Areas Of CH Research Articles

Evaluation of the dental plaque pH recovery effect of a xylitol lozenge on patients with fixed orthodontic appliances.

The purpose of this study was to evaluate the influence of a xylitol lozenge on the dental plaque pH profile of fixed orthodontic patients. Twelve volunteers participated in this study. Before the measurement of plaque pH, subjects were asked to refrain from brushing their teeth for 48 hours and from eating and drinking for two hours. The subjects' baseline dental plaque pH was recorded using the touch technique. It was followed by a one-minute rinse with 15 ml of a 10% solution of sucrose, and subsequent plaque pH measurements were carried out during the next one hour. Xylitol lozenges were taken five times a day during a 14-day period. The variables of resting-plaque pH, minimum-plaque pH (MP pH), time required to reach MP pH (TMP), last-plaque (LP) pH at the end of one hour, cH area (CH), and pH at each test time were calculated for each pH test of the subjects. The paired sample t-test was used for statistical comparison. The mean MP pH values increased from 4.81 to 5.09 in the experimental measurement (P < .05). The mean TMP was not affected by the use of xylitol (P > .05). Although the LP pH showed an increase during the experimental period, the difference between control and experimental periods was not statistically significant (P > .05). The CH of the experimental period was significantly less than that of the control period (P < .05). As a result, the use of a xylitol lozenge after a sucrose challenge can be an advisable practice for fixed orthodontic patients to prevent future dental caries.

The relationship of soil water repellency to aliphatic C and kaolin measured using DRIFT

In general, water repellency by soil increases with the increase of total organic matter and decreases as the clay and silt contents of the soil increase. The prediction of water repellency from soil organic carbon (OC) content may be improved by examining the types of carbon associated with water repellency. This paper examines the hypothesis that measurement of aliphatic C can provide a better prediction of water repellency than measurement of total OC and also looks at the effects of soil texture on water repellency and the amount of aliphatic C in the soil. DRIFT (diffuse reflectance infrared fourier transform) spectra were measured on sandy soils from the West Midland Sandplains north of Perth in Western Australia. The areas of the aliphatic CH stretching signal (3000–2800/cm) and the OH stretching signal due to kaolin (3750–3570/cm) were used as relative measures of aliphatic carbon and kaolin contents. The relationships of aliphatic C and kaolin to water repellency have been examined and compared with the relationships of water repellency to total OC and clay contents of soil.Hydrophobic organic C as measured by DRIFT gave a better prediction of soil water repellency (r2 = 0.45) than did the total OC (r2 = 0.36). The specific hydrophobicity of organic matter (aliphatic C/OC ratio) increased as sand content increased. However, the direct influence of soil texture on water repellency was of more significance than its indirect influence on the amounts and forms of soil organic matter. A multivariate model including aliphatic C and clay + silt content was the best model for describing water repellency (r2 = 0.58). DRIFT is an effective, rapid method for screening soils for water repellent properties.For individual sand grains there was a weak positive relationship (r2 = 0.26) between the size of the aliphatic CH peak measured from surfaces of sand grains and the water repellency of the grains. A discontinuous aliphatic surface layer was present on the surface of individual sand grains.

Adaptation of dental plaque to metabolise maltitol compared with other sweeteners

There is some evidence that plaque can adapt to regular exposure to some bulk sweeteners, leading to increased metabolism and acidogenic potential of the sweetener. This potential for adaptation varies between non-sugar sweeteners and has important implications for manufacturers of food, confectionery and medicines used long-term. Maltitol (99% purity crystalline d-maltitol) is a relatively newly approved non-sugar sweetener and appears to have potentially good dental properties. Objectives: To compare plaque adaptation to pure sucrose, sorbitol, xylitol or maltitol and the effect of their prolonged use on acid production by plaque from sucrose, in vivo. Methods: Two series of plaque pH experiments were carried out. Each experiment involved a 14 day adaptive period when four 5 g lozenges of the sweetener were taken between meals each day. Each experiment was separated by a 14 day wash-out period. Acid production was quantified as: (a) minimum pH; and (b) cH area (difference between plaque pH curve and resting value, expressed as cH units). Results: Thirteen adults, of mean age 41 years completed the study. When adaptation of dental plaque to the metabolism of sweeteners was compared, there was a statistically significant difference ( p=0.033) between xylitol and sorbitol, and between xylitol and sucrose but not between xylitol and maltitol. When the effect of prolonged use of sweeteners on acid production after sucrose rinsing was compared, there were no statistically significant differences between the sweeteners. Conclusion: Dental plaque does not adapt to metabolise xylitol or maltitol following prolonged exposure over 14 days.

Effects of lactate dehydrogenase and nicotinamide adenine dinucleotide on human dental plaque pH and acid anion concentrations

The effect of sucrose rinses supplemented with L-LDH and NAD was investigated. When LDH or NAD were added to the sucrose rinse, the pH fall was less marked than with rinsing with sucrose alone. Significant differences ( p < 0.05) in mean minimum pH and cH areas were observed when sucrose rinses were supplemented with LDH, NAD or with a combination of LDH and NAD, when compared with sucrose alone. Plaque fluid concentrations of lactate and acetate significantly decreased with all rinses when compared with sucrose alone. Phosphate levels also decreased, although not significantly, when NAD was the sole supplement. No significant decreases were observed in succinate, formate or propionate concentrations. The results confirm the beneficial effect of LDH in reducing the accumulation of lactate in plaque following a sucrose rinse. The inclusion of NAD in the rinse demonstrated the role of extracelluar hydrogen acceptors in the reaction. Further work is required to identify endogenous hydrogen receptors and to clarify the fate of pyruvate resulting from the oxidation of lactate before the potential role of LDH as a cariostatic agent can be fully understood.

Nutrient losses after clearfelling in Beddgelert Forest: a comparison of the effects of conventional and whole-tree harvest on soil water chemistry

The effects of conventional, bole only harvesting (CH) and whole-tree harvesting (WTH) on major inorganic nutrient concentrations (K, NO3-N, NH4-N, PO4-P and Ca) in soil water are described from Beddgelert forest in North Wales. Monitoring of nutrient leaching losses, and the timing thereof, from brash through the soil and into streams draining the CH areas allowed assessments to be made of the value of brash as a nutrient source for second rotation crops. Most of the K (around 100 kg ha-1) and one-third of the P (10 out of 30 kg ha-1) leached out of the brash lying on the CH plots within one year of felling. A pulse of K passed through the soil profile, but less than half this K reached the streams. In contrast, the P was immobilized in the soil. The lack of brash resulted in the absence of K and P pulses on the WTH plots. On the CH plots, brash was a net sink for inorganic-N for 3 years after felling. However, in both CH and WTH, a pulse of nitrate was observed in the soil and also in streams draining CH areas. The source of this nitrate may have been death of fine tree roots, followed by rapid mineralization and nitrification. Calculation of a nutrient budget for a complete crop rotation indicates that P and Ca losses in harvested material are likely to result in long-term depletion of these elements, and that the effects will be significantly more severe if WTH is practised.

The Effect of Increased Mastication by Daily Gum-chewing on Salivary Gland Output and Dental Plaque Acidogenicity

The effect of increased mastication on plaque metabolism and salivary gland function was determined in 11 human subjects who chewed a sugarless gum for ten minutes of each waking hour for two weeks. Prior to and at the conclusion of the gum-chewing regimen, unstimulated whole saliva and 2% citric-acid-stimulated parotid saliva were collected. Flow rates, pH, and buffer capacity were determined on all saliva samples. In addition, parotid saliva was analyzed for protein concentration and the proteins further studied by SDS-PAGE. The plaque pH response to a 10% sucrose rinse was also measured before and after the regimen. Significant increases were observed in the pH and buffer capacity of unstimulated whole saliva as were similar increases in the flow rate, pH, and buffer capacity of stimulated parotid saliva. Protein concentrations and profiles remained unaffected. In addition, the resting plaque pH and minimum plaque pH reached after a sucrose challenge were both raised significantly, with a significant reduction in the cH area. The results of this study indicate that increased masticatory effort by frequent consumption of sugar-free chewing gum over a prolonged time period resulted in a functional increase in the output of stimulated parotid saliva, as well as in increases in pH and buffer capacity of whole and parotid saliva, which may help to reduce plaque acidogenicity.

Extracellular Administration of Lactate Dehydrogenase and Its Effects on Human Plaque pH and Acid Anion Concentrations

The effect of lactate dehydrogenase (LDH) on human plaque pH and acid anion concentrations in vivo was investigated. Rinsing with sucrose solutions supplemented with LDH (1 or 2 U/ml) gave rise to reduced pH fall, decreased cH area and an increase in the mean minimum pH when compared with rinsing with sucrose only (p less than 0.05). Mean acid anion estimations showed that plaque fluid concentrations of lactate, acetate and proprionate significantly decrease (p less than 0.05) following rinsing with sucrose containing LDH at both levels and decreases in succinate when 1 U/ml LDH was present, whereas formate concentrations were only significantly lower when 2 U/ml LDH was added to sucrose rinses. It is thought that the ability of LDH to produce an alteration in the acid end-products of plaque metabolism may provide some protection against dental caries.

Hydrogeological activities in Peninsular Malaysia and Sarawak

The Geologi cal Survey in Penin sul ar Malaysia has been inv o lved in ground wat er investigations since it s inception in L903. ln 1953 in ves ti gations under th e Perl is Water S uppl y Scheme resulted i.n th e exploitation of groundwater in Arau. Between 1955-1 958 th e Department , in colJ abo­ ration with UNT AA (United Nations Technical Aid Ass istance) implemented a regional hydrogeologi­ cal investi gation of th e coastal areas of Penin sul ar Mala ysia whi ch res ulted in th e location of severa l potential water bearin g zones. During the Third Malays ia P lan ( 1976-1980) th e Department togeth er with the Ge rman Hydroge­ ological Mi ss ion success full y completed a programme of in ves ti gation in Kelantan , Terengganu, Pal1an g, Kedah and Perl is. Under the Fourth Malaysia Plan ( 198 1-1 985) th e Geological Survey embarked on a hydrogeologi cal in ves ti gation in Seri Gading, Johor and the Rembau-Tampin-Gemas area , Negeri Sembila.n/Me laka. ln Sarawak prior to 1970 the Publi c Works Depattment undertook hydrogeolog ical in ves ti gati on and exploitation in the state. However, si nce 1975 th e Geological Survey has been conductin g hydro­ geo logical investi gations along th e coastal pl ain . To-date I 5 areas have been stu d ied and fresh groundwater has been located in 9 of th ese areas. A hydrogeological map of Penin sul ar Malays ia on a scale of I :500.000 was publi shed in 1975. The hydrogeologica l map of Sarawak on th e same sca le has been compiled and will be publi shed in 1985.

HİDROLİK KONDAKTİVİTE TAYİN METOTLARININ ERZURUM OVASI DRENAJ PROBLEM SAHA TOPRAKLARINDA KULLANILABİLME İMKANLARI ÜZERİNDE BİR ARAŞTIRMA

HİDROLİK KONDAKTİVİTE TAYİN METOTLARININ ERZURUM OVASI DRENAJ PROBLEM SAHA TOPRAKLARINDA KULLANILABİLME İMKANLARI ÜZERİNDE BİR ARAŞTIRMA