Extraoral control of geometry for digital subtraction radiography

Gingival fluid IL-1beta in postmenopausal females on supportive periodontal therapy. A longitudinal 2-year study

Posterior interproximal alveolar bone in 59 women, within 5 years after menopause, was assessed at baseline and after 2 years of supportive periodontal therapy (history of moderate/advanced periodontitis) using digitized image analysis. Baseline lumbar spine bone mineral density, smoking status, and yearly serum estradiol (E2) levels also were obtained to group subjects. An additional 16 non-periodontitis postmenopausal women were followed 2 years for clinical and estrogen status. 2-min GCF IL-1beta levels averaged from 2 baseline periodontal pockets (in periodontitis subjects) and 2 non-periodontitis sites (in non-periodontitis and periodontitis subjects) were determined with an enzyme immunoassay. A progressive and stable site were also monitored every 6 months for GCF IL-1beta in 15 patients. Results after 2 years indicated that 17 subjects had no posterior interproximal sites losing > or =0.4 mm of alveolar crest bone height, while 13 subjects had > or =3 such sites. Using analysis of variance, none of the above clinical groupings resulted in a significant difference in mean baseline or longitudinal GCF IL-1beta levels. However, when subjects who lost alveolar crest bone height were considered, E2-sufficient subjects had significantly depressed baseline GCF IL-1beta (in past-periodontitis sites) compared to E2-deficient patients (9.1+/-2.1 versus 31.7+/-10.2 pg/2-min sample, p<0.05), suggesting E2 influences gingival IL-1beta production in progressive periodontitis patients.

Longitudinal changes in TCRB variable gene expression and markers of gingival inflammation in experimental gingivitis

The aim of this study was to gain information of the cellular and molecular events which occur during the development of experimental gingivitis and to determine whether such changes occur in the presence or absence of alveolar bone resorption. Clinical, radiographic, biochemical and immunological variables were monitored in a 3-week, single-centre, experimental gingivitis study of 10 healthy volunteers. Following screening and professional prophylaxis to achieve visibly healthy gingival status, subjects abstained from all oral hygiene practises in one maxillary (test) quadrant for a period of 21 days. At days 0 and 21, in test and (contralateral) control quadrants, % bleeding on controlled pressure probing (% BOP) was calculated, and radiographic alveolar bone status was assessed using bilateral standardised vertical bite-wing radiographs and digital subtraction radiography (DSR) analysis. In test quadrants, gingival crevicular fluid (GCF) was sampled from 4 sites per subject with Periopaper strips, and prostaglandin E2 (PGE2) levels measured using an enzyme immunoassay (EIA) kit. At days 0, 7 and 21, one interdental papilla was surgically excised from the test quadrant, and the expression of T cell receptor B variable (TCRBV) genes was investigated using a reverse transcription-polymerase chain reaction (RT-PCR) procedure. At days 0, 7 and 21, peripheral blood lymphocytes (PBL) were isolated and additionally investigated for TCRBV gene expression. Following 21 days of plaque accumulation in test quadrants, a statistically significant increase in % BOP scores confirmed the presence of gingival inflammation (p<0.001). DSR analysis revealed that there were no significant alveolar bone changes in either the test or control quadrants between days 0 and 21 (p>0.05). EIA analysis of GCF samples identified a significant decrease in mean GCF PGE2 concentrations from day 0 to day 21 (p<0.05). RT-PCR analysis indicated that genes from all 3 TCRBV families studied (TCRBV-2, -6, -8) were expressed in the PBL samples at all time points and in healthy gingival tissues at day 0. A restriction in the expression pattern of TCRBV genes similar to those which have previously been reported in chronic periodontitis was noted at gingivitis sites. It is possible that such an event may identify susceptibility to periodontal disease independently of other positive predictive markers such as GCF-PGE2.

Effect of projective aspects variations on estimates of changes in bone mass using digital subtraction radiography

This study tests the hypothesis that estimates of changes in bone mass derived from subtraction data obtained in accord with published methods are independent of the spatial aspect of the lesion being evaluated when calibrations are performed independently. Nineteen sliver-shaped bone chips ranging in mass from approximately 1 to 35 mg were orientated with broad side parallel to the facial surface of a hemisectioned dry human mandible and radiographed using conventional exposure parameters on conventional E-speed dental X-ray film. Also attached to the film was a standardized aluminium calibration wedge that facilitated quantitative analysis of resulting subtraction data using established methodology. The effects of scatter were simulated by the addition of a 1-cm-thick slab of tissue-equivalent plastic. A second series of exposures then was produced using the same respective spatial chip locations and projection geometries but each chip was reorientated such that its broad side was now positioned perpendicular to the mandibular facial surface. Finally, a comparable series of control exposures was produced without any chips or calibration wedge to facilitate subtraction. When paired bone estimates derived from the two chip orientations were compared (paired comparisons) using Student's t-test, a statistically significant difference (p < 0.05) was observed. These results also were tested for statistical significance using the non-parametric Wilcoxon test. As with the parametric analysis, the discrepancy between the parallel and perpendicular mass estimates was found to statistically significant (p < 0.05). The methods employed in this investigation thus resulted in bone mass estimates that varied significantly depending upon lesion orientation.

Quantitative radiographic follow-up of apical surgery: a radiometric and histologic correlation

The objective of this study was to establish an objective method for evaluating the treatment outcome of apical periodontitis (AP). AP was induced in the mandibular premolars of beagle dogs and apicoectomies were performed with retrofilling. Standardized periapical radiographs were taken immediately after completion of treatment and at 6 months. Ten pairs of standardized radiographs of 33 treated roots were analyzed. Radiographs were digitized and subtracted after warping and gamma correction. Areas of AP and adjacent normal areas (N) in digitized original and subtraction images were analyzed using eight radiometric computations. These computations were compared with subjective histologic evaluation and objective quantitative histomorphometry of the periapical condition at 6 months. The average gray value for AP on the subtraction images was found to have significant correlation with both objective (multiple regression p < 0.01) and subjective histology (logistic regression p < 0.01). Digital subtraction may be a useful tool in endodontic apical surgery assessment.

Accuracy of quantitative digital subtraction radiography for determining changes in calcium mass in mandibular bone: an in vitro study

The aim of this in vitro study was to determine the accuracy of digital subtraction radiography (DSR) to detect small changes in calcium mass in alveolar bone adjacent to tooth roots. In each of 4 dried porcine mandible segments, one interproximal and one buccal "defect" region was defined adjacent to a premolar root. A series of cortical and cancellous bone slices with a 50 microns--stepwise increasing thickness (0-5000 microns) were attached to the mandible segments covering the respective "defect" region. Standardized radiographs were quantitatively assessed for density changes using DSR. After dissolving each bone slice in hydrochloric acid, its calcium concentration was photometrically determined. For each bone slice, the mean calcium mass covering a single pixel of the subtraction image was calculated. The Wilcoxon signed-rank test and the Mann-Whitney U-test were used for statistical analysis (alpha = 0.05). A strong linear correlation (r2 = 0.86-1.00; p < or = 0.001) was found between the thickness of the bone slices and their calcium mass. Cortical bone showed a 3.5 times higher mean calcium mass/pixel than cancellous bone. Furthermore, a strong linear correlation (r2 = 0.63-1.00; p < or = 0.001) was found between the mean calcium mass per image pixel and the radiographic density changes. Neither the bone type nor the "defect" localization had a significant influence on radiographic density changes caused by changes in calcium mass. A change in mean calcium mass per image pixel of 0.1-0.15 mg was necessary to be detected by DSR. In conclusion, this study revealed a high accuracy of DSR to detect small changes in calcium mass in alveolar cortical and cancellous bone.

Evidence for healing of interproximal intrabony defects after conventional and regenerative therapy: digital radiography and clinical measurements

In 24 patients with advanced periodontitis 38 interproximal intrabony defects were treated by conventional surgery (C; n = 8) or guided tissue regeneration (GTR) using expanded polytetrafluoroethylene (G; n = 17) or Polyglactin 910 barriers (V; n = 13). Presurgically (BL), 6 and 12 months postsurgically clinical parameters (GI, PII, PPD, PAL-V) and 36 standardized radiographs were obtained generating 72 pairs (36 BL/6 months; 36 BL/12 months). Using linear measurements on the radiographs and subtraction analysis, bony fill within the defects was assessed. Intrasurgically the extension of the intrabony defects was measured. Statistically significant (p < 0.05) attachment gain was found after 6 (C: 2.4 +/- 1.6 mm; G: 3.2 +/- 1.6 mm; V: 3.4 +/- 1.5 mm) and 12 months in all groups (C: 2.4 +/- 1.7 mm; G: 3.1 +/- 1.7 mm; V: 4.0 +/- 1.7 mm). Thirty-nine of 72 pairs of radiographs were unsuitable for subtraction analysis. Significant (p < 0.05) bony fill was observed at 6 (C: 0.3 +/- 1.0 mm; G: 0.7 +/- 1.2 mm; V: 0.9 +/- 1.2 mm) and 12 months (C: 0.0 +/- 1.1 mm; G: 1.4 +/- 1.5 mm; V: 1.5 +/- 1.7 mm) only after GTR surgery. GTR therapy yielded significantly more bony fill than conventional surgery 12 months postsurgically (p < 0.1). Bony fill (linear measurement) was influenced by age, smoking, baseline bone loss and PAL-V gain (p < 0.0001). Significantly more radiographs taken with potentially unstable support of the filmholder were not suitable for subtraction analysis than those with stable support (p < 0.05). Bony gain (subtraction analysis) was positively modulated by bony fill (linear measurement) and use of biodegradable barriers (p = 0.002). There is a correlation between PAL-V gain and bony fill (linear measurement). Smoking impairs attachment gain and bony fill. Potentially stable support of the filmholder provided radiographs suitable for subtraction analysis.

Effect of immune T cells derived from mucosal or systemic tissue on host responses to Porphyromonas gingivalis

The purpose of this study was to compare the effects of immune T cells derived from mucosal and systemic tissues on specific humoral responses to the periodontal pathogen Porphyromonas gingivalis and to determine the effect these responses have on periodontal bone loss in an experimental rat model. T cells were derived from either the spleen or Peyer's patches of conventional Fischer rats given live P. gingivalis by the oral route and were adoptively transferred into groups of nude Fischer rats. A group of nude rats to which no T cells were transferred served as control. Within 24 h of the adoptive cell transfer, animals from all groups were orally challenged with live P. gingivalis. Serum and salivary responses were seen in rats given immune T cells, whereas a low, variable serum IgM and no serum IgG or salivary IgA response was detected in the control nude rats, indicating that the major host responses to P. gingivalis whole-cell antigens were T-cell dependent. Rats given immune Peyer's patch-derived T cells exhibited a different serum IgG and salivary IgA immune response pattern than animals given immune splenic T cells. A higher serum IgG, especially IgG2b, antibody response and less horizontal bone loss was seen in rats given splenic than Peyer's patch-derived T cells. Although some differences were seen in the levels of salivary IgA early in the study in the two experimental groups, the levels of IgA were comparable by the termination of the experimental period. Furthermore, no difference was seen in the amount of vertical bone support in these two groups, which was greater than in the controls. These results suggest a role for serum IgG and salivary IgA in periodontal disease protection. The presence of high serum IgG2b antibody activity suggest the involvement of Th1-like cells in the response, whereas salivary IgA antibodies indicates the participation of Th2-like cells. These results suggest that the balance between Th1 and Th2-like cells within the systemic and mucosal compartments and the humoral immune responses to P. gingivalis they mediate are important in determining whether the responses induced are protective against experimental bone loss after oral challenge with the periodontal pathogen P. gingivalis.

A digital subtraction radiography investigation of upper first molar proximal bone density changes in adolescents

The aim of this in vivo study was to investigate the ability of digital subtraction radiography to monitor changes in proximal bone density, adjacent to the upper first molars, in a group of adolescents using the Digora direct digital radiographic system to acquire images. For 57 adolescents, assessments of changes in probing attachment level at the mesio- and disto-buccal surfaces of both upper first molars and proximal crestal bone density using digital subtraction radiography were made. At the conclusion of this 21-month study attachment loss was identified in 34 (17%) of the 204 sites analysed. For sites with attachment loss a mean decrease in bone density equivalent to 5.51 mm3 aluminium (Al) was found compared to 2.96 mm3 Al for those without (p < 0.001). For the 17 subjects with attachment loss a mean equivalent to 4.66 mm3 Al was lost from the crestal bone compared with 2.56 mm3 Al for the 40 subjects without attachment loss (p < 0.01). The correlation between attachment loss and bone density changes was poor for both sites (r = 0.13), p = 0.067) and mean scores for subjects (r = 0.24, p = 0.069). A visual qualitative assessment of bone density change found that 70.6% of sites with attachment loss compared to 62.4% of those without had a decrease in crestal bone density. This study suggests that it is possible to monitor bone density changes in adolescents, with a developing dentition, using digital subtraction radiography. Further, it is suggested that conventional probing assessments of attachment level may underestimate the level of destructive periodontal disease in this age group.

Quantitative digital subtraction radiography for the determination of small changes in bone thickness: an in vitro study

OBJECTIVE

The objective of this study was to determine the ability of quantitative digital subtraction radiography to detect small changes in bone thickness adjacent to tooth roots.

STUDY DESIGN

A series of cortical or cancellous bone slices with a 50 microm-stepwise increasing thickness were attached to 4 porcine mandible sections covering buccal and interproximal "defect" regions. Standardized radiographs were quantitatively evaluated for radiographic density changes with the use of digital subtraction radiography. Furthermore, all radiographs were conventionally evaluated by 10 clinicians. The Wilcoxon signed-rank test and the Mann-Whitney U test were used for statistical analysis (alpha = 0.05).

RESULTS

A high linear correlation was found between the actual thickness of bone slices and radiographic density changes (cortical bone: r2 = 0.89 to 0.99; cancellous bone r2 = 0.61 to 0.86, p < or = 0.001). A certain increase in bone thickness caused a 3 times higher increase in radiographic density for cortical bone than for cancellous bone (p < or = 0.05). The detection limits of digital subtraction radiography were 200 microm for cortical and 500 microm for cancellous bone, whereas the detection limits of conventional radiography were 600 microm and 2850 microm, respectively.

CONCLUSIONS

This in vitro study demonstrated a very high correlation between the objective, quantitative assessment of subtle changes in alveolar bone by digital subtraction radiography and the true changes in bone thickness.

Semiautomated image registration for digital subtraction radiography

OBJECTIVE

The purpose of this study was to evaluate the semiautomatic alignment and correction of affine geometric discrepancies for digital subtraction radiography.

STUDY DESIGN

Algorithms were tested in vitro to determine their ability to semiautomatically select reference points on a second image based on points selected on a first (reference) image. A preserved human mandible was imaged with and without bone-equivalent material chips at varying degrees of angulation. Each chip had a mass of less than 10 mg and was no more than 0.3 mm thick. High levels of specificity and sensitivity for chip detection were achieved with 6 degrees of angular discrepancy or less. The algorithms were then applied to radiographs from six human subjects through use of the bone-chip validation model.

RESULTS

Sensitivity was 89% and 100% for the three-point and four-point affine warp algorithms, respectively. Specificity for both algorithms was 100%.

CONCLUSIONS

The data indicate that semiautomated alignment algorithms may enhance the efficacy of digital subtraction radiography while maintaining diagnostic efficacy in clinical trials.

Coordinate production of PGE2 and IL-1 beta in the gingival crevicular fluid of adults with periodontitis: its relationship to alveolar bone loss and disruption by twice daily treatment with ketorolac tromethamine oral rinse

The inflammatory mediators prostaglandin E2 (PGE2) and interleukin-1 beta (IL-1 beta) play critical roles in the inflammatory process leading to alveolar bone and connective tissue loss in periodontal disease. Data from a previously published 6-month clinical study demonstrated that twice daily use of 0.1% ketorolac tromethamine oral rinse prevented alveolar bone loss in adults with periodontitis. We further analyzed data from this study to examine the relationship between PGE2. IL-1 beta and bone loss. Patient mean PGE2 and IL-1 beta levels in gingival crevicular fluid (M-GCF) measured throughout the course of the study were directly compared to the maximum amount of alveolar bone height loss observed at a single study site in each patient. The maximum amount of bone loss measured was chosen for the analysis since the pattern of bone loss was clearly episodic in nature. A statistically significant correlation (r = 0.73, p = 0.001) exists between M-GCF PGE2 concentration and the maximum amount of bone height lost at individual patient study sites. The correlation between M-GCF IL-1 beta concentration and maximum bone height lost is also statistically significant (r = 0.66, p = 0.005). Over the 6-month duration of the study, both PGE2 and IL-1 beta were coordinately expressed in the placebo treatment group as reflected in the significant correlation between M-GCF concentrations of the 2 mediators (r = 0.81, p < 0.001). Treatment of patients with 0.1% ketorolac tromethamine twice daily for 6 months resulted in reductions of PGE2 in GCF and a negligible correlation between M-GCF PGE2 and M-GCF IL-1 beta (r = 0.42, p = 0.088). This lack of a strong association between the 2 mediators in the ketorolac treatment group provides a direct biochemical readout of the anti-inflammatory efficacy of ketorolac tromethamine oral rinse in patients with periodontitis. Further studies are warranted to determine the full diagnostic potential of M-GCF levels of PGE2 and IL-1 beta for predicting risk of alveolar bone loss in patients with periodontitis and monitoring periodontal therapy effectiveness.

The effect of image variations on fractal dimension calculations

OBJECTIVES

We used digitized dental radiographs of alveolar bone to test the hypothesis that the fractal dimension, as calculated with the program "ImageFractal" was independent of variations in X-ray exposure, beam alignment, and region of interest placement.

STUDY DESIGN

The radiographic data set consisted of 72 radiographs digitized with 200 microns pixels. Radiographs were obtained with the use of three time settings and two alignments. Rectangular regions of interest were placed on each digital image over the interdental bone between the mandibular first and second molars on six hemimandibles. Each of six hemimandibles had identical copies of a unique region of interest placed on every image in its series. New regions were made 3 months later. A fractal dimension was computed from each region of interest with the caliper method included in ImageFractal, a public domain program available through National Institutes of Health. The resulting fractal dimensions were evaluated with two repeated measures analysis of variance.

RESULTS

No significant differences were found between the fractal dimensions calculated for baseline images and those from overexposed and underexposed images, from images with 4 to 6 degrees of alignment variations, or from repeat regions of interest.

CONCLUSION

The results support the hypothesis that fractal dimensions derived from digitized dental radiographs are not affected by variations in exposure or small variations in alignment and imply an absolute region of interest placement may not be necessary. However, caution should be used with the use of the fractal dimension to discriminate among alveolar bone variations until further research is performed.

Evidence for healing of class II and III furcations after GTR therapy: digital subtraction and clinical measurements

In 21 patients with advanced periodontitis, 39 teeth exhibiting class II (n = 21) and class III (n = 18) furcations were treated by the guided tissue regeneration technique using expanded polytetrafluoroethylene (ePTFE) membranes (n = 20) or bioabsorbable barriers (n = 19), respectively. Clinical parameters were assessed before and 6 months after surgery. Presurgically and 6 months postsurgically, 35 pairs of standardized bitewing radiographs were taken. Using subtraction radiography, gain of bone density within furcation areas was assessed. Eighteen radiographs showed sufficiently accurate geometry to be analyzed by subtraction. Within the defects suitable for subtraction, the average gain of vertical attachment assessed was 1.35 +/- 1.27 mm in the class II furcation group and 1.58 +/- 1.37 mm in the class III furcation group. The average horizontal attachment gain in the class II furcation group was 1.96 +/- 0.59 mm. No statistically significant differences were observed between results after GTR therapy using non-resorbable and bioabsorbable barriers. Radiographic bone gain as assessed by subtraction analysis correlated with vertical (r = 0.458, P < 0.025) and horizontal (r = 0.734, P < 0.005) attachment gain. A statistically significant number of more radiographs for maxillary molars were not suitable for subtraction analysis than mandibular molars (P < 0.05). Further, statistically more radiographs that were taken with potentially unstable support of the filmholder were not suitable for subtraction analysis than those with stable support (P < 0.05). There is a statistically significant correlation between clinical improvements and bony fill within furcation defects. Only 18 of 35 pairs of radiographs were suitable for subtraction analysis. Subtraction analysis of maxillary molars seems to be more difficult than assessment of radiographic bone changes in mandibular molars. Potentially stable support of the filmholder seems to be a condition to provide radiographs suitable for subtraction analysis.

Efficacy of digital intra-oral radiography in clinical dentistry

OBJECTIVES

This article emphasizes the comparison of intra-oral digital imaging to film-based imaging. Additional possibilities of digital imaging that may contribute to system efficacy are discussed as well.

STUDY SELECTION

The main subjects for research in digital imaging are image quality, image acquisition, diagnostic quality, image manipulation, automated analysis, and application software.

DATA SOURCES

Representative articles on these subjects from the international literature are used for this review. Indirect digital imaging still requires film processing, sophisticated film digitizers, and time to digitize film. Although it is not an efficient method for the dental practice, digitization can be very useful for quantitative analysis of radiographs. Direct digital imaging is more efficient than indirect digital imaging. The main advantages are (semi) real time imaging, low X-ray dose requirements, and no need for chemical processing. In spite of a more limited resolution of the images, direct imaging may perform as accurately as film-based imaging. Direct image plate systems can well be used, for instance, for full-mouth series. The main application of direct sensor systems appears to be endodontology and implantology. In summary, direct digital imaging may be as efficient as film-based imaging in clinical dentistry. The computer provides for many additional options in digital imaging, such as the digital storage, compression, and exchange of radiographic information. Image manipulation (e.g. image enhancement, subtraction radiography and image reconstruction) and automated analysis may benefit radiodiagnosis.

CONCLUSION

It can be concluded that digital imaging certainly has great potential, especially with respect to improvement of diagnostic quality and automated image analysis.

A comparison of similarity measures for digital subtraction radiography

Subtraction is useful in detecting small changes in sequentially acquired radiographs. Even if the imaging geometry is constant, radiographs must be registered after their digitization. To compare different algorithms for image registration and to register digital X-rays themselves, various similarity measures have been proposed. This study compares eight mathematical similarity standards using 172 radiographs acquired in different, but exactly known projection. Whenever the computation time is a critical factor, e.g. registering images using methods similar to correlation techniques, the entropy of the subtraction image's histogram function (EHDI) is found to be the best similarity standard. If not, e.g. comparative assessing different image registration techniques, the cross covariance coefficient (CCC) is appropriate.

The use of biologic response modifiers in human clinical trials

To optimize regeneration of the periodontium, new cementum, periodontal ligament, and bone must be formed. Conventional periodontal surgery decreases the likelihood of continued progressive periodontal disease however, it does not lead to significant periodontal regeneration. In vitro studies have identified a class of biologic response modifiers loosely referred to as growth factors, which stimulate the cellular events of tissue regeneration. The most promising are mitogenic and differentiation factors. Based on promising results from animal studies, the application of growth factors to predictably stimulate periodontal regeneration is entering human clinical trials. This manuscript deals with several important considerations in testing biologic response modifiers in humans. Suggestions are made regarding the following parameters: 1) selection of the unit of measurement; 2) patient and lesion selection; 3) identification of controls; 4) selection of outcome parameters; 5) statistical approach; and 6) considerations in treatment regimens.

The use of periodontal probes and radiographs in clinical trials of diagnostic tests

Periodontal probing attachment level measurements and intraoral radiographs are used to assess the level of the clinical attachment and bone support in the diagnosis of periodontitis. Together these physical measurements of tooth support comprise the standard against which new diagnostic tests are compared. Since probing and radiographs provide a measure of the severity of attachment or bone loss at one point in time, serial measurements must be compared to determine whether periodontitis is progressive. Periodontal probing may be performed manually or by using controlled force electronic instruments. The resolution, depending on the instrument, will vary from 1.0 mm to 0.1 mm. Variations in probing force, size and shape of tip, location of tip placement, detection or reference landmarks for attachment level probing, degree of gingival inflammation, and transcription may adversely influence accuracy. Electronic probes offer the advantage of improved resolution, force control, and automatic recording, but the literature is inconsistent about the advantages in terms of repeatability and accuracy. Radiographic assessment of alveolar bone loss may be achieved by visual interpretation, measurement, or digital image analysis. While visual interpretation of unstandardized radiographs is insensitive to changes in bone, standardized radiographs can permit measurement of changes on the order of 0.2 mm when computerized methods are used. Newer techniques such as digital subtraction radiography permit detection of bony changes too small to be seen by the unaided eye and are over 95% sensitive and specific in detecting bony changes less than 10 mg.

Outcome variables for the study of periodontal regeneration

The most reliable outcome variable for assessing periodontal regeneration is human histology; however, the morbidity associated with this technique makes it feasible only in isolated case studies designed to prove that a drug, device, or technique is capable of regenerating the lost periodontium including bone, cementum, and functionally oriented periodontal ligament. In the absence of this genuine variable, other "surrogate" variables must be used. Of these, measurement of new bone is the primary alternative. Direct bone measurements, including linear and volumetric assessment, are by far the best tools; however, the need for a second surgical procedure is a definite drawback of this technique. To overcome this problem, other outcomes have been employed: sounding bone measurements is a less invasive method, albeit it is also less accurate. Another tool that has been tested extensively is radiographic analysis. Conventional radiography is not useful in most regenerative trails where minimal or no crestal changes occur. The use of standardized radiographs and image processing techniques to measure alveolar bone changes has not significantly enhanced the applicability of this method. Digital subtraction radiography (DSR) offers some improvement over previous techniques; however, the correlation between the magnitude of clinical bone changes and changes in the digital image is yet to be substantiated. Other variables have been successfully used in regenerative studies. These include clinical attachment level changes, change in probing depth, and gingival recession. The information derived from these variables, especially attachment level changes, supplement and substantiate the direct bone measurements. Other variables that may be monitored are those associated with plaque formation, periodontal pathogens and gingival inflammation; while not direct measures of regeneration, these variables are likely to affect future prognosis and treatment stability. In summary, direct bone measurements are the most ideal surrogate outcome variable, although clinical attachment level measurements are commonly used in large-scale regenerative clinical trials. Clinical response may be assessed at different time intervals; however, the endpoint measurements for regenerative studies should be taken at least 12-months postoperatively.

Evaluation of a dental subtraction radiography system

The aim of this in vitro study was to evaluate the ability of a dental subtraction radiography system to quantitatively detect differences in density between radiographic image pairs. Four periapical radiographs were taken of the upper first permanent molars on five human skulls using the Digora radiographic imaging system. The 4 images were a "baseline" image and 3 containing test objects consisting of either 0.5, 1 or 2 mm thick aluminium cylinders, 2.5 mm in diameter. Semi-automated image processing software was used to "warp" the 3 images with test objects into the same geometric/density registration as the corresponding baseline image using a process called patch minimization. "Difference" images were than produced and their contrast stretched. For regions of interest, with and without test objects present, the difference in density between the baseline and "test object" images was calculated using a reference aluminium step wedge. The test objects were clearly visible in all the "difference" images. The mean difference between the actual and estimated volume of the test object was 0.31 (95% CI [-0.55, 1.17]) mm3 Al. There was a strong association (r = 0.83) between the actual and estimated aluminium volumes. It is concluded that this system provides adequate precision for clinical evaluation.

The association between estrogen status and alveolar bone density changes in postmenopausal women with a history of periodontitis

While numerous studies have demonstrated a relationship between 17-beta-estradiol (E2) deficiencies and skeletal bone loss in postmenopausal females, the influence of E2 deficiency on alveolar bone resorption is poorly understood. The purpose of this study was to examine the association between the estrogen status of postmenopausal women and alveolar bone density changes in a 1-year longitudinal study. Twenty-four postmenopausal women, within 7 years of menopause, were divided into 2 groups, E2-sufficient (n = 10) and E2-deficient (n = 14). Venous blood samples were taken at baseline, 6 months, and 1 year for radioimmunoassay determination of serum E2 levels. At baseline and 1 year, 4 vertical bite-wing radiographs were taken for computer-assisted densitometric image analysis (CADIA). Areas of interest (AOIs) for CADIA were crestal and subcrestal regions of posterior interproximal alveolar bone. Serum E2 levels were significantly higher at all 3 time points in the E2-sufficient subjects (P < 0.002), repeated measures ANOVA). Overall, mean CADIA values (0.30 +/- 0.07 for the E2-sufficient women and -0.44 +/- 0.07 for the E2-deficient women) were statistically different between groups (P < 0.001, repeated measures ANOVA), indicating that the E2-sufficient women displayed a mean net gain in alveolar bone density and the E2-deficient women displayed a mean net loss in alveolar bone density. Furthermore, the E2-sufficient women exhibited a higher frequency of sites demonstrating a gain in alveolar bone density, while the E2-deficient women exhibited a higher frequency of sites demonstrating loss in alveolar bone density. These data suggest that estrogen status may influence alveolar bone density changes as demonstrated with CADIA.

Analysis of consecutively placed loaded root-form and plate-form implants in adult Macaca mulatta monkeys

The present paper describes 36 consecutively treated non-human primates (Macaca mulatta) as part of a balanced block design study to examine osseointegration in root- and plate-form implants prepared by atraumatic preparation of bone. Clinical measurements around selected teeth and digital radiology were utilized to monitor periodontal disease and bone loss around root- and plate-form implants which were loaded with a fixed prosthesis. Results indicate that once monthly regimen of scaling and root planing can prevent attachment loss in natural teeth, serving as abutments of loaded bridges. Root-form implants exhibited a significant loss of crestal bone height during the first year (P < 0.03) while plate-form implants showed less loss in bone height. There was an increase in bone mass over time for root-form or plate-form implants. Both root-form and plate-form implants provided radiographic evidence of osseointegration in loaded bridges.

The effect of ketoprofen creams on periodontal disease in rhesus monkeys

Ketoprofen creams were evaluated for the treatment of periodontal disease in a placebo-controlled, double-blind study in the rhesus monkeys, Macaca mulatta. Two formulations containing ketoprofen (1%), with or without vitamin E, were evaluated against appropriate controls (8 monkeys per group). Two weeks prior to treatment, the animals received prophylaxis on only the left side of the mouth (spontaneous model). Selected teeth on the right side of the mouth were ligated (ligature model). The creams were administered to the gingiva once daily at a standard dose of 1.8 ml per monkey for 6 months. Clinical assessments were made 2 wk before initiation, at baseline and 1, 2, 3 and 6 months post-treatment. The clinical parameters included plaque formation, gingival redness, edema, bleeding on probing and Ramfjord Attachment Level measurements (RAL). Radiographs were taken at 2 wk before initiation, baseline and at 3 and 6 months post-treatment. Digital, subtraction radiography was used to measure vertical linear bone loss along the interproximal root surfaces of the left and right mandibular first molars. Gingival crevicular fluid (GCF) was collected for biochemical assays on PGE2, TxB2, LTB4, IL-1 beta and TNF alpha. There were no significant differences among groups with respect to gingival indices. Radiographic data demonstrated significant positive effects on bone activity in both groups treated with ketoprofen formulations with improvement over time in the ligature model (0.01 < or = p < or = 0.04). The placebo group exhibited bone loss of 1.96 +/- 0.48 and 1.40 +/- 0.56 mm per site at 3 and 6 months, respectively. The group treated with ketoprofen cream showed an apparent bone gain of 0.28 +/- 0.41 and 0.78 +/- 0.47 mm per site at 3 and 6 months, respectively. The group treated with ketoprofen cream containing vitamin E showed a mean bone loss of 0.41-0.48 mm per site at 3 months with improvement to an apparent bone gain of 0.31 +/- 0.44 mm per site at 6 months. The biochemical data demonstrated early and significant suppression of GCF-LTB4 by both ketoprofen formulations at 1 month, which preceded the significant suppression of GCF-PGE2 at 2 and 3 months in the ligature model (p < 0.003) and at 2 to 6 months in the spontaneous model (p < 0.02). We conclude that ketoprofen at 1% level in suitable topical vehicles can effectively inhibit GCF-LTB4 and GCF-PGE2 and positively alter alveolar bone activity in the ligature-induced model of periodontitis in the monkey.

Effect of host responses on the pathogenicity of strains of Porphyromonas gingivalis

Porphyromonas gingivalis is implicated in the etiology of periodontitis. Strains of P. gingivalis have been classified as invasive or noninvasive based on their ability to form abscesses in a mouse model. The purpose of this study was to investigate the ability of P. gingivalis strains to cause abscesses and periodontal bone loss in an experimental rat model and the effect of serum and salivary responses on the pathogenicity of these strains. Subcutaneous injection of animals with P. gingivalis 33277, A7A1-28, W50 or 381 resulted in abscesses in a higher percentage of mice than rats. P. gingivalis 33277 caused lesions at the site of injection, whereas strains A7A1-28 and W50 induced abscesses at distant sites in both mice and rats. Local lesions were seen in rats injected with strain 381, whereas lesions formed distant from the site of injection in mice. When periodontal bone loss was assessed in the experimental rat model, animals challenged with 33277 had the highest amount of horizontal and vertical bone loss. Rats challenged with strain A7A1-28, W50 or 381 had some or no periodontal bone loss compared with controls. Assessment of antibody responses to P. gingivalis in these animals revealed that rats challenged with 33277 had lower levels of serum immunoglobulin G-(IgG) and especially salivary IgA antibody activity than A7A1-28-challenged rats. Serum IgG and in particular salivary IgA anti-P. gingivalis responses were seen in W50- and 381-challenged rats. These results indicate that the ability of P. gingivalis strains to cause abscesses does not relate directly to their periodontal pathogenicity as assessed by periodontal bone loss in the same animal model. The results further suggest the importance of salivary IgA antibody responses in protection against experimental periodontal bone loss after challenge with P. gingivalis.

Advanced imaging methods

Recent developments in imaging sciences have enabled dental researchers to visualize structural and biophysical changes effectively. New approaches for intra-oral radiography allow investigators to conduct densitometric assessments of dento-alveolar structures. Longitudinal changes in alveolar bone can be studied by computer-assisted image analysis programs. These techniques have been applied to dimensional analysis of the alveolar crest, detection of gain or loss of alveolar bone density, peri-implant bone healing, and caries detection. Dental applications of computed tomography (CT) include the detailed radiologic anatomy of alveolar processes, orofacial soft tissues and air spaces, and developmental defects. Image analysis software permits bone mass mineralization to be quantified by means of CT data. CT has also been used to study salivary gland disease, injuries of the facial skeleton, and dental implant treatment planning. Magnetic resonance imaging (MRI) has been used extensively in retrospective and prospective studies of internal derangements of the temporomandibular joint. Assessments based on MRI imaging of the salivary glands, paranasal sinuses, and cerebrovascular disease have also been reported. Magnetic resonance spectroscopy (MRS) has been applied to the study of skeletal muscle, tumors, and to monitor the healing of grafts. Nuclear imaging provides a sensitive technique for early detection of physiological changes in soft tissue and bone. It has been used in studies of periodontitis, osteomyelitis, oral and maxillofacial tumors, stress fractures, bone healing, temporomandibular joint, and blood flow. This article includes brief descriptions of the technical principles of each imaging modality, reviews their previous uses in oral biology research, and discusses potential future applications in research protocols.

Validation of quantitative digital subtraction radiography using the electronically guided alignment device/impression technique

The electronically guided alignment device (EGAD) has been demonstrated to function well with a custom fabricated stent for taking radiographs for subtraction. The objective of this study is to demonstrate that this device functions well when used with an impression bite-block rather than a full arch acrylic stent. Nineteen subjects participated. Two vinyl siloxane impressions were made for each subject and a pair of x-rays was taken with each impression. The location for study was divided among 7 for the maxillary premolar-1st molar region, 6 for the mandibular premolar-1st molar region, and 6 for the incisor-canine region. To simulate bone change 3 bone chips (approximately 1, 7, and 10 mg) were positioned in the mucobuccal fold when one of each pair of x-rays was taken. Pairs of radiographs were subtracted and the bone change (chips) isolated by thresholding to determine their area. An aluminum ramp was used to determine volume. A strong linear relationship between actual chip weight and equivalent aluminum volume (r2 = 0.64, P < 0.001) was obtained for all regions of the mouth when considered together. The strongest relationship of the 3 regions was for mandibular premolar-1st molar sites, r2 = 0.78. These data indicate that the EGAD/impression technique is suitable for taking radiographs in all areas of the mouth for quantitative digital subtraction.

Clinical evaluation of demineralized-unicortical-ilium-strips for guided tissue regeneration

This study compared demineralized-unicortical-ilium-strips (DUIS) and an expanded polytetrafluoroethylene (ePTFE) physical barrier in combination with decalcified freeze-dried bone allograft (DFDBA) for treatment of Class II mandibular furcations. Twenty patients with adult periodontitis and at least 2 furcation invasions participated in this study. Probing depth (PD), clinical attachment level (CAL), and bone fill were measured at 6 and 12 months. Standardized radiographs were analyzed using computer assisted densitometric image analysis (CADIA). Fifteen of 20 patients completed the 12-month evaluation. At 6 months both control and test groups showed significant reductions in PD from baseline (P < 0.01). PD reduction for the ePTFE + DFDBA sites was 2.13 mm +/- 1.25, and the DUIS + DFDBA, 1.77 mm +/- 1.21. CAL at 6 months was sustained to 12 months when the net gains in CAL for ePTFE + DFDBA being 1.30 mm +/- 1.45 (P < 0.01) and for DUIS + DFDBA sites 1.13 mm +/- 1.68 (P < 0.02). The horizontal furcation PD decreased 2.87 mm +/- 1.68 (P < 0.01) in the ePTFE + DFDBA and 1.70 mm +/- 1.69 (P < 0.01) for DUIS + DFDBA sites over 12 months. The evaluation of the hard tissue response at the 12-month re-entry demonstrated a bone fill of 2.37 mm (75%) +/- 2.04 (P < 0.01) with ePTFE + DFDBA and 1.83 mm (79%) +/- 1.57 (P < 0.01) with DUIS + DFDBA. DUIS material and ePTFE showed significant improvements in clinical parameters and neither material proved to be significantly better. However, a larger sample size may have permitted us to demonstrate statistically significant differences between the materials. The positive results from the utilization of DUIS for GTR and the advantage of its bioresorbability warrant further investigation. The study found limitations in the use of CADIA for evaluation of guided tissue regeneration in furcations.

Correlation between gingivain/gingipain and bacterial dipeptidyl peptidase activity in gingival crevicular fluid and periodontal attachment loss in chronic periodontitis patients. A 2-year longitudinal study

The aim of this study is to determine whether either gingival crevicular fluid (GCF) bacterial gingivain/gingipain or dipeptidyl peptidase (DPP) levels, total activity (TA) and concentration (EC), predict progressive attachment loss (AL) in 75 patients with moderate periodontitis. GCF was collected from 16 molar and premolar mesiobuccal sites and then clinical attachment level (CAL) and probing depth (PD) were measured with an electronic constant pressure probe. Lastly, gingival, gingival bleeding, and plaque indices were scored. Prior to the baseline visit, patients were given basic periodontal treatment after which the above procedures were repeated. In addition, carefully localized radiographs were taken of the test teeth and repeated annually. Patients were then seen every 3 months for 2 years and the clinical measurements repeated at each visit. In 48 patients, 124 AL sites, 91 rapid AL (RAL), and 33 gradual AL (GAL) were detected. Gingivain/gingipain and bacterial DPP levels (TA and EC) at RAL sites were significantly higher (P < or = 0.0001) than at paired control sites at the attachment loss time (ALT) and prediction time (PT). Mean levels over the study period of both proteases (TA and EC) at GAL sites were significantly higher (P < or = 0.0001) than those at paired control sites. The GCF levels of gingivain/gingipain were always higher than those of DPP. Critical values (CV) of 5 microU/30 seconds (TA) and 30 microU/microL (EC) for both proteases showed high sensitivity and specificity values for TA and EC, which were the same at both ALT and PT. The positive predictive values were higher for gingivain/ gingipain. Mean site levels, over the course of the study, of both proteases (TA and EC) were significantly higher (P < or = 0.0001) at AL, RAL, and GAL sites than non-attachment loss (NAL) sites in AL patients and mean patient levels were significantly higher (P < or = 0.0001) in AL, RAL, and GAL patients than NAL patients. These results indicate that both of these bacterial proteases in GCF may be predictors of periodontal attachment loss.

A case of localized juvenile periodontitis: treatment and 3 years follow-up with superimposable radiographs

A 17-year-old male patient with localized juvenile periodontitis was treated by subgingival instrumentation with full thickness flap on the lower molars, combined with a 3-week course of systemic tetracycline, and a programme of supervised oral hygiene. The treatment was rapidly followed by dramatic clinical and microbiological improvement. However, despite good oral hygiene, gingival inflammation recurred at regular intervals. It was necessary to maintain the clinical results by periodic subgingival instrumentation with an ultrasonic scaler. Healing of alveolar bone was monitored in the lower 1st molar regions over 3 years by using superimposable radiographs. Quantitative analysis of bone density performed with a high-resolution digitalisation technique showed a considerable improvement 1 year after therapy. However, continuous remodelling, probably related to variations in inflammation, occurred during the 3 postoperative years.

Efficacy of quantitative digital subtraction radiography using radiographs exposed in a multicenter trial

Digital subtraction radiography (DSR) has been shown to be a sensitive and specific method for the detection of small bony changes in periodontitis. The purpose of this study was to perform a multicenter validation of the DSR in human subjects. Seventeen subjects were enrolled at 3 centers. Feather-edged hydroxyapatite chips (approximately 1, 7 and 10 mg) were used to simulate osseous lesions. Bilateral radiographs were taken with and without chips. Geometry was standardized using a cephalostat and the order of radiographs was determined using a randomization plan. Radiographs were subtracted, lesions isolated, and quantified at a single center without knowledge of the randomization code or location of the chips used in each subject. The overall sensitivity and specificity in detecting 1 mg changes was 87.8% and 100%, respectively. Sensitivity and specificity in detecting 7 mg and 10 mg chips was 100%. A strong linear relationship between actual lesion mass and calculated mass was observed (R2 = 0.94, slope = 0.98, p < 0.0001). No significant differences were observed by center. These data indicate that the DSR is a valid technique for the assessment of alveolar bone changes in multicenter trials.

Radiographic evaluation of bone regeneration following periodontal surgery with or without expanded polytetrafluoroethylene barriers

In 16 patients with advanced periodontitis, 23 teeth exhibiting interproximal intrabony defects were treated by conventional periodontal surgery (n = 10, control) or guided tissue regeneration (GTR) technique using expanded polytetrafluoroethylene (ePTFE) barriers (n = 13, test), respectively. Clinical parameters were assessed before and 6 months after surgery. Presurgically and 3 and 6 months postsurgically standardized bite-wing radiographs were taken. Using a loupe and a computer-assisted system, respectively, the distances from the cemento-enamel junction (CEJ) to alveolar crest (AC) and CEJ to the most apical extension of bony defect (BD) were measured. The average gain of attachment was assessed 2.33 mm in the control group and 3.17 mm in the test group. The bony fill was measured 0.97 mm and 0.97 mm in the control group and 0.93 mm and 1.68 mm in the test group after 3 and 6 months, respectively, using a loupe. Using a computer-assisted system 0.83 mm and 1.82 mm of bone fill could be measured (control) and 0.76 mm and 1.79 mm (test) after 3 and 6 months, respectively. Compared to the gold standard of surgical measurements, the computer-assisted analysis of radiographs underestimated bone loss significantly less than evaluation with a loupe (P < 0.002). Compared to conventional periodontal surgery, the GTR technique resulted in higher attachment gain and bony fill. However, the high variation of surgical results in the test group prevented the calculation of a statistically significant difference.

Light source-induced error in computer-assisted image analysis with a video-based system

OBJECTIVE

We tested the hypothesis that two different light sources, an alternating current fluorescent viewbox and a direct current halogen viewbox, do not differ with respect to their ability to illuminate reproducibly a radiograph during image capture.

STUDY DESIGN

Two radiographs were taken: one with four hydroxyapatite chips mounted against a dry mandible and one without the chips. They were digitally subtracted with a video-based imaging system. The procedure was repeated at different times.

RESULTS

A statistically significant difference among optical density measurements was found when the alternating current fluorescent viewbox (p < 0.001) was used and was related to light intensity variation. Such effect was not observed with the direct current halogen viewbox (p = 0.873).

CONCLUSION

Study design efficiency was increased by 212% with the use of the direct current halogen viewbox so that to detect a specified treatment effect with a given level of statistical confidence, the sample size has to be 2.12 times greater if the alternating current fluorescent viewbox is used.

Digital radiographic images will benefit endodontic services

Future assurances for endodontic services and assessments of traumatized teeth will depend in part on significant improvements to the quality of dental radiographs. Whereas digital images offer many potential sensor, display and archival advantages over film-based radiographs, the marginal image improvements from intraoral sensors primarily benefit patient education. Precisely digitized conventional radiographs are more likely to yield quantum image resolution improvements, although neither dentists nor patients will benefit until cost-effective digitizing systems have been developed for the dental office.

Effect of logarithmic contrast enhancement on subtraction images

The aim of this study was to analyze logarithmic contrast enhancement as compared with regular digital subtraction and to consider effects of image texture and observer experience. Radiographs of three different textures, including computer-stimulated lesions of various sizes and densities, were subtracted from radiographs taken before lesions were placed. Logarithmically enhanced and regular subtraction images were put in random order with an equal number of nonlesion subtraction images to form a series of 300 images. Twenty subjects were asked to decide on a 5-point confidence scale whether a lesion was present. Plain texture images were diagnosed significantly better than bone and enamel images. Logarithmic contrast enhancement had a positive effect on plain texture images. There was no significant experience effect. In the student group, however, there was a significant difference between the two subtraction methods. Overall, logarithmic contrast enhancement provided better diagnostic validity than regular subtraction. Logarithmically enhanced subtraction radiography seems to be a promising method for images with low-contrast gradients.

Future trends in dental radiology

Direct digital dental radiographic systems offer the potential to radically change the way dentists diagnose and treat dental pathoses. They offer instantaneous availability of radiographs, markedly lower patient radiation exposure, and the elimination of developing chemicals and developing equipment. The storage of dental radiographs as digital data permits their transmittal over phone lines facilitating phone consultations and may someday allow expedited authorization of treatment plans by dental insurance companies. With the use of digital subtraction radiology the dental practitioner will be able to diagnose periodontal disease progression and dental caries progression long before current techniques can detect a change. With tuned aperture computed tomography, the owner of a filmless digital system can make tomographic radiographs that allow the visualization of slices through areas of interest without having to buy additional hardware. Computer-aided diagnosis will facilitate the detection of proximal dental caries and osteoporosis, and may someday allow automated tracing of cephalometric radiographs.

Reliability of a paralleling instrument for dental radiographs

The reliability of a paralleling instrument for dental radiographs was retrospectively evaluated in the course of a 6-month clinical study. The angular variation between successive exposures was precisely quantified. Ninety-one percent of the angular variations were below a 1.4 degree threshold, but some paired images were found unsuitable for quantitative analysis. A mathematic procedure to assess the global angular projection error of any similar coupled x-ray cone-film holder device is proposed. This mathematic procedure should be routinely used to check superimposability of serial radiographs before density quantification or subtraction.

A comparison of topical ketorolac, systemic flurbiprofen, and placebo for the inhibition of bone loss in adult periodontitis

Systemic non-steroidal anti-inflammatory drugs (NSAIDs) have been shown to reduce alveolar bone loss in periodontitis. This study assesses the efficacy of a topical NSAID rinse, containing ketorolac tromethamine as the active agent. Adult periodontitis patients (n = 55) were studied in this 6-month randomized, double blind, parallel, placebo and positive-controlled study. Each patient had a least 3 sites at high risk for bone loss as assessed by low dose bone scan. Groups, balanced for gender, were assigned to one of three regimens: bid ketorolac rinse (0.1%) with placebo capsule; 50 mg bid flurbiprofen capsule (positive control) with placebo rinse; or bid placebo rinse and capsule. Prophylaxes were provided every 3 months. Monthly examinations assessed safety, gingival condition, and gingival crevicular fluid PGE2. Standardized radiographs were taken at baseline and at 3 and 6 months for digital subtraction radiography. A significant loss in bone height was observed during the study period in the placebo group (-0.63 +/- 0.11; P < 0.001), but not in the flurbiprofen (-0.10 +/- 0.12; P = 0.40) or ketorolac rinse (+0.20 +/- 0.11 mm; P = 0.07) groups. Nested ANOVA revealed that ketorolac and flurbiprofen groups had less bone loss (P < 0.01) and reduced gingival crevicular fluid PGE2 levels (P < 0.03) compared to placebo. ANOVA suggests (P = 0.06) that ketorolac rinse preserved more alveolar bone than systemic flurbiprofen at the dose regimens utilized. These data indicate that ketorolac rinse may be beneficial in the treatment of adult periodontitis.

Reproducibility of beam alignment using different bite-wing radiographic techniques

Longitudinal radiographic assessment of crestal alveolar bone plays an important role in the diagnosis and long-term evaluation of periodontal disease in patients. Because practitioners use several radiographic techniques to obtain bite-wing radiographs, horizontal and vertical alignment errors could adversely affect the diagnostic impression gained from this type of radiographic examination. The objective of this study was to determine the alignment reproducibility of three different clinical techniques used to acquire bite-wing radiographs. Patients who require bite-wing radiographs as part of a dental school screening process were radiographed with modified standard bite-wing tabs and two different intraoral positioning devices. Horizontal and vertical angular deviations were measured and alignment errors were calculated for each radiograph. The mean total angular alignment error for the standard bite-wing tab technique was 6.2 degrees, whereas the mean alignment error for both positioning devices was less than 1.8 degrees. The results of this study suggest that an intraoral positioning device for acquiring bite-wing radiographs should be used.

The effect of systemic flurbiprofen on bone supporting dental implants

This article describes a study of the efficacy of the non-steroidal anti-inflammatory drug flurbiprofen in maintaining alveolar bone around mandibular root-form dental implants. The preliminary results indicate that, in appropriate doses, flurbiprofen may spare bone around such implants.

When will excellent radiographic images be available to the general dental office?

Dental radiography is a highly regarded diagnostic practice. More than 25% of all radiographs are taken for dental purposes, so their improvement will benefit many patients. Although recent advances in materials and processing have contributed to incremental improvements in film-based diagnoses, computer-based enhancement of digitized conventional radiographic images is likely to yield more significant benefits. However, until cost-effective digitizing systems have been developed for the general dental office, the benefits derived from precise radiographic diagnoses and associated improvements in the standards of care will continue to elude both dentist and public.

Effects of small angle discrepancies on interpretations of subtraction images

The present study examines interpretations of subtraction images of pairs of radiographs taken at 0 degrees, 1 degree, or 2 degrees of angle discrepancy. The radiographs were taken at each of 48 alveolar crestal sites on 15 dried human skulls. Computer-simulated lesions were induced at the sites on three fourths of the radiographs. Ten instructed dentists were asked to interpret the subtraction images as to the presence or absence of crestal change. A 2-degree angle discrepancy between radiographs resulted in a significant difference in sensitivity from that of radiographic pairs with a 0-degree discrepancy. However, we found no significant difference in sensitivity between 1-degree and 0-degree pairs of radiographs. In conclusion, a 1-degree geometric difference between pairs of radiographs does not significantly contribute to errors in interpretation of subsequent subtraction images.

Development of automated registration algorithms for subtraction radiography

An algorithm is described which provides necessary information for automated registration and computation of alveolar height for subtraction radiographic analysis. This procedure involves identification of the cemento-enamel junctions from radiographic images by incrementally comparing a characteristic image signature along computed tooth boundaries. The identification of these anatomically invariant structures provides information necessary to warp images and create automatic superimposition, correcting for geometric misalignment. The present report describes and demonstrates the feasibility of utilizing automated CEJ, edge finding and image warping algorithms to align automatically sequential radiographs and permit their subtraction.

Evaluation of consecutively placed unloaded root-form and plate-form implants in adult Macaca mulatta monkeys

The present paper describes 18 consecutively-treated non-human primates (Macaca mulatta) as part of a balanced block design study of 36 animals to examine osseointegration in root- and plate-form implants prepared by atraumatic preparation of bone. Clinical measurements around selected teeth and digital radiology were utilized to monitor periodontal disease and bone deposition around the unloaded implants. Once a month scaling procedures were utilized as a means of preventing further advance of periodontal disease. Results indicate that once-monthly regimen of scaling and root planing can prevent attachment loss of natural teeth and will not interfere with the healing of either type of implant; once-monthly scalings produce significant reduction in redness (P < .05) and reduced probing depths (P = .01). A second finding is that both root and blade implants show radiographic evidence of osseointegration in this primate model. The quantitative analysis demonstrates bone gain is not stabilized until 6 months after healing. The data may indicate that occlusal loading of mandibular implants at 3 months may be premature.

Studies of the angular reproducibility of positioning patients adjacent to an x-ray tube: 1. Stent-rod based and extra-oral systems

The usefulness of subtraction radiography for detecting small changes in crestal bone is dependent upon achieving reproducible geometry between x-ray beam and patient structures when serial radiographs are taken. This study evaluates 2 methods currently employed to maintain geometric correspondence: 1) a stent-based system which rigidly fixes a custom-made stent to the x-ray tube by the use of a rod and 2) an extra-oral system which positions a patient in the x-ray unit by means of ear rods. The projection of a light beam from a fixed subject reference was used to measure the change of the orientation of the reference at 2 different measurement times. The rod-stent system was able to maintain a discrepancy of less than 2 degrees 75% of the time over a time period of 6 months. For the extra-oral system this ranged from 72% to 92% during a 1-month period.

Comparison of stent versus laser- and cephalostat-aligned periapical film-positioning techniques for use in digital subtraction radiography

Digital subtraction radiography is a sensitive diagnostic technique that allows detection of subtle calcific changes in the jaws and teeth that would otherwise not be radiographically visible. However, a high failure rate associated with stent-based periapical film-positioning strategies combined with the complexity, expense, and time of image acquisition has limited the clinical utility of this technique. This study compares a new technique that uses film-positioning instruments, laser alignment beams, and a cephalostat with a previously validated method that used film positioners and elastic impression material. Two series of periapical radiographs were taken of six different anatomic areas of six phantoms using both techniques. Film pairs were digitally subtracted twice and analyzed. A paired t test for difference in standard deviation of mean pixel values revealed no difference in repositioning accuracy between the two techniques (p = .68). The new technique eliminates problems that are associated with the use of elastomeric impression materials.

Detection of mineral loss in approximal enamel by subtraction radiography

The purpose of the present study was to determine whether digital subtraction radiography will improve detectability of small, mechanically prepared defects within dental enamel. Lesions with an extent of 1 mm in vertical direction and representing 5% to 10% mineral loss in the direction of the x-ray beam were prepared in eight extracted molars. Radiographs of teeth with defects were subtracted from radiographs taken before the lesions were prepared. Seven observers evaluated the images using a five-point confidence rating scale (receiver operating characteristic technique). Examination of the original radiographs showed increasing accuracy of radiographic interpretation with increasing mineral loss as judged from the areas beneath the receiver operating characteristic curves. The same observation was made using subtraction images with and without contrast enhancement. There was no indication that subtracted images provided better diagnostic validity than the original radiographs. In conclusion, subtraction images do not seem to improve the diagnosis of well-defined lesions within dental enamel.

Longitudinal evaluation of elastase as a marker for the progression of periodontitis

To determine whether elastase levels in gingival crevicular fluid (GCF) could serve as a marker for the progression of periodontitis, we monitored GCF elastase and periodontal status in selected sites in 32 periodontally healthy volunteers and 31 periodontitis patients at intervals over a 6-month period. Clinical measurements included plaque index, gingival index, bleeding on probing, suppuration, probing depth, clinical attachment level, and relative attachment level measured with an automated disk probe. GCF elastase, detected by reaction with a fluorescent substrate, was assessed visually against fluorescence standards and quantitatively with a fluorometer. Bone loss was detected by subtraction radiography of standardized vertical bite-wing radiographs at baseline and 6 months. Mean visual elastase scores (VES) and quantitative elastase measurements were significantly higher (P < 0.001) in sites from periodontitis patients than in sites from healthy volunteers. When bone loss was used as the criterion for disease progression, significantly higher (P < 0.001) visual and quantitative GCF elastase levels were found at progressing sites than in nonprogressing sites in the periodontitis patients. The odds ratios (OR) for the event of developing bone loss with positive 4-minute and 8-minute VES tests were 4.2 (P < 0.001) and 7.4 (P < 0.001), respectively. When corrected for the tendency of progressing sites to be clustered within a subpopulation of patients, the OR for developing bone loss with the 4-minute and 8-minute VES tests were 3.1 (P < 0.007) and 4.9 (P < 0.001), respectively. These data indicate that sites with high levels of elastase are at significantly greater risk for progressive bone loss as assessed by digital subtraction radiography.