Name of the commercial Composite Degree of conversion (%) DENTAL BIOMATERIAL: CHEMISTRY AND PHYSICAL PROPERTIES A.Amirouche1 , M.Mouzali1 ,DC Watts2 1LPCMAE, Faculty of Chemistry, USTHB, BP32 El-Alia, Alger, Algeria 2University of Manchester School of Dentistry, Higher Cambridge Street, Manchester M15 6FH, UK. mouzali@hotmail.com RESULTS AND DISCUSSION 1-Variation shrinkage (VS) /( DC)   INTRODUCTION Studies were carried out on the additives effects in the dental composites formulations. The results showed the nature and proportions of salts, and the monomer composition had significant consequences on the final product. During the polymerization, the monomer shrinkage, was directly related to the degree of conversion.. According to proportionally increasing.. A linear correlation, between the shrinkage and the number of converted double bond moles, was established, for each mole of converted (C=C) into single bond, a volumic shrinkage of 23 (cm3/ mole) occurred. Studies on linear series of polymethacrylates, confirmed the change of molar volume due to the polymerization is 22.5 (cm3/mole). In this work, we proposed to study this direct relation between the DC and the shrinkage of our experimental composites. MATERIALS AND METHODS Monomers;-BisGMA , 2,2-bis[4-(2-hydroxy-3-methacryloyloxypropoxy)phenyl] propane -TEGDMA , triethylene glycol dimethacrylate Initiator system:- Camphoroquinone (CQ) and N,N’-dimethyl aminoethyl methacrylate (DMAEMA) Fillers: La2O3 BaO and BaSO4 contents in weight, 0 - 80%. The matrix phase was prepared by mixing (BisGMA/TEGDMA) : (50/50), (75/25) and (25/75) with initiator system, CQ and DMAEMA. The mineral filler added from 0 to 80 wt. %. The specimen cured for 40 s, a visible light source (500mW/cm2, 450–490 nm,) The shrinkage-strain was measured using the Watt’s bonded-disk technique during 1 hour and rate was calculated from derivative of shrinkage strain data.The degree of conversion (DC%) was measured using FTIR spectroscopy The spectrum of each sample before and after curing was than obtained.The DC% was calculated using the following expression: DC (%) = [ 1 –  ( Aaliphatic / Aaromatic) / ( Ualiphatic / Uaromatic)  ]  100 ; -Aaliphatic peak at 1638 cm-1 of the cured specimen. -Aaromatic , peack at 1608 cm-1 (internal standard) of the cured specimen.- Ualiphatic ;peak at 1638 cm-1 of the uncured specimen. -Uaromatic ; peak at 1608 cm-1 of the uncured specimen. VSmax increases with DC whatever the studied salt, La2O3, BaO and BaSO4. Increasing BisGMA / important increasing of VSmax. BisGMA has a more significant effect on the VS than the DC. 2- (VSmax / DC) vs volume content of the mineral fillers. The figures2 ; variation of (VSmax / DC) vs the La2O3 volume content: (BisGMA/TEGDMA): (50/50), (75/25), (25/75).. Whatever the monomers composition for a given salt, the variation of (VSmax/DC) with the increase of filler content is negligible. The VS and DC increase with the same proportion with fillers. (VSmax / DC) remains stable with salts volume .   3- VS and DC of commercial dental composites Table: Values of VS and DC of commercial dental composites Name of the commercial Composite Volumic shrinkage (%) Degree of conversion (%) Bright light 3.3 67.6 Arabesk-signal 2.9 62.4 LCM 2.8 60.5 Te-econom 2.2 57.1 CONCLUSION linear and proportional relation between VS and DC -Whatever the monomer composition , and the fillers content, VSmax increases with DC. - For high percentages of mineral fillers (> 70%), the VSmax diagrams are deviated of the linearity which is not observed for the DC. Te-econom presents the weakest VS and DC. Results show similar variation of the two studied properties, for the two categories: experimental and commercial.   REFERENCES 1-A.Amirouche,M.Mouzali,D.C.Watts,’’ Effects of monomer ratios and highly radiopaque fillers on degree of conversion and shrinkage-strain of dental resin-composites’’ 25,11(2009), Dental materials,1411-1418 2-A.Amirouche,M.Mouzali,D.C.Watts,”Shrinkage strain rates study of dental composites based on (Bis-GMA/TEGDMA) monomers” Arabian journal of chemistry,5,3, 2012 3-S.Bayou,M.Mouzali,F.Aloui,P.Lebaudy, L.Lecamp,”Simulation of conversion profiles inside a thick dental material photopolymerized in the presence of nanofillers”, Polymer Journal (2013), 1–8 4. S. Bayou, M. Mouzali, L. Lecamp, P. Lebaudy ‘’Photoinitiated polymerization of a dental formulation:1. Influence of photoinitiating system, temperature and luminous intensity’’ J Fundam Appl Sci. 2017, 9(2), 685-695