The Effect Of Mini-implants Without Force On The Dento-alveolar Development On Young Dogs

Objective: An experiment was carried out to study whether mini-implants have effects on growing dogs. Methods:For this purpose 6 pre-molars (lower P1,P2,P3) and 2 molar (lower M3) were extracted from each of the 6 mongrel (8~9m, 7~10kg). While the area of extraction was healing (8 weeks), 42 mini-implants were surgically placed, each dog with 7 mini-implants. In the edentulous mandibular C—P4 area 2 mini-implants (?1.3mm, L7mm) were surgically placed vertically, and in the M3 area 1 mini-implant ((?)1.3mm, L7mm) was surgically placed vertically. Between the roots of P4 and between the roots of M1 and M2, 2 mini-implants (?1.3mm, L6mm) were surgically placed at the buccal and lingual sides. The opposite mandibular bone without implants served as a control group. Compare the height and width of implanted area on the experimental side with that on the control side. After 9 weeks, 6 anesthetized animals were fixed by intracardiac perfusion, and the mandibles were removed for gross observation, measurement, taking X-ray. And the segments with mini-implant were dissected for evaluations by histological slice (calcified slice and decalcified slice) and bone morphometry(calcified slice). The rate of osseointegration was measured by Image-Pro. Plus 4.5 on the longitudinal calcified sections. Result: 1.Gross studies: In 42 mini-implants 85.71% are stable, 14.29% are failed. Few of them have some infection around the neck of the mini-implant and soft tissues hyperplasia. 2.The result of measurement was dealt with Windows SPSS 10.0 by Paired-Sample T. Test. The different of vertical distances between test group and control group is 0.025±0.215(P>0.05), which measured from gross specimen. The different of horizontal distances is 0.063±0.04(P>0.05), which measured from gross specimen. The different of vertical distances is 0.012±0.031(P>0.05), which measured from X-ray film of gross specimen. All of them have no significant difference. 3.For a few mini-implants there are some inflamed cells around the neck of them. Calcified slice and decalcified slice are shown peri-implant partially touched the mini-implant surface. The rate of osseointegration(%) between the bone and the titanium surface is 25.57±1.53%。Teeth near by the implants are normal. 4.We can easily pull out the mini-implants with the screws after being used. There was no broken. Conclusion: 1. Mini-implants without forces have no effect on the dento-alveolar development on young dogs. Teeth near by the implants are normal. 2. As for peri-implant bone, there was only a slight osseointegration between the bone and the titanium surface. 3. Mini-implant is easy to placing and pulling out with the screws. 4. The placing area should better avoid the labial and lingual frenula. It is very important to keep intraoral hygiene .