Effect of tricalcium aluminate on the physicochemical properties, bioactivity, and biocompatibility of partially stabilized cements

Abstract

Background/purpose: Mineral Trioxide Aggregate (MTA) was widely used as a root-end filling material and for vital pulp therapy. A significant disadvantage to MTA is the prolonged setting time has limited the application in endodontic treatments. This study examined the physicochemical properties and biological performance of novel partially stabilized cements (PSCs) prepared to address some of the drawbacks of MTA, without causing any change in biological properties. PSC has a great potential as the vital pulp therapy material in dentistry.

Methods: This study examined three experimental groups consisting of samples that were fabricated using sol-gel processes in C3S/C3A molar ratios of 9/1, 7/3, and 5/5 (denoted as PSC-91, PSC-73, and PSC-55, respectively). The comparison group consisted of MTA samples. The setting times, pH variation, compressive strength, morphology, and phase composition of hydration products and ex vivo bioactivity were evaluated. Moreover, biocompatibility was assessed by using lactate dehydrogenase to determine the cytotoxicity and a cell proliferation (WST-1) assay kit to determine cell viability. Mineralization was evaluated using Alizarin Red S staining.

Results: Crystalline phases, which were determined using X-ray diffraction analysis, confirmed that the C3A contents of the material powder differed. The initial setting times of PSC-73 and PSC-55 ranged between 15 and 25 min; these values are significantly (p<0.05, ANOVA and post-hoc test) lower than those obtained for MTA (165 min) and PSC-91 (80.5 min). All of the PSCs exhibited ex vivo bioactivity when immersed in simulated body fluid. The biocompatibility results for all of the tested cements were as favorable as those of the negative control, except for PSC-55, which exhibited mild cytotoxicity.

Conclusion: PSC-91 is a favorable material for vital pulp therapy because it exhibits optimal compressive strength, a short setting time, and high biocompatibility and bioactivity.

Figure 1. Schematic diagrams of the preparation of PSC.

ASB  =  aluminum sec-butoxide; CNT  =  calcium nitrate; TOES  =  tetraethyl orthosilicate; PSC  =  partial stabilized cement.

Figure 2. XRD powder patterns of unhydrated cements and hydrated PSCs stored in D.I. water for 1, 3 and 7 day.

(A) the unhydrated of PSC-91, PSC-73, and PSC-55 after calcined at 1400°C for 2 h and unhydrated MTA; (B) the hydrated patterns of PSC-91; (C) the hydrated patterns of PSC-73; (D) the hydrated patterns of PSC-55. [★ C3A; C3S; Bi₂O₃; ▪ Ca(OH)₂; ▴ CSH; • C₃AH₆].

Figure 3. SEM micrograph of the surface of specimens stored in simulated body fluid (SBF) various durations.

Soaked in SBF after 1 day: (A) PSC-91 (B) PSC-73 (C) PSC-55 (D) MTA; Soaked in SBF for 7 days: (E) PSC-91 (F) PSC-73 (G) PSC-55 (H) MTA

Figure 4. The pH value and physical properties of all tested cements.

(A) pH values variation of all tested cements at various time intervals. (B) The initial and final setting times of PSC-91, PSC-73, PSC-55 and MTA. (C) Compressive strength of PSC with different C3S and CSA content and MTA at 4-h, 24-h and 168-h.

Figure 5

(A) Cytotoxicity assessment of PSC-91, PSC-73, PSC-55 and mineral trioxide aggregate (MTA) by LDH assay according to ISO-10993 protocol standard. All tested cements on dental pulp cells were evaluated by LDH assay on 1day and 3 days. Each bar illustrated average absorbance (A490 nm) ± SD. No significant differences between PSC-91, PSC-73 and MTA (P>0.05); (B) Cell viability evaluation by WST-1 assay. Each bar illustrated average absorbance (A440 nm) ± SD.

Figure 6. The evaluation of biomineralization in human dental pulp cells by Alizarin Red S staining.