A novel biopsy scheme for prostate cancer: targeted and regional systematic biopsy.

PURPOSE: To explore a novel biopsy scheme for prostate cancer (PCa), and test the detection rate and pathological agreement of standard systematic (SB) + targeted (TB) biopsy and novel biopsy scheme. METHODS: Positive needles were collected from 194 patients who underwent SB + TB (STB) followed by radical prostatectomy (RP). Our novel biopsy scheme, targeted and regional systematic biopsy (TrSB) was defined as TB + regional SB (4 SB-needles closest to the TB-needles). The McNemar test was utilized to compare the detection rate performance for clinical significant PCa (csPCa) and clinical insignificant PCa (ciPCa). Moreover, the accuracy, positive predictive value (PPV) and negative predictive value (NPV) were investigated. The agreement between the different biopsy schemes grade group (GG) and RP GG were assessed. The concordance between the biopsy and the RP GG was evaluated using weighted κ coefficient analyses. RESULTS: In this study, the overall detection rate for csPCa was 83.5% (162 of 194) when SB and TB were combined. TrSB showed better NPV than TB (97.0% vs. 74.4%). Comparing to STB, the TB-detection rate of csPCa had a significant difference (p < 0.01), while TrSB showed no significant difference (p > 0.999). For ciPCa, the overall detection rate was 16.5% (32 of 194). TrSB showed better PPV (96.6% vs. 83.3%) and NPV (97.6% vs. 92.9%) than TB. Comparing to STB, the detection rate of both schemes showed no significant difference (p = 0.077 and p = 0.375). All three schemes GG showed poor agreement with RP GG (TB: 43.3%, TrSB: 46.4%, STB: 45.9%). Using weighted κ, all three schemes showed no difference (TB: 0.48, TrSB: 0.51, STB: 0.51). In our subgroup analysis (PI-RADS = 4/5, n = 154), all three schemes almost showed no difference (Weighted κ: TB-0.50, TrSB-0.51, STB-0.50). CONCLUSION: Our novel biopsy scheme TrSB (TB + 4 closest SB needles) may reduce 8 cores of biopsy compared with STB (standard SB + TB), which also showed better csPCa detection rate than TB only, but the same as STB. The pathological agreement between three different biopsy schemes (TB/TrSB/STB) GG and RP GG showed no difference.

Pseudomyopia treated with auricular point sticking combined with periocular needle-embedding therapy and prevention of true myopia: a multicenter randomized controlled trial. / è€³ç©´è´´åŽ‹è”åˆçœ¼å‘¨æ¿é’ˆæŠ€æœ¯é¢„é˜²å‡æ€§è¿‘è§†å‘çœŸæ€§è¿‘è§†è¿›å±•ï¼šå¤šä¸­å¿ƒéšæœºå¯¹ç §è¯•éªŒ.

OBJECTIVES: To observe the clinical effect and safety of auricular point sticking combined with periocular needle-embedding therapy for pseudomyopia and prevention of true myopia. METHODS: A total of 269 children with pseudomyopia were randomized into an observation group (134 cases, 2 cases dropped out) and a control group (135 cases, 5 cases dropped out). In the control group, the healthy education was provided. In the observation group, besides the intervention as the control group, the auricular point sticking was delivered at gan (CO12), pi (CO13), xin (CO15) and yan (LO5) on one ear in each treatment, combined with periocular needle-embedding technique at bilateral Cuanzhu (BL 2), Yuyao (EX-HN 4) and Sibai (ST 2). There were 2 weeks of interval after 4 weeks of treatment. One course of treatment was composed of 6 weeks and 2 courses were required. Separately, before treatment, after 6 and 12 weeks of treatment, and after 12 weeks (the 1st follow-up visit) and 24 weeks (the 2nd follow-up visit) of treatment completion, the spherical equivalent (SE), SE progression, axial length (AL) progression, accommodative amplitude (AMP), the score of the TCM symptom and the general symptom were observed in the two groups. The safety and compliance were evaluated in the two groups. RESULTS: After 6 and 12 weeks of treatment, and in the 1st and 2nd follow-up visits, SE increased when compared with that before treatment in the two groups (P<0.05), and AMP was larger than that before treatment in the observation group (P<0.05). After 12 weeks of treatment, and in the 1st and 2nd follow-up visits, the progression of SE was slower in the observation group compared with that in the control group (P<0.01, P<0.001). After 6 and 12 weeks of treatment, and in the 1st and 2nd follow-up visits, the progression of AL in the observation group was lower than that of the control group (P<0.05, P<0.01, P<0.001); and in the 1st and 2nd follow-up visits, AMP of the observation group was larger when compared with that in the control group (P<0.05, P<0.001). After 6 and 12 weeks of treatment, and in the 1st and 2nd follow-up visits, the total scores of TCM symptom and general symptom were reduced in comparison with those before treatment in the observation group (P<0.05); after 6 and 12 weeks of treatment, the total scores of TCM symptom and general symptom were lower than those before treatment in the control group (P<0.05). In the 1st and 2nd follow-up visits, the difference of the total score of TCM symptom and general symptom in the observation group was larger than that of the control group (P<0.05). In the observation group, compared with the control group, the scores for pale/dark complexion in the 1st and 2nd follow-up visits and that for lassitude in the 2nd follow-up visit were lower (P<0.05), the score for poor concentration after 12 weeks of treatment and that for poor sleep and memory in the 2nd follow-up visit were lower (P<0.05). There were no adverse reactions in the two groups. The compliance was 98.5% in the observation group and was 96.3% in the control group, without statistical difference (P>0.05). CONCLUSIONS: On the basis of health education, auricular point sticking combined with periocular needle-embedding therapy can effectively prevent from true myopia, control the increase of SE, delay the growth of AL and improve AMP in children with pseudomyopia. This compound therapeutic regimen can relieve the general symptom and comprehensively prevent from myopia through multiple approaches, with high safety and satisfactory compliance.

A mechanics-based model for predicting flexible needle bending with large curvature in soft tissue.

Percutaneous insertion is one of the most common minimally invasive procedures. Compared with traditional straight rigid needles, bevel-tipped flexible needle can generate curved trajectories to avoid obstacles and sensitive organs. However, the nonlinear large deflection problem challenges the bending prediction of the needle, which dramatically influences the surgical success rate. This paper analyzed the mechanism of needle-tissue interaction, and established a mechanics-based model of the needle bending during an insertion. And then, a discretization of the bending model was adopted to accurately predict the large bending of the needle in soft tissue. Insertion experiments were conducted to validate the bending prediction model. The results showed that the large needle bending was predicted with the mean/RMSE/maximumu error of 0.42 mm / 0.26 mm / 1.08 mm, which was clinically acceptable. This proved the rationality and accuracy of the proposed model.

Minoxidil Nanosuspension-Loaded Dissolved Microneedles for Hair Regrowth.

Minoxidil (MIN) is used topically to treat alopecia. However, its low absorption limits its use, warranting a new strategy to enhance its delivery into skin layers. The objective of this study was to evaluate the dermal delivery of MIN by utilizing dissolved microneedles (MNs) loaded with MIN nanosuspension (MIN-NS) for hair regrowth. MIN-NS was prepared by the solvent-antisolvent precipitation technique. The particle size of MIN-NS was 226.7 ± 9.3 nm with a polydispersity index of 0.29 ± 0.17 and a zeta potential of -29.97 ± 1.23 mV. An optimized formulation of MIN-NS was selected, freeze-dried, and loaded into MNs fabricated with sodium carboxymethyl cellulose (Na CMC) polymeric solutions (MIN-NS-loaded MNs). MNs were evaluated for morphology, dissolution rate, skin insertion, drug content, mechanical properties, ex vivo permeation, in vivo, and stability studies. MNs, prepared with 14% Na CMC, were able to withstand a compression force of 32 N for 30 s, penetrate Parafilm M® sheet at a depth of 374-504 µm, and dissolve completely in the skin within 30 min with MIN %recovery of 95.1 ± 6.5%. The release of MIN from MIN-NS-loaded MNs was controlled for 24 h. MIN-NS-loaded MNs were able to maintain their mechanical properties and chemical stability for 4 weeks, when kept at different storage conditions. The in vivo study of the freeze-dried MIN-NS and MIN-NS-loaded MNs proved hair regrowth on rat skin after 11 and 7 days, respectively. These results showed that MIN-NS-loaded MNs could potentially improve the dermal delivery of MIN through the skin to treat alopecia.

A Hollow Microneedle Equipped with a Micropillar for Improved Needle Insertion and Injection of Drug Solution.

PURPOSE: Hollow-type microneedles (hMNs) are a promising device for the effective administration of drugs into intradermal sites. Complete insertion of the needle into the skin and administration of the drug solution without leakage must be achieved to obtain bioavailability or a constant effect. In the present study, several types of hMN with or without a rounded blunt tip micropillar, which suppresses skin deformation, around a hollow needle, and the effect on successful needle insertion and administration of a drug solution was investigated. Six different types of hMNs with needle lengths of 1000, 1300, and 1500 µm with or without a micropillar were used. METHODS: Needle insertion and the disposition of a drug in rat skin were investigated. In addition, the displacement-force profile during application of hMNs was also investigated using a texture analyzer with an artificial membrane to examine needle factors affecting successful insertion and administration of a drug solution by comparing with in vivo results. RESULTS: According to the results with the drug distribution of iodine, hMN1300 with a micropillar was able to successfully inject drug solution into an intradermal site with a high success rate. In addition, the results of displacement-force profiles with an artificial membrane showed that a micropillar can be effective for depth control of the injected solution as well as the prevention of contact between the hMN pedestal and the deformed membrane. CONCLUSION: In the present study, hMN1300S showed effective solution delivery into an intradermal site. In particular, a micropillar can be effective for depth control of the injected solution as well as preventing contact between the hMN pedestal and the deformed membrane. The obtained results will help in the design and development of hMNs that ensure successful injection of an administered drug.

Novel tetrapolar single-needle electrode for electrochemotherapy in bone cavities: Modeling, design and validation.

Electrochemotherapy is a cancer treatment in which local pulsed electric fields are delivered through electrodes. The effectiveness of the treatment depends on exposing the tumor to a threshold electric field. Electrode geometry plays an important role in the resulting electric field distribution, especially in hard-to-reach areas and deep-seated tumors. We designed and developed a novel tetrapolar single-needle electrode for proper treatment in bone cavities. In silico and in vitro experiments were performed to evaluate the electric field and electric current produced by the electrode. In addition, tomography images of a real case of nasal cavity tumor were segmented into a 3D simulation to evaluate the electrode performance in a bone cavity. The proposed electrode was validated and its operating range was set up to 650 V. In the nasal cavity tumor, we found that the electrode can produce a circular electric field of 3 mm with an electric current of 14.1 A at 500 V, which is compatible with electrochemotherapy standards and commercial equipment.

A magnetic resonance conditional robot for lumbar spinal injection: Development and preliminary validation.

PURPOSE: This work presents the design and preliminary validation of a Magnetic Resonance (MR) conditional robot for lumbar injection for the treatment of lower back pain. METHODS: This is a 4-degree-of-freedom (DOF) robot that is 200 × 230 × 130 mm3 in volume and has a mass of 0.8 kg. Its lightweight and compact features allow it to be directly affixed to patient's back, establishing a rigid connection, thus reducing positional errors caused by patient movements during treatment. RESULTS: To validate the positioning accuracy of the needle by the robot, an electromagnetic (EM) tracking system and a needle with an EM sensor embedded in the tip were used for the free space evaluation with position accuracy of 0.88 ± 0.46 mm and phantom mock insertions using the Loop-X CBCT scanner with target position accuracy of 3.62 ± 0.92 mm. CONCLUSION: Preliminary experiments demonstrated that the proposed robot showed improvements and benefits in its rotation range, flexible needle adjustment, and sensor protection compared with previous and existing systems, offering broader clinical applications.

A mechanics-based model for a tendon-driven active needle navigating inside a multiple-layer tissue.

Percutaneous minimally invasive procedures such brachytherapy and biopsy require a flexible active needle for precise movement inside tissue and accurate placement at target positions for higher success rates for diagnosis and treatment, respectively. In a previous work, we presented a tendon-driven active needle to navigate inside tissue. This work presents a new model to predict the deflection of the tendon-driven needle while steering in a multiple-layer soft tissue. A multi-layer phantom tissue with different localized stiffness was developed for needle insertion tests followed by indentation tests to identify its mechanical properties. Using a robot that inserts and actively bends the tendon-driven needle inside the soft tissue while simultaneously tracking the needle through ultrasound imaging, various experiments were conducted for model validation. The proposed model was verified by comparing the simulation results to the empirical data. The results demonstrated the accuracy of the model in predicting the tendon-driven needle deflection in multiple-layer (different stiffness) soft tissue.

Rizatriptan benzoate-loaded dissolving microneedle patch for management of acute migraine therapy.

In this study, dissolving microneedles (MNs) using polyvinyl alcohol (PVA) and poly (1-vinylpyrrolidone-co-vinyl acetate) (P(VP-co-VA)) as matrix materials were developed for transdermal delivery of rizatriptan benzoate (RB) for acute migraine treatment. In-vitro permeation studies were conducted to assess the feasibility of the as-fabricated dissolving MNs to release RB. Drug skin penetration were tested by Franz diffusion cells, showing an increase of the transdermal flux compared to passive diffusion due to the as-fabricated dissolving MNs having a sufficient mechanical strength to penetrate the skin and form microchannels. The pharmacological study in vivo showed that RB-loaded dissolving MNs significantly alleviated migraine-related response by up-regulating the level of 5-hydroxytryptamine (5-HT) and down-regulating the levels of calcitonin gene-related peptide (CGRP) and substance P (SP). In conclusion, the RB-loaded dissolving MNs have advantages of safety, convenience, and high efficacy over conventional administrations, laying a foundation for the transdermal drug delivery system treatment for acute migraine.

Applications and prospects of microneedles in tumor drug delivery.

As drug delivery devices, microneedles are used widely in the local administration of various drugs. Such drug-loaded microneedles are minimally invasive, almost painless, and have high drug delivery efficiency. In recent decades, with advancements in microneedle technology, an increasing number of adaptive, engineered, and intelligent microneedles have been designed to meet increasing clinical needs. This article summarizes the types, preparation materials, and preparation methods of microneedles, as well as the latest research progress in the application of microneedles in tumor drug delivery. This article also discusses the current challenges and improvement strategies in the use of microneedles for tumor drug delivery.

Parallel needling technique for peripheral facial paralysis with qi deficiency and blood stasis: a randomized controlled trial. / å¹³è¡Œå¯¹åˆºæ³•æ²»ç–—æ°”è™šè¡€ç˜€åž‹å‘¨å›´æ€§é¢ç˜«ï¼šéšæœºå¯¹ç §è¯•éªŒ.

OBJECTIVES: To observe the clinical efficacy of the parallel needling technique for peripheral facial paralysis with qi deficiency and blood stasis. METHODS: Sixty-two patients with peripheral facial paralysis of qi deficiency and blood stasis were randomly assigned to a parallel needling group and a conventional acupuncture group, with 31 patients in each group. The conventional acupuncture group received needling at Yangbai (GB 14), Quanliao (SI 18), Jiache (ST 6), Dicang (ST 4), Yifeng (TE 17) on the affected side, Hegu (LI 4) on the healthy side, and bilateral Zusanli (ST 36), Sanyinjiao (SP 6), Xuehai (SP 10) and Qihai (CV 6) etc. The parallel needling group, in addition to the conventional acupuncture points, received parallel needling at three additional groups of acupoints, i.e. forehead wrinkle group, mid-face group, and corner of the mouth group. Both groups retained needles for 30 min, with one session every other day and a total of three sessions per week, lasting for four weeks. The House-Brackmann (H-B) facial nerve function grading, physical function (FDIP) and social function (FDIS) scores of facial disability index (FDI), TCM syndrome score before and after treatment were compared between the two groups, and the clinical efficacy was assessed. RESULTS: Compared with before treatment, after treatment, both groups showed improvements in H-B facial nerve function grading (P<0.05), FDIP total scores and sub-item scores were increased (P<0.05), FDIS total scores, sub-item scores, and TCM syndrome scores were decreased (P<0.05). After treatment, the parallel needling group showed the higher FDIP total score and eating sub-item score and lower FDIS total score and insomnia sub-item score compared with those in the conventional acupuncture group (P<0.05). The total effective rate was 90.3% (28/31) in the parallel needling group and 87.1% (27/31) in the conventional acupuncture group, with no statistically significant difference between the two groups (P>0.05). CONCLUSIONS: The parallel needling technique combined with conventional acupuncture, is as effective as conventional acupuncture alone in treating facial paralysis with qi deficiency and blood stasis. However, the parallel needling technique combined with conventional acupuncture shows advantages in the improvement of food intake and sleep quality.

3D Printed Ion-Responsive Personalized Transdermal Patch.

Microneedle patches are easy-to-use medical devices for transdermal administration. However, the insufficient insertion of microneedles due to the gap between planar patches and contoured skin affects drug delivery. Herein, we formulate a prepolymer for high-fidelity three-dimensional (3D) printed personalized transdermal patches. With the excellent photoinitiation ability of 2-(4-methoxystyryl)-4,6-bis(trichloromethyl)-1,3,5-triazine (Tz), a high-fidelity and precise microneedle patch is successfully fabricated. Upon irradiation of the white illuminator, the doped gold nanoparticles (AuNPs) in the patch release heat and promisingly induce sweat production. With the introduction of Na+, the dominant component of sweat, the curvature of the produced transdermal patch is observed due to the ion-induced network rearrangement. The alkanethiol-stabilized AuNP with an end group of a carboxyl group causes controlled drug release behavior. Furthermore, the irradiation-induced photothermal heating of AuNP can facilitate the sustainability of drug release thanks to the substantially increased particle size of AuNP. These findings demonstrate that the developed prepolymer is a promising candidate for the production of transdermal patches fitting the curvature of the body surface.

Photo-crosslinkable polyester microneedles as sustained drug release systems toward hypertrophic scar treatment.

Burn injuries can result in a significant inflammatory response, often leading to hypertrophic scarring (HTS). Local drug therapies e.g. corticoid injections are advised to treat HTS, although they are invasive, operator-dependent, extremely painful and do not permit extended drug release. Polymer-based microneedle (MN) arrays can offer a viable alternative to standard care, while allowing for direct, painless dermal drug delivery with tailorable drug release profile. In the current study, we synthesized photo-crosslinkable, acrylate-endcapped urethane-based poly(ε-caprolactone) (AUP-PCL) toward the fabrication of MNs. Physico-chemical characterization (1H-NMR, evaluation of swelling, gel fraction) of the developed polymer was performed and confirmed successful acrylation of PCL-diol. Subsequently, AUP-PCL, and commercially available PCL-based microneedle arrays were fabricated for comparative evaluation of the constructs. Hydrocortisone was chosen as model drug. To enhance the drug release efficiency of the MNs, Brij®35, a nonionic surfactant was exploited. The thermal properties of the MNs were evaluated via differential scanning calorimetry. Compression testing of the arrays confirmed that the MNs stay intact upon applying a load of 7 N, which correlates to the standard dermal insertion force of MNs. The drug release profile of the arrays was evaluated, suggesting that the developed PCL arrays can offer efficient drug delivery for up to two days, while the AUP-PCL arrays can provide a release up to three weeks. Finally, the insertion of MN arrays into skin samples was performed, followed by histological analysis demonstrating the AUP-PCL MNs outperforming the PCL arrays upon providing pyramidical-shaped perforations through the epidermal layer of the skin.

AUP-PCL MN arrays provide long-term transdermal drug delivery of hydrocortisoneAUP-PCL-based MN arrays provide superior drug release profiles compared to PCL MNsEffective skin penetration AUP-PCL-based MNs on skin was achieved.

A Review of Recent Advances in Microneedle-Based Sensing within the Dermal ISF That Could Transform Medical Testing.

Interstitial fluid (ISF) has attracted extensive attention in an extremely wide range of areas due to its unique advantages, such as portability, high precision, comfortable operation, and superior stability. In recent years, the microneedle (MN) technique has been considered to be an excellent tool for extracting ISF because it is painless and noninvasive. Recent reports have shown that MN has good application prospects in ISF extraction. In this review, we provide comprehensive and in-depth insight into integrated MN devices for ISF detection, covering the basic structure as well as the fabrication of integrated MN devices and various applications in ISF extraction. Challenges and prospects are highlighted, with a discussion on how to transition such MN-integrated devices toward personalized healthcare monitoring systems.

TipDet: A multi-keyframe motion-aware framework for tip detection during ultrasound-guided interventions.

BACKGROUND AND OBJECTIVE: Automatic needle tip detection is important in real-time ultrasound (US) images that are utilized to guide interventional needle puncture procedures in clinical settings. However, due to the spatial indiscernibility problem caused by the severe background interferences and the tip characteristics of small size, being grayscale and indistinctive appearance patterns, tip detection in US images is challenging. METHODS: To achieve precise tip detection in US images against spatial indiscernibility, a novel multi-keyframe motion-aware framework called TipDet is proposed. It can identify tips based on their short-term spatial-temporal pattern and long-term motion pattern. In TipDet, first, an adaptive keyframe model (AKM) is proposed to decide whether a frame is informative to serve as a keyframe for long-term motion pattern learning. Second, candidate tip detection is conducted using a two-stream backbone (TSB) based on their short-term spatial-temporal pattern. Third, to further identify the true one in the candidate tips, a novel method for learning the long-term motion pattern of the tips is proposed based on the proposed optical-flow-aware multi-head cross-attention (OFA-MHCA). RESULTS: On the clinical human puncture dataset, which includes 4195 B-mode images, the experimental results show that the proposed TipDet can achieve precise tip detection against the spatial indiscernibility problem, achieving 78.7 % AP0.1:0.5 and 8.9 % improvement over the base detector at approximately 20 FPS. Moreover, a tip localization error of 1.3±0.6 % is achieved, exceeding the existing method. CONCLUSIONS: The proposed TipDet can facilitate a wider and easier application of US-guided interventional procedures by providing robust and precise needle tip localization. The codes and data are available at https://github.com/ResonWang/TipDet.

Mechanical strength affecting the penetration in microneedles and PLGA nanoparticle-assisted drug delivery: Importance of preparation and formulation.

Microneedles (MNs) prepared from polymeric materials are painless and minimally invasive, safe and efficient, but they hindered by low mechanical strength and single diverse drug release pattern. Due to the distinctive mechanical strength and dimensions of poly(lactic-co-glycolic acid) (PLGA) nanoparticles (NPs), the integration of nano-technology with microneedles can effectively improve penetration and delivery efficiency through the stratum corneum. We herein designed a simple paroxetine (PAX)-loaded PLGA nanoparticles-integrated dissolving microneedles system (PAX-NPs-DMNs), aiming to improve the bioavailability of PAX through the synergistic permeation-enhancing effect of dissolving microneedles (DMNs) and NPs. PAX-NPs-DMNs had a complete tips molding rate (Neff) of (94.06 ± 2.16) %, a 15×15 quadrangular-conical microneedle array and an overall fracture force of 301.10 N, which were improved nearly 0.50 times compared with the blank microneedles (HA-DMNs) and PAX microneedles (PAX-DMNs). PAX-NPs-DMNs could extend the release duration of PAX from 1 h to 24 h and the cumulative permeability per unit area (Qn) was 47.66 times and 7.37 times higher than the PAX and the PAX-DMNs groups. PAX-NPs-DMNs could be rapidly dissolved within 10 min without hindering skin healing or causing adverse reactions. This study confirmed that PAX-NPs-DMNs can effectively improve the bioavailability of PAX and the mechanical strength of DMNs, which can easily penetrate the skin to provide sustained and painless delivery without causing adverse effects, thus offering a more convenient and effective method for central nervous diseases.

Protein-based microneedles for biomedical applications: A systematic review.

Microneedles are minimally-invasive devices with the unique capability of bypassing physiological barriers. Hence, they are widely used for different applications from drug/vaccine delivery to diagnosis and cosmetic fields. Recently, natural biopolymers (particularly carbohydrates and proteins) have garnered attention as safe and biocompatible materials with tailorable features for microneedle construction. Several review articles have dealt with carbohydrate-based microneedles. This review aims to highlight the less-noticed role of proteins through a systematic search strategy based on the PRISMA guideline from international databases of PubMed, Science Direct, Scopus, and Google Scholar. Original English articles with the keyword "microneedle(s)" in their titles along with at least one of the keywords "biopolymers, silk, gelatin, collagen, zein, keratin, fish-scale, mussel, and suckerin" were collected and those in which the proteins undertook a structural role were screened. Then, we focused on the structures and applications of protein-based microneedles. Also, the unique features of some protein biopolymers that make them ideal for microneedle construction (e.g., excellent mechanical strength, self-adhesion, and self-assembly), as well as the challenges associated with them were reviewed. Altogether, the proteins identified so far seem not only promising for the fabrication of "better" microneedles in the future but also inspiring for designing biomimetic structural biopolymers with ideal characteristics.

Computational fluid dynamics investigation on the irrigation of a real root canal with a side-vented needle.

BACKGROUND: Root canal therapy is one of the main treatments for root canal diseases, and effective irrigation is the key to successful treatment. Side-vented needle is one of the commonly used needle types in clinic. In the real root canal, due to the influence of the curvature of the root canal, the irrigation flow field in different needle directions shows obvious differences. At the same time, changes in root canal curvature and working depth will lead to changes in irrigation efficiency and the flow field. Both the mainstream of the irrigation flow and the shear stress near the wall changes significant. Consequently, either the replacement in the root canal or the removal efficiency of the smear layers is apparently modified. MATERIALS AND METHODS: In this paper, the permanent root canal of the maxillary first molar prepared until 15/04 were scanned by micro-CT, and then imported into the software for 3D reconstruction. The key parameters of flushing efficiency of 30G side needle at different working depths of 4.75 mm, 5 mm, 5.25 mm and 5.5 mm were compared. Meanwhile, the simulated models with different curvatures of 0°, 5°, 10°, 20° and 30° based on the real root canal were reconstructed to investigate the curvature effect on the irrigation efficiency. RESULTS: The results show that moderate working depth (such as 4.75 mm and 5.25 mm in present paper) helps to improve the replacement capacity of irrigation flow. At the same time, the apical pressure decreased as the working depth increased. The curvature of the root canal seriously affects the removal depth of the smear layers of the root canal. A root canal with a large curvature (especially 20° and 30°) can significantly improve the difficulty of irrigation. CONCLUSIONS: (1) Moderate working depth helps to improve the displacement capacity, the ERD of the irrigation flow is generally improved at the working depths of 4.75 mm and 5.25 mm, and the apical pressure will decrease with the increase of working depth. (2) The large curvature of the root canal can significantly improve the difficulty of irrigation. The curvature of the root canal can severely influence the removal depth of the smear layer on the wall. It can be found both the span and the depth of the ESS for little curvatures (5° and 10°) root canals are higher than those for large curvatures (20° and 30°).