Biomedical subjects

W F Caughman

Publications and source records attributed to W F Caughman.

At least 19 recordsLinked to original sources

PubMed2001

Curing potential of dual-polymerizable resin cements in simulated clinical situations.

STATEMENT OF PROBLEM: Little is known about the ability of dual-polymerizable resin cements to polymerize when they are used in various clinical scenarios. PURPOSE: This study was conducted to determine whether any of 6 commercially available dual-polymerizable resin cements should be classified as an "all-purpose" resin cement. MATERIAL AND METHODS: . Chemical conversion values (C=C converted to C-C, or the extent of the curing reaction) of 6 commercially available dual-polymerizable resin cements were determined with infrared spectroscopy in 5 clinically relevant scenarios. Scenarios included: using each cement in a dual-polymerizable mode (mixing of 2 pastes); light polymerizing curing through Mylar sheets (dual-Mylar), which served as the control; light polymerizing through 3-mm porcelain (dual-3 mm); and no exposure to light (dual-no light). The single-component light-polymerizable product was also tested as follows: exposed directly through Mylar (light-Mylar) or exposed through 3 mm of porcelain (light-3 mm). Results. For each product, dual-Mylar treatment yielded the highest conversion value of all treatments (control for each product). For all products, dual-3 mm conversion was at least 97% of control and equivalent to control, with the exception of Lute-It!. Dual-no light conversion was less than control treatment but at least 86% of control for all products except for Variolink II (62% of control). For all products in dual-no light mode, except Choice and Variolink II, conversion was at least equal to the light-Mylar values. Only 1 product (Variolink II) did not demonstrate increased conversion values for dual-Mylar compared with light-Mylar treatments. For most other products (Calibra, Insure, and Lute-It!), conversion values for light-3 mm were significantly less than for light-Mylar. Conversion values for Nexus, Choice, and Variolink II were equivalent between light-Mylar and light-3 mm treatments. CONCLUSION: The choice of a dual-polymerizable cement should be based on its intended use because not all products polymerize adequately in every clinical situation. Although no cement met the stated criteria for an "all-purpose" cement, those tested did produce a range of product-specific results.

Analysis of Variance↗

PubMed2001

Curing potential of dual-polymerizable resin cements in simulated clinical situations.

STATEMENT OF PROBLEM: Little is known about the ability of dual-polymerizable resin cements to polymerize when they are used in various clinical scenarios. Purpose. This study was conducted to determine whether any of 6 commercially available dual-polymerizable resin cements should be classified as an "all-purpose" resin cement. MATERIAL AND METHODS: Chemical conversion values (C=C converted to C-C, or the extent of the curing reaction) of 6 commercially available dual-polymerizable resin cements were determined with infrared spectroscopy in 5 clinically relevant scenarios. Scenarios included: using each cement in a dual-polymerizable mode (mixing of 2 pastes); light polymerizing curing through Mylar sheets (dual-Mylar), which served as the control; light polymerizing through 3-mm porcelain (dual-3 mm); and no exposure to light (dual-no light). The single-component light-polymerizable product was also tested as follows: exposed directly through Mylar (light-Mylar) or exposed through 3 mm of porcelain (light-3 mm). RESULTS: For each product, dual-Mylar treatment yielded the highest conversion value of all treatments (control for each product). For all products, dual-3 mm conversion was at least 97% of control and equivalent to control, with the exception of Lute-It!. Dual-no light conversion was less than control treatment but at least 86% of control for all products except for Variolink II (62% of control). For all products in dual-no light mode, except Choice and Variolink II, conversion was at least equal to the light-Mylar values. Only 1 product (Variolink II) did not demonstrate increased conversion values for dual-Mylar compared with light-Mylar treatments. For most other products (Calibra, Insure, and Lute-It!), conversion values for light-3 mm were significantly less than for light-Mylar. Conversion values for Nexus, Choice, and Variolink II were equivalent between light-Mylar and light-3 mm treatments. CONCLUSION: The choice of a dual-polymerizable cement should be based on its intended use because not all products polymerize adequately in every clinical situation. Although no cement met the stated criteria for an "all-purpose" cement, those tested did produce a range of product-specific results.

Analysis of Variance↗

PubMed2001

Tray delivery of potassium nitrate-fluoride to reduce bleaching sensitivity.

OBJECTIVE: Tooth sensitivity is a common side effect associated with tooth whitening. The purpose of this study was to determine if bleaching tray delivery of potassium nitrate-fluoride reduces bleaching sensitivity enough to allow continuation of whitening treatment. METHOD AND MATERIALS: Thirty patients were enrolled in a university-approved clinical study and had their teeth bleached at night with 10% carbamide peroxide in a custom-fitted tray. The bleaching tray was a rigid experimental design for which sensitivity was expected. If tooth sensitivity was experienced, the patient applied a gel containing 5% potassium nitrate and 1,000 ppm sodium fluoride in the bleaching tray for various time periods. Log forms were collected upon completion of bleaching, and patient interviews were used to compare effects of the gel before and after sensitivity treatment. RESULTS: Sixteen out of 30 patients experienced tooth sensitivity. Of those 16 patients, 12 used the gel, and 11 of the 12 reported a reduction in sensitivity. Treatment times ranged from 10 minutes before bleaching to 30 minutes before and after. The number of applications ranged from one to continuous use. Some patients were able to continue bleaching after one gel application with no subsequent sensitivity. Other patients were unable to continue bleaching unless they continued using the gel. The incidence of tooth sensitivity (53%) reported in this study is consistent with sensitivity reported in studies using semi-rigid custom-fitted trays made from stone casts with a nonscalloped, nonreservoir design. CONCLUSION: The use of a 5% potassium nitrate-fluoride gel applied in the tray as needed for tooth sensitivity associated with nightguard vital bleaching can reduce sensitivity in a majority of patients and allow most patients to continue bleaching to completion.

Carbamide Peroxide↗

PubMed2000

Effect of dentin desensitizers and cementing agents on retention of full crowns using standardized crown preparations.

STATEMENT OF PROBLEM: Past research has not controlled preparation surface area when examining the influence of dentin desensitizers on the retentive strength of cemented cast crowns, leading to inconsistent results. PURPOSE: This research controlled crown preparation surface area and evaluated the effect of various dentin desensitizers and conventional cementing agents on the in vitro retentive strength of cast crowns. METHODS AND MATERIAL: Freshly extracted human molars were prepared for a standardized crown preparation (26 degrees total convergence, 4 mm axial height) with a custom-made pantograph. Dentin desensitizers included none (control), a polymerizable material (All-Bond 2), and a nonpolymerizable desensitizer (Gluma Desensitizer). Cementing agents included zinc phosphate (Fleck's), glass ionomer (Ketac-Cem), resin-modified glass ionomer (Fuji II), and resin cement (Panavia 21). Twelve teeth were prepared for each test condition (144 teeth total). Individual castings were made from a base metal alloy (Rexillium III). Crowns were removed after storage at 26 degrees C for 48 hours at 100% relative humidity using a universal testing machine at a crosshead speed of 1.27 mm/min. The proportion of cement retained on the tooth and casting after debonding was quantified according to treatment. Statistical treatment included 1- and 2-way ANOVAs, followed by the Tukey-Kramer post hoc test at a preset alpha of 0.05.Results. Resin cement exhibited the highest retentive strength and all dentin treatments resulted in significantly different retentive values (All-Bond 2 (5.68 +/- 0.70 MPa) > control (4.67 +/- 0.48 MPa) > Gluma (4.12 +/- 0.37 MPa)). Retention of resin-modified glass ionomer was between the resin cement and glass ionomer groups: All-Bond 2 (3.46 +/- 0.26 MPa) > Gluma (2.81 +/- 0.15 MPa) = control (2.96 +/- 0.18 MPa). Conventional glass ionomer values were between those of Fuji Plus and zinc phosphate groups: All Bond 2 (2.23 +/- 0. 20 MPa) = control (2.36 +/- 0.20 MPa) > Gluma (1.98 +/- 0.23 MPa). Zinc phosphate had the lowest retention values: control (1.68 +/- 0. 08 MPa) > Gluma (0.81 +/- 0.11 MPa) > All-Bond 2 (0.67 +/- 0.14 MPa). The majority of cement was retained on the debonded tooth surface versus the casting, with the exception of zinc phosphate when used with dentin pretreatments. CONCLUSION: Controlled crown surface areas reduced the variation in strength values permitting high discrimination among retention values of desensitizer/cement combinations. In all but 1 combination, Gluma desensitizer significantly decreased crown retention. With resin cement and resin-modified glass ionomer, use of All-Bond 2 desensitizer significantly increased crown retention values.

Analysis of Variance↗

PubMed1999

Novel approach to measure composite conversion kinetics during exposure with stepped or continuous light-curing.

PURPOSE: The objective of this research was to evaluate a novel approach to monitor the polymerization reaction during a light-curing exposure by using infrared (IR) spectroscopy. MATERIALS AND METHODS: An IR spectrometer was equipped to use an attenuated total reflectance (ATR) element as an IR-active substrate. The uncured composite (Herculite XRV, Shade A2, Kerr, Orange, California) was placed against the crystal, and the IR spectrum was continuously obtained during various exposure scenarios. The degree of conversion and the maximum rate of reaction were monitored at 0 mm (top surface), 1 mm, 2 mm, and 3 mm beneath the surface. The exposure conditions included continuous 40-second or 60-second exposures at 100% intensity (800 mW/cm2) or a stepped output of 10 seconds at 17% maximal output (133 mW/cm2) followed by full output for the remainder of the 40-second or 60-second exposure (Elipar Highlight, ESPE, Norristown Pennsylvania). The results were analyzed using MANOVA with appropriate post hoc tests (p < or = .05). RESULTS: For 40-second exposures, the peak conversion rates were significantly reduced (p < .05) when using the stepped exposure mode compared to the continuous exposure: 40-second top surface: stepped = 5.5%/s +/- 0.4, continuous = 10.5%/s +/- 1.0; 1 mm step = 3.6%/s +/- 0.4, continuous mode = 4.8%/s +/- 0.2. The same trend was noted when using the 60-second exposure. Equivalent conversion values (p > .05) beneath the surface between stepped and continuous exposure modes at similar depths 60 seconds after light initiation were only attained at 3 mm 4 for the 40-second exposure. However, using the 60-second exposure, equivalent conversion values between step and continuous exposure modes at similar depths were obtained. Even with a reduced conversion rate at the surface using the stepped cure mode, polymerization shrinkage forces were sufficient to debond the specimens from the test crystal after only 20 seconds into the exposure. This result indicated that stress development in the curing composite was non-uniform, and stress values developed at the surface of the restoration were the greatest. CLINICAL SIGNIFICANCE: Stepped intensity curing for the ESPE Highlight unit was shown to produce significantly lower conversion rates at the surface and at 1-mm depths, but longer exposure times were still required to provide conversion values equivalent to continuous exposure.

Analysis of Variance↗

PubMed1999

Carbamide peroxide whitening of nonvital single discolored teeth: case reports.

Patients who present with a single discolored tooth represent a significant restorative challenge. These case reports describe an economic and conservative treatment option for these patients. The situations presented demonstrate techniques for bleaching with carbamide peroxide in a traditional nightguard or with an inside-outside technique to achieve acceptable esthetic results on isolated nonvital discolored teeth. Although these techniques may not be effective in all cases, they do not compromise or eliminate any future treatment options.

Adult↗

PubMed1998

Effect of heating delay on conversion and strength of a post-cured resin composite.

Physical property enhancement in light-cured resin composites from post-cure heating is attributed to free radicals created during initial photocuring, the number of which decreases following initial light-curing. Clinically, it is important to know when the number of remaining free radicals is too low to provide for additional conversion of monomer in post-cure-heated specimens. The hypothesis tested is that the potential for additional conversion in post-cure-heated resin composite restorations is dependent upon the time after initial light-curing at which the specimen is exposed to heat treatment. This research examined the effect of delay in post-cure heating after initial photo-activation on strength and monomer conversion of a commercial resin composite material. Discs (10 x 1 mm) of Herculite XRV (Kerr/Sybron, Orange, CA) were photocured at standardized conditions. One group was left unheated, and another was subjected to post-cure heating (Brilliant DI-500, Coltène AG, Altstätten, Switzerland) at the following times after being light-cured: 5 and 30 min, and 6, 24, 48, 72, 96, and 120 hrs. After the appropriate delay time, unheated and heated specimens (n = 10) were tested for biaxial flexural strength at a constant stressing rate. Recovered, fractured strength specimens (n = 10) were analyzed for cure by means of IR spectroscopy. Post-cure heating increased strength over that of the unheated specimens only for the shortest delay times: 5 or 30 min. Thereafter, strength values were statistically equivalent (p < 0.05). Delay in heating did not significantly enhance strength of post-cure-heated specimens, but delay in time did improve strength of the unheated groups. The greatest monomer conversion was obtained when post-cure heating was applied within 6 hrs following light-curing. The difference in cure between unheated and heated specimens remained significant up to 96 hrs of delay. Flexural strength of post-cure-heated specimens remained unchanged with time delay for heating specimens. Maximal monomer conversion of post-cured specimens is obtained only within 6 hrs of light-curing. The potential for additional conversion arising from post-cure heat treatment is dependent upon the time following initial curing at which heat is applied following initial light-curing. However, delay in heat application has no influence on flexural strength.

Analysis of Variance↗

PubMed1998

Assessing the effect of extraneous light on photoactivated resin composites.

The authors investigated the effect of an operatory light and ambient fluorescent illumination on the curve values of three photoactivated resin composite materials. Infrared spectroscopy was used to evaluate the specimens after they were exposed to an operatory light at a distance of 30 inches for two, five or 10 minutes as well as after a blue-blocker shield was placed between the light source and the composite. The authors also measured cure values after exposing some specimens to 10 minutes of ambient ceiling fluorescent light only. Maximal cure values were determined by conventionally photocuring specimens. After 10 minutes' exposure to the operatory light, specimens were cured at a level from 70 to 80 percent of the maximal cure resulting from conventional light curing. The blue-blocker shield reduced curing to a level equivalent to that of a 10-minute exposure to ambient fluorescent lighting, which was nearly 0 percent.

Analysis of Variance↗

PubMed1997

Effect of glutaraldehyde cold sterilants on light transmission of curing tips.

This research examined the effect of immersion in glutaraldehyde-based cold sterilizing solutions on the ability of light-curing tips to transmit a standardized light intensity. Five commercial cold sterilizing solutions were selected, based on their classification: neutral (Cetylcide-G, 3.2%), acidic (Banicide, 2.0%), or alkaline (Cidex Plus, 2.5%; Cidex 7, 3.4%; and Sporicidin, 0.5%). Distilled water was used as the control. The light intensity transmitted through 24, 8-mm-diameter curing tips of similar type was determined by applying a standardized intensity (500 m W/cm2). Three tips were placed into each type of solution. The percentage of preimmersion intensity was determined at periodic intervals until all tips had received a total of 1,000 hours of immersion. After 1,000 hours' immersion, light transmission decreased significantly more in tips subjected to Cidex 7 than in tips subjected to all other treatments, which were all equivalent to the water control (an average increase of 1.5% over preimmersion values). The decrease in intensity seen with Cidex 7 averaged 49% and could not be totally recovered after use of conventional tip-polishing methods. Reduction in light levels could not be correlated with the pH of the sterilizing solutions.

Cold Temperature↗

PubMed1996

The effect of autoclaving on energy transmission through light-curing tips.

The authors subjected three groups of curing lights to 25 sterilization cycles to test the effects of autoclaving on the curing tip's ability to transmit light. They also investigated whether polishing the tip at various intervals would reduce the effects of autoclaving on light transmission. They found that autoclaving does diminish the ability of the tips to transmit light, but that these effects can be minimized if the tip is polished at frequent intervals between autoclaving cycles.

Composite Resins↗

PubMed1995

Clinical guidelines for photocuring restorative resins.

Success in using light-cured resin composites relies heavily on proper curing time and intensity. Because these factors are so critical, the authors reviewed the literature to arrive at guidelines for optimal curing conditions. The guidelines emphasize maintenance of the curing lights, consideration of the type of restorative material used and duration of exposure.

Absorption↗

PubMed1994

Effect of restoration composition, shade, and thickness on the cure of a photoactivated resin cement.

PURPOSE: This study investigates the effect of selected properties of a restorative material (type, shade, and thickness) on the cure of a photoactivated resin cement. MATERIALS AND METHODS: Disks of ceramic and resin-based restorative materials of two extreme shades were made to provide thicknesses of 0.5 to 3.0 mm in 0.5-mm intervals. Light transmission was measured through various thicknesses and shades of each restorative material type. The effect of light transmission, as influenced by restorative material type, shade, and thickness on resin cement cure was also determined. RESULTS: Thickness and shade of restorative material had the greatest influence on light transmission. For simulated restoration thicknesses 1.5 mm and greater, Dicor (Dentsply International Inc, York, PA) had greater transmission of light than the other materials, regardless of shade. At equal restorative material thickness, light transmission was similar for identical shades of the other three materials. Restoration shade and thickness also had the greatest influence on resin cement cure. Material type, although significant, had only a minor influence. At thicknesses of 1 to 2 mm, Dicor consistently yielded greater resin cement cure values than any other material tested. CONCLUSIONS: When considering the ability of restorative materials to transmit light for curing of photo-activated resin cements, the thickness of the restoration and its shade are much more influential than the choice of restorative material. Dicor provides greater light transmission that results in the ability to photobond restorations of greater thicknesses than the other materials. For restorations greater than 1 mm in thickness, a dual cure or chemical cure resin cement should be used to provide maximal cement properties.

Analysis of Variance↗

PubMed1994

Provisional treatment for resin-bonded fixed partial dentures.

The resin-bonded fixed partial denture is a conservative option for the replacement of a missing tooth. It has a good prognosis and offers several advantages over a conventional fixed partial denture. However, it does not allow for placement of a provisional fixed partial denture. In some situations, it is important to provide some type of interim treatment. This can be accomplished by several techniques, that include placement of either a removable or bonded replacement tooth. The provisional treatment can provide an esthetic solution and maintain tooth position while the fixed partial denture is being made by the dental laboratory.

Denture Design↗

PubMed1993

Tensile fatigue of two composite cements bonding three base metal alloys to bovine enamel.

Tensile fatigue endurance limits were determined for three base metals (Ni-Cr, Ni-Cr-Be, and Co-Cr) bonded to bovine enamel using two composite cements: a Bis-GMA/phosphate ester composite cement which relies on a sand-blasted metal surface, and a Bis-GMA composite luting cement which relies on electrolytically etched metal surfaces. Samples were tested to failure or to 10(6) cycles at 5 hz in Ringer's solution at 37 degrees C, and endurance limits were determined using a two-point test strategy. SEM evaluation was performed on fractured samples to determine failure mode. Statistical analysis of the results showed no difference between cements when using Ni-Cr-Be; however when using Co-Cr, the Bis-GMA/phosphate ester cement produced greater values than the Bis-GMA cement that relied on electrolytical etching. The opposite result occurred when a Ni-Cr alloy was tested with both cements. Evaluation of the results for each cement with the three different alloys showed statistical significant differences. SEM fracture analysis revealed a mixed failure pattern with apparent adhesive fracture from both the composite-enamel and composite-metal interfaces and cohesive failure throughout the cement.

Animals↗

PubMed1993

Effect of powder/liquid ratio on physical and chemical properties of C&B Metabond.

The purpose of this study was to examine the effect of varying the powder/liquid ratio on the physical properties and the degree and rate of curing of C&B Metabond cement. The powder/liquid ratios evaluated had no effect on the tensile bond strength of Rexillium III to etched enamel or on the retention of cemented full cast crowns. The higher P/L ratio resulted in an increased vertical displacement of the cemented crowns. The rate of monomer conversion and the total conversion were not affected significantly by the different P/L ratios.

Analysis of Variance↗

PubMed1993

Factors affecting cure at depths within light-activated resin composites.

When confronted with all the variables that are influential in maximizing the cure in light-activated resin composites, a practitioner may require information that ranks the relative importance of these parameters, so that clinical time can be best utilized. The purpose of this study was to determine simultaneously the relative impact of filler type (hybrid or microfill), composite shade (universal or gray), exposure duration (20, 40, 60 and 80 seconds) and source intensity (800, 578, 400 and 233 mW/cm2) on the extent of cure in light-activated composite at selected depths (top surface, 1, 2, and 3 mm) of a simulated restoration. Thin wafers of composite (P-50 and Silux Plus) were made between a cured composite underlay and varying thicknesses of cured overlay to obtain a wafer that reproduced the curing environment within a cylinder of composite. The monomer conversion of each specimen was obtained by infrared spectroscopic techniques. Analysis of variance was used to determine the significance of factors contributing to the cure of composite at each thickness of overlay used. At the surface, filler type, exposure duration and resin shade predominated as the most influential factors respectively. At 1 mm depth, the order of influential factors were exposure duration, filler type and source intensity. At depths of 2 mm and more, the overwhelming influences on cure were related solely to source intensity and exposure duration. Resin shade and filler type exerted minimal influence at these depths.

Analysis of Variance↗

PubMed1992

Fatigue life of three core materials under simulated chewing conditions.

There has been an increase in the use of prefabricated post systems to restore endodontically treated teeth. Various restorative materials are being used as core buildups on these posts. The purpose of this study was to compare three core materials that are used with prefabricated stainless steel posts. Two types of prefabricated posts were placed in extracted teeth, followed by core buildups in amalgam, composite resin, or glass ionomer. The teeth were prepared for full cast crowns with the margins of the crown preparation extending 0.5 to 1.0 mm below the margins of the core buildup. Crowns were fabricated and cemented with zinc phosphate cement. A custom-designed chewing machine was used to cyclically load the teeth with vertical and horizontal forces for one million cycles or until failure occurred. Results indicated highly significant differences in the survival of the post-core-crown restorations depending on which core buildup material was used. Amalgam cores had the lowest failure rate, followed by composite resin cores. All teeth restored with crowns over glass-ionomer core buildup failed. The type of prefabricated post used had no effect on the survival of the post-core-crown restorations regardless of the core buildup used.

Bite Force↗

PubMed1992

Retention strengths of three cements using full crown preparations restored with amalgam.

The tensile bond strength of noble and non-noble castings luted with adhesive resin cements and zinc phosphate cement to prepared extracted teeth having received MOD amalgam restorations were compared. The crown preparations were standardized on the extracted teeth to produce axial wall length and taper consistent with that seen clinically. Results indicated the resin luting agents were significantly more retentive than the zinc phosphate cement and for each cement there was no difference in the casting alloy used.

Analysis of Variance↗