Effects of bracket slot size during en-masse retraction of the six maxillary anterior teeth using an induction-heating typodont simulation system / 대한치과교정학회지

OBJECTIVE: To investigate how bracket slot size affects the direction of maxillary anterior tooth movement when en-masse retraction is performed in sliding mechanics using an induction-heating typodont simulation system. METHODS: An induction-heating typodont simulation system was designed based on the Calorific Machine system. The typodont included metal anterior and resin posterior teeth embedded in a sticky wax arch. Three bracket slot groups (0.018, 0.020, and 0.022 inch [in]) were tested. A retraction force of 250 g was applied in the posterior-superior direction. RESULTS: In the anteroposterior direction, the cusp tip of the canine in the 0.020-in slot group moved more distally than in the 0.018-in slot group. In the vertical direction, all six anterior teeth were intruded in the 0.018-in slot group and extruded in the 0.020- and 0.022-in slot groups. The lateral incisor was significantly extruded in the 0.020- and 0.022-in slot groups. Significant differences in the crown linguoversion were found between the 0.018- and 0.020-in slot groups and 0.018- and 0.022-in slot groups for the central incisor and between the 0.018- and 0.022-in slot groups and 0.020- and 0.022-in slot groups for the canine. In the 0.018-in slot group, all anterior teeth showed crown mesial angulation. Significant differences were found between the 0.018- and 0.022-in slot groups for the lateral incisor and between the 0.018- and 0.020-in slot groups and 0.018- and 0.022-in slot groups for the canine. CONCLUSIONS: Use of 0.018-in slot brackets was effective for preventing extrusion and crown linguoversion of anterior teeth in sliding mechanics.

Assessment of impaired left ventricular diastolic function in patients with coronary artery disease, using radionuclide angiography.

Left ventricular (LV) diastolic filling at rest was assessed in 76 patients with coronary artery disease (CAD) and 16 healthy subjects using radionuclide angiography. Peak LV filling rate (PFR), expressed in end diastolic volume per second (EDV/sec), was subnormal in CAD patients (1.95 +/- 0.51 as compared to the normal 3.11 +/- 0.36, P < 0.001) and time to PFR (TPFR) was prolonged (171.1 +/- 79 msec versus 106.6 +/- 25 msec normal, P < 0.001). These indices were also abnormal in 60 patients with normal resting LV ejection fraction (PFR 2.17 +/- 0.48 EDV/sec, TPFR 163.9 +/- 68 msec). Abnormal LV filling at rest (PFR EDV/sec or TPFR 160 msec) was found in 88 percent of all patients with CAD, 85 percent of patients with normal resting LV ejection fraction, and 83 percent of patients without Q waves on resting electrocardiogram. Thus, LV diastolic filling, evaluated non invasively by radionuclide angiography, appears to be abnormal in a high percentage of patients with CAD independent of LV systolic function or previous myocardial infarction.

Phase analysis of radionuclide ventriculograms in patients with coronary artery disease.

Phase analysis of radionuclide ventriculograms were performed in eighty patients with coronary artery disease (CAD) and in sixteen healthy subjects. The phase image in the normal group revealed a homogeneous pattern and a narrow bell shaped histogram. In forty one patients with CAD whose Left ventriculogram showed hypokinetic segments, phase image was abnormal in twenty six revealing well demarcated areas of contraction abnormality and a histogram showing broad base with multiple peaks. The mean phase angle and the standard deviation (S.D.) of phase histogram of the abnormal segments was significantly different from normal. Eighteen patients with CAD had akinetic segments. Phase analysis was abnormal in all. Six patients with CAD had dyskinetic segments. It is concluded that phase image analysis is very useful in detecting segmental wall motion abnormalities.

Labetalol and nifedipine in the management of essential hypertension.

Antihypertensive effects of labetalol and nifedipine were evaluated in a double blind cross over trial in ambulatory patients with moderately severe hypertension (mean diastolic BP 101.2 +/- 1.78 mm Hg, 105 +/- 2.15 mm Hg respectively and mean systolic BP 164.2 +/- 4.2 mm Hg and 171.4 +/- 5.82 mm Hg respectively in each group of 10 patients). The effect of labetalol over the systolic and diastolic BP was highly significant (p less than 0.01). The effects of nifedipine on systolic and diastolic BP were also significant but effects on diastolic BP was highly significant (p less than 0.01). In cross over study it was seen that nifedipine was not much superior in lowering the systolic BP whereas diastolic BP was lowered to a significant level (p less than 0.05) as compared to labetalol.

Dipyridamole radionuclide ventriculography for localisation of coronary artery disease.

Nineteen consecutive patients who had coronary arteriography underwent dipyridamole stress testing with 0.14 mg/kg/min infusion over 4 minutes during computer assisted radionuclide ventriculography. Global ejection fraction, diastolic function and regional ejection fraction were calculated by a semiautomatic method. There were 17 patients with severe left anterior descending disease of which 12 involved the proximal segment of the LAD, 15 patients with left circumflex disease and 13 patients with right coronary artery disease. Abnormalities in resting or stress induced regional ejection fraction was used for localisation of severe coronary artery disease. The overall sensitivity was 75 per cent with a specificity of 75 per cent, a positive predictive value of 90 per cent and a negative predictive value of 45 per cent. For LAD disease the sensitivity was 94 per cent with a 100 per cent specificity while proximal segment of LAD had a sensitivity of 100 per cent and a specificity of 57 per cent. Identification of left circumflex disease had a sensitivity of 47 per cent and a 100 per cent specificity and right coronary artery had a 85 per cent sensitivity and a 50 per cent specificity. Four patients developed ST changes, 6 developed chest discomfort and 1 patient developed giddiness. All 7 were promptly reversed with intravenous aminophylline. Thus dipyridamole radionuclide ventriculography is a highly sensitive and specific method for localisation of CAD.

Severity of mitral regurgitation in mitral valve prolapse syndrome. A Doppler echocardiographic study.

Thirty-three consecutive patients with mitral valve prolapse with a systolic murmur were evaluated using pulsed doppler echocardiography to quantify the severity of mitral regurgitation. There were thirteen (39%) patients with mild regurgitation, twelve patients (36%) with moderate regurgitation and eight patients (24%) with severe regurgitation. It was noticed that, all the patients with severe regurgitation had posterior leaflet prolapse. In contrast, patients with anterior leaflet prolapse had either mild or moderate regurgitation only. Our results suggest that the degree of mitral regurgitation differs depending on the leaflet that shows the prolapse, which may be of importance in the followup of patients with mitral valve prolapse.

Electrocardiographic left atrial enlargement--correlation with echo.

To assess the utility of electrocardiogram in identifying left atrial enlargement, electrocardiogram of 600 consecutive patients were correlated with their M-mode echocardiographic findings. Left atrial enlargement, as reflected by P terminal force in V1 had sensitivity of 79%, specificity 91%, predictive value 85% and accuracy of 86%. Patients older than 30 years with large left atrium (greater than 5.0 cm) had atrial fibrillation more frequently than younger patients (P less than 0.001). It is concluded that P terminal force in V1 is a reliable indicator of left atrial enlargement.

Low dose metoprolol in acute myocardial infarction.

A study of the effects of low dose Metoprolol was undertaken in 37 patients with acute myocardial infarction. These patients were randomly divided into three groups depending on the dose of the drug per kg body weight. Group I, consisting of 18 patients, received 0.36 to 0.65 mg per kg per day, Group II (10 patients) received 0.66 to 0.99 mg/kg/day, and Group III (9 patients) 1 to 1.81 mg/kg/day. To assess the degree of beta blockade achieved, the parameters that were evaluated were the fall in blood pressure and heart rate. There was a fall in systolic blood pressure which ranged from 7 to 17%, and fall in heart rate of 6.6 to 12.8% in the 3 groups over the 48-hour study period. These observations were compared with the results obtained from the Goteberg Metoprolol trial and Metoprolol in acute myocardial infarction (MIAMI) trials wherein 200 mg of Metoprolol per day were used. Our preliminary observations suggest that Indian patients may not need such a high dose, and Metoprolol at 50-100 mg per day would probably be sufficient to get the desired effect.

Systolic time intervals in dilated cardiomyopathy.

Systolic Time Intervals (STI) were recorded in 45 patients with Dilated Cardiomyopathy (DCMY) to evaluate left ventricular function. Shortening of LVETI was seen in 37 (82%), prolongation of PEPI in 42 (93%), and increase in PEP/LVET ratio in 43 (95%) patients of DCMY. Global left ventricular dysfunction could be identified in all the patients (100%) with the combination of PEPI and PEP/LVET ratio. On follow up evaluation of 14 patients, change in STI status was seen to correlate with clinical status of the patients. STI as a non-invasive indicator of left ventricular function are useful in diagnosis and follow up of patients with DCMY.