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Biomedical subjects

G J Mount

Publications and source records attributed to G J Mount.

At least 19 recordsLinked to original sources
PubMed2006

A proposal for a new classification of lesions of exposed tooth surfaces.

In the presence of improved methods of identification and treatment of lesions on the exposed surfaces of teeth, it should now be acknowledged that the GV Black "classification of carious cavities" is out of date. This paper describes a new system, proposed in 1997, discussed broadly throughout the profession, and eventually modified. The system has been adopted in several regions around the world as being a useful corollary to the current developing concept of minimal intervention dentistry. It is now desirable to adopt a new approach to the identification and recording of the lesions caused by both caries and non-carious tooth loss. A major advantage arising from its adoption would be that it would encourage the profession to minimise the amount of normal healthy tooth structure that is often sacrificed in pursuit of the cavity designs as suggested by Black. The authors are members of a Project Group of the FDI Science Committee, and this paper explains the concept and offers justification for the adoption of the system.

Dental Caries↗
PubMed2002

Resin modified glass-ionomers: strength, cure depth and translucency.

BACKGROUND: According to the classification suggested by McLean, Wilson and Nicholson only three materials, currently marketed, fit the designation of resin modified glass-ionomers. These materials will undergo an acid/base setting reaction but also contain a limited quantity of a monomer that will polymerize as a result of irradiation. The quantity of polymer is limited to the extent that it will not interfere with the normal acid/base setting reaction and will therefore allow for the ion exchange adhesion with tooth structure that is typical of glass-ionomer. There is a third setting reaction incorporated to ensure remaining monomer, that is not affected by irradiation, will still polymerize. A series of experiments were carried out to determine the effect of the three types of setting reaction on the strength, depth of cure and translucency of these three materials. METHODS: Specimens, both with and without irradiation, were subjected to a shear punch strength test. To determine the depth of cure brought about through irradiation, specimens were tested immediately after construction according to the test in ISO - 4049 2000 (E). Translucency is clinically significant and will vary according to whether the material has been subjected to irradiation or cured through the acid/base reaction alone. RESULTS: The strength of all materials tested was higher in specimens subject to irradiation. The depth of cure was found to be both shade and irradiation time dependent. Irradiated specimens were found to be only marginally more translucent than those allowed to set without irradiation. CONCLUSIONS: It was concluded that, for cavities more than 3 mm deep, these materials should be placed incrementally to allow for a full irradiation initiated cure.

Acids↗
PubMed2000

Minimal intervention dentistry--a review. FDI Commission Project 1-97.

The concept of minimal intervention dentistry has evolved as a consequence of our increased understanding of the caries process and the development of adhesive restorative materials. It is now recognised that demineralised but noncavitated enamel and dentine can be 'healed', and that the surgical approach to the treatment of a caries lesion along with 'extension for prevention' as proposed by G V Black is no longer tenable. This paper gives an overview of the concepts of minimal intervention dentistry, describes suggested techniques for a minimally invasive operative approach, and reviews clinical studies which have been carried out in this area.

Composite Resins↗
PubMed2000

Minimal intervention: a new concept for operative dentistry.

The term minimal intervention is relatively new in dentistry and has been introduced to suggest to the profession that it is time for change in the principles of operative dentistry. The disease should be treated first; the surgical approach should be undertaken only as a last resort and then with the removal of as little natural tooth structure as possible. This article discusses the advances in techniques and materials that have led to change and attempts to put them into perspective. Treatment should begin with identification and elimination of the disease. There will then be a need for limited restoration of actual cavitation arising from demineralization of the tooth crown. Restorations, per se, will not prevent or eliminate disease. Caries is a bacterial infection and, until the microflora is controlled, all restorations are at risk of further demineralization in remaining tooth structure. This leads to the continuum of replacement dentistry that keeps the profession occupied for much of its productive time. If this cycle is to be broken, the profession must first acknowledge the primacy of prevention.

Bacterial Infections↗
PubMed2000

Minimal intervention: early lesions.

The use of modified cavity designs for the treatment of initial carious lesions can be justified on the grounds that, because no restorative material can adequately replace natural tooth structure for the long term, preservation of natural tooth structure is important. It is apparent that it is possible to remineralize and heal demineralized tooth structure to some degree. Therefore, neither enamel nor dentin should be removed simply because it has lost calcium and phosphate ions as a result of acid attack. The older surgical approach to cavity design was adopted in the absence of adhesive techniques and on the basis of Black's principle of "extension for prevention," but this theory is no longer tenable. The current availability of adhesive bioactive restorative materials makes it possible to maintain areas of tooth structure even though they appear to be undermined and weakened. Thus, the concept of geometric designs for prescribed cavities is no longer valid. The purpose of this article is to describe a series of simplified, modified cavity designs for small initial lesions; preservation of natural tooth structure is the principle objective of these designs.

Dental Caries↗
PubMed2000

Minimal intervention: advanced lesions.

Minimal intervention techniques are generally considered in relation to initial carious lesions. However, it appears logical to apply the same principles to extensive cavities as well as to the replacement of failed existing restorations. As the cavity becomes larger, there is an increasing need to consider protection of remaining cusps because they become seriously weakened by loss of the central core of the crown and therefore become subject to the development of splits at the base. However, it is possible to develop a protective cavity design without undue sacrifice of remaining tooth structure, at the same time that maintenance of occlusal anatomy and correct contact with the opposing arch are ensured. For larger cavities, special consideration needs to be given to the strength of the restorative material. Glass ionomer is relatively brittle and should not be exposed to undue occlusal load. Resin composites cannot be regarded as universal in their physical properties, and placement is time-consuming. A lamination technique is often useful, combining the advantages of both glass ionomer and resin composite. Amalgam should not be entirely discarded as an option because it has greater strength than both glass ionomer and resin composite and is still useful for the restoration of extensive cavities and for protection and retention of weakened cusps. Minimal intervention principles, designed to limit the loss of natural tooth structure, should be applied to all restorative dentistry. None of the available restorative materials is entirely satisfactory in the long term.

Bite Force↗
PubMed1999

The use of glass ionomer in special needs patients.

Placement of restorations for patients who are physically or intellectually disabled or mentally ill can pose considerable difficulties for the general practitioner. Access to the oral environment is often limited and patient tolerance and concentration may be reduced to rather brief periods of time. Oral hygiene routines may be less than ideal leading to a high caries rate. Enamel surfaces which do not normally become carious can develop broad but shallow lesions with a poorly defined outline. Selection of the most suitable restorative material will be important, with longevity of the restoration as the prime consideration. Other factors such as access, isolation of the lesion and patient co-operation must also be taken into account. Also, forces acting on restorative materials may be less than usual due to poor occlusion, teeth opposing dentures or being completely unopposed. Restoration by indirect techniques will often not be possible so the choice will be limited to the three plastic restorative materials normally used in restorative dentistry: amalgam, resin composite and glass ionomer. As a result of clinical experience it is suggested that glass ionomer will often be the material of choice. This paper describes five years experience with the resin-modified glass ionomers in an institutional practice which is limited to patients with special needs. Clinical significance Placement of restorations, with a reasonable expectation of longevity, can pose considerable problems for the patient with special needs. Resin-modified glass ionomer is a useful alternative material and has been placed with a high degree of success over a period of five years.

Dental Care for Persons with Disabilities↗
PubMed1998

Clinical performance of glass-ionomers.

Glass-ionomers were introduced to the profession 20 years ago and have been shown to be a very useful adjunct to restorative dentistry. Their major advantages include the ion exchange adhesion to both enamel and dentine and a continuing fluoride release throughout the life of the restoration. The chemistry of the setting reaction is essentially an acid/base reaction but recent research has introduced variations in an effort to improve clinical handling. Small additions of resin increase the physical properties to a degree and allow for a light-initiated setting mechanism. However, it is essential that the acid/base reaction remains dominant if the full advantages of the glass-ionomer are to be retained. The material has multiple uses in dentistry and it shows a high degree of biocompatibility to the pulp and surrounding soft tissues. The main limitation at this time is a relatively low fracture resistance but it is possible to protect it through lamination with stronger materials if the need arises. This paper examines the essential parameters for successful clinical placement and comments on its longevity.

Dental Bonding↗
PubMed1998

A new cavity classification.

With the development of adhesive restorative materials and a far better understanding of the action of the fluoride ion it is suggested that the time has arrived for a reassessment of the traditional cavity classification as set out by G.V. Black over one hundred years ago. When preventive measures and remineralization fail and a carious lesion has progressed through the enamel into the dentine there is a need to remove the infected dentine, and possibly some of the affected dentine as well, to eliminate cavitation and avoid further accumulation of plaque. In most situations this will involve removal of enamel to achieve access to the infected dentine but, in the presence of fluoride, both enamel and dentine are capable of being remineralized and therefore conserved, at least to a degree. The principle of minimal extension must be encouraged to allow maximum preservation of natural tooth structure. A new cavity classification is proposed which is designed to make the most of the potential for healing which is inherent in both enamel and dentine. However, it must be accepted that a considerable proportion of restorative dentistry is carried out to replace failed restorations and, in this case, cavity design will be complicated by existing loss of tooth structure.

Adhesives↗
PubMed1998

A new classification and techniques for simple restorative dentistry.

It is nearly one hundred years since G. V. Black proposed a simple, five-stage classification for carious lesions based upon the site of the lesion and the type of restorative material likely to be used for restoration. In the absence of both effective preventive measures and a knowledge of remineralization his approach was essentially surgical: having identified a lesion remove it surgically, as well as all surrounding susceptible tooth structure, to prevent recurrence. Surgery is no longer regarded as the primary choice for treatment of a disease and there are many factors which suggest that this system is out of date. Preservation of natural tooth structure should be the principal aim and this is best achieved through remineralization. Remaining cavitated areas can then be restored more conservatively, thus assisting in maintaining aesthetics as well as strength in the tooth crown. If the profession is to adopt a new approach to operative dentistry it is suggested that the psychology of introducing a new classification for carious lesions is a desirable move.

Dental Cavity Preparation↗
PubMed1997

Electron probe microanalysis and transverse microradiography studies of artificial lesions in enamel and dentin: a comparative study.

In cardiology and research involving the interactions between restorative materials and dental hard tissues, it is important for small changes in tooth mineral content to be measurable. Currently, transverse microradiography (TMR) is the most accepted tool for the above purpose. Electron Probe Microanalysis (EPMA) can yield both qualitative identification of elements and quantitative compositional information. The purpose of this study was to compare the mineral distribution in well-defined artificial lesions, in dentin and enamel, by the use of both TMR and EPMA on the same sample. The good correlation between the two sets of data validates EPMA as a technique and helps in the interpretation of its results. The data from TMR analysis are expressed as vol% of mineral, while EPMA gives the levels of Ca and phosphate in wt%. The conversion between the two sets of data is complicated by the fact that local density is, as yet, unknown.

Analysis of Variance↗
PubMed1997

A study of glass-ionomer cement and its interface with enamel and dentin using a low-temperature, high-resolution scanning electron microscopic technique.

This report describes a method of immobilizing the water contained in glass-ionomer cement and dental hard tissues and stabilizing the delicate organic component of dentin. With this method, the intact interface between glass-ionomer and dental hard tissues can be observed under scanning electron microscope with few of the artifacts that are caused by the desiccation associated with conventional scanning electron microscopic studies. There was a distinct zone of interaction between the glass-ionomer cement and enamel and dentin. Under severe thermal stress, glass-ionomer cement failed cohesively, leaving an intact interface with enamel and dentin. Machine-mixed glass-ionomer cements displayed a high level of porosity. Some glass particles were separated from the matrix, and there was evidence that some are dislodged from the matrix during specimen preparation.

Dental Enamel↗
PubMed1997

A revised classification of carious lesions by site and size.

The present classification used by the profession for the identification of carious lesions was devised by Black about 100 years ago. It was based, in part, on the location of the lesion but was modified to take into account the materials that were available for restoration. Over the last 20 years, there has been considerable modification of these materials; adhesion between the restoration and tooth structure is now possible, and the understanding of the relevance of fluoride and other ions in the prevention and repair of caries has improved. It would be logical at this time to adopt a new classification based on the site of the carious lesion and the extent to which it has progressed. More relevant detail could be recorded for each restoration, and this would be of value both for personal records and epidemiologic studies. The proposal is a simple digital system that is compatible with the use of computers for record keeping.

Dental Caries↗
PubMed1997

Longevity in glass-ionomer restorations: review of a successful technique.

It is just 20 years since glass-ionomer cements were introduced to the profession as a restorative material capable of an ion exchange adhesion to tooth structure as well as a continuing fluoride release. At the time of presentation there was considerable publicity, but, in retrospect, it is likely that the materials were marketed prematurely, before there had been a great deal of clinical investigation. The clinical short-term results were rather disappointing, particularly in relation to esthetics, because the original version lacked translucency. In the next few years, some manufacturers worked to refine the product and improve the properties and achieved reasonable results. In the early 1980s, it was shown that the main problem with both esthetics and physical properties was the need to maintain a proper water balance in the material during the early setting phase. Once this problem was identified and overcome, it became possible to achieve excellent results, but these have not been reported frequently. This article discusses a method of placement that will lead to acceptable glass-ionomer restorations and shows a series of restorations that are up to 15 years old.

Composite Resins↗