Authors /year Particle size Addition percentage Type of Acrylic Nanocomposite preparation Properties tested Specimen size Effects (Increase/Decrease/Unchanged) Chatterjee, 2010 [9 ] 5 nm 0%-15wt% PMMA from Scientific Polymer Products (Ontario, NY) (i) Measured TiO2 NP mixed with PMMA for 5-10 min (ii) DACA twin-screw extraction process at 190°C and 100 rpm. (iii) Acrylic mixed for 6-7 min and extruded 5 times (i) Tensile modulus (ii) Dimensional stability (iii) Glass transition temperature ( ) (iv) UV absorption 10 x 6 x 0.3 mm 5 mg (i) Improvement in tensile modulus. (ii) Increased thermal stability (iii) Increased (iv) Improvement in UV absorption maximum at 2% TiO2 NP Chatterjee, 2010 [10 ] 5 nm 0% 2.0% 5.0% 7.5% 10.0% 15.0% 30.0% PMMA from Scientific Polymer Products (Ontario, NY) (i) Measured TiO2 NP mixed with PMMA for 5-10 min (ii) DACA twin-screw extraction process at 190°C and 100 rpm. (iii) Acrylic mixed for 6-7 min and extruded 5 times (i) Glass transition temperature ( ) (ii) Thermal stability (iii) Decomposition temperature 10 x 6 x 0.3 mm (i) increased linearly up to 7.5% TiO2 NP. (ii) Thermal stability increased (2%-15% TiO2 NP) (iii) Decomposition temperatures increased with filler content up to 10% TiO2 NP. Anehosur et al., 2012 [11 ] 31 nm “Anatase phase” 3.0% In addition to surface coating. DPI heat cure acrylic resin, (India) (i) Visible light activated TiO2 NP were mixed with methyl methacrylate monomer. (i) Microbial inhibitory effect against S. Aureus 5 x 5 x 2 mm (i) 3w% of TiO2 shows antimicrobial activity against S. Aureus. Sodagar et al., 2013 [12 ] 21 nm “Anatase phase” 0% 0.5% 1.0% Selecta Plus (self-cure acrylic resin) (i) TiO2 NP were added to acrylic monomer. (i) Flexural strength 50 x 10 x 3.3 mm (i) Flexural strength decreased as the filler content increased. (i) Flexural modulus (i) No change in flexural modulus. Hamouda and Beyari, 2014 [13 ] 21 nm 5.0% Conventional heat cure acrylic resin (Acroston, WHN, England) and high impact (Metrocryl Hi, Metrodent, LTD, England) (i) TiO2 NP were mixed thoroughly with acrylic powder by hand. (ii) Flexural strength (iii) Toughness 65 x 10 x 2.5 mm (ii) Flexural strength and toughness decreased. (iv) Monomer release (iii) No difference between control and TiO2 reinforced regarding monomer release. Nazirkar et al., 2014 [14 ] 7 nm “Anatase phase” 0% 0.5% 1.0% DPI heat cure acrylic resin (i) TiO2 NP added to acrylic monomer. (i) Flexural strength 65 x 10 x 3.3 mm (i) Flexural strength decreased as the TiO2 amount increased. Shirkavand and Moslehifard, 2014 [15 ] <25 nm (average ~ 20.4 nm) “Anatase and Rutile phases” 0% 0.5% 1.0% 2.0% Heat cure acrylic resin from Ivoclar Vivadent (i) TiO2 NP were mixed with the acrylic resin polymer in an amalgamator for 20 min. (i) Tensile strength 60 x 12 x 4 mm (i) Tensile strength and elastic modulus improved with 1% TiO2 NP. (ii) 0.5% and 2% TiO2 were not significantly different from each other or control. Harini et al., 2014 [16 ] 0% 1.0% 2.0% 5.0%. Clear heat cure acrylic resin (i) Nanoparticles were incorporated into monomer by ultrasonic dispersion. (i) Flexural strength 65 x 10 x 3 mm (i) Flexural strength improved with TiO2 addition, significant difference noticed with 5%. Safi, 2014 [17 ] 5.0% Heat cure denture base acrylic (Superacryl plus, Czechoslovakia) (i) Nanoparticles added to monomer and sonically dispersed. (i) Coefficient of thermal expansion (ii) Modulus (iii) Glass transition 15 x 6 mm Cylinders 65 x 10 x 2.5 mm Powder form (10g) (i) Decrease in coefficient of thermal expansion. (ii) Decreased in modulus of elasticity (iii) Increased Alwan, and Alameer, 2015 [18 ] <50 nm size 0% 3.0% (i) Silanized with TMSPM Heat cure acrylic resin (i) Silanized TiO2 NP were added to monomer and sonicated. (i) Impact strength (ii) Transverse strength (iii) Hardness (iv) Surface roughness (v) Water sorption and solubility 80 x 10 x 4 mm 65 x10 x 2.5 mm 50 x 0.5 mm disc (i) Increased (ii) Increased (iii) Increased (iv) Increased (v) Decreased Ahmed et al., 2016 [19 ] 46 nm 0% 1.0% 5.0% Conventional heat cure acrylic resin (Implacryl, Vertex) and high impact heat cure acrylic resin (Vertex-Dental, Netherlands) (i) TiO2 NP were added into acrylic resin. (i) Flexural strength (ii) Impact strength (iii) Hardness 50 x 10 x 3 mm 60 x 6 x 4 mm 25 x 10 x 3 mm (i) Decreased with TiO2 addition. (ii) Increased only for conventional acrylic resin modified by 1%. (iii) Increased with 5% addition TiO2 NP for both types of acrylic. Sodagar et al., 2016 [20 ] 21 nm 0.5% 1.0% Selecta Plus (self-cure acrylic resin) (i) Nanoparticles were added to acrylic monomer and stirred (i) Antimicrobial properties 20 x 20 x 1 mm (i) TiO2 reduced microbial growth at both concentrations at 90 min under UVA exposure (ii) Antimicrobial activity of TiO2 is time dependent Ahmed et al., 2017 [21 ] <25 nm 0% 0.5% 1.0% Heat cure acrylic resin from Dentsply International Inc., (Chicago, IL, USA) (i) TiO2 NP were added to acrylic polymer and mixed using amalgam capsule. (i) Flexural strength (ii) Fracture toughness (iii) Hardness 65 x 10 x 2.5 mm 65 x 10 x 2.5 mm 30 x 10 x 2.5 mm (i) Increased with both filler percentages. (ii) No effect on fracture toughness of both filler percentages. (iii) Increased with 1% filler. Hashem et al., 2017 [22 ] 90 nm 0% 1.0% 2.0% 3.0% Self-cure acrylic resin from Eco-crylcold, Protechno, (Spain) (i) TiO2 NP were mixed with the monomer. (i) Flexural modulus and flexural strength (ii) Hardness (iii) Surface wetting 30 x 8 x 1 mm 50 x 1 mm discs (i) Increased linearly (ii) Increased. (iii) Reduced with 1% filler content and increased with higher percentages. (iv) decreased with TiO2 addition Ghahremani et al., 2017 [23 ] 20-30 nm “Anatase phase” 0% 1.0% SR Triplex Hot, heat cure acrylic resin (Ivoclar Vivadent Inc. Schaan, Liechtenstein) (i) TiO2 NP were mixed with acrylic resin powder in an ultrasonic mixer. (i) Tensile strength (ii) Impact strength 60 x 12 x 3.9 mm 75 x 10 x 10 mm (i) Increased (ii) Increased Totu et al., 2017 [24 ] 65-170 nm 0% 0.2% 0.4% 1% 2.5% PMMA+PEMA for 3D printing (eDent 100, EnvisionTec GmbH Gladbeck, Germany) (i) Nanoparticles were added into PMMA solution with continuous stirring and ultrasonic mixing for 1 hour. (i) Antimicrobial effect (Candida scotti ) (ii) Complete denture manufacturing using stereolithography (i) 0.4, 1% and 2.5% inhibited candida growth (ii) PMMA/0.4%TiO2 composite successfully used for denture fabrication Aziz, 2018 [25 ] 30 nm 0% 3.0% High impact heat cure acrylic resin (Vertex-Dental, Netherlands)- (i) TiO2 NP were dispersed in monomer and sonicated at 120W and 60 KHz for 3 minutes. (i) Impact strength (ii) Color stability (iii) Thermal conductivity 80 x 10 x 4 mm 35 x 15 x 0.5 mm 40 x 2.5 mm (i) Increased (ii) Increased color stability for test groups (iii) No effect Alrahlah et al., 2018 [26 ] 80-100 nm 0% 1% 2% 3% Heat cure acrylic resin (Lucitone 550, Dentsply Int. Inc. Pa, USA) (i) Hardness and modulus (ii) , degradation temperature and rate (iii) Creep-recovery and relaxation behavior (iv) Antibacterial adhesion 50 x 10 mm discs cut in different sizes for different tests 7 mg 5 x 10 mm (i) Increased (ii) Slight increase with 2% nano-filler content (iii) Improvement in behavior (iv) Decrease in bacterial attachment content Karci et al., 2018 [27 ] 13 nm 0% 1% 3% 5% (i) Auto-polyerized (Heraeus Kulzer, Newbury Berkshire, UK) (ii) Heat-polymerized Heraeus Kulzer, Newbury Berkshire, UK. (iii) Microwave-polymerized (GC Dental, Tokyo, Japan) (i) TiO2 NP were mixed with acrylic resin powder using ball milling at 400 rpm for 2 hours (i) Flexural strength 65 x 10 x 3 mm (i) Increased for heat- and auto-polymerized acrylic at 1% (ii) Decreased for all types of acrylic at 5% Totu et al., Totu et al., 2017 [28 ] “Anatase phase” 0% 0.2% 0.4% 0.6% 1.0% 2.5% (i) PMMA-MA (ii) PMMA-MMA-BPO (iii) 3D printed PMMA (eD, EnvisionTec GmbH Gladbeck, Germany) (i) TiO2 modified by methacrylic acid then manually mixed with PMMA mixture (i) Thermal stability (ii) Stereolithographic dentures (i) Increased (improved) (ii) Increased Totu et al., 2018 [29 ] “Anatase phase” 0% 0.2% 0.4% 0.6% 1.0% 2.0% 2.5% 5.0% PMMA for 3D printing (eDent 100, EnvisionTec GmbH Gladbeck, Germany) (i) Resistance (ii) Electrical conductivity (iii) Dielectric constant (i) Decreased with 1.0%, 2.0%, 2.5% and 5% (ii) Increased but material still maintained insulating properties (iii) Increased with 5%