Search Results - (Author, Cooperation:J. S. Rees)

2018-06-29

American Society of Hematology (ASH)

0006-4971

1528-0020

Biology

Medicine

Free Research Articles

2015-11-19

Nature Publishing Group (NPG)

0028-0836

1476-4687

Biology

Chemistry and Pharmacology

Medicine

Natural Sciences in General

Physics

Animals ; CLOCK Proteins/metabolism ; Circadian Clocks/*physiology ; Circadian Rhythm/*physiology ; Drosophila Proteins/genetics/*metabolism ; Drosophila melanogaster/cytology/*physiology ; Extremities/innervation ; Female ; Male ; Mechanoreceptors/cytology/metabolism ; Receptors, Ionotropic Glutamate/genetics/*metabolism ; Sensory Receptor Cells/metabolism ; *Temperature

1600-051X

Blackwell Publishing Journal Backfiles 1879-2005

Medicine

Aim: The aim of this study was to establish the prevalence of dentine hypersensitivity in a cross-sectional study of patients visiting general dental practitioners in the United Kingdom over a period of one calendar month.Methods: Nineteen dental practioners examined 4841 patients over a period of one calendar month and patients that had dentine hypersensitivity diagnosed were questioned further about their occupation and smoking habits. The amount of buccal gingival recession associated with the sensitive teeth was also recorded using a study form.Results: 201 patients were diagnosed as having dentine hypersensitivity, giving a prevalence figure of 4.1%. The commonest teeth affected were the upper premolar teeth and the commonest initiating factor was cold drinks. A tendency for a greater number of sensitive teeth was also found for patients with periodontal disease who also smoked. There was also a tendency for the patients with sensitive teeth to come from higher social groups.

Electronic Resource

1600-051X

Blackwell Publishing Journal Backfiles 1879-2005

Medicine

Abstract. This study investigated the ability of a new instrument designed for root debridement, the Periosonic®, to remove dentine compared to a hand curette and an ultrasonic scaler. The Periosonic system is a modification of the Micro-Mega® endodontic system and uses modified files to remove plaque, calculus and tooth substance. The Periosonic® has 2 file types; the Periosonic 1 is a more aggressive file for the removal of gross supra- and subgingival deposits, while the Periosonic 2 is a thinner more flexible file used for the removal of subgingival deposits. 40 human dentine specimens were ground flat and baseline measurements were made using a surfometer. The specimens were divided into 4 experimental groups and each group was treated with a hand curette, ultrasonic scaler, Periosonic 1 or 2 using 12, 1-s strokes. The specimens were remeasured blind in the surfometer. The curette removed 23.6 μm of dentine, the ultrasonic 6.8 μm, the Periosonic 1 18.8 μm and the Periosonic 2 12.5 μm. A qualitative assessment of the samples following mechanical preparation was also made. In conclusion, the Periosonic® instrument does not remove more tooth substance than a conventional curette and may be a useful addition for the debridement of root surfaces.

Electronic Resource

1600-051X

Blackwell Publishing Journal Backfiles 1879-2005

Medicine

Aim: The aim of this study was to establish the prevalence of dentine hypersensitivity in a cross-sectional study of patients visiting general dental practitioners in the South West region of the UK over a period of 1 calendar month.Method: Twelve dental practitioners examined 3593 patients over a period of 1 calendar month and 137 patients were diagnosed as having dentine hypersensitivity, giving a prevalence figure of 3.8%.Results: The commonest teeth affected were the upper premolar and molar teeth and the commonest initiating factor was cold drinks.Conclusions: The prevalence of dentine hypersensitivity in general dental practice in the UK was 3.8%.

Electronic Resource

1365-2842

Blackwell Publishing Journal Backfiles 1879-2005

Medicine

SUMMARY The finite element method was used to model an in vitro tooth loading system. The dentine was modelled as a linear elastic and isotropic material, while the enamel was modelled as an anisotropic material to take account of the biological variation in prism angulation. The elastic modulus values of enamel and dentine used in this analysis were altered in order to replicate the movement of the in vitro system. It was found that a dentine modulus of 15 GPa and an enamel modulus of 80 GPa in the principal prism direction gave the best replication of cuspal movement.

Electronic Resource

1365-2842

Blackwell Publishing Journal Backfiles 1879-2005

Medicine

Many finite element analyses studies have been published in the dental literature. Some of these have analysed just the crown of the tooth, others have included part or all of the root, while others have included the supporting periodontal ligament and alveolar bone. The aim of this study was to examine which of the supporting structures was important to the model when analysing the stress distribution within a tooth. A two-dimensional plane strain finite element model of a lower second pre-molar was developed, which included the supporting periodontal ligament and alveolar bone. Two 50 N loads were applied to simulate the effect of a load in centric occlusion. The nodal x, y and shear stresses were recorded along two horizontal planes, one in the crown and one in the cervical region. Each of the supporting structures was systematically removed and the remaining structures reanalysed. It was found that it was particularly important to include both the periodontal ligament and alveolar bone when undertaking the finite element analyses of teeth.

Electronic Resource

1365-2842

Blackwell Publishing Journal Backfiles 1879-2005

Medicine

Partial failure around the tooth–composite interface of a class V restoration is common due to the effects of polymerization shrinkage. The effect that this has on the force distribution of the remaining intact interfaces has not been investigated. The aim of this study was to quantify the effect that partial failure of an isolated cavity wall interface had on the force distribution around the remaining intact interfaces of a class V composite restoration in a lower first premolar using a two-dimensional plane strain finite element model. Partial failure resulted in a 4–6-fold increase in peak tensile and shear forces compared to a tooth with a fully intact cavity wall interface. In some instances, the peak stresses were greater than the known bond strengths of composite to dentine.

Electronic Resource

1365-2842

Blackwell Publishing Journal Backfiles 1879-2005

Medicine

summary  The cuspal flexure caused by a direct placement composite resin was measured using a technique that did not interfere with cuspal movement. Twenty upper premolar teeth with mesial-occlusal-distal (MOD) cavity preparations were restored using a posterior composite resin. Ten teeth were restored using a bulk packing technique and 10 were restored using three ‘U’ shaped bucco-lingual increments. Total cuspal movement was measured 1 h following the initiation of curing. Bulk placement of the composite resin produced slightly more cuspal movement (12.5 μm) compared with the incremental placement of composite (11.3 μm). This difference was not statistically significant. The technique of incremental packing to reduce cuspal flexure is therefore questioned.

Electronic Resource

1365-2842

Blackwell Publishing Journal Backfiles 1879-2005

Medicine

summary  The aim of this study was to compare the erosive susceptibility of cuspal and cervical enamel from human premolar and molar teeth. Small blocks of cervical and cuspal enamel were immersed in either orange juice or Coca-Cola at 37 °C and the surface enamel loss was measured by surfometry at 1, 2, 3 and 4 h. Additionally, once-hourly enamel loss was measured, specimens were placed in an ultrasonic bath containing water and ultrasonicated for 5 s to determine the degree of surface demineralization. A further set of enamel specimens were prepared that had 100 μm of the enamel surface removed. This was done to remove the hypermineralized surface enamel layer. Surface enamel loss in orange juice at 4 h, following ultrasonication, ranged from 13·2 to 16·9 μm. The surface enamel loss in Coca-Cola at 4 h, following ultrasonication, ranged from 21·7 to 27·5 μm. Subsurface enamel loss in orange juice at 4 h, following ultrasonication, ranged from 10·7 to 16·1 μm. The subsurface enamel loss in Coca-Cola for 4 h, following ultrasonication, ranged from 36·8 to 37·2 μm. Overall, little difference was found in the erosive susceptibility of cervical and cuspal enamel to the effects of orange juice or Coca-Cola.

Electronic Resource

1365-2842

Blackwell Publishing Journal Backfiles 1879-2005

Medicine

This study examined the stress reducing capacity of varying thicknesses of unfilled resin in a Class V cavity. A two dimensional plane strain mesh of a Class V cavity, 3 mm in diameter and 2 mm deep, was produced and the thickness of the unfilled resin layer was varied from 0 to 80 μm. A polymerization shrinkage of 1·5% was applied to the composite resin and the interfacial forces examined. The maximum shear stresses were found to occur along the pulpal floor of the restoration at the unfilled resin–dentine interface. The maximum shear stress values varied from 11·1 to 22·4 MPa and the shear stresses decreased by up to 38% as the thickness of the unfilled resin increased to 80 μm.

Electronic Resource

1365-2842

Blackwell Publishing Journal Backfiles 1879-2005

Medicine

Summary The aim of the present study was to investigate the effect of addition of an experimental poly (methyl methacrylate) (PMMA) fibre in linear form, 0·75 mm in diameter on the transverse strength of repaired heat-cured poly (methyl methacrylate) denture base material. Specimens of heat-cured PMMA were repaired with an autopolymerizing acrylic resin and an autopolymerizing acrylic resin together with the addition of untreated and surface-treated PMMA fibres in different arrangements. The transverse bend test was carried out using a LIoyd's Instrument Material Testing Machine. From the results, it can be concluded that the box incorporated into the repair joint produced a significant decrease in the moduli of elasticity and rupture which may be due to stress concentration effects. The addition of one layer of untreated PMMA fibres significantly decreased the modulus of rupture. The addition of two layers of untreated fibres produced a slight but statistically non-significant increase in the modulus of rupture. The addition of surface-treated (with butadiene styrene latex emulsion) fibres into the repair complex gave no improvement compared with the addition of untreated fibres in terms of transverse strength. There was an insignificant decrease in the modulus of rupture compared with the untreated fibres.

Electronic Resource

1365-2842

Blackwell Publishing Journal Backfiles 1879-2005

Medicine

summary This study reports a prospective clinical trial comparing a carbon fibre reinforced carbon (CFRC) endodontic post with a conventional prefabricated post. Twenty-seven single rooted maxillary anterior teeth in 18 patients (nine males and nine females; age range 18–60 years) were restored either with a CFRC post or a wrought precious alloy control. Cast type III gold alloy cores were used in conjunction with both post groups. The CRFC posts (n = 16) were cemented with a composite luting agent and the conventional posts (control) were cemented with zinc phosphate.Four failures were recorded in the CFRC post group at 24, 29, 56 and 87 months, compared with one failure in the control group at 84 months.These results suggest that post-retained crowns utilizing a CFRC material and a composite resin luting agent do not perform as well as conventional wrought precious alloy posts.

Electronic Resource

1365-2842

Blackwell Publishing Journal Backfiles 1879-2005

Medicine

Abfraction or non-carious cervical tooth loss is poorly understood and one factor thought to contribute to the development of these lesions is the effect of occlusal loading. The aim of this study was to examine the effect that varying the position of an occlusal load would have on the stress contour in the cervical region of a lower second premolar using a two-dimensional plane strain finite element model. A 500 N load was applied vertically to either of the cusp tips or in various positions along the cuspal inclines. It was found that loads applied to the inner aspects of the buccal or the lingual cuspal inclines produced maximum principal stress values of up to 358 MPa that exceed the known failure stresses for enamel.

Electronic Resource