Micro-CT Evaluation Research Articles

Comparative evaluation of cone beam CT and micro-CT on blooming artifacts in human teeth filled with bioceramic sealers.

To assess blooming artifacts caused by root canal sealers in CBCT images compared with those that appeared in micro-CT scan images used as references. Thirty freshly extracted human mandibular central incisors were used. Root canals were prepared with nickel titanium files with an ISO size 40/0.06 taper and filled with a single cone (40/0.06 taper) and three different sealers. The samples were divided into the following three groups with 10 roots each: (I) AH Plus sealer; (II) Sure Seal Root; and (III) Total BC sealer. Teeth were scanned with the same voxel sizes (0.2mm) in different CBCT devices and the micro-CT images were acquired as reference images. Significantly different results in terms of blooming artifacts were detected between CBCT and micro-CT images, as well as among the CBCTs images. The canals filled with AH Plus sealer showed more blooming artifacts than those filled with bioceramic sealers (p < 0.05). Additionally, the worst blooming artifact was observed when the images were acquired with lower kilovoltage peak. The appearance of blooming artifacts is dependent on sealer and CBCT, and their effects are significantly worse than they are in micro-CT images. The differential effect of different sealers and distinct CBCT protocols should be further investigated to enable the use of bioceramic sealers without a significant impact on post-treatment imaging. Root canal sealers showed a different extent of blooming artifact in CBCT images. Hence, researchers and clinicians should be aware of these artifacts before conducting endodontic evaluations using CBCT images.

Collagen Functionalized With Graphene Oxide Enhanced Biomimetic Mineralization and in Situ Bone Defect Repair.

Biomimetic mineralization using simulated body fluid (SBF) can form a bonelike apatite (Ap) on the natural polymers and enhance osteoconductivity and biocompatibility, and reduce immunological rejection. Nevertheless, the coating efficiency of the bonelike apatite layer on natural polymers still needs to be improved. Graphene oxide (GO) is rich in functional groups, such as carbonyls (-COOH) and hydroxyls (-OH), which can provide more active sites for biomimetic mineralization and improve the proliferation of the rat bone marrow stromal cells (r-BMSCs). In this study, we introduced 0%, 0.05%, 0.1%, and 0.2% w/v concentrations of GO into collagen (Col) scaffolds and immersed the fabricated scaffolds into SBF for 1, 7, and 14 days. In vitro environment scanning electron microscopy (ESEM), energy-dispersive spectrometry (EDS), thermogravimetric analysis (TGA), micro-CT, calcium quantitative analysis, and cellular analysis were used to evaluate the formation of bonelike apatite on the scaffolds. In vivo implantation of the scaffolds into the rat cranial defect was used to analyze the bone regeneration ability. The resulting GO-Col-Ap scaffolds exhibited a porous and interconnected structure coated with a homogeneous distribution of bonelike apatite on their surfaces. The Ca/P ratio of 0.1% GO-Col-Ap group was equal to that of natural bone tissue on the basis of EDS analysis. More apatites were observed in the 0.1% GO-Col-Ap group through TGA analysis, micro-CT evaluation, and calcium quantitative analysis. Furthermore, the 0.1% GO-Col-Ap group showed significantly higher r-BMSCs adhesion and proliferation in vitro and more than 2-fold higher bone formation than the Col-Ap group in vivo. Our study provides a new approach of introducing graphene oxide into bone tissue engineering scaffolds to enhance biomimetic mineralization.

Self-healing and injectable hybrid hydrogel for bone regeneration of femoral head necrosis and defect

BackgroundHA modified by bisphosphonate (BP) (HA-BP) was synthesized by chemical reaction and possessed promising properties such as self-healing, injection ability, and strong adhesion. The main aim of this study was to confirm its role in promoting osteogenic differentiation in vitro and bone regeneration in vivo. MethodsThe cell biocompatibility of this material was determined using the CCK-8 assay. Alkaline phosphatase (ALP), osteocalcin (OT), vascular endothelial growth factor (VEGF), and collagen I were assessed by quantitative real-time polymerase chain reaction (Q-PCR) in the treated group. The number and density of calcium nodules and ALP were evaluated by Alizarin Red staining and ALP staining. We have successfully developed an animal model simulating osteonecrosis of the femoral head (ONFH). Utilizing this animal model, the impact of HA-BP/CaP on bone formation was assessed. The amount of bone regeneration at 1 and 2 months after HA-BP/CaP injection was estimated by micro-computed tomography (micro-CT) analysis and H&E, collagen I, and periostin staining. ResultsThe number of cells gradually increased in the experimental group over time and was close to that of the blank control group. ALP, collagen I, and VEGF expression was significantly higher in the experimental group than in the blank group (VEGF, ALP, both **p < 0.01; collagen I, ***p<0.001). In addition, the number and density of calcium nodules and ALP was clearly greater in the material group than in the control group.The quantification analysis showed that the mineral contents of regenerated bone at 1 and 2 months after HA-BP/CaP injection were significantly greater than those in the control group, according to micro-CT evaluation (**p<0.01). The amount of organic components in the HA-BP/CaP group was greater than that in the control group after decalcification and H&E staining. In addition, collagen I and periostin staining further confirmed the results of H&E staining. ConclusionThis material can boost proliferation and osteogenic differentiation of MC3T3-E1 cells in vitro. It can intensely accelerate bone regeneration in vivo, which is a promising strategy for tissue engineering.

Effect of setting atmosphere on apatite cement resorption: An in vitro and in vivo study

ObjectivesThe aim of this present study was to investigate the effect of setting atmosphere on replacement of apatite cement with new bone both in vitro and in vivo. Material and methodsApatite cement consisting of an equimolar mixture of tetracalcium phosphate and anhydrous dicalcium phosphate was mixed with distilled water and allowed to set at 37 °C and 100% relative humidity under 0%, 5%, and 100% CO2 atmospheres. X-Ray diffraction and Fourier Transform Infrared Spectroscopy were employed to confirm the carbonate apatite formation. Micro-CT and histological evaluation was made at 1 and 6 month(s) using twelve 10-week-old specific-pathogen-free male Wistar rats. ResultsB-type carbonate apatite was found when the apatite cement was set under 100% CO2 and 5% CO2. More carbonate apatite was formed in the case of 100% CO2 when compared with 5% CO2, and none was formed under 0% CO2. Interestingly, unreacted tetracalcium phosphate was significant when apatite cement was set under 0% CO2, indicating the formation of Ca-deficient hydroxyapatite. When a bone defect of rat tibia was reconstructed in these conditions of apatite cement and sintered hydroxyapatite, replacement of the apatite cement was confirmed 6 months after implantation, whereas no replacement was observed in the case of sintered hydroxyapatite. The amount of replacement of apatite cement with bone was greater, on the order of 100% CO2 and 5% CO2, followed by 0% CO2. ConclusionThe results obtained in the present study demonstrated that setting atmosphere clearly plays an important role in the replacement of set apatite cement with bone.

Micro-CT evaluation on osteoconductivity of DCPD-coated β-TCP granule using experimental rats

β-tricalcium phosphate (β-TCP) bone substitutes have been widely used because of its excellent tissue response and good osteoconductivity. However, recent study reported that the osteoconductivity of β-TCP could be enhanced by treating β-TCP surfaces with saturated acidic calcium phosphate solution. In this study, the osteoconductivity of treated β-TCP granule were evaluated using micro-computed tomography (micro-CT) scan technique. The granule specimens were obtained by exposing β-TCP granules with saturated acidic calcium phosphate solution for 10, 30 and 60 mins, respectively. Then, critical bone defect size with dimension of 9 mm were made at rat calvarial, and the defect was reconstructed with 10, 30 and 60 mins treated β-TCP granules and β-TCP granules without treatment as a control. After 2 and 4 weeks implantation, the specimens with the surrounding bone tissue were taken out and examined using micro-CT machine. Based on the cross section of micro-CT images, new bone formations were observed from the edge of the defect towards the center of the bone defect area in all specimens. At 2 weeks, new bone formations were observed for 10 min and 30 min treated β-TCP granules when compared with other specimens. The 30 min treated β-TCP granules showed faster new bone formation rate after 4 weeks implantation. It can be concluded that 30 min treated β-TCP granules revealed the highest osteoconductivity in comparison to the other specimens.

Micro-CT evaluation of two different root canal filling techniques.

The aim of this study was to compare the frequency and volume of voids in root canals obturated with two different filling techniques using micro-computed tomography (micro-CT). Forty single-rooted permanent teeth were selected and decoronated. The roots were instrumented with WaveOne (Dentsply Maillefer, Ballaigues, Switzerland) to a large size until working length and irrigated with 5.25% sodium hypochlorite and 17% EDTA. Then, the samples were filled using a single-cone (n = 20) or the GuttaCore technique (n = 20). The presence and volume (mm3) of voids (internal, external, and combined) was calculated in the coronal, medium, and apical thirds using micro-CT (SkyScan 1072; SkyScan, Kartuizersweg, Belgium). Statistical analyses were performed using the χ2-test and Kruskal-Wallis tests (p<0.05). The frequency and total volume of voids in the middle third and the external voids in the coronal third were statistically significant (p<0.05). Within the same group, both techniques (single-cone and Guttacore) showed statistically significant differences in external and internal voids (p<0.05). The GuttaCore technique showed better results in the coronal and medium thirds than the single-cone technique. Our results showed that the single-cone and GuttaCore techniques were comparable in the apical third (p>0.05).

Osseointegration of zirconia implants with 3 varying surface textures and a titanium implant: A histological and micro-CT study

Zirconium - a bioinert metal - in comparison with titanium implants, offers a variety of potential advantages for use in the esthetic area of dentistry due to its tooth-like color. Zirconium dental implants are considered to be an alternative method of treatment to conventional titanium dental implants for patients with a thin gingival biotype. This study was designed to study the bone tissue response to new zirconia implants with modified surfaces in comparison with commercially available titanium dental implants and commercially available zirconia implants. The study was carried out on a group of 12 16-month-old minipigs. New zirconia implants with 3 different surfaces were used: M1 - blasted surface, M2 - etched surface and M3 - blasted and etched surface (Maxon Motor GmbH, Sexau, Germany) and compared to conventional titanium implants with an sandblasted and acid etched (SLA) surface (Straumann GmbH, Freiburg, Germany) and commercially available zirconia implants (Ziterion GmbH, Uffenheim, Germany). Histological and micro-computed tomopgraphy (micro-CT) evaluation was performed. In the micro-CT assessment, the average bone-implant contact (BIC) of the zirconia experimental implants was 41.44%. In particular, the BIC% for M1 was 39.72%, for M2 it was 43.97%, and for M3 - 40.63%; in the control group it was 49.63% and 27.77% for ceramic and titanium control implants, respectively. The intra-group analysis showed no statistically important differences between the BIC values for implants in any group. However, the analysis of BIC for different regions of the same implant showed statistically significant differences in all of the groups between the results of the threaded region and the neck and the apex. The results of our study suggest that zirconia implants with modified surfaces display features of osseointegration similar to those of titanium implants. These results are promising in using zirconia implants for dental applications in the future.

Micro-CT evaluation of marginal and internal fit of cemented polymer infiltrated ceramic network material crowns manufactured after conventional and digital impressions

PurposePurpose of this study was to evaluate the accuracy of fit of cemented polymer infiltrated ceramic network (PICN) material crowns manufactured after digital and conventional impression techniques using micro computed tomography (CT). Furthermore to determine the cement space volume and porosities in the cement layer. MethodsA molar typodont tooth was prepared for PICN material crowns and replicated thirty times. The dies were randomly divided into three groups of 10 specimens each according to the impression technique: 3M True Definition Scanner (TDS), cara TRIOS (Trios) and Impregum Penta Soft (Impregum). PICN material crowns were milled for each specimen from Vita Enamic blocks and cemented on their respective dies. The absolute marginal discrepancy (AMD), internal fit (IG), total cement space volume (TVC) and marginal porosities (VP) were measured using Micro-CT. ResultsMean and standard deviations values in μm for the AMD were: TDS 140.1 (28.4); Trios 253.7 (56.8); Impregum 220.2 (101.1). IG values in μm: TDS 173.1 (27.7); Trios 222.2 (22.4); Impregum 211.6 (55.9). TVC in mm3: TDS 19.82 (2.9); Trios 23.67 (2.01); Impregum 23.77 (5.09). VP in mm3: TDS 0.38 (0.09); Trios 0.36 (0.10); Impregum 0.51 (0.31). ConclusionsTDS group showed significantly better marginal and internal fit than the Trios group. No difference of the parameters was detected between the Impregum and both digital groups which implies that the digital impression technique is suitable in the manufacturing process of PICN material crowns.

Osteochondral Defects Healing Using Extracellular Matrix Mimetic Phosphate/Sulfate Decorated GAGs-Agarose Gel and Quantitative Micro-CT Evaluation.

Tissue engineering has a major emphasis in creating tissue specific extracellular ambiance by altering chemical functionalities of scaffold materials. Heterogeneity of osteochondral tissue necessitates tailorable bone and cartilage specific extracellular environment. Carboxylate- and sulfate-functionalized glycosaminoglycans (GAGs) in cartilage extracellular matrix (ECM) create an acidic ambience to support chondrogenic activity, whereas phosphate-rich environment in bone enables chelation of calcium leading to the formation of mineralized matrix along with an alkaline environment to support osteogenesis. In this study, chitosan, a naturally occurring GAGs, was functionalized with phosphate/sulfate groups analogous to bone/cartilage ECM and incorporated in thermogelling agarose hydrogel for delivery to osteochondral defects. In vitro studies revealed significantly higher adhesion and proliferation of adipose derived mesenchymal stem cells (ADMSCs) with blended hydrogels as compared to that of native agarose. Cell differentiation and RT-PCR studies of the phosphorylated hydrogels revealed higher osteogenic potential, while sulfated hydrogels demonstrated enhanced chondrogenic activity in comparison to agarose. Recovery of osteochondral defects after delivery of the thermoresponsive agarose-based hydrogels decorated with phosphorylated derivatives showed significantly higher bone formation. On the other hand, cartilage formation was significant with chitosan sulfate decorated hydrogels. The study highlights the role of chitosan derivatives in osteochondral defect healing, especially phosphorylated ones as bone promoter, whereas sulfated ones act as cartilage enhancer, which was quantitatively distinguished through micro-CT-based noninvasive imaging and analysis.

Micro-CT evaluation of different final irrigation protocols on the removal of hard-tissue debris from isthmus-containing mesial root of mandibular molars

This study aimed to compare four final irrigation protocols (passive ultrasonic irrigation [PUI], EndoVac, Self-Adjusting File [SAF] and EasyClean) on the removal of accumulated hard-tissue debris (AHTD) from mesial canals of mandibular molars through microcomputed tomographic (micro-CT) analysis. Forty mesial roots of mandibular molars presenting isthmuses type I or III were scanned in a micro-CT device and instrumented up to Reciproc R40 instrument. After the completion of canal preparations, root canals of each group were submitted to a final rinse using 20mL of solution (16mL of 5.25% NaOCl and 4mL of 17% EDTA) in a total time of 5min according to one of the four final irrigation protocols (n = 10): PUI, EndoVac, SAF and EasyClean operated at reciprocating motion. The sample was scanned again after canal preparation and after the use of the final irrigation protocols, and the registered data sets were examined to evaluate the percentage of AHTD. Data were statistically compared using the Tukey test with a significance level set at 5%. All groups presented a decrease on the accumulation of hard-tissue debris after the use of the final irrigation protocols (P < 0.05). No significant differences in the removal of AHTD were observed among the final irrigation protocols (P > 0.05). All final irrigation protocols showed the same effectiveness in the removal of AHTD. None of them was able to render mesial canals of mandibular molars completely free from packed debris. This study highlighted that all final irrigation protocols (PUI, EndoVac, SAF, and EasyClean) promoted a similar removal of AHTD. However, none of the final irrigation protocols was able to render mesial canals of mandibular molars completely free from packed debris.

In vitro and in vivo studies of anti-bacterial copper-bearing titanium alloy for dental application

ObjectiveA novel copper-bearing titanium alloy (Ti–Cu) was fabricated for dental application that is expected to efficiently restrain the growth of bacteria and discourage biofilm formation. The aim of this study was to investigate both the antibacterial activity and biofilm inhibition of Ti–Cu alloy in vitro, and the antibacterial effect of Ti–Cu implant in early stage of peri-implantitis in vivo. MethodsStaphylococcus aureus and Escherichia coli were selected to evaluate the antibacterial activity of Ti–Cu alloy and Ti served as control. The antibacterial rate, attached bacteria and developed biofilms were studied from quantitative antibacterial test, biofilm observation and bacterial morphological examination. Electrochemical tests were used to investigate the corrosion property of Ti–Cu alloy. Furthermore, both Ti and Ti–Cu dental implants were manufactured and then implanted in the mandibular premolar sites of beagle dogs for 3 months with ligature-infected treatment. Implant-tissue samples were prepared for radiographic analysis, Micro-CT evaluation and histological examination. ResultsTi–Cu alloy was found to efficiently kill the attached bacteria by ways of damaging cell membranes and cell walls and strongly inhibit the biofilm formation. However, Ti–Cu alloy had excellent corrosion resistance similar with Ti. Further, Ti–Cu dental implants showed superior capacities of inhibiting the bone resorption caused by bacterial infection and enhancing bone formation. SignificanceTi–Cu alloy strongly inhibited biofilm formation in vitro and prevented bacterial infection associated with dental implant in vivo, making it great potential for application in dental implants with excellent antibacterial viability and positive effect against bone resorption induced by peri-implantitis.

Systemic Delivery of Free Chitosan Accelerates Femur Fracture Healing in Rats.

Chitosan-containing compounds have been shown to be suitable for bone replacement, but few studies demonstrate the impact of the chitosan as a free drug on the fracture.In this study, we aimed to evaluate possible effects of free chitosan on fracture healing. Thirty adult male Sprague-Dawley rats with a mean body weight of 205 g (range from 200g to 210g) were randomly and equally divided into two groups. Standardized femur fractures were created in all rats. Treatments were administered intraperitoneally twice weekly at 1 mg chitosan per injection and the controls were administered physiological saline. The site of the fracture was compared with the control group at 1, 2 and 4 weeks after surgery (n=5 in each group). The weight, activity and reaction of the rats were observed at all the timepoints. Anterior-posterior radiographs and micro-CT scans of all fractures were taken after surgery, and the parameters included: the volume of callus that was calculated using the Perkins volume formula, BV/TV, BV, BMD of cortical bone, cortical thickness, and cortical number at the fracture sites. After sacrifice, fractured femurs from rats were dissected and carefully cleaned of muscle around the fracture callus to preserve callus integrity. Sections were stained with haematoxylin and eosin for histological evaluation of healing. Radiological (X-ray and micro-CT) evaluation showed that fracture healing of the experimental group was better than control group at the second week and fourth week. Histological evaluation revealed fracture healing of the experimental group was better than control group at the same time. There was no statistically significant difference in fracture healing between the two groups at the first week. Systemic delivery of free chitosan can accelerate the bone healing process in rat femur fracture at the early-middle stage.

Zoledronic Acid Induces Site-Specific Structural Changes and Decreases Vascular Area in the Alveolar Bone

The aim was to assess the effect of a relevant regimen of zoledronic acid (ZA) treatment for the study of bisphosphonate-related osteonecrosis of the jaw on alveolar bone microstructure and vasculature. A sub-objective was to use 3-dimensional imaging to describe site-specific changes induced by ZA in the alveolar bone. Five Wistar rats received ZA (0.6mg/kg) and five (controls) received saline solution in the same volume. The compounds were administered intraperitoneally in 5 doses every 28days. The rats were euthanized 150days after therapy onset. The mandibles were scanned using high-resolution (14-μm) micro-computed tomography (micro-CT), decalcified, cut into slices for histologic analysis (5μm), and stained with hematoxylin-eosin. Bone quality parameters were calculated using CT-Analyser software (Bruker, Kontich, Belgium) in 2 different volumes of interest (VOIs): the region between the first molar roots (VOI-1) and the periapical region under the first and secondmolars' apex (VOI-2). Blood vessel density and bone histomorphometric parameters were calculated only for the region between the roots of the first molar using AxioVision Imaging software (version 4.8; Carl Zeiss, Gottingen, Germany). ZA-treated rats showed a significant increase in percentage of bone volume and density (P<.05), with thicker and more connected trabeculae. Furthermore, the ZA group showed a significant decrease in the size of the marrow spaces and nutritive canals and in blood vessel density (P<.05). In the micro-CT evaluation, VOI-2 showed better outcomes in measuring the effect of ZA on alveolar bone. ZA treatment induced bone corticalization and decreased alveolar bone vascularization. VOI-2 should be preferred for micro-CT evaluation of the effect of bisphosphonates on alveolar bone. This analysis allowed the effect of ZA on alveolar bone and its vascularization to be characterized. The results of this analysis may add further knowledge to the understanding of the physiopathology of osteonecrosis of the jaw.

Biomechanical, Histologic, and Molecular Evaluation of Tendon Healing in a New Murine Model of Rotator Cuff Repair

To develop a clinically relevant, robust murine model of rotator cuff tendon repair to examine cellular and molecular mechanisms of healing. Sixty C57BL/6 male mice underwent rotator cuff transection and repair using microsurgical techniques. A modified Kessler suturing technique was used prior to tendon detachment. Sutures were passed through 2 intersecting bone tunnels that were made at the tendon attachment site. Mice were sacrificed at 2 and 4weeks with subsequent biomechanical, histologic, micro-CT, and gene expression evaluations. Failure forces in the 2- and 4-week groups were 36% and 75% of the intact tendon, respectively. Histologic evaluation revealed complete reattachment of the tendon with no observable gap. Healing occurred by formation of fibrovascular tissue at the tendon-bone interface, similar to larger animal models. Molecular analysis revealed gene expression consistent with gradual healing of the reattached tendon over a period of 4weeks. Comparisons were made using 1-way analysis of variance. This model is distinguished by use of microsurgical suturing techniques, which provides a robust, reproducible, and economic animal model to study various aspects of rotator cuff pathology. Improvement of clinical outcomes of rotator cuff pathology requires in-depth understanding of the underlying cellular and molecular mechanisms of healing. This study presents a robust murine model of supraspinatus repair to serve as a standard research tool for basic and translational investigations into signaling pathways, gene expression, and the effect of biologic augmentation approaches.

Stimulation of cell responses and bone ingrowth into macro-microporous implants of nano-bioglass/polyetheretherketone composite and enhanced antibacterial activity by release of hinokitiol.

Poor osteogenesis and bacterial infection lead to the failure of implants, thus enhancements of osteogenic activity and antibacterial activity of the implants have significances in orthopedic applications. In this study, macro-microporous bone implants of nano-bioglass (nBG) and polyetheretherketone (PK) composite (mBPC) were fabricated. The results indicated that the mBPC with the porosity of around 70% exhibited interconnected macropores (sizes of about 400 μm) and micropores (sizes of about 10 μm). The apatite mineralization ability of mBPC in simulated body fluid (SBF) was significantly improved compared with macroporous nBG/PK composite (BPC) without micropores and macroporous PK (mPK). Drug of hinokitiol (HK) was loaded into mBPC (dmBPC), which displayed excellent in vitro antibacterial activity against Staphylococcus aureus. The MC3T3-E1 cells proliferation and ALP activity were significantly promoted by mBPC and dmBPC as compared with BPC and mPK. The micro-CT and histological evaluation showed that both mBPC and dmBPC containing nBG and micropores induced higher new bone formation into porous implants than mPK and BPC. The immunohistochemistry analysis indicated that the expression of BMP-2 in mBPC and dmBPC exhibited obviously higher level than mPK and BPC. The results suggested that the incorporation of nBG and micropores in mBPC obviously improved the osteogenic activity, and mBPC load with HK also promoted osteogenesis, indicating good biocompatibility. The dmBPC with HK significantly enhanced osteogenesis and antibacterial activity, which had great potential as bone implant for hard tissue repair.

Effect of Hot Isostatic Pressure treatment on the Electron-Beam Melted Ti-6Al-4V specimens

The main advantages of additive manufacturing (AM), including fabrication of complex geometry lightweight objects, lattice structures, chain and gear mechanisms, better environment saving materials and resources and energy, better tool life of component, etc. are already well known. The main challenge in AM of metals is to achieve proper mechanical properties and performance, especially for safety critical parts. Thus, post-processing procedures for AM come to the front.In the framework of this research were prepared specimens by Electron Beam Melting (EBM). In case of the EBM, the greatest problem is porosity, which is especially critical for airspace components. One of the procedures recommended for decreasing porosity is Hot Isostatic Pressure (HIP) treatment, and its effect should be thoroughly studied to widespread its application.To investigate this aspect, Ti-6Al-4V cylinder parts were printed on the ARCAM EBM A2X machine using a 210×210 mm building platform. The microstructure and mechanical properties of the EBM specimens were tested before and after the HIP treatment. High cycle fatigue tests (HCFT), fracture surface examination, as well as micro-CT evaluation were performed.

Micro-CT Evaluation of Gutta-Percha Removal by Two Retreatment Systems.

Introduction:The aim of the present ex vivo research was to compare the remaining filling material and the volumes of dentine removed after retreatment of curved canals with two rotary systems naming ProTaper Universal Retreatment and Mani NRT-GPR using micro-computed tomography (micro-CT). Methods and Material: Forty mandibular molars containing two completely separated canals, with curvature angle of 25-35° and a curvature radius <10 mm were prepared to the Mtwo instrument 35/0.04 and filled with warm gutta-percha and AH-Plus sealer. The teeth were randomly divided into 2 groups (n=20), according to the retreatment system evaluated: ProTaper Universal Retreatment (PR group) or Mani NRT-GPR (MR group). Retreatment was considered complete when the working length was reached and when smooth dentinal walls were observed, with no evidence of filling material adhered to instruments or in the irrigating solution. Preoperative and postoperative micro-CT images were obtained with an isotropic voxel size of 11.88 µm to observe the volume of residual filling material in the canals and dentine removed after retreatment. Statistical analysis was performed by Student’s t-test (P<0.05). Results:The mean percentage of remaining filling material was 12.96% for PR group and 24.26% for MR group (P=0.0056). The percentage of dentin removal was greater in the PR group (5.02%) than MR group (1.36%) (P=0.0028). Both systems failed to completely remove the filling material from the canals. Conclusion: ProTaper Universal Retreatment system was more effective than Mani NRT-GPR system regarding removal of root filling material and also removed significantly more dentine after retreatment of curved mesial root canals of mandibular molars.

Evaluation of Bone Regeneration of Simvastatin Loaded Chitosan Nanofiber Membranes in Rodent Calvarial Defects

Chitosan nanofiber membranes have been known to have a high degree of biocompatibility and support new bone formation with controllable biodegradation. The surface area of these membranes may allow them to serve as local delivery carriers for different biologic mediators. Simvastatin, a drug commonly used for lowering cholesterol, has demonstrated promising bone regenerative capability. The aim of this study was to evaluate simvastatin loaded chitosan nanofiber membranes for guided bone regeneration (GBR) applications and their ability to enhance bone formation in rat calvarial defects. Nanofibrous chitosan membranes with random fiber orientation were fabricated by electrospinning technique and loaded with 0.25 mg of simvastatin under sterile conditions. One membrane was implanted subperiosteally to cover an 8 mm diameter critical size calvarial defect. Two groups: 1) Control: non-loaded chitosan membranes; 2) Experimental: chitosan membranes loaded with 0.25 mg of simvastatin were evaluated histologically and via micro-computed tomography (micro-CT) for bone formation at 4 and 8 weeks time points (n = 5/group per time point). Both groups exhibited good biocompatibility with only mild or moderate inflammatory response during the healing process. Histologic and micro-CT evaluations confirmed bone formation in calvarial defects as early as 4 weeks using control and experimental membranes. In addition, newly-formed bony bridges consolidating calvarial defects histologically along with partial radiographic defect coverage were observed at 8 weeks in both groups. Although control and experimental groups demonstrated no significant statistical differences in results of bone formation, biodegradable chitosan nanofiber membranes loaded with simvastatin showed a promising regenerative potential as a barrier material for guided bone regeneration applications.

Titanium-based implant comprising a porous microstructure assembled with nanoleaves and controllable silicon-ion release for enhanced osseointegration.

Osseointegration is crucial for early fixation as well as for long-term implantation success, hence numerous efforts have been made to tune the surface topography or chemical composition of biomedical implants to improve osseointegration. In this work, various nanostructures, including nanoflocs, nanobundles, nanorods, and nanoleaves, were introduced to the surface of silicon (Si)-incorporated microporous structure to form Si-incorporated micro-nano hierarchical structures on titanium (Ti)-based implants. The osseointegration of the implants were systemically assessed in vivo and in vitro. The in vitro evaluations showed that the nanostructures promoted the protein adsorption, thus modulating the early cellular responses, including the attachment and spreading of osteoblasts and human endothelial cells (HUVECs), and subsequent cell proliferation and differentiation. Furthermore, compared with the single microporous structure, the nanostructures located over the microporous structure protected the Si ions from quick release and allowed the long-term sustained Si-ions release, which further contributed to the proliferation and differentiation of osteoblasts and vascular endothelial growth factor (VEGF) secretion as well as the tube formation of HUVECs. Collectively, the favorable nano-surface structures, especially the nanoleaves structure, and the constant Si-ion release together led to robust osteogenic and angiogenic activities. More importantly, in vivo micro-CT evaluation and histological observations further verified that the Si-incorporated micro-nano hierarchical implant with nanoleaves structure could efficiently promote new bone formation, thus indicating it was an attractive candidate as a next-generation bone-implant material.

Effects of corticopuncture (CP) and low-level laser therapy (LLLT) on the rate of tooth movement and root resorption in rats using micro-CT evaluation.

The aim of this study was to compare the rate of tooth displacement, quantity of root resorption, and alveolar bone changes in five groups: corticopuncture (CP), low-level laser therapy (LLLT), CP combined with LLLT (CP + LLLT), control (C), and negative control (NC). A total of 60 half-maxilla from 30 male Wistar rats (10weeks old) were divided randomly into five groups: three (CP, LLLT, and CP + LLLT) test groups with different stimulation for accelerated-tooth-movement (ATM), one control (C) group, and one negative control (NC) group with no tooth movement. Nickel-titanium coil springs with 50g of force were tied from the upper left and right first molars to micro-implants placed behind the maxillary incisors. For the CP and CP + LLLT groups, two perforations in the palate and one mesially to the molars were performed. For the LLLT and CP + LLLT groups, GaAlAs diode laser was applied every other day for 14days (810nm, 100mW, 15s). The tooth displacements were measured directly from the rat's mouth and indirectly from microcomputer (micro-CT) tomographic images. Bone responses at the tension and compression sites and root resorption were analyzed from micro-CT images. The resulting alveolar bone responses were evaluated by measuring bone mineral density (BMD), bone volume fraction (BV/TV), and trabecular thickness (TbTh). Root resorption crater volumes were measured on both compression and tension sides of mesial and distal buccal roots. The tooth displacement in the CP + LLLT group was the greatest when measured clinically, followed by the CP, LLLT, and control groups (C and NC), respectively (p <0.05). The tooth movements measured from micro-CT images showed statistically higher displacement in the CP and CP + LLLT groups compared to the LLLT and control groups. The BMD, BV/TV, and TbTh values were lower at the compression side and higher at the tension side for all three test groups compared to the control group. The root resorption crater volume of the distal buccal root was higher in the control group, followed by CP, LLLT, and CP + LLLT, mostly at the compression site. Combining corticopuncture and low-level laser therapy (CP + LLLT) produced more tooth displacement and less root resorption at the compression side. The combined technique also promoted higher alveolar bone formation at the tension side.