[Removable appliance and closed of central incisors: report of 48 cases].

PURPOSE: To evaluate the treatment effect of orthodontic traction on embedded and inverted maxillary bending central incisors. METHODS: Fifty-two embedded and inverted maxillary central incisors without-eruption ability in 48 cases were treated by combined orthodontic traction with surgical treatment after spiral CT positioning and expanding the space, the eruption situation, gingival-breaking time and teeth pulp vitality after treatment were recorded, and the treatment effect was evaluated. RESULTS: Forty-eight cases with 52 impacted upper central incisors were treated with surgical and closed orthodontic traction, successful results were achieved in 36 cases, accounting for 69.23%; 15 cases had improvement, accounting for 28.85%; 1 case failed, accounting for 1.9%. Pulp vitality tests were all normal and there was no root absorption and ankylosis. CONCLUSIONS: Selecting appropriate cases, precise positioning with spiral CT, proper space expanding and rational application of removable traction appliance are the keys to successful treatment of impacted and inverted maxillary bending central incisors of children in mixed dentition.

[Expression of MMPs in gingival crevicular fluid of the rats in different age groups with orthodontic appliances].

PURPOSE: To detect the changes of MMP-1 and MMP-9 in gingival crevicular fluid (GCF) of the rats in different age groups with orthodontic appliances. METHODS: 40 female Wistar rats were selected as the animal model, in which there were 20 6-week-old rats and 20 12-week-old rats. The orthodontic appliances were fixed onto the maxilla of the rats after general anesthesia. The maxillary first molar in the experimental side was drawn medially by applying an excess force of 50 g, with both of the maxillary central incisors as anchorage. In the control side, the maxillary first molar was winded around the dental cervix with ligature wire. The GCF was collected every week, and MMP-1 and MMP-9 were assayed in quantitation by SDS-PAGE, Western blot and Gel Doc quantitative analysis system,respectively. The data were analyzed for ANOVA using SPSS11.0 software package. RESULTS: No statistical difference of the original concentration of MMP-1 and MMP-9 in GCF was found between adolescent group and adult group (P>0.05), but the adult group's contents were a little more than adolescent group's, and is the same as the 1st week's content. The concentration of MMPs in adult group changed more greatly than that in adolescent group. At the beginning of the experiment, the MMPs' increasing speed of adult group was higher than that of adolescent group. But at the end, the rate of descent of adult group was lower than that of adolescent group. CONCLUSIONS: The expression of MMPs in gingival crevicular fluid of adult rats is higher than that of adolescent rats. It may be more serious of the orthodontic root resorption in adult rats than in adolescent rats. Supported by Shandong Provincial Natural Science Foundation (Grant No.Y2007C023) and Jinan Science and Technology Development Plan (Grant No.200705089-9).