57 research outputs found
sj-docx-1-jct-10.1177_23800844221090444 – Supplemental material for Economic Evaluation of the Protecting Teeth @ 3 Randomized Controlled Trial
No full textSupplemental material, sj-docx-1-jct-10.1177_23800844221090444 for Economic Evaluation of the Protecting Teeth @ 3 Randomized Controlled Trial by Y. Anopa, L.M.D. Macpherson, A.D. McMahon, W. Wright, D.I. Conway and E. McIntosh in JDR Clinical & Translational Research</p
An in vitro stimulation of the effects of chewing sugar-free and sugar-containing chewing gums on pH changes in dental plaque
No full textThe objective of these studies was to simulate the effect of chewing sugar-free and sucrose-containing chewing gums on the return of the pH to neutrality after exposure to sucrose of plaque located on the buccal (BLM) and lingual (LLM) surfaces of the lower molar teeth. In study 1, a 0.5-mm-deep artificial plaque containing Streptococcus oralis cells was exposed to 10% sucrose for one min, and a 0.1-mm-thick film of sucrose-free artificial saliva was then flowed over the plaque surface at the unstimulated salivary film velocities previously found at the BLM and LLM sites. At the time of the pH minimum (pH 4-5), one of three conditions was simulated: (a) a no-gum-chewing control, or chewing for 20 min on either (b) a sugar-free gum or (c) a sucrose-containing gum. The recovery of the plaque pH to resting values was rapid during simulation of chewing a sugar-free gum (SFG), much slower with the no-gum control, and even slower with simulation of chewing a sucrose-containing gum (SCG). The pH recovery was slower with the BLM than the LLM plaque. In study 2, the BLM plaque was exposed to a 2% sucrose solution for 20 min under stimulated salivary conditions, to simulate the consumption of a meal, followed by one of conditions (a), (b), or (c) described above. The pH recovery with simulation of chewing a SCG was faster than with the no-gum control, but much slower than with the SFG simulation
The distribution of saliva and sucrose around the mouth during the use of chewing gum and the implications for the site-specificity of caries and calculus deposition
No full textOver a 20-minute period, subjects expectorated 8 samples of whole saliva (EWS) while chewing gum. Flow rates were calculated, and sucrose was analyzed in these samples as well as in saliva collected on filter paper strips from different tooth surfaces. Salivary film velocity (SFV), based on a 0.1-mm-thick film, was estimated from the clearance half-times of KCl in agarose disks positioned in different regions of the mouth. Salivary flow rate peaked at 5.1 mL/min in the first min but fell to about 1.25 mL/min by the end of the 20 min of gum-chewing. In contrast, flow rate when subjects sucked sour lemon drops averaged about 5.3 mL/min throughout the 20-minute period. The mean salivary sucrose concentration during gum-chewing peaked in the second min at 384 mmol/L (13.1%) but had fallen to 14 mmol/L by the 15-20-minute time interval. The sucrose concentrations on the palatal surfaces of the upper incisors and the facial and lingual surfaces of the lower molars were not significantly different from that in EWS but were much lower on the facial surfaces of the upper incisors and molars, and on the lingual surfaces of the lower incisors. When flow was unstimulated, SFV was 0.8-1.0 mm/min on the facial surfaces of the upper incisors and lower molars but about 5-8 mm/min on the facial surfaces of the upper molars and on the lingual surfaces of the lower incisors and molars
Effects of salivary film velocity on pH changes in an artificial plaque containing Streptococcus oralis, after exposure to sucrose
No full textResults from a computer model suggest that following exposure of dental plaque to sucrose, the rate of clearance of acids from plaque into the overlying salivary film will be greatly retarded at low film velocities. This was investigated with an in vitro technique in which artificial plaque containing S. oralis cells was exposed to 10% sucrose for one min. The pH at the proximal (P) and distal (D) undersurfaces of the plaque (0.5 or 1.5 mm thick) was then monitored during the passage of a 0.1-mm-thick film of a sucrose-free solution over the surface. Over the range of salivary film velocities that have been estimated to occur in vivo (0.8-8 mm/min), lower minimum pH values and increased times for the pH to recover toward neutrality occurred at the lower salivary film velocity. Lower pH values were also reached with the 0.5- than with the 1.5-mm-thick plaque. P/D pH gradients, with a lower pH distally, developed at film velocities of 0.8 and 8 mm/min, and the gradients were much more pronounced at the lower velocity. No P/D pH gradients developed when the film velocity was 86.2 mm/min. Incorporation of dead S. oralis cells into the plaque at percentages up to 57% reduced the extent of the pH fall and prolonged the recovery of the pH toward neutrality. The results support the prediction that, other factors being equal, plaque located in regions of the mouth with low salivary film velocity will achieve pH values lower than those of plaque of identical dimensions and microbial composition located in areas where salivary film velocity is high
Distribution of sucrose around the mouth and its clearance after a sucrose mouthrinse or consumption of three different foods
No full textThe distribution of sucrose in whole saliva and in saliva from seven different regions of the mouth was determined in 10 subjects over the 10-min period following the chewing of a doughnut, sucking on a mint candy, the drinking of orange juice, or use of a 10% sucrose mouthrinse. With all products, the sucrose was distributed non-uniformly, with particularly low concentrations on the lingual surfaces of the lower incisors and the facial surfaces of the upper molars. Clearance was also most rapid from these sites. Since the depth and duration of a Stephan curve in dental plaque is influenced by the sugar concentration to which the plaque is exposed, the results, together with previous results on salivary film velocity in different regions of the mouth, help to provide an explanation for the site-specificity of smooth-surface caries and of supragingival calculus deposition
Effects of nine different chewing-gums and lozenges on salivary flow rate and pH
No full textThe objectives of this study were to determine how salivary flow rate and pH vary with time during use of chewing-gums and lozenges. Twenty-four young adults collected unstimulated saliva and then, on different occasions, chewed one of six flavoured gums, or gum base, or sucked on one of two lozenges, for 20 min, during which time eight separate saliva samples were collected. Flow rate peaked during the 1st minute of stimulation with all nine products. With the lozenges, flow rate fell towards he unstimulated rate when the lozenges had dissolved. There were no significant differences in the flow rates elicited by cinnamon- or peppermint-flavoured gums or between sugar-containing or sugar-free gums. With the flavoured gums, the mean flow rate followed a power curve (r = -0.992) with time and within about 10 min was not significantly different from that when gum base was the stimulus. The initial stimulated flow rate with flavoured gums was about 10-12 times greater than the unstimulated rate (0.47 ml/min). After 20 min of chewing, it was still about 2.7 times that rate and about the same as the flow rate elicited by chewing-gum base alone. The pH of unstimulated saliva was about 6.95. With one gum containing about 1.5% organic acids, the salivary pH fell to a minimum of 6.18 in the 1st minute of stimulation, but then rose rapidly to a level above that in unstimulated saliva. With a sucrose-containing and a sucrose-free gum, the pH rose immediately on stimulation and then fell slightly with time to levels which were significantly above the pH of unstimulated saliva
A-priori inertia estimation from weight for goal-directed movement under weight compensation
No full textRobotic lifting aids aim to reduce the forces on the operator, but may thereby also change the experienced dynamics of the lifted object. In the case of weight compensation, the experienced ratio between object's weight and inertia is altered, exposing the operator to dynamics different from those experienced in daily life. This may affect execution of fast goal-directed movements, especially during first exposure to the altered dynamics. We hypothesize that the inertia, used in the internal model in the open-loop phase of the movement, must be estimated before movement onset and can be based on the object's weight. In an experimental study, subjects (n=18) performed fast vertical lifting movements of virtual objects of different inertia and weight in normal gravity (baseline experiment) and under weight compensation. In the catch trial experiment, the weight was kept constant and in catch trials weight compensation was applied, resulting in an unexpectedly increased inertia. We then fitted a simple open-loop model, based on minimum jerk trajectories, to best match the generated forces for the first of each trial, by varying one parameter: the modelled inertia, i.e. the inertia estimated a priori by the subject. The trajectories in the baseline experiment are minimum jerk like and are independent of inertia, which can only be due to properly applied force profiles. The minimum jerk related force profiles increased with increasing inertia and contained a static force equal to weight. In the catch trial experiment, the force profiles for the weight compensation condition were similar to those in the normal gravity condition up to approximately 80ms. After that, the force profiles of the catch trials deviated from the normal force profile and the movement in the catch trials was characterised by skewed velocity profiles and consistent overshoots. The Variance Accounted For, a measure for goodness of fit, for all conditions in both experiments were high (with the median around 95%), implying the model fitting procedure captured the essential open-loop movement behaviour. Weight and modelled inertia were linearly related in the baseline experiment, as was hypothesized, yet a positive offset was found for small inertias. In the catch trials, the modelled inertias were higher than expected purely based on weight information, but remained closely related to inertia as in normal gravity. We conclude that a priori inertia estimation, used in the open-loop phase of fast lifting movements, strongly depends on weight information and the known weight/inertia ratio. This insight can help in designing the control for lifting aids to support the operator more naturally.Haptic interfacesBiomechanical designMechanical, Maritime and Materials Engineerin
The effect of sucrose application and implantation of mutans streptococci on the microbial composition of three-week experimental plaque—an in situ study
No full textThis study describes the predominant cultivable microflora of three-week-old plaque samples obtained from human enamel sites, on the basis of microbial identification of over 9000 fresh isolates. Lower removable appliances, on which were mounted enamel sections and slabs, were worn by five young adult subjects under three experimental protocols. These were (1) 'normal' plaque conditions, (2) extra-oral sucrose applications nine times daily, and (3) inoculation of each subject's own mutans streptococci onto the enamel test sites and sucrose applications, as described above. With the exception of slightly higher proportions of Gram-negative bacilli associated with slab plaque following sucrose application, no significant differences in percentage or absolute counts of organisms were found between normal and sucrose plaques. The inoculation of mutans streptococci, combined with extra-oral sucrose applications, was associated with significantly higher percentages and absolute mean counts of both mutans streptococci and lactobacilli, and lower proportions of S. sanguis and S. oralis. Although the isolation frequency of mutans streptococci increased in all subjects and the overall mean proportion rose following inoculation, considerable inter-subject variation was seen in mean percentage counts of these organisms isolated from the three-week plaque samples
Effects of salivary bicarbonate content and film velocity on ph changes in an artificial plaque containing Streptococcus oralis, after exposure to sucrose
No full textChewing-gum stimulation of salivary flow (at the time of the pH minimum following exposure of plaque to carbohydrate) has been shown to cause a rapid increase in plaque pH. The objective of this study was to determine whether the rise in plaque pH is primarily due to the increased buffering capacity of stimulated saliva, or to the fact that an increased flow rate increases the concentration gradient for acid to diffuse from the plaque into the overlying salivary film, which will be moving at a higher velocity. This was investigated with an in vitro technique in which artificial plaque (0.5 or 1.5 mm deep) containing S. oralis cells was exposed to 10% sucrose for one min. The pH values at the proximal and distal undersurfaces of the plaque were then monitored during the passage of a 0.1-mm-thick film of a sucrose-free artificial saliva over the surface, at a range of film velocities (0.8-8 mm/min) that have been estimated to occur in vivo. When a minimum plaque pH had been achieved, the salivary film velocity was either (a) kept the same, with or without 15 mmol/L HCO3 (the concentration measured in chewing-gum-stimulated saliva), (b) increased to 86.2 mm/min, or (c) increased to 86.2 mm/min with 15 mmol/L HCO3 added to the artificial saliva. The findings suggest that after sucrose ingestion, the rapid rise from minimum plaque pH values, which can occur with gum-chewing stimulation of salivary flow, is due to the combined effects of the increase in salivary film velocity, and of a greater availability of bicarbonate
An intra-oral appliance study of the plaque microflora associated with early enamel demineralization
No full textAn intra-oral appliance model was used to investigate the composition of the plaque microflora associated with early enamel demineralization. Enamel sections, with exposed windows, were mounted on lower removable appliances, and the devices were worn by volunteers for three-week periods under three experimental conditions. These were: (1) "normal" plaque conditions, (2) extra-oral sucrose applications nine times daily, and (3) inoculation of each volunteer's own mutans streptococci onto the test sites and sucrose applications as described for (2). After 21 days, the plaque overlying each window was removed, and the bacterial composition was determined. Changes in mineral content of the associated enamel were measured by microradiography and microdensitometry, and the total mineral loss (delta z) that had occurred at each site was calculated. The 144 sites studied were divided into four demineralization groups by delta z value, with an increase in mineral loss from group 1 to group 4. A progressive and significant increase in the isolation frequency of mutans streptococci occurred from delta z group 1 to group 4 sites. These organisms were isolated from the plaque of every location with enamel mineral loss of over 1000 delta z units, but were not detected in 27% of the group 3 sites. Lactobacilli comprised 2% to 3% of the total cultivable microflora in groups 1-3 sites, but were found in significantly higher proportions (18%) at those enamel sites experiencing the most extensive mineral loss (group 4). No significant relationship was found between demineralization and the levels of Actinomyces species or Veillonella
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