Characterization of oral bacterial diversity of irradiated patients by high-throughput sequencing.

The objective of this study was to investigate the compositional profiles and microbial shifts of oral microbiota during head-and-neck radiotherapy. Bioinformatic analysis based on 16S rRNA gene pyrosequencing was performed to assess the diversity and variation of oral microbiota of irradiated patients. Eight patients with head and neck cancers were involved in this study. For each patient, supragingival plaque samples were collected at seven time points before and during radiotherapy. A total of 147,232 qualified sequences were obtained through pyrosequencing and bioinformatic analysis, representing 3,460 species level operational taxonomic units (OTUs) and 140 genus level taxa. Temporal variations were observed across different time points and supported by cluster analysis based on weighted UniFrac metrics. Moreover, the low evenness of oral microbial communities in relative abundance was revealed by Lorenz curves. This study contributed to a better understanding of the detailed characterization of oral bacterial diversity of irradiated patients.

[Effect of compound Chinese traditional medicine on periapical periodontitis in dogs and cytotoxic assay].

PURPOSE: To assess the efficacy of compound Chinese traditional medicine(CTM), which is composed of gallic acid, magnolol and polysaccharide of Bletilla, against apical periodontitis in dogs and cytotoxic assay. METHODS: A animal model of apical periodontitis was built, CTM was then used to disinfect the root canal. The effect of the restoration of periapical bone in dogs was investigated after regular root canal filling. SAS6.12 software package was used for statistical analysis, and MTT was used to test cell toxicity of CTM. RESULTS: CTM can cure inflammation effectively, and CTM had no cytotoxic effect on periodontal ligament cells at 5-week. CONCLUSIONS: The compound Chinese traditional medicine may be an effective disinfecting drug for root canal disinfection.

Six cases report of differential diagnosis of periapical diseases.

The distinction of some particular forms of periapical area, involving diseases from regular periapical disease, is a matter of considerable importance when choosing a correct treatment. The aim of this study is to describe the differential diagnosis of periapical diseases from six rare cases in clinical practice. The six rare cases are examples of situations where it is difficult to make a differential diagnosis in clinical practice. By retrospective surveys on the clinical examination, radiographs and pathological results, six patients referred to endodontic treatment in our department were analyzed for the accuracy of diagnosis and therapy. The pathoses of the six cases included two atypical radical cysts, periapical cemental dysplasia, cemento-ossifying fibroma, thymus cancer metastasis in the periapical site and tuberculosis. This report indicates that endodontists should be cognizant of a few particular circumstances when clinically treating periapical diseases.

[Effect of compound Chinese traditional medicine on infected root canal bacteria biofilm].

PURPOSE: To assess the efficacy of compound Chinese traditional medicine(CTM), which composed of gallic acid, magnolol and polysaccharide of Blettila striata, against the infected root canal bacterial biofilm. METHODS: Actinomyces viscosus (Av), Enterococcus faecalis (Ef), Fusobacterium nucleatum (Fn) were composed to form biofilm, then confocal laser scan microscope (CLSM) was used to observe and study the bacterial activity. SAS6.12 software package was used for statistical analysis. RESULTS: The biofilm thickness reduced after treatment by both CTM and ZnO (P>0.05),while there was a significant decrease of the percentage of vital bacterias after treatment by CTM (P<0.01). CONCLUSIONS: The compound Chinese traditional medicine is effective on biofilm control, so that it would be an effective disinfecting drug for root canal sealers. Supported by Research Fund of Bureau of Traditional Chinese Medicine of Shanghai Municipality (Grant No.2008L008A).

[Quantitative evaluation of residual endodontic microorganisms after mechanical root canal preparation different chemical preparations by real-time PCR].

PURPOSE: To establish a quick, sensitive method for quantifying root canal flora and investigate the effects of different root canal preparations on the pathogenic bacteria at RNA level. METHODS: A total of 24 single-rooted teeth with chronic apical periodontitis were selected and prepared using 3% H2O2 combined with 1% NaClO, EDTA combined with 3% H(2)O(2),1% NaClO, respectively,the samples were taken before and after root canal preparation. After isolation of total RNA from the root canal samples, cDNA was synthesized by reverse transcription, and detected by real-time PCR. The data were analyzed with SAS 6.12 software package. RESULTS: The number of bacteria in the root canal reduced dramatically after mechanical preparation and irrigated using 3% H(2)O(2) and 1% NaClO(P<0.01). Further combined with EDTA, its effect was better than that of simply irrigated using 3% H(2)O(2) and 1% NaClO(P<0.05). CONCLUSIONS: Real-time PCR can be employed in the identification of bacteria flora in the root canal, both methods of root canal preparation can effectively reduce the number of bacteria flora.

[Cloning and the sequence analysis of the fish glutathione transferase Pi gene].

Using RT-PCR method, the glutathione transferase Pi cDNAs were cloned from Cyprinus carpio, Hypophthalmichthys molitrix, and Carassius auratus. The open reading frames (ORFs) from the 3 fishes were 627 bp long (encoding for 208 amino acids) with the initial code ATG and the terminal code TGA. The sequence similarity was 50% between fish and mammals, 33% between fish and amphibian, and 15% between fish and arthropoda, respectively. The sequence similarity was big among fishes, and the average value of the 4 cyprinids was about 85%. Phylogenetic tree was constructed for 13 species based on GST Pi amino acid sequences using MP (Maximum Parsimony) method. Two major clusters were recognized: cluster one consisted of Mammals (bootstrap 100) and cluster two consisted of fishes (bootstrap 93). Based on the sequences analyses of N/C domain of GST Pi, we proposed the detoxification mechanism of freshwater fishes that were thought to have stronger tolerance to microcystins.

[Analysis the effect on the stress of root canal wall of pulpless teeth by different degree of root canal preparation].

OBJECTIVE: To analyze the stress variations of wall of root canal of pulpless teeth that resulted from different diameters of root canal. METHODS: On the basis of the finite-element model of the mandibular first molar that modified by routine, diameter of root canal was modified and enlarged so as to the diameter of root canal was 1/3 and 1/2 of root diameter, then modified models were loaded and the maximal stress of each part of teeth and wall of root canal was calculated. RESULTS: The results revealed that enlargement of root canal diameter will bring on increase of stress of root canal wall at the orifice and coronal 1/3. The stress difference of lateral loading was greater than that of vertical loading. CONCLUSION: The principle of root canal preparation should be infected material removed and good shape of root canal gained. Over-preparation is unnecessary and harmful.

[Histological evaluation on repair of furcation perforation in dogs using mineral trioxide aggregate].

OBJECTIVE: To investigate histological response to immediate repair of different sizes of furcation perforation using MTA, Dycal and GIC. METHODS: Forty-two posterior teeth in three adult beagle dogs were randomly divided into two groups, small perforation group and large perforation group. Each group was then divided into three sub-groups which were repaired with MTA, Dycal and GIC respectively. The dogs were sacrificed 4 months later, and the specimens processed and examined under the light microscope. Inflammation, epithelial proliferation, and formation of hard tissue over the material were evaluated. RESULTS: In teeth repaired with MTA, five cases were free of inflammation, and the other nine cases were associated with slight or moderate inflammation. There was formation of cementum with cementoblast cells around it in four cases. In the group of Dycal, all specimens had moderate or severe inflammation. The deposition of irregular calcified tissues as well as a large quantity of inflamed cells were found in two cases of small perforation. Six cases presented epithelial proliferation. In the group of GIC, moderate or severe inflammation was seen in all cases except for one case of large perforation with fibrous tissues and sparse inflammatory cells around the material. Four cases presented epithelial proliferation. There was some relation between epithelial proliferation and size of perforation. CONCLUSION: MTA is superior to GIC and Dycal for immediate repairing furcation perforation in dogs owing to its less irritation to surrounding tissues and its ability to induce the formation of hard tissues.

[Analysis of the effect on the stress of root canal wall by vertical and lateral condensation procedures].

OBJECTIVE: To analyse the stress variations of root canal wall that resulted from vertical and lateral condensation. METHODS: On the basis of the finite-element model of the mandibular first molar that modified by step-back technique, mesial-buccal root canal was chosen as tested root canal and simulated the procedure of vertical and lateral condensation. The maximal stress of root canal wall and its position were calculated by special software upon different loading condition. RESULTS: Stress of root canal wall caused by vertical condensation was higher than that by lateral condensation on the same loading condition. Maximal stress of vertical condensation was located on loading section and one of lateral condensation was located on coronal and middle 1/3 of root. The lower the position that was loaded, the higher the stress of wall of root canal. CONCLUSION: Lateral condensation will not bring on vertical root fracture directly,but over-force and improper operation are both dangerous that gives rise to vertical root fracture with whichever method.

[Analysis the effect on the stress of wall of root canal by different proportion between crown and root].

OBJECTIVE: Use FEM to observe the relationship between the change of alveolar ridge's height and the stress change of wall of root canal. METHODS: Modify the model on the basis of the set up model of the mandibular first molar, simulating the height of alveolar ridge and reducing 1/4, 1/3, 1/2 of the height to set up modified model, and load on the modified model by vertical and lateral forces. Then calculate the maximum mises stress of each part of teeth and wall of root canal. RESULTS: The stress-changing tendency of each part of wall was similar to the changing tendency of each part of teeth, but the stress of wall was fewer than the stress of teeth. The stress value of original model was close to the modified model at the orifice. Then the stress of original model obviously reduced, and the stress of the modified model reached maximum in the coronal thirds, and when the fixed height was lower, the stress was larger, the stress reduced more slowly. The lateral stress was larger than the vertical stress, and when the fixed height was lower, the difference was more obvious. CONCLUSION: The change of alveolar ridge's height will affect the stress change of wall of root canal, and which is in an inverse proportion.

[Analysis the stress variations of the root canal wall of pulpless tooth by different root canal preparation with finite-element method].

OBJECTIVE: To analyze the stress variations of the root canal wall of pulpless tooth by different root canal preparations. METHODS: On the basis of the set up model of the mandibular first molar, modified model was established by simulation of the routine or step-back root canal preparation and filling in. Then the maximum mises stress of each part of teeth and wall of root canal were calculated by special finite-element software. RESULTS: The stress-changing tendency is similar between two modified models but the maximum mises stress of the model by step-back technique is a little greater than one by routine. The stress of wall of mesial-buccal root canal was the greatest and one of mesial-lingual root canal was the least at three root canals. The stress-changing tendency of modified models was similar to original model. The maximum mises stress of modified models was near or less than one of original model except that of amalgam layer because of material property alteration. CONCLUSION: Not only routine but step-back technique is an effective and safe method. Dentist can choose them in practice.