M. Hattori et al. / Open Journal of Stomatology 3 (2013) 365-369
368
Figure 5. Speech recognition score and conversational intelli-
gibility showed a positive correlation when wearing the plate
(correlation coefficient (r) = 0.729, P = 0.017).
4. DISCUSSION
The advantages of the automatic conversation intelligi-
bility test system, which employs computerized recogni-
tion software based on a fast Fourier transform-based
cepstrum analysis and hidden Markov model matching
technology, are its easy operation, objective evaluation,
and the lack of the need for human listeners [9]. In this
study, the system was able to detect significant decreases
in the speech recognition score when subjects were wear-
ing the palatal plate, indicating that the system can detect
slight differences in articulation caused by the plate.
Wearing the plate not only blocked sensory feedback
from the palate but it also changed the positional rela-
tionship of the tongue and the articulators because of the
plate’s thickness. This affected consonant synthesis and
resulted in an unnatural-sounding speech. Such an im-
pairment created sufficient acoustic differences in some
instances that the computerized speech recognition soft-
ware recognized words that were different from the ac-
tual test words. This explains why the low conversational
intelligibility scores given by human subjects in the tra-
ditional testing method correlated positively with the
speech recognition score given by the automatic test sys-
tem. In future, the automatic testing system may prove
useful for evaluating the effects of different denture de-
signs or of denture adjustment on speech.
The present study compared the speech recognition
scores with and without wearing a dental appliance.
Based on these results, the null hypotheses-there is no
difference in the result of the automatic test between the
following 2 conditions: with the palatal plate placed and
with the palatal plate removed and speech recognition
score is not correlated with the result of conventional
intelligibility test—were rejected.
Future studies should examine the score using dental
appliances of different designs. The results of computer-
ized speech recognition are reported to be affected by
variability in speaker characteristics such as age, sex, and
accent [10,11]. Accordingly, the subjects in the present
study were limited to same sex, had a small age distribu-
tion, and spoke 1 language in the same regional accent.
Further study is warranted with a larger number of sub-
jects of both sexes, in different age groups, and speaking
with different accents. In addition, because utterances
were recorded immediately after placing the palatal plate
in this study, it will be interesting to examine changes in
the speech recognition score over time as the subject gets
habituated to the denture placement.
5. CONCLUSION
The automatic test system detected a significant differ-
ence in speech intelligibility, using the speech recogni-
tion score, in normal subjects with and without place-
ment of a palatal plate. The results of the automatic test
system and the conventional evaluation method by hu-
man listeners were positively correlated. These findings
suggest that the system can be used to evaluate speech
intelligibility of denture wearers.
6. ACKNOWLEDGEMENTS
This research was supported by the Japan Society for the Promotion of
Science Grants-in-Aid for Scientific Research (KAKENHI; KAKENHI
[Grant No. 23792207]).
This work was supported by a support program for women research-
ers from the Tokyo Medical and Dental University.
REFERENCES
[1] Chierici, G. and Lawson, L. (1973) Clinical speech con-
siderations in prosthodontics: Perspectives of the prost-
hodontist and speech pathologist. Journal of Prosthetic
Dentistry, 29, 29-39.
http://dx.doi.org/10.1016/0022-3913(73)90136-4
[2] Kong, H.J. and Hansen, C.A. (2008) Customizing palatal
contours of a denture to improve speech intelligibility.
Journal of Prosthetic Dentistry, 99, 243-248.
http://dx.doi.org/10.1016/S0022-3913(08)60049-9
[3] Umino, S., Masuda, G..G., Ono, S. and Fujita, K. (1998)
Speech intelligibility following maxillectomy with and
without a prosthesis: An analysis of 54 cases. Journal of
Oral Rehabilitation, 25, 153-158.
http://dx.doi.org/10.1046/j.1365-2842.1998.00238.x
[4] Rieger, J., Wolfaardt, J., Seikaly, H. and Jha, N. (2002)
Speech outcomes in patients rehabilitated with maxillary
obturator prostheses after maxillectomy: A prospective
study. The International Journal of Prosthodontics, 15,
139-144.
[5] Sullivan, M., Gaebler, C., Beukelman, D., Mahanna, G.,
Marshall, J., et al. (2002) Impact of palatal prosthodontic
intervention on communication performance of patients’
maxillectomy defects: A multilevel outcome study. Head
Neck, 15, 530-538. http://dx.doi.org/10.1002/hed.10095
[6] Terai, H. and Shimahara, M. (2001) Speech intelligibility
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