TITLE: NASAL AIRWAY OBSTRUCTION IN CHILDREN AND SECONDARY DENTAL DEFORMITIES
SOURCE: UTMB, Dept. of Otolaryngology, Grand Rounds Presentation
RESIDENT PHYSICIAN: Carl Schreiner, MD
FACULTY PHYSICIAN: Ronald Deskin, MD
DATE: December 18, 1996
SERIES EDITOR: Francis B. Quinn, Jr., M.D.

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"This material was prepared by resident physicians in partial fulfillment of educational requirements established for the Postgraduate Training Program of the UTMB Department of Otolaryngology/Head and Neck Surgery and was not intended for clinical use in its present form. It was prepared for the purpose of stimulating group discussion in a conference setting. No warranties, either express or implied, are made with respect to its accuracy, completeness, or timeliness. The material does not necessarily reflect the current or past opinions of members of the UTMB faculty and should not be used for purposes of diagnosis or treatment without consulting appropriate literature sources and informed professional opinion."

INTRODUCTION

Otolaryngologists are increasingly being asked to objectively evaluate the nasal airway of pediatric patients. This is in part due to recent interest in snoring, sleep apnea, and nasal obstruction as is relates to orthodontic deformities. The orthodontic literature concerning how nasal obstruction relates to dentofacial development is extensive and the debate over whether a cause-effect relationship exists has been debated for over a century. Although recent studies suggest a relationship between nasal obstruction and dentofacial deformities, many questions remain unanswered. This grand rounds will attempt to present both sides of the issue, provide some of the history and background behind the issue, and review some basic fundamentals of orthodontic therapy as is relates to otolaryngology.

SIGNIFICANCE OF THE ISSUE

The controversy involving both the dental and medical fields has persisted likely because there are clear treatment issues that revolve around the diagnosis of nasal obstruction in children. If there is a cause and effect relationship between nasal obstruction and orofacial development, early intervention to enhance nasal breathing would be clearly indicated. If, on the other hand, orofacial maldevelopment is purely genetically determined and is not affected by the mode of respiration, then intervention for nasal obstruction solely for the sake of preventing orofacial development or enhancing orthodontic treatment would not be justified. Orthodontic therapy is affected by the function of the lips, tongue, and masticatory musculature, all of which may accommodate to nasal obstruction in ways which can effect occlusion. Effective orthodontic therapy may require the elimination of the nasal obstruction to allow for normalization of the facial musculature surrounding the dentition. According to Meredith, the growth of the face (excluding the mandible) is completed at a relatively early age. 60% of craniofacial development takes place during the first 4 years of life and 90% by age 12. Development of the mandible is not complete until around age 18. Based on these observations, any intervention to open the airway must take place at an early age. Early communication and cooperation between the pediatrician, otolaryngologist and orthodontist cannot be overemphasized

HISTORY

In 1872, C.V Tomes coined the term "adenoid faces" to describe the dentofacial changes associated with chronic nasal airway obstruction. In 1912, Ketcham recommended a full evaluation by both the orthodontist and rhinologist for the child with dentofacial abnormalities. In 1918, Norland introduced the "compression theory" which stated that constriction of the maxillary arch is related to the absence of the lateralizing pressure of the tongue against the palate. In response to nasal obstruction, the tongue drops and the medializing effects of the buccal musculature is left unopposed. The effect is further enhanced by a pressure differential across the hard palate in the absence of nasal airflow, leading to a narrow, high-arched hard palate. In 1962, Moss developed the "functional matrix theory" in an attempt to explain the orthodontic findings in nasally obstructed patients. He described two distinct elements of the functional craniofacial component. The functional matrix is all the tissues organs and glands involved in carrying out a specific function (ie mastication). The skeletal unit provides protection and support (ie mandible) for its specific functional matrix. He felt that bone dynamically responds to both function and adjoining soft tissue forces and the presence, number, and position of the teeth directly determines the development and growth of the mandible. Proponents of this theory have noted that the mandibular gonial angle in chronic oral breathers is more obtuse, indicating transformative changes of the teeth and mandible in response to an open mouth.

Many of the early theories relating nasal obstruction to craniofacial development failed to recognize other causes of nasal obstruction not related to the adenoids and were not widely accepted until the 1970's. Over 20 years of studies by Linder-Aronsen in the 1970's and 80's consistently supported the relationship between nasal obstruction and certain dental patterns. He noted a significant relationship between enlarged adenoids (as determined by cephalometric x-rays) and certain craniofacial changes, including a "clockwise" rotation of the mandible in a more vertical and posterior direction, elongation of the lower face height, open bite, crossbite, and retrognathia. Linder-Aronsen also studied a group of postadenoidectomy patients who returned to nasal breathers and showed significant craniofacial changes towards normal. Kerr also studied mandibular growth patterns in 26 children treated with adenoidectomy for nasal obstruction and demonstrated a shift back to nasal breathing and some reversal of the initial posterior mandibular growth patterns. Evidence of reversibility is also strongly supported by studies of monozygotic twins in which one developed nasal obstruction due to trauma. The obstructed twin developed characteristics of the long face syndrome which partially normalized following correction of the obstruction.

Experiments in artificially nasally obstructed monkeys by Harvold showed several patterns of dentofacial adaptations that appeared to be dependent on the manner in which the monkeys maintained oral respiration. Consistent elongation of the face with various patterns of malocclusion occurred in monkeys who maintained their airway by protruding and lowering the mandible. In contrast, monkeys that rhythmically opened and closed their mouths with respiration developed less severe malocclusion. Harvold concluded that neuromuscular changes required to maintain an open oral airway contributed to the skeletal and dental changes. In 1986, Principato evaluated 211 consecutive orthodontic cases with rhinomanometry and demonstrated a definite correlation between nasal resistance and cephalometric measurements of the lower anterior facial height. A recent study by Cheng may explain the observation that not all nasally obstructed children develop an "adenoid faces." Cheng proposed that the degree of impact caused by nasal obstruction may vary with different facial types. A brachycephalic or broad faced pattern with strong facial musculature and a deep bite may be less affected by nasal obstruction, whereas dolichocephalic faces with a narrow, more elongated pattern may be more susceptible to these changes.

The view that chronic nasal obstruction can effect craniofacial development is not without opposition. Those who oppose this view site cases of craniofacial problems in the absence of nasal obstruction and vice versa. In 1889 Kingsley noted normal craniofacial development in children with severe nasal obstruction and Whitaker described severe palate malformations in patients who had undergone adenoidectomy at an early age. Hinton et. al. showed that merely opening the lips 1 to 2 mm can reduce nasal resistance by 50 to 70% and felt this would not lead to significant craniofacial changes. Vig feels that a major obstacle to resolving the issue revolves around the lack of a clearly defined definition of "mouth breathing." He observed that patients who breathe with an open mouth may actually be partial nasal breathers and that most people fall in between the extremes of total nasal and total oral respiration. He found that the nasal airflow in normal, "long-faced" and lip incompetent patients were not significantly different and that "surgical intervention to improve nasal respiration remains empirical and difficult to justify from an orthodontic standpoint."

THE LONG FACE SYNDROME

The common term "adenoid faces" erroneously attributes the familiar facial pattern to obstructing adenoid tissue. In reality, any condition that causes nasal obstruction (deviated septum, hypertrophic turbinates or external nasal deformity) could lead to this typical facial morphology which is better termed the "long face syndrome." This syndrome is characterized by an increased vertical facial height in the lower third of the face, excessive dentoalveolar height, "gummy smile", high arched palate and a steep mandibular plane. The appearance of the maxillary incisors is often excessive and an anterior marginal gingivitis around the anterior teeth may be present. Long-standing nasal obstruction may lead to "disuse atrophy" of the lower lateral cartilages, resulting in as slit-like external nose with a narrow nasal vault.

On cephalometric exams in normal patients, the tangent to the inferior border of the mandible usually passes inferior to the cranium. In cases with a steep mandibular angle, the tangent often passes into the cranium. The "long face syndrome" is often associated with crossbite, tension nose, and a Class-II (mandibular retrognathic) occlusion. Another group of children develop Class-III occlusion (mandibular prognathic) occlusion which may be due to anterior displacement of the tongue due to tonsillar hypertrophy. This creates a pressure affects on the lingual aspect of the lower dental arch, causing a prognathic mandible and undererupted lower teeth.

EVALUATION OF THE NASAL AIRWAY IN CHILDREN

The cause of nasal obstruction in children can usually be determined by a thorough history and physical exam, including anterior rhinoscopy and nasopharyngocopy if indicated. The reported usefulness of rhinomanometry and x-rays in conjunction with the physical exam is variable. In 1987, Weimert published a study of 1360 patients referred to otolaryngologists by orthodontists because of suspicion of nasal obstruction. Although it was not a solid scientific study, the findings suggest that orthodontists can effectively screen for nasal obstruction. The most common reasons for referral were: dentofacial characteristics suggestive of upper airway obstruction, inability to retain a dental appliance, and unsatisfactory results from an orthodontic program. Most patients had undergone PA and lateral cephalometric examinations which are utilized by orthodontists to both formulate a treatment program and to screen for upper airway obstruction. They found evidence nasal obstruction in 72% of cases. 39% of the children underwent adenoidectomy for adenoid enlargement (determined by indirect nasopharyngoscopy or cephalometric exam) and they reported a 96% correlation between the adenoid size on x-rays and intraoperatively. Others feel cephalometric analysis is a useful screening exam but have not shown them to consistently predict adenoid size and degree of obstruction (Poole 1980). Weimert noted a large number of patients (21%) whose obstruction was felt to be due to turbinate hypertrophy and sited this as a frequently overlooked cause of nasal obstruction in children.

PROPOSED SEQUENCE OF EVENTS

Based on numerous studies over the past century, a plausible sequence of events can be pieced together as described by Principato in a recent summary article. Long standing nasal obstruction appears to affect craniofacial morphology during periods of rapid facial growth in genetically susceptible children with narrow facial pattern. A change from nasal to oral respiration likely occurs when nasal resistance reaches two to three times normal. Since nasal resistance increases in the supine position, borderline airways may convert to oral respiration at night. During oral respiration, the mandible rotates to a more open position and the tongue assumes a lower position in the mouth and is no longer in contact with the palate. Prolonged periods of oral respiration lead to extensive eruption of the posterior molars, in response to a lack of surface contact. This phenomenon of superereruption is a common finding in the face of missing teeth due to trauma, extraction, etc. These overerupted teeth exert a downward vector of force on the mandible, causing the lower jaw to rotate down and back in a "clockwise" direction. The dental literature often sites a 1mm posterior molar eruption to correlate with a 3mm elongation of the lower vertical facial height. Because of the backward mandible rotation, retrognathia and open bite deformities are common. Tongue posture changes with chronic oral respiration can also affect the teeth. With a lowered tongue position, the lateral expansile forces of the tongue on the palate are lost, and the unopposed medial forces of the buccinator and masseter muscles lead to a narrow, high arched palate in susceptible children. The incomplete lateral expansion of the maxilla often leads to a unilateral or posterior crossbite.

Based on these observations, it would appear that chronic nasal obstruction not related to the adenoids, (nasal septal deformity, chronic rhinitis, external nasal deformity) can lead to similar dental patterns and an elongated lower face. Children with a predisposition to long narrow faces may be more susceptible to these changes. Referral to an otolaryngologist may occur after an unsuccessful attempt at orthodontic correction. Early recognition and treatment, with communication between the otolaryngologist, pediatrician, and orthodontist is critical for successful intervention.

TREATMENT

Adenoidectomy with or without tonsillectomy is by far the most common treatment for nasal obstruction in children. As stated earlier, several studies of postadenoidectomy children, animal models and monozygotic twin studies suggest that early intervention to correct nasal obstruction may lead to reversal of the associated craniofacial changes. Some of these changes can be noted as young as age three but most are commonly detected at about age five. The deleterious effects of nasal obstruction are virtually complete by puberty so the window of opportunity is relatively brief. Delay in intervention may result in unsuccessful orthodontic treatment which may require orhthagnathic surgery at an older age. If chronic mouth breathing persists or recurs after adenoidectomy, allergic rhinitis with turbinate hypertrophy should be ruled out. Some have suggested that this situation may represent an allergic "target-organ shift" from the tonsils and adenoid pad to the inferior turbinates. Partial inferior turbinate resection, elctrocautery, or cryosurgery may be considered in refractory cases. Rapid maxillary expansion (RME), also known as rapid palatal expansion, is an orthodontic treatment to broaden the maxillary arch which also serves to widen the nasal vault and improve nasal patency. The treatment is nonoperative and can be accomplished in about 3 weeks in patients 3 to 20 years of age. Many orthodontists feel RME is indicated for posterior crossbite but contraindicated in patients with normal occlusion, but slow expansion of the mandibular arch can be performed if both the maxillary and mandibular arches are constricted. RMA alone is seldom sufficient to improve severe cases of nasal obstruction.

Septoplasty in children for nasal obstruction is a long debated issue. Animal studies using large through-and-through cartilage excisions have been shown to retard midface growth in rabbits, dogs and guinea pigs. . The septal cartilage appears to be a factor in midface growth in the fetus but its role postnatally remains unclear. Studies looking at conservative cartilage resection with preservation of the mucoperichondrium have shown no deleterious effects (Bernstein, 1973). Healy advocates a sublabial approach to the septum due to the small size of the nasal vestibule. A recent study by Bejar, at. al. used twelve anthropometric measurements to evaluate 10 children aged 6 to 15 years who underwent septoplasty with a followup of at least 2 years. The surgical procedure involved the removal, modification and reinsertion of the entire quadrangular cartilage with preservation of both mucoperichondrial flaps. The majority of al linear and angular measurements fell within 2 standard deviations of the normal range except a substantial number of patients had an abnormally small nasal dorsum index. Whether this finding was due to the surgery or the initial insult could not be determined by photographic analysis of the preoperative photos. They concluded that external septoplasty may affect nasal dorsum length but not other aspects of facial growth. This question will require prospective studies with anthropometric measurements.

CONCLUSION

Evaluation of children with nasal obstruction and dental abnormalities requires a multidisciplinary approach. The medical and dental literature concerning the issue is vast and many question remain unanswered so clear cooperation between the pediatricians, orthodontists and otolaryngologists is imperative. As otolaryngologists, we are most capable of evaluating the upper airway and are frequently asked by dentists and orthodontists to evaluate the nasal airway and recommend treatment in children undergoing orthodontic treatment. We must be familiar with the dental literature regarding dentofacial development and basic concepts of orthodontic intervention to provide optimal care for our pediatric patients.

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