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.

Phosphatidylinositol phosphate kinases put PI4,5P(2) in its place.

Phosphatidylinositol 4,5 bisphosphate (PI4,5P(2)) is a critical second messenger that regulates a myriad of diverse cellular activities including modulation of the actin cytoskeleton, vesicle trafficking, focal adhesion formation, and nuclear events. In order to effectively regulate these disparate cellular events, synthesis of PI4,5P(2) by phosphatidylinositol phosphate kinases (PIP kinases) must be both spatially and temporally regulated. Two subfamilies of PIP kinases, types I and II, allow the generation of PI4,5P(2) from independent pools of substrate, PI(4)P and PI(5)P respectively. In turn, type I and II PIP kinases show different subcellular localization and thus are involved in distinct signaling pathways. Additionally, several type I isoforms, and their splice variants, have now been shown to be differentially localized throughout the cell and to be involved in the synthesis of PI4,5P(2) at distinct sites. These findings implicate PIP kinases as the major regulators of PI4,5P(2)-mediated events, making them key signaling enzymes in a variety of processes. Understanding the mechanisms regulating spatial and temporal synthesis of PI4,5P(2) by PIP kinases is vital for understanding these processes as a whole. This review examines both structural and regulatory features that modulate activity, localization, and substrate usage of PIPKs.

Ethanol inhibits spontaneous activity of central nucleus of the amygdala neurons but does not impair retention in the passive-avoidance task.

BACKGROUND: Behavioral studies using pharmacological manipulations that increase neuronal activity of the central nucleus of the amygdala (CeA) have implicated the CeA in enhancement of memory modulation. To date, however, there has been a dearth of studies investigating the effect of a drug that decreases CeA activity on memory modulation-a drug that inhibits the neuronal activity of the CeA might be expected to impair memory modulation. To determine whether ethanol inhibits CeA activity and, if so, whether decreased CeA activity is associated with impairment of memory modulation, this study investigated the effect of ethanol on spontaneous single-unit activity of CeA neurons and retention in the passive-avoidance task. METHODS: The effect of ethanol (0.35, 0.75, 1.5, 2.5 g/kg) was determined on spontaneously firing neurons in the CeA in urethane-anesthetized rats by use of standard in vivo single-unit electrophysiological recording techniques. Additionally, the effect of ethanol when administered immediately after training in a standard passive-avoidance task was determined on retention the following day. RESULTS: Ethanol profoundly inhibited spontaneous CeA firing rates in urethane-anesthetized rats at all doses tested. Maximal inhibition was related to dose. Each dose of ethanol significantly inhibited CeA activity within 15 min of administration; within 35 min of administration, 0.75 g/kg of ethanol inhibited CeA activity by 65.2%, and the highest dose (2.5 g/kg) produced nearly complete suppression of CeA activity (81.3%). Although ethanol markedly inhibited CeA activity, these same doses of ethanol failed to impair retention in the passive-avoidance task: 0.35, 0.75, 1.5, and 2.5 g/kg of ethanol, administered immediately after training, failed to alter latency to step-through the following day. CONCLUSIONS: These results show that ethanol profoundly inhibits spontaneous CeA activity and suggest that inhibition of the CeA is not sufficient to impair retention in the passive-avoidance task.

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.

In vivo diagnosis of fissure caries using a new electrical resistance monitor.

The aim of this investigation was to study the accuracy of a newly developed electrical resistance monitor in diagnosing occlusal fissure caries in vivo in teeth without cavitation. The electrical resistance was measured in vivo on human third molars without existing restorations and without any macroscopic carious cavitation. Data from 41 sites on 26 occlusal surfaces were obtained. After measurement, the teeth were extracted, histologically prepared, and serially sectioned perpendicular to the occlusal surface and examined for the presence of caries. Nineteen sites had no caries, 7 had enamel caries, and 15 sites showed dentinal caries, 4 of which deep dentinal caries. For the diagnosis of occlusal caries with the electrical resistance monitor, the specificity was 0.77, the sensitivity 0.93, and the accuracy 0.83. Likelihood ratios for four diagnostic levels (no caries, enamel caries, dentinal caries, and deep dentinal caries) were 0.09, 0, 3.47, and 4.16, respectively. Diagnosis of occlusal caries using conventional bite-wing radiographs showed a specificity of 0.77, a sensitivity of 0.62, and an accuracy of 0.71. The electrical resistance monitor was well suited to detect in vivo occlusal caries under clinically intact fissures. The rather high value (0.23) of false-positive ratings, however, might lead to a substantial number of sound teeth being restored unnecessarily. Substantial improvement of occlusal, caries diagnosis may be achieved by combining this method with others.

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 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.

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.

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.