Influence of sealer placement technique and powder/liquid mixing ratio on the quality of single cone root canal filling: a micro-CT analysis

Aim: To assess the influence of two different placement techniques and powder/liquid mixing ratio of a bioceramic sealer on the quality of root canal filling by single-cone using a micro-CT analysis. Methods: Thirty-two single-rooted elements with a mesio-distal diameter of 5,00\ub10,50 mm, a buccallingual diameter of 6,50 \ub10,50 mm and a root length of 14,50\ub10,50 mm measured at CEJ level were selected to be included in the study. After creating the coronal access cavity, root canals were scouted with manual files and the working length was acquired. Root canals were shaped with R40 Reciproc Blue and irrigated with NaOCl 5% and EDTA 17% solutions. Prepared samples were randomly assigned into four experimental groups (n=8), according to the sealer placement technique and the powder/liquid mixing ratio: G1, the sealer (BioRoot RCS, Septodont) was mixed in a 1:5 ratio, as suggested by the manufacturer, and carried into the root canal by a dedicated gutta-percha cone up to the working length; G2, sealer placement as group G1, but using 1:6 mixing ratio; G3, the sealer was mixed in a 1:5 ratio and carried into the root canal by a syringe with a cannula (Apexcal, Ivoclar) up to its complete filling, then a dedicated gutta-percha cone was inserted into the canal; G4, sealer placement as group G3, but using 1:6 mixing ratio. All the samples were submitted to micro-CT analysis. Micro-CT scans were acquired after shaping procedures (t0) and after canals obturation (t1) and then compared to evaluate the presence of voids in the gutta-percha, sealer and dentin interfaces. The normality of the distribution and the equality of variance of the microtomographic datasets were tested with a Shapiro-Wilk and Levene test, respectively; the significance of the differences between groups in terms of the formation of voids was ascertained with the Kruskal-Wallis test. The results were considered statistically significant for a p-value < 0.05. Results: Minimal void volumes were observed among groups. G1 performed the best result: total void volumes were 0,253\ub10,175% of the entire canal space. The other experimental groups follow in order of increasing volume: G3 (0,260\ub10,254%), G2 (0,532\ub10,528%), G4 (0,840\ub10,705%), but no statistically significant difference was observed. All groups showed a similar distribution of voids: in the apical and middle third of the root canal the presence of voids was minimal while the greatest void volumes were detected in the coronal third, due to the canal anatomy and the larger amount of sealer. In this canal portion voids were mainly distributed within the sealer. Concerning the sealer viscosity, the more fluid formulation (1:6) showed an increase of void volumes, although without statistical significance. Likewise, no statistically relevant influence was registered regarding the sealer placement technique. Conclusion: All the examined techniques should be considered effective for the clinician. Under the conditions of the present study, the 1:5 powder/liquid mixing ratio should be preferred when associated with both the sealer placement techniques, according to the clinical situation and the operator preferences. When using the low viscosity formulation, the clinician should insert the sealer slowly and in a controlled way, in order to minimize the formation of voids

Tuning the Drug Release from Antibacterial Polycaprolactone/Rifampicin-Based Core-Shell Electrospun Membranes: A Proof of Concept

The employment of coaxial fibers for guided tissue regeneration can be extremely advantageous since they allow the functionalization with bioactive compounds to be preserved and released with a long-term efficacy. Antibacterial coaxial membranes based on poly-epsilon-caprolactone (PCL) and rifampicin (Rif) were synthesized here, by analyzing the effects of loading the drug within the core or on the shell layer with respect to non-coaxial matrices. The membranes were, therefore, characterized for their surface properties in addition to analyzing drug release, antibacterial efficacy, and biocompatibility. The results showed that the lower drug surface density in coaxial fibers hinders the interaction with serum proteins, resulting in a hydrophobic behavior compared to non-coaxial mats. The air-plasma treatment increased their hydrophilicity, although it induced rifampicin degradation. Moreover, the substantially lower release of coaxial fibers influenced the antibacterial efficacy, tested against Escherichia coli, Staphylococcus aureus, and Pseudomonas aeruginosa. Indeed, the coaxial matrices were inhibitory and bactericidal only against S. aureus, while the higher release from non-coaxial mats rendered them active even against E. coli. The biocompatibility of the released rifampicin was assessed too on murine fibroblasts, revealing no cytotoxic effects. Hence, the presented coaxial system should be further optimized to tune the drug release according to the antibacterial effectiveness

Root-end resection without retrograde preparation: a micro-CT study

Aim: the gold standard in endodontic surgery is characterized by meticulous retrograde procedures that could be not performable in all teeth due to multiple clinical difficulties. The possibility to perform the only apical resection, when feasible, without further retrograde steps might represent a substantial clinical advantage. The present study analyzes the filling quality achieved with standard retrograde technique in comparison with alternative techniques with or without retrograde procedures. Methods: the sample size was determined using with the following parameters: \u3b1=0.05; \u3b2=0.20; \u3b4=3.0; \u3c3=1.5. Twenty-four single-rooted teeth were selected from a pool of freshly extracted teeth, discarding those with aberrant anatomy. Selected teeth of comparable size were decoronated to obtain 12 mm long roots. The canals were scouted with manual files and the working length acquired. After mechanical glide path establishment, canal shaping was performed with HyFlex EDM rotary files up to size 40.04 taper (500 rpm; 2.5 Ncm). The roots were analyzed with a computed microtomography scanner to identify the possible presence of dentine microcracks. Afterwards, the roots were randomly assigned to two groups: twelve canals were filled with the single cone technique (SCT) with dedicated cones and BioRoot RCS bioceramic sealer; twelve canals were filled with MTA cement (ProRoot MTA) for 6mm in the apical portion with the aid of the MAP System; the empty canal portion was backfilled with thermoplasticized gutta-percha (Obtura III Max System). After 24 h, the roots were apically resected with a carbide bur 3 mm from the apex. At this point, the two groups were randomly subdivided into two further groups of six elements each: G1, SCT and bioceramic sealer without retrograde procedures (n=6); G2, SCT and bioceramic sealer with standard retrograde ultrasonic preparation and MTA filling (n=6); G3, orthograde MTA placement without retrograde filling (n=6); G4, orthograde MTA placement and standard retrograde ultrasonic preparation and MTA filling (n=6). Lastly, the formation of internal and external voids was quantified by means of a second computed microtomographic analysis. The normality of the distribution and the equality of variance of the microtomographic datasets were tested with a Shapiro- Wilk and a Levene test, respectively; then, the volumes measured in the groups were statistically compared with the Kruskal-Wallis test and with the Mann-Withney test with Bonferroni\u2019s correction couple comparison. Results: All groups showed minimal voids volumes formation. In the groups characterized by standard retrograde procedures, the mean voids volumes were 1.16\ub10.40 % (G4) and 1.87\ub11.49 % (G2) of the entire canal space, in the groups with the only root-end resection 0.82\ub10.58 % (G1) and 1.08 \ub1 0.50% (G3). The difference between the groups was not statistically significant. Analyzing the volume within the apical 3 mm of the canal after root resection (G1=0.06 \ub1 0.10%; G2=0.76 \ub1 0.81%; G3=2.06 \ub1 .92%; G4=1.53 \ub1 1.79%) the difference between G1 and the other groups was statistically significant (p <0.05). Conclusion: When suitable, filling the canal with the single cone technique and bioceramic sealer or orthograde MTA placement combined with simple root-end resection appears to provide an efficient seal of the endodontic space. These technique could represent a good alternative to the retrograde preparation and filling

Antibacterial-Nanocomposite Bone Filler Based on Silver Nanoparticles and Polysaccharides

Injectable bone fillers represent an attractive strategy for the treatment of bone defects. These injectable materials should be biocompatible, capable of supporting cell growth and possibly able to exert antibacterial effects. In this work, nanocomposite microbeads based on alginate, chitlac, hydroxyapatite and silver nanoparticles were prepared and characterized. The dried microbeads displayed a rapid swelling in contact with simulated body fluid and maintained their integrity for more than 30\ua0days. The evaluation of silver leakage from the microbeads showed that the antibacterial metal is slowly released in saline solution, with less than 6% of silver released after 1\ua0week. Antibacterial tests proved that the microbeads displayed bactericidal effects toward S. aureus, P. aeruginosa and S. epidermidis and were also able to damage pre-formed bacterial biofilms. On the other hand, the microbeads did not exert any cytotoxic effect towards osteoblast-like cells. After characterization of the bioactive microbeads, a possible means to embed them in a fluid medium was explored in order to obtain an injectable paste. Upon suspension of the particles in alginate solution or alginate/hyaluronic acid mixtures, a homogenous and time-stable paste was obtained. Mechanical tests enabled to quantify the extrusion forces from surgical syringes, pointing out the proper injectability of the material. This novel antibacterial bone-filler appears as a promising material for the treatment of bone defects, in particular when possible infections could compromise the bone-healing process

Root-end resection with or without retrograde obturation after orthograde filling with two techniques: A micro-CT study

To evaluate the filling ability of two orthograde obturation techniques followed by the apical resection with or without retrograde obturation through micro-computed tomography (CT). Thirty-two single-rooted permanent teeth were prepared and randomised into four groups (n = 8) according to the orthograde obturation technique (single cone technique [SCT] and mineral trioxide aggregate placement) combined or not with retrograde obturation. The volume of voids (VoV) within the entire endodontic space, the apical 3 mm, and 1 mm after root resection was calculated by micro-CT. Statistical analysis showed no significant difference among the groups regarding the total VoV in all root canals, as well as within the apical 1 mm after root resection. The SCT and apical resection without retrograde filling showed significantly better results in terms of VoV at the apical 3 mm after root resection. Within the study limitations, SCT associated with apical resection without retrograde preparation exhibited a similar or less amount of voids than the other groups

Exploiting natural polysaccharides to enhance in vitro bio-constructs of primary neurons and progenitor cells

Current strategies in Central Nervous System (CNS) repair focus on the engineering of artificial scaffolds for guiding and promoting neuronal tissue regrowth. Ideally, one should combine such synthetic structures with stem cell therapies, encapsulating progenitor cells and instructing their differentiation and growth. We used developments in the design, synthesis, and characterization of polysaccharide-based bioactive polymeric materials for testing the ideal composite supporting neuronal network growth, synapse formation and stem cell differentiation into neurons and motor neurons. Moreover, we investigated the feasibility of combining these approaches with engineered mesenchymal stem cells able to release neurotrophic factors. We show here that composite bio-constructs made of Chitlac, a Chitosan derivative, favor hippocampal neuronal growth, synapse formation and the differentiation of progenitors into the proper neuronal lineage, that can be improved by local and continuous delivery of neurotrophins. Statement of Significance In our work, we characterized polysaccharide-based bioactive platforms as biocompatible materials for nerve tissue engineering. We show that Chitlac-thick substrates are able to promote neuronal growth, differentiation, maturation and formation of active synapses. These observations support this new material as a promising candidate for the development of complex bio-constructs promoting central nervous system regeneration. Our novel findings sustain the exploitation of polysaccharide-based scaffolds able to favour neuronal network reconstruction. Our study shows that Chitlac-thick may be an ideal candidate for the design of biomaterial scaffolds enriched with stem cell therapies as an innovative approach for central nervous system repair

A Critical Review on the Production of Electrospun Nanofibres for Guided Bone Regeneration in Oral Surgery

Nanofibre-based membranes or scaffolds exhibit high surface-to-volume ratio, which allows an improved cell adhesion, representing an attractive subgroup of biomaterials due to their unique properties. Among several techniques of nanofiber production, electrospinning is a cost-effective technique that has been, to date, attractive for several medical applications. Among these, guided bone regeneration is a surgical procedure in which bone regeneration, due to bone atrophy following tooth loss, is \u201cguided\u201d by an occlusive barrier. The membrane should protect the initial blood clot from any compression, shielding the bone matrix during maturation from infiltration of soft tissues cells. This review will focus its attention on the application of electrospinning (ELS) in oral surgery bone regeneration. Despite the abundance of published papers related to the electrospinning technique applied in the field of bone regeneration of the jaws, to the authors\u2019 knowledge, no articles report clinical application of these structures. Moreover, only a few records can be found with in vivo application. Therefore, no human studies have to date been detectable. New approaches such as multifunctional multilayering and coupling with bone promoting factors or antimicrobial agents, makes this technology very attractive. However, greater efforts should be made by researchers and companies to turn these results into clinical practic

CBCT Radiological Features as Predictors of Nerve Injuries in Third Molar Extractions: Multicenter Prospective Study on a Northeastern Italian Population

Background: Neurological alterations are one of the main complications occurring after the third molar extractions. The aim of this prospective multicenter cohort study was to find out Cone Beam Computed Tomography (CBCT) features and distribution of neurological complications in patients undergoing lower third molar surgery and to determine the radiological and patient-related factors that could be correlated to the occurrence of inferior alveolar and lingual nerves injury. Material and Methods: 378 patients who underwent lower third molar extraction from March 2018 to March 2019 were included. Clinical and radiological data were collected. CBCT features were recorded following Maglione et al. classification. Symptoms and characteristics of patients who experienced neurological alterations were evaluated. Results: 193 patients needed a second-level radiological exam (CBCT). In these patients, the most common feature was Maglione class 3: a higher frequency of apical or buccal mandibular canals in direct contact with the tooth was observed. 3.17% of the patients developed a neurological complication. Maglione class 4, increased age, and operative time were all positively correlated with neurological alterations. Conclusions: while the buccal or apical position of the mandibular canal was the more common findings, the lingual position was found to have a higher correlation with a negative outcome. Age and operative time were also found to be risk factors for developing nerve injury in the considered population

Reuse of Implant Healing Abutments: Comparative Evaluation of the Efficacy of Two Cleaning Procedures

PURPOSE: To compare the efficacy of two systems in cleaning used healing abutments (HAs). MATERIALS AND METHODS: A total of 60 used HAs were randomized into two groups: one treated with an automatic cleaning system, and the other with conventional decontamination procedures. After sterilization and staining, the HAs were microscopically analyzed and underwent a cellular adhesion in vitro assay. RESULTS: Contaminated areas were observed with different frequencies in the two groups (3.6% test; 78.2% control; P < .001). In vitro assay showed a uniform cell distribution in test HAs, while areas of debris without adhering cells were a common finding in the control HAs. CONCLUSION: Further studies investigating the chemical composition and clinical influence of biologic remnants are necessary before considering reusing HAs

Polymeric wound dressings, an insight into polysaccharide-based electrospun membranes

Chronic wounds deeply invalidate patient's quality of life, involving very high costs for the medical system. Numerous wound dressings have been studied over the years, and active wound dressings replaced traditional passive dressings to promote tissue regeneration and wound closure. Aiming at an optimal reproduction of the physiological environment, electrospun wound dressings are emerging since they mimic the architecture of the extracellular matrix and provide a large contact surface area, enabling exudate absorption and permeability as well as good conformability to the wound site. The use of polysaccharides offers an excellent biomimicry, as they ensure good biocompatibility, biodegradability, and non-immunogenicity. Furthermore, they possess bioactive properties, such as antimicrobial, anti-inflammatory, and antioxidant properties, which can promote and enhance the healing process. The aim of this review is to present the morphological, physical, and chemical features of an ideal wound dressing together with the traditional and the current strategies, and the already commercialized wound dressings. Moreover, the review is focused on the preparation of polysaccharide-based electrospun nanofibrous devices and on the strategies for the modulation and improvement of membrane stability and bioactivity. Lastly, a comprehensive consideration on the process and requirements that lead to the commercialization of the wound dressings is reported