Impact of head and neck radiotherapy on the mechanical behavior of composite resins and adhesive systems: A systematic review

• In vitro radiotherapy seems not to impair the mechanical properties of composite resins.
• Post-bonding in vitro radiotherapy does not weaken bond strength of adhesive systems.
• Pre-bonding in vitro radiotherapy decreases bond strength of adhesive systems.
• Bond strength of adhesive systems need to be investigated after in vivo radiotherapy.

ObjectivesTo analyze the evidence regarding the impact of head and neck radiotherapy (HNRT) on the mechanical behavior of composite resins and adhesive systems.MethodsSearches were conducted on PubMed, Embase, Scopus and ISI Web of Science databases using “Radiotherapy”, “Composite resins” and “Adhesive systems” as keywords. Selected studies were written in English and assessed the mechanical behavior of composite resins and/or adhesive systems when bonding procedure was conducted before and/or after a maximum radiation dose ≥50 Gy, applied under in vitro or in vivo conditions.ResultsIn total, 115 studies were found but only 16 were included, from which five evaluated the effect of in vitro HNRT on microhardness, wear resistance, diametral tensile and flexural strength of composite resins, showing no significant negative effect in most of reports. Regarding bond strength of adhesive systems, 11 studies were included from which five reported no meaningful negative effect when bonding procedure was conducted before simulated HNRT. Conversely, five studies showed that bond strength diminished when adhesive procedure was done after in vitro radiation therapy. Only two studies about dental adhesion were conducted after in vivo radiotherapy but the results were not conclusive.SignificanceThe mechanical behavior of composite resins and adhesive systems seems not to be affected when in vitro HNRT is applied after bonding procedure. However, bond strength of adhesive systems tends to decrease when simulated radiotherapy is used immediately before bonding procedure. Studies assessing dentin bond strength after in-vivo HNRT were limited and controversial.