[Influence of Polystyrene Microplastics on the Formation and Structural Change of Pseudomonas aeruginosa Biofilm].

Microplastic pollution in the water environment is becoming increasingly serious, impacting the growth and development of aquatic organisms. There are limited studies on the mechanisms of microplastic effects on biofilm formation. Therefore, in this study, the effects of polystyrene microplastics (PS-MPs) were investigated on the biofilm formation and development of Pseudomonas aeruginosa. Different concentrations and particle sizes of PS-MPs were selected for exposure tests to explore the effects on biofilm biomass, oxidative stress levels, biofilm structure, and population sensing system. The results showed that PS-MPs induced severe oxidative stress and inhibited biofilm formation and development, and the smaller the particle size, the stronger the inhibitory effect was. The inhibition effect was 0.1 µm>0.5 µm≈1 µm>5 µm. PS-MPs caused severe physical damage through contact with bacteria. The thickness of the biofilm was significantly reduced, damaging the structural stability. The bacteria in the biofilm secreted extracellular polymers to resist the stress of PS-MPs. Meanwhile, PS-MPs interfered with the QS system of P. aeruginosa; down-regulated the expression levels of key genes lasI, lasR, rhlI, and rhlR; inhibited the synthesis and secretion of signal molecules and related virulence factors; and ultimately affected the formation and structural stability of biofilms.

[Clinical evaluation of periapical endodontic surgery for endodontic failure].

OBJECTIVE: To evaluate the clinical outcome of periapical endodontic surgery for teeth that can't be treated by nonsurgical endodontic methods. METHODS: Sixty-two affected teeth were chosen for surgical endodontic treatment, of which 31 teeth underwent periapical curettage and the others were treated by root-end resection, retrograde preparation and filling. A radiography was taken immediately after surgery and was compared with those taken at 12 and 24 months. The results of two groups were analyzed using the chi2 test. RESULTS: The success rate for retrograde filling was higher (85% after 12 months, 88% after 24 months) compared with that of periapical curettage (52% after 12 months, 45% after 24 months). The difference in success rate between the two groups was statistically significant. CONCLUSIONS: Ultrasonic root-end preparation and retrograde filling is a good choice of treatment when the teeth can't be treated appropriately by nonsurgical treatment.

[Correction of dento-maxillofacial deformities following cleft lip and palate repair with orthognathic surgery and orthodontics].

OBJECTIVE: To restore good occlusion and face profile, the orthognathic operation and orthodontics were used to correct the dento-maxillofacial deformities following the repair of cleft lip and palate. METHODS: 21 patients (7 males and 14 females, mean age of 20.6 years) were included in this study. Their dento-maxillofacial deformities following the repair of cleft lip and palate have been corrected in our hospital since 1996. Of them, 17 patients received pre- and postoperative orthodontic treatments. 21 cases underwent the following surgical procedures: Le Fort I osteotomy in 7 cases, multisegmental Le Fort I osteotomy in 5 cases, Le Fort I osteotomy and bilateral sagittal split ramus osteotomy (BSSRO) in 4 cases, Le Fort I osteotomy and mandibular body osteotomy in 2 cases, BSSRO and genioplasty in 2 cases, BSSRO in 1 case. Rigid internal fixation was used in all patients. After multisegmental Le Fort I osteotomy, the rigid fixed palatine splint was used for 6 approximately 8 weeks. RESULTS: Osteotomy segments healed well in all cases without severe complications. 14 patients were followed-up for an average of 25.6 months. There was no evident relapse. 12 patients who received pre- and postoperative orthodontic treatments had satisfactory occlusion and face profile. CONCLUSIONS: Orthognathic operation combined with orthodontics can be used satisfactorily to correct the dento-maxillofacial deformities following cleft lip and palate repair.

[Study on etiology of retinoic acid-induced cleft palate in mouse].

OBJECTIVE: To investigate the morphologic changes of embryonic palatal development exposed to retinoic acid (RA) in mouse, and to detect the significance of the expression of TGFbeta1, TGFbeta3, EGF and BCL2. METHODS: The stage of palatal development was examined by light microscopy. S-P immunohistochemistry and in-situ hybridization was used to detect spatio-temporal patterns of expression of TGFbeta1, TGFbeta3, EGF and BCL2 in embryonic palate. RESULTS: The fetus exposed to RA resulted in formation of small palatal shelves without contact and fusion of each other to form and intact palate. RA can regulate the embryonic palatal expression of genes involved in RA-induced cleft palate. CONCLUSIONS: RA can inhibit the proliferation of MEPM cell to form small palatal shelves and induce abnormal differentiation of MEE cell causing the bi-palatal shelves no contact and fuse with each other, then induce the formation of cleft palate. RA can regulate the spatio-temporal patterns of expression of TGFbeta1, TGFbeta3 and EGF in embryonic palatal processes and the change of special expression of these genes in embryonic palatal processes are involved in RA-induced cleft palate.