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Biomedical subjects

E L Davis

Publications and source records attributed to E L Davis.

At least 19 recordsLinked to original sources

Secretory granule proteins from the subventral esophageal glands of the potato cyst nematode identified by monoclonal antibodies to a protein fraction from second-stage juveniles.

Sodium dodecyl sulfate-extracted proteins from second-stage juveniles (J2) of the potato cyst nematode Globodera rostochiensis were fractionated by preparative continuous flow electrophoresis, and monoclonal antibodies (MAbs) were raised against the 38- to 40.5-kDa protein fraction. Screening of the hybridoma culture fluids by immunofluorescence microscopy of J2 resulted in the identification of 12 MAbs that bound specifically to the subventral esophageal glands. On Western blots of J2 these MAbs identified four protein bands with apparent molecular masses of 30, 31, 39, and 49 kDa. Immunoelectron microscopy with one of these MAbs showed an intense labeling of the electron dense core of the secretory granules in the subventral gland cells of J2. It is concluded that one or more of these proteins are localized within these secretory granules. Immunofluorescence microscopy of J2 from other plant parasitic nematode species showed that most of these MAbs also bind to the subventral glands of G. pallida and G. tabacum but not of Heterodera schachtii, H. glycines, Meloidogyne incognita, or M. hapla.

Animals

Twelve-month results of a clinical wear study of three artificial tooth materials.

This study compared in vivo wear of a new artificial tooth material with that of existing artificial tooth materials. Artificial tooth wear was determined by measuring height changes of selected points on contacting tooth surfaces in patients with complete dentures during a 12-month period. These results are part of an ongoing 3-year clinical study. A total of 67 patients were randomized to one of three treatment groups in this double-blind study. Group 1 received dentures with existing artificial tooth materials. Group 2 received dentures that contained teeth with the new experimental material. Group 3 received dentures with Bioform IPN resin teeth (Dentsply International Inc., York, Pa). A computerized coordinate measuring machine and computer-controlled X-Y positioning stages were used for this study. Tooth wear was determined by measuring vertical heights of contacting points from baseline points at each of two time intervals. The calculation of wear was made by comparing the differences in height at the beginning of the experiment with those measured at each time interval. A repeated measures analysis of variance (ANOVA) was used to test the difference in mean wear among the three groups from baseline to 6 months and from 6 to 12 months. Group differences in total wear at 12 months were also tested. The ANOVA results revealed no statistically significant differences in the wear among the three types of denture teeth at the 6- or 12-month time intervals or at 12 months (p > 0.05). The average total wear value at 12 months was 90 microns. Group 1 averaged 102 microns of wear, group 2 averaged 88 microns of wear, and group 3 averaged 76 microns of wear.

Acrylic Resins

Effect of restorative materials on cuspal flexure.

The purposes of this study were (1) to establish a methodology for determining surface strains in two locations of the same tooth under intact, prepared, and restored conditions and (2) to compare the effects on stiffness of different restorative materials in a tooth subjected to cuspal loading. Two linear strain gauges were mounted on each of 30 extracted maxillary premolar teeth. Teeth were mounted in poly(methyl methacrylate) resin and randomly assigned to one of three study groups according to the restorative material and application technique to be used. Statistical analysis indicated a statistically significant interaction between restorative material and tooth condition at both proximal and buccal sites and a statistically significant difference in stiffness between teeth restored with Tenure/Marathon V and those restored with either amalgam or Scotchbond 2/P-50 at the proximal site. Results suggest that the methods employed provide a useful, nondestructive means of testing the same tooth under various conditions.

Analysis of Variance

Adhesion to dentin.

Significant advances have been made in the development of systems that adhere to dentin, and restorative dentistry is fast approaching the development of a group of materials that will provide a strong and durable bond to dentin. Newer dentin-bonding systems, requiring alteration or complete removal of the smear layer, in general produce stronger bonds, and appear to provide a more effective marginal seal, than smear layer-dependent bonding systems. Some of these newer bonding agents have developed bond strengths to dentin comparable to those achieved with acid-etched enamel surfaces. However, for situations in which the retentive form of the cavity preparation is particularly critical to the success of the restoration, traditional retentive features should be used in the cavity design.

Dental Bonding

Dentin bonding system shelf life and bond strength.

The purpose of this study was to assess the shelf life of dentin bonding systems by means of bond strength testing. The systems evaluated were Mirage-Bond, All-Bond and Tenure. Specimens were tested immediately, and 1, 2, 3, 4, 5 and 12 months after opening the kits. Flat dentin surfaces were created on 210 extracted human molars that had been stored in saline. Ten specimens were prepared for each dentin bonding system at each shelf time. Each material was prepared and placed following the manufacturer's instructions. Prisma MicroFine resin composite was then placed. Shear bond strength testing was conducted using a universal testing machine. A two-way ANOVA indicated a significant interaction between bonding system and storage time (F = 2.28, P = 0.01). Multiple comparison tests indicated statistically significant bond strength differences by storage time for All-Bond and Mirage-Bond. In addition, a comparison of bonding systems at each storage time revealed significant differences at three of the seven times. These results suggest that shelf life for two of the three dentin bonding systems may be significantly shorter than currently presumed.

Analysis of Variance

Shear strength and microleakage of light-cured glass ionomers.

Bond to dentin and marginal integrity of three light activated glass ionomer cements were evaluated, and compared to a traditional chemical-cured glass ionomer cement. Results indicated no significant difference in shear bond strength among the glass ionomer cements tested. However, there was a significant difference among glass ionomer cements in bond strength variability, with coefficients of variation ranging from 55 to 102%. A discrepancy between manufacturers' instructions and optimum curing times is one possible explanation for these results. There were also no significant differences in microleakage among glass ionomer cements. Most samples exhibited minimal or no microleakage.

Analysis of Variance

Systemic necrotizing vasculitis in nine young beagles.

A systemic necrotizing vasculitis of unknown etiopathogenesis may be termed juvenile polyarteritis syndrome (JPS). The syndrome has been recognized primarily in young Beagles used for toxicologic studies. We studied 9 young Beagles with JPS. Affected dogs had fever (40 to 41.5 C), anorexia, and signs of pain in the cervical area. They had a characteristic hunched stance, and were unwilling to move. Laboratory abnormalities in all dogs included nonregenerative anemia, hypoalbuminemia, and leukocytosis characterized by a mature neutrophilia. Analysis of CSF revealed a moderate to severe neutrophilic pleocytosis and a mildly high protein concentration in most dogs. Signs of disease resolved rapidly with high doses (2.2 mg/kg of body weight, PO) of prednisone. If untreated, clinical signs and laboratory abnormalities had a remitting and relapsing course in most dogs. Findings at necropsy included necrotizing arteritis with fibrinoid necrosis, periarteritis, thrombosis, and intimal proliferation that most frequently affected small- to medium-sized vessels in the cervical spinal cord, mediastinum, and heart. An immune-mediated pathogenesis for this disease is suspected.

Animals

Shear strength of resin developed by four bonding agents used with cast metal restorations.

The evolution of the acid etch technique has made possible a more conservative approach to the fabrication of cast metal restorations. The resin bonding technique, however, places a greater burden for success on the selection of a bonding agent. This study examined the shear bond strength durability of cast metal restorations bonded to tooth structure with one of four metal adhesive bonding agents. Results indicated stronger bonds for restorations cemented with Panavia EX bonding agent than with any of the other bonding agents tested, both with and without exposure to thermal stress. Although it was one of the easier materials with which to work, Panavia EX bonding agent requires the additional step of applying an agent to prevent oxygen contact in the setting process.

Acid Etching, Dental

Effect of a social cognitive intervention on oral health status, behavior reports, and cognitions.

An intervention designed to test the influence of cognitive restructuring on protective oral health behaviors was conducted with 108 patients with mild to moderate gingivitis. Subjects in the experimental group viewed slides of active, mobile bacteria taken from their mouths on 5 occasions: before and after prophylaxis and at 3 appointments, one month apart. A specially trained hygienist discussed with these participants the process of periodontal disease, the role of bacteria, and self-efficacy (self-control) for oral hygiene self-care. Both experimental and control group subjects received instruction in oral self-care procedures. Assessments of oral health using Löe and Silness' plaque and gingival indices (PI and GI) were taken throughout the study and at 3- and 6-month follow-up visits. Self-efficacy, oral hygiene intentions, attitudes, and values comprised the set of cognition variables. Plaque and gingival indices mean differences between groups approached significance at visit 6. Analyses were also performed using percent of gingival surfaces scored at "0" (no visible bleeding on probing). A trend occurred for group differences in percent "0" scores at visit 6, with the experimental group maintaining higher percent zeros (better health) at this 3-month follow-up. At visit 7 (9-month follow-up), PI and GI differences disappeared. No significant differences were found between groups for oral health cognitions or behavior reports over time. The data suggest that the cognitive-behavioral intervention produced a delayed relapse in protective oral self-care behaviors, and by extension, oral health status. Such a delay could be clinically relevant in promoting adherence to oral hygiene behavior between professional visits.

Adult

Origination and progression of microleakage in a restoration with a smear layer-mediated dentinal bonding agent.

Several recently marketed dentinal bonding agents modify, but do not remove, the smear layer. Some controversy exists as to whether the smear layer should be left in place or completely removed from preparations to be restored with composite resin systems. This study utilized scanning electron microscopy with energy dispersive x-ray analysis to evaluate the pathway of microleakage in a composite resin restorative material that utilizes a smear layer-mediated dentinal bonding agent. Microleakage occurred at the smear layer-dentin interface and progressed into both the smear layer and dentinal tubules, suggesting that the smear layer acts as a pathway for microleakage.

Composite Resins

Microleakage in various dentin bonding agent/composite resin systems.

One important consideration in the selection of a dentin bonding agent/composite resin system is its resistance to marginal leakage. The purpose of this study was to compare both the extent and the pathways of marginal leakage for four currently available dentin bonding agent/composite resin systems. Class 5 restorations were placed in the buccal and lingual surfaces of 20 extracted human teeth. Specimens were subjected to thermal stress before being placed in silver nitrate solution. They were then sectioned longitudinally and observed under a light microscope. Selected samples were further studied using scanning electron microscopy (SEM) and energy-dispersive x-ray analysis (EDX). Different systems exhibited different leakage patterns. Findings suggest that the smear layer should be either conditioned or removed prior to dentin bonding agent application to provide optimal resistance to microleakage.

Composite Resins

Adhesion of dentin bonding agents after smear layer treatments.

The effect on bond strength of smear layer removal (40% polyacrylic acid or 10% phosphoric acid) versus smear layer conditioning for dentin bonding agents requiring conditioning was compared. Results indicated no difference in shear bond strength for groups in which the smear layer was conditioned or removed with phosphoric acid. Smear layer removal with polyacrylic acid resulted in lower bond strengths between DBAs and dentin than either phosphoric acid removal or conditioning (P less than 0.01). Scanning electron photomicrographs of dentin treated with each dentin bonding agent revealed various surface morphologies.

Acid Etching, Dental

Scanning electron microscopic and energy dispersive x-ray evaluation of two smear layer-mediated dentinal bonding agents.

Teeth treated with smear layer-mediated dentinal bonding agents and restored with composite resin were examined at the dentin-restoration interface by means of scanning electron microscopy used in conjunction with energy dispersive x-ray analysis. Results indicated that these dentinal bonding agents actually bonded to the smear layer, and samples demonstrated delamination of the smear layer from underlying dentin following thermocycling. This finding suggests that the stresses developed within the composite resin exceeded the adhesive strength of the smear layer to dentin. Thus, the bond strength for dentinal bonding agents that require the presence of the smear layer cannot exceed the adhesion of the smear layer to dentin.

Acrylic Resins

Bond strength evaluation of a Class V composite resin restoration.

A three-dimensional cavity design was used to test the bond strength between restorative materials and tooth structure. Results indicated that bonding agents that rely on mechanical retention to the dentinal smear layer produced relatively low bond strengths. Bonding agents that require smear layer modification yielded mixed results, possibly because of differences in chemical formulation. The three-dimensional cavity design employed in this study is a replicable one, allowing the creation of standardized, clinically relevant preparations.

Acrylic Resins

Scanning electron microscopic study of dentinal surfaces treated with various dentinal bonding agents.

A three-dimensional cavity design was used to study the morphology of dentin in vitro both after dentinal pretreatment and after restoration failure (debonding). Dentinal bonding agents that require removal of the smear layer (third generation), as well as those that depend on attachment to the smear layer (second generation), were included. Results indicated cohesive failures within both the dentinal bonding agents and the smear layer in second-generation systems. Dentinal conditioners for the third-generation dentinal bonding agents and for an as-yet unclassified agent were effective in removing smear layer debris from the dentinal surface, but they varied in the degree to which they opened the dentinal tubules. Differences in morphology of the dentinal surface following debonding of the restoration were attributed to differences in chemical composition among the agents examined.

Composite Resins

Fracture resistance of posterior teeth restored with glass ionomer-composite resin systems.

This study compared the fracture resistance of posterior teeth restored with one of four composite resin systems or amalgam. Mesio-occlusodistal cavity preparations were placed in 50 maxillary premolars. Dimensions of the preparation were such that remaining tooth structure was weakened. Five groups of 10 specimens each were designated as follows: I, amalgam; II, Ketac-Bond glass-ionomer base; III, Ketac-Silver glass-ionomer base; IV, GC lining cement glass-ionomer base; and V, Tenure dentinal bonding agent. Specimens in groups II through V were restored with P-30 posterior composite resin. Testing was accomplished by applying an occlusal load to the point of failure for each specimen. Results indicated no significant difference among restorative systems in resistance to cuspal fracture. These findings suggest that neither Tenure nor glass-ionomer cement used in conjunction with posterior composite resin strengthen weakened cusps to any greater extent than does amalgam.

Bicuspid