Guided bone regeneration with the combined use of resorbable membranes and autogenous drilling dust or xenografts for the treatment of dehiscence-type defects around implants: an experimental study in dogs.

PURPOSE: This study aimed to measure the numbers of viable bone cells present in autogenous drilling dust (ADD) and mandibular particulated bone (MPB) and to histomorphometrically compare the effects of the combined use of resorbable membranes and ADD or xenografts for the treatment of dehiscence-type defects around implants. MATERIALS AND METHODS: The left mandibular premolars were extracted from 4 adult beagle dogs. After a 3-month healing period, 4 standardized bone defects were prepared on each mandible, and 1 implant was placed per defect. The 4 sites in each dog were allocated to 4 different treatment groups: 1 site received ADD alone (ADD); 1 site received a Cytoplast membrane supported by ADD (ADD+CP); 1 site received BioCera alone (BC); and the final site received a Cytoplast membrane supported by BioCera (BC+CP). Each animal received a series of 3 bone labels. Three months following these regenerative surgeries, animals were sacrificed and histomorphometric examinations were carried out. In addition, in 3 of the 4 dogs at the time of regenerative surgery, ADD was obtained using implant drills (group 1), MPB was obtained using a fissure bur and rongeur (group 2), and 1.0 cm3 of each was then cultured. Cultured cell counts and osteocalcin synthesis analysis using reverse transcription-polymerase chain reaction were performed on cells from these 2 groups at 4 and 9 weeks after regenerative surgery. Alkaline phosphatase activity (ALP) was measured at 9 weeks in both groups. RESULTS: MPB revealed greater cell counts than ADD after 4 and 9 weeks. Cells stained positively for ALP and osteocalcin in both groups. Fluorescence microscopy showed 22.4% bone formation with ADD+CP, 17.8% with BC+CP, 13.1% with ADD, and 6.4% with BC at 8 weeks. Bone regeneration heights were 2.0 mm with AD, 1.9 mm with ADD+CP, 1.7 mm with BC+CP, and 1.3 mm with BC. Bone regeneration areas measured 1.0 mm2 with ADD, 0.9 mm2 with ADD+CP, 0.6 mm2 with BC+CP, and 0.3 mm2 with BC. Bone-to-implant contacts were 53.1% with ADD, 46.6% with ADD+CP, 44.1% with BC, and 33.7% with BC+CP. CONCLUSIONS: ADD appears to be a useful material for closing dehiscence-type defects, and the use of a membrane was not found to affect bone formation during the treatment of dehiscence-type defects around implants in this study. However, larger studies are needed before fully endorsing its widespread use.

Ionic conduction in Zn3(PO4)2.4H2O enables efficient discharge of the zinc anode in serum.

Batteries contain corrosive or reactive components necessitating containment in a case, setting a limit to their miniaturization. Miniature, small-capacity batteries could power medical sensors in the body, for example sensing glucose for diabetes management. A miniature, case-less Zn-Ag/AgCl battery would consist merely of a zinc anode and a bioinert gel-coated Ag/AgCl cathode, if both operated efficiently in the interstitial fluid. Such a battery has not previously been built, primarily because of rapid corrosion of Zn. We show that the corrosion of zinc is significantly reduced by growth of Zn2+-ion-conducting, O2-impermeable, hopeite [Zn3(PO4)2.4H2O] lamellae on the Nafion-coated Zn anode. The hopeite lamellae allow discharge of the Zn anodes over three weeks at 86% current efficiency in physiological buffer and at 60% efficiency over two weeks in serum. The Zn|physiological buffer|Ag/AgCl cell operates at 1.00 V at 13 muA cm-2 and at 0.94 V at 0.2 mA cm-2 anodic current density.

Detection of approximately 10(3) copies of DNA by an electrochemical enzyme-amplified sandwich assay with ambient O(2) as the substrate.

The electrochemical sandwich-type, enzyme-amplified assay of Zhang, Kim, and Heller (Anal. Chem. 2003, 75, 3267-3269) was simplified by replacing the amplifying horseradish peroxidase with bilirubin oxidase (BOD). BOD catalyzes the reduction of ambient O(2) to water and obviates the need for adding H(2)O(2). Femtomolar (10(-)(15) M) concentrations of DNA were detected at a 10-microm-diameter tip of a carbon fiber electrode. Correspondingly, a few thousand copies of DNA were detected in approximately 5-microL samples. The sandwich is formed in an electron-conducting redox hydrogel, to the polymer of which a DNA capture sequence is bound. Capture of the analyte DNA and its hybridization with a BOD-labeled complementary DNA sequence, electrically connects the BOD label to the electron-conducting redox polymer, which is in electrical contact with the electrode. Placing the BOD in contact with the redox polymer thus converts the noncatalytic base layer into a catalyst for the electroreduction of O(2) to water at +0.12 V (vs Ag/AgCl) (Figure 1). In an exemplary assay, approximately 3000 copies of the iron transporting sequence of the sit gene of Shigella flexneri were detected without PCR amplification.

Highly selective electrocatalytic conversion of CO2 to CO at -0.57 V (NHE) by carbon monoxide dehydrogenase from Moorella thermoacetica.

We found that CODH is a fascinating enzyme for the electrochemical conversion of CO2 to CO. It could reduce CO2 to CO at -0.57 V vs NHE with approximately 100% current efficiency in 0.1 M phosphate buffer (pH 6.3). Nature's unique structure of C-cluster in CODH would be responsible for the low overpotential and the selective and fast conversion of CO2. The turnover number per C-cluster is 700 h-1, and the pH optimum is 6.3.

Oxygen is electroreduced to water on a "wired" enzyme electrode at a lesser overpotential than on platinum.

The first enzyme-based catalyst that is superior to platinum in the four-electron electroreduction of oxygen to water is reported. The smooth Pt cathode reached half and 90% of the mass transport-limited current density at respective overpotentials of -0.4 and -0.58 V in 0.5 M sulfuric acid, and only at even higher overpotentials in pH 7.2 phosphate buffer. In contrast, the smooth "wired" bilirubin oxidase cathode reached half and 90% of the mass transport-limited current density at respective overpotentials as low as -0.2 and -0.25 V. The mass transport-limited current density for the smooth "wired" enzyme cathode in PBS was twice that with smooth Pt in 0.5 M sulfuric acid. Under 1 atm O2 pressure, O2 was electroreduced to water on a polished carbon cathode, coated with the "wired" BOD film, in pH 7.2 saline buffer (PBS) at an overpotential of -0.31 V at a current density of 9.5 mA cm-2. At the same overpotential, the current density of the polished platinum cathode in 0.5 M H2SO4 was 16-fold lower, only 0.6 mA cm-2.