Effect of glazing technique and firing on surface roughness and flexural strength of an advanced lithium disilicate.

OBJECTIVE: The objective of this study was to investigate the effects of glazing technique and firing on the surface roughness and flexural strength of an advanced lithium disilicate (ALD) and lithium disilicate (LD). METHODS: Eight groups of bar-shaped specimens (1 mm × 1 mm × 12 mm, N=160, 20/group) were manufactured from ALD (CEREC Tessera, Dentsply Sirona) and LD (IPS e.max CAD, Ivoclar). The specimens were then submitted to various posttreatments: crystallization (c), crystallization followed by a second firing (c-r), crystallization with glaze in one step (cg), and crystallization followed by a glaze layer firing (c-g). Surface roughness was measured by means of a profilometer, and flexural strength was determined using a three-point bending test. Surface morphology, fractography, and crack healing analysis were conducted using scanning electron microscopy. RESULTS: Refiring (c-r) did not affect the surface roughness (Ra) while applying glaze at both cg and c-g procedures increased the roughness. ALDc-g (442.3 ± 92.5 MPa) promoted higher strength than ALDcg (282.1 ± 64.4 MPa), whereas LDcg (402.9 ± 78.4 MPa) was stronger than LDc-g (255.5 ± 68.7 MPa). Refiring completely closed the crack in ALD, but it had a limited effect on LD. CONCLUSIONS: Two-step crystallization and glazing improved ALD strength compared to the one-step protocol. Refiring and one-step glazing do not increase LD's strength, while two-step glazing has a negative effect. CLINICAL RELEVANCE: Besides both materials being lithium-disilicate glass ceramics, the glazing technique and firing protocol affected their roughness and flexural strength differently. A two-step crystallization and glazing should be the first choice for ALD, while for LD, glazing is optional and when necessary, should be applied in one-step.

Influence of surface finishing and printing layer orientation on surface roughness and flexural strength of stereolithography-manufactured dental zirconia.

OBJECTIVE: To evaluate the effect of surface finishing and printing layer orientation on the surface roughness and flexural strength of three-dimensionally (3D) printed 3 mol% yttria-stabilized zirconia manufactured by stereolithography (SLA). METHODS: Ninety bar-shaped zirconia specimens (1 mm x 1 mm x 12 mm) were 3D-printed via SLA. After debinding and sintering, they were randomly divided according to the printing layer orientation: parallel (PR) or perpendicular (PD) to the tensile surface for bending test. Each group was submitted to a surface finishing protocol (n=15/group): unpolished (subgroup 0), with polished tensile surface (subgroup 1), and with polished lateral and tensile surfaces (subgroup 3). Roughness of tensile surface was determined using a contact sensor and surface morphology was analyzed under Scanning Electron Microscopy (SEM). Flexural strength, apparent elastic modulus, and Weibull parameters were assessed using a 3-point bending test. Fractured specimens were examined to identify failure origins. Finite element analysis was used to evaluate tensile stress peaks and failure risk. RESULTS: PR orientation exhibited higher strength, higher apparent elastic modulus, higher maximum principal stress peaks, and lower failure risk. For both layer orientations, groups with polished lateral and tensile sides (PR3 and PD3) were the strongest. SEM revealed that polishing led to changes in defect type, location, and size. SIGNIFICANCE: SLA zirconia shows different mechanical properties according to surface roughness and defects. Orienting the printed layers parallel to the tensile side improves its mechanical performance. Polishing can significantly improve its flexural strength. It is necessary to reduce the final product's surface roughness and large pores for its best performance.

Systolic right ventricular adaptive changes in athletes as predictors of the maximal functional capacity: a pulsed tissue Doppler study.

AIM: The aim of this study was to extend the analysis of the systolic right ventricular (RV) adaptation to combined endurance and strength training, to assess the utility of tissue Doppler imaging in detecting the degree of these changes and to find independent RV predictors of the maximal functional capacity. METHODS: Standard Doppler and TDI were used to assess cardiac parameters at rest in 37 elite male athletes (16 wrestlers, 21 water polo players) and 20 sedentary subjects of similar age. Progressive maximal test on treadmill was used to assess VO2max. The obtained parameters were adjusted for HR, FFM, and BSA. RESULTS: Wrestlers showed higher VO2max than controls, but lesser than water polo players. RV diameter was larger in athletes. Right atrial pressure (RVE/e) was higher in water polo players than in other groups. Systolic function assessed by tricuspid annular plane systolic excursion (TAPSE) and RVs' was the highest in wrestlers. Global RV systolic parameters myocardial performance index (MPI) and preejection time/ejection time index (PET/ET) were similar. On multivariate analysis systolic parameters were independent predictors of VO2max only in wrestlers: RVs' (beta=3.18, P=0.001) and RV ET (beta=2.32, P=0.001). RVE/e` correlated with RVs' (r=-0.57, P=0.000). TAPSE correlated with RV ET (r=0.32, P=0.015) and RVs` (beta=0.28, P=0.033). CONCLUSION: Systolic function assessed by TAPSE and RVs` has more improved in less endurance athletes. RVs`and TDI ejection time predict VO2max in wrestlers, and possibly in other athletes with lesser right atrial pressure. TDI enables quantifying RV adaptation degree in athletes, but complementary to M-mode technique.

Lack of Buffering by Composites Promotes Shift to More Cariogenic Bacteria.

Secondary caries (SC) remains a very important problem with composite restorations. The objectives of this study were to test the acid-buffering ability of several restorative materials and to evaluate whether buffering of the restorative material has an impact on the microbial composition of the biofilm. Disk-shaped specimens of conventional composite, composite with surface prereacted glass-ionomer filler particles (so-called giomer), glass-ionomer cement (GIC), amalgam, and hydroxyapatite (HAp) (control) were exposed to aqueous solutions with pH 4, 5, 6, and 7 and to the medium containing bacteria-produced acids, and pH changes were recorded over several days. Next, material specimens were immersed in bacterial growth medium with pH adjusted to 5. After a 24-h incubation, the extracts were collected and inoculated with a cariogenic (Streptococcus mutans) and a noncariogenic (Streptococcus sanguinis) species. The bacterial growth was monitored both in a single-species model by spectrophotometry and in a dual-species model by viability quantitative polymerase chain reaction. Amalgam and HAp showed the strongest acid-buffering ability, followed by the GIC and the giomer, while the conventional composite did not exhibit any buffering capacity. Furthermore, due to the lack of acid-buffering abilities, composite was not able to increase the pH of the medium (pH 5), which, in the absence of antibacterial properties, allowed the growth of S. mutans, while the growth of S. sanguinis, a less aciduric species, was completely inhibited. A similar effect was observed when bacteria were cultured together: there was a higher percentage of S. mutans and lower percentage of S. sanguinis with the conventional composite than with other materials and HAp. In conclusion, conventional composites lack the ability to increase the local pH, which leads to the outgrowth of more acidogenic/aciduric bacteria and higher cariogenicity of the biofilm. Together with lack of antibacterial properties, lack of buffering may account for the higher susceptibility of composites to SC.

Combined low dose dipyridamole-dobutamine stress echocardiography to identify myocardial viability.

OBJECTIVES: We sought to evaluate the effects of combined administration of infra-low dose dipyridamole and low dose dobutamine on assessment of myocardial viability. BACKGROUND: Low dose pharmacologic stress echocardiography with either dobutamine or dipyridamole infusion has been proposed for the recognition of myocardial viability. METHODS: Thirty-four patients with rest wall motion dyssynergy by two-dimensional echocardiography and with angiographically proved coronary artery disease underwent in combination with two-dimensional echocardiographic monitoring: 1) low dose (5 to 10 microgram/kg per min over 3 min) dobutamine infusion; 2) infra-low dose (0.28 mg/kg over 4 min) dipyridamole infusion; 3) combination of infra-low dose dipyridamole infusion immediately followed by low dose dobutamine infusion (combined dipyridamole-dobutamine). RESULTS: Follow-up rest echocardiography was available in 30 patients. After revascularization, 82 segments showed a contractile improvement of > or = 1 grade, whereas 63 segments remained unchanged. The sensitivity of dobutamine, dipyridamole and combined dipyridamole-dobutamine for predicting recovery was 72% (95% confidence interval [CI] 60.9% to 81.3%), 67% (CI 55.8% to 77%) and 94% (CI 86.3% to 97.9%), respectively. The specificity of dipyridamole, dobutamine and combined dipyridamole-dobutamine was 95% (CI 86.7% to 99%), 92% (CI 82.4% to 97.3%) and 89% (CI 78.4% to 95.4%), respectively. The accuracy of the dobutamine, dipyridamole and combined dipyridamole-dobutamine test was 80%, 79% and 92%, respectively (combined dipyridamole-dobutamine vs. dobutamine, p < 0.05; combined dipyridamole-dobutamine vs. dipyridamole, p < 0.01). CONCLUSIONS: Infra-low dose dipyridamole added to low dose dobutamine recruits an inotropic reserve in asynergic segments that were nonresponders after either dobutamine or dipyridamole alone and destined to recover after revascularization.

High dose adenosine stress echocardiography for noninvasive detection of coronary artery disease.

OBJECTIVES: The aim of this study was to assess the tolerability and incremental diagnostic value of high adenosine doses in stress echocardiography testing in patients with coronary artery disease (CAD). BACKGROUND: In comparison with other pharmacologic stress echocardiography tests, standard dose adenosine stress has sub-optimal sensitivity for detecting milder forms of CAD. METHODS: Adenosine stress echocardiography was performed in 58 patients using a starting dose of 100 micrograms/kg body weight per min over 3 min followed by 140 micrograms/kg per min over 4 min (standard dose). If no new wall motion abnormality appeared, the dose was increased to 200 micrograms/kg per min over 4 min (high dose). All patients underwent coronary angiography. Significant CAD was defined as > or = 50% diameter stenosis in at least one major coronary artery. Thirty-three patients had one-vessel and seven had multivessel CAD. Coronary angiographic findings were normal in 18 patients. RESULTS: The high adenosine dose caused a slight but significant increase over baseline values in rate-pressure product. Limiting side effects occurred in two patients during the standard dose protocol and in one patient receiving the high dose regimen. The test was stopped in 30 patients after the standard adenosine dose regimen because of a provoked new wall motion abnormality. The sensitivity of adenosine echocardiography with the standard dose was 75% (95% confidence interval [CI] 63% to 87%). After completion of the standard dose protocol, 28 patients continued testing with the high dose adenosine protocol. The overall sensitivity of adenosine echocardiography, calculated as cumulative, increased to 92% (95% CI 84% to 100%) with the high dose (p < 0.05). The specificity of adenosine testing was 100% and 88%, respectively, with the standard and high dose regimen (p = 0.617). CONCLUSIONS: We believe that use of a higher than usual adenosine dose protocol for stress testing may improve the diagnostic value of adenosine echocardiography, mainly by increasing sensitivity in patients with single-vessel disease without deterioration of the safety profile and with only a mild reduction in specificity.

Integrated evaluation of relation between coronary lesion features and stress echocardiography results: the importance of coronary lesion morphology.

OBJECTIVES: The aim of this study was to analyze, in the same group of patients, the relationship between multiple variables of coronary lesion and results of exercise, dobutamine and dipyridamole stress echocardiography tests. BACKGROUND: Integrated evaluation of the relation between stress echocardiography results and angiographic variables should include not only the assessment of stenosis severity but also evaluation of other quantitative and qualitative features of coronary stenosis. METHODS: Study population consisted of 168 (138 male, 30 female, mean age 51+/-9 years) patients, on whom exercise (Bruce treadmill protocol), dobutamine (up to 40 mcg/kg/min) and dipyridamole (0.84 mg/kg over 10 min) stress echocardiography tests were performed. Stress echocardiography test was considered positive for myocardial ischemia when a new wall motion abnormality was observed. One-vessel coronary stenosis ranging from mild stenosis to complete obstruction of the vessel was present in 153 patients, and 15 patients had normal coronary arteries. The observed angiographic variables included particular coronary vessel, stenosis location, the presence of collaterals, plaque morphology according to Ambrose classification, percent diameter stenosis and obstruction diameter as assessed by quantitative coronary arteriography. RESULTS: Covariates significantly associated with the results of physical and pharmacological stress tests included for all three stress modalities presence of collateral circulation, percent diameter stenosis and obstruction diameter, as well as lesion morphology (p < 0.05 for all, except collaterals for dobutamine stress test, p = 0.06). By stepwise multiple logistic regression analysis, the strongest predictor of the outcome of exercise echocardiography test was only percent diameter stenosis (p = 0.0002). However, both dobutamine and particularly dipyridamole stress echocardiography results were associated not only with stenosis severity - percent diameter stenosis (dobutamine, p = 0.04; dipyridamole, p = 0.003) - but also, and even more strongly, with lesion morphology (dobutamine, p = 0.006; dipyridamole, p = 0.0009). As all of stress echocardiography results were significantly associated with percent diameter stenosis, the best angiographic cutoff in relation to the results of stress echocardiography test was: exercise, 54%; dobutamine, 58% and dipyridamole, 60% (p < 0.05 vs. exercise). CONCLUSIONS: Integrated evaluation of angiographic variables have shown that the results of dobutamine and dipyridamole stress echocardiography are not only influenced by stenosis severity but also, and even more importantly, by plaque morphology. The results of exercise stress echocardiography, although separately influenced by plaque morphology, are predominantly influenced by stenosis severity, due to a stronger exercise capacity in provoking myocardial ischemia in milder forms of coronary stenosis.

Prognostic value of myocardial viability determined by a 201Tl SPECT study in patients with previous myocardial infarction and mild-to-moderate myocardial dysfunction.

The prognostic meaning of myocardial viability is most important in patients with severe left ventricular dysfunction and ischaemic heart disease, but its prognostic significance in patients with previous myocardial infarction and mild-to-moderate myocardial dysfunction is uncertain. The aim of this study was to assess the prognostic value of a 201Tl single photon emission computed tomography (SPECT) rest-redistribution study in patients with previous myocardial infarction, ischaemic heart disease and mild-to-moderate myocardial dysfunction. Myocardial viability was assessed in 55 patients (50 male; mean age 58+/-9 years) by 201Tl SPECT rest-redistribution (after 4 h) scintigraphy. All patients had previous myocardial infarction (>3 months) and angiographically documented coronary artery disease, with the mean ejection fraction of 43+/-10%. Out of 55 patients, 20 were medically treated and 35 were revascularized. The follow-up period for adverse cardiac events, including death and non-fatal myocardial infarction, was 12 months. 201Tl SPECT study was positive for myocardial viability in 36 patients (65%) and negative in 19 patients (35%). Sensitivity, specificity, positive and negative predictive values for functional improvement in the follow-up period were 85%, 75%, 92% and 60%. Out of seven (13%) cardiac events in the follow-up period (four cardiac deaths and three reinfarctions), five occurred in 20 medically treated patients and two in 35 revascularized patients (25% vs 6%, P <0.05). Absence of myocardial viability was the only variable associated with adverse cardiac events (P =0.02). Survival at 12 months, as determined by using Kaplan-Meier analysis, was 56% for medically treated and non-viable patients, 80% for revascularized and non-viable patients, 91% for medically treated and viable patients, and 100% for revascularized and viable patients (P =0.0034). These findings suggest that in patients with previous myocardial infarction and mild-to-moderate myocardial dysfunction, the absence of myocardial viability as determined by the 201Tl SPECT study was the only variable associated with adverse cardiac events. The best 12 month survival was observed in revascularized viable patients, whereas the worse prognosis was found in non-viable, medically treated patients.

Pharmacological radionuclide ventriculography for detection of myocardial contractile reserve in patients after myocardial infarction: head-to-head comparison of low dose dobutamine and low dose dipyridamole.

BACKGROUND: Low dose pharmacological stress echocardiography with either dobutamine or dipyridamole infusion has been proposed for recognition of myocardial viability. However, dependence on adequate acoustic window, observer experience, and the mild degree of wall motion changes make the viability assessment by stress echocardiography especially bothersome. The objective of the study was to evaluate the ability of low dose dobutamine and low dose dipyridamole radionuclide ventriculography to detect contractile reserve in patients after myocardial infarction and functional recovery after coronary angioplasty. METHODS: The study group consisted of 20 consecutive patients (52 +/- 10 years, 17 male, 3 female) with previous myocardial infarction and resting regional dyssynergy, in whom diagnostic cardiac catheterization revealed significant one-vessel coronary artery stenosis suitable for angioplasty. Each patient underwent equilibrium 99m-Tc radionuclide ventriculography which was performed at rest and during low dose dipyridamole (0.28 mg/kg over 2 minutes) and low dose dobutamine infusion (up to 10 mcg/kg/min). Left ventricular global and regional ejection fractions were determined. Increase of regional ejection fraction for > 5% (inferoapical and posterolateral regions) or > 10% (anteroseptal regions) during low dose dobutamine and dipyridamole in infarcted regions, as well as in the followup period, was considered as index of contractile reserve. After 8 weeks of successful angioplasty, resting radionuclide ventriculography was repeated in all patients in order to identify functional recovery of the infarct zone. RESULTS: Out of the 180 analyzed segments (20 x 9), 90 regional ejection fractions have shown depressed contractility. The mean of the regional ejection fractions showing depressed contractility increased from the resting value of 34 +/- 12% to 42 +/- 14% in the follow-up period (p = 0.06). Of the 90 with baseline dyssynergy, 46 were responders during low-dose dobutamine (51%), whereas 32 segments were responders (36%, p = 0.05 vs. dobutamine) during low dose dipyridamole. Positive predictive value of dobutamine and dipyridamole for predicting functional recovery was 72% and 75% (p = ns), respectively. Negative predictive value of dobutamine and dipyridamole was 48% and 69% (p = 0.05), respectively. In the group of patients with most severe dyskinesia (regional ejection fraction < 35%, 42 segments) positive predictive value was 73% and 82%, while negative predictive value was 42% and 64% for low dose dobutamine and low dose dipyridamole respectively (p = ns). CONCLUSION: Although low dose dobutamine induced higher rate of positive responses during radionuclide ventriculography imaging, dipyridamole radionuclide ventriculography has shown superior, particularly negative, prognostic value for predicting functional recovery of infarcted regions.

Infra-low dose dipyridamole test. A novel dose regimen for selective assessment of myocardial viability by vasodilator stress echocardiography.

Low (0.56 mg.kg-1 over 4 min) and high (0.84 mg.kg-1 over 10 min) doses of dipyridamole can identify viable myocardium through the contractile recovery of basally dyssynergic regions; however, it also induces ischaemia in susceptible patients. The aim of this study was to assess the potential of an "infra-low' dose of dipyridamole to selectively identify myocardial viability, independently evaluated by low dose dobutamine. Forty patients with resting dyssynergy and angiographically assessed coronary artery disease (1-vessel in 18, 2-vessel in 12, and 3-vessel in 10 patients) separately underwent a low dose dobutamine (5-10 micrograms.kg-1.min-1 for 3 min) echo test and an infralow dose (0.28 mg.kg-1 over 4 min) dipyridamole echo test. Systolic blood pressure (rest: 131 +/- 19 mmHg) changed slightly after dobutamine (137 +/- 21, P < 0.05 vs rest) and remained stable after dipyridamole (130 +/- 17, P = ns vs rest). Heart rate (rest: 68 +/- 13 beats.min-1) was also unchanged after dipyridamole (69 +/- 12, P = ns vs rest) and increased slightly after dobutamine (71 +/- 15, P < 0.05 vs rest and vs dipyridamole). No patient developed echocardiographic or electrocardiographic signs of ischaemia after either dipyridamole or dobutamine. Of the 243 segments with baseline dyssynergy, 70 were responders (i.e. they showed an improvement of 1 grade or more, from 1 = normal/hyperkinetic to 4 = dyskinetic in a 16-segment model of the left ventricle) by both dipyridamole and dobutamine, 157 were non-responders (i.e. they showed no change) by both dipyridamole and dobutamine, and 16 showed discordant results (five responders by dipyridamole only; 11 by dobutamine only). The overall concordance of dipyridamole and dobutamine was 93%. An echocardiographic follow-up could be obtained > 6 weeks after successful revascularization (achieved with angioplasty in 17, with by pass surgery in 3) in 19 patients and showed an improvement of one grade or more in 50 segments (viable) and no improvement in 50 segments (necrotic). The sensitivity of dobutamine and dipyridamole for predicting recovery was 76 and 78% respectively (P = ns); the specificity of both tests was 94%. In conclusion, infra-low dose dipyridamole is a haemodynamically neutral stress test which does not affect either heart rate or systolic blood pressure; it allows myocardial viability to be explored selectively, without eliciting ischaemia; it shows excellent overall concordance with low dose dobutamine and has good sensitivity and excellent specificity for predicting functional recovery following successful revascularization.

Dipyridamole-atropine-induced myocardial infarction in a patient with patent epicardial coronary arteries.

BACKGROUND: The diagnostic accuracy of the physical and pharmacological stress echocardiography tests is higher than routine exercise electrocardiography. They have an acceptable safety profile and have been rarely associated with severe adverse effects. CASE REPORT: We present a case of acute anterior myocardial reinfarction immediately after exercise and pharmacological (dipyridamole-atropine) stress echocardiography testing 1 month after successful stent implantation in LAD. Our patient was a 43-year-old man with a history of heavy smoking and hypertension. Remarkably, the stress echocardiogram was non-diagnostic few hours before the infarction occurred. Angiography performed 4 months after the reinfarction revealed neither a culprit lesion nor stent thrombosis. CONCLUSION: Aggressive "last generation" pharmacological stress testing may provide optimal diagnostic accuracy, but as in our case, complications may occur, even after negative stress testing. To our knowledge, this is the first reported case of an acute myocardial infarction as a severe complication of stress testing, which developed in a patient after stent implantation.