Biomedical subjects

N J Jepson

Publications and source records attributed to N J Jepson.

9 recordsLinked to original sources

PubMed1998

A simple method for obtaining a uniform thickness for long-term soft denture linings.

The thickness of long-term soft denture linings influences both their compliance and durability. Increasing the thickness of the lining material increases its perceived softness but makes the restoration more likely to fail through weakening of the acrylic resin denture base. Such effects have led to broad recommendations as to an appropriate thickness, advice that assumes a constant thickness of the lining material within the same denture. Several procedures used to produce such a constant thickness have been described. The necessary spacer is produced by manually adapting materials in their plastic state to the cast. Such procedures are liable to distortion and variation in spacer thickness and can be considered unreliable. This article describes a method for obtaining a uniform thickness of soft denture lining through the use of a vacuum-formed, thermoplastic blank as a spacer. The method is simple, applicable to all ridge forms, and reliably results in a soft lining of a known, uniform thickness. The method can be applied to long-term soft linings placed in both old and newly fabricated dentures. The spacer can be modified to allow variations in the prescribed extension of the soft lining within the denture base.

Dental Prosthesis Design↗

PubMed1996

The influence of immersion solutions on the viscoelasticity of temporary soft lining materials.

OBJECTIVES: The purpose of this study was to examine the influence of laboratory immersion in a number of solvents on the viscoelasticity of temporary soft lining materials. It was an initial attempt to reproduce the changes seen clinically with a view to formulating more clinically relevant immersion regimes for the evaluation of these materials. METHODS: Changes in the viscoelasticity of four temporary soft lining materials following immersion at 37 + or - 1 degree C in 10% acetone/90% water, 20A% acetone/80% water and hexane was compared to a control immersion in distilled water using a penetrometer modified to record creep strain and strain during recovery. Testing was performed at 2 h and 24 h and then at 2, 4, 7, 21 and 28 d after sample preparation. Summary measures were used to describe individual specimen changes in derived values of initial and time dependent compliance and elastic recovery from 0-7, 7-28 and 0-28 d. RESULTS: Immersion in hexane resulted in at least a 50% reduction in compliance of 28 d. There was a significantly greater reduction in compliance for hexane immersion than for any other solvent (p<0.01). Immersion in 20% acetone resulted in an increase in compliance of around 1 mm/N after 1 wk compared with a reduction of up to 1 mm/N in distilled water. There was a reduction in elastic recovery for 3 out of 4 materials with 20% acetone/80% water solution. Changes in elastic recovery were smaller than those of compliance. SIGNIFICANCE: The reduction in compliance with hexane immersion suggests that this, or similar solvents, may form the basis of more clinically relevant immersion regimes. This may contribute to the development of improved temporary soft lining materials.

Acetone↗

PubMed1995

The influence of denture design on patient acceptance of partial dentures.

A study was designed to investigate the influence of denture design on patient acceptance of partial dentures. A total of 317 patients provided with partial dentures by the Department of Prosthodontics, Newcastle Dental School 2-3 years previously, were asked to complete a postal questionnaire about their use of these dentures. Denture status and partial denture design for these patients was established using hospital records. Design variables included material, the number and distribution of replaced teeth, denture support and connector design. In all, 86% of patients (273) returned the questionnaire. A total of 393 partial dentures (210 upper, 183 lower) had been constructed for these patients; 99 (25%) dentures were never worn and a further 57 (15%) dentures were only worn occasionally. Non-wearers were more likely to have no replacement anterior teeth, fewer replacement teeth and, in the lower, a lingual bar. When a multivariate model including all recorded variables was constructed using multiple logistic regression analysis, the presence of anterior replacement teeth for all dentures and the number of replacement teeth for upper dentures were found to be the only significant positive influences on denture wearing. Use of a lingual bar did not influence denture wearing habits.

Adult↗

PubMed1995

A new temporary soft lining material.

The viscoelastic properties of a new light-activated temporary denture soft lining material have been monitored in vitro using a force/distance probe. Its baseline behaviour was characteristic of an elastic material and its compliance considerably less than that of both a short-term and a long-term soft lining material which were used as controls. Sample thickness had no appreciable effect on this compliance. These results suggest that the new product is likely to be perceived as being significantly harder by a patient. Twenty-four weeks' immersion in distilled water had no significant effect on either the compliance or elasticity of the test material and would suggest an improved durability when compared to other conventional short-term resilient denture lining materials, albeit at the expense of compliance.

Compliance↗

PubMed1994

Intake of non-starch polysaccharide (dietary fibre) in edentulous and dentate persons: an observational study.

Compromised masticatory efficiency places edentulous persons at risk of consuming a diet low in non-starch polysaccharide (NSP) ('dietary fibre'). No study has quantified NSP intake in edentulous people using a valid and reliable method of dietary assessment. The aim of this study was to provide quantitative data on NSP intake of edentulous persons, together with information on its dietary sources. Using the dietary history method, habitual intake of NSP was compared between edentulous persons (n = 30) and dentate persons (n = 30) between the ages of 40 and 60. Groups were matched for sex and social class. The edentulous group had a median NSP intake of 73 (31-211) g/week. This was significantly lower than that of the dentate group of 106 (25-225) g/week (P = 0.014). Neither group completely met current UK guidelines. NSP intake of 56% (n = 17) of the edentulous group was below 84 g/week, whilst 17% (n = 5) of the dentate group was below this figure--a level of intake below which increased occurrence of gastrointestinal complaints has been observed. The dentate group obtained significantly more NSP from all rich sources, including wholemeal breads, cereals, vegetables and fruit. Depending on their form and preparation, such foods are not necessarily difficult to chew. Specific advice on food selection is required to ensure the edentulous patient has an adequate intake of NSP. Education of the dentist for this purpose is of paramount importance.

Adult↗

PubMed1994

The clinical serviceability of two permanent denture soft linings.

Forty-four patients, most of whom had previous experience of soft linings, had a total of 62 soft linings placed in their lower complete dentures:32 of the silicone-based Molloplast-band 30 of the heat-cured plasticised acrylic Palasiv 62. Linings were evaluated at insertion and then at 3-monthly intervals. Surface changes and the reasons for lining replacement were used to assess the clinical serviceability of the linings. The median survival time of Molloplast-b linings was significantly greater than that of Palasiv 62, whose performance was inadequate with frequent failure due to surface deterioration, with and without a failure of bonding. Denture fracture was the most common cause of lining failure for Molloplast-b and occurred more frequently than with Palasiv 62. Fading and lining discolouration was commonly observed for both materials.

Acrylic Resins↗

PubMed1993

Evaluation of the viscoelastic properties of denture soft lining materials.

Denture soft lining materials are widely used in prosthetic dentistry. Their success has been attributed to their softness and resilience, properties described by their viscoelasticity. Though these properties have been extensively investigated in laboratory studies, clinical studies have been limited. The viscoelastic properties of the temporary soft lining material Coe Soft and the permanent soft lining materials Palasiv 62 and Molloplast-B have been studied using a force/distance probe whereby penetration was measured against time under constant stress. Derived values of an initial and time-dependent compliance has allowed a quantitative in vivo and in vitro assessment of freshly prepared samples of each test material and comparison between materials. The baseline behaviour of each test material in response to the test regimen was similar for both clinical and laboratory specimens. Three types of behaviour could be identified: (i) constant strain in which penetration was clearly less than specimen thickness--elastic behaviour (Molloplast-B); (ii) constant strain in which the penetration was equal or nearly equal to specimen thickness--apparent elastic behaviour (Coe Soft); (iii) strain which increased with time of load application--viscoelastic behaviour (Palasiv 62). The mean and range of baseline clinical thickness for Coe Soft was approximately half that seen for the permanent soft lining materials. There was a much smaller range in the baseline compliance of all materials than might have been anticipated from a knowledge of their relative softness.

Acrylic Resins↗

PubMed1993

Age changes in the viscoelasticity of permanent soft lining materials.

Age-related changes in the viscoelasticity of an acrylic-based (Palasiv 62) and silicone (Molloplast-B) permanent soft lining material were evaluated in parallel clinical and laboratory longitudinal studies using a force/distance probe. Changes in the viscoelastic properties of Palasiv 62 in clinical use were characterized by a significant and continued reduction in both initial and delayed compliance. That is, the material became harder whilst still retaining the underlying pattern of viscoelasticity seen at baseline. Laboratory immersion in distilled water resulted in significant reductions in compliance values. These reductions were cumulatively similar to those seen clinically but did not occur as rapidly. There was evidence of small, continued reductions in the measured thickness of clinical linings of Palasiv 62. The clinical and laboratory compliance of Molloplast-B remained stable over time. Ageing did not affect the essential elasticity of this material.

Acrylic Resins↗

PubMed1993

Age changes in the viscoelasticity of a temporary soft lining material.

The viscoelastic properties of a widely used temporary soft lining material have been monitored in vivo and in vitro using a force distance probe. Over a period of 8 weeks' clinical use, Coe Soft demonstrated a significant and continued reduction in compliance with time, the reduction being particularly rapid over the first week. These changes were not associated with a reduction in measured lining thickness for which significant changes were not found. In vitro immersion in water, saline or artificial saliva was characterized by a rapid and significant reduction in compliance values over the first week. Further continued reductions in compliance values were only observed in artificial saliva over 8 weeks, and on prolonged immersion in distilled water over 96 weeks. All reductions in compliance were significantly less than those seen clinically.

Acrylic Resins↗