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The cost of urease enzyme production and complex extraction procedure are widely considered as a major barrier for the use of bio-cementation via enzyme-induced carbonate precipitation (EICP) in practical engineering applications. In this paper, crude urease was extracted from soybean using a series of extraction procedures, including coarse filtration, centrifuge, and micro-filtration. Together with the commercially available pure urease, extracts of crude urease after each extraction step were collected and evaluated for their efficiency in chemical conversion efficiency and strength enhancement of the EICP process. The results indicated that the impurities of coarse-filtrated urease could protect urease enzyme, promote precipitation yield, maintain enzyme activity and stability, and improve strength enhancement. The microstructure images of the coarse-filtered enzyme-treated samples showed the transformation of crystal morphology from metastable spherical shape to rhombohedral- and polyhedral shape, resulting in effective bonding between the sand grains. A preliminary estimation of the energy requirement for the urease extraction exhibited that about 0.6 kJ of energy could be saved per 1000 U activity produced using only coarse filtration without further labor and equipment intensive centrifugation, which represents a sustainable and cost-effective approach to utilize EICP technique.

Soil bio-cementation via microbially induced carbonate precipitation (MICP) has been extensively studied as a promising alternative technique to traditional chemical cementing agents for ground improvement. The multiple-phase injection methods are currently well adopted for MICP treatment, but it is rather complex and requires excessive number of injections. This paper presents a novel one-phase injection method using low-pH all-in-one biocement solution (i.e. a mixture of bacterial culture, urea, and CaCl2). The key feature of this method is that the lag period of the bio-cementation process can be controlled by adjusting the biomass concentration, urease activity, and pH. This process prevents the clogging of bio-flocs formation and thus allows the biocement solution to be well distributed inside the soil matrix before bio-cementation takes effect, allowing a relatively uniform MICP treatment to be achieved. Furthermore, the ammonia gas release would be reduced by more than 90%, which represents a significant improvement in the environmental friendliness of the technology. The new one-phase method is also effective in terms of the mechanical property of MICP-treated soil; an unconfined compressive strength of 2.5 MPa was achieved for sand after six treatments.

Microbially induced calcite precipitation (MICP) is used increasingly to improve the engineering properties of granular soils that are unsuitable for construction. This shows MICP technique significant advantages such as low energy consumption and environmentally friendly feature. The objective of the present study is to assess the strength behaviour of bio-cemented sand with varying cementation levels, and to provide an insight into the mechanism of MICP treatment. A series of isotropic consolidated undrained compression tests, calcite mass measurement and scanning electron microscopy tests were conducted. The experimental results show that the strength of bio-cemented sand depends heavily on the cementation level (or calcite content). The variations of strength parameters, i.e. effective friction angle φ ′ and effective cohesion c ′, with the increase in calcite content can be well evaluated by a linear function and an exponential function, respectively. Based on the precipitation mechanism of calcite crystals, bio-clogging and bio-cementation of calcite crystals are correlated to the amount of total calcite crystals and effective calcite crystals, respectively, and contributed to the improvement in the effective friction angle and effective cohesion of bio-cemented sand, separately.

Concentration of cementation solution (CCS) is one of the key factors influencing the cementation effect on soil improvement through the microbially induced carbonate precipitation (MICP) process. To precipitate more calcium carbonate per treatment, a higher CCS is needed. However, the MICP process may be retarded or even terminated with an increase in CCS. This retarding effect can be a major limitation for the MICP-based soil treatment and thus needs to be understood properly. This paper presents a systematic study on the conditions causing retarding and its effect on biocementation. The test results of this study have identified that there is retarding effect of CCS on the MICP process, showing that the calcium conversion efficiency, which represents the amount of calcium that has been converted into calcium carbonate in each treatment, reduces with the increase in CCS, and the concentration of calcium is the control factor. The retarding effect will dominate increasingly when CCS is higher than 1.0 M and the amount of calcium carbonate precipitation will reduce for the given amount and type of bacteria used in this study and become zero with CCS of 2.5 M. For the same calcium carbonate content, the unconfined compressive strength is greater for sand treated using a lower CCS as the contribution to the bonding strength by the calcium carbonate generated under a lower CCS is greater than that under a higher CCS.

Objectives To evaluate three temporary luting cements in terms of their restoration loss rates, biological interactions, esthetic properties, and handling characteristics. Materials and methods 75 adults requiring fixed prosthodontics voluntarily participated in a single-blind, randomized controlled trial. After preparation, temporary restorations were luted with a randomly selected temporary luting cement (either Provicol QM Plus (PQP), Bifix Temp (BT), or Provicol QM Aesthetic (PQA)). Clinical examinations were performed one to two weeks after cementation. The following criteria were evaluated: tooth vitality, percussion, hypersensitivity, gingival bleeding, odor formation, esthetics, cement handling, removability, cleanability, and retention loss. Antagonistic teeth served as controls. Statistical analysis was performed using the paired t-test, one-way ANOVA, Pearson’s chi-square and Fisher’s exact test, where appropriate. Results The overall loss rate of temporary restorations was 16.0%, showing no cement-specific differences. Postoperative hypersensitivity occurred in 8% of cases regardless of cement type. Esthetic impairment was reported by 31% of the PQP-fixed restorations, compared with 4.0% and 4.2% of the BT and PQA-bonded restorations. Cement application was reported to be easy in 100% of cases, excess removal in 88–96%, depending on the cement used. Conclusions The choice of luting material affects the esthetic appearance of a temporary restoration and should be considered, particularly in restorations in esthetically demanding areas. No significant differences between the cements were identified regarding biocompatibility, handling, and loss rate. Clinical relevance Translucent cements can help to reduce color interferences, resulting in a more appealing appearance of the temporary restoration.

Calcareous sands have abundant intraparticle pores and are prone to particle breakage. This often leads to poor engineering properties, which poses a challenge to coastal infrastructure construction. A study using bio-cementation to improve the engineering properties of calcareous sand is presented in this paper. The macro- and microscopic properties of bio-cemented calcareous sand were characterized by drained triaxial tests and scanning electron microscopy observations. Experimental results show that the precipitated calcium carbonate can effectively fill the intra- and interparticle pores and bond adjacent particles, thus enhancing the shear strength of calcareous sand. The special structures (e.g. abundant intraparticle pores and rough surface) and mineral components (i.e. calcium carbonate) of calcareous sand are beneficial for improving bacterial retention in soil, which leads to a relatively uniform and dense calcium carbonate distribution on the sand particle surface, exhibiting a layer-by-layer growth pattern. This growth pattern and the abundant interparticle pores would result in less effective calcium carbonate. The strength enhancement of bio-cemented calcareous sand is significantly lower than that of bio-cemented silica sand at the same calcium carbonate content, which may be caused by the differences in the following: (a) soil skeleton strength; (b) the amount of effective calcium carbonate; and (c) interparticle pore-filling of calcium carbonate.

ObjectivesThe objective of this study is to evaluate the longevity of two fiber post cementation strategies in a prospective, multicenter, non-inferiority, double-blind randomized controlled trial.MethodsA total of 152 teeth, with adequate endodontic treatment and loss of coronal structure and bilateral simultaneous posterior occlusal contacts, were randomly allocated to receive glass fiber posts cemented with a conventional cementation strategy (CRC group: adhesive system + resin cement) (Adper Single Bond + RelyX ARC; 3 M-ESPE) or a self-adhesive cementation strategy (SRC group: self-adhesive resin cement; RelyX U100/U200; 3 M-ESPE). The patients were recalled annually for clinical and radiographical evaluation with a 93% recall rate (142 teeth, with 74 at CR groups and 68 at SRC group). The primary outcome was survival rate, considering the fiber post debonding (loss of retention). The secondary outcome included the success rate of the prosthetic treatment with crown debonding, post fracture, and tooth loss (not related to post failure). Both outcomes were evaluated annually. The Kaplan–Meier method and Cox regression with 95% confidence interval were used for the statistical analysis.ResultsFor the primary outcome (failures directly related to fiber posts cementation strategy), there were 4 fiber post debondings (2 per group), 8 root fractures (3 for SRC group and 5 for CRC group), and one mixed failure (debonding combined with root fracture for CRC), with both strategies presenting similar survival rates (p = 0.331), with 88.9% for the CRC group and 90.9% for the SRC group. For the secondary outcome (failures not related to fiber post cementation strategies), there were 8 crown debondings, 3 post fractures, and 3 tooth losses, with no statistically difference between groups (p = 0.701), with 77% for SRC and 82% for CRC.ConclusionFiber post cementation strategies with conventional or self-adhesive resin cement presents similar tooth survival and success rates.Trial registrationNCT01461239Clinical relevanceBoth adhesive cementation strategies led to high survival and success rates and are indicated for fiber post cementation, even after a long follow-up period (up to 106 months).

The effect of grain size distribution on the unconfined compressive strength (UCS) of bio-cemented granular columns is examined. Fine and coarse aggregates were mixed in various percentages to obtain five different grain size distributions. A four-phase percolation strategy was adopted where a bacterial suspension and a cementation solution (urea and calcium chloride) were percolated sequentially. The results show that a gap-graded particle size distribution can improve the UCS of bio-cemented coarser granular materials. A maximum UCS of approximately 575 kPa was achieved with a particle size distribution containing 75% coarse aggregate and 25% fine aggregate. Furthermore, the minimum UCS obtained has applications where mitigation of excessive bulging of stone/sand columns, and possible slumping that might occur during their installation, is needed. The finding also implies that the amount of biochemical treatments can be reduced by adding fine aggregate to coarse aggregate resulting in effective bio-cementation within the pore matrix of the coarse aggregate column as it could substantially reduce the cost associated with bio-cementation process. Scanning electron microscopy results confirm that adding fine aggregate to coarse aggregate provides more bridging contacts (connected by calcium carbonate precipitation) between coarse aggregate particles, and hence, the maximum UCS achieved was not necessarily associated with the maximum calcium carbonate precipitation.

Purpose The aim of the study was to compare the distance of intrusion of the cement into the bone in different areas both in the femur and the tibia in vivo, measured in the radiograph after implanting a total knee arthroplasty (TKA) with three different cement techniques. Methods A prospective randomized study of 90 consecutive patients operated on at our institution with a cemented U2 Knee System TKA and medium viscosity Simplex P ® bone cement. After pulse lavage, the cement was applied on the bone surfaces (group 1), on the implant surfaces (group 2) or both on the bone and the implant surfaces (group 3). The cement intrusion was measured in the postoperative radiographs in eight different regions in the tibial component and in six regions in the femoral component. The cement employed was calculated by weighting the cement after mixing and weighting the discarded cement. Results The average intrusion of the cement was similar in all three groups of cementing techniques in the femoral components (1.6 mm; p  = 0.386), and in the tibial components (2.6 mm; p  = 0.144). The intrusion of the cement in the tibia was greater in women than in men ( p  = 0.04). We used 21.1 (SD 5.8) g of cement in average. The amount of cement employed was greater when the cement was applied on both (implant and bone) surfaces (group 3: 24.03 g in average) than when it was applied only on the bone (group 1: 20.13 g; p  = 0.01) or only on the implants (group 2: 19.20 g; p  = 0.001). The amount of cement employed was greater in men than in women ( p  = 0.002) and it was also greater when a PS femoral component was used ( p  = 0.03). The amount of cement employed was directly correlated with the height of the patients ( p  = 0.01) and with the bigger size of the components ( p  < 0.001). Conclusion All three cement application techniques have similar intrusion distance of the cement into the bone, and the intrusion depth of the cement into the trabecular tibial bone is greater than the minimum suggested for fixation.

IntroductionCephallomedullary nail fixation is currently the most popular treatment for pertrochanteric fractures. Despite continuous improvement in implant design, fixation failures still occur in a concerning number of cases. This study aims to evaluate the effect of cement augmentation of the new-generation Trochanteric Femoral Nail Advanced (TFNA) perforated spiral blade on complications including fixation failure in the elderly population.Materials and methodsWe retrospectively evaluated 107 patients aged 65 + treated for pertrochanteric fractures via TFNA between 2015 and 2019 based on whether cementation was used. Baseline demographics, fracture classifications, and reduction quality were compared. Patients with a follow-up of at least 6 months were analyzed for the primary outcome of fixation failure. All patients, regardless of loss to follow-up within 6 months, were analyzed for other complications including mortality.ResultsSeventy-six patients (47 cemented, 29 non-cemented) had a minimum follow-up of 6 months (mean 13 months). There were no statistically significant differences between the two treatment groups in terms of patient demographics, ASA or AO/OTA fracture classification, reduction quality, or length of follow-up. There was a lower rate of fixation failure in the cement-augmented (CA) group versus the non-cement-augmented (NCA) group (2.1% vs 13.8%; p = 0.047). No cut-out or cut-through was observed in the CA group. Seven patients had adverse intraoperative events, with a significantly higher rate of fixation failure in these patients (40% vs 2.8%; p = 0.00). There were no statistically significant differences in 30-day mortality (6.3% CA vs 4.3% NCA; p = 0.632) or 3-month mortality (9.5% CA vs 12.8% NCA; p = 0.589).ConclusionsCementation of TFNA blades may decrease risk of fixation failure, however, the surgeon must be aware of potential complications such as cement leakage into the hip joint and be able to manage them as they arise.