Mechanisms of propeller jet-induced migration, release, and distribution of perfluoroalkyl acids in sediment-water systems.

Perfluoroalkyl acids (PFAAs) are continuously accumulated in surface sediments due to extensive and long-term application. However, the mechanisms through which disturbances induced by ship propeller jets at the riverbed cause secondary release of PFAAs from sediments remain unclear. In this study, the effects of different propeller rotational speeds on PFAA migration, release, and distribution in multiphase media were investigated by performing indoor flume experiments combined with particle tracking velocimetry. Moreover, key factors influencing PFAA migration and distribution were identified, and partial least squares regression (PLS) method was applied to develop quantitative prediction models of relationships among hydrodynamics, physicochemical parameters, and PFAA distribution coefficients. The total PFAA concentrations (ΣPFAAs) in overlying water under propeller jet action exhibited transient characteristics and hysteresis with time after the disturbance. In contrast, the ΣPFAAs in suspended particulate matter (SPM) exhibited an upward trend throughout the process with consistent characteristics. The spatial distribution trends of PFAAs in overlying water and SPM at different propeller rotational speeds featured vertical variability and axial consistency. Furthermore, PFAA release from sediments was driven by axial flow velocity (Vx) and Reynolds normal stress Ryy, while PFAA release from porewater was inextricably linked to Reynolds stresses Rxx, Rxy, and Rzz (p < 0.05). PLS regression models showed that variations in Vorticity, dissolved organic carbon, and pH influenced the decreases in PFAA distribution coefficients between SPM and overlying water (KD-SW) as propeller rotational speed increased, except for very long-chain PFAAs (C > 10). The increases in PFAA distribution coefficients between sediment and porewater (KD-SP) were mainly determined by physicochemical parameters of sediments, and the direct effect of hydrodynamics was relatively weak. Our study provides valuable information regarding the migration and distribution of PFAAs in multiphase media under propeller jet disturbance (both during and after disturbance).

Prosthodontic Rehabilitation of a Patient with Hypophosphatasia Using Dental Implants: A Case Report with Seven Years Follow-Up.

Hypophosphatasia is a rare metabolic inherited dento-osseous disorder. Although there is some available literature on various dental characteristics of hypophosphatasia patients, few reports focus on the effects of hypophosphatasia on the permanent dentition and prosthodontic rehabilitation, particularly in relation to the use of dental implants. This paper reports a case with hypophosphatasia and prosthodontic rehabilitation using dental implants with 7-year follow-up.

Perfluoroalkyl acids in surface sediments from the lower Yangtze River: Occurrence, distribution, sources, inventory, and risk assessment.

In this study, the occurrence, spatial distribution, potential sources, mass inventory, and ecological risk assessment of perfluoroalkyl acids (PFAAs) in surface sediments from the lower Yangtze River were investigated based on field and laboratory assays conducted in November 2019. The total concentrations of 13 target PFAAs (∑PFAAs) ranged from 13.83 to 20.33 ng/g dw, and perfluorooctanoic acid (PFOA) and perfluorooctanesulfonate (PFOS) were predominant in the surface sediments with average concentrations of 2.89 and 4.07 ng/g dw, respectively. The ∑PFAAs concentrations in pore-water ranged from 23.30 to 58.81 ng/L, and PFOA and PFOS were predominant with mean concentrations of 6.29 and 5.04 ng/L, respectively. The profiles of PFAAs composition in surface sediments showed limited difference. Results of fugacity model revealed that PFOS was in relative equilibrium, whereas PFOA exhibited a diffusion trend from sediments to water body. Correlation analysis and positive matrix factorization demonstrated that the main sources of ∑PFAAs were electroplating and fast-food packaging, degradation products and textile, mixed sources, and PFOA-based products. The mass inventory of ∑PFAAs was estimated to be 1680.72 kg, and the results of ecological risk assessments based on equilibrium partition and species sensitivity distribution methods suggested that the hazards of PFAAs in sediments to local aquatic organisms are low. However, the evaluation methods and control measures of PFAAs in surface sediments are still limited, requiring further research.

Ship navigation disturbance alters multiphase distribution of perfluoroalkyl acids and increases their ecological risk in waterways.

As a global persistent organic pollutant, perfluoroalkyl acids (PFAAs) have aroused great public concern. However, little is known regarding the effect of ship navigation disturbance on the transport and fate of PFAAs in inland waterways developed regions. In the present study, overlying water, pore water, suspended particulate matter (SPM), and sediment were collected from waterways (WWs), non-navigable channels (NCs), and ports (PTs) in Taihu Lake Basin. The results revealed that the total concentrations of PFAAs (ΣPFAAs) in WWs, NCs, and PTs varied considerably in different media. In overlying water, the mean ΣPFAAs in WWs were the highest, while those of NCs were relatively higher in the remaining three media. A comparison of PFAA distribution coefficients revealed that the values in NCs were generally higher than those of WWs and PTs, suggesting the critical role of ship navigation in PFAA transport. Furthermore, a structural equation model was applied to estimate direct and indirect effects of environmental factors on PFAA partitioning behavior. The results revealed that ship traffic volume (STV) exerted indirect effects on PFAA distribution between solid and dissolved phases by influencing dissolved oxygen, total suspended solid concentration, clay and sand contents, and median diameter. PFAAs were more readily to be released into overlying water from pore water than in sediment, and the ΣPFAAs carried per gram of SPM decreased with an increase in STV. Ecological risk assessment and Monte Carlo simulation results revealed that ship navigation could exert adverse effects on aquatic organisms, making the average probability of RQmix values to exceed corresponding risk values in WWs, which were 1.3-2-fold higher than in NCs. The present study provides crucial information for simulating the environmental behaviors of PFAAs under the influence of ship navigation and is significant for the integration of inland water transport development and aquatic environmental protection.

Opinions Regarding Reuse or Replacement of Implant Prosthesis Retaining Screws: A Systematic Review.

PURPOSE: To identify whether reuse or replacement is better for managing loose screws. MATERIALS AND METHODS: An electronic search was performed utilizing PubMed, and a further manual search of the reference lists of relevant reviews and articles was conducted. Selected inclusion and exclusion criteria were used to limit the search. RESULTS: The electronic and manual search provided 243 titles and abstracts. Full-text analysis was performed for 98 articles, resulting in a total of 15 articles that qualified for inclusion in this study. All the included articles reported that loose screws were reused and retightened or were replaced by new screws. The time of screw loosening ranged from 1 month to 3 years after delivery. Available details of numbers and frequency of screw loosening permitted only limited analysis from very few articles. A total of 44 loose screws reported in two articles did not loosen again after retightening once. CONCLUSION: From the very limited available literature, it appears that retightening an occlusal screw or abutment screw is an acceptable procedure, as the evidence shows that retightened screws seem to remain tight. Replacement of screws as a routine procedure cannot be recommended. Routine assessment of screw tightness is recommended to minimize additional and more severe complications.

Effect of edentulous arch restored with implant supported telescopic overdenture / 口腔疾病防治

Objective@#To study the effect of the edentulous arch with implant supported telescopic overdenture. @*Methods@#Fifteen patients with edentulous jaws underwent telescopic overdenture restoration. A total of 26 prostheses were fabricated (11 in the upper jaws, 15 in the lower jaws) with 104 placed implants. The secondary crown was fabricated by wax-lost cast method. Clinical examination and radiographs were conducted. Changes in the marginal bone level around the implants were evaluated by radiograph. The satisfaction level of complete denture and implant-supported overdenture were compared. The mean follow-up time was 32 months (range 6-60 months).@*Results@#Twenty-six prostheses showed better stability, maintenance and occlusion. There were statistical differences between complete denture and implant-supported overdenture in comfort level and chewing function. 1 mm bone lost was found in two patients after 4 years. No implant was lost during the loading time. @*Conclusion @#The preliminary clinical results of this research showed that implant supported telescopic overdentures were reliable for edentulous patients.

[Clinical study of osteotome sinus floor elevation without grafting and with simultaneous implants placement].

OBJECTIVE: To investigate the clinical results of osteotome sinus floor elevation (OSFE) without grafting combined with simultaneous implant placement. METHODS: A total of 65 patients underwent maxillary sinus floor elevation from alveolus without any bone grafting from January 2000 to December 2008 and 96 implants were placed in the maxillary posterior edentulous region simultaneously. Clinical and radiography examinations were performed. The residual bone height ranged from 5 to 8 mm and the mean bone height was (6.78 ± 1.04) mm. The mean following period was 33.4 months. Statistical analysis was performed by chi square test. RESULTS: Ninety-five of 96 implants were clinically stable and functioned without any pain and other complaints. One implant was extracted 15 days after operation because of mobility and the other implants obtained osseointegration. The mean implant protrusion length was 2.6 mm, ranging from 1 to 5 mm. Different degree of new bone formation was observed in 51 (54%) of implants. New maxillary sinus floor outline was observed in 33 (35%) of implants and there was no obvious new bone in 11 (12%) of implants. There was no significant deference between the implant protrusion length and sinus floor remodeling. CONCLUSIONS: Under strict indications, the clinical results of OSFE without bone grafting combined with simultaneous implant placement were predictable in short term. The new sinus floor formation was not related to the implant protrusion length.

[Effect of two different desensitizers on bond strength of dentin bonding agents].

OBJECTIVE: To evaluate the bond strength of total-etch or self-etch dentin bonding agents after using two different dentin desensitizers on exposed dentin and investigate the bond interface by scanning electron microscope (SEM). METHODS: Thirty intact and non-carious human third molars were used. The occlusal enamel was removed with the use of a slow-speed saw under water cooling. These teeth were divided into three groups using a table of random numbers with 10 teeth each. These three groups were treated with water (Group C), UltraEZ (Group U) and MI Paste (Group M) respectively. Then 10 teeth from each group were divided into A subgroup (n = 5) bonded with Single Bond 2 adhesive system and B subgroup (n = 5) bonded with Xeno III adhesive system according to manufacturers' instructions. A block of composite resin was build up to 4-5 mm. All the teeth were sectioned occluso-gingivally to obtain bar-shaped specimens with bonded surface area about 0.9 mm x 0.9 mm. The tension of the sample was tested by a microtensile tester at 1 mm/min. The mean values of bond strength were compared using one-way ANOVA. Three samples were chosen randomly from each of six groups for SEM investigation. RESULTS: There were no significant differences between Group U and Group C both in A and B subgroups. While there were significant differences between Group M and Group C in two bonding-agent subgroups. For SEM, the hybrid layer was thin and dense in six groups. Both total-etch and self-etch bonding systems could get fair resin tag infiltration in Group C and Group U. In Group M, the resin tags were relatively shorter and fewer than the anterior mentioned two groups. CONCLUSIONS: UltraEZ had no effect on bond strength of both kinds of dentin bonding agents, while MI paste could diminish bond strength.

[Anti-fungal test of composite agastache lotion on seven pathogenic fungi and its clinical application].

OBJECTIVE: To study the effect of Chinese composite recipe in treating mycotic infection. METHODS: The growth condition of 7 kinds of fungi cultured on the media containing composite agastache lotion (CAL, consisted of 5 Chinese drugs) of different concentration was observed. Result showed that CAL could inhibit 7 kinds of fungi. Based on the above anti-fungus test, 110 patients with skin tinea or genital candidiasis were treated separately with CAL, western medicine and combined (CAL and western) medicines, the therapeutic effects of the 3 groups were observed and compared. RESULTS: The therapeutic effect in patients treated with combined medicine was significantly better than that in the other two groups (P < 0.05). CONCLUSION: Combined use of CAL and western medicine could enhance the cure rate in treating skin tinea and genital candidiasis. Attention should be paid on studying Chinese anti-fungal agents.