Comparison of micro-CT and cone beam CT-based assessments for relative difference of grey level distribution in a human mandible.

OBJECTIVES: The purpose of this study was to examine the ability of CT to assess the relative difference of degree of bone mineralization (grey level) parameters in a human mandible. METHODS: Ten mandibular sections from cadavers (81.5 ± 12.1 years) were scanned using micro-CT with 27.2 µm voxel size and cone beam CT (CBCT) with 200 µm, 300 µm, and 400 µm voxel sizes. In addition, 15 clinical CBCT images from young patients (mean age 18.9 ± 3.3 years) were identified. After segmentation of bone voxels, alveolar bone and basal cortical bone regions were digitally isolated. A histogram of grey level, which is equivalent to degree of bone mineralization, was obtained from each region of the CT images. Mean, standard deviation (SD), coefficient of variation (COV), fifth percentile low (Low(5)) and high (High(5)) of alveolar bone and basal cortical bone regions were obtained. Percentage differences of grey level parameters between alveolar and basal cortical bones were computed. RESULTS: The alveolar bone region had significantly lower Mean, Low(5) and High(5) values but significantly higher SD and COV than the basal cortical bone region for all CT images (p < 0.05). All parameters were significantly lower for the old cadaver group than for the young patient group (p < 0.05). CONCLUSIONS: CBCT and micro-CT provide comparable results in the assessment of relative difference in grey level distribution between alveolar and basal cortical bone regions in the human mandible. The percentage difference relative to an internal reference (basal cortical bone) can be a reliable method when assessing the degree of bone mineralization using CBCT images for both cross-sectional and longitudinal comparisons.

A comparison of the reliability and validity of 3 occlusal indexes of orthodontic treatment need.

Several occlusal indexes are currently used to ascertain eligibility for orthodontic treatment. A comparison of 3 indexes of orthodontic treatment need was made with the consensus opinion of a panel of 15 experienced orthodontists. Sets of study casts (170) representing the full spectrum of malocclusions were selected. An examiner, calibrated in the Dental Aesthetic Index, the Handicapping Labiolingual Deviation with the California Modification, and the Index of Orthodontic Treatment Need, scored the casts. The panel of orthodontists individually rated the same casts for their degree of orthodontic treatment need. The mean rating of the panel on the need for treatment was used as the gold standard for evaluating the validity of the indexes. Intrarater and interrater reliability was high (kappa > 0.8). Overall accuracy of the indexes, as reflected in area under receiver-operating characteristic curves, was also high: Dental Aesthetic Index, 95%; Handicapping Labiolingual Deviation with the California Modification, 94%; and Index of Orthodontic Treatment Need, 98%. Cutoff points for the indexes that resulted in the closest agreement with the gold standard differed from the published cutoff points for the indexes. The indexes appear to be valid measures of treatment need as perceived by orthodontists. The published cutoff points for the indexes were more conservative in assigning patients for treatment than a panel of orthodontists. However, adjusting the cutoff points moved all 3 indexes into close agreement with the experts.

Patients' anticipation of pain and pain-related side effects, and their perception of pain as a result of orthodontic treatment with fixed appliances.

The aim of this study was to investigate the relationship between (i) the pain and its side effects, anticipated by patients before orthodontic therapy, and (ii) the reported pain and its effects after the placement of initial archwires. Before treatment, 50 adolescent patients (median age 13.6 years, range 8.9-39.3 years, 28 female, 22 male) completed a questionnaire concerning their facial and dental appearance, and their expectations regarding pain, its influence on their daily lives, and changes in their facial and dental appearance as a result of orthodontic treatment. In the week following insertion of the initial archwires the patients completed a series of eight questionnaires, where they reported the level of pain experienced and its influence on their daily lives. In the week after archwire insertion, the maximum pain levels reported did not differ statistically from the anticipated pain levels. Patients significantly under-estimated the changes they would have to make in their diet as a response to pain after archwire insertion. Patients who anticipated a greater effect of pain on their leisure activities and those who had a history of frequent headaches reported higher levels of pain and more disruption of their daily lives as a result of pain. This pattern of response is consistent with a medical model where anxious patients and those with a history of chronic pain reported more pain after surgery.

The effect of multiple examinations on the diagnosis of approximal caries and the restoration of approximal surfaces.

OBJECTIVE: The aim of this study was to determine the effect of multiple examinations on sensitivity and specificity in the diagnosis and restoration of approximal caries. STUDY DESIGN: In 2 studies, dentists examined bitewing radiographic films for approximal caries and the need for restoration. To model the clinical situation of multiple examinations over time, all groups of combinations of 2 to 10 dentists were constructed. Mean sensitivity and specificity were determined. In addition, 2 new variables were created: the first, "sensitivity any," was calculated by assigning a correct diagnosis for disease if any dentist in the group identified the diseased surface correctly; the second, "specificity all," was calculated by assigning a correct response only when all dentists in the group correctly identify a nondiseased surface. RESULTS: The sensitivity and specificity means were the same for all group sizes. The "sensitivity any" means increased monotonically from group size 1 to group size 10, whereas the "specificity all" means decreased continually. There was a statistically significant difference between sensitivity and "sensitivity any" and between specificity and "specificity all" for all group sizes in both studies. CONCLUSIONS: Multiple examinations increase the number of carious surfaces correctly diagnosed and the number of surfaces appropriately restored; however, multiple examinations also increase the number of sound surfaces diagnosed as carious and the number of intact surfaces receiving restorations.

Treatment results in dental school orthodontic patients in 1983 and 1993.

The effect of incremental changes in materials and techniques on orthodontic treatment outcomes is difficult to evaluate objectively. Treatment results for two groups of patients whose treatments were completed approximately 10 years apart were evaluated using the peer assessment rating (PAR) index and the index of orthodontic treatment need (IOTN) using the Wilcoxon matched-pairs signed-rank test. Patients in the later group who had been treated by postgraduate students primarily (using fixed appliances) had significantly lower IOTN and PAR scores at the end of treatment and showed a significantly greater reduction in the PAR score than a similar group of patients in the earlier group. There were no significant differences in treatment results between patients in the early and late groups who were treated with removable appliances. Differences in treatment results were most likely the result of changes in materials and techniques that had occurred in the 10 intervening years.

The effect of a knowledge-based, image analysis and clinical decision support system on observer performance in the diagnosis of approximal caries from radiographic images.

The aim of this study was to investigate the effect of a knowledge-based image analysis and clinical decision support system (CariesFinder, CF) on diagnostic performance and therapeutic decisions. The study material consisted of radiographic images of 102 approximal surfaces, 35 sound, 67 caries (25 caries and cavitated and 42 caries). Sixteen general practitioners were presented with (1) radiographic film images and (2) digital filmless images with the results of CF. The viewers were asked to respond whether approximal caries was present and whether a restoration was indicated. Responses were analyzed for accuracy, sensitivity, specificity and agreement. Further, the practitioners were ranked according to the accuracy of their restorative decisions and assigned to ten overlapping groups of 7 practitioners. For each group the diagnostic and therapeutic decisions were then examined for unanimity. The parameters of accuracy, sensitivity and specificity were then established for each group based on only unanimous, correct decisions. The diagnostic and therapeutic accuracy of CF alone was equal or superior to the decisions of the practitioners viewing film images alone. For unanimous decisions, CF alone was more accurate than the most accurate group of practitioners and made fewer incorrect decisions to restore non-cavitated surfaces than the practitioners. In general, dental practitioners viewing the results of CF significantly increased their ability to diagnose caries correctly, their overall diagnostic accuracy, and their ability to recommend restorations for cavitated surfaces. There was a decrease in the accuracy of their restorative decisions overall and in the specificity in particular.

Measurement of blood perfusion in the dental pulp with laser Doppler flowmetry.

The reproducibility of laser Doppler flowmetry (LDF) in measuring the perfusion of the dental pulp was investigated. A second aim was to establish if the LDF signal from the dental pulp can be influenced by physiological stimuli, e.g. postural changes. A third aim was to apply the technique to clinical measurements of pulp perfusion in patients undergoing orthodontic therapy. A custom splint to position the probe was fabricated for 10 subjects, and measurements of pulpal perfusion in the maxillary six anterior teeth were repeated on eight occasions with the subject seated. Further, measurements of the dental pulp perfusion in one tooth were repeated with the subject in a standing and supine position. Mean perfusion (arbitrary perfusion units) for individual teeth varied from 2.7 for a central incisor to 15.5 for a lateral incisor. Perfusion was greatest for lateral incisors and least for central incisors. Pulpal perfusion was significantly higher in a supine than in a standing or sitting position. Initial clinical experience with LDF encourages further investigation of its potential as a diagnostic tool for determining pulp vitality. Preliminary experimental results suggest that LDF will be a valuable source indicating pulpal response to orthodontic therapy with fixed appliances.

Perception of pain as a result of orthodontic treatment with fixed appliances.

The aims of this study were to investigate the intensity, location and duration of patients' discomfort following insertion of orthodontic appliances, and to examine for interactions between patient age, gender, appliance type and the perception of pain. After insertion of orthodontic appliances, 170 patients received eight questionnaires, one they completed and returned after 4 h, then one daily for 7 days. The respondents' ages ranged from 8-53 years (median age 13 years 7 months); 45 per cent were male and 55 per cent female. Of the patients, 65 per cent reported pain after 4 h and 95 per cent after 24 h. After 7 days, 25 per cent of the patients still reported discomfort. Patients' pain intensity scores were significantly higher for the anterior than for the posterior teeth. On day 1, 16 per cent took analgesics and 18 per cent reported being awakened the first night. Comparing a 2 x 4 appliance, a full appliance in one arch and in both arches, no statistical differences were found for reported pain frequency, general intensity of pain, pain at the teeth, discomfort when biting and chewing and analgesic consumption. The perception of general pain intensity, analgesic consumption, pain when eating and the influence of discomfort on daily life were all significantly greater in girls than in boys. Patients younger than 13 years reported pain significantly less frequently than the older patients. The highest frequency of pain was found in the group of 13-16 year olds. The pain intensity did not differ among the age groups.

Using computers to diagnose and plan treatment of approximal caries. Detected in radiographs.

Two of the authors developed a computer-based software system that is capable of diagnosing approximal caries and making decisions about restorative care. The system was compared with decisions made by a group of experienced clinicians. The results indicate that the clinician viewers overall correctly identified a similar number of surfaces as the software, but from viewer to viewer, there was more variability in the number of surfaces identified correctly than in those identified correctly by the software users. Software packages such as this have the potential to raise overall accuracy by increasing the consistency of treatment decisions over time.

Radiographic evaluation of occlusal caries: effect of training and experience.

The purpose of this study was to investigate what effect differing levels of didactic education and clinical experience have on the ability to diagnose occlusal caries from radiographs. Freshman and senior dental students and dental school faculty were asked to evaluate bitewing radiographs for the presence of occlusal caries and for a recommendation for restorative treatment. The agreement between histologic and radiographic diagnosis was assessed by calculating sensitivity, specificity, accuracy, and interexaminer agreement. It was concluded that dental students and faculty did differ in their abilities to evaluate radiographs for occlusal caries, and that education and clinical experience especially affected interexaminer agreement.

Air-rotor stripping and enamel demineralization in vitro.

This investigation sought to evaluate the effects of air-rotor stripping on the susceptibility of human enamel to demineralization using an in vitro caries model. Crowns of extracted premolar teeth were abraded (0.5 mm) on one proximal surface by air-rotor stripping. The teeth were placed in a demineralizing gel and removed at various intervals up to 336 hours. Lesion depth and mineral content on the abraded and intact surfaces was measured with contact microradiography and computerized image analysis (double window technique). For each time interval measured, lesion depth was greater (p < 0.05) on the abraded surfaces and mineral density was significantly less (p < 0.05). In a second experiment, the effect of fluoride supplements (dentifrice or topical gel) were examined on abraded and intact enamel surfaces that were exposed to the acid gel for 192 hours. The data showed that fluoride treatments significantly reduced lesion penetration on intact and abraded surfaces compared with a no fluoride group. Lesion depth on the abraded, fluoride treated surfaces was significantly greater (p < 0.05) than on the intact untreated surfaces. No significant differences (p < 0.05) were apparent between the fluoride treatment groups with respect to lesion depth and mineral density within the lesion. These results suggest that air-rotor stripping significantly increases the susceptibility of proximal enamel surfaces to demineralization. As a result, the clinician should use caution in the application of this technique until the long-term effects on caries susceptibility have been determined.

The use of a computer-based image analysis program for the diagnosis of approximal caries from bitewing radiographs.

Approximal surfaces of 13 extracted molar and premolar teeth were classified directly and radiographically as sound or decayed. Eleven faculty dentists examined bitewing radiographs of the teeth and responded on a 5-point certainty scale, whether caries was present. Ten other faculty dentists used a computer-based program to examine the radiographs. For sensitivity, area under the receiver operating characteristic curve, and interexaminer agreement (Kappa), the computer-assisted faculty was significantly (p < 0.05) superior or equal to the unassisted faculty group.

The effect of experience and training on the diagnosis of approximal coronal caries from bitewing radiographs. A Swiss-American comparison.

The purpose of the present study was to compare the development of skills in the radiographic diagnosis of approximal coronal caries. Swiss (Bern) and American (Alabama) dental students with and without clinical experience, Swiss general practitioners, and Swiss and American dental school faculty viewed bitewing radiographic films of 13 teeth. The observers examined the 26 approximal surfaces on the radiographic films and responded, on a five point certainty scale, whether approximal caries was present. Mean sensitivity ranged from a low of 0.59 for American faculty to a high of 0.80 for Swiss students with clinical experience, mean specificity ranged from 0.84 for Swiss pre-clinical students to 0.95 for American faculty. For a summary measure of accuracy, i.e., area under the receiver operating characteristic (ROC) curve, the scores for student observers tended to increase with experience. The scores for Swiss and American students with clinical experience and faculty did not differ significantly. Inter-examiner agreement (Kappa) could only be characterized as moderate at best. Formal didactic instruction and clinical experience produced dental students with skills in the diagnosis of approximal caries from bitewing radiographs similar to that of faculty dentists.

In vitro demineralization by strains of Actinomyces viscosus and Streptococcus sobrinus of sound and demineralized root surfaces.

Root sections were inoculated with one of two strains of Actinomyces viscosus or a strain of Streptococcus sobrinus and then incubated for 9 days in Trypticase soy broth (TSB) containing 0.25% glucose or TSB supplemented with 0.25% sucrose (TSB+S). Lesion progression was measured from microradiographs. One section from each group was examined with a transmission electron microscope. Lesion progression was associated with a fall in the pH of the medium. However, lesion progression was not correlated with the mean 48-hour pH of the medium. In both TSB and TSB + S, lesion progression with A. viscosus was significantly greater than in the S. sobrinus group. However, the mean 48-hour pH value in TSB + S was lower than that in the S. sobrinus group. Plaque formation in TSB was, subjectively, least in the S. sobrinus group. Examination of transmission electron micrographs revealed bacteria penetrating the surfaces of the sections and extending into the lesion in the A. viscosus groups but not in the S. sobrinus group. This in vitro bacterial plaque model of root caries may be suitable for investigations of the bacterial etiology of root-surface caries and the virulence factors associated with pathogenicity.

Computer-based image analysis of natural approximal caries on radiographic films.

This paper reports on the development of computer software for automatic detection and measurement of approximal caries lesions on digital images obtained from radiographic films. If the program detects a lesion, it defines the lesion's border and measures and reports these lesion parameters: percent mineralization, area, maximum enamel penetration, and mean enamel penetration. Two experiments are reported; both were conducted with the use of extracted human premolar teeth. In the first experiment, thin sections were obtained from 13 approximal surfaces with caries lesions. Microradiographs were made of the sections, and software measurements of the lesions were obtained from the microradiographs. The software was able to separate the lesions into two groups: those that had penetrated less than 100% of the enamel and those that had penetrated 100% of the enamel. The software measurements agreed with evaluation of lesion penetration by polarized light microscopy of the thin sections. In the second experiment, simulated clinical radiographs were made of 16 approximal surfaces, 12 with lesions and four without. Thin sections were obtained for microradiography. Software was used for automatic detection and measurement of the lesions on both types of film. The ability of the software to detect the lesions on the clinical films was compared with that of 10 experienced clinicians. Correlations of the same parameter from the two types of radiographic films were statistically significant, 0.86 less than or equal to r less than or equal to 0.95 and p less than 0.05. The coefficients of variation were low for both microradiographs, 0.4-2.3%, and for clinical films, 0.7-8.5%.(ABSTRACT TRUNCATED AT 250 WORDS)

Quantitative radiographic measurement of dentinal lesions.

The purpose of this investigation was the comparison of the precision and accuracy of two reference ramp techniques for the quantification of radiographic density changes in teeth. Radiographs (65 kVp, 10 ma, 1 s, and intra-oral ultraspeed film) of transverse sections from extracted permanent human molars were made before and after dentinal lesions were created. Each radiograph contained the image of a tooth section and the aluminum reference ramp. Method A used the image of the ramp on both the before- and after-lesion radiographs, and method B used the image of the ramp only on the before-lesion radiograph. Three groups of lesions (0.525-mm diameter, n = 11; 0.675-mm diameter, n = 9; and the 0.525-mm holes enlarged to 0.675 mm) were measured radiographically by each technique and by direct planimetry of the lesions. Radiographic method B produced results in close agreement with the planimetric measurements. Method B differentiated (p less than 0.05) between groups that had a mean planimetric size difference of 0.10 mm (equivalent to a change in density difference of 0.6%). These density change measurements are in absolute units of mm of aluminum that can be compared between lesions and between samples. This technique may prove useful for the quantification of changes in mineral density of caries lesions detectable in longitudinal radiographic records.

Caries on root surfaces exposed following gingivectomy in conventional rats infected with Streptococcus sobrinus and Actinomyces viscosus.

To study the ability of bacteria associated with coronal caries to initiate root surface caries, a rat model was used. Root surfaces were exposed by gingivectomy in rats fed a caries-promoting diet and orally inoculated with either Actinomyces viscosus M-100, Streptococcus sobrinus (mutans) 6715, or both. A fourth group received a diet containing antibiotics. The animals were sacrificed 64 days following the gingivectomy performed on the right molar quadrants. Gingivectomy significantly increased exposed lingual root length and root caries incidence. There were no caries on non-gingivectomy root surfaces. Root surface caries incidence in the groups inoculated with A. viscosus and A. viscosus plus S. sobrinus did not differ. For both these groups, root caries incidence was significantly greater than that for the group inoculated with S. sobrinus alone. Root caries incidence in this latter group did not differ from that in the control group.

The effects of different levels of dietary sucrose on root caries subsequent to gingivectomy in conventional rats infected with Actinomyces viscosus M-100.

Three groups of weanling, Sprague-Dawley-derived rats were inoculated with Actinomyces viscosus M-100 and fed powdered diet containing either 67%, 5%, or 0% confectioner's sugar. Two further groups were fed diet containing 5% confectioner's sugar and inoculated with Streptococcus sobrinus 6715 or S. sobrinus 6715 plus A. viscosus M-100. The most coronal 1 mm of gingiva was removed from maxillary and mandibular right molar quadrants (gingivectomy), and the animals re-inoculated following gingivectomy. The animals were killed 64 days following gingivectomy, and the lingual surface of mandibular first molar roots was measured for exposed root-surface area and root caries. In the groups of rats infected with A. viscosus M-100, root caries area was significantly greater in the group fed diet containing 67% confectioner's sugar. Sucrose level did not significantly affect the amount of exposed lingual first molar root area regardless of whether the tooth had been subjected to a gingivectomy. In the groups of rats receiving diet containing 5% confectioner's sugar, there were no significant differences in root caries area or exposed root-surface area, regardless of the infection status of the animals. In the rat model presented here, a high level of dietary sucrose was a necessary condition for the initiation of root caries in the absence of other readily fermentable carbohydrates.

Sulcal plaque pH and remineralization of sulcal caries in rats exposed to dietary and water fluoride.

After being inoculated with Streptococcus (mutans) sobrinus 6715 and fed a mildly caries-promoting diet for 14 days, sulcal plaque pH response to topical application of a 10% sucrose solution was measured in two groups of rats. The first group (experimental) was then fed diet and drinking water to which 1 mmol (20 ppm) fluoride had been added (0.5 mmol for 7 days and 1 mmol for 14 days) and pH measurements were repeated. The second group was held as a control and a third group was sacrificed to provide baseline caries scores. There was no difference in the fall in pH after topical application of 10% sucrose solution between the control and experimental group, nor between the pre- and postfluoride measurements for the experimental group. Sulcal caries incidence in the experimental group was significantly lower than in the control group. The results of this experiment emphasize the importance of a cariostatic mechanism of action for fluoride based on remineralization of enamel lesions and do not support the in vivo adaptation to fluoride by oral microorganisms.