The main purpose of the present study was to improve the accuracy of measurement with a laser distance transducer and measure tooth displacement under small intrusive loading. The device for tooth displacement measurement which was composed of two pairs of semiconductor laser and Position Sarnpling Detector (PSD) was applied on 5 mongrel dogs' lower left 3'd premolar (P3) as experimental sites and applied on lower left 4th premolar (P4) as reference sites. The effects on tooth position were studied by using 1-100g of loading, each load being suddenly applied, maintained for 30 seconds, and then sllddenly removed. The experirnent tooth was unloaded for 5 minutes before the application of a further load. The time between each sampling was set as O.25 second. To reduce the influence of dogs' breathing and pulse, the difference of tooth displacement between experimental and reference sites was calculated to show the "true" displacement. The room condition during measurement was maintained at 25 OC, 50 % wet and the room was remained dark to exclude the influence of environmental light on PSD. Two-stage intrusion pattern was observed in all the animals and the stages were defined as phasel and phase2. The relationship between intrusion distance and loading was evaluated by multipleregression analysis. There was an obvious correlation between intrusion distance and loading of phasel (R=O,94, p<O.05). A strong correlation was also observed between intrusion velocity and loading in phasel (R=O.92, p<O.el) but not in phase2 (R=O.61, p=O.05). The result of the present study indicated that (1) the technique used in the present study can reduce the influence of artificial motion ; (2) a significant relationship was observed between intrusion velocity and loading; (3) tooth intrusion could be observed from the loading of 1g; (4) the two-stage intrusion pattern was observed from the loading of 5-9g. (it might
[1]
K. Karita,et al.
Acute response of periodontal ligament blood flow to external force application.
,
1992,
Journal of periodontal research.
[2]
D C Picton,et al.
Tooth mobility--an update.
,
1990,
European journal of orthodontics.
[3]
P. Gaengler,et al.
Effects of force application on periodontal blood circulation. A vital microscopic study in rats.
,
1983,
Journal of periodontal research.
[4]
D A Parry,et al.
A comparison of the size distribution of collagen fibrils in connective tissues as a function of age and a possible relation between fibril size distribution and mechanical properties
,
1978,
Proceedings of the Royal Society of London. Series B. Biological Sciences.
[5]
S. Ariga.
[The furcation problem--therapy and prognosis].
,
1987,
Nihon Rinsho Shishubyo Danwakai kaishi.
[6]
T. W. Walker,et al.
Fluid pressures in the periodontal ligament of the mandibular canine tooth in dogs.
,
1978,
Archives of oral biology.