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The objective of this study was to evaluate the fracture risk of ProTaper nickel-titanium (NiTi) rotary instruments under a continuous versus an alternating rotation when using the same instrumentation sequence. Plastic blocks with an embedded artificial root canal were used to investigate the fracture risk of NiTi instruments under a continuous rotation (360 degrees) and an alternating rotation (clockwise 60 degrees and counter-clockwise 45 degrees). A new instrument set was used until fracture of any instrument occurred. The number of times an instrument set and instrument type were used before fracture occurred was recorded and statistically evaluated. The results obtained in this investigation showed that the fracture risk of ProTaper instruments when used under continuous rotation was significantly higher (52.14% / P<0.001) compared with use under an alternating rotation. [ABSTRACT FROM AUTHOR]

Aim To determine the knowledge of undergraduate Spanish dental students regarding the indications of systemic antibiotics in the management of endodontic infections. Methodology The final year dental students from four Spanish dental schools were requested to answer a one-page questionnaire on the indications for systemic antibiotics in the treatment of endodontic infections. One hundred and seventy-five students were asked to participate in this research. Data were analysed using descriptive statistics and chi-square test. Results One hundred and four students (93.7%) completed satisfactorily the survey and were included in the study. The average duration of antibiotic therapy was 7.0 ± 2.0 days. All respondents chose amoxicillin as the first-choice antibiotic in patients with no medical allergies, alone (47%) or associated with clavulanic acid (53%). The first drug of choice for patients with an allergy to penicillin was clindamycin 300 mg (99%). For cases of irreversible pulpitis, up to 63% of students would prescribe antibiotics. For the scenario of a necrotic pulp, symptomatic apical periodontitis and no swelling, 44% would prescribe antibiotics. Almost 40% of students would prescribe antibiotics for necrotic pulps with asymptomatic apical periodontitis and a sinus tract. Conclusions It is necessary for the Spanish schools of dentistry to improve students' knowledge about antibiotics and their indications in endodontics. Interactive education analysing real endodontic cases using problem-based learning would help students acquire better skills in prescribing antibiotics in pulp-periapical pathosis. [ABSTRACT FROM AUTHOR]

Statement of Problem: Gingival irritation is a common side effect of at-home bleaching, but how the design of the bleaching tray affects its occurrence is unclear., Purpose: The purpose of this randomized clinical trial was to determine whether a direct relationship is present between the design of bleaching trays and the risk of gingival irritation during at-home bleaching treatments., Material and Methods: This clinical trial was registered at ClinicalTrials.gov. (NCT06371664). Seventy-two participants were randomly assigned to 2 experimental groups: extended bleaching tray (3 mm) and nonextended bleaching tray (1 mm). Over a period of 3 weeks, participants underwent a nightguard dental bleaching treatment (6 to 8 hours) using 16% carbamide peroxide gel. Gingival irritation was evaluated subjectively by participants daily and objectively by clinicians at each visit. Tooth sensitivity was recorded daily using a 5-point numerical scale. Tooth color measurements were also made with a dental spectrophotometer. The risk of gingival irritation and the risk and intensity of tooth sensitivity were analyzed with the Pearson chi squared test and Fisher exact test. The color analysis was conducted with the Student t test (α=.05)., Results: Subjectively, the risk of gingival irritation was 66.7% in the extended group and 47.2% in the nonextended group, showing no statistically significant difference (P>.05). However, objectively, the risk of gingival irritation was significantly higher in the extended group (88.9%) compared with the nonextended group (63.9%) (P=.01(95% CI 1.06 to 1.83). Tooth sensitivity intensity was significantly higher in the extended tray group (P<.001), although the design did not significantly influence the risk of tooth sensitivity (P>.05). No significant differences were found between groups regarding color change (P>.05)., Conclusions: The use of an extended bleaching tray design increases the risk of gingival irritation and the intensity of tooth sensitivity. Therefore, the nonextended tray is recommended to minimize adverse reactions., (Copyright © 2024 The Authors. Published by Elsevier Inc. All rights reserved.)

Background: This retrospective clinical study aimed to compare the sensitivity of cone-beam computed tomographic (CBCT) images and periapical (PA) radiographs to reveal cracked teeth, split teeth, and teeth with vertical root fractures (VRFs)., Methods: The authors included 98 patients (98 teeth) diagnosed with a longitudinal tooth fracture (LTF) (cracked tooth, split tooth, VRF) through direct visualization after extraction and with comprehensive clinical and radiographic records. They collected demographic, clinical, and radiographic data. The authors evaluated PA radiographs and CBCT images to identify fractures, fracture lines, and the different patterns of bone loss associated with these teeth. They used the McNemar test to compare PA radiographs and CBCT scans when assessing bone loss. They used the Fisher test to determine statistical relationships between fracture types and demographic, clinical, and radiologic traits. They used an analysis of variance test to compare patient age with fracture types., Results: CBCT images were significantly more effective (P < .05) in detecting bone loss patterns associated with LTFs than with PA radiographs, with 71% of cases detected via CBCT images compared with 42% via radiographs. Mean age was significantly greater (P < .05) in patients with teeth with VRFs than in patients with split teeth. A significant relationship was observed between the type of fracture and the following variables: root canal treatment (split, VRF, P = .002), deep probing depth (≥ 5 mm) (VRF, P = .026), and having more than 8 teeth extracted from the mouth (VRF, P = .032). Overall, there was a significant difference (P < .001) between the visualization of fracture lines (45% on PA radiographs, 65% on CBCT images)., Conclusions: CBCT scans provided more information on LTFs than PA radiographs, particularly in the identification of periradicular bone changes., Practical Implications: CBCT imaging can assist in making the clinical diagnosis of LTFs through observation of bone loss patterns, providing more information than PA radiographs., Competing Interests: Disclosures None of the authors reported any disclosures., (Copyright © 2024 American Dental Association. Published by Elsevier Inc. All rights reserved.)

PIEZO1 and PIEZO2 are essential components of mechanogated ion channels, which are required for mechanotransduction and biological processes associated with mechanical stimuli. There is evidence for the presence of PIEZO1 and PIEZO2 in teeth and periodontal ligaments, especially in cell lines and mice, but human studies are almost nonexistent. Decalcified permanent human teeth and mouse molars were processed for immunohistochemical detection of PIEZO1 and PIEZO2. Confocal laser microscopy was used to examine the co-localization of PIEZO 1 and PIEZO2 with vimentin (a marker of differentiated odontoblasts) in human teeth. In the outer layer of the human dental pulp, abundant PIEZO1- and PIEZO2-positive cells were found that had no odontoblast morphology and were vimentin-negative. Based on their morphology, location, and the absence of vimentin positivity, they were identified as dental pulp stem cells or pre-odontoblasts. However, in mice, PIEZO1 and PIEZO2 were ubiquitously detected and colocalized in odontoblasts. Intense immunoreactivity of PIEZO1 and PIEZO2 has been observed in human and murine periodontal ligaments. Our findings suggest that PIEZO1 and PIEZO2 may be mechanosensors/mechanotransducers in murine odontoblasts, as well as in the transmission of forces by the periodontal ligament in humans and mice., (© 2023 The Authors. The Anatomical Record published by Wiley Periodicals LLC on behalf of American Association for Anatomy.)

This study aimed to describe a support material removal protocol (SMRP) from inside the root canals of three-dimensional printed teeth (3DPT) obtained by the microcomputed tomography (microCT) of a natural tooth (NT), evaluate its effectiveness by comparing the 3DPT to NT in terms of internal anatomy and behaviour toward endodontic preparation, and evaluate if 3DPT are adequate to assess the differences between two preparation systems. After the SMRP, twenty 3DPT printed by PolyJet™ were microCT scanned before preparation and thereafter randomly assigned into two groups (n = 10). One group and NT were prepared using ProTaper Gold ® (PTG), and the other group with Endogal ® (ENDG). MicroCT scans were carried out after preparation, and the volume increase, volume of dentin removed, centroids, transportation, and unprepared areas were compared. For the parameters evaluated, no significant differences were found between the 3DPT and NT before and after preparation ( p > 0.05), and no significant differences were found between the 3DPT PTG group and the 3DPT ENDG group ( p > 0.05). It can be concluded that the SMRP described is effective in removing the support material SUP706B™. PolyJet™ is adequate for printing 3DPT. Furthermore, 3DPT printed with high-temperature RGD525™ have similar behaviour during endodontic preparation with PTG as the NT, and 3DPT can be used to compare two preparation systems.

The dental pulp chamber volume is a fundamental measurement in the field of endodontics, but also in forensic sciences, teaching and training, or tissue engineering. This study evaluates the precision of cone-beam computed tomography (CBCT) in comparison with computed micro-tomography (micro-CT) in evaluating the pulp chamber volume of the upper central incisors ex vivo. The intra-operator and inter-operator errors were evaluated, and the results for the two techniques were compared with those of a T-test for paired samples. The intra-operator and inter-operator errors were >0.05, indicating adequate reproducibility in each operator and no significant differences between their measurements. On the other hand, no significant differences between the two measurement techniques were found. The present results demonstrate that CBCT is a precise, feasible, and reproducible technique for the evaluation of the dental pulp chamber volume ex vivo. The results provided with this method are useful for different medical domains but also for the teaching and training of undergraduate and postgraduate students. Furthermore, the findings of this study carry significant clinical implications, as the accurate assessment of the pulp chamber volume is critical in the diagnosis and treatment of various endodontic conditions. The ability of CBCT to provide reliable 3D dental anatomy measurements can enhance the planning of endodontic treatments by allowing for a better understanding of the internal tooth morphology. Additionally, the precision and reproducibility of CBCT in assessing the pulp chamber volume can contribute to improved clinical outcomes and reduced complications during endodontic procedures. These findings further support the increasingly vital role of CBCT in modern clinical practice and underscore its value as an indispensable tool in the field of dentistry.

The objective of this study was to analyze the proprioceptive innervation of human lips, especially of the orbicularis oris muscle, since it is classically accepted that facial muscles lack typical proprioceptors, that is, muscle spindles, but recently this has been doubted. Upper and lower human lips (n = 5) from non-embalmed frozen cadavers were immunostained for detection of S100 protein (to identify nerves and sensory nerve formations), myosin heavy chain (to label muscle fibers within muscle spindles), and the mechano-gated ion channel PIEZO2. No muscle spindles were found, but there was a high density of sensory nerve formations, which were morphologically heterogeneous, and in some cases resemble Ruffini-like and Pacinian sensory corpuscles. The axons of these sensory formations displayed immunoreactivity for PIEZO2. Human lip muscles lack typical proprioceptors but possess a dense sensory innervation which can serve the lip proprioception., (© 2023 The Authors. The Anatomical Record published by Wiley Periodicals LLC on behalf of American Association for Anatomy.)

Background: Performing an appropriate Class II direct restoration is a great challenge. The correct selection of the matrix system and the elements used for its stabilization will have a great impact on the result. The aim of this study is to show a new digital method for a predictable selection of the wedge and compare it with the conventional method. Methods: Sixty patients were randomly divided into two groups. In Group 0, the wedge was selected intraoperatively by visual examination, while in Group 1 the wedge was selected preoperatively through the measurement of the cervical embrasure on the bite-wing radiography. The number of wedges used, modifications to them, and tissue damage were registered, along with the quality of the proximal contact and the marginal adaptation. Results: Student's t -test revealed a statistical difference between the number of wedges used, which was higher in Group 0 ( p < 0.05). Pearson Chi-square test showed that tissue damage was statistically higher in Group 0 ( p < 0.05), while there was no statistically significant difference between groups in wedge modifications ( p > 0.05). Group 1 revealed a higher frequency of satisfactory proximal contact and marginal adaptation ( p < 0.05). Conclusions: This new technique reduces wedges waste and tissue damage and provides an adequate interproximal anatomy.

Background: The cutaneous end organ complexes or cutaneous sensory corpuscles are specialized sensory organs associated to low-threshold mechanoreceptors. Mechano-gated proteins forming a part of ion channels have been detected in both the axon and terminal glial cells of Meissner corpuscles, a specific cutaneous end organ complex in the human glabrous skin. The main candidates to mechanotransduction in Meissner corpuscles are members of the Piezo family of cationic ion channels. PIEZO2 has been detected in the axon of these sensory structures whereas no data exists about the occurrence and cell localization of PIEZO1., Methods: Skin samples (n = 18) from the palmar aspect of the distal phalanx of the first and second fingers were analysed (8 female and 10 males; age range 26 to 61 26-61 years). Double immunofluorescence for PIEZO1 and PIEZO2 together with axonal or terminal glial cell markers was captured by laser confocal microscopy, and the percentage of PIEZOs positive Meissner corpuscles was evaluated., Results: MCs from human fingers showed variable morphology and degree of lobulation. Regarding the basic immunohistochemical profile, in all cases the axons were immunoreactive for neurofilament proteins, neuron specific enolase and synaptophysin, while the lamellar cells displayed strong S100P immunoreactivity. PIEZO1 was detected co-localizing with axonal markers, but never with terminal glial cell markers, in the 56% of Meissner corpuscles; weak but specific immunofluorescence was additionally detected in the epidermis, especially in basal keratinocytes. Similarly, PIEZO2 immunoreactivity was found restricted to the axon in the 85% of Meissner corpuscles. PIEZO2 positive Merkel cells were also regularly found., Conclusions: PIEZO1 and PIEZO2 are expressed exclusively in the axon of a subpopulation of human digital Meissner corpuscles, thus suggesting that not only PIEZO2, but also PIEZO1 may be involved in the mechanotransduction from low-threshold mechanoreceptors., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 The Authors. Published by Elsevier GmbH.. All rights reserved.)

Aim: Several factors influence the condition of the periapical tissues associated with root filled teeth. The primary objective of this study was to retrospectively evaluate the extent and speed of bone healing of large periapical lesions associated with nonsurgical root canal treatment or retreatment. The secondary objective was to analyse the relationship between the time to complete healing when analysed using cone beam computed tomography (CBCT) and other possible predictors that affect healing., Methodology: Seventy-nine patients were treated during the years 2013-2020 with large periapical lesions of endodontic origin (10-15 mm) as observed on intraoral periapical radiographs (IOPAR) were included. IOPAR and CBCT were available before treatment and during the follow-up (IOPAR every 6 months and CBCT every 12 months). The volume of periapical lesions was calculated by OsiriX Lite software. Variables such as initial volume of the lesion, age, gender, type of treatment or type of root canal filling were compared to identify the differences between healed and unhealed lesions. Pearson's Chi-square test was used for categorical variables, the t-test for age and the Wilcoxon test for initial volume of the lesion. The association between time to healing and the variables was assessed using univariate analysis and multivariate analysis. The Wilcoxon test was used to observe the association of healing time with categorical variables and the correlation index was measured with the quantitative variables., Results: Of the 79 cases analysed, 60 lesions (76%) were completely healed as verified by CBCT in a mean healing time of 19 months, of which 60% healed fully between 12 and 18 months. Increase in age of patient and larger initial volume of the lesion were associated with a significantly longer healing time (p < .001). Gender, filling material and type of treatment did not have a significant effect on the healing process (p > .05)., Conclusions: Clinicians should be aware that periapical lesions in older patients and larger areas of bone loss take longer to heal. CBCT monitoring of large periapical lesions is critical and it can help clinicians in the decision-making process., (© 2023 The Authors. International Endodontic Journal published by John Wiley & Sons Ltd on behalf of British Endodontic Society.)

The carotid body is a major peripheral chemoreceptor that senses changes in arterial blood oxygen, carbon dioxide, and pH, which is important for the regulation of breathing and cardiovascular function. The mechanisms by which the carotid body senses O 2 and CO 2 are well known; conversely, the mechanisms by which it senses pH variations are almost unknown. Here, we used immunohistochemistry to investigate how the human carotid body contributes to the detection of acidosis, analyzing whether it expresses acid-sensing ion channels (ASICs) and determining whether these channels are in the chemosensory glomic cells or in the afferent nerves. In ASIC1, ASIC2, and ASIC3, and to a much lesser extent ASIC4, immunoreactivity was detected in subpopulations of type I glomus cells, as well as in the nerves of the carotid body. In addition, immunoreactivity was found for all ASIC subunits in the neurons of the petrosal and superior cervical sympathetic ganglia, where afferent and efferent neurons are located, respectively, innervating the carotid body. This study reports for the first time the occurrence of ASIC proteins in the human carotid body, demonstrating that they are present in glomus chemosensory cells (ASIC1 < ASIC2 > ASIC3 > ASIC4) and nerves, presumably in both the afferent and efferent neurons supplying the organ. These results suggest that the detection of acidosis by the carotid body can be mediated via the ASIC ion channels present in the type I glomus cells or directly via sensory nerve fibers., Competing Interests: The authors declare no conflict of interest.

Background: The lips are a vital component of the face and are densely innervated to perform various functions. The lip edges are covered with mucocutaneous tissue called vermilion which is particularly receptive to touch and temperature. The aim of this study was to investigate the somatosensory innervation of human lips, focusing on sensory corpuscles and the presence of mechano-gated (ASIC2, PIEZO2, and TRPV4) and thermosensing (TRPV1, TRPM2, and RPM8) ion channels within them., Methods: Twelve intact lips (6 upper and 6 lower) were obtained from non-embalmed frozen cadavers (five females and seven males) with an age range of 60-80 years. The specimens were divided into three zones (medial, lateral, and median). The morphotypes of sensory corpuscles and their immunohistochemical profile was analysed. The occurrence of ion channels involved in mechanosensation and temperature detection was examined using various antibodies. Sensory corpuscle density was quantified in vermilion sections, and statistical analyses were conducted to assess differences between the upper and lower lips, as well as between females and males (p < 0.05)., Results: Different morphotypes of sensory corpuscles were identified: Ruffini-like associated with hair follicles, Meissner and glomerular corpuscles in the vermilion, and less classifiable sensory corpuscles within the mucosa. The density of sensory corpuscles in the vermilion was higher in the upper lip than in the lower lip; glomerular corpuscles predominated in the medial and median segments, whereas Meissner corpuscles were more abundant in the lateral segment. No sex-related differences were observed in the density or distribution of the two main corpuscular morphotypes. In contrast, the axons of both the glomeruli and Meissner corpuscles regularly displayed ASIC2 and PIEZO2 immunoreactivity, whereas immunoreactivity for TRPV1, TRPV4, TRPM2, and TRPV8 was absent., Conclusions: These results demonstrate that the sensory corpuscles of the vermilion are a mixture of those typical of glabrous skin mucocutaneous tissues. The presence of PIEZO2 and ASIC2 in their axons suggests that these sensory corpuscles function as mechanosensors., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 The Authors. Published by Elsevier GmbH.. All rights reserved.)

Background: Regenerative endodontics (RET) refers to biologically based procedures that aim to restore damaged tooth structures and reinstate the pulp-dentine complex to its normal physiological state., Aim: The purpose of this study was to examine the attitudes and practices of endodontists and paediatric dentists regarding RET., Design: A survey was conducted among endodontists and paediatric dentists from 13 countries. A number of factors were evaluated, including frequency of RET application, followed guidelines, disinfection techniques, intracanal medication type, scaffold type, preferred coronal seal material, and follow-up period., Results: Among the 1394 respondents, 853 (61.2%) and 541 (38.8%) were endodontists and paediatric dentists, respectively. Almost half (43%) of participants have not performed RET yet. The American Association of Endodontics guideline (47.3%) was selected as the primary source for the clinical protocol. The most frequently selected irrigant solution was 1.5%-3% NaOCl at the first (26.1%) and second (13.6%) sessions. A blood clot (68.7%) and MTA (61.9%) were the most frequently selected scaffold type and coronal barrier. Most participants preferred a 6-month follow-up period., Conclusion: According to this survey, deviations exist from current RET guidelines regarding all aspects evaluated. Standardizing clinical protocols and adhering to available guidelines would help to ensure more predictable outcomes., (© 2023 BSPD, IAPD and John Wiley & Sons Ltd.)

Gutta-percha's lack of adhesion has been presented as a drawback to avoid gaps at sealer/gutta-percha interface. Plasma treatments have been scarcely assessed on gutta-percha surfaces as a method of enhancing adhesiveness. This study aimed to evaluate the effect of low-pressure Argon and Oxygen plasma atmospheres on conventional and bioceramic gutta-percha standardized smooth discs, assessing their roughness, surface free energy, chemical structure, and sealer wettability. A Low-Pressure Plasma Cleaner by Diener Electronic (Zepto Model) was used. Different gases (Argon or Oxygen), powers (25 W, or 50 W), and exposure times (30 s, 60 s, 120 s, or 180 s) were tested in control and experimental groups. Kruskal-Wallis and Student's t-test were used in data analysis. Statistically significant differences were detected when P < 0.05. Both gases showed different behaviors according to the parameters selected. Even though chemical changes were detected, the basic molecular structure was maintained. Argon or Oxygen plasma treatments favoured the wetting of conventional and bioceramic gutta-perchas by Endoresin and AH Plus Bioceramic sealers (P < 0.001). Overall, the functionalization of gutta-percha surfaces with Argon or Oxygen plasma treatments can increase roughness, surface free energy and wettability, which might improve its adhesive properties when compared to non-treated gutta-percha., (© 2023. The Author(s).)

Background: PIEZO2 is a transmembrane protein forming part of an ion channel required for mechanotransduction. In humans, PIEZO2 is present in axon terminals of adult Meissner and Pacinian corpuscles, as well as Merkel cells in Merkel cell-neurite complexes., Methods: To study the acquisition of functional capability for mechanotransduction of developing type I slowly adapting low-threshold mechanoreceptors, i.e., Merkel cell-neurite complexes, a battery of immunohistochemical and immunofluorescence techniques was performed on human skin specimens covering the whole development and growth, from 11 weeks of estimated gestational age to 20 years of life. In addition, developmental expression of PIEZO2 type I (Meissner's corpuscles) and type II (Pacinian corpuscles) rapidly adapting mechanoreceptors was studied in parallel., Results: The first evidence of Merkel cells showing the typical morphology and placement was at 13 weeks of estimated gestation age, and at this time positive immunoreactivity for PIEZO2 was achieved. PIEZO2 expression in axons terminals started at 23 WEGA in Pacinian corpuscles and at 36 WEGA in the case of Meissner corpuscles. The occurrence of PIEZO2 in Merkel cells, Meissner and Pacinian corpuscles was maintained for all the time investigated. Interestingly PIEZO2 was absent in most Aβ type I slowly adapting low-threshold mechanoreceptors that innervate MC while it was regularly present in most Aβ type I and type II rapidly adapting low-threshold mechanoreceptors that supplies Meissner and Pacinian corpuscles., Conclusion: The present results provide evidence that human cutaneous mechanoreceptors could perform mechanotransduction already during embryonic development., Competing Interests: Conflict of interest The authors declare that there are no conflicts of interest regarding the publication of this paper., (Copyright © 2022 The Authors. Published by Elsevier GmbH.. All rights reserved.)

The present study aims to evaluate and contrast the function of the rotational speed of NiTi alloy endodontic rotary files on how resistant they are to dynamic cyclic fatigue. Methods: A total of 150 NiTi alloy endodontic rotary files with similar geometrical design and metallurgical properties were randomly divided into study groups: Group A: 200 rpm (n = 30); Group B: 350 rpm (n = 30); Group C: 500 rpm (n = 30); Group D: reciprocating movement at 350 rpm with 120° counterclockwise and 30° clockwise motion (350 rpm+) (n = 30); and Group E: reciprocating movement at 400 rpm with 120° counterclockwise and 30° clockwise motion (400 rpm+) (n = 30). A dynamic device was designed to carry out dynamic cyclic fatigue tests using artificial root canal systems made from stainless steel with an apical diameter of 250 µm, 5 mm radius of curvature, 60° curvature angle, and 6% taper, and 20 mm in length. A Weibull statistical analysis and ANOVA test were used to analyze the results. Results: The ANOVA analysis showed differences in time to failure among all the study groups that were of statistical significance (p < 0.001). Conclusions: NiTi alloy endodontic rotary files using reciprocating movement at 350 rpm with 120° counterclockwise and 30° clockwise motion exhibit greater resistance to dynamic cyclic fatigue than files used with a reciprocating movement at 400 rpm with 120° counterclockwise and 30° clockwise motion, continuous rotational speed at 200 rpm, continuous rotational speed at 350 rpm, or continuous rotational speed at 500 rpm; it is therefore advisable to use reciprocating movements at a low speed.

As an essential component of mechano-gated ion channels, critically required for mechanotransduction in mammalian cells, PIEZO2 is known to be characteristically expressed by Merkel cells in human skin. Here, we immunohistochemically investigated the occurrence of Piezo channels in a case series of Merkel cell carcinoma. A panel of antibodies was used to characterize Merkel cells, and to detect PIEZO2 expression. All analyzed tumors displayed PIEZO2 in nearly all cells, showing two patterns of immunostaining: membranous and perinuclear dot-like. PIEZO2 co-localized with cytokeratin 20, chromogranin A, synaptophysin and neurofilament. Moreover, neurofilament immunoreactive structures resembling nerve-Merkel cell contacts were occasionally found. PIEZO2 was also detected in cells of the sweat ducts. The role of PIEZO2 in Merkel cell carcinoma is still unknown, but it could be related with the mechanical regulation of the tumor biology or be a mere vestige of the Merkel cell derivation.

Clinicians should be aware of all the characteristics and capacities of the instruments that are possible to use when conducting a root canal treatment. The wide variety of nickel-titanium (Ni-Ti) rotary systems on the market and the lack of standardisation of this type of instrument makes the choice in each specific case difficult. Therefore, this review is intended to summarize the characteristics that should be taken into account when choosing one instrument over another. It will be essential to know characteristics, of alloy from which the instrument is made. Moreover, the geometry of the instrument will determine its behaviour, being the mass, the one that marks its resistance to a greater extent. The movement performed by the file is another of the fundamental keys to understand rotary instruments. In conclusion, when performing root canal treatment, the characteristics of the instrument and the tooth must be taken into account, and the operator's own limitations should be known. This paper provides the key points to keep in mind when making this type of treatment.

This study intended to help practitioners selecting the appropriate motion according to their level of expertise for glide path and complete root canal preparation of curved canals in terms of instrument fracture and preparation time. A total of 160 curved root canals (angle >30°, radius <6 mm) were allocated randomly to 4 groups: A/B for expert operators and C/D for nonexpert operators. A/C were shaped with rotary and B/D with reciprocating instruments. Preparation time was registered and compared with Kruskal-Wallis non-parametric test and Dunn's post hoc test. Instrument separation was also registered and compared with chi-square test. A fractographic analysis was performed with scanning electron microscopy. The use of reciprocation motions allowed nonexpert operators to avoid instrument breakage during glide path and to prepare root canals faster. Experts were equally effective in rotary/reciprocating root canal shaping and faster with rotary motions than nonexpert operators, who also fractured significantly more rotary instruments., (© 2021 Australian Society of Endodontology Inc.)

The aim of this study was to evaluate the effectiveness of smear layer removal after the use of different irrigation methods (passive ultrasonic irrigation (PUI), continuous ultrasonic irrigation (CUI), apical negative pressure irrigation and conventional irrigation) using scanning electron microscopy (SEM) as an analytical tool. A total of 100 single-canal teeth were decoronated and randomly divided into five groups ( n = 20) according to the irrigation method used: conventional irrigation with front outlet syringe, conventional irrigation with lateral outlet syringe, apical negative pressure irrigation (EndoVac), PUI with Irrisafe and CUI with ProUltra PiezoFlow ultrasonic irrigation needle. Root canal preparation was performed with the ProTaper Gold system up to the F4 instrument, and 5.25% NaOCl was used as an irrigant. After chemical-mechanical preparation, the roots were split longitudinally, and the coronal, middle and apical thirds were examined. SEM digital photomicrographs were taken at ×1000 magnification to evaluate the amount of smear layer in each root canal third; CUI significantly removed more smear layer than any other irrigant activation protocol ( p < 0.05); CUI was more effective in removing the smear layer than the other irrigation protocols. However, none of the irrigation protocols were able to produce root canals completely free from smear layer.

Although clustering by operational taxonomic units (OTUs) is widely used in the oral microbial literature, no research has specifically evaluated the extent of the limitations of this sequence clustering-based method in the oral microbiome. Consequently, our objectives were to: 1) evaluate in-silico the coverage of a set of previously selected primer pairs to detect oral species having 16S rRNA sequence segments with ≥97% similarity; 2) describe oral species with highly similar sequence segments and determine whether they belong to distinct genera or other higher taxonomic ranks. Thirty-nine primer pairs were employed to obtain the in-silico amplicons from the complete genomes of 186 bacterial and 135 archaeal species. Each fasta file for the same primer pair was inserted as subject and query in BLASTN for obtaining the similarity percentage between amplicons belonging to different oral species. Amplicons with 100% alignment coverage of the query sequences and with an amplicon similarity value ≥97% (ASI97) were selected. For each primer, the species coverage with no ASI97 (SC-NASI97) was calculated. Based on the SC-NASI97 parameter, the best primer pairs were OP&#95;F053-KP&#95;R020 for bacteria (region V1-V3; primer pair position for Escherichia coli J01859.1: 9-356); KP&#95;F018-KP&#95;R002 for archaea (V4; undefined-532); and OP&#95;F114-KP&#95;R031 for both (V3-V5; 340-801). Around 80% of the oral-bacteria and oral-archaea species analyzed had an ASI97 with at least one other species. These very similar species play different roles in the oral microbiota and belong to bacterial genera such as Campylobacter , Rothia , Streptococcus and Tannerella , and archaeal genera such as Halovivax , Methanosarcina and Methanosalsum . Moreover, ~20% and ~30% of these two-by-two similarity relationships were established between species from different bacterial and archaeal genera, respectively. Even taxa from distinct families, orders, and classes could be grouped in the same possible OTU. Consequently, regardless of the primer pair used, sequence clustering with a 97% similarity provides an inaccurate description of oral-bacterial and oral-archaeal species, which can greatly affect microbial diversity parameters. As a result, OTU clustering conditions the credibility of associations between some oral species and certain health and disease conditions. This significantly limits the comparability of the microbial diversity findings reported in oral microbiome literature., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2022 Regueira-Iglesias, Vázquez-González, Balsa-Castro, Blanco-Pintos, Martín-Biedma, Arce, Carreira and Tomás.)

The aim of this study was to evaluate the efficacy of continuous apical negative ultrasonic irrigation into simulated lateral canals and the apical third in straight and curved root canals. Two simulated lateral canals were created 2, 4 and 6 mm from the working length in 120 single-rooted teeth (6 canals/tooth, n = 360 straight, n = 360 curved). The teeth were randomly divided into 3 experimental groups: positive pressure irrigation (PPI) (n = 20); passive ultrasonic irrigation (PUI) (n = 20); continuous apical negative ultrasonic irrigation (CANUI) (n = 20). 20% Chinese ink was added to a 5% sodium hypochlorite solution and delivered into the root canals. The results showed a significantly higher (P < 0.05) penetration of irrigant into the lateral canals and up to working length in the CANUI group for straight and curved roots. CANUI improves penetration into the lateral canals and up to the working length of the cleared teeth in straight and curved roots.

Introduction: The aim of this study was to evaluate the influence of rotary (ProTaper Next [PTN; Dentsply Maillefer, Ballaigues, Switzerland] and ProTaper Gold [PTG, Dentsply Maillefer]) and reciprocating (WaveOne Gold [WOG, Dentsply Maillefer]) systems in dentinal microcrack generation after the preparation of curved root canals using micro-computed tomographic analysis., Methods: Twenty-four human mandibular molars with curved roots were scanned in a micro-computed tomographic device using an isotropic resolution of 6.78 μm and randomly assigned into 1 of 3 experimental groups (n = 8) according to the root canal instrumentation system used (PTN, PTG, or WOG). Then, the root canals were prepared up to PTN X2, PTG F2, and WOG Primary instruments in the PTN, PTG, and WOG groups, respectively. After canal preparation, each specimen was scanned again. Pre- and postoperative cross-sectional images of the roots (N = 35,304) were analyzed to identify the presence of dentinal microcracks., Results: Overall, 26% of the images presented dentinal defects (n = 9188). Dentinal microcracks were observed in 24.6%, 26%, and 27.4% of the postinstrumentation images from the PTN, PTG, and WOG groups, respectively. However, all of these dentinal microcracks were already present in the corresponding preoperative images. No new microcracks were generated after the preparation of curved root canals of mandibular molars using the aforementioned systems., Conclusions: Root canal instrumentation with PTN, PTG, and WOG systems did not induce the formation of new dentinal microcracks., (Copyright © 2020 American Association of Endodontists. Published by Elsevier Inc. All rights reserved.)

Heparan sulfate proteoglycans are pericellular/cell surface molecules involved in somatosensory axon guidance in the peripheral nervous system. However, the distribution of heparan sulfate proteoglycans in the extracellular matrix of human cutaneous sensory corpuscles is unknown. Immunohistochemistry and immunofluorescence assays were performed to define the localization of heparan sulfate proteoglycans in human cutaneous Meissner's and Pacinian corpuscles using two anti-heparan sulfate antibodies together with anti-S100 protein, anti-PGP9.5, anti-CD34 (to immunolabel basement membranes, Schwann cells, axon and the intermediate endoneurial layer of Pacinian corpuscles, respectively), anti-Type IV collagen, and anti-chondroitin sulfate antibodies. Heparan sulfate proteoglycans were colocalized with Type IV collagen in Meissner's corpuscles and were located in the outer core lamellae and capsule, but not in the inner core or the intermediate layer, in Pacinian corpuscles. Chondroitin sulfate was observed in the intermediate layer of Pacinian corpuscles but was never colocalized with heparan sulfate proteoglycans. The present results strongly suggest that heparan sulfate proteoglycans are associated with the basement membranes of the lamellar cells in Meissner's corpuscles and with the complex outer core capsule in Pacinian corpuscles. The functional significance of these results, if any, remains to be elucidated., (© 2019 American Association for Anatomy.)

Cusp fractures occur frequently in endodontically treated teeth with large restorations and no cusp protection. These fractures often lead to challenging clinical decisions, such as whether to undertake complex restorative management or extraction of the affected teeth. This article reports the surgical and restorative management of two teeth with fractures exceeding the biologic width to juxtacrestal and subcrestal levels, respectively, and describes a new technique for such treatment.

Decline of tactile sensation associated with ageing depends on modifications in skin and both central and peripheral nervous systems. At present, age-related changes in the periphery of the somatosensory system, particularly concerning the effects on mechanoreceptors, remain unknown. Here we used immunohistochemistry to analyse the age-dependent changes in Meissner's and Pacinian corpuscles as well as in Merkel cell-neurite complexes. Moreover, variations in the neurotrophic TrkB-BDNF system and the mechanoprotein Piezo2 (involved in maintenance of cutaneous mechanoreceptors and light touch, respectively) were evaluated. The number of Meissner's corpuscles and Merkel cells decreased progressively with ageing. Meissner's corpuscles were smaller, rounded in morphology and located deeper in the dermis, and signs of corpuscular denervation were found in the oldest subjects. Pacinian corpuscles generally showed no relevant age-related alterations. Reduced expression of Piezo2 in the axon of Meissner's corpuscles and in Merkel cells was observed in old subjects, as well was a decline in the BDNF-TrkB neurotrophic system. This study demonstrates that cutaneous Meissner's corpuscles and Merkel cell-neurite complexes (and less evidently Pacinian corpuscles) undergo morphological and size changes during the ageing process, as well as a reduction in terms of density. Furthermore, the mechanoprotein Piezo2 and the neurotrophic TrkB-BDNF system are reduced in aged corpuscles. Taken together, these alterations might explain part of the impairment of the somatosensory system associated with ageing., (© 2019 Anatomical Society.)

Surgical extrusion should be considered as an alternative treatment in patients with structurally compromised teeth that retain coronal integrity and have favorable root anatomy. The procedure described is straightforward and can be performed quickly. A situation in which it was used to treat a maxillary premolar with substantial structural loss but well-preserved periodontal attachment is presented. The biologically oriented preparation technique is a conservative method of tooth restoration., (Copyright © 2019 Editorial Council for the Journal of Prosthetic Dentistry. Published by Elsevier Inc. All rights reserved.)

Background: The aim of this study was to evaluate the fracture and defects observed in ProTaper Next files discarded after a normal clinical use., Material and Methods: 571 ProTaper Next rotary instruments were collected after clinical use from the clinic of endodontics over 12 months. The length of the files was measured using a digital caliper to determine any fracture, later all the files were evaluated under a stereomicroscope to observe defects such as unwinding, curving or fracture. The data obtained were analyzed using a chi-square and z test., Results: 13.83% of the discarded files showed defects, the most frequent defect was fracture (7.53%). The highest rate of fracture was observed in the X1 (17.04) files (19.87%). The presence of deformations without fracture was also more frequent in the 17.04 file (11.8%)., Conclusions: Because of the relatively high incidence of deformation of smaller files, these instruments should be considered as a single use. It is important not to exceed the maximum uses recommended by the manufacturer to reduce the risk of cyclic fatigue, the main cause of fracture of the files (79.07%). It is also important to observe each file after use to discard small defects or fractures. Key words: Clinical use, deformation, fracture, M-Wire, ProTaper Next., Competing Interests: Conflict of interest statement: The authors have declared that no conflict of interest exist.

Background: The incidence of endodontic infections is high. The contribution of Endodontics to the global problem of antibiotic resistance could be significant. The ESE, together with the World Health Organization, are promoting the World Antibiotic Awareness Week (13-19 November 2017) to promote the appropriate use of systemic antibiotics in Endodontics. The objective of this study was to determine the prescription pattern of antibiotics in the treatment of endodontic infections of Spanish dentists attending specialization programs in Endodontics., Material and Methods: Dentists from five Spanish endodontic postgraduate programs were requested to answer a one-page questionnaire surveying about antibiotics indications. Seventy-three dentists were required to participate in this investigation, and 67 (91.2%) fulfilled satisfactorily the survey and were included in the study. Data were analyzed using descriptive statistics and chi square test., Results: The average duration of antibiotic therapy was 6.8±1.2 days. All respondents chose amoxicillin as first choice antibiotic in patients with no medical allergies, alone (40%) or associated to clavulanic acid (60%). The first drug of choice for penicillin allergic patients was clindamycin (72%). For cases of irreversible pulpitis, 22% of respondents prescribed antibiotics. For the scenario of a necrotic pulp, symptomatic apical periodontitis and no swelling, 37% prescribed antibiotics. A quarter of dentists prescribed antibiotics for necrotic pulps with asymptomatic apical periodontitis and a sinus tract., Conclusions: The results of this study show that postgraduate training in Endodontics provides greater awareness of the correct indications of antibiotics. Dentists who have received specialized training in Endodontics have a prescription pattern of antibiotics more adjusted to the guidelines recommended by international organizations and by scientific societies. Key words: Antibiotics, apical periodontitis, dental curriculum, endodontic infections, postgraduate endodontic training., Competing Interests: Conflict of interest statement: Authors have no conflict of interest to declare.

Background: One of the causative factors of root defects is the increased friction produced by rotary instrumentation. A high canal curvature may increase stress, making the tooth more susceptible to dentinal cracks. The purpose of this study was to evaluate dentinal micro-crack formation with the ProTaper NEXT and ProTaper Universal systems using LED transillumination, and to analyze the micro-crack generated at the point of maximum canal curvature., Material and Methods: 60 human mandibular premolars with curvatures between 30-49° and radii between 2-4 mm were used. The root canals were instrumented using the Protaper Universal® and Protaper NEXT® systems, with the aid of the Proglider® system. The obtained samples were sectioned transversely before subsequent analysis with LED transillumination at 2 mm and 8 mm from the apex and at the point of maximum canal curvature. Defects were scored: 0 for no defects; and 1 for micro-cracks., Results: Root defects were not observed in the control group. The ProTaper NEXT system caused fewer defects (16.7%) than the ProTaper Universal system (40%) ( P <0.05). The ProTaper Universal system caused significantly more micro-cracks at the point of maximum canal curvature than the ProTaper NEXT system ( P <0.05)., Conclusions: Rotary instrumentation systems often generate root defects, but the ProTaper NEXT system generated fewer dentinal defects than the ProTaper Universal system. A higher prevalence of defects was found at the point of maximum curvature in the ProTaper Universal group. Key words: Curved root, Micro-crack, point of maximum canal curvature, ProTaper NEXT, ProTaper Universal, Vertical root fracture., Competing Interests: Conflict of interest statement:The authors declare that no competing interests exist.

Introduction: Regenerative endodontic procedures (REP) are a promising alternative for necrotic immature teeth in adolescents and children, but very little evidence is available on this alternative in long-lasting necrotic teeth with open apices in adults. REPs are designed to replace damaged structures of the pulp-dentin complex, but no regeneration has been obtained in any of the cases described in necrotic immature permanent teeth with apical periodontitis with histologic results. The results are limited to periapical tissue repair with increasing root length, thickening of the root walls, and apical closure in young patients. In this series of cases, we report on the outcomes of the adjuvant use of autologous platelet-rich plasma (PRP) in endodontic therapy in adults by monitoring periapical tissue healing with periodic periapical radiographs and cone-beam computed tomographic scanning., Methods: Three teeth with apical periodontitis and open apices in 3 different patients from 21 to 35 years-old were evaluated. An REP was performed with the adjuvant use of PRP., Results: At controls, complete disappearance of the radiolucent lesions and the presence of calcified structures forming bridges occupying the pulp lumen were observed but not an ostensible thickening of root walls with a regeneration of pulp-dentin complex., Conclusions: The repair of periapical tissues with REPs of open apex teeth with apical periodontitis and in nonsurgical endodontic retreatment appears to be feasible in adults, but no regeneration was obtained in any of the present cases. The use of PRP may be a good choice as an autologous matrix because of its stability and induction; it contains growth factors and bioactive molecules like transforming growth factor beta, bone morphogenic proteins, insulinlike growth factors, and angiogenetic growth factors, which stimulate collagen production, angiogenesis, and cell differentiation. Anti-inflammatory and antibacterial properties have also been reported for this preparation, which are involved in all processes of repair., (Copyright © 2017 American Association of Endodontists. Published by Elsevier Inc. All rights reserved.)