ObjectiveExploring the effect of class Ⅲlever biomechanical principles on the construction of a condylar resorption model in young rabbits.MethodsA total of sixteen 6-month-old female rabbits were randomizedly divided into four groups，i.e.，2-week experimental group，4-week experimental group，2-week control group，and 4-week control group，with 4 rabbits in each group.The experimental groups were treated with condylar resorption modeling，and the control groups were left untreated.The condylar resorption modeling method was as follows.The mandibular anterior teeth of rabbits were stacked with high-strength resin protrusions，which prevented the normal occlusion of the maxillary and mandibular teeth during mastication，so that the rabbits could passively perform mandibular backward movements to chew and grind food，and condylar resorption of bilateral temporomandibular joints occurred under the long-term pressure of the classⅢlever biological force.The 2-week experimental group and the 2-week control group were necropsied after 2 weeks of modeling，whereas the 4-week experimental group and the 4-week control group were necropsied after 4 weeks of modeling.Bone metabolism was measured by CT scanning and 3D reconstruction of the temporomandibular joints of rabbits.Specifically，condylar surface area and volume changes，hematoxylin-eosin staining of condylar tissues，and Elisa assay of peripheral blood were evaluated.Independent samples t-test was used for statistical analysis of the data with software（SPSS 19.0）.Results（1）CT 3D reconstruction：The volume of the condyle［（196±8）mm3］and the surface area［（280±12）mm2］in the 2-week experimental group significantly decreased compared to those of the control group［（204±9）mm3，（292±13）mm2；tvolume=4.409，Pvolume=0.022；tsurfacearea=3.660，Psurfacearea=0.035］.The volume of the condyle［（192±18）mm3］and the surface area［（280± 10）mm2］in the 4-week experimental group significantly decreased compared to those of the control group［（211±11）mm3，（309±10）mm2；tvolume=4.081，Pvolume=0.027；tsurfacearea=3.738，Psurfacearea = 0.033］.There was no significant difference in the degree of change in the surface area and volume of the right and left lateral condyles during the same modeling cycle.（2）Hematoxylin-eosin stain：In the 2-week experimental group，increase in the number of cells was observed in the proliferative layer of the condyle，with clustered aggregation of cells and the appearance of homogeneous cell-free areas.In the 4-week experimental group，there was no obvious stratification of the condylar cartilage，and the hypertrophic layer of cells and nuclei were markedly enlarged，with the interstitial space of the trabeculae filled with a large number of erythrocytes.（3）Articular disc in the naked-eye view：The degree of light transmission increased in the middle band of the articular disc in the 2-week experimental group and the 4-week experimental group compared to the control group.（4）Bone metabolism index：Serum osteocalcin concentration：The 2-week experimental group［（35.8±1.4）ng/mL］was higher than the 2-week control group［（18.1±8.1）ng/mL］，and the difference was statistically significant（t=7.814，P=0.004）；The 4-week experimental group［（37.6±1.7）ng/mL］also showed an increase compared with the 4-week control group［（19.3±6.4）ng/mL］，and the difference was statistically significant（t=4.752，P=0.018）.The 25 hydroxyvitamin D concentration：The 2-week experimental group［（126.5±16.8）nmol/mL］decreased compared with the 2-week control group［（176.0±8.9）nmol/mL］，and the difference was statistically significant（t=5.937，P=0.010）.There was no significant difference between the 4-week experimental group and the 4-week control group.Compared with the 2-week experimental group，the 4-week experimental group showed an increase in the concentration of 25 hydroxyvitamin D，while the serum osteocalcin concentration did not change significantly.ConclusionsThe young rabbit condylar resorption model established in this study could better simulate the histopathological changes of condylar resorption disease under mechanical effects and had the advantages of stable and reproducible results，which could provide references for the later experimental and clinical studies.
关键词
年轻家兔/髁突吸收/下颌后缩/Ⅲ类生物杠杆力/动物模型
Key words
Young rabbit/Condylar resorption/Mandibular recession/Class Ⅲbiological leverage force/Animal model
万方数据