Diffusion of HEMA through Human Carious and Non-Carious Dentin In Vitro

JNK-mediated blockage of autophagic flux exacerbates the triethylene glycol dimethacrylate-induced mitochondrial oxidative damage and apoptosis in preodontoblast

Mitochondrial dependent oxidative stress (OS) and subsequent cell death are considered as the major cytotoxicity caused by Triethylene glycol dimethacrylate (TEGDMA), a commonly monomer of many resin-based dental composites. Under OS microenvironment, autophagy serves as a cell homeostatic mechanism and maintains redox balance through degradation or turnover of cellular components in order to promote cell survival. However, whether autophagy is involved in the mitochondrial oxidative damage and apoptosis induced by TEGDMA, and the cellular signaling pathways underlying this process remain unclear. In the present study, we demonstrated that TEGDMA induced mouse preodontoblast cell line (mDPC6T) dysfunctional mitochondrial oxidative response. In further exploring the underlying mechanisms, we found that TEGDMA impaired autophagic flux, as evidenced by increased LC3-II expression and hindered p62 degradation, thereby causing both mitochondrial oxidative damage and cell apoptosis. These results were further verified by treatment with chloroquine (autophagy inhibitor) and rapamycin (autophagy promotor). More importantly, we found that the JNK/MAPK pathway was the key upstream regulator of above injury process. Collectively, our finding firstly demonstrated that TEGDMA induced JNK-dependent autophagy, thereby promoting mitochondrial dysfunction-associated oxidative damage and apoptosis in preodontoblast.

An alternate methodology for studying diffusion and elution kinetics of dimethacrylate monomers through dentinal tubules

OBJECTIVE

Ethoxylated bisphenol A dimethacrylate (bisEMA) is a base monomer in several dental resin composites. It was the main aim of the present study to determine if bisEMA can reach the dental pulp by generally passive diffusion through the coronal dentinal tubules stimulated via eluent liquids surrounding the root structures only.

METHODS

In 20 human third molar teeth, standard Class-I occlusal cavities were prepared and provided either with an adhesive system alone or additionally with a composite restoration, according to the instructions of the manufacturer. The teeth were placed in an elution chamber such that the elution media only came into contact with the tooth root/tooth base where they were incubated at 37 °C for up to 7 d. Samples were taken after 1, 2, 4 and 7 d. Gas chromatography/mass spectrometry was used to identify bisEMA and other monomers in ethanol/water (3:1) and aqueous eluates.

RESULTS

bisEMA was only found in ethanol/water eluates, where the teeth had received a composite restoration. Traces of bisEMA with up to three ethylene oxide units could be detected in these eluates. Depending on the dentin thickness, different elution kinetics of bisEMA were determined. Regardless of the treatment of teeth, triethylene glycol dimethacrylate (TEGDMA) and tetraethylene glycol dimethacrylate (TEEGDMA) were found in ethanolic/aqueous eluates in equal amounts. Most TEGDMA and TEEGDMA diffused through the dentin within the first 24 h.

SIGNIFICANCE

Depending on the dentin layer thickness, bisEMA was released for varied time periods, resulting in varied concentrations and exposure times for the different cells of the dental pulp. The concentrations of TEGDMA and TEEGDMA were greatest for cells of the dental pulp within the first 24 h.

Evaluation of monomer leaching from a resin cement through dentin by a novel model

OBJECTIVE

To evaluate the elution of HEMA, BPA, UDMA and BisGMA from a conventional resin cement (Multilink Automix^®, Ivoclar Vivadent) through human dentin, under constant positive pulpal pressure.

METHODS

Ten human dentin disks (n=10) were adjusted in a new testing device and transparent glass slabs were luted with Multilink Automix^® resin cement, following manufacturer's instructions, under a steady pressure of 25N. The device was filled with Ringer's solution. At 5min, 20min, 1h, 2h, 21h, 3 days, 7 days, 10days and 21days time intervals, the whole eluate was retrieved from each one of the ten specimens and then, the specimens were refilled with fresh Ringer's solution. The eluates were analyzed by High Performance Liquid Chromatography (HPLC).

RESULTS

HEMA was detected in the eluate of all of the specimens, from 5min until 10 days. At four of the specimens, HEMA was also detected in the 21days eluate at very low concentrations. BPA, UDMA and BisGMA were not detected at any eluate. An unknown compound was also detected at 4.4min.

SIGNIFICANCE

The concentrations of HEMA that enabled to diffuse from Multilink Automix^® cement in an aqueous solution, through a dentin barrier, did not reach toxic levels and BPA, UDMA and BisGMA were not detected at all.

Effect of indomethacin-loaded nanocapsules incorporation in a dentin adhesive resin

OBJECTIVES

The aim of this study was to produce indomethacin-loaded nanocapsules (IndOH-NCs) and evaluate the influence of their incorporation into an adhesive resin.

MATERIALS AND METHODS

Indomethacin was encapsulated by the deposition of preformed polymer. IndOH-NCs were characterized by laser diffractometry, Fourier transformed infrared spectrometry, transmission electron microscopy (TEM), scanning electron microscopy, high-performance liquid chromatography (HPLC), and MTT assay. Nanocapsules (NCs) were incorporated into an adhesive in concentrations of 1, 2, 5, and 10 %. The addition was visualized by TEM and drug release was evaluated by HPLC until 120 h of immersion in simulated body fluid (SBF). Drug diffusion through dentin was tested using a Franz diffusion cell apparatus and quantified by HPLC. The degree of conversion (DC), softening in ethanol, and microtensile bond strength (μTBS) were evaluated to determine whether the nanocapsules influenced the adhesive. Data were analyzed using one-way ANOVA and Tukey's post hoc test for DC, softening in ethanol, μTBS, and cytotoxicity, and paired t test for comparison between the initial and final Knoop microhardness.

RESULTS

IndOH-NCs, with a spherical shape and a mean diameter of 165 nm, were incorporated into an adhesive. Indomethacin content was 7 mg drug/g powder. IndOH-NCs maintained high cell viability. At 120 h, an amount of 13.83 % of indomethacin was released, and after 7 days, 7.07 % of this drug was diffused through dentin for an adhesive containing 10 % of nanocapsules. No alteration in the DC, softening in ethanol, and μTBS resulted from NC addition.

CONCLUSIONS

IndOH-NCs may be incorporated into adhesive systems, without compromising properties, to add an anti-inflammatory drug controlled release for restorative procedures in deep cavities.

CLINICAL SIGNIFICANCE

Here is the first step toward the goal of providing agents to act at an inflammatory process of pulp tissue through dental adhesives via encapsulation of drug.

Comparative clinical evaluation of the efficacy of a new method for caries diagnosis and excavation

Aim:

The purpose of this study is to compare the efficiency of fluorescence-aided caries excavation (FACE) to remove carious dentin primary teeth with that of conventional methods.

Methods and Materials:

After caries excavation was carried out, dentin surfaces were conventionally inspected using visual tactile criteria and 415 cavities which were classified as caries-free, re-inspected with Face-Light and caries detector dye (CDD) methods. Orange-red fluorescing areas classified as carious dentin, as well as stained carious dentin. All the data were recorded according to localization of the caries and determination efficiency of the methods. X² test was used to compare the mean values of both Face-Light and dye applications, while Wilcoxon test performed to evaluate the effectiveness for each diagnostic method.

Results:

A total of 273 patients with 415 Class II (OM/OD) cavities (1.65 ± 0.52 teeth per patient) with carious lesions in molar and premolar teeth, were examined. Out of 415 teeth, in 149 teeth (35.9%) no caries findings had been illustrated. While FACE detected remaining carious or partially removed areas in 237 teeth (57.2%), CDD stained only 29 teeth by itself (P < 0.05).

Conclusion:

In conclusion, FACE has a higher detectability compared to visual inspection and caries detector dye in diagnosis and removal of carious dentin.