Viscoelastic properties, creep behavior and degree of conversion of bulk fill composite resins.

Objectives: The aim of this study was to investigate the viscoelastic properties and creep behavior of bulk fill composites under different conditions and evaluate their degree of conversion.

Methods: Seven bulk fill composites were examined: everX Posterior (EV), SDR (SD), SonicFill (SF), Tetric EvoCeram Bulk Fill (TE), Venus Bulk Fill (VE), x-tra base (XB) and x-tra fil (XF). Each material was tested at 21°C, 37°C and 50°C under dry and wet conditions by applying a constant torque for static and creep testing and dynamic torsional loading for dynamic testing.

Mechanical viscoelastic behavior of dental adhesives.

Objectives: The purpose of the study was to evaluate the mechanical properties of dental adhesive materials at different testing temperatures after dry and wet storage.

Methods: Specimens (d=1 mm, l=18 mm) from six materials were tested: Silorane Adhesive System (SL), Heliobond (HE), One-Step Plus (OS), Optibond Solo Plus (OP), cmf Adhesive System (CF) and Protobond (PR). Static and creep testing was performed by applying a constant torque below the proportional limit of the materials, while dynamic testing consisted of dynamic torsional loading.

Dynamic and static mechanical analysis of resin luting cements.

Various types of indirect restorations are available for dental treatment and resin cements are commonly used as a luting medium. The aim of this study was to evaluate the mechanical properties of contemporary resin luting agents under different testing conditions and temperatures. The materials tested were Choice 2 (CH), Clearfil Esthetic Cement (EC), Resicem (RC) and RelyX Unicem (RX).

Viscoelastic properties of low-shrinking composite resins compared to packable composite resins.

The aim of this study was to evaluate the viscoelastic properties of novel low-shrinking composites and compare them to those of packable composites. Six materials were tested: Clearfil Majesty Posterior (CM), ELS Extra Low Shrinkage (EL), Filtek P60 (FP), Filtek Silorane (FS), Prodigy (PR) and Surefil (SU). Static and dynamic testing was performed and materials were tested dry and wet at different temperatures (21°C to 50°C).

Effect of storage time on the viscoelastic properties of elastomeric impression materials.

Purpose: The aim of this study was to evaluate creep and viscoelastic properties of dental impression materials after different storage times.

Methods: Six commercially available impression materials (one polyether and five silicones) were tested after being stored for 30 min to 2 weeks under both static and dynamic testing. Shear and Young's moduli, dynamic viscosity, loss tangent and other viscoelastic parameters were calculated.

Creep and dynamic viscoelastic behavior of endodontic fiber-reinforced composite posts.

Purpose: Fiber-reinforced composite (FRC) posts have gained much interest recently and understanding of their viscoelastic properties is important as they can be used in stress-bearing posterior restorations. The aim of this study was to evaluate the creep behavior and the viscoelastic properties of four commercial FRC posts under different temperatures and different storage conditions.

Methods: The FRC posts tested were Glassix, C-Post, Carbonite and Snowlight.

In vitro fluoride uptake by bovine enamel from aesthetic restorative materials.

Objectives: The purposes of this in vitro study were to determine whether different types of fluoride-containing restoratives produce differing levels of fluoride uptake by bovine enamel, and to determine the effect of time on this uptake.

Methods: Seven aesthetic restorative materials were evaluated. Forty bovine enamel slabs were prepared for each tested material, five of which were used to determine baseline fluoride concentrations.

The effect of temperature on the viscoelastic properties of nano-hybrid composites.

Objectives: The purpose of this study was to examine the viscoelastic properties of nanofilled dental composites under both static and dynamic testing and to determine the influence of temperature, medium of storage and storage time.

Methods: Three nanofilled composites, one packable and one ormocer were tested. The specimens were examined dry at 21 degrees C and wet at 21, 37 and 50 degrees C after being stored for 24h and 1 month under both static and dynamic testing.

The effect of temperature on viscoelastic properties of glass ionomer cements and compomers.

The objective of this study was to determine the viscoelastic properties of different types of glass ionomer cements (GICs) and compomers under varying temperature conditions found in the mouth. The materials tested were a conventional GIC (Aqua Ionofil U), a resin modified GIC (Fuji II LC), a highly viscous GIC (Voco Ionofil Molar), and two polyacid modified composite resins/compomers (Glasiosite and Dyract Flow). Six groups of four specimens were prepared from each material.

Fatigue of packable dental composites.

Objective: The purpose of the study was to measure the fatigue properties of four dental resin composites using a dynamic mechanical analysis and to relate the results with viscoelastic properties.

Methods: Dynamic torsional loading was conducted at resonance at 30-50Hz. Specimens were thoroughly cured and tested dry at 21 degrees C.

Dynamic and static elastic moduli of packable and flowable composite resins and their development after initial photo curing.

Objective: The purpose of this study was to evaluate the dynamic (storage) shear modulus and the static shear modulus of elasticity of packable and flowable composite resins and to investigate their development after initial photo-curing.

Methods: Three pairs of a packable versus a flowable composite and a microfill composite resin were tested (Alert/Flow It, Filtek P60/Filtek Flow, Admira/Admira Flow, A 110). Cylindrical specimens (0.

The effect of pulse activation on microleakage of a 'packable' composite resin and two 'ormocers'.

The purpose of the study was to examine the effect of pulse polymerization on microleakage of one packable composite resin and two organically modified ceramics (ormocers), within a high C-factor preparation. Class-V cavity preparations with occlusal margins in enamel and gingival margins in dentin were prepared on 60 freshly extracted premolars or molars. Teeth were randomly assigned to 12 experimental groups (five teeth each) representing the different restorative systems, mode of polymerization and thermal cycling test.

Dynamic mechanical analysis of viscoelastic functions in packable composite resins measured by torsional resonance.

The objective of this study was to evaluate the viscoelastic functions of packable composite resins with the use of a resonant dynamic mechanical analysis technique in torsion. The materials tested were: Alert (Jeneric Pentron), Prodigy Condensable (Kerr Corporation), Surefil (Dentsply DeTrey), and Filtek P60 (3M Dental Products). Dynamic torsional loading was conducted in the frequency range from 1 to 150 Hz.

Dynamic viscoelastic behavior of resin cements measured by torsional resonance.

Objective: The purpose of the study was to measure the viscoelastic properties of four dental resin composite cements using a dynamic mechanical analysis technique.

Methods: Dynamic torsional loading was conducted in the frequency range from 1 to 80 Hz. Cement specimens were tested after storage in 37 degrees C water for 24 h.

In vitro cytotoxicity of six dentin bonding agents.

The cytotoxicity of six dentin bonding agents (Syntac, Solobond, Bond 1, Scotchbond 1, Heliobond and F-2000) was tested against an established cell line, L929. Under aseptic conditions 3, 5 and 10 microL dentin bonding agents were placed in the centre of Petri dishes. Each dish was covered with a 5-mL suspension of fibroblasts at a concentration of 40 000 cells mL(-1).

Fluoride release from restorative materials and a luting cement.

Statement Of Problem: In addition to conventional glass ionomers, a considerable number of different types of materials have been formulated to release fluoride. Variation in composition results in quantitative differences in the amount of fluoride release by these materials.

Purpose: This study evaluated and compared fluoride release in distilled water from different types of restorative materials and a luting cement.

Microleakage of bonded amalgam restorations: effect of thermal cycling.

This study examined the effect of thermal cycling on the microleakage of bonded amalgam restorations. Three dental amalgam alloys and a gallium alloy were tested with two adhesive resin systems and copal varnish as a control. Class V cavity preparations were prepared on 168 freshly extracted premolars or molars.

Fluoride release from three glass ionomers, a compomer, and a composite resin in water, artificial saliva, and lactic acid.

The amounts and the pattern of fluoride release from one metal-reinforced glass ionomer cement, two resin-modified glass ionomer cements, one compomer, and one composite resin placed in double-distilled water, artificial saliva, and lactic acid were evaluated in this study. Measurements of fluoride ion release were made for a total of 105 cylindrical specimens (10 mm in diameter and 1.5 mm in height).

Development of a computer-assisted learning software package on dental traumatology.

The development of computer-assisted learning software packages is a relatively new field of computer application. The progress made in personal computer technology toward more user-friendly operating systems has stimulated the academic community to develop computer-assisted learning for pre- and postgraduate students. The ability of computers to combine audio and visual data in an interactive form provides a powerful educational tool.

Artificial caries formation around fluoride-releasing restorations in roots.

Secondary caries is one of the most important factors leading to replacement of dental restorations. This investigation assessed the capacity of fluoride-releasing restorative materials to resist caries in vitro when used in roots. Class 5 cavities were prepared in the buccal and lingual surfaces of 30 extracted premolars.

Viscoelasticity and aging of dental composites.

Effects of aging on several dental composites were studied using a torsion creep apparatus. A constant torque was applied from 1 second to 3 hours, and recovery was observed from 10 seconds to 2 days, for specimens aged from 3 hours to 8 weeks following polymerization. Specimens aged for shorter times exhibited more creep and less complete recovery than specimens aged for longer times.

Artificial secondary caries around two new F-containing restoratives.

Replacement of restorations due to secondary caries is a continuing problem in restorative dentistry. This investigation evaluated the ability of two new light-cured fluoride-containing restorative materials to inhibit caries in vitro. Class 5 cavities were prepared in buccal and lingual surfaces of 20 extracted premolars.

Degree of microleakage of some pit and fissure sealants: an in vitro study.

The purpose of this study was to evaluate and compare the degree of microleakage exhibited by five resin sealants (Concise, Helioseal, Durafil. Fissurit, Sci-Pharm) and a glass-ionomer sealant (Fuji Glass lonomer Type III). The fissure systems of the occlusal surfaces of freshly extracted teeth were opened using a pear-shaped bur; the preparations were confined to enamel.

A study of the microstructure of some dental retention pins and prefabricated root canal posts.

Pins and root canal posts are generally considered indispensible aids in clinical restorative dentistry. To secure the long-term efficiency of pins and posts, such devices should be of sufficient strength to carry the relevant loads. It is, however, essential that their properties do not decline as a consequence of corrosion, or that corrosion of metallic pins and posts does not cause unfavourable effect in contacting biological tissues.

Temperature dependence of the dynamic viscoelastic behavior of chemical- and light-cured composites.

The relationship of temperature to the viscoelastic properties of six composites, three light-cured and three chemical-cured, was studied, using constant dynamic loading over the narrow range of temperatures (20-60 degrees C) which can be encountered in the mouth. The parameters measured were: storage modulus G(1), loss modulus G(2), tan delta, quality factor Q, coefficient of decay alpha, and dynamic viscosity. It was found that the dynamic viscoelastic properties of the tested materials are temperature-dependent, but probably not to a clinically significant degree.