Table 2.

Studies that investigated the decreasing viscosity through monomer changes.

First author + Year	Monomer change	Variables tested	Result
Pereira, S.G [36] 2005	Replace TEGDMA in Bis-GMA mixture with either CH3 Bis-GMA or CF3 Bis-GMA	Mechanical properties	The analogue CH3 Bis-GMA, which allows the preparation of medium-viscosity resins, is a good candidate to replace TEGDMA in Bis-GMA mixtures.materials with CH3 Bis-GMA diluents showed an enhanced microhardness.
Okamura, H [37] 2006	Experimental composite resins of low-viscosity monomer mixtures of newly developed polyfunctional acrylates	Mechanical and physical properties	Mechanical (i.e., compressive, diametral tensile, and bending) strength of a polymer obtained from one new monomer mixture without fillers was similar to that of a bis-GMA/TEGDMA (2/1 weight ratio) based polymer. In terms of setting shrinkage, the composites consisting of new monomer mixtures exhibited significantly smaller shrinkage than the bis-GMA based composites, and decreased with increase in filler content.
Charton, C [38] 2007	co-monomer bis-GMA /TEGDMA (70/30 and 50/50 % and co-monomer UEDMA/TEGDMA (88.5/11.5 and 66.5/33.5 %)	Shrinkage stresses	The viscosities of the UEDMA bases were exactly the same as those of the bis-GMA ones. Shrinkage stress Statistically, there was a negative correlation between viscosity, Tg and shrinkage stress.
Prakki, A [39] 2008	Combining bis-GMA and TEGDMA, CH(3)bis-GMA or CF(3)bis-GMA, with aldehyde or diketone	Wear, roughness and hardness	The findings correlate with additives ability to improve degree of conversion of some composites/copolymers thereby enhancing mechanical properties. Bis-GMA/TEGDMA and bis-GMA/CH(3)bis-GMA copolymers with additives became smoother after abrasion test.
Prakki, A [40] 2009	Two additives, aldehyde or diketone,to Bis-GMA-based composites containing TEGDMA, (CH3Bis-GMA) or (CF3Bis-GMA).	Mechanical properties	The ability of additives to improve degree of conversion of some composite systems thereby enhancing mechanical properties.
Denis, A.B [41] 2012	Bis-GMA diluted with CH3bis-GMA containing 0, 2, 8, 16 and 24 mol% propionaldehyde	Physical, rheological, and mechanical properties	24 mol% of Propionaldehyde significantly increased comonomer degree of conversion; Increased %DC is known to improve resin mechanical properties such as surface hardness
Prakki, A [42] 2012	Additives of Bis-GMA based copolymers andthat of TEGDMA, CH3Bis-GMA or CF3Bis-GMA.	Water sorption characteristics	Aldehyde and diketone led to increases in the water sorption characteristics of experimental resins.