THE ROLE OF MOUTH BREATHING ON DENTITION DEVELOPMENT AND FORMATION

https://www.journal-imab-bg.org J of IMAB. 2018 Jan-Mar;24(1) ABSTRACT Introduction: The influence of mouth breathing on the development of the dentition and dento-facial deformities is a problem causes concerns among the medical specialists. Mouth breathing has a major impact on the development of the maxillo-facial region, occlusion and muscle tonus. Aim: The aim of this study is to assess the relationship between etiological factors, pathogenesis and disturbances in mastication in mouth breathing patients. Material and methods: For this article, data is obtained from 43 medical, literary sources. Results: Literature review demonstrated that mouth breathing habit affects mostly children aged 7 12 years. In the vast majority of studies, the authors established a relation between mouth breathing and the development of maxillo-facial region and occlusion. The malocclusions described include a distal occlusion, anterior open bite, increase overjet, posterior crossbite, crowding and average incisors inclination disturbances. These clinical conditions become more complicated in the late-mixed and permanent dentition if mouth breathing continues to persist. Conclusion: The habitual mouth breathing is a great medical problem nowadays. An increasing numbers of patients with this condition although the development of technology for early diagnostic is embarrassing. This condition is strongly related with different malocclusions such as anterior open bite, overjet, distal occlusion, underdeveloped and narrow upper jaw, increased anterior facial height.

with primitive people and native tribes who have normal breathing without exception [1].Probably this unnatural breath pattern of civilized people has been acquired because of improved wellbeing and life style changes such as limiting environmental influence and goods oversupply.
The purpose of breathing is to oxygenate the body and to remove the waste carbon dioxide.The body requires approximately 2 -3 % îf oxygen concentration in inhaled air, while its atmospheric level is 21 %, so there is no need for oxygen to be stored.Body can tolerate carbon dioxide concentration about 6.5 %, but atmosphere level is 0.03 % [2,3,4,5].So body should accumulate produced carbon dioxide in lungs and blood.Carbon dioxide expresses several functions in the body: to facilitate the release of oxygen from haemoglobin, to trigger the inhalation, to regulate pH through buffering with bicarbonates or carbonic acid.All these functions are limited or disturbed in mouth breathers.Respiration is a natural, spontaneous process which is not oxygen dependent but the subject of carbon dioxide concentration in the pulmonary alveoli and blood.
Nose breathing controls the volume of inhaled and, more important, the volume of exhaled air.Body oxygenation occurs during exhalation not during inhalation.The negative pressure created in lungs upon exhalation in nose breathing pattern versus mouth breathing provides more time for binding of oxygen to haemoglobin in the blood.This process requires appropriate concentration of carbon dioxide in the blood.For oxygenation of brain and muscle cells, the level of carbon dioxide has to be 5 % in alveoli and arterial blood [2 -9].
Nitric oxide has a role in the process of oxygenation and oxygen binding efficiency as well.The oxygen concentration in blood increases up to 18% [7, 10 -12].In fact, in mouth breathers, the carbon dioxide levels decrease in lungs and blood fall, and this leads to lower oxygen supply of the body cells.
The problem with mouth breathing begins with a change in tongue position which is meant to naturally rest on the roof of the mouth, but it drops down to the floor of the mouth and consequently inadequate skeletal growth results in the development of so called long face syndrome.

EXPOSITION I. DEFINITION:
Mouth breathing is clinically observed in patients with some nasal obstruction as well as in those who have a habit to stay and sleep with open mouth.We define a difficult nasal breathing when there is a partial or full, temporary or permanent obstruction of the upper airways, and the processes of breathing in and out are performed through the mouth.Mouth breathing is a deleterious habit.It may be determined as an oral habit in the cases when there is no anatomical factors and obstacle for nose breathing [13].
C. V. Tomes introduced in 1872 the term "adenoid facies" and determined typical dentofacial appearance in patients with nasal breathing difficulties.The face becomes long and narrow.
Open bite, hyperdivergent growth pattern, proclined upper incisors, increased lower facial hight, steeper mandibular plane angle, lowering of the chin and increase in the gonial angle are among these features.A little later, in 1889, Kingsley undertook another study, according to which we have a normal skeletal formation and development in children with severe nose breathing difficulties [14].Similar researches are aiming to compare the dentofacial development of mouth breathers towards nose-breathing patients and have been carried out by other scientists too [15 -18].
In Chacker's opinion, nasal breathing difficulties are defined as a long or prolonged exposition of the frontal facial tissues to the drying up effect of the inhaled air [16,17].
Sassouni determined mouth breathing as a habitual respiration through the mouth instead of the nose [16 -18].A little later, Merle offered the term oronasal breathing instead of oral or mouth breathing as he considers this term is more correct and exact [16,17].
Nowadays the viewpoint is adopted that mouth breathers are those people who breathe through the mouth even when at rest [19].They should be distinguished from nasal breathers who breathe through the mouth only upon intensive physical loads but through the nose at rest [19].
2. Bad habit to staying and sleeping with mouth open not related to medical conditions.

III. PATHOGENESIS OF MOUTH BREATHING
The change in the way of breathing leads to a change in the jaw, tongue and head position.The balance between the tongue action, on the one hand, and the mimic and masticatory muscles, on the other hand, is disturbed.The "forming" action to the mid-face of the air passing through nasal cavity is disturbed too, and it influences normal palatal development.In mouth breathing pattern the tongue is usually shifted back and downwards and doesn't participate in the development of the hard palate, which results in the formation of a deep gothic palate.A forward head posture is developed in order to make easier inhalation through mouth, the lower jaw is underdeveloped and placed downward and backwards, and this leads to its distal position and overjet formation.Taut cheek muscles apply an increased external force to the upper jaw which causes Vshaped form.

IV. CLINICAL PATTERN OF MOUTH BREATH-ING PATIENTS
Mouth breathing patients have characteristic intraoral and extraoral symptoms.In the period between 1970 and 1980, Linder-Aronson [21,22]  -gingivitis in frontal teeth.According to Subtelny [31], the deep palate in mouth breathers is an illusion due to the upper jaw compression.Brodie thinks that jaw compression is due to an imbalance between cheek muscles and tongue muscles [32 -34].As the pressure in the area of premolars and molars is bigger than this in the area of canines, the changes in the posterior region are greater.Angle, Brodie, Hawking and Moyers accept the role of muscles in upper jaw formation, while other authors like Brash, Linder-Aronson and Backstrom disclaim this theory.
Angle and Hawking do not find a deviation in the dental arch form in mouth breathing children versus such breathing through the nose.As opposed to this, many authors find crooked frontal teeth more often in upper jaw [35][36][37].
The Joshi's studies confirm that class II malocclusion is more often and related with mouth breathing patients [38,39].Angle, Huber and Reynolds [40] and Moyers report that mouth breathing has an impact on the development of all classes of malocclusions.In contrast to the above indicated, Howard examines a lot of mouths breathing children who are with class I molar relation ship.According to Rakosi and Schilli mouth breathing plays a role in aetiology and pathogenesis of class III malocclusion [41].
A not-insubstantial percentage of mouth breathing children have a deep bite.It is most often due to the distal position of the lower jaw and lack of incisor contact.Hawkins and Rachel found that deep bite is due to under-development of premolars and molars segments.

V. METHODS OF RESEARCH AND DIAGNOS-TICS OF MOUTH BREATHING.
Clinical and functional tests are made to diagnose the breathing pattern and to differentiate nasal breathing difficulties from the bad habit to stay and sleep with mouth open [42].Following tests belong to the clinical methods: -Dental mirror is placed at rest in front of the patient's nostrils, the one nostril is closed, and the patient is asked to make several respiratory movements.If the mirror becomes blurred and foggy, this would mean that the patient is able to breathe through this nostril.The same procedure is repeated for the other nostril too (Mirror test, Fog test); -A tiny piece of paper or cotton pellet is placed at rest underneath the nostrils.If they flutter upon several breathing in and out through the nose, then the child is able to breathe through the nose; -If sip of wake is kept in mouth up to 1 minute without swallowing or spilling it out, then the child can breathe through the nose (Massler's butterfly test); -If the child doesn't open its mouth upon complete contact of lips and several consecutive squats are done, then it can breathe through the nose.
There are objective anatomical characteristics which show the presence of a difficult nasal breathing.The size of tonsils (fig. 1) is also determined during the clinical intraoral examination [43]: Fig. 1.Illustration of tonsil grades [43] TS 0 -status post tonsillectomy; B. TS 1 -tonsils are behind the anterior palatal arches, the posterior and lateral walls of mesopharynx are accessible for examination; C. TS 2 -tonsils placed medially out of the arches but do not cover the lateral columns; D. TS 3 -tonsils cover the lateral columns but do not reach the midline; E. TS 4 -tonsils touch each other in the midline, the so called "kissing tonsils" The widely adopted at a global scale Friedman score is used for assessment of the obstruction stage on level mesopharynx on the part of the tongue.It is a modification of the Mallampati classification upon which the tongue is in the oral cavity during the examination [43].

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Changed position of tongue, jaws and head Tongue occupying a back and lower position ↓ Mandible dropped down, ↓ Disproportion between jaws and teeth ↓ Imbalance between masticatory, mimic and tongue muscles ↓ Adenoid facies or long face syndrome