Effects of Er:YAG and Er,Cr:YSGG laser irradiation on the adhesion to eroded dentin.

Limited information is available regarding the adhesion to eroded dentin. This study aims to evaluate the effect of different surface treatments on eroded dentin morphology and on microtensile bond strength (µTBS) of adhesive systems to this substrate. Ninety-six extracted third molars were randomly divided into eight groups (n = 12) according to the type of surface treatment and the adhesive system: G1 = Control + Clearfil SE Bond [SE], G2 = Diamond bur [DB] + SE, G3 = Er:YAG laser (60 mJ, 2 Hz, 0.12 W, 19.3 J/ cm(2)) + SE, G4 = Er,Cr:YSGG laser (50 mJ, 30 Hz, 1.5 W, 4.5 J/ cm(2)) + SE, G5 = Control + Single Bond [SB], G6 = DB + SB, G7 = Er:YAG + SB, G8 = Er,Cr:YSGG + SB. The erosive cycling was performed by immersion in 0.05 M citric acid (pH 2.3, 10 min, 6x/day) and in supersaturated solution (pH 7.0, 1 h, between acid attacks), during 5 days. Blocks of composite were bonded to the samples according to the manufacturers' instructions. After 24 h-storage in distilled/deionized water (37 °C), stick-shaped samples were obtained and submitted to µTBS test. Each surface treatment was analyzed under scanning electron microscopy (n = 4) and the bond strength values (megapascal) were analyzed by two-way ANOVA and Tukey tests (α = 0.05). All surface treatments lead to changes on eroded dentin. G4 showed the highest bond strength mean (28.3 ± 9.2 MPa), which was statistically significant higher than all the other groups (p < 0.05). The surface treatment with Er,Cr:YSGG laser irradiation (4.5 J/cm(2)/50 mJ/30 Hz/140 µs) prior to bonding with a self-etching adhesive system significantly increases adhesion to eroded dentin, as compared to conventional treatment.

Impact of caffeine and/or estrogen deficiency on trabecular bone area and healing: a study in rats.

PURPOSE: To evaluate the effects of caffeine and/or estrogen deficiency on trabecular bone area (TBA) and bone healing in rats. MATERIALS AND METHODS: Rats were divided into groups (n=15/group) as follows: control, caffeine, ovariectomy (OVX), and caffeine/OVX. Critical-sized defects were created in the tibiae (57 days after beginning caffeine administration and 43 days after OVX). The intact femurs were evaluated for TBA and the number of positive cells for tartrate-resistant acid phosphatase (TRAP), receptor activator of nuclear factor-κB ligand (RANKL), and osteoprotegerin (OPG). In the defects, bone healing, the number of TRAP+ and RANKL/OPG+ cells, and gene expression of bone morphogenetic protein (BMP)-2, BMP-7, osteopontin, and CBP/p300-interacting-transactivator-with-ED-rich-tail-2 (CITED-2) were evaluated. RESULTS: Bone healing was poorer in defects of the caffeine group than in those of the control group. The femurs of the OVX and OVX/caffeine groups presented lower TBAs and higher RANKL/OPG+ cell ratios. The number of TRAP+ cells was higher in femurs of the caffeine group and in defects of the OVX group. The caffeine/OVX group presented the highest RANKL/OPG+ cell ratio in femurs and defects. The OVX group presented the highest expression of BMP-2, BMP-7, and CITED-2. CONCLUSION: Caffeine affected bone healing, while estrogen deficiency mainly affected TBA, but no significant deleterious synergic effects of both conditions were observed.

Effects of photodynamic therapy on Gram-positive and Gram-negative bacterial biofilms by bioluminescence imaging and scanning electron microscopic analysis.

OBJECTIVE: The aim of this study was to test photodynamic therapy (PDT) as an alternative approach to biofilm disruption on dental hard tissue, We evaluated the effect of methylene blue and a 660 nm diode laser on the viability and architecture of Gram-positive and Gram-negative bacterial biofilms. MATERIALS AND METHODS: Ten human teeth were inoculated with bioluminescent Pseudomonas aeruginosa or Enterococcus faecalis to form 3 day biofilms in prepared root canals. Bioluminescence imaging was used to serially quantify and evaluate the bacterial viability, and scanning electron microscopic (SEM) imaging was used to assess architecture and morphology of bacterial biofilm before and after PDT employing methylene blue and 40 mW, 660 nm diode laser light delivered into the root canal via a 300 µm fiber for 240 sec, resulting in a total energy of 9.6 J. The data were statistically analyzed with analysis of variance (ANOVA) followed by Tukey test. RESULTS: The bacterial reduction showed a dose dependence; as the light energy increased, the bioluminescence decreased in both planktonic suspension and in biofilms. The SEM analysis showed a significant reduction of biofilm on the surface. PDT promoted disruption of the biofilm and the number of adherent bacteria was reduced. CONCLUSIONS: The photodynamic effect seems to disrupt the biofilm by acting both on bacterial cells and on the extracellular matrix.

Effects of ultramorphological changes on adhesion to lased dentin-Scanning electron microscopy and transmission electron microscopy analysis.

Dentin irradiation with erbium lasers has been reported to alter the composite resin bond to this treated surface. There is still a lack of studies reporting the effect of erbium lasers on dentin organic content and elucidating how laser treatment could interfere in the quality of the resin-dentin interface. This study aimed to evaluate the effect of erbium laser irradiation on dentin morphology and microtensile bond strength (µTBS) of an adhesive to dentin. Seventy-two dentin disks were divided into nine groups (n = 8): G1-Control (600-grit SiC paper); Er:YAG groups: G2- 250 mJ/4 Hz; G3- 200 mJ/4 Hz; G4- 180 mJ/10 Hz; G5- 160 mJ/10 Hz; Er,Cr:YSGG groups: G6- 2 W/20 Hz; G7- 2.5 W/20 Hz; G8- 3 W/20 Hz; G9- 4 W/20 Hz. Specimens were processed for cross-sectional analysis by scanning electron microscopy (SEM) (n = 3), transmission electron microscopy (TEM) (n = 2), and adhesive interface (n = 3). Forty-five dentin samples (n = 5) were restored and submitted to µTBS testing. ANOVA (α = 5%) revealed that G1 presented the highest µTBS values and irradiated groups did not differ from each other. TEM micrographs showed a superficial layer of denatured collagen fibrils. For SEM micrographs, it was possible to verify the laser effects extending to dentin subsurface presenting a rough aspect. Cross-sectional dentin micrographs of this hybridized surface revealed a pattern of modified tags with ringlike structures around it. This in vitro study showed that erbium laser irradiation interacts with the dental hard tissue resulting in a specific morphological pattern of dentin and collagen fibrils that negatively affected the bond strength to composite resin.

Secretion of collagen I and tenascin is modulated by laminin-111 in 3D culture of human adenoid cystic carcinoma cells.

Adenoid cystic carcinoma is a frequent malignant salivary gland neoplasm with high levels of recurrence and metastasis. This neoplasm expresses prominent extracellular matrix (ECM). We are studying regulatory mechanisms underlying secretion of ECM molecules in adenoid cystic carcinoma. We have previously demonstrated that laminin modulates the phenotype of a human adenoid cystic carcinoma (CAC2) cell line. Thus, this molecule would be a good candidate to regulate secretion of ECM molecules in these cells. Here we analysed the role played by laminin-111 [formerly laminin-1; Aumailley et al. (2005). Matrix Biol. 24, 326] stimulating secretory activity of CAC2 cells. Three-dimensional cultures of cells in laminin-111 (treated) or agarose (controls) were studied by light and electron microscopy. Ultrastructural analysis of CAC2 cells grown within laminin-111 showed pseudocysts filled with secretory-like material. Cells exhibited prominent and dilated endoplasmic reticulum and coated and uncoated vesicles. Ultrastructural findings suggested that laminin-111 induced secretory activity in CAC2 cells. We further investigated this point by light microscopy, immunofluorescence and confocal microscopy. Histochemistry showed periodic acid-Schiff (PAS)-positive diastase-resistant material in CAC2 cells treated by laminin-111. This material could represent laminin-induced secretion of ECM molecules. We searched for collagen I and tenascin in CAC2 cells treated by laminin-111. Confocal microscopy and immunoblot showed that laminin-111 enhanced secretion of collagen I and tenascin in CAC2 cells. We suggest that laminin-111 modulates secretion of collagen I and tenascin in cells derived from human adenoid cystic carcinoma.

Evaluation of the titanium Ti-6Al-7Nb alloy with and without plasma-sprayed hydroxyapatite coating on growth and viability of cultured osteoblast-like cells.

BACKGROUND: Osseointegrated dental implants are currently recognized as a standard treatment method in dentistry. Titanium (Ti) and its alloys are the metals of choice for endosseous parts of currently available dental implants. Ti-6Al-4V is the most used Ti alloy, however; an improved version, Ti-6Al-7Nb, has been recently developed. METHODS: Rat osteoblast-like cells (osteo- 1 culture) were used to analyze the biocompatibility of Ti-6Al-7Nb alloy with and without hydroxyapatite (HA) coating. The cells were grown on culture Petri dishes on the top of either plain Ti-6Al-7Nb or HA-coated Ti-6Al-7Nb disks. Osteo-1 cells grown on plain culture dishes were used as controls. Growth and cell viability curves were obtained by scanning electron microscopy. For the growth and viability curves, 10(4) cells were seeded on 35 mm dishes. Cells from each group were counted, in triplicate at 3, 7, 11, and 15 days after seeding using the Trypan blue dye exclusion assay. RESULTS: The cells grew as multiple layers on both Ti-6Al-7Nb substrates, showing extracellular matrix only when grown on HA-coated Ti-6Al-7Nb disks. The cells grown on HA-coated Ti-6Al-7Nb grew more slowly than the other 2 groups, with significantly smaller cell numbers than control cultures at the end of the experimental time. Additionally, the HA coated Ti-6Al-7Nb group presented smaller percentage of cell viability when compared to the control group. However, no significant differences were observed between the Ti groups. CONCLUSIONS: The presence of HA on the Ti-6Al-7Nb surface impaired the cell growth and viability of osteo-1 cells. However, this coating improved the extracellular matrix formation. Thus, our cell viability and structural studies showed that Ti-6Al-7Nb with or without HA coating has relevant physical and biological properties as an implant material.