Clinical application of direct composite resin in esthetic restoration / 中华口腔医学杂志

The direct composite resin bonding is widely used in the esthetic restorations of anterior teeth. Due to the technique sensitive procedure, the esthetic effect and long-term clinical performance of direct composite resin restoration have long been the focus of dental clinicians. This article will analyze the influencing factors of esthetic effect of composite resin from three aspects, including materials, teeth and technology. Also, it will summarize the clinical performance of direct composite resin from the perspective of esthetic evaluation. Eventually, this article will provide guidance for the clinical application of esthetic restoration of direct composite resin bonding.

Diagnosis and treatment strategy of permanent tooth developmental disturbances caused by primary tooth trauma / 中华口腔医学杂志

The trauma to primary tooth may lead to developmental disturbances of permanent tooth. Because the traumatic events are often forgotten as accurred earlier, the timely diagnosis and intervention treatment are not conducted, resulting in aesthetic and functional disorders. This paper systematically elaborates the types of developmental disturbances in permanent tooth after traumatic injuries to the primary predecessor, and the etiology, mechanism, related factors as well as the treatment options, in order to provide references for the prevention of serious complications in inherited permanent tooth caused by primary tooth trauma.

Causes, diagnosis and treatment strategies for dental pulp calcification / 中华口腔医学杂志

Dental pulp calcification can lead to root canal stenosis or obliteration. It is usually difficult to negotiate the root canal if the affected tooth needs to be treated and intraoperative complications are easily brought about during the root canal treatment. The etiologies of dental pulp calcification are complicated and careful considerations should be given to the diagnosis and treatment. Only by weighing the advantages and disadvantages can appropriate treatment plan be chosen. Based on the literature and authors' clinical experiences, the present article summarizes the causes, pathogenesis, diagnosis and treatment strategies of dental pulp calcification, in order to provide some references in diagnosis and treatment for the dental clinicians.

Effect of autoclave on surface microstructure and cyclic fatigue resistance of R-phase rotary instruments / 北京大学学报(医学版)

OBJECTIVE@#To compare the effects of autoclave on surface microstructure and cyclic fatigue resistance of K3XF and K3.@*METHODS@#Forty-eight size 25, 0.06 taper 25 mm-long K3XF or K3 were randomly divided into 4 groups (n=12). The instruments from group 1 were not autoclaved, and the groups 2 to 4 underwent autoclave for 10 cycles, 20 cycles, and 30 cycles, respectively. The surface microstructure of two instruments randomly selected from each group was observed using scanning electron microscope (SEM). The remaining 10 instruments were submitted to the cyclic fatigue test by using a simulated metal root canal with curvature of 60° and radius 3.5 mm. The time till fracture was recorded, the number of cyclic fatigue (NCF) calculated, the fragment length evaluated, and the topographic features were analyzed using SEM. The data were analyzed using the two-way ANOVA analysis by SAS 9.3 software at a significance level of P<0.05.@*RESULTS@#SEM observation identified rough features on the surface of K3XF with micropores existing evenly. K3 was characterized by machining grooves, which located specifically in the flute, leaving a smooth cutting edge. After autoclave, SEM observation indicated that the micropores in the surface of K3XF became larger and more, whereas the machining grooves in the surface of K3 were squeezed, out of shape and flaking. As far as the NCF was concerned, new K3XF was 210±59, and no significant difference was found after 10, 20, and 30 cycles of autoclave for K3XF, values being 178±37, 208±48, and 227±43, respectively (P>0.05). For K3, the new one was 145±38, and no significant difference in NCF was demonstrated after 10 and 20 cycles of autoclave, with the values of 128±43 and 124±46, respectively (P>0.05). However, after 30 cycles of autoclave of K3, significant increase to 216±38 was identified (P<0.05). Topographic features demonstrated typical cyclic fatigue for all the groups.@*CONCLUSION@#The surface roughness of K3XF was increased after autoclave, while the cyclic resistance remained stable after up to 30 cycles.

Microbial diversity in failed endodontic root-filled teeth / 中华医学杂志(英文版)

<p><b>BACKGROUND</b>Persistent/secondary infections of human root canals play an important role in the failure of endodontic treatment. This study used 16S rRNA sequencing to assess microbial diversity in root-filled teeth associated with failed endodontic treatment.</p><p><b>METHODS</b>DNA was extracted from 15 teeth with persistent intraradicular infections, and the 16S rRNA of all present bacteria were amplified by PCR, followed by cloning and sequencing of the 16S rRNA amplicons.</p><p><b>RESULTS</b>All sample extracts were positive for PCR amplification using the universal 16S rRNA gene primers. Negative control reactions yielded no amplicons. Sixty-five phylotypes belonging to seven phyla were identified from 760 clones; a mean of 9.4 phylotypes were detected in each sample (range 3 - 15). Twenty-eight phylotypes were detected in more than one sample, revealing a high inter-sample variability. Parvimonas micra (60%, 9/15), Solobacterium moore (47%, 7/15), Dialister invisus (33%, 5/15), Enterococcus faecalis (33%, 5/15), Filifactor alocis (27%, 4/15), and Fusobacterium nucleatum (27%, 4/15) were the prevalent species. Nineteen as-yet-uncultivated phylotypes were identified, comprising a substantial proportion of the bacteria in many cases.</p><p><b>CONCLUSIONS</b>Persistent intraradicular infections were present in all root-filled teeth associated with failed endodontic treatment. The current observations reveal new candidate endodontic pathogens, including as-yet-uncultivated bacteria and phylotypes that may participate in the mixed infections associated with post-treatment apical periodontitis.</p>

Treatment outcome of iatrogenic perforation repair by mineral trioxide aggregate / 中华口腔医学杂志

<p><b>OBJECTIVE</b>To observe the clinical effect of iatrogenic perforation repaired by mineral trioxide aggregate (MTA).</p><p><b>METHODS</b>Twenty-one iatrogenic perforation cases were included. The root canals were shaped and cleaned and then obturated after MTA was used to repair the perforation with microscopes. Preoperative, immediate postoperative, and follow-up radiographs were evaluated to determine the pathologic changes adjacent to the perforation site.</p><p><b>RESULTS</b>Nineteen cases healed and two cases were healing. No cases failed.</p><p><b>CONCLUSIONS</b>MTA is effective in the treatment of iatrogenic perforation.</p>

Torque resistance of three different types of nickel-titanium rotary instruments / 华西口腔医学杂志

<p><b>OBJECTIVE</b>To compare torsional fracture of three different types of nickel-titanium rotary instruments ProTaper, Hero642 and Mtwo by making a stimulate models in vitro.</p><p><b>METHODS</b>Through the establishment of model in vitro, compared the different time with 3 kinds of nickel titanium file in cutting-edge bound occurs, and to observe the section of fractured instruments by scanning electron microscope.</p><p><b>RESULTS</b>The resistence to torque was different from three types of nickel titanium instruments. The time to fracture of Mtwo was significantly longer than ProTaper's and Hero642's, but ProTaper's and Hero642's had no significant difference. Three kinds cross-sectional design were different, a lot of toughness nests were seen in broken surface. Most of them were ductile fracture. Time to fracture was influenced by the quality disfigurement.</p><p><b>CONCLUSION</b>The resistance to torque of Mtwo was better than ProTaper and Hero642. The lifespan was influenced by the design of cross-section. The quality disfigurement of the files reduced the resistance to flexual fatigue.</p>

The effect of curvature of simulated root canal and location of fragment on removal of broken file from simulated root canal / 华西口腔医学杂志

<p><b>OBJECTIVE</b>To evaluate effect of root canal curvature and location of the fragment on the removal of broken file from root canal.</p><p><b>METHODS</b>Sixty extracted mandibular premolars were divided equally into six groups according to location of fragment (2 mm or 8 mm below root canal orifice) and root canal curvature (20 degrees, 30 degrees or 40 degrees). Broken files were removed using ultrasonic tips combined with dental operating microscope. Number of successfully removed case and operating time were recorded. Pre- and post-operative digital radiographs were input into image analyzing software to calculate diameter variance of root canal at the level of tip of broken file.</p><p><b>RESULTS</b>All the 6 groups of broken files were successfully removed with out perforation. Among same fragment location groups, diameter variance was increased in greater curvature groups and the difference was significant (P < 0.05), while operation time was not significantly different (P > 0.05). Among same root canal curvature groups, the deeper the fragment, the longer operation time, difference being significant (P < 0.05), while difference of diameter variance was not significant (P > 0.05).</p><p><b>CONCLUSION</b>The more curvature of root canal, the more dentine removal amount at the level of broken file tip. Location of fragment has no effect on dentine removal amount. Safe straight-line access and adequate thickness of dentine are essential to removal of broken file from root canal.</p>

Evaluation of homogeneity and density of root canal filling with four obturation techniques / 中华口腔医学杂志

<p><b>OBJECTIVE</b>To evaluate the homogeneity and density of root canal filling with four obturation techniques.</p><p><b>METHODS</b>Forty extracted single root teeth were randomly divided into four groups with 10 teeth each. Under simulated clinical conditions, the root canals were shaped with Nickle titanium rotary files (Protaper) using crown-down technique and were filled with warm vertically condensed gutta-percha (group A), core carrier technique-thermafil (group B), guttaflow (group C) and conventional cold laterally condensed gutta-percha (group D). Roots were sectioned at four levels. The cross-sections were photographed through a microscope, the photos were analysed, and the percentage of gutta-percha filled area (PGFA) was measured.</p><p><b>RESULTS</b>The overall PGFA values were (96.5 ± 3.6)%, (95.6 ± 3.9)%, (86.5 ± 5.7)% and (81.5 ± 4.2)% for groups A, B, C and D, respectively. The differences between these groups were statistically significant (P < 0.01). Group A and B were significantly higher than group C and D (P < 0.01). The PGFA in group D was significantly lower than that in other groups (P < 0.01). The average PGFA in both group A and B was higher than that of group C and D at apical and middle level (P < 0.01).</p><p><b>CONCLUSIONS</b>Warm vertical condensation and thermafil produce significantly higher PGFA than guttaflow and cold lateral condensation technique.</p>

Theoretical research and clinical practices of contemporary root canal therapy / 中国医学科学院学报

Root canal therapy is currently the most effective treatment for pulpal and periapical diseases. With the innovation of endodontic theory and techniques, the concept of contemporary root canal therapy has been established and promoted gradually. Advances in endodontic technology, instruments, and materials have increased the safety and clinical success rate of root canal therapy. This article reviews the recent theoretical research and clinical practices of contemporary root canal therapy.

Bond strength of different adhesives to normal and caries-affected dentins / 中华医学杂志(英文版)

<p><b>BACKGROUND</b>Currently, several systems of dentin substrate-reacting adhesives are available for use in the restorative treatment against caries. However, the bond effectiveness and property of different adhesive systems to caries-affected dentin are not fully understood. The objective of this study was to evaluate the bond strength of different adhesives to both normal dentin (ND) and caries-affected dentin (CAD) and to analyze the dentin/adhesive interfacial characteristics.</p><p><b>METHODS</b>Twenty eight extracted human molars with coronal medium carious lesions were randomly assigned to four groups according to adhesives used. ND and CAD were bonded with etch-and-rinse adhesive Adper Single Bond 2 (SB2) or self-etching adhesives Clearfil SE Bond (CSE), Clearfil S(3) Bond (CS3), iBond GI (IB). Rectangular sticks of resin-dentin bonded interfaces 0.9 mm(2) were obtained. The specimens were subjected to microtensile bond strength (microTBS) testing at a crosshead speed of 1 mm/min. Mean microTBS was statistically analyzed with analysis of variance (ANOVA) and Student-Newman-Keuls tests. Interfacial morphologies were analyzed by Scanning Electron Microscopy (SEM).</p><p><b>RESULTS</b>Etch-and-rinse adhesive Adper(TM) Single Bond 2 yielded high bond strength when applied to both normal and caries-affected dentin. The two-step self-etching adhesive Clearfil SE Bond generated the highest bond strength to ND among all adhesives tested but a significantly reduced strength when applied to CAD. For the one-step self-etching adhesives, Clearfil S(3) Bond and iBond GI, the bond strength was relatively low regardless of the dentin type. SEM interfacial analysis revealed that hybrid layers were thicker with poorer resin tag formation and less resin-filled lateral branches in the CAD than in the ND for all the adhesives tested.</p><p><b>CONCLUSION</b>The etch-and-rinse adhesive performed more effectively to caries-affected dentin than the self-etching adhesives.</p>

Clinical effect of the use of dental operating microscope and ultrasonic instruments in the management of blocked canals / 华西口腔医学杂志

<p><b>OBJECTIVE</b>To evaluate the effect of using dental operating microscope and ultrasonic instruments in treating blocked canals.</p><p><b>METHODS</b>The etiology of canal blockage included calcification, broken instruments, posts, resinifying, etc. 236 blocked canals were treated with ultrasonic tips under dental operating microscope. The success rate was calculated.</p><p><b>RESULTS</b>178 blocked canals were successfully managed with a success rate of 75.4%. The success rate of each category of the blocked canals were: 71.7% for calcified canals, 81.1% for broken instruments, 100% for canals blocked by posts, 62.5% for canals blocked by resinifying therapy, and 84.1% for canals blocked by filling materials.</p><p><b>CONCLUSION</b>The use of dental operating microscope and ultrasonic instruments is proved to be an effective method in the management of blocked canals.</p>

Ultrasonic techniques for removing broken instruments from root canal / 华西口腔医学杂志

Instruments broken in root canal is one of the frequent complications of endodontic therapy and fortunately, as the rapid development of microscope using in the root canal treatment, most of the broken instruments can be removed with the assistance of ultrasonic appliances. In the present study, we talked about the causes, the removing methods of broken instruments and troubles during the procedures. We put much emphasis on the creation of a straight pathway along the canal as well as some concerns in using the ultrasonic appliances, such as the water spray, the rotating actions and the assistance of microscope, all of which are supposed to offer great benefits for clinically avoiding as well as dealing with broken instruments.

Expression of lipopolysaccharide receptors CD14 and TLR4 in a model of rat molar apical periodontitis / 中华口腔医学杂志

<p><b>OBJECTIVE</b>To characterize the expression of lipopolysaccharide (LPS) receptors-CD14 and TLR4 in rat peri-radicular tissue and to investigate the signal transduction pathway of LPS and its receptors in periapical periodontitis.</p><p><b>METHODS</b>After establishment of a model of rat molar LPS-induced apical periodontitis, CD14 and TLR4 expression in healthy and inflammatory periapical tissue were determined by immunohistochemistry.</p><p><b>RESULTS</b>CD14 and TLR4 were not detected in healthy periapical tissue but strongly positive in inflammatory periapical tissue. Positive cells were mostly monocytes/macrophages.</p><p><b>CONCLUSIONS</b>CD14 and TLR4 may play an important role in the pathogenesis of periapical periodontitis, probably via immune cells such as monocytes/macrophages and neutrophils.</p>

Expression of lipopolysaccharides signal receptors CD14 and TLR4 in human dental pulp tissue and fibroblasts / 中华口腔医学杂志

<p><b>OBJECTIVE</b>To investigate the expression of lipopolysaccharides (LPS) receptors CD14 and TLR4 in normal and inflamed human dental pulp tissue and fibroblasts and to determine the signal transduction pathway of LPS in pulpitis.</p><p><b>METHODS</b>CD14 and TLR4 expression in healthy and inflammatory pulps was observed by immunohistochemistry. The rates of CD14 and TLR4 positive cells and the mean fluorescence intensity in in vitro cultured pulp fibroblasts before and after being stimulated by LPS.</p><p><b>RESULTS</b>CD14 and TLR4 were not detected in healthy pulp tissues, but they were strongly positively stained in inflammatory pulps. Ratio of TLR4 positive cells and mean fluorescence intensity produced by the cells stimulated by LPS increased significantly compared with normal pulp cells. However, there were no CD14 expression in human dental pulp cells before and after LPS stimulation.</p><p><b>CONCLUSIONS</b>This study revealed a significant increase in the expression of CD14 and TLR4 in inflamed human dental pulp tissue. Human dental pulp cells could be induced by LPS to express TLR4, which may play an important role in the process of pulpitis.</p>