The role of the STAS domain in SLC26A9 for chloride ion transporter function.

The anion exchanger solute carrier family 26 (SLC26)A9, consisting of the transmembrane (TM) domain and the cytoplasmic STAS domain, plays an essential role in regulating chloride transport across cell membranes. Recent studies have indicated that C-terminal helices block the entrance of the putative ion transport pathway. However, the precise functions of the STAS domain and C-terminal helix, as well as the underlying molecular mechanisms governing the transport process, remain poorly understood. In this study, we performed molecular dynamics simulations of three distinct models of human SLC26A9, full-length, STAS domain removal (ΔSTAS), and C-terminus removal (ΔC), to investigate their conformational dynamics and ion-binding properties. Stable binding of ions to the binding sites was exclusively observed in the ΔC model in these simulations. Comparing the full-length and ΔC simulations, the ΔC model displayed enhanced motion of the STAS domain. Furthermore, comparing the ΔSTAS and ΔC simulations, the ΔSTAS simulation failed to exhibit stable ion bindings to the sites despite the absence of the C-terminus blocking the ion transmission pathway in both systems. These results suggest that the removal of the C-terminus not only unblocks the access of ions to the permeation pathway but also triggers STAS domain motion, gating the TM domain to promote ions' entry into their binding site. Further analysis revealed that the asymmetric motion of the STAS domain leads to the expansion of the ion permeation pathway within the TM domain, resulting in the stiffening of the flexible TM12 helix near the ion-binding site. This structural change in the TM12 helix stabilizes chloride ion binding, which is essential for SLC26A9's alternate-access mechanism. Overall, our study provides new insights into the molecular mechanisms of SLC26A9 transport and may pave the way for the development of novel treatments for diseases associated with dysregulated ion transport.

Phase transformation and mechanical properties of heat-treated nickel-titanium rotary endodontic instruments at room and body temperatures.

BACKGROUND: The aim of this study was to evaluate the phase composition, phase transformation temperatures, bending property, and cyclic fatigue resistance of different heat-treated nickel-titanium (NiTi) rotary instruments with the same tip diameter and taper at room (RT; 25 ± 1 °C) and body (BT; 37 ± 1 °C) temperatures. METHODS: Five heat-treated NiTi rotary instruments, HyFlex EDM (EDM), HyFlex CM (CM), Vortex Blue (VB), RE file CT (RE) and JIZAI, and a non-heat-treated NiTi rotary instrument (Mtwo) with a size 40, 0.04 taper were investigated. Temperature-dependent phase transformation was examined with differential scanning calorimetry (DSC). The bending loads of the instruments at RT and BT were evaluated using a cantilever-bending test. Cyclic fatigue resistance at RT and BT was measured using a dynamic test, during which the instruments were rotated in combination with a 2-mm back-and-forth motion in an artificial curved canal, and the number of cycles to failure (NCF) was determined. The results were analyzed using two-way repeated measures analysis of variance, a simple main effect test, and the Bonferroni test (α = 0.05). RESULTS: DSC results indicated that EDM and Mtwo were primarily composed of martensite/R-phase and austenite, respectively, while the other heat-treated instruments were composed of a mix of martensite/R-phase and austenite at the tested temperatures. Regardless of the temperature setting, the bending loads of heat-treated instruments were significantly lower than those of Mtwo (p < 0.05). EDM showed the lowest bending loads and highest NCF at both temperatures (p < 0.05). CM, VB, and JIZAI showed significantly higher bending loads at BT than at RT (p < 0.05). The NCF of all the heat-treated instruments, except VB, was lower at BT than at RT (p < 0.05). At BT, the NCF of CM, VB, RE, and JIZAI were not significantly higher than that of Mtwo (p > 0.05). CONCLUSIONS: Heat-treated NiTi instruments exhibited lower bending loads and higher NCF values than Mtwo. However, this tendency was less pronounced at BT than at RT, especially in the NCF values of instruments with a mixture of martensite/R-phase and austenite phases at the tested temperatures.

Effect of kinematics on the torque/force generation, surface characteristics, and shaping ability of a nickel-titanium rotary glide path instrument: An ex vivo study.

AIM: To evaluate the effect of various rotational motions on the torque/force generation, surface wear, and shaping ability of the ProGlider glide path instrument (Dentsply Sirona). METHODOLOGY: Mesiobuccal and mesiolingual canals of mandibular molars were selected based on the canal volume, length, angle of curvature (25°-40°), and radius of curvature (4-8 mm) after micro-computed tomographic scanning. The samples were randomly assigned to four groups (n = 13, each) according to movement kinematics [continuous rotation (CR; 300 rpm), optimum torque reverse motion (OTR; 180° forward and 90° reverse when torque >0.4 N cm), time-dependent reciprocal motion (TmR; 180° forward and 90° reverse), and optimal glide path motion (OGP; a combination of 90° forward, 90° reverse, 90° forward, and 120° reverse)]. Instrumentation was performed with an automated root canal instrument and torque/force analysing device. Maximum torque/force values, canal volume changes, and canal-centring ratios at 1, 3, 5, and 7 mm were evaluated. Surface defects (pits, grooves, microcracks, blunt cutting edges, and disruption of cutting edges) and spiral distortion on the ProGlider instrument were scored at the tip and 5 mm short of the tip before and after five consecutive uses with scanning electron microscopy. The Kruskal-Wallis test followed by Dunn's post-test with Bonferroni correction and Wilcoxon signed-rank test were used to analyse the data (α = 0.05). RESULTS: Optimal glide path motion generated significantly less clockwise torque and greater upward force than other groups (p < .05). OGP resulted in significantly fewer surface defects than CR (p < .05). In OGP and CR, the tip exhibited more surface defects than 5 mm short of the tip (p < .05). CR resulted in greater volume changes than OGP and TmR (p < .05) and greater centring ratios (i.e., more deviation) than OGP at 1 mm and OTR at 3 mm (p < .05). CONCLUSIONS: Under laboratory conditions using the ProGlider instrument, OGP generated significantly less clockwise torque and greater upward force than the other rotatory motions. OGP generated fewer superficial defects than CR, and the three modes of reciprocal rotation better maintained the apical curvature of root canals than CR with the ProGlider instrument.

Increased Stress Concentration in Prosthesis, Adhesive Cement, and Periodontal Tissue with Zirconia RBFDPs by the Reduced Alveolar Bone Height.

PURPOSE: To investigate the risk of debonding of resin-bonded fixed dental prosthesis frameworks and the effects on the periodontal tissue in patients with reduced alveolar bone levels. MATERIALS AND METHODS: The abutment teeth were the upper central incisor and the canine. Resin-bonded fixed dental prosthesis framework fabricated using zirconia was set to models with five different alveolar bone levels. A 200-N load (the maximum clenching force of the anterior teeth) was applied to the center of the pontic to analyze the internal stress on the framework, adhesive cement, and periodontal tissue using finite element analysis. RESULTS: The mean maximum principal stress generated in the framework was 25.33 and 29.35 MPa in the models with the normal and the lowest alveolar bone level, respectively. Regarding shear stress on the adhesive cement, stress concentration was observed on the connector side in all models, and it increased on the cervical side of the central incisor as the alveolar bone level decreased. In addition, the mean maximum and minimum principal strains generated on the periodontal ligament of the central incisor and canine tended to increase as alveolar bone loss progressed. Furthermore, the mean maximum principal stress on the cortical bone was the greatest in the model with the most significant bone loss at 5.10 MPa. CONCLUSIONS: This study suggested that the risk of debonding and periodontal tissue damage might be higher when resin-bonded fixed dental prosthesis frameworks were used in patients with reduced alveolar bone levels compared to those in a healthy state.

[Preventing Crying after Revascularization Surgery in Pediatric Patients with Moyamoya Disease:Sedation with Dexmedetomidine].

BACKGROUND: Hyperventilation is a well-known risk factor of ischemic events in pediatric patients with moyamoya disease. For young children, it is important to avoid crying to prevent ischemic events because of their unstable postoperative hemodynamics. To prevent crying in pediatric patients, we used dexmedetomidine(DEX)for sedation immediately after revascularization surgery. OBJECTIVE: We investigated the effects of postoperative DEX use on hemodynamic changes and the avoidance of crying and hypocapnia in pediatric patients with moyamoya disease. CASE: Ten consecutive patients(5 boys and 5 girls)who underwent surgical revascularization were enrolled, and 16 hemispheres(8 boys and 8 girls)were sedated with DEX postoperatively between August 2011 and August 2016. METHODS: During extubation after revascularization, DEX was started at 0.4µg/kg/hr under spontaneous breathing and its dose was increased depending on the degree of consciousness, to maintain sedation of at least 3 on the Ramsay scale. DEX administration was terminated the next morning. RESULTS: Sedation was maintained well in all patients without hypocapnia, and no ischemic complications were observed. One patient cried and needed additional intravenous DEX injections and was immediately re-sedated;no hypocapnia developed. Respiratory depression did not occur and changes in respiratory rate and decreases in SpO2 were not observed. No significant changes in systolic blood pressure and heart rate were observed. CONCLUSION: Dexmedetomidine is safe and useful for postoperative sedation in children with moyamoya disease.

Identification of the sequence determinants of protein N-terminal acetylation through a decision tree approach.

BACKGROUND: N-terminal acetylation is one of the most common protein modifications in eukaryotes and occurs co-translationally when the N-terminus of the nascent polypeptide is still attached to the ribosome. This modification has been shown to be involved in a wide range of biological phenomena such as protein half-life regulation, protein-protein and protein-membrane interactions, and protein subcellular localization. Thus, accurately predicting which proteins receive an acetyl group based on their protein sequence is expected to facilitate the functional study of this modification. As the occurrence of N-terminal acetylation strongly depends on the context of protein sequences, attempts to understand the sequence determinants of N-terminal acetylation were conducted initially by simply examining the N-terminal sequences of many acetylated and unacetylated proteins and more recently by machine learning approaches. However, a complete understanding of the sequence determinants of this modification remains to be elucidated. RESULTS: We obtained curated N-terminally acetylated and unacetylated sequences from the UniProt database and employed a decision tree algorithm to identify the sequence determinants of N-terminal acetylation for proteins whose initiator methionine (iMet) residues have been removed. The results suggested that the main determinants of N-terminal acetylation are contained within the first five residues following iMet and that the first and second positions are the most important discriminator for the occurrence of this phenomenon. The results also indicated the existence of position-specific preferred and inhibitory residues that determine the occurrence of N-terminal acetylation. The developed predictor software, termed NT-AcPredictor, accurately predicted the N-terminal acetylation, with an overall performance comparable or superior to those of preceding predictors incorporating machine learning algorithms. CONCLUSION: Our machine learning approach based on a decision tree algorithm successfully provided several sequence determinants of N-terminal acetylation for proteins lacking iMet, some of which have not previously been described. Although these sequence determinants remain insufficient to comprehensively predict the occurrence of this modification, indicating that further work on this topic is still required, the developed predictor, NT-AcPredictor, can be used to predict N-terminal acetylation with an accuracy of more than 80%.

NLDB: a database for 3D protein-ligand interactions in enzymatic reactions.

NLDB (Natural Ligand DataBase; URL: http://nldb.hgc.jp ) is a database of automatically collected and predicted 3D protein-ligand interactions for the enzymatic reactions of metabolic pathways registered in KEGG. Structural information about these reactions is important for studying the molecular functions of enzymes, however a large number of the 3D interactions are still unknown. Therefore, in order to complement such missing information, we predicted protein-ligand complex structures, and constructed a database of the 3D interactions in reactions. NLDB provides three different types of data resources; the natural complexes are experimentally determined protein-ligand complex structures in PDB, the analog complexes are predicted based on known protein structures in a complex with a similar ligand, and the ab initio complexes are predicted by docking simulations. In addition, NLDB shows the known polymorphisms found in human genome on protein structures. The database has a flexible search function based on various types of keywords, and an enrichment analysis function based on a set of KEGG compound IDs. NLDB will be a valuable resource for experimental biologists studying protein-ligand interactions in specific reactions, and for theoretical researchers wishing to undertake more precise simulations of interactions.

VaProS: a database-integration approach for protein/genome information retrieval.

Life science research now heavily relies on all sorts of databases for genome sequences, transcription, protein three-dimensional (3D) structures, protein-protein interactions, phenotypes and so forth. The knowledge accumulated by all the omics research is so vast that a computer-aided search of data is now a prerequisite for starting a new study. In addition, a combinatory search throughout these databases has a chance to extract new ideas and new hypotheses that can be examined by wet-lab experiments. By virtually integrating the related databases on the Internet, we have built a new web application that facilitates life science researchers for retrieving experts' knowledge stored in the databases and for building a new hypothesis of the research target. This web application, named VaProS, puts stress on the interconnection between the functional information of genome sequences and protein 3D structures, such as structural effect of the gene mutation. In this manuscript, we present the notion of VaProS, the databases and tools that can be accessed without any knowledge of database locations and data formats, and the power of search exemplified in quest of the molecular mechanisms of lysosomal storage disease. VaProS can be freely accessed at http://p4d-info.nig.ac.jp/vapros/ .

Results of pancreaticojejunal end-to-side anastomosis using the invagination method without a pancreatic stenting tube.

BACKGROUND/AIMS: Perioperative management of pancreaticoduodenectomy (PD) is a constant dilemma and challenging for gastrointestinal surgeons. Postoperative pancreatic fistula (POPF) and delayed gastric emptying (DGE) are of particular concern, and the onset of these conditions indicates a prolonged postoperative stay (POS). The procedure and postoperative outcomes of pancreaticojejunostomy performed at our hospital are reported. METHODOLOGY: POPF, DGE, and POS were investigated in 54 patients who had undergone PD at our hospital since June 2007. Pancreaticojejunal end-to-side anastomosis using the invagination method without a stenting tube and without duct-to-mucosa anastomosis was performed in all patients, regardless of pancreatic duct diameter. RESULTS: There were 26 patients (48.2%) without POPF, 24 (44.4%) with grade A, 4 (7.4%) with grade B, and none with grade C. The mean POS was 28.3 days. DGE was observed in 4 patients (7.4%) who underwent pylorus-preserving PD (PpPD). There were 34 patients with a soft pancreas. None of the patients experienced intraperitoneal bleeding or abscess, and no surgery-related deaths occurred. CONCLUSIONS: The reconstructive pancreaticojejunostomy procedure performed at our hospital appears to be safe and convenient, and we plan to collect additional data, including assessments of the function of the remaining pancreas, in the future.

Phase transformation behavior and mechanical properties of HyFlex EDM nickel-titanium endodontic rotary instrument: Evaluation at body temperature.

Background/purpose: Temperature-dependent phase compositional changes influence the mechanical properties of heat-treated nickel-titanium (NiTi) rotary instruments. This study evaluated the phase composition, bending properties, and cyclic fatigue resistance of HyFlex EDM NiTi rotary instruments against differently heat-treated and non-heat-treated NiTi instruments at body temperature (BT). Materials and methods: HyFlex EDM OneFile (EDM) instruments, heat-treated HyFlex CM (CM) and Twisted File (TF) instruments, and non-heat-treated K3 instruments (size #25/.08) were subjected to differential scanning calorimetry, and the martensitic, R-phase, and reverse transformation starting and finishing temperatures were determined. A cantilever bending test and a cyclic fatigue test were conducted at BT (37 °C ± 1.0 °C), and the bending load and number of cycles to failure (NCF) were recorded. Statistical analysis was performed using Kruskal-Wallis and Mann-Whitney U tests (α = 0.05). Results: TF and K3 had reverse transformation finishing temperatures lower than BT, while those for EDM and CM were higher than BT. The bending loads at a 0.5 mm deflection were in the order of EDM < TF < CM < K3 (P < 0.05), and those at a 2.0 mm deflection were EDM < CM and TF < K3 (P < 0.05). EDM had the highest NCF among the four instruments (P < 0.05). Conclusion: The EDM instrument had a reverse transformation finishing temperature higher than BT indicating its martensite/R-phase composition at BT. The EDM instrument had superior flexibility and greater resistance to cyclic fatigue than the CM, TF, and K3 instruments at BT.

A Case of a Huge Iliopsoas Abscess that Perforated and Communicated with the Ureter.

We experienced a rare case in which iliopsoas abscess (IPA), caused by an Extended Spectrum ß-Lactamase (ESBL)-producing Proteus mirabilis, perforated and communicated with the ureter and caused sepsis. An 84-year-old woman, bedridden due to sequelae of a cerebral hemorrhage, was brought to our hospital with a chief complaint of fever lasting for 3 weeks. Computed tomography (CT) revealed a huge 180 × 110 × 100 mm IPA in the right iliopsoas muscle. The ureter was also found to communicate with the iliopsoas muscle abscess, ureteral stenosis was detected at the same site, and dilatation of the renal pelvis occurred above the area of the ureteral stenosis, indicating hydronephrosis. Considering the mechanism of this case, if the ureter first ruptures and urine leaks, followed by the formation of an IPA, urine will flow along the surrounding fatty tissue and cause an abscess around the ureter and kidney. However, because almost no abscess was detected around the ureter, the abscess was thought to have originated from the iliopsoas muscle located near the center of the ureter. In summary, in this case, an abscess first formed within the iliopsoas muscle, which gradually expanded and compressed the right ureter, resulting in hydronephrosis. The upper ureter, which had become dilated and thinned due to ureteral obstruction, became even more fragile because of the spread of inflammation from the IPA, and the IPA perforated and communicated with the ureter. In patients who have difficulty communicating, the diagnosis of IPA may be delayed because the only symptom is fever. As in this case, if the diagnosis is delayed, the abscess may become large and perforate the ureter; thus, IPA should always be considered as a cause of fever of unknown origin.

CyClus: a fast, comprehensive cylindrical interface approximation clustering/reranking method for rigid-body protein-protein docking decoys.

We propose a fast clustering and reranking method, CyClus, for protein-protein docking decoys. This method enables comprehensive clustering of whole decoys generated by rigid-body docking using cylindrical approximation of the protein-proteininterface and hierarchical clustering procedures. We demonstrate the clustering and reranking of 54,000 decoy structures generated by ZDOCK for each complex within a few minutes. After parameter tuning for the test set in ZDOCK benchmark 2.0 with the ZDOCK and ZRANK scoring functions, blind tests for the incremental data in ZDOCK benchmark 3.0 and 4.0 were conducted. CyClus successfully generated smaller subsets of decoys containing near-native decoys. For example, the number of decoys required to create subsets containing near-native decoys with 80% probability was reduced from 22% to 50% of the number required in the original ZDOCK. Although specific ZDOCK and ZRANK results were demonstrated, the CyClus algorithm was designed to be more general and can be applied to a wide range of decoys and scoring functions by adjusting just two parameters, p and T. CyClus results were also compared to those from ClusPro.

A composite resin core with a new zirconia tube reduces the surface strain at the cervical area of a mandibular molar: A model tooth study.

PURPOSE: This study aimed to evaluate the surface strain at the cervical area of endodontically treated molars with a large pulp chamber restored using a composite resin core with three different types of core build-up systems. METHODS: Reproduction models of human mandibular molars with prepared post spaces were used in this study. Roots duplicated with a composite resin were used as the experimental teeth. Three types of core build-up systems were used: composite resin core(RC), composite resin core with fiber posts (FC), and composite resin core with a prefabricated zirconia tube (ZC). Each group comprised eight specimens. Crowns made of yttria partially stabilized zirconia were cemented with dual-cure resin cement. Four strain gauges were attached to the surfaces of each specimen: the cervical area of the root and crown, on the buccal and lingual sides. The surface strain at each cervical area was measured using a static loading test and statistically analyzed. RESULTS: In the case of static loading to the buccal cusp inner slope, ZC showed a significantly lower strain than RC in the crown on the buccal side and in the root and FC in the root. In the central fossa, ZC showed a significantly lower strain than FC in the root on the lingual side. CONCLUSIONS: The prefabricated zirconia tube reduced the surface strain at the cervical area of the buccal/lingual root in molars; however, the effect was small in the cervical area of the crown.

Influence of different kinematics on stationary and dynamic torsional behavior of JIZAI nickel-titanium rotary instruments: An in vitro study.

Background/purpose: Using conventional approach to examine stationary torque of nickel-titanium rotary instruments contradicts the clinical condition, and its validity for motions involving clockwise and counterclockwise rotations is questionable. This study aimed to examine the effect of different kinematics on the torsional behavior using a JIZAI instrument (#25/.04) under stationary/dynamic test conditions using clinical torque limit settings. Materials and methods: In the stationary test, the 5-mm tip of JIZAI was fixed in a cylinder-shaped vise and rotated in continuous rotation (CR) with auto-torque-reverse, optimum-torque-reverse (OTR), or reciprocation (REC) until fracture (n = 10, each). In the dynamic test, straight and severe curved canals were instrumented with JIZAI using the single-length technique with CR, OTR, or REC (n = 10, each). The stationary torque at fracture, time to fracture (Tf), dynamic torque, and screw-in force were recorded using automated-shaping-device with torque/force measuring unit. One-way ANOVA or Kruskal-Wallis test and Mann-Whitney U test with Bonferroni correction were used for statistical analysis (⍺ = 0.05). Results: The kinematics did not influence the stationary or dynamic torques (P > 0.05); however, did influence the screw-in force in straight canals (P < 0.05). REC had significantly longer Tf, and severe curved canals yielded significantly greater torque and screw-in force in CR (P < 0.05). Conclusion: Under the present experimental conditions, parameters other than torque showed significant effects on different kinematics. The dynamic torque and screw-in force of OTR were similar to the other rotational modes and not influenced by the canal curvature.

Comparison of Intra-articular Knee Injection of Corticosteroid between Hemodialysis and Non-hemodialysis Patients.

Introduction: Hemodialysis patients have various complications, and orthopedic diseases include carpal tunnel syndrome, spinal canal stenosis, spondylosis destruction, fractures, and osteoarthritis. As a treatment for knee osteoarthritis, intra-articular injections of hyaluronic acid and steroids are performed. In general, steroid injections have a strong short-term anti-inflammatory effect, but there is a risk of complications, such as infection. In addition to aging, dialysis patients are prone to weakened immune systems and susceptibility to infection. Therefore, more attention should be paid to the treatment of osteoarthritis in dialysis patients. This study aimed to compare the effects of steroid and complication of infection of dialysis and non-dialysis patients who underwent intra-articular steroid injection. Methods: A total of 20 dialysis patients (23 knees) and 20 non-dialysis patients (24 knees) with knee osteoarthritis who underwent steroid injections were investigated. All patients underwent radiographic diagnosis and were evaluated for the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) score, visual analog scale (VAS), range of motion (ROM), and side effects before, and at 3, and 6 months after injection. Results: The mean body mass index (BMI) was 21.3 (±standard deviation (SD) 2.8) and 24.9 (±SD 2.6) in dialysis and non-dialysis patients, respectively, showing a significant difference. Both dialysis and non-dialysis patients showed statistically significant improvement in VAS and WOMAC scores after steroid injection. There were no significant differences between dialysis and non-dialysis patients in the gender differences and mean age. There were no infection complications in both groups. Conclusions: This study revealed the analgesic effect of steroids on knee osteoarthritis in dialysis and non-dialysis patients. On the other hand, there were no infection complications in either patient. These findings suggest that intra-articular steroid injection is safe for dialysis patients.

Carbon nanotube recognition by human Siglec-14 provokes inflammation.

For the design and development of innovative carbon nanotube (CNT)-based tools and applications, an understanding of the molecular interactions between CNTs and biological systems is essential. In this study, a three-dimensional protein-structure-based in silico screen identified the paired immune receptors, sialic acid immunoglobulin-like binding lectin-5 (Siglec-5) and Siglec-14, as CNT-recognizing receptors. Molecular dynamics simulations showed the spatiotemporally stable association of aromatic residues on the extracellular loop of Siglec-5 with CNTs. Siglec-14 mediated spleen tyrosine kinase (Syk)-dependent phagocytosis of multiwalled CNTs and the subsequent secretion of interleukin-1ß from human monocytes. Ectopic in vivo expression of human Siglec-14 on mouse alveolar macrophages resulted in enhanced recognition of multiwalled CNTs and exacerbated pulmonary inflammation. Furthermore, fostamatinib, a Syk inhibitor, blocked Siglec-14-mediated proinflammatory responses. These results indicate that Siglec-14 is a human activating receptor recognizing CNTs and that blockade of Siglec-14 and the Syk pathway may overcome CNT-induced inflammation.

Effect of Different Downward Loads on Canal Centering Ability, Vertical Force, and Torque Generation during Nickel-Titanium Rotary Instrumentation.

This study aimed to examine how downward loads influence the torque/force and shaping outcome of ProTaper NEXT (PTN) rotary instrumentation. PTN X1, X2, and X3 were used to prepare J-shaped resin canals employing a load-controlled automated instrumentation and torque/force measuring device. Depending on the torque values, the handpiece was programmed to move as follows: up and down; downward at a preset downward load of 1 N, 2 N or 3 N (Group 1N, 2N, and 3N, respectively; each n = 10); or upward. The torque/force values and instrumentation time were recorded, and the canal centering ratio was calculated. The results were analyzed using a two-way or one-way analysis of variance and the Tukey test (α = 0.05). At the apex level, Group 3N exhibited the least canal deviation among the three groups (p < 0.05). The downward force was Group 3N > Group 2N > Group 1N (p < 0.05). The upward force, representing the screw-in force, was Group 3N > Group 1N (p < 0.05). The total instrumentation time was Group 1N > Group 3N (p < 0.05). In conclusion, increasing the downward load during PTN rotary instrumentation improved the canal centering ability, reduced the instrumentation time, and increased the upward force.

Effect of Rotational Modes on Torque/Force Generation and Canal Centering Ability during Rotary Root Canal Instrumentation with Differently Heat-Treated Nickel-Titanium Instruments.

This study aimed to evaluate how various rotational modes influence the torque/force production and shaping ability of ProTaper Universal (PTU; non-heat-treated) and ProTaper Gold (PTG; heat-treated) nickel−titanium instruments. J-shaped resin canals were instrumented with PTU or PTG using an automated instrumentation device operated with reciprocating rotation [150° clockwise and 30° counterclockwise (R150/30) or 240° clockwise and 120° counterclockwise (R240/120)], optimum torque reverse motion (OTR), or continuous rotation (CR) (n = 10 each). Maximum force and torque were recorded, and canal centering ratios were calculated. Statistical analysis was performed with two-way ANOVA and a Bonferroni test (α = 0.05). The results were considered with reference to previous studies on the microstructure of the instruments. The upward force generated by R240/120 and OTR was smaller than that generated by R150/30 and CR in PTG (p < 0.05). The clockwise torque produced by OTR was lower than that produced by R150/30 in PTU and R240/120 and CR in PTG (p < 0.05). R240/120 and OTR induced less canal deviation compared to CR in PTU at 0 mm from the apex (p < 0.05). In conclusion, R240/120 and OTR reduced the screw-in force in PTG and improved the canal centering ability in PTU, which may be associated with the heat treatment-induced microstructural difference of the two instruments.

Mechanical Properties and Root Canal Shaping Ability of a Nickel-Titanium Rotary System for Minimally Invasive Endodontic Treatment: A Comparative In Vitro Study.

Selection of an appropriate nickel−titanium (NiTi) rotary system is important for minimally invasive endodontic treatment, which aims to preserve as much root canal dentin as possible. This study aimed to evaluate selected mechanical properties and the root canal shaping ability of TruNatomy (TRN), a NiTi rotary system designed for minimally invasive endodontic shaping, in comparison with existing instruments: HyFlex EDM (HEDM), ProTaper Next (PTN), and WaveOne Gold (WOG). Load values measured with a cantilever bending test were ranked as TRN < HEDM < WOG < PTN (p < 0.05). A dynamic cyclic fatigue test revealed that the number of cycles to fracture was ranked as HEDM > WOG > TRN > PTN (p < 0.05). Torque and vertical force generated during instrumentation of J-shaped artificial resin canals were measured using an automated instrumentation device connected to a torque and vertical force measuring system; TRN exhibited smaller torque and vertical force values in most comparisons with the other instruments. The canal centering ratio for TRN was smaller than or comparable to that for the other instruments except for WOG at the apex level. Under the present experimental conditions, TRN showed higher flexibility and lower torque and vertical force values than the other instruments.

Strain analysis of anterior resin-bonded fixed dental prostheses with different thicknesses of high translucent zirconia.

BACKGROUND/PURPOSE: High translucent zirconia has been used as a new monolithic zirconia prosthesis, which has the potential to make anterior resin-bonded fixed dental prostheses (RBFDPs) without veneering porcelain. However, it is unclear whether the RBFDPs retainer can be thinned as much as conventional zirconia RBFDPs. The aim of this study was to assess the usability of high translucent zirconia RBFDPs with a thin retainer thickness by evaluating differences in retainer thickness on the surface strain. MATERIALS AND METHODS: A model with a missing upper lateral incisor was used. The abutment teeth were upper central incisor and canine. Three types of RBFDPs were fabricated as follows: metal RBFDPs with a retainer thickness of 0.8 mm (0.8M), and high translucent zirconia RBFDPs with a retainer thicknesses of 0.8 and 0.5 mm (0.8Z, 0.5Z) (n = 10). The fitness of the margins was evaluated by the silicone replica technique. The surface strain of each retainer under static loading was measured and statistically analyzed using a t-test with Bonferroni correction. RESULTS: The marginal fitness of all RBFDPs was under 76.1 µm, which was clinically acceptable. Each strain of the 0.8Z and 0.5Z groups was significantly lower than that of the 0.8M (p < 0.05). There was no difference in strain of the zirconia RBFDPs even if the retainer thickness was changed. CONCLUSION: Our results suggest that the high translucent zirconia RBFDPs can be manufactured with a retainer thickness of 0.5 mm, which reduces the amount of tooth preparation compared to the metal RBFDPs.