The Dental And Basal Arch Forms In Adult Patients With Bimaxillary Protrusion

OBJECTIVE:To compare the characteristics of dental and basal arch on the level of WALA ridge between bimaxillary protrusion and normal occlusion.Methods:This study mearsured 30 pretherapy bimaxillary dental casts,10 bimaxillary protrusions(average age 22.13±1.43 Y)were selected as experimental group A and 10 bimaxillary prognathisms(average age 23.09±0.98Y)were selected as group B.10 normal occlusion individuals(average age 21.38±1.36Y)as control group,and in all three groups,the male and female patients were selected by 1:1 ratio.FA points and WALA points were marked on the casts to represent the dental arch and basal bone,and data of three groups including width,depth and width/depth ratio of dental and basal arch were measured and analyzed with SPSS22.0.The sex difference intra-each group and items of measurements in three groups were analysized by means of t test,and correlations between dental and basal arch width were calculated by means of Pearson analyzation.Results:1.The measurement mean of each item of male patient was large than female ones.The normal occlusion group has significant sex difference in almost items except on dental width in maxillary molar,mandible canine and premolar area,and basal width in mandible premolar area.Bimaxillary protrusion group has significant sex difference only on bimaxillary dental and basal width in molar area and mandible basal depth.Bimaxillary prognathism has significant sex difference on bimaxillary dental and basal molar width and depth,and mandible premolar basal depth.The resault showed weakened sex difference in experimental group.2.Pearson analysis showed high correlation(r>0.73)on dental and basal width at most items in bimaxillary protrusion except mandible molar area(r=0.689).High correlation was found in bimaxillary prognathism at all items.(r>0.82)3.In respect of the dental width,group A displayed statistical.difference with control group in bimaxillary molar dental width,and the means of group B were larger than group A.In respect of basal arch width,the normal occlusion had statistical difference separately with group A and group B in molar area,and the two experimental group showed statistical difference of basal width in mandible canine,premolar area.In respect of dental depth,there existed strong difference in three groups,on the side of mean value,the bimaxillary protrusion>bimaxillary prognathism>normal occlusion,the group A showed high difference with control group,and items of group B had statistical difference except on maxillary posterior dental depth.On respect of basal depth,the group B had statistical difference separately with group A and control group,the mean value of group B was the highest.On respect of the dental and basal width/depth ratio,the control group had pronounced difference with two experimental groups,and the difference performed higher in dental items between group A and control group,contrarily,the difference performed higher in basal items between group B with control group,the difference between two groups embodied on maxillary dental arch.Conclusion:1.Bimaxillary protrusion and bimaxillary prognathism have growth difference with normal occlusion,thus diminished the sex difference in dental and basal arch.2.The dental and basal width of bimaxillary protrusion and bimaxillary prognathism possessed strong correlation,it not only testified that WALA Ridge had the reliability as the basal signalized point,and will also guide the clinical to bend the individual wire based on the basal arch form.3.Compared with bimaxillary protrusion malocclusions,the width and the length of the basal bone were larger in bimaxillary prognathism malocclusions.However,the length of dental arch of the former was larger the latter,which indicated bimaxillary protrusion malocclusions have shorter and more narrow basal bone.In addition,the analysis showed incisiors had more obvious labially inclination more in group of bimaxillary protrusion,which all indicated different therapy methods should be taken in bimaxillary prognathism and bimaxillary protrusion malocclusions.