The significance of fluoride in Kenyan Water and tea leaves in relation to fluoresis and its effect on the enamel structure and restorative dentistry in general
Opinya, Gladys Nabubwaya
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SECTION A In this study, 21 water samples obtained from springs, wells and boreholes were analyzed for fluoride using the fluoride electrode. Each water sample had a volume of 250ml. Spring water was found to have a fluoride concentration range of 0.2 - 1.2 ppm. Well water had a fluoride concentration range of 0.2 - 0.3 ppm. Borehole water was obtained from Nakuru and Naivasha in the Rift Valley and had a fluoride concentration range of 1.0 to 9.3 ppm. Concentrations above 1 ppm are considered high. Endemic dental fluorosis is of public concern in Kenya and has been associated with the high fluoride levels in domestic water. An analysis of tea infusions brewed from loose Kenyan tea having a mean weight of 3.9 grams in 195 ml of deionized water (equivalent to a regular cup of tea) showed 5 ppm fluoride. The tea infusions had been prepared in a manner similar to the way most Kenyan families brew tea, by boiling for a short period after placing the tea leaves in boiling water. In this study, the tea was boiled for 10 seconds. The tea was then steeped for 4 minutes prior to sieving the tea leaves. This indicates that an individual ingesting a cup of tea (195 ml) will have a fluoride intake of 980 [mu]g. The Kenyan tea bags with an average weight of 1.8 grams, yielded an average fluoride concentration of l.9 ppm fluoride. A cup of tea (195 ml) brewed from Kenyan tea bags yielded a mean fluoride concentration of 380 [mu]g. Extended boiling resulted in high concentrations in the tea being brewed. The fluoride concentration increased after boiling for 30 seconds then boiling for 5 minutes without steeping from 4.2 ppm to 16 ppm fluoride. The American Salada tea had a mean fluoride concentration of 520 [mu]g in 195 ml. Water and tea are sources of fluoride in Kenya that contribute to the development of unaesthetic fluorosed teeth observed in part of the population. In particular, it may be noted that many Kenyan children drink tea. Magnesium oxide and bone meal were used as chemical defluoridating agents to reduce excessive amounts of fluororide from artificial water samples which had been prepared to simulate Kenyan water samples with a fluoride concentration range of 1 – 9.3 ppm. These defluoridation procedures if utilized in rural areas will reduce the excess fluoride in borehole water to beneficial nontoxic levels. SECTION B The acid etch technique was employed on 8 "normal" American teeth, 8 "normal" Kenyan teeth, 8 moderately and 8 severely fluorosed teeth also from Kenya. The etching period ranged from 0 - 360 seconds. The enamel surface was observed in the scanning electron microscope. The ideal etching time for American normal teeth was found to be 60 seconds. The Kenyan normal teeth had an ideal etching period of 120 seconds. The fluorosed teeth had an ideal etch pattern at 180 seconds prior to grinding and 120 seconds after grinding. The predominant etch patterns were Class I and II even at etching times of 30 seconds. The enamel surface of normal American teeth appeared excessively etched at 120 seconds, normal Kenyan teeth had an apparent excessive etching of the enamel surface after 240 seconds. The fluorosed Kenyan teeth prior to grinding appeared excessively etched after 360 seconds. After grinding, there was no apparent extensive damage to the enamel surface after an etch period of 360 seconds. The brown staining of fluorosed enamel was macroscopically noted to reduce in intensity after grinding and polishing the enamel surface with a green stone and pumice. Acid etching for 150 seconds further produced a reduction in the intensity of the brown staining and improved the aesthetics. In the scanning electron microscope, the dark areas (areas of lower electron emission) macroscopically corresponded to the brown discoIored enamel in unground and unetched enamel surfaces. After grinding and without etching the dark area was reduced in size. The etched enamel had a similar changed appearance. Thus it appears that the changes in the enamel extend deeply into the enamel. “Craters" where enamel was lost were noted in a number of fluorosed teeth. The crater areas were generally poorly etched. This may be due to the inaccessibility of the area bordering the non-cratered enamel and the cratered enamel. The etch pattern in the cratered enamel had a moth-eaten appearance. The base of the crater had an ideal etch pattern class II after 360 seconds etching period. Removal of the surface enamel by grinding resulted in a surface exhibiting less discoloration and fewer craters. The etch pattern was evenly distributed after an etching period of 360 seconds. The enamel defects create a clinical problem of a possibly inadequate enamel etch which may cause clinical failure of the composite restorations. The brown staining is apparently deeply ingrained in the structure making gross grinding a destructive and inadequate way of improving the aesthetics of these teeth. Further more grinding may result in sensitivity. A combination of slight grinding approximately 1/10 mm of enamel polishing with the green stone, then applying the acid etch technique in conjunction with composite resins may greatly enhance the aesthetics. The experimental tensile bond strength tests were performed using the Instron machine and involved 120 specimens of an equal number of American, Kenyan normal and Kenyan fluorosed teeth. The mean experimental tensile bond strength for American teeth was 59. 08 [plus or minus] 15.81 Kg/cm2, Kenyan normal teeth 41.52 [plus or minus] 14. 64 Kg/cm2, and Kenyan fluorosed teeth prior to grinding 49.20 [plus or minus] 17.67 Kg/cm2. The coefficients of variation were 27 percent for normal American teeth, 35 percent for normal Kenyan teeth, 36 percent for Kenyan fluorosed teeth prior to grinding and 35 percent after grinding. There was an increase in the adhesive bond strength for fluorosed teeth after grinding and polishing with green stone and then pumice to a gloss (58.84 [plus or minus] 20. 65 Kg/cm2). The respective etching times were 60 seconds, 60 seconds, 150 seconds and 150 seconds, for American normal teeth, Kenyan normal teeth and for fluorosed teeth prior to and after grinding. The Kenyan normal teeth had a lower tensile bond strength than the American or Kenyan fluorosed teeth probably due to inadequate etching. Currently, composite materials may be employed with the acid etch technique to restore the unaesthetic teeth and the tooth morphology of fluorotic teeth. In this study, the use of the acid etch technique and composite restoration materials improved the tooth morphologγ and enhanced the aesthetics of these severely fluorosed teeth.
Includes photographs.Thesis (M.Sc.D.)--Boston University, Henry M. Goldman School of Graduate Dentistry, 1984 (Pedodontics)Bibliography : leaves 215-237.
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