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Biomedical subjects

P Shetty

Publications and source records attributed to P Shetty.

31 records · Page 2Linked to original sources
PubMed1983

Differentiation of focal intrahepatic lesions with 99mTc-red blood cell imaging.

The appearance of focal hepatic lesions on 99mTc-sulfur colloid images is nonspecific. As it is important to distinguish hemangiomas from other lesions prior to biopsy, a prospective study was performed using 99mTc-labeled red blood cells. Dynamic perfusion and delayed blood-pool images (1-2 hours) were obtained and lesion activity categorized as increased, equal, or decreased compared with the liver. Of 21 patients studied, 9 (43%) had one or more hepatic hemangiomas, and 8 of these 9 patients (89%) demonstrated increased blood-pool activity. The 12 nonhemangiomatous lesions consisted of 7 metastatic tumors, 2 hepatomas, 1 cirrhotic nodule, and 2 hepatic cysts. None of these 12 patients had increased activity on delayed blood-pool images. Early dynamic images of hepatic hemangiomas demonstrated variable activity (vascularity) and were not useful in differentiating hemangiomas from other lesions. Sensitivity was 89% and specificity 100%. Although liver enzymes are usually normal with hepatic hemangiomas, they may also be normal in metastatic disease. The authors recommend that delayed blood-pool imaging be performed prior to biopsy, particularly in patients without a known primary tumor or those with normal liver enzyme levels.

Adult↗
PubMedDate not supplied

Comparative evaluation of effect of auxiliary retentive features on retention of complete cast crowns in teeth with adequate and inadequate crown height. An invitro study.

This study was done to evaluate the retention of complete cast crowns in teeth with adequate and inadequate crown height and to evaluate the effects of auxiliary retentive features on retention from of complete cast crowns. Thirty-six extracted human maxillary first premolars were obtained. In one group teeth were prepared to a constant height of 3.5 mm and in the second group teeth were prepared to a constant height of 2.5 mm. Each group was further subgrouped into three. In the first subgroup teeth were prepared conventionally, second subgroup proximal grooves were incorporated and in the third subgroup proximal boxes were incorporated. Tensional forces required to dislodge each cemented casting from its preparation was used for comparison of retention quality. These results were then subjected to an analysis of variance (ANOVA). The retention of crown in tooth with adequate crown height were statistically highly significant (P < 0001), compared to inadequate crown height and in boxes compared to grooves and conventional preparation.

Analysis of Variance↗
PubMedDate not supplied

Finite element analysis of a three unit fixed partial denture cast with nickel-chromium alloy.

A two dimensional mathematical model was generated, representing a three unit fixed-fixed partial denture and its supporting structures. Second premolar and second molar were used as abutments with first molar as pontic. A load of 1 kg was applied to the occlusal surface of the casting. Stresses and displacement developed at various regions were analyzed with STAAD III/ISDS program. Maximum stresses were developed in the pontic and connectors with distal connector experiencing the maximum stresses. Stresses transmitted to the dentin were comparatively lower and more of compressive in nature. The underying bone experienced moderate amount of both compressive and tensile stresses but the displacement in this tissue were minimal compared to the rest.

Chromium Alloys↗
PubMedDate not supplied

Comparative evaluation of the effect of simulated porcelain firing cycle on the mechanical properties and microstructure of base metal ceramic alloys.

A comparison of mechanical properties and microstructure of four metal ceramic alloys in as-cast and heat-treated conditions resulted in significant differences. The alloys that were tested included two nickel-based and two cobalt-based metal ceramic alloys. Mechanical properties tested included strength, percent elongation and hardness. Ten tensile bars were cast for each alloy. Five of the ten bars for each alloy were randomly selected for heat treatment with the simulated porcelain firing cycle. Results indicated that the nickel-based alloys were weakened by the heat treatment and showed a decreased hardness and an increased elongation. The effects of heat treatment on the strength of cobalt-based alloys were variable, showing an increase in hardness and a decrease in elongation. Differences in mechanical properties exhibited by the alloys were related to compositional and microstructural changes.

Analysis of Variance↗
PubMedDate not supplied

An investigation into the effect of solidification shrinkage on distortion of casting and flexure strength of various solders for base metal alloys. A laboratory study.

This study was undertaken to determine the distortion due to solidification shrinkage and to evaluate the flexure strength properties of soldered joints between combination of three commercially available base metal alloys and solders. Ninety rectangular bars were cast using three commercially available alloys for soldering (30 bars of each alloys). Ten bars of each alloy were soldered using electrical soldering unit and solder recommended by respective manufacturers, twenty bars (ten pairs each) were soldered using other solders. Length between the references markings on the specimen were measured using a vernier caliper and travelling microscope to check the possible solidification shrinkage. The specimens were then subjected to flexure strength evaluation using a universal testing machine. Statistical comparison of dimensional changes due to solidification shrinkage and flexure strength evaluation of soldered joints was done using analysis of variance test. Recommended Ni-Cr solders showed less shrinkage compared to that of the Co-Cr solders from the tested specimens and superior flexure strength was found in Co-Cr alloy specimen (P value P > .001) soldered with Co-Cr alloy solders.

Analysis of Variance↗
PubMedDate not supplied

Stress variations in recast Ni-Cr alloy--a finite element analysis.

A finite element analysis was carried out to analyse the stress variations in a mandibular posterior fixed partial denture (FPD), made of recast nickel-chromium alloy. A two dimensional finite element model was developed and then analysed with STAAD III/ISDS program with an occlusal load of 1 kg applied to the casting surface. The analysis revealed that the connectors experienced maximum stresses and the generated stress values decreased within the fixed partial denture made of recast Ni-Cr alloy. It seemed unlikely that FPD inspite of being made of recast alloy might fail before the other tissue components show signs of degeneration thus establishing the potential for recycling the Ni-Cr alloy in actual dental practice.

Bite Force↗
PubMedDate not supplied

In vitro evaluation of ceramometal bond strength in anterior metal ceramic crowns with and without palatal coverage of porcelain.

This in vitro study compared the load necessary to cause porcelain bond failure on porcelain covering the labial and palatal surfaces compared with porcelain covering only labial surface in metal ceramic crowns of maxillary anterior teeth. 30 metal ceramic crowns for maxillary central incisor tooth were fabricated in two groups (Groups A and Group B) (15 samples in each group). In group A, palatal ceramo-metal junction was placed at cervical 1/5th of palatal surface. In Group B the palatal ceramo-metal junction was placed at palato incisal line angle and these crowns were subjected to load using Instron testing machine. Mean failure load for group A is statistically highly significant than Group B. (P value = 0.0025). But both these values are higher than the reported mean maximal incising forces.

Bite Force↗
PubMedDate not supplied

Evaluation of glycoproteins as prognosticators in head and neck malignancy.

Although several serum glycoprotein assays have been conducted for identifying tumor markers and prognosticators of malignancies, presently assessment of effectiveness of treatment of these malignancies remains subjective and good and effective tumor markers and prognosticators of head and neck malignancies are yet to be identified. In our study, serum samples from forty patients with head and neck cancers who were divided into four groups of ten patients each on the basis of their clinical staging and serum samples from ten healthy individuals comprising the control group was taken and subjected to biochemical analysis of serum protein bound hexose, serum fucose, serum sialic acid levels before starting treatment of the cancers and after completion of the cancer treatment and compared with the levels of these serum glycoproteins amongst the control group. All the head and neck cancer patients showed elevated levels of the serum glycoproteins as compared to the control group. It was further noted that the increased levels of the serum glycoproteins correlated well with the clinical staging of the malignancies. Post-treatment levels of all the serum glycoproteins were decreased significantly but, only the serum sialic acid level in 6 out of 10 patients with stage-I malignancy returned to the base line levels as seen in the control group. Serum sialic acid levels showed very close correlation with tumor staging and maybe considered as a good tumor marker and prognosticator for detection of cancer and evaluation of effectiveness of treatment of head and neck malignancies.

Biomarkers, Tumor↗
PubMedDate not supplied

Comparative evaluation of tensile bond strength of denture base resins to surface pretreated cobalt chromium base metal alloys--an in vitro study.

This study was undertaken to evaluate the tensile bond strength of acrylic resins to surface pretreated Cobalt-chromium base metal alloy. A total of 60 tensile bar specimens were prepared. One half of the bar was cast in cobalt-chromium alloy and the other half made of denture base resins attached to the alloy following surface pretreatment. Two denture base resins and five surface pre-treatments were used which included sandblasting, acid etching, use of metal adhesive primers and the combination of the above mentioned modes. Gradual axial loads were applied on the tensile bar specimen mounted on a Hounsfield tensometer till bond failure was evident. Statistical evaluation was done using Mann-Whitney U test. The study results indicate that the bond strength in those specimens wherein a combination of sandblasting, acid etching and priming was done as surface pretreatment, showed the maximum values as compared to the other groups.

Acid Etching, Dental↗
PubMedDate not supplied

Evaluation of the polished surface characteristic of cobalt-chrome castings subsequent to various finishing and polishing techniques.

Finishing and Polishing constitutes an essential requisite after the fabrication of removable partial dentures. Improper finishing and polishing of cast framework will adversely affect the quality of functional units of partial dentures due to reduced dimensions. In this study the polished surface characteristic and loss of weight of the casting were evaluated and compared following different finishing and polishing techniques. A total number of thirty test specimens were cast and each surface finishing and polishing technique was carried out with a high speed polishing motor and an electropolishing unit under standardised conditions. Surface roughness was evaluated by means of a surface roughness analyzing instrument, Perthometer. The loss of weight due to the metal lost was observed on a sensitive electronic balance. The results of polishing technique employed with G3 group revealed better surface characteristic. It may be understood that sandblasting causes initial roughness and the sequence of coarse cylindrical abrasive, Black hard rubber polisher (coarse grit-Dentauram), Grey hard rubber polisher (Med-grit-Dentauram), Green hard rubber polisher (Fine-grit-Dentauram), Grey flexible rubber polisher (Fine grit-Renfert), felt buff with pumice slurry and felt buff with green polishing compound (Degussa) produced improved surface in this case. The loss of weight due to metal lost show concern with technique groups G4, G5, G6. It can be avoided by judicious sandblasting and application of proper grit of abrasive agents.

Analysis of Variance↗
PubMedDate not supplied

Unusual subcutaneous sarcoidosis of the face.

Two unusual cases of sarcoidosis manifesting as subcutaneous masses of the face are reported: in the first, the lesion occurred at the site of an osteotomy for rhinoplasty and was the initial clinical manifestation of sarcoidosis; in the second, the skin lesion was part of a multisystemic disease. The cases were documented with CT. Sarcoidosis should be added to the differential of soft-tissue masses of the face.

Adult↗
PubMedDate not supplied

Ocular prosthesis in children--clinical report.

Children and adolescents are particularly susceptible to injuries because of their fearless manner of play and their athletic immaturity due to which irreparable trauma to the eye is very commonly seen. Glaucoma is another common cause for eye loss in children. The loss of an eye causes disfigurement of the face due to which the children become emotionally weak and conscious and avoid taking part in social events, which in turn causes anxiety, stress and depression at an early age in life. Recovery after the loss of an eye requires an adjustment to monocular vision and improvement of the appearance with the use of artificial eyes carefully prepared to match the remaining natural eye. The custom made ocular prostheses are very comfortable and help children improve their appearances, which in turn, encourages them to build up their self-confidence to return back to their social life.

Adolescent↗