Objective To evaluate the clinical effect of Wy 10 whitening combined with enamel microabrasion on bleaching dental fluorosis.Methods Forty patients with dental fluorosis were in-cluded and divided into two groups (20 each):group A was treated with Wy 10 whitening and enamel microabrasion,and group B only with Wy 10 whitening.Efficacy was measured according to the Vita classical shade guide before and after treatment.Sensitivity between groups was also tested.Results The effective rate of group A was significantly higher than that of group B (x2 =5.096,P＜0.05).The sensitive rates were 20.0％ (4/20) and 15.0％ (3/20) in group A and group B,respectively.No significant difference was found between the two groups in sensitivity (P＞0.05).Conclusions Wy 10 whitening combined with enamel microabrasion is an effective and safe method for bleaching dental fluorosis.

OBJECTIVETo investigate the effect of different length and diameters on the stability of mini implant and to select optimal length and diameter using continuous variation of parameters.

METHODSTo perform 3-dimensional finite element analysis, finite element models of a maxilla, and mini implants with length of 6-12 mm and diameters of 1.2-2.0 mm were generated. Load of two different forces were applied to the head of mini implant. One type was horizontal force (HF), the other was composite force (CF). The maximum equivalent stress (Max EQV) in maxilla and the maximum displacement (Max DM) of mini implant were evaluated.

RESULTSThe Max EQV in maxilla and Max DM of mini implant decreased as length and diameter increased. When length was more than 9 mm, the evaluation indexes were small and had a less change. Datas indicated that diameter played a more important role in reducing target, and was a more effective parameter in reducing Max EQV when CF was loaded.

CONCLUSIONFrom biomechanical point of view, the choice of the length should not be more than 9 mm. When CF is loaded using the mini implant, diameter exceeding 1.2 mm are optimal design for mini implant.

Dental Implants ; Dental Stress Analysis ; Finite Element Analysis ; Humans ; Maxilla ; Stress, Mechanical

Objective : To investigate the clinical efficacy of painless oral anesthesia combined with piezosurgery compared with ordinary cassette syringe combined with high speed turbine handpiece in the Fenestration operation of orthodontic traction of impacted maxillary anterior teeth. Methods : A total of 128 cases of impacted maxillary anterior teeth were treated with Fenestration operation and orthodontic traction, and the patients were randomly divided into two groups. Group A (64 patients) received painless oral anesthesia combined with piezosurgery. Group B (64 patients) received ordinary cassette syringe combined with high speed turbine handpiece. The cooperation of fenestration and the swelling and pain after operation were compared between the 2 groups. Results : The proportion of 0 and Ⅰ in the anesthesia group was 45.3% and 31.3% respectively, and the conventional group 0 and I accounted for 32.8% and 20.3% respectively. The difference between the two groups was statistically significant (Z=-2.676, P < 0.05). The pateints' cooperative degree in group A was better than that in group B (P < 0.05). The ratio of pain and swelling in the anesthesia instrument combined with Piezosurgery group was 81.2%, the conventional group had a grade I ratio of 59.4%, and the anesthesia instrument combined with Piezosurgery group was lighter than the conventional group, The difference was statistically significant (Z=-2.777, P < 0.05); anesthesia combined with Piezosurgery group after surgery accounted for 81.2% of the swelling, the conventional group of pain accounted for 71.9%, There was significant difference between the two groups (Z=-2.097, P < 0.05). Symptoms and signs as swelling and pain degree in group A were relatively minor than those in group B (P < 0.05). Conclusion It is worthy clinical promotion to use Painless oral anesthesia combined with piezosurgery in the fenestration and orthodontic traction of impacted maxillary anterior teeth, for its better cooperation and minor post-surgery reaction.