A Dynamic And Quantitative Study Of Bone Remodeling Of The Molar Region After Wearing The Functional Appliance To Guide The Mandibular Protrusion In Rats

Objective:For years, domestic and overseas scholars have been making various reseaches on the effects of functional appliance. Alveolar is one of the most active organizations in human bone tissue. It has been rebuilding constantly through age and youth. By use of the functional appliance to guide the mandibular protrusion in rats, this experiment wants to research on the dynamic change of alveolar bone remodeling of the molar region . With the purpose of provide laboratory basis for functional appliance and long-term efficacy,this experiment wants to probe into the situation of the alveolar bone remodeling of the molar region , and wants to know the stability after treatment.Methods:60 growing male SD rats (4 weeks old, weighing 90 ~ 100g) were divided equally and randomly into experimental group and control group. There were 30 rats in each group. The rats of the experimental group wore movable upper jaw inclined bite plate to keep the mandible protraction from 8:00 to 20:00,and the rats of the control group were natural growing . In addition to the rats in the experimental group were eating pap,all animals were eating pellets. Artificial light, free drinking water. The experiment lasted for six weeks. 10 rats were randomly selected in every week (five rats from experimental group , five rats from control group ), executed the rats by broken their necks . Take the right side alveolar bone to prepare HE slices, the experimenter observed the histologicalchange,counted the crest cells of the alveolar bone and counted the osteoblasts and the osteoclasts of the alveolar ridge in the near-and far side. Take the left side of the mandibular alveolar bone ,the the experimenter carried out X-ray spectrum analysis in the region of the alveolar ridge crest . The measurement data was fed into the SPSS 13.0 analysis software, calculated the mean value of each group: use the mean±standard deviation (x±SD) to represent. Using the t test to compare and analysis the various indicators between the experimental group and control group ,α= 0.05.Results:1 histological observation1.1 Alveolar ridge crest areaThe osteoblasts of the experimental group started to congregate in one-week group. There were a large number of osteoblasts banded together in two-week group, and a small amount of osteoid appeared belowed the osteoblasts. The number of the osteoblasts began to reduce in three-week group , the osteoid increased and calcified gradually. The number of the osteoblasts continued reducing in four to six-week group , and the activity of the alveolar ridge crest area weakened gradually.1.2 The near side of the alveolar ridgeThe experimental group mainly manifested osteoclastic activity. The osteoclasts of the experimental group started to increase in one-week group. The osteoclasts and bone lacunae of the experimental group continued increasing in two-week group. There showed a visible worm-eaten osteolytic-like performance in three-week group ,and the edge of the alveolar ridge showed reversed architecture performance. The osteoclasts in four to six-week group gradually decreased ,the osteoclasts activity weakened gradually ,and the edge of the alveolar ridge gradually repaired flat.1.3 The distal side of the alveolar ridgeThe experimental group mainly manifested osteogenic activity. The osteoblasts of the experimental group started to increase in one-week group. The osteoblasts of the experimental group continued increasing in two-week group and arranged in neat rows. There began to appear osteoid belowed the osteoblasts. The osteoblasts banded together apparently in three-week group, the osteogenic activity was obviouse,and the edge of the alveolar ridge was very smooth. The osteoblasts gradually reduced in four to six-week group, and the osteogenic activity weakened gradually .2 The number of osteoblasts in alveolar ridge crest area2.1 The number of osteoblasts in maxillary alveolar ridge crest areaCompared with the control group, the number of osteoblasts in the experimental group was increased in one-week group. The number of osteoblasts in the experimental group continued rising to the peak in two-week group . The number of osteoblasts in the experimental group decreased gradually in three to five-week group and tended to close the control group. The six-week group and five-week group were similar. Statistical analysis showed that:the experimental group and the control group were significantly different in one to six-week group (P<0.05).2.2 The number of osteoblasts in mandibular alveolar ridge crest areaCompared with the control group, the number of osteoblasts in the experimental group was increased in one-week group. The number of osteoblasts in the experimental group continued rising to the peak in two-week group . The number of osteoblasts in the experimental group decreased gradually in three to five-week group and tended to close the control group. The six-week group and five-week group were similar. Statistical analysis showed that:the experimental group and the control group were significantly different in one to six-week group(P<0.05).3 Ca/P in the alveolar ridge crest regionCompared with the control group, the Ca/P in the experimental group was decreased in one-week group. The Ca/P in the experimental group continued decreasing to the peak in two-week group . The Ca/P in the experimental group increased gradually in three to six-week group and tended to close the control group.Statistical analysis showed that:the experimental group and the control group were significantly different in one to six-week group(P<0.05).4 The number of osteoclasts in the mesial side of the alveolar ridge4.1 The number of osteoclasts in the mesial side of maxillary alveolar ridgeCompared with the control group, the number of osteoclasts in the experimental group was increased in one-week group. The number of osteoclasts in the experimental group continued rising to the peak in two-week group . The number of osteoclasts in the experimental group decreased gradually in three to five-week group and tended to close the control group. The number of osteoclasts in six-week group was less than the control group. Statistical analysis showed that:the experimental group and the control group were significantly different in one to six-week group(P<0.05).4.2 The number of osteoclasts in the mesial side of mandibular alveolar ridgeIn one-week group, the number of osteoclasts was similar between the experimental group and the control group. Compared with the control group, the number of osteoclasts in the experimental group was increased in two-week group. The number of osteoclasts in the experimental group continued rising to the peak in three-week group . The number of osteoclasts in the experimental group decreased gradually in four to six-week group and tended to close the control group. Statistical analysis showed that:the experimental group and the control group were no significantly different in one and six-week group(P>0.05),the experimental group and the control group were significantly different in two to five-week group (P<0.05).5 The number of osteoblasts in the distal side of the alveolar ridge5.1 The number of osteoblasts in the distal side of the maxillary alveolar ridgeCompared with the control group, the number of osteoblasts in the experimental group was increased in one-week group. The number of osteoblasts in the experimental group continued rising to the peak in two-week group . The number of osteoblasts in the experimental group decreased gradually in three to six-week group and tended to close the control group. Statistical analysis showed that:the experimental group and the control group were significantly different in one to six-week group(P<0.05).5.2 The number of osteoblasts in the distal side of the mandibular alveolar ridge Compared with the control group, the number of osteoblasts in the experimental group was increased gradually in one to three-week group. The number of osteoblasts in the experimental group continued rising to the peak in three-week group . The number of osteoblasts in the experimental group decreased gradually in four to six-week group and tended to close the control group. Statistical analysis showed that:the experimental group and the control group were significantly different in one to six-week group (P<0.05).Conclusion:1 The histological observation and the count of osteoblasts showed that:The bone regeneration of the molar alveolar crest was active in the process of wearing functional appliance, and the bone remodeling of the mandibular was more obvious. The bone remodeling of the alveolar ridge crest reached to the peak after the second week,then decreased gradually and was tending towards stability.2 In the process of wearing functional appliance,the Ca/P of the alveolar ridge crest decreased at the beginning,then increased gradually and tended to close the control group. It suggested that this region had existed the formation of new bone, and with the experimental cycle, the new bone was mineralizing and tending towards stability.3 The process of the molar occlusal building performed distal movement tendency. The law of tooth movement was similar in maxillary and mandibular, they both performed the tendency that was rise at the first and then reduced. In contrast, the mandibular distal movement reaction was far more slowly (in the three week reached its peak), but the activity was more intense.