The bonding properties of elastomer tray adhesives

Our plain-English summary of The bonding properties of elastomer tray adhesives, by G.B. Davis, J.B. Moser, G.I. Brinsden (The Journal of Prosthetic Dentistry, 1976).

The study

• Authors: G.B. Davis, J.B. Moser, G.I. Brinsden
• Journal: The Journal of Prosthetic Dentistry
• Published: 1976;36(3):278-85
• Cited by: 41 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

1. The surface yielded by the acrylic resin formed against tinfoil provided better retention for the rubber base than any other surface tested. 2. Wax consistently gave the worst results in spite of careful boiling out. 3. The use of wax or asbestos spacers would not degrade the resin surface if tinfoil, or presumably the more easily obtainable aluminum foil, were used as a separating medium. 4. For drying times of between 15 minutes and 72 hours, no significant change was found in bond strength of elastomer to tray material. 5. Drying times of less than 15 minutes were found to be inadequate and to decrease bond strength; they are clinically inadvisable. 6. If, as a result of unavoidable delay, a tray is painted and then left for a number of days prior to making the impression, satisfactory bonding will still occur. However, if the dentist wishes to apply a second coat and dry it for 15 minutes, an increase in bond strength is likely to occur. 7. In the six systems tested, failure occurred at varied levels, from a low of 20 p.s.i. to a high of 80 p.s.i. 8. In the silicone and polyether systems, cohesive failure of the elastomer occurred before the adhesive bond between elastomer and tray failed. This finding correlates with the clinical observation that silicones and polyethers are more difficult to remove completely from acrylic resin trays when an impression has to be repeated.

In plain English

This was a laboratory test of dental materials, not a study of asbestos and health. Asbestos appeared only as one of several materials used as a spacer when making acrylic resin impression trays. The authors, at Northwestern University Dental School, made one-square-inch acrylic resin blocks with one surface cured against baseplate wax, asbestos or tinfoil, or roughened with abrasive paper. They glued rubber impression material to the blocks with tray adhesive and pulled the joints apart in a testing machine, ten specimens for each surface and drying-time condition. Resin formed against tinfoil gave the strongest bond. Asbestos-formed and abraded surfaces gave slightly lower strength, and wax gave much lower strength. On some asbestos-formed blocks, traces of asbestos fibers were seen partly buried in the resin where the adhesive pulled off. Letting the adhesive dry 5 minutes gave the weakest bond. Among brands, silicone failed at about 22 p.s.i. and polyethers at about 80 p.s.i., but in both the impression material itself tore before the adhesive bond gave way. The authors concluded that wax or asbestos spacers would not degrade the resin surface if tinfoil was used as a separating layer.

We wrote this plain-English summary from the full article with the help of AI, and a second AI model checked each sentence against the article. It is not the authors' wording; the abstract and the article are their own account.

What the study did and found

• Design: Laboratory experiment on dental materials (tensile bond-strength testing), with ten specimens per surface-preparation and drying-time condition
• Who was studied: Test blocks of self-curing acrylic resin with one-square-inch surfaces, made at Northwestern University Dental School, Chicago. No people were studied, and no study dates are given.
• Exposure: Resin surfaces were cured against baseplate wax, asbestos (fiber type not named) or 0.003 inch tinfoil, or abraded with silicon carbide paper. Adhesive drying times ranged from 5 minutes to 72 hours. Six brands of polysulfide, silicone and polyether impression material were compared.
• Main results:
  • Resin formed against tinfoil gave the highest bond strength.
  • Asbestos-formed and abraded resin surfaces gave bond strength slightly lower than tinfoil.
  • Where adhesive pulled off asbestos-formed blocks, traces of asbestos fibers were seen partly buried in the resin. The authors took this as a weakness in the bond.
  • Wax-formed blocks gave much lower bond strength, with only 25 per cent of the adhesive left on the block.
  • Bond strength was lowest at 5 minutes of adhesive drying and reached a maximum at 30 minutes. Overnight storage did not weaken the bond. Repainting 72-hour trays and drying for 15 minutes gave a significant increase.
  • The silicone system was weakest, rupturing at about 22 p.s.i. within the impression material itself.
  • Among polysulfides, bond strength ranged from 39 p.s.i. (Rubberjel) to 63 p.s.i. (Permlastic), with Coe-flex at 60 p.s.i.
  • The polyether systems failed at about 80 psi, within the elastomer itself.
  • In the silicone and polyether systems, the impression material tore before the adhesive bond between it and the tray failed.
• The authors' conclusion: The authors concluded that a tinfoil-formed resin surface gave the best retention and wax the worst. They concluded that wax or asbestos spacers would not degrade the resin surface if tinfoil (or, presumably, aluminum foil) was used as a separating layer. They also concluded that drying times under 15 minutes were inadequate.
• Limitations the authors state:
  • The authors note that aluminum foil, which they suggest as a substitute for tinfoil, was not tested in this project.

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