Novel composite implant in craniofacial bone reconstruction

Bioactive glass (BAG) and polymethyl methacrylate (PMMA) have been used in clinical applications. Antimicrobial BAG has the ability to attach chemically to surrounding bone, but it is not possible to bend, drill or shape BAG during the operation. PMMA has advantages in terms of shaping during the operation, but it does not attach chemically to the bone and is an exothermic material. To increase the usefulness of BAG and PMMA in skull bone defect reconstructions, a new composite implant containing BAG and PMMA in craniofacial reconstructions is presented. Three patients had pre-existing large defects in the calvarial and one in the midface area. An additive manufacturing (AM) model was used preoperatively for treatment planning and custom-made implant production. The trunk of the PMMA implant was coated with BAG granules. Clinical and radiological follow-up was performed postoperatively at 1 week, and 3, 6 and 12 months, and thereafter annually up to 5 years. Computer tomography (CT) and positron emission tomography (PET-CT) were performed at 12 and 24 months postoperatively. Uneventful clinical recovery with good esthetic and functional outcome was seen. CT and PET-CT findings supported good clinical outcome. The BAG–PMMA implant seems to be a promising craniofacial reconstruction alternative. However, more clinical experience is needed.     

Dendritic copolymers and particulate filler composites for dental applications: degree of conversion and thermal properties.

OBJECTIVES: The aim of this study was to determine the degree of double bond conversion and thermal properties of photopolymerized dendritic copolymers and particulate filler composites that may be used as dental restorative materials. METHODS: The resins consisted of a multifunctional dendritic monomer, methyl methacrylate and varying proportions of acetoacetoxyethyl methacrylate. In addition, one of the composites contained 1,4-butanediol dimethacrylate. Camphorquinone and 2-(N,N-dimethylamino)ethyl methacrylate were used as the light-activated initiation system. The degree of conversion was determined with Fourier transform infrared spectroscopy and the thermal properties with differential scanning calorimetry. RESULTS: The degree of conversion of copolymers varied from 52 to 60% and increased with increasing concentration of acetoacetoxyethyl methacrylate. The values for the composites were 32-44%. Reaction exotherms of 0.2-9.6J/g were measured for the photopolymerized experimental materials indicating residual reactivity that increased with increasing concentration of acetoacetoxyethyl methacrylate. The residual reactivity trend seemed counter intuitive to the degree of conversion. The glass transition temperatures for the completely polymerized copolymers containing acetoacetoxyethyl methacrylate were 112-116 degrees C and for the particulate filler composites 84-87 degrees C. SIGNIFICANCE: The addition of acetoacetoxyethyl methacrylate increased the degree of conversion. The polymerization characteristics of the experimental materials were comparable to those of control materials.     

Bone tissue responses to glass fiber-reinforced composite implants – a histomorphometric study

Objectives: The aims of this study were to evaluate bone-to-implant contact (BIC) and the osteoconductive capacity of bioactive fiber-reinforced composite implant (FRC) in vivo .
Material and methods: Threaded sand-blasted FRC implants and threaded FRC implants with bioactive glass (BAG) were fabricated for the study. Titanium implants were used as a reference. Eighteen implants (diameter 4.1 mm, length 10 mm) were implanted in the tibia of six pigs using the press-fit technique. The animals were sacrificed after 4 and 12 weeks. Histomorphometric and scanning electron microscopic (SEM) analyses were performed to characterize BIC.
Results: In general, the highest values of BIC were measured in FRC-BAG implants, followed by FRC and Ti implants. At 4 weeks, the BIC was 33% for threaded FRC-BAG, 27% for FRC and 19% for Ti. At 12 weeks, BIC was 47% for threaded FRC-BAG, 40% for FRC and 42% for Ti. Four weeks after implantation, all the implants appeared biologically fixed by a newly formed woven bone arranged in the thin bone trabeculae filling the gap between the implant and the bone of the recipient site. Twelve weeks after implantation, the thickness of the woven bone trabeculae had increased, especially around the FRC-BAG implants.
Conclusion: Our results suggest that the FRC implant is biocompatible in bone. The biological behavior of FRC was comparable to that of Ti after 4 and 12 weeks of implantation. Furthermore, the addition of BAG to the FRC implant increased peri-implant osteogenesis and bone maturation.     

Influence of increment thickness on light transmission,degree of conversion and micro hardness of bulk fill composites

This study evaluated characteristics of light transmission, degree of monomer conversion and surface microhardness of bulk fill, conventional and fiber-reinforced resin based composites (RBCs) through different incremental thicknesses of resin composite. Working hypotheses was that there are differences in transmission of blue light through RBCs of different kinds and that the thickness of the increments influence the degree of monomer conversion of RBCs. Six bulk fill, three conventional nanohybrid, one short fiber reinforced and one flowable RBCs were evaluated. For each material, four different incremental thicknesses (1, 2, 3 and 4 mm) were considered (n = 5). The specimens were prepared in cylindrical Teflon molds that are open at the top and the bottom sides and cured for 40 s by applying the curing unit. After curing process, the specimens were ground with a silicon carbide paper with a grit size of 1200 and 4000, and then stored dry at 37 °C for 24 h. Light transmission, degree of monomer conversion, surface microhardness were measured and data were analyzed using ANOVA (p = 0.05). There were differences in light transmission of resin composites of various types and brands. Low-viscous bulk fill and short fiber-reinforced RBCs presented higher light transmission compared to resin composites of higher viscosity. Reduced light transmission and lower surface microhardness and DC % at bottom side of the specimen suggests that more attention needs to be paid to ensure proper curing of the resin composite in deep cavities.     

Delayed post-curing stage and oxygen inhibition of free-radical polymerization of dimethacrylate resin

Objective

It is known that after light-initiated free radical polymerization of a dimethacrylate monomer system, the curing continues for some period of time after the curing light emission has stopped (so-called delayed post-curing stage, DPCS). It is also known that during free radical polymerization, the presence of oxygen effectively inhibits polymerization of monomers. However, less is known of the influence of oxygen inhibition of light initiated polymerization during the DPCS. The aim of this study was to determine some polymerization related properties of a resin system during the DPCS.

Framework design and pontics of fiber-reinforced composite fixed dental prostheses — An overview

Purpose

Fiber-reinforced composite (FRC) fixed dental prostheses (FDPs) have shown good performance in clinical applications due to their good mechanical properties and minimally invasive approach. However, typical failure patterns of FRC FDPs are often localized at the pontic site. That reflects the structural considerations at the framework and pontic location that need to be examined when creating these kinds of prostheses.

Intra‐oral adhesive systems for ceramic repairs: a comparison

The aim of this investigation was to compare the bond strength of restorative composite resin to dental ceramic conditioned with primers and adhesives of various commercial repair kits. Three intra‐oral ceramic repair systems—Silistor (Heraeus Kulzer), Cimara (Voco), Ceramic Repair (Vivadent)—were used on all‐ceramic (IPS Empress 2, Ivoclar‐Vivadent) substrate. Shear bond strength of restorative composite resin to substrate was tested after thermocycling and without thermocycling (n=10). Substrate surfaces of the specimen after loading were examined microscopically (SEM). The highest bond strengths in both water‐stored (7.0±5.7 MPa) and thermocycled conditions (2.5±1.8 MPa) were obtained with the Vivadent repair system, while the lowest values were observed with the Cimara system (0.6±1.4 MPa and 0.0±0.0 MPa, respectively). Shear bond strengths appeared to be significantly affected by thermocycling (ANOVA, P<0.05). It is concluded that there are significant differences in the bond strengths of resin composites and ceramic substrate. The roughened surface does not necessarily provide a better bond strength; the bond strength of composite decreases with storage in water and after thermocycling. Bond strength values were generally low for all of the tested materials.     

Effect of the cross-linking silane concentration in a novel silane system on bonding resin-composite cement

Objective. Four experimental blends of an organo-functional silane monomer with a non-functional cross-linking silane monomer (a novel silane system) were evaluated as adhesion promoters in an experiment in which a resin-composite cement was bonded to silica-coated titanium. Material and Methods. 3-Acryloyloxypropyltrimethoxysilane (as constant 1.0 vol%) was blended with 1,2-bis-(triethoxysilyl)ethane, where its concentration was 0.1, 0.2, 0.3, or 0.5 vol%. Titanium slides (n=20) were grit-blasted, silica-coated, and silanized with four experimental silane solutions, with a pre-activated silane Cimara? (VOCO, Germany) as control. After silanization, resin-composite cement stubs (Bifix? QM; VOCO, Germany) were photo-polymerized. The shear bond strength was measured after dry storage (24 h) or after thermo-cycling (6000 cycles between 5°C and 55°C). The resin stub failure mode was determined. Results. Statistical analysis (ANOVA) showed that type of storage (p <0.05) and concentration of cross-linker silane (p<0.005) both significantly affected the shear bond strength. The highest shear bond strength was obtained with a blend of 1.0 vol% 3-acryloyloxypropyltrimethoxysilane+0.3 vol% 1,2-bis-(triethoxysilyl)ethane, 15.9 MPa (standard deviation SD 3.4 MPa) for both the thermo-cycled group and after dry storage (24 h), 14.3 MPa (SD 4.1 MPa) (n=8/group). The lowest values were obtained with Cimara? silane 7.3 MPa (SD 2.2 MPa) in dry storage and 7.9 MPa (SD 2.0 MPa) obtained with 1.0 vol% 3-acryloyloxypropyltrimethoxysilane+0.1 vol% 1,2-bis-(triethoxysilyl)ethane. The failure type was mainly cohesive. Conclusion. A novel silane system with an optimal concentration of the cross-linking silane may produce significantly higher shear bond strength between silica-coated titanium and resin-composite cement compared to a pre-activated silane product.