Influence of output energy and pulse repetition rate of the Er:YAG laser on dentin ablation

OBJECTIVE: We sought to improve the efficiency of dentin ablation with the Er:YAG laser by investigating the effects of output energy and pulse repetition rate on ablation. Background Data: The Er:YAG laser is superior to other lasers in ablating dental hard tissues. However, the factors affecting the efficiency of ablation with an Er:YAG laser remain unclear. METHODS: Fifty bovine root dentin plates were irradiated with an Er:YAG laser at an output power of 1.0 W, 1.5 W, or 2.0 W under a water spray while moving the plate at 1 mm/sec. After irradiation, the depth and volume of each ablated site were measured by laser microscopy and the ablated surfaces were examined by scanning electron microscopy. RESULTS: The output power showed a strong positive correlation with the depth and volume of ablation. The output energy had much more pronounced effects on the depth and volume of ablation compared to the pulse repetition rate. The shape of the ablated site varied with the output power, and no cracking or vitrification was observed under the irradiated dentin. The most effective parameters for dentin ablation were an output power of 2.0 W, with an output energy of 80 mJ/pulse at 25 pulses per second (pps) or 100 mJ/pulse at 20 pps. CONCLUSION: These findings suggest that the output energy is the main factor affecting the efficiency of dentin ablation with an Er:YAG laser. We propose that the efficiency of dentin ablation can be improved by choosing an optimal combination of output energy and repetition rate.     

Intracisternal infusion of magnesium sulfate solution improved reduced cerebral blood flow induced by experimental subarachnoid hemorrhage in the rat

Magnesium has neuroprotective and antivasospastic properties in the presence of subarachnoid hemorrhage (SAH). The present study investigated the effect of intracisternal administration of magnesium on cerebral vasospasm in the experimental SAH rat model. The rat double-SAH model (0.2 mL autologous blood injected twice into the cisterna magna) was used. Normal saline (SAH group, N = 8) or 10 mmol/L magnesium sulfate in normal saline (SAH + MG group, N = 8) was infused into the cisterna magna at 1.5 μL/min for 30 min on day 5. Control rats without SAH also received intracisternal infusion of normal saline (control group, N = 6). Local cerebral blood flow (CBF) at 24 locations and the weighted average were quantitatively measured by the autoradiographic technique using [¹⁴C]iodoantipyrine during infusion. The weighted average CBF was significantly reduced (P < 0.01, Student’s t-test) in the SAH group (0.78 ± 0.16 mL g⁻¹ min⁻¹) compared to the control group (1.0 ± 0.15 mL g⁻¹ min⁻¹) and was significantly improved (P < 0.01, Student’s t-test) in the SAH + MG group (0.98 ± 0.18 mL g⁻¹ min⁻¹). Local CBF was significantly reduced (P < 0.05, unpaired t test) in 16 locations in the SAH group and significantly improved (P < 0.05, unpaired t test) in 12 locations in the SAH + MG group. Intracisternal infusion of magnesium sulfate significantly improved reduced CBF induced by experimental SAH in the rat.     

Development of the Baylor Gyro Permanently Implantable Centrifugal Blood Pump as a Biventricular Assist Device

The Baylor Gyro permanently implantable centrifugal blood pump (Gyro PI pump) has been under development since 1995 at Baylor College of Medicine. Excellent results were achieved as a left ventricular assist device (LVAD) with survival up to 284 days. Based on these results, we are now focusing on the development of a biventricular assist device (BVAD) system, which requires 2 pumps to be implanted simultaneously in the preperitoneal space. Our hypothesis was that the Gyro PI pump would be an appropriate device for an implantable BVAD system. The Gyro PI 700 pump is fabricated from titanium alloy and has a 25 ml priming volume, pump weight of 204 g, height of 45 mm, and pump diameter of 65 mm. This pump can provide 5 L/min against 100 mm Hg at 2,000 rpm. In this study, 6 half-Dexter healthy calves have been used as the experimental model. The right pump was applied between the infundibular of the right ventricle and the main pulmonary artery. The left pump was applied between the apex of the left ventricle and the thoracic descending aorta. As for anticoagulation, heparin was administered at the first postoperative week and then converted to warfarin sodium from the second week after surgery. Both pump flow rates were controlled maintaining a pulmonary arterial flow of less than 160 ml/kg/min for the sake of avoidance of pulmonary congestion. Blood sampling was done to assess visceral organ function, and the data regarding pump performance were collected. After encountering the endpoint, which the study could not keep for any reasons, necropsy and histopathological examinations were performed. The first 2 cases were terminated within 1 week. Deterioration of the pump flow due to suction phenomenon was recognized in both cases. To avoid the suction phenomenon, a flexible conduit attached on the inlet conduit was designed and implanted. After using the flexible inflow conduit, the required power and the rotational speed were reduced. Furthermore, the suction phenomenon was not observed except for 1 case. There was no deterioration regarding visceral organ function, and pulmonary function was maintained within normal range except for 1 case. Even though the experimental animal survived up to 45 days with the flexible inflow conduit, an increase in power consumption due to thrombus formation behind the impeller became a problem. Lower rotational speed, which was probably produced by the effectiveness of the flexible inflow conduit, was speculated to be one of the reasons. And the minimum range of rotational speed was 1,950 rpm in these 6 BVAD cases and the previous 3 cases of LVAD. In conclusion, 6 cases of BVAD implantation were performed as in vivo animal studies and were observed up to 45 days. The flexible inflow conduit was applied in 4 of 6 cases, and it was effective in avoiding a suction phenomenon. The proper rotational speed of the Gyro PI 700 pump was detected from the viewpoint of antithrombogenicity, which is more than 1,950 rpm.     

Combined anteversion technique reduced the dislocation in cementless total hip arthroplasty

Purpose

The combined anteversion (CA) technique is a method in which the cup is placed according to the stem anteversion in total hip arthroplasty (THA). We examined whether the CA technique reduced the dislocation rate, and the distribution of CA with the manual placement of the cup.

Methods

We retrospectively reviewed 634 hips in 579 patients with primary cementless THA. In 230 hips using the CA technique [CA(+)], a CA of 50 ± 10° was the aim. In the remaining 404 hips [CA(−)], the cup was first placed targeting 20° of anteversion. The post-operative CA was measured using the computed tomography (CT) images in 111 hips.

Results

One hip (0.4 %) had a dislocation in the CA(+) group, whereas ten hips (2.5 %) had a dislocation in the CA(−) group. A multivariate analysis showed that primary diagnosis, head size and CA technique significantly influenced the dislocation rate. Patients in the CA(−) group were 5.8 times more likely to have a dislocation compared to the CA(+) group. In the 111 hips with CT images, 81 hips (73.0 %) achieved the intended CA.

Conclusions

Although the manual placement of the cup resulted in 27 % of outliers from the intended CA, the CA technique significantly reduced the dislocation after primary THA.     

Post injury changes in the properties of mesenchymal stem cells derived from human anterior cruciate ligaments

Purpose

The anterior cruciate ligament (ACL) rarely heals spontaneously after rupture. Mesenchymal stem cells (MSCs) contribute to healing in various tissues, therefore, they may also have a key role in healing after ACL rupture. The purpose of this study was to investigate the properties of MSCs in ruptured ACLs.

Methods

Human ACL samples were harvested from patients undergoing primary ACL reconstruction, and samples were classified by the number of days post rupture (phase I <21 days; phase II 21–56 days; phase III 57–139 days phase IV ≥140 days). We evaluated the characteristics of MSCs, such as colony-forming capacity, differentiation potential and cell-surface markers.

Results

There was a tendency for high colony-forming capacity during phases I and II, which tended to decrease in phase III. Chondrogenic, adipogenic and osteogenic differentiation potential was maintained until phase II but decreased in phase III. Most surface-epitope expression was consistent from phase I to III: positive for CD44, CD73, CD90 and CD105; negative for CD11b, CD19, CD34, CD45 and human leukocyte antigen-D-related (HLA-DR). The presence of these surface markers proved the existence of MSCs in ruptured ACL tissue.

Conclusions

Our results suggest that colony-forming and differentiation potential decrease over time. It is important to consider changes in properties of MSCs and use ACL tissue in the acute phase of rupture when biological manipulation is required.     

Nodal status of malignant lymphoma in pelvic and retroperitoneal lymphatic pathways: comparison of integrated PET/CT with or without contrast enhancement

AIM: To determine the diagnostic accuracy of integrated contrast-enhanced positron emission tomography (PET) and computed tomography (CT), as compared with non-contrasted PET/CT, in evaluating nodal status of malignant lymphoma in pelvic and retroperitoneal lymphatic pathways. MATERIALS AND METHODS: Sixty-six patients (33 men and 33 women) with malignant lymphoma underwent staging with integrated CT and fluorine-18-fluorodeoxyglucose ((18)FDG) PET. Tumor types were diffuse large B-cell lymphoma (n=26, 39%), follicular lymphoma (n=20, 30%), Hodgkin disease (n=16, 24%), and marginal zone B-cell lymphoma (n=4, 6%). Both non-contrasted PET/CT and contrast-enhanced PET/CT images were examined separately by two different qualified physicians for each imaging modality, and nodal status of pelvic and retroperitoneal lymphatic pathways was evaluated. Reference standard included follow-up with clinical, laboratory, and conventional CT findings. We compared diagnostic accuracy retrospectively on basis of per-patient and per-lesion analyses between two modalities using McNemar test, respectively. RESULTS: Nodal status of pelvic and retroperitoneal lymphatic pathways was more accurately determined on contrast-enhanced PET/CT (n=52, 79%) compared with non-contrasted PET/CT (n=47, 71%). Difference in the accuracy of nodal staging between non-contrasted PET/CT and contrast-enhanced PET/CT was significant (p=0.048). On basis of per-lesion analysis, contrast-enhanced PET/CT determined more accurately the status of external iliac lymph node (p=0.002), internal iliac lymph node (p<0.0001), and common iliac lymph node (p=0.002) compared with non-contrasted PET/CT. Diagnostic accuracies of paraaortic lymph node, aortocaval lymph node, and paracaval lymph node were similar by either non-contrasted PET/CT or contrast-enhanced PET/CT. CONCLUSION: Integrated contrast-enhanced PET/CT improves the diagnostic accuracy in evaluating nodal status of pelvic and retroperitoneal lymphatic pathways in patients with malignant lymphoma.     

C1 lateral mass screw insertion caudally from C2 nerve root – An alternate method for insertion of C1 screws: A technical note and preliminary clinical results

Background

C1 lateral mass screw was widely used for fixation of the upper cervical spine. However, massive bleeding from the C1–2 venous plexus is sometimes encountered. In this study, we proposed an alternate method for C1 lateral mass screw insertion, which involves insertion of the screws caudally from the C2 nerve root to reduce bleeding from C1–2 venous plexus.

The Results of Total Hip Arthroplasty After Sugioka Transtrochanteric Anterior Rotational Osteotomy for Osteonecrosis

Background

Since Sugioka transtrochanteric anterior rotational osteotomy (ARO) for osteonecrosis of the femoral head (ONFH) changes the morphology of the proximal femur, total hip arthroplasty (THA) after previous ARO is considered a technically demanding procedure. The purpose of this study was to compare the clinicoradiologic outcomes of THA after ARO with those of THA without any antecedent surgery for ONFH.

Flexion Model Simulating Spinal Cord Injury Without Radiographic Abnormality in Patients With Ossification of the Longitudinal Ligament: The Influence of Flexion Speed on the Cervical Spine

Background/Objective:

It is suspected that the speed of the motion of the spinal cord under static compression may be the cause of spinal cord injury (SCI). However, little is known about the relationship between the speed of the motion of the spinal cord and its stress distributions. The objective was to carry out a biomechanical study of SCI in patients with ossification of the longitudinal ligament without radiologic evidence of injury.

Methods:

A 3-dimensional finite element spinal cord model was established. After the application of static compression, the model underwent anterior flexion to simulate SCI in ossification of the longitudinal ligament patients without radiologic abnormality. Flexion of the spine was assumed to occur at 1 motor segment. Flexion angle was 5°, and flexion speeds were 0.5°/s, 5°/s, and 50°/s. Stress distributions inside of the spinal cord were evaluated.

Results:

Stresses on the spinal cord increased slightly after the application of 5° of flexion at a speed of 0.5°/s. Stresses became much higher at a speed of 5°/s and increased further at 50°s.

Conclusions:

The stress distribution of the spinal cord under static compression increased with faster flexion speed of the spinal cord. High-speed motion of the spinal cord under static compression may be one of the causes of SCI in the absence of radiologic abnormality.