Available online 29 November 2022

Author links open overlay panelAbstractStatement of problem

Prosthetic rehabilitation with an obturator can help to restore or improve the intelligibility of speech in patients after maxillectomy. The frequency of formants 1 and 2 as well as their ranges were initially reported in patients with maxillary defects in 2002, and the evaluation method that was used is now applied in clinical evaluation. However, the details of formant 3 are not known and warrant investigation because, according to speech science, formant 3 is related to the pharyngeal volume. Clarifying the formant frequency values of formant 3 in patients after maxillectomy would enable prosthodontists to refer to these data when planning treatment and when assessing the outcome of an obturator.

Purpose

The purpose of this clinical study was to determine the acoustic characteristics of formant 3, together with those of formants 1 and 2, by using a digital acoustic analysis during maxillofacial prosthetic treatment. The utility of determining formant 3 in the evaluation of speech in patients after maxillectomy was also evaluated.

Material and methods

Twenty-six male participants after a maxillectomy (mean age, 63 years; range, 20 to 93 years) were included, and the 5 Japanese vowels /a/, /e/, /i/, /o/, and /u/ produced with and without a definitive obturator prosthesis were recorded. The frequencies of the 3 formants were determined, and their ranges were calculated by using a speech analysis system (Computerized Speech Lab CSL 4400). The Wilcoxon signed rank test was used to compare the formants between the 2 use conditions (α=0.05).

Results

Significant differences were found in the frequencies and ranges of all 3 formants between the use conditions. The ranges of all 3 formants produced with the prosthesis were significantly greater than those produced without it.

Conclusions

Based on the findings, both the first 2 formants and the third formant were changed by wearing an obturator prosthesis. Because formant 3 is related to the volume of the pharynx, evaluation of this formant and its range can reflect the effectiveness of the prosthesis to seal the oronasal communication and help reduce hypernasality, suggesting the utility of formant 3 analysis in prosthodontic rehabilitation.

Section snippetsMaterial and methods

The participants were 26 men (mean age, 63 years; range, 20 to 93 years) who had undergone maxillary resection without skin grafting. In all individuals, the defect resulted in oronasal communication. All participants were native Japanese speakers with normal hearing and the ability to communicate verbally, with normal soft palate function and no obvious vocal fold disorders. All had received rehabilitation with a definitive obturator prosthesis at the Maxillofacial Prosthetic Clinic of the

Results

During the evaluations, hypernasality and general intelligibility of their speech clearly improved with the prosthesis than without it. Figure 3 shows the results for F1. The mean rank peak frequency for /a/ was significantly higher with the prosthesis (median 657.00 Hz) than without it (712.43 Hz; P=.013), whereas the mean rank peak frequency for /i/ was significantly lower with the prosthesis (297.65 Hz) than without it (270.18 Hz; P=.012). No significant changes in F1 were found for

Discussion

The null hypothesis was rejected because a difference was found in the mean rank peak frequency of F3 between wearing and not wearing the obturator in patients after maxillectomy. When participants were wearing their prosthesis, the mean rank peak frequency of F1 significantly decreased for /i/ and significantly increased for /a/ compared with that when not wearing it, becoming closer to the result of individuals without a maxillectomy.1 The result of the present study matched the theory of F1

Conclusions

Based on the findings of this clinical study, the following conclusions were drawn:

1.

The frequency of the first 3 formants was changed by wearing an obturator prosthesis.

2.

Given that F3 is related to the volume of the pharynx, the findings suggest that F3 and its range might reflect the effectiveness of the obturator prosthesis to seal the oronasal communication and help reduce hypernasality.

3.

The results of F3 measurement could be as helpful to maxillofacial prosthetists as information on F1 and F2

Acknowledgments

The authors thank all the members in the department of maxillofacial prosthetics for their help and support.

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© 2022 by the Editorial Council for the Journal of Prosthetic Dentistry.