The Comparison Of The Effect Of Vacuum-formed Or Hawley Retainers On The Patients With Slow Maxillary Expansion

Objective For the orthodontic patients treated with straight-wire appliance after slow expansion,the changes of arch width and PAR index were observed and compared during the retention period,and the retention effect of Vacuum-formed or Hawley retainers for such patients was compared;By comparing the changes of measurement values before and after the retainer,the recurrence stage after retention was determined.Methods According to the criteria of case selection,120 patients in stomatology department of Inner Mongolia Baogang hospital from June 2018 to December 2019 The subjects were randomly assigned to two groups.When wearing the retainers,the average age of female(13-16 years old)was14.6±0.95 years old,male(15-18 years old),and the average age was16.5±1.13 years old.At the end of orthodontic treatment,the subjects in all the groups received a fixed bonded retainer in the mandible.Numbered A and B.Group A received Vacuum-formed retainers with the thickness of 1.5 mm,group B received a with Hawley retainers.Reexamined every three month to check the durability and comfort of the retainers.At the end of treatment,before the delivery of the retainers(T0),after use the retainer for 6 months(T1),and after use the retainer for 12 months(T2),the arch width and PAR index of the model were measured.Results 1.Before the delivery of the retainers(T0),there was no significant difference in width of dental arch and PAR index between the two retainers(P > 0.05).2.After use the retainer for 6 months(T1),there was no difference in width of dental arch between the two kinds of retainers,p>0.05.The retention effect of the pressure film retainer on the overbite and the teeth alignment was better than that of Hawley retainer,but with no significant differences between the two groups,p>0.05.3.After use the retainer for 12 months(T2),there was no difference between the two kinds of retainers in retain the width of dental arch,p>0.05.There was significant differences between the two kinds of retainers about overbit and teeth alignment,p < 0.05.4.During the one-year observation,the changes of width of dental arch,teeth alignment,overbite,overjet and par in the first six months were significantly greater than those in the last six months,and the difference was statistically significant,p<0.05.The change of T1-T0 phase of mid-line and buccal side occlusion was larger than that of T2-T1 phase,but the difference was not statistically significant,p>0.05.Conclusion For the patients who were treated with straight-wire appliance after slow expansion,there was no significant difference in the retention of the width of the dental arch between the Vacuum-formed retainers and Hawley retainers.While the Vacuum-formed retainers was better than Hawley retainers in the retention of teeth alignment and overbite.The recurrence occurred mainly within half year after the retention,and the mid-line and buccal side occlusion effect was stable after the treatment.