Influence of base materials on stress distribution in endodontically treated maxillary premolars restored with endocrowns / 北京大学学报(医学版)

OBJECTIVE@#To evaluate the influence of base materials on stress distribution in endodontically treated maxillary premolars restored with endocrowns using three-dimensional finite element analysis.@*METHODS@#A maxillary second premolar was scanned by Micro-CT and a three-dimensional finite element model of ceramic endocrown with 1 mm thickness of base was established. A model without base was also established as a negative control. Four kinds of conventional base materials with different elastic modulus were adopted: light cure glass ionomer(3M Vitrebond, 3 657 MPa), flowable composite resin(3M Filtek Z350XT Flowable Restorative, 7 300 MPa), high strength glass ionomer(GC Fuji Ⅸ, 13 130 MPa), and posterior composite resin(3M Filtek P60, 19 700 MPa). With a 200 N force loaded vertically and obliquely, the distribution and magnitude of stress in the tooth tissue and adhesive layer were investigated by three-dimensional finite element analysis.@*RESULTS@#The maximum von Mises stress values(vertical/oblique) in dentin and adhesive layer were measured as follows: (1) no base material: 19.39/70.49 MPa in dentin and 6.97/17.97 MPa in adhesive layer; (2) light cure glass ionomer: 19.00/69.75 MPa in dentin and 6.87/16.30 MPa in adhesive layer; (3) flowable composite resin: 18.78/69.33 MPa in dentin and 6.79/16.17 MPa in adhesive layer; (4) high strength glass ionomer: 18.71/69.20 MPa in dentin and 6.74/16.07 MPa in adhesive layer; (5) posterior composite resin: 18.61/69.03 MPa in dentin and 6.70/16.01 MPa in adhesive layer. Under the same loading condition, models with different elastic moduli of base materials had similar stress distribution patterns. The von Mises stress of tooth tissue was mainly concentrated in the tooth cervix. Under oblique load, the regions where von Mises stress concentrated in were similar to those under a vertical load, but the values increased. The stress concentration in the tooth cervix was alleviated in models with base materials compared with the model without base material. The maximum von Mises stress in the tooth tissue and adhesive layer decreased when the elastic modulus of base materials increased and got close to that of dentin.@*CONCLUSION@#The posterior composite resin of which the elastic moduli is high and close to that of dentin is recommended as base material for premolar endocrowns to alleviate the concentration of stress in tooth cervix and adhesive layer.

Evaluation of wear property of Giomer and universal composite in vivo / 北京大学学报(医学版)

OBJECTIVE@#To observe the wear performance of Giomer and universal composite for posterior restorations by 3D laser scan method, in order to guide the material selection in clinic.@*METHODS@#In this study, 48 patients (108 teeth) were selected according to the inclusion and exclusion criteria. All the patients in need of a minimum of 2 Class Ⅰ and/or Class Ⅱ restorations were invited to join the study. The teeth were restored with Giomer (Beautifil Ⅱ, BF) and universal composite (Filtek Z350, Z350) randomly. The restorations were evaluated at baseline and after 6-, 18-, 48-month using the modified United States Public Health Service (USPHS) criteria for clinical performance. The in vivo images and gypsum replicas were taken at each recall. A 3D-laser scanner and Geomagic Studio 12 were used to analyze the wear depth quantitatively. Statistical analysis was performed with SPSS 20.0.@*RESULTS@#After 4 years, 89.6% patients were recalled. The survival rate of both materials was 95.8% (Kaplan-Meier survival analysis). Seven restorations of the two materials failed due to loss of restoration, bulk fracture, secondary caries and pulp necrosis. The wear patterns of restorations were divided into 2 classes. Pattern Ⅰ: occlusal contact areas showed the deepest and fastest wear depth; pattern Ⅱ: the wear depth was slow and uniform. Both materials showed a rapid wear in the first 6 months. Then the wear rate was decreased. The occlusal wear depth after 4 years were (58±22) μm and (54±16) μm for BF group and Z350 group respectively, which were in accordance with the American Dental Association (ADA) guidelines (wear depth for 3 years < 100 μm). No significant differences (P>0.05) were observed between the two groups. Regarding the restorations with wear pattern Ⅰ, the wear depth of BF group was higher than Z350 group at 6- and 48-month (P < 0.05), while there was no significant difference between restorations with wear pattern Ⅱ (P>0.05).@*CONCLUSION@#Within the limitation of the study, after 4 years, the survival rate and wear resistance of Giomer met ADA guidelines for tooth-colored restorative materials for posterior teeth. When the two materials were applied in occlusal contact areas, wear resistance of Giomer was slightly lower than universal composite resin. No significant difference was found when they were applied in none of the occlusal contact areas.

Evaluation of microtensile bond strength between resin composite and glass ceramic / 北京大学学报(医学版)

OBJECTIVE@#To evaluate the microtensile bond strength of resin composite to glass ceramic, and the effect of surface treatment of resin composite and thermal cycling aging on the microtensile bond strength.@*METHODS@#Rectangular blocks were made with dentin of extracted molars, resin composite or feldspathic glass ceramic respectively. The bonding surfaces of these rectangular blocks were sanded by 600-grit silicon carbide paper before luting. A self-etching resin cement was used as luting agent. The specimens were divided into groups according to the types of substrates of adhesion (dentin/glass ceramic or resin composite/glass ceramic), the way of surface treatments and whether thermal cycling aging ocurred. The dentin blocks were adhered to ceramic blocks as controls (group A1 and A2). The resin composite blocks were adhered to the ceramic blocks as experiment groups. The resin composite surfaces were treated by different ways before luting: no extra surface treatment (group B1 and B2), treated by ethyl methacrylate solution (group C1 and C2) or silane coupling agent (group D1 and D2), coarsened by 360-grit silicon carbide paper (group E1 and E2) or polished by 1 200-grit silicon carbide paper (group F1 and F2). After luting, the microtensile bond strength of the specimens were tested before (group A1-F1) or after (group A2-F2) thermal cycling aging. After microtensile bond strength test, the fracture bonding surfaces of the specimens were observed by a scanning electron microscopy to determine the type of bonding failure. The data were statistically analyzed using one-way analysis of variance.@*RESULTS@#The microtensile bond strength of resin composite to glass ceramic with no extra treatment achieved high bond values before and after thermal cycling [B1 (30.02±3.85) MPa, B2 (26.83±3.14) MPa], which were statistically different from those of the control groups [A1 (20.55±4.51) MPa, A2 (12.94±0.69) MPa, P < 0.05]. The microtensile bond strength between the glass ceramic and resin composite did not increase after different surface treatments of resin composite.@*CONCLUSIONS@#The microtensile bond strength between resin composite and glass ceramic achieved as similar bond strength as that between dentin and glass ceramic and even better. Surface treatment of resin composite via methyl methacrylate solution, silane coupling agent, coarsening, or polishing did not increase the microtensile bond strength effectually.

Nano-sized bioactive glass enhances osteogenesis of critical bone defect in rabbits / 北京大学学报(医学版)

OBJECTIVE@#To compare the osteogenic effects of a nano-sized 58S bioactive glass (nano-58S BG) and a traditional 45S5 bioactive glass(45S5 BG) in penetrating parietal critical bone defects.@*METHODS@#Critical bone defect with 9 mm diameter was created in the parietal bone of New Zealand rabbits. The bone defects were then filled with either nano-58S BG, or 45S5 BG, or nothing but the newly-formed blood clot as the blank control at random. For histological observation, specimens were gained 4 and 8 weeks after the surgery, sectioned and stained by HE. The amount of collagen type I was observed with Picric-Sirius Red staining through polarimetry. To observe the new bone formation with fluorescence under the laser confocal microscope, we injected fluorescent markers 14, 28, and 42 days after the surgery. The markers were tetracycline hydrochloride, alizarin red and calcin individually in chronological order. Image J software was used to quantify the bone regeneration.@*RESULTS@#HE staining showed that BG particulates were integrated with the surrounding tissue without any inflammatory cells infiltration 4 weeks after surgery. New bone regeneration was observed both from the border and in the center of the defects in both BG groups. No bone regeneration in defect center was observed in control group. At the end of 8 weeks, there was more bone regeneration in nano-58S group compared with 45S5 group and control group. The structure of the new bone in BG groups was hollow, which was similar to the natural normal parietal bone. No hollow structure was observed in the new bone of control group. Picric-sirius Red polarimetry showed that more amount of collagen type I was found in nano-58S group than in either 45S5 or control group. The fluorescent observation of the hard tissue slices at the end of 8 weeks showed statistically larger scope and faster new bone formation in nano-58S group with (29.4±4.48) μm thickness from 4-6 weeks and (35.3±3.74) μm from 6-8 weeks compared with 45S5 group [(13.43±3.44) μm and (17.64±4.13) μm] and control group [(5.88±2.92) μm and (6.07±3.02) μm, P<0.01].@*CONCLUSION@#Compared with the traditional 45S5 bioactive glass, 58S nano-sized bioactive glass showed better osteogenic effect in bone regeneration in parietal bones of rabbits.

Detection of root cracks after root canal preparation using rotary NiTi systems by optical coherence tomography (OCT) scan / 北京大学学报(医学版)

OBJECTIVE@#To evaluate the accuracy of optical coherence tomography (OCT) in detecting root cracks after root canal instrumentation using histological gold standard.@*METHODS@#Twenty complete extracted human mandibular incisors that were free of caries, calculus, and root treatment were chosen and accessed coronally with a diamond bur, then mounted in resin blocks with alginate impression material using simulated periodontal ligaments, and the apex was exposed 3 mm. The teeth were stored in water at room temperature. Then the teeth were then instrumented to the major apical foramen (AF) at #30/0.09 using ProTaper Universal rotary nickel titanium system (Dentsply Maillefer, Ballaigues, Switzerland), irrigation with 1% sodium hypochlorite (NaOCl) by using a 26-gauge needle followed after each instrument. The apical root was scanned with 360° of rotation by Swept-Source Optical Coherence Tomography (SS-OCT) (wavelength: 1 310 nm, scan rate: 20 kHz, axial resolution: 16 μm) with driving device (stepper motor and lifting platform). The reconstruction images of axial planes 1, 2 and 3 mm from the apex were examined and the root cracks were blindly diagnosed by two observers. The horizontal section was performed at 1, 2 and 3 mm from the apex using low speed disc saw (Leica SP1600, Wetzlar, Germany). The presence of cracks was noted under an optical stereomicroscope (ZOOM-630E) with a cold light source using as gold standard to evaluate the accuracy of OCT in detecting root cracks after root canal instrumentation.@*RESULTS@#After canals instrumentation with ProTaper Universal rotary nickel titanium system to #30/0.09, root cracks were detected in 9 of 20 teeth by histological examination. Crack lines were observed on 13 of 60 horizontal sections and cracks on 12 of the 13 sections were detected by OCT. No cracks were observed in the other 47 of the 60 horizontal sections,none of which was misdiagnosed by OCT. The overall accuracy rate for detection of root cracks with OCT was 0.983, the sensitivity was 0.923, the specificity was 1.000, the positive predictive value (PPV) was 1.000 and the negative predictive value (NPV) was 0.979.@*CONCLUSION@#OCT may be a promising nondestructive imaging method for diagnosing root canal cracks after canal instrumentation.

Efficacy and safety of levetiracetam for adult seizure: A randomized controlled trial / 第二军医大学学报

Objective To evaluate the efficacy and safety of levetiracetam (LTA) for adult seizure (AS). Methods A randomized, double-blinded, double-dummy, positive drug controlled trial was conducted. One hundred and twenty eligible AS patients were randomly divided into two groups: intervention group and control group, with 60 in each group. Patients in the intervention group received LTA tablet plus valproate sodium mimetic tablet, and patients in the control group received valproate sodium tablet and LTA mimetic tablet. The treatment course was 26 weeks in both groups, and the patients was followed up for 3 months after the treatment. The outcomes included total efficacy rate, weekly epilepsy seizure frequency, seizure duration, quality of life (measured by QOLIE-31 Scale) and adverse events related to drugs after 1-3 days of treatment and at 3 months of follow-up. Results The weekly epilepsy seizure frequency, seizure duration and QOLIE-31 score were not significantly different between the two groups before treatment. The total efficacy rates after treatment and at 3 months of follow-up in the intervention group were 95. 0% (57/60) and 91 7% (55/60), respectively, and were significantly higher than those in the control group of 71 7% (43/60) and 63. 3% (38/60) (P<0 01). The weekly epilepsy seizure frequency, seizure duration and QOLIE-31 score after treatment and at 3 months of follow-up were significantly different as compared with before treatment in both groups (P<3. 01); and there were significantly different between the two groups (P<3 01). The adverse events after treatment were similar between both groups. Conclusion The efficacy of LAT is superior to the valproate sodium tablet for AS, with the less toxicity, and it can be clinical drug of choice for AS.

Effect of bioactive glasses on angiogenic growth factors of human dental pulp cells / 中华口腔医学杂志

<p><b>OBJECTIVE</b>To investigate the effects of bioactive glasses (BG) including 45S5 and nano-58S on proliferation, angiogenic markers vascular endothelial growth factor (VEGF) and basic fibroblast growth factor (bFGF) secretion and gene expression of human dental pulp cells (HDPC).</p><p><b>METHODS</b>HDPC of 4th passage were cultured in Dulbecco's modified Eagle's medium (DMEM) which contained 0.1 g/L 45S5 or nano-58S ionic dissolution products. Meanwhile HDPC were cultured in DMEM without BG as control group. Proliferation of the cells was evaluated with methyl thiazolyl tetrazolium (MTT) assay on day 1, 2, 3. Quantitative real-time PCR and quantitative sandwich enzyme immunoassays were used to test VEGF and bFGF gene expression and protein secretion of HDPC on day 1, 2, 3.</p><p><b>RESULTS</b>The relative growth rate (RGR) of 45S5 and nano-58S groups were (134.5 ± 5.0)% and (146.3 ± 19.8)%, which was significantly different from that of control group (P < 0.05). The quantity of VEGF secretion of two experimental groups were (189.29 ± 4.64) and (216.18 ± 14.67) ng/L, respectively, significantly higher than that of the control group [(159.03 ± 11.69) ng/L] (P < 0.05). Furthermore, the nano-58S group secreted much more VEGF than 45S5 group (P < 0.05).bFGF secretion of HDPC was also enhanced by both 45S5 and nano-58S bioactive glasses. The VEGF gene expression of 45S5 and nano-58S on day 1 were (1.70 ± 0.19) and (1.63 ± 0.42), while the bFGF gene expressin on day 3 were (1.49 ± 0.02) and (2.30 ± 0.04), all significantly higher than that of control group (P < 0.05).</p><p><b>CONCLUSIONS</b>Bioactive glasses can enhance the proliferation, VEGF and bFGF secretion and gene expression of human dental pulp cells. Compared with 45S5, nano-58S showed a higher activation.</p>

The durability of three self-etch adhesives bonded to dentin / 中华口腔医学杂志

<p><b>OBJECTIVE</b>To investigate the durability of self-etch adhesives bonded to dentin in vitro.</p><p><b>METHODS</b>Forty-two extracted human molars were selected and occlusal dentin surfaces were exposed. The teeth were randomly distributed into three groups based on adhesives applied. The one-step self-etch adhesive B(Adper Prompt) and C(G-Bond) and two-step self-etch adhesive A (Clearfil SE bond) were used. After application of the adhesives to the dentin surfaces, composite crowns were built up, after 24 h water storage, the teeth were sectioned longitudinally into sticks (1.0 mm×1.0 mm bonding area) for microtensile testing or slabs (1 mm thick) for scanning electron microscopec (SEM) observation. Bonding strength (mTBS) and nano-leakage were evaluated immediately after cutting or after 6 months in water. The mTBS was analyzed using one-way ANOVA (SPSS 13.0). The nanoleakage was observed by SEM with a backscattered electron detector.</p><p><b>RESULTS</b>Both adhesives and water storage time affected the mTBS. All adhesives showed decreased bond strength after six-month water aging [A dropped from (40.60 ± 5.76) MPa to (36.04 ± 3.15) MPa; B dropped from (19.06 ± 1.50) MPa to (11.19 ± 1.97) MPa; C dropped from (17.75 ± 1.10) MPa to (9.14 ± 1.15) MPa] (P < 0.05). B and C showed lower mTBS than A after aging (P < 0.05). Compared to A, nanoleakage was more obvious after aging for B and C.</p><p><b>CONCLUSIONS</b>All self-etch adhesives tested were probably influenced by water aging, however, the two-step adhesive showed better durability than the one-step adhesives.</p>

Expression patterns of amelogenin and enamelin in developing mouse tooth germs / 中华口腔医学杂志

<p><b>OBJECTIVE</b>To invesitgate the expression patterns of amelogenin and enamelin in the developing tooth germs.</p><p><b>METHODS</b>Mandible sections of postnatal day 1, 3, 7 and 14 mouse were prepared, immunohistochemical analysis and reverse transcriptase polymerase chain reaction (RT-PCR) were performed to detect the expression patterns of amelogenin and enamelin in mandibular first molars.</p><p><b>RESULTS</b>Amelogenin was observed in the cytoplasm of secretory ameloblasts and the whole enamel matrix layer. It was also transiently expressed in the odontoblasts of postnatal day 1 molars. Enamelin proteins were observed in the enamel layer deposited by secretory ameloblasts, especially intense beneath the ameloblast process and dentino-enamel junction. The mRNA levels of both amelogenin and enamelin were highest on postnatal day 7 (the ratio to glyceraldehyde phosphate dehydrogenase of amelogenin and enamelin: 0.813 ± 0.085 and 0.799 ± 0.064, respectively, P < 0.05).</p><p><b>CONCLUSIONS</b>Amelogenin and enamelin were enamel matrix proteins predominately expressed by secretory ameloblasts. The temporal-spatial expression patterns of amelogenin and enamelin indicate the important roles they played in amelogenesis and biomineralization.</p>

Characterization of Streptococcus oligofermentans sucrose metabolism demonstrates reduced pyruvic and lactic acid production / 中华医学杂志(英文版)

<p><b>BACKGROUND</b>Streptococcus (S.) oligofermentans is a newly identified bacteria with a yet to be defined mechanism of sucrose metabolism that results in acid production. This study aimed to investigate the biochemical mechanisms of S. oligoferm-entans glucose metaolism.</p><p><b>METHODS</b>The S. oligofermentans LMG21532, Lactobacillus (L.) fermentum 38 and the S. mutans UA140 were used to characterize sucrose metabolism by measuring lactate dehydrogenase (LDH) activity and lactic acid production. Continuous dynamics and high performance capillary electrophoresis were used to determine LDH activity and lactic acid production, respectively, from bacteria collected at 0, 10 and 30 minutes after cultured in 10% sucrose.</p><p><b>RESULTS</b>These analyses demonstrated that LDH activity of the three bacterial strains examined remained stable but significantly different throughout the sucrose fermentation process. The S. oligofermentans LDH activity ((0.61 ± 0.05) U/mg) was significantly lower than that of L. fermentum ((52.91 ± 8.97) U/mg). In addition, the S. oligofermentans total lactate production ((0.048 ± 0.021) mmol/L) was also significantly lower than that of L. fermentum ((0.958 ± 0.201) mmol/L). Although the S. oligofermentans LDH production was almost double of that produced by S. mutans ((0.32 ± 0.07) U/mg), lactic acid production was approximately one sixth that of S. mutans ((0.296 ± 0.058) mmol/L). Additional tests examining pyruvic acid production (the LDH substrate) demonstrated that lactic acid concentrations correlated with pyruvic acid production. That is, pyruvic acid production by S. oligofermentans was undetectable following sucrose incubation, however, (0.074 ± 0.024) and (0.175 ± 0.098) mmol/L pyruvic acid were produced by S. mutans and L. fermentum, respectively.</p><p><b>CONCLUSION</b>S. oligofermentans is incapable of fermenting carbohydrates to produce enough pyruvic acid, which results in reduced lactic acid production.</p>

Relationship between Sp3 and the transcriptional regulation of enamelin gene / 中华口腔医学杂志

<p><b>OBJECTIVE</b>To investigate the role of Sp3 in the transcriptional regulation of enamelin gene.</p><p><b>METHODS</b>By bioinformatic analysis, a putative responsive element for Sp3 was identified. Electrophoretic mobility shift assay was used to examine the interaction between Sp3 and enamelin. 5'-flanking regulatory region of enamelin was cloned and ligated into pGL3-basic luciferase vector. Sp3 and the Enam-luc were cotransfected into mouse ameloblast-like cell line, and the activity of luciferase was examined.</p><p><b>RESULTS</b>The results showed that Sp3 could not directly bind to the enamelin regulation region and activate enamelin transcription.</p><p><b>CONCLUSIONS</b>Sp3 might not be involved in transcriptional regulation of enamelin gene via an indirect interaction.</p>

Evaluation of adaptation of root canal filled with three obturation techniques in vitro / 中华口腔医学杂志

<p><b>OBJECTIVE</b>To evaluate the adaptation of root canal filled with three obturation techniques in vitro.</p><p><b>METHODS</b>Fifty-seven cleaned and shaped premolars were divided into three groups, each group including 10 single root canal premolars and 9 double root canal premolars, and filled respectively with following techniques: GuttaFlow paste with single master cone (GF group), cold lateral compaction technique with AH plus sealer (LC group), warm vertical compaction technique with AH plus sealer (VC group). The roots were invested and sectioned at 1 mm interval from crown to apex using a microtome saw under water cooling. Both surfaces of the sections were digitally photographed and measured using a stereomicroscope. The number of sections with voids and the area of voids were measured and analyzed.</p><p><b>RESULTS</b>The frequency of sections with voids: VC group (21.4%, 76/355) was significantly lower than GF group (47.7%, 173/363) and LC group (52.6%, 190/361), P < 0.0167. There was no significant difference between GF and LC group (P > 0.0167). The percentage of voids area (AV%): GF group was significantly higher than LC and VC group (P = 0.000, P = 0.008). The median of GF group was 2.67, LC group was 1.55, VC group was 1.01. No significant difference between VC and LC group (P = 0.076). The filling quality of isthmus: 86% (85/99) isthmus were well filled in VC, significantly higher than GF group (55%, 43/78) and LC group (58%, 49/84), P < 0.0167. There was no significant difference between GF and LC group (P > 0.0167).</p><p><b>CONCLUSIONS</b>The adaptation of root canal filled with warm vertical compaction technique was superior to cold lateral compaction technique and GuttaFlow technique.</p>

Evaluation of shear bond strengths of self-etching and total-etching dental adhesives to enamel and dentin / 中华口腔医学杂志

<p><b>OBJECTIVE</b>To evaluate the shear bond strengths of four dental adhesives in vitro.</p><p><b>METHODS</b>The facial surfaces of 20 human maxillary incisors were prepared to expose fresh enamel and randomly divided into four groups, in each group 5 teeth were bonded with one adhesives: group A (Clearfil Protect Bond, self-etching two steps), group B (Adper( Prompt, self-etching one step), group C (SwissTEC SL Bond, total-etching two steps), group D (Single Bond, total-etching two steps). Shear bond strengths were determined using an universal testing machine after being stored in distilled water for 24 h at 37 degrees C.</p><p><b>RESULTS</b>The bond strengths to enamel and dentin were (25.33 +/- 2.84) and (26.07 +/- 5.56) MPa in group A, (17.08 +/- 5.13) and (17.93 +/- 4.70) MPa in group B, (33.14 +/- 6.05) and (41.92 +/- 6.25) MPa in group C, (22.51 +/- 6.25) and (21.45 +/- 7.34) MPa in group D. Group C showed the highest and group B the lowest shear bond strength to enamel and dentin among the four groups.</p><p><b>CONCLUSIONS</b>The two-step self-etching adhesive showed comparable shear bond strength to some of the total-etching adhesives and higher shear bond strength than one-step self-etching adhesive.</p>

Effects of application methods of self-etching adhesives on resin-dentin bonding / 中华口腔医学杂志

<p><b>OBJECTIVE</b>To investigate the effects of application time and rubbing action of self-etching adhesives on resin-dentin bond strength and interface morphology in vitro.</p><p><b>METHODS</b>Caries-free human third molars were wet ground to expose dentin surface. Three self-etching bonding agents were applied with varying application time and with/without rubbing. The microtensile bond strength and interface morphology were evaluated.</p><p><b>RESULTS</b>When etching time was shortened, normal and prolonged, the bond strength was bonding agent 1 (Adper Prompt): (16.30 +/- 2.59), (23.13 +/- 2.56), (22.28 +/- 2.83) MPa, bonding agent 2 (Xeno III): (15.17 +/- 6.07), (34.50 +/- 3.64), (24.87 +/- 7.01) MPa, bonding agent 3 (Clearfil SE Bond): (29.92 +/- 3.32), (42.21 +/- 6.28), (41.07 +/- 3.93) MPa. When etching was applied with and without rubbing, the bond strength was bonding agent 1 (23.13 +/- 2.56), (12.53 +/- 3.73) MPa, bonding agent 2 (23.98 +/- 3.86), (34.50 +/- 3.64) MPa, bonding agent 3 (48.37 +/- 4.95), (42.21 +/- 6.28) MPa.</p><p><b>CONCLUSIONS</b>Shortening application time decreased bond strength of self-etching adhesives, while prolonging application time did not increase bond strength of self-etching adhesives. Not all self-etching adhesives applied with rubbing showed increased bond strength to dentin, which is product-dependent. Manufactures' instructions should be followed to achieve optimum bonding.</p>

Analysis of short chain fatty acids in gingival crevicular fluid of patients with aggressive periodontitis / 中华口腔医学杂志

<p><b>OBJECTIVE</b>To investigate 7 short chain fatty acids (SCFA) concentrations in gingival crevicular fluid (GCF) of aggressive periodontitis (AgP) and to analyze the relationship between levels of SCFA and AgP clinical parameters.</p><p><b>METHODS</b>GCF was collected from 152 sites of 38 AgP patients and 56 sites of 14 healthy subjects. Formic acid, succinic acid, acetic acid, lactic acid, propionic acid, butyric acid and isovalerianic acid were detected by high performance capillary electrophoresis.</p><p><b>RESULTS</b>The concentrations of succinic acid, acetic acid, lactic acid, propionic acid, butyric acid and isovalerianic acid in GCF were significantly higher in AgP patients than in healthy group, while formic acid was lower in GCF of AgP group compared with healthy group. Correlation analysis showed that formic acid was negatively correlated with bleeding index (BI), probing depth (PD) and attachment loss (AL), while BI was positively correlated with succinic acid, acetic acid, lactic acid, propionic acid and butyric acid; PD and AL were positively correlated with succinic acid, acetic acid, propionic acid, butyric acid and isovalerianic acid.</p><p><b>CONCLUSIONS</b>The elevation of succinic acid, acetic acid, propionic acid, butyric acid and isovalerianic acid concentrations in GCF may be related with AgP destruction condition, while formic acid concentration was reduced.</p>

Comparison of antimicrobial efficacy of four endodontic irrigants using an in vitro model infected by Enterococcus faecalis / 中华口腔医学杂志

<p><b>OBJECTIVE</b>To compare the antimicrobial efficacy of four endodontic irrigants using an in vitro model infected by Enterococcus faecalis (Ef).</p><p><b>METHODS</b>The root canals of fifty extracted teeth were infected by Ef in vitro. The test groups were irrigated with 3% H(2)O(2), 2.5% sodium hypochlorite (SH), 2% chloramine-T (CR), and 2% chlorhexidine (CHX), respectively, and the control group was irrigated with 0.9% NaCl. The concentration of Ef in canals of each group was calculated before and after irrigation. The residual bacteria within the dentinal tubules and vitalities of the residual bacteria were also examined.</p><p><b>RESULTS</b>All chemical irrigants were significantly more effective than 0.9% NaCl (P < 0.05); 2.5% SH and 2% CHX were statistically more effective than 3% H(2)O(2) (P < 0.05). Residual bacteria could be found in the dentinal tubules and propagated 72 h after.</p><p><b>CONCLUSIONS</b>2% CR and 2% CHX had almost the equivalent antimicrobial effect as 2.5% SH, but 3% H(2)O(2) was less effective.</p>

Microtensile bond strengths of one-step self-etching adhesive systems / 中华口腔医学杂志

<p><b>OBJECTIVE</b>To evaluate the microtensile bond strength of one-step self-etching adhesives to dentin in vitro.</p><p><b>METHODS</b>Three commercially available one-step self-etching bonding systems (group A: Adper Prompt, group B: Clearfil S(3) Bond, group C: Xeno III) were compared with two-step self-etching adhesive (group D: Clearfil SE Bond) in this study. The microtensile bond strength was determined with microtensile tester and the fractured bonding surfaces were observed under stereomicroscope and scanning electronic microscope (SEM). The mean bond strengths were analyzed using one-way ANOVA test (P < 0.05).</p><p><b>RESULTS</b>Mean microtensile bond strengths of group C, B, A and D were (34.59 +/- 3.46), (30.46 +/- 3.82), (23.36 +/- 2.55) and (45.06 +/- 5.29) MPa, respectively. Group D showed the highest bond strength (P < 0.01).</p><p><b>CONCLUSIONS</b>Two-step self-etching adhesive had a higher bond strength than one-step self-etching adhesive systems, although all of them can satisfy the clinical requirements.</p>

In vitro evaluation of the antibacterial effectiveness of sodium hypochlorite on Enterococcus faecalis within root canals / 中华口腔医学杂志

<p><b>OBJECTIVE</b>To evaluate in vitro the antibacterial effectiveness of sodium hypochlorite on Enterococcus faecalis (E. faecalis) within root canals.</p><p><b>METHODS</b>Roots inoculated with E. faecalis were divided into six groups, which underwent different root canal irrigation and treatment: Group 1: 5.25% NaOCl, Group 2: 2.5% NaOCl, Group 3: 0.9% NaCl, Group 4: root canal preparation + 5.25% NaOCl, Group 5: root canal preparation + 2.5% NaOCl, Group 6: root canal preparation + 0.9% NaCl. Microbiological samples were collected from root canals at three time points (before irrigation, immediately after irrigation and three days after irrigation).</p><p><b>RESULTS</b>The numbers of E. faecalis in root canal in each of the six groups were effectively reduced. Group 1 and 2 were statistically more effective than Group 3. Group 4 was statistically more effective than Group 5 and 6. Group 5 was statistically more effective than Group 6. Bacterial survival was observed in all canals of each group after a 3-day-incubation.</p><p><b>CONCLUSIONS</b>2.5% NaOCl was highly effective for root canal irrigation. However residual bacteria remained in the root canals after chemical irrigation by NaOCl and mechanical preparation.</p>

Development of an identification method for Streptococcus oligofermentans: a new species of oral streptococci with molecular markers / 中华口腔医学杂志

<p><b>OBJECTIVE</b>To establish a quick and reliable method to identify Streptococcus oligofermentans, a new species of oral streptococci.</p><p><b>METHODS</b>With two-step PCR, a pair of the 16S rDNA-specific primers of Streptococcus oligofermentans and a pair of primers of lactate oxidase gene (lox) were used to amplify the gene fragments from the genomic DNAs of 11 strains consisting of 9 species of the pure culture of oral streptococci. Pooled plaque samples from 9 caries-free volunteers were cultured on a selective medium of MSA with erythromycin and tentative strains of Streptococcus oligofermentans were isolated. The isolates were further identified by the two-step PCR and finally confirmed by 16S rDNA sequence analysis.</p><p><b>RESULTS</b>With the two-step PCR, the two gene fragments were only amplified from the three identified strains of Streptococcus oligofermentans, but not the rest of 8 strains of oral streptococci. Isolates from the dental plaque of caries-free volunteers were identified as Streptococcus oligofermentans by PCR and then further confirmed by 16S rDNA sequence homology analysis.</p><p><b>CONCLUSIONS</b>Streptococcus oligofermentans could be identified by the two-step PCR approach with the specific 16S rDNA primers and lactate oxidase gene primers.</p>

Assessment of shaping ability of ProTaper in curved canals / 华西口腔医学杂志

<p><b>OBJECTIVE</b>To evaluate shaping ability of nickel-titanium rotary instruments (ProTaper) in curved root canals.</p><p><b>METHODS</b>The computer assistant measure system of simulated root canal was used for quantitative analysis of root shape of eight simulated root canals during ProTaper shaping process. Blue ink was injected into the simulated root canals before instrumentation, when F2 reached work length(WL) (F2) and when F3 reached WL(F3). Orifices and apexes were sealed with adhesive tapes. Root canal images were gained by Mustek BP4800TA scanner. The images before and after preparation were turned into Di-numerical images and fused. The changes of central line positions and curvatures were measured in quantity through this system. Data of seven preestablished point from orifice to apex were recorded and analysed by SPSS 10.0 soft ware.</p><p><b>RESULTS</b>ProTaper system reduced the angles of simulated canals. Selecting F2 or F3 as the master apical file (MAF) had no influence on the changing rate of the root angles. ProTaper had excess cutting on the outer wall of orifice and the inner wall of curve part, but the displacement of apex was minimal (only 0.021 mm).</p><p><b>CONCLUSION</b>ProTaper has preferable shaping ability. To prepare very difficult curved canals, the master apical file (MAF) could be F3. Attention should be taken when preparing some curved canals with hollows in their inner walls, in order to avoid the lateral perforation.</p>