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.

[Effectiveness of various procedures and instruments used in root canal treatment for reducing bacterial growth (in vitro comparison)]

In this study root canal preparation methods and instruments were compared by using forty extracted upper first bicuspids. The trepanated and extirpated teeth were sterilised in an autoclave, inoculated with Enterococcus faecalis and incubated for 24 hours at 37 degrees C. The teeth were divided into 5 groups as follows: those treated with K-file and K-file Nitiflex (step back technique, 1st, 2nd groups), with K-reamer (standard technique, 3rd group), those rinsed only with sterile saline solution (4th group), and those left untouched after incubation (5th group). Bacterial samples were taken before and after preparation and were inoculated onto special E67 plates. The plates were evaluated after 24 hours of incubation. It was concluded that the number of the bacteria could be significantly reduced with rinsing and mechanical preparation. There was no significant difference as to the efficacy of the preparation procedures or instruments applied.

[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.