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Corona virus disease 2019 (COVID-19) has become a Public Health Emergency of International Concern since its outbreak, and whether COVID-19 can transmit by aerosol remains controversial. The problem of bio-aerosol transmission in the relatively confined dental clinics has aroused wide attention in the field of dentistry. This review provided a most updated summary on the relation between bio-aerosols and dental clinics, which included the microorganisms in bio-aerosols, the bio-aerosol transmission and the sources testing methods, temporal and spatial distribution of dental bio-aerosols and summarized how to reduce the exposure to bio-aerosols in dental clinics.

Purpose: To evaluate the outcome of coronectomy for management of impacted mandibular third molars in close proximity to inferior alveolar nerve (IAN)., Methods: Ten patients with impacted mandibular third molars which approached or was close to the inferior alveolar nerve diagnosed on panoramic film and cone-beam CT (CBCT) scan were included in the study. Coronectomy was conducted at the cemento-enamel junction, leaving the roots below the alveolar crest and primary closure was performed. After the root apex was pushed away from the inferior alveolar nerve, the impacted lower third molar was then removed., Results: Ten patients had little post-operative pain and swelling, none of them had IAN injury or infection. Only 1 patient was failed to move the roots away from IAN and the roots were left in the alveolar socket, but without any symptoms and side effects during 1 year of follow-up., Conclusions: Coronectomy is effective in controlling inferior alveolar nerve injury following third molar surgery in radiographically evaluated high risk cases and it has very low incidence of complications.

Purpose: To evaluate the effect of Mtwo NiTi files in the management of calcified root canals., Methods: Thirty-five calcified root canals from 21 cases unsuccessfully prepared with C-Pilot files and EDTA were treated with Mtwo NiTi files and EDTA. The data was analyzed with SAS 9.4 software package., Results: Twenty-three calcified root canals were successfully prepared. The success rate was 65.71%. Instrument separation occurred in 4 root canals, and ledge occurred in 3 root canals. Categorized by calcified position, the success rate of three groups had no significant differences (P>0.05)., Conclusion: Mtwo NiTi files can effectively process calcified root canals.

Purpose: To analyze the profile features of soft tissues of beautiful young men and women with Han nationality by polar coordinates., Methods: Sixty-two beautiful college students (aged 18-23 years, average 20.1 years, 31 men, 31 women) were chosen according to inclusion criteria as study samples. The lateral cephalograms of the samples were taken in natural head position. The polar system was established with the Bolton (Bo) point as the pole, and the Bo-N line as the polar axis. The polar coordinates were measured of the mark points on the soft tissues of the samples' maxillofacial regions respectively. The measured data were statistically analyzed with SPSS 17.0 software package., Results: There were no significant differences among the polar angles of the marking points on the soft tissues (P>0.05), the results were not statistically significant; there were significant differences among the measured data of line distances (P<0.01); the ratios of the polar radius of each mark point and Bo-N were not significantly different (P>0.05); there were significant differences among the values of Bo-Pos/ Bo-Sn, Bo-LL/Bo-Pos between men and women, which was statistically significant (P<0.05)., Conclusions: Polar coordinates can be applied to cephalometry to accurately and integrally describe maxillofacial profile features. There are minor differences between the profile features of beautiful men and women, and the differences are mainly shown in mandible and the fullness of lips.

Purpose: To detect the effect of naringin on human periodontal ligament cells' (hPDLCs) proliferation,bone formation and OPG mRNA expression., Methods: hPDLCs were primarily cultured and identified in vitro through enzyme digestion combined tissue culture method. With 3-(4, 5-Dimethylthiazol-2- yl)-2, 5-diphenyltetrazolium bromide (MTT) method, enzyme linked immunosorbent assay and RT-PCR, the hPDLCs' proliferation, alkaline phosphatase (ALP) activity, expression of collagen protein-I and OPG mRNA were observed after treatment with different concentrations (100,10,1.0,0.1,0.01mg/L) of naringin at different times. SPSS16.0 software package was used for statistical analysis., Results: Primary cultured hPDLCs had good shape; Significant promotion of proliferation,ALP activity and collagen protein-I expression of hPDLCs with naringin was found at the dose of 1.0 mg/L; and 1.0mg/L naringin regulated the expression of OPG mRNA in time-dependent manner., Conclusion: Naringin might significantly promote the proliferation of hPDLCs and conversion into the osteoblast.

Purpose: To evaluate the possible antagonistic effects of Lactobacillus acidophilus (La) and Bifidobacterium adolescents (Ba) on Porphyromonas gingivalis (Pg) and Fusobacteriurn nuclearum (Fn)., Methods: Cylinder plate method was used to observe the inhibition zone formation.The suspensions of periodontal pathogens were mixed with cell free solutions of probiotics respectively, to investigate the antagonistic effect on the production of probiotics. The data were analyzed by ANOVA using SAS 9.0 software package., Results: La only inhibited the growth of Pg. The cell free extract of La also significantly inhibited the growth of Pg (P<0.001). There was no antagonistic effect of Ba on the two periodontal pathogens., Conclusions: La strongly inhibits the growth of Pg by its metabolites. The new strategy of confining periodontal pathogens with La as ecological modulator is worthy of further study.

Purpose: To analyze the effect of topical anesthetics in taking dental X-ray film., Methods: 300 patients, who needed to take dental X-ray photography of maxillary or mandibular molar were randomly assigned to 3 groups. Bisecting angle technique was used to take the film. Before taking the X-ray, the throats of the patients in Group I were treated by 1% dyclonine spraying anesthesia, Group II were treated by FRILJET local cryoanesthesia and pulp vitality test agent, and Group III were set as control. The anesthesia efficiency and imagine quality of the dental films were evaluated, and the anesthetic time was recorded. The data was analyzed with ANOVA and Chi-square test using SPSS12.2 software package., Results: The anesthesia efficiency was 99% in group I, 98% in Group II, and 62% in Group III. The imagine quality in Group I and II was higher than that in Group III. For both anesthesia efficiency and imagine quality, there was no significant difference between Group I and Group II, but there was significant difference between Group I and Group III, and between Group II and Group III (P<0.01).Significant difference of anesthetic time was showed between Group I and Group II . Compared with Group II, longer time(4 minutes) was needed in Group I to show the anesthetic effect, and it lasted longer for 21.62+/-3.54 minutes; while in Group II, the anesthetic effect lasted shorter, only for 2.07+/-1.22 minutes, but it developed immediately., Conclusion: The use of local anesthetics improves the accuracy, quality, and success rate in taking dental X-ray films.

Purpose: To evaluate the pharmacologic effect of garlic on oral bacteriostasis and root detoxification., Methods: Eight representative oral anaerobes (58 strains) including Streptococcus (9), Peptococcus (4), Lactobacillus (6), Actinomyces (3), Veillonella (10), Porphyromonas (12), Prevatella (3), Fusobacterium (11) to garlic juice were systematically studied by classical tube susceptibility test. The periodontally involved roots (12) were selected and the slices (6 mm x 3 mm x 1 mm) were prepared on the exposed root surface. Six slices were randomly treated by garlic juice for 5 minutes; the other six slices were treated by normal saline with same method as control. The attachment of cultured L-fibroblasts to the treated root surface was observed under phase contrast microscope and electron scanning microscope. The attachment cells were statistically analyzed using SPSS10.0 software package for Student's t test., Results: The minimal inhibitory concentration of garlic juice on most oral anaerobes (87.93%) was 1:64-1:512. The attachment L-fibroblasts to the garlic treated group increased significantly vs. the control group (P<0.05)., Conclusion: The study shows that garlic juice could effectively inhibit oral anaerobes and reestablish the root biological adaptation.

Purpose: To compare the effect of chloromycetin and normal saline on proliferation and ultrastructure of cultured periodontal ligament cells., Methods: Human periodontal ligament cells were exposed for 1 hour to 0.25% chloromycetin, normal saline and DMEM culture medium. The number of viable cells were counted immediately after exposure(0h) and at 12,24 and 48 hours,to test the proliferative capacity of the cells after treatment.The ultrastructure was observed under transmission electron microscope. The results were analyzed with ANOVA using SAS9.1 software package., Results: There was no significant difference in the number of viable cells between chloromycetin and normal saline at any time point. Most of mitochondrions changed to vacuole after the cells exposed to chloromycetin,and the number of endoplasmic reticulum decreased., Conclusions: The effect of chloromycetin on proliferation of human periodontal ligament cells is same as the effect of normal saline, but chloromycetin causes damage to the ultrastructure of human periodontal ligament cells.

Objective: In order to search the cause of dental caries and periodontitis., Methods: Selected 70 patients with severe chronic periodontitis (CP group) and 50 patients with caries sensitivity (CS group) in clinical adults of oral medicine (18 to 50-year-old) during 1 year. Parameters of oral hygiene, caries and periodontitis were recorded in the typical groups of CP and CS., Results: The patients of CP group had rare caries, DFS in the groups of CP and CS was 1.46+/-2.60 and 17.32+/-7.55 respectively(p<0.001),while the patients of CS group had relative periodontal health indeed, CPTNI in CS and CP groups were 0.98+/-0.63 and 3.24+/-0.62 respectively (p<0.001), and the number of missing teeth was 1.90+/-3.34 and 1.10+/-1.85 respectively(p>0.05). 3 patients(only 2.4%)confirmed the parameters of caries sensitive as well as severe periodontitis., Conclusion: The correlating pathogenesis of caries and periodontitis seems to have antiagonism tendency. The ecological connection and bacterial interaction are worthy of further study.

Objective: 9548 middle school students from 11-19 age at Huangpu District in Shanghai were investigated to study the prevalence of juvenile periodontitis(JP). The purpose of the present study was to discover JP at early stage and make correct diagnosis, so the patients can be treated on time., Methods: From January 2001 to April 2001, debris index(DI), calculus index(CI), sulcus bleeding index(SBI) and community periodontal index for treatment needs (CPITN) were examined in each student., Results: In 9548 investigated (4739 males and 4809 females), prevalence of JP was 0.76%, the ratio of males to females was 1:1.03 (P<0.05). With aging, the detectable rate of gingival bleeding and calculus was increasing, the prevalence of JP was also increasing., Conclusion: Since the new classification system of periodontal disease was established, the above cases are worth reevaluating. We should also enhance oral hygiene of the young people.