Dentinal fluid flow and cuspal displacement in response to resin composite restorative procedures

Objectives The aim of this study was to correlate the rate and magnitude of dentinal fluid flow (DFF) with cuspal displacement in response to resin composite restorative procedures. Methods Ten extracted human maxillary premolar teeth with an extensive MOD cavity preparation were connected to an automated fluid flow measurement apparatus (Flodec), and a direct current differencial transformer (DCDT) was attached to each cusp. The rate, magnitude and direction of DFF and cuspal displacement were recorded simultaneously in response to each stage of resin composite restorative procedures. Results Cuspal displacement and DFF in outward and inward directions accompanied each stage of the procedures. Drying produced rapid cuspal contraction. Bonding caused slight cuspal expansion, whereas light curing of resin induced gradual but extensive cuspal contraction, which persisted following light curing. During baseline outward DFF was low and increased slightly during etching. In contrast, substantial outward DFF occurred during drying. Light curing of the bonding agent and the resin composite produced inward DFF. Following light curing, an outward DFF began and continued for atleast 15 min. Significance The large, rapid fluid movement and cuspal displacement during restoration, and the prolonged outward fluid flow post-curing have implications for post-operative sensitivity. While mechanical stresses within dentin associated with cuspal displacement appear capable of inducing DFF, the net fluid movement is the result of complex interactions either directly or indirectly of several stimuli (thermal, evaporation, osmotic, and possibly mechanical).