A model system to demonstrate the role of cavitational activity in ultrasonic scaling.

A model system consisting of vacuum-deposited aluminum on glass was developed to demonstrate the effectiveness of cavitational activity (occurring within the cooling water supply of a dental ultrasonic scaler) in the removal of particulate material from solid surfaces. The amount of solid material removed from the model system by this cavitational activity was quantified by a spectrophotometric technique. It was shown that cavitational activity occurring within the cooling water is an important contributory factor in the cleaning efficacy of the ultrasonic scaler operated under conditions similar to those employed clinically.

Ultrasound in dentistry. Part 1--Biophysical interactions.

Ultrasound has many applications in the field of dentistry. However, it is only recently that the applications and effects of its physical properties have been rationalized and understood. Ultrasound may be generated by either magnetostriction or piezoelectricity, although the former is more commonly used in dental applications. Interactions of ultrasound with biological tissues may be caused by either thermal or mechanical mechanisms. The mechanical forces produced may be a result of cavitation, acoustic microstreaming and radiation pressure forces. An understanding of these interactions allows a more knowledgeable appreciation of the effectiveness, safety limitations and rationale of dental ultrasonic instrumentation.

Ultrasound in dentistry. Part 2--Periodontology and endodontics.

Ultrasound in the kHz frequency range is used widely in clinical dentistry. The most common uses are in the fields of periodontology and endodontics. The ultrasonic scaler works by the vibratory chipping action of the oscillating tip and is assisted by the presence of cavitational activity in the associated cooling water. When assessing clinical studies it is often difficult to interpret results from different workers due to the lack of standardization of the ultrasonic scaler. Operators should be aware of the oscillatory pattern of different instruments. Endosonics utilizes an ultrasonically oscillating endodontic file to clean and shape the root canal prior to obturation. The cleaning ability of such files is assisted by the occurrence of acoustic microstreaming forces. The endosonic file is prone to constraint when it contacts the canal wall which alters its oscillatory pattern. Clinical techniques should be modified to reduce this problem.

The development of criteria for the assessment of complete dentures.

Criteria for the assessment of complete dentures have been published by several groups of workers but none have proved universally reliable. The present study was undertaken in an attempt to develop criteria of proven reliability for the assessment of the occlusion, articulation, retention, stability and appearance of complete dentures and the health of their supporting tissues. The criteria formulated were subjected to a series of evaluations of their reliability followed by attempts at refinement where this was unsatisfactory. Although levels of agreement between independent assessments made using the criteria improved as the study progressed, an acceptable level of reliability was not attained. The possible reasons for this are discussed.

Problems in the assessment of complete dentures.

The evidence for the reliability of some of the most widely used criteria for the assessment of complete dentures is reviewed and a number of factors discussed which might account for the contradictory nature of this evidence, including methods of statistical analysis, the wording of criteria and possible extraneous influences on the judgment of observers using the criteria. Adequate and consistent reliability has not been demonstrated for any of the criteria which have been proposed and the development of either more reliable criteria or of objective tests of the performance of complete dentures is a priority if the results of epidemiological surveys of complete dentures are to be regarded as meaningful.

'The Yankee dodge': some new observations on the discovery of anaesthesia.

The discovery of general anaesthesia is arguably the most important advance in the practice of surgery. To whom the credit belongs has, however, remained controversial. A first-hand account has now indicated that this controversy can finally be resolved, and that the credit for the discovery of anaesthesia should be given to Horace Wells.

Jaw relationships and complete dentures.

In order to ensure comfort and efficiency from a denture it is important to record correct intermaxillary relationship both vertically and horizontally. A variety of techniques have been developed to produce accurate records and it would appear that a functional technique is most appropriate. Of the methods available evidence suggests that function of swallowing may be particularly useful in this respect.

Experience with ITI osseointegrated implants at five centres in the UK.

Experience with the two-part ITI titanium implant system at five centres in the UK is reported. A total of 461 implants were inserted in 176 patients, who received 189 prostheses. Criteria for the assessment of success following implantation are listed. Results over a 3-year period showed a success rate of 94% when implants were used for mandibular overdentures and crown and bridge prosthetics. A lower success rate in the edentulous maxilla was recorded.

Complete dentures: 1. Treatment planning and preliminary care.

Despite the increasing proportion of the population retaining their natural teeth, there will remain significant numbers of edentulous patients for some time to come. This four-part series aims to help practitioners improve their management of such patients. Part 1 reviews treatment planning and preparation of the mouth, Parts 2-4 will give guidance on impressions and cast preparation; jaw relationships and tooth selection; and insertion, review and denture hygiene.