PubMed Health⌕ Search

Biomedical subjects

G J Mount

Publications and source records attributed to G J Mount.

At least 19 recordsLinked to original sources
PubMed1992

Microleakage in the sandwich technique.

This study assessed the microleakage and if it was possible to reproduce the success that is seen in the oral cavity with properly placed "sandwich" restorations. Simulated Class V erosion lesions were prepared in extracted human molar teeth and restored using a Type III glass ionomer lining cement mixed mechanically at a high powder:liquid ratio of 3:1 or greater with resin composite laminated to it leaving cement exposed at the gingival margin. To update the technique for modern materials a dual cure glass ionomer lining cement was placed in a second series with resin composite laminated to it completely covering the gingival margin. The restorations were stored in water for two weeks before temperature cycled and immersed in dye. The results showed minimal leakage relative to most other published studies and that most leakage was related to the setting shrinkage of the resin composite.

Composite Resins↗
PubMed1992

Efficiency of protective sealants for glass ionomer cements.

This study compared the efficiency of protective sealants for glass ionomer cements. Scotchbond 2, Visar Seal, an experimental light activated silicone and Ketac Glaze were evaluated using liquid scintillation spectrometry. The results showed that Ketac Glaze was a very effective sealant for the newly placed glass ionomer cement and the resin component of Scotchbond 2 is in the same range.

Chi-Square Distribution↗
PubMed1991

The aged in dentistry.

Statistics show clearly the greying of our population and the profession must face the inevitable modifications to the delivery of dental care which will follow. We have spent many years fighting the high caries rate of youngsters and teenagers but, quite suddenly, that battle seems to be virtually won. Now we are faced with an ageing population who, with our help, have retained their teeth to an advanced age and they do not want to part with them. In fact, changing a patient to full dentures after the age of forty years is a very traumatic occurrence to both patient and operator. The profession now has two major problems to deal with in the area of restorative dentistry for the ageing patient. Firstly, teeth which have been retained but are heavily restored because of ongoing caries and bulk loss of tooth structure as a result of splitting or the application of careless restorative techniques. Secondly, the onset of root surface caries following migration of the epithelial attachment and exposure of root surfaces combined with a reduction in the efficacy of oral hygiene measures. Both problems are likely to appear after the age of sixty years and the patient may live for another twenty or thirty years in a gentle medical and physical decline. Maintenance of dental health presents a series of unique problems under these circumstances.

Aged↗
PubMed1991

Minimal treatment of the carious lesion.

The development of reliable adhesive technology in the oral cavity has opened the way to an entirely new approach to the treatment of active carious lesions. The initial lesion, prior to complete penetration of the enamel, can often be controlled with remineralization techniques. However, once the dentine is breached, surgical intervention is required. With modern instrumentation, including fibre-optic lighting and magnification with binocular loupes, a more surgical approach has been developed, allowing removal of caries with very limited destruction of sound tooth structure. Experience over the last 5 years has led to the development of a classification of cavity designs as well as a reliable method of instrumentation and restoration based on the use of glass-ionomer cement and composite resin. The remineralization available through the glass-ionomer cements and the adhesion developed with both the cement and composite resin allows for maintenance of the original strength of the tooth along with a high resistance to further breakdown. The classification of cavity design is presented as well as a detailed description of the suggested instrumentation for the development of the cavities.

Dental Caries↗
PubMed1990

The effect of etching on a number of glass ionomer cements.

In view of the continuing interest in the use of glass ionomer cements as a dentine substitute or base under composite resins, further investigations were carried out on the effects of the length of time of etching of the surface of the cement prior to the placement of the resin. A number of cements are available on the Australian market which are advocated for use in this technique. Each of them was subjected to etching for periods of 15, 30, 45, or 60 seconds and then stored in water for one week. Examination under a dissecting microscope and a scanning electron microscope revealed some variation in results between the different cements. It would appear that not all those materials presently marketed for this purpose are entirely suitable. Whilst 15 seconds is the preferred time for most cements, some require times up to 60 seconds to achieve the best result. Also, some of the cements showed signs of cracking, expansion and distortion after they had been stored in water for one week to allow for maturation before being prepared for viewing under the SEM. It is suggested that this group of cements is not suitable for the 'sandwich' technique.

Acid Etching, Dental↗
PubMed1990

Restorations of eroded areas.

Class V erosion lesions must be restored to reinstate esthetic appearance, overcome sensitivity, or prevent further loss of tooth structure. Restoration has been a problem, but, with the advent of adhesive techniques, it is far less traumatic. The most widely advocated method currently uses composite resin as the primary restorative material with dentin bonding agents. Type III glass ionomer lining cements are also suggested to provide bonding to the dentin. This paper details the requirements for clinical success in the restoration of the Class V erosion lesion using Type II restorative esthetic glass ionomer cements as the primary restorative material with the possible addition of composite resin as a final veneer only if circumstances warrant it.

Composite Resins↗
PubMed1990

Polyacrylic cements in dentistry.

The polyacrylic cements were first introduced to dentistry in the middle 1960's when Smith showed the value of the polyacids, in developing adhesion to enamel and dentine. Within 10 years, Wilson had advanced the concept by changing the powder from a zinc oxide to glass and at the same time varying the poly-acid used. Both cements depend on the development of complex polyacrylate chains which can be linked with metal ions and in turn can form dynamic linkages with both enamel and dentine. The original polycarboxylate cement has many desirable characteristics and is still a useful cement for luting crowns and bridges and for lining cavities. However it is no longer widely used because it has been somewhat overshadowed by the glass ionomer cements which are even more versatile and have superior physical properties. By varying the type of glass, the fluoride content of the glass and the powder/liquid ratio as well as adding inclusions of other metals such as silver they can fulfil a variety of roles in restorative dentistry. However, as with any restorative material, it is essential that the operator fully understand the requirements for successful placement. The basic rules are reviewed for each of the types currently available and the steps for clinical success are detailed.

Acrylic Resins↗
PubMed1990

Esthetics with glass-ionomer cements and the "sandwich" technique.

The Type II restorative esthetic glass-ionomer cement has not been generally regarded as a useful esthetic restorative. However, as long as its relatively slow-setting chemistry is understood and accepted and provision is made to maintain the water balance for the first 24 hours, it can be just as useful as composite resin. Taking into account the fluoride release, its tissue compatibility, and the chemical union with underlying tooth structure that is available, it is suggested that it has a valuable place in restorative routines. Manufacturers have been encouraged recently to try to produce a fast-setting cement that can be polished at the insertion appointment. A varnish to seal newly placed restorations is supplied by most manufacturers, but these are not completely waterproof. A low-viscosity, single-component, light-activated resin bonding agent has been shown to work satisfactorily as a sealant, and, with its use, it is possible to develop adequate translucency and optimal physical properties in the oral cavity.

Adult↗
PubMed1989

Clinical requirements for a successful 'sandwich'--dentine to glass ionomer cement to composite resin.

The composite resins are now being used extensively in restorative dentistry although there are still some problems remaining. Long-term prevention of microleakage continues to be an area of controversy particularly in relation to the margins between dentine and composite resin. Chemical adhesion between glass ionomer cement and dentine is accepted as being a long-term union and it has recently been shown that a mechanical union is possible between composite resin and glass ionomer cement. This has led to the development of the so-called 'sandwich technique' where glass ionomer cement is used as a lining under composite resin restorations particularly where the cavo-surface margin is in dentine. This paper discusses the various levels of adhesion in the 'sandwich' and suggests the best methods of obtaining optimum results from the clinical application of the technique. Particular attention is drawn to the wide variation in the strength of the union depending on the materials used and the methods of handling.

Chemical Phenomena↗
PubMed1989

The wettability of bonding resins used in the composite resin/glass ionomer 'sandwich technique'.

There is some controversy about the significance of the wettability of the unfilled resin bonding agent that is generally recommended for prior application when placing a composite resin restoration. It has been suggested that the degree of viscosity does not matter. However, when investigating the union which is developed between composite resin and glass ionomer cement in the 'sandwich technique', it was noted that when using certain composite resins and their prescribed bonding resins the failure under tensile stress was adhesive at the union rather than cohesive in the cement. Further investigation showed that the bonding resins involved in these failures were more viscous than those bonding resins used in the more successful unions. In this investigation the contact angle of the bonding resin on the surface of glass ionomer cement was used as the measure of viscosity. It is suggested that the degree of viscosity of the bonding resin is significant in the success or otherwise of the 'sandwich technique'.

Acid Etching, Dental↗
PubMed1989

The tensile strength of the union between various glass ionomer cements and various composite resins.

Increasing use is being made of the glass ionomer cements as a lining for composite resin restorations, particularly when restoring posterior teeth. It has been suggested that it is possible to obtain a mechanical union between the two materials by etching the surface of the cement. This paper discusses the result of testing a broad variety of combinations of different glass ionomer cements and composite resins that have been reported on previously, and suggests that a number of factors need to be taken into account if the optimum physical properties are to be achieved from the union. There would appear to be four main factors which dictate the final strength of the union. The tensile strength of the cement itself is of primary importance and it seems the wettability of the resin bonding agent is also significant. When using some of the less heavily filled composite resins, the stresses set up by the setting contraction of the resin may be too great and, finally, the more heavily filled composite resins for restoration of posterior teeth often prove difficult to adapt to the underlying cement. With careful clinical handling, the so-called 'sandwich' technique is very useful. However, not all combinations of glass ionomer cement and composite resin will unite with sufficient strength to be successful clinically.

Chemical Phenomena↗
PubMed1989

The effect of varnishes and other surface treatments on water movement across the glass ionomer cement surface. II.

The aesthetic restorative glass ionomer cements undergo a rather prolonged setting reaction during which time they are susceptible to water uptake and water loss. If they can be maintained in isolation long enough in the oral cavity then the clinical result will be superior. A further series of surface treatments has been tested and it has been shown that immediate covering of the immature glass ionomer cement surface with light-activated bonding resin is the most effective method of limiting water movement across the surface. This restriction of water movement is not effective for all light-activated bonding resins suggesting that there may be a physico-chemical interaction occurring on the glass ionomer cement surface with certain of the resins.

Composite Resins↗
PubMed1988

In vitro studies on the potential for pulpal cytotoxicity of glass-ionomer cements.

Elution samples of glass-ionomer cement were prepared in sterile tissue culture medium either by direct contact between the fluid and standard cement samples or through a layer of human dentin, and then tested for toxicity to cultured mouse fibroblasts (L929). The directly-prepared eluates of the cements were highly cytotoxic, but those prepared through dentin were of either limited or no cytotoxicity. The degree of toxicity of some directly-prepared eluates was reduced by adjustment of the pH to neutrality. It was apparent that dentin reduced the potential for cytotoxicity of glass-ionomer cements to a large degree. Proposed mechanisms for the reduction were limited availability of water at the dentin-cement interface and thus limited dissolution of components, buffering of acid components of the cements by dentin, or other chemical interactions with dentin.

Adolescent↗