BACKGROUND:Biomechanical compatibility is the necessary condition to ensure the stable osseointegration with implants that then can function over a long period; therefore, it is especialy important to get knowledge about distribution of stress and strain between the maxilary central incisor and its surrounding bone tissue. OBJECTIVE: Based on five different anatomical types of natural teeth, to study the regularity of stress distribution between the maxilary central incisor root and implant.METHODS: According to the five different anatomical types of natural maxilary central incisors, UGNX and ANSYS were used to set up three-dimensional finite element models (B1, B2, M1, M2, P1) for the implant and surrounding structures, which were under 100 N static load at angles of 0o, 30o, 45o, 60o, 90o with the long axis of teeth. Then, the stress distribution between the five kinds of maxilary central incisor roots and implants was analyzed. RESULTS AND CONCLUSION:Among the five different anatomical types, the equivalent stress for both the natural central incisor and implant were increased with the increasing of angles, and the implant had a higher raising trend. The equivalent stress for the natural tooth concentrated upon B1 for the maximum value and M1 for the minimum value; while the equivalent stress for the implant focused on the maximum value at M1 and the minimum value at M2. There was a gap of 2%-31% between the equivalent stresses for the natural tooth roots and a gap of 4%-21% for the implants. The stress distribution range for the implant was just smaler than that for the natural tooth roots. It implies that the bit force of implant and natural tooth is in positive proportion to the bite angles, and the bite force that implant can burden is smaler than that the central incisor can.

Objective: Objective To explore the role of the Er: YAG laser in periodontal surgery. Methods : Twenty patients with chronic periodontitis in two quadrants were selected for this study. One quadrant was subjected to pure periodontal flap surgery, whereas the other was subjected to flap surgery with an adjunctive Er: YAG laser. The preoperative and 3- and 6-month postoperative clinical parameters, including the probing depth, clinical attachment level, gingival recession, plaque index, gingival index and tooth mobility, were recorded. Results: Significant differences were not observed between the open flap surgery + Er: YAG laser-assisted treatment group and the open flap surgery group except for the gingival index after 3 months (0.36 ± 0.26 vs. 0.58 ± 0.29, t=3.831, P < 0.001) and 6 months (0.60 ± 0.23 vs. 0.83 ± 0.22, t=4.013, P < 0.001). Conclusion Er:YAG as an auxiliary treatment for periodontal flaps, does not significantly reduce the depth of periodontal pockets, nor could it improve the clinical adhesion level and the gingival recession, but it can improve the recovery of gingival inflammation and accelerate the healing of tissue.

Objective·To study the alterations in vestibular hair cell morphology and function of ATPase plasma membrane Ca2+transporting 2 oblivion(Atp2b2 Oblivion)heterozygous mice at different ages.Methods·Atp2b2 Oblivion heterozygous male mice aged 2 months and 8 months were selected with ten in each kind and C57BL/6J wild-type mice with the same gender,age and number were selected as the control group.Expression patterns of ATP2B2 in vestibular hair cells and numbers of hair cells in the striola zone and the extra striola zone in the two groups of mice at different ages were observed and calculated respectively through immunofluorescence assay.Hair bundle structures were detected by scanning electron microscopy(SEM),and mitochondria and ribbon synapse structures were observed by transmission electron microscopy(TEM).Vestibular evoked potential(VsEP),vestibular evoked myogenic potential(VEMP),rotarod rod test,and balance beam test were adopted for the evaluation of vestibular functions.Results·ATP2B2 was mainly expressed in the hair bundle of vestibular hair cells in the two groups of mice.Hair cell numbers in the striola zone and the extra-striola zone did not exhibit any differences between Atp2b2 Oblivion heterozygous mutant mice and wild-type mice of 2-month-old and 8-month-old.No visible structural abnormality in the hair bundle could be seen through SEM.TEM results implied no morphological abnormality in mitochondria or ribbon synapses in the 2-month-old heterozygous mutant mice,while vacuolar degeneration was discovered in the mitochondria under the cuticular plate in the 8-month-old heterozygous mutant mice with the normal ribbon synapses and the normal mitochondria near the innervation site.VsEP and VEMP thresholds of 2-month-old and 8-month-old Atp2b2 Oblivion heterozygous mutant mice were significantly elevated compared with the wild-type mice.Analysis of VsEP waveform manifested prolonged P1 latency and declined P1N1 amplitude in heterozygous mutant mice(P＜0.05).Results of rotarod rod test and balance beam test acquired from 2-month-old Atp2b2 Oblivion heterozygous mutant mice were not significantly different from the wild-type mice,while the ability of the mutant mice to accomplish the tests descended significantly at 8 months of age compared with the wild-type mice(P＜0.05).Conclusion·Atp2b2 Oblivion heterozygous mutant mice showed defective vestibular electrophysiological function at 2 months old,and abnormalities in vestibule-related behaviors can be detected at 8 months old.The vestibular function ofAtp2b2 Oblivion heterozygous mutant mice deteriorate progressively.