Microplastics induced the differential responses of microbial-driven soil carbon and nitrogen cycles under warming.

The input of microplastics (MPs) and warming interfere with soil carbon (C) or nitrogen (N) cycles. Although the effects of warming and/or MPs on the cycles have been well studied, the biological coupling of microbial-driven cycles was neglected. Here, the synergistic changes of the cycles were investigated using batch incubation experiments. As results, the influences of MPs were not significant at 15, 20, and 25 °C, and yet, high temperature (i.e., 30 °C) reduced the respiration of high-concentration MPs-amended soil by 9.80%, and increased dissolved organic carbon (DOC) by 14.74%. In contrast, high temperature did not change the effect of MPs on N. The decrease of microbial biomass carbon (MBC) and the constant of microbial biomass nitrogen (MBN) indicated that microbial N utilization was enhanced, which might be attributed to the enrichments of adapted populations, such as Conexibacter, Acidothermus, and Acidibacter. These observations revealed that high temperature and MPs drove the differential response of soil C and N cycles. Additionally, the transcriptomic provided genomic evidence of the response. In summary, the high temperature was a prerequisite for the MPs-driven response, which underscored new ecological risks of MPs under global warming and emphasized the need for carbon emission reduction and better plastic product regulation.

Cationic polyacrylamide alleviated the inhibitory impact of ZnO nanoparticles on anaerobic digestion of waste activated sludge through reducing reactive oxygen species induced.

The enrichment of zinc oxide nanoparticles (ZnO NPs) in waste activated sludge (WAS) has raised concerns about their potential impact on anaerobic digestion of WAS. To date, there is no information regarding how to attenuate the negative effects of ZnO NPs on WAS anaerobic digestion. In this study, it was found that the appropriate amount of cationic polyacrylamide (cPAM) could mitigate the toxicity of ZnO NPs. During short-term exposure, the supplement of 4.0 mg cPAM/g TSS significantly restored biochemical methane potential from 28.6% inhibition to 9.3% inhibition compared with the control digester (P < 0.01). The spiked cPAM promoted the solubilization and acidification stages by weakening the contact between ZnO NPs and anaerobes in anaerobic digestion process, thus providing abundant substance for sequent bio-utilization. In the long-term semi-continues operated reactor, the continuous replacement of cPAM (at 4.0 mg/g TSS) significantly strengthened the recovery of VS destruction rate (20.3% to 26.4%, P < 0.01) and the daily yield of methane (93.5 mL/d to 124.2 mL/d, P < 0.01). Consistent with the restored performance, the application of cPAM increased the total microbial communities and the relative abundances of dominant acidogens and methanogens. Further explorations showed decreased toxicity of ZnO NPs primarily attributed to the decline of reactive oxygen species (ROS) induced by ZnO NPs.

The effect of implant shape and screw pitch on microdamage in mandibular bone.

PURPOSE: The aim of this study was to investigate the effect of implant shape and screw pitch on microdamage in bone during insertion of dental implants. MATERIALS AND METHODS: Thirty custom-made implants (length, 10 mm; diameters, 4.1 mm; cylindrical, tapered, and taper-cylindrical shapes; screw pitches, 1.25 and 0.8 mm; classified as 1.25C, 0.8C, 1.25T, 0.8T, 1.25TC, 0.8TC) were placed with a surgical device in the mandibles of eight goats. Two implant sites were prepared in the edentulous area on each side of the mandible. Implants were placed in a randomized order. Immediately after placement of the implants, the bone blocks with the implants were collected, bulk stained with basic fuchsin, embedded in methyl methacrylate, and sectioned. Histomorphometric quantification of the microcrack length (Cr.Le, µm); microcrack surface density (Cr.Le/B.Ar, µm/mm(2) ), and damaged bone area fraction (DB.Ar/B.Ar, %) were measured. RESULTS: The Cr.Le, Cr.Le/B.Ar, and DB.Ar/B.Ar values of 0.8TC group were 80.96 ± 17.55, 478.75 ± 51.85, and 4.40 ± 0.36, respectively. All these parameters of microdamage induced by 0.8TC were significantly lower than those induced by other five types of implants (p < .05). CONCLUSION: Taper-cylindrical implants with 0.8 mm screw pitch caused the least microdamage to the bone in comparison with the other five types of implants during placement of implants.

Fracture resistance of endodontically treated premolars restored with lithium disilicate CAD/CAM crowns or onlays and luted with two luting agents.

The purpose of the present study is to evaluate the fracture resistance of endodontically treated maxillary premolars restored using CAD/CAM onlays or crowns and luted with two types of resin cement. Forty all-ceramic crowns and twenty onlays were fabricated on maxillary premolars using the Cerec 3 system (n=10). The abutments were randomly subjected to two different procedures: Endodontic treatment was performed on forty teeth restored through a mesio-occlusal-distal (MOD) cavity preparation with composite resin fillings; twenty teeth without endodontic treatment served as control. In endodontically treated teeth restored using IPS e.max CAD crowns or onlays, the fracture loads were lower than those of the control. Endodontic treatment of teeth restored using CAD/CAM crowns does not impair the fracture load but shows more severe fractures than teeth restored using CAD/CAM onlays. This suggests that a CAD/CAM onlay might be an effective method for the restoration of endodontically treated premolars with MOD cavity defect.

[Evaluation of bond strength of three resin cements on CAD/CAM ceramic-dentin].

PURPOSE: To evaluate the bond strength of 3 resin cements on ceramic-dentin. METHODS: Thirty sound human posterior tooth were selected for this study and the flat dentin surfaces were prepared. The specimens were divided into 3 groups(n=10) randomly, which were bonded to the CAD/CAM ceramics with RelyX ARC(etch-and-rinse adhesive), Clearfil DC Bond(self-etching resin cement) and RelyX Unicem(self-adhesive resin cement). The bond strengths were tested and the bond surfaces were observed under stereoscopic microscope.SPSS 11.0 software package was used for statistical analysis. RESULTS: The shear bond strength of RelyX ARC and Clearfil DC Bond was (15.90±6.15)MPa and (14.41±5.07)MPa, respectively. The shear strength of RelyX Unicem was(23.29±7.39)MPa, significantly higher than the others.The shear strength between the three resin cements was significantly different (P<0.05). CONCLUSION: Clearfil DC Bond and RelyX Unicem can achieve a successful bond on CAD/CAM ceramic crowns.

[Effect of polymerization-shrinkage of different resin composites curing by two different light curing units].

PURPOSE: To investigate the effect of light-emitting diode (LED) light curing unit (LCU) and quartz-tungsten (QTH) LCU on the polymerization-shrinkage of different resin composites. METHODS: Three composites Z100, Z250, AP-X were irradiated by QTH LCU and LED LCU. Polymerization-shrinkage of 50s and 400s after the composites curing were measured by 3D-profile measuring apparatus by phase-shifted projected grating.The polymerization-shrinkage of LED and QTH curing composites were analysed by SPSS12.0 software package of one-way ANOVA. RESULTS: At 50s curing and 400s curing period, the polymerization- shrinkage of Z100, Z250 resin was different by QTH LCU and LED LCU curing, the polymerization-shrinkage by LED LCU curing was less than that by QTH LCU (P < 0.05); the polymerization-shrinkage of AP-X was not statistically different by QTH LCU and LED LCU curing (P > 0.05). CONCLUSUINS: The polymerization-shrinkage of Z100,Z250 resin is statistically less cured by LED LCU than QTH; the polymerization-shrinkage of AP-X resin is not statistically different cured by QTH LCU and LED LCU. Supported by Research Fund of Science and Technology Commission of Shanghai Municipality (08DZ2271100).

[Preliminary study on DNA damage of ZrO(2)/LaPO(4) diphase ceramics on human peripheral blood lymphocytes in vitro].

PURPOSE: To detect the genotoxicity of dental machinable ZrO(2)/LaPO(4) diphase ceramics on human peripheral blood lymphocytes in vitro. METHODS: The evaluation of DNA damage on human lymphocytes was performed by comet assay for three groups of ZrO(2)/LaPO(4) diphase ceramics with 30wt% of LaPO(4) (with 3wt% and 5wt% of Y(2)O(3)) and 40wt% of LaPO(4) (with 5wt% of Y(2)O(3)). The results were analyzed with SPSS16.0 software package for one-factor ANOVA and LSD. RESULTS: Three experimental groups with different concentration of LaPO(4) of ZrO(2)/LaPO(4) diphase ceramics, the negative control of IPS Empress II ceramics and the blank behaved little migration of the DNA strands respectively after six-day test, and there was no significant difference in all the groups except the positive control (P>0.05). CONCLUSION: The study indicates little effect of DNA damage of ZrO(2)/LaPO(4) diphase ceramics.

[The construction and analysis of three-dimensional finite element model of human unilateral maxillary defect].

PURPOSE: To built a three-dimensional finite element model of the common unilateral maxillary defect, and to study the stress of the traditional maxillofacial prostheses for unilateral maxillary defect. METHODS: The three-dimensional finite element model of unilateral maxillary defect and maxillofacial obturator prosthesis were constructed by means of spiral CT scanning, digital image transfer, self-developed software MedGraphics, UG engineering design program and ANASYS software. Then 3-D finite element stress analysis was carried out, for the prosthesis. RESULTS: The three-finite element models of the unilateral maxillary defect and maxillofacial obturator prosthesis were established. In the traditional obturator prosthesis, the stress was on the posterior teeth of the healthy side; the area of stress concentration was on the palatal base near the position of the anterior teeth. CONCLUSIONS: The three-dimensional finite element models of the unilateral maxillary defect and maxillofacial obturator prosthesis have good similarity in geometry and biology. The obturator prosthesis is in accorded with the biomechanical demands.

[Stress analysis of the post and core system under loading].

PURPOSE: To analyze the stress of the post and core system by using finite element analysis and study the influence of the "crown materials" on the analytic results. METHODS: Three groups of 3D finite element models of maxillary incisors were established according to the fabricating standard of the post and core system by using I-DEAS finite element analysis software. Group A was consisted of the cast metal post and core, the tooth structure after preparation and the periodontal structure. Group B was composed of the PFM, the cast metal post and core, the tooth structure after preparation and the periodontal structure. Group C was composed of the resin crown, the cast metal post and core, the tooth structure after preparation and the periodontal structure. The three groups were loaded and analyzed under the same loading according to the mean value of the bite force of incisors. RESULTS: (1)The maximum stress of dentin in group A was twice higher than that in group B. The maximum primary stress, minimum primary stress and maximum shear stress of group A were respectively 236.35, 228.83 and 218.05 percent of those in group B. The difference of maximum stress values of group B and group C was neglectable. (2) The maximum stress distribution of dentin in group A and group B was quite different (the stress was concentrated in labial and lingual side of the cervical dentin in group A, otherwise in group B it was concentrated in the area around the alveolar and the labial and lingual side of the dentin which was opposite to the tip of the cast metal post and core). The maximum stress distribution of dentin in group A and group B was almost the same. CONCLUSIONS: Different materials of the crown did not influence the result of 3D finite element stress analysis of the post and core system.

[Preliminary analysis about influence of porcelain thickness on interfacial crack of PFM].

OBJECTIVE: This study was about the influence of porcelain thickness on crack at interface. METHODS: The effect of porcelain thickness on the flaw at the interface between porcelain and metal was studied in three groups with porcelain thickness of 0.5 mm, 1.5 mm and 2.5 mm (metal thickness of 0.5 mm) by means of moire interferometre and interfacial fracture mechanics. The parameter Jc was compared among the three groups and the growing of the flaw was observed. RESULTS: Jc and the extreme strength of group with porcelain thickness of 0.5 mm (2.813 N/m and 9.979 N) were lower than those of the groups with porcelain thickness of 1.5 mm and 2.5 mm (5.395 N/m, 19.134 N and 5.429 N/m, 19.256 N). Flaws extend along the interface in the groups with porcelain thickness of 1.5 mm and 0.5 mm. CONCLUSIONS: (1) Fracture resistance of the interface in the groups with porcelain thickness of 1.5 mm and 2.5 mm is similar and it decreases in the group with 0.5 mm thick porcelain. (2) When porcelain is 1.5 mm or 0.5 mm thick, flaws will extend along the interface. When porcelain is 2.5 mm thick, flaws will extend into the porcelain layer.

[Using moiré interferometre in the study of porcelain-fused-metal interfacial fracture mechanics].

OBJECTIVE: To evaluate the usage of moiré interferometre in porcelain-fused-metal interfacial fracture mechanics. METHODS: Raster was produced on the surface of samples with different thickness of porcelain and metal in 5 groups. The stripes of u field and v field under different load were collected. Then the rupture tenacity Jc was calculated and the extensions of flaws were observed. RESULTS: Stress concentration appeared around the flaws under load conditions. The stripe became denser under more load. The rupture tenacity Jc and the direction of flaw extension of each group were different. CONCLUSION: Moiré interferometre can be used in the study of porcelain-fused-metal interfacial fracture mechanics and to prognosticate the direction of flaw extension.

[Characteristics of stress distribution on bone adjacent to implants under three different loading directions].

OBJECTIVE: To evaluate the stress distribution on bone adjacent to an implant under the vertical load, oblique load and horizontal load. METHODS: Obtained three dimensional radiographic data of the jaw by dental CT scan. Based on the scanning sections, the three-dimensional finite element analysis mandible model was established. Loading vertical, oblique and horizontal forces on the implant, calculated the maximum stress, minimum stress and von mises stress. RESULTS: The peak stress occurred at the cervical bone margin adjacent to the implants;the stress concentration under the vertical loading is easily concentrated than that of vertical loading. CONCLUSION: In the clinical designation,not only the force of bite but also the direction of the force should both be emphasised.