Shear bond strength and quantitative microleakage of a multipurpose dental adhesive system resin bonded to dentin.

The shear bond strengths of a dental bonding system used in conjunction with a composite resin bonded to dentin were determined 1 minute after irradiation and after storage in saline at 37 degrees C for 24 hours, 1 week without and with temperature cycling, and 4 weeks without and with temperature cycling. The quantitative microleakage of class V preparations in cementum (dentin) restored with the system was determined by a spectrophotometric dye-recovery method. Excellent shear bond strengths ranging from 13.9 MPa (1 minute) to 19.5 MPa (1 week) were obtained. The shear bond strengths and quantitative microleakage of the multipurpose dental adhesive system compared favorably with the data obtained from other dental bonding systems under similar experimental conditions.

Laboratory evaluation of the Gluma 3-step bonding system.

PURPOSE: To determine in vitro (1) the shear bond strengths (SBS) of the modified Gluma system to enamel and dentin; (2) the qualitative and the quantitative microleakage (ML) of Class V preparations on the cemento-enamel junction (CEJ) and in dentin, respectively, restored with the Gluma system; and (3) the effect of the system's components on enamel and dentin by scanning electron microscopy. MATERIALS AND METHODS: Seventy-five extracted human maxillary permanent central incisors and 75 permanent first and second molars were embedded in brass tooth cups with cold-cure acrylic resin. The facial surfaces of the anterior and the occlusal surfaces of the molar teeth were ground wet on 180- followed by 600-grit silicon carbide paper. Demarcated sites on the surfaces were treated according to the manufacturer's instructions and Pekafill composite was bonded to the treated surfaces. Fifteen specimens prepared on enamel were removed 1 minute after cure (A) and the SBS determined. The remaining specimens were removed 15 minutes after final cure, stored in saline at 37 degrees C for 24 hours (B), for 1 week without (C) and with temperature cycling (D), and for 4 weeks (E). Similar regimens were used for dentin, groups F, G, H, I and J. The SBS were determined and expressed in MPa. The data were analyzed by ANOVA, Student-Newman-Keuls and t-tests. For the qualitative ML evaluation, Class V cavities were prepared on the CEJ of 30 human premolars and restored with Gluma/Pekafill. After thermocycling in 0.5% basic fuchsin, the teeth were sectioned and ranked according to the degree of microleakage. Class V cavities were prepared on the facial root surfaces of 15 human premolars and restored. The ML was determined quantitatively by a spectrophotometric dye-recovery method and expressed as microgram dye/restoration. RESULTS: The mean +/- SD of the SBS in MPa were: A: 14.6 +/- 2.2; B: 21.2 +/- 1.6; C: 20.5 +/- 1.4; D: 24.2 +/- 2.0; E: 22.8 +/- 3.7; F: 7.0 +/- 2.0; G: 16.1 +/- 4.0; H: 15.6 +/- 3.7; I: 10.9 +/- 3.3; J: 14.4 +/- 3.3. The quantitative ML was 1.00 +/- 0.39 microgram dye/restoration. The lowest SBS were obtained on specimens tested after 1 minute. Temperature cycling had a significantly adverse effect on the SBS to dentin (P = 0.0003). Etch patterns conducive to bonding were produced on the enamel. The resin system penetrated into the dentin tubules.

Laboratory evaluation of the A.R.T. bonding system.

PURPOSE: To determine (1) the in vitro shear bond strengths of the A.R.T. Bond System to dentin at different time intervals, (2) the quantitative microleakage of Class V preparations in dentin restored with the A.R.T. Bond System, and (3) the resin penetration into the dentin tubules by scanning electron microscopy. MATERIALS AND METHODS: The occlusal surfaces of 75 extracted human mandibular and maxillary permanent first and second molars were ground wet on 600-grit SiC to expose the superficial dentin. The A.R.T. Primer and the A.R.T. Adhesive were applied to demarcated bonding sites as recommended by the manufacturer. Brilliant Dentin resin composite was transferred to the opening in a split Teflon mold in the assembly apparatus in three increments, each compressed firmly and cured for 40 seconds. Fifteen specimens were disassembled 60 seconds after final cure and then tested. The remaining 60 teeth were disassembled 15 seconds after cure; one group was tested at this time and the others immersed in saline at 37 degrees C for 24 hours, 1 week and 4 weeks before being tested. A shear load was applied at a crosshead speed of 0.5 mm/minute, the shear bond strengths calculated and expressed in MPa. Data were analyzed by ANOVA and Student Newman-Keuls test. Class V cavities were prepared at the facial surfaces of 18 extracted human permanent premolars and restored. Microleakage was determined quantitatively by a spectrophotometric dye-recovery method and expressed as mg dye/restoration. RESULTS: Mean +/- SD of the shear bond strength in MPa were 13.07 +/- 3.59 (1 minute), 16.08 +/- 3.12 (15 minutes), 18.17 +/- 3.44 (24 hours), 17.54 +/- 5.35 (1 week), 17.90 +/- 2.61 (4 weeks). The mean +/- SD microleakage was 0.008 +/- 0.04 mg dye/restoration.

Laboratory evaluation of the XR-Bond Dentin/Enamel Bonding System.

The shear bond strengths of the XR-Bonding System used in conjunction with Herculite composite, to the dentine of forty extracted human permanent first and second molars were determined after the test specimens were stored in physiological saline at 37 degrees C for 48 hours, one week, two weeks and four weeks, respectively. A shear load was applied to the base of the bonded composite cylinders with a knife-edged rod at a crosshead speed of 0.5 mm/minute. The shear bond strengths were expressed in megapascals (MPa). The quantitative microleakage of Class V preparations in dentine (cementum) in forty-eight extracted human maxillary permanent canines restored with the same dentinal bonding system and after storage in physiological saline at 37 degrees C for the same time intervals as for the shear bond strength tests, was determined. On the final day of each time interval the teeth were thermocycled X 500 in a 2 per cent methylene blue solution between 8 degrees C and 50 degrees C with a dwell time of 15 seconds. Microleakage was determined by a spectrophotometric dye-recovery method and expressed in microgram dye/restoration. There was a significant trend for the shear bond strengths to increase with duration of storage (p = 0.01) but the quantitative microleakage was not significantly different (p = 0.75).

Laboratory evaluation of phosphate ester bonding agents.

Two dentin bonding agents that contain phosphorus esters, (Clearfil Photo Bond and Panavia), and a bonding agent for porcelain, (Clearfil Porcelain Bond), have been introduced for bonding to enamel, dentin, amalgam, cast metal alloys and porcelain. The shear bond strengths were determined to enamel (Procedure A), to dentin (Procedure B), to amalgam (Procedure C), of amalgam to dentin (Procedure D), to cast metal alloy (Procedure E) and to porcelain (Procedure F). Also the quantitative microleakage of Class V restorations in cementum (dentin) was evaluated (Procedure G). The components were applied as directed by the manufacturer and a light-cured resin composite for posterior teeth, (Clearfil Photo Posterior) used. The mean +/- SD of the shear bond strengths recorded in MPa were: A = 24.15 +/- 3.65; B = 11.30 +/- 3.12; C = 13.77 +/- 3.42; D = 4.26 +/- 0.92; E = 17.84 +/- 3.19; F = 13.45 +/- 4.12. The quantitative microleakage (G) was 0.55 +/- 0.34 mg dye/restoration.

In vitro demineralization by strains of Actinomyces viscosus and Streptococcus sobrinus of sound and demineralized root surfaces.

Root sections were inoculated with one of two strains of Actinomyces viscosus or a strain of Streptococcus sobrinus and then incubated for 9 days in Trypticase soy broth (TSB) containing 0.25% glucose or TSB supplemented with 0.25% sucrose (TSB+S). Lesion progression was measured from microradiographs. One section from each group was examined with a transmission electron microscope. Lesion progression was associated with a fall in the pH of the medium. However, lesion progression was not correlated with the mean 48-hour pH of the medium. In both TSB and TSB + S, lesion progression with A. viscosus was significantly greater than in the S. sobrinus group. However, the mean 48-hour pH value in TSB + S was lower than that in the S. sobrinus group. Plaque formation in TSB was, subjectively, least in the S. sobrinus group. Examination of transmission electron micrographs revealed bacteria penetrating the surfaces of the sections and extending into the lesion in the A. viscosus groups but not in the S. sobrinus group. This in vitro bacterial plaque model of root caries may be suitable for investigations of the bacterial etiology of root-surface caries and the virulence factors associated with pathogenicity.

Shear bond strength and microleakage of All-Bond.

The shear bond strengths (SBS) were determined to enamel etched with Uni-Etch (Procedure A) or treated with the mixed Primer A and B (Procedure B), to dentin treated with the Dentin Conditioner (Procedure C) or etched with All-Etch (Procedure D), to amalgam treated with the mixed Dual Opaquer Base and Catalyst which was allowed to self cure (Procedure E) or light cured (Procedure F), of amalgam to dentin (Procedure G), to cast metal alloy (Procedure H), and to porcelain (Procedure I). The test specimens were stored in physiological saline at 37 degrees C for 24 hours, and the SBS determined by the application of a shear load directed at the base of the bonded composite cylinders at a crosshead speed of 0.5 mm/minute. The SBS were calculated and expressed in MPa. Standardized Class V preparations were made at the facial aspects of the roots of the teeth, treated with the Dentin Conditioner (Procedure J) or etched with All-Etch (Procedure K). Quantitative microleakage (QM) was determined by means of a spectrophotometric dye-recovery method and expressed in microgram dye/restoration. The mean +/- SD of the SBS in MPa were: A: 18.3 +/- 2.1; B: 22.0 +/- 2.9; C: 17.2 +/- 3.6; D: 15.6 +/- 3.7; E: 12.9 +/- 1.9; F: 13.6 +/- 2.0; G: 13.0 +/- 3.5; H: 21.8 +/- 2.6; I: 8.2 +/- 2.8. The mean +/- SD of the QM in microgram dye/restoration were: J: 2.61 +/- 1.22 and K: 1.95 +/- 0.59. The analysis of the SBS data showed that the application of the Primer to enamel resulted in a significant increase in SBS.(ABSTRACT TRUNCATED AT 250 WORDS)

Evaluation of the Syntac bonding system.

The purpose of this in vitro study was to determine the shear bond strength [SBS] of Syntac to dentin; to determine the quantitative microleakage (ML) of Class V preparations in dentin restored with the Syntac system; and to study resin penetration into the dentin tubules by SEM. The occlusal surfaces of 30 extracted human mandibular permanent first and second molars were ground wet on 600-grit SiC to expose the superficial dentin. The teeth were embedded in brass tooth cups with cold cure acrylic resin. The Syntac Primer and the Syntac Adhesive were applied to the demarcated bonding sites as recommended by the manufacturer. Radiopaque Heliomolar was transferred to the opening in a split teflon mold in three increments, each compressed firmly and cured for 40 seconds. Fifteen of the test specimens were disassembled 60 seconds after cure [A], and the remainder 15 min after cure and the latter specimens stored in saline at 37 degrees C for 24 hours [B]. A shear load was applied at a crosshead speed of 0.5 mm/min, the SBS calculated and expressed in MPa. The data were analyzed by a two-sample t-test. Class V cavities were prepared on the facial surfaces of 15 human premolars and restored. The ML was determined quantitatively by a spectrophotometric dye recovery method and expressed as microgram dye/restoration. The mean +/- SD of the SBS in MPa were: A: 10.14 +/- 2.80; B: 15.90 +/- 2.13 and the ML 2.57 +/- 0.97 microgram dye/restoration. The SBS recorded after 24 hours storage was significantly greater than after 1 minute (P < 0.0001). The bonding resin penetrated deeply into the dentin tubules.

A laboratory study of the Amalgambond Adhesive System.

The shear bond strengths (SBS) of the Amalgambond Adhesive System to several substrates were determined in vitro. Ninety extracted human permanent first and second molars were used. In 30 teeth, the occlusal surfaces were ground wet on 600-grit SiC to expose the enamel and in 60 to expose the superficial dentin. Amalgam (Tytin) restorations were placed on 15 exposed dentin surfaces and sandblasted. The Metafil-A composite was transferred in three increments and each cured for 30 seconds. The SBS of the composite to enamel were determined 1 minute (A) and 24 hours after final cure (B); to dentin 1 minute (C) and 24 hours after final cure (D); of freshly mixed amalgam to dentin (E) and to previously placed amalgam (F) after 24 hours. All of the 24 hours specimens were stored in saline at 37 degrees C or 24 hours. A shear load was applied to the base of the bonded cylinders with a knife-edged rod in an Instron machine at a crosshead speed of 0.5 mm/min. The SBS were expressed in MPa and the data analyzed by Student t-test, ANOVA and Student-Newman-Keuls test. The mean +/- SD of SBS were: A: 8.15 +/- 1.74; B: 15.69 +/- 4.50; C: 6.64 +/- 1.72; D: 17.09 +/- 4.61; E: 5.10 +/- 1.73; F: 6.54 +/- 3.78. The SBS to enamel and to dentin, respectively, after 24 hours were significantly greater than after 1 minute (P = 0.0001), the SBS of A vs C (P = 0.1783), B vs D (P = 0.2180) and E vs F (P = 0.7149) were not significantly different.

Gluma shear bond strength to enamel and dentin treated with pyruvic acid and glycine.

The purpose of this study was to determine the effect of pyruvic acid and glycine on the shear bond strength (SBS) of the Gluma Bonding System to dentin and enamel. Forty-five mandibular and maxillary permanent first and second molars and 45 maxillary permanent central incisors were used in the study. Fifteen test specimens were prepared with each of the following procedures. Dentin: using the conventional Gluma Bonding System (A); the Gluma 2 Cleanser was replaced with 10% pyruvic acid containing 10% glycine with pH 2.8 (B); or the dentin was etched with 10% pyruvic acid (pH 1.5) followed by the application of 10% glycine with pH adjusted to 9.0 (C). Enamel: etched with Gluma 1 Etchant (D); etched with 10% pyruvic acid containing 10% glycine (E); or etched with 10% pyruvic acid followed by the application of 10% glycine (F). The test specimens were disassembled 15 minutes after cure, stored in physiological saline at 37 degrees C for 24 hours, and the SBS determined in an Instron machine at a crosshead speed of 0.5 mm.min.-1 The SBS was expressed in MPa. The data were analyzed by ANOVA and the Student-Newman-Keuls test. The mean +/- SD of the SBS in MPa were: A: 8.7 +/- 5.2; B: 14.7 +/- 4.6; C: 12.8 +/- 4.8; D: 19.8 +/- 3.8; E: 18.0 +/- 3.1; F: 17.6 +/- 3.5. The application of 10% pyruvic acid containing 10% glycine, and 10% pyruvic acid followed by 10% glycine, resulted in a significant increase in SBS to dentin. The SBS to enamel treated with the three procedures were not significantly different.

Phosphoric acid as a dentin etchant.

This study determined the effect of phosphoric acid (H3PO4) application to dentin on the shear bond strength (SBS) and microleakage of an experimental bonding system. Thirty human maxillary permanent first and second molars were used for the SBS evaluation. In 15 of the teeth the Dentin Conditioner was applied to dentin for 30 seconds (A), while in the remaining 15 teeth the smear layer was removed by the application of a 37% H3PO4 gel for 20 seconds (B). The Primers 1 and 2 were mixed and applied to the conditioned dentin followed by the application of the Dentin Bonding Resin prior to the placement in three increments of the Bisfil-M composite. The specimens were stored in physiological saline at 37 degrees C for 24 hours prior to applying a shear load at a crosshead speed of 0.5 mm. inch-1 in an Instron machine. Shear bond strengths were expressed in MPa. Circular Class V preparations were made on the roots of 30 maxillary permanent canines, 15 restored using the Dentin Conditioner (C) and 15 by removing the smear layer with the H3PO4 gel (D). Microleakage of the restorations was determined quantitatively by means of a spectrophotometric method. The quantitative microleakage was expressed as microgram dye/restoration. The data were analyzed by the Student t-test. The following results were obtained: A: 14.2 +/- 2.2 MPa; B: 7.2 +/- 4.2 MPa; C: 30.0 +/- 28.6 micrograms dye/restoration; (D) 10.3 +/- 8.2 micrograms dye/restoration. Removing the smear layer with H3PO4 reduced the SBS to dentin but decreased the quantitative microleakage significantly.

Marginal leakage and marginal gap dimensions of three dentinal bonding systems.

Standardized cylindrical Class V preparations, 3 mm in diameter and 1.5 mm deep, were made on the roots of 60 extracted human maxillary permanent canines. The teeth were restored with Scotchbond 2/Silux (S); Gluma/Lumifor (G); and Tenure/Perfection (T), respectively. The root apices were sealed with Copalite/amalgam and two coats of nail varnish applied to the teeth except for 1 mm around the restorations. For the qualitative microleakage evaluation the teeth were thermocycled x500 in 0.5% basic fuchsin between 8 degrees C and 50 degrees C and for the quantitative microleakage evaluation in 2% methylene blue solution. The marginal gap dimensions were measured on cylindrical restorations placed on the facial surfaces of ground root surfaces of 30 teeth. Epoxy replicas were made of the restorations, coated with gold/palladium and examined with the SEM. The maximum marginal gap dimensions were measured. The data were analyzed by ANOVA, Duncan's and their nonparametric analogues. In the qualitative microleakage evaluation the total microleakage was: S: 16; G: 50; T: 18. The quantitative microleakage (micrograms) was: S: 3.1 +/- 2.9; G: 16.1 +/- 5.3; T: 4.4 +/- 4.1. The maximum marginal gap dimensions (microns) were: S: 4.1 +/- 3.6; G: 9.3 +/- 3.4; T: 16.4 +/- 7.0.

Extracted human versus bovine teeth in laboratory studies.

The purpose of this study was to determine the shear bond strengths and microleakage of Scotchbond 2/Silux to dentin and to evaluate resin penetration into the dentinal tubules of human and bovine teeth. The shear bond strengths (SBS) were determined on occlusal dentin of 25 human permanent molars (H) and on facial dentin of 25 bovine permanent mandibular incisors (B). The test specimens were stored in physiological saline at 37 degrees C for 24 hours prior to the application of a shear load in an Instron machine at a speed of 0.5 mm/min. Microleakage (ML) of Class V restorations placed on the facial surfaces of the roots of 15 human canines (H) and 15 bovine incisors (B) was determined quantitatively. The restored teeth were thermocycled x500 in 2% methylene blue solution, the dye extracted in 50% HNO3 and the dye concentrations determined spectrophotometrically. The resin penetration into the dentinal tubules was evaluated in the SEM. The following results were obtained: SBS (MPa): H, 6.2 +/- 2.9; B, 4.4 +/- 1.2; ML (microgram dye): H, 4.7 +/- 3.2; B, 15.9 +/- 10.5. The data were analyzed by t-test. The shear bond strength of Scotchbond 2/Silux to human dentin was significantly greater (P = 0.0096) and the microleakage significantly less (P = 0.0004) than to bovine dentin despite the fact that the restorative system penetrated more densely into bovine dentin. The use of bovine teeth instead of human teeth in these types of tests is not indicated.

Four-year in vivo evaluation of the composite/bonding resin-tooth interface.

The objective of this study was to evaluate the color match, marginal discoloration, recurrent caries, anatomic form, and marginal adaptation of 41 paired Class III and Class V preparations restored with a conventional chemically cured resin composite with and without a low-viscosity bonding resin (LVBR). In addition, the wear of the restorations was evaluated from scanning electron micrographs of epoxy replicas of the restorations. The subjects were re-called 48 months after placement of the restorations. The marginal discoloration and wear of the composite restorations placed without a LVBR were significantly greater than in restorations placed with a LVBR. The results of this clinical study suggest that a LVBR should be applied prior to the placement of a conventional chemical-activated resin composite.

Ultrastructural study of liposome uptake by M cells of rat Peyer's patch: an oral vaccine system for delivery of purified antigen.

Liposomes (phospholipid artificial membrane vesicles) have been used in targeted drug delivery and recently in the development of oral vaccines using purified soluble antigens for the induction of mucosal immune responses. Although the mechanisms by which liposomes promote the induction of responses to soluble antigens have not been clearly shown, it has been suggested that these vesicles, when given orally, are taken up by M cells for delivery of antigen to underlying lymphoid cells of the Peyer's patch. This study investigated in vivo the uptake of liposomes by cells of Peyer's patch. Following exposure of surgically constricted segments of rat small intestine to small unilamellar liposomes or gold-labelled solid core liposomes, Peyer's patches were removed, fixed, and processed for examination by transmission electron microscopy. Sections of Peyer's patch from experimental animals showed M cells with endocytic vesicles containing liposomes. Vesicles containing liposomes were also observed between M cells and lymphoid cells. These results indicate that intact liposomes are endocytosed by M cells and provide evidence for a possible mechanism by which M cells deliver antigen to lymphoid cells in the Peyer's patch. These findings support the potential usefulness of liposomes in oral vaccine development.

Shear bond strength of light-cured glass ionomer to enamel and dentin.

The shear bond strengths of a light-cured glass-ionomer cement to enamel and dentin were determined with use of extracted human maxillary permanent canines and molars. Bonding sites on the ground, etched enamel and ground dentin surfaces were demarcated by the punching of a hole, 3 mm in diameter, in an adhesive tape. The mixed glass-ionomer cement was transferred to the demarcated site, cured by exposure to visible light for 30 s, and the cement surface treated with Scotchprep Dentin Primer followed by Scotchbond 2 Light Cure Dental Adhesive. The embedded teeth were positioned in an assembly apparatus, and Silux composite was bonded to the glass-ionomer-cement surfaces. The specimens were disassembled after 15 min and subjected to a shear load (in an Instron machine) immediately after disassembly; after storage in water at 37 degrees C for 24 h, without and with temperature cycling; and after storage in water for four weeks, without and with temperature cycling. The shear bond strength of the glass-ionomer cement to etched enamel was in the order of 12 MN.m-2, and to dentin it was 9 MN.m-2. Temperature cycling and duration of storage had no adverse effect on the shear bond strength. The enamel and dentin aspects of fractured test specimens were examined, and the percentage of the bonding area that failed in the cement was estimated. Most of the test specimens failed partly at the enamel and dentin interfaces and within the glass-ionomer cement.

Effects of phosphoric acid concentration and etch duration on the shear bond strength of an orthodontic bonding resin to enamel. An in vitro study.

The purpose of this in vitro study was to determine the effects of phosphoric acid (H3PO4) concentration and duration of etching on the shear bond strength of an orthodontic bonding resin to enamel. Nine bonding procedures, each involving 18 extracted human maxillary permanent canines, were used. Ground enamel surfaces were etched with a 37% H3PO4 solution, a 15% H3PO4 gel, or a 5% H3PO4 solution for 60, 30, and 15 seconds, respectively. Cylinders of an orthodontic bonding resin, Concise, were prepared in a special device. The test specimens were disassembled 15 minutes after preparation and stored in distilled water at 37 degrees C for 24 hours. A shear load was applied to the bonded cylinders at a crosshead speed of 0.02 in.min-1 in an Instron testing machine, and the shear bond strengths were calculated and expressed in MN.m-2. A two-factor analysis of the data showed that the H3PO4 concentration had no significant effect on the shear bond strength, but the duration of etching affected shear bond strength significantly. The enamel aspects of the fractured test specimens were examined microscopically and the percent failure within the bonding resin at the bonding sites estimated. The correlation between shear bond strength and percentage failure within the bonding resin was not significant. The effects of the nine etching procedures on ground and unground enamel surfaces were studied by scanning electron microscopy. The etching procedures produced well-defined etching patterns on both ground and unground enamel surfaces.

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

Adhesion to enamel and dentin.

The physical and chemical properties of restorative materials and procedures that influence the extent of microleakage at the tooth/restoration interface are discussed. Adhesion to enamel is achieved and microleakage at the enamel/restoration interface has been controlled by acid etching enamel surfaces with orthophosphoric acid. The acid concentration and the duration of etching are reviewed. Adhesion to dentin and microleakage at the restoration/dentin (cementum) interface are more difficult. The development of dentin bonding agents and the tremendous advances made with these restorative systems are reviewed. Particular attention is directed towards the Gluma/Lumifor dentin bonding restorative system and the development of an experimental conditioning solution for both enamel and dentin.

Characterization of liposome suspensions by flow cytometry.

Novel approaches to drug delivery and induction of immune responses using liposomes have received much attention in recent years. Liposomes, however, are not a singular entity, but can be produced with a diverse group of phospholipids that form microspheres of different sizes, physical structure, electrochemical characteristics, and most importantly, physiologic properties. The purpose of this study was to establish the usefulness of flow cytometry as a convenient, rapid method for assessing the relative size and uniformity of liposomal preparations. Liposomes were made from phospholipid suspensions by sonication alone, or sonication followed by microemulsification. Forward laser light scatter (FSC) analysis of liposomal preparations by flow cytometry indicated that microemulsification produced homogeneous, small vesicles which were less than 1 micron in diameter, compared to the more heterogeneous sized liposomes generated by sonication alone. Transmission electron micrographs of the liposomal preparations were used to confirm the FSC results and showed that liposomes prepared by microemulsification were homogeneous, unilamellar vesicles which exhibited a mean diameter of 99.8 nm, whereas the sonicated-only preparation was more heterogeneous in size, exhibiting a mean diameter of 154.1 nm. Analysis of various liposome preparations by FSC during a 9 week storage period showed that small vesicles were relatively stable. We conclude that flow cytometry using FSC analysis provides a rapid, reproducible and convenient method to evaluate the relative size, uniformity and stability of liposomes.