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Biomedical subjects

B Penugonda

Publications and source records attributed to B Penugonda.

17 recordsLinked to original sources
PubMed2001

Use of inductively coupled plasma-emission spectroscopy and mercury vapor analyses to evaluate elemental release from a high-copper dental amalgam: a pilot study.

STATEMENT OF PROBLEM: The use of dental amalgam as a direct restorative material has been a subject of controversy for many years. The potential safety of amalgam has been questioned because of leakage of elements such as mercury, copper, tin, and silver. PURPOSE: This study evaluated the elemental leaching from Tytin dental amalgam placed in deionized water for 2 months. Both mercury vapor and elemental (silver, copper, tin, and mercury) analyses were performed. MATERIAL AND METHODS: Two capsules of Tytin amalgam were triturated (one for the precipitate and liquid analysis, and the other for the mercury vapor analysis) and stored in a polypropylene tube with 10 mL deionized water for 60 days at room temperature. The amalgam pellet then was removed and rinsed with deionized water. The resulting liquid was separated from a precipitate, and 2 separate analyses were run: one on the liquid without any precipitate and another on the precipitate. Elemental analyses for copper (Cu), tin (Sn), mercury (Hg), and silver (Ag) were determined by inductively coupled plasma-emission spectroscopy with a Perkin-Elmer P2000 spectrometer. Mercury vapor analyses were performed daily for 60 days with a Jerome 431-X vapor analyzer. RESULTS: The maximum amount of copper (80 microg), silver (2.6 microg), mercury (15 microg), and tin (550 microg) was found in the precipitate. The maximum amount of mercury vapor released was 67 microg/m(3)/d. CONCLUSION: Under the conditions of this in vitro study, there was a significant amount of elemental leaching and mercury vapor release from the Tytin amalgam over a 60-day period.

Chemical Precipitation↗
PubMed2000

Torsional resistance of crowns cemented to composite cores involving three stainless steel endodontic post designs.

STATEMENT OF PROBLEM: There are no studies analyzing the effects of a crown in relationship to torsional resistance for a titanium-reinforced core material supported by a post. PURPOSE: This study investigated the effects of post design on the torsional resistance of a crown supported by a titanium-reinforced composite core material (Ti-Core) and 3 endodontic posts (AccessPost, Flexi-Post, and ParaPost). MATERIAL AND METHOD: Three groups of 10 specimens per group were studied. A total of 30 recently extracted human single-rooted (incisors) teeth with their crowns removed were used. Post holes preparations were created according to manufacturer's instructions. All posts were cemented using Flexi-Flow with titanium cement. Scotchbond Multi-Purpose bonding system was used as the bonding system for all groups. All cores were fabricated with Ti-Core with titanium core material with hard copper bands as the matrix. The Ti-Core core material was allowed to set for 1 hour. Metal crowns were fabricated and cemented with zinc phosphate cement. Specimens were placed in a special jig and a clockwise torsional force was applied. Torsional force was measured on a Lebow 1102-200 torque transducer and recorded on a Hewlett Packard 7015B X-Y recorder in inch x ounce. A 1-way analysis of variance (ANOVA) was used to test for statistical significance (P < .001). RESULTS: The torsional values (inch x ounce) were AccessPost 77.2 +/- 30.3, Flexi-Post 162.2 +/- 51.2, and ParaPost 60.9 +/- 28.4. SNK and Scheffé comparison tests revealed that the Flexi-Post group had significantly greater resistance to torque loading than the AccessPost and ParaPost groups, which were statistically similar to each other. CONCLUSION: Post design has an effect on torsional resistance of a crown supported by titanium-reinforced core build-up and post. The threaded split-shank design of the Flexi-Post dowel offers significantly greater resistance to torsional loading than the passive posts studied.

Analysis of Variance↗
PubMed1995

Intra-oral comparison and evaluation of the ability of fluoride dentifrices to promote the remineralization of caries-like lesions in dentin and enamel.

The effect of three types of fluoride dentifrices and one non-fluoride dentifrice were evaluated and compared intra-orally for their ability to promote the remineralization of caries-like lesions in thin sections of human dentin and enamel. The three fluoride dentifrices were silica based. One dentifrice contained 0.76% sodium monofluorophosphate (MFP), another contained 0.247% sodium fluoride (NaF), and the third contained 0.247% NaF plus 1.3% pyrophosphate and 1.5% polyvinylmethyl ether/maleic acid (PVM/MA) copolymer (denoted NaF/PPi). The fourth dentifrice (placebo) was also silica based, but contained no fluoride, and served as a negative control. Two week treatment resulted in the following percent mineral changes for the enamel specimens: +21 +/- 16 for MFP, +10 +/- 30 for NaF, +16 +/- 15 for NaF/PPi, and -30 +/- 30 for the placebo. The respective percent mineral change values for the dentin specimens were +28 +/- 20 for MFP, +22 +/- 19 for NaF, +28 +/- 18 for NaF/PPi, and -34 +O/- 61 for the placebo. A statistical analysis revealed that the three fluoride dentifrices were significantly better (p<0.05) than the placebo at promoting remineralization for both types of specimens. No significant differences were found among the three fluoride dentifrices. The following can be concluded from this study: 1) silica based dentifrices containing MFP and NaF are effective at remineralizing caries-like lesions in both enamel and dentin; 2) there was no statistical difference between NaF and MFP in their ability to promote remineralization; and 3) pyrophosphate does not interfere with the remineralizing effects of NaF.

Analysis of Variance↗
PubMed1994

Alcohol-containing mouthwashes: effect on composite hardness.

This study evaluated the effects of alcohol-containing mouthwashes on composite resin hardness. Eighty hybrid composite discs were fabricated and divided into eight equal groups: Listerine, Scope, Viadent, Plax, Lavoris, Clear Choice, and Rembrandt Mouth Refreshing Rinse. Water acted as a control. All of the discs were immersed by group in their respective liquids for two minutes a day over a period of six months. Disc hardness was measured six times at the center and periphery using a Barcol impressor. The baseline values were taken for each disc and compared to the test values at the end of six months. The results of the study indicate that the alcohol content in mouthwashes can affect composite hardness. This softening affect can be directly related to the percentage of alcohol in the mouthwash.

Analysis of Variance↗
PubMed1993

Dentifrice abrasiveness on microfill composite resin and dentin: a comparative study.

This in vitro study evaluated the abrasiveness of seven dentifrices on microfill composite resin discs and dentin surfaces. The composite resin discs and dentin surfaces were brushed in groups using slurries of the different dentifrices. Each specimen was subjected to 2400 strokes using medium bristle toothbrushes at a brush tension of 150 g. Any changes in surface roughness were noted through the use of a mechanical profiler or profileometer and scanning electron micrographs. The results of this study have indicated that Rembrandt Whitening Toothpaste was significantly less abrasive to the microfill composite discs and dentin surfaces compared to the other dentifrices tested (p < .05, ANOVA). Further clinical studies may be warranted to test the abrasiveness of dentifrices, especially if they are used over extended periods of time.

Analysis of Variance↗
PubMed1992

Bonding composite to glass ionomer with adhesive resin cements.

This study was to determine the bond strength of composite to glass ionomer using the following adhesive resin cements: Imperva Dual, CB Metabond, All-Bond, Geristore, and Panavia. All materials were mixed following the manufacturer's specifications. Bonded samples were thermocycled for 2000 x between 5 degrees C and 55 degrees C. Shear bond strengths were determined using an Instron Testing Machine. No statistical differences were noted between materials at the p < .05 level of significance. In addition, scanning electron micrographs were taken of the primed glass ionomer surfaces. These micrographs revealed varying amounts of matrix dissolution along with roughened surface topographies.

Analysis of Variance↗
PubMed1992

Bonding Ni-Cr alloy to tooth structure with adhesive resin cements.

This study was to determine the shear bond strengths of Ni-Cr alloy to Ni-Cr alloy (Group I), Ni-Cr alloy to enamel (Group II), and Ni-Cr alloy to dentin (Group III) using Imperva Dual, DC Metabond, All-Bond, Geristore, and Panavia. All bonded specimens were thermocycled 2000 x (5 degrees C-55 degrees C) after 24 hours and subjected to shear bond testing on a Universal Instron Testing Machine. In all groups of the study, Imperva Dual and CB Metabond had significantly (p < .05) higher bond values than Panavia.

Analysis of Variance↗
PubMed1992

Pit and fissure sealants. Current status.

Occlusal pits and fissures continue to frustrate dentists battling to control decay. Several techniques being studied now offer hope of eventually eliminating caries in these areas.

Bisphenol A-Glycidyl Methacrylate↗
PubMed1991

Profilometer, SEM, and visual assessment of porcelain polishing methods.

Research has indicated that polishing ground porcelain is essential to control the wear of opposing occlusal surfaces and reduce the inflammation of contacted soft tissue. Five popular methods for polishing porcelain were evaluated by use of a profilometer, SEM, and normal vision. Seventy disks, 35 Biobond disks and 35 Ceramco disks, were roughened with a green stone and polished with one of the methods according to the manufacturers' directions. Brasseler, Dedeco, Dentsply, and Shofu porcelain polishing systems were suitable for restoring ground porcelain. However, clinical evaluations correlated to the profilometer and SEM readings revealed that the Brasseler system was superior for polishing Ceramco porcelain whereas the Den-Mat system was unacceptable.

Analysis of Variance↗
PubMed1990

Mounting a maxillary cast transversely horizontal and constructing a plane of occlusion bilaterally symmetrical.

This article discusses a technique for mounting a maxillary cast to any semiadjustable articulator using the dentaplane. The dentaplane is a precision device that divides the articulator space into approximately equal upper and lower halves when attached to the lower member. The dentaplane mounts the maxillary cast with a transverse orientation that replicates conditions in a patient's head.

Cephalometry↗
PubMedDate not supplied

Bonding amalgam to tooth structure: a scanning electron microscope study.

The purpose of this scanning electron microscope study was to observe the interface between dentin and amalgam utilizing various adhesive resin cements. The adhesive resin materials used in this study were Imperva Dual, Geristore, and Panavia. The scanning electron micrographs revealed that bonds were established between amalgam, adhesive resins, and dentin.

Dental Amalgam↗
PubMedDate not supplied

Alcohol-containing mouthwasheses: effect on composite color.

This study investigated whether commercially available mouthwashes could affect or change the color of a hybrid composite resin. Twenty-four disks were fabricated and divided into eight equal groups for testing. At baseline, six colorimetric recordings and color parameters (L*, a*, b*) were recorded for each grouping of disks using a Chroma Meter CR-300 in reflectance mode. The groups of disks were immersed in their respective mouthwashes for 2 minutes a day in a vibratory fashion over a 6-month period. At the end of 6 months, color differences, delta E, were calculated between the base line and test recordings. The results indicate that rinsing with mouthwashes for 6 months can cause a hybrid resin to undergo color variations. Except for one product the color variations were not clinically significant.

Alkaloids↗