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Biomedical subjects

A D Walmsley

Publications and source records attributed to A D Walmsley.

At least 19 recordsLinked to original sources
PubMed1992

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.

Dental Scaling↗
PubMed1992

Effect of precurving on the performance of endosonic K files.

This study compared the performance of precurved and straight endosonic files. Size 15, 20, and 25 endosonic K files were precurved to different degrees (20 to 90 degrees) and the resultant oscillatory pattern showed no significant difference compared with corresponding straight files. Endovue blocks were prepared with either a #15, 20, or 25 endosonic file which was either straight or precurved. Those blocks prepared with precurved files had a continuous taper while blocks prepared with straight files had constrictions along their lengths. Finally, a curved root of a human natural tooth had windows prepared along its length so that the oscillatory pattern of the file could be observed. The precurved file oscillated more freely than a straight file as observed by the presence of antinodes along the file and the accumulation of dentin chips within the canal. The results of this study suggest that it is advantageous to precurve endosonic files before using them in curved canals.

Dental Cavity Preparation↗
PubMed1992

Effect of precurving endosonic files on the amount of debris and smear layer remaining in curved root canals.

Endosonic files are prone to constraint; this reduces their efficiency, particularly in the apical third and in curved root canals. Precurving the file may reduce constraint, thereby improving the file's ability to debride. This investigation was undertaken to compare both straight and precurved endosonic files as to debris and smear layer removal. Thirty-six curved root canals were randomly allocated into six groups. Each group was prepared using a step-down technique, then instrumented with either a straight or precurved endosonic file of size 15, 20, or 25. The tooth roots were split and examined under the scanning electron microscope. Blind examinations were made for debris and smear layer removal and evaluation scores were analyzed using a log linear approach. The root canals instrumented with the precurved files had a significantly lower debris score than those prepared with straight files. Precurving did not affect smear layer removal. In conclusion, precurving of files decreased the amount of debris but did not affect smear layer removal.

Dental Cavity Preparation↗
PubMed1992

Effect of subgingival irrigation with chlorhexidine during ultrasonic scaling.

This study examines the effect of a chlorhexidine irrigant during ultrasonic scaling and root planning and compares clinical results with those obtained using a water irrigant. The irrigant was delivered either through a conventional or a recently-introduced ultrasonic scaler, which allows the irrigant solution to be passed through the inside of the scaler tip. The study utilizes a split-mouth design and contrasts the effectiveness of both instruments in improving periodontal health, as measured by standard clinical indices. A preliminary investigation of patient tolerance to treatment performed throughout the clinical trial was also undertaken. Statistical analysis at the 3 and 6 month post-treatment stage revealed no significant differences between the 4 experimental groups in respect of probing attachment levels (P > 0.5), bleeding index (P > 0.1), or plaque index (P > 0.05). Clinical attachment gain assessed by probing ranged from 0.6 to 0.9 mm. Chlorhexidine increased patient tolerance in 77% of cases and the new model ultrasonic scaler was favored over the traditional model in 70% of cases. The magnitude of the tolerance differences was however not statistically significant. The possible potential of the new scaler and of chlorhexidine as an irrigant to reduce patient discomfort is worthy of further investigation than was possible in this study.

Adult↗
PubMed1992

Home bleaching.

In recent years the bleaching of teeth has become very popular. Bleaching regimes are based on the liberation of hydrogen peroxide at the tooth surface. The use of the bleaching products available in the UK as prescribed by a general dental practitioner appears to be valuable in the treatment of discoloured teeth if supervised by the practitioner, although a number of products have been released directly to patients. There is concern that these products are bought and used by patients without any professional supervision.

Acrylic Resins↗
PubMed1992

Postgraduate prosthetic training within the community dental service.

There is a need for clinical prosthetics training for community dentists. This was apparent when a postgraduate course, which dealt with prosthetic care of elderly people, was organised for dentists working in the community dental service. Over 100 community dentists applied for 40 places. At the outset they were asked to complete a questionnaire which addressed their professional career together with their current prosthetic experience. The majority of participants were employed at dental officer level; 18 per cent were at senior dental officer level. Many of the dentists worked in districts where one or more community dentists provided all the prosthetic treatment within the community dental service. The majority of districts receive their prosthetic patients as a result of referrals from a variety of sources. Only eight dentists saw the majority of their patients at domiciliary visits; many did not see any patients in this manner. The course participants considered that their greatest clinical weakness in prosthetic skills was in the production of copy dentures and in denture design. Many of the dentists who attended the course did not provide a prosthetic service but most of them said that they anticipated that the necessity for this would increase in the future.

Adult↗
PubMed1991

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.

Biophysical Phenomena↗
PubMed1991

Measurement of cavitational activity within ultrasonic baths.

The formation of free iodine from the KI/CCl4 chemical dosimeter has been used to quantify the amount of cavitational activity occurring within a 25 kHz cleaning bath under various exposure conditions. The amount of activity occurring within the bath was related to the supply voltage to the cleaning bath, the time of exposure and the volume of solution. An important observation was that the amount of cavitational activity occurring within a glass beaker suspended within a water-filled bath varied by as much as a factor of ten if that beaker contained different volumes of the test solution. Also, the amount of cavitation occurring within the exposure vessel and its contents of an ultrasonic cleaning bath will assist in the cleaning of dental instruments and their accessories.

Carbon Tetrachloride↗
PubMed1991

The efficacy of step-down procedures during endosonic instrumentation.

The step-back method of root canal preparation may not be suitable for endosonic files as they may be prevented from working efficiently within the apical region. This study determined the debris present in the apical portion of the canal after using three different endosonic instruments and compared the step-back versus the step-down technique; the latter involves initial preparation of the upper regions of the root canal which may reduce file constraint. Thirty-six teeth were prepared by either the step-back or step-down method using endosonic generators (magnetostrictive, piexoelectric, and sonic). Preparation times were standardized so that files were used for the same period. From scanning electron micrographs, debris removal was scored on a four-point scale by four clinicians. A log linear analysis showed that there was significantly less debris present with the step-down method using piezoelectric and sonic devices. More debris was present when files driven by a magnetostrictive instrument were used with the step-back method. This study showed that the step-down method may be useful when using certain types of endosonic generators.

Dental Cavity Preparation↗
PubMed1991

Streaming patterns produced around endosonic files.

Acoustic microstreaming is known to be an important phenomenon associated with the use of clinically available endosonic systems. However, it has proved difficult to calibrate its pattern and effectiveness around the oscillating file. An in-vitro model system consisting of slow setting plaster was developed to demonstrate the activity of streaming around both ultrasonically and sonically activated files. For ultrasonic files, streaming occurred mainly in front of and behind the file, in contrast to the sonic file, where the plaster was disturbed evenly around it. With both types of file most activity occurred around the file tip, and became reduced towards the driver. Streaming patterns associated with the ultrasonic device were found to be dependent on the power setting of the instrument and whether the side of the file was constrained or lightly touched. The sonic device produced a large disturbance around the freely oscillating tip. Under load this streaming occurred along the whole length of the file, and was unaffected by constraint. This investigation demonstrated that streaming does occur with the instruments currently available, although it is dependent on their operating conditions. Clinical users of such equipment should be aware of the characteristic three-dimensional patterns of streaming that occur around these endosonic files, in order to maximize their efficiency.

Acoustics↗
PubMed1991

Inherent variability in the power output of endosonic instruments.

The displacement amplitude of endosonic files was measured with the aid of light microscopy in order to determine the power output of different ultrasonic units. The results showed that there was a substantial difference in the displacement amplitudes when the same size of file was used in different ultrasonic units made by the same or different manufacturers. File fracture was found to be a problem when files were driven at high displacement amplitudes.

Dental Cavity Preparation↗
PubMed1991

A new method to assess damaging effects on the gingival tissues of non-surgical instrumentation.

A method of assessing the damaging effects of non-surgical instrumentation was developed. To test the technique, the effect of cavitational activity in the water supply of an ultrasonic scaler was investigated in an in vivo situation. Using a replication technique for the scanning electron microscope, it was shown that the water supply of the ultrasonic scaler caused superficial disruption of the surface of the gingiva, distant from the area of damage caused by mechanical contact. The results indicated that further investigations of this phenomenon using the technique were required.

Dental Scaling↗
PubMed1991

Scanning electron microscopic investigation of changes in the dentogingival area during experimental gingivitis.

The purpose of this study was to investigate the changes that occur in the dentogingival area during experimental gingivitis using a replication technique and scanning electron microscopy (SEM). The upper 1st premolars of 20 subjects were examined prior to plaque accumulation, after plaque had become clinically visible and after 3 weeks plaque accumulation. 3 distinct zones were examined: the tooth surface and its integuments, the gingival crevice and the oral gingiva. Surface features such as perichymata, pits, depressions and cracks were rapidly covered by plaque deposits. These had a raised globular surface with occasional embedded desquamated epithelial cells. Raised plaque colonies were frequently seen by the end of the study. Initially, the gingival crevice presented a layered undulating appearance. With plaque accumulation many desquamating epithelial cells were seen and variations occurred in the width of the crevice. These changes were mirrored in the oral gingiva. The junctional epithelium was initially smooth with occasional pores and emigrating leucocytes. As plaque accumulated, the presence of pores and leucocytes increased and considerable disruption by desquamating epithelial cells was noted. No subject proved resistant to the influence of plaque-induced changes.

Adolescent↗
PubMed1991

Canal markings produced by endosonic instruments.

It has been recognised that ultrasonic files leave a diagonal pattern within the canal following endosonic instrumentation. There is confusion on the causative factor on the production of these marks. Furthermore there is little information about the marks produced by sonic files. An in vitro system consisting of highly polished dentin discs demonstrated that the ultrasonic K-file made a diagonal pattern that was an imprint of the cutting edges of the file. The sonic files produced different markings which were the result of their longitudinal and transverse motion. Root canals of extracted teeth were prepared with these instruments and similar grooves were observed. The ultrasonic K-file had diagonal grooves in the coronal and middle third of the root canal but longitudinal marks in the apical third. The rispisonic and shaper files produced debris even in the presence of NaOCl. This debris was formed into discrete parallel bands. Both longitudinal and transverse grooves were present and the canal had many other scratches similar to those seen with the dentin discs. There were differences between the marks produced by either ultrasonic or sonic endosonic instruments but it is unknown whether this influences the long term prognosis of the root canal therapy.

Dental Cavity Preparation↗