Hans-Göran Gröndahl

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 2 yr, 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.

Intraoral storage phosphor radiography for approximal caries detection and effect of image magnification : Comparison with conventional radiography

OBJECTIVES The aim of this study was first to test the newly developed storage phosphor (SP) system Digora for diagnostic accuracy of approximal caries detection with special emphasis on image magnification compared with conventional radiography, and second, to test whether the image surroundings could have an influence on observer performance. DESIGN SP plates and Ektaspeed films were exposed simultaneously to 50 extracted premolars/molars, and the SP image files were transported to a different platform for processing. Ten observers rated 95 approximal surfaces for caries with four imaging modalities: (1) SP images at dental film size viewed with black surroundings, (2) magnified (x4) images viewed in the same manner, (3) magnified (x4) images viewed with text and graphics framing, and (4) films viewed on a light box. The observations were validated with microscopy. Diagnostic accuracy was calculated as the area beneath the receiver operating characteristic curve (AZ). RESULTS No significant differences were found between SP images and films. Magnified SP images with text and graphics demonstrated significantly higher AZ values than nonmagnified images both for enamel and dentin, and magnified images with black surroundings demonstrated similar results for dentin. CONCLUSIONS In this in vitro material the observer performance for approximal caries detection with SP images was comparable to that with Ektaspeed films. The magnified SP images generally showed a significantly higher diagnostic accuracy than the nonmagnified SP images.

The More Streptococcus mutans, the More Caries on Approximal Surfaces

The relationship between the presence of Streptococcus mutans and caries on approximal tooth surfaces was studied in a group of 28 children who were 13 years old at baseline. 700 surfaces in the pre-molar and molar region were studied. Sampling of S. mutans was performed with a toothpick method at the beginning of the study and after one and two years. From bite-wing radiographs, the approximal surfaces were recorded as caries-free, decayed, or restored. Progression of lesions during the two years was also studied. More new caries lesions and progression caries lesions were found on surfaces positive for S. mutans than on surfaces without, and the more S. mutans, the more lesions, 52% of the surfaces with positive S. mutans findings at all three sampling occasions became carious or had caries in a progressive form. Among the surfaces with no detectable S. mutans, the corresponding figure was 8%. 80 out of the 530 surfaces diagnosed as intact at the start of the study became carious over the two-year period. 69 of these were S. mutans-positive at the first and/or second sampling.

Accuracy of Proximal Caries Depth Measurements: Comparison between Limited Cone Beam Computed Tomography, Storage Phosphor and Film Radiography

The aim of this study was to compare the accuracy of limited cone beam computed tomography (LCBCT), an image plate system and F-speed film in assessing the depth of proximal carious lesions. Radiographs of a dry mandible with sound and carious teeth were obtained with all three methods. In 41 molar and premolar proximal surfaces, 2 observers independently measured lesion depth on the images from the three modalities. The correlation of measurements was assessed with Pearson’s correlation analysis. Results from imaging modalities and histological sectioning (gold standard) were compared using Bland-Altman plots. Overall comparison of the depth measurements from the imaging modalities and the gold standard was done using repeated-measures ANOVA. Pairwise comparisons of systems were done by the Bonferroni t test. The correlation between the measurements of the two observers was 0.977 for film, 0.997 for image plate system and 0.998 for LCBCT. Bland-Altman plots revealed that LCBCT agreed very closely with the gold standard while the agreement between the latter and the image plate – or film – images was moderate. The mean difference and 95% limits of agreement between LCBCT and the gold standard were smaller than those between either image plate or F-speed film and the gold standard. The LCBCT method appears as a promising tool for detection and monitoring of proximal carious lesions.

Influence of mandibular third molars on related supporting tissues

Abstract The supporting tissues of the distal surfaces of mandibular second molars in 33 patients with impacted and semi-impacted third molars were studied preoperatively, immediately after removal of the third molars, and 12 months postoperatively. The same tissues were studied in a group of 11 patients with congenital absence of mandibular third molars. Geometrically reproducible radiographs were obtained. In enlargements of the radiographs the height of the bony septum distal to the second molars was measured. Notes were made of the amount of plaque, the severity of gingival inflammation and the depth of the gingival pockets. Twelve months after operation no change was found in the supporting bony tissue, but significant improvements were noted in the clinical variables studied. No significant difference in the supporting bony tissue was found between age-matched groups of patients with and without impacted or semi-impacted third molars, but the clinical condition of the periodontium was significantly worse in the group with third molars. Prophylactic removal of impacted and semi-impacted mandibular third molars would seem to be indicated.

Image plate systems differ in physical performance.

OBJECTIVE The purpose of this study was to compare 2 storage phosphor image plate systems, the Digora and the DenOptix, with respect to physical performance. STUDY DESIGN The 2 systems were tested both with and without use of their default settings through physical and psychophysical measurements. A homogeneous 10-mm-thick aluminum block, a 10-mm-thick aluminum block with a pattern of holes varying in diameter and depth, and a resolving power target were used as test phantoms. The image plates were exposed at 50 kV and 8 mA with a focus-sensor distance of 30 cm and exposure times ranging from 10 to 3,200 ms. Measurements of large area transfer function, gray level variations, perceptibility, contrast resolution, exposure range, and modulation transfer function were performed. RESULTS When the two systems were used at their default settings, the DenOptix had a better dose response, a higher contrast index, and a higher modulation transfer function (MTF) than the Digora; however, the DenOptix also had higher noise than the Digora at lower exposures. CONCLUSIONS When image enhancement algorithms were applied with the Digora system, performance similar to that of the DenOptix could be obtained.

Association between radiographic findings in the mandibular condyle and temporomandibular dysfunction in an elderly population

Our aims were to study the prevalence of abnormal radiographic findings in mandibular condyles and the possible association between such findings and clinical signs and symptoms of temporomandibular dysfunction (TMD) and dental state. Two cohorts of 70-year-old people, 384 men and 484 women, living in Göteborg, Sweden, participated in the study. The first cohort was examined in 1972 and the other one in 1992. Besides a functional and clinical examination, a questionnaire on TMD and panoramic radiography were included. A deviation from the normal appearance of one or both condyles was found in 26% of the subjects (17% of the condyles). There was no significant difference in this respect between the two cohorts. There were in general only minor and no statistically significant differences between those with normal and deviating condylar findings with regard to various TMD signs and symptoms. The subjects in Eichner group A (with dental support in all zones) showed a slightly lower frequency of abnormal radiographic condylar findings (22%) than those in groups B (reduced dental support) and C (edentulous in one or both jaws; both B and C, 28%). It is concluded that abnormal radiographic condylar findings in these elderly people were not at all or only weakly correlated with signs and symptoms of TMD and dental status.

Utilization of dental care after the introduction of the Swedish dental health insurance

The dental care utilization rate in an urban Swedish population over an 11-year period was studied, starting at the time of the introduction of a national dental health insurance. The systematically selected samples comprised, for each calendar year of the period, approximately 11,000 inhabitants more than 20 years of age in the city of Göteborg. In 1976 and 1984 information on utilization was coupled to information about various demographic, socioeconomic, and disablement factors. In addition, a longitudinal study was performed of 8012 people who resided in Göteborg in 1976 and 1984, correlating dental attendance rates with the same factors. The results showed that dental care utilization increased among both men and women, mostly in age groups more than 65 years of age. Utilization rate in 1976 and in 1984 was independently associated with age, sex, income, marital status, disablement, and regions of the city, and it is concluded that the goal of the dental insurance act, which was, among other things, to contribute to a more equitable distribution of dental care, in many respects has not been achieved. Early identification of people with low utilization may provide a means to obtain the most pronounced improvement in dental health.

Effect of iterative restoration on the detection of artificially induced vertical radicular fractures by Tuned Aperture Computed Tomography

OBJECTIVE The purpose of this study was to evaluate the effect of the number of iterative restorations (IR) on the diagnostic accuracy of Tuned Aperture Computed Tomography images (TACT) for detection of induced vertical/oblique root fractures in mandibular teeth. STUDY DESIGN Fractures were induced in 28 single-rooted, endodontically treated cadaver mandibular teeth while another 26 such teeth served as controls. TACT slices reconstructed by using 9 arbitrary projections (angular disparity of 9 degrees -20 degrees) were iteratively restored 1, 2, and 3 times. Eight observers scored their diagnoses by using a confidence rating scale. Ground truth was available from direct examination with transillumination, following extraction. RESULTS Mean areas under the representative ROC curves for the 3 operations were 0.96 (3 IRs), 0.87 (2 IRs), and 0.86 (1 IRs). Analysis of variance demonstrated significant differences between 3 and 1 to 2 IRs (P <.01), as well as between observers (P <.01). CONCLUSION Diagnostic accuracy of TACT for vertical/oblique root fracture detection improved after 3 IRs.

Quality of preimplant low-dose tomography ☆ ☆☆

OBJECTIVES The aim of this study was to test the influence of radiation dose on image quality in mandibular preimplant computed tomographic examinations and to compare the quality of computed and conventional spiral tomographic images. STUDY DESIGN Cross-sectional images were obtained on 17 patients with conventional spiral tomography (Scanora technique) and reformatted computed tomography at 40 and 80 mAs. Observers graded the acceptability of images for implant planning and traced the contour of the mandibular body and canal. RESULTS Conventional spiral tomographic images scored significantly higher than computed tomographic images whereas mean score differences between computed tomographic techniques were not statistically significant. Anatomic structures, in particular the mandibular canal, were more frequently untraceable in high-dose than in low-dose computed tomography but always traceable in conventional tomograms. CONCLUSION Conventional spiral tomograms were subjectively preferred over computed tomographic images. For mandibular implant planning, computed tomography examinations can be performed with lower-than-standard mAs. Quantum noise seems to contribute to the visibility of anatomic structures in reformatted computed tomographic images.