The Secretion Of Condylar Cartilage PGE₂ Changes After Different Wearing Time Of Anterior Mandible Appliance In Growing Rats

Objective:Through years of clinical observation discoveried that functional appliance had positive effect on Angle's Classâ…¡malocclusion.But its curative effect was determined by Patient's coordination and wearing time,and the final result had plenty of uncertainty.The research confirmed that PGE₂ possessed a biorhythm together with a close relationship with the reconstruction in bones and cartilages.The purpose of this study was to find the effects of different wearing time of anterior mandible appliance to the circadian rhythm of condylar cartilage PGE₂.In order to investigate the best wearing time point or time period,which could direct clinical application properly.Methods:54 growing Sprague Dawley rats(4 weeks, weight 90～100g) wre feed with water and normal bait vessel after 6 hours soaking freely.Randomly they were devided into 3 groups(n=18):12h wearing group;24h wearing group;and control group.The rats of 12h group wore movable upper jaw inclined bite plate to keep the mandible protraction from 8:00 to 20:00,the rats of 24h group wore the upper jaw inclined bite plate for the whole day,and the rats of the control group were natural growing without appliance.The experiment last for 7 days.At the 8^th day of the experiment,3 rats were randomly chosen per group to put to death at six time points(0:00,4:00,8:00,12:00,16:00,20:00).Bilateral condylar cartilages were processed to examine the contents of PGE₂ with euzymelinked immunosorbent assay after conventional management.Will measure that various points in time the PGE₂ value according to the time is the X-axis,the content carries on the punctuation comparison for the Y-axis to observe its trend.Input all the values with time correspondence to the computer,use single cosine analysis software to analysis whether the trend conforms to the circadian rhythm feature and figure out the cosine formula. Simultaneously use SPSS 13.0 to compare the eigen value of the three group,search foe the differences throughout various time points.Results:1 The content of the PGE₂ in condylar cartilage: Input the data of 24h group,12h group and control group according to the time sequence into the computer,which drew up three curves.The result turns out that the content of PGE₂ in condylar cartilage of the 24h group is the highest,the 12h group is the second,and the control group is the lowest.The 24h group & control group,the 12h group & control group and the 24h group & 12h group all have statistics significances.2 The biorhythm of the PGE₂ in condylar cartilage:Use single cosine analysis software to analyse the three curves,the result indicates that the curve of control group and 12h group shows cosine tendency(p<0.05),crest value is between 12:00～16:00,valley value is between 2:00～6:00,which has the character of daily rhythm.The 24h group has no cosine rhythm(p>0.05).The formula of the 12h group's curve is Yi=129.5+16.5cos(15 ti-69),and the formula of the control group's curve is Yi=109.+12.4cos(15 ti-76).The result shows that the PGE₂ in condylar cartilage of the control group has biorhythm;the 12h group still keeps the rhythm,and the increase of the PGE₂ content of condylar cartilage indicates that the initially effect of the reconstruction;the PGE₂ content in condylar cartilage of the 24h group increases the most,which shows the largest effect of the condylar reconstruction,but loses the rhythm.Conclusion:1 The PGE₂ in condylar cartilage of the control group has the biorhythm,the crest value locates at 14:38,which is nearly 12 hours away from the valley value,shows a character of daily rhythm.2 The 12h group:The PGE₂ in condylar cartilage of the 12h group still has the rhythm,and the crest value locates at 15:38,which is near the crest value of the biorhythm(P<0.05).And the content of the PGE₂ in condylar cartilage increases(P<0.05),which indicates a initially effect of the reconstruction of the condylar cartilage.3 The 24h group loses the rhythm of the PGE₂ in condylar cartilage,probably because of the continuous force on the condyle.However,the long time wearing of the appliance enhances the secretion of the PGE₂,so the content increases obviously(P<0.05),and increases more than the 12h/d group(P<0.05).