Evaluation of several instrumentation techniques and irrigation methods on the percentage of untouched canal wall and accumulated dentine debris in C-shaped canals.

AIM: To evaluate the effect of instrumentation using Reciproc Blue (RB; VDW, Munich, Germany) and XP-endo Shaper (XP-S; FKG Dentaire, La Chaux-deFonds, Switzerland) systems on the area of untouched canal wall (AUCW), accumulated hard-tissue debris (AHTD) and the efficacy of three irrigation protocols on percentage reductions (red%) of AHTD within C-shaped canals of mandibular molars. METHODOLOGY: Seventy mandibular molars with C-shaped canals were scanned, matched and assigned to two shaping groups (n = 35): RB and XP-S. Following instrumentation, specimens were triple-matched with respect to the amount of remaining debris and assigned to three irrigation subgroups (n = 10): syringe-and-needle irrigation (SNI), XP-endo Finisher (XP-F; FKG Dentaire) and passive ultrasonic irrigation (PUI). The AUCW% and AHTD% after instrumentation and the red% of AHTD after irrigation were calculated from micro-computed tomography. Data were analysed using comparisons for two groups (RB vs. XP-S) or multiple subgroups followed by pairwise comparison procedures (SNI vs. XP-F vs. PUI) at α = 0.05. RESULTS: For RB and XP-S, 33.04% and 30.45%, respectively, of the canal wall remained untouched (P > 0.05). For both groups, the apical third had larger AUCW% than the coronal third (P < 0.05). Instrumentation with RB left more debris (2.8%) than XP-S (1.1%) (P < 0.05). The PUI and XP-F subgroups had higher mean red% of AHTD than the SNI subgroup; the difference was significant for RB (P < 0.05) but not for XP-S. CONCLUSIONS: Both RB and XP-S systems were associated with similar AUCW after instrumenting C-shaped canals. RB left significantly greater levels of AHTD compared with XP-S. PUI and XP-F irrigation removed more debris than SNI when using the RB system.

Three-dimensional morphological analysis of C-shaped canals in mandibular first premolars in a Chinese population.

AIM: To investigate and compare the unique anatomical features and positioning of C-shaped canals in mandibular first premolars with and without radicular grooves in a Chinese population. METHODOLOGY: A total of 327 extracted mandibular first premolars including 146 with radicular grooves and 181 without radicular grooves from a Chinese population were scanned by µCT-50 or µCT-80. After reconstruction, canal systems were classified according to a modified Vertucci method and the anatomical features evaluated. The data were analysed by one-way anova test, Chi-square test and Fisher's exact test (P < 0.05). RESULTS: Of 146 mandibular first premolars with a radicular groove, 97 had C-shaped canals, the predominant anatomical canal type being Vb (P < 0.001), which was characterized by an oval canal in the coronal part and a semicolon or continuous C-shape beneath the groove. Of the 181 mandibular first premolars without a radicular groove, no C-shaped canal system was observed, and the percentage of Ia (97.8%) was significantly higher than those of other types (P < 0.001). CONCLUSION: In teeth from a Chinese population, mandibular first premolars with radicular grooves had a high incidence of C-shaped canal systems with anatomical variations along the root.

Immunogenicity and persistence of a targeted anti-caries DNA vaccine.

We have previously reported that a targeted anti-caries DNA vaccine, pGJA-P, induced accelerated and increased antibody responses compared with a non-targeted anti-caries DNA vaccine. Recently, pGJA-P/VAX, a new targeted anti-caries DNA vaccine for human trials, was constructed by replacing the pCI vector used in the construction of pGJA-P with pVAX1, the only vector authorized by the US Food and Drug Administration in clinical trials. Here, we report on our exploration of the kinetics of the antibody responses generated following pGJA-P/VAX immunization and the persistence of pGJA-P/VAX at both the inoculation site and the draining lymph nodes. Intranasal vaccination of mice with pGJA-P/VAX induced strong antibody responses that lasted for more than 6 months. Furthermore, pGJA-P/VAX could still be detected at both the inoculation site and the draining cervical lymph nodes 6 months after immunization. Thus, the persistent immune responses are likely due to the DNA depot in the host, which acts as a booster immunization.

[Evaluating the accuracy of three-dimensional reconstruction of the intercuspal position for dentition casts aided by a mechanical appliance].

OBJECTIVE: To develop a aided mechanical appliance for rapid reconstruction of three-dimensional(3D)relationship of dentition model after scanning and evaluation of its accuracy. METHODS: The appliance was designed by forward engineering software and fabricated by a high precision computer numerical control(CNC)system. It contained upper and lower body, magnetic pedestal and three pillars. Nine 3 mm diameter hemispheres were distributed equally on the axial surface of each pedestal. Faro Edge 1.8m was used to directly obtain center of each hemisphere(contact method), defined as known center. A pair of die-stone standard dentition model were fixed in intercuspal position and then fixed on the magnetic pedestals with low expansion ratio plaster. Activity 880 dental scanner was used to scan casts after the plaster was completely set. In Geomagic 2012, the centers of each hemisphere were fitted and defined as scanning centers. Scanning centers were aligned to known centers by reference point system to finish the 3D reconstruction of the intercuspal occlusion for the dentition casts. An observation coordinate system was interactively established. The straight-line distances in the X(coronal), Y(saggital), and Z(vertical)between the remaining 6 pairs of center points derived from contact method and fitting method were measured respectively and analyzed using a paired t-test. RESULTS: The differences of the straight-line distances of the remaining 6 pairs of center points between the two methods were X:(-0.05±0.10)mm, Y:(0.02±0.06)mm, and Z:(0.01 ± 0.05)mm. The results of paired t-test showed no significant differences(P>0.05). CONCLUSIONS: The mechanical appliance can help to reconstruct 3D jaw relation by scanning single upper and lower dentition model with usual commercial available dental cast scanning system.

Leakage along apical root fillings in curved root canals. Part I: effects of apical transportation on seal of root fillings.

Occurrence of apical transportation (AT) may complicate the root filling procedure and result in a compromised seal. In part I of this study, human mandibular premolars with single, curved (21 to 39 degrees), or straight canals were prepared by Lightspeed or a step-back hand filing technique. An AT index was determined using a double exposure radiographic technique. The prepared canals were obturated using lateral condensation of gutta-percha. Leakage along the apical 3 mm of root filling was measured with a fluid transport model. After hand filing, AT and perforation occurred in 87% of the curved canals. The AT indices were > or = 0.4 mm. After Lightspeed preparation, AT occurred in only 19% of the curved canals. The hand filing/curved group leaked statistically significantly more than the hand filing/straight and Lightspeed/curved groups (p = 0.002). We conclude that occurrence of AT is a factor that negatively influences the apical seal when curved canals are obturated by lateral condensation of gutta-percha.

Morphometric study of the apical anatomy of C-shaped root canal systems in mandibular second molars.

AIM: To investigate the apical anatomy of C-shaped canal systems in mandibular second molars by micro-computerized tomography (microCT) and stereomicroscopy. METHODOLOGY: Forty-four permanent mandibular second molars with a C-shaped root canal systems from a native Chinese population were scanned at 100 microm intervals by microCT at a resolution of 30 x 30 microm. The apical 5 mm of each tooth was reconstructed three-dimensionally for visualization and classification of the canal configuration using Vertucci's criteria. The main and auxiliary (accessory) foramina were examined under a stereomicroscope. RESULTS: Type IV and VIII canal configurations were most often found in the apical 5 mm of these canal systems. The prevalence of accessory canals, lateral canals, inter-canal communications and apical delta were 41%, 25%, 27% and 11%, respectively. Approximately 80% of C-shaped canals had 1-3 apical foramina; the prevalence of accessory foramina was about 48%. The mean distance between the main foramen and the anatomic root apex was 0.84 mm, and that between the accessory foramen and the apex was 1.61 mm. The mean (shortest and longest) diameters of major and accessory foramina were 0.19 - 0.32 mm and 0.07 - 0.10 mm, with a mean form factor of 0.73 and 0.82, respectively. CONCLUSION: The apical anatomy of C-shaped root canal systems in mandibular second molars is extremely complex with many anatomical variations.

Evaluation of the accuracy of three electronic apex locators using glass tubules.

AIM: To evaluate the accuracy of three different electronic apex locators (EALs) using glass tubules. METHODOLOGY: Forty-eight glass tubules with different diameters and an agar model were used to mimic root canals. A size 15 stainless steel K-file was used as the measuring electrode. The Root ZX, Propex and Neosono Ultima EZ were used to measure the tubule length with tubules dry, or filled with 0.9% NaCl, 3% H(2)O(2), 2.5% NaOCl or 17% EDTA. The distance between the real length (RL) and measured length (ML) of the tubules was recorded. The range of RL +/- 0.5 mm and RL +/- 1 mm was used to evaluate the accuracy of the EALs. Results were subject to correlation analysis and Friedman's test. RESULTS: In dry tubules, the accuracy of Root ZX was 75-91.7% for RL +/- 0.5 mm and 100% for RL +/- 1 mm, whilst the measurements of the other two EALs were all within the RL +/- 0.5 mm. No influence from the increase in tubule diameter on the accuracy of all three EALs was observed in dry tubules. In tubules filled with electrolyte, the accuracy of the Root ZX decreased as tubule diameter increased (R(d) > 0, P < 0.05). The RL-ML distance recorded by Propex was inversely related to the tubule diameter (R(d) < 0, P < 0.05). The accuracy of Propex was 75-100% for RL +/- 0.5 mm and 100% for RL +/- 0.5 mm when the tubule diameter was not more than 0.80 mm, but decreased in tubules with diameter over 0.80 mm and filled with 2.5% NaOCl or 17% EDTA. Nearly, all the measurements (except for six tubules) using Neosono Ultima EZ were within 1 mm shorter than RL despite the contents in tubules and the increase of tubule diameter. CONCLUSIONS: The accuracy of the Root ZX decreased as the tubule diameter increased when tubules were filled with electrolytes. The electrolytes in the tubules decreased the accuracy of Propex when the tubule diameter was large. The electrolytes in tubules and tubule diameter had no influence on the accuracy of Neosono Ultima EZ. The Propex and Neosono Ultima EZ were more accurate than the Root ZX under various conditions in this laboratory study.

Cloning of pig parotid secretory protein gene upstream promoter and the establishment of a transgenic mouse model expressing bacterial phytase for agricultural phosphorus pollution control.

This study examined the feasibility of using the promoter of the pig parotid secretory protein (PSP) gene for expression of the phytase transgene in mouse models. The pig parotid secretory protein gene is specifically expressed at high levels in the salivary glands. The 10-kb upstream promoter region of the gene necessary for tissue-specific expression has been identified. We have constructed phytase transgenes composed of the appA phytase gene from Escherichia coli driven by the upstream promoter region of the pig PSP gene with a 3' tail of either bovine growth hormone or the pig PSP gene polyadenylation signal. Transgenic mouse models with the construct showed that the upstream region of the pig PSP gene is sufficient for directing the expression of phytase transgenes in the saliva. Expression of salivary phytase reduced fecal phytate by 8.5 and 12.5% in 2 transgenic mouse lines, respectively. These results suggest that the expression of phytase in salivary glands of monogastric animals offers a promising biological approach to relieve the requirement for dietary phosphate supplements and to reduce phosphorus pollution from animal agriculture.

[Clinical study on effects of root canal instrumentation on the root canal microflora].

OBJECTIVE: To investigate the effects of instrumentation and ultrasonic treatment on the root canal flora. METHODS: A total of 21 single-rooted teeth with chronic apical periodontitis were selected and prepared using step-back/ultrasonic technique, Samples were taken before and after the step-back preparation, and after the ultrasonic treatment. RESULTS: The number and species of bacteria in the root canal were both reduced dramatically and there were significant differences among the three groups (P < 0.05). CONCLUSION: The instrumentation and ultrasonic treatment of root canal can effectively reduce the number and species of root canal microflora.

Leakage along warm gutta-percha fillings in the apical canals of curved roots.

The aim of this study was to investigate the leakage along the apical portion of warm gutta-percha obturated curved canals. Human mandibular premolars with single, curved (21 degrees-40 degrees) canals were prepared using the Lightspeed technique. Two groups of prepared canals, matched according to curvature and prevalence of apical transportation, were obturated by two techniques. Coronal gutta-percha was removed immediately after root obturation was completed to simulate the procedure for post space preparation. Leakage along the apical 3 mm of root filling was measured with a fluid transport device. Vertical condensation of warm gutta-percha and Pulp Canal Sealer provided less leakage than Thermafil plastic obturators and AH26 sealer (P = 0.002).

Diminished leakage along root canals filled with gutta-percha without sealer over time: a laboratory study.

AIM: The aim of this study was to investigate the long-term seal of gutta-percha (GP) without sealer. METHODOLOGY: Extracted human maxillary central incisors were prepared and obturated using heat- or chloroform-softened GP only, or GP in combination with a root canal sealer. Leakage along root fillings was measured at 48 h and after a period of 6 months using a fluid transport model. RESULTS: At 48 h the GP-filled roots without sealer leaked more than the control roots filled with GP and sealer (P < 0.0001). At 6 months a significant reduction in leakage was found in the GP-only groups (P < 0.05 for both heat- and chloroform-softened GP). After 6 months, roots filled by vertical condensation of GP-only had similar leakage as vertically condensed GP with a sealer (P > 0.05). CONCLUSIONS: The long-term seal of root fillings is affected by the volume change of both GP and sealer. Leakage reduction due to expansion of GP may compensate to a certain extent for leakage that may occur from sealer dissolution.

[The meiosis arrest of mouse oocytes induced by adenine].

The effect of purine on the meiosis of mouse oocytes was studied. When adenine and benzyladenine, a similar substance of adenine, was microinjected into the germinal vesicle of oocytes, the meiotic maturation of oocytes could be obviously arrested depending on the dosage of injection. The stimulator of adenylate cyclase, NaF, could enhance the arrest effect of adenine. It indicated that cAMP played a important role in mouse oocytes meiotic resumption. Hypoxanthine and adenine had different effects in different medium. Hypoxanthine could obviously arrest the maturation of mouse cumulus oocyte complex (COC) and cumulus denuded oocytes (DO) in DMEM or EMEM. But only in DMEM adenine could obviously arrest the maturation of COC, and had co-effect with hypoxanthine in DMEM. They could almost arrest the maturation of COC and DO. Adenine in EMEM had little arrest effect on maturation of COC and DO. The different effects may result from the different adenine absorption by oocyte in DMEM and EMEM. Adding glutamine into EMEM could enhance the arrest effect of adenine to COC and DO.

Coronal leakage along apical root fillings after immediate and delayed post space preparation.

The seal provided by a full-length root canal filling may be compromised by post space preparation. Eighty human mandibular premolars each with a single canal were obturated with laterally condensed gutta-percha cones and a sealer. Immediate post space preparation was carried out on half the number of teeth and delayed post space preparation on the remaining 40 teeth. Leakage along the apical root fillings was determined using a fluid transport device under a head space pressure of 30 kPa (0.3 atm). More leakage was found after delayed preparation than after immediate preparation (P = 0.0059).

Inactivation of surfactant in rat lungs.

Although surfactant replacement therapy has dramatically improved the outcome of premature infants with respiratory distress syndrome, approximately 30% of treated infants show a transient or no response. Nonresponse to surfactant replacement therapy may be due to extreme lung immaturity and possibly surfactant inactivation. Surfactant inactivation involves aspecific biophysical events, such as interference with the formation or activity of an alveolar monolayer, and specific interactions with serum proteins, including antibodies, leaking into the alveolar space. As formulations containing surfactant proteins appear to better tolerate serum inactivation, we used an excised rat lung model to compare the susceptibility to serum inactivation of a mixture of synthetic phospholipids selected from surfactant lipid constituents, Exosurf (a protein-free synthetic surfactant), Survanta [containing surfactant proteins B and C (SP-B and -C)], and a porcine surfactant (containing SP-A, -B, and -C). For each of these preparations, we used pressure/volume determinations as an in situ measure of surfactant activity and retested the same preparations after mixing with human serum, a nonspecific surfactant inactivator. Human serum inactivated porcine surfactant to a lesser extent than Survanta, Exosurf, or synthetic phospholipids. Temperature exerted a significant effect on deflation stability, as shown by a greater lung compliance in untreated, normal lungs and a larger improvement in compliance after treating lavaged lungs with synthetic phospholipids at 37 degrees C than at 22 degrees C. We conclude that surfactant containing SP-A, -B, and -C is only moderately susceptible to inactivation with whole serum and may therefore exert a greater clinical response than protein-free surfactants or those containing only SP-B and -C.

[Autotrophic denitrification of groundwater by electrochemical process].

An autotrophic denitrification process and its reactor for removing nitrate from groundwater was investigated in this paper. Using activated carbon fiber(ACF) as electrodes, the electrochemical reactions could produce hydrogen as the donor for autotrophic denitrification. In the process, nitrate was removed effectively and no accumulation of nitrite in the effluent. The results in this study proved that some key factors, such as the applied current density, flow rate of water, oxidation-reduction potential and the nitrate concentration in raw water, influenced the electrochemically denitrifying effect. When the concentration of NO3(-)-N was 28.8 mg/L in inlet water, the optimum applied density was 9 mA, the highest hydraulic load of the reactor was 35 ml/h, and the reactor performed a practical buffering capacity to pH. After applying electricity to the reactor for 1 h, the oxidation-reduction potential decreased to below--200 mA, so an adaptable reductive environment could be provided in the reactor for denitrification.

Uptake of antioxidants in surfactant liposomes by cultured alveolar type II cells is enhanced by SP-A.

Antioxidant delivery may be targeted toward the alveolar epithelium by encapsulating superoxide dismutase (SOD) and catalase in liposomes made from pulmonary surfactant. We studied whether antioxidant-surfactant liposomes increase cellular antioxidant activity in alveolar type II cells and whether this effect is influenced by the presence of surfactant protein A (SP-A). Cu,Zn SOD and catalase were encapsulated in liposomes made from synthetic phospholipids with or without 5% SP-A or from natural cow surfactant. Alveolar type II cells from adult rats were preincubated for 20 h, and liposome mixtures were added for 24 h, followed by measurement of cellular SOD and catalase activities (U/mg DNA). Antioxidant-surfactant liposomes increased alveolar type II cell antioxidant activity sharply. Uptake of SOD/catalase from liposomes with synthetic phospholipids and SP-A was twice that from liposomes without SP-A and did not further improve in the presence of SP-B and -C. Encapsulation of antioxidants diminished the surface activity of the surfactant liposomes, but this feature was absent in the presence of SP-A. These data suggest that: 1) antioxidant-surfactant liposomes augment alveolar type II cell antioxidant activity, 2) liposomal uptake is facilitated by the presence of SP-A, and 3) inhibition of surface activity of surfactant by encapsulated antioxidants can be reversed by SP-A.

A comparison of instrument-centering ability within the root canal for three contemporary instrumentation techniques.

AIM: To study and compare Great Taper (GT) hand files using a reversed balanced force technique, nickel-titanium (NiTi)flex files with a balanced force technique and stainless steel (SS) K-type files using a step-back technique. METHODOLOGY: Forty-eight extracted mandibular premolar teeth with single root canals having curvatures between 15 and 45 degrees were prepared using a modified Bramante model and randomly divided into three groups. The teeth were cross-sectioned at 2, 6 and 10 mm from the working length. Preoperative images of canals at three levels were captured at 20x magnification using a stereomicroscope. Canals in each group were, respectively, prepared to an apical size.10 GT file with 0.2 mm tip diameter, size 30 NiTiflex file and size 30 SS K-file. The GT file was used in a reversed balanced force technique, the NiTiflex file was used in a balanced force technique, and the SS K-file was used in a step-back technique. Postoperative canals were imaged under the conditions same as those for the preoperative canals. The postoperative images were superimposed over the preoperative images using software photoshop 6.0. The ability to maintain the instrument in the central axis of the canal and the deviation from the central canal axis were determined and compared by statistical analysis, along with the assessment of the amount of dentine removed. RESULTS: At apical level, the centering ratio, the distance of transportation and the dentine removed in GT and NiTiflex groups were significantly less than those in SS group (P < 0.01), but no statistical differences were found between the two NiTi groups. At other levels, there were no substantial differences amongst the groups. CONCLUSIONS: Compared with SS K-files, GT hand files and NiTiflex files remain better centered and produce significantly less transportation in curved canals.