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Comparative assessment of the survival, stability and occlusal settling between two types of thermoplastic retainers: a prospective clinical trial

Bethany Cunning
Bethany Cunning
, 
Alison Sahhar
Alison Sahhar
, 
Sarah Lawrence
Sarah Lawrence
, 
David Manton
David Manton
 und 
Paul Schneider
Paul Schneider
   | 17. Feb. 2022
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Online veröffentlicht: 17. Feb. 2022
Seitenbereich: 74 - 87
Eingereicht: 01. Okt. 2021
Akzeptiert: 01. Jan. 2022
DOI: https://doi.org/10.21307/aoj-2022.011
© 2022 Bethany Cunning et al., published by Sciendo
This work is licensed under the Creative Commons Attribution 4.0 International License.

Figure 1

Demonstration of Little's Irregularity Index applied to the maxillary anterior teeth using MeshLab® software. The index is the sum of contact point displacements.
Demonstration of Little's Irregularity Index applied to the maxillary anterior teeth using MeshLab® software. The index is the sum of contact point displacements.

Figure 2

Demonstration of occlusal contacts using OrthoCAD® software. The coloured dots indicate occlusal contacts of less than 0.2 mm sensitivity.
Demonstration of occlusal contacts using OrthoCAD® software. The coloured dots indicate occlusal contacts of less than 0.2 mm sensitivity.

Figure 3

Flowchart of participants in the study.
Flowchart of participants in the study.

Figure 4

Kaplan-Meier plot comparing the proportion of retainers broken over time between the two retainer groups.
Kaplan-Meier plot comparing the proportion of retainers broken over time between the two retainer groups.

Figure 5

Mean Little's Irregularity Index (mm) for the maxillary arch at pre-treatment, T0, T2 and T3 for the Vivera® and Duran® retainer groups.
Mean Little's Irregularity Index (mm) for the maxillary arch at pre-treatment, T0, T2 and T3 for the Vivera® and Duran® retainer groups.

Figure 6

Mean Little's Irregularity Index (mm) for the mandibular arch at pre-treatment, T0, T2 and T3 for the Vivera® and Duran® retainer groups.
Mean Little's Irregularity Index (mm) for the mandibular arch at pre-treatment, T0, T2 and T3 for the Vivera® and Duran® retainer groups.

Figure 7

Median number of anterior and posterior occlusal contacts (<0.2 mm) at T0, T2 and T3 for the Vivera® and Duran® retainer groups.
Median number of anterior and posterior occlusal contacts (<0.2 mm) at T0, T2 and T3 for the Vivera® and Duran® retainer groups.

Figure 8

Median number of anterior and posterior near occlusal contacts (0.2 mm < x < 0.4 mm) at T0, T2 and T3 for the Vivera® and Duran® retainer groups.
Median number of anterior and posterior near occlusal contacts (0.2 mm < x < 0.4 mm) at T0, T2 and T3 for the Vivera® and Duran® retainer groups.

Occlusal and near occlusal contacts measured at T0, T2 and T3 for each retainer type. Recorded as median and IQR due to data not being of normal distribution.

T0 Median (IQR) T2 Median (IQR) T3 Median (IQR)
Sensitivity measurement (mm) Anterior Posterior Anterior Posterior Anterior Posterior
Vivera® < 0.2 1 (0–3) 7 (3–7) 2 (1–5) 1.5 (0.75–4.25) 6 (3.5–7) 8 (7–11)
0.2 < x < 0.4 7 (2–7.25) 7.5 (6.75–8) 5 (1.75–7) 8 (4–8) 7 (4.5–9) 14 (11–5.5)
Duran® < 0.2 1 (0–3) 7 (3–7) 2 (1–5) 7 (3–11) 4 (2–5) 12 (11–13)
0.2 < x < 0.4 3 (1–6) 11 (7–15) 4 (2–6) 14 (12–17) 6 (2–6) 18 (15–22)

Patient demographic information at the time of T0 and pre-treatment clinical characteristics of subjects in Vivera® and Duran® retainer groups.

Vivera®(n = 10) Duran®(n = 14)
Gender
  Male 4 (40%) 6 (42.8%)
  Female 6 (60%) 8 (57.1%)
Age (yr)
  Median (IQR) 34 (28–48) 31 (26–38)
Pre-treatment characteristics
  Skeletal classification
    Class I 5 (50%) 8 (57.1%)
    Class II 4 (40%) 6 (42.8%)
    Class III 1 (10%) 0
  Dental classification
    Class I 7 (70%) 10 (71.4%)
    Class II division 1 2 (20%) 1 (7.1%)
    Class II division 2 1 (10%) 3 (21.4%)
    Class III 0 0
  Missing teeth (excluding third molars)
    None 9 (90%) 14 (100%)
    Missing two premolars 1 (10%) 0
    Missing four premolars 0 0

The secondary outcomes (stability and occlusal settling) measurement methods are displayed.

Unit Description
Stability
  Little's Irregularity Index mm The sum of the five contact point displacements for the anterior teeth.
Occlusal settling
  Occlusal contacts Number of contacts The numerical value of contact points measured on the mandibular arch.Two sensitivity levels measured:‘Occlusal Contact’ = < 0.2 mm‘Near Occlusal Contact’ = 0.2 mm < x < 0.4 mm

Occlusal and near occlusal contact results analysed using non-parametric Mann–Whitney test and presented as median, IQR and P-value.

Sensitivity measurement Location Vivera® Median (IQR) Duran® Median (IQR) P-value
Number of occlusal contacts at T0
Occlusal contact Anterior 1 (0–3) 1 (0–3) 0.46
Posterior 7 (3–7) 7 (3–7) 0.01*
Near occlusal contact Anterior 7 (2–7.25) 3 (1–6) 0.37
Posterior 7.5 (6.75–8) 11 (7–15) 0.08
Change in number of occlusal contacts from T0 to T2
Occlusal contact Anterior 0.5 (−0.5 to 1.25) 1 (0–2) 0.65
Posterior 0.5 (−1.25 to 1.25) 1 (−1 to 2) 0.81
Near occlusal contact Anterior 0 (−1.25 to 0) 0 (−1 to 1) 0.41
Posterior 0.5 (−3.25 to 1.25) 0 (−1 to 4) 0.6
Change in number of occlusal contacts from T2 to T3
Occlusal contact Anterior 2 (0.5–3) 0 (0–1) 0.3
Posterior 7 (4–10) 5 (4–9) 0.54
Near occlusal contact Anterior 1 (−0.5 to 4) 0 (0–3) 0.06
Posterior 10 (3–11.5) 1 (0–6) 0.3

Reason for retainer failure over 6 months, including initial and subsequent retainers inserted.

Vivera® Retainer Duran® Retainer
Total number of subjects 9 14
Total number of retainers 18 41

Stability measurements of Little's Irregularity Index (mm). Data are presented in the form of mean, standard deviation and P-value due to normal distribution.

Vivera® Duran® 95% CI
Little's Irregularity Index Mean SD Mean SD P-value Difference in Mean Lower Upper
Pre-treatment maxillary 5.62 2.77 7.55 2.83 0.16 1.93 −4.67 0.83
Pre-treatment mandibular 7.53 4.1 8.03 3.9 0.8 0.5 −4.48 3.48
3-month relapse (T2–T0) maxillary 0.35 0.5 0.51 0.39 0.47 0.16 −0.62 0.3
3-month relapse (T2–T0) mandibular 0.34 0.31 0.24 0.4 0.55 0.1 −0.24 0.44
6-month relapse (T3–T2) maxillary 0.13 0.08 0.33 0.32 0.14 0.2 −0.46 0.08
6-month relapse (T3–T2) mandibular 0.51 0.53 0.29 0.55 0.43 0.22 −0.38 0.83

Comparison of the number of occlusal and near occlusal contacts following full-time and night-time wear regimes for each retainer type. Assessed using non-parametric, paired Wilcoxon Signed Rank test. P-value recorded.

T0 vs T2 T2 vs T3
Sensitivity Measurement (mm) Anterior Posterior Anterior Posterior
Vivera® (P-value) < 0.2 0.92 0.86 0.06 0.02*
0.2 < x < 0.4 0.11 0.73 0.21 0.05*
Duran® (P-value) < 0.2 0.11 0.43 0.75 0.03*
0.2 < x < 0.4 0.96 0.37 0.46 0.11
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