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Biomedical subjects

E S Duke

Publications and source records attributed to E S Duke.

At least 37 records · Page 2Linked to original sources
PubMed1996

Correlative transmission electron microscopy examination of nondemineralized and demineralized resin-dentin interfaces formed by two dentin adhesive systems.

The resin-dentin interface formed by two dentin adhesives, Optibond (OPTI, Kerr) and Scotchbond Multi-Purpose (SBMP, 3M), was ultramorphologically examined by transmission electron microscopy (TEM). Ultrastructural information from nondemineralized and demineralized sections was correlated. It was hypothesized that the different chemical formulations of the two adhesives would result in a different morphological appearance of the hybrid layer. Ultrastructural TEM examination proved that each of the two dentin adhesive systems was able to establish a micromechanical bond between dentin and resin with the formation of a hybrid layer. However, the interfacial hybridization process that took place to produce this resin-dentin bond appeared to be specifically related to the chemical composition and application modes of both systems. OPTI consistently presented with a hybrid layer with a relatively uniform ultrastructure, electron density, and acid resistance. These three parameters were found to be more variable for the hybrid layer formed by SBMP. Characteristic of SBMP was the identification of an amorphous phase deposited at the outer surface of the hybrid layer. Although both adhesive systems investigated follow a total-etch concept, their specific chemical formulations result in different interfacial ultrastructures that are probably related to different underlying bonding mechanisms. The clinical significance of these morphological findings, however, is still unknown.

Acid Etching, Dental↗
PubMed1995

Demonstration of a focused ion-beam cross-sectioning technique for ultrastructural examination of resin-dentin interfaces.

OBJECTIVES: focused ion-beam (FIB) etching, commonly used as a cross-sectioning technique for failure analysis of semiconductor devices, has recently been applied to biological tissues to expose their ultrastructure for examination. It was the aim of this investigation to determine the practical utility of FIB to cross-section resin-dentin interfaces in order to morphologically evaluate the completeness of resin penetration into the exposed collagen scaffold at the resin-dentin bond interface. METHODS: Two representative commercially available dentin adhesive systems were bonded to mid-coronal dentin. After appropriate fixation and dehydration of the resin-bonded dentin samples, a scanned focused ion-beam of a few tens of nano-meters in diameter was used to cross=section the resin-dentin interface. Examination of the interfacial ultrastructure was accomplished using a field-emission SEM. RESULTS: Results indicate possible artifact production at the cross-sectioned interface, hiding its actual ultrastructure, probably due to a heat-effect with possible recrystallization. Further studies of FIB are needed to optimize its usefulness for resin-dentin interface examinations and other biological tissue applications. SIGNIFICANCE: Complete resin saturation of the demineralized dentin surface-layer has been claimed to be the key factor for a long-lasting resin-dentin bond. A "clean" artifact-free micro-cross-sectioning technique may provide indisputable ultra-structural information about the depth of resin penetration into the demineralized zone. Such a test would be useful in the development of dentin adhesive systems.

Bisphenol A-Glycidyl Methacrylate↗
PubMed1995

Examination of a resin-modified glass-ionomer material as a pit and fissure sealant.

The purpose of this in vitro study was to examine the effect of various powder-liquid ratios of an experimental resin-modified glass-ionomer polymer cement on dye penetration when the cement was used as a pit and fissure sealant. Eighty extracted human third molars were randomly assigned to one of four pit and fissure sealant conditions: a resin-based sealant or one of three variations in powder-liquid ratios (1.4:1.0, 1.8:1.0, and 2.0:1.0) of an experimental, light-activated, resin-modified glass-ionomer cement. After sealant placement, the teeth were thermocycled and immersed in methylene blue dye. The teeth were sectioned, and the extent of dye penetration along the sealant-enamel interface was measured linearly. The resin-sealed occlusal fissures showed statistically significantly less dye penetration than did the three powder-liquid ratios of the experimental resin-modified glass-ionomer-cement sealant.

Analysis of Variance↗
PubMed1994

The clinical performance of a new adhesive resin system in class V and IV restorations.

A clinical trial was initiated to examine a new adhesive system introduced for dentin and enamel bonding of composite resins. Restorations were placed in patients in need of Class V and Class IV restorations. The clinical study was designed to examine the adhesive system in restorations involving mostly dentin surfaces (Class V) and in a population of restorations mostly involving enamel surfaces (Class IV). At the 1-year recall period, the adhesive system had demonstrated excellent adhesive qualities in both types of cavities. Initial results also showed improvement over previous adhesive systems with regard to moisture sensitivity and variation in dentin composition.

Acid Etching, Dental↗
PubMed1993

Adhesion and its application with restorative materials.

Significant progress has been made in the area of adhesion and esthetic restorative materials. Each generation of product development aims to address many of the previous inadequacies. Current resin-based dentin bonding agents are miles ahead of agents introduced only 10 years ago. The glass ionomer cement has undergone considerable evolution and barely resembles the original formulation. Whether these modified cement-resins will become established in the restorative practice remains to be seen. Or possibly, the glass ionomer cement will evolve itself out of existence into a new "class" of restorative. Numerous questions still remain unanswered in the area of adhesive materials. In particular, the confirmation of preliminary laboratory results with controlled clinical research often never surfaces, or is delayed beyond the commercial life of proprietary adhesive systems. Without such data, little confidence in adhesive behavior can be gained. More importantly, without a thorough understanding of the performance of adhesives in vivo, knowledge will never be gained relative to adhesive mechanisms that are necessary to further technology in this area.

Composite Resins↗
PubMed1992

Anatomy of a defective barrier: sequential glove leak detection in a surgical and dental environment.

OBJECTIVES: a) To determine the frequency of perforations in latex surgical gloves before, during, and after surgical and dental procedures; b) to evaluate the topographical distribution of perforations in latex surgical gloves after surgical and dental procedures; and c) to validate methods of testing for latex surgical glove patency. DESIGN: Multitrial tests under in vitro conditions and a prospective sequential patient study using consecutive testing. SETTING: An outpatient dental clinic at a university dental school, the operating suite in a medical school affiliated with the Veteran's Hospital, and a biomechanics laboratory. PERSONNEL: Surgeons, scrub nurses, and dental technicians participating in 50 surgical and 50 dental procedures. METHODS: We collected 679 latex surgical gloves after surgical procedures and tested them for patency by using a water pressure test. We also employed an electronic glove leak detector before donning, after sequential time intervals, and upon termination of 47 surgical (sequential surgical), 50 dental (sequential dental), and in three orthopedic cases where double gloving was used. The electronic glove leak detector was validated by using electronic point-by-point surface probing, fluorescein dye diffusion, as well as detecting glove punctures made with a 27-gauge needle. RESULTS: The random study indicated a leak rate of 33.0% (224 out of 679) in latex surgical gloves; the sequential surgical study demonstrated patency in 203 out of 347 gloves (58.5%); the sequential dental study showed 34 leaks in the 106 gloves used (32.1%); and with double gloving, the leak rate decreased to 25.0% (13 of 52 gloves tested). While the allowable FDA defect rate for unused latex surgical gloves is 1.5%, we noted defect rates in unused gloves of 5.5% in the sequential surgical, 1.9% in the sequential dental, and 4.0% in our electronic glove leak detector validating study. In the sequential surgical study, 52% of the leaks had occurred by 75 mins, and in the sequential dental study, 75% of the leaks developed by 30 mins. In terms of the anatomical localization, the thumb and forefinger accounted for more than 60% of the defects. There were no differences in the frequency of glove leaks between the left and right hand. Leak rates were highest for the surgeon (52%), followed by the first assistant (29%) and the scrub nurse (25%). No false negatives were noted using the electronic glove leak detector; one false positive was seen out of 225 gloves tested (0.44%), as noted in our validation studies. CONCLUSIONS: Significantly high glove leak rates were noted after surgical and dental procedures, indicating that the present day latex surgical gloves can become an incompetent barrier once they are used. Unused latex surgical gloves demonstrated a higher rate of defects than allowed by the Food and Drug Administration standards, indicating substantial noncompliance of quality control standards by manufacturers as well as inadequate governmental oversight. Double gloving, or the use of thicker latex surgical gloves, would probably reduce the frequency of glove leaks. Latex surgical gloves should be tested for patency before use and during surgical and dental procedures.

Dentistry↗
PubMed1991

Effect of metal design and technique on the marginal characteristics of the collarless metal ceramic restoration.

This investigation examined the marginal characteristics of the collarless metal ceramic restoration made with two commonly used direct-lift techniques: (1) a porcelain/wax paste and (2) a porcelain/liquid slurry. The metal copings touched the shoulder in half of the groups and were left 0.5 mm short in the other half to comprise the four experimental groups. Marginal seal was evaluated at facial and lingual surfaces on embedded and sectioned specimens for each group. Photo negatives were made of each specimen and projected at a constant magnification so that tracings could be made of the space between the die shoulder and corresponding porcelain. Composite surface measurements were made for each sample with a Zeiss Interactive Digital Analysis System instrument to evaluate porcelain adaptation to the shoulder. The porcelain/liquid groups demonstrated significantly smaller (p less than or equal to 0.05) facial marginal openings than the porcelain/wax groups. The group made with the porcelain/liquid technique with the metal on the die shoulder produced the most consistent overall results. The porcelain/liquid group with the metal off the shoulder had a statistically larger (p less than or equal to 0.05) mean marginal opening from the external margin to a point 0.75 mm to the interior than both techniques with the metal on the shoulder. Lingual marginal adaptation did not vary with each of the four experimental groups.

Crowns↗
PubMed1991

Comparison of wet and dry finishing of resin composites with aluminum oxide discs.

Samples of four composites (Herculite, Visio-Dispers, Silux, and Prisma-Fil) were finished with aluminum-oxide discs either wet or dry so that the effects of these two finishing procedures could be compared. The samples were evaluated for surface smoothness, color stability, and surface hardness. Surface smoothness was determined immediately after a sample was finished with a profilometer. Knoop hardness values were determined for each sample immediately after being finished and once a week for five weeks. Color stability was evaluated with a tristimulus colorimeter by the color of each sample being finished and once a week for five weeks. When surface smoothness was compared between the wet- and dry-finished samples, there was no significant difference between Prisma-Fil, Silux, or Herculite; however, the wet-finished Visio-Dispers was significantly rougher than the dry-finished. When surface hardness was compared, there was no significant difference in hardness values between the wet and dry samples when compared over time. When changes in color were evaluated, only Visio-Dispers had no significant change in color for both the wet- and dry-finished samples over the five-week evaluation period. Dry finishing of only one composite (Silux) produced a significant change in color. Dry finishing of composites was superior or equal to wet finishing in all tests except for the color change in Silux.

Aluminum Oxide↗
PubMed1991

Adhesion and tooth-colored restoratives.

Research aimed at developing durable adhesion between esthetic restorative materials and tooth surfaces has been progressing for over 35 years. Inherent deficiencies in many esthetic materials have directed research toward new adhesive agents and modifications in application techniques. Overcoming these deficiencies has been difficult and many questions remain despite encouraging developments. A new generation of resin dentin-bonding agents has surfaced and may further adhesive efforts with modern composite resins. The glass-ionomer cement continues to establish itself as a valuable adhesive direct restorative material. Recent advances in glass-ionomer technology have given rise to new lining materials that may also complement composite resin behavior. The use of dentin conditioners or pretreatments has been explored and may enhance the adhesion of esthetic restoratives as well. Finally, a better understanding of application techniques and of the tooth surface itself may offer new insights into developing more stable adhesion with esthetic restorative materials.

Composite Resins↗
PubMed1991

Variability of clinical dentin substrates.

Clinical trials remain the only conclusive research of dentin adhesive performance, but variables unique to the oral environment may influence the results. Dentin variability is one factor that may account for extreme variations in clinical evaluations. Despite the encouraging results of laboratory studies, clinical trials with adhesive systems have been disappointing. Current adhesives are reported to react with dentin surfaces by chemical and/or micro-mechanical mechanisms. Dentin surfaces, such as cervical abrasions, are subject to intraoral changes and dentin tubules commonly become obturated by the growth of peritubular dentin or by the precipitation of calcific deposits within the tubules. The resulting sclerotic dentin may be less receptive to current dentin adhesives. An examination of clinically aged dentin surfaces has revealed an inordinate variability in tubular morphology. The more sclerotic dentin present, the less effective was dentin conditioning and resin composite adaptation. Early correlations with current clinical trials appear to substantiate that the greatest failure of restorations occurred in sclerotic lesions.

Aging↗
PubMed1991

Clinical evaluation of a dentinal adhesive system: three-year results.

The dentinal adhesive Scotchbond 2 was evaluated with the microfilled composite resin Silux in cervical and root caries lesions for up to 3 years. Clinical criteria evaluated included retention, marginal integrity, marginal discoloration, color match, anatomic form, recurrent caries, gingival response, and postoperative sensitivity. Overall, the adhesive demonstrated improved performance over earlier dentinal adhesive systems. Retention was greatest at 3 years when available enamel margins had been etched (93%) and when root caries lesions (97%) had been restored. Other criteria were reported as generally favorable. Early findings suggest that the level of development of sclerotic dentin may influence behavior of the adhesive. The greatest difficulty was noted in lesions presenting with heavy sclerotic dentin.

Acid Etching, Dental↗
PubMed1990

Polymeric adhesion to dentin: contrasting substrates.

Clinical research has shown that resin dentin adhesive materials often fail prematurely despite encouraging laboratory-derived data. Current adhesives are reported to react with dentin surfaces by chemical and/or micro-mechanical mechanisms. The ionic bonding to calcium and the covalent coupling to collagen are representative chemical strategies employed today. Recent findings suggest that the mechanical interlocking of resins into open dentinal tubules may play an even more important role with present adhesive systems. Dentin surfaces, such as cervical abrasions, undergo changes in the oral cavity and dentinal tubules may become partially or completely obturated by the growth of peritubular dentin or by the precipitation of mineral salts within the tubules. The resulting sclerotic dentin may be less receptive to current dentin adhesives. An examination of clinically aged dentin surface types revealed extreme variability in tubular morphology. The more sclerotic dentin presented, the less effective was dentin conditioning and resin adaptation. Early correlations with ongoing clinical trials appear to substantiate this finding with the greatest failure of restorations occurring in more sclerotic lesions.

Adhesives↗
PubMed1989

The effect of sprue attachment design on castability and porosity.

Sprue attachment design is an important and controversial variable that can affect casting characteristics of castability and porosity. Four sprue attachment designs--straight, flared, abrupt constriction, and gradual constriction--were investigated. Standardized wax copings simulating complete veneer metal ceramic crowns with knife-edge margins were sculpted on refractory investment dies, sprued, invested, and cast with Olympia alloy. The specimens were embedded, sectioned, and polished. Castability was analyzed by measuring the width of the cast meniscus of the margins. The margin widths of the flared and the straight sprue attachment groups were significantly less than the abrupt or gradual constriction attachment group (p less than 0.05). Photomicrographs revealed discernible differences in the relative quantity and location of porosity in the sprue-coping junctions. The straight and flared sprue attachment groups were less porous than the abrupt or gradual constriction groups (p less than 0.01). Flared and straight sprue attachments optimized castability and minimized porosity.

Chemical Phenomena↗
PubMed1989

Glass-ionomer cement film thickness and working time.

Reports on film thickness for adhesive glass-ionomer cements have not been consistent, and confusion exists relative to proper working times. In this investigation, film thickness was measured over a range of times for three glass-ionomer cements by using a traditional ADA glass plate technique and a simulated clinical cementation technique with castings and dies. The cements were examined from 60 seconds to 255 seconds from the start of mix. Results indicated that the simulated clinical technique generally provided less film thickness. No significant differences in film thickness were found between the brands of cement through 240 seconds with film thickness ranging from 7.24 to 20.5 microns. Greater differences between the cements were observed with the ADA technique beyond 135 seconds from the time of mix. Relative to film thickness, working times would appear to be greater than previously reported for glass-ionomer cements.

Chemical Phenomena↗
PubMed1989

Effect of glass-ionomer base on composite resin hardness.

The effect of the glass-mm, and 3 mm thicknesses were placed over glass-ionomer bases, and the microhardness of the external surface was compared with that of controls without a base. A significant reduction in surface hardness (p less than 0.05) was determined only for the 1-mm test specimens.

Composite Resins↗
PubMed1989

The effect of trituration time on the mechanical properties of four high-copper amalgam alloys.

Several manipulative variables have been shown to influence the physical properties of dental amalgam. Variation in trituration time has been reported to affect creep, compressive strength, and diametral tensile strength in various amalgams. Recent classification of amalgam alloys by particle microstructure reveals four categories: single-composition lathe-cut; single-composition spherical; lathe-cut and eutectic admixture; and lathe-cut and single-composition spherical admixture. The effect of variation of trituration times has not been studied for these newer high-copper alloys. A representative from each classification was selected and physical properties tested, with varied times for trituration utilized. Results showed little compromise in laboratory values for the properties tested. Additional laboratory and clinical trials are warranted, but this study supports the premise that clinicians may vary trituration time to improve handling characteristics without significantly affecting mechanical properties.

Copper↗