Abstract :
[en] Computer-aided design and manufacturing (CAD-CAM) materials are gaining popularity
in the field of restorative dentistry. Among recently developed materials are polymerinfiltrated
ceramic network (PICN) materials, a sub-class of CAD-CAM composites,
comprised of 75 vol% sintered glass-ceramic network that is secondarily infiltrated with
monomers and polymerized under high-temperature and pressure; whereas the other
sub-class of CAD-CAM composites, dispersed fillers (DF), consist of inorganic fillers
classically incorporated by mixing in an organic matrix that is secondarily polymerized
under high-temperature.
The first objective of this work was to use fracture mechanics, particularly the notchless
triangular prism (NTP) specimen fracture toughness test to: 1) evaluate the interfacial
fracture toughness (IFT) of a resin composite luting agent (RCLA) with PICNs, represented
by an experimental and a commercial PICN (Vita Enamic), versus DF materials. Lithium
disilicate glass-ceramic (IPS e.max CAD, EMX) was also tested as a gold standard
for comparison. Samples were pretreated with hydrofluoric acid (HF) or gritblasting
(GR), and the results were correlated with the developed interfacial area ratio (Sdr) of
representative samples subjected to the same pretreatment procedures. 2) Evaluate
the influence of silane on the IFT of RCLA with PICN and DF after HF and GR, and
correlate the results with the Sdr and surface wettability of representative samples. The
results showed that the IFT of PICNs was significantly superior to DF, and IFT of etched
experimental PICN was significantly higher than EMX. In addition, there was a strong
correlation between the IFT and the Sdr of the representative samples, PICNs
demonstrating significantly higher surface roughness than DF when pretreated. These
results highlighted the importance of material microstructure and then class (DF vs PICN)
on the bonding interface performance. Etching of PICN led to the selective dissolution of
the glass-ceramic at the surface, creating an original polymer-based honeycomb structure
that promoted the micromechanical retention of RCLA. This micromechanical retention is
enhanced by the application of silane, which allows RCLA penetration in surface roughness.
On the other hand, IFT of DF was not influenced by silane, regardless of the surface
pretreatment, which was less effective in creating surface roughness.
The second objective was to introduce of a functionally-graded (FG) PICN block as a
biomimetic material for CAD-CAM prostheses. FG-PICN is characterized by a gradient of
mechanical and optical properties, in which the surface properties resemble the hardness
and modulus of enamel, while the deeper layers resemble those of dentin. The flexural
strength values at the dentin-like layer was similar to glass-ceramic EMX and flexural load
energy was significantly higher than EMX and monolithic zirconia. These properties couldpromote occlusal stress absorbance in treatment of patients with bruxism, such as worn dentition cases, and on implant restorations.
Finally, the third objective was to participate in two clinical studies performed following new treatment protocols developed with commercial PICN; a minimally invasive approach
of worn dentition treatment with Vita Enamic bonded restorations; the “One-step
No-prep” protocol and a novel approach for restoring a missing posterior tooth with
immediate loading of an implant and a final crown made of PICN in a single visit; the “One-tooth One-time, 1T1T” protocol. The restorations success rate after 2 years was high (93.75% for the former and 90% for the latter), highlighting some edge chipping in the first study, and debonding from the ti-base in the second.
In conclusion, PICNs show a promising potential to be used in a variety of restorative
applications, especially in minimally invasive dentistry, such as demonstrated in novel
clinical applications of Vita Enamic. Indeed, in vitro studies highlighted the superiority of PICN, particularly the new PICN generation, to DF and lithium disilicate glass-ceramic in
terms of IFT with RCLA. In addition, the original gradient of mechanical properties of
the FG-PICN, opens the door for restorations with an improved bio-mechanical
behavior compared to other CAD-CAM materials available on the market. Future
perspectives include fatigue tests and clinical studies with experimental PICN materials.
