Mongiorgi R

Innovative silicate‐based cements for endodontics: A study of osteoblast‐like cell response

Silicate-based filling materials were designed to obtain new endodontic sealers and root-end filling materials with adequate workability and consistency. Four different formulations (TC, TC 1%, TCf 1%, and TCf) were prepared incorporating calcium chloride as accelerant agent. A plasticizing compound (phyllosilicate) was added to TC 1% and TCf 1%. TC and TC 1% were prepared with water, whereas TCf and TCf 1% were mixed with a latex polymer as fluidizing agent. The aim of this study was to assess the in vitro biological compatibility of designed materials. White-MTA and AH Plus were tested as reference materials. Human osteoblast-like Saos-2 cells were challenged in short-term cultures (72 h) with solid materials and with material extracts in culture medium, and cell viability and number, cellular adhesion, and morphology were assessed. The new cements exerted no acute toxicity in the assay systems. Saos-2 like cells adhered and proliferated on solid samples of the experimental cements and MTA whilst AH Plus did not allowed cell growth. The extracts from the latex-containing cements showed some toxicity. By SEM analysis, osteoblast-like cells appeared adherent and spread on the new materials, and showed the maintenance of polygonal osteoblastic phenotype. Similar morphology was observed for cells on MTA, whereas only few cells were noted on the AH Plus surface. In conclusion, the new materials proved non toxic and supported the growth of bone-like cells, and resulted suitable to be used as endodontic sealers and root-end filling materials.

Experimental etch-and-rinse adhesives doped with bioactive calcium silicate-based micro-fillers to generate therapeutic resin–dentin interfaces

OBJECTIVES This study aimed at evaluating the therapeutic bioactive effects on the bond strength of three experimental bonding agents containing modified Portland cement-based micro-fillers applied to acid-etched dentin and submitted to aging in simulated body fluid solution (SBS). Confocal laser (CLSM) and scanning electron microscopy (SEM) were also performed. METHODS A type-I ordinary Portland cement was tailored using different compounds such as sodium-calcium-aluminum-magnesium silicate hydroxide (HOPC), aluminum-magnesium-carbonate hydroxide hydrates (HCPMM) and titanium oxide (HPCTO) to create three bioactive micro-fillers. A resin blend mainly constituted by Bis-GMA, PMDM and HEMA was used as control (RES-Ctr) or mixed with each micro-filler to create three experimental bonding agents: (i) Res-HOPC, (ii) Res-HCPMM and (iii) Res-HPCTO. The bonding agents were applied onto 37% H3PO4-etched dentin and light-cured for 30s. After build-ups, they were prepared for micro-tensile bond strength (μTBS) and tested after 24h or 6 months of SBS storage. SEM analysis was performed after de-bonding, while CLSM was used to evaluate the ultra-morphology/nanoleakage and the mineral deposition at the resin-dentin interface. RESULTS High μTBS values were achieved in all groups after 24h. Only Res-HOPC and Res-HCPMM showed stable μTBS after SBS storage (6 months). All the resin-dentin interfaces created using the bonding agents containing the bioactive micro-fillers tested in this study showed an evident reduction of nanoleakage and mineral deposition after SBS storage. CONCLUSION Resin bonding systems containing specifically tailored Portland cement micro-fillers may promote a therapeutic mineral deposition within the hybrid layer and increase the durability of the resin-dentin bond.

Scanning electron microscopic evaluation of different endodontic procedures on dentin morphology of human teeth

Four manual endodontic instruments, an ultrasonic and an endosonic system were studied with a view to evaluating the morphology of the smear layer and the amount of debris and pulpal residues in the apical third of human extracted straight teeth from 55- to 75-yr-old patients. The manual instruments were K files, Ergoflex files used with the step-back technique, Canal Master with its own technique, and Flex-R with the Roane technique. The ultrasonic system was Suprasson Piezo and the endosonic was Excalibur. Human extracted teeth with straight canals were used and examined under a scanning electron microscope. All manual instrumentations showed a homogeneous compact smear layer and no pulp residues. No statistical differences were observed among the four manual techniques. Ultrasonic technique showed the complete removal of the smear layer, leaving small amounts of pulp debris at the apical third, while the Excalibur showed an almost complete elimination of the smear layer, leaving a homogeneous layer of pulpal residues along the canal.

Nanopore Structure Buildup during Endodontic Cement Hydration Studied by time-Domain Nuclear Magnetic Resonance of Lower and Higher Mobility 1H

Time-domain nuclear magnetic resonance (TD-NMR) of (1)H nuclei has been used to monitor and model changes of endodontic cement pastes during hydration, from the initial reaction period up to hours and days. The (1)H in the samples are divided into two major spin groups by fitting each free induction decay, acquired after the second pulse of an inversion recovery (I-R) pulse sequence with variable interpulse delay, by the sum of a quasi-Gaussian (signal from low mobility nuclei) and an exponential (from higher mobility nuclei). The extrapolations to zero time of the signals from the two spin groups give two sets of I-R data that have been analyzed to give quasi-continuous T(1) distributions. After about a day, two clearly solid components appear. From a day to a few days, three liquid populations are identified, one of them mainly in the low-mobility spin group, which later merge, giving a single T(1) or T(2) peak. The rapid onset of the solid components, at the cost of the liquid, and the rapid changes of the relaxation time distributions of all components are clear indicators of the amount and kinetics of reaction products formation (C-S-H gel and Portlandite) and of the C-S-H micronanoporous structure buildup and evolution. At 30 days of hydration, the very short T(1) and T(2) liquid component (T(1) congruent with 200 micros and T(2) congruent with 50 micros) can be assigned to C-S-H intralayer water (thickness of the order of fractions of a nanometer) and the remaining liquid signal to interlayer water (thickness of the order of 1 nm). Comparisons are made among a widely used commercial endodontic cement paste and two more recent commercial pastes, with additive compounds to make the hydration process faster and to increase the workability. Parameters can be extracted from the data to characterize the different kinetics and nanostructure of the pore space formed up to 30 days. The parameters are in agreement with the expected effects of the additives, so the parameters can be used to optimize the formulation of new pastes, in order to improve their therapeutic performance.

The Mechanical Properties of Fluoride-Treated Bone in the Ovariectomized Rat

Abstract. The effect of fluoride therapy on the osteopenic bone of the ovariectomized rat was studied by comparing the densitometric and biomechanical data. Forty retired breeder female Sprague-Dawley rats aged 10 months were randomly divided into five groups. One group (Group A) was killed at the beginning of the study and was used as a baseline. Three groups were ovariectomized and one was sham-operated (Group B) and observed for the same period as a sham-aged group. A group of ovariectomized rats was used as a sham therapy control (Group C) and received only deionized drinking water; the other two groups (F1 and F2) received L-glutamine monofluorophosphate and calcium at a rate of 1:30 F/Ca at different doses by gavage (0.57 mg F/17 mg Ca per kg/day-Group F1; 0.21 mg F/6.30 mg Ca per kg/day-Group F2). Densitometric and biomechanical (compression and three-point bending test) assays, X-ray diffraction, and Fourier transformed infrared spectroscopy were performed on femoral specimens. Biomechanical data showed that the femoral heads of Group F2 required a significantly greater energy-to-failure than Group C (P < 0.05) as well as treated femoral diaphysis when compared with the others (P < 0.01). Significant increases in the elastic modules were observed in fluoride-treated groups (P < 0.001) when compared with other groups. Diffractometric and spectroscopic data showed the presence of fluorine-apatite in both treated groups with a high component of carbonates. Also, fluoride therapy causes an increase of bone stiffness due to the presence of fluoroapatite. It seems to produce two opposed properties in the osteopenic rat bone: a higher resistance to compression loading and a greater frailty to flexion loading.

Hydroxyethyl-methacrylate dentin bonding agents: Shear bond strength, marginal microleakage and SEM analysis

Abstract Dentinal bonding agents (BAs) have recently been developed to improve the clinical performance of dental light-cured restorative composite resins. The aim of this study was to evaluate in vitro the newest generation of BAs which are composed of HEMA (Hydroxy-ethyl-methacrylate), urethane diacrylate or cross-linked aromatic dimethacrylates (BIS GMA). Marginal microleakage tests, scanning electron microscopy (SEM) and shear bond strength tests were made to evaluate the interface between dentin and composite materials. Marginal microleakage tests revealed dye penetrations in a large number of composite resin restorations, while SEM demonstrated the presence of marginal gaps and fractures along the interface between dentin and composite materials. Shear bond strength tests demonstrated that BAs are able to bond the dentin surface.

Porosity, Micro-Hardness and Morphology of White and Gray Portland Cements in Relation to Their Potential in the Development of New Dental Filling Materials

Purpose: Portland cements may be used in dentistry due to their excellent biocompatibility, sealing ability and potential osteogenic induction. The aim of the present study was to identify the structural and physical properties of two basic Portland cements for their development as potential new dental filling materials. Methods: The two Portland cements, White Portland (WPC) and Gray Portland (GPC), were mixed with distilled water and immediately incubated in water (H2O) or Phosphate Buffered Saline (PBS) at 37°C. Knoop Micro-hardness, volumetric mass/porosity and SEM surface analysis were performed at different time intervals (7, 14, 28 days). Results: Knoop micro-hardness, volumetric mass \ porosity and SEM evaluations performed at different time intervals (7, 14, 28 days) revealed that the WPC had the highest micro-hardness, whereas Portland cement GPC presented higher level of porosity in the early stages of the setting phase. Conclusion: The different structural and physical characteristics showed by the two basic Portland cements should be taken in consideration during the identification of the most potential applications for the development of new dental filling materials.

DENSITOMETRY ANALYSIS IN IN VIVO EVALUATION OF SYNTHETIC SALMON CALCITONIN ACTIVITY

In women suffering from post‐menopausal osteoporosis, we evaluated the effectiveness of two cyclic treatments with synthetic salmon calcitonin over a whole year, using an average daily dose of 16 and 32 IU, respectively. This treatment was compared with treatment with oral calcium carbonate.

Reinforced Silver Glass-Ionomer Cement and Light-Cured H.E.M.A. Glass-Ionomer Cement Under Silver-Amalgam Restorations: A Microleakage Study

The lack of adhesion to dentine of amalgam restorations is responsable for insufficient marginal seal and for percolation of bacteria and chemical-hydrolitic solutions along the interface.

Dental Ceramics and Composite Resins as Restorative Materials

The aim of this study was to evaluate the marginal microleakage of different materials used to restore class II MOD cavities. Materials selected were: conventional BIS-GMA/urethane composite resin (Heliomolar RO), BIS-GMA/ceramic APC composite resin (P 50), ceramic (IVOCLAR-VTVODENT) and urethane resin (Isosit SR) (N=10). A bonding agent was used to improve the adhesion between materials and tooth structures.