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??Objective??To investigate the characteristics of the thickness of maxillary sinus membrane corresponding to molars with severe periodontitis??and observe the thickness changes of maxillary sinus membrane at six months after tooth extraction and alveolar ridge preservation by measurements of cone-beam computed tomography??CBCT?? images. Methods??Totally 8 patients with a total of 8 maxillary molars with severe periodontitis intending to receive alveolar ridge preservation and implant placement were recruited in Peking University School and Hospital of Stomatology from February 2016 to November 2017??and another 8 CBCT images of maxillary molars with mild periodontitis were included in the control group. The maximum membrane thickness??maxMT??of the maxillary sinus??and the minimum residual ridge height??minRRH??were measured by CBCT. In the experimental group??the maxMT corresponding to the affected tooth was measured 6 months after the tooth extraction and alveolar ridge preservation. Results??The maxMT of the maxillary sinus in the experimental group was??4.06 ± 1.80??mm??87.5% of the maxillary sinus membranes were found thickening compared to normal thickness??and the minRRH of the molar was??1.09 ± 0.68??mm. The maxMT of the maxillary sinus and the minRRH of the molar in the control group was??1.42 ± 0.38??mm and ??8.50 ± 1.72??mm respectively??and there was no mucosal thickening. There were statistically significant differences between two groups. In the experimental group??the maxMT of the maxillary sinus was changed from??4.06 ± 1.80??mm to??1.55 ± 0.63??mm in six months after alveolar ridge preservation??the proportion of mucosal thickening was decreased to 12.5%??and the difference was statistically significant??P < 0.05??. Conclusion??Maxillary sinus mucosa tends to be thickened in molars with severe periodontitis. The thickness of the maxillary sinus mucosa is likely to return to normal at 6 months after tooth extraction and alvedar ridge preservation.     

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?? Objective    To evaluate the efficacy between low-level diode laser with 810 nm and rhEGF gel in the treatment of recurrent aphthous ulcer ??RAU??. Methods    A total of 60 RAU patients were randomly divided into experimental and control groups??with 30 cases in each group. Experimental group received diode laser for local irradiation therapy??the control group received drug treatmemt with rhEGF gel until ulcer healing. The course of treatment was one week. Results    Compared with control group??the experimental group has more obvious reduction of pain from baseline values??shorter median healing time and better efficacy. The differences were statistically significant??P??0.05??. There was no statistical difference on recurrence rate ??P > 0.05??. However?? within the next one month??there was no recurrence on treatment areas in experimental group. Conclusion    Diode laser treatment for RAU proves to be more stable and lasting in pain relieving and proves to be more obvious in accelerating healing time. Recurrence rate also can be reduced in the same area in short term. Laser therapy is more effective in the treatment of RAU compared with the rhEGF gel.     

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??Objective    To analyze the risk factors and to evaluate the 2-year clinical anti-caries effect of pit and fissure sealant by investigating the prevalence of dental caries of the first permanent molar from 9-12 year-old students in Shenyang. Methods    Totally 729 students in Tiexi District were chosen from three primary schools??among whom 299 were selected as experimental group whose parents have signed the informed consent??while others were chosen as control group. Two years later??prevalence rate of dental caries in both groups were tested and risk factors were analyzed through combination with questionnaires. Results    The retention rate of sealant of the experimental group was 81.80%??the prevalence rate of caries was 2.01%??which was lower than that in control group??16.51%????P??0.05????the difference being statistically significant. Logistic regression analysis showed that pit and fissure sealant??Y/N????the frequency of teeth brushing and parents’ education were positively correlated with the incidence of caries. Conclusion    Pit and fissure sealant is a protective method to reduce the incidence of dental caries. Both pit and fissure sealants and oral health education in early stage for children and parents should be advocated and strengthened to acquire a better oral hygiene.