Permalink : http://hdl.handle.net/2115/68794

KEYWORDS : 微小血管;間歇力;糖尿病;矯正力;microvasculature;intermittent pressure;diabetes mellitus;orthodontic force

近年，歯科矯正治療を希望する成人，高齢者が増加しており糖尿病や糖尿病予備軍の患者が矯正治療の対象となる機会が増えている．しかし，高血糖下において矯正力による機械的刺激に対する微小血管の変化について不明な点が多い．高血糖下では血管の脆弱化が生じることから，我々はより短い荷重期間での間歇力に着目した．また，これまで正常血糖下において機械的刺激により毛細血管が毛細血管後細静脈の太さまで拡張すると新たに単球系細胞が血管外へ遊走する場となることは明らかにされている．そこで本研究では，ストレプトゾトシン（以下STZ）誘発糖尿病ハムスターを用いて，高血糖下における間歇力に対する微小血管の変化および血管構造を維持しつつ血管拡張が生じる時間条件を検討した．実験動物としてSTZ非投与ハムスター４匹（非糖尿病群）とSTZ誘発糖尿病ハムスター16匹（糖尿群）を用いた．糖尿病群は荷重を加えないcontrol群と３種類の条件で荷重を加える群の計４群（各群４匹ずつ）に分けた．間歇力として，20秒間のうち１秒間の荷重期間と19秒間の非荷重期間を繰り返す条件をT20群とし，同様の荷重期間でT40，T60群を設定した．それぞれ背側皮膚に独自に考案した任意の時間間隔で圧刺激（100 g/cm2）を付与できる荷重付与装置付きのdorsal skinfold chamberを装着し，荷重付与群の３群に間歇的荷重を与えた．各群の微小血管の変化を６日間，実体顕微鏡および蛍光顕微鏡で観察し，各群間における相違を比較し，以下の結果を得た．１．control群に比べT20群とT40群において有意に毛細血管径が増大していた．２．T20群が他群に比べ有意に出血傾向が強く，血流が停止している部分を認めた．３．T20群の毛細血管消失率が他群に比べ有意に高かった．これらより，糖尿病ハムスターにおいては，１秒間の荷重付与と39秒間の非荷重付与を繰り返す間歇的矯正力を用いることで歯周組織の血管構造を維持しつつ，毛細血管を毛細血管後細静脈の太さまで拡張させることが示唆された．
Recently, the number of adults and elderly people seeking orthodontic treatment has increased and we frequently encounter opportunities to treat patients with diabetes and of the diabetic corps. However, regarding tissue changes associated with orthodontic force to move teeth, much is still unclear about differences in the responsiveness of microvasculature to mechanical stimulus for those with hyperglycemia. In this study, we focused on intermittent pressure of shorter loading periods because the fragility of microvasculatures tends to advance in hyperglycemia. Thus far, it is clear that monocyte lineage cells are stimulated to migrate outside of blood vessels when capillaries are dilated to the width of post capillary venules by mechanical pressure in normoglycemia. However, there is no report examining microvascular changes in response to weak pressure stimulation, and in particular intermittent pressure, in hyperglycemia. The purpose of this study is to observe microvascular changes with intermittent pressure and to examine the load conditions under which sufficient vasodilation occurred with vascular structure maintained by streptozotocininduced diabetic hamsters. Non-diabetic male Syrian golden hamsters (6 weeks old) are termed “normal group” (unloading) and streptozotocin-induced diabetic hamsters (5 weeks old) are divided into “control group” (unloading) and three loading groups. The three loading groups were alternately repeated loading and unloading. The duration for loading/unloading was 1sec/19secs (T20), 1sec/39secs (T40), and 1sec/59 secs (T60). Each animal was fitted with a specially-designed, purpose-built dorsal skinfold chamber with a loading device capable of exerting an intermittent pressure of 100 g/cm2. Intermittent pressure was applied to the three loading groups. From day 1 until day 5, microvascular changes were observed with a stereoscopic microscope and a fluorescence microscope, and differences between the groups were observed with the following results. 1. Under loaded conditions, capillary diameters for the T20 and T40 groups were significantly higher than for the control group. 2. Under loaded conditions, the T20 group exhibited significantly stronger bleeding tendency than the control group. 3. Regarding disappearance rates of capillaries, the loss rate for the T20 group was significantly higher than for the other groups. The above results suggest that through the application of intermittent orthodontic force in intervals consisting of one second of pressure followed by 39 seconds of rest, it may be possible to bring about dilation of the capillaries of diabetic hamsters while their structure is maintained in periodontal tissue.