Fracture Resistance of Extensive Amalgam Restorations Retained by Pins, Amalgapins, and Amalgam Bonding Agents
Howard E. Strassler, DMD
Imberry TA, Coudron J, Moon PC. Oper Dent. 2008; 33(6):666-674.
This in vitro study compared the resistance of extensive amalgam restorations retained by either four Regular TMS Link Plus pins, four amalgapins, Amalgambond Plus, Amalgambond Plus with HPA, Scotchbond Multi-Purpose Plus, PQ Amalgam, Panavia F 2.0, All-Bond 2 or Resinomer. Ninety caries-free third molars were embedded in acrylic resin and their occlusal surfaces reduced to within 2 mm of their CEJ. Tytin amalgam alloy was hand-condensed into copper band matrices reinforced with modeling compound after placement of mechanical retention or application of the amalgam bonding agents. Modeling compound and copper bands were removed after 24 hours, and the restorations were adjusted to produce specimens 5 mm in height with a 1 mm bevel on the occlusal-axial surface. The specimens were stored in 100% humidity for one month followed by immersion in de-ionized water for 24 hours at 37°C. The specimens were loaded in compression at a 45° angle in an Instron Universal Testing Machine at a crosshead speed of 0.02 inches/minute. The mean failure loads and standard deviations recorded in Newtons were as follows: Amalgambond Plus with HPA 2160N (380), Scotchbond Multi-Purpose Plus 1900N (380), four Amalgapins 1770N (340), PQAmalgam 1660N (270), Panavia F 2.0 1620N (440), Amalgambond Plus 1570N (390), four Regular TMS Link Plus Pins 1325N (406), All-Bond 2 1300N (390) and Resinomer 1245N (310). A one-way ANOVA and Tukey post hoc analysis indicated all amalgam bonding agents were statistically equal to either four Regular TMS Link Plus pins or four amalgapins.
A recent survey reported that 57% of the respondents were still placing amalgam restorations. For extensively broken-down teeth with missing cusps, the retention choices for these restorations have traditionally been mechanical retention with dentinal pins, amalgapins, slots, and grooves. The introduction of amalgam bonding agents touted their use as a replacement for traditional mechanical retention.
This well-designed study investigated and compared traditional mechanical methods of retention to the use of amalgam bonding agents. Of interest, of the products tested, composite resin adhesives already used in our practices have components that will provide successful auxiliary retention to extensive amalgam preparations. In a recent survey, less than 50% of dentists reported the use of mechanical retention for large amalgam restorations. It was also reported that over half of the respondents are using adhesive resin liners exclusively when restoring complex restorations.1 Based on the testing methods, amalgam bonding agents provided as much retention and resistance for extensive amalgam restorations as traditional mechanical methods of retention. Also, the article provided a product comparison for estimated cost and time.
1. Vaught RL. Mechanical versus chemical retention for restoring complex restorations: what is the evidence? J Dent Educ. 2007;71:1356-1362.
About the Author
Howard E. Strassler, DMD
Professor and Director of Operative Dentistry
Department of Endodontics, Prosthodontics and Operative Dentistry
University of Maryland Dental School