Search Results - (Author, Cooperation:E. Reijerse)

2013-06-28

Nature Publishing Group (NPG)

0028-0836

1476-4687

Biology

Chemistry and Pharmacology

Medicine

Natural Sciences in General

Physics

Apoproteins/chemistry/metabolism ; Biocatalysis ; Biomimetic Materials/*chemical synthesis/*metabolism ; Biomimetics ; Catalytic Domain ; Chlamydomonas reinhardtii/*enzymology ; Clostridium acetobutylicum/genetics/metabolism ; Electron Spin Resonance Spectroscopy ; Enzyme Activation ; Hydrogenase/*metabolism ; Ligands ; Spectroscopy, Fourier Transform Infrared ; Thermotoga maritima/*enzymology

1089-7690

AIP Digital Archive

Physics

Chemistry and Pharmacology

Electron paramagnetic resonance (EPR) spectra recorded at X band on Cu(II) in the Cu(II) doped single crystals of (NH4)2[Zn(NH3)2(CrO4)2] and (NH4)2[Cd(NH3)2(CrO4)2] showed an unusual temperature dependence in the temperature range between 4.2 and 370 K. This unusual temperature dependence is attributed to the dynamics of NH3 molecules. It is concluded that NH3 undergoes an order–disorder transition. This transition occurs at 282±2 K (T*) for (NH4)2[Zn(NH3)2(CrO4)2] and at 300±5 K for (NH4)2[Cd(NH3)2(CrO4)2]. For temperatures above T* the EPR spectra are found independent of temperature. This observation indicates that the NH3 molecules behave as free rotors rotating about their threefold symmetry axis. As the temperature is lowered, the free rotation gradually becomes hindered which leads at T* to site doubling in the EPR spectra. The hindered rotation simultaneously induces a structural change at T* reducing the local symmetry at the Cu(II) site from C2/m to approximately Cs. In the temperature range between T* and about 80 K, the EPR spectra with the magnetic field perpendicular to the threefold axis of NH3 are temperature dependent, but those with the magnetic field parallel to the threefold axis remain unchanged. This behavior is qualitatively interpreted as being due to the torsional oscillation of NH3. At temperatures lower than 80 K, the NH3 molecules exhibit the torsional oscillation of the lowest state and accordingly, all the EPR spectra become temperature independent.

Electronic Resource

1089-7690

AIP Digital Archive

Physics

Chemistry and Pharmacology

The electron spin echo envelope modulation of S=1/2, I=1/2 spin systems is analyzed for orientationally disordered systems. Analytical expressions are derived for the position of the combination frequencies which can be observed in primary (two-pulse) ESEEM experiments. The conditions for which line shape singularities of the basic and combination frequencies emerge are conveniently mapped in a standard graph. Using this graph it is demonstrated that for virtually all combinations of hyperfine parameters the ESEEM spectra will contain interpretable features. Especially the application of multifrequency techniques (i.e., variation of the nuclear Larmor frequency) will enable full use of the line shape singularities of the combination frequencies.

Electronic Resource

1089-7623

AIP Digital Archive

Physics

Electrical Engineering, Measurement and Control Technology

A microwave resonator is described for performing electron spin-echo (ESE) and electron spin-echo electron nuclear double resonance (ESE–ENDOR) measurements on single crystals. The ENDOR coil arrangement allows the crystal to be rotated about two independent axes. The system operates in a temperature range from 4 to 300 K using a helium flow cryostat.

Electronic Resource

1600-051X

Blackwell Publishing Journal Backfiles 1879-2005

Medicine

Abstract. The purpose of the present study was to establish in vitro the inhibiting effect of a herbal extract mixture on a selected number of micro-organisms and to test in vivo the effect of a mouthwash containing 6.3 mg/ml herbal extract mixture on plaque and gingivitis as compared to a minus active control mouthrinse. The herbal extract was a mixture of: Juniperus communis (juniper), Urtica dioca (nettle), Achillaea millefolium (yarrow); 1:1:1. In the study, in-vitro, the effect of pure herbal extract mixture on acid production of Streptococcus mutans was tested and the minimum inhibitory concentrations (MIC) of the following micro-organisms were tested: Streptococcus mutans, Streptococcus mitis, Actynomyces viscosus, Actynomyces naeslundii, Actinobacillus actinomycetemcomitans, Prevotella intermedia, Campylobacter rectus, Fusobacterium nucleatum, Veillonella parvula. The MIC-values for A. viscosus and P. gingivalis were 100 mg/ml. The MIC-values for A. naeslundii and A. actinomycetemcomitans were considerably lower (10 mg/ml). S. mitis was the most susceptible of the tested organisms to the extract with a MIC value of 1 mg/ml. S. mutans, C. rectus, V. parvula, and F. nucleatum were not influenced by the extracts. No inhibitory effect of the 6.3 mg/ml herbal extract mixture was observed on the acid production of S. mutans. For the study in-vivo, 45 volunteers were selected on the basis of having moderate gingival inflammation. As efficacy parameters the plaque index, modified gingival index and angulated bleeding index were assessed. The subjects were randomly divided among 3 experimental groups (2× test and 1‘minus active’control). The participants were requested to rinse with 10 ml of mouthwash twice a day for a period of three months. After 6 weeks and 3 months, the same clinical indices as at baseline were recorded. The results show no difference between the two test groups and the control group. In conclusion, the results of the present study have shown that the mixture of the 3 herbal extracts, Juniperus communis, Urtica dioca and Achillaea millefolium when used in a mouthrinse has no effect on plaque growth and gingival health.

Electronic Resource

1089-7623

AIP Digital Archive

Physics

Electrical Engineering, Measurement and Control Technology

The design of an electron nuclear double resonance (ENDOR) resonator suitable for single crystal studies is reported. An outline is given of the mechanical and electronic construction of the resonator. This paper will focus on the construction suitable for studies at 4.2 K, but the design can be easily adapted to a flow cryostat for variable temperature measurements. The rf-coil efficiency has been measured and is high and fairly constant over the frequency range from 0.3 to 20 MHz. Measurements on a test compound, show that the baseline stability is good over this frequency range. Even for low abundant nuclei as 13C, the signal to noise ratio is very good.

Electronic Resource

1600-051X

Blackwell Publishing Journal Backfiles 1879-2005

Medicine

Abstract This was a 2-part study. The purpose of the 1st part was to examine the relationship between brushing force and plaque removal efficacy comparing a regular manual toothbrush (M) with an electric toothbrush the Braun Oral-B Plak Control* (B). The study consisted of a single oral prophylaxis followed by 5 experiments which differed solely in respect to toothbrushing force. At baseline (after 24-h plaque accumulation), the amount of dental plaque was evaluated and subsequently, the subject's mouth was brushed by a dental hygienist. Brushing was carried out in a random split-mouth order. Either the 1st and 3rd quadrants or the 2nd and 4th quadrants were brushed with 1 toothbrush and the 2 remaining quadrants with the other. The available time for the brushing procedure was 2 min. After brushing, the amount of remaining dental plaque was assessed. The force used in experiment 1 through 5 was 100, 150, 200, 250, 300 g, respectively. The results show that when brushing force is increased, more plaque is removed with either of the two brushes. Except for the high brushing force (300 g), the electric toothbrush removed more plaque than the manual brush. The purpose of the 2nd part was to evaluate the habitual brushing force which individuals use with various toothbrushes. Besides a manual toothbrush (M), 3 electric toothbrushes were examined, the Rotadent® (R). Interplak® (I) and Braun® (B). 20 subjects were selected on the basis of being ‘good brushers” (plaque score at screening 〈25%). At baseline, each subject randomly received 1 of the 4 brushes. They were allowed a training period of 3 weeks at the end of which they were asked to abstain from brushing for at least 24 h. The plaque (Turesky modification of the Quigley & Hein) was scored, after which the subjects brushed their teeth (2 min) with the assigned toothbrush equipped with a strain gauge. A computer set–up measured (100 Hz) and calculated the mean brushing force. After brushing, the amount of remaining plaque was assessed. The design of the study was a 4-way cross-over. The results show that with a manual brush, considerably more force is used than with the electric brushes (R=96. 1 = 119. B= 146, M=273). No significant relation between brushing force and plaque removal was demonstrated for any of the brushes.

Electronic Resource

1600-051X

Blackwell Publishing Journal Backfiles 1879-2005

Medicine

Abstract. The present study was carried out in a private periodontal practice. 8 clinical criteria were chosen to select patients for microbiological examination. These criteria characterize prominent features of disease which at the start, during, or in the maintenance phase of treatment suggest difficulties in the progress of the periodontal therapy. Based on these clinical characteristics, an inventory was made of the prevalence of the 3 putative periodontal pathogens: Actinobacillus actinomycetemcomitans, Porphyromonas gingivalis, Prevotella intermedia. Out of 320 referred patients 91 patients did meet 〈inlineGraphic alt="leqslant R: less-than-or-eq, slant" extraInfo="nonStandardEntity" href="urn:x-wiley:03036979:JCPE583:les" location="les.gif"/〉1 of the clinical criteria and consequently were selected for microbiological examination. Results showed that young patients (19–30 years) with periodontitis demonstrated the presence of A. actinomycetemcomitans more often (69%: p(0.005) compared to older age cohorts. A. actinomycetemcomitans was found more often when localized breakdown (in particular in the 1 st molar and incisor region) was observed and in patient who responded poorly to scaling and rootplaning. P. gingivalis and P. intermedia were most frequently recovered in patients showing primarily a bone loss pattern of angular defects of 〈inlineGraphic alt="leqslant R: less-than-or-eq, slant" extraInfo="nonStandardEntity" href="urn:x-wiley:03036979:JCPE583:les" location="les.gif"/〉5 mm. Retrospectively, these patients were further categorized, based on full mouth radiographs, in (1) patients with primarily horizontal bone loss and (2) patients with primarily angular bony defects. Results showed that A. actinomycetemcomitans occurred less frequently in patients showing horizontal bone loss (p(0.05).

Electronic Resource

1600-051X

Blackwell Publishing Journal Backfiles 1879-2005

Medicine

Abstract. The purpose of this study was to evaluate different methods of eliciting gingival bleeding as indicators of gingival inflammation in the experimental gingivitis model. Following a period of stringent oral hygiene, 103 dental students were scored for plaque and gingival bleeding assessed by 4 methods. From this group, 41 volunteers were randomly allocated to 2 treatment groups. Dental students with clean teeth and healthy gingivae were asked to abolish all mechanical tooth cleaning in the lower jaw for a period of 3-weeks. During the 21-day experimental period, chlorhexidine (Peridex®) or a placebo mouthrinse was applied to the lower jaw. Subjects brushed the upper jaw with a standard toothpaste. In principal, 2 different methods were employed to provoke bleeding: (1) at the marginal gingival tissue by running a probe along the soft tissue wall at the orifice of the pocket, and (2) by probing to the “bottom” of the pocket. Variations in the methods were based on angulation (AngBI, ParBI) of the probe in relation to the tooth surface and to the probing force (PPBI.25N, PPBI.757V). 1 randomly selected quadrant in the lower jaw was scored using the AngBI. The opposing quadrant was scored with a randomly-allocated bleeding index, either ParBI, PPBI.25N or PPBI.75N. The results of this study confirm earlier findings that the angulation of the probe determines the number of sites with bleeding observed. It also indicates that bleeding as elicited by probing to the bottom of the pocket is a poor indicator of early gingivitis. It is recommended that gingivitis should be assessed by probing the marginal gingiva.

Electronic Resource

1600-051X

Blackwell Publishing Journal Backfiles 1879-2005

Medicine

Abstract The purpose of the present study was to compare the Braun/Oral-B Plak Control® (D7) and Sonicare® (S) in their plaque-removing efficacy. For this study. 35 university students (non-dental) were selected. This was a 2-part study. Prior to each appointment, all subjects were asked to abstain from all oral hygiene procedures for at least 24 h. In Part 1. the efficacy of the toothbrush was studied when one of the investigators brushed the teeth of the panellists. In Part 2. the efficacy of toothbrushing was studied after the students had received professional instruction. The available time for the brushing amounted to a total of 2 min per mouth. Dental plaque was evaluated by means of the Silness and Löe plaque index assessed at 6 sites per tooth. Results showed that both in Parr 2 and Pan I the D7 removed significantly more plaque than the S-electric toothbrush. The plaque reduction assessed according to Silness and Löe in Part 1 was for the D7. 1.28 and for the S, 1.12. In Pan 2. the reductions were 0.90 and 0.80. respectively. The majority (n=34) of subjects preferred the D7 over the S. In conclusion, the results of the present study show that the oscillating/rotating toothbrush (Braun/ Oral-B Plak Control®) is more effective in plaque removal than the sonic electric toothbrush (Sonicare®). In addition, given a choice, the panellists preferred the oscillating/rotating electric toothbrush.

Electronic Resource

1600-051X

Blackwell Publishing Journal Backfiles 1879-2005

Medicine

Abstract The purpose of this study was to evaluate the safety and efficacy of the Braun Plak Control® for the removal of supragingival plaque and improving gingival health in a long-term clinical trial, and to compare it to a regular manual toothbrush. Assessed were plaque accumulation, amount of gingival inflammation, gingival bleeding on probing, and calculus. In total, 77 young individuals were selected on the basis of having moderate gingivitis'. They were monitored over 8 months and divided among 2 groups; a control group that used a manual toothbrush and a test group that used the Braun Plak Control. The clinical assessments were repeated after 1, 2, 5, and 8 months. At baseline, subjects were handed their assigned toothbrushes together with written oral hygiene instructions. They were instructed to brush for at least 2 min. 1 month after baseline examinations, all subjects received a professional prophylaxis and oral hygiene instruction from an experienced dental hygienist. Plaque removal was reinforced at the 2- and 5-month examination. In conclusion, results indicate that the Braun Plak Control is a safe and efficient home care device. At the end of this trial, this electric toothbrush proved to be more effective than a regular manual tooth brush.

Electronic Resource

1600-051X

Blackwell Publishing Journal Backfiles 1879-2005

Medicine

Abstract. The purpose of the present study was to compare the Braun Plak Control® (D7) and Philips HP 500® (MM) in their plaque removing efficacy. Furthermore the brushing force applied by the panellist on the brush-head with both these brushes was evaluated. For this study, 35 university students (non-dental) were selected. The study consisted of 3 experiments. Prior to each experiment, all subjects were asked to abstain from all oral hygiene procedures for at least 48 h. In Exp. I, the efficacy of toothbrushing was studied when one of the investigators brushed the teeth of the panellists. In Exp. II, the efficacy of the brushing was studied after the students had received a professional instruction. In Exp. III, the brushing force used during a single brushing exercise was evaluated. The available time for the brushing amounted to a total of 2 min per mouth. Dental plaque was evaluated by means of the Silness and Löe and Quigley and Hein plaque indices assessed at 6 sites per tooth. Results showed that both in Exp. I and Exp. II, the D7 removed significantly more plaque than the MM electric toothbrush. The plaque reduction assessed according to Silness and Löe in Exp. I was for the D7, 1.07 and for the MM, 0.78. In Exp. II, the reduction was 1.08 and 0.88, respectively. The results of Exp. III show that the mean brushing force was comparable for both brushes (D7=I73 g, MM=I75 g). All 35 subjects were allowed to choose one electric toothbrush as compensation for their participation. The majority (n=26) of subjects preferred the D7 to the MM. In conclusion, the results of the present study show that given a choice, there was a preference of the panellists for the D7. No difference in brushing force was observed between the 2 brushes. Evaluation of plaque removing efficacy showed that the Braun Plak Control® is more effective than the Philips HP 500®.

Electronic Resource

1600-051X

Blackwell Publishing Journal Backfiles 1879-2005

Medicine

Abstract The purpose of the present study was to evaluate the effect of an electronic toothbrush on established plaque and gingivitis in a 5-month clinical trial. This electronic toothbrush sends approximately a 0.15 mA current through the brushhead which presumedly enhances the efficacy of the brush in plaque elimination. For this study, 80 volunteers (non-dental University students) were selected on the basis of having moderate gingival inflammation. At baseline, plaque and bleeding upon probing were assessed on the vestibular, mesio-vestibular, disto-vestibular and lingual surfaces using the “half-mouth” design. After 2-months and 5-months, these clinical indices were again recorded. At each assessment, the participants received a new brushhead. All baseline indices appeared to be well-balanced. A mean Silness and Löe plaque score of 1.70 and 1.64 were found in the control and test groups, respectively. Little change was observed from baseline to 5-months. The Quigley and Hein plaque index behaved comparably. The mean bleeding upon probing score at baseline was 1.43 and 1.39 for the control and test group, respectively. Little to no improvement was observed in the course of this study. No beneficial effect could be shown for this ‘electronic’ design of manual toothbrush.

Electronic Resource