Biomedical subjects
C Longbottom
Publications and source records attributed to C Longbottom.
The challenges of validating diagnostic methods and selecting appropriate gold standards.
Caries diagnostic methods are usually methods for caries lesion detection and measurement. Caries lesions occur on a continuous scale of tissue damage, from subclinical surface changes to macroscopic cavities reaching the pulp. Any change of a lesion on this continuous scale offers the opportunity for the diagnosis of disease activity or remission. Research aimed at remineralizing agents may focus on lesions that are amenable to remineralization, and select a method that will measure small changes in early lesions. General caries management strategies depend on detecting all stages of lesion development, and methods covering early to late stages are preferred. This paper addresses some methodological issues in validating caries diagnostic methods. The available gold standards for caries lesions are discussed, with their suitability in different applications, and their "validity" as far as it is known or can be inferred. The gold standards are compared as far as their measurement of lesion parameters and reproducibility is concerned. Tentative conclusions are formulated, and recommendations for future research are given.
Electrical measurements for use in caries clinical trials.
This paper reviews the use of electrical measurements of caries, particularly in relation to caries clinical trials. Electrical measurements change as tooth tissue porosity alters in the caries process, but several other variables also have a significant effect on these electrical measurements and hence upon their diagnostic validity. Available electrical-method data, in the context of clinical trials, relate to the use of the Electronic Caries Monitor (ECM), which measures "bulk" resistance. The device is presently limited in scope to occlusal surfaces, and only limited ECM data from clinical trials are available. In the context of clinical trials, more work is needed to determine the potential role of electrical measurements. Such research will need to focus both on an understanding of those electrical parameters which are most valuable in identifying changes and stages in the caries process in individual teeth and also on identifying the extent of the effects of the variables affecting these measurements.
Tackling oral health inequalities.
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Does social deprivation in 1, 2, 3 and 4-year-old Scottish infants influence the frequency isolation of caries-associated micro-organisms?
OBJECTIVES: The aim of this study was to determine if there are associations between the level of social deprivation/affluence and the frequency isolation of caries-associated micro-organisms (Streptococcus mutans, Streptococcus sobrinus, lactobacilli and yeasts) in a large cohort of infants examined annually from 1 to 4 years of age. METHODS: DEPCAT was used to measure the socio-economic status of all consented infants (n=1099--1392) born in Dundee during a 1 year period (total n=1974). Caries-associated micro-organisms were cultured from saliva when the infants were 1, 2, 3 and 4 years of age. Standardised dental examinations were also carried out annually. Log linear analysis, which controlled for caries, was used to look for associations between DEPCAT and the isolation frequency of caries-associated micro-organisms. RESULTS: When controlling for caries, there was an association between DEPCAT and the isolation frequency of yeasts when the infants were 1 and 2 but not when 3 and 4 years old, whereas lactobacilli were associated only when the infants were 3 and 4 years old. Correlations between S. mutans and social deprivation were usually dependent on the caries status of the infants. CONCLUSIONS: The relationship between social deprivation and the isolation frequencies of caries-associated micro-organisms is complex with lactobacilli developing an association when the infants were 3 and 4 years old in contrast to yeasts which were only associated when the infants were 1 and 2 years old. Streptococcus mutans was associated with social deprivation when the infants were 2 years old and older, but dependent on caries status in the 3 and 4 year olds.
Clinical performance of a laser fluorescence device for detection of occlusal caries lesions.
Children and adolescents must be examined often for occlusal caries. Diagnosis of fissure caries is difficult especially when the tooth surface appears seemingly intact. It has been shown that using traditional clinical methods, as little as 20% of teeth with fissure caries under intact surfaces were correctly recognised as such. Therefore, new methods for increasing the accuracy of diagnosis have been sought for years. Recently, a new device, based on fluorescence measurements, was introduced. The purpose of this study was to test the device under in vivo conditions in order to provide recommendations for its use in the dental office. Seven general dental practitioners examined a total of 332 occlusal surfaces in 240 patients. Caries extent was determined for each site after operative intervention (='gold standard'). Clinical inspection and analysis of bitewing radiographs exhibited statistically significant lower sensitivities (31-63%) than did the DIAGNOdent device (sensitivity > or = 92%). It is recommended that the laser device is used in the decision-making process in relation to the diagnosis of occlusal caries as a second opinion in cases of doubt after visual inspection.
A clinical evaluation of an Erbium:YAG laser for dental cavity preparation.
OBJECTIVE: A randomised controlled trial to determine the acceptability to dentists and patients of cavity preparation with an Erbium:YAG laser as compared with conventional handpieces. METHODS: Fifteen dentists (9 GDPs, 1 community dentist and 5 hospital dentists) treated 77 patients (age range 3.5-68 years old) who had two matched cavities, in a split mouth, randomised trial. One cavity was prepared conventionally, the other with the laser, with dentist and patient preference determined by questionnaire. RESULTS: In the majority of cases, where dentists expressed a preference, it was for conventional cavity preparation, and this was significant (P < 0.001). In more than half of the laser appointments, dentists had to use conventional handpieces to complete the cavity. Principle difficulties reported with the laser were access (25 cases) and slow speed of cutting (11 cases). Patients aged > or = 10 years who expressed a preference, preferred laser treatment, and this was significant (P < 0.001). Patients aged < 10 years, assessed using a simplified pictorial questionnaire, did not show a significant preference for either technique. CONCLUSIONS: Dentists preferred conventional handpieces for cavity preparation while patients aged > or = 10 years old preferred laser treatment. Patients < 10 years old did not express a preference.
Caries-associated micro-organisms in infants from different socio-economic backgrounds in Scotland.
OBJECTIVES: The aims of this study were: (1) to compare the frequency of isolation of mutans streptococci, (Streptococcus mutans, Steptococcus sobrinus), lactobacilli and yeasts (caries-associated micro-organisms) in the saliva of 1-year-old infants with and without dental caries; and (2) to determine if socio-economic background influenced the frequency isolation of bacteria and caries status. METHODS: 1393 1-year-old consented infants, who comprised 70. 3% of children born in Dundee during a 1year period, had saliva samples taken (tongue-loop method) for microbiological culture and were examined for dental caries (d(1)-threshold: enamel and dentine diagnostic threshold). Thirty-nine infants were diagnosed with caries and the frequencies of isolation of caries-associated micro-organisms (and absolute microbial counts) were compared with infants who were caries-free. In addition, associations were sought between the infants' socio-economic background, the frequency of isolation of caries-associated micro-organisms and caries status. RESULTS: Streptococcus mutans, lactobacilli and yeasts were isolated more frequently from those infants with caries compared to those who were caries-free (S. mutans: 29.7 vs 9.8%, P=0.0008; lactobacilli: 15.4 vs 4.3%, P=0.0073; yeasts: 23.7 vs 10.4%, P=0.0016-Fisher's exact test). There were no significant differences between the isolation frequencies of S. sobrinus (2.7 vs 1.3%, P=0.39) from those with and without caries. Significantly, more infants living in areas of high deprivation had caries compared to those from more affluent areas (DEPCAT 6 and 7 vs 1-5: 3.6 vs 1.9%, P=0.049), but, apart from yeasts, socio-economic background was not significantly associated with the isolation frequencies of any of the caries-associated micro-organisms. CONCLUSIONS: In infants as young as 1year of age, salivary S. mutans, lactobacilli and yeasts but not S. sobrinus were isolated significantly more frequently from those with caries compared to those who were caries-free. Apart from yeasts, socio-economic background did not influence the frequency of isolation of caries-associated micro-organisms. However, infants living in areas of highest deprivation had significantly higher frequencies of caries compared to those from more affluent areas.
Temperature dependence of the electrical resistance of sound and carious teeth.
Temperature variations are expected to influence measurement error in electrical resistance of teeth. It was the aim of this study to determine the changes in electrical behavior of extracted human teeth due to temperature changes in the range of room temperature to intra-oral temperature. Nine extracted teeth were selected, and the occlusal or an approximal surface was chosen for measurement. Carious involvement of the surfaces ranged from sound to cavitated. Electrical impedance spectroscopy sweeps in a frequency range of about 100 kHz to 10 Hz were completed at selected temperatures between 22 degrees C and 40 degrees C. After fitting the data to equivalent circuits that yielded parameter values for components of the equivalent circuit, we calculated the dc bulk resistance (Rh). The temperature dependence of Rb of the surfaces with different carious involvement was very similar, and the mean drop of Rb from 20 to 35 degrees C was 45% (SD 2%). It was concluded that the electrical resistance of sound and carious tooth surfaces is inversely related to temperature.
The use of magnification in general dental practice in Scotland--a survey report.
OBJECTIVES: This study had two aims, first, to quantify the level of the use of magnification in general dental practice in Scotland and second, to determine the current and potential areas of clinical use of magnification by general dental practitioners. METHODS: A questionnaire was sent to all general dental practitioners in Scotland with a Health Board list number (n = 1790). The questionnaire asked the practitioners about their experience of magnification and their opinions on possible areas for clinical use. An information sheet and a prepaid envelope were included with the questionnaire. RESULTS: One thousand two hundred and eighty (72%) of the dentists replied to the questionnaire. Nine percent of the respondents routinely used magnification. The level of routine use of magnification by practitioners increased with time since qualification. The suggested areas of clinical use of magnification by all the respondents were crown and bridge work, diagnosis and radiography. The routine users of magnification had a more positive view of magnification than non-users. CONCLUSIONS: Routine use of magnification was associated with the length of time the practitioner had been qualified and the attendance at a course at which magnification was discussed. The perceived uses of magnification depended on the experience of the practitioner with magnification. It was considered suitable for all clinical procedures except orthodontics and prosthodontics.
Electrical methods in occlusal caries diagnosis: An in vitro comparison with visual inspection and bite-wing radiography.
The aim of this study was to compare in vitro diagnostic performance of three electrical methods for occlusal caries diagnosis with that of visual inspection and bite-wing radiography. One hundred and seven extracted molar and premolar teeth were subjected to the diagnostic methods by 2 operators and subsequently sectioned for histological validation. Electrical measurements were made at site level and at surface level using two different instruments. The diagnostic parameters calculated from the results were: sensitivity, specificity, diagnostic accuracy at a theoretical caries prevalence of 10% and area under the ROC curve. The electrical methods and bite-wing radiography showed higher sensitivity and lower specificity than visual inspection. Diagnostic accuracy was significantly lower for bite-wing radiography and one electrical method than for visual inspection. Overall diagnostic performance of two electrical methods was superior.
Surface-specific electrical occlusal caries diagnosis: reproducibility, correlation with histological lesion depth, and tooth type dependence.
Electrical conductance measurements are being used experimentally for occlusal caries detection. Recently, it was suggested to cover the fissure system with a conducting medium, resulting in a surface-specific measurement. It was the aim of this study to determine in vitro the reproducibility of this modified technique for occlusal caries in posterior teeth, to determine for a large study sample the correlation between the electrical measurements and histological lesion depth, and to evaluate the difference between results for premolars and molars. For the reproducibility determination, surface-specific electrical resistance measurements were made using a sample of 68 posterior teeth. Eight operators performed measurements on all teeth, and repeated measurements on 24 teeth. The validity study included the previous sample and the collected samples from two more studies, resulting in a total sample of 325 posterior teeth. One operator had performed electrical resistance measurements on all teeth in the sample. Reproducibility was good: mean Pearson's correlation coefficient 0.89 (+/-0.05) for interexaminer correlation, and 0.86 (+/-0.12) for intra-examiner correlation, using log (resistance) as the result parameter. The correlation coefficient between log(resistance) and histological lesion depth for the large sample was -0.78 for all teeth, -0.64 for premolars, and -0.73 for molars. The regression line for molars was located below the regression line for premolars: at a hypothetical histology score of 2.5 (a dentine caries threshold) the estimated resistance threshold would be 507 kOmega for premolars, and 233 kOmega for molars. Converted to Electronic Caries Monitor (ECM) readings, the difference is about 1.4 on the ECM scale. It was concluded that the in vitro reproducibility of the described surface-specific method for electrical resistance measurement is very good, even for inexperienced operators. The correlation between measurements and histological lesion depth is moderate to good. The method is sensitive to electrode area differences, which will result in different clinical cut-offs for caries diagnosis in premolar and molar teeth.
Detection of dental decay and its extent using a.c. impedance spectroscopy.
Dental caries (decay), the most prevalent of diseases, represents a health problem of immense proportions. It principally affects posterior (back) teeth on occlusal (biting) and approximal (adjacent contacting) surfaces. Caries starts as a subsurface demineralization of enamel, may progress to the underlying dentine and, eventually, to cavitation of the surface. Accurate diagnosis before cavitation would permit targeted preventive treatment, thereby significantly improving dental health and reducing the need for expensive drilling and filling. Inaccessibility of caries initiation sites and recent changes in lesion morphology contribute to the relatively poor accuracy of conventional diagnostic methods. Among alternative techniques, measurements of electrical resistance have shown the most promise. Here we describe a new experimental technique that demonstrates an outstanding 100% correlation between a.c. impedance measurements of whole teeth and the actual extent of approximal caries in vitro. Only relatively minor modifications should be required to transfer the technique to in vivo applications.
Impedance spectroscopy of teeth with and without approximal caries lesions--an in vitro study.
Caries diagnosis by the measurement of electrical resistance is hampered by polarization effects when dc or single-low-frequency ac currents are used. Electrical impedance spectroscopy, measuring impedance over a large range of frequencies, will provide more detailed information about the electrical characteristics of teeth. It was the aim of this study (a) to characterize the complex impedance behavior of whole extracted teeth, measured at the approximal surface, and (b) to identify parameters of the complex impedance behavior of the teeth which would be useful in distinguishing between degrees of carious involvement. Thirty-nine extracted premolar teeth with 59 unrestored and undamaged (excepting caries) approximal surfaces were selected. The tooth surfaces were divided into three groups according to their macroscopic appearance: sound (group S, n = 16), white- or brown-spot lesion present (group L, n = 33), or cavitated (group C, n = 10). The teeth were inserted into a jig which allowed for counter-electrode contact via a conducting gel. The working electrode consisted of a carbonated fiber material. Electrical impedance measurements were performed over a maximum range of about 1 MHz to 0.1 Hz. We analyzed electrical impedance data by fitting equivalent circuits. Fit was evaluated numerically and visually. The complex impedance spectra divided naturally into three groups which corresponded almost perfectly with the classifications of S,L, and C. The groups differed most in the dc resistance (Rdc), as calculated from the impedance parameters. Mean Rdc for groups S, L, and C were 68 M omega, 5.9 M omega, and 321 k omega, respectively. These means were significantly different from each other (log-transformed data, ANOVA, p < 0.001; Tukey multiple comparisons, p < 0.001). It is concluded that the in vitro performance of electrical impedance spectroscopy in differentiating among sound, non-cavitated carious, and cavitated approximal tooth surfaces is excellent.
Preventive Care Advised (PCA)/Operative Care Advised (OCA)--categorising caries by the management option.
Currently a range of systems and classifications are used by clinicians, epidemiologists and clinical research workers to sub-divide carious lesions into different grades. These systems are based on the depth of the lesion and/or the presence/absence of macroscopic cavitation. In order to improve upon the meaningfulness and comparability of such systems in the light of increasing knowledge about the disease process, lesion behaviour and caries management options, the authors propose a new system of categorisation that differentiates between lesions which normally require operative intervention and those which do not. In future, it is proposed that in addition to existing conventional criteria, diagnostic systems should also allow results to be expressed in terms of 1) lesions for which appropriate non-invasive Preventive Care Is Advised (PCA lesions) and 2) lesions for which Operative Care Is Advised (OCA lesions). Locally acceptable sub-divisions may have to be developed and agreed for certain specific applications. The adoption of this additional nomenclature and approach in the future should aid communications between the different groups involved in caries diagnosis and research. It may facilitate the dissemination of research findings, as well as helping to "drive" researchers working on caries diagnostic methods to focus on techniques which will aid in the accurate assessment of lesion activity and behaviour. Such a focus should also increase our understanding of treatment decision making and promote the development of clinical guidelines. The facility to retain existing criteria in parallel, for local and other purposes, would preserve comparability with data collected previously.
CO2 laser and the diagnosis of occlusal caries: in vitro study.
The diagnosis of small lesions in pit and fissure sites is becoming increasingly problematical. This study was designed to evaluate, in vitro, the potential use of a carbon dioxide (CO2) laser technique as an aid to the diagnosis of incipient pit and fissure caries. Vaporization of the organic material in the 'early' carious lesion should lead to its carbonization and thus make it more conspicuous. Pilot studies were carried out to identify lasing parameters which produced no visible effect on sound enamel but which caused charring (carbonization) of white spot fissure lesions. Fifty extracted human molars and premolars were air-polished on the occlusal surfaces and independently scored clinically for caries, both before and after lasing. The teeth were subsequently sectioned and examined histologically. Of the 37 sites histologically scored as sound or exhibiting precavitation lesions, eight were correctly scored as sound both prelasing and postlasing. Of the 29 precavitation lesions detected histologically, five were detected clinically prelasing and 11 were detected postlasing. This 21% difference in the sensitivity of caries diagnosis between the prelasing and postlasing examinations was statistically significant (at the 95% level). There were no false-positive caries diagnoses. Further research, in particular the refining of lasing parameters employed, is indicated.
Initial development and in vitro evaluation of the HPL device for obtaining reproducible bitewing radiographs of children.
A new beam-aiming and collimating film holder, the HPL device, has been developed to facilitate the production of reproducible serial bitewing radiographs. The device holds two films in the mouth simultaneously and is held in position extraorally. Serial bitewing radiographs of skulls of children aged 7, 10, and 14 years taken with (1) a "freehand" technique, (2) a Rinn film holder, and (3) the HPL device were evaluated for degree of reproducibility, potential diagnostic yield, and technical errors. Compared with the other techniques, the HPL device produced a smaller number of overlapped surfaces and substantially fewer technical errors. In vivo studies of the new device are therefore indicated. The restriction of the field of primary and secondary irradiation may lead to a substantial reduction in absorbed radiation dose compared with other techniques.
The use of bitewing positioning devices in children's dentistry.
The use of film-holding, beam-aiming devices have been shown to have a number of potential advantages in achieving high quality bitweing radiographs, however, little information is available about their acceptability to children. The aims of this study were: (1) to determine the level of acceptance of a conventional type of film positioner to child patients in a general practice setting in Scotland and (2) to compare the acceptability to children of bitewing procedures using: the freehand technique, a 'Rinn' positioner and a new positioner, the 'HPL' device. In the general practice group, following modifications made during a pilot study, 211 children aged 3-15 years were offered a bitewing examination with a modified Rinn positioner at recall. The overall acceptance rate of the bitewing procedure was 82.5%. All 10 children aged 3-4 years offered bitewings refused, while 77 (69%) of subjects aged 5-9 years accepted, as did all the 89 children aged 10-15 years. In the comparison of acceptability investigation, three groups of 30 children aged 6-15 years requiring bitewing radiographs were selected at random. Each group had a different bitewing technique carried out by the same operator. The children's acceptance of all three techniques was high (87-97%) and no statistically significant difference was found between the acceptability of the freehand method and those involving film positioning devices. Although the unmodified Rinn design suffered from a number of problems, the modified version was found to be acceptable by many children.(ABSTRACT TRUNCATED AT 250 WORDS)