Vascular response of current and potential dental etchants

Dental resin curing blue light induces vasoconstriction through release of hydrogen peroxide

Dental resin curing blue light (BL) is frequently used during treatments in dental clinics. However, little is known about the influence of BL irradiation on pulpal blood vessels. The aim of the present study was to investigate the mechanism of effect of BL irradiation on vascular tone. Rat aorta (RA) rings were irradiated with a BL source in organ baths, and the responses were recorded isometrically. Effect of BL irradiation on phenylephrine (PE) -precontraction and acetylcholine (ACh) -induced relaxation after PE -precontraction were obtained and compared in BL -irradiated and control RA rings. Effect of 20 min preincubation with catalase (enzyme that breaks down hydrogene peroxide, 1200 u/ml) on PE -precontraced and BL-irradiated rings was also evaluated. Total oxidative stress (TOS) and total antioxidant capacity (TAC) in BL-irradiated and control RA preparations were measured with special assay kits and spectrophotometry. BL slightly decreased ACh -induced endothelium -dependent relaxations in PE (1 μM) -precontracted RA rings (n = 6, p > 0.05 vs. control). BL induced marked contraction 23.88 + 3.10% of PE (maximum contraction) in isolated RA ring segments precontracted with PE (p < 0.05 vs. control). The contractile effect of BL was inhibited by 1200 u/ml catalase (n = 6, p < 0.05 vs. control). BL irradiation increased the level of TOS in RA rings (n = 6, p < 0.05 vs. control). TAC levels were similar in BL-irradiated and control preparations. These results suggest that BL induces contraction in RA, and the mechanism of this effect may to be through release of hydrogen peroxide.

Vasorelaxant effect of resin-based, single-bottle dentin bonding systems

Single-bottle dentin bonding systems are currently in wide use. Because these materials are sometimes inadvertently placed on microscopic pulp exposures while at other times deliberately on frank exposures, their effects on pulpal soft tissues need to be evaluated. The present study assessed the vascular effects of 3M Single Bond (3MSB) and Prime & Bond NT (PBNT), using rat aortic ring preparations. It is hypothesized that these bonding agents induce relaxation of these preparations. Both 3MSB and PBNT caused endothelium-dependent and -independent relaxations in a concentration-dependent manner. The endothelium-dependent relaxation was associated with the release of nitric oxide. However, the responses to both agents did not involve the generation of prostanoids or KATP channel activation. At relatively low concentrations, the responses of endothelium-denuded tissues to 3MSB were greater than those to PBNT, indicating certain differences in the vascular action between these products. The data suggest that 3MSB and PBNT interfere with vascular function by causing vasorelaxation via mechanisms occurring in the smooth muscle and endothelium, including the release of nitric oxide. Among others, this effect may promote bleeding if these adhesives are placed on pulp exposures.

Inhibition of compound action potentials following administration of dental self-etching primer/adhesives

Self-etching dentin adhesive systems, a new generation of dental-bonding agents, were investigated for their ability to block nerve conductance in the rat sciatic nerve model. Clearfil SE Bond, Mac Bond and FL Bond were used as test materials. Isolated rat sciatic nerves obtained from female albino rats were placed between two electrodes in a bath containing Tyrode solution. The bonding agents were brought into contact with the nerves and the evoked compound action potentials were recorded versus time before and after contact with the materials. Statistical analysis was performed using the Friedman and Wilcoxon Signed-Ranks tests (P = 0.01) to compare the mean percentage of inhibition between test materials versus time. All test materials were able to block nerve transmission rapidly (3.3 +/- 0.5, 5.1 +/- 2.3 and 8.0 +/- 1.9 min for SE Bond, Mac Bond and FL Bond, respectively). Significant differences were found between FL Bond and SE and Mac Bond (P < 0.01). These results indicated that the bonded systems tested, intended primarily as dentinal tubule occluders, may also exert some direct desensitizing effect on intratubular or pulpal nerve terminals in extremely deep cavities or pulpal microexposures, contributing to decreased postoperative pain.

Measurement of in vitro phagocytic activity using functional groups carrying monodisperse poly(glycidyl methacrylate) microspheres in rat blood

Phagocytic activity of monocyte and neutrophil leukocytes in rat blood was investigated using monodisperse poly(glycidyl methacrylate) (poly(GMA)) microspheres. Interactions of monocyte and neutrophil leukocytes with plain poly(GMA), charged poly(GMA)-NH2 and biomodified poly(GMA) (poly(GMA)-albumin and opsonized poly(GMA)) was studied as a function of time. Here we report the cellular phagocytosis rate of particles and the total internalised particle amount. Phagocytes showed higher phagocytic activity for poly(GMA) microspheres carrying functional groups versus plain poly(GMA) particles. Phagocytic activity was the highest for opsonized poly(GMA) microspheres (P < 0.05).

Cardiovascular Effects and Efficacy of a Hemostatic Agent in Periradicular Surgery

The purpose of this study was to evaluate the hemostatic efficacy and systemic cardiovascular effects of CollaCote collagen sponges saturated with 2.25% racemic epinephrine during endodontic surgery. A total of 48 patients participated in the study. Patients received CollaCote-saline or CollaCote-epinephrine placed in the bony crypt, after which hemostatic efficacy was evaluated. Blood pressure and pulse rate was recorded before and after administration of the local anesthetic, after the application of the test solutions, and before the patient's dismissal. Results showed no significant difference in blood pressure or pulse rate between the experimental and control groups. In the CollaCote-saline group, five of six cases failed to achieve hemorrhage control. In the CollaCote-epinephrine group, 1 of 42 cases had no hemorrhage control. Two patients had slight but apparent intermittent bleeding. Complete hemostasis was achieved in 39 of 42 cases. In conclusion, the results suggest that CollaCote collagen sponges saturated with 2.25% racemic epinephrine provide excellent hemostasis with no evident changes in blood pressure or pulse rate.

Vascular response to titanium dioxide: A study on the rat carotid artery

The purpose of this study was to explore the effects of titanium dioxide (TiO(2)) on vascular smooth muscle contractility with the use of the rat carotid-artery model. TiO(2) powder was implanted on right carotid arteries of five albino rats, the left arteries of which were left intact and served as controls. Fourteen days after placement, bilateral carotid arteries were removed and contraction/relaxation of isolated vessel rings were measured for dose-dependent epinephrine and acetylcholine administrations by a force displacement transducer. The data of each tissue specimen were collected with the use of a computerized system and corresponding software at a sample rate of 1000 kHz, and were expressed as contraction force. Contraction forces of control and TiO(2)-implanted vessel rings were similar (P > 0.05). TiO(2) does not appear to have adverse effects on vascular contractility.

Influence of a self-etching primer on compound nerve action potentials

The aim of this study was to evaluate the effect of self-etching primers on nerve conductance. A self-etching primer (One Up Bond F) which combines etching and bonding in one step, and a fifth-generation bonding agent (Prime&Bond NT ) were tested. Isolated rat sciatic nerves were placed between two platinum electrodes in a bath containing Tyrode solution. The bonding agents were brought into contact with the nerves and the evoked compound action potentials (CAP) were recorded before and after contact with the materials. One Up Bond F caused total inhibition of the CAP within an average time of 7 min. All CAPs in this group were blocked irreversibly. As with Prime&Bond NT, the reduction in CAP was 45.9% after an application time of 15 min, after which readings were terminated. Recovery of the CAP in this group were maintained after rinsing with fresh tyrode solution. One Up Bond F elicited faster blocking of nerve conductance under the conditions of this model. In the context of dentin desensitization with bonding agents, the self-etching primer may be more effective, clinically.