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Orofacial myology is the scientific and clinical knowledge related to the structure and function of the muscles of the mouth and face (orofacial muscles) (American Speech-Language-Hearing Association [ASHA], 1993). Orofacial myofunctional disorders are characterized by abnormal fronting of the tongue during speech or swallowing, or when the tongue is at rest. ASHA defines an orofacial myofunctional disorder as “any pattern involving oral and/or orofacial musculature that interferes with normal growth, development, or function of structures, or calls attention to itself” (ASHA, 1993, p. 22). With orofacial myofunctional disorders, the tongue moves forward in an exaggerated way and may protrude between the upper and lower teeth during speech, swallowing, or at rest. This exaggerated tongue fronting is also called a tongue thrust or a tongue thrust swallow and may contribute to malocclusion, lisping, or both (Young and Vogel, 1983; ASHA, 1989).
A tongue thrust type of swallow is normal for infants. The forward tongue posture typically diminishes as the child grows and matures. Orofacial myofunctional disorders may also be due to lip incompetence, which is a “lips-apart resting posture or the inability to achieve a lips-together resting posture without muscle strain” (ASHA, 1993, p. 22). During normal development, the lips are slightly separated in children. With orofacial myofunctional disorders, a lips-apart posture persists.
Orofacial myofunctional disorders may be due to a familial genetic pattern that determines the size of the mouth, the arrangement and number of teeth, and the strength of the lip, tongue, mouth, or face muscles (Hanson and Barrett, 1988). Environmental factors such as allergies may also lead to orofacial myofunctional disorders. For example, an open mouth posture may result from blocked nasal airways due to allergies or enlarged tonsils and adenoids. The open-mouth breathing pattern may persist even after medical treatment for the blocked airway. Other environmental causes of orofacial myofunctional disorders may be excessive thumb or finger sucking, excessive lip licking, teeth clenching, and grinding (Van Norman, 1997; Romero, Bravo, and Perez, 1998). Thumb sucking, for example, may change the shape of a child's upper and lower jaw and teeth, requiring speech, dental, and orthodontic intervention (Umberger and Van Reenen, 1995; Van Norman, 1997). The severity of the problem depends on how long the habit is maintained.
Typically, a team of professionals, including a dentist, orthodontist, physician, and speech-language pathologist, is involved in the assessment and treatment of children with orofacial myofunctional disorders (Benkert, 1997; Green and Green, 1999; Paul-Brown and Clausen, 1999). Assessment is conducted to diagnose normal and abnormal parameters of oral myofunctional patterns (ASHA, 1997). The dentist focuses on the effect of pressure of the tongue against the gums; this kind of tongue pressure may interfere with the normal process of tooth eruption. An orthodontist may be involved when the tongue pressure interferes with alignment of the teeth and jaw. A physician needs to verify that an airway obstruction is not causing the tongue thrust. Speech-language pathologists assess and treat swallowing disorders, speech disorders, or lip incompetence that result from orofacial myofunctional disorders. As with all other assessment and treatment processes, speech-language pathologists need to have the appropriate training, education, and experience to practice in the area of orofacial myofunctional disorders (ASHA, 2002).
An orofacial myofunctional assessment is typically prompted by referral or a failed speech screening for a child older than 4 years of age. Assessment should be based on orofacial myofunctional abilities and education, vocation, social, emotional, health, and medical status. An orofacial myofunctional assessment by a speech-language pathologist typically includes the following procedures (ASHA, 1997, p. 54):
• Case history
• Review of medical/clinical health history and status (including any structural or neurological abnormalities)
• Observation of orofacial myofunctional patterns
• Instrumental diagnostic procedures
• Structural assessment, including observation of the face, jaw, lips, tongue, teeth, hard palate, soft palate, and pharynx
• Perceptual and instrumental measures to assess oral and nasal airway functions as they pertain to orofacial myofunctional patterns and/or speech production (e.g., speech articulation testing, aerodynamic measures)
Speech may be unaffected by orofacial myofunctional disorders (Khinda and Grewal, 1999). However, some speech sound errors, called speech misarticulations, may be causally related to orofacial myofunctional disorders. The sounds most commonly affected by orofacial myofunctional disorders include s, z, sh, zh, ch, and j. Sound substitutions (e.g., th for s, as in “thun” for “sun”) or sound distortions may occur. A weak tongue tip may result in difficulties producing the sounds t, d, n, and l.
Speech-language pathologists evaluate speech sound errors resulting from orofacial myofunctional disorders, as well as lip incompetence and swallowing disorders (ASHA, 1991). The assessment information is used to develop appropriate treatment plans for individuals who are identified with orofacial myofunctional disorders. Before speech and swallowing treatment is initiated, medical treatment may be necessary if the airway is blocked due to enlarged tonsils and adenoids or allergies. Excessive and persistent oral habits, such as thumb and finger sucking or lip biting, may also need to be eliminated or reduced before speech and swallowing treatments are initiated.
Some speech and swallowing treatment techniques include
• Increasing awareness of mouth and facial muscles.
• Increasing awareness of mouth and tongue postures.
• Completing an individualized oral muscle exercise program to improve muscle strength and coordination. Treatment strategies may include alternation of tongue and lip resting postures and muscle retraining exercises (ASHA, 1997, p. 69).
• Establishing normal speech articulation.
• Establishing normal swallowing patterns. Treatment strategies may include modification of handling and swallowing of solids, liquids, and saliva (ASHA, 1997, p. 69).
The expected outcome of treatment is to improve or correct the patient's orofacial myofunctional swallowing and speech patterns. Orofacial myofunctional treatment may be conducted concurrently with speech treatment.
Oral myofunctional treatment is effective in modifying tongue and lip posture and movement and in improving dental occlusion and a dental open bite or overbite (Christensen and Hanson, 1981; ASHA, 1991; Benkert, 1997). Lip exercises may be successful in treating an open-mouth posture (ASHA, 1989; Pedrazzi, 1997). A combination treatment approach, with a focus on speech correction as well as exercises to treat tongue posture and swallowing patterns, appears to be the optimal way to improve speech and tongue thrust (Umberger and Johnston, 1997). The length of treatment varies according to the severity of the disorder, the age and maturity of the patient, and the timing of treatment in relation to orthodontia. Typically 14–20 sessions or more may occur over a period of 3 months to a year (ASHA, 1989). The value of early treatment is emphasized in the literature (Pedrazzi, 1997; Van Norman, 1997).
ASHA has identified the basic content areas to be covered in university curricula to promote competency in the assessment and treatment of orofacial myofunctional disorders (ASHA, 1989, p. 92), including the following:
1. Oral-facial-pharyngeal structure, development, and function
2. Interrelationships among oral-vegetative functions and adaptations, speech, and dental occlusion, using interdisciplinary approaches
3. Nature of atypical oral-facial patterns and their relationship to speech, dentition, airway competency, and facial appearance
4. Relevant theories such as those involving oral-motor control and dental malocclusion
5. Rationale and procedures for assessment of oral myofunctional patterns, and observation and participation in the evaluation and treatment of patients with orofacial myofunctional disorders
6. Application of current instrumental technologies to document clinical processes and phenomena associated with orofacial myofunctional disorders
7. Treatment options
A Joint Committee of ASHA and the International Association of Orofacial Myology has also delineated the knowledge and skills needed to evaluate and treat persons with orofacial myofunctional disorders (ASHA, 1993). The tasks required include the following:
• Understanding dentofacial patterns and applied physiology pertinent to orofacial myology
• Understanding factors causing, contributing, or related to orofacial myology
• Understanding basic orthodontic concepts
• Understanding interrelationships between speech and orofacial myofunctional disorders
• Demonstrating competence in comprehensive assessment procedures and in identifying factors affecting prognosis
• Demonstrating competence in selecting an appropriate, individualized, criterion-based treatment plan
• Demonstrating a clinical environment appropriate to the provision of professional services
• Demonstrating appropriate documentation of all clinical services
• Demonstrating professional conduct within the scope of practice for speech-language pathology (ASHA, 2001)
Further information on oral myofunction and oral myofunctional disorders is available from ASHA's Special Interest Division on Speech Science and Orofacial Disorders (www.asha.org) and the International Association of Orofacial Myology (www.iaom.com).
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