Single session of Nd:YAG laser intracanal irradiation neutralizes endotoxin in dental root dentin

Endotoxins released in the dental root by Gram-negative microorganisms can be neutralized by calcium hydroxide, when this medication is applied inside the root canal for at least seven days. However, several clinical situations demand faster root canal decontamination. Thus, for faster endotoxin neutralization, endodontists are seeking additional treatments. The in vitro study tested whether or not intracanal Nd:YAG laser irradiation would be able to neutralize endotoxin within the human dental root canal in a single session. Twenty-four human teeth with one root were mounted between two chambers. After conventional endodontic treatment, root canals were contaminated with Escherichia coli endotoxin. Then they were irradiated or not (controls) in contact mode with an Nd:YAG laser (1.5 W, 15 Hz, 100 mJ and pulse fluency of 124  J/cm2). The endotoxin activity was measured using the limulus lysate technique and data were statistically compared (p≤0.05). The concentration of active endotoxin measured in the negative control group was significantly lower than that of the positive control group (p=0.04). The concentrations of endotoxin in both irradiated groups were significantly lower than that of the positive control group (p=0.027) and similar to that of negative control group (p=0.20). A single session of intracanal Nd:YAG laser irradiation is able to neutralize endotoxin in the dental root tissues.

Mitochondrial swelling and incipient outer membrane rupture in preapoptotic and apoptotic cells

Outer mitochondrial membrane (OMM) rupture was first noted in isolated mitochondria in which the inner mitochondrial membrane (IMM) had lost its selective permeability. This phenomenon referred to as mitochondrial permeability transition (MPT) refers to a permeabilized inner membrane that originates a large swelling in the mitochondrial matrix, which distends the outer membrane until it ruptures. Here, we have expanded previous electron microscopic observations that in apoptotic cells, OMM rupture is not caused by a membrane stretching promoted by a markedly swollen matrix. It is shown that the widths of the ruptured regions of the OMM vary from 6 to 250 nm. Independent of the perforation size, herniation of the mitochondrial matrix appeared to have resulted in pushing the IMM through the perforation. A large, long focal herniation of the mitochondrial matrix, covered with the IMM, was associated with a rupture of the OMM that was as small as 6 nm. Contextually, the collapse of the selective permeability of the IMM may precede or follow the release of the mitochondrial proteins of the intermembrane space into the cytoplasm. When the MPT is a late event, exit of the intermembrane space proteins to the cytoplasm is unimpeded and occurs through channels that transverse the outer membrane, because so far, the inner membrane is impermeable. No channel within the outer membrane can expose to the cytoplasm a permeable inner membrane, because it would serve as a conduit for local herniation of the mitochondrial matrix. Anat Rec, 2012. © 2012 Wiley Periodicals, Inc.

In vitro and in vivo evaluation of the biocompatibility of a calcium phosphate/poly(lactic-co-glycolic acid) composite

This study assess the effects of bioceramic and poly(lactic-co-glycolic acid) composite (BCP/PLGA) on the viability of cultured macrophages and human dental pulp fibroblasts, and we sought to elucidate the temporal profile of the reaction of pulp capping with a composite of bioceramic of calcium phosphate and biodegradable polymer in the progression of delayed dentine bridge after (30 and 60 days) in vivo. Histological evaluation of inflammatory infiltrate and dentin bridge formation were performed after 30 and 60 days. There was similar progressive fibroblast growth in all groups and the macrophages showed viability. The in vivo study showed that of the three experimental groups: BCP/PLGA composite, BCP and calcium hydroxide (Ca(OH)(2)) dentin bridging was the most prevalent (90 %) in the BCP/PLGA composite after 30 days, mild to moderate inflammatory response was present throughout the pulp after 30 days. After 60 days was observed dentine bridging in 60 % and necrosis in 40 %, in both groups. The results indicate that understanding BCP/PLGA composite is biocompatible and by the best tissue response as compared to calcium hydroxide in direct pulp capping may be important in the mechanism of delayed dentine bridge after 30 and 60 days.

Effect of laser phototherapy on wound healing following cerebral ischemia by cryogenic injury

Laser phototherapy emerges as an alternative or auxiliary therapy for acute ischemic stroke, traumatic brain injury, degenerative brain disease, spinal cord injury, and peripheral nerve regeneration, but its effects are still controversial. We have previously found that laser phototherapy immunomodulates the response to focal brain damage. Following direct cortical cryogenic injury the effects of laser phototherapy on inflammation and repair was assessed after cryogenic injury (CI) to the central nervous system (CNS) of rats. The laser phototherapy was carried out with a 780 nm AlGaAs diode laser. The irradiation parameters were: power of 40 mW, beam area of 0.04 cm(2), energy density of 3 J/cm(2) (3s) in two points (0.12 J per point). Two irradiations were performed at 3 h-intervals, in contact mode. Rats (20 non-irradiated - controls and 20 irradiated) were used. The wound healing in the CNS was followed in 6 h, 1, 7 and 14 days after the last irradiation. The size of the lesions, the neuron cell viability percentages and the amount of positive GFAP labeling were statistically compared by ANOVA complemented by Tukey's test (p<0.05). The distribution of lymphocytes, leukocytes and macrophages were also analyzed. CI created focal lesions in the cortex represented by necrosis, edema, hemorrhage and inflammatory infiltrate. The most striking findings were: lased lesions showed smaller tissue loss than control lesions in 6 h. During the first 24 h the amount of viable neurons was significantly higher in the lased group. There was a remarkable increase in the amount of GFAP in the control group by 14 days. Moreover, the lesions of irradiated animals had fewer leukocytes and lymphocytes in the first 24 h than controls. Considering the experimental conditions of this study it was concluded that laser phototherapy exerts its effect in wound healing following CI by controlling the brain damage, preventing neuron death and severe astrogliosis that could indicate the possibility of a better clinical outcome.

p73 deficiency results in impaired self renewal and premature neuronal differentiation of mouse neural progenitors independently of p53

The question of how neural progenitor cells maintain its self-renewal throughout life is a fundamental problem in cell biology with implications in cancer, aging and neurodegenerative diseases. In this work, we have analyzed the p73 function in embryonic neural progenitor cell biology using the neurosphere (NS)-assay and showed that p73-loss has a significant role in the maintenance of neurosphere-forming cells in the embryonic brain. A comparative study of NS from Trp73−/−, p53KO, p53KO;Trp73−/− and their wild-type counterparts demonstrated that p73 deficiency results in two independent, but related, phenotypes: a smaller NS size (related to the proliferation and survival of the neural-progenitors) and a decreased capacity to form NS (self-renewal). The former seems to be the result of p53 compensatory activity, whereas the latter is p53 independent. We also demonstrate that p73 deficiency increases the population of neuronal progenitors ready to differentiate into neurons at the expense of depleting the pool of undifferentiated neurosphere-forming cells. Analysis of the neurogenic niches demonstrated that p73-loss depletes the number of neural-progenitor cells, rendering deficient niches in the adult mice. Altogether, our study identifies TP73 as a positive regulator of self-renewal with a role in the maintenance of the neurogenic capacity. Thus, proposing p73 as an important player in the development of neurodegenerative diseases and a potential therapeutic target.

Analysis in vitro of the cytotoxicity of potential implant materials. I: Zirconia-titania sintered ceramics

Zirconia (ZrO2) is a bioinert, strong, and tough ceramic, while titania (TiO2) is bioactive but has poor mechanical properties. It is expected that ZrO2-TiO2 mixed ceramics incorporate the individual properties of both ceramics, so that this material would exhibit better biological properties. Thus, the objective of this study was to compare the biocompatibility properties of ZrO2-TiO2 mixed ceramics. Sintered ceramics pellets, obtained from powders of TiO2, ZrO2, and three different ZrO2-TiO2 mixed oxides were used. Roughnesses, X-ray diffraction, microstructure through SEM, hardness, and DRIFT characterizations were performed. For biocompatibility analysis cultured FMM1 fibroblasts were plated on the top of disks and counted in SEM micrographs 1 and 2 days later. Data were compared by ANOVA complemented by Tukey's test. All samples presented high densities and similar microstructure. The H2O content in the mixed ceramics was more evident than in pure ceramics. The number of fibroblasts attached to the disks increased significantly independently of the experimental group. The cell growth on the top of the ZrO2-TiO2 samples was similar and significantly higher than those of TiO2 and ZrO2 samples. Our in vitro experiments showed that the ZrO2-TiO2 sintered ceramics are biocompatible allowing faster cell growth than pure oxides ceramics. The improvement of hardness is proportional to the ZrO2 content. Thus, the ZrO2-TiO2 sintered ceramics could be considered as potential implant material.

Laser phototherapy as topical prophylaxis against head and neck cancer radiotherapy-induced oral mucositis: comparison between low and high/low power lasers

BACKGROUND AND OBJECTIVE

Oral mucositis is a dose-limiting and painful side effect of radiotherapy (RT) and/or chemotherapy in cancer patients. The purpose of the present study was to analyze the effect of different protocols of laser phototherapy (LPT) on the grade of mucositis and degree of pain in patients under RT.

PATIENTS AND METHODS

Thirty-nine patients were divided into three groups: G1, where the irradiations were done three times a week using low power laser; G2, where combined high and low power lasers were used three time a week; and G3, where patients received low power laser irradiation once a week. The low power LPT was done using an InGaAlP laser (660 nm/40 mW/6 J cm(-2)/0.24 J per point). In the combined protocol, the high power LPT was done using a GaAlAs laser (808 nm, 1 W/cm(2)). Oral mucositis was assessed at each LPT session in accordance to the oral-mucositis scale of the National Institute of the Cancer-Common Toxicity criteria (NIC-CTC). The patient self-assessed pain was measured by means of the visual analogue scale.

RESULTS

All protocols of LPT led to the maintenance of oral mucositis scores in the same levels until the last RT session. Moreover, LPT three times a week also maintained the pain levels. However, the patients submitted to the once a week LPT had significant pain increase; and the association of low/high LPT led to increased healing time.

CONCLUSIONS

These findings are desired when dealing with oncologic patients under RT avoiding unplanned radiation treatment breaks and additional hospital costs.

Microarray-based gene expression analysis of human osteoblasts in response to different biomaterials

Several biomaterials have been widely used in bone regeneration/substitution procedures in orthopedic and oral surgery. However, how these biomaterials alter osteoblast gene expression is poorly understood. We therefore attempted to address this question by using cDNA microarray technique to identify genes that are differentially regulated in osteoblasts exposed to biomaterials comprehending the biocompatibility spectrum of bioactive (bioglass and hydroxyapatite), bioinert (Ti and stainless steel), and biotolerant (polymethylmethacrylate). By using a cDNA microarray containing 687 human IMAGE sequences, we identified in primary cultures of osteoblastic cells differentiated from the human bone marrow and exposed to these biomaterials, genes whose expression was significantly upregulated or downregulated. Among the differentially expressed genes we have found those involved with cell cycle regulation, cell differentiation and proliferation, apoptosis, cell adhesion, bone mineralization and skeletal development. These results can be relevant to a better understanding of the molecular mechanism underlying the behavior of osteoblasts in bone regenerative procedures.

Cultured epithelial cells response to phototherapy with low intensity laser

BACKGROUND AND OBJECTIVES

Little is known about the intracellular response of epithelial cells to phototherapy. The aim of this in vitro study was to analyze the effect of phototherapy with low-energy lasers with different wavelengths and powers on cultured epithelial cell growth under different nutritional conditions.

STUDY DESIGN/MATERIALS AND METHODS

Epithelial cell cultures (Vero cell line) grown in nutritional deficit in culture medium supplemented with 2% fetal bovine serum (FBS) were irradiated with low-energy laser from one to three times with a GaAlAs laser (660 nm) and InGaAlP (780 nm), 40 and 70 mW, respectively, with 3 or 5 J/cm2. Cell growth was indirectly assessed by measuring the cell mitochondrial activity.

RESULTS

Nonirradiated cell cultures grown in nutritional regular medium supplemented with 10% FBS produced higher cell growth than all cultures grown in nutritional deficit irradiated or not. The overall cell growth of cultures grown under nutritionally deficit conditions was significantly improved especially when irradiated with 780 nm for three times.

CONCLUSIONS

Phototherapy with the laser parameters tested increases epithelial cell growth rate for cells stressed by growth under nutritionally deficient states. This cell growth improvement is directly proportional to the number of irradiations; however, was not enough to reach the full cell growth potential rate of Vero epithelial cell line observed when growing under nutritional regular condition.

Effect of Matrigel on adenoid cystic carcinoma cell line differentiation

Adenoid cystic carcinoma (ACC) is a frequent malignant salivary gland neoplasm presenting different growth patterns described as tubular, cribriform and solid, which represent distinct differentiation stages. Cell lines originated from ACCs grown inside three-dimensional environments have not been capable to reproduce all in vivo ACC growth patterns. As ACC cells in vivo present replicated basement membrane, to mimic this situation in vitro ACC cells (CAC2 cells) were grown on the top of a reconstituted basement membrane (Matrigel). Phenotype differences were assessed by light, fluorescence and transmission electron microscopy. The cultures grown on the top of Matrigel presented three-dimensional arrangement of cells intercepted by cellular cords. At these, cell nests pseudocyst formations were observed. This morphological structure entirely reproduced the cribriform growth pattern of ACC. We suggest that the cribriform differentiation of ACC in culture is dependent of proteins and growth factors associated in a bi-dimensional structure.

Effects of Er:YAG Laser on the Sealing of Glass Ionomer Cement Restorations of Bacterial Artificial Root Caries

OBJECTIVE

The aim of this study was to test the effect of Er:YAG laser irradiation on the marginal sealing of root cavities restored with two glass ionomer cements.

BACKGROUND DATA

For preventing secondary root caries, new technologies for dental caries removal, such as the Er:YAG laser irradiation, have been proposed.

METHODS

Forty-five human teeth were used. Artificial root caries were induced using a microbiological model (Streptococcus mutans). The lesions were removed by three different methods: conventional technique using burs (controls; groups 1 and 2); Er:YAG laser irradiation using dentine preparation parameters (250 mJ, 4 Hz, 80.6 J/cm2; groups 3 and 4); irradiation with the dentine preparation parameters followed by surface conditioning parameters (60 mJ, 2 Hz, 19.2 J/cm2; groups 6 and 7). After each preparation method, three teeth were prepared for scanning electron microscopy morphological observation. The remaining teeth were restored by conventional glass ionomer cement (G1, G3, and G5) or resin modified glass ionomer cement (G2, G4, and G6). After restoration, the samples were thermocycled (1,000 cycles) and prepared for microleakage test.

RESULTS

Scores of less infiltrated samples were observed in groups treated by Er:YAG laser, and the smallest infiltration occurred in the group treated by the dentine preparation parameter, followed by cavity restoration with resin-modified glass ionomer (p < 0.05).

CONCLUSION

Our results suggest that root caries removal by Er:YAG laser irradiation, followed by restoration with resin-modified glass ionomer cement, is a suitable choice for dental root caries restoration.

Irradiation at 780 nm increases proliferation rate of osteoblasts independently of dexamethasone presence

BACKGROUND AND OBJECTIVES

We have previously shown that phototherapy increases cell growth and impairs protein secretion of fibroblasts. Our objective was to study the effect of phototherapy on osteoblast-like cells in culture treated with dexamethasone.

STUDY DESIGN/MATERIALS AND METHODS

Rat calvaria osteoblast-like cells were previously treated or not with dexamethasone and then, they were irradiated or not with a GaAlAs diode laser (wavelength of 780 nm, 10 mW, 3 J/cm2). Adhesion, proliferation, and osteonectin synthesis were analyzed.

RESULTS

Phototherapy increased the proliferation rate of cells independently of dexamethasone presence. Adhesion and osteonectin synthesis were not significantly influenced by laser and/or dexamethasone.

CONCLUSIONS

Based on the conditions of this study we concluded that phototherapy acts as a proliferative stimulus on osteoblast-like cells, even under the influence of dexamethasone. Thus, we suggest that phototherapy can be of importance as co-adjuvant in bone clinical manipulation in order to accelerate bone regeneration.

In vitro evaluation of the cytotoxic effects of acid solutions used as canal irrigants

Solutions of EDTA and citric acid have been used as canal irrigants. These substances must be compatible with apical periodontal tissue. The aim of this study was to evaluate comparatively the cytotoxicity of a 17% EDTA solution and that of three solutions with different concentrations of citric acid (10, 15, and 25%) on cultured fibroblasts. The solutions were diluted to 0.1% and 0.5% in culture medium and then applied to NIH 3T3 cells. After 0, 6, 12, and 24 h (short-term assay; viability) and 1, 3, 5, and 7 days (long-term assay; survival), the cells were counted. The data were compared by ANOVA. In the short-term experiments, all solutions presented a percentage of cell viability similar to that of control cells, except for the 17% EDTA solution diluted to 0.5%. After the long-term assay, all groups presented a continuous and progressive cell growth except for the 17% EDTA solution and for the 25% citric acid solution at a 0.5% dilution. The citric acid solution did not impair cell growth and viability, proving to be noncytotoxic in vitro.

Cytotoxicity of substances leached or dissolved from pulp capping materials

AIM

To evaluate the cytotoxic effects of substances leached or dissolved from pulp capping materials on human pulp fibroblasts.

METHODOLOGY

The substances were applied to cell cultures in conditioned media. The experimental groups were: GI (control; n = 24)--cultures treated with fresh medium; GII (n = 24)--cultures treated with calcium hydroxide cement; GIII (n = 24)--cultures treated with adhesive resin and GIV (n = 24)--cultures treated with 37% orthophosphoric acid. The media were conditioned by placing the crude materials in contact with fresh culture medium for 1 h. The cytotoxicity analysis was performed using the Trypan blue dye exclusion assay at times of 0, 6, 12 and 24 h for cell viability assay, and at 1, 3, 5 and 7 days for survival assay. Data were treated by anova (P < 0.05) and Tukey's test (P < 0.05).

RESULTS

GI and II presented similar cell viability and cell growth. GIII and IV exhibited statistically significant lower percentages of cell viability: GIV only at the 0 h experimental time, whereas in GIII this viability markedly diminished reaching values of 10% by 12 h. Cell growth was impaired only in cultures of GIII.

CONCLUSIONS

Substances dissolved from the adhesive system tested were cytotoxic for human dental pulp fibroblasts in culture, whilst substances leached from calcium hydroxide were biocompatible.

The effect of the renewal of calcium hydroxide paste on the apexification and periapical healing of teeth with incomplete root formation

AIM

To evaluate the influence of renewing calcium hydroxide paste on apexification and periapical healing of teeth in dogs with incomplete root formation and previously contaminated canals.

METHODOLOGY

Forty premolars from four 6-month-old dogs were used. After access to the root canals and complete removal of the pulp, the canal systems remained exposed to the oral environment for 2 weeks. Canal preparation was then carried out using Hedströem files, under irrigation with 1% sodium hypochlorite, 1 mm short of the radiographic apex. After drying, the canals of one premolar in each dog were left empty (group 4-control), and those of the other nine teeth in each animal were filled with a calcium hydroxide-propylene glycol paste. All teeth were restored with reinforced zinc oxide cement (IRM) or IRM and amalgam (group 4). The paste was renewed and the teeth restored again 1 week later. Then, the nine teeth in each animal were divided into three experimental groups: group 1 - paste not changed; group 2 - paste renewed every 4 weeks for 5 months; and group 3 - paste renewed after 3 months had elapsed. The teeth were restored with IRM and amalgam (groups 1 and 3) or IRM (group 2). The animals were killed 5 months later, and blocks of the teeth and surrounding tissues were submitted to histological processing. The sections were studied to evaluate six parameters: apical calcified tissue barrier, inflammatory reaction, bone and root resorption, paste extrusion and microorganisms. Results of experimental groups were analysed by Kruskal-Wallis nonparametric tests and by the test of proportions. The critical value of statistical significance was 5%.

RESULTS

Significant differences (P < 0.05) were found in relation to the presence of bone resorption and paste in the periradicular area, the formation of a calcified tissue barrier at the apex, and the intensity of the apical inflammatory reaction. Bone resorption was more evident in group 1 (medicament not changed), and the presence of paste in the periodontal tissues was more common in groups 2 and 3. Renewal of the paste reduced the intensity of the inflammatory reaction (groups 2 and 3), but the formation of apical calcified tissue was more noticeable in the teeth where the paste had not been renewed.

CONCLUSIONS

Replacement of calcium hydroxide paste was not necessary for apexification to occur, however, it did reduce significantly the intensity of the inflammatory process. Monthly renewal of calcium hydroxide paste reduced significantly the occurrence of apexification.

Morphology of mitochondrial permeability transition: morphometric volumetry in apoptotic cells

Here we report on the mitochondrial permeability transition (MPT), which refers to the morphology of mitochondria whose inner membrane has lost its selective permeability. In all types of apoptotic cells so far examined, we found outer mitochondrial membranes that had been ruptured. These mitochondria present a swollen matrix covered by an inner membrane herniating into the cytoplasm through the breached outer membrane. Similarly ruptured outer mitochondrial membranes have been reported in studies on mitochondrial fractions induced to undergo MPT, carried out by others. Our observations were made on five types of rat tissue cells and six different cultured cell lines in the early stages of apoptosis. Samples from the cell lines HL-60, HeLa, WEHI-164, and a special batch of PC-12 cells were subjected to various apoptogenic agents and analyzed morphometrically. Nonapoptotic companion cells with unaltered nuclear structure (CUNS) were also analyzed. The mitochondrial volume in microm(3) and the volume fraction of the cytoplasm occupied by mitochondria in cells with typical nuclear signs of apoptosis and also in CUNS were evaluated. The volume of the mitochondria with ruptured membrane represents at least 69% (47-89%) of the total mitochondrial volume of the apoptotic cells. Thus, a considerable fraction of the cellular mitochondrial mass is or was in the state of permeability transition and probably involved in enhancement of the apoptotic program. In all samples, a fraction of the cells with normal nuclei possessed mitochondria with breached outer membranes as described above. In these cells, MPT occurred before the appearance of the typical nuclear phenotype of the apoptotic cells.

Analysis of the accuracy of linear measurements obtained by cone beam computed tomography (CBCT-NewTom)

OBJECTIVES

The conical beam computed tomography (CBCT) technique presents an innovation of tomographic imaging systems and subsequent volumetric image reconstruction for dentistry. When compared with other methods of tomographic imaging CBCT is characterized by rapid volumetric image acquisition from a single low radiation dose scan of the patient. The NewTom (NewTom 9000; Quantitative Radiology, Verona, Italy) is an example of such a CBCT machine dedicated to dental and maxillofacial imaging, particularly for surgical and/or prosthetics implant planning in the field of dentistry. The aim of this study was to evaluate the accuracy of the linear measurements obtained in CBCT images using a NewTom.

METHODS

Thirteen measurements were obtained in dry skulls (n = 8) between internal and external anatomical sites using a caliper. These were considered as real measurements. Then the dry skulls were submitted to CBCT imaging examinations. Radiographic distance measurements of the same dry skull anatomical sites were made using the NewTom QR-DVT 9000 software of the 2 mm-CTs axial section images and sagittal or coronal reconstructions. The data were compared by paired Student's t-test.

RESULTS

The results showed that the real measurements were always larger than those for the CBCT images, but these differences were only significant for measurements of the internal structures of the skull base.

CONCLUSIONS

The conclusion of this study is that, although the CBCT image underestimates the real distances between skull sites, differences are only significant for the skull base and therefore it is reliable for linear evaluation measurements of other structures more closely associated with dentomaxillofacial imaging.