A prospective 10-year cephalometric follow-up study of patients with obstructive sleep apnea and snoring who used a mandibular protruding device


This 10-year prospective cephalometric study evaluates the influence of a mandibular protruding device (MPD) in people with obstructive sleep apnea and snoring.


A baseline study population of 77 people was followed biennially. After 10 years, 65 people (45 MPD users and 20 stopped-MPD users) were reexamined. At baseline and after 10 years, a lateral cephalogram was taken in the upright position.


MPD users showed significant changes in all cephalometric variables except for maxillary protrusion. The maxillary incisors were retroclined by a mean –4.2° (standard deviation [SD] 3.95; P <0.001), mandibular incisors were proclined by a mean 3.2° (SD, 5.02; P <0.001), and SNB was reduced by a mean –0.6° (SD 1.41; P = 0.01). In those who had stopped MPD use, these initial cephalometric values were retained. Significant changes in decreased overjet and overbite were seen in the MPD group but not in the MPD-stopped group. The length of the mandible (Cd-Pg) increased by a mean of 5.1 mm (SD 6.78; P <0.001) and 6.1 mm (SD 5.99; P <0.001) in MPD and MPD-stopped groups, respectively. The hyoid bone–mandibular plane distance (hy-ML) increased by a mean of 3.3 mm (SD, 2.90; P <0.001) and 3.8 mm (SD 3.67; P = 0.001) in MPD and MPD-stopped groups, respectively.


Long-term nocturnal MPD use causes retroclination of the maxillary incisors and proclination of the mandibular incisors with consequent decreased overjet and overbite. Both MPD and MPD-stopped users obtained increased mandibular length and lower position of the hyoid bone, which can be a normal physiological change with age.


  • Long-term use of an oral appliance for apnea treatment causes dentoalveolar changes.

  • Retroclination of maxillary incisors and proclination of mandibular incisors appeared.

  • Consequent decrease of overjet and overbite appeared.

  • Age is associated with an increased mandibular length and lower positioned hyoid bone, regardless of treatment.

Obstructive sleep apnea (OSA) is characterized by episodes of partial or total obstruction in the upper airways during sleep in combination with snoring and often daytime sleepiness and tiredness. The airway obstruction causes an arousal reaction with consequent sleep disturbance and impairment of sleep quality. The long-term medical consequences of untreated OSA are increased risk of developing high blood pressure, stroke, or heart failure.

The first choice of treatment for severe OSA is continuous positive airway pressure (CPAP). A mandibular protruding device (MPD) that advances the mandible in a protruded position is an alternative treatment that opens the airway and thus avoids the collapse of the pharynx during sleep. Compliance is higher for an MPD than for CPAP. Although CPAP reduces the apnea-hypopnea index more than an MPD, Anandam et al found that both CPAP and MPD are equally effective therapies in reducing the risk of fatal cardiovascular events in patients with severe OSA. White et al compared CPAP and MPD after 1-month use and found that most patients preferred using an MPD (51%) to using a CPAP (21%); this finding is in agreement with earlier reports.

Several different MPD designs are available commercially, and all seem to be associated with short- and long-term adverse experiences. The short-term adverse effects are complaints from the temporomandibular joint, jaw muscles, and teeth. Several articles have also reported on the long-term follow-up and have reported that forces from the MPD may cause proclination of the mandibular incisors and retroclination of the maxillary incisors, a well-known activator effect. Proclination of the mandibular incisors can cause an increase in lower face height and posterior rotation of the mandible. ,

Follow-up reports of natural lifetime changes have shown that the dentoalveolar skeleton continues to change with time, as reflected in a natural mesial drift of the mandibular teeth even without MPD treatment. In a 2-year follow-up study with MPD treatment, Fransson et al found a significant change in the proclination of the mandibular incisors, retroclination of the maxillary incisors, increased anterior face height, and posterior rotation of the mandible. Later studies with a follow-up of 7 years confirmed the same observations. , ,

Most patients consider that the positive treatment effect of an MPD outweighs the adverse effects. There is limited evidence of the risk of developing pain and functional impairment after long-term use of an MPD. It is more common for people to discontinue use of an MPD because of a reduced effect on OSA symptoms rather than adverse events. ,

The aim of this 10-year follow-up study of OSA and snoring patients was to use cephalometric measures to follow the dentofacial changes in association with the use of an MPD.

Material and methods

This prospective study examined observational effectiveness in people with OSA and snoring problems who were all treated with an MPD. Over 10 years, all patients still using their MPD were checked biennially, and the device was adjusted if needed. At the 10-year follow-up, all patients were re-called, including those who had stopped using their MPD. Upright lateral cephalograms were taken at the baseline and the 10-year follow-up.

The baseline study population comprised 77 consecutive adult patients referred from the University Hospital for treatment at the Department of Stomatognathic Physiology, Örebro University, with the diagnosis of OSA based on a polygraphic examination (oxygen desaturation index, ≥5) or snoring (oxygen desaturation index, <5). The inclusion criteria were a sufficient number of teeth to retain an MPD, good dental health, and a maximum protrusion range of ≥6 mm as measured with the George Gauge instrument (Boos Dental Laboratories, MN). The detailed patient eligibility and enrollment path have been previously described by. At the 10-year follow-up, all baseline patients (except 3 who had died), including those who had stopped using their MPD, were re-called (n = 74).

All subjects signed an informed consent form after being informed about the purpose of the study. Approval for the main study was obtained from the Medical Ethics Committee at Medical Centre Hospital, Örebro University. A second informed consent form was signed at the 10-year follow-up. For the 10-year follow-up, the application was approved by The Regional Ethical Review board, Uppsala, Sweden.

MPDs were fabricated after the clinical examination. A George Gauge construction bite was used to advance the mandible ≥75% of the maximal protrusion and ≥5 mm from the retruded position. The MPD used in this study was a monobloc of heat-cured methyl methacrylate covering all the teeth with an opening in the frontal region ( Fig 1 ).

Fig 1
The MPD covering all teeth was made of heat-cured methyl methacrylate resin.

At the 10-year follow-up, the actual degree of mandibular advancement was measured with a steel ruler.

At baseline and 10-year follow-up, a cephalogram was taken with the patient in the upright position with the teeth in intercuspation, the head supported by a cephalostat and orientated according to the Frankfort horizontal plane. The baseline analog cephalogram was obtained using a specially designed cephalostat equipped with an X-ray tube (Pantixhaube PH 125/80, Siemens, Stockholm, Sweden). The 10-year follow-up was made using a Cranex Tomé Ceph digital unit (Soredex, Tuusula, Finland).

The analog-to-digital transformation procedure was done by Depona AB (Vilhelmina, Sweden) to ensure high quality. The examination results were saved in Digital Imaging and Communications in Medicine format and used in the FACAD analysis program (Ilexis AB, Linköping, Sweden). A 12-bit gray scale (4096 shades) was used to optimize the quality. The cephalograms were calibrated before the analyses based on the distance C 2 to C 3 measured in millimeters on the analog cephalogram and calibrated in FACAD on the digitized cephalogram.

The following measures were included in the cephalometric analyses: hyoid position, incisor inclination, overjet, overbite, jaw position to the skull base, and skeletal measures such as the mandible length. All cephalometric measurements and analyses were performed by the same examiner (CBL) who was blinded to the continued or stopped use of the MPD.

The examiner’s consistency was evaluated by rereading 20 randomly selected cephalograms obtained at both the baseline and 10-year follow-up. The measurements were repeated after ≥1 month. A maximum of 10 cephalograms was analyzed at a time to avoid operator fatigue. Test-retest reliability was calculated using the intraclass correlation coefficient (ICC) using IBM SPSS Statistics, version 21 (IBM Corp, Armonk, NY).

Statistical analysis

No power calculation was made because of the structure of the study. The size of the sample was chosen to be able to describe effectiveness following long-term use of an MPD in a typical OSA population. Descriptive statistics are used to delineate the baseline patient characteristics. Changes from the baseline to the 10-year follow-up were analyzed using a paired Student t test for continuous data, and P <0.05 was considered to be significant.


At the 10-year follow-up, 65 patients were available for analysis: 45 were MPD users (30 with OSA and 15 snorers; Fig 2 ), and 20 had stopped using the MPD (12 primarily with OSA and 8 were snorers; Fig 2 ). The patients’ baseline characteristics are described in Table I . In the reference group of MPD-stopped users, 14 patients stopped using the MPD after 4 years, 2 patients stopped after 6 years, and 4 patients stopped after 8 years.

Fig 2
Flow diagram of the study participants.

Table I
Baseline demographics describing age, sex, body mass index, and neck size for MPD users and MPD-stopped patients
MPD users Patients who stopped using the MPD
Men (n = 35) Women (n = 10) Total (n = 45) Men (n = 17) Women (n = 3) Total (n = 20)
Age (y)
Mean (SD) 54 (8.3) 54 (7.1) 54 (8.0) 52 (7.2) 62 (4.6) 54 (7.7)
Range 37-73 42-61 37-73 39-65 57-66 39-66
BMI (kg/m 2 )
Mean (SD) 29 (3.8) 31 (3.8) 29 (3.8) 30 (3.0) 29 (2.5) 30 (2.9)
Range 21-36 26-36 21-36 25-38 26-31 25-38
Neck size (cm)
Mean (SD) 42.1 (2.7) 38.9 (1.9) 41.4 (2.9) 43.1 (2.9) 36.3 (2.1) 42.1 (3.7)
Range 37-49 36-41 36-49 39-51.5 34-38 34-51.5
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Jan 7, 2020 | Posted by in Orthodontics | Comments Off on A prospective 10-year cephalometric follow-up study of patients with obstructive sleep apnea and snoring who used a mandibular protruding device
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