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Role of function /certified fixed orthodontic courses by Indian dental academy

  1. 1. Role of Function In the Etiology of Malocclusion INDIAN DENTAL ACADEMY Leader in continuing dental education
  2. 2. Contents Introduction Orthodontic equation Classification Moyers Grabers Respiration Mechanics of respiration Modification of respiration by sensory feedback
  3. 3. Response of respiratory muscles to changes in respiratory feedback Clinical examination to assess mouth breathing Airflow measuring devices Mouth breathing and malocclusion Long face syndrome Obstructive sleep apnea syndrome
  4. 4. Deglutition Introduction Review of literature The swallowing pattern Infantile swallow Mature swallow Tongue thrust Simple tongue-thrust swallow Complex tongue-thrust swallow Retained infantile swallow
  5. 5. Mastication The masticatory cycle Speech
  7. 7. Traditionally any deviation from an ideal occlusion was termed as malocclusion. Unfortunately there is no clear-cut definition for an ideal occlusion. This is because it is difficult to establish an individual norm since function and physiologic adaptation should be considered to determine an individuals normal occlusion.
  8. 8. It is commonly accepted that the etiology of any problem should be contained in the diagnosis. Malocclusion is a developmental problem, not a pathologic one, and although we can say that both hereditary and environmental factors are important influences on development, often we are not able to ascertain which malocclusions are determined largely on genetic basis and which result largely from environmental factors and which are a combination of both.
  9. 9. Classification of etiology of Malocclusion It is traditional to discuss the etiology of malocclusion by beginning with a clinical classification and working back to causes of each problem. It must be recognized at the outset that any arbitrary division of causes is purely for the sake of analysis. The idea of studying etiology in terms of the primary tissue site was first suggested by Dockrell.
  10. 10. Dockrell’s Orthodontic equation
  11. 11. The primary etiologic sites are  Neuromuscular system  Bone  Teeth  Soft tissues Malocclusions may involve four tissue systems: teeth, bones,soft tissues, muscles and nerves. In some cases only the teeth are irregular; jaw relationships may be good and muscles and nerve functions normal. In other cases teeth may be regular in their alignment, but an abnormal jaw relationship may exist, so that the teeth do not meet properly during function. Or again, the malocclusion may involve all four systems, with individual tooth malpositions, abnormal jaw relationship and abnormal nerve and muscle function.
  12. 12. Moyers has classified the etiology of malocclusion into seven groups as 1) Heredity 2) Developmental defects of unknown origin 3) Trauma Prenatal trauma and birth injuries Postnatal trauma 4) Physical agents Premature extraction of primary teeth. Nature of food
  13. 13. 5) Habits Thumb sucking and finger sucking Tongue thrusting Lip sucking and lip biting Posture Nail-biting Other habits
  14. 14. 6) Disease Systemic diseases Endocrine disorders Local diseases Nasopharyngeal diseases and disturbed respiratory function Gingival and periodontal diseases Tumors Caries 7) Malnutrition
  15. 15. Graber has classified Etiology of Malocclusion into the following General factors Heredity Congenital defects Environmental Prenatal Postnatal Predisposing metabolic climate and disease Endocrine imbalances Metabolic imbalances Infectious diseases Dietary problems ( nutritional deficiency)
  16. 16. Abnormal pressure habits and functional aberrations Abnormal suckling Thumb and finger sucking Tongue thrust and tongue sucking Lip and nail biting Abnormal swallowing habits Speech defects Respiratory abnormalities Tonsils and adenoids Psychogenic tics and bruxism Posture Trauma and accidents
  17. 17. Local factors Anomalies of number Supernumerary teeth missing teeth Anomalies of tooth size Anomalies of tooth shape Abnormal labial frenum; mucosal barriers Premature loss Prolonged retention Delayed eruption of permanent teeth Abnormal eruptive path Ankylosis Dental caries Improper dental restorations
  19. 19. The effects of mouth breathing on the skeletal morphology and malocclusion have long been debated and are still unclear. Mouth breathing has long been considered a significant factor in the etiology of malocclusion. Throughout the history of orthodontics, there have been proponents of this concept. Equally, there have been opponents who dispute the role of mouth breathing as a clinically significant factor in orthodontics.
  20. 20. A major obstacle to resolving this issue lies in the absence of a clearly stated definition of "mouth breathing. " Who s a mouth breather? Is mouth breathing synonymous with an absence of nasal respiration? Is mouth breathing a combination of oral and nasal breathing? Is nasal obstruction (however measured) an indisputable indicator of oral breathing? Can nasal respiration exist with concurrent partial nasal obstruction?
  21. 21. These are fundamental questions which need to be addressed if clinically useful concepts are to develop in this area. It is obvious that, for survival, respiration must continue throughout life. It is equally clear that if the nasal passages are completely blocked, survival depends on adaptation to produce oral respiration. However, complete obstruction of the nasal airway is a relatively rare condition. Even transient nasal congestion is considered to be uncomfortable.
  22. 22. However, it does not follow that this automatically results in oral breathing. The preferred mode of respiration for human beings is apparently nasal. This is phylogenetically related to respiration in the primates and other mammals who are obligatory or near-obligatory nasal breathers. It is entirely conceivable that in the human being relatively high degrees of nasal obstruction are overcome to maintain nasal airflow if, indeed, nasal respiration is the preferred mode of function.
  23. 23. The critical value of the nasal obstruction at which this becomes impossible or too difficult is not yet known. In the absence of data which describe the physiologic and aerodynamic variability of respiration in a cross section of the population, one can only speculate on the possible morphogenetic role of this aspect of function.
  24. 24. MECHANICS OF RESPIRATION Breathing is the movement of air into and out of the lungs, results from contractions of the respiratory muscles which produce changes in the volume of the chest cage. The lungs fill the thoracic cavity and its outer surface (visceral pleura) is in intimate contact with the inner surface of the thoracic cavity (parietal pleura).
  25. 25. The two pleural layers are in apposition, separated only by a thin film of fluid which enables the lungs to slide freely within the cavity. Whenever the chest enlarges, the lungs also enlarge. At the end of expiration when the respiratory muscles are relaxed, pressure within the lungs (pulmonary pressure) is atmospheric and there is no airflow. This is the resting position. Both the lungs and the chest wall contain considerable elastic tissue, and at resting position these pull with equal force but in the opposite direction, creating a balance of elastic forces.
  26. 26. Although the lungs and chest operate as a unit, the two would have different resting positions if separated. That is, the lungs would collapse and the thoracic cavity would expand. When contraction of the diaphragm and the intercostals muscles occur during inspiration, the volume of the thoracic cage enlarges and the elastic forces of the two units change. When the diaphragm contracts, its dome moves downwards into the abdomen, thus enlarging the thoracic cavity. Simultaneously, the intercostals muscles move the ribcage upwards and outwards, also increasing the volume of the thoracic cavity.
  27. 27. This enlarges the volume of air within the lungs, pressure falls below atmospheric and air is drawn into the expanding lungs. While inspiration is an active process involving muscle contraction, normal expiration is primarily, a passive event. The elasticity of stretched tissues and gravitational forces tend to return the thorax to its resting position without any further expenditure of energy. Because the elements which have been stretched during inspiration are elastic, they have a natural tendency to return to their original position after relaxation of the inspiratory muscles.
  28. 28. As the thorax and lungs spring back to their original sizes, pulmonary air becomes temporarily compressed so that its pressure exceeds atmospheric pressure and air flows from the lungs to the outside. Most of the work in filling the lungs involves overcoming the elastic recoil, and the energy required to do this is stored during inspiration and used during expiration. The compliance of the respiratory system, or the degree of distensibility which occurs with the application of pressure, is an important factor in determining the amount of energy required to move air in and out of
  29. 29. The second factor determining the degree of work required for breathing is the magnitude of airway resistance. When the airway is open, the airflow is mostly smooth (laminar) and resistance is low. However, in disease states increased respiratory secretions or obstructions can increase resistance greatly. Airflow becomes turbulent and greater effort is necessary to move air in and out of the lungs. In order to understand the effects of oral respiration on the craniofacial region, a concept of the underlying principles of the neuromuscular function of the primary and accessory respiratory muscles of the trunk and neck is required.
  30. 30. The airflow through the respiratory tract is subject to resistance at various levels. Changes in the dimensions of the respiratory tract will decrease airflow. When changes in airway resistance modify airflow, respiratory muscles must increase their work to produce changes in the intrapulmonary pressure sufficient for air to be moved in and out of the alveoli.
  31. 31. Modification of respiration by sensory feedback In the initial adaptation to the partial obstruction of the nasal airway, the respiratory system increases its effort to compensate for the increased nasal resistance. The augmented effort in motor output is initiated reflexively by alterations in sensory feedback. Respiration is modified by input from sensory receptors which are located within the respiratory tract.
  32. 32. Receptors within the cardiovascular system include baroreceptors which respond to changes in blood pressure. The baroreceptors are situated within the carotid and aortic vessels, pulmonary veins and the right auricle of the heart. Sensory receptors within the joints increase pulmonary ventilation during exercise. The respiratory system has receptors in the upper respiratory tract responding to irritant gases, liquids, and particles evoking a variety of reflexive effects that alter respiration. The alveolar wall and chest wall have pulmonary stretch receptors that modify the respiratory phase and control respiratory frequency.
  33. 33. . The first few inspirations following nasal obstruction would be expected to be longer. This would be due to a decreased tidal volume and a resulting lack of stretch of the lungs which normally assist in terminating the inspiratory phase. The sensory receptors which are most affected by obstruction of the respiratory tract are chemoreceptors that monitor the levels of oxygen and carbon dioxide in the body. These receptors are located in three regions: the carotid bodies at the junction of external and internal carotid arteries; the aortic bodies within the wall of the large aortic vessel; and particular sites on the ventral surface of the medulla in the brain stem of the CNS.
  34. 34. The carotid bodies are the most sensitive to changes in oxygen in the blood while the medullary site is affected by levels of carbon dioxide. It is proposed that nasal obstruction leads to transient hypoxia and hypercapnia and that these states stimulate neural receptors which modulate the respiratory system.
  35. 35.
  36. 36.
  37. 37. Response of respiratory muscles to changes in respiratory feedback The respiratory system increases its effort to compensate for decreased airflow by using the muscles of neck and trunk. This increased effort is controlled by two neuromuscular mechanisms. One mechanism increases the tension developed by the primary muscles. The other recruits accessory respiratory muscles which are normally not active in quite respiration.
  38. 38. Both mechanisms assist in decreasing resistance of the upper airway and increasing the forces during inspiration and expiration. The primary muscles are – diaphragm, Intercostals muscles of upper two intercostals spaces, scalene muscles, several of the intrinsic and extrinsic laryngeal muscles. In normal, quiet breathing, most of these muscles contract during inspiration. The laryngeal adductor muscles, the lateral cricoarytenoid, and thyroarytenoid are active during expiration.
  39. 39. The contraction of these primary respiratory muscles enlarges the chest, lungs and respiratory tract during inspiration, as well as maintaining the larynx in a stable position. At the completion of the active inspiratory phase, the tension of the expanded chest and lungs is sufficient to cause their recoil and expulsion of the air during quiet expiration. These primary respiratory muscles increase their electromyographic activity and develop more tension during partial obstruction of the upper respiratory
  40. 40. The accessory respiratory muscles are the abdominal muscles which compress and force the diaphragm upwards during expiration. The serratus anterior, trapezius and sternomastoid muscles attach to the chest wall at various points to assist in its movement during increased pulmonary ventilation. The extrinsic laryngeal muscles assist in the respiratory effort. Increased ventilation also recruits the intercostals muscles in descending
  41. 41. At present the literature contains a volume of confusing and conflicting views on the precise details and mechanisms of respiratory mode and the possible effect on dentofacial growth. Some of this confusion may be attributed to the fact that in most studies, assessment of respiratory mode (oral or nasal breathing) has been made through rather subjective means, such as clinical judgments by orthodontists or otolaryngologists.
  42. 42. Patients have been classified as mouth breathers on the basis of morphologic criteria, such as lips-apart posture ("incompetent lips"), narrow facial dimensions ("adenoidal faces"), questionnaires, condensation on cold mirrors, and visual inspection of the nasal airway for obstruction both clinically and radiographically. On the basis of these observations, epidemiologic surveys have been used for making comparisons between mode of respiration and skeletal and dental characteristics.
  43. 43. Clinical Examination for assessment of mouth breathing
  44. 44. Dr. Bushey has given a six point clinical routine examination designed to alert the orthodontist to a significant morphologic and functional characteristics of a mouth breathing patient. Step 1: look for mouth gaping or lip incompetancy when the patient is in a relaxed posture. A short, flaccid and atrophic upper lip is typical of adenoid faces. Step 2: evaluation of nares and nasofacial angle. The nares are narrow and pinched-together the entire base of the nose is often tipped up.
  45. 45. Step 3: evaluation of the mode of respiration. Simple techniques can be used such as, first asking the patient to seal the lips for 1-2 minutes and assessing the ease of nasal breathing. Then ask the patient to seal the lips and alternately collapse each nostril to evaluate nasal and/or pharyngeal obstruction. The potential obstruction is amplified by having the patient to hum through one nostril while other is closed. A cold mirror test can also be used or a cotton tuft can be held at the nostrils to check for nasal breathing. Also ask history of upper respiratory infections, tonsillitis, respiratory allergies, middle ear infections etc.
  46. 46. Step 4: determination of whether there is a teeth- together or a tooth-apart swallow. The presence of a simple or a complex tongue thrust can alert the clinician to the potential complications caused by an adaptive or active tongue habit. Step 5: clinical assessment of frontal facial morphology. The long, dolichofacial form is more often associated with mouthbreathing. Step 6: assessment of the most significant clinical characteristics which are found within the oral cavity. The first five are dental and the next five are pharyngeal features.
  47. 47. Dental midlines significant deviations from rest o occlusion are indicative of posterior constriction leading to a functional shift. Incisor overbite or openbite and axial inclination should be noted. In mouth breathers there is an openbite and an increase in interincisal angle. Anterior crossbite or overjet should be noted as an additional indication of a potential skeletal open bite. Posterior crossbite as evidenced by a unilateral or bilateral narrowing of the maxillary segments. Posterior arch width initiates questions of relative and absolute size dimensions of maxillary and mandibular arch.
  48. 48. Palatal vault the height and contour of palatal vault is the first pharyngeal feature. It is determined in order to decide whether to treat the case with expansion procedure or not. Palatine tonsils should be evaluated for degree of enlargement. large and infected tonsils will often meet at the midline, indicating a significant potential for tongue displacement. Gag reflex is the next factor. It is elicited by tongue depression. Individuals extremely sensitive to tongue depression are often found to have inflamed tonsils which may not be enlarged. But it still causes a lower and forward tongue posture eliminating support for development of normal maxillary arch width.
  49. 49. Adenoid tissue can be examined clinically by moving the uvula to one side using a dental mirror. The dental mirror is then tilted above the posterior level of hard palate. But it is best viewed in a lateral cephalograms which are routinely used by orthodontists. Soft palate if the soft palate is observed to have a bifid uvula or a deep oropharynx or if there is any indication of palatopharyngeal insufficiency, adenoidectomy is contraindicated.
  50. 50. Instruments used for measuring Respiration Instruments capable of precisely measuring the respiratory parameters of breathing have been used to assess upper airway structures. Aerodynamic techniques are used routinely to estimate the area of constrictions, resistance to airflow and volume displacements. Airflow measuring devices there are two types of flowmeters used to measure airflow rate. The most widely used instrument is the pneumotachograph, the other less commonly used is the warm wire anemometer.
  51. 51. The pneumotachograph consists of a flowmeter and a differential pressure transducer and operates on the principle that as air flows across a resistance the pressure drop which results is linearly related to the volume of rate of airflow. In most cases the resistance is provided by a wire mesh screen that is heated to prevent condensation. A pressure tap is situated on each side of the screen, and both are connected to a very sensitive differential pressure transducer.
  52. 52. The pressure drop is converted to an electrical voltage that is amplified and recorded either on a magnetic tape or a chart recorder. Pneumotachographs are accurate, reliable, linear devices for measuring ingressive and egressive airflow rates. They are also inexpensive.
  53. 53. The warm wire anemometer uses a heated wire as a sensing unit. The cooling effect of airflow on the heated wire, through which an electric current flows, alters its resistance. The resultant change in voltage is amplified and recorded. However, it has poor linearity and does not sense the direction of airflow. So it is less popular.
  54. 54.
  55. 55. Pneumatograph
  57. 57. Effects on the Dentition Upper incisors retroclination is seen in mouth breathers. Studies have shown that with resumption of nasal breathing in patients who were treated with adenoidectomy, the upper incisor position dramatically improved. In mouth breathers the lower incisors are also retoclined. With adenoidectomy the lower incisors procline to normal within the first year, after which no change is seen.
  58. 58. Effect on Arch width There is a decrease in the arch-width in mouth breathers, in the upper jaw leading to a crossbite and crowding because of a narrow maxilla. There can be a deviated path of closure for the teeth to occlude and it may lead to skeletal asymmetery if not treated. But, when the patient reverts to nose- breathing, there is a yearly increase of 0.9mm growth in maxilla for the next 5 years is observed.
  59. 59. Effect on Nasopharynx The depth of the nasopharynx is decreased in mouth breathers. It is the distance measured from pterygomaxillary point to basion. When they resume nasal breathing, the depth is restored within the first I year.
  60. 60. Mandibular plane In mouth breathers the mandibular plane angle is severely increased which is a reason for the long face or adenoid faces. With the resumption of nasal breathing it is shown that the mandibular plane starts reducing in order to come towards normalcy. Though the first year post adenoidectomy values are not significant statistically when compared to controls.
  61. 61. Head posture One of the important functions of head posture is to maintain an adequate oronasopharyngeal airway. Therefore patients with impeded nasal airflow will have an extended head posture.
  62. 62. Long Face Syndrome Extreme clockwise rotation, high angle type, adenoid faces, idiopathic long face, total maxillary alveolar hyperplasia, and vertical maxillary excess all have excessive vertical growth of maxilla as their common denominator. The multiplicity of names describing this syndrome partially arises from the difficulty in describing vertical skeletal dysplasias by traditional antero- posterior classifications and failure to direct enough effort towards describing the frontal or full face esthetic aspects of dentofacial deformities.
  63. 63. Clinical features Frontal facial esthetics reveal : Upper facial third is within normal limits. Middle third of face reveals a narrow nose, narrow alar bases, and depressed nasolabial areas. Lower third of the face reveals excessive exposure of maxillary anterior teeth, poor upper lip-to-tooth relationship, large interlabial distance, long lower third of face, and inordinate exposure of the maxillary teeth and gingiva upon smiling.
  64. 64. In profile the upper third of the face is normal. The middle third often reveals a somewhat prominent nasal dorsum and recessed nasolabial areas. In assessment of the lower third of the face, the nasolabial angle is essentially normal; there is excessive exposure of maxillary anterior teeth, large interlabial distance and a retropositioned chin.
  65. 65. Occlusal analysis reveals most often a classII malocclusion, with or without open-bite deformity. Consistently, there is a high palatal vault with a large distance between the root apices and the nasal floor. All these are the general features of this syndrome but, they variably manifest.
  66. 66. Cephalometrically following features are seen The total anterior facial height is increased; specifically the lower anterior facial height. The increased facial height correlates with the excess development of maxilla in the vertical direction. Open-bite and non-open-bite are two variants of long face syndrome – A normal ramus height is seen in open-bite patients whereas an increased ramus height is seen in non-open-bite cases. A high mandibular plane is a characteristic feature. A normal lip length and excessive maxillary incisor exposure is seen.
  67. 67. Obstructive sleep apnea syndrome Obstructive sleep apnea (OSA) syndrome is a relatively common condition caused by recurrent upper airway obstruction during sleep. Patients complain of a range of symptoms, particularly excessive daytime sleepiness, and may develop physical complications that include systemic hypertension, right heart failure, and cardiac arrhythmias.
  68. 68. The patency of the upper airway is a result of many interrelated anatomic and physiologic factors. During inspiration a negative intrapharyngeal pressure develops but airway collapse is prevented by the action of the pharyngeal abductor and dilator muscles. These muscles are activated rhythmically during daytime respiration but, in common with other skeletal muscles, they become hypotonic during sleep, and airway stability becomes dependent upon pharyngeal size and pharyngeal tissue compliance.
  69. 69. As yet, little is known about the compliance of the pharyngeal tissues. However, conditions that reduce airway dimensions result in OSA. There are reports of OSA in patients with upper airway tumors, with adenotonsillar hypertrophy, and with conditions associated with macroglossia. Airway size is also affected by craniofacial morphology as reflected in the airway narrowing and sleep apnea observed in patients with significant retrognathia.
  70. 70. The Apnea index (Al) and body mass index (BMI) of patients were studied to check for correlation. The patients with a high Al and low BMI ratio had retruded mandibles with high mandibular plane angles and proclined lower incisors. The patients with a low Al and high BMI ratio had inferior hyoid bones and large soft palates. In the patients with a high Al and low BMI ratio, a high Al was related to a large skeletal anteroposterior discrepancy, a steep manidbular plane, and an inferoanterior position of the hyoid bone.
  71. 71. In the patients with a low Al and high BMI ratio, a high Al was related to a large tongue and a small upper airway. In both groups, BMI was the major contributor to Al. These two groups represent distinct subgroups of OSA patients and provide some insight into the contribution of obesity to the pathogenesis of OSA. The patients with a high Al and low BMI ratio have a skeletal mismatch, whereas the patients with a low Al and high BMI have atypical soft tissue structures.
  73. 73. An average individual swallows about once a minute. During meals he swallows about 9 times in a minute. Children show an increased frequency of swallowing. The rate of swallowing also depends on factors such as posture. Nervous states also increase the deglutitional frequency.
  74. 74. Patients having a class II div.1 and open bite tendency also show an increased frequency of deglutition. It is obvious from the above data that the act of swallowing, repeated so frequently, may have a profound effect on the maxilla or mandible, particularly if there is an abnormal swallowing pattern.
  76. 76. One of the earliest writings is that of Lefoulon published in 1839, in which it is obvious that he appreciated that among the causes of irregularities of teeth were "sounds of speech in which the tongue strikes against the upper anterior teeth, pushing them forward." An article by Desirabode published in 1843, is the first traceable reference to the fact that the lips on the outside and the tongue on the inside of the mouth constitute a balance of forces that may retain the teeth in their position.
  77. 77. In 1859, Bridgeman introduced the "lateral pressure theory" and described irregularities of the teeth due to Visincrementi (external muscle forces, as that of the lips and cheeks), visextensionis (internal muscle forces, as that of the tongue), and visocclusionis (occlusal forces). Kingsley in 1879 made a considerable study of speech sounds but did not relate movements of the soft tissues to dental arch form.
  78. 78. Angle (1907) recognized the problems of the muscular environment of the dental arches but would not accept the fact that in certain cases they might form an insurmountable difficulty in treatment. In the appendix to the seventh edition of Malocclusion of the Teeth, Angle states: "We are just beginning to realize how common and varied are the vicious habits of the lips and tongue, how powerful and persistent they are to overcome."
  79. 79.  Norman Bennett (1914) showed a clear understanding of the problem when he wrote: "The muscles of mastication produce conditions of vertical and lateral stress, the use of the tongue in mastication and speech reacts upon the teeth internally, and the lips and cheeks in their every movement, even of transient emotion, bring pressure to bear externally. Many of these forces are too slight and of insufficient duration to produce any definite movement of the teeth, but others are constantly acting; with the mouth shut and the teeth closed the buccal cavity is obliterated, and the teeth are compressed between the tongue and the lips and cheeks.
  80. 80. Very little experience in the movement of teeth by mechanical means is enough to show that even quite a small force acting continuously will produce a considerable movement, and it becomes clear that the teeth in their arches are but passive objects kept in a state of equilibrium under the influence of the muscles that react on them directly and indirectly." Bennett discussed Sim Wallace's theory that tongue size is dependent on tongue function and that this is a dominant factor in determining the size of the dental arches, but he rather dismissed the tongue as an all-important factor in arch development.
  81. 81. Friel (1926) having studied muscle activity, was convinced that it was static function, and not dynamic function, which molded the dental arches in their position of linguofacial balance and this, as we shall see, has been reaffirmed. Brash (1929) in his Dental Board lectures, did not place emphasis on the effect of the soft tissues of the tongue and lips on the dental arches, but he went so far as to state: "The growth of the tongue and the mandible are no doubt correlated, but it is improbable that the tongue exercises any important mechanical influence on the general form and size of the mandible or in moulding the form of the growing palate."
  82. 82. Van Thal (1935) was concerned with speech in relation to malocclusion. She deduced that malocclusion was not the cause of various types of speech defect. Froeschels (1937) found that lisping and open-bite originated from the same abnormality of tongue control. Rogers (1939) was a strong exponent of myofunctional exercises calculated to harness muscle forces in order to treat malocclusions. This scheme had a following, but it was based on the concept of function dictating form and was not widely accepted.
  83. 83. The papers which initiated intensive research on problems of tongue behavior in the next two decades were those of Rix (1946) and Ballard and Gwynne-Evans (1947). Similar observations were made on tongue behavior and speech. Rix drew attention to tongue activity which seemed to retain infantile characteristics, with the tongue showing great affinity for lower lip contact. He based his thesis on the belief that this represented a delay in maturation of behavior.
  84. 84. Ballard and Gwynne-Evans looked at the subject from the genetic point of view, stressing the familial patterns of behavior. Brodie (1946) regarded the whole facial pattern from the general morphologic point of view and was less interested in the tongue and its behavior as a single factor. In the early 1950's many of the exponents of multibanded techniques with excellent control of tooth movement recognized that there were a few cases in which the behavior of the tongue and lips formed a pattern of activity that caused relapse.
  85. 85. Other authorities, such as Straub (1960) gave the impression that tongue problems were very extensive and that re-education of orofacial behavior by trained speech therapists was necessary for many orthodontic procedures. Speech therapists and speech pathologists became increasingly involved.
  86. 86.  The confusion of thinking on the subject prompted a poem by Professor Bloomer entitled "The Inverted, Perverted, Reverted Swallow." In the same paper Bloomer (1963) sums up the general view when he states: “Some orthodontists and speech therapists are happy in their common endeavors in training patients to swallow. Others from both professions look on with a measure of disapproval. The concern represents not an antithesis to cooperation but uneasiness about prescribing 'cookbook' treatment programs for problems in which the dynamics of cause and effect are not yet understood. "
  87. 87. The infantile( visceral) swallow, an essential function in the neonate, is closely associated with suckling, and both are well developed by about 32nd week of intrauterine life. During the infantile swallow the tongue is between the gum pads in close apposition with the lips, and its contraction plus those of the facial muscles help to stabilize the mandible. THE SWALLOWING PATTERN
  88. 88. The swallow is guided, and to a great extent controlled by sensory interchange between the lips and the tongue. The mandibular elevators which play a prominent role in normal mature swallow, show minimal activity.
  89. 89. All occlusal functions are learned in stages as the nervous system and the orofacial and jaw musculature mature concomitantly with the development of the dentition. During the later half of the first year of life, several maturational events occur that alter markedly the functioning of the orofacial musculature. The arrival of the incisors cues the more precise opening and closing movements of the mandible, compels a more retracted tongue posture, and initiates learning of mastication.
  90. 90. As soon as bilateral posterior occlusion is established, true chewing motions are seen to start, and the learning of the mature swallow begins. Gradually, the fifth cranial nerve muscles assume the role of mandibular stabilization during the swallow, and the muscles of facial expression abandon suckling and infantile swallowing pattern and begin to learn the delicate and complicated functions of speech and facial expression.
  91. 91. The transition from infantile to mature (somatic) swallow takes place over several month, aided by maturation of neuromuscular elements. Most children achieve most characteristics of a mature swallow at 12 to 15 months.
  92. 92. The characteristic features of a mature (somatic) swallow are –  teeth are together.  the mandible is stabilized by contraction of muscles of fifth cranial nerve.  the tongue tip is held against the palate above and behind the incisors.  minimal contraction of the lips are seen during the swallow. Mature (somatic) swallow
  93. 93. The deglutitional cycle is divided into four phases which are highly integrated and synergestically coordinated. The four phases are- 1. The preparatory phase 2. The oral phase 3. The pharyngeal phase 4. The oesophageal phase The deglutiton cycle
  94. 94. The preparatory phase The preparatory phase starts as soon as liquids are taken in, or bolus has been masticated. The liquid or bolus is then in a swallow- preparatory position on the dorsum of the tongue. The oral cavity is sealed by the lip and the tongue.
  95. 95. The oral phase During the oral phase the soft palate moves upward and the tongue drops downward and backward. At the same time the larynx and the hyoid bone move upwards. These combined movements create a smooth path for the bolus as it is pushed from the oral cavity by a wave-like rippling of the tongue.
  96. 96. While solid food is pushed by the tongue, liquid food flows ahead of the lingual constrictions. The oral cavity, stabilized by the muscles of mastication, maintains an anterior and lateral seal during this phase.
  97. 97. The pharyngeal phase The pharyngeal phase of swallowing begins as the bolus passes through the fauces. The pharyngeal tube is raised upwards en masse, and the nasopharynx is sealed off by closure of the soft palate against the posterior pharyngeal wall ( Pasavant’s ridge). The hyoid bone and the base of the tongue move forward as both the pharynx and the tongue continue their peristaltic-like movement of the bolus of food.
  98. 98. The oesophageal phase The oesophageal phase of swallowing commences as the food passes the cricopharyngeal sphincter. While the peristaltic movement carries the food through the oesophagus, the hyoid bone, palate and tongue return to their original positions.
  99. 99. Tongue thrust The tongue thrust pattern of the oral cavity has been given many titles, some of which are the following: perverted or deviate swallow, reverse swallow, retained infantile swallow, tooth apart swallow, and so forth. Yet, because no single characteristic of tongue thrust activity is constant, all such terms become too restrictive. Even the term “normal” versus “abnormal” has been criticized.
  100. 100. There is no “norm” for the pattern of tongue thrust. Malocclusion may or may not be present. Teeth may or may not be brought together. Labial pressures may or may not be normal. Speech defects may or may not be observed. Even archform may or may not be affected, in spite of all evidence that tongue force is greater than opposing lip and cheek pressure.
  101. 101. Simple tongue thrust swallow The simple tongue thrust swallow typically displays contractions of the lips, mentalis muscle and mandibular elevators and the teeth are in occlusion as the tongue protrudes into an open bite. There is a normal teeth-together swallow, but a tongue-thrust is present to seal the open bite.
  102. 102. The so called tongue thrust is simply an adaptive mechanism to maintain an open bite created by something else, usually thumb-sucking. The open bite in a simple tongue thrust is well circumscribed; that is, if one studies the teeth or the casts in occlusion, the open bite has a definite beginning and ending. When a patient is observed with a simple tongue thrust, check carefully for any history of chronic digital pacifier sucking, for that is the most common primary etiologic factor.
  103. 103. A simple tongue thrust swallow may also be found with hypertrophied tonsils which are not enlarged and/or inflamed sufficiently to prompt a tooth–apart swallow. Problems in respiration are usually not associated with a simple tongue-thrust.
  104. 104. When one fits together the dental casts of a patient with a simple tongue-thrust, they have a precise and secure intercuspation, even though a malocclusion may be present, because the occlusal position is continually reinforced by the teeth-together swallow. The incidence of simple tongue thrust diminishes with increasing age, and its treatment is simpler and prognosis more certain than complex tongue thrust.
  105. 105. The complex tongue-thrust swallow is defined as a tongue-thrust with a teeth-apart swallow. Patients with complex tongue-thrust combine contraction of lips, facial and mentalis muscle, lack of contraction of the mandibular elevators, a tongue-thrust between the teeth and a teeth-apart swallow. Complex tongue-thrust swallow
  106. 106. The open bite associated with a complex tongue- thrust usually is more diffuse and difficult to define than that seen in simple tongue thrust. On occasions there is no open bite at all. Examination of the dental casts typically reveals a poor occlusal fit and instability of intercuspation, because the intercuspal position is not repeatedly reinforced during the swallow. Patients with complex tongue-thrust usually demonstrate occlusal interferences in the retruded contact position.
  107. 107. They are also far more likely to be mouth breathers and to have a history of chronic nasorespiratory disease or allergies. The incidence of complex tongue-thrusting does not diminish as much with age as does the simple tongue-thrust.
  108. 108. Retained infantile swallow Retained infantile swallowing behaviour is defined as a predominant persistence of the infantile swallowing reflex after the arrival of permanent teeth. Fortunately, a very few people have a true retained infantile swallow.
  109. 109. Those who do, demonstrate a very strong contraction of the lips and facial musculature, even a massive grimace. The tongue thrusts strongly between the teeth in front and on both sides. Particularly noticeable are the contractions of the buccinator muscle. Such patients have inexpressive faces, since the seventh cranial nerve muscles are not being used for the delicate purposes of facial expression but rather for the massive effort of stabilizing the mandible during the swallow.
  110. 110. Patients with a retained infantile swallow have serious difficulties in mastication, for ordinarily they occlude on only one molar in each quadrant. The gag threshold is typically low. These patients may restrict themselves to a soft diet and state frankly that they do not enjoy eating. Food often is placed on the dorsum of the tongue and mastication occurs between the tongue tip and palate because of the inadequacy of occlusal contacts.
  111. 111. The prognosis for conditioning of such a primitive reflex is poor. True retained infantile swallow is fortunately rare. Excessive anterior facial height often produces severe frontal open bites and extreme adaptive swallowing behavior as the neuromusculature attempts to cope with the skeletal imbalance. Such a strained adaptive swallowing behavior must be carefully discriminated from complex and retained infantile swallow.
  112. 112. Mastication
  113. 113. Human mastication has been examined by several authors with a variety of methods including cineradiography, light-emitting diodes, magnetic devices, and photooptical devices, to describe movements of the mandible. Comprehensive error analysis of these methods has seldom been reported, although such analysis should improve the value of the results, permitting interpretation of those results in light of the magnitude of the errors.
  114. 114. Mastication has most often been described in terms of single cycles; researchers have not attempted to treat the data from multiple cycles statistically, because the variability of the chewing cycles can make mean masticatory movements difficult to assess. While variability in the chewing pattern among individuals is the rule, rather than the exception, these patterns seem to have clear individual characteristics that are more or less unique for the individual.
  115. 115. Mastication has most often been described in terms of single cycles; researchers have not attempted to treat the data from multiple cycles statistically, because the variability of the chewing cycles can make mean masticatory movements difficult to assess. While variability in the chewing pattern among individuals is the rule, rather than the exception, these patterns seem to have clear individual characteristics that are more or less unique for the individual.
  116. 116. In the infant, as the bolus takes up the saliva it is forced between the gum pads or the occlusal surfaces of the erupting teeth. At the same time, the rhythmic action of the muscles of the cheek serves to force the food back towards the tongue, which mashes the bolus of food against the hard palate. To permit the bolus of food to interpose between the gum pads or teeth, the mandible is depressed by gravity and the hyoid, and lateral pterygoid muscles, with a simultaneous deflection towards the working side.
  117. 117. The lateral shift of the mandible is more apparent in hard-to-chew foods. After a portion of the bolus of food is accomodated between the occlusal surfaces, the amndible is forcibly closed, primarily by temporal and masseter muscle activity.
  118. 118. The masticatory freqency is variable, but appears to be one to two strokes per second with a normal bolus of food. The number of masticatory strokes before swallowing seems to be characteristic of an individual and is relatively constant. The masticatory stroke in an adult can be explained in six phases
  119. 119. 1. The preparatory phase- during this phase the food is ingested and positioned by the tongue within the oral cavity, and the mandible is moved toward the chewing side. There is a slight, constant deviation to the non-food side an instant before the mastication stroke begins and this point is used to identify the precise beginning of the preparatory phase.
  120. 120. 2.Food contact- this is characterized by a momentary hesitation in movement. This is interpreted to be a pause triggered by sensory receptors concerning the apparent viscosity of the food and probable transarticular pressures incident to chewing.
  121. 121. 3.The crushing phase- this starts with a high velocity and then slows down as the food is crushed and packed. When the central incisor is approximately 0.24”from closure, the jaw motion is stabilized at the condyle on the working side and the final closing stroke thereafter is guided by this braced condyle.the first three or four strokes in mastication typically emphasize the crushing phase and they usually display equal and synchronous activity on both sides.
  122. 122. 4.Tooth contact- it is accompanied by a slight change in direction but no delay. All reflex adjustments of the musculature for tooth contact are completed in the crushing phase before actual contact is made. There is a distinct and discrete pause , consistently elicited in the temporalis and masseter muscle following tooth contact.
  123. 123. 5. The grinding phase- this coincides with the transgression of the mandibular molars across their maxillary counterparts and is therefore highly constant from cycle to cycle. This phase is also called as the terminal functional orbit.during this phase the bilateral muscle discharge becomes unequal and asynchronous, indicating that the person is chewing unilaterally.
  124. 124. 6. Centric occlusion- when the movement of the teeth comes to a definite and distinct stop at a single terminal point, from which the preparatory phase of the next stroke begins. It is also seen that the jaws of subjects with normal occlusion stayed in this position for a considerable time compared to those with malocclusion.
  125. 125. There is no evidence suggesting the function of mastication as an etiologic factor for malocclusion. Although the function of mastication itself can be affected by malocclusions. The functions of the masticatory muscles though may be contributing factors in malocclusion.
  126. 126. The mastication of food is a primary function of the dentition in the process of digestion. Masticatory efficiency is known to be impaired with the loss of teeth, but almost no difference has been reported between subjects with excellent occlusion and those with most types of malocclusion.21 Although unmasticated food may leave undigested residues,22 the degree of mastication required for maximum absorption of foods is seemingly readily attained by subjects with inadequate dentitions.
  127. 127. Actually, little research has been done on mastication, and no evidence exists that malocclusion (excluding conditions that cause severe functional impairment) affects the digestive process and general health. Nevertheless, the ease of chewing and swallowing, freedom from interdental food impaction, self-cleansing action, and the enjoyment of taste are factors which cannot be quantitated but which must be satisfied according to individual requirements.
  128. 128. SPEECH
  129. 129. The function of speech is something unique only to the human beings. Unlike respiration, deglutition and mastication, which are reflexive in nature, speech is largely a learned activity dependant on the maturation of the organism. Speech is to be distinguished from the reflexive sounds thatare associated with physiologic states. Coming late in the evolutionary development of man, speech makes use of muscles which have many other functions.
  130. 130. Other than speech functions are Innate automatic vegetative reactions such as swallowing, gagging, vomiting and suckling. Learned automatic vegetative reactions such as biting, chewing and sucking. Learned automatic emotional reactions such as grimaces, mannerisms, tics. Innate automatic emotional reactions like laughing, sobbing, smiling.
  131. 131. Learned nonautomatic discriminatory and specially voluntary reactions like exploratory movements of tongue, spreading of the lips, kissing and blowing. Learned automatic practical reactions like whistling, humming a tune, playing a wind instrument.
  132. 132. It is easy to see why a large number of muscles are involved. The muscles of the walls of the torso, the respiratory tract, the pharynx, the soft palate, the tongue, the lips, and face, and the nasal passages are all concerned in the production of speech sounds. Simultaneous breathing to provide a column of air is essential to provide vibrations necessary for sound. The lips and tongue and velopharyngeal structures modify the outgoing breath stream to produce variations in the sound.
  133. 133. Assuming the presence of normal structures, speech production is dependant on the coordinated action and precise activity of muscles that may be performing other functions at the same time. If the structures are not normal, as with cleft palate, normal speeech sounds are not possible, despite the compensatory muscle activity. Even though the mechanisms for producing sound involve atleast parts of the same systems used for mastication, respiration and speech, actions used in producing language differ considerably.
  134. 134. The speech mechanism acts on the breath stream in a number of ways, controlling the air mechanism, air direction, air flow, air release, air pressure, general air path and lingual air path. These actions involve muscle groups and call for compensatory interaction if abnormality exists in one area. With respect to the tongue, which fills the oral cavity at bith, only the extrinsic muscles which largely control horizontal movement needed for the suckle swallow are well-developed.
  135. 135. Those intrinsic muscles needed for speech are poorly developed. The transition from gross movements of the tongue to precise and finely controlled ones extends over the first several years of life, through the infantile and transitional swallow periods into the mature deglutitional pattern era. The speech therapist is concerned over the residual infantile tongue posture and function, since lisp, open bite, anterior escape and substitute speech sounds are possible sequelae to a retained infantile swallowing habit.
  136. 136. The lips as well as the tongue undergo maturational changes preparatory to speech. In infants , suckling and rooting reflexes are dominant. The first sounds actually make no demand on the lips e.g. “aa.” the degree of lip protrusion is considered significant in varying the length of the vocal tract. with reduction in purse-string suckle-swallow activity, more delicate peripheral lip movements are seen, coinciding with tongue maturation.
  137. 137. Of particular importance to the dentist is the velopharyngeal valve. In children with cleft palate, inadequte valving seems to be the rule, not the exeption. Upward and backward movement of the soft palate in such problems does not emulate the normal pattern. Normally, the third quadrant of the soft palate contacts the pharyngeal wall with sounds like “p”, “b”, “f” and “w”.
  138. 138.
  139. 139. The general awareness that the teeth are involved in the production of speech does not imply a causal relationship between malocclusion and speech problems. The vocal tract functions as an integrated unit during speech production. Since the tract is flexible and modifiable, a deviation in one portion can be minimized frequently by modification of other portions of the tract. Sounds can therefore be produced in a variety of ways. Most speakers compensate automatically for all but the most severe structural deviations to maintain intelligibility of the acoustic signal because of the impelling need to communicate.
  140. 140. The adaptability and compensatory action of the vocal tract to a wide variety of deviations do not negate the fact that in individual instances improvement in speech disability can be secured by orthodontic treatment in conjunction with speech therapy. Moreover, the greater the number of structural deviations, the greater the demands placed upon compensatory adjustments and, consequently, the greater the likelihood that defective speech and particularly consonant production can be remedied by correction of the malocclusion.
  141. 141. Conclusion
  142. 142. Among the four functions namely respiration, deglutition, speech and mastication that we discussed; The first two can be contributiary factors to the etiology of malocclusion. Though there is lot of controversy in literature. The last two namely mastication and speech, by themselves are not shown to be etiologic factors for a malocclusion, but malocclusion may lead to an abnormality in these functions.
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