Biomedical subjects
Publications and source records attributed to M H Anderson.
Treating the disease, not the symptoms, is the change in managing dental caries. As researchers supply the tools, dentists can apply more efficient and realistic methods for better patient care.
When you balance the benefits and liabilities of a modern dental amalgam, it is one of the materials that comes closet to being an ideal restorative. Its numerous clinical advantages have, in the past, made it a standard in dental care. The profession's and public's awareness of the issues surrounding the mercury content, coupled with the biased reporting of the controversy by less than responsible journalists, have served to impung the material. The dental profession has used the material successfully in its present form for almost 100 years. There are still valid questions about the material that require further scientific investigation. Investigators continue to make improvements in the alloy's strength and handling properties while limiting the mercury-release potential of the material. As we move into the twenty-first century, we are again told we will soon have a suitable replacement for dental amalgam. That is an often repeated promise for this multifunctional product. Time and sound research into the longevity and liabilities of all restorative materials as applied in the office of the general practitioner will tell us if amalgam is or is not going to disappear from the dental armamentarium in the near future.
An in vitro study was conducted (1) to compare fracture strength of amalgam restorations retained with retentive slots of different lengths when stressed with a transverse force, (2) to determine if beveling the slot preparation resulted in an increase in fracture resistance to a transverse force, and (3) to evaluate the incidence of unrestorable tooth fracture as it relates to slot preparation length. Six groups of 10 specimens were prepared with slots of increasing length, with each specimen receiving four slots of equal length. Slot preparations in group 6 were beveled. Results showed that shorter slot preparations provided statistically equal amounts of resistance to a transverse force as did the longer preparations. Beveling the slot preparation did not significantly increase fracture strength. Specimens restored with longer slot preparations failed unrestorably more often than restorations retained with shorter slot preparations.
The incorporation of water-soluble polymers and/or vinyl monomers into glass-ionomer cements can yield toughened "hybrid cement-composites". This study compared a commercial water-hardening glass-ionomer cement and seven experimental hybrids in their bonding to both dentin and Silar composite. The cements were sanded and phosphoric-acid-etched or left with an unaltered matrix-formed surface when adhesion to composite was tested. The seven hybrids included: 15% 2-hydroxyethyl methacrylate (HEMA) with appropriate initiators/activators, 29% HEMA, 27% HEMA + 0.5% polyacrylic acid (PAA), 0.5% PAA, 1.5% PAA, 2.5% polyvinyl alcohol, and 2.5% gelatin. Acceptable bond strengths to applied composite and to dentin were observed for most of the modified hybrid cements. There were higher bond strengths with composite when the hybrids were left unetched. Bonding of some unetched, HEMA-containing cements achieved bond strengths (29% HEMA, 10.09 MPa) significantly higher than those of the unmodified cement (4.92 MPa). Resin-modified cements may promote better bonding by improved interaction and compatibility with the resin component of the composite.
The effects of procainamide and dofetilide (pure Class III antiarrhythmic agent) on the signal-averaged ECG (SAECG) were examined in relation to the results of programmed ventricular stimulation studies in 25 patients with inducible sustained monomorphic ventricular tachycardia. Procainamide prolonged significantly the total QRS and low amplitude signal durations (140 +/- 31 msec vs 166 +/- 48 msec, P < 0.0001; 50 +/- 25 msec vs 65 +/- 38 msec, P < 0.002, respectively) whereas the root mean square voltage of the last 40 msec of the QRS complex was significantly reduced (22 +/- 21 microV vs 13 +/- 12 microV, P < 0.006). Procainamide was effective (prevention of the inducibility of sustained ventricular tachycardia or prolongation of the cycle length of ventricular tachycardia by > 100 msec) in 15 of 27 drug trials. Of the procainamide induced SAECG changes, the fractional prolongation of the total QRS duration was the best parameter that identified effectively treated patients (24% +/- 16% in responders vs 10% +/- 11% in nonresponders, P < 0.014). A fractional prolongation of the total QRS duration by > 15% identified effectively treated patients with a sensitivity of 87%, specificity of 81%, and an overall predictive accuracy of 84%. Dofetilide did not change the SAECG, and no SAECG parameter predicted the results of programmed ventricular stimulation. The effects of both drugs on the spectral analysis (area ratios) and on the spectral temporal mapping (the values of normality factor) of the SAECG were not consistent. In conclusion, antiarrhythmic efficacy of procainamide can be predicted by the degree of drug induced prolongation of the signal-averaged QRS complex.(ABSTRACT TRUNCATED AT 250 WORDS)
Third generation implantable cardioverter defibrillators (ICDs) have extensive memory capability to store data about the patient's arrhythmias and the effect of therapies delivered by the ICD. However, this data has so far been accessible only when the patient attends the pacing clinic. Two Medtronic 9421 PCD TeletraceR transmitters have been used to interrogate Medtronic 7216A and 7217B PCD S at distances of up to 300 miles from our hospital and transmit the data to a 9420 PCD TeletraceR receiver. Successful transmission of data has been obtained on 50 occasions with 100% data concordance with repeat transmission. The system can reduce the number of unscheduled clinic visits, reduce delay in making a diagnosis following unexpected delivery of a shock therapy, and reassure patients about to be discharged following ICD implantation. The benefits are magnified where patients reside far away from the implanting center.
OBJECTIVE: To assess the accuracy of measurement of area of the lumen, and sensitivity, and specificity of detection of atheroma in coronary arteries in vitro with a commercially available 20 MHz intravascular ultrasound system. SETTING: A teaching hospital department of cardiology with the support of the department of cardiovascular pathology. PROCEDURE: 10 segments of coronary artery were removed from cadaver hearts. Intravascular ultrasound imaging was performed at fixed levels and the vessels were then sectioned and photographed before histological preparation. An independent blinded observer measured luminal area and assessed the presence of atheroma on the intravascular ultrasound images of 76 vessel sections (304 quadrants). The sensitivity and specificity of detection of atheroma was assessed in comparison with the histologically prepared sections. Luminal areas from intravascular ultrasound, photographs of cross sections of the vessels and histological sections were compared with the technique of limits of agreement. RESULTS: Overall 36% of the 304 quadrants studied histologically had identifiable atheroma. Intravascular ultrasound sensitivity for atheroma was 0.593 and the specificity was 0.839. The positive predictive value was 0.674, and the relative risk 3.139. Values for area of the vessel lumen were on average 9.4 mm2 (confidence interval (CI) 8.6-10.2 mm2) larger than those measured from photographs and 10.7 (CI 9.8-11.6 mm2) larger than those measured from the histological sections. CONCLUSIONS: The intravascular ultrasound system assessed in this study significantly overestimated coronary vessel luminal area and had low sensitivity and specificity for detection of atheroma. Improvements in image resolution are required before this system can provide useful information on coronary artery size and morphology.
Management of dental caries patients is taking on a new look. Caries is the clinical manifestation of an oral infection. The primary organisms involved are Streptococcus mutans. The infective nature of the disease has been well researched and reported. Treatment of this infection with antibacterial measures is becoming routine in developed countries. In the United States, the overall caries rate is decreasing. However, the distribution of caries is now skewed. Twenty percent of the population has 60% of the caries. These individuals have a significant level of infection or a major lack of resistance to the organisms and their by-products. Major strategies are being developed to control these infections and limit their recurrence. This review focuses on the developments in prevalence studies, diagnosis, and treatment of the caries infection.
OBJECTIVE: Preliminary assessment of the efficacy and safety of the low speed rotational angioplasty catheter system (ROTACS). DESIGN: Open prospective trial. SETTING: Department of cardiology in a teaching hospital. PATIENTS: Eleven patients (10 with chronic stable angina and one with acute coronary occlusion after conventional angioplasty) in whom a coronary angiogram showed occlusion or critical stenosis of the coronary artery (right in seven patients, circumflex in two, and left anterior descending in two). The nature or severity of the lesion ruled out conventional coronary angioplasty. INTERVENTIONS: An attempt was made to cross the lesion with a rotating guide wire with a blunt swelling at its tip. Where necessary progress was assessed by simultaneous injection of contrast into both main coronary arteries. MAIN OUTCOME MEASURES: Progress of the ROTACS through the lesion that allowed a guide wire to pass into the distal vessel was regarded as a device specific success. When a guide wire crossed the lesion aided only by the support of the ROTACS without the use of rotation this was counted as a success that was not device specific. Failure to cross the lesion and any associated complications were noted. RESULTS: The ROTACS crossed only two of the 10 chronic lesions (20% device specific success rate); however, the support it provided enabled a guide wire to cross a further two lesions and allowed subsequent successful angioplasty in four of the 10 patients. One of these four patients presented after five months with recurrent angina requiring bypass grafting. The other three were symptom free at follow up seven months after the procedure. In the one patient with acute coronary occlusion the ROTACS was advanced over the guide wire to allow passage of an angioplasty balloon where this had previously proved impossible. An excellent final result was obtained and this patient remains symptom free. Three of the six patients in whom the ROTACS was unsuccessful had coronary artery dissection without sequelae. Three patients required subsequent elective coronary bypass grafting for control of symptoms while the other three remain well on medical treatment. CONCLUSIONS: The ROTACS may extend the range of patients with coronary artery occlusion or critical stenosis who can be treated non-surgically. The low device specific success rate (20%) achieved in this study indicates that it should be compared with other simpler mechanical devices that may be just as effective.
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Bleaching techniques of both vital and nonvital teeth are reviewed. Current techniques and their origins are investigated, and the appropriate uses for various methods examined. The current research shows that bleaching, while highly effective, must be viewed with caution. The bleaching process cannot be viewed as entirely benign. The influx of bleaching agents prescribed for home-administration use by dentists is particularly deficient in the amount of independent, refereed research on their long-term effects on oral tissues.
The breakdown of pacemaker lead insulation under conditions of mechanical stress leading to failure of pacing is well recognized. We present a case where adjacent breakdown of insulation in two unipolar pacing leads resulted in inappropriate ventricular pacing. Replacement of the leads rectified the problem.
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Digital subtraction coronary angiograms (DSA) of 63 patients who had undergone coronary angioplasty (PTCA) for a total of 73 lesions were analyzed with an automated border-detecting computer program capable of simultaneous geometric and densitometric cross-sectional area estimation. The computer measurements were compared with visual interpretation of the 35 mm cineangiograms. The results indicated that visual reports of cineangiograms tend to overestimate the pre-PTCA diameter percent stenosis and to underestimate the post-PTCA residual stenosis in comparison with the computer (p less than 0.001 in bot cases). There was good agreement between geometric and densitometric area percent stenoses calculated by the program on the pre-PTCA digital angiograms (r = 0.82, p less than 0.001, mean of their differences = -0.2 with standard deviation = 6.1). Following PTCA, however, important discrepancies between the two methods existed (r = 0.71, p less than 0.001, mean of their differences = 1.0 with standard deviation = 18.6). Following PTCA (but not pre-PTCA), densitometric evaluation demonstrated a significantly greater mean coefficient of variation between different views (69%) than did the geometric evaluation on the same views (24%). We conclude (1) that visual interpretation of cine coronary angiograms compares poorly with quantitative methods for both the selection of PTCA candidates and the assessment of the results; (2) that the geometric and densitometric characteristics do not agree in describing the degree of post-PTCA residual stenosis; and (3) that after angioplasty, important discrepancies between densitometric evaluation in different views are observed.
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Through a standardized procedure using clinical examination, interviews, and dental history, this 2-year study documents 100 cases of tooth fracture in 98 patients. For comparison, pertinent information was also recorded for more than 2,000 teeth in a randomly selected sample population. Two chief types of fracture were found: incomplete crown-root fractures and root fractures associated with earlier endodontic therapy.
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