Biomedical subjects

D G Charlton

Publications and source records attributed to D G Charlton.

At least 19 recordsLinked to original sources

PubMed1999

Performance of high-speed dental handpieces subjected to simulated clinical use and sterilization.

BACKGROUND: The authors investigated the performance of nine commercially available high-speed air-turbine dental handpieces subjected to 1,000 simulated clinical uses and sterilizations. METHODS: Six new handpieces from each of nine different models were subjected to simulated clinical use with a custom-made handpiece wear tester and then autoclaved. Ten parameters related to clinical performance (longevity, power, turbine speed, fiberoptic transmission, eccentricity, noise, chuck performance, visibility angle, interocclusal clearance and water coolant spray pattern) were measured at baseline and after 250, 500, 750 and 1,000 use/sterilization cycles. RESULTS: Power, turbine speed, eccentricity and noise performance were statistically analyzed using one-way analysis of variance and Turkey post hoc pairwise comparison tests at the .05 significance level. At baseline, significant differences were found between models for all of these parameters. In general, from baseline to 1,000 cycles, the handpieces exhibited greater eccentricity and reduced fiberoptic performance. Longevity data analyzed by using Gehan's generalized Wilcoxon test for comparison of survival distributions (alpha = .05) revealed significant differences between the handpiece models. CONCLUSIONS: The results of this study indicate that no handpiece model is superior to the others in all parameters evaluated. All models evaluated can be expected to perform for at least 500 clinical use/sterilizations, or approximately one year, if properly maintained. CLINICAL IMPLICATIONS: Clinicians need to be able to identify handpieces that can withstand repeated heat sterilization without loss of performance or longevity. The results of this study will aid clinicians in selecting handpiece models that meet their needs.

Analysis of Variance↗

PubMed1999

Comparative radiopacity of flowable resin composites.

OBJECTIVE: This in vitro investigation aimed to determine the radiopacity of eight recently introduced "flowable" restorative resin composites and to compare their radiodensities to those of enamel, dentin, and a widely used composite marketed for universal application in anterior and posterior teeth. METHOD AND MATERIALS: A total of 45 composite specimens were fabricated in cylindrical molds and exposed to a curing light for 120 seconds. Two methods were used to determine radiopacity: a transmission densitometer and a computer-assisted densitometric image analysis station. RESULTS: Of the eight flowable resin composites tested, only three exhibited a radiopacity equal to or greater than that of enamel, a widely followed guideline for clinicians' diagnostic ability. The radiopacity of the remaining five materials was not statistically significantly greater than that of dentin. CONCLUSION: The level of radiopacity of the tested flowable composites was variable; those with low radiodensity should be avoided in Class II restorations, where a clear determination of recurrent caries by the examining clinician could be compromised.

Absorptiometry, Photon↗

PubMed1995

Effect of dentin moisture and storage time on resin bonding.

PURPOSE: To evaluate the effects of dentin moisture and two different storage times on the shear bond strength of resin composite bonded to dentin with Scotchbond Multi-Purpose Adhesive. MATERIALS AND METHODS: The occlusal surfaces of 60 extracted human molars were reduced to provide flat dentin surfaces. After being hand-finished using wet 400- and 600-grit SiC papers, the teeth were randomly divided into four groups of 15 specimens each. The teeth were etched, rinsed, and then either blotted with gauze which left a visibly moist surface or dried with compressed air. The primer and adhesive were applied according to the manufacturer's instructions and resin composite cylinders were bonded to the teeth. Two of the groups (one moist, one dry) were stored for 24 hours in 37 degrees C distilled water while the other two groups were stored for 90 days in 37 degrees C distilled water. At the end of their storage times, the specimens were loaded to failure in shear at 0.5 mm/minute. RESULTS: Mean bond strength values and standard deviations in MPa were: Dry dentin at 24 hrs, 13.30 +/- 5.1; Dry dentin at 90 days, 13.07 +/- 3.8; Moist dentin at 24 hours, 13.64 +/- 4.9; Moist dentin at 90 days, 15.58 +/- 5.3. No statistically significant differences were found for bond strengths to dry and to moist dentin for either storage time. Time had no significant effect for either the dry dentin group or the moist dentin group.

Absorption↗

PubMed1994

Dentin treatment with an oxalate solution and glass ionomer bond strength.

PURPOSE: To evaluate the effect of dentin surface treatment on shear bond strengths of two visible light-cured glass ionomer restorative materials to dentin. MATERIALS AND METHODS: Cylinders of Fuji II LC and VariGlass VLC were bonded to dentin surfaces that were (1) treated as directed by the manufacturer, (2) treated with a monohydrogen-monopotassium oxalate solution (Protect Dentin Desensitizer), or (3) treated with the monohydrogen-monopotassium oxalate solution followed by treatment per the manufacturer. Specimens were thermocycled and tested in shear at 7 days. Data for each restorative material were subjected to a one-way ANOVA and the Scheffé F-test (P < 0.05). After shear bond testing the specimens were examined using a stereomicroscope at x8 to determine the mode of failure (adhesive, cohesive or mixed). Dentin specimens were also surface treated as described above, sputter-coated, and examined using a scanning electron microscope. RESULTS: In every instance, the oxalate solution significantly reduced the shear bond strength of both materials.

Acid Etching, Dental↗

PubMed1994

Dentin surface treatment and bond strength of glass ionomers.

This study evaluated the effect of dentin surface treatment on shear bond strengths of two light- cured glass ionomer restorative materials to dentin. Cylinders of Fuji II LC and VariGlass VLC were bonded to dentin surfaces that were untreated, treated with a 10% polyacrylic acid (GC Conditioner), or treated with a dentin bonding agent primer (Prisma Universal Bond 3 Primer). Specimens were thermocycled and tested in shear at 7 days. Data for each restorative material were subjected to one way ANOVA and Tukey's procedure at the 0.05 probability level. For Fuji II LC, mean bond strength to conditioner-treated dentin was significantly higher than mean bond strength to primer-treated dentin and to untreated dentin. For VariGlass VLC, mean bond strength to primer-treated dentin was significantly higher than mean bond strength to untreated dentin. Bond strengths to primer-treated dentin and conditioner-treated dentin were not significantly different.

Acrylic Resins↗

PubMed1992

In vitro evaluation of two microleakage detection tests.

Two microleakage detection tests were evaluated to compare their capabilities for revealing the extent of leakage at the interface between amalgam restorations and tooth structure. Class V cavities were prepared in the buccal surfaces of extracted human canine and premolar teeth and were treated in one of the following ways: no liner or varnish, a copal varnish, or an adhesive resin liner. The cavities were restored with a high-copper single composition spherical amalgam alloy and the specimens thermally cycled. Following storage for 6 months, the teeth were exposed to separate solutions of 45Ca and an ultraviolet fluorescing dye. The teeth were hemisected longitudinally and leakage was evaluated by determining the degree of penetration of the two tracers at the occlusal and gingival margins. Statistical analysis revealed a significant difference between the two leakage techniques (P less than 0.05). The radioisotope test generally indicated a greater degree of leakage than did the ultraviolet dye test.

Acid Etching, Dental↗

PubMed1992

Amalgam in the restoration of posterior teeth.

The use of aesthetic restorative materials such as cast ceramic, porcelain, and composite resin for the restoration of posterior teeth has increased in recent years, but amalgam remains the most frequently used material. Although stories in the media recently renewed the debate over amalgam safety, amalgam has remained in the armamentarium of the average clinician in large part because of its long positive clinical history, beneficial physical properties, and forgiving handling characteristics.

Bicuspid↗

PubMed1991

Repairability of type II glass polyalkenoate (ionomer) cements.

Two Type II glass polyalkenoate (ionomer) cements were evaluated for their repairability by measuring tensile bond strength of new material added to previously placed cement. Variables included time of repair (20 min vs. 24 h) and surface condition prior to repair (smooth and unetched, smooth and etched, rough and unetched, rough and etched). Failures were evaluated using light microscopy and categorized as cohesive, adhesive, or mixed. Scanning electron microscopy was employed to view the cement surfaces following each of the four pretreatments. Surface pretreatment was found to significantly affect both materials when repaired at 20 min (P less than 0.05). The highest bond strength was achieved when bonding to the smooth, unetched surface. Surface pretreatment did not significantly affect bond strength when the cements were repaired at 24 h (P greater than 0.05). Tensile bond strengths were greater for repairs made at 20 min than for those made at 24 h, but the differences were not always statistically significant.

Acid Etching, Dental↗

PubMed1991

Incorporation of adhesive liners in amalgam: effect on compressive strength and creep.

This study evaluated the effects of two adhesive resin liners (Panavia EX and Amalgambond) on the compressive strength and creep rate of a single composition high-copper amalgam alloy (Tytin). Cylindrical specimens were prepared by dead-loading or hand-condensing amalgam in a Teflon mold which was unlined, lined with Panavia EX, or lined with Amalgambond. Compressive strength specimens were tested at 1 hour, 24 hours, and 7 days after preparation. Creep specimens were tested at 7 days. The adhesive resin liners did not significantly affect the strength of the Tytin specimens prepared by dead-loading (P greater than 0.05). The Panavia EX significantly reduced the strength of the Tytin specimens prepared by hand-condensing (P less than 0.05). The creep rate was not significantly affected by either resin liner.

Analysis of Variance↗

PubMedDate not supplied

Effect of curing-tip diameter on the accuracy of dental radiometers.

The purpose of this study was to determine the accuracy of four commercially available radiometers when curing tips of different diameters were used. A visible-light curing unit (Optilux 500) with a new 80-watt quartz-halogen bulb (OptiBulb) was used as the light source for all measurements. The unit's irradiance value was measured using three hand-held radiometers (Demetron model #100, Cure-Rite model #644726, and Coltolux Light Meter) and a built-in visible-light curing unit radiometer (Optilux 500). Measurements were made with four curing tips of diameters 4 mm, 7.5 mm, 10.5 mm, and 12 mm. For each tip, trials were made with five radiometers of each model. Student's t-tests at the 0.05 level of significance were used to compare the mean irradiance measured by each model of radiometer, to the irradiance value measured by a laboratory-grade power meter. A one-way analysis of variance at the 0.05 level of significance was used to compare the irradiance values among the five samples of each commercially available radiometer model. Except for the Optilux 500 built-in radiometer with the 10.5-mm tip, all the commercially available radiometers exhibited irradiance values significantly different from those of the laboratory-grade power meter. There were no statistically significant differences among the five samples of each commercially available radiometer model.

Analysis of Variance↗

PubMedDate not supplied

The use of resin composite pins to improve retention of Class IV resin composite restorations.

This study evaluated the effect of an intracoronal resin composite pin on Class IV resin composite restorations. A control group of 16 bovine teeth was prepared with standardized conventional Class IV preparations. For an experimental group, 16 similar Class IV preparations were made, with the addition of an intracoronal pin channel prepared with a #330 bur into the dentin. All specimens were restored with Herculite XRV and OptiBond according to the manufacturer's recommendations. After one week, specimens were placed in an Instron Universal Testing Machine and loaded at 90 degrees to the long axis until the restorations failed. Results indicated that the mean fracture load of the Class IV restoration group, with the resin composite pin, was 36% higher than the conventional Class IV group (p = 0.02). An intracoronal resin composite pin may aid the retention and resistance form of complex resin composite restorations.

Animals↗

PubMedDate not supplied

Repair of non-carious amalgam margin defects.

This study investigated the microleakage associated with the repair of non-carious amalgam defects using flowable resin composite. Occlusal amalgam preparations were accomplished on 36 non-carious mandibular molars. A standardized 40-micron marginal defect was made by condensing amalgam against a mylar matrix strip. Specimens then underwent a corrosion protocol designed to simulate intraoral corrosion seen with amalgam restorations. The resultant specimens were divided into three treatment groups: 1) No treatment (control); 2) Air abrasion of the amalgam defect surface, acid etching of both amalgam and enamel surfaces, then placement of a flowable composite and 3) Air abrasion of the amalgam defect, application of a fifth-generation dentin bonding agent and placement of the flowable composite. Specimens were thermocycled, sealed with glass ionomer and fingernail polish to within 1 mm of repaired margins, then immersed in basic fuchsin for 24 hours. Specimens were sectioned and microleakage assessed. Results indicated that a flowable resin composite significantly reduced marginal microleakage compared to the control (p < 0.05). There was no difference in microleakage between flowable resin composite repairs done with or without the use of a dentin-bonding agent.

Acid Etching, Dental↗

PubMedDate not supplied

Stylohyoid syndrome: a case report.

Elongation of the styloid process and/or ossification of the stylohyoid ligament can be associated with cervical pharyngeal pain, which may be detected both clinically and radiographically. Eagle's syndrome, stylohyoid syndrome, and pseudostylohyoid syndrome should be considered in the differential diagnosis.

Adult↗

PubMedDate not supplied

Carbamide peroxide bleaching: effects on enamel surface hardness and bonding.

Three 10% carbamide peroxide home bleaching agents were evaluated to determine their effects on tensile bond strength of resin to enamel and enamel surface hardness. Eighty extracted bicuspid crowns were divided into four groups (three bleaching agents and control), and treated with the bleaching agents for five consecutive days. A bonding site on the buccal surface of each crown was etched with phosphoric acid and an orthodontic bracket bonded in place. The specimens were thermocycled and loaded to failure in an Instron Universal Testing Machine. Five hardness specimens per group were measured prebleaching and after five days' exposure. Analysis by one-way ANOVA indicated no significant differences in bond strength between the four groups (P > 0.05). There were also no differences in pre- or postbleaching Knoop hardness values for the four groups (P > 0.05). This study indicated that in short-term regimens 10% carbamide peroxide does not significantly affect enamel surface hardness or bonding ability.

Analysis of Variance↗

PubMedDate not supplied

In vitro evaluation of the use of resin liners to reduce microleakage and improve retention of amalgam restorations.

This in vitro study evaluated the ability of three commercially available adhesive resins to reduce microleakage and provide retention between amalgam restorations and tooth structure. Results indicated that Amalgambond reduced leakage significantly more than Panavia EX, Prisma Universal Bond 2, and Copalite. In addition Amalgambond and Panavia EX exhibited the ability to bond amalgam to tooth structure. These results suggest that Amalgambond has the potential for serving successfully as a cavity liner with amalgam.

Analysis of Variance↗

PubMedDate not supplied

Effect of age of sample on the shear bond strength of dentin bonding agents to dentin.

The effect of sample age on the shear bond strengths of two dentin bonding agents to human dentin was evaluated by bonding composite resins to human dentin treated with either Imperva-Bond or Prisma Universal Bond 3. One-half of the specimens were tested at 5 minutes, while the remainder were thermocycled and tested at 2 weeks. Results were analyzed using two sample t tests at the 0.05 probability levels. Failures were evaluated using light microscopy and categorized as adhesive, cohesive within resin, cohesive within tooth, or mixed. The bond strengths were significantly higher for Imperva-Bond than for Prisma Universal Bond 3 at both time periods. For both bonding agents, the 2 week bond strengths were significantly higher than the 5 minute bond strengths. The 2 week bond strength of Imperva-Bond approaches that of unfilled resin to etched enamel.

Adhesives↗

PubMedDate not supplied

Direct surface pH determinations of setting cements.

Surface pH measurements were made over a 24-hour period for several luting cements and glass-ionomer lining and restorative materials. Of the luting cements, the water-mixed glass-ionomer cement, Ketac-Cem, had the lowest initial pH and the polycarboxylate, Durelon, had the highest. Three glass-ionomer lining materials showed differences in pH that increased over the entire test period. Two of the three visible-light-cured glass-ionomer liners evaluated showed similar pH values, while the third exhibited a considerably lower pH. The lower pH values found with the water-mixed glass-ionomer luting agent suggest that acidity may contribute to the posttreatment sensitivity associated with this material.

Dental Bonding↗

PubMedDate not supplied

Immersion disinfection of irreversible hydrocolloid impressions with sodium hypochlorite. Part II: Effect on gypsum.

This study investigated the effects of various immersion times and concentrations of sodium hypochlorite on irreversible hydrocolloid impressions and resultant gypsum casts. Irreversible hydrocolloid impressions of a test die were immersed for 1, 5, or 10 minutes in water (control), 5.25%, 0.525%, and 0.0525% sodium hypochlorite and then cast in a Type III stone and a Type V stone. Each stone specimen was evaluated for detail reproduction, dimensional change, surface roughness, and surface hardness. The results indicated that impressions may be immersed in sodium hypochlorite for any of the experimental times and concentrations without negative effects on Type V stone casts. However, immersion of impressions in 5.25% sodium hypochlorite causes some surface deterioration on Type III stone casts.

Alginates↗