Mentoring and pretenure faculty development.
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Career Mobility↗
Biomedical subjects
A A Lowe
Publications and source records attributed to A A Lowe.
Nasal continuous positive airway pressure (CPAP) therapy for obstructive sleep apnea in Hallermann-Streiff syndrome.
An 8-year-old girl with Hallermann-Streiff syndrome (oculomandibulofacial syndrome) was examined. She had a history of severe snoring, reported nocturnal apnea, excessive daytime hypersomnolence, nocturnal enuresis, and failure to thrive. Overnight polysomnography confirmed severe obstructive sleep apnea. Long-term nasal continuous positive airway pressure (CPAP) therapy completely relieved the obstructive sleep apnea and was associated with improved weight gain and growth.
Child↗
Upper airway measurements predict response to uvulopalatopharyngoplasty in obstructive sleep apnea.
Although uvulopalatopharyngoplasty relieves obstructive sleep apnea in the majority of patients, the factors that determine a successful response are not well defined. To determine whether preoperative awake upper airway measurements predict the response to uvulopalatopharyngoplasty, presurgical lateral cephalometric radiographs were evaluated on 60 consecutive patients with symptomatic obstructive sleep apnea. Patients underwent overnight polysomnograms before uvulopalatopharyngoplasty and 3 months afterwards. Forty-eight (80%) patients had a good response as defined by a postoperative apnea index of less than or equal to 4 apneas/hour or a reduction in apnea index of greater than or equal to 60%. Responders had a significantly narrower inferior airway space (P less than .0005) and a smaller ratio of inferior airway space to tongue length (P less than .001). Improvement in apnea severity following uvulopalatopharyngoplasty was related to the degree of airway narrowing (r = 0.36; P less than .01). This study shows that upper airway measurements help predict response to uvulopalatopharyngoplasty in patients with obstructive sleep apnea. Patients with a narrow airway, particularly relative to tongue size, have good responses to uvulopalatopharyngoplasty.
Adolescent↗
The tongue and airway.
Patency of the upper airway during sleep depends on a balance of forces. This article summarizes recent research undertaken by the author in the areas of tongue, soft palate and airway volume, tongue and pharyngeal edema, genioglossus muscle activity, and mandibular repositioning appliances. Three-dimensional relationships between airway, soft palate, and tongue can be quantified with accuracy, and such analyses may be of significant diagnostic importance.
Body Mass Index↗
Relationship between jaw muscle volume and craniofacial form.
To study the relationship between craniofacial form and jaw muscle function, we evaluated 25 adult male subjects with Obstructive Sleep Apnea (age, 30-61 years; weight, 58-122 kg) on the basis of CT scans obtained for routine diagnostic purposes. All scans were obtained with the Frankfort horizontal plane at right angles to the floor; each CT slice was 8 mm thick. Masseter and medial pterygoid muscle outlines were traced, digitized, and stored, and three-dimensional reconstructions were made for calculation of muscle volume. Lateral cephalometric radiographs were analyzed for quantification of selected craniofacial variables. Significant correlations could not be identified between physiological apnea variables and jaw muscle volume. An intersubject variability in masseter muscle volume was identified (range, 22.4-38.1 cm3). Medial pterygoid muscle volume revealed more variability (range, 7.4-15.2 cm3). Masseter muscle volume had a negative correlation with mandibular plane and gonial angle, and a positive correlation with posterior face height, ramus height, posterior face length, condylar center to first molar point length, gonion to pterygomaxillary fissure length, and the ramus height/anterior face height ratio. Medial pterygoid muscle volume showed a positive correlation with posterior face height, ramus height, posterior face length, and the lengths between condylar center to first molar contact point, gonion to pterygomaxillary fissure, and antegonion to key ridge. Subjects with large masseter and medial pterygoid muscle volumes had flat mandibular and occlusal planes, and small gonial angles.
Adult↗
Associations between jaw-opening muscle activity and craniofacial morphology.
The purpose of this study was to investigate the relationship between jaw-opening muscle activity and craniofacial morphology in a sample of 64 adults with skeletal Class I malocclusions. EMG recordings from the inferior head of the right lateral pterygoid and the anterior belly of the right digastric muscle were analyzed together with mandibular displacement data sampled simultaneously with a kinesiograph. Incisor separation at the rest position and the threshold mandibular rotation position which corresponded to the onset of muscle activity in response to a graduated mandibular rotation were identified. Incisor separation was converted to a mandibular angle on lateral cephalograms. Anatomic points were digitized and sixteen traditional cephalometric variables were determined. The rest position angle did not correlate with the threshold angle for the anterior belly of the digastric muscle, but a significant correlation was identified with the inferior head of the lateral pterygoid muscle. One canonical correlation (r = 0.741; p less than 0.01) was identified between the mandibular rotation and dentoskeletal variables. Negative loadings with lateral pterygoid muscle threshold and rest position angles were obtained. The corresponding dentoskeletal variables had a positive loading with mandibular plane angle, total and lower anterior face height and gonial angle and a negative loading with lower posterior face height. The results suggest a possible relationship between lateral pterygoid muscle activity at two specific mandibular positions and the resultant form and posture of the mandible.
Cephalometry↗
Unoperated adult cleft lip and palate: changes in form and function after operation.
This report describes the occlusion and craniofacial morphology--together with changes in tongue activity during swallowing before and after surgical correction--in a 26-year-old female patient with unilateral cleft lip and palate. Cross-bites were not observed before or after repair. Lateral cephalometric findings revealed a convex profile with a normal anterior cranial base length, a flat mandibular plane, and a short lower-anterior face height. Preoperative cineradiographic appraisal showed atypical tongue activity during swallowing. The dorsum of the tongue remained high to seal the cleft. The bolus was kept on the floor of the mouth and passed along the lateral margins of the tongue. The swallow duration, as determined by EMG of the tongue, was extremely long when compared with infant-operated cleft lip and palate patients and to noncleft subjects. Postoperatively, tongue function was similar to that in both cleft patients in whom closure was performed in infancy and to noncleft controls.
Adult↗
Undergraduate and continuing education in orthodontics: a view into the 1990s.
It has been projected that up to 40 per cent of clinical practice undertaken by general dentists in major cities in Canada may involve some type of orthodontic therapy by the mid-1990s. This major shift has already started and the University of British Columbia has begun to update its curriculum accordingly. Concomitant with a decrease in demand for two year postgraduate education courses and a reduced need for the control of decay, academic programmes across Canada are experiencing an increased demand for more extensive orthodontic education by both undergraduate dental students and general practitioners. Current practice trends indicate that more orthodontics is undertaken by general practitioners and that fewer orthodontists are being trained. The Department of Orthodontics at the University of British Columbia utilizes the Dental Performance Simulation System (J. Morita Corp., Japan) for preclinical training in straight-wire edgewise techniques. In their second year, students fit and cement bands, bond brackets, ligate archwires and fit and adjust headgears on the Simulation System. Two years of clinical sessions (3 hours/week) follow this preclinical training. By carefully selecting only Class I non-extraction cases that can be completed ideally in eight months or less of active edgewise therapy, a realistic generalist/specialist division of labour has been developed. To fully meet the anticipated general practice orthodontic demands in the 1990s, undergraduate academic programmes must be prepared to significantly alter current overall curriculum objectives.
Canada↗
Three-dimensional CT reconstructions of tongue and airway in adult subjects with obstructive sleep apnea.
The interaction between airway and tongue structures in a sample of 25 adult men with obstructive sleep apnea was quantified on the basis of a series of preoperative CT slices obtained for each subject. Tracings were completed for tongue, and right and left nasal, nasopharynx, oropharynx, and hypopharynx structures; computer graphics were used to obtain superior and lateral three-dimensional reconstructions of all structures for each subject. In addition, cross-sectional areas of specific sites of airway constriction, surface area, volume, and ratio calculations were completed. The majority of the constrictions occurred in the oropharynx (0.52 +/- 0.18 cm2), but six subjects had two constrictions--one in the oropharynx and one in the hypopharynx. The airway had a mean volume of 13.89 +/- 5.33 cm3, whereas tongue volume ranged from 44.03 to 99.56 cm3 with a mean of 71.96 +/- 13.41 cm3. Subjects with more severe obstructive sleep apnea tended to have larger tongue and smaller airway volumes. The more obese subjects showed larger tongue surface areas and smaller airway surface areas. To determine the structural relationships between airway and tongue variables, a series of logarithmic plots was determined. An isometric relationship characterized tongue surface area and tongue volume. A logarithmic plot of oropharyngeal airway vs. tongue volume showed a negative allometric relationship. Tongue volume increased more rapidly than airway volume in subjects with obstructive sleep apnea. Subjects with large tongue volumes were observed to experience significant complications at the time of surgical treatment. Quantification of the volume of the oropharynx and its relationship to tongue volume provide an overview of the interaction between these structures.
Adult↗
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.
Adult↗
Dentoskeletal and tongue soft-tissue correlates: a cephalometric analysis of rest position.
The relationship between dentoskeletal and tongue soft-tissue variables has been quantified in a sample of 60 adult females with normal and anterior open-bite malocclusions. Three lateral rest-position head films were obtained for each subject. A principal component analysis reduced the data base and six significant canonical correlations were identified. The first canonical correlation (r1 = 0.962) represented a size-related correlation factor between the two groups of variables. Subjects with characteristics of a short face syndrome and some evidence of overbite had tongue tips positioned below the lower occlusal plane (r2 = 0.929). In contrast, skeletal open-bite subjects (r4 = 0.759) revealed tongue tips ahead of and above the lower incisor teeth with the mandible in the rest position. Undererupted mandibular teeth (r5 = 0.666) were associated with a reduced tongue height and an inferior epiglottis; short tongue length (r6 = 0.563) correlated with a linear combination of upright central incisors, a small overjet, a low ANB angle, unerupted maxillary and mandibular teeth, and a steep occlusal plane. The multivariate statistical analysis extracted clinically significant associations between tongue soft-tissue and dentoskeletal variables. Tongue posture at rest in skeletal open-bite subjects appeared to be related to incisor position.
Adolescent↗
Multiple regression analysis of craniofacial and jaw muscle variables in control and deep-bite subjects.
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Adolescent↗
Associations between anterior temporal, masseter, and orbicularis oris muscle activity and craniofacial morphology in children.
In a sample of children with Class I (n = 18), Class II, Division 1 (n = 25) and Class II, Division 2 (n = 12) malocclusions, the relationship between jaw muscle activity and specific craniofacial variables has been quantified. Muscle data were obtained from the temporal, masseter, and orbicularis oris muscles at rest, in maximum intercuspation, and during clenching, jaw opening, and swallowing. Contrasts in means of the three skeletal groups identified differences in both the craniofacial and muscle variables. Orbicularis oris muscle amplitude was greater at rest and in maximum intercuspation in Class II, Division 2 subjects. Anterior temporal amplitude during clenching was significantly lower in Class II, Division 1 subjects. A principal component analysis reduced the data base, and three canonical correlations were identified at the 0.05 level of significance. Significant canonical correlations could not be found between the cephalometric data and clench, swallow, or jaw-opening tasks, which suggests no dependency between these factors. Two canonical correlations were found for the rest position data. A linear combination of masseter and orbicularis oris activity and incisor separation was correlated (r1 = 0.758) with a linear combination of mandibular unit length, upper and lower central incisor angulation, and SNOP. The second rest canonical correlation (r2 = 0.733) involved the anterior temporal muscle and a series of sixteen cephalometric variables. For the maximum intercuspation data, orbicularis oris amplitude was correlated with a linear combination of upper incisor angulation and SNOP variables (r1 = 0.727). The multivariate statistical analysis extracted a clinically significant association between orbicularis oris muscle activity and incisor position.
Cephalometry↗
Canonical correlations between masticatory muscle orientation and dentoskeletal morphology in children.
In order to identify associations between the orientation of the superficial masseter and temporalis muscles and dentoskeletal morphology in a sample of fifty-five children with various malocclusions, eight muscle-orientation variables (relative to the occlusal plane) and twenty-three dentoskeletal variables were evaluated from lateral head films. The thirty-one measurements were reduced to six muscle-orientation and sixteen dentoskeletal variables by a principal component analysis. Three canonical correlations were identified between the muscle orientation and dentoskeletal variable groups at the 0.05 level of significance and canonical loadings were determined for each set of variables. The first canonical correlation (r1 = 0.931) represents a growth-related correlation factor between the masticatory muscle insertion positions relative to the occlusal plane and the dimensional and positional changes of craniofacial structures during growth. The second canonical correlation (r2 = 0.846) may account for an operational artifact in the geometric measurement process, and the third canonical correlation (r3 = 0.813) suggests an association between superficial masseter muscle orientation relative to the occlusal plane and mandibular form. This report confirms the usefulness of multivariate statistical methods to extract latent associations between muscle orientation and craniofacial morphology; the results obtained suggest a contribution from the geometric orientation of the masticatory muscles to the development and maintenance of the dentoskeletal system.
Adolescent↗
Tongue movements--brainstem mechanisms and clinical postulates.
Specific excitatory and inhibitory influences on protrusive (P) and retrusive motoneurons in the hypoglossal nucleus of cat have been documented. Stimuli delivered to peripheral branches of the auriculotemporal nerve which innervate the temporomandibular joint activate both genioglossus (GG) single units and synaptically-evoked responses in P motoneurons. Similarly, stimuli delivered to the glossopharyngeal (IX) and superior laryngeal nerves activate P motoneurons. Any one of these three stimuli may contribute to the various responses in which the GG muscle is known to participate. In contrast, stimuli applied to the tongue itself (lingual and IX nerves) result in a retrusive tongue movement. These brainstem mechanisms suggest specific therapy regimens for the treatment of skeletal open-bite malocclusions where resting tongue posture appears to be a primary etiological factor.
Afferent Pathways↗
Operational performance of the Reflex Metrograph and its applicability to the three-dimensional analysis of dental casts.
The purpose of the present study was to investigate the applicability of a new instrument (the Reflex Metrograph) to the three-dimensional analysis of dental casts. In this system, a dental cast, placed in front of a semireflecting mirror, creates an identical image behind the mirror. The measurement of a point is made by aligning a light source behind the mirror in coincidence with the image of a specific point on the object. The light source is carried on a three-dimensional slide system, and coordinates are digitized for sampling by the computer. Measurement accuracy of the instrument was evaluated for three measuring points determined on a maxillary dental cast placed in six different locations. In addition, differences in the performance skills of ten operators were evaluated. The results indicate that digitization of a point in three planes of space can be undertaken without direct contact of the object and that a consistent measurement accuracy can be obtained, regardless of differences in the location of the cast relative to the mirror or in the anatomic shape of the measured areas. In addition, operators with no previous experience can determine specific points to an accuracy of +/- 0.1 mm, with a minimal amount of training. Finally, measurement by the same operator for a pooled sample is recommended in order to avoid interoperator measurement error when determining linear distances.
Computers↗
Muscle activity during function and its correlation with craniofacial morphology in a sample of subjects with Class II, Division 1 malocclusions.
To evaluate the relationship between craniofacial morphology and jaw muscle activity in a sample of skeletal Class II, Division 1 malocclusions, electromyographic and cephalometric analyses were undertaken in a sample of twenty adolescent children. For each subject, electromyographic activity was recorded from the left anterior temporal, masseter, and orbicularis oris muscles at rest, in maximum intercuspation, and during clenching. In addition, mandibular displacement was measured simultaneously with a kinesiograph, and twenty-seven anatomic points were digitized from a lateral head film. A computer-based system was used to sample the data and to determine correlation coefficients between selected parameters. Five significant correlations were found (at the 99 percent confidence level) for the rest position data. High anterior temporal amplitude was correlated with flat palatal planes and large ramus heights; high masseter amplitude correlated with upright maxillary incisors. Anterior positions of the mandible at rest correlated with flat occlusal planes and small pogonions. In contrast, significant correlation coefficients could not be identified for the maximum intercuspation recordings. However, low orbicularis oris muscle amplitude during clenching was correlated with high lower face height, overerupted mandibular molars, and elongated maxillary incisors. This interdependence of jaw muscle activity and craniofacial morphology in Class II, Division 1 subjects suggests a contribution from the musculature to the development of the dentition.
Cephalometry↗
[A dental performance simulation system for preclinical instruction in orthodontic education].
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Orthodontics↗