Posterior occlusion changes with a Hawley vs Perfector and Hawley retainer. A follow-up study

Abstract

Objective: To characterize postorthodontic settling of the posterior occlusion of patients wearing Hawley retainers vs patients who initially wore Perfector retainers and then switched to Hawley retainers.

Materials and methods: This follow-up study was based on 40 patients (25 Perfector and 15 Hawley), who were part of a larger sample of 50 patients randomly assigned to wear either Hawley or Perfector retainers. The Perfector patients were given Hawley retainers 2 months after retainer delivery. Occlusal bite registrations were scanned and traced to quantify posterior areas of contact and near contact (ACNC). A seven-item questionnaire was used to assess the patient's perception of occlusion. Measurements were obtained at the on the day of retainer delivery, 2 months post delivery, 6 months post delivery, and 8 months post delivery.

Results: ACNC increased significantly (P < .05) during the first 6 months of retainer wear. The ACNC of the Hawley and Perfector/Hawley groups increased by 129% and 105%, respectively, over 8 months of retention. The greatest increases in ACNC occurred during the first 2 months. The ACNC further increased between 2 and 6 months in both groups. The Perfector/Hawley group also showed slight increases in ACNC between 6 and 8 months. Overall group differences were not statistically significant. The Perfector/Hawley group perceived greater improvements in occlusion than the Hawley group, but group differences after 8 months were small.

Conclusions: Substantial amounts of settling occurred at decelerating rates during the first 6 months after retainer delivery. No significant differences in ACNC were found between the Hawley and Perfector/Hawley groups after 8 months of retainer wear.

Figure 1

Median cumulative areas of contact and near contact measured at 50 µm thickness levels between the day of delivery and 8 months post retainer delivery for patients initially wearing Hawley retainers.

Figure 2

Median cumulative areas of contact and near contact between the day of retainer delivery and 8 months post retainer delivery for patients initially wearing Perfector retainers.

Figure 3

Median changes in areas of contact and near contact that occurred during the first 8 months after retainer delivery at each of the thickness levels for patients initially wearing Hawley or Perfector retainers.

Figure 4

Median cumulative changes in areas of contact and near contact that occurred over the first 8 months after retainer delivery for patients initially wearing Hawley or Perfector retainers.