Crowns and fixed dental prostheses (FDP) of fiber-reinforced
composite (FRC) have opened the potential for fabrication of metal-free dental
restorations with direct and indirect techniques. Although direct FRC
restorations are gaining popularity over indirect ones, however multiple unit
restorations require fabrication in dental laboratories. FRC FDPs are composed
of two types of resin composite materials: load-bearing FRC substructure and
particulate filler resin composite (PFC) veneering. The objectives of this series
of studies were to investigate some structural and interfacial adhesion
elements of indirect FRC FPDs. In addition, incorporation of antimicrobial
agent chlorhexidine digluconate (CHX) to the FRC and its release from the FRC
was also evaluated.

In the first study, interfacial adhesion between E-glass FRC
substructure and PFC was investigated by the shear bond strength test. Attempts
to improve adhesion by intermediate resin (IMR) with different treatment times
were made. Applying the IMR increased the bond strength values of PFC to FRC
with multiphase polymer matrix (semiinterpenetrating polymer network of BisGMA
and PMMA, IPN). It was also found that the polymer matrix of FRC can be
polymerized to a high degree of monomer conversion without deteriorating the
bond strength between FRC and PFC. A second study demonstrated that PFC can be
better bonded to the FRC substructure with randomly oriented glass fibers than
to the continuous unidirectional FRC substructure. A third study analysed the
flexural properties and the release of CHX laced unidirectional FRC provisional
FPD polymer. Flexural properties of provisional FPD polymer were increased by
the addition of FRC, and the CHX was released into water by diffusion from the
FRC during the first three weeks. The fourth study aimed to characterize water
sorption, flexural properties, bonding properties, and elemental composition of
two different photopolymerizable FRC materials (cross-linked and IPN polymer
matrix FRC). Differences were found for the percentage of water sorption, but
the flexural strength and veneering PFC bonding properties did not show a
difference between the materials after 30 days of water storage.

These studies suggest that by using IMRs and randomly
oriented glass fiber FRC the interfacial adhesion to PFC can be improved.
Furthermore, it was found that FRC prepreg can be loaded with antimicrobial
agent CHX, and the diffusion base released into water from the FRC lasted for
three weeks.