Biomedical subjects

R P Chappell

Publications and source records attributed to R P Chappell.

At least 19 recordsLinked to original sources

PubMed1998

Microtensile testing of dentin adhesives.

OBJECTIVES: This study was conducted in order to compare the microtensile and shear bond strengths of five commercial dentin adhesive systems. Scotchbond Multipurpose with maleic acid (SM), Scotchbond Multipurpose with phosphoric acid (SP), Scotchbond Multipurpose Plus (SBP), Clearfil Liner Bond System (CL), and Prime and Bond (PB) were tested. METHODS: Thirty extracted unerupted third molars, in groups of six teeth per adhesive system, were prepared for microtensile testing. The specimens were tested following a 24 h incubation at 37 degrees C in normal saline. Shear bond testing was performed on 35 additional teeth, using seven teeth per adhesive system. After testing, the fracture sites were observed using light microscopy and a scanning electron microscope to determine the type of failure involved. RESULTS: The microtensile test results (mean +/- SD) were SM, 24.6 +/- 7.2 MPa; SP, 28.8 +/- 11.8 MPa; SBP, 22.7 +/- 6.5 MPa; PB, 25.5 +/- 9.4 MPa; and CL, 36.8 +/- 10.0 MPa. A Bonferroni post-hoc test showed significantly (p < 0.05) greater strength for CL compared to SM, SP, SBP, and PB. The shear bond strength test results were SM, 19.4 +/- 4.4 MPa; SP, 24.5 +/- 8.4 MPa; SBP, 15.3 +/- 4.9 MPa; PB, 23.2 +/- 7.1 MPa; and CL, 24.8 +/- 3.5 MPa. No statistically significant differences were found among the shear bond strength test results. The shear bond test produced significantly more failures within dentin and composite than the microtensile method. SIGNIFICANCE: It is concluded that the microtensile test produced a more definitive assessment of adhesive bond strength than the shear bond test. Microtensile testing showed CL to be significantly stronger than SM, SP, SBP, and PB (p < 0.05).

Analysis of Variance↗

PubMed1995

Scanning transmission electron microscopy/energy-dispersive spectroscopy analysis of the dentin adhesive interface using a labeled 2-hydroxyethylmethacrylate analogue.

In an attempt to compare the morphology of the dentin adhesive interface and the wetting and penetration of the adhesive in relation to the dentin surface, we studied four dentin adhesive systems using scanning transmission electron microscopy (STEM) and energy-dispersive spectroscopy (EDS). 2-Hydroxyethylmethacrylate (HEMA), a monomer common to many commercial dentin adhesive systems, was altered to produce a thiolated analogue (HETMA). Sulfur, traceable by EDS and STEM, was substituted for the oxygen atom in the backbone of the HEMA molecule. The resulting analogue, with solubility parameters and other wetting and physical properties very similar to those of HEMA, was applied to four sets of tooth specimens, each pre-treated with a different primer or etchant. Three separate pre-treatments--nitric acid, maleic acid, and citric acid/ferric chloride--created a demineralized zone approximately 1 to 3 microns thick at the dentin surface. The HETMA was found to permeate freely into this zone when either of the latter two pre-treatments was used. However, the band of dentin that was demineralized by the nitric acid pre-treatment appeared impermeable to the HETMA. The fourth pre-treatment, an alcohol-based solution including the phosphorus acid ester PENTA and HEMA, modified the smear layer of the tooth slightly and did not appear to demineralize the dentin. HETMA applied to the specimens pre-treated with PENTA and HEMA was clearly in intimate contact with the dentin or modified smear layer; however, it did not penetrate or diffuse into these areas. It did flow into the dentinal tubules, as was also evident with each of the other systems. It was concluded that the acid pre-treatment of the dentin greatly influenced the wetting behavior of the dentin adhesive and thus could substantially affect the resultant bond strength of the dentin adhesive systems.

Acid Etching, Dental↗

PubMed1995

Surface morphology and chemical characterization of abrasion/erosion lesions.

PURPOSE: To describe the dentin surface morphology of abrasion/erosion lesions and to chemically characterize in vivo samples of sclerotic dentin. MATERIALS AND METHODS: Baseline polyvinylsiloxane impressions of eight in vivo caries-free lesions were taken. Dentin was collected from retention grooves for FTIR photoacoustic spectroscopic analysis. The cavity preparation was etched for 30 seconds with 37% phosphoric acid, rinsed, and dried. Impressions were taken of the etched surfaces. Epoxy resin dies were made of baseline and etched impressions, sputter-coated and examined at x1000 with the SEM. RESULTS: Lateral dentin tubule orientation was observed at gingival margins and on occlusal walls. Open cross-sectional tubules were seen at the depth of the groove. The mineral/protein ratio in the FTIR/PAS spectra of in vivo unetched sclerotic dentin samples suggested an increased mineral content.

Acid Etching, Dental↗

PubMed1995

Marginal ridge strength of Class II tunnel restorations.

PURPOSE: To test the strength, at the marginal ridge, of the tunnel preparation vs the Class II traditional box preparation when restored with composite or glass ionomer (GI). MATERIALS AND METHODS: Eighty-four extracted maxillary molars stored in normal saline and thymol were randomly divided into six groups of 14 each (determined by pilot study where alpha = 0.05, beta = 0.2). Group A and C were tunnel preparations. Group B and D were traditional Class II preparations. Group E-whole tooth (negative control), and Group F-tunnel preparation unrestored (positive control). Group A and B were restored with Scotchbond 2/P-50 composite. Group C and D were restored with Ketac Fil-GI. The marginal ridge of each tooth was loaded at 0.5 mm/minute on the Instron. A loading rod produced a contact point of 1.0 mm in diameter. RESULTS: The mean compressive loads (kg) required for fracture were: (A): 42.2 +/- 11.9, (B): 53.1 +/- 10.7, (C): 52.0 +/- 10.9, (D): 23.8 +/- 8.4. (E): 79.1 +/- 16.1, (F): 27.0 +/- 10.6. A significant difference was found between whole teeth (E) and all other groups (P < 0.05). The Newman-Keuls test showed a significant difference between Class II composite (B) and tunnel composite (A) (P < 0.05), between tunnel GI (C) and tunnel composite (A) (P < 0.05) but no difference between tunnel GI (C) and Class II composite (B).

Analysis of Variance↗

PubMed1994

Dentinal tubule anastomosis: a potential factor in adhesive bonding?

This study investigated adhesive tag formation within dentinal tubules and the anastomosing of lateral canals observable with scanning electron microscopy. This mechanism of micromechanical bonding had not been studied previously. The following brands of adhesives were applied to the prepared dentin surface of unerupted human third molars: Scotchbond Multipurpose, C&B Metabond, All-Bond 2, both etched and unetched, Tenure Solution, and XR-Bond. The experimental specimens were decalcified and prepared for SEM examination. Many tubule resin tags with lateral branching were observed. The resin branches were the result of primer, adhesive, or both entering lateral canals and communicating with adjacent tubules. The polymerization of adhesive in lateral canals was more prevalent with Scotchbond Multipurpose, C & B Metabond, and etched All-Bond 2 adhesives. The network of interconnected adhesive tags formed with these materials may be fundamental to the development of a stronger dentin/resin bond.

Acid Etching, Dental↗

PubMed1994

Shear strength of ceramic brackets bonded to porcelain.

The purpose of this study was to compare the bond strengths of three different adhesive systems when used alone and combined with a porcelain priming agent to bond ceramic brackets to porcelain surfaces. Sixty porcelain specimens were randomly assigned to the six different treatment groups. Half were bonded with the porcelain priming agent and one of the adhesive systems and the other half with one of the adhesive systems alone. The shear bond strengths of all specimens were tested, with an Instron testing machine, 10 minutes after being bonded. The surface of the porcelain and the bracket base were examined, with scanning electron microscopy (SEM) and qualitative energy dispersive x-ray analysis (EDS), to determine the bond failure patterns and to check the porcelain surface for the presence of cracks and fractures. There was a statistically significant difference within each adhesive between those samples with the priming agent and those without the priming agent. Differences between the three adhesives were not statistically significant (p < or = 0.05).

Acid Etching, Dental↗

PubMed1994

The effects of current dentinal adhesives on the dentinal surface.

The effects of the dentinal surface treatments from six currently available commercial dentinal adhesives are presented. The adhesives are All-Bond 2, etched and unetched, Syntac, Prisma Universal Bond 3, Scotchbond Multipurpose, Tenure Solution, and Adhesive By Choice. Unerupted third molar human teeth were sectioned and treated with the appropriate adhesive according to the manufacturer's directions. After the teeth were treated, they were processed for observation by scanning electron microscopy. Scanning-electron microscopic photomicrographs were made of each step in the process to show the effects of the constituents, including the adhesives, on the dentinal surface. For All-Bond 2, unetched, the smear layer was not removed before the primer and the adhesive were applied. The primer for Prisma Universal Bond 3 altered the smear layer by reacting with it but did not produce a large demineralized zone in the dentin. All the other adhesives did remove the smear layer before the tooth was treated with the primer and adhesive.

Acid Etching, Dental↗

PubMed1994

Shear bond strength and scanning electron microscopic observation of six current dentinal adhesives.

This paper presents shear bond strength data and scanning electron photo micrographs of six dentinal adhesives: All-Bond 2, etched and unetched; Syntac; Prisma Universal Bond 3; Scotchbond Multi-Purpose; Tenure Solution; and Adhesive By Choice. The methods used in tooth treatment and scanning electron microscopic observation were identical to those used in previous studies. This permitted comparisons among a total of 13 dentinal adhesives (seven from previous studies), all treated under the same experimental conditions and all currently available to the practitioner. Scanning electron micrographs showed the types of failures that occurred when the composite resin was fractured from the dentin. Most of the fractures were adhesive, with the exception of Scotchbond Multi-Purpose, which had many cohesive failures in the dentin or the composite resin. There was no significant difference among any of the shear bond strength values with the exception of Scotchbond Multi-Purpose, which was significantly stronger than the other five adhesives studied.

Analysis of Variance↗

PubMed1993

Properties of expanding SOC/epoxy copolymers for dental use in dental composites.

The objective of this work was to develop copolymers of alicyclic spiroorthocarbonates (SOCs) and epoxies that would yield hard non-shrinking matrix resins suitable for formulating dental composites. Several reactant ratio combinations of a four-component SOC/epoxy comonomer system were developed that demonstrated a copolymer expansion of between 0.1 and 0.8% on polymerization. The physical properties of tensile strength (29-48 MPa), water solubility of less than 5 microgram/mm(3), and water sorption of less than 50 microgram/mm(3) for the copolymer containing 5% SOC suggest that these materials have potential as matrix resins for dental composites.

Carbonates↗

PubMed1993

Effects of air-powder polishing on the bond strength of orthodontic bracket adhesive systems.

PURPOSE: The purpose of this in vitro investigation was to evaluate the effects of air-powder polishing on the shear bond strength of two adhesive systems used for direct orthodontic bracket bonding. METHODS: Ninety-six third molar teeth were randomly assigned to be bonded with metal brackets using either a no-mix (System 1+) or a two-paste (Concise) orthodontic adhesive resin. Twelve samples in each test group were air-powder polished for either 0, 15, 30, or 60 seconds. The shear bond strength was determined for each bracket using the Instron. Scanning electron microscopy determined bond fracture patterns of tested samples. RESULTS: Mean shear bond strength values from baseline to 60 seconds varied from 22.9+/-1.9 megapascal units (MPa) to 18.2+/-4.1 MPa for Concise and from 15.5+/-2.1 MPa to 14.6+/-1.9 MPa for System 1+. A two-factor analysis of variance showed air-powder polishing significantly affected the mean shear bond strength of one adhesive. Results showed a significant decrease (p < or = .05) in the mean shear bond strength of the Concise adhesive at 60 seconds of air-powder polishing when compared to the 0-, 15-, and 30-second treatments. No significant within group time effect of air-powder polishing was found for System 1+. Differences in the fracture pattern of the Concise 60-second air-powder polishing group may account for the decrease in mean bond strength seen after treatment. CONCLUSION: Although in vitro results showed decreased bond strength for Concise, these values were well above the minimum values needed for successful bonding. Therefore, use of air-powder polishing on orthodontic bracket adhesive systems does not appear to be contraindicated.

Bisphenol A-Glycidyl Methacrylate↗

PubMed1993

The dentinal surface: its influence on dentinal adhesion. Part III.

This final paper in a series of three uses transmission and scanning electron microscopy to compare the category III dentinal adhesive systems--those with shear bond strength values near or exceeding 17 MPa. Contemporary commercial dentinal adhesive systems such as Superbond and Scotchbond Multi-Purpose, chosen for their varied chemical pretreatments, are contrasted; a contemporary commercial system (Prisma Universal Bond 3) with characteristics of category I and II dentinal adhesives is also included for comparison. The shear bond strength values attained with most category III systems are high enough to cause cohesive failure of the dentin during bond strength testing. This result is attributed to a combination of factors that include effective wetting and penetration of the prepared dentinal surface as well as a tendency to leave collagen fibers at the adhesive-dentin interface in an apparently structurally intact state.

Boron Compounds↗

PubMed1992

The dentinal surface: its influence on dentinal adhesion. 2.

The first paper in this series presented a categorization of dentinal adhesive systems that was organized roughly according to chronology, chemistry, and shear bond strength values. Category I dentinal adhesives demonstrate the lowest shear bond strength values, approximately 5 to 7 MPa. Category II dentinal adhesives, including experimental ferric and aluminum oxalate pretreatments and two commercial products, demonstrate shear bond strength values between 8 and 14 MPa. This second category of dentinal adhesives is the subject of this paper. An attempt is made to draw a parallel between the penetrative ability of the adhesive (the wettability of the dentinal substrate) and the efficacy of the adhesive bond as determined by shear bond strength values. Category III dentinal adhesives will be discussed in another paper.

Adhesives↗

PubMed1991

Comparison of two-surface and multiple-surface scoring methodologies for in vitro microleakage studies.

Investigators differ on the use of a two-surface or multiple-surface scoring methodology in sectional microleakage studies. This study compared microleakage scores using both two-surface and multiple-surface scoring methods for two preparation types and two different dentin bonding agents. Twenty freshly extracted molars each received one box-shaped and one V-shaped restoration on the mesial or distal surface. Each restoration was cut occlusogingivally into four sections, yielding eight surfaces for scoring. Surfaces were marked to identify central (I), lateral (II), and end (III) locations, then scored by two calibrated raters. The Wilcoxon Matched-Pairs Signed-Rank Test showed a statistically significant difference (p less than or equal to 0.05) in median microleakage scores obtained by an end two- surface and multiple-surface evaluation for V-shaped preparations restored with Scotchbond 2, P-50. No other statistically significant comparisons were detected. Results suggest that microleakage may be more extreme at end surfaces and that these end surfaces should be scored so that an accurate microleakage value could be assigned to composite restorations.

Analysis of Variance↗

PubMed1991

The dentinal surface: its influence on dentinal adhesion. Part I.

Three categories of dentinal adhesive are proposed: category I includes adhesives with shear bond strength values between 5 and 7 MPa; category II includes dentinal adhesives with shear bond strengths between 8 and 14 MPa; and category III includes adhesives with shear bond strength values up to 20 MPa. In part I of this article, photomicrographs of the dentinal smear layer and three category I first-generation dentin-adhesive interfaces are presented. The photomicrographs show that the wetting and penetration of the first-generation dentinal adhesives were not adequate to produce high shear bond strengths. When the category I adhesives were tested for shear bond strength, failures occurred at the interface or in the resin adhesive. Future articles will explain wetting and adhesive performance of category II and III adhesives.

Acrylic Resins↗

PubMed1991

The effect of storage and thermocycling on the shear bond strength of three dentinal adhesives.

The purpose of this investigation was to evaluate the effects of time of storage and thermocycling on the shear bond strength of three dentinal adhesives. The shear bond strength of Mirage Bond was significantly greater than that of Scotchbond 2, which was significantly greater than that of Scotchbond Dual Cure (P less than or equal to .05). Thermocycling significantly lowered the shear bond strength of Scotchbond Dual Cure and Scotchbond 2, but not that of Mirage Bond (P less than or equal to .05). Time of storage did not affect the shear bond strength of the other adhesives, but Mirage Bond had a significantly greater shear bond strength after 1 month of storage (P less than or equal to .05). Scanning electron microscopic observations showed that the fracture patterns were all at the smear layer-adhesive interface for Scotchbond Dual Cure, the majority of the fractures were at the primer-adhesive interface for Scotchbond 2, and most of the fractures were cohesive in the bonding agent for Mirage Bond.

Analysis of Variance↗

PubMed1990

Marginal fit of porcelain-fused-to-metal and two types of ceramic crown.

The marginal fit of Dicor, Cerestore, and porcelain-fused-to-metal crowns was evaluated. Ten premolars free of caries were prepared for each type of restoration and crowns were made. The vertical marginal openings were measured before cementation, after cementation, and after thermocycling. There were statistically significant differences between all three test conditions in each type of crown, between Dicor and porcelain-fused-to-metal crowns after cementation and after thermocycling, and between Cerestore and porcelain-fused-to-metal crowns after thermocycling. All 30 cemented crowns were then embedded in acrylic resin for serial sections for measurement of absolute marginal openings. Statistically significant differences between Dicor and Cerestore crowns and between Cerestore and porcelain-fused-to-metal crowns were found. It was concluded that marginal openings increased after cementation and after thermocycling, and porcelain-fused-to-metal crowns had significantly better marginal fit than that of Dicor and Cerestore crowns.

Aluminum↗

PubMed1990

Fracture strength of Class I versus Class II restored premolars tested at the marginal ridge. I. Standard preparations.

Two groups of maxillary premolars with Class I cavities were prepared with one marginal ridge thickness to a width of 1.0 mm. One group was restored with amalgam and the other group with composite resin. Two groups of Class II cavities also were prepared and restored with amalgam and composite resin. The teeth in the four treatment groups were subjected to a centric load at the marginal ridge until fracture occurred. A two-factor analysis of variance revealed a statistically significant difference between the class of preparation (Class I preparations were weaker than were Class II preparations) but differences in strength between restorative materials (composite resin versus amalgam) and the interaction effect (class of preparation x restorative materials) were not found to be statistically significant (alpha = .05). A Newman-Keuls sequential range test found no statistically significant differences in strength between groups (alpha = .05). Fracture patterns were observed under scanning electron microscope. Fractures extended into the enamel and into the material in the Class I composite resin, Class I amalgam, and Class II composite resin restorations. Fractures extended only into the material in Class II amalgam restorations.

Bicuspid↗

PubMed1990

Fracture strength of Class I versus Class II restored premolars tested at the marginal ridge. 2. Cavosurface bonding and cavosurface plus internal enamel bonding.

The purpose of this study was to test the difference between the strength of the marginal ridge of extracted teeth with a Class I composite resin restoration and the strength of the marginal ridge of teeth with a Class II amalgam restoration with retention grooves. A statistically significant difference in fracture strengths was found among groups. No statistically significant difference was found among restored preparations, beveling technique, and restorative material. Statistically significant differences in fracture strength were found between the whole tooth group and treatment groups; between the whole tooth group and Class II amalgam restoration group; and between the unrestored tooth preparation group and all other tooth groups.

Acid Etching, Dental↗