Research in anatomical relationship between maxillary first molar and odolescent maxillany sinus and standard value of movement using MDCT

Objective:To observe changes of inclining angle of different anatomical types of maxillary first molar under different force values,and to discuss the importance of relationship between maxillary first molar and adjacent anatomical structure in orthodontic study.Method: Maxillae of 62 cases were scanned and reconstructed before orthodontic treatment by MDCT and were divided into incarcerated group and non-incarcerated group.In all cases maxillary first molars were given constant force value,and the angle of long axis and central axis according to the CT scan pictures were measured.The angle difference before and after orthodontic treatment was inclining angle.The relationship of inclining angles of two groups were analysed by SPSS.Result:Inclining angle of incarcerated group was much bigger than non-incarcerated group.Conclusion:Orthodontic treatment plan design for maxillary first molar could use MDCT scanning result as a reference,and corrective force for maxillary first molar in incarcerated cases should be more conservative than for non-incarcerated cases.