Journal Information
Vol. 8. Issue 3.
Pages 2777-2785 (May - June 2019)
Share
Share
Download PDF
More article options
Visits
457
Vol. 8. Issue 3.
Pages 2777-2785 (May - June 2019)
Original Article
DOI: 10.1016/j.jmrt.2019.04.014
Open Access
Physical and mechanical properties of flowable composite incorporated with nanohybrid silica synthesised from rice husk
Visits
457
Nazrul M. Yusoffa, Yanti Joharia,b,
Corresponding author
yjohari@usm.my

Corresponding author at: School of Dental Sciences, Universiti Sains Malaysia, 16150 Kubang Kerian, Kelantan, Malaysia.
, Ismail Ab Rahmana, Dasmawati Mohamada, Mohd Fadhli Khamisa,b, Zaihan Ariffina,b, Adam Huseina,b
a School of Dental Sciences, Universiti Sains Malaysia, 16150, Kubang Kerian, Kelantan, Malaysia
b Hospital USM, Health Campus, Universiti Sains Malaysia, 16150, Kubang Kerian, Kelantan, Malaysia
This item has received
457
Visits

Under a Creative Commons license
Article information
Abstract
Full Text
Bibliography
Download PDF
Statistics
Figures (10)
Show moreShow less
Tables (2)
Table 1. Composition of all the studied FCs (NA means not available).
Table 2. Refractive indices of Bis-GMA, TEGDMA and the experimental monomer mixtures.
Show moreShow less
Abstract

This study aims to fabricate experimental flowable composites (FCs), by incorporating spherical nanohybrid silica as the filler and subsequently to evaluate their physical and mechanical properties in comparison to a commercial counterpart (Revolution Formula 2). The nanohybrid silica used in this study was synthesised from rice husk using sol–gel method and the dilution effect of Bis-GMA on the physical and mechanical properties of the experimental FCs was also investigated. Three experimental FCs (EF50B, EF45B and EF40B) were prepared by diluting the base monomer namely Bis-GMA to obtain the desired flowability. Surface roughness, surface morphology, Vickers hardness, compressive strength and compressive modulus of each group were determined. The data were statistically analysed using one-way ANOVA followed by Scheffe post hoc test. The surface roughness and Vickers hardness of the experimental FCs were comparable to Revolution Formula 2. Even though experimental FCs were inferior in compressive strength compared to Revolution Formula 2, they had passed the minimum requirement for compressive strength. The compressive modulus of experimental FCs was higher than Revolution Formula 2, but no statistically significant difference was detected except for EF50B. The dilution of the base monomer among the experimental FCs had no significant effect on their physical and mechanical strength. In conclusion, experimental FCs from rice husk had adequate physical and mechanical strength in comparison to the commercial counterpart rendering them a potential sustainable green-based product in dentistry.

Keywords:
Flowable composites
Nanohybrid silica
Rice husk
Dilution effect
Full Text
1Introduction

Flowable composite (FC) is a type of tooth-coloured restoration material with a lesser viscosity compared to other types of resin composites. The increasing interest in FC is due to its flow properties whereby it can flow into small cavities, irregularities and defects of the tooth. This criterion gives FC better handling ability, high wettability [1], good adaptation to tooth cavity [2] and low microleakage [3]. Generally, FC consists of three main components which are the monomer, filler and coupling agent [4].

Fillers that are typically incorporated in commercial FC or any other types of resin composites are silica, silicate glass (borosilicate glass, barium or lithium aluminium silicate), quartz, strontium, barium, zinc or zirconia [1]. None of these fillers are derived from bio-based materials. For example, silica and silicate glass are synthesised from chemical precursors while barium and zinc are grinded from mineral. Many researches on FC are mostly focused on improving the physical and mechanical strength of commercial FC by adding filler that are not bio-based material such as titanium dioxide nanotubes, glass fibre, zinc oxide nanoparticle and silver doped bioactive glass [5–8]. In this present study, silica from rice husk has been used to fabricate FC.

Rice husk is an agricultural biowaste that can be a good alternative source of silica [9,10]. The silica demonstrates great potential in a wide range of applications such as absorbent, coating, pigment, cement, insulator and semiconductor [11]. Bio-based materials have the advantages of being sustainable, renewable and eco-friendly that have minimal impact on the ecosystem. While many researches had been done to produce silica from rice husk, only a few were aimed as filler for dental uses [9,12–14].

In this study, new experimental FCs were fabricated from nanohybrid silica synthesised from rice husk using sol–gel method. Generally, FC is manufactured by reducing the filler content or increasing the diluent monomer [15]. The latter method is applied in this study to obtain the desired flowability of the FC by diluting bisphenol A-glycidyl methacrylate (Bis-GMA) monomer with triethylene glycol dimethacrylate (TEGDMA) monomer resulting in three experimental FCs.

To this date there are no known commercial FCs that have incorporated nanohybrid silica from rice husk in their products. Therefore, the aim of this paper is to fabricate experimental FCs by incorporating nanohybrid silica from rice husk and to evaluate their physical and mechanical properties in comparison to a commercial FC, Revolution Formula 2. Additionally, the dilution effect of the experimental FCs on their physical and mechanical properties was also studied. It is hoped that the experimental FCs utilising the nanohybrid silica from rice husk can offer a potential sustainable green-based product in dentistry.

2Materials and methods2.1Fabrication of experimental FCs

Experimental FCs from rice husk were fabricated according to the steps illustrated in Fig. 1. Bis-GMA (Esstech Inc., USA) as the base monomer was manually mixed with TEGDMA (Esstech Inc., USA) as the diluent at different mass ratio. A pilot study has been done to optimise the desired flowability in which three ratios were selected to further undergo physical and mechanical properties test. These three experimental FCs were EF50B, EF45B and EF40B which contained Bis-GMA and TEGDMA at ratio of 50:50, 45:55 and 40:60 respectively and 0.5wt.% of camphorquinone (CQ) and 2-(dimethylamino)ethyl methacrylate (DMAEMA) (Merck, Germany) were added to the mixture. Nanohybrid silica from rice husk was incrementally added and mixed thoroughly to make a homogenous paste. The nanohybrid silica was synthesised according to the step illustrated by Noushad et al. [16]. Then the paste was kept in a 1mL disposable syringe (Terumo Corporation, Tokyo, Japan) and wrapped with aluminium foil. The composition of all the studied FCs is shown in Table 1.

Fig. 1.

Flowchart for the fabrication of experimental FC.

(0.14MB).
Table 1.

Composition of all the studied FCs (NA means not available).

Type of FCs  FillerMonomer
  Type  Loading (wt.%)  Type  Loading (wt.%) 
Revolution Formula 2  Glass particle  60  NA  NA 
EF50B  48–448nm nanohybrid silica  50  Bis-GMA:TEGDMA  50:50 
EF45B  48–448nm nanohybrid silica  50  Bis-GMA:TEGDMA  45:55 
EF40B  48–448nm nanohybrid silica  50  Bis-GMA:TEGDMA  40:60 
2.2Characterisation of the nanohybrid silica

The size and morphology of the nanohybrid silica used in this study was investigated using scanning electron microscope, SEM (Quanta FEG 450, FEI) operating at 5kV under low vacuum.

2.3Specimens preparation

Cylindrical specimens (n=8 for each studied group) for surface roughness and Vickers hardness test were prepared in acrylic mould (5mm×2mm) while for compressive test, the specimens were prepared in split stainless-steel mould (4mm×6mm). Mylar strip and a glass slide were positioned on top of the specimens and a slight pressure was applied to remove the excess material. Specimens were light cured using a light curing unit (Elipar™ S10 LED, 3M ESPE, USA) at the top surface for 40s. Only for compressive test, the specimens were loaded in three 2mm incremental layer as recommended by most resin composite manufacturers and each layer was light cured for 40s. All the specimens were polished using Soflex disc. Prior to the test, specimens were immersed in 37°C distilled water for 24h.

2.4Surface roughness

The surface roughness of the specimens was measured using a two-dimensional surface profilometer (SURFCOM FLEX-50A, ACCRETECH, Japan). The cut off value, evaluation length and measure speed were set at 0.8mm, 2mm and 0.15mm/s respectively. The roughness parameter was evaluated as the arithmetic mean of the sum of roughness profile value, Ra.

2.5Surface morphology

Following surface roughness test, surface morphology of polished specimens from each group was examined using scanning electron microscope, SEM (Quanta FEG 450, FEI) operating at 5kV under low vacuum.

2.6Vickers hardness

The hardness of the specimens was tested using a Vickers hardness tester (Model VM 50, FIE, India) under 1kg load for 15s dwell time. Three indentations were made for each specimen.

2.7Compressive strength and modulus

Compressive test was conducted using a universal testing machine (AG-Xplus, SHIMADZU, Japan). The load, crosshead speed and span were set at 20kN, 1.0mm/min and 4mm respectively. The compressive strength, Sc was calculated based on the following equation:

where P is the maximum force applied and d is the diameter of the specimens in mm. The compressive modulus was determined from the slopes of a straight line fit to the initial linear portion of the stress–strain curve.

2.8Data analysis

Data were statistically analysed using IBM SPSS version 22. One-way ANOVA followed by Scheffe post hoc test were used to determine the difference in surface roughness, Vickers hardness, compressive strength and compressive modulus between the studied FCs. The significance level was set at p<0.05.

3Results and discussion3.1Characterisation of the nanohybrid silica

In this study, nanohybrid silica from rice husk was synthesised according to previous studies [14,16] and subsequently used to fabricate the experimental FCs. Fig. 2 shows the SEM image of the nanohybrid silica. The micrograph confirmed the spherical and nanohybrid properties of the silica. The size of the nanohybrid silica was between 48 and 448nm with mean and median diameter of 218±97nm and 208nm respectively. It is categorised as nanohybrid silica because it comprises of varying sizes of nano (particle in the size of 1–100nm) and micron (particle in the size of 100–1000nm) silica. Nanoparticles tend to agglutinate if their surface is not treated [17], and the agglutination may decrease the performance of the flowable composite as the particle tend to be bundles of particle in micron size instead of nanohybrid. To overcome this limitation, the nanohybrid silica used in this study was silanised using 3-(trimethoxysilyl) propyl methacrylate, γ-MPS and consequently the occurrence of nanohybrid silica particles agglomeration had been reduced as shown in the micrograph (Fig. 2). The findings on size and morphology of the nanohybrid silica in this study have been corroborated by the previous studies [14,16] indicating that simple and non-toxic technique used to obtain the nanohybrid silica is reproducible.

Fig. 2.

SEM image of the nanohybrid silica.

(0.06MB).
3.2Surface roughness

The physical and mechanical properties of the experimental FCs were evaluated to ensure that this new product is comparable to the commercial product hence offering a potential sustainable marketable product. Fig. 3 shows the surface roughness of all the studied FCs. Statistical analysis by one-way ANOVA showed that there was no significant difference in surface roughness of the experimental FCs and Revolution Formula 2 (p>0.05). The surface roughness was in the range of 0.17–0.19μm. Figs. 4(A–D) and 5(A–D) show the surface morphology of the studied FCs at low (10,000×) and high (1,00,000×) magnification respectively. All groups revealed a smooth homogenous surface texture with some matrix imperfections (Fig. 4(A–D)). All the studied FCs had surface roughness less than 0.2μm indicating that no increase in bacterial accumulation should be expected below this value [18]. In dentistry, surface roughness is a crucial aspect as it depicts aesthetic value, wear resistance and longevity of a dental restoration. Moreover, a smooth restoration provides comfort to patients. There was no occurrence of large grooves or pits due to filler plucking in experimental FCs and Revolution Formula 2 which demonstrated good filler–matrix bonding shown in Fig. 5(A–D). Grooves and pits may retain bacteria [19]. The dilution of Bis-GMA among the experimental FCs gave no significant effect on their surface roughness (p>0.05).

Fig. 3.

Surface roughness of the studied FCs.

(0.2MB).
Fig. 4.

Surface morphology of the studied FCs at low magnification (10,000×): (A) Revolution Formula 2, (B) EF50B, (C) EF45B, and (D) EF40B.

(1.17MB).
Fig. 5.

Surface morphology of the studied FCs at high magnification (1,00,000×): (A) Revolution Formula 2, (B) EF50B, (C) EF45B, and (D) EF40B.

(0.68MB).
3.3Vickers hardness

Fig. 6 shows the Vickers hardness of the studied FCs and the values were in the range of 29–31HV. Experimental FCs had slightly higher hardness than Revolution Formula 2, however one-way ANOVA revealed that there was no significant difference among them (p>0.05). During mastication process, the first part to receive biting and chewing forces is the surface of the tooth or dental restorative material. If it fails to withstand the forces, crack may occur leading to the destruction of the materials. A high hardness value depicts a good indication for a material to withstand wear and abrasion. Experimental FCs had a comparable Vickers hardness to Revolution Formula 2, although their filler loadings were 10wt.% lower than that of Revolution Formula 2. A few studies measured the Vickers hardness of several commercial FCs and they revealed that the result was in the range of 9.6–48.8HV [20], 15.8–59.9HV [21] and 25.3–55.3HV [22] respectively which were corroborated with this study. The dilution of Bis-GMA among the experimental FCs gave no significant effect on their Vickers hardness (p>0.05).

Fig. 6.

Vickers hardness of the studied FCs.

(0.2MB).
3.4Compressive strength and modulus

Fig. 7 shows the compressive strength of the studied FCs. One-way ANOVA showed that there was significant difference in compressive strength of the experimental FCs and Revolution Formula 2 (p<0.05). Experimental FCs had inferior compressive strength in comparison to the Revolution Formula 2 possibly due to some portions of the experimental FCs were partially cured. The phenomenon could be observed by the difference on the physical appearance of the experimental FCs and Revolution Formula 2 specimens after they were light cured prior to the compressive test as shown in Fig. 8(A–D). The presence of light yellowish layers instead of white layers spotted on the lateral side of the experimental FCs specimen as shown in Fig. 8(A) gave an indication of the possible partially cured sites. The yellow colour was believed to be the result of camphorquinone. On the contrary, the lateral side for Revolution Formula 2 specimen showed a homogenous colour as shown in Fig. 8(B), indicating that it was completely cured. In addition, it was also observed that the stress–strain curves for the Revolution Formula 2 and experimental FCs were different. The stress–strain curve for Revolution Formula 2 was smooth as shown in Fig. 9(A). On the other hand, the stress–strain curves for the experimental FCs as shown in Fig. 9(B–D) were stacked and the three stacked peaks may represent the partially cured site of the three incremental layers on the experimental FCs specimen. The incomplete curing in experimental FCs was caused by the scattered, absorbed and refracted visible light [23,24] due to the difference in refractive index of the nanohybrid silica and the monomers during the polymerisation process. As a result, the visible light was not sufficiently transmitted to each of the lower part of the incremental layers.

Fig. 7.

Compressive strength of the studied FCs. Asterisks indicate significant different to Revolution Formula 2.

(0.18MB).
Fig. 8.

Physical appearance of the compressive specimens prior to the compressive test. (A) and (B) are the lateral view for the experimental FCs and Revolution Formula 2 respectively. While (C) and (D) are the top view for the experimental FCs and Revolution Formula 2 respectively.

(0.13MB).
Fig. 9.

Stress–strain curves from compressive test of the studied FCs: (A) Revolution Formula 2, (B) EF50B, (C) EF45B, (D) EF40B.

(0.14MB).

Fig. 8(C) shows that the top view of the experimental FC is more whitish and opaquer compared to Revolution Formula 2 as shown in Fig. 8(D). A study found that given the difference of refractive index of the filler and monomer is high, the cured composite will appear very white with strong opacity [25]. Based on the rule of mixture, the refractive indices of the experimental monomers were calculated according to the following equation:

where nM, nB and nT are refractive index of the monomer, Bis-GMA, TEGDMA, while vB and vT are volume fraction of Bis-GMA and TEGDMA respectively. The refractive indices of the Bis-GMA and TEGDMA monomers were obtained from the manufacturer. All the values were listed in Table 2. From the calculation, the refractive indices of the experimental monomers were in the range of 1.500–1.510, much higher than the refractive index of nanohybrid silica (n=1.458–1.464) that was estimated based on a study [26].

Table 2.

Refractive indices of Bis-GMA, TEGDMA and the experimental monomer mixtures.

Monomer  Refractive index 
Bis-GMA  1.540 
TEGDMA  1.459 
50wt.% Bis-GMA:50wt.% TEGDMA (EF50B)  1.500 
45wt.% Bis-GMA:55wt.% TEGDMA (EF45B)  1.496 
40wt.% Bis-GMA:60wt.% TEGDMA (EF40B)  1.492 

Although the compressive strength of the experimental FCs was limited by the partially cured effect, we believed this shortcoming can be further improved. If the degree of curing depth can be improved, they could pose comparable or better strength as shown by the Vickers hardness results. The Vickers hardness test was performed on the top surface of the FCs where usually it is well cured [27]. Therefore, in future study and to overcome the problem it is suggested that the refractive index of the nanohybrid silica and the matrix should be matched by replacing the Bis-GMA with monomer that has closer refractive index to the nanohybrid silica for example, urethane dimethacrylate (UDMA) [28]. In addition, a dual cure experimental FCs can be another solving alternative as the lower part of the incremental layers can be polymerised chemically [29]. Unlike roughness and hardness which is a function of surface, compressive strength test revealed the bulk mechanical strength of the tested FCs where not only compression stress was involved but also tensile and shear stresses as well [30]. During mastication, the complex masticatory stresses (compressive, tensile and shear) occur throughout the whole dental restoration. Thus, a restorative material needs to be able to withstand all the aforementioned stresses. Comply within the acceptable value, the compressive strength of the experimental FCs were in the acceptable range which is within 210–300MPa [31], hence they are suitable for clinical use.

Fig. 10 shows the compressive modulus of all the studied FCs. The compressive modulus of the experimental FCs was higher than Revolution Formula 2 but no statistically significant difference was detected (p>0.05) except for EF50B. The compressive modulus depicts the stiffness or rigidity of the FCs within their elastic range. It is depended on the fundamental property of the material namely the intermolecular forces [32]. The stronger the intermolecular forces, the higher the compressive modulus value and the stiffness of the FCs. From the result, it was believed that the interaction of the intermolecular forces of the filler to filler and filler to matrix in experimental FCs was higher than Revolution Formula 2. This is possible as the spherical and nanohybrid silica in experimental FCs was ought to increase their packing density and volume fraction [33] to form a network of highly effective contact surface area as the nano silica fill the interstitial space between the micron silica [34]. Consequently, the experimental FCs were more elastic as force was transmitted and distributed evenly across the material by such interactions. The dense surface structure of experimental FCs as shown in Fig. 4(B–D) may verify their packing density. In comparison, Revolution Formula 2 has irregular shape filler as shown in Fig. 4(A) and this is supported by other findings [21,35], which may restrict its packing density. The dilution of Bis-GMA among the experimental FCs gave no significant effect on their compressive strength and modulus (p>0.05).

Fig. 10.

Compressive modulus of the studied FCs. Asterisk indicates significant different to Revolution Formula 2.

(0.2MB).
4Conclusion

Nanohybrid silica from rice husk has been used to fabricate experimental flowable composites (FCs). The experimental FCs demonstrated surface roughness and Vickers hardness comparable to Revolution Formula 2. Compressive strength test revealed that experimental FCs were inferior to Revolution Formula 2, however they have passed the minimum requirement for compressive strength. The compressive modulus of experimental FCs was higher as compared to Revolution Formula 2. The dilution of the Bis-GMA with TEGDMA among the experimental FCs did not significantly affect their physical and mechanical properties. Based on the results, the experimental FCs from rice husk can be a potential sustainable product in dentistry with acceptable physical and mechanical properties.

Conflicts of interest

The authors declare no conflicts of interest.

Acknowledgement

This work was supported by the Universiti Sains Malaysia under Research University Grant (RUI-1001/PPSG/812203).

References
[1]
A. Hervás-Garcia, M.A. Martinez-Lozano, J. Cabanes-Vila, A. Barjau-Escribano, P. Fos-Galve.
Composite resins. A review of the materials and clinical indications.
Med Oral Patol Oral Cir Bucal, 11 (2006), pp. 215-220
[2]
L.M. Petrovic, D.M. Zorica, I.L. Stojanac, V.S. Krstonosic, M.S. Hadnadjev, T.M. Atanackovic.
A model of the viscoelastic behavior of flowable resin composites prior to setting.
Dent Mater, 29 (2013), pp. 929-934
[3]
M. Sadeghi, C.D. Lynch.
The effect of flowable materials on the microleakage of class II composite restorations that extend apical to the cemento-enamel junction.
Oper Dent, 34 (2009), pp. 306-311
[4]
S.G. Pereira, R. Osorio, M. Toledano, T.G. Nunes.
Evaluation of two Bis-GMA analogues as potential monomer diluents to improve the mechanical properties of light-cured composite resins.
Dent Mater, 21 (2005), pp. 823-830
[5]
M.O. Dafar, M.W. Grol, P.B. Canham, S.J. Dixon, A.S. Rizkalla.
Reinforcement of flowable dental composites with titanium dioxide nanotubes.
Dent Mater, 32 (2016), pp. 817-826
[6]
P. Shouha, M. Swain, A. Ellakwa.
The effect of fiber aspect ratio and volume loading on the flexural properties of flowable dental composite.
Dent Mater, 30 (2014), pp. 1234-1244
[7]
S. Tavassoli Hojati, H. Alaghemand, F. Hamze, F. Ahmadian Babaki, R. Rajab-Nia, M.B. Rezvani, et al.
Antibacterial, physical and mechanical properties of flowable resin composites containing zinc oxide nanoparticles.
Dent Mater, 29 (2013), pp. 495-505
[8]
H. Kattan, X. Chatzistavrou, J. Boynton, J. Dennison, P. Yaman, P. Papagerakis.
Physical properties of an Ag-doped bioactive flowable composite resin.
Materials, 8 (2015), pp. 4668-4678
[9]
N.S.C. Zulkifli, I. Ab Rahman, D. Mohamad, A. Husein.
A green sol–gel route for the synthesis of structurally controlled silica particles from rice husk for dental composite filler.
Ceram Int, 39 (2013), pp. 4559-4567
[10]
N. Baccile, F. Babonneau, B. Thomas, T. Coradin.
Introducing ecodesign in silica sol–gel materials.
J Mater Chem, 19 (2009), pp. 8537-8559
[11]
N. Soltani, A. Bahrami, M.I. Pech-Canul, L.A. González.
Review on the physicochemical treatments of rice husk for production of advanced materials.
Chem Eng J, 264 (2015), pp. 899-935
[12]
R.A. Shiekh, V.R. Pasupuleti.
Mesoporous silica powder for dental restoration composites from rice husk: a green sol–gel synthesis.
Agricultural biomass based potential materials, pp. 245-258
[13]
N. Muhammad, S. Maitra, I. Ul Haq, M. Farooq.
Some studies on the wear resistance of artificial teeth in presence of amorphous SiO2 and TiO2 fillers.
Cerâmica, 57 (2011), pp. 324-328
[14]
M. Noushad, I. Ab Rahman, N.S. Che Zulkifli, A. Husein, D. Mohamad.
Low surface area nanosilica from an agricultural biomass for fabrication of dental nanocomposites.
Ceram Int, 40 (2014), pp. 4163-4171
[15]
K. Baroudi, A.M. Saleh, N. Silikas, D.C. Watts.
Shrinkage behaviour of flowable resin-composites related to conversion and filler-fraction.
[16]
M. Noushad, I. Ab Rahman, A. Husein, D. Mohamad.
Nanohybrid dental composite using silica from biomass waste.
Powder Technol, 299 (2016), pp. 19-25
[17]
C.R.G. Torres, H.M.C. Rêgo, L.C.C.C. Perote, L.F.T.F. Santos, M.B.B. Kamozaki, N.C. Gutierrez, et al.
A split-mouth randomized clinical trial of conventional and heavy flowable composites in class II restorations.
J Dent, 42 (2014), pp. 793-799
[18]
C.M. Bollen, P. Lambrechts, M. Quirynen.
Comparison of surface roughness of oral hard materials to the threshold surface roughness for bacterial plaque retention: a review of the literature.
Dent Mater, 13 (1997), pp. 258-269
[19]
M. Gharechahi, H. Moosavi, M. Forghani.
Effect of surface roughness and materials composition.
J Biomater Nanobiotechnol, 3 (2012), pp. 541-546
[20]
R.M. Ku, C.C. Ko, C.M. Jeong, M.G. Park, H.I. Kim, Y.H. Kwon.
Effect of flowability on the flow rate, polymerization shrinkage, and mass change of flowable composites.
Dent Mater J, 34 (2015), pp. 168-174
[21]
S. Beun, C. Bailly, J. Devaux, G. Leloup.
Physical, mechanical and rheological characterization of resin-based pit and fissure sealants compared to flowable resin composites.
Dent Mater, 28 (2012), pp. 349-359
[22]
C.-M. Jeong, Y.-J. Heo, Y.-C. Jeon, H.-I. Kim, Y.H. Kwon.
Microhardness and polymerization shrinkage of flowable resins that are light cured using a blue laser.
Lasers Med Sci, 27 (2012), pp. 729-733
[23]
F. Aloui, L. Lecamp, P. Lebaudy, F. Burel.
Relationships between refractive index change and light scattering during photopolymerization of acrylic composite formulations.
J Eur Ceram Soc, 36 (2016), pp. 1805-1809
[24]
K. Fujita, N. Nishiyama, K. Nemoto, T. Okada, T. Ikemi.
Effect of base monomer's refractive index on curing depth and polymerization conversion of photo-cured resin composites.
Dent Mater J, 24 (2005), pp. 403-408
[25]
H. Suzuki, M. Taira, K. Wakasa, M. Yamaki.
Refractive-index-adjustable fillers for visible-light-cured dental resin composites: preparation of TiO2–SiO2 glass powder by the sol–gel process.
J Dent Res, 70 (1991), pp. 883-888
[26]
K. Fujita, T. Ikemi, N. Nishiyama.
Effects of particle size of silica filler on polymerization conversion in a light-curing resin composite.
Dent Mater, 27 (2011), pp. 1079-1085
[27]
S. Bucuta, N. Ilie.
Light transmittance and micro-mechanical properties of bulk fill vs. conventional resin based composites.
Clin Oral Investig, 18 (2014), pp. 1991-2000
[28]
I. Sideridou, V. Tserki, G. Papanastasiou.
Effect of chemical structure on degree of conversion in light-cured dimethacrylate-based dental resins.
Biomaterials, 23 (2002), pp. 1819-1829
[29]
T.T. Tauböck, T. Bortolotto, W. Buchalla, T. Attin, I. Krejci.
Influence of light-curing protocols on polymerization shrinkage and shrinkage force of a dual-cured core build-up resin composite.
Eur J Oral Sci, 118 (2010), pp. 423-429
[30]
N. Ilie, T.J. Hilton, S.D. Heintze, R. Hickel, D.C. Watts, N. Silikas, et al.
Academy of dental materials guidance – resin composites: Part I – Mechanical properties.
Dent Mater, 33 (2017), pp. 880-894
[31]
R.L. Sakaguchi.
Chapter 9: restorative materials-composites and polymers.
Craigs's restorative dental materials, 13th ed., pp. 176
[32]
C.S. Pfeifer.
Chapter 4: fundamentals of materials science.
Craig's restorative dental materials, 13th ed., pp. 40
[33]
K. Masouras, N. Silikas, D.C. Watts.
Correlation of filler content and elastic properties of resin-composites.
Dent Mater, 24 (2008), pp. 932-939
[34]
H. Wang, M. Zhu, Y. Li, Q. Zhang, H. Wang.
Mechanical properties of dental resin composites by co-filling diatomite and nanosized silica particles.
Mater Sci Eng C, 31 (2011), pp. 600-605
[35]
S. Beun, C. Bailly, J. Devaux, G. Leloup.
Rheological properties of flowable resin composites and pit and fissure sealants.
Dent Mater, 24 (2008), pp. 548-555
Copyright © 2019. Brazilian Metallurgical, Materials and Mining Association
Journal of Materials Research and Technology

Subscribe to our newsletter

Article options
Tools
Cookies policy
To improve our services and products, we use cookies (own or third parties authorized) to show advertising related to client preferences through the analyses of navigation customer behavior. Continuing navigation will be considered as acceptance of this use. You can change the settings or obtain more information by clicking here.