ORIGINAL RESEARCH |
https://doi.org/10.5005/jp-journals-10015-2264 |
Effect of Nanoparticles on Mechanical Properties of Chemically Activated Provisional PMMA Resin:An In Vitro Study
1–3Department of Prosthodontics, SRM Dental College, Ramapuram, SRM University, Chennai, Tamil Nadu, India
Corresponding Author: Ahila S Chidambaranathan, Department of Prosthodontics, SRM Dental College, Ramapuram, SRM University, Chennai, Tamil Nadu, India, Phone: +91 9443607653, e-mail: ahilasc@yahoo.co.in
Received on: 06 June 2023; Accepted on: 07 July 2023; Published on: 31 August 2023
ABSTRACT
Aim: To evaluate the flexural strength and surface hardness of chemically activated provisional polymethyl methacrylate (PMMA) resin incorporated with 2.5% zirconia, titanium, and aluminum oxide (Al2O3)nanoparticles after 24 hours in distilled water and 2 weeks in artificial saliva after fabrication.
Materials and methods: According to International Organization for Standardization (ISO) 10477:2018, a rectangular-shaped die with 25 mm l × 2 mm w × 2 mm h and wheel shape die with a diameter of 15 mm and thickness of 1 mm were made to investigate the flexural strength and surface hardness. A total of 160 samples were prepared and categorized as groups F (flexural strength) and S (surface hardness). Groups F and S were further subdivided into two groups—group I (24 hours in distilled water) and group II (2 weeks in artificial saliva), then they were subdivided into group A (control) no nanoparticle, group II (2.5% zirconia), group III (2.5%titanium oxide), and group IV (2.5% Al2O3). A total of 10 samples were fabricated in each category the flexural strength test was done using a universal testing machine and the hardness test was done using a digital Vickers microhardness tester. The obtained values were statistically analyzed using a two-way analysis of variance (ANOVA) and Tukey’s honestly significant difference (HSD) test at a significant level of p < 0.05.
Results: The mean values of flexural strength of autopolymerized provisional PMMA resin control, zirconium dioxide (ZrO2), titanium dioxide (TiO2), and Al2O3 nanoparticles reinforced groups in 24 hours in distilled water were 97.96, 152.81, 140.79, and 137.85 MPa, respectively, and 2 weeks in artificial saliva were 98.43, 150.43, 141.06, and 139.00 MPa, respectively. The surface hardness of autopolymerized provisional PMMA resin control, ZrO2, TiO2, and Al2O3 nanoparticles reinforced groups in 24 hours in distilled water was 28, 33.9, 32, and 30.8 Vickers hardness test (VHN), respectively, and 2 weeks in artificial saliva were 28.7, 34, 32, and 32 VHN, respectively.
Conclusion: Autopolymerized provisional PMMA resin reinforced with 2.5% zirconium nanoparticles showed statistically significant flexural strength and surface hardness than conventional provisional PMMA resin and 2.5% TiO2 and 2.5% Al2O3 nanoparticles reinforced groups after 24 hours in distilled water and 2 weeks in artificial saliva after fabrication.
Clinical significance: The provisional restorations are subjected to masticatory forces during function and are easily prone to fracture. The use of autopolymerized provisional PMMA resin reinforced with 2.5% zirconium nanoparticles increased the mechanical properties of the provisional restoration; hence, it can be recommended for provisional restorations to increase the life span in clinical practice.
How to cite this article: Jehan A, Chidambaranathan AS, Balasubramanium M. Effect of Nanoparticles on Mechanical Properties of Chemically Activated Provisional PMMA Resin: An In Vitro Study. World J Dent 2023;14(7):617–624.
Source of support: Nil
Conflict of interest: None
Keywords: Autopolymerized polymethyl methacrylate resin, Flexural strength, Nanoparticles, Surface hardness
INTRODUCTION
Edentulism can be partial or complete,1 and it should be replaced with either a removable or fixed prosthesis. Temporary prosthetic treatment is a fixed or removable prosthesis, given for an esthetical reason, stabilization, and function, which later needs to be replaced with a permanent prosthesis.2 The functions of provisional restorations are biological (protection of pulp and periodontium, bearing the occlusal load, maintaining occlusion and contact points) and esthetically acceptable.3 The mechanical properties of the provisional materials used for making fixed dental prostheses are to be taken into account before choosing a temporary crown for clinical use.4 In clinical conditions such as full mouth rehabilitation with reduced vertical dimension, long-span bridges, temporomandibular joint disorders, and parafunctional habits, the mechanical properties of provisional restoration should be strong enough for such specific clinical conditions.5
In addition, patients under dental implant therapy need a healing period from a few months to a year.6 The polymethyl methacrylate (PMMA) resin is a commonly used provisional restorative material. The main drawback of acrylic material was low flexural strength and surface hardness, therefore; reinforcing with other materials to the PMMA resin may strengthen the acrylic material.7
Nanoparticles are solid tiny particles of size ranging from 1 to 100 nm, which are used to facilitate the mechanical properties of dental materials.8 Reinforcing dental polymers with different nanoparticles, like zinc, titanium, and aluminum. Zirconium dioxide (ZrO2) has been reported in many studies.9 Various studies, proved that the different concentrations of nanoparticles affected the properties of PMMA resin and not by incorporating different sizes of nanoparticles.10 The addition of zirconia in ceramics has been shown to improve the fracture toughness of ceramic composite matrix.11 Previous studies have proved that the addition of aluminum nanoparticles had significantly improved the flexural strength and surface hardness of heat cure denture base materials. Also, different concentrations of aluminum nanoparticles have been found to improve the flexural strength of denture base materials.12 Addition of nanoparticles of zinc, copper, and titanium has improved the tensile and tear strength of silicon elastomeric material.13 Breakage of temporary restorations can lead to migration of tooth, sensitivity, infection, poor esthetics, and fracture of the tooth. Zirconia, titanium, and aluminum oxide (Al2O3)nanoparticles had antibacterial and anticandidal effects; hence, the aim of the study was to evaluate and compare the flexural strengths and surface hardness of chemically activated provisional PMMA resin reinforced with 2.5% zirconia, titanium dioxide (TiO2), and Al2O3 nanoparticles after 24 hours in distilled water and 2 weeks in artificial saliva after fabrication. A hypothesis was formulated that the surface hardness and flexural strength of the nanoparticles reinforced conventional provisional PMMA resin would be the same after 24 hours in distilled water and 2 weeks in artificial saliva after fabrication.
MATERIALS AND METHODS
The study was executed in the laboratory of the Department of Prosthodontics, SRM Dental College, SRM University, Chennai, Tamil Nadu, India, during 2018–2020 (SRMDC/IRB/MDS/No.201). According to International Organization for Standardization (ISO), 10477:2018,14 a master split die was made in stainless steel using digital design was fabricated with a dimension of 25 mm l × 2 mm w × 2 h mm for flexural strength, and a wheel shape die was made with 15 mm diameter and 1 mm thickness for the micro-Vickers hardness test (VHN) (Fig. 1).
Fig. 1: Master die
Distribution of Samples
A total of 160 samples were made for the study, the flexural strength groups were considered group F, and the surface hardness groups were considered group S. Groups F and S samples were subdivided into two samples kept in distilled water for 24 hours after fabrication (group I) and samples kept in artificial saliva for 2 weeks after fabrication (group II). Further, the samples were subdivided into four subgroups, samples without any nanoparticles were considered group I (control), samples mixed with 2.5% zirconia nanoparticles (group II), samples mixed with 2.5% titanium nanoparticles (group III), samples mixed with 2.5% Al2O3 nanoparticles (group IV). A total of 10 samples were fabricated in each group, and the evaluation was done by a single evaluator.
Fabrication of Chemically Activated Provisional PMMA Resin Control Samples
To fabricate the control sample group I, first the polymer (chemically activated PMMA DPI cold cure, Mumbai, Maharashtra, India) was weighed, then it was mixed with monomer (chemically activated PMMA DPI cold cure, Mumbai, Maharashtra, India) in the ratio of polymer to monomer as 2:1 for 30 seconds on a vibrator machine (Vibron, Delta Lab Equipment, India), then it was poured into the die and removed after 1 hour.
Fabrication of Autopolymerized PMMA Provisional Resin Experimental Samples
To fabricate the experimental sample group II, 2.5 gm of zirconia nanoparticles (Ultrananotech, Hoodi, Bengaluru, Karnataka, India) of size 30–50 nm were weighed and incorporated into a 97.5 gms of polymer in the ball milling machine (MM 500, Nano, Retsh Laboratory mill). Similarly, for group III, 2.5% weight of TiO2, (Ultrananotech, Hoodi, Bengaluru, Karnataka, India), and for group IV, 2.5% weight of Al2O3 nanoparticles (Ultrananotech, Hoodi, Bengaluru, Karnataka, India) were mixed with polymethylmethacrylate powder in the ratio of 2:1, which was added to the liquid monomer (chemically activated PMMA DPI cold cure, Mumbai, India) and mixed for 30 seconds on a vibrator machine, then it was poured to the die. After 1 hour of polymerization, the samples were retrieved from the die. Then one group of samples was kept in distilled water (super pure, ECOgreen enviro services, Surat, Gujarat, India) for 24 hours, and the second group of samples was kept in artificial saliva (Banxero, Pharmakon health and beauty care Pvt ltd, Bhavana, Delhi, India) for 2 weeks.
Evaluation of Flexural Strength and Surface Hardness
The flexural strength of the samples was investigated using a three-point bending (3PB) test by UTM (1 mm) at 0.5 mm speed (Instron 3367, Instron Corp., Canton, Massachusetts, United States of America). The flexural strength was calculated by the formula S = 3FL/2bd2, where F was exerting force at the center of the sample till it fractured, L was the distance joining the two supports of the jaw, b, and d were the width and thickness of the sample, respectively. The flexural strength of resin depends on the type of filler material and processing techniques.15
The surface hardness was evaluated using digital VHN (Fig. 2) in which a 50 gm load was applied on the surface of the sample (Model MDV 401, Wilson Wolpert, Germany), and an indentation was made on the surface of the sample using diamond indenter for 10 seconds and the surface microhardness was calculated using—VHN = 1.854 Ld2 where, VHN—Vickers hardness in Kg/mm2, L—load in Kg, and d—length of the diagonals in mm.
Fig. 2: Surface hardness test
Scanning Electron Microscope Analysis
The samples were evaluated under a scanning electron microscope (SEM) before testing for distribution of nanoparticles in the sample (PhenomPro X, Phenom-World B V, Netherland) with the magnification of 1000×. SEM images of autopolymerized PMMA provisional resin showed rough surfaces with small cracks, which led to longer crack propagation (Fig. 3).
Fig. 3: SEM image of control
Statistical Analysis
The values obtained in this study were statistically analyzed using the Statistical Package for the Social Sciences software for Windows version 17 (Chicago, United States of America). The flexural strength and surface hardness values were statistically analyzed using two-way analysis of variance (ANOVA) for comparison within the group, and multiple group comparison was done using Tukey’s honestly significant difference (HSD) test. The results were considered significant if the p-value was < 0.05.
RESULTS
The mean values of flexural strength of autopolymerized provisional PMMA resin in distilled water for control, zirconia, TiO2, and Al2O3 nanoparticle groups are 97.96, 152.81, 140.79, and 137.85 MPa, respectively and in artificial saliva for control, zirconia, TiO2, Al2O3 nanoparticles groups are 98.43, 150.43, 141.06, and 139.00 MPa, respectively (Table 1). The comparison of flexural strength of autopolymerized PMMA provisional resin in distilled water for 24 hours and artificial saliva for 2 weeks after fabrication within the groups showed that the significance values p < 0.05; hence, it was considered statistically significant (Table 2). Multiple group comparisons of the flexural strength of autopolymerized PMMA provisional resin showed the significance values were p < 0.05, except for comparisons of 2.5% titanium and 2.5% Al2O3 group (Table 3). Hence, it was considered statistically significant.
| Group | N | Mean | Standard deviation | Standard error | 95% confidence interval | |
|---|---|---|---|---|---|---|
| Lower bound | Upper bound | |||||
| Control (after 24 hours fabrication) | 10 | 97.9688 | 4.10435 | 1.29791 | 95.0327 | 100.9048 |
| Zirconia | 10 | 152.8125 | 5.03891 | 1.59344 | 149.2079 | 156.4171 |
| Titanium | 10 | 140.7984 | 9.08094 | 2.87164 | 134.3023 | 147.2945 |
| Aluminum | 10 | 137.8545 | 5.64782 | 1.78600 | 133.8143 | 141.8947 |
| Total | 40 | 132.3585 | 21.74088 | 3.43754 | 125.4055 | 139.3116 |
| Control (2 weeks) | 10 | 98.4320 | 2.26576 | 0.71650 | 96.8112 | 100.0528 |
| Zirconia | 10 | 150.4303 | 4.33458 | 1.37071 | 147.3295 | 153.5310 |
| Titanium | 10 | 141.0654 | 6.41178 | 2.02758 | 136.4787 | 145.6521 |
| Aluminum | 10 | 139.0066 | 4.21392 | 1.33256 | 135.9921 | 142.0211 |
| Total | 40 | 132.2336 | 20.70583 | 3.27388 | 125.6115 | 138.8556 |
| Source | Dependent variable | Type III sum of squares | Degree of freedom | Mean square | F | Significance |
|---|---|---|---|---|---|---|
| Corrected model | Artificial saliva | 15975.405a | 3 | 5325.135 | 257.283 | 0.000 |
| Distilled water | 17024.596b | 3 | 5674.865 | 144.954 | 0.000 | |
| Intercept | Artificial saliva | 699428.602 | 1 | 699428.602 | 33792.769 | 0.000 |
| Distilled water | 700751.397 | 1 | 700751.397 | 17899.415 | 0.000 | |
| Group | Artificial saliva | 15975.405 | 3 | 5325.135 | 257.283 | 0.000 |
| Distilled water | 17024.596 | 3 | 5674.865 | 144.954 | 0.000 | |
| Error | Artificial saliva | 745.113 | 36 | 20.698 | ||
| Distilled water | 1409.379 | 36 | 39.149 | |||
| Total | Artificial saliva | 716149.120 | 40 | |||
| Distilled water | 719185.372 | 40 | ||||
| Corrected total | Artificial saliva | 16720.517 | 39 | |||
| Distilled water | 18433.974 | 39 |
aR squared = 0.955 (adjusted R squared = 0.952); bR squared = 0.924 (adjusted R squared = 0.917)
| Dependent variable | (I) Group | (J) Group | Mean difference (I-J) | Standard error | Significance | 95% confidence interval | |
|---|---|---|---|---|---|---|---|
| Lower bound | Upper bound | ||||||
| Artificial saliva | Control | Zirconia | −51.9983* | 2.03458 | 0.000 | −57.4778 | −46.5187 |
| Titanium | −42.6334* | 2.03458 | 0.000 | −48.1130 | −37.1538 | ||
| Aluminum | −40.5746* | 2.03458 | 0.000 | −46.0542 | −35.0950 | ||
| Zirconia | Control | 51.9983* | 2.03458 | 0.000 | 46.5187 | 57.4778 | |
| Titanium | 9.3648* | 2.03458 | 0.000 | 3.8853 | 14.8444 | ||
| Aluminum | 11.4237* | 2.03458 | 0.000 | 5.9441 | 16.9032 | ||
| Titanium | Control | 42.6334* | 2.03458 | 0.000 | 37.1538 | 48.1130 | |
| Zirconia | −9.3648* | 2.03458 | 0.000 | −14.8444 | −3.8853 | ||
| Aluminum | 2.0588 | 2.03458 | 0.744 | −3.4208 | 7.5384 | ||
| Aluminum | Control | 40.5746* | 2.03458 | 0.000 | 35.0950 | 46.0542 | |
| Zirconia | −11.4237* | 2.03458 | 0.000 | −16.9032 | −5.9441 | ||
| Titanium | −2.0588 | 2.03458 | 0.744 | −7.5384 | 3.4208 | ||
| Distilled water | Control | Zirconia | −54.8438* | 2.79819 | 0.000 | −62.3799 | −47.3076 |
| Titanium | −42.8297* | 2.79819 | 0.000 | −50.3659 | −35.2935 | ||
| Aluminum | −39.8858* | 2.79819 | 0.000 | −47.4219 | −32.3496 | ||
| Zirconia | Control | 54.8438* | 2.79819 | 0.000 | 47.3076 | 62.3799 | |
| Titanium | 12.0141* | 2.79819 | 0.001 | 4.4779 | 19.5502 | ||
| Aluminum | 14.9580* | 2.79819 | 0.000 | 7.4218 | 22.4942 | ||
| Titanium group | Control | 42.8297* | 2.79819 | 0.000 | 35.2935 | 50.3659 | |
| Zirconia | −12.0141* | 2.79819 | 0.001 | −19.5502 | −4.4779 | ||
| Aluminum | 2.9439 | 2.79819 | 0.720 | −4.5922 | 10.4801 | ||
| Aluminum | Control | 39.8858* | 2.79819 | 0.000 | 32.3496 | 47.4219 | |
| Zirconia | −14.9580* | 2.79819 | 0.000 | −22.4942 | −7.4218 | ||
| Titanium | −2.9439 | 2.79819 | 0.720 | −10.4801 | 4.5922 | ||
The error term is mean squared (error) = 39.149; *, the mean difference is significant at the 0.05 level
The surface hardness of autopolymerized provisional PMMA resin in distilled water for control, zirconia, TiO2, and Al2O3 nanoparticles groups were 28, 33.9, 32, and 30.8 VHN, respectively and in artificial saliva for control, zirconia, TiO2, and Al2O3 nanoparticles groups were 28.7, 34, 32, and 32 VHN, respectively (Table 4). The comparison of surface hardness of autopolymerized PMMA provisional resin in distilled water for 24 hours after fabrication within the groups showed the significance values were p < 0.05; hence, it is considered statistically significant (Table 5). Multiple group comparisons of the flexural strength of autopolymerized PMMA provisional resin showed that the significance values were p < 0.05, except for comparisons of 2.5% TiO2 and 2.5% Al2O3 group comparison (Table 6). Hence, it was considered statistically significant.
| Group | N | Mean | Standard deviation | Standard error | 95% confidence interval for mean | |
|---|---|---|---|---|---|---|
| Lower bound | Upper bound | |||||
| Control (24 hours of fabrication) | 10 | 28.0790 | 4.21025 | 1.33140 | 25.0672 | 31.0908 |
| Zirconia | 10 | 33.9050 | 1.83151 | 0.57917 | 32.5948 | 35.2152 |
| Titanium | 10 | 32.8750 | 2.25068 | 0.71173 | 31.2650 | 34.4850 |
| Aluminum | 10 | 30.8560 | 1.52596 | 0.48255 | 29.7644 | 31.9476 |
| Total | 40 | 31.4287 | 3.41188 | 0.53947 | 30.3376 | 32.5199 |
| Control (2 weeks) | 10 | 28.7430 | 2.78565 | 0.88090 | 26.7503 | 30.7357 |
| Zirconia | 10 | 34.2430 | 1.68361 | 0.53240 | 33.0386 | 35.4474 |
| Titanium | 10 | 32.4760 | 0.88206 | 0.27893 | 31.8450 | 33.1070 |
| Aluminum | 10 | 32.2830 | 1.15327 | 0.36469 | 31.4580 | 33.1080 |
| Total | 40 | 31.9362 | 2.64874 | 0.41880 | 31.0891 | 32.7834 |
| Source | Dependent variable | Type III sum of squares | Degree of freedom | Mean square | F | Significance |
|---|---|---|---|---|---|---|
| Corrected model | Artificial saliva | 159.295a | 3 | 53.098 | 16.721 | 0.000 |
| Distilled water | 197.723b | 3 | 65.908 | 9.258 | 0.000 | |
| Intercept | Artificial saliva | 40796.963 | 1 | 40796.963 | 12846.956 | 0.000 |
| Distilled water | 39510.653 | 1 | 39510.653 | 5550.270 | 0.000 | |
| Group | Artificial saliva | 159.295 | 3 | 53.098 | 16.721 | 0.000 |
| Distilled water | 197.723 | 3 | 65.908 | 9.258 | 0.000 | |
| Error | Artificial saliva | 114.322 | 36 | 3.176 | ||
| Distilled water | 256.273 | 36 | 7.119 | |||
| Total | Artificial saliva | 41070.580 | 40 | |||
| Distilled water | 39964.649 | 40 | ||||
| Corrected total | Artificial saliva | 273.617 | 39 | |||
| Distilled water | 453.996 | 39 |
aR squared = 0.582 (adjusted R squared = 0.547); bR squared = 0.436 (adjusted R squared = 0.388)
| Dependent variable | (I) Group | (J) Group | Mean difference (I-J) | Standard error | Significance | 95% confidence interval | |
|---|---|---|---|---|---|---|---|
| Lower bound | Upper bound | ||||||
| Artificial saliva | Control | Zirconia | −5.5000* | 0.79695 | 0.000 | −7.6464 | −3.3536 |
| Titanium | −3.7330* | 0.79695 | 0.000 | −5.8794 | −1.5866 | ||
| Aluminum | −3.5400* | 0.79695 | 0.000 | −5.6864 | −1.3936 | ||
| Zirconia | Control | 5.5000* | 0.79695 | 0.000 | 3.3536 | 7.6464 | |
| Titanium | 1.7670 | 0.79695 | 0.138 | −0.3794 | 3.9134 | ||
| Aluminum | 1.9600 | 0.79695 | 0.084 | −0.1864 | 4.1064 | ||
| Titanium | Control | 3.7330* | 0.79695 | 0.000 | 1.5866 | 5.8794 | |
| Zirconia | −1.7670 | 0.79695 | 0.138 | −3.9134 | 0.3794 | ||
| Aluminum | 0.1930 | 0.79695 | 0.995 | −1.9534 | 2.3394 | ||
| Aluminum | Control | 3.5400* | 0.79695 | 0.000 | 1.3936 | 5.6864 | |
| Zirconia | −1.9600 | 0.79695 | 0.084 | −4.1064 | 0.1864 | ||
| Titanium | −0.1930 | 0.79695 | 0.995 | −2.3394 | 1.9534 | ||
| Distilled water | Control | Zirconia | −5.8260* | 1.1932 | 0.000 | −9.0396 | −2.6124 |
| Titanium | −4.7960* | 1.1932 | 0.002 | −8.0096 | −1.5824 | ||
| Aluminum | −2.7770 | 1.1932 | 0.111 | −5.9906 | 0.4366 | ||
| Zirconia | Control | 5.8260* | 1.1932 | 0.000 | 2.6124 | 9.0396 | |
| Titanium | 1.0300 | 1.1932 | 0.824 | −2.1836 | 4.2436 | ||
| Aluminum | 3.0490 | 1.1932 | 0.068 | −0.1646 | 6.2626 | ||
| Titanium | Control | 4.7960* | 1.1932 | 0.002 | 1.5824 | 8.0096 | |
| Zirconia | −1.0300 | 1.1932 | 0.824 | −4.2436 | 2.1836 | ||
| Aluminum | 2.0190 | 1.1932 | 0.343 | −1.1946 | 5.2326 | ||
| Aluminum | Control | 2.7770 | 1.1932 | 0.111 | −0.4366 | 5.9906 | |
| Zirconia | −3.0490 | 1.1932 | 0.068 | −6.2626 | 0.1646 | ||
| Titanium | −2.0190 | 1.1932 | 0.343 | −5.2326 | 1.1946 | ||
The error term is mean squared (error) = 7.119; *, the mean difference is significant at the 0.05 level
The flexural strength of 2.5% zirconia-reinforced autopolymerized PMMA provisional resin was more than the flexural strengths of autopolymerized PMMA provisional resin control group and reinforced with 2.5% TiO2 and 2.5% Al2O3 nanoparticles. Also, the surface hardness of 2.5% zirconia-reinforced autopolymerized PMMA provisional resin was more than the flexural strengths of autopolymerized PMMA provisional resin control group and reinforced with 2.5% TiO2 and 2.5% Al2O3 nanoparticles.
SEM Analysis
Scanning electron microscope (SEM) analysis was done with a magnification of 1000×. Autopolymerized PMMA provisional resin reinforced with 2.5% zirconia nanoparticles showed reduced cracks as they were uniformly distributed, and therefore, propagation of cracks in the resin matrix was not easily possible (Fig. 4). Around 2.5% titanium nanoparticles reinforced with autopolymerized PMMA provisional resin showed voids and cracks which denotes poor binding of untreated nanoparticles with PMMA resin matrix (Fig. 5). Around 2.5% of aluminum nanoparticles reinforced with autopolymerized PMMA provisional resin showed bigger cracks which designated that 2.5% weight percent was not facilitated the flexural strength and hardness of the resin microstructure (Fig. 6).
Fig. 4: SEM image of provisional PMMA reinforced with 2.5% zirconia nanoparticles
Fig. 5 SEM image of provisional PMMA reinforced with 2.5% titania nanoparticles
Fig. 6 SEM image of provisional PMMA reinforced with 2.5% alumina nanoparticles
DISCUSSION
Provisional restorations are mandatory for patients requiring endodontic and periodontal therapy with fixed prosthetic treatment.16 The rationale for provisional treatment is to achieve esthetic and functional requirements, to prevent teeth from secondary caries, to prevent pulpal damage and dentinal sensitivity, to replace the missing teeth, to protect pontic space from the migration of adjacent abutment teeth, to preserve gingival and periodontal health of teeth, to provide self-cleansing areas by providing proper interproximal contact and covering embrasures, providing proper occlusal contact before placement of the definitive prosthesis, to verify the vertical dimension, phonetics, and masticatory function, and to assess the prognosis of questionable abutments during the treatment phase.17,18
The maintenance of these temporary restorations was difficult because they broke easily, which can lead to migration of the adjacent tooth. Hence, flexural strength is very important for any kind of removable or temporary dental prosthesis because the functional forces have a deforming effect during function which may fracture the restoration.19 The flexural strength of interim resin materials may be influenced by saliva, food components, beverages, and interactions among these materials. The purpose of storing samples in artificial saliva for 2 weeks was to partially simulate the oral environment.20-22 The most commonly used mode of evaluating the mechanical properties (flexural strength) of dental resin is the 3PB test. Wilson first used a 3PB test for brittle materials. The Knoop hardness number (microhardness test) was considered more reliable for the analysis of the relatively thin specimens of soft acrylic resins and microfilled composites. Surface hardness is used as an indicator of density, and it is therefore used to find out wear and surface deterioration of any dental materials.23
Zirconia nanoparticles possess strong ionic interatomic bonding with ceramics, acrylic, and restorative resins which showed its improvement in hardness and strength properties. Due to the inherent characteristic of the ZrO2 particles, it increases the hardness of the material by increasing the filler concentration. Mabrurkar et al.24 mentioned that reinforcement of zirconia nanoparticles had been shown to improve mechanical properties. This is due to better bonding of resin matrix with nanoparticles.
Titanium alloy has higher strength, less density, less weight, less shrinkage, good mechanical properties, is resistant to corrosion, and is biocompatible. TiO2 is used since it increases the surface hydrophobicity, reduces the adherence of biomolecules, aids in coloring, has antimicrobial properties, and improves the mechanical properties of PMMA resins.25
Due to strong ionic interatomic bonding, Al2O3 nanoparticles showed improved hardness and strength. This was due to the hexagonal phase of Al2O3, which is considered the toughest of all ceramic oxides. When Al2O3 nanoparticles dispersed in a matrix, they increased their hardness and strength. The results of the previous study supported that the addition of alumina did not facilitate the mechanical properties of denture base material.26
Safi and Ali27 concluded in his study that the incorporation of polymers, ceramics, and dental restorative resins with zirconia nanoparticles has been shown to improve mechanical properties. The bonding between nanofillers and resin matrix leads to improving the mechanical properties of resin materials. DeBoer et al.28 mentioned that TiO2 nanoparticles, when added to PMMA resin, improved the mechanical and surface properties of denture base resin as well as thermal conductivity. The incorporation of silanized TiO2 nanoparticles in provisional PMMA resin improved the surface hardness, impact strength, and transverse strength but decreased the water sorption and solubility. Harini et al.29 found that the addition of Al2O3 nanoparticles also increased the hardness and strength, which supported the results of the previous study. Asmath et al.30 reported decreased flexural strength of heat-activated PMMA resin reinforced with 5% Al2O3 nanoparticles.
According to Hasratiningsih et al.,31 56.69, 58.75, 63.86, and 60.9 MPa, were the mean flexural strength values of the control, 1, 2.5, and 5%, weight of untreated ZrO2 nanoparticles in autopolymerized provisional PMMMA resin respectively. Also, 16.07, 16.69, 17.96, and 18.5 VHN, were the mean surface hardness values of the groups with control, 1, 2.5, and 5%, of nanofiller, respectively. The addition of >2.5% by weight of untreated nanoparticles, may act as a flaw in a resin matrix. Hence it is expected to cause adverse effects on the mechanical properties of provisional PMMA resin material.
The result of previous studies showed that the flexural strength had increased with the addition of TiO2 nanoparticles. Group I without TiO2 nanoparticles had a mean of 176.06 ± 47.06 MPa, group II with 1% TiO2 nanoparticles had a mean of 182.51 ± 22.29 MPa, group III with 2% TiO2 nanoparticles had a mean of 204.75 ± 29.42 MPa, and group IV with 5% TiO2 nanoparticles had a mean of 223.43 ± 49.27 MPa. Also, the flexural strength of heat-PMMA resin was decreased after 5% reinforcement with Al2O3 nanoparticles. Hence, lower weight percentages of the filler (up to 5%) were selected for this study.32
Limitations of this study were that nanoparticles were expensive and needed special tools for mixing resin with nanoparticles. Also, the mechanical behavior of the resin depends on the form, concentrations, surface treatment, and storage media to simulate the oral environment. Hence, further clinical research is needed to get better results in the future.
CONCLUSION
Within the limitations of the present study, the authors concluded that both the flexural strength and surface hardness of 2.5% zirconia nanoparticles reinforced autopolymerized PMMA provisional resin after 24 hours of fabrication in distilled water and 2 weeks of fabrication in artificial saliva showed statistically significant results when compared to 2.5% TiO2 and 2.5% Al2O3 nanoparticles.
REFERENCES
1. Felton DA. Edentulism and comorbid factors. Tex Dent J 2010;127(4):389–401. PMID: 20446489.
2. Thakur K, Nagpal A, Gupta R, et al. Evaluation of the transverse strength of the heat cure PMMA resin reinforced with various concentrations of two different nanoparticles: an in vitro study. J Adv Med Med Res 2019;29:1–8. DOI: 10.9734/jammr/2019/v29i830116
3. Gilbert GH, Meng X, Duncan RP, et al. Incidence of tooth loss and prosthodontic dental care: effect on chewing difficulty onset, a component of oral health related quality of life. J Am Geriatr Soc 2004;52(6):880–885. DOI: 10.1111/j.1532-5415.2004.52253.x
4. Mathur S, Shah A, Makwana R, et al. Provisional restorative materials in fixed prosthodontics: a comprehensive review. B U J O D 2013;3:50–57.
5. Saisadan D, Manimaran P, Meenapriya PK. In vitro comparative evaluation of mechanical properties of temporary restorative materials used in fixed partial denture. J Pharm Bioall Sci 2016;8(Suppl 1):S105–S109. DOI: 10.4103/0975-7406.191936
6. Astudillo-Rubio D, Delgado-Gaete A, Bellot-Arcís C, et al. Correction: mechanical properties of provisional dental materials: a systematic review and meta-analysis. PLoS One 2018;13(4):e0196264. DOI: 10.1371/journal.pone.0193162
7. Debye K, Tuna T, Bishti S, et al. Influence of additional reinforcement of fixed long-term temporary restorations on fracture load. J Prosthodont Res 2018;62(4):416–421. DOI: 10.1016/j.jpor.2018.03.001
8. Burke FT, Murray MC, Shortall AC. Trends in indirect dentistry: 6. Provisional restorations, more than just a temporary. Dent Update 2005;32(8):443–452. DOI: 10.12968/denu.2005.32.8.443
9. Oleiwi JK, Hamad QA, Jabbar H. Studying the effect of natural bamboo and rice husk powders on compressive strength and hardness of acrylic resin. Iraqi J Mech Mater Eng 2019;19:105–113. DOI: 10.32852/iqjfmme.v19i1.265
10. Gad MM, Abualsaud R, Rahoma A, et al. Effect of zirconium oxide nanoparticles addition on the optical and tensile properties of polymethyl methacrylate denture base material. Int J Nanomedicine 2018;13:283–292. DOI: 10.2147/IJN.S152571
11. Saad-Eldeen MA, AL-Fallal AA, Abouelatta OB. Effect of zirconium oxide reinforcement on epithelial oral mucosa, immunoglobulin and surface roughness of complete acrylic heat-cured denture. Egypt Dent Associat 2007;53:941–946.
12. Aljafery AM. Flexural resistance and impact resistance of high-impact acrylic resin with addition of TiO2-Al2O3 nanoparticles. Nano Biomed Eng 2018;10(1):40–45. DOI: 10.5101/nbe.v10i1.p40-45
13. Sodagar A, Bahador A, Khalil S, et al. The effect of TiO2 and SiO2 nanoparticles on flexural strength of poly (methyl methacrylate) acrylic resins. J Prosthodont Res 2013;57(1):15–19. DOI:10.1016/j.jpor.2012.05.001
14. ISO 1. ISO 10477:2018(en). Dentistry-Polymer based crown and veneer materials. third edition
15. Lee HH, Lee CJ, Asaoka K. Correlation in the mechanical properties of acrylic denture base resins. Dent Mater J 2012;31(1):157–164. DOI:10.4012/dmj.2011-205
16. Patras M, Naka O, Doukoudakis S, et al. Management of provisional restorations deficiencies: a literature review. J Esthet Restor Dent 2012;24(1):26–38. DOI: 10.1111/j.1708-8240.2011.00467.x
17. Federick DR. The provisional fixed partial denture. J Prosthet Dent 1975;34(5):520–526. DOI: 10.1016/0022-3913(75)90039-6
18. Burns DR, Beck DA, Nelson SK. A review of selected dental literature on contemporary provisional fixed prosthodontic treatment: report of the Committee on Research in Fixed Prosthodontics of the Academy of Fixed Prosthodontics. J Prosthet Dent 2003;90(5):474–497. DOI:10.1016/s0022-3913(03)00259-2
19. Nejatidanesh F, Momeni G, Savabi O. Flexural strength of interim resin materials for fixed prosthodontics. J Prosthodont 2009;18(6):507–511. DOI: 10.1111/j.1532-849X.2009.00473.x
20. Akova T, Ozkomur A, Uysal H. Effect of food-simulating liquids on the mechanical properties of provisional restorative materials. Dent Mater 2006;22(12):1130–1134. DOI: 10.1016/j.dental.2005.09.009
21. Söderholm KJ, Roberts MJ. Influence of water exposure on the tensile strength of composites. J Dent Res 1990;69(12):1812–1816. DOI: 10.1177/00220345900690120501
22. Lee SY, Greener EH, Mueller HJ, et al. Effect of food and oral simulating fluids on dentine bond and composite strength. J Dent 1994;22(6):352–359. DOI: 10.1016/0300-5712(94)90088-4
23. Sun L, Gibson RF, Gordaninejad F, et al. Energy absorption capability of nanocomposites: a review. Compos Sci Technol 2009;69(14):2392–2409. DOI: https://doi.org/10.1016/j.compscitech.2009.06.020
24. Mabrurkar V, Habbu N, Hashmi SW, et al. In-vitro investigation to evaluate the flexural bond strengths of three commercially available ultra low fusing ceramic systems to Grade II Titanium. J Int Oral Health 2013;5(5):101–107. PMID: 24324312.
25. Gad MM, Fouda SM, Al-Harbi FA, et al. PMMA denture base material enhancement: a review of fiber, filler, and nanofiller addition. Int J Nanomedicine 2017;17(12):3801–3812. DOI: 10.2147/IJN.S130722
26. Hamouda IM, Beyari MM. Addition of glass fibers and titanium dioxide nanoparticles to the acrylic resin denture base material: comparative study with the conventional and high impact types. Oral Health Dent Manag 2014;13(1):107–112. PMID: 24603926.
27. Safi IN, Ali M. Evaluation the effect of modified nano-fillers addition on some properties of heat cured acrylic denture base material. J Baghdad Coll Dent 2011;23:23–29.
28. DeBoer J, Vermilyea SG, Brady RE. The effect of carbon fiber orientation on the fatigue resistance and bending properties of two denture resins. J Prosthet Dent 1984;51(1):119–121. DOI: 10.1016/s0022-3913(84)80117-1.
29. Harini P, Mohamed K, Padmanabhan TV. Effect of titanium dioxide nanoparticles on the flexural strength of polymethylmethacrylate: an in vitro study. Indian J Dent Res 2014;25(4):459–463. DOI: 10.1016/s0022-3913(84)80117-1
30. Asmath J, Ahila SC, Muthukumar B. Evaluation of flexural strength and surface hardness of heat activated provisional PMMA resin reinforced with nanoparticles-an in vitro study. J Med P’ceutical Allied Sci 2022;11:4340–4348. DOI: 10.22270/jmpas.V11I1.2171
31. Hasratiningsih Z, Takarini V, Cahyanto A, et al. Hardness evaluation of PMMA reinforced with two different calcinations temperatures of rO2-Al2O3-SiO2 filler system. IOP Conf Ser Mater Sci Eng 2017;172:012067. DOI: 10.1088/1757-899X/172/1/012067
32. Asar NV, Albayrak H, Korkmaz T, et al. Influence of various metal oxides on mechanical and physical properties of heat-cured polymethyl methacrylate denture base resins. J Adv Prosthodont 2013;5(3):241–247. DOI: 10.4047/jap.2013.5.3.241
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