The effect of local nitric oxide synthase inhibition on the diameter of pulpal arteriole in dental bond material-induced vasodilation in rat

Local application of dental bond materials can cause pulpal vasodilation and hyperemia. Such local hemodynamic changes may be mediated by alterations in the levels of locally generated nitric oxide (NO). In different species systemic administration of NO synthase inhibitors leads to a decrease in pulpal blood flow. In contrast, the local administration of these inhibitors has not been tested yet. Therefore, the effect of locally blocked NO synthase on the internal diameter of rat pulpal arterioles under basal conditions and immediately after dental bond material application was studied by using vitalmicroscopic technique. The NO synthase blocker (L-NAME) was locally administered on a thinned dentine layer of the left lower incisor. L-NAME reduced the diameter of the pulpal arteriole both in basal and after bond material-induced hyperaemic conditions. These data suggest that the local formation of NO may have a significant role in the acute vasodilation induced by bond material application and also in maintenance of basal pulpal arteriolar tone.

Comparative analysis of pulpal circulatory reaction to an acetone-containing and an acetone-free bonding agent as measured by vitalmicroscopy

Despite great progress in the production of new dental polymers, application of these products is still controversial. The unlined utilization of cytotoxic adhesive materials on pulpal dentin can adversely influence the pulp, leading to alterations in local microcirculation that can be an early sign of pathological changes. In a previous study by the authors, the effect of an acetone-free bondmaterial was examined on the vascular diameter of pulpal vessels by means of vitalmicroscopy. In this study, experiments comparing experimental data provided by an acetone-containing bondmaterial to these earlier findings with acetone-free ones have been performed. Thirty male Sprague-Dawley rats (weighing 333+/-9 g) were used for this investigation. The first lower incisor was prepared for vitalmicroscopy. Changes in vessel diameter were recorded prior to and 5, 15, 30 and 60 minutes after the investigated materials (Scotchbond Multi-Purpose Dental Adhesive System or Prime & Bond 2.1) were administered on dentin as recommended by the manufacturer. In control rats (saline administration), the vessel diameter was stable during the experiment. In the presence of acetone-free bondmaterial (Scotchbond), the vessel diameter was increased during the experimental period in relation to the baseline (12.15+/-2.85%; 16.36+/-2.39%; 14.16+/-3.48%; 12.12+/-3.72%). In the presence of acetone-containing bondmaterial (Prime & Bond 2.1), a similar result was observed (10.56+/-2.27%; 16.13+/-2.94%; 17.88+/-2.54%; 14.54+/-3.16%). The differences between the control values and those registered with test groups were significant (p<0.05; ANOVA). There was no significant difference among the test groups. The results of this study suggest that dental bond materials applied on a very thin layer of dentin may affect the blood supply to the dental pulp. However, no stasis or prestasis has been detected, indicating a possible reversible effect. The authors could not show any statistical difference between the vasodilatation caused by the acetone-containing and the acetone-free bond material.

[Acute effect of calcium hydroxide-containing material in the rat's dental pulp microcirculation]

Experimental stimulation and clinical procedures applied on the crown of the tooth cause vascular reaction in the dental pulp. Laser-Doppler flowmetry is a good method for determining the blood flow of the dental pulp. The aim of these experiments was to study the acute effect of a calcium hydroxide-containing pulp-capping material (Dycal, DeTrey) on blood flow of the dental pulp after the application into a deep test-cavity. Two groups of male Sprague-Dawley rats (308 g +/- 50 S.E.) were used: control- and test-group, n = 10. A standardised deep class five cavity was prepared in the left lower incisor of each rat. Laser-Doppler flowmeter was used to measure the vascular reaction of the pulp. The levels of blood flow were recorded prior to (0 min.) and after the application (1, 5, 15, 30, 60 min.) of Dycal. Results were evaluated with one-way ANOVA. Significantly higher pulpal blood flow was found only in the first minute after the application of Dycal. In any other time no significant difference was found between the results before and after (5, 15, 30, 60 min.) the application in test- and control-group.

The effect of acid etching on vascular diameter of pulp-vessels in rat incisor (vitalmicroscopic study)

Conditioning agents used on dentin with composite materials are biologically active and may have deleterious effects on the pulpal microcirculation. No data are available on the immediate vascular effect of etching materials applied on a constant thin pulpal dentin. In this study the authors examined whether the application of 36% phosphoric acid (Conditioner 36, 15 seconds) or itakonic acid with 10% maleic acid (NRC Non-Rinse Conditioner, 20 seconds), as recommended by the manufacturers, alters the blood circulation in the pulp of the rat's lower incisors. The effect of prolonged etching time (60 seconds) was also assessed (Conditioner 36). The application of saline served as the untreated control. The technique of vitalmicroscopy was used on the first lower incisor of 40 (10-10 in each group) male Sprague-Dawley rats (weighing 350 +/- 8 g SE) to record the changes in vessel diameter prior to and at 5, 15, 30 and 60 minutes after the test materials were administered on the dentin. In the control rats, the vessel diameter was stable during the entire experiment. Acid conditioning as recommended by the manufacturers tended to cause vasodilatation, though these alterations were statistically not significant when compared to the control group (ANOVA, p > 0.05). After prolonged etching time (Conditioner 36, 60 seconds) significant vasoconstriction (-14.4 +/- 6.13; -10.59 +/- 4.2; -11.96 +/- 6.75; -5.49 +/- 5.78%) was observed (ANOVA, p < 0.05). In this group, stasis developed in pulpal blood circulation in 40% of rats (Cochran's-Q test, p < 0.05), gas-bubble formation was observed in 30% and the disappearance of the pulpal wall occurred in 20%. These results suggest that exposition time with acid is crucial to the pulpal microcirculation. That is, acid conditioning applied as indicated (for 15-20 seconds) onto a very thin layer of dentin only slightly affects the blood supply to the dental pulp; however, prolonged etching time (for 60 seconds) results in immediate failure of microcirculation in the dental pulp of rats.

In vivo examination of the Scotchbond Multi-Purpose Dental Adhesive System in rat (vitalmicroscopic study)

No data are available on the direct acute vascular effect of dental bonding materials on the dental pulp. This study investigated the effects of the components of a composite resin-bonding system on pulpal vascular diameter. Three groups of 10 male Sprague-Dawley rats (weighing 330 +/- 51 g) were used for this investigation. The first lower incisor of the rats was prepared for vitalmicroscopy. Changes in vessel diameter were recorded prior to, and at 5, 15, 30 and 60 minutes after the bonding agents (with/without etching) or saline (control) were administered on dentin as recommended by the manufacturer. In control rats, the vessel diameter was elevated slightly (2.96 +/- 4.08%) during the whole experiment. However, in the presence of bonding materials, an enhancement of 12.58 +/- 7.1% without etching and 13.11 +/- 8.6% with acid etching was registered as the increase in vascular diameter. There were significant (p < 0.05) differences between the control group and those treated with bonding agent components. Results suggested that resin composite bonding agents applied to a thin layer of dentin have an acute vasodilating effect on the dental pulp. The clinical significance of this vascular alteration in the dental pulp requires further study.

[Effect of conditioning on the circulation of rat teeth]

Materials employed in "adhesive filling technique" often lack informative instructions concerning the depth of cavities which require lining. Etching-materials directly placed on the dentin can adversely influence the pulp leading to changes in local microcirculation which can be an early sign of the pathological changes in the pulp. Therefore, it is worth examining the effect of these materials on the diameters of pulpal vessels. In the present study we examined wether acid etching (test1: 15 s and test2: 60 s) alters the blood circulation of the pulp lower incisors, by applying it directly onto a thin layer of pulpal wall (40-50 microns) without any liner, and following the instructions provided by the manufacturer. Twenty male Sprague-Dawley rats (weighing 330 +/- 51 g) and the technique of vitalmicroscopy was used for this investigation. The left lower incisors of the rats were prepared for vitalmicroscopy. Changes in vessel diameter were recorded prior to and 5, 15, 30 and 60 minutes after investigated materials or saline (control) were administered on dentin. In control and test1 group the vessel diameter was unchanged during the experiment. However, in group test2 an intense vasoconstriction was registered. There were significant (p > 0.05, ANOVA) differences in diameter changes between the control group and those treated with acid etching for 60s. Our results suggest that extended etching time may affect the circulatory system in the dental pulp, when applied onto very thin layer of dentin.

[Comparison of the effect of acetone-containing and acetone-less bonding materials on dental pulp blood vessels in rats]

No data are available on the direct acute vascular effect of dental bond materials in the dental pulp. The purpose of the present study was to investigate the effect of composite resin bonding systems on the pulpal vascular diameter. Three groups of male Sprague-Dawley rats (weighing 300-490 g), each of 10 animals were used for this investigation. The left lower incisor of the rats was prepared for vitalmicroscopy. Changes in vessel diameter were recorded prior to; and 5, 15, 30, 60 minutes after the application of saline (control) or the bonding agents (test1: acetone containing--/Prime/Bond2.1, DeTrey/; test2: acetone free /Scotchbond Multi-Purpose Adhesive System, 3M/ bond material) on pulpal dentin as recommended by the manufacturer. In control rats, the vessel diameter was stable during the experiment. However, in the presence of bonding materials an enhancement was registered in vascular diameter (p < 0.05). The bond materials applied directly onto a very thin layer of dentin show acute vasodilating effect on the rat pulpal microvessels, but no stasis or prestasis has been detected, indicating a possible reversible effect. We could not show any statistical difference between the vasodilatation caused by the acetone containing and the acetone free bonding material.

[Clinical analysis of the sodium-fluoride and sodium-monofluorophosphate content of Colgate toothpaste]

After six weeks use of Colgate toothpaste (1000 ppm MFP and 450 ppm NaF) in case of 50 individuals (25 test and 25 control persons) both the Plaque Index of Silness and Löe and the modified Sulcus Bleeding Index--"bleeding on probing" (Mühlemann and Son) mean values showed a significant decrease. According to the results of cytological testing the effect of toothpaste containing MFP and NaF proved favourable. The investigation of the ionisable plaque fluoride content produced statistically significant rise in plaque fluoride content.

[Possibilities of testing the biological acceptability of composite filling materials, with special reference to the microscopic test for pulp vitality. Review of the literature]

The main problem of microscopically observing the living pulpa consists in that it lies embedded into hard tissue. The haemodynamics of the pulpa may be defined by studying the physical parameters by examining the characteristics of blood flow and by the factors determining them. By comparison with other tissues little work is dealing with regulating the blood flow. The vital microscopic model of the rat incisor pulpa was first employed by Gängler to testing dental filling materials. The results thereof well complete the findings of standardized tests. On basis of the foregoing the sublining in case of clinical employment of composite filling materials is unconditionally suggested.

[The effect of composite filling materials on the diameter of the blood vessels of the dental pulp in rat teeth]

The authors tested the effect of some of the characteristic types of composite filling materials in a vital-microscope test. The results show that all the four tested filling materials (Biogloss, Evicrol, Isomolar, Isopast) significantly widened the pulpal arteriola; the Biogloss was ineffective for the diameter of the venula, but employing Evicrol, Isomolar and Isopast it was significantly increased. Between the tested materials compared to each difference was observed only during the development of their effect. The hyperaemia observed by us is important in case of short-time inspections as the indicator of acute reactions. Further test is required whether is there any connection between the tested hyperaemia and the toxic effect.

Collaborative WHO xylitol field studies in Hungary. III. Longitudinal counts of lactobacilli and yeasts in saliva

The levels of salivary lactobacilli and yeasts were determined annually in half of the subjects of the xylitol (X) and fluoride (F) groups of a 3-year caries study. These measurements were carried out with Dentocult (DC) and Oricult (OC) dip-slide methods. A high level of lactobacilli prevailed throughout the study in these subjects. Significant changes were registered in some subgroups--that is, improvement in one of the X institutions and worsening in one of the F and one of the X institutions. At base line the counts of OC were worse in the X than in the F group. In the total material some improvement occurred during the course of the study, mainly in the X group. The changes associated with the preventive program should also be considered as related to the improvement in oral hygiene, restorative treatment, and the mere study effect.