Cephalometric Analysis Of Roth Appliance, MBT Appliance And SmartClip^TM Self-ligation Appliance In The Extraction Case

ObjectiveRoth straight wire appliance and MBT straight wire appliance are widely used in the world, SmartClipTM self-ligation appliance become an international popular one as a passive self-ligation appliance in recent years ,which provided by the 3M corporation, as well as MBT straight wire appliance. This study was conducted to examine some correlation parameters of molar anchorage and incisor torque in the extraction case, and to evaluate the differences between the MBT straight wire appliance and SmartClipTM self-ligation appliance, which in order to provide a reference about the traditional straight wire bracket and passive self-ligating bracket.Material and MethodsFrom 2004 to 2010, 109 subjects from the Orthodontics department of Jilin University Dental Hospital meet the study requirement. there are 59 subjects used Roth straight wire appliance, 38 subjects used MBT straight wire appliance, 12 subjects used SmartClipTM self-ligation appliance. These extraction cases both adopted the first molar only as the anchorage, one-step sliding technique to close spaces .The step of the treatment was pulling the first premolar, then aligning, leveling,space closure ,detailing with a fine occluding relation in the final.Cephalometric radiographs were taken before treatment and just after correction, and traced by one author to avoid interoperate errors. The reference points are shown in Figure 3.1, the reference planes are shown in Figure 3.2 and the reference angles are shown in Figure 3.3. The experiment one aimed at detecting some correlation parameters of molar anchorage and incisor torque after treatment by Roth straight wire appliance. The experiment two aimed at finding the differences between MBT appliance and SmartClipTM appliance. The means and standard deviations of the changes in various measurements were obtained with SPSS 11.5 software. The statistical methods we use including the correlation analysis, independent sample t-test, matched sample t-test, one-dimensional analysis of variance.Results1. After treatment by Roth straight wire appliance, the angle of SN/U1,MP/L1,U1/L1 tends to the lower area of the normal range, and the mesial approximal point of the maxillary first molar (U6E) moved forward about 0.28cm, the incisor ridge of the maxillary upper incisor moved backward about 0.27 cm, the root tip point of the maxillary upper incisor moved forward about 0.07cm.2. After treatment, take the related parameters of the maxillary upper incisor (SN/U1, MP/L1 and U1/L1) and the normal standard comparison, the differences are less with MBT appliance group, and are more with SmartClipTM appliance group. There is no significant differences in the course of treatment in the tow groups, as well as the distances of the mesial approximal point of the maxillary first molar(â–³U6E) moved forward. 3. There are three reference plane (1.SN: SN plane; 2.FH: Frankfort Frankfort plane; 3.PP: Maxillary plane) in this study to establish the X axis. There is no significant difference in the displacement related parameters in the three methods.4. After correction of the growth influence in the treatment process by the point of ANS (anterior nasal spine), the displacement about the root tip point of the maxillary upper incisor moved forward is less than before correction, the displacement about the incisor ridge of the maxillary upper incisor moved backward is more than before.Conclusion1. In the extraction cases, pulling out the four first premolars, which used fixed appliances, we can get a moderate intensity of anchorage only by the first molar as the anchorage structure to close space. This situation does not exclude using intermaxillary traction, reverse-curve arch wires, treating wires with positive torque in the anterior area, lace back.2. In the extraction cases ,which pulling out the four first premolars to correct crowding and/or protrusion, some measures should be provided during the treatment with additional palatal root torque to avoid the palatal root torque insufficient after correction.3. There is no significant difference between MBT appliance group and SmartClipTM self-ligation appliance group in the course of the treatment and the distance of the mesial approximal point of the maxillary first molar moved forward. The amount of the incisor instruction is more in the MBT appliance group. The MBT straight wire appliance is a reasonable choice rely on the controllability of anterior teeth torque.4. The variations after treatment about the mesial approximal point of the maxillary first molar(â–³U6E),the point of ANS and the root tip point of the maxillary upper incisor were largest in the maxillary plane group ,and smallest in the FH plane group. the incisor ridge of the maxillary upper incisor was in the opposite. No significant difference in the displacement related parameters in the three methods.5. After considering the growth influence, a higher control efficiency on the incisor torque appeared.