Assessment of the remineralisation induced by contemporary ion-releasing materials in mineral-depleted dentine

Characterisation of experimental flowable composites containing fluoride-doped calcium phosphates as promising remineralising materials

OBJECTIVE

Remineralising composites with antibacterial properties may seal the cavity and prevent secondary caries. This study aimed at developing experimental flowable composites containing different concentrations of fluoride-doped calcium phosphate fillers and evaluating their remineralising and antibacterial properties.

METHODS

Experimental resin-based composites containing different concentrations (0-20 %) of fluoride-doped calcium phosphate fillers (VS10/VS20) were formulated. The release of calcium (Ca), phosphate (PO) and fluoride (F) ions was assessed for 30 days. Remineralisation properties were evaluated through ATR-FTIR and SEM/EDX after storage in simulated body fluid (SBF). The metabolic activity and viability of Streptococcus gordonii was also evaluated through ATP, CFU and live/dead confocal microscopy. The evaluation of specific monomer elution from the experimental composites was conducted using high-performance liquid chromatography (HPLC).

RESULTS

The composites containing VS10 showed the highest release of Ca, those containing VS20 released more F over time (p < 0.05), while there was no significant difference in terms of PO ions release between the groups (p > 0.05). A quick 7-day mineral precipitation was observed in the tested composites containing VS10 or VS20 at 10 %; these materials also showed the greatest antibacterial activity (p < 0.05). Moreover, the tested composites containing VS10 presented the lowest elution of monomers (p < 0.05).

CONCLUSIONS

Innovative composites were developed with low monomers elution, evident antibacterial activity against S. gordonii and important remineralisation properties due to specific ions release.

CLINICAL SIGNIFICANCE

Novel composites containing fluoride-doped calcium phosphates may be promising to modulate bacteria growth, promote remineralisation and reduce the risk of cytotoxicity related to monomers' elution.

Bonding performance and interfacial adaptation of modern bulk-fill restorative composites after aging in artificial saliva: an in vitro study

OBJECTIVES

This study aimed at comparing the microtensile bond strength (MTBS) and interfacial adaptation of a modern self-curing and a light-curing restorative bulk-fill composite to a conventional composite applied with the layering technique.

METHODS

Forty-eight occlusal cavities were divided in three main groups (16/group) based on tested materials: (i) STELA, bulk-fill self-curing restorative (STELA, SDI Ltd.); (ii) 3 M-BULK, bulk-fill composite (Filtek One Bulk-Fill, 3 M Oral Care); and (iii) 3 M-CTR, a conventional composite (Filtek Supreme XTE, 3 M Oral Care). These were used in combination with their adhesives in self-etch (SE) or etch-and-rinse (ER) mode. Specimens stored in artificial saliva (24 h or 12 months) were evaluated for MTBS and fractography. The interfacial analysis was performed through confocal microscopy. ANOVA and Fisher's LSD post hoc tests were performed with a level of significance of 5%.

RESULTS

All the tested materials applied in ER mode presented (24 h) greater bond strength than in SE mode. Although all materials showed a significant drop in the bond strength after prolonged storage, STELA showed the highest bonding performance and interfaces with few gaps. 3 M-BULK had the lowest bond strength and an interface with several voids and gaps.

CONCLUSIONS

All materials were affected by interface degradation and bonding reduction over prolonged aging. However, their use in combination with adhesives applied in ER mode may offer greater immediate bonding performance.

CLINICAL RELEVANCE

The use of restorative light-curing bulk-fill composites may generate gaps at the bonding interface and voids. STELA may represent a suitable alternative to avoid such issues.

Dentine Remineralisation Induced by "Bioactive" Materials through Mineral Deposition: An In Vitro Study

This study aimed to assess the ability of modern resin-based "bioactive" materials (RBMs) to induce dentine remineralisation via mineral deposition and compare the results to those obtained with calcium silicate cements (CSMs). The following materials were employed for restoration of dentine cavities: CSMs: ProRoot MTA (Dentsply Sirona), MTA Angelus (Angelus), Biodentine (Septodont), and TheraCal LC (Bisco); RBMs: ACTIVA BioACTIVE Base/Liner (Pulpdent), ACTIVA Presto (Pulpdent), and Predicta Bioactive Bulk (Parkell). The evaluation of the mineral deposition was performed through scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDX) on the material and dentine surfaces, as well as at the dentine-material interface after immersion in simulated body fluid. Additionally, the Ca/P ratios were also calculated in all the tested groups. The specimens were analysed after setting (baseline) and at 24 h, 7, 14, and 28 days. ProRoot MTA, MTA Angelus, Biodentine, and TheraCal LC showed significant surface precipitation, which filled the gap between the material and the dentine. Conversely, the three RBMs showed only a slight ability to induce mineral precipitation, although none of them was able to remineralise the dentine-material interface. In conclusion, in terms of mineral precipitation, modern "bioactive" RBMs are not as effective as CSMs in inducing dentine remineralisation; these latter represent the only option to induce a possible reparative process at the dentin-material interface.

The Cytotoxicity and Genotoxicity of Bioactive Dental Materials

The promotion of biologically based treatment strategies in restorative dentistry is of paramount importance, as invasive treatments should be avoided to maintain the tooth's vitality. This study aimed to assess the biocompatibility of commercially available bioactive materials that can be used for dental pulp capping. The study was performed with a monocyte/macrophage peripheral blood SC cell line (ATCC CRL-9855) on the following six specific bioactive materials: ProRoot MTA (Dentsply Sirona), MTA Angelus (Angelus), Biodentine (Septodont), TheraCal LC (Bisco), ACTIVA BioACTIVE (Pulpdent) and Predicta Bioactive Bulk (Parkell). The cytotoxicity of the investigated agents was measured using a resazurin-based cell viability assay, while the genotoxicity was evaluated using an alkaline comet assay. Additionally, flow cytometry (FC) apoptosis detection was conducted with a FITC (fluorescein isothiocyanate) Annexin V Apoptosis Detection Kit I. FC cell-cycle arrest assessment was carried out with propidium iodide staining. The results of this study showed no significant cytotoxicity and genotoxicity (p > 0.05) in ProRoot MTA, MTA Angelus, Biodentine, ACTIVA BioACTIVE and Predicta Bioactive. Conversely, TheraCal LC presented a significant decrease (p < 0.001). In conclusion, due to excellent biocompatibility and low cytotoxicity, MTA, Biodentine, ACTIVA BioACTIVE and Predicta Bioactive may be suitable for pulp capping treatments. On the other hand, due to the high cytotoxicity of TheraCal LC, its use should be avoided in vital pulp therapies.

A Micro-CT Analysis of Initial and Long-Term Pores Volume and Porosity of Bioactive Endodontic Sealers

The evaluation of the porosities within the interface of root canals obturated with endodontics materials is extremely important for the long-term success of endodontic treatments. The aim of this study was to compare initial and long-term volume of pores (total, open, closed) and porosity (total, regional) of three bioactive endodontic sealers: GuttaFlow Bioseal, Total Fill BC Sealer, and BioRoot RCS. Root canals were obturated with three “bioactive” sealers using the single-cone technique. The volume of open and closed pores and porosity were calculated using a micro-computed tomography (MCT) method. The measurements were performed after 7 days (initial) and after 6 months (long-term) of incubation. Statistical significance was considered at p < 0.05. The total volume of pores remained unchanged after the 6-month storage. GuttaFlow Bioseal exhibited significantly higher long-term volume in open pores than Total Fill BC Sealer. The total porosity in all the tested sealers presented no statistically significant change after the 6-month storage, except for BioRoot RCS. The total porosity values of this latter material significantly increased after long-term incubation, especially in the apical region. In conclusion, the use of bioactive sealers with excessive tendency to create porosities both in shorth- and long-term periods of storage may compromise the long-term success of endodontic treatments.