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 biologicall y active and may have deleterious effects on the pulpal microcirculation. N o data are available on the immediate vascular effect of etching materials applied on a constant thin pulpal dentin. In this study the authors examine d whether the application of 36% phosphoric acid (Conditioner 36, 15 second s) or itakonic acid with 10% maleic acid (NRC Non-Rinse Conditioner, 20 sec onds), as recommended by the manufacturers, alters the blood circulation in the pulp of the rat's lower incisors. The effect of pro-longed etching tim e (60 seconds) was also assessed (Conditioner 36). The application of salin e served as the untreated control. The technique of vitalmicroscopy was use d on the first lower incisor of 40 (10-10 in each group) male Sprague-Dawle y rats (weighing 350 +/- 8g SE) to record the changes in vessel diameter pr ior to and at 5, 15, 30 and 60 minutes after the test materials were admini stered on the dentin. In the control rats, the vessel diameter was stable d uring the entire experiment. Acid conditioning as recommended by the manufa cturers tended to cause vasodilatation, though these alterations were stati stically not significant when compared to the control group (ANOVA p >0.05) . After prolonged etching time (Conditioner 36, 60 seconds) significant vas oconstriction (-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 pul pal blood circulation in 40% of rats (Cochran's-Q test, p <0.05), gas-bubbl e formation was observed in 30% and the disappearance of the pulpal wall oc curred in 20%. These results suggest that exposition time with acid is cruc ial to the pulpal microcirculation. That is, acid conditioning applied as i ndicated (for 15-20 seconds) onto a very thin layer of dentin only slightly affects the blood supply to the dental pulp; however, prolonged etching ti me (for 60 seconds) results in immediate failure of microcirculation in the dental pulp of rats.