Measurement of tooth movement

1. Tooth movement relative to the alveolar bone can be precisely described only by superimposing on fixed points in the bone. Implants are the best known way today. Over short-term studies laminagraphy and the use of bony trabeculations are also useful. Remodeling occurs extensively on bony surfaces, making them too labile for use as stable landmarks. To project small amounts of tooth movement based on the use of such methods is so questionable as to represent little better than a guess or a clinical impression. 2. Growth can be separated into vertical and anteroposterior vectors with respect to the dentition. Since the occlusion is the concern, orientation of vertical and anteroposterior vectors to the occlusal plane is a reasonable baseline. The vertical and anteroposterior dental changes may not show a linear relationship in the anterior and posterior parts of the mouth when jaw rotations are occurring. 3. Growth can be disproportionate in either the vertical and/or the anteroposteroir plane of space. If the vertical increments of the anterior face differ from the vertical increments at the posterior face, mandibular rotations occur. This growth is accompanied by dental compensations that tend to mask the rotation. Therefore, open bite and deep bite are frequently skeletal growth problems. 4. Disproportional forward growth of the maxilla or mandible in an anteroposterior direction can lead to Class II or III relations. The growth that leads to Class II or Class III is accompanied by dental migrations that tend to mask this disproportionate growth. Orthodontic treatment of growth disproportionalities usually represents attempts to make the teeth further compensate. If surgical options are elected, the dental compensations should be removed prior to surgery in order to achieve a full surgical correction. 5. The teeth tend to move and grow in the opposite direction of the growth disproportionality. The teeth tend to mask the disproportionality. Thus, in an open bite, the incisors tend to move vertically further than in deep bites. Vertical imbalances may be more difficult to mask. Backward rotation of the mandible requires more vertical movement at the incisor than at the molar just to maintain vertical incisor relationships.

Airway visualization by tantalum inhalation bronchography

A novel technique for the generation of tantalum aerosols (aerodynamic mass median diameter, 5.8 mum; sigma g, +/-2.14) for inhalation bronchography via the mouth was applied in 26 anesthetized dogs. Ventilatory patterns during periods of aerosol inhalation were controlled by either bilateral electrophrenic stimulation of the diaphragm (EPS), or by intermittent, negative pressure at the body surface (INPV). We studied patterns of tracheobronchial deposition with regard to both the sites of particle deposition longitudinally along airways within lobes, and the topographic distribution of aerosol among the lung lobes. Bronchographic patterns were accordingly studied after inhalations by either (1) EPS and INPV in the supine posture with constant tidal volumes, but varied inspiratory flow (30 to 90 liter per min); or (2) EPS with constant tidal volume and peak inspiratory flow in the prine, right, and left lateral decubitus body positions. Under all airflow conditions, the aerosol was deposited on the surfaces of ciliated airways. Deposition was nearly entirely confined to subsegmental bronchi and above with vigorous inspirations, but extended distally to subsegmental bronchi in greater proportion with decreases in the inspiratory flow. Airways among the basal lung lobes were particularly subject to distal subsegmental and bronchiolar deposition with low rates of inspiratory airflow. Regionally, the aerosol was deposited preferentially in dependent lung lobes after inhalations with EPS in the right and left lateral decubitus positions, and in the basal lung lobes with EPS in the supine posture. A greater caudocranial uniformity in lobar aerosol distribution occurred with inhalations by INPV in the supine posture, and by EPS in the prone posture. The canine model strongly suggests that for clinical inhalation bronchography, nonhomogeneities in lobar deposition may be averted by inhalations in multiple body positions, and that deposition of the aerosol may be confined to ciliated airway surfaces by inertial impaction accompanying high rates of inspiratory airflow.

Optimized collimators for scintillation cameras

The use of commerically available tantalum or lead tubes permits convenient fabrication of collimators optimized for specific imaging studies.

The r.b.e. of different energy neutrons as measured by the heamatopoietic spleen-colony technique

The spleen-colony technique has been used for determining the relative biological effectiveness (r.b.e.) for several energies of neutron radiation. Donor mice were exposed for fission and accelerator-generated neutrons at a variety of doses and energies. Immediately after exposure, donor bone-marrow was removed from the hind legs, and standard amounts were injected intravenously into lethally X-irradiated recipients. After 7 days the recipients spleens were evaluated for surface colonies. Dose-response curves were obtained for each type of radiation and the Do was determined. The neutron r.b.e. values from the Do compared with 250kVp X-rays were: reactor 1.58, 252Cf 1:59, and accelerator varied from 2.85 at 1.0 Mev to 0.85 at 13.4 MeV.

A fractured mandible, from initial operation to removal of tantalum mesh. Report of a case

Report is made of a case of fracture of the angle of the mandible. Treatment was attempted with the Sampson pericortical bone clamp, but was unsuccessful. Routine use of intraosseous wire led to a localized osteomyelitis, without union of the fracture. Treatment then was made with a particulate marrow graft contained within a tantalum mesh screen. The screen was removed 30 months postoperatively.

Measurement of midwall myocardial dynamics in intact man by radiography of surgically implanted markers

Tiny radiopaque helices (0.85 times 1.5 mm) of pure tantalum wire were implanted by means of a simple insertor instrument into the left ventricular myocardium in 24 patients at the time of cardiac surgery. The markers were positioned in such a way as to outline the profile of the left ventricle when viewed in a 30 degree right anterior oblique projection. Biplane studies showed that all markers could be placed very nearly in a plane using the surface anatomy of the heart as a guide to implantation. Implantation of markers required approximately two minutes. No intraoperative or postoperative complications ascribable to the markers have occurred. They remain firmly in place and allow acquisition of a noninvasive ventriculogram at any time after surgery. The dynamic geometry of the left ventricle was determined by analysis of cineradiograms of these markers. Utilization of a single-plane (right anterior oblique) cineradiogram to obtain measurements of major transverse ventricular diameters, mean circumferential shortening, and circumferential shortening velocity results in underestimation of lenghts by 1.4%, overestimation of shortening by 1.2% of end-diastolic length, and overestimation of velocity by 0.05 circ/sec, when compared with values obtained simultaneously from biplane cineradiograms.

Characteristics of tantalum dust and dust generator for bronchography

The two tantalum powders, "5mu" and "1.4mu", available from Fansteel Metals, are characterized with respect to particle size. Results show that these powders cannot be used directly for tantalum bronchography, but require fractionation to achieve a range of sizes for effective use in tantalum bronchography. This task can be accomplished with the BAHCO Micro Particle Classifier. The powder designated "1.4mu" is superior to the "5mu" powder because about 60% by weight can be salvaged by separation for use in bronchography, compared to only 7% by weight of the "5mu" powder. Theoretical considerations of particle deposition in the human respiratory tract indicate that the material obtained with throttle 16 of the BAHCO is best suited for tantalum bronchography. The dust generator is a good tool to deliver a dust cloud into the lung. The generator can operate for approximately 2 1/2 hours before the brush of the brush feed must be replaced; a procedure taking about 10 min. Additional maintenance is unnecessary. The breathing resistance of 1.1 inch of water imposed by the generator system, and which has to be overcome by the patient, is judged acceptable. The bronchograms obtained by introducing tantalum dust for 10 min into an artificially ventilated dog lung were clear, with deposition heaviest at bifurcations. These results suggest that the generator should now be used for human bronchography.

Non-contractile movement of tantalum powder in the canine rectum

Caudad movement of trantalum particles in the rectum was observed in 5 recumbent anesthetized beagle bitches in the absence of muscular contractions as monitored by intrarectal balloons. The movement did not occur after injections of atropine or glucagon alone but did occur when a bisacodyl suppository was introduced in addition to the injection of glucagon. Along with direct observation of rectal mucosa, this strongly suggests the role of mucus as a carrier of the particles.

Post mortem recovery of mandibular osseous graft with cellulose acetate filter. A case report

A surgical procedure was performed to re-establish both aesthetics and functional form to a post partial mandibulectomy patient. A particulate, autogenous osseous graft from the hip was supported by a mandibular tantalum splint lined with a cellulose acetate filter. The patient developed metastatic carcinoma in the donor graft site and lung. The mandibular graft and supporting tissue was removed postmortem and examined histologically. It was observed that normal bone reconstruction was taking place and that union of mandibular bone and graft was evident. Secondary squamous cell carcinoma had invaded the symphysis area of the graft. It is also of interest to note that the tumour was mot able to penetrate those areas where the cellulose acetate filter was present.

Natural history of pulmonary thromboemboli in dogs. Serial radiographic observation of clots labeled with powered tantalum

Powdered tantalum was blown onto the surface of blood clots from 10 dogs. After autologous, tantalum-labeled clots were injected into a systemic vein in each dog, the dogs were sacrificed at varying times over a 5-week period. Microscopic sections showed the tantalum remained attached to the intraluminal clots throughout this period. No appreciable dispersion of label into extravascular parenchyma was observed. Serial roentgenograms demonstrated (a) initially, the labeled clots in the pulmonary arterial tree, (b) lysis of the clots, as indicated by progressive decrease in the breadth of the tantalum labels, (c) peripheral movement of the labeled clots, and (d) eventual fragmentation of the labels.

A comparative study of the effects of dry vs. humidified ventilation on canine lungs

To compare the effects on canine ciliary and bronchial mucosal function of varying periods of ventilation with dry vs. humidified gas mixtures, 29 anesthetized dogs underwent 2, 4, and 6 hours of ventilation through a Carlen's double-lumen tube. Six dogs were evaluated by clearance studies, nine by differential bronchospirometry, six by surfactant studies, six by electron microscopy, and two by ventilation scanning. By means of two separate respiratory systems, dry gas (DG) was used to ventilate the right lung, and humidified gas (HG) ventilated the left lung in each dog. Serial chest roentgenograms showed more rapid clearance of inspired tantalum dust from the HG-ventilated lung in each of the six dogs, the disparity in clearance between the two lungs being more pronounced after longer periods of ventilation. The surface tension in DG-ventilated lungs increased fourfold, whereas in HG-ventilated lungs it increased only twofold as compared to preoperative values. Longer periods of ventilation did not change the surface tension appreciably in either DG- or HG-ventilated lungs. Scanning electron micrographs of bronchial mucosa from DG-ventilated lungs showed tangling and matting of cilia with a granular and stringy material attached to most cilia; these changes were much less pronounced in HG-ventilated lungs. Bronchospirometric studies showed an increase in ventilatory function in each of the lungs ventilated with the HG mixture (percent Vo2 on 100 percent oxygen increased 27.7 percent) to compensate for the decreased gas exchange provided by the contralateral DG-ventilated lung. Function in each of the lungs returned to normal within 24 hours. Ventilation scans with Xenon133 showed no apparent change in isotope uptake in the HG-ventilated lungs as compared to the DG lungs during the first 24 hours after ventilation. The observations from the present study suggest that ventilation of canine lungs with DG for 4 or more hours dries mucus and transiently retards mucociliary clearance and gas exchange. These changes may be minimized by ventilation with a humidified gas mixture. Application of these findings to patients undergoing prolonged general anesthesia and to lung preservation studies is suggested.

Postmortem assessment of chronic airways obstruction by tantalum bronchography

Tantalum bronchography was performed on 22 left lungs obtained at necropsy. Seven were from patients dying in cor pulmonale as a result of chronic airways obstruction and 15 were from unselected necropsies. Of the latter group, nine had no evidence of respiratory disease and six had pathological changes of emphysema and bronchial mucous gland enlargement when the lungs were examined following formalin fixation. A range of changes in the bronchographic appearances from the normal to the groosly abnormal is illustrated. The main changes in severely diseases lungs were: irregularity of the bronchial walls, failure of the walls to taper towards the periphery, areas of narrowing and dilatation, and 'pooling' of tantalum at the ends of airways. A count was made of the numbers of small airway branches in the most distal 4 cm of the lung and also of the number of airways of less than 1 mm in diameter. Patients dying in cor pulmonale had a significantly reduced total number of patent small airways in the area measured and also fewer patent airways of less than 1 mm diameter compared to both the other groups. Histological study of four of the lungs in greater detail revealed that the reduction in small airways filling was the result of a combination of obliteration and obstruction of the lumen by pus. Tantalum bronchography provides a good indication of the state of the bronchial tree at the time of death, and the changes seen are the result of both acute and chronic disease processes.

Simultaneous glottic and supraglottic laryngeal webs: report of a case

In a rare case of simultaneous glottic and supraglottic webbing a tantalum keel, as described by McNaught, and a silcone elastomer keel, as described by Montgomery, were placed simultaneously via laryngofissure. Use of different materials appeared to have no bearing on the final, successful outcome.

Bronchial hysteresis in excised lungs

1. Intrapulmonary bronchi in excised dog lungs were outlined with tantalum dust and stereoscopic radiographs taken during deflation and inflation of the lung with air, saline, Ringer or EDTA solutions. Dimensions of airways as a percentage of their values at full inflation were calculated from measurements of the stereoscopic X-ray images. 2. The mean deflation-inflation diameter difference at a transpulmonary pressure of 5 cm H2O was 20% in the air-filled lung, 9% in the saline filled preparation and 2% after filling with EDTA in saline. 3. These results show that the intrapulmonary bronchi have an intrinsic hysteresis separate from the hysteresis imposed on them by the expansion of the surrounding parenchyma. This intrinsic hysteresis is mainly due to the tone of the smooth muscle in the bronchial wall.

In vivo dimensional response of airways of different size to transpulmonary pressure

We studied four supine dogs that were anesthetized with pentobarbital, intubated, and ventilated with a piston pump. The dimensional response of central (CAW) (greater than 2 mm diam) and peripheral airways (PAW) (smaller than 2 mm diam) to changes in transpulmonary pressure (Ptp) was determined by progressive increments in tidal volume (VT). A specially designed electronics relay circuit permitted this relationship to be obtained for points of no flow during tidal volume breathing: i.e., preinspiration (FRC); end inspiration (FRC + VT). The airways were dusted with powdered tantalum. Six airway divisions were identified: four CAW: trachea, main stem, lobar, segmental; and two PAW: subsegmental, and lobular. AP and lateral roentgenograms were obtained by standard technics and primary magnification (mag factor 2). Airway diameters were plotted as a function of transpulmonary pressure between 3 and 26 cmH2O with the diameter at total lung capacity expressed as 100%. The data show that: 1) there is significant distensibility above 5 cmH2O for all airways from the trachea to the lobular airways; 2) that the pressure-diameter plot is a linear plot for each airway from 3 to 26 cmH2O with R values between 0.846 and 0.957; 3) the peripheral lobular airways are more distensible than the central airways (P smaller than 0.05). We attribute the difference in distensibility of the peripheral lobular airways to their lack of cartilaginous support, and their decreased muscular support when compared to the CAW.