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Randomized Controlled Trial
. 2024 Jul 8;29(3):e2423277.
doi: 10.1590/2177-6709.29.3.e2423277.oar. eCollection 2024.

Comparison of speech changes caused by four different orthodontic retainers: a crossover randomized clinical trial

Diego Coelho Lorenzoni  1   2 , José Fernando Castanha Henriques  1 , Letícia Korb da Silva  3 , Raquel Rodrigues Rosa  3 , Giédre Berretin-Felix  3 , Karina Maria Salvatore Freitas  4 , Guilherme Janson  1
Affiliations
Randomized Controlled Trial

Comparison of speech changes caused by four different orthodontic retainers: a crossover randomized clinical trial

Diego Coelho Lorenzoni et al. Dental Press J Orthod. .

Abstract
in English, Portuguese

Objective: This study aimed to compare the influence of four different maxillary removable orthodontic retainers on speech.

Material and methods: Eligibility criteria for sample selection were: 20-40-year subjects with acceptable occlusion, native speakers of Portuguese. The volunteers (n=21) were divided in four groups randomized with a 1:1:1:1 allocation ratio. The four groups used, in random order, the four types of retainers full-time for 21 days each, with a washout period of 7-days. The removable maxillary retainers were: conventional wraparound, wraparound with an anterior hole, U-shaped wraparound, and thermoplastic retainer. Three volunteers were excluded. The final sample comprised 18 subjects (11 male; 7 female) with mean age of 27.08 years (SD=4.65). The speech evaluation was performed in vocal excerpts recordings made before, immediately after, and 21 days after the installation of each retainer, with auditory-perceptual and acoustic analysis of formant frequencies F1 and F2 of the vowels. Repeated measures ANOVA and Friedman with Tukey tests were used for statistical comparison.

Results: Speech changes increased immediately after conventional wraparound and thermoplastic retainer installation, and reduced after 21 days, but not to normal levels. However, this increase was statistically significant only for the wraparound with anterior hole and the thermoplastic retainer. Formant frequencies of vowels were altered at initial time, and the changes remained in conventional, U-shaped and thermoplastic appliances after three weeks.

Conclusions: The thermoplastic retainer was more harmful to the speech than wraparound appliances. The conventional and U-shaped retainers interfered less in speech. The three-week period was not sufficient for speech adaptation.

Objetivo:: Este estudo teve como objetivo comparar a influência na fala causada por quatro diferentes contenções ortodônticas removíveis superiores.

Material e Métodos:: Os critérios de elegibilidade para seleção da amostra foram: indivíduos com 20 a 40 anos de idade, com oclusão aceitável, falantes nativos de português. Os voluntários (n=21) foram divididos em quatro grupos, randomizados com proporção de alocação de 1:1:1:1. Os quatro grupos utilizaram os quatro tipos de contenção, em ordem aleatória e em período integral por 21 dias cada, com período de wash-out de sete dias. As contenções superiores removíveis foram: wraparound convencional, wraparound com orifício anterior, wraparound em U e contenção termoplástica. Três voluntários foram excluídos. A amostra final foi composta por 18 indivíduos (11 homens; 7 mulheres) com idade média de 27,08 anos (DP=4,65). A avaliação da fala foi realizada em gravações de trechos vocais, realizadas antes, imediatamente após e 21 dias após a instalação de cada contenção, com análise perceptivo-auditiva e acústica das frequências formantes F1 e F2 das vogais. ANOVA de medidas repetidas e teste de Friedman com Tukey foram utilizados para comparação estatística.

Resultados:: As alterações de fala aumentaram imediatamente após a instalação das contenções wraparound e termoplástica, e reduziram após 21 dias, mas não para níveis normais. Porém, esse aumento foi estatisticamente significativo apenas para as contenções wraparound com orifício anterior e termoplástica. As frequências dos formantes das vogais foram alteradas no momento inicial e, após três semanas, as alterações se mantiveram com as contenções convencional, em forma de U e termoplástica.

Conclusões:: A contenção termoplástica foi mais prejudicial à fala do que os aparelhos wraparound. Oswraparounds convencional e em forma de U interferiram menos na fala. O período de três semanas não foi suficiente para adaptação da fala.

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Conflict of interest statement

The authors report no commercial, proprietary or financial interest in the products or companies described in this article.

Figures

Figure 1:
Figure 1:. Flow diagram of recruitment and interventions. CWA: Conventional wraparound appliance; WAH: Wraparound with an anterior hole; UWA: U-shaped wraparound; TR: thermoplastic retainer.
Figure 2:
Figure 2:. A) Conventional wraparound retainer. B) Wraparound with an anterior hole. C) U-shaped wraparound retainer. D) Thermoplastic retainer.
Figure 3:
Figure 3:. Vocal recordings in an acoustically treated studio.
Figure 4:
Figure 4:. Entries of the software (Praat 5404) used for the analyzes. Edited excerpt of 4 seconds of the vowel “A”, showing the registration of the formants within 1 second.
See this image and copyright information in PMC

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