This study will focus on the relapse of arch width in two types of retention regimes, which are modified vacuum-formed retainers and Hawley type retainers in patients after fixed appliance treatment in transverse arch expansion cases. This will subsequently be of valuable information for clinicians in choosing the appropriate type of retainers after removal of their fixed appliances. This is because the modified vacuum-formed retainers will be significantly cheaper, quicker and easier to fabricate.

Relapse is inevitable in orthodontic treatment. Teeth will want to return to their original position after fixed appliances are removed. Regardless with or without fixed appliances, changes and physiological relapse will still occur due to time and age changes. This is why retention is a crucial part of orthodontic treatment, where it would aim to maintain the corrections achieved after orthodontic treatment.

Literature regarding retainers is quite substantial, where a recent Cochrane review was published comparing the different types of retainers. However, the evidence is lacking in terms of comparison of arch width relapse between modified vacuum-formed retainers and Hawley retainers specifically in expansion cases.

This study aims to compare the relapse in arch width in expansion cases with modified vacuum-formed retainers with palatal coverage versus Hawley type retainers in Unit Ortodontik Universiti Kebangsaan Malaysia (UKM), Klinik Pakar Ortodontik Klinik Kesihatan Bandar Botanik and Unit Pakar Ortodontik Klinik Pergigian Sungai Chua patients. Although other types of modified vacuum-formed retainers effective for maintaining palatal expansion have been described, these retainers require a wire outlining the Cementoenamel junction of the teeth palatally. This technique requires the experience of the technician, is at a higher cost and requires more lab time. The modified retainer that investigators described in this study would be as efficient and as quick as the normal vacuum-formed retainers, which would usually take a couple of hours to make (same day or next day fit). The present practice at all 3 locations constructs Hawley and normal VFR retainers for all orthodontic patients. There are technicians and laboratory facilities to construct normal VFR as well as Hawley retainer. The only difference between modified and normal vacuum formed retainer is the outline of the retainers where the technician would trim the retainer, where it would cover the hard palate. Therefore it is only the location of trimming that is different using the same special trimming appliances for normal VFRs.

A number of subjects who fulfil the criteria will be invited to participate in this study. The study will involve arch width analysis using study models pre, post-debond, 3 months review post-debond, and 6 months review post-debond. All data will be analyses using Statistical Package for Social Sciences (SPSS). The arch width of participants post-fixed appliances will be compared. Most studies compare the arch width, as well as lower incisor irregularity in evaluating relapse in different groups of retainers. However, there are currently no randomized control trials comparing expansion cases of Hawley vs vacuum-formed retainers, hence why this study will be conducted.

The investigators expect to see no difference between the modified vacuum formed retainer and Hawley retainer in terms of maintaining arch expansion post-orthodontic treatment. This would, therefore, mean that there would be a simpler method and would be a suitable more cost-effective alternative as compared to constructing Hawley retainers or adding a palatal wire on the vacuum-formed retainers.

Inclusion Criteria:

1. Patients who are at least 13 years old at time of debond.
2. Treatment plan of extraction or non-extraction followed by straight wire appliances in the upper arch only or both arches
3. Undergone more than 3mm of maxillary dentoalveolar expansion. Initially, the amount of arch width expansion was measured intraorally at debond and compared to their respective pre-treatment dental casts. To ensure accuracy, the measurements were repeated on debond and pre-treatment dental casts. The following linear arch width measurements were made: intercanine width (ICW - the distance between the canine cusp tips), interpremolar width (IPMW - the distance between the premolar cusp tips), interfirst molar width 1 (IFMW1 - the distance between the mesiobuccal cusp), and interfirst molar width 2 (IFMW2 - the distance between the distobuccal cusp). At least two or more points were expanded (> 3mm) to be included in the trial.
4. No chronic medical conditions

Exclusion Criteria:

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2 years

Adverse event was not monitored