Dentin/Pulp Responses to a Hydrophobic Oxirane/Acrylate IPN Resin Composite

Objectives: To evaluate the effect of a new hydrophobic composite Oxirane/Acrylate Interpenetrating Network (IPN) Resin on dentin and pulp of miniature swine teeth.
Methods: The study was approved by Loma Linda University Institutional Animal Care and Use Committee; the procedures followed ISO 7405:2018. Six 20-25 month-old miniature swine randomly received hydrophobic Oxirane/Acrylate Interpenetrating Network Resin System (OASys) composite restorations made with a multifunctional oxirane (Epalloy 8370), a multifunctional acrylate (dipenta erythritol hexaacrylate), urethane dimethacrylate and a hydrophobic fluorinated acrylate (2-perfluorooctylethylacrylate) or control (Filtek Z250) composites, which were evaluated in either a deep-dentin (DD) or pulp-exposure (PE) cavity preparation. Under general anesthesia, buccal class V cavities (5x3x4mm) were prepared using high-speed burs with water irrigation to achieve approximately 0.5-0.3mm of remaining dentin thickness at the pulpal floor. Pulp exposure (Ø0.5-1.0mm) was created in the center of cavity when applicable. Restorations were placed according to standard clinical procedures. Animals were euthanized at 7d, 28d, or 70d. Teeth/bone blocks were recovered, fixed in 10% buffered formalin, demineralized in 10% formic acid, prepared for serial sections, and H&E stained for histopathological evaluation without knowledge of the treatment.
Results: Examinations of oral tissues and teeth revealed no anomalies. None of the samples showed evidence of inflammatory infiltration. Mild inflammation (20%) was found in the cavity openings of the PE group of the OASys composites at 28d, but was not observed at 7d and 70d. Tertiary dentin formation and foreign body reaction were comparable, both in frequency and distribution, between the two composite resins for the PE group. Foreign body reaction (33%) was observed for only the control resin at 28d for the DD group.
Conclusions: Under conditions of this study, hydrophobic OASys composite does not cause adverse responses of the dentin and pulp, and their biocompatibility is comparable to that of the Filtek Z250 control.