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 Table of Contents  
ORIGINAL ARTICLE
Year : 2016  |  Volume : 13  |  Issue : 4  |  Page : 193-198

The effect of changes in the intermaxillary distance in mandibular advancement splints as a treatment of obstructive sleep apnea


1 Department of Prosthodontics, Faculty of Dentistry, Tanta University, Tanta, Egypt
2 Department of Otolaryngology, Faculty of Medicine, Tanta University, Tanta, Egypt

Date of Submission17-Jul-2016
Date of Acceptance25-Aug-2016
Date of Web Publication14-Dec-2016

Correspondence Address:
Rehab M Abdallah
Department of Prosthodontics, Faculty of Dentistry, Tanta University, Tanta
Egypt
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/1687-8574.195711

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  Abstract 

Objective
To evaluate the effect of intermaxillary space variation induced by mandibular advancement splints (MAS) constructed with three different interocclusal distances on the efficacy of the treatment of the obstructive sleep apnea.
Materials and Methods
Ten patients were selected after polysomnography from the Sleep Laboratory in Tanta University. At the beginning of the study all patients were asked to complete the Epworth sleepiness scale and after the treatment period. Each patient received three MAS constructed with intermaxillary distance of 4, 8, and 10 mm and patients were recalled after 4-6 weeks for follow-up study using nasopharyngoscopy and polysomnogram after each appliance. The patients were instructed to withdraw and stop the use of their appliance for at least 1 week before using the next appliance. The recorded data for each patient with the three appliances were collected, tabulated and statistically analyzed using t-paired test and Friedman's test.
Results
There was statistically significant difference between the baseline records and the records obtained after the use of each MAS appliance (P < 0.05).
Conclusion
The use of MAS appliance with increased vertical dimension improved the velopharyngeal caliper and improvement in the polysomnographic variables especially Apnea/Hypopnea Index, sleep efficiency and Arousal Index was observed.

Keywords: mandibular advancement splint, obstructive sleep apnea, oral appliances


How to cite this article:
Abdallah RM, Rashad HA, Kashef NA, El-Sheikh MN. The effect of changes in the intermaxillary distance in mandibular advancement splints as a treatment of obstructive sleep apnea. Tanta Dent J 2016;13:193-8

How to cite this URL:
Abdallah RM, Rashad HA, Kashef NA, El-Sheikh MN. The effect of changes in the intermaxillary distance in mandibular advancement splints as a treatment of obstructive sleep apnea. Tanta Dent J [serial online] 2016 [cited 2023 Feb 3];13:193-8. Available from: http://www.tmj.eg.net/text.asp?2016/13/4/193/195711


  Introduction Top


Snoring is a well-known phenomenon among the general population. It is 'to breathe during sleep with harsh, snorting noises caused by vibration of the soft palate' [1]. Sleep disordered breathing is characterized by the frequent occurrence of pathological respiratory events, that is, apneas and hypopneas. An apnea is a Greek word for 'without breath' and is defined as a complete cessation of breathing for at least 10 s with oxygen desaturation of more than 3% and/or associated with arousals. During apneas there is no breathing sound. Resumption of breathing is associated with a sequence of snores. The sound quality of these consecutive interapneic snores may vary markedly [2]. Obstructive hypopneas are defined as decreased airflow with partial collapse of the upper airway but, without being abolished and it lasts for at least 10 s. Snoring persists during these hypopneas and may show a crescendo pattern of increasing loudness. The number of apneas plus hypopneas per hour of sleep is the Apnea-Hypopnea Index (AHI) [3]. A dentist can easily detect the less evident symptoms of sleep apnea and snoring at an early stage [4]. The dental practitioner may be the first to recognize a patient's sleep-disorder-affected breathing by witnessing repeated apneic events in patients undergoing sedation. Dentist will then send patients with symptoms of sleep apnea to a sleep medicine specialist who will assess and confirm the patient conditions and severity by polysomnogram (PSG) [5]. The American Academy of Sleep Medicine has recommended oral appliance (OA) as a treatment for use in patients with primary snoring and mild to moderate obstructive sleep apnea (OSA). It can also be used in patients with a lesser degree of oxygen saturation, relatively less day-time sleepiness, lower frequency of apnea, those who are intolerant of continuous positive air pressure, or those who refuse surgery [6]. The most common mechanism of action is to hold the lower jaw in a more anterior position. These appliances are variously termed 'mandibular advancement splints (MAS),' or 'mandibular repositioning appliances.' Imaging studies show that MAS enlarges the upper airway space, most notably in the lateral dimension of the velopharyngeal region [7].

There are conflicting data regarding the effect of the degree of bite opening; vertical dimension of opening induced by OA on treatment outcome. Hence, the aim of this study was to systematically assess the effect of increasing the vertical dimension of an oral mandibular advancement appliance on the treatment of OSA.


  Materials and methods Top


Study group

Patients with sleep apnea were referred from the Outpatient Clinic in the Department of Otolaryngology, Faculty of Medicine, Tanta University to the Department of Prosthodontics, Faculty of Dentistry, Tanta University, after performing a full night PSG, in the Sleep Laboratory in Tanta University. Criteria for inclusion were the presence of two symptoms at least of OSA (snoring, fragmented sleep, witnessed apneas, day-time sleepiness) and adequate dentition and periodontal status for support and retention of OA. No temporomandibular joint dysfunction.

Patients were excluded if there was evidence of hypothyroidism, central sleep apnea, inadequate dentition or previously operated for the treatment of sleep apnea.

All patients were informed and signed written consents to participate in this study according to the ethical committee of Faculty of Dentistry, Tanta University.

Mandibular advancement splint

Dental impression for upper and lower dentition was taken using rubber base impression material (C-silicon impression material) (Heavy body and light body wash, Zeta plus; Zhermack, Rovigo, Italy) [Figure 1].
Figure 1: Upper and lower impression

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A protrusive record was taken using the protrusive gauge included in the Erkodent Silensor Kit (Silensor; Erkodent, Tuttlingen, Germany) for MAS at 50% of maximum protrusion [Figure 2].

The final appliance was constructed starting with the vertical dimension 4 mm (MAS-1) then vertical dimension 8 mm (MAS-2) then vertical dimension 10 mm (MAS-3). Using different thicknesses of the Erkoloc-pro soft material [Figure 3].
Figure 2: Bite registration at 50% of maximum protrusion

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Figure 3: The final appliance

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Study design

In this prospective study, after receiving the first appliance (with 4 mm) vertical dimension (MAS-1) the patients were asked to wear it for 6 weeks then recalled to perform a full night PSG and nasopharyngoscopy analysis for the appliance.

Then a wash-out period of at least 1 week before delivering the second appliance (with 8 mm) vertical dimension (MAS-2).

Then, full night PSG and nasopharyngoscopy analyses were performed to assess the use of the second appliance. Again a wash-out period of at least 1 week before delivering the third appliance (with 10 mm) vertical dimension (MAS-3). Then the final PSG and nasopharyngoscopy analysis were done. Any side effects during the period of using the appliance were recorded for each patient.

Outcome measures

Questionnaire

At the beginning of the study all patients were asked to complete the Epworth sleepiness scale (ESS) and after the treatment period using each appliance.

Polysomnogram

The PSGs were scored according to the 2007 American Academy of Sleep Medicine guidelines for the scoring of sleep and associated events. All patients were evaluated in an accredited sleep laboratory in sound attenuated rooms, monitored by an infra-red camera. The digital PSG equipment used was Nicolet diagnostic sleep system. The electroencephalogram was divided into non-rapid eye movement (REM) and REM states.

Nasopharyngoscope

Nasopharyngoscopy was performed by a single operator before the beginning of treatment and after the completion of acclimatization to treatment with each MAS. For the purposes of assessing the association between nasopharyngoscopic findings and the treatment response on PSG, an increase in the cross-sectional area of the lumen of the upper airway was based on any increase in the quantitative assessment of the cross-sectional area on the nasopharyngoscopic images.

Statistical analysis

The data was analyzed with the statistical package for the social sciences, 22 software package (IBM Corporation, Armonk, New York, USA). All quantitative variables were presented as mean ± SD, minimum, and maximum. Qualitative data were presented as number of frequency and percentages. Comparison between two records for the same patient to study the changes at certain variable was done by t-paired test. Comparison among four records for the same patient was done by Friedman's test. A P value of less than 0.05 was considered statistically significant.


  Results Top


Study population

The mean age of the 10 included patients was 44.2 ± 8.24 years. The mean height was 172.7 ± 4.29 cm. The mean weight was 96.6 ± 19.92 kg. The mean BMI was 32.67 ± 6.26 kg/m 2 . All patients included in this study were males.

Subjective outcomes

The qualitative analysis of the patients included in the study showed that at baseline, there were eight patients with normal ESS score (0-10) and two patients with a borderline score (10-12). After using MAS-1, MAS-2, and MAS-3 all 10 patients included in this study had normal ESS score [Figure 4].
Figure 4: Nasopharyngoscopy images. A, Lateral walls of velopharynx. B, Anteroposterior walls of velopharynx. MAS, mandibular advancement splint

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Objective outcomes

PSG outcomes are outlined in [Table 1]. When comparing the mean of total sleep time at baseline and after using each of MAS-1, MAS-2, and MAS-3 there was a statistically significant increase. This is also evident in the mean of REM and non-REM sleep time.
Table 1 Polysomnographic results after using MAS-1, MAS-2 and MAS-3


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The Arousal Index/h decreased significantly after using the three appliances when compared with the baseline.

The AHI decreased significantly after the use of the three appliances when compared to the baseline. Also the minimum arterial oxygen saturation level increased significantly after the use of MAS-1, MAS-2, and MAS-3.


  Nasopharyngoscopic results Top


Images obtained from the video endoscopic evaluation of the velopharynx before starting the treatment and after using MAS-1, MAS-2, and MAS-3 are presented in [Figure 5].
Figure 5: Frequency of Epworth scale at baseline and after using MAS-1, MAS-2 and MAS-3. MAS, mandibular advancement splint

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The statistical analysis of changes in minimum cross section area of the velopharynx at baseline and after using MAS-1, MAS-2, and MAS-3 showed that there was a statistically significant increase in minimum cross section area after using MAS-1 (75.082 ± 5.873), MAS-2 (82.52 ± 6.302), and MAS-3 (86.19 ± 3.15) when compared to the baseline (53.58 ± 11.062) [Table 1].


  Discussion Top


The lack of emphasis on the amount of vertical opening may be one of the most important reasons for the efficacy of the OAs. Despite numerous studies addressing the effect of various mandibular protrusion degrees on the efficacy of mandibular advancement appliances, what constitutes the most effective degree of vertical opening remains undetermined and controversial [8,9].

In our study, three different vertical dimensions were used to construct the three mandibular advancement appliances for each patient starting with 4 mm vertical dimension (MAS-1) then 8 mm vertical dimension (MAS-2) then 10 mm vertical dimension (MAS-3) in agreement with the study of Pitsis et al. [9] who used two appliances with 4 and 14 mm vertical dimensions to assess their effect on the treatment of OSA, and found that both appliances decreased the PSG variables but the patient preference was for the lower vertical dimension.

There was a wash-out period of 1-2 weeks between the use of each mandibular advancement appliances in order to minimize the risk of carry-over effect and give a release period, which is supported with several studies [10,11].

In the current study the semirigid appliance was used as it produced a better compliance and less discomfort for the patients and this is advised also by McGown et al. [12].

On the other hand, the use of rigid mandibular advancement appliance restricts mandibular movement and this immobility sometimes produces discomfort, including temporomandibular disorders [13,14], this is why we preferred the use of the semirigid appliance.

Our study clinically evaluated three predetermined specific levels of vertical mouth opening. The three appliances significantly reduced the AHI in all patients to a great extent except for two patients the reduction in AHI was lower than the others. This may be attributed to the sever OSA, as explained by several studies [10, 15, 16].

In our study the Arousal Index/h was improved after the use of each MAS appliance compared to the baseline and this was statistically significant (P < 0.001), these findings are in agreement with several studies [17-19]. In contrast, two cross over trials found no effect on the Arousal Index when using the OAs [20,21]. Other studies found a greater effect of continuous positive airway pressure treatment in reducing the Arousal Index [22,23].

Also, sleep efficiency was improved after using the MAS with 4 mm vertical occlusal distance (MAS-1), MAS with 8 mm vertical occlusal distance (MAS-2), and MAS with 10 mm vertical occlusal distance (MAS-3) and the results were statistically significant (P < 0.001) supported by the finding of a recent study of Cilil et al. [24].

The AHI/h was significantly improved after the use of the MAS with 4 mm vertical occlusal distance (MAS-1), MAS with 8 mm vertical occlusal distance (MAS-2), and MAS with 10 mm vertical occlusal distance (MAS-3) when compared to the baseline (P < 0.001) and these findings are supported by previous studies [19,25-27].

The minimum arterial oxygen saturation% was significantly improved when comparing its level at baseline and after using MAS with 4, 8, and 10 mm vertical occlusal distance (P < 0.001), and this is in agreement with the study of Petri et al. [26].

In contrast to other studies that showed only nasal continuous positive airway pressure had an effect on the arterial oxygen saturation [21,22]. The findings of our study show that the use of the MAS with 4 mm vertical occlusal distance (MAS-1) increased the cross section of the velopharynx significantly (P < 0.001). It was also found that the use of MAS with 8 mm vertical occlusal distance (MAS-2) further increased the cross-sectional area of the velopharynx (P < 0.001) from the baseline. The use of MAS with 10 mm vertical occlusal distance (MAS-3) also increased the cross-sectional area of the velopharynx from the baseline (P < 0.001).

The previously mentioned findings came supported with the findings of the studies of Ng et al. [28] and Sanner et al. [29] who used the upper airway closing pressure method and demonstrated that OAs effectively improve upper airway collapsibility in OSA patients.

This may be explained as that OAs function as a rigid stent that stretches the parapharyngeal muscles forward and stiffens the velopharynx through the palatoglossus arch, making the upper airway less sensitive to intraluminal pressure as previously studied by Cohen-Levy et al. [30].


  Conclusion Top


Based on the limitation of our study it was concluded that:

  • The use of semirigid appliance gave better tolerance and acceptance of the patients, and relived the complaints of OSA
  • The use of increasing vertical dimension improved the PSG results and was accepted by the patients
  • The uses of the semirigid appliances with increasing vertical dimension seem to be useful aid in the treatment of OSA
  • Patients' preference was for the lower vertical dimension although the MAS-2 (8 mm vertical dimension) and MAS-3 (10 mm vertical dimension) produced a wider cross-sectional area of the velopharynx.
Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.

 
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    Figures

  [Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5]
 
 
    Tables

  [Table 1]


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