Environment-friendly soy flour-based resins without formaldehyde

Glyoxalated soy flour adhesives for wood particleboard added with a much smaller proportion of glyoxalated lignin or tannin and without any addition of either formaldehyde or formaldehyde-based resin are shown to yield results satisfying the relevant standard specifications for interior wood boards. Adhesive resin formulations in which the total content of natural material is either 70 or 80% of the total resin solids content gave good results. The resins comprising 70% by weight of natural material can be used in a much lower proportion on wood chips and can afford pressing times fast enough to be significant under industrial panel pressing conditions. The best formulation of all the ones tried was the one based on glyoxalated precooked soy flour (SG), to which a condensed tannin was added in water solution and a polymeric isocyanate (pMDI), where the proportions of the components SG/T/pMDI was 54/16/30 by weight. (C) 2008 Wiley Periodicals, Inc.

Three-Dimensional Stress Distribution in the Human Periodontal Ligament in Masticatory, Parafunctional, and Trauma Loads: Finite Element Analysis

Background: The presence of the periodontal ligament (PDL) makes it possible to absorb and distribute loads produced during masticatory function and other tooth contacts into the alveolar process via the alveolar bone proper. However, several factors affect the integrity of periodontal structures causing the destruction of the connective matrix and cells, the loss of fibrous attachment, and the resorption of alveolar bone. Methods: The purpose of this study was to evaluate the stress distribution by finite element analysis in a PDL in three-dimensional models of the upper central incisor under three different load conditions: 100 N occlusal loading at 45 degrees (model 1: masticatory load); 500 N at the incisal edge at 45 degrees (model 2: parafunctional habit); and 800 N at the buccal surface at 90 degrees (model 3: trauma case). The models were built from computed tomography scans. Results: The stress distribution was quite different among the models. The most significant values (harmful) of tensile and compressive stresses were observed in models 2 and 3, with similarly distinct patterns of stress distributions along the PDL. Tensile stresses were observed along the internal and external aspects of the PDL, mostly at the cervical and middle thirds. Conclusions: The stress generation in these models may affect the integrity of periodontal structures. A better understanding of the biomechanical behavior of the PDL under physiologic and traumatic loading conditions might enhance the understanding of the biologic reaction of the PDL in health and disease. J Periodontol 2009;80:1859-1867.

Three Dimensional Finite Element Analyses of Oral Structures by Computerized Tomography

Our aim was to document the benefits of three dimensional finite element model generations from computed tomography data as well as the realistic creation of all oral structures in a patient. The stresses resulting from the applied load in our study did not exceed the structure limitations, suggesting a clinically acceptable physiological condition.

A plateau detected in lead accumulation in subsurface deciduous enamel from individuals exposed to lead may be useful to identify children and regions exposed to higher levels of lead

In a previous study, we showed 4 times more lead in surface deciduous enamel (1.9-5.9 mu m) of a notoriously contaminated area (Bauru, Sao Paulo State, Brazil) in comparison to samples from a region with no lead contamination described (Ribeirao Preto, Sao Paulo State, Brazil). The samples from the more superficial enamel (1.9-3.18 mu m) showed higher amounts of lead and the highest variability, while in the subsurface enamel (3.18-5.9 mu m) a plateau in lead content was detected in children living in the contaminated environment (around 600 mu g/g). Here we expand our previous study, and use only samples obtained from subsurface enamel (Ribeirao Preto, n = 186; Bauru, n = 20). We tried to distinguish regions with more children with lead above the threshold of 600 mu g/g of lead in enamel. We tested whether differences in the percentage of children with ""high"" lead (>= 600 mu g/g) could be observed among the different Kindergartens studied in Ribeirao Preto. We also tested whether these results were different from the ones provided by conventional comparison of the data. Ribeirao Preto showed almost 4 times less lead than Bauru (p < 0.0001), and a statistically significant difference was found only in Ribeirao Preto between Kindergarten 2 and 5 (p<0.01). Twelve percent of the children from Ribeirao Preto had ""high"" lead, while 55% of the children from Bauru did so. However, when we looked at the percentages of children with ""high"" lead in each Kindergarten, and compared them, a whole new picture emerged, in which we could see children with ""high"" lead concentrated mainly in 3 Kindergartens from Ribeirao Preto, with Kindergarten 5 with 33% of the children with ""high"" lead, being statistically different from all Kindergartens, except 4 and 6. The threshold of 600 mu g/g of lead in subsurface enamel was tentatively settled here after the plateau seen in exposed children, and enabled us to identify locations with more children exposed to a higher amount of lead. (C) 2008 Elsevier Inc. All rights reserved.

Down-regulation of expression of osteoblast and osteocyte markers in periodontal tissues associated with the spontaneous alveolar bone loss of interleukin-10 knockout mice

The aim of this study was to unravel the mechanisms by which interleukin (IL)-10, a potent pleiotropic cytokine, modulates alveolar bone homeostasis in C57BL/6 wild-type (WT) and IL-10 knockout (IL-10 KO) mice, evaluated at 8, 24, and 48 wk of age. Interleukin-10 KO mice presented significant alveolar bone loss when compared with WT mice, and this was not associated with changes in leukocyte counts or bacterial load. The levels of expression of messenger RNA (mRNA) for tumor necrosis factor-alpha (TNF-alpha), IL-1 beta, IL-6, transforming growth factor-beta (TGF-beta), receptor activator of nuclear factor kappa B ligand (RANKL), osteoprotegerin (OPG), and matrix metalloproteinase 13 (MMP13) were similar between both strains, whereas a significant decrease of tissue inhibitor of metalloproteinase 1 (TIMP1) mRNA expression was found at 48 wk in IL-10 KO mice. The osteoblast markers core binding factor alpha1 (CBFA1) and type I collagen (COL-I) were expressed at similar levels in both strains, whereas the levels of alkaline phosphatase (ALP) and osteocalcin (OCN), and those of the osteocyte markers phosphate-regulating gene endopeptidases (PHEX) and dentin matrix protein 1 (DMP1) were significantly lower in IL-10 KO mice. Our results demonstrate that the alveolar bone loss in the absence of IL-10 was associated with a reduced expression of osteoblast and osteocyte markers, an effect independent of microbial, inflammatory or bone-resorptive pathways.

Effects of intrapulpal temperature change induced by visible light units on the metabolism of odontoblast-like cells

Purpose: To investigate the effects of intrapulpal temperature changes induced by a quartz tungsten halogen (QTH) and a light emitting diode (LED) curing units on the metabolism of odontoblast-like cells. Methods: Thirty-six 0.5 mm-thick dentin discs obtained from sound human teeth were randomly assigned into three groups: QTH, LED and no light (control). After placement of the dentin discs in pulp chamber devices, a thermistor was attached to the pulpal surface of each disc and the light sources were applied on the occlusal surface. After registering the temperature change, odontoblast-like cells MDPC-23 were seeded on the pulpal side of the discs and the curing lights were again applied. Cell metabolism was evaluated by the MTT assay and cell morphology was assessed by SEM. Results: In groups QTH and LED the intrapulpal temperature increased by 6.4 degrees C and 3.4 degrees C, respectively. The difference between both groups was statistically significant (Mann-Whitney; P< 0.05). QTH and LED reduced the cell metabolism by 36.4% and 33.4%, respectively. Regarding the cell metabolism, no statistically significant difference was observed between both groups (Mann-Whitney; P> 0.05). However, when compared to the control, only QTH significantly reduced the cell metabolism (Mann-Whitney; P< 0.05). It was concluded that the irradiance of 0.5 mm-thick human dentin discs with a QTH in comparison to a LED curing unit promoted a higher temperature rise, which propagates through the dentin negatively affecting the metabolism of the underlying cultured pulp cells. (Am J Dent 2009;22:151-156).

Prevention of toothbrushing abrasion of acid-softened enamel by CO(2) laser irradiation

Objective: The aim of the present study was to evaluate the effect of CO(2) laser irradiation (10.6 mu m) at 0.3 J/cm(2) (0.5 mu s; 226 Hz) on the resistance of softened enamel to toothbrushing abrasion, in vitro. Methods: Sixty human enamel samples were obtained, polished with silicon carbide papers and randomly divided into five groups (n = 12), receiving 5 different surface treatments: laser irradiation (L), fluoride (AmF/NaF gel) application (F), laser prior to fluoride (LF), fluoride prior to laser (FL), non-treated control (C). After surface treatment they were submitted to a 25-day erosive-abrasive cycle in 100 ml sprite light (90 s) and brushed twice daily with an electric toothbrush. Between the demineralization periods samples were immersed in supersaturated mineral solution. At the end of the experiments enamel surface loss was determined using a contact profilometer and morphological analysis was performed using scanning electron microscopy (SEM). For SEM analysis of demineralization pattern, cross-sectional cuts of cycled samples were prepared. The data were statistically analysed by one-way ANOVA model with subsequent pairwise comparison of treatments. Results: Abrasive surface loss was significantly lower in all laser groups compared to both control and fluoride groups (p < 0.0001 in all cases). Amongst the laser groups no significant difference was observed. Softened enamel layer underneath lesions was less pronounced in laser-irradiated samples. Conclusion: Irradiation of dental enamel with a CO(2) laser at 0.3 J/cm(2) (5 mu s, 226 Hz) either alone or in combination with amine fluoride gel significantly decreases toothbrushing abrasion of softened-enamel, in vitro. (C) 2011 Elsevier Ltd. All rights reserved.

Influence of laser irradiation on fiber post retention

The purpose of this in vitro study was to compare the bond strength between fiber post and laser-treated root canals. Forty single-rooted bovine teeth were endodontically treated and randomly divided into four groups of equal size according to the root canal treatment: group 1 conventional treatment (without laser irradiation); group 2 Nd:YAG laser (1.5 W, 10 Hz, 100 mJ); group 3 Er,Cr:YSGG laser (0.75 W, 20 Hz); and group 4 Nd:YAG + Er,Cr:YSGG lasers. The fiber posts were cemented with an adhesive system + resin cement, in accordance with the manufacturer`s instructions. A mini acrylic pipe was fixed on the coronal section of the post using a light-polymerized resin. Specimens were mounted on an acrylic pipe with a self-polymerized resin. Retention forces were determined using a universal testing machine (0.5 mm/min). Data were analyzed using one-way ANOVA and Tukey tests (p < 0.05). The post retention force in group 2 was found to be lower than that in the other experimental groups. Fractures were observed at the interface between the dentin and the resin in all groups. High-intensity lasers can be used in conventional endodontic treatment; however, root canal surface irradiation using the Nd:YAG laser was shown to negatively affect the post retention force.

The influence of erbium:yttrium-aluminum-garnet laser ablation with variable pulse width on morphology and microleakage of composite restorations

The objective of this study was to evaluate the influence of various pulse widths with different energy parameters of erbium:yttrium-aluminum-garnet (Er:YAG) laser (2.94 mu m) on the morphology and microleakage of cavities restored with composite resin. Identically sized class V cavities were prepared on the buccal surfaces of 54 bovine teeth by high-speed drill (n = 6, control, group 1) and prepared by Er:YAG laser (Fidelis 320A, Fotona, Slovenia) with irradiation parameters of 350 mJ/ 4 Hz or 400 mJ/2 Hz and pulse width: group 2, very short pulse (VSP); group 3, short pulse (SP); group 4, long pulse (LP); group 5, very long pulse (VLP). All cavities were filled with composite resin (Z-250-3 M), stored at 37A degrees C in distilled water, polished after 24 h, and thermally stressed (700 cycles/5-55A degrees C). The teeth were impermeabilized, immersed in 50% silver nitrate solution for 8 h, sectioned longitudinally, and exposed to Photoflood light for 10 min to reveal the stain. The leakage was evaluated under stereomicroscope by three different examiners, in a double-blind fashion, and scored (0-3). The results were analyzed by Kruskal-Wallis test (P > 0.05) and showed that there was no significant differences between the groups tested. Under scanning electron microscopy (SEM) the morphology of the cavities prepared by laser showed irregular enamel margins and dentin internal walls, and a more conservative pattern than that of conventional cavities. The different power settings and pulse widths of Er:YAG laser in cavity preparation had no influence on microleakage of composite resin restorations.

Comparative analysis of root surface smear layer removal by different etching modalities or erbium:yttrium-aluminum-garnet laser irradiation. A scanning electron microscopy study

The purpose of this study was to evaluate the effect of erbium:yttrium-aluminum-garnet (Er:YAG) laser (2.94 mu m) irradiation on the removal of root surface smear layer of extracted human teeth and to compare its efficacy with that of citric acid, ethylenediamine tetra-acetic acid (EDTA), or a gel containing a mixture of tetracycline hydrochloride (HCl) and citric acid, using scanning electron microscopy (SEM). Thirty human dentin specimens were randomly divided into six groups: G1 (control group), irrigated with 10 ml of physiologic saline solution; G2, conditioned with 24% citric acid gel; G3, conditioned with 24% EDTA gel; G4, conditioned with a 50% citric acid and tetracycline gel; G5, irradiated with Er:YAG laser (47 mJ/10 Hz/5.8 J/cm(2)/pulse); G6, irradiated with Er:YAG laser (83 mJ/10 Hz/10.3 J/cm(2)/pulse). Electron micrographs were obtained and analyzed according to a rating system. Statistical analysis was conducted with Kruskal-Wallis and Mann-Whitney tests (P < 0.05). G1 was statistically different from all the other groups; no statistically significant differences were observed between the Er:YAG laser groups and those undergoing the other treatment modalities. When the two Er:YAG laser groups were compared, the fluency of G6 was statistically more effective in smear layer removal than the one used in G5 (Mann-Whitney test, P < 0.01). Root surfaces irradiated by Er:YAG laser had more irregular contours than those treated by chemical agents. It can be concluded that all treatment modalities were effective in smear layer removal. The results of our study suggest that the Er:YAG laser can be safely used to condition diseased root surfaces effectively. Furthermore, the effect of Er:YAG laser irradiation on root surfaces should be evaluated in vivo so that its potential to enhance the healing of periodontal tissues can be assessed.

Diode Laser Irradiation Effects on the Sealing Ability of Root Canal Sealers

This study aimed to test the hypothesis that dentine alterations induced by 810 nm-diode laser may affect the interaction between root canal sealers and the dentin wall. Seventy-two single root human teeth were selected and root canals were enlarged with K-files. Dentine was treated with 0.5% NaOCl and 17% EDTA-T and irradiated (laser group) by diode laser (810 nm/P = 2.5W/I = 1989 W/cm(2)) or remained non-irradiated (control group). Six samples per group were analyzed by scanning electron microscopy (SEM). The remaining samples of each group were divided into three subgroups (n = 10) and sealed with one of the tested sealers (N-Rickert/AHPlus (TM)/Apexit (R)). Apical leakage was estimated by evaluating penetration of 0.5% methylene-blue dye. SEM analysis revealed that dentine at the apical third in irradiated samples was melted and fusioned whereas non-irradiated samples exhibited opened dentinal tubules. Despite the morphological changes induced by irradiation, laser did not affect the sealing ability of N-Rickert and AHPlus (TM) sealers. However, the length of apical leakage in roots filled with Apexit (R) was lower in irradiated root canals than in non-irradiated samples (p < 0.05). Morphological changes of root canal walls promoted by diode laser irradiation may improve de sealing ability of Apexit (R), a calcium hydroxide-based sealer, suggesting that improved sealing promoted by irradiation may represent an additional factor contributing to the endodontic clinical outcome.

Influence of etching with erbium, chromium:yttrium-scandium-gallium-garnet laser on microleakage of class V restoration

The aim of this in vitro study was to evaluate some parameters of dental etching when irradiated with an erbium, chromium:yttrium-scandium-gallium-garnet (Er,Cr:YSGG) laser. One-hundred sound human third molars were selected and randomly distributed into ten groups (n = 10). The class V cavities of group 1 (control) were prepared with a bur and etched with 37% phosphoric acid, while groups G2 to G10, were prepared with laser (5 W, 88.46 J/cm(2), 90/70% air/water) and etched with the following powers: G3 and G4, 0.25 W; G5 and G6, 0.5 W; G7 and G8, 0.75 W; G9 and G10, 1 W. Group G2 received no laser etching. Prior to restoration, G2, G4, G6, G8 and G10 received acid etching. After restoration, all samples were submitted to a microleakage test. According to statistical analysis (Kruskal-Wallis and Dunn`s tests), G10 presented the lowest microleakage values (P < 0.05). The other groups showed no differences between them. Etching with Er,Cr:YSGG laser (1 W) followed by phosphoric acid was effective in reducing the microleakage of class V restorations.

Calcitonin, sodium alendronate and high intensity laser in the treatment of traumatized teeth: a preliminary study

The aim of this study was to evaluate the influence of erbium:yttrium-aluminum-garnet (Er:YAG) laser compared with traditional treatment on dentin permeability to calcitonin and sodium alendronate. Forty bovine roots were sectioned and divided into eight groups. Groups 1 and 2 (G1/G2) were immersed in saline solution; G1T/G2T were immersed in ethylene diamine tetra-acetic acid plus sodium lauryl ether sulfate (EDTA-T) and sodium hypochlorite (NaOCl); G1I/G2I were irradiated with Er:YAG laser (2.94 mu m, 6 Hz, 40.4 J/cm(2)); G1TI/G2TI were immersed in EDTA-T, NaOCl and subjected to Er:YAG irradiation. After 4 h the radioactivity of the saline solution was measured. Statistical analysis revealed a significant difference (P < 0.05) when the groups treated with EDTA-T and NaOCl followed by Er:YAG laser irradiation were compared with the groups treated with EDTA-T only and with the groups that received no treatment. Er:YAG laser associated with traditional procedures significantly increased the diffusion of calcitonin and sodium alendronate through dentin. All groups showed calcitonin and sodium alendronate diffusion.

Influence of Final Rinse Technique on Ability of Ethylenediaminetetraacetic Acid of Removing Smear Layer

Introduction: There is ongoing debate regarding the ideal sequence, volume, and concentration of irrigants, length of time for irrigation, and irrigation technique to achieve debridement of the root canal system. The aim of this study was to verify the impact of the final rinse technique on smear layer removal ability of 17% ethylenediaminetetraacetic acid (EDTA). Methods: Sixteen single-rooted human teeth were instrumented and divided into 2 groups at the final rinse step according to the following final rinse techniques used: continuous rinse group, continuous rinse with EDTA during 3 minutes, and rinse and soaking group, rinse with 1 mL of EDTA, soaking of the canal for 2 minutes and 30 seconds, and rinse completion with the remaining 4 mL for 30 seconds. The specimens were split lengthwise and observed under scanning electron microscope. Results: Data were analyzed with Kruskal-Wallis and Dunn tests. The continuous rinse group presented more debris-free surfaces when compared with the rinse and soaking group (P <. 01). When the root canal areas were compared within the groups, no statistical differences were found (P > .05). Conclusions: It can be concluded that a continuous rinse with 5 mL of EDTA for 3 minutes can more efficiently remove the smear layer from root canal walls. (J Endod 2010;36:512-514)

In vitro analysis of inhibitory effects of the antibacterial monomer MDPB-containing restorations on the progression of secondary root caries

Objective: This study aimed to analyze in vitro inhibitory effects of restorative materials containing the antibacterial monomer 12-methacryloyloxydodecylpyridinium bromide (MDPB) on the formation of artificial secondary root caries lesions. Methods: Class V cavities (2 mm x 2 mm) were prepared in 75 human root fragments. Specimens were randomly divided into five groups (n = 15 fragments per group) and restored as follows: (I) MDPB-free adhesive system + MDPB-free composite (negative control); (II) resin modified glass ionomer (RM-GIC; positive control); (III) MDPB-free adhesive system + MDPB-containing composite (2.83% MDPB); (IV) MDPB-containing adhesive system + MDPB-free composite; M MDPB-containing adhesive system + MDPB-containing composite. Artificial secondary root caries lesions were produced by a biological artificial caries challenge. The restored specimens were immersed into a culture medium containing Streptococcus mutans and sucrose for 15 days. Histological slices (80 +/- 20 mu m) of the specimens were used for measuring the mean depths of the artificial lesions produced in both margins of the restorations using polarized light microscopy. Results were expressed in percentage related to the mean depth of the negative control, considered 100%. Data were compared by ANOVA followed by the Tukey`s test (p <= 0.05). Results: The depths of lesions adjacent to cavities filled with RM-GIC (GII; 85.17 +/- 15.2%) were significantly (p < 0.01) shallower than those adjacent to restorations with MDPB-free composite (GI; 100.00 +/- 10.04%), despite the presence of MDPB in the adhesive system (GIV; 101.95 +/- 21.32%). The depths of lesions adjacent to cavities restored with MDPB-containing composite (GIII; 82.68 +/- 12.81% and GV; 85.65 +/- 15.42%), despite the adhesive system used, were similar to those of RM-GIC (GII). Mean lesions depths in these groups decreased from 13% (GV) to 17% (GIII) in relation to the negative control (GI). Conclusions: MDPB-containing composite inhibits the progression of artificial secondary root caries lesions regardless of adhesive systems. (C) 2009 Elsevier Ltd. All rights reserved.