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| IMC Wiki | Physical properties III

Physical properties III

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Bending strength

An important property of calcium silicate-based materials is that they release calcium hydroxide on their surface during hydrolytic processes. However, it was shown by Doyon et al. (2005) and Soares et al. (2007) that a prolonged contact time between root dentin and calcium hydroxide and also MTA weakens and therefore has a deleterious effect on the resistance of the root dentin. The release of calcium hydroxide ions to the collagen structures of the dentin must also be regarded quite critically especially if long-term contact between the dentin and a calcium silicate-based material is to be produced.
Sawyer et al. investigated the effect on the mechanical properties of dentin of sustained contact between the two components. They found that both Biodentine and MTA Plus impair the bending and inherent stability and thus ultimately the strength and resistance of dentin. However, the authors assume that the negative effects are relative if the materials are applied or used sparingly, e.g., as capping material or retrograde root filling material. The authors are critical of these products, however, when they are used extensively as sole root filling material or dentin substitute.

The aspect of bending strength is interesting especially when Biodentine is used to treat class I, II and IV cavities. The higher the resistance to bending stress and torsion, the lower the tooth's clinical fracture risk. Biodentine's bending resistance is c. 34 Mpa after two hours. By contrast, the value is 5-25 MPa for classic glass ionomer cement, 17-54 MPa for resin-modified glass ionomer cement and 61-182 Mpa for composite (O’Brien 2008).
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Microhardness

The hardening reaction of a cement is accelerated if distilled water is used for mixing the material (Goldberg 2009, Goldberg et al. 2009). Two hours after mixing, Biodentine has a microhardness of 51 HVN (Vickers method). This increases further in the initial phase and attains a microhardness of 69 HVN after one month. This process is based on the production of CSH gel, which subsequently reduces the porosity of the Biodentine by gradual crystallization processes, thereby positively influencing other mechanical properties (compressive strength, impermeability etc.) as well as microhardness.
Grech et al. (2013) also address the microhardness aspect. According to their results, Biodentine has outstanding levels compared with bioaggregates and IRM. Camilleri (2013) compared the physical properties of Biodentine with those of a conventional glass ionomer cement (Fuji IX) and those of a resin-modified glass ionomer (Vitrebond). In the unetched state, Biodentine in fact had higher microhardness of its surface than the other two materials, which were also unetched. However, Camilleri's study (2013) qualified this finding as there were no differences in microhardness between the aforementioned materials in the etched state.

From the materials science aspect, Biodentine and natural dentin are not identical but analysis of these studies shows that they are very similar in some respects.

  Biodentine Dentin
Elastic modulus 22.0 GPa 18.5 GPa
Compressive strength ~ 220 MPa ~290 MPa
Microhardness ~ 60 HV (Vickers hardness) ~ 82.5 HV (entire tooth)
~ 50-60 HV (beside pulp)
(Schemel et al. 1984)

According to the product information provided by the manufacturer Septodont, a particular advantage of Biodentine is the continuous improvement of its physical properties, especially the increase in compressive strength, which is roughly equivalent to that of natural dentin in the final phase.
The studies presented above corroborate this assumption. Grech et al. (2013) also found that Biodentine demonstrated the highest compressive strength among all the tested materials. The authors attributed this circumstance to the relatively low water content in Biodentine. In their study, Koubi et al. (2013) used Biodentine as restoration material in the posterior region. They showed that the material exhibited positive surface properties and good marginal adaptive capacity over a six-month observation period.

Acid resistance

The quality and stability of a restorative filling material under clinical conditions are important characteristics of a dental product.
The marginal seal and acid stability, along with adhesion to other structures (enamel, dentin, composites and other dental materials), are important aspects. Various tests were used to study the clinical properties of Biodentine, which investigated the erosion behavior in acid solutions (corresponding to the oral milieu) and also the development of microleakages.
Laurent et al. (2008) studied the effects of erosive solutions (pH 2.74) and simulated aging on the structure of Biodentine stored in artificial saliva containing phosphate (pH 5.3).

#pic#

The study showed that a layer of apatite-like needle-shaped calcium phosphate crystals was deposited on the surface of the Biodentine in a phosphate-containing liquid.
A fall in the calcium concentration was obtained in parallel in the artificial saliva.
Accordingly, a precipitation reaction has taken place, in which the precipitation product has assumed an apatite-like structure. This reaction suggests that an improved adhesion layer between Biodentine and natural phosphate-rich dentin is possible over time.
Erosions were not found in the artificial saliva. This form of precipitation process with deposition of a crystalline layer is not new, however, but was already known from MTA systems.
Overall, it can be noted that Biodentine has no or hardly any tendencies to surface dissolution (Laurent et al. 2008).

Microleakages

Biodentine's resistance to microlesions was examined in different studies. Goldberg et al. (2009) investigated the boundary between Biodentine and dentin using a dye penetration method with silver nitrate. This is a common method for studying the sealing behavior of a substance. Infiltration or percolation of the dye is measured, which in turn permits conclusions regarding the sealing capacity.
Under the electron microscope, the bond between Biodentine and natural dentin shows direct and gapless contact between the two structures.
On magnification, the Biodentine surface shows a crystalline deposit, which developed after the sample was re-embedded in an aqueous milieu (Dejou and Raskin 2003 and 2012, Colon and Pradelle 2004).

#pic# #pic#

Recrystallization processes that lead to the formation of mineralized "tags" are observed at the entrances to the dentin tubules.
The development of these tags is the basis for the micromechanical fixation of Biodentine in the natural dentin (Colon and Pradelle 2004).

#pic#

The next illustration shows an extracted wisdom tooth, which has recrystallization processes with subsequent obturation of the dentin tubules after treatment with Biodentine and storage in distilled water for 28 days (Franquin 2001).

#pic# #pic#

If Biodentine is used as a liner, hypersensitivity and secondary caries may possibly occur as a result of microleakage. Koubi et al. (2012) were among the first to analyze more precisely the marginal integrity of a filling placed with glass ionomer cements or with calcium silicate-based materials.
The one-year results confirm that similar leakage patterns occurred with both groups of materials. The authors attribute the good marginal adaptation of Biodentine to its ability to deposit and form hydroxyapatite-like crystals on the interface with dentin. The apatite crystals probably have the potential to increase the impermeability on direct contact with dentin (Koubi et al. 2012). Moreover, the interaction between the phosphate ions of the saliva and the calcium silicate-based cements also appears to increase the deposition of apatite crystals. The authors also mention that the nanostructure and the small particle size of the components of the calcium silicate gel that forms are among the important factors that ultimately ensure the good impermeability and sealing character of the Biodentine. A slight increase in the volume of the expanding Biodentine was observed and thus confirms to a certain extent its very good adaptation ability (Koubi et al. 2012).

Color stability

A study by Vallés et al. (2013) concentrated on the aspect of Biodentine's color stability compared with four other products. The materials were exposed to different oxygen and light conditions and analyzed by spectrophotometry at several times during a series of tests over 5 days. Good results were obtained with Portland cement and Biodentine, which both showed color stability over the test period of 5 days. For this reason, Vallés et al. suggest that Biodentine can also be used in aesthetically relevant regions, e.g., as liner material.


sources

  • Camilleri J (2013) Investigation of Biodentine as dentine replacement material. J Dent 41(7):600-610
  • Colon P, Pradelle-Plasse N, Wenger F, Picard B (2004) Quantitative evaluation of self-etchiing primer action on dentine permeability: a correlation between impedance measurements and acidity. Am J Dent 17(2):131-136
  • Doyon GE, Dumsha T, Von Fraunhofer JA (2005) Fracture resistance of human root dentin exposed to intracanal calcium hydroxide. J Endodont 31(12):895-897
  • Franquin JC, Murray PE, About I, Remusat M, Smith AJ (2001) Restorative pulpal and repair responses. J Am Dent Assoc 132(4):482-491
  • Grech L, Mallia B, Camilleri J (2013) Investigation of the physical properties of tricalcium silicate cement-based root-end filling materials. Dent Mater 29(2):20-28
  • Golberg M, Pradelle-Plasse N, Tran X, Colon P, Laurent P, Aubut V, About I, Boukpessi T, Septier D (2009) Chapter VI: Emerging trends in (bio)material researches: VI-1-Repair or regeneration, a short review. VI-2: An example of new material: preclinical multicentric studies on a new Ca3SiO5-based dental material. Coxmoor Publishing Company: 181-203
  • Golberg M, Six N, Chaussain C, DenBesten P, Veis A, Poliard A (2009) Dentin extracellular matrix molecules implanted into exposed pulps generate reparative dentin : a novel strategy in regenerative dentistry. J Dent Res 88(5):396-399
  • Koubi G, Colon P, Franquin JC (2013) Clinical evaluation of the performance and safety of a new dentine substitute, Biodentine, in the restoration of posterior teeth – a prospective study. Clin Oral Invest 17(1):243-249
  • Laurent P, Camps J, De Méo M, Déjou J, About I (2008) Induction of specific cell responses to a Ca3SiO5-based posterior restorative material. Dent Mater 24(11):1486-1494
  • O’Brien W (2008) Dental Materials and their Selection. In: O’Brien W 4th ed. Ed.
  • Raskin A, Tassery H, D’Hoore W, Gonthier S, Vreven J, Degrange M, Déjou J (2003) Influence of the number of sections on reliability of in vitro microleakage evaluations. Am J Dent 16(3):207-210
  • Soares CJ, Santana FR, Silva NR, Preira JC, Pereira CA (2007) Influence of endodontic treatment on mechanical properties of root dentin. J Endodont 33(5):603-606
  • Vallés M, Mercadé M, Duran-Sindreu F, Bourdelande JL, Roig M (2013) Influence of light and oxygen on the color stability of five calcium silicate-based materials. J Endodont 39(4):525-528