Biomedical subjects

M Sherriff

Publications and source records attributed to M Sherriff.

At least 55 records · Page 3Linked to original sources

PubMed1999

Association between the accuracy of intermaxillary relations and complete denture usage.

STATEMENT OF PROBLEM: Previous studies have investigated possible associations between the accuracy of intermaxillary relations and complete denture usage with variable results. PURPOSE: This study investigated the association between the intermaxillary relations in new complete dentures and the use of these dentures for daily wear and eating. METHODS: A prospective study of patients (n = 523) attending Guy's Dental Hospital for complete dentures was undertaken. Patients were examined at the beginning of treatment and at the first post insertion visit. Rest vertical dimension and vertical dimension of occlusion were measured with a Willis gauge. Quality of registration of centric relation position was assessed and, 3 months later, a postal questionnaire was sent to investigate patients' use of dentures. Data were analyzed with Pearson's chi-squared test with exact nonparametric inference. RESULTS: Adequate interocclusal rest space was associated with daily wear of dentures (chi2 = 7.97, P =. 018). Quality of registration of centric relation was associated with daily wear (chi2 = 32.43, P <.001) and use of dentures for eating (chi2 = 20.23, P =.003). CONCLUSION: Positive associations were found between the accuracy of intermaxillary relations and complete denture usage.

Aged↗

PubMed1999

Transition metal salt solutions and anaerobic adhesives in dental bonding.

OBJECTIVES: The objectives of this experiment were twofold. Firstly to determine whether an anaerobic adhesive could be used to bond steel attachments to etched human enamel, following treatment of this surface with various concentrations of copper (II) sulphate solution. Secondly, to determine the effect of 0.05 M solutions of other transition metal sulphates and chlorides on the same bonding process. METHODS: Stainless steel attachments were bonded to human enamel using an anaerobic adhesive. In each case the enamel, which had been ground flat, was etched with 37% o-phosphoric acid and then treated with copper (II) sulphate solution prior to bonding. After bench curing for one hour, the specimens were shear tested to failure, and the load at bebond recorded in each case. The effect of varying the concentration of copper (II) sulphate solution was determined. Following determination of the optimal copper (II) sulphate concentration, the experiment was repeated using the same concentration of various other transition metal sulphates and chlorides. 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. CONCLUSIONS: Under the conditions of this experiment the optimal concentration of copper (II) sulphate solution was found to be 0.05 M. Of the various transition metal sulphates and chlorides under test, the sulphates appeared to provide a more active surface for the polymerisation of the anaerobic adhesive than the chlorides. Of the sulphate solutions, the most effective was that of copper. SIGNIFICANCE: Anaerobic adhesives show promise as dental bonding agents capable of bonding metal attachments to enamel following enamel pretreatment with 0.05 M copper (II) sulphate solution.

Adhesives↗

PubMed1999

The influence of dentine bonding systems and their handling characteristics on the morphology and micropermeability of the dentine adhesive interface.

OBJECTIVES: Development of an adequate interfacial seal is fundamental to achieving a good dentine bond. This study investigates the influence of the properties and application of primers and resin adhesives on dentine interfacial morphology and micropermeability, using a fluorescence confocal microscopy technique. METHODS: Three commercially available (Optibond, Clearfil Liner Bond 2, Pertac Universal Bond) and four experimental dentine bonding systems based on the total each technique were used in the study. Approximal cavities were prepared in third molar teeth and restored using the dentine bonding system (DBS) and resin composite. In the interfacial morphology study the primer and adhesive bonding system were labelled with fluorescent dyes, while in the micropermeability study the pulp chambers were filled with fluorescent labelled saline for 3 h. Ten teeth were prepared in each study for each dentine bonding system. Teeth were sectioned longitudinally and viewed with a tandem or laser scanning confocal microscope. Interfacial micropermeability from the pulpal wall was measured using image analysis techniques. RESULTS: All primers and adhesives showed good penetration of the prepared dentine, except Pertac Universal Bond which manifested 100% micropermeability. The lowest micropermeability results were obtained with Clearfil Liner Bond 2, Optibond and a total etch experimental system where the primer was applied with agitation and contained no photo-initiators and the adhesive resin was unfilled. The latter, when used with a photosensitive version of the same primer, demonstrated a detrimental effect on micropermeability. Light activation of primers in the experimental systems coincided with very variable patterns of leakage. CONCLUSIONS: This high resolution confocal fluorescence technique enabled both the degree and site of micropermeability within the interfaces to be recorded. Matching of primers and adhesives in DBS is important to minimize micropermeability. The non-polymerized primer system probably retained some elasticity in the hybrid zone and so gave less leakage than experimental primers with photo-initiators.

Dentin↗

PubMed1999

The influence of alloy copper content on the polymerisation of anaerobic adhesives.

OBJECTIVES: Anaerobic adhesives are capable of bonding copper-containing metal attachments to etched human enamel, where the latter surface has been rendered reactive by the use of a copper-containing surface activator. The aims of the present study were to determine whether copper attachments could also be successfully bonded to etched human enamel, using anaerobic adhesives, where no such surface activator was used. In addition, the effect of alteration in the copper content of the attachment alloy was also investigated. METHODS: Metal attachments suitable for use with anaerobic adhesives were made from one of three copper-containing alloys. Their copper contents were 8%, 19% and 99.9%. They were bonded to human enamel, which had been ground flat and etched with 37% o-phosphoric acid, using one of three anaerobic adhesives. After bench curing for one of four time periods, 10 min, 1 h, 24 h and 2 weeks, shear testing to failure was performed. The load at debond was recorded in each case. RESULTS: The results were analysed using mean force to debond (N) and 95% confidence intervals. Kaplan-Meier survival probabilities and log-rank tests were performed for the 10 min and 1 h test times. CONCLUSIONS: Each of the three anaerobic adhesives under test demonstrated a concentration effect for the copper in the metal attachments. The higher the copper content of the attachment the greater the measured force to debond and the more rapid its attainment. As determined by measured force to debond, only one adhesive. Loctite 326, underwent any significant degree of activation and, therefore, polymerisation by the lowest copper content alloy under test.

Acid Etching, Dental↗

PubMed1999

Failure of resin-modified glass-ionomers subjected to shear loading.

The mechanism of bond failure of resin-modified glass-ionomers is unknown. This study examined the failure on shear loading at the dentine interface of these materials. Twenty-five teeth (embedded in acrylic blocks) were sectioned longitudinally to expose a flat dentine surface. Cylinders of materials were made by injecting into a tube placed on the dentine of each section surface. The materials used were Fuji Cap II and Fuji II LC (GC Corp., Japan), Vitremer (3M Dental Products, USA), Photac-Fil (original) and Photac-Fil* (new) (ESPE Dental-AG, Germany). After a week, a fluorescent dye was placed in the pulp chamber of each tooth and left for 3 h. The specimens were sectioned through the cylinders before both halves were tested in shear. The failure was observed using a confocal microscope, with video rate images (stored) digitally. The shear load at failure and locus of failure were recorded. All specimens had intact interfaces before testing, except the original Photac-Fil specimens which dislodged from their tooth surfaces even before testing, while being mounted on the device. An amorphous zone or absorption layer was noted at the dentine interface of 60% of Fuji II LC, 22% of Vitremer and all of the Photac-Fil* (new) specimens, but not in Fuji Cap II. Failure was cohesive in Fuji II LC, adhesive in Vitremer, cohesive/adhesive in Photac-Fil* (new) and cohesive in Fuji Cap II. In specimens with the absorption layer present, the failure was at the material/absorption layer interface, leaving it behind on the dentine surface. The mean stresses at failure (MPa) and standard deviations were 5.60, 2.46 (Fuji II LC); 4.82, 0.99 (Vitremer); 4.97, 2.10 MPa (Photac-Fil*); and 3.48, 1.06 (Fuji Cap II). All data were normally distributed as tested by the Shapiro-Francia test. One-way analysis of variance using exact inferential statistics indicated no significant difference between the mean failure stress for all the systems, p = 0.08. The mechanism of failure of resin-modified glass-ionomer materials to shear loading at the dentine interface varies between products. In materials in which the absorption layer is present, it appears to play an important role in mediating the bond of the glass-ionomer to dentine.

Adhesiveness↗

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

Properties of crimpable archwire hooks: a laboratory investigation.

The aim of the present study was to utilize a strain gauge, which enabled the force applied to produce firmly attached crimpable hooks to rectangular stainless steel arch wires, to be measured. In vitro testing of two hooks, American Orthodontic (AO) and TP Orthodontic (TP), and two dimensions of stainless steel archwire, 0.019 x 0.025 and 0.018 x 0.025-inch, was carried out using an Instron Universal Testing machine. The results demonstrate that there was a significant difference in the behaviour of the two types of crimpable hooks, with almost twice the force needed to dislodge the TP hooks compared with the AO hooks (11.7 and 6.22 N, respectively). When using TP hooks attached to either 0.019 x 0.025 or 0.018 x 0.025-inch stainless steel wires, the archwire size makes little difference to the force required to produce movement. The clinical significance of these findings is discussed.

Dental Stress Analysis↗

PubMed1999

Flexural properties and surface finishing of acetal resin denture clasps.

PURPOSE: This study examined flexural properties of acetal resin to determine the appropriate design for an acetal resin removable partial denture clasp. The effectiveness of various acetal resin polishing procedures was also evaluated using scanning electron microscopy. MATERIALS AND METHODS: Loads of up to 1,500 g were applied to cylindrical acetal resin specimen lengths of 5, 10, and 15 mm, and the degree of deflection of the specimen tip was measured. Specimens were 2 mm and 1.5 mm in diameter with a round cross-section (R2 and R1.5, respectively), as well as 2 mm in diameter and half-round in cross-section. Half-round specimens were loaded with their flat surface vertical and then horizontal (HRV and HRH, respectively). Contour plots showing load and deflection for varying lengths of resin were developed for each cross-sectional type based on specimen length, and the stiffness was calculated. Additional acetal resin specimens underwent polishing techniques including tungsten carbide burs, aluminium oxide stones, abrasive impregnated rubber points, and "Polish-D." Polished specimens were examined with scanning electron microscopy to compare surface roughness. RESULTS: For the 5-mm-length specimens, the median stiffness values decreased in the following order: R2 > HRV > HRH > R1.5. The median stiffness values for the 10-mm and 15-mm lengths followed a similar trend. At each length, the R2 specimen was generally at least twice as stiff as other designs. Regarding polishing, the smoothest surface was seen on the specimen that was polished with the rubber point followed by "Polish-D." CONCLUSIONS: To have stiffness similar to a cast cobalt-chromium clasp 15 mm long and 1 mm in diameter, a suitable acetal resin clasp must be shorter (approximately 5 mm) with greater cross-sectional diameter (approximately 1.4 mm). To obtain a smooth surface, the acetal resin clasp should be polished with a rubber point followed by a material such as "Polish-D."

Chromium Alloys↗

PubMed1999

Operator agreement in the use of a descriptive index of edentulous alveolar ridge form.

CAWOOD & HOWELL have proposed a classification of the anatomical form of the residual alveolar processes of edentulous patients. The purpose of this study was to test observer agreement in the clinical assessment of edentulous alveolar ridge form using this classification. This was tested in a pilot study involving 57 edentulous patients, and subsequently in a study of 557 edentulous patients. High levels of observer agreement were found when using this classification for upper and lower edentulous alveolar ridges, suggesting that the classification may be useful as a research tool.

Alveolar Bone Loss↗

PubMed1999

Operator agreement in the use of a descriptive index of complete denture quality.

BACKGROUND AND DESIGN: No generally accepted method for classification of clinical quality of complete dentures exists. While various methods have been proposed, little effort has been made to test observer agreement. The purpose of this study was to test observer agreement in the clinical assessment of complete denture quality using a systematic classification. RESULTS: Fifty seven (57) complete denture-wearing patients were examined on two occasions separated by two weeks. Observer agreement was measured using Cohen's? (kappa). High levels of observer agreement were found for upper and lower retention and stability and for quality of retruded jaw relationship. CONCLUSION: High levels of operator agreement were found for a method for classification of clinical quality of complete dentures suggesting that the classification may be useful as a research tool.

Denture Retention↗

PubMed1999

Comparison of patients' appreciation of 500 complete dentures and clinical assessment of quality.

To compare patients' appreciation and clinical assessment of quality of complete dentures 500 patients attending a dental teaching hospital for provision of new complete dentures were recruited. In each case denture quality was assessed by an experienced prosthodontist using a validated classification of aspects of denture quality. Patients graded their appreciation of features of the dentures on a four point scale. Multiple correspondence analysis demonstrated close correspondence between dentist and patient appreciation of dentures when the dentures were rated as poor, but little or no correspondence when dentists or patients rated the dentures highly.

Attitude of Health Personnel↗

PubMed1999

Variable polymerisation shrinkage and the interfacial micropermeability of a dentin bonding system.

PURPOSE: Adhesive bonds are subjected to competing stresses whilst a restoration is setting. This study aimed to determine the effect of these stresses on a chemically- and light-activated dentin adhesive (Scotch Bond MultiPurpose Plus: SBMP+) by assessing the morphology and micropermeability of the interfacial region. MATERIALS AND METHODS: Restorative materials and techniques were selected to impart differing setting stresses to the adhesive interface. An amalgam (Dispersalloy), a light-activated composite (Z100) with a high- or low-intensity curing light, and chemically-activated composite (Adaptic) were placed either in bulk (4 mm thickness) or in one thin layer (2 mm) in occlusal cavities in 55 freshly extracted third molars. In addition, thin composite restorations were placed on 15 horizontally sectioned teeth using a glass slide as a rigid clear matrix. The pulp chambers of all samples were filled with rhodamine B dye solution for 4 hours. Samples were longitudinally sectioned and the interfacial dye leakage measured using a confocal optical microscope. Data were analysed using the Kolmogorov-Smirnov test. RESULTS: In occlusal cavities, Z100 had significantly more leakage than the amalgam and Adaptic. There was no significant difference in micropermeability between large and small increments, or curing light intensity for Z100, but when placed in bulk, there was evidence of incomplete composite polymerisation near the cavity floor, especially with the low intensity curing light. Cohesive failure of the deep resin composite and gap formation were a frequent finding with the high-intensity light curing. The least leakage for Z100 was achieved with a thin layer on flat dentin. In contrast, the chemically-activated composite performed well in bulk when the surface of the restoration was freely exposed, but badly when constrained by the glass matrix. CONCLUSION: Restoration setting stress is critical in the microscopic integrity of the adhesive bond to dentin.

Bisphenol A-Glycidyl Methacrylate↗

PubMed1998

The influence of alloy composition on anaerobic adhesives in dental bonding.

OBJECTIVES: Single-component anaerobic adhesives are in common use in the electronics and engineering industries. They are generally diacrylate monomers which do not require conventional sources of heat, light or chemicals for activation. Their advantages include activation by the bonding substrate, as well as inhibition of polymerisation until the necessary anaerobic environment is created. The aim of this experiment was to determine whether metal attachments could be successfully bonded to enamel in vitro by such adhesives. METHODS: Metal attachments capable of providing an anaerobic environment were fabricated from one of three alloys: stainless steel, copper or cobalt-chromium. They were bonded to prepared human enamel with one of four adhesives: Orthodontic Concise, as a control, and three anaerobic adhesives, Perma Metal, Permabond A134 and Loctite 326. The specimens were then bond tested in shear to failure after bench curing for one of four time periods. RESULTS: The results were analysed in terms of mean force to debond (N) and 95% confidence intervals. Kaplan-Meier survival probabilities and log-rank tests were performed for the 10 min test times. CONCLUSIONS: Both Orthodontic Concise and the three anaerobic adhesives displayed a specificity towards different attachment alloys. Whereas Orthodontic Concise displayed the highest force to debond with stainless steel attachments, for the anaerobic adhesives this was true of the copper attachments. With stainless steel attachments, however, the force to debond with the anaerobic adhesives was similar to that observed with Orthodontic Concise and steel, at least after the relatively short 10 min bench curing time.

Adhesives↗

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

The relationship between pure tone thresholds and the radiological dimensions of acoustic neuromas.

A retrospective analysis of 109 consecutive patients presenting with acoustic neuromas between 1986 and 1997 were undertaken. Sufficient data were available in 104 cases for comparison. In 65 cases patients had undergone surgery and the radiological diagnosis of acoustic neuroma was confirmed histologically. In this group there were 25 large and 40 small tumors when a maximal radiological diameter of 2.5 cm was used to subdivide the groups. When pure tone thresholds were compared at specific frequencies, in those with hearing ears, there was no significant difference between the two groups. Our results are compared with recent series and the causes of hearing loss associated with acoustic neuroma are discussed.

Journal Article↗

PubMed1998

The effect of environmental factors on elastomeric chain and nickel titanium coil springs.

It is well known that elastomers exhibit viscoelasticity and as such have their mechanical properties modified by temperature. Nickel titanium archwires are also affected by temperature and have been modified with specific temperature related properties for clinical use. What is less well known is the effect that other environmental factors, such as food, might have on the force delivery properties of both elastomeric materials and nickel titanium coil springs used for space closure. For instance gross colour change in elastomeric chain is a common clinical finding in patients who consume spiced foods. The aim of this work was to determine the effect three common environmental factors namely, water, Coke, and turmeric solution have on elastomeric chain and nickel titanium coil springs. In addition, it was decided to re-examine the effect of temperature at 10, 22, and 37 degrees C on both these space closing materials. Unlike many previous investigations, the test specimens were held at a constant stretch throughout the test period, including during their transfer to the Instron Universal Testing machine for force measurement. Six force measurements were made over the first hour, then at 24 hours and 7 days. A control group of dry specimens, maintained at 22 degrees C, had additional measurements made weekly for a 4-week period. The results indicated that elastomeric chain was affected by all the test environments while nickel titanium springs were only affected by temperature.

Carbonated Beverages↗

PubMed1998

A comparative in vitro study of the frictional characteristics of two types of self-ligating brackets and two types of pre-adjusted edgewise brackets tied with elastomeric ligatures.

The aim of this in vitro study was to investigate the frictional characteristics of two types of self-ligating brackets ('A' Company Damon SL and Adenta Time brackets) and two types of pre-adjusted edgewise brackets (TP Tip-Edge and 'A' Company Standard Twin brackets). The test brackets were glued to steel bars and aligned using a preformed jig. Five combinations of archwire size and material were used (0.014-inch nickel titanium, 0.0175-inch multistrand stainless steel, 0.016 x 0.022-inch nickel titanium, 0.016 x 0.022-inch stainless steel and 0.019 x 0.025-inch stainless steel wires). The wires were drawn through the brackets and the frictional resistance was measured using an Instron 1193 testing machine. The data were analysed using a one-way analysis of variance and Scheffe's multiple comparison of means test. The results revealed that the Damon brackets demonstrated the lowest friction for all dimensions of test wires followed by the Time bracket. The 'A' Company Standard Twin brackets produced the highest friction with all wire dimensions tested, followed by the Tip-Edge bracket. With all brackets the 0.016 x 0.022-inch nickel titanium wires produced a higher frictional resistance than the 0.016 x 0.022-inch stainless steel wires. The results indicate that these self-ligating brackets produce less frictional resistance than elastomerically-tied pre-adjusted edgewise brackets.

Analysis of Variance↗