Biomedical subjects

S L Wendt

Publications and source records attributed to S L Wendt.

At least 19 recordsLinked to original sources

PubMed1996

Influence of enzymes and plaque acids on in vitro wear of dental composites.

The purpose of this investigation was to test the effect of an enzymatic and an acidic medium on in vitro wear of dental resin composites and an amalgam. Wear was evaluated in two-body and three-body wear conditions. The third body was a food slurry either in water, an esterase solution or an acid solution at a composition and concentration as found in caries active plaque fluid. In the two-body tests the slurry was left out. Under three-body wear conditions neither the enzyme nor the acids showed any significant (P < 0.05) effect on wear. Enzyme inactivation from a large excess of food constituents in the slurry or the absence of an effect from surface diffusion rates of the acids resulted in the lack of an effect on wear. The two-body/acids wear rates were statistically (P < 0.05) lower than the two-body/water wear rates caused by increased lubrication from the acids between sliding surfaces. A significant (P < 0.05) increase in wear was found in the two-body/enzyme experiments, showing that the enzymatic activity can start directly at the outer surface of the composites.

Acids↗

PubMed1995

Thermocycling and dwell times in microleakage evaluation for bonded restorations.

OBJECTIVES: To answer criticisms of an insufficient number of cycles in thermocycling in an earlier paper (Wendt et al., 1992), this study was initiated to evaluate the effect of different dwell times during long-term thermocycling in microleakage analysis of bonded restoratives. METHODS: A total of 90 resin-bonded restorations, Tytin/Liner F, (Kerr/Bisco), APH/Universal Bond 3, (LD Caulk) and Heliomolar/Syntac, (Vivadent), were inserted in Class V preparations in human third molars. Group A restorations were stored in 0.5% basic fuchsin dye for 166 h. Group B restorations were thermocycled for 5000 cycles in 0.5% basic fuchsin dye baths at 5 +/- 1 degrees C and 55 +/- 1 degrees C with a dwell time of 10 s in each bath. Group C was thermocycled as in Group B but with a dwell time of 60 s. Readings by defined criteria were taken from each of two 1 mm sections along the cemental margin. RESULTS: There were no significant differences (p < 0.05) in the extent of dye penetration at the tooth restoration interface for the thermocycled composite restorations when compared to composite restorations with no thermocycling. There was a significant difference (p < 0.05) in the extent of dye penetration at the tooth restoration interface for the thermocycled amalgam restorations when compared to dye-exposed amalgam specimens with no thermocycling. SIGNIFICANCE: During microleakage analysis, the need for thermocycling is dependent upon the extent the restorative is thermally conductive in relation to its mass. The dwell time should be clinically relevant, i.e., 10 s, and is important only if the restorative is thermally conductive.

Acrylic Resins↗

PubMed1995

Visualizing taste papillae in vivo with scanning electron microscopy of a high resolution cast.

A method using polyvinylsiloxane (PVS), a high-resolution dental impression material, to obtain negative images of lingual surfaces is described. Epoxy-resin tongue replicas made from these impressions were examined with scanning electron microscopy (SEM). This method has been developed to visualize structural details of the tongue surface of living human beings and laboratory animals. The utility of the method is demonstrated with hamster tongues, which have well-defined fungiform papillae with single taste pores, and human tongues, which have more variable surface structures. Replicas made from PVS impressions of tongues of living hamsters were compared with the same tongues after fixation. The replicas contained much of the detail present in fixed tongues. With SEM, it was possible to identify individual fungiform papillae, which contained depressions with the size and the location of hamster taste pores. Individual papillae could also be recognized in human-tongue replicas, but taste pores could not be identified with certainty. These replicas provide permanent, three-dimensional records of tongue topography that could be used to document changes due to trauma, disease and aging.

Animals↗

PubMed1995

Microleakage of "surface-sealing" materials.

PURPOSE: To test several dental materials for their sealing properties by subjecting restored teeth to thermal cycling. MATERIALS AND METHODS: Ten teeth per group were assigned at random to six experimental and six control groups. In the experimental groups a resin composite was surface-sealed with IRM, glass ionomer, amalgam, dentin bonding agent and resin composite, experimental hybrid cement, or zinc oxide and eugenol. These six surface-seal materials were placed in bulk in the control group. After cavity preparation, restoration, cut back and application of the surface-seal material, the teeth were subjected to thermal cycling, imbedded and sectioned. A score of 0-3 was given to the amount of dye leakage observed. RESULTS: Zinc oxide and eugenol demonstrated the most leakage, whereas the resin composite system TPH had the least. The results of this in vitro study render the recommendation of zinc oxide and eugenol as a surface-seal material questionable.

Analysis of Variance↗

PubMed1994

Clinical evaluation of a posterior resin composite: 3-year results.

PURPOSE: To clinically evaluate a resin composite. MATERIALS AND METHODS: Sixty restorations were inserted at a ratio of 1:3 in Class I and II preparations in molars. Caulk Prisma AP.H/Prisma Universal Bond resin composite restorative system was placed. All the restorations were evaluated using the USPHS system and M-L indirect scale; 6, 12, 24 and 36 month recalls were compared to baseline. RESULTS: Color, interfacial staining, secondary caries, marginal integrity and surface texture (Alfa = 89%, 94%, 97%, and 100% respectively) were essentially unchanged from baseline for all restorations. One restoration failed due to secondary caries. Two were assessed with Charlie (C) ratings for marginal defects and one for wear. Direct wear analysis (Alfa = 12%) was significantly changed from the baseline. Indirect mean estimated wear measurements for each recall period, adjusted for baseline, were 21 +/- 18 microns, 54 +/- 29 microns, 67 +/- 29 microns, and 98 +/- 43 microns respectively. The wear of AP.H was characteristically linear (g2 = 0.987) for composites whose mean filler particle size approaches 1 micron or less.

Composite Resins↗

PubMed1993

Dentinal surface roughness: a comparison of tooth preparation techniques.

Standardization of prepared dentinal surfaces for in vitro investigations is needed for evaluation of luting and bonding agents. Forty-eight intact, noncarious human molars were prepared either with silicon carbide paper mounted on a circular grinder or with carbide bur or a diamond mounted in a dental handpiece, and the dentinal surfaces were analyzed in a profilometer for surface roughness. The results were computed with a parametric ANOVA and Student-Newman-Keuls post hoc test. The dentinal surfaces prepared by Brasseler super coarse, coarse, medium, and Premier coarse diamonds by use of a high-speed dental handpiece with water spray were statistically different (p < 0.0001) but closely resembled a dentinal surface prepared by a 60-grit silicon carbide abrasive on a circular grinder. The fine diamonds resembled a prepared dentinal surface similar to a spectrum of SiC papers from 60 to 120 grits, whereas the carbide burs appeared to create various surfaces, depending on the manufacturer.

Carbon↗

PubMed1993

Indirect cytotoxic evaluation of dental materials.

The standard for cellular biocompatibility in vitro testing is American National Standards Institute/American Dental Association Document No. 41a (1982). The standard allows for the contact testing of solid dental materials for cytotoxicity with HeLa or mouse fibroblasts (L929). The purpose of this study was to evaluate a new method of cytotoxicity testing of biomaterials that allows for an economic standardized indirect cytotoxic screening of the originally dispensed material over a period of time at intervals decided by the investigator. The results show a significant difference of cytotoxicity on the basis of the material between the direct contact method and the indirect or diffusion method described.

American Dental Association↗

PubMed1992

The effect of thermocycling in microleakage analysis.

The purpose of this study was to evaluate the effect of thermocycling on dye penetration during in vitro microleakage analysis of composites. Fifty non-carious human molars, stored in 75% ethanol, were divided into five groups (N = 10). Each tooth was prepared for a MOD slot preparation using a high speed handpiece and water, one proximal cervical margin in cementum, the other in enamel. The enamel margins were etched, rinsed, dried, and the composite inserted and cured in multiple increments. Group A was not thermocycled (TC) and was immersed in 0.5% basic fuchsin dye for 24 h at 37 degrees +/- 1 degrees C. Group A' was not TC and was immersed in 0.5% basic fuchsin dye for 4 h at 37 degrees +/- 1 degree C. Group B was TC in a water bath and immersed in dye as with Group A, Group B' was TC and immersed in dye as in Group A'. Group C was TC, as in Group B, but in a basic fuchsin dye bath. Thermocycling consisted of 250 cycles, 15 s dwell time each in 5 degrees C and 50 degrees C bath. The teeth were mounted in acrylic, and multiple cross-sections of all surfaces were prepared. Dye penetration was read on a scale of 0 (no leakage) to 4 (leakage to the pulpal floor) and means calculated for each surface and tooth. There was no significant increase of microleakage in restorations when thermocycling was used to simulate temperature extremes, either in dye or water baths, as opposed to restorations which were not thermocycled.

Composite Resins↗

PubMed1992

Methodology for proximal wear evaluation in posterior resin composites.

The purpose of this study was to utilize a methodology to measure proximal wear of posterior resin composites with respect to time. A group of 10 teeth (5 premolars and 5 molars) were restored with P-30, a posterior resin composite restorative. At placement the proximal contacts were judged to be closed visually, and with unwaxed dental floss. The patients were then recalled at intervals of 6, 12, and 36 months for indirect wear evaluations. Resin composite transfer copings were made and indexed on baseline models. A zoom stereomicroscope, at 20 microns resolution, was used to determine proximal wear. For the posterior restorative material the premolar and molar teeth wore at the same rate. The amount of wear was statistically greater for premolar teeth at 6 and 12-month evaluation periods than molar teeth. At 36 months, there was no statistical difference in wear between premolar and molar teeth.

Bicuspid↗

PubMed1992

Clinical evaluation of a heat-treated resin composite inlay: 3-year results.

The purpose of this study was to evaluate a resin composite inlay system in clinical trials involving human subjects. A total of 60 restorations were inserted equally in Class I and II preparations and in premolars and molars. A glass ionomer liner was applied to the dentin. Light-cured direct inlays were fabricated in the oral environment. Thirty inlays were heat-treated for 7.5 minutes at 125 degrees C in a dry heat oven. Enamel margins of the preparations were etched with 37% phosphoric acid gel. All inlays were cemented with a light-cured enamel bonding resin. Restorations were evaluated using the USPHS system and M-L indirect scale. Six, 12, 24 and 36-month recalls were compared to baseline. Color, interfacial staining, secondary caries, and wear were unchanged from baseline for all restorations. Marginal integrity and surface texture show a differential change from baseline and with respect to restoration type. Indirect wear was not significantly different between restoration types (P < 0.05). Wear resistance was not significantly improved with heat treatment, but marginal integrity and surface characteristics showed marked improvement in the heat-treated group at 24 and 36-month recalls.

Analysis of Variance↗

PubMed1992

Clinical evaluation of Clearfil photoposterior: 3-year results.

The purpose of this study was to evaluate a new resin composite/bonding restorative system in clinical trials involving human subjects. Sixty restorations were inserted in Class I and Class II preparations in premolars and molars. The enamel margins of the preparations were etched for 60 seconds with 37% phosphoric acid gel. The dentinal surfaces of cavity preparations were etched for 40 seconds with 37% phosphoric acid in glycerine (K-etchant gel) and bonding agent (Clearfil Photo Bond) applied. A resin composite (Clearfil Photoposterior) was placed in three increments with a 20 second light cure of each increment and a 60 second light cure of the final increment. All the restorations were evaluated using the USPHS system and M-L indirect scale. At 36 month recalls, compared to baseline, surface texture for essentially all the restorations was rated Bravo, while all other characteristics were rated Alpha. Secondary caries was reported for one restoration during the third year of clinical use. Wear showed an adjusted mean value of 14.6 microns at 36 months or 4.9 microns per year. No cases of clinical post-operative sensitivity to hot, cold, percussion and foods were reported during the length of the study. Clearfil Photoposterior resin composite system has exhibited remarkable wear resistance and no post-operative sensitivity throughout the length of the study.

Acid Etching, Dental↗

PubMed1991

Nonprecious cast-metal alloys in dentistry.

This review of selected articles from October 1989 to October 1990 is divided into two sections: a review of clinical studies and a review of laboratory studies for nonprecious cast metals. The clinical articles are centered on biological compatibility issues, such as taste anomalies (dysgeusia) attributed to cast metals and allergy correlation to base metals, and on technique and longevity evaluations involving resin-bonded fixed partial dentures. Laboratory articles are mainly devoted to metal preparation before bonding of etched or resin-bonded fixed partial dentures and the estimated bond strengths of the metal castings. Other selected articles are based on studies of physical properties and physical testing of nonprecious alloys, such as modulus of rupture, to determine ceramic compatibility, castibility testing, marginal fit of fixed partial dentures, and flexure testing of of traditional and experimental designs for cast major connectors. Additionally, a low-cost method of titanium casting is reviewed.

Biocompatible Materials↗

PubMed1991

Microleakage and cusp fracture resistance of heat-treated composite resin inlays.

The purpose of this study was to examine the microleakage and cusp fracture resistance of heat-treated composite resin inlays. One hundred and twenty extracted human bicuspid teeth were prepared with MOD Class II preparations and divided into 12 experimental groups. Ten extracted human teeth were kept sound as positive controls and 10 of the prepared teeth were left unrestored as negative controls for the cusp fracture resistance experiment. The remaining prepared teeth were grouped and restored with the following restorations: bulk or incremental placement, light-cured inlays, heat-treated inlays "cemented" with enamel bonding agent, enamel bonding agent/glass ionomer "sandwich", or a dentinal bonding agent. Heat-treated inlays showed significantly (P less than 0.05) less microleakage than all other groups. The cusp fracture resistance of the heat-treated inlays was in the same magnitude as that of the traditionally placed composite resin restoration. All restorations were significantly (P less than 0.05) lower in cusp fracture resistance than sound non-carious teeth.

Adhesives↗

PubMed1990

Effect of dentin surface roughness on shear bond strength.

The aim of this investigation was to evaluate the effect of dentin surface roughness on the shear bond strength of a dentin bonding agent. Seventy-five dentin samples were divided into five surface preparation groups: (1) 60-grit SiC; (2) 320-grit SiC; (3) 600-grit SiC; (4) 600-grit SiC followed by AI2O3, and (5) 320-grit SiC followed by a #245 carbide bur. The prepared dentin was treated with a dentin primer, and one coat of dentin bonding agent was applied and light-cured for 30 s. Each dentin specimen was mounted in a device with a split Teflon mold (I.D. = 3.5 mm, depth = 5.0 mm). Three increments of a restorative composite were placed, compressed firmly, and light-cured for 30 s in the mold. After 24 h of storage, the bonds were stressed to failure in a mechanical testing machine at a cross-head speed of 0.5 mm/min. Weibull analysis was used to obtain a shape factor and characteristic level for each group. The results showed that, with the possible exception of the 600-grit SiC and AI2O3 group, the grit size used for preparation of dentin specimens for shear bond strength testing in this study did not significantly affect bond strength.

Dental Bonding↗

PubMed1990

The effect of two smear layer cleansers on shear bond strength to dentin.

Prevention of microleakage and post-operative sensitivity depends upon maintenance of the integrity of the bond between the resin composite and the tooth. Removal of the dentinal smear layer allows for better bond strengths for the newer dentinal bonding agents. The purpose of this study was to evaluate the shear bond strengths of a light-cured composite to dentin treated with one proprietary and one experimental cleansing agent. Bond strengths for the teeth cleansed with the experimental cleansing agent were significantly (p less than 0.05) greater than bond strengths of teeth cleansed with EDTA.

Acrylic Resins↗

PubMed1990

The clinical evaluation of heat-treated composite resin inlays.

Laboratory research indicates the physical properties of composite resin used for posterior restorations can be significantly increased if a secondary dry heat treatment of the material was accomplished. This study investigated the clinical performance of a heat-treated composite resin inlay, using both the direct and indirect methods of clinical evaluation. Contrary to laboratory results, no significant differences in wear could be measured between conventional light-cured inlays and those with secondary dry heat treatment. Other clinical advantages of the heat-treated inlays were observed.

Analysis of Variance↗

PubMed1989

The effect of storage media and duration of storage of extracted teeth on the shear bond strength of Scotchbond 2/Silux to dentin.

The objective was to determine the effect of storage media and the duration of storage of extracted teeth on the shear bond strength (SBS) of Scotchbond 2/Silux to dentin. Extracted human mandibular and maxillary first permanent molars were stored in buffered formalin (A), 1% chloramine (B), 70% ethanol (C), physiological saline (D), or 0.05% thymol (E). Fifteen test specimens were prepared on teeth stored in each medium two days after extraction (Procedures A1 to E1) or after six months storage (Procedures A2 to E2). The teeth were embedded in brass tooth cups and the occlusal surfaces ground wet on 180 and then 600 grit SiC immediately prior to the preparation of a test specimen. The Scotchprep Primer and the Scotchbond 2 Adhesive were applied to the dentin surfaces as directed by the manufacturer. Cylinders of Silux Composite were bonded to the treated dentin surfaces in a special device. The specimens were removed 15 minutes after cure and stored in distilled water at 37 degrees C for 24 hours. A shear load was applied to the bonded cylinders in an Instron machine at a crosshead speed of 0.02 inch.min-1. The SBS were calculated and expressed in MN.m-2. The data were analyzed by ANOVA and Duncan's multiple range test at the 5% level of significance.2+e mean SBS + SD

Bisphenol A-Glycidyl Methacrylate↗

PubMed1989

Effect of adhesive thickness on the shear bond strength of Scotchbond 2/Silux to dentin.

Seventy-five extracted human permanent molars were embedded in brass cups with cold-cure acrylic. Immediately prior to the preparation of a test specimen, the occlusal surface was ground wet on 180 followed by 600 grit SiC to expose dentin. The Scotchprep Dentin Primer was applied to the dried dentin surface with a brush for 60 seconds, and dried with compressed air for 15 seconds. The tooth was mounted in a special device containing a split Teflon mold with a circular hole, 3.5 mm in diameter and 5 mm deep, and A:0.5 microL (50 microns), B:1.0 microL (100 microns), C:2.5 microL (250 microns), D:5 microL (500 microns) or E:10 microL (1000 microns) Scotchbond 2 pipetted into the teflon mold. The adhesive was cured by visible light for 30 seconds. Three increments of Silux were transferred to the Teflon mold, compressed firmly, and each cured for 30 seconds. The test specimens were disassembled 15 minutes after cure and stored in distilled water at 37 degrees C for 24 hours. A shear load was applied via a knife-edge rod in an Instron machine. The shear bond strength was expressed in MPa. The data were analyzed by ANOVA and Duncan's multiple range test. The mean (+/- SD) of the shear bond strengths were: A: 8.8 (3.5), B: 7.9 (2.7), C: 6.8 (2.5), D: 8.1 (4.2), E: 5.3 (2.4). Adhesive thickness from 50 microns to 500 microns (A, B, C and D) had no significantly different effect on shear bond strength. An adhesive thickness of 1000 microns resulted in a significant reduction in shear bond strength.

Bisphenol A-Glycidyl Methacrylate↗