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A randomized controlled trial comparing retainers in bimaxillary proclination cases

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Clinical Oral Investigations
Authors:
Nurulhuda Maskim
Nurulhuda Maskim
Nurulhuda Maskim
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Norhidayah Mohd Tahir at University of Malaya
Norhidayah Mohd Tahir
Wan Nurazreena Wan Hassan at University of Malaya
Wan Nurazreena Wan Hassan
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Abstract and Figures

Introduction There is currently no recommendation for retaining corrected bimaxillary proclination cases. This study aimed to compare retention protocols for maintaining stability of such cases. Materials and methods In this single-center, single-blinded parallel control trial, 27 participants were assigned to three groups using block randomization with a 1:1:1 allocation ratio; fixed bonded retention (FBR), vacuum-formed retention (VFR), and dual retention (DR) comprising both types. Data were collected every 3-months from debond (T0) for 12 months (T4). The primary outcomes measured changes in soft and dental tissue parameters on traced lateral cephalograms. Secondary outcomes included intra-arch changes and the oral health impact profile (OHIP-14[M]). This trial was registered with Clinicaltrial.gov (NCT04578704). Results At T4, the upper lip, lower lip, and upper incisors moved anteriorly (mean difference (MD) of 1.63 mm (SD 3.7), 0.48 mm (SD 1.1), and 0.54 mm (SD 0.97), respectively). The upper and lower incisors were proclined by 0.96 degrees (SD 2.1) and 1.11 degrees (SD 2.63), respectively. The interincisal angle was reduced by 0.56 degrees (SD 1.23). Only the upper incisor inclination (UII) change showed significant differences between groups (η² = 0.296; p = 0.015). Post-hoc comparisons revealed that the FBR and VFR groups exhibited greater proclination than the DR group (UII, MD = 3.33 degrees and 3.22 degrees, respectively). No differences were observed in OHIP-14[M] scores between the groups. Conclusion All three retention protocols showed statistically small but clinically insignificant changes. Clinical relevance Dual retention offers better control in preventing upper incisor proclination in bimaxillary proclination cases. Trial registration This trial was registered with Clinicaltrial.gov (NCT04578704).
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RESEARCH
Clinical Oral Investigations (2025) 29:117
https://doi.org/10.1007/s00784-025-06199-3
Background
Bimaxillary dental proclination is a condition where the
upper and lower dental arches are proclined. This condition
is commonly observed among Asian [1–3], Caucasian [4],
and Afro-Caribbean populations [5, 6] and is characterized
by increased lip fullness, a convex facial form, everted and
protrusive lips, acute nasolabial angles, proclined incisors,
steep mandibular planes, and a tendency for reduced over-
bite or anterior open bite, irrespective of ethnicity [5].
Patients generally prefer having a straighter prole com-
pared to what is considered normal for the bimaxillary
dental proclination population. Because of this, their orth-
odontic treatment aims to achieve a straight prole [1, 7, 8].
This can be achieved by the extraction of premolar teeth to
Norhidayah Nor Zahidah Mohd Tahir
norhidayahmt@um.edu.my
Nurulhuda Maskim
drnurulhuda.m@moh.gov.my
Wan Nurazreena Wan Hassan
wannurazreena@um.edu.my
1 Orthodontic Unit, Klinik Pergigian Pekan, Hospital Pekan,
Ministry of Health Malaysia, Pekan, Pahang 26600, Malaysia
2 Department of Paediatric Dentistry and Orthodontic, Faculty
of Dentistry, Universiti Malaya, Kuala Lumpur
50603, Malaysia
Abstract
Introduction There is currently no recommendation for retaining corrected bimaxillary proclination cases. This study aimed
to compare retention protocols for maintaining stability of such cases.
Materials and methods In this single-center, single-blinded parallel control trial, 27 participants were assigned to three
groups using block randomization with a 1:1:1 allocation ratio; xed bonded retention (FBR), vacuum-formed retention
(VFR), and dual retention (DR) comprising both types. Data were collected every 3-months from debond (T0) for 12 months
(T4). The primary outcomes measured changes in soft and dental tissue parameters on traced lateral cephalograms. Second-
ary outcomes included intra-arch changes and the oral health impact prole (OHIP-14[M]). This trial was registered with
Clinicaltrial.gov (NCT04578704).
Results At T4, the upper lip, lower lip, and upper incisors moved anteriorly (mean dierence (MD) of 1.63 mm (SD 3.7),
0.48 mm (SD 1.1), and 0.54 mm (SD 0.97), respectively). The upper and lower incisors were proclined by 0.96 degrees (SD
2.1) and 1.11 degrees (SD 2.63), respectively. The interincisal angle was reduced by 0.56 degrees (SD 1.23). Only the upper
incisor inclination (UII) change showed signicant dierences between groups (η² = 0.296; p = 0.015). Post-hoc comparisons
revealed that the FBR and VFR groups exhibited greater proclination than the DR group (UII, MD = 3.33 degrees and 3.22
degrees, respectively). No dierences were observed in OHIP-14[M] scores between the groups.
Conclusion All three retention protocols showed statistically small but clinically insignicant changes.
Clinical relevance Dual retention oers better control in preventing upper incisor proclination in bimaxillary proclination
cases.
Trial registration This trial was registered with Clinicaltrial.gov (NCT04578704).
Keywords Bimaxillary proclination · Stability · Retainers · Fixed bonded retainer · Vacuum formed retainer · Dual
retention
Received: 30 October 2024 / Accepted: 26 January 2025 / Published online: 6 February 2025
© The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature 2025
A randomized controlled trial comparing retainers in bimaxillary
proclination cases
NurulhudaMaskim1· Norhidayah Nor ZahidahMohd Tahir2· Wan NurazreenaWan Hassan2
1 3
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Orthodontic retention is defined as maintaining teeth in optimal aesthetic and functional position after treatment. Despite the necessity of retention phase and the factors influencing the stability of the teeth after orthodontic treatment was discussed by the orthodontist for a long time, it is accepted that a retention phase is essential for stability of orthodontic treatment results nowadays. Therefore, the application of a suitable retention method is important both for prevention of relapse after orthodontic treatment and for increasing patient satisfaction. Removable appliances had been used for many years for retention purposes. Later, fixed retainers were introduced to prevent relapse as having a number of advantages, such as better aesthetics, no need for patient cooperation, effectiveness, and suitability for lifelong retention. However, their need for precise bonding technique, fragility, and tendency to cause periodontal problems by weakening oral hygiene are some of their disadvantages.
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