[Effect of serum starvation and culture to confluence on cell cycle synchronization and mineralization of human dental pulp cells].

PURPOSE: To compare the effect of serum starvation and culture to confluence on cell cycle synchronization and mineralization of human dental pulp cells (hDPCs). METHODS: HDPCs were cultured to 80% and 100% confluence respectively, and then cultured for 24, 48 and 72 hours by culture medium containing 0.5% fetal bovine serum(FBS). Cell cycle of hDPCs were identified by flow cytometry. Then hDPCs cultured by serum starvation for 48h after culturing to 100% confluence were used as the experimental group, and hDPCs cultured to 80% confluence were used as the control group. The expression of alkaline phosphatase(ALP), collagen type Ⅰ(COL-Ⅰ) and osteocalcin(OCN) was detected at gene level; activity of ALPase was detected at protein level. SPSS 13.0 software was used for statistical analysis. RESULTS: When hDPCs were cultured by serum starvation for 48h after culturing to 100% confluence, cells at G0/G1 stage were more than culture to 100% confluence and serum starvation group (P＜0.05). At the genetic level, the expression of COL-Ⅰand OC in the experimental group was not statistically different from that of the control group, but can promote the expression of ALP(P＜0.05), and stimulate the secretion of hDPCs at protein level at the same time (P＜0.05). CONCLUSIONS: Culture to confluence combined serum starvation can synchronize more hDPCs at G0/G1 stage and promote mineralization of hDPCs.

[Evaluation of the efficacy of two kinds of NiTi retreatment instruments for removing filling material during root canal retreatment].

PURPOSE: To compare the efficacy of Mtwo R and Reciproc with that of hand files in removing filling material during root canal retreatment. METHODS: The root canals of forty-five human extracted mandibular central incisors were cleaned and shaped to a size 40 and filled with gutta-percha and sealer using a lateral compaction technique. The teeth were divided into 3 groups. The filling material was removed with hand files, Mtwo R and Reciproc, respectively. The debris extruded out of the apical foramen was collected and weighted. The working time was recorded. Then the teeth were split longitudinally, observed under microscope, and evaluated. The data were statistically analyzed with SPSS 13.0 software package. RESULTS: There was no significant difference among 3 groups for debris extrusion (P>0.05). Removal of filling material with Mtwo R and Reciproc consumed less time (P<0.05). CONCLUTIONS: NiTi retreatment instruments can not remove all filling material during root canal retreatment, but can reduce working time.

[Clinical management of calcified root canal with Mtwo NiTi files].

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.

[Analysis of interappointment flare-ups after root canal preparation with Mtwo NiTi rotary system].

PURPOSE: To study the interappointment flare-ups after root canal preparation with Mtwo NiTi rotary system and explore the influence factors. METHODS: Ninty-seven pulp cases caused by caries or invisible cracks which consisted of 37 males and 60 females,16 to 62 years old were selected and divided into 2 groups randomly. One group was treated with Mtwo NiTi rotary system while the other was treated with K file, the interappointment flare-ups after root canal preparation was compared between the 2 groups. The data were subjected to Mann-Whitney U test and X(2) test with SPSS13.0 software package. RESULTS: Less flare-ups occurred in the group of root canal preparation with NiTi rotary system, the difference was statistically significant (P=0.027). CONCLUSIONS: Root canal preparation with Mtwo NiTi rotary system could decrease the flare-ups after root canal therapy.

[Analysis of canal morphology of mandibular first premolar].

PURPOSE: To investigate the canal morphology of bilateral mandibular first premolar using cone-beam CT(CBCT). METHODS: Ninety-seven CBCT images of bilateral mandibular first premolar were selected . The images were analyzed with NNT software for the number and morphology of canal, groove, position of bifurcation and symmetry of bilateral canal classification. RESULTS: The canal configuration of mandibular first premolar was type I:83.5%, type III:3.6%, type v:8.8% and C-shaped canal:4.1% by Vertucci's classification.The incidence of groove in complicated canal (75%)was obviously higher than single canal (3.7%). 56.3% of complicated canal bifurcated in middle third, and 31.3% in apical third. 93.8% of mandibular first premolar had bilateral canal symmetry, the symmetry rate of single canal(95.2%) was higher than complicated canal (66.7%). CONCLUSIONS: CBCT can provide accurate information of canal system, the canal anatomy of mandibular first premolar is complex.

[Effect of different polishing time on microleakage of resin composite restorations].

PURPOSE: To evaluate the effect of different polishing time on microleakage of different resin composite restorations (Filtek Z350 and Filtek Z250). METHODS: Standardized preparation (the box-type cavities, 3 mm in length and width,2 mm in depth) was performed at the cemento-enamel junction on buccal surface of 80 premolars.They were randomly divided into two groups,and restored with composite resin(Filtek Z350 or Filtek Z250). According to polishing time, the specimens of each group were randomly classified into four subgroups. They were the subgroups of no polishing, polishing immediately after restoring, polishing after 10 minutes and polishing after 24 hours. All of the restorations were polished with Sof-lex discs. After thermal circulation and soaked for 24 hours in 2% methyl blue solution, the specimens were cut through the midline of the restoration, the microleakage at the occlusal margin and the gingival margin were observed under a stereomicroscope and the leakage depth was measured with Spot version 4.6 software package. The microleakage degree and microleakage depth of different groups were analyzed with SPSS 17.0 software package for Mann -Whitney U test and Kruskal -Wallis test. RESULTS: The microleakage depth of Filtek Z350 groups were(0.655±0.486)mm,(0.626±0.497)mm,(0.648±0.370)mm and (0.639±0.453)mm,respectively. The microleakage depths of Filtek Z250 groups were (0.785±0.553)mm,(0.763±0.491)mm,±0.749±0.608)mm and (0.715±0.588)mm,respectively. No significant differences (P>0.05) of microleakage was found among the different groups and subgroups. CONCLUSION: The polishing system of Sof-lex discs have no significant influence on microleakage of resin composite restorations at different polishing time.

[Clinical study on prevention root absorption after teeth replantation with Vitapex paste].

PURPOSE: To evaluate the result of using Vitapex paste for preventing root absorption after replanting the avulsed teeth. METHODS: Thirty patients with 36 avulsed upper anterior teeth with fully developed apices within 5 hours of trauma were enrolled in this study. For each case, the tooth and its alveolar site were irrigated with 0.9%NaCl, then the tooth was put into its original site and fixed with steel wires and composite resin. Two weeks later,the involved teeth underwent pulpectomy and were randomly divided into two groups. Ca(OH)2 paste was used for temporary root canal filling in group A, and Vitapex paste in group B. The patients were asked to recall every three months, X-ray film was taken to evaluate root absorption and the same temporary root canal filling material was replaced. The permanent root canal filling was performed about one and a half years after treatment when root absorption stopped. Statistical analysis was carried out using SPSS12.0 software package. RESULT: The success rate of two groups was not significantly different, though which was a little higher one year after treatment in group A than group B (88.9% vs. 83.3%). Vitapex paste had the benefits of both Ca(OH)2 and iodoform. The radiopaque of iodoform made Vitapex paste observed easily for the status of filling or absorption. CONCLUSIONS: The injection style of Vitapex paste makes it easily being manipulated. Vitapex paste is an ideal material for preventing root absorption of replanted avulsed teeth. Supported by Research Fund of Science and Technology Commission of Shanghai Municipality (Grant No. 08DZ2271100).

[Evaluation of X-ray beam angulation for successful four canals identification in the mandibular first molars].

PURPOSE: This study was aimed to determine the most effective horizontal beam angulation to identify 4 canals in the mandibular first molars, so as to provide full and accurate information for the clinic. METHODS: One hundred and twenty mandibular first molars with four canals that needed endodontic treatment in vivo were selected. Radiographs were taken at horizontal angles of 0,10,20 degrees from distal direction and 0,10,20,30 degrees from mesial direction of the tooth. The numbers of root canal and the degree of resolution were identified and recorded by 3 independent observers. Data were analyzed using SPSS10.0 software package or Chi-square test. RESULTS: At 30 and 20 degrees from mesial direction, 93.3% and 90.0% of all the 120 teeth were correctly identified as 4 canals, compared with 0 degree of 40.0%(P<0.01). Of them, 71.5% and 89.7% could be classified as with high resolution, respectively. The latter was not significantly lower than 0 degree of 95.0% (P>0.05). CONCLUSION: Twenty degrees from mesial direction is the most effective X-ray beam angle in diagnosing 4 canals of the first mandibular molars. Supported by Research Fund of Science and Technology Commission of Shanghai Municipality (Grant No.08DZ2271100).

[Clinical effect of three kinds of rotary nickel-titanium instruments on root canal preparation of molars].

PURPOSE: To evaluate three kinds of nickel-titanium instruments applied to molar root canal preparation. METHODS: A total of 90 molars treated by root canal therapy were randomly assigned to three groups: ProTaper group. K3 group and Mtwo group. Crown-down technique was used in ProTaper and K3 group, while Mtwo group was treated with routine preparation technique. All teeth in 3 groups were filled by lateral condensation technique. Treatment effect of 3 groups was evaluated according to pre- and post-operative X-ray films. Wearing and tearing degree of equipment, preparation time and postoperative complications incidence of 3 groups were also compared. All statistical analysis was performed using SAS9.0 software package. Data of root canal curvatures and preparation time was compared using t test; the incidence of complications of root canal treatment and postoperative pain was analyzed using Chi-square test. RESULTS: In three groups, root canals had no deviation or no ledge, could maintain the root canal anatomy in early form, and achieved good preparation results. In this study, four ProTapers, three K3s and one Mtwo instrument were fractured. The average root canal preparation time of the Mtwo group was 3.94 min, significantly less than the ProTaper (4.71 min) group and the K3(4.58 min) group. CONCLUSIONS: Three rotary nickel-titanium systems tested in this study are effective in the molar root canal preparation. The Mtwo instrument is much easier and faster during preparation with routine preparation technique.Supported by Research Fund of Science and Technology Commission of Shanghai Municipality(Grant No.08DZ2271100).

[Comparison of three kinds of root canal disinfection medications in treatment of chronic apical periodontitis with fistula].

PURPOSE: To evaluate Vitapex paste, calcium hydroxide paste and paper points of povidone iodine as medications of root canal disinfection and their abilities of pain control in treatment of chronic apical periodontitis with fistula. METHODS: A total of 90 patients of chronic apical periodontitis with fistula were randomly assigned to 3 groups,30 patients in each group. After regular root canal preparation, group 1 was given Vitapex paste, group 2 was given calcium hydroxide paste, and group 3 was given paper points of povidone iodine as medications of root canal disinfection. Visual analogue scales of pain were given to the patients and method of filling the scale was also introduced to them at the same time. The scales were taken back one week later. Both the data of the scales and the effects of root canal disinfection were recorded and analyzed. All statistical analysis was performed using SPSS 17.0 software package. RESULTS: The effect of root canal disinfection had no significant difference among the three groups. Group 1 achieved better result of pain control than the others. CONCLUSIONS: The three root canal disinfection medications are effective in treatment of chronic apical periodontitis with fistula. Vitapex paste is better for controlling the pain after root canal preparation than culcium hydroxide and paper points of povidone iodine.

[Prevention of endodontic interappointment emergencies after one-visit root canal therapy on deciduous teeth with METAPEX].

PURPOSE: To evaluate the clinical effect of calcium hydroxide-iodoform (METAPEX) in one-visit root canal therapy on deciduous teeth and the prevention of endodontic interappointment emergencies (EIAE). METHODS: Two hundred and thirty-eight deciduous anterior and molar teeth from 178 patients were randomly divided into two groups treated with one-visit root canal therapy of METAPEX (experimental group) and zinc oxide eugenol paste (control group). The data was analyzed by Chi-square text with the SPSS14.0 software package. RESULTS: The rate of EIAE after one-visit root canal therapy in the experimental group was significantly lower than in the control group (P<0.05). CONCLUSION: The METAPEX could reduce the occurrence rate of EIAE in the one-visit root canal therapy on deciduous teeth.

[The investigation and analysis of children with dental fear].

PURPOSE: The purpose of this study was to investigate and analyze the clinical behavior and factors causing dental fear (DF) in children of different ages to provide some valuable information for preventing and reducing the incidence of DF in clinical practice. METHODS: 571 cases of children patients receiving treatment in the pedodontics were evaluated and analyzed according to the evaluation standards of DF. RESULTS: The results suggested that the incidence of DF differed in different age groups. The ratio was higher in younger groups while it was lower in elder groups. The ratio also varied with living conditions,education level of mothers,past experience of dental treatment and other children's response at the clinic. CONCLUSION: The DF caused by various factors can be reduced by the combined effort of children, parents and the medical practitioners.