Biomedical subjects

A D Walmsley

Publications and source records attributed to A D Walmsley.

At least 73 records · Page 4Linked to original sources

PubMed1996

Analysis of the surface cut by sonic files.

The purpose of this investigation was to compare 3D profilometry and SEM analysis of a polished surface of bovine bone instrumented by sonic files. Two situations where investigated, i) no operator assisted movement, ii) operator assisted movement. Heliosonic, Rispisonic and Shaper files were investigated at full power setting and an interfacial load of 100 grams. The specimens were subjected to analysis using a 3D Form Talysurf prior to being sputter coated with gold and viewed under an SEM. The 3D surface analysis was found to be complimentary to SEM evaluation in that each provided additional information to the other. 3D analysis proved to be excellent for showing the topographical nature of the cut surface and gave a better indication of depth than the SEM. Debris was however more apparent on SEM evaluation. Each file showed distinctive characteristics in the shape that was cut. The cutting appeared to be as a result of abrasion with no operator assisted movement and was as a result of the longitudinal file action. However when movement was superimposed on this action continuous chip formation was apparent especially for the Rispisonic and Shaper files.

Animals↗

PubMed1995

Cutting ability of an ultrasonic retrograde cavity preparation instrument.

The aim of this study was to investigate the cutting ability of a working ultrasonic instrument designed for surgical endodontic use (Neosonic, Amadent Corp, Cherry Hill, NJ, USA). Three designs of tip, designated CT 1 to CT 3 were calibrated by measuring their displacement amplitudes in air using light microscopy over a range of power settings. Extracted teeth were sectioned longitudinally and polished to produce a smooth dentine surface onto which the tips were applied for 1 minute over the above range of power settings at a load of approximately 20 g. The depth of cut in the dentine surface was measured using a two dimensional surface profilometry technique. Results showed that a raising of the power setting produced an increase in displacement amplitude and cutting ability for all tip designs. This increase was linear, with minimal cutting occurring at lower power settings. In conclusion the ultrasonic tips could be successfully used to remove dentine, and medium to high power settings optimised their efficiency.

Analysis of Variance↗

PubMed1995

Applying composite luting agent ultrasonically: a successful alternative.

The authors conducted research to determine if sonic vibration affected the viscosity of a composite luting agent. They found that using either an ultrasonic or a sonic scaler can thin composite resin. The thickness of the lute is similar to that resulting from manual loading methods, but it is obtained in much shorter time periods and with lower loads.

Composite Resins↗

PubMed1995

Effect of instrument power setting during ultrasonic scaling upon treatment outcome.

Ultrasonic scalers may be operated at different power settings which may influence the final therapeutic result. The displacement amplitude of the scaling tip may affect scaling efficiency or the degree of root surface damage. This investigation aimed to determine whether there was any difference in periodontal healing, as assessed by standard clinical methods, when an ultrasonic scaler was operated at full or half power in patients suffering from mild to moderate adult periodontitis. Seventeen patients with chronic adult periodontitis were entered into the study and a split mouth design utilized. Quadrant allocation was randomized, 2 quadrants being treated at full power and 2 at half power. At baseline, probing attachment levels, bleeding and plaque indices (BI and PI) were recorded and oral hygiene instruction given. Two weeks later all measurements were repeated and further recordings made at 1, 3, and 6 months post-therapy. Statistical analysis demonstrated no differences between groups at baseline (P > 0.3) for all parameters. At the post-oral hygiene stage, there were significant attachment gains for both experimental groups (P < 0.04), but no differences were found between the groups (P > 0.6). At 6 months, mean attachment gains for the half power and full power groups over baseline measures were 0.5 +/- 0.5 mm and 0.4 +/- 0.3 mm, respectively (P < 0.002), and there were no significant differences between the groups (P > 0.5). The results show that the use of the half power setting was as effective as using the ultrasonic scaler at full power.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗

PubMed1995

An in vitro evaluation of electric toothbrushes.

Four commercially available electric toothbrushes (Sonicare, Braun Electric Toothbrush, Interplak, and Blend-a-Dent) were assessed both for their operating characteristics and their ability to remove a "food debris" medium. The Sonicare and Blend-a-Dent have a lateral vibratory action, while the Interplak and Braun produce a rotary movement of the brush head. The vibratory action of the Sonicare was susceptible to loading. All devices produced both stable-pulsating cavitation and acoustic microstreaming that was demonstrated in vitro using a suspension of particles in water. Their effectiveness in removing a food debris medium was assessed with and without water. Three of the brushes (Sonicare, Braun, and Blend-a-Dent) were similar in their ability to remove the plaque, and all were superior to the Interplak; its streaming forces removed no food debris. The results indicated that the Blend-a-Dent was the most effective brush design in vitro, although the differences between Blend-a-Dent and Sonicare were not statistically significant.

Dental Plaque↗

PubMed1995

Sonic instruments in root canal therapy.

Although hand instrumentation is considered the most acceptable method of preparing root canals, sonic instruments may be useful additions to the endodontic armamentarium. Sonic instrumentation may be incorporated as an adjunct to traditional techniques for shaping the root canal. The use of such instruments may assist the practitioner during root canal treatment in general practice.

Dental Instruments↗

PubMed1994

Effect of air inlet ring opening on sonic handpiece performance.

This study investigated the effect of air inlet ring opening on the oscillatory pattern of the MM 1500 sonic handpiece and files. The oscillatory pattern of the driver head and files in air and under load was determined microscopically. The results showed that a critical opening of the air inlet ring was necessary to elicit oscillation of the driver head and sonic file. The driver oscillated in an elliptical manner, the displacement of which varied with air inlet ring opening. When operated in air the file exhibited an elliptical movement which was influenced by different design, length and thickness. This action was constrained under load and replaced by a longitudinal action of the same dimension for all files which appeared to have an efficient cutting action. This work shows that air inlet ring opening increases oscillation of the driver head once a critical opening has been reached and that clinical loading does not constrain the cutting action of the file.

Oscillometry↗

PubMed1994

A model system for evaluating filing technique.

The aim of this study was to develop a model system to demonstrate the pattern of load and how much is applied. A lower molar was mounted on a beam and attached to a mandibular phantom head jaw. A strain gauge fitted to the beam allowed loading of the molar to be recorded, during root canal preparation. Ten operators were asked to instrument the distal root canal; after preparation the operators were shown a graphical representation of the loads applied. This formed the basis of discussion and instruction in filing technique. The operators then repeated the filing. The results showed that prior to instruction operators used a push-pull motion, applying a constant lateral force to the canal wall. After instruction and discussion of the graphical representation of the loads applied the stroke rates used were slower and loads applied were higher (two-sample t-test, n = 10, P < 0.01). The experiment was repeated 1 year later and this showed that the change in technique had been retained. In conclusion, this model system allows visual feedback to the operator and can be used as an aid to teaching filing technique.

Analysis of Variance↗

PubMed1994

Variability of sonic scaling tip movement.

The sonic scaler operates at frequencies of 2 to 6 kHz and is powered by pressurised air from the dental unit. Variables likely to affect how these instruments perform include the air pressure input and load applied by the operator. Other variables include the brand of scaler used and the clinical technique of the operator. The aim of this study was to investigate differences in instrument performance within a dental teaching hospital. Light microscopy was used to measure the displacement amplitudes in air of 32 Sonic scalers which were in regular clinical use in three departments (Periodontal Unit, Restorative Unit and School of Hygiene). During operation, the air pressure was kept at a constant 2.8 kg cm-2 and measurements were made on each instrument with three scaling tips (universal, sickle and periodontal). The periodontal scaling tip exhibited the greatest vibration although this was not significant (p > 0.1). There was a significant difference in performance between the different clinical environments where the scalers were used (p < 0.01). 4 new sonic scaling instruments made by different manufacturers were selected for displacement amplitude measurements. One brand of sonic scaler demonstrated a significantly greater displacement amplitude in comparative measurements between instruments (p < 0.01). This study demonstrated differences in the oscillation of sonic scalers which should be recognised by clinicians when using these instruments, since they may influence clinical performance.

Calibration↗

PubMed1994

An in vitro investigation into the cutting ability of ultrasonic K files.

Endosonic files vary in their oscillation when operated in air with the greatest displacement at the unconstrained tip. It was the aim of this study to investigate how files of different lengths and sizes varied in their ability to cut dentine. Single rooted teeth were sectioned to produce 1 mm dentine discs. These were positioned on a plastic block connected to a load transducer. Endosonic K-files (#15 to 25) were used to cut the disc for 10 s using operator assisted movement. The files contacted the disc at the following points along their length; apical (3 mm from tip), middle (8 mm from tip) and coronal (13 mm from tip) under applied loads of 30 and 50 g. The depth of cut produced by each file was measured using light microscopy. The #15 and #25 were similar in their pattern of dentine removal. The #20 file produced a large variation in its cutting ability and was also susceptible to fracture. The tip of the files was prone to constraint at higher loading with the thicker part of the file producing more cutting. It was concluded that the pattern of dentine removal of endosonic files was affected by the amount of load applied. The displacement amplitudes of endosonic files in air would not appear to be a good indicator of file cutting ability.

Analysis of Variance↗

PubMed1993

Magnet retained overdentures using the Astra dental implant system.

The Astra Implant System (AIS) is a biologically sound and simple way of providing stability for the complete lower denture where anatomical changes have made retention, stability and comfort difficult to achieve. An ongoing clinical study has been undertaken where 20 patients have been provided with magnet retained overdentures using this implant system. This represented a total of 70 implants placed. Seven implants were removed from four patients (three at exposure, one infection). The remaining implants have been followed up for 12 to 25 months and are considered to have achieved successful osseointegration. All the patients in the study are successfully wearing a lower denture retained by magnets. The overall success rate for the implants placed is 90% but if implants less than 9 mm in length are excluded from the results then the success rate is 97.7%.

Aged↗

PubMed1993

Cleaning of oval canals using ultrasonic or sonic instrumentation.

This study investigated the effect of direction of file oscillation on the amount of debris and smear remaining within oval canals. Sixty-five lower premolars were allocated to six experimental groups (n = 10) and one control group (n = 5). Canals were prepared using Gates Glidden burs and hand instruments. Preparations were completed using either an ultrasonic size 15 K file or a sonic size 15 shaper file. Three preparation techniques were used: (a) file oscillation toward oval recesses within the canal, (b) file oscillation at right angles to the recesses, and (c) rotational movement of handpiece. Canals were examined under the scanning electron microscope and blindly scored for debris and smear layer. Log linear analysis revealed no significant difference (p > 0.05) between sonic or ultrasonic instrumentation as to debris or smear layer remaining. File oscillation directed toward oval recesses left the least amount of debris (p < 0.05). Smear layer remained unaffected by all techniques.

Chi-Square Distribution↗

PubMed1993

Variations in stroke rate and loading using hand sonic or ultrasonic instrumentation.

An in vitro model system was developed to investigate the stroke rate and loading during hand, sonic, or ultrasonic instrumentation. The model system consisted of a mandibular molar tooth attached to a strain gauge and interface to a computer. Ten clinicians instrumented the distal canal of lower molar teeth. Stroke rates used and loads applied were measured using different sized files with the three different preparation techniques. There was no significant difference in stroke rates between different file sizes (p > 0.05) within the same generator, however, stroke rate for hand was significantly slower than for sonic or ultrasonic (p < 0.01). Loading of the canal wall rose with increase in file size which was significant for hand (p < 0.01) and sonic (p < 0.05) but not ultrasonic (p > 0.05). There was a tendency for loading to be higher with hand instrumentation, this however was not significant (p > 0.05).

Calibration↗

PubMed1993

West Midlands regional training scheme for orthodontics in dental practice.

The need for continuing education in orthodontics is recognised by many practitioners and the demand for post-graduate courses is high. The limitations of such courses, particularly the short technique type, are recognised and within the West Midlands the value of a longer term clinical attachment has been emphasised. The West Midlands has a well established orthodontic consultant service with fifteen NHS and one honorary consultant; the specialist practitioner service is small by national standards. All of the orthodontic consultants have long supported the clinical assistant post as a valuable vehicle for practitioners' continuing education. Building on the example given by the consultants in the four Thames Regions, a structured, centralised academic programme has been developed to enhance the clinical training given during these two year posts.

Curriculum↗

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↗