Objective:To explore the effect of maxillary expansion on orthodontics.Methods:Eight beagle dogs were randomly divided into two groups,with 4 dogs in each group.Dogs in group1 were executed immediately and received the direct physical measurement.The magnetic expansion appliance was used in group 2 for the maxillary expansion.After the expansion,the model was taken again and they were executed after cone beam CT(CBCT) scanning.The model measurement method was adopted in group 1 to measure the dental measurement indicators and width of base bone arch.The CBCT measurement method was employed to measure the above dental indicators and bone indicators.The difference in the indicators measured by different methods was compared and analyzed.Results:Before the expansion,there was no significant difference in the bone measurement indicators between the CBCT measurement method and direct physical measurement method.After the expansion,there was no significant difference in indicators between the CBCT measurement method and direct physical measurement.But there was significant difference among the model measurement method,CBCT measurement method and direct physical measurement method.There was the significant difference in the dental indicators between the CBCT measurement method and model measurement,as well as the bone indicators of posterior marginal spacing of greater palatine foramen,posterior marginal spacing of incisive foramen,width of base bone arch and spacing of implant anchorage.Conclusions:There is no significant difference between the effect of CBCT measurement method and direct physical measurement method,but CBCT is significantly better than the model measurement. Objective: To explore the effect of maxillary expansion on orthodontics. Methods: Eight beagle dogs were randomly divided into two groups, with 4 dogs in each group. Dogs in group1 were executed immediately and received the direct physical measurement. Magnetic expansion appliance was used in group 2 for the maxillary expansion. After the expansion, the model was taken again and they were executed after cone beam CT (CBCT) scanning. The model measurement method was adopted in group 1 to measure the dental measurement indicators and width of base bone arch. CBCT measurement method was employed to measure the above dental indicators and bone indicators. The difference in the indicators measured by different methods was compared and analyzed. Results: Before the expansion, there was no significant difference in the bone measurement indicators between the CBCT measurement method and direct physical measurement method. After the expansion, there was no significant difference in indicators between th CBCT measurement method and direct physical measurement method. CBCT measurement method and direct physical measurement method. There was a significant difference in the dental indicators between the CBCT measurement method and model measurement, as well as the bone indicators of posterior marginal spacing of greater palatine foramen, posterior marginal spacing of incisive foramen, width of base bone arch and spacing of implant anchorage. Conclusions: There is no significant difference between the effect of CBCT measurement method and direct physical measurement method, but CBCT is significantly better than the model measurement.