Modulatory effect of fluoride and irradiation on rat molar rate of wear

The hypothesis was tested that fluoride (F-) modulates molar wear rate in the irradiated rat and that enamel solubility and dentin hardness are involved in this process. Seventy five 21 day-old rats were divided into 5 groups. Groups received either F-(25 ppm) in the drinking water or irradiation to the head (15 Gy in a single dose), or a combination of the two. The rate of occlusal wear was assessed by computerized planimetry.The amount of wear was significantly higher in the F- and irradiation monotreated rats, while under combined treatment it did nor differ significantly from the control values. Fluoridation or irradiation suppressed enamel solubility, as measured by calcium release in the etchant. Dentin microhardness, expressed in Vickers hardness number, was enhanced after either treatment, but remained unaffected when F- administration preceded irradiation. Enamel solubility and dentin microhardness did not correlate significantly with the rate of occlusal wear.L’hypothèse vérifiée dans cette recherche a été la modulation par le fluoré (F-) de l’usure des molaires du rat irradié et de l’éventuelle contribution de la solubilité de l’émail et de la dureté dentinaire dans ce processus. Soixante-dix rats âgés de 21 jours ont été divisés en 5 groupes. Les groupes ont reçu soit 25ppm F- dans l’eau de boisson, soit une dose unique d’irradiation (15 Gy) dans la sphère cranio-faciale, soit les deux traitements combinés. Le niveau d’usure occlusale des molaires a été déterminée par planimétrie computerisée.La quantité d’usure a été plus prononcée chez les animaux recevant uniquement du F- ou une irradiation tandis que les deux traitements combinés ont été suivis par des valeurs d’usure semblables a celles mesurées chez les témoins. La solubilité de l’émail, établie selon la quantité de calcium présente dans la solution corrosive et exprimée en mg/l Ca+ +, a été réduite par chacun des deux traitements. La dureté de la dentine, exprimée en unités Vickers, a été amplifiée par chaque traitement, restant toutefois inchangée uniquement chez les animaux recevant du F- avant l’irradiation. Les resultats de l’étude corrélative entre l’usure occlusale et la solubilité de l’émail ou la dureté dentinaire n’ont pas atteint des valeurs significatives

The effects of acute and chronic lithium treatment on rat submandibular salivation

OBJECTIVE: Acute and chronic actions of lithium on salivation induced by agonists associated with receptor-linked hydrolysis of membrane inositol phospholipids (carbachol and phenylephrine) and by agonist linked to activation of adenylate cyclase (isoproterenol) were investigated. MATERIAL AND METHODS: In anaesthetized rats, submandibular salivation induced by intravenous injection of carbachol, phenylephrine and isoproterenol, was measured and expressed as volume of fluid (mul) elicited per 100 mg wet weight of each gland per minute. The experiments were repeated after acute and chronic treatment of lithium (7 mg kg(-1)). The results were analysed with unpaired t-test. RESULTS: Chronic, but not acute lithium treatment significantly decreases carbachol- and phenylephrine-induced salivation while isoproterenol-induced salivation was not changed neither after acute nor after chronic administration of lithium. CONCLUSION: The results suggest that hyposalivation during chronic lithium therapy could be mediated by alterations in the phosphatidylinositol cycle and a consequent lack of inositol after agonist stimulation