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Biomedical subjects

J F McCabe

Publications and source records attributed to J F McCabe.

At least 73 records · Page 4Linked to original sources
PubMed1995

A comparison of the bond strengths of two different dentine-bonding agents to bone.

PURPOSE: This study was performed to test the bond strength obtained between composite and bone using two different dentine-bonding agents. MATERIALS AND METHODS: P50 composite was bonded to 60 specimens of pig calvarium using All bond 2 (Bisco, Itaska, IL) or A.R.T. bond (Coltene, Altstatten, Switzerland) dentine-bonding agents. The bonds were tested to failure in an Instron Universal Testing machine (High Wycombe, UK) and the bond strength calculated. Data were analysed using the Weibull distribution. RESULTS: All-bond 2 and A.R.T. bond produced mean bond strengths of 8.5 MPa and 8.4 MPa, respectively, in the model used. The Weibull moduli were 2.4 and 2.1, respectively. CONCLUSIONS: There was no significant difference in the performance of the adhesives tested when used to bond composite to bone. The bond strengths obtained give rise to some optimism over the possible use of these systems in bone fracture fixation.

Animals↗
PubMed1995

A comparative study of three dental adhesives.

The shear bond strengths of three dental adhesives to dentine and a NiCrBe alloy were determined. Forty human third permanent molar teeth were ground to expose superficial dentine, to 20 of which P50 composite was bonded, using All-Bond 2 (n = 10) or Scotchbond 2 (n = 10). Alloy discs were bonded to the remaining 20 specimens, using either All-Bond 2 (n = 10) or Panavia Ex (n = 10). All specimens were stored at 37 degrees C. 100% RH, for 24 h. Testing was carried out using a shear jig at a cross-head speed of 1 mm min-1, following which a 0.5 mm increment was removed to expose middle dentine for further bond tests (n = 10 for each adhesive). Removal of a further 0.5 mm increment exposed 'deep' dentine for final dentine bond strength tests. Results were then aggregated for each substrate/adhesive combination (n = 30). Alloy/alloy bond strengths were determined after bonding alloy discs together using Panavia Ex (n = 30) or All-Bond 2 (n = 30). Results were analysed using ANOVA and Weibull analysis. All-Bond 2 produced significantly greater and more reliable bond strengths to dentine than did either Scotchbond 2 or Panavia Ex. The bond strength of Scotchbond 2 and Panavia Ex to dentine was dependent upon the dentine depth whereas the bond strength of All-Bond 2 to dentine was independent of dentine depth. Alloy/alloy bond strengths were significantly greater when using Panavia Ex compared with All-Bond 2.

Acid Etching, Dental↗
PubMed1995

Antibacterial activity of MDPB polymer incorporated in dental resin.

OBJECTIVES: Previously, we have reported that dental composite incorporating the new monomer methacryloyloxydodecylpyridinium bromide (MDB) showed no release of antibacterial components after being cured but still exhibited antibacterial activity against Streptococcus mutants on its surface. In this study, in order to elucidate the mechanism of the antibacterial effect of immobilized MDPB, the bactericidal activity of MDPB polymer in water-soluble and -insoluble form was investigated, and the effect of MDPB polymer on bacterial attachment was estimated. METHODS: Solutions of homo-polymer of MDPB and co-polymer of MDPB with acrylamide were prepared and the viability of seven major oral streptococci was determined after incubation with each polymer solution. For the estimation of bactericidal activity of insolubilized MDPB polymer, bacteria were kept in contact with cured unfilled Bis-GMA-based resin discs with or without MDPB, and the recovery of viable cells was measured. Attachment of streptococci to cured resin discs with or without MDPB was also compared using radiolabelled bacteria. RESULTS: Water-soluble homo-polymer of MDPB and co-polymer with acrylamide showed bactericidal activity against oral streptococci. However, cured resin incorporating MDPB, which is in water-insoluble form, had little bactericidal activity. Attachment of streptococci, including species which are early colonizers in dental plaque formation, to the cured resin containing MDPB was significantly less than to the control without MDPB. CONCLUSIONS: These results indicate that the bactericidal activity of MDPB polymer is reduced after immobilization, but MDPB on the surface of a resin-based material still shows a bacteriostatic effect and antiadhesion property against oral streptococci.

Analysis of Variance↗
PubMed1995

A new temporary soft lining material.

The viscoelastic properties of a new light-activated temporary denture soft lining material have been monitored in vitro using a force/distance probe. Its baseline behaviour was characteristic of an elastic material and its compliance considerably less than that of both a short-term and a long-term soft lining material which were used as controls. Sample thickness had no appreciable effect on this compliance. These results suggest that the new product is likely to be perceived as being significantly harder by a patient. Twenty-four weeks' immersion in distilled water had no significant effect on either the compliance or elasticity of the test material and would suggest an improved durability when compared to other conventional short-term resilient denture lining materials, albeit at the expense of compliance.

Compliance↗
PubMed1995

Stability of dental waxes following repeated heatings.

The flow and strength properties of dental waxes were examined following excessive and repeated heatings of the materials. For one product, the flow at 40 +/- 0.5 degrees C was reduced by 25.3% following heating above 200 degrees C. A decrease of the elastic modulus at 20 +/- 1 degree C by approximately 66% was observed in some cases after the heating temperature had been increased to 300 degrees C. Property variations were related to compositional changes, which were investigated by infrared spectoscopy and thermal analysis. Exposure of dental waxes to temperatures higher than 200 degrees C, particularly if it is repeated, may affect the composition and properties, resulting in inferior materials.

Dental Materials↗
PubMed1995

The effects of cross-linking agents on some properties of HEMA-based resins.

The use of 2-hydroxyethyl methacrylate (HEMA)-based polymer as a biocompatible material has been well-established. HEMA-based resins containing cross-linking agents have several potential clinical applications. It is hypothesized that the incorporation of cross-linking agent will improve the mechanical properties of HEMA-based polymers while reducing water absorption and solubility. The purpose of the work reported here was to test this hypothesis and to determine the most effective cross-linking agent. A relationship among flexural strength, modulus, water absorption and solubility, and concentration of cross-linking agent was demonstrated. Strength and modulus tend to increase as the cross-linking agent concentration is increased, up to about 50%, after which the values level out or begin to fall. Water absorption drops with increasing cross-linking agent over the whole range of concentrations. Solubility tends to show a small decrease initially (up to 40%), followed by a noticeable increase as cross-linking agent concentration is increased. The trends were similar for all cross-linking agents, although there were differences in the absolute values in all properties depending upon the type of cross-linking agent used.

Absorption↗
PubMed1995

The effect of artificial saliva on the frictional forces between orthodontic brackets and archwires.

The effect of artificial saliva on the static and kinetic frictional forces of stainless steel (Dentaurum) and polycrystalline ceramic (Transcend) brackets in combination with 0.018-inch round and 0.019 x 0.025-inch Edgewise archwire sizes and stainless steel, nickel-titanium and beta-titanium archwire materials, under a constant ligature force were investigated. In all cases, artificial saliva had the effect of increasing the frictional force when compared with the dry state.

Ceramics↗
PubMed1995

The effect of sandblasting on the retention of first molar orthodontic bands cemented with glass ionomer cement.

This study examined the effect of sandblasting, in vitro, on the bond strength and survival time of first molar orthodontic bands. Survival time was assessed following simulated mechanical fatigue in a ball mill. The amount of cement left attached to the band after debanding was also assessed. In addition, the effect of sandblasting on the failure rate of 320 first molar bands cemented in 107 patients was examined in a half-mouth trial. Ketac-cem, mixed according to manufacturers' instructions was used as the luting agent for both laboratory and clinical trials. In vitro, sandblasting increased bond strength by 27 per cent (P < 0.01) and produced a three-fold increase in the median survival time relative to the untreated sample (P < 0.001) in the ball mill experiment. Sandblasting resulted in more cement remaining on the band rather than on the tooth enamel after band removal. In vivo, sandblasting reduced the clinical failure rate of the first molar bands (P < 0.001).

Adolescent↗
PubMed1995

Ex vivo bond strength of adhesive precoated metallic and ceramic brackets.

Compared with conventional adhesive systems, adhesive precoated (APC) are reported to have advantages in clinical use. The ex vivo bond strength to human premolar teeth of metallic and ceramic APC brackets was compared with that of identical brackets bonded with Transbond (3M Unitek) light cured orthodontic adhesive, and patterns of failure were examined. There was no significant difference (P > 0.05) in mean bond strength between metallic brackets bonded with the two systems. Ceramic brackets bonded with Transbond had significantly higher (P < 0.05) mean bond strength and failure more normally occurred at the composite/enamel interface when compared with APC ceramic brackets and metallic brackets. Following debonding no enamel damage was observed with either APC or conventionally bonded ceramic brackets.

Analysis of Variance↗
PubMed1995

An ex vivo study of self-, light-, and dual-cured composites for orthodontic bonding.

It was postulated that using a dual-cured composite to bond orthodontic brackets could result in bond strengths comparable with those of chemically-activated materials and higher than those for light-activated materials. The shear bond strength of four composite resins used to attach mesh-backed orthodontic brackets was measured at 24 hours and following mechanical insult in the ball-mill. Analysis of variance and an SNK range test showed that at 24 hours Dual-cured Porcelite gave a significantly higher mean bond strength than the other materials (P < 0.05). However, following ball-milling the mean bond strength for Right-on was apparently significantly higher than that of the other materials. (P < 0.05). In this study, the mode of bond failure is also analysed and the use of Weibull analysis in bond strength testing is described.

Acid Etching, Dental↗
PubMed1995

Flexural properties of resin-modified "hybrid" glass-ionomers in comparison with conventional acid-base glass-ionomers.

The mechanical properties of resin-modified "hybrid" glass-ionomers, for both restorative and liner/base applications, were assessed by a flexural test and compared with those of conventional acid-base glass-ionomers. Flexural strength, flexural modulus, and the modulus of resilience were determined 30 minutes after mixing, and at 24 hours and 3 months after aging in distilled water at 37 degrees C. With a microscope and SEM observations, a comparison of marginal breakdown was made between a resin-modified and a conventional glass-ionomer restoration in bovine cavities, after cyclic loading with steel balls. It was found that resin-modified glass-ionomers were stronger, more flexible, and more resilient than conventional acid-base glass-ionomers. This was in accord with the finding that less marginal breakdown and surface deterioration occurred in a resin-modified glass-ionomer than in a conventional analogue. For some materials the flexural properties progressively improved between 24 hours and 3 months, while others showed no improvement or even deteriorated.

Analysis of Variance↗
PubMed1995

Long-term soft lining materials--the relationship between prosthodontic opinion and compliance.

This study investigated the relationship between expert prosthodontic opinion of the suitability of long-term soft lining materials and compliance, as measured by depth of penetration measurements. It showed that there was very good agreement between subjective assessment and objective measurement. Opinion on satisfaction ranged from 82.4% for a heat-cured silicone to 10.8% for a heat-cured soft acrylic which had been stored in water for four weeks. The findings make it possible to set realistic values for a standard test of compliance. The results for depth of penetration allow valuable information to be given to the clinician as to the varying compliance of long-term soft lining materials.

Acrylic Resins↗
PubMed1995

The efficacy of denture cleansers.

The efficacy of two soaking cleansers, a toothbrush/paste and a brush with soap and water have been compared in relation to their ability to remove three types of soil from dentures. A 4 week cross-over trial involving a panel of 80 volunteers was used. Each denture was scored for stain, calculus and disclosed plaque, both before and after cleaning with one of the chosen cleaners. A soaking cleanser used at 50 degrees C was more effective than the other products at removing plaque and stain. There was no difference amongst the materials in terms of calculus removal, the scores being low in all cases. The reliability of scoring is influenced by the presence of large numbers of low 'before-cleaning' scores. This problem can be overcome by using a selection criterion which requires a certain minimum level of soil to be present before cleaning.

Aged↗
PubMed1995

The effect of glass ionomer cement on the surface hardness of resin based materials.

The potential interaction between resin-based materials and glass ionomer cements was investigated by comparing the hardness of the non-adjacent surface of two different resin materials when cured over the cements. Control specimens were made by curing the resin materials over an acrylic surface. Two glass ionomer cements were tested and neither were shown to cause a significant reduction in the surface hardness of either of the resin based materials. The 0.5 mm thick specimens of both resin based materials were significantly softer than the thicker specimens irrespective of the base material.

Analysis of Variance↗
PubMed1994

The clinical serviceability of two permanent denture soft linings.

Forty-four patients, most of whom had previous experience of soft linings, had a total of 62 soft linings placed in their lower complete dentures:32 of the silicone-based Molloplast-band 30 of the heat-cured plasticised acrylic Palasiv 62. Linings were evaluated at insertion and then at 3-monthly intervals. Surface changes and the reasons for lining replacement were used to assess the clinical serviceability of the linings. The median survival time of Molloplast-b linings was significantly greater than that of Palasiv 62, whose performance was inadequate with frequent failure due to surface deterioration, with and without a failure of bonding. Denture fracture was the most common cause of lining failure for Molloplast-b and occurred more frequently than with Palasiv 62. Fading and lining discolouration was commonly observed for both materials.

Acrylic Resins↗
PubMed1994

Dentine bonding--the effect of pre-curing the bonding resin.

The 24-hour shear bond strength of two dentine bonding agents was determined under two conditions. In the first, the adhesive bonding resin was cured prior to placing and curing the composite. In the second, the adhesive resin and composite were cured together. Significantly greater bond strength values were obtained for both materials using the first conditions. These differences in bonding characteristics are likely to be significant from a clinical viewpoint as well as from a statistical viewpoint. It is concluded that there is a need to establish the adhesive-dentine bond before applying and curing the composite.

Composite Resins↗
PubMed1994

Hygroscopic expansion of resin based composites during 6 months of water storage.

Water absorption of composite materials causes an expansion (hygroscopic) which may result in an outward force being generated against the cavity walls. The purpose of this work was to investigate the relationship between this force and the water absorption of the material over a 6 month period of water storage. This investigation was performed by measuring the force required to displace specimens of the test materials from near cylindrical cavities. An outward force developed over a period of a few days of water storage for all test materials. The magnitude of the force was greatest for a microfilled composite, which also had the greatest water absorption. The smallest forces were observed for a hybrid composite. The magnitude of the force was independent of the Young's modulus of the test material. It would appear that expansion due to water absorption is able to rapidly compensate the effects of polymerisation shrinkage. In some cases the forces produced against the cavity walls give rise to some concern for the integrity of the restored tooth.

Absorption↗