Biomedical subjects

M Sherriff

Publications and source records attributed to M Sherriff.

At least 37 records · Page 2Linked to original sources

PubMed2004

An in vivo study to compare a plasma arc light and a conventional quartz halogen curing light in orthodontic bonding.

The purpose of this study was to compare the effectiveness of a plasma arc lamp with a conventional tungsten quartz halogen lamp in orthodontic bonding. Twenty consecutive patients had their brackets bonded either with Transbond XT (n = 10) or Fuji Ortho LC (n = 10). In total, 352 teeth were bonded, 176 in each group. Using a randomized cross-mouth control study design, where diagonally opposite quadrants were assigned a particular treatment, the bonds were then either cured with the control light, namely a halogen lamp, or a plasma arc lamp. The halogen light was used for 20 seconds per tooth and the plasma arc lamp for 3 seconds per tooth. The measurement parameter used was bond failure and the patients were monitored for a period of 6 months following initial bond placement. In the Transbond XT group, the proportion of bond failures was 3.41 per cent for both the halogen and the plasma arc lamp. For the Fuji Ortho LC group, the proportions were 11.4 and 10.2 per cent, respectively. No difference was observed with respect to in-service bond failure proportions between bonds cured with the plasma arc or the conventional halogen lamp, irrespective of the bonding agent. Use of the plasma arc lamp could therefore lead to considerable savings in clinical time. However, this must be weighed against the increased purchase price of the plasma arc lamp.

Adhesives↗

PubMed2003

An in vivo and ex vivo study to evaluate the use of a glass polyphosphonate cement in orthodontic banding.

The purpose of this study was to examine the effectiveness of a new glass polyphosphonate cement (Diamond) for orthodontic banding. Thirty-one subjects underwent in vivo testing to compare the failure rate of bands cemented using the test cement and bands cemented using a conventional glass polyalkenoate cement (Ketac-Cem) over a 6-month period at the beginning of active appliance therapy. In an ex vivo experiment 60 extracted teeth were banded using either the test cement or a glass polyalkenoate cement, and subjected to a debanding force using a Lloyd universal testing machine until failure. In the in vivo study the overall proportion of failure of the bands cemented with each cement was identical at 0.048. However, in the ex vivo study the probability of failure for the glass polyphosphonate cement was significantly higher than for the glass polyalkenoate cement, and the force to deband the glass polyalkenoate cement was greater than that of the glass polyphosphonate cement. In the clinical setting the new glass polyphosphonate cement performed as well as a conventional glass polyalkenoate cement, and these results suggest that it could be used as an alternative cement for orthodontic banding. The results of the ex vivo test bring into question the usefulness of this laboratory test as an indicator of clinical performance.

Dental Bonding↗

PubMed2002

Twenty years of mercury monitoring in dental surgeries.

From 1981 to 2001 disposable mercury monitors based on palladium chloride have been deployed in 3,568 dental surgeries throughout the United Kingdom. They have performed well as first-level indicators of high concentrations of mercury vapour in surgeries that had become contaminated by spillage of mercury or faulty equipment. Whilst accumulated data suggests that mercury hygiene practices have improved over the past 20 years, the move to the use of disposable capsules rather than automatic amalgamators does not appear to have been a major factor in this improvement.

Accidents, Occupational↗

PubMed2002

The effect of pumicing on the in vivo use of a resin modified glass poly(alkenoate) cement and a conventional no-mix composite for bonding orthodontic brackets.

OBJECTIVE: Pumicing of the enamel prior to direct bonding with conventional diacrylate bonding agents has been shown to be unnecessary. It is not known whether this is also the case with resin-modified glass poly(alkenoate) cements. The aims of this study were two-fold: (a). to determine whether pumicing prior to bonding has an effect on the in vivo failure of brackets bonded with either Right-On or Fuji II LC; (b). to determine whether there is a difference in the in vivo failure of brackets bonded with either Right-On or Fuji II LC. Design A cross-mouth controlled clinical trial was performed on a total of 60 patients in which the variables under test were pumicing or not pumicing of the enamel prior to bonding using two different bonding agents. MAIN OUTCOME MEASURES: The measurement variable was bond failure over an 18-month period. RESULTS AND CONCLUSIONS: Prior pumicing of the enamel has no effect on in vivo failure when using either a conventional diacrylate or a resin modified glass poly(alkenoate) cement. A greater number of bonds failed with the resin-modified glass poly(alkenoate) cement.

Dental Bonding↗

PubMed2001

Phosphoric acid and copper (II) sulphate as a combined etchant and activator prior to the use of an anaerobic adhesive.

OBJECTIVES: Previous work has shown that steel attachments can be bonded to etched human enamel using anaerobic adhesives, following treatment with a solution of 0.05M copper (II) sulphate. The objectives of this experiment were to determine whether simultaneous etching and activation could be performed with a combined solution of o-phosphoric acid and copper (II) sulphate. METHOD: Stainless steel attachments were bonded to human enamel using an anaerobic adhesive. In each case the enamel was etched and activated using a solution of 37% o-phosphoric acid containing various concentrations of copper (II) sulphate. After bench curing for one hour, the specimens were shear bond tested to failure and the load at debond recorded in each case. Following determination of the optimum copper (II) sulphate concentration the experiment was repeated, but this time the acid was made into a gel using colloidal silica. The effect of rinse time after etching was also investigated with the gel. RESULTS: The results were analysed using mean force to debond (N) and 95% confidence intervals. Kaplan-Meier survival probabilities and log rank tests were also performed. Under the conditions of this experiment the optimum concentration of copper (II) sulphate was found to be 1M. When the acid was made into a gel the optimum rinsing time was found to be 60s. SIGNIFICANCE: This experiment demonstrates that steel attachments can be bonded to enamel using anaerobic adhesives where the enamel has been simultaneously etched and activated. A combined o-phosphoric acid and copper (II) sulphate solution or gel can be used, but a conventional etch pattern is not produced.

Acid Etching, Dental↗

PubMed2001

A laboratory investigation of the role of guide planes in the retention of cast cobalt-chromium alloy partial denture frameworks.

OBJECTIVES: This in vitro study examined the resistance to displacement offered by guide planes and the displacement mechanics of a bilateral bounded saddle cast cobalt chrome alloy removable partial denture framework under conditions simulating an average initial fit. METHODS: A specially designed model mouth jig fitted with strain gauges to monitor the forces across the guiding plane/guiding surface interfaces was used. Guiding planes of enamel, silver tin amalgam and dental composite with seven combinations of guide planes and three angles of withdrawal were examined. Guiding plane size was also examined for dental enamel. RESULTS: A statistically significant difference in retention was found for all factors examined. Retention increased with increasing angle of withdrawal. Size effects were found but considered unreliable. CONCLUSIONS: It was concluded that with a tight fit guiding plane retention may be readily predicted for any given material, combination of mesial, distal and lingual guiding planes and angulation conditions by the application of mechanical principles providing the basic parameters are known. Attention is drawn to the reasons for further work to fully understand the clinical situation.

Analysis of Variance↗

PubMed2001

The measurement and prevention of erosion and abrasion.

OBJECTIVES: To develop a reproducible method to measure tooth wear and assess the protection given by dentine bonding agents in an erosive/abrasive wear regime. METHODS: Seal and Protect (Dentsply, UK) and Optibond Solo (Kerr, UK) were each applied to 20 extracted teeth and subjected to 3000 cycles in a reciprocating erosion/abrasion wear machine. A further 20 teeth, without protection, were subjected to the same wear regime and were either brushed in water or immersed in acid. Impressions were taken by a standardised technique and were scanned with a non-contacting laser profilometer. The amount of erosion was measured at the same co-ordinates before and after erosion using 2mm diameter metal discs as reference points. RESULTS: The amount of wear on Seal and Protect had a mean 24.8 microm (SD 57.4 microm) and for Solo it was 1.4 microm (24.5 microm), and this difference was statistically significant (p=0.02). There was no statistically significant difference in the wear measured on the teeth brushed in water or immersed in acid. The wear measured on the unprotected teeth was 243 microm (SD 120 microm) and was statistically significantly different to the protected surfaces (p=0.001). CONCLUSION: Both Seal and Protect and Solo protected the teeth in this wear regime and the technique could be used clinically for patients with uncontrolled dental erosion.

Analysis of Variance↗

PubMed2001

A survey of interfacial forces used during endosonic instrumentation of root canals.

AIM: The aim of this in-vitro study was to measure interfacial forces acting between root canal dentine and ultrasonic files during endosonic instrumentation. METHODOLOGY: Single-rooted teeth were mounted on a cantilevered aluminium beam to which two pairs of single element strain gauges were joined in a half-bridge configuration mounted at right angles to each other. The strain gauges were connected to an analogue-to-digital converter fitted in a microcomputer via a conditioning amplifier. This enabled strains to be recorded as a function of interfacial forces over a period of time. Twenty operators instrumented root canals using sizes 15, 20 and 25 ultrasonically energized K-type files. The lateral forces generated were calculated. RESULTS: The mean interfacial forces used varied widely between operators and files, ranging from 18 g to 149 g, but there was a consistency in the relative magnitude for each operator. The average force used by the operators increased with file size; the differences between file sizes were significant (P < 0.05). CONCLUSIONS: The range of forces measured is broader than previously reported and may have a bearing on possible uncontrolled dentine removal, even during ultrasonically activated irrigation.

Analog-Digital Conversion↗

PubMed2001

An in vitro investigation into the use of resin-modified glass poly(alkenoate) cements as orthodontic bonding agents.

This in vitro study was designed to determine the effect of time on the measured mean force to debond when brackets were bonded using resin-modified glass poly(alkenoate) cements and to compare them with a light-cured diacrylate. Changes in surface topography and composition of the cements were also investigated. Stainless steel orthodontic brackets were bonded to 160 upper premolar teeth in four test groups: Transbond, Fuji Ortho LC, and 3 M Multi-Cure with and without enamel etching. Shear bond testing to failure was performed after 1 hour, 1 week, 1 month, and 1 year. The first three groups were then rebonded and stored for the same time periods before being shear tested again. Debond force was recorded in Newtons and the locus of bond failure was scored using the Adhesive Remnant Index (ARI). Surface topography and composition of the test materials were also studied at time periods of 1 day, and 1, 6, and 18 months, using scanning electron microscopy (SEM) and energy dispersive X-ray analysis (EDAX). The mean force to debond (N) was observed to increase with time in all four test groups, with there being little significant difference between the groups. When the same brackets were rebonded, the mean force to debond reduced. Surface topography and compositional changes over time were only observed with the resin-modified glass poly(alkenoate) cements. Resin-modified glass poly(alkenoate) cements have a mean force to debond comparable with diacrylate bonding agents. However, unlike diacrylates they undergo surface changes with time, the significance of which is unknown.

Acrylic Resins↗

PubMed2001

An in vivo investigation into the use of resin-modified glass poly(alkenote) cements as orthodontic bonding agents.

The aim of this study was to investigate the in vivo bonding of orthodontic brackets using two resin-modified glass poly(alkenoate) cements and to compare them with a conventional light-cured diacrylate bonding agent. Twenty consecutive patients attending for bond up appointments took part in this randomized cross-mouth control study. Alternate quadrants were bonded with either Fuji Ortho LC or 3 M Multi-Cure. Transbond [Adhesive Pre-Coated Brackets (APC)] acted as the control in the other quadrants. Failed brackets were rebonded with the same material. Bond failure rates were collected over a 1-year period. The bond failure rates over 1 year were 7.2 per cent for Transbond (APC), 5.9 per cent for 3 M Multi-Cure, and 5.8 per cent for Fuji Ortho LC. Statistically, there was no significant difference between the bond failure rates of the materials and there was no effect of time. This clinical investigation confirmed the suitability of the resin-modified glass poly(alkenoate) cements under test as orthodontic bonding agents.

Acrylic Resins↗

PubMed2001

An ex vivo investigation into the use of a plasma arc lamp when using a visible light-cured composite and a resin-modified glass poly(alkenoate) cement in orthodontic bonding.

OBJECTIVE: To determine the usefulness of the plasma arc lamp in orthodontic bonding when used with both a light curable diacrylate and a resin modified glass poly(alkenoate) cement. DESIGN: Ex-vivo study. METHOD: 160 second premolar teeth were divided into 2 groups. 80 teeth had steel brackets bonded using Transbond XT and 80 were bonded using Fuji Ortho LC. One of four light curing regimes were used, with 20 specimens in each group: (i) 20 seconds curing with a halogen lamp; (ii) 1 second; (iii) 2 seconds or; (iv) 3 seconds with the plasma lamp. OUTCOMES: Shear bond tested to failure and the force to debond (N) and locus of bond failure recorded in each case. RESULTS: Force to debond increases in the case of both bonding materials as the curing time with the plasma lamp increases. The force to debond with 1 and 2 seconds with the plasma lamp was significantly lower in each case. In all instances the force to debond was lower in the case of the resin modified glass poly(alkenoate) cement specimens. Locus of bond failure was unaffected by the method and length of light curing and was generally mixed mode. CONCLUSIONS: Use of the plasma arc lamp in orthodontic bonding could result in significant time saving.

Acrylic Resins↗

PubMed2001

Three-point bending test of fiber posts.

Five different types of fiber posts (carbon fiber Composipost radio-opaque, quartz fiber Aestheti-Plus, carbon fiber Carbotech, glass fiber Light post, and silica fiber Snowpost) were submitted to a three-point bending test after being stored for 1 yr under three different conditions: dry storage at room temperature, storage in 37 degrees C water, and storage in bovine teeth that were endodontically treated and restored with composite resin. The posts were observed before and during the test by confocal microscopy. More voids were found within the Composipost radio-opaque than in other posts. Posts of all groups that were stored in water showed flexural strength values lower than posts that were stored dry. In all storage conditions, Carbotech posts showed higher flexural strength values than Composiposts and Snowposts, and Aestheti-Plus posts showed higher flexural strength values than Snowposts. Posts that were stored in bovine teeth showed flexural strength values similar to those of posts that were stored dry. It was concluded that fiber posts must not be in contact with oral fluids and that during the 1-yr storage in bovine teeth, they were sufficiently protected from this contact by the apical root canal filling and by the coronal composite resin filling.

Animals↗

PubMed2001

Microtensile bond strength and confocal microscopy of dental adhesives bonded to root canal dentin.

PURPOSE: To evaluate the bond strength of two dentin-bonding systems to root canal dentin. MATERIALS AND METHODS: Six central incisors, extracted for periodontal reasons, were endodontically treated, no obturation of the root canal space was performed. The teeth were cut parallel to their long axis. One half of each tooth was randomly assigned to one of two experimental groups. The teeth of the first group were treated with All-Bond 2 dental adhesive and those of the second group with Panavia F. The root canal dentin was conditioned as suggested by the manufacturers and, after the application of the dental adhesives, a layer of resin-based composite was polymerized over the adhesive layer. After the composite had completely set, the sections were prepared for microtensile test and kept in a wet environment at a relative humidity of 90 +/- 2% measured with a digital relative humidity meter and at a temperature of 22 degrees C for 24 hrs. The specimens were sectioned perpendicularly to the bonded interface, into slabs 1.5 mm thick (10 sections for each experimental group). The slabs were then trimmed by super fine diamond burs for the microtensile bond test with the narrowest region located at the respective bonded interface. The thickness of the slab was then exactly established by three measurements performed in three points of each slab by a digital micrometer. The specimens were then subjected to a tensile force at a crosshead speed of 0.2 mm/min. The test was observed using a confocal microscope and the failure modes were noted. The load at failure was registered and the bonded area was measured using a confocal microscope at a magnification of x25 in conjunction with an image-processing program. The failure data were analyzed using the Wilcoxon-Gehan test with exact non-parametric inference. RESULTS: The mean value at failure was the same for the two experimental groups (17.1 MPa). There was no statistically significant difference between Panavia F and All-Bond 2 (P> 0.8671). Most of the specimens showed a debonding of the adhesive from the hybrid layer. The results showed that the bond strength of the two bonding systems tested to the dentin of the root canal are slightly lower than to those obtained with the latest adhesive systems, in the coronal dentin.

Composite Resins↗

PubMed2000

An investigation of factors influencing patients' use of new complete dentures using structural equation modelling techniques.

UNLABELLED: A review of the literature demonstrated that research had not identified a set of prognostic indicators for prospective complete denture patients, with different authors publishing contradictory results. OBJECTIVE: To investigate possible relationships between patient and clinical factors and denture wear and use of dentures for eating. METHODS: Patients attending Guy's Dental Hospital, London, for provision of complete dentures were recruited. For each patient relevant history was recorded and an examination of the edentulous mouth and existing dentures, where present, was undertaken at the beginning of treatment. At the first post-insertion appointment the edentulous mouth, previous and new dentures were examined. Three months after the review appointment patients were sent a postal questionnaire to assess patient use of dentures and patient satisfaction. Data were analysed using structural equation modelling techniques. RESULTS: 723 patients were recruited. Significant relationships were found between quality of complete dentures and patients' use of complete dentures and between quality of residual edentulous ridges and patients' use of complete dentures. These results contrast with most previous research into prognostic indicators for success in complete denture treatments. CONCLUSIONS: Quality of residual edentulous ridges and quality of new complete dentures predict patients' use of new complete dentures.

Aged↗

PubMed2000

A survey of interfacial forces used during filing of root canals.

The pattern of dentine removal during endodontic instrumentation is influenced by many factors including the interfacial forces applied by the operator. The aim of this study was to investigate the influence of operators and different sizes and types of instruments on the magnitude of these interfacial forces. Single-rooted teeth were mounted on a cantilevered aluminium beam to which two pairs of single element strain gauges were joined in a half-bridge configuration and mounted at right angles to each other. The strain gauges were connected to an analogue-to-digital converter fitted in a micro-computer via conditioning amplifiers. This enabled strains to be recorded over a period of time. Twenty operators instrumented root canals using a series of hand instruments for 1 min each. The mean interfacial forces used by operators demonstrated a wide variation ranging from 9.06 g to 149.42 g (range of forces from 0-331 g) but there was a consistency in the relative magnitude for each operator. The 20 operators could be divided into 13 groups which were significantly different (alpha = 0.05) from each other. There were significant differences (alpha = 0.05) between the forces used for each of the K-Flex files (15, 25, 35, 45, and 70), the force increasing with the file size. There was also a significant difference (alpha = 0.05) in the forces used between the Flexofile (#25) and the #25 K-Flex and Hedström files. However, there was no significant difference between the K-Flex and Hedström files.

Amplifiers, Electronic↗

PubMed2000

The influence of interfacial forces and duration of filing on root canal shaping.

The aim of this study was to investigate the possible relationship between interfacial forces, duration of instrumentation and effectiveness of root canal shaping by filing. All factors were standardised except the manner of manipulation of the files and the dependent variables (interfacial force and duration of filing). The outcome measured was the final prepared canal shape. The study tested the hypothesis that if interfacial forces and duration of filing had predictive value for effective canal shaping, a relationship between them should be apparent. If it was not, it could be inferred that the remaining uncontrollable variable, "manner of file manipulation" had a dominating influence. 18 operators used a standard filing technique to instrument a root canal each in single rooted teeth matched for anatomy. The teeth were mounted in a custom-made transducer designed to measure laterally applied interfacial forces between file and dentine. The length of time taken with each instrument in the series was measured giving a total duration of instrumentation. The final canal shape measured by standardised "before" and "after" radiographic images of the roots was judged against an "ideal" canal shape calculated from the size of instruments used and based on the preliminary canal shape. Although some trends were revealed, no obvious relationship was demonstrated between interfacial force, duration of filing and final canal shape. Operators clearly used a range of interfacial forces characteristic for each individual and for the different file sizes. Both light and heavy forces could produce a satisfactory canal shape. Use of light or heavy forces did not obviously affect speed of preparation. Tactile discrimination was not dependent on use of light or heavy forces. It was inferred that the "manner of file manipulation" remained undefined and was probably the dominant factor influencing outcome of canal shaping.

Analysis of Variance↗

PubMed2000

Video rate confocal microscopic imaging of dentin/adhesive interfacial failure under load.

PURPOSE: To obtain information on interfacial failure by recording video rate images of the interface as it failed, while simultaneously recording the load applied. MATERIALS AND METHODS: Fluorescent labeled adhesives were used to retain resin-based composite bobbins on the flat exposed dentin surface of teeth included in epoxy resin blocks. The teeth were secured in a miniature straining stage while the bobbins were loaded in shear mode and the interface viewed with a tandem scanning confocal microscope. Images of the interface during failure were recorded with the aid of computer image processing and storage. The dynamic failure pattern, site of failure (after repositioning the fractured bobbin under the microscope) and shear bond stress were analyzed for four dentin adhesives [OptiBond (OB), Scotchbond Multi-Purpose Plus (SBMP+), Clearfil Liner Bond 2 (CFLB2) and ESPE Bonding System (EBS)]. Control specimens without fluorescent dyes were also studied. Four dynamic patterns of failure were observed: snap, slip/stick, peel and shock wave were seen respectively with OB, SBMP+, CFLB2 and EBS adhesive. The shear bond strengths were ranked EBS*>OB>SBMP+>CFLB2* (*statistically different at alpha=0.05). No significant difference was found between specimens with and without fluorescent dye.

Acid Etching, Dental↗

PubMed1999

A confocal microscopic study relating the autofluorescence of carious dentine to its microhardness.

OBJECTIVE: An in-vitro study to examine the correlation between the distribution of the autofluorescent signal emitted from carious dentine (detected using confocal laser scanning microscopy) and its microhardness, within the depths of human dentine lesions. MATERIALS AND METHODS: Twelve carious teeth were sectioned longitudinally, the cut faces marked with a grid reference line system and colour photomicrographs taken. The same samples were imaged using confocal laser-scanning microscopy for autofluorescence and then subjected to microhardness testing using a Knoop microhardness indenter. Adjacent sound dentine was used as a control reference. Digital image superimposition allowed direct comparisons to be made between the colour, autofluorescence and microhardness of each lesion. RESULTS: Sound enamel and dentine did not autofluorescence. Autofluorescence distribution from carious dentine correlated with the highly softened tissue (detected using the Knoop indenter) and terminated at a level superficial to the translucent zone. This zone was still pigmented. Normal, sound dentine hardness levels were found deep to the translucent zone. CONCLUSIONS: A correlation existed between the zone of autofluorescence and carious dentine that was markedly softened by the carious process. These findings highlighted a possibility that the autofluorescence might be used as an in-vitro, objective histological marker for the softened, carious dentine requiring clinical excavation.

Color↗