Investigation and analysis of underground noise in Sichuan coal mines / 中华劳动卫生职业病杂志

Objective: To understand the harm degree of underground noise and provide basis for noise control. Methods: In November 2019, 13 typical coal mines in Sichuan Province were selected as the research objects, and a total of 1203 sites and 609 jobs of noise exposure were investigated. Results: The noise intensity P75 >80 dB (A) was measured. The noise intensity of the inspection place of the air compressor is >86 dB (A) , the noise intensity of the inspection place of the gas drainage and the operation place of the main fan is between 80-85 dB (A) . Conclusion: Besides the harm of dust, noise exposure should also be paid attention to, and the measures of sound absorption and sound insulation should be taken or personal protection should be strengthened.

Detection and functional analysis of CD-4+ CD-25+ regulatory T cells in the peripheral blood of patients with generalized aggressive periodontitis / 中华口腔医学杂志

<p><b>OBJECTIVE</b>To investigate the changes of proportion and suppression function of CD-4+ CD-25+ regulatory T cells in the peripheral blood of patients with aggressive periodontitis.</p><p><b>METHODS</b>Flow cytometric analysis was used to detect the frequency of CD-4+ CD-25+ regulatory T cells in the peripheral blood of 16 patients with generalized aggressive periodontitis and 17 patients with chronic periodontitis, as well as 17 periodontal healthy controls. Furthermore, CD-4+ CD-25+ regulatory T cells and CD-4+ CD-25- T cells were separated from peripheral blood of each enrolling subject using magnetic cell sorting technology. The direct suppression effect of CD-4+ CD-25+ regulatory T cells on CD-4+ CD-25- T lymphocytes proliferation was performed by the mixed lymphocytes reaction and measured by 3H-thymidine radioactive assay.</p><p><b>RESULTS</b>The patients with generalized aggressive periodontitis had a lower frequency of CD4+ CD-25+ regulatory T cells (9.71 +/- 4.01)% in the peripheral blood than periodontal healthy controls [(14.72 +/- 3.51)%] and chronic periodontitis patients [(17.01 +/- 5.16 )%], P < 0.05. A significant decrease was found in the suppression function of CD-4+ CD-25+ regulatory T cells from peripheral blood of patients with generalized aggressive periodontitis when co-cultured with CD-4+ CD-25- T lymphocytes in the proportion of 2 : 1, 1 : 1 and 1 : 2 as compared with chronic periodontitis patients and periodontal healthy controls (P < 0.05).</p><p><b>CONCLUSIONS</b>Diminished numbers and decreased suppression function of CD-4+ CD-25+ regulatory T cells were found in patients with generalized aggressive periodontitis.</p>

Use of angulated radiograph in clinical judgement of obturation quality of molars with multiple root canals / 中华口腔医学杂志

<p><b>OBJECTIVE</b>To investigate different angle projection technique for clinical judgment of obturation quality of molars with multiple root canals.</p><p><b>METHODS</b>Eighty-seven maxillary first molars with second mesiobuccal canal (MB2) and 105 mandibular first molars were selected. The canals were instrumented by Ni-Ti rotary instruments and obturated with lateral condensation technique. To judge the obturation quality of the root canals, the radiograph was taken at a horizontal angles of 0 and 20 - 30 degrees from distal direction of the tooth after the treatment.</p><p><b>RESULTS</b>For maxillary first molars, periapical radiographs showed 23.0% of MB2. Distally angulated radiographs showed 81.6% of MB2. For mandibular first molars, periapical radiographs showed 38.1% of mesiobuccal and mesiolingual canals, and distally angulated radiographs showed 90.5% of two mesial root canals.</p><p><b>CONCLUSIONS</b>Most buccal-lingual distributed root canals of the first molar can be shown more clearly by distally angulated radiographs.</p>