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Biomedical subjects

J S Rees

Publications and source records attributed to J S Rees.

At least 37 records · Page 2Linked to original sources
PubMed2003

Oral corticosteroid prescribing in women over 50, use of fracture prevention therapy, and bone densitometry service.

OBJECTIVE: To identify the most common diseases and age of corticosteroid use in women over 50, dosage in last year, duration of oral corticosteroid use, prescription for fracture prevention (drug used), and referrals for bone densitometry. METHODS: General practice records from 41 practices in Shropshire identified 62,230 women aged >50 from a population of 80,082. Data on fractures, duration of corticosteroid use, dose in the study year (1 April 1997-31 March 1998), use of fracture prevention therapy and bone densitometry were sampled from one out of three records. RESULTS: 3.2% were prescribed corticosteroids; 633 patients investigated in detail aged 70.1 (SD 10.5) years, had been prescribed 1526 (SD 1727) mg prednisolone (median 1040 mg) for 3.31 (SD 3.20) years (median 2.0 years). Patients with asthma/lung disease, most common in the younger group, had the lowest annual corticosteroid use; patients with rheumatoid arthritis (RA), polymyalgia rheumatica/temporal arteritis (PMR/TA), who were more likely to be elderly, had the highest annual use. Between the age of 70 and 79 years patients with RA had significantly more hip fractures than the other groups, and corticosteroid prescribing was most common. Bisphosphonates or hormone replacement therapy were prescribed for 48% aged 50-59 years but only 32% at 70-79 years (p<0.01); patients with asthma and RA being less likely recipients (p<0.01). Referrals for bone densitometry had occurred in 20.2%,with 60.2% having osteoporosis. Referrals were more common in those taking corticosteroids for longer periods (p<0.01). CONCLUSIONS: The elderly had the most prescriptions for corticosteroid treatment but the fewest for effective fracture prevention therapy. Patients with RA, PMR/TA had the greatest corticosteroid dosage, for the longest time. Patients with RA sustained more hip fractures than other groups but were least likely to have effective fracture prevention therapy prescribed.

Absorptiometry, Photon↗
PubMed2002

A cross-sectional study of dentine hypersensitivity.

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.

Adolescent↗
PubMed2002

The effect of variation in occlusal loading on the development of abfraction lesions: a finite element study.

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.

Bite Force↗
PubMed2001

An investigation into the importance of the periodontal ligament and alveolar bone as supporting structures in finite element studies.

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.

Alveolar Process↗
PubMed2001

The erosive susceptibility of cervical versus occlusal enamel.

Clinical studies have strongly suggested a multifactorial aetiology for abfraction lesions or non-carious cervical tooth loss, with a contribution from erosive agents. Structural studies have shown that cervical enamel is more porous with a poorly developed crystal structure that may be more prone to erosion. The aim of this study was to examine the susceptibility to erosion of cervical and occlusal enamel from human premolar and molar teeth. Small blocks of cervical and cuspal enamel were immersed in either orange juice or Coca-Cola and the surface enamel loss was measured using profilometry. The enamel loss was essentially linear at a rate of 2.2-8.8 microns/hr. It was concluded that there was little difference in the susceptibility to erosion between cervical and cuspal enamel, even when the surface hypermineralised layer was removed.

Analysis of Variance↗
PubMed2000

The prevalence of dentine hypersensitivity in general dental practice in the UK.

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%.

Adolescent↗
PubMed2000

An unusual case of furcation external resorption.

AIM: To describe the presentation and management of an unusual external root resorption. SUMMARY: An unusual external inflammatory root resorption presented in the furcation of a mandibular first molar. Review of earlier radiographs suggested that the lesion was non-progressive. Occlusal trauma associated with anterior open bite was the most likely aetiological factor. No active treatment was prescribed. KEY LEARNING POINTS: External resorption may occur following loss of the external root surface. Occlusal trauma may be a propagating stimulus for progressive resorption. Lesions may sometimes be non-progressive, and treatment may therefore be more damaging than observation.

Adult↗
PubMed2000

The effect of interfacial failure around a class V composite restoration analysed by the finite element method.

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.

Bicuspid↗
PubMed2000

A review of the biomechanics of abfraction.

Loss of tooth substance in the cervical region is usually attributed to abrasion or erosion. However, the role of occlusal loading is becoming increasingly prominent. It is suggested that high occlusal loads result in large stress concentrations in the cervical region of the teeth. These stresses may be high enough to cause disruption of the bonds between the hydroxyapatite crystals, eventually resulting in the loss of cervical enamel. This article reviews the available evidence to support the thesis that occlusal loading can contribute to the process of non-carious cervical tooth loss or abfraction. It also reviews the potential interactions between occlusal loading and erosion that may contribute to non-carious cervical tooth loss.

Biomechanical Phenomena↗
PubMed2000

An in vitro assessment of the erosive potential of some designer drinks.

The aim of this study was to establish the amount of surface enamel lost following immersion in a number of designer drinks using surface profilometry. Orange juice was used as a positive control. Twenty four designer drinks were tested and it was found that 18 out of 24 of these drinks produced surface enamel loss that was significantly greater by between two and six times than the orange juice control. It was concluded that many of the commercially available designer drinks had considerable erosive potential.

Alcoholic Beverages↗
PubMed1999

An in vitro assessment of the dentine lost during instrumentation using the Periosonic system.

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-Megax 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 microm of dentine, the ultrasonic 6.8 microm, the Periosonic 1 18.8 microm and the Periosonic 2 12.5 microm. 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.

Dental Instruments↗
PubMed1999

The stress reducing capacity of unfilled resin in a Class V cavity.

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 microm. 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 microm.

Composite Resins↗
PubMed1998

The effect of cuspal flexure on a buccal Class V restoration: a finite element study.

OBJECTIVES: Failure of Class V restorations is a clinical occurrence which is often blamed on inadequate moisture control. However, the effects of occlusal forces and cuspal movement may also have an effect. The aim of this study was to examine the effects that cuspal movement had on the shear forces around a buccal Class V restoration in a lower first premolar. METHOD: A lower first premolar restored with a buccal Class V composite restoration and a Class I composite or amalgam restoration were modelled using the finite element method. The width of the occlusal restoration was varied from 2.1 to 3.7 mm and the depth varied from 1.7 to 3.7 mm. RESULTS: Compared to the unrestored premolar, the presence of an occlusal preparation restored with composite increased the interfacial forces around the buccal Class V restoration by 1-67%. Similarly, the presence of an amalgam occlusal restoration increased the interfacial forces by 9-228%. CONCLUSIONS: It was found that the presence of an occlusal restoration increased cuspal movement, which in turn increased the shear forces around the buccal Class V cavity. This effect was more pronounced with increases in cavity depth compared to cavity width, and when amalgam was the occlusal restorative material.

Bicuspid↗
PubMed1998

The role of cuspal flexure in the development of abfraction lesions: a finite element study.

A tooth flexure mechanism has been proposed over the past 15 yr to explain non-carious cervical tooth loss. It is well established that cavity preparation weakens a tooth, resulting in more cuspal movement under occlusal load. The aim of this study was to investigate the effect that an occlusal restoration would have on the stress profile in the cervical region of a lower second premolar using two-dimensional finite element stress analysis. Under an eccentric 100 N occlusal load, a premolar with an occlusal amalgam restoration showed peak tensile and shear stresses in the buccal cervical region that were in excess of the known failure stress for enamel. Increases in the cavity depth of the occlusal amalgam restoration were found to increase cervical stress more than increases in cavity width. It was concluded that the weakening effect of cavity preparation may contribute to the development of non-carious cervical tooth loss.

Bicuspid↗
PubMed1998

The erosive potential of the alcoholic lemonade Hooch.

The aim of this in vitro study was to assess the erosive potential of four flavours of the alcoholic lemonade Hooch. This study measured the pH on opening, the volume of 0.1M sodium hydroxide required to raise the pH of 20 mls of the lemonade to neutrality and the fluoride content. The amount of surface enamel lost following immersion for one hour was also assessed compared to water as a control. The pH on opening ranged from 2.57-2.86 and the volume of 0.1M sodium hydroxide required to neutralise 50 mls of the lemonade ranged from 15.4-23.1 mls. The fluoride content of the drinks ranged from 0.36-0.45 p.p.m. The amount of surface enamel lost over one hour ranged from 1.80-3.28 microns. This study suggests that the alcoholic lemonade Hooch has considerable erosive potential and seems likely to be as erosive as orange juice.

Alcoholic Beverages↗
PubMed1997

Elastic modulus of the periodontal ligament.

This study used a two-dimensional finite element mesh of a lower first premolar to model two different tooth loading systems which measured either the vertical or the horizontal displacements of this particular tooth. The elastic modulus of the periodontal ligament was varied in the finite element model until the horizontal and vertical displacements of the model correlated with the two experimental systems. It was found that an elastic modulus of 50 MPa gave good correlation between the finite element model and the experimental systems.

Bicuspid↗