A low-shrinkage-stress and anti-bacterial adherent dental resin composite: physicochemical properties and biocompatibility.

Polymerisation shrinkage and biofilm accumulation are the two main problems associated with dental resin composites (DRCs) that induce secondary caries, which can cause restoration failure. Polymerisation shrinkage can lead to microleakage gaps between the tooth and the DRCs, causing the aggregation of bacteria and development of secondary caries. Reducing the shrinkage stress (SS) and improving the resistance to bacterial adhesion have always been the focus of this field in modifying DRCs. A thiol-ene resin system can effectively reduce the polymerisation SS via its step-growth mechanism for delaying the gel point. Fluorinated compounds can reduce the surface free energies, thereby reducing bacterial adhesion. Thus, in this study, a range of mass fractions (0, 10, 20, 30, and 40 wt%) of a fluorinated thiol-ene resin system were added to a fluorinated dimethacrylate resin system/tricyclo decanedimethanol diacrylate to create a fluorinated methacrylate-thiol-ene ternary resin matrix. DRCs were prepared using the obtained ternary resin matrix, and their physical and chemical properties, effect on bacterial adhesion, and biocompatibility were investigated. The results demonstrated that the volumetric shrinkage and SS of the DRCs were reduced with no reduction in conversion degree even after the thiol-ene resin system was added. All DRC-based fluorinated resin systems exhibited an excellent anti-bacterial adhesion effect, as evidenced by the colony-forming unit counts, live/dead bacterial staining, and crystal violet staining tests against Streptococcus mutans (S. mutans). The genetic expressions associated with the bacterial adhesion of S. mutans were substantially affected after being cultured with fluorinated DRCs. All fluorinated DRCs demonstrated good biocompatibility through the in vitro cytotoxicity test and live/dead staining images of the L-929 cells. The above results illustrate that the DRCs based on the fluorinated methacrylate-thiol-ene resin matrix can be potentially applied in clinical practice due to their low SS and anti-bacterial adhesion effect.

Expert consensus on digital guided therapy for endodontic diseases.

Digital guided therapy (DGT) has been advocated as a contemporary computer-aided technique for treating endodontic diseases in recent decades. The concept of DGT for endodontic diseases is categorized into static guided endodontics (SGE), necessitating a meticulously designed template, and dynamic guided endodontics (DGE), which utilizes an optical triangulation tracking system. Based on cone-beam computed tomography (CBCT) images superimposed with or without oral scan (OS) data, a virtual template is crafted through software and subsequently translated into a 3-dimensional (3D) printing for SGE, while the system guides the drilling path with a real-time navigation in DGE. DGT was reported to resolve a series of challenging endodontic cases, including teeth with pulp obliteration, teeth with anatomical abnormalities, teeth requiring retreatment, posterior teeth needing endodontic microsurgery, and tooth autotransplantation. Case reports and basic researches all demonstrate that DGT stand as a precise, time-saving, and minimally invasive approach in contrast to conventional freehand method. This expert consensus mainly introduces the case selection, general workflow, evaluation, and impact factor of DGT, which could provide an alternative working strategy in endodontic treatment.

Low shrinkage bulk-filled dental resin composites with non-estrogenic dimethacrylate.

This study synthesized and characterized different proportions of nonestrogenic di(meth)acrylate 9,9-bis[4-((2-(2-methacryloyloxy)ethyl-carbamate)ethoxy)phenyl] fluorine (Bis-EFMA)-based resin composite systems to study their physical, chemical, optical and biological characteristics, and adhesive properties after bonding to a tooth. The estrogenic activity of raw materials was evaluated and compared with estrogen and commercial bisphenol A. After photopolymerization, all resin composite systems were prepared, and their properties were systematically investigated. Notably, the nonestrogenic di(meth)acrylate Bis-EFMA exhibited a more suitable refractive index, excellent biocompatibility, low marginal microleakage and improved bonding strength. Except for the pure UDMA and Bis-EFMA groups, the depth of cure and Vickers microhardness ratios of all the other groups met the requirements of bulk filling (one-time curing depth of more than 4 mm). Bis-EFMA resin systems exhibited lower volumetric polymerization shrinkage (about 3-5%), higher curing depth (>6 mm in specific proportions), mechanical properties (flexural strength of 120-130 MPa, etc.), and microtensile bonding strength (>27.8 MPa), which were comparable or superior to Bis-GMA or commercial composites. Herein, we believe that the novel nonestrogenic di(meth)acrylate (Bis-EFMA) has a wide application prospect as an alternative to Bis-GMA.

Predicting case difficulty in endodontic microsurgery using machine learning algorithms.

OBJECTIVES: The study aimed to develop and validate machine learning models for case difficulty prediction in endodontic microsurgery, assisting clinicians in preoperative analysis. METHODS: The cone-beam computed tomographic images were collected from 261 patients with 341 teeth and used for radiographic examination and measurement. Through linear regression (LR), support vector regression (SVR), and extreme gradient boosting (XGBoost) algorithms, four models were established according to different loss functions, including the L1-loss LR model, L2-loss LR model, SVR model and XGBoost model. Five-fold cross-validation was applied in model training and validation. Explained variance score (EVS), coefficient of determination (R2), mean absolute error (MAE), mean squared error (MSE) and median absolute error (MedAE) were calculated to evaluate the prediction performance. RESULTS: The MAE, MSE and MedAE values ​​of the XGBoost model were the lowest, which were 0.1010, 0.0391 and 0.0235, respectively. The EVS and R2 values ​​of the XGBoost model were the highest, which were 0.7885 and 0.7967, respectively. The factors used to predict the case difficulty in endodontic microsurgery were ordered according to their relative importance, including lesion size, the distance between apex and adjacent important anatomical structures, root filling density, root apex diameter, root resorption, tooth type, tooth length, root filling length, root canal curvature and the number of root canals. CONCLUSIONS: The XGBoost model outperformed the LR and SVR models on all evaluation metrics, which can assist clinicians in preoperative analysis. The relative feature importance provides a reference to develop the scoring system for case difficulty assessment in endodontic microsurgery. CLINICAL SIGNIFICANCE: Preoperative case assessment is a crucial step to identify potential risks and make referral decisions. Machine learning models for case difficulty prediction in endodontic microsurgery can assist clinicians in preoperative analysis efficiently and accurately.

A novel model to evaluate the fatigue resistance of NiTi instruments: Rotational and axial movement at body temperature.

To develop a model to test cyclic fatigue resistance of TruNatomy instruments undergoing rotational and axial movement at body temperature. A total of 288 Prime and Medium instruments were subjected to cyclic fatigue testing in simulated canals (at 37°C) using a model with either rotational movement only or rotational and axial movement simultaneously. Two different sized canals and three different types of curvatures were tested for each instrument (30/0.04 and 30/0.06 for Prime; 38/0.04 and 40/0.06 for Medium). The number of cycles to failure (fatigue resistance) was recorded. Rotational and axial movement of instruments led to greater fatigue resistance compared with rotational movement alone. Apical curvatures led to greater fatigue resistance than curvatures in the coronal and middle third. The developed dynamic model at body temperature to evaluate fatigue resistance of instrument closer simulates clinical scenarios.

Combined Application of Virtual Simulation Technology and 3-Dimensional-Printed Computer-Aided Rapid Prototyping in Autotransplantation of a Mature Third Molar.

The use of computer-aided rapid prototyping (CARP) models was considered to reduce surgical trauma and improve outcomes when autotransplantation of teeth (ATT) became a viable alternative for dental rehabilitation. However, ATT is considered technique-sensitive due to its series of complicated surgical procedures and unfavorable outcomes in complex cases. This study reported a novel autotransplantation technique of a 28-year-old patient with an unrestorable lower first molar (#36) with double roots. Regardless of a large shape deviation, a lower third molar (#38) with a completely single root formation was used as the donor tooth. ATT was performed with a combined use of virtual simulation, CARP model-based rehearsed surgery, and tooth replica-guided surgery. A 3D virtual model of the donor and recipient site was generated from cone-beam computed tomographic (CBCT) radiographs prior to surgery for direct virtual superimposition simulation and CARP model fabrication. The virtual simulation indicated that it was necessary to retain cervical alveolar bone during the surgical socket preparation, and an intensive surgical rehearsal was performed on the CARP models. The donor tooth replica was used during the procedure to guide precise socket preparation and avoid periodontal ligament injury. Without an additional fitting trial and extra-alveolar storage, the donor tooth settled naturally into the recipient socket within 30 s. The transplanted tooth showed excellent stability and received routine root canal treatment three weeks post-surgery, and the one-year follow-up examination verified the PDL healing outcome and normal functioning. Patient was satisfied with the transplanted tooth. This cutting-edge technology combines virtual simulation, digital surgery planning, and guided surgery implementation to ensure predictable and minimally invasive therapy in complex cases.

Preparation of Bis-GMA free dental resin composites with anti-adhesion effect against Streptococcus mutans using synthesized fluorine-containing methacrylate (DFMA).

With purpose of preparing Bis-GMA free dental resin composites (DRCs) with anti-adhesion effect against Streptococcus mutans (S. mutans), a new fluorinated dimethacrylate (DFMA) was synthesized and used as base resin of DRCs. Two reactive diluents TEGDMA and SR833s were mixed with DFMA separately to prepare resin matrixes. After mixing with inorganic fillers, two DFMA based DRCs were obtained and named as DT (DFMA/TEGDMA) and DS (DFMA/SR833s) according to the resin matrix composition. Bis-GMA based DRC (BT) was used as control. The double bond conversion (DC), bacteria adhesion, mucin adsorption, contact angle, surface free energy, volumetric shrinkage (VS), shrinkage stress (SS), water sorption (WS) and solubility (SL), flexural strength (FS) and modulus (FM) before and after water immersion were investigated, and all the results were statistically analyzed with ANOVA analysis. The results showed that DT and DS had comparable (ρ > 0.05) surface free energy which was lower than that of BT (ρ < 0.05). Compared with BT, with the same surface roughness (ρ > 0.05), less amount of S. mutans was accumulated on the surface of DT and DS (ρ < 0.05). In all DRCs, the DS had the best resistance to mucin adsorption (ρ < 0.05) due to its high hydrophobicity. Compared with BT, both DFMA based DRCs had advantages such as lower VS and SS (ρ < 0.05), lower WS and SL (ρ < 0.05), and better water resistance. The DS, which had antibacterial adhesion effect, mucin adsorption resistance, lowest VS and SL (ρ < 0.05), and the highest FS and FM no matter before or after water immersion (ρ < 0.05) was considered to have the best comprehensive properties in all DRCs.

Machine learning models for prognosis prediction in endodontic microsurgery.

OBJECTIVES: This study aimed to establish and validate machine learning models for prognosis prediction in endodontic microsurgery, avoiding treatment failure and supporting clinical decision-making. METHODS: A total of 234 teeth from 178 patients were included in this study. We developed gradient boosting machine (GBM) and random forest (RF) models. For each model, 80% of the data were randomly selected for the training set and the remaining 20% were used as the test set. A stratified 5-fold cross-validation approach was used in model training and testing. Correlation analysis and importance ranking were conducted for feature selection. The predictive accuracy, sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV), F1 score, and the area under the curve (AUC) of receiver operating characteristic (ROC) curves were calculated to evaluate the predictive performance. RESULTS: There were eight important predictors, including tooth type, lesion size, type of bone defect, root filling density, root filling length, apical extension of post, age, and sex. For the GBM model, the predictive accuracy was 0.80, with a sensitivity of 0.92, specificity of 0.71, PPV of 0.71, NPV of 0.92, F1 of 0.80, and AUC of 0.88. For the RF model, the accuracy was 0.80, with a sensitivity of 0.85, specificity of 0.76, PPV of 0.73, NPV of 0.87, F1 of 0.79, and AUC of 0.83. CONCLUSIONS: The trained models were developed by eight common variables, showing the potential ability to predict the prognosis of endodontic microsurgery. The GBM model outperformed the RF model slightly on our dataset. CLINICAL SIGNIFICANCE: Clinicians can use machine learning models for preoperative analysis in endodontic microsurgery. The models are expected to improve the efficiency of clinical decision-making and assist in clinician-patient communication.

A comparative study of dentinal tubule penetration and the retreatability of EndoSequence BC Sealer HiFlow, iRoot SP, and AH Plus with different obturation techniques.

OBJECTIVES: This study aimed to evaluate dentinal tubule penetration and the retreatability of EndoSequence BC Sealer HiFlow (HiFlow), iRoot SP, and AH Plus when using the single-cone (SC) or continuous wave condensation (CWC) technique. MATERIALS AND METHODS: Sixty-five single-rooted teeth were instrumented and randomly divided into 5 groups: group 1, AH Plus/CWC; group 2, iRoot SP/CWC; group 3, iRoot SP/SC; group 4, HiFlow/CWC; and group 5, HiFlow/SC. The ability to re-establish patency during endodontic retreatment was recorded, as was the time taken to reach the working length. Dentinal tubule penetration and remaining debris after retreatment were evaluated by confocal microscopy and scanning electron microscopy. Data were analyzed by Kruskal-Wallis test and Dunn's multiple comparisons test (α = 0.05). RESULTS: The HiFlow/CWC and iRoot SP/CWC groups required more time to reach the working length than groups that underwent the SC technique regardless of the sealer used (P < .05). The HiFlow/CWC group showed a significantly higher percentage of sealer penetration area than that of the iRoot SP/SC at 4 mm from the apex (P < .05) and penetrated deeper into dentinal tubules than iRoot SP/SC at both 8-mm and 12-mm levels (P < .05). Moreover, the HiFlow/CWC and HiFlow/SC groups demonstrated less remaining sealer along the canal wall than AH Plus/CWC group at 4-mm level (P < .05). CONCLUSIONS: HiFlow/CWC technique showed better performance in dentinal tubule penetration than that of iRoot SP/SC. Both HiFlow and iRoot SP combined with CWC technique groups required more retreatment time than the other groups. Furthermore, using HiFlow with either the CWC or SC technique left less remaining sealer at 4-mm level than using AH Plus with the CWC technique during retreatment. CLINICAL RELEVANCE: With favorable performance in dentinal tubule penetration and retreatability in endodontic retreatment, the combined use of EndoSequence BC Sealer HiFlow with the recommended continuous wave condensation technique may be a worthwhile choice in root canal treatment.

Effect of canal curvature location on the cyclic fatigue resistance of reciprocating files.

OBJECTIVES: To determine the effect of the location of the canal curvature on the fatigue resistance of WaveOne (WO), WaveOne Gold (WOG), Reciproc (Rec), and Reciproc Blue (RecB) files, and to examine the phase transformation behaviors of the reciprocating file systems. MATERIAL AND METHODS: The instruments were subjected to fatigue testing in five artificial canals with a curvature of 60° angle and a 3-mm radius. The location of the curvature was unique for each canal. Each file was inserted 16 mm into the canal and operated until fracture occurred. The time to fracture was recorded and the length of the fragment was measured. Differential scanning calorimetry was used to characterize the thermal behavior of the files. The number of cycles to failure was analyzed using two-way analysis of variance and the post hoc Tukey test. The Kruskal-Wallis test was used to compare the mean fragment lengths between groups. RESULTS: The instruments had significantly lower fatigue resistance in canals with curvatures in the middle and coronal canals compared with those with apical curvatures (p < 0.05). At all tested curvature locations, RecB had superior fatigue resistance compared with WO and Rec (p < 0.05). There were no significant differences between WOG and Rec in canals with curvatures in the middle and coronal canals. The DSC thermograms for RecB exhibit a single exothermic peak during cooling but double endothermic peaks during heating indicating that a two-step phase transformation from martensite to R-phase to austenite takes place. CONCLUSIONS: The reciprocating instruments experience decreased cyclic fatigue resistance when operated in canals with coronal- and middle-third curvatures when compared with curvatures in the apical-third. Instrumenting coronally positioned curvatures with reciprocating files needs to be performed with caution. CLINICAL RELEVANCE: The location of the root canal's curvature influences the fracture resistance of rotary files that are used with reciprocating movements. Therefore, caution needs to be exercised when using reciprocating instruments in canals with coronal or middle curvatures.

Cone beam computed tomography analysis of accessory canals of the canalis sinuosus: A prevalent but often overlooked anatomical variation in the anterior maxilla.

STATEMENT OF PROBLEM: Accessory canals of the canalis sinuosus, a bony canal carrying the anterior superior alveolar nerve and vessels, can often be present but overlooked in the anterior maxilla. Dental implant placement in this area may damage neurovascular branches if this anatomic variation is not carefully identified, resulting in unexpected complications. PURPOSE: The purpose of this retrospective study was to identify accessory canals of the canalis sinuosus and analyze their relationship to the terminal canalis sinuosus and anterior maxilla in Chinese patients to provide a warning for surgeons operating in the anterior maxilla. MATERIAL AND METHODS: Cone beam computed tomography (CBCT) scans of 1007 Chinese patients were examined to identify the prevalence and size of accessory canals with at least 1.0-mm diameter. Axial position of this canal was classified referring to the nasal cavity and adjacent teeth. Its sagittal position was determined by the distance from the bifurcation site of canalis sinuosus to the buccal alveolar crest and the distance from the canal opening to the palatal alveolar crest. Diameter of the terminal canalis sinuosus, distance from the terminal canalis sinuosus to the buccal alveolar crest, and anterior maxillary volume were measured on all scans. Binary logistic regression and the Spearman rank correlation coefficient were used for prevalence and diameter analysis. RESULTS: The prevalence of the accessory canal was 36.9%, positively correlated the anterior maxillary volume (OR 1.408) and negatively correlated with the distance from the terminal canalis sinuosus to the buccal alveolar crest (OR 0.921). Average diameter of such canal was 1.1 ±0.1 mm, significantly higher in men, positively correlated with the diameter of terminal canalis sinuosus (rs=0.163) and the distance from the canal opening to the palatal alveolar crest (rs=0.192). All accessory canals started below the buccal cortical bone, 19.3 ±2.7 mm away from the buccal alveolar crest. There were 61.9% accessory canals opened between the central and the lateral incisors. Openings here and in the central incisor region were closer to the alveolar crest than that between the lateral incisor and the canine (P<.05). CONCLUSIONS: Accessory canals of the canalis sinuosus have high prevalence in the anterior maxilla in a Chinese population. Large anterior maxillary volume has been demonstrated as a risk factor associated with the presence of such canals. The region between the central and the lateral incisors was a predominant location. Openings in this region were closer to the alveolar crest than those between the lateral incisor and the canine.

Full-cycle management of endodontic microsurgery / 口腔疾病防治

@#Contemporary endodontic microsurgery has emerged as a significant treatment modality in the retention of teeth with persistent apical periodontitis. This article proposes the concept of the full-cycle clinical management of endodontic microsurgery based on the condition of the patient and tooth, attempting to develop a comprehensive strategy for the examination, treatment and follow-up to save natural teeth. Full-cycle clinical management included preoperative consideration of the general condition and surgical site and selection of cases for endodontic microsurgery; intraoperative application of techniques such as lasers, "bone window" technique and targeted endodontic microsurgery to make the surgical approaches more varied and the operation minimally invasive; postoperative outcome assessment according to the history, clinical and radiographic examination; and analysis of the short- and long-term outcomes.

Effect of Curvature Location on Fatigue Resistance of Five Nickel-titanium Files Determined at Body Temperature.

INTRODUCTION: The purpose of this study was to evaluate the effect of 5 different curvature locations on the fatigue resistance of thermomechanically treated nickel-titanium (NiTi) files and superelastic NiTi files at body temperature and to document the corresponding phase transformations. METHODS: EndoSequence (ES; Brasseler USA, Savannah, GA), EndoSequence CM (ESCM, Brasseler USA), K3 (SybronEndo, Orange, CA), K3XF (SybronEndo), and Vortex Blue (VB; Dentsply Tulsa Dental Specialties, Tulsa, OK) NiTi files (size 25/.04) were subjected to fatigue tests inside customized artificial canals containing a curvature of 60° and a 3-mm radius. There were 5 different canals based on the location of initial curvature; these included groups in which the distance between the canal orifice and the location of the curvature (DOC) was 5, 6, 8, 10, and 11 mm. The model canal was immersed in water at 37°C ± 1°C. The number of cycles to failure (Nf) was recorded, and the fracture surface of the fragments was examined by scanning electron microscopy. Two unused files of each brand were examined by differential scanning calorimetry. RESULTS: The Nf was highest in the 10-mm and 11-mm DOC groups and lowest with the 5-mm and 6-mm DOC groups (P < .05). ESCM files had the highest fatigue resistance followed by the VB, K3XF, K3, and ES files (P < .05). ESCM files had the highest Nf (P < .05), and ES and K3 files had the lowest Nf (P < .05) depending on the curvature location. Two endothermic peaks were observed on the heating curve of the heat-treated files (ESCM, K3XF, and VB). CONCLUSIONS: The location of the canal curvature had a significant effect on the fatigue resistance of both heat-treated and superelastic NiTi files. The fatigue life of files in the coronal curve was quite short.

Effect of Long-term Exposure to Peptides on Mono- and Multispecies Biofilms in Dentinal Tubules.

INTRODUCTION: The aim of this study was to evaluate the antibiofilm effectiveness of 2% chlorhexidine (CHX) and peptides 1018 and DJK-5 used either alone or in a mixture (peptide and 2% CHX) against Enterococcus faecalis and multispecies biofilms in dentin canals after short-term and long-term exposure. METHODS: One hundred eighty dentin blocks were prepared and filled with E. faecalis or multispecies bacteria by centrifugation. Three-week-old biofilms in dentin were subjected to 2% CHX, DJK-5 (10 µg/mL), 1018 (10 µg/mL), DJK-5 + 2% CHX, or 1018 + 2% CHX for short-term (1 or 3 minutes), short-term exposure after 24 hours, and long-term exposure (24 hours of exposure). The antibacterial efficacy was determined by live/dead bacterial viability staining and confocal laser scanning microscopy. RESULTS: Peptide DJK-5 with or without CHX was the most effective agent against all the biofilms (P < .05), killing 77% of biofilm bacteria in 1 minute. No significant difference in bacterial killing was detected between the first 3 minutes of exposure (>81%) and after 24 hours of exposure (83%) to DJK-5 or DJK-5 + CHX. Chlorhexidine and peptide 1018 had a weaker antibiofilm effect than DJK-5, and their effect was time dependent (P < .05) with a maximum killing of 60% after 24 hours of exposure. CONCLUSIONS: Peptide DJK-5 alone and together with CHX had a rapid antibacterial effect against dentin infection. An additional antibacterial effect by CHX and peptide 1018 was achieved after a 24-hour long-term exposure.

Fatigue resistance of ProTaper gold exposed to high-concentration sodium hypochlorite in double curvature artificial canal.

This study aimed to evaluate and compare the fatigue resistance of ProTaper Gold (PTG) and ProTaper Universal (PTU) in artificial single and double curvature canals in 5% sodium hypochlorite (NaOCl) at body temperature (37 °C). PTG and PTU files (size F1) were subjected to fatigue tests in two different artificial ceramic canals. The single curvature model had a 60° curvature angle with a 5 mm radius. The double curvature model had a 60° curvature angle with a 5 mm radius and a second 30° curvature with a 2 mm radius. A file segment was introduced into the artificial canal and immersed in water or 5% NaOCl at 37 °C. The total number of cycles to fracture (NCF) was recorded. Data were analyzed using t-test and linear regression analysis. The NCF of all files was significantly influenced by the type of NiTi metal alloy (P < .01), canal curvatures (P < .01), and the environmental conditions (P < .05). PTG had higher fatigue resistance than PTU files in both single and double curvature canals (P < .05). The NCF of PTU files in 5% NaOCl was shorter than that in water (P < .05). The mean length of broken PTG was significantly shorter than those of PTU files in both single and double curvature canals (P < .01). The fatigue performance of PTG is better than that of PTU in both single and double curvature. Environmental conditions may affect the fatigue behavior of PTU files with single curvature.

Modeling Oral Multispecies Biofilm Recovery After Antibacterial Treatment.

Recovery of multispecies oral biofilms is investigated following treatment by chlorhexidine gluconate (CHX), iodine-potassium iodide (IPI) and Sodium hypochlorite (NaOCl) both experimentally and theoretically. Experimentally, biofilms taken from two donors were exposed to the three antibacterial solutions (irrigants), respectively, for 10 minutes. We observe that (a) live bacterial cell ratios decline for a week after the exposure and the trend then reverses beyond the week; after fifteen weeks, live bacterial cell ratios in biofilms fully return to their pretreatment levels; (b) NaOCl is shown as the strongest antibacterial agent for the oral biofilms; (c) multispecies oral biofilms from different donors showed no difference in their susceptibility to all the bacterial solutions. Guided by the experiment, a mathematical model for biofilm dynamics is developed, accounting for multiple bacterial phenotypes, quorum sensing, and growth factor proteins, to describe the nonlinear time evolutionary behavior of the biofilms. The model captures time evolutionary dynamics of biofilms before and after antibacterial treatment very well. It reveals the important role played by quorum sensing molecules and growth factors in biofilm recovery and verifies that the source of biofilms has a minimal effect to their recovery. The model is also applied to describe the state of biofilms of various ages treated respectively by CHX, IPI and NaOCl, taken from different donors. Good agreement with experimental data predicted by the model is obtained as well, confirming its applicability to modeling biofilm dynamics in general.

Selective activities of STAMPs against Streptococcus mutans.

The present study aimed to design, synthesize and screen specifically targeted antimicrobial peptides (STAMPs) that can selectively kill Streptococcus mutans (S. mutans) in the biofilm, and to detect protein metabolism, in order to investigate the mechanism of the antibacterial functions of STAMPs against S. mutans. A series of STAMPs were synthesized, and their effects on the selective antibacterial activity of S. mutans on single species and multi-species biofilms under the condition of the planktonic state were studied. The total protein of S. mutans was extracted before and after C11H, and matrix-assisted laser adsorption ionization-time of flight mass spectrometry identification was performed. The antibacterial activity on planktonic S. mutans was increased 3- to 4-fold via C8H, C11H, C12H, C13H, and C14H compared with hLF1-11 (H) alone, and there was no difference between Streptococcus gordonii (S. gordonii) and Streptococcus sanguis (S. sanguis). C8H, C11H, C12H, C13H, and C14H had significant inhibitory effects on the growth of S. mutans biofilm, but there were no significant effects on S. gordonii and S. sanguis biofilms. The number of S. mutans in biofilm decreased at 4 h after C8H, C11H, C12H, C13H and C14H and C8, C11, C12, C13 and C14 had no effect on the growth of planktonic and biofilm states of S. mutans, S. gordonii and S. sanguis species. C11H and C12H exhibited the most obvious effects, followed by C13H and C14H, and then C8H. A total of 21 protein spots with a mean change ratio of 1.5 were identified, all of which were downregulated after C11H. A total of 19 proteins were successfully identified, including cell cycle-relative proteins, nucleic acid metabolism-related enzymes and proteins, virulence factors, protein biosynthesis and regulation, proteins involved in energy metabolism, and proteins with unknown function. In the present study, STAMPs with selective antibacterial activity against S. mutans grown in planktonic or biofilm states but without obvious effects on oral Streptococci and multi-species biofilm were successfully designed and synthesized. Differential protein expression before and after C11H was identified. The mechanism of the antibacterial function was also discussed. Results of the present study laid the foundation for application of STAMPs in the prevention and treatment of dental caries.

Low Environmental Temperature Influences the Fatigue Resistance of Nickel-titanium Files.

INTRODUCTION: The purpose of this study was to evaluate the effect of different temperatures (0°C, 10°C, 22°C, 37°C, and 60°C) on the cyclic fatigue life of nickel-titanium (NiTi) files using a new fatigue test model in zirconium oxide. METHODS: Three superelastic NiTi files (EndoSequence [Brasseler USA, Savannah, GA], ProFile [Dentsply Tulsa Dental Specialties, Tulsa, OK], and K3 [SybronEndo, Orange, CA]), and 3 heat-treated (K3XF [SybronEndo], Vortex [Dentsply Tulsa Dental Specialties], and HyFlex CM [Coltene-Whaledent, Allstetten, Switzerland]) NiTi files, all size 25/.04, were subjected to cyclic fatigue tests inside a novel, artificial ceramic canal with a curvature of 60° and a 5-mm radius. The model was immersed in water at 5 different preset temperatures. The number of cycles to failure (NCF) was recorded, and the fracture surface of the fragments was examined by a scanning electron microscope. The data were analyzed using 2-way analysis of variance with the significance level at 0.05. RESULTS: When the temperature was reduced from 60°C to 0°C, the NCF significantly increased from over 2 to 10 times for the NiTi file groups (P < .01). K3XF had the highest fatigue resistance of all files at 0°C (P < .05). Vortex files had the highest NCF at 10°C-60°C. The NCF of heat-treated files was significantly higher than superelastic NiTi files at 10°C and 20°C (P < .05). There was no significant difference in the NCF of HyFlex CM at 0°C and 22°C. There was little difference in the fractographic appearance among different temperatures, except that the fraction area occupied by the dimple region of some instruments at 0°C was slightly smaller than at 60°C. CONCLUSIONS: Cooling down to low temperatures may be an interesting strategy to improve the fatigue resistance of rotary NiTi files.

Biomarker MicroRNAs for Diagnosis of Oral Squamous Cell Carcinoma Identified Based on Gene Expression Data and MicroRNA-mRNA Network Analysis.

Oral squamous cell carcinoma is one of the most malignant tumors with high mortality rate worldwide. Biomarker discovery is critical for early diagnosis and precision treatment of this disease. MicroRNAs are small noncoding RNA molecules which often regulate essential biological processes and are good candidates for biomarkers. By integrative analysis of both the cancer-associated gene expression data and microRNA-mRNA network, miR-148b-3p, miR-629-3p, miR-27a-3p, and miR-142-3p were screened as novel diagnostic biomarkers for oral squamous cell carcinoma based on their unique regulatory abilities in the network structure of the conditional microRNA-mRNA network and their important functions. These findings were confirmed by literature verification and functional enrichment analysis. Future experimental validation is expected for the further investigation of their molecular mechanisms.

Fatigue Resistance of Nickel-titanium Instruments Exposed to High-concentration Hypochlorite.

INTRODUCTION: The purpose of this study was to introduce a new fatigue test model that simulates the clinical situation for evaluating the corrosion effect of 5.25% sodium hypochlorite (NaOCl) on nickel-titanium (NiTi) files and to evaluate the effect of 3 different temperatures (22°C, 37°C, and 60°C) on the cyclic fatigue of these files. METHODS: Three NiTi files (size 25/.04), K3 (SybronEndo, Orange, CA), K3XF (SybronEndo), and Vortex (Dentsply Tulsa Dental Specialties, Tulsa, OK), were subjected to cyclic fatigue tests inside a novel artificial ceramic canal with a curvature of 60° and a 5-mm radius. A 19-mm-long file segment from the tip was introduced into the canal and immersed in water or 5.25% NaOCl at 3 different temperatures, and the number of revolutions to fracture (Nf) was recorded. The fracture surface of all fragments was examined by a scanning electron microscope. Data were analyzed using univariate analysis of variance with the significance level at 0.05. RESULTS: The Nf of Vortex files was the highest followed by K3XF and K3 (P < .05) at all conditions. The Nf of all files was highest at 22°C and lowest at 60°C (P < .05). However, no difference in Nf was detected in Vortex files between 22°C and 37°C. The Nf of all files in 5.25% NaOCl was shorter than that in water although there was no statistically significant difference. No pitting or crevice corrosion was observed on the fracture surface. CONCLUSIONS: NaOCl, 5.25%, does not significantly affect the fatigue behavior of NiTi files. The fatigue resistance should be tested under specific temperature conditions. The austenite finish temperature of a file is important in determining the fracture risk at body temperature.