Arachnoid webs causing rostral syrinx due to ball-valve effect: an illustrative report of two cases.

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.

Stereotactic Radiosurgery for Intractable Tremor-Dominant Parkinson Disease: A Retrospective Analysis.

OBJECTIVE: The purpose of this study was to retrospectively analyze the outcomes of stereotactic radiosurgery for patients suffering from medically refractory Parkinson disease (PD) tremor. METHODS: We retrospectively studied the outcomes of 33 patients who were treated with gamma knife thalamotomy (GKT) over a 19-year period. Twelve patients were ≥80 years. A median dose of 140 Gy (range, 130-150 Gy) was delivered to the nucleus ventralis intermedius through a single 4-mm isocenter. We used the Fahn-Tolosa-Marin clinical tremor rating scale to score tremor, handwriting, drawing, and ability to drink fluids. The median time to the last follow-up was 23 months (range, 9-144 months). RESULTS: After GKT, 31 patients (93.9%) experienced improvement in tremor. Twenty-three patients (70.0%) had complete or nearly complete tremor arrest. Nine patients (27.2%) noted tremor arrest and resolution of impairment in writing, drawing, and ability to drink fluids. One patient (3%) improved in bradykinesia, 3 patients (9%) improved in rigidity, and 3 patients (9%) decreased their dosage of dopa after GKT. Tremor relief was fully maintained in the last follow-up for 96.8% of responding patients. Two patients (6%) experienced temporary adverse radiation effects. CONCLUSIONS: GKT is a safe and effective treatment for medically refractory PD tremor, especially for the elderly or those not suitable for deep brain stimulation or thermal thalamotomy.

Implementation of a New UPMC Gamma Knife Radiosurgery Quality Assurance Registry.

OBJECT: In this report, we discuss the development of a new, comprehensive, Health Insurance Portability and Accountability Act-compliant electronic quality assurance (QA) registry for Gamma Knife (GK) radiosurgery patients. This registry can be used to query outcomes, link with current hospital electronic medical records, and share data with future corporate or national professional society registries under development. METHODS: A clinical task force comprising physicians and regulatory, legal, and information technology (IT) experts was created to define the nomenclature, regulatory requirements, hosting site, and required capabilities of the proposed system. A team of physicians and IT experts defined the clinical parameters and designed the query functions for the registry. RESULTS: The UPMC GK Registry was established as a QA registry exempt from Institutional Review Board oversight. In order to facilitate subsequent query functions (analytics), data entry was created for 3 main categories: brain tumors, vascular malformations, and functional disorders. A Microsoft SQL-based database infrastructure was employed. CONCLUSIONS: We developed a new UPMC GK QA registry and successfully migrated our previous data on 13,000 patients into the registry. This simplified and user-friendly registry offers clinicians the opportunity to participate in national registries and to contribute to multicenter evidence-based outcome analyses.

Stereotactic Radiosurgery as Initial Surgical Management for Elderly Patients with Trigeminal Neuralgia.

BACKGROUND: Management of older patients with medically refractory trigeminal neuralgia (TN) is yet a matter of debate. OBJECTIVE: We sought to determine the benefit of stereotactic radiosurgery (SRS) as the sole surgical management in older patients (≥70 years). METHODS: One hundred and twenty-seven patients (≥70 years) with typical TN underwent SRS as initial surgical management. The median maximum dose for the first procedure was 80 Gy. Repeat SRS was performed in 46 patients who developed recurrent pain. RESULTS: After the first SRS, the initial pain control was achieved in 91% of patients. Complete pain relief (Barrow Neurological Institute [BNI] score I) developed in 75 patients (59%) and was maintained in 59, 39, and 22% of patients at 1, 3, and 5 years. Following repeat SRS, the rate of complete pain relief was 79, 55, and 41% at 1, 3, and 5 years. The chance of BNI I preservation was greater after repeat SRS compared to initial SRS (hazards ratio: 2.02, p < 0.0001). The incidence of trigeminal sensory loss was 17% after initial SRS but increased to 39% after repeat SRS. CONCLUSIONS: SRS alone was used effectively in older TN patients to achieve pain control. Recurrent pain responded to retreatment but was associated with an increased risk of sensory dysfunction.

Traumatic L4-5 bilateral locked facet joints.

INTRODUCTION: Traumatic bilateral locked facet joints occur with extreme rarity in the lumbar spine. A careful review of the literature revealed only three case reports. CLINICAL PRESENTATION: We present the case of a 36 year-old male who suffered bilateral L4-5 facet fracture dislocations following a motor vehicle collision. The dislocation was associated with disruption of the posterior elements and a Grade II anterolisthesis of L4 on L5 as well as an epidural hematoma resulting in severe canal narrowing, with the patient remaining neurologically intact on presentation. The patient underwent open reduction with L3 to S1 pedicle screw fixation and arthrodesis to treat this highly unstable injury. CONCLUSION: The existing literature and a biomechanics review of the lumbar spine are described in the context of the presented case in addition to a proposed mechanism for such dislocations.

Histopathological examination of spine tumors after treatment with radiosurgery.

OBJECTIVE Increased survival time after diagnosis of neoplastic disease has resulted in a gradual increase in spine tumor incidence. Radiosurgery is frequently a viable alternative to operative management in a population with severe medical comorbidities. The authors sought to assess the histopathological consequences of radiosurgery in the subset of patients progressing to operative intervention. METHODS Eighteen patients who underwent radiosurgery for spine tumors between 2008 and 2014 subsequently progressed to surgical treatment. A histopathological examination of these cases was performed. Indications for surgery included symptomatic compression fractures, radiographic instability, and symptoms of cord or cauda equina compression. Biopsy samples were obtained from the tumor within the radiosurgical zone in all cases and were permanently fixated. Viable tumor samples were stained for Ki 67. RESULTS Fifteen patients had metastatic lesions and 3 patients had neurofibromas. The mean patient age was 57 years. The operative indication was symptomatic compression in 10 cases (67%). The most frequent metastatic lesions were breast cancer (4 cases), renal cell carcinoma (3), prostate cancer (2), and endometrial cancer (2). In 9 (60%) of the 15 metastatic cases, histological examination of the lesions showed minimal evidence of inflammation. Viable tumor at the margins of the radiosurgery was seen in 9 (60%) of the metastatic cases. Necrosis in the tumor bed was frequent, as was fibrotic bone marrow. Vascular ectasia was seen in 2 of 15 metastatic cases, but sclerosis with ectasia was frequent. No evidence of malignant conversion was seen in the periphery of the lesions in the 3 neurofibroma cases. In 1 case of neurofibroma, the lesion demonstrated some small areas of remnant tumor in the radiosurgical target zone. CONCLUSIONS This case series demonstrates important histopathological characteristics of spinal lesions treated by SRS. Regions with the highest exposure to radiation appear to be densely necrotic and show little evidence of tumor growth, whereas peripheral regions distant from the radiation dosage are more likely to demonstrate viable tumor in malignant and benign neoplasms. Physiological tissue appears to be similarly affected. With additional investigation, a more homogenized field of hypofractionated radiation exposure may allow for tumor obliteration with relative preservation of critical anatomical structures.

Microglia in Glia-Neuron Co-cultures Exhibit Robust Phagocytic Activity Without Concomitant Inflammation or Cytotoxicity.

A simple method to co-culture granule neurons and glia from a single brain region is described, and microglia activation profiles are assessed in response to naturally occurring neuronal apoptosis, excitotoxin-induced neuronal death, and lipopolysaccharide (LPS) addition. Using neonatal rat cerebellar cortex as a tissue source, glial proliferation is regulated by omission or addition of the mitotic inhibitor cytosine arabinoside (AraC). After 7-8 days in vitro, microglia in AraC(-) cultures are abundant and activated based on their amoeboid morphology, expressions of ED1 and Iba1, and ability to phagocytose polystyrene beads and the majority of neurons undergoing spontaneous apoptosis. Microglia and phagocytic activities are sparse in AraC(+) cultures. Following exposure to excitotoxic kainate concentrations, microglia in AraC(-) cultures phagocytose most dead neurons within 24 h without exacerbating neuronal loss or mounting a strong or sustained inflammatory response. LPS addition induces a robust inflammatory response, based on microglial expressions of TNF-α, COX-2 and iNOS proteins, and mRNAs, whereas these markers are essentially undetectable in control cultures. Thus, the functional effector state of microglia is primed for phagocytosis but not inflammation or cytotoxicity even after kainate exposure that triggers death in the majority of neurons. This model should prove useful in studying the progressive activation states of microglia and factors that promote their conversion to inflammatory and cytotoxic phenotypes.

White matter changes in breast cancer brain metastases patients who undergo radiosurgery alone compared to whole brain radiation therapy plus radiosurgery.

Delayed toxicity after whole brain radiation therapy (WBRT) is of increasing concern in patients who survive more than one year with brain metastases from breast cancer. Radiation-related white matter toxicity is detected by magnetic resonance imaging (MRI) and has been correlated with neurocognitive dysfunction. This study assessed the risk of developing white matter changes (WMC) in breast cancer patients who underwent either WBRT plus stereotactic radiosurgery (SRS) or SRS alone. We retrospectively compared 35 patients with breast cancer brain metastases who received WBRT and SRS to 30 patients who only received SRS. All patients had evaluable imaging at a median of one year after their initial management. The development of white matter T2 prolongation as detected by T2 or FLAIR imaging was graded: grade 1 = little or no white matter T2 hyperintensity; grade 2 = limited periventricular hyperintensity; and grade 3 = diffuse white matter hyperintensity. After WBRT plus SRS, patients demonstrated a significantly higher incidence of WMC (p < 0.0001). After one year, 71.5 % of patients whose treatment included WBRT demonstrated WMC (42.9 % grade 2; 28.6 % grade 3). Only one patient receiving only SRS developed WMC. In long-term survivors of breast cancer, the risk of WMC was significantly reduced when SRS alone was used for management. Further prospective studies are necessary to determine how these findings correlate with neurocognitive toxicity. WBRT usage as initial management of limited brain disease should be replaced by SRS alone to reduce the risk of delayed white matter toxicity.

Microtensile bond strength of different acrylic teeth to high-impact denture base resins.

PURPOSE: This study evaluated the effect of denture base acrylic, denture tooth composition, and ridge-lap surface treatment on the microtensile bond strength (µTBS) of three commercially available denture teeth and two injection denture processing systems. MATERIALS AND METHODS: Sixteen experimental groups were formed (n = 3), according to denture tooth surface treatment (no treatment or surface treatment recommended by the manufacturer), denture base processing technique and acrylic (SR-Ivocap-Ivocap Plus or Success-Lucitone 199), and tooth type-composition at bonding interface (BlueLine DCL-PMMA, Portrait IPN-PMMA, Phonares II-PMMA, Phonares II-NHC). Rectangular bar specimens with a 1 mm(2) cross sectional area were fabricated and subsequently thermocycled at 10,000 cycles between 5°C and 55°C with a 15-second dwell time. Select specimens underwent µTBS testing in a universal testing machine with a 1 kN load cell at 0.5 mm/min crosshead speed. Data were analyzed statistically by two and three-way ANOVA and Tukey post hoc test (α = 0.05). RESULTS: Mean µTBS ranged between 56.2 ± 5.6 and 60.8 ± 5.0 N/mm(2) for the Ivocap Plus specimens and 13.3 ± 5.12 to 60.1 ± 6.0 N/mm(2) for the Lucitone 199 specimens. Among the Ivocap specimens, BlueLine DCL and Phonares II NHC had significantly higher µTBS than Portrait IPN to Ivocap Plus acrylic. There were no statistically significant differences among Blueline, Phonares II PMMA, and Phonares II NHC, or between Phonares II PMMA and Portrait IPN. Within the Luctione 199 specimens, there was a significantly higher µTBS for BlueLine DCL and Phonares II NHC denture teeth with the manufacturer-recommended surface treatment when compared to control surface. BlueLine, Portrait, and Phonares II PMMA groups achieved significantly higher mean µTBS than the Phonares II NHC group. There were no statistically significant differences among BlueLine, Portrait, and Phonares II PMMA groups. CONCLUSION: When evaluating the µTBS of PMMA and NHC denture teeth to base resins, a stronger bond was achieved using materials produced by the same manufacturer. Within the Luctione 199 specimens, the Phonares II NHC group demonstrated significantly lower bond strength than other specimens, suggesting that gross ridge-lap reduction of NHC denture teeth is not recommended if a base acrylic by a different manufacturer from the tooth is going to be used.

Maxillary implant-retained partial overdenture with Dolder bar attachment: a clinical report.

This article describes a technique for maintaining a maxillary Kennedy III partial removable dental prosthesis design in a patient who had non-restorable failing abutments by replacing the abutments with dental implants. Two implants were placed immediately after extraction of the abutment teeth in the anterior maxilla. After the implants were fully integrated, a Dolder bar attachment was fitted onto the implants. A new maxillary partial removable dental prosthesis was fabricated using the implants and the remaining natural teeth as abutments to restore function and esthetics. With the aid of dental implants, this Kennedy III maxillary removable dental prosthesis design could provide additional retention and support by promoting cross-arch stability and tissue, implant and tooth support. The patient's satisfaction was significantly increased.

Evaluation of tumor progression and detection of new tumors during repeat Gamma Knife® stereotactic radiosurgery utilizing the co-registration tool in Leksell Gamma Plan®: technical note.

BACKGROUND: Repeat Gamma Knife stereotactic radiosurgery (GKSR) procedures are becoming common, especially for brain metastases. It is important to identify tumors requiring treatment at repeat GKSR and it can be challenging to distinguish treated tumors, tumor progression and new tumors. Using the image co-registration tool within the Leksell Gamma Plan software, we developed a technique to aid in the identification of tumors needing treatment. OBJECTIVES: The objective was to explore a new co-registration technique to identify tumors requiring treatment at repeat GKSR procedures. METHODS: Ten patients who underwent repeat GKSR for brain metastases were identified. Contrast-enhanced volumetric T1 magnetic resonance images (MRI) from the previous GKSR were co-registered with the new images and the resulting two-color format image was used to evaluate tumor status. RESULTS: Using the co-registered images, tumors were characterized as: resolved, regressed, stable, larger or new. Overall, 13.6% of tumors completely resolved, 26.2% regressed, 13.1% remained stable, while 7.9% progressed. Thirty-nine percent of tumors were new. CONCLUSIONS: The co-registration technique makes clinically relevant changes conspicuous on MRI. It distinguishes between tumors potentially requiring treatment and those that have been treated successfully. It can be used with tumors other than metastases and for evaluating tumor response at follow-up.

Strength properties of preceramic brazed joints of a gold-palladium alloy with a microwave-assisted oven and gas/oxygen torch technique.

STATEMENT OF PROBLEM: The effect of microwave brazing on the strength properties of dental casting alloys is not yet known. PURPOSE: The purpose of this study was to compare the strength properties of preceramic brazed joints obtained by using a microwave oven and a conventional torch flame for a high noble alloy (Au-Pd). MATERIAL AND METHODS: A total of 18 tensile bars made of an Au-Pd ceramic alloy were fabricated. Six specimens were cut and joined with a high-fusing preceramic solder in a specially designed microwave oven, and 6 specimens were joined with a conventional natural gas/oxygen torch. The remaining 6 uncut specimens were tested as a control. All the specimens were subjected to testing with a universal testing machine. A 1-way ANOVA was performed for each strength property tested. RESULTS: The tensile strength of the uncut group was the highest (745 ±19 MPa), followed by the microwave group (420 ±68 MPa) and the conventional torch group (348 ±103 MPa) (P<.001); however, no significant difference in tensile strength was found between the microwave group and gas torch group. The tensile strength of the microwave group exceeded ANSI/ADA Standard No. 88, Dental Brazing Alloys (a joint standard of the American National Standards Institute and the American Dental Association). CONCLUSIONS: The microwave heating preceramic solder method demonstrated the excellent tensile strength of an Au-Pd alloy and may be an alternative way of joining alloys when a torch flame is contraindicated.

Effects of soldering methods on tensile strength of a gold-palladium metal ceramic alloy.

STATEMENT OF PROBLEM: The tensile strength obtained by conventional postceramic application soldering and laser postceramic welding may require more energy than microwave postceramic soldering, which could provide similar tensile strength values. PURPOSE: The purpose of the study was to compare the tensile strength obtained by microwave postceramic soldering, conventional postceramic soldering, and laser postceramic welding. MATERIAL AND METHODS: A gold-palladium metal ceramic alloy and gold-based solder were used in this study. Twenty-seven wax specimens were cast in gold-palladium noble metal and divided into 4 groups: laser welding with a specific postfiller noble metal, microwave soldering with a postceramic solder, conventional soldering with the same postceramic solder used in the microwave soldering group, and a nonsectioned control group. All the specimens were heat treated to simulate a normal porcelain sintering sequence. An Instron Universal Testing Machine was used to measure the tensile strength for the 4 groups. The means were analyzed statistically with 1-way ANOVA. The surface and fracture sites of the specimens were subjectively evaluated for fracture type and porosities by using a scanning electron microscope. RESULTS: The mean (standard deviation) ultimate tensile strength values were as follows: nonsectioned control 818 ±30 MPa, microwave 516 ±34 MPa, conventional 454 ±37 MPa, and laser weld 191 ±39 MPa. A 1-way ANOVA showed a significant difference in ultimate tensile strength among the groups (F3,23=334.5; P<.001). Follow-up multiple comparisons showed a significant difference among all the groups. Microwave soldering resulted in a higher tensile strength for gold and palladium noble metals than either conventional soldering or laser welding. CONCLUSION: Conventional soldering resulted in a higher tensile strength than laser welding. Under the experimental conditions described, either microwave or conventional postceramic soldering would appear to satisfy clinical requirements related to tensile strength.

Practical applications of three-dimensional printing for process improvement in the cytopathology laboratory.

With the increased availability of three-dimensional (3D) printers, innovative teaching and training materials have been created in medical fields. For pathology, the use of 3D printing has been largely limited to anatomic representations of disease processes or the development of supplies during the coronavirus disease 2019 pandemic. Herein, an institution's 3D printing laboratory and staff with expertise in additive manufacturing illustrate how this can address design issues in cytopathology specimen collection and processing. The authors' institutional 3D printing laboratory, along with students and trainees, used computer-aided design and 3D printers to iterate on design, create prototypes, and generate final usable materials using additive manufacturing. The program Microsoft Forms was used to solicit qualitative and quantitative feedback. The 3D-printed models were created to assist with cytopreparation, rapid on-site evaluation, and storage of materials in the preanalytical phase of processing. These parts provided better organization of materials for cytology specimen collection and staining, in addition to optimizing storage of specimens with multiple sized containers to optimize patient safety. The apparatus also allowed liquids to be stabilized in transport and removed faster at the time of rapid on-site evaluation. Rectangular boxes were also created to optimally organize all components of a specimen in cytopreparation to simplify and expedite the processes of accessioning and processing, which can minimize errors. These practical applications of 3D printing in the cytopathology laboratory demonstrate the utility of the design and printing process on improving aspects of the workflow in cytopathology laboratories to maximize efficiency, organization, and patient safety.

Benchmarking cytology support for ROSE during endoscopic and bronchoscopic procedures.

INTRODUCTION: 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). MATERIALS AND METHODS: 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. RESULTS: 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. CONCLUSIONS: 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.

Leukoencephalopathy after whole-brain radiation therapy plus radiosurgery versus radiosurgery alone for metastatic lung cancer.

BACKGROUND: As systemic therapies improve and patients live longer, concerns mount about the toxicity of whole-brain radiation therapy (WBRT) for treatment of brain metastases. Development of delayed white matter abnormalities indicative of leukoencephalopathy have been correlated with cognitive dysfunction. This study assesses the risk of imaging-defined leukoencephalopathy in patients whose management included WBRT in addition to stereotactic radiosurgery (SRS). This risk is compared to patients who only underwent SRS. METHODS: We retrospectively compared 37 patients with non-small cell lung cancer who underwent WBRT plus SRS to 31 patients who underwent only SRS. All patients survived at least 1 year after treatment. We graded the development of delayed white matter changes on magnetic resonance imaging using a scale to evaluate T(2) /FLAIR (fluid attenuated image recovery) images: grade 1 = little or no white matter hyperintensity; grade 2 = limited periventricular hyperintensity; and grade 3 = diffuse white matter hyperintensity. RESULTS: Patients treated with WBRT and SRS had a significantly greater incidence of delayed white matter leukoencephalopathy compared to patients who underwent SRS alone (P < .001). On final imaging, 36 of 37 patients (97.3%) treated by WBRT developed leukoencephalopathy (25% with grade 2; 70.8% with grade 3). Only 1 patient treated with SRS alone developed leukoencephalopathy. CONCLUSIONS: Risk of leukoencephalopathy in patients treated with SRS alone for brain metastases was significantly lower than that for patients treated with WBRT plus SRS. A prospective study is necessary to correlate these findings with neurocognition and quality of life. These data supplement existing reports regarding the differential effects of WBRT and SRS on normal brain structure and function.

Comparison of fracture resistance of pressable metal ceramic custom implant abutment with a commercially fabricated CAD/CAM zirconia implant abutment.

STATEMENT OF PROBLEM: The predictable nature of the hot pressing ceramic technique has several applications, but no study was identified that evaluated its application to the fabrication of custom implant abutments. PURPOSE: The purpose of this study was to compare the fracture resistance of an experimentally designed pressable metal ceramic custom implant abutment (PR) with that of a duplicate zirconia abutment (ZR). MATERIALS AND METHODS: Two groups of narrow platform (NP) (Nobel Replace) implant abutment specimens were fabricated (n=10). The experimental abutment (PR) had a metal substructure cast with ceramic alloy (Lodestar) and veneered with leucite pressable glass ceramic (InLine PoM). Each PR abutment was individually scanned and 10 duplicate CAD/CAM ZR abutments were fabricated for the control group. Ceramic crowns (n=20) with the average dimensions of a human lateral incisor were pressed with lithium disilicate glass ceramic (IPS e.max Press) and bonded on the abutments with a resin luting agent (Multilink Automix). The specimens were subjected to thermocycling, cyclic loading, and finally static loading to failure with a computer-controlled Universal Testing Machine. An independent t test (1 sided) determined whether the mean values of the fracture load differed significantly (α=.05) between the 2 groups. RESULTS: No specimen failed during cyclic loading. Upon static loading, the mean (SD) load to failure was significantly higher for the PR group (525.89 [143.547] N) than for the ZR group (413.70 [35.515] N) for internal connection narrow platform bone-level implants (P=.025). Failure was initiated at the screw and internal connection level for both groups. CONCLUSIONS: It is possible to fabricate PR abutments that are stronger than ZR abutments for Nobel Biocare internal connection NP bone-level implants. The screw and the internal connection are the weak links for both groups.

Pre-operative stereotactic radiosurgery for cerebral metastatic disease: A retrospective dose-volume study.

BACKGROUND AND PURPOSE: 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. METHODS: 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. RESULTS: Higher planned tumor volume post-operatively (median[IQR] 12.28 [6.54, 18.69]cc vs 10.20 [4.53, 21.70]cc 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 (1.23[1.20, 1.29] vs 1.29[1.23, 1.39], p = 0.0098) and gradient index (2.72[2.59, 2.98] vs 2.94[2.69, 3.47], p = 0.0004). A significant difference was found in normal brain tissue exposed to 10 Gy (12.97[6.78, 25.54]cc vs 32.13[19.42, 48.40]cc, p < 0.0001), 12 Gy (9.31[4.56, 17.43]cc vs 23.80[14.74, 36.56]cc, p < 0.0001), and 14 Gy (5.62[3.23, 11.61]cc vs 17.47[9.00, 28.31]cc, p < 0.0001), favoring pre-operative SRS. CONCLUSIONS: 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.

Applying microwave technology to sintering dental zirconia.

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.

Glioblastoma Adjacent to Radiosurgically Treated Arteriovenous Malformation: A Case Report and Review of the Literature.

Stereotactic radiosurgery (SRS) is a noninvasive therapy for patients suffering from both benign and malignant intracranial pathologies. While SRS allows for increased precision and efficacy, significant risks have been reported, such as radiation necrosis. Although traditional radiation therapies are associated with a well-understood risk of causing tumors or inducing malignancy, the risks associated with SRS are not well understood. Here, we present the case of a patient who underwent SRS post-Onyx embolization of a Spetzler-Martin grade 4 left parasagittal arteriovenous malformation. Four years later, the patient presented with a high-grade glioma adjacent to where the SRS was targeted. SRS has fundamentally altered the way we treat intracranial pathologies. While the risks for SRS-induced glioma appear to be extremely low, this case illustrates that they ought to be considered. Here, we discuss the details of our case and explore the currently available literature. Knowing these potential risks will further aid physicians and patients balance the associated benefits and risks.