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Biomedical subjects

J F McCabe

Publications and source records attributed to J F McCabe.

At least 55 records · Page 3Linked to original sources
PubMed1997

Wear rates of regular and tempered composites.

OBJECTIVES: One of the reasons for using composite inlays is that restorations can be tempered. Composites tempered with heat and light have, at least initially, an enhanced degree of cure which, it is claimed, improves their physical properties, including wear resistance. The aim of this study was to compare the wear rates of a selection of composites in their regular and tempered conditions. METHODS: Two hybrid composites (Brilliant Dentin, Coltène; Occlusin, ICI) and a microfilled material (Heliomolar, Ivoclar-Vivadent) were chosen to provide a variety of filler particle and resin systems. Regular composites were cured normally with light while tempered composites were given an additional 8 min secondary cure at 120 degrees C in the Coltène DI500 heat and light oven. Specimens of an amalgam (Dispersalloy, Johnson & Johnson) and a heat/pressure cured composite (Isosit, Ivoclar-Vivadent) were used for comparison. The specimens were stored for either 7 days or 1 year to determine if prolonged water storage affected wear rate. Wear testing was carried out in a two-body wear machine using a steatite abrader as an enamel substitute. ANOVA was used to test the effects on wear rate of tempering, storage time and type of material. RESULTS: Significant differences were found in wear rate between materials (p < 0.001), but not for tempering or prolonged storage time. CONCLUSION: These findings agree with clinical studies which have shown that tempering has little or no influence on the occlusal wear of composite inlays.

Acrylic Resins↗
PubMed1997

In vitro toothbrush-dentifrice abrasion of resin-modified glass ionomers.

OBJECTIVES: This study was conducted to compare the rate of abrasive wear and change in surface roughness of resin-modified and conventional acid-base glass ionomers when subjected to toothbrush-dentifrice abrasion. METHODS: Two resin-modified and two conventional glass ionomers were used. Samples of a high-copper amalgam and a hybrid resin composite were used as reference materials. Specimens of each material were prepared and subjected to toothbrush-dentifrice abrasion using 20,000 strokes of brushing. The amount of vertical loss of material was determined by profilometry (Surfcom-4A, Tokyo-Seimitsu, Tokyo, Japan). The surface characteristics after abrasion were evaluated on secondary electron images by SEM, and the surface hardness (KHN) was also measured for all materials. Data were analyzed by one-way ANOVA (p < 0.05), followed by a multiple comparisons test using LSD (Least-significant difference) at a level of p < 0.05. RESULTS: The abrasion resistance of resin-modified glass-ionomers was statistically lower for the amalgam and the resin composite reference materials. Statistically lower abrasion resistance and surface hardness were observed for the resin-modified glass ionomers than for their conventional acid-base counterparts when two forms of products from the same manufacturer were compared. SEM observations made after abrasion testing showed a significantly rougher surface for all glass ionomer materials than for the amalgam and the resin composite. SIGNIFICANCE: When comparisons were made between products from the same manufacturers, it was found that in vitro resistance to toothbrush-dentifrice abrasion of the resin-modified glass ionomers is inferior to that of the conventional acid-base glass ionomers. The lower abrasion resistance found in the resin-modified products appears to be related to their lower surface hardness.

Aluminum Hydroxide↗
PubMed1997

The determination of working time and gelation time of temporary soft lining materials.

OBJECTIVE: The purpose of this study was to establish a new method for the determination of working time and gelation time of temporary soft lining materials using a displacement rheometer. METHOD: A displacement rheometer (The Dental School, University of Newcastle, Newcastle upon Tyne, UK) was used to apply a rapid displacement of 0.25 mm held for 1 s at intervals of 60 s to samples of four temporary soft lining materials. Material displacement and elastic recovery at each test time was recorded. The test procedure was repeated three times at 23 degrees C and at 37 degrees C for each material. For one material, the displacement time was varied (1, 5, 10 s). The working time was defined as the time corresponding to the initial observation of elastic recovery at 23 degrees C. Gelation time was the time when a material achieved 95% of its maximum elastic recovery at 37 degrees C. Values were compared between materials using one-way analysis of variance and Student-Newman-Keuls test at the 5% level of significance. RESULTS: The gelation rate of all materials increased with increasing temperature although the extent of this influence varied between materials. The development of elastic recovery in the materials during gelation accurately fitted asymmetric sigmoids. The correlation coefficient (r) ranged from 0.982 to 0.999. Statistically significant variations in both the working and gelation times of the test materials were established. The time of displacement affected both the rate of development of elasticity and the value of elastic recovery but this effect was only statistically significant when the displacement time was increased to 10 s. SIGNIFICANCE: The displacement rheometer may be suited for use as a standard test method for the determination of the working time, gelation time and elastic behavior of temporary soft lining materials.

Acrylic Resins↗
PubMed1997

Bonded orthodontic retainers: the wire-composite interface.

The bonded orthodontic retainer constructed from multistrand wire and composite is an efficient esthetic retainer, which can be maintained long-term. Clinical failures of bonded orthodontic retainers, most commonly at the wire/composite interface, have been reported. This in vitro investigation aimed to evaluate selected multistrand wires and composite materials that are available for use in the construction of bonded fixed retainers. An in vitro model was developed to simulate the forces encountered at the wire/composite interface. No significant difference was detected between different multistrand wire types and diameters with regard to retention in composite. Wires were placed in one of three groups according to surface characteristics identified with scanning electron microscopy. Increasing the thickness of composite overlying the wire increased the force required to detach the wire from the composite. Thickness of composite greater than 1.0 mm overlying the wire may give little clinical advantage. Greater force was required to detach the wire from Concise Orthodontic (3M Unitek) than any other composite tested. In vitro abrasion resistance testing found Heliosit Orthodontic (Vivadent) and Right On (TP Orthodontics, Inc.) to have poor abrasion resistance, whereas Concise Orthodontic and Transbond (3M Unitek) had abrasion resistance comparable with restorative composites. Clinical recommendations are made based on these findings.

Adhesiveness↗
PubMed1997

Experimental wax mixtures for dental use.

Improvements in the properties of dental waxes were sought by alterations in their composition. Twenty-six blends of paraffin wax, beeswax and inorganic filler were subjected to the following tests: plastic deformation (flow), linear thermal expansion, elastic modulus and flexural strength. Flow tests were conducted in accordance with the corresponding ISO specification. Thermal expansion coefficients were estimated using thermomechanical analysis. Mechanical properties were tested using a universal testing machine. Pure paraffin and beeswax were used as controls. The results were subjected to analysis using correlation and regression. Regression coefficients in the range of 0.90-0.99 were obtained in most cases, flow tests exhibiting the highest coefficients and flexural strength the lowest. The incorporated filler particles reduced the flow of the natural waxes, especially of the ester-containing beeswax, and improved the elastic modulus and strength. Good correlation was found between the ingredient proportions and measured properties, suggesting a relationship between them, although this is quite complicated in the case of tertiary wax mixtures. The experimental blends exhibited properties that are potentially useful for a range of clinical applications.

Chemical Phenomena↗
PubMed1997

Incorporation of antibacterial monomer MDPB into dentin primer.

The polymerizable monomer methacryloyloxydodecylpyridinium bromide (MDPB) shows antibacterial activity when immobilized in a resin-based material. In this study, the antibacterial effect of a dentin primer incorporating MDPB was investigated. The influence of incorporation of MDPB on bond strength to dentin and on the curing performance of the adhesive system was also evaluated. Experimental primers were prepared by addition of MDPB into a proprietary primer at 1, 2, or 5%. Antibacterial effects of experimental primers were compared with those of control primer and two other proprietary primers by an agar disc-diffusion method and bactericidal activity test. Experimental primers produced greater inhibition zones against Streptococcus mutans, Actinomyces viscosus, and Lactobacillus casei than any of three proprietary primers, and inhibition increased as the concentration of MDPB was increased. Bactericidal activity of MDPB-containing primers against Streptococcus mutans was greater than those of the other three primers, with incorporation of MDPB at 5% showing complete killing of bacteria after 30 s contact. No decrease in tensile bond strength was observed for materials containing MDPB. On the contrary, the primer incorporating 1 and 2% MDPB showed higher bond strength than all the others, including the control (p < 0.05). When the degree of conversion of the complex of primer and adhesive resin was determined with Fourier Transform Infrared Spectroscopy, there were no significant differences between any of the experimental primers and the control (p > 0.05). These results indicate that incorporation of the antibacterial monomer MDPB enhanced the antibacterial effect of a proprietary dentin primer before curing, and had no adverse influence on bond strength to dentin and curing of the adhesive system.

Actinomyces viscosus↗
PubMed1996

A clinical comparison of a light cured glass ionomer sealant restoration with a composite sealant restoration.

OBJECTIVE: To compare the durability of a minimal composite sealant restoration (MCR) with that of a glass ionomer sealant restoration (GSR). METHODS: Under local anaesthesia, a MCR and a GSR were placed in the mouths of selected patients; allocation of restoration type was made randomly. All restorations were placed by one operator using standard procedures and were then assessed clinically at baseline and thereafter every 6 months. RESULTS: Fifty-eight patients, with a total of 66 pairs of restorations, were reviewed for up to 27 months. Assessment criteria were based upon the amount of sealant lost, the state of the pit restoration and the occurrence of caries. There were no cases of recurrent caries, and a total of only four pit restorations failed, three (4.5%) GSRs and one (1.5%) MCR. Three MCRs and seven GSRs required further additions of sealant. Survival analysis was carried out using the loss of more than a third of the sealant as the failed status. At this level, the MCRs had a significantly greater Median Survival Time (MST) (24.7 months) than the GSRs (20.7 months) (p < 0.05). Only seven (10.6%) of the MCRs lost more than a third of their sealant as compared with 17 (25.8%) of the GSRs. CONCLUSIONS: There was no significant difference in the durability of the MCR compared with the GSR in the treatment of occlusal caries. However, there was significantly better retention of the fissure sealant over the composite restoration than over the glass ionomer.

Adolescent↗
PubMed1996

The influence of immersion solutions on the viscoelasticity of temporary soft lining materials.

OBJECTIVES: The purpose of this study was to examine the influence of laboratory immersion in a number of solvents on the viscoelasticity of temporary soft lining materials. It was an initial attempt to reproduce the changes seen clinically with a view to formulating more clinically relevant immersion regimes for the evaluation of these materials. METHODS: Changes in the viscoelasticity of four temporary soft lining materials following immersion at 37 + or - 1 degree C in 10% acetone/90% water, 20A% acetone/80% water and hexane was compared to a control immersion in distilled water using a penetrometer modified to record creep strain and strain during recovery. Testing was performed at 2 h and 24 h and then at 2, 4, 7, 21 and 28 d after sample preparation. Summary measures were used to describe individual specimen changes in derived values of initial and time dependent compliance and elastic recovery from 0-7, 7-28 and 0-28 d. RESULTS: Immersion in hexane resulted in at least a 50% reduction in compliance of 28 d. There was a significantly greater reduction in compliance for hexane immersion than for any other solvent (p<0.01). Immersion in 20% acetone resulted in an increase in compliance of around 1 mm/N after 1 wk compared with a reduction of up to 1 mm/N in distilled water. There was a reduction in elastic recovery for 3 out of 4 materials with 20% acetone/80% water solution. Changes in elastic recovery were smaller than those of compliance. SIGNIFICANCE: The reduction in compliance with hexane immersion suggests that this, or similar solvents, may form the basis of more clinically relevant immersion regimes. This may contribute to the development of improved temporary soft lining materials.

Acetone↗
PubMed1996

Bonding of composite to bone: durability and effect of drying time.

This paper describes a further step in the evaluation of dentine-bonding agents as a means of securing fixation devices to bone. This screening study investigated the durability and effect of bone drying time on the bond strength obtained between composite and bone using the dentine-bonding agent All-bond 2. The strength of bond obtained after air-drying bone for 1 sec did not alter significantly over a 6-week period. However, the bond strength became significantly poorer over the 6-week period in bone which had been air-dried for 1 min.

Analysis of Variance↗
PubMed1996

Orthodontic bonding with glass ionomer cement--a review.

Orthodontic bonding with glass ionomer cement is comparatively new. The purpose of this article is to review the current literature covering both in vitro and in vivo studies of various glass ionomer cements that have been used for orthodontic bonding. The review indicates that there is little support in the literature to suggest that the currently available conventional glass ionomer cements are suitable for routine clinical use in orthodontics. Dual- or tri-cured hybrid materials, however, comprising both glass ionomer and resin components, appear to have greater potential with regard to clinical performance.

Dental Bonding↗
PubMed1996

Waxes for functional impressions.

The aim of this study was to develop a wax suitable to serve as a functional impression material. Several binary mixtures of paraffin, beeswax and rosin were prepared. They were characterized by differential thermal analysis (DTA), and tested for plastic deformation, thermal expansion, detail reproduction and mechanical properties. It was found that the combinations of paraffin with rosin can function well as impression materials, as they combine a high value of plastic deformation at 37 degrees C with relatively low values at room temperature. Concentrations of rosin as small as 1% or 2% are adequate to produce this result. The flow of paraffin was significantly reduced by the addition of beeswax. A linear relationship was found between the 37 degrees C flow values of paraffin-beeswax mixtures and the proportions of the ingredients.

Dental Impression Materials↗
PubMed1996

A method for scoring denture plaque.

Many studies have reported on the comparative efficiency of denture cleaning materials in their ability to remove deposits from dentures, but because of the variety of scoring methods used it is often difficult to make direct comparisons between materials. It is important that any measurements obtained should not only be accurate, reliable and reproducible but that inter-examiner error should be kept to a minimum. In this work three operators were asked to score 'blind' the total amount of disclosed plaque on a whole denture using a 0-10 scale. The overall conclusions of this test was that of poor inter-examiner agreement. A second test was therefore undertaken at a later date using the same three operators and protocol but on this occasion each surface of the denture was evaluated by reference to a series of standard reference dentures painted to simulate plaque scores in the 0-10 range. This test showed there to be no significant difference in the plaque scores recorded by the three operators and that the plaque scores recorded on the polished surfaces were significantly lower than those on the teeth and fitting surfaces (F = 10.55, P < 0.001).

Aged↗
PubMed1996

The development of a simple test method to characterise the compliance and viscoelasticity of long-term soft lining materials.

A simple test, based on the measurement of depth of penetration, has been devised to characterise long-term soft lining materials. Inter-laboratory testing has shown the method to be reproducible and to be capable of comparing and contrasting the compliance and viscoelastic behaviour of commercially available materials. Additional results emphasise the point that it is imperative to control the testing temperature, especially for the soft acrylic materials.

Acrylic Resins↗
PubMed1995

Direct composite inlays versus conventional composite restorations: three-year clinical results.

A clinical trial of direct composite inlays versus conventionally (incrementally) placed restorations made from the same material was started in January 1989. Restorations were randomly allocated to matched pairs of cavities. This study reports the 3-year performance of 71 of the 100 pairs of restorations placed over a 2-year period and followed-up every 6 months. Clinical assessments were made using USPHS criteria (indirect measurements of occlusal wear were made using Ivoclar standard dies) and annual bite wing radiographs. Direct inlays showed significantly less occlusal wear than conventional restorations, but the difference was small. The clinical performance of both types of restoration was similar and compared favourably with studies of other materials. No secondary decay was diagnosed. The direct inlays, however, took longer to place and did not reduce postoperative sensitivity or failure rate (8% failure of inlays and 4% of conventional composites over 3 years). Contouring of proximal and occlusal aspects was not facilitated with direct inlays but may be easier with indirect inlays on removable dies.

Adult↗
PubMed1995

Porcelain veneers: the effects of contaminants and cleaning regimens on the bond strength of porcelain to composite.

An in-vitro study was carried out to investigate the effects of contamination of the porcelain surface on the shear-bond strength of a dual-cure composite luting cement to etched, silanated porcelain. Furthermore, the effects of different cleaning regimens were studied. A total of 390 etched, silanated porcelain specimens were randomly divided into 13 groups of 30. Shear-bond strengths were measured for a control group and for specimens contaminated with saliva, die stone, and latex gloves. Freshly contaminated samples were subject to three cleaning regiments; water wash and dry, cleansing with acetone, and cleansing with 37% phosphoric acid gel. Bond strengths to the cleansed surfaces were measured. Weibull analysis and analysis of variance were applied to the results. Saliva and latex glove contamination did not significantly affect shear-bond strength. Die stone contamination markedly reduced the bond strength and cleaning did not restore the bond strength for these specimens. Contact between porcelain veneers and stone models should therefore be avoided. The wash/dry and phosphoric acid cleaning regimens did not significantly improve or reduce bond strengths for contaminated specimens. Acetone cleaning produced a marked reduction in bond strength under all experimental conditions and should not be used.

Acetone↗
PubMed1995

The use of a reinforced glass-ionomer cermet for the restoration of primary molars: a clinical trial.

The development of adhesive restorative materials has led to more conservative cavity design with greater reliance being placed upon the bond of a material with tooth tissue for retention of the restoration. Glass-ionomer cements may offer particular advantages but have yet to achieve the durability reported for amalgam. This study reports on the results of a 2.5-year prospective clinical trial comparing the durability of two glass-ionomer cements, a conventional material (Ketac Fil) and a metal reinforced cermet (Ketac Silver) in the restoration of Class II lesions in primary molars. Forty-six pairs of restorations were assessed in 37 children. The failure rate of Ketac Fil, 23%, was significantly lower than that of Ketac Silver, 41% (P < 0.05). The median survival time of the Ketac Fil restorations was significantly greater, 25.3 months, than that of the Ketac Silver restorations, 20.3 months (P < 0.05). These values may be an underestimate of the true longevity of both restoration types as many of the restorations survived intact at the censor date. Neither the age of the child nor the tooth restored influenced the durability of the restoration. The deterioration in both marginal integrity and anatomic form of the Ketac Silver restorations was significantly greater than the Ketac Fil restorations (P < 0.05). The durability of Ketac Silver was such that it cannot be recommended for use in restoring carious primary molars.

Cermet Cements↗
PubMed1995

The physical properties of a gallium alloy restorative material.

OBJECTIVES: This study was conducted to compare the physical properties of a gallium alloy restorative material and a widely used mercury-containing dental amalgam. METHODS: Although the specimens were not prepared according to ISO specifications, specimens of both materials were subjected to ISO standard (ISO 1559; 1986) tests. The results were analyzed by ANOVA, Mann-Whitney U test and Student's t-test. RESULTS: The gallium alloy showed setting expansion which was greater than that for the other amalgam and greater than the upper limit set by the ISO standard. For other properties, gallium alloy performed as well as, and in the case of creep, was superior to that of the amalgam. SIGNIFICANCE: The gallium alloy proved difficult to manipulate even when using the PTFE coated instruments recommended by the manufacturer. It is suggested that while the material may prove to be a viable alternative to conventional dental amalgam, a considerable improvement in its handling characteristics would be required before it would gain widespread acceptance for clinical use.

Alloys↗