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Biomedical subjects

V D Williams

Publications and source records attributed to V D Williams.

14 recordsLinked to original sources
PubMed1992

Bond versus rebond strengths of three luting agents for resin-bonded fixed partial dentures.

Recently, new luting materials have been claimed to have adhesion to metal and tooth structure. This study determined if rebonding the specimens affected their tensile bond strength. Ten samples each of Rexillium III metal cylinders (12 x 6.3 mm) were bonded and rebonded with Comspan Panavia and Super-bond materials. The film thickness was controlled with a micrometer device at 20 microns. The samples were stored for 24 hours in deionized water at 37 degrees C and were then thermocycled for 24 hours and tested for tensile failure on an Instron testing machine. A stereomicroscope was used to determine adhesive/cohesive failure. The results showed a significant difference at p greater than 0.01 in tensile bond strengths (bond versus rebond strength) for all three luting agents. Most of the failures were adhesive in nature.

Acid Etching, Dental↗
PubMed1992

Measurement of water sorption by resin composite adhesives with near-infrared spectroscopy.

Spectroscopic methodology was used to follow the water uptake of disks of two resin composite luting agents during long-term storage. Fourier-transform near-infrared (FT-NIR) spectroscopy was used for collection of spectra over the 4200-6500 cm-1 spectral region. The 5200-cm-1 absorption band of water was monitored initially, at 24 h, seven days, two weeks, and then monthly over a period of 12 months. The disks were stored in water, air, and desiccated conditions. Disks were also subjected to two alternate cycles (two weeks each) of hydration and desiccation. A spectral manipulation program was used for quantitation of the area under the water absorbance band. Area ratios demonstrated similar water-uptake patterns for the two adhesives. Rapid water uptake was seen within the first two weeks of storage. Alternate hydration and desiccation of the samples showed that water uptake by the filler/polymer network was partially reversible. The desiccant was unable to remove all the water from the samples, which indicated that some water was tightly held within the sample matrix. FT-NIR spectroscopy is recommended as an effective method for study of the equilibration of resin composites in water.

Absorption↗
PubMed1991

The effect of film thickness on the tensile bond strength of a prosthodontic adhesive.

This study investigated the effect of cement film thickness on the tensile bond strength of a prosthodontic adhesive. Rexillium III alloy cylinders were bonded end-to-end with Panavia Opaque adhesive cement and film thicknesses of 20, 50, 80, 110, 140, and 200 microns were evaluated. The specimens were thermocycled for 24 hours (1080 cycles) between 5 degrees and 60 degrees C, stored for 30 days at 37 degrees C, and the mean bonds for tensile strength, including the mode of failures, were recorded. Statistical analysis revealed significant differences, but the strongest bond strengths were recorded for the 80 microns cement film thickness.

Adhesives↗
PubMed1991

A method for testing denture adhesives.

An in vitro test method is described simulating the in vivo fate of a denture adhesive, i.e., destruction of the adhesive, dilution, and dissolution, by measuring the bond strength for the adhesive placed between acrylic resin plates. Between each measurement, the adhesive was exposed to isotonic saline. The bond strength for two ointment denture adhesives, Super Corega and Fixodent, was measured and the results were compared with those obtained for one of them in a previous in vivo test. The test method described for denture adhesives seems useful to depict the fate of a denture adhesive in clinical use.

Adhesives↗
PubMed1990

Effect of microbial contamination and pH changes in storage solutions during in vitro assays of bonding agents.

A study of pH changes in, and microbial colonization of, storage solutions being utilized during an in vitro evaluation of luting agent solubility has been made. Microbial growth in storage solutions was observed to occur at as high as 10(5) colony-forming units (cfu)/mL after seven days' incubation. A strong time-dependent inverse correlation between pH and cfu was found, with the pH dropping to as low as 5.3 (p less than 0.01). Decreases in pH were not found in presterilized control samples (p less than 0.05). Further, it was demonstrated that presterilization with ethylene oxide or the addition of respiratory inhibitors prevented both microbial colonization and the pH drop when compared with controls (p less than 0.001). These data suggest that studies of dental materials which include incubations in various fluids should be controlled for the potential effects of micro-organisms and their effect on pH.

Colony Count, Microbial↗
PubMed1989

Cast metal, resin-bonded prostheses: a 10-year retrospective study.

A sample of 99 resin-bonded prostheses placed over a 10-year period were examined by four clinicians using a standardized criteria sheet. Areas examined included hard tissues, periodontium, retainer and pontic design, retention, the effect of occlusion on framework design and retention rate, and bonding media. The data from 7- and 10-year retrospective studies were compared for meaningful trends. Results showed (1) caries on retainer teeth was 3%, (2) gingival index of the retainer teeth was less than the gingival index of the rest of the mouth (0.7 +/- 0.5 versus 0.9 +/- 0.6), (3) the respective mean probing depths of retainer teeth of 34 patients in the 7- and 10-year studies were 2.2 +/- 0.4 mm and 1.9 +/- 0.7 mm, (4) the debond rate of all the prostheses from all causes was 31%, (5) the debond rate comparing etched metal and perforated retainers from all causes was 32% and 31% [corrected], respectively, and (6) 83% liked the prosthesis; 17% were noncommittal. The authors concluded that the resin-bonded prosthesis may be considered a permanent restoration and a valuable asset in the clinician's armamentarium.

Adult↗
PubMed1985

The effect of five-year storage prior to bonding on enamel/composite bond strength.

The purpose of this study was to examine the effect of pre-bonding storage durations on the shear strength of light-cured composite bonded to enamel. Thirty whole extracted human molars--12 with a storage time of five years, 12 with a storage time of three or fewer months, and six with a storage time of 24 hours or less--were mounted in improved dental stone in copper tubing. The molars were faced 90 degrees to the horizontal with a milling device to produce 120 surfaces, 48 each for two groups, and 24 for one group. Composite buttons 2.3 mm in diameter were bonded to the enamel using the acid-etch light-curing system. The samples were tested in shear utilizing a cross-head speed of 0.5 cm/min with a 500-kg load cell. The results showed that: there was no significant difference, at the 0.05 confidence level, in composite/enamel bond strength between teeth stored for 24 hours, three months, and five years prior to bonding; the lingual surface developed the highest composite/enamel bond strength in all three groups; and enamel fracture occurred 29% of the time on de-bonding.

Acid Etching, Dental↗
PubMedDate not supplied

Review of dentinal bonding in vitro: the substrate.

This article reviews common substrates and testing conditions used in dentinal bond strength studies in vitro. The available literature supports the use of freshly extracted, hydrated human teeth for studies in vitro. No one testing condition has proven superior accuracy over the others. Evidence is presented to support the implementation of infection control measures when handling the substrates.

Dental Bonding↗
PubMedDate not supplied

Tensile strengths of three luting agents for adhesion fixed partial dentures.

This study investigated the effects of thermal stress and specimen storage time on the tensile bond strength of three prosthodontic adhesives: Comspan (LD Caulk), Panavia Opaque (Kuraray), and Super-Bond (Sun Medical). Rexillium III alloy cylinders were cast, bonded end-to-end, and subsequently tested for tensile strength. Storage conditions of 2 and 30 days at 37 degrees C were evaluated. Half of the specimens were thermocycled for 24 hours (1,080 cycles) between 5 and 60 degrees C. Mean bond strengths and mode of failures were recorded. Significant differences related to the adhesive systems and the specimen storage time were noted. Thermocycling did not significantly affect the bond strength of the systems tested.

Dental Cements↗