Nanostructured Ti-Zr-Pd-Si-(Nb) bulk metallic composites: Novel biocompatible materials with superior mechanical strength and elastic recovery.

The microstructure, mechanical behaviour, and biocompatibility (cell culture, morphology, and cell adhesion) of nanostructured Ti45 Zr15 Pd35- x Si5 Nbx with x = 0, 5 (at. %) alloys, synthesized by arc melting and subsequent Cu mould suction casting, in the form of rods with 3 mm in diameter, are investigated. Both Ti-Zr-Pd-Si-(Nb) materials show a multi-phase (composite-like) microstructure. The main phase is cubic ß-Ti phase (Im3m) but hexagonal α-Ti (P63/mmc), cubic TiPd (Pm3m), cubic PdZr (Fm3m), and hexagonal (Ti, Zr)5 Si3 (P63/mmc) phases are also present. Nanoindentation experiments show that the Ti45 Zr15 Pd30 Si5 Nb5 sample exhibits lower Young's modulus than Ti45 Zr15 Pd35 Si5 . Conversely, Ti45 Zr15 Pd35 Si5 is mechanically harder. Actually, both alloys exhibit larger values of hardness when compared with commercial Ti-40Nb, (HTi-Zr-Pd-Si ≈ 14 GPa, HTi-Zr-Pd-Si-Nb ≈ 10 GPa and HTi-40Nb ≈ 2.7 GPa). Concerning the biological behaviour, preliminary results of cell viability performed on several Ti-Zr-Pd-Si-(Nb) discs indicate that the number of live cells is superior to 94% in both cases. The studied Ti-Zr-Pd-Si-(Nb) bulk metallic system is thus interesting for biomedical applications because of the outstanding mechanical properties (relatively low Young's modulus combined with large hardness), together with the excellent biocompatibility.

Improved mechanical performance and delayed corrosion phenomena in biodegradable Mg-Zn-Ca alloys through Pd-alloying.

The influence of partial substitution of Mg by Pd on the microstructure, mechanical properties and corrosion behaviour of Mg(72-x)Zn(23)Ca(5)Pd(x) (x=0, 2 and 6 at.%) alloys, synthesized by copper mould casting, is investigated. While the Mg(72)Zn(23)Ca(5) alloy is mainly amorphous, the addition of Pd decreases the glass-forming ability, thus favouring the formation of crystalline phases. From a mechanical viewpoint, the hardness increases with the addition of Pd, from 2.71 GPa for x=0 to 3.9 GPa for x=6, mainly due to the formation of high-strength phases. In turn, the wear resistance is maximized for an intermediate Pd content (i.e., Mg(70)Zn(23)Ca(5)Pd(2)). Corrosion tests in a simulated body fluid (Hank's solution) indicate that Pd causes a shift in the corrosion potential towards more positive values, thus delaying the biodegradability of this alloy. Moreover, since the cytotoxic studies with mouse preosteoblasts do not show dead cells after culturing for 27 h, these alloys are potential candidates to be used as biomaterials.

Enhanced mechanical properties and in vitro corrosion behavior of amorphous and devitrified Ti40Zr10Cu38Pd12 metallic glass.

The effects of annealing treatments on the microstructure, elastic/mechanical properties, wear resistance and corrosion behavior of rod-shaped Ti40Zr10Cu38Pd12 bulk glassy alloys, synthesized by copper mold casting, are investigated. Formation of ultrafine crystals embedded in an amorphous matrix is observed for intermediate annealing temperatures, whereas a fully crystalline microstructure develops after heating to sufficiently high temperatures. The glassy alloy exhibits large hardness, relatively low Young's modulus, good wear resistance and excellent corrosion behavior. Nanoindentation measurements reveal that the sample annealed in the supercooled liquid region exhibits a hardness value of 9.4 GPa, which is 20% larger than in the completely amorphous state and much larger than the hardness of commercial Ti-6Al-4V alloy. The Young's modulus of the as-cast alloy (around 100 GPa, as determined from acoustic measurements) increases only slightly during partial devitrification. Finally, the anticorrosion performance of the Ti40Zr10Cu38Pd12 alloy in Hank's solution has been shown to ameliorate as crystallization proceeds and is roughly as good as in the commercial Ti-6Al-4V alloy. The outstanding mechanical and corrosion properties of the Ti40Zr10Cu38Pd12 alloy, both in amorphous and crystalline states, are appealing for its use in biomedical applications.

[Multiple nosocomial infections. An incidence study]. / Infecciones nosocomiales múltiples. Un estudio de incidencia.

BACKGROUND: Some studies point out that around 30%-50% of the nosocomial infections (NI) are multiple (MNI) and are found in 21%-30% of the patients with NI. The significance of these data and their potential consequences have led the authors to perform this study. PATIENTS AND METHODS: A longitudinal descriptive study was carried out on the incidence and characteristics of NI (MNI and single nosocomial infection [SNI]) in 26,977 patients admitted to a county hospital from 1991 to 1993. RESULTS: NI was detected in 1,246 patients with 31% presenting MNI appearing in 15% of the patients. MNI predominated in males, had a mean age were 5 to 12 years higher than the patients with SNI with a mean hospital stay of between 13-28 days more than the SNI group. The MNI were significantly less frequent in the Urology, Gynecology and Obstetrics Departments and were more frequent in the Intensive Care Unit. The localization of the infection varied significantly among the patients with one or several infections. Bacteremia, pneumonia and soft tissue infections were significantly more frequent in MNI patients. CONCLUSIONS: Multiple nosocomial infections are frequent and their basic characteristics are significantly different from those of single nosocomial infections. The patients who acquire SNI should be carefully followed to avoid the appearance of MNI.

Treatment of class II furcation involvements in humans with bioresorbable and nonresorbable guided tissue regeneration barriers. A randomized multi-center study.

In this multi-center study 38 patients with contralateral molar Class II furcation defects were treated with GTR therapy using a bioresorbable matrix barrier (test) and a nonresorbable expanded polytetrafluoroethylene (ePTFE) barrier (control). Following flap elevation, scaling, root planing, and removal of granulation tissue, each device was adjusted to cover the furcation defect. The flaps were repositioned and sutured to complete coverage of the barriers. A second surgical procedure was performed at control sites after 4 to 6 weeks to remove the nonresorbable barrier. Before treatment and 12 months postsurgery all patients were examined and probing depths, clinical attachment levels, and position of the gingival margin were recorded. The primary response variable was the change in clinical attachment level in a horizontal direction (CAL-H change). Both treatment procedures reduced the probing depths (P < or = 0.001). Statistically significant gain of clinical attachment level in both horizontal and vertical direction was found at the test sites. At control sites gain of attachment in horizontal direction was statistically significant. The gain of CAL-H was 2.2 mm at test sites compared to 1.4 mm at control sites (P < or = 0.05). At test sites, the gingival margin was maintained close to the pre-surgical level (0.3 mm), whereas at control sites gingival recession was evident (0.9 mm), the difference being statistically significant (P < or = 0.01). Postsurgical complications, such as swelling and pain were more frequent following the control treatment (P < or = 0.05).

Clinical use of a bioresorbable matrix barrier in guided tissue regeneration therapy. Case series.

In this case series study 19 Class II furcations and 47 intrabony defects in 59 patients were treated according to the principles of guided tissue regeneration using a bioresorbable matrix barrier. Gingival condition and device exposure were assessed at 2 weeks, and 1, 3, 6, and 12 months after surgery. The effect of therapy was evaluated by assessing probing depths (PD), probing attachment level (PAL), and the position of the gingival margin prior to surgery and 12 months after surgery. Mild clinical signs of inflammation in the soft tissue covering the device was found adjacent to 3 defects only and limited to the first month of healing. Device exposure occurred at 10 out of the 66 defects. At the furcation defects, the mean PD reduction amounted to 3.7 mm (P < or = 0.001). Mean gain PAL vertical was 3.4 mm and PAL horizontal 3.3 mm (P < or = 0.001), resulting in complete closure of 9 out of the 19 defects. Mean gingival recession was 0.2 mm. At the intrabony defects mean PD reduction was 5.4 mm and mean gain of PAL 4.9 mm (P < or = 0.001). Gingival recession averaged 0.5 mm (P < or = 0.05). It was concluded that the use of the matrix barrier in GTR therapy resulted in 1) reduced probing depths; 2) pronounced gain of clinical attachment; and 3) a very low incidence of gingival pathology, gingival recession, and device exposure.

Partial trisomy of chromosome 18 (pter leads to q11): a discussion on the identification of the critical segment.

Partial trisomy for the short arm and the proximal region of the long arm of chromosome 18 was observed in a male child of 4 years of age. The trisomy appeared de novo as a free, practically metacentric chromosome. A review of other cases of partial trisomy 18 suggests that there is a critical segment of the chromosome responsible for typical phenotype of the trisomy 18. In this report we add the description of a new case to the work already carried out in the delimitation of this critical segment.

Effect of a field program based on systematic plaque control on caries and gingivitis in schoolchildren after 3 years.

The effect of a field program, based on systematic plaque control, on caries and gingivitis was tested during a 3-year period on 1,100 schoolchildren. Once every 3rd week the children were given oral hygiene instructions, professional toothcleaning and fluorides topically delivered by specially trained dental nurses. The children of a control group of approximately the same number of pupils, participated in a preventive program consisting of mouthrinsings once every 2nd week with a 0.2% sodium fluoride solution. The children of the third and fourth grades were, at the start of the experiment, selected as reference groups and then continuously examined once every year. At the end of the trial the mean reduction of surfaces haboring plaque and units with gingival inflammation was 59% and 73%, respectively. The reduction in caries increment was 51%.

Effect of toothbrushing with chlorhexidine gel on salivary microflora, oral hygiene, and caries.

The effect of daily toothbrushing with 0.5% chlorhexidine-containing gel for 12 months was evaluated in a double-blind study in 37 dental students. The active gel did not markedly influence plaque formation, gingival conditions, or caries as compared with placebo gel treatment. Salivary bacterial counts were performed on subgroups of six subjects using chlorhexidine gel and on six using placebo gel. No differences in the effect of treatment on the microorganisms studied in the two subgroups could be detected except for S. sanguis. The percentage of this species decrease in the placebo group and increased in the chlorhexidine group. The difference became significant after 2 weeks. A tendency to a greater reduction of S. mutans noted in the chlorhexidine group was most marked in individuals who had high initial counts of this species. The proportion of S. sanguis, which could grow on chlorhexidinei-containing mitis salivarius medium, increased and after 12 months of chlorhexidine treatment averaged 34% of cultivable S. sanguis compared with 0.002% prior to treatment. The number of less sensitive S. sanguis decreased in the 12 months following termination of treatment. There was no observed tendency for the selection or proliferation of other streptococci, gram-negative rods, yeasts, or staphylococci.

Effect of listerine on dental plaque and gingivitis.

The present study was performed in 10 adults in order to evaluate the effect of an antiseptic mouthrinse (Listerine) on the rate of dental plaque formation and gingivitis development during a 2-week period when all efforts towards active mechanical oral hygiene were withdrawn. The study was performed as a crossover study and was carried out during four consecutive 2-week periods. During the first and third periods (preparatory periods) the participants were subjected to repeated professional tooth cleanings in order to establish plaque- and gingivitis-free dentitions. During the second and fourth periods (test and control periods) the participants were not allowed to brush their teeth but rinsed their mouths three times a day with Listerine or a placebo mouthwash. Plaque Index, Gingival Index, gingival fluid flow, and crevicular leukocytes were assessed on d 0, 2, 4, 7, and 14. On d 7 and 14, dental plaque was removed from the right and left jaws respectively and the wet weights determined. The chemotactic activity elaborated by the plaques was studied in Boyden chambers. During the Listerine test period, significantly lower Plaque and Gingival Index values were scored and lower amounts of plaque could be sampled in comparison to the control period.