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Biomedical subjects

V D Williams

Publications and source records attributed to V D Williams.

At least 19 recordsLinked to original sources
PubMed1997

Alumni self-perception of competence at time of dental school graduation.

A survey instrument was administered to recent alumni to evaluate self-perceived competency in twenty-one selected areas at the time of graduation. The questionnaire was completed by 439 (62.8 percent) alumni who graduated between the years 1985 and 1994, inclusive. Graduates generally felt most competent in their ability to treat dental caries and its sequelae and least competent in their ability to recognize myofascial pain and temporomandibular joint disorders. Very little association was demonstrated between demographic characteristics of the respondents and their competency self-ratings. The survey identified areas of strengths and weakness within the present comprehensive care curriculum as perceived by the graduating dentists.

Clinical Competence↗
PubMed1996

Bond strength and surface characterization of a Ni-Cr-Be alloy.

OBJECTIVES: Since resin composite cements adhere directly to base metal surfaces, the composition and integrity of the surface oxide layer is considered critical for adequate bonding. The aims of this study were to determine the tensile bond strength, and assess predominant surface oxides and oxide layer depth on the surface of a Ni-Cr-Be alloy after subjecting the alloy to various surface treatments. METHODS: Cylinders of Ni-Cr-Be (Rexillium III, Jeneric/Pentron) were cast and the following test groups were investigated: Group 0: no furnace oxidation, no air abrasion; Group 1: air fired, starting temperature 650 degrees C, ending temperature 1000 degrees C (1 min hold); Group 2: same firing sequence under vacuum; Group 3: same air firing sequence followed by air abrasion with 50 micrometers Al2O3; Group 4: vacuum fired, air abraded with 50 micrometers Al2O3; Group 5: air fired, air abraded with 280 micrometers Al2O3; Group 6: vacuum fired, air abraded with 280 micrometers Al2O3; Group 7: no furnace oxidation, air abraded with 50 micrometers Al2O3; and Group 8: no furnace oxidation, air abraded with 280 micrometers Al2O3. The oxide composition of three cylinders per group was analyzed with x-ray photoelectron spectroscopy (XPS) and Auger electron spectroscopy (AES). Twenty cylinders from each group were bonded together with Panavia 21 (Kuraray), stored in water for 30 d, and tensile tested. Data were analyzed using one-way ANOVA and Duncan's Multiple-Range test (p=0.05). RESULTS: Furnace oxidation brought Be to the surface and increased the oxide thickness. Air abrasion removed the oxide layer and resulted in surfaces containing significant amounts of Al2O3. Bond strengths for Group 0 were significantly lower than bond strengths for Groups 1, 3, 4, 5, 6, 8, but not significantly different from bond strengths for Groups 2 and 7 (p<0.05). SIGNIFICANCE: Results of this study suggest differences in oxide composition and thickness due to various surface treatments. Furnace oxidation did not significantly affect bond strength and may not be required as a separate step for metal preparation if a resin adhesive is used.

Air Pressure↗
PubMed1996

Panavia/sandblasted resin bonded prostheses: a five year retrospective study.

The authors feel that this study suggests that the Panavia/sandblasted retention method, with its low debond rate, is a viable method for luting resin bonded prostheses. The authors wish to acknowledge the services of Ms. Jane Jakobsen (statistician) and Ms. Connie Norton (secretary) who made significant contributions to the completion of this article. Their help was much appreciated.

Adolescent↗
PubMed1994

Disinfectant storage media and composite/metal bond strength.

PURPOSE: To evaluate the effect of three disinfection procedures on the tensile bond strength of Panavia resin composite cement. MATERIALS AND METHODS: Alloy cylinders were bonded and stored in: (1) 0.2% chlorhexidine; (2) 2% activated glutaraldehyde; (3) distilled water and sterilized with ethylene oxide; and (4) distilled water. Solutions were monitored for bacterial cultures and pH changes regularly for 90 days after which all samples were tested to tensile failure. RESULTS: ANOVA showed no significant difference between mean group bond strengths. A direct positive correlation was demonstrated between solution pH and bond strengths (r = 0.98). All groups were found to represent effective methods for preventing bacterial growth in storage solutions during long term cement bonding studies.

Analysis of Variance↗
PubMed1993

Analysis of debond rates of resin-bonded prostheses.

Debonding rates of 164 resin-bonded prostheses (RBP) placed from 1974 to 1985 were examined at recall. The yearly debond rates were calculated, the cumulative probability of failure was determined for the debonded RBPs, and Weibull distribution parameters were determined. For perforated prostheses, there was a high initial debond rate, followed by slowly decreasing rates for about 5 years. Increasing rates after 5 years indicated the beginning of wear-out. The Weibull parameters for the wear-out period of the perforated prostheses were: characteristic life = 128 (SE = 2) months, modulus = 1.27 (0.06), and threshold parameter = 0. Data were available for etched frameworks for 6 years and showed decreasing debond rates during this time. The characteristic life of the etched bridges was 318 (84) months. The cumulative failure data were also modeled with a cubic polynomial distribution that resulted in a U-shaped hazard function.

Adolescent↗
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↗
PubMed1984

Acid-etch retained cast metal prostheses: a seven-year retrospective study.

The results of this study showed: retention rate was good, caries on the retainer teeth was almost nonexistent, and the supporting tissue clinically did not appear to have a greater incidence of periodontal problems. We believe that these results indicate that the cast acid-etch retained anterior prosthesis should be considered a permanent restoration and a valuable aid for the dental patient.

Acid Etching, Dental↗
PubMed1984

Electrosurgery and wound healing: a review of the literature.

This literature review and discussion has presented evidence that some additional research needs to be done in this area. Particular attention should be paid to control certain variables: kind and type of waveform, shape and size of electrode, and speed of the electrode through the tissue so that meaningful results may be given to the dental profession. The evaluation of the literature seems to show that when the variables are controlled, untoward results of wound healing after electrosurgery seem unwarranted.

Animals↗