The Bond Strength of a Highly Cross-linked Denture Tooth to Denture Base Polymers: A Comparative Study

Department of Prosthodontics, Faculty oF Dentistry, Gazi University, Ankara, Turkey.
The journal of adhesive dentistry (Impact Factor: 1.31). 02/2011; 13(1):85-92. DOI: 10.3290/j.jad.a18241
Source: PubMed


This study compared shear bond strength and type of bond failure between a highly cross-linked tooth and different denture base polymers.
Cross-linked denture teeth were bonded to either a heat-, an auto-, a microwave-polymerized denture base resin or a relatively new injection-molded, microwave-polymerizable polyurethane-based resin. Six experimental groups were established for each of the shear and peel tests. In four of the groups, teeth were used as received and bonded to each of the denture base resins; in the remaining two groups, they were treated with dichloromethane to determine its effect on the bonding with heat or auto-polymerized denture base resins. Bond strength was determined by compressive load applied at 45 degrees on the palatal surface of each tooth until fracture; the type of bond failure was assessed by the peel test.
The results showed that heat-cured PMMA groups failed cohesively and demonstrated significantly higher bond strengths than the other resins used. The application of dichloromethane on the ridge lap areas of teeth resulted in a significant improvement of bond strengths in heat- and auto-cured resins.
Within the limitations of this experimental study, the results suggest that type of denture base material and processing methods may have an influence upon the bond strength between interpenetrating polymer network (IPN) denture teeth and base materials. Treatment of denture teeth with dichloromethane could provide substantial improvement in the bond strength of teeth with heat and auto-cured denture base resins; however, this finding should be validated in further investigations on the long-term effect of such treatment on the bond strength.

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    ABSTRACT: Laboratory processing techniques have been refined in an attempt to achieve complete dentures with better clinical performance. Regardless of the type of denture base material (microwave-, light-, or heat-polymerized polymethyl methacrylate, for example), materials as well as handling and polymerization methods have been continuously modified with a view to obtaining more resistant dentures. In an attempt to improve the mechanical properties of base materials and to try to overcome the low impact and flexural strength of currently available dentures, which often results in clinical failure, various laboratory treatments have been proposed. The incorporation of reinforcing structures such as glass fiber, carbon fiber, Kevlar, aramid, and fiber-reinforced composite, which can be found in different sizes and shapes and are sometimes impregnated with substances such as silanes, has been successfully tested in some cases. However, incorporation of such compounds can culminate in undesirable effects such as larger amount of residual monomer, difficult polishing, and unsatisfactory aesthetics. Metal wires have also been used over time for this purpose, as well as substances such as methyl acetate and methyl formate. The increased bond strength between artificial teeth and the denture base material has also been relentlessly pursued. New positive results are being obtained by means of techniques that promote interpenetration of the polymer networks of the two materials and make use of substances such as dichloromethane. To improve the biological properties of dentures, simple procedures such as immersion in water for defined time periods has been evaluated, in order to reduce their totoxicity. Studies have shown that dibenzoyl peroxide, used as initiator in polymethyl methacrylate resin and associated with allergic processes, is released from conventional dentures after polymerization, but this event can be substantially reduced with completion of an additional polymerization cycle. Still, in order to reduce dentures contamination, several antimicrobial agents such as silver have been incorporated into the base material, which has led to positive effects with regard to their antimicrobial action. However, decrease in flexural and impact strength has sometimes been observed. In this context, this book chapter intends to update the reader on materials and laboratory techniques that can optimize the physical, mechanical, and biological properties of dentures that are considered to be the most relevant to the clinical performance of complete dentures.
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