Biomedical subjects

J F McCabe

Publications and source records attributed to J F McCabe.

At least 37 records · Page 2Linked to original sources

PubMed2000

Direct composite inlays versus conventional composite restorations: 5-year follow-up.

OBJECTIVES: To determine at 5 year follow-up the failure rate, wear rates and other aspects of clinical performance of direct composite inlays compared with conventional composite restorations placed incrementally. METHODS: 100 matched pairs of restorations were originally entered into the trial. Each pair consisted of a direct composite inlay and a conventional composite restoration made from the same material. At 5 years it was possible to recall 65 pairs, of which 54 were complete. Clinical assessments were made using USPHS criteria (indirect measurements of occlusal wear were made using Ivoclar standard dies) and annual bite wing radiographs. RESULTS: There was a trend to more failure of inlays than conventional composites (17.4 c.f. 7.5%) but this was not significant. The clinical performance of both types of restoration was similar and compared favourably with the results of studies of other materials. Secondary decay was diagnosed in only one restoration. Between 3 and 5 years there was some deterioration in cavo-marginal discoloration, marginal adaptation (occlusally) and surface roughness (occlusally). There was no apparent deterioration in colour match, proximal contact, shim stock contacts and Gingival Index. Wear rates of both types of restoration showed no significant difference and were essentially linear with a mean of 33-34 microm per year. CONCLUSIONS: Both inlays and conventional composite restorations complied with ADA specification minimum requirements for posterior composite restorations. In this study the direct inlay technique gave no clinical advantage over conventional, incremental placement.

Adult↗

PubMed2000

The effect of food simulants on enamel-composite bond strength.

The effect of food simulants upon the enamel-composite bond strength of two orthodontic adhesive composites was studied. Thirty extracted premolars were used in each experimental group. Orthodontic brackets were bonded with either Transbond (3M Unitek) or Right-On (TP orthodontics) and were then exposed to either distilled water (control), 8 per cent ethanol (aqueous food), 50 per cent ethanol (alcoholic food), buffered lactic acid pH4 (acidic food), or corn oil (fatty food) for 12 weeks. Bond strength and Adhesive Remnant Index was recorded. It was found that 50 per cent ethanol had a significant effect upon the bond strength of both Transbond and Right-On. Right-On was affected to a greater extent. The clinical significance of this finding is that alcoholic mouth rinses, and alcohol-containing foods and drinks may be a causative factor in bond failure. However, the use of an alcoholic mouthrinse late in treatment may aid bracket removal. This potential use requires more research. Refereed Scientific Paper

Alcoholic Beverages↗

PubMed2000

An ex vivo assessment of resin-modified glass ionomer bonding systems in relation to ceramic bracket debond.

This ex vivo study assessed three new resin-modified glass ionomer cements (Fuji ORTHO LC, Vitremer, and Dyract-Cem) in relation to ceramic bracket removal. It was hypothesized that the use of these cements would facilitate bracket removal and eliminate debond complications Eighty extracted premolar teeth were divided into four groups of 20 teeth and bonded with Intrigue brackets using each of the resin-modified cements (groups 1, 2, and 3), the control group 4 was bonded with Concise chemically-cured adhesive. The teeth were debonded by applying a shear load using an Instron universal testing machine. The mean force to debond was calculated for each group and each tooth was examined under the stereomicroscope to record the site of bond failure and the Adhesive Remnant Index (ARI). The results showed that the resin-modified cements were very effective at eliminating ceramic bracket debond problems. Bracket fracture was eliminated compared with a 40 per cent fracture rate with the control and the ARI scores were all reduced. The elimination of debond problems appears to be related to the significantly reduced (P < 0.001 using ANOVA and Tukey tests) mean and maximal debond forces compared with the control.

Acrylic Resins↗

PubMed2000

The use of a cyanoacrylate adhesive for bonding orthodontic brackets: an ex-vivo study.

The purpose of this study was to evaluate the performance of a cyanoacrylate orthodontic adhesive with regard to tensile bond strength and bond failure location in comparison with a conventional no-mix orthodontic composite adhesive using stainless steel and ceramic brackets. One-hundred-and-twenty caries-free extracted premolar teeth were used in this study. There were 30 specimens for each tooth, adhesive, and bracket combination, and of these half were tested at 24 hours and half at 3 months. Hence, there were 15 samples in each test group. Bond strengths were assessed using an Instron Universal Testing Machine after storage for 24 hours and for 3 months at 37 degrees C in distilled water. Analysis of variance showed the mean bond strength of specimens bonded with cyanoacrylate was significantly lower than for those bonded with Right-on (P < 0.001). Weibull analysis showed that at a given stress the probability of failure significantly increased after 3 months for brackets bonded with cyanoacrylate. A Chi-square test of the ARI scores revealed no significant difference among the groups tested. This study showed that cyanoacrylate adhesives are unsuitable for use as a bonding agent in routine orthodontic practice.

Adhesives↗

PubMed1999

The design of a simulated forcible entry test for fire fighters.

This study investigated the physiological responses and performances for 20 fire fighters when completing simulated forcible entry tests. The purpose was to establish the validity of using a tire striking test and to examine the effects of varying the test parameters. The tests consisted of striking a reinforced structure and a weighted truck tire on a plywood covered table with either a 4.54 or a 5.60 kg sledge hammer. The results indicate that the simulated forcible entry tests are short in duration (range = 8.0-17.6 s), but are also physically demanding in terms of cardiovascular response (range = 86.5-97.2 for a percentage of heart rate reserve). The differences in striking a reinforced structure versus hitting a tire were insignificant according to most of the measures taken. The parameters for the simulated forcible entry test that were determined to be most appropriate were to move the tire 30 cm and use the 4.54 kg sledge hammer.

Adult↗

PubMed1999

Aluminium radiopacity standards for dentistry: an international survey.

OBJECTIVE: The aims of this study were to determine the appropriate composition and purity limits of aluminium alloy radiopacity standards for dental biomaterials, taking into account the current status in representative laboratories worldwide, and to formalise the calculation procedure for processing radiopacity data. METHODS: A series of aluminium step-wedges were obtained from academic and industrial research laboratories. These were analysed by energy dispersive X-ray procedures. The set of step-wedges were independently characterised for radiopacity at two University dental schools. RESULTS: The percentage of aluminium together with the percentages of minor alloying elements (magnesium, manganese, iron and silicon) have been determined as mass percentages. For each centre, the optical density versus step-height for all wedges was judged to fall on a common curve, with the main exception of one step-wedge that was found to contain 4% copper, by mass. A suitable calculation procedure was described explicitly. CONCLUSION: Of the examined representative step-wedges, all but the aluminium--4% copper material were satisfactory and gave results comparable with wedges of high purity. Limits should therefore be revised for composition of aluminium radiopacity step-wedges or test blocks to a more realistic level of purity. Alloys with more than 0.05% copper or 1.0% iron should be excluded and the aluminium content should be at least 98% by mass. In the calculations deployed for deriving radiopacity as 'equivalent aluminium thicknesses', an appropriate linear regression procedure should be employed and considerable care taken in the evaluation of materials of low or borderline radiopacity, relative to specification limits. The method described is principally suitable for materials with radiopacity greater than 1 mm. For materials with radiopacity less than 1 mm aluminium, thicker specimens (2 mm) should be used.

Aluminum↗

PubMed1999

Dental materials: 1997 literature review.

This review of the published literature on dental materials for the year 1997 has been compiled by the Dental Materials Panel of UK. It continues a series of annual reviews started in 1973. Emphasis has been placed upon publications, which report upon the materials science or clinical performance of the materials. The review has been divided by accepted materials classifications (fissure sealants, glass polyalkenoate cements, dentine bonding, dental amalgam, endodontic materials, casting alloys, ceramometallic restorations and resin-bonded bridges, ceramics, denture base resins and soft lining materials, impression materials, dental implant materials, orthodontic materials, biomechanics and image processing, resin composites, and casting investment materials and waxes). Three hundred and thirty three articles have been reviewed.

Dental Materials↗

PubMed1999

Hardness of model dental composites - the effect of filler volume fraction and silanation.

The relationship between structure and mechanical properties for dental composites has often proved difficult to determine due to the use of commercially available materials having a number of differences in composition i.e. different type of resin, different type of filler, etc. This makes a scientific study of any one variable such as filler content difficult if not impossible. In the current study it was the aim to test the hypothesis that hardness measurements of dental composites could be used to monitor the status of the resin-filler interface and to determine the efficacy of any particle silanation process. Ten model composites formulated from a single batch of resin and containing a common type of glass filler were formulated to contain varying amounts of filler. Some materials contained silanated filler, others contained unsilanated filler. Specimens were prepared and stored in water and hardness (Vickers') was determined at 24 h using loads of 50, 100, 200 and 300 g. Composites containing silanated fillers were significantly harder than materials containing unsilanated fillers. For unsilanated products hardness was independent of applied load and in this respect they behaved like homogeneous materials. For composites containing silanated fillers there was a marked increase in measured hardness as applied load was increased. This suggests that the hardness-load profile could be used to monitor the status of the resin-filler interface.

Journal Article↗

PubMed1999

Cure behaviour of visible light-activated pattern materials.

AIM: This study tested the hypothesis that the cure behaviour (depth of cure and polymerization contraction) of light-activated pattern materials was no worse than that of light-activated composite resins, allowing them to be handled in a similar fashion. METHODOLOGY: Depth of cure was measured by a penetrometer method. RESULTS: Cure depths were comparable to those of composite resins, ranging from 3.52 mm (Lumin-X paste) to 6.76 mm (Visioform) after visible light activation for 30 s. There were significant differences in the depth of cure of the three materials tested (P < 0.001). Polymerization contraction was assessed by a minimal load transducer method. Values ranged from 0.45% (Lumin-X paste) to 1.89% (Visioform), lower than that of composite resins. There were significant differences in the polymerization contraction values for each of the three materials (P < 0.001). CONCLUSIONS: It was concluded that light-activated pattern materials cure in a manner comparable to composite resins, and may be built up incrementally in a similar fashion.

Analysis of Variance↗

PubMed1999

A laboratory investigation to compare enamel preparation by sandblasting or acid etching prior to bracket bonding.

A laboratory investigation to compare the mean shear debonding force and mode of bond failure of metallic brackets bonded to sandblasted and acid-etched enamel is described. The buccal surfaces of 30 extracted human premolars were sandblasted for 5 seconds with 50 mu alumina and the buccal surfaces of a further 30 human premolars were etched with 37 per cent phosphoric acid for 15 seconds. Following storage for 24 hours at 37 degrees C in distilled water, shear debonding force was measured using an Instron Universal Testing Machine with a cross-head speed of 10 mm/minute. Mean shear debonding force was significantly lower for brackets bonded to sandblasted enamel compared to acid etched enamel (P < 0.001). Weibull analysis showed that at a given stress the probability of failure was significantly greater for brackets bonded to sandblasted enamel. Brackets bonded to etched enamel showed a mixed mode of bond failure whereas following sandblasting, failure was adhesive at the enamel/composite interface (P < 0.01).

Acid Etching, Dental↗

PubMed1998

Resin-modified glass-ionomers.

This paper reviews the current status of resin-modified glass-ionomers and presents the results of recent findings of research in some key areas. The debate on nomenclature pertaining to these products is perceived as being pointless and the need for application-based ISO standards is raised. Setting characteristics are similar in many respects to those of light-activated composites, although some products have limited working time due to the influence of the acid-base setting reaction and sensitivity to ambient light. Water absorption and swelling are generally very high. The clinical significance of swelling after water exposure is unknown. Mechanical properties of most materials lie between those of the composites and conventional glass-ionomers depending upon the resin content of the matrix phase of the set material. Some products demonstrate an inherent adhesion to enamel, although etching may be required in order to make the bond clinically effective. Bonding to dentine is probably through a more complex mechanism than that involved with conventional glass-ionomers. Conditioning and priming of dentine is often advocated. Fluoride release rates and their clinical significance is an area which requires clarification and standardization. The key factor appears to be the frequency with which the storage water is changed. Equilibration is reached within minutes for some materials and their true fluoride-releasing potential can only be judged under dynamic test conditions.

Biocompatible Materials↗

PubMed1998

Fluoride release from glass-ionomer and compomer restorative materials: 6-month data.

OBJECTIVES: To investigate the daily fluoride release of two glass ionomers (Ketac-Fil and ChemFil Superior) and two compomers (Compoglass and Dyract Restorative) over 6 months. METHODS: A pilot study evaluated the time taken for sample solutions to equilibrate to establish an appropriate time period for sample solution storage between fluoride ion measurements. In the main study storage water replacement and fluoride ion determination was made daily using a specific ion electrode, TISAB buffer and standard solutions for calibration. RESULTS: Equilibration of fluoride concentration in aqueous solution occurred in under 48 h for all materials. Total fluoride released (microgram mm-2) after 6 months by Ketac-Fil (30.6, s.d. 4.9) was significantly greater than ChemFil Superior (12.7, s.d. 2.5), Compoglass (10.4, s.d. 1.0) and Dyract Restorative (7.7, s.d. 1.7) (P < 0.05). Daily fluoride release at 24 h and 10 days was significantly higher for the glass ionomers than the compomers (P < 0.05). After 40 days the daily fluoride release (microgram mm-2) from ChemFil Superior (0.05, s.d. 0.01) was not significantly different from Compoglass (0.04, s.d. 0.01) and Dyract Restorative (0.03, s.d. 0.00) (P > 0.05). Daily fluoride release from Ketac-Fil remains significantly higher than the compomers at 3 and 6 months (P < 0.05). CONCLUSIONS: Specimens stored in water equilibrate rapidly, suggesting the rate at which storage water is changed may alter the relative fluoride release rates of materials. This important fact is often overlooked. Fluoride release from the glass ionomers is initially higher than for the compomers. Fluoride release from glass ionomers falls rapidly to approach levels released by compomers. Compomers produce no initial burst of fluoride and levels of release remain relatively constant.

Aluminum Silicates↗

PubMed1998

Dental materials: 1996 literature review.

This critical review of the published literature on dental materials for the year 1996 has been compiled by the Dental Materials Panel of the UK. It continues the series of annual reviews started in 1973 and published in the Journal of Dentistry. Emphasis has been placed upon publications which report upon the materials science or clinical performance of the materials. The review has been divided by accepted materials classifications (fissure sealants, glass polyalkenoate cements, dentine bonding, dental amalgam, endodontic materials, casting alloys, resin-bonded bridges and ceramo-metallic restorations, ceramics, denture base resins and soft lining materials, impression materials, implants materials, orthodontic materials, biomechanics and image processing, resin composites and casting investment materials and waxes). Three hundred and thirteen articles have been reviewed.

Dental Alloys↗

PubMed1998

Dental materials: 1996 literature review. Part 2.

Ceramics↗

PubMed1998

An ex vivo investigation into the effects of chemical solvents on the debond behaviour of ceramic orthodontic brackets.

The problems of ceramic bracket debond have been well documented. A peppermint oil material has been marketed previously as a debonding agent. This study assessed ex vivo the effects of peppermint oil application on the debond behaviour of ceramic brackets compared with ethanol and acetone which are recognized softening agents. Intrigue brackets were bonded to 100 extracted premolar teeth. Groups of 20 bonded teeth were then placed in a test solution, control (distilled water), peppermint oil (5 minutes and 1 hour), acetone (1 hour), and ethanol (1 hour). The teeth were debonded using an Instron. Universal Testing Machine and debond forces recorded. The site of bond failure along with the adhesive remnant index was recorded for each tooth. One hour placement in peppermint oil produced the lowest mean and maximal debond forces (77 and 114 N, respectively). Weibull analysis showed that the probability of failure at 100 N was increased for the 1-hour peppermint group at 88 per cent compared with 52 per cent for the control. Placement in peppermint oil produced the lowest levels of retained resin. There was no evidence of enamel fracture with any of the groups, but bracket fracture remained a problem.

Acetone↗

PubMed1998

Notching of orthodontic bonding resin to facilitate ceramic bracket debond--an ex vivo investigation.

This ex vivo study assessed the potential of introducing a notch in the bond layer, as a means of facilitating the removal of ceramic brackets. Sixty extracted premolar teeth were divided into three groups of 20 teeth and bonded with Intrigue brackets using Concise chemically-cured adhesive. The bonding technique was modified with groups 1 and 2 by introducing a notch in the bond layer. Group 1 was notched from the gingival aspect, group 2 from the occlusal, and group 3 served as a control. The brackets were removed by applying a shear load from the gingival aspect using an Instron universal testing machine. The mean force to debond was calculated for each group. The results showed that introducing a notch significantly reduced the mean and maximal debond forces. This was confirmed with Weibull analysis with the notched specimens having a higher probability of failure at any force. In addition, ceramic bracket fracture was eliminated. Notching the bonding resin may be helpful in facilitating the removal of ceramic brackets.

Ceramics↗

PubMed1998

Comparison of erosion of dental enamel by four drinks using an intra-oral applicance.

There are several causes of erosion - acidic foods and drinks have been implicated and reducing their erosive potential would seem an important area of research. Calcium-citrate-malate (CCM) appeared to have potentially useful properties as an anti-erosion additive. The study aims were to test the ability of an intra-oral enamel slab system to measure erosion and to compare the erosive potential of a citric acid-based orange juice drink either with or without added CCM and a positive and negative control. Eleven adults wore an upper removable appliance for four periods each of 6 days. Each appliance held two enamel slabs which were inserted into the test drinks for 15 min 4 times a day for 6 days. Loss of enamel was quantified by profiling casts of the enamel slabs taken before and after the test period. Loss of enamal was greatest during exposure to a diet phosphoric acid-based cola drink (p < 0.001) but was similar during exposure to the two citric acid-based orange drinks, with or without CCM, and distilled water. The loss of surface enamel measured from a scanning electron micrograph agreed well with the measurement obtained by profilometry. It can be concluded that (a) the intra-oral enamel slab system was able to discriminate between drinks in their erosive potential, and (b) it was not possible to determine if CCM had any potential for reduction in erosion in an acid beverage as the level of erosion observed for both the critic acid-based orange drinks was not statistically significantly different from that observed with distilled water.

Acids↗

PubMed1998

Rheological properties of elastomeric impression materials before and during setting.

In this study, we examined the rheological properties of elastomeric impression materials, both before and during setting, to assess the clinical significance of certain key characteristics such as viscosity, pseudoplasticity, and the rate of development of elasticity. The hypothesis to be tested was that monitoring the change in tan delta is the most appropriate means of monitoring the setting characteristics of elastomers. The loss tangent (tan delta) and the dynamic viscosity (eta') for five impression materials (both unmixed pastes and mixed/setting materials) were measured by means of a controlled-stress rheometer in a cone/plate configuration. For unmixed pastes, tests were performed at various frequencies (0.1 to 10 Hz) and torques (from 1 to 50 x 10(-4) Nm), while testing on setting materials was performed at constant frequency (1 Hz) and torque (3 x 10(-3) Nm). Most base and catalyst pastes were pseudoplastic before being mixed. Immediately after being mixed, the polyether (tan delta = 9.85) and polysulfide (tan delta = 9.54) elastomers showed tan delta markedly higher than those of other mixed materials (tan delta = 4.96 to 3.01). The polyvinylsiloxane elastomers showed lower initial tan delta, which rapidly reduced even further with time. This suggests that these materials should be used as soon as possible after being mixed. The polyether elastomer had a comparatively long induction period during which the tan delta remained at a high value. These characteristics are thought to be key factors in controlling clinical efficacy and therefore support the hypothesis that monitoring tan delta is an appropriate method for evaluating the setting characteristics of elastomers. One limitation was that the controlled-stress rheometer was unable to monitor rheological properties through to completion of setting.

Dental Impression Materials↗