTAL THE PROPERTIES OF SOME EXPERIMENTAL DENTAL

INDIRECT RESIN COMPOSITESINDIRECT RESIN COMPOSITES

C. PrejmereanC. Prejmerean,, M. Moldovan, L. Vezsenyi, D. Borzea,M. Moldovan, L. Vezsenyi, D. Borzea,C. Nicola, S. Sava, & A. FarcasC. Nicola, S. Sava, & A. Farcas

21emes Journees Scientifiques du College Francais de Biomateriaux Dentaires 10-11 Juin 2004,

Neuchatel, SUISSE

“Raluca Ripan” Chemistry Research Institute, Department of Polymeric Composites, Cluj-Napoca, ROMANIA

“Iuliu Hatieganu”University of Medicine and Pharmacy, Faculty of Dentistry, Department of Propaedeutics and Dental Materials,

Cluj-Napoca, ROMANIA

ICCRRICCRR

Purpose and materialsPurpose and materials

The purposepurpose of the present study was focused on obtaining a series of experimental indirect resin composites based on different resin matrix and on investigating the effect of post-curing upon the degree of conversion of the resin and respectively on the mechanical properties of the cured experimental indirect composites. MaterialsMaterials: The resins were prepared from (Bis-GMA)0-2 aromatic dimethacrylic oligomers synthesized in our laboratory, having 39 mol % Bis-GMA0 monomer - 2,2-bis[4-(2-hydroxy-3-methacryloyloxypropoxy) phenyl]-propane, 60 mol % Bis-GMA1 dimer and 1 mol % Bis-GMA2 trimer; and aliphatic monomers TEGDMA, EGDMA, and HEMA. The inorganic filler consisted of 90% silanized SrO glass and 10% silanized colloidal silica. The powder/liquid ratio was 4/1.

For the obtaining of specimens, the resin composites were light-cured by exposing to a visible radiation for 40 sec (Optilux stomatological lamp). After initial polymerization, the specimens were postcured by barro-thermic treatment at 1350C temperature and 60 psi pressure, for 20 minutes, using a “belleGlass” warmer.

Determination of the residual double bonds (RDB)Determination of the residual double bonds (RDB)

Schematic representation of the crosslinked polymer network in diacrylic resins

NO BIS-GMA0-2 EGDMA TEG-DMA HEMA1 50 - - 502 50 50 - -3 50 - 50 -4 50 - 25 25

Composition of the resin matrix in the Composition of the resin matrix in the experimental indirect composites (%)experimental indirect composites (%)

0

5

10

15

20

25

30

35

MPa

1 2 3 4

The RDB values for the light-cured The RDB values for the light-cured and postcured and postcured resin compositesresin composites

Determination of the mechanical propertiesDetermination of the mechanical properties

The compressive strength The compressive strength values for the light-cured values for the light-cured

and postcured and postcured resin resin compositescomposites

0

50

100

150

200

250

300

350

MPa

1 2 3 40

10

20

30

40

50

60

MPa

1 2 3 40

20

40

60

80

100

120

140

160

MPa

1 2 3 4

The diametral tensile The diametral tensile strength values for the light-strength values for the light-

cured cured and postcured and postcured resin compositesresin composites

The flexural strength values The flexural strength values for the light-cured for the light-cured and and

postcured postcured resin compositesresin composites

CONCLUSIONSCONCLUSIONS

All the values obtained for the RDB in the case of post-cured resin composites were lower than the RDB values recorded for the corresponding untreated materials.

The decrease of RDB quantity was maximum for the Bis-GMA0-2/ HEMA/ TEGDMA matrix (45% from RDB of untreated copolymer polymerized after post-curing), followed by the Bis-GMA0-2/HEMA copolymer (42% RDB).

The lowest RDB value (14,8%) was recorded for the post-cured Bis-GMA0-2/ HEMA based resin composite.

The values for the mechanical properties are increased in the case of resin composites subjected to the barro-thermic treatment compared to the corresponding untreated materials. The increase of compressive strength was maximum in the case of Bis-GMA0-2/HEMA/TEGDMA based composite (21,5%). Diametral tensile strength has a higher increase, approximately 30% in the case of the same composite, and the increase of flexural strength was maximum for the Bis-GMA0-2/HEMA composite (18%).

Taking into consideration the quantity of RDB and the values obtained for the mechanical properties in the case of post-cured resins, the Bis-GMA0-2/HEMA based experimental resin composite was proposed for further investigations, toxicological

and clinical tests, in order to be used as restorative material in indirect tecniques.