Evaluation of articulation simulation system using artificial maxillectomy models

Abstract

Acoustic evaluation is valuable for guiding the treatment of maxillofacial defects and determining the effectiveness of rehabilitation with an obturator prosthesis. Model simulations are important in terms of pre-surgical planning and pre- and post-operative speech function. This study aimed to evaluate the acoustic characteristics of voice generated by an articulation simulation system using a vocal tract model with or without artificial maxillectomy defects. More specifically, we aimed to establish a speech simulation system for maxillectomy defect models that both surgeons and maxillofacial prosthodontists can use in guiding treatment planning. Artificially simulated maxillectomy defects were prepared according to Aramany's classification (Classes I-VI) in a three-dimensional vocal tract plaster model of a subject uttering the vowel /a/. Formant and nasalance acoustic data were analysed using Computerized Speech Lab and the Nasometer, respectively. Formants and nasalance of simulated /a/ sounds were successfully detected and analysed. Values of Formants 1 and 2 for the non-defect model were 675.43 and 976.64 Hz, respectively. Median values of Formants 1 and 2 for the defect models were 634.36 and 1026.84 Hz, respectively. Nasalance was 11% in the non-defect model, whereas median nasalance was 28% in the defect models. The results suggest that an articulation simulation system can be used to help surgeons and maxillofacial prosthodontists to plan post-surgical defects that will be facilitate maxillofacial rehabilitation.

Digitized Speech Characteristics in Patients with Maxillectomy Defects

“…Formant frequencies were calculated using linear predictive coding (LPC), an autocorrelation method. An LPC filter order with 12 coefficients was chosen because it provides clearly defined formant peaks . Pre‐emphasis on 0.9 and 1024 waveform points per frame was selected, and a Hamming window was applied.…”

“…Because speech is a major determining factor, it must be accurately evaluated to achieve proper rehabilitation, which in turn helps patients to reintegrate into society. Previous studies have evaluated speech in patients after maxillectomy; a few have used speech intelligibility evaluation tests, while many others have used digital processing methods that do not depend on perceptual determinants . Digital speech analysis aids in the reproducible evaluation of objective wave patterns and allows easier data processing.…”

“…Previous studies have evaluated speech in patients after maxillectomy; a few have used speech intelligibility evaluation tests, [5][6][7] while many others have used digital processing methods that do not depend on perceptual determinants. 1,[8][9][10] Digital speech analysis aids in the reproducible evaluation of objective wave patterns and allows easier data processing.…”

“…The shape of the vocal tract determines the resonance of sounds, characterizing vowels and consonants. 1,8 The oral tract is highly mobile and consists of the tongue, pharynx, palate, lips, jaw, and teeth. The nasal tract is immobile but is coupled with the oral tract.…”

“…1 Formant frequency measurement is a speech analysis method used to evaluate speech outcomes in patients after maxillectomy. Several speech evaluation methods have previously been reported, 1,[7][8][9][10]12,13 including data analysis of the F1-F2 ranges of five vowels. This method revealed that the F2 range is useful for evaluating the speech of maxillectomy patients without a prosthesis.…”