Effectiveness of various interventions on maintenance of gingival health during 1 year - a randomized clinical trial.

BACKGROUND: Rinsing with the combined use of an oxygenating-agent (OA) and chlorhexidine (CHX) in addition to mechanical oral hygiene could improve and/or maintain good gingival health over a long period. METHODS: This study had an examiner-blinded, randomized, six-group parallel design consisting of two-phases: a 3-week treatment phase and a subsequent 12-month experimental phase. A total of 267 subjects in good general health (≥18 years), without periodontitis, with at least five teeth per quadrant, and with moderate to advanced gingivitis were enrolled. A 3-week treatment phase was initiated to improve gingival health. Subjects were assigned to one of the six groups: two basic oral hygiene groups (Control I & II), one professional oral hygiene instruction group (OHI), one professional prophylaxis group (PP), an OA&CHX rinse group and a group receiving a combination of all regimens (COMBI group), being OHI + PP + OA&CHX. Dental plaque, gingival bleeding and staining assessments were performed at the start of the treatment phase, at baseline and at 4, 7, 10, and 12 months. RESULTS: There was a significant reduction in dental plaque-scores for the OA&CHX and COMBI-group (0.51 [SD = 0.37], 0.38 [SD = 0.33] respectively) and a significant reduction in gingivitis scores for the OA&CHX and COMBI group (6.9% [SD = 14.0], 13.4% [SD = 13.4] respectively) from the start of the treatment phase to baseline. No clinically relevant changes were observed for the other four groups. After baseline, bleeding and plaque-scores increased back to a non-significant level between groups, and this level remained throughout the study. CONCLUSION: OA&CHX and COMBI-group showed a clinically relevant improvement after the treatment phase in terms of dental plaque and gingival bleeding levels. At the 4-month clinical assessment, there was no longer a significant difference between groups.

Long-term efficacy of a 0.07% cetylpyridinium chloride mouth rinse in relation to plaque and gingivitis: a 6-month randomized, vehicle-controlled clinical trial.

OBJECTIVE: To evaluate the effectiveness of 0.07% cetylpyridinium chloride (CPC) mouth rinse for reduction of gingival inflammation and inhibition of plaque compared to a vehicle control (VC) mouth rinse over a 6-month period. MATERIALS & METHODS: Participants (n = 62) used their randomly assigned product as adjunct to toothbrushing. Bleeding, plaque and staining scores were assessed at baseline, 3 and 6 months. Plaque and saliva samples were taken at each assessment monitoring possible shifts in the composition of the microbiota. RESULTS: A significant difference (P = 0.002) in favour of the CPC mouth rinse, with respect to plaque scores, was found. Bleeding scores at 6 months were not significantly different (P = 0.089). However, when correcting for baseline values, a tendency towards a significant difference in bleeding scores at end trail was observed in favour of the CPC mouth rinse (P = 0.061). Regarding staining at 3 and 6 months, a small but significant difference (8.6% and 10.4%, respectively) (P < 0.0001) was observed with lower scores for the VC group. There was a significant reduction in total anaerobic count in the CPC group at 6 months (P < 0.05). The ratio of aerobes/anaerobes was markedly increased at 3 months, especially in the CPC group. No further differences were observed between groups at 6 months. CONCLUSIONS: The use of 0.07% CPC mouth rinse was significantly more effective in reducing plaque scores than the vehicle control. Bleeding scores were not different at 6 months. The test product was well accepted and did not cause any serious clinical side effects or negatively affected the microbiota.

Plaque-removing efficacy of new and used manual toothbrushes--a professional brushing study.

OBJECTIVES: The present study assessed whether 3-month-old used manual toothbrushes are less effective in reducing plaque scores compared with new toothbrushes with or without the use of dentifrice. MATERIAL AND METHODS: The present study was performed employing a single-use, examiner-blinded, professional brushing model. Four brushing modalities were randomly allocated to one of four quadrants, that is, 3-month-old used toothbrushes and new toothbrushes both with and without the use of dentifrice. Prebrushing and post-brushing plaque scores (Quigley Hein plaque index) and gingival abrasion (GA) scores were obtained. A dental hygienist performed the professional brushing procedure. The 3-month-old used toothbrushes were assessed for wear. RESULTS: No significant differences were observed among the treatments with regard to the prebrushing scores. The post-brushing plaque scores ranged from 1.59 for the new brush with dentifrice to 1.76 for the old brush with dentifrice. There was a significant difference (P = 0.036) among the four treatments regarding the old brush with dentifrice, which removed less plaque than the other treatment modalities. Regarding GA scores, no significant differences were observed. With regard to toothbrush wear after 3 months of use, the scores varied widely among the individually evaluated brushes. CONCLUSION: The present study did not show a clinically relevant difference in plaque score reductions following a 2-minute brushing exercise among 3-month-old used and new manual toothbrushes. However, the wear rate of the brushes seemed to be the determining factor in loss of efficacy, rather than the age of the toothbrush. Furthermore, dentifrice did not show an additional effect on instant plaque removal.

The plaque inhibitory effect of a CPC mouthrinse in a 3-day plaque accumulation model - a cross-over study.

OBJECTIVE: To test the plaque inhibitory effect of an experimental 0.07% cetylpyridinium chloride (CPC) mouthrinse in a 3-day plaque accumulation model in a cross-over design. MATERIAL AND METHODS: A total of 30 subjects (non-dental students), ≥18 years of age, were randomly assigned to use one of three different mouthrinses three times a day. After 3 days, the subjects returned for the clinical assessments and received a questionnaire to evaluate their attitude towards the product used by them. The cross-over procedure was repeated twice to have all subjects use all products. RESULTS: A total of 29 subjects completed the protocol and this resulted in a statistically significant difference between the three groups (P < 0.001) with regard to plaque scores. Over three sessions, the mean plaque scores were 2.17 for the control product, 1.14 for the CPC group and 1.12 for the 0.1% Hexetidine product (positive control). Results of the questionnaire show that, compared with hexetidine, the taste of the CPC was appreciated better, and less oral sensations were observed following rinsing. CONCLUSION: The CPC mouthrinse proved to be effective in inhibiting 'de novo' plaque formation to an extent similar to that of a 0.1% hexetidine product. Compared with hexetidine, the taste of the CPC was appreciated better and less oral sensations were observed following rinsing.

Safety and efficacy of two manual toothbrushes.

OBJECTIVE: The purpose of this study was to test the efficacy and safety of a newly designed multi-level manual toothbrush (Profit-Haije-Brush) compared with a control flat-trimmed manual reference toothbrush from the American Dental Association (ADA). MATERIAL AND METHODS: For this study, 36 healthy subjects without previous experience in the use of the Profit-Haije-Brush (PHB) were selected. Subjects were given a period of 2 weeks to become familiar with both types of brushes and were instructed to use them on alternate days for 2 min twice daily. Prior to their visit, subjects refrained from all oral hygiene procedures for 48 h. Prebrushing plaque and gingival abrasion scores were assessed. Subsequently, two randomly chosen contra-lateral quadrants were brushed with one of both brushes and the other two quadrants with the alternate brush. Subjects were supervised during their 2-min brushing exercise. After brushing, plaque and gingival abrasion were re-assessed. A questionnaire was filled out to investigate the subjects' attitudes towards both brushes. RESULTS: The overall mean prebrushing PI was 2.47 for the PHB and 2.44 for the ADA. The reduction in PI was 1.32 and 1.23 respectively (P < 0.05). With regard to gingival abrasion the overall mean prebrushing scores were 4.57 (PHB) and 5.34 (ADA). Post-brushing scores were 13.49 and 13.77 for the PHB and ADA respectively. CONCLUSION: Statistically, the multi-level PHB was significantly more efficacious than the flat-trimmed ADA. However, the difference is clinically considered small and the amount of remaining plaque was not significantly different between brushes. No greater potential to cause gingival abrasion to the oral tissues was observed.

The effect of 1% chlorhexidine gel and 0.12% dentifrice gel on plaque accumulation: a 3-day non-brushing model.

AIM: The purpose of the study was to compare the effects of four treatments on 'de novo' plaque accumulation. Treatments included tray application of 1% chlorhexidine gel (CHX-Gel), 0.12% chlorhexidine dentifrice-gel (CHX-DFG), a regular dentifrice (RDF) tray application, or 0.2% chlorhexidine mouthwash (CHX-MW) in a 3-day non-brushing model. MATERIAL AND METHODS: The study was designed as a single blind, randomized parallel clinical trial. After professional prophylaxis, subjects abstained from all other forms of oral hygiene during a 3-day non-brushing period. Subjects were randomly assigned to one of the four test groups (CHX-Gel, CHX-DFG, RDF applied in a fluoride gel tray or rinsing with a CHX-MW). After 3 days, the Quigley & Hein plaque index (PI) and Bleeding on Marginal Probing (BOMP) index was assessed. Subsequently, all subjects received a questionnaire to evaluate their attitude, appreciation and perception towards the products used employing a Visual Analogue Scale. RESULTS: After 3 days, the full-mouth PI means were 0.88 for the CHX-gel regimen, 0.79 for CHX-MW, 1.16 for CHX-DFG and 1.31 for the RDF regimen. The two dentifrices (CHX-DFG and RDF) were significantly less effective than the CHX-Gel or the CHX-MW. CONCLUSION: Within the limitations of the present 3-day non-brushing study design, it can be concluded that the effect of a 1% CHX-Gel application tray is significantly greater than that of 0.12% CHX-DFG or RDF in inhibiting plaque accumulation. The 1% CHX-Gel applied via a tray and 0.2% CHX-MW rinse were comparably effective.

Evaluation of two soft manual toothbrushes with different filament designs in relation to gingival abrasion and plaque removing efficacy.

OBJECTIVES: To evaluate the effect of two soft manual toothbrushes with different filament and brush head designs in relation to gingival abrasion and plaque removing efficacy to the in relation flat trimmed manual reference toothbrush of the American Dental Association (ADA). METHODS: The study had a randomized single use cross-over model (n = 76) with three sessions whereby all brushes were used by each subject. Subjects were asked to abstain from all oral hygiene procedures for 48 h. They brushed according to split-mouth design. Pre- and post-brushing plaque and gingival abrasion were assessed. RESULTS: The Sensodyne Sensitive (SENS) was more abrasive than the ADA (P < 0.001) while the Oral-B Sensitive Advantage (OBSA) was less abrasive than the SENS (P < 0.001). There was no statistically significant difference between the OBSA and the ADA (P = 0.319). All three brushes showed statistically significant reductions (49-56%) in plaque versus baseline. Compared to the ADA and the SENS, the OBSA had a smaller percentage of plaque removal (56% versus 49%, P

Tapered toothbrush filaments in relation to gingival abrasion, removal of plaque and treatment of gingivitis.

OBJECTIVES: To compare a tapered filament toothbrush (TFTB) to a control toothbrush (ADA) in their potential to cause gingival abrasion and improve the gingival condition following a period of experimental gingivitis. METHODS: Thirty-two subjects refrained from brushing mandibular teeth for 21 days. During a subsequent 4-week treatment phase, the left or right side of the mouth was brushed with either the TFTB or ADA as randomly allocated. Gingival abrasion, plaque and gingival bleeding were assessed. RESULTS: During the treatment phase gingival abrasion showed a trend to be lower with the TFTB than the ADA, which was significant at the 2-week assessment. The mean plaque scores changed from 2.98 (day 21) to 1.59 for the TFTB and from 3.00 (day 21) to 1.31 for the ADA. The mean bleeding scores changed from 1.86 (day 21) to 1.35 for the TFTB and from 1.85 (day 21) to 1.20 for the ADA. Plaque and bleeding scores were significantly lower with the ADA. CONCLUSIONS: Both toothbrushes improved gingival health and effectively removed plaque. Although there was a tendency towards fewer sites with gingival abrasion with the TFTB brush, it was less effective than the ADA in the removal of plaque biofilm and reduction of bleeding. Subjects considered the TFTB to be more pleasant to use.

Effect of cannabis usage on the oral environment: a review.

AIM: To evaluate oral environmental changes in cannabis users. MATERIAL AND METHODS: The MEDLINE and Cochrane Central register of controlled trails (CENTRAL) were searched up to April 2007 to identify appropriate studies. RESULTS: Independent screening of 982 titles and abstracts (MEDLINE-Pubmed) and (Cochrane) papers resulted in seven eligible publications. CONCLUSION: Based on the limited data, it seems justified to conclude that with increasing prevalence of cannabis use, oral health care providers should be aware of cannabis-associated oral side effects, such as xerostemia, leukoedema and an increased prevalence and density of Candida albicans.

The additional effect of a dentifrice on the instant efficacy of toothbrushing: a crossover study.

BACKGROUND: Inconclusive evidence exists in the literature with regard to the additional (beneficial) mechanical effect of a dentifrice on plaque removal. A previous split-mouth study found that a dentifrice did not contribute to plaque removal. Because of limitations of the split-mouth model, a crossover design was used to evaluate whether a commercially available dentifrice had an additional effect on mechanical plaque removal during manual toothbrushing. METHODS: Thirty-six subjects were given a manual toothbrush and a standard dentifrice. After a 48-hour plaque accumulation, subjects brushed under supervision with or without a dentifrice (total time of 2 minutes) in a 2 x 2 crossover design. RESULTS: Plaque reductions were 50% with and 56% without the use of dentifrice. This 6% difference was statistically significant (P = 0.034). Explorative analysis showed that brushing without a dentifrice was more effective in removing plaque on the approximal surfaces. CONCLUSIONS: The use of a dentifrice did not contribute to mechanical plaque removal during manual toothbrushing. It seemed that the mechanical action provided by the toothbrush was the main factor in the plaque-removing process.

Inhibition of "de novo" plaque formation with 0.12% chlorhexidine spray compared to 0.2% spray and 0.2% chlorhexidine mouthwash.

BACKGROUND: Chlorhexidine (CHX) is widely accepted as the most effective product in the control of supragingival plaque. It is available in different delivery devices. The aim of this study was to test whether 0.12% CHX spray was as effective as 0.2% CHX spray and 0.2% CHX mouthwash in a 3-day "de novo" plaque formation model. METHODS: Ninety volunteers were enrolled into a single-blind, randomized, three-group parallel study. They received a thorough dental prophylaxis prior to the test period. Subjects were divided randomly into three equal groups. They were requested to refrain from all forms of mechanical oral hygiene and instructed to use only their assigned product during the 3-day experimental period. After 3 days, the plaque growth was assessed using the Quigley and Hein plaque index (Q&H PI) at six sites per tooth. RESULTS: After 3 days, the CHX mouthwash group had a mean Q&H PI of 1.17 compared to 1.41 for the 0.2% CHX spray and 1.49 for the 0.12% CHX spray. The difference between the mouthwash and the two sprays was statistically significant, whereas the two sprays did not differ significantly from each other. CONCLUSIONS: Within the limitations of this 3-day "de novo" plaque formation study, the two sprays were not as effective as the mouthwash in plaque inhibition. No significant difference was found between the two sprays. To achieve the same effectiveness as a mouthwash, a higher dose (number of puffs) of CHX spray may be necessary.

Evaluation of several brushing motion combinations in relation to plaque-removing efficacy with Oral-B CrossAction Power: a professional brushing study.

AIM: The aim of this study was to evaluate the additional effect of a newly developed battery-operated brush Oral-B CrossAction Power with a hybrid brush head design (CAPB). The brush combines an oscillating/rotating part, a PowerHead(R), with a non-moving part with CrissCross bristles. It was compared with a manual control toothbrush Butler GUM 311 (CTB). MATERIAL AND METHODS: Thirty subjects were requested not to brush their teeth 48 h prior to the examination, when plaque removal efficacy was assessed by scoring plaque before and after brushing. Plaque was assessed according to the Silness & Loë Index at six sites per tooth. Subjects were brushed by a dentist using one of the four randomly chosen procedures of brushing in each quadrant. The CAPB was used with three different modes of brushing each in different randomly chosen quadrants, with the manual toothbrush being used in the remaining quadrant as a control. RESULTS: The baseline plaque levels ranged from 1.69 to 1.74 and the end levels ranged from 0.39 to 0.45. In terms of percentage, the results with the four procedures run from 75% to 79%. These differences between the battery brush and manual brush irrespective of the brushing mode used were not statistically significant. CONCLUSION: The results of this Professional Brushing Study show that the CrossAction Power toothbrush was as effective as a regular manual toothbrush.

[Tooth brushing and gingival abrasion]. / Tandenpoetsen en gingivalaesies.

It has been known for some time that tooth brushing can have unwanted effects on the gingiva and hard dental tissues. The aim of this study is to evaluate two factors that may be of influence on the incidence of gingival abrasion during tooth brushing. The first factor being the possible influence of feedback through oral sensory perception and the second the possible abrasive effects of dentifrice. From the sensory feedback experiment it became clear that a significantly greater number of abrasions occurred when the test subjects would brush their own teeth than when they would have their teeth brushed by a dental hygienist. From the dentifrice experiment it became clear that the use of dentifrice has no significant effect on the occurrence of gingival lesions.

Sonic-powered toothbrushes and reversal of experimental gingivitis.

OBJECTIVE: To compare two sonic toothbrushes in relation to the reversal of experimental gingivitis. MATERIALS AND METHODS: Subjects refrained from brushing mandibular teeth for 21 days. During a 4-week treatment phase, the right or left side of the mouth was brushed with either the Sonic Complete (SC) or Sonicare Elite (SE) toothbrush as randomly allocated. Plaque and gingivitis were assessed on day 0, after 21 days of no oral hygiene and after 1, 2 and 4 weeks of brushing twice daily. RESULTS: Thirty-four subjects provided evaluable data. The experimentally induced gingivitis (EIG) resulted in higher bleeding and plaque scores compared with day 0. The mean plaque scores at day 21 changed from 3.09 to 1.30 for the SC, and from 3.02 to 1.21 for the SE. At the end of the treatment period, there was no significant difference between the two brushes. The mean bleeding scores changed from 1.87 (day 21) to 0.97 for the SC, and from 1.83 to 0.92 for the SE. For the assessments at 1, 2 and 4 weeks post-EIG, both brushes showed a significant decrease in bleeding scores. There were no statistically significant differences between brushes.

The effect of a dentifrice and mouth rinse combination containing amine fluoride/stannous fluoride on plaque and gingivitis: a 6-month field study.

AIM: To examine the effect of amine fluoride/stannous fluoride (AmF/SnF(2))-containing dentifrice and mouth rinse on plaque formation and gingivitis as compared with habitual oral hygiene procedures with a regular sodium fluoride (NaF) dentifrice. MATERIAL AND METHODS: In total, 22 general practices participated in this research project. The participants (N=281) were randomly assigned into two groups: the test group received an AmF/SnF(2) dentifrice-mouth rinse combination and the control group received a NaF-containing dentifrice. The patients were requested to brush twice daily for approximately 2 min. The subjects of the test group had to rinse additionally in the evening for 30 s with 10 ml of the mouth rinse. RESULTS: Both groups started with comparable scores of plaque, bleeding and staining. At 6 months, the plaque scores were 0.95 for the AmF/SnF(2) group and 0.99 for the NaF group (decrease of 16% and 10%, respectively). Bleeding scores, although significantly different from baseline, did not show differences between the two regimes. At the end of the experimental period, the overall staining was more pronounced in the AmF/SnF(2) group (41%) than the NaF group (26%). Both plaque reduction and increase in staining seemed to be correlated to the amount of mouth rinse used in the test group. CONCLUSION: In instruction-resistant patients recruited from dental practices, the combined use of AmF/SnF(2) did not decrease gingivitis at a significant level in comparison with the regular regime of two times daily brushing with an NaF-containing dentifrice. However, the above-mentioned combination resulted in greater plaque reduction than that observed with the use of the conventional dentifrice. When used according to the manufacturer's instructions, this effect on plaque scores was more pronounced.

Brushing with and without dentifrice on gingival abrasion.

OBJECTIVES: This study was designed to evaluate two factors possibly influencing incidence of gingival abrasion during toothbrushing: (1) the abrasiveness of a dentifrice and (2) the possible influence of feedback of oral sensory perception. MATERIAL AND METHODS: For this purpose, two separate, single blind, randomized clinical experiments were performed. The two groups of subjects were requested not to brush their teeth 48 h, prior to the experiments. After staining with disclosing solution gingival abrasion sites were recorded as small (< or =5 mm) and large (>5 mm), both before and after brushing. The dentifrice experiment was a split-mouth design, including 36 subjects, brushing their teeth in two randomly selected contra-lateral quadrants, either with or without dentifrice, whereas the remaining two quadrants were brushed, using the alternative choice. The sensory perception feedback experiment was a full-mouth design, including 43 subjects and two separate brushing exercises with use of dentifrice. The first brushing-exercise was performed by a dental hygienist, excluding the feedback of oral sensory perception of the brusher. After a 4 weeks period of familiarization to the manual toothbrush, subjects brushed themselves in the same random order as the hygienist, using a fresh brush, thus including oral sensory perception. RESULTS: In the dentifrice experiment, the increment of small abrasion sites was 5.86 for brushing with and 5.75 without dentifrice. There was no statistically significant difference between brushing with and without dentifrice. Both with and without dentifrice, more small abrasions were found vestibular, (3.78 and 4.22, respectively) as compared with lingual (2.22 and 1.42, respectively) (p=0.027, p<0.001). In the sensory perception feedback experiment, the increment in small gingival abrasion sites was larger for the subjects brushing themselves (8.86) as compared with the professional brushing (2.94, p <0.0001). Subjects caused more abrasion on the vestibular surfaces (6.28) as compared with the lingual (0.60, p=0.0001), where the professional did not show this difference (vestibular: 1.88, lingual: 1.30, p=0. 1388). CONCLUSIONS: No statistically significant difference in the incidence of gingival abrasion was found between brushing with dentifrice or without dentifrice. Neither did oral sensory perception seem to affect the incidence of gingival abrasion.

High and low brushing force in relation to efficacy and gingival abrasion.

OBJECTIVES: Does a high brushing force induce more gingival abrasion than a low (regular) brushing force? Furthermore, what is the effect of a low or high force on the efficacy? METHODS: Thirty-five non-dental students were selected. All received an appointment prior to which they abstained from oral hygiene for at least 48 h. At baseline the teeth and surrounding tissues were disclosed using Mira-2-Tone disclosing solution. Next, the examiner (PAV) evaluated the number of sites with gingival abrasion and the amount of dental plaque (Quigley & Hein) at 6 surfaces of each tooth. In the absence of this examiner, the subject's teeth were brushed by a hygienist (MP) using the Braun/Oral-B-D17 oscillating rotating toothbrush. Brushing was performed in two randomly selected contra-lateral quadrants for 60 s with either a low force (+/-1.5 N) or high force (+/-3.5 N) and in the opposing quadrants for 60 s with the alternative force. Visual feedback was given to control force. The brush was moved from the distal tooth to the central incisor perpendicular to the tooth surface with an angle of approximately 10-15 degrees towards the gingival margin. Next, the number of sites with abrasion and the remaining plaque were assessed again. RESULTS: The overall baseline gingival abrasion scores were 3.1 and 3.2 sites for high and low force, respectively, and increased to 5.0 and 5.9 sites respectively after brushing. There was no significant difference with respect to incidence of abrasion. At baseline, 48 h. plaque levels were 2.2. The reduction in plaque scores with the low force was 60% and with the high force 56%. This difference was significant. CONCLUSION: With the oscillating rotating power toothbrush (Braun/Oral-B D17) the use of high force (+/-3.5 N) is less efficacious as compared to a regular low force (+/-1.5 N) while the incidence of gingival abrasion sites was comparable.

Feasibility of expanded granular sludge bed reactors for the anaerobic treatment of low-strength soluble wastewaters.

The application of the expanded granular sludge bed (EGSB) reactor for the anaerobic treatment of low-strength soluble wastewaters using ethanol as a model substrate was investigated in laboratory-scale reactors at 30oC. Chemical oxygen demand (COD) removal efficiency was above 80% at organic loading rates up to12 g COD/L . d with influent concentrations as low as 100 to 200 mg COD/L. These results demonstrate the suitability of the EGBS reactor for the anaerobic treatment of low-strength wastewaters. The high treatment performance can be attributed to the intense mixing regime obtained by high hydraulic and organic loads. Good mixing of the bulk liquid phase for the substrate-biomass contact and adequate expansion of the substrate-biomass contact and adequate expansion of the sludge bed for the degassing were obtained when the liquid upflow velocity (V(up)) was greater than 2.5 m/h. Under such conditions, an extremely low apparent K(s) value for acetoclastic methanogenesis of 9.8 mg COD/L was observed. The presence of dissolved oxygen in the wastewater had no detrimental effect on the treatment performance. Sludge piston flotation from pockets of biogas accumulating under the sludge bed occurred at V(up) lower than 2.5 m/h due to poor bed expansion. This problem is expected only in small diameter laboratory-scale reactors. A. more important restriction of the EGSB reactor was the sludge washout occurring at V(up) higher than 5.5 m/h and which was intensified at organic loads higher than 7 g COD/L. d due to buoyancy forces from the gas production. To achieve an equilibrium between the mixing intensity and the sludge hold-up, the operation should be limited to an organic loading rate of 7 g COD/L d. and to a liquid up-flow velocity between 2.5 and 5.5 m/h (c) 1994 John Wiley & Sons, Inc.

Mechanical properties of skinned rabbit psoas and soleus muscle fibres during lengthening: effects of phosphate and Ca2+.

1. Mechanical properties of permeabilized single fibres from rabbit psoas and soleus muscle were determined by measuring the length responses due to abrupt changes in load and the force responses due to isovelocity length changes at different phosphate and Ca2+ concentrations. 2. The length responses due to abrupt increases in load from psoas fibres showed a rapid lengthening during the change in load followed by a phase of lengthening during which the velocity gradually decreased. In soleus fibres an abrupt lengthening during the change in load was followed by a phase of lengthening during which the velocity remained constant or decreased slightly for increases in load to less than 1.45 of the isometric force (F0). For larger increases in load the velocity during this later phase first increased and thereafter decreased. 3. The initial force-velocity curve, derived from the early part of the isotonic responses after the change in load, as well as the late force-velocity curve derived from the force level attained during isovelocity length changes, were sensitive to phosphate. Phosphate caused a shift of the absolute force-velocity curves of both psoas and soleus fibres towards lower values of force. In psoas fibres, the relative force-velocity curves derived by normalization of the force level to the force developed isometrically was shifted by phosphate to smaller velocities. In soleus fibres, the initial velocity at low and intermediate relative loads (less than 1.75 F0) was increased by phosphate but at higher loads it decreased, while the late force-velocity curve showed an overall decrease in velocity. 4. The force responses during isovelocity lengthening of psoas fibres showed an early rapid increase in force followed by a slow rise in force. The position of this break point in force was sensitive to the phosphate concentration. In soleus fibres, the force responses without phosphate showed an overshoot followed by a slow rise in force. The overshoot diminished with increasing phosphate concentration. 5. Phosphate and Ca2+ affected the force responses in psoas and soleus fibres in different ways. When the isometric starting levels were the same, force during and after the length change at submaximal activation was always less than at maximal activation in the presence of 15 mM-phosphate. 6. The changes in the mechanical performance during lengthening caused by phosphate in psoas as well as in soleus fibres, are in agreement with a decrease in the average force per attached crossbridge.(ABSTRACT TRUNCATED AT 400 WORDS)

Automated systems for measurement of oxygen uptake during exercise testing.

We evaluated three automated systems for measurement of O2 uptake and compared them with the conventional Douglas bag method. One system (9000 IV Ergometric system) was only tested with respect to its oxygen kinetics, the other two (MMC-Horizon and EOS-Sprint) were tested during three exercise programs: (1) steady-state exercise at 50-W steps from 0 to 200 W, (2) progressive increasing exercise to maximal load, and (3) single-step exercise from 0 to 250 W. The regression lines of mean O2 uptake and load for six subjects were different for intercept (MMC-Horizon) or slope (EOS-Sprint) compared with the conventional method. The maximal O2 uptake values of six subjects were not significantly different for the two systems when compared with the Douglas bag method. The time constants of the exponential function describing oxygen kinetics during repeated (6 times) step changes in load in two subjects were different for the three systems. MMC-Horizon and 9000 IV Ergometric system had lower (51.8 s and 55.1 s, respectively, vs 62.5 s) and EOS-Sprint higher time constant (94.6 vs 47.7 s) than the conventional method. The automated systems were convenient and efficient for measurement of O2 uptake during steady-state and maximal exercise. When O2 uptake kinetics are essential, one has to take into account the response time of the system.