Dental health of the Rendille and Samburu of the northern frontier district of Kenya

Nomadic groups inhabiting the Kaisut desert region of Kenya were treated and studied during two successive trips. It was found that dental decay was relatively rare and advanced periodontal disease was present mostly in older patients. The mechanical action and contents of the locally available miswak stick (toothbrush tree) seem to play a significant role in control of dental diseases.     

Effectiveness of autologous blood replacement in rheumatoid arthritis surgery--a report of 10 years experience

The use of a wood stick (meswak or chewing stick) for brushing the teeth continues to be an important tool for oral hygiene care in many Afro-Asian communities. It is inexpensive, customary and used for religious reasons as well. Despite the wide use of meswak, information on its chemical and pharmaceutical contents are scant, particularly in regard to an anticaries effect. In the present study, sticks from Salvadora persica, the most common source for meswak, were analyzed for their soluble and total content of fluoride, calcium, phosphorus and silica. Results showed that the fluoride released from meswak soaked in water was negligible (< 0.07 microgram/ml). Approximately 39% of the total fluoride in the sticks was in a form that could be leached out. The leached calcium and phosphorus averaged 582 micrograms/ml and 34 g/ml, respectively, representing 19.6% and 26.4% of their total content in the sticks. There was a substantial amount of silica in the ashes of meswak. It appears that meswak is probably not particularly active against caries through its fluoride content, but it does act as a brush for removing dental plaque and polishing the teeth.     

Three clinical trials comparing xylitol- and sorbitol-containing chewing gums for their effect on supragingival plaque accumulation

Studies have evaluated the effects of xylitol when administered in chewing gum, as a dietary substitute for sugar, in dentifrice and in mouthrinse. Three clinical trials were conducted to further investigate chewing gums containing xylitol or xylitol/sorbitol mixtures for their ability to reduce plaque accumulation when compared to a sorbitol containing gum. These studies all had two phases; supragingival prophylaxis with an assessment of plaque accumulation to be used for balanced assignment for the second phase, which assessed plaque regrowth following a second supragingival prophylaxis and various chewing gum regimens. In the first trial of xylitol/sorbitol versus sorbitol gum only, the combination gum had a significantly greater reduction in plaque growth. In the second trial, different regimens of chewing gums with xylitol/sorbitol and sorbitol alone were compared. The combined average of the plaque regrowth scores for the subjects chewing the xylitol/sorbitol gum was significantly better than that for the sorbitol gum alone. The final trial evaluated two regimens in two forms (stick and pellet) of a xylitol gum versus a sorbitol gum. Both xylitol-containing gum forms were statistically superior to the sorbitol gum in retarding plaque regrowth.     

Efficacy of chewing gum in preventing extrinsic tooth staining

The purpose of this six-week clinical study was to determine the efficacy of sugar-free chewing gum versus no chewing on preventing Peridex (0.12% chlorhexidine)-associated stain. One-hundred and fifty healthy adult subjects, categorized by tea or coffee intake and smoking, were randomly assigned to a chewing or no chewing gum group. All subjects were given Peridex and an ADA-approved toothbrush and fluoride toothpaste to use twice a day. Gum was chewed for 20 minutes five times each day, after toothbrushing and Peridex rinse in the morning and evening, and after each meal. At baseline, all subjects received a professional cleaning to remove all supragingival deposits and extrinsic strain. At three and six weeks, safety and stain intensity and area were monitored on the anterior teeth and posterior Ramfjord teeth using the Lobene stain scoring method. Seventy-two subjects in each group completed the study. Attrition was unrelated to product use. No untoward reactions were reported or observed at any time in the study. At the six-week evaluations, the chewing gum group exhibited significantly lower (p < 0.05-0.001) total stain scores on both anterior and posterior areas evaluated compared to the no chewing group scores. In addition to the stain evaluations, a randomly selected subset of 60 subjects was evaluated for gingivitis at baseline prior to cleaning, and at three and six weeks, on the buccal and lingual surfaces of the Ramfjord teeth. Both the chewing gum and no chewing gum subset subjects had a significant decrease in gingivitis scores from baseline to three weeks (p < 0.001) and from baseline to six weeks (p < 0.05-0.001). There were no significant statistical differences between the two groups at anytime during the study on gingivitis levels. Chewing gum, after product use, did not reduce the efficacy of chlorhexidine on gingivitis scores.     

Extensive salivary contamination due to concurrent use of chewing tobacco during I-131 radioablative therapy

Although multiple authors have reported on various causes of external I-131 contamination after administration of radioiodine, to the authors' knowledge there have been no reported cases of external contamination from salivary secretions due to expectoration of chewing tobacco. A case of extensive I-131 contamination of a hospital room, furniture, and plumbing due to indiscriminate use of chewing tobacco during an inpatient I-131 radioablative therapy is presented.     

Refined Stick Model for Dynamic Analysis of Skew Highway Bridges

Stick models are widely employed in the dynamic analysis of bridges when only approximate results are desired or when detailed models are difficult or time-consuming to construct. Although the use of stick models for regular bridges has been validated by various researchers, the application of such models to skew highway bridges continues to present challenges. The conventional single-beam stick model used to represent the bridge deck often fails to capture certain predominant vibration modes that are important in obtaining the true dynamic response of the bridge. In this paper, a refined stick model is proposed for the preliminary dynamic analysis of skew bridges. The model utilizes a dual-beam stick representation of the bridge deck. The validity of the model is established by comparing results obtained from the proposed model with numerical solutions obtained for skew plates and a skew bridge. It is shown that this dual-beam stick model is superior to the conventional single-beam model in estimating the natural vibration frequencies and in predicting the predominant vibration modes of the bridge. Because of its simplicity and relative accuracy, this model is recommended for the preliminary dynamic analysis of skew highway bridges.     

Assessing the nicotine content of smokeless tobacco products

The nicotine content of 11 popular brands of smokeless tobacco--including moist snuff, plug and loose-leaf chewing tobacco--was analyzed. In general, moist snuff has the highest nicotine content and loose-leaf chewing tobacco has the lowest, with plug tobacco falling in the middle. Variability in nicotine content may affect smokeless tobacco use and should be considered when studying usage as a variable for adverse effects of ST use.     

Coca chewing for exercise: hormonal and metabolic responses of nonhabitual chewers

To determine the effects of acute coca use on the hormonal and metabolic responses to exercise, 12 healthy nonhabitual coca users were submitted twice to steady-state exercise (approximately 75% maximal O2 uptake). On one occasion, they were asked to chew 15 g of coca leaves 1 h before exercise, whereas on the other occasion, exercise was performed after 1 h of chewing a sugar-free chewing gum. Plasma epinephrine, norepinephrine, insulin, glucagon, and metabolites (glucose, lactate, glycerol, and free fatty acids) were determined at rest before and after coca chewing and during the 5th, 15th, 30th, and 60th min of exercise. Simultaneously to these determinations, cardiorespiratory variables (heart rate, mean arterial blood pressure, oxygen uptake, and respiratory gas exchange ratio) were also measured. At rest, coca chewing had no effect on plasma hormonal and metabolic levels except for a significantly reduced insulin concentration. During exercise, the oxygen uptake, heart rate, and respiratory gas exchange ratio were significantly increased in the coca-chewing trial compared with the control (gum-chewing) test. The exercise-induced drop in plasma glucose and insulin was prevented by prior coca chewing. These results contrast with previous data obtained in chronic coca users who display during prolonged submaximal exercise an exaggerated plasma sympathetic response, an enhanced availability and utilization of fat (R. Favier, E. Caceres, H. Koubi, B. Sempore, M. Sauvain, and H. Spielvogel. J. Appl. Physiol. 80: 650-655, 1996). We conclude that, whereas coca chewing might affect glucose homeostasis during exercise, none of the physiological data provided by this study would suggest that acute coca chewing in nonhabitual users could enhance tolerance to exercise.     

Role of chewing and smoking habits in the etiology of oral submucous fibrosis (OSF): a case-control study

Oral submucous fibrosis (OSF), a premalignant and crippling condition of the oral mucous membrane, was studied to identify its relationship to various chewing and smoking habits. Two hundred and thirty-six consecutive cases of OSF were compared with 221 control subjects matched for age, sex and socio-economic conditions. It was found that chewing of areca nut/quid or pan masala (a commercial preparation of areca nuts, lime, catechu and undisclosed colouring, flavouring and sweetening agents) was directly related to OSF. Also, pan masala was chewed by a comparatively younger age group and was associated with OSF changes earlier than areca nut/quid chewing. However, chewing or smoking tobacco with various other chewing habits did not increase the risk of developing OSF. It was also found that frequency of chewing rather than the total duration of the habit was directly correlated to OSF.     

RNA-binding proteins tamed

OBJECTIVES: Enhancement of the remineralisation of artificial enamel lesions has been observed in an intraoral model whether subjects chewed gum sweetened with a non-cariogenic sweetener such as sorbitol [1-3] or sucrose [4] after meals or snacks, and with use of a conventional (1500 ppm F) fluoride dentifrice. Since most of the clinical surveys which have shown the potential cariogenicity of sucrose chewing gum [5] were conducted before use of fluoridated dentifrices became widespread, the effect of fluoride dentifrice on de- and remineralisation of artificial lesions in enamel in response to chewing sucrose-sweetened gum has been examined with the aim of attempting to resolve this apparent discrepancy. METHODS: Subjects wore an intraoral device bearing an enamel lesion and chewed one piece of sucrose gum for 20 min after each of three meals and two snacks daily for two 3-week periods, during which they used a dentifrice containing either 0 or 1500 ppm F in a double-blind, cross-over design. Measurement of the mineral content of the lesions was determined by microradiography or polarised light microscopy. RESULTS: It was found that remineralisation tended to occur with 1500 ppm F dentifrice, but demineralisation with non-F dentifrice; the difference in enamel mineral content between the two periods was significant (P < 0.05). CONCLUSIONS: The results indicate that the potential cariogenicity of sucrose-containing chewing gum may indeed be negated by the use of a conventional fluoride dentifrice.     

Effects of coca chewing on hormonal and metabolic responses during prolonged submaximal exercise

The effects of coca chewing on prolonged submaximal exercise responses were investigated in chronic coca chewers and compared with a group of nonchewers. At rest, coca chewing during a 1-h period was followed by a significant increase in blood glucose, free fatty acid, and norepinephrine concentrations and a significant reduction in insulin plasma level. During prolonged (1-h) submaximal (65-70% peak O2 uptake) exercise, chewers displayed a significantly greater adrenergic activation (as evidenced by a higher level of plasma epinephrine) and an increased use of fat (as evidenced by a lower respiratory exchange ratio). The gradual increase in oxygen uptake (O2 drift) commonly observed during prolonged exercise was blunted in coca chewers. This blunting in O2 drift is not related to coca-induced changes in ventilatory or lactate responses to exercise but could possible be related to an enhanced glucose utilization by chewers during the late phase of exercise. The present results provide experimental evidence of the physiological effects of coca chewing that could explain the better ability of coca users to sustain strenuous work for an extended period of time.     

What do rooks (Corvus frugilegus) understand about physical contact?

Rooks (Corvus frugilegus) do not use tools, but rapidly solve tests of physical cognition. The authors tested whether rooks understand the concept of physical contact using a task comprising a clear horizontal tube containing a stick with a disk attached to it and a piece of food. The rooks chose which side to pull the stick from to make the food accessible. Two configurations were used, with either the food or disk central along the tube. All 8 rooks solved the food-central configuration, but failed the disk-central configuration. Although they did not demonstrate an understanding of contact, further tests established that they could learn to solve these tasks provided there were salient stick cues. This result may arise because sticks are ecologically important for rooks. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Changes in chewing patterns after implantation in the edentulous mandible

Almost all edentulous patients with implant-supported prostheses in mandibles describe an improvement in their chewing function and quality of life. This was reason to believe that an implant prosthetic treatment actually influences mandibular border movements, as well as the chewing patterns. The present study compares border movements and chewing patterns in 15 patients recorded with the Sirognathograph. The first measurements were made with existing complete dentures. After implantation and rehabilitation with a Dolder-bar and clip-to-bar overdenture, the movements were recorded again. The measurements revealed an improved guidance of the mandibular movements and larger borderline patterns following stabilization of the complete denture with the bar. This leads to more harmonic shapes in the movements and better chewing efficiency.     

Effects of postirradiation temperature on the yields of radiation-induced single- and double-strand breakage in SV40 DNA

This report describes a case of lead poisoning occurring in an electrician as the result of an unusual personal habit, namely, the chewing of lead-containing coatings of electric wires. A coating chewing test showed that a few minutes after beginning chewing, saliva lead concentration increased from 10 micrograms/l to several milligrams per liter. This case is an example of poisoning caused by an occupationally related source (coatings containing lead) as a consequence of a singular and unconventional worker's habit.     

Does the presence of xylitol in a sorbitol-containing chewing gum affect the adaptation to sorbitol by dental plaque?

It is known that xylitol inhibits sorbitol metabolism in some bacteria in vitro. The effect of xylitol/sorbitol-containing chewing gum on sorbitol adaptation of dental plaque was therefore examined. Ten subjects used this chewing gum for 12 wk, and plaque was collected before (control plaque) and after (test plaque) the exposure to sorbitol/xylitol. The metabolism of sorbitol by the plaque was examined with 14C-labeled sorbitol, and the radioactive metabolites were detected by high-performance liquid chromatography (HPLC). A considerable individual variation in acid formation was found. The mean values of total acids in the test plaque increased, as compared with the control plaque. An adaptation of dental plaque to sorbitol thus occurred in spite of the presence of xylitol in the chewing gum. The concentration of acetic acid predominated over other acids in both the control and test plaques. The proportions of acids expressed in percentage of total acids differed only slightly. Thus, long-term use of xylitol/sorbitol-containing chewing gum did not eliminate the adaptation of dental plaque to sorbitol.     

Localization of mRNAs for synaptojanin isoforms in the brain of developing and mature rats

STATEMENT OF PROBLEM: Knowledge of mastication is based on studies that use jaw tracking equipment in nonroutine settings. Ethologists would argue that such data probably does not reflect routine masticatory function. If jaw movements could be tracked noninvasively, then the hypothesis that jaw tracking equipment and nonroutine settings alter mastication could be investigated. PURPOSE: This study quantitatively evaluated the relationship between chin and jaw movements during a gum-chewing task. MATERIAL AND METHODS: Masticatory chin and jaw movements of 50 subjects were tracked in the x-, y-, and z-axes for 15 seconds, which resulted in approximately 15 chewing cycles obtained per subject. For each chewing cycle, magnitude and timing of displacement, velocity, and acceleration extrema in each axis were computed for both jaw and chin movement data. Extrema means were calculated for each 15-second trial. The respective means representing chin versus jaw movements were compared with linear regression and correlation analyses. RESULTS: All mean extrema were significantly correlated (r range 0. 30-0.99; P <.05). Magnitude correlations were larger than timing correlations for acceleration extrema. In contrast, magnitude correlations were smaller than timing correlations for displacement extrema. The highest correlation occurred for chewing rate. CONCLUSIONS: Chin and jaw movements were correlated during chewing; however, only chewing rate was highly predictable from chin movement data.     

Effect of three months' frequent use of sugar-free chewing gum with and without urea on calculus formation

Studies on the relationship between gum-chewing and calculus formation have produced contradictory results, and it is not clear whether frequent use of chewing gum promotes or inhibits calculus formation. Also, little is known about whether the addition of a small amount of urea to the chewing gum influences calculus formation. The aim of this investigation was to study the effect of sugar-free chewing gum--with and without urea--on calculus formation and some associated clinical variables. Three three-month periods were studied in a double-blind, crossover design, during which the subjects: (1) chewed 5 pieces/day of a sugar-free, urea-containing chewing gum (20 mg urea/piece); (2) chewed 5 pieces/day of a sugar-free, non-urea-containing gum; or (3) performed no gum-chewing. Twenty-nine persons, all calculus-formers, participated. They were scored for calculus at mesio-lingual, lingual, and disto-lingual sites on the 6 anterior mandibular teeth according to the Volpe-Manhold index. Plaque and gingival bleeding index, stimulated salivary secretion rate and buffer capacity, resting plaque pH, mutans streptococci in saliva and plaque, and lactobacilli in saliva were also determined. No differences in calculus formation were found among the 3 periods. The resting plaque pH was higher after the period with urea-containing gum than after the period with non-urea-containing gum and the no-gum period (p < 0.05). A slight increase in stimulated salivary secretion rate was found after the 2 gum periods (p < 0.05). The plaque and gingival bleeding indices decreased, while resting plaque pH and salivary buffer capacity increased throughout the entire study (p < 0.05). No significant differences in prevalence of the acidogenic micro-organisms were found among the test periods. The main conclusion from this study is that three months' frequent use of sugar-free chewing gum--with or without urea--neither promotes nor inhibits calculus formation.     

Seismic communication between the burrows of kangaroo rats, Dipodomys spectabilis

Data from the September 1985 Current Population Survey are used to estimate the effects of tobacco excise taxes and state laws restricting smoking in public places on the likelihood of current use of cigarettes or smokeless tobacco (ST) products (moist snuff or chewing tobacco) among males in the USA. The results indicate that higher ST excise tax rates are associated with a reduced probability of ST use, whereas higher cigarette excise tax rates are associated with an increased probability of ST use, holding other factors constant. State laws restricting smoking have no apparent effect on ST use.     

连铸结晶器铜板与坯壳间摩擦力的分析与研究

通过连铸机在生产过程中结晶器铜板与坯壳间摩擦力及摩擦功的分析与研究,得出其数学模型,并根据其特征值的变化预报粘结与裂纹漏钢.     

What do bonobos (Pan paniscus) understand about physical contact?

The present study aimed to test what bonobos (Pan paniscus) understand about contact. The task consisted of a clear horizontal tube containing a piece of food and a stick with a disk attached. The bonobos chose which side to push or pull the stick for the disk to contact the food and make it accessible. There were 9 variations in tube design, which differed in the positions of the stick, disk, and food. All 5 bonobos passed at least 1 configuration. A recent study (A. E. Helme, N. S. Clayton, & N. J. Emery, 2006) found that rooks could learn only tube configurations that provided an asymmetrical stick cue, whereas bonobos did not demonstrate an understanding of contact but showed more individual variation, attending to the positions of the food, disk, and stick. (PsycINFO Database Record (c) 2010 APA, all rights reserved)