Tooth anatomy risk factors influencing root canal working length accessibility

The aim of this study was to analyze the specific influence of root canal anatomy on the accessibility of working length during root canal therapy. Four hundred seventy-six root canal therapy cases （amounting to a total of 1 005 root canals） were examined. The anatomy risk factors assessed in each case included： tooth type （tooth location）, root canal curvature, and root canal calcification, as well as endodontic retreatment. The investigation examined the correlation between each of these anatomic factors and the working length, with statistical analysis consisting of Chi-square tests and multiple logistic regression analysis. In an independent factor analysis, tooth type （tooth iocation）, root canal curvature, canal calcification, and endodontic retreatment were determined to be the primary risk factors. In a multiple-factor regression model, root curvature and canal calcification were found to most significantly influence root canal working length accessibility （P〈0.05）. Root canal anatomy increases the difficulty of root canal preparation. Appropriate consideration of tooth anatomy will assist in accurate determination of preparation difficulty before instrumentation. This study alerts clinical therapists to anatomical factors influencing the working length accessibility, and allows for a direct estimate of success rate given in situ measurements of tooth factors during the root canal treatment procedure.

Bone morphogenetic protein 2-induced human dental pulp cell differentiation involves p38 mitogen-activated protein kinase-activated canonical WNT pathway

Both bone morphogenetic protein 2（BMP2） and the wingless-type MMTV integration site（WNT）/p-catenin signalling pathway play important roles in odontoblast differentiation and dentinogenesis.Cross-talk between BMP2 and WNT/p-catenin in osteoblast differentiation and bone formation has been identified.However,the roles and mechanisms of the canonical WNT pathway in the regulation of BMP2 in dental pulp injury and repair remain largely unknown.Here,we demonstrate that BMP2 promotes the differentiation of human dental pulp cells（HDPCs） by activating WNT/p-catenin signalling,which is further mediated by p38mitogen-activated protein kinase（MAPK） in vitro.BMP2 stimulation upregulated the expression of p-catenin in HDPCs,which was abolished by SB203580 but not by Noggin or LDN193189.Furthermore,BMP2 enhanced cell differentiation,which was not fully inhibited by Noggin or LDN193189.Instead,SB203580 partially blocked BMP2-induced p-catenin expression and cell differentiation.Taken together,these data suggest a possible mechanism by which the elevation of p-catenin resulting from BMP2 stimulation is mediated by the p38 MAPK pathway,which sheds light on the molecular mechanisms of BMP2-mediated pulp reparative dentin formation.

Diverse microbiota in palatal radicular groove analyzed by Illumina sequencing:Four case reports

BACKGROUND A palatal radicular groove is an unusual developmental deformity of the tooth,which may serve as a channel linking the periodontal and periapical inflammation,and yet no literature could be obtained analyzing microbiota within the palatal radicular grooves.CASE SUMMARY Four patients diagnosed with palatal radicular groove and concomitant periodontal-endodontic deformity in permanent maxillary lateral incisors were enrolled in this work.Twelve bacterial samples from 4 patients were collected from different parts of the palatal radicular groove during intentional replantation surgery.Illumina sequencing was performed to analyze the taxonomical composition and microbiome structure inside the palatal grooves,and 1162 operational taxonomic units were obtained.The phyla of Firmicutes and Proteobacteria predominated in most of the samples.An unknown genus from the Bacillaceae family,Lactococcus,and Porphyromonas were the most abundant genera identified.There was no difference in the microbiota richness and diversity in three sections of the groove.CONCLUSION The unique ecological niches inside the palatal grooves harbored bacterial communities that shared some component features of both the endodontic and periodontal infections.The existence of palatal groove may play an interaction bridge between the root apex and tooth cervix and thus impair the outcome of traditional therapeutic methods such as root canal treatment and periodontal management.

Bufferless Epitaxial Growth of GaAs on Step-Free Ge(001)Mesa

GaAs/Ge heterostructures have been employed in various semiconductor devices such as solar cells,high-performance CMOS transistors,andⅢ-Ⅴ/Ⅳheterogeneous optoelectronic devices.The performance of these devices is directly dependent on the material quality of the GaAs/Ge heterostructure,while the material quality of the epitaxial GaAs layer on the Ge is limited by issues such as the antiphase domain(APD),and stacking-fault pyramids(SFP).We investigate the epitaxial growth of high-quality GaAs on a Ge(001)mesa array,via molecular beam epitaxy.Following a systematic study of the Ge terrace via an in situ scanning tunneling microscope,an atomically step-free terrace on the Ge mesa measuring up to 5×5μm^(2) is obtained,under optimized growth conditions.The step-free terrace has a single-phase c(4×2)surface reconstruction.The deposition of a high-quality GaAs layer with no APD and SFP is then achieved on this step-free Ge terrace.High-resolution transmission electron microscopy and electron channel contrast image characterizations reveal the defect-free growth of the GaAs layer on the step-free Ge mesa.Furthermore,InAs quantum dots on this GaAs/Ge mesa reveal photoluminescent intensity comparable to that achieved on a GaAs substrate,which further confirms the high quality of the GaAs layer on Ge.