Controversy Speech Defect and Orthodontics: a Contemporary Review
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Controversy Speech defect and orthodontics: A contemporary review Umal Hiralal Doshi, BDS, MDS1 Wasundhara A. Bhad-Patil, BDS, MDS2 In conjunction with the lips, tongue, and oropharynx, the teeth play an important role in the articulation of consonants via airflow obstruction and modification. Therefore, along with these articulators, any orthodontic therapy that changes their position may play a role in speech disorders. This paper examines the relevant studies and discusses the difficulties of scientific investigation in this area. The ability of patients to adapt their speech to compensate for most handicapping occlusion and facial deformities is recognized, but the mechanism for this adaptation remains incompletely understood. The overall conclusion is that while certain malocclusions show a relationship with speech defects, this does not appear to correlate with the severity of the condition. There is no direct cause-and-effect relationship. Similarly, no guarantees of improvement can be given to patients undergoing orthodontic or orthognathic correction of malocclusion. ORTHODONTICS (CHIC) 2011;12:340–353. Key words: cleft palate, hearing loss, malocclusion, orthognathic surgery, speech defect peech production is much like looking through a window to the scene beyond, an invisible means of conveying an articulate, intelligible Smessage in a seemingly effortless and inconspicuous manner. Speech is a learned process unique to humans. Normal speech may seem 1 Assistant Professor, effortless, but it is actually a complex process that requires precise timing and Department of nerve and muscle control. Speech formation requires selective modification of Orthodontics and an outgoing air stream by structures designed for respiration and deglutition.1 Dentofacial Orthopedics, Government Dental College and Hospital, Maharashtra, India. Speech 2 Associate Professor, Department of Orthodontics and West and Kantner2 gave five components of speech. A sixth was later added Dentofacial Orthopedics, by Chierici and Lawson3: respiration, phonation, resonation, articulation, neu- Government Dental College and Hospital, rologic integration, and audition. Maharashtra, India. In the English language, there are 44 speech sounds or phonemes (Table 1),4 which are subdivided into vowels, voiceless consonants, and voiced consonants. CORRESPONDENCE Dr Umal Hiralal Doshi Government Dental • Vowels (a, e, i, o, and u). These are primarily phonated sounds. There is little College and Hospital air flow through the oral cavity. They have low frequency and high intensity. Aurangabad 68, Builder’s Society, • Voiceless consonants (eg, /p/, /t/, /f/, /s/). Production of these sounds in- Near Nandanvan Colony volves a column of air without laryngeal phonation. They have high fre- Aurangabad 431002 quency and low intensity. India Email: • Voiced consonants (eg, /b/, /d/, /g/). Production of these sounds involves la- [email protected] ryngeal phonation plus air flow. They have variable frequency and intensity. 340 ORTHODONTICS The Art and Practice of Dentofacial Enhancement © 2011 BY QUINTESSENCE PUBLISHING CO, INC. PRINTING OF THIS DOCUMENT IS RESTRICTED TO PERSONAL USE ONLY. NO PART OF MAY BE REPRODUCED OR TRANSMITTED IN ANY FORM WITHOUT WRITTEN PERMISSION FROM THE PUBLISHER. THERAP dysarthria articulation teethDEFORMITIES malocclusion Y orthodontics sounds SPEECH DISORDERSSpeechoropharynx TYpes OF soUnds prodUced and deVELopMent The first speech sounds to be produced are bilabial (eg, /p/ and /b/). This is why children’s first meaningful words are usually mama and papa. The second sounds to be developed are tongue-tip consonants such as /t/ and /d/. The third to develop are sibilants—/s/ and /z/. The final speech sound to develop is /r/, which requires precise positioning of the posterior tongue.5 This develop- ment reinforces the theory of front-to-back maturation described by Bosma.6 Speech develops over an extended period. A child usually starts to produce speech sounds at around 10 to 12 months of age. In girls, speech development is complete at 6 ½ years of age. In boys, it occurs at 7 ½ years of age.7 Speech DEFects Speech defects can be defined as any condition that interferes with the mental formation of words or their physical production and generally become appar- ent in the early school years. Classifying speech into normal and disordered is more problematic than it first seems. Based on examination of 189 children with speech disorders, Ingram8 clas- sified speech disorders as follows: • Disorders of voicing (dysphonia) • Disorders of rhythm (dysrhythmia): clutter and stammer • Disorders of articulation with demonstrable dysfunction of articulatory apparatus (dysarthria) as a result of neurologic abnormalities or local abnor- malities • Disorders of articulation without demonstrable dysfunction of articulato- ry apparatus (secondary speech disorders) secondary to hearing defects, mental retardation, psychogenic disorders, or aphasia due to brain damage • Specific developmental speech disorders (functional speech disorders) that involve language development and articulation or only articulation • Mixed cases CorreLation BetWEEN deFectiVE speech and MALoccLUsion Orthodontists are not usually primarily involved in the diagnosis of speech defects, except in cases of lisping associated with malocclusion of the anterior teeth. An orthodontist’s assistance may be sought in cases in which the rela- tionship of the jaw and malocclusion of the teeth are thought to be possible etiologic factors in speech defects.9 Volume 12, Number 4, 2011 341 © 2011 BY QUINTESSENCE PUBLISHING CO, INC. PRINTING OF THIS DOCUMENT IS RESTRICTED TO PERSONAL USE ONLY. NO PART OF MAY BE REPRODUCED OR TRANSMITTED IN ANY FORM WITHOUT WRITTEN PERMISSION FROM THE PUBLISHER. Speech defect and orthodontics ControversyTable 1 Structural component of articulatory valve Closed valve Constricted valve Structural component Voiceless Voiced Voiceless Voiced Voiced nasals Labiodental (maxillary teeth and lower lip) /f/ /v/ Bilabial (lips) /p/ /b/ /w/ /m/ Linguodental (tongue tip and maxillary teeth) /th/ /th/ Linguoalveolar (tongue tip and alveolar ridge) /t/ /d/ /s/ /z/ /n/ Linguopalatal (tongue blade and hard palate) /ch/ /j/ /sh/ /zh/ Linguovelar (tongue back and velum) /ng/ Linguo-velor-pharyngeal (tongue back, /k/ /g/ velum, and pharyngeal wall) Glottal (glottis) /h/ Since 80% of specific speech movements are made in the anterior part of the mouth, it is not surprising that a causal relationship between speech de- fects and malocclusion has long been assumed to exist.10 Bloomer11 noted that the effects on speech may be both direct and indi- rect—direct by virtue of the mechanical difficulties imposed as the person tries to obtain the proper position and movement of the articulators of the speech and indirect because of the influence the deformities may have on the physical and mental health of the individual. Roth,12 Bakes,13 and Gardner14 showed how dental disorders affect the application of sounds. Students with malocclu- sions found more difficulty with dental sounds.15 Bruggeman16 further estab- lished the fact that there was a definite relationship between malocclusion and speech defects. Approximately 87% of the defective speech group presented a malocclusion. But this correlation is not absolute. Studies by Hopkin and McEwen,17 Lubit,18 and Oliver and Evans19 do not support this cause-and-effect relationship. Hop- kin and McEwen17 noted that more than half the children attending speech therapy clinics had normal occlusions. In a study of severe malocclusion, Frow- ine and Moser20 showed that regardless of the severity of malocclusion, pa- tients presented satisfactory speech. A series of publications by Laine21–23 and Laine et al24 explored oral mor- phology and speech disorders in a Finnish population. Laine22 found that the same sounds tended to be distorted in Finnish as in other languages. These studies outlined the fact that there may be an association between tooth posi- tion and speech, but there is enormous potential for compensation. To quote Rathbone, ”Without question, poor speech and malocclusion were related, but there was no direct relationship between the severity of the malocclusion and severity of the speech defects.”25 A complex relationship clearly exists between tooth position and speech defects. According to Harvold,26 there are three possibilities regarding this relation- ship: occlusal/skeletal problems coincidently with speech defects, genetic/ metabolic disorders affecting speech and dental morphogenesis, or a true cause-and-effect relationship. It is generally agreed that where malocclusion is present and in the absence of any pathology, other factors are of greater importance, such as character, level of intelligence, muscle control, emotional state, and social conditions that influence the ability of the patient to adapt the flexible parts of the organs of speech to compensate for the defects of the rigid parts.27 342 ORTHODONTICS The Art and Practice of Dentofacial Enhancement © 2011 BY QUINTESSENCE PUBLISHING CO, INC. PRINTING OF THIS DOCUMENT IS RESTRICTED TO PERSONAL USE ONLY. NO PART OF MAY BE REPRODUCED OR TRANSMITTED IN ANY FORM WITHOUT WRITTEN PERMISSION FROM THE PUBLISHER. Doshi et al Along with labial segment tooth positions, buccal segment relationships Controversy have also been implicated to influence articulation. Exactly how these varia- tions affect speech is not fully understood. Class II The relationship between increased