Effect of the CAD/CAM Milling Protocol on the Fracture Behavior of Zirconia Monolithic Crowns.

Although advancements in CAD/CAM technology allow for more personalized treatments, it is not clear how modifications in the CAD/CAM milling process could affect the restoration surface conditions and their mechanical behavior. The objective of this study was to evaluate the effect of different CAD/CAM milling protocols on the topography and fracture behavior of zirconia monolithic crowns (3Y-PSZ) subjected to a chewing simulation. Monolithic 3Y-PSZ premolar crowns were milled using three protocols (n = 13) (slow (S), normal (N), and fast (F)). Crowns were cemented on a dentin analog abutment and subjected to mechanical aging (200 N, 2 Hz, 1,500,000 cycles, 37 °C water). Surviving crowns were subjected to compressive load test and analyzed using fractography. Fracture load data were analyzed with two-parameter Weibull analysis. The surface topography of the crowns was examined with a stereomicroscope and a 3D non-contact profiler. All crowns survived the chewing simulation. Crowns milled using the F protocol had the greatest characteristic fracture load, while crowns produced with the S protocol showed high Weibull modulus. Groups N and S had a more uniform surface and detailed occlusal anatomy than group F. The CAD/CAM milling protocol affected the topography and mechanical behavior of 3Y-PSZ monolithic crowns.

CAD/CAM versus 3D-printing/pressed lithium disilicate monolithic crowns: Adaptation and fatigue behavior.

OBJECTIVES: this study aimed to evaluate the adaptation and fatigue behavior of lithium disilicate glass-ceramic (LD) monolithic crowns produced by press (combined with 3D-printing) and CAD/CAM milling (control) techniques. METHODS: thirty abutment preparations with a chamfer finish line were produced with a dentin analogue material and scanned with extraoral scanner. Captured images were processed using CAD software to design a premolar. Blocks of LD were milled using CAD/CAM system. For the press technique, crowns were first 3D-printed using a polymeric material and the heat-pressing protocol was performed. Crowns were adhesively cemented to the abutments and scanned using micro-CT. Files were processed and cross-sectional images were analysed in five measuring points: marginal, axial angle, axial, occlusal angle and occlusal. Fatigue test was performed in a MTS universal testing machine (2 Hz, 37°C distilled water) using an anatomic composite piston, following the step-stress method. Failures were detected with an acoustic system and confirmed by transillumination. A cumulative damage-Weibull distribution (95% CI) was used to analyze the fatigue data. Gap thickness data were analyzed using Kruskal-Wallis and Student-Newman-Keuls tests (α=0.05). RESULTS: CAD/CAM milling resulted in larger gap thickness in the occlusal area and smaller gap thickness in the axial angle and axial area than press (p<0.05). The probability of failure was similar for crowns produced with CAD/CAM milling and press. The most frequent failure mode was radial crack. CONCLUSIONS: LD crowns produced using the combination of 3D-printing/press technique showed similar fatigue behavior than CAD/CAM milled control group, and resulted in smaller gap thickness at the occlusal region. CLINICAL SIGNIFICANCE: A more controlled process can be achieved by replacing conventional restoration waxing with 3D printing, which in combination with the press technique produces lithium disilicate glass-ceramic monolithic crowns with good adaptation and high fatigue survival.

Modified Manikin for Tracheoinnominate Artery Fistula.

Audience: This simulator is designed to instruct emergency medicine residents in tracheostomy training that involves bleeding from the tracheostomy site. Any resident, fellow, or attending physician who cares for patients with complications from their tracheostomy might benefit from this innovation. Introduction: The emergency medicine provider must maintain proficiency in caring for patients with complications from their tracheostomy. In the United States, over 110,000 patients receive tracheostomies per year.1 A rare but catastrophic complication of tracheostomies, usually within the first month of placement, is a tracheoinnominate artery fistula (TIAF). This complication occurs in 0.7% of tracheostomy patients and carries a 50-70% mortality.1,2 We modified a low-fidelity tracheostomy manikin to instruct learners in the stepwise management of hemorrhage from a TIAF. Educational Objectives: By the end of this educational session, learners will be able to:Perform a focused history and physical exam on any patient who presents with bleeding from the tracheostomy site.Describe the differential diagnosis of bleeding from a tracheostomy site, including a TIAF.Demonstrate the stepwise management of bleeding from a suspected TIAF, including cuff hyperinflation and the Utley Maneuver.Verify that definitive airway control via endotracheal intubation is only feasible in the tracheostomy patient when it is clear, upon history and exam, that the patient can be intubated from above.Demonstrate additional critical actions in the management of a patient with a TIAF, including early consultation with otolaryngology and cardiothoracic surgery as well as emergent blood transfusion and activation of a massive transfusion protocol. Educational Methods: This modified manikin is a useful training tool for any healthcare provider who is involved in the treatment and stabilization of a variety of tracheostomy emergencies, from bleeding to infection to obstruction or dislodgement. Our case was presented on two separate occasions, to otolaryngology interns (PGY-1), and emergency medicine residents (PGY 1-3). It involved the care of a patient with a sentinel bleed and subsequent hemorrhage from a tracheoinnominate artery fistula (TIAF). This low-fidelity tracheostomy manikin provides the ideal platform for any complex, tracheostomy case, particularly where ongoing bleeding from the tracheostomy site might permanently damage the electrical circuitry of a high-fidelity model. We initially fashioned this modified manikin for tracheostomy training during a simulation "boot camp" for otolaryngology PGY-1 residents. Our use of this modified manikin for tracheostomy training was a useful teaching tool during our otolaryngology intern "boot camp." As a result, we organized a subsequent simulation training session with our PGY 1-3 emergency medicine residents to provide similar instruction in management of a TIAF. Research Methods: We provided a pre- and a post-simulation survey for the 33 emergency medicine residents who participated in the TIAF simulation with our modified tracheostomy manikin. There were 11 residents from each of the PGY-1, PGY-2, and PGY-3 year-groups. Thirty-two residents (97%) completed the pre-simulation survey, and 33 residents (100%) completed the post-simulation survey. We used a 6-point Likert Scale from "strongly agree" to "strongly disagree" to assess a resident's knowledge of multiple learning objectives within this simulation. Results: The pre- and post-simulation survey supported this simulation and manikin innovation as a useful teaching tool for tracheostomy emergencies such as a TIAF. Discussion: This was a useful innovation for emergency provider training in the recognition and management of a TIAF, a rare but emergent tracheostomy complication. In addition to this bleeding complication, this innovation might be useful for a variety of tracheostomy emergencies such as site infection, obstruction, and tube dislodgement. We highly recommend the involvement of both an emergency medicine and otolaryngology content expert in the design and debriefing of tracheostomy cases with this modified manikin. In our experience, a facilitated debriefing by an experienced clinician and educator from both fields provided a diverse perspective for challenging cases such as bleeding from a TIAF. Topics: Difficult airway, tracheostomy, tracheoinnominate fistula, hemorrhagic shock, tracheostomy complications, Utley Maneuver.

Effect of disinfectant solutions on a denture base acrylic resin.

The aim of this study was to evaluate the hardness, roughness and mass loss of an acrylic denture base resin after in vitro exposure to four disinfectant solutions. Forty specimens (Clássico, Brazil) were prepared and randomly assigned to 4 groups n = 10) according to the disinfectant solution: G1: control, stored in distilled water at 37 degrees C; G2: 1% sodium hypochlorite; G3: 2% glutaraldehyde; G4: 4% chlorhexidine. G2 to G4 were immersed for 60 minutes in the disinfectant solution. Measurements were carried out both before and after immersion in the solution. The surface was analyzed with a surface roughness tester (Surfcorder SE 1700 KOZAKALAB), a microdurometer FM-700 (Future Tech) and a scanning electron microscope (DSM 962-ZEISS). Loss of mass was determined with a digital weighing scale. After disinfection procedures, values were analyzed statistically. The acrylic denture base resin may be vulnerable to surface changes after in vitro immersion in the disinfectant solutions studied.

Effect of disinfectant solutions on a denture base acrylic resin

El objetivo de este estudio fue evaluar la microdureza, rugosidad y pérdida de masa de resinas acrílicas para base de dentadura, después de su exposición a soluciones desinfectantes, in vitro. Cuarenta especimenes de resina acrílica para base de dentadura (Clássico, Brasil) fueron confeccionados y asignados randomizadamente a 4 grupos (n=10) según la solución desinfectante: G1: control, almacenado en agua destilada a 37 °C; G2: 1 por ciento hipoclorito de sodio; G3: 2 por ciento Glutaraldehído; G4: 4 por ciento clorhexidina. Los especimenes fueroninmersos por 60 minutos en la solución correspondiente. Posteriormente, los especimenes fueron analizados antes ydespués de cada inmersión usando un rugosímetro (Surfcorder SE 1700 KOZAKALAB), un microdurómetro FM-700 (Future Tech), un microscopio Electrónico de Barrido (MEB) (DSM 962-ZEISS) y una escala digital. Después de los procedimientos de desinfección, los valores promedios obtenidos de cada análisis fueron evaluados estadísticamente. Las resinas para base de dentadura pueden ser vulnerables a los cambios de superficie cuando son inmersos en soluciones desinfectantes.

Effect of disinfectant solutions on a denture base acrylic resin

El objetivo de este estudio fue evaluar la microdureza, rugosidad y pérdida de masa de resinas acrílicas para base de dentadura, después de su exposición a soluciones desinfectantes, in vitro. Cuarenta especimenes de resina acrílica para base de dentadura (Clássico, Brasil) fueron confeccionados y asignados randomizadamente a 4 grupos (n=10) según la solución desinfectante: G1: control, almacenado en agua destilada a 37 °C; G2: 1 por ciento hipoclorito de sodio; G3: 2 por ciento Glutaraldehído; G4: 4 por ciento clorhexidina. Los especimenes fueroninmersos por 60 minutos en la solución correspondiente. Posteriormente, los especimenes fueron analizados antes ydespués de cada inmersión usando un rugosímetro (Surfcorder SE 1700 KOZAKALAB), un microdurómetro FM-700 (Future Tech), un microscopio Electrónico de Barrido (MEB) (DSM 962-ZEISS) y una escala digital. Después de los procedimientos de desinfección, los valores promedios obtenidos de cada análisis fueron evaluados estadísticamente. Las resinas para base de dentadura pueden ser vulnerables a los cambios de superficie cuando son inmersos en soluciones desinfectantes.(AU)