Cephalometric changes in adult pharyngeal morphology

Positional changes of oropharyngeal structures due to gravity in the upright and supine positions

OBJECTIVES

To compare the responses of oropharyngeal structures to gravity while sitting upright or lying down in a supine position.

METHODS

Seven subjects were evaluated by cone beam CT (CBCT) while in the upright position and by a four-row multidetector helical CT (MDCT) while in the supine position. All of the voxel sizes were adjusted to be 0.3x0.3x0.3 mm3 in the x-y-z axis. The posterior nasal spine, basion and fourth cervical bone were used as references to measure positional changes in the oropharyngeal structures between the upright and supine positions. The smallest areas in the oropharynx were also evaluated.

RESULTS

The soft palate, epiglottis and entrance of the oesophagus moved caudally with the positional change from supine to sitting upright, and moved posteriorly when the position changed from an upright to a supine position. The hyoid bone moved caudally but not posteriorly in response to the same positional changes. The width and length of the smallest area present in the oropharynx was larger in the upright position than in the supine position.

CONCLUSIONS

Gravity can produce movements in oropharyngeal structures in response to postural changes between sitting upright and lying in the supine position.

The relationship between craniofacial anatomy and obstructive sleep apnoea: a case-controlled study

The aim of the study was to identify craniofacial and pharyngeal anatomical factors directly related to obstructive sleep apnoea (OSA). The design and setting was a hospital-based, case-controlled study. Ninety-nine subjects (78 males and 21 females) with a confirmed diagnosis of OSA, who were referred to the Dental Hospital for construction of a mandibular advancement splint were recruited. A similar number of control subjects, matched for age and sex, were recruited after completing snoring and Epworth Sleepiness Scale questionnaires to exclude habitual snoring and daytime sleepiness. An upright cephalogram was obtained and skeletal and soft tissue landmarks were traced and digitized. In OSA subjects the anteroposterior skeletal measurements, including maxillary and mandibular length were reduced (P < 0.001). The intermaxillary space was found to be 3.1 mm shorter in OSA subjects (P = 0.001). The nasopharyngeal airway in OSA subjects was narrower (P < 0.001) but pharyngeal length showed no difference. The tongue size was increased (P = 0.021), soft plate length, thickness and area were all greater (P < 0.001) and the hyoid bone was more inferiorly positioned in OSA subjects (P < 0.001). This study identifies a significant number of craniofacial and pharyngeal anatomical factors directly related to OSA.

Nasopharyngeal cephalometric study of ideal occlusions

INTRODUCTION

The aim of this study was to assess nasopharyngeal soft-tissue patterns in patients with ideal occlusion.

METHODS

A sample of 91 patients was selected from the Dental School at Complutense University of Madrid. None of the subjects had a history of sleep disorder, snoring, sleep apnea, upper airway disease, adenoidectomy, or pathology in the pharynx. Lateral cephalograms were digitized, and linear and area measures were made to define the airway pattern. Error analysis was performed to prevent systematic or random errors. The Student t test and the Pearson correlation analysis were applied to compare sex differences and variable correlations. A factorial data analysis was also applied to prove a group-dependant relationship between variables.

RESULTS

Nasopharyngeal soft-tissue patterns were different in men and women. Nasal fossa, cranial base, and adenoidal tissue were larger in men. All variables except lower pharynx dimension were statistically related. Great dependence was observed between some variables: upper airway thickness explained 60% of the changes in upper pharyngeal dimension and 67% of the changes in aerial area. Cranial base length was also statistically related with different variables that define the airway, mainly nasal fossa length and lower airway thickness. Nasal fossa length was statistically correlated with upper airway thickness. McNamara's lower pharyngeal dimension did not depend on other variables used in this study. Five groups of variables tended to be related among themselves but not with others.

CONCLUSIONS

This study suggests new lines of investigation into the relationship between skeletal and dental anomalies and airway obstruction, and possible specific respiratory patterns for each type of malocclusion.

A comparison of responders and nonresponders to oral appliance therapy for the treatment of obstructive sleep apnea

INTRODUCTION

This retrospective study compared cephalometric variables between responders and nonresponders to a titratable oral appliance (OA) in a group of subjects matched for sex, pretreatment age, and body mass index (BMI).

METHODS

Nine nonresponders as defined by an improvement in the apnea hypopnea index (AHI; <20%) and their individually matched responders were selected for this study. The difference in age for each matched pair was +/-5 years, and, for BMI, the difference was +/-15%. The pretreatment AHI was matched to the same category (moderate, >15 to < or =30; severe I, >30 to < or =45; and severe II, >45 AHI).

RESULTS

Middle and inferior airway space and oropharyngeal airway cross-sectional area were significantly larger in the nonresponders. Position of the mandible relative to the cervical spine was the only significant skeletal variable and was larger in nonresponders. Changes in BMI between the groups were statistically significant; the averages were a 2.9% increase in the nonresponders and a 0.5% decrease in responders. The wider airway in nonresponders might reflect an enhanced neuromuscular compensation while awake. The weight gain in nonresponders was relatively small, but it might have reduced the effectiveness of the OA.

CONCLUSION

When treating OSA patients with OA therapy, clinicians should pay particular attention to airway size and weight changes.

Factors related to the resting tongue position among partially and completely edentulous subjects

The prevalence of abnormal (retracted) position of the tongue at rest was examined in subjects with varying number of natural lower teeth. The aim of the study was to explore the relationship between tongue retraction and state of dentition and to identify potentially related parameters. The resting tongue positions were recorded in subjects partially edentulous in the lower jaw (n = 164) and compared with those met in dentate (n = 57) and completely edentulous participants (n = 84). Potentially related parameters, such as age, sex, duration of edentulism, palate vault and signs of temporomandibular disorders were also recorded. Tongue retraction was observed in a small percentage (12.3%) of the dentate, almost half (45.7%) of the partially edentulous and in the majority (67.8%) of the completely edentulous participants. The number of natural lower teeth correlated with the resting tongue position in the partially edentulous group. The tongue position at rest was also found weakly related to signs of temporomandibular disorders in the dentate group and to the sex and duration of edentulism in the partially edentulous group. It was concluded that the abnormal positioning of the resting tongue is increasingly observed with decreasing number of natural teeth, possibly in accordance with the morphological and functional alterations that result from teeth loss. The presence of a retracted tongue affects the complete denture construction; however, its effect on denture function remains questionable.