Time course of platelet counts in critically ill patients

BACKGROUND: Although thrombocytopenia in the intensive care unit (ICU) is associated with a poorer outcome, the precise relationship between the time course of platelet counts and the mortality rate has not been well defined. OBJECTIVE: To describe the time course of the platelet count in relation to the mortality rate in critically ill patients. DESIGN: Substudy of a prospective, multicenter, observational cohort analysis. SETTING: Forty ICUs in 16 countries from Europe, America, and Australia. PATIENTS: Data were collected from all ICU admissions in a 1-month period, excluding patients younger than 12 yrs old and those who stayed in the ICU for <48 hrs after uncomplicated surgery. A total of 1,449 critically ill patients were enrolled, including 257 who stayed in the ICU for >2 wks. INTERVENTIONS: None. MEASUREMENTS: Platelet counts were collected daily throughout the ICU stay, together with other measures of organ dysfunction. Thrombocytopenia was defined as a platelet count of <150 x 103/mm3. A relative increase in platelet count was defined as a 25% increase above the admission value, together with an absolute platelet count of > or =150 x 103/mm3. MAIN RESULTS: For the entire population, the platelet count was lower in the 313 nonsurvivors than in the 1,131 survivors throughout the ICU course. Of the 257 patients who stayed in the ICU for >2 wks, 187 (64%) survived. The platelet count decreased significantly in the first days after admission to reach a nadir on day 4 in both survivors and nonsurvivors. In the survivors, the platelet count returned to the admission value by the end of the first week and continued to rise to become significantly greater than the admission value by day 9. In the nonsurvivors, the platelet count also returned to the admission value after 1 wk, but there was no subsequent increase in platelet count. A total of 138 (54%) patients had thrombocytopenia on day 4, and these patients had a greater mortality rate than the other patients (33% vs. 16%; p <.05). On day 14, 51 (20%) patients had thrombocytopenia, and these patients had a greater mortality rate than the other patients (66% vs. 16%; p <.05). Thrombocytopenia was less common on day 14 than on day 4 (20% vs. 54%; p <.05), but the mortality rate was greater in the thrombocytopenic patients on day 14 than those who were thrombocytopenic on day 4 (66% vs. 33%; p <.05). The ICU mortality rate of nonthrombocytopenic patients on day 14 was also significantly lower in patients with, than without, a relative increase in platelet count on day 14 (11% vs. 30%; p <.05). CONCLUSION: Platelet count changes in the critically ill have a biphasic pattern that is different in survivors and nonsurvivors. Late thrombocytopenia is more predictive of death than early thrombocytopenia. A relative increase in platelet count after thrombocytopenia was present in survivors but not in nonsurvivors. Although a single measured platelet count is of little value for predicting outcome, changes in platelet count over time are related to patient outcome.     

Increased antibacterial activity of zinc polycarboxylate cement by the addition of chlorhexidine gluconate in fixed prosthodontics

PURPOSE: This study evaluated the antibacterial activity of water-activated zinc polycarboxylate cement with adjunctive 0.12% chlorhexidine gluconate on the subgingival microbiota in fixed partial dentures. MATERIALS AND METHODS: Thirty-six teeth prepared as fixed partial denture abutments in 9 patients were cemented randomly using water-activated zinc polycarboxylate cement (control group) or water-activated zinc polycarboxylate cement, including 0.12% chlorhexidine gluconate (test group). A total of 108 subgingival plaque samples were analyzed at baseline, immediately before permanent cementation (5 weeks), and 8 weeks later (at 13 weeks). RESULTS: In the control group, the subgingival microbiota altered to closely resemble the flora of chronic gingivitis (increased proportions of gram-negative anaerobes such as Prevotella intermedia, Fusobacterium nucleatum) by 13 weeks. In contrast, the microflora at test sites comprised predominantly gram-positive facultative cocci and rods at 13 weeks. CONCLUSION: This study demonstrated that the addition of 0.12% chlorhexidine gluconate may enhance the antimicrobial action of polycarboxylate cements to ensure the maintenance of a microflora compatible with periodontal health, at least up to 13 weeks post-cementation.     

Human ex vivo bone tissue strains around natural teeth vs. immediate oral implants

Purpose: To compare ex vivo bone tissue strains around natural teeth with immediate implants supporting unsplinted and splinted fixed prostheses. Material and methods: Six linear strain gauges were bonded on the labial marginal bone of bilateral maxillary anterior teeth in two fresh‐frozen human cadavers. The natural teeth were loaded in centric occlusion via an occlusal splint with integrated miniature load cells. Strain measurements were performed at a sample rate of 10 kHz and under a maximum load of 100 N, simultaneously monitored from a computer connected to data acquisition system. Upon extraction of the anterior teeth, Ø 4.1 mm and Ø 4.8 mm ITI^® dental implants were placed into sockets of incisors and canines, respectively. Installation torque value (ITV) of each implant was measured by a custom‐made torque wrench and resonance frequency analyses (RFA) were also undertaken. Strain measurements were performed for (1) single‐tooth implant restorations, (2) unilateral splinted anterior implants, and (3) bilateral splinted anterior implants. Finally, an autopolymerizing acrylic resin was injected into the implant sockets for simulation of osseointegration and strain measurements were performed. Results: Microstrains of all groups were statistically comparable (P>0.05), although lower strains were elicited for implants in sockets of incisors in comparison with natural teeth. Microstrains around canine implants were comparable or higher than those induced around natural canines. For all groups, microstrains around canines were higher than those around lateral (P<0.05) and central incisors (P<0.01), which had similar strain levels (P>0.05). The RFA values of implants were comparable. The ITVs of implants in sockets of lateral incisors and canines were similar and were higher than those of implants in central incisor regions. Conclusion: The labial marginal bone having no contact with immediate implants may experience strain gradients within physiologic levels due to deformation of bone under load. Although one prosthetic design does not seem to have clear advantages over another, splinting of implants may be considered as a safety measure for immediately loaded immediate implants, if possible.     

Bond strength of a self-etching adhesive system to caries-affected dentin

This in vitro study evaluated the microtensile bond strengths of sound versus caries-affected dentin using a self-etching adhesive system, Clearfil SE Bond, with or without additional acid pre-conditioning. Extracted human mandibular molars with occlusal caries extending halfway through the dentin were used. In the first group, the teeth were bonded with the self-etching adhesive Clearfil SE Bond according to the manufacturer's instructions. In the second group, prepared dentin surfaces were etched with 37% phosphoric acid prior to applying the same self-etching adhesive. After the bonding procedure, all specimens were built up with composite resin and stored in water for 24 hours. The teeth were serially sectioned vertically into 0.7-mm slabs and trimmed into an hourglass shape for measuring microtensile bond strength. Each specimen was attached to a Bencor device and stressed in tension at a crosshead speed of 1 mm/minute. Statistical analysis was performed using two-way ANOVA and the Tukey HSD test (p<0.05). The microtensile bond strengths of Clearfil SE Bond to sound dentin (32.9) were significantly higher than to caries-affected dentin (15.9). In the second group where acid etching was performed prior to applying Clearfil SE Bond, there were no statistically significant differences between the microtensile bond strengths of sound (19.2) and caries-affected dentin (16.3). While bond strengths to sound dentin were decreased by using additional acid etching prior to applying Clearfil SE Bond, this procedure revealed no statistically significant differences in bond strengths for the caries-affected dentin.     

Prepolymerized vs. in situ-polymerized fiber-reinforced composite implants--a pilot study

The aim of this study was to investigate bone response to bioactive fiber-reinforced composite (FRC) implants under two polymerization conditions. Glass-fiber-dimethacrylate composite was tested as prepolymerized cylinder-shaped FRC implants and as cylindrical FRC implants polymerized in situ with blue light transmitted and scattered by the glass fibers. Ten FRC implants (6 prepolymerized and 4 in situ-polymerized implants) were placed in the right tibias of 3 pigs by means of a press-fit technique. After 12 weeks, light microscopy revealed only mild foreign-body reaction, with no accumulation of inflammatory cells on both the prepolymerized and the in situ-polymerized implants. The prepolymerized implants appeared to be fully integrated, whereas the in situ-polymerized implants were almost completely surrounded by a fibrous capsule. The present study suggests that in situ polymerization of FRC implants results in fibrous capsule formation and prevents integration with bone.     

Antibacterial activity of Propolis versus conventional endodontic disinfectants against Enterococcus faecalis in infected dentinal tubules

Introduction

The antibacterial activity against Enterococcus faecalis of 2 propolis samples was investigated in a dentin block model, and their effectiveness was compared with that of established endodontic disinfectants, chlorhexidine (CHX) and calcium hydroxide [Ca(OH)₂].

Methods

Standardized dentin blocks were infected with E. faecalis ATCC 29212. The root canal space was filled with one of the ethanolic extracts of propolis (Artvin or Tekirda? mix [TM]), CHX 2%, Ca(OH)₂, or ethanol or phosphate-buffered saline for control. Canal dentin was sampled after 1 or 7 days by using a standard-size bur. The dentinal shavings were vortexed vigorously in phosphate-buffered saline, and aliquots were cultured on tryptone soy agar plates. Colonies were counted after 2 days of incubation. Statistical significance was set to 5%.

Results

All experimental agents significantly reduced the number of the cultivable bacteria. CHX was the most potent disinfectant at both times. Compared with the ethanol control, no significant reduction in the number of colonies was found for the propolis extracts at day 1; however, significant reduction was found at day 7. The 2 propolis samples were statistically similar to each other and to Ca(OH)₂, but the TM sample was also similar to CHX at day 7. This has been linked to the greater concentration of flavonoids, a group of antibacterially active compounds, in the TM sample as determined by gas chromatography-mass spectrometry analysis.

Conclusions

The antimicrobial activity of the propolis samples tested in this study was between Ca(OH)₂ and CHX. Both propolis samples were antimicrobially effective; however, their activity did not exceed CHX.