Residual Cement Research Articles

SİMAN ARTIĞININ NEDEN OLDUĞU PERİ-İMPLANTİTİS:

Implant-supported restorations have become commonly used by physicians in developing technology. However, different problems may occur in implant-supported prosthesis or implant. Periimplantitis is at the forefront of these problems and has been traditionally used in the evaluation of implant restorations. Peri-implantitis is a common complication and occurs with bone loss after the implant application. Implant-supported fixed restorations are divided into screw or cement retained. The form of prosthesis retention depends on the physician's decision. Cement-retained prosthesis are used with wide range due to ease of use, easy to check the occlusion, easy to adaptation, aesthetic and economic than screw-retained implant prosthesis. Despite all these advantages, abutment-cemented implant restorations can cause problems in the future. The most important result of these problems is the residual cement in gingival crevicular. Residual cement allows accumulation of bacteria and causes peri-implant diseases. Peri-implantitis due to residual cement was discussed in this case report

Method for Estimating Quantity of Non-Hydrated Cement in a Cement Recycling System

Abstract The objective of this research was to develop a method for the rapid estimation of the quantity of residual cement in sludge water and to control its hydration reaction using sodium gluconate in order to enable the residual cement in sludge water to be effectively utilized. The quantity of residual cement in sludge water can be estimated by measuring the heat of hydration liberated in 24 h using a conduction calorimeter. It is possible to recommence sodium glucon-ate-controlled cement hydration using magnesium nitrate. A method was developed to simulate the rate of the hydration reaction, which makes it possible to estimate the quantity of residual cement in sludge water by measuring the rate of heat liberation of hydration over 10 h. 1. Introduction In today’s society, where there is a need to implement low carbon recycling systems, the reduction and reuse of waste sludge water from the production of ready-mixed concrete at factories is an important issue. Data from 2006 indicate that about 1 million tons of sludge are generated annually in Japan. Sludge is a mixture of cement and very fine aggregate that occurs as waste at construction sites or forms when residual recycled concrete is sieved to remove aggregates. Cleaning water that contains a sludge component, which is referred to as sludge water, is formed when water is used to clean equipment such as ready-mixed-concrete mixers and agitators. To reduce the quantity of sludge formation at ready-mixed-concrete factories, Japanese Industrial Standard A 5308 “Ready-mixed Concrete” prescribes a method of using mortar that adheres to the inside of truck agitator drums. This allows for a solid sludge component of up to 3% (the mass of the solid sludge component as a percentage of the unit cement quantity in the concrete mix) to exist in sludge water when it is used as concrete mixing water. However, if sludge water is added, the concrete fluidity is reduced and the quantity of water required to produce the concrete increases. This method is not used widely because of its high cost and compli-cated management of sludge water. The number of ready-mixed-concrete factories that use sludge water as concrete mixing water is low and the amount of indus-trial waste that they generate after the dewatering process is large. Sludge water contains fine particles that originate from cement that has already been hydrated, and from non-hydrated cement and aggregates. By using a set retarder such as sodium gluconate (GLNa) or similar, the hydration reaction of the unhydrated cement in the sludge water can be controlled (Atarashi

Property investigation of individual phases in cementitious composites containing silica fume and fly ash

In this study, nanoindentation was used to investigate the microstructures of cementitious composites containing silica fume and fly ash. With the help of scanning electron microscope, the mechanical properties (elastic modulus and hardness) of individual phases (like outer product, inner product, calcium hydroxide, remained fly ash particles, residual cement grains) in cementitious composites containing silica fume and fly ash were investigated and analyzed. Additionally, this study examined the differences between the ‘C–S–H’ phases in the different cementitious composites and provided an insight into the influence of mineral admixtures (silica fume and fly ash) on the properties of the ‘C–S–H’ phase.

Prevention and treatment of periodontal diseases in primary care.

The aim of this guidance is to support the dental team to; manage patients with periodontal diseases in primary care appropriately; improve the quality of decision making for referral to secondary care; improve the overall oral health of the population. It focuses on the prevention and non-surgical treatment of periodontal diseases and implant diseases in primary care. The surgical treatment of periodontal and implant diseases and the management of patients by periodontal specialists or in a secondary care setting are outwith the scope of this guidance and are not discussed in detail. The guidance is based on existing guidelines, including those from the British Society of Periodontology, relevant systematic reviews, research evidence and the opinion of experts and experienced practitioners. The methodological approach is based on the international standards set out by the Appraisal of Guidelines Research and Evaluation (AGREE) Collaboration (www.agreetrust.org). The guiding principle for developing guidance within SDCEP is to first source existing guidelines, policy documents, legislation or other recommendations. Similarly, relevant systematic reviews are also initially identified. These documents are appraised for their quality of development, evidence base and applicability to the remit of the guidance under development. In the absence of these documents or when supplementary information is required, other published literature and unpublished work may be sought.Review and updating. The guidance will be reviewed in three years and updated accordingly. Recommendations are provided for assessment and diagnosis; changing patient behaviour; treatment of gingival conditions; periodontal conditions; long term maintenance; management of patients with dental implants; referral and record keeping. The key recommendations highlighted are: Assess and explain risk factors for periodontal diseases to patients. Screen all patients for periodontal diseases at every routine examination. Carry out a full periodontal examination for patients with BPE scores 3, 4 and (*)Use the Oral Hygiene TIPPS (talk, instruct, practise, plan, support) behaviour change strategy to address inadequate plaque removal. Raise the issue of smoking cessation where appropriate. Encourage patients to modify other lifestyle factors that may impact on their oral health. Ensure the patient is able to perform optimal plaque removal. Remove supra-gingival plaque, calculus and stain and sub-gingival deposits. Ensure that local plaque retentive factors are corrected. Remove supra-gingival plaque, calculus and stain and correct any local plaque retentive factors. Carry out root surface instrumentation at sites ≥ 4 mm probing depth where sub-gingival deposits are present or which bleed on probing. Do not use antimicrobial medication to treat chronic periodontitis. Remove supra-gingival plaque, calculus and stain and sub-gingival deposits and ensure that local plaque retentive factors are corrected. Assign an individual's risk level based on the patient's medical history and oral health status and schedule recall appointments accordingly. Ensure the patient is able to perform optimal plaque removal around the dental implant(s)Examine the peri-implant tissues for signs of inflammation and bleeding on probing and/or suppuration and remove supra- and sub- mucosal plaque and calculus deposits and excess residual cement. Perform radiographic examination only where clinically indicated. Consult any locally produced referral guidelines and the BSP 'Referral Policy and Parameters of Care' to determine if the patient is a suitable candidate for referral. Carry out initial therapy to address inadequate plaque removal, smoking status (if applicable) and to remove supra- and sub-gingival deposits. Provide supportive periodontal therapy and monitoring for patients who have been discharged from secondary care. Record the results of the periodontal examinations (basic and/or full) carried out and the current standard of oral hygiene. Record the diagnosis, suggested treatment plan and details of costs. Document any discussions you have with the patient, for example, treatment options, risks and benefits of treatment, oral hygiene advice, smoking cessation, alcohol consumption and/or other lifestyle factors. There is a need for high-quality research carried out within an appropriate governance framework to improve the evidence base in the following areas: barriers and facilitators to the delivery of oral hygiene interventions in primary care;behaviour change interventions to improve inadequate oral hygiene;optimal timescales for provision of routine supra-gingival debridement (dental prophylaxis) and supportive periodontal therapy;effectiveness of supportive periodontal therapy regimens;effectiveness of supportive therapy regimens to maintain peri-implant tissues;effectiveness of interventions to treat peri-implant mucositis and peri-implantitis.Consensus is urgently required on the importance and validity of surrogate periodontal outcomes (eg bleeding on probing, changes in clinical probing depth and clinical attachment level and bone levels) and their relationship to true outcomes (eg tooth loss and patient-centred outcomes) so that consistency can be achieved across studies. There is also a need for independent research into the effectiveness of oral hygiene tools such as toothbrushes, interdental aids, toothpastes and mouthwashes and gels containing antibacterial agents.

Mid term results with the curved modular tapered, fluted titanium Revitan stem in revision hip replacement.

We report our experience of revision total hip replacement (THR) using the Revitan curved modular titanium fluted revision stem in patients with a full spectrum of proximal femoral defects. A total of 112 patients (116 revisions) with a mean age of 73.4 years (39 to 90) were included in the study. The mean follow-up was 7.5 years (5.3 to 9.1). A total of 12 patients (12 hips) died but their data were included in the survival analysis, and four patients (4 hips) were lost to follow-up. The clinical outcome, proximal bone regeneration and subsidence were assessed for 101 hips. The mean Harris Hip Score was 88.2 (45.8 to 100) after five years and there was an increase of the mean Barnett and Nordin-Score, a measure of the proximal bone regeneration, of 20.8 (-3.1 to 52.7). Five stems had to be revised (4.3%), three (2.9%) showed subsidence, five (4.3%) a dislocation and two of 85 aseptic revisions (2.3%) a periprosthetic infection. At the latest follow-up, the survival with revision of the stem as the endpoint was 95.7% (95% confidence interval 91.9% to 99.4%) and with aseptic loosening as the endpoint, was 100%. Peri-prosthetic fractures were not observed. We report excellent results with respect to subsidence, the risk of fracture, and loosening after femoral revision using a modular curved revision stem with distal cone-in-cone fixation. A successful outcome depends on careful pre-operative planning and the use of a transfemoral approach when the anatomy is distorted or a fracture is imminent, or residual cement or a partially-secured existing stem cannot be removed. The shortest appropriate stem should, in our opinion, be used and secured with > 3 cm fixation at the femoral isthmus, and distal interlocking screws should be used for additional stability when this goal cannot be realised.

Structure, properties and animal study of a calcium phosphate/calcium sulfate composite cement

In-vitro and in-vivo studies have been conducted on an in-house-developed tetracalcium phosphate (TTCP)/dicalcium phosphate anhydrous (DCPA)/calcium sulfate hemihydrate (CSH)-derived composite cement. Unlike most commercial calcium-based cement pastes, the investigated cement paste can be directly injected into water and harden without dispersion. The viability value of cells incubated with a conditioned medium of cement extraction is >90% that of Al2O3 control and >80% that of blank medium. Histological examination reveals excellent bonding between host bone and cement without interposition of fibrous tissues. At 12weeks-post implantation, significant remodeling activities are found and a new bone network is developed within the femoral defect. The 26-week samples show that the newly formed bone becomes more mature, while the interface between residual cement and the new bone appears less identifiable. Image analysis indicates that the resorption rate of the present cement is much higher than that of TTCP or TTCP/DCPA-derived cement under similar implantation conditions.

GENETIC-ALGORITHM-BASED MIX PROPORTION DESIGN METHOD FOR RECYCLED AGGREGATE CONCRETE

Several desirable characteristics of concrete, such as strength, slump, durability and low CO2 emission, cannot always be obtained by current conventional mix proportion design methods for recycled aggregate concrete (RAC), because Recycled aggregate generally has lower quality than natural aggregate owing to residual cement paste and various impurities. We treat optimal concrete mix proportioning as a multi-criteria problem, and suggest a new method based on genetic algorithms (GAs) to solve the mix proportion design problem for RAC through a simulated biological evolutionary process. In this method, several fitness functions for the desired properties of concrete, i.e., slump, strength, carbonation speed coefficient, price, and emission of CO2, were considered based on conventional data or adopted from previous studies. We thus arrived at optimal mix proportions for RAC that meet the desired performance criteria.

Cement paste content and water absorption of recycled concrete coarse aggregates

In this paper, we first show that the amount of residual cement paste in recycled concrete aggregates (RCA) depends on the initial paste content, on the mechanical properties of the initial cement paste and on the mechanical quality of the transition zone at the interface between the initial natural aggregates and cement paste. Our results suggest that water absorption of RCA at 24 h can be seen as the simple sum of the capillary absorption of both residual cement paste and initial natural aggregates. The absorption kinetics is similar to the capillary absorption of traditional uncrushed concretes but, on the industrial time scale of interest, is strongly affected by the size and configuration of the residual cement paste patches at the surface of the initial natural aggregates. We finally propose a tentative frame for a classification of RCA based on water absorption rate and water absorption capacity at 24 h.

Desain pin hole mempengaruhi kuat rekat geser gigitiruan jembatan adesif Pin hole design affect shear bond strength of adhesive bridge

To overcome the failure of adhesive bridge due to release of the adhesive bond cement between teeth and metal,preparation modification was performed with a pin hole in the teeth cingulum. This study aimed to determine the effectof thread on a pin hole to shear strength adhesion of adhesive bridge. Forty maxillary incisors were prepared at theirpalatinal surfaces 0.3 mm thick, and were divided into four treatments (threaded hole+threaded pin, threaded holes+non-threaded pin, non-threaded holes+threaded pin, non-threaded holes+non-threaded pin). Casted-plates made fromnickel chromium alloy were cemented to the palatal surface of the tooth with adhesive cement (Panavia TMF 2.0), andthen adhesion shear strength tested. The test and evaluation of the residual cement on the surface were performed inLaboratory Metallurgy, Department of Engineering ITB. Data were analyzed by one-way ANOVA test (p=0.05).Adhesion shear strength of plate with threaded holes+threaded pin has the highest retention. Residual cement onthreaded hole+threaded pin plates similar to threaded hole+non-threaded pin, but more than any other groups. theconclusions were, the adhesion shear strength depends on the design of pin hole. The wider surface of cementremaining on the plates, the greater adhesion shear strength.

Mineralogical and microstructural characteristics of historic Roman cement renders from Budapest, Hungary

Abstract Roman cements, one of the most extensively produced types of hydraulic binders of the second half of the 19th century, played an important role in the architecture of many European countries. This paper deals with the chemical-mineralogical and microstructural characterisation of historic Roman cement renders from Budapest, Hungary. Different microscopic techniques were used on polished thin sections and fracture surfaces in order to understand the method of producing these renders and the effect of urban pollution on them. The renders exhibited characteristics typical to a Roman cement mortar, such as high binder to aggregate ratios (b/a), mostly fine-grained aggregates and high capillary porosity, but without the shrinkage cracks that are also normally present. This research suggests that coarse residual cement grains may have acted in a manner similar to aggregates by absorbing stress and thereby reducing the formation of shrinkage cracks. Based on the mineral characteristics of residual cement grains, the samples could be divided into two groups, which correspond to either a higher or lower temperature of calcination of the original source material of the cement. Chemical characteristics of the binders suggest the presence of intermixed CaCO 3 originating from the carbonation of hydration products and partly from residual calcium carbonate of the raw material. Despite dense and often impermeable coats applied in later renovations and exposure to a polluted urban environment, which resulted in formation of gypsum on the surface of the renders, the samples show good to excellent state of preservation after more than a century. The strong “house of cards”-like arrangement of the complex C-(A)-S-H-type phases is responsible for both the high capillary porosity and the good resistance of Roman cement renders to atmospheric pollution and potentially damaging salts such as Na- and K-chlorides which are found near the base of the building due to sidewalk de-icing. These results help to better understand the behaviour of historic Roman cement renders, which in turn assists in making good decisions in choosing a repair material to future restorations of 19th century facades built with this material.

A Study on the GA-Based Design for Recycled Aggregate Concrete

Various desired performances of concrete, i.e. strength, slump, durability, etc., cannot be always obtained by current conventional mix proportion design methods for recycled aggregate concrete (RAC), because recycled aggregate (RA) generally has lower quality than natural aggregate due to the residual cement paste attached on RA and various impurities. On the other hand, design of concrete mix proportion using RA can be solved as the multi-criteria problem to meet the various required performances. This paper suggests a new method for the mix proportion of RAC to reduce the number of trial mixes using genetic algorithm (GA) which has been an optimization technique to solve the multi-object problem throughout the simulated biological evolutionary process. In mix design method by GA, several fitness functions for the required properties of concrete, i.e., slump, strength, carbonation speed coefficient, price, and emission of CO2 were considered based on conventional data or adapted from various early studies. As a result, various optimum mix proportions for RAC that meet required performances were obtained according to assumed case studies.

A Study on Provisional Cements, Cementation Techniques, and Their Effects on Bonding of Porcelain Laminate Veneers

Minimal tooth preparation is required for porcelain laminate veneers, but interim restorations are a must to protect their teeth against thermal insult, chemical irritation, and to provide aesthetics. Cement remaining after the removal of the provisional restoration can impair the etching quality of the tooth surface and fit and final bonding of the porcelain laminate veneer. This in vitro study examined the tooth surface for remaining debris of cement after removal of a provisional restoration. Determine the presence of cement debris on prepared tooth surface subsequent to the removal of provisional restoration. Determine the cement with the least residue following the cleansing procedures. Determine the effect of smear layer on the amount of residual luting cement. Eighty-four extracted natural anterior teeth were prepared for porcelain laminate veneers. For half of the teeth, the smear layer was removed before luting provisional restorations. Veneer provisional restorations were fabricated and luted to teeth with six bonding methods: varnish combined with glass ionomer cement (GIC), varnish combined with resin modified GIC, varnish, spot etching combined with dual-cure luting cement, adhesive combined with GIC, adhesive combined with resin modified GIC, and adhesive, spot etching combined with dual-cure luting cement. After removal of provisional restorations 1week later, the tooth surface was examined for residual luting material with SEM. Traces of cement debris were found on all the prepared teeth surfaces for all six groups which were cemented with different methods. Cement debris was seen on teeth subsequent to the removal of provisional's. Dual-cure cement had the least residue following the cleansing procedures. Presence of smear layer had no statistical significance in comparison with cement residue. With the use of adhesive the cement debris was always found to be more than with the use of varnish. GIC showed maximum residual cement followed by dual-cure.

Does residual cement around implant‐supported restorations cause peri‐implant disease? A retrospective case analysis

The purpose of this study was to determine the relationship between patients with a history of periodontitis and development of cement-related peri-implant disease. Seventy-seven patients with 129 implants for this retrospective analysis were selected from completed implant cases that were scheduled for regular maintenance or had experienced mechanical or biological complications between years 2006 and 2011 in private practice. Implants with extracoronal residual cement and implants without cement remnants were analyzed. The selected cases were further divided into two groups--implants in patients with history of periodontitis (1) and implants in periodontitis-free individuals (2). The selection of these groups was made on the basis of treatment history and orthopantomograph. As a control group, a set of 238 screw-retained implant restorations, delivered to 66 patients during the same period of time was examined. The incidence of peri-implant disease among implants in all groups was calculated. Peri-implant disease was evident in 62 of 73 implants with cement remnants (85%). All implants in group 1 developed peri-implantitis--4 early and 35 delayed disease cases. In the periodontally healthy group, 20 of 31 implants were diagnosed with peri-implant mucositis, 3 implants had early peri-implantitis, and 11 implants with cement remnants did not develop biological complications. In the group of implants without cement remnants, peri-implant disease was diagnosed in 17 of 56 cases (30%). In contrast, only two occurrences of peri-implant disease were registered in the control group of screw-retained restorations (1.08%). Implants with cement remnants in patients with history of periodontitis may be more likely to develop peri-implantitis, compared with patients without history of periodontal infection.

Effect of Artificial Aging and Surface Treatment on Bond Strengths to Dental Zirconia

The objective of this project was to study the influence of artificial aging and surface treatment on the microtensile bond strengths (μTBS) between zirconia and a phosphate monomer-based self-adhesive cement. Thirty zirconia disks (IPS e.max ZirCAD, Ivoclar Vivadent) were randomly assigned to two aging regimens: AR, used as received, which served as a control, and AG, artificial aging to simulate low-temperature degradation. Subsequently, the disks of each aging regimen were assigned to three surface treatments: NT, no surface treatment; CO, surface silicatization with CoJet sand (3M ESPE); and ZP, zirconia surface treated with Z-Prime Plus (Bisco Inc). Thirty discs were made of Filtek Z250 (3M ESPE) composite resin and luted to the zirconia discs using RelyX Unicem (3M ESPE). The specimens were sectioned with a diamond blade in X and Y directions to obtain bonded beams with a cross-section of 1.0 ± 0.2 mm. The beams were tested in tensile mode in a universal testing machine at a speed of 0.5 mm/min to measure μTBS. Selected beams were selected for fractographic analysis under the SEM. Statistical analysis was carried out with two-way analysis of variance and Dunnett T3 post hoc test at a significance level of 95%. The mean μTBS for the three AR subgroups (AR-NT, AR-CO, and AR-ZP) were significantly higher than those of the corresponding AG groups (p<0.0001). Both AR-CO and AR-ZP resulted in statistically significant higher mean bond strengths than the group AR-NT (p<0.006 and p<0.0001, respectively). Both AG-CO and AG-ZP resulted in statistically significant higher mean bond strengths than the group AG-NT (both at p<0.0001). Overall, AG decreased mean μTBS. Under the SEM, mixed failures showed residual cement attached to the zirconia side of the beams. CO resulted in a characteristic roughness of the zirconia surface. AR-ZP was the only group for which the amount of residual cement occupied at least 50% of the interface in mixed failures.

Diffusion of Multi-Ionic Species in Recycled Aggregate Concrete

In recent years, recycled aggregate concrete has been used in reinforced concrete structures. Concrete structures exposed to chloride environment often encountera premature deterioration due to corrosion of steel reinforcement. In order to avoid unplanned maintenances or repairs, it is necessary to develop a reliable prediction model for the chloride diffusion in concrete. The basic formulation of the transport theory will be presented first and then its application to Recycled Aggregate Concrete (RAC) will follow. Chloride diffusion in RAC is different from the diffusion in regular concrete, because the material parameters of RAC such as chloride diffusion coefficient are different from those of regular concrete. In this paper, a multi-scale and multi-phase model will be developed to characterize theinternal structure of the recycled aggregate with a layer of residual cement paste on the surface of natural aggregate and another layer of surface treatment material on the surface of the residual cement paste. The multi-scale and multi-phase model will also be used to characterize the chloride diffusion coefficient of RAC. The numerical analysis of the diffusion equations is performed by using finite element method.

The influence of margin location on the amount of undetected cement excess after delivery of cement‐retained implant restorations

The aim of this study was to evaluate the amount of the residual cement excess after cementation and cleaning of implant-supported restorations with various positions of the margins. Twenty-five casts with embedded implant analogs and flexible soft-tissue imitation were used in the study. Individual abutments with different position of the margin - from 1 mm supragingivally to 3 mm below the gingival level - were modelled and divided equally into five groups. The same amount of polished metal crowns was luted to prosthetic abutments, excess cement was cleaned and the restorations were removed for evaluation of the undetected cement remnants. All quadrants of each specimen were photographed for calculation of the ratio between the cement remnants area and the total specimen area using Adobe Photoshop. Afterwards, cement remnants were cleared from each specimen and weighed with analytical balances. The measurements in all the groups consisted of (1) the relation between the cement remnants area and the total area of the specimen; and (2) cement excess weight in grams after cleaning: group 1 (0.0111 ± 0.021; 0.0003 ± 0.0001 g); group 2 (0.0165 ± 0.019; 0.0008 ± 0.0003 g); group 3 (0.0572 ± 0.028; 0.0013 ± 0.0005 g); group 4 (0.1158 ± 0.054; 0.0051 ± 0.0013 g); and group 5 (0.1171 ± 0.059; 0.0063 ± 0.0021 g). Results showed significant increase of undetected cement quantity, as the restoration margins were located deeper subgingivally, using weighting (P=0) and calculation of proportion (P=0). There was a significant correlation between evaluation techniques (r=0.889; P=0). The amount of residual cement after cleaning increased as the restoration margins were located more subgingivally.

The effect of ultrasonic removal of various root‐end filling materials

To compare residual root-end filling material in apical root-end cavities following their removal with ultrasonic retrotips. Thirty single-rooted teeth were filled with Thermafil and AH Plus sealer. Root-ends were resected at 90 degrees, 3 mm from the apex. Root-end cavities were prepared with diamond burs and ultrasonic retrotips and filled with one of three filling materials: group I: Retro-TC (calcium silicate-based cement), group II: IRM (Dentsply, Germany), group III: Vitrebond (3M ESPE, USA). After 30 days of storage, ultrasonic retrotips were used to remove materials from the root-end cavities. The ultrasonic application time was fixed at 60 s. Polyether impressions and replicas of the root-ends were made. Root apices and replicas were examined by one operator under a scanning electron microscope. Remnants of residual materials were evaluated using a four-level scoring system; fractures, smear layer and exposed dentinal tubules were also examined. Forty per cent of the specimens filled with Retro-TC revealed complete removal of the material with exposure of dentinal tubules, whilst 60% contained residual cement. Twenty per cent of specimens filled with IRM were completely devoid of material, whereas 80% had retained material. Ten per cent of specimens filled with Vitrebond retained a moderate amount of material whilst 90% had substantial retention of the material. Statistically significant differences were found (P < 0.05) amongst the three groups of materials. Retro-TC was successfully removed in 40% of cases using ultrasonics retrotips for 60 s, whereas IRM and Vitrebond specimens had evidence of retained material in 80% and 90% of all specimens respectively.

Long‐term evaluation of a calcium phosphate bone cement with carboxymethyl cellulose in a vertebral defect model

We investigated histological and compressive properties of a calcium phosphate bone cement (BoneSource (CPC); Stryker Orthopaedics, Mahwah, New Jersey) plus carboxymethyl cellulose (CMC) using a sheep vertebral bone void model. Bone voids were surgically created in L3 and L5 in each of 40 sheep, and the voids were filled with the cement. Histological and radiographic evaluations were performed on one vertebral body from each animal at either: 0, 3, 6, 12, 24, or 36 months after surgery; mechanical testing was performed on operated and non-operated vertebral bodies from 35 sheep. Undecalcified sections were digitized, and the area of the original defect, new bone formation, empty space, fibrous tissue, and residual cement were quantified with histomorphometry. Decalcified sections were evaluated qualitatively. The cement was biocompatible, extremely osteoconductive and underwent steady resorption and replacement by bone and bone marrow. Histomorphometry showed variations in the rate of cement remodeling among animals in each time group, but on average, at 36 months the original defect area was occupied by approximately 14% bone, 82% cement, and 4% bone marrow. Even in animals that had greater resorption of cement, there was good bone ingrowth with no fibrous tissue. Compressive testing did not reveal a significant difference in the mechanical properties between vertebral bodies augmented with cement and non-augmented controls, irrespective of the postoperative time. BoneSource mixed with CMC had adequate osteoconductivity, biocompatibility, and adequate compressive strength. There was variability among animals, but histology suggests that considerable cement was still present in most samples after 36 months.

Bioresorption behavior of tetracalcium phosphate-derived calcium phosphate cement implanted in femur of rabbits

One primary focus of the present study was to clarify the crucial resorption–location relationship of a recently developed single-phase TTCP-derived calcium phosphate cement (CPC) implanted in rabbit femur in a systematic and quantitative way. Gross examination of retrieved CPC/bone composite samples indicated that the CPC implant did not evoke inflammatory response, necrosis or fibrous encapsulation in surrounding bony tissues. Histological examination revealed excellent CPC–host bone bonding. At 4 weeks, the resorption-induced voids between terminals of bone defects and implants were largely filled with new bone. CPC resorption, new blood vessels, osteocytes, osteons and osteoblast-like cells lining up with active new bone were observed at remodeling sites. At 12 weeks, a new bone network was developed within femoral defect, while CPC became islands incorporated in the new bone. At this stage, crevices filled with lamellar new bone structure were frequently observed. At 24 weeks, bone ingrowth and remodeling activities became so extensive that the interface between residual cement and new bone became less identifiable. In general, at all implant locations the resorption ratio values increased with implantation time, while at all implantation times the resorption ratios decreased from the exterior (cortical site) to the interior (cancellous site) of implants. At the end of 24 weeks, CPC was almost completely resorbed and bone remodeling almost finished at the cortical site.

Microstructural features of a mortar as seen by computed microtomography

While low resolution limits the use of computed microtomography for microstructural investigation, the method has a unique advantage in that no specimen preparation is required; the images produced are thus entirely free of specimen preparation artifacts. In the present communication we report examination of the microstructure of a w:c 0.6 mortar, with the tomographic information resolved on a set of more than 500 successive planar images each 1.2 μm apart. Selected images are compared with backscatter SEM images taken from similar materials at comparable magnifications. The same features are observed, including sand grains, air voids, residual cement grains, hydrated cement paste components, and hollow-shell pores. The “patchy” microstructure of different areas of hardened cement paste, previously reported for mortars and concretes in backscatter SEM, is clearly also present in images derived from computed microtomography, and are not artifacts of SEM specimen preparation.