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Objective To compare the disinfection effect of 3% (v/v) hydrogen peroxide and 500 mg/L chlorine-containing disinfectants in the independent waterway of a periodontal ultrasonic scaler to provide a reference for clinical waterway disinfection management in stomatology departments. Methods The 18 ultrasonic scalers were randomly divided into 3 groups of 6 units: the control group, experimental group 1 (3% hydrogen peroxide disinfectant group), and experimental group 2 (500 mg/L chlorine-containing disinfectant group). The replaceable parts of the independent waterway pipes of the 3 groups of ultrasonic scalers were replaced, and the water supply was supplied with sterile distilled water (DW). In the control group, special treatment was not applied to the nonreplaceable pipe part. In experimental group 1, the 3% hydrogen peroxide was used to disinfect nonreplaceable pipelines. In experimental group 2, the nonreplaceable part was disinfected with the 500 mg/L chlorine-containing disinfectant. The water sample was taken from the outlet of the scaler working part in the three groups for monitoring before disinfection, immediately after disinfection and 10 consecutive days after disinfection. Bacteria in the water samples were cultured for the colony counts. Then, the bacterial culture data were compared between groups. The qualified criterion of the water sample was that the number of bacterial colonies was less than or equal to 100 CFU/mL. After disinfection, a bacterial species mass spectrometry identification analysis was carried out when the number of bacterial colonies in each group exceeded the standard for the first time. Biofilms from the inner wall of the tube in the three groups were observed under an electron microscope on the 10th day after disinfection. Results There were no significant differences between the three groups before disinfection (F = 2.549, P = 0.111). The number of bacterial colonies in the spout of 6 scalers in the control group all exceeded the standard, and three kinds of bacteria were cultured: Sphingomonas melonis, Herbaspirillum huttiense, and Ralstonia pickettii. Compared with those in the control group, the number of bacterial colonies in experimental group 1 decreased significantly for 1-2 days after disinfection (P

Gingival recessions (GRs) result in root hypersensitivity, root surface caries, and esthetic problems. Various root coverage surgeries are being developed for periodontal plastic therapy. The tunnel technique (TUN) is one of the most widely applied surgeries due to its features of being minimally invasive, practical, excellent outcomes and long-term stability; however, there are still some limitations of this technique. The history and evolution from the envelope flap to TUN, including its efficiency when compared with coronally advanced flaps with a connective tissue graft (CTG), are reviewed in this paper. The limitations of TUN are discussed in consideration of our clinical experience; for example, there is high technique sensitivity when TUN is applied in GR>5 mm because of the great difficulty in covering the grafts. The advantages of surgical access, including vertical incisions in the vestibule, “W” type and pinhole access, are discussed for different situations. Mattress sutures and sling sutures in a single tooth or multiple teeth are applied in TUN. The different types of grafts, such as CTG, platelet-rich plasma, articular dermal matrix and xenogeneic collagen matrix, are described. Mechanical, chemical and biological conditioning of the root surface are recommended during surgery. Protecting the surgical area and taking antibiotics postoperatively are also very important. Finally, the modifications when TUN is applied with other kinds of techniques are discussed, including lateral closed TUN, laterally positioned flaps, double papilla flaps and frenuloplasty. Minimally invasive, esthetic, long-term stability and simplified techniques are the development trends of TUN in the future.

The principle of cotton fiber creep recovery and stress relaxation based on viscoelasticity was studied. The constitutive model for cotton fiber creep and stress relaxation was established. The creep value and variation of cotton fibers were tested under different compressive load. The results showed that the creep and stress relaxation of cotton fibers represented nonlinear viscoelasticity. The mechanical behaviors like creep recovery and stress relaxation for cotton fibers were well evaluated by nonlinear viscoelasticity model. In the scope of the study, by adding more load, the creep recovery value of cotton fibers was increased and the creep recovery mechanical index was enlarged. As the strain value of cotton fibers increase, the mechanical index of stress relaxation was enlarged. [ABSTRACT FROM AUTHOR]