Establish An Osteoporosis SD Rat Bisphosphonate Relatedosteonecrosis Of Jaw-liked Model And Evaluate Local Risk Factors

Part ? Establish a SD rat animal model of osteoporosisObjective:To establish a safe and stable SD rat animal model of osteoporosis.Methods:Ten female Sprague-Dawley rats?6 months old?were randomly divided into two groups,each Grouphad five rats:model-Grouprats underwent bilateral ovariectomy and control-Grouprats had sham operation by resecting approximately isopycnic fat around the ovaries.All rats were executed at 12 weeks after the operations,then compared the values of the rats'weight,BMD,serum Ca²⁺?P³⁺and ALP concertrations before and after the surgry and the pathomorphologic changes of Vertebral body were demonstrated by HE staining.Result:All of the rats gained weight at 12 weeks after the operations,the increment in model Groupwas more significant?P<0.05?;Compared with preoperative values,BMD and serum Ca²⁺had declined while serum P³⁺and ALP had increased of model group;In control group,BMD had reduced while serum Ca²⁺?P³⁺and ALP had multiplied,the variations were statistically significant between each other?P<0.05?.Histomorphological examinations found that vertebral trabeculae of model Grouprats demonstrated intact morphological feature and well-regulated structure,while the fragmental vertebral trabecula turned to be thiner and with smaller quantity,positive fragmental,the marrow cavities enlarged and the bone mass significantly reduced in model group.Conclusions:A stable and reliable osteoporosis animal model was established in 12weeks after bilateral ovariectomy of 6-months-old female SD rats.Part ? Different local risk factors induce to develop an osteoporosis rat bisphosphonate related-osteonecrosis of jawliked modelObjective: To establish an osteoporosis rat bisphosphonate related-osteonecrosis of jawliked model and observe the influences from different local risk factors.Methods: Forty-five osteoporosis Sprague-Dawley rats were created by bilateral ovariectomy according to experiment one?T0?.After 12 weeks?T1?,all of the rats were administrated by subcutaneous injections of alendronate?1.0 mg/kg/day dosage?for 60 days?T2?and classified in to three groups: Group1: control Groupwith no intervention;Group2: ALN + tooth extraction Groupwith maxillary and mandible first molars extraction after alendronate administration;Group3: ALN+ periodontal scaling Grouprats were ligated all of the first molars with steer wire at the 11 th day after drug administration to establish a chronic periodontitis model,then had periodontal scaling when ALN injection ended.Five rats were randomly executed in 2 weeks?T3?,4 weeks?T4?and 8 weeks?T5?after the interventions from each group.Result:?1?Clinical observation demonstrated that the incidence of BRONJ had nostatistic difference between Group1 and Group3,though the occurrence rate of BRONJ in Group2 was 100%,much higher than the others.The maxillary had a probability of BRONJ of 26.7%?8/30?,while mandibular had higher incidence of 56.7%?17/30?.No remarkable correlation was found between ponderal growth and BRONJ;?2?The time-varying serum concentration of RANKL and OPG were unrelated with the occurrence;The RANKL/OPG ratio diminished distinctly at T4?P<0.05?,the differences was statically significant;?3?HE staining demonstrated that trabecular bone structure of BRONJ lesion areas was disorganized,large number of empty bone sinkholes were generated by the nuclear of osteocyte karyolysis?P<0.05?,TRAP staining showed that the number of osteoclasts remarkable decreased in BRONJ rats than Non-BRONJ rats?P<0.01?;?4?According to the degrees of osteonecrosis lesion and soft tissue damage,All BRONJ rats were divided into four stages.There was one BRONJ lesion?1.67%,1/60?having Stage1 in Group1;In Group2 rats,the incidence of Stage0 was 46.67%?28/60?,that rate of Stage1 was 21.67%?13/60?,while there were 19 Stage2 lesions?31.67%,19/60?happened;In Group3 animals,the incidence of Stage1 was 3.33%?2/60?and the rate of Stage2 was 1.67%?1/60?;It was found that the morbidity and pathological degree of Group1 and Group3 were significantly lower than that of Group2,and the degree of Group2 lesions was escalated over time;?5?Micro CT revealed that the BRONJ lesion area had microcracks and osteolysis.Duration time had no significant change in Group1 and Group3?P>0.05?.Compared to Group1,the values of BMD?Tb.N and Tb.Sp in Group2 and the values of Tb.Th and Tb.Sp in Group3 showed statistical difference at T3?P<0.05?,while the differences of BMD,BV/TV,BS/BV,Tb.N and Tb.Th between Group2 and Group3 were statistically significant?P<0.05?;At T4,the characteristic decline of Tb.N in Group2 was statistically significant compared to Group1?P<0.01?;No statistical difference was found among all groups at T5;The value of Tb.N markedly reduced in BRONJ rats compared to Non-BRONJ rats?P<0.01?,while no significant change happened among all stages?P>0.05?;The values of BMD showed significantly changes among all stages?P<0.05?;Compared to Non-BRONJ rats,the Tb.Th value in Stage1 and Stage 2 had significantly differences?P<0.05?,and the difference of Tb.Sp between Stage0 and Stage 1 was statistically significant?P<0.01?.Conclusions: The BRONJ animal model had been successful established by high dose ALN subcutaneous injection for 60 days accociate with teeth extraction in osteoporosis rats,the typical lesions had been observed in 2 weeks after the intervention.The lesion degree of BRONJ had closed relation to time growth.With regard to local rksk factors of BRONJ,this study had confirmed that teeth extraction was a remarkable risk factor of BRONJ,and there was no significant correlation between periodontal scaling and the occurrence.The variation of serum RANKL/OPG ratio might be related to BRONJ,but it had been insensitivity at the early stage.Tb.N and Tb.Th might be effective bone morphogenetic markers associated with BRONJ in the early stage,and microcracks had been observed in the lesion area.Part ? Biomechanical study of bisphosphonate relatedosteonecrosis of jaw in osteoporosis SD ratsObjective: To study the biomechanical properties of BRONJ mandible in SD rats.Methods: Forty-five osteoporosis Sprague-Dawley rats were created by bilateral ovariectomy according to experiment one as Group A,the saline was subcutaneous injected under the 1.0mg/kg/d dosage and lasted for 60 days,then the first molars were extracted after the administrations.Rats were executed in 4 weeks after the extraction.Randomly selected five rats of Group2 whose left mandible were not detected BRONJ as Group B,another five rats of Group2 whose left mandible were identified BRONJ as Group C.Three-point bending test was carried out for the measurement of the left mandibles biomechanical properties after geometrical measure.Result:?1?Postoperative weight of Group A was significantly higher than Group B and Group C,the difference was statistically significant?P<0.05?;?2?No statistically differences in the geometric morphological measurement of mandible were found among different groups?P>0.05?;?3?The values of Wm?Dm and Dy of Group A were statistically lower than Group B?P < 0.05?,while the standard slope showed to be significantly higher than that of Group B and Group C?P<0.01?.The value of Dm of Group C was significantly less than Group B,while the standard slope was significantly higher?P<0.05?.Conclusions: OP rats mandible strength and stiffness,BRONJ showed no significant effect on mandible stiffness,but the strength of mandible was significantly reduced.The bone tissue was prone to fracture under stress,which may be one of the causes of pathological fracture after BRONJ.