INTRODUCTION

Dental materials have been evolving alongside dentistry due to technological advances, which have assisted these materials to possess better physical, chemical and biological properties.

Retro-filling materials are commonly used in endodontic surgical procedures. An ideal endodontic reparation material should be radio-opaque, biocompatible, with anti-bacterial effect, dimensionally stable, easy to manipulate and not be contaminated or affected by blood. Other desirable characteristics for the selected material would include for it to be osteo-inductor, provide suitable sealing against bacteria and fluids as well as being able to avoid filtrations when placed in humid environment and possessing sufficient resistance to compression and hardness.¹

Many materials have been used to perform retrograde filling. Among them we can count amalgam, zinc oxide-eugenol, polycarboxylate cements, glass ionomer cements, composite resin, epoxy-resin, guttapercha and mineral trioxide aggregate (MTA) type cements based on Portland cement.

Main disadvantages of the aforementioned materials include micro-leakage, varied degrees of toxicity, as well as sensitivity to presence of humidity.^2,3 Among these MTA has been recognized as a bioactive material,⁴ hard tissue conductor⁵ hard tissue inductor as well as biocompatible.⁶

MTA is a material commonly used for retrograde filling procedures, apex formation and perforation repairs, nevertheless its handling is less than ideal due to its long setting time and difficulties in preserving mix consistency.⁷

Calcium silicate cements, especially those derived from Portland cement, such as mineral trioxide aggregate (MTA) and others have been designed and are used in clinical dental applications.

Self-adjusting properties of calcium silicate cements are due to the progressive hydration reaction of orthosilicate ions (SiO₄).

When calcium silicate particles react to water a hydrated calcium silicate nanoporous amorphous gel is formed (HCS gel) in the cement particles, while calcium hydroxide ( Ca(OH)₂) (portlandite) forms nuclei and grows in available gaps and spaces of the pores. With time, HCS gel polymerizes and hardens, forming thus a solid net which is associated to greater mechanical resistance. HCS gel is soluble in Ca(OH)₂ ,released by the cement surface and increases alkalinity of surrounding environment.⁸

The purpose of the present study was to explore the components of MTA Angelus^® White cement (Angelus, Lodrina, Paraná Brazil) and Biodentine ^TM (Septodont, Saint-Maur-des Fosses, France) by means of X-ray diffraction and electron dispersion spectrometry, X -ray fluorescence, as well as observing the surface with scanning electron microscope and infra red spectroscopy.

MATERIALS AND METHODS

Both cements used for the present project were divided into two groups:

One gram of the powder provided by the manufacturer was used for XRD and XRF analyses. For DES, SEM and IRS analyses all products were mixed using powder and liquid provided by the manufacturer. Manufacturer's instructions were strictly followed. One 8 mm diameter x 4 mm thickness sample was manufactured for each group. Five points were randomly taken for the analysis.

X ray diffraction analysis was conducted with a diffractometer Phillips Mod 1130/96 (generator) and pw1050/24 (goniometer) using CuKα at angular intervals ranging from 4^o to 70^o.

X ray fluorescence analysis (XRF): An X ray fluorescence quantitative chemical analysis was conducted with a Siemens SRS 3000 spectrometer, gauged with Geochemical Reference materials. This analysis was conducted with the sample in dry base, and loss by calcination (LBC) was determined by calcinating 1 g of the sample at 950 ^oC during one hour.

Dispersive energy spectrometry (DES) and scanning electron microscopy (SEM): Once hardened, the samples were placed on the sample holder with a carbon film to which they adhered. Observations were made with Scanning Electron Microscope (leol model 5900 LV, Tokio, Japan). Used magnifications were 500X, 1000X and 2000X.

For the dispersive energy spectrometry analysis (DES) an elemental chemical analysis was conducted with an Oxford device, ISIS model, with 133 eV resolution, with carbon to uranium element detection.

For the present study amplifications of 500X, 1000X and 2000X were used in all samples at four predetermined points.

Infrared spectroscopy (IRS): Samples were analyzed with attenuated total reflectance technique (ATR) in a Bruker Brand spectrometer, model Vector 33 with 32 scanning and resolution of 4 cm^-1. Samples to be analyzed were directly placed on the diamond crystal for analysis, since this technique did not require previous preparation.

RESULTS

XRD results of MTA and Biodentine were the following:

In XRF analysis, the following were identified in both cements: SiO₂ Al₂0₃, Fe₂O₃t, MgO, CaO, K₂O, P₂O₅ TiO₂. MTA exhibited Cr₂O₃ and BiO₂, these materials were not detected in Biodentine. Biodentine exhibited N_a2O and Z_rO₂. which were absent in MTA Angelus ( Table I).

SEM analysis of samples revealed Biodentine structure with fibrillar and irregular shape, with crystal appearance ( Figure 1) whereas MTA samples exhibited irregular and porous structure, loose granules were observed and identified as Bismuth ( Figure 2).

DES results revealed presence of Bi in Group 1 (MTA Angelus). Bi wasn't present in any other group. In Group 2 (Biodentine) CI presence was observed, which was absent in Group 1.

C, O, Al, Si, Ca were regularly detected in both groups ( Tables II and ^III).

T Student test was used for statistical analysis. Results revealed that points from where samples were taken were homogeneous, and there were statistically significant differences in the percentages of the varied detected components in both cements with DES tests ( Tables IV and ^V).

Figure 1. Biodentine Scanning electron micrographs at magnifications of 500X, 1000X and 2000X where irregular and filiform shaped crystals can be observed. 

Figure 2. MTA Angelus scanning electron micrographs at magnifications of 500X, 1000X, and 2000X where irregular and porous structure can be observed. Bismuth can be observed in the shape of loose granules. 

INFRARED SPECTROSCOPY

Results obtained from MTA sample ( Figure 3) revealed calcium carbonate characteristic groups in the absorption bands in 1410,869 and 660 cm^-1 in the C-O group. The band 952cm^-1 corresponded to calcium chloride (CaCl₂).

Figure 4 shows the Biodentine sample spectrum. It can be observed that bands at 3567 7 3426 cm^-1 correspond to groups N-H. The band at 2925 cm^-1 corresponds to methylene groups (CH₂) The band at 1739 cm^-1 is assigned to C=O of a carboxylic acid, this is corroborated with bands at 1558 and 1419 cm^-1 with the group COO^- of carboxylic acids. The band at 1620 cancorrespond to an aromaticring or a secondary amine. The aromatic ring can be corroborated in the region of 1410 to 1500 cm^-1 and the amine group at the 795 cm^-1 band. The 1168 cm^-1 band corresponds to the CN group. Bands between 702 and 676 cm^-1 correspond to monosubstituted groups (in the aromatic ring) C-CH2 and C-H respectively.

DISCUSSION

Hydroxyapatite as such and other materials which contain Ca exhibit excellent biocompatibility, which is expressed in minimal tissue toxicity and reaction to foreign body, osteoconductivity and osteogenicity (LeGeros, 1991).⁹

Figure 3. Infra-red spectroscopy of MTA simple. 

Figure 4. Infrared spectroscopy of Biodentine sample. 

The composition of Biodentine powder is tricalcium silicate, calcium carbonate and zirconium oxide (Koubi et al, 2011).¹⁰

Calcium chloride is one of the most efficient accelerators for Portland cement hydration and configuration (Camilleri et al, 2006).¹¹

Calcite (CaCO₃), which was observed in both cements, has two different functions: 1. as active agent involved in the hydration process and 2. as filling which improves the cement's mechanical properties. (Garrault et al 2006).¹²

Hydration of tricalcium silicate (3CaO.SiO₂) leads to the formation of a hydrated calcium, gel silicate hydroxide (gel CSH) and calcium hydroxide (Ca(OH)₂) (Taylor 1997).¹³

Biodentine surface examined with SEM reveals crystals of varied sizes in the shape of hexagonal plates of Ca(OH) 2 (Taylor 1997)¹³ which differs from the present study which observed crystals of filament shape.

Asgary¹⁴ reported in his XRD analysis of white MTA the presence of CaO, SiO₂ Bi₂O₃Al₂O₃, MgO, SO₃ Cl, FeO, P₂O₅, TiO₂. In the present study, no Cl was found in MTA and contrary to Asgarty's reports presence of Cr₂O₃, K₂O was observed.

White MTA is composed of a variety of oxides typically of SiO₂ CaO and Al₂O₃ Among oxides, aluminum (Al), a neurotoxin, is harmful to human health due to its ability to alter cellular calcium homeostasis, and promote cellular oxidation (Zatta 2002).¹⁵

Gandolfi¹⁶ reported that in his DES analysis of MTA he obtained the following elements: Ca, Si, Cl, Bi, and O. No Cl was found in the analysis we conducted, and C and Al were found in addition to results reported by Gandolfi.

Song¹⁷ in an DES analysis of MTA reported presence of Ca, Si, C, O, Mg, Al, S and Bi. Our analysis differed from Song's inasmuch as S and Mg were not present.

MTA has a proportion of 4:1 of bismuth, radio-opacity oxide (Camilleri 2007 ¹⁸, Torabinejad 1995 ¹⁹) In the present study proportion of bismuth oxide was 16.5% as shown in Table I .

Asgary S et al ²⁰ reported in DES analysis the highest peaks of calcium, silica and bismuth contents. Nevertheless, aluminum, magnesium and especially iron peaks were significantly lower in white MTA, this could explain color differences. We concur with results obtained in our study.

CONCLUSION

Chemical components of MTA Angelus and Biodentine are very similar, the exception would be inthechemical components which provide opacity, size and shape of grain, and in the case of Biodentine, calcium chloride.