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Biomedical subjects

S E Northeast

Publications and source records attributed to S E Northeast.

10 recordsLinked to original sources
PubMed1999

Bonding procedures for intraoral repair of exposed metal with resin composite.

PURPOSE: To determine if tin plating can be recommended for intraoral repair of ceramic veneered cast restorations where metal of unknown composition is exposed by loss of ceramic. This study investigated the effectiveness of surface treatments incorporating tin plating and unfilled resin to enhance the tensile bond strength of a resin composite restorative to three different metal ceramic casting alloys. MATERIALS AND METHODS: Gold-platinum, palladium-tin and nickel-chromium alloys were used to fabricate 120 rods of each alloy, 4 x 15 mm. The end of each rod was ground perpendicular on 600-grit SiC paper and grit blasted with 50-micron alumina. Rods from each alloy were divided into four groups of 30 to receive one of the following treatments before bonding pairs end to end with a visible light-polymerized resin composite (Herculite XRV): 1) direct bonding with the resin composite; 2) tin plating (Micro-Tin) and bonding; 3) application of unfilled resin (Chameleon) and bonding; 4) tin plated, application of unfilled resin and bonding. The bonded samples were stored in distilled water, incubated at 37 degrees C for 24 hours and tested for tensile bond strength at a crosshead speed of 1 mm/min in a Lloyd 1000R machine. The mode of failure was examined using a stereo zoom microscope. RESULTS: A statistically significant increase in tensile bond strength was demonstrated between the control (group 1) and both the gold and palladium alloy treated with tin plating and unfilled resin (group 4). Tin plating, or tin plating with the application of unfilled resin had no statistically significant effect on the tensile bond strength of resin composite to the nickel-chromium alloy. CONCLUSION: The results demonstrate that tin plating, in conjunction with the application of a low-viscosity unfilled resin, optimizes the tensile bond of a resin composite to the three alloys used in the study. This procedure can be recommended for intraoral repair of exposed metal when the type of alloy belongs to one of the investigated alloy groups.

Analysis of Variance↗
PubMed1994

Shear bond strength of resin bonded ceramic after different try-in procedures.

Final cementation of porcelain laminate veneers may require a previous colour match try-in. The purpose of this in vitro study was to evaluate the effect on shear bond strength of resin bonded to porcelain after the application of different try-in procedures. Forty porcelain specimens were fabricated, flattened with 600 grit SiC, etched with hydrofluoric acid and silane treated. After 24 h the specimens were divided into four groups at random and prior to bonding of a dual cure resin composite button were treated as follows: Group 1, no treatment (control); Group 2, non-activated resin applied for 5 min, cleaned in acetone for 3 min; Group 3, as for Group 2, with silane reapplied; Group 4, as for group 3, but re-etched for 30 s before reapplication of silane. After bonding the specimens were stored in water at room temperature for 7 days. Shear bond strength data were as follows: Group 1, 18.6 +/- 1.6; Group 2, 15.9 +/- 1.7; Group 3, 16.7 +/- 2.6; Group 4, 15.3 +/- 3.0 MPa. Fractured surfaces examined, under light microscopy and scanning electron microscopy (SEM), showed cohesive failure within the porcelain in all cases. The reduction in mean bond strength after application of a try-in resin was significant in Groups 2 and 4 compared with the control (ANOVA P < 0.05). No other significant differences were measured. In conclusion a single reapplication of silane maintained the bond strength of resin to porcelain when final cementation was preceded by a try-in procedure and cleaning.

Acetone↗
PubMed1994

Tensile peel failure of resin-bonded Ni/Cr beams: an experimental and finite element study.

Tensile bond strength data for resin-bonded bridge cements would predict failure loads in excess of 1000 N when based on available bonded surface area. Such loads are unlikely to be encountered clinically, yet these bridges frequently fail. Loading conditions resulting in a peeling action at the adhesive interface may provide a more probable explanation for failure rather than being attributable to poor clinical or laboratory technique. This hypothesis was investigated by bonding grit-blasted Ni/Cr alloy beams of different thicknesses to a block of the same alloy using a resin-bonded bridge cement, leaving half the length of the beam free. Beams were pulled off the block with a peeling action by applying a tensile load to the free end of the beam and load at failure recorded. Fractured surfaces were examined under SEM. A two-dimensional finite element model of a section through the peel test arrangement was used to produce data of the stress distribution in the adhesive layer. Load at failure was closely correlated to beam thickness. Using this data and known tensile bond strength values it was possible to predict the loads necessary to cause adhesive failure of the beam, which were found to correlate closely with the experimental measurements. It was concluded that design and the stiffness of the retainers can have a potentially profound effect on the adhesive quality of resin-bonded bridges.

Adhesives↗
PubMed1992

Metal-ceramic bridges from commercial dental laboratories: alloy composition, cost and quality of fit.

The quality of construction of fixed bridge prostheses directly affects their long-term survival. The cost, alloy composition and marginal fit of bridges made by 30 commercial dental laboratories is assessed. Duplicate models of a three unit bridge preparation were sent to 30 different laboratories, as if required for a patient receiving treatment under the General Dental Service. Material was sent via general dental practitioners, requesting metal-ceramic bridges made from 45% Au alloy, precious metal or non-precious metal. Proximal contacts were overbuilt at 65% of sites and pontic tissue contacts were excessive in all but one bridge. Eight laboratories did not use alloys corresponding to the request made. The mean marginal gaps of non-precious metal bridges (145 microns) were significantly greater than those for 45% gold alloy (106 microns). Marginal fit was poor and a number of factors have been observed, with other postulated, which may have contributed to this problem.

Ceramics↗
PubMed1992

The effect of air-polishing occlusal surfaces on the penetration of fissures by a sealant.

An in vitro study was performed to assess the depth of penetration of a fissure sealant after cleaning the occlusal surfaces with an air-polishing unit, and to compare the results with those obtained after cleaning with pumice and water and after no cleaning. Forty-six clinically non-carious premolars and permanent molars were randomly distributed into three groups. Following cleaning, etching and fissure sealing, the teeth were sectioned. Each section was examined under a light reflecting microscope and the depth of resin penetration was determined. Fissure cleaning with an air-polishing unit produced a statistically significant increase in depth of penetration of sealant resin, and its use as a standard cleaning method before fissure sealing is recommended.

Air Pressure↗
PubMed1991

Variations in bridge construction in commercial laboratories.

Identical working models for the construction of a porcelain bonded to metal three unit fixed bridge were sent to 30 different commercial dental laboratories in the United Kingdom. The material was sent from general dental practice addresses with the implication for treatment under the National Health Service. Each bridge on its return was examined for acceptability using subjective criteria based on clinical and technical factors. There was a wide variation between bridges which gave cause for concern. Lack of a satisfactory prescription for the laboratories to work to must have played a part in this variation. However, it is stressed that the prescription used in this work was deliberately chosen as representative of that which may be used by clinicians.

Color↗
PubMed1989

The unstable lower full denture--a practical and simple solution.

Advanced resorption of the mandibular residual ridge produces a flat or even concave base, which is characteristic of the "difficult lower jaw". The provision of dentures for such patients using conventional techniques often leads to an unstable and unsatisfactory result regardless of the accuracy of the fit of the denture base.

Bone Resorption↗