Types of tooth movement, bodily or tipping, do not affect the displacement of the tooth's center of resistance but do affect the alveolar bone resorption.

OBJECTIVE: To investigate how types of tooth movement, bodily or tipping, influence the displacement of the center of resistance in teeth and alveolar bone resorption. MATERIALS AND METHODS: Ten-week-old female Wistar rats were divided into eight groups of different factors, as follows: type of movement (bodily and tipping) and force magnitude (10, 25, 50, and 100 cN). The maxillary left first molars were moved mesially with nickel-titanium coil springs for 28 days. Micro-computed tomography (micro-CT) images were taken before and after tooth movement. The position of the center of resistance was determined by using finite element models constructed from the micro-CT image. The displacement of the center of resistance and the volume of alveolar bone resorption were measured. RESULTS: The displacement of the center of resistance showed no significant difference between the bodily and tipping groups. The displacements of the center of resistance were increased with force magnitude at 10 and 25 cN, whereas they were not further increased at 50 and 100 cN. On the other hand, cervical alveolar bone resorption was significantly greater in the tipping group than in the bodily group. CONCLUSIONS: Displacement of the center of resistance was not influenced by the types of tooth movement. However, volume of cervical alveolar bone resorption was greater in the tipping movement group than in the bodily movement group.

Increasing the amount of corticotomy does not affect orthodontic tooth movement or root resorption, but accelerates alveolar bone resorption in rats.

Objectives: The purpose of this study was to evaluate the relationships among the volume of bone cut during corticotomy, amount of tooth movement, volume of root resorption, and volume of the resultant alveolar bone resorption after tooth movement. Methods: Ten-week-old female Wistar rats were distributed into the corticotomy groups and a control group that underwent sham corticotomy. Two experiments employing two different orthodontic forces (10 or 25g) and experimental periods (14 or 21 days) were performed. The volumes of the bone cut by corticotomy were 0.1, 1.0, and 1.7mm3 in the 25g groups, and 1.0 and 1.7mm3 in the 10g groups. Nickel-titanium closed-coil springs were set on the maxillary left first molars to induce mesial movement. After orthodontic tooth movement, the amount of tooth movement, volume of root resorption, and volume of alveolar bone resorption were measured. Results: Despite differences in the volume of bone cut among the different corticotomy groups, there were not significant differences in the amount of tooth movement and volume of root resorption between the control group and any of the corticotomy groups. However, higher volume of bone cut during corticotomy was significantly related to the decreased alveolar bone volume-in particular, to the reduced height of the alveolar bone crest after tooth movement. Conclusions: The volume of the alveolar bone cut during corticotomy does not affect tooth movement or root resorption in 10-week-old female Wistar rats; however, it may increase alveolar bone loss after tooth movement.

Local regulation of skin blood flow during cooling involving presynaptic P2 purinoceptors in rats.

1. This study investigated a local effect of cooling on the plantar skin blood flow (PSBF) of tetrodotoxin-treated rats by laser-Doppler flowmetry. 2. When the air temperature around the left foot was locally cooled from 25 to 10 degrees C, the PSBF of the left foot decreased. 3. The response was inhibited by the alpha-adrenoceptor antagonist phentolamine, the alpha1-adrenoceptor antagonist bunazosin, the alpha2-adrenoceptor antagonist RS79948, and bretylium and guanethidine that inhibit noradrenaline release from sympathetic nerves. Adrenalectomy of the rats did not affect the cooling-induced response. 4. The P2 purinoceptor antagonists suramin and PPADS also significantly suppressed the cooling-induced reduction of PSBF. However, the inhibitory effect of PPADS on the cooling-induced response was abolished after the treatment with phentolamine. Intra-arterial injections of ATPgammaS, a stable P2 purinoceptor agonist, at 25 degrees C caused a transient decrease in PSBF in a dose-dependent manner, which was significantly inhibited by phentolamine and guanethidine. 5. These results suggest a novel mechanism for local cooling-induced reduction of skin blood flow in vivo; moderate cooling of the skin induces the release of ATP, which stimulates presynaptic P2 purinoceptors on sympathetic nerve terminals and facilitates the release of noradrenaline, thereby causing contractions of skin blood vessels via the activation of alpha1-and alpha2-adrenoceptors.

Biphasic response of cutaneous blood flow induced by passive cutaneous anaphylaxis in rats.

In the immediate phase of passive cutaneous anaphylaxis, sensitized skin mast cells release various mediators when activated by antigen. The present study investigated the effects of the mediators on cutaneous blood flow at the antigen-antibody reaction site. Induction of passive cutaneous anaphylaxis produced a biphasic response consisting of an initial decrease, followed by a sustained increase, in the cutaneous blood flow. The initial phase was almost eliminated by the 5-hydroxytryptamine receptor antagonist methysergide, whereas the second phase was sensitive to the histamine H(2) receptor antagonist ranitidine. The histamine H(1) receptor antagonist chlorpheniramine, the denervation of sensory nerves with capsaicin, the cyclooxygenase inhibitor indomethacin, or the bradykinin B(2) receptor antagonist D-arginyl-L-arginyl-L-prolyl-trans-4-hydroxy-L-prolylglycyl-3-(2-thienyl)-L-alanyl-L-seryl-D-1,2,3,4-tetrahydro-3-isoquinolinecarbonyl-L-(2alpha,3beta,7abeta)-octahydro-1H-indole-2-carbonyl-L-arginine (HOE140) did not affect the blood-flow changes caused by the anaphylaxis. These results suggest that 5-hydroxytryptamine and histamine H(2) receptors mediate the initial decrease and the subsequent increase in cutaneous blood flow, respectively, induced by passive cutaneous anaphylaxis in rats.