The DOME approach to breathing, bite, and beauty

Drs. Claudia Pinter and Stanley Liu illustrate a protocol to improve nasal breathing in orthodontic care

Bestselling author James Nestor highlights in his book, Breath: The New Science of a Lost Art that nasal breathing has profound effects on overall health, including respiratory function, cardiovascular health, mental clarity, sleep quality, and athletic performance. Of all the contributors to overall wellness, a healthy way to breathe has eluded attention from modern medicine and dentistry. This is especially true with breathing during sleep.

Breathing interruptions during sleep make up a constellation of conditions called “sleep-disordered breathing,” (SDB) with common diagnoses including snoring, upper airway resistance syndrome, and obstructive sleep apnea. A contemporary population-based study on adults estimates SDB to be present in 23.4% of women, and 49.7% of men. SDB is independently associated with hypertension, diabetes, metabolic syndrome, and depression.¹

Regarding nasal breathing, the internal nasal valve (INV) is the narrowest part of the nasal cavity and is the location of greatest airflow resistance.^2,3 Located about 1.3 cm posterior to the nostril opening, it is surrounded by the dorsal septum medially, the head of inferior turbinate laterally, upper lateral cartilages superiorly, and the maxillary roof (nasal floor) inferiorly. Anatomic causes of nasal obstruction frequently involve structures of the INV. Beyond anatomy, there are physiologic and pathophysiologic causes of nasal obstruction (Figure 1).

When it comes to anatomic treatment, surgical approaches to the septum, inferior turbinate, and upper lateral cartilage of the INV are well described. What has been less discussed until recently is maxillary expansion at the nasal floor.⁴ This is likely a byproduct of otolaryngologists (ear, nose, throat surgeons) focusing on structures treated within their scope. Historically though, otolaryngologists have collaborated with orthodontists to treat nasal obstruction via maxillary expansion.⁵

In 2017, Dr. Ryan Williams and Dr. Stanley Liu at Stanford Otolaryngology performed a retrospective case-control study to identify phenotypes of patients who complain of persistent nasal obstruction after surgery.⁶ Eighty-nine subjects with perioperative validated questionnaires and computed tomography imaging were included. The study showed that patients with persistent nasal obstruction after intranasal surgery (septoplasty, inferior turbinate reduction) presented with a narrower maxilla (and nasal floor), near the region of the internal nasal valve.

In parallel, Dr. Christian Guilleminault mentored Dr. Audrey Yoon and Dr. Stanley Liu at Stanford Sleep Medicine to apply maxillary expansion techniques for SDB patients. From around 2015, Dr. Stanley Liu described the change as converting a high-arched palate to a “dome”-shaped palate. As the surgical-orthodontic techniques progressed, “dome” became an acronym of “maxillary expansion” with “distraction osteogenesis.” This shifted maxillary expansion from a dentoalveolar-first to a nasal-floor first process, and as an approach rather than specific surgical or dental techniques.

Subsequent studies were undertaken to understand the mechanism of action of DOME using treatment-specific rhinomanometry and patient-specific computational fluid dynamics analysis. With expansion at the INV region, nasal airflow slows significantly, and the downstream negative pressure that collapses the pharyngeal airway decreases.⁷ DOME for both the adult and pediatric populations had similar outcomes, most notably a patient-reported decrease in nasal obstruction.^8-10 The decrease in apnea-hypopnea index (AHI) was associated with increase of INV surface area and angle.^8,11

For patients requiring surgical osteotomies, endoscopic approaches to DOME were introduced.¹² Finally, to complete the full circle dating back to Williams and Liu’s original study, patients who underwent DOME after nasal surgery were examined. The study found that a transverse increase of at least 6 mm at the INV was associated with resolution of nasal obstruction and improvement of sleep-related symptoms.¹³ Since then, many colleagues in the field of SDB across different disciplines have continued to expand (puns intended) upon DOME.^14,15

Today, the need of invasive maxillary osteotomy to expand the adult maxilla has become markedly reduced. The advent of custom, temporary anchorage device supported expanders have increased the phenotype of eligible patients for non-surgical expansion. Moreover, restoration of cosmesis and occlusion evolved rapidly. European leaders including Dr. Christian Leonardt and Dr. Claudia Pinter have further streamlined the DOME approach to a dentist-friendly ecosystem. In this article, the contemporary DOME approach for dentists is highlighted.

Case report No. 1

A 51-year-old male was referred by the treating dentist to address malocclusion before doing extensive restorative work. The patient presented equal facial thirds and pronounced buccal corridors. Intraorally, the teeth presented in Class I, with an anterior open bite, a narrow upper jaw, and a high-arched palate.

In cases with maxillary deficiency, the narrowing of the nasal cavity increases airflow resistance, potentially leading to nasal obstruction snoring and resulting in sleep breathing disturbances.

Upon investigation, the NOSE Score indicated nasal obstruction, and the patient reported frequent and loud snoring.

Insufficient lateral overjet could have been addressed with dental expansion of the upper arch, which would not have effects on the nasal cavity.

The patient opted for a DOME (Distraction Osteogenesis Maxillary Expansion) approach to address malocclusion, create more space for the tongue, and to facilitate nasal breathing both during wakefulness and sleep.

To ensure predictable suture separation of the maxillary halves, minimally invasive osteotomies were performed (Periodontist: Dr. Christian Leonhardt). During the same appointment, four mini-screws were placed: two in the anterior palate (Benefit PSM Medical, 2 mm x 11 mm) and two between the roots of the second premolar and first molar (Benefit PSM Medical, 2 mm x 13 mm). Surgical guides were used to place the mini-screw in areas with sufficient bone and navigate from the roots. An intraoral scan was then taken to produce a custom-made expander that could be mounted onto the bone screws.

Following the successful orthopedic expansion, aligners were employed to close the diastema and restore the occlusion.

The initial setup in the aligners software (Spark™ Approver™) yielded an esthetically pleasing result, with ideal incisor inclination. While aligners generally perform well in expressing root movements, clinicians should anticipate that not all lingual root torque will be fully expressed in the upper incisors. To prevent retroclination and a steep interincisal angle, an additional 10° of palatal root torque should be incorporated into the ideal inclination.

The result shows an adequate overjet and overbite in both the incisors and the posterior teeth. The palate is now dome-shaped, allowing for proper tongue positioning. Additionally, after the palatal expansion, the patient ceased to snore.

Case report No. 2

A 12-year-old female presented with her mother to evaluate a need for orthodontic treatment.

Clinical examination revealed maxillary transverse deficiency, high-arched palate, mild crowding, and enlarged tonsils. The mother reported that the patient exhibited mouth breathing and “loud breathing” sounds during sleep. To further assess nasal breathing, the patient completed the Nasal Obstruction Symptom Evaluation (NOSE) questionnaire, which indicated nasal obstruction. A home sleep study showed an apnea-hypopnea index (AHI) of 6.4, confirming the presence of moderate obstructive sleep apnea. Patient also was referred to an ENT specialist.

Although the patient’s malocclusion could be corrected with dental expansion, skeletal expansion was chosen to achieve greater effect on the nasal cavity. Her DOME approach aimed to enhance nasal breathing both during wakefulness and sleep.

A bone-borne expander was selected to maximize skeletal expansion while minimizing dentoalveolar bending. Aligners were then used to restore the occlusion while the expander remained on the palate as a skeletal retainer for another 6 months.

After maxillary expansion, the mother reported that the patient’s breathing during sleep had become silent and that she now slept with her mouth closed. Additionally, the patient’s NOSE score improved from 6/20 to 0/20 — indicating a significant improvement in nasal breathing. The patient also noted that she previously woke up during the night, but this ceased after orthopedic expansion of the maxilla.

After completion of orthodontic treatment, a repeat sleep study may help determine need of further treatment including tonsillectomy.

Discussion

Resolving nasal obstruction is central to the care of sleep-disordered breathing (SDB). Nasal breathing confers significant advantages over mouth breathing during sleep, particularly with the physiologic stimulation of upper airway dilator muscles.¹⁶ Effective treatment of SDB is based on changing the negative pressure that can collapse the downstream pharyngeal airway. This is the critical negative pressure, referred to as P-crit, and is the basis of anatomic treatment of SDB.¹⁷ Slower and smoother airflow through the internal nasal valve results in less negative pressure to collapse pharyngeal muscles during sleep. Procedures such as septoplasty, inferior turbinate reduction, and upper lateral cartilage grafts including spreaders reduce and realign structures of the INV. To expand the actual INV surface area with volumetric increase of the nasal passage, maxillary expansion is our most efficient means today. Beyond changes to the INV to improve nasal breathing, expansion of the maxilla also allows the tongue to be positioned favorably during sleep. This process is further augmented by breathing and myofunctional exercises.^18,19

A great day begins with consistent, high-quality sleep. One of the most prevalent, but under-diagnosed and under-treated detractors, is sleep-disordered breathing. Ranging from snoring, upper airway resistance syndrome (UARS) to obstructive sleep apnea (OSA), airflow interruptions during sleep take a detrimental toll on cognitive, mental, and physical health. In 2001, Dr. Christian Guilleminault called upon the dental profession to help, stating that “dentists and orthodontists have the greatest opportunity to [identify these patients] … and may obviate the need for aggressive surgical treatment later in life.”¹⁶ In the past, the collaboration of an orthodontist and surgeon to treat SDB began with maxillomandibular advancement (MMA). MMA is still needed for severe, persistent OSA, or patients with concomitant dentofacial deformity. Today, for mild OSA and UARS patients, the creation of a dome-shaped palate by the orthodontist, alongside any necessary intranasal treatments for SDB fills in the gap (puns intended again). As restoring sleep airway health is a gateway to wellness, the contemporary orthodontist is the chief architect of the “dome” to breathe.