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PubMed1997

Fiber-reinforced framework and Ceromer restorations: a technical review.

The utilization of synthetic resins and ceramics in combination with metal frameworks continues to be the mainstay of crown and bridge prosthetics. Although most of these systems have resulted in years of clinical success, each material when used in combination has inherent properties that induce stresses to the system. The combination of ceramic technology and polymer research, in addition to fiber integration, has resulted in the development and introduction of a new category of crown and bridge materials--a ceromer and fiber-reinforced restorative system. This article examines the history of polymer and ceramic technology, and reports the clinical and research data currently available on one indirect ceromer system (Targis System, Ivoclar Williams, Amherst, NY).

Ceramics↗
PubMed2006

A thermodynamic approach to the hydration of sulphate-resisting Portland cement.

A thermodynamic approach is used to model changes in the hydrate assemblage and the composition of the pore solution during the hydration of calcite-free and calcite-containing sulphate-resisting Portland cement CEM I 52.5 N HTS. Modelling is based on thermodynamic data for the hydration products and calculated hydration rates for the individual clinker phases, which are used as time-dependent input parameters. Model predictions compare well with the composition of the hydrate assemblage as observed by TGA and semi-quantitative XRD and with the experimentally determined compositions of the pore solutions. The calculations show that in the presence of small amounts of calcite typically associated with Portland cement, C-S-H, portlandite, ettringite and calcium monocarbonate are the main hydration products. In the absence of calcite in the cement, however, siliceous hydrogarnet instead of calcium monocarbonate is observed to precipitate. The use of a higher water-to-cement ratio for the preparation of a calcite-containing cement paste has a minor effect on the composition of the hydrate assemblage, while it significantly changes the composition of the pore solution. In particular, lower pH value and higher Ca concentrations appear that could potentially influence the solubility and uptake of heavy metals and anions by cementitious materials.

Construction Materials↗
PubMedDate not supplied

Stress distribution on the metal framework of the implant-supported fixed prosthesis using different veneering materials.

PURPOSE: This study evaluated stress distribution in metal frameworks constructed on implants under masticatory forces using computer simulations. MATERIALS AND METHODS: Three-dimensional finite element analysis was used to study four different veneering materials-metal framework combinations using Calcitek implants. The veneering materials used in the study were porcelain, heat-polymerized poly(methyl methacrylate) resin, microfilled composite resin, and glass-modified composite resin. All computations were conducted for different levels on the buccal and lingual sides. RESULTS: Changing the veneering material on the prosthesis produced significant effects on stress levels and stress distribution on the metal frameworks. Stresses were concentrated along the marginal area of the prosthesis. Acrylic resin showed greater displacement than porcelain, probably because of its lower modulus of elasticity. CONCLUSION: In comparison to porcelain, more stress is borne by the acrylic resin-veneered metal framework under static loading.

Acrylic Resins↗
PubMed1996

Long-life physical property preservation and postendodontic rehabilitation with the Composipost.

Most coronal radicular reconstructions are made of cast inlay core metals or prefabricated posts covered in composite. The differences in the mechanical properties of these elements create a heterogeneous mass with inconsistent mechanical behavior. Studies using the Finite Element Method have shown the biomechanical disturbances caused by the inclusion of materials with a modulus of elasticity that is superior to that of dentine (i.e., nickel, chrome, zircon, etc). The use of materials with a modulus of elasticity close to that of dentine does not disturb the flow of stress inside the root. To our knowledge, only a composite material structured with programmable mechanical properties would be capable of producing both high mechanical performance and a modulus of elasticity adapted to dentine values. The C-POST, made of carbon epoxy, accommodates the demands of the dentine, as well as the in vitro stress linked to the prosthesis. The internal structure, consisting of long high-performance carbon fibers, unidirectionally and equally stretched, confers a totally original behavior that is adapted to clinical objectives. In addition, the C-POST has a fracture resistance superior to most metals.

Biomechanical Phenomena↗
PubMedDate not supplied

Probability of failure of veneered glass fiber-reinforced composites and glass-infiltrated alumina with or without zirconia reinforcement.

PURPOSE: The probability of failure under flexural load of veneered specimens of a unidirectional glass fiber-reinforced composite (FibreKor/Sculpture), a bidirectional glass fiber-reinforced composite (Vectris/Targis), a glass-infiltrated alumina (In-Ceram Alumina/Vita alpha), and a zirconia-reinforced glass-infiltrated alumina (In-Ceram Zirconia/Vita alpha) was investigated; a metal-ceramic (PG200/Vita omega) system served as a control. MATERIALS AND METHODS: Ten uniform beams of the veneered core materials were fabricated for each system and subjected to a three-point bending test. The data were analyzed using the Weibull method. The failure load of specimens at a 10% probability of failure (B10 load) was compared. The mode of failure was analyzed. RESULTS: The B10 load of the systems investigated was not significantly different from that of the metal-ceramic system. FibreKor possessed significantly higher B10 load than Vectris, In-Ceram Alumina, and In-Ceram Zirconia. The B10 strength loads of Vectris, In-Ceram Alumina, and In-Ceram Zirconia were not significantly different from one another. CONCLUSION: The probability of FibreKor to fracture under a flexural load was significantly lower than that of Vectris, In-Ceram Alumina, or In-Ceram Zirconia.

Aluminum Oxide↗
PubMedDate not supplied

Adhesive strength between fiber-reinforced composites and veneering composites and fracture load of combinations of these materials.

PURPOSE: This study examined the influence of the adhesive strength between fiber-reinforced composites (FRC) and veneering composites on the fracture load of combinations of these materials. MATERIALS AND METHODS: Six materials were used. An experimental material called BR-100, Vectris, and FibreKor were the types of FRC. Estenia, Targis, and Sculpture were used as veneering composites. With the Estenia/BR-100 combination, the surface of the FRC was subjected to three different conditions before veneering. Ten specimens of each combination were fabricated and divided into two groups: One group was stored in 37 degrees C distilled water for 24 hours, and the other was thermocycled (4 degrees C/60 degrees C, 10,000 cycles). Adhesive strength between FRCs and veneering composites was determined using the compressive shear strength test. In addition, fracture loads of laminate specimens were determined. RESULTS: Good adhesive strength was obtained by leaving an unpolymerized layer on the surface of the FRC or by performing silane and bonding treatment. In the Estenia/BR-100 combination, when the adhesive strength was low, the fracture load of the laminate specimens was also low. However, the difference in fracture load was not as large as that seen in adhesive strength. The fracture load of each laminate specimen was significantly lower after thermocycling. CONCLUSION: The adhesive strength between the FRCs and veneering composite had an effect on the fracture load of the combination.

Adhesiveness↗
PubMed1981

Effect of surface contamination on band retention.

Laboratory investigations on the retention of orthodontic bands have been concerned with testing the retentive strength of different cements. This study reported here was designed to evaluate the effect of tooth-surface contamination on band retention. Zinc phosphate, silicophosphate, and polycarboxylate (powder: liquid ratio 1.5:1 and 1:1) cements were each tested on different groups of ten teeth. Preformed bands were selected, prepared, and cemented under controlled conditions. Specially designed jigs were used for cementing and for testing. For each cement, the tooth surfaces were pretreated prior to cementing as follows: (1) cleaned with pumice, (2) covered with wet saliva, (3) covered with saliva which was allowed to dry, and (4) covered with liquid paraffin. All specimens were stored in water at 37 degrees C. for 1 week prior to testing. Retention values were established by determining the tensile load required to dislodge the band divided by the surface area of the band. The retention of bands cemented with zinc phosphate and silicophosphate cements was unaffected by contamination of the enamel. The presence of dry saliva and of liquid paraffin significantly reduced the retention of bands cemented with polycarboxylate (P:L 1,5:1) (P less than 0.01). Only the presence of dry saliva reduced band retention when polycarboxylate (P:L 1:1) was used (P less than 0.05).

Acrylic Resins↗
PubMed1980

Antimicrobial action of dental cements.

It was observed that some of the cements tested had bacteriostatic and/or bactericidal action. The cements listed in decreasing order of effectiveness are (1) zinc oxide-eugenol, (2) silicophosphate, (3) zinc phosphate, and (4) silicate. The two newer cements, polycarboxylate and composite resin, exhibited no measurable antimicrobial action.

Anti-Infective Agents, Local↗