Serial Bitewing Radiographs Research Articles

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 frequency of bitewing radiographs

A model for use in analyzing the implications of different rates of caries incidence and progression for the timing of bitewing radiographs was developed. Estimates of progression rates and incidence patterns were derived from an analysis of serial bitewing radiographs. A time schedule for taking the next radiographs was determined so that carious lesions would be detected before radiolucencies reach the inner half of the dentin. For asymptomatic persons with extensive exposure to fluorides and no unrestored enamel lesions on the last radiographs, bitewing films could be scheduled every 2.5 to 3 years. For persons with little exposure to fluorides or with many early enamel lesions or at least one deep enamel lesion that has not been restored, radiographs should be performed every 6 months to 1 year.

Score system for behaviour of radiologically diagnosed approximal carious lesions.

The evolution of systems which monitor changes in the severity of approximal carious lesions diagnosed from serial bitewing radiographs is reviewed. These systems derive a 'score' for each individual lesion based upon the extent of its progression. A new lesion behaviour score system is described which, unlike its predecessors, allows both lesion regression and data from partially overlapped but readable surfaces to contribute to scores. It employs scoring codes from a previously proposed standardized grading system which is compatible with WHO recommendations for grading clinical caries. The score system is designed to be used as a computer program capable of running on a variety of readily available microcomputers; this allows the incorporation of a flexible range of additional options which use the standard data files to calculate scores according to differing conventions. These accommodate variations in: the threshold at which restorative intervention is practiced, the treatment of reversals of caries diagnosis, the threshold of caries diagnosis and the way in which partially overlapped surfaces are scored. These options allow the system to be configured to suit the local needs of different investigations and workers, and also permit the study of the effects of these various methodologies.

Reproducibility of computer-aided image-analysis-derived estimates of the depth and area of radiolucencies in approximal enamel.

In vivo studies of caries progression from serial bite-wing radiographs require the reproducible detection and measurement of approximal radiolucencies in enamel; the aim of this study was to evaluate the reproducibility of a new computer-aided image analysis method. Three series of radiographs depicting natural caries lesions were employed: films of 11-12-year-old (Hounslow) schoolchildren, dental students from Hong Kong (HKDS), and extracted Hong Kong teeth (EXT). Each surface was "searched" three times, resulting in data from 450, 600, and 180 searches, respectively. Lesion detection was consistent for all but two of the 1230 searches. Average values for the standard error of the mean (SEM) of triple determinations of depth % were between 2.0 and 3.5%, while the mean SEM for area was from 0.03 to 0.04 mm2. Average test/re-test correlations ranged from 0.963 to 0.871 for depth and from 0.963 to 0.884 for area, while average reliability coefficients ranged from 0.937 to 0.821 for depth and 0.963 to 0.886 for area. There was a significant difference (P less than 0.001) between the reproducibility of the two clinical series, with measurements of the Hounslow lesions being more consistent. When compared with the reproducibility of attempts to grade radiolucency size visually, the image analysis method appears to offer considerable advantages, in that consistent estimates of radiolucency size are now possible. This method may facilitate more sensitive assessments of the behavior of lesions over time than has hitherto been possible.

Reliability of coding depth of approximal carious lesions from non-independent interpretation of serial bitewing radiographs.

In order to help understand the effectiveness of preventive care and the source of variation in treatment decisions, it is important to determine intra- and interexaminer agreement on the presence and depth of radiolucencies on bitewing radiographs when serial radiographs on individuals are available for interpretation. Serial radiographs on 24 subjects were read in succession, and one of four depth codes was assigned to approximal lesions. The radiographs were then read a second time, both by the person who had initially read the radiographs and by a second reader. Intraexaminer agreement on presence of a lesion ranged from 60% to 90%; four of the five readers had an agreement of over 78%. Interexaminer agreement on presence of a lesion ranged from 71% to 84%. Intraexaminer agreement on depth of lesion ranged from 64% to 80%; four readers had an agreement of over 73%. Interexaminer agreement on depth of lesion ranged from 59% to 76%.

A longitudinal analysis from bite-wing radiographs of the rate of progression of approximal carious lesions through human dental enamel

Four to ten years of serial bite-wing radiographs from over 700 children from five groups, three in Sweden and two in the U.S., were interpreted. By analysing changes in the depth of unfilled lesions over time, the mean time and probability distribution for the time a lesion remains in both the outer half and inner half of the enamel were estimated. The procedure incorporated information on filled lesions and non-progressing lesions and thus minimized bias that results in overestimation of the progression rate. In primary teeth, in both the U.S. and Swedish groups, it took on average 12 months for a lesion to progress through the outer half of the enamel and on average 10–12 months for a lesion to progress through the inner half. In newly-erupted first permanent molars, it took 21–23 months for a lesion to progress through the outer half of the enamel and between 19 (U.S. data) and 28 months (Swedish data) for progression through the inner half. In older adolescents in the two Swedish groups, progression was slower: 38–41 months through the outer-half and 47–56 months through the inner-half. In older U.S. adolescents, progression appeared to be more rapid: 16 months through the outer half of the enamel and 27 months through the inner half. The duration of time a lesion remains in different halves of the enamel could be approximated by a piecewise exponential or exponential probability distribution, which exhibits extreme variability. Assuming duration in each half of the enamel follows an exponential distribution with a mean of 2yr, about 10 per cent of new lesions will progress through the enamel in one year and 25 per cent in two years. However, over 40 per cent of the lesions will not have progressed in 4 yr. There were no consistent differences in the rate of progression by sex, between upper and lower dentitions, for premolars versus molars, or between high and low-risk individuals.

The influence of location on the rate of spread of human approximal dental caries

Seventy-two approximal initial carious lesions in 51 patients were followed on serial bite-wing radiographs. The average rate of spread of the lesion was compared in three types of approximal embrasures: between premolars, premolars and molars and first andsecond molars. There was a gradual increase in the rate of progress of the carious lesion from anterior to more posterior embrasures. The average time for spread through half the depth of the enamel was 16.86, 15.10 and 13.27 months, respectively, for the 3 types.

A longitudinal radiographic study of the rate of spread of human approximal dental caries

Ninety-six approximal initial carious lesions in 51 patients were followed up to 4 years on serial bite-wing radiographs. The average rate of spread of the lesion from the surface of the tooth up to the dentine-enamel junction was 26.4 months in the 14–15 yr-old group, and 32.3 months in the 21–24 yr-old group, the difference being significant ( p < 0.01). Less than 20 per cent of the initial lesions reached the dentine within 24 months. Twelve per cent of the initial lesions had not changed after 36 months. The “50 per cent survival time” of the initial carious lesions was 9.7 months, while it was 12.5 months for the more advanced enamel lesions. When the lesions were classified according to their morphology, it was found that 66 per cent of lesions were of triangular morphology, 16 per cent were diffused and 18 per cent were unclassifiable in shape.