Nitrogen-containing flavonoid and their analogs with diverse B-ring in acetylcholinesterase and butyrylcholinesterase inhibition.

In this study, a series of new flavones (2-phenyl-chromone), 2-naphthyl chromone, 2-anthryl-chromone, or 2-biphenyl-chromone derivatives containing 6 or 7-substituted tertiary amine side chain were designed, synthesized, and evaluated in acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) inhibition. The results indicated that the alteration of aromatic ring connecting to chromone scaffold brings about a significant impact on biological activity. Compared with flavones, the inhibitory activity of 2-naphthyl chromone, 2-anthryl-chromone derivatives against AChE significantly decreased, while that of 2-biphenyl chromone derivatives with 7-substituted tertiary amine side chain is better than relative flavones derivatives. For all new synthesized compounds, the position of tertiary amine side chain obviously influenced the activity of inhibiting AChE. The results above provide great worthy information for the further development of new AChE inhibitors. Among the newly synthesized compounds, compound 5a is potent in AChE inhibition (IC50 = 1.29 ± 0.10 µmol/L) with high selectivity for AChE over BChE (selectivity ratio: 27.96). An enzyme kinetic study of compound 5a suggests that it produces a mixed-type inhibitory effect against AChE.

Influence of the indirect restoration design on the fracture resistance: a finite element study.

OBJECTIVES: To establish a three-dimensional (3D) finite element (FE) model of a maxillary first premolar and to evaluate the stress generated on the tooth (dentine) and on the indirect composite resin restorations by occlusal forces. METHODS: An embedded intact maxillary first premolar tooth was sliced serially and scanned digitally parallel to the occlusal surface. The 64 images were assembled in a 3D FE mesh and exported to generate a 3D solid tooth model. Simulated, adhesively cemented indirect mesial-occlusal-distal (MOD) inlays of 2 mm (I1), 3 mm (I2) and 4 mm (I3) in width, and MOD onlays with occlusal cusp coverage of 2 mm (O1) and 3 mm (O2) in depth were created. The peak von Mises stress values in the five tooth models resulting from static vertical and oblique occlusal forces (300 N) were evaluated using Patran FE software. RESULTS: The peak stress values generated by vertical occlusal force generated in dentine of I1, I2, I3, O1 and O2 restoration were 67, 32, 29, 38 and 27 MPa, respectively, and those generated by oblique occlusal force were 52, 114, 168, 54 and 55 MPa, respectively. The peak von Mises stress values in I1, I2, I3, O1 and O2 restoration subjected to oblique occlusal loading were 79, 120, 1740, 1400 and 1170 MPa, respectively. CONCLUSION: A 3D FE model of a maxillary first premolar was established. Simulated cemented composite resin onlay markedly reduces occlusal stress in the underlying dentine of large MOD preparation. Oblique occlusal force imparts substantially higher stress to large composite resin inlay than to the adjacent dentine.

Antimicrobial effects of a bioactive glass combined with fluoride or triclosan on Streptococcus mutans biofilm.

OBJECTIVE: The objective of this study was to investigate the antibacterial effects on a cariogenic biofilm of a bioactive glass (BAG) combined with either sodium fluoride (NaF) or triclosan (TCS). DESIGN: According to minimal bactericidal concentrations, 37.5mg/ml of BAG, 4.69 mg/ml of NaF, and 15.53 µg/ml of TCS solutions were prepared. When used alone, the three antimicrobial solutions were increased to double-dosage strength (2 MBC). The study contained the following experimental groups: group 1, BAG (2 MBC); group 2, NaF (2 MBC); group 3, TCS (2 MBC); group 4, BAG+NaF; group 5, BAG+TCS; group 6, control (saline). Streptococcus mutans biofilm was cultured with 0.1% sucrose anaerobically on 66 sterilized coverslips (1 × 1 cm(2)) for 24h uninterrupted. After 10 min of exposure to the experimental groups, the microbial kinetics, morphology, and viability of the S. mutans biofilms were assessed by evaluation of colony-forming units (CFUs), scanning electron microscopy (SEM), and confocal laser scanning microscopy (CLSM). RESULTS: BAG (2 MBC) used alone showed significantly stronger antibacterial effects than the other two antimicrobials used alone. The combination groups also displayed the same or greater biofilm inactivation effects as BAG (2 MBC) in the plate count test. SEM showed smaller stacks (towers) and fewer surrounding bacteria in groups BAG (2 MBC), BAG+NaF, and BAG+TCS. Confocal microscopy also determined higher live/dead ratios in groups NaF (2 MBC), TCS (2 MBC), and control than in groups BAG (2 MBC), BAG+NaF, and BAG+TCS. CONCLUSIONS: The combinations of BAG with either NaF or TCS enhanced the inactivation effects of BAG (2 MBC) on S. mutans biofilm, and these findings should be further investigated clinically for the control of dental biofilms.

Phase segregation of polymerizable lipids to construct filters for separating lipid-membrane-embedded species.

Supported lipid bilayer (SLB) platforms have been developed to transport and separate membrane-embedded species in the species' native bilayer environment. In this study, we used the phase segregation phenomenon of lipid mixtures containing a polymerizable diacetylene phospholipid, 1,2-bis(10,12-tricosadiynoyl)-sn-glycero-3-phosphocholine (DiynePC), and a nonpolymerizable phospholipid, 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC), to create filter barrier structures in SLBs. Upon exposing the phase segregated samples to UV light, the DiynePC-rich domains could become crosslinked and remain fixed on the surface of the support, while the DOPC-rich regions, where no crosslinking could happen, could be removed later by detergent washing, and thus became the void regions in the filter. During the filter fabrication process, we used the laminar flow configuration in a microfluidic channel to control the spatial locations of the feed region and filter region in the SLB. The flow in a microfluidic channel was also used to apply a strong hydrodynamic shear stress to the SLB to transport the membrane-embedded species from the feed region to the filter region. We varied the DiynePC/DOPC molar ratio from 60/40 to 80/20 to adjust the cutoff size of the filter barriers and used two model membrane-embedded species of different sizes to examine the filtering capability. One of the model species, Texas Red 1,2-dihexa-decanoyl-sn-glycero-3-phosphoethanolamine triethylammonium salt (Texas Red DHPE), had a single-lipid size, and the other species, cholera toxin subunit B-GM1 complex, had a multilipid size. When the DiynePC/DOPC molar ratio was 60/40, both species had high penetration ratios in the filter region. However, when the ratio was increased to 70/30, only the Texas Red DHPE, which was the smaller of the two model species, could penetrate the filter to a considerable extent. When the ratio was increased to 80/20, neither of the model species could penetrate the filter region. The results showed the possibility of using phase segregation of a mixture containing a polymerizable lipid and a nonpolymerizable lipid to fabricate filter barrier structures with tunable cutoff sizes in SLBs.

Using crosslinkable diacetylene phospholipids to construct two-dimensional packed beds in supported lipid bilayer separation platforms.

Separating and purifying cell membrane-associated biomolecules has been a challenge owing to their amphiphilic property. Taking these species out of their native lipid membrane environment usually results in biomolecule degradation. One of the new directions is to use supported lipid bilayer (SLB) platforms to separate the membrane species while they are protected in their native environment. Here we used a type of crosslinkable diacetylene phospholipids, diynePC (1,2-bis(10,12-tricosadiynoyl)-sn-glycero-3-phosphocholine), as a packed material to create a 'two-dimensional (2D) packed bed' in a SLB platform. After the diynePC SLB is exposed to UV light, some of the diynePC lipids in the SLB can crosslink and the non-crosslinked monomer lipids can be washed away, leaving a 2D porous solid matrix. We incorporated the lipid vesicle deposition method with a microfluidic device to pattern the location of the packed-bed region and the feed region with species to be separated in a SLB platform. Our atomic force microscopy result shows that the nano-scaled structure density of the '2D packed bed' can be tuned by the UV dose applied to the diynePC membrane. When the model membrane biomolecules were forced to transport through the packed-bed region, their concentration front velocities were found to decrease linearly with the UV dose, indicating the successful creation of packed obstacles in these 2D lipid membrane separation platforms.

[Occluding effects of three new calcium desensitizers on dentinal tubules in vitro].

OBJECTIVE: To evaluate the occluding effects of three new calcium desensitizers on dentinal tubules in vitro. METHODS: Twenty-five dentin specimens of 1.00 mm thick from freshly extracted third molars were divided into five groups randomly. After treatment with 6% citric acid, group A was treated with distilled water, and group B-E were treated with NovaMin, Pro-Argin, casein phosphopeptide-amorphous calcium phosphate (CPP-ACP), and 75% NaF glycerin for 2 min respectively. Then the teeth were vertically cleaved into two sections. The surfaces and cross sections were observed by the scanning electron microscope (SEM) and energy dispersive X-ray (EDX), which were analyzed by the Image-Pro Plus software. RESULTS: The percentage of dentin tubules sealed were (81.6 ± 6.1)%, (71.5 ± 6.3)%, (43.2 ± 2.6)%, (39.9 ± 4.1)% for groups B, C, D and E respectively, and the occluding depth were (30.33 ± 2.26), (24.55 ± 2.58), (16.10 ± 4.65) and (8.90 ± 1.51) µm respectively. The differences between these groups were statistically significant (P < 0.01) except for group B and C (P > 0.05). However, there was no significant difference between all the groups for the Ca/P ratios (P = 0.342). CONCLUSIONS: NovaMin may have better immediate occluding effects than other desensitizers and could deposit a dentin-like mineral.

[Effects of radicular dentin treatments and luting materials on the bond of quartz fiber posts: scanning electron microscope study].

OBJECTIVE: To investigate the effects of radicular dentin treatments of sodium hypochlorite (NaOCl) and ethylenediaminetetraacetic acid (EDTA) on the regional root canal bonding interface of quartz fiber posts using 2 luting materials with SEM analysis. METHODS: Nine intact maxillary central incisors were sectioned and endodontically treated. Standardized post space preparations and acid etch were performed. All specimens were randomly divided into 3 groups (n = 3). D.T.LIGHT posts were placed into the root canal using one of three radicular dentin treatments (0.9% NaCl for 60 s, 10% NaOCl for 60 s, 17% EDTA for 60 s followed by 5.25% NaOCl for 60 s) in combination of one of two luting materials (DuoLink, LuxaCore) respectively (factorial design). Cervical, middle, apical sections of each teeth are used for SEM study and spectroscopy of dispersion energy (EDS) microanalysis. RESULTS: With the radicular dentin treatment with 10% NaOCl alone or with 17% EDTA followed by 5.25% NaOCl, longer and increased number of penetration of resin tags into the dentinal tubules were observed at the resin-dentin interfaces, and adhesive lateral branches could be found easily. EDS microanalysis showed increase in the infiltration behavior of the luting cement. CONCLUSIONS: Radicular dentin treatments provide good resin infiltration, which can produce a three-dimensional interlocking micronetwork of resin tags in the dentin tubules with multiple lateral branches that penetrate the intertubular dentin, thus positively influence the adhesion between dentin and the luting materials.

[Epidemiological investigation on major depressive disorder in the most heavily damaged areas from Wenchuan earthquake in 2008].

OBJECTIVE: To assess the prevalence, demographic characteristics, risk factors and protective factors on major depression disorder (MDD) among the affected people in the epicenter, 7 months after the 2008-earthquake in Wenchuan, China. METHODS: Stratified multistage cluster randomization was conducted to choose 14 503 subjects aged 15 years or over in the city of Dujiangyan, Beichuan county and Qingchuan county, Sichuan province. We used the general health questionnaire (GHQ-12) as the screening instrument, and the structured clinical interview for DSM-IV-TR axis I disorder-patient edition (SCID-I/P) as the tool for diagnosis. RESULTS: There were 180 persons diagnosed as MDD with other 13 asymptomatic ones. The point prevalence of MDD was 1.27% and the lifetime prevalence was 1.36%. Risk factors were including:being female (OR = 1.56, 95%CI: 1.136 ∼ 2.143, P < 0.05), co-morbidity with somatic diseases (OR = 4.02, 95%CI: 2.75 - 5.90, P < 0.05), wounded in the earthquake (OR = 3.29, 95%CI: 1.92 - 5.65, P < 0.05), property loss up to 10 000 - 20 000 Yuan (OR = 2.09, 95%CI: 1.18 - 3.69, P < 0.05), property loss up to > 20 000 Yuan (OR = 2.54, 95% CI: 1.38 - 4.68, P < 0.05), death or missing of family members (OR = 3.79, 95%CI: 2.08 - 6.89, P < 0.05) and in middle-age (OR = 2.31, 95%CI: 1.38 - 3.86, P < 0.05) etc. Having had a job seemed to be a protective factor (OR = 0.60, 95%CI: 0.43 - 0.83, P < 0.05). CONCLUSION: Major depressive disorder appeared to be a common psychiatric disease in these quake-stricken areas, that causing serious problems. Sustained follow-up and care provided to the affected people in these areas were of extreme importance.

Fracture resistance after simulated crown lengthening and forced tooth eruption of endodontically-treated teeth restored with a fiber post-and-core system.

PURPOSE: To evaluate the effect of ferrule preparation length on the fracture resistance after simulated surgical crown lengthening and after forced tooth eruption of endodontically-treated teeth restored with a carbon fiber-reinforced post-and-core system. METHODS: 40 extracted endodontically-treated mandibular first premolars were decoronated 1.0 mm coronal to the buccal cemento-enamel junction. The teeth were divided randomly into five equal groups. The control group had no ferrule preparation (Group A). Simulated crown lengthening provided ferrule preparations of 1.0 mm (Group B) and 2.0 mm (Group C). Simulated forced tooth eruption provided ferrule preparations of 1.0 mm (Group D) and 2.0 mm (Group E). After restoration with a carbon fiber post-and-core system, each root was embedded in an acrylic resin block from 2.0 mm apical to the margins of a cast Ni-Cr alloy crown, and loaded at 150 degrees from the long axis in a universal testing machine at a crosshead speed of 1.0 mm/minute until fracture. Data were analyzed using ANOVA with Tukey HSD tests, and Fisher's exact test, with alpha = 0.05. RESULTS: Mean failure loads (kN) for Groups A, B, C, D and E were: 1.13 (SD = 0.15), 1.27 (0.18), 1.02 (0.11), 1.63 (0.14) and 1.92 (0.19), respectively. Significant differences were shown for the effects of treatment method and ferrule length, with significant interaction between these two sources of variation (P < 0.0001). Increased apical ferrule preparation lengths resulted in significantly increased fracture resistance for simulated forced tooth eruption (P < 0.0001), but not for simulated crown lengthening (P > or = 0.24).

Optimum post and tooth root diameters for a cast post-core system.

PURPOSE: To investigate the optimum diameter for the tapered post of a cast alloy post-core system relative to the root diameter, when measured at the root face, that is required to minimize both post and root failures. METHODS: 32 extracted maxillary central incisor teeth were each decoronated perpendicular to the long axis at a point 2.0 mm occlusal to the labial cemento-enamel junction. Following endodontic canal obturation, the teeth were assigned randomly to four equal groups for different diameter tapered post space preparations. Then 1.10, 1.50, 1.70, and 2.00 mm diameter cast Ni-Cr alloy post-cores and complete crowns without ferrules were fabricated. Each root was embedded in a large gypsum stone block and the crown loaded palatally at 135 degrees from the long axis in a universal testing machine at a crosshead speed of 1.0 mm/minute until failure. Results were analyzed using one-way ANOVA with Tukey-Kramer post hoc tests, and Fisher's exact test, with alpha = 0.05 for statistical significance. RESULTS: Mean failure resistance loads were: 0.60, 0.91, 1.00, and 1.38 kN (P < 0.001). All of the 1.10 mm posts failed, without any root fractures. Conversely, none of the 2.00 mm posts failed, but all of the roots fractured. The optimum post to root diameter ratio to minimize failures was approximately 1:4.

Fracture resistance and microtensile bond strength of maxillary premolars restored with two resin composite inlay systems.

PURPOSE: To compare the in vitro fracture resistance and the microtensile bond strength (muTBS) of premolar teeth restored with two light-cured resin composite inlay systems. METHODS: 50 sound human maxillary premolars were divided randomly into five equal groups. Four groups received mesial-occlusal-distal (MOD) inlay preparations. Restorative treatments comprised: Group 1 (Renew direct resin composite), Group 2 (Renew direct resin composite inlay), Group 3 (Tescera indirect resin composite inlay), Group 4 (non-restored), Group 5 (intact). All teeth were loaded axially until fracture. The same resin-based materials as used in Groups 1-3 were bonded to the superficial coronal dentin of 15 teeth. Beams approximately 1.0 mm x 1.0 mm were prepared and tested in microtensile mode. Results were compared using one-way ANOVA and Tukey's multiple comparison tests. RESULTS: Mean fracture strengths (KN): Group 1, 2.06 (0.76); Group 2, 2.30 (0.49); Group 3, 2.62 (0.68); Group 4, 1.24 (0.44); Group 5, 2.40 (0.71). Group 4 was significantly weaker that the other four groups, P < 0.01. Mean muTBSs (MPa): Group 1, 33.38 (6.24); Group 2, 20.38 (6.24); Group 3, 20.87 (4.62). Group 1 was significantly stronger than the other two groups, P < 0.01.

Translucency and biaxial flexural strength of four ceramic core materials.

OBJECTIVES: To assess the relative translucencies and flexural strengths of four dental restorative ceramic core materials. METHODS: Eight disk specimens (14 mm in diameterx 0.5+/-0.05 mm in thickness) were prepared for each group of four ceramic core materials (IPS Empress 2 dentin, VITA In-Ceram Alumina, VITA In-Ceram Zirconia, Cercon Base Zirconia), according to the manufacturers' instructions. A color meter was used to measure the relative translucencies of the specimens. The biaxial flexure test (ISO 6872) was then used to measure their flexural strengths. Data for relative translucency (0.0-1.0), fracture load (N) and biaxial flexural strength (MPa) were analyzed by one-way ANOVA, followed by Tukey's multiple comparison test for significant findings (alpha = 0.05). RESULTS: For relative translucency: IPS Empress 2 (0.78+/-0.03), VITA In-Ceram Alumina (0.94+/-0.01), VITA In-Ceram Zirconia (1.00+/-0.01), Cercon Base Zirconia (1.00+/-0.01), P<0.0001. For biaxial flexural strength: IPS Empress 2 (355.1+/-25.7), VITA In-Ceram Alumina (514.0+/-49.5), VITA In-Ceram Zirconia (592.4+/-84.7), Cercon Base Zirconia (910.5+/-95.3), P<0.0001. SIGNIFICANCE: IPS Empress 2 and VITA In-Ceram Alumina were significantly more translucent than the two opaque zirconia-containing core materials. IPS Empress 2 was significantly weaker, and Cercon Base Zirconia was significantly stronger, than the other two ceramic core materials.

Effect of two fiber post types and two luting cement systems on regional post retention using the push-out test.

OBJECTIVE: To investigate regional root canal push-out bond strengths for two fiber-reinforced post types using two adhesive systems. METHODS: The crowns of 24 recently extracted sound maxillary central incisors were sectioned transversely 2 mm coronal to the labial cemento-enamel junction, and the roots treated endodontically. Following standardized post space preparations, fiber-reinforced posts (C-POST; AESTHETI-PLUS) were placed using two adhesive systems (acid-etch ONE-STEP PLUS/C&B CEMENT; self-adhesive RelyX Unicem), in four equal groups. Push-out bond strength tests were performed at four sites in each root. Results were analyzed using split-plot ANOVA, with a=0.05 for statistical significance. RESULTS: AESTHETI-PLUS quartz fiber-reinforced posts showed significantly higher push-out strengths than C-POST carbon fiber-reinforced posts (P<0.0001). The separate acid-etch adhesive system resulted in significantly higher bond strengths than the self-etch self-adhesive system (P<0.0001). Bond strengths decreased significantly from coronal to apical root canal regions (P<0.0001). SIGNIFICANCE: The quartz fiber-reinforced post placed using the separate acid-etch adhesive system provided significantly better post retention than the carbon fiber-reinforced post placed using the self-etch self-adhesive system.

Effect of a ferrule and increased clinical crown length on the in vitro fracture resistance of premolars restored using two dowel-and-core systems.

This study investigated the effect of a crown-lengthening ferrule on the fracture resistance of endodontically-treated teeth restored with two dowel-core systems. Thirty-two extracted mandibular first premolars were sectioned perpendicular to the long axis at a point 1.0 mm occlusal to the buccal cementoenamel junction. Following endodontic treatment, the teeth were randomly assigned to four groups: cast Ni-Cr alloy dowel-core with no ferrule (Group A1), cast Ni-Cr alloy dowel-core with 2.0 mm ferrule (Group A2), prefabricated carbon fiber-reinforced dowel-resin core with no ferrule (Group B1) and carbon fiber-reinforced dowel-resin core with 2.0 mm ferrule (Group B2). Each specimen was embedded in a self-cured acrylic resin block from 2.0 mm apical to the margins of a cast Ni-Cr alloy crown, then loaded at 150 degrees from the long axis in a universal testing machine at a crosshead speed of 1.0 mm/minute until fracture. The data were recorded and analyzed using ANOVA and Fisher's exact tests, with alpha = 0.05. Mean failure loads (kN) for the A1, A2, B1 and B2 Groups were: 1.46 (S.D. 0.45), 1.07 (0.21), 1.13 (0.30) and 1.02 (0.27). The teeth restored with cast Ni-Cr dowel-cores and 2.0 mm ferrules demonstrated significantly lower fracture strengths, p = 0.04. There were significant differences in the root fracture patterns between the two dowel systems, with the carbon fiber-reinforced dowel-resin core system, being the less severe p < 0.05. Crown lengthening with a 2.0 mm apical extended ferrule resulted in reduced fracture strengths for endodontically-treated teeth restored using two dowel-core systems and cast metal crowns. The carbon fiber-reinforced dowel-resin core system reduced the severity of the root fractures.

Fracture resistance of roots with thin walls restored using an intermediate resin composite layer placed between the dentine and a cast metal post.

Thin-walled roots restored using conventional cast metal post-cores are at risk of fracture. Placing a thick intermediate layer of resin-based composite (RBC), sandwiched between the root dentine and a small-diameter metal post or dowel, may improve the fracture resistance of such roots. In this initial laboratory study, two similar groups each of six decoronated maxillary central incisor teeth were prepared with approximately 1.0 mm thick tapered root canal walls. Cast metal alloy post-cores and metal-ceramic crowns were fabricated and cemented for one group with, and for the other control group without, a thick intermediate layer of RBC. The mean force (N) to fracture the roots was 639.3 (SD 51.6) for the intermediate layer of RBC group and 360.8 (42.9) for the control group, P < 0.0001. These significantly different findings require clinical confirmation.

Mathematical analysis of occlusal rest design for cast removable partial dentures.

AIMS: To establish the minimum dimensions for a non-precious cast metal occlusal rest by using mathematical analysis. An occlusal rest in a removable partial denture (RPD) provides vertical support and allows occlusal forces to be transmitted through the long axis of the abutment tooth. METHODS: The stress status of an occlusal rest in a posterior tooth-bounded RPD resembles that of a cantilever beam under a uniformly distributed load. A mathematical model based on a short rectangular cantilever beam was derived by using the yield strengths of a cast cobalt-chromium alloy and a cast titanium alloy (Ti-6Al-4V), with an applied static occlusal force of 400 N. RESULTS: For the cobalt-chromium alloy, the minimum rectangular dimensions for a 2.0 mm long occlusal rest are; when the width is 2.0 mm, the depth or thickness should be at least 1.03 mm. For the titanium alloy, the minimum dimensions are; when the width is 2.0 mm, the depth or thickness should be at least 0.85 mm. A decrease in the occlusal width will increase the bending stress, requiring a thicker rest for compensation, which may lead to dentin exposure during the rest seat preparation. CONCLUSION: The mathematical analysis found that the traditional spoon-shaped occlusal rest seat dimensions comply with the mechanical requirements for non-precious cast metal occlusal rests in RPDs.

Effectiveness and dentin bond strengths of two materials for reinforcing thin-walled roots.

OBJECTIVES: To investigate the effectiveness of two restorative materials for reinforcing thin-walled roots and their microtensile bond strengths to root canal dentin. METHODS: Twenty-one decoronated maxillary central incisor roots were root filled and the canals enlarged to leave approximately 1.0 mm thick dentin walls. The roots were distributed randomly to three equal groups. Group 1 (control): a large tapered cast post-core was fabricated. Group 2 (BIS-CORE): a thick layer of dual-cured composite was placed in the post-hole before fabrication of a small-diameter tapered cast post-core. Group 3 (ChemFil Superior): a thick layer of glass-ionomer was placed, as before. Metal-ceramic crowns were fabricated for all teeth. Microtensile bond strength tests and optical and atomic force microscope observations were employed to examine adhesion between the two restorative materials and the root canal dentin. RESULTS: Mechanical loading (kN) demonstrated that composite 0.64 (S.D. 0.05), but not glass-ionomer 0.49 (0.05), significantly reinforced the fracture resistance of thin-walled roots, P<0.001. Microtensile bond strengths (MPa) were 21.7 (1.6) for composite and 12.9 (1.7) for glass-ionomer, P=002. SIGNIFICANCE: A thick intermediate layer of resin-bonded composite, sandwiched between the root dentin and a small-diameter cast Ni-Cr post or dowel, increased significantly the fracture resistance of the roots.

Copper deficiency in yaks on pasture in western China.

The clinical signs of a disorder in yaks (Bos grunniens), known locally as "swayback ailment," in the Qing Hai-Tibetan Plateau are described. The purpose of this study is to investigate the possibility that swayback ailment is iron (Fe)-induced copper (Cu) deficiency. The mean concentrations of Cu in soil and forage from affected areas and unaffected areas are similar and within the normal ranges. The mean concentrations of Cu in blood and hair from the affected yaks was significantly lower (P < 0.01) than that in unaffected yaks. The mean concentrations of Fe in soil and forage were significantly higher (P < 0.01) in affected than in unaffected areas. Affected yaks showed a hypochromic microcytic anemia and a low level of ceruloplasmin. Oral administration of copper sulphate prevented and cured the disease. We conclude that "swayback disorder" of yaks is caused by secondary Cu deficiency, mainly due to the high Fe content in forage.