Toxicity and efficiency study of plant extracts-based bleaching agents

OBJECTIVES

Tooth bleaching is one of the most required dental esthetic treatments. However, it can generate side effects like oral irritation, enamel alteration, tooth sensitivity, especially caused by hydrogen peroxide, the main bleaching component of the commercial products. Therefore, development of new tooth bleaching agents, based on natural products, with comparable esthetic results and lower side effects is needed. The aim of this study was to evaluate the biological effects and bleaching efficacy of four experimental bleaching agents, derived from fruit juices, against the commercially available Opalescence (Ultradent, USA).

MATERIALS AND METHODS

Organic acid composition of the gels was characterized by HPLC. Bleaching efficiency was tested by spectrophotometry on composite restorative materials. Biological testing was done in vitro, on human fibroblasts. Cells were exposed to dilutions of the bleaching gel-conditioned medium. Viability was measured by MTS, apoptosis by FACS-AnnexinV FITC/Propidium iodide, NF-kB activation by western blot, malondyaldehide, and superoxide dismutase activity by spectrophotometry.

RESULTS

All gels exhibited physical stability and dental bleaching capabilities. Experimental gels induced significantly better viability and apoptosis rates, lower lipid peroxidation, and increased antioxidant defense, compared to Opalescence.

CONCLUSIONS

The studied experimental gel formulations exhibited a good safety profile in vitro, as well as bleaching efficiency on restorative composite materials.

CLINICAL RELEVANCE

These data open new possibilities for the use of new natural products in dental bleaching treatments that can insure significant esthetic results and lower side effects.

Natural chemopreventive alternatives in oral cancer chemoprevention

We studied the effect of grape seed extract Burgund Mare (BM) on oral carcinogenesis and compared it with that of curcumin (CU). Wistar rats were divided into six groups (n = 10): 4-nitro-quinoline-1-oxide (4NQO) oral carcinogenesis was induced to groups 1 - 5; groups 2 and 3 received BM and CU respectively during initiation and groups 4 and 5 BM and CU during post-initiation of carcinogenesis; group 6 represented the negative control group. Total malondialdehyde (MDA) and reduced glutathione (GSH) were assayed fluorometrically in oral tissue (gingival, jugal, palatal, lingual mucosa) and serum. Histopathological exam was performed and a dysplasia score given to each oral mucosal lesion. Ki67, cyclin D1, p63, Bcl2 and p53 were immunohistochemically evaluated. BM and CU reduced tissue MDA values elevated by 4NQO (P = 0.000). The difference between CU and BM effect was significant in the initiation (P = 0.02) but not in the post-initiation phase of carcinogenesis (P = 0.58). Tissue GSH levels decreased by 4NQO (P < 0.001) were not significantly modified by BM or CU. Serum MDA levels increased by 4NQO (P = 0.000) were significantly lowered by CU (P = 0.04) and BM (P = 0.04) during initiation and by CU during post-initiation of carcinogenesis (P = 0.01). CU was more potent than BM during post-initiation of carcinogenesis (P = 0.01). Serum GSH lowered by 4NQO (P = 0.55) was significantly decreased by BM and CU (P < 0.012), with no significant difference between groups receiving BM or CU. Moderate dysplasia was the most advanced dysplasia induced and gingival localization the most frequent. Both BM and CU lowered dysplasia scores, with BM being the most efficient during post-initiation of carcinogenesis (P = 0.001). Ki67, cyclin D1, p63, Bcl2 and p53 expression increased with dysplasia scores. BM showed chemopreventive properties during initiation and post-initiation of oral carcinogenesis, reducing local and general oxidative stress and the intensity of dysplasia. During post-initiation of carcinogenesis BM and CU exhibited similar effects.

Cytotoxicity assessment of graphene-based nanomaterials on human dental follicle stem cells

Graphene-oxide (GO) and its most encountered derivatives, thermally reduced graphene oxide (TRGO) and nitrogen-doped graphene (N-Gr), were synthesized and structurally characterized by spectroscopic techniques, like Raman and (13)C MAS solid state NMR. Several biological effects (cytotoxicity, oxidative stress induction, and cellular and mithocondrial membrane alterations) induced by such graphene-based materials on human dental follicle stem cells were investigated. Graphene oxide shows the lowest cytotoxic effect, followed by the nitrogen-doped graphene, while thermally reduced graphene oxide exhibits high cytotoxic effects. Graphene oxide induces oxidative stress without causing cell membrane damage. Nitrogen-doped graphene shows a slight antioxidant activity; however, at high doses (20 and 40 μg/ml) it causes membrane damage. Both graphene oxide and nitrogen-doped graphene seem to be valuable candidates for usage in dental nanocomposites.

Effect of Cimetidine on Nitro-Oxidative Stress in a Rat Model of Periodontitis

Background and aims

Periodontitis is a chronic inflammation that involves nitro-oxidative stress with damaging periodontal structural effects. We aimed to evaluate the consequences of low-dose cimetidine on nitro-oxidative stress in periodontitis.

Methods

A rat model of ligature-induced periodontitis was used. After two weeks, the periodontitis groups were treated with cimetidine, aminoguanidine, N-nitro-L-arginine methyl ester and trolox for one week. On day 21, blood was drawn and the serum analyzed for measurement of total nitrites and nitrates, total oxidative status, total antioxidant response, and oxidative stress index.

Results

Cimetidine had an inhibitory effect on the synthesis of nitric oxide (p=0.001), total oxidative status (p=0.01) and oxidative stress index (p=0.01). Total antioxidant reactivity was increased by cimetidine (p=0.01). The effects of cimetidine were almost like those of aminoguanidine, NG-nitro-L-arginine methyl ester, and trolox.

Conclusions

Low-dose cimetidine can be used as adjunctive host modulatory therapy in chronic periodontitis because it reduces nitro-oxidative stress.

Fractal analysis of ibuprofen effect on experimental dog peri-implantitis

INTRODUCTION

The aim of this study was to assess the correlation between the fractal analysis of gingival changes and systemic nitro-oxidative stress in a short-term low-dose ibuprofen (IBU) treatment at experimental peri-implantitis (PI).

MATERIALS AND METHODS

Six adult male mixed-breed dogs with PI were randomly treated for 2 weeks, 3 with IBU (5 mg/kg b.w.) and 3 with placebo. Clinical and radiological evaluation were performed. Gingival biopsies were assessed by light microscopy, transmission electron microscopy, and fractal analysis. Blood was collected to assay nitric oxide (NOx), total oxidative status (TOS), total antioxidant response (TAR), and oxidative stress index (OSI).

RESULTS

Specific gingival ultrastructural alterations, bone loss, and systemic nitro-oxidative stress were evident in PI-placebo animals. IBU caused significant clinical, microscopic, fractal dimensions (P < 0.01), NOx, TOS, and OSI improvements. IBU caused no important bone and TAR changes.

CONCLUSION

This study confirms that fractal analysis was a good method to assess the complex morphological changes and correlations with the nitro-oxidative stress in PI. Short-term low-dose IBU treatment consistently improved gingival status and reduced systemic nitro-oxidative stress.

In vitro testing of an experimental dental composite resin and adhesive system

In vitro testing of new experimental materials has been introduced for many years as a method to evaluate them in simulated conditions, before the clinical trials. Our study has investigated a new experimental composite resin C1 and adhesive system Ad1 by scanning electron microscope (SEM) studies and microleakage tests.

MATERIALS AND METHODS

Both in vitro test were performed on extracted human teeth, that were prepared for standardized class II and V restorations and restored with three composite resins (experimental C1, TetricCeram TC and Solitaire2 S2) and their total-etch adhesive systems (Ad1, Excite EX and GlumaOneBond GB). Teeth were sectioned and investigated under the SEM microscope for the interfaces created and under the optical microscope for dye penetration and microleakage.

RESULTS

The Romanian experimental composite C1 has shown lower alpha "ideal" interfaces than TC and S2, with no significant difference between the latter. Microleakage was significantly lower at the enamel margin and significantly higher at the gingival margin placed below the CEJ for all three compared composites. C1 presented similar dye penetration scores with the commercial available systems.

DISCUSSION

The differences in SEM analysis can be attributed to higher viscosity and handling properties in the experimental adhesive Adl and to technique sensitivity.

CONCLUSIONS

Further investigation is required to obtain better working properties for the experimental adhesive and higher "ideal" scores at the interfaces. Also the SEM investigation is more sensitive than the optical microscope analysis.