Speech is the coordinated function of the vocal tract includes respiratory, phonatory, resonatory and articulatory systems. Hindrance to any of these systems results in speech disorders. Cleft lip and palate (CLP) is one such congenital disorder leading to speech disorder. The abnormal speech of these individuals with cleft lip and palate can be analyzed interms of acoustical, perceptual and physiological measurements. The speech of individuals with cleft palate is primarily characterized by abnormalities in nasal resonance.
This is a direct result of unoperated cleft / fistula and or velopharyngeal dysfunction. The individuals with velopharyngeal dysfunction cannot either adequately or consistently close the velopharyngeal port during speech leading to nasal escape of sound energy. In addition, there may be articulatory errors, including compensatory articulations and reduced voice quality resulting in poor speech intelligibility (McWilliams, Morris & Shelton, 1990; Kuehn & Moller, 2000; Kummer, 2001; Peterson-Falzone, Hardin-Jones & Karnell, 2001; Bzoch, 2004).
Nasal resonance increases and is perceived as hypernasality if the durations of the velopharyngeal opening and closing movements in relation to the opening and closing of the oral cavity become prolonged. Many investigators have showed that certain timing measures reflecting the movements of speech articulators are related to the degree of oral-nasal resonance imbalance in individuals with cleft palate with or without cleft lip (Warren et al. , 1985; Jones, 2000; Dotevall et al. 2001, 2002; Ha et al. , 2004). Jones (2000) opined that excessive perceived nasalization could result from a mistiming of velopharyngeal movements, relative to voice onset and offset. Few studies (Ha, Sim, Zhi, & Kuehn, 2003; Ha, David, & Kuehn, 2010) concluded that individuals with cleft palate exhibit longer acoustic nasalization than normal speakers and also temporal measures of their speech are positively correlated with the perceived hypernasality.
Hence they concluded that acoustic measures of temporal characteristics of speech can provide supplementary diagnostic information in relation to the degree of hypernasality. Hoopes, (1970) demonstrated that speed of velar movement during speech was slower for individuals with cleft palate than normal subjects. Forner (1983) observed some difficulty with normal rate and range of movement and interarticulatory timing based on the results of significantly longer than normal speech segment durations.
The rehabilitation of individuals born with cleft lip and palate and related craniofacial anomalies require coordination of plastic surgery, prosthetic intervention and behavioral therapy. A multidisciplinary approach is essential to achieve optimum results. To permit development of normal speech patterns, habilitation of these individuals should be considered surgically or prosthetically as early as possible (Riski, 1979; Dorf & Curtin, 1982; Witzel et al. , 1984).
Definitive prosthodontic treatment is usually one of the final therapies instituted and it must attempt to alleviate any anatomical and functional deficiencies that may remain after the gamut of other treatment is essentially completed. The concept of using speech prosthesis was introduced as early as 1860 in treating velopharyngeal dysfunction in clients with cleft lip and palate (Mc Grath and Anderson 1991) and has since been adopted by others (Leeper et al. 1996).
The use of speech bulb obturator in the treatment of hypernasality became less popular in the 19th century, but was revived in the 20th century. This was partly due to the development of techniques that permitted direct visualization of the velopharyngeal mechanism and advances in the surgical procedures. A prosthetic device palatal lift can be suggested for the persons in whom adequate tissue is present but poor control of coordination and timing of velopharyngeal (VP) movements are observed.
The palatal lift aims to lift the soft palate in a posterior and superior direction through the use of acrylic additions on the back of a dental appliance. It is used to prosthetically create a normal VP closure for speech development until the surgical repair can be performed. Hence this can assist for the better velopharyngeal closure by improving the oral – nasal coupling. The velopharyngeal closure dynamics can be studied using acoustic analysis of the speech, along with the perceptual evaluation.
Acoustic analysis offers the opportunity to observe the speech patterns resulting from simultaneous and sequential interactions of phonation, resonation and articulation as these occur in real time speech production. Spectrographic data have been used frequently to study cleft palate speech (Horii, 1980). McGrath and Anderson (1990) reported a review of the outcome management of 200 individuals with cleft palate and found that 95% were able to eliminate both hypernasality and nasal emission distortions in speech through prosthetic management.
Jian Ningyi & Guilan (2002) investigated the effect of a temporary obturator to treat VPD and found that velopharyngeal closure can be greatly improved by using a temporary oral prosthesis and speech training. Most of these studies have used obturator or speech bulb in individuals with cleft palate, and very few studies included speech training along with the prosthetic management and shows positive results. There are dearths of studies using palatal lift in persons with submucous cleft palate along with the speech therapy.
The present study is a part of the longitudinal study which is aimed to determine the effect of palatal lift prosthesis on temporal parameters of speech and correlating with the physiological findings. The aims of the study are three fold. First, is to compare the temporal parameters of nasalization and nasalence values with the normal subjects. Second, is to investigate the temporal parameters of nasalization and nasalance values without prosthesis, with prosthesis and after undergoing 10 sessions of speech therapy. Third, is to investigate the velopharyngeal closure with and without prosthesis using nasoendoscopy.