Success of OCSE examinations.
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Clinical Competence↗
Biomedical subjects
A D Walmsley
Publications and source records attributed to A D Walmsley.
Web site of the month.
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Computer Communication Networks↗
Low intensity ultrasound as a probe to elucidate the relative follicular contribution to total transdermal absorption.
PURPOSE: To investigate the effect of ultrasound on the histological integrity and permeability properties of whole rat skin in vitro. METHODS: A defined, field-free source of ultrasound was used to irradiate excised rat skin prior to in vitro transport studies in Franz-type cells using sucrose, mannitol, hydrocortisone, 5-fluorouracil and aminopyrine. RESULTS: High intensity ultrasound irradiation (1 to 2 W cm-2) irreversibly damaged cutaneous structures and increased the percutaneous transport rate of permeants. In contrast, skin integrity was largely maintained with low intensity ultrasound (0.1 to 1 W cm-2) which merely discharged sebum from the sebaceous glands so as to fill much of the hair follicle shafts. This effect caused the transfollicular absorption pathway to be blocked for hydrophilic molecules that penetrate via this route and reduced the transport rate significantly. CONCLUSIONS: This phenomenon may be used as a probe to elucidate the relative follicular contribution to total penetration for hydrophilic permeants. It was demonstrated that the shunt pathway was responsible for virtually all mannitol and sucrose penetration, perhaps half of hydrocortisone transport but negligible aminopyrine and 5-fluorouracil penetration.
Aminopyrine↗
The external and internal anatomy of human mandibular canine teeth with two roots.
This study investigated the internal anatomy of 65 human mandibular canines with two well-defined roots. The teeth were decalcified and injected with gelatin coloured with india ink. Diaphanization was carried out using clear resin to allow permanent preservation. It was found that all mandibular canines with two roots had two root canals. Lateral canals were found in 68.9% of teeth and 19.7% had lateral canals at the bifurcation. The results of the external measurements (cusp tip to root apex) showed that the average buccal root length was 23.0 mm and the average lingual root length was 22.7 mm. The maximum and minimum buccal lengths were 26.7 mm and 17.9 mm respectively and the maximum and minimum lingual lengths were 27.2 mm and 17.1 mm respectively. The buccal root was the larger of the two in 47.7% of teeth and 43.1% had roots of equal size. The lingual root was larger than the buccal root in 9.2% of cases. Clinicians should be aware of the anatomical variation that exists for mandibular canines.
Cuspid↗
A testing system for electric toothbrushes.
PURPOSE: To assess in vitro the contributions of mechanical and acoustic microstreaming forces around electric toothbrushes to remove cheese using an experimental model. MATERIALS AND METHODS: Four toothbrushes, Braun Oral-B Plaque Remover (D7), Braun Oral-B Ultra Plaque Remover (D9), Interplak (IP) & Sonicare (SC), were investigated. A model system consisting of a layer of 0.2 mm thick cheese was applied to a microscope slide. The toothbrushes were operated in contact with the slide under loads of 0.3 N dry or with the bristles immersed in 2 mm of water. Turbulence around the moving head was assessed with the bristles placed non-contacting, 1 mm above the slide. An experiment with contact for 2 seconds and then 10 seconds non-contact was also made. The slides were stained and image analyzed. The area of removal was measured together with the "average cleaning/brush contact unit area", (the area of removal was divided by bristle contact area. RESULTS: The removal pattern varied. D9 and SC were efficient when operated dry. When the brushes were operated in water, the D9, SC, and IP were efficient in removing the cheese. With no contact, SC produced disruption of the cheese layer while the other brushes did disturb the surface but did not remove completely the cheese. This disturbance without removal was not recorded by image analysis. When the vibrating brushes were allowed to touch the medium and then moved away, a large amount of removal occurred. Larger amounts of removal took place with the D7, D9 and the SC. The use of brushes with a larger head and bristle contact produced a larger area of removal. However, when the "average cleaning/brush contact unit area" was used, the smaller headed brushes produced a larger amount of removal relative to their size. These differences in the removal characteristics between the four electric toothbrushes in vitro suggest that such a model system may prove useful in testing such devices before they are assessed clinically.
Analysis of Variance↗
The electric toothbrush: a review.
OBJECTIVE: To review the use of the vibratory motion of electric toothbrushes to remove plaque and improve gingival health. Recent developments of such devices include the introduction of a small rotary head motion and increasing the frequency of vibration. DATA SOURCES: Articles published in the international literature over the last 10 years. STUDY SELECTION: There are two distinct areas of research: in-vitro studies and clinical trials. In-vitro studies have investigated the effects of cavitation and acoustic microstreaming. Their potential contribution to the action of the working electric toothbrush has been demonstrated in vitro. However their occurrence in the clinical situation has not been fully described. Clinical studies on electric toothbrushes have compared their plaque removing efficacy to either manual brushing or to other commercial electric toothbrushes. CONCLUSIONS: Electric toothbrushes are more effective in plaque removal than manual brushing in closely supervised trials. There is clinical evidence that a small rotating brush rather than a side to side motion is more effective. However, further long-term clinical trials are needed to demonstrate improvements in gingival health which incorporate better controls for the different variables involved. This will assist practitioners to reach an objective assessment of such devices.
Clinical Trials as Topic↗
Web site of the month.
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Computer Communication Networks↗
Overdentures--when and how.
Implant borne overdentures are a reliable and simple solution to denture retention and stability problems. Such a treatment option requires careful planning and the basis for this is made from the results of clinical trials. An overdenture symposium on this subject was held at Naantali, Finland on 26th August, 1994. The following paper is a summary of the proceedings.
Dental Prosthesis, Implant-Supported↗
Implant supported overdentures--the Birmingham experience.
OBJECTIVES: The use of an implant retained overdenture with magnets offers a simple treatment approach to the problem of instability of the complete denture. Advantages with magnets include a simplified clinical technique and reduced lateral stresses on the abutments. This paper reports on a long-term study undertaken at Wordsley Hospital and Birmingham Dental teaching hospital in the West Midlands. METHODS: Twenty-one patients received implant-retained overdentures with magnets over a 5-year period. The average age of the patients was 63 years (range 44-83 years). Seventy-eight Astra (Astra Tech AB, Mölndal, Sweden) implants were placed: 17 patients had four, two had three and two had two implants placed. RESULTS: During the 5-year study, 11 implants were lost, one from infection, and the remaining 10 were lost because of a failure of osseointegration. This equates to an 86% success rate which increases to 97% when implants shorter than 1 cm are discounted. Over this period, the average number of dentures constructed per patient was 2.3. The main reason for denture replacement was a loss of function of the magnets. When the steel casing around the magnets was breached, then corrosion resulted. The life expectancy of the magnets over the 5-year period was 77 weeks (+/-50 weeks). One denture was replaced due to problems of instability. Patient satisfaction with the treatment remains high, and all patients can now wear dentures satisfactorily. CONCLUSIONS: The use of a magnet retained overdenture offers a simple reconstructive approach to complete denture instability. Methods are currently being investigated to improve the clinical function and durability of the magnets. The success rate with the implants remains good after 5 years in function.
Adult↗
Incidence of root face alteration after ultrasonic retrograde cavity preparation.
PROBLEM: Ultrasonic root end preparation is now a recognized clinical procedure. Advantages claimed include improved access to the surgical site (because of reduced root end bevel), and faster more conservative preparation of the root end cavity. However, cracking of the root face has been reported after preparation. OBJECTIVES: The aim of this study was to determine the incidence of root end cracking at varying ultrasonic power levels with a replica technique and scanning electron microscopy. STUDY DESIGN: The root canals of 55 single-rooted teeth were prepared to size 40 apically and obturated with laterally condensed gutta perch and sealer. Root ends were resected at 90 degrees 3 mm from the apex. Class 1 cavities (n = 5) were prepared with retro tips in a Neosonic handpiece with different power settings. Time of preparation and load applied were constant. Another experimental group (n = 5) was prepared with a no. 1 rotary bur. A replica technique with addition-cured silicone impression material and epoxy resin was used to prevent drying artefacts. Specimens were viewed under scanning electron microscope for alterations of the root face. RESULTS: Results showed no root face cracking across the full range of instrument power settings, although chipping of the retrograde cavity margins was observed. No cracking was noted in bur-prepared teeth.
Analysis of Variance↗
Simultaneous kinetic method for the determination of vitamin C, citrate and oxalate employing the Kalman filter.
A kinetic method for the determination of vitamin C, citrate and oxalate in their mixture is described. The method involves the use of cerium(IV) as an oxidant and measurement of reaction rates spectrophotometrically by following the decrease in absorbance of cerium(IV) at 410 nm. The adaptive Kalman filter was used for data manipulation and analysis. It is shown that the use of the Kalman filter is superior to the classical differential kinetic methods owing to its suitability for the determination of analytes that react with a single reagent and exhibit a reaction rate constant ratio of less than 1.5. The results obtained were found to be highly precise and accurate even in the presence of some expected interferents.
Absorption↗
Should clinical lecturers produce their own CAL material?
Clinical lecturers may embark upon the task of creating CAL material unaware of the effort required to produce the simplest of programs. This study aimed to measure the effort involved in such a task in order that those contemplating such development might make a judgement which is well informed. The study entailed a computer literate, yet non-programming clinical lecturer producing a ten-minute CAL program using three different authoring templates. A diary and time log were kept. The resulting pleces of software are discussed as well as the process by which they were created.
Computer-Assisted Instruction↗
Surface integrity of composite inlays following ultrasonic vibration.
PURPOSE: To assess the effect of ultrasonic vibration on the surface integrity of a resin composite inlay. MATERIALS AND METHODS: Ultrasonic vibration in the form of a scaling tip oriented either parallel or perpendicular to the surface was applied to 2 mm thick, 10 mm wide composite discs and the experiment was repeated with the probe oriented perpendicular using composite or rubber shields. The indentations produced were measured using a form Talysurf profilometer. The surfaces of the discs were also observed using scanning electron microscopy. Five discs were used for each experiment. RESULTS: Both parallel and perpendicular orientations produced an indentation with a scattering of composite debris. A significant increase in the depth of indentation occurred if the vibrations of the ultrasonic scaler were oriented parallel to the composite surface (Two sample t- test, P < 0.01). The presence of a composite shield significantly reduced (Mann-Whitney, P < 0.05) the depth of indentation but produced roughening of the surface with impaction of material from the shield onto the surface. The rubber shield, however, polished the surface significantly smoother than the control specimens (Mann-Whitney, P < 0.05). Microscope slide separation was used to measure the thickness of composite luting agent following vibration with an ultrasonic scaling tip with and without a protective sleeve. There was a significantly thinner film of luting agent when an unsleeved scaler was used (ANOVA, P < 0.001). Although an unguarded tip oriented perpendicular to the surface appears to result in the best energy transfer for a thin layer of composite luting agent, it does, however, create minimal surface damage.
Analysis of Variance↗
Caught in the web.
The web is an exciting medium and if carefully used can provide a wealth of information; the sites described in this article are useful starting points. However, the process of getting the information down the telephone line can be time consuming. The collection of pictures for this article, for example, took one hour of surfing the web. However, such activity is fun, educational and when started becomes addictive.
Communication↗
Breakage of ultrasonic root-end preparation tips.
Modified ultrasonic tips are used to prepare rootend cavities during endodontic surgery. The purpose of this study was to determine whether such tips are prone to breakage during use. Ten different tip designs were driven by an ultrasonic unit at maximum power. Multirooted teeth were instrumented, the apex removed, and the tooth was placed horizontally on a pan balance. The apex was instrumented by each ultrasonic tip in turn for 15 min, with the load being increased by 100 g every 5 min. Those tips with curvatures of 70 degrees or greater fractured within the first 5-min loading period. Breakage occurred approximately 2 to 3 mm from the end and always at a bend. Scanning electron microscopy revealed that the fractures were brittle in nature, with little change in the remaining section. Two tips bent: one isthmus preparation tip and one silver point removal tip. All the other designs were deemed satisfactory after experimentation. This study shows that fracture of ultrasonic tips can occur and is related to the degree of bending.
Apicoectomy↗
Factors affecting the cutting ability of sonic files.
The aim of this study was to investigate the cutting ability of sonic files. A model system was developed and the following variables evaluated: file type. Heliosonic or Shaper; file length, 21 or 29 mm; power, air inlet ring opening of half or fully open; stroke length, 2 or 4 mm; stroke rate, one or two cycles per second; and load 50 or 100 g. A 2(6) full-factorial analysis with two replications into the effect of the above variables on the cutting ability of the MM1500 sonic instrument was performed. A new size 25 file was used for each cut, together with water irrigation, and the substrate used was 1-mm thick sections of bovine bone. The differences between the variables were significant (ANOVA, P < 0.001). However, examination of the F-values showed that the most significant variable to affect cutting was load, followed by power, file type, stroke length and stroke rate, with the least significant variable being file length. The most significant interaction was between rate and length of stroke. An increase in stroke rate from one to two cycles per second at a stroke length of 2 mm produced an increase in cutting for both the Heliosonic and Shaper files. However, at the longer stroke length of 4 mm, the same increase in rate resulted in a decrease in cutting for the Shaper files. Therefore, it is suggested that operators should press the file against the canal wall and move it slowly to maximise cutting.
Analysis of Variance↗
Intra-canal cutting ability of MM1500 files.
The aims of this study were to develop a model system capable of monitoring lateral forces during root canal preparation and to measure the cutting ability of files activated by the MM1500 sonic handpiece. Forces were monitored by a calibrated model system which utilized a combination of spring steel beams fitted with strain gauges, these were interfaced through two strain gauge amplifiers to an x-y recorder. Single rooted canine teeth (n = 36; 32 experimental, four control) were mounted in a two-part acrylic mould (which was an integral part of the model system) prior to sectioning horizontally 11 mm from the tooth apex. A 2(4) full factorial experiment with two replications was performed. Four variables were selected for evaluation, load (50 and 100 g), power (air inlet ring half or fully open), file type (Heliosonic or Shaper) and stroke rate (1 or 2 cycles per second). A new file (size 25) was used for 1 min in each canal with water irrigation. The control group was not instrumented. The cross-sectional root canal area was measured before and after instrumentation using image analysis and increase in area was used as an indication of cutting ability. The results showed that the increase in load, power and the Shaper file all produced a significant increase in cutting ability (ANOVA, P < 0.001). However, stroke rate was not found to have a significant effect (P > 0.05). None of the interactions between the variables were significant and there was no significant difference in the control group (P > 0.05). In conclusion, this work has developed a model system to monitor lateral forces and has shown that instrument design and operator usage affect dentine removal from a root canal wall.
Analysis of Variance↗
Taper and stiffness of sonic endodontic files.
The aims of this investigation were to measure the thickness and taper of the different files (Heliosonic 15-40. Shaper 15-40 and Rispisonic 1-6) supplied with the MM1500 sonic instrument and relate this to their stiffness. The diameter of the files (n = 5 for each file type) was measured at 2 mm intervals using light microscopy and a calibrated graticule (mag x 120). A model system was developed for the stiffness testing. The file was held 3 mm from its tip and the load in g required to produce a 45 degrees deflection of the file was recorded. Measurements of file diameter showed that the width of the Heliosonic and Shaper increased in a linear manner and that the file taper was the same for increasing file sizes in accordance with ISO recommendations. The Rispisonic files however showed differing widths and degrees of taper which were not consistent with ISO standards. The stiffness testing results showed the Heliosonic files to be less flexible than the Rispisonic and Shaper files for all sizes (ANOVA, p < 0.001). The differences in stiffness of the Heliosonic, Shaper and Rispisonic files were due to the variation in cross sectional area of metal. In conclusion sonic endodontic files do not have the same taper and stiffness.
Analysis of Variance↗