Initiation of a fixed-dose four-factor prothrombin complex concentrate protocol.

Patients who require urgent warfarin reversal often receive four-factor prothrombin complex concentrate (4F-PCC), which is traditionally dosed according to weight and initial INR. Our institution implemented a fixed-dose 4F-PCC strategy, using an initial dose of 1500 units. We evaluated the frequency with which the initial fixed dose 4F-PCC was inadequate, as defined by need for supplemental dosing. As part of the protocol, if the initial fixed-dose 4F-PCC is administered and does not achieve INR goal, then the remainder of the standard weight- and INR-based dosing can be given. During the study period, 63 patients on warfarin received 4F-PCC using the fixed-dose protocol. Based on the INR following 4F-PCC administration, 11 patients (17%) were eligible to receive a supplemental dose based on failure to achieve their specified INR goal. Two of the 11 patients eligible for supplemental 4F-PCC dosing received the second dose, both with initial supratherapeutic INRs > 3.5. We found that most patients given an initial fixed-dose 4F-PCC achieved their INR goals, and of those who did not, most did not receive supplemental dosing, suggesting that clinical providers felt that adequate hemostasis had been achieved. In addition, fixed-dose 4F-PCC was able to be given rapidly, with few dosing errors, suggesting that this is a reasonable option for 4F-PCC delivery.

Variations in bone density at dental implant sites in different regions of the jawbone.

The survival rate of dental implants is markedly influenced by the quality of the bone into which they are placed. The purpose of this study was to determine the trabecular bone density at potential dental implant sites in different regions of the Chinese jawbone using computed tomography (CT) images. One hundred and fifty-four potential implant sites (15 in the anterior mandible, 47 in the anterior maxilla, 55 in the posterior mandible, and 37 in the posterior maxilla) were selected from the jawbones of 62 humans. The data were subjected to statistical analysis to determine any correlation between bone density (in Hounsfield units, HU) and jawbone region using the Kruskal-Wallis test. The bone densities in the four regions decreased in the following order: anterior mandible (530 +/- 161 HU, mean +/- s.d.) approximately equal anterior maxilla (516 +/- 132 HU) > posterior mandible (359 +/- 150 HU) approximately equal posterior maxilla (332 +/- 136 HU). The CT data demonstrate that trabecular bone density varies markedly with potential implant site in the anterior and posterior regions of the maxilla and mandible. These findings may provide the clinician with guidelines for dental implant surgical procedures (i.e., to determine whether a one-stage or a two-stage protocol is required).

Effects of implant surface roughness and stiffness of grafted bone on an immediately loaded maxillary implant: a 3D numerical analysis.

This study investigated the effects of the stiffness of a maxillary sinus graft and the surface roughness of an immediately loaded implant using a non-linear three-dimensional finite element (FE) analysis (3D). Six FE models were created, including two stiffness values of grafted bone (345 and 3450 MPa of elastic modulus) and three conditions of implant-bone interfaces (Frictional coefficient of 0.3 for machined surface, 0.45 for rough implant surface and a bonded implant-bone interface for an osseointegrated implant). Computer tomographic images of a human skull were used to construct a posterior maxillary model. All implants were designed via the computer aided design software with a spiral threaded configuration. Three loading scenarios were investigated for each of the six models; axial loading and lateral loadings at 30 degrees and 60 degrees . The results showed that a 60 degrees lateral loading has scored the highest level of bone stresses among the three loading conditions. Immediately loaded implants with 0.3 frictional coefficient have suffered the highest bone stresses which were higher than those with bonded interface by about 57%. Increasing the frictional coeffecient to 0.45, however, did not show any benefits in reducing the peak bone stress. Raising the stiffness of grafted bone diminished the bone stress by about 10% in both the immediately loaded and the osseointegrated implants. It was also noted that increasing graft stiffness and implant surface roughness reduced the sliding at the implant-bone interface which may improve the implant stability and long-term survival.

Kinetics of inorganic carbon utilization by microalgal biofilm in a flat plate photoreactor.

A kinetic model was developed to describe inorganic carbon utilization by microalgae biofilm in a flat plate photoreactor. The model incorporates the fundamental mechanisms of diffusive mass transport and biological reaction of inorganic carbon by microalgal biofilm. An advanced numerical technique, the orthogonal collocation method and Gear's method, was employed to solve this kinetic model. The model solutions included the concentration profiles of inorganic carbon in the microalgal biofilm, the growths of suspended microalgae and microalgal biofilm, the effluent concentrations of inorganic carbon, and the flux of inorganic carbon from bulk liquid into biofilm. The batch kinetic test was independently conducted to determine biokinetic parameters used in the microalgal biofilm model simulation while initial thickness of microalgal biofilm were assumed. A laboratory-scale flat plate photoreactor with a high recycle flow rate was setup and conducted to verify the model. The volume of photoreactor is 60 l which yields a hydraulic retention time of 1.67 days. The model-generated inorganic carbon and the suspended microalgae concentration curves agreed well with those obtained in the laboratory-scale test. The fixation efficiencies of HCO(3)(-) and CO(2) are 98.5% and 90% at a steady-state condition, respectively. The concentration of suspended microalgal cell reached up to 12 mg/l at a maximum growth rate while the thickness of microalgal biofilm was estimated to be 104 microm at a steady-state condition. The approaches of experiments and model simulation presented in this study could be employed for the design of a flat plate photoreactor to treat CO(2) by microalgal biofilm in a fossil-fuel power plant.

A retrospective study of implant-abutment connections on crestal bone level.

This study compared the effects of external hex, internal octagon, and internal Morse taper implant-abutment connections on the peri-implant bone level before and after the occlusal loading of dental implants. Periapical radiographs of 103 implants (63 patients) placed between 2002 and 2010 were collected, digitized, standardized, and classified into groups based on the type of implant-abutment connection. These radiographs were then analyzed with image-processing software to measure the peri-implant crestal bone change during the healing phase (4 months after implant placement) and at loading phases 1 and 2 (3 and 6 months after occlusal loading, respectively). A generalized estimating equation method was employed for statistical analysis. The amount of peri-implant crestal bone change differed significantly among all time-phase pairs for all 3 types of implant-abutment connection, being greater in the healing phase than in loading phase 1 or 2. However, the peri-implant crestal bone change did not differ significantly among the 3 types of implant-abutment connections during the healing phase, loading phase 1, or loading phase 2. This retrospective clinical study reveals that the design of the implant-abutment connection appears to have no significant impact on short-term peri-implant crestal bone change.

Effects of the 3D bone-to-implant contact and bone stiffness on the initial stability of a dental implant: micro-CT and resonance frequency analyses.

This study investigated the effects of bone stiffness (elastic modulus) and three-dimensional (3D) bone-to-implant contact ratio (BIC%) on the primary stabilities of dental implants using micro-computed tomography (micro-CT) and resonance frequency analyses. Artificial sawbone models with five values of elastic modulus (137, 123, 47.5, 22, and 12.4 MPa) comprising two types of trabecular structure (solid-rigid and cellular-rigid) were investigated for initial implant stability quotient (ISQ), measured using the wireless Osstell resonance frequency analyzer. Bone specimens were attached to 2 mm fibre-filled epoxy sheets mimicking the cortical shell. ISQ was measured after placing a dental implant into the bone specimen. Each bone specimen with an implant was subjected to micro-CT scanning to calculate the 3D BIC% values. The similarity of the cellular type of artificial bone to the trabecular structure might make it more appropriate for obtaining accurate values of primary implant stability than solid-bone blocks. For the cellular-rigid bone models, the ISQ increased with the elastic modulus of cancellous bone. The regression correlation coefficient was 0.96 for correlations of the ISQ with the elasticity of cancellous bone and with the 3D BIC%. The initial implant stability was moderately positively correlated with the elasticity of cancellous bone and with the 3D BIC%.