Statement of problem Despite the expanded applications for zirconia in restorative dentistry, there is no clear recommendation in the literature regarding surface treatment before bonding. Purpose ...The purpose of this study was to evaluate the effect of mechanical surface treatment of yttria-partially stabilized zirconia on its flexural strength and the effect of mechanical and chemical surface treatments on its bond strength to a resin cement. Material and methods For flexural strength evaluation, zirconia bars (4 × 5 × 40 mm) were prepared from zirconia blocks, finished using a diamond rotary cutting instrument, sintered, then assigned into 4 groups: (1) control (no treatment), (2) airborne-particle abrasion, (3) silicoating, and (4) wet hand grinding. After storage for 24 hours at 37°C, flexural strength was determined using a 3-point bending test, and the results were analyzed using 1-way ANOVA (α=.05). For shear bond strength evaluation, zirconia rods (2.5 × 3 mm) were prepared from zirconia blocks, sintered, and assigned into 16 groups. Each group underwent a combination of the following mechanical and chemical treatments. Mechanical treatment included: (1) control (no treatment), (2) airborne-particle abrasion, (3) silicoating, or (4) wet hand grinding. Chemical treatment included: (1) control (no treatment), (2) acid etching followed by silanation, (3) silanation only, or (4) application of zirconia primer. Dentin specimens were prepared from extracted molars stored in 0.5% chloramine-T. Zirconia rods were bonded to dentin using a resin cement (Multilink Automix), then light polymerized. After storage, the specimens were loaded to failure with the notched shear bond test method in a universal loading apparatus. For artificial aging analysis, the groups that achieved the highest bond strength values were duplicated, stored at 37°C and 100% humidity for 90 days, and thermal cycled before being loaded to failure. Results were analyzed using 2-way ANOVA (α=.05). Results Airborne-particle abrasion and hand grinding significantly increased flexural strength. The highest shear bond strength values were achieved for the following groups: silicoated + silanated > hand ground + zirconia primer > airborne-particle abraded + silanated > zirconia primer > airborne-particle abraded + zirconia primer. Artificial aging resulted in significantly lower shear bond strength for the silicoated/silanated and the zirconia primer groups. Conclusions Mechanical modification of the surface increased the flexural strength of Y-TZP. The resin bond to Y-TZP was improved by surface treatment. A combination of mechanical and chemical conditioning of the zirconia surface was essential to develop a durable resin bond to zirconia. (J Prosthet Dent 2010;103:210-220)
•Neoadjuvant SRS is associated with decreased radiation dosage and improved conformality profile due to enhanced target delineation.•Pre-operative SRS can decrease delivery of radiation to important ...structures such as optic apparatus, hippocampal cortex and brain stem.•These findings better characterize the role of neoadjuvant SRS in brain metastatic disease and could support further clinical trials.
Stereotactic radiosurgery (SRS) after maximal safe resection is an accepted treatment strategy for patients with cerebral metastatic disease. Despite its high conformality profile, the incidence of radionecrosis (RN) remains high. SRS delivered pre-operatively could be associated with a reduced incidence of RN. We sought to evaluate whether neoadjuvant SRS could reduce radiotherapy doses in a cohort of patients treated with post-operative SRS.
A cohort of 47 brain metastases (BM) treated at 2 academic institutions was retrospectively analyzed. Subjects underwent surgical extirpation of BMs and subsequent SRS to surgical bed. Post-operative volumetric and dosimetric data was collected from records or recreations of delivered plans; pre-operative data were derived from hypothetical radiotherapy courses and compared using Wilcoxon signed-rank tests.
Higher planned tumor volume post-operatively (medianIQR 12.28 6.54, 18.69cc vs 10.20 4.53, 21.70cc respectively, p = 0.4150) was observed. The median prescribed radiotherapy dose (DRx) was 16 Gy pre-operatively and 24 Gy post-operatively (p < 0.0001). Further investigations revealed improved pre-operative conformity index (1.231.20, 1.29 vs 1.291.23, 1.39, p = 0.0098) and gradient index (2.722.59, 2.98 vs 2.942.69, 3.47, p = 0.0004). A significant difference was found in normal brain tissue exposed to 10 Gy (12.976.78, 25.54cc vs 32.1319.42, 48.40cc, p < 0.0001), 12 Gy (9.314.56, 17.43cc vs 23.8014.74, 36.56cc, p < 0.0001), and 14 Gy (5.623.23, 11.61cc vs 17.479.00, 28.31cc, p < 0.0001), favoring pre-operative SRS.
Neoadjuvant SRS is associated reduced DRx, better conformality profile and decreased radiation to normal tissue. These findings could support the use of neoadjuvant SRS for the treatment of BMs.
An arachnoid web is a pathological formation of the arachnoid membrane. It is a rare phenomenon but is known to lead to syrinx formation in the spinal cord along with pain and neurological deficits. ...On imaging, the 'scalpel sign' is pathognomonic for an arachnoid web. The etiology of syrinx formation from an arachnoid web is currently unknown. This report documents the only two cases of arachnoid webs with an extensive syrinx in which a likely pathophysiologic mechanism is identified. Both cases presented with motor deficits. The patients had no history of trauma or infection. After extensive workup in both patients and observation of the scalpel sign an arachnoid web was suspected. In both cases, the patients were treated surgically after an arachnoid web was suspected. Intra-operative ultrasound visualized in both cases demonstrates a fenestration in the web that allowed passage of cerebrospinal fluid in a rostral-caudal direction due to a ball-valve effect.
Celotno besedilo
Dostopno za:
DOBA, IJS, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
OBJECTIVE The goal of this retrospective cohort study was to assess long-term outcomes in patients with vestibular schwannoma (VS) who underwent stereotactic radiosurgery (SRS) after initial ...microsurgical resection. METHODS From the authors' database of 1770 patients with VS, the authors retrospectively analyzed data from 173 Gamma Knife SRS procedures for VS after 1 (128 procedures) or multiple (45 procedures) microsurgical resections. The median length of the interval between the last resection and SRS was 42 months (range 2-329 months). The median length of clinical follow-up was 74 months (range 6-285 months). Progression-free survival after SRS was determined with Kaplan-Meier analysis. RESULTS At the time of SRS, the hearing of 161 patients (93%) was Gardner-Robertson Class V, and 81 patients (47%) had facial neuropathy (i.e., facial function with House-Brackmann HB grades of III-VI), 87 (50%) had trigeminal neuropathy, and 71 (41%) reported imbalance or disequilibrium disorders. The median tumor volume was 2.7 cm
(range 0.2-21.6 cm
), and the median dose to the tumor margin was 13 Gy (range 11-20 Gy). Radiosurgery controlled growth of 163 (94%) tumors. Progression-free survival after SRS was 97% at 3 years, 95% at 5 years, and 90% at 10 years. Four patients with delayed tumor progression underwent repeat SRS at a median of 35 months (range 23-64 months) after the first SRS. Four patients (2.3%) with tumor progression underwent repeat resection at a median of 25 months (range 19-33 months). Among the patients with any facial dysfunction (indicated by HB grades of II-VI), 19% had improvement in this condition after SRS, and 5.5% with some facial function (indicated by HB grades of I-V) developed more facial weakness. Among patients with trigeminal neuropathy, 20% had improvement in this condition, and 5.8% developed or had worsened trigeminal neuropathy after SRS. CONCLUSIONS Stereotactic radiosurgery offered a safe and effective long-term management strategy for VS patients whose tumors remained or recurred after initial microsurgery.
Applying microwave technology to sintering dental zirconia Almazdi, Abdulredha A., DDS, MS; Khajah, Hasan M., DDS, MS; Monaco, Edward A., DDS ...
The Journal of prosthetic dentistry,
11/2012, Letnik:
108, Številka:
5
Journal Article
Recenzirano
Statement of problem When sintering zirconia, conventional processing may not provide uniform heating and consumes more energy than an alternative method using microwave energy. Purpose The purpose ...of this study was to compare the surface quality, mechanical and physical properties, and dimensional stability obtained by sintering yttria-stabilized tetragonal zirconia polycrystal (Y-TZP) in a conventional furnace versus a microwave furnace. Material and methods Twenty bars of Y-TZP were prepared from Zircad blocks. Ten specimens were used for sintering in a conventional furnace. The remaining 10 specimens were sintered in a microwave furnace. The sintering temperature used for both techniques was 1500°C. The flexural strength of all specimens was measured with the 3-point bend test with a universal testing machine with a cross head speed of 1.0 mm/min. Density was measured by applying the Archimedes method, and specimen length, width, and thickness were measured with a digital micrometer. The phase composition and average grain size of these ceramics were examined by using X-ray diffraction, and microstructure characteristics were studied with scanning electron microscopy. Data obtained were analyzed by using independent t tests (α=.05). Results No significant difference between conventional and microwave sintering for either flexural strength, t18=0.49 ( P =.63) or density, t18=0.07 ( P =.95) was found. Specimens in both groups exhibited a uniform firing shrinkage of approximately 24.6% in all dimensions. The surface of selected specimens examined with a scanning electron microscope showed no visible difference in grain shape or porosity size between the 2 sintering methods. Conclusions Under the conditions of this study, it appears that either microwave or conventional zirconia sintering may be used for processing zirconia for dental use. However, microwave energy provides uniformity of heating, allowing the use of higher heating rates, which can increase productivity and save energy.
There has been an increase in endoscopic and bronchoscopic biopsies as minimally invasive methods to obtain specimens from gastrointestinal (GI) or pancreatobiliary lesions and thoracic or ...mediastinal lesions, respectively. As hospitals undertake more of these procedures, it is important to consider the staffing implications that this has on cytopathology laboratories with respect to support for rapid on-site evaluation (ROSE).
Volume and time data from endoscopic ultrasound and bronchoscopic procedures (including endobronchial ultrasound-guided transbronchial needle aspirations and small biopsies with touch preparation) in the GI suite, bronchoscopy suite, or operating room were reviewed for 2 months at 2 different medical centers with ROSE services provided by cytologists or fellows physically present at the procedure and cytopathologists located remotely using telecytology. Statistical analysis was performed to investigate significant trends based on the location of the biopsies and other factors.
A total of 16 proceduralists performed 159 procedures and submitted 276 different specimens during 16 total weeks at 2 institutions. The total ROSE time for the on-site personnel to cover these procedures was 109.3 hours (bronchoscopy, 62.3 hours 57%; GI, 29.8 hours 27%; OR, 17.2 hours 16%), which represents an average of 0.69 hour (41.4 minutes) per procedure or 0.40 hour (24.0 minutes) per part, with the shortest procedure times per sample recorded during bronchoscopy. When stratified by practice volume for individual proceduralists, the average time per specimen sample submitted was shorter for proceduralists with high volume practices and was most pronounced during bronchoscopy procedures.
Endoscopic and bronchoscopic procedures account for an increasing amount of the ROSE time for the cytology team. On average, each ROSE procedure takes 0.69 hour (41.4 minutes) or approximately 0.40 hour (24.0 minutes) per specimen, with shorter time requirements for specimens obtained in bronchoscopy procedures and for operators with high volume practices for endobronchial ultrasound-guided transbronchial needle aspirations. This provides important benchmarking data to calculate staffing needs for cytology to provide ROSE support for different proceduralists.
OBJECTIVE The authors of this study found that, given the latency period required for arteriovenous malformation (AVM) obliteration after stereotactic radiosurgery (SRS), a study with limited ...follow-up cannot assess the benefit of SRS for unruptured AVMs. METHODS The authors reviewed their institutional experience with "ARUBA (A Randomized Trial of Unruptured Brain Arteriovenous Malformations)-eligible" AVMs treated with SRS between 1987 and 2016, with the primary outcome defined as stroke (ischemic or hemorrhagic) or death (AVM related or AVM unrelated). Patients with at least 3 years of follow-up in addition to those who experienced stroke or died during the latency period were included. Secondary outcome measures included obliteration rates, patients with new seizure disorders, and those with new focal deficits without stroke. RESULTS Of 233 patients included in this study, 32 had a stroke or died after SRS over the mean 8.4-year follow-up (14%). Utilizing the 10% stroke or death rate at a mean 2.8-year follow-up for untreated AVMs in ARUBA, the rate in the authors' study is significantly lower than that anticipated at the 8.4-year follow-up for an untreated cohort (14% vs 30%, p = 0.0003). Notwithstanding obliteration, in this study, annualized rates of hemorrhage and stroke or death after 3 years following SRS were 0.4% and 0.8%, respectively. The overall obliteration rate was 72%; new seizure disorders, temporary new focal deficits without stroke, and permanent new focal deficits without stroke occurred in 2% of patients each. CONCLUSIONS After a sensible follow-up period exceeding the latency period, there is a lower rate of stroke/death for patients with treated, unruptured AVMs with SRS than for patients with untreated AVMs.
We evaluated clinical outcomes in patients with symptomatic brainstem cavernous malformations (CMs) treated by stereotactic radiosurgery (SRS).
Between 1988 and 2016, Gamma Knife SRS was performed in ...76 evaluable patients with solitary symptomatic brainstem CMs. Forty-nine (66%) were intrinsic (not reaching a pial or ependymal surface). Most patients (91%) had experienced 2 or more hemorrhages associated with new neurologic deficits. Fourteen patients (18%) underwent resection before radiosurgery. The median CM volume was 0.66 cm3 (range, 0.05–6.8), and the median margin dose was 15.0 Gy.
After SRS, 15 patients (20%) had an imaging confirmed new hemorrhage at a median follow-up of 48 months. The hemorrhage-free survival after SRS for brainstem CMs was 92% at 1 year, 87% at 3 years, and 85% at 5 years. The annual hemorrhage rate was 31% before and 4% after SRS. In univariate analysis, CM volume, previous surgical resection, and increased number of hemorrhages before SRS were significantly associated with a higher rate of hemorrhage after SRS. In multivariate analysis, only number of previous hemorrhages was significant (P < 0.0005; hazard ratio, 1.51, 95% confidence interval, 1.23–1.85). Symptomatic adverse radiation effects developed in 7 patients (9%). The rate of symptom deterioration related to hemorrhage or symptomatic adverse radiation effects was 10% at 1 year, 18% at 3 years, and 20% at 5 years.
Patients with an increased rate of hemorrhage before SRS had an increased risk of repeat hemorrhage and symptom deterioration rate after SRS. Intrinsic CM location did not significantly affect rates of symptom deterioration or rebleeding.
PDF
