Management Of Obstructive Sleep Apnea Syndrome By Mandibular Advancement Sleep Apnea Prosthesis: A CASE REPORT

INTRODUCTION

Sleep apnea syndrome is relatively common and potentially life threatening disorder. The sleep apnea syndrome was first described by Gastaut¹ and the disorder is associated with repetitive cessation of breathing during sleep. Apnea is defined as the cessation of airflow with a complete obstruction for at least 10 sec-with a concomitant 2 to 4% drop in arterial oxygen saturation². Sleep apnea is not a single disease but rather a pathophysiologic syndrome resulting from many diseases and abnormalities. Sleep apnea is classified as obstructive, central and mixed and it may be mild (5-20 apneic episodes per hour), moderate (20-40 apneic episodes per hour) or severe (40 or more apneic episodes per hour). Amongst these patterns the most common is obstructive sleep apnea (OSA), which is characterized by cessation of airflow because of upper airway obstruction with the presence of simultaneous respiratory effort. When the tone of the pharyngeal dilating muscles is reduced or when a patient falls asleep in the supine position, the muscle relaxation or force of gravity causes the base of the tongue to approach the posterior wall of the pharynx causing reduction in the diameter of the upper airway. With the consequent reduced air flow, the patient increases the speed of the airflow to maintain the required oxygen supply to the lungs. This increase in airflow velocity causes vibration of soft tissues, which produces snoring. At the severe end of the spectrum, the pharyngeal airway of the sleeping patient repeatedly collapses and obstructs completely. Each apnea is ultimately terminated when the patient arouses from sleep. Arousals increase the tone of the pharyngeal dilating muscles, allowing unobstructed breathing and rapid return of arterial oxygen saturation to normal. The possible treatment options for adult patient with OSA are based on the severity of the disorder. In case of mild to moderate OSA, less invasive options like behaviour modification or insertion of oral appliance are used. Continuous positive airway pressure and surgical options are chosen for patients with moderate to severe OSA. This article describes the management of OSA syndrome by mandibular advancement sleep apnea prosthesis.

Case Presentation

A 22 year old male patient was referred to the Department of Prosthodontics, P.M.N.M Dental College and Hospital, Bagalkot, Karnataka, from S.N Medical College and Hospital, Bagalkot for the fabrication of sleep apnea prosthesis for treatment of OSA. Patient was diagnosed to have mild to moderate sleep apnea. (Fig-1) Mandible advancement oral prosthesis was planned and the treatment plan was discussed with the patient and an informed consent was signed.

Technique

The technique followed for fabrication of sleep apnea prosthesis was done as advocated by Rodney 3 C. Knudson et al.

1. Accurate maxillary and mandibular impressions were made using irreversible hydro colloid impression material (Imprint Dust Free, Dental Products of India, Mumbai) and was poured in type III dental stone (Gold stone, Asian chemicals, Rajkot) to get master casts (Fig-2).

2. The maxillary and mandibular master cast were blocked out using block out wax and were duplicated using irreversible hydrocolloid impression material (Imprint Dust Free, Dental products of India, Mumbai) (Fig-3).

3. The wax interocclusal record was made at an increased vertical and protrusive jaw relation. Mandible was protruded till incisal edge to edge relation was achieved with the vertical opening of 12 mm (Fig-4).

4. Mounting of the master casts and cross mounting of the duplicate casts was done on the semi-adjustable articulator using the wax interocclusal record (Fig-5).

5. A layer of separating media (Cold mould seal, Dental Products of India, Mumbai) was applied on the duplicate mounted casts and modelling wax was adapted on the surfaces of maxillary and mandibular casts such that the wax should overlap the incisal edges and the buccal surfaces by 3mm and extend onto the soft tissue palatolingually. The occluding surfaces were made smooth and flat and at the level approximately half the intermaxillary space. 1mm separation was maintained between the maxillary and mandibular surfaces to facilitate the joining of two surfaces after processing (Fig-6).

6. The wax patterns were removed from the duplicate casts and invested in type III dental stone (Gold stone, Asian chemicals, Rajkot) in the flask.

7. After dewaxing, clear heat cured acrylic resin (Dental Products of India, Mumbai) was packed in the mold and polymerization was done according to manufacturer's instructions.

8. After deflasking, the external surfaces were finished and polished and were fitted on master casts and intraorally before joining the portions.

9. The joining of the maxillary and mandibular portions on the prosthesis was done on articulator by using clear self cure resin (Dental Products of India, Mumbai). An anterior orifice was created for oral ventilation (Fig-7).

10. The sleep apnea prosthesis was disinfected and inserted in patient's mouth and patient was instructed about its use and maintenance (Fig-8).

Follow Up

The patient was asked to return on day 1 and 7 for prosthesis evaluation for stability, retention and comfort. The patient had no complaints and was satisfied with the fit and comfort of the prosthesis. After 2 months, during follow up appointment it was revealed that there was remarkable decrease in the snoring and apenic episodes.

DISCUSSION

An oral appliance was considered as treatment for mandibular deficiency and upper airway obstruction as early as 1902.⁴ The basic indications for dental sleep appliances are to treat primary snoring and mild to moderate obstructive sleep apnea. Moreover, oral appliances offer an alternative that may be attractive for OSA patients dissatisfied with other therapies or unwilling to accept more complex interventions. Numerous appliances are available to treat snoring and obstructive sleep apnea. They may be mandibular repositioning or advancement devices, tongue repositioning or retaining devices, soft-palate lifters, tongue trainers and combination of oral appliance and continuous positive airway pressure (CPAP).²

Mandibular advancement devices were first described by Robin in 1934. Mandibular advancement devices consists of form fitting trays that fit over the maxillary and mandibular teeth and they may be fixed position, with no allowance for adjustment for advancement or retrusion of mandible or may be adjustable.⁵

The goal of therapy with an oral appliance is to modify the position of upper airway structures so as to enlarge the airway or otherwise reduce its collapsibility. In addition to airway size, it can also increase muscle tone. Specifically, there is an increase in pharyngeal and genioglossus muscle activity⁶. Kazuya Yoshida⁷ concluded in his study that the apnea appliance activated masticatory and tongue muscles during sleep and prevented the upper airway from collapsing.

The main advantages of using oral appliances are that, they are worn only during sleep and there is good patient compliance. The appliances are non-invasive and relatively inexpensive; they can also be easily carried anywhere by the patient.

CONCLUSION

Sleep apnea prosthesis is one of the conservative modes of therapy for mild to moderate forms of OSA. By maintaining the mandible and tongue in protrusive position during sleep, airway collapse can be prevented or minimized. It also increases the muscle tone and reduces its collapsibility. Fabrication of prosthesis is simple, non expensive and has good patient compliance.