Objective: To investigate the effects of He-Ne laser irradiation on orthodontic bone remodeling. Method: Thirt y rabbits were randomly divided into 6 groups with 5 in each group.Another 5 r abbits with no treatment were used as the unforced control. The animals were a nesthetized with 0.05 mol/L pentabarbetal (2 ml/kg). The maxillary first molar a nd the incisor were connected with coil spring ,fixed with ligature wire. Orthod ontic force of 7.84 N was applied on the teeth.The left side was served as contr ol and the right side received irradiation of He-Ne laser at 20 mW with the wav e length of 632.8 nm. Periodontal tissue samples of the experimental teeth were obtainned 1,3,5,7,14 and 21 days respectively after irradation. Tartrate-resist ant acid phosphatase (TRAP) in the tissues was studied with histochemistry. Results: The activity of TRAP in the irradiated tissues was higher than that in the unirradiated 3 and 7 days after treatment (P

Objective: To investigate the influence of sodium hypochlorite and alcohol disinfection in the enamel during acid etching, and to provide reference for the orthodontic treatment. Methods: Sixty extracted permanent teeth were selected and randomly divided into two groups (group A and group B), with 30 teeth in each group. The teeth in group A were pretreated with 5. 25% sodium hypochlorite and the teeth in group B were pretreated with 75% alcohol. After pretreatment, group Aand group B were randomly divided into three groups (groups A0 , A1, A2, B0, B1, and B2), with 10 teeth in each group and the teeth were etched with 37% phosphoric acid for 0, 15 and 30 s. Forty extracted deciduous teeth were selected and randomly divided into 2 groups (group C and D), with 20 teeth in each group. In group C, the teeth were pretreated with 5. 25% sodium hypochlorite; in group D, the teeth were pretreated with 75% alcohol. After pretreatment, group C and group D were randomly divided into two groups (groups C0 , C1, D0, and D1) with 10 teeth in each group, and the teeth were etched with 37% phosphoric acid for 0 and 30 s. The morphology of enamel was observed by scanning electron microscope (SEM) after the extracted teeth were cleaned with ultrasound; the pore diameters of enamel surface were detected and the shear strength of samples in each group was detected. Results: The differences in pore diameters between various groups were statistically significant (P < 0.01) . In the permanent teeth test group, the pore diameter in group A2 was the maximum (P < 0.01), the surface protein residues were less, and the enamel was fully exposed, and the shear strength was the highest (P < 0.01) . The pore diameter in group B1 was the minimum (P < 0.01), the surface protein residues were more, and the shear strength was the lowest (P < 0.01) . In the deciduous teeth test group, the pore diameter in group CI was the maximum (P < 0.01), the surface protein residues were less, and the shear strength was the highest (P < 0.01) . The pore diameter in group D1 was the minimum, and the surface protein residues were more, and the shear strength was the lowest (P < 0.01) . Conclusion: Compared with the traditional alcohol disinfection method, pretreatment of 5. 2 5 % sodium hypochlorite in tooth enamel for 30 s can significantly increase the surface roughness and cleanliness of enamel, and enhance the shear strength of orthodontic bracket.

Objective To evaluate the effects of different loading occasions of orthodontic force on the stability of miniscrew as an anchorage.Methods The titanium miniscrews were respectively implanted into canine and posterior region of both upper and lower jaws of 3 crossbred dogs.The implants were immediately loaded with 200 g orthodontic force or loaded after 2 weeks of implantation.The dogs were sacrificed after 8 weeks.The samples including the microscrew implant and its around bone tissue were extracted,fixed and X-ray photographed.Then the specimens were decalcified,embedded,sectioned and stained with HE and GOMORI.The sections were examined under light microscope.Results The stability of miniscrew in posterior region of jaws was higher than that in canine region in X-ray photograph.There was more bone trabecular formation between miniscrew and jaw bone in non-immediately loaded group than those in immediately loaded group with HE and GOMORI.Conclusion The non-immediately loaded implant as an anchorage can afford more stability than the immediately loaded implant.