1069 D3000 new imprint Word template Vol 13, No 1 (2025) ISSN 2167-8677 (online) DOI 10.5195/d3000.2025.1069 http://dentistry3000.pitt.edu Effect of Nanoparticles on the Mechanical Properties of Polymethyl Methacrylate Denture Base Material Omar M. Faruq Abdlrahman1, Farhad Wahid Rasool2, Fahd Sudad Ikram3 1Khanzad Teaching Dental Center, Erbil, Iraq 2Soran Health Center, Soran, Iraq 3College of Den;stry, Hawler Medical University, Erbil, Iraq Abstract Polymethylmethacrylate (PMMA) has been widely used as a denture base material due to its favorable properNes but exhibits limitaNons in mechanical strength. This study invesNgated the effects of incorporaNng three different nanoparNcles - zirconium dioxide (ZrO₂), silicon dioxide (SiO₂), and diamond nanoparNcles (DNPs) at varying concentraNons (0.5%, 1.0%, 2.5%, and 5.0%) on the mechanical properNes of PMMA denture base material. The incorpo- raNon of nanoparNcles demonstrated concentraNon-dependent effects on PMMA proper- Nes. ZrO₂ nanoparNcles at 1.0% concentraNon showed opNmal results with improved hard- ness (21.4 ± 0.8 VHN) while maintaining acceptable surface roughness. Higher concentraNons (2.5% and 5.0%) led to increased surface roughness and decreased hardness across all nano- parNcle types. Diamond nanoparNcles exhibited the highest surface roughness (0.146 ± 0.017 μm) at 5.0% concentraNon, while SiO₂ showed moderate improvements in mechanical prop- erNes at lower concentraNons. Surface morphology analysis revealed excellent parNcle dis- persion at 0.5-1.0% concentraNons, with significant agglomeraNon observed at higher con- centraNons. The study determines that 1.0% concentraNon is the opNmum level to uNlize for the addiNon of nanoparNcles into PMMA denture base materials, wherein ZrO₂ nanoparNcles show the opNmum balance of enhanced material properNes and preserved surface features. The findings show that precise control of parNcle concentraNon is required to achieve enhanced material properNes without compromising surface integrity that will in turn translate to enhanced clinical performance of dental prosthe- ses. Open Access Cita%on: Abdlrahman OMF, et al. (2025) Effect of Nano- par%cles on the Mechanical Proper%es of Polymethyl Methacrylate Denture Base Material. Den%stry 3000. 1:a001 doi:10.5195/d3000.2025.1069 Received: October 8, 2025 Accepted: October 15, 2025 Published: November 10, 2025 Copyright: ©2025 Abdlrahman OMF, et al. This is an open access ar%cle licensed under a Crea%ve Commons ATribu%on Work 4.0 United States License. Email: zeenaadwal.a@gmail.com Introduc)on Polymethylmethacrylate (PMMA) has re- mained the preferred material in the process of making denture bases since the 1930s based on its advantageous traits of biocom- patibility, esthetics of look, ease of processa- bility, and cost-effectiveness. Notwithstand- ing these, though, there are some disad- vantages of PMMA to a larger extent on the aspect of mechanics that could lead to break- age along with failure of the denture base in use in clinical practice [1,2]. Mechanical shortcomings of conventional PMMA have evoked investigations of new methods of reinforcement. Promising leads that origi- nate from advances in the realm of nanotech- nology open new opportunities for prostho- dontic material enhancement. Incorporation of nanoparticles in PMMA has emerged as an important method of its physical and me- chanical enhancement. Due to the small di- ameter size and high surface area to volume ratio, the nanoparticles can improve the ma- terial's functionality if properly distributed in the polymer matrix [3]. Some of the nanoparticles that have been in- vestigated for reinforcement of PMMA den- ture bases include metal oxides zirconium oxide (ZrO2), titanium dioxide (TiO2), and silicon dioxide (SiO2). Nanoparticles found some level of success in improving Qlexural strength, impact resistance, and surface hardness. Reinforcement with nanoparticles is based on several parameters like particle size, concentration, dispersion within poly- mer matrix, and particle-matrix interface [4]. Zirconium oxide nanoparticles have particu- larly captured interest since they are highly biocompatible, very strong, and white in na- ture that will never undermine the esthetics of the denture base. It has been established by research that ZrO2 nanoparticles can Effect of NanoparNcles on the Mechanical ProperNes of Polymethyl Methacrylate Denture Base Material Vol 13, No 1 (2025) DOI 10.5195/d3000.2025.1069 http://dentistry3000.pitt.edu 2 signiQicantly improve the mechanical strength of PMMA when used in appropriate concentrations and along with proper sur- face modiQication [5]. Titanium dioxide nanoparticles incorpora- tion is also proving to be beneQicial in modi- fying the property of PMMA. Besides enhanc- ing the material's mechanical property, TiO2 nanoparticles possess some level of antimi- crobial activity that can be useful in avoiding infection of the denture. The level of TiO2 na- noparticles incorporation should be con- trolled in such a way that there is optimal performance without sacriQicing other mate- rial's properties [6]. Silicon dioxide nanopar- ticles have also been found to improve the mechanical performance of PMMA without degrading its transparency. The addition of SiO2 nanoparticles has been found to im- prove the wear resistance as well as tensile strength of the material but will be particle concentration- and surface treatment-sensi- tive [7]. Nanoparticle reinforcement is highly reliant on proper dispersion within the PMMA ma- trix as well as between polymer and nano- particles with good bonding. Nanoparticles are surface-functionalized using silanization or with some coupling agents to improve particle dispersion as well as inorganic nano- particles-polymer matrix interface. The changes are of utmost signiQicance in regu- lating the Qinal property of the resulting na- noparticle-reinforced PMMA denture base material [2]. Addition of nanoparticles in polymethyl methacrylate has increased its mechanical characteristics. It has been proved by research that addition of nanopar- ticles of SiO2, TiO2, Al2O3, ZrO2, and dia- mond increases the impact resistance, trans- verse resistance, hardness, and Young's modulus of polymethyl methacrylate [8,9,2]. Yet, the performance is based on the type and concentration of nanoparticles added. Low concentrations (less than 1% wt.) are generally recommended for minimizing ag- glomeration impacts and achieving optimum beneQits [10]. The surface roughness can sig- niQicantly increase at concentrations above 0.5%, while hardness is increased at various concentrations [2]. A silane coupling agent can resolve agglom- eration problems [10]. PMMA's mechanical properties can generally be enhanced by in- corporating nanoparticles, but the optimum type and quantity need to be established. Materials and Methods Zirconium dioxide nanoparticles (ZNPs) with an average particle size of 14 nm and 99.9% purity (Aritech Chemazone Pvt. Ltd., Iraq) were selected and silanized with 97% γ-MPS (Shanghai Richem International Co., Ltd.) Surface treatment process was carried out according to standard procedures to op- timize the interfacial adhesion between na- noparticles and the polymer matrix. Silicon dioxide nanoparticles (SNPs) (AEROSIL R812; Evonik Degussa) having particle size 12 nm, speciQic surface area 150-550 m²/g, and intensity 2.2 g/cm³ were purchased. The SNPs were processed through a saliniza- tion process performed according to previ- ously reported methods to improve their compatibility with the acrylic resin matrix. Diamond nanoparticles (DNPs) of about 19 nm in size (Shanghai Richem International Co. Ltd) were procured and processed ac- cording to routine surface modiQication pro- cedures. Surface treatment of DNPs was per- formed to improve their dispersion behavior in the polymer matrix and prevent agglom- eration. All nanoparticles were weighed using a high- precision electronic balance (S-234; Denver Instrument GmbH, Göttingen, Germany) to prepare concentrations of 0.5%, 1.0%, 2.5%, and 5.0% by weight of the acrylic powder. The weighed nanoparticles were then com- bined with the acrylic powder to form differ- ent mixtures of PMMA/nanoparticles. These mixtures were mechanically stirred for 30 minutes using an electric mixer operating at 400 rpm at room temperature to ensure uni- form distribution of the nanoparticles throughout the acrylic powder. The pre- pared nanoparticle-PMMA mixtures were stored in sealed containers in a dry environ- ment until further processing to prevent moisture contamination and maintain the in- tegrity of the surface treatment. The han- dling and preparation of all nanoparticles were conducted in accordance with material safety guidelines and manufacturer recom- mendations. Heat-polymerized acrylic resin powder (Ma- jor base 20 resin; Prodotti Dentari SPA) was selected as the primary denture base mate- rial for this study. The material was supplied as a two-component system consisting of pre-polymerized polymethyl methacrylate powder and methyl methacrylate monomer liquid. The powder and liquid components were stored at room temperature (23 ± 1°C) in their original sealed containers until use, following the manufacturer's storage recom- mendations. The ratio of the polymer powder to mono- mer liquid employed for blending was care- fully maintained at the suggested 2.5:1 weight ratio by the manufacturer. This was ascertained with a calibrated electronic bal- ance with the potential to achieve an accu- racy of 0.001g. Room temperature (23 ± 1°C) and controlled humidity (50 ± 10%) were employed in a clean ceramic mixing bowl to blend the contents. Prior to the inclusion of the nanoparticles, the base material was quality-checked and proven for uniformity. The monomer was inspected for transpar- ency and lack of premature polymerization, while the powder was examined for signs of moisture contamination or agglomeration. All materials were handled in accordance with the manufacturer's guidelines and ma- terial safety protocols. The conventional mixing technique was employed where the polymer powder was gradually incorporated into the monomer liquid. The mixture was stirred gently with a clean, dry spatula to en- sure complete wetting of the powder parti- cles. The material was then allowed to reach a dough-like consistency suitable for pack- ing, as per the manufacturer's working time speciQications. This standardized prepara- tion process was maintained throughout the study to ensure consistency in the base ma- terial properties before nanoparticle incor- poration. ZNPs were surface treated using 97% γ-MPS silane coupling agent following established protocols. SNPs were silanized according to previously documented procedures, while DNPs were treated following standardized surface modiQication methods. All surface treatments were performed under con- trolled laboratory conditions to enhance the interfacial bonding between the nanoparti- cles and the PMMA matrix. The treated nano- particles were mechanically mixed with the acrylic powder using an electric mixer oper- ating at 400 rpm for 30 minutes at room tem- perature to ensure homogeneous distribu- tion. A total of 260 specimens were fabricated and divided into thirteen groups (n=10/group). The control group was prepared using pure PMMA without any nanoparticle reinforce- ment. For the experimental groups, three dif- ferent types of nanoparticles (ZNPs, SNPs, and DNPs) were incorporated into the PMMA powder at four different concentra- tions (0.5%, 1.0%, 2.5%, and 5.0% by weight). The nanoparticle-modiQied powder was then mixed with the monomer following the manufacturer's recommended powder- to-liquid ratio. Disk-shaped specimens measuring 15 mm in diameter and 2 mm in thickness were fabri- cated using standardized metal molds. The molds were Qirst isolated using a separating medium and allowed to dry. The mixed PMMA dough was packed into the molds at the dough stage, following conventional den- ture processing techniques. The molds were then compressed under hydraulic pressure of 3000 psi and maintained under pressure during the initial setting period. The packed specimens were heat-polymer- ized following a standardized curing cycle. The curing process was initiated at 74°C for 90 minutes, followed by a terminal boiling at Effect of NanoparNcles on the Mechanical ProperNes of Polymethyl Methacrylate Denture Base Material Vol 13, No 1 (2025) DOI 10.5195/d3000.2025.1069 http://dentistry3000.pitt.edu 3 100°C for 30 minutes. After polymerization, the Qlasks were allowed to cool slowly to room temperature for 30 minutes on the bench and then for 15 minutes under run- ning water to minimize residual monomer content and prevent warpage. Ten specimens were fabricated for each con- centration of each type of nanoparticle, re- sulting in a total of 120 experimental speci- mens (40 specimens per nanoparticle type) and 10 control specimens (Table 1). After demolding, all specimens were Qinished us- ing tungsten carbide burs to remove excess material and Qlash. The specimens were then stored in distilled water at 37°C for 48 hours before testing to ensure complete polymeri- zation and to simulate oral conditions. Following polymerization, all specimens were subjected to a standardized Qinishing and polishing protocol. Initial Qinishing was performed using tungsten carbide burs (HM79GX-040-HP; Meisinger, Centennial, CO) operating at 18,000 rpm to remove sur- face irregularities. This was followed by pro- gressive polishing using a series of rubber polishing tips (FINOPOL Polishers, 64830, LABOSHOP GmbH, Germany) to achieve a uniform surface texture. Surface standardization was accomplished using a mechanical polisher (Metaserve 250 grinder-polisher, Buehler) equipped with a polishing cloth disc (TexMet C10in, 42-3210, Buehler GmbH). The specimens were pol- ished at 100 rpm under wet conditions for 5 minutes to ensure consistent surface Qinish. After polishing, all specimens were stored in distilled water maintained at 37°C for 7 days before testing to simulate oral conditions and ensure dimensional stability. Surface roughness measurements were con- ducted using a noncontact optical proQilome- ter (Contour Gt-K1 optical proQiler; Bruker Nano, Inc., Tucson, AZ) with a resolution of 0.01 mm. Five areas were randomly selected and scanned on each specimen using a stand- ard camera at 20× magniQication. The ac- quired images were analyzed using special- ized software (Vision64, Bruker Nano) to de- termine the average roughness (Ra) values. Five readings were recorded for each speci- men, and the mean Ra value was calculated to represent the surface roughness. The surface hardness of the specimens was evaluated using a Vickers hardness tester (Tukon 1102, Wilson Hardness, ITW Test & Measurement, Shanghai, China). A diamond pyramid indenter was applied to put a 300g load for 15 seconds at a right an- gle to the surface of the test piece. Five in- dentations were created at different loca- tions in each test piece with sufQicient spac- ing between them not to interfere with each other. The Qive values' average was considered to obtain the Qinal hardness read- ing for each test piece. Scanning electron microscopy (SEM) (FEI, INSPECT S50) was used to study the topog- raphy and surface features of the specimens. The specimens were gold-coated in a dedi- cated coating unit (Quorum, Q150R ES, UK) prior to SEM observation to enhance the sur- face conductivity and image quality. SEM im- aging was performed at various magniQica- tions ranging from 500× to 10,000× to ob- serve the surface features, nanoparticles' distribution, and probable agglomeration patterns. Several areas in each sample were examined to ensure comprehensive surface analysis and documentation of characteristic surface details. Results The roughness of the PMMA samples' sur- face was evaluated following the inclusion of various nanoparticles at varying concentra- tions. Control samples that were not pro- vided with any inclusion of nanoparticles were determined to possess a surface rough- ness of 0.113 ± 0.012 μm, and it was taken as the reference for comparison. When ZrO₂ nanoparticles were incorpo- rated, no signiQicant changes in surface roughness were observed at concentrations of 0.5% and 1.0% (p>0.05). However, signif- icant increases in surface roughness were detected at higher concentrations, with measurements of 0.125 ± 0.015 μm at 2.5% (p=0.028) and 0.138 ± 0.018 μm at 5.0% (p=0.008) being recorded as shown in Table 2. In specimens modiQied with SiO₂ nanoparti- cles, similar trends were observed. The roughness of surface was not signiQicantly af- fected at lower concentrations of 0.5% and 1.0%. SigniQicant increases were noted at 2.5% concentration, where the roughness was measured at 0.127 ± 0.012 μm (p=0.023), and at 5.0% concentration, where it was measured at 0.135 ± 0.016 μm (p=0.014). The incorporation of diamond na- noparticles produced the most pronounced effects on surface roughness at higher con- centrations. While no signiQicant changes were detected at 0.5% and 1.0% concentra- tions, substantial increases were measured at 2.5% (0.133 ± 0.014 μm, p=0.013) and 5.0% (0.146 ± 0.017 μm, p=0.002). The high- est surface roughness among all tested spec- imens was recorded in the 5.0% diamond na- noparticle group. It was concluded that all three types of nano- particles demonstrated a concentration-de- pendent effect on surface roughness, with signiQicant increases being observed at con- centrations of 2.5% and above. Lower con- centrations (0.5% and 1.0%) were found to maintain surface roughness values comparable to the control specimens, re- gardless of the nanoparticle type used (Fig- ure 1). Vickers hardness of PMMA specimens was evaluated following the incorporation of dif- ferent nanoparticles at varying concentra- tions. The control specimens, which con- tained no nanoparticle additions, were measured to have a baseline hardness value of 18.3 ± 0.9 VHN. For ZrO₂ nanoparticle- modiQied specimens, signiQicant improve- ments in hardness were observed at speciQic concentrations. While the 0.5% concentra- tion showed a marginal increase (19.7 ± 0.7 VHN, p=0.051), signiQicant enhancements were recorded at 1.0% (21.4 ± 0.8 VHN, p=0.001) and 2.5% (20.9 ± 0.9 VHN, p=0.003) concentrations. However, at 5.0% concentration, the hardness was found to de- crease to 19.4 ± 1.0 VHN (p=0.07), showing no signiQicant difference from the control as shown in Table 3. In specimens modiQied with SiO₂ nanoparti- cles, moderate improvements in hardness were detected. The 0.5% concentration showed no signiQicant change (19.0 ± 0.8 VHN, p=0.09), while signiQicant increases were measured at 1.0% (20.1 ± 0.9 VHN, p=0.02) and 2.5% (19.6 ± 0.8 VHN, p=0.032) concentrations. Like ZrO₂, the hardness at 5.0% concentration (18.7 ± 0.9 VHN, p=0.42) was not signiQicantly different from the con- trol. The addition of diamond nanoparticles was found to have minimal impact on the hardness of PMMA specimens. No statisti- cally signiQicant differences were observed across all concentrations tested (0.5% to 5.0%), with values ranging from 18.4 to 19.2 VHN (all p-values >0.05). It was concluded that ZrO₂ nanoparticles demonstrated the most effective enhance- ment of PMMA hardness, particularly at 1.0% and 2.5% concentrations. SiO₂ nano- particles showed moderate improvement at similar concentrations, while diamond nano- particles were found to have no signiQicant effect on hardness. Higher concentrations (5.0%) of all nanoparticle types were ob- served to result in decreased hardness val- ues compared to their optimal concentra- tions. The surface morphology and nanoparticle dispersion characteristics of PMMA speci- mens were analyzed using scanning electron microscopy (SEM). The control specimens were observed to exhibit a smooth, continu- ous matrix with a homogeneous surface structure and no inclusions, receiving the highest dispersion quality rating of 5. In ZrO₂ nanoparticle-modiQied specimens, excellent dispersion was observed at lower concentra- tions (0.5% and 1.0%), with uniform parti- cle-matrix interfaces and optimal integration being noted. However, at 2.5% Effect of NanoparNcles on the Mechanical ProperNes of Polymethyl Methacrylate Denture Base Material Vol 13, No 1 (2025) DOI 10.5195/d3000.2025.1069 http://dentistry3000.pitt.edu 4 concentration, mild agglomeration and slightly rougher surfaces with clustered ar- eas were detected. The highest concentra- tion (5.0%) was characterized by visible ag- glomeration, uneven surfaces, and the pres- ence of microvoids as shown in Table 4. For SiO₂ nanoparticle specimens, good dis- persion quality was documented at 0.5% and 1.0% concentrations, with largely smooth surfaces and Qine nanoparticle distribution being observed. As concentration increased to 2.5%, noticeable clusters were detected on the surface topography. At 5.0% concen- tration, irregular surfaces with numerous agglomerates were identiQied, leading to a disrupted matrix with cluster artifacts. The incorporation of diamond nanoparticles was found to result in varying surface character- istics across concentrations. Lower concen- trations (0.5% and 1.0%) showed smooth surfaces with slight undulation and rare cluster formation. However, signiQicant dete- rioration in surface quality was observed at higher concentrations, with 2.5% showing uneven surfaces and moderate clustering. The most severe effects were noted at 5.0% concentration, where discontinuous sur- faces with high agglomeration, large clusters, numerous voids, and matrix gaps were ob- served. It was concluded that optimal nanoparticle dispersion was achieved at lower concentra- tions (0.5-1.0%) for all types of nanoparti- cles, with ZrO₂ showing the most favorable integration characteristics (Figure 2). Sur- face quality and dispersion were found to de- teriorate signiQicantly at higher concentra- tions (2.5-5.0%), with diamond nanoparti- cles showing the most pronounced negative effects at elevated concentrations. A comparative analysis was conducted to evaluate the effects of different nanoparti- cles on the mechanical properties of PMMA denture base material (Table 5). The surface roughness, surface hardness, and dispersion quality were assessed, and signiQicant varia- tions were observed across different nano- particle groups. For surface roughness meas- urements, DNP-5.0 (5% diamond nanoparti- cles) was found to exhibit the highest value, while ZNP-1.0 (1% zirconia nanoparticles) demonstrated the lowest surface roughness. Statistically signiQicant differences (p < 0.001) were observed between the control group and several modiQied groups, includ- ing ZNP-2.5, ZNP-5.0, SNP-2.5, SNP-5.0, DNP- 2.5, and DNP-5.0. In terms of surface hardness, the highest val- ues were recorded in the ZNP-1.0 group (1% zirconia nanoparticles), while the lowest val- ues were observed in both the control group and DNP-5.0 group. SigniQicant improve- ments in hardness (p < 0.001) were noted in ZNP-1.0, ZNP-2.5, SNP-1.0, and SNP-2.5 groups compared to the control. The disper- sion quality evaluation revealed that both the control group and ZNP-1.0 demonstrated the highest quality of particle dispersion, while DNP-5.0 showed the poorest disper- sion characteristics. SigniQicantly lower dis- persion quality (p < 0.001) was observed in ZNP-2.5, ZNP-5.0, SNP-5.0, DNP-2.5, and DNP-5.0 groups compared to the control. Overall, these results indicated that the type and concentration of nanoparticles signiQi- cantly inQluenced the mechanical properties of PMMA denture base material, with each nanoparticle type showing distinct effects on different parameters. The concentration-dependent effects of dif- ferent nanoparticles on PMMA denture base material were evaluated (Table 6 and Figure 3), revealing distinct patterns of inQluence on surface roughness and hardness properties. For ZrO₂ nanoparticles (ZNPs), values com- parable to the control were observed at 0.5% concentration. At 1.0% concentration, which was identiQied as optimal, a decrease in sur- face roughness and a signiQicant increase in hardness were documented. When the con- centration was increased to 2.5%, an in- crease in surface roughness was noted along with maintained improved hardness. How- ever, at 5.0% concentration, a substantial in- crease in surface roughness was observed while hardness values were found to de- crease. In specimens modiQied with SiO₂ nanoparti- cles (SNPs), control-like values were main- tained at 0.5% concentration. The 1.0% con- centration resulted in a slight decrease in surface roughness and improved hardness. At 2.5% concentration, increased surface roughness was noted while hardness im- provements were maintained. The highest concentration of 5.0% led to a substantial in- crease in surface roughness, while hardness values returned to levels like the control. For diamond nanoparticles (DNPs), the 0.5% concentration showed values like the control group. At 1.0% concentration, a slight de- crease in surface roughness was observed while hardness remained unchanged. The 2.5% concentration resulted in increased surface roughness with no signiQicant change in hardness. At the highest concentration of 5.0%, a substantial increase in surface roughness was recorded along with a de- crease in hardness values. It was concluded that the optimal concentra- tion for all nanoparticle types was found to be 1.0%, with ZrO₂ nanoparticles showing the most favorable combination of proper- ties. Higher concentrations were generally associated with deteriorating mechanical properties, particularly at 5.0% concentra- tion across all nanoparticle types. Discussion Incorporation of nanoparticles into polymethylmethacrylate (PMMA) denture base material has yielded varied effects on its properties. Incorporation of zirconium oxide (ZrO₂), silicon dioxide (SiO₂), and dia- mond nanoparticles at concentrations of up to 1% had no signiQicant effect on surface roughness, whereas 2.5% and higher con- centrations led to higher roughness [2]. Sim- ilarly, titanium oxide nanoparticles made the surface roughness increase in comparison to ZrO₂ nanoparticles [11]. Nanodiamond ad- dition (0.1-0.5%) improved elastic modulus, Qlexural strength, and surface hardness and conferred fungal resistance [4]. ZrO₂ nano- particle addition improved hardness but de- creased transverse strength of PMMA, the water sorption and solubility rising with in- creasing concentration [3]. The above Qind- ings suggest that the addition of nanoparti- cles can improve certain properties of PMMA but that care should be taken in selecting the concentration and kind of nanoparticles to achieve the best result. The addition of nano- particles to polyethyl methacrylate (PMMA) denture base material has had various im- pacts on its mechanical performance. ZrO₂ nanoparticles were found to enhance the hardest by the highest amount at 1.0% and 2.5% concentrations [2]. Also, the incorpora- tion of ZrO₂, TiO₂, and glass Qlakes mi- cronized enhanced fracture toughness and hardness of PMMA [7]. There was signiQicant enhancement in impact strength, transverse strength, and radio-opacity with 5% concen- tration of nano-modiQied ZrO₂ in PMMA [5]. However, higher nano-ZrO₂ concentrations (10% and 20%) decreased transverse strength but improved water sorption and solubility [3]. Surface roughness was also improved with nanoparticle addition but within the acceptable clinical practice limits [2,3]. From the Qindings, there are optimum amounts of nanoparticles that improve some mechanical characteristics of PMMA denture base materials. This summary integrates re- sults of four studies on nanoparticle-modi- Qied polymethylmethacrylate (PMMA) den- ture base materials. Nanoparticle incorpora- tion generally enhanced mechanical proper- ties with optimum results at low concentra- tions. ZrO₂ nanoparticles enhanced hardness but adversely affected surface roughness above 0.5% [2]. Incorporation of nanodia- mond (0.1-0.5 wt%) signiQicantly enhanced Qlexural strength, elastic modulus, and sur- face hardness and prevented fungal adhe- sion (Mangal et al., 2019). ZrO₂ nanoparticles improved hardness at 5- 10% concentrations but decreased trans- verse strength and increased water sorp- tion/solubility at higher concentrations [3]. Silica nanoparticles improved Effect of NanoparNcles on the Mechanical ProperNes of Polymethyl Methacrylate Denture Base Material Vol 13, No 1 (2025) DOI 10.5195/d3000.2025.1069 http://dentistry3000.pitt.edu 5 microhardness and fracture toughness at as low as 0.023% concentration, while higher concentrations led to agglomeration and lesser effect [1]. These tests altogether sug- gest that nanoparticles can be incorporated to improve PMMA but its optimal concentra- tion is also required to cause desired im- provement without impacting other proper- ties. The addition of different nanoparticles to PMMA denture base materials showed contrasting effects on mechanical proper- ties, wherein the optimal concentration was the limiting factor in the desired outcome. It was observed that the addition of 1.0% con- centration of zirconia nanoparticles (ZrO2) showed the optimal balance of properties, with enhanced hardness and still clinically acceptable values of surface roughness. However, higher concentrations of all three tested nanoparticles (ZrO2, SiO2, and DNPs) tended to impair mechanical properties at particularly 5.0% concentration [2]. This is in line with other studies whereby high nanoparticle loading has led to aggrega- tion and loss of material properties [4]. The test for surface roughness also indicated that loadings over 0.5% had signiQicantly in- creased Ra values compared to the clinical maximum of 0.2 μm [3]. Interestingly, alt- hough the diamond nanoparticles exhibited mechanical improvement properties, they also tended to agglomerate at higher concen- trations, thus presenting higher surface roughness and lower hardness values [12]. The Qindings illustrate the need to preserve the optimal concentration of the nanoparti- cles, around 1.0%, to achieve better mechan- ical properties while not compromising the clinical performance of the material. Conclusion The incorporation of nanoparticles into PMMA denture base material exhibited sig- niQicant concentration-dependent altera- tions on mechanical and surface properties. The study revealed that lower concentration levels (0.5-1.0%) of all the tested nanoparti- cles-retained surface properties comparable to those of control specimens, while 2.5% or greater led to signiQicant alterations in mate- rial properties. This trend was always observed for all kinds of tested nanoparticles, although to different degrees of effect. The best modiQier was found to be the ZrO₂ nanoparticles, particu- larly at 1.0% concentration, where these maintained the optimal compromise be- tween enhanced hardness (21.4 ± 0.8 VHN) and retained smoothness of the surface. The excellent performance of ZrO₂ was also com- plemented by excellent particle dispersion and uniform integration with the PMMA ma- trix at this concentration. SiO₂ nanoparticles exhibited mild improvements in mechanical properties, whereas diamond nanoparticles, to the contrary, exhibited mild beneQits with a high drawback at higher concentration lev- els. Surface morphology analysis revealed a threshold concentration of nanoparticles, beyond which material properties began to deteriorate. The 5.0% concentration always resulted in adverse effects in all forms of na- noparticles, with characteristics of higher surface roughness, lower hardness, and poor particle dispersion. This was particularly true for diamond nanoparticle samples, which exhibited the highest surface rough- ness (0.146 ± 0.017 μm) and poorest agglom- eration at this concentration. These Qindings strongly suggest 1.0% con- centration as the optimal level of nanoparti- cle addition to PMMA denture base materi- als, with ZrO₂ nanoparticles providing the most favorable balance of enhanced mechan- ical properties and maintained surface qual- ities. The results also emphasize the neces- sity of strict concentration control of nano- particle-modiQied dental materials, as con- centrations higher than the optimum can lead to property degradation instead of im- provement. Systematic exploration of surface morphol- ogy, hardness and roughness across differ- ent types and concentrations of nanoparti- cles provides valuable information for the development of improved dental materials. This work demonstrates that it is possible to improve material properties by selective PMMA modiQication with some nanoparti- cles at precisely controlled concentrations while maintaining important surface proper- ties, potentially leading to improved clinical performance of dental prostheses. There are many recommendations for research: 1) Maintain 1.0% levels of nanoparti- cles for optimal performance as higher con- centration levels provide poor properties. This is very crucial in the case of ZrO₂ nano- particles, whose performance was optimal when concentration was at this level. 2) Utilize ZrO₂ nanoparticles instead of SiO₂ and diamond nanoparticles for PMMA modiQication, as they exhibited better mechanical properties and integration with the matrix. Implement strong quality checks during the incorporation of nanoparticles to determine uniform dispersion and prevent agglomera- tion to maintain the best possible surface properties as well as mechanical properties. References 1. Baloš, S., Pilic B., Markovic D., Pavlicevic J., and Luzanin O. “Poly(methyl-methacrylate) Nanocomposites with Low Silica Addition.” *The Journal of Prosthetic Dentistry*, vol. 111, no. 4, 2014, pp. 327–34. https://doi.org/10.1016/j.prosdent.2013.06.021. 2. Gad, M. M., Al-Thobity, A. M., Rahoma, A., ArRejaie, A. S., and Al-Harbi, F. 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S. “Evaluation of the Effect of ModiQied Nano-Fillers Addi- tion on Some Properties of Heat Cured Acrylic Denture Base Material.” *Journal of Baghdad College of Dentistry,* vol. 23, no. 1, 2011, pp. 23–29. 6. Kaurani, A., Tomar, P., and Kaurani, M. “Ef- fect of Addition of Titanium Oxide and Zirco- nium Oxide Nanoparticles on the Surface Roughness of Heat Cured Denture Base Res- ins: An In -Vitro Study.” Manuscript, 2021. 7. Nejatian, T., Johnson, A., and Van Noort, R. “Reinforcement of Denture Base Resin.” *Ad- vances in Science and Technology,* vol. 49, 2006, pp. 124–130. https://doi.org/10.4028/www.scien- tiBic.net/AST.49.124. 8. Salman, A. D., Jani, G. H., and Fatalla, A. A. “Comparative Study of the Effect of Incorpo- rating SiO₂ Nano-Particles on Properties of Poly Methyl Methacrylate Denture Bases.” *Biomedical & Pharmacology Journal,* vol. 10, no. 3, 2017, pp. 1499–1506. https://doi.org/10.13005/BPJ/1262. 9. Rashahmadi, S., Mosalman, S., and Ha- sanzadeh, R. “Improving the Mechanical Properties of Poly Methyl Methacrylate Nanocomposites for Dentistry Applications Reinforced with Different Nanoparticles.” *Polymer-Plastics Technology and Engineer- ing,* vol. 56, no. 16, 2017, pp. 1730–40. https://doi.org/10.1080/03602559.2017.12894 02. Effect of NanoparNcles on the Mechanical ProperNes of Polymethyl Methacrylate Denture Base Material Vol 13, No 1 (2025) DOI 10.5195/d3000.2025.1069 http://dentistry3000.pitt.edu 6 10. Naguib, Ghada H., et al. “InQluence of In- organic Nanoparticles on Dental Materials’ Mechanical Properties. A Narrative Review.” *BMC Oral Health,* vol. 23, 2023, article no. 3652. https://doi.org/10.1186/s12903-023- 03652-1. 11. Kaurani, A., Tomar, P., and Kaurani, M. “Effect of Addition of Titanium Oxide and Zir- conium Oxide Nanoparticles on the Surface Roughness of Heat Cured Denture Base Res- ins: An In - Vitro Study.” Manuscript, 2021. 12. Zidan, S., Silikas, N., Alhotan, A., Haider, J., and Yates, J. “Investigating the Mechanical Properties of ZrO₂-Impregnated PMMA Nanocomposite for Denture-Based Applica- tions.” *Materials,* vol. 12, no. 8, 2019, arti- cle no. 1344. https://doi.org/10.3390/ma12081344. Table 1. Experimental grouping and specimen distribution. Group No. of Speci- mens (n) Nanoparticle Type Concentration (% wt) No. of Specimens (n) Key Notes Control 10 None 0% 10 Pure PMMA baseline ZNP-0.5 10 ZrO2 0.5% 10 ZNP, silanized ZNP-1.0 10 ZrO2 1.0% 10 SNP, silanized ZNP-2.5 10 ZrO2 2.5% 10 ZNP-5.0 10 ZrO2 5.0% 10 SNP-0.5 10 SiO2 0.5% 10 SNP-1.0 10 SiO2 1.0% 10 SNP-2.5 10 SiO2 2.5% 10 SNP-5.0 10 SiO2 5.0% 10 DNP-0.5 10 Diamond 0.5% 10 DNP, surface-modi- Qied DNP-1.0 10 Diamond 1.0% 10 DNP-2.5 10 Diamond 2.5% 10 DNP-5.0 10 Diamond 5.0% 10 TOTAL 130 130 x2 for testing/dupli- cate sets Table 2. Surface roughness (Ra, μm) of PMMA specimens with various nanoparticle additions. Group Nanoparticle Type Concentra- tion (% wt) Surface Roughness Mean (Ra, μm) ± SD SigniQicance vs Control (p- value) SigniQicant Differ- ence (Yes/No) Control None 0 0.113 ± 0.012 NA NA ZNP-0.5 ZrO₂ 0.5 0.112 ± 0.01 0.87 No ZNP-1.0 ZrO₂ 1.0 0.108 ± 0.011 0.59 No ZNP-2.5 ZrO₂ 2.5 0.125 ± 0.015 0.028 Yes ZNP-5.0 ZrO₂ 5.0 0.138 ± 0.018 0.008 Yes SNP-0.5 SiO₂ 0.5 0.115 ± 0.011 0.94 No SNP-1.0 SiO₂ 1.0 0.114 ± 0.009 0.88 No SNP-2.5 SiO₂ 2.5 0.127 ± 0.012 0.023 Yes SNP-5.0 SiO₂ 5.0 0.135 ± 0.016 0.014 Yes DNP-0.5 Diamond 0.5 0.114 ± 0.010 0.91 No DNP-1.0 Diamond 1.0 0.116 ± 0.011 0.80 No DNP-2.5 Diamond 2.5 0.133 ± 0.014 0.013 Yes DNP-5.0 Diamond 5.0 0.146 ± 0.017 0.002 Yes Effect of NanoparNcles on the Mechanical ProperNes of Polymethyl Methacrylate Denture Base Material Vol 13, No 1 (2025) DOI 10.5195/d3000.2025.1069 http://dentistry3000.pitt.edu 7 Figure 1. Surface roughness (Ra) evaluation of PMMA specimens reinforced with various nanoparticles and concentrations. Table 3. Vickers hardness values of PMMA specimens with different nanoparticle additions. Group Nanoparticle Type Concen- tration (% wt) Vickers Hardness Mean ± SD SigniQicance vs Control (p- value) SigniQicant Dif- ference (Yes/No) Control None 0 18.3 ± 0.9 NA NA ZNP-0.5 ZrO₂ 0.5 19.7 ± 0.7 0.051 No ZNP-1.0 ZrO₂ 1.0 21.4 ± 0.8 0.001 Yes ZNP-2.5 ZrO₂ 2.5 20.9 ± 0.9 0.003 Yes ZNP-5.0 ZrO₂ 5.0 19.4 ± 1.0 0.07 No SNP-0.5 SiO₂ 0.5 19.0 ± 0.8 0.09 No SNP-1.0 SiO₂ 1.0 20.1 ± 0.9 0.02 Yes SNP-2.5 SiO₂ 2.5 19.6 ± 0.8 0.032 Yes SNP-5.0 SiO₂ 5.0 18.7 ± 0.9 0.42 No DNP-0.5 Diamond 0.5 18.7 ± 0.7 0.38 No DNP-1.0 Diamond 1.0 19.2 ± 0.8 0.19 No DNP-2.5 Diamond 2.5 18.8 ± 0.9 0.32 No DNP-5.0 Diamond 5.0 18.4 ± 1.0 0.75 No Effect of NanoparNcles on the Mechanical ProperNes of Polymethyl Methacrylate Denture Base Material Vol 13, No 1 (2025) DOI 10.5195/d3000.2025.1069 http://dentistry3000.pitt.edu 8 Table 4. SEM qualitative assessment of surface morphology and nanoparticle dispersion. Group Dispersion Quality (1–5) Surface Morphology De- scription Agglomeration Ob- served Representative Features Control 5 Smooth, continuous ma- trix No Homogeneous surface, no inclu- sions ZNP-0.5 5 Uniform, minor rough- ness No Even particle-matrix interface ZNP-1.0 5 Homogeneous, optimal integration No Nanoparticles integrated with matrix ZNP-2.5 3 Slightly rougher, some clustered areas Mild Limited zones of nanoparticle clusters ZNP-5.0 2 Visible agglomeration, uneven surface Yes Agglomeration, microvoids noted SNP-0.5 4 Largely smooth, isolated minor roughness No Good dispersion, minor inclu- sions SNP-1.0 4 Smooth, Qine nanoparti- cle distribution No Uniform distribution SNP-2.5 3 Noticeable clusters on topography Mild Clustering at certain regions SNP-5.0 2 Irregular, numerous ag- glomerates Yes Disrupted matrix with cluster artifacts DNP-0.5 4 Smooth, slight undula- tion Rare Some isolated nano-clusters DNP-1.0 4 Moderately smooth, Qine particulate Rare Dispersed, but some cluster for- mation DNP-2.5 2 Uneven, moderate num- bers of clusters Moderate More frequent cluster sites DNP-5.0 1 Discontinuous, high ag- glomeration High Large clusters, many voids, ma- trix gaps Figure 2. Dispersion quality assessment of nanoparticles in PMMA specimens at varying concentrations. Table 5. Comparative analysis of surface properties and dispersion quality of PMMA denture base material modiQied with ZrO₂, SiO₂, and diamond nanoparticles. Parameter Highest value group Lowest value group Groups with Statistically SigniQicant Difference (p < 0.05) vs Control Overall ANOVA Re- sult Surface Rough- ness DNP-5.0 ZNP-1.0 ZNP-2.5, ZNP-5.0, SNP-2.5, SNP-5.0, DNP-2.5, DNP-5.0 p < 0.001 Surface Hard- ness ZNP-1.0 Control/DNP-5.0 ZNP-1.0, ZNP-2.5, SNP-1.0, SNP-2.5 p < 0.001 Dispersion Quality Control/ZNP-1.0 DNP-5.0 ZNP-2.5, ZNP-5.0, SNP-5.0, DNP-2.5, DNP-5.0 (all signiQicantly lower) p < 0.001 Effect of NanoparNcles on the Mechanical ProperNes of Polymethyl Methacrylate Denture Base Material Vol 13, No 1 (2025) DOI 10.5195/d3000.2025.1069 http://dentistry3000.pitt.edu 9 Table 6. Summary of concentration-dependent effects of different nanoparticles on surface roughness (Ra) and hardness values of PMMA denture base material. Nanoparticle 0.5% 1.0% (optimal) 2.5% 5.0% ZNPs (ZrO₂) ~Control values ↓Ra, ↑↑ Hardness ↑Ra, ↑ Hardness ↑↑Ra, Hardness↓ SNPs (SiO₂) ~Control values Slight ↓Ra, ↑HN ↑Ra, ↑ Hardness ↑↑Ra, ~HN DNPs (Diamond) ~Control values Slight ↓Ra, ~HN ↑Ra, ~HN ↑↑Ra, HN↓ Figure 3. SEM images of PMMA specimens with (3a) zirconium dioxide 0.5, (3b) zirconium dioxide (2.5), (3c) silicon dioxide 0.5, (3d) PMMA + silicon dioxide 5%, (3e) PMMA + diamond 0.5%, (3f) PMMA + diamond 2.5%, (3g) pure PMMA, and 3h comparative reference group (for visual benchmarking).