MMP-9 Levels and NaOCl Lavage in Randomized Trial on Direct Pulp Capping.

Outcome expectations of direct pulp capping in carious teeth are obscured by a clinically unknown infiltration and breakdown of the dental pulp tissue. Histologic studies showed that this soft tissue breakdown is related to the innate immune system. We hypothesized 1) that a neutrophil biomarker could predict the outcome of direct pulp capping and 2) that using sodium hypochlorite (NaOCl) as a lavage solution to remove necrotized infected pulp tissue could improve it. In this randomized trial in mature posterior teeth causing no or mild discomfort with carious pulpal exposures, pulpal fluid was collected to assess neutrophil gelatinase (matrix metalloproteinase 9 [MMP-9]) per total protein (TP) levels as a predictive local biomarker. Subsequently, the dentin-pulp wound was randomly washed with a 2.5% NaOCl or a physiologic saline solution (1:1 allocation), capped with mineral trioxide aggregate, and the tooth was immediately restored with a resin-based composite restoration. Ninety-six patients were included, and 84 individuals could be followed up to treatment failure or clinically confirmed pulp survival after a minimum of 1 y. The entire data were fitted to a Cox proportional hazards model to assess the influence of the observational variables MMP-9/TP and discomfort with the randomized lavage treatment on pulp survival. The Kaplan-Meier pulp survival rates after 1 y were 55% for saline and 89% for NaOCl lavage. The inflammatory state of the pulp tissue as reflected by MMP-9/TP levels and NaOCl lavage had a highly significant (P < 0.001 and P = 0.004, respectively) impact on pulp survival, while mild preoperative discomfort did not. In conclusion, MMP-9/TP showed great promise as a predictive local biomarker, and NaOCl lavage considerably improved the survival time of cariously exposed and directly capped pulps.

Therapeutic potential of mesenchymal stem cell-derived extracellular vesicles in regenerative endodontics.

Regenerative endodontic procedures are an alternative to conventional root-canal treatment and apexification. There are two different tissue engineering approaches that are currently followed, both aiming at the colonisation of the cleaned pulp space by pluripotent cells and subsequent pulp regeneration. Firstly, the transplantation of mesenchymal stem cells (MSCs), and secondly a cell-free strategy that relies on bioactive molecules to trigger the recruitment of the patient's own cells. The first approach is hampered by costs and regulatory issues. Despite great initial enthusiasm with a clinically used cell-free approach that relies on induced bleeding into the pulp space, results have been revealed to be rather unpredictable, and mere repair rather than regeneration of the pulp-dentin complex is what is typically achieved. Moreover, the extent of further root development is variable, and the concept is limited to immature teeth. This article discusses a third possible way of regenerative endodontics that involves the application of MSC-derived exosomes. These are extracellular vesicles that contain proteins, lipids, and nucleic acids, reflecting the secretome of MSCs. Based on the first in vitro and in vivo studies, exosomes appear to be a potent tool to improve pulp regeneration. This narrative review aims to investigate the therapeutic use of human MSCs or dental pulp-derived exosomes in regenerative endodontics. Furthermore, the focus of this review is on targeting important questions that should be investigated in future in-vivo and clinical studies, such as the choice of scaffold material for exosome delivery into the pulp space.

Contrast-enhanced micro-CT to assess dental pulp tissue debridement in root canals of extracted teeth: a series of cascading experiments towards method validation.

AIM: To validate a new method for the evaluation of pulp tissue debridement in the root canals of extracted teeth using an impregnation protocol involving potassium triiodide, a radiocontrast solution known as Lugol's, combined with micro-computed tomographic (micro-CT) imaging. METHODOLOGY: The impact of NaOCl on the radiopacity of Lugol's solution was assessed using a two-fold dilution series of Lugol in distilled water and 5.25% NaOCl, which were then pipetted into transparent dishes and radiographed. To verify the influence of Lugol on the proteolytic effect of NaOCl, a dissolution test was performed using fresh bovine meat. Ten slices did not undergo any tissue processing, whilst twenty slices were fixed in formaldehyde for 24 h. After that, 10 of them were immersed in Lugol for another 24 h. Then, all specimens were placed in NaOCl and the time required for a complete tissue dissolution was recorded. For the last experiments (histological validation and micro-CT assessment), 8 extracted mandibular premolars with formerly vital pulps were immersed in buffered formalin, scanned in a micro-CT device, accessed, immersed in Lugol for 7 days and scanned again. Then, the root canals of 5 teeth were prepared and scanned, and the volume of remaining pulp tissue identified and quantified, whilst 3 teeth were histologically processed. The same specimens were subjected to histological assessment, and the images of the histologic sections were registered with the corresponding micro-CT images to verify whether the pulp tissue in the histological sections matched its counterpart in the Lugol-impregnated tissues identified in the micro-CT slices. RESULTS: There was no discernible effect on radiopacity when NaOCl was mixed with Lugol's solution. Tissue processing did not affect the time required for the complete dissolution of fresh bovine meat. Histological evaluation revealed a correlation between micro-CT and histological images confirming the identification of Lugol-impregnated pulp tissue in micro-CT images. CONCLUSIONS: The radiocontrast Lugol's solution was unaffected by NaOCl and did not interfere with its soft tissue dissolution capability. The impregnation protocol using Lugol's solution allowed the visualization of pulp tissue on the micro-CT images and the identification of pulp remnants after chemical-mechanical canal procedures.

Correlation between the clinically diagnosed inflammatory process and periapical index scores in severely painful endodontically involved teeth.

AIM: To assess and correlate three distinct states of severely painful endodontically derived inflammation with their depiction on periapical radiographs using periapical index (PAI) scores. METHODOLOGY: During a period of 15 months, 368 consecutively enrolled patients with suspected endodontic emergency conditions were examined at the University of Zurich, Center of Dental Medicine. Cases with a severely painful (numeric rating scale, NRS-11 > 6) endodontically involved tooth and a clear pulpal and apical diagnosis (n = 162) were selected (one tooth per patient). Teeth were divided into three groups according to the clinically diagnosed main location of the inflammatory process: level 1: pulp (positive response to cold test), level 2: periodontium (no response to cold without swelling) and level 3: periapical tissues (no response to cold with swelling). Periapical radiographs were obtained using a digital unit and analysed by two calibrated observers. For level 2, which had the highest PAI variance (n = 76), the PAI scores were further scrutinized regarding their dependence on tooth location and the duration of pain. Data were analysed using chi-squared and non-parametric tests, alpha = 0.05. RESULTS: Overall, the PAI scores correlated well with the clinically diagnosed main location of periapical inflammation (Spearman's rho = 0.5131, P < 0.001), with level 1 having the lowest scores by far (P < 0.001) and level 2 having significantly lower scores compared to level 3 (P < 0.05). However, a PAI score of 5 was found in merely 3 teeth within the entire cohort, and 49% of the teeth in the level 2 group had no radiolucency (PAI < 3). Within level 2, the PAI scores were not dependent on tooth location but were substantially (P < 0.001) higher for teeth which had hurt for more than one week, and for root filled teeth. CONCLUSIONS: For the analysed, severely painful endodontically involved teeth, the clinically diagnosed main location of inflammation was reflected by the periapical index. PAI scores were not significantly influenced by anatomical noise, yet in some cases under-estimated the clinical situation.

Effect of dentine cutting efficiency on the lateral force created by torque-controlled rotary instruments.

AIM: To study the impact of dentine cutting efficiency of rotary instruments on the lateral force they create when instrumenting simulated root canals in bovine dentine. METHODOLOGY: Lateral cutting efficiency of austenitic files (ProTaper Universal) was compared to that of counterparts of a reported identical geometrical design with a martensite phase component (ProTaper Gold) in bovine dentine disks (n = 6). Instrument shapes were studied using digital microscopy. The intracanal lateral force exerted by the two systems in simulated premolars (n = 9) made from bovine incisor roots containing a standardized narrow root canal of 16 mm length was monitored using a testing apparatus equipped with a torque-controlled endodontic motor/handpiece. Data were compared using parametric statistics, alpha error = 0.05. RESULTS: The geometrical design of the two systems under investigation was found to be identical. The martensitic nickel-titanium rotary files had a significantly (t-test, P < 0.05) higher lateral cutting efficiency than austenitic counterparts. This difference, however, did not impact the lateral force that was created when instrumenting simulated premolar root canals. Furthermore, lateral force peaks were generated with the progressively tapered instruments under investigation towards the full working length. Even though a glide path was prepared, the first instrument in the full-length sequence (S1) created the highest lateral force (anova/Tukey's HSD, P < 0.05). CONCLUSIONS: The current experimental set-up allows the study of the lateral force generated during root canal instrumentation. This force was not influenced by the dentine cutting efficiency of the instruments under investigation, but rather by their geometrical design.

Safety assessment of an etidronate in a sodium hypochlorite solution: randomized double-blind trial.

AIM: To assess whether Dual Rinse HEDP, an etidronate that can be combined with NaOCl to create an endodontic irrigating solution containing both hypochlorite and a chelator in the form of 1-hydroxyethane 1,1-diphosphonic acid (HEDP), alters the clinical efficacy of NaOCl or adds any untoward clinical effects. METHODOLOGY: In this randomized controlled double-blind single-centre trial, a pure NaOCl solution was compared to a HEDP-containing counterpart regarding antimicrobial efficacy, postoperative pain, and the host response by means of changes in MMP-9 levels in periapical fluid. Sixty patients presenting with asymptomatic apical periodontitis (one tooth each) were randomly divided into two groups (N = 30) based on irrigation regime. Pre- and post-treatment microbial aerobic and anaerobic cultures and MMP-9/total protein (TP) periapical fluid samples were collected. Postoperative pain levels were assessed 24 h after treatment. Categorical data were compared between groups using the Fisher's exact test, continuous data using the Wilcoxon signed-rank test, α = 0.05. RESULTS: Irrigation with pure NaOCl rendered 40% canals free of culturable microorganisms, compared to 50% with the NaOCl/HEDP mixture (P = 0.60). As assessed by matrix-assisted laser desorption/ionization-time-of-flight analysis (MALDI-TOF), no apparent selection of aerobic or anaerobic taxa occurred in either group. One patient in the NaOCl group experienced moderate pain, whilst two patients in the NaOCl/HEDP group experienced mild postoperative pain. MMP-9/TP levels in periapical fluid declined significantly (P < 0.001) after 1 week with no medication in the root canal, without significant difference between treatment groups (P > 0.05). CONCLUSIONS: This trial found no influence of HEDP on clinical NaOCl effects.

Chemical, cytotoxic and genotoxic analysis of etidronate in sodium hypochlorite solution.

AIM: To test whether the incorporation of a chelation powder, etidronate, marketed for root canal irrigation (Dual Rinse HEDP) into a sodium hypochlorite (NaOCl) solution induced additional cytotoxic and genotoxic effects not observed with NaOCl alone. METHODOLOGY: Fresh and 24-h-old mixtures of 0.9 g of etidronate in 10 mL of 2.5% NaOCl were assessed for their basic chemical features including pH and the ability to chelate Ca2+ from hydroxylapatite. Pure NaOCl and phosphate-buffered saline (PBS) with/without etidronate served as control solutions. Cytotoxic and genotoxic effects of diluted solutions (1:10, 1:100, and 1:1000) were assessed on Chinese hamster lung fibroblast (V79) using the MTT, clonogenic and micronucleus assays, respectively. One-way ANOVA and Tukey's HSD test were applied with an alpha-type error of 5% (P < 0.05). RESULTS: In mixtures of NaOCl and etidronate, the free available chlorine was lost completely after 24 h, and the pH dropped by more than 3 units. However, the ability of the etidronate to chelate Ca2+ was maintained. The fresh mixtures of NaOCl and etidronate were not more toxic than NaOCl alone (P > 0.05), whilst the 24-h-old mixtures were less toxic (P < 0.05) and statistically similar to pure etidronate. Etidronate per se showed little cytotoxicity and no genotoxicity at the tested dilutions. CONCLUSIONS: The ability of the used etidronate, Dual Rinse HEDP, to chelate calcium is not affected by NaOCl. Cytotoxicity and genotoxicity of mixed solutions is dictated by the presence of free available chlorine therein.

European Society of Endodontology position statement: Management of deep caries and the exposed pulp.

This position statement on the management of deep caries and the exposed pulp represents the consensus of an expert committee, convened by the European Society of Endodontology (ESE). Preserving the pulp in a healthy state with sustained vitality, preventing apical periodontitis and developing minimally invasive biologically based therapies are key themes within contemporary clinical endodontics. The aim of this statement was to summarize current best evidence on the diagnosis and classification of deep caries and caries-induced pulpal disease, as well as indicating appropriate clinical management strategies for avoiding and treating pulp exposure in permanent teeth with deep or extremely deep caries. In presenting these findings, areas of controversy, low-quality evidence and uncertainties are highlighted, prior to recommendations for each area of interest. A recently published review article provides more detailed information and was the basis for this position statement (Bjørndal et al. 2019, International Endodontic Journal, doi:10.1111/iej.13128). The intention of this position statement is to provide the practitioner with relevant clinical guidance in this rapidly developing area. An update will be provided within 5 years as further evidence emerges.

Dentine decalcification and smear layer removal by different ethylenediaminetetraacetic acid and 1-hydroxyethane-1,1-diphosphonic acid species.

AIM: To compare solutions of di- and tetrasodium ethylenediaminetetraacetic acid (EDTA) and 1-hydroxyethane-1,1-diphosphonic acid (HEDP) regarding their ability to solubilize calcium from dentine and remove smear layer. METHODOLOGY: Solutions with a molarity corresponding to that of 17% Na2 EDTA (pH adjusted to 8.5) were prepared by dissolving Na2 and Na4 salts of HEDP (etidronate), or Na4 EDTA in deionized water. Standardized root dentine discs covered by a smear layer were prepared from human third molars. These discs (n = 10 per group) were immersed in test solutions or phosphate-buffered saline for 1 min. The dissolved Ca2+ was determined by atomic absorption spectroscopy, apparently opened dentinal tubules by laser scanning microscopy and automated image analysis. Ca2+ values were compared between groups by parametric, tubular areas by nonparametric methods, α = 0.05. RESULTS: Solutions prepared from the tetrasodium salts were alkaline (pH 11.3-11.4), whilst counterparts made from the disodium salts were acidic. The EDTA solutions dissolved more calcium than the HEDP counterparts (P < 0.05); solutions prepared with the disodium salts dissolved more calcium than those made from the tetrasodium salts (P < 0.05). There was a high correlation between dissolved calcium and the apparently opened tubular areas (Spearman's ρ = 0.81). Differences between groups regarding opened tubules were similar to those observed regarding the Ca2+ values, with a slightly reduced discerning power due to high variance. CONCLUSION: Calcium chelation and thus smear layer removal by EDTA and HEDP are influenced by pH.

Whisky, microwave or hairdryer? Exploring the most efficient way to reduce bacterial colonisation on contaminated toothbrushes.

Aims: It is the holiday season, but your toothbrush does not look very festive. It is damp and has been used and contaminated by someone else. To rectify this heinous crime, this study investigates the effectiveness of three household objects to disinfect toothbrushes. Design: In-vitro study performed under conditions simulating everyday life. Materials and methods: Twenty toothbrushes were contaminated using a mixture of saliva and trypticase soy broth containing Escherichia coli and Enterococcus faecalis. These contaminated toothbrushes were submerged in whisky, cooked in a microwave oven, or exposed to the hot air stream of a hairdryer, separately. Each treatment was performed on five toothbrushes for one minute. Untreated specimens (n = 5) served as controls. Toothbrushes were subsequently sonicated in sterile physiological saline, which was plated on selective agars. Bacterial counts were graded as low, medium, or high. Results: Residual contamination was influenced by the disinfectant applied, both in E. coli (p <0.001) and E. faecalis (p = 0.019). Microwave cooking achieved highest decontamination, while whisky had no significant effect on bacterial counts over no treatment (p = 0.8). Hot air showed some limited effectiveness under current conditions. Conclusions: Microwave oven cooking appears to be a simple, cheap, and effective way to reduce bacterial contamination of your toothbrush.

Short-term storage stability of NaOCl solutions when combined with Dual Rinse HEDP.

AIM: To assess the stability of NaOCl solutions when combined with a novel product for clinical use, Dual Rinse HEDP, which contains etidronate (1-hydroxyethane 1,1-diphosphonate). METHODOLOGY: Mixtures of NaOCl solutions with Dual Rinse HEDP were prepared so that they initially contained 5.0%, 2.5% or 1.0% NaOCl and always 9.0% of dissolved Dual Rinse HEDP powder per total weight. NaOCl solutions alone were used as controls. The stability of these solutions over 8 h was assessed in transparent borosilicate glass bottles at ambient temperature (23 °C). Subsequently, the effects of heating (60 °C) or storing the solutions at 5 °C were studied in polypropylene syringes. NaOCl concentrations were measured by iodometric titration, that is free available chlorine contents. Experiments were performed in triplicate. RESULTS: In the glass bottles at 23 °C, the 5.0% NaOCl/9.0% Dual Rinse HEDP solution lost 20% of the available chlorine after 1 h, whilst the corresponding 2.5% NaOCl and 1.0% NaOCl solutions retained this relative amount of available chlorine for 2 and 4 h, respectively. Results obtained in the glass bottles were similar to those achieved in the syringes. Heating of the NaOCl/Dual Rinse HEDP mixtures had a detrimental effect on available chlorine, with a complete loss after 1 h. In contrast, storing the NaOCl/Dual Rinse HEDP mixtures in a refrigerator at 5 °C kept the available chlorine high for 7 h, with the expected loss after a further hour of storage at 23 °C. CONCLUSIONS: Initial NaOCl concentration and temperature both affected short-term storage stability of combined solutions containing Dual Rinse HEDP.

Microguided Endodontics: a method to achieve minimally invasive access cavity preparation and root canal location in mandibular incisors using a novel computer-guided technique.

AIM: To present a novel miniaturized and minimally invasive treatment approach for root canal localization in mandibular incisors with pulp canal calcification and apical periodontitis. SUMMARY: A 51-year-old male patient presented with pain from his mandibular incisors. The patient had a history of severe dental trauma over 30 years ago. Both mandibular central incisors (teeth 31, 41) were tender to percussion and had a yellowish discoloration. They did not respond to thermal and electrical sensitivity tests. Two periapical radiographs from different projections revealed severe pulp canal calcifications and signs of periapical periodontitis. To facilitate the 'Microguided Endodontics' technique, a CBCT and an intra-oral surface scan were aligned using special software. This allowed the virtual planning of optimal access cavities up to the apical third of the root. In this technique, a 3D-printed template guides a customized drill to the orifice of the root canal. After negotiation of the root canals, conventional root canal treatment was performed. This case report demonstrates that minimally invasive and apically extended access cavities are feasible in mandibular incisors with this technique. KEY LEARNING POINTS: The 'Microguided Endodontics' technique is a safe and minimally invasive method for root canal location and prevention of technical failures in anterior teeth with pulp canal calcification.

Effect of endodontic irrigants on biofilm matrix polysaccharides.

AIM: To specifically investigate the effect of endodontic irrigants at their clinical concentration on matrix polysaccharides of cultured biofilms. METHODOLOGY: Saccharolytic effects of 3% H2 O2 , 2% chlorhexidine (CHX), 17% EDTA, 5% NaOCl and 0.9% saline (control) were tested using agarose (α 1-3 and ß 1-4 glycosidic bonds) blocks (n = 3) in a weight assay. The irrigants were also applied to three-species biofilms (Streptococcus mutans UAB 159, Streptococcus oralis OMZ 607 and Actinomyces oris OMZ 745) grown anaerobically on hydroxyapatite discs (n = 6). Glycoconjugates in the matrix and total bacterial cell volumes were determined using combined Concanavalin A-/Syto 59-staining and confocal laser-scanning microscopy. Volumes of each scanned area (triplicates/sample) were calculated using Imaris software. Data were compared between groups using one-way anova/Tukey HSD, α = 0.05. RESULTS: The weight assay revealed that NaOCl was the only irrigant under investigation capable of dissolving the agarose blocks. NaOCl eradicated stainable matrix and bacteria in cultured biofilms after 1 min of exposure (P < 0.05 compared to all groups, volumes in means ± standard deviation, 10-3  mm3 per 0.6 mm2 disc; NaOCl matrix: 0.10 ± 0.08, bacteria: 0.03 ± 0.06; saline control matrix: 4.01 ± 1.14, bacteria: 11.56 ± 3.02). EDTA also appeared to have some effect on the biofilm matrix (EDTA matrix: 1.90 ± 0.33, bacteria: 9.26 ± 2.21), whilst H2 O2 and CHX merely reduced bacterial cell volumes. CONCLUSION: Sodium hypochlorite can break glycosidic bonds. It dissolves glycoconjugates in the biofilm matrix. It also lyses bacterial cells.

FISHing for gutta-percha-adhered biofilms in purulent post-treatment apical periodontitis.

This study investigated the possibility of depicting individual taxa in clinically relevant biofilms using fluorescent in situ hybridization (FISH). Gutta-percha samples were collected from the apical aspect of root canals associated with a chronic apical abscess (test samples, n = 8). Corresponding control samples were obtained from previously filled root canals with apparently normal periapical tissues (n = 3). The transport medium was investigated for detached biofilm fragments using FISH staining and conventional epifluorescence microscopy. Gutta-percha samples were stained by multiplex FISH, and inspected using confocal laser scanning microscopy. FISH of the transport medium confirmed the presence of the main species formerly identified by conventional methods in post-treatment purulent endodontic infections, most prominently Fusobacterium spp., Bacteroidetes and Prevotellaceae. Treponemes were identified in five of eight cases associated with purulent infections, but Enterococcus faecalis and Staphylococcus spp. were not identified. The biofilms on gutta-percha from root canals associated with apical periodontitis showed dense aggregates of variable composition. Control samples contained few, if any, bacteria in the transport medium, and featured no biofilms on the respective gutta-percha specimens. The current study revealed some direct, visual in situ information on the nature of biofilms associated with purulent periapical infections in man.

IgG4 but no IgG1 antibody production after intralymphatic immunotherapy with recombinant MAT-Feld1 in human.

Allergy immunotherapy (AIT) mediates protection against allergen exposure in part due to allergen-specific antibodies. While immunization typically stimulated IgG1 and IgG2, AIT is often associated with production of IgG4. Here, twenty cat dander-sensitized patients were randomized to receive three injections of intralymphatic immunotherapy (ILIT) with MAT-Feld1 adsorbed to aluminum hydroxide or just aluminum hydroxide (placebo) in a double-blind setting (ClinicalTrials.gov NCT00718679). Whereas the clinical data, showing benefit of Mat-Feld1 ILIT was published in 2012 (Senti et al., J Allergy Clin Immunol, vol 129(5):1290-1296), the current study investigated the cat allergen-specific antibody responses. Blood was drawn prior to ILIT, as well as 1, 3, and 12 months after first ILIT. The sera were analyzed to characterize all IgG subclasses and IgE antibody responses. ILIT with MAT-Feld1 elicited high levels of total IgG that were maintained for at least 12 months. Interestingly, a strong increase in IgG4 and some increase in IgG2 were observed throughout the study, while production of cat-specific IgG1 and IgG3 was not stimulated by MAT-Feld1 ILIT. The IgE levels remained constant.

Guided endodontics: accuracy of a novel method for guided access cavity preparation and root canal location.

AIM: To present a novel method utilizing 3D printed templates to gain guided access to root canals and to evaluate its accuracy in vitro. METHODOLOGY: Sixty extracted human teeth were placed into six maxillary jaw models. Preoperative CBCT scans were matched with intra-oral scans using the coDiagnostix(™) software. Access cavities, sleeves and templates for guidance were virtually planned. Templates were produced by a 3D printer. After access cavity preparation by two operators, a postoperative CBCT scan was superimposed on the virtual planning. Accuracy was measured by calculating the deviation of planned and prepared cavities in three dimensions and angle. Ninety-five per cent confidence intervals were calculated for both operators. RESULTS: All root canals were accessible after cavity preparation with 'Guided Endodontics'. Deviations of planned and prepared access cavities were low with means ranging from 0.16 to 0.21 mm for different aspects at the base of the bur and 0.17-0.47 mm at the tip of the bur. Mean of angle deviation was 1.81°. Overlapping 95% confidence intervals revealed no significant difference between operators. CONCLUSION: 'Guided Endodontics' allowed an accurate access cavity preparation up to the apical third of the root utilizing printed templates for guidance. All root canals were accessible after preparation.

Comparison of two contemporary rotary systems in a pre-clinical student course setting.

AIM: To assess two contemporary rotary instrumenting systems subjectively and objectively in a pre-clinical student course setting. METHODOLOGY: Undergraduate dental students (n = 44) prepared mesiolingual canals of 3D-printed mandibular molar replicas (RepliDens, Zurich, Switzerland). The HyFlex and BioRace rotary systems, both previously unknown to the students, were used according to the manufacturers' guidelines after a short theoretical introduction. For comparison, a first-generation rotary system (ProFile .04), which the students knew from their previous education, was then used in a third RepliDens. Questionnaires were issued to note subjective experiences immediately after instrumentation. Objectively, time to instrument to size 40, .04 taper and shaping outcomes were analysed. Categorical data were compared using chi-square and Fisher's exact tests, numerical data according to goodness of fit to the normal distribution, P < 0.05. RESULTS: Subjectively, the students liked the file size and sequence designation in the BioRace system significantly (P < 0.05) better than in the HyFlex counterpart, whilst they found better controllability with the HyFlex (P < 0.05), and reported no difference in cutting efficiency. They preferred both systems to the ProFile. Objectively, canal transportation was significantly less with the HyFlex (and the ProFile) systems compared to BioRace (P < 0.05). Both systems under investigation were statistically similar in terms of file fractures (nil), length control, and instrumentation time, which was considerably faster than with the ProFile control system. CONCLUSIONS: HyFlex and BioRace had perceived and quantifiable strengths and weaknesses. Both systems were equally liked by the students and preferred over the ProFile first-generation rotary system.

Short-term cardiorespiratory adaptation to high altitude in children compared with adults.

As short-term cardiorespiratory adaptation to high altitude (HA) exposure has not yet been studied in children, we assessed acute mountain sickness (AMS), hypoxic ventilatory response (HVR) at rest and maximal exercise capacity (CPET) at low altitude (LA) and HA in pre-pubertal children and their fathers. Twenty father-child pairs (11 ± 1 years and 44 ± 4 years) were tested at LA (450 m) and HA (3450 m) at days 1, 2, and 3 after fast ascent (HA1/2/3). HVR was measured at rest and CPET was performed on a cycle ergometer. AMS severity was mild to moderate with no differences between generations. HVR was higher in children than adults at LA and increased at HA similarly in both groups. Peak oxygen uptake (VO2 peak) relative to body weight was similar in children and adults at LA and decreased significantly by 20% in both groups at HA; maximal heart rate did not change at HA in children while it decreased by 16% in adults (P < 0.001). Changes in HVR and VO2 peak from LA to HA were correlated among the biological child-father pairs. In conclusion, cardiorespiratory adaptation to altitude seems to be at least partly hereditary. Even though children and their fathers lose similar fractions of aerobic capacity going to high altitude, the mechanisms might be different.

Available chlorine consumption from NaOCl solutions passively placed in instrumented human root canals.

AIM: To monitor chlorine consumption from nonagitated aqueous sodium hypochlorite (NaOCl) solutions in human root canals using a recently developed assay, which can determine the order of magnitude of available chlorine in small volumes of liquid. METHODOLOGY: The root canals of 80 extracted single-rooted human teeth were instrumented to ProTaper Universal F4 and irrigated using 1% NaOCl. Subsequently, canals were irrigated with copious amounts of deionized water to rinse out the residual chlorine. Subsequently, the teeth were sealed externally and placed in a water bath of 37 °C. Root canals were filled with NaOCl of 1%, 2.75%, 5.5%, or distilled water for 1, 10, 100 or 1000 min (n = 5 teeth per solution and time). Consumption of chlorine was measured using paper points pre-impregnated with 15% potassium iodide. Colour change of the paper points was determined photo-electronically, assessing their red value after absorbing solutions from root canals. Measurements were compared to a standard series of NaOCl down to 0.001% (n = 5 paper points per concentration). RESULTS: Red values of the paper points inserted into the root canal were affected by initial NaOCl concentration and time (two-way anova, P < 0.05). If NaOCl concentrations above 0.1% are considered to be clinically relevant, then 5.5% NaOCl retained its activity in the root canal for more than 100 min, whereas 1% NaOCl lost its activity between 10 and 100 min. CONCLUSIONS: Nonagitated NaOCl solutions can remain biologically active in human root canals for extended time periods.