R E V I E W A R T I C L E B i o m e c h a n i c a l C h a n g e s o f t h e O r a l a n d C r a n i o f a c i a l R e g i o n s a s a R e s u l t o f A l t e r e d B r e a t h in g P a t t e r n s A B S T R A C T : The purpose o f this report is to discuss the biom echanical changes in the oral and craniofacial regions as a result o f altered breathing patterns. The increase in air pollution and allergens, resulting in allergic reactions, is often the cause o f chronic nasal obstruction. The biom echancis o f the oral, cranial and fa c ia l areas are intim ately linked, an d will be adversely affected by any change in the breathing pattern. A s a result o f nasal obstruction, the biom echanics o f respiration changes to fa c ilita te m outh breathing, and the resting position o f the tongue and mandible is disrupted. The lips are parted, the freew a y space and craniocervical angulation increase. The m uscle activity o f the posterior cervical musculature, anterior tem poralis and suprahyoid muscles will be increased. The equilibrium o f fo rces in the oral an d craniofacial region is disturbed, an d these abnorm al fo rc e s could lead to the developm ent o f “adenoid f a d e s ”, m alocclusions and dysfunction over a p erio d o f time. It is important to diagnose chronic nasal obstruction and mouth breathing early and start treatm ent before the negative effects o f the m usculoskeletal system occur. A sound understanding o f the biom echanical changes w ill enable the physiotherapist to carry out a skillful exam ination and p lan a treatment program, based on informed decisions. KEYW ORDS: BIOMECHANICS, BREATHING PATTERNS, ORO-CRANIO-FACIAL REGION, NASAL OBSTRUCTION JORDAAN R, M PHYST (UP)1; PAPADOPOULOS M, MSc PHYSIO (WITS)'; 1 Department of Physiotherapy , University of Pretoria INTRODUCTION Approxim ately 137 years ago, a well- know n Am erican artist George Catlin w rote about the n o xious effects o f mouth breathing. The title o f this publi­ cation was: “T he breath o f life” . This title was subsequently changed to “Shut your mouth and save your life” . Catlin was the first to direct attention to the fact that mouth breathing can lead to facial deform ity and m alocclusion (abnorm al alignm ent) o f the teeth (G oldsm ith and Sylvan, 1994). The effects o f oral respiration on the growth and developm ent o f craniofacial structures have been extensively studied for several decades, and have been shown to be one o f the im portant external influ­ ences on the growth and developm ent o f C O RR E SP O N D E N C E TO: M rs R Jordaan D epartm ent o f Physiotherapy U niversity o f Pretoria PO Box 667, Pretoria 0001 Tel: (012) 354-2023 (W) Tel: (012) 329-2178 (H) Email: rjordaan@ postillion.up.ac.za these structures. K now ledge regarding the neurom uscular adaptation to factors that affect function in the craniofacial region, is essential in the assessm ent o f the long-term effects o f such factors (Ono et al, 1998). R ocabado becam e the first physio­ therapist to analyse growth, develop­ m ent and soft tissue characteristics o f the craniom andibular region, w hich he related to dentistry. From this he esta­ blished a rationale for physiotherapy treatm en t o f the m ax illo -o ral-facial region. He highlighted the im portance o f m echanical influences on the hum an body. A lm ost all tissues are sensitive to tension, com pression, torsional or bending loads, and abnorm al forces applied over a long period o f time, may lead to skeletal deform ation (R ocabado and Iglarsh, 1991). In the orthodontic literature, m any stu d ies d em o n strate the relatio n sh ip between obstruction o f the upper airways, m alocclusions, craniofacial m orphology and craniocervical posture (Hellsing et al, 1987; O zbek and Koklii, 1993; Tallgren and Solow, 1987). W iltshire (1996), a South A frican orthodontist, in his study on chronic nasal obstruction and m aloc­ clusion, m entioned the increasing pre­ valence o f urban children in need o f orthodontic treatm ent for malocclusions, com pared to rural children. This was partly ascribed to air pollution and the possibility o f increased allergen expo­ sure in urban areas. T he high degree of pollution in South A frica is a cause for increasing concern, and could have a direct effect on the incidence o f m aloc­ clusions in people living in these areas. I f nasal obstruction, mouth breathing and m alocclusions are related to changed biom echanics o f the oro-cranio-facial region, it should be a cause for increasing concern, not only for the orthodontist, but also for the p hysiotherap ist. No m ention was m ade in any o f these stu­ dies o f physiotherapy involvem ent in the m anagem ent o f these patients. R ocabado and Iglarsh (1991) postu­ lated that the com plexity o f the head, neck and m axillofacial regions requires the evaluation and treatm ent skills of m any health pro fessionals, including physiotherapists and dentists. The report therefore m akes a valuable contribution to clinical practice, as it enables the p h y s io th e ra p ist to screen potential patients at an early stage in order to prevent dysfunction and sym ptom s from developing. This can be done by careful 26 SA J o u r n a l o f P h y s io th e ra p y 2001 V o l 57 No 1 R ep ro du ce d by S ab in et G at ew ay u nd er li ce nc e gr an te d by th e P ub lis he r (d at ed 2 01 3. ) mailto:rjordaan@postillion.up.ac.za planning o f suitable rehabilitation pro­ gram s, based on inform ed decisions. T he purpose o f this review article is to discuss the effects o f altered breathing patterns on the biom echanics o f the oro- cranio-facial region. Norm al and abnor­ mal breathing patterns, the causative factors o f changed breathing patterns, and the biomechanical effects o f changed breathing patterns will be discussed. BREATHING PATTERNS No two persons breathe in exactly the sam e m anner, and no single person b re ath es in exactly the sam e way under all conditions. A variety o f normal breathing patterns are used under differ­ ent conditions. Before discussing altered breathing patterns, it is im perative to understand normal breathing patterns and the relevant biom echanics o f the oral and craniofacial structures involved in breathing, to be able to recognize and com pare changed breathing patterns and biom echanics. Normal breathing patterns R espiration is an im portant life sustain­ ing function and jaw and tongue pos­ tures are intim ately associated therewith (W iltshire, 1996). R ocabado and Iglarsh (1991) also support this idea, but add to it, stating that the axial musculature o f the spinal vertebrae is also involved in m a in ta in in g the u p p er airw ay. Furtherm ore, due to the fact that physio­ logical m aintenance o f the airway is essential to life, it m ust be dynam ic to accom m odate the growth and develop­ m ent o f the musculoskeletal system and its response to physical activity. It is thus clear that respiration is not an isolated function, but involves num erous other structures. A ccording to Ricketts (1968), normal breathing takes place through the nasal cavity, with little or no strain, w hile the m outh is closed. A lthough hum ans are prim arily nasal breathers, everyone breathes partially through the mouth under certain physiological conditions. For the average individual, there is a transition to partial oral breathing when ventilatory exchange rates above 40 to 45 liters per minute are reached. This can happen during exercise, heavy mental concentration or even normal conversa­ tion, all leading to an increase in airflow (Proffit and Fields, 1993; Ricketts, 1968). The mandibular resting position Respiratory needs are the prim ary deter­ m inant o f the posture o f the jaw and tongue, and o f the head itself (Proffit and Fields, 1993). The natural resting p o sitio n o f the m andib le prev en ts breathing through the mouth. In this position a nasal breathing pattern is present with the tongue in a resting position, the m alar bone aligned with the sternum and the cranium in 15° anterior rotation (R ocabado, 1998). The resting position o f the m andible is -the result o f co-ordination betw een the posterior cervical muscles and the m uscles that lie anterior to the cervical spine. These anterior muscles are used for inspiration, m asticatio n , d e g lu titio n and speech. B ecause the m andible is contained w ith­ in this group o f m uscles, the resting position o f the m andible is dependent on the b alan ce betw een these m uscles (D arling et al, 1984). In the resting position, the m andible is suspended by passive m yotonic acti­ vity o f the craniom andibular and the infra-m andibular m usculature associated with the facial m uscles. This passive activity occurs with the head held in an orthostatic position, with the m alar bone o f the craniofacial region aligned verti­ cally with the sternum . In this resting position, the teeth are not in occlusion and the m andible creates an interoc- clusal or freeway space (space between the upper and low er teeth) (R ocabado and Iglarsh, 1991). All the stom atognatic structures are in balance in the m andibular rest posi­ tion. This entails light lip contact or lips slightly apart, opposing teeth sepa­ rated, jaw muscles at rest from function, m andible passively suspended against gravity, and the tongue at rest. The posi­ tion o f the m andible im pacts directly on the position o f the head on the neck, and indirectly on the entire upper body posture (Ayub et al, 1984; Rocabado and Iglarsh, 1991). The resting position of the tongue T he restin g p osition o f the tongue against the palate o ccu rs w hen the anterior part o f the tongue is in contact with the rugae o f the palate. The lateral margins o f the tongue are contained w ithin the lingual aspects o f the m axil­ lary bone, and the base o f the tongue is in contact with the soft palate. The dorsum o f the tongue is held against the hard palate by the space ofm egative air pressure created by the vacuiim system o f the tongue against the palate. This triple seal during lip closure enables the tongue to overcom e the force o f gravity (Ricketts, 1968; Rocabado and Iglarsh, 1991). W hen the tongue assum es its normal rest position, m usculatu re o f the c ra ­ niom andibular system enters a reflex re la x a tio n sta g e and the m a n d ib le descends into its rest position to create the freew ay space. T he lips, cheeks and tongue exert a balanced internal and external force against the teeth. Therefore, norm al lip seal and tongue position prom ote normal developm ent o f the dental alveolar region by equa­ lizing fo rces ap p lied to the teeth (Rocabado and Iglarsh, 1991). Norm al nasal breathing depends on a balan ced , in teractiv e relatio n sh ip between all the head, neck and shoulder girdle com ponents. An im balance o f one com ponent, will have an effect on all the other com ponents, causing an altered breathing pattern. Abnormal breathing patterns It is clear from the above, that the nor­ mal breathing pattern is through the nasal passages, but it is also normal to breathe through the nose and mouth under certain conditions. W hat is an abnorm al breathing pattern? Wenzel et al (1983), describes an increased oral involvem ent in respira­ tion with obstruction o f the nasal airway as an abnorm al b re ath in g pattern. According to W iltshire (1996), when the nasal passagew ays prove ineffective in perform ing the life sustaining breathing function, the m outh exists as an em er­ gency alternative breathing route. R oca­ bado and Iglarsh (1991) define mouth breathing syndrom e as a habitual pattern through the mouth instead o f the nose. They also m ention that a com bination o f nasal and oral breathing is often observed w hich is not a n o rm al breath­ ing pattern. SA J o u r n a l o f P h y s io th e ra p y 2001 V o l 57 No 1 27 R ep ro du ce d by S ab in et G at ew ay u nd er li ce nc e gr an te d by th e P ub lis he r (d at ed 2 01 3. ) R espiration is m ost efficient with modest resistance present in the respira­ tory system , but increased w ork for nasal resp iratio n is p h y sio lo g ically acceptable only to a point. W ith partial nose obstruction, the w ork associated with nasal breathing increases, and at a certain level o f resistance to nasal airflow, the individual sw itches to par­ tial m outh breathing. This crossover point varies am ong individuals. Total nasal obstruction in hum ans is rare, but partial nasal obstruction can occur occasionally for a short tim e, or in some children chronically. It is very difficult to determ ine w hat the pattern o f respira­ tion in hum ans really is at any given tim e (Proffit and Fields, 1993). B ecause the respiratory need is the prim ary determ inant o f the posture o f the jaw, tongue and head, it seem s re a ­ so n ab le that an altered resp irato ry pattern, such as breathing through the m outh rather than the nose, can change posture o f the head, jaw and tongue (Proffit and Fields, 1993). A ccording to R ocabado and Iglarsh (1991), a chain o f body adaptations to abnorm al breathing patterns leads to dysfunctional patterns. W iltshire (1996), agrees w ith this statem ent by Rocabado and Iglarsh, saying that altered breathing patterns, such as m outh breathing, could change the equilibrial position o f the tongue and jaw, w hich could have a significant deleterious effect on cranio­ facial growth and tooth positions. T h ese ch an g ed breathing p atterns trigger the next question: W hat factors can contribute to change norm al breath­ ing patterns to physiologically abnorm al breathing patterns? Causative factors of changed breathing patterns There are num erous factors that can obstruct or partially obstruct the nasal airways, either for a short tim e or even chronically. From the literature, it is clear that these contributing factors can be divided into three categories: Diseases of the upper respiratory tract Chronic respiratory obstruction can be produced by prolonged inflam m ation o f the nasal m ucosa associated with allergies, chronic respiratory infection, and asthma. Nasal allergies and respiratory infec­ tions in early childhood are com m on causes o f adenoidal hypertrophy, causing obstruction and restricted respiratory flow through the nasal passages. Sym p­ toms associated w ith adenoidal hyper­ trophy and secretory otitis m edia, are blocked nose, m outh breathing, snoring o r rhinitis (H aapaniem i, 1995; Solow et al, 1993). Developmental conditions The size o f the posterior nasopharyngeal soft tissue, or adenoids, increase rapidly after birth. From fou r to six years, m axim um size is attained, after which they stay the sam e until eight to nine years o f age. T hereafter they gradually begin to involute (H aapaniem i, 1995). A ny c o n d itio n cau sin g h y p ertrophy o f the adenoids, can cause respiratory obstruction. R ocabado and Iglarsh (1991) also m ention that developm ental deficiencies in the facial skeleton m ay predispose a patient to m outh breathing, for exam ple a m axilla deficient in vertical height, or m andibular grow th deficiencies in the m andibular head, can im pair nasopha­ ryngeal function. Physical conditions Extrem e obesity can be a predisposing factor to a dorsal position o f the tongue w ith a short p o sterio r airw ay space betw een the tongue and the posterior pharyngeal wall, causing obstruction of the upper airw ay in adults (Solow et al, 1993). O ther interesting physical condi­ tions that can be triggering factors for changed breathing patterns, are: distur­ bances in the visual or proprioceptive system and cervical spine anom alies (Solow et al, 1984). The biomechanical effects of changed breathing patterns C hanged breathing patterns will change the biom echanics o f respiration. This will result in a changed m andibular pos­ ture, leading to changes in forces in the oral and craniofacial regions, and conse­ quently this will have an effect on the head-on-neck posture, or craniocervical angulation (M iller et al, 1984; Ricketts, 1968). This chain o f reactions, is due to the fact that all the craniofacial and craniocervical structures are intim ately linked biom echanically. Changes in the biomechanics of respiration Nasal obstruction induces a change in respiratory function w hich involves the anterior portion o f the upper respiratory tract. A ccording to M iller et al (1984), nasal obstruction initiates a change in w hich the oral cavity m ust then serve as the m ajor or perhaps the only pathw ay for periodic airflow during all respiratory dem ands. In adapting the oral passages for chronic respiratory work, the anterior portal is achieved by two m echanisms - raising the upper lip and lowering the man­ dible. The posterior cavity can be widened by a protrusive action o f the tongue. In contrast to M ille r’s (1984) and to re s e a rc h e rs’ p ro p o sed m echanism to achieve oral breathing, R icketts (1968) suggests that by lifting the head into extension, away from the hyo-m andi- b u lar co m p lex , the tra n sitio n from nose to m outh breathing is facilitated. A ccording to Solow et al (1993), with obstruction o f the upper airway, the craniocervical angulation increases and the possib le reason could be that a changed head posture will increase the diam eter o f the airway, and thus reduce the airw ay resistance. W ith m outh breathing, the accessory m uscles o f respiration are hyperactive. T hese include the sternocleidom astoid, scaleni and the p ecto ralis m uscles. R ocabado and Iglarsh (1991) describe the typical posture associated with an increase in m uscle activity o f the acces­ sory m uscles o f respiration, as follows: forw ard shoulders, depressed sternum and abnorm al developm ent o f the upper thoracic region. D ecreased activity o f the diaphragm and hypotonicity o f the abdom inal m usculature will perpetuate the fau lty po stu re, c h a racterised by protrusion o f the abdom inal region and an increased lum bar lordosis. A lthough there are different opinions on the exact m echanism s involved in m outh breathing, it is clear that the m andible is lowered, the head is tilted into extension and the total body posture changes as a result. This will lead to changed biom echanics in the orofacial and craniofacial regions, w ith changed m uscle activity in the associated muscles. 28 SA J o u r n a l o f P h y s io th e ra p y 2001 V o l 57 No 1 R ep ro du ce d by S ab in et G at ew ay u nd er li ce nc e gr an te d by th e P ub lis he r (d at ed 2 01 3. ) Changes in the biomechanics of the oral and craniofacial regions M any studies agree on the adaptive changes that take place as a result o f m outh breathing due to obstruction o f the upper airways: the lowered position o f the jaw and tongue, the parting o f the lips - breaking the seal, and the extended position o f the head which assists in opening the ja w by elevating the m axilla (H ellsing et al, 1987; Wenzel et al, 1985; W iltshire, 1996). R o cab ad o and Ig larsh (1991), described the sequence o f oral and cra­ niofacial changes that take place as a result o f mouth breathing as follows: the resting position o f the m andible is disrupted, a larger freew ay space is adopted and the lips are further apart than in the nasal breather. Sim ultaneously, the cranium rotates posteriorly, adopting a typical forw ard head posture. In this head-neck position, the tongue cannot maintain a normal resting position against the palate. The tongue is pulled down onto the floor o f the m outh, and slightly anterior against the posterior surface o f the teeth in a thrust relation. The protrusive action o f the tongue helps to open the posterior oral cavity to facili­ tate m outh breathing (M iller et al, 1984; R ocabado and Iglarsh, 1991). M iller et al (1984) studied the neuro­ m uscular changes by means o f electro­ m yography in rhesus m onkeys, in which the nasal passages w ere obstructed with silicone plugs for two years. M ore than eighty percent o f the m onkeys dem on­ strated a low ered m andible, and sixty percent rhythm ic tongue and upper lip m ovem ents. Certain o f the craniofacial and tongue m uscles w ere recruited and rem ain ed activ e thro u g h o u t the two years. To change and m aintain the new m an d ib u lar positio n req uires m uscle control. According to M iller et al (1984), the geniohyoid m uscle is the prim ary suprahyoid m uscle that becom es more tonically active with nasal obstruction. O th e r m u s c le s re c ru ite d a re the genioglossus, inferior orbicularis oris o f the low er lip and the lip elevator fibers o f the upper lip. It is evident that nasal o b stru ctio n causes a n eu ro m u scu lar adaptation and an active change in the synaptic m otor control o f the cranio­ facial and oral muscles. H ellsing et al (1986), dem onstrated in a study on adults, that induced mouth breathing changed the electromyographic activity significantly in neck and m asti­ catory m uscles. The changed head pos­ ture associated with m outh breathing, causes the p o stu ral activity in the posterior cervical m uscles to decrease. The postural activity in the anterior tem ­ poral m uscle was significantly reduced to keep the m an d ib le low ered for m outh breathing. In the suprahyoid area, increased activity was found in the ante­ rior digastric, the geniohyoid and the genioglossus m uscles. T he activity in the anterior belly o f the digastric m uscle increased in order to depress and hold the m andible in a low ered position. The geniohyoid m uscle helps to m aintain the position o f the hyoid bone and airway adequacy, and the genioglossus m uscle helps to m aintain the changed position o f the tongue. The results from the above studies dem onstrate that the com pensatory m us­ cle function due to m outh breathing, causes a change in postural activity in specific neck and m asticatory muscles. This stresses the fact that the m ode o f breathing, head posture and m andibular posture are intim ately related, and that change in the one com ponent will have an effect on the others. B ut w hat is the long term effect o f the changed biom e­ chanics o f the oral and craniofacial regions? Changes in oral and craniofacial morphology The changed posture o f the head, jaw and tongue with m outh breathing, could alter the equilibrium o f pressures on the jaw and teeth, and affect jaw growth and tooth positions (Turner et al, 1997; W einstein, 1994). Subjects who convert to mouth breathing for a short tim e w ill not have any effect on craniofacial growth. However, chronic respiratory o b stru ctio n and m ain tain ed p ostural changes could have a definite effect on the craniofacial growth in the growing child (H uggare, 1998). T he rela tio n ­ ship between mouth breathing, changed posture and the developm ent o f m aloc­ c lusions is n o t clearly defined, and experim ental studies have only attem pted to partially clarify the enigm a (Proffit and Fields, 1993; W iltshire, 1996). “A denoid f a d e s ” is the popular term asso ciated w ith m outh b reathing, consisting o f narrow facial dim ensions, protruding teeth and narrow ed dental arches, as well as nonfunctional lips w hich are separated at rest. The changed position o f the tongue causes a decrease in lingual pressure on the m axillary arches, consequently losing the tongue’s expansion force for norm al growth and developm ent (R ocabado and Iglarsh, 1991). With the increased pressure from the stretched cheeks due to an open m outh position, a narrow ed m axillary d en tal arch w ill re su lt (P ro ffit and Fields, 1993). The transverse com pres­ sion o f the m axillary arch causes a cross bite, and a high arched or deep palate. W ith cross bite, the m axillary incisors are cro w d ed o r protruded. T he lips becom e shortened, hypertonic and non­ functional, w ith less pressure on the a n terio r teeth w hich w o u ld tend to procline. A dow nw ard and backw ard rotation o f the m andible will occur with m o uth b re ath in g , w ith an in creased overjet and developm ent o f an anterior open bite (Proffit and Fields, 1993; R ocabado and Iglarsh, 1991; Turner et al., 1997; W iltshire, 1996). In the search for determ inants o f craniofacial developm ent, an association between craniocervical angulation and craniofacial m orphology was noticed. A m ong the characteristics w ere reduced facial prognatism , a large m andibular plane inclination and a large low er ante­ rior facial height (Solow et al, 1994). Solow and K reiborg (1977) proposed a hypothesis to account for the asso­ ciatio n b etw een airw ay ob stru ctio n , head posture and craniofacial m orpho­ logy. They suggested that head exten­ sion causes an increase in tension, or stretching o f the soft tissue layer cover­ ing the face and continuing into the investing fascia o f the neck. A subse­ quent retrusive force on facial m orphol­ ogy will result. Further consideration o f the m echa­ nism relating head posture to craniofacial m orphology leads to a chain o f inter­ actions involving six factors (Figure 1). Any link in this sequence o f events could be the site o f prim ary affliction, triggering a chain o f reactions (Solow and Kreiborg, 1977). SA J o u r n a l o f P h y s io th e ra p y 2001 V o l 57 No 1 29 R ep ro du ce d by S ab in et G at ew ay u nd er li ce nc e gr an te d by th e P ub lis he r (d at ed 2 01 3. ) FIGURE 1. Chain of factors relating nasal obstruction, head posture and craniofacial morphology Soft tissue Differential forces on skeleton stretching I Postural change of the head * Morphologic change t I Neuromuscular Obstruction feedback of airways In children an exam ple o f triggering factors could be enlarged adenoid tissue, perennial allergies or asthm a, causing airway obstruction, changed biomechanics o f respiration, changed neurom uscular feedback and chang ed craniocervical posture. This will lead to stretching forces on the soft tissue. T he soft tissue exerts forces on the skeletal structures as a result o f the pulling effect o f the stretched soft tissue on the bony ele­ m ents to w hich they attach, leading to m orphologic changes (Solow and Kreiborg, 1977; Solow et al, 1984). Solow and Sonnesen (1998) found a clear pattern o f associations between malocclusions and craniocervical posture. T hey described an increased cran io ­ cervical angle in children with anterior crow ding of the teeth. T hese findings w ere in accordance with the soft tissue stretching hypothesis, where the increased do rsally directed soft tissue pressure causes im pedem ent o f the sagittal d evel­ opm ent o f the dentalalveolar arches. Biomechanics of a changed cranioce vical angulation M any studies were done to determ ine the relationship betw een obstruction o f the upper airw ays, m outh breathing and the position or posture o f the head (Solow e ta l., 1993; Wenzel e ta l., 1983; W iltshire, 1996). Solow et al (1993) exam ined the effect o f airw ay obstruc­ tion on c ra n io cerv ic al p o stu re in a sam ple o f adult patients with obstructive sleep apnoea. The findings did provide evidence for the hypothesis that upper airw ay o b stru ctio n m ay trig g e r an increase in craniocervical angulation. A ccording to the authors, a reason for this physiological m echanism could be that such a ch an g e in p o stu re will increase the diam eter o f the airw ay and thus red u ce the airw ay resistan ce. A nother reason for an increase in cranio­ cervical angulation could be that, as observed by R icketts (1968), an increase in the cra n io cerv ic al angle w ill lift the head away from the hyom andibular com plex, and thus facilitate the transi­ tion from nose to m outh breathing. Studies o f head posture in children w ith adenoidal obstruction have dem on­ strated an increase in craniocervical angulation or a forw ard head posture. A fter ad eno idectom y, this ex ten d ed head posture has been shown to change, with a decrease o f up to nine degrees, o f the craniocervical angle (Solow et al, 1993). Wenzel et al (1985), determ ined that an intranasal corticosteroid in chil­ dren with asthm a and perennial rhinitis, is capable o f reducing nasal obstruction resistan ce, leading to a decrease in craniocervical angulation. All these studies m ention an increase in craniocervical angulation or head extension in relation to the cervical colum n. But w hat happens to the visual axis if the head is tilted backw ard into extension? T he patient will be staring in an u p w ard d irectio n , lim itin g the patien t’s functioning. A ccording to Solow et al (1993), an increase in the craniocervical angulation can be m ediated by extension o f the head in relation to the true vertical line, or by a forward inclination o f the cervical colum n or by a com bination o f both. An explanation for the different m echanism s observed, could possibly be that a need for m aintaining the visual axis in its original horizontal position allow s only for m inor adaptations o f the craniovertical angulation. A physio­ logical requirem ent for a m ajor increase in craniocervical angulation due to air­ way obstruction can therefore only be met by a forw ard inclination o f the cervical column. It is clear that the biom echanics o f an increased craniocervical angulation was not studied in m uch detail in m ost o f the studies. CONCLUSION T he purpose o f this report was to discuss the effects o f altered breathing patterns on the biom echanics o f the oro-cranio- facial region. O bstruction o f the upper airway, changing the breathing pattern to mouth breathing, induces a widespread chain o f reactive changes. It affects the posture, biom echanics, growth and developm ent o f the orofacial, cranio­ facial and craniocervical regions. N ot all the changes are within physiological lim its and the developm ent o f stress and strain on certain neurom usculoskeletal structures, could eventually result in dysfunction. A ccording to Jull and Janda (1987), the im p o rtan c e o f ad eq u ate sensory input, proprioceptive control and proper function o f sensorim otor integration, has been underestim ated in the pathogenes is o f m uscle im balances and the patho­ genesis o f pain. T here is a possible link b etw e en rec u rrin g h ead a ch es and c ra n io m a n d ib u la r d iso rd ers during adolescence (C apurso et al, 1997). Early d iag n o sis, p re v e n ta tiv e id en tificatio n o f the subject at risk and an interdis­ cip lin ary co-o p eratio n could prevent progression o f sym ptom s. 30 SA J o u r n a l o f P h ysio th e ra p y 2001 V o l 57 No 1 R ep ro du ce d by S ab in et G at ew ay u nd er li ce nc e gr an te d by th e P ub lis he r (d at ed 2 01 3. ) T he p h y sio th e ra p ist m ust have a sound u n d erstandin g o f the specific reactions o f tissues and growth processes to forces acting on them, as well as the principles o f basic biom echanics (Leveau and Bernhardt, 1984). In plan­ ning a treatm ent program , it is im portant that the aetio lo g ical fac to rs should always firstly be reduced, before a phy­ sio th e ra p e u tic reh ab ilita tiv e p ro gram can be introduced successfully. In the case o f m outh breathing, it is im portant that chronic nasal obstruction be diag­ nosed and treated early in childhood, b e fo re n eg ativ e effects on m u scu ­ lo sk eletal g ro w th could be induced (W iltshire, 1996). W ith good know ledge and applica­ tion o f these principles, clinicians can help direct the norm al growth and devel­ opm ent o f the m usculoskeletal system, preventing sym ptom s from developing in later life (Leveau and Bernhardt, 1984; Jull and Janda, 1987). This is p artic u la rly im p o rtan t since cran io facial grow th does not cease in the late teens, but continues well into adulthood (H arris et al, 1999). Ayub E, G lasheen-W ray M B, K raus S 1984 H ead posture: a case study o f the effects on the re st p osition o f the m andible. Jo u rn a l o f O rthopaedic and Sports P hysical T herapy 5: 179-183 C apurso U, M arini I, Vecchiet F, B onetti G A 1997 H eadache and cran io -m an d ib u la r d is­ orders during adolescence. Journal o f C linical P ediatric D entistry 21: 117-123 D arling D W ,K raus S, G lasheen-W ray M B 1984 R elationship o f head posture and the rest position o f the m andible. Journal o f Prosthetic D entistry 52: 111-115 G oldsm ith J L, Sylvan E S 1994 G eorge C a tlin ’s co n c ep ts on m outh b re a th in g , as presented by D r E dw ard H A ngle. A m erican Journal o f O rthodontics 64: 75-78 H aapaniem i J J 1995 A denoids in school- aged children. Journal o f L aryngol O tol 109: 196-202 H arris E, G ardner R Z, Vaden J L 1999 A longitudinal cephalom etric study o f postortho- dontic craniofacial changes. A m erican Journal o f O rthodontics and D entofacial O rthopedics 115: 77-82 H ellsing E, F orsberg C M , L inder-A ronson S, Sheikholeslam A 1986 C hanges in postural E M G activity in the neck and m asticatory m uscles follow ing obstruction o f the nasal air­ w ays. E uropean Journal o f O rthodontics 8: 247-253 H ellsing E, M cW illiam J, R eigo T, S pangfort E 1987 T he relationship betw een craniofacial m o rp h o lo g y , h ea d p o stu re and sp in al c urvature in 8, 11 and 15-year old children. E uropean Journal o f O rthodontics 9: 254- 264 H u ggare J 1998 Postural disorders and d en to ­ facial m orphology. ACTA O dontol Scand 56: 383-386 Jull G A, Jan d a V 1987 M uscles and m otor control in low back pain: assessm ent and m an­ agem ent. Physical T herapy o f the Low B ack pp253-278. C hurchill L ivingstone, M elbourne L ev ea u B, B e rn h a rd t D B 1984 D evelopm ental biom echanics: effect o f forces on the grow th, d evelopm ent, and m aintenance o f the hum an body. P hysical T herapy 62: 1874-1881 M iller A J, V argervik K, C hierici G 1984 E x p e rim e n ta lly in d u c e d n e u ro m u sc u la r changes during and after nasal airw ay o b stru c­ tion. A m erican Journal o f O rthodontics 85: 385-392 O no T, Ishiw ata Y, K uroda T 1998 Inhibition o f m a s se te ric e le c tro m y o g ra p h ic a c tiv ity d u rin g o ra l re sp ira tio n . A m erican Jo u rn a l o f O rth o d o n tic s and D en to facial O rth o p e ­ dics 113: 518-525 REFERENCES O zb ek M M , Koklii A 1993 N atural cervical in c lin a tio n and c ra n io fa c ia l stru c tu re . A m erican Journal o f O rthodontics and D ento­ facial O rthopedics 104: 584-591 P ro ffit W R, F ields H W 1993 C ontem porary O rthodontics 2nd edn. pp 18 - 1 3 9 . M osby Year book, M issouri R ic k e tts R 1968 R e sp ira to ry o b stru c tio n syndrom e. A m erican Jo urnal o f O rthodontics 54: 459-507 R ocabado M 1998 T em porom andibular jo in t and the cervical spine. P roceedings o f the W orld C o nfederation o f Physical T herapy - A frica C ongress, South A frica R o c a b a d o M , Ig la rsh Z A 1991 M u s c u ­ lo sk e le ta l a p p ro a c h to m a x illo fa cia l pain, p p 3 - 137. B L ip p in co tt C om pany, Philadelphia Solow B, K reiborg S 1977 Soft tissue stretch­ ing: a possible control facto r in craniofacial m orphogenesis. Scandanavian Journal o f Dental R esearch 85: 505-507 S o lo w B, O v e se n J, N ie lse n P W, W ildschiodtz G, T allgren A 1993 H ead posture in o bstructive sleep apnoea. E uropean Journal o f O rthodontics 15: 107-114 S olow B, Siersbaek-Nielsen S, G re ve E 1984 A irw ay adequacy, head posture, and cran io ­ facial m o rph o lo g y . A m e ric a n Jo u rn a l o f O rthodontics 86: 214-223 Solow B, S onnesen L 1998 H ead posture an d m a lo c c lu sio n s . E u ro p e a n Jo u rn a l o f O rthodontics 20: 685-693 Tallgren A, Solow B 1987 H yoid bone p o si­ tion, facial m orphology and head posture in adults. E uropean Jo urnal o f O rth o d o n tic s 9: 1-8 T urner S, N attrass C, Sandy J R 1997 T he role o f soft tissues in the aetiology o f m aloc­ clusion. D ental U pdate 24: 209-214 W einstein S L 1994 T h e p ediatric spine: Principles and p ractice, Volum e 1 pp3-104. R aven Press, N ew York W enzel A, H enriksen J, M elsen B 1983 Nasal re sp ira to ry resista n ce: e ffe ct o f in tran asal corticosteroid (B udesonide) in children with asth m a and p eren n ia l rh in n itis. A m erican Jo urnal o f O rthodontics 84: 422-426 W enzel A, H ojensgaard E, H enriksen J M 1985 C raniofacial m orphology and head p o s­ ture in children w ith asthm a and perennial rhinnitis. E uropean Jo urnal o f O rthodontics 7: 83-92 W iltshire W A 1996 O rthodontics and chronic n asa l o b stru c tio n . C u rre n t A llerg y and C linical Im m unology 7: 16-18 SA J o u r n a l o f P h y s io th e ra p y 2001 V o l 57 No 1 31 R ep ro du ce d by S ab in et G at ew ay u nd er li ce nc e gr an te d by th e P ub lis he r (d at ed 2 01 3. )