The use of self-instructional materials in dental education as applied to clinical epidemiology and decision making.
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Computer-Assisted Instruction↗
Biomedical subjects
C A McCulloch
Publications and source records attributed to C A McCulloch.
Automated probe: futuristic technology for diagnosis of periodontal disease.
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Diagnosis, Computer-Assisted↗
Comparison of self-instruction methods for teaching diagnostic testing.
In a randomized controlled trial, self-teaching booklets and computer media were evaluated for teaching diagnostic testing to dental students as a foundation for further development of clinical decision making skills. Effectiveness was assessed by pre- and post-tests. Reliability of these test instruments was examined by analyzing the pre- and post-test scores of 49 first year dental students who received no instruction. Forty-one second year dental students were exposed to clinical epidemiological principles applied to endodontic diagnosis through either self-teaching booklets or computer media. No statistically significant difference was found between the mean test scores of the students through self-teaching booklets and computer media. Although first and second year students showed a statistically significant improvement between the pre-test and post-test, the improvement in the second year class was greater. An addendum was later made to the main trial to compare the self-teaching booklet to the traditional lecture format in teaching endodontic diagnosis. Seventy-one third year dental students were exposed to these same materials through either a lecture or the self-teaching booklet and then similarly tested. There was no significant difference between the self-teaching booklet and traditional lecture for the third year students.
Computer-Assisted Instruction↗
Stimulation of the differentiation of osteogenic rat bone marrow stromal cells by osteoblast cultures.
The effect of conditioned medium (CM) from rat calvaria (RC) cel cultures on the growth and differentiation of osteogenic cells in rat bone marrow stromal cell (BMSC) cultures was investigated. Control cultures received either CM from periodontal ligament fibroblast cultures or fresh medium. RCCM stimulated the formation of nodules of bonelike tissue in bone marrow stromal cell cultures in a dose-dependent manner,and the maximal stimulation was associated with the osteoblast-enriched cell populations of the RC cultures. Ultrafiltration demonstrated that activity was confined to a CM fraction of 10- to 30-kilodalton molecular size. The activity was sensitive to boiling and trypsin treatments, but was not affected by neutralizing antibodies to transforming growth factor beta or insulin-like growth factor I or II. RCCM was found to initially increase the number and proportion of cells that expressed alkaline phosphatase activity, although the proportion of alkaline phosphatase-positive cells subsequently declined. These data were consistent with an initial stimulation of proliferation of a subpopulation of osteoprogenitor cells within the cultures, followed by their differentiation. The results suggest that mature osteoblasts may produce a paracrine growth factor that can stimulate the differentiation of osteoblasts from precursor cells.
Alkaline Phosphatase↗
Dose/response relationships in clinical studies of mercury toxicity: statistical considerations.
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Clinical Trials as Topic↗
Effects of donor age on osteogenic cells of rat bone marrow in vitro.
The effect of donor age on the production of bone-like tissue and expression of cellular alkaline phosphatase was examined in cultures of cells obtained from rat bone marrow. Stromal cells were obtained from the bone marrow of young (5-6 weeks) and old (18 months) rats and cultured in vitro. After 28 days in first subculture, the following were quantified: (1) the total number of mineralised nodules and the size distribution of nodules and (2) the density of osteoblasts and osteocytes associated with nodules in histological sections. The doubling times of the cultures and the numbers of cells in cultures which expressed alkaline phosphatase activity were determined in separate experiments. Cells from young cultures produced three times more bone-like nodules than old cultures, although no differences were seen in the size distribution of nodules, or on osteoblast and osteocyte density. Doubling times for both groups were similar. The numbers of alkaline phosphatase (AP) positive cells was reduced by half in old cultures. These data show that this model may be useful for the study of the mechanisms of ageing on osteogenesis, and demonstrate a reduced osteogenic capacity in old cultures. The results suggest that this effect may be due to a reduction in the generation of cells of osteoblast lineage during ageing.
Aging↗
Role of the cellular attachment domain of fibronectin in the phagocytosis of beads by human gingival fibroblasts in vitro.
To study the role of phagocytosis in periodontal tissues, internalization of fibronectin-coated latex beads by Gin-1 fibroblast populations was investigated. Demonstration of phagocytosis by internalization of beads was confirmed by immunofluorescence microscopy, electron microscopy, and flow-cytometry. The percent of cells phagocytosing beads measured by flow-cytometry was negligible at 4 degrees and 23 degrees C, but increased to approximately 17% at 37 degrees C. As measured by automated image analysis, the percentage of phagocytosing cells increased linearly from 8 to 22 with increasing fibronectin concentration of the incubation solution from 30 ng to 300 micrograms/ml. Similar linear increases in the percentage of phagocytosing cells were observed when beads were incubated with cells for periods ranging from 2 h to 2 days. To examine the role of the Arg-Gly-Asp receptor in mediating phagocytosis, fibronectin-coated beads were first coated with either Gly-Arg-Gly-Asp-Ser-Pro or Gly-Arg-Gly-Glu-Ser-Pro peptides at concentrations of 0.125, 0.5, and 1 mg/ml, or with control vehicle, and then incubated with cells. Phagocytosis was completely blocked at 1 mg/ml of the Gly-Arg-Gly-Asp-Ser-Pro peptide, but the Gly-Arg-Gly-Glu-Ser-Pro peptide showed no significant inhibition compared to control values. Blocking antibodies to the cell attachment domain of the fibronectin molecule also reduced the percentage of phagocytosing cells significantly. The data show that these phagocytic assays are sensitive enough to detect the influence of incubation temperature and time, cellular heterogeneity, ligand type, and ligand concentration on the percentage of phagocytosing cells.(ABSTRACT TRUNCATED AT 250 WORDS)
Cell Adhesion↗
Clonal distribution of osteoprogenitor cells in cultured chick periostea: functional relationship to bone formation.
Folded explants of periosteum from embryonic chick calvaria form bone-like tissue when grown in the presence of ascorbic acid, organic phosphate, and dexamethasone. All osteoblast-like cells in these cultures arise de novo by differentiation of osteoprogenitor cells present in the periosteum. To study the spatial and functional relationships between bone formation and osteoprogenitor cells, cultures were continuously labeled with [3H]thymidine for periods of 1-5 days. Radioautographs of serial 2-microns plastic sections stained for alkaline phosphatase (AP) showed maximal labeling of 30% of fibroblastic (AP-negative) cells by 3 days while osteogenic cells (AP-positive) exhibited over 95% labeling by 5 days. No differential shifts in labeling indices, grain count histograms of fibroblastic and osteogenic cells or numbers of AP-positive cells were observed, indicating no significant recruitment of cells from the fibroblastic to the osteogenic compartment. Despite the continuous presence of [3H]thymidine, less than 35% of both osteoblasts and osteocytes were labeled at 5 days, indicating that only one-third of the osteoprogenitor cells had cycled prior to differentiation. Spatial clustering of [3H]thymidine-labeled cells was measured by computer-assisted morphometry and application of the Poisson distribution to assess contagion. Cluster size and number of labeled cells per cluster did not vary between 1-3 days, but the number of clusters increased 20-fold between Day 1 and Day 3. Clusters were predominantly AP-positive and located close to bone. Three-dimensional reconstruction from serial sections showed that clusters formed long, tubular arrays of osteogenic cells up to eight cells in length and located within 2-3 cell layers from the bone surface. Selective killing of S-phase cells with two pulse labels of high specific activity [3H]thymidine at 1 and 2 days of culture completely blocked bone formation. These data indicate that a very small population of cycling osteoprogenitor cells is essential for bone formation in vitro and give rise to relatively small numbers of clonally distributed progenitors with limited proliferative capacity. The progeny of these clusters undergo restricted migration and differentiate into osteoblasts.
Alkaline Phosphatase↗
Identification of polymorphonuclear leukocyte collagenase and gelatinase activities in mouthrinse samples: correlation with periodontal disease activity in adult and juvenile periodontitis.
In previous studies, elevations in the levels of active and latent collagenase in gingival crevicular fluid (GCF) have been correlated positively with periodontal disease activity. To provide a simple diagnostic approach for testing collagenolytic activity, the feasibility of using a 3.0 ml water mouthrinse to collect GCF simultaneously from all sites in the mouth was assessed. Patients with adult periodontitis (AP, n = 23) and local juvenile periodontitis (LJP, n = 7) were sampled before periodontal therapy and some (12 AP, 4 LJP) were also assessed longitudinally after scaling and root planing, administration of antibiotics, and following periodontal surgery. Healthy patients (n = 19) were used as controls. The levels of active collagenase, procollagenase, and collagenase inhibitor activity were determined by functional assays and quantitated after SDS-PAGE and fluorography. Gelatinase and progelatinase were assayed by enzymography on gelatin-substrate gels. Active collagenase levels were found to be significantly higher (14- to 20-fold) in AP and LJP patients compared to controls, whereas matrix metalloproteinase activity was not detected in mouthrinses from edentulous patients. Collagenase inhibitor levels were generally low in all groups of subjects tested. Following clinical treatment the levels of active collagenase and gelatinase were reduced; the reduction was significant for active collagenase after tetracycline treatment and scaling in LJP patients. Of the clinical indices recorded (gingival index, plaque index, and pocket depth) there were no significant correlations with enzyme activity but similar trends were observed between the changes in active collagenase and gingival index. In patients with untreated periodontal disease, collagenase occurred predominantly in the active form. N-ethylmaleimide (NEM) and p-aminophenylmercuric acetate (AMPA) were equally effective as activators of the latent collagenase, indicating that the collagenase was derived from PMNs, which were also the source of gelatinase. The results of these studies indicate that measurement of active collagenase and gelatinase in mouthrinse samples is potentially useful in the diagnosis and assessment of periodontal disease activity.
Adolescent↗
Randomized controlled trial of doxycycline in prevention of recurrent periodontitis in high-risk patients: antimicrobial activity and collagenase inhibition.
82 patients with a recent history of periodontal abscesses and/or loss of gingival attachment (GAL) despite active periodontal therapy were enrolled in a double-blind, randomized, placebo-controlled trial. Clinical measurements and subgingival scaling were performed every 2 months. If any site exhibited greater than or equal to 2 mm loss of GAL or a periodontal abscess, patients were administered either 100 mg Doxycycline per day for 3 weeks or placebo. During 12 months of monitoring, 55 patients exhibited recurrent active disease and were then randomly assigned to either the Doxycycline or placebo groups. Clinical measurements of GAL and microbiological culture of subgingival bacteria were made at intervals between 1 week and 7 months after completion of the drug regime. Within 7 months, 15 out of 19 patients on placebo exhibited recurrent disease compared to 13 out of 29 patients on Doxycycline, a relative risk reduction of 43% (p less than 0.05) for Doxycycline compared to placebo. Minimal inhibitory concentrations of Doxycycline for subgingival plaque samples from active sites ranged between 25-100 micrograms/ml, which are several fold higher than reported crevicular fluid concentrations for this drug. However gingival crevicular fluid collagenase was inhibited in vitro at concentrations of 5-10 micrograms/ml Doxycycline. These data indicate that Doxycycline provides significant risk reduction of recurrent periodontitis in patients with active disease.
Adult↗
Controlled force measurements of gingival attachment level made with the Toronto automated probe using electronic guidance.
Precise reproduction of probe placement, probing force and probing angulation may influence the reliability of replicate gingival attachment level measurements (GAL). Reproducibility of GAL measurements was determined with the Toronto automated periodontal probe (TAPP) in which a novel electronic guidance system was incorporated to improve the precision of probing angulation. Bench testing of forces produced at the probe tip was performed with an electronic balance. Reproducibility and precision of force generation were tested in a variety of instrument configurations using laboratory models. The data indicated that highly precise and reproducible probing forces can be generated with the TAPP over a large (10 to 90 g) probing range. Instrument precision was +/- 0.27 mm when probing forces of 40-60 g were used. The guidance system provided accurate and reproducible measurements of the probe handle in both roll and pitch axes when compared with precisely machined wedges (R = 0.99, roll; R = 0.98, pitch). Deviation of probing angulation greater than 5 degrees on replicate measurements of GAL was associated with significant alterations in the location of circumferential probe placement and in the size of the difference between GAL measurements (delta GAL). Clinical assessment of probing angulation in 6 patients demonstrated that delta GAL was 0.40 +/- 0.05 mm when probing angulation deviation was less than 5 degrees but increased to 0.96 +/- 0.11 mm when deviations exceeded 5 degrees. Taken together, these data indicate that the regulation of probing angulation in clinical measurement of GAL with the TAPP is an important determinant of the reproducibility of periodontal probing.
Calibration↗
Site-specific regulation of osteogenesis: maintenance of discrete levels of phenotypic expression in vitro.
Intrinsic differences in bone formation rate, cell numbers, and the percentages of cells expressing alkaline phosphatase activity were studied in explants of chick calvaria periosteum cultured for 4 days and 6 days. Proliferation, differentiation, and bone production were examined in radioautographs of plastic sections and by using whole-culture biochemical assays of protein and alkaline phosphatase. Ectocranial explants at both 4 days and 6 days exhibited more alkaline phosphatase-positive cells and significantly more bone formation than endocranial cultures. There were no detectable differences in cell numbers or 3H-thymidine labeling indices. The volume of bone synthesized per osteoblast was significantly higher in the ectocranial group. Examination of bone stripped of periostea and then cultured for 4 days revealed that large areas of bone were covered by osteoblasts, indicating that the periosteal explant cultures were composed almost exclusively of osteoprogenitor cells and fibroblasts. The data suggest that the level of expression of predetermined osteogenic phenotypes can be maintained in vitro for 6 days following explantation and that variations in the rate of osteogenesis are programmed into progenitor cells prior to their differentiation into osteoblasts.
Animals↗
Coordinated regulation of endothelial and fibroblast cell proliferation and matrix synthesis in periodontal ligament adjacent to appositional and resorptive bone surfaces.
Little is known about the remodeling of blood vessels and soft connective tissue or the proliferation of endothelial cells in the periodontal ligament (PL) of teeth undergoing physiological drift. To determine whether there is evidence for coordinated regulation of endothelial cell and fibroblast proliferation and matrix synthesis in sites within the PL adjacent to bone-appositional (A) and bone-resorptive (R) surfaces, the PL in mouse mandibular molar was subdivided into A and R sectors on the basis of 3H-proline incorporation into alveolar bone. Computer-assisted morphometry of radioautographs showed that the number and area of blood vessels were similar in A and R sectors. Proliferation of endothelial cells and fibroblasts was assessed from radioautographs prepared from mice continuously labeled with 3H-thymidine at times between 2 and 60 days. Significantly more labeled endothelial cells (P less than .001) and fibroblasts (P less than .05) were seen in the A sector. The percent of labeled endothelial cells and the percent of labeled fibroblasts increased linearly to 25 days and then formed a plateau. The rate of increase of labeled fibroblasts was higher in the A sector than in the R sector (P less than .025). In addition, 3H-proline grain counts over extracellular matrix were significantly higher in the appositional sector than in the resorptive sector (P less than .025).(ABSTRACT TRUNCATED AT 250 WORDS)
Animals↗
The regulatory effect of phosphates on bone metabolism in vitro.
One of the most important indicators in vitro of the bone-cell phenotype is the synthesis of mineralized bone-like tissue. This has been achieved by supplementing isolated bone-cell and tissue cultures with organic phosphates, in particular, beta-glycerophosphate. To analyze the effects of beta-glycerophosphate on bone-cell metabolism and osteogenesis in vitro, both biochemical analyses and computer-assisted morphometry were used. Simultaneous autoradiographic and histochemical analyses of proliferating and alkaline phosphatase-positive cells were used to measure osteogenic events at the cellular level. Morphometric data showed that beta-glycerophosphate-treated cultures mineralized, but exhibited significantly less bone matrix (P less than 0.05) than non-mineralizing controls. Cultures treated with inorganic phosphate failed to mineralize. Cellular proliferation was unaffected by beta-glycerophosphate; however, there was a decrease in the amount of 3H-thymidine incorporation into the DNA of beta-glycerophosphate-treated cells as detected by autoradiography. The percentage of alkaline phosphatase-positive cells was identical in beta-glycerophosphate-treated or control cultures. In agreement with previous biochemical results, there was a decrease in the amount of alkaline phosphatase enzyme activity per cell. The kinetics of alkaline phosphatase enzymes were measured on individual cells by microdensitometry. beta-Glycerophosphate-treated cultures exhibited more rapid reaction rates than control cultures (p less than 0.05). Taken together, the results suggest that beta-glycerophosphate has global effects on bone-cell metabolism in vitro including its importance in mineralization.
Alkaline Phosphatase↗
Cell death and the regulation of populations of cells in the periodontal ligament.
The contribution of cell death in regulating cellular populations of periodontal ligament was studied in young adult rats. Mandibular first molar periodontium was prepared for light-microscopic radioautography after a pulse of 3H-thymidine in 6 rats and for electron microscopy in 4 rats. The labeling index for 3H-thymidine and the density of fibroblast-like cells were computed from radioautographs. The percentages of dying or dead cells and macrophages were computed from electron micrographs. The labeling index of cells within 20 microns of bone and cementum was significantly lower (p less than 0.01) than the labeling index within the body of the periodontal ligament. The patterns of cellular density and indices of death were the inverse of the labeling indices. Macrophages were plentiful (% macrophages = 3.68% +/- 0.30) and were clustered around blood vessels (mean distance from blood vessel = 2.3 microns). However, only 10% of dying or dead cells were within 10 microns of blood vessels. These data show that death of cells in the periodontal ligament may, in part, balance production of cells by mitosis. The relationships between labeling index, index of death, and cellular density suggest that cells born in the middle of the periodontal ligament may migrate to regions of high cellular density near bone and cementum, and that they may die there. Macrophages do not appear to be associated with dying cells of the periodontal ligament.
Animals↗
Measurements of probing velocity with an automated periodontal probe and the relationship with experimental periodontitis in the Cynomolgus monkey (Macaca fascicularis).
The Toronto Automated Periodontal Probe allows simultaneous measurements of gingival attachment level and probing velocity. The efficacy of probing velocity in measuring the integrity of the dento-gingival junction was studied and compared with loss of gingival attachment level, gingival inflammation, tooth mobility and gingival crevicular fluid collagenolytic activity. The gingiva around the maxillary and mandibular incisor teeth of 2 monkeys were first brought to clinical health by daily prophylaxis. Baseline measurements were made and inflammation was then induced around the maxillary incisors by withdrawing plaque control and by placing silk ligatures subgingivally. The mandibular incisors served as controls. After 10 weeks, the ligatures were removed and the teeth scaled and polished daily for 1 week. The plaque index and gingival index reached maximum values within 1 week; crevicular fluid flow was significantly increased at 1 and 3 weeks but mobility did not change significantly. There was progressive loss of the gingival attachment level, which peaked at 10 weeks on experimental teeth; there was no significant loss on control teeth. Probing velocity around experimental teeth exhibited large and significant increases above controls between 1 and 3 weeks, coinciding with the largest weekly losses of the gingival attachment level. Thus probing velocity may be a useful clinical method for the ancillary measurement of early loss of the gingival attachment level. It can also detect biophysical changes in the dento-gingival junction of progressive inflammatory lesions.
Animals↗
Dexamethasone effects on induction of neoplastic transformation by Fujinami sarcoma virus in an in vitro chick embryo periosteal model for osteosarcoma.
Recently we have developed a model in vitro system for the study of factors regulating the histogenesis of osteosarcoma. In this system, Fujinami sarcoma virus (FSV) induces osteosarcomatous changes such as increased cell proliferation and altered patterns of bone and nonmineralized matrix (osteoid) formation. Such changes can be quantitated at the individual cell level, by computer-assisted morphometry. Here we report on the effects of dexamethasone (DEX) on FSV-induced neoplastic transformation and osteogenesis in chick embryonic periosteum cultures, as reflected by a series of histopathological parameters. Most significantly, it was found that compared to 10(-9) M DEX treated cultures, in 10(-7) M DEX pretreated cultures, the bone/osteoid ratio was increased due to a relative increase in the area of bone and a decrease in the area of osteoid. The number of [3H]thymidine-labeled cells decreased significantly, while the proportion of alkaline phosphatase positive cells increased. Double-label immunohistochemistry (with anti-P140gag-fps) and histochemistry for alkaline phosphatase activity was performed, to demonstrate production of the oncogene-encoded protein, and osteoblastic differentiation, respectively. In an in vitro transformation assay single cells derived from 10(-9) M DEX treated cultures formed a significantly higher number of colonies than those obtained from 10(-7) M DEX pretreated cultures. Taken together, the data indicate that in the chick embryonic periosteum culture system, pretreatment with 10(-7) M DEX inhibits the ability of FSV to induce neoplastic transformation. This effect is probably the result of DEX-induced cell differentiation, prior to infection with FSV.
Alkaline Phosphatase↗
Lifetime of the osteoblast in mouse periodontium.
The kinetics of osteoblasts and osteocytes on appositional and resorptive surfaces of mouse alveolar bone were examined using 3H-thymidine and 3H-proline radioautography. Our results show that the osteoblasts at the appositional surface of the mouse periodontium are recruited from a progenitor population in the G1 phase of the cell cycle that goes through a single S-phase before differentiating into osteoblasts and that the active lifetime of the osteoblast on the periodontal surface is approximately 20 days. The lifetime of the osteoblasts on periosteal and endosteal surfaces is 10 days. The active lifetime of an osteoblast appears to be independent of the amount of matrix produced.
Alveolar Process↗