The 7/8 crown: a lost art.

Historically, the longevity of teeth restored with gold inlays, onlays, crowns, and partial veneer restorations is excellent. However, in-office computer-aided design and computer-aided manufacturing restorations, laboratory-constructed all-ceramic bonded restorations, and conventional ceramo-metal restorations are more common. The high price of gold, the difficulty of the preparation, and the fact that most dental schools are de-emphasizing the teaching of partial veneer restorations has created a situation whereby the 7/8 crown is rarely viewed as the treatment of choice. Time and experience will determine if the new ceramic materials, along with the all-important bonding agents, can achieve the success of a well-done, all-gold restoration.

Beta blockade to prevent atrial dysrhythmias following coronary bypass surgery.

BACKGROUND: Atrial fibrillation and atrial flutter (AF) frequently complicate coronary artery bypass surgery (CABG) and increase hospital stay as well as morbidity. Studies of drug prophylaxis to prevent AF with beta-adrenergic blocking agents administered in fixed doses have had conflicting results. METHODS: One hundred patients were randomized to receive metoprolol or placebo following CABG. A dosing algorithm was used to achieve clinically significant beta-adrenergic blockade. RESULTS: There was no significant difference between the incidence of AF in the metoprolol (24%) and placebo (26%) groups. However, the incidence of AF in all patients having CABG at this institution declined over the period of the study from 31% to 23% (P < .025), in association with the adoption of a continuous technique of cardioplegia delivery. CONCLUSIONS: Metoprolol is not efficacious for the prevention of post-CABG AF even when dosage is titrated to achieve clinical evidence of beta blockade. It is likely that the adoption of a continuous cardioplegia technique caused a reduction in our incidence of post-CABG AF.

Marginal fit of electroformed ceramometal crowns.

PURPOSE: A method of fabricating ceramometal crowns using gold copings produced by an electroforming process has been described, which purportedly results in restorations exhibiting an excellent marginal fit. This study compares the fit of electroformed ceramometal crowns with ceramometal crowns fabricated using conventional lost wax casting techniques. MATERIALS AND METHODS: Electroformed and conventional ceramometal crowns were fabricated for prepared extracted teeth. Specimens were cemented, embedded in acrylic resin, sectioned, polished, photographed, and measured to compare marginal fit. RESULTS: Marginal fit of electroformed ceramometal crowns was superior to the fit of ceramometal crowns fabricated using conventional casting techniques. The difference was statistically significant at a P = .05 level. CONCLUSIONS: Crowns utilizing copings fabricated by electroforming methods appear to have a fit superior to conventional ceramometal crowns fabricated using copings made by lost wax casting. The ease in laboratory electroforming techniques and the esthetic advantages of a gold-colored coping can be capitalized on without concerns of a poorer fit.

Reliability of standard foot radiographic measurements.

Fifty standing dorsoplantar and lateral foot radiographs were obtained on a consecutive series of patients seen in an orthopaedic foot and ankle clinic. These radiographs were duplicated, and eight common foot measurements were made on each pair by six experienced examiners. Measurements were made in two ways: first by a subjective visual assessment, and second by quantitative evaluation made according to strictly defined criteria. All measurements were made under controlled, ideal conditions with similar high quality goniometers. The results demonstrated overall greater reliability in the quantitative methods than the non-quantitative methods. For each of the quantitative techniques, a cumulated frequency distribution of differences between examiners was calculated. The approximate 95% bounds for these measures were: hallux-metatarsophalangeal angle = 6 degrees, first intermetatarsal angle = 4 degrees, metatarsophalangeal-5 angle = 11 degrees, fourth intermetatarsal angle = 4 degrees, AP talocalcaneal angle = 20 degrees, lateral talocalcaneal angle = 12 degrees, sesamoid station = 2 grades, and forefoot width = 5 mm. Physicians using these parameters to make decisions regarding patient care and clinical outcomes need to keep in mind these potential errors in making foot radiographic measurements.

The influence of x-ray orientation on the first metatarsocuneiform joint angle.

The purpose of this study was to determine whether the first metatarsocuneiform (MC) joint angle is affected by the orientation of the x-ray beam, whether it can be reliably measured, and, therefore, whether it is a valid indication of tarsometatarsal fusion as an adjunct to hallux valgus surgery. Each of seven cadaver feet were loaded to 350 newtons in a Plexiglas apparatus that maintained the foot in a plantigrade position. The loading apparatus was positioned to simulate a 10 degrees, 20 degrees, and 30 degrees dorsal angulation of the x-ray beam. At each position, simulated weight-bearing radiographs were obtained for each foot. Three observers independently measured the first MC angle and the first intermetatarsal (IM) angle on all the radiographs. The data collected were analyzed by the components of variance. The inclination of the first MC joint lessons significantly as the orientation of the x-ray beam changes from a 10 degrees to a 20 degrees tilt. The three examiners' mean MC angles and mean IM angles from the three sets of radiographs were not statistically different from each other, implying that there were minimal examiner-to-examiner differences in measuring these angles. There were no significant differences in measurements between examiners, suggesting that the first MC and first IM angles can be measured reliably. There was a significant difference in the first MC angle, with different orientations of the foot with respect to the x-ray beam, suggesting that this angular measurement should not be used as an indication for tarsometatarsal arthrodesis.

Cuboid stress fractures: a report of two cases.

Stress fractures of the tarsal cuboid are rare. The literature contains three reported cases. This report presents two additional cases. These two occurred in collegiate athletes, and mimicked peroneal tendonitis on presentation. History, physical examination, plain radiographs, and bone scan were used for diagnosis. Treatment consisted of immobilization and activity modification, with complete resolution of symptoms in both cases.

Foot and ankle manifestations of Charcot-Marie-Tooth disease.

The term Charcot-Marie-Tooth disease represents a spectrum of neurological dysfunction more recently described as hereditary motor-sensory neuropathies. An abnormality of myelination is thought to be responsible for the clinical manifestations. While histological findings have been well described, the exact biochemical basis for this disorder remains unknown. Over one half of patients with Charcot-Marie-Tooth disease manifest foot and ankle problems, including pain, weakness, deformity, and, rarely, paresthesias. Characteristic patterns of neuromuscular weakness have been identified. Bilateral pes cavovarus is the most common pathologic foot deformity seen. The specific components include hindfoot varus, anterior or forefoot cavus, and, often clawtoes. The etiology of this abnormal foot posture usually results from tibialis posterior overpowering peroneus brevis coupled with peroneus longus overpowering tibialis anterior. Multiple treatment options have been described. Rationale for specific tendon transfers, soft tissue release, osteotomies, and arthrodesis is discussed. Results of surgical intervention are difficult to interpret and compare because of the wide spectrum of both neurological dysfunction and described operative procedures. In the presence of flexible deformity, early soft tissue release and tendon transfers may help prevent or delay more extensive bony procedures. The clinical results of triple arthrodesis in the Charcot-Marie-Tooth disease patient appear to deteriorate with time. Genetic transmission, progression of the neurological dysfunction, flexibility of the deformity, distribution of muscular weakness, and anticipated foot demands vary a great deal within this patient population. Treatment decisions, therefore, must be individualized and based upon a clear history, careful examination, and well-defined patient goals.

Reactivity-based hydrocarbon controls: scientific issues and potential regulatory applications.

The California Air Resources Board and the South Coast Air Quality Management District hosted a conference on April 8-9, 1991 to examine the scientific issues associated with reactivity-based hydrocarbon controls, and to identify the obstacles to potential regulatory applications. Owing to residual uncertainties in the underlying science, and the complex emission measurement capabilities required for enforcement, a general consensus emerged on the need for further research before application of reactivity-based controls. A number of recommendations were made for research on the remaining scientific, enforcement, and policy issues, many of which have led to cooperative efforts initiated since the conference.

Marginal fit of castable ceramic crowns.

The objective of this study was to measure marginal fit of castable ceramic versus gold crowns. Full veneer gold and ceramic crowns were made on Ivorine dies. Crowns were cemented, embedded, sectioned faciolingually and mesiodistally, and photographed for measurement of absolute marginal discrepancies (cavosurface angle to casting margin) to evaluate fit. Results revealed no statistically significant differences in fit among four locations around the margins of either ceramic or gold crowns. There was no statistically significant difference in the combined absolute marginal discrepancy (fit) between ceramic and gold crowns. The variance of the combined absolute marginal discrepancy (fit) of the ceramic crowns was significantly different than that of the gold crowns (p = 0.01 level). The standard deviation (variability) of the gold crowns was more than twice that of the ceramic crowns. Randomized block ANOVA demonstrated statistically significant differences among individual gold crown specimens, but none among individual ceramic crown specimens.

Measurement of cardiac dimensions with two-dimensional echocardiography in the living horse.

Two-dimensional echocardiography (2DE) was performed on 22 unsedated Thoroughbred and part Thoroughbred horses weighing between 411 and 650 kg to establish normal reference values for 2DE measurements. Animals stood during examinations performed with a 3.5 MHz mechanical sector transducer using various transducer positions and tomographic planes. Right ventricular diameter (RVD), ventricular septal thickness (VSTh), aortic diameter (AoD), area of the chordal lumen of the left ventricle (CTA), left ventricular diameter (LVD) and left atrial diameter (LAD) were determined at ventricular end-diastole (Ed) and/or end-systole (Es). Fractional shortening (FS) of the left ventricle and end-systolic left atrial to aortic ratio (LAD-Es:AoD-Es) also were calculated. Echocardiographic data were related to body weight by linear regression analysis. Intra-observer variability was checked in five horses by measuring each parameter during each of 10 consecutive cardiac cycles. The 2DE data were compared with M-mode values in published reports. In the 18 horses whose weight did not exceed 551 kg, repeatable recordings of good quality were obtained, and 2DE measurements could be made using intra-cardiac reference points. Increasing body weight proved to impose substantial limitations on measurements taken with the available machine and transducer. This problem might be overcome by using probes of lower frequency or equipment with higher quality image display at greater depth. The following parameters correlated significantly to body weight: VSTh-Es (r = 0.69; P less than 0.01). AoD-Es (r = 0.64; P less than 0.01) and CTA-Es (r = 0.84; P less than 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)

Postoperative pulmonary edema in young, athletic adults.

Pulmonary edema secondary to postextubation laryngospasm is a potentially life-threatening problem, demanding early diagnosis and prompt treatment. We believe that this problem has been grossly underestimated in its incidence, as only seven adults have been reported in the English literature, whereas seven adults have been observed at our institution in only a 24 month period. All were young, healthy, athletic adult males (average weight, 218 pounds) who underwent relatively minor, uncomplicated surgical procedures under general anesthesia. Five of these patients were collegiate and/or professional athletes and had meticulous medical records detailing their clinical course. Clinical laryngospasm was noted immediately following extubation and anesthesia by mask with subsequent pulmonary edema. The diagnoses were confirmed by clinical examination, arterial blood gas determinations or pulse oximetry, and chest roentgenogram. Four adults required reintubation. Six of the seven adults demonstrated very rapid resolution of the pulmonary edema with prompt diagnosis and institution of a therapeutic regimen including oxygen, diuretics, reintubation, and/or positive pressure ventilation. In one patient, the problem was not immediately recognized, and progressed to florid pulmonary edema requiring emergent intubation 14 hours later in the emergency room, and 3 days of mechanical ventilation. The etiology of pulmonary edema following upper airway obstruction represents an interplay between several factors: cardiogenic and neurogenic mechanisms, as well as hypoxia contribute. In this group, excessive negative intrathoracic pressure generated by forced inspiration against a closed glottis is the most likely, consistent, and logical explanation. This study suggests that young, healthy, athletic males may be at increased risk for this complication.(ABSTRACT TRUNCATED AT 250 WORDS)

Anatomical validation of two-dimensional echocardiography in the horse.

This study was performed on 15 horses to validate the cardiac anatomy as imaged with two dimensional echocardiography (2DE) and to determine the accuracy of intracardiac measurements. 2DE images were recorded in five horses in life with a Diasonics DRF100 ultrasound system and a 3.5 MHz transducer in different tomographic planes. After slaughter, the hearts were fixed in 10 per cent formalin. To compare in vivo and in vitro results, the specimens were suspended in a water-filled tank and 2DE images were made using the same transducer positions as in life. In vitro 2DE and autopsy measurements of the same planes and parameters were also taken on a further 10 hearts, and the results were statistically compared. The in vivo 2DE images corresponded well with both in vitro 2DE recordings and anatomical sections. Repeatable imaging of each tomographic plane was possible on the post mortem hearts using intracardiac reference points. Comparison of parameters measured during in vitro 2DE and autopsy demonstrated a significant correlation between all 2DE and autopsy data (r: 0.879 to 0.926; P less than 0.001). Repeated 2DE measurements of each parameter showed a good reproducibility with coefficients of variation (CV%) varying between 4.6 to 10.6 per cent. The results suggest that 2DE is a reliable method for accurate anatomical evaluation of the equine heart and show the potential application of quantitative two dimensional echocardiography in the living horse.

Left ventricular volume determination in the horse by two-dimensional echocardiography: an in vitro study.

This study was designed to evaluate the accuracy of two-dimensional echocardiography (2DE) in determining the left ventricular volume (LVV) of the horse in vitro. After examining the shape of the left ventricular silicon rubber casts of four equine hearts, two modified Simpson's rule methods (Model A and Model B) as combinations of conical shapes and one biplane area-length method as a single cone (Model C) were chosen for volume calculations. One long axis and three short axis planes were used for linear and area 2DE measurements, respectively. The ventricular length (L) was calculated from the chordal length (CL) by using a linear regression equation (L = 5.54 + 1.83 CL) obtained by anatomical measurement of these two parameters on 40 normal hearts. The LVV was calculated in 15 formalin-fixed hearts from 2DE measurements with the three geometric models. Left ventricular casts were then made using silicon rubber, and their volumes were determined by water displacement. The calculated volumes were plotted against cast volumes with linear regression analysis. All calculated LVVs correlated well with the cast LVVs (R = 0.921 to 0.957; P less than 0.001). The highest correlation was provided by Model A which best represented the shape of the left ventricle. This model consisted of a truncated cone bordered by the area at the level of the mitral valve and by the area at the level of the chordae tendineae, plus a cone the base of which was the area at the level of the papillary muscles. The results demonstrate the applicability of 2DE for equine LVV determinations in vitro, similar to other species.(ABSTRACT TRUNCATED AT 250 WORDS)

Intraoperative positioning for arthrodesis of the hip with the double beanbag technique.

The double beanbag technique allows the surgeon to select the position of the lower limb before an arthrodesis of the hip. During the procedure, the surgeon can freely manipulate the limb, confident that it can be replaced in the exact position that was chosen for the arthrodesis. The technique is not cumbersome, and only commonly available equipment is needed. For the method to be effective, there must be enough residual motion of the hip to allow positioning and preparation of the skin. Also, rigid internal fixation must be used to maintain the selected position of arthrodesis at the conclusion of the operation.

Considerations in measurement of marginal fit.

The terminology describing "fit" and the techniques used for measuring fit vary considerably in the literature. Although fit can be most easily defined in terms of "misfit," there are many different locations between a tooth and a restoration where the measurements can be made. In this work, the measurements of misfit at different locations are geometrically related to each other and defined as internal gap, marginal gap, vertical marginal discrepancy, horizontal marginal discrepancy, overextended margin, underextended margin, absolute marginal discrepancy, and seating discrepancy. The significance and difference in magnitude of different locations are presented. The best alternative is perhaps the absolute marginal discrepancy, which would always be the largest measurement of error at the margin and would reflect the total misfit at that point.