Shaping Ability of F6 SkyTaper®, Hyflex® EDM One File, and One Curve®: A Micro-computed Tomographic Evaluation in Curved Root Canals.

OBJECTIVE: The present study aimed to compare the shaping ability of the F6 SkyTaper® (F6S), HyFlex® EDM OneFile (HEDM), and One Curve® (OC) nickel-titanium single-file instruments using micro-computed tomography. METHODS: Fifty-two mesiobuccal roots of maxillary first molars, with a degree of curvature between 20° and 42°, were randomised into three experimental groups (n=15 per group): F6S, HEDM, and OC, and a non-instrumented control group (n=7). All specimens were scanned by micro-computed tomography before and after instrumentation. The following parameters were evaluated: preparation time, volume of dentine removed, cutting efficiency, unshaped surfaces, and canal transportation. Cutting efficiency was analysed using an ANOVA parametric test and Tukey's multiple comparison post hoc test. Other parameters were analysed using a non-parametric Kruskall-Wallis test followed by Dunn's multiple comparison post hoc test. RESULTS: No instrument separation occurred during instrumentation. No significant differences were found between the instrument groups with respect to all the parameters (p>0.05). All the instruments induced morphological changes in the root canal dentine (p<0.05) and tended to increase canal transportation toward the coronal portion of the root canals (p>0.05). CONCLUSION: All instruments were able to shape curved canals and preserve their original anatomy. Single-file endodontic procedures with these instruments can be used with comparable changes in the root canal shape with minimal transportation. (EEJ-2022-01-06).

In Vitro and In Vivo Evaluation of a Bio-Inspired Adhesive for Bone Fixation.

Compared to metallic hardware, an effective bone adhesive can revolutionize the treatment of clinically challenging situations such as comminuted, articular, and pediatric fractures. The present study aims to develop such a bio-inspired bone adhesive, based upon a modified mineral-organic adhesive with tetracalcium phosphate (TTCP) and phosphoserine (OPS) by incorporating nanoparticles of polydopamine (nPDA). The optimal formulation, which was screened using in vitro instrumental tensile adhesion tests, was found to be 50%molTTCP/50%molOPS-2%wtnPDA with a liquid-to-powder ratio of 0.21 mL/g. This adhesive has a substantially stronger adhesive strength (1.0-1.6 MPa) to bovine cortical bone than the adhesive without nPDA (0.5-0.6 MPa). To simulate a clinical scenario of autograft fixation under low mechanical load, we presented the first in vivo model: a rat fibula glued to the tibia, on which the TTCP/OPS-nPDA adhesive (n = 7) was shown to be effective in stabilizing the graft without displacement (a clinical success rate of 86% and 71% at 5 and 12 weeks, respectively) compared to a sham control (0%). Significant coverage of newly formed bone was particularly observed on the surface of the adhesive, thanks to the osteoinductive property of nPDA. To conclude, the TTCP/OPS-nPDA adhesive fulfilled many clinical requirements for the bone fixation, and potentially could be functionalized via nPDA to offer more biological activities, e.g., anti-infection after antibiotic loading.

Isthmus morphology influences debridement efficacy of activated irrigation: A laboratory study involving biofilm mimicking hydrogel removal and high-speed imaging.

AIM: Little is known about the influence of isthmus morphology on the debridement efficacy of activated irrigation. The aim of this study was to investigate the influence of isthmus morphology on the debridement efficacy of laser-activated irrigation (LAI), EDDY and needle irrigation (NI), and to explain the methods of isthmus cleaning by LAI and EDDY. METHODOLOGY: Four root canal models (apical diameter: 0.30 mm, taper: 0.06, curvature: 23°, length: 20 mm) were produced by CAD-CAM with different isthmus morphologies: long-wide (4 mm; 0.4 mm), long-narrow (4 mm; 0.15 mm), short-wide (2 mm; 0.4 mm) and short-narrow (2 mm; 0.15 mm). The isthmuses were filled with a hydrogel containing dentine debris. The canals were filled with irrigant and models were assigned to the following irrigation protocols (n = 240): needle irrigation (NI) with a 30G needle, Eddy, and LAI (2940 nm Er:YAG-laser, 15 Hz, 40 mJ, SWEEPS, tip at the canal entrance). Standardized images of the isthmuses were taken before and after irrigation, and the amount of removed hydrogel was determined using image analysis software and compared across groups using Kruskal-Wallis test followed by Dunn's multiple comparison. Visualization of the isthmus during activation was achieved using a high-speed camera. The pattern and speed of the flow in the isthmus as well as transient and stable cavitation were analysed using imaging software. RESULTS: Laser-activated irrigation, EDDY and NI removed more hydrogel in short-wide isthmuses than in narrow isthmuses (p < .001). LAI and EDDY removed more hydrogel than NI in every isthmus configuration (p < .001). EDDY showed eddies and stable cavitation, and LAI showed transient cavitation at each pulse, and pulsed horizontal flow with the highest particle speed in closed short isthmuses. CONCLUSIONS: Isthmus morphology influences debridement in all irrigation groups. Short-wide isthmuses were the easiest to clean while narrow isthmuses were the most challenging to clean. Width seems to be a more critical anatomical parameter than length. LAI and EDDY resulted in the greatest biofilm removal and performed better than NI. EDDY produced eddies and stable cavitation in the isthmus, and LAI showed transient cavitation and pulsed horizontal flow.

Effect of dimensional variations on the manufacturing process and the 3D shrinkage ratio of stereolithographic dental alumina ceramics.

The purpose of the present study was to evaluate the influence of height and length variations of alumina ceramics manufactured by stereolithography on deformations caused by the manufacturing process and on the 3D shrinkage ratio to control the final dimensions and improve the adaptation of stereolithographic ceramic dental prostheses. Two different U-shaped models were designed with variable heights or lengths. The specimens were manufactured by stereolithography and were scanned using a microtomographic device before and after the heat treatment. Dimensional variations were measured using inspection software. The number and surface of layers of alumina ceramic influenced the reliability of the stereolithography manufacturing but did not influence the 3D shrinkage ratio. The larger the layer surface, the larger the deformation of the ceramic. Dental ceramics manufactured by stereolithography with smallest layer surface are the most reliable. This helps in the selection of the build orientation.

Severity Level and Duration of Energy Deficit in Mice Affect Bone Phenotype and Bone Marrow Stromal Cell Differentiation Capacity.

Anorexia nervosa is known to induce changes in bone parameters and an increase in bone marrow adiposity (BMA) that depend on the duration and seriousness of the disease. Previous studies have found that bone loss is associated with BMA accumulation. Sirtuin of type 1 (Sirt1), a histone deacetylase that is partly regulated by energy balance, was shown to have pro-osteoblastogenic and anti-adipogenic effects. To study the effects of the severity and duration of energy deficits related to bone loss, a mouse model of separation-based anorexia (SBA) was established. We recently demonstrated that moderate body weight loss (18%) 8-week SBA protocol in mice resulted in an increase in BMA, bone loss, and a significant reduction in Sirt1 expression in bone marrow stromal cells (BMSCs) extracted from SBA mice. We hypothesised that Sirt1 deficit in BMSCs is associated with bone and BMA alterations and could potentially depend on the severity of weight loss and the length of SBA protocol. We studied bone parameters, BMA, BMSC differentiation capacity, and Sirt1 expression after induction of 4 different levels of body weight loss (0%,12%,18%,24%), after 4 or 10 weeks of the SBA protocol. Our results demonstrated that 10 week SBA protocols associated with body weight loss (12%, 18%, 24%) induced a significant decrease in bone parameters without any increase in BMA. BMSCs extracted from 12% and 18% SBA groups showed a significant decrease in Sirt1 mRNA levels before and after co-differentiation. For these two groups, decrease in Sirt1 was associated with a significant increase in the mRNA level of adipogenic markers and a reduction of osteoblastogenesis. Inducing an 18% body weight loss, we tested a short SBA protocol (4-week). We demonstrated that a 4-week SBA protocol caused a significant decrease in Tb.Th only, without change in other bone parameters, BMA, Sirt1 expression, or differentiation capacity of BMSCs. In conclusion, this study showed, for the first time, that the duration and severity of energy deficits are critical for changes in bone parameters, BMSC differentiation, and Sirt1 expression. Furthermore, we showed that in this context, Sirt1 expression could impact BMSC differentiation with further effects on bone phenotype.

Bilateral double site (calvarial and mandibular) critical-size bone defect model in rabbits for evaluation of a craniofacial tissue engineering constructs.

Most existing preclinical models for evaluating the biosafety and bone-regeneration efficacy of innovative bone substitute materials (BSMs) or tissue engineering (TE) constructs only consisted of a single-site defect and the anatomical locations of defect varied drastically. While the compelling evidence showed that the bone healing pattern is location-dependent, owing to developmental, structural, and functional differences of anatomical locations, this is particularly true for the craniofacial region. Taking this into account, the bone healing efficiency of a BSM shown at one anatomical defect location cannot ensure the same impact at another. This prompted us to develop, for the first time, a model of bilateral critical-sized defect (CSD) at two distinctly different locations (non-load-bearing parietal calvaria and load-bearing mandibular body) co-existing in one rabbit to reduce the number of animals needed and avoid the influence of interindividual variability and evaluation bias on comparisons. 24 healthy adult male New Zealand White rabbits were randomly assigned to a group, either control, autograft (considered the "gold standard") or a clinically relevant BSM (biphasic calcium phosphate granules) (BCPg, Mastergraft®, Medronics). The full-thickness cylindrical calvarial defect (ø10 mm) on frontoparietal region and mandibular composite defect (ø11 mm) on the body of the mandible were created bilaterally using low-speed drilling with saline irrigation. The defect on one side was filled with autograft debris or BCPg, and the other side was no graft (empty). Following the euthanasia of animals at the predetermined intervals (4w and 12w), the defect zones were examined macroscopically and then sampled and processed for microcomputed tomography (microCT) and histological analysis. All surgeries went uneventfully, and all rabbits recovered slowly but steadily. No symptoms of infection or inflammation associated with the defect were observed during the experiment. At 4w and 12w, macroscopic views of all defect sites were clean without any signs of necrosis or abscess, and no intraoral communication was found. The analysis of microCT and histological findings showed the non-healing nature of the empty defect, thereby both calvaria and mandible CSDs can be validated. The study of the application of BCPg in this defect model highlighted good osteointegration and excellent osteoconductive properties but compromised the osteoinductive properties of this material (compared with autograft). To conclude, this novel double-site CSD model holds great promise in the application for preclinical evaluation of BSMs, TE construct, etc. With a reduced number of animals in use, and lower interindividual variability and evaluation bias for comparisons.

T1-weighted MRI images accurately represent the volume and surface of architectural mineral damage of osteonecrosis of the femoral head: Comparison with high-resolution computed tomography.

The potency of magnetic resonance imaging (MRI) to measure the exact extent of osteonecrosis of the femoral head (ONFH) remains uncertain. The objective of this study was to determine if the volume of necrosis assessed with MRI accurately reflects the volume of architectural mineral alterations in osteonecrosis of the femoral head by comparison with high-resolution microfocus X-ray computed tomography (HR-µCT). Fourteen male patients aged 53 years [46.2;59.0] suffering from ONFH were prospectively enrolled to undergo preoperative MRI and ex vivo analysis using HR-µCT. The necrotic zone on T1-weighted MRI scans was defined as total necrosis (delimited by the low-signal peripheral band) or dark necrosis (low-signal lesions only). The HR-µCT scans delimited outer necrosis and inner necrosis by including or excluding the sclerotic zone. The intra-class correlation coefficient (ICC) was calculated to compare the agreement of surface areas and volumes of necrosis measurements with the two techniques. There was an overall excellent agreement between MRI dark necrosis volume and HR-µCT outer necrosis volume (ICC=0.91[0.54;0.98]) while the MRI total necrosis volume showed poor agreement with both HR-µCT delimitations of necrosis volume. For surface area, agreement between MRI dark necrosis and HR-µCT delimitations was good for inner necrosis (ICC=0.70[0.21;0.9]) and moderate for outer necrosis (ICC=0.58[0.07;0.85]). This study demonstrates that measurement of the MRI lesions provides a reliable assessment of the extent of ONFH-related architectural damage.

Mandibular bone is protected against microarchitectural alterations and bone marrow adipose conversion in ovariectomized rats.

Osteoporosis is a disease that leads to a loss of bone mass and to alterations in the bone microarchitecture that occur in a site-specific manner; however it remains controversial in the jaw. The involvement of bone marrow adipose tissue (BMAT) in the bone metabolism has been suggested in several physiopathological contexts, such as in aging and osteoporosis. To test whether the BMAT content is related to mandibular bone loss, this study aimed to investigate the potential correlations between the trabecular bone microarchitecture on one hand and BMAT content and its spatial distribution in relation to bone surface on the other hand during aging and ovariectomy (OVX) during a long-term follow-up in a mature rat model. No age-related microarchitectural or BMAT changes were observed in the mandible. The OVX-induced bone loss was three-fold lower in the mandible than in the tibia and was observed only in the alveolar bone (not in the condyle). We also report a delayed increase in the mandibular BMAT content that remained 4-6-fold lower compared to tibia. This low BMAT content in the mandible was located at a distance from the trabecular bone surface (only 5% in contact with the bone surface versus 87% in the tibia). These findings highlight a specific mandibular response to OVX, in particular fewer microarchitectural alterations compared to that in the tibia. For the latter, the trabecular bone thickness and surface were correlated with the BMAT content. Oral functions may have a protective effect on the mandibular BMAT conversion in an OVX context.

A Novel microCT Method for Bone and Marrow Adipose Tissue Alignment Identifies Key Differences Between Mandible and Tibia in Rats.

Bone homeostasis is influenced by the bone marrow adipose tissue (BMAT). BMAT distribution varies from one anatomical location in the skeleton to another. We developed an advanced microfocus computed tomography imaging and analysis protocol that allows accurate alignment of both the BMAT distribution and bone micro-architecture as well as calculation of the distance of the BMAT adipocytes from the bone surface. Using this protocol, we detected a different spatial BMAT distribution between the rat tibia and mandible: in the proximal metaphysis of the tibia a large amount of BMAT (~ 20% of the total BMAT) was located close to the bone surface (< 20 µm), whereas in the alveolar ridge ~ 30% of the total BMAT was located between 40 and 60 µm from the bone surface. In the alveolar ridge of rats, the trabecular bone volume was 48.3% higher compared to the proximal metaphysis of the tibia (p < 0.0001) and the percentage of adiposity determined to the relative marrow volume was lower (1.5%) compared to the proximal metaphysis of the tibia (9%, p = 0.0002). Interestingly, in the tibia a negative correlation was found between the percentage of adiposity in the total volume and the trabecular thickness (r =- 0.74, p = 0.037). The present study highlights that in comparison to tibial proximal metaphysis, the mandibular bone exhibits a massive trabecular network and a low BMAT content with almost no contact with the bone surface. These findings are of great interest because of the importance of the fat-bone interaction and its potential relevance to several resorptive bone diseases.

Congenital stapes ankylosis: study of 28 cases and surgical results.

OBJECTIVE: The objective of this study was to analyze functional results after stapes surgery in patients with congenital nonprogressive conductive deafness resulting from an isolated fixation of the stapes according to age and surgical procedure. STUDY DESIGN: The authors conducted a retrospective case series from March 1993 to December 2003 in patients from two tertiary referral centers. METHODS: Twenty-eight patients were operated on by stapedotomy or partial stapedectomy using Teflon stapes prostheses. The median age at surgery was 14.2 years (range, 8.3-29.1 years). Main outcome measures were clinical and audiometric evaluation before and after surgery. Mean air conduction (MAC) and bone conduction (MBC) thresholds were recorded at 0.5, 1, 2, and 4 kHz. The evaluation of functional outcome was based on the MAC gain, the MBC comparison, and the mean postoperative and residual air-bone gaps. RESULTS: The median preoperative MAC was 50 dB (range, 19.0-65.0 dB) with a 35.0 dB median dB air-bone gap. With a mean follow up of 19 months, postoperative hearing improvement was statistically significant: median gain of 32.5 dB (P<.001) and median residual air-bone gap of 3.5 dB. The MBC was also statistically improved with median pre- and postoperative MBC of 11.5 and 6.5 dB, respectively (P<.001). Results were not dependent on the age group or type of surgery (stapedotomy or partial stapedectomy). No perceptive hearing loss was observed despite one gusher case. CONCLUSION: Surgical treatment of isolated congenital stapes ankylosis allows good functional results regardless of age or type of surgery.

Cricotracheal resection in children weighing less than 10 kg.

OBJECTIVE: To review cricotracheal resection (CTR) in children weighing less than 10 kg. DESIGN AND SETTING: Retrospective study of 17 patients (mean follow-up, 23 months) from 3 ear, nose, and throat pediatric centers. PATIENTS: Seventeen children (10 boys and 7 girls; mean age, 14.6 months; and mean weight, 7.6 kg) undergoing CTR from June 1995 to March 2003. MAIN OUTCOME MEASURES: Decannulation rates and endoscopies. RESULTS: The cause was congenital subglottic stenosis in 2 children (12%) and acquired subglottic stenosis in 15 (88%). All but 1 had grade 3 or 4 stenosis. The mean hospitalization duration was 34 days. Single-stage CTR was performed in 11 children (65%), with peroperative decannulation in 7. Extubation of these patients occurred between days 3 and 9. Decannulation of the other 6 patients was performed after a median of 15 days. Sixteen (94%) of the 17 children were decannulated. Four patients required additional carbon dioxide laser treatment for subsequent glottic or subglottic edema or granulomas, but no reintubation was necessary. One child could not be decannulated because of bronchopulmonary disease, and subglottic stenosis recurred. Long-term tracheotomy was avoided in all other patients. Another child died of cardiac disease. All other patients remained free of significant subglottic stenosis at follow-up. CONCLUSIONS: Cricotracheal resection in small children weighing less than 10 kg was a safe and effective procedure for severe subglottic stenosis. To our knowledge, this is the first reported attempt of CTR in this weight category, providing results comparable to those published in older children.