A Clinical Study And Application In Individualized Retention Of Fixed And Removable Retainers

A working definition of retention might be stated as follows:the holding of teeth in ideal esthetic and functional positions.The question of long-term retention and stability after orthodontic treatment has always engaged the attention of specialty.After improvements of achieved from long and painstaking treatment,the orthodontist and the patient always hope the results would keep stability and satisfactory.But they found that varying changes always took place after the retainer were removed. Sometimes relapse in tooth position was noted even during the phase of retention. Varying follow-up studies have indicated that relapse occurs in most cases.The instability of orthodontic results objectively exists,so retention is necessary.For keeping stable maximumly,some author advocated "individualized retention".The related clinical study of fixed and removable retainers which were used longest and most widely undoubtedly has most important significance. The study consisted of three parts as follows: l.The comparative study of fixed versus removable retainer 36 patients were selected and comparative study which include periodontal implications and stabilizing effects was performed. Results:The assessments of MGI and PI of the group with removable retainer at 6-month recall were found to be very close to the values before debonding,whereas the increases of the mean PI of thegroup wearing fixed retainer were statistically significant.The differences of the mean MGI of the two groups were statistically significant at 6-month recall. And the mean values of the group with fixed retainers at a lower than those with the removable retainer group.The evaluation of stabilising effects according to the irregularity index showed fixed retainer group was much better than removable retainer group.Conclusion:l)As far as oral hygiene condition was concerned,there were no significant differences between fixed and removable retainers in the short-term.But adverse effects on oral hygiene of fixed retainer objectively exists.This indicates that we must selectively apply to fixed retainers on the adult patients and express caution regarding the indiscriminate use of extended retention in routine orthodontics.On the other hand,a repeated oral hygiene instruction and periodontal cleaning at least on a 6-month interval were needed.2)As to the stabilizing effects in the short-term, fixed retainer group was much better than removable retainer group.Considering the nature of the two ways of retention,the rationality of fixed retainer is open to question.2.The clinical application research of fixed and removable retainer and recognization of posttreatment results72 study models taken before(T-l) and after (T-2) orthodontic treatment and at least 6 months out of active treatment(T-S) of patients who were still in the phase of retention and 10 study models of nontreated good-to-ideal occlusion were evaluated according to Ideal Tooth Relationship Index(ITRi) and changes of occlusion relationship in the phase of orthodontic retention were studied.Results:The occlusion relationship in the phase of retention is not stable and there exists a dynamic change;It shows that the improved relationship is closely related to the visible position in dental arch and subjective factors of clinicians .The better these positions are,the higher degree of the improvement,visa versa.Conclusion:l)The instability of the results of orthodontic treatment do exist,and good interdigitation after treatment is very important.As far as the application of the retainer was concerned ,either fixed retainer or removable one,should not add new4unstable factor as far as possible to avoid interfere the settling of occlusion.2)Because of variations in craniofacial complex and limitations of orthodontic treatment, "ideal occlusion" is ralely obtained.The differences of changing tendency of static and dynamic occlusion relationship in the phase of retention indicated sometimes mild crowding was exchanged for improvement of occlusal function...