Production method of titanium dioxide nanotubes reinforced glass ionomer cements

Abstract

The invention relates to the production method of titanium dioxide nanotubes reinforced glass ionomer cements.

Description

[0001] PRODUCTION METHOD OF TITANIUM DIOXIDE NANOTUBES REINFORCED GLASS IONOMER CEMENTS

[0002] Technical Field

[0003] The invention relates to the production method of titanium dioxide nanotubes reinforced glass ionomer cements.

[0004] State of the Art

[0005] Glass ionomer cements (GICs) were first introduced to dentistry in 1972. Their adhesive and fluoride-releasing properties have led to their widespread use as cavity liner and base material, and restorative materials. In addition, the coefficient of thermal expansion for GICs is close to that of the tooth structure and is considered biocompatible with low cytotoxicity. Although GICs are often used as restorative materials, they cannot withstand the forces that usually occur in the posterior region of the mouth due to their lower mechanical properties, especially lower fracture toughness. Consequently, GIC restorative materials are recommended for anterior restorations where stress is lower in these areas of the mouth. Since the invention of GIC, significant advances have occured to improve their performance, and their physical properties and enable them to be used as restorative materials in posterior regions A variety of filler components have been added, including montmorillonite clay, zirconia, glass fibers, hydroxyapatite (HA), bioactive glass particles, and casein phosphopeptide-amorphous calcium phosphate (CPP-ACP).

[0006] Some attempts to add substances related to metabolic activity or prevention the dental plaque adhesion to GICs have been reported in the literature. The additives must not compromise the basic mechanical properties of GIC materials. The use of nanoparticles has become an important field of research in dentistry. The addition of HA and fluorapatite nanobioceramics to conventional GIC cements has been shown to improve their mechanical properties and bond strength between GIC and dentin. On the other hand, the addition of ytterbium fluoride and barium sulfate nanoparticles to GIC cement significantly reduced the 24-hour compressive strength and surface hardness. In the literature, titanium dioxide (TiO2) nanoparticles are reported to be used as additive materials for dental resin composites and epoxy. As an inorganic additive, TiO2 has many promising properties due to chemically stable. Descriptions of the Figures

[0007] Figure 1. SEM image of TiCh nanotubes

[0008] Figure 2. TEM image of TiCh nanotubes

[0009] Figure 3. TEM image of TiCh nanotubes

[0010] Figure 4: Flow chart of synthesis method

[0011] Figure 5: Flow chart of functionalization method

[0012] Figure 6. XRD spectrum of TiCh nanotubes

[0013] Figure 7. XRD spectrum of functionalized TiCh nanotubes

[0014] Figure 8. FT-IR spectrum of TiCF nanotubes

[0015] Figure 9. FT-IR spectrum of functionalized TiCh nanotubes

[0016] Figure 10. BET analysis results of TiCh nanotubes

[0017] Figure 11. BET analysis results of functionalized TiCh nanotubes

[0018] Figure 12: Representative SEM images after flexural properties test from a) to i), respectively 0,l,2,3,4,lf-2f,3f,4f

[0019] Figure 13.: Representative SEM images after fracture toughness test from a)to i), 0,l,2,3,4,lf-2f,3 respectively

[0020] Detailed Description of the Invention

[0021] The invention relates to titanium dioxide nanotubes reinforced glass ionomer cements (GIC) which are developed to overcome microleakage and secondary caries problems and their production method. Since those aforementioned problems cannot be solved by existing restorative materials.

[0022] Synthesis of TiCh nanotubes

[0023] TiCh nanotubes were synthesized by reaction of TiCh nanoparticles in sodium hydroxide (NaOH) solution with hydrothermal method principles. Synthesis was carried out in the form of mixing at a process temperature of 110°C. The nanomaterials synthesized at the end of the synthesis period were washed with distilled water until pH=7, and the TiCh nanotubes obtained after the washing process were dried with an oven / drying oven around 90°C. The dried nanotubes were baked at 600°C for 2 hours to obtain a mixed crystal structure of anatase and rutile. The synthesis methodology described above is shown in Figure 4.

[0024] SEM and TEM analyses were carried out to examine the morphological and dimensional properties of the synthesized TiCh nanotubes. As shown in the figures given in Figures 1, 2 and 3, the synthesized TiCh nanotubes have an average length of 100 nm and a diameter of 15 nm, although they are morphologically and dimensionally close. The unique appearance of the layered structure of nanotubes can also be seen from the TEM images in Figure 3. Morphological and dimensional verification characterizations of the obtained nanotubes were carried out with high resolution scanning electron microscopy (SEM). In order to determine the specific surface areas of nanotubes, Specific Surface Area obtained by multipoint Brunauer-Emmett-Teller (BET) adsorption test was examined and the determination of the surface area-related properties of the reinforcement material and the relationship between the matrix and the reinforcement material was evaluated. After determining that the synthesized TiCh nanotubes reached the desired morphological properties, detailed dimensional measurements were carried out by transmission electron microscopy (TEM) analysis. Within the scope of the study, nanotubes below 50 nm diameter were synthesized in order to decrease below 100 nm outer diameter measurements and to improve mechanical properties in the desired direction. SEM (Figure 1) and TEM images (Figures 2 and 3) of the obtained TiCh nanotubes were taken.

[0025] Functionalization of Synthesized TiCh Nanotubes

[0026] In addition to improving the homogeneous distribution of the obtained TiCh nanotubes in GIC, a chemical functionalization process was applied to the nanotubes in order to ensure a successful interface with the matrix material. The functionalization process was carried out chemically by adding methacrylic acid (MA) after homogeneously dispersing the synthesized TiCh nanotubes in 2-propanol. The synthesis product obtained for pH neutralization was washed with distilled water and the obtained functional TiCF nanotubes were dried with an oven / drying oven at 45°C. A flowchart of the methodology followed in functionalization is given in Figure 5.

[0027] After functionalization processes, it was determined whether the necessary functional groups were obtained or not by FT-IR spectroscopy method. Specific surface area of functionalized TiCh nanotubes were also examined by multipoint BET test.

[0028] XRD and FT-IR characterizations of synthesized and functionalized TiCh nanotube groups were made separately. The nanotubes obtained after synthesis were called TiCh-NT, and the nanotubes applied functionalization were called TiCh-NT-F. The XRD spectra of both groups of nanotubes are provided in Figures 6 and 7, and the FT-IR spectra are provided in Figures 8 and 9. According to the XRD spectra, the mixed crystal structure of anatase and rutile were provided after calcination, and this structure was preserved after functionalization. As a result of functionalization according to FT-IR spectra, carbon-carbon and carbon-oxygen bonds are observed, unlike TiCh nanotubes obtained from synthesis.

[0029] In order to show the effect of functionalization on the specific surface area of the synthesized nanotubes, BET analyzes were performed for both normal TiCh nanotubes and functionalized TiC>2 nanotubes.

[0030] BET analysis is frequently used to measure the gas adsorption tendency of powders, thus calculating the specific surface areas of the analyzed powders. The BET results for both normal TiCh nanotubes and functionalized TiCh nanotubes are given in Figures 10 and 11 in terms of adsorption equal temperature curves that vary depending on the relative pressure during the test. The curves are used to calculate the specific surface area for each nanotube group. According to the test results, the specific surface area of normal TiCF nanotubes was calculated as 20.764 m2 / g, whereas it was calculated as 29.008 m2 / g for functionalized TiCh nanotubes. As a result of functionalization, the specific surface area was increased by 39.7%. That improvement allows the synthesized TiCh nanotubes to reflect their properties to the material better when used as a nanocomposite supplement, which is confirmed by the improvement in mechanical properties.

[0031] Preparation of TiCh Nanotube reinforced GIC material

[0032] First of all, 5 different groups were formed by using TiCF nanotubes such as without acrylicbased radicalfunctionalization and reinforced with 0.1%, 0.5%, 1% and 2% by weight. Then, 4 different functional TiCh nanotube reinforced groups were prepared by using functionalized TiCh nanotubes by binding acrylic-based groups. TiCh nanotube dosing and mixing processes were carried out in a completely dark room under heat and light conditions that prevent polymerization. It was continued mechanically and ultrasonically until an ideal homogeneous distribution was achieved in macro and micro dimensions. Ideal homogeneous distribution; TiCh nanotubes are evenly distributed in the glass ionomer cement, and the absence of any visible TiCh nanotube agglomerate lump is an indicator of the homogeneous distribution condition. It was checked by visual inspection eye and electron microscope images after curing that the precipitation status did not occur

[0033] A total of 9 groups of conventional glass ionomers containing TiCF and functionalized TiCF (f-TiCh) nanotubes in different ratios (0.1%, 0.5%, 1% and 2% by weight) are as follows. Group IMO: Glass ionomer cement (unreinforced)

[0034] Group IM1: wt. 0.1% TiO2 nanotube + glass ionomer cement

[0035] Group IM2: wt. 0.5% TiO2 nanotube + glass ionomer cement Group IM3: wt. 1% TiCh nanotube + glass ionomer cement

[0036] Group IM4: wt. 2% TiCh nanotube + glass ionomer cement

[0037] Group IMlf: wt. 0.1% f-TiCF nanotube + glass ionomer cement

[0038] Group IM2f: wt. 0.5% f-TiCF nanotube + glass ionomer cement

[0039] Group IM3f: wt. 1% f-TiCh nanotube + glass ionomer cement Group IM4f: wt. 2% f-TiCh nanotube + glass ionomer cement

[0040] In a preferred application, lonofil Molar (Voco GmBh, Germany) brand product was used as glass ionomer cement. In accordance with the manufacturer's instructions, the powder / liquid ratio was adjusted to 4 / 1 by weight using a precision scale. Then, the powder and liquid of the glass ionomer cement at this ratio were mixed and samples were prepared for three-point flexural test, surface roughness tests, fracture toughness and microhardness tests.

[0041] Flexural strength test (Three-point flexural test)

[0042] A rectangular standard metal mold (2 mm width x 2 mm thickness x 25 mm length) prepared in accordance with ISO 4049 standards was used for the flexural strength test. A total of 90 samples were prepared with 10 samples in each group. In order to create a flat surface on the lower and upper surfaces of the samples, glass slides and transparent polyester matrix stripswere placed and GICs were applied into the molds. Then, it was kept in distilled water at 37°C for 24 hours. Then, it was placed in the Universal test device (AGS-X, Shimadzu Corp., Japan) and subjected to a three-point flexural test. Force was applied to the samples whose midpoint was determined by using a digital micrometer, with a angle of 90°. Loading was performed until the fracture occurred in the samples and the maximum force values causing the fracture were determined. Statistical analysis of the data was performed. The fracture surface of the samples (9 samples in total), which showed the closest value to the average data obtained from flexural strength test for each group, was examined under a scanning electron microscope (SEM, Thermo Fisher Scientific, Phenom XL, Netherlands).

[0043] Table 1 - Mean flexural strength values and standard deviations (Mpa) obtained by the three- point flexural test.

[0044] Different superscript small letters indicate the significant differences in the same column

[0045] (p<0.05)

[0046] Table 1 shows the mean flexural strength values and standard deviations obtained by the three-point flexural test.

[0047] When the non-functionalized TiCh reinforced groups were compared, the group to which 2% TiC>2 was added (Group IM4) showed statistically lower mean flexural strength than the control group. The mean flexural strength values of the other non-functionalized TiCh- reinforced groups showed statistically similar values to the unreinforced group (control). There were no significant differences between the non-functionalized groups in terms of mean flexural strength.

[0048] When the functionalized Ti Ch-reinforced groups were compared, the mean flexural strength values of all reinforced groups showed statistically similar flexural strength values to the unreinforced group (control). In addition, the mean flexural strength values of all functionalized TiCh-reinforced groups showed statistically similar values.

[0049] When evaluated according to the presence of functionalization, in the groups where 1% and 2% TiCh were added, the functionalized group showed a statistically higher flexural strength value compared to the non-functionalized group.

[0050] Table 2 - Mean elasticity modulus values and standard deviations (GPa) obtained by the three-point flexural test)

[0051] *Different superscript small letters indicate the significant differences in the same column (p<0.05) Table 2 shows the mean elasticity modulus values and standard deviations obtained by the three-point flexural test.

[0052] When the non-functionalized TiCh-reinforced groups were compared, the group that added 0.1% TiC>2 (Group IM1) showed a statistically lower mean elasticity modulus than the control group. The mean elasticity modulus values of the other non-functionalized TiCh-reinforced groups showed statistically similar values to the unreinforced group (control). There were no significant differences between the non-functionalized groups in terms of mean elasticity modulus values.

[0053] When the functionalized TiCh-reinforced groups were compared, the group to which 0.5% TiC>2 was added (Group IM2f) showed a statistically lower mean elasticity modulus than the control group. The mean elasticity modulus values of the other functionalized TiCh-reinforced groups showed a statistically similar elasticity modulus to the control group. In addition, there were no significant differences in terms of mean elasticity modulus values of all functionalized Ti Ch-reinforced groups.

[0054] When evaluated according to the presence of functionalization, statistically similar elasticity modulus values were determined between the non-functionalized group and the functionalized group.

[0055] Since the samples used in the study were brittle materials, the resilience calculation approach used presented very realistic values.

[0056] Table 3 - Mean resilience modulus values and standard deviations obtained by the three-point flexural test

[0057] *Different superscript small letters indicate the significant differences in the same column (p<0.05) Table 3 shows the mean resilience modulus values and standard deviations obtained by the three-point flexural test.

[0058] When the non-functionalized TiCh-reinforced groups were compared, the group with 2% TiCb addition (Group IM4) showed statistically higher mean resilience modulus values than the control group. The mean resilience modulus values of the other non-functionalized TiCh- reinforced groups showed statistically similar values to the unreinforced group (control). Group IM4 showed statistically higher mean resilience modulus values than the other non- functionalized groups.

[0059] When the functionalized TiCh-reinforced groups were compared, the mean resilience modulus values of all reinforced groups showed statistically similar elasticity modulus values to the unreinforced group (control). In addition, the mean modulus elasticity values of all functionalized TiCb-reinforced groups showed statistically similar values.

[0060] When evaluated according to the presence of functionalization, in the groups where 1% TiCh was added, the functionalized group showed a statistically higher resilience modulus value compared to the non-functionalized group. In the groups where 2% TiCh was added, the functionalized group showed a statistically lower resilience modulus value compared to the non-functionalized group.

[0061] SEM images taken from the fracture surfaces of the samples after flexural strength tests are given below. While all of the samples exhibited brittle fracture, porosities caused by the production method were encountered throughout the sample. (Figure 12)

[0062] Fracture toughness test

[0063] For the fracture toughness test, samples were prepared according to ISO 20795-2 standards using a standard metal mold (2.5 mm x 5 mm x 25 mm3). A total of 90 samples were prepared with 10 samples in each group. In order to create a flat surface on the lower and upper surfaces of the samples, glass slides and transparent polyester matrix strips were placed and GICs were applied into the molds. Then, it was kept in distilled water at 37°C for 24 hours. The samples were placed in the Universal test device and tested at a speed of 1 mm / min, as in the three-point flexural test. Fracture toughness can be calculated using the following formulas:

[0064] Statistical analysis of the data was performed. The fractured surface of the sample (9 samples in total), which showed the closest value to the average data obtained from the fracture toughness test for each group, was examined under a scanning electron microscope (SEM, Thermo Fisher Scientific, Phenom XL, Netherlands). (Figure 13)

[0065] Table 4 - Mean fracture toughness values and standard deviations (units)

[0066] *Different superscript small letters indicate the significant differences in the same column (p<0.05)

[0067] Table 4 shows the mean fracture toughness values and standard deviations.

[0068] When non-functionalized TiCh-reinforced groups were compared, the group to which 1% Ti O2 was added (Group IM3) showed statistically lower mean fracture toughness values than the control group. The mean fracture toughness values of the other non-functionalized TiCb- reinforced groups showed statistically similar values to the unreinforced group (control). Group IM3 showed statistically lower mean fracture toughness values than the group that added 0.1% TiCh (Group IM1).

[0069] When functionalized TiCh-reinforced groups were compared, the functionalized 0.1% TiCh- added group (Group IMlf) showed statistically lower mean fracture toughness values than the unreinforced group (control). The mean fracture toughness values of the other functionalized TiCb-reinforced groups showed statistically similar values to the unreinforced group (control). The mean fracture toughness values of all reinforced groups showed statistically similar values. When evaluated according to the presence of functionalization, in the groups where 0.5% and 1% TiCb were added, the functionalized groups showed a statistically higher fracture toughness value compared to the non-functionalized group.

[0070] SEM images taken from the fracture toughness samples are given below. All of the samples exhibit brittle fracture, and the fracture surfaces of the samples reinforced with a functionalized TiCh nanotube have less void apperance. (Figure 13)

[0071] Vickers microhardness measurement

[0072] Teflon molds with a diameter of 5 mm and a height of 2 mm will be used for microhardness measurement. A total of 90 samples were prepared with 10 samples in each group. Samples were stored in a 100% humid environment at 37°C for 24 hours. Microhardness measurements were made from the upper surfaces of each sample using a microhardness tester (HMV Microhardness, Shimadzu, Japan) with an application time of 10 seconds and a load of 200 g. 5 measurements were made from the upper surfaces of each sample and their mean value was calculated. Statistical analysis of the data was performed.

[0073] Table 5- Mean Vickers microhardness values and standard deviations

[0074] *Different superscript small letters indicate the significant differences in the same column (p<0.05)

[0075] Table 5 shows the Vickers microhardness values and standard deviations.

[0076] When the non-functionalized TiCh-reinforced groups were compared, the mean microhardness values of all non-functionalized TiCh-reinforced groups were statistically similar to the non-functionalized group (control). In addition, there were no statistically significant differences between the non-functionalized TiCh-reinforced groups in terms of mean microhardness values. When the functionalized TiCh-reinforced groups were compared, the mean microhardness values of all reinforced groups showed statistically similar values to the unreinforced group (control). In addition, there were no statistically significant differences between all functionalized TiCh-reinforced groups in terms of mean microhardness values.

[0077] When evaluated according to the presence of functionalization, in the groups where 0.5% TiCb was added, the functionalized group showed a statistically lower microhardness value compared to the non-functionalized group.

[0078] Measurement of surface roughness with 3D profilometer module

[0079] For surface roughness analysis, 27 samples were prepared using Teflon molds (5mmx2mm), with 3 samples in each group. Samples were stored at 100% humidity at 37°C for 24 hours. Surface roughness analysis was performed with 3D Profilometer or Desktop type SEM (Thermo Fisher Scientific, Phenom XL, Netherlands) in Yildiz Technical University Laboratory. The 3D profilometer module used has a fast and contactless scanning feature and can be measured at a resolution below 14nm. The measurements were carried out randomly in 4 different directions on the surface to be examined for each sample. The Ra, Rz and Sa values defined in the general information are measured by each unit's own equation. In order to obtain more comprehensive mean values for the overall surface, roughness measurements were taken in different radial directions on the sample surface. Statistical analysis of the data was performed. A 3D optical profilometer was performed for one sample from each group, which gave close to the mean value. 3D optical profilometry was carried out with the "Roughness Reconstruction" module used with the SEM used in the study.

[0080] For surface roughness analysis with a mechanical (contact) profilometer, 90 samples were prepared using Teflon molds (5mmx2mm), with 10 samples in each group. From the upper surface of each sample, measurements were made from 5 different places. With the contact profilometer device (MarSurf PSI; Mahr GmbH, Gottingen, Germany), Lt = 1.75 mm, Lc = 0.25 were measured using a diamond tip. Selecting the Lt and Lc values for such small samples allows more accurate roughness values to be obtained as it reduces the sample distances. The mean of these values was calculated (Ra, pm). Statistical analysis of the data was performed. Table 6 - Mean surface roughness values and standard deviations (Ra, gm) obtained by mechanical profilometer.

[0081] * Different superscript small letters indicate the significant differences in the same column (p<0.05)

[0082] Table 6 shows the mean surface roughness values and standard deviations obtained with the mechanic profilometer. The surface roughness values of all non-functionalized TiCh- reinforced groups showed statistically similar to the unreinforced group (control). In addition, the surface roughness values of all non-functionalized TiCh-reinforced groups showed statistically similar values.

[0083] The surface roughness values of all functionalized Ti Ch-reinforced groups showed a statistically higher than the unreinforced group (control). In addition, the surface roughness values of all functionalized TiCh-reinforced groups showed statistically similar.

[0084] When evaluated according to the presence of functionalization, in the groups where 0.1% TiCh was added, the functionalized groups showed a statistically higher surface roughness value compared to the non-functionalized group.

[0085] Table 7 - Mean surface roughness values and standard deviations obtained by 3D profilometer (SEM) are shown. *Different superscript small letters indicate the significant differences in the same column (p<O.O5)

[0086] Table 7 shows the mean surface roughness values and standard deviations obtained by optical profilometer (SEM).

[0087] When the non-functionalized TiCh-reinforced groups were compared, the surface roughness values of the non-functionalized 1% (Group IM3) and 2% TiCh-reinforced groups (Group IM4) showed statistically higher compared to the non-functionalized group (control). In addition, these groups showed a statistically lower surface roughness compared to other non- functionalized TiCh-reinforced groups. The 2% TiCh-reinforced group (Group IM4) showed statistically higher surface roughness compared to the 1% TiCh-reinforced group (Group IM3).

[0088] When the functionalized TiCh-reinforced groups were compared, the surface roughness values of the 0.5% (Group IM2f), %1 (Group IM3f) and 2% TiCb (Group IM4f) reinforced groups showed statistically lower surface roughness compared to the unreinforced group (control). The surface roughness values of the 0.1% TiCh-reinforced group (Group IMlf) showed statistically higher surface roughness compared to the other reinforced groups.

[0089] When evaluated according to the presence of functionalization, in the groups where 0.5% and 2% Ti O2 were added, the functionalized groups showed statistically lower surface roughness values compared to the non-functionalized groups.

Claims

CLAIMS1. A glass ionomer cement characterized in comprising functionalized titanium dioxide nanotubes.

2. A production method of titanium dioxide nanotube reinforced glass ionomer cements, characterized comprising steps of a. Homogeneously dispersing titanium dioxide nanotubes in 2-propanol b. Adding methacrylic acid (MA) and mixing c. Mixing the obtained functionalized TiCh nanotubes with glass ionomer cement.

3. A method according to claim 2, characterized in comprising steps of a. Homogeneously dispersing 1.2g titanium dioxide nanotubes in 24mL 2- propanol by ultrasonic mixing b. Adding 14.4 mL methacrylic acid (MA) and mixing at 30°C for 2 hours c. Mixing the obtained functionalized titanium dioxide nanotubes with glass ionomer cement.

4. A method according to claim 3, characterized in that, in the step of mixing the obtained functionalized titanium dioxide nanotubes with glass ionomer cement, 0.1%, 0.5%, 1% or 2% of the total weight is functionalized TiCh.

5. A glass ionomer cement according to claim 1, characterized in comprising functionalized titanium dioxide nanotubes by weight of 0.1%, 0.5%, 1% or 2%

Images