Effect of Die Spacer Thickness on the Microshear Bond Strength of CAD/CAM Lithium Disilicate Veneers.

AIM: The aim of this study was to compare the microshear bond strength of ceramic veneers with digital die spacer settings at 20, 40, and 100 µm. MATERIALS AND METHODS: Eighteen milled lithium disilicate microdiscs (IPS e.max CAD, Ivoclar Vivadent) were divided into three groups (n = 6) according to their digital die spacer settings: group A = 20 µm, group B = 40 µm, and group C = 100 µm. Six randomly selected sound maxillary premolars received three microdiscs each. Each microdisc was 1 mm in diameter and 1 mm in height. The buccal surfaces of the premolars were prepared with a 0.5 mm depth in enamel. After cementation, the specimens were thermocycled for 2,500 cycles between 5 and 55°C. Microshear bond strength testing was performed using a universal testing machine until bonding failure. Failure modes were evaluated using a stereomicroscope. Statistical analyses included one-way ANOVA, Tukey's post hoc test, and chi-square test with a 5% alpha error and 80% study power. RESULTS: The mean microshear bond strength values were calculated in MPa for group A = 31.91 ± 12.41, group B = 29.58 ± 5.03, and group C = 13.85 ± 4.12. One-way ANOVA (p ≤ 0.05) showed a statistically significant difference in microshear bond strength among the three groups. Tukey's post hoc test showed significant differences between groups A and C (p=0.004) and between groups B and C (p=0.011). The failure modes were presented as cohesive, adhesive, and mixed failures. Chi-square test indicated that the failure mode distribution was not significantly different among the three groups (p=0.970). CONCLUSION: Higher digital die spacer settings decrease the microshear bond strength of CAD/CAM lithium disilicate veneers.

The Clinical Characteristics of Patients with Pre-Existing Leukoaraiosis Compared to Those Without Leukoaraiosis in Acute Ischemic Stroke.

BACKGROUND: Leukoaraiosis (LA) is a finding in the elderly, that might be asymptomatic or can impact their motor and cognitive functions. We studied the presence of LA in the MRI of patients with AIS and its impact on functional outcome at 3 months. METHODS: 500 consecutive patients diagnosed as AIS were enrolled. Medical history included pre-medication by antiplatelets or statins, and vascular risk factors were reported by history and laboratory investigations. Severity of stroke was assessed by NIHSS and stroke outcome was evaluated on discharge and at 3 months by modified Rankin scale (mRS). LA was diagnosed by MRI-FLAIR sequence and delineated from acute infarction by diffusion-weighted image. And accordingly, patients were divided into group A (absent LA) and group B (present LA). RESULTS: 460 patients completed the study, with 53% of patients on antiplatelet therapy and 11.7% on statins prior to stroke. The percentage of patients with LA was significantly more than those without LA. Patients with LA showed a significantly higher age, more frequent and longer duration of diabetes and hypertension, ischemic heart disease, previous stroke/TIA and antiplatelet intake. Microbleeds were more and mRS was worse in LA group. CONCLUSION: The presence of LA in the background MRI of AIS patients is accompanied by the presence of more risk factors, and unfavorable outcome. Pre-medication with antiplatelets did not prevent the incidence of a new stroke especially in LA group. This might necessitate the identification of some medication for secondary prevention in patients with small vessel disease.

Effect of Die Spacer Thickness on the Fracture Resistance of CAD/CAM Lithium Disilicate Veneers on Maxillary First Premolars.

OBJECTIVE: The purpose of this study was to compare the fracture resistance of ceramic veneers with digital die spacer settings at 20 µm, 40 µm, and 100 µm. MATERIALS AND METHODS: Eighteen sound maxillary first premolars were divided into three groups (n=6) according to their digital die spacer settings: group A=20 µm, group B=40 µm, group C=100 µm. Each tooth was prepared to a depth of 0.5 mm to receive lithium disilicate veneers (IPS e.max CAD, Ivoclar Vivadent). All groups were thermocycled (2500 cycles at 5-55°C) and subjected to fracture resistance test using a universal testing machine until failure. Failure modes were examined using a stereomicroscope. RESULTS: The values (N) for group A=1181.34±301.33, group B=1014.29±291.12, and group C=841.89±244.59. One-way ANOVA showed no statistical difference among the three groups (p=0.145). However, chi-square test showed that a significant difference was present in the modes of failure (p=0.009). Tukey's post hoc test indicated that the failure modes of group A were statistically different from those of group C, showing 83.3% adhesive failure for group A compared to 0% adhesive failures in group C. A p-value of ≤0.05 was considered as statistically significant. CONCLUSION: Digital die spacer thickness did not influence the mean fracture resistance values of CAD/CAM lithium disilicate veneers. However, the way the failure occurred differed significantly at various die spacer thicknesses.

Clinical Characteristics of Borderzone Infarction in Egyptian Population.

OBJECTIVES: In this research we wanted to highlight the importance of defining Borderzone infarctions (BZI) as a separate subtype in stroke classifications. We thus studied cases of isolated BZI, small vessel disease (SVD), and large vessel disease (LVD), to identify their points of similarities and difference in a sample of Egyptian patients. METHODS: This is a cross-sectional (observational) study. Consecutive 637 acute ischemic stroke patients were recruited over a 2 year period, from 2 stroke units of Ain Shams University hospitals in Egypt. Medical history and laboratory investigations were done to identify risk factors. National Institute of Health Stroke Scale (NIHSS) was performed on admission, and modified Rankin scale (mRS) on admission, and after 3 months. MRI brain was done to identify stroke subtype; MRA and carotid duplex were used to define vascular status. RESULTS: Among the studied group of patients, 72 (11.3%) had BZI, 145 (22.8%) had SVD, 165 (26%) had LVD, and 255 were excluded as they had either undetermined, or mixed etiology. BZI showed significantly older age, early confluent lesions, more disease severity by NIHSS, and worst outcome by mRS (P < 0.05). SVD had more microbleeds than BZI and LVD. LVD showed lower prevalence of hypertension and lower high-density lipoprotein levels. CONCLUSIONS: Isolated BZI, SVD, and LVD infarctions have characteristic risk factors and clinical patterns. Further studies are needed to identify if they are different from cases with mixed pathology. This could have an impact on the selection of primary and secondary preventive measures appropriate to each type.