Influence of oral and craniofacial dimensions on mandibular advancement splint treatment outcome in patients with obstructive sleep apnea

Abstract

Background: Mandibular advancement splints (MASs) can effectively treat obstructive sleep apnea (OSA); however, no validated and reliable prediction method for treatment outcome currently exists. The efficacy of MAS may relate to anatomic factors, including craniofacial size and upper-airway soft-tissue volume and anatomic balance between them. We aimed to assess whether craniofacial and oral measurements are associated with MAS treatment outcome.

Methods: Dental impressions and lateral cephalometric radiographs were obtained from patients with OSA prior to commencing MAS treatment. Intertooth distances and palatal depths were measured on dental casts, and standard cephalometric analysis was performed with the addition of cross-sectional area (CSA) of the tongue and bony oral enclosure. Treatment outcome was determined by polysomnography.

Results: Of 53 patients, 25 were complete responders (posttreatment apnea-hypopnea index [AHI] < 5/h), 17 were partial responders (≥ 50% AHI reduction), and 11 were nonresponders (< 50% AHI reduction). Cephalometric analyses did not reveal any significant differences between responders and nonresponders. Oral cavity measurements or CSA did not differ with treatment outcome; however, there was a trend toward a larger tongue CSA in complete vs partial and nonresponders (39.5 ± 1.3 cm(2) vs 35.5 ± 0.5 cm(2), P = .09). Tongue/oral enclosure CSA ratio, indicating a larger tongue for a given oral cavity size, was greater in complete responders (P = .012, n = 30).

Conclusions: Oral dimensions do not appear to differ between patients who respond and those who do not respond to MAS treatment. However, the larger tongue for a given oral cavity size in responders suggests that MAS may help to correct anatomic imbalance. Further research to assess whether the ratio between tongue and bony oral enclosure size may be useful in selecting patients for MAS treatment is warranted.

Figure 1

Schematic diagram of dental arch illustrating the linear dental measurements taken from the upper- and lower-dental arch study models. IC = intercanine; IP1 = first interpremolar; IP2 = second interpremolar; IM = intermolar; ITD = intertooth distance. Maximal palatal height also was measured on the upper dental arch along each line intersecting the centroids of each set of teeth.

Figure 2

Schematic of lateral cephalogram illustrating identified cephalometric landmarks. A = subspinal; ANS = anterior nasal spine; B = supramentale; Ba = basion; C2 = tangent point on the dorsal surface of C2 vertebrato a line from C4; C4 = C4 vertebra inferoposterior; Eb = epiglottis base; Gn = gnathion; Go = gonion; H = hyoidale; Me = menton; N = nasion; P = soft-palate tip; PAS = posterior airway space; phw = posterior pharyngeal wall; pm = posterior nasal spine; S = sella; spt = soft palate tangent; T = tongue tip.

Figure 3

Lateral cephalogram showing the trace of the outline of the tongue of which cross-sectional area (CSA) was determined. Tongue height and length also are marked. The oral enclosure box, the sides of which are lines drawn between the points PNS, ANS, Me, and Go, is shown. A ratio of the CSA of the tongue and oral enclosure area was calculated. h = tongue height; l = tongue length; PNS = posterior nasal spine. See Figure 2 legend for expansion of other abbreviations.

Figure 4

Tongue/oral area ratio by mandibular advancement splint (MAS) treatment outcome. Tongue/oral area ratio in shown for complete (n = 13), partial (n = 13), and nonresponders (n = 4) to MAS treatment. Tongue/oral area ratio was significantly greater in complete responders than in nonresponders, *P = .012. Data are presented as mean ± SEM.