The effects of instrument lubricants on the physical and mechanical properties of resin-based composites

Uncured resin-based composites (RBCs) tend to stick to the placement instrument instead of cavity walls, potentially increasing void formation and margin discrepancy. Instrument lubricants (ILs) are used to overcome this problem, but they may affect the properties of RBC restorations. One hundred registered UK dentists were surveyed using a bespoke questionnaire to investigate their perspective on IL use and understand why and how they used them. Additionally, different laboratory investigations were conducted, based on the survey data, to test the effects of ILs on the physical and mechanical properties of RBCs. Two RBCs were treated with three classes of ILs -solvents, bonding agents and wetting resins -to investigate the effects different ILs have on the physical and mechanical properties of RBCs. Several areas were tested: degree of conversion, water uptake, Martens hardness, diametral tensile strength, microtensile bonding strength (μTBS), and the appearance of changes at the increment interface. The survey revealed that about 50% of the dentists used lubricants (32% response rate), of which bonding agents (67%) and wetting resins (33%) were most common. These were applied with microbrushes (47%) and by wiping the placement instruments (40%). The solvents, bonding agents and wetting resins created significant reductions in diametral tensile strength and Martens hardness, and increased water uptake compared to control groups fabricated without lubricants. The μTBS significantly reduced following treatment with solvents and bonding agents, but there was no reduction from the wetting resins. The respondents used lubricants to aid manipulation during placement. However, these materials have an impact upon physical and mechanical properties with solvents and bonding agents having the greater effect. Therefore, the use of ILs to manipulate the RBC should be limited or avoided.