A new instrument for placement of self-threading retention pins.
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Biomedical subjects
Publications and source records attributed to A G Podshadley.
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The force required to remove self-threading retention pins from dentin when the holes were drilled with two different methods was determined. The two methods employed to drill the holes were (1) using a conventional slow-speed contra-angle handpiece and (2) using a 10-to-1 gear reduction contra-angle handpiece attached to a conventional slow-speed handpiece. Also determined were the number of drills broken in the process of drilling the holes. Results demonstrated no difference in the retention of pins placed in holes drilled using these two methods. Two drills were broken in the process of drilling well over 100 holes, and both breaks occurred with the gear-reduced handpiece. Either of the two methods tested is acceptable, but we recommended using a conventional slow-speed contra-angle handpiece because of the ease of producing the holes.
The force required to remove three self-threading retention pins from amalgam and the pin length for optimum retention was determined. Link series TMS Minuta, TMS Minikin, and TMS Minim pins were tested; Minim pins were tested at various lengths. The amalgam materials used were representative of a high-copper admixture type and a ternary spherical-type alloy. Results demonstrate that the Minim pin of 2 to 2.5 mm length is the optimum pin for retention in high-copper type amalgam. Minuta and Minikin pins are removed with only a small amount of force and should be used only when clinical prudence requires a small pin; and when used, the strongest possible amalgam should be selected.
The force required to remove three threaded retention pins from composite resin and the pin length for optimum retention were determined. TMS Minuta, TMS Minikin, and TMS Minim pins were tested. Composite resin materials used were representative of large particle, small particle, and microfilled type materials. Results demonstrate that the Minim pin of 2 mm length is the optimum pin for use with large- and small-particle composite resin. However, microfilled composite resin requires a 2.25 mm length of the Minim pin for optimum retention. Minuta and Minikin pins are removed with only a small amount of force and should be used only when clinical prudence requires a small pin. When these tiny pins are used, the strongest possible composite resin should be selected.
An investigation was conducted to determine the quality of seal at the interface when a visible light-cured composite resin was placed and cured in increments. Five samples of each of the following composite materials were tested: Aurafill, Command, Command Ultrafine, Durafill, Prisma-Fil, and Silux. Samples of each material were placed in a thermocycling dye bath that contained a 0.5% aqueous solution of basic fuchsin dye for 25 hours. The samples were removed from the dye bath, rinsed, dried, and prepared for examination with a x25 microscope by two examiners. Neither examiner reported dye penetration at the interface of the materials tested. These findings effectively highlight the practicality of the incremental placement of light-cured composite resins.
The strength of bond at the interface was determined when a visible light-cured composite resin is immediately added to a previously cured surface. In general, small particle composites (Aurafill excepted) tend to lose a small amount of strength at the interface, whereas the microfilled and hybrid composites do not.
The rationale for the use of treatment radiographs in the construction of cast-gold restorations has been presented. Radiographs are made in the University of Louisville Fixed Prosthodontics Clinic at the precementation and postcementation stage of treatment when casting margins are inaccessible. Radiographs at this stage of treatment permit detection and correction of a variety of problems that may not be discovered clinically and allow the construction of excellent cast-gold restorations that would be impossible otherwise. Because all radiation safety factors are observed, the amount of radiation a patient receives is minimized.
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An investigation was conducted to compare the time and amount of material used in a corrective reline impression procedure and in a complete remake of a new double-mix impression. The reline technique required 22.22 gm less material, and the reline technique was achieved in approximately 7.6 minutes less time than that required for a complete remake. This results in a monetary saving while preserving quality.
As a result of our survey, we have reservations about the reliability of radiographic examination for detection of caries under old restorations. Except in rare cases, all old restorative material should be removed and replaced before the construction of a cast crown restoration.
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