Colin Price

Facial morphology and obstructive sleep apnea.

In a sample of 25 adult male subjects with moderate to severe obstructive sleep apnea, the interaction among craniofacial, airway, tongue, and hyoid variables was quantified by means of a canonical correlation analysis. One lateral cephalometric radiograph with the teeth in occlusion was obtained for each subject together with overnight polysomnographic measurements before the initiation of therapy. A principal component analysis reduced the data base and one significant canonical correlation (r1 = 0.994) was identified for the 22 variables. Sleep apnea subjects showed a posteriorly positioned maxilla and mandible, a steep occlusal plane, overerupted maxillary and mandibular teeth, proclined incisors, a steep mandibular plane, a large gonial angle, high upper and lower facial heights, and an anterior open bite in association with a long tongue and a posteriorly placed pharyngeal wall. A multivariate statistical analysis extracted clinically significant associations among craniofacial, tongue, and airway variables. Subjects with sleep apnea demonstrated several alterations in craniofacial form that may reduce the upper airway dimensions and subsequently impair upper airway stability.

A cephalometric and electromyographic study of upper airway structures in the upright and supine positions

Obstructive sleep apnea (OSA) is characterized by recurrent upper airway obstruction during sleep, usually in the supine position. To investigate the relationship between upper airway size and genioglossus (GG) muscle activity, upright and supine cephalograms were obtained in 20 OSA patients and 10 symptom-free control subjects. Tongue electromyographic (EMG) recordings were obtained with surface electrodes, and pressure transducers were placed in the 10 symptom-free controls. The tongue cross-sectional area increased 4.3% (p < 0.05), and the oropharyngeal area decreased 36.5% (p < 0.01) when the OSA patients changed their body position from upright to supine. No changes were observed in the tongue area, but soft palate thickness increased (p < 0.01) when the control subjects changed from the upright to the supine position. Furthermore, the oropharyngeal cross-sectional area decreased 28.8% (p < 0.01) despite a 34% increase (p < 0.05) in resting GG EMG activity. Posterior tongue pressure increased 17% (p < 0.05) with the change from upright to supine. On the basis of these findings, we propose that body posture has a substantial effect on upper airway structure and muscle activity. This postural effect should be taken into account when assessing upper airway size in the erect posture (conventional cephalography) and in the supine position (computed tomography). The vertical and anteroposterior position of the tongue and its relationship to airway size may be more important than soft palate size in the pathogenesis of OSA.

The effects of beam quality and optical density on image quality in dental radiography

The literature relating to the choice of beam quality in dental radiography is reviewed. Twenty observers were asked to select radiographs of a test object at different beam qualities and densities. The same observers were asked to identify numbers of circular areas of small density differences in zones of high and low density. Subjectively, the observers favored radiographs produced with lower beam energies; 90 kVp aluminum filtration and 3.5 mm was least popular, and 70 kVp with 2.5 mm aluminum was most popular. Objectively, there was little difference in the success of identification between the beams of different energies. Masking of radiographs improved success apart from the low density zones in less exposed radiographs. Little evidence has been found within the range investigated for selecting one beam quality over another, other than subjective preference. However, low beam energies should be avoided because of reduced emulsion sensitivity.

Computerized three-dimensional magnetic resonance imaging reconstructions of temporomandibular joints for both a model and patients with temporomandibular pain dysfunction

The aim of this study was to assess computerized three-dimensional reconstruction of magnetic resonance images generated of a temporomandibular joint model and the temporomandibular joints of five patients with varying degrees of temporomandibular joint pain and dysfunction. The three-dimensional image reconstruction of an artificial temporomandibular joint model, consisting of a human dried skull and synthetic disk, was used to test the accuracy and reproducibility of the three-dimensional technique. It was found that computerized three-dimensional reconstruction improved the display format of magnetic resonance imaging by enabling multiple two-dimensional images in shades of grey to be viewed as one three-dimensional image with anatomic structures colored as desired. Further, by rotating this image, the anatomic relationships of the temporomandibular joint could be seen from any viewpoint. Volume measurements showed accuracy and reproducibility by independent operators. Computerized three-dimensional reconstruction was applied to the magnetic resonance images obtained from patients. They were used to assess magnetic resonance imaging technique and its applications for interpreting the clinical findings. Disk position, as revealed by the three-dimensional images, was found to correspond with the clinical assessment, except in two instances when the original, right-sided, magnetic resonance imaging was unclear. Three-dimensional reconstruction was simple to apply, required no patient involvement, and made multiple magnetic resonance images easier to interpret.

A method of determining the sensitometric properties of emulsions and processing techniques used in dental radiography

The principles and applications of sensitometry in dental radiography are discussed. A method is described for determining the sensitometric properties of films and processing techniques used in dental radiography. This method has been used to demonstrate the relationship between density and exposure for a dental emulsion processed in an automatic processor. Examples of other applications of the method are included.

A densitometric evaluation of two radiographic duplicating films under differing conditions of exposure and processing

A method for the evaluation of radiographic duplicating films under differing conditions of exposure and processing is described. Two duplicating films are compared under exposure of incandescent and ultraviolet light sources and processing by one automatic and two manual methods. Differences in response relating to film type, light source, and processing method are demonstrated.

The so-called eruption sequestrum

The literature relating to so-called eruption sequestra is reviewed. Two cases in which there were calcified fragments adjacent to the crowns of all four first molars are described. Histologic evidence suggests that these calcified fragments consist of a cementum-like substance formed within the follicle, and not sequestrated bone.

A method of determining the radiopacity of dental materials and foreign bodies

The desirability of radiopacity in dental materials and other materials that may become foreign bodies is documented. No simple, reliable methods are available for the determination of radiopacity, and no standard specifications have been devised with regard to the radiopacity of dental materials. A method that enables radiopacity to be determined is described. The theoretical aspects of radiopacity in relation to the method are considered. Possible applications of this method in the development of standards for radiopacity are suggested.

Scattered radiation grids in cephalometric radiography

Scattered radiation grids are routinely used in medical radiological examinations of the skull, but less commonly in cephalometric radiography. Because the grids involve an increased radiation dose, it is necessary to determine whether the diagnostic quality of cephalometric radiographs is improved by a grid to an extent that justifies this increased dose. This investigation has failed to demonstrate any improvement in the identification of five landmarks. It is thus concluded that there is no justification for the use of scattered radiation grids in cephalometric radiography.

The effects of kilovoltage and filtration on dental radiographic film sensitivity.

A sensitometric method was used to compare the effects of changing kilovoltage and filtration on the sensitivity of a dental radiographic emulsion. Five combinations were investigated: 90 kVp, 3.5 mm. aluminum filtration; 90 kVp, 2.5 mm. Al; 70 kVP, 2.5 mm. Al; 70 kVp, 1.5 mm Al; and 50 kVp, 1.5 mm. Al. Maximum emulsion sensitivity was demonstrated at 90 kVp and 3.5 mm.aluminum filtration; 90 kVp, 2.5 mm. Al and 70 kVp, 2.5 mm. Al showed slight reductions in sensitivity (4 percent and 6 percent, respectively). A progressively greater reduction in emulsion sensitivity was observed at 70 kVp, 1.5 mm. Al (10 percent) and 50 kVp, 1.5 mm. Al (26 percent). Emulsion sensitivity is one factor to be considered when one is selecting beam quality.