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Biomedical subjects

S Koka

Publications and source records attributed to S Koka.

28 records · Page 2Linked to original sources
PubMed1995

The effect of cementing agent and technique on the retention of a CeraOne gold cylinder: a pilot study.

Endosseous dental implants are routinely used for the replacement of missing teeth. The CeraOne system uses a gold cylinder that is luted to a metal abutment. This study evaluated two luting agents and two luting techniques on the retention of a CeraOne gold cylinder to a CeraOne titanium abutment. A mechanical testing instrument was used to provide an uniaxial tensile force on the gold cylinder, which was cemented with zinc phosphate or Tempbond NE. The access opening to the gold abutment screw was filled or unfilled. Filling the access opening resulted in significantly higher retentive values (P < 0.01) compared to leaving the access opening unfilled. The gold cylinder was significantly more retentive when cemented with zinc phosphate as compared with Tempbond NE (P < 0.01). A Tukey post hoc test demonstrated that all means were significantly different at the P = 0.01 level. The results suggest that the choice of luting agent and luting technique may affect retention of a CeraOne gold cylinder.

Analysis of Variance↗
PubMed1994

In vitro analysis of the effects of two air-abrasive prophylaxis systems and inlet air pressure on the surface of titanium abutment cylinders.

PURPOSE: The purpose of this study was to investigate the effects of two air-abrasive prophylaxis systems and the effect of inlet air pressure on the surface of Brånemark titanium abutment cylinders. MATERIALS AND METHODS: Single abutment cylinders were treated with either the Prophy-Jet system (sodium bicarbonate abrasive) (Dentsply International, York, PA) or the Microprophy system (aluminum oxide abrasive) (Danville Engineering Co, Danville, CA) for 60 seconds at an inlet air pressure of 60 psi or 90 psi. The effects on the surface of each abutment cylinder were visually inspected by scanning electron microscopy. RESULTS: A comparison of abutment cylinder surfaces after treatment showed that the Prophy-Jet system removed machining marks to a greater degree than the Microprophy system. Sodium bicarbonate particles from the Prophy-Jet system were significantly larger than the aluminum oxide particles used with the Microprophy system, potentially accounting for the difference in abrasivity. In addition, inlet air pressure of 60 psi caused removal of machining marks to a greater degree than an inlet air pressure of 90 psi. The principle of phase separation may account for the lower inlet air pressure causing more removal of machining marks than the higher inlet air pressure. CONCLUSIONS: Under the experimental conditions tested, neither of the two systems tested seemed to cause significant abrasion of the surface of titanium abutment cylinders.

Air Pressure↗
PubMed1993

Microbial colonization of dental implants in partially edentulous subjects.

This study assessed the colonization of Brånemark dental implants by periodontopathic bacteria in four partially edentulous patients with a total of 10 implants. Marginal and subgingival plaque on the implants was sampled 14 days and 28 days after second-stage surgery and compared with plaque from three teeth closest to the implant sites sampled before second-stage surgery (baseline) and at 14 and 28 days. Slot immunoblot assay was used to determine the presence or absence of bacterial antigen to six different periodontopathic microorganisms. In general, colonization of marginal implant plaque occurred within 14 days, whereas subgingival colonization took longer and occurred within 28 days. It appears that Brånemark dental implants placed in partially edentulous patients may be colonized by disease-associated bacteria within 14 days of second-stage surgery.

Actinomyces viscosus↗
PubMed1992

The effects of two air-powder abrasive prophylaxis systems on the surface of machined titanium: a pilot study.

This in vitro pilot project compared the effect of two air-abrasive prophylaxis systems on the surface of machined titanium. Single Brånemark titanium abutment cylinders were exposed to the Prophy-Jet and Microprophy systems for 90 seconds each. Both of the test cylinders were compared with an untreated control cylinder by scanning electron microscopy. Machining marks were completely removed by the Prophy-Jet and only partially removed by the Microprophy. Both of the resultant surfaces appeared to be smoother and thus may be more resistant to plaque formation. A rationale for the removal of machining marks is presented, although the reason for the difference in removal by the two systems is unclear. The prophylaxis cleaning powders were also examined by scanning electron microscopy and exhibited similar particle dimensions and morphology. A noncrystalline deposit was observed on the surface of the abutment cylinder exposed to the Microprophy. Energy dispersive spectroscopy analysis revealed that the deposit consisted almost entirely of sodium. Further investigation of the deposit is needed.

Air Pressure↗
PubMedDate not supplied

Cytotoxicity of denture base resins.

This in vitro study examined the effect of eluate from heat-activated, chemically activated, and microwave-activated denture base resins on cell viability of primary cultures of human gingival fibroblasts. Eluates corresponding to 24, 48, 72, and 96 hours of resin disk immersion were prepared. Fibroblasts were plated at a density of 3 x 10(4) cells in 96-well plates and exposed to a medium containing eluate. After 24 hours, the cytotoxic effect was determined by cellular mitochondrial function. The effect of eluates was compared to control cultures containing culture medium without eluate. Results indicated that at all time periods tested, all three resins leached materials that were cytotoxic to the fibroblasts. Eluate from chemically activated resin disks was more cytotoxic than eluate from heat-activated and microwave-activated disks. In general, cytotoxicity appeared to diminish as disk immersion time was increased. The greatest cytotoxic effect on cell viability was observed with eluates recovered after 24 hours of disk immersion, and the least cytotoxic effect was observed with eluates recovered after 96 hours of immersion.

Acrylic Resins↗
PubMedDate not supplied

The implant-mucosal interface and its role in the long-term success of endosseous oral implants: a review of the literature.

PURPOSE: This article reviews the literature on the anatomy and the role of the implant-mucosal interface in the long-term success of oral endosseous implants. MATERIALS AND METHODS: In vitro, in vivo animal, and in vivo human studies are reviewed and discussed. RESULTS: The anatomy of the implant-mucosal interface is described. The interface shares many features with periodontal mucosa. A clinically healthy implant-mucosal interface is a routine and predictable occurrence. The validity of using traditional clinical periodontal parameters to indicate or predict changes in peri-implant marginal bone height is unproven, especially if inflamed mucosal tissues are present. CONCLUSION: In general, the human host response of peri-implant mucosa to long-term functional challenges is favorable.

Alveolar Bone Loss↗