Introduction

Mouth breathing also termed as oronasal breathing [Merle (1980)] is defined as habitual respiration through the mouth instead of the nose. Sassouni (1971). It is common in children between 5-15 years of age. Incidence being 5% to 75% and is estimated that 85% of mouth breathers suffer from some degree of nasal obstruction.

Finn classified mouth breathing as:

• Anatomic: Mouth breather whose short upper lip does not permit complete closure without undue effort.
• Obstructive: Children who have an increased resistance to, or a complete obstruction of the normal flow of air through the nasal passages. The child is forced by sheer necessity to breathe through the mouth. For example:
  1. Ectomorphic children with long narrow face and nasopharyngeal spaces
  2. Hypertrophy of turbinate due to allergy
  3. Deviated nasal septum
  4. Enlarged adenoids
• Habitual: A child who continually breathes through his mouth by force of habit, although the abnormal obstruction has been removed.

Reasons why mouth breathing occurs

Most of the children suffer from some degree of nasal insufficiency. Allergies, physical obstructions and chronic infections cause many children to breathe through the mouth.

• Developmental and Morphological Anomalies which interferes with nasal breathing
  1. Asymmetry of the face resulting in asymmetry of nasal passage due to intra uterine pressure during the period of embryogenic development.
  2. Hereditary characteristics of facial form may be a factor in a size of nasal passage and position of the septum.
  3. Abnormal development of nasal cavity.
  4. Abnormal development of nasal turbinates.
  5. Abnormally Short upper lip- preventing proper lip-seal.
  6. Under development or abnormal facial musculature.
• Partial obstruction
  1. DNS – DNS or deviated nasal septum may be due to birth injuries or exogenous nasal trauma. It can cause bilateral blockage creating an S shaped deformity or more typically a unilateral one creating a C shaped obstruction.
  2. Localized benign tumours
  3. Narrow nasal passage associated with narrow maxilla
  4. Leontiasis ossea
• Infection and inflammation
  1. Chronic inflammation of nasal mucosa
  2. Allergic rhinitis, nasal polyps
  3. Enlarged adenoids or tonsils- most frequent cause in children
  4. Traumatic injuries to nasal cavity
• Genetic Pattern: Ectomorphic children having genetic type of tapering face and nasopharynx are prone to nasal obstruction.

Features of mouth breathers

General effects

1. With oral respiration, the negative pressure that promote airflow into the lungs created by diaphragm and intercostals muscles is lacking, therefore poor pulmonary compliance is seen leading to pigeon chest appearance.
2. In mouth breathers the oropharynx is dry leading to low grade esophagitis.

Effects on dentofacial structures

Adenoid facies is a particular type of facial configuration frequently associated with mouth breathing characterized by a long, expressionless, narrow face with an accompanying narrow nose and nasal passages, flaccid lips with the upper lip being short and dolico facial skeletal patterns. Often the nose is tipped superiorly in front so as an observer can look directly into the nares. The buccal segments of the maxilla are collapsed, leading to the 'V' - shaped and high palatal vault.

1. Dental effects: Retroclined incisors, posterior cross bites and tendency towards an open bite is commonly observed along with narrow palatal and cranial widths. This is due to the low set position of the tongue in order to allow an adequate inflow of air through the mouth. Thus an imbalance of forces exerted by the tongue and facial musculature on the maxilla leads to a constricted maxillary arch. There may also be flaring of incisors and a decrease in the vertical overlap of the anterior teeth.
2. Speech defects: Nasal tone in voice is observed.
3. Lip: These patients frequently have a lip apart posture with 'gummy smile'. They have short thick incompetent upper lip and a voluminous curled over lower lip.
4. External nares: Long standing nasal airway obstruction can lead to a disuse atrophy of the lateral cartilage which results in a slit like external nares with a narrow nose and nasal mucosa becomes atrophic due to a disturbed ciliary action.
5. Gingiva: Gingival tissue in the anterior maxillary arch is inflamed and irritated and hyperplastic due to continuous exposure of the tissues to air drying. Gingiva exhibits a classic rolled margin and an enlarged interdental papilla.
6. Other effects: Mouth breathing may lead to otitis media.

Examination and Diagnosis

History associated with mouth breathing may include snoring, observed apnea, restless sleep, daytime neurobehavioral abnormalities or sleepiness and bedwetting. Physical findings may include growth abnormalities, signs of nasal obstruction, adenoidal faces or enlarged tonsils. The identification of an abnormal habit and the assessment of its potential immediate and long-term effects on the craniofacial complex and dentition should be made as early as possible.

Study breathing pattern of patient should be observed unnoticed. Nasal breathers usually have their lips touching lightly during relaxed breathing whereas mouth breathers must keep their lips apart. When asked to take a deep breath, most respond by inspiring through the mouth, although occasionally a nasal breather will inspire through the nose and lips tightly closed. Mouth breather when asked to close the lips and take deep breath will not appreciably change the size and shape of the external nares and occasionally contract the nasal orifices while inspiring whereas normal nose breather will usually dilate the nostrils when breathing deeply and also have good reflex control of the alar muscles which control the size and shape of the external nares.

Clinical tests for mouth breathing

• Mirror test (fog test): A double sided mirror is held between nose and mouth. Fogging on the nasal side of the mirror indicates nasal breathing while fogging towards the oral side indicates mouth breathing.
• Jwemen’s Butterfly test: A butterfly shaped piece of cotton is placed over the upper lip below the nostrils. If the cotton flutters down it indicates nasal breathing.
• Water Holding Test (Masslers test): The patient is asked to fill his mouth with water and retain it for a period of time. While nasal breathers accomplish this with ease, mouth breathers find the task difficult.

Inductive plethysmography (Rhinomanometry)

The only reliable way to quantify the extent of mouth breathing is to establish how much of the total airflow goes through nose and how much through mouth using inductive plethysmography. This allows the percentage of nasal and oral respiration to be calculated.

Treatment considerations

• Age of the child: As the child matures correction of mouth breathing habit can be expected due to increase in nasal passages thereby relieving the obstructions caused by enlarged adenoids. In many instances it is self correcting after puberty.
• E.N.T Examination: To institute a treatment of the actual cause, it is important to determine the type and degree of mouth breathing, whether it is habitual or obstructive. An otorhinolaryngologist examination may be advised to determine the conditions requiring the treatment resides in tonsils, adenoids or nasal septum. Correction should first aim at removing any anatomic or functional causes.
• Correction of mouth breathing: Mouth breathing should be treated during mixed dentition period.
• Symptomatic treatment: The gingival should be restored to normal health by coating the gingiva with petroleum jelly.

Treatment

Elimination of cause

If nasal or pharyngeal obstruction has been diagnosed as the cause of mouth breathing attempts should be made at treating the etiological factors first. If respiratory allergy is present then it has to be brought under control first.

Correction of malocclusion:

1. For class I malocclusion with spacing: Oral shield appliance can be used.
2. For class II div. 1 malocclusion without crowding: Monobloc activator can be used.
3. For class III malocclusion: Chin cap is used

Interception of the habit: If the habit continues even after removal of the obstruction then it should be corrected.

Exercises

If there is no physiologic cause the patient should be instructed in breathing and lip exercises.

Lip exercises: It improves the tonicity of upper lip.

1. Extend the upper lip as far as possible to cover the vermilion border under and behind the maxillary incisors. This exercise should be done 15-30 minutes a day for 4-5 months.
2. Playing a wind instrument
3. A celluloid strip or metal disk held between the lips.

Mechanotherapy

1. Oral screen: An oral screen is a myofunctional appliance which is most effective way to re-establish nasal breathing that prevents air from entering the oral cavity so the lips or oral cavity should be closed. For this oral screen made of material compatible to oral tissue can be used. An effective device during the sleeping hours is a thin rubber membrane either cut or cast to fit over the labial and buccal surfaces of the teeth and gums included in the vestibule of the mouth. During the initial phase windows are placed on the oral screen so as not to completely block the airway passage.
2. Pre-orthodontic trainer: It is a prefabricated dental positioner, that improves the face as well as the teeth by correction to myofunctional habits like mouth breathing.

References

1. Dental clinics of North America, pediatric dentistry. 2000.
2. McDonald, Avery, Dean. Dentistry for the Child and Adolescent. 8th edition; 2004; Mosby Publications.
3. Pinkham, Casamassimo, Fields, McTigue, Nowak. Pediatric Dentistry. Infancy through Adolescense. 4th edition;2005; Saunders Company.
4. Richard J. Mathewson. Fundamentals of pediatric dentistry. 3rd edition, 1995, Quintessence Publishing Co.
5. Shobha Tandon. Textbook of Pedodontics. 1st edition; 2001; Paras Publications
6. Sidney B. Finn. Clinical Pedodontics. 4th edition; 2004; Saunders Company.
7. S.G Damle. Textbook of Pediatric Dentistry. 2nd edition; 2002; Arya Publishing House.