Stability of mandibular implants with Morse taper and external hexagon connections placed under immediate loading: a longitudinal clinical study

The aim of this study was to compare the longitudinal stability of implants with Morse taper and external hexagon connections placed in the anterior mandible and subjected to immediate functional loading. Nine patients each received 4 mandibular implants placed between the mental foramina. In each patient, 2 implants on the left side of the arch had Morse taper prosthetic connections, and 2 implants on the right side had external hexagon prosthetic connections. Mandibular overdentures and opposing removable complete dentures were placed within 72 hours after implant surgery. Clinical evaluation of the implants via magnetic transduction resonance frequency analysis was performed immediately following surgery and 3 months, 6 months, and 2 years following surgery to obtain the implant stability quotient (ISQ). The data obtained were parametric according to the Kolmogorov-Smirnov normality test. The lowest ISQ of any implant was approximately 67, representing reliable osseointegration. The only statistically significant difference between the 2 types of prosthetic connection was found in the initial period (immediately following surgery), when the external hexagon connection in the distal position presented greater stability than did the Morse taper connection in the same position on the opposite side (P < 0.05; Student t test). In intragroup comparisons, no statistically significant differences were found regarding the positions of the implants in the mandible. When the different follow-up periods were evaluated, there were statistically significant differences only in the external hexagon group, with significant reductions in stability of both mesial and distal implants at 6 months compared to other time periods (P < 0.05; Tukey test). Within the limitations of the study, it can be concluded that both Morse taper and external hexagon prosthetic connections provide good stability in an immediate functional loading protocol.

Is interdental papilla filling using hyaluronic acid a stable approach to treat black triangles? A systematic review

PURPOSE

To evaluate the stability of interdental papilla filling using hyaluronic acid (HA) to treat black triangles in esthetic regions.

METHODS

The protocol was registered in PROSPERO. Six databases (PubMed, Scopus, Embase, Lilacs, SciELO, and Web of Science) were used as primary search sources, and OpenGrey and OpenThesis were used to capture the "gray literature." Only before-after studies were included. The JBI Checklist assessed the risk of bias. Only four studies met the inclusion criteria and were considered for the analyses. The studies were published from 2010 to 2016. All studies presented a low risk of bias. Considering the studies do not have control groups, a weighted average by sample size was calculated to obtain a general estimate of the percentage of papillary filling after 6 months and the number of HA applications.

RESULTS

The studies showed the percentage of papillary reconstruction after 6 months of application, the weighted average by sample size was 77.41% (SD = 20.68), with an average number of applications of 3.17 (SD = 0.31).

CONCLUSION

The application of HA may be used to repair anesthetic defects in the papilla.

CLINICAL SIGNIFICANCE

Interdental papilla reconstruction with injectable HA is an option of nonsurgical treatment for interdental papilla deficiencies. However, there is still concern about the quality of the evidence available, considering that studies with different experimental designs can produce contradictory results. Moreover, further understanding is required on the stability of tissue gain promoted by HA in black triangles.

Morse taper performance: A finite element analysis study

OBJECTIVES

To evaluate and compare the magnitude and distribution of stresses generated on implants, abutments and first molar metal-ceramic crowns using finite element analysis.

METHODS

Preliminary three-dimensional models were created using the computer-aided design software SolidWorks. Stress and strain values were observed for two distinct virtual models: model 1 - Morse taper and solid abutment; model 2 - Morse taper and abutment with screw. A load (250 N) was applied to a single point of the occlusal surface at 15° to the implant long axis. Von Mises stresses were recorded for both groups at four main points: 1) abutment-retaining screws; 2) abutment neck; 3) cervical bone area; 4) implant neck.

RESULTS AND CONCLUSION

Model 1 showed a higher stress value (1477.5 MPa) at the abutment-retaining screw area than the stresses found in model 2 (1091.1 MPa for the same area). The cervical bone strain values did not exceed 105 µm for either model.

Expression of glyceraldehyde 3-phosphate dehydrogenase is enhanced in Leishmania spp naturally resistant to nitric oxide

Leishmania spp are the causative agents of a spectrum of diseases termed leishmaniasis that affect mammals, including humans and dogs. Although reactive nitrogen species are employed in the control of parasitism by the immune system, it is known that Leishmania can withstand this oxidative stress. As the mechanism by which these species are resistant to nitric oxide (NO) is poorly understood, the main objective of this study was to evaluate the expression of glyceraldehyde 3-phosphate dehydrogenase (GAPDH) in Leishmania amazonensis and Leishmania chagasi promastigotes showing natural resistance to NO. GAPDH transcript levels were quantified by real-time polymerase chain reaction amplification, and GAPDH activity (assessed by levels of NADH oxidation) was measured by spectrophotometry. The level of nitration in total protein was assessed by immunoblotting. The results demonstrated an increase in GAPDH expression in resistant isolates of both species compared to susceptible isolates. The increase in GAPDH expression led to an increase in the activity of GAPDH in L. amazonensis human isolates resistant to NO. The pattern of protein nitration did not differ between sensitive and resistant isolates. Our results suggest that changes in expression of GAPDH may be responsible, at least in part, to natural resistance to NO found in human and canine Leishmania spp.

Leishmania chagasi naturally resistant to nitric oxide isolated from humans and dogs with visceral leishmaniasis in Brazil

Nitric oxide (NO) plays an important role as a leishmanicidal agent in murine macrophages. NO resistant Escherichia coli and Mycobacterium tuberculosis have been associated with poor outcomes of their resulting diseases. NO resistant Leishmania braziliensis has also been identified and exacerbates the clinical course of human leishmaniasis. We report, for the first time, natural resistance of Leishmania chagasi promastigotes to NO. These parasites were isolated from humans and dogs with visceral leishmaniasis. We also demonstrate that this resistance profile was associated with a greater survival capacity and a greater parasite burden in murine macrophages, independent of activation and after activation by IFN-γ and LPS.

Measurement of interchain and intrachain exciton hopping barriers in luminescent polymer

The integrated photoluminescence intensity in thin films of 'Super Yellow' copolymer has been analyzed using a Mott-like temperature dependence. This has enabled us to observe contributions from two emission channels, indicative of exciton recombination proceeding from two distinct origins. At high temperature, interchain thermally activated exciton energy transfer and migration dominates, resulting in large scale quenching of the integrated emission intensity and hence the photoluminescence quantum yield. However, at relatively low temperature, an additional increase of the integrated emission intensity occurs. This new channel of emission has been attributed to recombination from excitons where intrachain exciton energy transfer between adjacent subunits of the copolymer backbone becomes hindered. The activation energy barriers that control both of these emission channels have been obtained and are correlated with chain backbone degrees of freedom.

Human occupational radioactive contamination from the use of phosphated fertilizers

210Po and 210Pb concentrations in urine, hair and skin smear samples from individuals using phosphated fertilizers have been compared with a control group of occupationally unexposed individuals. Urine and hair samples of the test group showed slightly higher concentrations of 210Po and 210Pb than those observed for the control group. These concentrations remained, however, lower than those for uranium mine workers. Skin smear values indicated contamination by direct contact with dust from fertilizers and this may contribute to skin cancer induction in this risk population.

Concentrations of 210Pb and 210Po in hair and urine of workers, of the uranium mine at Poços de Caldas (Brazil)

210Po and 210Pb concentrations in urine and hair samples from individuals working in different areas of the uranium industrial complex of Poços de Caldas (Brazil) have been determined and compared with a control group of occupationally unexposed individuals. In the control group, smokers showed higher urinary excretion of these radionuclides. Such difference could not be detected in the workers group, which showed an increase in urinary excretion of 210Po for the group working in the chemical laboratory. Accumulation of 210Po and 210Pb in hair showed the same trends as for urinary excretion. The workers group, with the exception of the office employees, showed a 210Po/210Pb ratio > 1 in hair.

Lead-210 in vegetables and soils from an area of high natural radioactivity in Brazil

Contamination of vegetables and associates soils by 210Pb, originating either by natural fallout from uranium or by the processing mills of Poços de Caldas (CIPC), State of Minas Gerais, Brazil is estimated by comparison with similar control samples collected from areas distant from the mining and milling operations. For lichens and bryophytes, the mean values of 210Pb concentrations were significantly higher than those of the control region. Similarly, vegetables and soils from kitchen-gardens located near the mill contained much higher concentrations of 210Pb than those observed for other regions.