关键词: 微种植钉, 磨牙压低, MMP-2

Abstract: PURPOSE: To observe the expression of MMP-2 in the periodontal tissues of molars in Beagle dogs after different times of intrusion by miniscrew with cyclic intrusive force. METHODS: Three mature Beagle dogs were used for the experiment. On the buccal and palatal sites of the left maxillary second and third premolars, a miniscrew was placed at the interradicular septa separately, intruding the tooth with 150 g initial force, which would be reinforced every 4 weeks. The teeth of left side as the experimental group were divided into 3 subgroups, as being intruded 12, 24 and 36 weeks, and the right side as blank control. Then the dogs were sacrificed, and the second and the third premolars with the surrounding periodontal tissue were cut down, fixed, decalcified, wrapped and cut into slices. Immunohistochemical staining with MMP-2 was performed. The average optical density (OD) of MMP-2 was calculated with IPP software, which represented the expression of MMP-2. SPSS 17.0 software package was used for statistical analysis. RESULTS: Immunohistochemical staining revealed that the expression of MMP-2 in control group was low. After tooth intrusion, MMP-2 expression significantly increased in the periodontal tissues of molars, and reached the maximum in the group of 24 weeks. Then MMP-2 expression decreased in the 36-week group but still significantly higher than the control group. There was no significant difference among the 3 subgroups for different intrusion times(P>0.05). CONCLUSIONS: MMP-2 participates in remodeling of the periodontal tissue during tooth intrusion. The expression of MMP-2 is not significantly increased with the extension of the intrusion time with cyclic intrusive force, which suggests that with the use of miniscrew to intrude the molars with cyclic intrusive force, the periodontal tissues of the intruded tooth maintain dynamic balance of bone remodeling.

Key words: Miniscrew, Intruding posterior tooth, MMP-2