Biomedical subjects

T J Fruits

Publications and source records attributed to T J Fruits.

7 recordsLinked to original sources

PubMed1999

Effects of cyclic loading on selected post-and-core systems.

OBJECTIVE: The purpose of this study was to evaluate the resistance of selected post-and-core systems to fatigue testing. METHOD AND MATERIALS: A fatigue-testing machine and data acquisition software were developed for this in vitro test. Pulpless mandibular second premolars were treated with three different types of post-and-core system: (1) two different prefabricated posts with amalgam cores, (2) the same two prefabricated posts with resin composite cores, and (3) cast post and cores, which served as the control group. The fatigue-testing machine applied alternating buccal and lingual forces to the core until lateral movement of 0.0025 inches (63.5 microns) was detected by a transducer contacting the surface of the core. This criterion represented initial cement failure. RESULTS: Although groups using the resin composite core material exhibited a higher number of cycles prior to failure, there was no statistically significant difference between the different post-and-core systems. CONCLUSION: All of the post-and-core systems that were tested may be acceptable for restoring endodontically treated teeth.

Analysis of Variance↗

PubMed1998

Interfacial bond strengths of amalgam bonded to amalgam and resin composite bonded to amalgam.

OBJECTIVE: The effects of time, surface preparation, and use of a bonding agent on the ability to bond amalgam or resin composite to amalgam were studied. METHOD AND MATERIALS: Cylindrical amalgam specimens were prepared in a split die (32 groups of 10 each). The 32 groups were divided into two groups of 16 each: amalgam bonded to amalgam and resin composite bonded to amalgam. One half of each group of 16 was bonded within 1 hour after the initial condensation (fresh) and the other half was bonded after 21 days' storage in physiologic saline (old). Four bonding methods (control [no bonding agent], Advance, All-Bond 2, or Amalgambond Plus) were each utilized on one abraded group (air abrasion with 50-microns aluminum oxide) and one unabraded group. After an additional 21 days of storage, bond strengths were measured with a three-point flexure test. Solid amalgam cylinders also tested. RESULTS: Solid amalgam control cylinders exhibited mean bond strengths 10,000 psi greater than any of the bonded specimens. Among specimens of amalgam bonded to amalgam, those that were abraded after 21 days and used no bonding agent showed a significantly greater bond strength than did specimens utilizing any of the other combinations of the selected independent variables. Among specimens of resin composite bonded to amalgam, those bonded after 21 days and utilizing a bonding agent exhibited significantly greater bond strengths than did specimens utilizing any of the other combinations of the selected independent variables. CONCLUSIONS: The results of this in vitro study suggest that the strength of a repaired amalgam is only about 40% of that of an unrepaired amalgam. They also indicate that the strongest repair of amalgam using additional amalgam material may be accomplished without the use of any bonding agents utilized in this study. When adding resin composite material to amalgam, the resin composite should be added after the amalgam has had adequate time to set, and the use of a bonding agent increases the strength of the repair.

Air↗

PubMed1997

In vitro weathering of selected direct esthetic restorative materials.

Reflectance spectroscopy measurements were used to compare the degree of surface color shift in two classes of visible light-cured resin composites (hybrid and small-particle) and a glass-ionomer restorative. The weathering times investigated were 0, 100, 200, 300, and 400 hours. Environmental factors of heat, ultraviolet light, and moisture were used to affect the surface integrity of the restoratives. The parameter of delta E * ab (overall color difference) of the CIELAB system for measuring small color differences was used. Chroma changes [delta C * ab] and hue differences [delta H * ab] were also determined. Color shifts, chroma changes, and hue differences were observed for all restorative materials evaluated, regardless of the weathering conditions or time intervals imposed. Glass-ionomer cement demonstrated a significantly greater degree of color shift than did the resin composites. There was no significant difference in the amount of overall color change between the two resin composites, although the difference in change in lightness was significant.

Color↗

PubMed1996

Effects of equivalent abrasive grit sizes utilizing differing polishing motions on selected restorative materials.

The effects on surface roughness of three specific classifications of abrasive motion during the polishing of selected amalgam and resin composite materials were evaluated with a profilometer. Equivalent grit sizes were used to evaluate the character of the surface created by each class of abrasive motion. The motions investigated were rotary (diamond), planar (sandpaper disk), and reciprocal (reciprocating handpiece). Fine, medium, and coarse abrasives were used with each motion. Average roughness values for each abraded specimen were used to compare the effects of the type of motion on the surface. Results indicated that, among all of the combinations of motions and abrasive grits evaluated, the planar motion produced significantly lower surface roughness values on both amalgam and resin composite surfaces.

Composite Resins↗

PubMed1996

Resin-modified glass ionomers: a new option in restorative dentistry.

New dental materials and products are constantly being introduced in hopes of replacing or improving established materials. Although this onslaught of dental innovation can eventually lead to major improvements in the ease and success of clinical dentistry, it also presents a nightmare for the practitioner wishing to keep pace with these products. The introduction of the resin-modified glass ionomers at first glance appears to offer some very promising applications. Only time and clinical trials will give practitioners a true account of their benefits as well as their shortcomings.

Composite Resins↗

PubMed1996

Bond strengths of fluoride-releasing restorative materials.

PURPOSE: To compare the shear bond strengths to dentin of four tooth-colored fluoride-releasing restorative materials that utilize different mechanisms of dentin-bonding. MATERIALS AND METHODS: Four materials were tested: a chemically-cured glass ionomer (Ketac-Fil); a light-cured resin-modified glass ionomer (Photac-Fil); a light-cured resin-modified glass ionomer in conjunction with a resin dentin-bonding agent (Vitremer); and a light-cured resin composite in conjunction with a resin dentin-bonding agent (Tetric). The enamel was removed from four sides of the twenty human noncarious extracted molars which had their roots embedded in acrylic blocks. Cylindrical samples of the materials were prepared in plastic molds and bonded to the dentin surface according to the manufacturers' instructions. After 24 hours of storage in a humidor, the samples were sheared with an Instron testing machine at a crosshead speed of 0.5 mm/minute. RESULTS: Statistical evaluation (ANOVA and Duncan's test) suggests that the fluoride-releasing resin composite material utilizing a resin dentin-bonding agent provided a significantly greater mean shear bond strength (16.5 MPa) after 24 hours storage than any of the selected glass ionomer materials. Of the three glass ionomer materials compared, the light-cured resin-modified material with a resin dentin-bonding agent provided a significantly greater mean shear bond strength (6.7 MPa) than the light-cured resin-modified material without a resin dentin-bonding agent (3.0 MPa) or the chemically-cured material (3.8 MPa).

Analysis of Variance↗

PubMedDate not supplied

Uses and properties of current glass ionomer cements: a review.

Glass ionomer cements have been used for a variety of restorative purposes. Recently, the formulation of these and other restorative materials has changed rapidly, so it is difficult to keep pace with the literature concerning effective use. A major modification to glass ionomer cements has been incorporation of resin components. This and other modifications over the years have changed some handling characteristics and physical properties of glass ionomer cements. A general review of some changes is reported here.

Dental Bonding↗