Effects of low fluoride concentrations on formation of caries-like lesions in human enamel in a sequential-transfer bacterial system.

Human enamel surfaces were exposed to sequential batch cultures of Streptococcus mutans NCTC 10832 in a sucrose-rich medium containing 0-5 mg/l added fluoride (F). In 10-day experiments, subsurface lesion formation was partly inhibited by 1 mg/l F and completely by 2 and 5 mg/l F, but small lesions formed in 2 mg/l F in 21-day experiments. Analysis of the spent media, together with analogous, bacteria-free experiments, suggested that lesion inhibition involved two main effects. First, inhibition of bacterial acid production reduced the pH fall, resulting in reduced undersaturation with respect to hydroxyapatite and consequently reduced rate of demineralization. Secondly, interaction of F with enamel mineral resulted in a small increase in reprecipitation during periods of supersaturation and a much larger reduction in demineralization during periods of undersaturation. It is concluded that, at low F concentrations, inhibition of bacterial acid production is a major factor in lesion inhibition, which may contribute significantly to caries prevention in vivo where plaque fluid F levels are raised by frequent topical applications.

Bonding of a light-curing glass-ionomer cement to dental amalgam.

In the clinical situation, the need may arise for placement of a glass-ionomer cement over an existing amalgam restoration. This study assessed the tensile bond strength of a recently developed light-curing glass ionomer (Vitrabond) to dental amalgam (Dispersalloy), with and without the use of Scotchbond dual cure as an intermediary. Amalgam adherend specimens were prepared, then aged in water at 37 degrees C for seven days. Immediately before being bonded, the amalgam surfaces were finished flat on 600-grit paper. Forty specimens were used for bonding in this condition, and another 40 were covered with a thin layer of Scotchbond, which was light-cured for 10 s. The glass-ionomer was applied to the adherend surface in two increments, each light-cured for 30 s. After being bonded, half the specimens were stored in water at 37 degrees C, while half were stored in an environment of 95 +/- 5% RH at 37 degrees C. The 24-hour tensile bond strengths, in MPa, were: for specimens stored in water, without Scotchbond 8.4 +/- 1.2, with Scotchbond 4.7 +/- 1.3%; and for specimens stored in 95 +/- 5% RH, without Scotchbond 9.2 +/- 2.1, with Scotchbond 4.6 +/- 1.5. The data were further analyzed by the Weibull distribution function. It was concluded that a strong reliable bond can be achieved between Vitrabond and set Dispersalloy, and that the use of Scotchbond as an intermediary is contra-indicated.

Technical note: resin-to-metal bonds mediated by adhesion promoters.

This study aimed to establish whether the bonding between a composite cement (Comspan Opaque) and grit-blasted nickel-chromium alloy (Biobond Plus) could be enhanced by pre-treatment of the alloy surface with adhesion promoters. Six groups of metal adherends, of ten specimens each, were prepared. The specimens in each group were finished flat and blasted with 50 microns alumina. The first group was used without further treatment of the metal surface. A second group was electrolytically etched. Each of the remaining four groups was treated with an adhesion promoter. The resin cement was bonded to the adherend and, after 24 h in water at 37 degrees C, the tensile bond strengths were determined. ANOVA and the Scheffé test at the 0.05 level showed that Scotchbond dual-cure dental adhesive enhanced the resin-to-metal bond significantly and produced a mean bond strength value (30.9 MPa) higher than that obtained with electrolytic etching (22.7 MPa) or grit-blasting (14.6 MPa). This would appear to be of considerable significance. The metal primers, ABC primer and GoldLink, and the ceramic primer, Scotchprime, were much less effective than Scotchbond dual-cure.

Biological and clinical investigations of a glass ionomer base material.

OBJECTIVES: The purpose of this study was to investigate the biological properties of a new glass ionomer base material containing strontium glass. METHODS: The glass ionomer base material (Base Line, De Trey Dentsply) was tested for cytotoxicity using a standard agar diffusion test, for its effect upon the pulp in subhuman primates, and in a clinical study as base beneath both composite fillings and amalgam fillings. RESULTS: The material showed a cytotoxicity pattern similar to reference materials, a zinc phosphate cement and a reference glass ionomer base material, which are used successfully in clinical applications. With the pulp/dentin usage test in subhuman primates, there were no statistically significant differences between the experimental glass ionomer base material and the negative control group if bacterial contamination of the cavity floor or direct contact with the pulp was avoided. The results of the clinical study also indicated no pulp damage after one year. SIGNIFICANCE: The experimental glass ionomer base material proved to be acceptable both biologically and clinically.

Comparison of dental status determined in an epidemiological survey with prosthetic treatment received.

The potential need for prosthetic treatment among 720 dentate Scottish subjects of the 1978 UK Adult Dental Health Survey, was assessed by applying treatment criteria to the epidemiological data. The need was compared with the prosthetic treatment that was received under the National Health Service within 1 and 3 yr. It was found that 220 people had a need for dentures. 12.7% of the people who attended a dentist with a prosthetic need received the predicted treatment within 1 yr and 21.3% within 3 yr. Considered at the community level, as would be the case when planning a service, only 10% of those with a predicted need received the predicted treatment within 3 yr. 5.1% of the whole sample received more than the predicted treatment. This included 25 of the 500 people for whom the criteria predicted no need for dentures. 25.3% of the sample received less treatment than predicted. Taken overall, these findings indicate that the amount of prosthetic treatment demanded in the community was 28.6% of the amount predicted by the epidemiological survey. It would seem that prosthetic services in Scotland should be planned on this basis.

Dental health services research in Scotland: a review of some 5-year results.

A longitudinal study of dental treatment carried out by the Dental Health Services Research Unit in Dundee has provided a unique opportunity to investigate a variety of aspects of dental care received by a sample of dentate individuals over 5 yr. The distribution of treatment indicated that frequent attenders, especially those who changed dentist, were particularly prone to having teeth filled and that two-thirds of the restorative cost was spent on restoring tooth surfaces that had previously been filled. A quarter of the sample had severe periodontal disease and they tended to visit a dentist less frequently than those with mild periodontal disease. They were also more likely to have teeth extracted but less likely to have a scaling or other periodontal treatment than the moderately diseased. The findings suggest that there is considerable scope for a less treatment-orientated approach to the management of dental caries for those who currently receive most of the restorative treatment. The majority of the population who receive little dental care, especially those with severe periodontal disease, would probably gain by visiting a dentist more frequently. Dentists need to acquire a more positive attitude towards prevention and an increased ability to make intellectually based decisions not to treat.

Implications of recent dental health services research on the future of operative dentistry.

Recent dental health services research has shown that restorations often last only a few years and has suggested that the compromising nature of some basic operative skills is at least partly responsible. Further, gross inconsistencies of diagnosis and treatment planning exist among dentists, leading to a considerable lack of agreement about when restorative treatment is necessary. In the interests of high-quality dental care, some of the long-standing dogma concerning restorative dental services and attitudes toward them should be questioned. At the public health level, the dental profession should strive to find ways of achieving satisfaction with less emphasis upon restoring and re-restoring teeth so that dentistry will attract the public and remain fully relevant to their needs.

The effect of changes in caries prevalence on dental education.

While rising levels of dental caries were primarily responsible for the growth in dental schools in developed countries, the recent decline in caries prevalence has not resulted in a major decline in dental education. Indeed, the reduction in caries prevalence has had very little influence upon a group of major changes that arguably should have had a marked effect upon dental education in recent years, but which have failed so to do. These include a quantum leap in applying the scientific basis of caries management, focused down to the teaching of minimally invasive restorative care within a context of risk assessment and maximum non-invasive care where appropriate. A possible way forward in accelerating the necessary changes in dental practice would be for only a proportion of dental undergraduates in the future to be taught practical restorative procedures, leaving the remainder to concentrate on diagnostic and non-invasive care without the distraction of possible restorative treatment.

Overtreatment with restorative dentistry: when to intervene?

Traditional restorative dental treatment has many shortcomings and has not been shown to be an effective method for managing caries. In spite of this, many dentists continue to be powered by an aggressive restorative approach which may result in unnecessary treatment and which must now be seen as inappropriate. There is a pressing need for a greater understanding as to the precise criteria that dictate the need for both non-invasive (reversible) preventive measures and invasive (irreversible) restorative treatment. This paper examines these criteria and provides decision trees with respect to the clinical management of carious lesions and teeth with existing restorations, showing when, and what type of, intervention is required. The assessment and management of fissured tooth surfaces receives special attention. It is demonstrated that while many clinical situations warrant clinical intervention, often this should be entirely preventive and of a non-invasive type.

Restorations without conventional cavity preparations.

Dentists in developed countries tend to provide highly restoration-oriented dental care, yet recent research has shown that restorations have many shortcomings and that a costly and repetitious restorative cycle is easily established. In particular, caries diagnosis and restorative treatment planning are subject to considerable idiosyncrasies. Coupled with mediocrity in cavity preparation and restorative technique, this results in many restorations having poor life expectancy. The non-invasive management of small carious lesions in a manner that will bring about some remineralization offers, under certain circumstances, a viable and superior alternative to conventional restorations. However, carious lesions in smooth surfaces of the teeth present very different diagnostic and assessment problems from those in fissured surfaces and the methods of clinical management differ markedly. Fissure sealants have been applied to early or moderately sized pit and fissure carious lesions in many studies during the last 20 years. Where the sealant has remained intact, evidence has been provided to show that the caries has not progressed. There would seem, therefore, to be a strong case for using fissure sealants more widely in the management of pit and fissure lesions and, in this way, to provide restorations without cavity preparations. In situations where invasive procedures are required, conventional 'Black' cavity preparations should not be used. Rather, they should be ultra-conservative and of very high quality. Clearly, a preventive philosophy in caries management should actively be encouraged in countries with developed dental services.(ABSTRACT TRUNCATED AT 250 WORDS)

Treating restorative dentistry to health.

The concepts that underpin much of dental practice need refocusing so as to accommodate the many scientific advances that have been made in recent years in understanding oral disease processes and their management. "Treatment' should come to mean what it says, namely the curing of diseases- and much of this can only be accomplished by non-invasive means. Restorative procedures should be seen simply as prosthetic, making up for lost tissues. The sequence of events with respect to caries should usually be diagnosis followed by treatment, and then the option of restoration if appropriate. In order to achieve this state of affairs for the whole population, I believe it will be necessary to stream dental undergraduates so that, while a portion learn restorative techniques and become licensed to practise them, the remainder concentrate on the non-restorative aspects of dentistry, having a special emphasis on the prevention and non-invasive "treatment' of oral and dental diseases, including caries, on a community scale. This latter group of dentists would not be licensed to undertake restorative procedures.

Keeping up-to-date with tooth notation.

Methods of tooth notation have evolved over the years and there is now an increasing desirability for a system which offers the maximum in precision, clarity and compatibility with typing and computing requirements. A review of the many available methods leads to the FDI two-digit system as being highly appropriate for today's needs. This system is being adopted increasingly, worldwide.

Bonding dental amalgam to a light-curing glass-ionomer liner/base.

At a time when amalgam is used widely, yet when the criteria for its use are still evolving, the incorporation of an element of adhesive bonding between the amalgam and the base material may come into greater prominence and aid the general move towards more conservative new or replacement cavity preparations. This study assessed the 24-hour tensile bond strength of amalgam (Dispersalloy) to a light-curing glass-ionomer liner/base (Vitrabond), using Scotchbond dual cure, uncured Vitrabond or Vitrabond liquid as intermediaries. Using the Weibull distribution function, it was found that uncured Vitrabond was a better intermediary than Scotchbond or Vitrabond liquid. The bond strengths obtained with uncured Vitrabond intermediary were of the same order as those which can be expected between a glass-ionomer cement and dentine. This suggests scope for developing techniques for bonding amalgam to parts of cavity preparations.

Resin-to-enamel bonds: effect of cleaning the enamel surface with prophylaxis pastes containing fluoride or oil.

A thorough dental prophylaxis before acid-etching of enamel is often recommended. In the method most commonly used, a slurry of pumice is applied with a rubber cup. Oil-based and fluoride-containing prophylaxis pastes are not generally recommended because of fears that they might hinder the etching process. This study assessed the 24-hour shear strength of resin (Scotchbond 2/Silux Plus) bonded to etched enamel which had been cleaned before acid-etching with a slowly rotating rubber cup loaded with: (1) wet pumice; (2) fluoride-containing non-oil-based pastes (En-De-Kay fluoride paste, Nupro fluoride paste); (3) non-fluoride oil-based paste (Kemdent); and (4) nonfluoride non-oil-based pastes (Nupro, Orapol). The bond strength values obtained after using the various cleaning agents were similar. Furthermore, bond failure in all the test groups was of the cohesive type. It therefore appears that prophylaxis pastes containing fluoride or oil may be used to clean the enamel before acid-etching.

Bond strengths of dentine bonding agents to dentine.

This study assessed comparatively the tensile bond strengths to dentine of four resin dentine bonding agents. Flat surfaces were produced in the occlusal dentine of human third molars, finished with 600-grit paper and prepared for bonding to Silux Plus composite with Gluma, Prisma Universal Bond 2, Scotchbond 2 and Tenure. After 24 hours in water and 250 thermal cycles, the specimens were loaded in tension to failure on an Instron machine. There were 20 specimens in each test group. An analysis of variance and Duncan's test showed that the bond strengths of Scotchbond 2 (22.8 +/- 7.2 MPa) and Prisma Universal Bond 2 (20.1 +/- 7.8 MPa) were similar but significantly higher than those of Tenure (14.3 +/- 5.3 MPa) or Gluma (12.3 +/- 6.4 MPa). A Weibull analysis confirmed the superiority of Scotchbond 2 and Prisma Universal Bond 2. Scotchbond 2 and Prisma Universal Bond 2 specimens failed either in an adhesive-cohesive mode, or cohesively through the composite or the dentine. It was concluded that Scotchbond 2 and Prisma Universal Bond 2 are effective and are the dentine bonding agents of choice.

Bonded amalgam restorations: a comparative study of glass-ionomer and resin adhesives.

This study assessed the effectiveness of a glass-ionomer liner/base (Vitrebond) and two adhesive resins (Amalgambond and Panavia Ex) in bonding amalgam to enamel/dentine cavities in vitro. Restorations placed without any intermediary, or with varnish, served for comparison purposes. Standardised unretentive cavities on the buccal sides of a total of 78 extracted human molar teeth were prepared to receive the restorations. After application of the adhesive materials (without light curing the Vitrebond), the cavities were filled with amalgam (Dispersalloy). Each specimen was stored for 24 hours in distilled water at 37 degrees C. The amalgam restorations were then pulled from the cavities using an Instron machine and the retentive strength values were recorded. The results showed that any of the three adhesive intermediary agents substantially enhanced the retention of the amalgam restorations. The Vitrebond specimens had the highest mean retentive strength value (133 N), followed by Amalgambond (18% lower) and Panavia Ex (38% lower); the difference between the value for the Vitrebond specimens and that for the Panavia Ex specimens was statistically significant. The Vitrebond specimens failed due to gross enamel fractures and a cohesive failure of the glass-ionomer layer. The Amalgambond specimens failed at the resin/amalgam interface, while the Panavia Ex specimens showed enamel fractures and failure at the resin/dentine interface. It appears that Vitrebond has the potential for being an effective amalgam adhesive in vivo.

Changing perceptions of the requirements of cavity preparations.

Perceptions of the requirements of cavity preparations have changed over the years. These have had a significant effect on undergraduate teaching at the University of Bristol Dental School, an explanation of which may help general dental practitioners in their quest for information on this important aspect of dental practice. A method is described for teaching undergraduate dental students cavity preparation in caries-free teeth, based upon the position, shape and extent of imaginary carious lesions. Scale diagrams of teeth are used, on which imaginary caries at the amelodentinal junction has been marked. The students are instructed to apply the principles of cavity preparation to equivalent, but caries-free, teeth in the laboratory. 'Outline forms' and other predetermined cavity shapes are not taught. Dental practitioners may find it appropriate to apply similar thinking to cavities they prepare in everyday practice, in an endeavour to avoid the unnecessary removal of tooth tissue that would be better retained.

Diagnosis and treatment of dental caries: the clinicians' dilemma. Scope for change in clinical practice.

The prevalence of dental caries is decreasing, yet the proportion of General Dental Service expenditure devoted to restoring teeth continues to rise. This appears to reflect a deep-seated restorative philosophy, yet some carious lesions can be arrested. New restorations often contain characteristics consistent with in-built obsolescence, which explains why restorations are often not very durable and why two-thirds of all restorative treatment involves replacing them. The problem is compounded by the fact that disagreement among dentists as to which restorations should be replaced and why, is of alarming proportions. The universal adoption of a preventive approach to making treatment decisions, especially with respect to early carious lesions and mechanically imperfect restorations, could be a major factor in reducing the restorative burden of the dental service.

Inhibition of demineralization in vitro around amalgam restorations.

OBJECTIVE: The purpose of this in vitro study was to evaluate some forms of preventing or avoiding demineralization within enamel cavity walls adjacent to amalgam restorations. METHODS AND MATERIALS: Third molar teeth were sectioned to obtain 72 specimens, divided into one control and five experimental groups: amalgam only; varnish plus amalgam; acidulated phosphate fluoride plus amalgam; adhesive amalgam; glass-ionomer cement plus amalgam; control (amalgam only, not subjected to a demineralization challenge). The experimental groups were subjected to PH and thermal cycling and then submitted to enamel hardness determinations. RESULTS: Significant differences between the treatment groups revealed that the bonded amalgam technique offered the best resistance to demineralization. The use of cavity varnish resulted in greater mineral loss than amalgam placed alone. CONCLUSION: The use of an adhesive system, glass-ionomer cement, or acidulated phosphate fluoride under amalgam restorations may interfere with development of secondary caries.