The Effect of a Mineralized Bone Graft on the Surface Microhardness of Mineral Trioxide Aggregate and Biodentine

The Effect of Chitosan Incorporation on Physico-Mechanical and Biological Characteristics of a Calcium Silicate Filling Material

OBJECTIVES

A tricalcium silicate-based cement, Biodentine™, has displayed antibiofilm activity when mixed with chitosan powder. This study aimed to assess the effect of chitosan incorporation on the physico-mechanical and biological properties of Biodentine™.

METHODS

In this study, medium molecular weight chitosan powder was incorporated into Biodentine™ in varying proportions (2.5 wt%, 5 wt%, 10 wt%, and 20 wt%). The setting time was determined using a Vicat apparatus, solubility was assessed by calculating weight variation after water immersion, radiopacity was evaluated and expressed in millimeters of aluminum, the compressive strength was evaluated using an Instron testing machine, and the microhardness was measured with a Vickers microhardness tester. In addition, surface topography of specimens was analyzed using scanning electron microscopy, and the effect of chitosan on the viability of human embryonic kidney (HEK 293) cells was measured by a colorimetric MTT assay.

RESULTS

Incorporation of 2.5 wt% and 5 wt% chitosan powder delivered an advantage by speeding up the setting time of Biodentine material. However, the incorporation of chitosan compromised all other material properties and the crystalline structure in a dose-dependent manner. The chitosan-modified material also showed significant decreases in the proliferation of the HEK 293 cells, signifying decreased biocompatibility.

SIGNIFICANCE

Chitosan incorporation into calcium silicate materials adversely affects the physical and biological properties of the material. Despite the increased antimicrobial activity of the modified material, the diminution in these properties is likely to reduce its clinical value.

Microhardness of Calcium-enriched Mixture Cement and Covering Glass Ionomers after Different Time Periods of Application

Introduction

Various studies have recommended using calcium-enriched mixture (CEM) cement in different endodontic treatments, including vital pulp therapy. However, possible reciprocal effects of the covering glass ionomer cement (GIC) on their mechanical properties have not been yet investigated in detail. The current research aimed to experimentally evaluate the surface microhardness of CEM cement and the covering GICs after different application/testing times.

Materials and Methods

Using stainless steel moulds (8×4×4 mm), CEM cement samples were prepared (n=120) and randomly divided into 12 experimental groups (n=10). CEM cement with thickness of 4 mm was inserted into the moulds, and the remaining spaces were filled with self-cured or light-cured resin-modified GICs at three-time intervals; immediate, in 15 min and after 24 h. Then, the samples were incubated for one and seven days. Using a Vickers microhardness tester, the microhardness of CEM and GICs was measured. The data were analyzed using two-way ANOVA and Tukey's test, and the significance level was set at 5% (P<0.05).

Results

The reciprocal effects of the type/time of application of GICs on the surface microhardness of CEM cement or GICs were statistically significant (P<0.001). The surface microhardness of CEM cement and both covering GICs significantly increased over time and in seven-day samples was significantly higher than in one-day samples (P<0.05).

Conclusions

Low surface microhardness of CEM/GICs in short-term (24 h) seems transient; and appears to be compensated over a longer period (i.e. 7-day). Therefore, using GICs adjacent to CEM cement in single-visit restorative treatments may be advocated.

Management of root canal stenosis and external inflammatory resorption by surgical root reconstruction using biodentine

Root canal stenosis and external inflammatory root resorption are potential consequence of trauma that can occur depending on the severity of the injury. Luxation injuries induce reduced blood supply to the pulp, which leads to calcification/narrowing of root canals leading to root canal stenosis. External inflammatory cervical resorption occurs when there has been the loss of cementum due to damage to the external surface of tooth root during trauma, plus root canal system becoming infected with bacteria. External inflammatory resorption can ultimately lead to loss of tooth if it is not managed in a timely manner. The treatment should aim toward the complete suppression of all tissues undergoing resorption and the reconstruction of the resorptive defect by the placement of a suitable bioactive material. This case report presents the management of root canal stenosis in the maxillary left central incisor in 35-year-old female and management of Class IV external invasive cervical and apical inflammatory resorption in maxillary right central incisor, both of which were diagnosed with the help of cone-beam computed tomography scan. The treatment of external inflammatory resorption included surgical excision of granulation tissue and root reconstruction with Biodentine. Twelve months follow-up showed successful outcomes for both the teeth treated for root canal stenosis and external invasive inflammatory resorption leading retention of the traumatized teeth with otherwise poor prognosis.

Setting Time and Surface Microhardness of Mineral Trioxide Aggregate and 1% and 5% Fluoride-Doped Mineral Trioxide Aggregate Mixed with Water and Gel-like Polymer

Introduction

Mineral trioxide aggregate (MTA) is extensively used in endodontics. However, it has limitations such as long setting time, low compressive strength and poor handling properties. Our study aimed to compare the setting time and surface microhardness of MTA and fluoride-doped MTA (FMTA) using gel-like polymer (GLP) or distilled water (DW) as liquid.

Methods and Materials

An MTA-like cement was prepared by mixing Portland cement, bismuth oxide and gypsum (75%, 20% and 5%, respectively). FMTA (1% and 5%) was made by substituting 1% and 5% of MTA powder with fluoride. GLP, composed of methyl cellulose (MC) and propylene glycol (PG), was used as the hydrating liquid and compared with distilled water. Six experimental groups (n=10) were examined for each test. The samples were subjected to Vickers surface microhardness test after 4 and 28 days. Setting time was measured using ANSI/ADA standards. Data was analyzed using two-way and repeated measured ANOVA and the Tukey HSD tests.

Results

The MTA-like cement hydrated with GLP showed a significantly reduced setting time (P<0.05); 1% FMTA, mixed with GLP, had the shortest initial and final setting times. The microhardness values of all samples increased at different rates during 28 days (P<0.00001). The microhardness significantly decreased by addition of fluoride to MTA (P<0.001).

Conclusions

The results of the present in vitro study suggested that using GLP as the hydrating liquid enhances the setting time with no adverse effect on the surface microhardness. However, adding fluoride can negatively affect the microhardness of MTA.

Effect of the Bone Graft on the Surface Microhardness of Endodontic Biomaterials

Introduction

During periapical surgery, using of bone products in large endodontic lesions, is a treatment option that could affect the properties of the retro-filling endodontic material. The aim of present study was to evaluate the effect of Osteon II bone powder on the surface microhardness of calcium-enriched mixture (CEM) and mineral trioxide aggregate (MTA).

Methods and Materials

Each material was mixed and carried into 40 sterile custom-made plastic cylinders. Half of the samples in each group were exposed to Osteon II. All cylinders were submerged in simulated tissue fluid and incubated at 37^°C and 100% relative humidity for 7 days. Surface microhardness values of each study group was attained using Vickers microhardness test. The data were analyzed statistically using two-way ANOVA and independent t-test at a significance level of 0.05.

Results

The highest and lowest microhardness values were recorded in the MTA/without Osteon and MTA/with Osteon groups, respectively. Irrespective of the presence or absence of bone powder, the overall microhardness of CEM cement and MTA was not significantly different. In the MTA group, the presence of the powder resulted in a significant decrease (P<0.05) of the microhardness; however, its effect on CEM cement was not significant (P>0.05).

Conclusion

Under the limitations of the present in vitro study, the presence of Osteon bone powder had no negative effect on the microhardness of CEM cement, contrary to its effect on MTA.