应力环境影响老年大鼠下颌骨骨小梁结构变化的形态计量学研究

The effects of local stress on trabecular bone structure of mandibles in aged rats:a bone histomorphometric study

目的 观察成年和老年大鼠下颌骨应力环境改变与下颌骨骨小梁结构的关系。方法 以 6月龄及15月龄雄性大鼠分别代表成年组和老年组大鼠 ,拔除大鼠右侧上颌全部磨牙使咀嚼 (左 )侧、非咀嚼 (右 )侧下颌骨分别处于相对的高低应力环境中 ;依此将老年和成年大鼠各 2 4只分为四组 ;①老年 +拔牙组 ;②老年 +非拔牙组 ;③成年 +拔牙组④成年 +非拔牙组 ;在实验 1.5个月和 3个月时对各组双侧下颌骨的组织切片进行骨组织形态计量学分析。结果 老年组大鼠下颌骨松质骨面积比 (Cn .Ar%)、骨小梁宽度 (Tb .Wi)较成年大鼠显著降低 ,骨小梁间隔宽度 (Tb .Sp)有部分增宽 ,但骨小梁数目 (Tb .N)无显著变化 ;对于成年大鼠 ,低应力和高应力侧以及非拔牙对照组相互间下颌骨Cn .Ar %、Tb .Wi、Tb .N和Tb .Sp均无显著差异 (P >0 .0 5 ) ;而对于老年组 ,实验 3个月时 ,低应力侧Cn .Ar%、Tb .Wi和Tb .N均比高应力侧及同期非拔牙对照组显著偏低 ,Tb .Sp则显著增宽 ;而高应力侧与同期对照组相比 ,两组间各值均无显著性差异。结论 咀嚼功能低下或缺失 (低应力环境 )可加速老年因素引起的下颌骨骨小梁吸收 ,对于老年患者应尽早恢复其咀嚼功能 ,减少颌骨骨丢失。

Objective To observe the relationship between the stress environment of mandibles and their trabecular bone structures in adult and aged male rats.Methods 24 male rats of 6 months old were used in the adult group,and 24 male rats of 15months old were used in the senile group.The high and low stress environment models of mandibles were established by unilateral maxillary molars extraction.The masticatory sides of the mandibles were regarded as the high stress sides and the non-masticatory sides were regarded as the low stress sides.The rats without teeth extraction were used as the control.According to these,48 rats were divided into 4 groups:①adult+extraction group;②adult+non-extraction group;③senile+extraction group;④senile+Nnn-extraction group.The trabecular bone of mandibles were measured by bone histomorphometry bilaterally 1.5 months and 3 months after extraction respectively.Results The mandibles of senile rats had lower cancellous bone area(Cn.Ar%)and trabecular width(Tb.Wi)than those of adult rats(P< 0.05 ).There was no significant difference in trabecular separation(Tb.Sp)and trabecular number(Tb.N)in mandibles between the senile and adult rats.To adult rats,the low stress sides,the high stress sides of mandibles and the non-extraction control mandibles (P> 0.05 between each two)had similar values of Cn.Ar%,Tb.Wi,Tb,N,and Tb.Sp.To senile rats,after 3 months of teeth extraction,Cn,Ar%,Tb.Wi,and Tb.N of the low stress sides of mandibles were significantly lower than those of the high stress sides and the non-extraction control mandibles.Their Tb.Sp were significantly larger than those of the high stress sides and the non-extraction control mandibles.But Cn.Ar%,Tb.Wi,Tb.N and Tb.Sp of the high stress sides were similar to those of the non-extraction control mandibles(P> 0.05 ).Conclusion The results indicate that the masticatory deficiency(the low stress envionment)tends to aggravate the resorption and edterioration of the trabecular structures of jaws induced by aging.In order to inhibit the bone loss of the jaws,the masticatory functions should be rehabilitated for these aged patients as early as possible.