Fatigue of Narrow Dental Implants: Influence of the Hardening Method.

The use of narrow titanium dental implants (NDI) for small ridges, reduced interdental space, or missing lateral incisors can be a viable option when compared to the conventional wider dental implants. Furthermore, in many cases, standard diameter implant placement may not be possible without grafting procedures, which increases the healing time, cost, and morbidity. The aim of this study was to analyze the mechanical viability of the current narrow implants and how narrow implants can be improved. Different commercially available implants (n = 150) were tested to determine maximum strength, strain to fracture, microhardness, residual stress, and fatigue obtaining the stress-number of cycles to fracture (SN) curve. Fractography was studied by scanning electron microscopy. The results showed that when the titanium was hardened by the addition of 15% of Zr or 12% cold worked, the fatigue limit was higher than the commercially pure grade 4 Ti without hardening treatment. Grade 4 titanium without hardening treatment in narrow dental implants can present fractures by fatigue. These narrow implants are subjected to high mechanical stresses and the mechanical properties of titanium do not meet the minimal requirements, which lead to frequent fractures. New hardening treatments allow for the mechanical limitations of conventional narrow implants to be overcome in dynamic conditions. These hardening treatments allow for the design of narrow dental implants with enhanced fatigue life and long-term behavior.

Learning curves of basic laparoscopic psychomotor skills in SINERGIA VR simulator.

PURPOSE: Surgical simulators are currently essential within any laparoscopic training program because they provide a low-stakes, reproducible and reliable environment to acquire basic skills. The purpose of this study is to determine the training learning curve based on different metrics corresponding to five tasks included in SINERGIA laparoscopic virtual reality simulator. METHODS: Thirty medical students without surgical experience participated in the study. Five tasks of SINERGIA were included: Coordination, Navigation, Navigation and touch, Accurate grasping and Coordinated pulling. Each participant was trained in SINERGIA. This training consisted of eight sessions (R1-R8) of the five mentioned tasks and was carried out in two consecutive days with four sessions per day. A statistical analysis was made, and the results of R1, R4 and R8 were pair-wise compared with Wilcoxon signed-rank test. Significance is considered at P value <0.005. RESULTS: In total, 84.38% of the metrics provided by SINERGIA and included in this study show significant differences when comparing R1 and R8. Metrics are mostly improved in the first session of training (75.00% when R1 and R4 are compared vs. 37.50% when R4 and R8 are compared). In tasks Coordination and Navigation and touch, all metrics are improved. On the other hand, Navigation just improves 60% of the analyzed metrics. Most learning curves show an improvement with better results in the fulfillment of the different tasks. CONCLUSIONS: Learning curves of metrics that assess the basic psychomotor laparoscopic skills acquired in SINERGIA virtual reality simulator show a faster learning rate during the first part of the training. Nevertheless, eight repetitions of the tasks are not enough to acquire all psychomotor skills that can be trained in SINERGIA. Therefore, and based on these results together with previous works, SINERGIA could be used as training tool with a properly designed training program.

Decomposition and analysis of laparoscopic suturing task using tool-motion analysis (TMA): improving the objective assessment.

PURPOSE: The laparoscopic suturing task is a complex procedure that requires objective assessment of surgical skills. Analysis of laparoscopic suturing task components was performed to improve current objective assessment tools. METHODS: Twelve subjects participated in this study as three groups of four surgeons (novices, intermediates and experts). A box-trainer and organic tissue were used to perform the experiment while tool movements were recorded with the augmented reality haptic system. All subjects were right-handed and developed a surgeon's knot. The laparoscopic suturing procedure was decomposed into four subtasks. Different objective metrics were applied during tool-motion analysis (TMA). Statistical analysis was performed, and results from three groups were compared using the Jonckheere-Terpstra test, considering significant differences when P ≤ 0.05. RESULTS: Several first, second and fourth subtask metrics had significant differences between the three groups. Subtasks 1 and 2 had more significant differences in metrics than subtask 4. Almost all metrics showed superior task executions accomplished by experts (lower time, total path length and number of movements) compared with intermediates and novices. CONCLUSION: The most important subtasks during suture learning process are needle puncture and first knot. The TMA could be a useful objective assessment tool to discriminate surgical experience and could be used in the future to measure and certify surgical proficiency.

Validation of SINERGIA as training tool: a randomized study to test the transfer of acquired basic psychomotor skills to LapMentor.

PURPOSE: Laparoscopic surgery is commonly used in many surgical procedures but requires a learning process to develop the necessary skills. Virtual reality simulators play an essential role within the training curricula. This paper aims to determine whether training in SINERGIA VR simulator allows novice surgeons to improve their basic psychomotor laparoscopic skills. METHODS: Forty-two people participated in this study, including 28 unexperience medical students and 14 expert surgeons who developed previously more than 100 laparoscopic procedures. Medical students made a pre-training test in LapMentor II; then, they trained in SINERGIA and they finally accomplished a post-training test in LapMentor II. Experts just made one trial in LapMentor II. A statistical analysis was carried out and results of pre- and post-training tests of novices were compared with Wilcoxon signed-rank test. Pre- and post-training tests of novices were also compared with results of experts with Mann-Whitney U test. RESULTS: Most metrics provided by LapMentor II and included in this study show significant differences when comparing pre- and post-training tests of novices. Analysis of pre-training test of novices and experts results show significant differences in all analyzed metrics for all studied tasks. On the other hand, LapMentor was not able to distinguish between experts and novices after training in SINERGIA for any metric in the camera manipulation task and for some metrics of the other tasks. CONCLUSIONS: Training in SINERGIA VR simulator allows improvement of basic psychomotor laparoscpic skills and transferring them to another virtual simulator. Therefore, it could be used in laparoscopic surgery training programs.

Anatomical changes due to pneumoperitoneum analyzed by MRI: an experimental study in pigs.

PURPOSE: Different effects on cardiovascular and respiratory systems and liver are associated with pneumoperitoneum. This study aimed to determine the morphological changes in the abdominal anatomy as a result of increased intra-abdominal pressure due to pneumoperitoneum using MRI. METHODS: Ten healthy female pigs were used in this study. MRI studies of the abdomen in supine position were made before the creation of pneumoperitoneum and 1 h after increasing the pressure to 14 mmHg. Changes in area, volume, and longitudinal and transverse length of the liver were measured. The diameters of the lumen of the abdominal aorta, the inferior vena cava and portal vein were observed in three positions along the abdominal cavity. The position of the diaphragm after the induction of pneumoperitoneum was also analyzed. RESULTS: After induction of pneumoperitoneum, volume and transverse length of the liver was significantly increased, while peak area was decreased. Stenosis in the aortic lumen was observed (P < 0.05). Longitudinal and transverse diameters of the portal lumen were reduced, but significant differences were only found in the longitudinal diameter. Alterations in the diameter of the inferior vena cava lumen were obtained in three analyzed positions, but differences were significant only in two of them. A mean cranial displacement of the diaphragm equal to 25 mm was also observed. CONCLUSION: Increasing abdominal pressure up to laparoscopic pressure (14 mmHg) provokes morphological changes in the liver, vascular structures and diaphragm. These changes could be related to functional alterations that different organs experience after the induction of pneumoperitoneum.

Empleo del modelo animal en la formación enendoscopia diagnóstica y terapéutica de la vía biliar / Animal model training in diagnostic and therapeutic biliary tract endoscopy teaching

Objetivo. Mostrar nuestra experiencia en la formación en endoscopia terapéutica de la vía biliar en modelo animal. Materiales y métodos. Esta actividad formativa tiene una duración de 13 horas y comienza iniciando al alumno en las diferencias anatómicas de las especies que se emplean, la porcina y la canina, con respecto a la anatomía humana. Las prácticas consisten en habituar al endoscopista a la visión lateral del duodenoscopio; se realizan en un modelo porcino debido a que es más sencillo atravesar el esfínter pilórico, aunque no suele ser muy adecuado para la canulación de la papila duodenal. Tras superar la primera fase se utiliza el modelo canino, que permite adquirir las habilidades y destrezas propias de esta técnica. La evaluación de los resultados se realiza mediante una encuesta anónima. Resultados. El 76% de los alumnos confirma que ha avanzado mucho con este entrenamiento, un 18% regular y un 6% poco. El 75% considera que, tras realizar esta actividad de formación, se encontraría capacitado para llevar a cabo la técnica en su hospital. El 94% de los alumnos recomendaría esta actividad a sus compañeros. Conclusiones. El empleo del modelo animal en la formación en colangio pancreatografía retrógada endoscópica (CPRE)permite la adquisición de habilidades básicas necesarias para la práctica, ya que posibilita la repetición de las maniobras y la tutela continuada. Consideramos que con esta metodología mixta se podría acortar la curva de aprendizaje de la CPRE y disminuiría la iatrogenia en las primeras fases (AU)

Aim. To show our experience in training in therapeutic endoscopy of the biliary tract in animal model. Materials and methods. This training activity has duration of 13 hours and starts initiating the trainee in anatomical differences with regard to human anatomy that occur between species that are used, the swine and canine. The practices consist of endoscopist to habituate the lateral view of duodenoscope, performing on pig model because it is easier to pass through the pyloricsphincter, although this is not very suitable for cannulation of the duodenal papilla. After passing the first stage, we used the canine model to acquire the skills and abilities specific to this technique. The performance evaluation is done through an anonymous survey. Results. 76% of students confirmed that they have made good progress with this training, 18% regular and 6% that shortly. 75% believed that after making this training would be found competent to carry out the technique in their hospitals. About 94% of students would recommend this activity. Conclusions. The use of animal model in training in endoscopic retrograde cholangiopancreatography (ERCP)permits the acquisition of basic skills needed for practice, a sit enables the repetition of the maneuvers and continuing care. We believe that this mixed methodology could shorten the learning curve for ERCP and reduce iatrogenic in the early stages (AU)

Effects of premedication with tiletamine/zolazepam/medetomidine during general anesthesia using sevoflurane/fentanyl in swine undergoing pancreas transplantation.

OBJECTIVE: To assess cardiac and hemodynamic responses and body temperature during long-term general anesthesia using sevoflurane/fentanyl after premedication with a tiletamine/zolazepam/medetomidine combination in swine undergoing experimental pancreas transplantation. MATERIALS AND METHODS: Twelve Landrace female pigs of means weight 46.4 +/- 5.1 kg were premedicated by intramuscular administration of tiletamine/zolazepam (3.5 mg/kg), medetomidine (0.03 mg/kg), and atropine (0.02 mg/kg), before anesthesia with 0.75 minimum alveolar concentration sevoflurane and continuous intravenous fentanyl infusion (5.7 +/- 0.7 microg/kg/h). Assessment of heart rate, arterial blood pressure, and temperature in pigs undergoing allogenic pancreas transplant surgery were registered at the start of anesthesia (T0), as well as at 60 (T60), 120 (T120), and 180 (T180) minutes after T0, and finally at the end of anesthesia (T anesthesia end), when we switched off the sevoflurane vaporizer. Analysis of variance was used to determine differences between times with P < .05 considered significant. Results are given as mean values +/- standard deviations. RESULTS: Arterial blood pressure significantly decreased from T120 to the end of anesthesia, while a significantly decreased heart rate was only evident at T60. Body temperature decreased significantly from T60 to the end of anesthesia. These decreases, however, lacked clinical relevance; all parameters were within normal range. No major anesthetic complications were observed in this study. CONCLUSIONS: The administration of a tiletamine/zolazepam/medetomidine combination as premedication in swine subjected to pancreas transplantation allowed for a safe reduction of sevoflurane/fentanyl requirements during long-term general anesthesia. Despite arterial blood pressure and body temperature evidencing a decrease during anesthetic maintenance, all parameters remained within normal range values.

[Usefulness of renal resistive index in the diagnosis and evolution of the obstructive uropathy. Experimental study]. / Utilidad del indice de resistencia renal en la valoración y evolución de la uropatía obstructiva. Estudio experimental.

OBJECTIVE: The study was focused on determining the effectiveness and reliability of using the renal resistance index as a method of diagnosing and monitoring the evolution of obstructive uropathy treatment. For this purpose, we conducted an experimental study on a homogenous group of animals that all had the same level of obstruction. MATERIAL AND METHODS: 15 healthy female pigs were used. The experiment was divided into three phases: phase I consisted of a study prior to unilateral pyeloureteral junction obstruction, performing retrograde ureteropyelography, renal B-mode ultrasound and duplex-Doppler (of both kidneys) at a level of the arcuate arteries. Then, the obstruction was performed on the animals. Phase II commenced by diagnosing the lesion, 6 weeks after the previous phase, by means of the aforementioned diagnostic methods. Finally, the endourological treatment was completed. Animals were monitored (Phase III) 15 weeks after the endopyelotomy, using the same methods as in the study, by assessing the urinary tract (fluoroscopy) and both kidneys by determining the renal resistance index and ratio. RESULTS: All the animals in the study showed signs of urinary obstruction on radiology and renal ultrasound 6 weeks after ureteral ligature. After treatment and follow-up, all animals showed signs of having recovered from the obstructive uropathy. Values of deltaRI during the 3 phases are detailed below. Fase I deltaIR = 0.01, Fase II deltaIR = 0.11, Fase III deltaIR = 0.02. CONCLUSION: RI determination using duplex-Doppler is effective for distinguishing obstructive dilatation using non-invasive techniques. However, this parameter provides very slight differences and it can also be influenced by too many direct and indirect factors (observational, patient age, anaesthesia, haemodynamic parameters, etc.), to supplant the classic diagnostic methods.

Utilidad del índice de resistencia renal en la valoración y evolución de la uropatía obstructiva. Estudio experimental / Usefulness of renal resistive index in the diagnosis and evolution of the obstructive uropathy. Experimental study

Objetivo: El planteamiento del estudio va enfocado a determinar la efectividad y fiabilidad de la medición del índice de resistencia renal (IR) para el diagnóstico y evolución tras el tratamiento de la uropatía obstructiva. Para ello realizamos un estudio experimental con un grupo homogéneo y con un grado de obstrucción uniforme. Material y métodos: Se emplean 15 animales de la especie porcina, todas hembras sanas. El planteamiento experimental está vertebrado en tres fases; la primera consiste en el estudio previo a la obstrucción de la unión pieloureteral unilateral mediante ureteropielografía retrógrada, nefrosonografía en modo B y dúplex-Doppler (ambos riñones) al nivel de las arterias arciformes. Posteriormente se procede a la creación del modelo animal de obstrucción. La Fase II comienza con el diagnóstico de la lesión 6 semanas después de la anterior fase, mediante los medios diagnósticos citados. Finalmente se completa el tratamiento endourológico. El seguimiento de los animales (Fase III) se realiza transcurridas 15 semanas tras la endopielotomía, valorando al igual que durante el estudio, la vía urinaria (fluoroscopia) y la afectación en ambos riñones mediante la determinación del índice de resistencia renal y su ratio. Resultados: Todos los animales del estudio mostraron signos radiológicos y nefrosonográficos de obstrucción urinaria tras 6 semanas de la ligadura ureteral. Tras el tratamiento y seguimiento todos los animales mostraron signos de recuperación de la uropatía obstructiva. Los valores del DeltaIR a lo largo de las 3 fases se detallan a continuación. Fase I DeltaIR = 0.01, Fase II DeltaIR = 0.11, Fase III DeltaIR = 0.02. Conclusiones: La valoración del IR mediante dúplex-Doppler es efectiva para la diferenciación de la dilatación obstructiva mediante técnicas no invasivas. Pero este parámetro aporta unas diferencias muy leves y además puede verse afectado por demasiados factores de modo directo o indirecto (observador, edad del paciente, anestesia, parámetros hemodinámicos, etc.), como para relegar los métodos de diagnóstico clásicos

Objective: The study was focused on determining the effectiveness and reliability of using the renal resistance index as a method of diagnosing and monitoring the evolution of obstructive uropathy treatment. For this purpose, we conducted an experimental study on a homogenous group of animals that all had the same level of obstruction. Material and methods: 15 healthy female pigs were used. The experiment was divided into three phases: phase I consisted of a study prior to unilateral pyeloureteral junction obstruction, performing retrograde ureteropyelography, renal Bmode ultrasound and duplex-Doppler (of both kidneys) at a level of the arcuate arteries. Then, the obstruction was performed on the animals. Phase II commenced by diagnosing the lesion, 6 weeks after the previous phase, by means of the aforementioned diagnostic methods. Finally, the endourological treatment was completed. Animals were monitored (Phase III) 15 weeks after the endopyelotomy, using the same methods as in the study, by assessing the urinary tract (fluoroscopy) and both kidneys by determining the renal resistance index and ratio. Results: All the animals in the study showed signs of urinary obstruction on radiology and renal ultrasound 6 weeks after ureteral ligature. After treatment and follow-up, all animals showed signs of having recovered from the obstructive uropathy. Values of DeltaRI during the 3 phases are detailed below. Fase I DeltaIR = 0.01, Fase II DeltaIR = 0.11, Fase III DeltaIR = 0.02. Conclusion: RI determination using duplex-Doppler is effective for distinguishing obstructive dilatation using non-invasive techniques. However, this parameter provides very slight differences and it can also be influenced by too many direct and indirect factors (observational, patient age, anaesthesia, haemodynamic parameters, etc.), to supplant the classic diagnostic methods