In vitro staining effects of stannous fluoride and sodium fluoride on ceramic material.

STATEMENT OF PROBLEM: Long-term fluoride application on the teeth of patients receiving radiation therapy for head and neck tumors results in excessive staining and roughening of ceramic restorations. PURPOSE: The purpose of this in vitro study was to compare the staining effects of 2 fluoride treatments on ceramic disks by simulating 1 year of clinical exposure at 10 minutes per day. In addition, 2 different surface preparations were tested. MATERIAL AND METHODS: Eighty ceramic disks (IPS Empress), 20 x 2 mm, were fabricated. Half of the disks were glazed, and the remaining disks were polished. All disks were brushed for 3 minutes with a soft-bristle power toothbrush and mild dentifrice (baseline) and were immersed in 1 of the 2 fluoride products (0.4% SnF(2), Gel-Kam Gel, or 1.1% NaF, Prevident 5000) for 10 days (n=20). Means and standard deviations of color change (Delta E), surface roughness (Ra, um), and surface gloss (GU) of the ceramic material were measured with a reflection spectrophotometer, a profilometer, and a gloss meter, respectively, at baseline and after fluoride treatment. Two- and 3-way ANOVA (alpha=.05), with surface preparation (polished vs. glazed) and fluoride treatment (0.4% SnF(2) or 1.1% NaF) as independent variables and condition (baseline vs. after fluoride treatment) as a repeated measure, was used to analyze the data. Fisher's PLSD intervals (alpha=.05) were calculated for comparisons among the means. RESULTS: The polished specimens had significantly higher Delta E values, significantly higher surface gloss values, and significantly lower surface roughness values than the glazed specimens before fluoride treatment (P<.001). After both fluoride treatments, ceramic disks exhibited significantly higher surface roughness values when polished and significantly lower surface gloss values when glazed or polished (P<.001). The glazed specimens presented significantly higher surface roughness (P<.001) and lower surface gloss values (P<.001) when treated with 0.4% SnF(2) as compared to NaF. For the polished specimens, there was no significant difference in surface roughness and surface gloss values between the 2 fluoride treatments. CONCLUSIONS: Use of 0.4% SnF(2) and 1.1% NaF gels, in vitro, caused significant color change in the polished IPS Empress ceramic disks. Polishing of the ceramic surface before immersion in either fluoride agent caused the ceramic tested to be more resistant to etching by the 2 solutions tested. The NaF caused less deterioration of the porcelain surface and was less stain inducing than SnF(2).

ANALYSIS OF SEROTONERGIC MODULATION OF NEURONS INVOLVED IN TWO DEFENSIVE BEHAVIORS IN APLYSIA CALIFORNICA (CYCLIC-AMP, AROUSAL, CALCIUM, POTASSIUM)

Sensitization is a simple form of learning which refers to an enhancement of a behavioral response resulting from an exposure to a novel stimulus. While sensitization is found throughout the animal world, little is known regarding the underlying neural mechanisms. By taking advantage of the simple nervous system of the marine mollusc Aplysia, I have begun to examine the cellular and molecular mechanisms underlying this simple form of learning. In an attempt to determine the generality of the mechanisms of neuromodulation underlying sensitization, I have investigated and compared the modulation of neurons involved in two defensive behaviors in Aplysia, the defensive inking response and defensive tail withdrawal.^ The motor neurons that produce the defensive release of ink receive a slow decreased conductance excitatory postsynaptic potential (EPSP) in response to sensitizing stimuli. Using electrophysiological techniques, it was found that serotonin (5-HT) mimicked the physiologically produced slow EPSP. 5-HT produced its response through a reduction in a voltage-independent conductance to K('+). The 5-HT sensitive K('+) conductance of the ink motor neurons was separate from the fast K('+), delayed K('+), and Ca('2+)-activated K('+) conductances found in these and other molluscan neurons. 5-HT was shown to produce a decrease in K('+) conductance in the ink motor neurons through an elevation of cellular cAMP.^ The mechanosensory neurons that participate in the defensive tail withdrawal response are also modulated by sensitizing stimuli through the action of 5-HT. Using electrophysiological techniques, it was found that 5-HT modulated the tail sensory neurons through a reduction in a voltage-dependent conductance to K('+). The serotonin-sensitive K('+) conductance was found to be largely a Ca('2+)-activated K('+) conductance. Much like the ink motor neurons, 5-HT produced its modulation through an elevation of cellular cAMP. While the actual K('+) conductance modulated by 5-HT in these two classes of neurons differs, the following generalizations can be made: (1) the effects of sensitizing stimuli are mimicked by 5-HT, (2) 5-HT produces its effect through an elevation of cellular cAMP, and (3) the conductance to K('+) is modulated by 5-HT. ^

The relationship between calcium and fluoride intake, pregnancy and lactation and the risk of height loss in white women

This study was designed to investigate the effect of calcium and fluoride intake, and parity and lactation on the risk of spinal osteoporosis. Height loss was used as a surrogate measure for spinal fractures by taking advantage of documented changes in height found during the 25-year follow-up of the Charleston Heart Study cohort. Women who had lost 2-4" in height or who had no change in height during the follow-up period were defined as case and comparison subjects respectively. Calcium intake when the subjects were "about 25" and in the recent past, average intake of fluoride over 25 years, and parity and history of breastfeeding were ascertained by questionnaire from 54 case and 77 comparison subjects. Low calcium intake in the past decreased the risk of height loss (age-adjusted OR = 0.3, 95%CI: 0.1-0.96) although several potentially important confounding variables could not be adjusted for. There was no association between risk of height loss and present calcium intake (OR = 0.8, 95%CI: 0.3-2.6 for low versus high intake) after adjustment for past calcium intake. High fluoride intake decreased the risk of height loss (adjusted OR = 0.4, 95%CI: 0.1-1.2). The effect of fluoride or calcium intake in the present was modified by the level of the other nutrient. Compared to a low intake of both calcium and fluoride, a high intake of one increased the risk of height loss (crude OR = 3.3 for high fluoride/low calcium, crude OR = 6.0 for high calcium/low fluoride) although a high intake of both was slightly protective (crude OR = 0.7). It is estimated that a "high" nutrient intake in this population was greater than 850mg/day for calcium and 2mg/day for fluoride. After adjustment for age, increasing parity decreased the risk of height loss in women who had never breastfed (OR = 0.2, 95%CI: 0.01-1.7 for 4 or more children). Women who had breastfed were also at lower risk of height loss than nulliparous women (OR = 0.3, 95%CI: 0.1-1.2 for 4 or more children) although at any level of parity, breastfeeding women had a greater risk of height loss than did non-breastfeeding women. ^