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 Table of Contents  
ORIGINAL RESEARCH
Year : 2017  |  Volume : 9  |  Issue : 2  |  Page : 49-54

An In vivo study to compare the difference in speech sounds observed with conventional and customized palatal contour dentures


1 Department of Prosthodontics, Government Dental College and Hospital, Jamnagar, Gujarat, India
2 Department of Prosthodontics, A.B. Shetty Memorial Institute of Dental Sciences, Mangalore, Karnataka, India
3 Department of Prosthodontist, Takvani Dental and Children Hospital, Jamnagar, Gujarat, India

Date of Web Publication13-Apr-2017

Correspondence Address:
Takvani Rimmy
Department of Prosthodontics, Government Dental College and Hospital, Jamnagar - 361 008, Gujarat
India
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/jioh.jioh_42_17

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  Abstract 


Aims: The aim of this study is to compare the difference in speech sounds of different phonemes at different syllable positioning observed with conventional and customized palatal contoured dentures. Materials and Methods: A case–control and single-blinded study was conducted on thirty completely edentulous subjects with no previous denture experience. Digital recordings of all subjects were made without denture which served as control, with conventional denture (denture I) and with customized palatal contour denture (denture II) in a sound treated room. The recordings were then compared for phonemes “ch,” “j,” “sh,” “s,” “t,” “d,” “n,” and “l” at initial and middle positions. The permission for conducting the study was taken from the ethical committee. For comparison of both the types of dentures, Chi-square test and for finding inter-examiner reliability, Cronbach's alpha was used. Results and Conclusions: The results showed that there is a difference between the pronunciation of different phonemes at different positions. Customized palatal contour dentures are better for enunciation of middle “ch,” initial “j,” middle “sh,” initial “s,” middle “t,” initial “d,” middle “n,” and initial “l” phonemes and the results were statistically significant. Conventional dentures are better for enunciation of middle “j,” initial “sh,” middle “s,” and initial “t” phonemes and the results were statistically significant. It can be concluded customized dentures prove to be better when compared to conventional dentures. There lies a difference in pronunciation of the same phoneme when it occupies different syllable positioning. It can also be concluded that during any dental evaluation concerning phonetics, a series of words with the same phoneme at different positions should be used for assessment instead of a single word.

Keywords: Conventional dentures, customized palatal contour denture, phonetics, speech evaluation, speech sounds, syllable positioning


How to cite this article:
Rimmy T, Prasad D K, Takvani A. An In vivo study to compare the difference in speech sounds observed with conventional and customized palatal contour dentures. J Int Oral Health 2017;9:49-54

How to cite this URL:
Rimmy T, Prasad D K, Takvani A. An In vivo study to compare the difference in speech sounds observed with conventional and customized palatal contour dentures. J Int Oral Health [serial online] 2017 [cited 2017 Dec 13];9:49-54. Available from: http://www.jioh.org/text.asp?2017/9/2/49/204537




  Introduction Top


When steps in completion of successful prosthesis are considered, considerable attention is given to esthetics and mechanics, but very little importance has been given to improve phonetics.[1] In the field of dentistry, it is observed that more emphasis is placed on conducting researches on elements such as esthetics, function, occlusion, and comfort for achieving successful treatment outcome than phonetics.[2],[3],[4] This neglect can be attributed to the fact that speech returns to normal after a practice period in most of the prosthesis although it causes lot of embarrassment to the patient during that period.

Tongue contacts different areas of stomatognathic system while articulating different speech sounds.[5] Furthermore, the areas and position of contact varies when the same phoneme or when the phoneme occupies different syllable positions in a word, i.e., phoneme “p” in pink, spin, and tip. In “pink,” it occupies initial syllable positioning. In “spin,” it occupies middle syllable positioning and in “tip,” it occupies final syllable positioning. It has been documented well in the text of speech science that articulation of the same phoneme in different positions varies.

In complete dentures, it is suggested that placing a familiar palatal morphology or rugae pattern which is present in the patient's mouth when incorporated in complete denture prosthesis may increase speech intelligibility of the patient and thus, its adaptation to the new denture.[5]

There are many studies which have been conducted to understand the palatograms or tongue-palate position with articulation of different speech sounds in normal dentate individuals as well as patients with complete denture prosthesis. However, there stands no study which compares and evaluates the perceptual analysis of speech sounds with smooth polished surface and polished surface with familiar palatal morphology.

Hence, it is thought desirable to undertake this present study with following objectives:

  • To evaluate different speech sounds after insertion of conventional dentures and customized palatal contour complete denture
  • To compare the difference in speech sounds observed with conventional and customized palatal contoured dentures.



  Materials and Methods Top


Thirty completely edentulous subjects with no previous denture experience were selected for the study. At 90% power, assuming 50% improvement needs the sample size to be 26, so a rounding it to a figure of thirty was selected as sample size. Subjects who were native speakers of and who could read Kannada and Malayalam language script were included in the study. Subjects which had any complaint of hearing impairment, mental retardation, neurological problem, and language delay or with a history of laryngeal or palatal surgeries were excluded from the study. Subjects were informed about instruments and procedures to be performed and consent was taken. The waitlist of completely edentulous patients which was prepared in the Department of Prosthodontics according to the date and time of reporting of the patients was used for selecting the subjects. All complete edentulous patients who were first-time denture wearers and reported in the past 6 months before the commencement of the study were selected to form the sample pool. It consisted of around 350 numbers in sample pool, out of which 30 random numbers were selected. Informed consent was taken from all the subjects who were a part of the study.

The variables used in the study were conventional dentures and customized palatal contour dentures. The conventional dentures were fabricated in the usual protocol, and the thickness of all the dentures in the palatal area was kept 2 mm. For customized palatal contour dentures, putty index of palatal rugae area of the patient was made [Figure 1]a and [Figure 1]b and poured with melted modeling wax to obtain the exact replica of rugae and incisive papilla of the subject [Figure 2]. After hardening, this wax replica was adapted to the polished surface of the denture in the corresponding region [Figure 3]. For correct placement of the wax replica, the denture was placed against an illuminated source of light, and corresponding rugae pattern were marked with marker pen and wax replica was then oriented and adapted on the polished surface of the denture by flowing a thin layer of molten wax on the margins of the replica.
Figure 1: (a) Palatal view of the maxillary arch. (b) Putty index/negative replica of the rugae pattern and palatal morphology

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Figure 2: Wax replica of rugae pattern and palatal morphology

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Figure 3: Wax replica adapted on the palatal surface of denture

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Ethical clearance for the study was obtained from NGSM Institute of Pharmaceutical Sciences, Mangalore, Karnataka, India.

Recordings

The speech samples were recorded in a sound treated room. Subject was seated comfortably on a chair opposite to the investigator across the table. The material contained word list from Kannada Articulation Test (Babu and Rathna, 1985) and Malayalam Articulation Test (Maya, 1990).

The instruments used for the study were Logitech Microphone (Laussane, Switzerland), Acer Desktop Computer. (New Taipei City, Taiwan), Praat software, University of Amsterdam, Netherlands (Paul and David, 2009; version 5.0.37 [Figure 4]) and speaker/headphone. The subjects were asked to read the word list aloud as they would normally read. The speech output was recorded using Praat software (University of Amsterdam, Netherlands), through the microphone kept at a distance of 10 cm away from the mouth of the subject at a sampling rate of 16 kHz and stored for further analysis.
Figure 4: Recording on PRAAT software

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The recordings were made in three different conditions. In condition I, the recordings were done without denture which served as control and in condition II and III, the recordings were done when the subjects were wearing conventional dentures and customized palatal contour dentures, respectively.

The data recorded from thirty complete edentulous patients formed the material and was provided to the trained speech therapists for perceptual analysis. The test groups were randomized and named as denture I and denture II and study design was a single-blind study as the speech pathologist analyzing the samples is unaware of which sample he/she is analyzing. The recordings were compared for phonemes “ch,” “j,” “sh,” “s,” “t,” “d,” “n,” and “l” at initial and middle positions. The difference between the variables was assessed on subjective parameters by speech therapists on the scale of 1-5 in which score 1 was given if the speech was very poor as compared to control, slight deterioration a score of 2, average or similar to control group a score of 3, slightly better than control group a score of 4, and a score of 5 was given if considerable improvement from control sample was observed. The assessed data thus obtained from three trained speech therapists were statistically analyzed using Chi-square test and inter-examiner reliability were found out by Cronbach's alpha. The total duration of study commencing from sample selection to statistical analysis was 15 months.


  Results Top


The data obtained from three speech therapists and statistical analysis using Epi info software version 3.5.4 developed by CDC, Atlanta, USA for Windows and is demonstrated in the form of tables. Inter-examiner reliability was assessed by Cronbach's alpha which yielded results with poor, questionable, and unacceptable results.

For customized palatal contour, poor reliability was observed for phonemes such as initial “j” and middle “s,” questionable reliability for phonemes such as middle “ch” and initial “s” and unacceptable reliability was observed for initial “ch,” initial “sh,” middle “j,” middle “s,” initial and middle “t,” “d,” “n,” and “l” [Table 1].
Table 1: Cronbach's alpha values for inter-examiner reliability for customized palatal contour dentures

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For conventional dentures, poor reliability was observed for phonemes like middle “j,” initial “sh” and middle “n,” questionable reliability for phonemes such as middle “ch,” initial “s” and initial “l” and unacceptable reliability was observed for initial “ch,” middle “sh,” initial “j,” middle “s,” initial and middle “t” and “d,” initial “n,” and middle “l” [Table 2].
Table 2: Cronbach's alpha values for inter-examiner reliability for conventional dentures

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There is a varied distribution which can be observed for phonemes under the scores of 1-5 for thirty edentulous patients for phonemes “ch,” “j,” “sh,” “s,” “t,” “d,” “n,” and “l” at initial and middle positions [Table 3],[Table 4],[Table 5],[Table 6]. The values of Chi-square test depicts that customized palatal contour dentures are better for enunciation of middle “ch,” initial “j,” middle “sh,” initial “s,” middle “t,” initial “d,” middle “n,” and initial “l” phonemes [Table 7]. It also demonstrates that conventional dentures are better for enunciation of middle “j,” initial “sh,” middle “s” and initial “t” phonemes while there is no difference between conventional and customized palatal contour dentures in pronunciation of initial “ch,” middle “d,” initial “n,” and middle “l” phonemes.
Table 3: Distribution of scores of different phonemes at initial position with conventional denture in thirty edentulous patients

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Table 4: Distribution of scores of different phonemes at initial position with customized palatal contour dentures

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Table 5: Distribution of scores of different phonemes at middle position with conventional denture

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Table 6: Distribution of scores of different phonemes at middle position with customized palatal contour dentures

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Table 7: Chi-square values for different phonemes at different positions

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  Discussion Top


Phonetics play a major part in complete denture construction. It may take several weeks to several months for the same which is a period of embarrassment for the patients.[1] Several studies have demonstrated that modifying the palatal contours improves the speech intelligibility of the patient, but there are many controversies to the thickness of the denture in palatal region.[1],[2],[6],[7]

The concept of initial, middle, and final positions of the same phoneme is well known in the field of speech therapy but has been neglected in the field of dentistry since the beginning era. Phonetic methods are used in many steps of complete denture construction, but always a single word is used to assess accuracy during the procedure instead of a series of words in which the particular consonant takes all initial, middle, and final positions.[8],[9],[10]

The current study differs from previous studies in this field as it evaluates the phonemes at different syllable positioning, which have stayed as the neglected part in the field of dentistry.

Final positions were not assessed as the subjects in the current study were Kannada and Malayalam speaking which are bi-syllabic languages, i.e., these languages do not have any words with final positions or, in other words, all the words end with vowels. The phonemes assessed were “ch,” “j,” “sh,” “s,” “t,” “d,” “n,” and “l.” The phonemes “zh” and “z” as assessed in other studies could not be assessed as it does not exist in these languages.[6],[11] The words spoken by the subjects for test were in their local language, and only meaningful words were taken to eliminate the deterioration which may be encountered while speaking new words. It is noteworthy that not only these languages have limitations but most of the languages spoken worldwide have some or the other limitations, for example, natives of Arabic language speak “b” in place of “p” and in some places in Rajasthan, initial “sh” or “s” phoneme is replaced by “h.” Furthermore, according to authors” observation, the most widely used language for communication, i.e., English, also does not have phoneme “t” as in pasta and has only “t” as in total.

For standardization, the parameters such as vertical dimension of occlusion, Silvermann's closest speaking space, tongue space, and positioning of teeth were within normal limits.[12] The thickness of the denture base was constant for conventional denture, but customized dentures were thicker in the region of palate due to the addition of extra layer of wax to incorporate palatal contours.

Landa correlates achievement of proper phonetics with vertical dimension.[13] Sears and Pound have shown contouring and fashioning of palatal surface of denture result in improvement in phonation.[14]

It can be observed that in most of the phonemes, except middle j, initial sh, initial t, customized palatal contour dentures were either better or similar to conventional dentures and the findings were statistically significant. This result can be attributed to either the familiar anatomy of the dentures in customized palatal contour dentures due to replication of the similar palatal morphology and avoidance of slippage of tongue to meticulously polished flat dentures. In the current study, persons with no previous experience of dentures were chosen as such patients will not be adapted to the flat and smooth contours of conventional dentures. The method to replicate palatal anatomy is also very simple.

There are varied results which have been obtained in the current study like differences in pronunciation of the same phoneme at different positions which imply that there may be the difference in the oral format of speech pattern in the same sound when it occupies a different position in the word.

In the current study, the Cronbach's alpha values for finding inter-examiner reliability yielded results with poor, questionable, and unacceptable results. This may not be accepted by many of the clinicians, but it is to be noted that high reliability is not always “a good entity and high item homogeneity is also not always desirable. When you have comparisons which are on a broader construct, for example, comparison of intelligence or tests of personality, the issue of reliability is complex.[15] It may also be observed that although inter-examiner reliability may not be there for such subjective researches, intra-examiner reliability would be there if the same sample is assessed by the same examiner at different times.

It is also to be noted that the customized denture yielded better results for most of the phonemes at different positions even though they were thicker in the palatal region as compared to the conventional dentures.[16],[17]

The strength of the study lies in the fact that there exists a difference in enunciation of the same phoneme when it occupies different syllable position. This finding may not be very distinctive for normal patients, but in case of patients with cleft lip and palate, who require regular follow-ups for evaluating improvement in speech, this difference may play a major role.[18],[19],[20] In case of patients where evaluation of speech after surgery or palatal lift prosthesis is also a necessity, the speech evaluation of same phoneme with different syllable positioning may play a major role.[21] The study is limited by the fact that it uses subjective method for analysis of the speech samples which causes variability in the evaluation. Future studies can be conducted using other methods for evaluation of such samples.

There can be many other factors which may influence the articulation and speech intelligibility in a person who needs complete denture service.[22] One of the influencing factors can be improperly scored posterior palatal seal in the denture. The reason may be attributed to the fear which the patient encounters related to falling of maxillary denture and consciousness about the gap between the denture and tissues of soft palate while speaking. Such a fear may result in conscious effort of placing the tongue posteriorly to stabilize the denture and hence cause deterioration in speech. The other attributing factor is poor retention of the lower denture which causes distortion in speech. Many authors have utilized phonetical approach to improve the retention of mandibular dentures.[23] These factors may also be included in future studies.

The results obtained from the present study imply that during any prosthodontic evaluation concerning phonetics, a series of words with the same phoneme at different positions instead of single word used for assessment.


  Conclusions Top


Familiar anatomical replication or incorporation of rugae pattern causes less deterioration of the speech in patients with no previous denture experience. The above study complies that there exists a clear difference in pronunciation even when the same phoneme occupies different positions in a word. Hence, during any prosthodontic evaluation concerning phonetics, a series of words with same phoneme at different positions should be used for assessment instead of a single word.

The evidence of concept of evaluating same phoneme at different positions is already existent in the fields of speech sciences. There exists a need for better understanding or oral formats of speech patterns of different phonemes at initial, middle, and final position in the field of dentistry as well.

Acknowledgment

We are thankful to Prof. T. Dattatreya, Head and Principal, Nitte Institute of Speech and Hearing and all the lecturers and interns in Department of Audiology and Speech Pathology for supporting and helping us during the study.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.



 
  References Top

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    Figures

  [Figure 1], [Figure 2], [Figure 3], [Figure 4]
 
 
    Tables

  [Table 1], [Table 2], [Table 3], [Table 4], [Table 5], [Table 6], [Table 7]



 

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