Objective:To study the osseointegration after implantation of dental mini-screw under unloaded condition by histomorphometric observations.Methods:30 titanium mini-screws were used. 3 titanium implant miniscrews were implanted into each tibia of 10 New Zeland White rabbits at a distance of 10 mm between 2 mini-screws. 2 animals were sacrificed immediately,1,2,4 and 8 weeks after operation respectively.Samples of the screws with surrounding bone tissue were examined by HE staining.Results:Progressive changes were observed in the implant-bone interface.1 and 2 weeks after operation collagen fibers, locally absorbed areas and cancellous bones with loose connective tissues were found.4 weeks after operation compact cortical bone was observed.8 weeks after operatoin lamellar bone and second remodeling were found.Conclusion:Osseointegration between implanted mini-screw and bone tissue may complete in 8 weeks in rabbit tibia.

OBJECTIVETo observe the occlusal contacts during protrusion and lateral movements in adolescent patients after orthodontic treatment.

METHODSSixteen adolescent patients who achieved normal dentition after orthodontic treatment were selected as experimental group and 17 healthy adolescents and young adults with normal occlusion were selected as control group. The occlusal contacts during protrusion and lateral movements in the two groups were recorded with T-Scan II system and compared.

RESULTSThe prevalence of occlusal interferences in the posterior segment in the experimental group was high and most of them were on the second molars. The value of disclusion time during left lateral movements, right lateral movements and protrusion in the experimental group were (1.504 +/- 0.681), (1.532 +/- 0.913), (1.358 +/- 0.791) s. The value of disclusion time during left lateral movements, right lateral movements and protrusion in the control group were (0.470 +/- 0.059), (0.483 +/- 0.045), (0.482 +/- 0.047) s. The results in the experimental group were significantly longer than those of control group (P < 0.01).

CONCLUSIONAlthough the patients achieved normal dentition after orthodontic treatment, their disclusion time were longer than those in healthy adolescents and young adults with normal occlusion.

Adolescent ; Adult ; Dental Occlusion ; Humans ; Molar ; Tooth Movement Techniques ; Young Adult

OBJECTIVETo investigate the prevalence of malocclusion in China.

METHODSBased on individual normal occlusion and Angle's classification of malocclusion, standard investigation form was made. 25,392 children of different dental ages were evaluated by orthodontic professionals.

RESULTSThe prevalence of malocclusion among Chinese children was 67.82%. The prevalence of malocclusion among children with different dental age and the proportion of the different types of malocclusions were revealed.

CONCLUSIONThe prevalence of malocclusion among Chinese children had increased from 40% to 67% over the last 40 years.

Child ; Child, Preschool ; China ; epidemiology ; Female ; Humans ; Male ; Malocclusion ; classification ; epidemiology ; Mass Screening ; methods ; Prevalence