Alveolar bone resorption is common outcome after tooth extraction, often resulting in bone deficiency and aesthetic problem in implant and repair. Periodontal sites preservation technology is taken to reduce alveolar bone and soft tissue absorption, or increase bone formation after the tooth extraction. Filling of autogenous bone graft or bone substitute material is the most commonly used method of periodontal sites preservation technology. In the article, the preservation technology status and the properties of different bone filling material were reviewed.

Objective To evaluate the effects of two kinds of typical edible acid (acetic acid and citric acid) on the mechanical properties and microstructures of yttriastabilized tetragonal zirconia polycrystal (YTZP) at ambient temperature, and to investigate the safety of edible acids to YTZP restorations clinically. Methods 30 barshaped zirconia ceramics specimens were randomly divided into 6 groups. The specimens in the control group (Group A) received no surface treatment, while those in group LTD (Group B) were hydrothermally aged at 134 ℃ and 0.2 MPa in an autoclave for 20 hours. Specimens were immersed at ambient temperature in 10% acetic acid or 20% citric acid for 7 (Group C, E) or 14 days (Group D, F), respectively. Surface Vickers hardness and fracture toughness were measured. Scanning electron microscopy (SEM) was used to observe the surface microstructure of each typical specimen. Results Acetic acid and citric acid immersion didn’t deteriorate the surface Vickers hardness. Specimens in Group D exhibited decreased fracture toughness. All the groups did not show significant microstructure changes on SEM observations. Conclusions Citric acid has no influence on the mechanical properties and microstructures of YTZP restorations at ambient temperature. Longterm immersion in acetic acid reduces fracture toughness of YTZP significantly and shortens the service life of YTZP restorations clinically.

Objective To investigate the effect of chitooligosaccharide (COS) on the growth, acid production and adhesion of streptococcus mutans(S. mutans). Methods Minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) of COS against S. mutans(ATCC 25175) were determined by microdilution technique. The influence of COS on the growth rate of S. mutans was assessed by timekill curve. To measure the impact of COS on acid production of S. mutans, 1 mL bacterial cell suspension containing 1/2 MIC, 1/4 MIC or 1/8 MIC COS was seeded in the sterile culture tubes, and pH value in the collected supernatant was analyzed and pH curve was then figured out. With liquid scintillation counting method, the adverse effect of COS on the bacterial adhesion ability to hydroxylapatite was also fully investigated. Results COS inhibited S. mutans growth with MIC at 2.00 g/L and MBC at 4.00 g/L, respectively. At low concentration, COS exhibited an inhibitory effect on S. mutans growth, while at high concentration, COS was capable of directly killing bacteria. 2.00 g/L (MIC) COS could significantly reduce the acid production and adhesion of S. mutans and this inhibitory effects was in concentrationdependent manners. Conclusion COS can inhibit the growth, acid production and adhesion of S. mutans.

Objective To evaluate the effect of titanium dioxide (TiO2) nanoparticles on tensile bonding strength (TBS) and antibacterial properties of an orthodontic adhesive. Methods Light cure orthodontic adhesive (Grengloo) was blended with TiO2 nanoparticles by 1%, 2%, 3% (mass fraction). The control was not blended with TiO2. Brackets were bonded to extracted premolars by these new adhesives. TBS of four groups was determined, and the adhesive remnant index (ARI) scores were assessed. A total of 20 composite discs specimen were prepared, and incubated with bacterial suspension for 48 hours and tested for antibacterial properties. Results No significant difference was found among TBS and ARI of the four groups. PH values of group 2% and 3% were significantly increased and lactate production was significantly reduced compared with the control group, but no significant difference was found between these two groups. The colony unit counts of the three groups containing TiO2 were significantly reduced, but no significant difference among these three groups was observed. Conclusion Adding 2%TiO2 to Grengloo enhances its antibacterial effects without increasing the tensile bonding strength.

Objective To investigate the relationship between the morphology and content of collagen fibers and the development of tumor in human oral squamous carcinoma. Methods Paraffin sections from the 80 clinical specimens of oral squamous cell carcinoma that were stained with HE and Masson’s trichrome stain were observed for collagen fibers under the microscope. Statistical analysis was used to analyze the expression of collagen fiber and its correlation with tumor differentiation. Results Oral submucous fiber deposition was observed in severe atypical hyperplasia. The morphology and distribution of collagen fibers obviously decreased in infiltrating carcinoma with different invasiveness as well as in highly, moderately and lowly differentiated carcinomas. The difference in collagen per area among groups was statistically significant (P<0.05), and the tumor differentiation degree was negatively related to the tumor progression(r=-0.800, P<0.05). Conclusion The distribution and morphology of collagen fibers are closely related to the development of human oral mucous carcinoma and the differentiation degree of carcinomas. 

Objective To explore the apoptosis mechanism of human periodontal ligament cells (HPDLCs) induced by Caspase under stretching force. Methods HPDLCs were cultured in vitro, and cells were stretched by dynamic mechanical strain 1%, 10% and 20% for 6 h, 12 h, 24 h and 48 h. The Caspase3 activity was measured after stretching in PDL cells that were treated with a specific inhibitor of either Caspase8 or Caspase9 prior to the application of stretching force. Results The activity of Caspase3 increased substantially in a time and force dependent manner after the application of a cyclic stretching force. It reached a peak at 24 h. The Caspase9 inhibitor abolished the stretching forceinduced activation of Caspase3, whereas the Caspase8 inhibitor demonstrated no effect. Conclusion Cyclic stretching force can induce apoptosis in HPDLCs through the activation of Caspase3 via the Caspase9 signaling cascade.

Objective To observe the effects of quercetin on the expression of IL6 (interleukin6) by LPS (lipopolysaccharide) induced human periodontal ligament cells (hPDLCs), and to explore the antiinflammatory action of quercetin (Que). Methods hPDLCs were cultured in enzymic digestion tissue blocks and then identified. The inhibitory effects of quercetin with different concentrations on the expression of IL6 by LPSstimulated hPLDCs at different time points were assayed by ELISA (enzymelinked immunosorbent assay). Results IL6 secreted by hPLDCs peaked after the stimulation of LPS for 24 h. Compared with the LPS group, however, IL6 expressed by cells treated with quercetin before the stimulation of LPS significantly decreased with a statistical significance. No significant difference was found in different concentrations of quercetin groups. Conclusion Quercetin can inhibit the LPSinduced expression of IL6 in hPDLCs, suggesting that it may regulate the synthesis and secretion of IL6 in some way, thus alleviating inflammatory reaction in the early stage of inflammation.

Objective To investigate the relationship between halitosis and helicobacter pylori infection in stomach. Methods 226 subjects without periodontal diseases or systematic disease (except helicobacter pylori infection) were included. Nasal measurement method was used to divide the participants into the halitosis group (case group) and the nonhalitosis group (control group). Basic information such as gender and age and oral health situation was matched between groups with no statistical difference. Halitosis was diagnosed by OS≥2 and VSC≥110 μg/L respectively. Infection of helicobacter pylori was diagnosed by biopsy. Clinical examination (including malodour test and oral examination) and questionnaire survey were conducted before gastroscopy. SPSS19.0 software package was used to analyze the data. The logistic regression model was used to analyze the relationship between halitosis and helicobacter pylori infection. Results All the subjects were periodontally healthy according to the periodontal index, with 117 in the case group and 109 in the control group. The prevalence of helicobacter pylori infection in halitosis subjects diagnosed by OS≥2 was significantly higher than that in the normal subjects (60.7% vs 22.9%, P<0.01). Logistic regression analysis showed helicobacter pylori infection was the significant variable in the equation, and the adjusted OR was 4.6 (P<0.05). When diagnosed by VSC≥110 μg/L, adjusted OR was 9.3. Conclusion Helicobacter pylori infection in stomach may be involved in the presence of halitosis in periodontally healthy subjects. Further large scale sample prospective studies should be done.

Objective To observe the expression of Th cytokines IFNγ, IL10 and IL17 in serum of patients with oral lichen planus (OLP), and to explore its role in the genesis and development of OLP. Methods 15 patients with OLP and 15 healthy controls participated in the study. Interferon (IFN)γ, interleukin (IL)10 and IL17 levels in serum were examined by enzyme linked immunosorbent assay (ELISA). Results The levels of Th1 cytokines IFNγ in serum of patients with OLP group and healthy controls were （20.8±8.3）pg/mL and （20.6±3.1）pg/mL, respectively, with no statistical difference between groups (P>0.05). The levels of Th2 cytokines IL10 in serum of patients with OLP and healthy controls were （43.3±4.6）pg/mL and （29.0±5.1）pg/mL, respectively, and the difference was statistically significant (P<0.05). The ratio of IFNγ to IL10 was 0.418 for the OLP group and 0.712 for the control group, which demonstrated a decrease in the experimental group compared the control group. The level of Th17 cytokines IL17 in serum of patients with OLP group was （23.6±2.7）pg/mL, which was significantly higher than （16.8±3.3）pg/mL in the control group (P<0.05). Conclusion The change in Th cytokines balance is involved in the pathogenesis of OLP.

Objective To compare the effects of conventional and hybrid Hyrax appliances on arch widths, dentoalveolar and basal bone. Methods 30 patients requiring maxillary expansion were randomly divided into two groups. A conventional hyrax appliance was applied in one group, consisting of 15 patients (8 boys, 7 girls; mean age (14.1±2.5) years), and a hybrid hyrax appliance was used in the other group of 15 patients (9 boys, 6 girls; mean age (13.9±2.6) years). Conebeam computed tomography records were taken before and 3 months after expansion, and dental arch width, dentoalveolar, and basal bone variables were measured on the rebuild 3D images. The pairedsamples test was used to evaluate treatment changes for both groups. The independentsamples test and the t test were used to compare the variables between the two groups. Results Significant basal bone changes and increases in dental arch width were observed in both groups. However, the widths between the first and second premolars were significantly greater in conventional Hyrax appliance than those in hybrid Hyrax appliance. There were no significantly differences in buccal and palatal alveolar bone thickness changes of the first molar between the two groups, whereas changes of the first premolars significantly differed between the two groups. No significant intergroup difference was found in the absolute dental tipping. Conclusions The two rapid expansions are both effective methods for a narrow maxilla treatment. However, the conventional hyrax appliance can result in greater expansion in the premolar dental arch width and the buccal and palatal alveolar bone thickness.

Objective To evaluate the ability to keep the original root canal anatomy flow by Reciproc single file in preparing molar curved root canals. Methods Patients aged from 18 to 59 years old who were newly diagnosed with pulp disease were selected. According to Schneider measurement, 100 first molar curved root canals (20°～30°) and 200 canals (cheek, tongue curved root canals) were randomly divided into Reciproc group of 50 cases with 100 canals, and Protaper group of 50 cases with 100 canals. Then root canals were prepared, followed by the measurement of root canal curvature of the dental film chip in first root canal file, the final root canal file, and the trial point root canal file. The apical transportation of root canals in two groups were compared, and the effects of root canal formation as well as root tip closure were evaluated. Results Success rate in Reciproc group was 99%, while success rate in Protaper group was 92%, and the difference was significant (P<0.05). Conclusion With its innovative design, the Reciproc single file enables the preparation molar curved root canals to have fine formation, light reaction, good closure in the apex, quickness and high efficiency, making a single file take place of a set of files.

Objective To analyze the effect of Bite turbo combined with early class Ⅲ elastics on the treatment of anterior crossbite. Methods 16 patients with anterior crossbite and deep overbite participated in the experiment. Bite turbo combined with early class Ⅲ elastics was used and the clinical effect was observed. Lateral cephalograms were taken before treatment and after bite opening. The related hard tissues were estimated through the cephalograms. Results After a short period of treatment, the anterior crossbite and deep overbite were corrected in all cases. SNB, ANB, MPSN, ANSMe, ANSMe /NMe, U1-SN, U6-PP, L6-MP, L1-MP, overjet and overbite were significantly changed. Conclusion Bite turbo combined with early class Ⅲ elastics can be used effectively for anterior crosssbite correction.

Objective To compare alveolar bone conditions around mandibular incisors in the adult of skeletal classⅢ malocclusion before treatment and after the presurgical orthodontic treatment. Methods 15 patients treated with orthodontic treatment and orthognathic surgery (9 men, 6 women, average age: 23.6 years) took CBCT before treatment (T0) and 1 month before orthognathic surgery (T1).The amount of alveolar bone thickness, the vertical alveolar level and the root length were measured. Paired ttest was performed for the comparisons of the differences between pre and postoperative variables using SPSS15.0. Results ① The lower incisors inclination was increased and the incisors root apex was closer to the lingual side of alveolar bone (P<0.01); ② The alveolar bone thickness at apex was not statistically changed; ③ The vertical alveolar bone levels at the labial and lingual sides were both significantly reduced especially at the lingual side after presurgical orthodontic treatment (P<0.01); ④ The root length was not significantly changed. When the lower incisor inclined to the lip in a wide range, the tooth root moved closer to the lingual bone cortex, and the attachment height of alveolar bone lowered more. Conclusion In the treatment of adults with skeletal class Ⅲ malocclusion, special attention should be given to the patients’ periodontal health, the change of alveolar bone and the relationship between root and alveolar bone. A right plan should be chosen to decrease the excessive movement of lower incisors so as to avoid adverse reaction.

Objective To compare the therapeutic efficacy of the matchedtaper single cone obturation, warm guttapercha Beefill 2 in 1 and the cold lateral condensation. Methods 180 patients were randomly divided into group A, B, C, each containing 60 patients (60 teeth), and were treated with the cold lateral condensation, the warm guttapercha Beefill 2 in 1 and the matchedtaper single cone obturation, respectively. The obturation time, postoperative pain, filling fitness rate, incidence of vertical root fracture, and success rate of obturation were observed. Results The obturation time of group C was （62.6±7.2）s, shorter than that in the other two groups(P＜0.01). Occurrence rate of postoperative pain in group C was 1.67%, lower than that in the other two groups(P＜0.05). Filling fitness rate in group C was 98.33%, higher than that in the other two groups (P＜0.05). The incidence of vertical root fracture in group C was low. Success rate of obturation in group C (96.61%) showed no significant difference compared with the other two groups (P>0.05). Conclusion Given its high curative effect, short operation time, and low incidence of tooth fracture, matched taper single cone obturation is worthy of clinical application.

Objective To detect the evaluation effect of the integrated testing items in the National Dental Licensure Exam. Methods A portion of testing items which had been measured previously were selected randomly. The items were transformed through multidisciplinary integration and then measured again. The variation of the degree of difficulty and discrimination of the items before and after the integration were analyzed with paired ttest method for statistical analysis. Results The degree of difficulty didnt obviously change after multidisciplinary integration, but discrimination was significantly increased. This result was mainly reflected in the median score group of candidates. Conclusion Integrated items might have a better evaluation effect in the Dental Licensure Exam.

Objective To compare the preventive effect of fluoride varnish and fluoride foam on caries increment in deciduous teeth over a twoyear period and to provide theoretical basis for the caries prevention in the primary dentition in China. Method 220 children at 3~4 years old from two kindergartens were chosen with cluster sampling method and were randomly divided into two groups, fluoride foam group and fluoride varnish group. They received topical fluoride application four times over a 2year period of time. Oral examination was carried out every year. All the data were collected and the caries incidence, the mean increments of dmft (decayed, missing and filled teeth) and dmfs (decayed, missing and filled surfaces) of the two groups were compared. Results The mean increments of dmfs of the foam group after one and two years’ intervention were 2.58±4.36 and 3.85±5.15; and those of the varnish group were 0.95±2.28 and 1.94±3.32. The differences between the two groups were statistically significant(P＜0.01). Conclusion Fluoride varnish is more effective than fluoride foam in preventing caries of primary teeth.

Surgery combined with radiotherapy is a conventional treatment for oral and maxillofacial tumors. Recently, an increasing number of patients have resorted to dental implantation after oral and maxillofacial surgery to restore the missing teeth. Satisfactory osseointegration between dental implants and the surrounding bone tissues is the key to success. However, postradiotherapy jawbone tissues may suffer damages to some extent, which could affect the osseointegration and increase the risk of complications. The research progress on prevention and treatment of postradiotherapy dental implant complications were reviewed in this paper.

Paraneoplastic pemphigus (PNP) is a rare, lifethreatening, autoimmune, and mucocutaneous blistering disease associated with neoplasia. The clinical features of PNP are mucosal erosion and polymorphic skin lesions in patients with concomitant tumor. Due to the complexity of the clinical manifestations, the misdiagnosis rate of the first diagnosis is high. In recent years, the pathogenesis and clinical manifestations of this disease have been more intensively studied. This article expounded and summarized PNP in terms of its pathogenesis, clinical manifestation, pathological and immunological features, as well as diagnosis and treatment to better understand this disease and improve the effect of diagnosis and treatment.

Lightcuring resin composites are widely used as dental restorative materials in clinic. Partial monomers don’t polymerize when the resin composites are cured with light, thus turning into residual monomers which will release in the oral environment. In addition, resin can release some components due to biodegradation induced by saliva and enzyme. All of these components may affect body tissues. Released monomers can be measured by numerous techniques including HPLC, LC/MS, HPLC/MS, and GS/MS.The aim of this article was to review the reasons for the released components, their effects on human body and detection methods of these residual monomers.

As a noninvasive technique, microCT can not only accurately measure the differences between teeth canal anatomy, but also reconstruct the original root canal morphology. By comparing the data before and after root canal preparation, microCT makes it possible to study root canal preparation qualitatively and quantitatively. This article reviewed the application of microCT in root canal preparation.

Dental unit waterline (DUWL) output water can be heavily contaminated with microorganisms. Since patients and dental staff are regularly exposed to water and aerosols generated from the dental unit, contaminated DUWL water is considered as an occupational hazard. The features of DUWL contamination, the causes of DUWL contamination and the control methods of DUWL contamination have been researched for many years. The article reviewed these issues.

Glucanbinding proteins (Gbps) are important virulence factors in the cariogenicity of streptococcus mutans (S.mutans). Glucanbinding proteins play an important role in the adhesion and aggregation of S.mutans, and are involved in physiological function of cell wall and enzyme activity; they also have an effect on the biofilm formation and maintain the stability of biofilm architecture. The article reviewed current status of four glucanbinding proteins, their relationships with biofilm and anticaries vaccine, and existing problems.

The pathogeny of the parotid hypertrophy is complex. Sialosis is defined as painless, diffuse, noninflammatory, nonneoplastic enlargement of the major salivary glands.The causes include diabetesmellitus, endocrinopathy (hypothyroidism), starvation,medications (thiourea, diuretics),and alcohol abuse. Clinical manifestation, histological and imaging performance should be taken into account. Botulinum toxin is a highly efficacious and costeffective, nonsurgical option for reducing the width. Many related pathogeny and treatments have been reported, but there are still many problems remaining to be studied.

Vacuum sealing drainage (VSD) combines negative pressure drainage with traditional sealing dressing. It was applied to the open fracture wounds in the early time and has achieved wider application now. In this article, the author summarized the characteristics and application of VSD in soft tissue wound, bone tissue wound, dermal chronic ulcer, and skin and bone transplantation, and gave the future prospect for its application in the oral and maxillofacial surgery.