Research Article Characterization of Morphology and...

Research ArticleCharacterization of Morphology and Composition ofInorganic Fillers in Dental Alginates

Ricardo Danil Guiraldo,1 Sandrine Bittencourt Berger,1 Rafael Leonardo Xediek Consani,2

Simonides Consani,3 Rodrigo Varella de Carvalho,1 Murilo Baena Lopes,1

Luciana Lira Meneghel,1 Fabiane Borges da Silva,1 and Mário Alexandre Coelho Sinhoreti3

1 Department of Restorative Dentistry, School of Dentistry, University North of Parana (UNOPAR), Rua Marselha 183,86041-140 Londrina, PR, Brazil

2 Department of Prosthodontics and Periodontics, Piracicaba Dental School, State University of Campinas (UNICAMP),Avenida Limeira 901, 13414-903 Piracicaba, SP, Brazil

3 Department of Restorative Dentistry, Piracicaba Dental School, State University of Campinas (UNICAMP), Avenida Limeira 901,13414-903 Piracicaba, SP, Brazil

Correspondence should be addressed to Ricardo Danil Guiraldo; [email protected]

Received 22 February 2014; Revised 27 June 2014; Accepted 14 July 2014; Published 24 July 2014

Academic Editor: Konstantinos Michalakis

Copyright © 2014 Ricardo Danil Guiraldo et al.This is an open access article distributed under the Creative Commons AttributionLicense, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properlycited.

Energy dispersive X-ray spectroscopy microanalysis (EDX), scanning electron microscopy (SEM), and Archimedes’ Principlewere used to determine the characteristics of inorganic filler particles in five dental alginates, including Cavex ColorChange (C),Hydrogum 5 (H5), Hydrogum (H), Orthoprint (O), and Jeltrate Plus (JP). The different alginate powders (0.5mg) were fixed onplastic stubs (𝑛 = 5) and sputter coated with carbon for EDX analysis, then coated with gold, and observed using SEM. Volumefractions were determined by weighing a sample of each material in water before and after calcining at 450∘C for 3 h. The alginatematerials were mainly composed of silicon (Si) by weight (C—81.59%, H—79.89%, O—78.87%, H5—77.95%, JP—66.88%, wt).The filler fractions in volume (vt) were as follows: H5—84.85%, JP—74.76%, H—70.03%, O—68.31%, and C—56.10%. The testedmaterials demonstrated important differences in the inorganic elemental composition, filler fraction, and particle morphology.

1. Introduction

Alginate impressionmaterials are commonly used formakingdiagnostic and working casts due to their ease of use, low cost[1], and good patient acceptance [2]. Many factors influencethe ultimate success of prostheses, including the settingcharacteristics [2, 3], the rheological properties after setting[4], and compatibility with dental stones [1, 5]. Alginatesare a two-component molding system in which a powderedmaterial is mixed with water.The powder contains sodium orpotassium alginate (soluble alginate), a diatomaceous earthfiller, calcium sulfate as a reactant, fluoride as an accelerator,and sodium phosphate as a retarder [6]. Excellent surfacedetail reproduction and dimensional accuracy are necessaryto produce a true copy of an anatomical structure, and these

properties are commonly used to analyze the performance ofimpression materials [7].

Although the hydrophilic nature of irreversible hydrocol-loids is valuable for making impressions in moist environ-ments, this characteristic also limits their use. Irreversiblehydrocolloids are affected by syneresis and imbibition, andstone casts must therefore be fabricated as soon as pos-sible to avoid dimensional changes. The effects of storageon the dimensional accuracy and deformation of gypsumcasts formed from alginate impressions have previouslybeen described, with one study reporting that dimensionalchanges in alginate impressions varied between brands [8].Impressions are generally filledwith dental gypsumas quicklyas possible to avoid long exposure to air and the resultingsyneresis and evaporation. If immediate pouring is not

Hindawi Publishing CorporationBioMed Research InternationalVolume 2014, Article ID 178064, 6 pageshttp://dx.doi.org/10.1155/2014/178064

2 BioMed Research International

possible, it is recommended that the impression be keptin a 100% relative humidity environment to preserve thewater balance within the material. Alginate manufacturerstypically recommend that models be poured within 12 hoursbecause an increased dimensional change occurs after 12–24hours [9]. It was found that storage for up to 3 hours afterthe impressions were sprayed with the disinfectant resultedin less than 24𝜇m change; therefore, no deformation wasobserved in the casts [10]. However, manufacturers (CavexHolland BV and Zhermack) claim that their alginates (CavexColorChange and Hydrogum 5, resp.) may remain stable for5 days without any change in their properties.

Therefore, the purpose of this study was to investigatewhether there are differences in the inorganic compositionof filler particles in several dental alginate formulations byenergy dispersive X-ray spectroscopy microanalysis (EDX).In addition, the filler particles morphology/size were deter-mined using scanning electron microscopy (SEM) and thefiller fraction of commercial alginates was investigated byArchimedes’ Principle. The null hypotheses tested were thatthere is no difference in (1) composition, (2) filler particlemorphology/size, or (3) filler content among dental alginatematerials.

2. Materials and Methods

Thealginate impressionmaterials Cavex ColorChange (batchnumber 100221, Cavex Holland BV, Haartem, The Nether-lands), Hydrogum 5 (batch number C302070, Zhermack,Badia Polesine, RO, Italy), Hydrogum (batch number 116304,Zhermack, Badia Polesine, RO, Italy), Orthoprint (batchnumber 118190, Zhermack, Badia Polesine, RO, Italy), and Jel-trate Plus (batch number 420010C, Dentsply Caulk, Milford,DE, USA) were used in this study.

2.1. Inorganic Composition. Alginate powder amounts of0.5mgwere used from eachmaterial (𝑛 = 5), according to theprevious study [6].The alginate powders were fixed in plasticstubs, sputter coated with carbon (MED 010, Balzers, Balzer,Liechtenstein) to eliminate the charging effects. After that,the samples were observed by scanning electron microscope(SEM)/energy dispersive X-ray analysis (EDX).

The EDX was used to detect the main inorganic compo-nents of the tested materials. Specimens were identified byusing a SEM operating with a Vantage System (Noran Instru-ments, Middleton, WI). The spectra for EDX measurementswere obtained for 100 s livetime (voltage: 15 kV; dead time 20–25%; working distance: 20mm) [11].

2.2. Filler Morphology and Size. Following the EDX analysis,the samples were coated with gold/palladium under highvacuum (SCD 050, Bal-tec AG, Liechtenstein) and placed ina JSM5600 SEM system (JEOL Ltd., Tokyo, Japan). Imagesof the filler particles in each alginate material were obtainedat 1200x magnification (voltage: 15 kV; beam width: 25–30 nm; working distance: 10–15mm) [11]. The SEM imageswere imported and analyzed using an image-analysis system(ImageJ 1.41;WayneRasband,National of Institutes ofHealth,

Bethesda, MD, USA). At least 20 particles of each materialwere analyzed during this procedure to determine the maxi-mum,minimum, andmean particle diameter inmicrometers(𝜇m).

2.3. Volumetric Filler Fraction. The percentage of inorganicparticles by volume was determined by calculating the dif-ference between the mass of each material tested in air andin water (Archimedes’ Principle) [12]. The materials weremanipulated according to the manufacturers’ instructionsand placed in an aluminum matrix to produce cylindricalspecimens (12mm diameter, 20mm high) of each material.These specimens were weighed in an analytical balance (JK180, Chyo Balance Corp., Tokyo, Japan) with an accuracyof 0.0001 g (𝑛 = 5), according to a previous study [6]. Thedried mass (Md) of the material after the setting time wasdetermined in the air. To determine the wet mass (Mi), arecipient and a stainless steel mesh were placed over thebalance plate and filled with distilled water, and the specimenwas immersed. The volume of the specimen after the settingtime was measured according to the following Equation (1)[6]:

Vs = Md −Mi. (1)

The specimens were then calcined in an oven (BravacLtda, Sao Paulo, SP, Brazil) to remove the organic con-stituents. The temperature was gradually increased fromroom temperature for 1.5 hours to reach 450∘C and main-tained at this temperature for 3 hours [6]. The remaininginorganic material was intact and pill shaped.Themass in air(Mp) was then measured as described above. To determinethe wet mass of the particles (Mpi), the specimens wereimmersed in distilled water as described above, and at thistime, the pill shape was disarranged because of its contactwith the water. The volume of the inorganic particles wasmeasured according to the following equation [6]:

Vp = Mp −Mpi. (2)

The volume percentage of the inorganic phase was calcu-lated using the following [6]:

Inorganic particle percentage = (VpVs) × 100. (3)

3. Results

3.1. Inorganic Composition. The elements identified usingenergy dispersive X-ray microanalysis appear in Figures 1, 2,3, 4, and 5. Silicon (Si) was the main component by weightin all of the formulations (Cavex ColorChange—81.59%wt,Hydrogum—79.89%wt, Orthoprint—78.87%wt, Hydrogum5—77.95%wt, Jeltrate Plus—66.88%wt).The remaining com-ponents are described in Figures 1–5.

3.2. FillerMorphology and Size. Themorphology of the fillersis shown in the SEM images in Figures 6, 7, 8, 9, and 10.The inorganic particles of the tested materials showed several

BioMed Research International 3

0.0274 1.331 1.64 3.640.0285 1.269 4.38 3.620.0134 1.197 1.74 1.600.7277 1.121 85.44 81.590.0099 1.677 1.52 1.660.0212 1.279 2.04 2.710.0207 1.199 1.82 2.480.0228 1.181 1.42 2.70

Cou

nts

10000

0.000

0

10.240

(keV)

C OFe

MgAl

Si

S K Ca Fe

Element (calc.) ZAF Element

Zn-L ±0.30

Mg-K ±0.21

Al-K ±0.13

Si-K ±0.41

S-K ±0.14

K-K ±0.15

Ca-K ±0.16

Fe-K ±0.39

Total 100.00 100.00

Cavex ColorChange

(1-sigma)k-ratio Err. (wt%)

(wt%)Atom (%)

Figure 1: Elements identified by energy dispersive X-ray spec-troscopy microanalysis for Cavex ColorChange.

Cou

nts

10000

0.000

0

10.240

(keV)

C

FeF Na Al

Si

CaFeCa Zn

0.0205 1.394 1.30 2.860.0088 1.283 1.38 1.120.0075 1.163 0.97 0.880.7327 1.090 84.86 79.890.0193 1.639 2.94 3.160.0042 1.266 0.41 0.530.0794 1.185 7.00 9.400.0182 1.185 1.15 2.15

Hydrogum

±0.28

±0.18

±0.12

±0.38

±0.22

±0.13

±0.18

±0.36

Element (calc.) ZAF

Zn-LMg-KAl-KSi-KS-KK-KCa-KFe-KTotal 100.00 100.00

(1-sigma)k-ratio Element Err. (wt%)

(wt%)Atom (%)

Figure 2: Elements identified by energy dispersive X-ray spec-troscopy microanalysis for Hydrogum.

shapes and sizes. The Hydrogum 5 and Jeltrate Plus materialsshowed circular and helical particles with several perfora-tions. The Hydrogum, Cavex ColorChange, and Ortoprintmaterials showed particles with cylindrical and perforatedsticks’ shapes.

Themaximum,minimum, andmean diameter size valuesof the inorganic particles are listed in Table 1. Jeltrate Plusshowed the highest mean values for diameter size. Becauseof the difference of Cavex ColorChange, Hydrogum, andOrthoprint particle shapes, which had a considerable lengthto be measured, Table 1 presents its maximum, minimum,and mean length values beyond the values for diameter.

3.3. Volumetric Filler Fraction. The mean values of the per-centage content of inorganic particles in volume are listedin Table 2. Hydrogum 5 presented the highest mean values(84.85% vt), while Cavex ColorChange presented the lowestvalues (56.10% vt). Jeltrate Plus, Hydrogum, and Orthoprintshowed 74.76% vt and 70.03% vt and 68.31% vt, respectively.

Element (calc.) ZAF

Zn-LMg-KAl-KSi-KS-KK-KCa-KFe-KTotal

(1-sigma)k-ratio

0.0057 1.410 0.37 0.810.0141 1.232 2.12 1.740.0086 1.139 1.07 0.980.7238 1.077 82.21 77.950.0267 1.616 3.98 4.310.0211 1.265 2.03 2.670.0840 1.194 7.42 10.030.0126 1.193 0.80 1.51

100.00 100.00

Hydrogum 5

±0.26

±0.10

±0.11

±0.37

±0.24

±0.14

±0.33

±0.31

Cou

nts

11000

0.000

0

(keV)

C Fe Na Al

Si

CaCa

K

10.240

Element Err. (wt%)(wt%)Atom (%)

Figure 3: Elements identified by energy dispersive X-ray spec-troscopy microanalysis for Hydrogum 5.

9000

0.000

0

10.240

C Fe

Si

CaCa

KO Fe

Cou

nts

(keV)

AlS

Element (calc.) ZAF


(1-sigma)k-ratio

0.0146 1.498 1.02 2.180.0172 1.325 2.88 2.280.0104 1.212 1.43 1.260.5989 1.117 72.91 66.880.0432 1.535 6.34 6.640.0679 1.241 6.59 8.420.0801 1.197 7.33 9.590.0232 1.184 1.51 2.75

100.00 100.00

±0.26

±0.11

±0.18

±0.34

±0.23

±0.32

±0.35

±0.34

Element Err. (wt%)(wt%)

Atom (%)

Jeltrate Plus

Figure 4: Elements identified by energy dispersive X-ray spec-troscopy microanalysis for Jeltrate Plus.

Table 1: Maximum, minimum, and mean values for alginate filersize (𝜇m).

Material Maximum Minimum MeanCavex ColorChange (diameter) 16.32 6.48 11.16Cavex ColorChange (length) 20.16 6.63 12.79Hydrogum 5 (diameter) 28.64 4.02 11.43Hydrogum (diameter) 24.23 4.43 8.52Hydrogum (length) 29.02 4.82 13.16Orthoprint (diameter) 18.82 4.04 7.94Jeltrate Plus (diameter) 24.18 7.83 13.07

Table 2: Mean values for volumetric filler fraction of alginates (%).

Material Volumetric filler fractionHydrogum 5 84.85Jeltrate Plus 74.76Hydrogum 70.03Orthoprint 68.31Cavex ColorChange 56.10


Element (calc.) ZAF


(1-sigma)k-ratio

100.00 100.00

±0.29

±0.19

±0.12

±0.39

±0.24

±0.14

±0.33

±0.35

Cou

nts

10000

0.000

0

10.240

C

FeF Al

Si

Ca

Orthoprint

CaK Fe

Na

Zn

0.0328 1.349 2.02 4.430.0158 1.302 2.52 2.060.0076 1.192 1.00 0.900.7118 1.108 83.77 78.870.0255 1.641 3.89 4.180.0085 1.273 0.82 1.080.0577 1.190 5.11 6.860.0137 1.181 0.86 1.61

(keV)

Element Err. (wt%)(wt%)Atom (%)

Figure 5: Elements identified by energy dispersive X-ray spec-troscopy microanalysis for Orthoprint.

Figure 6: SEMmicrograph of Cavex ColorChange alginate impres-sion material; original magnification 1.200x.

4. Discussion

The inorganic composition of the alginate materials isdescribed in Figures 1–5. In the past, lead salts were used toreplace calcium to enhance the gel through the formationof lead alginate [9]. However, lead is not essential to theformulation of high-quality alginates. de Freitas [13] analyzedthe Pb content of 25 dental alginate powders, 20 of whichcontained Pb in small amounts varying from 0.0007 to0.095%wt. The materials analyzed in this study did notcontain lead, which is considered undesirable due to itstoxicity. Although the exposure risk to the dental patient isminimal, even with alginates containing relatively high Pbconcentrations [9], there may be some risks associated withthe inadvertent ingestion of the alginates or the inhalation ofalginate powder during preparation [9].

Alginate powders typically contain sodium or potas-sium (most commonly found in approximately 15%wt)alginates (soluble alginates), diatomaceous earth (approxi-mately 60%wt) acting as filler particles (consisting of silicon,aluminum, iron, calcium, sodium, magnesium, titanium,and potassium), zinc oxide (approximately 4%wt) acting asfiller particles, calcium sulfate (approximately 16%wt) as areactant, a fluoride (approximately 2%wt) as an accelerator,and sodium phosphate (approximately 2%wt) as a retarder

Figure 7: SEM micrograph of Hydrogum alginate impressionmaterial; original magnification 1.200x.

Figure 8: SEM micrograph of Hydrogum 5 alginate impressionmaterial; original magnification 1.200x.

[6, 14]. The main constituent of diatomaceous earth is silica(silicon dioxide) in weight percentages ranging from 58 to91%wt with more than 12,000 different species. However, inthe present study, the silicon content of 5 products variedfrom 81.59% to 66.88%wt in the EDX analysis. Thus, thecurrent study suggests that this percentage is higher in algi-nates studied. Furthermore, two other secondary chemicalelements of diatomaceous earth (aluminum oxide and ironoxide) did not show high percentages in weight (from 1.51to 2.75%wt for iron element and from 0.88 to 1.60%wt forthe aluminum element). For this reason, the filler loadingwas calculated using the Archimedes’ Principle. Zinc con-centrations (filler particles) ranged from 0.81 to 4.43%wt,with Cavex ColorChange and Orthoprint, having the highestvalues of 3.64 and 4.43%wt, respectively. The MgO presenceprovides a material with higher tear strength and hardnessand a smaller setting time, thus indicating its very importantrole [15]. Magnesium concentrations ranged from 1.38 to4.38wt, with the highest values for Cavex ColorChange. Itwould be expected that this alginate impression materialshow improvements in these properties.

The findings of this investigation showed Cavex Col-orChange as the material with the lowest results for thevolumetric filler fraction (56.10% vt), while Hydrogum 5 hadthe highest values (84.85% vt). Thus, it is expected that thedecrease of soluble alginate on Hydrogum 5 will cause alower alteration in stability because a lowerweight percentage

BioMed Research International 5

Figure 9: SEM micrograph of Jeltrate Plus alginate impressionmaterial; original magnification 1.200x.

Figure 10: SEM micrograph of Orthoprint alginate impressionmaterial; original magnification 1.200x.

gel is invariably subject to fewer changes in dimension bysyneresis, evaporation, and imbibition of water. Differencesamong materials are not directly related to filler content, butit seems to be very important to be considered [6]. Thisfact was observed in the study of the Sedda et al. [16], inwhich the accuracy of castsmadewith five alginates (differentfrom those used in this study) were assessed immediatelyand afterward poured with different storage periods, andonly the Hydrogum 5 remained stable after a period of120 hours. On the other hand, materials with a higherpercentage of inorganic filler particles may be less susceptibleto degradation by disinfection. However, Guiraldo et al.[17] observed no differences in dimensional accuracy whentesting various combinations of disinfectant procedures (2%sodium hypochlorite, 2% chlorhexidine digluconate, or 0.2%peracetic acid) and alginate impression materials (CavexColorChange,Hydrogum5, or Jeltrate Plus), possibly becauseof the disinfection method (spraying) or short contact time(15 minutes).

The inorganic filler particles observed by SEM picturesappear to be the cell walls of algae from the division Chrys-ophyta, class Bacillariophyceae. The members of this class,referred to as diatoms, are essentially unicellular, althoughchains of cells and colonial aggregationsmay occur [6].Thereare records of these algae dating from the Cretaceous period.The classification of diatoms is almost entirely based on thestructure and ornamentation of the cell wall, which is termedthe frustule [6]. Due to their siliceous nature and resistance

to natural degradation, the frustules accumulate in geologicallayers within the earth’s crust, eventually forming significantdeposits. Known as diatomaceous earth, or diatomite, thismaterial is mined and used for a variety of commercialpurposes [6].

When added in proper amounts, diatomaceous earthcan improve the strength and stiffness of the alginate gel;produce a smooth texture; and ensure a firm, tack-free gelsurface [6]. It also aids in dispersing the alginate powderparticles in water. Without filler, alginate gels lack firmnessand possess a sticky surface covered with an exudate pro-duced as a result of syneresis [14]. The size and amount offiller and gel affect the accuracy of the alginate impression[14]. Because of this, Orthoprint and Cavex ColorChangeshould provide the best detail reproduction because of theirlower mean diameters (Orthoprint—7.94𝜇m) and low fillerfraction (Cavex ColorChange—56%). However, this was notobserved by Guiraldo et al. [17] when testing three brandsof alginate (Cavex ColorChange, Hydrogum 5, and JeltratePlus) possibly because the accuracy was evaluated solely onthe basis of reproduction of a 50𝜇m line in accordance withthe ISO standard. The comparisons are also hindered by thefact that the fillers in Hydrogum 5 and Jeltrate Plus exhibita morphology different from the other materials, resemblingcolonial aggregates from a different order, suborder, or genus.

Moreover, the ideal properties of impressionmaterials areas follows: be fluid to reproduce details with accuracy; havesufficient viscosity to stay in tray; set in the oral environmentin a short period of time, up to 7 minutes; do not distortafter set; have dimensional stability until pouring; have thepossibility of pouring more than once; be biocompatible; anddo not tear during removal from the mouth. Thus, alginatesshould meet the maximum of these requisites. The stiffnessand strength are directly related to the filler concentration ofhydrocolloid [14]. The strength of reversible (alginates’) gelscan be increased by the addition of fillers [14].Thus, clinically,alginates with higher filler concentrations could have highertear strength. In the present study, Hydrogum 5 showedbetter values of filler concentration and could show bettertear strength. However, this fact is a limitation of this studybecause the tear strengthwas not assessed, and further studiesare needed to confirm these results. Therefore, based on theobtained results, the null hypotheses were not accepted, asthere were differences in (1) composition, (2) filler particlemorphology/size, or (3) filler content among dental alginatematerials.

5. Conclusions

Based on the results fromour study andwithin its limitations,the tested materials demonstrated important differences inthe inorganic elemental composition, filler fraction, and par-ticle morphology. These differences can predict the mechan-ical properties and clinical outcome of these alginates.

Conflict of Interests

The authors declare that there is no conflict of interestsregarding the publication of this paper.


Acknowledgments

The authors thank Mr. Adriano Martins for assistance withthe SEM/EDX analysis and engineerMarcos Blanco Cangianifor his assistance with the matrix.

References

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