Changes in blood circulation in teeth and supporting tissues incident to experimental tooth movement.

Fluorescent microspheres (FM) were used to semi-quantify the effect of orthodontic forces on blood flow in oral tissues in young rats. Forty-five animals had an orthodontic appliance inserted on the first maxillary molar on one side exerting a mesial force of approximately 50 g. Ten animals served as unoperated controls. On days 1, 3, 7, 14, and 21 after the start of the experiment, FM were injected into the left ventricle through an abdominal approach in the experimental and control animals. FM were counted in serial sections from the jaws in the periodontal ligament, pulp, and alveolar bone in a fluorescent microscope. The number of FM per tissue volume and/or tissue weight was taken as a measure of blood flow. The experimental side had significantly lower numbers of FM/mm3 in the periodontal ligament of the first and the second molar on the first day, compared with the contralateral side. However, a steady, significant increase in the number of FM/mm3 in the periodontal and pulpal tissues, and FM/mg in the alveolar bone could be observed on the third and seventh days on the experimental side of the first, second, and third molars compared with the contralateral side, while in the later stages the values of the two sides approached each other. The results of this study indicate that a localized experimental tooth movement initiates a more generalized blood flow response in the periodontal ligament, dental pulp and alveolar bone.

[Is routine microscopy of tissue from induced abortions necessary?]. / Er rutinemaessig mikroskopi af vaev fra provokerede aborter nødvendig?

This study was performed in order to evaluate the importance of routine microscopy of tissue from legal abortions performed before the end of the 12th week of pregnancy. The tissues recovered from 580 abortions were examined carefully macroscopically before they were sent to microscopy. Five hundred and fifty-four samples (95.5%) were judged by macroscopic examination to contain the normal products of pregnancy. These all contained chorionic villi when examined histologically. Macroscopic examination was inconclusive in the remaining 26 samples (4.5%), 22 of these samples proved after all to contain chorionic villi when examined histologically. We conclude that histological examination of tissue from legal abortions is unnecessary in most cases if it is replaced by careful clinical examination of the sample, only to be followed by microscopy if the findings are uncertain.

Effect of experimental traumatic occlusion on blood flow in the temporomandibular joint of the rat.

Fluorescent microspheres (FM) were used to visualize and semi-quantify blood flow in the temporomandibular joint (TMJ) during experimental unilateral traumatic occlusion of the maxillary and mandibular molar teeth in 30 young rats. At different postoperative observation periods varying from 1 to 30 days FM were injected systemically, and the number of FM were counted in serial sections from the TMJ in a fluorescent microscope. Blood flow was related to the number of FM found in the fibrous connective tissue and bony condyle of the TMJ. A percentage increase in blood flow was found at 15 to 20 days on the experimental side, compared with the contralateral side. Furthermore, there was an increase in blood flow in both TMJs in the experimental animals compared with an unoperated control material of 10 animals. The study thus indicates that a local unilateral occlusal trauma initiates blood flow responses not only unilaterally but also in the TMJ on both sides in rats.

Increased pressure in venous sinusoids during decongestion of rat nasal mucosa induced by adrenergic agonists.

The haemodynamic effects of sympathetic agonists causing decongestion of the nasal mucosa have been investigated in rats. Access to mucosa was obtained from the dorsal side through a small cavity drilled in the nasal bone. The pressures in the venous sinusoids and in the interstitial fluid of nasal mucosa were recorded by micropuncture technique. The local red cell flux (LDF) was monitored by laser Doppler flowmetry, and the blood volume in the mucosa was measured by radio-labelled erythrocytes and albumin. In control rats the tissue blood volume was 0.25 +/- 0.03 g (g wet wt)-1. The interstitial fluid pressure (IFP) was 2.4 +/- 0.6 mmHg and the average blood pressure in venous sinusoids (Ps) was 12.8 +/- 2.7 mmHg. After topical application of noradrenaline (NA) the local blood volume was reduced to 0.12 +/- 0.03 g g-1. Ps was increased to 18.0 +/- 4.0 mmHg, whereas IFP was maintained and LDF was reduced to 40.4% of control, indicating a greater rise in post than in presinusoid vascular resistance. Blocking of both alpha 1 and alpha 2-receptors by phentolamine caused a rise in mucosa blood volume and in LDF by 16 and 20% of control, respectively. Ps increased significantly to 15.2 +/- 3.3 mmHg. Specific stimulation or blocking of alpha 1-receptors by phenylephrine or prazosin induced similar or slightly smaller vascular responses than NA or phentolamine. The effects of the specific alpha 2-agonist (clonidine) or antagonist (yohimbine) on rat mucosa were small, indicating a domination of the alpha 1-receptors. Thus, application of NA caused a rise in blood pressure in the venous sinusoids of nasal mucosa. As LDF fell simultaneously, the reduced blood volume must be due to an increased tone in the muscular wall of venous sinusoids.

Safety and tolerability of iodixanol in healthy volunteers with reference to two monomeric X-ray contrast media.

The low osmolar, non-ionic X-ray contrast media have shown a lower frequency of adverse events than the older ionic ones. In this study changes in routine clinical-chemical parameters in blood and urine, vital signs and adverse events were recorded in six groups of 10 healthy male volunteers receiving either iodixanol, a new non-ionic, dimeric X-ray contrast medium for general vascular use, or one of the two non-ionic, monomeric contrast media iopentol and iopamidol. Minor decreases were observed in the values for haemoglobin, haematocrit and erythrocytes 5 min and 3 days after injection of iodixanol. A minor increase was seen in platelets and total protein after 3 days. A transient increase in serum osmolality was seen 5 min after the injections of iopentol and iopamidol. This was not seen in any iodixanol group. The level of thyrotropin showed an increase in all groups at 3 days. It was back to normal within 21 days. No changes of clinical importance were seen regarding blood pressure, heart rate or ECG in any volunteer. No severe adverse events were reported. All events were of short duration, and of mild or moderate intensity. The results, however, may indicate a lower frequency of adverse events/discomfort after the administration of the dimeric iodixanol than the 2 monomeric contrast media iopentol and iopamidol.

Effect of experimental traumatic occlusion on periodontal and pulpal blood flow.

Fluorescent microspheres (FM) were used to visualize and semi-quantify flood flow in the periodontal ligament (PDL) and dental pulp during experimental traumatic occlusion of the maxillary and mandibular molar teeth in young rats. At different observation points FM were injected systemically, and the number of FM was counted in serial sections from the jaws in the PDL and pulp of the molar teeth in a fluorescent microscope. Blood flow was related to the number of FM in the tissues and in a reference blood sample. In the early stages an increase in blood flow in the PDL and dental pulp was found on the experimental side compared with the contralateral side. Furthermore, there was an increase in blood flow on both sides of the jaws compared with an unoperated control material. The study thus indicates that a local unilateral occlusal trauma initiates blood flow responses in the total molar dentition in rats.

Micropuncture measurements of interstitial fluid pressure in the rat periodontal ligament.

The interstitial fluid pressure (IFP) or so-called tissue pressure in the periodontal ligament (PDL) has been suggested to play a role in tooth position and affect periodontal blood flow. However, few investigators have actually measured the tissue pressure in the PDL and measurements in the PDL of rat continuously erupting incisors are lacking. The present study was aimed to develop the micropuncture technique for measurements of IFP in the PDL. The PDL of rat incisors was exposed by partial removal of the crown, the coronal pulp was removed. Viewed through a stereomicroscope, a cavity was drilled until the vessels of the PDL were visible through a thin layer (20 microns) of root cement. The cavity was covered with saline and the PDL punctured with glass micropipettes, diameter 2-6 microns, through tiny cracks of the root cement. The periodontal tissue pressure (IFP) was measured by connecting the micropipette to a servocontrolled counter-pressure pump system (Wiederhielm 1964). Mean IFP in 22 Sprague-Dawley rats was 15.2(SD +/- 3.6) mmHg and simultaneously measured systemic arterial pressure (PA) averaged 125 mmHg. Intravenous administration of an antiflogisticum, indomethacin (15 rats), did not change IFP significantly (mean 14.3, SD +/- 4.2 mmHg). Increased blood volume in the PDL, induced by bilateral clamping of the jugular veins, resulted in an immediate rise in IFP, whereas reduced blood volume due to cardiac arrest arrest resulted in an abrupt fall in IFP, indicating low compliance in the rat PDL. It is concluded that the measurements with the present micropuncture technique are relatively atraumatic and thus it seems to be a reliable method for recordings of IFP in the PDL.